WO2022215581A1 - Positive electrode active material and manufacturing method therefor - Google Patents
Positive electrode active material and manufacturing method therefor Download PDFInfo
- Publication number
- WO2022215581A1 WO2022215581A1 PCT/JP2022/015076 JP2022015076W WO2022215581A1 WO 2022215581 A1 WO2022215581 A1 WO 2022215581A1 JP 2022015076 W JP2022015076 W JP 2022015076W WO 2022215581 A1 WO2022215581 A1 WO 2022215581A1
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- WIPO (PCT)
- Prior art keywords
- active material
- positive electrode
- electrode active
- atomic
- ion secondary
- Prior art date
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- 238000004611 spectroscopical analysis Methods 0.000 claims abstract description 16
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Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
Definitions
- the present invention relates to a positive electrode active material with an olivine structure and a method for producing the same.
- Lithium ion secondary batteries which have excellent capacity, are used as power sources for mobile terminals, personal computers, electric vehicles, and the like.
- a high-capacity positive electrode active material and a high-capacity negative electrode active material may be employed.
- positive electrode active materials having a layered rock salt structure such as LiCoO 2 , LiNiO 2 and LiNi 1/3 Co 1/3 Mn 1/3 O 2 are known as high-capacity positive electrode active materials.
- the Si-containing negative electrode active material since the Si-containing negative electrode active material has a high ability to absorb lithium, it is known as a high-capacity negative electrode active material.
- lithium-ion secondary batteries that employ a positive electrode active material with a layered rock salt structure and lithium-ion secondary batteries that employ a Si-containing negative electrode active material generate a large amount of heat when an abnormality such as a short circuit occurs. It had its shortcomings.
- a positive electrode active material with an olivine structure which has a lower capacity than a positive electrode active material with a layered rock salt structure but is superior in thermal stability.
- a negative electrode active material to be combined with the positive electrode active material there is a means of adopting graphite, which has a lower capacity than the Si-containing negative electrode active material but has excellent thermal stability. Lithium-ion secondary batteries with graphite as positive and negative electrode active materials of olivine structure have been described in the literature.
- Patent Document 1 describes that a lithium-ion secondary battery equipped with a positive electrode active material having an olivine structure is excellent in safety ( see paragraph 0014).
- a lithium ion secondary battery comprising graphite as a negative electrode active material is specifically described (see Experimental Examples 1 to 6).
- Patent Document 2 describes that the positive electrode active material with an olivine structure has high thermal stability (see paragraph 0011), and includes LiFePO 4 with an olivine structure as a positive electrode active material and graphite as a negative electrode active material. is specifically described (see Examples 1-3).
- Patent Document 3 introduces lithium iron phosphate (LiFePO 4 ) and lithium manganese phosphate (LiMnPO 4 ) as positive electrode active materials having an olivine structure, and further introduces lithium iron manganese phosphate, which is a solid solution thereof.
- lithium iron manganese phosphate is expected to have a higher average operating voltage and a higher energy density as the element ratio of Mn to iron increases. explained.
- the above lithium iron-manganese phosphate has a high energy density and is expected to be useful as a positive electrode active material, it has properties that are not suitable as a positive electrode active material.
- Patent Document 3 explains that the development of the theoretical discharge capacity and theoretical operating voltage of lithium iron-manganese phosphate becomes more difficult as the element ratio of manganese to iron increases. Furthermore, Patent Document 3 states that this problem is caused by the fact that lithium iron manganese phosphate has poor electronic and ionic conductivity, and that the structure of lithium iron manganese phosphate changes due to charging and discharging. is explained. It is considered that the structural change of lithium iron manganese phosphate causes the capacity deterioration of lithium iron manganese phosphate as a positive electrode active material.
- Patent Document 3 discloses that a phosphoric acid compound obtained by doping lithium iron manganese phosphate with niobium stabilizes its structure and increases electronic conductivity and ionic conductivity (for example, [0032 ] to [0034]).
- the inventor of the present invention aimed to develop a novel positive electrode active material, which is an iron-manganese-lithium phosphate-based positive electrode active material having an olivine structure, in which capacity deterioration after endurance is suppressed.
- the present invention has been made in view of such circumstances, and it is an object of the present invention to provide a positive electrode active material of iron manganese lithium phosphate having an olivine structure, in which capacity deterioration after endurance is suppressed. should be the subject.
- the inventors of the present invention have diligently studied factors that cause capacity deterioration after endurance of an iron-manganese-lithium phosphate-based positive electrode active material having an olivine structure. As a result, the inventors have come up with the idea that hydrogen fluoride generated during charging and discharging of a lithium ion secondary battery can be a cause of deterioration of the positive electrode active material.
- lithium salts containing fluorine such as LiPF 6 are generally used as the lithium salt contained in the electrolyte. Since a small amount of water is present in the electrolytic solution of a general lithium-ion secondary battery, it is considered that hydrogen fluoride is generated in the electrolytic solution by the reaction between the lithium salt and water. In a lithium-ion secondary battery using this type of electrolyte, the positive electrode active material may deteriorate due to the reaction between the hydrogen fluoride in the electrolyte and the positive electrode active material.
- the inventors of the present invention conducted further research based on this idea, and found that the positive electrode active material can be protected from hydrogen fluoride by containing a specific element in a specific state in the positive electrode active material. got Based on such findings, the inventor of the present invention completed the present invention.
- the positive electrode active material of the present invention is Li a Mn b Fe c W d D 1 e D 2 f P g O h
- D 1 is a metal element
- D 2 is an element of groups 13 to 16 with a valence of 4 or less
- a, b, c, d, e, f, g, and h are 0 ⁇ a ⁇ 1.5, 0 ⁇ b ⁇ 1, 0 ⁇ c ⁇ 1, 0 ⁇ d ⁇ 1, 0 ⁇ e ⁇ 1, 0 ⁇ f ⁇ 1 , 0 ⁇ g ⁇ 1 and 0 ⁇ h ⁇ 5.
- a peak derived from WO 2 is confirmed by X-ray photoelectric spectroscopy.
- the positive electrode active material of the present invention is Li a Mn b Fe c W d D 1 e D 2 f P g F i O h
- D 1 is a metal element
- D 2 is an element of Groups 13 to 16 and has a valence of 4 or less
- a, b, c, d, e, f, g, h, i are 0 ⁇ a ⁇ 1.5, 0 ⁇ b ⁇ 1, 0 ⁇ c ⁇ 1, 0 ⁇ d ⁇ 1, 0 ⁇ e ⁇ 1, 0 ⁇ f ⁇ 1, 0 ⁇ g ⁇ 1, 0 ⁇ h ⁇ 5, 0 ⁇ i ⁇ 1 are satisfied.
- a peak derived from WO2 is confirmed by X-ray photoelectric spectroscopy, and/or D 1 is at least one selected from Cr, Ti and V, in the positive electrode active material.
- the positive electrode active material of the present invention is less likely to deteriorate in capacity even after endurance.
- FIG. 4 is a graph showing discharge capacities of positive electrode half cells of Examples 1 to 3 and Comparative Example 1 in Evaluation Example 1.
- FIG. 10 is a graph showing the discharge capacity of the positive electrode half-cell of Reference Example 1 in Evaluation Example 2.
- FIG. 4 is an SEM image of the positive electrode active material of Example 4 in Evaluation Example 5.
- FIG. 4 is an SEM image of the positive electrode active material of Example 4 in Evaluation Example 5.
- FIG. 4 is an EDX image of the positive electrode active material of Example 4 in Evaluation Example 5.
- FIG. 4 is an EDX image of the positive electrode active material of Example 4 in Evaluation Example 5.
- FIG. 4 is an EDX image of the positive electrode active material of Example 4 in Evaluation Example 5.
- FIG. 4 is an EDX image of the positive electrode active material of Example 4 in Evaluation Example 5.
- FIG. 4 is an EDX image of the positive electrode active material of Example 4 in Evaluation Example 5.
- FIG. 4 is an EDX image of the positive electrode active material of Example 4 in Evaluation Example 5.
- FIG. 4 is an
- FIG. 10 is an XPS chart of the positive electrode active material of Example 4 in Evaluation Example 6.
- FIG. 10 is an XPS chart of the positive electrode active material of Example 2 in Evaluation Example 6.
- FIG. 10 is an XPS chart of the positive electrode active material of Example 3 in Evaluation Example 6.
- FIG. 10 is a graph showing the results of a high-temperature charge-discharge cycle test of lithium ion secondary batteries of Comparative Examples 2 to 5 in Evaluation Example 7.
- FIG. 10 is an XPS chart of the positive electrode active material of Comparative Example 2 in Evaluation Example 8.
- FIG. 10 is a graph showing the results of a high-temperature charge-discharge cycle test of lithium-ion secondary batteries of Examples 17, 18 and Comparative Example 6 in Evaluation Example 12.
- FIG. 10 is a graph showing the results of a high-temperature charge-discharge cycle test of lithium-ion secondary batteries of Example 16 and Comparative Example 6 in Evaluation Example 19.
- FIG. 10 is an XPS chart of the positive electrode active material of Example 4 in Evaluation Example
- the numerical range "x to y" described in this specification includes the lower limit x and the upper limit y.
- a new numerical range can be formed by arbitrarily combining these upper and lower limits and the numerical values listed in the examples.
- numerical values arbitrarily selected from any of the above numerical ranges can be used as upper and lower numerical values of the new numerical range.
- the positive electrode active material of the present invention is represented by the following formula (1) and is a positive electrode active material in which a peak derived from tungsten is confirmed by X-ray photoelectric spectroscopy.
- the positive electrode active material of the present invention is represented by the following formula (1-1), and a peak derived from WO 2 is confirmed by X-ray photoelectric spectroscopy, and/or D 1 is Cr, Ti, It is at least one selected from V and is a positive electrode active material.
- the positive electrode active material of the present invention it is believed that part of tungsten is precipitated at the crystal grain boundaries of LiMna1Feb1PO4 and the other part is present inside the crystal structure. It is presumed that the other part of tungsten is probably replaced by metal sites of LiMn a1 Fe b1 PO 4 , that is, Fe or Mn sites. Tungsten present in the crystal structure is believed to contain WO 2 , and WO 2 is believed to suppress the elution of the transition metal from the positive electrode active material of the present invention. It is believed that the tungsten precipitated at the grain boundaries plays a role in protecting the positive electrode active material of the present invention from hydrogen fluoride. It can be said that due to the cooperation of these, the positive electrode active material of the present invention is resistant to capacity deterioration even after endurance and has excellent durability.
- the positive electrode active material of the present invention contains WO 2 can be confirmed by X-ray photoelectric spectroscopy. Specifically, when the positive electrode active material of the present invention is analyzed by X-ray photoelectric spectroscopy, a peak derived from WO2 is confirmed. Concrete methods are exemplified in Examples. The details of the positive electrode active material of the present invention are described below.
- tungsten is preferably replaced with a metal site. If the amount of tungsten is too large relative to manganese and iron, which are metals constituting the metal site, the capacity of the positive electrode active material will decrease, and if the amount of tungsten is too small, the durability of the positive electrode active material will be improved. descend. Therefore, there is a preferred range for the amount of tungsten.
- the amount of tungsten in the positive electrode active material of the present invention is such that d in formulas (1) and (1-1) is in the range of 0.05/100 to 2.5/100. is preferred.
- the amount of tungsten is 0.05 to 2 when the total of metal elements other than lithium that can form metal sites, that is, manganese element, iron element, tungsten element and D1 element is 100 atomic %.
- An amount within the range of 0.5 atomic percent is preferred.
- the inventors of the present invention came up with the idea that the elution of the transition metal contained in the positive electrode active material as the lithium ion secondary battery is charged and discharged can be another cause of deterioration of the positive electrode active material. Obtained.
- the iron-manganese-lithium phosphate-based positive electrode active material having an olivine structure contains iron and manganese as transition metals. These transition metals are believed to exist in a state of being bound to oxygen in the iron-manganese-lithium phosphate-based positive electrode active material having an olivine structure.
- fluorine in the electrolytic solution has a higher electronegativity than oxygen, it can deprive oxygen of transition metals such as iron and manganese.
- iron and manganese may be eluted from the iron-manganese-lithium phosphate-based positive electrode active material having an olivine structure, and as a result, the capacity of the positive electrode active material may deteriorate.
- iron and manganese eluted from the positive electrode active material are deposited on the negative electrode and irreversibly combined with lithium. As a result, it is thought that the positive electrode active material deteriorates and its capacity decreases.
- the inventors of the present invention intended to replace part of iron and manganese with a metal element capable of strongly bonding with oxygen in an iron-manganese-lithium phosphate-based positive electrode active material having an olivine structure.
- a metal element capable of strongly bonding with oxygen is used as D 1 in the above formulas (1) and (1-1). This makes it possible to suppress the above-described elution of iron and manganese, and thus to suppress deterioration of the capacity of the positive electrode active material.
- D 1 element examples include magnesium, cobalt, nickel, niobium, vanadium, tellurium, aluminum, titanium, zinc, copper, bismuth, chromium, zinc, calcium, and zirconium. Among them, chromium, titanium, and vanadium are particularly preferable as elements of D 1 .
- the positive electrode active material of the present invention may contain one of these elements as D 1 , or may contain a plurality of these elements.
- the positive electrode active material of the present invention when the D 1 element is substituted with a metal site, if the amount of the D 1 element is excessive relative to manganese and iron that constitute the metal site, the positive electrode active material If the amount of the D 1 element is too small, the effect of improving the durability of the positive electrode active material is reduced. Therefore, there is also a preferred range for the amount of elements in D 1 .
- the amount of element D 1 in the positive electrode active material of the present invention is such that e in formulas (1) and (1-1) falls within the range of 0.5/100 to 10/100. is preferred.
- the amount of the element D 1 is 0.00% when the total of the metal elements other than lithium that can form the metal sites, that is, the manganese element, the iron element, the tungsten element and the D 1 element is 100 atomic %.
- the amount is preferably within the range of 5 to 10 atomic %.
- a range of 1/100 to 5/100 and a range of 2/100 to 4/100 can be exemplified.
- the preferred range of the amount of chromium in the positive electrode active material is 0.1 to 10 atomic % when the total of metal elements other than lithium that can constitute the metal site is 100 atomic %. Among them, the range of 1 to 2.5 atomic % or the range of 2 to 4 atomic % can be mentioned.
- the preferable range of the amount of titanium in the positive electrode active material is 0.5 to 10 atomic % when the total of metal elements other than lithium that can constitute the metal site is 100 atomic %. Among them, within the range of 1 to 10 atomic %, within the range of 1.5 to 6 atomic %, and within the range of 1.5 to 4 atomic %.
- the preferable range of the amount of vanadium in the positive electrode active material is 0 atomic % or more and 10 atomic % or less when the total of metal elements other than lithium that can constitute the metal site is 100 atomic %, 0 atomic % or more and 3 atomic % or less, 0.5 atomic % or more and 2.9 atomic % or less, 0.8 atomic % or more and 2.9 atomic % or less, 1.0 atomic % or more and 2.9 atomic % or less; Each range of 5 atomic % or more and 2.8 atomic % or less can be exemplified.
- the preferable range of the amount of magnesium in the positive electrode active material is 0.5 to 10 atomic % when the total of metal elements other than lithium that can constitute the metal site is 100 atomic %. , 1 to 10 atomic %, 1 to 8 atomic %, and 2 to 5 atomic %.
- the inventors of the present invention believe that when the metal sites are replaced with tungsten, the crystal neutrality, that is, the electrical neutrality of the crystal is broken, and as a result, the capacity of the positive electrode active material may deteriorate.
- the positive electrode active material is The constituent valences are out of balance. As a result, the crystal neutrality of the positive electrode active material is no longer maintained, and monovalent lithium is likely to be lost from the crystal. As a result, the positive electrode capacity may decrease.
- the inventor of the present invention believes that by substituting the phosphorus site of the positive electrode active material with an element capable of compensating for the difference in valence between iron and tungsten, the valences constituting the positive electrode active material can be balanced. Thought. By doing so, the crystal neutrality of the positive electrode active material can be maintained, the above-described lithium deficiency can be suppressed, and a decrease in the positive electrode capacity can be suppressed.
- the positive electrode active material of the present invention preferably contains an element of Groups 13 to 16 with a valence of 4 or less as the element D2 in the above formulas (1) and (1-1). .
- the positive electrode active material of the present invention it is possible to maintain the crystal neutrality of the positive electrode active material of the present invention while containing tungsten in the positive electrode active material of the present invention.
- the positive electrode active material of the present invention it is preferable to replace the metal site with tungsten and at the same time replace the phosphorus site with the D2 element.
- the D2 element is preferably silicon or boron.
- the D2 element is silicon
- phosphorus has a valence of +5 and silicon has a valence of +4
- the amount f of the D2 element is twice the amount d of tungsten.
- the positive electrode active material of the present invention contains tungsten.
- XPS X-ray photoelectric spectroscopy
- ESCA X-ray photoelectric spectroscopy
- tungsten is believed to precipitate at the grain boundaries of LiMn a1 Fe b1 PO 4 .
- the tungsten is presumed to be present primarily as WO3 , combined with oxygen. Since WO 3 has a low solubility in hydrofluoric acid, it is believed that the positive electrode active material of the present invention as a whole is protected from hydrogen fluoride by tungsten present at the grain boundaries.
- a peak derived from WO 3 will be detected in addition to the peak derived from WO 2 . Since it is believed that tungsten precipitated at grain boundaries contributes to protecting the positive electrode active material from hydrogen fluoride, it is preferable that a peak derived from WO 3 is also detected from the positive electrode active material of the present invention.
- the positive electrode active material of the present invention preferably further contains fluorine. That is, it is preferable that i in the above-mentioned Li a Mn b Fe c W d D 1 e D 2 f P g F i O h formula (1-1) satisfies 0 ⁇ i.
- the fluorine is presumed to be substituted at the oxygen site of LiMn a1 Fe b1 PO 4 which is the basic skeleton described above.
- the positive electrode active material of the present invention is thought to improve the balance of capacity, life and resistance by containing fluorine.
- the amount of fluorine is preferably in the range of 0.1 to 10 atomic % when the total of fluorine and oxygen is 400 atomic %.
- a more preferable range of the amount of fluorine is 0.5 to 20 atomic %, 1 to 10 atomic %, 2 to 10 atomic %, or 3 to 8 atomic % when the total of fluorine and oxygen is 400 atomic % % can be exemplified.
- preferable ranges of the amount of fluorine can be exemplified as 0.2 to 5 atomic % and 0.5 to 2 atomic %.
- a carbon coating layer may be formed on the positive electrode active material of the present invention to improve conductivity.
- the positive electrode active material of the present invention is preferably in the form of particles.
- the average particle size is preferably 100 ⁇ m or less, more preferably 0.01 ⁇ m or more and 10 ⁇ m or less, and most preferably 1 ⁇ m or more and 10 ⁇ m or less.
- the average particle size means the D50 value measured with a general laser diffraction particle size distribution analyzer. A method for producing the positive electrode active material of the present invention will be described below.
- the raw materials are a lithium source, a manganese source, an iron source, a tungsten source, a phosphorus source, an oxygen source, and, if necessary, the positive electrode active material may be produced by including a D 1 source, a D 2 source, and a fluorine source in an appropriate elemental ratio.
- the tungsten source is preferably soluble in water.
- the method for producing a positive electrode active material of the present invention preferably includes a step of making the tungsten compound, which is the source of tungsten, soluble in water.
- the method for producing a positive electrode active material of the present invention preferably includes a step of reducing the tungsten compound with a reducing agent. This method is called the manufacturing method of the present invention.
- the step of reducing the tungsten compound with a reducing agent may be performed prior to synthesizing the positive electrode active material of the present invention, or may be performed simultaneously with synthesizing the positive electrode active material of the present invention.
- reducing a tungsten compound with a reducing agent to obtain a reaction product thereof includes heating and reacting the reaction product and other raw materials for the positive electrode active material, ie, a lithium source, a manganese source, an iron source, a phosphorus source, and water.
- a D 1 source, a D 2 source, or a fluorine source may be added, if desired.
- a production method comprising heating and reacting a tungsten compound, a reducing agent, a lithium source, a manganese source, an iron source, a phosphorus source and water can be exemplified.
- a D 1 source, a D 2 source, or a fluorine source may be added in the reacting step, if desired.
- a reaction product of the tungsten compound and the reducing agent is generated in the reaction system, and the reaction product of the tungsten compound and the reducing agent and other raw materials coexist in the reaction system.
- the reaction product of the tungsten compound and the reducing agent and other raw materials for the positive electrode active material coexist in the reaction system.
- These raw materials are collectively referred to as active material raw materials.
- Specific examples of tungsten compounds include tungstic acid and ammonium tungstate.
- the raw material for the active material preferably exhibits a gel state.
- lithium source manganese source, tungsten source, iron source, phosphorus source, and optionally added D 1 source, D 2 source, and fluorine source in the raw material of the active material
- an alkoxide in which a hydroxide is substituted with an alkoxy group may be used.
- the number of carbon atoms in the alkoxy group is preferably as small as possible, preferably 3 or less, 2 or less, or 1 or less.
- a substance capable of reducing the tungsten compound may be used, and a substance having a small number of carbon atoms or a substance in which carbon disappears from the reaction system as CO 2 gas or the like when synthesizing the positive electrode active material is preferable.
- Specific reducing agents include formic acid, hydrazine, catechol, pyrogallol, and ascorbic acid. Of these, formic acid or hydrazine is particularly preferred as the reducing agent.
- the temperature for heating the raw material of the active material is not particularly limited, but it is preferably 200°C or higher and 800°C or lower, more preferably 300°C or higher and 700°C or lower.
- a positive electrode and a lithium ion secondary battery comprising the positive electrode active material of the present invention will be described below.
- a positive electrode comprising the positive electrode active material of the present invention specifically comprises a current collector and a positive electrode active material layer containing the positive electrode active material formed on the surface of the current collector.
- a current collector is a chemically inactive electronic conductor that keeps current flowing through an electrode during discharging or charging of a lithium-ion secondary battery.
- At least one selected from silver, copper, gold, aluminum, magnesium, tungsten, cobalt, zinc, nickel, iron, platinum, tin, indium, titanium, ruthenium, tantalum, chromium, molybdenum, and stainless steel as the current collector. can be exemplified by metal materials such as
- the current collector may be covered with a known protective layer.
- a current collector whose surface has been treated by a known method may be used as the current collector.
- the current collector can be in the form of foil, sheet, film, wire, rod, mesh, etc. Therefore, metal foils such as copper foil, nickel foil, aluminum foil, and stainless steel foil can be preferably used as the current collector.
- the thickness is preferably in the range of 1 ⁇ m to 100 ⁇ m.
- the positive electrode active material having an olivine structure has poor electronic conductivity compared to the positive electrode active material having a layered rock salt structure such as LiCoO 2 , LiNiO 2 and LiNi 1/3 Co 1/3 Mn 1/3 O 2 . Therefore, by using a current collector foil with a rough surface, specifically, by using a current collector foil with an arithmetic mean height Sa of surface roughness of 0.1 ⁇ m ⁇ Sa, the current collector foil and the positive electrode active material interlayer It is preferable to reduce the resistance of
- the arithmetic mean height of surface roughness Sa means the arithmetic mean height of surface roughness defined by ISO 25178, and is the absolute value of the difference in height of each point with respect to the average surface on the surface of the current collector foil. Average value.
- a current collector foil with a rough surface it may be manufactured by a method of coating a metal current collector foil with carbon, a method of treating a metal current collector foil with an acid or an alkali, or a commercially available one. You can also purchase current collector foil that has a rough surface.
- the positive electrode active material layer may contain a positive electrode active material other than the positive electrode active material of the present invention.
- the positive electrode active material other than the positive electrode active material of the present invention is not particularly limited, those having a layered rock salt structure such as LiCoO 2 , LiNiO 2 and LiNi 1/3 Co 1/3 Mn 1/3 O 2 are selected. is preferred.
- a positive electrode active material having an olivine structure, such as the positive electrode active material of the present invention is known to be superior in heat resistance but inferior in capacity to a positive electrode active material having a layered rock salt structure.
- the positive electrode active material having the layered rock salt structure described above has a high capacity although it is inferior in heat resistance.
- the positive electrode active material of the present invention and the positive electrode active material having a layered rock salt structure, which have properties that complement each other, are used in combination with the positive electrode active material of the present invention, thereby improving the battery characteristics of the lithium ion secondary battery. is possible.
- the ratio of the positive electrode active material of the present invention in the positive electrode active material layer can be exemplified within the range of 70-99% by mass, within the range of 80-98% by mass, and within the range of 90-97% by mass.
- the positive electrode active material layer may contain additives such as a conductive aid, a binder, and a dispersant in addition to the positive electrode active material.
- the conductive aid is added to increase the conductivity of the electrode. Therefore, the conductive aid may be added arbitrarily when the conductivity of the electrode is insufficient, and may not be added when the conductivity of the electrode is sufficiently excellent.
- the conductive aid may be any chemically inactive electron conductor, and examples include carbon black, graphite, vapor grown carbon fiber, carbon nanotube, and various metal particles, which are carbonaceous fine particles. be done. Examples of carbon black include acetylene black, Ketjenblack (registered trademark), furnace black, and channel black. These conductive aids can be added to the positive electrode active material layer singly or in combination of two or more.
- the blending amount of the conductive aid is not particularly limited.
- the proportion of the conductive aid in the positive electrode active material layer is preferably in the range of 1 to 7% by mass, more preferably in the range of 2 to 6% by mass, and even more preferably in the range of 3 to 5% by mass.
- Binders serve to bind the positive electrode active material and conductive aid to the surface of the current collector.
- Binders include fluorine-containing resins such as polyvinylidene fluoride, polytetrafluoroethylene, and fluororubber; thermoplastic resins such as polypropylene and polyethylene; imide resins such as polyimide and polyamideimide; alkoxysilyl group-containing resins; Examples include meth)acrylate resins, polyacrylic acid, polyvinyl alcohol, polyvinylpyrrolidone, carboxymethylcellulose, and styrene-butadiene rubber.
- the blending amount of the binder is not particularly limited.
- the proportion of the binder in the positive electrode active material layer is preferably in the range of 0.5 to 7% by mass, more preferably in the range of 1 to 5% by mass, and even more preferably in the range of 2 to 4% by mass.
- additives such as dispersants other than conductive aids and binders can be used.
- the positive electrode active material layer on the surface of the current collector, conventionally known methods such as roll coating, die coating, dip coating, doctor blade, spray coating, and curtain coating may be used. Specifically, an active material, a solvent, and, if necessary, a binder and a conductive aid are mixed to produce a slurry composition for forming an active material layer, and the composition for forming an active material layer is collected. After coating on the surface of the electric body, it is dried.
- solvents include N-methyl-2-pyrrolidone, methanol, methyl isobutyl ketone, and water. In order to increase the electrode density, it may be compressed after drying.
- the active material layer may be formed using a manufacturing method disclosed in Japanese Patent Application Laid-Open No. 2015-201318. Specifically, a wet granule is obtained by granulating a mixture containing an active material, a binder, and a solvent. An aggregate of the granules is placed in a predetermined mold to obtain a flat molded body. After that, a positive electrode active material layer can be formed by attaching a flat molded body to the surface of the current collector using a transfer roll. Alternatively, the positive electrode active material layer may be formed on the surface of the current collector by directly supplying the granules to the surface of the current collector and pressing and integrating them.
- a lithium ion secondary battery comprising the positive electrode active material of the present invention includes a positive electrode comprising the positive electrode active material of the present invention, a negative electrode, an electrolytic solution, and optionally a separator.
- the negative electrode has a current collector and a negative electrode active material layer formed on the surface of the current collector.
- the negative electrode active material layer contains a negative electrode active material, and may further contain additives such as a conductive aid, a binder, and a dispersant.
- a conductive aid such as a conductive aid, a binder, and a dispersant.
- conductive aid and binder those described for the positive electrode may be employed.
- a known dispersant can be used.
- the negative electrode may be manufactured by a method similar to the manufacturing method described for the positive electrode.
- negative electrode active materials include carbon-based materials that can occlude and release lithium, elements that can be alloyed with lithium, compounds containing elements that can be alloyed with lithium, and polymer materials.
- Examples of carbon-based materials include non-graphitizable carbon, natural graphite, artificial graphite, cokes, graphites, vitreous carbons, organic polymer compound sintered bodies, carbon fibers, activated carbon, and carbon blacks.
- the calcined organic polymer compound refers to a carbonized material obtained by calcining a polymer material such as phenols and furans at an appropriate temperature.
- polymer materials include polyacetylene and polypyrrole.
- elements that can be alloyed with lithium include Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Ti, Ag, Zn, Cd, Al, Ga, In, Si , Ge, Sn, Pb, Sb, and Bi, and Si or Sn is particularly preferred.
- compounds having an element capable of being alloyed with lithium include ZnLiAl , AlSb, SiB4 , SiB6 , Mg2Si, Mg2Sn , Ni2Si , TiSi2 , MoSi2 , CoSi2 , NiSi2 , CaSi2, CrSi2 , Cu5Si , FeSi2, MnSi2 , NbSi2 , TaSi2 , VSi2 , WSi2 , ZnSi2 , SiC , Si3N4 , Si2N2O , SiOv ( 0 ⁇ v ⁇ 2), SnO w (0 ⁇ w ⁇ 2), SnSiO 3 , LiSiO or LiSnO.
- tin compounds such as tin alloys (Cu--Sn alloys, Co--Sn alloys, etc.) can be exemplified as compounds having elements capable of alloying with lithium.
- the electrolyte contains a non-aqueous solvent and an electrolyte dissolved in this non-aqueous solvent.
- Cyclic esters, chain esters, ethers, etc. can be used as non-aqueous solvents.
- cyclic esters include ethylene carbonate, propylene carbonate, butylene carbonate, fluoroethylene carbonate, gamma-butyrolactone, vinylene carbonate, 2-methyl-gamma-butyrolactone, acetyl-gamma-butyrolactone, and gamma-valerolactone.
- chain esters include dimethyl carbonate, diethyl carbonate, dibutyl carbonate, dipropyl carbonate, ethylmethyl carbonate, alkyl propionate, dialkyl malonate, and alkyl acetate.
- ethers examples include tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-diethoxyethane, and 1,2-dibutoxyethane.
- One of these non-aqueous solvents may be used in the electrolytic solution, or two or more of them may be used in combination.
- the alkylene cyclic carbonate selected from ethylene carbonate and propylene carbonate is a non-aqueous solvent with a high dielectric constant and is considered to contribute to the dissolution and ion dissociation of the lithium salt.
- an SEI Solid Electrolyte Interphase
- an SEI coating is formed on the surface of the negative electrode by reductive decomposition of the alkylene cyclic carbonate during charging of the lithium ion secondary battery. It is believed that the presence of such an SEI coating allows reversible insertion and extraction of lithium ions, especially when the negative electrode comprises graphite.
- alkylene cyclic carbonates are useful as non-aqueous solvents for electrolytes, they are highly viscous. Therefore, if the ratio of the alkylene cyclic carbonate is too high, the ionic conductivity of the electrolyte and the diffusion of lithium ions in the electrolyte may be adversely affected. In addition, since the alkylene cyclic carbonate has a relatively high melting point, if the proportion of the alkylene cyclic carbonate is too high, the electrolytic solution may solidify under low temperature conditions.
- methyl propionate which is a type of propionic acid alkyl ester, is a non-aqueous solvent with a low dielectric constant, low viscosity, and a low melting point.
- methyl propionate offsets the disadvantages of alkylene cyclic carbonate. That is, methyl propionate can contribute to lowering the viscosity of the electrolytic solution, optimizing the ionic conductivity, optimizing the diffusion coefficient of lithium ions, and preventing solidification under low temperature conditions. Therefore, it is preferable to use a non-aqueous solvent in which alkylene cyclic carbonate and methyl propionate coexist.
- the amount of electrolyte in the electrolytic solution is not particularly limited, but can be exemplified within the range of 1.0 mol/L to 2.5 mol/L and within the range of 1.2 mol/L to 2.2 mol/L.
- the separator As the separator, a known one may be adopted, and synthetic resins such as polytetrafluoroethylene, polypropylene, polyethylene, polyimide, polyamide, polyaramid (aromatic polyamide), polyester, polyacrylonitrile, etc., polysaccharides such as cellulose, amylose, fibroin, etc. , natural polymers such as keratin, lignin and suberin, and porous bodies, non-woven fabrics, and woven fabrics using one or a plurality of electrically insulating materials such as ceramics.
- the separator may have a multilayer structure.
- an electrode body is formed by sandwiching a separator between a positive electrode and a negative electrode.
- the electrode body may be of either a laminated type in which a positive electrode, a separator and a negative electrode are laminated, or a wound type in which a laminated body of a positive electrode, a separator and a negative electrode is wound.
- the cathode active material layer of one bipolar electrode and the anode active material layer of the bipolar electrode adjacent to the one bipolar electrode are laminated so as to face each other with a separator interposed therebetween to form an electrode assembly.
- a separator interposed therebetween By coating the periphery of the electrode body with a resin or the like, a space is formed between one bipolar electrode and the adjacent bipolar electrode, and an electrolytic solution is added to the space to generate lithium ions.
- a secondary battery is preferable.
- the shape of the lithium-ion secondary battery of the present invention is not particularly limited, and various shapes such as cylindrical, square, coin, and laminate can be adopted.
- the lithium-ion secondary battery of the present invention may be mounted on a vehicle.
- the vehicle may be any vehicle that uses electrical energy from a lithium-ion secondary battery as a power source in whole or in part, and may be, for example, an electric vehicle or a hybrid vehicle.
- a lithium ion secondary battery is mounted on a vehicle, it is preferable to connect a plurality of lithium ion secondary batteries in series to form an assembled battery.
- Devices equipped with lithium ion secondary batteries include, in addition to vehicles, personal computers, mobile communication devices, various home electric appliances driven by batteries, office equipment, industrial equipment, and the like.
- the lithium ion secondary battery of the present invention is used for wind power generation, solar power generation, hydraulic power generation, and other power storage devices and power smoothing devices for power systems, power sources for ships and/or auxiliary equipment, aircraft, power source for spacecraft and/or auxiliary equipment, auxiliary power source for vehicles that do not use electricity as a power source, power source for mobile home robots, power source for system backup, power source for uninterruptible power supply, It may be used as a power storage device that temporarily stores electric power required for charging in a charging station for an electric vehicle.
- Example 1 [Synthesis of positive electrode active material] To 50 ml of pure water, 2.57 g of LiOH monohydrate as a lithium source, 8.21 g of malic acid as a pH adjuster, 11.25 g of manganese (II) acetate tetrahydrate as a manganese source, and iron (II) sulfate as an iron source. 4.17 g heptahydrate, 0.076 g tungstic acid as tungsten source, 0.3 g formic acid as reducing agent, 0.13 g tetraethyl orthosilicate (TEOS) as silicon source, and 6.99 g 85% phosphoric acid as phosphorus source. was dissolved and heated at 50° C. for 12 hours to obtain a gel-like active material raw material. In addition, in Example 1, silicon corresponds to the D2 element in the formula ( 1 ).
- the amount of tungsten is 0.5 atomic % when the total of manganese, iron and tungsten, that is, the total of metal elements other than lithium that can form metal sites is taken as 100 atomic %. was the amount. Also, the amount of silicon was such that the total amount of silicon and phosphorus was 1.0 atomic % when the total was 100 atomic %. Furthermore, the ratio of lithium:(sum of manganese, iron and tungsten):(sum of silicon and phosphorus) was 1:1:1. The elemental ratios of lithium, manganese, iron, tungsten, silicon and phosphorus in the raw material of the active material approximately match those in the positive electrode active material. The same applies to the following examples and comparative examples.
- composition of each element in the positive electrode active material raw material of Example 1 is shown in Table 1, which will be described later, together with the composition of each element in the positive electrode active material raw material of each Example, Comparative Example 1, and Reference Example 1, which will be described later.
- the gel-like active material raw material was vacuum-dried at 60° C. for 24 hours, then heated at 350° C. for 5 hours under a nitrogen atmosphere, and then heated at 650° C. for 15 hours under a nitrogen atmosphere.
- a positive electrode active material was produced.
- the positive electrode active material of Example 1, acetylene black as a conductive aid, and polyvinylidene fluoride as a binder were mixed so that the mass ratio of the positive electrode active material, conductive aid, and binder was 85:5:10. , and N-methyl-2-pyrrolidone was added as a solvent to prepare a composition for forming a positive electrode active material layer in slurry form.
- An aluminum foil was prepared as a positive electrode current collector.
- a positive electrode active material layer is formed on the surface of the aluminum foil by pressing the positive electrode precursor produced by applying the composition for forming the positive electrode active material layer in the form of a film on the surface of the aluminum foil and then removing the solvent, in the thickness direction.
- the target value for the basis weight of the positive electrode was 14 mg/cm 2
- the target value for the density of the positive electrode active material layer was 1.9 g/mL.
- the basis weight of the positive electrode means the mass of the positive electrode active material layer present on the area of 1 square centimeter on one side of the current collector foil of the positive electrode.
- LiPF 6 was dissolved at a concentration of 1 mol/L and (FSO 2 ) 2 NLi at a concentration of 0.1 mol/L in a mixed solvent of ethylene carbonate, methyl ethyl carbonate and dimethyl carbonate at a volume ratio of 3:3:4. to obtain a mother liquor.
- An electrolytic solution was produced by adding and dissolving vinylene carbonate in an amount corresponding to 1% by mass with respect to the mother liquor.
- a copper foil to which a 0.2 ⁇ m thick lithium foil was attached was prepared as a counter electrode.
- a polyolefin porous membrane was prepared as a separator.
- a positive electrode, a separator, and a counter electrode were laminated in this order to form an electrode plate group. After covering the electrode group with a set of two laminate films and sealing three sides, an electrolytic solution was injected into the bag-shaped laminate film. After that, the remaining one side was sealed to obtain a laminate type battery in which the four sides were airtightly sealed, and the electrode plate group and the electrolytic solution were sealed. This was used as the positive electrode half cell of Example 1.
- Graphite as a negative electrode active material, carboxymethyl cellulose and styrene-butadiene rubber as binders were mixed so that the mass ratio of graphite, carboxymethyl cellulose and styrene-butadiene rubber was 97:2.2:0.8, and water was used as a solvent. It was added to prepare a slurry composition for forming a negative electrode active material layer.
- a copper foil was prepared as a current collector for the negative electrode.
- a negative electrode active material layer is formed on the surface of the copper foil by pressing the negative electrode precursor produced by applying the negative electrode active material layer forming composition to the surface of the copper foil in the form of a film and then removing the solvent, in the thickness direction. was formed on the negative electrode.
- the basis weight of the negative electrode was 4.8 mg/cm 2 and the density of the negative electrode active material layer was 1.1 g/cm 3 .
- the positive electrode active material of Example 1 was used as the positive electrode active material layer, acetylene black was used as the conductive aid, and polyvinylidene fluoride was used as the binder. N-methyl-2-pyrrolidone was added as a solvent to obtain a slurry composition for forming a positive electrode active material layer.
- An aluminum foil was prepared as a positive electrode current collector. A positive electrode active material layer is formed on the surface of the aluminum foil by pressing the positive electrode precursor produced by applying the composition for forming the positive electrode active material layer in the form of a film on the surface of the aluminum foil and then removing the solvent, in the thickness direction. was formed on the positive electrode.
- the target value for the basis weight of the positive electrode was 14 mg/cm 2
- the target value for the density of the positive electrode active material layer was 1.9 g/cm 3 .
- LiPF 6 was dissolved at a concentration of 1 mol/L and (FSO 2 ) 2 NLi at a concentration of 0.1 mol/L in a mixed solvent of ethylene carbonate, methyl ethyl carbonate and dimethyl carbonate at a volume ratio of 3:3:4. to obtain a mother liquor.
- An electrolytic solution was produced by adding and dissolving vinylene carbonate in an amount corresponding to 1% by mass with respect to the mother liquor.
- a polypropylene porous membrane was prepared as a separator.
- An electrode body was formed by sandwiching a separator between the positive electrode and the negative electrode.
- the lithium ion secondary battery of Example 1 was manufactured by putting this electrode assembly into a bag-like laminate film and sealing it together with the electrolyte solution.
- Example 2 In the method for producing a positive electrode active material of Example 2, when the amount of tungsten in the active material raw material is 100 atomic % of the total of metal elements other than lithium that can constitute the metal site, that is, manganese, iron and tungsten The amount was 1 atomic %, and the amount of silicon was 2 atomic % when the total of silicon and phosphorus was 100 atomic %.
- a positive electrode active material, a positive electrode half cell, and a lithium ion secondary battery of Example 2 were manufactured in the same manner as in Example 1 except for this. Also in Example 2 , silicon corresponds to the D2 element.
- Example 3 In the method for producing a positive electrode active material of Example 3, the amount of tungsten in the active material raw material is an amount that becomes 3 atomic % when the total of manganese, iron and tungsten is 100 atomic %, and the amount of silicon is The amount was 6 atomic % when the total of silicon and phosphorus was 100 atomic %. Except for this, in the same manner as in Example 1, a positive electrode active material, a positive electrode half cell, and a lithium ion secondary battery of Example 3 were manufactured. Also in Example 3 , silicon corresponds to the D2 element.
- the amount of tungsten is 0.5 atomic % when the total of metal elements other than lithium that can form metal sites, that is, manganese, iron, tungsten and magnesium is 100 atomic %. was the amount.
- the amount of magnesium was 3 atomic % when the total of metal elements other than lithium that could constitute the metal site was taken as 100 atomic %.
- the amount of silicon was 1 atomic % when the sum of silicon and phosphorus was 100 atomic %.
- the elemental ratio of lithium:(total of metal elements other than lithium that can constitute metal sites):(total of silicon and phosphorus) was 1:1:1.
- the element ratio of each of the above substances in the raw material of the active material approximately matches the element ratio of these elements in the positive electrode active material.
- a positive electrode half cell and a lithium ion secondary battery of Example 4 were manufactured in the same manner as in Example 1 using the positive electrode active material of Example 4.
- Comparative example 1 In the manufacturing method of the positive electrode active material of Comparative Example 1, the raw material of the active material does not contain tungsten and silicon, and the ratio of lithium: (metal elements other than lithium that can form metal sites): phosphorus element is 1:1:1. there were. Moreover, in the manufacturing method of the positive electrode active material of Comparative Example 1, tungstic acid, 0.3 g of formic acid, and tetraethyl orthosilicate were not used. A positive electrode active material, a positive electrode half cell, and a lithium ion secondary battery of Comparative Example 1 were manufactured in the same manner as in Example 1 except for this.
- Comparative example 2 In the manufacturing method of the positive electrode active material of Comparative Example 2, the positive electrode active material of Comparative Example 1 was coated with tungsten. The specific procedure is as follows. A coating solution was obtained by dissolving 0.074 g of tungsten alkoxide [W(OC 2 H 5 ) 6 ] in 100 ml of ethanol. 10 g of the positive electrode active material of Comparative Example 1 was added to this coating solution, and the mixture was heated under reduced pressure at 100° C. for 3 to 5 hours using an evaporator to volatilize the solvent. After that, the remaining solid content was heated at 500° C. for 1 hour in a nitrogen atmosphere to produce a positive electrode active material of Comparative Example 2. In the positive electrode active material of Comparative Example 2, the amount of tungsten relative to the positive electrode active material of Comparative Example 1 to be coated was 0.74% by mass with respect to 100% by mass of the positive electrode active material of Comparative Example 1.
- the positive electrode active material of Comparative Example 2 acetylene black as a conductive aid, and polyvinylidene fluoride as a binder were mixed so that the mass ratio of the positive electrode active material, conductive aid, and binder was 90:5:5. , and N-methyl-2-pyrrolidone was added as a solvent to prepare a composition for forming a positive electrode active material layer in slurry form.
- An aluminum foil was prepared as a positive electrode current collector.
- a positive electrode active material layer is formed on the surface of the aluminum foil by pressing the positive electrode precursor produced by applying the composition for forming the positive electrode active material layer in the form of a film on the surface of the aluminum foil and then removing the solvent, in the thickness direction. was produced as a comparative positive electrode.
- the target value for the basis weight of the positive electrode was 16 mg/cm 2
- the target value for the density of the positive electrode active material layer was 1.9 g/mL.
- Graphite as a negative electrode active material, carboxymethyl cellulose and styrene-butadiene rubber as binders were mixed so that the mass ratio of graphite, carboxymethyl cellulose and styrene-butadiene rubber was 97:2.2:0.8, and water was used as a solvent. It was added to prepare a slurry composition for forming a negative electrode active material layer.
- a copper foil was prepared as a current collector for the negative electrode.
- a negative electrode active material layer is formed on the surface of the copper foil by pressing the negative electrode precursor produced by applying the negative electrode active material layer forming composition to the surface of the copper foil in the form of a film and then removing the solvent, in the thickness direction. was formed on the negative electrode.
- the target value for the basis weight of the negative electrode was 6.8 mg/cm 2
- the target value for the density of the negative electrode active material layer was 1.4 g/cm 3 .
- a mother liquor was prepared by dissolving LiPF 6 at a concentration of 1.2 mol/L in a mixed solvent of ethylene carbonate and methyl propionate at a volume ratio of 15:85.
- An electrolytic solution was produced by adding and dissolving vinylene carbonate in an amount corresponding to 1% by mass and lithium difluoro(oxalate)borate in an amount corresponding to 1% by mass with respect to the mother liquor.
- a polypropylene porous membrane was prepared as a separator.
- An electrode body was formed by sandwiching a separator between the positive electrode and the negative electrode.
- a lithium ion secondary battery of Comparative Example 2 was manufactured by putting this electrode assembly into a bag-like laminate film and sealing it together with the electrolyte solution.
- Comparative Example 3 In the method for producing the positive electrode active material of Comparative Example 3, the positive electrode active material of Comparative Example 3 and the lithium ion secondary battery were produced in substantially the same manner as in Comparative Example 2, except that the amount of tungsten alkoxide in the coating solution was 0.148 g. got The amount of tungsten alkoxide in the positive electrode active material of Comparative Example 3 was 1.48% by mass with respect to 100% by mass of the positive electrode active material of Comparative Example 1 to be coated.
- Comparative Example 4 In the method for producing the positive electrode active material of Comparative Example 4, the positive electrode active material and the lithium ion secondary battery of Comparative Example 4 were produced in substantially the same manner as in Comparative Example 2 except that the amount of tungsten alkoxide in the coating solution was 0.222 g. got The amount of tungsten alkoxide in the positive electrode active material of Comparative Example 4 was 2.22% by mass with respect to 100% by mass of the positive electrode active material of Comparative Example 1 to be coated.
- Comparative Example 5 A lithium ion secondary battery of Comparative Example 5 was obtained in substantially the same manner as in Comparative Example 2 using the positive electrode active material of Comparative Example 1.
- the lithium ion secondary battery of Comparative Example 1 does not contain tungsten in the positive electrode active material.
- This gel-like active material raw material was vacuum-dried at 60° C. for 24 hours, then heated at 350° C. for 5 hours under a nitrogen atmosphere, and then heated at 650° C. for 15 hours under a nitrogen atmosphere. An active material was produced.
- magnesium corresponds to the D1 element in the formula ( 1 ).
- the amount of magnesium was 3 atomic % when the total of manganese, iron and magnesium was taken as 100 atomic %. Also, the ratio of lithium:(total of metal elements other than lithium that can form metal sites):phosphorus was 1:1:1. The elemental ratios of lithium, manganese, iron, magnesium and phosphorus in the raw material of the active material approximately match those in the positive electrode active material.
- Example 1 Using the positive electrode active material of Reference Example 1, a positive electrode half cell and a lithium ion secondary battery of Reference Example 1 were manufactured in the same manner as in Example 1.
- Example 5 magnesium corresponds to the D 1 element in formula (1-1), and silicon corresponds to the D 2 element in formula (1-1). Moreover, in the composition ratio of each element in the positive electrode active material of Example 5, the amount of Li derived from LiF is not considered. The same applies to the following examples and the like.
- the amount of tungsten was 0.25 atomic % when the total of manganese, iron, tungsten and magnesium was taken as 100 atomic %.
- the amount of magnesium was 3 atomic % when the total of manganese, iron, tungsten and magnesium was taken as 100 atomic %.
- the amount of silicon was 0.5 atomic % when the sum of silicon and phosphorus was 100 atomic %.
- the amount of fluorine was 1 atomic % when the total of fluorine and oxygen was 400 atomic %.
- the elemental ratio of lithium:(total of metal elements other than lithium that can constitute metal sites):(total of silicon and phosphorus) was 1:1:1.
- the element ratio of each of the above substances in the raw material of the active material approximately matches the element ratio of these elements in the positive electrode active material.
- An aluminum foil having a thickness of 10 ⁇ m was prepared as a current collector for positive electrode.
- the slurry was applied to the surface of the positive electrode current collector in the form of a film using a doctor blade.
- the positive electrode current collector coated with the slurry was dried at 80° C. for 15 minutes to remove N-methyl-2-pyrrolidone. Then, by pressing, the positive electrode of Example 5 in which a positive electrode active material layer was formed on the positive electrode current collector was manufactured.
- the positive electrode of Example 5 was cut to a diameter of 11 mm and used as an evaluation electrode.
- a metallic lithium foil having a thickness of 500 ⁇ m was cut into a diameter of 13 mm to form a counter electrode.
- This electrode assembly was housed in a coin-shaped battery case CR2032 (Hosen Co., Ltd.), and the same electrolytic solution as in Example 1 was injected to obtain a coin-shaped battery. This was used as a half cell of Example 5.
- Example 6 In the manufacturing method of the positive electrode active material of Example 6, the amount of fluorine in the raw material of the active material was 5 atomic % when the total of fluorine and oxygen was 400 atomic %. A cathode active material and a half cell of Example 6 were manufactured in the same manner as in Example 5 except for this. Also in Example 6, magnesium corresponds to the D 1 element in formula (1-1), and silicon corresponds to the D 2 element in formula (1-1). In the active material raw material of Example 6, the amount of tungsten was 0.25 atomic % when the total of manganese, iron, tungsten and magnesium was taken as 100 atomic %.
- the amount of magnesium was 3 atomic % when the total of manganese, iron, tungsten and magnesium was taken as 100 atomic %.
- the amount of silicon was 0.5 atomic % when the sum of silicon and phosphorus was 100 atomic %.
- the elemental ratio of lithium:(total of metal elements other than lithium that can constitute metal sites):(total of silicon and phosphorus) was 1:1:1.
- the element ratio of each of the above substances in the raw material of the active material approximately matches the element ratio of these elements in the positive electrode active material.
- Example 7 [Synthesis of positive electrode active material] To 50 ml of pure water, 2.57 g of LiOH monohydrate as a lithium source, 8.21 g of malic acid as a pH adjuster, 11.25 g of manganese (II) acetate tetrahydrate as a manganese source, and iron (II) sulfate as an iron source.
- This gel-like active material raw material was vacuum-dried at 60° C. for 24 hours, then heated at 350° C. for 5 hours under a nitrogen atmosphere, and then heated at 650° C. for 15 hours under a nitrogen atmosphere. An active material was produced.
- a half cell of Example 7 was manufactured in the same manner as in Example 5 using the positive electrode active material of Example 7.
- a lithium ion secondary battery was produced in the same manner as in Example 1 using the positive electrode active material of Example 7.
- the basis weight of the negative electrode was 5 mg/cm 2
- the density of the negative electrode active material layer was 1.35 g/cm 3
- the target value of the basis weight of the positive electrode was 14 mg/cm 2
- the target value of the density of the positive electrode active material layer was 1.8 g/cm 3 .
- magnesium and chromium correspond to the D1 element in formula (1)
- silicon corresponds to the D2 element in formula ( 1 ).
- the amount of tungsten was 0.25 atomic % when the total of manganese, iron, tungsten, magnesium and chromium was taken as 100 atomic %.
- the amount of magnesium was 3 atomic % when the total of manganese, iron, tungsten, magnesium and chromium was taken as 100 atomic %.
- the amount of chromium was 1.5 atomic percent when the sum of manganese, iron, tungsten, magnesium and chromium was 100 atomic percent.
- the amount of silicon was 0.5 atomic % when the sum of silicon and phosphorus was 100 atomic %.
- the elemental ratio of lithium:(sum of metal elements other than lithium that can form metal sites):(sum of silicon and phosphorus) was 1:1:1.
- the element ratio of each of the above substances in the raw material of the active material approximately matches the element ratio of these elements in the positive electrode active material.
