WO2012057340A1 - Silicate-phosphate compound, secondary-battery positive electrode, secondary battery, and manufacturing methods therefor - Google Patents

Silicate-phosphate compound, secondary-battery positive electrode, secondary battery, and manufacturing methods therefor Download PDF

Info

Publication number
WO2012057340A1
WO2012057340A1 PCT/JP2011/074999 JP2011074999W WO2012057340A1 WO 2012057340 A1 WO2012057340 A1 WO 2012057340A1 JP 2011074999 W JP2011074999 W JP 2011074999W WO 2012057340 A1 WO2012057340 A1 WO 2012057340A1
Authority
WO
WIPO (PCT)
Prior art keywords
silicic acid
phosphoric acid
compound
formula
group
Prior art date
Application number
PCT/JP2011/074999
Other languages
French (fr)
Japanese (ja)
Inventor
義久 別府
Original Assignee
旭硝子株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 旭硝子株式会社 filed Critical 旭硝子株式会社
Priority to JP2012540985A priority Critical patent/JPWO2012057340A1/en
Publication of WO2012057340A1 publication Critical patent/WO2012057340A1/en

Links

Images

Classifications

    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/20—Silicates
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B25/00—Phosphorus; Compounds thereof
    • C01B25/16—Oxyacids of phosphorus; Salts thereof
    • C01B25/26—Phosphates
    • C01B25/37—Phosphates of heavy metals
    • 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
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • 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
    • H01M4/139—Processes of manufacture
    • H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • 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
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • 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
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • 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
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • 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
    • 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

