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WO2024095810A1 - Negative electrode for secondary battery, secondary battery, and method for producing same - Google Patents

Negative electrode for secondary battery, secondary battery, and method for producing same Download PDF

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Publication number
WO2024095810A1
WO2024095810A1 PCT/JP2023/038216 JP2023038216W WO2024095810A1 WO 2024095810 A1 WO2024095810 A1 WO 2024095810A1 JP 2023038216 W JP2023038216 W JP 2023038216W WO 2024095810 A1 WO2024095810 A1 WO 2024095810A1
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Prior art keywords
secondary battery
graphite
negative electrode
composite layer
silicon particles
Prior art date
Application number
PCT/JP2023/038216
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French (fr)
Japanese (ja)
Inventor
祐輔 久野
和倫 岡野
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京セラ株式会社
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Publication of WO2024095810A1 publication Critical patent/WO2024095810A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1393—Processes of manufacture of 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
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • 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

Definitions

  • This disclosure relates to negative electrodes for secondary batteries, secondary batteries, and methods for manufacturing the same.
  • lithium ion secondary batteries generally use LiCoO2 for the positive electrode and graphite for the negative electrode.
  • graphite negative electrodes have excellent charge/discharge reversibility, their discharge capacity has already reached a value close to the theoretical value of 372 mAh/g, which corresponds to the intercalation compound LiC6 .
  • a negative electrode material with a larger discharge capacity than graphite is needed.
  • Graphite-based carbon materials such as metallic lithium, metallic substances that form alloys with lithium, natural graphite, artificial graphite obtained by graphitizing coke, graphitized mesophase pitch, and graphitized carbon fiber have been considered as negative electrode materials for batteries.
  • metallic lithium has a high discharge capacity as a negative electrode material
  • lithium precipitates in the form of dendrites during charging causing the negative electrode to deteriorate and shortening the charge/discharge cycle.
  • lithium precipitated in the form of dendrites may penetrate the separator and reach the positive electrode, causing a short circuit.
  • Patent Document 1 discloses a method of mixing amorphous carbon and a metallic oxide material to form a composite.
  • Patent Document 2 discloses a method of producing metal-carbon composite particles by firing a mixture of fine powder of a silicon compound, which is a metallic material, graphite, and pitch, which is a carbonaceous material precursor.
  • Patent Document 3 discloses a method of producing metal-graphite particles by attaching metal particles having an average particle size of 1/2 or less of the average particle size of the graphite particles to the surface of graphite particles having an average particle size of 2 to 5 ⁇ m and an aspect ratio of 3 or less, and then heat treating the particles at a high temperature.
  • Patent Document 4 discloses a method of heat treating composite carbon particles containing silicon, which is a metallic material, at a high temperature and blending the particles with a graphite material to provide voids to mitigate the expansion of the metallic material.
  • Patent Documents 1 to 4 has room for further study as follows.
  • a reaction between the metal oxide material and the electrolyte is likely to occur, and there is a concern that the irreversible capacity will increase due to decomposition of the electrolyte.
  • Patent Document 2 With the technology described in Patent Document 2, there is a concern that the expansion and contraction during charging and discharging cannot be adequately controlled, and contact points between particles are likely to separate, resulting in insufficient cycle characteristics.
  • the metal particles are simply attached onto the graphite, and the adhesion is insufficient, so there is a concern that the metal particles may fall off and segregate from the graphite.
  • Patent Document 4 describes that the cycle characteristics can be improved by mixing composite carbon particles containing metallic materials, but the effect of reducing battery swelling (i.e., expansion of the metallic materials) is not sufficient, and there is room for improvement in the cycle characteristics.
  • This disclosure relates to the following:
  • a negative electrode (3) for a secondary battery comprising a current collecting layer (1) and a composite layer (2),
  • the composite layer (2) contains carbon particles (A) and silicon particles (B),
  • the carbon particles (A) contain spherical graphite (A1) and plate-like graphite (A2),
  • the ratio of the proportion of the silicon particles (B) to the proportion of the voids (D) is 1.0:6.0 to 1.0:10.0.
  • [5] The negative electrode for a secondary battery according to any one of [1] to [4], wherein the spherical graphite (A1) has a median diameter (d50) of 10 ⁇ m to 30 ⁇ m, the plate-like graphite (A2) has a median diameter (d50) of 5 ⁇ m to 40 ⁇ m, and the silicon particles (B) have a median diameter (d50) of 1 ⁇ m or less.
  • the plate-like graphite (A2) has a thickness (Z direction) of 1 to 500 nm and a length (X and Y directions) of 5 to 40 ⁇ m.
  • a secondary battery comprising the negative electrode for a secondary battery (3) according to any one of [1] to [6], a positive electrode for a secondary battery (4), and an electrolyte (5).
  • ⁇ Secondary Battery Manufacturing Method> [8] A method for producing a secondary battery according to [7], a step of superposing the composite layer (2) and the current collecting layer (1) to obtain a negative electrode material; The method for producing a secondary battery includes a step of rolling the negative electrode material at a pressure of 1 MPa or more to obtain a negative electrode for a secondary battery (3).
  • FIG. 2 is a schematic cross-sectional view of a composite layer 2 and a current collecting layer 1 that constitute a negative electrode 3 for a secondary battery in one embodiment of the present disclosure.
  • FIG. 1 is an explanatory diagram of a secondary battery according to an embodiment of the present disclosure.
  • a secondary battery negative electrode 3 in one embodiment is configured by laminating a composite layer 2 on a current collecting layer 1 which is a conductive member.
  • the composite layer 2 contains carbon particles (A), silicon particles (B), and a binder (C), and the carbon particles (A) contain spherical graphite (A1) and plate-like graphite (A2). 1, voids (D) are present in the composite layer 2.
  • the ratio of the proportion of silicon particles (B) to the proportion of voids (D) (silicon particles (B):voids (D)) (hereinafter also referred to as "void ratio”) may be 1.0:6.0 to 1.0:10.0, 1.0:6.3 to 1.0:9.7, or 1.0:6.5 to 1.0:9.5.
  • silicon particles (B) As the active material, a high capacity can be achieved.
  • the volume expands to about three times, but in the secondary battery negative electrode 3 of the present disclosure, the voids (D) existing at the above void ratio in the composite layer 2 in which the spherical graphite (A1) and the plate-like graphite (A2) are mixed serve as a cushioning material for the volume change of the silicon particles (B). Therefore, interruption of electrical continuity is less likely to occur, the cycle characteristics are improved, and the cycle characteristics can be stably maintained for a long period of time.
  • the carbon particles (A) contain at least both spherical graphite (A1) and platelet graphite (A2).
  • the spherical graphite (A1) may be any one having a spherical shape, and the specific type and production method are not particularly limited.
  • the shape of the spherical graphite (A1) is not limited to a perfect sphere, and also includes graphite in the form of a pellet, an ellipse, etc. A shape close to a sphere is also acceptable.
  • the aspect ratio of the spherical graphite (A1) may be 1.8 or less, 1.6 or less, or 1.5 or less.
  • the aspect ratio is the ratio of the length of the major axis to the length of the minor axis of a particle. Since the minimum value of the aspect ratio is 1, the lower limit of the aspect ratio is usually 1.
  • the particle shape becomes elliptical or close to spherical.
  • the proportion of voids (D) in the composite layer 2 can be set within a predetermined range.
  • the presence of voids (D) makes it difficult for expansion and deterioration of the silicon particles (B) to occur.
  • the electrolyte held in the voids (D) increases the mobility of the lithium ions 7, making it possible to achieve rapid charge and discharge characteristics.
  • the spherical graphite (A1) may contain graphite or may consist of graphite.
  • Examples of such graphite include natural graphite, and artificial graphite obtained by finally heat-treating tar or pitch at 1500° C. or higher.
  • the artificial graphite may be a mesophase fired body obtained by heat-treating and polycondensing petroleum- or coal-based tar pitches, which are called graphitizable carbon materials, or may be graphitized at 1500° C. or higher or from 2800 to 3300° C.
  • the shape may be produced by subjecting natural graphite or artificial graphite to mechanical energy treatment.
  • the shape may be produced by using a device having a blade and a rotor, and applying mechanical actions such as impact compression, friction, and shear force to the graphite material by rotating the rotor at high speed.
  • the 50% particle size (d50) of the spherical graphite (A1) may be 10 to 30 ⁇ m, 13 to 27 ⁇ m, or 15 to 25 ⁇ m.
  • the 50% particle size (d50) is a volume-based median size measured by laser diffraction/scattering particle size distribution measurement.
  • the specific surface area of the graphite in the composite layer 2 increases, the irreversible capacity increases.
  • the 50% particle size (d50) of the spherical graphite (A1) is within the above range, the increase in the irreversible capacity can be reduced.
  • the plate-like graphite (A2) may be natural graphite or artificially formed graphite.
  • plate-like means a shape with an average flatness of 10.0 or more, expressed as the ratio (Ly/t) of the short axis length Ly to the thickness t of one particle of the plate-like graphite (A2).
  • This average flatness is calculated as the simple average of the flatness of each particle measured by observing 100 pieces of plate-like graphite with a scanning electron microscope.
  • the 50% particle size (d50) of the platelet graphite (A2) may be 5 to 40 ⁇ m, 8 to 37 ⁇ m, or 10 to 35 ⁇ m.
  • the specific surface area of graphite in the composite layer 2 increases, the irreversible capacity increases.
  • the 50% particle size (d50) of the flake graphite (A2) is within the above range, the increase in the irreversible capacity can be reduced.
  • the 50% particle size (d50) of the platelet graphite (A2) is 40 ⁇ m or less, the possibility of streaks or unevenness caused by large particles occurring in the step of forming the composite layer 2 can be reduced.
  • the thickness (Z direction) of the plate-like graphite (A2) may be 1 to 500 nm or 3 to 200 nm.
  • the length (X and Y directions) of the plate-like graphite (A2) may be 5 to 40 ⁇ m or 10 to 30 ⁇ m.
  • the thickness (Z direction) of the plate-like graphite (A2) is calculated as a simple average value of the thicknesses of 100 particles of plate-like graphite measured by observing them with a scanning electron microscope.
  • the length (X and Y directions) of the plate-like graphite (A2) is calculated in the same manner as the thickness.
  • the average flatness of the platelet graphite (A2) may be 100 to 5,000, or 300 to 4,000.
  • the ratio of voids (D) in the composite layer 2 can be set to a predetermined range.
  • the voids (D) present at the above ratio make it difficult for the silicon particles (B) to expand and deteriorate.
  • the voids (D) present at the above ratio increase the mobility of lithium ions 7 in the electrolyte solution held by the voids (D), thereby realizing rapid charge and discharge characteristics.
  • the plate-shaped graphite (A2) may be produced by any method as long as it has the above-mentioned properties.
  • natural graphite or artificial graphite can be obtained by removing impurities, pulverizing, sieving, and classifying, as necessary.
  • the ratio of the voids (D) in the composite layer 2 can be set within a predetermined range.
  • the voids (D) act as a cushioning material for the volume change of the silicon particles (B), making it difficult for interruption of electrical continuity to occur.
  • the total amount of the spherical graphite (A1) and the plate-like graphite (A2) in the carbon particles (A) may be 60 to 95 mass %, or 70 to 85 mass %.
  • silicon particles (B) examples include particles of simple silicon particles, silicon-based alloys, silicon monoxide composites, silicon dioxide composites, etc.
  • the shape of the particles may be any shape, such as granular, spherical, plate-like, scaly, needle-like, etc. From the viewpoint of capacity, the silicon particles may be used alone. The shape may be spherical.