- Example 8 In the method for producing a positive electrode active material of Example 8, the amount of iron in the active material raw material is 18.75 atomic % when the total of manganese, iron, tungsten, magnesium and chromium is 100 atomic %, The amount of chromium was 3 atomic % when the total of manganese, iron, tungsten, magnesium and chromium was 100 atomic %.
- a positive electrode active material and a half cell of Example 8 were manufactured in the same manner as in Example 7 except for this. Also, using the positive electrode active material of Example 8, a lithium ion secondary battery of Example 8 was manufactured in the same manner as in Example 7.
- magnesium and chromium correspond to the D1 element in formula (1)
- silicon corresponds to the D2 element in formula ( 1 ).
- the amount of tungsten was 0.25 atomic % when the total of manganese, iron, tungsten, magnesium and chromium was taken as 100 atomic %.
- the amount of magnesium was 3 atomic % when the total of manganese, iron, tungsten, magnesium and chromium was taken as 100 atomic %.
- the amount of silicon was 0.5 atomic % when the sum of silicon and phosphorus was 100 atomic %.
- the elemental ratio of lithium:(sum of metal elements other than lithium that can form metal sites):(sum of silicon and phosphorus) was 1:1:1.
- the element ratio of each of the above substances in the raw material of the active material approximately matches the element ratio of these elements in the positive electrode active material.
- Example 9 0.044 g of vanadium (V) oxide, 0.3 g of formic acid as a reducing agent, 0.079 g of LiF as a fluorine source, and 7.06 g of 85% phosphoric acid as a phosphorus source are dissolved and heated at 50° C. for 12 hours to form a gel.
- a raw material for an active material was obtained.
- This gel-like active material raw material was vacuum-dried at 60° C. for 24 hours, then heated at 350° C. for 5 hours under a nitrogen atmosphere, and then heated at 650° C. for 15 hours under a nitrogen atmosphere.
- An active material was produced.
- a half cell of Example 9 was manufactured in the same manner as in Example 5 using the positive electrode active material of Example 9.
- a lithium ion secondary battery of Example 9 was manufactured in the same manner as the lithium ion secondary battery of Example 7, except that the positive electrode active material of Example 9 was used as the positive electrode active material layer.
- magnesium, titanium and vanadium correspond to the D1 element in formula ( 1-1 ).
- the amount of tungsten was 0.25 atomic % when the total of metal elements other than lithium that can form the metal sites is 100 atomic %.
- the amount of magnesium was 3 atomic % when the total of metal elements other than lithium that could constitute the metal site was taken as 100 atomic %.
- the amount of titanium was 2.5 atomic % when the total of the metal elements other than lithium that can constitute the metal sites is 100 atomic %.
- the amount of vanadium was 0.8 atomic % when the total of metal elements other than lithium that can form the metal sites was taken as 100 atomic %.
- the elemental ratio of lithium:(sum of metal elements other than lithium that can form metal sites):phosphorus was 1:1:1.
- the element ratio of each of the above substances in the raw material of the active material approximately matches the element ratio of these elements in the positive electrode active material.
- Example 10 The above gel-like active material raw material was vacuum-dried at 60° C. for 24 hours, then heated at 350° C. for 5 hours under a nitrogen atmosphere, and then heated at 650° C. for 15 hours under a nitrogen atmosphere. A positive electrode active material was produced. A half cell of Example 10 was manufactured in the same manner as in Example 5 using the positive electrode active material of Example 10. Furthermore, a lithium ion secondary battery of Example 10 was manufactured in the same manner as in Example 7 using the positive electrode active material of Example 10.
- magnesium, titanium and chromium correspond to the D 1 element in formula (1-1).
- the amount of tungsten was 0.25 atomic % when the total of manganese, iron, tungsten, magnesium, titanium and chromium was taken as 100 atomic %.
- the amount of magnesium was 3 atomic % when the total of manganese, iron, tungsten, magnesium, titanium and chromium was taken as 100 atomic %.
- the amount of titanium was 2.5 atomic % when the sum of manganese, iron, tungsten, magnesium, titanium and chromium was 100 atomic %.
- the amount of chromium was 3 atomic % when the total of manganese, iron, tungsten, magnesium, titanium and chromium was 100 atomic %.
- the amount of fluorine was 2.5 atomic % when the total of fluorine and oxygen was 400 atomic %.
- the elemental ratio of lithium:(sum of metal elements other than lithium that can form metal sites):phosphorus was 1:1:1.
- the element ratio of each of the above substances in the raw material of the active material approximately matches the element ratio of these elements in the positive electrode active material.
- Example 11 3.19 g of heptahydrate, 0.394 g of magnesium acetate tetrahydrate as a magnesium source, 0.038 g of tungstic acid as a tungsten source, 0.434 g of chromium acetate hydrate (containing 22% by mass of chromium) as a chromium source, 0.3 g of formic acid as a reducing agent and 7.06 g of 85% phosphoric acid as a phosphorus source were dissolved and heated at 50° C. for 12 hours to obtain a gel-like active material raw material. This gel-like active material raw material was vacuum-dried at 60° C. for 24 hours, then heated at 350° C. for 5 hours under a nitrogen atmosphere, and then heated at 650° C. for 15 hours under a nitrogen atmosphere. An active material was produced. A half cell of Example 11 was manufactured in the same manner as in Example 5 using the positive electrode active material of Example 11.
- magnesium and chromium correspond to the D 1 element in formula (1-1).
- the amount of tungsten was 0.25 atomic % when the total of metal elements other than lithium that can form metal sites is 100 atomic %.
- the amount of magnesium was 3 atomic % when the total of metal elements other than lithium that could constitute the metal site was taken as 100 atomic %.
- the amount of chromium was 3 atomic % when the total of metal elements other than lithium that could form the metal sites was taken as 100 atomic %.
- the elemental ratio of lithium:(sum of metal elements other than lithium that can form metal sites):phosphorus was 1:1:1.
- the element ratio of each of the above substances in the raw material of the active material approximately matches the element ratio of these elements in the positive electrode active material.
- Example 12 In the method for producing a positive electrode active material of Example 12, the active material raw material does not contain chromium, and iron is 19.25 atomic % when the total of metal elements other than lithium that can constitute the metal site is 100 atomic %. there were. The amount of fluorine was 5 atomic % when the total of fluorine and oxygen was 400 atomic %.
- a cathode active material of Example 12 was produced in the same manner as in Example 10 except for this.
- a positive electrode and a positive electrode half cell of Example 12 were manufactured in the same manner as in Example 5 using the positive electrode active material of Example 12.
- Example 13 In the manufacturing method of the positive electrode active material of Example 13, the raw material of the active material did not contain chromium but contained vanadium. In the raw material for the active material of Example 13, iron was 18 atomic % and vanadium was 1.25 atomic % when the total of metal elements other than lithium that could form the metal sites was taken as 100 atomic %. The amount of fluorine was 5 atomic % when the total of fluorine and oxygen was 400 atomic %. A cathode active material of Example 13 was produced in the same manner as in Example 10 except for this. A positive electrode and a positive electrode half cell of Example 13 were manufactured in the same manner as in Example 5 using the positive electrode active material of Example 13.
- Example 14 In the manufacturing method of the positive electrode active material of Example 14, the raw material of the active material did not contain chromium but contained vanadium. In the active material raw material of Example 14, iron was 16.75 atomic % and vanadium was 2.5 atomic % when the total of metal elements other than lithium that could constitute the metal site was 100 atomic %. . The amount of fluorine was 5 atomic % when the total of fluorine and oxygen was 400 atomic %. A cathode active material of Example 14 was produced in the same manner as in Example 10 except for this. A positive electrode and a positive electrode half cell of Example 14 were manufactured in the same manner as in Example 5 using the positive electrode active material of Example 14.
- Example 15 In the manufacturing method of the positive electrode active material of Example 15, the raw material of the active material did not contain chromium but contained vanadium. In the raw material for the active material of Example 15, iron was 16.25 atomic % and vanadium was 3 atomic % when the total of metal elements other than lithium that could constitute the metal sites was 100 atomic %. The amount of fluorine was 5 atomic % when the total of fluorine and oxygen was 400 atomic %. A cathode active material of Example 15 was produced in the same manner as in Example 5 except for this. A positive electrode and a positive electrode half cell of Example 15 were manufactured in the same manner as in Example 5 using the positive electrode active material of Example 15.
- Example 16 In the manufacturing method of the positive electrode active material of Example 16, the amount of fluorine in the raw material of the active material was such that the total amount of fluorine and oxygen was 5 atomic %.
- a cathode active material of Example 16 was produced in the same manner as in Example 10 except for this.
- a positive electrode and a lithium ion secondary battery of Example 16 were produced in the same manner as in Example 7 using the positive electrode active material of Example 16.
- Example 17 In the manufacturing method of the positive electrode active material of Example 17, silicon was not included in the raw material of the active material. Further, the amount of fluorine in the raw material for the active material was such that the total amount of fluorine and oxygen was 5 atomic %. A cathode active material of Example 17 was produced in the same manner as in Example 5 except for this. Using the positive electrode active material of Example 17, the positive electrode and half cell of Example 17 were manufactured in the same manner as in Example 5, and the positive electrode and lithium ion secondary battery of Example 17 were manufactured in the same manner as in Example 7.
- Example 18 In the manufacturing method of the positive electrode active material of Example 18, silicon was not included in the raw material of the active material. Further, the amount of fluorine in the raw material for the active material was such that the total amount of fluorine and oxygen was 1 atomic % when the total was 400 atomic %. A cathode active material of Example 18 was produced in the same manner as in Example 5 except for this. Using the positive electrode active material of Example 18, the positive electrode and half cell of Example 18 were manufactured in the same manner as in Example 5, and the positive electrode and lithium ion secondary battery of Example 18 were manufactured in the same manner as in Example 7.
- Comparative Example 6 A half cell of Comparative Example 6 was obtained in the same manner as in Example 5 using the positive electrode active material of Comparative Example 1.
- a lithium ion secondary battery of Comparative Example 6 was manufactured in the same manner as in Example 7 using the positive electrode active material of Comparative Example 1.
- the half cell and the lithium ion secondary battery of Comparative Example 6 do not contain tungsten in the positive electrode active material.
- the positive electrode half-cell of Comparative Example 1 had the maximum discharge capacity, and decreased in the order of Example 1>Example 2>Example 3. From this result, it can be said that there is a suitable range for the amount of tungsten in the positive electrode active material in consideration of the discharge capacity. Specifically, the preferable range of the amount of tungsten is 0.05 to 2.5 atomic %, 0.05 to 1 0.5 atomic %, 0.05-1.0 atomic %, 0.05-0.8 atomic %, or 0.05-0.5 atomic %.
- the amount of tungsten that is, the preferred range of d is in the range of 0.05/100 to 2.5/100. within the range of 0.05/100 to 1.5/100, within the range of 0.05/100 to 1.0/100, within the range of 0.05/100 to 0.8/100, or 0 It can be said to be in the range of 0.05/100 to 0.5/100.
- the discharge capacity of the positive electrode half-cell of Reference Example 1 was equivalent to the discharge capacity of the positive electrode half-cell of Comparative Example 1. From this result, if the amount of magnesium in the positive electrode active material is 3 atomic % or less when the total of metal elements other than lithium that can constitute the metal site described above is 100 atomic %, then when magnesium is not added It can be seen that there is no decrease in the capacity of the positive electrode active material compared to . In addition, in Reference Example 1, no decrease in capacity is observed as compared with Comparative Example 1. Therefore, it can be said that the upper limit of the preferable range of the amount of magnesium in the positive electrode active material is a value larger than the above 3 atomic %.
- the preferable range of the amount of magnesium in the positive electrode active material is 0.5 to 5 atomic % when the total of metal elements other than lithium that can constitute the metal site is 100 atomic %. within the range of 0.5 to 4 atomic %.
- the amount of magnesium, that is, the preferred range of e is within the range of 0.5/100 to 5/100, It can be said that it is in the range of 0.5/100 to 4/100.
- a high-temperature charge-discharge cycle was repeated 150 times at 60° C. at a constant current of 1 C, where the battery was charged to an SOC of 100% and then discharged to an SOC of 10%.
- the percentage of the discharge capacity at the 150th charge/discharge was calculated with the discharge capacity at the first charge/discharge as 100%. This percentage was taken as the capacity retention rate of each lithium ion secondary battery.
- Table 2 shows the capacity retention rate of each lithium ion secondary battery.
- the lithium ion secondary battery of Reference Example 1 in which magnesium was added to the positive electrode active material had a capacity retention rate improved by about 3% compared to the lithium ion secondary battery of Comparative Example 1 without magnesium. did. This means that the deterioration of the positive electrode active material was suppressed by adding magnesium, that is, the D1 element to the positive electrode active material.
- the lithium ion secondary battery of Example 4 in which magnesium and tungsten were added to the positive electrode active material was compared to the lithium ion secondary battery of Reference Example 1 in which only magnesium was added to the positive electrode active material.
- the capacity retention rate was further improved by about 2%. From this result, it is found that the deterioration of the positive electrode active material is further suppressed by adding tungsten to the positive electrode active material, and the usefulness of the positive electrode active material of the present invention containing tungsten is supported.
- Example 5 Surface Analysis of Positive Electrode Active Material
- the positive electrode active material of Example 4 was imaged with a scanning electron microscope (SEM). The results are shown in FIGS. 3 and 4.
- FIG. Also, the composition of the surface of the positive electrode active material was analyzed for the same region as in FIGS. 3 and 4 by energy dispersive X-ray spectroscopy (SEM-EDX) attached to the SEM.
- SEM-EDX energy dispersive X-ray spectroscopy
- FIGS. 5-8. 5 and 6 are parts where manganese is detected
- the parts shown in light color in FIG. 7 are parts where magnesium is detected
- the parts are shown in light color in FIG.
- the part that is detected is the detected part of the tungsten.
- the positive electrode active material of Example 4 is resistant to capacity deterioration and exhibits excellent durability. presumably because it protects
- the positive electrode active materials of Examples 2 to 4 were analyzed for the chemical bonding state on the surface by X-ray photoelectric spectroscopy (XPS). Specific measurement conditions are: radiation source: Al-K ⁇ ray (1486.6 eV), X-ray beam diameter: 200 ⁇ m, acceleration voltage: 15 kV, output: 50.35 W, measurement time: 1 hour, transmission energy: 2.95 eV , Elapsed time per step (Time Per Step): 20 ms, Measurement range: 2 mm x 2 mm. The results are shown in FIGS. 9-11. 9 is a chart showing the results of XPS analysis of the positive electrode active material of Example 4, FIG. 10 is a chart showing the results of XPS analysis of the positive electrode active material of Example 2, and FIG. It is a chart showing the result of XPS analysis of the positive electrode active material.
- XPS X-ray photoelectric spectroscopy
- WO 2 appearing at 30 to 34 eV in the XPS chart of the positive electrode active material is required to suppress the decrease in charge/discharge capacity of the lithium ion secondary battery.
- the height of the peak derived from is preferably lower than the height of the peak derived from WO3 appearing between 34 and 36 eV, and is not more than half the height of the peak derived from WO3 appearing between 34 and 36 eV. can be said to be more preferable.
- the lithium ion secondary batteries of Comparative Examples 2 to 4 using the tungsten-coated positive electrode active material were compared with the lithium ion secondary batteries of Comparative Example 5 using the positive electrode active material without tungsten coating. It was about the same as the ion secondary battery. From this result, it can be seen that simply coating the positive electrode active material with tungsten cannot suppress the deterioration of the capacity of the positive electrode active material after endurance.
- the addition of fluorine to the positive electrode active material improves the initial charge capacity.
- fluorine is presumed to be substituted at the oxygen site. Therefore, when considering the improvement of the initial charge capacity, the preferable range of the amount of fluorine in the positive electrode active material is 1 to 20 atomic % when the total of oxygen and fluorine is 400 atomic %. It can be said to be within the range of 10 atomic %, or within the range of 3 to 8 atomic %.
- the initial charge capacity of the half-cell of Example 18 is comparable to the initial charge capacity of the half-cell of Comparative Example 6, but the initial charge capacity of the half-cell of Example 17 is the same as that of the half-cell of Comparative Example 6. It was increased compared to the initial charge capacity of the half-cell of Example 18. Since Examples 17 and 18 do not contain silicon in the positive electrode active material, from this result, even if the positive electrode active material does not contain silicon, considering the initial charge capacity, the amount of fluorine contained in the positive electrode active material is It can be said that more is preferable.
- the amount of fluorine contained in the positive electrode active material is within the above range, that is, within the range of 1 to 20 atomic % when the total of oxygen and fluorine is 400 atomic %, and 2 to 10 atomic %. It is confirmed that the range of 3 to 8 atomic % is more preferable.
- the positive electrode active material may not contain silicon and may contain fluorine. obtain.
- the lithium ion secondary battery of Example 17 and the lithium ion secondary battery of Example 18 containing fluorine and magnesium as the element D1 in the positive electrode active material are comparative examples containing neither fluorine nor magnesium. 6, the discharge resistance was reduced. Further, the lithium ion secondary battery of Example 18 containing 1 atomic % of fluorine in the positive electrode active material has a higher discharge resistance than the lithium ion secondary battery of Example 17 containing 5 atomic % of fluorine in the positive electrode active material. had decreased.
- the positive electrode active material contains fluorine and / or magnesium as the D1 element, the discharge resistance of the lithium ion secondary battery is reduced and the conductivity is improved.
- the amount of fluorine contained in the positive electrode active material is in the range of 0.1 to 10 atomic % when the total of oxygen and fluorine is 400 atomic %. It can be said that it is more preferably in the range of 5 atomic %, more preferably in the range of 0.5 to 2 atomic %.
- both the lithium ion secondary battery of Example 17 and the lithium ion secondary battery of Example 18 had better cycle characteristics than the lithium ion secondary battery of Comparative Example 6.
- the lithium ion secondary battery of Example 17 and the lithium ion secondary battery of Example 18 differ from the lithium ion secondary battery of Comparative Example 6 in that the positive electrode active material contains fluorine and magnesium as the element D1. . Therefore, from this result, it can be said that the inclusion of fluorine and / or magnesium as the D1 element in the positive electrode active material improves the cycle characteristics of the lithium ion secondary battery.
- the amount of tungsten contained in the positive electrode active material is within an appropriate range, specifically, the amount of tungsten when the total of metal elements other than lithium that can form metal sites is 100 atomic%. is set to a value in the vicinity of 0.25 atomic %, it is possible to suppress the decrease in the initial capacity of the half-cell. This is the same as the results of Evaluation Example 1 and FIG. From the results of Evaluation Example 13, it can also be said that the decrease in capacity due to tungsten can be further suppressed by adding magnesium and/or chromium to the positive electrode active material together with tungsten.
- the preferable range of the amount of magnesium in the positive electrode active material is 0.5 to 10 atomic % when the total of metal elements other than lithium that can constitute the metal site is 100 atomic %. Within the range, it can be said to be within the range of 1 to 10 atomic %, within the range of 1 to 8 atomic %, and within the range of 2 to 5 atomic %.
- the preferable range of the amount of chromium in the positive electrode active material is 0.2 to 5 atomic %, 0.3 to 5 atomic %, when the total of metal elements other than lithium that can constitute the metal site is 100 atomic %. atomic %, 0.5 to 3 atomic %, and 1 to 2.5 atomic %.
- the percentage of the discharge capacity in each cycle was calculated, with the discharge capacity at the time of the first charge and discharge as 100%. This percentage was taken as the capacity retention rate of each lithium ion secondary battery.
- the capacity retention rate of each lithium ion secondary battery after 100 cycles was 80% for the lithium ion secondary battery of Example 7 and 88% for the lithium ion secondary battery of Example 8. rice field. From this result, it can be said that a larger amount of chromium contained in the positive electrode active material is preferable from the viewpoint of improving durability. From the viewpoint of improving durability, the preferable range of the amount of chromium in the positive electrode active material is 1 atomic % or more and 1.5 atomic % when the total of metal elements other than lithium that can constitute the metal site is 100 atomic %. % or more, 2 atomic % or more, and 3 atomic % or more. Although there is no upper limit to the amount of chromium at this time, it is in the range of 10 atomic % or less and 5 atomic % or less.
- Example 9 In Examples 9, 13 and 14 in which magnesium, titanium, vanadium and fluorine were added to the positive electrode active material along with tungsten, and in Example 10 in which magnesium, titanium, chromium and fluorine were added to the positive electrode active material along with tungsten, The initial charge capacity was improved as compared with Comparative Example 6 in which tungsten was not added to the positive electrode active material.
- the lithium ion secondary batteries of Examples 9 and 12 to 15 differ in the amount of vanadium contained in the positive electrode active material.
- the amount of vanadium when the total of manganese element, iron element, tungsten element and D1 element contained in the positive electrode active material, that is, the metal element other than lithium that can constitute the metal site is 100 atomic% , 0.8 atomic % in the lithium ion secondary battery of Example 9, 0 atomic % in the lithium ion secondary battery of Example 12, 1.25 atomic % in the lithium ion secondary battery of Example 13, Example 14 2.5 atomic % in the lithium ion secondary battery of Example 15 and 3 atomic % in the lithium ion secondary battery of Example 15.
- the charging capacity was Example 14>Example 13>Example 9>Example 12>Example 15. From this, it is considered that there is a particularly suitable range for the amount of vanadium contained in the positive electrode active material.
- the amount of vanadium is preferably 0 atomic % or more and less than 3 atomic %, 0.5 atomic % or more and 0.5 atomic % or more,2.
- Each range of 9 atomic % or less, 0.8 atomic % or more and 2.9 atomic % or less, 1.0 atomic % or more and 2.9 atomic % or less, and 1.5 atomic % or more and 2.8 atomic % or less can be exemplified.
- the preferable range of the amount of titanium in the positive electrode active material is 0.5 to 10 atomic % when the total of metal elements other than lithium that can constitute the metal site is 100 atomic %. , 1 to 10 atomic %, 1.5 to 6 atomic %, and 1.5 to 4 atomic %.
- a preferable range of the amount of chromium in the positive electrode active material is 0.1 to 10 atomic % and 0.5 to 8 atomic % when the total of metal elements other than lithium that can constitute the metal site is 100 atomic %. within the range of, within the range of 1 to 6 atomic %, and within the range of 2 to 4 atomic %.
- the half cell of Example 11 containing magnesium and chromium as well as tungsten in the positive electrode active material had an improved initial charge capacity compared to the half cell of Comparative Example 6 containing no tungsten in the positive electrode active material.
- the initial charge capacity (%) of the half cell of Example 11 in Evaluation Example 16 is slightly inferior to the initial charge capacity (%) of the half cell of Example 10 in Evaluation Example 15. This is presumed to be due to the fact that the positive electrode active material of the half cell of Example 11 does not contain titanium and fluorine. It can be said that it is particularly preferable to blend fluorine.
- Table 11 shows the discharge capacity of each lithium ion secondary battery together with the results of Evaluation Example 18, which will be described later.
- the discharge capacity of the lithium ion secondary battery of each example is shown in percentage, with the discharge capacity of the lithium ion secondary battery of Comparative Example 6 set to 100%.
- Each lithium ion secondary battery has an SOC of 100% at 4.2V and an SOC of 0% at 3.0V.
- the lithium ion secondary battery of Example 9 has a larger initial discharge capacity than the lithium ion secondary battery of Comparative Example 6. This is presumably because in the lithium ion secondary battery of Example 9, magnesium, titanium, vanadium and fluorine were added to the positive electrode active material together with tungsten. In other words, by substituting a portion of the oxygen site of the positive electrode active material with fluorine and substituting a portion of the metal site with tungsten and the above - described D element, the initial charge capacity of the lithium ion secondary battery improves.
- the lithium ion secondary battery of Example 9 and the lithium ion secondary battery of Example 16 are different from each other in that the positive electrode active material contains vanadium or chromium as the D1 element.
- the lithium ion secondary battery of Example 9 had a higher initial discharge capacity than the lithium ion secondary battery of Example 16.
- chromium is included as an element D1. It can be said that it is more preferable to contain vanadium as the D1 element than
- the lithium ion secondary battery of Example 10 and the lithium ion secondary battery of Example 16 differ from each other in the content of fluorine in the positive electrode active material. Specifically, the fluorine content of the positive electrode active material in the lithium ion secondary battery of Example 10 is 2.5 atomic %, whereas the fluorine content of the positive electrode active material in the lithium ion secondary battery of Example 16 The amount is 5 atomic %.
- the lithium ion secondary battery of Example 10 had a higher initial discharge capacity than the lithium ion secondary battery of Example 16. Therefore, considering the initial capacity, the fluorine content in the positive electrode active material It can be said that the amount is more preferably 2.5 atomic % than 5 atomic % when the total of fluorine and oxygen is 400 atomic %. Furthermore, from the above results, the preferable range of fluorine content when considering the initial capacity is more than 0 atomic % and 10 atomic % or less, 1 atomic % when the total of fluorine and oxygen in the positive electrode active material is 400 atomic %. 5 atomic % or less, 1.5 atomic % or more and 4 atomic % or less, or 2 atomic % or more and 3 atomic % or less can be exemplified.
- the lithium ion secondary battery of Example 9 has a lower resistance than the lithium ion secondary battery of Comparative Example 6. This is presumably because in the lithium ion secondary battery of Example 9, magnesium, titanium, vanadium and fluorine were added to the positive electrode active material together with tungsten. In other words, by substituting a portion of the oxygen sites of the positive electrode active material with fluorine and substituting a portion of the metal sites with tungsten and the above - described D element, the conductivity of the lithium ion secondary battery is improved. improves.
- the lithium ion secondary battery of Example 9 and the lithium ion secondary battery of Example 16 are different in that the lithium ion secondary battery of Example 9 contains vanadium as an element D1, whereas the lithium ion secondary battery of Example 16 contains vanadium. They differ from each other in that the secondary batteries contain chromium as the D1 element.
- the lithium ion secondary battery of Example 9 has a smaller resistance than the lithium ion secondary battery of Example 16, so considering the resistance, D It can be said that it is preferable to contain vanadium as one element.
- the lithium ion secondary battery of Example 10 and the lithium ion secondary battery of Example 16 differ from each other in the content of fluorine in the positive electrode active material.
- the fluorine content of the positive electrode active material in the lithium ion secondary battery of Example 10 was 2.5 atomic %
- the fluorine content of the positive electrode active material in the lithium ion secondary battery of Example 16 was The content is 5 atomic %.
- the lithium ion secondary battery of Example 16 has a lower discharge resistance than the lithium ion secondary battery of Example 10. Therefore, considering the discharge resistance, the fluorine content in the positive electrode active material is , 5 atomic % is more preferable than 2.5 atomic % when the total of fluorine and oxygen is 400 atomic %. Furthermore, from the above results, the preferable fluorine content range when considering the discharge resistance is 2.5 atomic % or more and 3.5 atomic % when the total of fluorine and oxygen in the positive electrode active material is 400 atomic %. Above, 4.5 atomic % or more, or 5 atomic % or more can be exemplified. Although there is no particular upper limit to the preferred range of fluorine content in this case, 50 atomic % or less, 20 atomic % or less, and 10 atomic % or less can be exemplified.
- the percentage of the discharge capacity in each cycle was calculated, with the discharge capacity at the time of the first charge and discharge as 100%. This percentage was taken as the capacity retention rate of each lithium ion secondary battery.
- Table 12 shows the capacity retention rates of the lithium ion secondary battery of Example 9 and the lithium ion secondary battery of Comparative Example 6 at the 42nd cycle.
- FIG. 15 shows changes in the capacity retention rate of the following batteries.
- the lithium ion secondary battery of Example 9 compared with the lithium ion secondary battery of Comparative Example 6, the capacity retention rate is improved. In other words, the lithium ion secondary battery of Example 9 is superior to the lithium ion secondary battery of Comparative Example 6 in cycle characteristics. From this result, by replacing a part of the oxygen site of the positive electrode active material with fluorine, and replacing a part of the metal site with tungsten and the above-mentioned D 1 element, the capacity of the lithium ion secondary battery, It can be said that the electrical conductivity and cycle characteristics are well balanced, and excellent electrical characteristics are imparted to the lithium ion secondary battery.
- the lithium ion secondary battery of Example 16 shows a smaller decrease in the capacity retention rate with the lapse of cycles than the lithium ion secondary battery of Comparative Example 6.
- This result also supports the usefulness of substituting a portion of the oxygen sites of the positive electrode active material with fluorine, and substituting a portion of the metal sites with tungsten and the aforementioned D 1 element.
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Abstract
This positive electrode active material is represented by LiaMnbFecWdD1
eD2
fPgOh (where D1 is a metal element, D2 is an element in group-13 to group-16 and has a valence of 4 or lower, and a, b, c, d, e, f, g, and h satisfy 0<a<1.5, 0<b<1, 0<c<1, 0<d<1, 0≤e<1, 0≤f<1, 0<g<1, and 0<h<5, respectively). In the positive electrode active material, a peak derived from WO2 is observed by X-ray photoelectric spectroscopy.
Description
本発明は、オリビン構造の正極活物質とその製造方法に関する。
The present invention relates to a positive electrode active material with an olivine structure and a method for producing the same.
携帯端末、パーソナルコンピュータ、電気自動車などの電源として、容量に優れるリチウムイオン二次電池が使用されている。リチウムイオン二次電池の容量をより高くするためには、高容量の正極活物質及び高容量の負極活物質を採用すればよい。
例えば、ＬｉＣｏＯ2、ＬｉＮｉＯ2、ＬｉＮｉ1/3Ｃｏ1/3Ｍｎ1/3Ｏ2等の層状岩塩構造の正極活物質は、高容量の正極活物質として知られている。また、Ｓｉ含有負極活物質はリチウムの吸蔵能力が高いため、高容量の負極活物質として知られている。 2. Description of the Related Art Lithium ion secondary batteries, which have excellent capacity, are used as power sources for mobile terminals, personal computers, electric vehicles, and the like. In order to increase the capacity of the lithium-ion secondary battery, a high-capacity positive electrode active material and a high-capacity negative electrode active material may be employed.
For example, positive electrode active materials having a layered rock salt structure such as LiCoO 2 , LiNiO 2 and LiNi 1/3 Co 1/3 Mn 1/3 O 2 are known as high-capacity positive electrode active materials. In addition, since the Si-containing negative electrode active material has a high ability to absorb lithium, it is known as a high-capacity negative electrode active material.
例えば、ＬｉＣｏＯ2、ＬｉＮｉＯ2、ＬｉＮｉ1/3Ｃｏ1/3Ｍｎ1/3Ｏ2等の層状岩塩構造の正極活物質は、高容量の正極活物質として知られている。また、Ｓｉ含有負極活物質はリチウムの吸蔵能力が高いため、高容量の負極活物質として知られている。 2. Description of the Related Art Lithium ion secondary batteries, which have excellent capacity, are used as power sources for mobile terminals, personal computers, electric vehicles, and the like. In order to increase the capacity of the lithium-ion secondary battery, a high-capacity positive electrode active material and a high-capacity negative electrode active material may be employed.
For example, positive electrode active materials having a layered rock salt structure such as LiCoO 2 , LiNiO 2 and LiNi 1/3 Co 1/3 Mn 1/3 O 2 are known as high-capacity positive electrode active materials. In addition, since the Si-containing negative electrode active material has a high ability to absorb lithium, it is known as a high-capacity negative electrode active material.
しかしながら、層状岩塩構造の正極活物質を採用したリチウムイオン二次電池や、Ｓｉ含有負極活物質を採用したリチウムイオン二次電池は、短絡などの異常が生じた際に、発熱量が大きいとの欠点があった。
However, lithium-ion secondary batteries that employ a positive electrode active material with a layered rock salt structure and lithium-ion secondary batteries that employ a Si-containing negative electrode active material generate a large amount of heat when an abnormality such as a short circuit occurs. It had its shortcomings.
かかる欠点を解消するため、層状岩塩構造の正極活物質と比較して低容量であるものの熱安定性に優れるオリビン構造の正極活物質を採用する手段がある。当該正極活物質に組み合わせる負極活物質としては、Ｓｉ含有負極活物質と比較して低容量であるものの熱安定性に優れる黒鉛を採用する手段がある。
オリビン構造の正極活物質及び負極活物質として黒鉛を備えるリチウムイオン二次電池は、文献に記載されている。 In order to overcome such drawbacks, there is a means of adopting a positive electrode active material with an olivine structure, which has a lower capacity than a positive electrode active material with a layered rock salt structure but is superior in thermal stability. As a negative electrode active material to be combined with the positive electrode active material, there is a means of adopting graphite, which has a lower capacity than the Si-containing negative electrode active material but has excellent thermal stability.
Lithium-ion secondary batteries with graphite as positive and negative electrode active materials of olivine structure have been described in the literature.
オリビン構造の正極活物質及び負極活物質として黒鉛を備えるリチウムイオン二次電池は、文献に記載されている。 In order to overcome such drawbacks, there is a means of adopting a positive electrode active material with an olivine structure, which has a lower capacity than a positive electrode active material with a layered rock salt structure but is superior in thermal stability. As a negative electrode active material to be combined with the positive electrode active material, there is a means of adopting graphite, which has a lower capacity than the Si-containing negative electrode active material but has excellent thermal stability.
Lithium-ion secondary batteries with graphite as positive and negative electrode active materials of olivine structure have been described in the literature.
特許文献１には、オリビン構造の正極活物質を具備するリチウムイオン二次電池は安全性に優れる旨が記載されており（００１４段落を参照）、そして、オリビン構造のＬｉＦｅＰＯ4を正極活物質として備え、負極活物質として黒鉛を備えるリチウムイオン二次電池が具体的に記載されている（実験例１～６を参照）。
Patent Document 1 describes that a lithium-ion secondary battery equipped with a positive electrode active material having an olivine structure is excellent in safety ( see paragraph 0014). A lithium ion secondary battery comprising graphite as a negative electrode active material is specifically described (see Experimental Examples 1 to 6).
特許文献２には、オリビン構造の正極活物質は熱安定性が高い旨が記載されており（００１１段落を参照）、そして、オリビン構造のＬｉＦｅＰＯ4を正極活物質として備え、負極活物質として黒鉛を備えるリチウムイオン二次電池が具体的に記載されている（実施例１～３を参照）。
Patent Document 2 describes that the positive electrode active material with an olivine structure has high thermal stability (see paragraph 0011), and includes LiFePO 4 with an olivine structure as a positive electrode active material and graphite as a negative electrode active material. is specifically described (see Examples 1-3).
特許文献３には、オリビン構造の正極活物質としてのリン酸鉄リチウム（ＬｉＦｅＰＯ4）およびリン酸マンガンリチウム（ＬｉＭｎＰＯ4）が紹介され、さらにこれらの固溶体であるリン酸鉄マンガンリチウムも紹介されている。特許文献３の背景技術の欄には、このうちリン酸鉄マンガンリチウムについては、鉄に対するＭｎの元素比が大きくなるほど、平均作動電圧が高くなり、エネルギー密度は大きくなることが期待される旨が説明されている。
Patent Document 3 introduces lithium iron phosphate (LiFePO 4 ) and lithium manganese phosphate (LiMnPO 4 ) as positive electrode active materials having an olivine structure, and further introduces lithium iron manganese phosphate, which is a solid solution thereof. there is In the background art column of Patent Document 3, it is stated that, among these, lithium iron manganese phosphate is expected to have a higher average operating voltage and a higher energy density as the element ratio of Mn to iron increases. explained.
ところで、上記したリン酸鉄マンガンリチウムは、エネルギー密度が高く正極活物質として有用と期待される半面、正極活物質として好適とは言い難い性質を有する。
By the way, while the above lithium iron-manganese phosphate has a high energy density and is expected to be useful as a positive electrode active material, it has properties that are not suitable as a positive electrode active material.
例えば、特許文献３には、リン酸鉄マンガンリチウムの理論放電容量および理論作動電圧の発現は、鉄に対するマンガンの元素比が大きくなる程困難になる旨が説明されている。さらに同特許文献３には、この不具合は、リン酸鉄マンガンリチウムが電子伝導性およびイオン導電性に劣ること、および、充放電によってリン酸鉄マンガンリチウムの構造に変化が生じることに起因する旨が説明されている。
リン酸鉄マンガンリチウムの構造変化は、正極活物質としてのリン酸鉄マンガンリチウムの容量劣化を招くと考えられる。 For example,Patent Document 3 explains that the development of the theoretical discharge capacity and theoretical operating voltage of lithium iron-manganese phosphate becomes more difficult as the element ratio of manganese to iron increases. Furthermore, Patent Document 3 states that this problem is caused by the fact that lithium iron manganese phosphate has poor electronic and ionic conductivity, and that the structure of lithium iron manganese phosphate changes due to charging and discharging. is explained.
It is considered that the structural change of lithium iron manganese phosphate causes the capacity deterioration of lithium iron manganese phosphate as a positive electrode active material.
リン酸鉄マンガンリチウムの構造変化は、正極活物質としてのリン酸鉄マンガンリチウムの容量劣化を招くと考えられる。 For example,
It is considered that the structural change of lithium iron manganese phosphate causes the capacity deterioration of lithium iron manganese phosphate as a positive electrode active material.
なお、特許文献３には、リン酸鉄マンガンリチウムにニオブをドープしたリン酸化合物においては、その構造が安定化し、電子伝導性およびイオン導電性を高められる旨が開示されている（例えば〔００３２〕～〔００３４〕段落参照）。
In addition, Patent Document 3 discloses that a phosphoric acid compound obtained by doping lithium iron manganese phosphate with niobium stabilizes its structure and increases electronic conductivity and ionic conductivity (for example, [0032 ] to [0034]).
本発明の発明者は、オリビン構造を有するリン酸鉄マンガンリチウム系の正極活物質であって、耐久後の容量劣化が抑制された、新規な正極活物質を開発することを志向した。
The inventor of the present invention aimed to develop a novel positive electrode active material, which is an iron-manganese-lithium phosphate-based positive electrode active material having an olivine structure, in which capacity deterioration after endurance is suppressed.
本発明はかかる事情に鑑みて為されたものであり、オリビン構造を有するリン酸鉄マンガンリチウム系の正極活物質であって、耐久後の容量劣化が抑制されたものを提供することを解決すべき課題とする。
The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a positive electrode active material of iron manganese lithium phosphate having an olivine structure, in which capacity deterioration after endurance is suppressed. should be the subject.
本発明の発明者は、オリビン構造を有するリン酸鉄マンガンリチウム系の正極活物質につき、その耐久後の容量劣化が生じる要因を鋭意研究した。その結果、リチウムイオン二次電池の充放電に伴い生じるフッ化水素が、当該正極活物質の劣化の一因となり得るという着想を得た。
The inventors of the present invention have diligently studied factors that cause capacity deterioration after endurance of an iron-manganese-lithium phosphate-based positive electrode active material having an olivine structure. As a result, the inventors have come up with the idea that hydrogen fluoride generated during charging and discharging of a lithium ion secondary battery can be a cause of deterioration of the positive electrode active material.
つまり、電解液に含まれるリチウム塩としては、ＬｉＰＦ6等のフッ素を含有するものが一般に用いられている。一般的なリチウムイオン二次電池の電解液には微量の水が存在するために、当該電解液中には、リチウム塩と水との反応によりフッ化水素が生じると考えられる。そしてこの種の電解液を用いたリチウムイオン二次電池においては、電解液中のフッ化水素と正極活物質とが反応することにより、正極活物質が劣化する可能性がある。
That is, lithium salts containing fluorine such as LiPF 6 are generally used as the lithium salt contained in the electrolyte. Since a small amount of water is present in the electrolytic solution of a general lithium-ion secondary battery, it is considered that hydrogen fluoride is generated in the electrolytic solution by the reaction between the lithium salt and water. In a lithium-ion secondary battery using this type of electrolyte, the positive electrode active material may deteriorate due to the reaction between the hydrogen fluoride in the electrolyte and the positive electrode active material.
本発明の発明者は、この着想を基に更なる研究を重ね、特定の元素を特定の状態で正極活物質に含有させることにより、当該正極活物質をフッ化水素から保護し得ることという知見を得た。かかる知見に基づき、本発明の発明者は本発明を完成した。
The inventors of the present invention conducted further research based on this idea, and found that the positive electrode active material can be protected from hydrogen fluoride by containing a specific element in a specific state in the positive electrode active material. got Based on such findings, the inventor of the present invention completed the present invention.
本発明の正極活物質は、
ＬｉaＭｎbＦｅcＷdＤ1 eＤ2 fＰgＯh（Ｄ1は金属元素、Ｄ2は第１３族から第１６族の元素かつ価数が４以下であり、ａ、ｂ、ｃ、ｄ、ｅ、ｆ、ｇ、ｈは、０＜ａ＜１．５、０＜ｂ＜１、０＜ｃ＜１、０＜ｄ＜１、０≦ｅ＜１、０≦ｆ＜１、０＜ｇ＜１、０＜ｈ＜５を満足する。）で表され、Ｘ線光電分光法によりＷＯ2に由来するピークが確認される、正極活物質である。
また、本発明の正極活物質は、
ＬｉaＭｎbＦｅcＷdＤ1 eＤ2 fＰgＦiＯh（Ｄ1は金属元素、Ｄ2は第１３族から第１６族の元素かつ価数が４以下であり、ａ、ｂ、ｃ、ｄ、ｅ、ｆ、ｇ、ｈ、ｉは、０＜ａ＜１．５、０＜ｂ＜１、０＜ｃ＜１、０＜ｄ＜１、０≦ｅ＜１、０≦ｆ＜１、０＜ｇ＜１、０＜ｈ＜５、０＜ｉ＜１を満足する。）で表され、
Ｘ線光電分光法によりＷＯ2に由来するピークが確認されるか、及び／又は、
前記Ｄ1がＣｒ、Ｔｉ、Ｖから選ばれる少なくとも一種である、正極活物質である。 The positive electrode active material of the present invention is
Li a Mn b Fe c W d D 1 e D 2 f P g O h (D 1 is a metal element, D 2 is an element of groups 13 to 16 with a valence of 4 or less, a, b, c, d, e, f, g, and h are 0<a<1.5, 0<b<1, 0<c<1, 0<d<1, 0≤e<1, 0≤f<1 , 0<g<1 and 0<h<5.), and a peak derived from WO 2 is confirmed by X-ray photoelectric spectroscopy.
Further, the positive electrode active material of the present invention is
Li a Mn b Fe c W d D 1 e D 2 f P g F i O h (D 1 is a metal element, D 2 is an element of Groups 13 to 16 and has a valence of 4 or less, a, b, c, d, e, f, g, h, i are 0<a<1.5, 0<b<1, 0<c<1, 0<d<1, 0≤e<1, 0 ≤ f < 1, 0 < g < 1, 0 < h < 5, 0 < i < 1 are satisfied.),
A peak derived from WO2 is confirmed by X-ray photoelectric spectroscopy, and/or
D 1 is at least one selected from Cr, Ti and V, in the positive electrode active material.
ＬｉaＭｎbＦｅcＷdＤ1 eＤ2 fＰgＯh（Ｄ1は金属元素、Ｄ2は第１３族から第１６族の元素かつ価数が４以下であり、ａ、ｂ、ｃ、ｄ、ｅ、ｆ、ｇ、ｈは、０＜ａ＜１．５、０＜ｂ＜１、０＜ｃ＜１、０＜ｄ＜１、０≦ｅ＜１、０≦ｆ＜１、０＜ｇ＜１、０＜ｈ＜５を満足する。）で表され、Ｘ線光電分光法によりＷＯ2に由来するピークが確認される、正極活物質である。
また、本発明の正極活物質は、
ＬｉaＭｎbＦｅcＷdＤ1 eＤ2 fＰgＦiＯh（Ｄ1は金属元素、Ｄ2は第１３族から第１６族の元素かつ価数が４以下であり、ａ、ｂ、ｃ、ｄ、ｅ、ｆ、ｇ、ｈ、ｉは、０＜ａ＜１．５、０＜ｂ＜１、０＜ｃ＜１、０＜ｄ＜１、０≦ｅ＜１、０≦ｆ＜１、０＜ｇ＜１、０＜ｈ＜５、０＜ｉ＜１を満足する。）で表され、
Ｘ線光電分光法によりＷＯ2に由来するピークが確認されるか、及び／又は、
前記Ｄ1がＣｒ、Ｔｉ、Ｖから選ばれる少なくとも一種である、正極活物質である。 The positive electrode active material of the present invention is
Li a Mn b Fe c W d D 1 e D 2 f P g O h (D 1 is a metal element, D 2 is an element of groups 13 to 16 with a valence of 4 or less, a, b, c, d, e, f, g, and h are 0<a<1.5, 0<b<1, 0<c<1, 0<d<1, 0≤e<1, 0≤f<1 , 0<g<1 and 0<h<5.), and a peak derived from WO 2 is confirmed by X-ray photoelectric spectroscopy.
Further, the positive electrode active material of the present invention is
Li a Mn b Fe c W d D 1 e D 2 f P g F i O h (D 1 is a metal element, D 2 is an element of Groups 13 to 16 and has a valence of 4 or less, a, b, c, d, e, f, g, h, i are 0<a<1.5, 0<b<1, 0<c<1, 0<d<1, 0≤e<1, 0 ≤ f < 1, 0 < g < 1, 0 < h < 5, 0 < i < 1 are satisfied.),
A peak derived from WO2 is confirmed by X-ray photoelectric spectroscopy, and/or
D 1 is at least one selected from Cr, Ti and V, in the positive electrode active material.
本発明の正極活物質は、耐久後にも容量劣化し難い。
The positive electrode active material of the present invention is less likely to deteriorate in capacity even after endurance.
以下に、本発明を実施するための形態を説明する。なお、特に断らない限り、本明細書に記載された数値範囲「ｘ～ｙ」は、下限ｘ及び上限ｙをその範囲に含む。そして、これらの上限値及び下限値、並びに実施例中に列記した数値も含めてそれらを任意に組み合わせることで新たな数値範囲を構成し得る。更に、上記の何れかの数値範囲内から任意に選択した数値を新たな数値範囲の上限、下限の数値とすることができる。
The following describes a mode for carrying out the present invention. Unless otherwise specified, the numerical range "x to y" described in this specification includes the lower limit x and the upper limit y. A new numerical range can be formed by arbitrarily combining these upper and lower limits and the numerical values listed in the examples. Furthermore, numerical values arbitrarily selected from any of the above numerical ranges can be used as upper and lower numerical values of the new numerical range.
本発明の正極活物質は、下式（１）で表され、Ｘ線光電分光法によりタングステンに由来するピークが確認される、正極活物質である。
ＬｉaＭｎbＦｅcＷdＤ1 eＤ2 fＰgＯh 式（１）
（Ｄ1は金属元素、Ｄ2は第１３族から第１６族の元素かつ価数が４以下であり、ａ、ｂ、ｃ、ｄ、ｅ、ｆ、ｇ、ｈは、０＜ａ＜１．５、０＜ｂ＜１、０＜ｃ＜１、０＜ｄ＜１、０≦ｅ＜１、０≦ｆ＜１、０＜ｇ＜１、０＜ｈ＜５を満足する。） The positive electrode active material of the present invention is represented by the following formula (1) and is a positive electrode active material in which a peak derived from tungsten is confirmed by X-ray photoelectric spectroscopy.
LiaMnbFecWdD1eD2fPgOH Formula ( 1 ) _ _ _ _ _
(D 1 is a metal element, D 2 is an element of Groups 13 to 16 and has a valence of 4 or less, and a, b, c, d, e, f, g, and h are 0<a<1 .5, 0<b<1, 0<c<1, 0<d<1, 0≤e<1, 0≤f<1, 0<g<1, 0<h<5.)
ＬｉaＭｎbＦｅcＷdＤ1 eＤ2 fＰgＯh 式（１）
（Ｄ1は金属元素、Ｄ2は第１３族から第１６族の元素かつ価数が４以下であり、ａ、ｂ、ｃ、ｄ、ｅ、ｆ、ｇ、ｈは、０＜ａ＜１．５、０＜ｂ＜１、０＜ｃ＜１、０＜ｄ＜１、０≦ｅ＜１、０≦ｆ＜１、０＜ｇ＜１、０＜ｈ＜５を満足する。） The positive electrode active material of the present invention is represented by the following formula (1) and is a positive electrode active material in which a peak derived from tungsten is confirmed by X-ray photoelectric spectroscopy.
LiaMnbFecWdD1eD2fPgOH Formula ( 1 ) _ _ _ _ _
(D 1 is a metal element, D 2 is an element of Groups 13 to 16 and has a valence of 4 or less, and a, b, c, d, e, f, g, and h are 0<a<1 .5, 0<b<1, 0<c<1, 0<d<1, 0≤e<1, 0≤f<1, 0<g<1, 0<h<5.)
または、本発明の正極活物質は下式（１－１）で表され、Ｘ線光電分光法によりＷＯ2に由来するピークが確認されるか、及び／又は、前記Ｄ1がＣｒ、Ｔｉ、Ｖから選ばれる少なくとも一種である、正極活物質である。
ＬｉaＭｎbＦｅcＷdＤ1 eＤ2 fＰgＦiＯh 式（１－１）
（Ｄ1は金属元素、Ｄ2は第１３族から第１６族の元素かつ価数が４以下であり、ａ、ｂ、ｃ、ｄ、ｅ、ｆ、ｇ、ｈ、ｉは、０＜ａ＜１．５、０＜ｂ＜１、０＜ｃ＜１、０＜ｄ＜１、０≦ｅ＜１、０≦ｆ＜１、０＜ｇ＜１、０＜ｈ＜５、０＜ｉ＜１を満足する。） Alternatively, the positive electrode active material of the present invention is represented by the following formula (1-1), and a peak derived from WO 2 is confirmed by X-ray photoelectric spectroscopy, and/or D 1 is Cr, Ti, It is at least one selected from V and is a positive electrode active material.
Li a Mn b Fe c W d D 1 e D 2 f P g F i O h formula (1-1)
(D 1 is a metal element, D 2 is an element of Groups 13 to 16 and has a valence of 4 or less, and a, b, c, d, e, f, g, h, and i are 0<a <1.5, 0<b<1, 0<c<1, 0<d<1, 0<e<1, 0<f<1, 0<g<1, 0<h<5, 0<i < satisfies 1.)
ＬｉaＭｎbＦｅcＷdＤ1 eＤ2 fＰgＦiＯh 式（１－１）
（Ｄ1は金属元素、Ｄ2は第１３族から第１６族の元素かつ価数が４以下であり、ａ、ｂ、ｃ、ｄ、ｅ、ｆ、ｇ、ｈ、ｉは、０＜ａ＜１．５、０＜ｂ＜１、０＜ｃ＜１、０＜ｄ＜１、０≦ｅ＜１、０≦ｆ＜１、０＜ｇ＜１、０＜ｈ＜５、０＜ｉ＜１を満足する。） Alternatively, the positive electrode active material of the present invention is represented by the following formula (1-1), and a peak derived from WO 2 is confirmed by X-ray photoelectric spectroscopy, and/or D 1 is Cr, Ti, It is at least one selected from V and is a positive electrode active material.
Li a Mn b Fe c W d D 1 e D 2 f P g F i O h formula (1-1)
(D 1 is a metal element, D 2 is an element of Groups 13 to 16 and has a valence of 4 or less, and a, b, c, d, e, f, g, h, and i are 0<a <1.5, 0<b<1, 0<c<1, 0<d<1, 0<e<1, 0<f<1, 0<g<1, 0<h<5, 0<i < satisfies 1.)
本発明の正極活物質は、オリビン構造を有するリン酸鉄マンガンリチウム系の正極活物質における基本骨格であるＬｉＭｎa1Ｆｅb1ＰＯ4（ａ１、ｂ１は、ａ１＋ｂ１＝１、０＜ａ１＜１、０＜ｂ１＜１を満足する。）を有するものと考えられ、さらに、ＷＯ2を必須とし、必要に応じてその他の元素を含有するものともいい得る。
The positive electrode active material of the present invention is LiMn a1 Fe b1 PO 4 (a1 and b1 are a1+b1=1, 0<a1<1, 0 <b1<1.), and furthermore, it can be said that WO2 is essential and other elements are contained as necessary.
