WO2019009072A1 - Negative electrode for all-solid-state batteries and all-solid-state battery provided with same - Google Patents

Negative electrode for all-solid-state batteries and all-solid-state battery provided with same Download PDF

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Publication number
WO2019009072A1
WO2019009072A1 PCT/JP2018/023434 JP2018023434W WO2019009072A1 WO 2019009072 A1 WO2019009072 A1 WO 2019009072A1 JP 2018023434 W JP2018023434 W JP 2018023434W WO 2019009072 A1 WO2019009072 A1 WO 2019009072A1
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negative electrode
graphite particles
solid electrolyte
particles
solid
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PCT/JP2018/023434
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French (fr)
Japanese (ja)
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孝友 松井
英丈 岡本
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日立造船株式会社
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/20—Graphite
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
    • H01B1/06—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors mainly consisting of other non-metallic substances
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
    • H01B1/06—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors mainly consisting of other non-metallic substances
    • H01B1/10—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors mainly consisting of other non-metallic substances sulfides
    • 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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • 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 an anode for an all solid battery containing graphite particles and an all solid battery provided with the same.
  • LIB lithium ion secondary battery
  • a lithium ion secondary battery which can easily obtain high energy density
  • large-sized batteries such as automotive batteries and stationary batteries are attracting attention.
  • ensuring safety is more important than in small batteries.
  • the all-solid-state battery using an inorganic solid electrolyte is easier to ensure safety and larger in capacity even if it is larger than LIB using an electrolytic solution.
  • the all-solid-state battery generally includes an electrode group including a positive electrode, a negative electrode, and a solid electrolyte layer interposed therebetween.
  • a mixture containing active material particles and solid electrolyte particles is used for the electrode.
  • the electrode mixture is prepared by a wet method or a dry method (eg, Patent Document 1).
  • a mixture is prepared by mixing active material particles and solid electrolyte particles with a liquid dispersion medium.
  • the active material particles and the solid electrolyte particles are dry mixed to prepare a composite material.
  • graphite particles capable of electrochemically inserting and desorbing ions are used as an active material.
  • One aspect of the present invention comprises a negative electrode composite layer including graphite particles and ion conductive solid electrolyte particles,
  • the graphite particles have a specific surface area of 3.5 m 2 / g or more
  • the present invention relates to a negative electrode for an all solid battery, wherein the content of the graphite particles in the negative electrode mixture layer is 70% by mass or more and 90% by mass or less.
  • Another aspect of the present invention relates to an all-solid-state battery including the above-described negative electrode, a positive electrode, and an ion conductive solid electrolyte layer interposed between the negative electrode and the positive electrode.
  • the negative electrode for an all solid battery includes a negative electrode mixture layer including graphite particles and ion conductive solid electrolyte particles.
  • Graphite particles have a specific surface area of 3.5 m 2 / g or more.
  • the content of the graphite particles in the negative electrode mixture layer is 70% by mass or more and 90% by mass or less.
  • the compatibility with the solid electrolyte particles is not good, and when the amount of the graphite particles is large, the dispersibility of the graphite particles and the solid electrolyte particles in the negative electrode mixture layer is greatly reduced.
  • the negative electrode mixture layer is formed using a negative electrode mixture prepared by a dry method, such low dispersibility becomes remarkable. If the dispersibility of the graphite particles and the solid electrolyte particles in the negative electrode mixture layer is low, the ion conduction path is insufficient, and the contact area at the interface between the graphite particles and the solid electrolyte particles decreases, so the utilization of the negative electrode active material decreases. Do. As a result, it becomes difficult to secure a high capacity.
  • the graphite particles and the solid electrolyte particles are used. You can improve your familiarity with Therefore, aggregation of the graphite particles is suppressed, and the graphite particles and the solid electrolyte particles can be mixed more uniformly. Thereby, many ion conduction paths are formed in the negative electrode mixture layer, and the contact area at the interface between the graphite particles and the solid electrolyte particles is increased, so that the utilization of the negative electrode active material can be increased. Therefore, the capacity of the all solid battery can be increased. Moreover, the fall of the capacity
  • the specific surface area of the graphite particles is less than 3.5 m 2 / g, even if the content of the graphite particles in the negative electrode mixture layer is increased to 70% by mass or more, it is less than 70% by mass. In addition to the fact that the capacity after charge and discharge does not change so much, the capacity retention rate decreases. That is, when the specific surface area of the graphite particles is less than 3.5 m 2 / g, the utilization rate of the graphite particles can not be increased even if the content of the graphite particles is increased to 70% by mass or more. This is considered to be due to the fact that when the content of the graphite particles is large in the negative electrode mixture layer, the graphite particles and the solid electrolyte particles can not be sufficiently dispersed.
  • graphite shall mean a carbon material whose average interplanar spacing d 002 of (002) plane measured by X-ray diffraction method is 0.340 nm or less.
  • the content of the graphite particles in the negative electrode mixture layer is preferably 75% by mass or more and 90% by mass or less.
  • the content of the graphite particles is in such a range, in particular, the dispersibility of the graphite particles and the solid electrolyte particles in the negative electrode mixture layer is likely to decrease, but in the present embodiment, 3.5 m 2 / g Since the graphite particles having the above specific surface area are used, high dispersibility of the graphite particles and the solid electrolyte particles can be secured. Therefore, even if the content of the graphite particles is in such a range, the utilization of the negative electrode active material can be increased, and thus the capacity of the all-solid battery can be further increased.
  • the specific surface area of the graphite particles is preferably 3.8 m 2 / g or more. In this case, the compatibility between the graphite particles and the solid electrolyte particles is further improved, which is advantageous from the viewpoint of increasing the capacity.
  • the specific surface area of the graphite particles is a specific surface area (BET specific surface area) obtained using a BET equation by a gas adsorption method (nitrogen adsorption method or the like).
  • the specific surface area of the graphite particles may be a value determined for the graphite particles used to prepare the negative electrode mixture layer.
  • the graphite particles When analyzing the graphite particles contained in the negative electrode taken out of the all solid battery, the graphite particles may be separated from the negative electrode, and the separated graphite particles may be analyzed.
  • the all solid battery is disassembled, the negative electrode is taken out, and the negative electrode mixture layer is scraped out.
  • the scraped sample is crushed and the mass of the crushed sample obtained is measured.
  • the ground particles are dispersed in an organic solvent, and the solid electrolyte particles are dissolved in the organic solvent to separate the graphite particles.
  • the mass of the separated graphite particles is measured, and the content (mass%) of the graphite particles in the negative electrode mixture layer is determined from this mass and the mass of the crushed sample.
  • the specific surface area of the graphite particles may be determined by the above method for the separated graphite particles.
  • the average aspect ratio of the graphite particles is preferably 2 or less.
  • Graphite particles having such an average aspect ratio usually tend to be incompatible with solid electrolyte particles.
  • the specific surface area of the graphite particles is in the above range, even when the average aspect ratio is in such a range, the graphite particles and the solid electrolyte particles in the negative electrode mixture layer are more It can be dispersed uniformly.
  • the average aspect ratio of the graphite particles may be the average aspect ratio of the graphite particles used for preparation of the negative electrode mixture layer.
  • it can be obtained based on the electron micrograph of the cross section of the negative electrode mixture layer.
  • the maximum diameter d1 and the maximum diameter d2 in the direction orthogonal to the maximum diameter d1 are measured for the arbitrarily selected graphite particles, and the aspect ratio d1 / d2 Ask for Similarly, in the cross-sectional photograph, the aspect ratio is obtained for a plurality of (for example, 10) graphite particles arbitrarily selected, and the averaged value is taken as the average aspect ratio of the graphite particles.
  • the graphite particles may have a core of graphite and an amorphous carbon layer covering the core.
  • Such graphite particles are generally incompatible with solid electrolyte particles.
  • the compatibility with the solid electrolyte particle is improved, and the graphite particle and the solid electrolyte particle are made more uniform in the negative electrode mixture layer. It can be dispersed.
  • the dispersibility of the graphite particles and the solid electrolyte particles in the negative electrode mixture tends to be reduced.
  • the content of the negative electrode is small even if it does not contain such organic component residue (organic residue) or contains an organic residue.
  • the content of the organic residue in the negative electrode mixture layer is preferably 1% by mass or less, and more preferably 0.5% by mass or less.
  • the graphite particles and the solid electrolyte particles can be dispersed more uniformly in the negative electrode mixture layer.
  • the “organic residue” includes the dispersion medium, the binder itself, and the components generated by the decomposition of the dispersion medium and the binder.
  • the amount of organic residue can be determined, for example, using gas chromatography mass spectrometry (GC / MS) method or the like.
  • the filling rate in the negative electrode mixture layer can be improved to, for example, 95% by volume or more (specifically, 95% by volume or more and 100% by volume or less).
  • the filling rate of the negative electrode mixture layer can be determined, for example, based on an electron micrograph of a cross section of the negative electrode mixture layer. More specifically, the void and the portion other than the void are binarized in the cross-sectional photograph of the negative electrode mixture layer. Then, the area ratio (area%) occupied by the portion other than the void in the area of a predetermined area (for example, 100 ⁇ m ⁇ 100 ⁇ m) of the cross-sectional photograph is determined, and this area ratio It shall be regarded as volume%).
  • the solid electrolyte particles preferably contain at least one selected from the group consisting of sulfides and hydrides. Since such solid electrolyte particles are easily compatible with the graphite particles, the dispersibility of the graphite particles and the solid electrolyte particles in the negative electrode mixture can be further enhanced, and the contact resistance between the graphite particles and the solid electrolyte particles can be reduced. Can. Thus, a higher capacity can be obtained more easily.
  • the present invention also encompasses an all-solid-state battery including the above-described negative electrode, a positive electrode, and an ion conductive solid electrolyte layer interposed between the negative electrode and the positive electrode.
  • the negative electrode includes a negative electrode mixture layer including graphite particles having a specific surface area of 3.5 m 2 / g or more and solid electrolyte particles having ion conductivity.
  • Graphite particles can reversibly insert and desorb lithium ions, and function as a negative electrode active material. Natural graphite and / or artificial graphite etc. are used for the graphite.
  • the graphite particles may be coated particles having a core containing graphite and a layer containing a carbon material coating the core.
  • the carbon material contained in the layer covering the core include hard carbon and / or amorphous carbon.
  • one having a graphite core and an amorphous carbon layer coating the core is preferable.
  • d 002 of such a carbon material is 0.340 nm or less.
  • coated particles are usually incompatible with solid electrolyte particles, but the graphite particles and solid electrolyte in the negative electrode mixture layer can be increased by increasing the specific surface area (to 3.5 m 2 / g or more). The dispersibility of the particles can be enhanced.
  • the specific surface area of the graphite particles may be 3.5 m 2 / g or more, preferably 3.8 m 2 / g or more, and more preferably 3.9 m 2 / g or more.
  • the upper limit of the specific surface area of the graphite particles is, for example, 10 m 2 / g or less, preferably 6 m 2 / g or less, and more preferably 5 m 2 / g or less or 4.8 m 2 / g or less. These lower limit value and upper limit value can be arbitrarily combined.
  • the specific surface area of the graphite particles is in such a range, the graphite particles and the solid electrolyte particles in the negative electrode mixture layer are in spite of the fact that the content of the graphite particles in the negative electrode mixture layer is 70% by mass or more. Can be dispersed more uniformly. As a result, the utilization of the graphite particles is increased, a high capacity can be obtained, and a decrease in capacity retention after charge and discharge can be suppressed.
  • Graphite particles having such a specific surface area can be obtained by roughening the surface of the graphite particles as a raw material.
  • Roughening of the graphite particles as a raw material may be performed by a method capable of roughening the surface of the graphite particles, and can be performed by, for example, activation treatment, plasma treatment, etc., but is limited thereto is not.
  • roughening may be performed by combining a plurality of treatments.
  • the activation treatment include chemical activation such as steam activation and alkali activation.
  • the activation treatment can be performed by a known procedure. The conditions of the activation treatment may be adjusted so that the specific surface area falls within the above range.
  • the average aspect ratio of the graphite particles is, for example, 3 or less, preferably 2.5 or less, and more preferably 2 or less.
  • Graphite particles having an average aspect ratio in such a range generally have poor compatibility with solid electrolyte particles.
  • the specific surface area of the graphite particles is within the above range, the compatibility with the solid electrolyte particles is improved, and the content of the graphite particles in the negative electrode mixture layer is increased to 70% by mass or more. Also, the dispersibility of the graphite particles and the solid electrolyte particles can be enhanced.
  • the average aspect ratio of the graphite particles is preferably 1 or more.
  • the average particle diameter of the graphite particles is, for example, 1 ⁇ m to 50 ⁇ m, preferably 3 ⁇ m to 30 ⁇ m, and more preferably 5 ⁇ m to 20 ⁇ m. When the average particle diameter is in such a range, the dispersibility of the graphite particles and the solid electrolyte particles in the negative electrode mixture layer can be easily improved.
  • the average particle size of the graphite particles is preferably larger than the average particle size of the solid electrolyte particles. In this case, solid electrolyte particles are easily distributed among the graphite particles, and aggregation of the graphite particles is easily suppressed.
  • the average particle size is a median diameter (D 50 ) in a volume-based particle size distribution measured using a laser diffraction type particle size distribution measuring apparatus.
  • D 50 the average particle diameter of the graphite particles
  • the cross section of a plurality of (for example, 10) graphite particles arbitrarily selected in the electron micrograph of the cross section of the negative electrode mixture layer The average particle diameter can be determined by calculating the average diameter of the particles. If the shape of the cross section of the graphite particle is not circular, the diameter of a circle (equivalent circle) having the same area as the area of the cross section may be taken as the diameter of the cross section of the graphite particle.
  • the content of the graphite particles in the negative electrode mixture layer is 70% by mass or more, preferably 75% by mass or more, and more preferably 78% by mass or more.
  • the content of the graphite particles in the negative electrode mixture layer is 90% by mass or less, and preferably 85% by mass or less.
  • the solid electrolyte particles contained in the negative electrode mixture layer are not particularly limited as long as they exhibit ion conductivity corresponding to the all solid battery, but for example, solid electrolyte particles as used for the solid electrolyte layer in all solid batteries It can be used.
  • a solid electrolyte for example, an inorganic solid electrolyte is preferable, and in particular, a sulfide and a hydride are preferable.
  • the crystalline state of the solid electrolyte is not particularly limited, and may be either crystalline or amorphous.