  • the term "silicon particles" refers to crystalline or amorphous silicon having a purity of 95% by mass or more.
  • the 50% particle size (d50) of the silicon particles (B) may be 1 ⁇ m or less, or 0.8 ⁇ m or less. Although there is no particular lower limit, from the viewpoint of workability, it may be 0.08 ⁇ m or more, or 0.1 ⁇ m or more. When the 50% particle size (d50) of the silicon particles (B) is 1 ⁇ m or less, deterioration of the composite layer 2 and/or deterioration of the cycle characteristics caused by the volume expansion of the silicon particles (B) can be avoided.
  • the proportion of the silicon particles (B) in the composite layer 2 may be 5.0 to 40.0 parts by mass, or 8.0 to 37.0 parts by mass, based on the total materials constituting the composite layer 2 .
  • the proportion of the silicon particles (B) is 5.0 to 40.0 parts by mass, the capacity can be improved, and the cycle characteristics can be improved.
  • the negative electrode for a secondary battery 3 can be produced by mixing carbon particles (A), silicon particles (B), and, if necessary, a binder (C), a thickener, and a conductive assistant in a solvent to form a slurry, which is then applied to the current collecting layer 1 and dried.
  • the method for mixing the slurry may be either a dry method or a wet method, such as a rotary ball mill, a planetary ball mill, a disperser, or a homogenizer.
  • binder (C) examples include carboxymethyl cellulose, polyvinylidene fluoride resin, polytetrafluoroethylene, styrene-butadiene copolymer, polyimide resin, polyamide resin, polyvinyl alcohol, polyvinyl butyral, polyacrylic acid or its alkali salt, polyamic acid, etc. These may be modified by surface modification, etc.
  • the proportion of the binder (C) may be 0.5 to 10.0 parts by mass, or 1.0 to 8.0 parts by mass, relative to the total materials constituting the composite layer 2.
  • the proportion of the binder (C) is 0.5 parts by mass or more, sufficient binding force can be obtained between the negative electrode materials or between the negative electrode material and the current collector, and the strength required for the electrode can be ensured.
  • the proportion of the binder (C) is 10.0 parts by mass or less, the phenomenon in which the battery capacity decreases due to an increase in resistance value can be avoided, and the cycle characteristics can be improved.
  • Conductive additives that can be used include those commonly known for use in secondary batteries, such as acetylene black, ketjen black, conductive resins, conductive fibers, and flat graphite (graphene) with a particle size of 5 ⁇ m or less.
  • the solvent or dispersion medium is not particularly limited as long as it is a material that can be mixed uniformly, and examples include water, alcohols such as methanol and ethanol, N-methyl-2-pyrrolidone, acetonitrile, etc. These may be modified by surface modification, etc.
  • the current collecting layer 1 can be made of copper, copper alloys, stainless steel, nickel, titanium, carbon, and other materials that have traditionally been used for this purpose.
  • the shape of the current collecting layer 1 may be sheet-like.
  • the current collecting layer 1 may have an uneven surface, or may be a net, punched metal, etc.
  • the method for applying the composite layer-forming slurry to the current collecting layer 1 is not particularly limited, and may be a method of continuous application by roll-to-roll, a method of sheet-by-sheet application, or the like.
  • the coating device for example, a die coater, a multi-layer die coater, a gravure coater, a comma coater, a reverse roll coater, a doctor blade coater, or the like is used.
  • the temperature at which the composite layer forming slurry is dried after being applied to the current collecting layer 1 may be 80°C to 200°C, or 100°C to 180°C. If the drying temperature is 80° C. to 200° C., the productivity of the composite layer 2 can be improved, and curling due to shrinkage of the composite layer 2 can also be reduced.
  • the composite layer 2 may be subjected to a pressurizing and rolling process to increase the density of the composite layer 2 formed on the current collecting layer 1, thereby increasing the battery capacity per unit volume of the negative electrode.
  • the pressure in the rolling process may be 1.0 to 3.0 MPa, or 1.2 to 2.8 MPa. When the pressure is 1.0 MPa or more, a more uniform rolling process can be achieved. When the pressure is 3.0 MPa or less, curling of the negative electrode after the rolling process can be reduced.
  • the density of the composite layer 2 after the rolling process may be 0.5 to 1.3 g/ cm3 , or 0.6 to 1.2 g/ cm3 .
  • the density of the composite layer 2 is 0.5 g/cm3 or more , the capacity of the battery is less likely to decrease due to an increase in the thickness of the electrode.
  • the density of the composite layer 2 is 1.3 g/ cm3 or less, the rapid charge/discharge characteristics are less likely to decrease. It can be presumed that when the gaps (D) between the particles in the electrode are sufficient, the amount of electrolyte held in the gaps (D) can be maintained, alkali ions such as lithium (Li) ions can move, and the rapid charge/discharge characteristics are less likely to decrease.
  • the proportion of voids (D) (hereinafter also referred to as "porosity”) may be 15.0 to 35.0%, or 18.0 to 32.0%.
  • the porosity can be measured using the method described in the examples below. When the porosity is 15.0 to 35.0%, deterioration of the composite layer 2 due to expansion and contraction of the silicon particles is unlikely to occur, and the cycle characteristics are improved.
  • the proportion of silicon particles (B) (hereinafter also referred to as the "silicon abundance ratio”) may be 2.0 to 5.0%, or may be 2.5 to 4.5%. If the silicon content is 2.0 to 5.0%, the battery capacity is improved, and deterioration of the composite layer 2 due to excessive expansion and contraction is unlikely to occur, improving cycle characteristics.
  • the secondary battery in one embodiment is composed of a secondary battery negative electrode 3, a secondary battery positive electrode 4, an electrolyte 5, and a separator 6, and absorbs and releases lithium ions 7 during charging and discharging.
  • the secondary battery negative electrode 3 may be a secondary battery negative electrode sheet
  • the secondary battery positive electrode 4 may be a secondary battery positive electrode sheet.
  • Positive electrode materials that can be used include lithium cobalt composite oxides whose basic composition is LiCoO2 , lithium nickel composite oxides whose basic composition is LiNiO2 , lithium manganese composite oxides whose basic composition is LiMnO2 or LiMn2O4 , and other lithium transition metal composite oxides, such as manganese dioxide , as well as mixtures of these composite oxides, and further , TiS2 , FeS2 , Nb3S4 , Mo3S4 , CoS2 , V2O5 , CrO3 , V3O3 , FeO2 , GeO2 , LiNi0.33Mn0.33Co0.33O2 , and the like.
  • the secondary battery positive electrode 4 can be produced by mixing these positive electrode materials with a binder, forming a slurry in a suitable solvent, and applying the slurry to a current collector and drying it.
  • a binder a binder well known for this purpose, for example, one exemplified for the preparation of the negative electrode 3 for the secondary battery, may be used.
  • the slurry can contain conductive additives commonly known for use in secondary batteries, such as acetylene black, ketjen black, conductive resins, conductive fibers, and flat graphite (graphene) with a particle size of 5 ⁇ m or less.
  • conductive additives commonly known for use in secondary batteries, such as acetylene black, ketjen black, conductive resins, conductive fibers, and flat graphite (graphene) with a particle size of 5 ⁇ m or less.
  • the mixing ratio of the conductive agent to 100 parts by mass of the positive electrode material may be 0.5 to 20 parts by mass, or 1 to 15 parts by mass.
  • the mixing ratio of the binder to 100 parts by mass of the positive electrode material may be 0.2 to 10 parts by mass, or 0.5 to 7 parts by mass.
  • the mixing ratio to 100 parts by mass of the positive electrode material may be 0.2 to 10 parts by mass, or 0.5 to 7 parts by mass.
  • the binder resin is slurried with an organic solvent that dissolves the binder resin, such as N-methylpyrrolidone
  • the mixing ratio to 100 parts by mass of the positive electrode material may be 0.5 to 20 parts by mass, or 1 to 15 parts by mass.
  • the positive electrode current collector may be made of aluminum, titanium, zirconium, hafnium, niobium, tantalum, or an alloy of these.
  • the method for manufacturing the positive electrode 4 for the secondary battery may be a well-known method, such as the method exemplified as the method for manufacturing the negative electrode.
  • Electrolyte 5 As the electrolyte 5, a known electrolytic solution, a room temperature molten salt (ionic liquid), an organic or inorganic solid electrolyte, or the like can be used.
  • Known electrolytes include, for example, cyclic carbonates such as ethylene carbonate and propylene carbonate, and chain carbonates such as ethyl methyl carbonate and diethyl carbonate.
  • room temperature molten salts examples include imidazolium salts, pyrrolidinium salts, pyridinium salts, ammonium salts, phosphonium salts, and sulfonium salts.
  • Solid electrolytes include, for example, organic polymer gels such as polyether polymers, polyester polymers, polyimine polymers, polyvinyl acetal polymers, polyacrylonitrile polymers, polyfluorinated alkene polymers, polyvinyl chloride polymers, poly(vinyl chloride-vinylidene fluoride) polymers, poly(styrene-acrylonitrile) polymers, and linear polymers such as nitrile rubber; inorganic ceramics such as zirconia; inorganic electrolytes such as silver iodide, silver iodide sulfur compounds, and silver iodide rubidium compounds; etc.
  • organic polymer gels such as polyether polymers, polyester polymers, polyimine polymers, polyvinyl acetal polymers, polyacrylonitrile polymers, polyfluorinated alkene polymers, polyvinyl chloride polymers, poly(vinyl chloride-vinylidene fluoride) polymers, poly(sty
  • the electrolyte 5 may be one in which a lithium salt is dissolved.
  • a flame-retardant electrolyte dissolving agent may be added to impart flame retardancy to the electrolyte 5.
  • a plasticizer may be added to reduce the viscosity of the electrolyte 5.
  • lithium salts dissolved in the electrolyte 5 include LiPF6 , LiClO4 , LiCF3SO3 , LiBF4 , LiAsF6 , LiN( CF3SO2 ) 2 , LiN( C2F5SO2 ) 2 , and LiC ( CF3SO2 ) 3 .
  • the lithium salts may be used alone or in combination of two or more kinds.
  • the content of the lithium salt may be 0.1 to 89.9% by mass, or 1.0 to 79.0% by mass, based on the total mass of the electrolyte 5 .
  • Components other than the lithium salt of the electrolyte 5 can be added in appropriate amounts, provided that the content of the lithium salt is within the above range.
  • the separator 6 may be used from the viewpoint of preventing a short circuit between the secondary battery positive electrode 4 and the secondary battery negative electrode 3.
  • the material of the separator 6 may be a conventionally known material that is electrochemically stable. Examples of the separator 6 include a polyethylene separator, a polypropylene separator, a cellulose separator, a nonwoven fabric, an inorganic separator, a glass filter, and the like.
  • the electrolyte 5 contains a polymer
  • the electrolyte 5 may also function as the separator 6, in which case an independent separator 6 is not necessary.
  • the secondary battery may be manufactured by a manufacturing method including a step of superposing the composite layer 2 and the current collecting layer 1 to obtain a negative electrode material, and a step of rolling the negative electrode material at a pressure of 1 MPa or more to obtain a negative electrode 3 for a secondary battery.
  • the negative electrode forming slurry was applied by gravure coating while being supplied onto one side of a current collector foil SUS444 H BD (manufactured by Nippon Steel Chemical & Material Co., Ltd.), and after coating, the slurry was dried under conditions of a temperature of 100° C. and a speed of 0.2 m/min to prepare a negative electrode sheet for a secondary battery having a thickness of 60 ⁇ m.
