WO2015050031A1 - Covered cathode active material and lithium battery - Google Patents

Covered cathode active material and lithium battery Download PDF

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Publication number
WO2015050031A1
WO2015050031A1 PCT/JP2014/075438 JP2014075438W WO2015050031A1 WO 2015050031 A1 WO2015050031 A1 WO 2015050031A1 JP 2014075438 W JP2014075438 W JP 2014075438W WO 2015050031 A1 WO2015050031 A1 WO 2015050031A1
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active material
electrode active
positive electrode
layer
solid electrolyte
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PCT/JP2014/075438
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French (fr)
Japanese (ja)
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昌士 児玉
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トヨタ自動車株式会社
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0561—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of inorganic materials only
    • H01M10/0562—Solid materials
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • 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
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0065—Solid electrolytes
    • H01M2300/0068—Solid electrolytes inorganic
    • 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 coated positive electrode active material capable of reducing battery resistance.
  • lithium batteries currently on the market use an electrolyte containing a flammable organic solvent, it is possible to install safety devices that suppress the temperature rise during short circuits and to improve the structure and materials to prevent short circuits. Necessary.
  • a lithium battery in which the electrolyte is changed to a solid electrolyte layer to make the battery completely solid does not use a flammable organic solvent in the battery, so the safety device can be simplified, and manufacturing costs and productivity can be reduced. It is considered excellent.
  • Patent Document 1 discloses that the formation of a high resistance layer is suppressed by interposing a lithium ion conductive oxide at the interface between a positive electrode active material and a sulfide-based solid electrolyte.
  • Patent Document 2 between the positive electrode layer and the solid electrolyte layer, the intermediate layer is a solid electrolyte battery provided consisting of LiNbO 3 film part of Li component of LiNbO 3 is Li 2 CO 3 of Is disclosed.
  • This invention is made
  • the present inventor has conducted extensive research. As a result, residual alkali derived from the positive electrode active material (particularly Li 2 CO 3 ) deteriorates the interface state between the positive electrode active material and the coating layer, It was confirmed that the battery resistance was increased. Therefore, the battery resistance was actually reduced by lowering the carbonate concentration. On the other hand, when the carbonate concentration was too low, the battery resistance was unexpectedly increased. From these findings, it has been found that in order to reduce battery resistance, it is important that the carbonate concentration is not too high, not too low, and within a predetermined range, and the present invention has been completed. It was.
  • a coated positive electrode active material having a positive electrode active material and a coating layer formed on the positive electrode active material and made of a Li ion conductive oxide, the coated positive electrode active material
  • the coated positive electrode active material is characterized in that the carbonate concentration in is in the range of 800 ppm to 3500 ppm.
  • the coated positive electrode active material can reduce battery resistance.
  • a lithium solid state battery having a positive electrode active material layer, a negative electrode active material layer, and a solid electrolyte layer formed between the positive electrode active material layer and the negative electrode active material layer,
  • the positive electrode active material layer contains the above-described coated positive electrode active material, and the coated positive electrode active material is in contact with a solid electrolyte material.
  • the solid electrolyte material is preferably a sulfide solid electrolyte material.
  • the coated positive electrode active material of the present invention has an effect that battery resistance can be reduced.
  • FIG. 1 is a result of battery resistance measurement for evaluation batteries obtained in Examples 1 to 3 and Comparative Examples 1 to 4.
  • FIG. 1 is a result of battery resistance measurement for evaluation batteries obtained in Examples 1 to 3 and Comparative Examples 1 to 4.
  • coated positive electrode active material and the lithium solid state battery of the present invention will be described in detail.
  • FIG. 1 is a schematic cross-sectional view showing an example of the coated positive electrode active material of the present invention.
  • a coated positive electrode active material 10 shown in FIG. 1 has a particulate positive electrode active material 1 and a coating layer 2 formed on the particulate positive electrode active material 1 and made of a Li ion conductive oxide.
  • FIG. 2 is a schematic cross-sectional view showing another example of the coated positive electrode active material of the present invention.
  • a coated positive electrode active material 10 shown in FIG. 2 has a thin-film positive electrode active material 1 and a coating layer 2 formed on the thin-film positive electrode active material 1 and made of a Li ion conductive oxide.
  • the present invention is greatly characterized in that the carbonate concentration in the coated positive electrode active material 10 is within a predetermined range.
  • the coated positive electrode active material can reduce battery resistance.
  • a high resistance layer formed between a positive electrode active material and a solid electrolyte material especially a sulfide solid electrolyte material
  • a lithium ion conductive oxide is interposed at the interface between the positive electrode active material and the solid electrolyte material in order to suppress the reaction between the positive electrode active material and the solid electrolyte material.
  • the high resistance layer is easily formed depends on the type of the positive electrode active material. Therefore, as to whether a high resistance layer is easily formed, the reactivity between the positive electrode active material and the solid electrolyte material (for example, whether the positive electrode active material is easily sulfided) is being studied. Further, compatibility in the material aspect between the positive electrode active material and the coating layer or the solid electrolyte material, compatibility in the manufacturing process between the positive electrode active material and the coating layer or the solid electrolyte material, and the like have been studied. In addition, from the viewpoint of reducing battery resistance, the electron conductivity of the positive electrode active material has also been studied.
  • the surface properties of the positive electrode active material in particular, residual alkali derived from the positive electrode active material has not been studied.
  • the present inventors have confirmed that the reaction resistance is increased by reacting the residual alkali derived from the positive electrode active material with the lithium ion conductive oxide (coating layer) to prevent Li ion conduction.
  • the proportion of residual alkali (particularly Li 2 CO 3 ) derived from the positive electrode active material it was possible to suppress an increase in reaction resistance and reduce battery resistance.
  • Li 2 CO 3 derived from the positive electrode active material may be facilitated during the formation of the coating layer.
  • the coating layer is formed by uniformly coating the powdered positive electrode active material, it takes about 5 to 10 hours even if the coating time is short. At that time, the positive electrode active material may be exposed to air or water for a long time, and the alkali component may be dissolved from the positive electrode active material, and the production of Li 2 CO 3 may be promoted through several reactions.
  • a precursor layer is formed on the surface of the positive electrode active material and heat treatment is performed, the interface state between the positive electrode active material and the coating layer may deteriorate.
  • cathode active material in the present invention is an oxide active material.
  • the oxide active material easily forms a high resistance layer with the sulfide solid electrolyte material.
  • the oxide active material include rock salt layer type active materials such as LiCoO 2 , LiMnO 2 , LiNiO 2 , LiVO 2 , LiNi 1/3 Co 1/3 Mn 1/3 O 2 , LiMn 2 O 4 , Li 4.
  • Spinel active materials such as Ti 5 O 12 and Li (Ni 0.5 Mn 1.5 ) O 4 , olivine active materials such as LiFePO 4 , LiMnPO 4 , LiNiPO 4 and LiCoPO 4 , Li 2 Ti 3 O 7 and the like And a solid solution type active material containing Li 2 MnO 3 .
  • M is preferably at least one selected from the group consisting of Co, Mn, Ni, V, Fe and Si, and is at least one selected from the group consisting of Co, Ni and Mn. It is more preferable.
  • the oxide active material is preferably lithium nickelate, lithium nickel cobaltaluminate, or nickel cobalt lithium manganate.
  • a particulate shape as shown in FIG. 1 can be exemplified.
  • the average particle diameter (D 50 ) of the particles is preferably in the range of 0.1 ⁇ m to 50 ⁇ m, for example.
  • Another example of the shape of the positive electrode active material is a thin film as shown in FIG. The thickness of the thin film is preferably in the range of 0.01 ⁇ m to 1 ⁇ m, for example.
  • Coating layer is a layer formed on the said positive electrode active material, and is comprised from Li ion conductive oxide.
  • Li ion conductive oxide in the present invention is not particularly limited, for example, the general formula Li x AO y (A, Nb , B, Al, Si, P, S, Ti, Zr, Mo, At least one selected from the group consisting of Ta and W, and x and y are positive numbers.) LiNbO 3 , specifically, LiNbO 3 , Li 3 BO 3 , LiBO 2 , LiAlO 2 , Li 4 SiO 4 , Li 2 SiO 3 , Li 3 PO 4 , Li 2 SO 4 , Li 2 TiO 3 , Li 4 Ti 5 O 12 , Li 2 Ti 2 O 5 , it can be mentioned Li 2 ZrO 3, Li 2 MoO 4, Li 2 WO 4 , and the like.
  • the Li ion conductive oxide may be a composite compound of Li ion conductive oxide.
  • the thickness of the coating layer may be any thickness that can suppress the reaction between the positive electrode active material and the solid electrolyte material, and is preferably in the range of 0.1 nm to 100 nm, for example, in the range of 1 nm to 20 nm. More preferably. This is because if the coating layer is too thin, the positive electrode active material and the solid electrolyte material may react, and if the coating layer is too thick, Li ion conductivity and electronic conductivity may be reduced. is there. In addition, as a measuring method of the thickness of a coating layer, a transmission electron microscope (TEM) etc. can be mentioned, for example.
  • TEM transmission electron microscope
  • the coverage of the coating layer on the surface of the positive electrode active material is preferably high. Specifically, it is preferably 50% or more, more preferably 80% or more. Moreover, the coating layer may cover the entire surface of the positive electrode active material.
  • TEM transmission electron microscope
  • XPS X-ray photoelectron spectroscopy
  • Coated positive electrode active material The coated positive electrode active material of the present invention has a predetermined carbonate concentration.
  • the carbonate concentration in the coated positive electrode active material is usually 800 ppm or more, and preferably 1000 ppm or more.
  • the carbonate concentration is usually 3500 ppm or less, and preferably 2000 ppm or less.
  • the carbonate concentration in the coated positive electrode active material refers to the CO 3 2 ⁇ concentration obtained by the following method. That is, it can be determined by quantitative determination of carbonate ions (CO 3 2 ⁇ ) by capillary electrophoresis (CE).
  • CE capillary electrophoresis
  • the pretreatment is performed in a glove box that is completely replaced with nitrogen gas.
  • the measurement conditions for CE are shown below.
  • a capillary electrophoresis system manufactured by Agilent Technologies is used, and Fused Silica is used for the capillary.
  • a 2,6-pyridinedicarboxylic acid aqueous solution is used as the electrophoresis solution, and the voltage applied between the electrophoresis solutions is ⁇ 30 kV to 30 kV.
  • Indirect spectrophotometry is used for detection. Thereby, the density
  • the coated positive electrode active material of the present invention is usually used for a lithium battery, and particularly preferably used for a lithium solid state battery.
  • the method for producing a coated positive electrode active material of the present invention is not particularly limited as long as the above-described coated positive electrode active material can be obtained.
  • a positive electrode active material preparation step for preparing a positive electrode active material, and the positive electrode active material described above are prepared.
  • at the time of the heat treatment in the positive electrode active material preparation step it is preferable to reduce at least one of the water content and the carbon dioxide concentration, and it is preferable to reduce both the water content and the carbon dioxide concentration.
  • the water content and the carbon dioxide concentration during the heat treatment in the coating layer forming step, and it is preferable to reduce both the water content and the carbon dioxide concentration.
  • the method for synthesizing the positive electrode active material is not particularly limited, and examples thereof include a method in which a transition metal source and a Li source are mixed and heat-treated.
  • the transition metal source include transition metal hydroxides.
  • the Li source include lithium carbonate (Li 2 CO 3 ) and lithium hydroxide (LiOH).
  • the heat treatment temperature is not particularly limited as long as it is a temperature at which a desired positive electrode active material can be obtained.
  • the atmosphere for performing the heat treatment is not particularly limited, and examples thereof include an atmosphere containing oxygen. Among these, in the present invention, it is preferable to perform the heat treatment in a dry air atmosphere, a pure oxygen atmosphere, or a mixed atmosphere of dry air and pure oxygen. This is because the generation of carbonate can be suppressed.
  • the heat treatment method include a method using a firing furnace.
  • the firing furnace include a muffle furnace.
  • the method for forming the coating layer is not particularly limited as long as the above-described coated positive electrode active material can be obtained, and examples thereof include a sol-gel method, a mechano-fusion method, a CVD method, and a PVD method. Is preferred.
  • a sol-gel solution containing a raw material for the coating layer is applied to the positive electrode active material, and a coating step for forming a precursor layer on the surface of the positive electrode active material, and a heat treatment step for performing heat treatment on the precursor layer Do.