本発明の正極活物質においては、タングステンの一部は、ＬｉＭｎa1Ｆｅb1ＰＯ4の結晶粒界に析出し、他の一部は結晶構造の内部に存在すると考えられる。タングステンの当該他の一部は、恐らく、ＬｉＭｎa1Ｆｅb1ＰＯ4のメタルサイトすなわちＦｅまたはＭｎのサイトに置換されると推測される。結晶構造の内部に存在するタングステンはＷＯ2を含むと考えられ、当該ＷＯ2に起因して、本発明の正極活物質からの遷移金属の溶出が抑制されると考えられる。なお、結晶粒界に析出したタングステンは、本発明の正極活物質をフッ化水素から保護する役割を担うと考えられる。これらの協働により、本発明の正極活物質は、耐久後にも容量劣化し難く、耐久性に優れるといい得る。
In the positive electrode active material of the present invention, it is believed that part of tungsten is precipitated at the crystal grain boundaries of LiMna1Feb1PO4 and the other part is present inside the crystal structure. It is presumed that the other part of tungsten is probably replaced by metal sites of LiMn a1 Fe b1 PO 4 , that is, Fe or Mn sites. Tungsten present in the crystal structure is believed to contain WO 2 , and WO 2 is believed to suppress the elution of the transition metal from the positive electrode active material of the present invention. It is believed that the tungsten precipitated at the grain boundaries plays a role in protecting the positive electrode active material of the present invention from hydrogen fluoride. It can be said that due to the cooperation of these, the positive electrode active material of the present invention is resistant to capacity deterioration even after endurance and has excellent durability.
なお、本発明の正極活物質がＷＯ2を含むことは、Ｘ線光電分光法により確認できる。具体的には、本発明の正極活物質をＸ線光電分光法により分析すると、ＷＯ2に由来するピークが確認される。具体的な方法については実施例の欄に例示する。
以下、本発明の正極活物質の詳細を説明する。 The fact that the positive electrode active material of the present invention contains WO 2 can be confirmed by X-ray photoelectric spectroscopy. Specifically, when the positive electrode active material of the present invention is analyzed by X-ray photoelectric spectroscopy, a peak derived from WO2 is confirmed. Concrete methods are exemplified in Examples.
The details of the positive electrode active material of the present invention are described below.
以下、本発明の正極活物質の詳細を説明する。 The fact that the positive electrode active material of the present invention contains WO 2 can be confirmed by X-ray photoelectric spectroscopy. Specifically, when the positive electrode active material of the present invention is analyzed by X-ray photoelectric spectroscopy, a peak derived from WO2 is confirmed. Concrete methods are exemplified in Examples.
The details of the positive electrode active material of the present invention are described below.
本発明の正極活物質は、上式（１）または（１－１）で表されるものであり、基本骨格であるＬｉＭｎa1Ｆｅb1ＰＯ4（ａ１、ｂ１は、ａ１＋ｂ１＝１、０＜ａ１＜１、０＜ｂ１＜１を満足する。）に、さらに、ＷＯ2を必須とし、必要に応じてその他の元素を含有するものと考えられる。したがって、本発明の正極活物質もまたオリビン構造を有すると考えられる。
The positive electrode active material of the present invention is represented by the above formula (1) or (1-1) and has a basic skeleton of LiMn a1 Fe b1 PO 4 (a1 and b1 are a1+b1=1, 0<a1 <1, 0<b1<1.), WO2 is essential, and other elements are considered to be contained as necessary. Therefore, it is considered that the positive electrode active material of the present invention also has an olivine structure.
式（１）および（１－１）におけるａの範囲として、０．８＜ａ＜１．２、０．９＜ａ＜１．１、ａ＝１を例示できる。また、式（１）および（１－１）におけるｈの範囲として、３＜ｈ＜５、３．５＜ｈ＜４．５、３．８＜ｈ＜４．２、ｈ＝４を例示できる。
Examples of the range of a in formulas (1) and (1-1) are 0.8<a<1.2, 0.9<a<1.1, and a=1. Examples of the range of h in formulas (1) and (1-1) include 3<h<5, 3.5<h<4.5, 3.8<h<4.2, and h=4. .
式（１）および（１－１）におけるｂおよびｃの範囲として、０．５≦ｂ≦０．９、０．１≦ｃ≦０．５や、０．６≦ｂ≦０．８、０．２≦ｃ≦０．４、更には０．７≦ｂ≦０．８、０．２≦ｃ≦０．３を例示できる。
As the range of b and c in formulas (1) and (1-1), 0.5 ≤ b ≤ 0.9, 0.1 ≤ c ≤ 0.5, 0.6 ≤ b ≤ 0.8, 0 Examples include 0.2≦c≦0.4, 0.7≦b≦0.8, and 0.2≦c≦0.3.
本発明の正極活物質において、タングステンはメタルサイトに置換されることが好ましい。メタルサイトを構成する金属であるマンガンおよび鉄に対してタングステンの量が過大であれば、正極活物質の容量が低下し、当該タングステンの量が過少であれば正極活物質の耐久性向上効果が低下する。したがって、タングステンの量には好ましい範囲が存在する。
In the positive electrode active material of the present invention, tungsten is preferably replaced with a metal site. If the amount of tungsten is too large relative to manganese and iron, which are metals constituting the metal site, the capacity of the positive electrode active material will decrease, and if the amount of tungsten is too small, the durability of the positive electrode active material will be improved. descend. Therefore, there is a preferred range for the amount of tungsten.
具体的には、本発明の正極活物質におけるタングステンの量は、式（１）および（１－１）におけるｄが０．０５／１００～２．５／１００の範囲内となる量であるのが好ましい。
換言すると、タングステンの量は、メタルサイトを構成し得るリチウム以外の金属元素、すなわち、マンガン元素、鉄元素、タングステン元素およびＤ1元素の合計を１００原子％としたときに、０．０５～２．５原子％の範囲内となる量であるのが好ましい。 Specifically, the amount of tungsten in the positive electrode active material of the present invention is such that d in formulas (1) and (1-1) is in the range of 0.05/100 to 2.5/100. is preferred.
In other words, the amount of tungsten is 0.05 to 2 when the total of metal elements other than lithium that can form metal sites, that is, manganese element, iron element, tungsten element and D1 element is 100 atomic %. An amount within the range of 0.5 atomic percent is preferred.
換言すると、タングステンの量は、メタルサイトを構成し得るリチウム以外の金属元素、すなわち、マンガン元素、鉄元素、タングステン元素およびＤ1元素の合計を１００原子％としたときに、０．０５～２．５原子％の範囲内となる量であるのが好ましい。 Specifically, the amount of tungsten in the positive electrode active material of the present invention is such that d in formulas (1) and (1-1) is in the range of 0.05/100 to 2.5/100. is preferred.
In other words, the amount of tungsten is 0.05 to 2 when the total of metal elements other than lithium that can form metal sites, that is, manganese element, iron element, tungsten element and D1 element is 100 atomic %. An amount within the range of 0.5 atomic percent is preferred.
上記ｄのより好ましい範囲として、０．０５／１００～１．５／１００の範囲内、０．０５／１００～１．０／１００の範囲内、０．１／１００～０．５／１００の範囲内、０．１／１００～０．３／１００の範囲内を例示できる。
As a more preferable range of the above d, in the range of 0.05/100 to 1.5/100, in the range of 0.05/100 to 1.0/100, 0.1/100 to 0.5/100 Within the range, the range of 0.1/100 to 0.3/100 can be exemplified.
ところで、本発明の発明者は、リチウムイオン二次電池の充放電に伴って正極活物質に含まれる遷移金属が溶出することが、当該正極活物質の劣化の他の一因となり得るという着想を得た。
By the way, the inventors of the present invention came up with the idea that the elution of the transition metal contained in the positive electrode active material as the lithium ion secondary battery is charged and discharged can be another cause of deterioration of the positive electrode active material. Obtained.
オリビン構造を有するリン酸鉄マンガンリチウム系の正極活物質には、遷移金属として鉄やマンガンが含まれる。これらの遷移金属は、オリビン構造を有するリン酸鉄マンガンリチウム系の正極活物質において、酸素と結合した状態で存在すると考えられている。
ここで、電解液中のフッ素は、酸素よりも電気陰性度が高いために、遷移金属である鉄やマンガンを酸素から奪い得る。これにより、オリビン構造を有するリン酸鉄マンガンリチウム系の正極活物質から鉄やマンガンが溶出する可能性があり、その結果、正極活物質の容量が劣化する可能性がある。なお、正極活物質から溶出した鉄やマンガンは負極に析出してリチウムと不可逆的に結合し、その結果、正極活物質が劣化し、その容量が低下すると考えられる。 The iron-manganese-lithium phosphate-based positive electrode active material having an olivine structure contains iron and manganese as transition metals. These transition metals are believed to exist in a state of being bound to oxygen in the iron-manganese-lithium phosphate-based positive electrode active material having an olivine structure.
Here, since fluorine in the electrolytic solution has a higher electronegativity than oxygen, it can deprive oxygen of transition metals such as iron and manganese. As a result, iron and manganese may be eluted from the iron-manganese-lithium phosphate-based positive electrode active material having an olivine structure, and as a result, the capacity of the positive electrode active material may deteriorate. Note that iron and manganese eluted from the positive electrode active material are deposited on the negative electrode and irreversibly combined with lithium. As a result, it is thought that the positive electrode active material deteriorates and its capacity decreases.
ここで、電解液中のフッ素は、酸素よりも電気陰性度が高いために、遷移金属である鉄やマンガンを酸素から奪い得る。これにより、オリビン構造を有するリン酸鉄マンガンリチウム系の正極活物質から鉄やマンガンが溶出する可能性があり、その結果、正極活物質の容量が劣化する可能性がある。なお、正極活物質から溶出した鉄やマンガンは負極に析出してリチウムと不可逆的に結合し、その結果、正極活物質が劣化し、その容量が低下すると考えられる。 The iron-manganese-lithium phosphate-based positive electrode active material having an olivine structure contains iron and manganese as transition metals. These transition metals are believed to exist in a state of being bound to oxygen in the iron-manganese-lithium phosphate-based positive electrode active material having an olivine structure.
Here, since fluorine in the electrolytic solution has a higher electronegativity than oxygen, it can deprive oxygen of transition metals such as iron and manganese. As a result, iron and manganese may be eluted from the iron-manganese-lithium phosphate-based positive electrode active material having an olivine structure, and as a result, the capacity of the positive electrode active material may deteriorate. Note that iron and manganese eluted from the positive electrode active material are deposited on the negative electrode and irreversibly combined with lithium. As a result, it is thought that the positive electrode active material deteriorates and its capacity decreases.
本発明の発明者は、オリビン構造を有するリン酸鉄マンガンリチウム系の正極活物質において、鉄やマンガンの一部を、酸素と強く結合し得る金属元素で置換することを志向した。具体的には、上記式（１）および（１－１）におけるＤ1として、酸素と強く結合し得る金属元素を用いる。このことにより、上記した鉄やマンガンの溶出を抑制することが可能になり、ひいては、正極活物質の容量劣化を抑制することが可能になる。
The inventors of the present invention intended to replace part of iron and manganese with a metal element capable of strongly bonding with oxygen in an iron-manganese-lithium phosphate-based positive electrode active material having an olivine structure. Specifically, a metal element capable of strongly bonding with oxygen is used as D 1 in the above formulas (1) and (1-1). This makes it possible to suppress the above-described elution of iron and manganese, and thus to suppress deterioration of the capacity of the positive electrode active material.
当該Ｄ1の元素としては、具体的には、マグネシウム、コバルト、ニッケル、ニオブ、バナジウム、テルル、アルミニウム、チタン、亜鉛、銅、ビスマス、クロム、亜鉛、カルシウムまたはジルコニウムを例示できる。このうち、クロム、チタン、バナジウムは、Ｄ1の元素として特に好ましい。本発明の正極活物質は、Ｄ1として、これらの元素を単独で含んでも良いし、これらの元素を複数含んでも良い。
Specific examples of the D 1 element include magnesium, cobalt, nickel, niobium, vanadium, tellurium, aluminum, titanium, zinc, copper, bismuth, chromium, zinc, calcium, and zirconium. Among them, chromium, titanium, and vanadium are particularly preferable as elements of D 1 . The positive electrode active material of the present invention may contain one of these elements as D 1 , or may contain a plurality of these elements.
本発明の正極活物質において、Ｄ1の元素がメタルサイトに置換される場合、メタルサイトを構成する金属であるマンガンおよび鉄に対してＤ1の元素の量が過大であれば、正極活物質の容量が低下し、当該Ｄ1の元素の量が過少であれば正極活物質の耐久性向上効果が低下する。したがって、Ｄ1の元素の量にもまた好ましい範囲が存在する。
In the positive electrode active material of the present invention, when the D 1 element is substituted with a metal site, if the amount of the D 1 element is excessive relative to manganese and iron that constitute the metal site, the positive electrode active material If the amount of the D 1 element is too small, the effect of improving the durability of the positive electrode active material is reduced. Therefore, there is also a preferred range for the amount of elements in D 1 .
具体的には、本発明の正極活物質におけるＤ1の元素の量は、式（１）および（１－１）におけるｅが０．５／１００～１０／１００の範囲内となる量であるのが好ましい。
換言すると、Ｄ1の元素の量は、メタルサイトを構成し得るリチウム以外の金属元素、すなわち、マンガン元素、鉄元素、タングステン元素およびＤ1元素の合計を１００原子％としたときに、０．５～１０原子％の範囲内となる量であるのが好ましい。 Specifically, the amount of element D 1 in the positive electrode active material of the present invention is such that e in formulas (1) and (1-1) falls within the range of 0.5/100 to 10/100. is preferred.
In other words, the amount of the element D 1 is 0.00% when the total of the metal elements other than lithium that can form the metal sites, that is, the manganese element, the iron element, the tungsten element and the D 1 element is 100 atomic %. The amount is preferably within the range of 5 to 10 atomic %.
換言すると、Ｄ1の元素の量は、メタルサイトを構成し得るリチウム以外の金属元素、すなわち、マンガン元素、鉄元素、タングステン元素およびＤ1元素の合計を１００原子％としたときに、０．５～１０原子％の範囲内となる量であるのが好ましい。 Specifically, the amount of element D 1 in the positive electrode active material of the present invention is such that e in formulas (1) and (1-1) falls within the range of 0.5/100 to 10/100. is preferred.
In other words, the amount of the element D 1 is 0.00% when the total of the metal elements other than lithium that can form the metal sites, that is, the manganese element, the iron element, the tungsten element and the D 1 element is 100 atomic %. The amount is preferably within the range of 5 to 10 atomic %.
上記ｅのより好ましい範囲として、１／１００～５／１００の範囲内、２／１００～４/１００の範囲内を例示できる。
As a more preferable range of e, a range of 1/100 to 5/100 and a range of 2/100 to 4/100 can be exemplified.
Ｄ1元素がクロムを含む場合、正極活物質におけるクロム量の好ましい範囲として、メタルサイトを構成し得るリチウム以外の金属元素の合計を１００原子％としたときに０．１～１０原子％の範囲内、1～２．５原子％の範囲内または２～４原子％の範囲内を挙げ得る。
When the D1 element contains chromium, the preferred range of the amount of chromium in the positive electrode active material is 0.1 to 10 atomic % when the total of metal elements other than lithium that can constitute the metal site is 100 atomic %. Among them, the range of 1 to 2.5 atomic % or the range of 2 to 4 atomic % can be mentioned.
Ｄ1元素がチタンを含む場合、正極活物質におけるチタン量の好ましい範囲として、メタルサイトを構成し得るリチウム以外の金属元素の合計を１００原子％としたときに０．５～１０原子％の範囲内、１～１０原子％の範囲内、１．５～６原子％の範囲内、１．５～４原子％の範囲内を挙げ得る。
When the D1 element contains titanium, the preferable range of the amount of titanium in the positive electrode active material is 0.5 to 10 atomic % when the total of metal elements other than lithium that can constitute the metal site is 100 atomic %. Among them, within the range of 1 to 10 atomic %, within the range of 1.5 to 6 atomic %, and within the range of 1.5 to 4 atomic %.
Ｄ1元素がバナジウムを含む場合、正極活物質におけるバナジウム量の好ましい範囲として、メタルサイトを構成し得るリチウム以外の金属元素の合計を１００原子％としたときに０原子％以上１０原子％以下、０原子％以上３原子％以下、０．５原子％以上２．９原子％以下、０．８原子％以上２．９原子％以下、１．０原子％以上２．９原子％以下、１．５原子％以上２．８原子％以下の各範囲を例示できる。
When the D1 element contains vanadium, the preferable range of the amount of vanadium in the positive electrode active material is 0 atomic % or more and 10 atomic % or less when the total of metal elements other than lithium that can constitute the metal site is 100 atomic %, 0 atomic % or more and 3 atomic % or less, 0.5 atomic % or more and 2.9 atomic % or less, 0.8 atomic % or more and 2.9 atomic % or less, 1.0 atomic % or more and 2.9 atomic % or less; Each range of 5 atomic % or more and 2.8 atomic % or less can be exemplified.
さらに、Ｄ1元素がマグネシウムを含む場合、正極活物質におけるマグネシウム量の好ましい範囲として、メタルサイトを構成し得るリチウム以外の金属元素の合計を１００原子％としたときに０．５～１０原子％の範囲内、１～１０原子％の範囲内、１～８原子％の範囲内、２～５原子％の範囲内を挙げ得る。
Furthermore, when the D1 element contains magnesium, the preferable range of the amount of magnesium in the positive electrode active material is 0.5 to 10 atomic % when the total of metal elements other than lithium that can constitute the metal site is 100 atomic %. , 1 to 10 atomic %, 1 to 8 atomic %, and 2 to 5 atomic %.
さらに、本発明の発明者は、メタルサイトがタングステンで置換される場合には、結晶中性、すなわち、結晶の電気的中性が崩され、その結果、正極活物質の容量劣化が生じ得るという着想を得た。
つまり、メタルサイトを構成する鉄がタングステンで置換される場合、鉄の価数（２価）とタングステンの価数（４価）との間には２の差があるために、正極活物質を構成する原子価が釣り合わなくなる。これにより、正極活物質の結晶中性が維持されなくなり、１価のリチウムが当該結晶から欠損し易くなると考えられる。そしてその結果、正極容量が低下する虞がある。 Furthermore, the inventors of the present invention believe that when the metal sites are replaced with tungsten, the crystal neutrality, that is, the electrical neutrality of the crystal is broken, and as a result, the capacity of the positive electrode active material may deteriorate. Got an idea.
That is, when the iron constituting the metal site is replaced with tungsten, there is a difference of 2 between the valence of iron (divalent) and the valence of tungsten (tetravalent), so the positive electrode active material is The constituent valences are out of balance. As a result, the crystal neutrality of the positive electrode active material is no longer maintained, and monovalent lithium is likely to be lost from the crystal. As a result, the positive electrode capacity may decrease.
つまり、メタルサイトを構成する鉄がタングステンで置換される場合、鉄の価数（２価）とタングステンの価数（４価）との間には２の差があるために、正極活物質を構成する原子価が釣り合わなくなる。これにより、正極活物質の結晶中性が維持されなくなり、１価のリチウムが当該結晶から欠損し易くなると考えられる。そしてその結果、正極容量が低下する虞がある。 Furthermore, the inventors of the present invention believe that when the metal sites are replaced with tungsten, the crystal neutrality, that is, the electrical neutrality of the crystal is broken, and as a result, the capacity of the positive electrode active material may deteriorate. Got an idea.
That is, when the iron constituting the metal site is replaced with tungsten, there is a difference of 2 between the valence of iron (divalent) and the valence of tungsten (tetravalent), so the positive electrode active material is The constituent valences are out of balance. As a result, the crystal neutrality of the positive electrode active material is no longer maintained, and monovalent lithium is likely to be lost from the crystal. As a result, the positive electrode capacity may decrease.
本発明の発明者は、鉄とタングステンとの価数の差を補い得る元素によって正極活物質のリンサイトを置換することで、上記した正極活物質を構成する原子価を釣り合わせることができると考えた。こうすることで、正極活物質の結晶中性を維持でき、上記したリチウムの欠損を抑制でき、ひいては正極容量の低下を抑制することが可能である。
The inventor of the present invention believes that by substituting the phosphorus site of the positive electrode active material with an element capable of compensating for the difference in valence between iron and tungsten, the valences constituting the positive electrode active material can be balanced. Thought. By doing so, the crystal neutrality of the positive electrode active material can be maintained, the above-described lithium deficiency can be suppressed, and a decrease in the positive electrode capacity can be suppressed.
すなわち、本発明の正極活物質は、上記式（１）および（１－１）におけるＤ2元素として、第１３族から第１６族の元素かつ価数が４以下のものを含有することが好ましい。これにより、本発明の正極活物質にタングステンを含みつつ、本発明の正極活物質の結晶中性を維持することが可能である。換言すると、本発明の正極活物質においては、メタルサイトをタングステンで置換すると同時にリンサイトをＤ2元素で置換するのが好ましい。
なお、当該Ｄ2元素はケイ素またはホウ素であるのが好ましい。 That is, the positive electrode active material of the present invention preferably contains an element of Groups 13 to 16 with a valence of 4 or less as the element D2 in the above formulas (1) and (1-1). . Thereby, it is possible to maintain the crystal neutrality of the positive electrode active material of the present invention while containing tungsten in the positive electrode active material of the present invention. In other words, in the positive electrode active material of the present invention, it is preferable to replace the metal site with tungsten and at the same time replace the phosphorus site with the D2 element.
The D2 element is preferably silicon or boron.
なお、当該Ｄ2元素はケイ素またはホウ素であるのが好ましい。 That is, the positive electrode active material of the present invention preferably contains an element of Groups 13 to 16 with a valence of 4 or less as the element D2 in the above formulas (1) and (1-1). . Thereby, it is possible to maintain the crystal neutrality of the positive electrode active material of the present invention while containing tungsten in the positive electrode active material of the present invention. In other words, in the positive electrode active material of the present invention, it is preferable to replace the metal site with tungsten and at the same time replace the phosphorus site with the D2 element.
The D2 element is preferably silicon or boron.
本発明の正極活物質におけるＤ2元素の量ｆは、タングステンの量ｄに応じて、正極活物資を構成する原子価が釣り合うように適宜適切に決定すれば良い。Ｄ2元素の価数とリンの価数との差をｚとすると、タングステンの量ｄに対するＤ2元素の量ｆはｆ＝２ｄ／ｚと定義される。当該ｆの好ましい範囲としては、０．７５×（２×ｄ／ｚ）≦ｆ≦１．２５×（２×ｄ／ｚ）を例示できる。当該ｆのより好ましい範囲は０．９×（２×ｄ／ｚ）≦ｆ≦１．１×（２×ｄ／ｚ）である。
なお、例えばＤ2元素がケイ素であれば、リンが＋５価、ケイ素が＋４価であることからｚ＝１となり、Ｄ2元素の量ｆ＝２ｄとなる。この場合、上記の０．７５×（２×ｄ／ｚ）≦ｆ≦１．２５×（２×ｄ／ｚ）より、１．５ｄ≦ｆ≦２．５ｄの範囲が得られ、０．９×（２×ｄ／ｚ）≦ｆ≦１．１×（２×ｄ／ｚ）より１．８ｄ≦ｆ≦２．２ｄの範囲が得られる。この場合、Ｄ2元素の量ｆはタングステンの量ｄの２倍であるのが特に好ましい。 The amount f of the D2 element in the positive electrode active material of the present invention may be appropriately determined according to the amount d of tungsten so that the atomic valences constituting the positive electrode active material are balanced. If the difference between the valence of the D2 element and the valence of phosphorus is z, the amount f of the D2 element with respect to the amount of tungsten d is defined as f = 2d /z. A preferable range of f is 0.75×(2×d/z)≦f≦1.25×(2×d/z). A more preferable range of f is 0.9×(2×d/z)≦f≦1.1×(2×d/z).
For example, if the D2 element is silicon, since phosphorus has a valence of +5 and silicon has a valence of +4, z= 1 and the amount of the D2 element f= 2d . In this case, from the above 0.75×(2×d/z)≦f≦1.25×(2×d/z), a range of 1.5d≦f≦2.5d is obtained, and 0.9 A range of 1.8d≦f≦2.2d is obtained from x(2×d/z)≦f≦1.1×(2×d/z). In this case, it is particularly preferred that the amount f of the D2 element is twice the amount d of tungsten.
なお、例えばＤ2元素がケイ素であれば、リンが＋５価、ケイ素が＋４価であることからｚ＝１となり、Ｄ2元素の量ｆ＝２ｄとなる。この場合、上記の０．７５×（２×ｄ／ｚ）≦ｆ≦１．２５×（２×ｄ／ｚ）より、１．５ｄ≦ｆ≦２．５ｄの範囲が得られ、０．９×（２×ｄ／ｚ）≦ｆ≦１．１×（２×ｄ／ｚ）より１．８ｄ≦ｆ≦２．２ｄの範囲が得られる。この場合、Ｄ2元素の量ｆはタングステンの量ｄの２倍であるのが特に好ましい。 The amount f of the D2 element in the positive electrode active material of the present invention may be appropriately determined according to the amount d of tungsten so that the atomic valences constituting the positive electrode active material are balanced. If the difference between the valence of the D2 element and the valence of phosphorus is z, the amount f of the D2 element with respect to the amount of tungsten d is defined as f = 2d /z. A preferable range of f is 0.75×(2×d/z)≦f≦1.25×(2×d/z). A more preferable range of f is 0.9×(2×d/z)≦f≦1.1×(2×d/z).
For example, if the D2 element is silicon, since phosphorus has a valence of +5 and silicon has a valence of +4, z= 1 and the amount of the D2 element f= 2d . In this case, from the above 0.75×(2×d/z)≦f≦1.25×(2×d/z), a range of 1.5d≦f≦2.5d is obtained, and 0.9 A range of 1.8d≦f≦2.2d is obtained from x(2×d/z)≦f≦1.1×(2×d/z). In this case, it is particularly preferred that the amount f of the D2 element is twice the amount d of tungsten.
既述したように、本発明の正極活物質がタングステンを含むことは、Ｘ線光電分光法（所謂ＸＰＳまたはＥＳＣＡ）により確認できる。
ここで、本発明の正極活物質において、タングステンの一部は、結晶の内部に存在すると推測される。当該タングステンは、酸素と結合し、主としてＷＯ2として存在すると推測される。このため、本発明の正極活物質をＸ線光電分光法により分析すると、当該ＷＯ2に由来するピークが検出される。 As described above, it can be confirmed by X-ray photoelectric spectroscopy (so-called XPS or ESCA) that the positive electrode active material of the present invention contains tungsten.
Here, in the positive electrode active material of the present invention, part of tungsten is presumed to exist inside the crystal. The tungsten is presumed to be present primarily as WO2 , combined with oxygen. Therefore, when the positive electrode active material of the present invention is analyzed by X-ray photoelectric spectroscopy, a peak derived from the WO 2 is detected.
ここで、本発明の正極活物質において、タングステンの一部は、結晶の内部に存在すると推測される。当該タングステンは、酸素と結合し、主としてＷＯ2として存在すると推測される。このため、本発明の正極活物質をＸ線光電分光法により分析すると、当該ＷＯ2に由来するピークが検出される。 As described above, it can be confirmed by X-ray photoelectric spectroscopy (so-called XPS or ESCA) that the positive electrode active material of the present invention contains tungsten.
Here, in the positive electrode active material of the present invention, part of tungsten is presumed to exist inside the crystal. The tungsten is presumed to be present primarily as WO2 , combined with oxygen. Therefore, when the positive electrode active material of the present invention is analyzed by X-ray photoelectric spectroscopy, a peak derived from the WO 2 is detected.
タングステンの他の一部は、ＬｉＭｎa1Ｆｅb1ＰＯ4の結晶粒界に析出すると考えられる。当該タングステンは、酸素と結合し、主としてＷＯ3として存在すると推測される。
当該ＷＯ3はフッ化水素酸への溶解度が低いために、本発明の正極活物質は、全体として、結晶粒界に存在するタングステンによってフッ化水素から保護されると考えられる。 Another portion of tungsten is believed to precipitate at the grain boundaries of LiMn a1 Fe b1 PO 4 . The tungsten is presumed to be present primarily as WO3 , combined with oxygen.
Since WO 3 has a low solubility in hydrofluoric acid, it is believed that the positive electrode active material of the present invention as a whole is protected from hydrogen fluoride by tungsten present at the grain boundaries.
当該ＷＯ3はフッ化水素酸への溶解度が低いために、本発明の正極活物質は、全体として、結晶粒界に存在するタングステンによってフッ化水素から保護されると考えられる。 Another portion of tungsten is believed to precipitate at the grain boundaries of LiMn a1 Fe b1 PO 4 . The tungsten is presumed to be present primarily as WO3 , combined with oxygen.
Since WO 3 has a low solubility in hydrofluoric acid, it is believed that the positive electrode active material of the present invention as a whole is protected from hydrogen fluoride by tungsten present at the grain boundaries.
このため、本発明の正極活物質をＸ線光電分光法により分析すると、ＷＯ2に由来するピークに加えて、ＷＯ3に由来するピークも検出されると考えられる。結晶粒界に析出するタングステンは正極活物質をフッ化水素から保護するのに寄与すると考えられるため、本発明の正極活物質からはＷＯ3に由来するピークも検出されることが好ましい。
なお、ｂ、ｃ、ｄ、ｅ、ｆ、ｇの好ましい関係として、ｂ＋ｃ＋ｄ＋ｅ＝０．８～１．２かつｆ＋ｇ＝０．８～１．２、ｂ＋ｃ＋ｄ＋ｅ＝１かつｆ＋ｇ＝１、を例示できる。 Therefore, when the positive electrode active material of the present invention is analyzed by X-ray photoelectric spectroscopy, it is considered that a peak derived from WO 3 will be detected in addition to the peak derived from WO 2 . Since it is believed that tungsten precipitated at grain boundaries contributes to protecting the positive electrode active material from hydrogen fluoride, it is preferable that a peak derived from WO 3 is also detected from the positive electrode active material of the present invention.
Preferred relationships among b, c, d, e, f, and g are b+c+d+e=0.8 to 1.2 and f+g=0.8 to 1.2, and b+c+d+e=1 and f+g=1.
なお、ｂ、ｃ、ｄ、ｅ、ｆ、ｇの好ましい関係として、ｂ＋ｃ＋ｄ＋ｅ＝０．８～１．２かつｆ＋ｇ＝０．８～１．２、ｂ＋ｃ＋ｄ＋ｅ＝１かつｆ＋ｇ＝１、を例示できる。 Therefore, when the positive electrode active material of the present invention is analyzed by X-ray photoelectric spectroscopy, it is considered that a peak derived from WO 3 will be detected in addition to the peak derived from WO 2 . Since it is believed that tungsten precipitated at grain boundaries contributes to protecting the positive electrode active material from hydrogen fluoride, it is preferable that a peak derived from WO 3 is also detected from the positive electrode active material of the present invention.
Preferred relationships among b, c, d, e, f, and g are b+c+d+e=0.8 to 1.2 and f+g=0.8 to 1.2, and b+c+d+e=1 and f+g=1.
ところで、本発明の正極活物質は、さらに、フッ素を含むのも好ましい。つまり、既述したＬｉaＭｎbＦｅcＷdＤ1
eＤ2
fＰgＦiＯh 式（１－１）におけるｉが０＜ｉであるのが好ましい。
この場合のフッ素は、上記した基本骨格であるＬｉＭｎa1Ｆｅb1ＰＯ4の酸素のサイトに置換されると推測される。何れの場合にも、上記式（１－１）におけるｈ、ｉの関係は、ｈ＞ｉかつｈ＋ｉ＝１かつであるのが好ましい。 By the way, the positive electrode active material of the present invention preferably further contains fluorine. That is, it is preferable that i in the above-mentioned Li a Mn b Fe c W d D 1 e D 2 f P g F i O h formula (1-1) satisfies 0<i.
In this case, the fluorine is presumed to be substituted at the oxygen site of LiMn a1 Fe b1 PO 4 which is the basic skeleton described above. In any case, the relationship between h and i in the above formula (1-1) is preferably h>i and h+i=1.
この場合のフッ素は、上記した基本骨格であるＬｉＭｎa1Ｆｅb1ＰＯ4の酸素のサイトに置換されると推測される。何れの場合にも、上記式（１－１）におけるｈ、ｉの関係は、ｈ＞ｉかつｈ＋ｉ＝１かつであるのが好ましい。 By the way, the positive electrode active material of the present invention preferably further contains fluorine. That is, it is preferable that i in the above-mentioned Li a Mn b Fe c W d D 1 e D 2 f P g F i O h formula (1-1) satisfies 0<i.
In this case, the fluorine is presumed to be substituted at the oxygen site of LiMn a1 Fe b1 PO 4 which is the basic skeleton described above. In any case, the relationship between h and i in the above formula (1-1) is preferably h>i and h+i=1.
後述するように、本発明の正極活物質は、フッ素を含有することで、容量、寿命および抵抗のバランスが向上すると考えられる。当該フッ素の量は、フッ素および酸素の合計を４００原子％としたときに、０．１～１０原子％の範囲内となる量であるのが好ましい。当該フッ素の量のより好ましい範囲としては、フッ素および酸素の合計を４００原子％としたときに、０．５～２０原子％、１～１０原子％、２～１０原子％、または３～８原子％となる量を例示できる。または、当該フッ素の量の好ましい範囲として、０．２～５原子％の範囲内、０．５～２原子％の範囲内を例示することもできる。
As will be described later, the positive electrode active material of the present invention is thought to improve the balance of capacity, life and resistance by containing fluorine. The amount of fluorine is preferably in the range of 0.1 to 10 atomic % when the total of fluorine and oxygen is 400 atomic %. A more preferable range of the amount of fluorine is 0.5 to 20 atomic %, 1 to 10 atomic %, 2 to 10 atomic %, or 3 to 8 atomic % when the total of fluorine and oxygen is 400 atomic % % can be exemplified. Alternatively, preferable ranges of the amount of fluorine can be exemplified as 0.2 to 5 atomic % and 0.5 to 2 atomic %.
本発明の正極活物質には、導電性向上のための炭素コート層を形成しても良い。炭素コート層を形成する場合、本発明の正極活物質は粒子状であるのが良い。
A carbon coating layer may be formed on the positive electrode active material of the present invention to improve conductivity. When forming the carbon coat layer, the positive electrode active material of the present invention is preferably in the form of particles.
本発明の正極活物質の形状は特に制限されないが、平均粒子径でいうと、１００μｍ以下が好ましく、０．０１μｍ以上１０μｍ以下がより好ましく、１μｍ以上１０μｍ以下が最も好ましい。
なお、本明細書において特に説明のない場合には、平均粒子径とは、一般的なレーザー回折式粒度分布測定装置で計測した場合のＤ５０の値を意味する。
本発明の正極活物質を製造する方法を以下に説明する。 Although the shape of the positive electrode active material of the present invention is not particularly limited, the average particle size is preferably 100 μm or less, more preferably 0.01 μm or more and 10 μm or less, and most preferably 1 μm or more and 10 μm or less.
In this specification, unless otherwise specified, the average particle size means the D50 value measured with a general laser diffraction particle size distribution analyzer.
A method for producing the positive electrode active material of the present invention will be described below.
なお、本明細書において特に説明のない場合には、平均粒子径とは、一般的なレーザー回折式粒度分布測定装置で計測した場合のＤ５０の値を意味する。
本発明の正極活物質を製造する方法を以下に説明する。 Although the shape of the positive electrode active material of the present invention is not particularly limited, the average particle size is preferably 100 μm or less, more preferably 0.01 μm or more and 10 μm or less, and most preferably 1 μm or more and 10 μm or less.
In this specification, unless otherwise specified, the average particle size means the D50 value measured with a general laser diffraction particle size distribution analyzer.
A method for producing the positive electrode active material of the present invention will be described below.
本発明の正極活物質は、既述したように、オリビン構造を有するリン酸鉄マンガンリチウム系の正極活物質と同様の基本骨格を有する。したがって、本発明の正極活物質を製造する方法としては、オリビン構造を有するリン酸鉄マンガンリチウム系の正極活物質すなわちＬｉＭｎa1Ｆｅb1ＰＯ4（ａ１、ｂ１は、ａ１＋ｂ１＝１、０＜ａ１＜１、０＜ｂ１＜１を満足する。）の製造方法や、オリビン構造を有するリン酸鉄リチウムすなわちＬｉＦｅb2Ｍb3ＰＯ4（ＭはＭｎ、Ｃｏ、Ｎｉ、Ｃｕ、Ｍｇ、Ｚｎ、Ｖ、Ｃａ、Ｓｒ、Ｂａ、Ｔｉ、Ａｌ、Ｓｉ、Ｂ、Ｔｅ、Ｍｏ、Ｂｉ、Ｎｂ、Ｃｒ、Ｚｒから選ばれる少なくとも１の元素である。ｂ２、ｂ３は０．６≦ｂ２+ｂ３≦１．１を満足する。）、またはオリビン構造を有するＬｉＦｅＰＯ4の製造方法に準拠した方法を採用できる。
具体的には、上記したＬｉＭｎa1Ｆｅb1ＰＯ4、ＬｉＦｅb2Ｍb3ＰＯ4、ＬｉＦｅＰＯ4の製造方法に基づき、その原料がリチウム源、マンガン源、鉄源、タングステン源、リン源、酸素源、および、必要に応じてＤ1源、Ｄ2源、フッ素源を適切な元素比で含むようにして、正極活物質を製造すれば良い。 As described above, the positive electrode active material of the present invention has a basic skeleton similar to that of the iron-manganese-lithium-phosphate-based positive electrode active material having an olivine structure. Therefore, as a method for producing the positive electrode active material of the present invention, an iron manganese phosphate lithium-based positive electrode active material having an olivine structure, that is, LiMn a1 Fe b1 PO 4 (a1 and b1 are a1+b1=1, 0<a1< 1, 0<b1<1.) and lithium iron phosphate having an olivine structure, namely LiFe b2 M b3 PO 4 (M is Mn, Co, Ni, Cu, Mg, Zn, V, Ca , Sr, Ba, Ti, Al, Si, B, Te, Mo, Bi, Nb, Cr, and Zr, and b2 and b3 satisfy 0.6≤b2+b3≤1.1. satisfying.), or a method conforming to the method for producing LiFePO 4 having an olivine structure can be adopted.
Specifically, based on the method for producing LiMn a1 Fe b1 PO 4 , LiFe b2 M b3 PO 4 and LiFePO 4 described above, the raw materials are a lithium source, a manganese source, an iron source, a tungsten source, a phosphorus source, an oxygen source, And, if necessary, the positive electrode active material may be produced by including a D 1 source, a D 2 source, and a fluorine source in an appropriate elemental ratio.
具体的には、上記したＬｉＭｎa1Ｆｅb1ＰＯ4、ＬｉＦｅb2Ｍb3ＰＯ4、ＬｉＦｅＰＯ4の製造方法に基づき、その原料がリチウム源、マンガン源、鉄源、タングステン源、リン源、酸素源、および、必要に応じてＤ1源、Ｄ2源、フッ素源を適切な元素比で含むようにして、正極活物質を製造すれば良い。 As described above, the positive electrode active material of the present invention has a basic skeleton similar to that of the iron-manganese-lithium-phosphate-based positive electrode active material having an olivine structure. Therefore, as a method for producing the positive electrode active material of the present invention, an iron manganese phosphate lithium-based positive electrode active material having an olivine structure, that is, LiMn a1 Fe b1 PO 4 (a1 and b1 are a1+b1=1, 0<a1< 1, 0<b1<1.) and lithium iron phosphate having an olivine structure, namely LiFe b2 M b3 PO 4 (M is Mn, Co, Ni, Cu, Mg, Zn, V, Ca , Sr, Ba, Ti, Al, Si, B, Te, Mo, Bi, Nb, Cr, and Zr, and b2 and b3 satisfy 0.6≤b2+b3≤1.1. satisfying.), or a method conforming to the method for producing LiFePO 4 having an olivine structure can be adopted.
Specifically, based on the method for producing LiMn a1 Fe b1 PO 4 , LiFe b2 M b3 PO 4 and LiFePO 4 described above, the raw materials are a lithium source, a manganese source, an iron source, a tungsten source, a phosphorus source, an oxygen source, And, if necessary, the positive electrode active material may be produced by including a D 1 source, a D 2 source, and a fluorine source in an appropriate elemental ratio.
オリビン構造の正極活物質の製造方法として、以下の文献などに記載された方法を参考に製造してもよい。
As a method for manufacturing a positive electrode active material having an olivine structure, the method described in the following documents may be used as a reference.
特開平１１－２５９８３号公報
特開２００２－１９８０５０号公報
特表２００５－５２２００９号公報
特開２０１２－７９５５４号公報 JP-A-11-25983 JP-A-2002-198050 JP-A-2005-522009 JP-A-2012-79554
特開２００２－１９８０５０号公報
特表２００５－５２２００９号公報
特開２０１２－７９５５４号公報 JP-A-11-25983 JP-A-2002-198050 JP-A-2005-522009 JP-A-2012-79554
ここで、本発明の正極活物質の製造方法は、水溶液中で行うのが好ましい。このため、タングステン源は水に可溶であるのが好ましい。そして、本発明の正極活物質の製造方法においては、タングステン源たるタングステン化合物を水に可溶な状態にする工程を有するのが好ましい。
具体的には、本発明の正極活物質の製造方法は、タングステン化合物を還元剤により還元する工程を有するのが好ましい。当該方法を本発明の製造方法と称する。
本発明の製造方法において、タングステン化合物を還元剤により還元する工程は、本発明の正極活物質を合成するのに先立って行っても良いし、本発明の正極活物質を合成する際に同時に行っても良い。 Here, it is preferable to carry out the method for producing the positive electrode active material of the present invention in an aqueous solution. For this reason, the tungsten source is preferably soluble in water. The method for producing a positive electrode active material of the present invention preferably includes a step of making the tungsten compound, which is the source of tungsten, soluble in water.
Specifically, the method for producing a positive electrode active material of the present invention preferably includes a step of reducing the tungsten compound with a reducing agent. This method is called the manufacturing method of the present invention.
In the production method of the present invention, the step of reducing the tungsten compound with a reducing agent may be performed prior to synthesizing the positive electrode active material of the present invention, or may be performed simultaneously with synthesizing the positive electrode active material of the present invention. can be
具体的には、本発明の正極活物質の製造方法は、タングステン化合物を還元剤により還元する工程を有するのが好ましい。当該方法を本発明の製造方法と称する。
本発明の製造方法において、タングステン化合物を還元剤により還元する工程は、本発明の正極活物質を合成するのに先立って行っても良いし、本発明の正極活物質を合成する際に同時に行っても良い。 Here, it is preferable to carry out the method for producing the positive electrode active material of the present invention in an aqueous solution. For this reason, the tungsten source is preferably soluble in water. The method for producing a positive electrode active material of the present invention preferably includes a step of making the tungsten compound, which is the source of tungsten, soluble in water.
Specifically, the method for producing a positive electrode active material of the present invention preferably includes a step of reducing the tungsten compound with a reducing agent. This method is called the manufacturing method of the present invention.
In the production method of the present invention, the step of reducing the tungsten compound with a reducing agent may be performed prior to synthesizing the positive electrode active material of the present invention, or may be performed simultaneously with synthesizing the positive electrode active material of the present invention. can be
つまり、本発明の製造方法の一態様として、
タングステン化合物を還元剤により還元し、その反応生成物を得る工程、および、
当該反応生成物と正極活物質用のその他の原料、すなわち、リチウム源、マンガン源、鉄源、リン源および水を加熱し反応させる工程、を有する製造方法を例示できる。反応させる工程では、必要に応じて、Ｄ1源、Ｄ2源またはフッ素源を加えても良い。
または、本発明の製造方法の他の一態様として、
タングステン化合物、還元剤、リチウム源、マンガン源、鉄源、リン源および水を加熱し反応させる工程、を有する製造方法を例示できる。この場合にも、反応させる工程では、必要に応じて、Ｄ1源、Ｄ2源またはフッ素源を加えても良い。この場合、反応系内においてタングステン化合物と還元剤との反応生成物が生じ、当該反応系内でタングステン化合物と還元剤との反応生成物と、その他の原料とが共存する。 That is, as one aspect of the production method of the present invention,
reducing a tungsten compound with a reducing agent to obtain a reaction product thereof; and
An example of a production method includes heating and reacting the reaction product and other raw materials for the positive electrode active material, ie, a lithium source, a manganese source, an iron source, a phosphorus source, and water. In the reacting step, a D 1 source, a D 2 source, or a fluorine source may be added, if desired.
Alternatively, as another aspect of the production method of the present invention,
A production method comprising heating and reacting a tungsten compound, a reducing agent, a lithium source, a manganese source, an iron source, a phosphorus source and water can be exemplified. Also in this case, a D 1 source, a D 2 source, or a fluorine source may be added in the reacting step, if desired. In this case, a reaction product of the tungsten compound and the reducing agent is generated in the reaction system, and the reaction product of the tungsten compound and the reducing agent and other raw materials coexist in the reaction system.
タングステン化合物を還元剤により還元し、その反応生成物を得る工程、および、
当該反応生成物と正極活物質用のその他の原料、すなわち、リチウム源、マンガン源、鉄源、リン源および水を加熱し反応させる工程、を有する製造方法を例示できる。反応させる工程では、必要に応じて、Ｄ1源、Ｄ2源またはフッ素源を加えても良い。
または、本発明の製造方法の他の一態様として、
タングステン化合物、還元剤、リチウム源、マンガン源、鉄源、リン源および水を加熱し反応させる工程、を有する製造方法を例示できる。この場合にも、反応させる工程では、必要に応じて、Ｄ1源、Ｄ2源またはフッ素源を加えても良い。この場合、反応系内においてタングステン化合物と還元剤との反応生成物が生じ、当該反応系内でタングステン化合物と還元剤との反応生成物と、その他の原料とが共存する。 That is, as one aspect of the production method of the present invention,
reducing a tungsten compound with a reducing agent to obtain a reaction product thereof; and
An example of a production method includes heating and reacting the reaction product and other raw materials for the positive electrode active material, ie, a lithium source, a manganese source, an iron source, a phosphorus source, and water. In the reacting step, a D 1 source, a D 2 source, or a fluorine source may be added, if desired.
Alternatively, as another aspect of the production method of the present invention,
A production method comprising heating and reacting a tungsten compound, a reducing agent, a lithium source, a manganese source, an iron source, a phosphorus source and water can be exemplified. Also in this case, a D 1 source, a D 2 source, or a fluorine source may be added in the reacting step, if desired. In this case, a reaction product of the tungsten compound and the reducing agent is generated in the reaction system, and the reaction product of the tungsten compound and the reducing agent and other raw materials coexist in the reaction system.
このように、何れの場合にも、反応系内には、タングステン化合物と還元剤との反応生成物と、正極活物質用のその他の原料とが共存する。これらの原料を総称して活物質原料と称する。具体的なタングステン化合物としては、タングステン酸、タングステン酸アンモニウムを例示できる。当該活物質原料はゲル状を呈するのが好ましい。
Thus, in any case, the reaction product of the tungsten compound and the reducing agent and other raw materials for the positive electrode active material coexist in the reaction system. These raw materials are collectively referred to as active material raw materials. Specific examples of tungsten compounds include tungstic acid and ammonium tungstate. The raw material for the active material preferably exhibits a gel state.
活物質原料におけるリチウム源、マンガン源、タングステン源、鉄源、リン源および、必要に応じて追加されるＤ1源、Ｄ2源、フッ素源としては、その他の元素の持ち込み量が少ないよう、酸化物または水酸化物を用いるのが好ましい。場合によっては、水酸化物をアルコキシ基で置換したアルコキシドを用いても良い。アルコキシ基の炭素数は少ない方が好ましく、炭素数３以下、２以下、または１以下であるのが良い。
As the lithium source, manganese source, tungsten source, iron source, phosphorus source, and optionally added D 1 source, D 2 source, and fluorine source in the raw material of the active material, Preference is given to using oxides or hydroxides. In some cases, an alkoxide in which a hydroxide is substituted with an alkoxy group may be used. The number of carbon atoms in the alkoxy group is preferably as small as possible, preferably 3 or less, 2 or less, or 1 or less.
還元剤としては、タングステン化合物を還元可能なものを用いれば良く、炭素数の少ないもの、または、正極活物質を合成する際に炭素がＣＯ2ガス等として反応系から消失するものが好ましい。具体的な還元剤としては、ギ酸、ヒドラジン、カテコール、ピロガロール、アスコルビン酸を例示できる。このうちギ酸またはヒドラジンは、還元剤として特に好ましい。
As the reducing agent, a substance capable of reducing the tungsten compound may be used, and a substance having a small number of carbon atoms or a substance in which carbon disappears from the reaction system as CO 2 gas or the like when synthesizing the positive electrode active material is preferable. Specific reducing agents include formic acid, hydrazine, catechol, pyrogallol, and ascorbic acid. Of these, formic acid or hydrazine is particularly preferred as the reducing agent.
本発明の正極活物質を合成する工程において、活物質原料を加熱する温度は特に問わないが、２００℃以上８００℃以下であるのが好ましく、３００℃以上７００℃以下であるのがより好ましい。
In the step of synthesizing the positive electrode active material of the present invention, the temperature for heating the raw material of the active material is not particularly limited, but it is preferably 200°C or higher and 800°C or lower, more preferably 300°C or higher and 700°C or lower.
以下、本発明の正極活物質を備える正極およびリチウムイオン二次電池について説明する。
A positive electrode and a lithium ion secondary battery comprising the positive electrode active material of the present invention will be described below.
本発明の正極活物質を備える正極は、具体的には、集電体と、集電体の表面に形成された、正極活物質を含有する正極活物質層とを備える。
A positive electrode comprising the positive electrode active material of the present invention specifically comprises a current collector and a positive electrode active material layer containing the positive electrode active material formed on the surface of the current collector.
集電体は、リチウムイオン二次電池の放電又は充電の間、電極に電流を流し続けるための化学的に不活性な電子伝導体をいう。集電体としては、銀、銅、金、アルミニウム、マグネシウム、タングステン、コバルト、亜鉛、ニッケル、鉄、白金、錫、インジウム、チタン、ルテニウム、タンタル、クロム、モリブデンから選ばれる少なくとも一種、並びにステンレス鋼などの金属材料を例示することができる。
A current collector is a chemically inactive electronic conductor that keeps current flowing through an electrode during discharging or charging of a lithium-ion secondary battery. At least one selected from silver, copper, gold, aluminum, magnesium, tungsten, cobalt, zinc, nickel, iron, platinum, tin, indium, titanium, ruthenium, tantalum, chromium, molybdenum, and stainless steel as the current collector. can be exemplified by metal materials such as
集電体は公知の保護層で被覆されていても良い。集電体の表面を公知の方法で処理したものを集電体として用いても良い。
The current collector may be covered with a known protective layer. A current collector whose surface has been treated by a known method may be used as the current collector.
集電体は箔、シート、フィルム、線状、棒状、メッシュなどの形態をとることができる。そのため、集電体として、例えば、銅箔、ニッケル箔、アルミニウム箔、ステンレス箔などの金属箔を好適に用いることができる。箔状の集電体（以下、集電箔という。）の場合は、その厚みが１μｍ～１００μｍの範囲内であることが好ましい。
The current collector can be in the form of foil, sheet, film, wire, rod, mesh, etc. Therefore, metal foils such as copper foil, nickel foil, aluminum foil, and stainless steel foil can be preferably used as the current collector. In the case of a foil-shaped current collector (hereinafter referred to as current collector foil), the thickness is preferably in the range of 1 μm to 100 μm.
オリビン構造の正極活物質は、ＬｉＣｏＯ2、ＬｉＮｉＯ2、ＬｉＮｉ1/3Ｃｏ1/3Ｍｎ1/3Ｏ2等の層状岩塩構造の正極活物質に比べて電子伝導性に乏しい。そのため、表面が粗い集電箔を用いること、具体的には、面粗さの算術平均高さＳａが０．１μｍ≦Ｓａである集電箔を用いることで、集電箔と正極活物質層間の抵抗を低減させることが好ましい。
The positive electrode active material having an olivine structure has poor electronic conductivity compared to the positive electrode active material having a layered rock salt structure such as LiCoO 2 , LiNiO 2 and LiNi 1/3 Co 1/3 Mn 1/3 O 2 . Therefore, by using a current collector foil with a rough surface, specifically, by using a current collector foil with an arithmetic mean height Sa of surface roughness of 0.1 μm≦Sa, the current collector foil and the positive electrode active material interlayer It is preferable to reduce the resistance of
面粗さの算術平均高さＳａとは、ＩＳＯ ２５１７８で規定される面粗さの算術平均高さを意味し、集電箔の表面における平均面に対する各点の高さの差の絶対値の平均値である。
The arithmetic mean height of surface roughness Sa means the arithmetic mean height of surface roughness defined by ISO 25178, and is the absolute value of the difference in height of each point with respect to the average surface on the surface of the current collector foil. Average value.