  • the sulfide examples include Li 2 S-SiS 2 , Li 2 S-P 2 S 5 , Li 2 S-GeS 2 , Li 2 S-B 2 S 3 , Li 2 S-Ga 2 S 3 , Li 2 S-Al 2 S 3 , Li 2 S-GeS 2 -P 2 S 5 , Li 2 S-Al 2 S 3 -P 2 S 5 , Li 2 S-P 2 S 3 , Li 2 S-P 2 S 3- P 2 S 5 , LiX-Li 2 S-P 2 S 5 , LiX-Li 2 S-SiS 2 , LiX-Li 2 S-B 2 S 3 (X: I, Br, or Cl) and the like Be Among these, sulfides containing Li and P are preferable from the viewpoint of being compatible with the graphite particles.
  • the complex hydride of lithium borohydride etc. are mentioned, for example.
  • Specific examples of the complex hydrides, LiBH 4 -LiI-based complex hydrides, LiBH 4 -LiNH 2 based complex hydrides, LiBH 4 -P 2 S 5, and LiBH 4 etc. -P 2 I 4 can be cited.
  • the negative electrode mixture layer may contain one of these solid electrolytes or may contain two or more of these solid electrolytes in combination.
  • the average particle diameter of the solid electrolyte particles is, for example, 1 ⁇ m to 50 ⁇ m, preferably 1 ⁇ m to 20 ⁇ m, and more preferably 1 ⁇ m to 10 ⁇ m or 1 ⁇ m to 5 ⁇ m.
  • the average particle size of the solid electrolyte particles is in such a range, the dispersibility of the graphite particles and the solid electrolyte particles can be easily improved.
  • the average particle size of the solid electrolyte particles is determined for the negative electrode taken out of the all solid battery, it can be determined according to the case of the graphite particles.
  • the negative electrode does not contain the organic residue or has a small content even if it contains the organic residue.
  • a negative electrode mixture layer of the negative electrode preferably has a high filling rate, for example, a filling rate of 95% or more.
  • Such a negative electrode mixture layer of the negative electrode can be formed by preparing a negative electrode mixture by a dry method and compressing and molding the negative electrode mixture. In the dry method, in particular, it is difficult to improve the dispersibility of the graphite particles and the solid electrolyte particles in the negative electrode mixture layer.
  • the dispersibility of the graphite particles and the solid electrolyte particles can be improved even when the negative electrode mixture layer is formed using the dry method. It can be increased and the utilization rate can be improved.
  • the negative electrode may include a negative electrode current collector and a negative electrode mixture layer carried on the negative electrode current collector.
  • Examples of the form of the negative electrode current collector include a metal foil, a plate-like body, an aggregate of powder, and the like, and a film of a material of the negative electrode current collector may be used.
  • the metal foil may be an electrolytic foil, an etched foil or the like. It is desirable that the negative electrode current collector has a strength that does not corrugate or break when forming the negative electrode mixture layer.
  • the material of the negative electrode current collector examples include materials which are stable at the redox potential of the negative electrode, such as copper, nickel, stainless steel, titanium, and alloys thereof.
  • a material not alloyed with lithium is used for the negative electrode current collector.
  • the thickness of the negative electrode current collector is preferably 10 ⁇ m or more and 50 ⁇ m or less.
  • the thickness of the negative electrode is, for example, 50 ⁇ m or more and 200 ⁇ m or less.
  • the all-solid battery according to the present embodiment includes the above-described negative electrode, a positive electrode, and an ion conductive solid electrolyte layer interposed between the negative electrode and the positive electrode.
  • components of the all-solid-state battery those other than the negative electrode will be described.
  • the positive electrode only needs to contain a positive electrode active material, and may contain, in addition to the positive electrode active material, known components used for the positive electrode in an all solid battery. From the viewpoint of enhancing the ion conductivity in the positive electrode, the positive electrode preferably contains a solid electrolyte exhibiting ion conductivity together with the positive electrode active material.
  • a positive electrode active material what is used as a positive electrode active material in an all-solid-state battery can be used without particular limitation.
  • an oxide is mentioned, for example. Examples of oxides include lithium-containing oxides containing cobalt, nickel, and / or manganese etc.
  • compounds other than oxides can also be used.
  • the compound other than an oxide e.g., olivine compounds (LiMPO 4), sulfur-containing compounds (Li 2 S, etc.) and the like.
  • M represents a transition metal.
  • the positive electrode active materials can be used singly or in combination of two or more. From the viewpoint of easily obtaining a high capacity, a lithium-containing oxide containing at least one selected from the group consisting of Co, Ni and Mn is preferable.
  • the lithium-containing oxide may further contain a typical metal element such as Al.
  • the positive electrode active materials LiNi 0.8 Co 0.15 Al 0.05 O 2 , LiCoO 2 , LiNi 1/3 Co 1/3 Mn 1/3 O 2 and the like are preferable.
  • coated particles in which positive electrode active material particles are coated with a metal oxide may be used for the positive electrode.
  • the metal oxide may be any complex oxide as long as it has the function of suppressing the diffusion of elements at the interface between the positive electrode active material particles and the solid electrolyte particles.
  • the metal oxide (such as Li 4 Ti 5 O 12, LiNbO 3, Li 2 ZrO 3) Li conductivity of the composite oxide, Al 2 O 3, ZrO 2 or the like can be mentioned.
  • the average particle diameter of the positive electrode active material is, for example, 1 ⁇ m or more and 20 ⁇ m or less, and preferably 3 ⁇ m or more and 15 ⁇ m or less.
  • the solid electrolyte is not particularly limited as long as it exhibits ion conductivity according to the all-solid-state battery.
  • the solid electrolyte can be selected, for example, from the solid electrolytes exemplified for the negative electrode mixture layer. Sulfides and / or hydrides are preferred.
  • the solid electrolyte contained in the positive electrode and the solid electrolyte layer contained in the negative electrode mixture layer may be the same or different.
  • the ratio of the solid electrolyte to the total amount of the positive electrode active material and the solid electrolyte is not particularly limited, but is, for example, 5% by mass or more and 50% by mass or less from the viewpoint of easily securing high ion conductivity of the positive electrode.
  • the positive electrode may include a positive electrode current collector and a positive electrode active material or a positive electrode mixture carried on the positive electrode current collector.
  • the positive electrode mixture is a mixture containing a positive electrode active material and a solid electrolyte.
  • the positive electrode current collector can be used without particular limitation as long as it is used as a positive electrode current collector of an all solid battery. The form of such a positive electrode current collector may be selected from those described for the negative electrode current collector.
  • the material of the positive electrode current collector examples include materials that are stable at the redox potential of the positive electrode, such as aluminum, magnesium, stainless steel, titanium, iron, cobalt, zinc, tin, or an alloy of these.
  • a material which is not alloyed with lithium is used for the positive electrode current collector.
  • the thickness of the positive electrode current collector can be appropriately selected, for example, from the range of 5 ⁇ m to 300 ⁇ m.
  • the thickness of the positive electrode is, for example, 50 ⁇ m or more and 200 ⁇ m or less.
  • the solid electrolyte layer interposed between the negative electrode and the positive electrode includes a solid electrolyte.
  • the solid electrolyte layer can be formed by depositing a solid electrolyte and pressurizing it.
  • the film formation of the solid electrolyte can be performed by a known procedure, but from the viewpoint of easily securing high ion conductivity, the dry method is preferable, and no binder or dispersion medium such as resin is used in film formation. Is preferred.
  • the solid electrolyte illustrated about the negative electrode compound material layer is mentioned, A sulfide and / or a hydride are preferable.
  • the solid electrolyte used may be the same for the positive electrode and / or the negative electrode, or may be different from any of the electrodes.
  • the solid electrolyte layer is preferably produced without using an organic component such as a dispersion medium or a binder as in the case of the negative electrode mixture layer.
  • the thickness of the solid electrolyte layer is, for example, 20 ⁇ m or more and 200 ⁇ m or less.
  • FIG. 1 is a longitudinal sectional view schematically showing an electrode group included in the all solid state battery according to the present embodiment.
  • An electrode group 1 included in the all solid battery includes a positive electrode 2, a negative electrode 4, and a solid electrolyte layer 3 interposed therebetween.
  • the positive electrode 2 includes a positive electrode current collector 2 b and a positive electrode mixture layer 2 a supported thereon.
  • the negative electrode 4 includes a negative electrode current collector 4 b and a negative electrode mixture layer 4 a supported thereon.
  • the positive electrode 2 and the negative electrode 4 are disposed such that the positive electrode mixture layer 2a and the negative electrode mixture layer 4a face each other.
  • the solid electrolyte layer 3 is disposed between the positive electrode mixture layer 2a and the negative electrode mixture layer 4a.
  • the positive electrode 2, the solid electrolyte layer 3, and the negative electrode 4 include a solid electrolyte.
  • the positive electrode mixture layer 2a, the negative electrode mixture layer 4a, and the solid electrolyte layer 3 in FIG. 1 have a disk shape of substantially the same size, and are stacked in a state in which the solid electrolyte layer 3 is sandwiched therebetween.
  • the insulator 5 is mounted on the side surface of the laminate 6 so as to cover the side surface of the negative electrode mixture layer 4 a and the side surface of the solid electrolyte layer 3 on the negative electrode mixture layer 4 a side.
  • the positive electrode current collector 2b and the negative electrode current collector 4b are circular or polygonal (such as square) metal foils that are larger in size than the positive electrode mixture layer 2a and the negative electrode mixture layer 4a.
  • the positive electrode current collector 2 b and the negative electrode current collector 4 b are formed to have substantially the same size as the laminate 6 in a state in which the insulator 5 is mounted.
  • the all-solid-state battery is not limited to the example shown in FIG. 1, and may be various types such as round, cylindrical, square, thin flat, and the like.
  • the electrode group may include a plurality of positive electrodes and / or a plurality of negative electrodes.
  • Examples of the all-solid battery according to the present embodiment include all-solid alkali metal ion batteries such as all-solid lithium ion batteries and all-solid sodium ion batteries; all-solid polyion batteries such as all-solid alkaline earth metal batteries .
  • the all-solid-state battery according to the present embodiment can be formed, for example, by a manufacturing method including a step of forming an electrode group and a step of pressing the electrode group. Each process will be described below.
  • the electrode group can be formed by laminating the positive electrode, the solid electrolyte layer, and the negative electrode.
  • Each of the electrodes and the solid electrolyte layer is preferably formed by a dry method. Further, either of the electrodes and the solid electrolyte layer may be formed first.
  • the solid electrolyte layer is formed on the main surface of one of the positive electrode and the negative electrode, and the other electrode is formed on the main surface of the formed solid electrolyte layer (the main surface opposite to the one electrode) You may Alternatively, the positive electrode and the negative electrode may be respectively formed, and a solid electrolyte may be filled between them to pressurize to form an electrode group.
  • the solid electrolyte layer may be formed first, one electrode may be formed on one main surface, and the other electrode may be formed on the other main surface.
  • the positive electrode can be obtained, for example, by forming a film of a positive electrode active material or a positive electrode mixture, and compressing and forming the film.
  • the positive electrode may be formed by forming a layer of a positive electrode active material or a positive electrode mixture on the surface of the positive electrode current collector.
  • the negative electrode can be produced according to the case of a positive electrode, using, for example, a negative electrode composite containing graphite particles and solid electrolyte particles, and, if necessary, a negative electrode current collector.
  • the pressure at the time of compression molding is, for example, 1 MPa or more and 300 MPa or less, and may be 1 MPa or more and 30 MPa or less.
  • the unevenness of the surface of the graphite particles having a large specific surface area can be cut into the surface of the solid electrolyte particles.
  • the dispersibility of the graphite particles and the solid electrolyte particles is further enhanced, and the contact resistance at the interface between the particles can be reduced.
  • pressure may be applied once or plural times to the deposited electrode material.
  • the solid electrolyte layer can be formed, for example, by forming a film of the above-described solid electrolyte or a mixture containing the above-mentioned solid electrolyte (for example, a mixture containing a solid electrolyte and an additive) by a dry method and compression molding.
  • the pressure at the time of compression molding is, for example, I MPa or more and 300 MPa or less, and may be 1 MPa or more and 10 MPa or less. In compression molding, pressure may be applied once or plural times to the formed solid electrolyte or mixture.
  • the electrodes and the solid electrolyte layer may be stacked such that the solid electrolyte layer is interposed between the positive electrodes and the negative electrodes.
  • Step of pressurizing the electrode group The electrode group is accommodated in the battery case, but pressurization to the electrode group may be performed before being accommodated in the battery case, or may be performed after being accommodated in the battery case.
  • the electrode group may be accommodated in the battery case and then the electrode group may be pressurized together with the battery case (that is, the battery).
  • the pressure at the time of pressurizing the electrode group is, for example, 100 MPa or more, preferably 200 MPa or more, and may be 500 MPa or more or 800 MPa or more. By applying such pressure to the electrode group (or battery), even when forming an electrode or a solid electrolyte layer by a dry method, the interfacial resistance between solid electrolyte particles and between solid electrolyte particles and active material particles is reduced. can do.
  • the pressure at the time of pressurizing the electrode group is, for example, 1500 MPa or less.
  • the pressurization may be performed once or plural times.
  • Example 1 The all solid state battery shown in FIG. 1 was produced in the following procedure. (1) Assembly of all solid battery (a) Preparation of solid electrolyte layer 3 A cylindrical die (inner diameter 10 mm, height 30 mm) made of cold die steel (SKD) is erected and a bottom plate is placed on the bottom of the cylindrical die. I inserted a short pin. In this state, 90 mg of a Li 2 S—P 2 S 5 solid solution, which is a lithium ion conductive solid electrolyte, was layered in a cylindrical mold.
  • a Li 2 S—P 2 S 5 solid solution which is a lithium ion conductive solid electrolyte
  • a cylindrical long pin of a size matched to the inner diameter of the cylindrical mold is inserted into the inside from the top of the cylindrical mold and pressed once at a pressure of 188 MPa in the thickness direction of the layer to obtain a solid electrolyte layer 3 was produced.
  • the heat-treated graphite powder was washed with a 0.1 mol / L aqueous salt solution and pure water until the pH of the solution after washing became 7.
  • Graphite particles were obtained by vacuum drying the washed graphite particles at 120 ° C. overnight.
  • the BET specific surface area of the obtained graphite particles was 3.9 m 2 / g, and d 002 was 0.3371 nm.
  • the used graphite particle is provided with the core of graphite and the amorphous carbon layer which coats a core.
  • (B-2) Preparation of Negative Electrode Mixture Layer 4a
  • the graphite particles and solid electrolyte particles (Li 2 S—P 2 S 5 solid solution, D 50 : 8.2 ⁇ m) prepared in the above (1-1) are prepared by the following procedure 8: Used at a mass ratio of 2 and mixed thoroughly in a mortar. 13.5 mg of the obtained mixture was layeredly loaded on the solid electrolyte layer 3 in the cylindrical mold produced in (a). Then, in the thickness direction of the layer, the negative electrode mixture layer 4a was manufactured by pressing three times. The pressure of the pressure press was 188 MPa each time.