  • the sol-gel solution contains the raw material for the coating layer.
  • the sol-gel solution preferably contains at least an alkoxide.
  • the ion conductive oxide is represented by the general formula Li x AO y
  • the sol-gel solution contains a Li-containing compound and an A-containing compound.
  • the Li-containing compound include Li alkoxides such as ethoxylithium and methoxylithium, lithium acetate, and lithium hydroxide.
  • the A-containing compound include alkoxides containing A, acetates containing A, hydroxides containing A, and the like.
  • Nb-containing compounds include pentaethoxyniobium, pentamethoxyniobium, penta-i-propoxyniobium, penta-n-propoxyniobium, and penta-i-butoxyniobium.
  • Nb alkoxides such as penta-n-butoxyniobium and penta-sec-butoxyniobium, niobium acetate and niobium hydroxide.
  • the solvent used in the sol-gel solution examples include a polar solvent having a polar functional group such as a hydroxyl group.
  • alcohol is preferable.
  • examples of the alcohol include ethanol, methanol, propanol, butanol and the like.
  • the amount of water contained in the solvent is, for example, preferably 0.005% by weight or less, more preferably 0.0025% by weight or less, and even more preferably 0.00025% by weight or less.
  • the fluidized bed coating method is a film coating technique using a fluidized bed granulation / coating apparatus, and a uniform coating can be applied by repeating spraying and drying of liquid on particles.
  • Examples of such an apparatus include a multiplex manufactured by Paulex and a flow coater manufactured by Freund Corporation.
  • the fluidized bed coating method when the sol-gel solution is sprayed / dried, an air current is generated in the container in order to bring the active material into a fluid state, and a rotor or the like is rotated as necessary.
  • a mixed gas of dry nitrogen and (usually) air is used as at least one of the furnace atmosphere during spraying and the spray gas, and this mixing ratio is appropriately set. It is preferable.
  • the conditions of the gas flow and the rotation conditions of the rotor may be set as appropriate, and are not particularly limited. From the viewpoint of efficiently drying the sol-gel solution, the airflow temperature (gas flow temperature) in the container is preferably 80 ° C. or higher.
  • the heat treatment temperature of the precursor layer is preferably in the range of 250 ° C. to 500 ° C., for example.
  • the atmosphere for performing the heat treatment is not particularly limited, and examples thereof include an atmosphere containing oxygen.
  • the positive electrode active material is dry air or inert gas (nitrogen gas, argon gas, etc.) It is preferable to move in the atmosphere.
  • the heat treatment time is preferably in the range of 0.5 hours to 48 hours, for example.
  • Examples of the heat treatment method include a method using a firing furnace.
  • Examples of the firing furnace include a muffle furnace.
  • FIG. 3 is a schematic cross-sectional view showing an example of the lithium solid state battery of the present invention.
  • 3 includes a positive electrode active material layer 11, a negative electrode active material layer 12, a solid electrolyte layer 13 formed between the positive electrode active material layer 11 and the negative electrode active material layer 12, and a positive electrode active material. It has a positive electrode current collector 14 for collecting the material layer 11, a negative electrode current collector 15 for collecting the negative electrode active material layer 12, and a battery case 16 for housing these members.
  • the positive electrode active material layer 11 contains the above-described coated positive electrode active material.
  • the coated positive electrode active material is in contact with the solid electrolyte material.
  • the coated positive electrode active material may be in contact with the solid electrolyte material included in the positive electrode active material layer, or may be in contact with the solid electrolyte material included in the solid electrolyte layer.
  • the positive electrode active material layer contains the above-described coated positive electrode active material, a lithium solid battery with low battery resistance can be obtained.
  • the lithium solid state battery of the present invention will be described for each configuration.
  • Positive electrode active material layer is a layer containing at least a positive electrode active material, and further contains at least one of a solid electrolyte material, a conductive material and a binder as necessary. Also good.
  • the positive electrode active material in the present invention is the coated positive electrode active material described in “A. Coated positive electrode active material” above.
  • the positive electrode active material layer preferably contains a solid electrolyte material, and more preferably contains a sulfide solid electrolyte material. This is because the Li ion conductivity in the positive electrode active material layer can be improved.
  • the solid electrolyte material contained in the positive electrode active material layer is the same as the solid electrolyte material described in “3. Solid electrolyte layer” described later.
  • the positive electrode active material layer in the present invention may further contain a conductive material.
  • a conductive material By adding a conductive material, the conductivity of the positive electrode active material layer can be improved.
  • the conductive material include carbon materials such as acetylene black, ketjen black, and carbon fiber, and metal materials.
  • the positive electrode active material layer may further contain a binder. Examples of the binder include fluorine-containing binders such as PTFE and PVDF.
  • the thickness of the positive electrode active material layer varies depending on the configuration of the target lithium solid state battery, but is preferably in the range of 0.1 ⁇ m to 1000 ⁇ m, for example.
  • Negative electrode active material layer is a layer containing at least a negative electrode active material, and further contains at least one of a solid electrolyte material, a conductive material and a binder as necessary. Also good.
  • Examples of the negative electrode active material include a metal active material and a carbon active material.
  • Examples of the metal active material include Li alloy, In, Al, Si, and Sn.
  • examples of the carbon active material include graphite such as mesocarbon microbeads (MCMB) and highly oriented graphite (HOPG), and amorphous carbon such as hard carbon and soft carbon. Note that SiC or the like can also be used as the negative electrode active material.
  • the negative electrode active material layer preferably contains a solid electrolyte material. This is because the Li ion conductivity in the negative electrode active material layer can be improved.
  • the solid electrolyte material contained in a negative electrode active material layer it is the same as that of the solid electrolyte material described in "3. Solid electrolyte layer" mentioned later.
  • the conductive material and the binder used for the negative electrode active material layer are the same as those in the positive electrode active material layer described above. Further, the thickness of the negative electrode active material layer varies depending on the structure of the target lithium solid state battery, but is preferably in the range of 0.1 ⁇ m to 1000 ⁇ m, for example.
  • the solid electrolyte layer in the present invention is a layer formed between the positive electrode active material layer and the negative electrode active material layer, and is a layer containing at least a solid electrolyte material.
  • the solid electrolyte material is not particularly limited as long as it has Li ion conductivity.
  • sulfide solid electrolyte material, oxide solid electrolyte material, nitride solid electrolyte material, halide solid electrolyte material Among them, a sulfide solid electrolyte material is preferable. This is because the Li ion conductivity is higher than that of the oxide solid electrolyte material. Since the sulfide solid electrolyte material has higher reactivity than the oxide solid electrolyte material, it easily reacts with the positive electrode active material and easily forms a high resistance layer between the positive electrode active material.
  • Examples of the sulfide solid electrolyte material include Li 2 S—P 2 S 5 , Li 2 S—P 2 S 5 —LiI, Li 2 S—P 2 S 5 —Li 2 O, and Li 2 S—P 2 S. 5 -Li 2 O—LiI, Li 2 S—SiS 2 , Li 2 S—SiS 2 —LiI, Li 2 S—SiS 2 —LiBr, Li 2 S—SiS 2 —LiCl, Li 2 S—SiS 2 —B 2 S 3 -LiI, Li 2 S -SiS 2 -P 2 S 5 -LiI, Li 2 S-B 2 S 3, Li 2 S-P 2 S 5 -Z m S n ( however, m, n are positive Z is one of Ge, Zn, and Ga.), Li 2 S—GeS 2 , Li 2 S—SiS 2 —Li 3 PO 4 , Li 2 S—SiS 2 —
  • the sulfide solid electrolyte material preferably has an ortho composition. This is because a sulfide solid electrolyte material having high chemical stability can be obtained.
  • ortho generally refers to one having the highest degree of hydration among oxo acids obtained by hydrating the same oxide.
  • the crystal composition in which Li 2 S is added most in the sulfide is called the ortho composition.
  • Li 3 PS 4 corresponds to the ortho composition.
  • “having an ortho composition” includes not only a strict ortho composition but also a composition in the vicinity thereof.
  • the main component is an ortho - structure anion structure (PS 4 3- structure, GeS 4 4- structure, SiS 4 4- structure, AlS 3 3- structure, BS 3 3- structure).
  • the ratio of the anion structure of the ortho composition is preferably 60 mol% or more, more preferably 70 mol% or more, still more preferably 80 mol% or more, based on the total anion structure in the ion conductor, 90 mol % Or more is particularly preferable.
  • the ratio of the anion structure of the ortho composition can be determined by Raman spectroscopy, NMR, XPS, or the like.
  • the sulfide solid electrolyte material if it is made by using the raw material composition containing Li 2 S and P 2 S 5, the proportion of Li 2 S to the total of Li 2 S and P 2 S 5 is For example, it is preferably in the range of 70 mol% to 80 mol%, more preferably in the range of 72 mol% to 78 mol%, and still more preferably in the range of 74 mol% to 76 mol%. This is because a sulfide solid electrolyte material having an ortho composition can be obtained.
  • P 2 S 5 in the raw material composition even when using the Al 2 S 3, or B 2 S 3, a preferred range is the same.
  • the sulfide solid electrolyte material if it is made by using the raw material composition containing Li 2 S and SiS 2, the ratio of Li 2 S to the total of Li 2 S and SiS 2, for example, 60 mol% It is preferably in the range of ⁇ 72 mol%, more preferably in the range of 62 mol% to 70 mol%, and still more preferably in the range of 64 mol% to 68 mol%.
  • SiS 2 in the raw material composition even when using a GeS 2, the preferred range is the same.
  • the ratio of LiX is within a range of 1 mol% to 60 mol%, for example. It is preferably within a range of 5 mol% to 50 mol%, more preferably within a range of 10 mol% to 40 mol%.
  • examples of the oxide solid electrolyte material include NASICON type oxide, garnet type oxide, and perovskite type oxide.
  • NASICON type oxide for example, an oxide containing Li, Al, Ti, P and O (for example, Li 1.5 Al 0.5 Ti 1.5 (PO 4 ) 3 ), Li, Al, Ge, An oxide containing P and O (for example, Li 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3 ) can be given.
  • the garnet-type oxide include oxides containing Li, La, Zr, and O (for example, Li 7 La 3 Zr 2 O 12 ).
  • perovskite oxides include oxides containing Li, La, Ti, and O (for example, LiLaTiO 3 ).
  • the solid electrolyte material may be crystalline, amorphous, or glass ceramic (crystallized glass).
  • the shape of the solid electrolyte material examples include a particle shape.
  • the average particle diameter (D 50 ) is preferably in the range of 0.01 ⁇ m to 40 ⁇ m, for example, and more preferably in the range of 0.1 ⁇ m to 20 ⁇ m.
  • the Li ion conductivity of the solid electrolyte material at 25 ° C. is, for example, preferably 1 ⁇ 10 ⁇ 4 S / cm or more, and more preferably 1 ⁇ 10 ⁇ 3 S / cm or more.
  • the content of the solid electrolyte material in the solid electrolyte layer is preferably in the range of 10% by weight to 100% by weight, for example, and more preferably in the range of 50% by weight to 100% by weight.
  • the solid electrolyte layer may contain a binder. Examples of the binder include fluorine-containing binders such as PTFE and PVDF.
  • the thickness of the solid electrolyte layer is not particularly limited, but is preferably in the range of 0.1 ⁇ m to 1000 ⁇ m, for example, and more preferably in the range of 0.1 ⁇ m to 300 ⁇ m.
  • the lithium solid state battery of the present invention has at least the positive electrode active material layer, the negative electrode active material layer, and the solid electrolyte layer described above. Furthermore, it usually has a positive electrode current collector for collecting current of the positive electrode active material layer and a negative electrode current collector for collecting current of the negative electrode active material layer. Moreover, the battery case of a general lithium solid battery can be used for the battery case used for this invention.
  • Lithium solid battery The lithium solid battery of the present invention may be a primary battery or a secondary battery, and among these, a secondary battery is preferable. This is because it can be repeatedly charged and discharged and is useful, for example, as a vehicle-mounted battery.
  • Examples of the shape of the lithium solid state battery of the present invention include a coin type, a laminate type, a cylindrical type, and a square type.
  • the present invention is not limited to the above embodiment.
  • the above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.
  • Example 1 Synthesis of sulfide solid electrolyte materials
  • lithium sulfide Li 2 S, manufactured by Nippon Chemical Industry Co., Ltd.