表面が粗い集電箔を準備するには、金属製の集電箔を炭素で被覆する方法や、金属製の集電箔を酸やアルカリで処理する方法で製造してもよいし、市販の表面が粗い集電箔を購入してもよい。
In order to prepare a current collector foil with a rough surface, it may be manufactured by a method of coating a metal current collector foil with carbon, a method of treating a metal current collector foil with an acid or an alkali, or a commercially available one. You can also purchase current collector foil that has a rough surface.
正極活物質層は、本発明の正極活物質以外の正極活物質を含み得る。本発明の正極活物質以外の正極活物質は特に限定しないが、上記したＬｉＣｏＯ2、ＬｉＮｉＯ2、ＬｉＮｉ1/3Ｃｏ1/3Ｍｎ1/3Ｏ2等の層状岩塩構造を有するものを選択するのが好適である。
本発明の正極活物質のようなオリビン構造を有する正極活物質は、層状岩塩構造を有する正極活物質に比べて、熱耐性に優れるものの容量については劣ることが知られている。一方、上記した層状岩塩構造を有する正極活物質は、熱耐性に劣るものの高容量であることが知られている。
このように、本発明の正極活物質と互いに補いあう特性を有する層状岩塩構造の正極活物質を、本発明の正極活物質と併用することで、リチウムイオン二次電池の電池特性を向上させることが可能である。 The positive electrode active material layer may contain a positive electrode active material other than the positive electrode active material of the present invention. Although the positive electrode active material other than the positive electrode active material of the present invention is not particularly limited, those having a layered rock salt structure such as LiCoO 2 , LiNiO 2 and LiNi 1/3 Co 1/3 Mn 1/3 O 2 are selected. is preferred.
A positive electrode active material having an olivine structure, such as the positive electrode active material of the present invention, is known to be superior in heat resistance but inferior in capacity to a positive electrode active material having a layered rock salt structure. On the other hand, it is known that the positive electrode active material having the layered rock salt structure described above has a high capacity although it is inferior in heat resistance.
In this way, the positive electrode active material of the present invention and the positive electrode active material having a layered rock salt structure, which have properties that complement each other, are used in combination with the positive electrode active material of the present invention, thereby improving the battery characteristics of the lithium ion secondary battery. is possible.
本発明の正極活物質のようなオリビン構造を有する正極活物質は、層状岩塩構造を有する正極活物質に比べて、熱耐性に優れるものの容量については劣ることが知られている。一方、上記した層状岩塩構造を有する正極活物質は、熱耐性に劣るものの高容量であることが知られている。
このように、本発明の正極活物質と互いに補いあう特性を有する層状岩塩構造の正極活物質を、本発明の正極活物質と併用することで、リチウムイオン二次電池の電池特性を向上させることが可能である。 The positive electrode active material layer may contain a positive electrode active material other than the positive electrode active material of the present invention. Although the positive electrode active material other than the positive electrode active material of the present invention is not particularly limited, those having a layered rock salt structure such as LiCoO 2 , LiNiO 2 and LiNi 1/3 Co 1/3 Mn 1/3 O 2 are selected. is preferred.
A positive electrode active material having an olivine structure, such as the positive electrode active material of the present invention, is known to be superior in heat resistance but inferior in capacity to a positive electrode active material having a layered rock salt structure. On the other hand, it is known that the positive electrode active material having the layered rock salt structure described above has a high capacity although it is inferior in heat resistance.
In this way, the positive electrode active material of the present invention and the positive electrode active material having a layered rock salt structure, which have properties that complement each other, are used in combination with the positive electrode active material of the present invention, thereby improving the battery characteristics of the lithium ion secondary battery. is possible.
正極活物質層における本発明の正極活物質の割合として、７０～９９質量％の範囲内、８０～９８質量％の範囲内、９０～９７質量％の範囲内を例示できる。
The ratio of the positive electrode active material of the present invention in the positive electrode active material layer can be exemplified within the range of 70-99% by mass, within the range of 80-98% by mass, and within the range of 90-97% by mass.
正極活物質層は、正極活物質以外に、導電助剤、結着剤、分散剤などの添加剤を含むことがある。
このうち導電助剤は、電極の導電性を高めるために添加される。そのため、導電助剤は、電極の導電性が不足する場合に任意に加えればよく、電極の導電性が十分に優れている場合には加えなくても良い。 The positive electrode active material layer may contain additives such as a conductive aid, a binder, and a dispersant in addition to the positive electrode active material.
Among them, the conductive aid is added to increase the conductivity of the electrode. Therefore, the conductive aid may be added arbitrarily when the conductivity of the electrode is insufficient, and may not be added when the conductivity of the electrode is sufficiently excellent.
このうち導電助剤は、電極の導電性を高めるために添加される。そのため、導電助剤は、電極の導電性が不足する場合に任意に加えればよく、電極の導電性が十分に優れている場合には加えなくても良い。 The positive electrode active material layer may contain additives such as a conductive aid, a binder, and a dispersant in addition to the positive electrode active material.
Among them, the conductive aid is added to increase the conductivity of the electrode. Therefore, the conductive aid may be added arbitrarily when the conductivity of the electrode is insufficient, and may not be added when the conductivity of the electrode is sufficiently excellent.
導電助剤は化学的に不活性な電子伝導体であれば良く、炭素質微粒子であるカーボンブラック、黒鉛、気相法炭素繊維（Vapor Grown Carbon Fiber）、カーボンナノチューブ、及び各種金属粒子等が例示される。カーボンブラックとしては、アセチレンブラック、ケッチェンブラック（登録商標）、ファーネスブラック、チャンネルブラック等が例示される。これらの導電助剤を単独又は二種以上組み合わせて正極活物質層に添加することができる。
The conductive aid may be any chemically inactive electron conductor, and examples include carbon black, graphite, vapor grown carbon fiber, carbon nanotube, and various metal particles, which are carbonaceous fine particles. be done. Examples of carbon black include acetylene black, Ketjenblack (registered trademark), furnace black, and channel black. These conductive aids can be added to the positive electrode active material layer singly or in combination of two or more.
導電助剤の配合量は特に限定されない。正極活物質層における導電助剤の割合は、１～７質量％の範囲内が好ましく、２～６質量％の範囲内がより好ましく、３～５質量％の範囲内がさらに好ましい。
The blending amount of the conductive aid is not particularly limited. The proportion of the conductive aid in the positive electrode active material layer is preferably in the range of 1 to 7% by mass, more preferably in the range of 2 to 6% by mass, and even more preferably in the range of 3 to 5% by mass.
結着剤は、正極活物質や導電助剤を集電体の表面に繋ぎ止める役割をするものである。結着剤としては、ポリフッ化ビニリデン、ポリテトラフルオロエチレン、フッ素ゴム等の含フッ素樹脂、ポリプロピレン、ポリエチレン等の熱可塑性樹脂、ポリイミド、ポリアミドイミド等のイミド系樹脂、アルコキシシリル基含有樹脂、ポリ（メタ）アクリレート系樹脂、ポリアクリル酸、ポリビニルアルコール、ポリビニルピロリドン、カルボキシメチルセルロース、スチレンブタジエンゴムを例示できる。
The binder serves to bind the positive electrode active material and conductive aid to the surface of the current collector. Binders include fluorine-containing resins such as polyvinylidene fluoride, polytetrafluoroethylene, and fluororubber; thermoplastic resins such as polypropylene and polyethylene; imide resins such as polyimide and polyamideimide; alkoxysilyl group-containing resins; Examples include meth)acrylate resins, polyacrylic acid, polyvinyl alcohol, polyvinylpyrrolidone, carboxymethylcellulose, and styrene-butadiene rubber.
結着剤の配合量は特に限定されない。正極活物質層における結着剤の割合は、０．５～７質量％の範囲内が好ましく、１～５質量％の範囲内がより好ましく、２～４質量％の範囲内がさらに好ましい。
The blending amount of the binder is not particularly limited. The proportion of the binder in the positive electrode active material layer is preferably in the range of 0.5 to 7% by mass, more preferably in the range of 1 to 5% by mass, and even more preferably in the range of 2 to 4% by mass.
導電助剤及び結着剤以外の分散剤などの添加剤は、公知のものを採用することができる。
Known additives such as dispersants other than conductive aids and binders can be used.
集電体の表面に正極活物質層を形成するには、ロールコート法、ダイコート法、ディップコート法、ドクターブレード法、スプレーコート法、カーテンコート法などの従来から公知の方法を用いれば良い。具体的には、活物質、溶剤、並びに必要に応じて結着剤及び導電助剤を混合してスラリー状の活物質層形成用組成物を製造し、当該活物質層形成用組成物を集電体の表面に塗布後、乾燥する。溶剤としては、Ｎ－メチル－２－ピロリドン、メタノール、メチルイソブチルケトン、水を例示できる。電極密度を高めるべく、乾燥後のものを圧縮しても良い。
In order to form the positive electrode active material layer on the surface of the current collector, conventionally known methods such as roll coating, die coating, dip coating, doctor blade, spray coating, and curtain coating may be used. Specifically, an active material, a solvent, and, if necessary, a binder and a conductive aid are mixed to produce a slurry composition for forming an active material layer, and the composition for forming an active material layer is collected. After coating on the surface of the electric body, it is dried. Examples of solvents include N-methyl-2-pyrrolidone, methanol, methyl isobutyl ketone, and water. In order to increase the electrode density, it may be compressed after drying.
また、特開２０１５－２０１３１８号等に開示される製造方法を用いて活物質層を形成してもよい。
具体的には、活物質と結着剤と溶媒とを含む合剤を造粒することで湿潤状態の造粒体を得る。当該造粒体の集合物を予め定められた型枠に入れ、平板状の成形体を得る。その後、転写ロールを用いて平板状の成形体を集電体の表面に付着させることで正極活物質層を形成することができる。
または、上記の造粒体を集電体の表面に直接供給しつつ、これらを圧着し一体化することで、集電体の表面に正極活物質層を形成しても良い。 Alternatively, the active material layer may be formed using a manufacturing method disclosed in Japanese Patent Application Laid-Open No. 2015-201318.
Specifically, a wet granule is obtained by granulating a mixture containing an active material, a binder, and a solvent. An aggregate of the granules is placed in a predetermined mold to obtain a flat molded body. After that, a positive electrode active material layer can be formed by attaching a flat molded body to the surface of the current collector using a transfer roll.
Alternatively, the positive electrode active material layer may be formed on the surface of the current collector by directly supplying the granules to the surface of the current collector and pressing and integrating them.
具体的には、活物質と結着剤と溶媒とを含む合剤を造粒することで湿潤状態の造粒体を得る。当該造粒体の集合物を予め定められた型枠に入れ、平板状の成形体を得る。その後、転写ロールを用いて平板状の成形体を集電体の表面に付着させることで正極活物質層を形成することができる。
または、上記の造粒体を集電体の表面に直接供給しつつ、これらを圧着し一体化することで、集電体の表面に正極活物質層を形成しても良い。 Alternatively, the active material layer may be formed using a manufacturing method disclosed in Japanese Patent Application Laid-Open No. 2015-201318.
Specifically, a wet granule is obtained by granulating a mixture containing an active material, a binder, and a solvent. An aggregate of the granules is placed in a predetermined mold to obtain a flat molded body. After that, a positive electrode active material layer can be formed by attaching a flat molded body to the surface of the current collector using a transfer roll.
Alternatively, the positive electrode active material layer may be formed on the surface of the current collector by directly supplying the granules to the surface of the current collector and pressing and integrating them.
本発明の正極活物質を備えるリチウムイオン二次電池は、本発明の正極活物質を備える正極、負極、電解液、及び必要に応じてセパレータを含む。
A lithium ion secondary battery comprising the positive electrode active material of the present invention includes a positive electrode comprising the positive electrode active material of the present invention, a negative electrode, an electrolytic solution, and optionally a separator.
負極は、集電体と、集電体の表面に形成された負極活物質層を有する。負極活物質層は負極活物質を含み、さらに、導電助剤、結着剤、分散剤などの添加剤を含むことがある。
集電体、導電助剤および結着剤は、正極で説明したものを採用すればよい。分散剤は公知のものを採用することができる。負極は、正極で説明した製造方法と同様の方法で製造すればよい。 The negative electrode has a current collector and a negative electrode active material layer formed on the surface of the current collector. The negative electrode active material layer contains a negative electrode active material, and may further contain additives such as a conductive aid, a binder, and a dispersant.
As the current collector, conductive aid and binder, those described for the positive electrode may be employed. A known dispersant can be used. The negative electrode may be manufactured by a method similar to the manufacturing method described for the positive electrode.
集電体、導電助剤および結着剤は、正極で説明したものを採用すればよい。分散剤は公知のものを採用することができる。負極は、正極で説明した製造方法と同様の方法で製造すればよい。 The negative electrode has a current collector and a negative electrode active material layer formed on the surface of the current collector. The negative electrode active material layer contains a negative electrode active material, and may further contain additives such as a conductive aid, a binder, and a dispersant.
As the current collector, conductive aid and binder, those described for the positive electrode may be employed. A known dispersant can be used. The negative electrode may be manufactured by a method similar to the manufacturing method described for the positive electrode.
負極活物質としては、リチウムを吸蔵及び放出可能な炭素系材料、リチウムと合金化可能な元素、リチウムと合金化可能な元素を有する化合物、あるいは高分子材料などを例示することができる。
Examples of negative electrode active materials include carbon-based materials that can occlude and release lithium, elements that can be alloyed with lithium, compounds containing elements that can be alloyed with lithium, and polymer materials.
炭素系材料としては、難黒鉛化性炭素、天然黒鉛、人造黒鉛、コークス類、グラファイト類、ガラス状炭素類、有機高分子化合物焼成体、炭素繊維、活性炭あるいはカーボンブラック類が例示できる。ここで、有機高分子化合物焼成体とは、フェノール類やフラン類などの高分子材料を適当な温度で焼成して炭素化したものをいう。高分子材料としては、具体的にポリアセチレン、ポリピロールを例示できる。
Examples of carbon-based materials include non-graphitizable carbon, natural graphite, artificial graphite, cokes, graphites, vitreous carbons, organic polymer compound sintered bodies, carbon fibers, activated carbon, and carbon blacks. Here, the calcined organic polymer compound refers to a carbonized material obtained by calcining a polymer material such as phenols and furans at an appropriate temperature. Specific examples of polymer materials include polyacetylene and polypyrrole.
リチウムと合金化可能な元素としては、具体的にＮａ、Ｋ、Ｒｂ、Ｃｓ、Ｆｒ、Ｂｅ、Ｍｇ、Ｃａ、Ｓｒ、Ｂａ、Ｒａ、Ｔｉ、Ａｇ、Ｚｎ、Ｃｄ、Ａｌ、Ｇａ、Ｉｎ、Ｓｉ、Ｇｅ、Ｓｎ、Ｐｂ、Ｓｂ、Ｂｉが例示でき、特に、Ｓｉ又はＳｎが好ましい。
Specific examples of elements that can be alloyed with lithium include Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Ti, Ag, Zn, Cd, Al, Ga, In, Si , Ge, Sn, Pb, Sb, and Bi, and Si or Sn is particularly preferred.
リチウムと合金化可能な元素を有する化合物としては、具体的にＺｎＬｉＡｌ、ＡｌＳｂ、ＳｉＢ4、ＳｉＢ6、Ｍｇ2Ｓｉ、Ｍｇ2Ｓｎ、Ｎｉ2Ｓｉ、ＴｉＳｉ2、ＭｏＳｉ2、ＣｏＳｉ2、ＮｉＳｉ2、ＣａＳｉ2、ＣｒＳｉ2、Ｃｕ5Ｓｉ、ＦｅＳｉ2、ＭｎＳｉ2、ＮｂＳｉ2、ＴａＳｉ2、ＶＳｉ2、ＷＳｉ2、ＺｎＳｉ2、ＳｉＣ、Ｓｉ3Ｎ4、Ｓｉ2Ｎ2Ｏ、ＳｉＯv（０＜ｖ≦２）、ＳｎＯw（０＜ｗ≦２）、ＳｎＳｉＯ3、ＬｉＳｉＯあるいはＬｉＳｎＯを例示できる。また、リチウムと合金化反応可能な元素を有する化合物として、スズ合金（Ｃｕ－Ｓｎ合金、Ｃｏ－Ｓｎ合金等）などの錫化合物を例示できる。
Specific examples of compounds having an element capable of being alloyed with lithium include ZnLiAl , AlSb, SiB4 , SiB6 , Mg2Si, Mg2Sn , Ni2Si , TiSi2 , MoSi2 , CoSi2 , NiSi2 , CaSi2, CrSi2 , Cu5Si , FeSi2, MnSi2 , NbSi2 , TaSi2 , VSi2 , WSi2 , ZnSi2 , SiC , Si3N4 , Si2N2O , SiOv ( 0 < v ≦2), SnO w (0<w≦2), SnSiO 3 , LiSiO or LiSnO. In addition, tin compounds such as tin alloys (Cu--Sn alloys, Co--Sn alloys, etc.) can be exemplified as compounds having elements capable of alloying with lithium.
電解液は、非水溶媒とこの非水溶媒に溶解された電解質とを含んでいる。
The electrolyte contains a non-aqueous solvent and an electrolyte dissolved in this non-aqueous solvent.
非水溶媒としては、環状エステル類、鎖状エステル類、エーテル類等が使用できる。環状エステル類としては、エチレンカーボネート、プロピレンカーボネート、ブチレンカーボネート、フルオロエチレンカーボネート、ガンマブチロラクトン、ビニレンカーボネート、２－メチル－ガンマブチロラクトン、アセチル－ガンマブチロラクトン、ガンマバレロラクトンを例示できる。鎖状エステル類としては、ジメチルカーボネート、ジエチルカーボネート、ジブチルカーボネート、ジプロピルカーボネート、エチルメチルカーボネート、プロピオン酸アルキルエステル、マロン酸ジアルキルエステル、酢酸アルキルエステル等を例示できる。エーテル類としては、テトラヒドロフラン、２－メチルテトラヒドロフラン、１，４－ジオキサン、１，２－ジメトキシエタン、１，２－ジエトキシエタン、１，２－ジブトキシエタンを例示できる。電解液には、これらの非水溶媒を単独で用いてもよいし、又は、複数を併用してもよい。
Cyclic esters, chain esters, ethers, etc. can be used as non-aqueous solvents. Examples of cyclic esters include ethylene carbonate, propylene carbonate, butylene carbonate, fluoroethylene carbonate, gamma-butyrolactone, vinylene carbonate, 2-methyl-gamma-butyrolactone, acetyl-gamma-butyrolactone, and gamma-valerolactone. Examples of chain esters include dimethyl carbonate, diethyl carbonate, dibutyl carbonate, dipropyl carbonate, ethylmethyl carbonate, alkyl propionate, dialkyl malonate, and alkyl acetate. Examples of ethers include tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-diethoxyethane, and 1,2-dibutoxyethane. One of these non-aqueous solvents may be used in the electrolytic solution, or two or more of them may be used in combination.
ここで、エチレンカーボネート及びプロピレンカーボネートから選択されるアルキレン環状カーボネートは高誘電率の非水溶媒であり、リチウム塩の溶解及びイオン解離に寄与すると考えられる。
また、一般に、アルキレン環状カーボネートがリチウムイオン二次電池の充電時に還元分解されることにより、負極表面にＳＥＩ（Ｓｏｌｉｄ Ｅｌｅｃｔｒｏｌｙｔｅ Ｉｎｔｅｒｐｈａｓｅ）被膜が形成されることが知られている。かかるＳＥＩ被膜の存在に因り、特に負極が黒鉛を備える場合に、リチウムイオンの可逆的な挿入及び離脱が可能になると考えられている。 Here, the alkylene cyclic carbonate selected from ethylene carbonate and propylene carbonate is a non-aqueous solvent with a high dielectric constant and is considered to contribute to the dissolution and ion dissociation of the lithium salt.
Further, it is generally known that an SEI (Solid Electrolyte Interphase) film is formed on the surface of the negative electrode by reductive decomposition of the alkylene cyclic carbonate during charging of the lithium ion secondary battery. It is believed that the presence of such an SEI coating allows reversible insertion and extraction of lithium ions, especially when the negative electrode comprises graphite.
また、一般に、アルキレン環状カーボネートがリチウムイオン二次電池の充電時に還元分解されることにより、負極表面にＳＥＩ（Ｓｏｌｉｄ Ｅｌｅｃｔｒｏｌｙｔｅ Ｉｎｔｅｒｐｈａｓｅ）被膜が形成されることが知られている。かかるＳＥＩ被膜の存在に因り、特に負極が黒鉛を備える場合に、リチウムイオンの可逆的な挿入及び離脱が可能になると考えられている。 Here, the alkylene cyclic carbonate selected from ethylene carbonate and propylene carbonate is a non-aqueous solvent with a high dielectric constant and is considered to contribute to the dissolution and ion dissociation of the lithium salt.
Further, it is generally known that an SEI (Solid Electrolyte Interphase) film is formed on the surface of the negative electrode by reductive decomposition of the alkylene cyclic carbonate during charging of the lithium ion secondary battery. It is believed that the presence of such an SEI coating allows reversible insertion and extraction of lithium ions, especially when the negative electrode comprises graphite.
アルキレン環状カーボネートは電解液の非水溶媒として有益ではあるものの、高粘度である。そのため、アルキレン環状カーボネートの割合が高すぎると、電解液のイオン伝導度や電解液中でのリチウムイオンの拡散に悪影響を及ぼす場合がある。また、アルキレン環状カーボネートは融点が比較的高いため、アルキレン環状カーボネートの割合が高すぎると、低温条件下にて、電解液が固化するおそれがある。
Although alkylene cyclic carbonates are useful as non-aqueous solvents for electrolytes, they are highly viscous. Therefore, if the ratio of the alkylene cyclic carbonate is too high, the ionic conductivity of the electrolyte and the diffusion of lithium ions in the electrolyte may be adversely affected. In addition, since the alkylene cyclic carbonate has a relatively high melting point, if the proportion of the alkylene cyclic carbonate is too high, the electrolytic solution may solidify under low temperature conditions.
他方、プロピオン酸アルキルエステルの一種であるプロピオン酸メチルは、低誘電率、低粘度、かつ、融点が低い非水溶媒である。
電解液の非水溶媒として、アルキレン環状カーボネートとプロピオン酸メチルとが共存するものを用いることで、アルキレン環状カーボネートの不利な点をプロピオン酸メチルが相殺する。すなわち、プロピオン酸メチルは、電解液の低粘度化、イオン伝導度の好適化、リチウムイオンの拡散係数の好適化及び低温条件下での固化防止に寄与し得る。よって、非水溶媒として、アルキレン環状カーボネートとプロピオン酸メチルとが共存するものを用いるのが好適である。 On the other hand, methyl propionate, which is a type of propionic acid alkyl ester, is a non-aqueous solvent with a low dielectric constant, low viscosity, and a low melting point.
By using a mixture of alkylene cyclic carbonate and methyl propionate as the non-aqueous solvent for the electrolytic solution, methyl propionate offsets the disadvantages of alkylene cyclic carbonate. That is, methyl propionate can contribute to lowering the viscosity of the electrolytic solution, optimizing the ionic conductivity, optimizing the diffusion coefficient of lithium ions, and preventing solidification under low temperature conditions. Therefore, it is preferable to use a non-aqueous solvent in which alkylene cyclic carbonate and methyl propionate coexist.
電解液の非水溶媒として、アルキレン環状カーボネートとプロピオン酸メチルとが共存するものを用いることで、アルキレン環状カーボネートの不利な点をプロピオン酸メチルが相殺する。すなわち、プロピオン酸メチルは、電解液の低粘度化、イオン伝導度の好適化、リチウムイオンの拡散係数の好適化及び低温条件下での固化防止に寄与し得る。よって、非水溶媒として、アルキレン環状カーボネートとプロピオン酸メチルとが共存するものを用いるのが好適である。 On the other hand, methyl propionate, which is a type of propionic acid alkyl ester, is a non-aqueous solvent with a low dielectric constant, low viscosity, and a low melting point.
By using a mixture of alkylene cyclic carbonate and methyl propionate as the non-aqueous solvent for the electrolytic solution, methyl propionate offsets the disadvantages of alkylene cyclic carbonate. That is, methyl propionate can contribute to lowering the viscosity of the electrolytic solution, optimizing the ionic conductivity, optimizing the diffusion coefficient of lithium ions, and preventing solidification under low temperature conditions. Therefore, it is preferable to use a non-aqueous solvent in which alkylene cyclic carbonate and methyl propionate coexist.
電解質としては、ＬｉＰＦ6、ＬｉＣｌＯ4、ＬｉＡｓＦ6、ＬｉＢＦ4、ＦＳＯ3Ｌｉ、ＣＦ3ＳＯ3Ｌｉ、Ｃ2Ｆ5ＳＯ3Ｌｉ、Ｃ3Ｆ7ＳＯ3Ｌｉ、Ｃ4Ｆ9ＳＯ3Ｌｉ、Ｃ5Ｆ11ＳＯ3Ｌｉ、Ｃ6Ｆ13ＳＯ3Ｌｉ、ＣＨ3ＳＯ3Ｌｉ、Ｃ2Ｈ5ＳＯ3Ｌｉ、Ｃ3Ｈ7ＳＯ3Ｌｉ、ＣＦ3ＣＨ2ＳＯ3Ｌｉ、ＣＦ3Ｃ2Ｈ4ＳＯ3Ｌｉ、（ＦＳＯ2）2ＮＬｉ、（ＣＦ3ＳＯ2）2ＮＬｉ、（Ｃ2Ｆ5ＳＯ2）2ＮＬｉ、ＦＳＯ2（ＣＦ3ＳＯ2）ＮＬｉ、ＦＳＯ2（Ｃ2Ｆ5ＳＯ2）ＮＬｉ、（ＳＯ2ＣＦ2ＣＦ2ＳＯ2）ＮＬｉ、（ＳＯ2ＣＦ2ＣＦ2ＣＦ2ＳＯ2）ＮＬｉ、ＦＳＯ2（ＣＨ3ＳＯ2）ＮＬｉ、ＦＳＯ2（Ｃ2Ｈ5ＳＯ2）ＮＬｉ、ＬｉＰＯ2Ｆ2、ＬｉＢＦ2（Ｃ2Ｏ4）、ＬｉＢ（Ｃ2Ｏ4）2を例示できる。これらの電解質は単独でも用いても良いし２種以上を併用しても良い。
LiPF6 , LiClO4 , LiAsF6 , LiBF4 , FSO3Li , CF3SO3Li , C2F5SO3Li , C3F7SO3Li , C4F9SO3Li , C5F11SO3Li , C6F13SO3Li , CH3SO3Li , C2H5SO3Li , C3H7SO3Li , CF3CH2SO3Li , CF3C2 _ _ _ _ _ _ H4SO3Li , ( FSO2 ) 2NLi , ( CF3SO2 ) 2NLi , ( C2F5SO2 ) 2NLi , FSO2 ( CF3SO2 )NLi, FSO2 ( C2F5 SO2 ) NLi , ( SO2CF2CF2SO2 ) NLi , ( SO2CF2CF2CF2SO2 ) NLi , FSO2 ( CH3SO2 ) NLi , FSO2 ( C2H5SO2 ) ) NLi, LiPO2F2 , LiBF2 ( C2O4 ), and LiB ( C2O4 ) 2 . These electrolytes may be used alone or in combination of two or more.
電解液における電解質の量は特に限定しないが、１．０モル／Ｌ～２．５モル／Ｌの範囲内、１．２モル／Ｌ～２．２モル／Ｌの範囲内を例示できる。
The amount of electrolyte in the electrolytic solution is not particularly limited, but can be exemplified within the range of 1.0 mol/L to 2.5 mol/L and within the range of 1.2 mol/L to 2.2 mol/L.
セパレータとしては、公知のものを採用すればよく、ポリテトラフルオロエチレン、ポリプロピレン、ポリエチレン、ポリイミド、ポリアミド、ポリアラミド（Ａｒｏｍａｔｉｃ ｐｏｌｙａｍｉｄｅ）、ポリエステル、ポリアクリロニトリル等の合成樹脂、セルロース、アミロース等の多糖類、フィブロイン、ケラチン、リグニン、スベリン等の天然高分子、セラミックスなどの電気絶縁性材料を１種若しくは複数用いた多孔体、不織布、織布などを挙げることができる。また、セパレータは多層構造としてもよい。具体的には、電極とセパレータ間の高い接着性を実現するためにセパレータに接着層を設けた接着型のセパレータや、セパレータに無機フィラー等を含むコーティング膜を形成することで高温耐熱性を高めた塗布型セパレータなどを挙げることができる。
As the separator, a known one may be adopted, and synthetic resins such as polytetrafluoroethylene, polypropylene, polyethylene, polyimide, polyamide, polyaramid (aromatic polyamide), polyester, polyacrylonitrile, etc., polysaccharides such as cellulose, amylose, fibroin, etc. , natural polymers such as keratin, lignin and suberin, and porous bodies, non-woven fabrics, and woven fabrics using one or a plurality of electrically insulating materials such as ceramics. Also, the separator may have a multilayer structure. Specifically, in order to achieve high adhesion between the electrode and the separator, we have developed an adhesive separator with an adhesive layer, and a coating film containing inorganic filler etc. on the separator to improve high-temperature heat resistance. and a coating type separator.
リチウムイオン二次電池の具体的な製造方法について説明する。例えば、正極と負極とでセパレータを挟持して電極体とする。電極体は、正極、セパレータ及び負極を重ねた積層型、又は、正極、セパレータ及び負極の積層体を捲いた捲回型のいずれの型にしても良い。正極の集電体及び負極の集電体から外部に通ずる正極端子及び負極端子までを、集電用リード等を用いて接続した後に、電極体に電解液を加えてリチウムイオン二次電池とするとよい。
A specific manufacturing method for lithium-ion secondary batteries will be explained. For example, an electrode body is formed by sandwiching a separator between a positive electrode and a negative electrode. The electrode body may be of either a laminated type in which a positive electrode, a separator and a negative electrode are laminated, or a wound type in which a laminated body of a positive electrode, a separator and a negative electrode is wound. After connecting the current collector of the positive electrode and the current collector of the negative electrode to the positive electrode terminal and the negative electrode terminal leading to the outside using a current collecting lead or the like, an electrolyte is added to the electrode body to make a lithium ion secondary battery. good.
また、リチウムイオン二次電池の電極として、双極型電極を用いた場合の具体的な製造方法について説明する。例えば、一の双極型電極の正極活物質層と、一の双極型電極と隣り合う双極型電極の負極活物質層とがセパレータを介して対向するように積層し電極体とする。電極体の周縁を樹脂等で被覆することで、一の双極型電極と一の双極型電極と隣り合う双極型電極との間に空間を形成し、当該空間内に電解液を加えてリチウムイオン二次電池とするとよい。
Also, a specific manufacturing method in the case of using a bipolar electrode as the electrode of the lithium ion secondary battery will be described. For example, the cathode active material layer of one bipolar electrode and the anode active material layer of the bipolar electrode adjacent to the one bipolar electrode are laminated so as to face each other with a separator interposed therebetween to form an electrode assembly. By coating the periphery of the electrode body with a resin or the like, a space is formed between one bipolar electrode and the adjacent bipolar electrode, and an electrolytic solution is added to the space to generate lithium ions. A secondary battery is preferable.
本発明のリチウムイオン二次電池の形状は特に限定されるものでなく、円筒型、角型、コイン型、ラミネート型等、種々の形状を採用することができる。
The shape of the lithium-ion secondary battery of the present invention is not particularly limited, and various shapes such as cylindrical, square, coin, and laminate can be adopted.
本発明のリチウムイオン二次電池は、車両に搭載してもよい。車両は、その動力源の全部あるいは一部にリチウムイオン二次電池による電気エネルギーを使用している車両であればよく、例えば、電気車両、ハイブリッド車両などであるとよい。車両にリチウムイオン二次電池を搭載する場合には、リチウムイオン二次電池を複数直列に接続して組電池とするとよい。リチウムイオン二次電池を搭載する機器としては、車両以外にも、パーソナルコンピュータ、携帯通信機器など、電池で駆動される各種の家電製品、オフィス機器、産業機器などが挙げられる。さらに、本発明のリチウムイオン二次電池は、風力発電、太陽光発電、水力発電その他電力系統の蓄電装置及び電力平滑化装置、船舶等の動力及び／又は補機類の電力供給源、航空機、宇宙船等の動力及び／又は補機類の電力供給源、電気を動力源に用いない車両の補助用電源、移動式の家庭用ロボットの電源、システムバックアップ用電源、無停電電源装置の電源、電動車両用充電ステーションなどにおいて充電に必要な電力を一時蓄える蓄電装置に用いてもよい。
The lithium-ion secondary battery of the present invention may be mounted on a vehicle. The vehicle may be any vehicle that uses electrical energy from a lithium-ion secondary battery as a power source in whole or in part, and may be, for example, an electric vehicle or a hybrid vehicle. When a lithium ion secondary battery is mounted on a vehicle, it is preferable to connect a plurality of lithium ion secondary batteries in series to form an assembled battery. Devices equipped with lithium ion secondary batteries include, in addition to vehicles, personal computers, mobile communication devices, various home electric appliances driven by batteries, office equipment, industrial equipment, and the like. Furthermore, the lithium ion secondary battery of the present invention is used for wind power generation, solar power generation, hydraulic power generation, and other power storage devices and power smoothing devices for power systems, power sources for ships and/or auxiliary equipment, aircraft, power source for spacecraft and/or auxiliary equipment, auxiliary power source for vehicles that do not use electricity as a power source, power source for mobile home robots, power source for system backup, power source for uninterruptible power supply, It may be used as a power storage device that temporarily stores electric power required for charging in a charging station for an electric vehicle.
以上、本発明を説明したが、本発明は上記実施形態に限定されるものではない。本発明の要旨を逸脱しない範囲において、当業者が行い得る変更、改良等を施した種々の形態にて実施することができる。
Although the present invention has been described above, the present invention is not limited to the above embodiments. Various modifications, improvements, etc. that can be made by those skilled in the art can be implemented without departing from the scope of the present invention.
以下に、実施例、比較例及び参考例などを示し、本発明をより具体的に説明する。なお、本発明は、これらの実施例によって限定されるものではない。
Examples, comparative examples, reference examples, etc. are shown below to describe the present invention more specifically. It should be noted that the present invention is not limited by these examples.
（実施例１）
〔正極活物質の合成〕
純水５０ｍｌに、リチウム源としてＬｉＯＨ１水和物２．５７ｇ、ｐＨ調整剤としてリンゴ酸８．２１ｇ、マンガン源として酢酸マンガン（ＩＩ）４水和物１１．２５ｇ、鉄源として硫酸鉄（ＩＩ）７水和物４．１７ｇ、タングステン源としてタングステン酸０．０７６ｇ、還元剤としてギ酸０．３ｇ、ケイ素源としてオルトケイ酸テトラエチル(ＴＥＯＳ)０．１３ｇ、および、リン源として８５％リン酸６．９９ｇを溶解し、５０℃で１２時間加熱して、ゲル状の活物質原料を得た。
なお、実施例１においては、ケイ素が式（１）におけるＤ2元素に相当する。 (Example 1)
[Synthesis of positive electrode active material]
To 50 ml of pure water, 2.57 g of LiOH monohydrate as a lithium source, 8.21 g of malic acid as a pH adjuster, 11.25 g of manganese (II) acetate tetrahydrate as a manganese source, and iron (II) sulfate as an iron source. 4.17 g heptahydrate, 0.076 g tungstic acid as tungsten source, 0.3 g formic acid as reducing agent, 0.13 g tetraethyl orthosilicate (TEOS) as silicon source, and 6.99g 85% phosphoric acid as phosphorus source. was dissolved and heated at 50° C. for 12 hours to obtain a gel-like active material raw material.
In addition, in Example 1, silicon corresponds to the D2 element in the formula ( 1 ).
〔正極活物質の合成〕
純水５０ｍｌに、リチウム源としてＬｉＯＨ１水和物２．５７ｇ、ｐＨ調整剤としてリンゴ酸８．２１ｇ、マンガン源として酢酸マンガン（ＩＩ）４水和物１１．２５ｇ、鉄源として硫酸鉄（ＩＩ）７水和物４．１７ｇ、タングステン源としてタングステン酸０．０７６ｇ、還元剤としてギ酸０．３ｇ、ケイ素源としてオルトケイ酸テトラエチル(ＴＥＯＳ)０．１３ｇ、および、リン源として８５％リン酸６．９９ｇを溶解し、５０℃で１２時間加熱して、ゲル状の活物質原料を得た。
なお、実施例１においては、ケイ素が式（１）におけるＤ2元素に相当する。 (Example 1)
[Synthesis of positive electrode active material]
To 50 ml of pure water, 2.57 g of LiOH monohydrate as a lithium source, 8.21 g of malic acid as a pH adjuster, 11.25 g of manganese (II) acetate tetrahydrate as a manganese source, and iron (II) sulfate as an iron source. 4.17 g heptahydrate, 0.076 g tungstic acid as tungsten source, 0.3 g formic acid as reducing agent, 0.13 g tetraethyl orthosilicate (TEOS) as silicon source, and 6.99
In addition, in Example 1, silicon corresponds to the D2 element in the formula ( 1 ).
実施例１の活物質原料において、タングステンの量は、マンガン、鉄およびタングステンの合計、すなわち、メタルサイトを構成し得るリチウム以外の金属元素の合計を１００原子％としたときに０．５原子％となる量であった。また、ケイ素の量は、ケイ素およびリンの合計を１００原子％としたときに１．０原子％となる量であった。さらに、リチウム：（マンガン、鉄およびタングステンの合計）：（ケイ素とリンとの合計）は１：１：１であった。なお、活物質原料におけるリチウム、マンガン、鉄、タングステン、ケイ素およびリンの元素比は、正極活物質におけるこれらの元素比と概略一致する。以下の実施例及び比較例についても同様である。
In the active material raw material of Example 1, the amount of tungsten is 0.5 atomic % when the total of manganese, iron and tungsten, that is, the total of metal elements other than lithium that can form metal sites is taken as 100 atomic %. was the amount. Also, the amount of silicon was such that the total amount of silicon and phosphorus was 1.0 atomic % when the total was 100 atomic %. Furthermore, the ratio of lithium:(sum of manganese, iron and tungsten):(sum of silicon and phosphorus) was 1:1:1. The elemental ratios of lithium, manganese, iron, tungsten, silicon and phosphorus in the raw material of the active material approximately match those in the positive electrode active material. The same applies to the following examples and comparative examples.
実施例１の正極活物質原料における各元素の組成を、後述する各実施例、比較例１及び参考例１の正極活物質原料における各元素の組成とともに、後述する表１に示す。
The composition of each element in the positive electrode active material raw material of Example 1 is shown in Table 1, which will be described later, together with the composition of each element in the positive electrode active material raw material of each Example, Comparative Example 1, and Reference Example 1, which will be described later.
上記のゲル状の活物質原料を６０℃で２４時間真空乾燥し、その後、窒素雰囲気下３５０℃で５時間加熱し、次いで、窒素雰囲気下６５０℃で１５時間加熱することで、実施例１の正極活物質を製造した。
The gel-like active material raw material was vacuum-dried at 60° C. for 24 hours, then heated at 350° C. for 5 hours under a nitrogen atmosphere, and then heated at 650° C. for 15 hours under a nitrogen atmosphere. A positive electrode active material was produced.
〔正極の製造〕
実施例１の正極活物質、導電助剤としてアセチレンブラック及び結着剤としてポリフッ化ビニリデンを、正極活物質と導電助剤と結着剤の質量比が８５：５：１０となるように混合し、溶剤としてＮ－メチル－２－ピロリドンを添加してスラリー状の正極活物質層形成用組成物とした。正極用集電体としてアルミニウム箔を準備した。アルミニウム箔の表面に正極活物質層形成用組成物を膜状に塗布した後に溶剤を除去して製造された正極前駆体を、厚み方向にプレスすることで、アルミニウム箔の表面に正極活物質層が形成された正極を製造した。
なお、正極の目付け量の目標値は１４ｍｇ／ｃｍ2であり、正極活物質層の密度の目標値は１．９ｇ／ｍＬであった。ここで、正極の目付け量とは、正極の集電箔の片面１平方センチメートルの面積上に存在する正極活物質層の質量を意味する。 [Manufacturing of positive electrode]
The positive electrode active material of Example 1, acetylene black as a conductive aid, and polyvinylidene fluoride as a binder were mixed so that the mass ratio of the positive electrode active material, conductive aid, and binder was 85:5:10. , and N-methyl-2-pyrrolidone was added as a solvent to prepare a composition for forming a positive electrode active material layer in slurry form. An aluminum foil was prepared as a positive electrode current collector. A positive electrode active material layer is formed on the surface of the aluminum foil by pressing the positive electrode precursor produced by applying the composition for forming the positive electrode active material layer in the form of a film on the surface of the aluminum foil and then removing the solvent, in the thickness direction. was formed on the positive electrode.
The target value for the basis weight of the positive electrode was 14 mg/cm 2 , and the target value for the density of the positive electrode active material layer was 1.9 g/mL. Here, the basis weight of the positive electrode means the mass of the positive electrode active material layer present on the area of 1 square centimeter on one side of the current collector foil of the positive electrode.
実施例１の正極活物質、導電助剤としてアセチレンブラック及び結着剤としてポリフッ化ビニリデンを、正極活物質と導電助剤と結着剤の質量比が８５：５：１０となるように混合し、溶剤としてＮ－メチル－２－ピロリドンを添加してスラリー状の正極活物質層形成用組成物とした。正極用集電体としてアルミニウム箔を準備した。アルミニウム箔の表面に正極活物質層形成用組成物を膜状に塗布した後に溶剤を除去して製造された正極前駆体を、厚み方向にプレスすることで、アルミニウム箔の表面に正極活物質層が形成された正極を製造した。
なお、正極の目付け量の目標値は１４ｍｇ／ｃｍ2であり、正極活物質層の密度の目標値は１．９ｇ／ｍＬであった。ここで、正極の目付け量とは、正極の集電箔の片面１平方センチメートルの面積上に存在する正極活物質層の質量を意味する。 [Manufacturing of positive electrode]
The positive electrode active material of Example 1, acetylene black as a conductive aid, and polyvinylidene fluoride as a binder were mixed so that the mass ratio of the positive electrode active material, conductive aid, and binder was 85:5:10. , and N-methyl-2-pyrrolidone was added as a solvent to prepare a composition for forming a positive electrode active material layer in slurry form. An aluminum foil was prepared as a positive electrode current collector. A positive electrode active material layer is formed on the surface of the aluminum foil by pressing the positive electrode precursor produced by applying the composition for forming the positive electrode active material layer in the form of a film on the surface of the aluminum foil and then removing the solvent, in the thickness direction. was formed on the positive electrode.
The target value for the basis weight of the positive electrode was 14 mg/cm 2 , and the target value for the density of the positive electrode active material layer was 1.9 g/mL. Here, the basis weight of the positive electrode means the mass of the positive electrode active material layer present on the area of 1 square centimeter on one side of the current collector foil of the positive electrode.
〔正極ハーフセルの製造〕
エチレンカーボネート、メチルエチルカーボネートおよびジメチルカーボネートを体積比３：３：４で混合した混合溶媒に、ＬｉＰＦ6を濃度１モル／Ｌで溶解しかつ（ＦＳＯ2）2ＮＬｉを濃度０．１モル／Ｌで溶解して母液とした。当該母液に対して１質量％に相当する量のビニレンカーボネートを加えて溶解することで、電解液を製造した。
対極として、厚さ０．２μｍのリチウム箔が貼り付けられた銅箔を準備した。
セパレータとしてポリオレフィン製の多孔質膜を準備した。正極、セパレータ、対極の順に積層して極板群とした。極板群を二枚一組のラミネートフィルムで覆い、三辺をシールした後、袋状となったラミネートフィルムに電解液を注入した。その後、残りの一辺をシールすることで、四辺が気密にシールされ、極板群及び電解液が密閉されたラミネート型電池を得た。これを実施例１の正極ハーフセルとした。 [Manufacturing of positive electrode half-cell]
LiPF 6 was dissolved at a concentration of 1 mol/L and (FSO 2 ) 2 NLi at a concentration of 0.1 mol/L in a mixed solvent of ethylene carbonate, methyl ethyl carbonate and dimethyl carbonate at a volume ratio of 3:3:4. to obtain a mother liquor. An electrolytic solution was produced by adding and dissolving vinylene carbonate in an amount corresponding to 1% by mass with respect to the mother liquor.
A copper foil to which a 0.2 μm thick lithium foil was attached was prepared as a counter electrode.
A polyolefin porous membrane was prepared as a separator. A positive electrode, a separator, and a counter electrode were laminated in this order to form an electrode plate group. After covering the electrode group with a set of two laminate films and sealing three sides, an electrolytic solution was injected into the bag-shaped laminate film. After that, the remaining one side was sealed to obtain a laminate type battery in which the four sides were airtightly sealed, and the electrode plate group and the electrolytic solution were sealed. This was used as the positive electrode half cell of Example 1.
エチレンカーボネート、メチルエチルカーボネートおよびジメチルカーボネートを体積比３：３：４で混合した混合溶媒に、ＬｉＰＦ6を濃度１モル／Ｌで溶解しかつ（ＦＳＯ2）2ＮＬｉを濃度０．１モル／Ｌで溶解して母液とした。当該母液に対して１質量％に相当する量のビニレンカーボネートを加えて溶解することで、電解液を製造した。
対極として、厚さ０．２μｍのリチウム箔が貼り付けられた銅箔を準備した。
セパレータとしてポリオレフィン製の多孔質膜を準備した。正極、セパレータ、対極の順に積層して極板群とした。極板群を二枚一組のラミネートフィルムで覆い、三辺をシールした後、袋状となったラミネートフィルムに電解液を注入した。その後、残りの一辺をシールすることで、四辺が気密にシールされ、極板群及び電解液が密閉されたラミネート型電池を得た。これを実施例１の正極ハーフセルとした。 [Manufacturing of positive electrode half-cell]
LiPF 6 was dissolved at a concentration of 1 mol/L and (FSO 2 ) 2 NLi at a concentration of 0.1 mol/L in a mixed solvent of ethylene carbonate, methyl ethyl carbonate and dimethyl carbonate at a volume ratio of 3:3:4. to obtain a mother liquor. An electrolytic solution was produced by adding and dissolving vinylene carbonate in an amount corresponding to 1% by mass with respect to the mother liquor.
A copper foil to which a 0.2 μm thick lithium foil was attached was prepared as a counter electrode.
A polyolefin porous membrane was prepared as a separator. A positive electrode, a separator, and a counter electrode were laminated in this order to form an electrode plate group. After covering the electrode group with a set of two laminate films and sealing three sides, an electrolytic solution was injected into the bag-shaped laminate film. After that, the remaining one side was sealed to obtain a laminate type battery in which the four sides were airtightly sealed, and the electrode plate group and the electrolytic solution were sealed. This was used as the positive electrode half cell of Example 1.
〔リチウムイオン二次電池の製造〕
負極活物質として黒鉛、結着剤としてカルボキシメチルセルロース及びスチレンブタジエンゴムを、黒鉛とカルボキシメチルセルロースとスチレンブタジエンゴムの質量比が９７：２．２：０．８となるように混合し、溶剤として水を添加してスラリー状の負極活物質層形成用組成物とした。負極用集電体として銅箔を準備した。銅箔の表面に負極活物質層形成用組成物を膜状に塗布した後に溶剤を除去して製造された負極前駆体を、厚み方向にプレスすることで、銅箔の表面に負極活物質層が形成された負極を製造した。
なお、負極の目付け量は４．８ｍｇ／ｃｍ2であり、負極活物質層の密度は１．１ｇ／ｃｍ3であった。 [Manufacture of lithium-ion secondary battery]
Graphite as a negative electrode active material, carboxymethyl cellulose and styrene-butadiene rubber as binders were mixed so that the mass ratio of graphite, carboxymethyl cellulose and styrene-butadiene rubber was 97:2.2:0.8, and water was used as a solvent. It was added to prepare a slurry composition for forming a negative electrode active material layer. A copper foil was prepared as a current collector for the negative electrode. A negative electrode active material layer is formed on the surface of the copper foil by pressing the negative electrode precursor produced by applying the negative electrode active material layer forming composition to the surface of the copper foil in the form of a film and then removing the solvent, in the thickness direction. was formed on the negative electrode.
The basis weight of the negative electrode was 4.8 mg/cm 2 and the density of the negative electrode active material layer was 1.1 g/cm 3 .
負極活物質として黒鉛、結着剤としてカルボキシメチルセルロース及びスチレンブタジエンゴムを、黒鉛とカルボキシメチルセルロースとスチレンブタジエンゴムの質量比が９７：２．２：０．８となるように混合し、溶剤として水を添加してスラリー状の負極活物質層形成用組成物とした。負極用集電体として銅箔を準備した。銅箔の表面に負極活物質層形成用組成物を膜状に塗布した後に溶剤を除去して製造された負極前駆体を、厚み方向にプレスすることで、銅箔の表面に負極活物質層が形成された負極を製造した。
なお、負極の目付け量は４．８ｍｇ／ｃｍ2であり、負極活物質層の密度は１．１ｇ／ｃｍ3であった。 [Manufacture of lithium-ion secondary battery]
Graphite as a negative electrode active material, carboxymethyl cellulose and styrene-butadiene rubber as binders were mixed so that the mass ratio of graphite, carboxymethyl cellulose and styrene-butadiene rubber was 97:2.2:0.8, and water was used as a solvent. It was added to prepare a slurry composition for forming a negative electrode active material layer. A copper foil was prepared as a current collector for the negative electrode. A negative electrode active material layer is formed on the surface of the copper foil by pressing the negative electrode precursor produced by applying the negative electrode active material layer forming composition to the surface of the copper foil in the form of a film and then removing the solvent, in the thickness direction. was formed on the negative electrode.
The basis weight of the negative electrode was 4.8 mg/cm 2 and the density of the negative electrode active material layer was 1.1 g/cm 3 .
正極活物質層として実施例１の正極活物質、導電助剤としてアセチレンブラック及び結着剤としてポリフッ化ビニリデンを、正極活物質と導電助剤と結着剤の質量比が８５：５：１０となるように混合し、溶剤としてＮ－メチル－２－ピロリドンを添加してスラリー状の正極活物質層形成用組成物とした。正極用集電体としてアルミニウム箔を準備した。
アルミニウム箔の表面に正極活物質層形成用組成物を膜状に塗布した後に溶剤を除去して製造された正極前駆体を、厚み方向にプレスすることで、アルミニウム箔の表面に正極活物質層が形成された正極を製造した。
なお、正極の目付け量の目標値は１４ｍｇ／ｃｍ2であり、正極活物質層の密度の目標値は１．９ｇ／ｃｍ3であった。 The positive electrode active material of Example 1 was used as the positive electrode active material layer, acetylene black was used as the conductive aid, and polyvinylidene fluoride was used as the binder. N-methyl-2-pyrrolidone was added as a solvent to obtain a slurry composition for forming a positive electrode active material layer. An aluminum foil was prepared as a positive electrode current collector.
A positive electrode active material layer is formed on the surface of the aluminum foil by pressing the positive electrode precursor produced by applying the composition for forming the positive electrode active material layer in the form of a film on the surface of the aluminum foil and then removing the solvent, in the thickness direction. was formed on the positive electrode.
The target value for the basis weight of the positive electrode was 14 mg/cm 2 , and the target value for the density of the positive electrode active material layer was 1.9 g/cm 3 .
アルミニウム箔の表面に正極活物質層形成用組成物を膜状に塗布した後に溶剤を除去して製造された正極前駆体を、厚み方向にプレスすることで、アルミニウム箔の表面に正極活物質層が形成された正極を製造した。
なお、正極の目付け量の目標値は１４ｍｇ／ｃｍ2であり、正極活物質層の密度の目標値は１．９ｇ／ｃｍ3であった。 The positive electrode active material of Example 1 was used as the positive electrode active material layer, acetylene black was used as the conductive aid, and polyvinylidene fluoride was used as the binder. N-methyl-2-pyrrolidone was added as a solvent to obtain a slurry composition for forming a positive electrode active material layer. An aluminum foil was prepared as a positive electrode current collector.