  • the short pin was taken out with the top and bottom of the cylindrical mold turned upside down, the short pin was inserted into the negative electrode composite material layer 4a side, and the cylindrical mold was placed so that the short pin was at the bottom. Subsequently, the solid electrolyte layer 3 and the negative electrode mixture layer 4a were pressed from the solid electrolyte layer 3 side using a long pin.
  • an electrode group 1 was produced by arranging an aluminum foil (40 mm long ⁇ 40 mm wide, 15 ⁇ m thickness) as the positive electrode current collector 2 b on the positive electrode mixture layer 2 a of the laminate 6.
  • the insulator 5 is disposed to suppress the contact between the negative electrode mixture layer 4a and the negative electrode current collector 4b, and the positive electrode mixture layer 2a and the positive electrode current collector 2b.
  • the electrode group 1 was housed in a laminate cell having a negative electrode lead and a positive electrode lead, and the gas in the cell was sealed while being sucked by a vacuum pump. Thus, an all solid state battery was produced.
  • 1st cycle Charged to a charge termination voltage of 4.2 V at a current of 0.04 C, and then discharged to a discharge termination voltage of 2.7 V at a current of 0.04 C.
  • Second cycle charge was performed to a charge termination voltage of 4.2 V at a current of 0.04 C, and then discharged to a discharge termination voltage of 2.7 V at a current of 0.7 C.
  • Third cycle The battery was charged to a charge termination voltage of 4.2 V at a current of 0.04 C, and then discharged to a discharge termination voltage of 2.7 V at a current of 3 C.
  • Fourth cycle The battery was charged to a charge termination voltage of 4.2 V at a current of 0.04 C, and then discharged to a discharge termination voltage of 2.7 V at a current of 4 C.
  • the discharge capacity at the first cycle and the discharge capacity at the fourth cycle were determined, and the ratio of the discharge capacity at the fourth cycle when the discharge capacity at the first cycle was 100% was evaluated as the capacity retention ratio.
  • the discharge capacity was a value per 1 g of the negative electrode mixture.
  • a negative electrode was produced in the same manner as in Example 1 except that the obtained graphite particles were used, and an all solid battery was assembled and evaluated.
  • a negative electrode was produced in the same manner as in Example 1 except that the obtained graphite particles were used, and an all solid battery was assembled and evaluated.
  • Comparative example 3 In (b-2), the mass ratio of the graphite particles to the solid electrolyte particles is 6.5: 3.5.
  • a graphite particle As a graphite particle, the same one as Comparative Example 2 was used.
  • a negative electrode was produced in the same manner as in Example 1 except for the above, and an all solid battery was assembled and evaluated.
  • Table 1 also shows the specific surface area of the graphite particles used in the negative electrode mixture layer and the content of the graphite particles in the negative electrode mixture layer.
  • the discharge capacity in the fourth cycle is compared with Comparative Example 1 Compared to the above-mentioned, the improvement is large (Examples 1 to 3). Further, unlike the comparative example 2, the high capacity retention rate can be secured in the first to third embodiments.
  • the discharge capacity at the fourth cycle in Comparative Example 2 decreases because the specific surface area of the graphite particles is small, and the dispersibility of the graphite particles and the solid electrolyte particles in the negative electrode mixture decreases, and the graphite particles and the solid electrolyte It is thought that the presence of the graphite particles which do not contribute to charge and discharge is manifested by the reduction of the bite of the surface with the particles.
  • the all-solid-state battery according to the present invention is useful in various applications where high capacity is required.
  • Electrode group 1: Electrode group, 2: Positive electrode, 2a: Positive electrode mixture layer, 2b: Positive electrode current collector, 3: Solid electrolyte layer, 4: Negative electrode, 4a: Negative electrode mixture layer, 4b: Negative electrode current collector, 5: Insulation Body, 6: stack

Abstract

This negative electrode for all-solid-state batteries is provided with a negative electrode mixture layer that contains graphite particles and ion-conductive solid electrolyte particles. The graphite particles have a specific surface area of 3.5 m2/g or more. The content of the graphite particles in the negative electrode mixture layer is from 70% by mass to 90% by mass (inclusive).

Description

全固体電池用負極およびそれを備える全固体電池Negative electrode for all solid battery and all solid battery provided with the same
　本発明は、黒鉛粒子を含む全固体電池用負極およびそれを備える全固体電池に関する。 The present invention relates to an anode for an all solid battery containing graphite particles and an all solid battery provided with the same.
　様々な二次電池が開発されている中、高いエネルギー密度が得られ易いリチウムイオン二次電池（ＬＩＢ）が最も有望視されている。一方、電池の用途拡大に伴って、自動車用電池や据え置き型電池などの大型電池が注目されている。大型電池では、小型電池に比べて安全性の確保がさらに重要になる。無機系の固体電解質を用いる全固体電池は、電解液を用いるＬＩＢに比べて、大型化しても安全性を確保し易く、高容量化し易いと期待されている。 Among various secondary batteries being developed, a lithium ion secondary battery (LIB), which can easily obtain high energy density, is considered most promising. On the other hand, with the expansion of battery applications, large-sized batteries such as automotive batteries and stationary batteries are attracting attention. In large batteries, ensuring safety is more important than in small batteries. It is expected that the all-solid-state battery using an inorganic solid electrolyte is easier to ensure safety and larger in capacity even if it is larger than LIB using an electrolytic solution.
　全固体電池は、一般に、正極、負極、およびこれらの間に介在する固体電解質層を備える電極群を含む。電極には、活物質粒子と固体電解質粒子とを含む合材が用いられる。電極合材は、湿式法や乾式法で調製される（特許文献１など）。湿式法では、活物質粒子および固体電解質粒子を液体の分散媒とともに混合することにより合材が調製される。また、乾式法では、活物質粒子および固体電解質粒子を乾式混合することにより合材が調製される。なお、全固体電池の負極では、電気化学的にイオンを挿入および脱離可能な黒鉛粒子などが活物質として利用されている。 The all-solid-state battery generally includes an electrode group including a positive electrode, a negative electrode, and a solid electrolyte layer interposed therebetween. For the electrode, a mixture containing active material particles and solid electrolyte particles is used. The electrode mixture is prepared by a wet method or a dry method (eg, Patent Document 1). In the wet method, a mixture is prepared by mixing active material particles and solid electrolyte particles with a liquid dispersion medium. In the dry method, the active material particles and the solid electrolyte particles are dry mixed to prepare a composite material. In the negative electrode of the all solid battery, graphite particles capable of electrochemically inserting and desorbing ions are used as an active material.
国際公開第２０１４／１４１９６２号パンフレットInternational Publication No. 2014/141962 brochure
　高容量化の観点からは、全固体電池において、負極合材中の黒鉛粒子の含有量を多くすることが有利であると考えられる。しかし、黒鉛粒子を多く含む負極合材を調製する場合には、黒鉛粒子の種類によっては、負極合材中に黒鉛粒子および固体電解質粒子を均一に分散させることが難しい。乾式法により負極合材を調製する場合には、特に、負極合材における黒鉛粒子および固体電解質粒子の分散性を高め難い。そのため、黒鉛粒子の含有量を多くしても、充分な放電容量を得ることは難しい。 From the viewpoint of increasing the capacity, it is considered to be advantageous to increase the content of graphite particles in the negative electrode mixture in the all-solid-state battery. However, when preparing a negative electrode mixture containing a large amount of graphite particles, it is difficult to uniformly disperse the graphite particles and the solid electrolyte particles in the negative electrode mixture depending on the type of the graphite particles. In the case of preparing the negative electrode mixture by the dry method, in particular, it is difficult to improve the dispersibility of the graphite particles and the solid electrolyte particles in the negative electrode mixture. Therefore, even if the content of the graphite particles is increased, it is difficult to obtain a sufficient discharge capacity.
　本発明の一局面は、黒鉛粒子と、イオン伝導性の固体電解質粒子とを含む負極合材層を備え、
　前記黒鉛粒子は、３．５ｍ2／ｇ以上の比表面積を有し、
　前記負極合材層中の前記黒鉛粒子の含有量は、７０質量％以上９０質量％以下である、全固体電池用負極に関する。 One aspect of the present invention comprises a negative electrode composite layer including graphite particles and ion conductive solid electrolyte particles,
The graphite particles have a specific surface area of 3.5 m 2 / g or more,
The present invention relates to a negative electrode for an all solid battery, wherein the content of the graphite particles in the negative electrode mixture layer is 70% by mass or more and 90% by mass or less.
　本発明の他の局面は、上記の負極と、正極と、前記負極および前記正極の間に介在するイオン伝導性の固体電解質層とを含む、全固体電池に関する。 Another aspect of the present invention relates to an all-solid-state battery including the above-described negative electrode, a positive electrode, and an ion conductive solid electrolyte layer interposed between the negative electrode and the positive electrode.
　全固体電池において、負極が多くの黒鉛粒子を含む場合に、高容量を確保することができる。 In the all-solid-state battery, when the negative electrode contains a large number of graphite particles, high capacity can be secured.
　本発明の新規な特徴を添付の請求の範囲に記述するが、本発明は、構成および内容の両方に関し、本発明の他の目的および特徴と併せ、図面を照合した以下の詳細な説明によりさらによく理解されるであろう。 While the novel features of the present invention are set forth in the appended claims, the present invention, both in terms of construction and content, together with other objects and features of the present invention, will It will be well understood.
本発明の一実施形態に係る全固体電池に含まれる電極群を概略的に示す縦断面図である。It is a longitudinal cross-sectional view which shows roughly the electrode group contained in the all-solid-state battery which concerns on one Embodiment of this invention.
　本発明の一実施形態に係る全固体電池用負極は、黒鉛粒子と、イオン伝導性の固体電解質粒子とを含む負極合材層を備える。黒鉛粒子は、３．５ｍ2／ｇ以上の比表面積を有する。負極合材層中の黒鉛粒子の含有量は、７０質量％以上９０質量％以下である。 The negative electrode for an all solid battery according to one embodiment of the present invention includes a negative electrode mixture layer including graphite particles and ion conductive solid electrolyte particles. Graphite particles have a specific surface area of 3.5 m 2 / g or more. The content of the graphite particles in the negative electrode mixture layer is 70% by mass or more and 90% by mass or less.
　黒鉛粒子によっては、固体電解質粒子とのなじみが悪く、黒鉛粒子の量が多くなると、負極合材層における黒鉛粒子および固体電解質粒子の分散性が大きく低下する。特に、乾式法により調製した負極合材を用いて負極合材層を形成する場合には、このような分散性の低さが顕著になる。負極合材層における黒鉛粒子および固体電解質粒子の分散性が低いと、イオン伝導パスが不足し、黒鉛粒子と固体電解質粒子との界面における接触面積が小さくなるため、負極活物質の利用率が低下する。その結果、高容量を確保することが難しくなる。 Depending on the graphite particles, the compatibility with the solid electrolyte particles is not good, and when the amount of the graphite particles is large, the dispersibility of the graphite particles and the solid electrolyte particles in the negative electrode mixture layer is greatly reduced. In particular, when the negative electrode mixture layer is formed using a negative electrode mixture prepared by a dry method, such low dispersibility becomes remarkable. If the dispersibility of the graphite particles and the solid electrolyte particles in the negative electrode mixture layer is low, the ion conduction path is insufficient, and the contact area at the interface between the graphite particles and the solid electrolyte particles decreases, so the utilization of the negative electrode active material decreases. Do. As a result, it becomes difficult to secure a high capacity.
　本実施形態では、３．５ｍ2／ｇ以上の比表面積を有する黒鉛粒子を用いることで、黒鉛粒子の含有量が７０質量％以上９０質量％以下である場合に、黒鉛粒子と固体電解質粒子とのなじみをよくすることができる。よって、黒鉛粒子が凝集することが抑制され、黒鉛粒子と固体電解質粒子とをより均一に混合することができる。これにより、負極合材層中に多くのイオン伝導パスが形成されるとともに、黒鉛粒子と固体電解質粒子との界面における接触面積が大きくなるため、負極活物質の利用率を高めることができる。よって、全固体電池を高容量化することができる。また、充放電後の容量維持率の低下を抑制することができる。 In the present embodiment, by using graphite particles having a specific surface area of 3.5 m 2 / g or more, when the content of the graphite particles is 70% by mass to 90% by mass, the graphite particles and the solid electrolyte particles are used. You can improve your familiarity with Therefore, aggregation of the graphite particles is suppressed, and the graphite particles and the solid electrolyte particles can be mixed more uniformly. Thereby, many ion conduction paths are formed in the negative electrode mixture layer, and the contact area at the interface between the graphite particles and the solid electrolyte particles is increased, so that the utilization of the negative electrode active material can be increased. Therefore, the capacity of the all solid battery can be increased. Moreover, the fall of the capacity | capacitance maintenance factor after charging / discharging can be suppressed.
　それに対し、黒鉛粒子の比表面積が３．５ｍ2／ｇ未満では、負極合材層中の黒鉛粒子の含有量を、７０質量％以上に多くしても、７０質量％未満の場合に比べて、充放電後の容量はそれほど変わらないことに加え、容量維持率は低下する。つまり、黒鉛粒子の比表面積が３．５ｍ2／ｇ未満の場合、黒鉛粒子の含有量を７０質量％以上に多くしても、黒鉛粒子の利用率を高めることができない。これは、負極合材層において、黒鉛粒子の含有量が多いと、黒鉛粒子および固体電解質粒子を充分に分散させることができないことによるものと考えられる。 On the other hand, if the specific surface area of the graphite particles is less than 3.5 m 2 / g, even if the content of the graphite particles in the negative electrode mixture layer is increased to 70% by mass or more, it is less than 70% by mass. In addition to the fact that the capacity after charge and discharge does not change so much, the capacity retention rate decreases. That is, when the specific surface area of the graphite particles is less than 3.5 m 2 / g, the utilization rate of the graphite particles can not be increased even if the content of the graphite particles is increased to 70% by mass or more. This is considered to be due to the fact that when the content of the graphite particles is large in the negative electrode mixture layer, the graphite particles and the solid electrolyte particles can not be sufficiently dispersed.
　なお、本明細書中、黒鉛とは、Ｘ線回折法により測定される（００２）面の平均面間隔ｄ002が０．３４０ｎｍ以下の炭素材料を言うものとする。 In addition, in this specification, graphite shall mean a carbon material whose average interplanar spacing d 002 of (002) plane measured by X-ray diffraction method is 0.340 nm or less.
