WO2013128936A1 - Active material composite, method for producing same, positive electrode active material for nonaqueous electrolyte secondary batteries, and nonaquoeus electrolyte secondary battery - Google Patents

Active material composite, method for producing same, positive electrode active material for nonaqueous electrolyte secondary batteries, and nonaquoeus electrolyte secondary battery Download PDF

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WO2013128936A1
WO2013128936A1 PCT/JP2013/001242 JP2013001242W WO2013128936A1 WO 2013128936 A1 WO2013128936 A1 WO 2013128936A1 JP 2013001242 W JP2013001242 W JP 2013001242W WO 2013128936 A1 WO2013128936 A1 WO 2013128936A1
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active material
particles
lithium
electrolyte secondary
sample
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PCT/JP2013/001242
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French (fr)
Japanese (ja)
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晶 小島
敏勝 小島
田渕　光春
境　哲男
一仁 川澄
淳一 丹羽
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株式会社豊田自動織機
独立行政法人産業技術総合研究所
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Publication of WO2013128936A1 publication Critical patent/WO2013128936A1/en

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    • 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
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L50/00—Electric propulsion with power supplied within the vehicle
    • B60L50/50—Electric propulsion with power supplied within the vehicle using propulsion power supplied by batteries or fuel cells
    • B60L50/52—Electric propulsion with power supplied within the vehicle using propulsion power supplied by batteries or fuel cells characterised by DC-motors
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L50/00—Electric propulsion with power supplied within the vehicle
    • B60L50/50—Electric propulsion with power supplied within the vehicle using propulsion power supplied by batteries or fuel cells
    • B60L50/60—Electric propulsion with power supplied within the vehicle using propulsion power supplied by batteries or fuel cells using power supplied by batteries
    • B60L50/64—Constructional details of batteries specially adapted for electric vehicles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L53/00—Methods of charging batteries, specially adapted for electric vehicles; Charging stations or on-board charging equipment therefor; Exchange of energy storage elements in electric vehicles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L58/00—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles
    • B60L58/10—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles for monitoring or controlling batteries
    • B60L58/24—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles for monitoring or controlling batteries for controlling the temperature of batteries
    • B60L58/27—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles for monitoring or controlling batteries for controlling the temperature of batteries by heating
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L2240/00—Control parameters of input or output; Target parameters
    • B60L2240/40—Drive Train control parameters
    • B60L2240/54—Drive Train control parameters related to batteries
    • B60L2240/545—Temperature
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L2270/00—Problem solutions or means not otherwise provided for
    • B60L2270/10—Emission reduction
    • B60L2270/14—Emission reduction of noise
    • B60L2270/145—Structure borne vibrations
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/60—Other road transportation technologies with climate change mitigation effect
    • Y02T10/70—Energy storage systems for electromobility, e.g. batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/60—Other road transportation technologies with climate change mitigation effect
    • Y02T10/7072—Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T90/00—Enabling technologies or technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02T90/10—Technologies relating to charging of electric vehicles
    • Y02T90/14—Plug-in electric vehicles

Definitions

  • the present invention relates to an active material composite used for an active material for a nonaqueous electrolyte secondary battery and a method for producing the same, a positive electrode active material for a nonaqueous electrolyte secondary battery, and a nonaqueous electrolyte secondary battery.
  • lithium ion secondary batteries are small and have high energy density, and are widely used as power sources for portable electronic devices.
  • a lithium ion secondary battery is used as a vehicle drive source.
  • lithium silicate compounds, lithium borate compounds, and lithium phosphate compounds are known as positive electrode active materials for lithium ion secondary batteries.
  • lithium silicate compounds are inexpensive and have a low environmental impact because they are composed of abundant constituent metal elements.
  • the material has a high theoretical charge / discharge capacity and does not release oxygen at a high temperature.
  • Li 2 FeSiO 4 theoretical capacity 331.3 mAh / g
  • Li 2 MnSiO 4 theoretical capacity 333.2 mAh
  • Lithium silicate compounds such as / g
  • lithium borate compounds are also inexpensive, have a large amount of resources, have a low environmental burden, have a high theoretical charge / discharge capacity, and do not release oxygen at high temperatures. It is attracting attention as a material.
  • a lithium borate compound for example, LiFeBO 3 (theoretical capacity 220 mAh / g), LiMnBO 3 (theoretical capacity 222 mAh / g), and the like are known.
  • the lithium borate material is a material that can be expected to improve the energy density by using boron (B), which is the lightest element in the polyanion unit, and the true density (3.46 g / cm 3) of the borate material. ) Is smaller than the true density (3.60 g / cm 3 ) of the olivine iron phosphate material, and weight reduction can also be expected.
  • the lithium phosphate compound is represented by LiMPO 4 (M is a metal such as Mn, Fe, Co), and a hetero element PO 4 3- polyanion having a large electronegativity is arranged around the central metal M. For this reason, it is said that the thermal stability is higher than that of layered LiCoO 2 or the like in which oxygen atoms are directly coordinated to the transition metal.
  • each compound is also subjected to a carbon coating treatment.
  • carbon is further added to the lithium silicate compound. It is also disclosed that the coating process is performed.
  • the present invention has been made in view of such circumstances, and an active material composite capable of increasing the charge / discharge capacity of a battery, a method for producing the same, a positive electrode active material for a non-aqueous electrolyte secondary battery, and a non-aqueous electrolyte two. It is an object to provide a secondary battery.
  • active material particles made of an active material and having an average particle size of 100 nm or less are bonded to conductive particles made of a conductive material and having an average particle size of 100 nm or less.
  • the specific surface area is 150 m 2 / g or more.
  • the method for producing an active material composite according to the present invention is a method for producing the active material composite as described above, and includes an energy application step for applying mechanical energy to the active material and the conductive material. It is characterized by that.
  • the positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention is characterized by comprising the active material composite described above or the active material composite manufactured by the manufacturing method described above.
  • the positive electrode for nonaqueous electrolyte secondary batteries of the present invention is characterized by having the positive electrode active material for nonaqueous electrolyte secondary batteries described above.
  • the nonaqueous electrolyte secondary battery of the present invention is characterized by comprising the positive electrode for a nonaqueous electrolyte secondary battery described above, a negative electrode, and an electrolyte.
  • the active material composite of the present invention fine active material particles and fine conductive particles are bonded to each other, so that the charge / discharge capacity of the battery can be increased. Since the positive electrode active material for a nonaqueous electrolyte secondary battery, the positive electrode for a nonaqueous electrolyte secondary battery, and the nonaqueous electrolyte secondary battery of the present invention use the active material composite, the charge / discharge capacity can be increased. it can.
  • FIG. 1 The upper diagram of FIG. 1 is an SEM cross-sectional photograph of sample 1 (one scale of 1 ⁇ m), and the lower diagram of FIG. 1 is an SEM cross-sectional photograph of sample 1 (one scale of 0.2 ⁇ m), surrounded by a dotted line in FIG. It is an enlarged photograph of. 2 is a SEM cross-sectional photograph of sample 1 (one scale 0.1 ⁇ m). It is a figure which shows the element mapping using the energy dispersive X-ray-analysis apparatus (EDX) of the surface vicinity of the secondary particle of the sample 1.
  • EDX energy dispersive X-ray-analysis apparatus
  • FIG. 2 is a SEM photograph (one scale 0.1 ⁇ m) of the surface of secondary particles of sample 1.
  • 2 is a cross-sectional explanatory view of an active material composite of Sample 1.
  • FIG. 2 is a SEM cross-sectional photograph of sample 2 (one scale 0.2 ⁇ m).
  • 3 is a SEM cross-sectional photograph (one scale 0.5 ⁇ m) of Sample 3.
  • 4 is a SEM cross-sectional photograph of sample 3 (one scale 0.1 ⁇ m).
  • FIG. 4 is an SEM photograph (one scale 0.1 ⁇ m) of the particle surface of sample 3.
  • FIG. 4 is an SEM photograph (one scale 0.1 ⁇ m) of the particle surface of sample 5.
  • FIG. 4 is a diagram showing a charge / discharge curve of a battery produced using Sample 1.
  • FIG. 3 is a diagram showing a charge / discharge curve of a battery produced using Sample 2.
  • FIG. 3 is a diagram showing a charge / discharge curve of a battery manufactured using Sample 3.
  • FIG. 6 is a diagram showing a charge / discharge curve of a battery manufactured using Sample 4.
  • FIG. 4 is a diagram showing a cycle test result of a battery manufactured using Sample 1. It is a figure which shows the rate test result of the battery produced using the sample 1.
  • FIG. 4 is a diagram showing a cycle test result of a battery manufactured using Sample 1. It is a figure which shows the rate test result of the battery produced using the sample 1.
  • FIG. 20 is an SEM photograph of Li 2 MnSiO 4 immediately after synthesis, and the upper diagram in FIG. 20 is a high-magnification SEM photograph, and the lower diagram in FIG. 20 is a low-magnification SEM photograph.
  • FIG. 21 is an SEM photograph of Sample 6, the upper drawing of FIG. 21 is a low magnification SEM photograph, and the lower drawing of FIG. 21 is a high magnification SEM photograph. 3 is a SEM photograph of Sample 8.
  • the XRD patterns of Li 2 MnSiO 4 immediately after synthesis and Samples 6 to 8 are shown.
  • the charging / discharging curve of the battery using the sample 6 is shown.
  • the charging / discharging curve of the battery using the sample 7 is shown.
  • the charging / discharging curve of the battery using the sample 8 is shown.
  • An active material composite according to an embodiment of the present invention and a manufacturing method thereof, a positive electrode active material for a nonaqueous electrolyte secondary battery, a nonaqueous electrolyte secondary battery, and a vehicle will be described in detail.
  • the active material composite according to the present invention comprises active material particles made of an active material having an average particle size of 100 nm or less, and conductive particles made of a conductive material having an average particle size of 100 nm or less. It consists of a composite formed by bonding.
  • the charge / discharge capacity of the battery can be increased as shown in Examples described later.
  • the reason is that the active material particles and the conductive particles are joined to each other in a fine particle state at the nano level, thereby increasing the number of conductive paths composed of the conductive particles in the active material complex. This is presumed to be due to the increase in the utilization rate of the active material due to the active movement of electrons. *
  • the specific surface area of the active material composite is 150 m 2 / g or more, preferably 170 m 2 / g or more.
  • the average particle diameter of the active material particles is 100 nm or less
  • the average particle diameter of the conductive particles is 100 nm or less.
  • the average particle diameter of each particle is the maximum diameter of a plurality of particles obtained by analyzing an image of the active material complex using a transmission electron microscope (TEM) or the like (the distance between two parallel lines sandwiching the particles). (Maximum value) is a value calculated by actual measurement. *
  • the average particle diameter of the active material particles exceeds 100 nm, or when the average particle diameter of the conductive particles exceeds 100 nm, the effect of increasing the charge / discharge capacity of the battery may be reduced.
  • the average particle diameter of the active material particles is 10 nm or more and 90 nm or less, and the average particle diameter of the conductive particles is 2 nm or more and 50 nm or less. In this case, the charge / discharge capacity of the battery is further increased. More preferably, the average particle size of the active material particles is 10 nm to 50 nm, and the average particle size of the conductive particles is 2 nm to 10 nm.
  • the active material particles and the conductive particles are mixed and bonded as primary particles to each other in a nano-level fine particle state to form a composite that is a secondary particle.
  • the average particle size of the active material complex is preferably 0.7 ⁇ m or more and 20 ⁇ m or less, and more preferably 1 ⁇ m or more and 10 ⁇ m or less.
  • the average particle diameter of the active material composite is too small, granulation of the active material composite is not yet developed, and the composite of the active material particles and the conductive particles is insufficient.
  • the average particle size of the active material complex is excessive, the rate at which the active material complex occludes / releases lithium ions may decrease.
  • the specific surface area of the active material composite is 150 m 2 / g or more, preferably 170 m 2 / g or more.
  • the specific surface area refers to the BET specific surface area.
  • the upper limit of the specific surface area of the active material composite is preferably 300 m 2 / g, and more preferably 250 m 2 / g.
  • the specific surface area of the active material composite is too small, the charge / discharge capacity of the battery may be reduced.
  • the specific surface area of the active material composite is excessive, the active material composite is too small, and there is a possibility that the composite of the conductive particles and the active material particles is insufficient.
  • the active material particles and the conductive particles may be uniformly finely mixed and bonded to each other.
  • the active material complex is preferably composed of a core part and a surface layer covering the core part.
  • the surface layer may contain more carbon than the core portion.
  • the thickness of the surface layer is preferably 500 nm or more and 2 ⁇ m or less.
  • Fine surface particles are preferably adhered to the surface of the active material composite.
  • the average particle size of the surface particles is preferably 20 nm or more and 100 nm or less, more preferably 30 nm or more and 90 nm or less, and preferably 35 nm or more and 75 nm or less.
  • Examples of surface particles include: A part of the raw material of the active material particles may be included. When the active material composite has the surface particles, the reaction in which the active material particles occlude / release lithium ions is promoted.
  • the active material constituting the active material particles may be made of a material that can occlude and release lithium ions.
  • the active material for nonaqueous electrolyte secondary batteries can be used for the electrode of a lithium ion secondary battery.
  • the active material is preferably composed of one or more members selected from the group consisting of a lithium silicate compound, a lithium phosphate compound, and a lithium borate compound. According to the active material composite including the active material particles made of such an active material, it constitutes an active material for a non-aqueous electrolyte secondary battery, and further an active material for a lithium ion secondary battery or a lithium secondary battery. can do.
  • the lithium silicate-based compound may be, for example, at least one selected from the group consisting of lithium iron silicate (Li 2 FeSiO 4 ) and lithium manganese silicate (Li 2 MnSiO 4 ).
  • the lithium iron silicate is represented by, for example, Li 2 FeSiO 4 .
  • the lithium manganese silicate is represented by, for example, Li 2 MnSiO 4 .
  • the conductive material constituting the conductive particles a material having higher conductivity than the active material is used.
  • a carbon material is preferably used as the conductive material.
  • the carbon material acetylene black (AB), ketjen black (KB), carbon black, carbon nanotube, graphene, carbon fiber, graphite, or the like can be used. Among these, acetylene black (AB), ketjen black (KB), and carbon black are preferable.
  • the mass ratio of the conductive particles when the active material particles are 100 parts by mass is preferably 2 parts by mass or more and 60 parts by mass or less, and more preferably 5 parts by mass or more and 30 parts by mass. It may be the following. In this case, the active material particles and the conductive particles are uniformly dispersed, and the electric capacity can be greatly extracted.
  • the active material used in the energy application step may be, for example, any one of a lithium silicate compound, a lithium phosphate compound, and a lithium borate compound.
  • the lithium silicate compound is, for example, a lithium silicate compound having a composition formula of Li 2 M 1 SiO 4 (M 1 is Fe, Mn, Co), or a composition formula of Li 2 + ab Ab M 1-x M ' x SiO 4 + ⁇ (wherein A is at least one element selected from the group consisting of Na, K, Rb and Cs, and M is at least one element selected from the group consisting of Fe, Mn and Co) , M ′ is at least one element selected from the group consisting of Mg, Ca, Al, Ni, Nb, Ti, Cr, Cu, Zn, Zr, V, Mo, and W.
  • the subscripts are as follows.
  • it is made of a compound represented by 0 ⁇ a ⁇ 1, 0 ⁇ b ⁇ 0.2, 0 ⁇ x ⁇ 0.5, ⁇ ⁇ 0).
  • Li 2 FeSiO 4, Li 2 MnSiO 4, Li 2 CoSiO 4 can be cited.
  • the lithium silicate compound can be produced, for example, by a molten salt method, a solid phase method, a hydrothermal method, or the like. Especially, it is good to manufacture by the molten salt method.
  • the molten salt method is a method of synthesizing a lithium silicate compound in a molten salt containing an alkali metal salt.
  • the alkali metal salt used in the molten salt method include at least one selected from the group consisting of a lithium salt, a potassium salt, a sodium salt, a rubium salt, and a cesium salt. Of these, lithium salts are desirable.
  • a molten salt containing a lithium salt is used, the formation of an impurity phase is small, and a lithium silicate compound containing excessive lithium atoms is likely to be formed.
  • the lithium silicate compound thus obtained is a positive electrode material for lithium ion batteries having good cycle characteristics and high capacity. *
  • the alkali metal salt used in the molten salt method contains at least one of alkali metal chloride, alkali metal carbonate, alkali metal nitrate, and alkali metal hydroxide.
  • the alkali metal carbonate is preferably an alkali metal carbonate, and further preferably contains lithium carbonate.
  • a carbonate mixture comprising at least one alkali metal carbonate selected from the group consisting of potassium carbonate, sodium carbonate, rubidium carbonate and cesium carbonate and lithium carbonate is preferable.
  • the reaction by performing the reaction at a relatively low temperature of 400 to 650 ° C. in the molten salt of the mixture, the growth of crystal grains is suppressed, and the average particle diameter becomes fine particles of 50 nm to 10 ⁇ m. The amount is greatly reduced. As a result, when used as a positive electrode active material for a non-aqueous electrolyte secondary battery, the material has good cycle characteristics and high capacity.
  • a molten salt of a carbonate mixture consisting of at least one alkali metal carbonate and lithium carbonate selected from the group consisting of potassium carbonate, sodium carbonate, rubidium carbonate and cesium carbonate it is represented by Li 2 SiO 3.
  • the lithium silicate compound may be reacted with a substance containing at least one metal element selected from the group consisting of iron and manganese at 400 to 650 ° C.
  • the specific reaction method is not particularly limited.
  • the above-described carbonate mixture, lithium silicate compound, and a substance containing a metal element are mixed to form a ball mill. Or the like, and then the carbonate mixture may be melted by heating. Thereby, in molten carbonate, reaction with a lithium silicate compound and the said metal element advances, and a lithium silicate type compound can be obtained.
  • the mixing ratio of the raw material composed of the lithium silicate compound and the metal element-containing material and the carbonate mixture is not particularly limited, and the amount of the raw material can be uniformly dispersed in the molten salt of the carbonate mixture.
  • the total amount of the molten salt raw material is preferably in the range of 20 to 300 parts by mass with respect to 100 parts by mass of the total amount of the carbonate mixture.
  • the amount is more preferably in the range of ⁇ 80 parts by mass.
  • the above-described reaction is performed in a mixed gas atmosphere containing carbon dioxide and a reducing gas because the metal element stably exists as a divalent ion during the reaction. Under this atmosphere, the metal element can be stably maintained in a divalent state.
  • the reducing gas may be 0.01 to 0.5 mol, preferably 0.03 to 0.4 mol, per 1 mol of carbon dioxide.
  • the reducing gas for example, hydrogen, carbon monoxide and the like can be used, and hydrogen is particularly preferable.
  • the pressure of the mixed gas of carbon dioxide and reducing gas there is no particular limitation on the pressure of the mixed gas of carbon dioxide and reducing gas, and it may be usually atmospheric pressure, but it may be under pressure or under reduced pressure.
  • the reaction time between the lithium silicate compound and the substance containing the metal element is usually 0.1 to 30 hours, preferably 5 to 25 hours.
  • the target lithium silicate compound can be obtained by removing the alkali metal carbonate used as the flux.
  • the alkali metal carbonate may be dissolved and removed by washing the product using a solvent capable of dissolving the alkali metal carbonate.
  • a solvent capable of dissolving the alkali metal carbonate for example, although water can be used as the solvent, it is preferable to use a nonaqueous solvent such as alcohol or acetone in order to prevent oxidation of the transition metal contained in the lithium silicate compound.
  • acetic anhydride and acetic acid in a mass ratio of 2: 1 to 1: 1.
  • this mixed solvent when acetic acid reacts with the alkali metal carbonate to produce water, acetic anhydride takes in the water and produces acetic acid. Therefore, it is possible to suppress the separation of water.
  • acetic anhydride and acetic acid are used, first, acetic anhydride is mixed with the product, ground with a mortar or the like to make particles fine, and then acetic anhydride is added in a state where acetic anhydride is intimately mixed with the particles. It is preferable. According to this method, since the water produced by the reaction of acetic acid and alkali metal carbonate reacts quickly with acetic anhydride, the chance of the product and water coming into contact with each other can be reduced. Can be suppressed. *
  • lithium borate compound examples include LiM 2 BO 3 (M 2 is composed of at least one selected from the group consisting of Mn, Fe, and Co).
  • M 2 is composed of at least one selected from the group consisting of Mn, Fe, and Co.
  • M 2 is at least one element selected from the group consisting of Fe, Mn, and Co
  • M ′ is a group consisting of Mg, Ca, Al, Ni, Nb, Mo, W, Ti, and Zr.
  • This compound is, for example, in a reducing atmosphere in a molten salt of a carbonate mixture comprising at least one alkali metal carbonate and lithium carbonate selected from the group consisting of potassium carbonate, sodium carbonate, rubidium carbonate and cesium carbonate.
  • a divalent metal compound containing at least one compound selected from the group consisting of a divalent iron compound and a divalent manganese compound, boric acid, and lithium hydroxide at 400 to 650 ° C. can do.
  • a lithium borate compound containing iron or manganese can be obtained under relatively mild conditions.
  • the obtained lithium borate compound is a borate compound that is fine, has a small impurity phase, contains excessive lithium atoms, and has good cycle characteristics when used as a positive electrode active material of a lithium ion secondary battery. It becomes a material having a capacity.
  • the conductive material used in the energy application step is made of, for example, a carbon material.
  • a carbon material acetylene black (AB), ketjen black (KB), carbon black, carbon nanotube, graphene, carbon fiber, graphite and the like can be used.
  • acetylene black (AB) is preferred because of its high specific surface area.