Definitions

  • the present invention relates to a silicic acid-phosphoric acid compound, a positive electrode for a secondary battery, a secondary battery, and a production method thereof.
  • Patent Document 1 describes a positive electrode using an active material containing a silicon phosphate salt.
  • the active material includes the formula Li 3 M ′ (2-b) M ′′ b SiP 2 O 12 (M ′ is +3 valent).
  • M ′ is +3 valent
  • an active material represented by a metal or metalloid element, M ′′ is a +4 valent metal or metalloid element, and b is 0 to 2 is proposed.
  • Patent Document 2 describes a solid solution represented by the formula Li 1.7 Mn 0.7 Fe 0.3 Si 0.7 P 0.3 O 4 as a positive electrode material for a secondary battery containing P and Si. Has been. In addition, it is described that the solid solution was obtained by a method in which Li 2 MnSiO 4 and LiFePO 4 were pulverized, heated and then allowed to cool.
  • Li 2 FeSiO 4 described in Non-Patent Document 1 is manufactured by a solid-phase reaction, the manufacturing process is complicated and the manufacturing cost increases.
  • Patent Document 1 does not describe the compound of the present invention in which the composition ratio of Li, M ′ and M ′′, Si, and P is a specific ratio. Further, only the NASICON structure is disclosed as the crystal structure of the obtained active material.
  • the NASICON active material is a material that does not provide a sufficient capacity per unit mass.
  • the manufacturing method described in Patent Document 1 is a method in which a raw material is heated at 170 ° C. for 4 hours, then held at about 900 ° C. for about 16 hours, and is allowed to react by repeating cooling, polishing and reheating as necessary. . In this method, the manufacturing process is complicated, takes time, and increases the manufacturing cost.
  • Patent Document 2 The production method described in Patent Document 2 is a method for producing Li 2 MnSiO 4 and LiFePO 4 by solid-phase reaction.
  • the solid-phase reaction has a complicated manufacturing process, is expensive to manufacture, is difficult to mass-produce, and composition control is not easy.
  • Patent Document 3 Since the manufacturing method of Patent Document 3 is manufactured by a solid-phase reaction, the manufacturing process is complicated and the manufacturing cost increases.
  • An object of the present invention is to provide a production method in which the composition and particle size of a silicic acid-phosphoric acid compound capable of increasing the capacity per unit mass can be easily controlled.
  • the compound is useful as an active material used for a positive electrode for a secondary battery and a positive electrode for a secondary battery.
  • the present invention also provides a positive electrode for a secondary battery having excellent characteristics and reliability and a method for producing the secondary battery.
  • a method for producing a silicic acid-phosphoric acid compound In this order.
  • element A is at least one element selected from the group consisting of Li, Na and K
  • element M is at least one element selected from the group consisting of Fe, Mn, Co and Ni.
  • the melting step includes Compound containing element A is A carbonate, A bicarbonate, A hydroxide, A silicate, A phosphate, A hydrogen phosphate, A nitrate, A chloride Or at least one selected from the group consisting of A sulfate, A acetate, and A oxalate (however, some
  • the compound comprising element M is M oxide, M oxyhydroxide, M silicate, M metal, M phosphate, M chloride, M nitrate, M sulfate, and Included as at least one selected from the group consisting of organic salts of M;
  • a compound containing Si is included as at least one selected from the group consisting of silicon oxide, A silicate, M silicate, and silicon alkoxide,
  • the compound containing P is selected from the group consisting of phosphorus oxide, ammonium phosphate, ammonium hydrogen phosphate, phosphoric acid, polyphosphoric acid, phosphorous acid, hypophosphorous acid, A phosphate, and M phosphate Included as at least one The method for producing a silicic acid-phosphoric acid compound according to [1], wherein the raw material preparation is heated to obtain a melt having a composition represented by the formula (1).
  • the melt having the composition represented by the formula (1) is a melt having the composition represented by the following formula (3A), and the silicic acid having the composition represented by the formula (2)
  • the solidified product includes at least one carbon source selected from the group consisting of an organic compound and carbon powder, and a ratio of a carbon conversion amount (mass) in the carbon source is
  • the silicic acid-phosphoric acid compound of [1] to [6] is 0.1 to 20% by mass relative to the total mass of the mass of the solidified product and the carbon equivalent amount (mass) in the carbon source. Production method.
  • a silicic acid-phosphoric acid compound is obtained by the production method of [1] to [8], and then a positive electrode for a secondary battery is produced using the silicic acid-phosphoric acid compound as a positive electrode material for a secondary battery.
  • a method for producing a positive electrode for a secondary battery comprising obtaining a positive electrode for a secondary battery by the production method of [9], and then producing a secondary battery using the positive electrode for a secondary battery.
  • element A is at least one element selected from the group consisting of Li, Na and K
  • element M is at least one element selected from the group consisting of Fe, Mn, Co and Ni.
  • a is ⁇ 0.1 ⁇ a ⁇ 0.4
  • b is 0.7 ⁇ b ⁇ 1.3
  • x is 0.3 ⁇ x ⁇ 0.7
  • c2 is a, b, and M
  • the number depends on the valence N of [12]
  • the production method of the present invention is useful as an electrode material because the composition, particle size and uniformity of the silicic acid-phosphoric acid compound can be easily controlled, and the silicic acid-phosphoric acid compound having various compositions is efficiently used. Can be manufactured.
  • the silicic acid-phosphoric acid compound of the present invention is a compound that exhibits a multi-electron type reaction. Therefore, by using the silicic acid-phosphoric acid compound of the present invention, a positive electrode material for a secondary battery and a secondary battery having excellent characteristics and reliability can be manufactured. Furthermore, the present invention provides a silicic acid-phosphoric acid compound.
  • FIG. 4 is a view showing an X-ray diffraction pattern of silicic acid-phosphoric acid compounds produced in Examples 1, 2, 3 and 4.
  • FIG. 6 is a view showing an X-ray diffraction pattern of silicic acid-phosphoric acid compounds produced in Examples 5, 6 and 7.
  • FIG. 4 is a diagram showing an X-ray diffraction pattern of silicic acid-phosphoric acid compounds produced in Examples 19, 20, 21 and 22.
  • FIG. 4 is a view showing an X-ray diffraction pattern of silicic acid-phosphoric acid compounds produced in Examples 32, 33, 34 and 35.
  • ⁇ Method for producing silicic acid-phosphoric acid compound> In the method for producing a silicic acid-phosphoric acid compound of the present invention, the following melting step (I), cooling step (II), pulverization step (III), and heating step (IV) are performed in this order. Other steps may be performed before, between, and after the steps (I) to (IV) as long as each step is not affected.
  • Melting step (I) a step of obtaining a melt having a composition represented by the formula A 1 + x + a M b Si x P 1-x O 4 + c1 (wherein the symbols have the same meaning as described above), Cooling step (II): a step of cooling the melt to obtain a solidified product, Grinding step (III): step of obtaining the pulverized product by pulverizing the solidified product, and heating step (IV): heating the pulverized product to obtain a formula A 1 + x + a M b Si x P 1-x O 4 + c2 (wherein The symbols have the same meaning as above.)
  • the melting step (I) in the production method of the present invention is a step for obtaining a melt represented by the following formula (1).
  • a raw material formulation prepared by adjusting a raw material containing an element source (element A, element M, Si, and P) to have a composition represented by the formula (1) is prepared. It is preferable to do this.
  • a is in the range of ⁇ 0.1 ⁇ a ⁇ 0.4
  • b is in the range of 0.7 ⁇ b ⁇ 1.3.
  • a silicic acid-phosphoric acid compound having a target composition can be produced by setting a and b in the raw material formulation within the above ranges.
  • the raw material formulation can be melted well, and a uniform melt can be obtained.
  • a and b can cause a multi-electron type reaction more easily, so that ⁇ 0.1 ⁇ a ⁇ 0.3 and 0.8 ⁇ b ⁇ 1.3 are more preferable. preferable. Moreover, 0.3 ⁇ x ⁇ 1.0 may be sufficient.
  • the element A in the formula (1) is at least one element selected from the group consisting of Li, Na, and K. Since the element A is suitable as a positive electrode material for a secondary battery, it is preferable to make Li essential, and it is particularly preferable to use only Li.
  • the silicic acid-phosphoric acid compound containing Li increases the capacity per unit volume (mass) of the secondary battery.
  • the element M in the formula (1) is at least one element selected from the group consisting of Fe, Mn, Co, and Ni.
  • the element M is preferably composed of only one kind or two kinds.
  • the element M consists of only Fe, Mn alone, or Fe and Mn. This is preferable in terms of cost.
  • the valence N of the element M is a numerical value that can be changed in each step of the production method of the present invention, and is in the range of +2 to +4.
  • the valence N is +2, +8/3 or +3 when the element M is Fe, +2, +3 or +4 when Mn, +2, +8/3 or +3 when Co, and +2 or when Ni +4 is preferred.
  • the valence N is more preferably +2 in order to simplify the melting step (I). In the present invention, melting in the melting step (I) can be facilitated by setting the composition of the raw material formulation to a specific range.
  • the compound containing element A in the raw material formulation includes A carbonate (A 2 CO 3 ), A hydrogen carbonate (AHCO 3 ), A hydroxide (AOH), and A silicate (A 2 O ⁇ 2SiO 2 , A 2 O ⁇ SiO 2 , 2A 2 O ⁇ SiO 2, etc.), A phosphate, A hydrogen phosphate, A nitrate (ANO 3 ), A chloride (ACl), A sulfate (A 2 SO 4 ) of A and at least one selected from the group consisting of organic acid salts such as acetate (CH 3 COOA) and oxalate ((COOA) 2 ) of A are preferred.
  • the element A is preferably Li. Furthermore, these compounds may be hydrates. Of these, carbonates and bicarbonates of A are more preferred because they are inexpensive and easy to handle.
  • the compound containing the element M is at least selected from the group consisting of Fe 3 O 4 , Fe 2 O 3 , MnO, Mn 2 O 3 , MnO 2 , Co 3 O 4 , and NiO because of availability and cost.
  • One type is more preferable, and at least one selected from the group consisting of Fe 3 O 4 , Fe 2 O 3 , and MnO 2 is particularly preferable.
  • These Fe 3 O 4 , Fe 2 O 3 , and MnO 2 may be used alone or in combination of two or more.
  • the compound containing Si in the raw material preparation includes silicon oxide (SiO 2 ), A silicate, M silicate, and silicon alkoxide (Si (OCH 3 ) 4 , Si (OC 2 H 5 ) 4. Etc.) is preferred, and silicon oxide is particularly preferred because it is inexpensive.
  • the compound containing Si may be crystalline or amorphous.
  • the phosphate of A is preferably Li 3 PO 4
  • the phosphate of M is at least 1 selected from the group consisting of Fe 3 (PO 4 ) 2 , FePO 4 , and Mn 3 (PO 4 ) 2. Species are preferred.
  • a combination of A carbonate or hydrogen carbonate, M oxide or M oxyhydroxide, silicon oxide, and ammonium hydrogen phosphate is preferable.
  • Li 2 CO 3 or LiHCO 3 one or more compounds selected from the group consisting of Fe 3 O 4 , Fe 2 O 3 , and MnO 2 ; silicon oxide; and a combination of ammonium hydrogen phosphate Is particularly preferred.
  • the composition of the raw material preparation is made to correspond to the composition of the melt in the method for producing a silicate-phosphate compound.
  • the composition of the obtained melt is the composition of the raw material formulation And may be slightly different. In such a case, it is preferable to appropriately change the composition of the raw material formulation in consideration of the amount lost due to volatilization or the like.
  • the purity of each raw material included in the raw material preparation is not particularly limited. Considering reactivity, characteristics of the positive electrode material for secondary batteries, and the like, the purity excluding hydrated water is preferably 99% by mass or more.
  • the melting step (I) in the present invention is a step of obtaining a melt having a composition represented by the formula (1). This step is preferably carried out by heating and melting the raw material formulation. Prior to melting, each raw material or raw material preparation is preferably pulverized and / or mixed dry or wet using a mixer, ball mill, jet mill, planetary mill or the like. The particle size of the raw material in each raw material preparation is not limited as long as it does not adversely affect the mixing operation, the filling operation of the raw material preparation into the melting container, the meltability of the raw material preparation, and the like.
  • the container is preferably made of alumina, carbon, silicon carbide, zirconium boride, titanium boride, boron nitride, carbon, platinum, or a platinum alloy containing rhodium.
  • a container made of a refractory-based brick and a reducing material (eg, graphite) can also be employed.
  • a lid to the container and melt it.
  • the heating furnace is preferably a resistance heating furnace, a high frequency induction furnace, or a plasma arc furnace.
  • the resistance heating furnace is preferably an electric furnace provided with a heating element made of an alloy such as a nichrome alloy, silicon carbide, or molybdenum silicide.
  • the melting step (I) is preferably carried out in air, in an inert gas or in a reducing gas. Melting conditions can be changed as appropriate depending on conditions such as the type of container or heating furnace and the heating method such as a heat source.
  • the pressure may be any of normal pressure, pressurization, and reduced pressure (0.9 ⁇ 10 5 Pa or less). Although it is preferably in reducing gas, it may be in oxidizing gas. In the case of the oxidation conditions, reduction (for example, change from M 3+ to M 2+ ) can be performed in the next heating step (IV).
  • the inert gas is a gas containing 99% by volume or more of at least one inert gas selected from the group consisting of nitrogen gas (N 2 ) and rare gases such as helium gas (He) and argon gas (Ar). It is a condition.
  • the term “in the reducing gas” refers to a gas condition in which a reducing gas is added to the inert gas and substantially does not contain oxygen. Examples of the reducing gas include hydrogen gas (H 2 ), carbon monoxide gas (CO), and ammonia gas (NH 3 ).
  • the amount of the reducing gas in the inert gas is preferably 0.1% by volume or more, and particularly preferably 1 to 10% by volume of the reducing gas in the total gas.
  • the oxygen content in the gas is preferably 1% by volume or less, particularly preferably 0.1% by volume or less.
  • the heating temperature in the melting step (I) is preferably 1,300 to 1,600 ° C., particularly preferably 1,400 to 1,550 ° C.
  • melting means that each raw material is melted and is in a transparent state visually.
  • the heating time is preferably 0.2 to 2 hours, particularly preferably 0.5 to 2 hours. By setting the time, the homogeneity of the melt is sufficient, and the raw material is difficult to volatilize.
  • stirring may be performed to increase the uniformity of the melt.
  • the melt may be clarified at a temperature lower than the heating temperature until the next cooling step (II) is performed. Furthermore, the melt obtained in the melting step (I) may be subjected to another step before the cooling step (II) as long as it does not adversely affect the next cooling step (II).
  • the cooling step (II) is a step of cooling the melt obtained in the melting step (I) to near room temperature to obtain a solidified product.
  • the solidified product is preferably an amorphous material, but a part of the solidified product may be a crystallized product.
  • the next pulverization step (III) can be easily performed, and the composition and particle size of the silicic acid-phosphoric acid compound can be easily controlled. Further, in the subsequent heating step (IV), there is an advantage that the product can be prevented from being agglomerated and the particle size of the product can be easily controlled.
  • the crystallized product becomes a crystal nucleus in the heating step (IV), which is a subsequent step, and it is easy to crystallize.
  • the amount of crystallized product in the solidified product is preferably 0 to 30% by mass with respect to the total mass of the solidified product.
  • the cooling step (II) is preferably performed in air from the viewpoint of equipment and the like.
  • the cooling step (II) may be performed in an inert gas or a reducing gas.
  • the cooling rate of the melt is preferably not less than -1 ⁇ 10 3 °C / sec, -1 ⁇ 10 4 °C / sec or more is particularly preferable.
  • a temperature change per unit time (ie, cooling rate) in the case of cooling is indicated by a negative value
  • a temperature change per unit time in case of heating ie, the heating rate
  • the cooling rate is higher than this value, an amorphous material is easily obtained.
  • the upper limit of the cooling rate is preferably about ⁇ 1 ⁇ 10 10 ° C./second from the viewpoint of manufacturing equipment and mass productivity, and is particularly preferably ⁇ 1 ⁇ 10 8 ° C./second from the viewpoint of practicality.
  • the cooling rate of the melt is particularly preferably from -10 3 ° C / second to -10 10 ° C / second from 1000 ° C to 50 ° C.
  • the method of cooling the melt is, for example, a method in which a melt is dropped between twin rollers rotating at high speed to obtain a flake-like solidified product, or a melt is dropped on a rotating single roller to form a flake-like or plate-like solidified product. It is preferable that the method is obtained by sweeping an object, or a method in which a melt is pressed on a cooled carbon plate or metal plate to obtain a lump solidified product. Among these, a cooling method using twin rollers is more preferable because the cooling rate is high and a large amount of processing can be performed. As the double roller, it is preferable to use one made of metal, carbon, or ceramic.
  • a cooling method there is a method in which the melt is directly poured into water, but this method is difficult to control, and the cooling rate is about ⁇ 1 ⁇ 10 ° C./second to ⁇ 1 ⁇ 10 2 ° C./second. It is difficult to obtain a crystalline material. Further, the solidified product becomes a lump and requires a lot of labor for pulverization.
  • a cooling method there is also a method in which a melt is directly charged into liquid nitrogen, and the cooling rate can be made faster than in the case of water, but there are problems similar to the method using water and the cost is high.
  • the solidified product obtained in the cooling step (II) is preferably flaky or fibrous.
  • the flaky solidified product preferably has an average thickness of 200 ⁇ m or less, particularly preferably 100 ⁇ m or less.
  • the average diameter of the plane perpendicular to the average thickness as the flaky solidified product is not particularly limited.
  • the fibrous solidified product preferably has an average diameter of 50 ⁇ m or less, particularly preferably 30 ⁇ m or less.
  • the average thickness and average diameter can be measured with a caliper or a micrometer. The average diameter can also be measured by microscopic observation.
  • the solidified product obtained in the cooling step (II) may be subjected to other steps before the pulverization step (III) as long as the pulverization step (III) is not adversely affected.
  • the pulverization step (III) is a step in which the solidified product obtained in the cooling step (II) is pulverized to obtain a pulverized product. Since the solidified product usually contains a large amount of amorphous material or consists of an amorphous material, there is an advantage that it is easy to grind. Further, there is an advantage that grinding can be performed without imposing a burden on the apparatus used for grinding and the particle size can be easily controlled. On the other hand, in the conventional solid phase reaction, pulverization is performed after the heating step (IV), but the present inventor has noticed that there is a problem that residual stress is generated by pulverization and battery characteristics are deteriorated. Therefore, the manufacturing method of the present invention employs a method of pulverizing before the heating step (IV) and reducing or removing the generated residual stress in the subsequent heating step (IV).
  • the pulverization is preferably performed using a jaw crusher, a hammer mill, a ball mill, a jet mill, a planetary mill or the like.
  • the method of pulverization may be either dry or wet.
  • the solidified product be struck by hand or a hammer to make it finer, because the burden of the pulverization step (III) is reduced.
  • the heating step (IV) after removing the dispersion medium by sedimentation, filtration, drying under reduced pressure, heat drying and the like.
  • the heating step (IV) may be performed with the pulverized product containing the dispersion medium as it is.
  • the silicic acid-phosphoric acid compound in the present invention is an insulating substance, when used as a positive electrode material for a secondary battery, it is preferable to include a conductive material in the solidified product. Moreover, when using as a positive electrode material for secondary batteries, it is preferable that it is a fine particle form.
  • the average particle diameter of the pulverized product is preferably 10 nm to 10 ⁇ m, and particularly preferably 10 nm to 5 ⁇ m, in terms of volume-based median diameter.
  • the particle size can be measured by a sedimentation method or a laser diffraction / scattering particle size measuring device.
  • the particle size of the pulverized product When the particle size of the pulverized product is small, the reduction reaction is promoted, and the heating temperature and time in the heating step (IV) can be reduced, which is preferable.
  • the average particle size of the pulverized product By making the average particle size of the pulverized product within the above range, the workability of the pulverization step (III) and the heating step (IV) is improved, and the average particle size of the product of the heating step (IV) can be easily controlled. There is.
  • the conductive material is preferably at least one carbon source selected from the group consisting of organic compounds and carbon powder.
  • the amount of at least one carbon source selected from the group consisting of an organic compound and carbon powder is such that the carbon equivalent amount (mass) in the carbon source is the mass of the solidified product and the carbon equivalent amount (mass in the carbon source). ) In an amount of 0.1 to 20% by mass, particularly preferably 2 to 10% by mass.
  • the organic compound and carbon powder contained in the solidified product prevent oxidation in the pulverization step (III) and the heating step (IV), and further promote reduction. Further, the organic compound and the carbon powder remain after the heating step (IV) and function as a conductive material. Therefore, the conductivity of the positive electrode material for secondary batteries can be increased.
  • the organic compound at least one selected from the group consisting of saccharides, amino acids, peptides, aldehydes, ketones, glycols, polyvinyl alcohol, and fatty acids is preferable, and saccharides, glycols, or polyvinyl alcohol is particularly preferable.
  • the saccharide include monosaccharides such as glucose, fructose, and galactose, oligosaccharides such as sucrose, maltose, cellobiose, and trehalose, invert sugar, polysaccharides such as dextrin, amylose, amylopectin, and cellulose, and ascorbic acid. It is done.
  • amino acids examples include amino acids such as alanine and glycine.
  • Peptides include low molecular weight peptides having a molecular weight of 1,000 or less.
  • carbon powder carbon black, graphite, acetylene black and the like are preferable.
  • the carbon powder may be fibrous carbon or plate-like carbon.
  • the pulverization step (III) when the solidified product is pulverized with an organic compound or carbon powder, there is an advantage that the step of mixing the conductive material can be omitted after the heating step (IV). Moreover, the organic compound and carbon powder can suppress the grain growth of the solidified product.
  • wet pulverization is preferably employed in order to uniformly disperse the pulverized product on the surface.
  • a dispersion medium for pulverization water or an organic solvent such as ethanol, isopropyl alcohol, acetone, hexane, or toluene can be used. Of these, water is preferable because it is inexpensive.
  • a dry method is preferable for the pulverization step (III) when the solidified product contains carbon powder.
  • the pulverized product obtained in the pulverization step (III) may be subjected to another step before the heating step (IV) as long as it does not adversely affect the next heating step (IV).
  • the heating step (IV) is a step of heating the pulverized product obtained in the pulverizing step (III).
  • a silicic acid-phosphoric acid compound having a composition represented by the following formula (2) is obtained.
  • a 1 + x + a M b Si x P 1-x O 4 + c2 (2) (In the formula, A, M, a, b and x have the same meaning as described above, but take an independent value from the value in formula (1), and c2 depends on the valence N of a, b and M. Number to do.)
  • the valence of N is preferably +2.
  • the product of the heating step (IV) is preferably crystal particles, and more preferably olivine type crystal particles.
  • the pulverized material is heated, so that the relaxation of the residual stress is promoted.
  • the composition, grain size, and distribution thereof are easier to control than those in the temperature lowering process.
  • the heating step (IV) in the case where the organic compound and / or carbon powder is included in the solidified product in the pulverizing step (III) causes the conductive material to be bonded to the surface of the product, preferably the crystal grains of the product. It can be a process.
  • the organic compound is thermally decomposed in the heating step (IV) and becomes a carbide to function as a conductive material.
  • the heating temperature in the heating step (IV) is preferably 500 to 1,000 ° C. When the heating temperature is 500 ° C. or higher, crystals are easily generated. When the heating temperature is 1,000 ° C. or less, melting of the pulverized product can be prevented.
  • the heating temperature is more preferably 600 to 900 ° C. When the heating temperature is used, crystal particles having appropriate crystallinity, particle diameter, particle size distribution, and the like are easily obtained, and olivine-type crystal particles are preferably obtained.
  • the heating step (IV) can be a step of removing the dispersion medium when the heating step (IV) is performed while the dispersion medium is included.
  • the heating in the heating step (IV) may be performed at a constant temperature after raising the temperature at once, or may be performed by changing the temperature in multiple stages. Since the particle diameter to be generated tends to increase as the heating temperature increases, the heating temperature is preferably set according to the desired particle diameter.
  • the heating time (holding time depending on the heating temperature) is preferably 1 to 72 hours in consideration of a desired particle size. Heating is preferably performed in a box furnace, tunnel kiln furnace, roller hearth furnace, rotary kiln furnace, microwave heating furnace, or the like that uses electricity, oil, gas, or the like as a heat source.
  • the heating step (IV) can be carried out in air, in an inert gas or in a reducing gas, and is preferably carried out in an inert gas or in a reducing gas.
  • the conditions in the inert gas and the reducing gas are the same as those in the melting step (I).
  • the heating step (IV) may be performed under reduced pressure (0.9 ⁇ 10 5 Pa or less) in an inert gas or a reducing gas.
  • a reducing agent eg, graphite
  • pulverized material eg, change from M 3+ to M 2+
  • the heating step (IV) after the heating step (IV), it is usually cooled to room temperature.
  • the cooling rate in the cooling is preferably ⁇ 30 ° C./hour to ⁇ 300 ° C./hour. By setting the cooling rate within this range, distortion due to heating can be removed, and when the product is a crystal, the target product can be obtained while maintaining the crystal structure. Moreover, it can cool without using a cooling means.
  • the cooling is preferably allowed to cool to room temperature. Cooling is preferably performed in an inert gas or a reducing gas.
  • the silicic acid-phosphoric acid compound obtained by the production method of the present invention is a novel compound useful as a positive electrode material for secondary batteries.
  • the silicic acid-phosphoric acid compound in the present invention has a multi-electron type as compared with the case where the number of atoms of the element A is 1.2 or more and is less than 1.2. Sometimes the capacity per unit mass increases. That is, when the element A is Li, the silicic acid-phosphoric acid compound in the present invention has a structure containing more than one and not more than two Li per unit ([SiO 4 ] + [PO 4 ]) tetrahedron.
  • the number of Li atoms can be 1.2 or more.
  • a silicic acid-phosphate compound in which [SiO 4 ] tetrahedron, [PO 4 ] tetrahedron, [LiO 4 ] tetrahedron and [MO 4 ] tetrahedron are uniformly distributed can be obtained.
  • the silicic acid-phosphoric acid compound preferably contains olivine type crystal particles.
  • the crystal particles include both primary particles and secondary particles. When secondary particles are present in the product, they may be crushed and pulverized as long as the primary particles are not destroyed.
  • a conductive material made of carbon derived from the organic compound or carbon powder on the surface of the silicic acid-phosphoric acid compound can be bonded uniformly and firmly.
  • the silicic acid-phosphoric acid compound to which the conductive material is bonded can be used as a positive electrode material for a secondary battery as it is.
  • the silicic acid-phosphate compound produced by the production method of the present invention preferably contains olivine type crystal particles, and is preferably olivine type crystal particles.
  • the olivine type crystal particle is a material that exhibits a multi-electron type theoretical electric capacity.
  • the composition of the silicic acid-phosphoric acid compound is preferably a compound represented by the following formula (3), wherein A is Li and M is at least one selected from the group consisting of Fe and Mn. y is particularly preferably 0 ⁇ y ⁇ 1.
  • the silicic acid-phosphoric acid compound having the composition represented by the formula (2) is a crystal, it is preferably a solid solution crystal or a eutectic crystal.
  • a solid solution crystal is likely to be formed. The reason is considered that a part of Si is substituted with P by the formula represented by formula (4).
  • AMPO 4 A 1 + x M [Si x P 1-x ] O 4 (4) (In the formula, x is 0.7 ⁇ x ⁇ 1.0, and [] represents a solid solution.)
  • the solid solution crystal has a sparse crystal structure and a Li ion easily moves in the crystal as compared with a crystal made of only Si. Therefore, a high capacity can be obtained and the electrical conductivity can be increased. Therefore, when used as a positive electrode material for a secondary battery, charge / discharge cycleability can be improved.
  • the silicic acid-phosphoric acid compound in the present invention contains a solid solution crystalline silicic acid-phosphoric acid compound
  • the silicic acid-phosphoric acid compound includes olivine type crystal particles which are solid solution crystals in which a part of Si is substituted with P. Is preferred.
  • the silicic acid-phosphoric acid compound is a solid solution crystal
  • Li ions easily move in the crystal, resulting in high capacity and increased electrical conductivity. To do. Therefore, when used as a positive electrode material for a secondary battery, a theoretical capacity is easily obtained, and it is considered that the charge / discharge cycleability is improved.
  • silicic acid-phosphoric acid compound eutectic when x is 0.3 ⁇ x ⁇ 0.7, eutectic is likely to occur. 0.3 ⁇ x ⁇ 0.7 is preferable, and 0.35 ⁇ x ⁇ 0.65 is more preferable.
  • the eutectic silicic acid-phosphoric acid compound (hereinafter referred to as “silicic acid-phosphoric acid compound eutectic” or simply “eutectic”) includes a crystal containing a silicon atom, a crystal containing a phosphorus atom, And a crystal containing a phosphorus atom and a silicon atom-containing crystal.
  • a eutectic containing at least one selected from the group consisting of type crystals is preferred.
  • the silicic acid-phosphoric acid compound eutectic is considered to be produced by the reaction mechanism represented by the following formula (5).
  • xA 2 MSiO 4 + (1-x) AMPO 4 (x ⁇ w 1 ) A 2 MSiO 4 + (1-x ⁇ w 2 ) AMPO 4 + wA 1 + z MSi z P 1 ⁇ z O 4 (5)
  • the silicic acid-phosphoric acid compound of the present invention is preferably a eutectic because it tends to increase electrical conductivity.
  • the reason is that, due to the generation of crystallites having a plurality of crystal structures and different electrical conductivities, a potential difference is generated between the crystallites when a potential is applied. This is thought to be due to the rise.
  • a structure having a grain boundary is formed between the crystallites in the primary particle, and this grain boundary is extremely thin as compared with the inside of the primary particle, which is considered to be because the electrical conductivity of the primary particle itself is increased.
  • the silicic acid-phosphoric acid compound of the present invention is particularly preferably an eutectic because it is easy to obtain high electric conductivity and charge / discharge cycleability is improved.
  • the silicic acid-phosphoric acid compound of the present invention has a high capacity when the silicic acid-phosphoric acid compound is applied to a positive electrode for a secondary battery, and solid solution crystals are particularly preferable in that good cycle characteristics can be easily obtained.
  • eutectic is particularly preferable from the viewpoint that high electrical conductivity is easily obtained when applied to a positive electrode for a secondary battery.
  • the average particle diameter of the silicic acid-phosphoric acid compound of the present invention is preferably 10 nm to 10 ⁇ m, more preferably 10 nm to 6 ⁇ m, and particularly preferably 10 nm to 2 ⁇ m in terms of volume-based median diameter.
  • the lower limit value may be 100 nm. By making the average particle diameter within this range, the conductivity becomes higher.
  • the average particle size can be determined by, for example, observation with an electron microscope or measurement with a laser diffraction particle size distribution meter.
  • Silicate - specific surface area of the phosphoric acid compound is preferably 0.2 ⁇ 200m 2 / g, preferably 0.5 ⁇ 200m 2 / g, 1 ⁇ 200m 2 / g is particularly preferred.
  • the upper limit value may be 100 m 2 / g or 10 m 2 / g.
  • the specific surface area can be measured by, for example, a specific surface area measuring apparatus using a nitrogen adsorption method.
  • the silicic acid-phosphoric acid compound obtained by the method for producing a silicic acid-phosphoric acid compound of the present invention is useful as a positive electrode material for a secondary battery. Therefore, a positive electrode for a secondary battery and a secondary battery can be produced using the silicic acid-phosphoric acid compound.
  • the secondary battery include a metal lithium secondary battery, a lithium ion secondary battery, and a lithium polymer secondary battery, and a lithium ion secondary battery is preferable.
  • the battery shape is not limited, and various shapes and sizes such as a cylindrical shape, a square shape, and a coin shape can be appropriately employed.
  • the production of the positive electrode for the secondary battery may be carried out in accordance with a known electrode production method except that the silicic acid-phosphate compound obtained by the production method of the present invention is used.
  • a known binder polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl chloride, ethylene propylene diene polymer, styrene-butadiene rubber, acrylonitrile-butadiene rubber, Fluorine rubber, polyvinyl acetate, polymethyl methacrylate, polyethylene, nitrocellulose, etc.
  • known conductive materials acetylene black, carbon, graphite, natural graphite, artificial graphite, needle coke, etc.
  • the obtained mixed powder may be pressure-bonded on a support made of stainless steel or filled in a metal container.
  • the mixed powder is mixed with an organic solvent (N-methylpyrrolidone, toluene, cyclohexane, dimethylformamide, dimethylacetamide, methyl ethyl ketone, methyl acetate, methyl acrylate, diethyltriamine, NN-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran.
  • organic solvent N-methylpyrrolidone, toluene, cyclohexane, dimethylformamide, dimethylacetamide, methyl ethyl ketone, methyl acetate, methyl acrylate, diethyltriamine, NN-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran.
  • the electrode can also be produced by a method such as applying a slurry obtained by mixing with a metal substrate such as aluminum, nickel, stainless steel or copper.
  • the positive electrode for a secondary battery obtained by the production method of the present invention is used as an electrode.
  • the negative electrode a known negative electrode active material can be used as the active material, but it is preferable to use at least one selected from the group consisting of a carbon material, an alkali metal material, and an alkaline earth metal material.
  • the electrolyte solution is preferably non-aqueous. That is, as the secondary battery obtained by the production method of the present invention, a nonaqueous electrolyte lithium ion secondary battery is preferable.
  • Lithium (Li 2 CO 3 ), sodium carbonate (Na 2 CO 3 ), triiron tetroxide (Fe 3 O 4 ), manganese dioxide (MnO 2 ), tricobalt tetroxide (Co 3 O 4 ), nickel oxide (NiO ), Silicon dioxide (SiO 2 ), and ammonium dihydrogen phosphate (NH 4 H 2 PO 4 ) were weighed, mixed and pulverized in a dry process to obtain a raw material formulation.
  • Each raw material formulation was filled in a platinum alloy crucible containing 20% by mass of rhodium.
  • the crucible was placed in an electric furnace (manufactured by Motoyama, apparatus name: NH-3035) equipped with a heating element made of molybdenum silicide.
  • the temperature was raised at a rate of + 300 ° C./hour and heated at 1,450 to 1,500 ° C. for 0.5 hour.
  • Each melt was obtained after confirming that it became transparent visually.
  • the composition formula of the obtained melt is shown in the right column of Table 1.
  • the flake solidified product obtained in the cooling step was lightly kneaded and finely ground, and then coarsely pulverized using a pestle and mortar. Further, the coarsely pulverized solidified product was pulverized in a dry manner using a planetary mill using zirconia balls as a pulverizing medium to obtain a pulverized product.
  • the particle diameter of the pulverized product of Example 1 was measured using a laser diffraction / scattering particle size analyzer (manufactured by Horiba, Ltd., apparatus name: LA-950), the median diameter in terms of volume was 2.8 ⁇ m.
  • the pulverized product obtained in the pulverization step was placed in a 3% by volume H 2 —Ar atmosphere, and each example was heated for 8 hours at four temperature conditions of 600 ° C., 700 ° C., 800 ° C., and 900 ° C. Then, the mixture was cooled (air-cooled) at a rate of ⁇ 200 ° C./hour to precipitate silicic acid-phosphoric acid compound particles.
  • X-ray diffraction, particle size distribution, and composition analysis were performed on the particles subjected to the heating step at 700 ° C.
  • the mineral phase of the obtained silicic acid-phosphate compound particles was measured using an X-ray diffraction apparatus (manufactured by Rigaku Corporation, apparatus name: RINT TTRIII).
  • the particles obtained in Examples 1 to 4 and Examples 8 to 24 are all orthorhombic olivine type Li 2 MSiO 4 (K. Zaghib et al., Journal of Power Sources, 160, 1381-1386, 2006 and R. Dominko et al., Electrochemistry Communications, 8, 217-222 (2006)). From the results, it was confirmed that the silicic acid-phosphoric acid compound particles were crystals and consisted of solid solution crystals in which part of Si in the A 2 MSiO 4 crystals was substituted with P.
  • FIGS. 2 (a), 2 (b), and 2 (c), respectively, in Examples 19, 20, 21, and 22. are shown in (a), (b), (c), and (d) of FIG. 3, respectively.
  • composition analysis The chemical composition of the resulting silicic acid-phosphoric acid compound particles was measured. First, the particles were heated and decomposed at 120 ° C. with a 2.5 mol / L KOH solution, and the decomposition solution was dried under hydrochloric acid acidity. Next, after filtration as a hydrochloric acid acidic solution, a filtrate and a residue were obtained. The amounts of Si, Fe, Mn, Co, and Ni in the filtrate were quantified using an inductively coupled emission spectroscopic analyzer (manufactured by Seiko Instruments Inc., apparatus name: SPS3100).
  • the amounts of Li and Na in the filtrate were quantified using an atomic absorption photometer (manufactured by Hitachi High-Technologies Corporation, apparatus name: Z-2310). Calculate the amounts of SiO 2 , P 2 O 5 , FeO, MnO, CoO, NiO, Li 2 O, and Na 2 O from the quantitative values of Si, P, Fe, Mn, Co, Ni, Li, and Na, respectively. did. Further, the residue was ashed and then decomposed with hydrofluoric acid-sulfuric acid, and the weight loss due to this treatment was defined as the amount of SiO 2 . The total amount of SiO 2 was the sum of the amount calculated from the weight loss and the amount of SiO 2 in the filtrate. Table 2 shows the quantitative values of the chemical composition of the silicic acid-phosphate compound particles obtained in Examples 1 to 7 and Examples 15 to 18.
  • Examples 25 to 35 The coarsely pulverized product obtained by melting, cooling, and coarsely pulverizing in Examples 1 to 7 and Examples 19 to 22 and carbon black were mixed at a mass ratio of 9: 1 between the pulverized product and the amount of carbon in the carbon black. Each was mixed and ground using a planetary mill in the same manner as in Example 1.
  • the carbon-containing pulverized product in each example was heated in Ar gas at two temperatures of 700 ° C. and 800 ° C. for 8 hours, cooled (air-cooled) at a rate of ⁇ 200 ° C./hour, and then silicic acid-phosphoric acid. Compound particles were obtained.
  • the X-ray diffraction pattern of the resulting silicate-phosphate compound was consistent with that of olivine type lithium iron silicate.
  • Examples 32, 33, 34, and 35 the X-ray diffraction patterns of silicic acid-phosphoric acid compounds obtained by heating at 700 ° C. are shown in FIGS. 4 (a), (b), (c), ( d).
  • Example 27 the carbon content of silicic acid-phosphate compound particles obtained by heating at 700 ° C. for 8 hours and cooling (air cooling) at a rate of ⁇ 200 ° C./hour was measured using a carbon analyzer (Horiba). They were 9.5% by mass and 9.1% by mass, respectively, as measured by Seisakusho, apparatus name: EMIA-920V. Moreover, when the specific surface area of this particle
  • Example 36 The composition of the melt is 32.8%, 34.5%, 31.0%, 1.7% in terms of Li 2 O, FeO, SiO 2 and P 2 O 5 (unit: mol%).
  • Lithium carbonate (Li 2 CO 3 ), ferric trioxide (Fe 2 O 3 ), silicon dioxide (SiO 2 ), and ammonium dihydrogen phosphate (NH 4 H 2 PO 4 ) were weighed and dried
  • a raw material formulation was prepared by mixing and grinding. Except that this raw material formulation was melted in air without controlling the atmosphere, it was melted, cooled, and coarsely pulverized in the same manner as in Example 3 to obtain a coarsely pulverized product.
  • the obtained coarsely pulverized product and carbon black were mixed and pulverized in the same manner as in Example 27, and the carbon-containing pulverized product was heated in Ar gas at 700 ° C. for 8 hours, at a rate of ⁇ 200 ° C./hour.
  • silica-phosphate compound particles were obtained.
  • the X-ray diffraction pattern of the resulting silicate-phosphate compound was consistent with that of olivine type lithium iron silicate.
  • the carbon content of the obtained silicic acid-phosphoric acid compound particles was measured and found to be 7.2% by mass.
  • the specific surface area was measured and found to be 24 m 2 / g.
  • the composition of the melt is 27.1%, 50.3%, 20.1%, and 2.5% in terms of Li 2 O, FeO, SiO 2 , and P 2 O 5 (unit: mol%).
  • Lithium carbonate (Li 2 CO 3 ), triiron tetroxide (Fe 3 O 4 ), silicon dioxide (SiO 2 ), and ammonium dihydrogen phosphate (NH 4 H 2 PO 4 ) were weighed and dried Were mixed and pulverized to obtain a raw material formulation.
  • the raw material formulation was melted in the same manner as in Example 1, but could not be melted.
  • the composition of the melt is Li 2 O, FeO, SiO 2 , P 2 O 5 equivalent (unit: mol%), 50.6. %, 25.3%, 22.8%, and 1.3% to be lithium carbonate (Li 2 CO 3 ), triiron tetroxide (Fe 3 O 4 ), silicon dioxide (SiO 2 ), phosphorus Ammonium dihydrogenammonium (NH 4 H 2 PO 4 ) was weighed, mixed and pulverized in a dry process to obtain a raw material formulation. Although this raw material formulation was melted in the same manner as in Example 1, the melt was crystallized by the cooling step, and the cooling step could not be performed.
  • the composition of the melt is 31.6%, 35.0%, 31.6%, and 1.8% in terms of Li 2 O, FeO, SiO 2 , and P 2 O 5 (unit: mol%).
  • Lithium carbonate (Li 2 CO 3 ), triiron tetroxide (Fe 3 O 4 ), silicon dioxide (SiO 2 ), and ammonium dihydrogen phosphate (NH 4 H 2 PO 4 ) were weighed and dried And mixed and pulverized to obtain a raw material formulation.
  • the raw material formulation was melted at 1,450 ° C. and then cooled at ⁇ 300 ° C./hour to obtain a crystallized product.
  • the mineral phase of the obtained crystallized product was identified using XRD, it was mainly composed of Li 2 SiO 3 and Fe 3 O 4 . That is, the target compound cannot be obtained unless the cooling step, the pulverizing step and the heating step are performed.
  • Examples 37 to 40 Production examples of positive electrode for Li-ion secondary battery and battery for evaluation
  • a pulverized product of silicic acid-phosphate compound particles obtained by heating at 700 ° C. for 8 hours and cooling (air cooling) at a rate of ⁇ 200 ° C./hour
  • the mass% sucrose solution was mixed and pulverized so that the mass ratio of the pulverized product and the amount of carbon in the sucrose was 95: 5, heated in N 2 gas at 600 ° C. for 2 hours, and cooled. After pulverization, an active material was obtained.
  • the active material, polyvinylidene fluoride resin (binder) and acetylene black (conductive material) are weighed so that the mass ratio is 85: 5: 10, and uniform in N-methylpyrrolidone (solvent)
  • a slurry was prepared by mixing until Next, the slurry was applied to an aluminum foil having a thickness of 30 ⁇ m with a bar coater. After drying this at 120 degreeC in the air and removing a solvent, after consolidating the coating layer with the roll press, it cut out to the strip shape of width 10mm * length 40mm.
  • the coating layer was peeled off leaving a 10 ⁇ 10 mm tip of strip-shaped aluminum foil, which was used as an electrode.
  • the coating thickness of the obtained electrode after roll pressing was 20 ⁇ m.
  • the obtained electrode was vacuum-dried at 150 ° C., then carried into a glove box filled with purified Ar gas, and opposed to a counter electrode in which a lithium foil was pressure-bonded to a nickel mesh with a porous polyethylene film separator. Both sides were fixed with a polyethylene plate.
  • the discharge capacities at the third cycle were 161 mAh / g (Example 37), 145 mAh / g (Example 38), 203 mAh / g (Example 39), and 241 mAh / g (Example 40), respectively.
  • Example 41 to 42 Using the silicic acid-phosphoric acid compound particles obtained in Examples 26 and 33 as an active material, the mass ratio of this to polyvinylidene fluoride resin (binder) and acetylene black (conductive material) is 90: 5.
  • the electrode was produced in the same manner as in Example 37 except that the weight was adjusted so that the ratio was 5 and the charge / discharge characteristics were evaluated in the same manner as in Example 37.
  • the discharge capacity at the third cycle was 153 mAh / g (Example 41) and 191 mAh / g (Example 42).
  • Examples 1 to 36 a silicic acid-phosphoric acid compound having a desired composition could be easily produced. Further, it was confirmed that the produced silicic acid-phosphoric acid compound had excellent characteristics as a positive electrode material for a secondary battery and further as a secondary battery (Examples 37 to 42).
  • the method for producing a silicic acid-phosphoric acid compound of the present invention is useful because the composition of the silicic acid-phosphoric acid compound can be easily controlled and produced.
  • the obtained silicic acid-phosphoric acid compound is useful for a positive electrode material for a secondary battery and further for a secondary battery.
  • a secondary battery using the silicate-phosphate compound of the present invention as a positive electrode material is useful as a secondary battery mounted in a plug-in hybrid vehicle or an electric vehicle, and as a storage battery for storing power.

Abstract

A method for manufacturing a silicate-phosphate compound, said method providing increased control over composition and particle size. After a solidified material is obtained by cooling a molten material represented by A1+ x + a M b Si x P1− x O4+ c1 (wherein A represents at least one element selected from the group comprising lithium, sodium, and potassium; M represents at least one element selected from the group comprising iron, manganese, cobalt, and nickel; a satisfies −0.1 ≤ a ≤ 0.4; b satisfies 0.7 ≤ b ≤ 1.3; x satisfies 0.3 ≤ x < 1.0; and c1 is a number that depends on a, b, and the valence (N) of M and becomes c2 after a heating step), a pulverized material is obtained by pulverizing said solidified material. A silicate-phosphate compound having a composition represented by A1+ x + a M b Si x P1− x O4+ c2 (wherein A, M, a, b, and x have the same meanings as above, and c2 is a number that depends on a, b, and the valence (N) of M) is manufactured by heating the pulverized material.