  • the slurry for forming the positive electrode was applied by gravure coating while being supplied onto one side of a current collector foil SUS444 H BD (manufactured by Nippon Steel Chemical & Material Co., Ltd.), and after coating, the slurry was dried under conditions of a temperature of 100° C. and a speed of 0.2 m/min to prepare a positive electrode sheet for a secondary battery having a thickness of 60 ⁇ m.
  • the negative electrode sheet for secondary batteries and the positive electrode sheet for secondary batteries were roll-pressed (pressure: 1.5 MPa) using a 250 mm ⁇ roll press equipped with a load cell, punched out into circular shapes with a diameter of 12.5 mm, and vacuum-dried at 110° C. for 2 hours to obtain negative and positive electrodes for evaluation.
  • the negative electrode and the positive electrode were stacked with a separator (S703-1, manufactured by Sumitomo Chemical Co., Ltd.) impregnated with an electrolytic solution therebetween to prepare a secondary battery for charge/discharge tests.
  • the electrolyte was a mixture of ethylene carbonate and diethylene carbonate (volume ratio 1:1) in which lithium perchlorate was dissolved at a concentration of 1 mol/liter, and the solution was poured.
  • the porosity is a value calculated by "the sum of the areas of the voids (D) in the SEM cross section/the total area of the SEM cross section", and means the ratio of the voids (D) to the cross section of the negative electrode sheet for secondary batteries in a cross-sectional SEM image (5000x).
  • the silicon abundance ratio is a value calculated by "the total area of silicon particles (B) in the SEM cross section/the total area of the SEM cross section", and means the ratio of silicon particles (B) to the cross section of the negative electrode sheet for secondary batteries in a cross-sectional SEM image (5000x).
  • the void ratio is a value calculated by "void ratio/silicon abundance ratio” and means the ratio of the proportion of voids (D) to the proportion of silicon particles (B) in a cross-sectional SEM image (5000x).
  • cycle characteristics means the "capacity retention rate" at the 500th cycle, and the target is 80% or more.
  • the present disclosure it is possible to provide a negative electrode for a secondary battery in which expansion and deterioration of the metallic material is unlikely to occur even when the secondary battery is repeatedly charged and discharged, and in a secondary battery using the negative electrode for a secondary battery, the capacity, charge and discharge efficiency, and cycle characteristics are all improved.
  • the negative electrode for secondary batteries of the present disclosure can be used as the negative electrode of lithium ion secondary batteries.

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Abstract

Provided is a negative electrode for a secondary battery, the negative electrode including a current collector layer (1) and a composite layer (2), wherein: the composite layer (2) includes carbon particles (A) and silicon particles (B); the carbon particles (A) include spherical graphite (A1) and plate-form graphite (A2); and, in a cross-sectional SEM image (5000× magnification) of the composite layer (2), the ratio (silicon particles:air gaps) of the proportion occupied by silicon particles (B) and the proportion occupied by air gaps (D) is 1.0:6.0-1.0:10.0.

Description

二次電池用負極、二次電池及びその製造方法Anode for secondary battery, secondary battery and method for producing the same
　本開示は、二次電池用負極、二次電池及びその製造方法に関する。 This disclosure relates to negative electrodes for secondary batteries, secondary batteries, and methods for manufacturing the same.
　近年、電子材料の小型軽量化、及び、ＨＥＶ又はＥＶの進展に伴い、大容量、高速充放電特性、良好なサイクル特性、かつ、より安全な電池への要望がある。なかでも、リチウムイオン二次電池が、他の二次電池に比べて高電圧、高エネルギー密度という特性を有するため、有望な電池として注目されている。 In recent years, with the trend toward smaller and lighter electronic materials and the advancement of HEVs and EVs, there is a demand for batteries that have large capacity, high-speed charge/discharge characteristics, good cycle characteristics, and are safer. In particular, lithium-ion secondary batteries have attracted attention as a promising battery because they have higher voltage and higher energy density than other secondary batteries.
　現在、リチウムイオン二次電池は、正極にＬｉＣｏＯ２、負極に黒鉛を用いたものが一般的である。しかし、黒鉛負極は充放電の可逆性に優れるものの、その放電容量はすでに層間化合物ＬｉＣ６に相当する理論値３７２ｍＡｈ／ｇに近い値まで到達している。さらなる高エネルギー密度化を達成するためには、黒鉛より放電容量の大きい負極材料が必要である。 Currently, lithium ion secondary batteries generally use LiCoO2 for the positive electrode and graphite for the negative electrode. Although graphite negative electrodes have excellent charge/discharge reversibility, their discharge capacity has already reached a value close to the theoretical value of 372 mAh/g, which corresponds to the intercalation compound LiC6 . In order to achieve even higher energy density, a negative electrode material with a larger discharge capacity than graphite is needed.
　電池の負極材料として、例えば、金属リチウム、リチウムと合金を形成する金属質物、天然黒鉛、コークス等の黒鉛化で得られる人造黒鉛、黒鉛化メソフェーズピッチ、黒鉛化炭素繊維等の黒鉛質の炭素材料が検討されてきた。 Graphite-based carbon materials such as metallic lithium, metallic substances that form alloys with lithium, natural graphite, artificial graphite obtained by graphitizing coke, graphitized mesophase pitch, and graphitized carbon fiber have been considered as negative electrode materials for batteries.
　しかしながら、金属リチウムは負極材料として高い放電容量を有するが、充電時にリチウムがデンドライト状に析出して負極が劣化し、充放電サイクルが短くなる。また、デンドライト状に析出したリチウムがセパレータを貫通して正極に達し、短絡する可能性もある。 However, although metallic lithium has a high discharge capacity as a negative electrode material, lithium precipitates in the form of dendrites during charging, causing the negative electrode to deteriorate and shortening the charge/discharge cycle. In addition, lithium precipitated in the form of dendrites may penetrate the separator and reach the positive electrode, causing a short circuit.
　一方、リチウムと合金を形成する金属質物では充放電時の体積膨張により活物質の粉化、剥離が発生し、未だ実用レベルのサイクル特性は得られていない。
　リチウムと合金を形成する金属質物の前記欠点を改善するため、金属質物と、黒鉛質物又は炭素質物の少なくとも一方との複合化が検討されている。 On the other hand, metallic materials that form alloys with lithium undergo volume expansion during charging and discharging, causing the active material to powder and peel off, and cycle characteristics at a practical level have not yet been achieved.
In order to overcome the above-mentioned drawbacks of metallic materials which form alloys with lithium, the formation of a composite of a metallic material with at least one of a graphite material and a carbon material has been investigated.
　前記複合化に関し、特許文献１は、非晶質炭素と酸化金属質物を混合して複合化する方法を開示している。特許文献２は、金属質物であるケイ素化合物の微粉末と黒鉛と炭素質物前駆体であるピッチ等との混合物を焼成して、金属複合炭素粒を製造する方法を開示している。特許文献３は、平均粒径が２～５μｍ、アスペクト比が３以下の黒鉛質粒子表面に、該黒鉛質粒子の平均粒径の１／２以下の平均粒径である金属粒子を付着させた後、高温で熱処理して、金属－黒鉛質粒子を製造する方法を開示している。特許文献４は、金属質物であるケイ素元素を含有した複合的な炭素粒子を高温で熱処理し、黒鉛材料と配合することで金属質物の膨張を緩和するための空隙を設ける方法を開示している。 With regard to the above-mentioned composites, Patent Document 1 discloses a method of mixing amorphous carbon and a metallic oxide material to form a composite. Patent Document 2 discloses a method of producing metal-carbon composite particles by firing a mixture of fine powder of a silicon compound, which is a metallic material, graphite, and pitch, which is a carbonaceous material precursor. Patent Document 3 discloses a method of producing metal-graphite particles by attaching metal particles having an average particle size of 1/2 or less of the average particle size of the graphite particles to the surface of graphite particles having an average particle size of 2 to 5 μm and an aspect ratio of 3 or less, and then heat treating the particles at a high temperature. Patent Document 4 discloses a method of heat treating composite carbon particles containing silicon, which is a metallic material, at a high temperature and blending the particles with a graphite material to provide voids to mitigate the expansion of the metallic material.
　しかし、本発明者らの検討によると、特許文献１～４には、それぞれ以下の検討余地がある。
　特許文献１に記載の技術では、酸化金属質物と電解液の反応が生じやすく、電解液の分解により不可逆容量が大きくなることが懸念される。
　特許文献２に記載の技術では、充放電時の膨張収縮が十分制御できず、粒子間の接点が離れやすく十分なサイクル特性が得られないことが懸念される。
　特許文献３に記載の技術は、金属粒子は黒鉛上に付着しているのみであり、密着性が十分でなく、金属粒子が黒鉛から脱落・偏析することが懸念される。
　特許文献４には、金属質物を含有した複合的な炭素粒子を混合させることで、サイクル特性が向上できることが記載されているが、電池膨れ（すなわち金属質物の膨張）を軽減する効果は十分ではなく、サイクル特性に改善の余地がある。 However, according to the studies of the present inventors, each of Patent Documents 1 to 4 has room for further study as follows.
In the technology described in Patent Document 1, a reaction between the metal oxide material and the electrolyte is likely to occur, and there is a concern that the irreversible capacity will increase due to decomposition of the electrolyte.
With the technology described in Patent Document 2, there is a concern that the expansion and contraction during charging and discharging cannot be adequately controlled, and contact points between particles are likely to separate, resulting in insufficient cycle characteristics.
In the technique described in Patent Document 3, the metal particles are simply attached onto the graphite, and the adhesion is insufficient, so there is a concern that the metal particles may fall off and segregate from the graphite.
Patent Document 4 describes that the cycle characteristics can be improved by mixing composite carbon particles containing metallic materials, but the effect of reducing battery swelling (i.e., expansion of the metallic materials) is not sufficient, and there is room for improvement in the cycle characteristics.
特開２０１０－０９２８３４号公報JP 2010-092834 A 特開２００３－２２３８９２号公報JP 2003-223892 A 特開２００６－２９４４７６号公報JP 2006-294476 A 特開２０１５－１６４１２７号公報JP 2015-164127 A
　本開示は、以下に関する。 This disclosure relates to the following:
＜二次電池用負極＞
［１］
　集電層（１）と複合層（２）を含む二次電池用負極（３）であって、
　前記複合層（２）が、炭素粒子（Ａ）とケイ素粒子（Ｂ）を含み、
　前記炭素粒子（Ａ）が、球状黒鉛（Ａ１）及び板状黒鉛（Ａ２）を含み、
　前記複合層（２）の断面ＳＥＭ画像（５０００倍）において、前記ケイ素粒子（Ｂ）の占める割合と空隙（Ｄ）の占める割合の比（ケイ素粒子（Ｂ）：空隙（Ｄ））が、１．０：６．０～１．０：１０．０である、二次電池用負極。
［２］
　　前記複合層（２）の断面ＳＥＭ画像（５０００倍）において、前記空隙（Ｄ）の占める割合が、１５．０％～３５．０％である、［１］の二次電池用負極。
［３］
　前記複合層（２）の断面ＳＥＭ画像（５０００倍）において、前記ケイ素粒子（Ｂ）の占める割合が、２．０％～５．０％である、［１］又は［２］の二次電池用負極。
［４］
　前記球状黒鉛（Ａ１）と前記板状黒鉛（Ａ２）の質量比（Ａ１：Ａ２）が、６０：４０～９５：５である、［１］～［３］の何れかの二次電池用負極。
［５］
　前記球状黒鉛（Ａ１）のメディアン径（ｄ５０）が１０μｍ～３０μｍであり、前記板状黒鉛（Ａ２）のメディアン径（ｄ５０）が５μｍ～４０μｍであり、前記ケイ素粒子（Ｂ）のメディアン径（ｄ５０）が１μｍ以下である、［１］～［４］の何れかの二次電池用負極。
［６］
　前記板状黒鉛（Ａ２）が、厚み（Ｚ方向）１～５００ｎｍ及び長さ（Ｘ及びＹ方向）５～４０μｍの形状を有する、［１］～［５］の何れかの二次電池用負極。
＜二次電池＞
［７］
　［１］～［６］の何れかの二次電池用負極（３）と、二次電池用正極（４）と、電解質（５）とを備える、二次電池。
＜二次電池の製造方法＞
［８］
　［７］の二次電池の製造方法であって、
　前記複合層（２）と前記集電層（１）を重ね合わせて負極材料を得る工程と、
　前記負極材料に、１ＭＰａ以上の圧力で圧延処理を施して二次電池用負極（３）を得る工程を有する、二次電池の製造方法。 <Negative electrode for secondary battery>
[1]
A negative electrode (3) for a secondary battery comprising a current collecting layer (1) and a composite layer (2),
The composite layer (2) contains carbon particles (A) and silicon particles (B),
The carbon particles (A) contain spherical graphite (A1) and plate-like graphite (A2),
In a cross-sectional SEM image (magnification: 5000) of the composite layer (2), the ratio of the proportion of the silicon particles (B) to the proportion of the voids (D) (silicon particles (B):voids (D)) is 1.0:6.0 to 1.0:10.0.