　負極合材層中の黒鉛粒子の含有量は、７５質量％以上９０質量％以下であることが好ましい。黒鉛粒子の含有量がこのような範囲である場合、特に、負極合材層中における黒鉛粒子および固体電解質粒子の互いの分散性が低下し易いが、本実施形態では、３．５ｍ2／ｇ以上の比表面積を有する黒鉛粒子を用いるため、黒鉛粒子および固体電解質粒子の高い分散性を確保することができる。よって、黒鉛粒子の含有量がこのような範囲であっても、負極活物質の利用率を高めることができるため、全固体電池をさらに高容量化することができる。 The content of the graphite particles in the negative electrode mixture layer is preferably 75% by mass or more and 90% by mass or less. When the content of the graphite particles is in such a range, in particular, the dispersibility of the graphite particles and the solid electrolyte particles in the negative electrode mixture layer is likely to decrease, but in the present embodiment, 3.5 m 2 / g Since the graphite particles having the above specific surface area are used, high dispersibility of the graphite particles and the solid electrolyte particles can be secured. Therefore, even if the content of the graphite particles is in such a range, the utilization of the negative electrode active material can be increased, and thus the capacity of the all-solid battery can be further increased.
　黒鉛粒子の比表面積は、３．８ｍ2／ｇ以上であることが好ましい。この場合、黒鉛粒子と固体電解質粒子とのなじみがさらによくなるため、高容量化の観点から有利である。
　なお、本明細書中、黒鉛粒子の比表面積は、ガス吸着法（窒素吸着法など）により、ＢＥＴ式を用いて得られる比表面積（ＢＥＴ比表面積）である。黒鉛粒子の比表面積は、負極合材層の調製に使用される黒鉛粒子について求められる値であってもよい。 The specific surface area of the graphite particles is preferably 3.8 m 2 / g or more. In this case, the compatibility between the graphite particles and the solid electrolyte particles is further improved, which is advantageous from the viewpoint of increasing the capacity.
In the present specification, the specific surface area of the graphite particles is a specific surface area (BET specific surface area) obtained using a BET equation by a gas adsorption method (nitrogen adsorption method or the like). The specific surface area of the graphite particles may be a value determined for the graphite particles used to prepare the negative electrode mixture layer.
　全固体電池から取り出した負極に含まれる黒鉛粒子を分析する場合、負極から黒鉛粒子を分離し、分離した黒鉛粒子について分析すればよい。例えば、全固体電池を分解して、負極を取り出し、負極合材層をかき出す。かき出した試料を粉砕し、得られる粉砕試料の質量を測定する。粉砕試料を有機溶媒中に分散させ、固体電解質粒子を有機溶媒に溶解させることにより、黒鉛粒子を分離する。分離した黒鉛粒子の質量を測定し、この質量と粉砕試料の質量とから、負極合材層中の黒鉛粒子の含有量（質量％）が求められる。また、黒鉛粒子の比表面積については、分離した黒鉛粒子について上記の方法で求めればよい。 When analyzing the graphite particles contained in the negative electrode taken out of the all solid battery, the graphite particles may be separated from the negative electrode, and the separated graphite particles may be analyzed. For example, the all solid battery is disassembled, the negative electrode is taken out, and the negative electrode mixture layer is scraped out. The scraped sample is crushed and the mass of the crushed sample obtained is measured. The ground particles are dispersed in an organic solvent, and the solid electrolyte particles are dissolved in the organic solvent to separate the graphite particles. The mass of the separated graphite particles is measured, and the content (mass%) of the graphite particles in the negative electrode mixture layer is determined from this mass and the mass of the crushed sample. The specific surface area of the graphite particles may be determined by the above method for the separated graphite particles.
　黒鉛粒子の平均アスペクト比は、２以下であることが好ましい。このような平均アスペクト比を有する黒鉛粒子は、通常は、固体電解質粒子とのなじみが悪くなり易い。それに対し、本実施形態では、黒鉛粒子の比表面積が上記のような範囲であるため、平均アスペクト比がこのような範囲である場合でも、負極合材層中に黒鉛粒子および固体電解質粒子をより均一に分散させることができる。 The average aspect ratio of the graphite particles is preferably 2 or less. Graphite particles having such an average aspect ratio usually tend to be incompatible with solid electrolyte particles. On the other hand, in the present embodiment, since the specific surface area of the graphite particles is in the above range, even when the average aspect ratio is in such a range, the graphite particles and the solid electrolyte particles in the negative electrode mixture layer are more It can be dispersed uniformly.
　黒鉛粒子の平均アスペクト比は、負極合材層の調製に使用される黒鉛粒子の平均アスペクト比であってもよい。また、全固体電池から取り出した負極について、黒鉛粒子の平均アスペクト比を求める場合には、例えば、負極合材層の断面の電子顕微鏡写真に基づいて求めることができる。より具体的には、負極合材層の断面写真について、まず、任意に選択した黒鉛粒子について最大径ｄ１と、最大径ｄ１と直交する方向における最大径ｄ２とを計測し、アスペクト比ｄ１／ｄ２を求める。同様に、断面写真において、任意に選択した複数（例えば、１０個）の黒鉛粒子について、アスペクト比を求め、平均化した値を、黒鉛粒子の平均アスペクト比とする。 The average aspect ratio of the graphite particles may be the average aspect ratio of the graphite particles used for preparation of the negative electrode mixture layer. In addition, in the case of obtaining the average aspect ratio of the graphite particles for the negative electrode taken out of the all solid battery, for example, it can be obtained based on the electron micrograph of the cross section of the negative electrode mixture layer. More specifically, for the cross-sectional photograph of the negative electrode mixture layer, first, the maximum diameter d1 and the maximum diameter d2 in the direction orthogonal to the maximum diameter d1 are measured for the arbitrarily selected graphite particles, and the aspect ratio d1 / d2 Ask for Similarly, in the cross-sectional photograph, the aspect ratio is obtained for a plurality of (for example, 10) graphite particles arbitrarily selected, and the averaged value is taken as the average aspect ratio of the graphite particles.
　黒鉛粒子は、黒鉛のコアと、コアを被覆する非晶質炭素層とを有するものであってもよい。このような黒鉛粒子は、一般には、固体電解質粒子とのなじみが悪い。本実施形態では、このような黒鉛粒子でも、比表面積を上記のような範囲とすることで、固体電解質粒子とのなじみがよくなり、黒鉛粒子および固体電解質粒子を負極合材層中により均一に分散させることができる。 The graphite particles may have a core of graphite and an amorphous carbon layer covering the core. Such graphite particles are generally incompatible with solid electrolyte particles. In this embodiment, even with such a graphite particle, by setting the specific surface area in the above range, the compatibility with the solid electrolyte particle is improved, and the graphite particle and the solid electrolyte particle are made more uniform in the negative electrode mixture layer. It can be dispersed.
　乾式法により負極合材を調製する場合には、負極合材中の黒鉛粒子および固体電解質粒子の分散性が低下しやすい。乾式法では、湿式法とは異なり、分散媒やバインダ（樹脂など）などの有機成分を用いないか用いる場合でもその量が少ない。そのため、負極は、このような有機成分の残渣（有機残渣）を含まないか、もしくは有機残渣を含む場合でも、その含有量は少ないことが好ましい。例えば、負極合材層中の有機残渣の含有量は、１質量％以下であることが好ましく、０．５質量％以下であることがさらに好ましい。本実施形態では、このような場合でも、黒鉛粒子および固体電解質粒子を負極合材層中により均一に分散させることができる。
　なお、「有機残渣」には、分散媒やバインダ自体、および分散媒やバインダの分解により生成された成分が含まれるものとする。有機残渣の量は、例えば、ガスクロマトグラフィー質量分析（ＧＣ／ＭＳ）法などを利用して求めることができる。 When the negative electrode mixture is prepared by a dry method, the dispersibility of the graphite particles and the solid electrolyte particles in the negative electrode mixture tends to be reduced. In the dry method, unlike the wet method, even when using or not using an organic component such as a dispersion medium or a binder (such as a resin), the amount is small. Therefore, it is preferable that the content of the negative electrode is small even if it does not contain such organic component residue (organic residue) or contains an organic residue. For example, the content of the organic residue in the negative electrode mixture layer is preferably 1% by mass or less, and more preferably 0.5% by mass or less. In this embodiment, even in such a case, the graphite particles and the solid electrolyte particles can be dispersed more uniformly in the negative electrode mixture layer.
The “organic residue” includes the dispersion medium, the binder itself, and the components generated by the decomposition of the dispersion medium and the binder. The amount of organic residue can be determined, for example, using gas chromatography mass spectrometry (GC / MS) method or the like.
　一般に、負極合材層を形成する際に、分散媒やバインダなどの有機成分を用いると、有機成分の除去により、空隙が形成される。本実施形態では、負極合材中に黒鉛粒子および固体電解質粒子をより均一に分散させることができるため、黒鉛粒子および固体電解質粒子の充填性を高めることができるとともに、空隙の容積を低減することができる。従って、本実施形態では、負極合材層における充填率を、例えば、９５体積％以上（具体的には、９５体積％以上１００体積％以下）にまで向上することができる。 In general, when an organic component such as a dispersion medium or a binder is used in forming the negative electrode mixture layer, a void is formed by the removal of the organic component. In the present embodiment, since the graphite particles and the solid electrolyte particles can be dispersed more uniformly in the negative electrode mixture, the packing properties of the graphite particles and the solid electrolyte particles can be enhanced, and the volume of the voids can be reduced. Can. Therefore, in the present embodiment, the filling rate in the negative electrode mixture layer can be improved to, for example, 95% by volume or more (specifically, 95% by volume or more and 100% by volume or less).
　負極合材層の充填率は、例えば、負極合材層の断面の電子顕微鏡写真に基づいて求めることができる。より具体的には、負極合材層の断面写真について、空隙と空隙以外の部分とを二値化処理する。そして、断面写真の所定面積（例えば、縦１００μｍ×横１００μｍ）の領域において、空隙以外の部分が占める面積比率（面積％）を求め、この面積比率を負極合材層の体積基準の充填率（体積％）と見なすものとする。 The filling rate of the negative electrode mixture layer can be determined, for example, based on an electron micrograph of a cross section of the negative electrode mixture layer. More specifically, the void and the portion other than the void are binarized in the cross-sectional photograph of the negative electrode mixture layer. Then, the area ratio (area%) occupied by the portion other than the void in the area of a predetermined area (for example, 100 μm × 100 μm) of the cross-sectional photograph is determined, and this area ratio It shall be regarded as volume%).
　固体電解質粒子は、硫化物および水素化物からなる群より選択される少なくとも一種を含むことが好ましい。このような固体電解質粒子は、黒鉛粒子となじみ易いため、負極合材中の黒鉛粒子および固体電解質粒子の分散性をさらに高め易くなるとともに、黒鉛粒子と固体電解質粒子との接触抵抗を低減することができる。よって、さらに高容量が得られ易くなる。 The solid electrolyte particles preferably contain at least one selected from the group consisting of sulfides and hydrides. Since such solid electrolyte particles are easily compatible with the graphite particles, the dispersibility of the graphite particles and the solid electrolyte particles in the negative electrode mixture can be further enhanced, and the contact resistance between the graphite particles and the solid electrolyte particles can be reduced. Can. Thus, a higher capacity can be obtained more easily.
　本発明には、上記の負極と、正極と、負極および正極の間に介在するイオン伝導性の固体電解質層とを含む、全固体電池も包含される。 The present invention also encompasses an all-solid-state battery including the above-described negative electrode, a positive electrode, and an ion conductive solid electrolyte layer interposed between the negative electrode and the positive electrode.
　以下に、本実施形態に係る全固体電池用負極および全固体電池についてより詳細に説明する。
（負極）
　負極は、３．５ｍ2／ｇ以上の比表面積を有する黒鉛粒子と、イオン伝導性の固体電解質粒子とを含む負極合材層を備える。
　黒鉛粒子は、リチウムイオンを可逆的に挿入および脱離可能であり、負極活物質として機能する。黒鉛には、天然黒鉛、および／または人造黒鉛などが使用される。 Hereinafter, the negative electrode for the all solid battery and the all solid battery according to the present embodiment will be described in more detail.
(Negative electrode)
The negative electrode includes a negative electrode mixture layer including graphite particles having a specific surface area of 3.5 m 2 / g or more and solid electrolyte particles having ion conductivity.
Graphite particles can reversibly insert and desorb lithium ions, and function as a negative electrode active material. Natural graphite and / or artificial graphite etc. are used for the graphite.
　黒鉛粒子は、黒鉛を含むコアと、コアを被覆する炭素材料を含む層とを有する被覆粒子であってもよい。コアを被覆する層に含まれる炭素材料としては、ハードカーボン、および／または非晶質炭素などが挙げられる。このような被覆粒子のうち、黒鉛のコアと、コアを被覆する非晶質炭素層とを有するものが好ましい。なお、このような炭素材料のｄ002は、０．３４０ｎｍ以下であることが好ましい。このような被覆粒子を用いる場合、非晶質炭素の有する高いイオンの受け入れ性により、高い放電効率やサイクル特性を確保することができる。また、このような被覆粒子は、通常は、固体電解質粒子とのなじみが悪いが、比表面積を大きく（３．５ｍ2／ｇ以上に）することで、負極合材層における黒鉛粒子および固体電解質粒子の分散性を高めることができる。 The graphite particles may be coated particles having a core containing graphite and a layer containing a carbon material coating the core. Examples of the carbon material contained in the layer covering the core include hard carbon and / or amorphous carbon. Among such coated particles, one having a graphite core and an amorphous carbon layer coating the core is preferable. In addition, it is preferable that d 002 of such a carbon material is 0.340 nm or less. When such coated particles are used, high discharge efficiency and cycle characteristics can be ensured by the high ion acceptance of amorphous carbon. Moreover, such coated particles are usually incompatible with solid electrolyte particles, but the graphite particles and solid electrolyte in the negative electrode mixture layer can be increased by increasing the specific surface area (to 3.5 m 2 / g or more). The dispersibility of the particles can be enhanced.