Description

ケイ酸－リン酸化合物、二次電池用正極、二次電池、およびそれらの製造方法Silicic acid-phosphoric acid compound, positive electrode for secondary battery, secondary battery, and production method thereof
　本発明はケイ酸－リン酸化合物、二次電池用正極、二次電池、およびそれらの製造方法に関する。 The present invention relates to a silicic acid-phosphoric acid compound, a positive electrode for a secondary battery, a secondary battery, and a production method thereof.
　近年、世界的なＣＯ２排出規制や省エネルギーの観点から、プラグインハイブリッド自動車や電気自動車の開発が進められている。また、スマートシティやスマートコミュニティの構想の実現のために、電力貯蔵用の蓄電池の開発が望まれている。これらの実現には、使用される二次電池が、安全性を維持しつつ、高容量化、高エネルギー化、大型化することが課題とされている。そして、次世代のリチウムイオン二次電池用正極材料等として、資源面、安全面、コスト面、安定性等の点での優位性から、オリビン型の正極材料が注目されている。 In recent years, plug-in hybrid vehicles and electric vehicles have been developed from the viewpoint of global CO 2 emission regulations and energy saving. In addition, in order to realize the concept of a smart city and a smart community, development of a storage battery for power storage is desired. In order to realize these, it is a problem that the secondary battery to be used is increased in capacity, energy, and size while maintaining safety. As the next-generation lithium ion secondary battery positive electrode material and the like, an olivine-type positive electrode material has attracted attention because of its advantages in terms of resources, safety, cost, and stability.
　二次電池の正極の候補材料として、単位式中に２個のＬｉを含み、多電子反応による高容量化が可能なオリビン型ケイ酸化合物（Ｌｉ２ＦｅＳｉＯ４）が提案されている（非特許文献１参照）。 As a candidate material for a positive electrode of a secondary battery, an olivine-type silicic acid compound (Li 2 FeSiO 4 ) containing two Li in a unit formula and capable of increasing the capacity by a multi-electron reaction has been proposed (non-patent) Reference 1).
　特許文献１には、リン酸ケイ素塩を含む活物質を使用した正極が記載され、該活物質として式Ｌｉ３Ｍ'（２－ｂ）Ｍ''ｂＳｉＰ２Ｏ１２（Ｍ'は＋３価の金属または半金属元素、Ｍ''は＋４価の金属または半金属元素、ｂは０～２である。）で表される活物質が提案されている。 Patent Document 1 describes a positive electrode using an active material containing a silicon phosphate salt. The active material includes the formula Li 3 M ′ (2-b) M ″ b SiP 2 O 12 (M ′ is +3 valent). In this case, an active material represented by a metal or metalloid element, M ″ is a +4 valent metal or metalloid element, and b is 0 to 2 is proposed.
　特許文献２には、ＰおよびＳｉを含有する二次電池用正極材料として、式Ｌｉ１．７Ｍｎ０．７Ｆｅ０．３Ｓｉ０．７Ｐ０．３Ｏ４で表される固溶体が記載されている。また該固溶体を、Ｌｉ２ＭｎＳｉＯ４と、ＬｉＦｅＰＯ４とを粉砕して、加熱した後に放冷する方法で得たことが記載されている。 Patent Document 2 describes a solid solution represented by the formula Li 1.7 Mn 0.7 Fe 0.3 Si 0.7 P 0.3 O 4 as a positive electrode material for a secondary battery containing P and Si. Has been. In addition, it is described that the solid solution was obtained by a method in which Li 2 MnSiO 4 and LiFePO 4 were pulverized, heated and then allowed to cool.
　特許文献３には、式Ａａ＋ｘＭ'１＋（ｘ／２）Ｍ''（１－ａ）／２Ｐ１－ｘＳｉｘＯ４で表される化合物を含む電極活物質および式Ａａ＋ｘＭ'１＋（ｘ／２）Ｍ''（１－ａ）／３Ｐ１－ｘＳｉｘＯ４で表される化合物を含む電極活物質（ＡはＬｉ等、ｘ＝０、０＜ａ＜１、Ｍ'はＭｎ、Ｆｅ、Ｃｏ等、Ｍ''はＴｉ、Ｖ、Ｃｒ、Ｍｎである。）が提案されている。 Patent Document 3 discloses an electrode active material containing a compound represented by the formula A a + x M ′ 1+ (x / 2) M ″ (1-a) / 2 P 1-x Si x O 4 and the formula A a + x M ' 1+ (x / 2) M'' (1-a) / 3 P 1-x Si x O 4 -containing electrode active material (A is Li, etc., x = 0, 0 <a <1 M ′ is Mn, Fe, Co, etc., and M ″ is Ti, V, Cr, Mn.).
特表２００２－５１９８３６号公報Special table 2002-519836 gazette 特開２００１－２６６８８２号公報JP 2001-266882 A 特表２００５－５１９４５１号公報Special table 2005-519451 gazette
　非特許文献１に記載されたＬｉ２ＦｅＳｉＯ４は、固相反応により製造されるため、製造工程が複雑で、製造コストがかさむ。 Since Li 2 FeSiO 4 described in Non-Patent Document 1 is manufactured by a solid-phase reaction, the manufacturing process is complicated and the manufacturing cost increases.
　特許文献１には、Ｌｉ、Ｍ'およびＭ''、Ｓｉ、およびＰの組成比が特定の比率にある本発明の化合物は記載されていない。また、得られる活物質の結晶構造として開示されているのはナシコン構造のみである。ナシコン型の活物質は、単位質量当たりの容量が充分には得られない材料である。特許文献１に記載された製造方法は、原料を１７０℃で４時間加熱した後、約９００℃で約１６時間保持し、必要に応じて冷却、研磨および再加熱を繰り返して反応させる方法である。該方法は、製造工程が複雑で、かつ時間がかかり、製造コストがかさむ。 Patent Document 1 does not describe the compound of the present invention in which the composition ratio of Li, M ′ and M ″, Si, and P is a specific ratio. Further, only the NASICON structure is disclosed as the crystal structure of the obtained active material. The NASICON active material is a material that does not provide a sufficient capacity per unit mass. The manufacturing method described in Patent Document 1 is a method in which a raw material is heated at 170 ° C. for 4 hours, then held at about 900 ° C. for about 16 hours, and is allowed to react by repeating cooling, polishing and reheating as necessary. . In this method, the manufacturing process is complicated, takes time, and increases the manufacturing cost.
　特許文献２に記載されている製造方法は、Ｌｉ２ＭｎＳｉＯ４およびＬｉＦｅＰＯ４を固相反応させて製造する方法である。固相反応は製造工程が複雑で、製造コストがかさみ、大量生産することが困難であり、組成制御も容易でない。 The production method described in Patent Document 2 is a method for producing Li 2 MnSiO 4 and LiFePO 4 by solid-phase reaction. The solid-phase reaction has a complicated manufacturing process, is expensive to manufacture, is difficult to mass-produce, and composition control is not easy.
　特許文献３の製造方法は、固相反応により製造されるため、製造工程が複雑で、製造コストがかさむ。 Since the manufacturing method of Patent Document 3 is manufactured by a solid-phase reaction, the manufacturing process is complicated and the manufacturing cost increases.
　本発明の目的は、単位質量当たりの高容量化が可能なケイ酸－リン酸化合物の、組成および粒径の制御がしやすい、製造方法の提供にある。該化合物は、二次電池用正極および二次電池の正極に用いる活物質として有用である。本発明は、特性や信頼性に優れる二次電池用正極および二次電池を製造する方法をも提供する。 An object of the present invention is to provide a production method in which the composition and particle size of a silicic acid-phosphoric acid compound capable of increasing the capacity per unit mass can be easily controlled. The compound is useful as an active material used for a positive electrode for a secondary battery and a positive electrode for a secondary battery. The present invention also provides a positive electrode for a secondary battery having excellent characteristics and reliability and a method for producing the secondary battery.
　本発明は、以下の［１］～［１２］の発明である。
［１］下式（１）で表される組成を有する溶融物を得る溶融工程、
　前記溶融物を冷却し固化物を得る冷却工程、
　前記固化物を粉砕し粉砕物を得る粉砕工程、および
　前記粉砕物を加熱して下式（２）で表される組成を有するケイ酸－リン酸化合物を得る加熱工程、
をこの順に具備することを特徴とするケイ酸－リン酸化合物の製造方法。
　Ａ１＋ｘ＋ａＭｂＳｉｘＰ１－ｘＯ４＋ｃ１　　　　　（１）
（式中、元素ＡはＬｉ、ＮａおよびＫからなる群より選ばれる少なくとも１種の元素であり、元素ＭはＦｅ、Ｍｎ、ＣｏおよびＮｉからなる群より選ばれる少なくとも１種の元素である。ａは－０．１≦ａ≦０．４であり、ｂは０．７≦ｂ≦１．３であり、ｘは０．３≦ｘ＜１．０であり、ｃ１はａ、ｂおよびＭの価数Ｎに依存する数であり、加熱工程後にｃ２となる数である。）
　Ａ１＋ｘ＋ａＭｂＳｉｘＰ１－ｘＯ４＋ｃ２　　　　　（２）
（式中、Ａ、Ｍ、ａ、ｂおよびｘは前記と同じ意味を示すが、前記とは独立した値であり、ｃ２はａ、ｂおよびＭの価数Ｎに依存する数である。）
［２］前記溶融工程が、
　元素Ａを含む化合物が、Ａの炭酸塩、Ａの炭酸水素塩、Ａの水酸化物、Ａのケイ酸塩、Ａのリン酸塩、Ａのリン酸水素塩、Ａの硝酸塩、Ａの塩化物、Ａの硫酸塩、Ａの酢酸塩、およびＡのシュウ酸塩からなる群より選ばれる少なくとも１種（ただし、該１種以上の一部または全部は、それぞれ、水和塩を形成していてもよい。）として含まれ、
　元素Ｍを含む化合物が、Ｍの酸化物、Ｍのオキシ水酸化物、Ｍのケイ酸塩、Ｍの金属、Ｍのリン酸塩、Ｍの塩化物、Ｍの硝酸塩、Ｍの硫酸塩、およびＭの有機塩からなる群より選ばれる少なくとも１種として含まれ、
　Ｓｉを含む化合物が、酸化ケイ素、Ａのケイ酸塩、Ｍのケイ酸塩、およびケイ素のアルコキシドからなる群より選ばれる少なくとも１種として含まれ、
　Ｐを含む化合物が、酸化リン、リン酸アンモニウム、リン酸水素アンモニウム、リン酸、ポリリン酸、亜リン酸、次亜リン酸、Ａのリン酸塩、およびＭのリン酸塩からなる群より選ばれる少なくとも１種として含まれる、
原料調合物を加熱して、前記式（１）で表される組成を有する溶融物を得る工程である、［１］のケイ酸－リン酸化合物の製造方法。
［３］前記元素ＡがＬｉである、［１］または［２］のケイ酸－リン酸化合物の製造方法。
［４］前記元素ＭがＦｅおよびＭｎからなる群より選ばれる少なくとも１種である、［１］～［３］のケイ酸－リン酸化合物の製造方法。
［５］前記式（１）で表される組成を有する溶融物が、下式（３Ａ）で表される組成を有する溶融物であり、前記式（２）で表される組成を有するケイ酸－リン酸化合物が、下式（３）で表される組成を有するオリビン型結晶粒子を含む化合物である、［１］のケイ酸－リン酸化合物の製造方法。
　Ｌｉ１＋ｘ＋ａ（ＦｅｙＭｎ１－ｙ）ｂＳｉｘＰ１－ｘＯ４＋ｃ１　　　（３Ａ）
　Ｌｉ１＋ｘ＋ａ（ＦｅｙＭｎ１－ｙ）ｂＳｉｘＰ１－ｘＯ４＋ｃ２　　　（３）
（式中、ａ、ｂ、ｃ１、ｃ２およびｘは前記と同じ意味を示し、ｙは０≦ｙ≦１である。ただし、式（３Ａ）と式（３）において、ａ、ｂ、ｘおよびｙは独立した値を示す。）
［６］前記冷却工程において、冷却速度を－１０３℃／秒～－１０１０ ℃／秒とする、［１］～［５］のケイ酸－リン酸化合物の製造方法。
［７］前記粉砕工程において、前記固化物に、有機化合物および炭素粉末からなる群より選択される少なくとも１種の炭素源を含ませ、かつ該炭素源中の炭素換算量（質量）の割合が、固化物の質量と、該炭素源中の炭素換算量（質量）との合計質量に対して０．１～２０質量％である、［１］～［６］のケイ酸－リン酸化合物の製造方法。 The present invention is the following [1] to [12].
[1] A melting step for obtaining a melt having a composition represented by the following formula (1):
A cooling step of cooling the melt to obtain a solidified product,
A pulverizing step of pulverizing the solidified product to obtain a pulverized product, and a heating step of heating the pulverized product to obtain a silicic acid-phosphate compound having a composition represented by the following formula (2):
In this order. A method for producing a silicic acid-phosphoric acid compound.
A 1 + x + a M b Si x P 1-x O 4 + c1 (1)
(In the formula, element A is at least one element selected from the group consisting of Li, Na and K, and element M is at least one element selected from the group consisting of Fe, Mn, Co and Ni. a is −0.1 ≦ a ≦ 0.4, b is 0.7 ≦ b ≦ 1.3, x is 0.3 ≦ x <1.0, and c1 is a, b and M (It is a number that depends on the valence N of and is a number that becomes c2 after the heating step.)
A 1 + x + a M b Si x P 1-x O 4 + c2 (2)
(In the formula, A, M, a, b and x have the same meaning as described above, but are values independent of the above, and c2 is a number depending on the valence N of a, b and M.)
[2] The melting step includes
Compound containing element A is A carbonate, A bicarbonate, A hydroxide, A silicate, A phosphate, A hydrogen phosphate, A nitrate, A chloride Or at least one selected from the group consisting of A sulfate, A acetate, and A oxalate (however, some or all of the one or more form a hydrate salt). May be included),
The compound comprising element M is M oxide, M oxyhydroxide, M silicate, M metal, M phosphate, M chloride, M nitrate, M sulfate, and Included as at least one selected from the group consisting of organic salts of M;
A compound containing Si is included as at least one selected from the group consisting of silicon oxide, A silicate, M silicate, and silicon alkoxide,
The compound containing P is selected from the group consisting of phosphorus oxide, ammonium phosphate, ammonium hydrogen phosphate, phosphoric acid, polyphosphoric acid, phosphorous acid, hypophosphorous acid, A phosphate, and M phosphate Included as at least one
The method for producing a silicic acid-phosphoric acid compound according to [1], wherein the raw material preparation is heated to obtain a melt having a composition represented by the formula (1).
[3] The method for producing a silicic acid-phosphoric acid compound according to [1] or [2], wherein the element A is Li.
[4] The method for producing a silicic acid-phosphate compound according to [1] to [3], wherein the element M is at least one selected from the group consisting of Fe and Mn.
[5] The melt having the composition represented by the formula (1) is a melt having the composition represented by the following formula (3A), and the silicic acid having the composition represented by the formula (2) The method for producing a silicic acid-phosphoric acid compound according to [1], wherein the phosphoric acid compound is a compound containing olivine type crystal particles having a composition represented by the following formula (3):
Li 1 + x + a (Fe y Mn 1-y ) b Si x P 1-x O 4 + c1 (3A)
Li 1 + x + a (Fe y Mn 1-y ) b Si x P 1-x O 4 + c2 (3)
(Wherein, a, b, c1, c2 and x have the same meaning as described above, and y is 0 ≦ y ≦ 1, provided that in formula (3A) and formula (3), a, b, x and y represents an independent value.)
[6] The method for producing a silicic acid-phosphate compound according to [1] to [5], wherein, in the cooling step, the cooling rate is −10 3 ° C./second to −10 10 ° C./second.
[7] In the pulverization step, the solidified product includes at least one carbon source selected from the group consisting of an organic compound and carbon powder, and a ratio of a carbon conversion amount (mass) in the carbon source is The silicic acid-phosphoric acid compound of [1] to [6] is 0.1 to 20% by mass relative to the total mass of the mass of the solidified product and the carbon equivalent amount (mass) in the carbon source. Production method.
［８］前記加熱工程を５００～１，０００℃に加熱することにより行う、［１］～［７］のケイ酸－リン酸化合物の製造方法。
［９］［１］～［８］の製造方法によってケイ酸－リン酸化合物を得て、次に該ケイ酸－リン酸化合物を二次電池用正極材料に用いて二次電池用正極を製造することを特徴とする二次電池用正極の製造方法。
［１０］［９］の製造方法で二次電池用正極を得て、次に、該二次電池用正極を用いて二次電池を製造することを特徴とする二次電池の製造方法。
［１１］下式（２）で表される組成を有することを特徴とするケイ酸－リン酸化合物。
　Ａ１＋ｘ＋ａＭｂＳｉｘＰ１－ｘＯ４＋ｃ２　　　　　（２）
（式中、元素ＡはＬｉ、ＮａおよびＫからなる群より選ばれる少なくとも１種の元素であり、元素ＭはＦｅ、Ｍｎ、ＣｏおよびＮｉからなる群より選ばれる少なくとも１種の元素である。ａは－０．１≦ａ≦０．４であり、ｂは０．７≦ｂ≦１．３であり、ｘは０．３≦ｘ＜０．７であり、ｃ２はａ、ｂおよびＭの価数Ｎに依存する数である。）
［１２］下式（３）で表される組成を有し、オリビン型結晶粒子を含む、［１１］に記載のケイ酸－リン酸化合物。
　Ｌｉ１＋ｘ＋ａ（ＦｅｙＭｎ１－ｙ）ｂＳｉｘＰ１－ｘＯ４＋ｃ２　　　　（３）
（式中の記号は前記式（２）におけると同じ意味を示し、０≦ｙ≦１である。） [8] The method for producing a silicic acid-phosphoric acid compound according to [1] to [7], wherein the heating step is performed by heating to 500 to 1,000 ° C.
[9] A silicic acid-phosphoric acid compound is obtained by the production method of [1] to [8], and then a positive electrode for a secondary battery is produced using the silicic acid-phosphoric acid compound as a positive electrode material for a secondary battery. A method for producing a positive electrode for a secondary battery.
[10] A method for producing a secondary battery, comprising obtaining a positive electrode for a secondary battery by the production method of [9], and then producing a secondary battery using the positive electrode for a secondary battery.
[11] A silicic acid-phosphoric acid compound having a composition represented by the following formula (2):
A 1 + x + a M b Si x P 1-x O 4 + c2 (2)
(In the formula, element A is at least one element selected from the group consisting of Li, Na and K, and element M is at least one element selected from the group consisting of Fe, Mn, Co and Ni. a is −0.1 ≦ a ≦ 0.4, b is 0.7 ≦ b ≦ 1.3, x is 0.3 ≦ x <0.7, and c2 is a, b, and M The number depends on the valence N of
[12] The silicic acid-phosphate compound according to [11], which has a composition represented by the following formula (3) and includes olivine type crystal particles.
Li 1 + x + a (Fe y Mn 1-y ) b Si x P 1-x O 4 + c2 (3)
(The symbols in the formula have the same meaning as in formula (2), and 0 ≦ y ≦ 1.)
　本発明の製造方法は、ケイ酸－リン酸化合物の組成、粒径およびこれらの均一性を制御しやすいため、電極材料として有用であり、種々の組成を有するケイ酸－リン酸化合物を効率的に製造できる。本発明のケイ酸－リン酸化合物は多電子型の反応を示す化合物である。よって、本発明のケイ酸－リン酸化合物を用いることにより、特性や信頼性に優れる二次電池用正極材料、および二次電池が製造できる。さらに、本発明は、ケイ酸－リン酸化合物を提供する。 The production method of the present invention is useful as an electrode material because the composition, particle size and uniformity of the silicic acid-phosphoric acid compound can be easily controlled, and the silicic acid-phosphoric acid compound having various compositions is efficiently used. Can be manufactured. The silicic acid-phosphoric acid compound of the present invention is a compound that exhibits a multi-electron type reaction. Therefore, by using the silicic acid-phosphoric acid compound of the present invention, a positive electrode material for a secondary battery and a secondary battery having excellent characteristics and reliability can be manufactured. Furthermore, the present invention provides a silicic acid-phosphoric acid compound.
実施例１、２、３および４で製造したケイ酸－リン酸化合物のＸ線回折パターンを示す図である。FIG. 4 is a view showing an X-ray diffraction pattern of silicic acid-phosphoric acid compounds produced in Examples 1, 2, 3 and 4. 実施例５、６および７で製造したケイ酸－リン酸化合物のＸ線回折パターンを示す図である。FIG. 6 is a view showing an X-ray diffraction pattern of silicic acid-phosphoric acid compounds produced in Examples 5, 6 and 7. 実施例１９、２０、２１および２２で製造したケイ酸－リン酸化合物のＸ線回折パターンを示す図である。FIG. 4 is a diagram showing an X-ray diffraction pattern of silicic acid-phosphoric acid compounds produced in Examples 19, 20, 21 and 22. 実施例３２、３３、３４および３５で製造したケイ酸－リン酸化合物のＸ線回折パターンを示す図である。FIG. 4 is a view showing an X-ray diffraction pattern of silicic acid-phosphoric acid compounds produced in Examples 32, 33, 34 and 35.
＜ケイ酸－リン酸化合物の製造方法＞
　本発明のケイ酸－リン酸化合物の製造方法は、以下の溶融工程（Ｉ）、冷却工程（ＩＩ）、粉砕工程（ＩＩＩ）、および加熱工程（ＩＶ）の各工程を、この順に行う。（Ｉ）～（ＩＶ）の工程前、工程間、および工程後には、各工程に影響を及ぼさない限り、他の工程を行ってもよい。 <Method for producing silicic acid-phosphoric acid compound>
In the method for producing a silicic acid-phosphoric acid compound of the present invention, the following melting step (I), cooling step (II), pulverization step (III), and heating step (IV) are performed in this order. Other steps may be performed before, between, and after the steps (I) to (IV) as long as each step is not affected.
溶融工程（Ｉ）：式Ａ１＋ｘ＋ａＭｂＳｉｘＰ１－ｘＯ４＋ｃ１（式中の記号は前記と同じ意味を示す。）で表される組成を有する溶融物を得る工程、
冷却工程（ＩＩ）：前記溶融物を冷却し固化物を得る工程、
粉砕工程（ＩＩＩ）：前記固化物を粉砕し粉砕物を得る工程、および
加熱工程（ＩＶ）：前記粉砕物を加熱して、式Ａ１＋ｘ＋ａＭｂＳｉｘＰ１－ｘＯ４＋ｃ２（式中の記号は前記と同じ意味を示す。）
で表される組成を有するケイ酸－リン酸化合物を得る工程。
　以下、各工程について具体的に説明する。 Melting step (I): a step of obtaining a melt having a composition represented by the formula A 1 + x + a M b Si x P 1-x O 4 + c1 (wherein the symbols have the same meaning as described above),
Cooling step (II): a step of cooling the melt to obtain a solidified product,
Grinding step (III): step of obtaining the pulverized product by pulverizing the solidified product, and heating step (IV): heating the pulverized product to obtain a formula A 1 + x + a M b Si x P 1-x O 4 + c2 (wherein The symbols have the same meaning as above.)
A step of obtaining a silicic acid-phosphoric acid compound having a composition represented by:
Hereinafter, each step will be specifically described.
［溶融工程（Ｉ）］
　本発明の製造方法における溶融工程（Ｉ）は、下式（１）で表される溶融物を得る工程である。
　Ａ１＋ｘ＋ａＭｂＳｉｘＰ１－ｘＯ４＋ｃ１　　　　　（１）
（式中の記号は前記と同じ意味を示す。） [Melting step (I)]
The melting step (I) in the production method of the present invention is a step for obtaining a melt represented by the following formula (1).
A 1 + x + a M b Si x P 1-x O 4 + c1 (1)
(The symbols in the formula have the same meaning as described above.)
　溶融工程（Ｉ）においては、元素源（元素Ａ、元素Ｍ、Ｓｉ、およびＰ）を含む原料を、式（１）で表される組成となるように調整してなる原料調合物をまず準備するのが好ましい。
　式（１）において、ａは－０．１≦ａ≦０．４、ｂは０．７≦ｂ≦１．３の範囲である。原料調合物におけるａおよびｂを該範囲にすることによって、目的とする組成を有するケイ酸－リン酸化合物を製造できる。加えて、原料調合物を良好に溶融でき、均一な溶融物が得られる。また、ｘを０．３≦ｘ＜１．０にすることによって、二次電池用正極材料として用いた場合に多電子型の反応（単位モル数当たり１ｍｏｌを超えるＡを引き抜く反応）を起こす化合物を製造することができ、二次電池の理論電気容量を高めることができる。 In the melting step (I), first, a raw material formulation prepared by adjusting a raw material containing an element source (element A, element M, Si, and P) to have a composition represented by the formula (1) is prepared. It is preferable to do this.
In the formula (1), a is in the range of −0.1 ≦ a ≦ 0.4, and b is in the range of 0.7 ≦ b ≦ 1.3. A silicic acid-phosphoric acid compound having a target composition can be produced by setting a and b in the raw material formulation within the above ranges. In addition, the raw material formulation can be melted well, and a uniform melt can be obtained. Further, when x is set to 0.3 ≦ x <1.0, a compound that causes a multi-electron type reaction (reaction that pulls out more than 1 mol per unit mole) when used as a positive electrode material for a secondary battery. And the theoretical electric capacity of the secondary battery can be increased.
　式（１）中、ａおよびｂは、多電子型の反応をより容易に起こさせうることから－０．１≦ａ≦０．３、０．８≦ｂ≦１．３にすることがより好ましい。また、０．３＜ｘ＜１．０であってもよい。 In formula (1), a and b can cause a multi-electron type reaction more easily, so that −0.1 ≦ a ≦ 0.3 and 0.8 ≦ b ≦ 1.3 are more preferable. preferable. Moreover, 0.3 <x <1.0 may be sufficient.
　式（１）中、ｃ１の値は、ａ、ｂおよびＭの価数Ｎに依存する数である。一般にはｃ１＝０．５ａ＋０．５Ｎｂ－１で表される。組成式中の元素の価数は、後の粉砕工程（ＩＩＩ）および／または加熱工程（ＩＶ）で変化しうることから、加熱工程（ＩＶ）後にｃ２となる値にｃ１を調節する。例えば、加熱工程（ＩＶ）で成分の酸化還元、揮発等によりｃ１の値が増減する場合には、該増減を考慮に入れた値とするのが好ましい。本発明の製造方法においては、ｃ１を目的物のｃ２に対して０．９～１．２倍値としておくのが好ましい。 In the formula (1), the value of c1 is a number depending on the valence N of a, b, and M. Generally, it is represented by c1 = 0.5a + 0.5Nb-1. Since the valence of the element in the composition formula can be changed in the subsequent pulverization step (III) and / or the heating step (IV), c1 is adjusted to a value that becomes c2 after the heating step (IV). For example, when the value of c1 increases or decreases due to oxidation / reduction or volatilization of the components in the heating step (IV), it is preferable to set the value in consideration of the increase / decrease. In the production method of the present invention, c1 is preferably 0.9 to 1.2 times the value of c2 of the target product.
　式（１）の元素Ａは、Ｌｉ、ＮａおよびＫからなる群より選ばれる少なくとも１種の元素である。元素Ａは二次電池用正極材料として適しているため、Ｌｉを必須とするのが好ましく、Ｌｉのみであることが特に好ましい。Ｌｉを含むケイ酸－リン酸化合物は、二次電池の単位体積（質量）当たりの容量を高くする。 The element A in the formula (1) is at least one element selected from the group consisting of Li, Na, and K. Since the element A is suitable as a positive electrode material for a secondary battery, it is preferable to make Li essential, and it is particularly preferable to use only Li. The silicic acid-phosphoric acid compound containing Li increases the capacity per unit volume (mass) of the secondary battery.
　式（１）の元素Ｍは、Ｆｅ、Ｍｎ、ＣｏおよびＮｉからなる群より選ばれる少なくとも１種の元素である。元素Ｍは１種のみ、または、２種からなるのが好ましい。特に本発明の製造方法で製造するケイ酸－リン酸化合物を二次電池用正極材料に使用する場合には、元素ＭはＦｅのみ、Ｍｎのみ、またはＦｅとＭｎとの２種からなるのが、コストの点で好ましい。元素Ｍの価数Ｎは本発明の製造方法の各工程で変化しうる数値であり、＋２～＋４の範囲である。該価数Ｎは、元素ＭがＦｅの場合は＋２、＋８／３または＋３、Ｍｎの場合は＋２、＋３または＋４、Ｃｏの場合は＋２、＋８／３または＋３、およびＮｉの場合は＋２または＋４が好ましい。また、該価数Ｎは、溶融工程（Ｉ）が単純化するために＋２であることがより好ましい。
　本発明においては、原料調合物の組成を特定の範囲にすることによって溶融工程（Ｉ）における溶融を容易にすることができる。 The element M in the formula (1) is at least one element selected from the group consisting of Fe, Mn, Co, and Ni. The element M is preferably composed of only one kind or two kinds. In particular, when the silicic acid-phosphoric acid compound produced by the production method of the present invention is used for a positive electrode material for a secondary battery, the element M consists of only Fe, Mn alone, or Fe and Mn. This is preferable in terms of cost. The valence N of the element M is a numerical value that can be changed in each step of the production method of the present invention, and is in the range of +2 to +4. The valence N is +2, +8/3 or +3 when the element M is Fe, +2, +3 or +4 when Mn, +2, +8/3 or +3 when Co, and +2 or when Ni +4 is preferred. The valence N is more preferably +2 in order to simplify the melting step (I).
In the present invention, melting in the melting step (I) can be facilitated by setting the composition of the raw material formulation to a specific range.
（原料調合物：元素Ａを含む化合物）
　原料調合物における元素Ａを含む化合物としては、Ａの炭酸塩（Ａ２ＣＯ３）、Ａの炭酸水素塩（ＡＨＣＯ３）、Ａの水酸化物（ＡＯＨ）、Ａのケイ酸塩（Ａ２Ｏ・２ＳｉＯ２、Ａ２Ｏ・ＳｉＯ２、２Ａ２Ｏ・ＳｉＯ２等）、Ａのリン酸塩、Ａのリン酸水素塩、Ａの硝酸塩（ＡＮＯ３）、Ａの塩化物（ＡＣｌ）、Ａの硫酸塩（Ａ２ＳＯ４）およびＡの酢酸塩（ＣＨ３ＣＯＯＡ）やシュウ酸塩（（ＣＯＯＡ）２）等の有機酸塩からなる群より選ばれる少なくとも１種が好ましい。元素ＡはＬｉが好ましい。さらに、これらの化合物は水和物であってもよい。これらのうち、Ａの炭酸塩や炭酸水素塩は安価であり、また取扱いが容易であるのでより好ましい。 (Raw material formulation: Compound containing element A)
The compound containing element A in the raw material formulation includes A carbonate (A 2 CO 3 ), A hydrogen carbonate (AHCO 3 ), A hydroxide (AOH), and A silicate (A 2 O · 2SiO 2 , A 2 O · SiO 2 , 2A 2 O · SiO 2, etc.), A phosphate, A hydrogen phosphate, A nitrate (ANO 3 ), A chloride (ACl), A sulfate (A 2 SO 4 ) of A and at least one selected from the group consisting of organic acid salts such as acetate (CH 3 COOA) and oxalate ((COOA) 2 ) of A are preferred. The element A is preferably Li. Furthermore, these compounds may be hydrates. Of these, carbonates and bicarbonates of A are more preferred because they are inexpensive and easy to handle.
（原料調合物：元素Ｍを含む化合物）