  • diphosphorus pentasulfide P 2 S 5 , manufactured by Aldrich
  • These powders were mixed in a glove box under an argon atmosphere at a rate of 0.7656 g of Li 2 S and 1.2344 g of P 2 S 5 to obtain a raw material composition.
  • the raw material composition was mixed in an agate mortar for 5 minutes, and then placed in a zirconia pot together with 4 g of dehydrated heptane.
  • This pot was attached to a planetary ball mill and mechanical milling was performed for 40 hours at a base plate rotation speed of 370 rpm. As a result, a sulfide solid electrolyte material (75Li 2 S-25P 2 S 5 glass) was obtained.
  • the coated positive electrode active material a material having a positive electrode active material (LiNi 3/5 Co 1/5 Mn 1/5 O 2 ) and a coating layer (LiNbO 3 ) and having a carbonate concentration of 1100 ppm was prepared.
  • heat treatment was performed in a pure oxygen atmosphere (an atmosphere in which moisture and carbon dioxide are not mixed) in order to suppress the generation of carbonate.
  • the sol-gel method was used for forming the coating layer.
  • MP-01 manufactured by Paulex Co. was used as a coating apparatus, and dry nitrogen gas and (usually) air were used at appropriate mixing ratios as gas used for coating to control the carbonate concentration. Further, after coating, heat treatment was performed in a dry air atmosphere in order to suppress an increase in carbonate concentration.
  • Examples 2 to 3 Comparative Examples 1 to 4
  • An evaluation battery was produced in the same manner as in Example 1 except that coated positive electrode active materials having different compositions and carbonate concentrations were used.
  • the composition and carbon salt concentration are shown in Table 1 below.

Abstract

The problem addressed by the present invention is to provide a covered cathode active material that can effect a decrease in battery resistance. The problem is solved by means of a covered cathode active material, which has a cathode active material and a covering layer formed on the cathode active material and configured from a Li-ion conductive oxide, being characterized by the carbonate concentration in the covered cathode active material being in the range of 800-3500 ppm.

Description

被覆正極活物質およびリチウム固体電池Coated positive electrode active material and lithium solid state battery
　本発明は、電池抵抗の低減を図ることができる被覆正極活物質に関する。 The present invention relates to a coated positive electrode active material capable of reducing battery resistance.
　近年におけるパソコン、ビデオカメラおよび携帯電話等の情報関連機器や通信機器等の急速な普及に伴い、その電源として利用される電池の開発が重要視されている。また、自動車産業界等においても、電気自動車用あるいはハイブリッド自動車用の高出力かつ高容量の電池の開発が進められている。現在、種々の電池の中でも、エネルギー密度が高いという観点から、リチウム電池が注目を浴びている。 In recent years, with the rapid spread of information-related equipment and communication equipment such as personal computers, video cameras and mobile phones, development of batteries used as power sources has been regarded as important. Also in the automobile industry and the like, development of high-power and high-capacity batteries for electric vehicles or hybrid vehicles is being promoted. Currently, lithium batteries are attracting attention among various batteries from the viewpoint of high energy density.
　現在市販されているリチウム電池は、可燃性の有機溶媒を含む電解液が使用されているため、短絡時の温度上昇を抑える安全装置の取り付けや短絡防止のための構造・材料面での改善が必要となる。これに対し、電解液を固体電解質層に変えて、電池を全固体化したリチウム電池は、電池内に可燃性の有機溶媒を用いないので、安全装置の簡素化が図れ、製造コストや生産性に優れると考えられている。 Since lithium batteries currently on the market use an electrolyte containing a flammable organic solvent, it is possible to install safety devices that suppress the temperature rise during short circuits and to improve the structure and materials to prevent short circuits. Necessary. In contrast, a lithium battery in which the electrolyte is changed to a solid electrolyte layer to make the battery completely solid does not use a flammable organic solvent in the battery, so the safety device can be simplified, and manufacturing costs and productivity can be reduced. It is considered excellent.
　このような全固体電池の分野において、従来から、正極活物質および固体電解質材料の界面に着目し、全固体電池の性能向上を図る試みがある。例えば、特許文献１においては、正極活物質と硫化物系固体電解質の界面に、リチウムイオン伝導性酸化物を介在させることにより、高抵抗層の形成を抑制することが開示されている。また、特許文献２においては、正極層と固体電解質層との間に、ＬｉＮｂＯ３のＬｉ成分の一部がＬｉ２ＣＯ３化されているＬｉＮｂＯ３膜からなる中間層が設けられた固体電解質電池が開示されている。また、特許文献３においては、正極活物質の合成において、その雰囲気より水分、二酸化炭素ガスを除去することにより、合成過程における不純物の生成を防ぎ、充放電特性の優れた正極活物質を得ることが記載されている。 In the field of such all solid state batteries, there have been attempts to improve the performance of all solid state batteries by focusing attention on the interface between the positive electrode active material and the solid electrolyte material. For example, Patent Document 1 discloses that the formation of a high resistance layer is suppressed by interposing a lithium ion conductive oxide at the interface between a positive electrode active material and a sulfide-based solid electrolyte. Further, in Patent Document 2, between the positive electrode layer and the solid electrolyte layer, the intermediate layer is a solid electrolyte battery provided consisting of LiNbO 3 film part of Li component of LiNbO 3 is Li 2 CO 3 of Is disclosed. Moreover, in patent document 3, in the synthesis | combination of a positive electrode active material, the production | generation of the impurity in a synthesis process is prevented by removing a water | moisture content and a carbon dioxide gas from the atmosphere, and obtaining the positive electrode active material excellent in the charge / discharge characteristic. Is described.
国際公開第２００７／００４５９０号International Publication No. 2007/004590 特開２０１１－０９０８７７号公報JP 2011-090877 A 特開２０００－０５８０５３号公報JP 2000-058053 A
　電池性能向上の観点から、電池抵抗の低減が望まれている。本発明は、上記実情に鑑みてなされたものであり、電池抵抗の低減を図ることができる被覆正極活物質を提供することを主目的とする。 From the viewpoint of improving battery performance, reduction of battery resistance is desired. This invention is made | formed in view of the said situation, and it aims at providing the covering positive electrode active material which can aim at reduction of battery resistance.
　上記課題を解決するために、本発明者が鋭意研究を重ねたところ、正極活物質に由来する残留アルカリ（特にＬｉ２ＣＯ３）が、正極活物質と被覆層との界面状態を劣化させ、電池抵抗を増大させていることを確認した。そこで、炭酸塩濃度を低くすることで、実際に電池抵抗の低減が図れた。一方で、炭酸塩濃度が低すぎると、意外にも電池抵抗が増加した。これらの知見から、電池抵抗の低減を図るためには、炭酸塩濃度が、高すぎず、低すぎず、所定の範囲内にあることが重要であることを見出し、本発明を完成させるに至った。 In order to solve the above-mentioned problems, the present inventor has conducted extensive research. As a result, residual alkali derived from the positive electrode active material (particularly Li 2 CO 3 ) deteriorates the interface state between the positive electrode active material and the coating layer, It was confirmed that the battery resistance was increased. Therefore, the battery resistance was actually reduced by lowering the carbonate concentration. On the other hand, when the carbonate concentration was too low, the battery resistance was unexpectedly increased. From these findings, it has been found that in order to reduce battery resistance, it is important that the carbonate concentration is not too high, not too low, and within a predetermined range, and the present invention has been completed. It was.
　すなわち、本発明においては、正極活物質と、上記正極活物質上に形成され、Ｌｉイオン伝導性酸化物から構成される被覆層と、を有する被覆正極活物質であって、上記被覆正極活物質における炭酸塩濃度が、８００ｐｐｍ～３５００ｐｐｍの範囲内であることを特徴とする被覆正極活物質を提供する。 That is, in the present invention, a coated positive electrode active material having a positive electrode active material and a coating layer formed on the positive electrode active material and made of a Li ion conductive oxide, the coated positive electrode active material The coated positive electrode active material is characterized in that the carbonate concentration in is in the range of 800 ppm to 3500 ppm.
　本発明によれば、被覆正極活物質における炭酸塩濃度が所定の範囲内にあることから、電池抵抗の低減を図ることができる被覆正極活物質となる。 According to the present invention, since the carbonate concentration in the coated positive electrode active material is within a predetermined range, the coated positive electrode active material can reduce battery resistance.
　また、本発明においては、正極活物質層と、負極活物質層と、上記正極活物質層および上記負極活物質層との間に形成された固体電解質層とを有するリチウム固体電池であって、上記正極活物質層が、上述した被覆正極活物質を含有し、上記被覆正極活物質が、固体電解質材料と接することを特徴とするリチウム固体電池を提供する。 Further, in the present invention, a lithium solid state battery having a positive electrode active material layer, a negative electrode active material layer, and a solid electrolyte layer formed between the positive electrode active material layer and the negative electrode active material layer, The positive electrode active material layer contains the above-described coated positive electrode active material, and the coated positive electrode active material is in contact with a solid electrolyte material.
　本発明によれば、正極活物質層が上述した被覆正極活物質を含有することから、電池抵抗が低いリチウム固体電池とすることができる。 According to the present invention, since the positive electrode active material layer contains the above-described coated positive electrode active material, a lithium solid battery with low battery resistance can be obtained.
　上記発明においては、上記固体電解質材料が、硫化物固体電解質材料であることが好ましい。 In the above invention, the solid electrolyte material is preferably a sulfide solid electrolyte material.
　本発明の被覆正極活物質は、電池抵抗の低減を図ることができるという効果を奏する。 The coated positive electrode active material of the present invention has an effect that battery resistance can be reduced.
本発明の被覆正極活物質の一例を示す概略断面図である。It is a schematic sectional drawing which shows an example of the covering positive electrode active material of this invention. 本発明の被覆正極活物質の他の例を示す概略断面図である。It is a schematic sectional drawing which shows the other example of the covering positive electrode active material of this invention. 本発明のリチウム固体電池の一例を示す概略断面図である。It is a schematic sectional drawing which shows an example of the lithium solid battery of this invention. 実施例１～３および比較例１～４で得られた評価用電池に対する電池抵抗測定の結果である。3 is a result of battery resistance measurement for evaluation batteries obtained in Examples 1 to 3 and Comparative Examples 1 to 4. FIG.
　以下、本発明の被覆正極活物質およびリチウム固体電池について、詳細に説明する。 Hereinafter, the coated positive electrode active material and the lithium solid state battery of the present invention will be described in detail.
Ａ．被覆正極活物質
　図１は、本発明の被覆正極活物質の一例を示す概略断面図である。図１に示される被覆正極活物質１０は、粒子状の正極活物質１と、粒子状の正極活物質１上に形成され、Ｌｉイオン伝導性酸化物から構成される被覆層２と、を有する。また、図２は、本発明の被覆正極活物質の他の例を示す概略断面図である。図２に示される被覆正極活物質１０は、薄膜状の正極活物質１と、薄膜状の正極活物質１上に形成され、Ｌｉイオン伝導性酸化物から構成される被覆層２と、を有する。ここで、本発明においては、被覆正極活物質１０における炭酸塩濃度が、所定の範囲内にあることを大きな特徴とする。 A. Coated Positive Electrode Active Material FIG. 1 is a schematic cross-sectional view showing an example of the coated positive electrode active material of the present invention. A coated positive electrode active material 10 shown in FIG. 1 has a particulate positive electrode active material 1 and a coating layer 2 formed on the particulate positive electrode active material 1 and made of a Li ion conductive oxide. . FIG. 2 is a schematic cross-sectional view showing another example of the coated positive electrode active material of the present invention. A coated positive electrode active material 10 shown in FIG. 2 has a thin-film positive electrode active material 1 and a coating layer 2 formed on the thin-film positive electrode active material 1 and made of a Li ion conductive oxide. . Here, the present invention is greatly characterized in that the carbonate concentration in the coated positive electrode active material 10 is within a predetermined range.