[2]
The negative electrode for a secondary battery according to [1], wherein in a cross-sectional SEM image (magnification: 5000) of the composite layer (2), the proportion of the voids (D) is 15.0% to 35.0%.
[3]
The negative electrode for a secondary battery according to [1] or [2], wherein in a cross-sectional SEM image (magnification: 5000) of the composite layer (2), the proportion of the silicon particles (B) is 2.0% to 5.0%.
[4]
The negative electrode for a secondary battery according to any one of [1] to [3], wherein a mass ratio (A1:A2) of the spherical graphite (A1) to the plate-like graphite (A2) is 60:40 to 95:5.
[5]
The negative electrode for a secondary battery according to any one of [1] to [4], wherein the spherical graphite (A1) has a median diameter (d50) of 10 μm to 30 μm, the plate-like graphite (A2) has a median diameter (d50) of 5 μm to 40 μm, and the silicon particles (B) have a median diameter (d50) of 1 μm or less.
[6]
The negative electrode for a secondary battery according to any one of [1] to [5], wherein the plate-like graphite (A2) has a thickness (Z direction) of 1 to 500 nm and a length (X and Y directions) of 5 to 40 μm.
<Secondary battery>
[7]
A secondary battery comprising the negative electrode for a secondary battery (3) according to any one of [1] to [6], a positive electrode for a secondary battery (4), and an electrolyte (5).
<Secondary Battery Manufacturing Method>
[8]
A method for producing a secondary battery according to [7],
a step of superposing the composite layer (2) and the current collecting layer (1) to obtain a negative electrode material;
The method for producing a secondary battery includes a step of rolling the negative electrode material at a pressure of 1 MPa or more to obtain a negative electrode for a secondary battery (3).
本開示の一実施形態における二次電池用負極３を構成する複合層２と集電層１の模式的な断面図である。FIG. 2 is a schematic cross-sectional view of a composite layer 2 and a current collecting layer 1 that constitute a negative electrode 3 for a secondary battery in one embodiment of the present disclosure. 本開示の一実施形態における二次電池の説明図である。FIG. 1 is an explanatory diagram of a secondary battery according to an embodiment of the present disclosure.
　以下、本開示の実施形態について詳細に説明する。
　以下の説明において、数値範囲を示す「Ａ～Ｂ」の記載は、端点を含む「Ａ以上Ｂ以下」を意味し、「Ａ～Ｂであってもよく、Ｃ～Ｄであってもよく、Ｅ～Ｆであってもよい」と記載した場合、その上限、下限は任意に組み合わせられる。 Hereinafter, embodiments of the present disclosure will be described in detail.
In the following description, the description of "A to B" indicating a numerical range means "greater than or equal to A and less than or equal to B," including the endpoints, and when describing "may be A to B, may be C to D, or may be E to F," the upper and lower limits can be combined in any combination.
［二次電池用負極３］
　一実施形態における二次電池用負極３は、図１に示すように、導電性を有する部材である集電層１に、複合層２を重ね合わせて構成される。 [Secondary battery negative electrode 3]
As shown in FIG. 1, a secondary battery negative electrode 3 in one embodiment is configured by laminating a composite layer 2 on a current collecting layer 1 which is a conductive member.
＜複合層２＞
　図１に示すように、複合層２は、炭素粒子（Ａ）と、ケイ素粒子（Ｂ）と、結着剤（Ｃ）を含み、炭素粒子（Ａ）は、球状黒鉛（Ａ１）及び板状黒鉛（Ａ２）を含む。
　図１に示すように、複合層２には空隙（Ｄ）が存在する。複合層２の断面ＳＥＭ画像（５０００倍）において、ケイ素粒子（Ｂ）の占める割合と空隙（Ｄ）の占める割合の比（ケイ素粒子（Ｂ）：空隙（Ｄ））（以下「空隙倍率」ともいう）が、１．０：６．０～１．０：１０．０であってもよく、１．０：６．３～１．０：９．７であってもよく、１．０：６．５～１．０：９．５であってもよい。 <Composite layer 2>
As shown in FIG. 1, the composite layer 2 contains carbon particles (A), silicon particles (B), and a binder (C), and the carbon particles (A) contain spherical graphite (A1) and plate-like graphite (A2).
1, voids (D) are present in the composite layer 2. In a cross-sectional SEM image (5000x) of the composite layer 2, the ratio of the proportion of silicon particles (B) to the proportion of voids (D) (silicon particles (B):voids (D)) (hereinafter also referred to as "void ratio") may be 1.0:6.0 to 1.0:10.0, 1.0:6.3 to 1.0:9.7, or 1.0:6.5 to 1.0:9.5.
　活物質としてケイ素粒子（Ｂ）を用いることにより、高い容量を実現することができる。
　ケイ素粒子（Ｂ）にリチウムイオンを充填すると体積が３倍程度に膨張するが、本開示の二次電池用負極３では、球状黒鉛（Ａ１）及び板状黒鉛（Ａ２）が混在する複合層２に、前記空隙倍率で存在する空隙（Ｄ）によって、空隙（Ｄ）がケイ素粒子（Ｂ）の体積変化のクッション材となる。その為、導通の遮断が起こりにくくなり、サイクル特性が向上し、そのサイクル特性を安定的かつ長期的に維持することができる。 By using silicon particles (B) as the active material, a high capacity can be achieved.
When lithium ions are filled into silicon particles (B), the volume expands to about three times, but in the secondary battery negative electrode 3 of the present disclosure, the voids (D) existing at the above void ratio in the composite layer 2 in which the spherical graphite (A1) and the plate-like graphite (A2) are mixed serve as a cushioning material for the volume change of the silicon particles (B). Therefore, interruption of electrical continuity is less likely to occur, the cycle characteristics are improved, and the cycle characteristics can be stably maintained for a long period of time.
＜炭素粒子（Ａ）＞
　炭素粒子（Ａ）は、少なくとも球状黒鉛（Ａ１）と板状黒鉛（Ａ２）の両方を含む。 <Carbon particles (A)>
The carbon particles (A) contain at least both spherical graphite (A1) and platelet graphite (A2).
＜球状黒鉛（Ａ１）＞
　球状黒鉛（Ａ１）は、形状が球状であればよく、具体的な種類及び製法は特に制限されない。 <Spherical graphite (A1)>
The spherical graphite (A1) may be any one having a spherical shape, and the specific type and production method are not particularly limited.
　球状黒鉛（Ａ１）の形状は、真球に限定されず、ペレット状、楕円等の形状の黒鉛も含まれる。球に近い形状であってもよい。
　球状黒鉛（Ａ１）のアスペクト比は、１．８以下であってもよく、１．６以下であってもよく、１．５以下であってもよい。ここで、アスペクト比は、粒子の短径に対する長径の長さの比である。アスペクト比の最小値は１となるので、アスペクト比の下限は通常１である。 The shape of the spherical graphite (A1) is not limited to a perfect sphere, and also includes graphite in the form of a pellet, an ellipse, etc. A shape close to a sphere is also acceptable.
The aspect ratio of the spherical graphite (A1) may be 1.8 or less, 1.6 or less, or 1.5 or less. Here, the aspect ratio is the ratio of the length of the major axis to the length of the minor axis of a particle. Since the minimum value of the aspect ratio is 1, the lower limit of the aspect ratio is usually 1.
　アスペクト比が上記範囲では、粒子形状が楕円形又は、球形に近い状態になる。当該形状の球状黒鉛（Ａ１）と後述する形状の板状黒鉛（Ａ２）を、所定の比率で複合層２に混在させて、複合層２に占める空隙（Ｄ）の割合を所定の範囲とすることができる。空隙（Ｄ）の存在により、ケイ素粒子（Ｂ）の膨張劣化が起こりにくくなる。また、空隙（Ｄ）に保持される電解液により、リチウムイオン７の移動性が高まり、急速充放電特性を実現することができる。 When the aspect ratio is within the above range, the particle shape becomes elliptical or close to spherical. By mixing spherical graphite (A1) of this shape and plate-like graphite (A2) of a shape described below in the composite layer 2 at a predetermined ratio, the proportion of voids (D) in the composite layer 2 can be set within a predetermined range. The presence of voids (D) makes it difficult for expansion and deterioration of the silicon particles (B) to occur. In addition, the electrolyte held in the voids (D) increases the mobility of the lithium ions 7, making it possible to achieve rapid charge and discharge characteristics.
　球状黒鉛（Ａ１）は、黒鉛質を含むものでもよく、黒鉛質からなるものでもよい。
　例えば、天然黒鉛又は、タール、ピッチ類を最終的に１５００℃以上で熱処理してなる人造黒鉛等が挙げられる。人造黒鉛は、易黒鉛化性炭素材料とよばれる石油系又は石炭系のタールピッチ類を熱処理して重縮合させたメソフェーズ焼成体であってもよく、コークス類を１５００℃以上でもよく、２８００～３３００℃で黒鉛化処理してもよい。
　前記形状は、天然黒鉛又は、人造黒鉛等に力学的エネルギー処理を施して製造してもよい。例えば、前記形状はブレード及びローターを有する装置を用い、そのローターを高速回転することにより、黒鉛材料に対して、衝撃圧縮、摩擦及びせん断力等の機械的作用を与えて製造してもよい。 The spherical graphite (A1) may contain graphite or may consist of graphite.
Examples of such graphite include natural graphite, and artificial graphite obtained by finally heat-treating tar or pitch at 1500° C. or higher. The artificial graphite may be a mesophase fired body obtained by heat-treating and polycondensing petroleum- or coal-based tar pitches, which are called graphitizable carbon materials, or may be graphitized at 1500° C. or higher or from 2800 to 3300° C.
The shape may be produced by subjecting natural graphite or artificial graphite to mechanical energy treatment. For example, the shape may be produced by using a device having a blade and a rotor, and applying mechanical actions such as impact compression, friction, and shear force to the graphite material by rotating the rotor at high speed.