　黒鉛粒子の比表面積は、３．５ｍ2／ｇ以上であればよく、３．８ｍ2／ｇ以上であることが好ましく、３．９ｍ2／ｇ以上であることがさらに好ましい。黒鉛粒子の比表面積の上限は、例えば、１０ｍ2／ｇ以下であり、６ｍ2／ｇ以下であることが好ましく、５ｍ2／ｇ以下または４．８ｍ2／ｇ以下がさらに好ましい。これらの下限値と上限値とは任意に組み合わせることができる。黒鉛粒子の比表面積がこのような範囲であることで、負極合材層中の黒鉛粒子の含有量が７０質量％以上であるにも拘わらず、負極合材層中に黒鉛粒子および固体電解質粒子をより均一に分散させることができる。その結果、黒鉛粒子の利用率が高まり、高容量が得られるとともに、充放電後の容量維持率の低下を抑制できる。 The specific surface area of the graphite particles may be 3.5 m 2 / g or more, preferably 3.8 m 2 / g or more, and more preferably 3.9 m 2 / g or more. The upper limit of the specific surface area of the graphite particles is, for example, 10 m 2 / g or less, preferably 6 m 2 / g or less, and more preferably 5 m 2 / g or less or 4.8 m 2 / g or less. These lower limit value and upper limit value can be arbitrarily combined. Although the specific surface area of the graphite particles is in such a range, the graphite particles and the solid electrolyte particles in the negative electrode mixture layer are in spite of the fact that the content of the graphite particles in the negative electrode mixture layer is 70% by mass or more. Can be dispersed more uniformly. As a result, the utilization of the graphite particles is increased, a high capacity can be obtained, and a decrease in capacity retention after charge and discharge can be suppressed.
　このような比表面積を有する黒鉛粒子は、原料となる黒鉛粒子の表面を粗面化することにより得ることができる。原料となる黒鉛粒子の粗面化は、黒鉛粒子の表面を粗面化することができる方法により行えばよく、例えば、賦活処理、プラズマ処理などにより行うことができるが、これらに限定されるものではない。また、複数の処理を組み合わせて粗面化を行ってもよい。賦活処理としては、例えば、水蒸気賦活、アルカリ賦活などの薬品賦活などが挙げられる。賦活処理は、公知の手順で行なうことができる。比表面積が上記の範囲となるように、賦活処理の条件を調節すればよい。 Graphite particles having such a specific surface area can be obtained by roughening the surface of the graphite particles as a raw material. Roughening of the graphite particles as a raw material may be performed by a method capable of roughening the surface of the graphite particles, and can be performed by, for example, activation treatment, plasma treatment, etc., but is limited thereto is not. In addition, roughening may be performed by combining a plurality of treatments. Examples of the activation treatment include chemical activation such as steam activation and alkali activation. The activation treatment can be performed by a known procedure. The conditions of the activation treatment may be adjusted so that the specific surface area falls within the above range.
　黒鉛粒子の平均アスペクト比は、例えば、３以下であり、２．５以下であることが好ましく、２以下であることがさらに好ましい。平均アスペクト比がこのような範囲である黒鉛粒子は、一般に、固体電解質粒子とのなじみが悪い。それに対し、本実施形態では、黒鉛粒子の比表面積が上記の範囲であるため、固体電解質粒子とのなじみがよくなり、負極合材層における黒鉛粒子の含有量を７０質量％以上に多くしても、黒鉛粒子および固体電解質粒子の分散性を高めることができる。なお、黒鉛粒子の平均アスペクト比は、１以上であることが好ましい。 The average aspect ratio of the graphite particles is, for example, 3 or less, preferably 2.5 or less, and more preferably 2 or less. Graphite particles having an average aspect ratio in such a range generally have poor compatibility with solid electrolyte particles. On the other hand, in the present embodiment, since the specific surface area of the graphite particles is within the above range, the compatibility with the solid electrolyte particles is improved, and the content of the graphite particles in the negative electrode mixture layer is increased to 70% by mass or more. Also, the dispersibility of the graphite particles and the solid electrolyte particles can be enhanced. The average aspect ratio of the graphite particles is preferably 1 or more.
　黒鉛粒子の平均粒子径は、例えば、１μｍ以上５０μｍ以下であり、３μｍ以上３０μｍ以下であることが好ましく、５μｍ以下２０μｍ以下であることがさらに好ましい。平均粒子径がこのような範囲である場合、負極合材層における黒鉛粒子と固体電解質粒子の分散性を高め易い。また、黒鉛粒子の平均粒子径は、固体電解質粒子の平均粒子径よりも大きいことが好ましい。この場合、黒鉛粒子間に固体電解質粒子が分布し易くなり、黒鉛粒子の凝集を抑制し易くなる。 The average particle diameter of the graphite particles is, for example, 1 μm to 50 μm, preferably 3 μm to 30 μm, and more preferably 5 μm to 20 μm. When the average particle diameter is in such a range, the dispersibility of the graphite particles and the solid electrolyte particles in the negative electrode mixture layer can be easily improved. The average particle size of the graphite particles is preferably larger than the average particle size of the solid electrolyte particles. In this case, solid electrolyte particles are easily distributed among the graphite particles, and aggregation of the graphite particles is easily suppressed.
　本明細書中、平均粒子径とは、レーザー回折式粒度分布測定装置を用いて測定される体積基準の粒度分布におけるメディアン径（Ｄ50）である。
　なお、全固体電池から取り出した負極について黒鉛粒子の平均粒子径を求める場合には、負極合材層の断面の電子顕微鏡写真において、任意に選択した複数（例えば、１０個）の黒鉛粒子の断面の直径を求め、平均化することにより求めた値を平均粒子径とすることができる。黒鉛粒子の断面の形状が円形でない場合には、断面の面積と同じ面積を有する円（相当円）の直径を黒鉛粒子の断面の直径とすればよい。 In the present specification, the average particle size is a median diameter (D 50 ) in a volume-based particle size distribution measured using a laser diffraction type particle size distribution measuring apparatus.
When the average particle diameter of the graphite particles is determined for the negative electrode taken out of the all solid battery, the cross section of a plurality of (for example, 10) graphite particles arbitrarily selected in the electron micrograph of the cross section of the negative electrode mixture layer The average particle diameter can be determined by calculating the average diameter of the particles. If the shape of the cross section of the graphite particle is not circular, the diameter of a circle (equivalent circle) having the same area as the area of the cross section may be taken as the diameter of the cross section of the graphite particle.
　負極合材層中の黒鉛粒子の含有量は、７０質量％以上であり、７５質量％以上であることが好ましく、７８質量％以上であることがさらに好ましい。負極合材層中の黒鉛粒子の含有量は、９０質量％以下であり、８５質量％以下であることが好ましい。これらの下限値と上限値とは任意に組み合わせることができる。黒鉛粒子の比表面積が上記の範囲であることで、黒鉛粒子の含有量がこのように多くても、負極合材層中の黒鉛粒子および固体電解質粒子の高い分散性を確保することができ、黒鉛粒子の利用率を高めることができるため、高容量が得られる。また、充放電後の容量維持率の低下を抑制することができる。 The content of the graphite particles in the negative electrode mixture layer is 70% by mass or more, preferably 75% by mass or more, and more preferably 78% by mass or more. The content of the graphite particles in the negative electrode mixture layer is 90% by mass or less, and preferably 85% by mass or less. These lower limit value and upper limit value can be arbitrarily combined. When the specific surface area of the graphite particles is in the above range, high dispersibility of the graphite particles and the solid electrolyte particles in the negative electrode composite material layer can be ensured even if the content of the graphite particles is thus large. Since the utilization of graphite particles can be increased, a high capacity can be obtained. Moreover, the fall of the capacity | capacitance maintenance factor after charging / discharging can be suppressed.
　負極合材層に含まれる固体電解質粒子としては、全固体電池に応じたイオン伝導性を示す限り、特に制限されないが、例えば、全固体電池で固体電解質層に使用されるような固体電解質粒子が使用できる。固体電解質としては、例えば、無機固体電解質が好ましく、中でも、硫化物、水素化物が好ましい。固体電解質の結晶状態は、特に制限されず、結晶性および非晶質のいずれであってもよい。 The solid electrolyte particles contained in the negative electrode mixture layer are not particularly limited as long as they exhibit ion conductivity corresponding to the all solid battery, but for example, solid electrolyte particles as used for the solid electrolyte layer in all solid batteries It can be used. As a solid electrolyte, for example, an inorganic solid electrolyte is preferable, and in particular, a sulfide and a hydride are preferable. The crystalline state of the solid electrolyte is not particularly limited, and may be either crystalline or amorphous.
　硫化物の具体例としては、Ｌｉ2Ｓ－ＳｉＳ2、Ｌｉ2Ｓ－Ｐ2Ｓ5、Ｌｉ2Ｓ－ＧｅＳ2、Ｌｉ2Ｓ－Ｂ2Ｓ3、Ｌｉ2Ｓ－Ｇａ2Ｓ3、Ｌｉ2Ｓ－Ａｌ2Ｓ3、Ｌｉ2Ｓ－ＧｅＳ2－Ｐ2Ｓ5、Ｌｉ2Ｓ－Ａｌ2Ｓ3－Ｐ2Ｓ5、Ｌｉ2Ｓ－Ｐ2Ｓ3、Ｌｉ2Ｓ－Ｐ2Ｓ3－Ｐ2Ｓ5、ＬｉＸ－Ｌｉ2Ｓ－Ｐ2Ｓ5、ＬｉＸ－Ｌｉ2Ｓ－ＳｉＳ2、ＬｉＸ－Ｌｉ2Ｓ－Ｂ2Ｓ3（Ｘ：Ｉ、Ｂｒ、またはＣｌ）などが挙げられる。これらのうち、黒鉛粒子となじみ易い観点から、ＬｉおよびＰを含む硫化物が好ましい。 Specific examples of the sulfide include Li 2 S-SiS 2 , Li 2 S-P 2 S 5 , Li 2 S-GeS 2 , Li 2 S-B 2 S 3 , Li 2 S-Ga 2 S 3 , Li 2 S-Al 2 S 3 , Li 2 S-GeS 2 -P 2 S 5 , Li 2 S-Al 2 S 3 -P 2 S 5 , Li 2 S-P 2 S 3 , Li 2 S-P 2 S 3- P 2 S 5 , LiX-Li 2 S-P 2 S 5 , LiX-Li 2 S-SiS 2 , LiX-Li 2 S-B 2 S 3 (X: I, Br, or Cl) and the like Be Among these, sulfides containing Li and P are preferable from the viewpoint of being compatible with the graphite particles.
　水素化物としては、例えば、水素化ホウ素リチウムの錯体水素化物などが挙げられる。錯体水素化物の具体例としては、ＬｉＢＨ4－ＬｉＩ系錯体水素化物、ＬｉＢＨ4－ＬｉＮＨ2系錯体水素化物、ＬｉＢＨ4－Ｐ2Ｓ5、およびＬｉＢＨ4－Ｐ2Ｉ4などが挙げられる。
　負極合材層は、これらの固体電解質を、一種含んでもよく、二種以上組み合わせて含んでもよい。 As a hydride, the complex hydride of lithium borohydride etc. are mentioned, for example. Specific examples of the complex hydrides, LiBH 4 -LiI-based complex hydrides, LiBH 4 -LiNH 2 based complex hydrides, LiBH 4 -P 2 S 5, and LiBH 4 etc. -P 2 I 4 can be cited.
The negative electrode mixture layer may contain one of these solid electrolytes or may contain two or more of these solid electrolytes in combination.
　固体電解質粒子の平均粒子径は、例えば、１μｍ以上５０μｍ以下であり、１μｍ以上２０μｍ以下であることが好ましく、１μｍ以上１０μｍ以下または１μｍ以上５μｍ以下であることがさらに好ましい。固体電解質粒子の平均粒子径がこのような範囲である場合、黒鉛粒子および固体電解質粒子の分散性を高め易い。全固体電池から取り出した負極について固体電解質粒子の平均粒子径を求める場合には、黒鉛粒子の場合に準じて求めることができる。 The average particle diameter of the solid electrolyte particles is, for example, 1 μm to 50 μm, preferably 1 μm to 20 μm, and more preferably 1 μm to 10 μm or 1 μm to 5 μm. When the average particle size of the solid electrolyte particles is in such a range, the dispersibility of the graphite particles and the solid electrolyte particles can be easily improved. When the average particle size of the solid electrolyte particles is determined for the negative electrode taken out of the all solid battery, it can be determined according to the case of the graphite particles.
　上述のように、負極は、有機残渣を含まないか、含む場合でも、その含有量は少ないことが好ましい。このような負極の負極合材層は、上述のように充填率が高く、例えば、９５％以上の充填率を有することが好ましい。このような負極の負極合材層は、乾式法により負極合材を調製し、負極合材を圧縮成形することにより形成することができる。乾式法では、特に、負極合材層における黒鉛粒子および固体電解質粒子の分散性を高めることが難しい。しかし、本実施形態では、黒鉛粒子の比表面積を上記のような範囲に制御することで、乾式法を利用して負極合材層を形成する場合でも、黒鉛粒子および固体電解質粒子の分散性を高めることができ、利用率を向上できる。 As described above, it is preferable that the negative electrode does not contain the organic residue or has a small content even if it contains the organic residue. As described above, such a negative electrode mixture layer of the negative electrode preferably has a high filling rate, for example, a filling rate of 95% or more. Such a negative electrode mixture layer of the negative electrode can be formed by preparing a negative electrode mixture by a dry method and compressing and molding the negative electrode mixture. In the dry method, in particular, it is difficult to improve the dispersibility of the graphite particles and the solid electrolyte particles in the negative electrode mixture layer. However, in the present embodiment, by controlling the specific surface area of the graphite particles in the above range, the dispersibility of the graphite particles and the solid electrolyte particles can be improved even when the negative electrode mixture layer is formed using the dry method. It can be increased and the utilization rate can be improved.
　負極は、負極集電体と、負極集電体に担持された負極合材層とを含んでもよい。負極集電体の形態としては、例えば、金属箔、板状体、粉体の集合体などが挙げられ、負極集電体の材質を成膜したものを用いてもよい。金属箔は、電解箔、エッチド箔などであってもよい。負極集電体は、負極合材層を形成する際に、波打ったり、破れたりしない強度を有するものが望ましい。 The negative electrode may include a negative electrode current collector and a negative electrode mixture layer carried on the negative electrode current collector. Examples of the form of the negative electrode current collector include a metal foil, a plate-like body, an aggregate of powder, and the like, and a film of a material of the negative electrode current collector may be used. The metal foil may be an electrolytic foil, an etched foil or the like. It is desirable that the negative electrode current collector has a strength that does not corrugate or break when forming the negative electrode mixture layer.
　負極集電体の材質としては、負極の酸化還元電位において安定な材質、例えば、銅、ニッケル、ステンレス鋼、チタン、これらの合金などが挙げられる。例えば、全固体電池では、リチウムと合金化しない材質が負極集電体に利用される。負極集電体の厚みは、１０μｍ以上５０μｍ以下であることが好ましい。
　負極の厚みは、例えば、５０μｍ以上２００μｍ以下である。 Examples of the material of the negative electrode current collector include materials which are stable at the redox potential of the negative electrode, such as copper, nickel, stainless steel, titanium, and alloys thereof. For example, in the all solid battery, a material not alloyed with lithium is used for the negative electrode current collector. The thickness of the negative electrode current collector is preferably 10 μm or more and 50 μm or less.