A positive electrode active material layer is formed on the surface of the aluminum foil by pressing the positive electrode precursor produced by applying the composition for forming the positive electrode active material layer in the form of a film on the surface of the aluminum foil and then removing the solvent, in the thickness direction. was formed on the positive electrode.
The target value for the basis weight of the positive electrode was 14 mg/cm 2 , and the target value for the density of the positive electrode active material layer was 1.9 g/cm 3 .
エチレンカーボネート、メチルエチルカーボネートおよびジメチルカーボネートを体積比３：３：４で混合した混合溶媒に、ＬｉＰＦ6を濃度１モル／Ｌで溶解しかつ（ＦＳＯ2）2ＮＬｉを濃度０．１モル／Ｌで溶解して母液とした。当該母液に対して１質量％に相当する量のビニレンカーボネートを加えて溶解することで、電解液を製造した。
セパレータとしてポリプロピレン製の多孔質膜を準備した。正極と負極でセパレータを挟持して電極体とした。この電極体を上記の電解液と共に、袋状のラミネートフィルムに入れて密閉することで、実施例１のリチウムイオン二次電池を製造した。 LiPF 6 was dissolved at a concentration of 1 mol/L and (FSO 2 ) 2 NLi at a concentration of 0.1 mol/L in a mixed solvent of ethylene carbonate, methyl ethyl carbonate and dimethyl carbonate at a volume ratio of 3:3:4. to obtain a mother liquor. An electrolytic solution was produced by adding and dissolving vinylene carbonate in an amount corresponding to 1% by mass with respect to the mother liquor.
A polypropylene porous membrane was prepared as a separator. An electrode body was formed by sandwiching a separator between the positive electrode and the negative electrode. The lithium ion secondary battery of Example 1 was manufactured by putting this electrode assembly into a bag-like laminate film and sealing it together with the electrolyte solution.
セパレータとしてポリプロピレン製の多孔質膜を準備した。正極と負極でセパレータを挟持して電極体とした。この電極体を上記の電解液と共に、袋状のラミネートフィルムに入れて密閉することで、実施例１のリチウムイオン二次電池を製造した。 LiPF 6 was dissolved at a concentration of 1 mol/L and (FSO 2 ) 2 NLi at a concentration of 0.1 mol/L in a mixed solvent of ethylene carbonate, methyl ethyl carbonate and dimethyl carbonate at a volume ratio of 3:3:4. to obtain a mother liquor. An electrolytic solution was produced by adding and dissolving vinylene carbonate in an amount corresponding to 1% by mass with respect to the mother liquor.
A polypropylene porous membrane was prepared as a separator. An electrode body was formed by sandwiching a separator between the positive electrode and the negative electrode. The lithium ion secondary battery of Example 1 was manufactured by putting this electrode assembly into a bag-like laminate film and sealing it together with the electrolyte solution.
（実施例２）
実施例２の正極活物質の製造方法では、活物質原料におけるタングステンの量が、メタルサイトを構成し得るリチウム以外の金属元素、すなわち、マンガン、鉄およびタングステンの合計を１００原子％としたときに１原子％となる量であり、ケイ素の量が、ケイ素およびリンの合計を１００原子％としたときに２原子％となる量であった。これ以外は、実施例１と同様にして、実施例２の正極活物質、正極ハーフセル及びリチウムイオン二次電池を製造した。なお、実施例２においても、ケイ素がＤ2元素に相当する。 (Example 2)
In the method for producing a positive electrode active material of Example 2, when the amount of tungsten in the active material raw material is 100 atomic % of the total of metal elements other than lithium that can constitute the metal site, that is, manganese, iron and tungsten The amount was 1 atomic %, and the amount of silicon was 2 atomic % when the total of silicon and phosphorus was 100 atomic %. A positive electrode active material, a positive electrode half cell, and a lithium ion secondary battery of Example 2 were manufactured in the same manner as in Example 1 except for this. Also in Example 2 , silicon corresponds to the D2 element.
実施例２の正極活物質の製造方法では、活物質原料におけるタングステンの量が、メタルサイトを構成し得るリチウム以外の金属元素、すなわち、マンガン、鉄およびタングステンの合計を１００原子％としたときに１原子％となる量であり、ケイ素の量が、ケイ素およびリンの合計を１００原子％としたときに２原子％となる量であった。これ以外は、実施例１と同様にして、実施例２の正極活物質、正極ハーフセル及びリチウムイオン二次電池を製造した。なお、実施例２においても、ケイ素がＤ2元素に相当する。 (Example 2)
In the method for producing a positive electrode active material of Example 2, when the amount of tungsten in the active material raw material is 100 atomic % of the total of metal elements other than lithium that can constitute the metal site, that is, manganese, iron and tungsten The amount was 1 atomic %, and the amount of silicon was 2 atomic % when the total of silicon and phosphorus was 100 atomic %. A positive electrode active material, a positive electrode half cell, and a lithium ion secondary battery of Example 2 were manufactured in the same manner as in Example 1 except for this. Also in Example 2 , silicon corresponds to the D2 element.
（実施例３）
実施例３の正極活物質の製造方法では、活物質原料におけるタングステンの量が、マンガン、鉄およびタングステンの合計を１００原子％としたときに３原子％となる量であり、ケイ素の量が、ケイ素およびリンの合計を１００原子％としたときに６原子％となる量であった。これ以外は、実施例１と同様にして、実施例３の正極活物質、正極ハーフセル及びリチウムイオン二次電池を製造した。なお、実施例３においても、ケイ素がＤ2元素に相当する。 (Example 3)
In the method for producing a positive electrode active material of Example 3, the amount of tungsten in the active material raw material is an amount that becomes 3 atomic % when the total of manganese, iron and tungsten is 100 atomic %, and the amount of silicon is The amount was 6 atomic % when the total of silicon and phosphorus was 100 atomic %. Except for this, in the same manner as in Example 1, a positive electrode active material, a positive electrode half cell, and a lithium ion secondary battery of Example 3 were manufactured. Also in Example 3 , silicon corresponds to the D2 element.
実施例３の正極活物質の製造方法では、活物質原料におけるタングステンの量が、マンガン、鉄およびタングステンの合計を１００原子％としたときに３原子％となる量であり、ケイ素の量が、ケイ素およびリンの合計を１００原子％としたときに６原子％となる量であった。これ以外は、実施例１と同様にして、実施例３の正極活物質、正極ハーフセル及びリチウムイオン二次電池を製造した。なお、実施例３においても、ケイ素がＤ2元素に相当する。 (Example 3)
In the method for producing a positive electrode active material of Example 3, the amount of tungsten in the active material raw material is an amount that becomes 3 atomic % when the total of manganese, iron and tungsten is 100 atomic %, and the amount of silicon is The amount was 6 atomic % when the total of silicon and phosphorus was 100 atomic %. Except for this, in the same manner as in Example 1, a positive electrode active material, a positive electrode half cell, and a lithium ion secondary battery of Example 3 were manufactured. Also in Example 3 , silicon corresponds to the D2 element.
（実施例４）
〔正極活物質の合成〕
純水５０ｍｌに、リチウム源としてＬｉＯＨ１水和物２．５７ｇ、ｐＨ調整剤としてリンゴ酸８．２１ｇ、マンガン源として酢酸マンガン（ＩＩ）４水和物１１．２５ｇ、鉄源として硫酸鉄（ＩＩ）７水和物３．６６ｇ、タングステン源としてタングステン酸０．０７６ｇ、マグネシウム源として酢酸マグネシウム４水和物０．３９４ｇ、還元剤としてギ酸０．３ｇ、ケイ素源としてオルトケイ酸テトラエチル(TEOS)０．１３ｇ、および、リン源として８５％リン酸６．９９ｇを溶解し、５０℃で１２時間加熱して、ゲル状の活物質原料を得た。
このゲル状の活物質原料を６０℃で２４時間真空乾燥し、その後、窒素雰囲気下３５０℃で５時間加熱し、次いで、窒素雰囲気下６５０℃で１５時間加熱することで、実施例４の正極活物質を製造した。
なお、実施例４においては、マグネシウムが式（１）におけるＤ1元素に相当し、ケイ素が式（１）におけるＤ2元素に相当する。 (Example 4)
[Synthesis of positive electrode active material]
To 50 ml of pure water, 2.57 g of LiOH monohydrate as a lithium source, 8.21 g of malic acid as a pH adjuster, 11.25 g of manganese (II) acetate tetrahydrate as a manganese source, and iron (II) sulfate as an iron source. 3.66 g heptahydrate, 0.076 g tungstic acid as tungsten source, 0.394 g magnesium acetate tetrahydrate as magnesium source, 0.3 g formic acid as reducing agent, 0.13 g tetraethyl orthosilicate (TEOS) as silicon source , and 6.99 g of 85% phosphoric acid as a phosphorus source were dissolved and heated at 50° C. for 12 hours to obtain a gel-like active material raw material.
This gel-like active material raw material was vacuum-dried at 60° C. for 24 hours, then heated at 350° C. for 5 hours under a nitrogen atmosphere, and then heated at 650° C. for 15 hours under a nitrogen atmosphere. An active material was produced.
In addition, in Example 4, magnesium corresponds to the D1 element in the formula (1), and silicon corresponds to the D2 element in the formula ( 1 ).
〔正極活物質の合成〕
純水５０ｍｌに、リチウム源としてＬｉＯＨ１水和物２．５７ｇ、ｐＨ調整剤としてリンゴ酸８．２１ｇ、マンガン源として酢酸マンガン（ＩＩ）４水和物１１．２５ｇ、鉄源として硫酸鉄（ＩＩ）７水和物３．６６ｇ、タングステン源としてタングステン酸０．０７６ｇ、マグネシウム源として酢酸マグネシウム４水和物０．３９４ｇ、還元剤としてギ酸０．３ｇ、ケイ素源としてオルトケイ酸テトラエチル(TEOS)０．１３ｇ、および、リン源として８５％リン酸６．９９ｇを溶解し、５０℃で１２時間加熱して、ゲル状の活物質原料を得た。
このゲル状の活物質原料を６０℃で２４時間真空乾燥し、その後、窒素雰囲気下３５０℃で５時間加熱し、次いで、窒素雰囲気下６５０℃で１５時間加熱することで、実施例４の正極活物質を製造した。
なお、実施例４においては、マグネシウムが式（１）におけるＤ1元素に相当し、ケイ素が式（１）におけるＤ2元素に相当する。 (Example 4)
[Synthesis of positive electrode active material]
To 50 ml of pure water, 2.57 g of LiOH monohydrate as a lithium source, 8.21 g of malic acid as a pH adjuster, 11.25 g of manganese (II) acetate tetrahydrate as a manganese source, and iron (II) sulfate as an iron source. 3.66 g heptahydrate, 0.076 g tungstic acid as tungsten source, 0.394 g magnesium acetate tetrahydrate as magnesium source, 0.3 g formic acid as reducing agent, 0.13 g tetraethyl orthosilicate (TEOS) as silicon source , and 6.99 g of 85% phosphoric acid as a phosphorus source were dissolved and heated at 50° C. for 12 hours to obtain a gel-like active material raw material.
This gel-like active material raw material was vacuum-dried at 60° C. for 24 hours, then heated at 350° C. for 5 hours under a nitrogen atmosphere, and then heated at 650° C. for 15 hours under a nitrogen atmosphere. An active material was produced.
In addition, in Example 4, magnesium corresponds to the D1 element in the formula (1), and silicon corresponds to the D2 element in the formula ( 1 ).
実施例４の活物質原料において、タングステンの量は、メタルサイトを構成し得るリチウム以外の金属元素、すなわち、マンガン、鉄、タングステンおよびマグネシウムの合計を１００原子％としたときに０．５原子％となる量であった。また、マグネシウムの量は、メタルサイトを構成し得るリチウム以外の金属元素の合計を１００原子％としたときに３原子％となる量であった。ケイ素の量は、ケイ素およびリンの合計を１００原子％としたときに１原子％となる量であった。さらに、リチウム：（メタルサイトを構成し得るリチウム以外の金属元素の合計）：（ケイ素とリンとの合計）の元素比は１：１：１であった。なお、活物質原料における上記の各物質の元素比は、正極活物質におけるこれらの元素比と概略一致する。
実施例４の正極活物質を用い、実施例１と同様にして、実施例４の正極ハーフセル及びリチウムイオン二次電池を製造した。 In the active material raw material of Example 4, the amount of tungsten is 0.5 atomic % when the total of metal elements other than lithium that can form metal sites, that is, manganese, iron, tungsten and magnesium is 100 atomic %. was the amount. The amount of magnesium was 3 atomic % when the total of metal elements other than lithium that could constitute the metal site was taken as 100 atomic %. The amount of silicon was 1 atomic % when the sum of silicon and phosphorus was 100 atomic %. Furthermore, the elemental ratio of lithium:(total of metal elements other than lithium that can constitute metal sites):(total of silicon and phosphorus) was 1:1:1. In addition, the element ratio of each of the above substances in the raw material of the active material approximately matches the element ratio of these elements in the positive electrode active material.
A positive electrode half cell and a lithium ion secondary battery of Example 4 were manufactured in the same manner as in Example 1 using the positive electrode active material of Example 4.
実施例４の正極活物質を用い、実施例１と同様にして、実施例４の正極ハーフセル及びリチウムイオン二次電池を製造した。 In the active material raw material of Example 4, the amount of tungsten is 0.5 atomic % when the total of metal elements other than lithium that can form metal sites, that is, manganese, iron, tungsten and magnesium is 100 atomic %. was the amount. The amount of magnesium was 3 atomic % when the total of metal elements other than lithium that could constitute the metal site was taken as 100 atomic %. The amount of silicon was 1 atomic % when the sum of silicon and phosphorus was 100 atomic %. Furthermore, the elemental ratio of lithium:(total of metal elements other than lithium that can constitute metal sites):(total of silicon and phosphorus) was 1:1:1. In addition, the element ratio of each of the above substances in the raw material of the active material approximately matches the element ratio of these elements in the positive electrode active material.
A positive electrode half cell and a lithium ion secondary battery of Example 4 were manufactured in the same manner as in Example 1 using the positive electrode active material of Example 4.
（比較例１）
比較例１の正極活物質の製造方法では、活物質原料がタングステンおよびケイ素を含まず、リチウム：（メタルサイトを構成し得るリチウム以外の金属元素）：リン元素の比は１：１：１であった。また、比較例１の正極活物質の製造方法においては、タングステン酸、ギ酸０．３ｇおよびオルトケイ酸テトラエチルを用いなかった。これ以外は、実施例１と同様にして、比較例１の正極活物質、正極ハーフセル及びリチウムイオン二次電池を製造した。 (Comparative example 1)
In the manufacturing method of the positive electrode active material of Comparative Example 1, the raw material of the active material does not contain tungsten and silicon, and the ratio of lithium: (metal elements other than lithium that can form metal sites): phosphorus element is 1:1:1. there were. Moreover, in the manufacturing method of the positive electrode active material of Comparative Example 1, tungstic acid, 0.3 g of formic acid, and tetraethyl orthosilicate were not used. A positive electrode active material, a positive electrode half cell, and a lithium ion secondary battery of Comparative Example 1 were manufactured in the same manner as in Example 1 except for this.
比較例１の正極活物質の製造方法では、活物質原料がタングステンおよびケイ素を含まず、リチウム：（メタルサイトを構成し得るリチウム以外の金属元素）：リン元素の比は１：１：１であった。また、比較例１の正極活物質の製造方法においては、タングステン酸、ギ酸０．３ｇおよびオルトケイ酸テトラエチルを用いなかった。これ以外は、実施例１と同様にして、比較例１の正極活物質、正極ハーフセル及びリチウムイオン二次電池を製造した。 (Comparative example 1)
In the manufacturing method of the positive electrode active material of Comparative Example 1, the raw material of the active material does not contain tungsten and silicon, and the ratio of lithium: (metal elements other than lithium that can form metal sites): phosphorus element is 1:1:1. there were. Moreover, in the manufacturing method of the positive electrode active material of Comparative Example 1, tungstic acid, 0.3 g of formic acid, and tetraethyl orthosilicate were not used. A positive electrode active material, a positive electrode half cell, and a lithium ion secondary battery of Comparative Example 1 were manufactured in the same manner as in Example 1 except for this.
（比較例２）
比較例２の正極活物質の製造方法では、比較例１の正極活物質をタングステンコートした。具体的な手順は以下の通りである。
タングステンアルコキシド〔Ｗ（ＯＣ2Ｈ5）6〕０．０７４ｇをエタノール１００ｍｌに溶解して、コート溶液を得た。このコート溶液に、比較例１の正極活物質１０ｇを投入し、これらをエバポレータにより１００℃で３～５時間減圧加熱し、溶媒を揮発させた。その後、残った固形分を５００℃で１時間、窒素雰囲気下で加熱することで、比較例２の正極活物質を製造した。なお、比較例２の正極活物質において、コート対象である比較例１の正極活物質に対するタングステンの量は、比較例１の正極活物質１００質量％に対して０．７４質量％であった。 (Comparative example 2)
In the manufacturing method of the positive electrode active material of Comparative Example 2, the positive electrode active material of Comparative Example 1 was coated with tungsten. The specific procedure is as follows.
A coating solution was obtained by dissolving 0.074 g of tungsten alkoxide [W(OC 2 H 5 ) 6 ] in 100 ml of ethanol. 10 g of the positive electrode active material of Comparative Example 1 was added to this coating solution, and the mixture was heated under reduced pressure at 100° C. for 3 to 5 hours using an evaporator to volatilize the solvent. After that, the remaining solid content was heated at 500° C. for 1 hour in a nitrogen atmosphere to produce a positive electrode active material of Comparative Example 2. In the positive electrode active material of Comparative Example 2, the amount of tungsten relative to the positive electrode active material of Comparative Example 1 to be coated was 0.74% by mass with respect to 100% by mass of the positive electrode active material of Comparative Example 1.
比較例２の正極活物質の製造方法では、比較例１の正極活物質をタングステンコートした。具体的な手順は以下の通りである。
タングステンアルコキシド〔Ｗ（ＯＣ2Ｈ5）6〕０．０７４ｇをエタノール１００ｍｌに溶解して、コート溶液を得た。このコート溶液に、比較例１の正極活物質１０ｇを投入し、これらをエバポレータにより１００℃で３～５時間減圧加熱し、溶媒を揮発させた。その後、残った固形分を５００℃で１時間、窒素雰囲気下で加熱することで、比較例２の正極活物質を製造した。なお、比較例２の正極活物質において、コート対象である比較例１の正極活物質に対するタングステンの量は、比較例１の正極活物質１００質量％に対して０．７４質量％であった。 (Comparative example 2)
In the manufacturing method of the positive electrode active material of Comparative Example 2, the positive electrode active material of Comparative Example 1 was coated with tungsten. The specific procedure is as follows.
A coating solution was obtained by dissolving 0.074 g of tungsten alkoxide [W(OC 2 H 5 ) 6 ] in 100 ml of ethanol. 10 g of the positive electrode active material of Comparative Example 1 was added to this coating solution, and the mixture was heated under reduced pressure at 100° C. for 3 to 5 hours using an evaporator to volatilize the solvent. After that, the remaining solid content was heated at 500° C. for 1 hour in a nitrogen atmosphere to produce a positive electrode active material of Comparative Example 2. In the positive electrode active material of Comparative Example 2, the amount of tungsten relative to the positive electrode active material of Comparative Example 1 to be coated was 0.74% by mass with respect to 100% by mass of the positive electrode active material of Comparative Example 1.
〔正極の製造〕
比較例２の正極活物質、導電助剤としてアセチレンブラック及び結着剤としてポリフッ化ビニリデンを、正極活物質と導電助剤と結着剤の質量比が９０：５：５となるように混合し、溶剤としてＮ－メチル－２－ピロリドンを添加してスラリー状の正極活物質層形成用組成物とした。正極用集電体としてアルミニウム箔を準備した。アルミニウム箔の表面に正極活物質層形成用組成物を膜状に塗布した後に溶剤を除去して製造された正極前駆体を、厚み方向にプレスすることで、アルミニウム箔の表面に正極活物質層が形成された比較例の正極を製造した。
なお、正極の目付け量の目標値は１６ｍｇ／ｃｍ2であり、正極活物質層の密度の目標値は１．９ｇ／ｍＬであった。 [Manufacturing of positive electrode]
The positive electrode active material of Comparative Example 2, acetylene black as a conductive aid, and polyvinylidene fluoride as a binder were mixed so that the mass ratio of the positive electrode active material, conductive aid, and binder was 90:5:5. , and N-methyl-2-pyrrolidone was added as a solvent to prepare a composition for forming a positive electrode active material layer in slurry form. An aluminum foil was prepared as a positive electrode current collector. A positive electrode active material layer is formed on the surface of the aluminum foil by pressing the positive electrode precursor produced by applying the composition for forming the positive electrode active material layer in the form of a film on the surface of the aluminum foil and then removing the solvent, in the thickness direction. was produced as a comparative positive electrode.
The target value for the basis weight of the positive electrode was 16 mg/cm 2 , and the target value for the density of the positive electrode active material layer was 1.9 g/mL.
比較例２の正極活物質、導電助剤としてアセチレンブラック及び結着剤としてポリフッ化ビニリデンを、正極活物質と導電助剤と結着剤の質量比が９０：５：５となるように混合し、溶剤としてＮ－メチル－２－ピロリドンを添加してスラリー状の正極活物質層形成用組成物とした。正極用集電体としてアルミニウム箔を準備した。アルミニウム箔の表面に正極活物質層形成用組成物を膜状に塗布した後に溶剤を除去して製造された正極前駆体を、厚み方向にプレスすることで、アルミニウム箔の表面に正極活物質層が形成された比較例の正極を製造した。
なお、正極の目付け量の目標値は１６ｍｇ／ｃｍ2であり、正極活物質層の密度の目標値は１．９ｇ／ｍＬであった。 [Manufacturing of positive electrode]
The positive electrode active material of Comparative Example 2, acetylene black as a conductive aid, and polyvinylidene fluoride as a binder were mixed so that the mass ratio of the positive electrode active material, conductive aid, and binder was 90:5:5. , and N-methyl-2-pyrrolidone was added as a solvent to prepare a composition for forming a positive electrode active material layer in slurry form. An aluminum foil was prepared as a positive electrode current collector. A positive electrode active material layer is formed on the surface of the aluminum foil by pressing the positive electrode precursor produced by applying the composition for forming the positive electrode active material layer in the form of a film on the surface of the aluminum foil and then removing the solvent, in the thickness direction. was produced as a comparative positive electrode.
The target value for the basis weight of the positive electrode was 16 mg/cm 2 , and the target value for the density of the positive electrode active material layer was 1.9 g/mL.
〔リチウムイオン二次電池の製造〕
負極活物質として黒鉛、結着剤としてカルボキシメチルセルロース及びスチレンブタジエンゴムを、黒鉛とカルボキシメチルセルロースとスチレンブタジエンゴムの質量比が９７：２．２：０．８となるように混合し、溶剤として水を添加してスラリー状の負極活物質層形成用組成物とした。負極用集電体として銅箔を準備した。銅箔の表面に負極活物質層形成用組成物を膜状に塗布した後に溶剤を除去して製造された負極前駆体を、厚み方向にプレスすることで、銅箔の表面に負極活物質層が形成された負極を製造した。
なお、負極の目付け量の目標値は６．８ｍｇ／ｃｍ2であり、負極活物質層の密度の目標値は１．４ｇ／ｃｍ3であった。 [Manufacture of lithium-ion secondary battery]
Graphite as a negative electrode active material, carboxymethyl cellulose and styrene-butadiene rubber as binders were mixed so that the mass ratio of graphite, carboxymethyl cellulose and styrene-butadiene rubber was 97:2.2:0.8, and water was used as a solvent. It was added to prepare a slurry composition for forming a negative electrode active material layer. A copper foil was prepared as a current collector for the negative electrode. A negative electrode active material layer is formed on the surface of the copper foil by pressing the negative electrode precursor produced by applying the negative electrode active material layer forming composition to the surface of the copper foil in the form of a film and then removing the solvent, in the thickness direction. was formed on the negative electrode.
The target value for the basis weight of the negative electrode was 6.8 mg/cm 2 , and the target value for the density of the negative electrode active material layer was 1.4 g/cm 3 .
負極活物質として黒鉛、結着剤としてカルボキシメチルセルロース及びスチレンブタジエンゴムを、黒鉛とカルボキシメチルセルロースとスチレンブタジエンゴムの質量比が９７：２．２：０．８となるように混合し、溶剤として水を添加してスラリー状の負極活物質層形成用組成物とした。負極用集電体として銅箔を準備した。銅箔の表面に負極活物質層形成用組成物を膜状に塗布した後に溶剤を除去して製造された負極前駆体を、厚み方向にプレスすることで、銅箔の表面に負極活物質層が形成された負極を製造した。
なお、負極の目付け量の目標値は６．８ｍｇ／ｃｍ2であり、負極活物質層の密度の目標値は１．４ｇ／ｃｍ3であった。 [Manufacture of lithium-ion secondary battery]
Graphite as a negative electrode active material, carboxymethyl cellulose and styrene-butadiene rubber as binders were mixed so that the mass ratio of graphite, carboxymethyl cellulose and styrene-butadiene rubber was 97:2.2:0.8, and water was used as a solvent. It was added to prepare a slurry composition for forming a negative electrode active material layer. A copper foil was prepared as a current collector for the negative electrode. A negative electrode active material layer is formed on the surface of the copper foil by pressing the negative electrode precursor produced by applying the negative electrode active material layer forming composition to the surface of the copper foil in the form of a film and then removing the solvent, in the thickness direction. was formed on the negative electrode.
The target value for the basis weight of the negative electrode was 6.8 mg/cm 2 , and the target value for the density of the negative electrode active material layer was 1.4 g/cm 3 .
エチレンカーボネートとプロピオン酸メチルとを体積比１５：８５で混合した混合溶媒に、ＬｉＰＦ6を濃度１．２モル／Ｌで溶解し母液とした。当該母液に対して１質量％に相当する量のビニレンカーボネート、および、１質量％に相当する量のリチウムジフルオロ（オキサラート）ボラートを加えて溶解することで、電解液を製造した。
セパレータとしてポリプロピレン製の多孔質膜を準備した。正極と負極でセパレータを挟持して電極体とした。この電極体を上記の電解液と共に、袋状のラミネートフィルムに入れて密閉することで、比較例２のリチウムイオン二次電池を製造した。 A mother liquor was prepared by dissolving LiPF 6 at a concentration of 1.2 mol/L in a mixed solvent of ethylene carbonate and methyl propionate at a volume ratio of 15:85. An electrolytic solution was produced by adding and dissolving vinylene carbonate in an amount corresponding to 1% by mass and lithium difluoro(oxalate)borate in an amount corresponding to 1% by mass with respect to the mother liquor.
A polypropylene porous membrane was prepared as a separator. An electrode body was formed by sandwiching a separator between the positive electrode and the negative electrode. A lithium ion secondary battery of Comparative Example 2 was manufactured by putting this electrode assembly into a bag-like laminate film and sealing it together with the electrolyte solution.
セパレータとしてポリプロピレン製の多孔質膜を準備した。正極と負極でセパレータを挟持して電極体とした。この電極体を上記の電解液と共に、袋状のラミネートフィルムに入れて密閉することで、比較例２のリチウムイオン二次電池を製造した。 A mother liquor was prepared by dissolving LiPF 6 at a concentration of 1.2 mol/L in a mixed solvent of ethylene carbonate and methyl propionate at a volume ratio of 15:85. An electrolytic solution was produced by adding and dissolving vinylene carbonate in an amount corresponding to 1% by mass and lithium difluoro(oxalate)borate in an amount corresponding to 1% by mass with respect to the mother liquor.
A polypropylene porous membrane was prepared as a separator. An electrode body was formed by sandwiching a separator between the positive electrode and the negative electrode. A lithium ion secondary battery of Comparative Example 2 was manufactured by putting this electrode assembly into a bag-like laminate film and sealing it together with the electrolyte solution.
（比較例３）
比較例３の正極活物質の製造方法では、コート溶液におけるタングステンアルコキシドの量を０．１４８ｇとしたこと以外は比較例２と概略同じ方法で、比較例３の正極活物質およびリチウムイオン二次電池を得た。なお、比較例３の正極活物質におけるタングステンアルコキシドの量は、コート対象である比較例１の正極活物質１００質量％に対して１．４８質量％であった。 (Comparative Example 3)
In the method for producing the positive electrode active material of Comparative Example 3, the positive electrode active material of Comparative Example 3 and the lithium ion secondary battery were produced in substantially the same manner as in Comparative Example 2, except that the amount of tungsten alkoxide in the coating solution was 0.148 g. got The amount of tungsten alkoxide in the positive electrode active material of Comparative Example 3 was 1.48% by mass with respect to 100% by mass of the positive electrode active material of Comparative Example 1 to be coated.
比較例３の正極活物質の製造方法では、コート溶液におけるタングステンアルコキシドの量を０．１４８ｇとしたこと以外は比較例２と概略同じ方法で、比較例３の正極活物質およびリチウムイオン二次電池を得た。なお、比較例３の正極活物質におけるタングステンアルコキシドの量は、コート対象である比較例１の正極活物質１００質量％に対して１．４８質量％であった。 (Comparative Example 3)
In the method for producing the positive electrode active material of Comparative Example 3, the positive electrode active material of Comparative Example 3 and the lithium ion secondary battery were produced in substantially the same manner as in Comparative Example 2, except that the amount of tungsten alkoxide in the coating solution was 0.148 g. got The amount of tungsten alkoxide in the positive electrode active material of Comparative Example 3 was 1.48% by mass with respect to 100% by mass of the positive electrode active material of Comparative Example 1 to be coated.
（比較例４）
比較例４の正極活物質の製造方法では、コート溶液におけるタングステンアルコキシドの量を０．２２２ｇとしたこと以外は比較例２と概略同じ方法で、比較例４の正極活物質およびリチウムイオン二次電池を得た。比較例４の正極活物質におけるタングステンアルコキシドの量は、コート対象である比較例１の正極活物質１００質量％に対して２．２２質量％であった。 (Comparative Example 4)
In the method for producing the positive electrode active material of Comparative Example 4, the positive electrode active material and the lithium ion secondary battery of Comparative Example 4 were produced in substantially the same manner as in Comparative Example 2 except that the amount of tungsten alkoxide in the coating solution was 0.222 g. got The amount of tungsten alkoxide in the positive electrode active material of Comparative Example 4 was 2.22% by mass with respect to 100% by mass of the positive electrode active material of Comparative Example 1 to be coated.
比較例４の正極活物質の製造方法では、コート溶液におけるタングステンアルコキシドの量を０．２２２ｇとしたこと以外は比較例２と概略同じ方法で、比較例４の正極活物質およびリチウムイオン二次電池を得た。比較例４の正極活物質におけるタングステンアルコキシドの量は、コート対象である比較例１の正極活物質１００質量％に対して２．２２質量％であった。 (Comparative Example 4)
In the method for producing the positive electrode active material of Comparative Example 4, the positive electrode active material and the lithium ion secondary battery of Comparative Example 4 were produced in substantially the same manner as in Comparative Example 2 except that the amount of tungsten alkoxide in the coating solution was 0.222 g. got The amount of tungsten alkoxide in the positive electrode active material of Comparative Example 4 was 2.22% by mass with respect to 100% by mass of the positive electrode active material of Comparative Example 1 to be coated.
（比較例５）
比較例１の正極活物質を用い、比較例２と概略同じ方法で、比較例５のリチウムイオン二次電池を得た。比較例１のリチウムイオン二次電池は、正極活物質にタングステンを含まない。 (Comparative Example 5)
A lithium ion secondary battery of Comparative Example 5 was obtained in substantially the same manner as in Comparative Example 2 using the positive electrode active material of Comparative Example 1. The lithium ion secondary battery of Comparative Example 1 does not contain tungsten in the positive electrode active material.
比較例１の正極活物質を用い、比較例２と概略同じ方法で、比較例５のリチウムイオン二次電池を得た。比較例１のリチウムイオン二次電池は、正極活物質にタングステンを含まない。 (Comparative Example 5)
A lithium ion secondary battery of Comparative Example 5 was obtained in substantially the same manner as in Comparative Example 2 using the positive electrode active material of Comparative Example 1. The lithium ion secondary battery of Comparative Example 1 does not contain tungsten in the positive electrode active material.
（参考例１）
〔正極活物質の合成〕
純水５０ｍｌに、リチウム源としてＬｉＯＨ１水和物２．７ｇ、ｐＨ調整剤としてリンゴ酸８．２１ｇ、マンガン源として酢酸マンガン（ＩＩ）５水和物１１．２５ｇ、鉄源として硫酸鉄（ＩＩ）７水和物３．７５ｇ、マグネシウム源として酢酸マグネシウム４水和物０．３９３ｇ、および、リン源として８５％リン酸７．０６ｇを溶解し、５０℃で１２時間加熱して、ゲル状の活物質原料を得た。
このゲル状の活物質原料を６０℃で２４時間真空乾燥し、その後、窒素雰囲気下３５０℃で５時間加熱し、次いで、窒素雰囲気下６５０℃で１５時間加熱することで、参考例１の正極活物質を製造した。
なお、参考例１においては、マグネシウムが式（１）におけるＤ1元素に相当する。 (Reference example 1)
[Synthesis of positive electrode active material]
To 50 ml of pure water, 2.7 g of LiOH monohydrate as a lithium source, 8.21 g of malic acid as a pH adjuster, 11.25 g of manganese (II) acetate pentahydrate as a manganese source, and iron (II) sulfate as an iron source. 3.75 g of heptahydrate, 0.393 g of magnesium acetate tetrahydrate as a magnesium source, and 7.06 g of 85% phosphoric acid as a phosphorus source were dissolved and heated at 50° C. for 12 hours to form a gel-like active material. A raw material was obtained.
This gel-like active material raw material was vacuum-dried at 60° C. for 24 hours, then heated at 350° C. for 5 hours under a nitrogen atmosphere, and then heated at 650° C. for 15 hours under a nitrogen atmosphere. An active material was produced.
Incidentally, in Reference Example 1, magnesium corresponds to the D1 element in the formula ( 1 ).
〔正極活物質の合成〕
純水５０ｍｌに、リチウム源としてＬｉＯＨ１水和物２．７ｇ、ｐＨ調整剤としてリンゴ酸８．２１ｇ、マンガン源として酢酸マンガン（ＩＩ）５水和物１１．２５ｇ、鉄源として硫酸鉄（ＩＩ）７水和物３．７５ｇ、マグネシウム源として酢酸マグネシウム４水和物０．３９３ｇ、および、リン源として８５％リン酸７．０６ｇを溶解し、５０℃で１２時間加熱して、ゲル状の活物質原料を得た。
このゲル状の活物質原料を６０℃で２４時間真空乾燥し、その後、窒素雰囲気下３５０℃で５時間加熱し、次いで、窒素雰囲気下６５０℃で１５時間加熱することで、参考例１の正極活物質を製造した。
なお、参考例１においては、マグネシウムが式（１）におけるＤ1元素に相当する。 (Reference example 1)
[Synthesis of positive electrode active material]
To 50 ml of pure water, 2.7 g of LiOH monohydrate as a lithium source, 8.21 g of malic acid as a pH adjuster, 11.25 g of manganese (II) acetate pentahydrate as a manganese source, and iron (II) sulfate as an iron source. 3.75 g of heptahydrate, 0.393 g of magnesium acetate tetrahydrate as a magnesium source, and 7.06 g of 85% phosphoric acid as a phosphorus source were dissolved and heated at 50° C. for 12 hours to form a gel-like active material. A raw material was obtained.
This gel-like active material raw material was vacuum-dried at 60° C. for 24 hours, then heated at 350° C. for 5 hours under a nitrogen atmosphere, and then heated at 650° C. for 15 hours under a nitrogen atmosphere. An active material was produced.
Incidentally, in Reference Example 1, magnesium corresponds to the D1 element in the formula ( 1 ).
参考例１の活物質原料において、マグネシウムの量は、マンガン、鉄およびマグネシウムの合計を１００原子％としたときに３原子％となる量であった。また、リチウム：（メタルサイトを構成し得るリチウム以外の金属元素の合計）：リンは１：１：１であった。なお、活物質原料におけるリチウム、マンガン、鉄、マグネシウムおよびリンの元素比は、正極活物質におけるこれらの元素比と概略一致する。
In the active material raw material of Reference Example 1, the amount of magnesium was 3 atomic % when the total of manganese, iron and magnesium was taken as 100 atomic %. Also, the ratio of lithium:(total of metal elements other than lithium that can form metal sites):phosphorus was 1:1:1. The elemental ratios of lithium, manganese, iron, magnesium and phosphorus in the raw material of the active material approximately match those in the positive electrode active material.
参考例１の正極活物質を用い、実施例１と同様にして、参考例１の正極ハーフセル及びリチウムイオン二次電池を製造した。
Using the positive electrode active material of Reference Example 1, a positive electrode half cell and a lithium ion secondary battery of Reference Example 1 were manufactured in the same manner as in Example 1.
（実施例５）
〔正極活物質の合成〕
純水５０ｍｌに、リチウム源としてＬｉＯＨ１水和物２．５７ｇ、ｐＨ調整剤としてリンゴ酸８．２１ｇ、マンガン源として酢酸マンガン（ＩＩ）４水和物１１．２５ｇ、鉄源として硫酸鉄（ＩＩ）７水和物３．７０ｇ、マグネシウム源として酢酸マグネシウム４水和物０．３９４ｇ、タングステン源としてタングステン酸０．０３８ｇ、還元剤としてギ酸０．３ｇ、ケイ素源としてオルトケイ酸テトラエチル(TEOS)０．０６４ｇ、フッ素源としてＬｉＦ０．０１６ｇ、および、リン源として８５％リン酸７．０３ｇを溶解し、５０℃で１２時間加熱して、ゲル状の活物質原料を得た。
このゲル状の活物質原料を６０℃で２４時間真空乾燥し、その後、窒素雰囲気下３５０℃で５時間加熱し、次いで、窒素雰囲気下６５０℃で１５時間加熱することで、実施例５の正極活物質を製造した。 (Example 5)
[Synthesis of positive electrode active material]
To 50 ml of pure water, 2.57 g of LiOH monohydrate as a lithium source, 8.21 g of malic acid as a pH adjuster, 11.25 g of manganese (II) acetate tetrahydrate as a manganese source, and iron (II) sulfate as an iron source. 3.70 g heptahydrate, 0.394 g magnesium acetate tetrahydrate as magnesium source, 0.038 g tungstic acid as tungsten source, 0.3 g formic acid as reducing agent, 0.064 g tetraethyl orthosilicate (TEOS) as silicon source , 0.016 g of LiF as a fluorine source and 7.03 g of 85% phosphoric acid as a phosphorus source were dissolved and heated at 50° C. for 12 hours to obtain a gel-like active material raw material.
This gel-like active material raw material was vacuum-dried at 60° C. for 24 hours, then heated at 350° C. for 5 hours under a nitrogen atmosphere, and then heated at 650° C. for 15 hours under a nitrogen atmosphere. An active material was produced.
〔正極活物質の合成〕
純水５０ｍｌに、リチウム源としてＬｉＯＨ１水和物２．５７ｇ、ｐＨ調整剤としてリンゴ酸８．２１ｇ、マンガン源として酢酸マンガン（ＩＩ）４水和物１１．２５ｇ、鉄源として硫酸鉄（ＩＩ）７水和物３．７０ｇ、マグネシウム源として酢酸マグネシウム４水和物０．３９４ｇ、タングステン源としてタングステン酸０．０３８ｇ、還元剤としてギ酸０．３ｇ、ケイ素源としてオルトケイ酸テトラエチル(TEOS)０．０６４ｇ、フッ素源としてＬｉＦ０．０１６ｇ、および、リン源として８５％リン酸７．０３ｇを溶解し、５０℃で１２時間加熱して、ゲル状の活物質原料を得た。
このゲル状の活物質原料を６０℃で２４時間真空乾燥し、その後、窒素雰囲気下３５０℃で５時間加熱し、次いで、窒素雰囲気下６５０℃で１５時間加熱することで、実施例５の正極活物質を製造した。 (Example 5)
[Synthesis of positive electrode active material]
To 50 ml of pure water, 2.57 g of LiOH monohydrate as a lithium source, 8.21 g of malic acid as a pH adjuster, 11.25 g of manganese (II) acetate tetrahydrate as a manganese source, and iron (II) sulfate as an iron source. 3.70 g heptahydrate, 0.394 g magnesium acetate tetrahydrate as magnesium source, 0.038 g tungstic acid as tungsten source, 0.3 g formic acid as reducing agent, 0.064 g tetraethyl orthosilicate (TEOS) as silicon source , 0.016 g of LiF as a fluorine source and 7.03 g of 85% phosphoric acid as a phosphorus source were dissolved and heated at 50° C. for 12 hours to obtain a gel-like active material raw material.
This gel-like active material raw material was vacuum-dried at 60° C. for 24 hours, then heated at 350° C. for 5 hours under a nitrogen atmosphere, and then heated at 650° C. for 15 hours under a nitrogen atmosphere. An active material was produced.
なお、実施例５においては、マグネシウムが式（１－１）におけるＤ1元素に相当し、ケイ素が式（１－１）におけるＤ2元素に相当する。
また、実施例５の正極活物質における各元素の組成比において、ＬｉＦに由来するＬｉ量は考慮しないものとする。以下の実施例等においても同様である。 In Example 5, magnesium corresponds to the D 1 element in formula (1-1), and silicon corresponds to the D 2 element in formula (1-1).
Moreover, in the composition ratio of each element in the positive electrode active material of Example 5, the amount of Li derived from LiF is not considered. The same applies to the following examples and the like.
また、実施例５の正極活物質における各元素の組成比において、ＬｉＦに由来するＬｉ量は考慮しないものとする。以下の実施例等においても同様である。 In Example 5, magnesium corresponds to the D 1 element in formula (1-1), and silicon corresponds to the D 2 element in formula (1-1).
Moreover, in the composition ratio of each element in the positive electrode active material of Example 5, the amount of Li derived from LiF is not considered. The same applies to the following examples and the like.
実施例５の活物質原料において、タングステンの量は、マンガン、鉄、タングステンおよびマグネシウムの合計を１００原子％としたときに０．２５原子％となる量であった。また、マグネシウムの量は、マンガン、鉄、タングステンおよびマグネシウムの合計を１００原子％としたときに３原子％となる量であった。ケイ素の量は、ケイ素およびリンの合計を１００原子％としたときに０．５原子％となる量であった。フッ素の量は、フッ素および酸素の合計を４００原子％としたときに１原子％となる量であった。さらに、リチウム：（メタルサイトを構成し得るリチウム以外の金属元素の合計）：（ケイ素とリンとの合計）の元素比は１：１：１であった。なお、活物質原料における上記の各物質の元素比は、正極活物質におけるこれらの元素比と概略一致する。
実施例５の正極活物質を用い、以下のように実施例５のハーフセルを製造した。 In the raw material for the active material of Example 5, the amount of tungsten was 0.25 atomic % when the total of manganese, iron, tungsten and magnesium was taken as 100 atomic %. The amount of magnesium was 3 atomic % when the total of manganese, iron, tungsten and magnesium was taken as 100 atomic %. The amount of silicon was 0.5 atomic % when the sum of silicon and phosphorus was 100 atomic %. The amount of fluorine was 1 atomic % when the total of fluorine and oxygen was 400 atomic %. Furthermore, the elemental ratio of lithium:(total of metal elements other than lithium that can constitute metal sites):(total of silicon and phosphorus) was 1:1:1. In addition, the element ratio of each of the above substances in the raw material of the active material approximately matches the element ratio of these elements in the positive electrode active material.
Using the positive electrode active material of Example 5, a half cell of Example 5 was manufactured as follows.
実施例５の正極活物質を用い、以下のように実施例５のハーフセルを製造した。 In the raw material for the active material of Example 5, the amount of tungsten was 0.25 atomic % when the total of manganese, iron, tungsten and magnesium was taken as 100 atomic %. The amount of magnesium was 3 atomic % when the total of manganese, iron, tungsten and magnesium was taken as 100 atomic %. The amount of silicon was 0.5 atomic % when the sum of silicon and phosphorus was 100 atomic %. The amount of fluorine was 1 atomic % when the total of fluorine and oxygen was 400 atomic %. Furthermore, the elemental ratio of lithium:(total of metal elements other than lithium that can constitute metal sites):(total of silicon and phosphorus) was 1:1:1. In addition, the element ratio of each of the above substances in the raw material of the active material approximately matches the element ratio of these elements in the positive electrode active material.
Using the positive electrode active material of Example 5, a half cell of Example 5 was manufactured as follows.
実施例５の正極活物質を３質量部に対して、導電助剤としてのアセチレンブラック（ＡＢ）を１質量部、ＡＢと結着剤としてのポリテトラフルオロエチレン（ＰＴＦＥ）との混合物（ＡＢ：ＰＴＦＥ（質量比）＝２：１）を１質量部、及び、適量のＮ－メチル－２－ピロリドンを混合して、スラリーを製造した。正極用集電体として厚み１０μｍのアルミニウム箔を準備した。当該正極集電体の表面に、ドクターブレードを用いて、上記スラリーを膜状に塗布した。スラリーが塗布された正極集電体を８０℃、１５分間乾燥することで、Ｎ－メチル－２－ピロリドンを除去した。その後、プレスすることで、正極集電体上に正極活物質層が形成された実施例５の正極を製造した。
A mixture (AB: A slurry was prepared by mixing 1 part by mass of PTFE (mass ratio)=2:1) and an appropriate amount of N-methyl-2-pyrrolidone. An aluminum foil having a thickness of 10 μm was prepared as a current collector for positive electrode. The slurry was applied to the surface of the positive electrode current collector in the form of a film using a doctor blade. The positive electrode current collector coated with the slurry was dried at 80° C. for 15 minutes to remove N-methyl-2-pyrrolidone. Then, by pressing, the positive electrode of Example 5 in which a positive electrode active material layer was formed on the positive electrode current collector was manufactured.
実施例５の正極を径１１ｍｍに裁断し、評価極とした。厚さ５００μｍの金属リチウム箔を径１３ｍｍに裁断し対極とした。セパレータとしてガラスフィルター（ヘキストセラニーズ社）及び単層ポリプロピレンであるｃｅｌｇａｒｄ２４００（ポリポア株式会社）を準備した。対極、ガラスフィルター、ｃｅｌｇａｒｄ２４００、評価極の順に、２種のセパレータを対極と評価極で挟持し電極体とした。この電極体をコイン型電池ケースＣＲ２０３２（宝泉株式会社）に収容し、さらに実施例１と同じ電解液を注入して、コイン型電池を得た。これを実施例５のハーフセルとした。
The positive electrode of Example 5 was cut to a diameter of 11 mm and used as an evaluation electrode. A metallic lithium foil having a thickness of 500 μm was cut into a diameter of 13 mm to form a counter electrode. A glass filter (Hoechst Celanese) and celgard 2400 (Polypore Co., Ltd.), which is a single-layer polypropylene, were prepared as separators. Two types of separators were sandwiched between the counter electrode and the evaluation electrode in the order of the counter electrode, the glass filter, celgard2400, and the evaluation electrode to form an electrode assembly. This electrode assembly was housed in a coin-shaped battery case CR2032 (Hosen Co., Ltd.), and the same electrolytic solution as in Example 1 was injected to obtain a coin-shaped battery. This was used as a half cell of Example 5.
（実施例６）
実施例６の正極活物質の製造方法では、活物質原料におけるフッ素の量が、フッ素および酸素の合計を４００原子％としたときに５原子％となる量であった。これ以外は、実施例５と同様にして、実施例６の正極活物質及びハーフセルを製造した。なお、実施例６においても、マグネシウムが式（１－１）におけるＤ1元素に相当し、ケイ素が式（１－１）におけるＤ2元素に相当する。
実施例６の活物質原料において、タングステンの量は、マンガン、鉄、タングステンおよびマグネシウムの合計を１００原子％としたときに０．２５原子％となる量であった。また、マグネシウムの量は、マンガン、鉄、タングステンおよびマグネシウムの合計を１００原子％としたときに３原子％となる量であった。ケイ素の量は、ケイ素およびリンの合計を１００原子％としたときに０．５原子％となる量であった。さらに、リチウム：（メタルサイトを構成し得るリチウム以外の金属元素の合計）：（ケイ素とリンとの合計）の元素比は１：１：１であった。なお、活物質原料における上記の各物質の元素比は、正極活物質におけるこれらの元素比と概略一致する。 (Example 6)
In the manufacturing method of the positive electrode active material of Example 6, the amount of fluorine in the raw material of the active material was 5 atomic % when the total of fluorine and oxygen was 400 atomic %. A cathode active material and a half cell of Example 6 were manufactured in the same manner as in Example 5 except for this. Also in Example 6, magnesium corresponds to the D 1 element in formula (1-1), and silicon corresponds to the D 2 element in formula (1-1).
In the active material raw material of Example 6, the amount of tungsten was 0.25 atomic % when the total of manganese, iron, tungsten and magnesium was taken as 100 atomic %. The amount of magnesium was 3 atomic % when the total of manganese, iron, tungsten and magnesium was taken as 100 atomic %. The amount of silicon was 0.5 atomic % when the sum of silicon and phosphorus was 100 atomic %. Furthermore, the elemental ratio of lithium:(total of metal elements other than lithium that can constitute metal sites):(total of silicon and phosphorus) was 1:1:1. In addition, the element ratio of each of the above substances in the raw material of the active material approximately matches the element ratio of these elements in the positive electrode active material.
実施例６の正極活物質の製造方法では、活物質原料におけるフッ素の量が、フッ素および酸素の合計を４００原子％としたときに５原子％となる量であった。これ以外は、実施例５と同様にして、実施例６の正極活物質及びハーフセルを製造した。なお、実施例６においても、マグネシウムが式（１－１）におけるＤ1元素に相当し、ケイ素が式（１－１）におけるＤ2元素に相当する。
実施例６の活物質原料において、タングステンの量は、マンガン、鉄、タングステンおよびマグネシウムの合計を１００原子％としたときに０．２５原子％となる量であった。また、マグネシウムの量は、マンガン、鉄、タングステンおよびマグネシウムの合計を１００原子％としたときに３原子％となる量であった。ケイ素の量は、ケイ素およびリンの合計を１００原子％としたときに０．５原子％となる量であった。さらに、リチウム：（メタルサイトを構成し得るリチウム以外の金属元素の合計）：（ケイ素とリンとの合計）の元素比は１：１：１であった。なお、活物質原料における上記の各物質の元素比は、正極活物質におけるこれらの元素比と概略一致する。 (Example 6)
In the manufacturing method of the positive electrode active material of Example 6, the amount of fluorine in the raw material of the active material was 5 atomic % when the total of fluorine and oxygen was 400 atomic %. A cathode active material and a half cell of Example 6 were manufactured in the same manner as in Example 5 except for this. Also in Example 6, magnesium corresponds to the D 1 element in formula (1-1), and silicon corresponds to the D 2 element in formula (1-1).
In the active material raw material of Example 6, the amount of tungsten was 0.25 atomic % when the total of manganese, iron, tungsten and magnesium was taken as 100 atomic %. The amount of magnesium was 3 atomic % when the total of manganese, iron, tungsten and magnesium was taken as 100 atomic %. The amount of silicon was 0.5 atomic % when the sum of silicon and phosphorus was 100 atomic %. Furthermore, the elemental ratio of lithium:(total of metal elements other than lithium that can constitute metal sites):(total of silicon and phosphorus) was 1:1:1. In addition, the element ratio of each of the above substances in the raw material of the active material approximately matches the element ratio of these elements in the positive electrode active material.