　本発明によれば、被覆正極活物質における炭酸塩濃度が所定の範囲内にあることから、電池抵抗の低減を図ることができる被覆正極活物質となる。従来、電池抵抗が非常に大きくなる理由として、正極活物質と固体電解質材料（特に硫化物固体電解質材料）との間に形成される高抵抗層の存在が知られている。また、正極活物質と固体電解質材料との反応を抑制するために、両者の界面にリチウムイオン伝導性酸化物を介在させることも知られている。 According to the present invention, since the carbonate concentration in the coated positive electrode active material is within a predetermined range, the coated positive electrode active material can reduce battery resistance. Conventionally, as a reason why battery resistance becomes very large, the existence of a high resistance layer formed between a positive electrode active material and a solid electrolyte material (especially a sulfide solid electrolyte material) is known. It is also known that a lithium ion conductive oxide is interposed at the interface between the positive electrode active material and the solid electrolyte material in order to suppress the reaction between the positive electrode active material and the solid electrolyte material.
　ここで、高抵抗層が形成され易いか否かは、正極活物質の種類によって異なる。そこで、高抵抗層が形成され易いか否かについて、正極活物質と固体電解質材料との反応性（例えば正極活物質が硫化され易いか否か）が検討されている。さらに、正極活物質と被覆層または固体電解質材料との材料面での相性、および、正極活物質と被覆層または固体電解質材料との製造プロセスでの相性等も検討されている。また、電池抵抗を低減する観点から、正極活物質の電子伝導性についても検討されている。 Here, whether or not the high resistance layer is easily formed depends on the type of the positive electrode active material. Therefore, as to whether a high resistance layer is easily formed, the reactivity between the positive electrode active material and the solid electrolyte material (for example, whether the positive electrode active material is easily sulfided) is being studied. Further, compatibility in the material aspect between the positive electrode active material and the coating layer or the solid electrolyte material, compatibility in the manufacturing process between the positive electrode active material and the coating layer or the solid electrolyte material, and the like have been studied. In addition, from the viewpoint of reducing battery resistance, the electron conductivity of the positive electrode active material has also been studied.
　一方、正極活物質の表面物性、特に正極活物質に由来する残留アルカリについては、従来検討されていない。本発明者等は、正極活物質に由来する残留アルカリと、リチウムイオン伝導性酸化物（被覆層）とが反応し、Ｌｉイオン伝導を妨げることにより、反応抵抗が増大することを確認した。そこで、正極活物質に由来する残留アルカリ（特にＬｉ２ＣＯ３）の割合を適切に制御することで、反応抵抗の増大を抑制し、電池抵抗を低減することができた。 On the other hand, the surface properties of the positive electrode active material, in particular, residual alkali derived from the positive electrode active material has not been studied. The present inventors have confirmed that the reaction resistance is increased by reacting the residual alkali derived from the positive electrode active material with the lithium ion conductive oxide (coating layer) to prevent Li ion conduction. Thus, by appropriately controlling the proportion of residual alkali (particularly Li 2 CO 3 ) derived from the positive electrode active material, it was possible to suppress an increase in reaction resistance and reduce battery resistance.
　また、正極活物質に由来するＬｉ２ＣＯ３の生成は、被覆層の形成時に促進される場合がある。被覆層の形成方法にも依るが、例えば、粉体状の正極活物質に均一なコーティングを行うことで被覆層を形成する場合、コーティング時間が短くても５時間～１０時間程度必要となる。その際に、正極活物質が空気や水に長時間晒されて、正極活物質からアルカリ成分が溶け出して、幾つかの反応を経て、Ｌｉ２ＣＯ３の生成が促進される場合がある。その正極活物質の表面に前駆体層を形成し熱処理を行うと、正極活物質と被覆層との界面状態が劣化する可能性がある。 Further, generation of Li 2 CO 3 derived from the positive electrode active material may be facilitated during the formation of the coating layer. Although depending on the method of forming the coating layer, for example, when the coating layer is formed by uniformly coating the powdered positive electrode active material, it takes about 5 to 10 hours even if the coating time is short. At that time, the positive electrode active material may be exposed to air or water for a long time, and the alkali component may be dissolved from the positive electrode active material, and the production of Li 2 CO 3 may be promoted through several reactions. When a precursor layer is formed on the surface of the positive electrode active material and heat treatment is performed, the interface state between the positive electrode active material and the coating layer may deteriorate.
　一方、後述する比較例に記載するように、被覆正極活物質における炭酸塩濃度が低すぎると、意外にも、電池抵抗が増加した。その理由としては、正極活物質の表面に前駆体層を形成し熱処理を行うと、正極活物質表面に、原子数個分の深さで、Ｌｉイオンまたは電子の欠乏層が形成され、この欠乏層が高い（反応）抵抗になっている可能性が考えられる。また、正極活物質の表面に極微量のＬｉ２ＣＯ３が存在する場合、そのＬｉ２ＣＯ３が犠牲となって消費され、正極活物質と被覆層との界面状態が良好になっている可能性がある。
　以下、本発明の被覆正極活物質について、構成ごとに説明する。 On the other hand, as described in Comparative Examples described later, when the carbonate concentration in the coated positive electrode active material was too low, the battery resistance was unexpectedly increased. The reason is that when a precursor layer is formed on the surface of the positive electrode active material and heat treatment is performed, a Li ion or electron deficient layer is formed on the surface of the positive electrode active material at a depth of several atoms. It is possible that the layer has a high (reaction) resistance. Further, when a very small amount of Li 2 CO 3 is present on the surface of the positive electrode active material, the Li 2 CO 3 may be consumed at the expense of the interface state between the positive electrode active material and the coating layer. There is sex.
Hereinafter, the coated positive electrode active material of the present invention will be described for each configuration.
１．正極活物質
　本発明における正極活物質の一例としては、酸化物活物質を挙げることができる。酸化物活物質は、特に硫化物固体電解質材料との間に高抵抗層を形成しやすい。酸化物活物質としては、例えば、ＬｉＣｏＯ２、ＬｉＭｎＯ２、ＬｉＮｉＯ２、ＬｉＶＯ２、ＬｉＮｉ１／３Ｃｏ１／３Ｍｎ１／３Ｏ２等の岩塩層状型活物質、ＬｉＭｎ２Ｏ４、Ｌｉ４Ｔｉ５Ｏ１２、Ｌｉ（Ｎｉ０．５Ｍｎ１．５）Ｏ４等のスピネル型活物質、ＬｉＦｅＰＯ４、ＬｉＭｎＰＯ４、ＬｉＮｉＰＯ４、ＬｉＣｏＰＯ４等のオリビン型活物質、Ｌｉ２Ｔｉ３Ｏ７等のラムスデライト型活物質、Ｌｉ２ＭｎＯ３を含む固溶体型活物質等を挙げることができる。 1. Cathode Active Material An example of the cathode active material in the present invention is an oxide active material. In particular, the oxide active material easily forms a high resistance layer with the sulfide solid electrolyte material. Examples of the oxide active material include rock salt layer type active materials such as LiCoO 2 , LiMnO 2 , LiNiO 2 , LiVO 2 , LiNi 1/3 Co 1/3 Mn 1/3 O 2 , LiMn 2 O 4 , Li 4. Spinel active materials such as Ti 5 O 12 and Li (Ni 0.5 Mn 1.5 ) O 4 , olivine active materials such as LiFePO 4 , LiMnPO 4 , LiNiPO 4 and LiCoPO 4 , Li 2 Ti 3 O 7 and the like And a solid solution type active material containing Li 2 MnO 3 .
　また、酸化物活物質は、例えば、一般式ＬｉｘＭｙＯｚ（Ｍは遷移金属元素であり、ｘ＝０．０２～２．２、ｙ＝１～２、ｚ＝１．４～４）で表されるものであっても良い。上記一般式において、Ｍは、Ｃｏ、Ｍｎ、Ｎｉ、Ｖ、ＦｅおよびＳｉからなる群から選択される少なくとも一種であることが好ましく、Ｃｏ、ＮｉおよびＭｎからなる群から選択される少なくとも一種であることがより好ましい。 The oxide active material is, for example, a general formula Li x M y O z (M is a transition metal element, x = 0.02 to 2.2, y = 1 to 2, z = 1.4 to 4 ) May be used. In the above general formula, M is preferably at least one selected from the group consisting of Co, Mn, Ni, V, Fe and Si, and is at least one selected from the group consisting of Co, Ni and Mn. It is more preferable.
　中でも、酸化物活物質は、ニッケル酸リチウム、ニッケルコバルトアルミニウム酸リチウム、ニッケルコバルトマンガン酸リチウムであることが好ましい。 Among these, the oxide active material is preferably lithium nickelate, lithium nickel cobaltaluminate, or nickel cobalt lithium manganate.
　正極活物質の形状の一例としては、図１のような粒子状を挙げることができる。粒子の平均粒径（Ｄ５０）は、例えば、０．１μｍ～５０μｍの範囲内であることが好ましい。正極活物質の形状の他の例としては、図２のような薄膜状を挙げることができる。薄膜の厚さは、例えば、０．０１μｍ～１μｍの範囲内であることが好ましい。 As an example of the shape of the positive electrode active material, a particulate shape as shown in FIG. 1 can be exemplified. The average particle diameter (D 50 ) of the particles is preferably in the range of 0.1 μm to 50 μm, for example. Another example of the shape of the positive electrode active material is a thin film as shown in FIG. The thickness of the thin film is preferably in the range of 0.01 μm to 1 μm, for example.
２．被覆層
　本発明における被覆層は、上記正極活物質上に形成され、Ｌｉイオン伝導性酸化物から構成される層である。 2. Coating layer The coating layer in this invention is a layer formed on the said positive electrode active material, and is comprised from Li ion conductive oxide.
　本発明におけるＬｉイオン伝導性酸化物は、特に限定されるものではないが、例えば、一般式ＬｉｘＡＯｙ（Ａは、Ｎｂ、Ｂ、Ａｌ、Ｓｉ、Ｐ、Ｓ、Ｔｉ、Ｚｒ、Ｍｏ、Ｔａ、Ｗからなる群から選択される少なくとも一種であり、ｘおよびｙは正の数である。）で表されるＬｉイオン伝導性酸化物を挙げることができ、具体的には、ＬｉＮｂＯ３、Ｌｉ３ＢＯ３、ＬｉＢＯ２、ＬｉＡｌＯ２、Ｌｉ４ＳｉＯ４、Ｌｉ２ＳｉＯ３、Ｌｉ３ＰＯ４、Ｌｉ２ＳＯ４、Ｌｉ２ＴｉＯ３、Ｌｉ４Ｔｉ５Ｏ１２、Ｌｉ２Ｔｉ２Ｏ５、Ｌｉ２ＺｒＯ３、Ｌｉ２ＭｏＯ４、Ｌｉ２ＷＯ４等を挙げることができる。また、Ｌｉイオン伝導性酸化物は、Ｌｉイオン伝導性酸化物の複合化合物であっても良い。 Li ion conductive oxide in the present invention is not particularly limited, for example, the general formula Li x AO y (A, Nb , B, Al, Si, P, S, Ti, Zr, Mo, At least one selected from the group consisting of Ta and W, and x and y are positive numbers.) LiNbO 3 , specifically, LiNbO 3 , Li 3 BO 3 , LiBO 2 , LiAlO 2 , Li 4 SiO 4 , Li 2 SiO 3 , Li 3 PO 4 , Li 2 SO 4 , Li 2 TiO 3 , Li 4 Ti 5 O 12 , Li 2 Ti 2 O 5 , it can be mentioned Li 2 ZrO 3, Li 2 MoO 4, Li 2 WO 4 , and the like. The Li ion conductive oxide may be a composite compound of Li ion conductive oxide.
　被覆層の厚さは、正極活物質と固体電解質材料との反応を抑制できる厚さであれば良く、例えば、０．１ｎｍ～１００ｎｍの範囲内であることが好ましく、１ｎｍ～２０ｎｍの範囲内であることがより好ましい。被覆層が薄すぎると、正極活物質と固体電解質材料とが反応する可能性があるからであり、被覆層が厚すぎると、Ｌｉイオン伝導性および電子伝導性が低下する可能性があるからである。なお、被覆層の厚さの測定方法としては、例えば、透過型電子顕微鏡（ＴＥＭ）等を挙げることができる。 The thickness of the coating layer may be any thickness that can suppress the reaction between the positive electrode active material and the solid electrolyte material, and is preferably in the range of 0.1 nm to 100 nm, for example, in the range of 1 nm to 20 nm. More preferably. This is because if the coating layer is too thin, the positive electrode active material and the solid electrolyte material may react, and if the coating layer is too thick, Li ion conductivity and electronic conductivity may be reduced. is there. In addition, as a measuring method of the thickness of a coating layer, a transmission electron microscope (TEM) etc. can be mentioned, for example.