　球状黒鉛（Ａ１）の５０％粒子径（ｄ５０）は、１０～３０μｍであってもよく、１３～２７μｍであってもよく、１５～２５μｍであってもよい。
　本明細書において、５０％粒子径（ｄ５０）は、レーザー回折・散乱式粒度分布測定により測定される体積基準のメディアン径である。
　複合層２で黒鉛の比表面積が大きくなると不可逆容量が増加するが、球状黒鉛（Ａ１）の５０％粒子径（ｄ５０）が上記範囲であると、不可逆容量の増加を低減できる。 The 50% particle size (d50) of the spherical graphite (A1) may be 10 to 30 μm, 13 to 27 μm, or 15 to 25 μm.
In this specification, the 50% particle size (d50) is a volume-based median size measured by laser diffraction/scattering particle size distribution measurement.
When the specific surface area of the graphite in the composite layer 2 increases, the irreversible capacity increases. However, when the 50% particle size (d50) of the spherical graphite (A1) is within the above range, the increase in the irreversible capacity can be reduced.
＜板状黒鉛（Ａ２）＞
　板状黒鉛（Ａ２）は、天然黒鉛であってもよく、人工的に形成した黒鉛であってもよい。 <Plate graphite (A2)>
The plate-like graphite (A2) may be natural graphite or artificially formed graphite.
　ここで、板状とは、板状黒鉛（Ａ２）の１粒子の厚さｔに対する短軸長Ｌｙの比（Ｌｙ／ｔ）で表される平均扁平度が１０．０以上の形状を意味する。この平均扁平度は、走査型電子顕微鏡によって１００個の板状黒鉛を観察して測定した各粒子の扁平度の単純平均値として算出する。 Here, plate-like means a shape with an average flatness of 10.0 or more, expressed as the ratio (Ly/t) of the short axis length Ly to the thickness t of one particle of the plate-like graphite (A2). This average flatness is calculated as the simple average of the flatness of each particle measured by observing 100 pieces of plate-like graphite with a scanning electron microscope.
　板状黒鉛（Ａ２）の５０％粒子径（ｄ５０）は、５～４０μｍであってもよく、８～３７μｍであってもよく、１０～３５μｍであってもよい。
　複合層２で黒鉛の比表面積が大きくなると不可逆容量が増加するが、板状黒鉛（Ａ２）の５０％粒子径（ｄ５０）が上記範囲であると、不可逆容量の増加を低減できる。
　板状黒鉛（Ａ２）の５０％粒子径（ｄ５０）が４０μｍ以下の場合、複合層２を形成する工程で、大粒子に起因してスジ引き又は凹凸が発生する可能性を低減できる。 The 50% particle size (d50) of the platelet graphite (A2) may be 5 to 40 μm, 8 to 37 μm, or 10 to 35 μm.
When the specific surface area of graphite in the composite layer 2 increases, the irreversible capacity increases. However, when the 50% particle size (d50) of the flake graphite (A2) is within the above range, the increase in the irreversible capacity can be reduced.
When the 50% particle size (d50) of the platelet graphite (A2) is 40 μm or less, the possibility of streaks or unevenness caused by large particles occurring in the step of forming the composite layer 2 can be reduced.
　板状黒鉛（Ａ２）の厚み（Ｚ方向）は、１～５００ｎｍであってもよく、３～２００ｎｍであってもよい。板状黒鉛（Ａ２）の長さ（Ｘ及びＹ方向）は、５～４０μｍであってもよく、１０～３０μｍであってもよい。
　板状黒鉛（Ａ２）の厚み（Ｚ方向）は、走査型電子顕微鏡によって１００個の板状黒鉛を観察して測定した各粒子の厚みの単純平均値として算出する。板状黒鉛（Ａ２）の長さ（Ｘ及びＹ方向）は、厚みと同一の方法で算出する。 The thickness (Z direction) of the plate-like graphite (A2) may be 1 to 500 nm or 3 to 200 nm. The length (X and Y directions) of the plate-like graphite (A2) may be 5 to 40 μm or 10 to 30 μm.
The thickness (Z direction) of the plate-like graphite (A2) is calculated as a simple average value of the thicknesses of 100 particles of plate-like graphite measured by observing them with a scanning electron microscope. The length (X and Y directions) of the plate-like graphite (A2) is calculated in the same manner as the thickness.
　板状黒鉛（Ａ２）の平均扁平度は、１００～５０００であってもよく、３００～４０００であってもよい。
　当該形状の板状黒鉛（Ａ２）と前述した形状の球状黒鉛（Ａ１）が、所定の比率で複合層２に混在することで、複合層２に占める空隙（Ｄ）の割合を所定の範囲とすることができる。前記割合で存在する空隙（Ｄ）により、ケイ素粒子（Ｂ）の膨張劣化が生じにくくなる。また、前記割合で存在する空隙（Ｄ）により、空隙（Ｄ）が保持した電解液中のリチウムイオン７の移動性が高まり、急速充放電特性を実現することができる。 The average flatness of the platelet graphite (A2) may be 100 to 5,000, or 300 to 4,000.
By mixing the plate-like graphite (A2) having this shape and the spherical graphite (A1) having the above-mentioned shape in the composite layer 2 at a predetermined ratio, the ratio of voids (D) in the composite layer 2 can be set to a predetermined range. The voids (D) present at the above ratio make it difficult for the silicon particles (B) to expand and deteriorate. In addition, the voids (D) present at the above ratio increase the mobility of lithium ions 7 in the electrolyte solution held by the voids (D), thereby realizing rapid charge and discharge characteristics.
　板状黒鉛（Ａ２）は、前述の性状であれば、どのような製法で作製してもよい。例えば、天然黒鉛又は人造黒鉛を、必要により、不純物除去、粉砕、篩い分けや分級処理を行って得ることができる。 The plate-shaped graphite (A2) may be produced by any method as long as it has the above-mentioned properties. For example, natural graphite or artificial graphite can be obtained by removing impurities, pulverizing, sieving, and classifying, as necessary.
＜球状黒鉛（Ａ１）と板状黒鉛（Ａ２）の質量比＞
　球状黒鉛（Ａ１）と板状黒鉛（Ａ２）の質量比は、球状黒鉛（Ａ１）：板状黒鉛（Ａ２）＝６０：４０～９５：５であってもよく、７０：３０～９０：１０であってもよい。
　球状黒鉛（Ａ１）と板状黒鉛（Ａ２）の質量比が上記範囲であると、複合層２に占める空隙（Ｄ）の割合を所定の範囲にすることができる。空隙（Ｄ）がケイ素粒子（Ｂ）の体積変化のクッション材となることで、導通の遮断が起こりにくくなる。その為、サイクル特性を安定的かつ長期的に維持することができる。
　また、炭素粒子（Ａ）中における、球状黒鉛（Ａ１）及び板状黒鉛（Ａ２）の総量は、６０～９５質量％であってもよく、７０～８５質量％であってもよい。 <Mass ratio of spherical graphite (A1) to platelet graphite (A2)>
The mass ratio of the spherical graphite (A1) to the plate-like graphite (A2) may be, for example, spherical graphite (A1):plate-like graphite (A2)=60:40 to 95:5, or 70:30 to 90:10.
When the mass ratio of the spherical graphite (A1) to the plate-like graphite (A2) is within the above range, the ratio of the voids (D) in the composite layer 2 can be set within a predetermined range. The voids (D) act as a cushioning material for the volume change of the silicon particles (B), making it difficult for interruption of electrical continuity to occur. As a result, the cycle characteristics can be maintained stably for a long period of time.
The total amount of the spherical graphite (A1) and the plate-like graphite (A2) in the carbon particles (A) may be 60 to 95 mass %, or 70 to 85 mass %.
＜ケイ素粒子（Ｂ）＞
　ケイ素粒子（Ｂ）は、例えば、ケイ素粒子単体、ケイ素系合金、一酸化ケイ素複合体、二酸化ケイ素複合体等の粒子が挙げられる。その形状は、粒状、球状、板状、鱗片状、針状等、いかなる形状でもよい。
　容量の観点から、ケイ素粒子単体であってもよい。形状は球状であってもよい。
　ここで、ケイ素粒子単体とは、純度が９５質量％以上の結晶質又は非晶質のケイ素を意味する。 <Silicon particles (B)>
Examples of the silicon particles (B) include particles of simple silicon particles, silicon-based alloys, silicon monoxide composites, silicon dioxide composites, etc. The shape of the particles may be any shape, such as granular, spherical, plate-like, scaly, needle-like, etc.
From the viewpoint of capacity, the silicon particles may be used alone. The shape may be spherical.
Here, the term "silicon particles" refers to crystalline or amorphous silicon having a purity of 95% by mass or more.
　ケイ素粒子（Ｂ）の５０％粒子径（ｄ５０）は、１μｍ以下であってもよく、０．８μｍ以下であってもよい。下限は特に設けないが、作業性の観点から、０．０８μｍ以上であってもよく、０．１μｍ以上であってもよい。
　ケイ素粒子（Ｂ）の５０％粒子径（ｄ５０）が１μｍ以下であると、ケイ素粒子（Ｂ）の体積膨張に起因する複合層２の劣化及び/又はサイクル特性の悪化を回避することができる。 The 50% particle size (d50) of the silicon particles (B) may be 1 μm or less, or 0.8 μm or less. Although there is no particular lower limit, from the viewpoint of workability, it may be 0.08 μm or more, or 0.1 μm or more.
When the 50% particle size (d50) of the silicon particles (B) is 1 μm or less, deterioration of the composite layer 2 and/or deterioration of the cycle characteristics caused by the volume expansion of the silicon particles (B) can be avoided.
　また、複合層２に占めるケイ素粒子（Ｂ）の割合は、複合層２を構成する全材料に対して、５．０～４０．０質量部であってもよく、８．０～３７．０質量部であってもよい。
　ケイ素粒子（Ｂ）の割合が５．０～４０．０質量部であると、容量を向上させ、サイクル特性の向上を図ることができる。 The proportion of the silicon particles (B) in the composite layer 2 may be 5.0 to 40.0 parts by mass, or 8.0 to 37.0 parts by mass, based on the total materials constituting the composite layer 2 .
When the proportion of the silicon particles (B) is 5.0 to 40.0 parts by mass, the capacity can be improved, and the cycle characteristics can be improved.
［二次電池用負極３の製造方法］
　一実施形態における二次電池用負極３は、炭素粒子（Ａ）と、ケイ素粒子（Ｂ）と必要に応じて結着剤（Ｃ）、増粘剤、導電助剤を溶剤中に混ぜてスラリーとし、集電層１に塗工及び乾燥して製造することができる。 [Method of manufacturing negative electrode 3 for secondary battery]
In one embodiment, the negative electrode for a secondary battery 3 can be produced by mixing carbon particles (A), silicon particles (B), and, if necessary, a binder (C), a thickener, and a conductive assistant in a solvent to form a slurry, which is then applied to the current collecting layer 1 and dried.
　スラリーの混合方法としては、乾式法又は湿式法のいずれでもよく、例えば回転ボールミル、遊星ボールミル、ディスパーサー、ホモジナイザー等が挙げられる。 The method for mixing the slurry may be either a dry method or a wet method, such as a rotary ball mill, a planetary ball mill, a disperser, or a homogenizer.
　結着剤（Ｃ）としては例えば、カルボキシメチルセルロース、ポリフッ化ビニリデン樹脂、ポリテトラフルオロエチレン、スチレン・ブタジエン共重合体、ポリイミド樹脂、ポリアミド樹脂、ポリビニルアルコール、ポリビニルブチラール、ポリアクリル酸又はそのアルカリ塩、ポリアミック酸等が挙げられる。これらは、表面修飾等により改質されてもよい。 Examples of the binder (C) include carboxymethyl cellulose, polyvinylidene fluoride resin, polytetrafluoroethylene, styrene-butadiene copolymer, polyimide resin, polyamide resin, polyvinyl alcohol, polyvinyl butyral, polyacrylic acid or its alkali salt, polyamic acid, etc. These may be modified by surface modification, etc.