The thickness of the negative electrode is, for example, 50 μm or more and 200 μm or less.
　本実施形態に係る全固体電池は、上記の負極と、正極と、負極および正極の間に介在するイオン伝導性の固体電解質層とを含む。全固体電池の構成要素のうち、負極以外のものについて説明する。 The all-solid battery according to the present embodiment includes the above-described negative electrode, a positive electrode, and an ion conductive solid electrolyte layer interposed between the negative electrode and the positive electrode. Among components of the all-solid-state battery, those other than the negative electrode will be described.
（正極）
　正極は、正極活物質を含んでいればよく、正極活物質に加え、全固体電池で正極に使用される公知の成分を含んでもよい。正極におけるイオン伝導性を高める観点から、正極は、正極活物質とともに、イオン伝導性を示す固体電解質を含むことが好ましい。 (Positive electrode)
The positive electrode only needs to contain a positive electrode active material, and may contain, in addition to the positive electrode active material, known components used for the positive electrode in an all solid battery. From the viewpoint of enhancing the ion conductivity in the positive electrode, the positive electrode preferably contains a solid electrolyte exhibiting ion conductivity together with the positive electrode active material.
　正極活物質としては、全固体電池において、正極活物質として使用されるものを特に制限なく用いることができる。全固体リチウムイオン電池で使用される正極活物質を例に挙げると、例えば、酸化物が挙げられる。酸化物としては、コバルト、ニッケル、および／またはマンガンなどを含むリチウム含有酸化物［例えば、コバルト酸リチウム（ＬｉＣｏＯ2）、ニッケル酸リチウム（ＬｉＮｉＯ2）、マンガン酸リチウム（スピネル型マンガン酸リチウム（ＬｉＭｎ2Ｏ4など）、ニッケルコバルトマンガン酸リチウムなど）、ＬｉＮｉ0.8Ｃｏ0.15Ａｌ0.05Ｏ2など］、Ｌｉ過剰の複合酸化物（Ｌｉ2ＭｎＯ3－ＬｉＭＯ2）などが挙げられる。正極活物質としては、酸化物以外の化合物も使用できる。酸化物以外の化合物としては、例えば、オリビン系化合物（ＬｉＭＰＯ4）、イオウ含有化合物（Ｌｉ2Ｓなど）などが挙げられる。なお、上記式中、Ｍは遷移金属を示す。 As a positive electrode active material, what is used as a positive electrode active material in an all-solid-state battery can be used without particular limitation. When the positive electrode active material used by an all-solid-state lithium ion battery is mentioned as an example, an oxide is mentioned, for example. Examples of oxides include lithium-containing oxides containing cobalt, nickel, and / or manganese etc. [eg, lithium cobaltate (LiCoO 2 ), lithium nickelate (LiNiO 2 ), lithium manganate (spinel type lithium manganate (LiMn) 2 O 4 and the like), nickel cobalt lithium manganese oxide and the like), LiNi 0.8 Co 0.15 Al 0.05 O 2 and the like], Li-excess composite oxides (Li 2 MnO 3 -LiMO 2 ) and the like. As the positive electrode active material, compounds other than oxides can also be used. As the compound other than an oxide, e.g., olivine compounds (LiMPO 4), sulfur-containing compounds (Li 2 S, etc.) and the like. In the above formulae, M represents a transition metal.
　正極活物質は、一種を単独でまたは二種以上を組み合わせて使用できる。
　高容量が得られ易い観点からは、Ｃｏ、ＮｉおよびＭｎからなる群より選択される少なくとも一種を含むリチウム含有酸化物が好ましい。リチウム含有酸化物は、さらにＡｌなどの典型金属元素を含んでもよい。Ａｌを含むリチウム含有酸化物としては、例えば、アルミニウム含有ニッケルコバルト酸リチウムなどが挙げられる。正極活物質のうち、ＬｉＮｉ0.8Ｃｏ0.15Ａｌ0.05Ｏ2、ＬｉＣｏＯ2、ＬｉＮｉ1/3Ｃｏ1/3Ｍｎ1/3Ｏ2などが好ましい。 The positive electrode active materials can be used singly or in combination of two or more.
From the viewpoint of easily obtaining a high capacity, a lithium-containing oxide containing at least one selected from the group consisting of Co, Ni and Mn is preferable. The lithium-containing oxide may further contain a typical metal element such as Al. As a lithium containing oxide containing Al, aluminum containing nickel lithium cobaltate etc. are mentioned, for example. Among the positive electrode active materials, LiNi 0.8 Co 0.15 Al 0.05 O 2 , LiCoO 2 , LiNi 1/3 Co 1/3 Mn 1/3 O 2 and the like are preferable.
　また、正極活物質粒子を金属酸化物で被覆した被覆粒子を、正極に用いてもよい。金属酸化物は、正極活物質粒子と固体電解質粒子との界面において元素の拡散を抑制する作用を有するものであればよく、複合酸化物であってもよい。金属酸化物としては、Ｌｉ伝導性の複合酸化物（Ｌｉ4Ｔｉ5Ｏ12、ＬｉＮｂＯ3、Ｌｉ2ＺｒＯ3など）、Ａｌ2Ｏ3、ＺｒＯ2などが挙げられる。 In addition, coated particles in which positive electrode active material particles are coated with a metal oxide may be used for the positive electrode. The metal oxide may be any complex oxide as long as it has the function of suppressing the diffusion of elements at the interface between the positive electrode active material particles and the solid electrolyte particles. As the metal oxide, (such as Li 4 Ti 5 O 12, LiNbO 3, Li 2 ZrO 3) Li conductivity of the composite oxide, Al 2 O 3, ZrO 2 or the like can be mentioned.
　正極活物質の平均粒子径は、例えば、１μｍ以上２０μｍ以下であり、３μｍ以上１５μｍ以下であることが好ましい。 The average particle diameter of the positive electrode active material is, for example, 1 μm or more and 20 μm or less, and preferably 3 μm or more and 15 μm or less.
　固体電解質としては、全固体電池に応じたイオン伝導性を示す限り、特に制限されない。固体電解質は、例えば、負極合材層について例示した固体電解質から選択できる。硫化物および／または水素化物が好ましい。正極に含まれる固体電解質と、負極合材層に含まれる固体電解質層とは同じであってもよく、異なっていてもよい。 The solid electrolyte is not particularly limited as long as it exhibits ion conductivity according to the all-solid-state battery. The solid electrolyte can be selected, for example, from the solid electrolytes exemplified for the negative electrode mixture layer. Sulfides and / or hydrides are preferred. The solid electrolyte contained in the positive electrode and the solid electrolyte layer contained in the negative electrode mixture layer may be the same or different.
　正極活物質と固体電解質との総量に占める固体電解質の割合は、特に制限されないが、正極の高いイオン伝導性を確保し易い観点からは、例えば、５質量％以上５０質量％以下である。 The ratio of the solid electrolyte to the total amount of the positive electrode active material and the solid electrolyte is not particularly limited, but is, for example, 5% by mass or more and 50% by mass or less from the viewpoint of easily securing high ion conductivity of the positive electrode.
　正極は、正極集電体と、正極集電体に担持された正極活物質または正極合材とを含んでもよい。正極合材とは、正極活物質および固体電解質を含む混合物である。
　正極集電体としては、全固体電池の正極集電体として使用されるものであれば特に制限なく使用することができる。このような正極集電体の形態としては、負極集電体について記載したものから選択すればよい。 The positive electrode may include a positive electrode current collector and a positive electrode active material or a positive electrode mixture carried on the positive electrode current collector. The positive electrode mixture is a mixture containing a positive electrode active material and a solid electrolyte.
The positive electrode current collector can be used without particular limitation as long as it is used as a positive electrode current collector of an all solid battery. The form of such a positive electrode current collector may be selected from those described for the negative electrode current collector.
　正極集電体の材質としては、正極の酸化還元電位において安定な材質、例えば、アルミニウム、マグネシウム、ステンレス鋼、チタン、鉄、コバルト、亜鉛、スズ、またはこれらの合金などが例示される。例えば、全固体リチウムイオン電池では、リチウムと合金化しない材質が正極集電体に利用される。
　正極集電体の厚みは、例えば、５μｍ以上３００μｍ以下の範囲から適宜選択できる。
　正極の厚みは、例えば、５０μｍ以上２００μｍ以下である。 Examples of the material of the positive electrode current collector include materials that are stable at the redox potential of the positive electrode, such as aluminum, magnesium, stainless steel, titanium, iron, cobalt, zinc, tin, or an alloy of these. For example, in the all solid lithium ion battery, a material which is not alloyed with lithium is used for the positive electrode current collector.
The thickness of the positive electrode current collector can be appropriately selected, for example, from the range of 5 μm to 300 μm.
The thickness of the positive electrode is, for example, 50 μm or more and 200 μm or less.
（固体電解質層）
　負極と正極との間に介在する固体電解質層は、固体電解質を含む。固体電解質層は、固体電解質を成膜し、加圧することにより形成できる。固体電解質の成膜は、公知の手順で行なうことができるが、高いイオン伝導性を確保し易い観点からは、乾式法が好ましく、成膜の際に樹脂などのバインダや分散媒を用いないことが好ましい。 (Solid electrolyte layer)
The solid electrolyte layer interposed between the negative electrode and the positive electrode includes a solid electrolyte. The solid electrolyte layer can be formed by depositing a solid electrolyte and pressurizing it. The film formation of the solid electrolyte can be performed by a known procedure, but from the viewpoint of easily securing high ion conductivity, the dry method is preferable, and no binder or dispersion medium such as resin is used in film formation. Is preferred.
　固体電解質としては、負極合材層について例示した固体電解質が挙げられ、硫化物および／または水素化物が好ましい。
　使用する固体電解質は、正極および／または負極とで同じであってもよく、いずれの電極とも異なっていてもよい。 As a solid electrolyte, the solid electrolyte illustrated about the negative electrode compound material layer is mentioned, A sulfide and / or a hydride are preferable.
The solid electrolyte used may be the same for the positive electrode and / or the negative electrode, or may be different from any of the electrodes.
　固体電解質層には、必要に応じて、全固体電池の固体電解質層に用いられる公知の添加剤を添加してもよい。固体電解質層において高いイオン伝導性を確保する観点から、固体電解質層は、負極合材層の場合と同様に、分散媒やバインダなどの有機成分を用いずに作製することが好ましい。
　固体電解質層の厚みは、例えば、２０μｍ以上２００μｍ以下である。 If necessary, known additives used for the solid electrolyte layer of the all solid battery may be added to the solid electrolyte layer. From the viewpoint of securing high ion conductivity in the solid electrolyte layer, the solid electrolyte layer is preferably produced without using an organic component such as a dispersion medium or a binder as in the case of the negative electrode mixture layer.
The thickness of the solid electrolyte layer is, for example, 20 μm or more and 200 μm or less.
　図１は、本実施形態に係る全固体電池に含まれる電極群を概略的に示す縦断面図である。全固体電池が備える電極群１は、正極２と、負極４と、これらの間に介在する固体電解質層３とを備える。正極２は、正極集電体２ｂとこれに担持された正極合材層２ａとを備える。負極４は、負極集電体４ｂとこれに担持された負極合材層４ａとを備える。正極２と負極４とは、正極合材層２ａと負極合材層４ａとが対向するように配置される。正極合材層２ａと負極合材層４ａとの間に、固体電解質層３が配置されている。正極２、固体電解質層３、および負極４は、固体電解質を含む。 FIG. 1 is a longitudinal sectional view schematically showing an electrode group included in the all solid state battery according to the present embodiment. An electrode group 1 included in the all solid battery includes a positive electrode 2, a negative electrode 4, and a solid electrolyte layer 3 interposed therebetween. The positive electrode 2 includes a positive electrode current collector 2 b and a positive electrode mixture layer 2 a supported thereon. The negative electrode 4 includes a negative electrode current collector 4 b and a negative electrode mixture layer 4 a supported thereon. The positive electrode 2 and the negative electrode 4 are disposed such that the positive electrode mixture layer 2a and the negative electrode mixture layer 4a face each other. The solid electrolyte layer 3 is disposed between the positive electrode mixture layer 2a and the negative electrode mixture layer 4a. The positive electrode 2, the solid electrolyte layer 3, and the negative electrode 4 include a solid electrolyte.
　図１の正極合材層２ａと負極合材層４ａと固体電解質層３とはほぼ同じサイズの円盤状であり、固体電解質層３を間に挟持した状態で積層され、円柱状の積層体６を形成している。積層体６の側面には、負極合材層４ａの側面および固体電解質層３の負極合材層４ａ側の側面を覆うように、絶縁体５が装着されている。正極集電体２ｂおよび負極集電体４ｂは、正極合材層２ａおよび負極合材層４ａよりもサイズが大きな円状または多角形状（四角形など）の金属箔である。正極集電体２ｂおよび負極集電体４ｂは、絶縁体５を装着した状態の積層体６とほぼ同じサイズとなるように形成されている。 The positive electrode mixture layer 2a, the negative electrode mixture layer 4a, and the solid electrolyte layer 3 in FIG. 1 have a disk shape of substantially the same size, and are stacked in a state in which the solid electrolyte layer 3 is sandwiched therebetween. Form. The insulator 5 is mounted on the side surface of the laminate 6 so as to cover the side surface of the negative electrode mixture layer 4 a and the side surface of the solid electrolyte layer 3 on the negative electrode mixture layer 4 a side. The positive electrode current collector 2b and the negative electrode current collector 4b are circular or polygonal (such as square) metal foils that are larger in size than the positive electrode mixture layer 2a and the negative electrode mixture layer 4a. The positive electrode current collector 2 b and the negative electrode current collector 4 b are formed to have substantially the same size as the laminate 6 in a state in which the insulator 5 is mounted.
　全固体電池は、図１に示す例に限らず、丸型、円筒型、角型、薄層フラット型などの様々なタイプであってもよい。電極群は、複数の正極および／または複数の負極を含んでもよい。 The all-solid-state battery is not limited to the example shown in FIG. 1, and may be various types such as round, cylindrical, square, thin flat, and the like. The electrode group may include a plurality of positive electrodes and / or a plurality of negative electrodes.
　本実施形態に係る全固体電池としては、全固体リチウムイオン電池、全固体ナトリウムイオン電池などの全固体アルカリ金属イオン電池；全固体アルカリ土類金属電池などの全固体多価イオン電池などが挙げられる。 Examples of the all-solid battery according to the present embodiment include all-solid alkali metal ion batteries such as all-solid lithium ion batteries and all-solid sodium ion batteries; all-solid polyion batteries such as all-solid alkaline earth metal batteries .