　また、正極活物質表面における被覆層の被覆率は高いことが好ましく、具体的には、５０％以上であることが好ましく、８０％以上であることがより好ましい。また、被覆層は、正極活物質の表面全てを覆っていても良い。なお、被覆層の被覆率の測定方法としては、例えば、透過型電子顕微鏡（ＴＥＭ）およびＸ線光電子分光法（ＸＰＳ）等を挙げることができる。 Further, the coverage of the coating layer on the surface of the positive electrode active material is preferably high. Specifically, it is preferably 50% or more, more preferably 80% or more. Moreover, the coating layer may cover the entire surface of the positive electrode active material. In addition, as a measuring method of the coating rate of a coating layer, a transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), etc. can be mentioned, for example.
３．被覆正極活物質
　本発明の被覆正極活物質は、所定の炭酸塩濃度を有する。被覆正極活物質における炭酸塩濃度は、通常、８００ｐｐｍ以上であり、１０００ｐｐｍ以上であることが好ましい。一方、上記炭酸塩濃度は、通常、３５００ｐｐｍ以下であり、２０００ｐｐｍ以下であることが好ましい。 3. Coated positive electrode active material The coated positive electrode active material of the present invention has a predetermined carbonate concentration. The carbonate concentration in the coated positive electrode active material is usually 800 ppm or more, and preferably 1000 ppm or more. On the other hand, the carbonate concentration is usually 3500 ppm or less, and preferably 2000 ppm or less.
　被覆正極活物質における炭酸塩濃度は、以下の方法で求められるＣＯ３ ２－濃度をいう。すなわち、キャピラリー電気泳動法（ＣＥ）による炭酸イオン（ＣＯ３ ２－)の定量で求めることができる。ＣＥを行うにあたり、まず前処理として、被覆正極活物質を純水に投入し、攪拌することで、炭酸イオンの抽出を行う。さらに遠心分離により、不純物を沈殿させ、得られた上澄み液を用いてＣＥを行う。前処理は、すべて窒素ガスで置換されたグローブボックス内で実施する。ＣＥの測定条件を以下に示す。測定装置として、Agilent Technologies社製のキャピラリー電気泳動システムを使用し、キャピラリーにFused Silicaを用いる。泳動液には２，６－ピリジンジカルボン酸水溶液を用い、泳動液間への印加電圧は－３０ｋＶ～３０ｋＶとする。検出には、間接吸光光度法を使用する。これにより、各成分の濃度を求め、炭酸イオン量を算出する。 The carbonate concentration in the coated positive electrode active material refers to the CO 3 2− concentration obtained by the following method. That is, it can be determined by quantitative determination of carbonate ions (CO 3 2− ) by capillary electrophoresis (CE). In performing CE, first, as a pretreatment, the coated positive electrode active material is put into pure water and stirred to extract carbonate ions. Further, impurities are precipitated by centrifugation, and CE is performed using the obtained supernatant. The pretreatment is performed in a glove box that is completely replaced with nitrogen gas. The measurement conditions for CE are shown below. As a measuring apparatus, a capillary electrophoresis system manufactured by Agilent Technologies is used, and Fused Silica is used for the capillary. A 2,6-pyridinedicarboxylic acid aqueous solution is used as the electrophoresis solution, and the voltage applied between the electrophoresis solutions is −30 kV to 30 kV. Indirect spectrophotometry is used for detection. Thereby, the density | concentration of each component is calculated | required and the amount of carbonate ions is calculated.
　本発明の被覆正極活物質は、通常、リチウム電池に用いられるものであり、中でもリチウム固体電池に用いられるものであることが好ましい。 The coated positive electrode active material of the present invention is usually used for a lithium battery, and particularly preferably used for a lithium solid state battery.
　本発明の被覆正極活物質の製造方法は、上述した被覆正極活物質を得ることができれば特に限定されるものではないが、通常、正極活物質を準備する正極活物質準備工程と、上記正極活物質上に被覆層を形成する被覆層形成工程とを有する。中でも、本発明においては、上記正極活物質準備工程の熱処理時に、水分量および二酸化炭素濃度の少なくとも一方を低減することが好ましく、水分量および二酸化炭素濃度の両方を低減することが好ましい。また、上記被覆層形成工程の熱処理時に、水分量および二酸化炭素濃度の少なくとも一方を低減することを行うことが好ましく、水分量および二酸化炭素濃度の両方を低減することが好ましい。水分量や二酸化炭素濃度を大気雰囲気よりも低減することで、炭酸塩の発生や増加を抑制できる。 The method for producing a coated positive electrode active material of the present invention is not particularly limited as long as the above-described coated positive electrode active material can be obtained. Usually, a positive electrode active material preparation step for preparing a positive electrode active material, and the positive electrode active material described above are prepared. A coating layer forming step of forming a coating layer on the material. In particular, in the present invention, at the time of the heat treatment in the positive electrode active material preparation step, it is preferable to reduce at least one of the water content and the carbon dioxide concentration, and it is preferable to reduce both the water content and the carbon dioxide concentration. Further, it is preferable to reduce at least one of the water content and the carbon dioxide concentration during the heat treatment in the coating layer forming step, and it is preferable to reduce both the water content and the carbon dioxide concentration. By reducing the amount of water and the concentration of carbon dioxide compared to the atmosphere, the generation and increase of carbonate can be suppressed.
　正極活物質の合成方法は、特に限定されるものではないが、例えば、遷移金属源およびＬｉ源を混合し、熱処理する方法を挙げることができる。遷移金属源としては、例えば、遷移金属の水酸化物を挙げることができる。Ｌｉ源としては、例えば、炭酸リチウム（Ｌｉ２ＣＯ３）および水酸化リチウム（ＬｉＯＨ）を挙げることができる。また、熱処理温度は、所望の正極活物質を得ることができる温度であれば特に限定されるものではない。熱処理を行う際の雰囲気としては、特に限定されるものではないが、例えば酸素を含有する雰囲気を挙げることができる。中でも、本発明においては、ドライエア雰囲気、純酸素雰囲気、または、ドライエアおよび純酸素の混合雰囲気で熱処理を行うことが好ましい。炭酸塩の発生を抑制できるからである。特に、本発明においては、熱処理時に炭酸塩を発生させないことが好ましい。そのため、上記雰囲気のように、水分量および二酸化炭素濃度の少なくとも一方が十分に低い雰囲気で熱処理を行うことが好ましい。また、熱処理時間は、所望の正極活物質を得ることができる時間であれば特に限定されるものではない。熱処理方法としては、例えば焼成炉を用いた方法等を挙げることができる。焼成炉としては、例えばマッフル炉等を挙げることができる。 The method for synthesizing the positive electrode active material is not particularly limited, and examples thereof include a method in which a transition metal source and a Li source are mixed and heat-treated. Examples of the transition metal source include transition metal hydroxides. Examples of the Li source include lithium carbonate (Li 2 CO 3 ) and lithium hydroxide (LiOH). The heat treatment temperature is not particularly limited as long as it is a temperature at which a desired positive electrode active material can be obtained. The atmosphere for performing the heat treatment is not particularly limited, and examples thereof include an atmosphere containing oxygen. Among these, in the present invention, it is preferable to perform the heat treatment in a dry air atmosphere, a pure oxygen atmosphere, or a mixed atmosphere of dry air and pure oxygen. This is because the generation of carbonate can be suppressed. In particular, in the present invention, it is preferable not to generate carbonate during heat treatment. Therefore, it is preferable to perform the heat treatment in an atmosphere in which at least one of the water content and the carbon dioxide concentration is sufficiently low, as in the above atmosphere. The heat treatment time is not particularly limited as long as the desired positive electrode active material can be obtained. Examples of the heat treatment method include a method using a firing furnace. Examples of the firing furnace include a muffle furnace.
　被覆層の形成方法は、上述した被覆正極活物質を得ることができれば特に限定されるものではなく、例えば、ゾルゲル法、メカノフュージョン法、ＣＶＤ法およびＰＶＤ法等を挙げることができ、中でもゾルゲル法が好ましい。 The method for forming the coating layer is not particularly limited as long as the above-described coated positive electrode active material can be obtained, and examples thereof include a sol-gel method, a mechano-fusion method, a CVD method, and a PVD method. Is preferred.
　ゾルゲル法では、通常、被覆層の原料を含有するゾルゲル溶液を正極活物質に塗布し、正極活物質の表面に前駆体層を形成する塗布工程と、前駆体層に熱処理を行う熱処理工程とを行う。 In the sol-gel method, usually, a sol-gel solution containing a raw material for the coating layer is applied to the positive electrode active material, and a coating step for forming a precursor layer on the surface of the positive electrode active material, and a heat treatment step for performing heat treatment on the precursor layer Do.
　ゾルゲル溶液は、被覆層の原料を含有する。また、ゾルゲル溶液は、少なくともアルコキシドを含有することが好ましい。また、イオン伝導性酸化物が一般式ＬｉｘＡＯｙで表される場合、ゾルゲル溶液は、Ｌｉ含有化合物およびＡ含有化合物を含有する。Ｌｉ含有化合物としては、例えば、エトキシリチウム、メトキシリチウム等のＬｉアルコキシド、酢酸リチウム、水酸化リチウム等を挙げることができる。Ａ含有化合物としては、例えば、Ａを含有するアルコキシド、Ａを含有する酢酸塩、Ａを含有する水酸化物等を挙げることができる。Ａの具体例としてニオブ（Ｎｂ）を挙げた場合、Ｎｂ含有化合物としては、例えば、ペンタエトキシニオブ、ペンタメトキシニオブ、ペンタ－ｉ－プロポキシニオブ、ペンタ－ｎ－プロポキシニオブ、ペンタ－ｉ－ブトキシニオブ、ペンタ－ｎ－ブトキシニオブ、ペンタ－ｓｅｃ－ブトキシニオブ等のＮｂアルコキシド、酢酸ニオブ、水酸化ニオブ等を挙げることができる。 The sol-gel solution contains the raw material for the coating layer. The sol-gel solution preferably contains at least an alkoxide. Further, when the ion conductive oxide is represented by the general formula Li x AO y , the sol-gel solution contains a Li-containing compound and an A-containing compound. Examples of the Li-containing compound include Li alkoxides such as ethoxylithium and methoxylithium, lithium acetate, and lithium hydroxide. Examples of the A-containing compound include alkoxides containing A, acetates containing A, hydroxides containing A, and the like. When niobium (Nb) is given as a specific example of A, examples of Nb-containing compounds include pentaethoxyniobium, pentamethoxyniobium, penta-i-propoxyniobium, penta-n-propoxyniobium, and penta-i-butoxyniobium. Nb alkoxides such as penta-n-butoxyniobium and penta-sec-butoxyniobium, niobium acetate and niobium hydroxide.
　ゾルゲル溶液に用いられる溶媒としては、例えば、水酸基等の極性官能基を有する極性溶媒を挙げることができ、具体的には、アルコールが好ましい。さらに、アルコールとしては、エタノール、メタノール、プロパノール、ブタノール等を挙げることができる。上記溶媒に含まれる水分量は、例えば０．００５重量％以下であることが好ましく、０．００２５重量％以下となることがより好ましく、０．０００２５重量％以下となることがより好ましい。 Examples of the solvent used in the sol-gel solution include a polar solvent having a polar functional group such as a hydroxyl group. Specifically, alcohol is preferable. Further, examples of the alcohol include ethanol, methanol, propanol, butanol and the like. The amount of water contained in the solvent is, for example, preferably 0.005% by weight or less, more preferably 0.0025% by weight or less, and even more preferably 0.00025% by weight or less.