  • Ketjen black (KB) and carbon black are preferred. *
  • the average particle diameter of the active material used in the energy application step is preferably 200 nm to 5 ⁇ m, and the average particle diameter of the conductive material is preferably 100 nm to 5 ⁇ m.
  • active material particles having an average particle size of 100 nm or less and conductive particles having an average particle size of 100 nm or less by applying mechanical energy to the active material and the conductive material in the energy application step. Can be easily obtained.
  • the energy application step may be a step of applying mechanical energy by milling.
  • mechanical energy can be uniformly given to the active material and the conductive material.
  • the milling method ball milling in which mechanical energy is introduced by moving the container by an external force in a state where a hard ball is accommodated in the container together with the sample is preferable.
  • the ball milling device any of a planetary type that gives energy to the sample by rotation and revolution and a vibration type that gives energy to the sample by vibration in the horizontal direction or the vertical direction can be adopted. *
  • the active material and the conductive material may be rotated by a ball mill at a relatively high speed.
  • a mechanical milling device Fritch Japan Co., Ltd., planetary ball mill P-7 series
  • the rotational speed of the ball mill is preferably greater than 700 rpm and less than 1100 rpm.
  • both the active material particles and the conductive particles can be uniformly dispersed and mixed with an average particle size of 100 nm or less to be amorphized and combined.
  • the average particle diameter of the active material particles and the conductive particles may be larger than 100 nm. If it exceeds 1100 rpm, there is a risk of increased contamination of impurities.
  • the rotation speed of a ball mill is 750 rpm or more and less than 1000 rpm.
  • the active material particles and the conductive particles can be more uniformly dispersed and mixed.
  • a diffraction peak derived from the (111) plane (2 ⁇ ) for a sample containing a lithium silicate compound precursor having crystallinity before milling is B (111) crystal, and when the half width of the same peak of the sample after milling is B (111) mill, B (111) crystal / B (111) mill.
  • the ratio is preferably in the range of 0.7 to 1.1, more preferably 0.8 to 1.0.
  • the active material is a lithium silicate compound
  • Li 2 CO 3 is added to the lithium silicate compound, and the lithium silicate compound is made amorphous by ball milling. Mix evenly until By the presence of Li 2 CO 3 , lithium deficiency of the lithium silicate compound is suppressed, and a high charge / discharge capacity is exhibited.
  • the active material and the conductive material can be mixed in an inert gas atmosphere (argon gas, nitrogen gas) or in an air atmosphere.
  • the mixing ratio of the lithium silicate compound and the conductive material may be 5 to 50 parts by mass of the carbon material with respect to 100 parts by mass of the lithium silicate compound. . *
  • a heat treatment step may be performed in which heat treatment is performed on the mixture of the active material and the conductive material to which mechanical energy is applied.
  • the mixed active material and conductive material are heated at a predetermined temperature.
  • the heat treatment temperature is preferably 500 to 800 ° C. If the heat treatment temperature is too low, it is difficult to deposit carbon uniformly around the lithium silicate compound, while if the heat treatment temperature is too high, decomposition of the lithium silicate compound and lithium deficiency may occur. This is not preferable because the charge / discharge capacity decreases.
  • the heat treatment time is usually 1 to 10 hours. *
  • the heat treatment is preferably performed in a reducing atmosphere in order to keep the transition metal ions contained in the lithium silicate compound divalent.
  • a reducing atmosphere in this case, in order to suppress the reduction of the divalent transition metal ion to the metal state, as in the synthesis reaction of the lithium silicate compound in the molten salt, the reducing atmosphere is reduced with carbon dioxide.
  • a gas mixed gas atmosphere is preferred. The mixing ratio of carbon dioxide and reducing gas may be the same as in the synthesis reaction of the lithium silicate compound. *
  • the heat treatment is preferably performed in a mixed atmosphere of carbon dioxide and a reducing gas. The reason is that decomposition of the lithium borate compound is suppressed.
  • the heat treatment is preferably performed in a mixed atmosphere of carbon dioxide and a reducing gas or in an inert gas atmosphere. The reason is that decomposition of the lithium phosphate compound can be suppressed.
  • Positive electrode active material for nonaqueous electrolyte secondary battery is composed of the above active material composite. According to such a non-aqueous electrolyte secondary battery positive electrode active material, a battery having excellent charge / discharge characteristics can be configured.
  • the positive electrode for nonaqueous electrolyte secondary battery is composed of the positive electrode active material for nonaqueous electrolyte secondary battery and a current collector.
  • the positive electrode for a nonaqueous electrolyte secondary battery has a positive electrode active material made of the above active material composite, and can have the same structure as a normal positive electrode for a nonaqueous electrolyte secondary battery.
  • the active material composite may include acetylene black (AB), ketjen black (KB), a conductive additive such as vapor grown carbon fiber (Vapor Grown Carbon Fiber: VGCF), polyvinylidene fluoride (Polyvinylidene Fluoride: PVdF),
  • a binder such as polytetrafluoroethylene (PTFE) and styrene-butadiene rubber (SBR) and a solvent such as N-methyl-2-pyrrolidone (NMP)
  • the amount of the conductive aid used is not particularly limited, but can be 5 to 20 parts by mass with respect to 100 parts by mass of the active material composite, for example.
  • the amount of the binder used is not particularly limited, but may be 5 to 20 parts by mass with respect to 100 parts by mass of the active material composite, for example.
  • a mixture of the active material composite, the conductive aid and the binder described above is kneaded using a mortar or a press to form a film, and this is crimped to the current collector with a press.
  • the positive electrode can be manufactured also by the method to do. *
  • the current collector is not particularly limited, and materials conventionally used as positive electrodes for nonaqueous electrolyte secondary batteries, such as aluminum foil, aluminum mesh, and stainless steel mesh, can be used. Furthermore, a carbon nonwoven fabric, a carbon woven fabric, etc. can be used as a collector. *
  • the shape and thickness of the positive electrode for a nonaqueous electrolyte secondary battery is not particularly limited.
  • the positive electrode for a nonaqueous electrolyte secondary battery is filled with an active material and then compressed to have a thickness of 10 to 200 ⁇ m, more preferably 20 ⁇ m. It is preferable that the thickness is 100 ⁇ m. Therefore, the filling amount of the active material may be appropriately determined so as to have the above-described thickness after compression according to the type and structure of the current collector to be used. *
  • Nonaqueous electrolyte secondary battery includes the above-described positive electrode for a nonaqueous electrolyte secondary battery.
  • the nonaqueous electrolyte secondary battery can be manufactured by a known method.
  • the positive electrode described above is used as the positive electrode material.
  • the negative electrode material is composed of an element compound that can occlude and release lithium ions and can be alloyed with lithium or / and an element compound that can be alloyed with lithium.
  • Elements capable of alloying with lithium are Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Ti, Ag, Zn, Cd, Al, Ga, In, Si, Ge.
  • the negative electrode material examples include known metal-based materials such as lithium metal and graphite, silicon-based materials such as SiOx (0.5 ⁇ x ⁇ 1.5), alloy-based materials such as copper-tin and cobalt-tin, An oxide material such as lithium titanate is preferably used. *
  • a lithium salt such as lithium perchlorate, LiPF 6 , LiBF 4 , LiCF 3 SO 3 or the like is added to a known non-aqueous solvent such as ethylene carbonate, dimethyl carbonate, propylene carbonate, dimethyl carbonate to 0.5 mol / L to 1
  • a solution dissolved at a concentration of 7 mol / L may be used, and other known battery components may be used.
  • lithium secondary battery When metal lithium is used as the negative electrode, a lithium secondary battery is obtained, and when a material other than metal lithium is used as the negative electrode, a lithium ion secondary battery is obtained.
  • many secondary batteries that perform a battery reaction with these lithium ions are non-aqueous electrolyte secondary batteries.
  • the non-aqueous electrolyte secondary battery can be mounted on a vehicle.
  • the vehicle may be an electric vehicle or a hybrid vehicle.
  • the nonaqueous electrolyte secondary battery is preferably connected to, for example, a traveling motor mounted on a vehicle and used as a drive source. In this case, a high driving torque can be output for a long time.
  • the non-aqueous electrolyte secondary battery can be mounted on devices other than vehicles such as personal computers and portable communication devices. *
  • the active material complexes of Samples 1 to 5 were manufactured by the following method.
  • the active material composites of Samples 1 to 5 are composed of Li 2 FeSiO 4 and carbon.
  • the mixing ratio is 100 parts by mass of the total amount of iron and lithium silicate. It was set as the mass part. Acetone (20 ml) was added thereto, mixed in a zirconia ball mill at 500 rpm for 60 minutes, and dried.
  • the obtained powder was heated in a gold crucible and heated to 500 ° C. in a mixed gas atmosphere of carbon dioxide (flow rate: 100 ml min-1) and hydrogen (flow rate: 3 ml min-1) to form carbonate.
  • the mixture was allowed to react for 13 hours in the molten state. After the reaction, when the temperature was lowered to 400 ° C., the entire reactor core was taken out from the electric furnace, which was a heater, and rapidly cooled to room temperature through the gas.
  • the obtained active material particles and acetylene black (AB, average particle size 0.3 ⁇ m) were mixed at a mass ratio of 5: 4, and a mechanical milling device (French Japan Co., Ltd., planetary ball mill P-7) was used. Then, mechanical milling treatment was performed under the following predetermined conditions in an air atmosphere to give mechanical energy to the mixture. This step was performed by putting 50 g of ⁇ 4 mm zirconia balls and 300 mg of the mixture in a ball mill grinding container made of zirconia and having a volume of 45 cc. *
  • Sample 1 When mixing the obtained powder and AB, the material obtained when the rotation speed of the ball mill was 800 rpm and the rotation time was 5 hours was designated as Sample 1.
  • the material obtained when the rotation speed of the ball mill was 700 rpm and the rotation time was 5 hours was designated as Sample 2.
  • Sample 3 The material obtained when the rotation speed of the ball mill was 450 rpm and the rotation time was 5 hours was designated as Sample 3.
  • Sample 4 The material obtained when the rotation speed of the ball mill was 200 rpm and the rotation time was 5 hours was designated as Sample 4.
  • Sample 5 was obtained by mixing Li 2 FeSiO 4 and carbon by hand using a mortar for 30 minutes. Each sample was heat-treated.
  • FIGS. 1, 2, 7, 8, and 9 are SEM cross-sectional photographs of materials taken at various magnifications
  • FIGS. 5, 10, and 11 are images of the surface of particles. It is the SEM photograph which was done. *
  • Sample 1 As shown in FIGS. 1 and 2, relatively large large particles having a major axis of about 20 ⁇ m and fine particles having a particle size of about 1 to 4 ⁇ m were mixed. As shown in the lower diagram of FIG. 1 and FIG. 2, a large number of fine particles were uniformly dispersed inside the large particles. That is, the large particles are those in which fine primary particles are combined into secondary particles. As a result of measuring the specific surface area using the BET method, the composite showed a high value of 171.7 m 2 / g.
  • the upper left photograph of FIG. 3 shows an annular dark field scanning transmission electron microscope (ADF-STEM) image of the large secondary particles of Sample 1.
  • ADF-STEM annular dark field scanning transmission electron microscope
  • the mapping of oxygen (O), carbon (C), iron (Fe), and silicon (Si) by an energy dispersive X-ray analyzer (EDX) of secondary particles is shown.
  • the part extending from the center to the left is the site where the secondary particles are present, and the lower right part is the site where the secondary particles are not present.
  • O, C, Fe, and Si were uniformly dispersed in the site where the secondary particles were present. From this, it was found that the secondary particles contain O, C, Fe, and Si as constituent elements. C was also present outside the secondary particles. *
  • the photograph located on the upper left side of FIG. 4 is a transmission electron microscope (TEM) photograph of the secondary particles of Sample 1. From this photograph, it can be seen that the inside of the secondary particles is an aggregate of a plurality of primary particles.
  • the photograph located on the lower left side of FIG. 4 is a photograph obtained by photographing electron diffraction on the circular black box portion of the secondary particles in the upper left TEM photograph. From the figure, since the diffraction line has a halo pattern, it can be seen that the secondary particles are composed of a large number of particles and the size of each particle is small.
  • the structure of Li 2 FeSiO 4 was confirmed, and it was found that the secondary particles contained Li 2 FeSiO 4 .
  • FIG. 5 is a mapping of carbon (C), oxygen (O), silicon (Si), and iron (Fe) in order from the upper side to the lower side of the central portion of FIG. From the figure, all of C, O, Si, and Fe were uniformly dispersed in the portion where the secondary particles were present. About C, it existed also in the part (the upper right part of each photograph) in which secondary particles do not exist. This result was similar to the element mapping by EDX in FIG. *
  • the right side of FIG. 4 shows a mixed image in which the mapping of each element shown in the central part of FIG. 4 is overlaid.
  • the dark color portion indicates carbon (C)
  • the light color portion indicates Fe, Si, and O.
  • the secondary particles contain Li 2 FeSiO 4 , Fe, Si, and O in the light-colored portion are elements constituting Li 2 FeSiO 4 It is. From this figure, it was found that in the secondary particles, Li 2 FeSiO 4 was uniformly dispersed and compounded in carbon to form an active material complex.
  • the light color portion where Li 2 FeSiO 4 exists in the mixed image corresponds to the white or light gray portion of the TEM, and C in the mixed image.
  • the existing dark color portion corresponds to the dark gray or black portion of the TEM.
  • the abundance ratio of CO in the surface layer having a thickness of about 1 ⁇ m It was found to be higher than the abundance ratio of CO.
  • Li 2 FeSiO 4 and carbon are refined and mixed by applying high energy by high-speed rotation, and then they are granulated and bonded together to form an active material composite. After that, it is considered that further refined carbon entered the surface of the active material composite.
  • the reason why the surface layer is rich in oxygen is considered to be due to milling treatment in an air atmosphere.
  • FIG. 5 is a photograph of the appearance of the active material composite taken with a scanning electron microscope (SEM). From the figure, many fine particles having an average particle diameter of about 100 nm were attached to the surface of the active material composite. *
  • the structure of the active material complex is as shown in FIG.
  • the active material composite 10 is composed of a core part 1 and a surface layer 2 covering the surface of the core part 1, and the core part 1 has an average particle size of 10 to 10 made of Li 2 FeSiO 4. 30 nm active material particles 11 are uniformly dispersed in a matrix 12 made of carbon.
  • the surface layer 2 has a thickness of about 1 ⁇ m and constitutes a CO rich layer.
  • the active material particles and the conductive particles were gradually aggregated to form aggregates, but a hollow portion remained in the aggregates. There were various sizes. For this reason, it cannot be said that the active material particles and the conductive particles are bonded to each other in a finely dispersed state.
  • the specific surface area of the aggregate was 130.7 m 2 / g.
  • Sample 4 was not posted with SEM photographs, but was observed with SEM.
  • the active material particles and the conductive particles were mixed by being smaller than the particle size before mixing.
  • the active material particles and the conductive particles were mixed as they were primary particles, and secondary particles were not formed.
  • the specific surface area of this mixture was 59.3 m 2 / g.
  • sample 5 As shown in FIG. 11, active material particles having an average particle diameter of 1000 nm (particulate white portions) and conductive particles having an average particle diameter of 100 nm (fluffy light gray portions) were mixed. . Each particle had the same shape and size before mixing and was not agglomerated. *
  • the battery using Sample 1 had a significantly larger discharge capacity at the second cycle than the batteries using Samples 2 to 4.
  • the discharge capacity of the sample 1 battery is 1.2 times the discharge capacity of the sample 2 battery, 1.6 times the discharge capacity of the sample 3 battery, and 2 times the discharge capacity of the sample 4 battery. .2 times. From this, it was found that the charge / discharge capacity was improved by increasing the milling speed, and in particular, the charge / discharge capacity was significantly improved by setting the milling speed to 800 rpm as in Sample 1. *
  • the battery of Sample 1 is 42 No significant reduction in discharge capacity was observed until the cycle. From this, it was found that the battery of Sample 1 was excellent in cycle characteristics.
  • a rate characteristic test of the coin battery prepared using Sample 1 was performed.
  • the test conditions were as follows: discharge rate 0.1C at 1-5th cycle, 0.2C at 6-10th cycle, 0.5C at 11-15th cycle, 1C at 16-20th cycle, 21-25th cycle 2C for the eyes, 5C for the 26th to 30th cycles, 0.1C for the 31st to 55th cycles, and the rate during charging was kept constant at 0.1C.
  • the test was conducted at 30 ° C. The test results are shown in FIG. *
  • the discharge capacity at 1C was 200 mAh / g
  • the discharge capacity at 5C was 170 mAh / g
  • excellent rate characteristics were exhibited.
  • reaction resistance The reaction resistance of the materials of Samples 1 and 3 was measured.
  • the test of the reaction resistance was performed on each battery after charging and discharging using a measuring device (trade name: SI 1280B, manufactured by Solartron) using an AC impedance method.
  • the amplitude of the alternating current at the time of measurement was set to 10 mV, the maximum value of the frequency was 20 kHz, and the minimum value was 0.1 Hz.
  • the charging condition was a constant voltage charging at 4.8V for 10 hours, and the discharging condition was a constant current discharging at 1.5V. *
  • FIGS. FIG. 18 shows the reaction resistance of each material after charging
  • FIG. 19 shows the reaction resistance of each material after discharging.
  • the horizontal axis indicates the real axis of the impedance resistance
  • the vertical axis indicates the imaginary axis of the impedance resistance.
  • the width between both ends of the arc-shaped portion indicates the reaction resistance inside the particle and at the particle interface included in each material, and the resistance having a larger real part than the arc-shaped portion. The part shows the diffusion resistance outside the particle.
  • the reaction resistance of the material of Sample 1 was about one-fourth that of Sample 3. This is a factor that the initial discharge capacity of the battery manufactured using the material of Sample 1 as the positive electrode active material is larger than that of Sample 3.
  • the reaction resistance (impedance) of each material indicates the resistance inside the particle contained in each material and at the particle interface.
  • the impedance decreases as the particle size of the active material particles decreases, and the reaction resistance tends to decrease as the contact area with the conductive particles at the active material particle interface increases.
  • the active material particles are as fine as an average particle size of 100 nm or less, and the conductive particles are also as fine as an average particle size of 100 nm or less, and these particles are uniformly dispersed.
  • the active material particles and the conductive particles are in close contact with each other, and the contact area is large. For this reason, the reaction resistance of the sample 1 becomes small, and it is estimated that the battery produced using this as a positive electrode active material has a large discharge capacity.
  • the active material complexes of Samples 6 to 8 were manufactured by the following method.
  • the active material composites of Samples 6 to 8 are composed of Li 2 MnSiO 4 and carbon.
  • Lithium silicate compound Li 2 SiO 3 (lithium silicate, manufactured by Kishida Chemical Co., Ltd., purity 99.5%) 0.03 mol and manganese oxalate (Kishida Chemical Co., Ltd., purity 99.9%) 0.03 mol 20 ml of acetone was added to the mixture and mixed with a zirconia ball mill at 500 rpm for 60 minutes and dried. This was mixed with the carbonate mixture.
  • the carbonate mixture consists of lithium carbonate (Kishida Chemical Co., Ltd., purity 99.9%), sodium carbonate (Kishida Chemical Co., Ltd., purity 99.5%), and potassium carbonate (Kishida Chemical Co., Ltd., purity 99.5%).
  • the obtained powder was heated in a gold crucible and heated to 500 ° C. in an electric furnace in a mixed gas atmosphere of carbon dioxide (flow rate: 100 mL / min) and hydrogen (flow rate: 3 mL / min).
  • the mixture was reacted for 13 hours in a molten state of the carbonate mixture.
  • the entire reactor core as a reaction system was taken out from the electric furnace and rapidly cooled to room temperature through a mixed gas.
  • FIG. 20 is an SEM photograph of active material particles made of Li 2 MnSiO 4 .
  • the active material particles immediately after synthesis are in the form of flakes and distributed in a particle size of 0.5 to 3 ⁇ m.
  • the average particle size was 0.7 ⁇ m.
  • the specific surface area was 12.5 m 2 / g.
  • the obtained active material particles and acetylene black (AB, average particle size 0.3 ⁇ m) were mixed at a mass ratio of 5: 4.
  • the mixture is mechanically milled under the following predetermined conditions in an air atmosphere using a mechanical milling device (French Japan Co., Ltd., planetary ball mill P-7). Energized. This step was performed by putting 50 g of ⁇ 4 mm zirconia balls and 300 mg of the mixture in a ball mill grinding container made of zirconia and having a volume of 45 cc. *
  • FIG. 21 is a SEM (Scanning Electron Microscope) photograph of Sample 6.
  • relatively large large particles having a major axis of about 10 ⁇ m and fine particles having a particle size of about 0.5 to 5 ⁇ m were mixed. Inside these particles, many fine particles were uniformly dispersed. Large particles are secondary particles obtained by compositing fine primary particles.
  • the large particles were Li 2 MnSiO 4 / C composites in which Li 2 MnSiO 4 having a particle size of 10 to 50 nm and carbon having a particle size of 10 to 50 nm were bonded together to form a composite.
  • this composite showed a high value of 170.2 m 2 / g.
  • the active material particles and the conductive particles were mixed in a size larger than that of Sample 6.
  • the active material particles and the conductive particles are gradually aggregated to form aggregates.
  • the average particle diameter of the aggregates is about 1000 nm, which is smaller than the secondary particles of the sample 6, and has a hollow portion inside. was there.
  • the sizes of the active material particles and the conductive particles varied, and the active material particles and the conductive particles were dispersed unevenly. Further, as a result of measuring the specific surface area using the BET method, this complex showed 101 m 2 / g.