　原料調合物における元素Ｍを含む化合物としては、Ｍの酸化物（ＦｅＯ、Ｆｅ３Ｏ４、Ｆｅ２Ｏ３、ＭｎＯ、Ｍｎ２Ｏ３、ＭｎＯ２、ＣｏＯ、Ｃｏ３Ｏ４、Ｃｏ２Ｏ３、ＮｉＯ等）、Ｍのオキシ水酸化物（ＭＯ（ＯＨ）等）、Ｍのケイ酸塩（ＭＯ・ＳｉＯ２、２ＭＯ・ＳｉＯ２等）、金属Ｍ、Ｍの塩化物（ＭＣｌ２、ＭＣｌ３）、Ｍの硝酸塩（Ｍ（ＮＯ３）２、Ｍ（ＮＯ３）３）、Ｍの硫酸塩（ＭＳＯ４、Ｍ２（ＳＯ４）３）およびＭの酢酸塩（Ｍ（ＣＨ３ＣＯＯ）２）やシュウ酸塩（Ｍ（ＣＯＯ）２）等の有機酸塩からなる群より選ばれる少なくとも１種が好ましい。元素Ｍを含む化合物としては、入手のしやすさやコストから、Ｆｅ３Ｏ４、Ｆｅ２Ｏ３、ＭｎＯ、Ｍｎ２Ｏ３、ＭｎＯ２、Ｃｏ３Ｏ４、およびＮｉＯからなる群より選ばれる少なくとも１種がより好ましく、Ｆｅ３Ｏ４、Ｆｅ２Ｏ３、およびＭｎＯ２からなる群より選ばれる少なくとも１種が特に好ましい。これらのＦｅ３Ｏ４、Ｆｅ２Ｏ３、およびＭｎＯ２は、１種のみを用いても、２種以上を用いてもよい。 (Raw material formulation: Compound containing element M)
As the compound containing the element M in the raw material preparation, oxides of M (FeO, Fe 3 O 4 , Fe 2 O 3 , MnO, Mn 2 O 3 , MnO 2 , CoO, Co 3 O 4 , Co 2 O 3 , NiO, etc.), M of oxyhydroxide (MO (OH), etc.), silicates M (MO · SiO 2, 2MO · SiO 2 , etc.), a metal M, chlorides M (MCl 2, MCl 3 ), M nitrate (M (NO 3 ) 2 , M (NO 3 ) 3 ), M sulfate (MSO 4 , M 2 (SO 4 ) 3 ) and M acetate (M (CH 3 COO) 2 And at least one selected from the group consisting of organic acid salts such as oxalate (M (COO) 2 ). The compound containing the element M is at least selected from the group consisting of Fe 3 O 4 , Fe 2 O 3 , MnO, Mn 2 O 3 , MnO 2 , Co 3 O 4 , and NiO because of availability and cost. One type is more preferable, and at least one selected from the group consisting of Fe 3 O 4 , Fe 2 O 3 , and MnO 2 is particularly preferable. These Fe 3 O 4 , Fe 2 O 3 , and MnO 2 may be used alone or in combination of two or more.
（原料調合物：Ｓｉ（ケイ素）を含む化合物）
　原料調合物におけるＳｉを含む化合物としては、酸化ケイ素（ＳｉＯ２）、Ａのケイ酸塩、Ｍのケイ酸塩、およびケイ素のアルコキシド（Ｓｉ（ＯＣＨ３）４、Ｓｉ（ＯＣ２Ｈ５）４等）からなる群より選ばれる少なくとも１種が好ましく、酸化ケイ素が安価であるので特に好ましい。Ｓｉを含む化合物は結晶質であっても、非晶質であってもよい。 (Raw material preparation: Compound containing Si (silicon))
The compound containing Si in the raw material preparation includes silicon oxide (SiO 2 ), A silicate, M silicate, and silicon alkoxide (Si (OCH 3 ) 4 , Si (OC 2 H 5 ) 4. Etc.) is preferred, and silicon oxide is particularly preferred because it is inexpensive. The compound containing Si may be crystalline or amorphous.
（原料調合物：Ｐ（リン）を含む化合物）
　原料調合物におけるＰを含む化合物としては、酸化リン（Ｐ２Ｏ５）、リン酸アンモニウム（（ＮＨ４）３ＰＯ４）、リン酸水素アンモニウム（（ＮＨ４）２ＨＰＯ４、ＮＨ４Ｈ２ＰＯ４）、リン酸（Ｈ３ＰＯ４）、ポリリン酸（Ｈ（ｎ＋２）ＰnＯ（３ｎ＋１））、亜リン酸（Ｈ３ＰＯ３）、次亜リン酸（Ｈ３ＰＯ２）、ＡおよびＭのリン酸塩からなる群より選ばれる少なくとも１種が好ましく、リン酸アンモニウム、およびリン酸水素アンモニウムからなる群より選ばれる少なくとも１種がより好ましく、安価かつ取扱いが容易な点で、リン酸水素アンモニウムが特に好ましい。Ａのリン酸塩としては、Ｌｉ３ＰＯ４が好ましく、Ｍのリン酸塩としては、Ｆｅ３（ＰＯ４）２、ＦｅＰＯ４、およびＭｎ３（ＰＯ４）２からなる群より選ばれる少なくとも１種が好ましい。 (Raw material formulation: Compound containing P (phosphorus))
As the compound containing P in the raw material preparation, phosphorus oxide (P 2 O 5 ), ammonium phosphate ((NH 4 ) 3 PO 4 ), ammonium hydrogen phosphate ((NH 4 ) 2 HPO 4 , NH 4 H 2 PO 4 ), phosphoric acid (H 3 PO 4 ), polyphosphoric acid (H (n + 2) P n O (3n + 1) ), phosphorous acid (H 3 PO 3 ), hypophosphorous acid (H 3 PO 2 ), A And at least one selected from the group consisting of M phosphates, and more preferably at least one selected from the group consisting of ammonium phosphate and ammonium hydrogen phosphate. Particularly preferred is ammonium oxyhydrogen. The phosphate of A is preferably Li 3 PO 4 , and the phosphate of M is at least 1 selected from the group consisting of Fe 3 (PO 4 ) 2 , FePO 4 , and Mn 3 (PO 4 ) 2. Species are preferred.
（原料調合物の好適な組み合わせ）
　原料調合物としては、Ａの炭酸塩または炭酸水素塩、Ｍの酸化物またはＭのオキシ水酸化物、酸化ケイ素、およびリン酸水素アンモニウムの組み合わせが好ましい。
　さらに原料調合物としては、Ｌｉ２ＣＯ３またはＬｉＨＣＯ３；Ｆｅ３Ｏ４、Ｆｅ２Ｏ３、およびＭｎＯ２からなる群より選ばれる１種以上の化合物；酸化ケイ素；およびリン酸水素アンモニウムの組み合わせが特に好ましい。 (Preferred combination of raw material formulations)
As the raw material preparation, a combination of A carbonate or hydrogen carbonate, M oxide or M oxyhydroxide, silicon oxide, and ammonium hydrogen phosphate is preferable.
Furthermore, as a raw material preparation, Li 2 CO 3 or LiHCO 3 ; one or more compounds selected from the group consisting of Fe 3 O 4 , Fe 2 O 3 , and MnO 2 ; silicon oxide; and a combination of ammonium hydrogen phosphate Is particularly preferred.
　原料調合物の組成は、ケイ酸－リン酸化合物の製造方法において、原則として、溶融物の組成と対応させる。ただし、該原料調合物中に、溶融工程（Ｉ）中に揮発等により失われやすい成分、例えばＬｉ、Ｐ等、を存在させた場合には、得られる溶融物の組成は原料調合物の組成と若干相違する場合がある。そのような場合には、揮発等により失われる量を考慮して、原料調合物の組成を適宜変更するのが好ましい。 In principle, the composition of the raw material preparation is made to correspond to the composition of the melt in the method for producing a silicate-phosphate compound. However, in the raw material formulation, when a component that is easily lost due to volatilization or the like during the melting step (I), such as Li, P, etc., is present, the composition of the obtained melt is the composition of the raw material formulation And may be slightly different. In such a case, it is preferable to appropriately change the composition of the raw material formulation in consideration of the amount lost due to volatilization or the like.
　原料調合物に含ませる各原料の純度は特に限定されない。反応性や二次電池用正極材料の特性等を考慮すると、水和水を除く純度が９９質量％以上であることが好ましい。 The purity of each raw material included in the raw material preparation is not particularly limited. Considering reactivity, characteristics of the positive electrode material for secondary batteries, and the like, the purity excluding hydrated water is preferably 99% by mass or more.
（溶融工程（Ｉ）の実施条件）
　本発明における溶融工程（Ｉ）は、式（１）で表される組成を有する溶融物を得る工程である。該工程は、前記の原料調合物を加熱して溶融させることにより実施するのが好ましい。溶融を行う前に、各原料または原料調合物を、ミキサー、ボールミル、ジェットミル、または遊星ミル等を用いて、乾式または湿式で粉砕および／または混合することが好ましい。各原料調合物中の原料の粒度は、混合操作、原料調合物の溶融容器への充填操作、原料調合物の溶融性等に悪影響を及ぼさない範囲であれば、限定されない。 (Conditions for melting step (I))
The melting step (I) in the present invention is a step of obtaining a melt having a composition represented by the formula (1). This step is preferably carried out by heating and melting the raw material formulation. Prior to melting, each raw material or raw material preparation is preferably pulverized and / or mixed dry or wet using a mixer, ball mill, jet mill, planetary mill or the like. The particle size of the raw material in each raw material preparation is not limited as long as it does not adversely affect the mixing operation, the filling operation of the raw material preparation into the melting container, the meltability of the raw material preparation, and the like.
　次に、原料調合物は容器等に入れて加熱することが好ましい。加熱は該容器を加熱炉に入れて行うことが好ましい。容器は、アルミナ製、カーボン製、炭化ケイ素製、ホウ化ジルコニウム製、ホウ化チタン製、窒化ホウ素製、炭素製、白金製、またはロジウムを含む白金合金製等が好ましい。耐火物系練瓦、還元材料（例えばグラファイト）からなる容器も採用できる。さらに、加熱炉内に揮発および蒸発防止のために、容器に蓋を装着して溶融することが好ましい。加熱炉は、抵抗加熱炉、高周波誘導炉、またはプラズマアーク炉が好ましい。抵抗加熱炉はニクロム合金等の合金製、炭化ケイ素製、またはケイ化モリブデン製の発熱体を備えた電気炉であることが好ましい。 Next, it is preferable to heat the raw material mixture in a container or the like. Heating is preferably performed by placing the container in a heating furnace. The container is preferably made of alumina, carbon, silicon carbide, zirconium boride, titanium boride, boron nitride, carbon, platinum, or a platinum alloy containing rhodium. A container made of a refractory-based brick and a reducing material (eg, graphite) can also be employed. Furthermore, in order to prevent volatilization and evaporation in the heating furnace, it is preferable to attach a lid to the container and melt it. The heating furnace is preferably a resistance heating furnace, a high frequency induction furnace, or a plasma arc furnace. The resistance heating furnace is preferably an electric furnace provided with a heating element made of an alloy such as a nichrome alloy, silicon carbide, or molybdenum silicide.
　溶融工程（Ｉ）は、空気中、不活性ガス中または還元ガス中で実施することが好ましい。溶融の条件は、容器または加熱炉の種類や熱源等の加熱方法等の条件により、適宜変更できる。圧力は、常圧、加圧、減圧（０．９×１０５Ｐａ以下）のいずれであってもよい。還元ガス中が好ましいが、酸化ガス中であってもよい。酸化条件であった場合には、次工程の加熱工程（ＩＶ）において還元（例えばＭ３＋からＭ２＋への変化）を行うことができる。
　不活性ガス中とは、窒素ガス（Ｎ２）、およびヘリウムガス（Ｈｅ）およびアルゴンガス（Ａｒ）等の希ガスからなる群より選ばれる少なくとも１種の不活性ガスを９９体積％以上含む気体条件であることをいう。還元ガス中とは、上記した不活性ガスに、還元性を有する気体を添加し、実質に酸素を含まない気体条件であることをいう。還元性を有する気体としては、水素ガス（Ｈ２）、一酸化炭素ガス（ＣＯ）およびアンモニアガス（ＮＨ３）等が挙げられる。不活性ガス中の還元性を有する気体の量は、全気体中に還元性を有する気体が０．１体積％以上であるのが好ましく、１～１０体積％が特に好ましい。酸素の含有量は、該気体中に１体積％以下が好ましく、０．１体積％以下が特に好ましい。 The melting step (I) is preferably carried out in air, in an inert gas or in a reducing gas. Melting conditions can be changed as appropriate depending on conditions such as the type of container or heating furnace and the heating method such as a heat source. The pressure may be any of normal pressure, pressurization, and reduced pressure (0.9 × 10 5 Pa or less). Although it is preferably in reducing gas, it may be in oxidizing gas. In the case of the oxidation conditions, reduction (for example, change from M 3+ to M 2+ ) can be performed in the next heating step (IV).
In the inert gas is a gas containing 99% by volume or more of at least one inert gas selected from the group consisting of nitrogen gas (N 2 ) and rare gases such as helium gas (He) and argon gas (Ar). It is a condition. The term “in the reducing gas” refers to a gas condition in which a reducing gas is added to the inert gas and substantially does not contain oxygen. Examples of the reducing gas include hydrogen gas (H 2 ), carbon monoxide gas (CO), and ammonia gas (NH 3 ). The amount of the reducing gas in the inert gas is preferably 0.1% by volume or more, and particularly preferably 1 to 10% by volume of the reducing gas in the total gas. The oxygen content in the gas is preferably 1% by volume or less, particularly preferably 0.1% by volume or less.
　溶融工程（Ｉ）における加熱温度は、１，３００～１，６００℃が好ましく、１，４００～１，５５０℃が特に好ましい。ここで、溶融とは各原料が融解し、目視で透明な状態となることをいう。加熱温度が上記範囲の下限値以上であると溶融が容易になり、加熱温度が上記範囲の上限値以下であると原料の揮発がしにくくなる。加熱時間は０．２～２時間が好ましく、０．５～２時間が特に好ましい。該時間とすることにより溶融物の均一性が充分になり、また原料が揮発しにくい。
　溶融工程（Ｉ）においては、溶融物の均一性を上げるために撹拌してもよい。また、次の冷却工程（ＩＩ）を行うまで、加熱温度より低い温度で溶融物を清澄させてもよい。さらに、溶融工程（Ｉ）で得た溶融物は、次の冷却工程（ＩＩ）に悪影響を与えない限り、該冷却工程（ＩＩ）前に他の工程を行ってもよい。 The heating temperature in the melting step (I) is preferably 1,300 to 1,600 ° C., particularly preferably 1,400 to 1,550 ° C. Here, melting means that each raw material is melted and is in a transparent state visually. When the heating temperature is equal to or higher than the lower limit value in the above range, melting becomes easy, and when the heating temperature is equal to or lower than the upper limit value in the above range, the raw material is hardly volatilized. The heating time is preferably 0.2 to 2 hours, particularly preferably 0.5 to 2 hours. By setting the time, the homogeneity of the melt is sufficient, and the raw material is difficult to volatilize.
In the melting step (I), stirring may be performed to increase the uniformity of the melt. Further, the melt may be clarified at a temperature lower than the heating temperature until the next cooling step (II) is performed. Furthermore, the melt obtained in the melting step (I) may be subjected to another step before the cooling step (II) as long as it does not adversely affect the next cooling step (II).
［冷却工程（ＩＩ）］
　冷却工程（ＩＩ）は、溶融工程（Ｉ）で得た溶融物を室温付近まで冷却して固化物を得る工程である。固化物は非晶質物であることが好ましいが、固化物の一部は結晶化物であってもよい。固化物が非晶質物を含むことにより、次工程の粉砕工程（ＩＩＩ）が実施しやすくなり、ケイ酸－リン酸化合物の組成および粒度を制御しやすくなる。さらに、後工程の加熱工程（ＩＶ）において、生成物が塊状になるのを防ぐことができ、かつ、生成物の粒度が制御しやすくなる利点がある。
　固化物が結晶化物を含む場合、後工程の加熱工程（ＩＶ）で結晶化物が結晶核となり、結晶化しやすくなる。固化物中の結晶化物量は固化物の全質量に対して０～３０質量％であることが好ましい。結晶化物を多く含むと粒状やフレーク状の固化物を得ることが困難となる。また、冷却機器の損耗を早め、その後の粉砕工程（ＩＩＩ）の負担が大きくなる。 [Cooling step (II)]
The cooling step (II) is a step of cooling the melt obtained in the melting step (I) to near room temperature to obtain a solidified product. The solidified product is preferably an amorphous material, but a part of the solidified product may be a crystallized product. When the solidified product contains an amorphous material, the next pulverization step (III) can be easily performed, and the composition and particle size of the silicic acid-phosphoric acid compound can be easily controlled. Further, in the subsequent heating step (IV), there is an advantage that the product can be prevented from being agglomerated and the particle size of the product can be easily controlled.
In the case where the solidified product contains a crystallized product, the crystallized product becomes a crystal nucleus in the heating step (IV), which is a subsequent step, and it is easy to crystallize. The amount of crystallized product in the solidified product is preferably 0 to 30% by mass with respect to the total mass of the solidified product. When a large amount of crystallized material is contained, it becomes difficult to obtain a granular or flaky solidified material. Moreover, the wear of the cooling device is accelerated, and the burden of the subsequent pulverization step (III) is increased.
　冷却工程（ＩＩ）は設備等の点から空気中で行うことが好ましい。また冷却工程（ＩＩ）を不活性ガス中または還元ガス中で行ってもよい。溶融物の冷却速度は－１×１０３℃／秒以上が好ましく、－１×１０４ ℃／秒以上が特に好ましい。本明細書では、冷却する場合の単位時間当たりの温度変化（すなわち冷却速度）を負の値で示し、加熱する場合の単位時間当たりの温度変化（すなわち加熱速度）を正の値で示す。冷却速度を該値以上にすると非晶質物が得られやすい。冷却速度の上限値は製造設備や大量生産性の点からは－１×１０１０ ℃／秒程度が好ましく、実用性の点からは－１×１０８ ℃／秒が特に好ましい。溶融物の冷却速度は１０００℃から５０℃までの冷却速度を－１０３℃／秒～－１０１０ ℃／秒とすることが特に好ましい。 The cooling step (II) is preferably performed in air from the viewpoint of equipment and the like. The cooling step (II) may be performed in an inert gas or a reducing gas. The cooling rate of the melt is preferably not less than -1 × 10 3 ℃ / sec, -1 × 10 4 ℃ / sec or more is particularly preferable. In the present specification, a temperature change per unit time (ie, cooling rate) in the case of cooling is indicated by a negative value, and a temperature change per unit time in case of heating (ie, the heating rate) is indicated by a positive value. When the cooling rate is higher than this value, an amorphous material is easily obtained. The upper limit of the cooling rate is preferably about −1 × 10 10 ° C./second from the viewpoint of manufacturing equipment and mass productivity, and is particularly preferably −1 × 10 8 ° C./second from the viewpoint of practicality. The cooling rate of the melt is particularly preferably from -10 3 ° C / second to -10 10 ° C / second from 1000 ° C to 50 ° C.
　溶融物の冷却方法は、例えば高速で回転する双ローラの間に溶融物を滴下してフレーク状の固化物を得る方法、回転する単ローラに溶融物を滴下してフレーク状もしくは板状の固化物を掃引して得る方法、または冷却したカーボン板や金属板に溶融物をプレスして塊状の固化物を得る方法であることが好ましい。なかでも、双ローラを用いた冷却方法が、冷却速度が速く、大量に処理できるのでより好ましい。双ローラとしては、金属製、カーボン製、またはセラミックス製のものを用いることが好ましい。 The method of cooling the melt is, for example, a method in which a melt is dropped between twin rollers rotating at high speed to obtain a flake-like solidified product, or a melt is dropped on a rotating single roller to form a flake-like or plate-like solidified product. It is preferable that the method is obtained by sweeping an object, or a method in which a melt is pressed on a cooled carbon plate or metal plate to obtain a lump solidified product. Among these, a cooling method using twin rollers is more preferable because the cooling rate is high and a large amount of processing can be performed. As the double roller, it is preferable to use one made of metal, carbon, or ceramic.
　冷却方法としては、溶融物を水に直接投入する方法もあるが、該方法は、制御が難しく、冷却速度は－１×１０℃／秒～－１×１０２℃／秒程度であり、非晶質物を得るのが難しい。また固化物が塊状となり、粉砕に多くの労力を要する。冷却方法として、液体窒素に溶融物を直接投入する方法もあり、水の場合よりも冷却速度を速くできるが、水を使用する方法と同様の問題があり、また高コストである。 As a cooling method, there is a method in which the melt is directly poured into water, but this method is difficult to control, and the cooling rate is about −1 × 10 ° C./second to −1 × 10 2 ° C./second. It is difficult to obtain a crystalline material. Further, the solidified product becomes a lump and requires a lot of labor for pulverization. As a cooling method, there is also a method in which a melt is directly charged into liquid nitrogen, and the cooling rate can be made faster than in the case of water, but there are problems similar to the method using water and the cost is high.
　冷却工程（ＩＩ）で得る固化物は、フレーク状または繊維状が好ましい。フレーク状の固化物としては、平均厚さが２００μｍ以下が好ましく、１００μｍ以下が特に好ましい。フレーク状の固化物としての、平均厚さに垂直の面の平均直径は、特に限定されない。繊維状の固化物としては、平均直径が５０μｍ以下が好ましく、３０μｍ以下が特に好ましい。平均厚さや平均直径の上限値以下であると、次工程の粉砕工程（ＩＩＩ）の手間を軽減することができ、結晶化効率を高くすることができる。平均厚さおよび平均直径は、ノギスやマイクロメータにより測定することができる。また、平均直径は、顕微鏡観察により測定することもできる。
　冷却工程（ＩＩ）で得た固化物は、次の粉砕工程（ＩＩＩ）に悪影響を与えない限り、該粉砕工程（ＩＩＩ）前に他の工程を行ってもよい。 The solidified product obtained in the cooling step (II) is preferably flaky or fibrous. The flaky solidified product preferably has an average thickness of 200 μm or less, particularly preferably 100 μm or less. The average diameter of the plane perpendicular to the average thickness as the flaky solidified product is not particularly limited. The fibrous solidified product preferably has an average diameter of 50 μm or less, particularly preferably 30 μm or less. When the average thickness or the average diameter is less than or equal to the upper limit value, it is possible to reduce the labor of the subsequent pulverization step (III) and increase the crystallization efficiency. The average thickness and average diameter can be measured with a caliper or a micrometer. The average diameter can also be measured by microscopic observation.
The solidified product obtained in the cooling step (II) may be subjected to other steps before the pulverization step (III) as long as the pulverization step (III) is not adversely affected.
［粉砕工程（ＩＩＩ）］
　粉砕工程（ＩＩＩ）とは、冷却工程（ＩＩ）で得た固化物を粉砕して粉砕物を得る工程である。固化物は通常の場合、非晶質物を多く含む、または、非晶質物からなるため、粉砕がしやすい利点がある。また、粉砕に使用する装置に負担をかけずに粉砕ができかつ粒径の制御がしやすい利点がある。一方、従来の固相反応は、加熱工程（ＩＶ）の後で粉砕を行うが、粉砕によって残留応力が生じ、電池特性を悪化させる問題があることに本発明者は気づいた。よって、本発明の製造方法では、加熱工程（ＩＶ）の前に粉砕し、生じた残留応力は、後工程の加熱工程（ＩＶ）で低減または除去する方法を採用する。 [Crushing step (III)]
The pulverization step (III) is a step in which the solidified product obtained in the cooling step (II) is pulverized to obtain a pulverized product. Since the solidified product usually contains a large amount of amorphous material or consists of an amorphous material, there is an advantage that it is easy to grind. Further, there is an advantage that grinding can be performed without imposing a burden on the apparatus used for grinding and the particle size can be easily controlled. On the other hand, in the conventional solid phase reaction, pulverization is performed after the heating step (IV), but the present inventor has noticed that there is a problem that residual stress is generated by pulverization and battery characteristics are deteriorated. Therefore, the manufacturing method of the present invention employs a method of pulverizing before the heating step (IV) and reducing or removing the generated residual stress in the subsequent heating step (IV).
　粉砕は、ジョークラッシャー、ハンマーミル、ボールミル、ジェットミル、遊星ミル等を用いて行うことが好ましい。粉砕の方式は、乾式または湿式のいずれであってもよい。粉砕工程（ＩＩＩ）の前に固化物を手揉みやハンマー等で叩いて予備的に細かくすると、粉砕工程（ＩＩＩ）の負担が軽減するので好ましい。粉砕を湿式で行った場合、分散媒を沈降、濾過、減圧乾燥、加熱乾燥等で除去した後に、加熱工程（ＩＶ）を実施するのが好ましい。ただし、分散媒が少ない場合、特に粉砕物の質量に占める固形分の質量の割合が３０％以上の場合、分散媒を含んだ粉砕物のままで加熱工程（ＩＶ）を行ってもよい。 The pulverization is preferably performed using a jaw crusher, a hammer mill, a ball mill, a jet mill, a planetary mill or the like. The method of pulverization may be either dry or wet. Before the pulverization step (III), it is preferable that the solidified product be struck by hand or a hammer to make it finer, because the burden of the pulverization step (III) is reduced. When the pulverization is performed in a wet manner, it is preferable to carry out the heating step (IV) after removing the dispersion medium by sedimentation, filtration, drying under reduced pressure, heat drying and the like. However, when there are few dispersion media, especially when the ratio of the mass of the solid content to the mass of the pulverized product is 30% or more, the heating step (IV) may be performed with the pulverized product containing the dispersion medium as it is.
　本発明におけるケイ酸－リン酸化合物は絶縁物質であることから、二次電池用正極材料として用いる場合には、固化物に導電材を含ませるのが好ましい。また、二次電池用正極材料として用いる場合には、微粒子状であるのが好ましい。粉砕物の平均粒径は、体積換算のメディアン径で１０ｎｍ～１０μｍが好ましく、１０ｎｍ～５μｍが特に好ましい。粒径の測定は、沈降法やレーザ回折／散乱式粒子径測定装置で測定できる。粉砕物の粒径が小さい場合には、還元反応が促進され、加熱工程（ＩＶ）の加熱温度や時間を低減できるため好ましい。粉砕物の平均粒径を上記範囲とすることにより、粉砕工程（ＩＩＩ）および加熱工程（ＩＶ）の作業性を向上させ、加熱工程（ＩＶ）の生成物の平均粒径を制御しやすくなる利点がある。 Since the silicic acid-phosphoric acid compound in the present invention is an insulating substance, when used as a positive electrode material for a secondary battery, it is preferable to include a conductive material in the solidified product. Moreover, when using as a positive electrode material for secondary batteries, it is preferable that it is a fine particle form. The average particle diameter of the pulverized product is preferably 10 nm to 10 μm, and particularly preferably 10 nm to 5 μm, in terms of volume-based median diameter. The particle size can be measured by a sedimentation method or a laser diffraction / scattering particle size measuring device. When the particle size of the pulverized product is small, the reduction reaction is promoted, and the heating temperature and time in the heating step (IV) can be reduced, which is preferable. By making the average particle size of the pulverized product within the above range, the workability of the pulverization step (III) and the heating step (IV) is improved, and the average particle size of the product of the heating step (IV) can be easily controlled. There is.
　導電材としては、有機化合物および炭素粉末からなる群より選ばれる少なくとも１種の炭素源が好ましい。有機化合物および炭素粉末からなる群より選ばれる少なくとも１種の炭素源の量は、該炭素源中の炭素換算量（質量）が、固化物の質量と、該炭素源中の炭素換算量（質量）との合計質量に対して、０．１～２０質量％となる量が好ましく、２～１０質量％となる量が特に好ましい。炭素量を上記範囲とすることにより、二次電池用正極材料としての導電性を充分に高めることができる。
　固化物に含ませた有機化合物および炭素粉末は、粉砕工程（ＩＩＩ）や加熱工程（ＩＶ）における酸化を防止し、さらに還元を促進する。また、有機化合物および炭素粉末は、加熱工程（ＩＶ）後に残り、導電材として機能する。よって、二次電池用正極材料の導電性を高めることができる。 The conductive material is preferably at least one carbon source selected from the group consisting of organic compounds and carbon powder. The amount of at least one carbon source selected from the group consisting of an organic compound and carbon powder is such that the carbon equivalent amount (mass) in the carbon source is the mass of the solidified product and the carbon equivalent amount (mass in the carbon source). ) In an amount of 0.1 to 20% by mass, particularly preferably 2 to 10% by mass. By setting the amount of carbon in the above range, the conductivity as the positive electrode material for secondary batteries can be sufficiently increased.
The organic compound and carbon powder contained in the solidified product prevent oxidation in the pulverization step (III) and the heating step (IV), and further promote reduction. Further, the organic compound and the carbon powder remain after the heating step (IV) and function as a conductive material. Therefore, the conductivity of the positive electrode material for secondary batteries can be increased.
　有機化合物としては、糖類、アミノ酸類、ペプチド類、アルデヒド類、ケトン類、グリコール類、ポリビニルアルコール、および脂肪酸からなる群より選ばれる少なくとも１種が好ましく、糖類、グリコール類、またはポリビニルアルコールが特に好ましい。糖類としては、グルコース、フラクトース、およびガラクトース等の単糖類、スクロース、マルトース、セロビオース、およびトレハロース等のオリゴ糖、転化糖、デキストリン、アミロース、アミロペクチン、およびセルロース等の多糖類、ならびにアスコルビン酸等が挙げられる。アミノ酸類としては、アラニン、グリシン等のアミノ酸が挙げられる。ペプチド類としては、分子量が１，０００以下の低分子ペプチドが挙げられる。