　結着剤（Ｃ）の割合は、複合層２を構成する全材料に対して、０．５～１０．０質量部であってもよく、１．０～８．０質量部であってもよい。結着剤（Ｃ）の割合が０．５質量部以上であると、負極材料相互間又は負極材料と集電体との結着力が十分に得ることができ、電極として必要な強度を確保することができる。結着剤（Ｃ）の割合が１０．０質量部以下であると、抵抗値向上によって電池容量が減少する現象を回避して、サイクル特性の向上を図ることができる。 The proportion of the binder (C) may be 0.5 to 10.0 parts by mass, or 1.0 to 8.0 parts by mass, relative to the total materials constituting the composite layer 2. When the proportion of the binder (C) is 0.5 parts by mass or more, sufficient binding force can be obtained between the negative electrode materials or between the negative electrode material and the current collector, and the strength required for the electrode can be ensured. When the proportion of the binder (C) is 10.0 parts by mass or less, the phenomenon in which the battery capacity decreases due to an increase in resistance value can be avoided, and the cycle characteristics can be improved.
　導電助剤としては、例えば、アセチレンブラック、ケッチェンブラック、導電性樹脂、導電性繊維、粒径５μｍ以下の扁平状黒鉛（グラフェン）等、二次電池用として一般に知られているものを使用することができる。 Conductive additives that can be used include those commonly known for use in secondary batteries, such as acetylene black, ketjen black, conductive resins, conductive fibers, and flat graphite (graphene) with a particle size of 5 μm or less.
　溶媒又は分散媒としては、均一に混合できる材料であれば特に限定されることはなく、例えば、水、メタノール、エタノール等のアルコール類、Ｎ－メチル－２－ピロリドン、アセトニトリル等が挙げられる。これらは、表面修飾等により改質されてもよい。 The solvent or dispersion medium is not particularly limited as long as it is a material that can be mixed uniformly, and examples include water, alcohols such as methanol and ethanol, N-methyl-2-pyrrolidone, acetonitrile, etc. These may be modified by surface modification, etc.
　集電層１としては、従来からこの用途に用いられている銅、銅合金、ステンレス鋼、ニッケル、チタン、炭素等を用いることができる。 The current collecting layer 1 can be made of copper, copper alloys, stainless steel, nickel, titanium, carbon, and other materials that have traditionally been used for this purpose.
　集電層１の形状はシート状であってもよい。集電層１は、表面に凹凸をつけたもの又は、ネット、パンチングメタル等であってもよい。 The shape of the current collecting layer 1 may be sheet-like. The current collecting layer 1 may have an uneven surface, or may be a net, punched metal, etc.
　複合層形成用のスラリーを集電層１に塗工する方法は、特に限定することはなく、ロールツーロールにより連続的に塗布する方法、枚葉で塗布する方法等を用いてもよい。
　塗布装置としては、例えば、ダイコータ、多層ダイコータ、グラビアコータ、コンマコータ、リバースロールコータ、ドクタブレードコータ等が用いられる。 The method for applying the composite layer-forming slurry to the current collecting layer 1 is not particularly limited, and may be a method of continuous application by roll-to-roll, a method of sheet-by-sheet application, or the like.
As the coating device, for example, a die coater, a multi-layer die coater, a gravure coater, a comma coater, a reverse roll coater, a doctor blade coater, or the like is used.
　複合層形成用のスラリーを集電層１に塗工した後に乾燥させる温度は、８０℃～２００℃であってもよく、１００～１８０℃であってもよい。
　乾燥温度が８０℃～２００℃であると、複合層２の生産性を向上することができ、複合層２の収縮によるカールも軽減できる。 The temperature at which the composite layer forming slurry is dried after being applied to the current collecting layer 1 may be 80°C to 200°C, or 100°C to 180°C.
If the drying temperature is 80° C. to 200° C., the productivity of the composite layer 2 can be improved, and curling due to shrinkage of the composite layer 2 can also be reduced.
　集電層１に複合層２を塗工及び乾燥したのちは、加圧、圧延処理して集電層１に形成された複合層２の密度を大きくし、負極の単位体積当たりの電池容量を大きくしてもよい。
　前記圧延処理における圧力は、１．０～３．０ＭＰａであってもよく、１．２～２．８ＭＰａであってもよい。圧力が１．０ＭＰａ以上であると、より均一な圧延処理ができる。圧力が３．０ＭＰａ以下であると、圧延処理後の負極のカールを軽減できる。 After the composite layer 2 is applied to the current collecting layer 1 and dried, the composite layer 2 may be subjected to a pressurizing and rolling process to increase the density of the composite layer 2 formed on the current collecting layer 1, thereby increasing the battery capacity per unit volume of the negative electrode.
The pressure in the rolling process may be 1.0 to 3.0 MPa, or 1.2 to 2.8 MPa. When the pressure is 1.0 MPa or more, a more uniform rolling process can be achieved. When the pressure is 3.0 MPa or less, curling of the negative electrode after the rolling process can be reduced.
　前記圧延処理後の複合層２の密度は、０．５～１．３ｇ／ｃｍ３であってもよく、０．６～１．２ｇ／ｃｍ３であってもよい。複合層２の密度が０．５ｇ／ｃｍ３以上であると、電極の厚みの増大に伴う電池の容量の低下が起こりにくい。複合層２の密度が１．３ｇ／ｃｍ３以下であると、前記急速充放電特性の低下が起こりにくい。電極内の粒子間の空隙（Ｄ）が十分であると、空隙（Ｄ）に保持された電解液量が維持でき、リチウム（Ｌｉ）イオン等のアルカリイオンが移動でき、急速充放電特性の低下が起こりにくいと推察できる。 The density of the composite layer 2 after the rolling process may be 0.5 to 1.3 g/ cm3 , or 0.6 to 1.2 g/ cm3 . When the density of the composite layer 2 is 0.5 g/cm3 or more , the capacity of the battery is less likely to decrease due to an increase in the thickness of the electrode. When the density of the composite layer 2 is 1.3 g/ cm3 or less, the rapid charge/discharge characteristics are less likely to decrease. It can be presumed that when the gaps (D) between the particles in the electrode are sufficient, the amount of electrolyte held in the gaps (D) can be maintained, alkali ions such as lithium (Li) ions can move, and the rapid charge/discharge characteristics are less likely to decrease.
　前記圧延処理後の複合層２の断面ＳＥＭ画像（５０００倍）において、空隙（Ｄ）の占める割合（以下「空隙率」ともいう）は、１５．０～３５．０％であってもよく、１８．０～３２．０％であってもよい。空隙率は、後述する実施例の方法を用いて測定することができる。
　空隙率が１５．０～３５．０％であると、ケイ素粒子の膨張収縮による複合層２の劣化が起こりにくく、サイクル特性が向上する。 In a cross-sectional SEM image (magnification: 5000) of the composite layer 2 after the rolling treatment, the proportion of voids (D) (hereinafter also referred to as "porosity") may be 15.0 to 35.0%, or 18.0 to 32.0%. The porosity can be measured using the method described in the examples below.
When the porosity is 15.0 to 35.0%, deterioration of the composite layer 2 due to expansion and contraction of the silicon particles is unlikely to occur, and the cycle characteristics are improved.
　前記圧延処理後の複合層２の断面ＳＥＭ画像（５０００倍）において、ケイ素粒子（Ｂ）の占める割合（以下「ケイ素存在割合」ともいう）は、２．０～５．０％であってもよく、２．５～４．５％であってもよい。
　ケイ素存在割合が２．０～５．０％であると、電池容量の向上と過剰な膨張収縮による複合層２の劣化が起こりにくく、サイクル特性が向上する。 In a cross-sectional SEM image (magnification: 5000) of the composite layer 2 after the rolling treatment, the proportion of silicon particles (B) (hereinafter also referred to as the "silicon abundance ratio") may be 2.0 to 5.0%, or may be 2.5 to 4.5%.
If the silicon content is 2.0 to 5.0%, the battery capacity is improved, and deterioration of the composite layer 2 due to excessive expansion and contraction is unlikely to occur, improving cycle characteristics.
［二次電池］
　一実施形態における二次電池は、図２に示すように、二次電池用負極３と、二次電池用正極４と、電解質５、セパレータ６とで構成され、充放電時にリチウムイオン７の吸蔵放出が生じる。二次電池用負極３は、二次電池用負極シートであってもよく、二次電池用正極４は、二次電池用正極シートであってもよい。 [Secondary battery]
2, the secondary battery in one embodiment is composed of a secondary battery negative electrode 3, a secondary battery positive electrode 4, an electrolyte 5, and a separator 6, and absorbs and releases lithium ions 7 during charging and discharging. The secondary battery negative electrode 3 may be a secondary battery negative electrode sheet, and the secondary battery positive electrode 4 may be a secondary battery positive electrode sheet.
＜二次電池用正極４＞
　正極材料としては、基本組成がＬｉＣｏＯ２で表されるリチウムコバルト複合酸化物、ＬｉＮｉＯ２で表されるリチウムニッケル複合酸化物、ＬｉＭｎＯ２又はＬｉＭｎ２Ｏ４で表されるリチウムマンガン複合酸化物等のリチウム遷移金属複合酸化物、二酸化マンガン等の遷移金属酸化物、並びにこれらの複合酸化物混合物、更にはＴｉＳ２、ＦｅＳ２、Ｎｂ３Ｓ４、Ｍｏ３Ｓ４、ＣｏＳ２、Ｖ２Ｏ５、ＣｒＯ３、Ｖ３Ｏ３、ＦｅＯ２、ＧｅＯ２、ＬｉＮｉ０．３３Ｍｎ０．３３Ｃｏ０．３３Ｏ２等を用いることができる。 <Positive electrode 4 for secondary battery>
Positive electrode materials that can be used include lithium cobalt composite oxides whose basic composition is LiCoO2 , lithium nickel composite oxides whose basic composition is LiNiO2 , lithium manganese composite oxides whose basic composition is LiMnO2 or LiMn2O4 , and other lithium transition metal composite oxides, such as manganese dioxide , as well as mixtures of these composite oxides, and further , TiS2 , FeS2 , Nb3S4 , Mo3S4 , CoS2 , V2O5 , CrO3 , V3O3 , FeO2 , GeO2 , LiNi0.33Mn0.33Co0.33O2 , and the like.
　二次電池用正極４は、これらの正極材料に結着剤を配合したものを適当な溶媒でスラリー化して集電体に塗布・乾燥することにより作製できる。
　結着剤としてはこの用途に周知のもの、例えば二次電池用負極３の作製に例示したものを用いてもよい。 The secondary battery positive electrode 4 can be produced by mixing these positive electrode materials with a binder, forming a slurry in a suitable solvent, and applying the slurry to a current collector and drying it.
As the binder, a binder well known for this purpose, for example, one exemplified for the preparation of the negative electrode 3 for the secondary battery, may be used.
　スラリー中には、アセチレンブラック、ケッチェンブラック、導電性樹脂、導電性繊維、粒径５μｍ以下の扁平状黒鉛（グラフェン）等、二次電池用として一般に知られている導電助剤を使用することができる。 The slurry can contain conductive additives commonly known for use in secondary batteries, such as acetylene black, ketjen black, conductive resins, conductive fibers, and flat graphite (graphene) with a particle size of 5 μm or less.