  • FIG. 23 shows XRD patterns of Li 2 MnSiO 4 immediately after synthesis and samples 6 to 8. As shown in FIG. 23, the intensity of the diffraction peak is lower in Sample 6 than in Samples 7 and 8. This is presumed to be due to a decrease in crystallinity and finer particles.
  • Sample 7 was a Li 2 MnSiO 4 / C composite in which Li 2 MnSiO 4 having a particle size of 400 nm and carbon having a particle size of 240 nm were bonded together to form a composite.
  • the specific surface area of Sample 7 was 115 m 2 / g.
  • Sample 8 was a Li 2 MnSiO 4 / C composite in which Li 2 MnSiO 4 having a particle diameter of 500 nm and carbon having a particle diameter of 300 nm were bonded to each other to form a composite.
  • the specific surface area of Sample 7 was 101 m 2 / g.
  • Each positive electrode active material Li 2 MnSiO 4 / C composite
  • AB acetylene black
  • PTFE polytetrafluoroethylene
  • a polypropylene membrane (Celgard 2400, manufactured by Celgard) and a glass filter were used as the separator. Lithium metal foil was used as the negative electrode. From these, a coin-type half battery was produced.
  • the battery using the sample 6 has an initial charge capacity, an initial discharge capacity, an initial efficiency, and an initial discharge average voltage, as compared with the battery using the samples 7 and 8. High value was shown.
  • the initial discharge capacity of the sample 6 battery was 2.6 times the initial discharge capacity of the sample 7 battery and 2.7 times the discharge capacity of the sample 8 battery.
  • the initial efficiency of the sample 6 battery was 1.2 times the initial efficiency of the sample 7 battery and 1.4 times the initial efficiency of the sample 8 battery.
  • the initial discharge average voltage of the sample 6 battery was 0.1 V higher than the initial discharge average voltage of the sample 7 battery, and 0.2 V higher than the initial discharge average voltage of the sample 8 battery. From this, it was found that the charge / discharge capacity, the initial efficiency, and the average discharge voltage are improved by increasing the milling speed and milling time.
  • the active material particles are as fine as an average particle size of 100 nm or less, and the conductive particles are as fine as an average particle size of 100 nm or less, and these particles are uniformly dispersed. Further, in the portion where the active material composite is formed, the active material particles and the conductive particles are in close contact with each other, and the contact area is large. For this reason, the reaction resistance of the sample 6 becomes small, and it is estimated that the battery produced using this as a positive electrode active material has a large discharge capacity.
  • the nanoparticles as described above are uniformly dispersed, a lithium ion conductive path is well formed, so that lithium ions released from the active material at the time of charging easily return at the time of discharging. For this reason, it is estimated that the initial efficiency of the sample 6 has improved. Furthermore, it is presumed that due to the reduced reaction resistance, the charge / discharge curve inherent to the active material was obtained, leading to an improvement in the discharge average voltage.

Abstract

This positive electrode active material for nonaqueous electrolyte secondary batteries is obtained by bonding active material particles, which are formed of an active material and have an average particle diameter of 100 nm or less, and conductive particles, which are formed of a conductive material and have an average particle diameter of 100 nm or less, with each other. This positive electrode active material for nonaqueous electrolyte secondary batteries has a specific surface area of 150 m2/g or more.

Description

活物質複合体及びその製造方法、非水電解質二次電池用正極活物質、並びに非水電解質二次電池Active material composite and production method thereof, positive electrode active material for non-aqueous electrolyte secondary battery, and non-aqueous electrolyte secondary battery
本発明は、非水電解質二次電池用活物質に用いられる活物質複合体及びその製造方法、非水電解質二次電池用正極活物質、並びに非水電解質二次電池に関する。 The present invention relates to an active material composite used for an active material for a nonaqueous electrolyte secondary battery and a method for producing the same, a positive electrode active material for a nonaqueous electrolyte secondary battery, and a nonaqueous electrolyte secondary battery.
非水電解質二次電池の中でもリチウムイオン二次電池は、小型でエネルギー密度が高く、ポータブル電子機器の電源として広く用いられている。また、リチウムイオン二次電池を車両の駆動源として用いることが考えられている。近年、リチウムイオン二次電池の正極活物質として、リチウムシリケート系化合物、リチウムボレート系化合物、リチウムホスフェート系化合物が知られている。　 Among nonaqueous electrolyte secondary batteries, lithium ion secondary batteries are small and have high energy density, and are widely used as power sources for portable electronic devices. In addition, it is considered that a lithium ion secondary battery is used as a vehicle drive source. In recent years, lithium silicate compounds, lithium borate compounds, and lithium phosphate compounds are known as positive electrode active materials for lithium ion secondary batteries. *
国際公開２０１０／０８９９３１号及び特開２０１０－２５７５９２号公報に記載されているように、リチウムシリケート系化合物は、安価で、資源量の豊富な構成金属元素からなるために環境負荷が低く、リチウムイオンの高い理論充放電容量を有し、かつ高温時に酸素を放出しない材料であり、具体的には、Ｌｉ２ＦｅＳｉＯ４（理論容量３３１．３ｍＡｈ／ｇ）、Ｌｉ２ＭｎＳｉＯ４（理論容量３３３．２ｍＡｈ／ｇ）等のリチウムシリケート系化合物が開発されている。　 As described in International Publication No. 2010/089931 and Japanese Patent Application Laid-Open No. 2010-257592, lithium silicate compounds are inexpensive and have a low environmental impact because they are composed of abundant constituent metal elements. The material has a high theoretical charge / discharge capacity and does not release oxygen at a high temperature. Specifically, Li 2 FeSiO 4 (theoretical capacity 331.3 mAh / g), Li 2 MnSiO 4 (theoretical capacity 333.2 mAh). Lithium silicate compounds such as / g) have been developed.
国際公開２０１０／１０４１３７号に記載されているように、リチウムボレート系化合物も、安価で、資源量が多く、環境負荷が低く、高い理論充放電容量を有し、且つ高温時に酸素を放出しないカソード材料として注目されている。リチウムボレート系化合物としては、例えば、ＬｉＦｅＢＯ３（理論容量２２０ｍＡｈ/ｇ）、ＬｉＭｎＢＯ３（理論容量２２２ｍＡｈ/ｇ）等が知られている。リチウムボレート系材料はポリアニオンユニットの中で最も軽い元素であるホウ素（Ｂ）を用いることで、エネルギー密度の向上が期待できる材料であり、また、ボレート系材料の真密度（３．４６ｇ/ｃｍ３）はリン酸オリビン鉄材料の真密度（３．６０ｇ/ｃｍ３）よりも小さく、軽量化も期待できる。　 As described in International Publication No. 2010/104137, lithium borate compounds are also inexpensive, have a large amount of resources, have a low environmental burden, have a high theoretical charge / discharge capacity, and do not release oxygen at high temperatures. It is attracting attention as a material. As a lithium borate compound, for example, LiFeBO 3 (theoretical capacity 220 mAh / g), LiMnBO 3 (theoretical capacity 222 mAh / g), and the like are known. The lithium borate material is a material that can be expected to improve the energy density by using boron (B), which is the lightest element in the polyanion unit, and the true density (3.46 g / cm 3) of the borate material. ) Is smaller than the true density (3.60 g / cm 3 ) of the olivine iron phosphate material, and weight reduction can also be expected.
リチウムホスフェート系化合物は、ＬｉＭＰＯ４（ＭはＭｎ、Ｆｅ、Ｃｏなどの金属）で表され、中心金属Ｍの回りに電気陰性度の大きいヘテロ元素のＰＯ４ 3-ポリアニオンを配置している。このため、遷移金属に酸素原子が直接配位している層状のＬiＣｏＯ２などに比べて熱的安定性が高いといわれている。　 The lithium phosphate compound is represented by LiMPO 4 (M is a metal such as Mn, Fe, Co), and a hetero element PO 4 3- polyanion having a large electronegativity is arranged around the central metal M. For this reason, it is said that the thermal stability is higher than that of layered LiCoO 2 or the like in which oxygen atoms are directly coordinated to the transition metal.
しかし、これらの材料は、伝導性が低く、ほとんど絶縁体レベルにある。このため、これらの材料から本来の容量を取り出すことが出来ず、充放電特性を改良する必要がある。そこで、上記の各種正極活物質の充放電容量を高めるために、各化合物にカーボン被覆処理をすることも行われている。国際公開２０１０／０８９９３１号及び国際公開２０１０／１０４１３７号には、リチウムシリケート系化合物を正極活物質として用いた非水電解質二次電池の充放電容量を更に高めるため、リチウムシリケート系化合物に、更にカーボンによる被覆処理を行うことも開示されている。 However, these materials have low conductivity and are almost at the insulator level. For this reason, the original capacity cannot be taken out from these materials, and it is necessary to improve the charge / discharge characteristics. Therefore, in order to increase the charge / discharge capacity of the various positive electrode active materials, each compound is also subjected to a carbon coating treatment. In WO 2010/089931 and WO 2010/104137, in order to further increase the charge / discharge capacity of a non-aqueous electrolyte secondary battery using a lithium silicate compound as a positive electrode active material, carbon is further added to the lithium silicate compound. It is also disclosed that the coating process is performed.
国際公開２０１０／０８９９３１号International Publication No. 2010/089931 特開２０１０－２５７５９２号公報JP 2010-257592 A 国際公開２０１０／１０４１３７号International Publication No. 2010/104137
しかしながら、リチウムイオン二次電池で車両を駆動するには、高い充放電容量の電池が必要とされる。この要求に応ずべく、正極活物質の更なる改良が望まれている。　 However, in order to drive a vehicle with a lithium ion secondary battery, a battery with a high charge / discharge capacity is required. In order to meet this demand, further improvement of the positive electrode active material is desired. *
本発明はかかる事情に鑑みてなされたものであり、電池の充放電容量を大きくすることができる活物質複合体及びその製造方法、非水電解質二次電池用正極活物質、並びに非水電解質二次電池を提供することを課題とする。 The present invention has been made in view of such circumstances, and an active material composite capable of increasing the charge / discharge capacity of a battery, a method for producing the same, a positive electrode active material for a non-aqueous electrolyte secondary battery, and a non-aqueous electrolyte two. It is an object to provide a secondary battery.
（１）本発明の活物質複合体は、活物質材料からなり平均粒径が１００ｎｍ以下である活物質粒子と、導電性材料からなり平均粒径が１００ｎｍ以下である導電性粒子とが互いに接合し、比表面積が１５０ｍ２／ｇ以上であることからなることを特徴とする。　 (1) In the active material composite of the present invention, active material particles made of an active material and having an average particle size of 100 nm or less are bonded to conductive particles made of a conductive material and having an average particle size of 100 nm or less. And the specific surface area is 150 m 2 / g or more.
（２）本発明の活物質複合体の製造方法は、上記に記載の活物質複合体を製造する方法であって、活物質材料及び導電性材料に機械的エネルギーを付与するエネルギー付与工程をもつことを特徴とする。　 (2) The method for producing an active material composite according to the present invention is a method for producing the active material composite as described above, and includes an energy application step for applying mechanical energy to the active material and the conductive material. It is characterized by that. *
（３）本発明の非水電解質二次電池用正極活物質は、上記に記載の活物質複合体、又は上記に記載の製造方法により製造された活物質複合体からなることを特徴とする。　 (3) The positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention is characterized by comprising the active material composite described above or the active material composite manufactured by the manufacturing method described above. *
（４）本発明の非水電解質二次電池用正極は、上記に記載の非水電解質二次電池用正極活物質を有することを特徴とする。　 (4) The positive electrode for nonaqueous electrolyte secondary batteries of the present invention is characterized by having the positive electrode active material for nonaqueous electrolyte secondary batteries described above. *
（５）本発明の非水電解質二次電池は、上記に記載の非水電解質二次電池用正極と、負極と、電解質とを備えたことを特徴とする。　 (5) The nonaqueous electrolyte secondary battery of the present invention is characterized by comprising the positive electrode for a nonaqueous electrolyte secondary battery described above, a negative electrode, and an electrolyte. *
本発明の活物質複合体は、微細な活物質粒子と微細な導電性粒子とが互いに接合してなるため、電池の充放電容量を大きくすることができる。本発明の非水電解質二次電池用正極活物質、非水電解質二次電池用正極、非水電解質二次電池は、上記活物質複合体を用いているため、充放電容量を大きくすることができる。 In the active material composite of the present invention, fine active material particles and fine conductive particles are bonded to each other, so that the charge / discharge capacity of the battery can be increased. Since the positive electrode active material for a nonaqueous electrolyte secondary battery, the positive electrode for a nonaqueous electrolyte secondary battery, and the nonaqueous electrolyte secondary battery of the present invention use the active material composite, the charge / discharge capacity can be increased. it can.
図１の上図は、試料１のＳＥＭ断面写真（１目盛１μｍ）であり、図１の下図は、試料１のＳＥＭ断面写真（１目盛０．２μｍ）であって、図１の点線囲み部分の拡大写真である。The upper diagram of FIG. 1 is an SEM cross-sectional photograph of sample 1 (one scale of 1 μm), and the lower diagram of FIG. 1 is an SEM cross-sectional photograph of sample 1 (one scale of 0.2 μm), surrounded by a dotted line in FIG. It is an enlarged photograph of. 試料１のＳＥＭ断面写真（１目盛０．１μｍ）である。2 is a SEM cross-sectional photograph of sample 1 (one scale 0.1 μm). 試料１の二次粒子の表面近傍のエネルギー分散型X線分析装置（ＥＤＸ）を用いた元素マッピングを示す図である。It is a figure which shows the element mapping using the energy dispersive X-ray-analysis apparatus (EDX) of the surface vicinity of the secondary particle of the sample 1. FIG. 試料１の二次粒子の表面近傍の透過型電子顕微鏡（ＴＥＭ）写真、電子線回折を示す図、及び電子エネルギー損失分析法（ＥＥＬＳ）による元素マッピングを示す図である。It is a figure which shows the elemental mapping by the transmission electron microscope (TEM) photograph of the surface vicinity of the secondary particle of the sample 1, the figure which shows an electron beam diffraction, and an electron energy loss analysis method (EELS). 試料１の二次粒子の表面を撮影したＳＥＭ写真（１目盛０．１μｍ）である。2 is a SEM photograph (one scale 0.1 μm) of the surface of secondary particles of sample 1. 試料１の活物質複合体の断面説明図である。2 is a cross-sectional explanatory view of an active material composite of Sample 1. FIG. 試料２のＳＥＭ断面写真（１目盛０．２μｍ）である。2 is a SEM cross-sectional photograph of sample 2 (one scale 0.2 μm). 試料３のＳＥＭ断面写真（１目盛０．５μｍ）である。3 is a SEM cross-sectional photograph (one scale 0.5 μm) of Sample 3. 試料３のＳＥＭ断面写真（１目盛０．１μｍ）である。4 is a SEM cross-sectional photograph of sample 3 (one scale 0.1 μm). 試料３の粒子表面を撮影したＳＥＭ写真（１目盛０．１μｍ）である。4 is an SEM photograph (one scale 0.1 μm) of the particle surface of sample 3. FIG. 試料５の粒子表面を撮影したＳＥＭ写真（１目盛０．１μｍ）である。4 is an SEM photograph (one scale 0.1 μm) of the particle surface of sample 5. FIG. 試料１を用いて作製した電池の充放電曲線を示す図である。4 is a diagram showing a charge / discharge curve of a battery produced using Sample 1. FIG. 試料２を用いて作製した電池の充放電曲線を示す図である。3 is a diagram showing a charge / discharge curve of a battery produced using Sample 2. FIG. 試料３を用いて作製した電池の充放電曲線を示す図である。3 is a diagram showing a charge / discharge curve of a battery manufactured using Sample 3. FIG. 試料４を用いて作製した電池の充放電曲線を示す図である。FIG. 6 is a diagram showing a charge / discharge curve of a battery manufactured using Sample 4. 試料１を用いて作製した電池のサイクル試験結果を示す図である。FIG. 4 is a diagram showing a cycle test result of a battery manufactured using Sample 1. 試料１を用いて作製した電池のレート試験結果を示す図である。It is a figure which shows the rate test result of the battery produced using the sample 1. FIG. 試料１，３を用いて作製した電池の充電後の交流インピーダンスプロットを示す図である。It is a figure which shows the alternating current impedance plot after the charge of the battery produced using the samples 1 and 3. FIG. 試料１，３を用いて作製した電池の放電後の交流インピーダンスプロットを示す図である。It is a figure which shows the alternating current impedance plot after the discharge of the battery produced using the samples 1 and 3. FIG. 合成直後のＬｉ２ＭｎＳｉＯ４のＳＥＭ写真であって、図２０の上図は高倍率のＳＥＭ写真であり、図２０の下図は低倍率のＳＥＭ写真である。FIG. 20 is an SEM photograph of Li 2 MnSiO 4 immediately after synthesis, and the upper diagram in FIG. 20 is a high-magnification SEM photograph, and the lower diagram in FIG. 20 is a low-magnification SEM photograph. 試料６のＳＥＭ写真であって、図２１の上図は低倍率のＳＥＭ写真であり、図２１の下図は高倍率のＳＥＭ写真である。FIG. 21 is an SEM photograph of Sample 6, the upper drawing of FIG. 21 is a low magnification SEM photograph, and the lower drawing of FIG. 21 is a high magnification SEM photograph. 試料８のＳＥＭ写真である。3 is a SEM photograph of Sample 8. 合成直後のＬｉ２ＭｎＳｉＯ４、及び試料６～８のＸＲＤパターンを示す。The XRD patterns of Li 2 MnSiO 4 immediately after synthesis and Samples 6 to 8 are shown. 試料６を用いた電池の充放電曲線を示す。The charging / discharging curve of the battery using the sample 6 is shown. 試料７を用いた電池の充放電曲線を示す。The charging / discharging curve of the battery using the sample 7 is shown. 試料８を用いた電池の充放電曲線を示す。The charging / discharging curve of the battery using the sample 8 is shown.
本発明の実施形態に係る活物質複合体及びその製造方法、非水電解質二次電池用正極活物質、非水電解質二次電池、並びに車両について詳細に説明する。　 An active material composite according to an embodiment of the present invention and a manufacturing method thereof, a positive electrode active material for a nonaqueous electrolyte secondary battery, a nonaqueous electrolyte secondary battery, and a vehicle will be described in detail. *
（１）活物質複合体　本発明に係る活物質複合体は、平均粒径が１００ｎｍ以下の活物質材料からなる活物質粒子と、平均粒径が１００ｎｍ以下の導電性材料からなる導電性粒子とが接合してなる複合体からなる。活物質粒子と導電性粒子とが、１００ｎｍ以下という極めて小さいナノレベルの微粒子状態で互いに混合され接合することにより、後述する実施例で示されるように、電池の充放電容量を高めることができる。その理由は、活物質粒子と導電性粒子とがナノレベルで微粒子状態で互いに接合されることにより、活物質複合体の中で導電性粒子から構成される導電パスが増え、活物質複合体内での電子の移動が活発化されて、活物質の利用率が増加するためと推測される。　 (1) Active material composite The active material composite according to the present invention comprises active material particles made of an active material having an average particle size of 100 nm or less, and conductive particles made of a conductive material having an average particle size of 100 nm or less. It consists of a composite formed by bonding. By mixing and joining the active material particles and the conductive particles in a very small nano-level fine particle state of 100 nm or less, the charge / discharge capacity of the battery can be increased as shown in Examples described later. The reason is that the active material particles and the conductive particles are joined to each other in a fine particle state at the nano level, thereby increasing the number of conductive paths composed of the conductive particles in the active material complex. This is presumed to be due to the increase in the utilization rate of the active material due to the active movement of electrons. *
また、活物質複合体の比表面積は、１５０ｍ２／ｇ以上、好ましくは１７０ｍ２／ｇ以上である。このように活物質複合体の比表面積が大きいことにより、電解液との接触面積が大きくなり、リチウムイオンの吸蔵・放出がし易くなり、電池の充放電容量を高めることができる。　 The specific surface area of the active material composite is 150 m 2 / g or more, preferably 170 m 2 / g or more. Thus, when the specific surface area of an active material composite is large, a contact area with electrolyte solution becomes large, it becomes easy to occlude and discharge | release lithium ion, and can improve the charge / discharge capacity of a battery.