（実施例７）
〔正極活物質の合成〕
純水５０ｍｌに、リチウム源としてＬｉＯＨ１水和物２．５７ｇ、ｐＨ調整剤としてリンゴ酸８．２１ｇ、マンガン源として酢酸マンガン（ＩＩ）４水和物１１．２５ｇ、鉄源として硫酸鉄（ＩＩ）７水和物３．４５ｇ、マグネシウム源として酢酸マグネシウム４水和物０．３９４ｇ、タングステン源としてタングステン酸０．０３８ｇ、クロム源として酢酸クロム水和物（クロムを２２質量％含有）０．２１７ｇ、還元剤としてギ酸０．３ｇ、ケイ素源としてオルトケイ酸テトラエチル(TEOS)０．０６４ｇ、および、リン源として８５％リン酸７．０２３ｇを溶解し、５０℃で１２時間加熱して、ゲル状の活物質原料を得た。
このゲル状の活物質原料を６０℃で２４時間真空乾燥し、その後、窒素雰囲気下３５０℃で５時間加熱し、次いで、窒素雰囲気下６５０℃で１５時間加熱することで、実施例７の正極活物質を製造した。当該実施例７の正極活物質を用い、実施例５と同様にして、実施例７のハーフセルを製造した。 (Example 7)
[Synthesis of positive electrode active material]
To 50 ml of pure water, 2.57 g of LiOH monohydrate as a lithium source, 8.21 g of malic acid as a pH adjuster, 11.25 g of manganese (II) acetate tetrahydrate as a manganese source, and iron (II) sulfate as an iron source. 3.45 g of heptahydrate, 0.394 g of magnesium acetate tetrahydrate as a magnesium source, 0.038 g of tungstic acid as a tungsten source, 0.217 g of chromium acetate hydrate (containing 22% by mass of chromium) as a chromium source, 0.3 g of formic acid as a reducing agent, 0.064 g of tetraethyl orthosilicate (TEOS) as a silicon source, and 7.023 g of 85% phosphoric acid as a phosphorus source were dissolved and heated at 50° C. for 12 hours to form a gel-like active material. A raw material was obtained.
This gel-like active material raw material was vacuum-dried at 60° C. for 24 hours, then heated at 350° C. for 5 hours under a nitrogen atmosphere, and then heated at 650° C. for 15 hours under a nitrogen atmosphere. An active material was produced. A half cell of Example 7 was manufactured in the same manner as in Example 5 using the positive electrode active material of Example 7.
〔正極活物質の合成〕
純水５０ｍｌに、リチウム源としてＬｉＯＨ１水和物２．５７ｇ、ｐＨ調整剤としてリンゴ酸８．２１ｇ、マンガン源として酢酸マンガン（ＩＩ）４水和物１１．２５ｇ、鉄源として硫酸鉄（ＩＩ）７水和物３．４５ｇ、マグネシウム源として酢酸マグネシウム４水和物０．３９４ｇ、タングステン源としてタングステン酸０．０３８ｇ、クロム源として酢酸クロム水和物（クロムを２２質量％含有）０．２１７ｇ、還元剤としてギ酸０．３ｇ、ケイ素源としてオルトケイ酸テトラエチル(TEOS)０．０６４ｇ、および、リン源として８５％リン酸７．０２３ｇを溶解し、５０℃で１２時間加熱して、ゲル状の活物質原料を得た。
このゲル状の活物質原料を６０℃で２４時間真空乾燥し、その後、窒素雰囲気下３５０℃で５時間加熱し、次いで、窒素雰囲気下６５０℃で１５時間加熱することで、実施例７の正極活物質を製造した。当該実施例７の正極活物質を用い、実施例５と同様にして、実施例７のハーフセルを製造した。 (Example 7)
[Synthesis of positive electrode active material]
To 50 ml of pure water, 2.57 g of LiOH monohydrate as a lithium source, 8.21 g of malic acid as a pH adjuster, 11.25 g of manganese (II) acetate tetrahydrate as a manganese source, and iron (II) sulfate as an iron source. 3.45 g of heptahydrate, 0.394 g of magnesium acetate tetrahydrate as a magnesium source, 0.038 g of tungstic acid as a tungsten source, 0.217 g of chromium acetate hydrate (containing 22% by mass of chromium) as a chromium source, 0.3 g of formic acid as a reducing agent, 0.064 g of tetraethyl orthosilicate (TEOS) as a silicon source, and 7.023 g of 85% phosphoric acid as a phosphorus source were dissolved and heated at 50° C. for 12 hours to form a gel-like active material. A raw material was obtained.
This gel-like active material raw material was vacuum-dried at 60° C. for 24 hours, then heated at 350° C. for 5 hours under a nitrogen atmosphere, and then heated at 650° C. for 15 hours under a nitrogen atmosphere. An active material was produced. A half cell of Example 7 was manufactured in the same manner as in Example 5 using the positive electrode active material of Example 7.
実施例７の正極活物質を用いて、実施例１と同様にしてリチウムイオン二次電池を製造した。なお、実施例７のリチウムイオン二次電池において、負極の目付け量は５ｍｇ／ｃｍ2、負極活物質層の密度は１．３５ｇ／ｃｍ3、正極の目付け量の目標値は１４ｍｇ／ｃｍ2、および、正極活物質層の密度の目標値は１．８ｇ／ｃｍ3であった。
A lithium ion secondary battery was produced in the same manner as in Example 1 using the positive electrode active material of Example 7. In the lithium ion secondary battery of Example 7, the basis weight of the negative electrode was 5 mg/cm 2 , the density of the negative electrode active material layer was 1.35 g/cm 3 , the target value of the basis weight of the positive electrode was 14 mg/cm 2 , And the target value of the density of the positive electrode active material layer was 1.8 g/cm 3 .
実施例７においては、マグネシウムおよびクロムが式（１）におけるＤ1元素に相当し、ケイ素が式（１）におけるＤ2元素に相当する。
実施例７の活物質原料において、タングステンの量は、マンガン、鉄、タングステン、マグネシウムおよびクロムの合計を１００原子％としたときに０．２５原子％となる量であった。また、マグネシウムの量は、マンガン、鉄、タングステン、マグネシウムおよびクロムの合計を１００原子％としたときに３原子％となる量であった。クロムの量は、マンガン、鉄、タングステン、マグネシウムおよびクロムの合計を１００原子％としたときに１．５原子％となる量であった。ケイ素の量は、ケイ素およびリンの合計を１００原子％としたときに０．５原子％となる量であった。リチウム：（メタルサイトを構成し得るリチウム以外の金属元素の合計）：（ケイ素とリンとの合計）の元素比は１：１：１であった。なお、活物質原料における上記の各物質の元素比は、正極活物質におけるこれらの元素比と概略一致する。 In Example 7, magnesium and chromium correspond to the D1 element in formula (1), and silicon corresponds to the D2 element in formula ( 1 ).
In the active material raw material of Example 7, the amount of tungsten was 0.25 atomic % when the total of manganese, iron, tungsten, magnesium and chromium was taken as 100 atomic %. The amount of magnesium was 3 atomic % when the total of manganese, iron, tungsten, magnesium and chromium was taken as 100 atomic %. The amount of chromium was 1.5 atomic percent when the sum of manganese, iron, tungsten, magnesium and chromium was 100 atomic percent. The amount of silicon was 0.5 atomic % when the sum of silicon and phosphorus was 100 atomic %. The elemental ratio of lithium:(sum of metal elements other than lithium that can form metal sites):(sum of silicon and phosphorus) was 1:1:1. In addition, the element ratio of each of the above substances in the raw material of the active material approximately matches the element ratio of these elements in the positive electrode active material.
実施例７の活物質原料において、タングステンの量は、マンガン、鉄、タングステン、マグネシウムおよびクロムの合計を１００原子％としたときに０．２５原子％となる量であった。また、マグネシウムの量は、マンガン、鉄、タングステン、マグネシウムおよびクロムの合計を１００原子％としたときに３原子％となる量であった。クロムの量は、マンガン、鉄、タングステン、マグネシウムおよびクロムの合計を１００原子％としたときに１．５原子％となる量であった。ケイ素の量は、ケイ素およびリンの合計を１００原子％としたときに０．５原子％となる量であった。リチウム：（メタルサイトを構成し得るリチウム以外の金属元素の合計）：（ケイ素とリンとの合計）の元素比は１：１：１であった。なお、活物質原料における上記の各物質の元素比は、正極活物質におけるこれらの元素比と概略一致する。 In Example 7, magnesium and chromium correspond to the D1 element in formula (1), and silicon corresponds to the D2 element in formula ( 1 ).
In the active material raw material of Example 7, the amount of tungsten was 0.25 atomic % when the total of manganese, iron, tungsten, magnesium and chromium was taken as 100 atomic %. The amount of magnesium was 3 atomic % when the total of manganese, iron, tungsten, magnesium and chromium was taken as 100 atomic %. The amount of chromium was 1.5 atomic percent when the sum of manganese, iron, tungsten, magnesium and chromium was 100 atomic percent. The amount of silicon was 0.5 atomic % when the sum of silicon and phosphorus was 100 atomic %. The elemental ratio of lithium:(sum of metal elements other than lithium that can form metal sites):(sum of silicon and phosphorus) was 1:1:1. In addition, the element ratio of each of the above substances in the raw material of the active material approximately matches the element ratio of these elements in the positive electrode active material.
（実施例８）
実施例８の正極活物質の製造方法では、活物質原料における鉄の量がマンガン、鉄、タングステン、マグネシウムおよびクロムの合計を１００原子％としたときに１８．７５原子％となる量であり、クロムの量がマンガン、鉄、タングステン、マグネシウムおよびクロムの合計を１００原子％としたときに３原子％となる量であった。これ以外は、実施例７と同様にして、実施例８の正極活物質及びハーフセルを製造した。
また、実施例８の正極活物質を用いて、実施例７と同様にして実施例８のリチウムイオン二次電池を製造した。 (Example 8)
In the method for producing a positive electrode active material of Example 8, the amount of iron in the active material raw material is 18.75 atomic % when the total of manganese, iron, tungsten, magnesium and chromium is 100 atomic %, The amount of chromium was 3 atomic % when the total of manganese, iron, tungsten, magnesium and chromium was 100 atomic %. A positive electrode active material and a half cell of Example 8 were manufactured in the same manner as in Example 7 except for this.
Also, using the positive electrode active material of Example 8, a lithium ion secondary battery of Example 8 was manufactured in the same manner as in Example 7.
実施例８の正極活物質の製造方法では、活物質原料における鉄の量がマンガン、鉄、タングステン、マグネシウムおよびクロムの合計を１００原子％としたときに１８．７５原子％となる量であり、クロムの量がマンガン、鉄、タングステン、マグネシウムおよびクロムの合計を１００原子％としたときに３原子％となる量であった。これ以外は、実施例７と同様にして、実施例８の正極活物質及びハーフセルを製造した。
また、実施例８の正極活物質を用いて、実施例７と同様にして実施例８のリチウムイオン二次電池を製造した。 (Example 8)
In the method for producing a positive electrode active material of Example 8, the amount of iron in the active material raw material is 18.75 atomic % when the total of manganese, iron, tungsten, magnesium and chromium is 100 atomic %, The amount of chromium was 3 atomic % when the total of manganese, iron, tungsten, magnesium and chromium was 100 atomic %. A positive electrode active material and a half cell of Example 8 were manufactured in the same manner as in Example 7 except for this.
Also, using the positive electrode active material of Example 8, a lithium ion secondary battery of Example 8 was manufactured in the same manner as in Example 7.
なお、実施例８においても、マグネシウムおよびクロムが式（１）におけるＤ1元素に相当し、ケイ素が式（１）におけるＤ2元素に相当する。
実施例８の活物質原料において、タングステンの量は、マンガン、鉄、タングステン、マグネシウムおよびクロムの合計を１００原子％としたときに０．２５原子％となる量であった。また、マグネシウムの量は、マンガン、鉄、タングステン、マグネシウムおよびクロムの合計を１００原子％としたときに３原子％となる量であった。ケイ素の量は、ケイ素およびリンの合計を１００原子％としたときに０．５原子％となる量であった。リチウム：（メタルサイトを構成し得るリチウム以外の金属元素の合計）：（ケイ素とリンとの合計）の元素比は１：１：１であった。なお、活物質原料における上記の各物質の元素比は、正極活物質におけるこれらの元素比と概略一致する。 Also in Example 8, magnesium and chromium correspond to the D1 element in formula (1), and silicon corresponds to the D2 element in formula ( 1 ).
In the active material raw material of Example 8, the amount of tungsten was 0.25 atomic % when the total of manganese, iron, tungsten, magnesium and chromium was taken as 100 atomic %. The amount of magnesium was 3 atomic % when the total of manganese, iron, tungsten, magnesium and chromium was taken as 100 atomic %. The amount of silicon was 0.5 atomic % when the sum of silicon and phosphorus was 100 atomic %. The elemental ratio of lithium:(sum of metal elements other than lithium that can form metal sites):(sum of silicon and phosphorus) was 1:1:1. In addition, the element ratio of each of the above substances in the raw material of the active material approximately matches the element ratio of these elements in the positive electrode active material.
実施例８の活物質原料において、タングステンの量は、マンガン、鉄、タングステン、マグネシウムおよびクロムの合計を１００原子％としたときに０．２５原子％となる量であった。また、マグネシウムの量は、マンガン、鉄、タングステン、マグネシウムおよびクロムの合計を１００原子％としたときに３原子％となる量であった。ケイ素の量は、ケイ素およびリンの合計を１００原子％としたときに０．５原子％となる量であった。リチウム：（メタルサイトを構成し得るリチウム以外の金属元素の合計）：（ケイ素とリンとの合計）の元素比は１：１：１であった。なお、活物質原料における上記の各物質の元素比は、正極活物質におけるこれらの元素比と概略一致する。 Also in Example 8, magnesium and chromium correspond to the D1 element in formula (1), and silicon corresponds to the D2 element in formula ( 1 ).
In the active material raw material of Example 8, the amount of tungsten was 0.25 atomic % when the total of manganese, iron, tungsten, magnesium and chromium was taken as 100 atomic %. The amount of magnesium was 3 atomic % when the total of manganese, iron, tungsten, magnesium and chromium was taken as 100 atomic %. The amount of silicon was 0.5 atomic % when the sum of silicon and phosphorus was 100 atomic %. The elemental ratio of lithium:(sum of metal elements other than lithium that can form metal sites):(sum of silicon and phosphorus) was 1:1:1. In addition, the element ratio of each of the above substances in the raw material of the active material approximately matches the element ratio of these elements in the positive electrode active material.
（実施例９）
〔正極活物質の合成〕
純水５０ｍｌに、リチウム源としてＬｉＯＨ１水和物２．５７ｇｇ、ｐＨ調整剤としてリンゴ酸８．２１ｇ、マンガン源として酢酸マンガン（ＩＩ）４水和物１１．２５ｇ、鉄源として硫酸鉄（ＩＩ）７水和物３．１４ｇ、マグネシウム源として酢酸マグネシウム４水和物０．３９４ｇ、タングステン源としてタングステン酸０．０３８ｇ、チタン源として硫酸チタン（ＩＶ）３０質量％溶液を１．２２ｇ、バナジウム源として酸化バナジウム（Ｖ）０．０４４ｇ、還元剤としてギ酸０．３ｇ、フッ素源としてＬｉＦ０．０７９ｇ、および、リン源として８５％リン酸７．０６ｇを溶解し、５０℃で１２時間加熱して、ゲル状の活物質原料を得た。
このゲル状の活物質原料を６０℃で２４時間真空乾燥し、その後、窒素雰囲気下３５０℃で５時間加熱し、次いで、窒素雰囲気下６５０℃で１５時間加熱することで、実施例９の正極活物質を製造した。当該実施例９の正極活物質を用い、実施例５と同様にして、実施例９のハーフセルを製造した。また、正極活物質層として実施例９の正極活物質を用いたこと以外は、実施例７のリチウムイオン二次電池と同様にして、実施例９のリチウムイオン二次電池を製造した。 (Example 9)
[Synthesis of positive electrode active material]
In 50 ml of pure water, 2.57 g of LiOH monohydrate as a lithium source, 8.21 g of malic acid as a pH adjuster, 11.25 g of manganese (II) acetate tetrahydrate as a manganese source, and iron (II) sulfate as an iron source. 3.14 g of heptahydrate, 0.394 g of magnesium acetate tetrahydrate as a magnesium source, 0.038 g of tungstic acid as a tungsten source, 1.22 g of a 30% by weight solution of titanium (IV) sulfate as a titanium source, and vanadium as a source. 0.044 g of vanadium (V) oxide, 0.3 g of formic acid as a reducing agent, 0.079 g of LiF as a fluorine source, and 7.06 g of 85% phosphoric acid as a phosphorus source are dissolved and heated at 50° C. for 12 hours to form a gel. A raw material for an active material was obtained.
This gel-like active material raw material was vacuum-dried at 60° C. for 24 hours, then heated at 350° C. for 5 hours under a nitrogen atmosphere, and then heated at 650° C. for 15 hours under a nitrogen atmosphere. An active material was produced. A half cell of Example 9 was manufactured in the same manner as in Example 5 using the positive electrode active material of Example 9. A lithium ion secondary battery of Example 9 was manufactured in the same manner as the lithium ion secondary battery of Example 7, except that the positive electrode active material of Example 9 was used as the positive electrode active material layer.
〔正極活物質の合成〕
純水５０ｍｌに、リチウム源としてＬｉＯＨ１水和物２．５７ｇｇ、ｐＨ調整剤としてリンゴ酸８．２１ｇ、マンガン源として酢酸マンガン（ＩＩ）４水和物１１．２５ｇ、鉄源として硫酸鉄（ＩＩ）７水和物３．１４ｇ、マグネシウム源として酢酸マグネシウム４水和物０．３９４ｇ、タングステン源としてタングステン酸０．０３８ｇ、チタン源として硫酸チタン（ＩＶ）３０質量％溶液を１．２２ｇ、バナジウム源として酸化バナジウム（Ｖ）０．０４４ｇ、還元剤としてギ酸０．３ｇ、フッ素源としてＬｉＦ０．０７９ｇ、および、リン源として８５％リン酸７．０６ｇを溶解し、５０℃で１２時間加熱して、ゲル状の活物質原料を得た。
このゲル状の活物質原料を６０℃で２４時間真空乾燥し、その後、窒素雰囲気下３５０℃で５時間加熱し、次いで、窒素雰囲気下６５０℃で１５時間加熱することで、実施例９の正極活物質を製造した。当該実施例９の正極活物質を用い、実施例５と同様にして、実施例９のハーフセルを製造した。また、正極活物質層として実施例９の正極活物質を用いたこと以外は、実施例７のリチウムイオン二次電池と同様にして、実施例９のリチウムイオン二次電池を製造した。 (Example 9)
[Synthesis of positive electrode active material]
In 50 ml of pure water, 2.57 g of LiOH monohydrate as a lithium source, 8.21 g of malic acid as a pH adjuster, 11.25 g of manganese (II) acetate tetrahydrate as a manganese source, and iron (II) sulfate as an iron source. 3.14 g of heptahydrate, 0.394 g of magnesium acetate tetrahydrate as a magnesium source, 0.038 g of tungstic acid as a tungsten source, 1.22 g of a 30% by weight solution of titanium (IV) sulfate as a titanium source, and vanadium as a source. 0.044 g of vanadium (V) oxide, 0.3 g of formic acid as a reducing agent, 0.079 g of LiF as a fluorine source, and 7.06 g of 85% phosphoric acid as a phosphorus source are dissolved and heated at 50° C. for 12 hours to form a gel. A raw material for an active material was obtained.
This gel-like active material raw material was vacuum-dried at 60° C. for 24 hours, then heated at 350° C. for 5 hours under a nitrogen atmosphere, and then heated at 650° C. for 15 hours under a nitrogen atmosphere. An active material was produced. A half cell of Example 9 was manufactured in the same manner as in Example 5 using the positive electrode active material of Example 9. A lithium ion secondary battery of Example 9 was manufactured in the same manner as the lithium ion secondary battery of Example 7, except that the positive electrode active material of Example 9 was used as the positive electrode active material layer.
実施例９においては、マグネシウム、チタンおよびバナジウムが式（１－１）におけるＤ1元素に相当する。
実施例９の活物質原料において、タングステンの量は、メタルサイトを構成し得るリチウム以外の金属元素の合計を１００原子％としたときに０．２５原子％となる量であった。また、マグネシウムの量は、メタルサイトを構成し得るリチウム以外の金属元素の合計を１００原子％としたときに３原子％となる量であった。チタンの量は、メタルサイトを構成し得るリチウム以外の金属元素の合計を１００原子％としたときに２．５原子％となる量であった。バナジウムの量は、メタルサイトを構成し得るリチウム以外の金属元素の合計を１００原子％としたときに０．８原子％となる量であった。リチウム：（メタルサイトを構成し得るリチウム以外の金属元素の合計）：リンの元素比は１：１：１であった。なお、活物質原料における上記の各物質の元素比は、正極活物質におけるこれらの元素比と概略一致する。 In Example 9, magnesium, titanium and vanadium correspond to the D1 element in formula ( 1-1 ).
In the raw material for the active material of Example 9, the amount of tungsten was 0.25 atomic % when the total of metal elements other than lithium that can form the metal sites is 100 atomic %. The amount of magnesium was 3 atomic % when the total of metal elements other than lithium that could constitute the metal site was taken as 100 atomic %. The amount of titanium was 2.5 atomic % when the total of the metal elements other than lithium that can constitute the metal sites is 100 atomic %. The amount of vanadium was 0.8 atomic % when the total of metal elements other than lithium that can form the metal sites was taken as 100 atomic %. The elemental ratio of lithium:(sum of metal elements other than lithium that can form metal sites):phosphorus was 1:1:1. In addition, the element ratio of each of the above substances in the raw material of the active material approximately matches the element ratio of these elements in the positive electrode active material.
実施例９の活物質原料において、タングステンの量は、メタルサイトを構成し得るリチウム以外の金属元素の合計を１００原子％としたときに０．２５原子％となる量であった。また、マグネシウムの量は、メタルサイトを構成し得るリチウム以外の金属元素の合計を１００原子％としたときに３原子％となる量であった。チタンの量は、メタルサイトを構成し得るリチウム以外の金属元素の合計を１００原子％としたときに２．５原子％となる量であった。バナジウムの量は、メタルサイトを構成し得るリチウム以外の金属元素の合計を１００原子％としたときに０．８原子％となる量であった。リチウム：（メタルサイトを構成し得るリチウム以外の金属元素の合計）：リンの元素比は１：１：１であった。なお、活物質原料における上記の各物質の元素比は、正極活物質におけるこれらの元素比と概略一致する。 In Example 9, magnesium, titanium and vanadium correspond to the D1 element in formula ( 1-1 ).
In the raw material for the active material of Example 9, the amount of tungsten was 0.25 atomic % when the total of metal elements other than lithium that can form the metal sites is 100 atomic %. The amount of magnesium was 3 atomic % when the total of metal elements other than lithium that could constitute the metal site was taken as 100 atomic %. The amount of titanium was 2.5 atomic % when the total of the metal elements other than lithium that can constitute the metal sites is 100 atomic %. The amount of vanadium was 0.8 atomic % when the total of metal elements other than lithium that can form the metal sites was taken as 100 atomic %. The elemental ratio of lithium:(sum of metal elements other than lithium that can form metal sites):phosphorus was 1:1:1. In addition, the element ratio of each of the above substances in the raw material of the active material approximately matches the element ratio of these elements in the positive electrode active material.
（実施例１０）
〔正極活物質の合成〕
純水５０ｍｌに、リチウム源としてＬｉＯＨ１水和物２．５７ｇ、ｐＨ調整剤としてリンゴ酸８．２１ｇ、マンガン源として酢酸マンガン（ＩＩ）４水和物１１．２５ｇ、鉄源として硫酸鉄（ＩＩ）７水和物３．７４ｇ、マグネシウム源として酢酸マグネシウム４水和物０．３９４ｇ、タングステン源としてタングステン酸０．０３８ｇ、チタン源として硫酸チタン（ＩＶ）３０質量％溶液を１．２２ｇ、クロム源として酢酸クロム水和物（クロムを２２質量％含有）０．４３４ｇ、還元剤としてギ酸０．３ｇ、フッ素源としてＬｉＦ０．０３９６ｇ、および、リン源として８５％リン酸７．０６ｇを溶解し、５０℃で１２時間加熱して、ゲル状の活物質原料を得た。 (Example 10)
[Synthesis of positive electrode active material]
To 50 ml of pure water, 2.57 g of LiOH monohydrate as a lithium source, 8.21 g of malic acid as a pH adjuster, 11.25 g of manganese (II) acetate tetrahydrate as a manganese source, and iron (II) sulfate as an iron source. 3.74 g of heptahydrate, 0.394 g of magnesium acetate tetrahydrate as magnesium source, 0.038 g of tungstic acid as tungsten source, 1.22 g of 30% by weight titanium (IV) sulfate solution as titanium source, and chromium source. 0.434 g of chromium acetate hydrate (containing 22% by mass of chromium), 0.3 g of formic acid as a reducing agent, 0.0396 g of LiF as a fluorine source, and 7.06 g of 85% phosphoric acid as a phosphorus source were dissolved at 50°C. and heated for 12 hours to obtain a gel-like active material raw material.
〔正極活物質の合成〕
純水５０ｍｌに、リチウム源としてＬｉＯＨ１水和物２．５７ｇ、ｐＨ調整剤としてリンゴ酸８．２１ｇ、マンガン源として酢酸マンガン（ＩＩ）４水和物１１．２５ｇ、鉄源として硫酸鉄（ＩＩ）７水和物３．７４ｇ、マグネシウム源として酢酸マグネシウム４水和物０．３９４ｇ、タングステン源としてタングステン酸０．０３８ｇ、チタン源として硫酸チタン（ＩＶ）３０質量％溶液を１．２２ｇ、クロム源として酢酸クロム水和物（クロムを２２質量％含有）０．４３４ｇ、還元剤としてギ酸０．３ｇ、フッ素源としてＬｉＦ０．０３９６ｇ、および、リン源として８５％リン酸７．０６ｇを溶解し、５０℃で１２時間加熱して、ゲル状の活物質原料を得た。 (Example 10)
[Synthesis of positive electrode active material]
To 50 ml of pure water, 2.57 g of LiOH monohydrate as a lithium source, 8.21 g of malic acid as a pH adjuster, 11.25 g of manganese (II) acetate tetrahydrate as a manganese source, and iron (II) sulfate as an iron source. 3.74 g of heptahydrate, 0.394 g of magnesium acetate tetrahydrate as magnesium source, 0.038 g of tungstic acid as tungsten source, 1.22 g of 30% by weight titanium (IV) sulfate solution as titanium source, and chromium source. 0.434 g of chromium acetate hydrate (containing 22% by mass of chromium), 0.3 g of formic acid as a reducing agent, 0.0396 g of LiF as a fluorine source, and 7.06 g of 85% phosphoric acid as a phosphorus source were dissolved at 50°C. and heated for 12 hours to obtain a gel-like active material raw material.
上記したゲル状の活物質原料を６０℃で２４時間真空乾燥し、その後、窒素雰囲気下３５０℃で５時間加熱し、次いで、窒素雰囲気下６５０℃で１５時間加熱することで、実施例１０の正極活物質を製造した。当該実施例１０の正極活物質を用い、実施例５と同様にして、実施例１０のハーフセルを製造した。
さらに、実施例１０の正極活物質を用いて実施例７と同様にして実施例１０のリチウムイオン二次電池を製造した。 The above gel-like active material raw material was vacuum-dried at 60° C. for 24 hours, then heated at 350° C. for 5 hours under a nitrogen atmosphere, and then heated at 650° C. for 15 hours under a nitrogen atmosphere. A positive electrode active material was produced. A half cell of Example 10 was manufactured in the same manner as in Example 5 using the positive electrode active material of Example 10.
Furthermore, a lithium ion secondary battery of Example 10 was manufactured in the same manner as in Example 7 using the positive electrode active material of Example 10.
さらに、実施例１０の正極活物質を用いて実施例７と同様にして実施例１０のリチウムイオン二次電池を製造した。 The above gel-like active material raw material was vacuum-dried at 60° C. for 24 hours, then heated at 350° C. for 5 hours under a nitrogen atmosphere, and then heated at 650° C. for 15 hours under a nitrogen atmosphere. A positive electrode active material was produced. A half cell of Example 10 was manufactured in the same manner as in Example 5 using the positive electrode active material of Example 10.
Furthermore, a lithium ion secondary battery of Example 10 was manufactured in the same manner as in Example 7 using the positive electrode active material of Example 10.
実施例１０においては、マグネシウム、チタンおよびクロムが式（１－１）におけるＤ1元素に相当する。
実施例１０の活物質原料において、タングステンの量は、マンガン、鉄、タングステン、マグネシウム、チタンおよびクロムの合計を１００原子％としたときに０．２５原子％となる量であった。また、マグネシウムの量は、マンガン、鉄、タングステン、マグネシウム、チタンおよびクロムの合計を１００原子％としたときに３原子％となる量であった。チタンの量は、マンガン、鉄、タングステン、マグネシウム、チタンおよびクロムの合計を１００原子％としたときに２．５原子％となる量であった。クロムの量は、マンガン、鉄、タングステン、マグネシウム、チタンおよびクロムの合計を１００原子％としたときに３原子％となる量であった。フッ素の量は、フッ素および酸素の合計を４００原子％としたときに２．５原子％となる量であった。リチウム：（メタルサイトを構成し得るリチウム以外の金属元素の合計）：リンの元素比は１：１：１であった。なお、活物質原料における上記の各物質の元素比は、正極活物質におけるこれらの元素比と概略一致する。 In Example 10, magnesium, titanium and chromium correspond to the D 1 element in formula (1-1).
In the active material raw material of Example 10, the amount of tungsten was 0.25 atomic % when the total of manganese, iron, tungsten, magnesium, titanium and chromium was taken as 100 atomic %. The amount of magnesium was 3 atomic % when the total of manganese, iron, tungsten, magnesium, titanium and chromium was taken as 100 atomic %. The amount of titanium was 2.5 atomic % when the sum of manganese, iron, tungsten, magnesium, titanium and chromium was 100 atomic %. The amount of chromium was 3 atomic % when the total of manganese, iron, tungsten, magnesium, titanium and chromium was 100 atomic %. The amount of fluorine was 2.5 atomic % when the total of fluorine and oxygen was 400 atomic %. The elemental ratio of lithium:(sum of metal elements other than lithium that can form metal sites):phosphorus was 1:1:1. In addition, the element ratio of each of the above substances in the raw material of the active material approximately matches the element ratio of these elements in the positive electrode active material.
実施例１０の活物質原料において、タングステンの量は、マンガン、鉄、タングステン、マグネシウム、チタンおよびクロムの合計を１００原子％としたときに０．２５原子％となる量であった。また、マグネシウムの量は、マンガン、鉄、タングステン、マグネシウム、チタンおよびクロムの合計を１００原子％としたときに３原子％となる量であった。チタンの量は、マンガン、鉄、タングステン、マグネシウム、チタンおよびクロムの合計を１００原子％としたときに２．５原子％となる量であった。クロムの量は、マンガン、鉄、タングステン、マグネシウム、チタンおよびクロムの合計を１００原子％としたときに３原子％となる量であった。フッ素の量は、フッ素および酸素の合計を４００原子％としたときに２．５原子％となる量であった。リチウム：（メタルサイトを構成し得るリチウム以外の金属元素の合計）：リンの元素比は１：１：１であった。なお、活物質原料における上記の各物質の元素比は、正極活物質におけるこれらの元素比と概略一致する。 In Example 10, magnesium, titanium and chromium correspond to the D 1 element in formula (1-1).
In the active material raw material of Example 10, the amount of tungsten was 0.25 atomic % when the total of manganese, iron, tungsten, magnesium, titanium and chromium was taken as 100 atomic %. The amount of magnesium was 3 atomic % when the total of manganese, iron, tungsten, magnesium, titanium and chromium was taken as 100 atomic %. The amount of titanium was 2.5 atomic % when the sum of manganese, iron, tungsten, magnesium, titanium and chromium was 100 atomic %. The amount of chromium was 3 atomic % when the total of manganese, iron, tungsten, magnesium, titanium and chromium was 100 atomic %. The amount of fluorine was 2.5 atomic % when the total of fluorine and oxygen was 400 atomic %. The elemental ratio of lithium:(sum of metal elements other than lithium that can form metal sites):phosphorus was 1:1:1. In addition, the element ratio of each of the above substances in the raw material of the active material approximately matches the element ratio of these elements in the positive electrode active material.
（実施例１１）
〔正極活物質の合成〕
純水５０ｍｌに、リチウム源としてＬｉＯＨ１水和物２．５７ｇ、ｐＨ調整剤としてリンゴ酸８．２１ｇ、マンガン源として酢酸マンガン（ＩＩ）４水和物１１．２５ｇ、鉄源として硫酸鉄（ＩＩ）７水和物３．１９ｇ、マグネシウム源として酢酸マグネシウム４水和物０．３９４ｇ、タングステン源としてタングステン酸０．０３８ｇ、クロム源として酢酸クロム水和物（クロムを２２質量％含有）０．４３４ｇ、還元剤としてギ酸０．３ｇおよび、リン源として８５％リン酸７．０６ｇを溶解し、５０℃で１２時間加熱して、ゲル状の活物質原料を得た。
このゲル状の活物質原料を６０℃で２４時間真空乾燥し、その後、窒素雰囲気下３５０℃で５時間加熱し、次いで、窒素雰囲気下６５０℃で１５時間加熱することで、実施例１１の正極活物質を製造した。当該実施例１１の正極活物質を用い、実施例５と同様にして、実施例１１のハーフセルを製造した。 (Example 11)
[Synthesis of positive electrode active material]
To 50 ml of pure water, 2.57 g of LiOH monohydrate as a lithium source, 8.21 g of malic acid as a pH adjuster, 11.25 g of manganese (II) acetate tetrahydrate as a manganese source, and iron (II) sulfate as an iron source. 3.19 g of heptahydrate, 0.394 g of magnesium acetate tetrahydrate as a magnesium source, 0.038 g of tungstic acid as a tungsten source, 0.434 g of chromium acetate hydrate (containing 22% by mass of chromium) as a chromium source, 0.3 g of formic acid as a reducing agent and 7.06 g of 85% phosphoric acid as a phosphorus source were dissolved and heated at 50° C. for 12 hours to obtain a gel-like active material raw material.
This gel-like active material raw material was vacuum-dried at 60° C. for 24 hours, then heated at 350° C. for 5 hours under a nitrogen atmosphere, and then heated at 650° C. for 15 hours under a nitrogen atmosphere. An active material was produced. A half cell of Example 11 was manufactured in the same manner as in Example 5 using the positive electrode active material of Example 11.
〔正極活物質の合成〕
純水５０ｍｌに、リチウム源としてＬｉＯＨ１水和物２．５７ｇ、ｐＨ調整剤としてリンゴ酸８．２１ｇ、マンガン源として酢酸マンガン（ＩＩ）４水和物１１．２５ｇ、鉄源として硫酸鉄（ＩＩ）７水和物３．１９ｇ、マグネシウム源として酢酸マグネシウム４水和物０．３９４ｇ、タングステン源としてタングステン酸０．０３８ｇ、クロム源として酢酸クロム水和物（クロムを２２質量％含有）０．４３４ｇ、還元剤としてギ酸０．３ｇおよび、リン源として８５％リン酸７．０６ｇを溶解し、５０℃で１２時間加熱して、ゲル状の活物質原料を得た。
このゲル状の活物質原料を６０℃で２４時間真空乾燥し、その後、窒素雰囲気下３５０℃で５時間加熱し、次いで、窒素雰囲気下６５０℃で１５時間加熱することで、実施例１１の正極活物質を製造した。当該実施例１１の正極活物質を用い、実施例５と同様にして、実施例１１のハーフセルを製造した。 (Example 11)
[Synthesis of positive electrode active material]
To 50 ml of pure water, 2.57 g of LiOH monohydrate as a lithium source, 8.21 g of malic acid as a pH adjuster, 11.25 g of manganese (II) acetate tetrahydrate as a manganese source, and iron (II) sulfate as an iron source. 3.19 g of heptahydrate, 0.394 g of magnesium acetate tetrahydrate as a magnesium source, 0.038 g of tungstic acid as a tungsten source, 0.434 g of chromium acetate hydrate (containing 22% by mass of chromium) as a chromium source, 0.3 g of formic acid as a reducing agent and 7.06 g of 85% phosphoric acid as a phosphorus source were dissolved and heated at 50° C. for 12 hours to obtain a gel-like active material raw material.
This gel-like active material raw material was vacuum-dried at 60° C. for 24 hours, then heated at 350° C. for 5 hours under a nitrogen atmosphere, and then heated at 650° C. for 15 hours under a nitrogen atmosphere. An active material was produced. A half cell of Example 11 was manufactured in the same manner as in Example 5 using the positive electrode active material of Example 11.
実施例１１においては、マグネシウムおよびクロムが式（１－１）におけるＤ1元素に相当する。
実施例１１の活物質原料において、タングステンの量は、メタルサイトを構成し得るリチウム以外の金属元素の合計を１００原子％としたときに０．２５原子％となる量であった。また、マグネシウムの量は、メタルサイトを構成し得るリチウム以外の金属元素の合計を１００原子％としたときに３原子％となる量であった。クロムの量は、メタルサイトを構成し得るリチウム以外の金属元素の合計を１００原子％としたときに３原子％となる量であった。リチウム：（メタルサイトを構成し得るリチウム以外の金属元素の合計）：リンの元素比は１：１：１であった。なお、活物質原料における上記の各物質の元素比は、正極活物質におけるこれらの元素比と概略一致する。 In Example 11, magnesium and chromium correspond to the D 1 element in formula (1-1).
In the raw material for the active material of Example 11, the amount of tungsten was 0.25 atomic % when the total of metal elements other than lithium that can form metal sites is 100 atomic %. The amount of magnesium was 3 atomic % when the total of metal elements other than lithium that could constitute the metal site was taken as 100 atomic %. The amount of chromium was 3 atomic % when the total of metal elements other than lithium that could form the metal sites was taken as 100 atomic %. The elemental ratio of lithium:(sum of metal elements other than lithium that can form metal sites):phosphorus was 1:1:1. In addition, the element ratio of each of the above substances in the raw material of the active material approximately matches the element ratio of these elements in the positive electrode active material.
実施例１１の活物質原料において、タングステンの量は、メタルサイトを構成し得るリチウム以外の金属元素の合計を１００原子％としたときに０．２５原子％となる量であった。また、マグネシウムの量は、メタルサイトを構成し得るリチウム以外の金属元素の合計を１００原子％としたときに３原子％となる量であった。クロムの量は、メタルサイトを構成し得るリチウム以外の金属元素の合計を１００原子％としたときに３原子％となる量であった。リチウム：（メタルサイトを構成し得るリチウム以外の金属元素の合計）：リンの元素比は１：１：１であった。なお、活物質原料における上記の各物質の元素比は、正極活物質におけるこれらの元素比と概略一致する。 In Example 11, magnesium and chromium correspond to the D 1 element in formula (1-1).
In the raw material for the active material of Example 11, the amount of tungsten was 0.25 atomic % when the total of metal elements other than lithium that can form metal sites is 100 atomic %. The amount of magnesium was 3 atomic % when the total of metal elements other than lithium that could constitute the metal site was taken as 100 atomic %. The amount of chromium was 3 atomic % when the total of metal elements other than lithium that could form the metal sites was taken as 100 atomic %. The elemental ratio of lithium:(sum of metal elements other than lithium that can form metal sites):phosphorus was 1:1:1. In addition, the element ratio of each of the above substances in the raw material of the active material approximately matches the element ratio of these elements in the positive electrode active material.
（実施例１２）
実施例１２の正極活物質の製造方法では、活物質原料にクロムを含まず、メタルサイトを構成し得るリチウム以外の金属元素の合計を１００原子％としたときに鉄が１９．２５原子％であった。フッ素の量は、フッ素および酸素の合計を４００原子％としたときに５原子％となる量であった。これ以外は、実施例１０と同様にして実施例１２の正極活物質を製造した。実施例１２の正極活物質を用い、実施例５と同様にして、実施例１２の正極及び正極ハーフセルを製造した。 (Example 12)
In the method for producing a positive electrode active material of Example 12, the active material raw material does not contain chromium, and iron is 19.25 atomic % when the total of metal elements other than lithium that can constitute the metal site is 100 atomic %. there were. The amount of fluorine was 5 atomic % when the total of fluorine and oxygen was 400 atomic %. A cathode active material of Example 12 was produced in the same manner as in Example 10 except for this. A positive electrode and a positive electrode half cell of Example 12 were manufactured in the same manner as in Example 5 using the positive electrode active material of Example 12.
実施例１２の正極活物質の製造方法では、活物質原料にクロムを含まず、メタルサイトを構成し得るリチウム以外の金属元素の合計を１００原子％としたときに鉄が１９．２５原子％であった。フッ素の量は、フッ素および酸素の合計を４００原子％としたときに５原子％となる量であった。これ以外は、実施例１０と同様にして実施例１２の正極活物質を製造した。実施例１２の正極活物質を用い、実施例５と同様にして、実施例１２の正極及び正極ハーフセルを製造した。 (Example 12)
In the method for producing a positive electrode active material of Example 12, the active material raw material does not contain chromium, and iron is 19.25 atomic % when the total of metal elements other than lithium that can constitute the metal site is 100 atomic %. there were. The amount of fluorine was 5 atomic % when the total of fluorine and oxygen was 400 atomic %. A cathode active material of Example 12 was produced in the same manner as in Example 10 except for this. A positive electrode and a positive electrode half cell of Example 12 were manufactured in the same manner as in Example 5 using the positive electrode active material of Example 12.
（実施例１３）
実施例１３の正極活物質の製造方法では、活物質原料にクロムを含まず、バナジウムを含んでいた。実施例１３の活物質原料では、メタルサイトを構成し得るリチウム以外の金属元素の合計を１００原子％としたときに鉄が１８原子％であり、バナジウムが１．２５原子％であった。フッ素の量は、フッ素および酸素の合計を４００原子％としたときに５原子％となる量であった。これ以外は、実施例１０と同様にして実施例１３の正極活物質を製造した。実施例１３の正極活物質を用い、実施例５と同様にして、実施例１３の正極及び正極ハーフセルを製造した。 (Example 13)
In the manufacturing method of the positive electrode active material of Example 13, the raw material of the active material did not contain chromium but contained vanadium. In the raw material for the active material of Example 13, iron was 18 atomic % and vanadium was 1.25 atomic % when the total of metal elements other than lithium that could form the metal sites was taken as 100 atomic %. The amount of fluorine was 5 atomic % when the total of fluorine and oxygen was 400 atomic %. A cathode active material of Example 13 was produced in the same manner as in Example 10 except for this. A positive electrode and a positive electrode half cell of Example 13 were manufactured in the same manner as in Example 5 using the positive electrode active material of Example 13.
実施例１３の正極活物質の製造方法では、活物質原料にクロムを含まず、バナジウムを含んでいた。実施例１３の活物質原料では、メタルサイトを構成し得るリチウム以外の金属元素の合計を１００原子％としたときに鉄が１８原子％であり、バナジウムが１．２５原子％であった。フッ素の量は、フッ素および酸素の合計を４００原子％としたときに５原子％となる量であった。これ以外は、実施例１０と同様にして実施例１３の正極活物質を製造した。実施例１３の正極活物質を用い、実施例５と同様にして、実施例１３の正極及び正極ハーフセルを製造した。 (Example 13)
In the manufacturing method of the positive electrode active material of Example 13, the raw material of the active material did not contain chromium but contained vanadium. In the raw material for the active material of Example 13, iron was 18 atomic % and vanadium was 1.25 atomic % when the total of metal elements other than lithium that could form the metal sites was taken as 100 atomic %. The amount of fluorine was 5 atomic % when the total of fluorine and oxygen was 400 atomic %. A cathode active material of Example 13 was produced in the same manner as in Example 10 except for this. A positive electrode and a positive electrode half cell of Example 13 were manufactured in the same manner as in Example 5 using the positive electrode active material of Example 13.
（実施例１４）
実施例１４の正極活物質の製造方法では、活物質原料にクロムを含まず、バナジウムを含んでいた。実施例１４の活物質原料では、メタルサイトを構成し得るリチウム以外の金属元素の合計を１００原子％としたときに鉄が１６．７５原子％であり、バナジウムが２．５原子％であった。フッ素の量は、フッ素および酸素の合計を４００原子％としたときに５原子％となる量であった。これ以外は、実施例１０と同様にして実施例１４の正極活物質を製造した。実施例１４の正極活物質を用い、実施例５と同様にして、実施例１４の正極及び正極ハーフセルを製造した。 (Example 14)
In the manufacturing method of the positive electrode active material of Example 14, the raw material of the active material did not contain chromium but contained vanadium. In the active material raw material of Example 14, iron was 16.75 atomic % and vanadium was 2.5 atomic % when the total of metal elements other than lithium that could constitute the metal site was 100 atomic %. . The amount of fluorine was 5 atomic % when the total of fluorine and oxygen was 400 atomic %. A cathode active material of Example 14 was produced in the same manner as in Example 10 except for this. A positive electrode and a positive electrode half cell of Example 14 were manufactured in the same manner as in Example 5 using the positive electrode active material of Example 14.
実施例１４の正極活物質の製造方法では、活物質原料にクロムを含まず、バナジウムを含んでいた。実施例１４の活物質原料では、メタルサイトを構成し得るリチウム以外の金属元素の合計を１００原子％としたときに鉄が１６．７５原子％であり、バナジウムが２．５原子％であった。フッ素の量は、フッ素および酸素の合計を４００原子％としたときに５原子％となる量であった。これ以外は、実施例１０と同様にして実施例１４の正極活物質を製造した。実施例１４の正極活物質を用い、実施例５と同様にして、実施例１４の正極及び正極ハーフセルを製造した。 (Example 14)
In the manufacturing method of the positive electrode active material of Example 14, the raw material of the active material did not contain chromium but contained vanadium. In the active material raw material of Example 14, iron was 16.75 atomic % and vanadium was 2.5 atomic % when the total of metal elements other than lithium that could constitute the metal site was 100 atomic %. . The amount of fluorine was 5 atomic % when the total of fluorine and oxygen was 400 atomic %. A cathode active material of Example 14 was produced in the same manner as in Example 10 except for this. A positive electrode and a positive electrode half cell of Example 14 were manufactured in the same manner as in Example 5 using the positive electrode active material of Example 14.
（実施例１５）
実施例１５の正極活物質の製造方法では、活物質原料にクロムを含まず、バナジウムを含んでいた。実施例１５の活物質原料では、メタルサイトを構成し得るリチウム以外の金属元素の合計を１００原子％としたときに鉄が１６．２５原子％であり、バナジウムが３原子％であった。フッ素の量は、フッ素および酸素の合計を４００原子％としたときに５原子％となる量であった。これ以外は、実施例５と同様にして実施例１５の正極活物質を製造した。実施例１５の正極活物質を用い、実施例５と同様にして、実施例１５の正極及び正極ハーフセルを製造した。 (Example 15)
In the manufacturing method of the positive electrode active material of Example 15, the raw material of the active material did not contain chromium but contained vanadium. In the raw material for the active material of Example 15, iron was 16.25 atomic % and vanadium was 3 atomic % when the total of metal elements other than lithium that could constitute the metal sites was 100 atomic %. The amount of fluorine was 5 atomic % when the total of fluorine and oxygen was 400 atomic %. A cathode active material of Example 15 was produced in the same manner as in Example 5 except for this. A positive electrode and a positive electrode half cell of Example 15 were manufactured in the same manner as in Example 5 using the positive electrode active material of Example 15.
実施例１５の正極活物質の製造方法では、活物質原料にクロムを含まず、バナジウムを含んでいた。実施例１５の活物質原料では、メタルサイトを構成し得るリチウム以外の金属元素の合計を１００原子％としたときに鉄が１６．２５原子％であり、バナジウムが３原子％であった。フッ素の量は、フッ素および酸素の合計を４００原子％としたときに５原子％となる量であった。これ以外は、実施例５と同様にして実施例１５の正極活物質を製造した。実施例１５の正極活物質を用い、実施例５と同様にして、実施例１５の正極及び正極ハーフセルを製造した。 (Example 15)
In the manufacturing method of the positive electrode active material of Example 15, the raw material of the active material did not contain chromium but contained vanadium. In the raw material for the active material of Example 15, iron was 16.25 atomic % and vanadium was 3 atomic % when the total of metal elements other than lithium that could constitute the metal sites was 100 atomic %. The amount of fluorine was 5 atomic % when the total of fluorine and oxygen was 400 atomic %. A cathode active material of Example 15 was produced in the same manner as in Example 5 except for this. A positive electrode and a positive electrode half cell of Example 15 were manufactured in the same manner as in Example 5 using the positive electrode active material of Example 15.
（実施例１６）
実施例１６の正極活物質の製造方法では、活物質原料におけるフッ素の量が、フッ素および酸素の合計を４００原子％としたときに５原子％となる量であった。これ以外は、実施例１０と同様にして実施例１６の正極活物質を製造した。実施例１６の正極活物質を用い、実施例７と同様にして、実施例１６の正極及びリチウムイオン二次電池を製造した。 (Example 16)
In the manufacturing method of the positive electrode active material of Example 16, the amount of fluorine in the raw material of the active material was such that the total amount of fluorine and oxygen was 5 atomic %. A cathode active material of Example 16 was produced in the same manner as in Example 10 except for this. A positive electrode and a lithium ion secondary battery of Example 16 were produced in the same manner as in Example 7 using the positive electrode active material of Example 16.
実施例１６の正極活物質の製造方法では、活物質原料におけるフッ素の量が、フッ素および酸素の合計を４００原子％としたときに５原子％となる量であった。これ以外は、実施例１０と同様にして実施例１６の正極活物質を製造した。実施例１６の正極活物質を用い、実施例７と同様にして、実施例１６の正極及びリチウムイオン二次電池を製造した。 (Example 16)
In the manufacturing method of the positive electrode active material of Example 16, the amount of fluorine in the raw material of the active material was such that the total amount of fluorine and oxygen was 5 atomic %. A cathode active material of Example 16 was produced in the same manner as in Example 10 except for this. A positive electrode and a lithium ion secondary battery of Example 16 were produced in the same manner as in Example 7 using the positive electrode active material of Example 16.
（実施例１７）
実施例１７の正極活物質の製造方法では、活物質原料にケイ素を含まなかった。また、活物質原料におけるフッ素の量が、フッ素および酸素の合計を４００原子％としたときに５原子％となる量であった。これ以外は、実施例５と同様にして実施例１７の正極活物質を製造した。実施例１７の正極活物質を用い、実施例５と同様にして実施例１７の正極及びハーフセルを製造し、実施例７と同様にして実施例１７の正極及びリチウムイオン二次電池を製造した。 (Example 17)
In the manufacturing method of the positive electrode active material of Example 17, silicon was not included in the raw material of the active material. Further, the amount of fluorine in the raw material for the active material was such that the total amount of fluorine and oxygen was 5 atomic %. A cathode active material of Example 17 was produced in the same manner as in Example 5 except for this. Using the positive electrode active material of Example 17, the positive electrode and half cell of Example 17 were manufactured in the same manner as in Example 5, and the positive electrode and lithium ion secondary battery of Example 17 were manufactured in the same manner as in Example 7.
実施例１７の正極活物質の製造方法では、活物質原料にケイ素を含まなかった。また、活物質原料におけるフッ素の量が、フッ素および酸素の合計を４００原子％としたときに５原子％となる量であった。これ以外は、実施例５と同様にして実施例１７の正極活物質を製造した。実施例１７の正極活物質を用い、実施例５と同様にして実施例１７の正極及びハーフセルを製造し、実施例７と同様にして実施例１７の正極及びリチウムイオン二次電池を製造した。 (Example 17)
In the manufacturing method of the positive electrode active material of Example 17, silicon was not included in the raw material of the active material. Further, the amount of fluorine in the raw material for the active material was such that the total amount of fluorine and oxygen was 5 atomic %. A cathode active material of Example 17 was produced in the same manner as in Example 5 except for this. Using the positive electrode active material of Example 17, the positive electrode and half cell of Example 17 were manufactured in the same manner as in Example 5, and the positive electrode and lithium ion secondary battery of Example 17 were manufactured in the same manner as in Example 7.
（実施例１８）
実施例１８の正極活物質の製造方法では、活物質原料にケイ素を含まなかった。また、活物質原料におけるフッ素の量が、フッ素および酸素の合計を４００原子％としたときに１原子％となる量であった。これ以外は、実施例５と同様にして実施例１８の正極活物質を製造した。実施例１８の正極活物質を用い、実施例５と同様にして実施例１８の正極及びハーフセルを製造し、実施例７と同様にして実施例１８の正極及びリチウムイオン二次電池を製造した。 (Example 18)
In the manufacturing method of the positive electrode active material of Example 18, silicon was not included in the raw material of the active material. Further, the amount of fluorine in the raw material for the active material was such that the total amount of fluorine and oxygen was 1 atomic % when the total was 400 atomic %. A cathode active material of Example 18 was produced in the same manner as in Example 5 except for this. Using the positive electrode active material of Example 18, the positive electrode and half cell of Example 18 were manufactured in the same manner as in Example 5, and the positive electrode and lithium ion secondary battery of Example 18 were manufactured in the same manner as in Example 7.