　炭素粉末としては、カーボンブラック、グラファイト、アセチレンブラック等が好ましい。また、炭素粉末は繊維状炭素または板状炭素であってもよい。 As the organic compound, at least one selected from the group consisting of saccharides, amino acids, peptides, aldehydes, ketones, glycols, polyvinyl alcohol, and fatty acids is preferable, and saccharides, glycols, or polyvinyl alcohol is particularly preferable. . Examples of the saccharide include monosaccharides such as glucose, fructose, and galactose, oligosaccharides such as sucrose, maltose, cellobiose, and trehalose, invert sugar, polysaccharides such as dextrin, amylose, amylopectin, and cellulose, and ascorbic acid. It is done. Examples of amino acids include amino acids such as alanine and glycine. Peptides include low molecular weight peptides having a molecular weight of 1,000 or less.
As the carbon powder, carbon black, graphite, acetylene black and the like are preferable. The carbon powder may be fibrous carbon or plate-like carbon.
　粉砕工程（ＩＩＩ）において、固化物に有機化合物や炭素粉末を含ませて粉砕した場合には、加熱工程（ＩＶ）後に、導電材を混合する工程を省略できる利点がある。また、有機化合物や炭素粉末は、固化物の粒成長を抑制しうる。固化物に有機化合物を含ませる場合の粉砕工程（ＩＩＩ）には、粉砕物の表面に均一に分散させるために、湿式粉砕を採用するのが好ましい。粉砕する際の分散媒としては、水、または、エタノール、イソプロピルアルコール、アセトン、ヘキサン、トルエン等の有機溶媒を用いることができる。なかでも、水は安価であるために好ましい。固化物に炭素粉末を含ませる場合の粉砕工程（ＩＩＩ）には、乾式が好ましい。 In the pulverization step (III), when the solidified product is pulverized with an organic compound or carbon powder, there is an advantage that the step of mixing the conductive material can be omitted after the heating step (IV). Moreover, the organic compound and carbon powder can suppress the grain growth of the solidified product. In the pulverization step (III) when the organic compound is included in the solidified product, wet pulverization is preferably employed in order to uniformly disperse the pulverized product on the surface. As a dispersion medium for pulverization, water or an organic solvent such as ethanol, isopropyl alcohol, acetone, hexane, or toluene can be used. Of these, water is preferable because it is inexpensive. A dry method is preferable for the pulverization step (III) when the solidified product contains carbon powder.
　さらに、粉砕工程（ＩＩＩ）で得た粉砕物は、次の加熱工程（ＩＶ）に悪影響を与えない限り、該加熱工程（ＩＶ）前に他の工程を行ってもよい。 Further, the pulverized product obtained in the pulverization step (III) may be subjected to another step before the heating step (IV) as long as it does not adversely affect the next heating step (IV).
　［加熱工程（ＩＶ）］
　加熱工程（ＩＶ）は、粉砕工程（ＩＩＩ）で得た粉砕物を加熱する工程である。加熱工程（ＩＶ）では、下式（２）で表される組成を有するケイ酸－リン酸化合物を得る。
Ａ１＋ｘ＋ａＭｂＳｉｘＰ１－ｘＯ４＋ｃ２　　　　（２）
（式中、Ａ、Ｍ、ａ、ｂおよびｘは、前記と同じ意味を示すが、式（１）における値とは独立した値をとり、ｃ２はａ、ｂおよびＭの価数Ｎに依存する数である。） [Heating step (IV)]
The heating step (IV) is a step of heating the pulverized product obtained in the pulverizing step (III). In the heating step (IV), a silicic acid-phosphoric acid compound having a composition represented by the following formula (2) is obtained.
A 1 + x + a M b Si x P 1-x O 4 + c2 (2)
(In the formula, A, M, a, b and x have the same meaning as described above, but take an independent value from the value in formula (1), and c2 depends on the valence N of a, b and M. Number to do.)
　式（２）のｃ２の値は、ａ、ｂおよびＭの価数Ｎに依存する数であり、例えばａ＝０、ｂ＝１、ｘ＝０．５およびＮ＝＋２であればｃ２＝０であり、一般にはｃ２＝０．５ａ＋０．５Ｎｂ－１で表される。Ｎの価数は、＋２であるのが好ましい。 The value of c2 in equation (2) is a number that depends on the valence N of a, b, and M. For example, if a = 0, b = 1, x = 0.5, and N = + 2, c2 = 0 And is generally represented by c2 = 0.5a + 0.5Nb-1. The valence of N is preferably +2.
　加熱工程（ＩＶ）の生成物は、結晶粒子が好ましく、さらにオリビン型の結晶粒子がより好ましい。本発明における加熱工程（ＩＶ）は、粉砕物を加熱することから、残留応力の緩和が促進される。また、加熱により結晶核の生成および粒成長を行うことから、降温過程で行うものに比べて、組成、粒径およびその分布の制御が容易である。 The product of the heating step (IV) is preferably crystal particles, and more preferably olivine type crystal particles. In the heating step (IV) in the present invention, the pulverized material is heated, so that the relaxation of the residual stress is promoted. In addition, since the formation of crystal nuclei and grain growth are performed by heating, the composition, grain size, and distribution thereof are easier to control than those in the temperature lowering process.
　さらに、粉砕工程（ＩＩＩ）で有機化合物および／または炭素粉末を固化物に含ませた場合の加熱工程（ＩＶ）は、生成物、好ましくは生成物の結晶粒子の表面に、導電材を結合させる工程となりうる。有機化合物は加熱工程（ＩＶ）で熱分解され、炭化物となって導電材として機能しうる。 Furthermore, the heating step (IV) in the case where the organic compound and / or carbon powder is included in the solidified product in the pulverizing step (III) causes the conductive material to be bonded to the surface of the product, preferably the crystal grains of the product. It can be a process. The organic compound is thermally decomposed in the heating step (IV) and becomes a carbide to function as a conductive material.
　加熱工程（ＩＶ）における加熱温度は、５００～１，０００℃が好ましい。加熱温度が５００℃以上であると、結晶を生成しやすい。加熱温度が１，０００℃以下であると、粉砕物の融解を防ぐことができる。加熱温度は６００～９００℃がより好ましい。該加熱温度である場合には、適度な結晶性、粒子径、粒度分布等を有する結晶粒子が得られやすく、好ましくはオリビン型の結晶粒子が得られやすくなる。
　粉砕工程（ＩＩＩ）を湿式で行った場合には、分散媒を含むまま加熱工程（ＩＶ）を行った場合、加熱工程（ＩＶ）は分散媒を除く工程になりうる。 The heating temperature in the heating step (IV) is preferably 500 to 1,000 ° C. When the heating temperature is 500 ° C. or higher, crystals are easily generated. When the heating temperature is 1,000 ° C. or less, melting of the pulverized product can be prevented. The heating temperature is more preferably 600 to 900 ° C. When the heating temperature is used, crystal particles having appropriate crystallinity, particle diameter, particle size distribution, and the like are easily obtained, and olivine-type crystal particles are preferably obtained.
When the pulverization step (III) is performed in a wet manner, the heating step (IV) can be a step of removing the dispersion medium when the heating step (IV) is performed while the dispersion medium is included.
　加熱工程（ＩＶ）における加熱は、一気に温度を上げた後に一定温度で保持してもよいし、また多段階に温度を変化させて行ってもよい。加熱温度が高くなると、生成する粒子径が大きくなる傾向があるため、所望の粒子径に応じて加熱温度を設定することが好ましい。また、加熱時間（加熱温度による保持時間）は所望の粒子径を考慮して１～７２時間が好ましい。加熱は、電気、石油、ガス等を熱源とする、ボックス炉、トンネルキルン炉、ローラーハース炉、ロータリーキルン炉、マイクロウェーブ加熱炉等で行うことが好ましい。 The heating in the heating step (IV) may be performed at a constant temperature after raising the temperature at once, or may be performed by changing the temperature in multiple stages. Since the particle diameter to be generated tends to increase as the heating temperature increases, the heating temperature is preferably set according to the desired particle diameter. The heating time (holding time depending on the heating temperature) is preferably 1 to 72 hours in consideration of a desired particle size. Heating is preferably performed in a box furnace, tunnel kiln furnace, roller hearth furnace, rotary kiln furnace, microwave heating furnace, or the like that uses electricity, oil, gas, or the like as a heat source.
　加熱工程（ＩＶ）は、溶融工程（Ｉ）における加熱と同様に、空気中、不活性ガス中または還元ガス中で実施でき、不活性ガス中または還元ガス中で実施することが好ましい。不活性ガス中および還元ガス中の条件は、溶融工程（Ｉ）における条件と同じである。加熱工程（ＩＶ）は不活性ガス中や還元ガス中で減圧（０．９×１０５Ｐａ以下）して実施してもよい。また、加熱炉内に、還元剤（例えばグラファイト）と粉砕物とを入れた容器を装填して加熱を実施した場合には、粉砕物中のＭの還元（例えばＭ３＋からＭ２＋への変化）を促進することができる。 Similar to the heating in the melting step (I), the heating step (IV) can be carried out in air, in an inert gas or in a reducing gas, and is preferably carried out in an inert gas or in a reducing gas. The conditions in the inert gas and the reducing gas are the same as those in the melting step (I). The heating step (IV) may be performed under reduced pressure (0.9 × 10 5 Pa or less) in an inert gas or a reducing gas. In addition, when heating is performed by charging a container containing a reducing agent (eg, graphite) and pulverized material in a heating furnace, reduction of M in the pulverized material (eg, change from M 3+ to M 2+) . ) Can be promoted.
　本発明において、加熱工程（ＩＶ）の後は、通常は常温まで冷却する。該冷却における冷却速度は－３０℃／時間～－３００℃／時間が好ましい。冷却速度を該範囲にすることにより、加熱による歪みを除去でき、生成物が結晶体である場合は、結晶構造を保ったまま目的物を得ることができる。また、冷却手段を用いずに冷却ができる。冷却は、放置して常温まで冷却させるのが好ましい。冷却は不活性ガス中または還元ガス中で行うのが好ましい。 In the present invention, after the heating step (IV), it is usually cooled to room temperature. The cooling rate in the cooling is preferably −30 ° C./hour to −300 ° C./hour. By setting the cooling rate within this range, distortion due to heating can be removed, and when the product is a crystal, the target product can be obtained while maintaining the crystal structure. Moreover, it can cool without using a cooling means. The cooling is preferably allowed to cool to room temperature. Cooling is preferably performed in an inert gas or a reducing gas.
＜ケイ酸－リン酸化合物＞
　本発明の製造方法により得られるケイ酸－リン酸化合物は、二次電池用正極材料として有用な新規化合物である。
　本発明におけるケイ酸－リン酸化合物は、元素Ａの原子数が１．２以上であるため、１．２未満である場合に比べて多電子型になり、二次電池用正極材料に用いたときに単位質量当たりの容量が大きくなる。
　すなわち、本発明におけるケイ酸－リン酸化合物は、元素ＡがＬｉである場合、単位（[ＳｉＯ４]＋[ＰＯ４]）四面体中に対し１個超２個以下のＬｉを含む構造を有するケイ酸－リン酸化合物であるため、Ｌｉの原子数を１．２以上にすることができる。本発明の製造方法によれば、[ＳｉＯ４]四面体、[ＰＯ４]四面体、[ＬｉＯ４]四面体および[ＭＯ４]四面体が均一に分布するケイ酸－リン酸化合物を得ることができる。
　該ケイ酸－リン酸化合物は、オリビン型結晶粒子を含むものであることが好ましい。該結晶粒子としては、一次粒子および二次粒子の双方を含む。生成物中に二次粒子が存在する場合、一次粒子が破壊されない程度の範囲で解砕および粉砕してもよい。
　本発明の製造方法において、有機化合物および炭素粉末からなる群より選ばれる少なくとも１種を添加した場合には、ケイ酸－リン酸化合物の表面に有機化合物や炭素粉末に由来する炭素からなる導電材を均一にかつ強固に結合させうる。導電材が結合したケイ酸－リン酸化合物は、そのまま二次電池用正極材料に用いうる。 <Silic acid-phosphate compound>
The silicic acid-phosphoric acid compound obtained by the production method of the present invention is a novel compound useful as a positive electrode material for secondary batteries.
The silicic acid-phosphoric acid compound in the present invention has a multi-electron type as compared with the case where the number of atoms of the element A is 1.2 or more and is less than 1.2. Sometimes the capacity per unit mass increases.
That is, when the element A is Li, the silicic acid-phosphoric acid compound in the present invention has a structure containing more than one and not more than two Li per unit ([SiO 4 ] + [PO 4 ]) tetrahedron. Since it is a silicic acid-phosphoric acid compound, the number of Li atoms can be 1.2 or more. According to the production method of the present invention, a silicic acid-phosphate compound in which [SiO 4 ] tetrahedron, [PO 4 ] tetrahedron, [LiO 4 ] tetrahedron and [MO 4 ] tetrahedron are uniformly distributed can be obtained. Can do.
The silicic acid-phosphoric acid compound preferably contains olivine type crystal particles. The crystal particles include both primary particles and secondary particles. When secondary particles are present in the product, they may be crushed and pulverized as long as the primary particles are not destroyed.
In the production method of the present invention, when at least one selected from the group consisting of an organic compound and carbon powder is added, a conductive material made of carbon derived from the organic compound or carbon powder on the surface of the silicic acid-phosphoric acid compound Can be bonded uniformly and firmly. The silicic acid-phosphoric acid compound to which the conductive material is bonded can be used as a positive electrode material for a secondary battery as it is.
　本発明の製造方法で製造されるケイ酸－リン酸化合物は、オリビン型結晶粒子を含むことが好ましく、オリビン型結晶粒子であることが好ましい。オリビン型結晶粒子は、多電子型の理論電気容量を発揮する材料である。ケイ酸－リン酸化合物の組成は、ＡがＬｉであり、ＭがＦｅおよびＭｎからなる群より選ばれる少なくとも１種を使用した組成である、下式（３）で表される化合物が好ましい。ｙは０＜ｙ＜１が特に好ましい。
　Ｌｉ１＋ｘ＋ａ（ＦｅｙＭｎ１－ｙ）ｂＳｉｘＰ１－ｘＯ４＋ｃ２　　　　（３）
（式中の記号は前記と同じ意味を示し、０≦ｙ≦１である。）
　式（３）の組成のケイ酸－リン酸化合物を得るために、溶融工程（Ｉ）において式（３Ａ）で表される組成を有する溶融物を得ることが好ましい。
　Ｌｉ１＋ｘ＋ａ（ＦｅｙＭｎ１－ｙ）ｂＳｉｘＰ１－ｘＯ４＋ｃ１　　　（３Ａ）
（式中の記号は前記と同じ意味を示し、ｙは０≦ｙ≦１である。ただし、式（３Ａ）と式（３）において、ａ、ｂ、ｘおよびｙは独立した値を示す。） The silicic acid-phosphate compound produced by the production method of the present invention preferably contains olivine type crystal particles, and is preferably olivine type crystal particles. The olivine type crystal particle is a material that exhibits a multi-electron type theoretical electric capacity. The composition of the silicic acid-phosphoric acid compound is preferably a compound represented by the following formula (3), wherein A is Li and M is at least one selected from the group consisting of Fe and Mn. y is particularly preferably 0 <y <1.
Li 1 + x + a (Fe y Mn 1-y ) b Si x P 1-x O 4 + c2 (3)
(The symbols in the formula have the same meaning as above, and 0 ≦ y ≦ 1.)
In order to obtain the silicic acid-phosphoric acid compound having the composition of the formula (3), it is preferable to obtain a melt having the composition represented by the formula (3A) in the melting step (I).
Li 1 + x + a (Fe y Mn 1-y ) b Si x P 1-x O 4 + c1 (3A)
(The symbols in the formula have the same meaning as described above, and y is 0 ≦ y ≦ 1. However, in formula (3A) and formula (3), a, b, x, and y represent independent values. )
　式（２）で表される組成を有するケイ酸－リン酸化合物が結晶である場合、固溶体結晶または共晶であるのが好ましい。
　このうち、式（２）中、ｘが０．７≦ｘ＜１．０である場合には、固溶体結晶になりやすい。その理由は、式（４）で表される式によって、Ｓｉの一部がＰで置換されるためと考えられる。
　ｘＡ２ＭＳｉＯ４　＋　（１－ｘ）ＡＭＰＯ４　＝　Ａ１＋ｘＭ[ＳｉｘＰ１－ｘ]Ｏ４　　　　　（４）
（式中、ｘは０．７≦ｘ＜１．０であり、[　]は固溶体であることを表す。）
　該固溶体結晶は、Ｓｉのみからなる結晶に比べ、結晶構造が疎になり、Ｌｉイオンが結晶内で移動しやすくなる。よって高い容量が得られ、かつ電気伝導度が上昇するため、二次電池用正極材料に用いた場合に充放電のサイクル性が向上しうる。
　本発明におけるケイ酸－リン酸化合物は、固溶体結晶のケイ酸－リン酸化合物を含む場合は、Ｓｉの一部をＰで置換した固溶体結晶であるオリビン型結晶粒子を含むケイ酸－リン酸化合物であるのが好ましい。
　ケイ酸－リン酸化合物が、固溶体結晶であると、二次電池用正極材料に用いた場合に、Ｌｉイオンが結晶内で移動しやすくなるために高容量になり、かつ、電気伝導度が上昇する。よって、二次電池用正極材料に使用する場合には、理論容量が得られやすく、充放電のサイクル性が向上すると考えられる。 When the silicic acid-phosphoric acid compound having the composition represented by the formula (2) is a crystal, it is preferably a solid solution crystal or a eutectic crystal.
Among these, in the formula (2), when x is 0.7 ≦ x <1.0, a solid solution crystal is likely to be formed. The reason is considered that a part of Si is substituted with P by the formula represented by formula (4).
xA 2 MSiO 4 + (1-x) AMPO 4 = A 1 + x M [Si x P 1-x ] O 4 (4)
(In the formula, x is 0.7 ≦ x <1.0, and [] represents a solid solution.)
The solid solution crystal has a sparse crystal structure and a Li ion easily moves in the crystal as compared with a crystal made of only Si. Therefore, a high capacity can be obtained and the electrical conductivity can be increased. Therefore, when used as a positive electrode material for a secondary battery, charge / discharge cycleability can be improved.
When the silicic acid-phosphoric acid compound in the present invention contains a solid solution crystalline silicic acid-phosphoric acid compound, the silicic acid-phosphoric acid compound includes olivine type crystal particles which are solid solution crystals in which a part of Si is substituted with P. Is preferred.
When the silicic acid-phosphoric acid compound is a solid solution crystal, when it is used as a positive electrode material for a secondary battery, Li ions easily move in the crystal, resulting in high capacity and increased electrical conductivity. To do. Therefore, when used as a positive electrode material for a secondary battery, a theoretical capacity is easily obtained, and it is considered that the charge / discharge cycleability is improved.
　また、式（２）中、ｘが０．３≦ｘ＜０．７である場合には、共晶になりやすい。０．３＜ｘ＜０．７であることが好ましく、０．３５≦ｘ≦０．６５であることがより好ましい。共晶であるケイ酸－リン酸化合物（以下、「ケイ酸－リン酸化合物の共晶体」、または単に「共晶体」という。）とは、ケイ素原子を含む結晶と、リン原子を含む結晶と、リン原子およびケイ素原子を含む結晶とが、共存している結晶体、をいう。本発明においては、Ａ１＋ｚＭＳｉｚＰ１－ｚＯ４（ｚは０．２＜ｚ＜０．８である。）のオリビン型結晶とともに、Ａ２ＭＳｉＯ４のオリビン型結晶およびＡＭＰＯ４のオリビン型結晶からなる群より選ばれる少なくとも１種とを含む共晶体が好ましい。
　ケイ酸－リン酸化合物の共晶体は、下式（５）で表される反応メカニズムにより生成すると考えられる。
　ｘＡ２ＭＳｉＯ４　＋　（１－ｘ）ＡＭＰＯ４　＝　（ｘ－ｗ１）Ａ２ＭＳｉＯ４　＋　（１－ｘ－ｗ２）ＡＭＰＯ４　＋　ｗＡ１＋ｚＭＳｉｚＰ１－ｚＯ４　（５）
（式中、Ａ、Ｍは前記と同じ意味を示し、ｘおよびｚは、０．３≦ｘ＜０．７および０．２＜ｚ＜０．８であり、ｗ１、ｗ２、ｗはそれぞれ０～１の数であり、かつ、ｗ１＋ｗ２＝ｗである。）
　本発明のケイ酸－リン酸化合物が共晶体であると、電気伝導度が上昇する傾向があり好ましい。その理由は、複数の結晶構造を有し、電気導電度が異なる結晶子が生成することにより、電位が負荷されたときに結晶子間に電位差が生じることから、一次粒子自体の電気伝導度が上昇するため、と考えられる。また、一次粒子内の各結晶子間に、粒界を有する構造をなし、この粒界は一次粒子内に比べ極めて薄いので、一次粒子自体の電気伝導度が上昇するためとも考えられる。
　本発明のケイ酸－リン酸化合物としては、高い電気伝導度を得やすく、充放電サイクル性が向上するため、共晶体であるのが特に好ましい。 Further, in the formula (2), when x is 0.3 ≦ x <0.7, eutectic is likely to occur. 0.3 <x <0.7 is preferable, and 0.35 ≦ x ≦ 0.65 is more preferable. The eutectic silicic acid-phosphoric acid compound (hereinafter referred to as “silicic acid-phosphoric acid compound eutectic” or simply “eutectic”) includes a crystal containing a silicon atom, a crystal containing a phosphorus atom, And a crystal containing a phosphorus atom and a silicon atom-containing crystal. In the present invention, the olivine type crystal of A 2 MSiO 4 and the olivine of AMPO 4 together with the olivine type crystal of A 1 + z MSi z P 1-z O 4 (z is 0.2 <z <0.8). A eutectic containing at least one selected from the group consisting of type crystals is preferred.
The silicic acid-phosphoric acid compound eutectic is considered to be produced by the reaction mechanism represented by the following formula (5).
xA 2 MSiO 4 + (1-x) AMPO 4 = (x−w 1 ) A 2 MSiO 4 + (1-x−w 2 ) AMPO 4 + wA 1 + z MSi z P 1−z O 4 (5)
(In the formula, A and M have the same meaning as described above, x and z are 0.3 ≦ x <0.7 and 0.2 <z <0.8, and w 1 , w 2 and w are Each is a number between 0 and 1 and w 1 + w 2 = w.)
The silicic acid-phosphoric acid compound of the present invention is preferably a eutectic because it tends to increase electrical conductivity. The reason is that, due to the generation of crystallites having a plurality of crystal structures and different electrical conductivities, a potential difference is generated between the crystallites when a potential is applied. This is thought to be due to the rise. In addition, a structure having a grain boundary is formed between the crystallites in the primary particle, and this grain boundary is extremely thin as compared with the inside of the primary particle, which is considered to be because the electrical conductivity of the primary particle itself is increased.
The silicic acid-phosphoric acid compound of the present invention is particularly preferably an eutectic because it is easy to obtain high electric conductivity and charge / discharge cycleability is improved.
　本発明のケイ酸－リン酸化合物は、ケイ酸－リン酸化合物を二次電池用正極に適用した場合に高い容量を有し、良好なサイクル特性を得やすいという点からは、固溶体結晶が特に好ましく、二次電池用正極に適用した場合に高い電気伝導度を得やすいという点からは、共晶が特に好ましい。 The silicic acid-phosphoric acid compound of the present invention has a high capacity when the silicic acid-phosphoric acid compound is applied to a positive electrode for a secondary battery, and solid solution crystals are particularly preferable in that good cycle characteristics can be easily obtained. Preferably, eutectic is particularly preferable from the viewpoint that high electrical conductivity is easily obtained when applied to a positive electrode for a secondary battery.
　本発明のケイ酸－リン酸化合物の平均粒径は、体積換算のメディアン径で１０ｎｍ～１０μｍが好ましく、１０ｎｍ～６μｍがより好ましく、１０ｎｍ～２μｍが特に好ましい。下限の値は１００ｎｍであってもよい。平均粒径を該範囲とすることにより、より導電性が高くなる。平均粒径は、例えば電子顕微鏡による観察やレーザー回折式粒度分布計による測定等によって求められる。
　ケイ酸－リン酸化合物の比表面積は、０．２～２００ｍ２／ｇが好ましく、０．５～２００ｍ２／ｇが好ましく、１～２００ｍ２／ｇが特に好ましい。上限の値は１００ｍ２／ｇであってもよく１０ｍ２／ｇであってもよい。比表面積を該範囲とすることにより、導電性が高くなる。比表面積は、例えば窒素吸着法による比表面積測定装置で測定できる。 The average particle diameter of the silicic acid-phosphoric acid compound of the present invention is preferably 10 nm to 10 μm, more preferably 10 nm to 6 μm, and particularly preferably 10 nm to 2 μm in terms of volume-based median diameter. The lower limit value may be 100 nm. By making the average particle diameter within this range, the conductivity becomes higher. The average particle size can be determined by, for example, observation with an electron microscope or measurement with a laser diffraction particle size distribution meter.
Silicate - specific surface area of the phosphoric acid compound is preferably 0.2 ~ 200m 2 / g, preferably 0.5 ~ 200m 2 / g, 1 ~ 200m 2 / g is particularly preferred. The upper limit value may be 100 m 2 / g or 10 m 2 / g. By setting the specific surface area within this range, the conductivity is increased. The specific surface area can be measured by, for example, a specific surface area measuring apparatus using a nitrogen adsorption method.
＜二次電池用正極および二次電池の製造方法＞
　本発明のケイ酸－リン酸化合物の製造方法によって得られたケイ酸－リン酸化合物は、二次電池用正極材料として有用である。よって、該ケイ酸－リン酸化合物を用いて、二次電池用正極および二次電池を製造できる。
　二次電池としては、金属リチウム二次電池、リチウムイオン二次電池、リチウムポリマー二次電池等が挙げられるが、リチウムイオン二次電池が好ましい。電池形状は制限されることはなく、例えば円筒状、角型、コイン型等、種々の形状、サイズを適宜採用することができる。 <Positive electrode for secondary battery and method for producing secondary battery>
The silicic acid-phosphoric acid compound obtained by the method for producing a silicic acid-phosphoric acid compound of the present invention is useful as a positive electrode material for a secondary battery. Therefore, a positive electrode for a secondary battery and a secondary battery can be produced using the silicic acid-phosphoric acid compound.
Examples of the secondary battery include a metal lithium secondary battery, a lithium ion secondary battery, and a lithium polymer secondary battery, and a lithium ion secondary battery is preferable. The battery shape is not limited, and various shapes and sizes such as a cylindrical shape, a square shape, and a coin shape can be appropriately employed.
　二次電池用正極の製造は、本発明の製造方法で得られるケイ酸－リン酸化合物を用いるほかは公知の電極の製造方法に従えばよい。例えば、本発明のケイ酸－リン酸化合物を必要に応じて公知の結着材（ポリテトラフルオロエチレン、ポリビニリデンフルオライド、ポリビニルクロライド、エチレンプロピレンジエンポリマー、スチレン－ブタジエンゴム、アクリロニトリル－ブタジエンゴム、フッ素ゴム、ポリ酢酸ビニル、ポリメチルメタクリレート、ポリエチレン、ニトロセルロース等）、さらに必要に応じて公知の導電材（アセチレンブラック、カーボン、グラファイト、天然黒鉛、人造黒鉛、ニードルコークス等）と混合した後、得られた混合粉末をステンレス鋼製等の支持体上に圧着成形したり、金属製容器に充填すればよい。あるいは、例えば、該混合粉末を有機溶剤（Ｎ－メチルピロリドン、トルエン、シクロヘキサン、ジメチルホルムアミド、ジメチルアセトアミド、メチルエチルケトン、酢酸メチル、アクリル酸メチル、ジエチルトリアミン、Ｎ－Ｎ－ジメチルアミノプロピルアミン、エチレンオキシド、テトラヒドロフラン等）と混合して得られたスラリーをアルミニウム、ニッケル、ステンレス、銅等の金属基板上に塗布する等の方法によっても電極を製造できる。 The production of the positive electrode for the secondary battery may be carried out in accordance with a known electrode production method except that the silicic acid-phosphate compound obtained by the production method of the present invention is used. For example, a known binder (polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl chloride, ethylene propylene diene polymer, styrene-butadiene rubber, acrylonitrile-butadiene rubber, Fluorine rubber, polyvinyl acetate, polymethyl methacrylate, polyethylene, nitrocellulose, etc.), and further mixed with known conductive materials (acetylene black, carbon, graphite, natural graphite, artificial graphite, needle coke, etc.) if necessary, The obtained mixed powder may be pressure-bonded on a support made of stainless steel or filled in a metal container. Alternatively, for example, the mixed powder is mixed with an organic solvent (N-methylpyrrolidone, toluene, cyclohexane, dimethylformamide, dimethylacetamide, methyl ethyl ketone, methyl acetate, methyl acrylate, diethyltriamine, NN-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran. The electrode can also be produced by a method such as applying a slurry obtained by mixing with a metal substrate such as aluminum, nickel, stainless steel or copper.
　二次電池の製造は、本発明の製造方法で得られる二次電池用正極を電極として用いる以外は、公知の二次電池における構成要素を採用することができる。セパレータ、電池ケース等の要素についても同様である。負極としては、活物質として公知の負極用活物質を使用することが可能であるが、炭素材料、アルカリ金属材料およびアルカリ土類金属材料からなる群から選ばれる少なくとも１種を用いることが好ましい。電解液としては、非水系が好ましい。すなわち、本発明の製造方法で得られる二次電池としては、非水電解質リチウムイオン二次電池が好ましい。 For the production of the secondary battery, components in a known secondary battery can be adopted except that the positive electrode for a secondary battery obtained by the production method of the present invention is used as an electrode. The same applies to elements such as a separator and a battery case. As the negative electrode, a known negative electrode active material can be used as the active material, but it is preferable to use at least one selected from the group consisting of a carbon material, an alkali metal material, and an alkaline earth metal material. The electrolyte solution is preferably non-aqueous. That is, as the secondary battery obtained by the production method of the present invention, a nonaqueous electrolyte lithium ion secondary battery is preferable.