　本発明においては、流動層コーティング法を用いてゾルゲル溶液を塗布することが好ましい。流動層コーティング法は、流動層造粒・コーティング装置を用いたフィルムコーティングの手法であり、粒子に液体の噴霧・乾燥を繰り返すことで均一なコーティングを施すことができる。このような装置としては、パウレックス社製マルチプレックス、フロイント産業社製フローコーター等を挙げることできる。また、流動層コーティング法では、ゾルゲル溶液の噴霧・乾燥を行う際に、活物質を流動状態にするため、容器内に気流を生じさせ、さらに必要に応じてローター等を回転させる。また、本発明においては、炭酸塩濃度を制御するため、コーティング時の炉内雰囲気および噴霧の気体の少なくとも一方として、ドライ窒素および(通常)空気の混合気体を用い、この混合比を適宜設定することが好ましい。また、気体気流の条件やローターの回転条件等は、適宜設定すればよく、特に限定されるものではない。また、ゾルゲル溶液を効率的に乾燥させる観点から、容器内の気流温度（ガス流温度）は、８０℃以上であることが好ましい。 In the present invention, it is preferable to apply the sol-gel solution using a fluidized bed coating method. The fluidized bed coating method is a film coating technique using a fluidized bed granulation / coating apparatus, and a uniform coating can be applied by repeating spraying and drying of liquid on particles. Examples of such an apparatus include a multiplex manufactured by Paulex and a flow coater manufactured by Freund Corporation. Further, in the fluidized bed coating method, when the sol-gel solution is sprayed / dried, an air current is generated in the container in order to bring the active material into a fluid state, and a rotor or the like is rotated as necessary. Further, in the present invention, in order to control the carbonate concentration, a mixed gas of dry nitrogen and (usually) air is used as at least one of the furnace atmosphere during spraying and the spray gas, and this mixing ratio is appropriately set. It is preferable. Moreover, the conditions of the gas flow and the rotation conditions of the rotor may be set as appropriate, and are not particularly limited. From the viewpoint of efficiently drying the sol-gel solution, the airflow temperature (gas flow temperature) in the container is preferably 80 ° C. or higher.
　また、前駆体層の熱処理温度は、例えば２５０℃～５００℃の範囲内であることが好ましい。また、熱処理を行う際の雰囲気としては、特に限定されるものではないが、例えば酸素を含有する雰囲気を挙げることができる。中でも、本発明においては、ドライエア雰囲気、純酸素雰囲気、または、ドライエアおよび純酸素の混合雰囲気で熱処理を行うことが好ましい。炭酸塩濃度の増加を防止できるからである。特に、本発明においては、上記コーティング時に炭酸塩濃度の制御を行い、熱処理時には炭酸塩濃度を増加させないことが好ましい。そのため、上記雰囲気のように、水分量および二酸化炭素濃度の少なくとも一方が十分に低い雰囲気で熱処理を行うことが好ましい。また、炭酸塩濃度の増加を防止するために、前駆体層を備える正極活物質をコーティング装置から焼成炉に移動させる際に、正極活物質をドライエアまたは不活性ガス（窒素ガス、アルゴンガス等）の雰囲気中で移動させることが好ましい。また、熱処理時間は、例えば０．５時間～４８時間の範囲内であることが好ましい。熱処理方法としては、例えば焼成炉を用いた方法等を挙げることができる。焼成炉としては、例えばマッフル炉等を挙げることができる。 Also, the heat treatment temperature of the precursor layer is preferably in the range of 250 ° C. to 500 ° C., for example. In addition, the atmosphere for performing the heat treatment is not particularly limited, and examples thereof include an atmosphere containing oxygen. Among these, in the present invention, it is preferable to perform the heat treatment in a dry air atmosphere, a pure oxygen atmosphere, or a mixed atmosphere of dry air and pure oxygen. This is because an increase in carbonate concentration can be prevented. In particular, in the present invention, it is preferable to control the carbonate concentration at the time of coating and not to increase the carbonate concentration at the time of heat treatment. Therefore, it is preferable to perform the heat treatment in an atmosphere in which at least one of the water content and the carbon dioxide concentration is sufficiently low, as in the above atmosphere. In order to prevent an increase in the carbonate concentration, when the positive electrode active material provided with the precursor layer is moved from the coating apparatus to the baking furnace, the positive electrode active material is dry air or inert gas (nitrogen gas, argon gas, etc.) It is preferable to move in the atmosphere. The heat treatment time is preferably in the range of 0.5 hours to 48 hours, for example. Examples of the heat treatment method include a method using a firing furnace. Examples of the firing furnace include a muffle furnace.
Ｂ．リチウム固体電池
　次に、本発明のリチウム固体電池について説明する。図３は、本発明のリチウム固体電池の一例を示す概略断面図である。図３に示されるリチウム固体電池２０は、正極活物質層１１と、負極活物質層１２と、正極活物質層１１および負極活物質層１２の間に形成された固体電解質層１３と、正極活物質層１１の集電を行う正極集電体１４と、負極活物質層１２の集電を行う負極集電体１５と、これらの部材を収納する電池ケース１６と、を有する。本発明においては、正極活物質層１１が、上述した被覆正極活物質を含有する。また、その被覆正極活物質は固体電解質材料と接する。被覆正極活物質は、正極活物質層に含まれる固体電解質材料と接していても良く、固体電解質層に含まれる固体電解質材料と接していても良い。 B. Next, the lithium solid state battery of the present invention will be described. FIG. 3 is a schematic cross-sectional view showing an example of the lithium solid state battery of the present invention. 3 includes a positive electrode active material layer 11, a negative electrode active material layer 12, a solid electrolyte layer 13 formed between the positive electrode active material layer 11 and the negative electrode active material layer 12, and a positive electrode active material. It has a positive electrode current collector 14 for collecting the material layer 11, a negative electrode current collector 15 for collecting the negative electrode active material layer 12, and a battery case 16 for housing these members. In the present invention, the positive electrode active material layer 11 contains the above-described coated positive electrode active material. The coated positive electrode active material is in contact with the solid electrolyte material. The coated positive electrode active material may be in contact with the solid electrolyte material included in the positive electrode active material layer, or may be in contact with the solid electrolyte material included in the solid electrolyte layer.
　本発明によれば、正極活物質層が上述した被覆正極活物質を含有することから、電池抵抗が低いリチウム固体電池とすることができる。
　以下、本発明のリチウム固体電池について、構成ごとに説明する。 According to the present invention, since the positive electrode active material layer contains the above-described coated positive electrode active material, a lithium solid battery with low battery resistance can be obtained.
Hereinafter, the lithium solid state battery of the present invention will be described for each configuration.
１．正極活物質層
　本発明における正極活物質層は、少なくとも正極活物質を含有する層であり、必要に応じて、固体電解質材料、導電化材および結着材の少なくとも一つをさらに含有していても良い。 1. Positive electrode active material layer The positive electrode active material layer in the present invention is a layer containing at least a positive electrode active material, and further contains at least one of a solid electrolyte material, a conductive material and a binder as necessary. Also good.
　本発明における正極活物質は、上記「Ａ．被覆正極活物質」に記載した被覆正極活物質である。また、正極活物質層は、固体電解質材料を含有することが好ましく、中でも硫化物固体電解質材料を含有することがより好ましい。正極活物質層中のＬｉイオン伝導性を向上させることができるからである。なお、正極活物質層に含有させる固体電解質材料については、後述する「３．固体電解質層」に記載する固体電解質材料と同様である。 The positive electrode active material in the present invention is the coated positive electrode active material described in “A. Coated positive electrode active material” above. The positive electrode active material layer preferably contains a solid electrolyte material, and more preferably contains a sulfide solid electrolyte material. This is because the Li ion conductivity in the positive electrode active material layer can be improved. The solid electrolyte material contained in the positive electrode active material layer is the same as the solid electrolyte material described in “3. Solid electrolyte layer” described later.
　本発明における正極活物質層は、さらに導電化材を含有していても良い。導電化材の添加により、正極活物質層の導電性を向上させることができる。導電化材としては、例えば、アセチレンブラック、ケッチェンブラック、カーボンファイバー等の炭素材料、および、金属材料を挙げることができる。また、正極活物質層は、さらに結着材を含有していても良い。結着材としては、例えば、ＰＴＦＥ、ＰＶＤＦ等のフッ素含有結着材等を挙げることができる。また、正極活物質層の厚さは、目的とするリチウム固体電池の構成によって異なるものであるが、例えば、０．１μｍ～１０００μｍの範囲内であることが好ましい。 The positive electrode active material layer in the present invention may further contain a conductive material. By adding a conductive material, the conductivity of the positive electrode active material layer can be improved. Examples of the conductive material include carbon materials such as acetylene black, ketjen black, and carbon fiber, and metal materials. The positive electrode active material layer may further contain a binder. Examples of the binder include fluorine-containing binders such as PTFE and PVDF. Further, the thickness of the positive electrode active material layer varies depending on the configuration of the target lithium solid state battery, but is preferably in the range of 0.1 μm to 1000 μm, for example.
２．負極活物質層
　本発明における負極活物質層は、少なくとも負極活物質を含有する層であり、必要に応じて、固体電解質材料、導電化材および結着材の少なくとも一つをさらに含有していても良い。 2. Negative electrode active material layer The negative electrode active material layer in the present invention is a layer containing at least a negative electrode active material, and further contains at least one of a solid electrolyte material, a conductive material and a binder as necessary. Also good.
　負極活物質としては、例えば、金属活物質およびカーボン活物質を挙げることができる。金属活物質としては、例えば、Ｌｉ合金、Ｉｎ、Ａｌ、ＳｉおよびＳｎ等を挙げることができる。一方、カーボン活物質としては、例えば、メソカーボンマイクロビーズ（ＭＣＭＢ）、高配向性グラファイト（ＨＯＰＧ）等の黒鉛、ハードカーボンおよびソフトカーボン等の非晶質炭素等を挙げることができる。なお、負極活物質として、ＳｉＣ等を用いることもできる。 Examples of the negative electrode active material include a metal active material and a carbon active material. Examples of the metal active material include Li alloy, In, Al, Si, and Sn. On the other hand, examples of the carbon active material include graphite such as mesocarbon microbeads (MCMB) and highly oriented graphite (HOPG), and amorphous carbon such as hard carbon and soft carbon. Note that SiC or the like can also be used as the negative electrode active material.
　負極活物質層は、固体電解質材料を含有することが好ましい。負極活物質層中のＬｉイオン伝導性を向上させることができるからである。なお、負極活物質層に含有させる固体電解質材料については、後述する「３．固体電解質層」に記載する固体電解質材料と同様である。 The negative electrode active material layer preferably contains a solid electrolyte material. This is because the Li ion conductivity in the negative electrode active material layer can be improved. In addition, about the solid electrolyte material contained in a negative electrode active material layer, it is the same as that of the solid electrolyte material described in "3. Solid electrolyte layer" mentioned later.
　なお、負極活物質層に用いられる導電化材および結着材については、上述した正極活物質層における場合と同様である。また、負極活物質層の厚さは、目的とするリチウム固体電池の構成によって異なるものであるが、例えば、０．１μｍ～１０００μｍの範囲内であることが好ましい。 The conductive material and the binder used for the negative electrode active material layer are the same as those in the positive electrode active material layer described above. Further, the thickness of the negative electrode active material layer varies depending on the structure of the target lithium solid state battery, but is preferably in the range of 0.1 μm to 1000 μm, for example.
３．固体電解質層
　本発明における固体電解質層は、正極活物質層および負極活物質層の間に形成される層であり、少なくとも固体電解質材料を含有する層である。固体電解質材料としては、Ｌｉイオン伝導性を有するものであれば特に限定されるものではないが、例えば、硫化物固体電解質材料、酸化物固体電解質材料、窒化物固体電解質材料、ハロゲン化物固体電解質材料等を挙げることができ、中でも、硫化物固体電解質材料が好ましい。酸化物固体電解質材料に比べて、Ｌｉイオン伝導性が高いからである。なお、硫化物固体電解質材料は、酸化物固体電解質材料よりも反応性が高いため、正極活物質と反応しやすく、正極活物質との間に高抵抗層を形成しやすい。 3. Solid electrolyte layer The solid electrolyte layer in the present invention is a layer formed between the positive electrode active material layer and the negative electrode active material layer, and is a layer containing at least a solid electrolyte material. The solid electrolyte material is not particularly limited as long as it has Li ion conductivity. For example, sulfide solid electrolyte material, oxide solid electrolyte material, nitride solid electrolyte material, halide solid electrolyte material Among them, a sulfide solid electrolyte material is preferable. This is because the Li ion conductivity is higher than that of the oxide solid electrolyte material. Since the sulfide solid electrolyte material has higher reactivity than the oxide solid electrolyte material, it easily reacts with the positive electrode active material and easily forms a high resistance layer between the positive electrode active material.