実施例１８の正極活物質の製造方法では、活物質原料にケイ素を含まなかった。また、活物質原料におけるフッ素の量が、フッ素および酸素の合計を４００原子％としたときに１原子％となる量であった。これ以外は、実施例５と同様にして実施例１８の正極活物質を製造した。実施例１８の正極活物質を用い、実施例５と同様にして実施例１８の正極及びハーフセルを製造し、実施例７と同様にして実施例１８の正極及びリチウムイオン二次電池を製造した。 (Example 18)
In the manufacturing method of the positive electrode active material of Example 18, silicon was not included in the raw material of the active material. Further, the amount of fluorine in the raw material for the active material was such that the total amount of fluorine and oxygen was 1 atomic % when the total was 400 atomic %. A cathode active material of Example 18 was produced in the same manner as in Example 5 except for this. Using the positive electrode active material of Example 18, the positive electrode and half cell of Example 18 were manufactured in the same manner as in Example 5, and the positive electrode and lithium ion secondary battery of Example 18 were manufactured in the same manner as in Example 7.
（比較例６）
比較例１の正極活物質を用い、実施例５と同様にして、比較例６のハーフセルを得た。比較例１の正極活物質を用い、実施例７と同様にして、比較例６のリチウムイオン二次電池を製造した。比較例６のハーフセル及びリチウムイオン二次電池は、正極活物質にタングステンを含まない。 (Comparative Example 6)
A half cell of Comparative Example 6 was obtained in the same manner as in Example 5 using the positive electrode active material of Comparative Example 1. A lithium ion secondary battery of Comparative Example 6 was manufactured in the same manner as in Example 7 using the positive electrode active material of Comparative Example 1. The half cell and the lithium ion secondary battery of Comparative Example 6 do not contain tungsten in the positive electrode active material.
比較例１の正極活物質を用い、実施例５と同様にして、比較例６のハーフセルを得た。比較例１の正極活物質を用い、実施例７と同様にして、比較例６のリチウムイオン二次電池を製造した。比較例６のハーフセル及びリチウムイオン二次電池は、正極活物質にタングステンを含まない。 (Comparative Example 6)
A half cell of Comparative Example 6 was obtained in the same manner as in Example 5 using the positive electrode active material of Comparative Example 1. A lithium ion secondary battery of Comparative Example 6 was manufactured in the same manner as in Example 7 using the positive electrode active material of Comparative Example 1. The half cell and the lithium ion secondary battery of Comparative Example 6 do not contain tungsten in the positive electrode active material.
〔評価例１ 正極ハーフセルの容量〕
実施例１～実施例３および比較例１の正極ハーフセルに対して、２５℃、０．１Ｃの一定電流にて、４．３Ｖまで充電を行い、２．５Ｖまで放電を行った。このときの放電容量を測定した。結果を図１に示す。 [Evaluation Example 1 Capacity of Positive Electrode Half Cell]
The positive half cells of Examples 1 to 3 and Comparative Example 1 were charged to 4.3V and discharged to 2.5V at 25° C. and a constant current of 0.1C. The discharge capacity at this time was measured. The results are shown in FIG.
実施例１～実施例３および比較例１の正極ハーフセルに対して、２５℃、０．１Ｃの一定電流にて、４．３Ｖまで充電を行い、２．５Ｖまで放電を行った。このときの放電容量を測定した。結果を図１に示す。 [Evaluation Example 1 Capacity of Positive Electrode Half Cell]
The positive half cells of Examples 1 to 3 and Comparative Example 1 were charged to 4.3V and discharged to 2.5V at 25° C. and a constant current of 0.1C. The discharge capacity at this time was measured. The results are shown in FIG.
図１に示すように、放電容量は比較例１の正極ハーフセルで最大であり、実施例１＞実施例２＞実施例３の順に低下した。この結果から、放電容量を考慮すると、正極活物質におけるタングステンの量には好適な範囲があるといえる。具体的には、タングステンの量の好ましい範囲は、メタルサイトを構成し得るリチウム以外の金属元素の合計を１００原子％としたときに、０．０５～２．５原子％、０．０５～１．５原子％、０．０５～１．０原子％、０．０５～０．８原子％、または、０．０５～０．５原子％といい得る。
換言すると、ＬｉaＭｎbＦｅcＷdＤ1 eＤ2 fＰgＯh 式（１）において、タングステンの量すなわちｄの好ましい範囲は、０．０５／１００～２．５／１００の範囲内、０．０５／１００～１．５／１００の範囲内、０．０５／１００～１．０／１００の範囲内、０．０５／１００～０．８／１００の範囲内、または、０．０５／１００～０．５／１００の範囲内といい得る。 As shown in FIG. 1, the positive electrode half-cell of Comparative Example 1 had the maximum discharge capacity, and decreased in the order of Example 1>Example 2>Example 3. From this result, it can be said that there is a suitable range for the amount of tungsten in the positive electrode active material in consideration of the discharge capacity. Specifically, the preferable range of the amount of tungsten is 0.05 to 2.5 atomic %, 0.05 to 1 0.5 atomic %, 0.05-1.0 atomic %, 0.05-0.8 atomic %, or 0.05-0.5 atomic %.
In other words, in the Li a Mn b Fe c W d D 1 e D 2 f P g O h formula (1), the amount of tungsten, that is, the preferred range of d is in the range of 0.05/100 to 2.5/100. within the range of 0.05/100 to 1.5/100, within the range of 0.05/100 to 1.0/100, within the range of 0.05/100 to 0.8/100, or 0 It can be said to be in the range of 0.05/100 to 0.5/100.
換言すると、ＬｉaＭｎbＦｅcＷdＤ1 eＤ2 fＰgＯh 式（１）において、タングステンの量すなわちｄの好ましい範囲は、０．０５／１００～２．５／１００の範囲内、０．０５／１００～１．５／１００の範囲内、０．０５／１００～１．０／１００の範囲内、０．０５／１００～０．８／１００の範囲内、または、０．０５／１００～０．５／１００の範囲内といい得る。 As shown in FIG. 1, the positive electrode half-cell of Comparative Example 1 had the maximum discharge capacity, and decreased in the order of Example 1>Example 2>Example 3. From this result, it can be said that there is a suitable range for the amount of tungsten in the positive electrode active material in consideration of the discharge capacity. Specifically, the preferable range of the amount of tungsten is 0.05 to 2.5 atomic %, 0.05 to 1 0.5 atomic %, 0.05-1.0 atomic %, 0.05-0.8 atomic %, or 0.05-0.5 atomic %.
In other words, in the Li a Mn b Fe c W d D 1 e D 2 f P g O h formula (1), the amount of tungsten, that is, the preferred range of d is in the range of 0.05/100 to 2.5/100. within the range of 0.05/100 to 1.5/100, within the range of 0.05/100 to 1.0/100, within the range of 0.05/100 to 0.8/100, or 0 It can be said to be in the range of 0.05/100 to 0.5/100.
〔評価例２ 正極ハーフセルの容量〕
参考例１の正極ハーフセルにつき、評価例１と同様にして放電容量を測定した。結果を図２に示す。なお、図２には評価例１における比較例１の正極ハーフセルの結果を併記した。 [Evaluation Example 2 Capacity of Positive Electrode Half Cell]
The discharge capacity of the positive electrode half-cell of Reference Example 1 was measured in the same manner as in Evaluation Example 1. The results are shown in FIG. The results of the positive electrode half-cell of Comparative Example 1 in Evaluation Example 1 are also shown in FIG.
参考例１の正極ハーフセルにつき、評価例１と同様にして放電容量を測定した。結果を図２に示す。なお、図２には評価例１における比較例１の正極ハーフセルの結果を併記した。 [Evaluation Example 2 Capacity of Positive Electrode Half Cell]
The discharge capacity of the positive electrode half-cell of Reference Example 1 was measured in the same manner as in Evaluation Example 1. The results are shown in FIG. The results of the positive electrode half-cell of Comparative Example 1 in Evaluation Example 1 are also shown in FIG.
図２に示すように、参考例１の正極ハーフセルの放電容量は、比較例１の正極ハーフセルの放電容量と同等であった。この結果から、正極活物質におけるマグネシウム量が、既述したメタルサイトを構成し得るリチウム以外の金属元素の合計を１００原子％としたときに、３原子％以下であれば、マグネシウム未添加の場合に比べて正極活物質の容量低下がないことがわかる。
なお、参考例１においては比較例１に対して容量低下がみられないことから、正極活物質におけるマグネシウム量の好ましい範囲の上限は、上記の３原子％よりも大きい値であるといい得る。具体的には、容量を考慮すると、正極活物質におけるマグネシウム量の好ましい範囲として、メタルサイトを構成し得るリチウム以外の金属元素の合計を１００原子％としたときに、０．５～５原子％の範囲内、０．５～４原子％の範囲内を例示できる。
換言すると、ＬｉaＭｎbＦｅcＷdＤ1 eＤ2 fＰgＯh 式（１）において、マグネシウムの量すなわちｅの好ましい範囲は、０．５／１００～５／１００の範囲内、０．５／１００～４／１００の範囲内といい得る。 As shown in FIG. 2, the discharge capacity of the positive electrode half-cell of Reference Example 1 was equivalent to the discharge capacity of the positive electrode half-cell of Comparative Example 1. From this result, if the amount of magnesium in the positive electrode active material is 3 atomic % or less when the total of metal elements other than lithium that can constitute the metal site described above is 100 atomic %, then when magnesium is not added It can be seen that there is no decrease in the capacity of the positive electrode active material compared to .
In addition, in Reference Example 1, no decrease in capacity is observed as compared with Comparative Example 1. Therefore, it can be said that the upper limit of the preferable range of the amount of magnesium in the positive electrode active material is a value larger than the above 3 atomic %. Specifically, considering the capacity, the preferable range of the amount of magnesium in the positive electrode active material is 0.5 to 5 atomic % when the total of metal elements other than lithium that can constitute the metal site is 100 atomic %. within the range of 0.5 to 4 atomic %.
In other words, in the Li a Mn b Fe c W d D 1 e D 2 f P g O h formula (1), the amount of magnesium, that is, the preferred range of e is within the range of 0.5/100 to 5/100, It can be said that it is in the range of 0.5/100 to 4/100.
なお、参考例１においては比較例１に対して容量低下がみられないことから、正極活物質におけるマグネシウム量の好ましい範囲の上限は、上記の３原子％よりも大きい値であるといい得る。具体的には、容量を考慮すると、正極活物質におけるマグネシウム量の好ましい範囲として、メタルサイトを構成し得るリチウム以外の金属元素の合計を１００原子％としたときに、０．５～５原子％の範囲内、０．５～４原子％の範囲内を例示できる。
換言すると、ＬｉaＭｎbＦｅcＷdＤ1 eＤ2 fＰgＯh 式（１）において、マグネシウムの量すなわちｅの好ましい範囲は、０．５／１００～５／１００の範囲内、０．５／１００～４／１００の範囲内といい得る。 As shown in FIG. 2, the discharge capacity of the positive electrode half-cell of Reference Example 1 was equivalent to the discharge capacity of the positive electrode half-cell of Comparative Example 1. From this result, if the amount of magnesium in the positive electrode active material is 3 atomic % or less when the total of metal elements other than lithium that can constitute the metal site described above is 100 atomic %, then when magnesium is not added It can be seen that there is no decrease in the capacity of the positive electrode active material compared to .
In addition, in Reference Example 1, no decrease in capacity is observed as compared with Comparative Example 1. Therefore, it can be said that the upper limit of the preferable range of the amount of magnesium in the positive electrode active material is a value larger than the above 3 atomic %. Specifically, considering the capacity, the preferable range of the amount of magnesium in the positive electrode active material is 0.5 to 5 atomic % when the total of metal elements other than lithium that can constitute the metal site is 100 atomic %. within the range of 0.5 to 4 atomic %.
In other words, in the Li a Mn b Fe c W d D 1 e D 2 f P g O h formula (1), the amount of magnesium, that is, the preferred range of e is within the range of 0.5/100 to 5/100, It can be said that it is in the range of 0.5/100 to 4/100.
〔評価例３ リチウムイオン二次電池の高温充放電サイクル試験〕
実施例４、参考例１および比較例１のリチウムイオン二次電池に対して、高温充放電サイクル試験を行った。 [Evaluation Example 3 High temperature charge/discharge cycle test of lithium ion secondary battery]
The lithium ion secondary batteries of Example 4, Reference Example 1 and Comparative Example 1 were subjected to a high temperature charge/discharge cycle test.
実施例４、参考例１および比較例１のリチウムイオン二次電池に対して、高温充放電サイクル試験を行った。 [Evaluation Example 3 High temperature charge/discharge cycle test of lithium ion secondary battery]
The lithium ion secondary batteries of Example 4, Reference Example 1 and Comparative Example 1 were subjected to a high temperature charge/discharge cycle test.
６０℃で、１Ｃの一定電流にて、ＳＯＣ１００％となるまで充電し、その後ＳＯＣ１０％となるまで放電する高温充放電サイクルを１５０回繰り返した。
各リチウムイオン二次電池につき、初回の充放電時における放電容量を１００％として、１５０回目の充放電時における放電容量の百分率を算出した。当該百分率を各リチウムイオン二次電池における容量維持率とした。各リチウムイオン二次電池の容量維持率を表２に示す。 A high-temperature charge-discharge cycle was repeated 150 times at 60° C. at a constant current of 1 C, where the battery was charged to an SOC of 100% and then discharged to an SOC of 10%.
For each lithium ion secondary battery, the percentage of the discharge capacity at the 150th charge/discharge was calculated with the discharge capacity at the first charge/discharge as 100%. This percentage was taken as the capacity retention rate of each lithium ion secondary battery. Table 2 shows the capacity retention rate of each lithium ion secondary battery.
各リチウムイオン二次電池につき、初回の充放電時における放電容量を１００％として、１５０回目の充放電時における放電容量の百分率を算出した。当該百分率を各リチウムイオン二次電池における容量維持率とした。各リチウムイオン二次電池の容量維持率を表２に示す。 A high-temperature charge-discharge cycle was repeated 150 times at 60° C. at a constant current of 1 C, where the battery was charged to an SOC of 100% and then discharged to an SOC of 10%.
For each lithium ion secondary battery, the percentage of the discharge capacity at the 150th charge/discharge was calculated with the discharge capacity at the first charge/discharge as 100%. This percentage was taken as the capacity retention rate of each lithium ion secondary battery. Table 2 shows the capacity retention rate of each lithium ion secondary battery.
表２に示すように、正極活物質にマグネシウムを加えた参考例１のリチウムイオン二次電池は、マグネシウムなしの比較例１のリチウムイオン二次電池に比べて、容量維持率が３％程度向上した。このことは、正極活物質にマグネシウムすなわちＤ1元素を加えることにより、正極活物質の劣化が抑制されたことを意味する。
As shown in Table 2, the lithium ion secondary battery of Reference Example 1 in which magnesium was added to the positive electrode active material had a capacity retention rate improved by about 3% compared to the lithium ion secondary battery of Comparative Example 1 without magnesium. did. This means that the deterioration of the positive electrode active material was suppressed by adding magnesium, that is, the D1 element to the positive electrode active material.
また、表２に示すように、正極活物質にマグネシウムおよびタングステンを加えた実施例４のリチウムイオン二次電池は、正極活物質にマグネシウムのみを加えた参考例１のリチウムイオン二次電池に比べて、さらに容量維持率が２％程度向上した。この結果から、正極活物質にタングステンを加えることにより、正極活物質の劣化がさらに抑制されることがわかり、タングステンを含む本発明の正極活物質の有用性が裏付けられる。
Further, as shown in Table 2, the lithium ion secondary battery of Example 4 in which magnesium and tungsten were added to the positive electrode active material was compared to the lithium ion secondary battery of Reference Example 1 in which only magnesium was added to the positive electrode active material. As a result, the capacity retention rate was further improved by about 2%. From this result, it is found that the deterioration of the positive electrode active material is further suppressed by adding tungsten to the positive electrode active material, and the usefulness of the positive electrode active material of the present invention containing tungsten is supported.
〔評価例４ リチウムイオン二次電池の充放電容量〕
実施例２、３および比較例１のリチウムイオン二次電池に対して、０．４Ｃレートで４．０ＶまでＣＣ－ＣＶ充電を行った。その後、１Ｃレートで２.５Ｖまで２時間かけてＣＣ－ＣＶ放電を行った。これにより、各リチウムイオン二次電池の充電容量及び放電容量を確認した。
各リチウムイオン二次電池の充電容量及び放電容量を表３に示す。 [Evaluation Example 4 Charge/Discharge Capacity of Lithium Ion Secondary Battery]
The lithium ion secondary batteries of Examples 2 and 3 and Comparative Example 1 were CC-CV charged to 4.0 V at a 0.4 C rate. After that, CC-CV discharge was performed at a rate of 1C to 2.5V over 2 hours. Thereby, the charge capacity and discharge capacity of each lithium ion secondary battery were confirmed.
Table 3 shows the charge capacity and discharge capacity of each lithium ion secondary battery.
実施例２、３および比較例１のリチウムイオン二次電池に対して、０．４Ｃレートで４．０ＶまでＣＣ－ＣＶ充電を行った。その後、１Ｃレートで２.５Ｖまで２時間かけてＣＣ－ＣＶ放電を行った。これにより、各リチウムイオン二次電池の充電容量及び放電容量を確認した。
各リチウムイオン二次電池の充電容量及び放電容量を表３に示す。 [Evaluation Example 4 Charge/Discharge Capacity of Lithium Ion Secondary Battery]
The lithium ion secondary batteries of Examples 2 and 3 and Comparative Example 1 were CC-CV charged to 4.0 V at a 0.4 C rate. After that, CC-CV discharge was performed at a rate of 1C to 2.5V over 2 hours. Thereby, the charge capacity and discharge capacity of each lithium ion secondary battery were confirmed.
Table 3 shows the charge capacity and discharge capacity of each lithium ion secondary battery.
表３に示すように、タングステンの量が多いほど、リチウムイオン二次電池の充電容量および放電容量は低下するものの、正極活物質におけるタングステンの量が、メタルサイトを構成し得るリチウム以外の金属元素の合計を１００原子％としたときに１原子％以下であれば、リチウムイオン二次電池の充電容量及び放電容量は十分な値を示すといい得る。
As shown in Table 3, the larger the amount of tungsten, the lower the charge capacity and discharge capacity of the lithium ion secondary battery, but the amount of tungsten in the positive electrode active material is a metal element other than lithium that can constitute a metal site. It can be said that the charge capacity and discharge capacity of the lithium-ion secondary battery exhibit sufficient values if the total is 1 atomic % or less when the total of is 100 atomic %.
〔評価例５ 正極活物質の表面分析〕
実施例４の正極活物質につき、走査電子顕微鏡（ＳＥＭ）による撮像を行った。結果を図３および図４に示す。また、ＳＥＭに付属のエネルギー分散型Ｘ線分光法（ＳＥＭ－ＥＤＸ）により、図３および図４と同じ領域について正極活物質の表面における組成を分析した。結果を図５～図８に示す。なお、図５および図６において淡色で表示される部分はマンガンの検出された部分であり、図７において淡色で表示される部分はマグネシウムの検出された部分であり、図８において淡色で表示される部分はタングステンの検出された部分である。 [Evaluation Example 5 Surface Analysis of Positive Electrode Active Material]
The positive electrode active material of Example 4 was imaged with a scanning electron microscope (SEM). The results are shown in FIGS. 3 and 4. FIG. Also, the composition of the surface of the positive electrode active material was analyzed for the same region as in FIGS. 3 and 4 by energy dispersive X-ray spectroscopy (SEM-EDX) attached to the SEM. The results are shown in FIGS. 5-8. 5 and 6 are parts where manganese is detected, the parts shown in light color in FIG. 7 are parts where magnesium is detected, and the parts are shown in light color in FIG. The part that is detected is the detected part of the tungsten.
実施例４の正極活物質につき、走査電子顕微鏡（ＳＥＭ）による撮像を行った。結果を図３および図４に示す。また、ＳＥＭに付属のエネルギー分散型Ｘ線分光法（ＳＥＭ－ＥＤＸ）により、図３および図４と同じ領域について正極活物質の表面における組成を分析した。結果を図５～図８に示す。なお、図５および図６において淡色で表示される部分はマンガンの検出された部分であり、図７において淡色で表示される部分はマグネシウムの検出された部分であり、図８において淡色で表示される部分はタングステンの検出された部分である。 [Evaluation Example 5 Surface Analysis of Positive Electrode Active Material]
The positive electrode active material of Example 4 was imaged with a scanning electron microscope (SEM). The results are shown in FIGS. 3 and 4. FIG. Also, the composition of the surface of the positive electrode active material was analyzed for the same region as in FIGS. 3 and 4 by energy dispersive X-ray spectroscopy (SEM-EDX) attached to the SEM. The results are shown in FIGS. 5-8. 5 and 6 are parts where manganese is detected, the parts shown in light color in FIG. 7 are parts where magnesium is detected, and the parts are shown in light color in FIG. The part that is detected is the detected part of the tungsten.
図５～図７に示すように、マンガンおよびマグネシウムは正極活物質の全体に均一に固溶されていると考えられる。これに対して、図８に示すように、タングステンの一部は結晶粒界に偏析していると考えられる。
As shown in FIGS. 5 to 7, manganese and magnesium are considered to be uniformly dissolved in the entire positive electrode active material. On the other hand, as shown in FIG. 8, it is considered that part of the tungsten is segregated at the grain boundaries.
既述した評価例３の結果から、実施例４の正極活物質は、容量劣化し難く、優れた耐久性を示すが、これは、タングステンの一部が結晶粒界に偏析して正極活物質を保護しているためと推測される。
From the results of Evaluation Example 3 described above, the positive electrode active material of Example 4 is resistant to capacity deterioration and exhibits excellent durability. presumably because it protects
〔評価例６ 正極活物質の表面分析〕
実施例２～実施例４の正極活物質につき、Ｘ線光電分光法（ＸＰＳ）により、表面における化学結合状態を分析した。具体的な測定条件は、線源：Ａｌ－Ｋα線（１４８６．６ｅＶ）、Ｘ線ビーム径：２００μｍ、加速電圧：１５ｋＶ、出力：５０．３５Ｗ、測定時間：１時間、透過エネルギー：２．９５ｅＶ、ステップ毎の経過時間（Ｔｉｍｅ Ｐｅｒ Ｓｔｅｐ）：２０ミリ秒、測定範囲：２ｍｍ×２ｍｍであった。
結果を図９～図１１に示す。なお、図９は実施例４の正極活物質をＸＰＳ分析した結果を表すチャートであり、図１０は実施例２の正極活物質をＸＰＳ分析した結果を表すチャートであり、図１１は実施例３の正極活物質をＸＰＳ分析した結果を表すチャートである。 [Evaluation Example 6 Surface Analysis of Positive Electrode Active Material]
The positive electrode active materials of Examples 2 to 4 were analyzed for the chemical bonding state on the surface by X-ray photoelectric spectroscopy (XPS). Specific measurement conditions are: radiation source: Al-Kα ray (1486.6 eV), X-ray beam diameter: 200 μm, acceleration voltage: 15 kV, output: 50.35 W, measurement time: 1 hour, transmission energy: 2.95 eV , Elapsed time per step (Time Per Step): 20 ms, Measurement range: 2 mm x 2 mm.
The results are shown in FIGS. 9-11. 9 is a chart showing the results of XPS analysis of the positive electrode active material of Example 4, FIG. 10 is a chart showing the results of XPS analysis of the positive electrode active material of Example 2, and FIG. It is a chart showing the result of XPS analysis of the positive electrode active material.
実施例２～実施例４の正極活物質につき、Ｘ線光電分光法（ＸＰＳ）により、表面における化学結合状態を分析した。具体的な測定条件は、線源：Ａｌ－Ｋα線（１４８６．６ｅＶ）、Ｘ線ビーム径：２００μｍ、加速電圧：１５ｋＶ、出力：５０．３５Ｗ、測定時間：１時間、透過エネルギー：２．９５ｅＶ、ステップ毎の経過時間（Ｔｉｍｅ Ｐｅｒ Ｓｔｅｐ）：２０ミリ秒、測定範囲：２ｍｍ×２ｍｍであった。
結果を図９～図１１に示す。なお、図９は実施例４の正極活物質をＸＰＳ分析した結果を表すチャートであり、図１０は実施例２の正極活物質をＸＰＳ分析した結果を表すチャートであり、図１１は実施例３の正極活物質をＸＰＳ分析した結果を表すチャートである。 [Evaluation Example 6 Surface Analysis of Positive Electrode Active Material]
The positive electrode active materials of Examples 2 to 4 were analyzed for the chemical bonding state on the surface by X-ray photoelectric spectroscopy (XPS). Specific measurement conditions are: radiation source: Al-Kα ray (1486.6 eV), X-ray beam diameter: 200 μm, acceleration voltage: 15 kV, output: 50.35 W, measurement time: 1 hour, transmission energy: 2.95 eV , Elapsed time per step (Time Per Step): 20 ms, Measurement range: 2 mm x 2 mm.
The results are shown in FIGS. 9-11. 9 is a chart showing the results of XPS analysis of the positive electrode active material of Example 4, FIG. 10 is a chart showing the results of XPS analysis of the positive electrode active material of Example 2, and FIG. It is a chart showing the result of XPS analysis of the positive electrode active material.
図９～図１１に示すように、実施例２～実施例４の正極活物質の表面からは、ＷＯ3すなわち６価のタングステンに由来するピーク、および、ＷＯ2すなわち４価のタングステンに由来するピークが検出された。この結果から、実施例２～実施例４の正極活物質はタングステンを含むこと、当該正極活物質の表面には、主として、フッ化水素に対する保護効果の高いＷＯ3が存在することがわかる。
As shown in FIGS. 9 to 11, from the surfaces of the positive electrode active materials of Examples 2 to 4, WO 3 , a peak derived from hexavalent tungsten, and WO 2 , a peak derived from tetravalent tungsten, A peak was detected. From these results, it can be seen that the positive electrode active materials of Examples 2 to 4 contain tungsten, and that WO 3 having a high protective effect against hydrogen fluoride mainly exists on the surface of the positive electrode active materials.
さらに、評価例４の結果を考慮し図１０および図１１を比較すると、リチウムイオン二次電池の充放電容量低下を抑制するためには、正極活物質のＸＰＳチャートにおいて３０～３４ｅＶに現れるＷＯ2に由来するピークの高さは、３４～３６ｅＶに現れるＷＯ3に由来するピークの高さよりも低いのが好ましく、３４～３６ｅＶに現れるＷＯ3に由来するピークの高さの１/２以下であるのがより好ましいといい得る。
10 and 11 in consideration of the results of Evaluation Example 4, WO 2 appearing at 30 to 34 eV in the XPS chart of the positive electrode active material is required to suppress the decrease in charge/discharge capacity of the lithium ion secondary battery. The height of the peak derived from is preferably lower than the height of the peak derived from WO3 appearing between 34 and 36 eV, and is not more than half the height of the peak derived from WO3 appearing between 34 and 36 eV. can be said to be more preferable.
〔評価例７ リチウムイオン二次電池の高温充放電サイクル試験〕
比較例２～５のリチウムイオン二次電池に対して、高温充放電サイクル試験を行った。
６０℃で、１Ｃの一定電流にて、ＳＯＣ１００％となるまで充電し、その後ＳＯＣ１０％となるまで放電する高温充放電サイクルを繰り返した。
各リチウムイオン二次電池につき、初回の充放電時における放電容量を１００％とする放電容量の百分率をサイクル毎に算出した。当該百分率を各リチウムイオン二次電池における容量維持率とした。試験はｎ＝２で行った。各リチウムイオン二次電池の容量維持率を図１２に示す。 [Evaluation Example 7 High temperature charge/discharge cycle test of lithium ion secondary battery]
A high-temperature charge-discharge cycle test was performed on the lithium-ion secondary batteries of Comparative Examples 2-5.
A high-temperature charge-discharge cycle was repeated at 60° C. at a constant current of 1 C, where the battery was charged to an SOC of 100% and then discharged to an SOC of 10%.
For each lithium ion secondary battery, the percentage of discharge capacity was calculated for each cycle, with the discharge capacity at the time of initial charge/discharge being 100%. This percentage was taken as the capacity retention rate of each lithium ion secondary battery. The test was performed with n=2. FIG. 12 shows the capacity retention rate of each lithium ion secondary battery.
比較例２～５のリチウムイオン二次電池に対して、高温充放電サイクル試験を行った。
６０℃で、１Ｃの一定電流にて、ＳＯＣ１００％となるまで充電し、その後ＳＯＣ１０％となるまで放電する高温充放電サイクルを繰り返した。
各リチウムイオン二次電池につき、初回の充放電時における放電容量を１００％とする放電容量の百分率をサイクル毎に算出した。当該百分率を各リチウムイオン二次電池における容量維持率とした。試験はｎ＝２で行った。各リチウムイオン二次電池の容量維持率を図１２に示す。 [Evaluation Example 7 High temperature charge/discharge cycle test of lithium ion secondary battery]
A high-temperature charge-discharge cycle test was performed on the lithium-ion secondary batteries of Comparative Examples 2-5.
A high-temperature charge-discharge cycle was repeated at 60° C. at a constant current of 1 C, where the battery was charged to an SOC of 100% and then discharged to an SOC of 10%.
For each lithium ion secondary battery, the percentage of discharge capacity was calculated for each cycle, with the discharge capacity at the time of initial charge/discharge being 100%. This percentage was taken as the capacity retention rate of each lithium ion secondary battery. The test was performed with n=2. FIG. 12 shows the capacity retention rate of each lithium ion secondary battery.
図１２に示すように、容量維持率に関しては、タングステンコートした正極活物質を用いた比較例２～４のリチウムイオン二次電池は、タングステンコートのない正極活物質を用いた比較例５のリチウムイオン二次電池と同程度であった。この結果から、単に正極活物質にタングステンコートを施すだけでは、正極活物質における耐久後の容量劣化を抑制できないことがわかる。
As shown in FIG. 12, regarding the capacity retention rate, the lithium ion secondary batteries of Comparative Examples 2 to 4 using the tungsten-coated positive electrode active material were compared with the lithium ion secondary batteries of Comparative Example 5 using the positive electrode active material without tungsten coating. It was about the same as the ion secondary battery. From this result, it can be seen that simply coating the positive electrode active material with tungsten cannot suppress the deterioration of the capacity of the positive electrode active material after endurance.
〔評価例８ 正極活物質の表面分析〕
比較例２の正極活物質につき、Ｘ線光電分光法（ＸＰＳ）により、表面における化学結合状態を分析した。結果を図１３に示す。 [Evaluation Example 8 Surface Analysis of Positive Electrode Active Material]
The chemical bonding state on the surface of the positive electrode active material of Comparative Example 2 was analyzed by X-ray photoelectric spectroscopy (XPS). The results are shown in FIG.
比較例２の正極活物質につき、Ｘ線光電分光法（ＸＰＳ）により、表面における化学結合状態を分析した。結果を図１３に示す。 [Evaluation Example 8 Surface Analysis of Positive Electrode Active Material]
The chemical bonding state on the surface of the positive electrode active material of Comparative Example 2 was analyzed by X-ray photoelectric spectroscopy (XPS). The results are shown in FIG.
図１３に示すように、比較例２の正極活物質の表面からは、ＷＯ3すなわち６価のタングステンに由来するピークが検出されたものの、ＷＯ2すなわち４価のタングステンに由来するピークは検出されなかった。この結果から、比較例２の正極活物質、すなわち、正極活物質にタングステンコートを行ったものについてはＷＯ2が形成されないことがわかる。
評価例８の結果と評価例７の結果とを考慮すると、比較例２の正極活物質からＷＯ2が検出されなかったことと、正極活物質における耐久後の容量劣化が抑制されないこととが関連づけられる。つまり、タングステンコートでは正極活物質の結晶の内部にタングステンが入らず、遷移金属の溶出が十分に抑制されないと推測され、正極活物質における耐久後の容量劣化を抑制するためには、Ｘ線光電分光法によりＷＯ2に由来するピークが確認されることが重要であることが理解される。 As shown in FIG. 13, from the surface of the positive electrode active material of Comparative Example 2, a peak derived from WO 3 , i.e., hexavalent tungsten, was detected, but a peak derived from WO 2 , i.e., tetravalent tungsten was detected. I didn't. From this result, it can be seen that WO 2 is not formed in the positive electrode active material of Comparative Example 2, ie, the positive electrode active material coated with tungsten.
Considering the results of Evaluation Example 8 and Evaluation Example 7, the fact that WO 2 was not detected from the positive electrode active material of Comparative Example 2 correlated with the fact that the capacity deterioration of the positive electrode active material after endurance was not suppressed. be done. In other words, it is presumed that tungsten does not enter the inside of the crystal of the positive electrode active material in the tungsten coating, and the elution of the transition metal is not sufficiently suppressed. It is understood that it is important to confirm the peaks originating from WO2 by spectroscopy.
評価例８の結果と評価例７の結果とを考慮すると、比較例２の正極活物質からＷＯ2が検出されなかったことと、正極活物質における耐久後の容量劣化が抑制されないこととが関連づけられる。つまり、タングステンコートでは正極活物質の結晶の内部にタングステンが入らず、遷移金属の溶出が十分に抑制されないと推測され、正極活物質における耐久後の容量劣化を抑制するためには、Ｘ線光電分光法によりＷＯ2に由来するピークが確認されることが重要であることが理解される。 As shown in FIG. 13, from the surface of the positive electrode active material of Comparative Example 2, a peak derived from WO 3 , i.e., hexavalent tungsten, was detected, but a peak derived from WO 2 , i.e., tetravalent tungsten was detected. I didn't. From this result, it can be seen that WO 2 is not formed in the positive electrode active material of Comparative Example 2, ie, the positive electrode active material coated with tungsten.
Considering the results of Evaluation Example 8 and Evaluation Example 7, the fact that WO 2 was not detected from the positive electrode active material of Comparative Example 2 correlated with the fact that the capacity deterioration of the positive electrode active material after endurance was not suppressed. be done. In other words, it is presumed that tungsten does not enter the inside of the crystal of the positive electrode active material in the tungsten coating, and the elution of the transition metal is not sufficiently suppressed. It is understood that it is important to confirm the peaks originating from WO2 by spectroscopy.
〔評価例９ ハーフセルの充電容量〕
実施例５、６および比較例６のハーフセルに対して、２５℃、０．１Ｃレートで２．５Ｖから４．３ＶまでＣＣ－ＣＶ充電を行い、初期充電容量を確認した。各ハーフセルの初期充電容量につき、比較例６のハーフセルの初期充電容量を１００％としたときの百分率を算出した。
各ハーフセルの初期充電容量（％）を表４に示す。 [Evaluation Example 9 Charge capacity of half cell]
The half cells of Examples 5 and 6 and Comparative Example 6 were CC-CV charged from 2.5 V to 4.3 V at a rate of 0.1 C at 25° C. to confirm the initial charge capacity. The percentage of the initial charge capacity of each half-cell was calculated when the initial charge capacity of the half-cell of Comparative Example 6 was taken as 100%.
Table 4 shows the initial charge capacity (%) of each half cell.
実施例５、６および比較例６のハーフセルに対して、２５℃、０．１Ｃレートで２．５Ｖから４．３ＶまでＣＣ－ＣＶ充電を行い、初期充電容量を確認した。各ハーフセルの初期充電容量につき、比較例６のハーフセルの初期充電容量を１００％としたときの百分率を算出した。
各ハーフセルの初期充電容量（％）を表４に示す。 [Evaluation Example 9 Charge capacity of half cell]
The half cells of Examples 5 and 6 and Comparative Example 6 were CC-CV charged from 2.5 V to 4.3 V at a rate of 0.1 C at 25° C. to confirm the initial charge capacity. The percentage of the initial charge capacity of each half-cell was calculated when the initial charge capacity of the half-cell of Comparative Example 6 was taken as 100%.
Table 4 shows the initial charge capacity (%) of each half cell.
〔評価例１０ ハーフセルの充電容量〕
実施例１７、実施例１８及び比較例６の各ハーフセルに対して、評価例９と同様に初期充電容量を確認した。各ハーフセルの初期充電容量につき、比較例６のハーフセルの初期充電容量を１００％としたときの百分率を算出した。
各ハーフセルの初期充電容量（％）を表５に示す。 [Evaluation Example 10 Charge capacity of half cell]
As in Evaluation Example 9, the initial charge capacities of the half cells of Examples 17, 18, and Comparative Example 6 were confirmed. The percentage of the initial charge capacity of each half-cell was calculated when the initial charge capacity of the half-cell of Comparative Example 6 was taken as 100%.
Table 5 shows the initial charge capacity (%) of each half cell.
実施例１７、実施例１８及び比較例６の各ハーフセルに対して、評価例９と同様に初期充電容量を確認した。各ハーフセルの初期充電容量につき、比較例６のハーフセルの初期充電容量を１００％としたときの百分率を算出した。
各ハーフセルの初期充電容量（％）を表５に示す。 [Evaluation Example 10 Charge capacity of half cell]
As in Evaluation Example 9, the initial charge capacities of the half cells of Examples 17, 18, and Comparative Example 6 were confirmed. The percentage of the initial charge capacity of each half-cell was calculated when the initial charge capacity of the half-cell of Comparative Example 6 was taken as 100%.
Table 5 shows the initial charge capacity (%) of each half cell.
表４に示すように、正極活物質にフッ素を加えたことで、初期充電容量が向上する。既述したように、フッ素は酸素サイトに置換されると推測される。このため、初期充電容量の向上を考慮する場合、正極活物質におけるフッ素の量の好ましい範囲は、酸素とフッ素との合計を４００原子％としたときに１～２０原子％の範囲内、２～１０原子％の範囲内、３～８原子％の範囲内といい得る。
As shown in Table 4, the addition of fluorine to the positive electrode active material improves the initial charge capacity. As already mentioned, fluorine is presumed to be substituted at the oxygen site. Therefore, when considering the improvement of the initial charge capacity, the preferable range of the amount of fluorine in the positive electrode active material is 1 to 20 atomic % when the total of oxygen and fluorine is 400 atomic %. It can be said to be within the range of 10 atomic %, or within the range of 3 to 8 atomic %.
表５に示すように、実施例１８のハーフセルの初期充電容量は比較例６のハーフセルの初期充電容量と同程度であるが、実施例１７のハーフセルの初期充電容量は比較例６のハーフセル及び実施例１８のハーフセルの初期充電容量に比べて増大していた。
実施例１７及び実施例１８は正極活物質にケイ素を含まないため、この結果から、正極活物質にケイ素を含まない場合にも、初期充電容量を考慮すると正極活物質に含まれるフッ素の量は多い方が好ましいといい得る。また、この結果から、正極活物質に含まれるフッ素の量は、上記した範囲内、すなわち、酸素とフッ素との合計を４００原子％としたときに１～２０原子％の範囲内、２～１０原子％の範囲内、３～８原子％の範囲内であるのがより好適であることが裏付けられる。 As shown in Table 5, the initial charge capacity of the half-cell of Example 18 is comparable to the initial charge capacity of the half-cell of Comparative Example 6, but the initial charge capacity of the half-cell of Example 17 is the same as that of the half-cell of Comparative Example 6. It was increased compared to the initial charge capacity of the half-cell of Example 18.
Since Examples 17 and 18 do not contain silicon in the positive electrode active material, from this result, even if the positive electrode active material does not contain silicon, considering the initial charge capacity, the amount of fluorine contained in the positive electrode active material is It can be said that more is preferable. Further, from this result, the amount of fluorine contained in the positive electrode active material is within the above range, that is, within the range of 1 to 20 atomic % when the total of oxygen and fluorine is 400 atomic %, and 2 to 10 atomic %. It is confirmed that the range of 3 to 8 atomic % is more preferable.
実施例１７及び実施例１８は正極活物質にケイ素を含まないため、この結果から、正極活物質にケイ素を含まない場合にも、初期充電容量を考慮すると正極活物質に含まれるフッ素の量は多い方が好ましいといい得る。また、この結果から、正極活物質に含まれるフッ素の量は、上記した範囲内、すなわち、酸素とフッ素との合計を４００原子％としたときに１～２０原子％の範囲内、２～１０原子％の範囲内、３～８原子％の範囲内であるのがより好適であることが裏付けられる。 As shown in Table 5, the initial charge capacity of the half-cell of Example 18 is comparable to the initial charge capacity of the half-cell of Comparative Example 6, but the initial charge capacity of the half-cell of Example 17 is the same as that of the half-cell of Comparative Example 6. It was increased compared to the initial charge capacity of the half-cell of Example 18.
Since Examples 17 and 18 do not contain silicon in the positive electrode active material, from this result, even if the positive electrode active material does not contain silicon, considering the initial charge capacity, the amount of fluorine contained in the positive electrode active material is It can be said that more is preferable. Further, from this result, the amount of fluorine contained in the positive electrode active material is within the above range, that is, within the range of 1 to 20 atomic % when the total of oxygen and fluorine is 400 atomic %, and 2 to 10 atomic %. It is confirmed that the range of 3 to 8 atomic % is more preferable.
さらに、実施例１７のハーフセル及び実施例１８のハーフセルは正極活物質にケイ素を含まないため、初期放電容量を考慮すると、正極活物質にケイ素を含まなくても良く、フッ素を含めば良いともいい得る。
Furthermore, since the half-cell of Example 17 and the half-cell of Example 18 do not contain silicon in the positive electrode active material, considering the initial discharge capacity, the positive electrode active material may not contain silicon and may contain fluorine. obtain.
〔評価例１１ リチウムイオン二次電池の５秒放電抵抗〕
実施例１７、実施例１８及び比較例６の各リチウムイオン二次電池に対して、２５℃、０．０５ＣレートでＳＯＣ８０％まで充電し、その後６０℃で２０時間静置することで、コンディショニングを行った。コンディショニング後に、温度２５℃、ＳＯＣ６０％まで充電し、その後、１Ｃ，２Ｃ，３Ｃ，４Ｃの順で各々５秒間ＣＣ放電した際の電圧降下量（放電前電圧と４Ｃ放電５秒後電圧との差）及び電流値からオームの法則により放電抵抗（直流抵抗）を測定した。結果を表６に示す。なお、表６には、比較例６のリチウムイオン二次電池の抵抗値（Ω）を１００％としたときの実施例１７及び実施例１８のリチウムイオン二次電池の抵抗値を百分率（％）で示した。 [Evaluation Example 11 5-second discharge resistance of lithium-ion secondary battery]
The lithium ion secondary batteries of Examples 17, 18, and Comparative Example 6 were charged toSOC 80% at 25° C. at a rate of 0.05 C, and then left standing at 60° C. for 20 hours to perform conditioning. gone. After conditioning, charge to 60% SOC at a temperature of 25 ° C., then the amount of voltage drop when CC discharging for 5 seconds each in the order of 1C, 2C, 3C, 4C (difference between the voltage before discharge and the voltage after 5 seconds of 4C discharge ) and the current value, the discharge resistance (direct current resistance) was measured according to Ohm's law. Table 6 shows the results. Table 6 shows the resistance values of the lithium ion secondary batteries of Examples 17 and 18 when the resistance value (Ω) of the lithium ion secondary battery of Comparative Example 6 is 100% (%). indicated by
実施例１７、実施例１８及び比較例６の各リチウムイオン二次電池に対して、２５℃、０．０５ＣレートでＳＯＣ８０％まで充電し、その後６０℃で２０時間静置することで、コンディショニングを行った。コンディショニング後に、温度２５℃、ＳＯＣ６０％まで充電し、その後、１Ｃ，２Ｃ，３Ｃ，４Ｃの順で各々５秒間ＣＣ放電した際の電圧降下量（放電前電圧と４Ｃ放電５秒後電圧との差）及び電流値からオームの法則により放電抵抗（直流抵抗）を測定した。結果を表６に示す。なお、表６には、比較例６のリチウムイオン二次電池の抵抗値（Ω）を１００％としたときの実施例１７及び実施例１８のリチウムイオン二次電池の抵抗値を百分率（％）で示した。 [Evaluation Example 11 5-second discharge resistance of lithium-ion secondary battery]
The lithium ion secondary batteries of Examples 17, 18, and Comparative Example 6 were charged to
表６に示すように、正極活物質にフッ素及びＤ1元素としてのマグネシウムを含む実施例１７のリチウムイオン二次電池及び実施例１８のリチウムイオン二次電池は、フッ素もマグネシウムも含まない比較例６のリチウムイオン二次電池に比べて、放電抵抗が低減した。
また、正極活物質にフッ素を１原子％含む実施例１８のリチウムイオン二次電池は、正極活物質にフッ素を５原子％含む実施例１７のリチウムイオン二次電池に比べて、放電抵抗がさらに低減していた。 As shown in Table 6 , the lithium ion secondary battery of Example 17 and the lithium ion secondary battery of Example 18 containing fluorine and magnesium as the element D1 in the positive electrode active material are comparative examples containing neither fluorine nor magnesium. 6, the discharge resistance was reduced.
Further, the lithium ion secondary battery of Example 18 containing 1 atomic % of fluorine in the positive electrode active material has a higher discharge resistance than the lithium ion secondary battery of Example 17 containing 5 atomic % of fluorine in the positive electrode active material. had decreased.
また、正極活物質にフッ素を１原子％含む実施例１８のリチウムイオン二次電池は、正極活物質にフッ素を５原子％含む実施例１７のリチウムイオン二次電池に比べて、放電抵抗がさらに低減していた。 As shown in Table 6 , the lithium ion secondary battery of Example 17 and the lithium ion secondary battery of Example 18 containing fluorine and magnesium as the element D1 in the positive electrode active material are comparative examples containing neither fluorine nor magnesium. 6, the discharge resistance was reduced.
Further, the lithium ion secondary battery of Example 18 containing 1 atomic % of fluorine in the positive electrode active material has a higher discharge resistance than the lithium ion secondary battery of Example 17 containing 5 atomic % of fluorine in the positive electrode active material. had decreased.
この結果から、正極活物質がフッ素および／またはＤ1元素としてのマグネシウムを含むことで、リチウムイオン二次電池の放電抵抗が低減し、導電性が向上することがわかる。また、放電抵抗の低減を考慮すると、正極活物質に含まれるフッ素の量は、酸素とフッ素との合計を４００原子％としたときに０．１～１０原子％の範囲内、０．２～５原子％の範囲内、０．５～２原子％の範囲内であるのがより好適であることいい得る。
From this result, it can be seen that when the positive electrode active material contains fluorine and / or magnesium as the D1 element, the discharge resistance of the lithium ion secondary battery is reduced and the conductivity is improved. In addition, considering the reduction of discharge resistance, the amount of fluorine contained in the positive electrode active material is in the range of 0.1 to 10 atomic % when the total of oxygen and fluorine is 400 atomic %. It can be said that it is more preferably in the range of 5 atomic %, more preferably in the range of 0.5 to 2 atomic %.
〔評価例１２ リチウムイオン二次電池の高温充放電サイクル試験〕
実施例１７、実施例１８及び比較例６のリチウムイオン二次電池につき、上記のコンディショニングの後に、６０℃で、１Ｃの一定電流にて、ＳＯＣ１００％となるまで充電し、その後ＳＯＣ１０％となるまで放電する高温充放電サイクルを繰り返した。このときのカットオフ電圧は２．５７Ｖまたは初期容量すなわちＳＯＣ１００％に対してＳＯＣ９０％となる電圧である。上記の高温充放電サイクルに際し、放電容量を随時測定して、初回の充放電時における放電容量を１００％として百分率を算出した。そして当該百分率を各リチウムイオン二次電池における容量維持率とした。各リチウムイオン二次電池の容量維持率の推移を図１４に示す。図１４においてはサイクル数の平方根を横軸とした。 [Evaluation Example 12 High temperature charge/discharge cycle test of lithium ion secondary battery]
After the above conditioning, the lithium ion secondary batteries of Examples 17, 18 and Comparative Example 6 were charged at 60° C. at a constant current of 1 C until the SOC reached 100%, and then until the SOC reached 10%. A high temperature charge/discharge cycle of discharging was repeated. The cutoff voltage at this time is 2.57 V or the voltage at which SOC is 90% with respect to the initial capacity, that is,SOC 100%. During the high-temperature charge/discharge cycle, the discharge capacity was measured at any time, and the percentage was calculated with the discharge capacity at the time of the first charge/discharge as 100%. This percentage was taken as the capacity retention rate of each lithium ion secondary battery. FIG. 14 shows changes in the capacity retention rate of each lithium ion secondary battery. In FIG. 14, the horizontal axis is the square root of the number of cycles.
実施例１７、実施例１８及び比較例６のリチウムイオン二次電池につき、上記のコンディショニングの後に、６０℃で、１Ｃの一定電流にて、ＳＯＣ１００％となるまで充電し、その後ＳＯＣ１０％となるまで放電する高温充放電サイクルを繰り返した。このときのカットオフ電圧は２．５７Ｖまたは初期容量すなわちＳＯＣ１００％に対してＳＯＣ９０％となる電圧である。上記の高温充放電サイクルに際し、放電容量を随時測定して、初回の充放電時における放電容量を１００％として百分率を算出した。そして当該百分率を各リチウムイオン二次電池における容量維持率とした。各リチウムイオン二次電池の容量維持率の推移を図１４に示す。図１４においてはサイクル数の平方根を横軸とした。 [Evaluation Example 12 High temperature charge/discharge cycle test of lithium ion secondary battery]
After the above conditioning, the lithium ion secondary batteries of Examples 17, 18 and Comparative Example 6 were charged at 60° C. at a constant current of 1 C until the SOC reached 100%, and then until the SOC reached 10%. A high temperature charge/discharge cycle of discharging was repeated. The cutoff voltage at this time is 2.57 V or the voltage at which SOC is 90% with respect to the initial capacity, that is,
図１４に示すように、実施例１７のリチウムイオン二次電池及び実施例１８のリチウムイオン二次電池は、何れも、比較例６のリチウムイオン二次電池よりもサイクル特性が向上していた。実施例１７のリチウムイオン二次電池及び実施例１８のリチウムイオン二次電池は、正極活物質にフッ素及びＤ1元素としてのマグネシウムを含む点で、比較例６のリチウムイオン二次電池と相違する。したがって、この結果から、正極活物質にフッ素および／またはＤ1元素としてのマグネシウムを含むことで、リチウムイオン二次電池のサイクル特性が向上するといい得る。
As shown in FIG. 14 , both the lithium ion secondary battery of Example 17 and the lithium ion secondary battery of Example 18 had better cycle characteristics than the lithium ion secondary battery of Comparative Example 6. The lithium ion secondary battery of Example 17 and the lithium ion secondary battery of Example 18 differ from the lithium ion secondary battery of Comparative Example 6 in that the positive electrode active material contains fluorine and magnesium as the element D1. . Therefore, from this result, it can be said that the inclusion of fluorine and / or magnesium as the D1 element in the positive electrode active material improves the cycle characteristics of the lithium ion secondary battery.
さらに既述した評価例１０～評価例１２の結果を勘案すると、リン酸鉄マンガンリチウム系の正極活物質に導入する元素として、フッ素と、Ｄ1元素としてのマグネシウムとを併用することが、リチウムイオン二次電池の電池特性向上に有用ともいい得る。
Furthermore, considering the results of Evaluation Examples 10 to 12 described above, it is found that the combined use of fluorine and magnesium as the element D1 as elements to be introduced into the lithium iron manganese phosphate - based positive electrode active material is preferable for lithium. It can also be said to be useful for improving the battery characteristics of ion secondary batteries.
〔評価例１３ ハーフセルの充電容量〕
実施例７、８および比較例６のハーフセルに対して、評価例９と同様に初期充電容量を確認し、各ハーフセルの初期充電容量につき、比較例６のハーフセルの初期充電容量を１００％としたときの百分率を算出した。
各ハーフセルの初期充電容量（％）を表７に示す。 [Evaluation Example 13 Charge capacity of half cell]
The initial charge capacities of the half cells of Examples 7 and 8 and Comparative Example 6 were checked in the same manner as in Evaluation Example 9, and the initial charge capacity of the half cell of Comparative Example 6 was taken as 100% for the initial charge capacity of each half cell. The percentage of time was calculated.