　本発明を実施例を挙げて具体的に説明するが、本発明は以下の説明に限定されない。
［実施例１～２４］
（溶融工程）
　溶融物の組成がＬｉ２Ｏ、Ｎａ２Ｏ、ＦｅＯ、ＭｎＯ、ＣｏＯ、ＮｉＯ、ＳｉＯ２、Ｐ２Ｏ５換算量（単位：モル％）で、それぞれ表１に示す割合となるように、炭酸リチウム（Ｌｉ２ＣＯ３）、炭酸ナトリウム（Ｎａ２ＣＯ３）、四酸化三鉄（Ｆｅ３Ｏ４）、二酸化マンガン（ＭｎＯ２）、四酸化三コバルト（Ｃｏ３Ｏ４）、酸化ニッケル（ＮｉＯ）、二酸化ケイ素（ＳｉＯ２）、およびリン酸二水素アンモニウム（ＮＨ４Ｈ２ＰＯ４）を秤量し、乾式で混合・粉砕して、原料調合物を得た。 The present invention will be specifically described with reference to examples, but the present invention is not limited to the following description.
[Examples 1 to 24]
(Melting process)
Carbon dioxide so that the composition of the melt is Li 2 O, Na 2 O, FeO, MnO, CoO, NiO, SiO 2 , P 2 O 5 equivalent (unit: mol%), and the ratio shown in Table 1 respectively. Lithium (Li 2 CO 3 ), sodium carbonate (Na 2 CO 3 ), triiron tetroxide (Fe 3 O 4 ), manganese dioxide (MnO 2 ), tricobalt tetroxide (Co 3 O 4 ), nickel oxide (NiO ), Silicon dioxide (SiO 2 ), and ammonium dihydrogen phosphate (NH 4 H 2 PO 4 ) were weighed, mixed and pulverized in a dry process to obtain a raw material formulation.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　各原料調合物を、ロジウムを２０質量％含む白金合金製のるつぼにそれぞれ充填した。次に、るつぼをケイ化モリブデン製の発熱体を備える電気炉（モトヤマ社製、装置名：ＮＨ－３０３５）の中に入れた。該電気炉内を２Ｌ／分でＮ２ガスを流通しつつ、＋３００℃／時間の速度で昇温し、１，４５０～１，５００℃で０．５時間加熱した。目視で透明になったことを確認して、それぞれの溶融物を得た。得られた溶融物の組成式を表１の右欄に示す。 Each raw material formulation was filled in a platinum alloy crucible containing 20% by mass of rhodium. Next, the crucible was placed in an electric furnace (manufactured by Motoyama, apparatus name: NH-3035) equipped with a heating element made of molybdenum silicide. While flowing N 2 gas at a rate of 2 L / min in the electric furnace, the temperature was raised at a rate of + 300 ° C./hour and heated at 1,450 to 1,500 ° C. for 0.5 hour. Each melt was obtained after confirming that it became transparent visually. The composition formula of the obtained melt is shown in the right column of Table 1.
（冷却工程）
　溶融工程で得たるつぼ中の溶融物を、毎分４００回転で回転する直径約１５ｃｍの双ローラを通すことにより、－１×１０５ ℃／秒で冷却し、フレーク状の固化物を得た。 (Cooling process)
The melt in the crucible obtained in the melting step was cooled at −1 × 10 5 ° C./second by passing through a twin roller having a diameter of about 15 cm rotating at 400 revolutions per minute to obtain a flaky solidified product. .
（粉砕工程）
　冷却工程で得たフレーク状固化物を軽く手で揉んで細かくした後、乳棒と乳鉢を用いて粗粉砕した。さらに、粉砕媒体としてジルコニア製ボールを用いた遊星ミルで、粗粉砕後の固化物を乾式で粉砕して粉砕物を得た。実施例１の粉砕物をレーザ回折／散乱式粒度分析計（堀場製作所製、装置名：ＬＡ－９５０）を用いて粒子径を測定したところ、体積換算のメディアン径は２．８μｍであった。 (Crushing process)
The flake solidified product obtained in the cooling step was lightly kneaded and finely ground, and then coarsely pulverized using a pestle and mortar. Further, the coarsely pulverized solidified product was pulverized in a dry manner using a planetary mill using zirconia balls as a pulverizing medium to obtain a pulverized product. When the particle diameter of the pulverized product of Example 1 was measured using a laser diffraction / scattering particle size analyzer (manufactured by Horiba, Ltd., apparatus name: LA-950), the median diameter in terms of volume was 2.8 μm.
（加熱工程）
　粉砕工程で得た粉砕物を３体積％Ｈ２－Ａｒ雰囲気におき、それぞれの実施例について、６００℃、７００℃、８００℃、および９００℃の４種類の温度条件で８時間加熱し、次に－２００℃／時間の速度で冷却（空冷）し、ケイ酸－リン酸化合物粒子を析出させた。各実施例のうち、加熱工程を７００℃で実施した粒子について、Ｘ線回折、粒度分布、組成分析を行った。 (Heating process)
The pulverized product obtained in the pulverization step was placed in a 3% by volume H 2 —Ar atmosphere, and each example was heated for 8 hours at four temperature conditions of 600 ° C., 700 ° C., 800 ° C., and 900 ° C. Then, the mixture was cooled (air-cooled) at a rate of −200 ° C./hour to precipitate silicic acid-phosphoric acid compound particles. Among the examples, X-ray diffraction, particle size distribution, and composition analysis were performed on the particles subjected to the heating step at 700 ° C.
（Ｘ線回折）
　得られたケイ酸－リン酸化合物粒子の鉱物相を、Ｘ線回折装置（リガク社製、装置名：ＲＩＮＴ　ＴＴＲIII）を用いて測定した。実施例１～４、実施例８～２４で得た粒子は、いずれも斜方晶のオリビン型Ｌｉ２ＭＳｉＯ４（Ｋ．Ｚａｇｈｉｂ　ｅｔ　ａｌ．，　Ｊｏｕｒｎａｌ　ｏｆ　Ｐｏｗｅｒ　Ｓｏｕｒｃｅｓ，　１６０，　１３８１－１３８６，　２００６　及び　Ｒ．Ｄｏｍｉｎｋｏ　ｅｔ　ａｌ．，　Ｅｌｅｃｔｒｏｃｈｅｍｉｓｔｒｙ　Ｃｏｍｍｕｎｉｃａｔｉｏｎｓ，　８，　２１７－２２２　（２００６）参照）に類似した回折パターンを示した。該結果から、ケイ酸－リン酸化合物粒子が結晶であり、かつ、Ａ２ＭＳｉＯ４結晶のＳｉの一部がＰに置換された固溶体結晶からなることが確認できた。よって、ｘが０．７≦ｘ＜１．０である場合には、Ａ２ＭＳｉＯ４結晶のＳｉの一部がＰに置換された固溶体結晶が得られることが確認できた。実施例５～７で得た粒子は、Ａ２ＭＳｉＯ４、ＡＭＰＯ４、およびこれらの固溶体を含む共晶と考えられる回折パターンを示した。該結果から、ｘが０．３≦ｘ＜０．７である場合には、Ａ２ＭＳｉＯ４、ＡＭＰＯ４、およびこれらの固溶体を含む共晶が得られることが確認できた。
　実施例１、２、３、および４で得た各結晶のＸ線回折パターンを、それぞれ図１の（ａ）、（ｂ）、（ｃ）、（ｄ）に、実施例５、６、および７で得た各結晶のＸ線回折パターンを、それぞれ図２の（ａ）、（ｂ）、（ｃ）に、実施例１９、２０、２１、および２２で得た各結晶のＸ線回折パターンを、それぞれ図３の（ａ）、（ｂ）、（ｃ）、（ｄ）に、示す。 (X-ray diffraction)
The mineral phase of the obtained silicic acid-phosphate compound particles was measured using an X-ray diffraction apparatus (manufactured by Rigaku Corporation, apparatus name: RINT TTRIII). The particles obtained in Examples 1 to 4 and Examples 8 to 24 are all orthorhombic olivine type Li 2 MSiO 4 (K. Zaghib et al., Journal of Power Sources, 160, 1381-1386, 2006 and R. Dominko et al., Electrochemistry Communications, 8, 217-222 (2006)). From the results, it was confirmed that the silicic acid-phosphoric acid compound particles were crystals and consisted of solid solution crystals in which part of Si in the A 2 MSiO 4 crystals was substituted with P. Therefore, when x is 0.7 ≦ x <1.0, it was confirmed that a solid solution crystal in which a part of Si in the A 2 MSiO 4 crystal was substituted with P was obtained. The particles obtained in Examples 5 to 7 exhibited a diffraction pattern considered to be a eutectic containing A 2 MSiO 4 , AMPO 4 , and solid solutions thereof. From the results, it was confirmed that when x is 0.3 ≦ x <0.7, a eutectic containing A 2 MSiO 4 , AMPO 4 , and a solid solution thereof can be obtained.
The X-ray diffraction patterns of the crystals obtained in Examples 1, 2, 3, and 4 are respectively shown in (a), (b), (c), and (d) of FIG. The X-ray diffraction patterns of the crystals obtained in Example 7 are shown in FIGS. 2 (a), 2 (b), and 2 (c), respectively, in Examples 19, 20, 21, and 22. Are shown in (a), (b), (c), and (d) of FIG. 3, respectively.
（粒度分布）
　実施例２、および６で得たケイ酸－リン酸化合物の粒径分布をレーザ回折／散乱式粒度分布測定装置（堀場製作所製、装置名：ＬＡ－９２０）で測定した。体積換算のメディアン径はそれぞれ２．５μｍ（実施例２）、２．７μｍ（実施例６）であった。さらに、ケイ酸－リン酸化合物の比表面積を比表面積測定装置（島津製作所製、装置名：ＡＳＡＰ２０２０）で測定したところ、いずれも０．７ｍ２／ｇであった。 (Particle size distribution)
The particle size distribution of the silicic acid-phosphoric acid compounds obtained in Examples 2 and 6 was measured with a laser diffraction / scattering particle size distribution measuring apparatus (manufactured by Horiba, apparatus name: LA-920). The median diameters in terms of volume were 2.5 μm (Example 2) and 2.7 μm (Example 6), respectively. Furthermore, when the specific surface area of the silicic acid-phosphoric acid compound was measured with a specific surface area measuring apparatus (manufactured by Shimadzu Corporation, apparatus name: ASAP2020), all were 0.7 m 2 / g.
（組成分析）
　得られたケイ酸－リン酸化合物粒子の化学組成を測定した。まず、粒子を２．５ｍｏｌ／ＬのＫＯＨ溶液で１２０℃にて加熱密閉分解し、分解液を塩酸酸性下で乾固した。次に塩酸酸性溶液として濾過した後、濾液および残渣を得た。濾液中のＳｉ、Ｆｅ、Ｍｎ、Ｃｏ、およびＮｉ量は、誘導結合発光分光分析装置（セイコーインスツル社製、装置名：ＳＰＳ３１００）を用いて定量した。濾液中のＬｉ、およびＮａ量は原子吸光光度計（日立ハイテクノロジーズ社製、装置名：Ｚ－２３１０）を用いて定量した。Ｓｉ、Ｐ、Ｆｅ、Ｍｎ、Ｃｏ、Ｎｉ、Ｌｉ、およびＮａの定量値から、ＳｉＯ２、Ｐ２Ｏ５、ＦｅＯ、ＭｎＯ、ＣｏＯ、ＮｉＯ、Ｌｉ２Ｏ、およびＮａ２Ｏの量をそれぞれ算出した。さらに、残渣は灰化した後、フッ酸－硫酸で分解処理し、この処理による重量減少をＳｉＯ２量とした。全ＳｉＯ２量は、重量減少量から算出される量と濾液中のＳｉＯ２量の合量とした。実施例１～７、実施例１５～１８で得たケイ酸－リン酸化合物粒子の化学組成の定量値を、表２に示す。 (Composition analysis)
The chemical composition of the resulting silicic acid-phosphoric acid compound particles was measured. First, the particles were heated and decomposed at 120 ° C. with a 2.5 mol / L KOH solution, and the decomposition solution was dried under hydrochloric acid acidity. Next, after filtration as a hydrochloric acid acidic solution, a filtrate and a residue were obtained. The amounts of Si, Fe, Mn, Co, and Ni in the filtrate were quantified using an inductively coupled emission spectroscopic analyzer (manufactured by Seiko Instruments Inc., apparatus name: SPS3100). The amounts of Li and Na in the filtrate were quantified using an atomic absorption photometer (manufactured by Hitachi High-Technologies Corporation, apparatus name: Z-2310). Calculate the amounts of SiO 2 , P 2 O 5 , FeO, MnO, CoO, NiO, Li 2 O, and Na 2 O from the quantitative values of Si, P, Fe, Mn, Co, Ni, Li, and Na, respectively. did. Further, the residue was ashed and then decomposed with hydrofluoric acid-sulfuric acid, and the weight loss due to this treatment was defined as the amount of SiO 2 . The total amount of SiO 2 was the sum of the amount calculated from the weight loss and the amount of SiO 2 in the filtrate. Table 2 shows the quantitative values of the chemical composition of the silicic acid-phosphate compound particles obtained in Examples 1 to 7 and Examples 15 to 18.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
［実施例２５～３５］
　実施例１～７、実施例１９～２２で溶融、冷却、粗粉砕して得られた粗粉砕物とカーボンブラックとを、粉砕物とカーボンブラック中の炭素量との質量比が９：１となるようにそれぞれ混合し、実施例１と同様に遊星ミルを用いて粉砕した。各実施例における炭素含有粉砕物をＡｒガス中にて７００℃および８００℃の２種類の温度で８時間加熱し、－２００℃／時間の速度で冷却（空冷）して、ケイ酸－リン酸化合物粒子を得た。得られたケイ酸－リン酸化合物のＸ線回折パターンは、オリビン型ケイ酸鉄リチウムのそれと一致した。 [Examples 25 to 35]
The coarsely pulverized product obtained by melting, cooling, and coarsely pulverizing in Examples 1 to 7 and Examples 19 to 22 and carbon black were mixed at a mass ratio of 9: 1 between the pulverized product and the amount of carbon in the carbon black. Each was mixed and ground using a planetary mill in the same manner as in Example 1. The carbon-containing pulverized product in each example was heated in Ar gas at two temperatures of 700 ° C. and 800 ° C. for 8 hours, cooled (air-cooled) at a rate of −200 ° C./hour, and then silicic acid-phosphoric acid. Compound particles were obtained. The X-ray diffraction pattern of the resulting silicate-phosphate compound was consistent with that of olivine type lithium iron silicate.
　実施例３２、３３、３４、および３５において、７００℃で加熱して得られたケイ酸－リン酸化合物のＸ線回折パターンをそれぞれ図４の（ａ）、（ｂ）、（ｃ）、（ｄ）に示す。 In Examples 32, 33, 34, and 35, the X-ray diffraction patterns of silicic acid-phosphoric acid compounds obtained by heating at 700 ° C. are shown in FIGS. 4 (a), (b), (c), ( d).
　実施例２７、および３４において、７００℃で８時間加熱し、－２００℃／時間の速度で冷却（空冷）して得られたケイ酸－リン酸化合物粒子の炭素含有量を炭素分析装置（堀場製作所製、装置名：ＥＭＩＡ－９２０Ｖ）で測定したところ、それぞれ９．５質量％、９．１質量％であった。また、該粒子の比表面積を測定したところ、それぞれ、１５．６ｍ２／ｇ（実施例２７）、１７．２ｍ２／ｇ（実施例３４）であった。 In Examples 27 and 34, the carbon content of silicic acid-phosphate compound particles obtained by heating at 700 ° C. for 8 hours and cooling (air cooling) at a rate of −200 ° C./hour was measured using a carbon analyzer (Horiba). They were 9.5% by mass and 9.1% by mass, respectively, as measured by Seisakusho, apparatus name: EMIA-920V. Moreover, when the specific surface area of this particle | grain was measured, they were 15.6 m < 2 > / g (Example 27) and 17.2 m < 2 > / g (Example 34), respectively.
［実施例３６］
　溶融物の組成がＬｉ２Ｏ、ＦｅＯ、ＳｉＯ２、Ｐ２Ｏ５換算量（単位：モル％）で、３２．８％、３４．５％、３１．０％、１．７％となるように、炭酸リチウム（Ｌｉ２ＣＯ３）、三酸化二鉄（Ｆｅ２Ｏ３）、二酸化ケイ素（ＳｉＯ２）、およびリン酸二水素アンモニウム（ＮＨ４Ｈ２ＰＯ４）をそれぞれ秤量し、乾式で混合・粉砕して原料調合物を調製した。この原料調合物を雰囲気制御することなく空気中で溶融すること以外は実施例３と同様に、溶融、冷却、粗粉砕して粗粉砕物を得た。得られた粗粉砕物とカーボンブラックとを、実施例２７と同様に混合、粉砕し、さらに炭素含有粉砕物をＡｒガス中にて７００℃で８時間加熱し、－２００℃／時間の速度で冷却（空冷）してケイ酸－リン酸化合物粒子を得た。得られたケイ酸－リン酸化合物のＸ線回折パターンは、オリビン型ケイ酸鉄リチウムのそれと一致した。得られたケイ酸－リン酸化合物粒子の炭素含有量を測定したところ、７．２質量％であり、比表面積を測定したところ、２４ｍ２／ｇであった。 [Example 36]
The composition of the melt is 32.8%, 34.5%, 31.0%, 1.7% in terms of Li 2 O, FeO, SiO 2 and P 2 O 5 (unit: mol%). Lithium carbonate (Li 2 CO 3 ), ferric trioxide (Fe 2 O 3 ), silicon dioxide (SiO 2 ), and ammonium dihydrogen phosphate (NH 4 H 2 PO 4 ) were weighed and dried A raw material formulation was prepared by mixing and grinding. Except that this raw material formulation was melted in air without controlling the atmosphere, it was melted, cooled, and coarsely pulverized in the same manner as in Example 3 to obtain a coarsely pulverized product. The obtained coarsely pulverized product and carbon black were mixed and pulverized in the same manner as in Example 27, and the carbon-containing pulverized product was heated in Ar gas at 700 ° C. for 8 hours, at a rate of −200 ° C./hour. By cooling (air cooling), silica-phosphate compound particles were obtained. The X-ray diffraction pattern of the resulting silicate-phosphate compound was consistent with that of olivine type lithium iron silicate. The carbon content of the obtained silicic acid-phosphoric acid compound particles was measured and found to be 7.2% by mass. The specific surface area was measured and found to be 24 m 2 / g.
［参考例１］
　溶融物の組成がＬｉ２Ｏ、ＦｅＯ、ＳｉＯ２、Ｐ２Ｏ５換算量（単位：モル％）で、２７．１％、５０．３％、２０．１％、および２．５％となるように、炭酸リチウム（Ｌｉ２ＣＯ３）、四酸化三鉄（Ｆｅ３Ｏ４）、二酸化ケイ素（ＳｉＯ２）、およびリン酸二水素アンモニウム（ＮＨ４Ｈ２ＰＯ４）をそれぞれ秤量し、乾式で混合・粉砕して原料調合物を得た。原料調合物を実施例１と同様に溶融したが、溶融できなかった。該原料調合物の組成は、本発明の式（１）においてａ＝０．３６、ｂ＝２．０、ｘ＝０．８に相当する。 [Reference Example 1]
The composition of the melt is 27.1%, 50.3%, 20.1%, and 2.5% in terms of Li 2 O, FeO, SiO 2 , and P 2 O 5 (unit: mol%). Lithium carbonate (Li 2 CO 3 ), triiron tetroxide (Fe 3 O 4 ), silicon dioxide (SiO 2 ), and ammonium dihydrogen phosphate (NH 4 H 2 PO 4 ) were weighed and dried Were mixed and pulverized to obtain a raw material formulation. The raw material formulation was melted in the same manner as in Example 1, but could not be melted. The composition of the raw material formulation corresponds to a = 0.36, b = 2.0, and x = 0.8 in the formula (1) of the present invention.
［参考例２］
　溶融物の組成がＬｉ２Ｏ、ＦｅＯ、ＳｉＯ２、Ｐ２Ｏ５換算量（単位：モル％）で、５０．６．％、２５．３％、２２．８％、および１．３％となるように、炭酸リチウム（Ｌｉ２ＣＯ３）、四酸化三鉄（Ｆｅ３Ｏ４）、二酸化ケイ素（ＳｉＯ２）、リン酸二水素アンモニウム（ＮＨ４Ｈ２ＰＯ４）をそれぞれ秤量し、乾式で混合・粉砕して原料調合物を得た。この原料調合物を実施例１と同様に溶融したが、溶融物は冷却工程までに結晶化し、冷却工程を行うことができなかった。該原料調合物の組成は、本発明の式（１）においてａ＝２．１、ｂ＝１．０、ｘ＝０．９に相当する。 [Reference Example 2]
The composition of the melt is Li 2 O, FeO, SiO 2 , P 2 O 5 equivalent (unit: mol%), 50.6. %, 25.3%, 22.8%, and 1.3% to be lithium carbonate (Li 2 CO 3 ), triiron tetroxide (Fe 3 O 4 ), silicon dioxide (SiO 2 ), phosphorus Ammonium dihydrogenammonium (NH 4 H 2 PO 4 ) was weighed, mixed and pulverized in a dry process to obtain a raw material formulation. Although this raw material formulation was melted in the same manner as in Example 1, the melt was crystallized by the cooling step, and the cooling step could not be performed. The composition of the raw material formulation corresponds to a = 2.1, b = 1.0, and x = 0.9 in the formula (1) of the present invention.
［参考例３］
　溶融物の組成がＬｉ２Ｏ、ＦｅＯ、ＳｉＯ２、Ｐ２Ｏ５換算量（単位：モル％）で、３１．６％、３５．０％、３１．６％、および１．８％となるように、炭酸リチウム（Ｌｉ２ＣＯ３）、四酸化三鉄（Ｆｅ３Ｏ４）、二酸化ケイ素（ＳｉＯ２）、およびリン酸二水素アンモニウム（ＮＨ４Ｈ２ＰＯ４）をそれぞれ秤量し、乾式で混合・粉砕し、原料調合物を得た。該原料調合物を実施例１と同様に、１，４５０℃で溶融した後、－３００℃／時間で冷却し、結晶化物を得た。得られた結晶化物の鉱物相をＸＲＤを用いて同定したところ、Ｌｉ２ＳｉＯ３及びＦｅ３Ｏ４を主成分とするものであった。すなわち、冷却工程、粉砕工程および加熱工程を行わない場合には、目的化合物を得ることができない。 [Reference Example 3]
The composition of the melt is 31.6%, 35.0%, 31.6%, and 1.8% in terms of Li 2 O, FeO, SiO 2 , and P 2 O 5 (unit: mol%). Lithium carbonate (Li 2 CO 3 ), triiron tetroxide (Fe 3 O 4 ), silicon dioxide (SiO 2 ), and ammonium dihydrogen phosphate (NH 4 H 2 PO 4 ) were weighed and dried And mixed and pulverized to obtain a raw material formulation. In the same manner as in Example 1, the raw material formulation was melted at 1,450 ° C. and then cooled at −300 ° C./hour to obtain a crystallized product. When the mineral phase of the obtained crystallized product was identified using XRD, it was mainly composed of Li 2 SiO 3 and Fe 3 O 4 . That is, the target compound cannot be obtained unless the cooling step, the pulverizing step and the heating step are performed.
［実施例３７～４０：Ｌｉイオン二次電池用正極および評価用電池の製造例］
　実施例２、６、１９、および２０において、７００℃で８時間加熱し、－２００℃／時間の速度で冷却（空冷）して得られたケイ酸－リン酸化合物粒子の粉砕物と、２０質量％ショ糖溶液とを、粉砕物とショ糖中の炭素量との質量比が９５：５となるようにそれぞれ混合、粉砕し、Ｎ２ガス中で、６００℃で２時間加熱し、冷却後粉砕して活物質を得た。該活物質とポリフッ化ビニリデン樹脂（結着剤）とアセチレンブラック（導電材）とを、質量比が８５：５：１０の比率となるように秤量し、Ｎ－メチルピロリドン（溶媒）中で均一になるまで混合してスラリーを調製した。次いで、該スラリーをバーコーターで厚さ３０μｍのアルミニウム箔に塗布した。これを空気中にて１２０℃で乾燥させて溶媒を除去した後、ロールプレスで塗工層を圧密化した後、幅１０ｍｍ×長さ４０ｍｍの短冊状に切り出した。 [Examples 37 to 40: Production examples of positive electrode for Li-ion secondary battery and battery for evaluation]
In Examples 2, 6, 19, and 20, a pulverized product of silicic acid-phosphate compound particles obtained by heating at 700 ° C. for 8 hours and cooling (air cooling) at a rate of −200 ° C./hour, The mass% sucrose solution was mixed and pulverized so that the mass ratio of the pulverized product and the amount of carbon in the sucrose was 95: 5, heated in N 2 gas at 600 ° C. for 2 hours, and cooled. After pulverization, an active material was obtained. The active material, polyvinylidene fluoride resin (binder) and acetylene black (conductive material) are weighed so that the mass ratio is 85: 5: 10, and uniform in N-methylpyrrolidone (solvent) A slurry was prepared by mixing until Next, the slurry was applied to an aluminum foil having a thickness of 30 μm with a bar coater. After drying this at 120 degreeC in the air and removing a solvent, after consolidating the coating layer with the roll press, it cut out to the strip shape of width 10mm * length 40mm.
　塗工層は短冊状アルミニウム箔の先端１０×１０ｍｍの部分を残して剥離し、これを電極とした。得られた電極のロールプレス後の塗工層厚は２０μｍであった。得られた電極は１５０℃で真空乾燥した後、精製Ａｒガスが満たされたグローブボックス中に搬入し、ニッケルメッシュにリチウム箔を圧着した対極と多孔質ポリエチレンフィルム製セパレータを介して対向させ、さらに両側をポリエチレン板で挟んで固定した。 The coating layer was peeled off leaving a 10 × 10 mm tip of strip-shaped aluminum foil, which was used as an electrode. The coating thickness of the obtained electrode after roll pressing was 20 μm. The obtained electrode was vacuum-dried at 150 ° C., then carried into a glove box filled with purified Ar gas, and opposed to a counter electrode in which a lithium foil was pressure-bonded to a nickel mesh with a porous polyethylene film separator. Both sides were fixed with a polyethylene plate.
　対向電極をポリエチレン製ビーカに入れ、六フッ化リン酸リチウムをエチレンカーボネートとエチルメチルカーボネートの混合溶媒（１：１体積比）に１ｍｏｌ／Ｌの濃度で溶解した非水電解液を注入して充分に含浸させた。電解液含浸後の電極をビーカから取り出し、アルミニウムラミネートフィルム袋に入れ、リード線部を取り出して封止して半電池を構成した。この半電池の特性を以下のようにして測定した。 Put the counter electrode in a polyethylene beaker and inject a non-aqueous electrolyte solution of lithium hexafluorophosphate dissolved in a mixed solvent of ethylene carbonate and ethyl methyl carbonate (1: 1 volume ratio) at a concentration of 1 mol / L. Was impregnated. The electrode after impregnation with the electrolytic solution was taken out from the beaker, put in an aluminum laminate film bag, the lead wire part was taken out and sealed to form a half battery. The characteristics of this half-cell were measured as follows.
（Ｌｉイオン二次電池用正極の充放電特性評価）
　得られた半電池を６０℃の恒温槽に入れ、定電流充放電試験機（北斗電工社製、装置名：ＨＪ２０１Ｂ）に接続して充放電試験を行った。電流密度は電極活物質の質量（導電材と結着剤とを除いた質量）当たりの電流値を１０ｍＡ／ｇとして充放電を行った。充電終止電位はＬｉ対極基準で４．５Ｖとし、終止電圧に到達後即座に放電を開始した。放電終止電圧はＬｉ対極基準で１．５Ｖとした。この充放電サイクルを３サイクル繰り返した。３サイクル目の放電容量は、それぞれ、１６１ｍＡｈ／ｇ（実施例３７）、１４５ｍＡｈ／ｇ（実施例３８）、２０３ｍＡｈ／ｇ（実施例３９）、２４１ｍＡｈ／ｇ（実施例４０）であった。 (Charge / discharge characteristic evaluation of positive electrode for Li ion secondary battery)
The obtained half-cell was placed in a constant temperature bath at 60 ° C. and connected to a constant current charge / discharge tester (manufactured by Hokuto Denko Co., Ltd., device name: HJ201B) to conduct a charge / discharge test. The current density was charged / discharged with the current value per mass of the electrode active material (the mass excluding the conductive material and the binder) being 10 mA / g. The end-of-charge potential was 4.5 V with respect to the Li counter electrode, and discharge was started immediately after reaching the end voltage. The end-of-discharge voltage was 1.5 V with respect to the Li counter electrode. This charge / discharge cycle was repeated three times. The discharge capacities at the third cycle were 161 mAh / g (Example 37), 145 mAh / g (Example 38), 203 mAh / g (Example 39), and 241 mAh / g (Example 40), respectively.
［実施例４１～４２］
　実施例２６、および３３で得たケイ酸－リン酸化合物粒子を活物質として用いて、これとポリフッ化ビニリデン樹脂（結着剤）とアセチレンブラック（導電材）とを、質量比が９０：５：５の比率となるように秤量する以外は実施例３７と同様にして電極を製造し、その充放電特性を実施例３７と同様にして評価した。３サイクル目の放電容量は、１５３ｍＡｈ／ｇ（実施例４１）、１９１ｍＡｈ／ｇ（実施例４２）であった。 [Examples 41 to 42]
Using the silicic acid-phosphoric acid compound particles obtained in Examples 26 and 33 as an active material, the mass ratio of this to polyvinylidene fluoride resin (binder) and acetylene black (conductive material) is 90: 5. The electrode was produced in the same manner as in Example 37 except that the weight was adjusted so that the ratio was 5 and the charge / discharge characteristics were evaluated in the same manner as in Example 37. The discharge capacity at the third cycle was 153 mAh / g (Example 41) and 191 mAh / g (Example 42).
［参考例４］
　参考例３で溶融、冷却、粗粉砕して得られた結晶化物とカーボンブラックとを溶融物の組成が実施例３７と同様になるようにして電極を製造し、その充放電特性を実施例３７と同様にして評価した。１サイクル目の放電容量は、５ｍＡｈ／ｇであった。 [Reference Example 4]
An electrode was produced from the crystallized product obtained by melting, cooling, and coarsely pulverizing in Reference Example 3 and carbon black so that the composition of the melt was the same as in Example 37, and the charge / discharge characteristics were measured in Example 37. And evaluated in the same manner. The discharge capacity at the first cycle was 5 mAh / g.
　実施例１～３６では、所望の組成のケイ酸－リン酸化合物を簡便に製造することができた。また、製造されたケイ酸－リン酸化合物は、二次電池用正極材料、さらには二次電池として優れた特性を有することを確認した（実施例３７～４２）。 In Examples 1 to 36, a silicic acid-phosphoric acid compound having a desired composition could be easily produced. Further, it was confirmed that the produced silicic acid-phosphoric acid compound had excellent characteristics as a positive electrode material for a secondary battery and further as a secondary battery (Examples 37 to 42).
　本発明のケイ酸－リン酸化合物の製造方法は、ケイ酸－リン酸化合物の組成制御がしやすく、製造しやすいので有用である。得られたケイ酸－リン酸化合物は、二次電池用正極材料さらには二次電池に有用である。本発明のケイ酸－リン酸化合物を正極材料として用いた二次電池は、プラグインハイブリッド自動車や電気自動車に搭載する二次電池として、また、電力貯蔵用の蓄電池として有用である。
　なお、２０１０年１０月２９日に出願された日本特許出願２０１０－２４４７６３号の明細書、特許請求の範囲、図面及び要約書の全内容をここに引用し、本発明の明細書の開示として、取り入れるものである。 The method for producing a silicic acid-phosphoric acid compound of the present invention is useful because the composition of the silicic acid-phosphoric acid compound can be easily controlled and produced. The obtained silicic acid-phosphoric acid compound is useful for a positive electrode material for a secondary battery and further for a secondary battery. A secondary battery using the silicate-phosphate compound of the present invention as a positive electrode material is useful as a secondary battery mounted in a plug-in hybrid vehicle or an electric vehicle, and as a storage battery for storing power.
It should be noted that the entire content of the specification, claims, drawings and abstract of Japanese Patent Application No. 2010-244663 filed on October 29, 2010 is cited herein as the disclosure of the specification of the present invention. Incorporated.