　硫化物固体電解質材料としては、例えば、Ｌｉ２Ｓ－Ｐ２Ｓ５、Ｌｉ２Ｓ－Ｐ２Ｓ５－ＬｉＩ、Ｌｉ２Ｓ－Ｐ２Ｓ５－Ｌｉ２Ｏ、Ｌｉ２Ｓ－Ｐ２Ｓ５－Ｌｉ２Ｏ－ＬｉＩ、Ｌｉ２Ｓ－ＳｉＳ２、Ｌｉ２Ｓ－ＳｉＳ２－ＬｉＩ、Ｌｉ２Ｓ－ＳｉＳ２－ＬｉＢｒ、Ｌｉ２Ｓ－ＳｉＳ２－ＬｉＣｌ、Ｌｉ２Ｓ－ＳｉＳ２－Ｂ２Ｓ３－ＬｉＩ、Ｌｉ２Ｓ－ＳｉＳ２－Ｐ２Ｓ５－ＬｉＩ、Ｌｉ２Ｓ－Ｂ２Ｓ３、Ｌｉ２Ｓ－Ｐ２Ｓ５－ＺｍＳｎ（ただし、ｍ、ｎは正の数。Ｚは、Ｇｅ、Ｚｎ、Ｇａのいずれか。）、Ｌｉ２Ｓ－ＧｅＳ２、Ｌｉ２Ｓ－ＳｉＳ２－Ｌｉ３ＰＯ４、Ｌｉ２Ｓ－ＳｉＳ２－ＬｉｘＭＯｙ（ただし、ｘ、ｙは正の数。Ｍは、Ｐ、Ｓｉ、Ｇｅ、Ｂ、Ａｌ、Ｇａ、Ｉｎのいずれか。）等を挙げることができる。なお、上記「Ｌｉ２Ｓ－Ｐ２Ｓ５」の記載は、Ｌｉ２ＳおよびＰ２Ｓ５を含む原料組成物を用いてなる硫化物固体電解質材料を意味し、他の記載についても同様である。 Examples of the sulfide solid electrolyte material include Li 2 S—P 2 S 5 , Li 2 S—P 2 S 5 —LiI, Li 2 S—P 2 S 5 —Li 2 O, and Li 2 S—P 2 S. 5 -Li 2 O—LiI, Li 2 S—SiS 2 , Li 2 S—SiS 2 —LiI, Li 2 S—SiS 2 —LiBr, Li 2 S—SiS 2 —LiCl, Li 2 S—SiS 2 —B 2 S 3 -LiI, Li 2 S -SiS 2 -P 2 S 5 -LiI, Li 2 S-B 2 S 3, Li 2 S-P 2 S 5 -Z m S n ( however, m, n are positive Z is one of Ge, Zn, and Ga.), Li 2 S—GeS 2 , Li 2 S—SiS 2 —Li 3 PO 4 , Li 2 S—SiS 2 —Li x MO y (where x and y are positive numbers, M is P, Si, Ge, B, Al, Ga, I One of the.), And the like can be given. The description of “Li 2 S—P 2 S 5 ” means a sulfide solid electrolyte material using a raw material composition containing Li 2 S and P 2 S 5, and the same applies to other descriptions. is there.
　硫化物固体電解質材料は、オルト組成を有することが好ましい。化学的安定性の高い硫化物固体電解質材料とすることができるからである。ここで、オルトとは、一般的に、同じ酸化物を水和して得られるオキソ酸の中で、最も水和度の高いものをいう。本発明においては、硫化物で最もＬｉ２Ｓが付加している結晶組成をオルト組成という。例えば、Ｌｉ２Ｓ－Ｐ２Ｓ５系ではＬｉ３ＰＳ４がオルト組成に該当する。 The sulfide solid electrolyte material preferably has an ortho composition. This is because a sulfide solid electrolyte material having high chemical stability can be obtained. Here, ortho generally refers to one having the highest degree of hydration among oxo acids obtained by hydrating the same oxide. In the present invention, the crystal composition in which Li 2 S is added most in the sulfide is called the ortho composition. For example, in the Li 2 S—P 2 S 5 system, Li 3 PS 4 corresponds to the ortho composition.
　また、本発明において、「オルト組成を有する」とは、厳密なオルト組成のみならず、その近傍の組成をも含むものである。具体的には、オルト組成のアニオン構造（ＰＳ４ ３－構造、ＧｅＳ４ ４－構造、ＳｉＳ４ ４－構造、ＡｌＳ３ ３－構造、ＢＳ３ ３－構造、）を主体とすることをいう。オルト組成のアニオン構造の割合は、イオン伝導体における全アニオン構造に対して、６０ｍｏｌ％以上であることが好ましく、７０ｍｏｌ％以上であることがより好ましく、８０ｍｏｌ％以上であることがさらに好ましく、９０ｍｏｌ％以上であることが特に好ましい。なお、オルト組成のアニオン構造の割合は、ラマン分光法、ＮＭＲ、ＸＰＳ等により決定することができる。 In the present invention, “having an ortho composition” includes not only a strict ortho composition but also a composition in the vicinity thereof. Specifically, the main component is an ortho - structure anion structure (PS 4 3- structure, GeS 4 4- structure, SiS 4 4- structure, AlS 3 3- structure, BS 3 3- structure). The ratio of the anion structure of the ortho composition is preferably 60 mol% or more, more preferably 70 mol% or more, still more preferably 80 mol% or more, based on the total anion structure in the ion conductor, 90 mol % Or more is particularly preferable. The ratio of the anion structure of the ortho composition can be determined by Raman spectroscopy, NMR, XPS, or the like.
　また、硫化物固体電解質材料が、Ｌｉ２ＳおよびＰ２Ｓ５を含有する原料組成物を用いてなるものである場合、Ｌｉ２ＳおよびＰ２Ｓ５の合計に対するＬｉ２Ｓの割合は、例えば、７０ｍｏｌ％～８０ｍｏｌ％の範囲内であることが好ましく、７２ｍｏｌ％～７８ｍｏｌ％の範囲内であることがより好ましく、７４ｍｏｌ％～７６ｍｏｌ％の範囲内であることがさらに好ましい。オルト組成を有する硫化物固体電解質材料とすることができるからである。なお、上記原料組成物におけるＰ２Ｓ５の代わりに、Ａｌ２Ｓ３またはＢ２Ｓ３を用いる場合も、好ましい範囲は同様である。 Also, the sulfide solid electrolyte material, if it is made by using the raw material composition containing Li 2 S and P 2 S 5, the proportion of Li 2 S to the total of Li 2 S and P 2 S 5 is For example, it is preferably in the range of 70 mol% to 80 mol%, more preferably in the range of 72 mol% to 78 mol%, and still more preferably in the range of 74 mol% to 76 mol%. This is because a sulfide solid electrolyte material having an ortho composition can be obtained. Instead of P 2 S 5 in the raw material composition, even when using the Al 2 S 3, or B 2 S 3, a preferred range is the same.
　また、硫化物固体電解質材料が、Ｌｉ２ＳおよびＳｉＳ２を含有する原料組成物を用いてなるものである場合、Ｌｉ２ＳおよびＳｉＳ２の合計に対するＬｉ２Ｓの割合は、例えば、６０ｍｏｌ％～７２ｍｏｌ％の範囲内であることが好ましく、６２ｍｏｌ％～７０ｍｏｌ％の範囲内であることがより好ましく、６４ｍｏｌ％～６８ｍｏｌ％の範囲内であることがさらに好ましい。なお、上記原料組成物におけるＳｉＳ２の代わりに、ＧｅＳ２を用いる場合も、好ましい範囲は同様である。 Also, the sulfide solid electrolyte material, if it is made by using the raw material composition containing Li 2 S and SiS 2, the ratio of Li 2 S to the total of Li 2 S and SiS 2, for example, 60 mol% It is preferably in the range of ˜72 mol%, more preferably in the range of 62 mol% to 70 mol%, and still more preferably in the range of 64 mol% to 68 mol%. Instead of SiS 2 in the raw material composition, even when using a GeS 2, the preferred range is the same.
　また、硫化物固体電解質材料が、ＬｉＸ（Ｘ＝Ｃｌ、Ｂｒ、Ｉ）を含有する原料組成物を用いてなるものである場合、ＬｉＸの割合は、例えば、１ｍｏｌ％～６０ｍｏｌ％の範囲内であることが好ましく、５ｍｏｌ％～５０ｍｏｌ％の範囲内であることがより好ましく、１０ｍｏｌ％～４０ｍｏｌ％の範囲内であることがさらに好ましい。 In addition, when the sulfide solid electrolyte material is formed using a raw material composition containing LiX (X = Cl, Br, I), the ratio of LiX is within a range of 1 mol% to 60 mol%, for example. It is preferably within a range of 5 mol% to 50 mol%, more preferably within a range of 10 mol% to 40 mol%.
　一方、酸化物固体電解質材料としては、例えば、ＮＡＳＩＣＯＮ型酸化物、ガーネット型酸化物、ペロブスカイト型酸化物等を挙げることができる。ＮＡＳＩＣＯＮ型酸化物としては、例えば、Ｌｉ、Ａｌ、Ｔｉ、ＰおよびＯを含有する酸化物（例えばＬｉ１．５Ａｌ０．５Ｔｉ１．５（ＰＯ４）３）、Ｌｉ、Ａｌ、Ｇｅ、ＰおよびＯを含有する酸化物（例えばＬｉ１．５Ａｌ０．５Ｇｅ１．５（ＰＯ４）３）を挙げることができる。ガーネット型酸化物としては、例えば、Ｌｉ、Ｌａ、ＺｒおよびＯを含有する酸化物（例えばＬｉ７Ｌａ３Ｚｒ２Ｏ１２）を挙げることができる。ペロブスカイト型酸化物としては、例えば、Ｌｉ、Ｌａ、ＴｉおよびＯを含有する酸化物（例えばＬｉＬａＴｉＯ３）を挙げることができる。 On the other hand, examples of the oxide solid electrolyte material include NASICON type oxide, garnet type oxide, and perovskite type oxide. As the NASICON type oxide, for example, an oxide containing Li, Al, Ti, P and O (for example, Li 1.5 Al 0.5 Ti 1.5 (PO 4 ) 3 ), Li, Al, Ge, An oxide containing P and O (for example, Li 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3 ) can be given. Examples of the garnet-type oxide include oxides containing Li, La, Zr, and O (for example, Li 7 La 3 Zr 2 O 12 ). Examples of perovskite oxides include oxides containing Li, La, Ti, and O (for example, LiLaTiO 3 ).
　また、固体電解質材料は、結晶質であっても良く、非晶質であっても良く、ガラスセラミックス（結晶化ガラス）であっても良い。 The solid electrolyte material may be crystalline, amorphous, or glass ceramic (crystallized glass).
　固体電解質材料の形状としては、例えば、粒子形状を挙げることができる。また、固体電解質材料が粒子形状である場合、その平均粒径（Ｄ５０）は、例えば、０．０１μｍ～４０μｍの範囲内であることが好ましく、０．１μｍ２０μｍの範囲内であることがより好ましい。また、２５℃における固体電解質材料のＬｉイオン伝導度は、例えば、１×１０－４Ｓ／ｃｍ以上であることが好ましく、１×１０－３Ｓ／ｃｍ以上であることがより好ましい。 Examples of the shape of the solid electrolyte material include a particle shape. When the solid electrolyte material has a particle shape, the average particle diameter (D 50 ) is preferably in the range of 0.01 μm to 40 μm, for example, and more preferably in the range of 0.1 μm to 20 μm. . Further, the Li ion conductivity of the solid electrolyte material at 25 ° C. is, for example, preferably 1 × 10 −4 S / cm or more, and more preferably 1 × 10 −3 S / cm or more.
　固体電解質層における固体電解質材料の含有量は、例えば、１０重量％～１００重量％の範囲内であることが好ましく、５０重量％～１００重量％の範囲内であることがより好ましい。また、固体電解質層は、結着材を含有していても良い。結着材としては、例えば、ＰＴＦＥ、ＰＶＤＦ等のフッ素含有結着材等を挙げることができる。また、固体電解質層の厚さは、特に限定されるものではないが、例えば、０．１μｍ～１０００μｍの範囲内であることが好ましく、０．１μｍ～３００μｍの範囲内であることがより好ましい。 The content of the solid electrolyte material in the solid electrolyte layer is preferably in the range of 10% by weight to 100% by weight, for example, and more preferably in the range of 50% by weight to 100% by weight. The solid electrolyte layer may contain a binder. Examples of the binder include fluorine-containing binders such as PTFE and PVDF. The thickness of the solid electrolyte layer is not particularly limited, but is preferably in the range of 0.1 μm to 1000 μm, for example, and more preferably in the range of 0.1 μm to 300 μm.