ここで、活物質粒子の平均粒径は１００ｎｍ以下であり、導電性粒子の平均粒径は１００ｎｍ以下である。各粒子の平均粒径は、透過型電子顕微鏡（ＴＥＭ）などによる活物質複合体の画像を解析することで得られた複数個の粒子の最大径（粒子を挟む二本の平行線の距離の最大値）を実測して算出した値である。　 Here, the average particle diameter of the active material particles is 100 nm or less, and the average particle diameter of the conductive particles is 100 nm or less. The average particle diameter of each particle is the maximum diameter of a plurality of particles obtained by analyzing an image of the active material complex using a transmission electron microscope (TEM) or the like (the distance between two parallel lines sandwiching the particles). (Maximum value) is a value calculated by actual measurement. *
活物質粒子の平均粒径が１００ｎｍを超える場合、又は導電性粒子の平均粒径が１００ｎｍを超える場合には、電池の充放電容量を高める効果が少なくなるおそれがある。好ましくは、活物質粒子の平均粒径は１０ｎｍ以上９０ｎｍ以下であり、導電性粒子の平均粒径は２ｎｍ以上５０ｎｍ以下である。この場合には、電池の充放電容量が更に高くなる。さらに好ましくは、活物質粒子の平均粒径は１０ｎｍ以上５０ｎｍ以下であり、導電性粒子の平均粒径は２ｎｍ以上１０ｎｍ以下である。　 When the average particle diameter of the active material particles exceeds 100 nm, or when the average particle diameter of the conductive particles exceeds 100 nm, the effect of increasing the charge / discharge capacity of the battery may be reduced. Preferably, the average particle diameter of the active material particles is 10 nm or more and 90 nm or less, and the average particle diameter of the conductive particles is 2 nm or more and 50 nm or less. In this case, the charge / discharge capacity of the battery is further increased. More preferably, the average particle size of the active material particles is 10 nm to 50 nm, and the average particle size of the conductive particles is 2 nm to 10 nm. *
活物質粒子及び導電性粒子は、それぞれ一次粒子として、互いにナノレベルの微粒子状態で混合され接合されて、二次粒子である複合体を構成している。　 The active material particles and the conductive particles are mixed and bonded as primary particles to each other in a nano-level fine particle state to form a composite that is a secondary particle. *
活物質複合体の平均粒径は０．７μｍ以上２０μｍ以下であることがよく、更には１μｍ以上１０μｍ以下であるとよい。活物質複合体の平均粒径が過小の場合には、活物質複合体の造粒化が未発達で、活物質粒子と導電性粒子との複合化が不十分である。活物質複合体の平均粒径が過大の場合には、活物質複合体がリチウムイオンを吸蔵・放出する速度が低下するおそれがある。　 The average particle size of the active material complex is preferably 0.7 μm or more and 20 μm or less, and more preferably 1 μm or more and 10 μm or less. When the average particle diameter of the active material composite is too small, granulation of the active material composite is not yet developed, and the composite of the active material particles and the conductive particles is insufficient. When the average particle size of the active material complex is excessive, the rate at which the active material complex occludes / releases lithium ions may decrease. *
活物質複合体の比表面積は、１５０ｍ２／ｇ以上、好ましくは１７０ｍ２／ｇ以上である。比表面積は、ＢＥＴ比表面積をいう。活物質複合体の比表面積の上限は３００ｍ２／ｇであるとよく、更には、２５０ｍ２／ｇであることが好ましい。活物質複合体の比表面積が過小の場合には、電池の充放電容量が低くなるおそれがある。活物質複合体の比表面積が過大である場合には、活物質複合体が小さすぎて、導電性粒子と活物質粒子との複合化が不十分であるおそれがある。　 The specific surface area of the active material composite is 150 m 2 / g or more, preferably 170 m 2 / g or more. The specific surface area refers to the BET specific surface area. The upper limit of the specific surface area of the active material composite is preferably 300 m 2 / g, and more preferably 250 m 2 / g. When the specific surface area of the active material composite is too small, the charge / discharge capacity of the battery may be reduced. When the specific surface area of the active material composite is excessive, the active material composite is too small, and there is a possibility that the composite of the conductive particles and the active material particles is insufficient.
活物質複合体の全体で、活物質粒子及び導電性粒子が均一に微細混合され互いに接合していてもよい。また、活物質複合体は、コア部と、コア部を被覆する表面層とからなるとよい。表面層は、コア部よりも多くの炭素が含まれているとよい。表面層の厚みは、５００ｎｍ以上２μｍ以下であることがよい。活物質複合体が表面層を有することにより、複合体同士の導電ネットワークが増える。　 In the entire active material composite, the active material particles and the conductive particles may be uniformly finely mixed and bonded to each other. Moreover, the active material complex is preferably composed of a core part and a surface layer covering the core part. The surface layer may contain more carbon than the core portion. The thickness of the surface layer is preferably 500 nm or more and 2 μm or less. When the active material composite has the surface layer, the conductive network between the composites increases. *
活物質複合体の表面には、微細な表面粒子が付着しているとよい。表面粒子の平均粒径は２０ｎｍ以上１００ｎｍ以下であるとよく、更には、３０ｎｍ以上９０ｎｍ以下であり、３５ｎｍ以上７５ｎｍ以下であることが望ましい。表面粒子には、例えば、
活物質粒子の原料の一部が含まれていても良い。活物質複合体が表面粒子を有することにより、活物質粒子がリチウムイオンを吸蔵・放出する反応が促進される。　 Fine surface particles are preferably adhered to the surface of the active material composite. The average particle size of the surface particles is preferably 20 nm or more and 100 nm or less, more preferably 30 nm or more and 90 nm or less, and preferably 35 nm or more and 75 nm or less. Examples of surface particles include:
A part of the raw material of the active material particles may be included. When the active material composite has the surface particles, the reaction in which the active material particles occlude / release lithium ions is promoted.
活物質粒子を構成する活物質材料は、リチウムイオンを吸蔵・放出し得る材料からなるとよい。この場合には、非水電解質二次電池用活物質をリチウムイオン二次電池の電極に用いることができる。　 The active material constituting the active material particles may be made of a material that can occlude and release lithium ions. In this case, the active material for nonaqueous electrolyte secondary batteries can be used for the electrode of a lithium ion secondary battery. *
活物質材料は、リチウムシリケート系化合物、リチウムホスフェート系化合物、及びリチウムボレート系化合物の群のいずれか１種以上からなることがよい。このような活物質材料からなる活物質粒子を含む活物質複合体によれば、非水電解質二次電池用活物質、更にはリチウムイオン二次電池用又はリチウム二次電池用の活物質を構成することができる。リチウムシリケート系化合物は、例えば、リチウム鉄シリケート（Ｌｉ２ＦｅＳｉＯ４）、及びリチウムマンガンシリケート（Ｌｉ２ＭｎＳｉＯ４）の群から選ばれる少なくとも１種からなるとよい。リチウム鉄シリケートは、例えば、Ｌｉ２ＦｅＳｉＯ４で表される。リチウムマンガンシリケートは、例えば、Ｌｉ２ＭｎＳｉＯ４で表される。　 The active material is preferably composed of one or more members selected from the group consisting of a lithium silicate compound, a lithium phosphate compound, and a lithium borate compound. According to the active material composite including the active material particles made of such an active material, it constitutes an active material for a non-aqueous electrolyte secondary battery, and further an active material for a lithium ion secondary battery or a lithium secondary battery. can do. The lithium silicate-based compound may be, for example, at least one selected from the group consisting of lithium iron silicate (Li 2 FeSiO 4 ) and lithium manganese silicate (Li 2 MnSiO 4 ). The lithium iron silicate is represented by, for example, Li 2 FeSiO 4 . The lithium manganese silicate is represented by, for example, Li 2 MnSiO 4 .
導電性粒子を構成する導電性材料は、活物質材料よりも導電性が高い材料を用いる。導電性材料は、例えば、炭素材料を用いることが好ましい。炭素材料としては、アセチレンブラック（ＡＢ）、ケッチェンブラック（ＫＢ）、カーボンブラック、カーボンナノチューブ、グラフェーン、カーボン繊維、黒鉛等を用いることができる。中でも、アセチレンブラック（ＡＢ）、ケッチェンブラック（ＫＢ）、カーボンブラックが好ましい。　 As the conductive material constituting the conductive particles, a material having higher conductivity than the active material is used. For example, a carbon material is preferably used as the conductive material. As the carbon material, acetylene black (AB), ketjen black (KB), carbon black, carbon nanotube, graphene, carbon fiber, graphite, or the like can be used. Among these, acetylene black (AB), ketjen black (KB), and carbon black are preferable. *
活物質複合体の中において、活物質粒子を１００質量部としたときの導電性粒子の質量比は、２質量部以上６０質量部以下であることがよく、更には５質量部以上３０質量部以下であることがよい。この場合には、活物質粒子と導電性粒子とが均一に分散して、電気容量を大きく引き出すことができる。　 In the active material composite, the mass ratio of the conductive particles when the active material particles are 100 parts by mass is preferably 2 parts by mass or more and 60 parts by mass or less, and more preferably 5 parts by mass or more and 30 parts by mass. It may be the following. In this case, the active material particles and the conductive particles are uniformly dispersed, and the electric capacity can be greatly extracted. *
（２）活物質複合体の製造方法　前記の活物質複合体を製造する方法であって、活物質材料及び導電性材料に機械的エネルギーを付与するエネルギー付与工程をもつことを特徴とする。　 (2) Method for Producing Active Material Complex A method for producing the above active material complex, characterized in that it has an energy imparting step for imparting mechanical energy to the active material and the conductive material. *
エネルギー付与工程で用いられる活物質材料は、例えば、リチウムシリケート系化合物、リチウムホスフェート系化合物、及びリチウムボレート系化合物のいずれかであるとよい。　 The active material used in the energy application step may be, for example, any one of a lithium silicate compound, a lithium phosphate compound, and a lithium borate compound. *
また、リチウムシリケート系化合物は、例えば、リチウムシリケート系化合物は、組成式Ｌｉ２Ｍ１ＳｉＯ４（Ｍ１は、Ｆｅ、Ｍｎ、Ｃｏ）、または組成式Ｌｉ２＋ａ―ｂＡｂＭ１－ｘＭ’ｘＳｉＯ４＋δ（式中、ＡはＮａ、Ｋ、Ｒｂ、Ｃｓの群から選ばれた少なくとも一種の元素であり、ＭはＦｅ及びＭｎ、Ｃｏからなる群から選ばれた少なくとも一種の元素であり、Ｍ’はＭｇ、Ｃａ、Ａｌ、Ｎｉ、Ｎｂ、Ｔｉ、Ｃｒ、Ｃｕ、Ｚｎ、Ｚｒ、Ｖ、Ｍｏ及びＷからなる群から選ばれた少なくとも一種の元素である。各添字は次のとおりである。０≦ａ＜１、０≦ｂ＜０．２、０≦ｘ≦０．５、δ≧０）で表される化合物からなることが好ましい。　 The lithium silicate compound is, for example, a lithium silicate compound having a composition formula of Li 2 M 1 SiO 4 (M 1 is Fe, Mn, Co), or a composition formula of Li 2 + ab Ab M 1-x M ' x SiO 4 + δ (wherein A is at least one element selected from the group consisting of Na, K, Rb and Cs, and M is at least one element selected from the group consisting of Fe, Mn and Co) , M ′ is at least one element selected from the group consisting of Mg, Ca, Al, Ni, Nb, Ti, Cr, Cu, Zn, Zr, V, Mo, and W. The subscripts are as follows. Preferably, it is made of a compound represented by 0 ≦ a <1, 0 ≦ b <0.2, 0 ≦ x ≦ 0.5, δ ≧ 0).
具体的には、例えば、Ｌｉ２ＦｅＳｉＯ４、Ｌｉ２ＭｎＳｉＯ４、Ｌｉ２ＣｏＳｉＯ４が挙げられる。　 Specifically, for example, Li 2 FeSiO 4, Li 2 MnSiO 4, Li 2 CoSiO 4 can be cited.
リチウムシリケート系化合物は、例えば、溶融塩法、固相法、水熱法などにより製造することができる。中でも、溶融塩法で製造するとよい。　 The lithium silicate compound can be produced, for example, by a molten salt method, a solid phase method, a hydrothermal method, or the like. Especially, it is good to manufacture by the molten salt method. *
溶融塩法は、アルカリ金属塩を含む溶融塩中においてリチウムシリケート系化合物を合成する方法である。溶融塩法に用いるアルカリ金属塩は、リチウム塩、カリウム塩、ナトリウム塩、ルビシウム塩およびセシウム塩からなる群から選ばれる少なくとも一種が挙げられる。なかでも望ましいのは、リチウム塩である。リチウム塩を含む溶融塩を使用する場合には、不純物相の形成が少なく、リチウム原子を過剰に含むリチウムシリケート系化合物が形成されやすい。この様にして得られるリチウムシリケート系化合物は、良好なサイクル特性と高い容量を有するリチウムイオン電池用正極材料となる。　 The molten salt method is a method of synthesizing a lithium silicate compound in a molten salt containing an alkali metal salt. Examples of the alkali metal salt used in the molten salt method include at least one selected from the group consisting of a lithium salt, a potassium salt, a sodium salt, a rubium salt, and a cesium salt. Of these, lithium salts are desirable. When a molten salt containing a lithium salt is used, the formation of an impurity phase is small, and a lithium silicate compound containing excessive lithium atoms is likely to be formed. The lithium silicate compound thus obtained is a positive electrode material for lithium ion batteries having good cycle characteristics and high capacity. *
また、溶融塩法に用いるアルカリ金属塩は、アルカリ金属塩化物、アルカリ金属炭酸塩、アルカリ金属硝酸塩及びアルカリ金属水酸化物のうちの少なくとも１種を含むことが望ましい。具体的には、塩化リチウム（ＬｉＣｌ）、塩化カリウム（ＫＣｌ）、塩化ルビシウム（ＲｂＣｌ）、塩化セシウム（ＣｓＣｌ）、炭酸リチウム（Ｌｉ２ＣＯ３）、炭酸カリウム（Ｋ２ＣＯ３）、炭酸ナトリウム（Ｎａ２ＣＯ３）、炭酸ルビシウム（Ｒｂ２ＣＯ３）、炭酸セシウム（Ｃｓ２ＣＯ３）、硝酸リチウム（ＬｉＮＯ３）、硝酸カリウム（ＫＮＯ３）、硝酸ナトリウム（ＮａＮＯ３）、硝酸ルビシウム（ＲｂＮＯ３）、硝酸セシウム（ＣｓＮＯ３）、水酸化リチウム（ＬｉＯＨ）、水酸化カリウム（ＫＯＨ）、水酸化ナトリウム（ＮａＯＨ）、水酸化ルビシウム（ＲｂＯＨ）および水酸化セシウム（ＣｓＯＨ）が挙げられ、これらのうちの一種を単独または二種以上を混合して使用するとよい。　 Moreover, it is desirable that the alkali metal salt used in the molten salt method contains at least one of alkali metal chloride, alkali metal carbonate, alkali metal nitrate, and alkali metal hydroxide. Specifically, lithium chloride (LiCl), potassium chloride (KCl), rubidium chloride (RbCl), cesium chloride (CsCl), lithium carbonate (Li 2 CO 3 ), potassium carbonate (K 2 CO 3 ), sodium carbonate ( Na 2 CO 3 ), rubidium carbonate (Rb 2 CO 3 ), cesium carbonate (Cs 2 CO 3 ), lithium nitrate (LiNO 3 ), potassium nitrate (KNO 3 ), sodium nitrate (NaNO 3 ), rubidium nitrate (RbNO 3 ) , Cesium nitrate (CsNO 3 ), lithium hydroxide (LiOH), potassium hydroxide (KOH), sodium hydroxide (NaOH), rubidium hydroxide (RbOH) and cesium hydroxide (CsOH), of which One kind may be used alone, or two or more kinds may be mixed and used.
アルカリ金属塩は、中でも、アルカリ金属炭酸塩がよく、更には炭酸リチウムを含むことがよい。望ましくは、炭酸カリウム、炭酸ナトリウム、炭酸ルビシウム及び炭酸セシウムからなる群から選ばれた少なくとも一種のアルカリ金属炭酸塩と炭酸リチウムとからなる炭酸塩混合物がよい。２種以上の炭酸塩を混合することにより、溶融塩の溶融温度を低くすることができ、４００～６５０℃という低い温度で合成反応を行うことができる。　 Among them, the alkali metal carbonate is preferably an alkali metal carbonate, and further preferably contains lithium carbonate. Desirably, a carbonate mixture comprising at least one alkali metal carbonate selected from the group consisting of potassium carbonate, sodium carbonate, rubidium carbonate and cesium carbonate and lithium carbonate is preferable. By mixing two or more carbonates, the melting temperature of the molten salt can be lowered, and the synthesis reaction can be performed at a low temperature of 400 to 650 ° C. *
また、混合物の溶融塩中において、４００～６５０℃という比較的低温で反応を行うことによって、結晶粒の成長が抑制され、平均粒径が５０ｎｍ～１０μｍという微細な粒子となり、更に、不純物相の量が大きく減少する。その結果、非水電解質二次電池の正極活物質として用いる場合に、良好なサイクル特性と高容量を有する材料となる。　 Further, by performing the reaction at a relatively low temperature of 400 to 650 ° C. in the molten salt of the mixture, the growth of crystal grains is suppressed, and the average particle diameter becomes fine particles of 50 nm to 10 μm. The amount is greatly reduced. As a result, when used as a positive electrode active material for a non-aqueous electrolyte secondary battery, the material has good cycle characteristics and high capacity. *
更に、炭酸カリウム、炭酸ナトリウム、炭酸ルビシウム及び炭酸セシウムからなる群から選ばれた少なくとも一種のアルカリ金属炭酸塩と炭酸リチウムとからなる炭酸塩混合物の溶融塩中で、Ｌｉ２ＳｉＯ３で表される珪酸リチウム化合物と、鉄及びマンガンからなる群から選ばれた少なくとも一種の前記金属元素を含む物質とを４００～６５０℃で反応させるとよい。　 Furthermore, in a molten salt of a carbonate mixture consisting of at least one alkali metal carbonate and lithium carbonate selected from the group consisting of potassium carbonate, sodium carbonate, rubidium carbonate and cesium carbonate, it is represented by Li 2 SiO 3. The lithium silicate compound may be reacted with a substance containing at least one metal element selected from the group consisting of iron and manganese at 400 to 650 ° C.
具体的な反応方法については特に限定的ではないが、例えば、上記した炭酸塩混合物、珪酸リチウム化合物及び金属元素（組成式中のＭ１に相当。以下、同様）を含む物質を混合し、ボールミル等を用いて均一に混合した後、加熱して炭酸塩混合物を溶融させればよい。これにより、溶融した炭酸塩中において、珪酸リチウム化合物と前記金属元素との反応が進行して、リチウムシリケート系化合物を得ることができる。　 The specific reaction method is not particularly limited. For example, the above-described carbonate mixture, lithium silicate compound, and a substance containing a metal element (corresponding to M 1 in the composition formula; the same shall apply hereinafter) are mixed to form a ball mill. Or the like, and then the carbonate mixture may be melted by heating. Thereby, in molten carbonate, reaction with a lithium silicate compound and the said metal element advances, and a lithium silicate type compound can be obtained.