　本実施形態に係る全固体電池は、例えば、電極群を形成する工程と、電極群を加圧する工程とを備える製造方法により形成できる。以下に各工程について説明する。 The all-solid-state battery according to the present embodiment can be formed, for example, by a manufacturing method including a step of forming an electrode group and a step of pressing the electrode group. Each process will be described below.
（電極群を形成する工程）
　本工程では、正極、固体電解質層、および負極を積層することにより電極群を形成できる。各電極および固体電解質層は、それぞれ、乾式法により形成することが好ましい。また、各電極と固体電解質層とはいずれを先に形成してもよい。例えば、正極および負極のいずれか一方の電極の主面に、固体電解質層を形成し、形成した固体電解質層の主面（一方の電極とは反対側の主面）に、他方の電極を形成してもよい。また、正極および負極をそれぞれ形成し、これらの間に固体電解質を充填し、加圧することにより、電極群を形成してもよい。固体電解質層を先に形成し、一方の主面に一方の電極を形成し、他方の主面に他方の電極を形成してもよい。 (Step of forming an electrode group)
In this step, the electrode group can be formed by laminating the positive electrode, the solid electrolyte layer, and the negative electrode. Each of the electrodes and the solid electrolyte layer is preferably formed by a dry method. Further, either of the electrodes and the solid electrolyte layer may be formed first. For example, the solid electrolyte layer is formed on the main surface of one of the positive electrode and the negative electrode, and the other electrode is formed on the main surface of the formed solid electrolyte layer (the main surface opposite to the one electrode) You may Alternatively, the positive electrode and the negative electrode may be respectively formed, and a solid electrolyte may be filled between them to pressurize to form an electrode group. The solid electrolyte layer may be formed first, one electrode may be formed on one main surface, and the other electrode may be formed on the other main surface.
　正極は、例えば、正極活物質または正極合材を成膜し、圧縮成形することにより得ることができる。正極集電体の表面に、正極活物質や正極合材の層を形成することにより正極を形成してもよい。負極は、例えば、黒鉛粒子および固体電解質粒子を含む負極合材と、必要に応じて負極集電体とを用いて、正極の場合に準じて作製できる。圧縮成形する際の圧力は、例えば、１ＭＰａ以上３００ＭＰａ以下であり、１ＭＰａ以上３０ＭＰａ以下であってもよい。特に、成膜した負極合材を、このような圧力で圧縮成形することで、比表面積が大きい黒鉛粒子の表面の凹凸を固体電解質粒子の表面に食い込ませることができる。これにより、黒鉛粒子および固体電解質粒子の分散性がさらに高くなるとともに、粒子間の界面における接触抵抗を低減できる。圧縮成形では、成膜した電極材料に、圧力を１回加えてもよく、複数回加えてもよい。 The positive electrode can be obtained, for example, by forming a film of a positive electrode active material or a positive electrode mixture, and compressing and forming the film. The positive electrode may be formed by forming a layer of a positive electrode active material or a positive electrode mixture on the surface of the positive electrode current collector. The negative electrode can be produced according to the case of a positive electrode, using, for example, a negative electrode composite containing graphite particles and solid electrolyte particles, and, if necessary, a negative electrode current collector. The pressure at the time of compression molding is, for example, 1 MPa or more and 300 MPa or less, and may be 1 MPa or more and 30 MPa or less. In particular, by compressing and molding the formed negative electrode mixture under such pressure, the unevenness of the surface of the graphite particles having a large specific surface area can be cut into the surface of the solid electrolyte particles. As a result, the dispersibility of the graphite particles and the solid electrolyte particles is further enhanced, and the contact resistance at the interface between the particles can be reduced. In compression molding, pressure may be applied once or plural times to the deposited electrode material.
　固体電解質層は、例えば、上記の固体電解質または上記の固体電解質を含む混合物（例えば、固体電解質と添加剤などとを含む混合物）を乾式法にて成膜し、圧縮成形することにより形成できる。圧縮成形する際の圧力は、例えば、ＩＭＰａ以上３００ＭＰａ以下であり、１ＭＰａ以上１０ＭＰａ以下であってもよい。圧縮成形では、成膜した固体電解質または混合物に、圧力を１回加えてもよく、複数回加えてもよい。 The solid electrolyte layer can be formed, for example, by forming a film of the above-described solid electrolyte or a mixture containing the above-mentioned solid electrolyte (for example, a mixture containing a solid electrolyte and an additive) by a dry method and compression molding. The pressure at the time of compression molding is, for example, I MPa or more and 300 MPa or less, and may be 1 MPa or more and 10 MPa or less. In compression molding, pressure may be applied once or plural times to the formed solid electrolyte or mixture.
　電極群が複数の正極および／または負極と、複数の固体電解質層とを有する場合には、正極および負極の間に固体電解質層が介在するように、電極および固体電解質層を積層すればよい。 When the electrode group includes a plurality of positive electrodes and / or negative electrodes and a plurality of solid electrolyte layers, the electrodes and the solid electrolyte layer may be stacked such that the solid electrolyte layer is interposed between the positive electrodes and the negative electrodes.
（電極群を加圧する工程）
　電極群は、電池ケースに収容されるが、電極群への加圧は、電池ケースに収容する前に行なってもよく、電池ケースに収容した後に行なってもよい。例えば、電池ケースがラミネートフィルムなどである場合には、電極群を電池ケースに収容した後に電池ケース（つまり、電池）ごと電極群を加圧すればよい。 (Step of pressurizing the electrode group)
The electrode group is accommodated in the battery case, but pressurization to the electrode group may be performed before being accommodated in the battery case, or may be performed after being accommodated in the battery case. For example, in the case where the battery case is a laminate film or the like, the electrode group may be accommodated in the battery case and then the electrode group may be pressurized together with the battery case (that is, the battery).
　電極群を加圧する際の圧力は、例えば、１００ＭＰａ以上であり、２００ＭＰａ以上が好ましく、５００ＭＰａ以上または８００ＭＰａ以上であってもよい。このような圧力を電極群（または電池）に加えることで、乾式法で電極や固体電解質層を形成する場合でも、固体電解質粒子間や固体電解質粒子と活物質粒子との間の界面抵抗を低減することができる。電極群を加圧する際の圧力は、例えば、１５００ＭＰａ以下である。なお、電極および／または固体電解質層を形成する際に圧縮成形せずに、電極群をこのような圧力で加圧してもよい。この場合、電極群を作製する際にこのような圧力が電極群に加えられる。加圧は、１回行ってもよく、複数回行ってもよい。 The pressure at the time of pressurizing the electrode group is, for example, 100 MPa or more, preferably 200 MPa or more, and may be 500 MPa or more or 800 MPa or more. By applying such pressure to the electrode group (or battery), even when forming an electrode or a solid electrolyte layer by a dry method, the interfacial resistance between solid electrolyte particles and between solid electrolyte particles and active material particles is reduced. can do. The pressure at the time of pressurizing the electrode group is, for example, 1500 MPa or less. In addition, when forming an electrode and / or a solid electrolyte layer, you may press an electrode group by such pressure, without carrying out compression molding. In this case, such pressure is applied to the electrode group when producing the electrode group. The pressurization may be performed once or plural times.
［実施例］
　以下、本発明を実施例および比較例に基づいて具体的に説明するが、本発明は以下の実施例に限定されるものではない。 [Example]
Hereinafter, the present invention will be specifically described based on examples and comparative examples, but the present invention is not limited to the following examples.
　実施例１
　下記の手順で図１に示す全固体電池を作製した。
（１）全固体電池の組み立て
　（ａ）固体電解質層３の作製
　冷間ダイス鋼（ＳＫＤ）製の円筒金型（内径１０ｍｍ、高さ３０ｍｍ）を立てて設置し、円筒金型の底部に底板となる短ピンを差し込んだ。この状態で、リチウムイオン伝導性の固体電解質であるＬｉ2Ｓ－Ｐ2Ｓ5固溶体９０ｍｇを円筒金型内に層状に充填した。そして、円筒金型の内径に合わせたサイズの円柱状の長ピンを、円筒金型の頂部から内部に差し込み、層の厚み方向に１８８ＭＰａの圧力で１回加圧プレスすることにより、固体電解質層３を作製した。 Example 1
The all solid state battery shown in FIG. 1 was produced in the following procedure.
(1) Assembly of all solid battery (a) Preparation of solid electrolyte layer 3 A cylindrical die (inner diameter 10 mm, height 30 mm) made of cold die steel (SKD) is erected and a bottom plate is placed on the bottom of the cylindrical die. I inserted a short pin. In this state, 90 mg of a Li 2 S—P 2 S 5 solid solution, which is a lithium ion conductive solid electrolyte, was layered in a cylindrical mold. Then, a cylindrical long pin of a size matched to the inner diameter of the cylindrical mold is inserted into the inside from the top of the cylindrical mold and pressed once at a pressure of 188 MPa in the thickness direction of the layer to obtain a solid electrolyte layer 3 was produced.
　（ｂ）負極の作製
　（ｂ－１）黒鉛粒子の準備
　人造黒鉛粉末（Ｄ50：１５μｍ、ＢＥＴ比表面積：２．９ｍ2／ｇ）３．０ｇを、１ｍｏｌ／Ｌ濃度の水酸化カリウム水溶液（１００ｍｌ）に浸漬し、室温で１時間撹拌した。このとき、水酸化カリウムと黒鉛との質量比（＝水酸化カリウム／黒鉛）は、１．９であった。撹拌後の混合物を真空濾過することにより黒鉛を分離し、１２０℃の乾燥機内で一晩乾燥し、溶媒を揮発させた。得られる黒鉛粉末を、窒素雰囲気下、８００℃にて１時間熱処理した。熱処理後の黒鉛粉末を０．１ｍｏｌ／Ｌ濃度の塩水溶液と純水とで、洗浄後の溶液のｐＨが７になるまで、洗浄を行った。洗浄後の黒鉛粒子を、１２０℃にて一晩真空乾燥することにより、黒鉛粒子を得た。得られた黒鉛粒子のＢＥＴ比表面積は、３．９ｍ2／ｇであり、ｄ002は、０．３３７１ｎｍであった。なお、使用した黒鉛粒子は、黒鉛のコアとコアを被覆する非晶質炭素層とを備えるものである。 (B) Preparation of Negative Electrode (b-1) Preparation of Graphite Particles 3.0 g of artificial graphite powder (D 50 : 15 μm, BET specific surface area: 2.9 m 2 / g), 1 mol / L aqueous potassium hydroxide solution ( It was immersed in 100 ml) and stirred at room temperature for 1 hour. At this time, the mass ratio of potassium hydroxide to graphite (= potassium hydroxide / graphite) was 1.9. The graphite after separation was separated by vacuum filtration to separate the graphite, dried overnight in a dryer at 120 ° C., and the solvent was evaporated. The obtained graphite powder was heat-treated at 800 ° C. for 1 hour in a nitrogen atmosphere. The heat-treated graphite powder was washed with a 0.1 mol / L aqueous salt solution and pure water until the pH of the solution after washing became 7. Graphite particles were obtained by vacuum drying the washed graphite particles at 120 ° C. overnight. The BET specific surface area of the obtained graphite particles was 3.9 m 2 / g, and d 002 was 0.3371 nm. In addition, the used graphite particle is provided with the core of graphite and the amorphous carbon layer which coats a core.
　（ｂ－２）負極合材層４ａの作製
　上記（１－１）で準備した黒鉛粒子と固体電解質粒子（Ｌｉ2Ｓ－Ｐ2Ｓ5固溶体、Ｄ50：８．２μｍ）とを、８：２の質量比で用いて、乳鉢内で十分に混合した。得られた混合物１３．５ｍｇを、（ａ）で作製した、円筒金型内の固体電解質層３上に層状に充填した。そして、層の厚み方向に、３回加圧プレスすることにより、負極合材層４ａを作製した。加圧プレスの圧力は、毎回１８８ＭＰａとした。 (B-2) Preparation of Negative Electrode Mixture Layer 4a The graphite particles and solid electrolyte particles (Li 2 S—P 2 S 5 solid solution, D 50 : 8.2 μm) prepared in the above (1-1) are prepared by the following procedure 8: Used at a mass ratio of 2 and mixed thoroughly in a mortar. 13.5 mg of the obtained mixture was layeredly loaded on the solid electrolyte layer 3 in the cylindrical mold produced in (a). Then, in the thickness direction of the layer, the negative electrode mixture layer 4a was manufactured by pressing three times. The pressure of the pressure press was 188 MPa each time.
　次いで、円筒金型の上下を反対にして短ピンを取り出し、負極合材層４ａ側に短ピンを差し込み、短ピンが底になるように、円筒金型を配置した。次いで、長ピンを用いて、固体電解質層３および負極合材層４ａを、固体電解質層３側から押圧した。 Next, the short pin was taken out with the top and bottom of the cylindrical mold turned upside down, the short pin was inserted into the negative electrode composite material layer 4a side, and the cylindrical mold was placed so that the short pin was at the bottom. Subsequently, the solid electrolyte layer 3 and the negative electrode mixture layer 4a were pressed from the solid electrolyte layer 3 side using a long pin.
　（ｃ）正極（正極合材層２ａ）の作製
　ＬｉＮｉ0.8Ｃｏ0.15Ａｌ0.05Ｏ2およびＬｉ2Ｓ－Ｐ2Ｓ5固溶体を、７：３の質量比で用いて、乳鉢内で十分に混合することにより混合物を得た。混合物２０ｍｇを、後述の円筒金型内の固体電解質層３上に層状に充填し、層の厚み方向に、それぞれ、３７６ＭＰａ、７５２ＭＰａ、および１０５０ＭＰａの順で３回加圧プレスすることにより、正極（正極合材層２ａ）を作製した。 (C) Preparation of positive electrode (positive electrode mixture layer 2a) LiNi 0.8 Co 0.15 Al 0.05 O 2 and Li 2 S-P 2 S 5 solid solution are thoroughly mixed in a mortar using a mass ratio of 7: 3. To give a mixture. 20 mg of the mixture is layered on solid electrolyte layer 3 in a cylindrical mold described later, and pressed in the order of 376 MPa, 752 MPa, and 1050 MPa in the thickness direction of the layer three times in this order. The positive electrode mixture layer 2a) was produced.