４．その他の構成
　本発明のリチウム固体電池は、上述した正極活物質層、負極活物質層および固体電解質層を少なくとも有するものである。さらに通常は、正極活物質層の集電を行う正極集電体、および負極活物質層の集電を行う負極集電体を有する。また、本発明に用いられる電池ケースには、一般的なリチウム固体電池の電池ケースを用いることができる。 4). Other Configurations The lithium solid state battery of the present invention has at least the positive electrode active material layer, the negative electrode active material layer, and the solid electrolyte layer described above. Furthermore, it usually has a positive electrode current collector for collecting current of the positive electrode active material layer and a negative electrode current collector for collecting current of the negative electrode active material layer. Moreover, the battery case of a general lithium solid battery can be used for the battery case used for this invention.
５．リチウム固体電池
　本発明のリチウム固体電池は、一次電池であっても良く、二次電池であっても良いが、中でも、二次電池であることが好ましい。繰り返し充放電でき、例えば、車載用電池として有用だからである。本発明のリチウム固体電池の形状としては、例えば、コイン型、ラミネート型、円筒型および角型等を挙げることができる。 5. Lithium solid battery The lithium solid battery of the present invention may be a primary battery or a secondary battery, and among these, a secondary battery is preferable. This is because it can be repeatedly charged and discharged and is useful, for example, as a vehicle-mounted battery. Examples of the shape of the lithium solid state battery of the present invention include a coin type, a laminate type, a cylindrical type, and a square type.
　なお、本発明は、上記実施形態に限定されるものではない。上記実施形態は、例示であり、本発明の特許請求の範囲に記載された技術的思想と実質的に同一な構成を有し、同様な作用効果を奏するものは、いかなるものであっても本発明の技術的範囲に包含される。 Note that the present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.
　以下に実施例を示して本発明をさらに具体的に説明する。 The present invention will be described more specifically with reference to the following examples.
［実施例１］
（硫化物固体電解質材料の合成）
　出発原料として、硫化リチウム（Ｌｉ２Ｓ、日本化学工業社製）と、五硫化二リン（Ｐ２Ｓ５、アルドリッチ社製）とを用いた。これらの粉末をアルゴン雰囲気下のグローブボックス内で、Ｌｉ２Ｓを０．７６５６ｇ、Ｐ２Ｓ５を１．２３４４ｇの割合で混合し、原料組成物を得た。次に、原料組成物をメノウ乳鉢で５分間混合し、その後、脱水ヘプタン４ｇとともに、ジルコニア製ポットに入れた。このポットを遊星型ボールミル機に取り付け、台盤回転数３７０ｒｐｍで、４０時間メカニカルミリングを行った。これにより、硫化物固体電解質材料（７５Ｌｉ２Ｓ－２５Ｐ２Ｓ５ガラス）を得た。 [Example 1]
(Synthesis of sulfide solid electrolyte materials)
As starting materials, lithium sulfide (Li 2 S, manufactured by Nippon Chemical Industry Co., Ltd.) and diphosphorus pentasulfide (P 2 S 5 , manufactured by Aldrich) were used. These powders were mixed in a glove box under an argon atmosphere at a rate of 0.7656 g of Li 2 S and 1.2344 g of P 2 S 5 to obtain a raw material composition. Next, the raw material composition was mixed in an agate mortar for 5 minutes, and then placed in a zirconia pot together with 4 g of dehydrated heptane. This pot was attached to a planetary ball mill and mechanical milling was performed for 40 hours at a base plate rotation speed of 370 rpm. As a result, a sulfide solid electrolyte material (75Li 2 S-25P 2 S 5 glass) was obtained.
（評価用電池の作製）
　被覆正極活物質として、正極活物質（ＬｉＮｉ３／５Ｃｏ１／５Ｍｎ１／５Ｏ２）と、被覆層（ＬｉＮｂＯ３）とを有し、炭酸塩濃度が１１００ｐｐｍである材料を準備した。正極活物質の合成の際には、炭酸塩の発生を抑制するために、純酸素雰囲気（水分および二酸化炭素が混入しない雰囲気）で熱処理を行った。また、被覆層の形成はゾルゲル法を用いた。コーティング装置にはパウレックス社製ＭＰ－０１を用い、コーティング時の使用ガスとして、ドライ窒素ガスおよび（通常）空気を適切な混合比で用い、炭酸塩濃度を制御した。さらに、コーティング後に、炭酸塩濃度の増加を抑制するために、ドライエア雰囲で熱処理を行った。 (Production of evaluation battery)
As the coated positive electrode active material, a material having a positive electrode active material (LiNi 3/5 Co 1/5 Mn 1/5 O 2 ) and a coating layer (LiNbO 3 ) and having a carbonate concentration of 1100 ppm was prepared. During the synthesis of the positive electrode active material, heat treatment was performed in a pure oxygen atmosphere (an atmosphere in which moisture and carbon dioxide are not mixed) in order to suppress the generation of carbonate. Further, the sol-gel method was used for forming the coating layer. MP-01 manufactured by Paulex Co. was used as a coating apparatus, and dry nitrogen gas and (usually) air were used at appropriate mixing ratios as gas used for coating to control the carbonate concentration. Further, after coating, heat treatment was performed in a dry air atmosphere in order to suppress an increase in carbonate concentration.
　この被覆正極活物質を１２．０３ｍｇ、導電化材であるＶＧＣＦ（昭和電工社製）を０．５１ｍｇ、７５Ｌｉ２Ｓ－２５Ｐ２Ｓ５ガラスを５．０３ｍｇ秤量し、混合することで、正極合材を得た。次に、負極活物質であるグラファイト（三菱化学社製）を９．０６ｍｇ、７５Ｌｉ２Ｓ－２５Ｐ２Ｓ５ガラスを８.２４ｍｇ秤量し、混合することで、負極合材を得た。 By weighing and mixing 12.03 mg of this coated positive electrode active material, 0.51 mg of VGCF (made by Showa Denko) as a conductive material, and 5.03 mg of 75Li 2 S-25P 2 S 5 glass, and mixing them, The material was obtained. Next, 9.06 mg of graphite (manufactured by Mitsubishi Chemical Corporation) as a negative electrode active material and 8.24 mg of 75Li 2 S-25P 2 S 5 glass were weighed and mixed to obtain a negative electrode mixture.
　その後、１ｃｍ２のセラミックス製の型に、７５Ｌｉ２Ｓ－２５Ｐ２Ｓ５ガラスを１８ｍｇ添加し、１ｔｏｎ／ｃｍ２の圧力でプレスし、固体電解質層を形成した。次に、固体電解質層の一方の表面上に正極合材を１７．５７ｍｇ添加し、１ｔｏｎ／ｃｍ２の圧力でプレスし、正極活物質層を形成した。次に、固体電解質層の他方の表面上に負極合材を１７．３ｍｇ添加し、３ｔｏｎ／ｃｍ２の圧力でプレスし、負極活物質層を形成した。次に、正極集電体としてアルミニウム箔を用い、負極集電体として銅箔を用い、評価用電池を作製した。 Thereafter, 18 mg of 75Li 2 S-25P 2 S 5 glass was added to a 1 cm 2 ceramic mold and pressed at a pressure of 1 ton / cm 2 to form a solid electrolyte layer. Next, 17.57 mg of the positive electrode mixture was added on one surface of the solid electrolyte layer and pressed at a pressure of 1 ton / cm 2 to form a positive electrode active material layer. Next, 17.3 mg of the negative electrode mixture was added on the other surface of the solid electrolyte layer and pressed at a pressure of 3 ton / cm 2 to form a negative electrode active material layer. Next, an evaluation battery was produced using an aluminum foil as the positive electrode current collector and a copper foil as the negative electrode current collector.
［実施例２～３、比較例１～４］
　組成および炭酸塩濃度が異なる被覆正極活物質を用いたこと以外は、実施例１と同様にして評価用電池を作製した。なお、組成および炭素塩濃度については下記表１に示す。 [Examples 2 to 3, Comparative Examples 1 to 4]
An evaluation battery was produced in the same manner as in Example 1 except that coated positive electrode active materials having different compositions and carbonate concentrations were used. The composition and carbon salt concentration are shown in Table 1 below.
［評価］
（電池抵抗測定）
　実施例１～３および比較例１～４で得られた評価用電池に対して、抵抗測定を行った。まず、０．３ｍＡで４．４ＶまでＣＣ／ＣＶ充電し、次に、０．３ｍＡで３．０ＶまでＣＣ／ＣＶ放電した。その後、３.５Ｖの電圧まで再び充電し、交流インピーダンス法によりインピーダンスを測定し、電池抵抗を求めた。その結果を図４および表１に示す。なお、図４および表１では、電池抵抗の値を比較例１に対する比率で示している。 [Evaluation]
(Battery resistance measurement)
Resistance measurements were performed on the evaluation batteries obtained in Examples 1 to 3 and Comparative Examples 1 to 4. First, CC / CV charge was performed up to 4.4 V at 0.3 mA, and then CC / CV discharge was performed up to 3.0 V at 0.3 mA. Thereafter, the battery was charged again to a voltage of 3.5 V, the impedance was measured by the AC impedance method, and the battery resistance was obtained. The results are shown in FIG. In FIG. 4 and Table 1, the value of the battery resistance is shown as a ratio with respect to Comparative Example 1.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　図４および表１に示すように、炭酸塩濃度が８００ｐｐｍ～３５００ｐｐｍの範囲内にある場合、電池抵抗が大幅に低減した。このような抵抗の低さは、正極活物質と被覆層との界面が理想的な状態であることを示唆している。 As shown in FIG. 4 and Table 1, when the carbonate concentration was in the range of 800 ppm to 3500 ppm, the battery resistance was significantly reduced. Such low resistance suggests that the interface between the positive electrode active material and the coating layer is in an ideal state.
　１　…　正極活物質
　２　…　被覆層
　１０　…　被覆正極活物質
　１１　…　正極活物質層
　１２　…　負極活物質層
　１３　…　固体電解質層
　１４　…　正極集電体
　１５　…　負極集電体
　１６　…　電池ケース
　２０　…　リチウム固体電池 DESCRIPTION OF SYMBOLS 1 ... Positive electrode active material 2 ... Covering layer 10 ... Covered positive electrode active material 11 ... Positive electrode active material layer 12 ... Negative electrode active material layer 13 ... Solid electrolyte layer 14 ... Positive electrode collector 15 ... Negative electrode collector 16 ... Battery case 20 ... Lithium solid state battery

Claims (3)

  1. 　正極活物質と、前記正極活物質上に形成され、Ｌｉイオン伝導性酸化物から構成される被覆層と、を有する被覆正極活物質であって、
    　前記被覆正極活物質における炭酸塩濃度が、８００ｐｐｍ～３５００ｐｐｍの範囲内であることを特徴とする被覆正極活物質。     A coated positive electrode active material comprising: a positive electrode active material; and a coating layer formed on the positive electrode active material and made of a Li ion conductive oxide,
    A coated positive electrode active material, wherein a carbonate concentration in the coated positive electrode active material is in a range of 800 ppm to 3500 ppm.
  2. 　正極活物質層と、負極活物質層と、前記正極活物質層および前記負極活物質層との間に形成された固体電解質層とを有するリチウム固体電池であって、
    　前記正極活物質層が、請求項１に記載の被覆正極活物質を含有し、
    　前記被覆正極活物質が、固体電解質材料と接することを特徴とするリチウム固体電池。     A lithium solid state battery having a positive electrode active material layer, a negative electrode active material layer, and a solid electrolyte layer formed between the positive electrode active material layer and the negative electrode active material layer,
    The positive electrode active material layer contains the coated positive electrode active material according to claim 1,
    A lithium solid state battery wherein the coated positive electrode active material is in contact with a solid electrolyte material.
  3. 　前記固体電解質材料が、硫化物固体電解質材料であることを特徴とする請求項２に記載のリチウム固体電池。 3. The lithium solid state battery according to claim 2, wherein the solid electrolyte material is a sulfide solid electrolyte material.
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