この際、珪酸リチウム化合物と前記金属元素を含む物質からなる原料と、炭酸塩混合物との混合割合については特に限定的ではなく、炭酸塩混合物の溶融塩中において、原料を均一に分散できる量であればよく、例えば、炭酸塩混合物の合計量１００質量部に対して、溶融塩原料の合計量が２０～３００質量部の範囲となる量であることが好ましく、５０～２００質量部さらには６０～８０質量部の範囲となる量であることがより好ましい。　 At this time, the mixing ratio of the raw material composed of the lithium silicate compound and the metal element-containing material and the carbonate mixture is not particularly limited, and the amount of the raw material can be uniformly dispersed in the molten salt of the carbonate mixture. For example, the total amount of the molten salt raw material is preferably in the range of 20 to 300 parts by mass with respect to 100 parts by mass of the total amount of the carbonate mixture. The amount is more preferably in the range of ˜80 parts by mass. *
上記した反応は、反応時において、前記金属元素が２価イオンとして安定に存在するために、二酸化炭素及び還元性ガスを含む混合ガス雰囲気下で行う。この雰囲気下では、前記金属元素を２価の状態で安定に維持することが可能となる。二酸化炭素と還元性ガスの比率については、例えば、二酸化炭素１モルに対して還元性ガスを０．０１～０．５モルとすればよく、０．０３～０．４モルとすることが好ましい。還元性ガスとしては、例えば、水素、一酸化炭素などを用いることができ、水素が特に好ましい。　 The above-described reaction is performed in a mixed gas atmosphere containing carbon dioxide and a reducing gas because the metal element stably exists as a divalent ion during the reaction. Under this atmosphere, the metal element can be stably maintained in a divalent state. Regarding the ratio of carbon dioxide and reducing gas, for example, the reducing gas may be 0.01 to 0.5 mol, preferably 0.03 to 0.4 mol, per 1 mol of carbon dioxide. . As the reducing gas, for example, hydrogen, carbon monoxide and the like can be used, and hydrogen is particularly preferable. *
二酸化炭素と還元性ガスの混合ガスの圧力については、特に限定はなく、通常、大気圧とすればよいが、加圧下、或いは減圧下のいずれであっても良い。　 There is no particular limitation on the pressure of the mixed gas of carbon dioxide and reducing gas, and it may be usually atmospheric pressure, but it may be under pressure or under reduced pressure. *
珪酸リチウム化合物と前記金属元素を含む物質との反応時間は、通常、０．１～３０時間とすればよく、好ましくは５～２５時間とすればよい。　 The reaction time between the lithium silicate compound and the substance containing the metal element is usually 0.1 to 30 hours, preferably 5 to 25 hours. *
上記した反応を行った後、フラックスとして用いたアルカリ金属炭酸塩を除去することによって、目的とするリチウムシリケート系化合物を得ることができる。　 After the above reaction is performed, the target lithium silicate compound can be obtained by removing the alkali metal carbonate used as the flux. *
アルカリ金属炭酸塩を除去する方法としては、アルカリ金属炭酸塩を溶解できる溶媒を用いて、生成物を洗浄することによって、アルカリ金属炭酸塩を溶解除去すればよい。例えば、溶媒として、水を用いることも可能であるが、リチウムシリケート系化合物に含まれる遷移金属の酸化を防止するために、アルコール、アセトンなどの非水溶媒等を用いることが好ましい。特に、無水酢酸と酢酸とを質量比で２：１～１：１の割合で用いることが好ましい。この混合溶媒は、アルカリ金属炭酸塩を溶解除去する作用に優れていることに加えて、酢酸がアルカリ金属炭酸塩と反応して水が生成した場合に、無水酢酸が水を取り込んで酢酸を生じることによって、水が分離することを抑制できる。尚、無水酢酸と酢酸を用いる場合には、まず、無水酢酸を生成物に混合して、乳鉢等を用いてすりつぶして粒子を細かくした後、無水酢酸を粒子になじませた状態で酢酸を加えることが好ましい。この方法によれば、酢酸とアルカリ金属炭酸塩とが反応して生成した水が速やかに無水酢酸と反応して、生成物と水が触れ合う機会を低減できるので、目的物の酸化と分解を効果的に抑制することができる。　 As a method for removing the alkali metal carbonate, the alkali metal carbonate may be dissolved and removed by washing the product using a solvent capable of dissolving the alkali metal carbonate. For example, although water can be used as the solvent, it is preferable to use a nonaqueous solvent such as alcohol or acetone in order to prevent oxidation of the transition metal contained in the lithium silicate compound. In particular, it is preferable to use acetic anhydride and acetic acid in a mass ratio of 2: 1 to 1: 1. In addition to being excellent in the action of dissolving and removing the alkali metal carbonate, this mixed solvent, when acetic acid reacts with the alkali metal carbonate to produce water, acetic anhydride takes in the water and produces acetic acid. Therefore, it is possible to suppress the separation of water. When acetic anhydride and acetic acid are used, first, acetic anhydride is mixed with the product, ground with a mortar or the like to make particles fine, and then acetic anhydride is added in a state where acetic anhydride is intimately mixed with the particles. It is preferable. According to this method, since the water produced by the reaction of acetic acid and alkali metal carbonate reacts quickly with acetic anhydride, the chance of the product and water coming into contact with each other can be reduced. Can be suppressed. *
リチウムボレート系化合物としては、例えば、ＬｉＭ２ＢＯ３（Ｍ２は、Ｍｎ、Ｆｅ、Coの群から選ばれる少なくとも1種からなる。）が挙げられる。中でも、組成式：Ｌｉ１+ａ-ｂＡｂＭ２ １－ｘＭ’ｘＢＯ３+ｃ（式中、Ａは、Ｎａ、Ｋ、Ｒｂ及びＣｓからなる群から選ばれた少なくとも一種の元素であり、Ｍ２は、Ｆｅ及びＭｎ、Ｃｏからなる群から選ばれた少なくとも一種の元素であり、Ｍ’は、Ｍｇ、Ｃａ、Ａｌ、Ｎｉ、Ｎｂ、Ｍｏ、Ｗ、Ｔｉ及びＺｒからなる群から選ばれた少なくとも一種の元素である。各添字は次の通りである：０≦ｘ≦０．５、０＜ａ＜１、０≦ｂ＜０．２、０＜ｃ＜０．３であって、且つａ＞ｂである）で表される化合物であることが好ましい。この化合物は、例えば、炭酸カリウム、炭酸ナトリウム、炭酸ルビシウム及び炭酸セシウムからなる群から選ばれた少なくとも一種のアルカリ金属炭酸塩と炭酸リチウムとからなる炭酸塩混合物の溶融塩中で、還元性雰囲気下において、２価の鉄化合物及び２価のマンガン化合物からなる群から選ばれた少なくとも一種の化合物を含む２価の金属化合物、ホウ酸、並びに水酸化リチウムを４００～６５０℃で反応させることにより製造することができる。このように鉄化合物又はマンガン化合物を含む金属化合物、ホウ酸、及び水酸化リチウムを原料として用いて、炭酸リチウムとその他のアルカリ金属炭酸塩との混合物の溶融塩中で、還元性雰囲気下において、上記原料を反応させる方法によれば、比較的穏和な条件下において、鉄又はマンガンを含むリチウムボレート系化合物を得ることができる。そして、得られたリチウムボレート系化合物は、微細で不純物相が少なく、リチウム原子を過剰に含むボレート系化合物となり、リチウムイオン二次電池の正極活物質として用いる場合に、サイクル特性が良好で、高容量を有する材料となる。　 Examples of the lithium borate compound include LiM 2 BO 3 (M 2 is composed of at least one selected from the group consisting of Mn, Fe, and Co). Among them, composition formula: Li 1 + ab Ab M 2 1-x M ′ x BO 3 + c (wherein A is at least one element selected from the group consisting of Na, K, Rb and Cs) M 2 is at least one element selected from the group consisting of Fe, Mn, and Co, and M ′ is a group consisting of Mg, Ca, Al, Ni, Nb, Mo, W, Ti, and Zr. Each subscript is as follows: 0 ≦ x ≦ 0.5, 0 <a <1, 0 ≦ b <0.2, 0 <c <0.3 And a> b) is preferred. This compound is, for example, in a reducing atmosphere in a molten salt of a carbonate mixture comprising at least one alkali metal carbonate and lithium carbonate selected from the group consisting of potassium carbonate, sodium carbonate, rubidium carbonate and cesium carbonate. Produced by reacting a divalent metal compound containing at least one compound selected from the group consisting of a divalent iron compound and a divalent manganese compound, boric acid, and lithium hydroxide at 400 to 650 ° C. can do. In this way, using a metal compound containing an iron compound or a manganese compound, boric acid, and lithium hydroxide as raw materials, in a molten salt of a mixture of lithium carbonate and other alkali metal carbonate, in a reducing atmosphere, According to the method of reacting the raw materials, a lithium borate compound containing iron or manganese can be obtained under relatively mild conditions. The obtained lithium borate compound is a borate compound that is fine, has a small impurity phase, contains excessive lithium atoms, and has good cycle characteristics when used as a positive electrode active material of a lithium ion secondary battery. It becomes a material having a capacity.
リチウムホ
スフェート系化合物としては、ＬｉＭ３ＰＯ４（Ｍ３は、Ｍｎ、Ｆｅ、Ｃｏの群から選ばれる少なくとも1種からなる。）、Ｌｉ３Ｍ２（ＰＯ４）３（Ｍ＝Ｆｅ、Ｖ）、Ｌｉ２ＦｅＰ２Ｏ７、Ｌｉ２ＭｎＰ２Ｏ７、Ｌｉ２ＭＰＯ４Ｆ（Ｍ＝Ｆｅ、Ｍｎ、Ｃｏ、Ｎｉ）などが挙げられる。中でも、ＬｉＭｎＰＯ４、ＬｉＦｅＰＯ４、ＬｉＣｏＰＯ４が好ましい。　 Examples of the lithium phosphate compound include LiM 3 PO 4 (M 3 is at least one selected from the group consisting of Mn, Fe, and Co), Li 3 M 2 (PO 4 ) 3 (M = Fe, V). , Li 2 FeP 2 O 7 , Li 2 MnP 2 O 7 , Li 2 MPO 4 F (M = Fe, Mn, Co, Ni) and the like. Among these, LiMnPO 4 , LiFePO 4 , and LiCoPO 4 are preferable.
エネルギー付与工程で用いられる導電性材料は、例えば、炭素材料からなる。炭素材料は、アセチレンブラック（ＡＢ）、ケッチェンブラック（ＫＢ）、カーボンブラック、カーボンナノチューブ、グラフェーン、カーボン繊維、黒鉛等を用いることができ、中でも、比表面積が高い理由から、アセチレンブラック（ＡＢ）、ケッチェンブラック（ＫＢ）、カーボンブラックであるとよい。　 The conductive material used in the energy application step is made of, for example, a carbon material. As the carbon material, acetylene black (AB), ketjen black (KB), carbon black, carbon nanotube, graphene, carbon fiber, graphite and the like can be used. Among them, acetylene black (AB) is preferred because of its high specific surface area. Ketjen black (KB) and carbon black are preferred. *
エネルギー付与工程で用いる活物質材料の平均粒径は２００ｎｍ以上５μｍ以下であるとよく、また、導電性材料の平均粒径は１００ｎｍ以上５μｍ以下であるとよい。この場合には、エネルギー付与工程で活物質材料と導電性材料とに機械的エネルギーを付与することで、平均粒径が１００ｎｍ以下の活物質粒子と、平均粒径が１００ｎｍ以下である導電性粒子とが接合してなる活物質複合体を容易に得ることができる。　 The average particle diameter of the active material used in the energy application step is preferably 200 nm to 5 μm, and the average particle diameter of the conductive material is preferably 100 nm to 5 μm. In this case, active material particles having an average particle size of 100 nm or less and conductive particles having an average particle size of 100 nm or less by applying mechanical energy to the active material and the conductive material in the energy application step. Can be easily obtained. *
エネルギー付与工程は、ミリングにより機械的エネルギーを付与する工程であるとよい。これにより、活物質材料及び導電性材料に均一に機械的エネルギーを付与することができる。ミリング方法に特に限定はないが、硬質のボールを試料とともに容器に収容した状態で外力によって容器を運動させることにより機械的エネルギーを導入するボールミリングが好適である。ボールミリング装置としては、自転および公転により試料にエネルギーを与える遊星型、水平方向または垂直方向などへの振動により試料にエネルギーを与える振動型、のいずれも採用できる。　 The energy application step may be a step of applying mechanical energy by milling. Thereby, mechanical energy can be uniformly given to the active material and the conductive material. Although there is no particular limitation on the milling method, ball milling in which mechanical energy is introduced by moving the container by an external force in a state where a hard ball is accommodated in the container together with the sample is preferable. As the ball milling device, any of a planetary type that gives energy to the sample by rotation and revolution and a vibration type that gives energy to the sample by vibration in the horizontal direction or the vertical direction can be adopted. *
エネルギー付与工程では、活物質材料と導電性材料とをボールミルで比較的高速で回転させることにより行うとよい。メカニカルミリング装置（フリッチュ・ジャパン株式会社製、遊星型ボールミルＰ－７シリーズ）を用いた場合、ボールミルの回転数は、７００ｒｐｍを超えて大きく、１１００ｒｐｍ以下であることがよい。この場合には、活物質粒子及び導電性粒子が共に平均粒径が１００ｎｍ以下で均一に分散混合されアモルファス化されて複合化することができる。７００ｒｐｍ未満の場合には、活物質粒子及び導電性粒子の平均粒径が１００ｎｍを超えて大きくなるおそれがある。１１００ｒｐｍを超える場合には、不純物の混入の増大のおそれがある。　 In the energy application step, the active material and the conductive material may be rotated by a ball mill at a relatively high speed. When a mechanical milling device (Fritch Japan Co., Ltd., planetary ball mill P-7 series) is used, the rotational speed of the ball mill is preferably greater than 700 rpm and less than 1100 rpm. In this case, both the active material particles and the conductive particles can be uniformly dispersed and mixed with an average particle size of 100 nm or less to be amorphized and combined. When it is less than 700 rpm, the average particle diameter of the active material particles and the conductive particles may be larger than 100 nm. If it exceeds 1100 rpm, there is a risk of increased contamination of impurities. *
更に、ボールミルの回転数は、７５０ｒｐｍ以上１０００ｒｐｍ未満であることが好ましい。この場合には、活物質粒子及び導電性粒子が更に均一に分散混合することができる。　 Furthermore, it is preferable that the rotation speed of a ball mill is 750 rpm or more and less than 1000 rpm. In this case, the active material particles and the conductive particles can be more uniformly dispersed and mixed. *
ミリング条件を敢えて規定するのであれば、ＣｕＫα線を光源とするＸ線回折測定において、ミリング前の結晶性を有するリチウムシリケート系化合物前駆体を含む試料についての（１１１）面由来の回折ピーク（２θ＝２３°～２６°に検出）の半値幅をＢ（１１１）ｃｒｙｓｔａｌ、ミリング後の試料の同ピークの半値幅をＢ（１１１）ｍｉｌｌとした場合にＢ（１１１）ｃｒｙｓｔａｌ／Ｂ（１１１）ｍｉｌｌの比が０．７～１．１、さらには０．８～１．０の範囲であるのが望ましい。　 If the milling conditions are daringly specified, in the X-ray diffraction measurement using CuKα rays as a light source, a diffraction peak derived from the (111) plane (2θ) for a sample containing a lithium silicate compound precursor having crystallinity before milling. (Detected at 23 ° to 26 °) is B (111) crystal, and when the half width of the same peak of the sample after milling is B (111) mill, B (111) crystal / B (111) mill The ratio is preferably in the range of 0.7 to 1.1, more preferably 0.8 to 1.0. *
活物質材料がリチウムシリケート系化合物である場合には、エネルギー付与工程の際に、リチウムシリケート系化合物に、導電性材料だけでなくＬｉ２ＣＯ３も加えて、ボールミルによってリチウムシリケート系化合物がアモルファス化するまで均一に混合するとよい。Ｌｉ２ＣＯ３が存在することにより、リチウムシリケート系化合物のリチウム欠損が抑えられ、高い充放電容量を示すものとなる。　 When the active material is a lithium silicate compound, in addition to the lithium silicate compound, in addition to the conductive material, Li 2 CO 3 is added to the lithium silicate compound, and the lithium silicate compound is made amorphous by ball milling. Mix evenly until By the presence of Li 2 CO 3 , lithium deficiency of the lithium silicate compound is suppressed, and a high charge / discharge capacity is exhibited.
エネルギー付与工程では、不活性ガス雰囲気（アルゴンガス、窒素ガス）あるいは大気雰囲気下で活物質材料と導電性材料とを混合することができる。　 In the energy application step, the active material and the conductive material can be mixed in an inert gas atmosphere (argon gas, nitrogen gas) or in an air atmosphere. *
活物質材料がリチウムシリケート系化合物である場合、リチウムシリケート系化合物と導電性材料との混合割合については、リチウムシリケート系化合物１００質量部に対して、炭素材料を５～５０質量部とすればよい。　 When the active material is a lithium silicate compound, the mixing ratio of the lithium silicate compound and the conductive material may be 5 to 50 parts by mass of the carbon material with respect to 100 parts by mass of the lithium silicate compound. . *
エネルギー付与工程の後には、機械的エネルギーが付与された活物質材料と導電性材料の混合物に熱処理を行う熱処理工程を行うとよい。熱処理工程では、混合された活物質材料と導電性材料とを所定の温度で加熱する。熱処理により、活物質材料の再結晶化とともに焼結することで粒子同士が密着することにより導電性が向上する。　 After the energy application step, a heat treatment step may be performed in which heat treatment is performed on the mixture of the active material and the conductive material to which mechanical energy is applied. In the heat treatment step, the mixed active material and conductive material are heated at a predetermined temperature. By heat treatment and sintering together with recrystallization of the active material, the particles are brought into close contact with each other to improve conductivity. *
熱処理温度は、５００～８００℃とすることが好ましい。熱処理温度が低すぎる場合には、リチウムシリケート系化合物の周りに炭素を均一に析出させることが難しく、一方、熱処理温度が高すぎると、リチウムシリケート系化合物の分解やリチウム欠損が生じることがあり、充放電容量が低下するので好ましくない。また、熱処理時間は、通常、１～１０時間とすればよい。　 The heat treatment temperature is preferably 500 to 800 ° C. If the heat treatment temperature is too low, it is difficult to deposit carbon uniformly around the lithium silicate compound, while if the heat treatment temperature is too high, decomposition of the lithium silicate compound and lithium deficiency may occur. This is not preferable because the charge / discharge capacity decreases. The heat treatment time is usually 1 to 10 hours. *
活物質材料がリチウムシリケート系化合物である場合、熱処理は、リチウムシリケート系化合物に含まれる遷移金属イオンを２価に保持するために、還元性雰囲気下で行うとよい。この場合の還元性雰囲気としては、溶融塩中でのリチウムシリケート系化合物の合成反応と同様に、２価の遷移金属イオンが金属状態まで還元されることを抑制するために、二酸化炭素と還元性ガスの混合ガス雰囲気中であることが好ましい。二酸化炭素と還元性ガスの混合割合は、リチウムシリケート系化合物の合成反応時と同様とすればよい。　 When the active material is a lithium silicate compound, the heat treatment is preferably performed in a reducing atmosphere in order to keep the transition metal ions contained in the lithium silicate compound divalent. As the reducing atmosphere in this case, in order to suppress the reduction of the divalent transition metal ion to the metal state, as in the synthesis reaction of the lithium silicate compound in the molten salt, the reducing atmosphere is reduced with carbon dioxide. A gas mixed gas atmosphere is preferred. The mixing ratio of carbon dioxide and reducing gas may be the same as in the synthesis reaction of the lithium silicate compound. *
活物質材料がリチウムボレート系化合物である場合、熱処理は、二酸化炭素と還元性ガスの混合雰囲気下で行うとよい。その理由は、リチウムボレート系化合物の分解が抑制されるからである。　 When the active material is a lithium borate compound, the heat treatment is preferably performed in a mixed atmosphere of carbon dioxide and a reducing gas. The reason is that decomposition of the lithium borate compound is suppressed. *
活物質材料がリチウムホスフェート系化合物である場合、熱処理は、二酸化炭素と還元性ガスの混合雰囲気下あるいは不活性ガス雰囲気下で行うとよい。その理由は、リチウムホスフェート系化合物の分解が抑制できるからである。　 When the active material is a lithium phosphate compound, the heat treatment is preferably performed in a mixed atmosphere of carbon dioxide and a reducing gas or in an inert gas atmosphere. The reason is that decomposition of the lithium phosphate compound can be suppressed. *
（３）非水電解質二次電池用正極活物質　非水電解質二次電池用正極活物質は、上記の活物質複合体からなる。かかる非水電解質二次電池正極用活物質によれば、充放電特性に優れた電池を構成することができる。　 (3) Positive electrode active material for nonaqueous electrolyte secondary battery The positive electrode active material for nonaqueous electrolyte secondary battery is composed of the above active material composite. According to such a non-aqueous electrolyte secondary battery positive electrode active material, a battery having excellent charge / discharge characteristics can be configured. *
（４）非水電解質二次電池用正極　非水電解質二次電池用正極は、上記非水電解質二次電池用正極活物質と、集電体とからなる。非水電解質二次電池用正極は、上記の活物質複合体からなる正極活物質を有しており、通常の非水電解質二次電池用正極と同様の構造とすることができる。　 (4) Positive electrode for nonaqueous electrolyte secondary battery The positive electrode for nonaqueous electrolyte secondary battery is composed of the positive electrode active material for nonaqueous electrolyte secondary battery and a current collector. The positive electrode for a nonaqueous electrolyte secondary battery has a positive electrode active material made of the above active material composite, and can have the same structure as a normal positive electrode for a nonaqueous electrolyte secondary battery. *
例えば、上記活物質複合体に、アセチレンブラック（ＡＢ）、ケッチェンブラック（ＫＢ）、気相法炭素繊維（Ｖａｐｏｒ Ｇｒｏｗｎ Ｃａｒｂｏｎ Ｆｉｂｅｒ：ＶＧＣＦ）等の導電助剤、ポリフッ化ビニリデン（ＰｏｌｙＶｉｎｙｌｉｄｉｎｅＤｉＦｌｕｏｒｉｄｅ：ＰＶｄＦ）、ポリ四フッ化エチレン（ＰＴＦＥ）、スチレン-ブタジエンゴム（ＳＢＲ）等のバインダー、Ｎ-メチル-2-ピロリドン（ＮＭＰ）等の溶媒を加えてペースト状として、これを集電体に塗布することによって正極を作製することができる。導電助剤の使用量については、特に限定的ではないが、例えば、活物質複合体１００質量部に対して、５～２０質量部とすることができる。また、バインダーの使用量についても、特に限定的ではないが、例えば、活物質複合体１００質量部に対して、５～２０質量部とすることができる。また、その他の方法として、活物質複合体と、上記の導電助剤およびバインダーを混合したものを、乳鉢やプレス機を用いて混練してフィルム状とし、これを集電体へプレス機で圧着する方法によっても正極を製造することが出来る。　 For example, the active material composite may include acetylene black (AB), ketjen black (KB), a conductive additive such as vapor grown carbon fiber (Vapor Grown Carbon Fiber: VGCF), polyvinylidene fluoride (Polyvinylidene Fluoride: PVdF), By adding a binder such as polytetrafluoroethylene (PTFE) and styrene-butadiene rubber (SBR) and a solvent such as N-methyl-2-pyrrolidone (NMP) to form a paste and applying it to the current collector A positive electrode can be produced. The amount of the conductive aid used is not particularly limited, but can be 5 to 20 parts by mass with respect to 100 parts by mass of the active material composite, for example. Further, the amount of the binder used is not particularly limited, but may be 5 to 20 parts by mass with respect to 100 parts by mass of the active material composite, for example. In addition, as another method, a mixture of the active material composite, the conductive aid and the binder described above is kneaded using a mortar or a press to form a film, and this is crimped to the current collector with a press. The positive electrode can be manufactured also by the method to do. *
集電体としては、特に限定はなく、従来から非水電解質二次電池用正極として使用されている材料、例えば、アルミ箔、アルミメッシュ、ステンレスメッシュなどを用いることができる。更に、カーボン不織布、カーボン織布なども集電体として使用できる。　 The current collector is not particularly limited, and materials conventionally used as positive electrodes for nonaqueous electrolyte secondary batteries, such as aluminum foil, aluminum mesh, and stainless steel mesh, can be used. Furthermore, a carbon nonwoven fabric, a carbon woven fabric, etc. can be used as a collector. *
非水電解質二次電池用正極は、その形状、厚さなどについては特に限定的ではないが、例えば、活物質を充填した後、圧縮することによって、厚さを１０～２００μｍ、より好ましくは２０～１００μｍとすることが好ましい。従って、使用する集電体の種類、構造等に応じて、圧縮後に上記した厚さとなるように、活物質の充填量を適宜決めればよい。　 The shape and thickness of the positive electrode for a nonaqueous electrolyte secondary battery is not particularly limited. For example, the positive electrode for a nonaqueous electrolyte secondary battery is filled with an active material and then compressed to have a thickness of 10 to 200 μm, more preferably 20 μm. It is preferable that the thickness is 100 μm. Therefore, the filling amount of the active material may be appropriately determined so as to have the above-described thickness after compression according to the type and structure of the current collector to be used. *
（５）非水電解質二次電池　非水電解質二次電池は、上記した非水電解質二次電池用正極を備えている。非水電解質二次電池は、公知の手法により製造することができる。正極材料として、上記した正極を使用する。負極材料として、リチウムイオンを吸蔵・放出可能であってリチウムと合金化可能な元素又は／及びリチウムと合金化可能な元素を有する元素化合物からなる。前記リチウムと合金化反応可能な元素は、Ｎａ、Ｋ、Ｒｂ、Ｃｓ、Ｆｒ、Ｂｅ、Ｍｇ、Ｃａ、Ｓｒ、Ｂａ、Ｒａ、Ｔｉ、Ａｇ、Ｚｎ、Ｃｄ、Ａｌ、Ｇａ、Ｉｎ、Ｓｉ、Ｇｅ、Ｓｎ、Ｐｂ、Ｓｂ、Ｂｉの少なくとも１種を有するとよい。負極材料としては、例えば、公知の金属リチウム、黒鉛などの炭素系材料、ＳｉＯｘ（０．５≦ｘ≦１．５）などのシリコン系材料、銅－錫やコバルト－錫などの合金系材料、チタン酸リチウムなどの酸化物材料を使用するとよい。　 (5) Nonaqueous electrolyte secondary battery The nonaqueous electrolyte secondary battery includes the above-described positive electrode for a nonaqueous electrolyte secondary battery. The nonaqueous electrolyte secondary battery can be manufactured by a known method. The positive electrode described above is used as the positive electrode material. The negative electrode material is composed of an element compound that can occlude and release lithium ions and can be alloyed with lithium or / and an element compound that can be alloyed with lithium. Elements capable of alloying with lithium are Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Ti, Ag, Zn, Cd, Al, Ga, In, Si, Ge. , Sn, Pb, Sb, Bi may be included. Examples of the negative electrode material include known metal-based materials such as lithium metal and graphite, silicon-based materials such as SiOx (0.5 ≦ x ≦ 1.5), alloy-based materials such as copper-tin and cobalt-tin, An oxide material such as lithium titanate is preferably used. *
電解液として、公知のエチレンカーボネート、ジメチルカーボネート、プロピレンカーボネート、ジメチルカーボネートなどの非水系溶媒に過塩素酸リチウム、ＬｉＰＦ６、ＬｉＢＦ４、ＬｉＣＦ３ＳＯ３などのリチウム塩を０．５ｍｏｌ/Ｌから１．７ｍｏｌ/Ｌの濃度で溶解させた溶液を使用し、さらにその他の公知の電池構成要素を使用するとよい。　 As an electrolytic solution, a lithium salt such as lithium perchlorate, LiPF 6 , LiBF 4 , LiCF 3 SO 3 or the like is added to a known non-aqueous solvent such as ethylene carbonate, dimethyl carbonate, propylene carbonate, dimethyl carbonate to 0.5 mol / L to 1 A solution dissolved at a concentration of 7 mol / L may be used, and other known battery components may be used.