　正極材料１００質量部に対する導電剤の配合比率は、０．５～２０質量部であってもよく、１～１５質量部であってもよい。正極材料１００質量部に対する結着剤の配合比率は、０．２～１０質量部であってもよく、０．５～７質量部であってもよい。結着樹脂が、水でスラリー化するときは、正極材料１００質量部に対する配合比率は、０．２～１０質量部であってもよく、０．５～７質量部であってもよい。Ｎ－メチルピロリドン等の結着樹脂を溶解する有機溶媒でスラリー化するときは、正極材料１００質量部に対する配合比率は、０．５～２０質量部であってもよく、１～１５質量部であってもよい。 The mixing ratio of the conductive agent to 100 parts by mass of the positive electrode material may be 0.5 to 20 parts by mass, or 1 to 15 parts by mass. The mixing ratio of the binder to 100 parts by mass of the positive electrode material may be 0.2 to 10 parts by mass, or 0.5 to 7 parts by mass. When the binder resin is slurried with water, the mixing ratio to 100 parts by mass of the positive electrode material may be 0.2 to 10 parts by mass, or 0.5 to 7 parts by mass. When the binder resin is slurried with an organic solvent that dissolves the binder resin, such as N-methylpyrrolidone, the mixing ratio to 100 parts by mass of the positive electrode material may be 0.5 to 20 parts by mass, or 1 to 15 parts by mass.
　正極集電体としては、アルミニウム、チタン、ジルコニウム、ハフニウム、ニオブ、タンタル等又はこれらの合金を用いればよい。 The positive electrode current collector may be made of aluminum, titanium, zirconium, hafnium, niobium, tantalum, or an alloy of these.
　二次電池用正極４の製造方法としては、周知方法、例えば負極の作製方法として例示した方法を用いればよい。 The method for manufacturing the positive electrode 4 for the secondary battery may be a well-known method, such as the method exemplified as the method for manufacturing the negative electrode.
＜電解質５＞
　電解質５としては、公知の電解液、常温溶融塩（イオン液体）、及び有機系又は無機系の固体電解質等を用いることができる。 <Electrolyte 5>
As the electrolyte 5, a known electrolytic solution, a room temperature molten salt (ionic liquid), an organic or inorganic solid electrolyte, or the like can be used.
　公知の電解液としては、例えば、エチレンカーボネート及びプロピレンカーボネート等の環状炭酸エステル、エチルメチルカーボネート及びジエチルカーボネート等の鎖状炭酸エステル等が挙げられる。 Known electrolytes include, for example, cyclic carbonates such as ethylene carbonate and propylene carbonate, and chain carbonates such as ethyl methyl carbonate and diethyl carbonate.
　常温溶融塩（イオン液体）としては、例えば、イミダゾリウム系塩、ピロリジニウム系塩、ピリジニウム系塩、アンモニウム系塩、ホスホニウム系塩、スルホニウム系塩等が挙げられる。 Examples of room temperature molten salts (ionic liquids) include imidazolium salts, pyrrolidinium salts, pyridinium salts, ammonium salts, phosphonium salts, and sulfonium salts.
　固体電解質としては、例えば、ポリエーテル系ポリマー、ポリエステル系ポリマー、ポリイミン系ポリマー、ポリビニルアセタール系ポリマー、ポリアクリロニトリル系ポリマー、ポリフッ化アルケン系ポリマー、ポリ塩化ビニル系ポリマー、ポリ（塩化ビニル－フッ化ビニリデン）系ポリマー、ポリ（スチレン－アクリロニトリル）系ポリマー、及びニトリルゴム等の直鎖型ポリマー等に代表される有機系ポリマーゲル；ジルコニア等の無機セラミックス；ヨウ化銀、ヨウ化銀硫黄化合物、ヨウ化銀ルビジウム化合物等の無機系電解質；等が挙げられる。 Solid electrolytes include, for example, organic polymer gels such as polyether polymers, polyester polymers, polyimine polymers, polyvinyl acetal polymers, polyacrylonitrile polymers, polyfluorinated alkene polymers, polyvinyl chloride polymers, poly(vinyl chloride-vinylidene fluoride) polymers, poly(styrene-acrylonitrile) polymers, and linear polymers such as nitrile rubber; inorganic ceramics such as zirconia; inorganic electrolytes such as silver iodide, silver iodide sulfur compounds, and silver iodide rubidium compounds; etc.
　電解質５にはリチウム塩を溶解したものを用いることができる。
　電解質５に難燃性を付与するためには、難燃性電解質溶解剤を加えることもできる。電解質５の粘度を低下させるためには、可塑剤を加えることもできる。 The electrolyte 5 may be one in which a lithium salt is dissolved.
A flame-retardant electrolyte dissolving agent may be added to impart flame retardancy to the electrolyte 5. A plasticizer may be added to reduce the viscosity of the electrolyte 5.
　電解質５に溶解させるリチウム塩としては、例えば、ＬｉＰＦ６、ＬｉＣｌＯ４、ＬｉＣＦ３ＳＯ３、ＬｉＢＦ４、ＬｉＡｓＦ６、ＬｉＮ（ＣＦ３ＳＯ２）２、ＬｉＮ（Ｃ２Ｆ５ＳＯ２）２及びＬｉＣ（ＣＦ３ＳＯ２）３等が挙げられる。
　前記リチウム塩は、単独で用いても、また２種以上を組み合わせて用いてもよい。
　前記リチウム塩は、電解質５全体に対して、０．１～８９．９質量％であってもよく、１．０～７９．０質量％の含有量であってもよい。 Examples of lithium salts dissolved in the electrolyte 5 include LiPF6 , LiClO4 , LiCF3SO3 , LiBF4 , LiAsF6 , LiN( CF3SO2 ) 2 , LiN( C2F5SO2 ) 2 , and LiC ( CF3SO2 ) 3 .
The lithium salts may be used alone or in combination of two or more kinds.
The content of the lithium salt may be 0.1 to 89.9% by mass, or 1.0 to 79.0% by mass, based on the total mass of the electrolyte 5 .
　電解質５のリチウム塩以外の成分は、リチウム塩の含有量が上記範囲内にあることを条件に、適当な量で添加することができる。 Components other than the lithium salt of the electrolyte 5 can be added in appropriate amounts, provided that the content of the lithium salt is within the above range.
＜セパレータ６＞
　セパレータ６は、二次電池用正極４と二次電池用負極３の間の短絡を回避する観点から用いてもよい。セパレータ６の材料は、電気化学的に安定である従来公知の材料を使用してもよい。
　セパレータ６の例としては、ポリエチレン製セパレータ、ポリプロピレン製セパレータ、セルロース製セパレータ、不織布、無機系セパレータ、グラスフィルター等が挙げられる。
　電解質５にポリマーを含める場合には、その電解質５がセパレータ６の機能を兼ね備える場合もあり、その場合、独立したセパレータ６は不要である。 <Separator 6>
The separator 6 may be used from the viewpoint of preventing a short circuit between the secondary battery positive electrode 4 and the secondary battery negative electrode 3. The material of the separator 6 may be a conventionally known material that is electrochemically stable.
Examples of the separator 6 include a polyethylene separator, a polypropylene separator, a cellulose separator, a nonwoven fabric, an inorganic separator, a glass filter, and the like.
When the electrolyte 5 contains a polymer, the electrolyte 5 may also function as the separator 6, in which case an independent separator 6 is not necessary.
［二次電池の製造方法］
　一実施形態における二次電池は、複合層２と集電層１を重ね合わせて負極材料を得る工程と、前記負極材料に１ＭＰａ以上の圧力で圧延処理を施して二次電池用負極３を得る工程、を含む製造方法で製造してもよい。 [Secondary battery manufacturing method]
In one embodiment, the secondary battery may be manufactured by a manufacturing method including a step of superposing the composite layer 2 and the current collecting layer 1 to obtain a negative electrode material, and a step of rolling the negative electrode material at a pressure of 1 MPa or more to obtain a negative electrode 3 for a secondary battery.
　次に、本開示の具体的実施例について説明するが、本開示はこれら実施例に限定されるものではない。 Next, specific examples of the present disclosure will be described, but the present disclosure is not limited to these examples.
＜板状黒鉛（Ａ２）の製造＞
　天然に産出する黒鉛を、不純物除去、粉砕、分級して、「板状黒鉛（Ａ２－１）」、「板状黒鉛（Ａ２－２）」、「板状黒鉛（Ａ２－３）」、「板状黒鉛（Ａ２－４）」を製造した。
　各板状黒鉛の５０％粒子径（ｄ５０）、厚み、平均扁平度、ＢＥＴ比表面積を下記表１に示す。 <Production of platelet graphite (A2)>
Naturally occurring graphite was subjected to removal of impurities, pulverization, and classification to produce "plate-like graphite (A2-1),""plate-like graphite (A2-2),""plate-like graphite (A2-3)," and "plate-like graphite (A2-4)."
The 50% particle size (d50), thickness, average flatness, and BET specific surface area of each plate-shaped graphite are shown in Table 1 below.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
＜表２に記載のその他の成分＿第一成分＞
《（Ａ１）成分＿ＣＧＢ－２０》
　球状黒鉛（日本黒鉛工業（株）社製、平均粒子径：２０μｍ、見掛密度：０．５３ｇ／ｃｍ３、比表面積：４．６５ｍ２／ｇ、アスペクト比：１．２）
《（Ａ２）成分＿ａｖ－ＰＬＡＴ－２》
　板状黒鉛（ＡＶＡＮＺＡＲＥ　Ｉｎｎｏｖａｃｉｏｎ　Ｔｅｃｎｏｌｏｇｉｃａ　Ｓ．Ｌ．社製、一次粒子の平均粒子径：２μｍ、厚み：１０ｎｍ、平均扁平度：１００）
《（Ｂ）成分＿ｅ－Ｓｉ１０３０》
　ケイ素粒子（Ｓｉｌｇｒａｉｎ　ｅ－Ｓｉ１０３０、エルケムジャパン（株）社製、平均粒子径：５００ｎｍ、純度：９９．６％）
《（Ｂ）成分＿ｅ－Ｓｉ４０８》
　ケイ素粒子（Ｓｉｌｇｒａｉｎ　ｅ－Ｓｉ４０８エルケムジャパン（株）社製、平均粒子径：２μｍ、純度：９９．６％）
《（Ｃ）成分＿Ｌ＃１１２０》
　結着剤（ＫＦポリマーＬ＃１１２０、（株）クレハ社製、分子量（Ｍｗ）：２．８×１０５） <Other components listed in Table 2 - First component>
<<Component (A1) CGB-20>>
Spherical graphite (manufactured by Nippon Graphite Industries Co., Ltd., average particle size: 20 μm, apparent density: 0.53 g/cm 3 , specific surface area: 4.65 m 2 /g, aspect ratio: 1.2)
<<Component (A2) _av-PLAT-2>>
Plate-shaped graphite (AVANZARE Innovación Tecnologica S.L., average particle size of primary particles: 2 μm, thickness: 10 nm, average flatness: 100)
<<Component (B) e-Si1030>>
Silicon particles (Silgrain e-Si1030, manufactured by Elkem Japan Co., Ltd., average particle size: 500 nm, purity: 99.6%)
<<Component (B) e-Si408>>
Silicon particles (Silgrain e-Si408, manufactured by Elkem Japan Co., Ltd., average particle size: 2 μm, purity: 99.6%)
<<Component (C) L#1120>>
Binder (KF Polymer L#1120, manufactured by Kureha Corporation, molecular weight (Mw): 2.8×10 5 )
＜表２に記載のその他の成分＿第二成分＞
《活物質＿５０３ＬＰ》
　５０３ＬＰ（ＪＦＥミネラル（株）社製、平均粒子径：１３μｍ、比表面積：０．６ｍ２／ｇ）
《導電助剤＿Ｌｉ－４００》
　Ｌｉ－４００（（株）デンカ社製、平均粒子径：４８ｎｍ、比表面積：４０ｍ２／ｇ） <Other components listed in Table 2 - second component>
"Active material_503LP"
503LP (manufactured by JFE Mineral Co., Ltd., average particle size: 13 μm, specific surface area: 0.6 m 2 /g)
Conductive additive Li-400
Li-400 (manufactured by Denka Co., Ltd., average particle size: 48 nm, specific surface area: 40 m 2 /g)
＜電極形成用スラリーの調製＞
　表２に「第一成分」として記載の各成分を、２５℃で自公転ミキサー（（株）シンキー社製、型番：ＡＲＶ－３１０）を用いて混合し、負極形成用スラリーを調製した。
　表２に「第二成分」として記載の各成分を、２５℃で自公転ミキサー（（株）シンキー社製、型番：ＡＲＶ－３１０）を用いて混合し、正極形成用スラリーを調製した。
　各成分の配合量は、表２に記載の数値の通り。表２中、空欄は配合なしを意味する。 <Preparation of Slurry for Forming Electrodes>
The components shown as "first component" in Table 2 were mixed at 25°C using a planetary mixer (model number: ARV-310, manufactured by Thinky Corporation) to prepare a slurry for forming a negative electrode.