　（ｄ）全固体電池の組み立て
　（ａ）～（ｃ）のようにして形成された正極合材層２ａと負極合材層４ａとで固体電解質層３を挟持した状態の積層体６を、円筒金型から取り出した。負極集電体４ｂとしての銅箔（縦４０ｍｍ×横４０ｍｍ、厚み１００μｍ）の一方の表面上に、中央に孔を有する絶縁体５（内径１１ｍｍ、高さ２００μｍ）を配置した。そして、積層体６（外径１０ｍｍ）を、負極合材層４ａが負極集電体４ｂに接するように、絶縁体５の孔内に収容した。次いで、積層体６の正極合材層２ａ上に、正極集電体２ｂとしてのアルミニウム箔（縦４０ｍｍ×横４０ｍｍ、厚み１５μｍ）を配置することにより電極群１を作製した。なお、絶縁体５は、負極合材層４ａおよび負極集電体４ｂと、正極合材層２ａおよび正極集電体２ｂとの接触を抑制するように配される。 (D) Assembly of All-Solid-State Battery The laminated body 6 in a state in which the solid electrolyte layer 3 is sandwiched between the positive electrode mixture layer 2a and the negative electrode mixture layer 4a formed as in (a) to (c) is a cylinder. I took it out of the mold. On one surface of a copper foil (40 mm long × 40 mm wide, 100 μm thick) as the negative electrode current collector 4 b, an insulator 5 (inner diameter 11 mm, height 200 μm) having a hole at the center was disposed. Then, the laminate 6 (outside diameter 10 mm) was accommodated in the hole of the insulator 5 so that the negative electrode mixture layer 4 a was in contact with the negative electrode current collector 4 b. Subsequently, an electrode group 1 was produced by arranging an aluminum foil (40 mm long × 40 mm wide, 15 μm thickness) as the positive electrode current collector 2 b on the positive electrode mixture layer 2 a of the laminate 6. The insulator 5 is disposed to suppress the contact between the negative electrode mixture layer 4a and the negative electrode current collector 4b, and the positive electrode mixture layer 2a and the positive electrode current collector 2b.
　負極リードおよび正極リードを有するラミネートセルに、電極群１を収容し、セル内のガスを真空ポンプで吸引しながら密封した。このようにして、全固体電池を作製した。 The electrode group 1 was housed in a laminate cell having a negative electrode lead and a positive electrode lead, and the gas in the cell was sealed while being sucked by a vacuum pump. Thus, an all solid state battery was produced.
（２）評価
　全固体電池の充電容量および放電容量を下記の手順で測定した。
　組み立てた全固体電池を、２５℃に設定された恒温槽内に入れて、電池温度を２５℃に維持し、５８．８ＭＰａで加圧した。この状態で、下記の条件で充放電を行なった。 (2) Evaluation The charge capacity and the discharge capacity of all solid state batteries were measured by the following procedure.
The assembled all solid battery was placed in a thermostat set at 25 ° C., the battery temperature was maintained at 25 ° C., and pressure was applied at 58.8 MPa. In this state, charge and discharge were performed under the following conditions.
　１サイクル目：０．０４Ｃの電流で充電終止電圧４．２Ｖまで充電し、次いで、０．０４Ｃの電流で、放電終止電圧２．７Ｖまで放電した。
　２サイクル目：０．０４Ｃの電流で充電終止電圧４．２Ｖまで充電し、次いで、０．７Ｃの電流で、放電終止電圧２．７Ｖまで放電した。
　３サイクル目：０．０４Ｃの電流で充電終止電圧４．２Ｖまで充電し、次いで、３Ｃの電流で、放電終止電圧２．７Ｖまで放電した。
　４サイクル目：０．０４Ｃの電流で充電終止電圧４．２Ｖまで充電し、次いで、４Ｃの電流で、放電終止電圧２．７Ｖまで放電した。 1st cycle: Charged to a charge termination voltage of 4.2 V at a current of 0.04 C, and then discharged to a discharge termination voltage of 2.7 V at a current of 0.04 C.
Second cycle: charge was performed to a charge termination voltage of 4.2 V at a current of 0.04 C, and then discharged to a discharge termination voltage of 2.7 V at a current of 0.7 C.
Third cycle: The battery was charged to a charge termination voltage of 4.2 V at a current of 0.04 C, and then discharged to a discharge termination voltage of 2.7 V at a current of 3 C.
Fourth cycle: The battery was charged to a charge termination voltage of 4.2 V at a current of 0.04 C, and then discharged to a discharge termination voltage of 2.7 V at a current of 4 C.
　１サイクル目の放電容量と、４サイクル目の放電容量とを求め、１サイクル目の放電容量を１００％としたときの４サイクル目の放電容量の比率を容量維持率として評価した。なお、放電容量は、負極合材１ｇあたりの値とした。 The discharge capacity at the first cycle and the discharge capacity at the fourth cycle were determined, and the ratio of the discharge capacity at the fourth cycle when the discharge capacity at the first cycle was 100% was evaluated as the capacity retention ratio. The discharge capacity was a value per 1 g of the negative electrode mixture.
　実施例２
　（ｂ－１）において、水酸化カリウムと黒鉛との質量比（＝水酸化カリウム／黒鉛）が５．７となるように、水酸化カリウム水溶液の濃度を調整したこと以外は、実施例１と同様にして黒鉛粒子を準備した。得られた黒鉛粒子を用いたこと以外は、実施例１と同様にして負極を作製し、全固体電池を組み立て、評価を行なった。 Example 2
In (b-1), the concentration of the aqueous potassium hydroxide solution is adjusted so that the mass ratio of potassium hydroxide to graphite (= potassium hydroxide / graphite) is 5.7, and Graphite particles were prepared in the same manner. A negative electrode was produced in the same manner as in Example 1 except that the obtained graphite particles were used, and an all solid battery was assembled and evaluated.
　実施例３
　（ｂ－１）において、水酸化カリウムと黒鉛との質量比（＝水酸化カリウム／黒鉛）が９．５となるように、水酸化カリウム水溶液の濃度を調整したこと以外は、実施例１と同様にして黒鉛粒子を準備した。得られた黒鉛粒子を用いたこと以外は、実施例１と同様にして負極を作製し、全固体電池を組み立て、評価を行なった。 Example 3
In (b-1), the concentration of the aqueous potassium hydroxide solution is adjusted so that the mass ratio of potassium hydroxide to graphite (= potassium hydroxide / graphite) is 9.5, and Graphite particles were prepared in the same manner. A negative electrode was produced in the same manner as in Example 1 except that the obtained graphite particles were used, and an all solid battery was assembled and evaluated.
　比較例１
　（ｂ－２）において、黒鉛粒子と固体電解質粒子との質量比を６．５：３．５とした。黒鉛粒子としては、実施例３と同じものを用いた。これら以外は、実施例１と同様にして負極を作製し、全固体電池を組み立て、評価を行なった。 Comparative Example 1
In (b-2), the mass ratio of the graphite particles to the solid electrolyte particles is 6.5: 3.5. As a graphite particle, the same one as in Example 3 was used. A negative electrode was produced in the same manner as in Example 1 except for the above, and an all solid battery was assembled and evaluated.
　比較例２
　（ｂ－２）において、黒鉛粒子として、人造黒鉛粉末（Ｄ50：１５μｍ、ＢＥＴ比表面積：２．９ｍ2／ｇ）を用いた。これ以外は、実施例１と同様にして負極を作製し、全固体電池を組み立て、評価を行なった。 Comparative example 2
In (b-2), artificial graphite powder (D 50 : 15 μm, BET specific surface area: 2.9 m 2 / g) was used as the graphite particles. Except for this, a negative electrode was produced in the same manner as in Example 1, and an all solid battery was assembled and evaluated.
　比較例３
　（ｂ－２）において、黒鉛粒子と固体電解質粒子との質量比を６．５：３．５とした。黒鉛粒子としては、比較例２と同じものを用いた。これら以外は、実施例１と同様にして負極を作製し、全固体電池を組み立て、評価を行なった。
　実施例および比較例の結果を表１に示す。表１には、負極合材層に使用した黒鉛粒子の比表面積、および負極合材層における黒鉛粒子の含有量も合わせて示す。 Comparative example 3
In (b-2), the mass ratio of the graphite particles to the solid electrolyte particles is 6.5: 3.5. As a graphite particle, the same one as Comparative Example 2 was used. A negative electrode was produced in the same manner as in Example 1 except for the above, and an all solid battery was assembled and evaluated.
The results of Examples and Comparative Examples are shown in Table 1. Table 1 also shows the specific surface area of the graphite particles used in the negative electrode mixture layer and the content of the graphite particles in the negative electrode mixture layer.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　表１に示されるように、比較例１と比較例３とを対比すると、負極合材層中の黒鉛粒子の含有量が７０質量％未満である場合、４サイクル目の放電容量はいずれも黒鉛粒子の比表面積の大小によらずほとんど変わらない。比表面積が３．５ｍ2／ｇ未満の場合、負極合材層中の黒鉛粒子の含有量が７０質量％以上になっても（比較例２）、４サイクル目の放電容量は、比較例１や比較例３と変わらない。また、比較例２では、７０質量％以上の黒鉛粒子を用いるにも拘わらず、容量維持率が大きく低下する。ところが、負極合材層中の黒鉛粒子の含有量が７０質量％以上の場合に、比表面積が３．５ｍ2／ｇ以上の黒鉛粒子を用いると、４サイクル目の放電容量は、比較例１～３に比べて、大きく向上する（実施例１～３）。また、実施例１～３では、比較例２とは異なり、高い容量維持率を確保することができる。比較例２で４サイクル目の放電容量が低下するのは、黒鉛粒子の比表面積が小さいことで、負極合材中における黒鉛粒子および固体電解質粒子の分散性が低下するとともに、黒鉛粒子と固体電解質粒子との表面の食い込みが少なくなることで、充放電に寄与しない黒鉛粒子の存在が顕在化するためと考えられる。 As shown in Table 1, when Comparative Example 1 and Comparative Example 3 are compared, when the content of the graphite particles in the negative electrode mixture layer is less than 70% by mass, the discharge capacity at the fourth cycle is all graphite. It hardly changes, regardless of the specific surface area of the particles. When the specific surface area is less than 3.5 m 2 / g, even if the content of the graphite particles in the negative electrode mixture layer is 70% by mass or more (Comparative Example 2), the discharge capacity at the fourth cycle is Comparative Example 1 There is no difference with Comparative Example 3. In addition, in Comparative Example 2, the capacity retention rate is significantly reduced despite the use of 70% by mass or more of the graphite particles. However, when the content of the graphite particles in the negative electrode mixture layer is 70% by mass or more and the graphite particles having a specific surface area of 3.5 m 2 / g or more are used, the discharge capacity in the fourth cycle is compared with Comparative Example 1 Compared to the above-mentioned, the improvement is large (Examples 1 to 3). Further, unlike the comparative example 2, the high capacity retention rate can be secured in the first to third embodiments. The discharge capacity at the fourth cycle in Comparative Example 2 decreases because the specific surface area of the graphite particles is small, and the dispersibility of the graphite particles and the solid electrolyte particles in the negative electrode mixture decreases, and the graphite particles and the solid electrolyte It is thought that the presence of the graphite particles which do not contribute to charge and discharge is manifested by the reduction of the bite of the surface with the particles.
　本発明を現時点での好ましい実施態様に関して説明したが、そのような開示を限定的に解釈してはならない。種々の変形および改変は、上記開示を読むことによって本発明に属する技術分野における当業者には間違いなく明らかになるであろう。したがって、添付の請求の範囲は、本発明の真の精神および範囲から逸脱することなく、すべての変形および改変を包含する、と解釈されるべきものである。 While the present invention has been described in terms of the presently preferred embodiments, such disclosure should not be construed as limiting. Various modifications and alterations will no doubt become apparent to those skilled in the art to which the present invention pertains upon reading the foregoing disclosure. Therefore, the appended claims should be construed to include all variations and modifications without departing from the true spirit and scope of the present invention.
　本発明に係る全固体電池は、高容量が求められる様々な用途に有用である。 The all-solid-state battery according to the present invention is useful in various applications where high capacity is required.
　１：電極群、２：正極、２ａ：正極合材層、２ｂ：正極集電体、３：固体電解質層、４：負極、４ａ：負極合材層、４ｂ：負極集電体、５：絶縁体、６：積層体 1: Electrode group, 2: Positive electrode, 2a: Positive electrode mixture layer, 2b: Positive electrode current collector, 3: Solid electrolyte layer, 4: Negative electrode, 4a: Negative electrode mixture layer, 4b: Negative electrode current collector, 5: Insulation Body, 6: stack

Claims (8)

  1. 　黒鉛粒子と、イオン伝導性の固体電解質粒子とを含む負極合材層を備え、
    　前記黒鉛粒子は、３．５ｍ2／ｇ以上の比表面積を有し、
    　前記負極合材層中の前記黒鉛粒子の含有量は、７０質量％以上９０質量％以下である、全固体電池用負極。     A negative electrode mixture layer including graphite particles and ion conductive solid electrolyte particles;
    The graphite particles have a specific surface area of 3.5 m 2 / g or more,
    The negative electrode for an all solid battery, wherein the content of the graphite particles in the negative electrode mixture layer is 70% by mass or more and 90% by mass or less.
  2. 　前記黒鉛粒子の比表面積は、３．８ｍ2／ｇ以上である、請求項１に記載の全固体電池用負極。 The negative electrode for the all solid battery according to claim 1, wherein the specific surface area of the graphite particles is 3.8 m 2 / g or more.
  3. 　前記黒鉛粒子の平均アスペクト比は、２以下である、請求項１または２に記載の全固体電池用負極。 The negative electrode for the all solid battery according to claim 1, wherein an average aspect ratio of the graphite particles is 2 or less.
  4. 　前記黒鉛粒子は、黒鉛のコアと、前記コアを被覆する非晶質炭素層とを有する、請求項１～３のいずれか１項に記載の全固体電池用負極。 The negative electrode for the all solid battery according to any one of claims 1 to 3, wherein the graphite particles have a core of graphite and an amorphous carbon layer covering the core.
  5. 　有機残渣を含まない、請求項１～４のいずれか１項に記載の全固体電池用負極。 The negative electrode for an all solid battery according to any one of claims 1 to 4, which does not contain an organic residue.
  6. 　前記負極合材層の充填率は、９５体積％以上である、請求項１～５のいずれか１項に記載の全固体電池用負極。 The negative electrode for the all solid battery according to any one of claims 1 to 5, wherein a filling rate of the negative electrode mixture layer is 95% by volume or more.
  7. 　前記固体電解質粒子は、硫化物および水素化物からなる群より選択される少なくとも一種を含む、請求項１～６のいずれか１項に記載の全固体電池用負極。 The negative electrode for an all solid battery according to any one of claims 1 to 6, wherein the solid electrolyte particles contain at least one selected from the group consisting of sulfides and hydrides.
  8. 　請求項１～７のいずれか１項に記載の負極と、正極と、前記負極および前記正極の間に介在するイオン伝導性の固体電解質層とを含む、全固体電池。 An all solid battery comprising the negative electrode according to any one of claims 1 to 7, a positive electrode, and an ion conductive solid electrolyte layer interposed between the negative electrode and the positive electrode.
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