負極として金属リチウムを用いた場合にはリチウム二次電池、負極として金属リチウム以外の材料を用いた場合にはリチウムイオン二次電池となる。これらのリチウムイオンにより電池反応を行う二次電池は、一般に、非水電解質二次電池のものが多い。　 When metal lithium is used as the negative electrode, a lithium secondary battery is obtained, and when a material other than metal lithium is used as the negative electrode, a lithium ion secondary battery is obtained. In general, many secondary batteries that perform a battery reaction with these lithium ions are non-aqueous electrolyte secondary batteries. *
（６）車両など　上記非水電解質二次電池は、車両に搭載することができる。車両は、電気車両又はハイブリッド車両などであるとよい。非水電解質二次電池は、例えば、車両に搭載された走行用モータに連結されていて、駆動源として用いられているとよい。この場合には、長時間高い駆動トルクを出力させることができる。また、上記非水電解質二次電池は、パーソナルコンピュータ、携帯通信機器などの、車両以外のものにも搭載することができる。　 (6) Vehicle etc. The non-aqueous electrolyte secondary battery can be mounted on a vehicle. The vehicle may be an electric vehicle or a hybrid vehicle. The nonaqueous electrolyte secondary battery is preferably connected to, for example, a traveling motor mounted on a vehicle and used as a drive source. In this case, a high driving torque can be output for a long time. Further, the non-aqueous electrolyte secondary battery can be mounted on devices other than vehicles such as personal computers and portable communication devices. *
以上、本発明の実施形態を説明したが、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。 As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment. The present invention can be implemented in various forms without departing from the gist of the present invention, with modifications and improvements that can be made by those skilled in the art.
＜活物質複合体の製造（１）＞　以下の方法により、試料１～５の活物質複合体を製造した。試料１～５の活物質複合体は、Ｌｉ２ＦｅＳｉＯ４とカーボンとからなる。　 <Manufacture of Active Material Complex (1)> The active material complexes of Samples 1 to 5 were manufactured by the following method. The active material composites of Samples 1 to 5 are composed of Li 2 FeSiO 4 and carbon.
鉄（高純度化学株式会社製、純度９９．９％）０．０３モルと、リチウムシリケート系化合物Ｌｉ２ＳｉＯ３（キシダ化学株式会社製、純度９９．５％）０．０３モルと、の混合物にアセトン２０ｍｌを加えてジルコニア製ボールミルにて５００ｒｐｍで６０分混合し、乾燥した。これを炭酸塩混合物（炭酸リチウム（キシダ化学製、純度９９．９％）、炭酸ナトリウム（キシダ化学製、純度９９．５％）、及び炭酸カリウム（キシダ化学製、純度99.5%）をモル比０．４３５:０．３１５:０．２５で混合した。混合割合は、鉄とリチウムシリケートとの合計量を１００質量部に対して、炭酸塩混合物８０
質量部とした。これにアセトン２０ｍｌを加えてジルコニア製ボールミルにて５００ｒｐｍで６０分混合し、乾燥した。　 A mixture of 0.03 mol of iron (purity 99.9%, manufactured by High Purity Chemical Co., Ltd.) and 0.03 mol of lithium silicate compound Li 2 SiO 3 (Kishida Chemical Co., Ltd., purity 99.5%) Acetone (20 ml) was added to the mixture, and mixed with a zirconia ball mill at 500 rpm for 60 minutes and dried. This was mixed with a carbonate mixture (lithium carbonate (manufactured by Kishida Chemical, purity 99.9%), sodium carbonate (manufactured by Kishida Chemical, purity 99.5%), and potassium carbonate (manufactured by Kishida Chemical, purity 99.5%) in a molar ratio of 0. 435: 0.315: 0.25, and the mixing ratio is 100 parts by mass of the total amount of iron and lithium silicate.
It was set as the mass part. Acetone (20 ml) was added thereto, mixed in a zirconia ball mill at 500 rpm for 60 minutes, and dried.
その後、得られた粉体を金坩堝中で加熱して、二酸化炭素（流量：１００ｍｌｍｉｎ-1）と水素（流量：３ｍｌｍｉｎ-1）の混合ガス雰囲気下で、５００℃に加熱して、炭酸塩混合物を溶融させた状態で１３時間反応させた。反応後、温度を下げ４００℃になった時点で反応系である炉心全体を、加熱器である電気炉から取り出して、ガスを通じたまま室温まで急冷した。　 Thereafter, the obtained powder was heated in a gold crucible and heated to 500 ° C. in a mixed gas atmosphere of carbon dioxide (flow rate: 100 ml min-1) and hydrogen (flow rate: 3 ml min-1) to form carbonate. The mixture was allowed to react for 13 hours in the molten state. After the reaction, when the temperature was lowered to 400 ° C., the entire reactor core was taken out from the electric furnace, which was a heater, and rapidly cooled to room temperature through the gas. *
次いで、得られた反応物に水（２０ｍｌ）を加えて乳鉢ですりつぶし、塩等を取り除くために水に溶解させてからろ過した粉体を得た。この粉体を１００℃の乾燥機に入れて１時間程度乾燥した。その後、粉末Ｘ線回折（ＸＲＤ）により結晶構造を確認した結果、ほぼ単相のＬｉ２ＦｅＳｉＯ４が得られたことがわかった。Ｌｉ２ＦｅＳｉＯ４からなる活物質粒子の平均粒径は、０．５μｍであった。　 Next, water (20 ml) was added to the obtained reaction product and ground in a mortar, and dissolved in water to remove salts and the like, and then a filtered powder was obtained. This powder was put into a dryer at 100 ° C. and dried for about 1 hour. Thereafter, as a result of confirming the crystal structure by powder X-ray diffraction (XRD), it was found that substantially single-phase Li 2 FeSiO 4 was obtained. The average particle diameter of the active material particles made of Li 2 FeSiO 4 was 0.5 μm.
得られた活物質粒子とアセチレンブラック（ＡＢ、平均粒径０．３μｍ）とを質量比５：４で混合し、メカニカルミリング装置（フリッチュ・ジャパン株式会社製、遊星型ボールミルＰ－７）を用い、大気雰囲気下において下記の所定の条件でメカニカルミリング処理を行い、混合物に対して機械的エネルギーを付与した。本工程は、ジルコニア製で容積４５ｃｃのボールミル用粉砕容器に、φ４ｍｍジルコニア製ボールを５０ｇおよび混合物を３００ｍｇを入れて行った。　 The obtained active material particles and acetylene black (AB, average particle size 0.3 μm) were mixed at a mass ratio of 5: 4, and a mechanical milling device (French Japan Co., Ltd., planetary ball mill P-7) was used. Then, mechanical milling treatment was performed under the following predetermined conditions in an air atmosphere to give mechanical energy to the mixture. This step was performed by putting 50 g of φ4 mm zirconia balls and 300 mg of the mixture in a ball mill grinding container made of zirconia and having a volume of 45 cc. *
得られた粉体とＡＢとを混合する際に、ボールミルの回転数を８００ｒｐｍ、回転時間を５時間とした場合に得られた材料を試料１とした。ボールミルの回転数を７００ｒｐｍ、回転時間を５時間とした場合に得られた材料を試料２とした。ボールミルの回転数を４５０ｒｐｍ、回転時間を５時間とした場合に得られた材料を試料３とした。ボールミルの回転数を２００ｒｐｍ、回転時間を５時間とした場合に得られた材料を試料４とした。Ｌｉ２ＦｅＳｉＯ４とカーボンとを混合する際に、手で乳鉢を用いて30分間混合して得られた材料を試料５とした。各試料とも、熱処理を行った。熱処理条件は、７００℃、２時間、ＣＯ２／Ｈ２=１００／３ｃｃｍ（二酸化炭素（流量１００ｍＬ／分）と水素（流量３ｍＬ／分）の混合ガス）の雰囲気とした。　 When mixing the obtained powder and AB, the material obtained when the rotation speed of the ball mill was 800 rpm and the rotation time was 5 hours was designated as Sample 1. The material obtained when the rotation speed of the ball mill was 700 rpm and the rotation time was 5 hours was designated as Sample 2. The material obtained when the rotation speed of the ball mill was 450 rpm and the rotation time was 5 hours was designated as Sample 3. The material obtained when the rotation speed of the ball mill was 200 rpm and the rotation time was 5 hours was designated as Sample 4. Sample 5 was obtained by mixing Li 2 FeSiO 4 and carbon by hand using a mortar for 30 minutes. Each sample was heat-treated. The heat treatment conditions were 700 ° C., 2 hours, and an atmosphere of CO 2 / H 2 = 100/3 ccm (mixed gas of carbon dioxide (flow rate 100 mL / min) and hydrogen (flow rate 3 mL / min)).
（ＳＥＭ観察）　試料１～５について、ＳＥＭ（走査型電子顕微鏡）での観察を行なった。試料１の材料のＳＥＭ写真を、図１、図２に示した。試料２の活物質複合体のＳＥＭ写真を、図７に示した。試料３の活物質複合体のＳＥＭ写真を、図８～図１０に示した。試料５の活物質複合体のＳＥＭ写真を、図１１に示した。これらの図面のうち、図１，図２，図７，図８，図９は、各倍率で撮影した材料のＳＥＭ断面写真であり、図５，図１０，図１１は、粒子の表面を撮影したＳＥＭ写真である。　 (SEM Observation) Samples 1 to 5 were observed with a SEM (scanning electron microscope). SEM photographs of the material of Sample 1 are shown in FIGS. A SEM photograph of the active material composite of Sample 2 is shown in FIG. SEM photographs of the active material composite of Sample 3 are shown in FIGS. An SEM photograph of the active material composite of Sample 5 is shown in FIG. Among these drawings, FIGS. 1, 2, 7, 8, and 9 are SEM cross-sectional photographs of materials taken at various magnifications, and FIGS. 5, 10, and 11 are images of the surface of particles. It is the SEM photograph which was done. *
試料１では、図１、図２に示すように、長径２０μｍ程度の比較的大きい大型粒子と、粒径１～４μｍ程度の微細な粒子とが混在していた。図1の下図及び図２に示すように、大型粒子の内部では、多数の微細な粒子が均一に分散していた。即ち、大型粒子は、微細な一次粒子が複合化して二次粒子となったものである。またＢＥＴ法を用いた比表面積測定の結果、この複合体は171.7ｍ２/gという高い値を示した。　 In Sample 1, as shown in FIGS. 1 and 2, relatively large large particles having a major axis of about 20 μm and fine particles having a particle size of about 1 to 4 μm were mixed. As shown in the lower diagram of FIG. 1 and FIG. 2, a large number of fine particles were uniformly dispersed inside the large particles. That is, the large particles are those in which fine primary particles are combined into secondary particles. As a result of measuring the specific surface area using the BET method, the composite showed a high value of 171.7 m 2 / g.
図３の上段左の写真は、試料１の大型の二次粒子の環状暗視野走査透過型電子顕微鏡（ＡＤＦ－ＳＴＥＭ）像を示し、上段中、上段右、下段左、下段中は、順に、二次粒子のエネルギー分散型X線分析装置（ＥＤＸ）による、酸素（Ｏ）、炭素（Ｃ）、鉄（Ｆｅ）、珪素（Ｓｉ）のマッピングを示す。図３の各図では、中央から左側にわたる部分が二次粒子の存在部位であり、右側下部が二次粒子の存在していない部位である。図３より、Ｏ、Ｃ、Ｆｅ、Ｓｉは、二次粒子の存在部位に均一に分散していた。このことから、二次粒子は、Ｏ、Ｃ、Ｆｅ、Ｓｉを構成元素として含むことがわかった。Ｃについては、二次粒子外部にも存在していた。　 The upper left photograph of FIG. 3 shows an annular dark field scanning transmission electron microscope (ADF-STEM) image of the large secondary particles of Sample 1. In the upper stage, the upper stage right, the lower stage left, and the lower stage in order, The mapping of oxygen (O), carbon (C), iron (Fe), and silicon (Si) by an energy dispersive X-ray analyzer (EDX) of secondary particles is shown. In each figure of FIG. 3, the part extending from the center to the left is the site where the secondary particles are present, and the lower right part is the site where the secondary particles are not present. As shown in FIG. 3, O, C, Fe, and Si were uniformly dispersed in the site where the secondary particles were present. From this, it was found that the secondary particles contain O, C, Fe, and Si as constituent elements. C was also present outside the secondary particles. *
図４の左上側に位置する写真は、試料１の二次粒子の透過型電子顕微鏡（ＴＥＭ）写真である。この写真から、二次粒子の内部は、複数の一次粒子の集合体であることがわかる。図４の左下側に位置する写真は、左上側のＴＥＭ写真の二次粒子の円形の黒色囲み部分についての電子線回折を撮影した写真である。同図より、回折線がハロー状のパターンになっていることから、二次粒子が多数の粒子から構成されていて、各粒子のサイズが小さいことがわかる。この電子線回折の結果を分析したところ、Ｌｉ２ＦｅＳｉＯ４の構造が確認され、二次粒子には、Ｌｉ２ＦｅＳｉＯ４が含まれていることがわかった。　 The photograph located on the upper left side of FIG. 4 is a transmission electron microscope (TEM) photograph of the secondary particles of Sample 1. From this photograph, it can be seen that the inside of the secondary particles is an aggregate of a plurality of primary particles. The photograph located on the lower left side of FIG. 4 is a photograph obtained by photographing electron diffraction on the circular black box portion of the secondary particles in the upper left TEM photograph. From the figure, since the diffraction line has a halo pattern, it can be seen that the secondary particles are composed of a large number of particles and the size of each particle is small. When the result of this electron beam diffraction was analyzed, the structure of Li 2 FeSiO 4 was confirmed, and it was found that the secondary particles contained Li 2 FeSiO 4 .
図４の中央部分には、電子エネルギー損失分光法（ＥＥＬＳ）を用いた元素マッピングであって、図４の左側の写真に付した横長の四角形の白色囲み部分の各種元素のマッピングを示す。図４の中央部分の上側から下側に向けて順に、炭素（Ｃ）、酸素（Ｏ）、珪素（Ｓｉ）、鉄（Ｆｅ）のマッピングである。同図より、二次粒子の存在している部分には、Ｃ，Ｏ、Ｓｉ、Ｆｅの全てが均一に分散していた。Ｃについては、二次粒子の存在していない部分（各写真の右上部分）にも存在していた。この結果は、図３のＥＤＸによる元素マッピングと同様であった。　 In the central part of FIG. 4, element mapping using electron energy loss spectroscopy (EELS) is shown, and mapping of various elements in the horizontally-enclosed square white box attached to the photograph on the left side of FIG. 4 is shown. FIG. 5 is a mapping of carbon (C), oxygen (O), silicon (Si), and iron (Fe) in order from the upper side to the lower side of the central portion of FIG. From the figure, all of C, O, Si, and Fe were uniformly dispersed in the portion where the secondary particles were present. About C, it existed also in the part (the upper right part of each photograph) in which secondary particles do not exist. This result was similar to the element mapping by EDX in FIG. *
図４の右側には、図４の中央部分に示した各元素のマッピングを、重ね合わせた混合イメージを示した。同図において、濃色部分が炭素（Ｃ）を示し、薄色部分がＦｅ、Ｓｉ、Ｏを示す。図４の左下側に示す電子線回折結果から、二次粒子にＬｉ２ＦｅＳｉＯ４が含まれていることがわかったので、薄色部分のＦｅ、Ｓｉ、ＯはＬｉ２ＦｅＳｉＯ４を構成する元素である。この図から、二次粒子の内部では、炭素の中にＬｉ２ＦｅＳｉＯ４が均一に分散して複合化されて、活物質複合体を形成していることがわかった。図４の右側の混合イメージ図と左上側のＴＥＭとを照らし合わせると、混合イメージでＬｉ２ＦｅＳｉＯ４が存在する薄色部分が、ＴＥＭの白色又は薄い灰色の部分に相当し、混合イメージでＣが存在する濃色部分が、ＴＥＭの濃い灰色又は黒色の部分に相当する。　 The right side of FIG. 4 shows a mixed image in which the mapping of each element shown in the central part of FIG. 4 is overlaid. In the figure, the dark color portion indicates carbon (C), and the light color portion indicates Fe, Si, and O. From the electron diffraction results shown in the lower left side of FIG. 4, since it was found that the secondary particles contain Li 2 FeSiO 4 , Fe, Si, and O in the light-colored portion are elements constituting Li 2 FeSiO 4 It is. From this figure, it was found that in the secondary particles, Li 2 FeSiO 4 was uniformly dispersed and compounded in carbon to form an active material complex. When the mixed image diagram on the right side of FIG. 4 is compared with the TEM on the upper left side, the light color portion where Li 2 FeSiO 4 exists in the mixed image corresponds to the white or light gray portion of the TEM, and C in the mixed image. The existing dark color portion corresponds to the dark gray or black portion of the TEM.
上記の図４のＥＥＬＳ法による分析を活物質複合体（二次粒子）の表面近傍だけでなく内部まで行ったところ、厚み１μｍ程度の表面層でのＣ－Ｏの存在比率が、内部でのＣ－Ｏの存在比率よりも高いことがわかった。この理由は、高速回転による高エネルギー付与によりＬｉ２ＦｅＳｉＯ４と炭素とが微細化、混合された後にこれらが造粒され互いに接合することで均一に複合化されて活物質複合体を形成し、その後に、活物質複合体の表面に更に微細化された炭素が進入したものと考えられる。また、表面層で酸素が多いのは、大気雰囲気でミリング処理したためであると考えられる。　 When the analysis by the EELS method shown in FIG. 4 was performed not only in the vicinity of the surface of the active material composite (secondary particles) but also in the interior, the abundance ratio of CO in the surface layer having a thickness of about 1 μm It was found to be higher than the abundance ratio of CO. The reason for this is that Li 2 FeSiO 4 and carbon are refined and mixed by applying high energy by high-speed rotation, and then they are granulated and bonded together to form an active material composite. After that, it is considered that further refined carbon entered the surface of the active material composite. The reason why the surface layer is rich in oxygen is considered to be due to milling treatment in an air atmosphere.
図５は、活物質複合体の外観を走査型電子顕微鏡（ＳＥＭ）で撮影した写真である。同図より、活物質複合体の表面には、平均粒径が１００ｎｍ程度の微細な粒子が多数付着していた。　 FIG. 5 is a photograph of the appearance of the active material composite taken with a scanning electron microscope (SEM). From the figure, many fine particles having an average particle diameter of about 100 nm were attached to the surface of the active material composite. *
図１～図５の結果から、活物質複合体の構造は、図６に示すとおりであることが考えられる。図６に示すように、活物質複合体１０は、コア部１と、コア部１の表面を覆う表面層２とからなり、コア部１には、Ｌｉ２ＦｅＳｉＯ４からなる平均粒径１０～３０ｎｍの活物質粒子１１が、炭素（カーボン）からなるマトリックス１２の中で均一に分散している。表面層２は、厚みが１μｍ程度であり、Ｃ－Ｏリッチ層を構成している。　 From the results of FIG. 1 to FIG. 5, it is considered that the structure of the active material complex is as shown in FIG. As shown in FIG. 6, the active material composite 10 is composed of a core part 1 and a surface layer 2 covering the surface of the core part 1, and the core part 1 has an average particle size of 10 to 10 made of Li 2 FeSiO 4. 30 nm active material particles 11 are uniformly dispersed in a matrix 12 made of carbon. The surface layer 2 has a thickness of about 1 μm and constitutes a CO rich layer.