Table 7 shows the initial charge capacity (%) of each half cell.
実施例７、８および比較例６のハーフセルに対して、評価例９と同様に初期充電容量を確認し、各ハーフセルの初期充電容量につき、比較例６のハーフセルの初期充電容量を１００％としたときの百分率を算出した。
各ハーフセルの初期充電容量（％）を表７に示す。 [Evaluation Example 13 Charge capacity of half cell]
The initial charge capacities of the half cells of Examples 7 and 8 and Comparative Example 6 were checked in the same manner as in Evaluation Example 9, and the initial charge capacity of the half cell of Comparative Example 6 was taken as 100% for the initial charge capacity of each half cell. The percentage of time was calculated.
Table 7 shows the initial charge capacity (%) of each half cell.
表７に示すように、正極活物質に含まれるタングステンの量を適切な範囲内、具体的にはメタルサイトを構成し得るリチウム以外の金属元素の合計を１００原子％としたときのタングステンの量を０．２５原子％近傍の値とすることで、ハーフセルの初期容量低下を抑制することが可能である。
これは既述した評価例１および図１の結果と同様であり、タングステン量の好適な範囲も評価例１に記載したとおりである。
評価例１３の結果からは、さらに、タングステンとともにマグネシウムおよび／またはクロムを正極活物質に加えることによって、タングステンに由来する容量低下をさらに抑制することが可能であるともいい得る。 As shown in Table 7, the amount of tungsten contained in the positive electrode active material is within an appropriate range, specifically, the amount of tungsten when the total of metal elements other than lithium that can form metal sites is 100 atomic%. is set to a value in the vicinity of 0.25 atomic %, it is possible to suppress the decrease in the initial capacity of the half-cell.
This is the same as the results of Evaluation Example 1 and FIG.
From the results of Evaluation Example 13, it can also be said that the decrease in capacity due to tungsten can be further suppressed by adding magnesium and/or chromium to the positive electrode active material together with tungsten.
これは既述した評価例１および図１の結果と同様であり、タングステン量の好適な範囲も評価例１に記載したとおりである。
評価例１３の結果からは、さらに、タングステンとともにマグネシウムおよび／またはクロムを正極活物質に加えることによって、タングステンに由来する容量低下をさらに抑制することが可能であるともいい得る。 As shown in Table 7, the amount of tungsten contained in the positive electrode active material is within an appropriate range, specifically, the amount of tungsten when the total of metal elements other than lithium that can form metal sites is 100 atomic%. is set to a value in the vicinity of 0.25 atomic %, it is possible to suppress the decrease in the initial capacity of the half-cell.
This is the same as the results of Evaluation Example 1 and FIG.
From the results of Evaluation Example 13, it can also be said that the decrease in capacity due to tungsten can be further suppressed by adding magnesium and/or chromium to the positive electrode active material together with tungsten.
容量低下の抑制を考慮する場合、正極活物質におけるマグネシウム量の好ましい範囲は、メタルサイトを構成し得るリチウム以外の金属元素の合計を１００原子％としたときに０．５～１０原子％の範囲内、１～１０原子％の範囲内、１～８原子％の範囲内、２～５原子％の範囲内といい得る。また、正極活物質におけるクロム量の好ましい範囲は、メタルサイトを構成し得るリチウム以外の金属元素の合計を１００原子％としたときに０．２～５原子％の範囲内、０．３～５原子％の範囲内、０．５～３原子％の範囲内、１～２．５原子％の範囲内といい得る。
When considering the suppression of capacity reduction, the preferable range of the amount of magnesium in the positive electrode active material is 0.5 to 10 atomic % when the total of metal elements other than lithium that can constitute the metal site is 100 atomic %. Within the range, it can be said to be within the range of 1 to 10 atomic %, within the range of 1 to 8 atomic %, and within the range of 2 to 5 atomic %. In addition, the preferable range of the amount of chromium in the positive electrode active material is 0.2 to 5 atomic %, 0.3 to 5 atomic %, when the total of metal elements other than lithium that can constitute the metal site is 100 atomic %. atomic %, 0.5 to 3 atomic %, and 1 to 2.5 atomic %.
〔評価例１４ リチウムイオン二次電池の高温充放電サイクル試験〕
実施例７及び実施例８のリチウムイオン二次電池に対して、高温充放電サイクル試験を行った。
具体的には、２５℃、０．０５ＣレートでＳＯＣ８０％まで充電し、その後６０℃で２０時間静置することで、コンディショニングを行った。コンディショニング後に、６０℃で、１Ｃの一定電流にて、ＳＯＣ１００％となるまで充電し、その後ＳＯＣ１０％となるまで放電する高温充放電サイクルを１００回繰り返した。
このときのカットオフ電圧は２．５７Ｖまたは初期容量すなわちＳＯＣ１００％に対してＳＯＣ９０％となる電圧である。 [Evaluation Example 14 High temperature charge/discharge cycle test of lithium ion secondary battery]
A high-temperature charge-discharge cycle test was performed on the lithium-ion secondary batteries of Examples 7 and 8.
Specifically, the battery was conditioned at 25° C. at a rate of 0.05 C to charge toSOC 80%, and then allowed to stand at 60° C. for 20 hours. After conditioning, a high-temperature charge-discharge cycle was repeated 100 times at 60° C. at a constant current of 1 C to charge to an SOC of 100% and then to discharge to an SOC of 10%.
The cutoff voltage at this time is 2.57 V or the voltage at which SOC is 90% with respect to the initial capacity, that is,SOC 100%.
実施例７及び実施例８のリチウムイオン二次電池に対して、高温充放電サイクル試験を行った。
具体的には、２５℃、０．０５ＣレートでＳＯＣ８０％まで充電し、その後６０℃で２０時間静置することで、コンディショニングを行った。コンディショニング後に、６０℃で、１Ｃの一定電流にて、ＳＯＣ１００％となるまで充電し、その後ＳＯＣ１０％となるまで放電する高温充放電サイクルを１００回繰り返した。
このときのカットオフ電圧は２．５７Ｖまたは初期容量すなわちＳＯＣ１００％に対してＳＯＣ９０％となる電圧である。 [Evaluation Example 14 High temperature charge/discharge cycle test of lithium ion secondary battery]
A high-temperature charge-discharge cycle test was performed on the lithium-ion secondary batteries of Examples 7 and 8.
Specifically, the battery was conditioned at 25° C. at a rate of 0.05 C to charge to
The cutoff voltage at this time is 2.57 V or the voltage at which SOC is 90% with respect to the initial capacity, that is,
各リチウムイオン二次電池につき、初回の充放電時における放電容量を１００％として、各サイクルの放電容量の百分率を算出した。当該百分率を各リチウムイオン二次電池における容量維持率とした。１００サイクル時の実施例７のリチウムイオン二次電池の容量維持率及び実施例８のリチウムイオン二次電池の容量維持率（％）を、表８に示す。なお、試験はｎ＝２で行い、表８にはその平均値を示した。
For each lithium-ion secondary battery, the percentage of the discharge capacity in each cycle was calculated, with the discharge capacity at the time of the first charge and discharge as 100%. This percentage was taken as the capacity retention rate of each lithium ion secondary battery. Table 8 shows the capacity retention rate (%) of the lithium ion secondary battery of Example 7 and the capacity retention rate (%) of the lithium ion secondary battery of Example 8 after 100 cycles. The test was conducted with n=2, and Table 8 shows the average values.
表８に示すように、１００サイクル時の各リチウムイオン二次電池の容量維持率は、実施例７のリチウムイオン二次電池で８０％、実施例８のリチウムイオン二次電池で８８％であった。この結果から、耐久性向上の観点からは、正極活物質に含まれるクロム量が多い方が好適といい得る。また耐久性向上の観点からは、正極活物質におけるクロム量の好ましい範囲として、メタルサイトを構成し得るリチウム以外の金属元素の合計を１００原子％としたときに１原子％以上、１．５原子％以上、２原子％以上、３原子％以上、の各範囲を挙げ得る。このときのクロム量に上限はないが、強いて挙げるならば、１０原子％以下の範囲内、５原子％以下の範囲内である。
As shown in Table 8, the capacity retention rate of each lithium ion secondary battery after 100 cycles was 80% for the lithium ion secondary battery of Example 7 and 88% for the lithium ion secondary battery of Example 8. rice field. From this result, it can be said that a larger amount of chromium contained in the positive electrode active material is preferable from the viewpoint of improving durability. From the viewpoint of improving durability, the preferable range of the amount of chromium in the positive electrode active material is 1 atomic % or more and 1.5 atomic % when the total of metal elements other than lithium that can constitute the metal site is 100 atomic %. % or more, 2 atomic % or more, and 3 atomic % or more. Although there is no upper limit to the amount of chromium at this time, it is in the range of 10 atomic % or less and 5 atomic % or less.
〔評価例１５ ハーフセルの充電容量〕
実施例９、実施例１０、実施例１２～実施例１５および比較例６のハーフセルに対して、評価例９と同様に初期充電容量を確認し、各ハーフセルの初期充電容量につき、比較例６のハーフセルの初期充電容量を１００％としたときの百分率を算出した。
各ハーフセルの初期充電容量（％）を表９に示す。 [Evaluation Example 15 Charge capacity of half cell]
For the half cells of Examples 9, 10, 12 to 15, and Comparative Example 6, the initial charge capacity was confirmed in the same manner as in Evaluation Example 9, and the initial charge capacity of each half cell was compared with that of Comparative Example 6. The percentage was calculated when the initial charge capacity of the half cell was taken as 100%.
Table 9 shows the initial charge capacity (%) of each half cell.
実施例９、実施例１０、実施例１２～実施例１５および比較例６のハーフセルに対して、評価例９と同様に初期充電容量を確認し、各ハーフセルの初期充電容量につき、比較例６のハーフセルの初期充電容量を１００％としたときの百分率を算出した。
各ハーフセルの初期充電容量（％）を表９に示す。 [Evaluation Example 15 Charge capacity of half cell]
For the half cells of Examples 9, 10, 12 to 15, and Comparative Example 6, the initial charge capacity was confirmed in the same manner as in Evaluation Example 9, and the initial charge capacity of each half cell was compared with that of Comparative Example 6. The percentage was calculated when the initial charge capacity of the half cell was taken as 100%.
Table 9 shows the initial charge capacity (%) of each half cell.
タングステンとともにマグネシウム、チタン、バナジウムおよびフッ素を正極活物質に加えた実施例９、実施例１３～実施例１４および、タングステンとともにマグネシウム、チタン、クロムおよびフッ素を正極活物質に加えた実施例１０では、正極活物質にタングステンを加えていない比較例６よりも初期充電容量が向上した。
In Examples 9, 13 and 14 in which magnesium, titanium, vanadium and fluorine were added to the positive electrode active material along with tungsten, and in Example 10 in which magnesium, titanium, chromium and fluorine were added to the positive electrode active material along with tungsten, The initial charge capacity was improved as compared with Comparative Example 6 in which tungsten was not added to the positive electrode active material.
この結果から、タングステンに加えて、チタン、バナジウム、クロムから選ばれる少なくとも一種の元素をフッ素と併用することは、初期充電容量の向上に有効であると考えられる。さらに、タングステンとともに正極活物質に加えるのに好適な元素として、フッ素を必須とし、マグネシウム、チタン、バナジウム、クロムから選ばれる少なくとも一種を用いるのが好適だとも考えられる。そして、実施例１０のハーフセルの初期容量は実施例９のハーフセルの初期容量よりも高い値を示したことから、特に、正極活物質にクロムを加える場合には初期充電容量の向上が顕著になるとも考えられる。
From this result, it is considered that the use of at least one element selected from titanium, vanadium, and chromium, in addition to tungsten, together with fluorine is effective in improving the initial charge capacity. Furthermore, as an element suitable to be added to the positive electrode active material together with tungsten, fluorine is essential, and it is considered suitable to use at least one element selected from magnesium, titanium, vanadium and chromium. Since the initial capacity of the half-cell of Example 10 was higher than the initial capacity of the half-cell of Example 9, the improvement in the initial charge capacity was particularly pronounced when chromium was added to the positive electrode active material. is also conceivable.
次に、正極活物質に含まれるバナジウムの量に着目して評価例１３の結果を検討する。
実施例９、実施例１２～実施例１５のリチウムイオン二次電池は、正極活物質に含まれるバナジウムの量において相違する。具体的には、正極活物質に含まれるマンガン元素、鉄元素、タングステン元素およびＤ1元素の合計、すなわちメタルサイトを構成し得るリチウム以外の金属元素を１００原子％としたときのバナジウムの量は、実施例９のリチウムイオン二次電池で０．８原子％、実施例１２のリチウムイオン二次電池で０原子％、実施例１３のリチウムイオン二次電池で１．２５原子％、実施例１４のリチウムイオン二次電池で２．５原子％、実施例１５のリチウムイオン二次電池で３原子％である。 Next, the results of Evaluation Example 13 will be examined focusing on the amount of vanadium contained in the positive electrode active material.
The lithium ion secondary batteries of Examples 9 and 12 to 15 differ in the amount of vanadium contained in the positive electrode active material. Specifically, the amount of vanadium when the total of manganese element, iron element, tungsten element and D1 element contained in the positive electrode active material, that is, the metal element other than lithium that can constitute the metal site is 100 atomic% , 0.8 atomic % in the lithium ion secondary battery of Example 9, 0 atomic % in the lithium ion secondary battery of Example 12, 1.25 atomic % in the lithium ion secondary battery of Example 13, Example 14 2.5 atomic % in the lithium ion secondary battery of Example 15 and 3 atomic % in the lithium ion secondary battery of Example 15.
実施例９、実施例１２～実施例１５のリチウムイオン二次電池は、正極活物質に含まれるバナジウムの量において相違する。具体的には、正極活物質に含まれるマンガン元素、鉄元素、タングステン元素およびＤ1元素の合計、すなわちメタルサイトを構成し得るリチウム以外の金属元素を１００原子％としたときのバナジウムの量は、実施例９のリチウムイオン二次電池で０．８原子％、実施例１２のリチウムイオン二次電池で０原子％、実施例１３のリチウムイオン二次電池で１．２５原子％、実施例１４のリチウムイオン二次電池で２．５原子％、実施例１５のリチウムイオン二次電池で３原子％である。 Next, the results of Evaluation Example 13 will be examined focusing on the amount of vanadium contained in the positive electrode active material.
The lithium ion secondary batteries of Examples 9 and 12 to 15 differ in the amount of vanadium contained in the positive electrode active material. Specifically, the amount of vanadium when the total of manganese element, iron element, tungsten element and D1 element contained in the positive electrode active material, that is, the metal element other than lithium that can constitute the metal site is 100 atomic% , 0.8 atomic % in the lithium ion secondary battery of Example 9, 0 atomic % in the lithium ion secondary battery of Example 12, 1.25 atomic % in the lithium ion secondary battery of Example 13, Example 14 2.5 atomic % in the lithium ion secondary battery of Example 15 and 3 atomic % in the lithium ion secondary battery of Example 15.
このような実施例９、実施例１２～実施例５のリチウムイオン二次電池において、その充電容量は実施例１４＞実施例１３＞実施例９＞実施例１２＞実施例１５であった。
このことから、正極活物質に含まれるバナジウムの量には特に好適な範囲があると考えられる。具体的には、メタルサイトを構成し得るリチウム以外の金属元素の合計を１００原子％としたときの好ましいバナジウムの量としては、０原子％以上３原子％未満、０．５原子％以上２．９原子％以下、０．８原子％以上２．９原子％以下、１．０原子％以上２．９原子％以下、１．５原子％以上２．８原子％以下の各範囲を例示できる。 In the lithium ion secondary batteries of Examples 9 and 12 to 5, the charging capacity was Example 14>Example 13>Example 9>Example 12>Example 15.
From this, it is considered that there is a particularly suitable range for the amount of vanadium contained in the positive electrode active material. Specifically, the amount of vanadium is preferably 0 atomic % or more and less than 3 atomic %, 0.5 atomic % or more and 0.5 atomic % or more,2. Each range of 9 atomic % or less, 0.8 atomic % or more and 2.9 atomic % or less, 1.0 atomic % or more and 2.9 atomic % or less, and 1.5 atomic % or more and 2.8 atomic % or less can be exemplified.
このことから、正極活物質に含まれるバナジウムの量には特に好適な範囲があると考えられる。具体的には、メタルサイトを構成し得るリチウム以外の金属元素の合計を１００原子％としたときの好ましいバナジウムの量としては、０原子％以上３原子％未満、０．５原子％以上２．９原子％以下、０．８原子％以上２．９原子％以下、１．０原子％以上２．９原子％以下、１．５原子％以上２．８原子％以下の各範囲を例示できる。 In the lithium ion secondary batteries of Examples 9 and 12 to 5, the charging capacity was Example 14>Example 13>Example 9>Example 12>Example 15.
From this, it is considered that there is a particularly suitable range for the amount of vanadium contained in the positive electrode active material. Specifically, the amount of vanadium is preferably 0 atomic % or more and less than 3 atomic %, 0.5 atomic % or more and 0.5 atomic % or more,2. Each range of 9 atomic % or less, 0.8 atomic % or more and 2.9 atomic % or less, 1.0 atomic % or more and 2.9 atomic % or less, and 1.5 atomic % or more and 2.8 atomic % or less can be exemplified.
一方、容量低下の抑制を考慮する場合、正極活物質におけるチタン量の好ましい範囲は、メタルサイトを構成し得るリチウム以外の金属元素の合計を１００原子％としたときに０．５～１０原子％の範囲内、１～１０原子％の範囲内、１．５～６原子％の範囲内、１．５～４原子％の範囲内といい得る。正極活物質におけるクロム量の好ましい範囲は、メタルサイトを構成し得るリチウム以外の金属元素の合計を１００原子％としたときに０．１～１０原子％の範囲内、０．５～８原子％の範囲内、１～６原子％の範囲内、２～４原子％の範囲内といい得る。
On the other hand, when considering the suppression of capacity decrease, the preferable range of the amount of titanium in the positive electrode active material is 0.5 to 10 atomic % when the total of metal elements other than lithium that can constitute the metal site is 100 atomic %. , 1 to 10 atomic %, 1.5 to 6 atomic %, and 1.5 to 4 atomic %. A preferable range of the amount of chromium in the positive electrode active material is 0.1 to 10 atomic % and 0.5 to 8 atomic % when the total of metal elements other than lithium that can constitute the metal site is 100 atomic %. within the range of, within the range of 1 to 6 atomic %, and within the range of 2 to 4 atomic %.
〔評価例１６ ハーフセルの充電容量〕
実施例１１および比較例６のハーフセルに対して、評価例９と同様に初期充電容量を確認し、各ハーフセルの初期充電容量につき、比較例６のハーフセルの初期充電容量を１００％としたときの百分率を算出した。
各ハーフセルの初期充電容量（％）を表１０に示す。 [Evaluation Example 16 Charge capacity of half cell]
The initial charge capacities of the half cells of Example 11 and Comparative Example 6 were checked in the same manner as in Evaluation Example 9, and the initial charge capacity of each half cell was compared with the initial charge capacity of the half cell of Comparative Example 6 as 100%. Percentages were calculated.
Table 10 shows the initial charge capacity (%) of each half cell.
実施例１１および比較例６のハーフセルに対して、評価例９と同様に初期充電容量を確認し、各ハーフセルの初期充電容量につき、比較例６のハーフセルの初期充電容量を１００％としたときの百分率を算出した。
各ハーフセルの初期充電容量（％）を表１０に示す。 [Evaluation Example 16 Charge capacity of half cell]
The initial charge capacities of the half cells of Example 11 and Comparative Example 6 were checked in the same manner as in Evaluation Example 9, and the initial charge capacity of each half cell was compared with the initial charge capacity of the half cell of Comparative Example 6 as 100%. Percentages were calculated.
Table 10 shows the initial charge capacity (%) of each half cell.
表９に示すように、正極活物質にタングステンとともにマグネシウム及びクロムを含む実施例１１のハーフセルでは、正極活物質にタングステンを含まない比較例６のハーフセルよりも初期充電容量が向上した。
なお、評価例１６における実施例１１のハーフセルの初期充電容量（％）は、評価例１５における実施例１０のハーフセルの初期充電容量（％）に比べてやや劣る。これは、実施例１１のハーフセルが正極活物質にチタン及びフッ素を含まないことに因るものと推測され、この結果からも、初期充電容量の向上を考慮すると正極活物質にはタングステンとともにチタン及びフッ素を配合するのが特に好適といい得る。 As shown in Table 9, the half cell of Example 11 containing magnesium and chromium as well as tungsten in the positive electrode active material had an improved initial charge capacity compared to the half cell of Comparative Example 6 containing no tungsten in the positive electrode active material.
The initial charge capacity (%) of the half cell of Example 11 in Evaluation Example 16 is slightly inferior to the initial charge capacity (%) of the half cell of Example 10 in Evaluation Example 15. This is presumed to be due to the fact that the positive electrode active material of the half cell of Example 11 does not contain titanium and fluorine. It can be said that it is particularly preferable to blend fluorine.
なお、評価例１６における実施例１１のハーフセルの初期充電容量（％）は、評価例１５における実施例１０のハーフセルの初期充電容量（％）に比べてやや劣る。これは、実施例１１のハーフセルが正極活物質にチタン及びフッ素を含まないことに因るものと推測され、この結果からも、初期充電容量の向上を考慮すると正極活物質にはタングステンとともにチタン及びフッ素を配合するのが特に好適といい得る。 As shown in Table 9, the half cell of Example 11 containing magnesium and chromium as well as tungsten in the positive electrode active material had an improved initial charge capacity compared to the half cell of Comparative Example 6 containing no tungsten in the positive electrode active material.
The initial charge capacity (%) of the half cell of Example 11 in Evaluation Example 16 is slightly inferior to the initial charge capacity (%) of the half cell of Example 10 in Evaluation Example 15. This is presumed to be due to the fact that the positive electrode active material of the half cell of Example 11 does not contain titanium and fluorine. It can be said that it is particularly preferable to blend fluorine.
〔評価例１７ リチウムイオン二次電池の放電容量〕
実施例９、実施例１０、実施例１６および比較例６のリチウムイオン二次電池に対して、２５℃、０．０５ＣレートでＳＯＣ８０％まで充電し、その後６０℃で２０時間静置することで、コンディショニングを行った。コンディショニング後に、２５℃、１Ｃレートで４．２Ｖまで２時間かけてＣＣ－ＣＶ充電を行った。その後、１／３Ｃレートで３Ｖまで５時間かけてＣＣ－ＣＶ放電を行った。これにより、各リチウムイオン二次電池の放電容量を確認した。 [Evaluation Example 17 Discharge capacity of lithium ion secondary battery]
The lithium ion secondary batteries of Examples 9, 10, 16 and Comparative Example 6 were charged toSOC 80% at 25°C at a rate of 0.05C, and then allowed to stand at 60°C for 20 hours. , was conditioned. After conditioning, CC-CV charging was performed at 25° C. and 1C rate to 4.2 V over 2 hours. After that, CC-CV discharge was performed at a rate of 1/3C to 3V over 5 hours. Thereby, the discharge capacity of each lithium ion secondary battery was confirmed.
実施例９、実施例１０、実施例１６および比較例６のリチウムイオン二次電池に対して、２５℃、０．０５ＣレートでＳＯＣ８０％まで充電し、その後６０℃で２０時間静置することで、コンディショニングを行った。コンディショニング後に、２５℃、１Ｃレートで４．２Ｖまで２時間かけてＣＣ－ＣＶ充電を行った。その後、１／３Ｃレートで３Ｖまで５時間かけてＣＣ－ＣＶ放電を行った。これにより、各リチウムイオン二次電池の放電容量を確認した。 [Evaluation Example 17 Discharge capacity of lithium ion secondary battery]
The lithium ion secondary batteries of Examples 9, 10, 16 and Comparative Example 6 were charged to
各リチウムイオン二次電池の放電容量を後述する評価例１８の結果とともに表１１に示す。なお、表１１においては、比較例６のリチウムイオン二次電池の放電容量を１００％として、各実施例のリチウムイオン二次電池の放電容量を百分率で示した。
なお、各リチウムイオン二次電池は、４．２ＶでＳＯＣ１００％となり、３．０ＶでＳＯＣ０％となる。 Table 11 shows the discharge capacity of each lithium ion secondary battery together with the results of Evaluation Example 18, which will be described later. In Table 11, the discharge capacity of the lithium ion secondary battery of each example is shown in percentage, with the discharge capacity of the lithium ion secondary battery of Comparative Example 6 set to 100%.
Each lithium ion secondary battery has an SOC of 100% at 4.2V and an SOC of 0% at 3.0V.
なお、各リチウムイオン二次電池は、４．２ＶでＳＯＣ１００％となり、３．０ＶでＳＯＣ０％となる。 Table 11 shows the discharge capacity of each lithium ion secondary battery together with the results of Evaluation Example 18, which will be described later. In Table 11, the discharge capacity of the lithium ion secondary battery of each example is shown in percentage, with the discharge capacity of the lithium ion secondary battery of Comparative Example 6 set to 100%.
Each lithium ion secondary battery has an SOC of 100% at 4.2V and an SOC of 0% at 3.0V.
表１１に示すように、実施例９のリチウムイオン二次電池は、比較例６のリチウムイオン二次電池よりも、初期放電容量が大きい。これは、実施例９のリチウムイオン二次電池では、タングステンとともにマグネシウム、チタン、バナジウムおよびフッ素を正極活物質に加えたことに因るものと考えられる。換言すると、正極活物質の酸素サイトの一部をフッ素で置換し、かつ、メタルサイトの一部をタングステンおよび既述したＤ1の元素で置換することで、リチウムイオン二次電池の初期充電容量が向上する。
As shown in Table 11, the lithium ion secondary battery of Example 9 has a larger initial discharge capacity than the lithium ion secondary battery of Comparative Example 6. This is presumably because in the lithium ion secondary battery of Example 9, magnesium, titanium, vanadium and fluorine were added to the positive electrode active material together with tungsten. In other words, by substituting a portion of the oxygen site of the positive electrode active material with fluorine and substituting a portion of the metal site with tungsten and the above - described D element, the initial charge capacity of the lithium ion secondary battery improves.
Ｄ1元素に着目して評価する。
実施例９のリチウムイオン二次電池と実施例１６のリチウムイオン二次電池とは、正極活物質がＤ1元素としてバナジウムを含む又はクロムを含む点で互いに相違する。 Focusing on the D1 element for evaluation.
The lithium ion secondary battery of Example 9 and the lithium ion secondary battery of Example 16 are different from each other in that the positive electrode active material contains vanadium or chromium as the D1 element.
実施例９のリチウムイオン二次電池と実施例１６のリチウムイオン二次電池とは、正極活物質がＤ1元素としてバナジウムを含む又はクロムを含む点で互いに相違する。 Focusing on the D1 element for evaluation.
The lithium ion secondary battery of Example 9 and the lithium ion secondary battery of Example 16 are different from each other in that the positive electrode active material contains vanadium or chromium as the D1 element.
表１１に示すように、実施例９のリチウムイオン二次電池は実施例１６のリチウムイオン二次電池に比べて初期放電容量が高かったことから、初期容量を考慮するとＤ1元素としてクロムを含むよりもＤ1元素としてバナジウムを含む方が好適といい得る。
As shown in Table 11, the lithium ion secondary battery of Example 9 had a higher initial discharge capacity than the lithium ion secondary battery of Example 16. Considering the initial capacity, chromium is included as an element D1. It can be said that it is more preferable to contain vanadium as the D1 element than
フッ素に着目して評価する。
実施例１０のリチウムイオン二次電池と実施例１６のリチウムイオン二次電池とは、正極活物質におけるフッ素の含有量において互いに相違する。具体的には、実施例１０のリチウムイオン二次電池における正極活物質のフッ素含有量は２．５原子％であるのに対し、実施例１６のリチウムイオン二次電池における正極活物質のフッ素含有量は５原子％である。 Evaluate with a focus on fluorine.
The lithium ion secondary battery of Example 10 and the lithium ion secondary battery of Example 16 differ from each other in the content of fluorine in the positive electrode active material. Specifically, the fluorine content of the positive electrode active material in the lithium ion secondary battery of Example 10 is 2.5 atomic %, whereas the fluorine content of the positive electrode active material in the lithium ion secondary battery of Example 16 The amount is 5 atomic %.
実施例１０のリチウムイオン二次電池と実施例１６のリチウムイオン二次電池とは、正極活物質におけるフッ素の含有量において互いに相違する。具体的には、実施例１０のリチウムイオン二次電池における正極活物質のフッ素含有量は２．５原子％であるのに対し、実施例１６のリチウムイオン二次電池における正極活物質のフッ素含有量は５原子％である。 Evaluate with a focus on fluorine.
The lithium ion secondary battery of Example 10 and the lithium ion secondary battery of Example 16 differ from each other in the content of fluorine in the positive electrode active material. Specifically, the fluorine content of the positive electrode active material in the lithium ion secondary battery of Example 10 is 2.5 atomic %, whereas the fluorine content of the positive electrode active material in the lithium ion secondary battery of Example 16 The amount is 5 atomic %.
表１１に示すように、実施例１０のリチウムイオン二次電池は実施例１６のリチウムイオン二次電池に比べて初期放電容量が高かったことから、初期容量を考慮すると、正極活物質におけるフッ素含有量は、フッ素および酸素の合計を４００原子％としたときに５原子％である場合よりも２．５原子％である場合の方が好適といい得る。
さらに上記の結果から、初期容量を考慮した場合の好ましいフッ素含有量の範囲として、正極活物質においてフッ素および酸素の合計を４００原子％としたときに０原子％超１０原子％以下、１原子％以上５原子％以下、１．５原子％以上４原子％以下、または２原子％以上３原子％以下を例示できる。 As shown in Table 11, the lithium ion secondary battery of Example 10 had a higher initial discharge capacity than the lithium ion secondary battery of Example 16. Therefore, considering the initial capacity, the fluorine content in the positive electrode active material It can be said that the amount is more preferably 2.5 atomic % than 5 atomic % when the total of fluorine and oxygen is 400 atomic %.
Furthermore, from the above results, the preferable range of fluorine content when considering the initial capacity is more than 0 atomic % and 10 atomic % or less, 1 atomic % when the total of fluorine and oxygen in the positive electrode active material is 400 atomic %. 5 atomic % or less, 1.5 atomic % or more and 4 atomic % or less, or 2 atomic % or more and 3 atomic % or less can be exemplified.
さらに上記の結果から、初期容量を考慮した場合の好ましいフッ素含有量の範囲として、正極活物質においてフッ素および酸素の合計を４００原子％としたときに０原子％超１０原子％以下、１原子％以上５原子％以下、１．５原子％以上４原子％以下、または２原子％以上３原子％以下を例示できる。 As shown in Table 11, the lithium ion secondary battery of Example 10 had a higher initial discharge capacity than the lithium ion secondary battery of Example 16. Therefore, considering the initial capacity, the fluorine content in the positive electrode active material It can be said that the amount is more preferably 2.5 atomic % than 5 atomic % when the total of fluorine and oxygen is 400 atomic %.
Furthermore, from the above results, the preferable range of fluorine content when considering the initial capacity is more than 0 atomic % and 10 atomic % or less, 1 atomic % when the total of fluorine and oxygen in the positive electrode active material is 400 atomic %. 5 atomic % or less, 1.5 atomic % or more and 4 atomic % or less, or 2 atomic % or more and 3 atomic % or less can be exemplified.
〔評価例１８ リチウムイオン二次電池の抵抗測定〕
実施例９、実施例１０、実施例１６および比較例６のリチウムイオン二次電池に対して、上記のコンディショニング後に、温度２５℃、ＳＯＣ６０％まで充電し、その後、１Ｃ、２Ｃ、３Ｃ、４Ｃの順で各々５秒ずつＣＣ放電をした際の電圧変化量（放電前電圧と４Ｃ放電５秒後電圧との差）及び電流値からオームの法則により放電抵抗（直流抵抗）を測定した。結果を上記の評価例１７の結果とともに表１１に示す。なお、表１１においては、比較例６のリチウムイオン二次電池の放電抵抗を１００％として、各実施例のリチウムイオン二次電池の放電抵抗を百分率で示した。 [Evaluation Example 18 Measurement of resistance of lithium ion secondary battery]
After the above conditioning, the lithium ion secondary batteries of Examples 9, 10, 16 and Comparative Example 6 were charged to a temperature of 25°C and an SOC of 60%, and then charged to 1C, 2C, 3C and 4C. The discharge resistance (DC resistance) was measured by Ohm's law from the amount of voltage change (difference between the voltage before discharge and the voltage after 5 seconds of 4C discharge) and the current value when CC discharge was performed for 5 seconds each in order. The results are shown in Table 11 together with the results of Evaluation Example 17 above. In addition, in Table 11, the discharge resistance of the lithium ion secondary battery of each example is shown in percentage, assuming that the discharge resistance of the lithium ion secondary battery of Comparative Example 6 is 100%.
実施例９、実施例１０、実施例１６および比較例６のリチウムイオン二次電池に対して、上記のコンディショニング後に、温度２５℃、ＳＯＣ６０％まで充電し、その後、１Ｃ、２Ｃ、３Ｃ、４Ｃの順で各々５秒ずつＣＣ放電をした際の電圧変化量（放電前電圧と４Ｃ放電５秒後電圧との差）及び電流値からオームの法則により放電抵抗（直流抵抗）を測定した。結果を上記の評価例１７の結果とともに表１１に示す。なお、表１１においては、比較例６のリチウムイオン二次電池の放電抵抗を１００％として、各実施例のリチウムイオン二次電池の放電抵抗を百分率で示した。 [Evaluation Example 18 Measurement of resistance of lithium ion secondary battery]
After the above conditioning, the lithium ion secondary batteries of Examples 9, 10, 16 and Comparative Example 6 were charged to a temperature of 25°C and an SOC of 60%, and then charged to 1C, 2C, 3C and 4C. The discharge resistance (DC resistance) was measured by Ohm's law from the amount of voltage change (difference between the voltage before discharge and the voltage after 5 seconds of 4C discharge) and the current value when CC discharge was performed for 5 seconds each in order. The results are shown in Table 11 together with the results of Evaluation Example 17 above. In addition, in Table 11, the discharge resistance of the lithium ion secondary battery of each example is shown in percentage, assuming that the discharge resistance of the lithium ion secondary battery of Comparative Example 6 is 100%.
表１１に示すように、実施例９のリチウムイオン二次電池は、比較例６のリチウムイオン二次電池よりも、抵抗が小さい。これは、実施例９のリチウムイオン二次電池では、タングステンとともにマグネシウム、チタン、バナジウムおよびフッ素を正極活物質に加えたことに因るものと考えられる。換言すると、正極活物質の酸素サイトの一部をフッ素で置換し、かつ、メタルサイトの一部をタングステンおよび既述したＤ1の元素で置換することで、リチウムイオン二次電池の導電性が向上する。
As shown in Table 11, the lithium ion secondary battery of Example 9 has a lower resistance than the lithium ion secondary battery of Comparative Example 6. This is presumably because in the lithium ion secondary battery of Example 9, magnesium, titanium, vanadium and fluorine were added to the positive electrode active material together with tungsten. In other words, by substituting a portion of the oxygen sites of the positive electrode active material with fluorine and substituting a portion of the metal sites with tungsten and the above - described D element, the conductivity of the lithium ion secondary battery is improved. improves.
Ｄ1元素に着目して評価する。
実施例９のリチウムイオン二次電池と実施例１６のリチウムイオン二次電池とは、実施例９のリチウムイオン二次電池がＤ1元素としてバナジウムを含むのに対し、実施例１６のリチウムイオン二次電池がＤ1元素としてクロムを含む点で互いに相違する。 Focusing on the D1 element for evaluation.
The lithium ion secondary battery of Example 9 and the lithium ion secondary battery of Example 16 are different in that the lithium ion secondary battery of Example 9 contains vanadium as an element D1, whereas the lithium ion secondary battery of Example 16 contains vanadium. They differ from each other in that the secondary batteries contain chromium as the D1 element.
実施例９のリチウムイオン二次電池と実施例１６のリチウムイオン二次電池とは、実施例９のリチウムイオン二次電池がＤ1元素としてバナジウムを含むのに対し、実施例１６のリチウムイオン二次電池がＤ1元素としてクロムを含む点で互いに相違する。 Focusing on the D1 element for evaluation.
The lithium ion secondary battery of Example 9 and the lithium ion secondary battery of Example 16 are different in that the lithium ion secondary battery of Example 9 contains vanadium as an element D1, whereas the lithium ion secondary battery of Example 16 contains vanadium. They differ from each other in that the secondary batteries contain chromium as the D1 element.
表１１に示すように、実施例９のリチウムイオン二次電池は実施例１６のリチウムイオン二次電池に比べてさらに抵抗が小さいことから、抵抗を考慮するとＤ1元素としてクロムを含むよりもＤ1元素としてバナジウムを含む方が好適といい得る。
As shown in Table 11, the lithium ion secondary battery of Example 9 has a smaller resistance than the lithium ion secondary battery of Example 16, so considering the resistance, D It can be said that it is preferable to contain vanadium as one element.
フッ素に着目して評価する。
実施例１０のリチウムイオン二次電池と実施例１６のリチウムイオン二次電池とは、正極活物質におけるフッ素の含有量において互いに相違する。既述したように、実施例１０のリチウムイオン二次電池における正極活物質のフッ素含有量は２．５原子％であるのに対し、実施例１６のリチウムイオン二次電池における正極活物質のフッ素含有量は５原子％である。 Evaluate with a focus on fluorine.
The lithium ion secondary battery of Example 10 and the lithium ion secondary battery of Example 16 differ from each other in the content of fluorine in the positive electrode active material. As described above, the fluorine content of the positive electrode active material in the lithium ion secondary battery of Example 10 was 2.5 atomic %, whereas the fluorine content of the positive electrode active material in the lithium ion secondary battery of Example 16 was The content is 5 atomic %.
実施例１０のリチウムイオン二次電池と実施例１６のリチウムイオン二次電池とは、正極活物質におけるフッ素の含有量において互いに相違する。既述したように、実施例１０のリチウムイオン二次電池における正極活物質のフッ素含有量は２．５原子％であるのに対し、実施例１６のリチウムイオン二次電池における正極活物質のフッ素含有量は５原子％である。 Evaluate with a focus on fluorine.
The lithium ion secondary battery of Example 10 and the lithium ion secondary battery of Example 16 differ from each other in the content of fluorine in the positive electrode active material. As described above, the fluorine content of the positive electrode active material in the lithium ion secondary battery of Example 10 was 2.5 atomic %, whereas the fluorine content of the positive electrode active material in the lithium ion secondary battery of Example 16 was The content is 5 atomic %.
表１１に示すように、実施例１６のリチウムイオン二次電池は実施例１０のリチウムイオン二次電池に比べて放電抵抗が低いことから、放電抵抗を考慮すると、正極活物質におけるフッ素含有量は、フッ素および酸素の合計を４００原子％としたときに２．５原子％である場合よりも５原子％である場合の方が好適といい得る。
さらに上記の結果から、放電抵抗を考慮した場合の好ましいフッ素含有量の範囲として、正極活物質においてフッ素および酸素の合計を４００原子％としたときに２．５原子％以上、３．５原子％以上、４．５原子％以上、または５原子％以上を例示できる。この場合のフッ素量の好ましい範囲に特に上限はないが、５０原子％以下、２０原子％以下、１０原子％以下を例示できる。 As shown in Table 11, the lithium ion secondary battery of Example 16 has a lower discharge resistance than the lithium ion secondary battery of Example 10. Therefore, considering the discharge resistance, the fluorine content in the positive electrode active material is , 5 atomic % is more preferable than 2.5 atomic % when the total of fluorine and oxygen is 400 atomic %.
Furthermore, from the above results, the preferable fluorine content range when considering the discharge resistance is 2.5 atomic % or more and 3.5 atomic % when the total of fluorine and oxygen in the positive electrode active material is 400 atomic %. Above, 4.5 atomic % or more, or 5 atomic % or more can be exemplified. Although there is no particular upper limit to the preferred range of fluorine content in this case, 50 atomic % or less, 20 atomic % or less, and 10 atomic % or less can be exemplified.
さらに上記の結果から、放電抵抗を考慮した場合の好ましいフッ素含有量の範囲として、正極活物質においてフッ素および酸素の合計を４００原子％としたときに２．５原子％以上、３．５原子％以上、４．５原子％以上、または５原子％以上を例示できる。この場合のフッ素量の好ましい範囲に特に上限はないが、５０原子％以下、２０原子％以下、１０原子％以下を例示できる。 As shown in Table 11, the lithium ion secondary battery of Example 16 has a lower discharge resistance than the lithium ion secondary battery of Example 10. Therefore, considering the discharge resistance, the fluorine content in the positive electrode active material is , 5 atomic % is more preferable than 2.5 atomic % when the total of fluorine and oxygen is 400 atomic %.
Furthermore, from the above results, the preferable fluorine content range when considering the discharge resistance is 2.5 atomic % or more and 3.5 atomic % when the total of fluorine and oxygen in the positive electrode active material is 400 atomic %. Above, 4.5 atomic % or more, or 5 atomic % or more can be exemplified. Although there is no particular upper limit to the preferred range of fluorine content in this case, 50 atomic % or less, 20 atomic % or less, and 10 atomic % or less can be exemplified.
〔評価例１９ リチウムイオン二次電池の高温充放電サイクル試験〕
実施例９、実施例１６および比較例６のリチウムイオン二次電池に対して、高温充放電サイクル試験を行った。
具体的には、実施例９、実施例１６および比較例６のリチウムイオン二次電池に対して、上記のコンディショニング後に、６０℃で、１Ｃの一定電流にて、ＳＯＣ１００％となるまで充電し、その後ＳＯＣ１０％となるまで放電する高温充放電サイクルを繰り返した。このときのカットオフ電圧は２．５７Ｖまたは初期容量すなわちＳＯＣ１００％に対してＳＯＣ９０％となる電圧である。 [Evaluation Example 19 High temperature charge/discharge cycle test of lithium ion secondary battery]
The lithium ion secondary batteries of Examples 9, 16 and Comparative Example 6 were subjected to a high temperature charge/discharge cycle test.
Specifically, the lithium ion secondary batteries of Examples 9, 16 and Comparative Example 6 were charged at 60° C. at a constant current of 1 C until the SOC reached 100% after the above conditioning, After that, a high-temperature charge-discharge cycle was repeated until the SOC reached 10%. The cutoff voltage at this time is 2.57 V or the voltage at which SOC is 90% with respect to the initial capacity, that is,SOC 100%.
実施例９、実施例１６および比較例６のリチウムイオン二次電池に対して、高温充放電サイクル試験を行った。
具体的には、実施例９、実施例１６および比較例６のリチウムイオン二次電池に対して、上記のコンディショニング後に、６０℃で、１Ｃの一定電流にて、ＳＯＣ１００％となるまで充電し、その後ＳＯＣ１０％となるまで放電する高温充放電サイクルを繰り返した。このときのカットオフ電圧は２．５７Ｖまたは初期容量すなわちＳＯＣ１００％に対してＳＯＣ９０％となる電圧である。 [Evaluation Example 19 High temperature charge/discharge cycle test of lithium ion secondary battery]
The lithium ion secondary batteries of Examples 9, 16 and Comparative Example 6 were subjected to a high temperature charge/discharge cycle test.
Specifically, the lithium ion secondary batteries of Examples 9, 16 and Comparative Example 6 were charged at 60° C. at a constant current of 1 C until the SOC reached 100% after the above conditioning, After that, a high-temperature charge-discharge cycle was repeated until the SOC reached 10%. The cutoff voltage at this time is 2.57 V or the voltage at which SOC is 90% with respect to the initial capacity, that is,
各リチウムイオン二次電池につき、初回の充放電時における放電容量を１００％として、各サイクルの放電容量の百分率を算出した。当該百分率を各リチウムイオン二次電池における容量維持率とした。実施例９のリチウムイオン二次電池及び比較例６のリチウムイオン二次電池の４２サイクル目における容量維持率を表１２に示し、実施例１６のリチウムイオン二次電池及び比較例６のリチウムイオン二次電池の容量維持率の推移を図１５に示す。
For each lithium-ion secondary battery, the percentage of the discharge capacity in each cycle was calculated, with the discharge capacity at the time of the first charge and discharge as 100%. This percentage was taken as the capacity retention rate of each lithium ion secondary battery. Table 12 shows the capacity retention rates of the lithium ion secondary battery of Example 9 and the lithium ion secondary battery of Comparative Example 6 at the 42nd cycle. FIG. 15 shows changes in the capacity retention rate of the following batteries.
表１２に示すように、実施例９のリチウムイオン二次電池では、比較例６のリチウムイオン二次電池に比べて、容量維持率が向上している。換言すると、実施例９のリチウムイオン二次電池は比較例６のリチウムイオン二次電池に比べてサイクル特性に優れる。
この結果から、正極活物質の酸素サイトの一部をフッ素で置換し、かつ、メタルサイトの一部をタングステンおよび既述したＤ1の元素で置換することで、リチウムイオン二次電池の容量、導電性、およびサイクル特性の全てがバランスし、リチウムイオン二次電池に優れた電気特性が付与されるといい得る。 As shown in Table 12, in the lithium ion secondary battery of Example 9, compared with the lithium ion secondary battery of Comparative Example 6, the capacity retention rate is improved. In other words, the lithium ion secondary battery of Example 9 is superior to the lithium ion secondary battery of Comparative Example 6 in cycle characteristics.
From this result, by replacing a part of the oxygen site of the positive electrode active material with fluorine, and replacing a part of the metal site with tungsten and the above-mentioned D 1 element, the capacity of the lithium ion secondary battery, It can be said that the electrical conductivity and cycle characteristics are well balanced, and excellent electrical characteristics are imparted to the lithium ion secondary battery.
この結果から、正極活物質の酸素サイトの一部をフッ素で置換し、かつ、メタルサイトの一部をタングステンおよび既述したＤ1の元素で置換することで、リチウムイオン二次電池の容量、導電性、およびサイクル特性の全てがバランスし、リチウムイオン二次電池に優れた電気特性が付与されるといい得る。 As shown in Table 12, in the lithium ion secondary battery of Example 9, compared with the lithium ion secondary battery of Comparative Example 6, the capacity retention rate is improved. In other words, the lithium ion secondary battery of Example 9 is superior to the lithium ion secondary battery of Comparative Example 6 in cycle characteristics.
From this result, by replacing a part of the oxygen site of the positive electrode active material with fluorine, and replacing a part of the metal site with tungsten and the above-mentioned D 1 element, the capacity of the lithium ion secondary battery, It can be said that the electrical conductivity and cycle characteristics are well balanced, and excellent electrical characteristics are imparted to the lithium ion secondary battery.
また図１５に示すように、実施例１６のリチウムイオン二次電池は比較例６のリチウムイオン二次電池に比べてサイクル経過に伴う容量維持率の低下が小さい。この結果からも、正極活物質の酸素サイトの一部をフッ素で置換し、かつ、メタルサイトの一部をタングステンおよび既述したＤ1の元素で置換することの有用性が裏付けられる。さらに、この結果から、Ｄ1の元素としてバナジウムにかえてクロムを選択する場合にも、リチウムイオン二次電池に優れたサイクル特性が付与されることがわかる。
In addition, as shown in FIG. 15, the lithium ion secondary battery of Example 16 shows a smaller decrease in the capacity retention rate with the lapse of cycles than the lithium ion secondary battery of Comparative Example 6. This result also supports the usefulness of substituting a portion of the oxygen sites of the positive electrode active material with fluorine, and substituting a portion of the metal sites with tungsten and the aforementioned D 1 element. Furthermore, from this result, it can be seen that even when chromium is selected instead of vanadium as the element of D 1 , excellent cycle characteristics are imparted to the lithium ion secondary battery.
Claims (10)
- ＬｉaＭｎbＦｅcＷdＤ1 eＤ2 fＰgＯh（Ｄ1は金属元素、Ｄ2は第１３族から第１６族の元素かつ価数が４以下であり、ａ、ｂ、ｃ、ｄ、ｅ、ｆ、ｇ、ｈは、０＜ａ＜１．５、０＜ｂ＜１、０＜ｃ＜１、０＜ｄ＜１、０≦ｅ＜１、０≦ｆ＜１、０＜ｇ＜１、０＜ｈ＜５を満足する。）で表され、Ｘ線光電分光法によりＷＯ2に由来するピークが確認される、正極活物質。 Li a Mn b Fe c W d D 1 e D 2 f P g O h (D 1 is a metal element, D 2 is an element of groups 13 to 16 with a valence of 4 or less, a, b, c, d, e, f, g, and h are 0<a<1.5, 0<b<1, 0<c<1, 0<d<1, 0≤e<1, 0≤f<1 , 0<g<1 and 0<h<5.), and a peak derived from WO 2 is confirmed by X-ray photoelectric spectroscopy.
- ＬｉaＭｎbＦｅcＷdＤ1 eＤ2 fＰgＦiＯh（Ｄ1は金属元素、Ｄ2は第１３族から第１６族の元素かつ価数が４以下であり、ａ、ｂ、ｃ、ｄ、ｅ、ｆ、ｇ、ｈ、ｉは、０＜ａ＜１．５、０＜ｂ＜１、０＜ｃ＜１、０＜ｄ＜１、０≦ｅ＜１、０≦ｆ＜１、０＜ｇ＜１、０＜ｈ＜５、０＜ｉ＜１を満足する。）で表され、
Ｘ線光電分光法によりＷＯ2に由来するピークが確認されるか、及び／又は、
前記Ｄ1がＣｒ、Ｔｉ、Ｖから選ばれる少なくとも一種である、正極活物質。 Li a Mn b Fe c W d D 1 e D 2 f P g F i O h (D 1 is a metal element, D 2 is an element of Groups 13 to 16 and has a valence of 4 or less, a, b, c, d, e, f, g, h, i are 0<a<1.5, 0<b<1, 0<c<1, 0<d<1, 0≤e<1, 0 ≤ f < 1, 0 < g < 1, 0 < h < 5, 0 < i < 1 are satisfied.),
A peak derived from WO2 is confirmed by X-ray photoelectric spectroscopy, and/or
The positive electrode active material, wherein D 1 is at least one selected from Cr, Ti and V. - 前記ｄが０．０５／１００～２．５／１００の範囲内である、請求項１又は２に記載の正極活物質。 The positive electrode active material according to claim 1 or 2, wherein said d is in the range of 0.05/100 to 2.5/100.
- 前記Ｄ2がケイ素を含み、前記ｄおよびｆの関係が１．５ｄ≦ｆ≦２．５ｄを満足する、請求項１～請求項３の何れか一項に記載の正極活物質。 The cathode active material according to any one of claims 1 to 3, wherein said D 2 contains silicon and said d and f satisfy 1.5d≦f≦2.5d.
- 前記Ｄ1がマグネシウムを含む、請求項１～請求項４の何れか一項に記載の正極活物質。 The cathode active material according to any one of claims 1 to 4, wherein said D 1 comprises magnesium.
- Ｘ線光電分光法によりＷＯ3に由来するピークが確認される、請求項１～請求項５の何れか一項に記載の正極活物質。 6. The positive electrode active material according to claim 1, wherein a peak derived from WO 3 is confirmed by X-ray photoelectric spectroscopy.
- 前記Ｄ1がＣｒ、Ｔｉ、Ｖから選ばれる少なくとも一種である、請求項１～請求項６の何れか一項に記載の正極活物質 The positive electrode active material according to any one of claims 1 to 6, wherein said D 1 is at least one selected from Cr, Ti and V.
- 請求項１～請求項７の何れか一項に記載の正極活物質を製造する方法であって、
タングステン化合物と還元剤との反応生成物、リチウム源、マンガン源、鉄源、リン源および水を含む活物質原料を加熱する工程を含む、正極活物質の製造方法。 A method for producing the positive electrode active material according to any one of claims 1 to 7,
A method for producing a positive electrode active material, comprising heating an active material raw material containing a reaction product of a tungsten compound and a reducing agent, a lithium source, a manganese source, an iron source, a phosphorus source and water. - 請求項１～請求項７の何れか一項に記載の正極活物質を有する正極。 A positive electrode comprising the positive electrode active material according to any one of claims 1 to 7.
- 請求項９に記載の正極を有するリチウムイオン二次電池。 A lithium ion secondary battery having the positive electrode according to claim 9.
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