Claims (12)

  1. 　下式（１）で表される組成を有する溶融物を得る溶融工程、
    　前記溶融物を冷却し固化物を得る冷却工程、
    　前記固化物を粉砕し粉砕物を得る粉砕工程、および
    　前記粉砕物を加熱して下式（２）で表される組成を有するケイ酸－リン酸化合物を得る加熱工程、
    をこの順に具備することを特徴とするケイ酸－リン酸化合物の製造方法。
    　Ａ１＋ｘ＋ａＭｂＳｉｘＰ１－ｘＯ４＋ｃ１　　　　　（１）
    （式中、元素ＡはＬｉ、ＮａおよびＫからなる群より選ばれる少なくとも１種の元素であり、元素ＭはＦｅ、Ｍｎ、ＣｏおよびＮｉからなる群より選ばれる少なくとも１種の元素である。ａは－０．１≦ａ≦０．４であり、ｂは０．７≦ｂ≦１．３であり、ｘは０．３≦ｘ＜１．０であり、ｃ１はａ、ｂおよびＭの価数Ｎに依存する数であり、加熱工程後にｃ２となる数である。）
    　Ａ１＋ｘ＋ａＭｂＳｉｘＰ１－ｘＯ４＋ｃ２　　　　　（２）
    （式中、Ａ、Ｍ、ａ、ｂおよびｘは前記と同じ意味を示すが、前記とは独立した値であり、ｃ２はａ、ｂおよびＭの価数Ｎに依存する数である。）     A melting step for obtaining a melt having a composition represented by the following formula (1):
    A cooling step of cooling the melt to obtain a solidified product,
    A pulverizing step of pulverizing the solidified product to obtain a pulverized product, and a heating step of heating the pulverized product to obtain a silicic acid-phosphate compound having a composition represented by the following formula (2):
    In this order. A method for producing a silicic acid-phosphoric acid compound.
    A 1 + x + a M b Si x P 1-x O 4 + c1 (1)
    (In the formula, element A is at least one element selected from the group consisting of Li, Na and K, and element M is at least one element selected from the group consisting of Fe, Mn, Co and Ni. a is −0.1 ≦ a ≦ 0.4, b is 0.7 ≦ b ≦ 1.3, x is 0.3 ≦ x <1.0, and c1 is a, b and M (It is a number that depends on the valence N of and is a number that becomes c2 after the heating step.)
    A 1 + x + a M b Si x P 1-x O 4 + c2 (2)
    (In the formula, A, M, a, b and x have the same meaning as described above, but are values independent of the above, and c2 is a number depending on the valence N of a, b and M.)
  2. 　前記溶融工程が、
    　元素Ａを含む化合物が、Ａの炭酸塩、Ａの炭酸水素塩、Ａの水酸化物、Ａのケイ酸塩、Ａのリン酸塩、Ａのリン酸水素塩、Ａの硝酸塩、Ａの塩化物、Ａの硫酸塩、Ａの酢酸塩、およびＡのシュウ酸塩からなる群より選ばれる少なくとも１種（ただし、該１種以上の一部または全部は、それぞれ、水和塩を形成していてもよい。）として含まれ、
    　元素Ｍを含む化合物が、Ｍの酸化物、Ｍのオキシ水酸化物、Ｍのケイ酸塩、Ｍの金属、Ｍのリン酸塩、Ｍの塩化物、Ｍの硝酸塩、Ｍの硫酸塩、およびＭの有機塩からなる群より選ばれる少なくとも１種として含まれ、
    　Ｓｉを含む化合物が、酸化ケイ素、Ａのケイ酸塩、Ｍのケイ酸塩、およびケイ素のアルコキシドからなる群より選ばれる少なくとも１種として含まれ、
    　Ｐを含む化合物が、酸化リン、リン酸アンモニウム、リン酸水素アンモニウム、リン酸、ポリリン酸、亜リン酸、次亜リン酸、Ａのリン酸塩、およびＭのリン酸塩からなる群より選ばれる少なくとも１種として含まれる、
    原料調合物を加熱して、前記式（１）で表される組成を有する溶融物を得る工程である、請求項１に記載のケイ酸－リン酸化合物の製造方法。     The melting step is
    Compound containing element A is A carbonate, A bicarbonate, A hydroxide, A silicate, A phosphate, A hydrogen phosphate, A nitrate, A chloride Or at least one selected from the group consisting of A sulfate, A acetate, and A oxalate (however, some or all of the one or more form a hydrate salt). May be included),
    The compound comprising element M is M oxide, M oxyhydroxide, M silicate, M metal, M phosphate, M chloride, M nitrate, M sulfate, and Included as at least one selected from the group consisting of organic salts of M;
    A compound containing Si is included as at least one selected from the group consisting of silicon oxide, A silicate, M silicate, and silicon alkoxide,
    The compound containing P is selected from the group consisting of phosphorus oxide, ammonium phosphate, ammonium hydrogen phosphate, phosphoric acid, polyphosphoric acid, phosphorous acid, hypophosphorous acid, A phosphate, and M phosphate Included as at least one
    The method for producing a silicic acid-phosphoric acid compound according to claim 1, wherein the raw material preparation is heated to obtain a melt having a composition represented by the formula (1).
  3. 　前記元素ＡがＬｉである、請求項１または２に記載のケイ酸－リン酸化合物の製造方法。 The method for producing a silicic acid-phosphoric acid compound according to claim 1 or 2, wherein the element A is Li.
  4. 　前記元素ＭがＦｅおよびＭｎからなる群より選ばれる少なくとも１種である、請求項１～３のいずれか一項に記載のケイ酸－リン酸化合物の製造方法。 The method for producing a silicic acid-phosphate compound according to any one of claims 1 to 3, wherein the element M is at least one selected from the group consisting of Fe and Mn.
  5. 　前記式（１）で表される組成を有する溶融物が、下式（３Ａ）で表される組成を有する溶融物であり、前記式（２）で表される組成を有するケイ酸－リン酸化合物が、下式（３）で表される組成を有するオリビン型結晶粒子を含む化合物である、請求項１に記載のケイ酸－リン酸化合物の製造方法。
    　Ｌｉ１＋ｘ＋ａ（ＦｅｙＭｎ１－ｙ）ｂＳｉｘＰ１－ｘＯ４＋ｃ１　　　（３Ａ）
    　Ｌｉ１＋ｘ＋ａ（ＦｅｙＭｎ１－ｙ）ｂＳｉｘＰ１－ｘＯ４＋ｃ２　　　（３）
    （式中、ａ、ｂ、ｃ１、ｃ２およびｘは前記と同じ意味を示し、ｙは０≦ｙ≦１である。ただし、式（３Ａ）と式（３）において、ａ、ｂ、ｘおよびｙは独立した値を示す。）     The melt having the composition represented by the formula (1) is a melt having the composition represented by the following formula (3A), and the silicic acid-phosphoric acid having the composition represented by the formula (2) The method for producing a silicic acid-phosphoric acid compound according to claim 1, wherein the compound is a compound containing olivine type crystal particles having a composition represented by the following formula (3).
    Li 1 + x + a (Fe y Mn 1-y ) b Si x P 1-x O 4 + c1 (3A)
    Li 1 + x + a (Fe y Mn 1-y ) b Si x P 1-x O 4 + c2 (3)
    (Wherein, a, b, c1, c2 and x have the same meaning as described above, and y is 0 ≦ y ≦ 1, provided that in formula (3A) and formula (3), a, b, x and y represents an independent value.)
  6. 　前記冷却工程において、冷却速度を－１０３℃／秒～－１０１０℃／秒とする、請求項１～５のいずれか一項に記載のケイ酸－リン酸化合物の製造方法。 The method for producing a silicic acid-phosphoric acid compound according to any one of claims 1 to 5, wherein in the cooling step, a cooling rate is set to -10 3 ° C / second to -10 10 ° C / second.
  7. 　前記粉砕工程において、前記固化物に、有機化合物および炭素粉末からなる群より選択される少なくとも１種の炭素源を含ませ、かつ該炭素源中の炭素換算量（質量）の割合が、固化物の質量と、該炭素源中の炭素換算量（質量）との合計質量に対して０．１～２０質量％である、請求項１～６のいずれか一項に記載のケイ酸－リン酸化合物の製造方法。 In the pulverization step, the solidified product contains at least one carbon source selected from the group consisting of an organic compound and a carbon powder, and a ratio of a carbon conversion amount (mass) in the carbon source is a solidified product. The silicic acid-phosphoric acid according to any one of claims 1 to 6, which is 0.1 to 20% by mass with respect to the total mass of the mass of the carbon and the carbon equivalent amount (mass) in the carbon source. Compound production method.
  8. 　前記加熱工程を５００～１，０００℃に加熱することにより行う、請求項１～７のいずれか一項に記載のケイ酸－リン酸化合物の製造方法。 The method for producing a silicic acid-phosphoric acid compound according to any one of claims 1 to 7, wherein the heating step is performed by heating to 500 to 1,000 ° C.
  9. 　請求項１～８のいずれか一項に記載の製造方法によってケイ酸－リン酸化合物を得て、次に該ケイ酸－リン酸化合物を二次電池用正極材料に用いて二次電池用正極を製造することを特徴とする二次電池用正極の製造方法。 A silicic acid-phosphoric acid compound is obtained by the production method according to any one of claims 1 to 8, and then the silicic acid-phosphoric acid compound is used as a positive electrode material for a secondary battery. The manufacturing method of the positive electrode for secondary batteries characterized by manufacturing.
  10. 　請求項９に記載の製造方法で二次電池用正極を得て、次に、該二次電池用正極を用いて二次電池を製造することを特徴とする二次電池の製造方法。 A method for producing a secondary battery, comprising: obtaining a positive electrode for a secondary battery by the production method according to claim 9, and then producing a secondary battery using the positive electrode for the secondary battery.
  11. 　下式（２）で表される組成を有することを特徴とするケイ酸－リン酸化合物。
    　Ａ１＋ｘ＋ａＭｂＳｉｘＰ１－ｘＯ４＋ｃ２　　　　　（２）
    （式中、元素ＡはＬｉ、ＮａおよびＫからなる群より選ばれる少なくとも１種の元素であり、元素ＭはＦｅ、Ｍｎ、ＣｏおよびＮｉからなる群より選ばれる少なくとも１種の元素である。ａは－０．１≦ａ≦０．４であり、ｂは０．７≦ｂ≦１．３であり、ｘは０．３≦ｘ＜０．７であり、ｃ２はａ、ｂおよびＭの価数Ｎに依存する数である。）     A silicic acid-phosphoric acid compound having a composition represented by the following formula (2):
    A 1 + x + a M b Si x P 1-x O 4 + c2 (2)
    (In the formula, element A is at least one element selected from the group consisting of Li, Na and K, and element M is at least one element selected from the group consisting of Fe, Mn, Co and Ni. a is −0.1 ≦ a ≦ 0.4, b is 0.7 ≦ b ≦ 1.3, x is 0.3 ≦ x <0.7, and c2 is a, b, and M The number depends on the valence N of
  12. 下式（３）で表される組成を有し、オリビン型結晶粒子を含む、請求項１１に記載のケイ酸－リン酸化合物。
    　Ｌｉ１＋ｘ＋ａ（ＦｅｙＭｎ１－ｙ）ｂＳｉｘＰ１－ｘＯ４＋ｃ２　　　　（３）
    （式中の記号は前記式（２）におけると同じ意味を示し、０≦ｙ≦１である。）     The silicic acid-phosphoric acid compound according to claim 11, which has a composition represented by the following formula (3) and contains olivine type crystal particles.
    Li 1 + x + a (Fe y Mn 1-y ) b Si x P 1-x O 4 + c2 (3)
    (The symbols in the formula have the same meaning as in formula (2), and 0 ≦ y ≦ 1.)
PCT/JP2011/074999 2010-10-29 2011-10-28 Silicate-phosphate compound, secondary-battery positive electrode, secondary battery, and manufacturing methods therefor WO2012057340A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP2012540985A JPWO2012057340A1 (en) 2010-10-29 2011-10-28 Silicic acid-phosphoric acid compound, positive electrode for secondary battery, secondary battery, and production method thereof