試料２について、図７に示すように、活物質粒子と導電性粒子とは、緩やかに凝集して凝集体を形成していたが、凝集体の中には空洞部が残り、この両者の大きさは大小様々であった。このため、活物質粒子と導電性粒子とが微細に分散された状態で互いに接合しているとはいえないものであった。ＢＥＴ法を用いた比表面積の測定の結果、この凝集体の比表面積は１３０．７ｍ２／ｇを示した。　 For sample 2, as shown in FIG. 7, the active material particles and the conductive particles were gradually aggregated to form aggregates, but a hollow portion remained in the aggregates. There were various sizes. For this reason, it cannot be said that the active material particles and the conductive particles are bonded to each other in a finely dispersed state. As a result of measuring the specific surface area using the BET method, the specific surface area of the aggregate was 130.7 m 2 / g.
試料３では、図８～図１０に示すように、活物質粒子（灰色部分）と導電性粒子（黒色部分）とが、試料１に比べて大きなサイズで混合されていた。活物質粒子の平均粒径は、５００ｎｍであり、導電性粒子の平均粒径は３００ｎｍであった。活物質粒子と導電性粒子とは、緩やかに凝集して凝集体を形成しているが、凝集体の平均粒径は１０００ｎｍ程度で、試料１の二次粒子よりも小さく、また内部に空洞部があった。図９に示すように、二次粒子では、活物質粒子及び導電性粒子の大きさは、ばらつきがあり、活物質粒子と導電性粒子とは不均一に分散していた。またＢＥＴ法を用いた比表面積測定の結果、この複合体は１０６ｍ２/gを示した。　 In Sample 3, as shown in FIGS. 8 to 10, active material particles (gray portion) and conductive particles (black portion) were mixed in a larger size than Sample 1. The average particle diameter of the active material particles was 500 nm, and the average particle diameter of the conductive particles was 300 nm. The active material particles and the conductive particles are gradually aggregated to form aggregates. The average particle diameter of the aggregates is about 1000 nm, which is smaller than the secondary particles of the sample 1, and has a hollow portion inside. was there. As shown in FIG. 9, in the secondary particles, the sizes of the active material particles and the conductive particles varied, and the active material particles and the conductive particles were dispersed unevenly. As a result of measuring the specific surface area using the BET method, this composite showed 106 m 2 / g.
試料４については、ＳＥＭ写真は掲載していないが、ＳＥＭでの観察を行った。試料４では、活物質粒子と導電性粒子とが、混合前の粒径よりも小さくなって、混合されていた。活物質粒子と導電性粒子とは、一次粒子のままで混合されており、二次粒子は形成していなかった。ＢＥＴ法を用いた比表面積の測定の結果、この混合体の比表面積は５９．３ｍ２／ｇを示した。　 Sample 4 was not posted with SEM photographs, but was observed with SEM. In sample 4, the active material particles and the conductive particles were mixed by being smaller than the particle size before mixing. The active material particles and the conductive particles were mixed as they were primary particles, and secondary particles were not formed. As a result of measuring the specific surface area using the BET method, the specific surface area of this mixture was 59.3 m 2 / g.
試料５では、図１１に示すように、平均粒径１０００ｎｍの活物質粒子（粒子状の白色部分）と、平均粒径１００ｎｍの導電性粒子（綿毛状の薄灰色部分）が、混合されていた。各粒子は、混合前の形状及び大きさと同じであり、凝集していなかった。　 In sample 5, as shown in FIG. 11, active material particles having an average particle diameter of 1000 nm (particulate white portions) and conductive particles having an average particle diameter of 100 nm (fluffy light gray portions) were mixed. . Each particle had the same shape and size before mixing and was not agglomerated. *
＜充放電特性＞　以下に示すように、試料１～５の材料を正極活物質として用いて電池を作製し、充放電試験を行った。　 <Charge / Discharge Characteristics> As shown below, batteries were prepared using the materials of Samples 1 to 5 as the positive electrode active material, and a charge / discharge test was performed. *
試料１～５の各正極活物質、アセチレンブラック（ＡＢ）、ポリテトラフルオロエチレン（ＰＴＦＥ）を、正極活物質：ＡＢ：ＰＴＦＥ＝１７：５：１の質量比で混合して混合物とした。混合物を混練した後にシート状にして、アルミニウム製の集電体に圧着して電極を製作し、１４０℃で３時間真空乾燥したものを正極として用いた。その後、エチレンカーボネート（ＥＣ）：ジメチルカーボネート（ＤＭＣ）＝３：７にＬｉＰＦ６を溶解して１ｍｏｌ／Ｌとした溶液を電解液として用い、セパレータとしてポリプロピレン膜（セルガード製、Celgard2400）、負極としてリチウム金属箔を用いたコイン電池を試作した。　 The positive electrode active materials of samples 1 to 5, acetylene black (AB), and polytetrafluoroethylene (PTFE) were mixed at a mass ratio of positive electrode active material: AB: PTFE = 17: 5: 1 to obtain a mixture. After the mixture was kneaded, it was made into a sheet shape, pressed onto an aluminum current collector to produce an electrode, and vacuum-dried at 140 ° C. for 3 hours was used as the positive electrode. Thereafter, a solution obtained by dissolving LiPF 6 in ethylene carbonate (EC): dimethyl carbonate (DMC) = 3: 7 to 1 mol / L was used as an electrolytic solution, a polypropylene film (Celgard 2400, manufactured by Celgard) as a separator, and lithium as a negative electrode. A coin battery using metal foil was prototyped.
＜充放電試験＞　このコイン電池について、３０℃にて充放電試験を行った。試験条件は、０．０５ｍＡ／ｃｍ２にて電圧１．５～４．５Ｖ（初回充電のみ４．８Ｖで１０時間定電圧充電）とした。試料１，２，３，４の各正極活物質を用いて作製した電池の充放電曲線を、図１２、図１３、図１４、図１５に示した。また、２サイクル目の放電容量を表１に示した。　 <Charge / Discharge Test> The coin battery was subjected to a charge / discharge test at 30 ° C. The test conditions were 0.05 mA / cm 2 and a voltage of 1.5 to 4.5 V (only the initial charge was 4.8 V and constant voltage charge for 10 hours). The charge / discharge curves of the batteries prepared using the positive electrode active materials of Samples 1, 2, 3, and 4 are shown in FIGS. 12, 13, 14, and 15. The discharge capacity at the second cycle is shown in Table 1.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
図１２～図１５及び表１に示すように、試料１を用いた電池は、試料２～４を用いた電池に比べて、２サイクル目放電容量が格段に大きかった。試料１の電池の放電容量は、試料２の電池の放電容量に対して１．２倍であり、試料３の電池の放電容量の１．６倍であり、試料４の電池の放電容量の２．２倍であった。このことから、ミリングの速度を上げることで、充放電容量が向上し、特に試料１のようにミリング速度を８００ｒｐｍとすることで、格段に充放電容量が向上することがわかった。　 As shown in FIGS. 12 to 15 and Table 1, the battery using Sample 1 had a significantly larger discharge capacity at the second cycle than the batteries using Samples 2 to 4. The discharge capacity of the sample 1 battery is 1.2 times the discharge capacity of the sample 2 battery, 1.6 times the discharge capacity of the sample 3 battery, and 2 times the discharge capacity of the sample 4 battery. .2 times. From this, it was found that the charge / discharge capacity was improved by increasing the milling speed, and in particular, the charge / discharge capacity was significantly improved by setting the milling speed to 800 rpm as in Sample 1. *
＜サイクル特性＞　試料１を用いて作製した電池のサイクル試験を行った。サイクル試験の条件は、上記充放電試験と同様に、３０℃、０．０５ｍＡ／ｃｍ２にて電圧１．５～４．５Ｖ（初回充電のみ４．８Ｖで１０時間定電圧充電）とし、４２回までの放電容量を測定した。測定結果を図１６に示した。　 <Cycle Characteristics> A cycle test of a battery manufactured using Sample 1 was performed. The cycle test conditions were the same as those in the charge / discharge test, with a voltage of 1.5 to 4.5 V at 30 ° C. and 0.05 mA / cm 2 (only the initial charge was 4.8 V and constant voltage charge for 10 hours). The discharge capacity up to 1 time was measured. The measurement results are shown in FIG.
図１６に示すように、試料１の電池は、４２
サイクル目まで放電容量の顕著な低下は見られなかった。このことから、試料１の電池はサイクル特性に優れていることがわかった。　 As shown in FIG. 16, the battery of Sample 1 is 42
No significant reduction in discharge capacity was observed until the cycle. From this, it was found that the battery of Sample 1 was excellent in cycle characteristics.
＜レート特性＞　試料１を用いて作製した上記コイン電池のレート特性試験を行った。試験の条件は、放電レートを１～５サイクル目で０．１Ｃ、６～１０サイクル目で０．２Ｃ、１１～１５サイクル目で０．５Ｃ、１６～２０サイクル目で１Ｃ、２１～２５サイクル目で２Ｃ、２６～３０サイクル目で５Ｃ、３１～５５サイクル目で０．１Ｃとし、充電時のレートは０．１Ｃと一定にした。試験は３０℃で行った。試験の結果を図１７に示した。　 <Rate Characteristic> A rate characteristic test of the coin battery prepared using Sample 1 was performed. The test conditions were as follows: discharge rate 0.1C at 1-5th cycle, 0.2C at 6-10th cycle, 0.5C at 11-15th cycle, 1C at 16-20th cycle, 21-25th cycle 2C for the eyes, 5C for the 26th to 30th cycles, 0.1C for the 31st to 55th cycles, and the rate during charging was kept constant at 0.1C. The test was conducted at 30 ° C. The test results are shown in FIG. *
図１７に示すように、１Ｃのときの放電容量は２００ｍＡｈ／ｇ、５Ｃのときの放電容量は１７０ｍＡｈ／ｇであり、優れたレート特性を発揮した。　 As shown in FIG. 17, the discharge capacity at 1C was 200 mAh / g, the discharge capacity at 5C was 170 mAh / g, and excellent rate characteristics were exhibited. *
＜反応抵抗＞　試料１、３の材料の反応抵抗を測定した。反応抵抗の試験は、充電後、放電後の各電池について、交流インピータンス法による測定装置（Solartron社製 商品名SI 1280B）を用いて行った。測定時の交流電流の振幅は１０ｍＶに設定して、周波数の最大値は２０ｋＨｚ、最小値は０．1Ｈｚとした。充電時の条件は、４．８Ｖで１０時間定電圧充電したものであり、放電時の条件は、１．５Ｖで定電流放電したものとした。　 <Reaction resistance> The reaction resistance of the materials of Samples 1 and 3 was measured. The test of the reaction resistance was performed on each battery after charging and discharging using a measuring device (trade name: SI 1280B, manufactured by Solartron) using an AC impedance method. The amplitude of the alternating current at the time of measurement was set to 10 mV, the maximum value of the frequency was 20 kHz, and the minimum value was 0.1 Hz. The charging condition was a constant voltage charging at 4.8V for 10 hours, and the discharging condition was a constant current discharging at 1.5V. *
測定結果を図１８，図１９に示した。図１８は、充電後の各材料の反応抵抗を示し、図１９は、放電後の各材料の反応抵抗を示す。図１８、図１９において、横軸は、インピーダンス抵抗の実数軸を示し、縦軸はインピーダンス抵抗の虚数軸を示す。図１８、図１９に示す線部において、円弧状部の両端部間の幅は、各材料に含まれる粒子の内部及び粒子界面での反応抵抗を示し、円弧状部よりも実数部の大きい抵抗部分は、粒子の外部での拡散抵抗を示す。　 The measurement results are shown in FIGS. FIG. 18 shows the reaction resistance of each material after charging, and FIG. 19 shows the reaction resistance of each material after discharging. 18 and 19, the horizontal axis indicates the real axis of the impedance resistance, and the vertical axis indicates the imaginary axis of the impedance resistance. In the line portions shown in FIGS. 18 and 19, the width between both ends of the arc-shaped portion indicates the reaction resistance inside the particle and at the particle interface included in each material, and the resistance having a larger real part than the arc-shaped portion. The part shows the diffusion resistance outside the particle. *
図１８、図１９に示すように、試料１の材料の反応抵抗は、試料３の４分の１程度であった。このことは、試料１の材料を正極活物質として用いて作製した電池の初回放電容量が、試料３よりも大きい要因となる。　 As shown in FIGS. 18 and 19, the reaction resistance of the material of Sample 1 was about one-fourth that of Sample 3. This is a factor that the initial discharge capacity of the battery manufactured using the material of Sample 1 as the positive electrode active material is larger than that of Sample 3. *
図１８，図１９に示す試料１，３の各材料の反応抵抗の結果を、図１～図１１の写真などで観察された粒子形態と照らし合わせると、以下のことが推定される。各材料の反応抵抗（インピーダンス）は、各材料に含まれる粒子の内部及び粒子界面での抵抗を示す。一般に、活物質粒子の粒径が小さくなるほどインピーダンスが小さくなり、活物質粒子界面での導電性粒子との接触面積が大きいほど、反応抵抗が小さくなる傾向がある。試料１では、活物質粒子は平均粒径１００ｎｍ以下と微細であり、また、導電性粒子も平均粒径が１００ｎｍ以下と微細であり、これらの粒子は均一に分散している。さらに、活物質複合体を形成している部分では、活物質粒子と導電性粒子とが密に接触し、接触面積が大きい。このため、試料１の反応抵抗が小さくなり、これを正極活物質として用いて作製した電池は、放電容量が大きくなったと推定される。 When the reaction resistance results of the materials of Samples 1 and 3 shown in FIGS. 18 and 19 are compared with the particle morphology observed in the photographs of FIGS. 1 to 11, the following can be estimated. The reaction resistance (impedance) of each material indicates the resistance inside the particle contained in each material and at the particle interface. In general, the impedance decreases as the particle size of the active material particles decreases, and the reaction resistance tends to decrease as the contact area with the conductive particles at the active material particle interface increases. In Sample 1, the active material particles are as fine as an average particle size of 100 nm or less, and the conductive particles are also as fine as an average particle size of 100 nm or less, and these particles are uniformly dispersed. Further, in the portion where the active material composite is formed, the active material particles and the conductive particles are in close contact with each other, and the contact area is large. For this reason, the reaction resistance of the sample 1 becomes small, and it is estimated that the battery produced using this as a positive electrode active material has a large discharge capacity.
＜活物質複合体の製造（２）＞　以下の方法により、試料６～８の活物質複合体を製造した。試料６～８の活物質複合体は、Ｌｉ２ＭｎＳｉＯ４とカーボンとからなる。　 <Manufacture of Active Material Complex (2)> The active material complexes of Samples 6 to 8 were manufactured by the following method. The active material composites of Samples 6 to 8 are composed of Li 2 MnSiO 4 and carbon.
リチウムシリケート系化合物Ｌｉ２ＳｉＯ３（珪酸リチウム、キシダ化学株式会社製、純度９９．５％）０．０３モルと、シュウ酸マンガン（キシダ化学株式会社製、純度９９．９％）０．０３モルとの混合物に、アセトン２０ｍｌを加えてジルコニア製ボールミルにて５００ｒｐｍで６０分混合し、乾燥した。これを炭酸塩混合物と混合した。炭酸塩混合物は、炭酸リチウム（キシダ化学株式会社製、純度９９．９％）、炭酸ナトリウム（キシダ化学株式会社製、純度９９．５％）、及び炭酸カリウム（キシダ化学製、純度９９．５％）を０．４３５モル:０．３１５モル:０．２５モルのモル比で混合した。混合割合は、珪酸リチウムとシュウ酸マンガンとの合計量を１００質量部に対して、炭酸塩混合物８０質量部とした。上記混合物にアセトン２０ｍｌを加えてジルコニア製ボールミルにて５００ｒｐｍで６０分混合し、乾燥した。　 Lithium silicate compound Li 2 SiO 3 (lithium silicate, manufactured by Kishida Chemical Co., Ltd., purity 99.5%) 0.03 mol and manganese oxalate (Kishida Chemical Co., Ltd., purity 99.9%) 0.03 mol 20 ml of acetone was added to the mixture and mixed with a zirconia ball mill at 500 rpm for 60 minutes and dried. This was mixed with the carbonate mixture. The carbonate mixture consists of lithium carbonate (Kishida Chemical Co., Ltd., purity 99.9%), sodium carbonate (Kishida Chemical Co., Ltd., purity 99.5%), and potassium carbonate (Kishida Chemical Co., Ltd., purity 99.5%). ) In a molar ratio of 0.435 mol: 0.315 mol: 0.25 mol. The mixing ratio was 80 parts by mass of the carbonate mixture with respect to 100 parts by mass of the total amount of lithium silicate and manganese oxalate. 20 ml of acetone was added to the above mixture, mixed at 500 rpm for 60 minutes in a zirconia ball mill, and dried.
その後、得られた粉体を金坩堝中で加熱して、二酸化炭素（流量：１００ｍＬ／分）と水素（流量：３ｍＬ／分）の混合ガス雰囲気下で、電気炉で５００℃に加熱して、炭酸塩混合物が溶融した状態で１３時間反応させた。反応後、温度を下げ４００℃になった時点で、反応系である炉心全体を電気炉から取り出して、混合ガスを通じた状態で室温まで急冷した。　 Thereafter, the obtained powder was heated in a gold crucible and heated to 500 ° C. in an electric furnace in a mixed gas atmosphere of carbon dioxide (flow rate: 100 mL / min) and hydrogen (flow rate: 3 mL / min). The mixture was reacted for 13 hours in a molten state of the carbonate mixture. After the reaction, when the temperature was lowered to 400 ° C., the entire reactor core as a reaction system was taken out from the electric furnace and rapidly cooled to room temperature through a mixed gas. *
次いで、得られた反応物に水２０ｍＬを加えて乳鉢ですりつぶし、水を用いて洗浄と濾過を繰り返して、塩が除去された粉体を得た。この粉体を１００℃の乾燥機に入れて１時間程度乾燥して、リチウムマンガンシリケート化合物を得た。　 Next, 20 mL of water was added to the obtained reaction product and ground in a mortar, and washing and filtration were repeated using water to obtain a powder from which salt had been removed. This powder was put into a dryer at 100 ° C. and dried for about 1 hour to obtain a lithium manganese silicate compound. *
その後、粉末Ｘ線回折（ＸＲＤ）により結晶構造を確認した結果、斜方晶、空間群Ｐｍｎ２１に属するＬｉ２ＭｎＳｉＯ４が得られたことがわかった。図２０は、Ｌｉ２ＭｎＳｉＯ４からなる活物質粒子のＳＥＭ写真である。図２０に示すように、合成直後の活物質粒子はフレーク状からなり、粒径０．５～３μｍに分布している。平均粒径は０．７μｍであった。ＢＥＴ法を用いた比表面積の測定の結果、比表面積は１２．５ｍ２／ｇであった。　 Then, as a result of confirming the crystal structure by powder X-ray diffraction (XRD), it was found that Li 2 MnSiO 4 belonging to orthorhombic crystal and space group Pmn2 1 was obtained. FIG. 20 is an SEM photograph of active material particles made of Li 2 MnSiO 4 . As shown in FIG. 20, the active material particles immediately after synthesis are in the form of flakes and distributed in a particle size of 0.5 to 3 μm. The average particle size was 0.7 μm. As a result of measuring the specific surface area using the BET method, the specific surface area was 12.5 m 2 / g.
得られた活物質粒子とアセチレンブラック（ＡＢ、平均粒径０．３μｍ）とを質量比５：４で混合した。この混合物に対して、メカニカルミリング装置（フリッチュ・ジャパン株式会社製、遊星型ボールミルＰ－７）を用いて、大気雰囲気下において下記の所定の条件でメカニカルミリング処理を行うことで、混合物に機械的エネルギーを付与した。本工程は、ジルコニア製で容積４５ｃｃのボールミル用粉砕容器に、φ４ｍｍジルコニア製ボールを５０ｇおよび混合物を３００ｍｇを入れて行った。　 The obtained active material particles and acetylene black (AB, average particle size 0.3 μm) were mixed at a mass ratio of 5: 4. The mixture is mechanically milled under the following predetermined conditions in an air atmosphere using a mechanical milling device (French Japan Co., Ltd., planetary ball mill P-7). Energized. This step was performed by putting 50 g of φ4 mm zirconia balls and 300 mg of the mixture in a ball mill grinding container made of zirconia and having a volume of 45 cc. *
粉体とＡＢとを混合する際に、ボールミルの回転数を８００ｒｐｍ、回転時間を１０時間とした場合に得られた材料を試料６とした。ボールミルの回転数を８００ｒｐｍ、回転時間を５時間とした場合に得られた材料を試料７とした。ボールミルの回転数を４５０ｒｐｍ、回転時間を５時間とした場合に得られた材料を試料８とした。各試料とも、熱処理を行った。熱処理条件は、７００℃、２時間、ＣＯ２：Ｈ２=１００：３ｃｍ３雰囲気とした。　 When the powder and AB were mixed, the material obtained when the rotation speed of the ball mill was 800 rpm and the rotation time was 10 hours was designated as Sample 6. The material obtained when the rotation speed of the ball mill was 800 rpm and the rotation time was 5 hours was designated as Sample 7. The material obtained when the rotation speed of the ball mill was 450 rpm and the rotation time was 5 hours was designated as Sample 8. Each sample was heat-treated. The heat treatment conditions were 700 ° C., 2 hours, and CO 2 : H 2 = 100: 3 cm 3 atmosphere.
図２１は、試料６のＳＥＭ（走査型電子顕微鏡）写真である。図２１に示すように、長径１０μｍ程度の比較的大きい大型粒子と、粒径０．５～５μｍ程度の微細な粒子とが混在していた。これらの粒子の内部では、多数の微細な粒子が均一に分散していた。大型粒子は、微細な一次粒子が複合化して二次粒子となったものである。大型粒子は、粒径１０～５０ｎｍのＬｉ２ＭｎＳｉＯ４と、粒径１０～５０ｎｍのカーボンとが互いに接合して複合化したＬｉ２ＭｎＳｉＯ４／Ｃ複合体であった。ＢＥＴ法を用いた比表面積測定の結果、この複合体は１７０．２ｍ２/gという高い値を示した。　 FIG. 21 is a SEM (Scanning Electron Microscope) photograph of Sample 6. As shown in FIG. 21, relatively large large particles having a major axis of about 10 μm and fine particles having a particle size of about 0.5 to 5 μm were mixed. Inside these particles, many fine particles were uniformly dispersed. Large particles are secondary particles obtained by compositing fine primary particles. The large particles were Li 2 MnSiO 4 / C composites in which Li 2 MnSiO 4 having a particle size of 10 to 50 nm and carbon having a particle size of 10 to 50 nm were bonded together to form a composite. As a result of measuring the specific surface area using the BET method, this composite showed a high value of 170.2 m 2 / g.
図２１に示す試料６のＳＥＭ写真を、図２に示す試料１のＳＥＭ写真と比較すると、試料６のＬｉ２ＭｎＳｉＯ４／Ｃ複合体は、試料１のＬｉ２ＦｅＳｉＯ４／Ｃ複合体と類似した組織を有していることが判った。　 When the SEM photograph of sample 6 shown in FIG. 21 is compared with the SEM photograph of sample 1 shown in FIG. 2, the Li 2 MnSiO 4 / C composite of sample 6 is similar to the Li 2 FeSiO 4 / C composite of sample 1. It was found to have the organization.
試料６の二次粒子のエネルギー分散型X線分析装置（ＥＤＸ）による酸素（Ｏ）、炭素（Ｃ）、鉄マンガン（Ｍｎ）、珪素（Ｓｉ）のマッピングから、Ｏ、Ｃ、Ｍｎ、Ｓｉは、二次粒子の存在部位に均一に分散していた。このことから、二次粒子は、Ｏ、Ｃ、Ｍｎ、Ｓｉを構成元素として含むことがわかった。Ｃについては、二次粒子外部にも存在していた。　 From the mapping of oxygen (O), carbon (C), iron manganese (Mn), and silicon (Si) by the energy dispersive X-ray analyzer (EDX) of the secondary particles of sample 6, O, C, Mn, and Si are , And were uniformly dispersed in the site where the secondary particles were present. From this, it was found that the secondary particles contain O, C, Mn, and Si as constituent elements. C was also present outside the secondary particles. *
試料６の二次粒子の透過型電子顕微鏡（ＴＥＭ）写真から、二次粒子の内部は、複数の一次粒子の集合体であることがわかる。この電子線回折の結果を分析したところ、Ｌｉ２ＭｎＳｉＯ４の構造が確認され、二次粒子には、Ｌｉ２ＭｎＳｉＯ４が含まれていることがわかった。　 From the transmission electron microscope (TEM) photograph of the secondary particles of Sample 6, it can be seen that the inside of the secondary particles is an aggregate of a plurality of primary particles. When the result of this electron beam diffraction was analyzed, the structure of Li 2 MnSiO 4 was confirmed, and it was found that the secondary particles contained Li 2 MnSiO 4 .
試料７について、ＳＥＭ写真は掲載していないが、活物質粒子と導電性粒子とは、緩やかに凝集して凝集体を形成していたが、凝集体の中には空洞部が残り、この両者の大きさは大小様々であった。このため、活物質粒子と導電性粒子とが微細に分散された状態で互いに接合しているとはいえないものであった。二次粒子では、活物質粒子及び導電性粒子の大きさは、ばらつきがあり、活物質粒子と導電性粒子とは不均一に分散していた。またＢＥＴ法を用いた比表面積測定の結果、この複合体は１１５ｍ２/gを示した。　 Although the SEM photograph is not shown for sample 7, the active material particles and the conductive particles were gradually aggregated to form aggregates, but the hollow portions remained in the aggregates. The size of was varied. For this reason, it cannot be said that the active material particles and the conductive particles are bonded to each other in a finely dispersed state. In the secondary particles, the sizes of the active material particles and the conductive particles varied, and the active material particles and the conductive particles were dispersed unevenly. As a result of measuring the specific surface area using the BET method, this complex showed 115 m 2 / g.
試料８では、図２２に示すように、活物質粒子と導電性粒子とが、試料６に比べて大きなサイズで混合されていた。活物質粒子と導電性粒子とは、緩やかに凝集して凝集体を形成しているが、凝集体の平均粒径は１０００ｎｍ程度で、試料６の二次粒子よりも小さく、また内部に空洞部があった。二次粒子では、活物質粒子及び導電性粒子の大きさは、ばらつきがあり、活物質粒子と導電性粒子とは不均一に分散していた。またＢＥＴ法を用いた比表面積測定の結果、この複合体は１０１ｍ２/gを示した。　 In Sample 8, as shown in FIG. 22, the active material particles and the conductive particles were mixed in a size larger than that of Sample 6. The active material particles and the conductive particles are gradually aggregated to form aggregates. The average particle diameter of the aggregates is about 1000 nm, which is smaller than the secondary particles of the sample 6, and has a hollow portion inside. was there. In the secondary particles, the sizes of the active material particles and the conductive particles varied, and the active material particles and the conductive particles were dispersed unevenly. Further, as a result of measuring the specific surface area using the BET method, this complex showed 101 m 2 / g.
図２３は、合成直後のＬｉ２ＭｎＳｉＯ４と、試料６～８とのＸＲＤパターンを示す。図２３に示すように、試料６では、試料７，８に比べて、回折ピークの強度が低くブロードになっている。これは、結晶性の低下と粒子の微細化に由来すると推測される。　 FIG. 23 shows XRD patterns of Li 2 MnSiO 4 immediately after synthesis and samples 6 to 8. As shown in FIG. 23, the intensity of the diffraction peak is lower in Sample 6 than in Samples 7 and 8. This is presumed to be due to a decrease in crystallinity and finer particles.
一方、試料７は、粒径４００ｎｍのＬｉ２ＭｎＳｉＯ４と、粒径２４０ｎｍのカーボンとが互いに接合して複合化したＬｉ２ＭｎＳｉＯ４／Ｃ複合体であった。試料７の比表面積は１１５ｍ２/gであった。　 On the other hand, Sample 7 was a Li 2 MnSiO 4 / C composite in which Li 2 MnSiO 4 having a particle size of 400 nm and carbon having a particle size of 240 nm were bonded together to form a composite. The specific surface area of Sample 7 was 115 m 2 / g.
試料８は、粒径５００ｎｍのＬｉ２ＭｎＳｉＯ４と、粒径３００ｎｍのカーボンとが互いに接合して複合化したＬｉ２ＭｎＳｉＯ４／Ｃ複合体であった。試料７の比表面積は１０１ｍ２/gであった。　 Sample 8 was a Li 2 MnSiO 4 / C composite in which Li 2 MnSiO 4 having a particle diameter of 500 nm and carbon having a particle diameter of 300 nm were bonded to each other to form a composite. The specific surface area of Sample 7 was 101 m 2 / g.
＜充放電特性＞　以下に示すように、試料６～８の材料を正極活物質として用いて半電池を作製し、充放電試験を行った。　 <Charge / Discharge Characteristics> As shown below, half-cells were prepared using the materials of Samples 6 to 8 as the positive electrode active material, and a charge / discharge test was performed. *
電極構成は、次のようである。試料６～８の各正極活物質（Ｌｉ２ＭｎＳｉＯ４／Ｃ複合体）、アセチレンブラック（ＡＢ）、ポリテトラフルオロエチレン（ＰＴＦＥ）を、正極活物質：ＡＢ：ＰＴＦＥ＝１７：５：１の質量比で混合して混合物とした。混合物を混練した後にシート状にし、アルミニウム製の集電体に圧着して電極を製作した。その後、１４０℃で３時間真空乾燥したものを正極として用いた。　 The electrode configuration is as follows. Each positive electrode active material (Li 2 MnSiO 4 / C composite), acetylene black (AB), and polytetrafluoroethylene (PTFE) of Samples 6 to 8 were mixed in a mass of positive electrode active material: AB: PTFE = 17: 5: 1. The mixture was mixed at a ratio. After the mixture was kneaded, it was made into a sheet and pressed onto an aluminum current collector to produce an electrode. Then, what was vacuum-dried at 140 degreeC for 3 hours was used as a positive electrode.
エチレンカーボネート（ＥＣ）：ジメチルカーボネート（ＤＭＣ）＝３：７にＬｉＰＦ６を溶解して１ｍｏｌ／Ｌとした溶液を電解液として用いた。セパレータとしてポリプロピレン膜（セルガード製、Celgard2400）とガラスフィルターを用いた。負極としてリチウム金属箔を用いた。これらよりコイン型の半電池を作製した。　 A solution obtained by dissolving LiPF 6 in ethylene carbonate (EC): dimethyl carbonate (DMC) = 3: 7 to 1 mol / L was used as an electrolytic solution. A polypropylene membrane (Celgard 2400, manufactured by Celgard) and a glass filter were used as the separator. Lithium metal foil was used as the negative electrode. From these, a coin-type half battery was produced.
＜充放電試験＞　この電池について、３０℃にて充放電試験を行った。試験条件は、０．０５ｍＡ／ｃｍ２にて電圧１．５～４．５Ｖ（初回充電のみ４．５Ｖで１０時間定電圧充電）とした。試料６，７，８の各正極活物質を用いて作製した電池の充放電曲線を、図２４、図２５、図２６に示した。また、各電池の初期充電容量、初期放電容量、初期効率、及び初期放電平均電圧を表２に示した。初期効率は、初期充電容量に対する初期放電容量の百分率である。　 <Charge / Discharge Test> This battery was subjected to a charge / discharge test at 30 ° C. The test conditions were 0.05 mA / cm 2 and a voltage of 1.5 to 4.5 V (first charge only at 4.5 V and constant voltage charge for 10 hours). The charge / discharge curves of the batteries prepared using the positive electrode active materials of Samples 6, 7, and 8 are shown in FIG. 24, FIG. 25, and FIG. Table 2 shows the initial charge capacity, initial discharge capacity, initial efficiency, and initial discharge average voltage of each battery. The initial efficiency is a percentage of the initial discharge capacity with respect to the initial charge capacity.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
図２４～図２６及び表２に示すように、試料６を用いた電池は、試料７、８を用い
た電池に比べて、初期充電容量、初期放電容量、初期効率、初期放電平均電圧ともに、高い値を示した。試料６の電池の初期放電容量は、試料７の電池の初期放電容量に対して２．６倍であり、試料８の電池の放電容量の２．７倍であった。試料６の電池の初期効率は、試料７の電池の初期効率に対して１．２倍であり、試料８の電池の初期効率の１．４倍であった。試料６の電池の初期放電平均電圧は、試料７の電池の初期放電平均電圧より０．１Vと高く、試料８の電池の初期放電平均電圧より０．２Vと高い値を示した。このことから、ミリングの速度とミリング時間を上げることで、充放電容量、初期効率、放電平均電圧が向上することがわかった。　 As shown in FIGS. 24 to 26 and Table 2, the battery using the sample 6 has an initial charge capacity, an initial discharge capacity, an initial efficiency, and an initial discharge average voltage, as compared with the battery using the samples 7 and 8. High value was shown. The initial discharge capacity of the sample 6 battery was 2.6 times the initial discharge capacity of the sample 7 battery and 2.7 times the discharge capacity of the sample 8 battery. The initial efficiency of the sample 6 battery was 1.2 times the initial efficiency of the sample 7 battery and 1.4 times the initial efficiency of the sample 8 battery. The initial discharge average voltage of the sample 6 battery was 0.1 V higher than the initial discharge average voltage of the sample 7 battery, and 0.2 V higher than the initial discharge average voltage of the sample 8 battery. From this, it was found that the charge / discharge capacity, the initial efficiency, and the average discharge voltage are improved by increasing the milling speed and milling time.
この要因は、実施例１の試料１の場合と同様であると推定される。つまり、試料６では、活物質粒子は平均粒径１００ｎｍ以下と微細であり、また、導電性粒子も平均粒径が１００ｎｍ以下と微細であり、これらの粒子は均一に分散している。さらに、活物質複合体を形成している部分では、活物質粒子と導電性粒子とが密に接触し、接触面積が大きい。このため、試料６の反応抵抗が小さくなり、これを正極活物質として用いて作製した電池は、放電容量が大きくなったと推定される。また前記のようなナノ粒子同士が均一に分散することで、リチウムイオンの導電パスが良好に形成されるため、充電時に活物質から抜けたリチウムイオンが放電時に戻りやすくなる。このため、試料６の初期効率が向上したと推定される。さらに、反応抵抗が小さくなることで、活物質本来の充放電曲線が得られ、放電平均電圧の向上につながったと推定される。 This factor is estimated to be the same as in the case of the sample 1 of Example 1. That is, in the sample 6, the active material particles are as fine as an average particle size of 100 nm or less, and the conductive particles are as fine as an average particle size of 100 nm or less, and these particles are uniformly dispersed. Further, in the portion where the active material composite is formed, the active material particles and the conductive particles are in close contact with each other, and the contact area is large. For this reason, the reaction resistance of the sample 6 becomes small, and it is estimated that the battery produced using this as a positive electrode active material has a large discharge capacity. Further, since the nanoparticles as described above are uniformly dispersed, a lithium ion conductive path is well formed, so that lithium ions released from the active material at the time of charging easily return at the time of discharging. For this reason, it is estimated that the initial efficiency of the sample 6 has improved. Furthermore, it is presumed that due to the reduced reaction resistance, the charge / discharge curve inherent to the active material was obtained, leading to an improvement in the discharge average voltage.
１：コア部、１０：活物質複合体、１１：活物質粒子、１２：マトリックス、２：表面層。 1: Core part, 10: Active material composite, 11: Active material particles, 12: Matrix, 2: Surface layer.

Claims (17)

  1. 活物質材料からなり平均粒径が１００ｎｍ以下である活物質粒子と、導電性材料からなり平均粒径が１００ｎｍ以下である導電性粒子とが互いに接合し、比表面積が１５０ｍ２／ｇ以上であることを特徴とする活物質複合体。 Active material particles made of an active material and having an average particle diameter of 100 nm or less and conductive particles made of a conductive material and having an average particle diameter of 100 nm or less are bonded to each other, and the specific surface area is 150 m 2 / g or more. An active material complex characterized by the above.
  2. 平均粒径が０．７μｍ以上２０μｍ以下からなる二次粒子である請求項１記載の活物質複合体。 The active material composite according to claim 1, which is a secondary particle having an average particle diameter of 0.7 μm or more and 20 μm or less.
  3. コア部と、コア部を被覆する表面層とからなり、前記表面層に含まれる前記導電性粒子の含有量は、前記コア部に含まれる前記導電性粒子の含有量よりも多い請求項１又は２に記載の活物質複合体。 The core part and the surface layer which coat | covers a core part, Content of the said electroconductive particle contained in the said surface layer is larger than content of the said electroconductive particle contained in the said core part. 2. The active material complex according to 2.
  4. 前記活物質複合体の表面に、表面粒子が付着している請求項１～３のいずれか１項に記載の活物質複合体。 The active material composite according to any one of claims 1 to 3, wherein surface particles are attached to a surface of the active material composite.
  5. 前記活物質材料は、リチウムイオンを吸蔵・放出し得る材料からなる請求項１～４のいずれか１項に記載の活物質複合体。 The active material composite according to any one of claims 1 to 4, wherein the active material is made of a material capable of inserting and extracting lithium ions.
  6. 前記活物質材料は、リチウムシリケート系化合物、リチウムホスフェート系化合物、及びリチウムボレート系化合物の群のいずれか１種以上からなる請求項５記載の活物質複合体。 The active material composite according to claim 5, wherein the active material is made of at least one member selected from the group consisting of a lithium silicate compound, a lithium phosphate compound, and a lithium borate compound.
  7. 前記リチウムシリケート系化合物は、組成式Ｌｉ２Ｍ１ＳｉＯ４（Ｍ１は、Ｆｅ、Ｍｎ、Ｃｏ）、または組成式Ｌｉ２＋ａ―ｂＡｂＭ１－ｘＭ’ｘＳｉＯ４＋δ（式中、ＡはＮａ、Ｋ、Ｒｂ、Ｃｓの群から選ばれた少なくとも一種の元素であり、ＭはＦｅ及びＭｎ、Ｃｏからなる群から選ばれた少なくとも一種の元素であり、Ｍ’はＭｇ、Ｃａ、Ａｌ、Ｎｉ、Ｎｂ、Ｔｉ、Ｃｒ、Ｃｕ、Ｚｎ、Ｚｒ、Ｖ、Ｍｏ及びＷからなる群から選ばれた少なくとも一種の元素である。各添字は次のとおりである。０≦ａ＜１、０≦ｂ＜０．２、０≦ｘ≦０．５、δ≧０）で表される化合物からなる請求項６記載の活物質複合体。 The lithium silicate-based compound has a composition formula of Li 2 M 1 SiO 4 (M 1 is Fe, Mn, Co) or a composition formula of Li 2 + ab Ab M 1-x M ′ x SiO 4 + δ (where A 1 Is at least one element selected from the group consisting of Na, K, Rb, and Cs, M is at least one element selected from the group consisting of Fe, Mn, and Co, and M ′ is Mg, Ca, Al , Ni, Nb, Ti, Cr, Cu, Zn, Zr, V, Mo and W. Each of the subscripts is as follows: 0 ≦ a <1, 0 The active material composite according to claim 6, comprising a compound represented by ≦ b <0.2, 0 ≦ x ≦ 0.5, δ ≧ 0).
  8. 前記リチウムシリケート系化合物は、リチウム鉄シリケート、及びリチウムマンガンシリケートの群から選ばれる少なくとも１種からなる請求項６又は７に記載の活物質複合体。 The active material composite according to claim 6 or 7, wherein the lithium silicate-based compound comprises at least one selected from the group of lithium iron silicate and lithium manganese silicate.
  9. 前記導電性材料は、炭素材料からなる請求項１～８のいずれか１項に記載の活物質複合体。 The active material composite according to any one of claims 1 to 8, wherein the conductive material is made of a carbon material.
  10. 前記炭素材料は、アセチレンブラック（ＡＢ）、ケッチェンブラック（ＫＢ）、黒鉛の群の中から選ばれた少なくとも1種からなる請求項９記載の活物質複合体。 The active material composite according to claim 9, wherein the carbon material is at least one selected from the group consisting of acetylene black (AB), ketjen black (KB), and graphite.
  11. 請求項１～１０のいずれか１項に記載の活物質複合体を製造する方法であって、　活物質材料及び導電性材料に機械的エネルギーを付与するエネルギー付与工程をもつことを特徴とする活物質複合体の製造方法。 A method for producing the active material composite according to any one of claims 1 to 10, comprising an energy application step for applying mechanical energy to the active material and the conductive material. A method for producing a substance complex.
  12. 前記エネルギー付与工程は、ミリングにより機械的エネルギーを付与する工程である請求項１１記載の活物質複合体の製造方法。 The method for producing an active material composite according to claim 11, wherein the energy applying step is a step of applying mechanical energy by milling.
  13. 前記エネルギー付与工程で用いる前記活物質材料の平均粒径は２００ｎｍ以上５μｍ以下であり、且つ前記導電性材料の平均粒径は１００ｎｍ以上５μｍ以下である請求項１２記載の活物質複合体の製造方法。 The method for producing an active material composite according to claim 12, wherein an average particle size of the active material used in the energy application step is 200 nm to 5 µm, and an average particle size of the conductive material is 100 nm to 5 µm. .
  14. 前記エネルギー付与工程の後に、機械的エネルギーが付与された前記活物質材料と前記導電性材料とに熱処理を行う熱処理工程をもつ請求項１１～１３のいずれか１項に記載の活物質複合体の製造方法。 The active material composite according to any one of claims 11 to 13, further comprising a heat treatment step of performing a heat treatment on the active material material to which mechanical energy is applied and the conductive material after the energy application step. Production method.
  15. 請求項１～１０のいずれか１項に記載の活物質複合体、又は請求項１１～１４のいずれか１項に記載の製造方法により製造された活物質複合体からなることを特徴とする非水電解質二次電池用正極活物質。 A non-material comprising the active material complex according to any one of claims 1 to 10, or the active material complex produced by the production method according to any one of claims 11 to 14. Positive electrode active material for water electrolyte secondary battery.
  16. 請求項１５に記載の非水電解質二次電池用正極活物質を含むことを特徴とする非水電解質二次電池用正極。 A positive electrode for a non-aqueous electrolyte secondary battery comprising the positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 15.
  17. 請求項１６に記載の非水電解質二次電池用正極を構成要素として含むことを特徴とする非水電解質二次電池。 A nonaqueous electrolyte secondary battery comprising the positive electrode for a nonaqueous electrolyte secondary battery according to claim 16 as a constituent element.
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