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2010244763 2010-10-29
JP2010-244763 2010-10-29

Publications (1)

Publication Number Publication Date
WO2012057340A1 true WO2012057340A1 (en) 2012-05-03

Family

ID=45994042

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/JP2011/074999 WO2012057340A1 (en) 2010-10-29 2011-10-28 Silicate-phosphate compound, secondary-battery positive electrode, secondary battery, and manufacturing methods therefor

Country Status (2)

Country Link
JP (1) JPWO2012057340A1 (en)
WO (1) WO2012057340A1 (en)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2015177567A1 (en) * 2014-05-22 2015-11-26 Faradion Limited Sodium transition metal silicates
WO2022176627A1 (en) * 2021-02-16 2022-08-25 国立大学法人長岡技術科学大学 Method for producing positive electrode active material for alkali ion secondary batteries
WO2023162040A1 (en) * 2022-02-22 2023-08-31 株式会社オキサイド Method for preparing lithium metal phosphate, lithium metal phosphate, positive electrode material for lithium ion secondary battery, positive electrode for lithium ion secondary battery, and lithium ion secondary battery

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2005519451A (en) * 2002-03-06 2005-06-30 ヴァレンス　テクノロジー　インコーポレーテッド Alkali / transition metal phosphate and electrode active material related thereto
JP2009104794A (en) * 2007-10-19 2009-05-14 Toyota Central R&D Labs Inc Active material for lithium secondary battery, its manufacturing method, and lithium secondary battery
JP2009170401A (en) * 2007-12-19 2009-07-30 Gs Yuasa Corporation Nonaqueous electrolyte secondary battery
WO2010089931A1 (en) * 2009-02-04 2010-08-12 独立行政法人産業技術総合研究所 Method for producing lithium silicate compound

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2005519451A (en) * 2002-03-06 2005-06-30 ヴァレンス　テクノロジー　インコーポレーテッド Alkali / transition metal phosphate and electrode active material related thereto
JP2009104794A (en) * 2007-10-19 2009-05-14 Toyota Central R&D Labs Inc Active material for lithium secondary battery, its manufacturing method, and lithium secondary battery
JP2009170401A (en) * 2007-12-19 2009-07-30 Gs Yuasa Corporation Nonaqueous electrolyte secondary battery
WO2010089931A1 (en) * 2009-02-04 2010-08-12 独立行政法人産業技術総合研究所 Method for producing lithium silicate compound

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2015177567A1 (en) * 2014-05-22 2015-11-26 Faradion Limited Sodium transition metal silicates
US10205168B2 (en) 2014-05-22 2019-02-12 Faradion Limited Sodium transition metal silicates
WO2022176627A1 (en) * 2021-02-16 2022-08-25 国立大学法人長岡技術科学大学 Method for producing positive electrode active material for alkali ion secondary batteries
WO2023162040A1 (en) * 2022-02-22 2023-08-31 株式会社オキサイド Method for preparing lithium metal phosphate, lithium metal phosphate, positive electrode material for lithium ion secondary battery, positive electrode for lithium ion secondary battery, and lithium ion secondary battery

Also Published As

Publication number Publication date
JPWO2012057340A1 (en) 2014-05-12

Similar Documents

Publication Publication Date Title
WO2010114104A1 (en) Process for production of lithium iron phosphate particles and process for production of secondary battery
WO2011162348A1 (en) Silicic acid compound, positive electrode for secondary cell, and method for producing secondary cell
WO2011111628A1 (en) Phosphate compound, positive electrode for secondary battery and method for producing secondary battery
JP2014056722A (en) Phosphate compound, positive electrode material for secondary battery, and method for producing secondary battery
WO2011138964A1 (en) (silicic acid)-(phosphoric acid) compound, positive electrode for secondary battery, and process for production of secondary battery
WO2010150889A1 (en) Process for production of positive electrode material for secondary batteries, and positive electrode material for secondary batteries
WO2012133581A1 (en) Positive electrode active material for secondary battery, positive electrode for secondary battery, and method for producing secondary battery
WO2012133584A1 (en) Positive electrode active material for secondary battery, positive electrode for secondary battery, and method for producing secondary battery
JP5364523B2 (en) Method for synthesizing olivine-type lithium M silicate and lithium ion secondary battery
US20120217451A1 (en) Process for producing phosphate compound and method for producing secondary battery
WO2012067249A1 (en) Silicate compound, secondary-battery positive electrode, secondary battery, and manufacturing methods therefor
WO2012057341A1 (en) Silicate compound, secondary-battery positive electrode, secondary battery, and manufacturing methods therefor
WO2012086722A1 (en) Silicic acid-vanadic acid compound, positive electrode for secondary battery, and manufacturing method for secondary battery
Yang et al. A facile synthesis of Li2Fe1/3Mn1/3Ni1/3SiO4/C composites as cathode materials for lithium-ion batteries
JP2013067543A (en) Silicate compound, positive electrode for secondary battery, and method for producing secondary battery
WO2012057340A1 (en) Silicate-phosphate compound, secondary-battery positive electrode, secondary battery, and manufacturing methods therefor
JP2013047162A (en) Methods for production of silicic acid compound, positive electrode for secondary battery and secondary battery
WO2012067250A1 (en) Silicate compound, secondary-battery positive electrode, secondary battery, and manufacturing methods therefor
JP2013047161A (en) Silicate compound, positive electrode for secondary battery, and method for producing secondary battery
JP2012126589A (en) Method for producing fluorine-containing phosphoric acid compound, positive electrode for secondary battery, and secondary battery
JP2014055085A (en) Phosphate compound, cathode material for second battery, and method for producing second battery
WO2011138965A1 (en) (silicic acid)-(boric acid) compound, (silicic acid)-(boric acid)-(phosphoric acid) compound, positive electrode for secondary battery, and process for production of secondary battery
WO2011099575A1 (en) Boric acid compound, positive electrode for secondary battery, and method for manufacturing secondary battery
JP2014056721A (en) Phosphate compound, positive electrode material for secondary battery, and method for producing secondary battery

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 11836473

Country of ref document: EP

Kind code of ref document: A1

WWE Wipo information: entry into national phase

Ref document number: 2012540985

Country of ref document: JP

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 11836473

Country of ref document: EP

Kind code of ref document: A1