The components shown as "second component" in Table 2 were mixed at 25°C using a planetary mixer (model ARV-310, manufactured by Thinky Corporation) to prepare a slurry for forming a positive electrode.
The amounts of each component are as shown in Table 2. In Table 2, blank spaces indicate no component was added.
＜電極シートの作成＞
　（株）康井精機社製のμコート３５０を用いて、前記負極形成用スラリーを、集電箔ＳＵＳ４４４　Ｈ　ＢＤ（日鉄ケミカル＆マテリアル（株）社製）の一方の面上に供給しながらグラビア塗工方式にて塗工し、塗工後に、温度１００℃・速度０．２ｍ／分の条件で乾燥を行って、厚さ６０μｍの二次電池用負極シートを作成した。
　（株）康井精機社製のμコート３５０を用いて、前記正極形成用スラリーを、集電箔ＳＵＳ４４４　Ｈ　ＢＤ（日鉄ケミカル＆マテリアル（株）社製）の一方の面上に供給しながらグラビア塗工方式にて塗工し、塗工後に、温度１００℃・速度０．２ｍ／分の条件で乾燥を行って、厚さ６０μｍの二次電池用正極シートを作成した。 <Creating electrode sheets>
Using a μ-coat 350 manufactured by Yasui Seiki Co., Ltd., the negative electrode forming slurry was applied by gravure coating while being supplied onto one side of a current collector foil SUS444 H BD (manufactured by Nippon Steel Chemical & Material Co., Ltd.), and after coating, the slurry was dried under conditions of a temperature of 100° C. and a speed of 0.2 m/min to prepare a negative electrode sheet for a secondary battery having a thickness of 60 μm.
Using a μ-coat 350 manufactured by Yasui Seiki Co., Ltd., the slurry for forming the positive electrode was applied by gravure coating while being supplied onto one side of a current collector foil SUS444 H BD (manufactured by Nippon Steel Chemical & Material Co., Ltd.), and after coating, the slurry was dried under conditions of a temperature of 100° C. and a speed of 0.2 m/min to prepare a positive electrode sheet for a secondary battery having a thickness of 60 μm.
＜二次電池の作成＞
　前記二次電池用負極シート及び前記二次電池用正極シートをロードセル付きの２５０ｍφロールプレスにてロールプレス（圧力：１．５ＭＰａ）し、直径１２．５ｍｍの円形状に打ち抜き、１１０℃で２時間、真空乾燥し、評価用の負極と正極とした。
　前記負極及び前記正極と電解液を含浸させたセパレータ（Ｓ７０３－１、住友化学（株）社製）を介して重ねて、充放電試験用の二次電池を作製した。
　電解液としてはエチレンカーボネートとジエチレンカーボネートの混合液（体積比が１：１）に、過塩素酸リチウムを１［モル／リットル］の濃度で溶解させたものを注液した。 <Creating a secondary battery>
The negative electrode sheet for secondary batteries and the positive electrode sheet for secondary batteries were roll-pressed (pressure: 1.5 MPa) using a 250 mmφ roll press equipped with a load cell, punched out into circular shapes with a diameter of 12.5 mm, and vacuum-dried at 110° C. for 2 hours to obtain negative and positive electrodes for evaluation.
The negative electrode and the positive electrode were stacked with a separator (S703-1, manufactured by Sumitomo Chemical Co., Ltd.) impregnated with an electrolytic solution therebetween to prepare a secondary battery for charge/discharge tests.
The electrolyte was a mixture of ethylene carbonate and diethylene carbonate (volume ratio 1:1) in which lithium perchlorate was dissolved at a concentration of 1 mol/liter, and the solution was poured.
＜評価方法＿二次電池用負極シート＞
　作成した二次電池用負極シートの断面を、日本電子株式会社製　ＳＥＭ装置（ＪＳＭ－ＩＦ１００）を用いて、二次電子像及び反射電子像を取得した。観察倍率は５０００倍であった。
　取得した二次電子像又は反射電子像を用いて、下記の方法で「空隙率」、「ケイ素存在割合」、「空隙倍率（空隙／Ｓｉ）」を算出した。算出結果を表２に示す。 <Evaluation method: negative electrode sheet for secondary batteries>
A secondary electron image and a backscattered electron image of the cross section of the produced negative electrode sheet for secondary batteries were obtained using a SEM device (JSM-IF100) manufactured by JEOL Ltd. The observation magnification was 5000 times.
Using the acquired secondary electron image or backscattered electron image, the "porosity,""siliconcontent," and "porosity ratio (void/Si)" were calculated by the following method. The calculation results are shown in Table 2.
《空隙率》
　ここで、空隙率とは、「ＳＥＭ断面中に占める空隙（Ｄ）の面積の合計値／ＳＥＭ断面の総面積」で算出される値であって、断面ＳＥＭ画像（５０００倍）において、二次電池用負極シートの断面に対する空隙（Ｄ）の占める割合を意味する。
　二次電子像（ｎ＝５）を２値化処理し、空隙（Ｄ）の面積の平均値から、空隙率（％）を算出した。 Porosity
Here, the porosity is a value calculated by "the sum of the areas of the voids (D) in the SEM cross section/the total area of the SEM cross section", and means the ratio of the voids (D) to the cross section of the negative electrode sheet for secondary batteries in a cross-sectional SEM image (5000x).
The secondary electron images (n=5) were binarized, and the porosity (%) was calculated from the average area of the voids (D).
《ケイ素存在割合》
　ここで、ケイ素存在割合とは、「ＳＥＭ断面中に占めるケイ素粒子（Ｂ）の面積の合計値／ＳＥＭ断面の総面積」で算出される値であって、断面ＳＥＭ画像（５０００倍）において、二次電池用負極シートの断面に対するケイ素粒子（Ｂ）の占める割合を意味する。
　反射電子像（ｎ＝５）を２値化処理し、ケイ素粒子（Ｂ）の面積率の平均値から、ケイ素存在割合（％）を算出した。 <Silicon content>
Here, the silicon abundance ratio is a value calculated by "the total area of silicon particles (B) in the SEM cross section/the total area of the SEM cross section", and means the ratio of silicon particles (B) to the cross section of the negative electrode sheet for secondary batteries in a cross-sectional SEM image (5000x).
The reflected electron images (n=5) were binarized, and the silicon abundance ratio (%) was calculated from the average value of the area ratio of the silicon particles (B).
《空隙倍率（空隙／Ｓｉ）》
　ここで、空隙倍率とは、「空隙率／ケイ素存在割合」で算出される値であって、断面ＳＥＭ画像（５０００倍）において、空隙（Ｄ）の占める割合とケイ素粒子（Ｂ）の占める割合の比を意味する。 <<Void ratio (void/Si)>>
Here, the void ratio is a value calculated by "void ratio/silicon abundance ratio" and means the ratio of the proportion of voids (D) to the proportion of silicon particles (B) in a cross-sectional SEM image (5000x).
＜評価方法＿負極＞
　作成した二次電池用負極シートについて、下記の方法で「活物質容量」を測定した。測定結果を表２に示す。
《活物質容量（ｍＡｈ／ｇ）》
　前記二次電池用負極シートとＬｉ箔を用いて構成したハーフセルで、０．５ｍＡの電流値で回路電圧が０ｍＶに達する迄定電流充電を行い、回路電圧が０ｍＶに達した時点で定電圧充電に切替え、さらに電流値が０．０５ｍＡになるまで充電を続けた。その後、３０分間休止した。次に、０．５ｍＡの電流値で回路電圧が３．０Ｖに達するまで定電流放電を行い、回路電圧が３．０Ｖに達した時点で定電圧放電に切替え、さらに電流値が０．０５ｍＡになるまで放電を続けた。
　この充放電を２サイクル行い、次式から活物質容量を計算した。なお、この試験では、リチウムを活物質へ吸蔵する過程を充電、離脱する過程を放電とした。
　　活物質容量（ｍＡｈ／ｇ）＝第２サイクルの放電容量／負極活物質質量 <Evaluation method: negative electrode>
The "active material capacity" of the produced negative electrode sheet for secondary batteries was measured by the following method. The measurement results are shown in Table 2.
Active material capacity (mAh/g)
A half cell composed of the negative electrode sheet for secondary batteries and Li foil was charged at a constant current of 0.5 mA until the circuit voltage reached 0 mV, and then switched to constant voltage charging when the circuit voltage reached 0 mV, and continued charging until the current value reached 0.05 mA. Then, the cell was paused for 30 minutes. Next, a constant current discharge was performed at a current value of 0.5 mA until the circuit voltage reached 3.0 V, and then switched to constant voltage discharge when the circuit voltage reached 3.0 V, and continued discharging until the current value reached 0.05 mA.
This charge/discharge cycle was repeated for two cycles, and the capacity of the active material was calculated from the following formula: In this test, the process of absorbing and releasing lithium into the active material was defined as charge, and the process of absorbing and releasing lithium was defined as discharge.
Active material capacity (mAh/g) = Discharge capacity in the second cycle / Mass of negative electrode active material
＜評価方法＿二次電池＞
　作成した二次電池について、下記の方法で「サイクル特性」を測定した。測定結果を表２に示す。
《サイクル特性》
　ここで、サイクル特性とは、５００サイクル目の「容量維持率」を意味し、目標は８０％以上である。
　フルセルで、２．５ｍＡの電流値で回路電圧が２．０Ｖに達する迄定電流充電を行い、回路電圧が０ｍＶに達した時点で定電圧充電に切替え、さらに電流値が０．２５ｍＡになるまで充電を続けた。その後、３０分間休止した。次に、２．５ｍＡの電流値で回路電圧が４．６Ｖに達するまで定電流放電を行い、回路電圧が４．６Ｖに達した時点で定電圧放電に切替え、さらに電流値が０．２５ｍＡになるまで放電を続けた。
　この充放電を５００回繰り返し、次式を用いてサイクル特性を計算した。
　　容量維持率＝第５００サイクルの放電容量／第１サイクルの放電容量 <Evaluation method: secondary battery>
The cycle characteristics of the secondary batteries thus produced were measured by the following method. The results are shown in Table 2.
Cycle characteristics
Here, the cycle characteristic means the "capacity retention rate" at the 500th cycle, and the target is 80% or more.
A full cell was charged at a constant current of 2.5 mA until the circuit voltage reached 2.0 V, then switched to constant voltage charging when the circuit voltage reached 0 mV, and continued charging until the current value reached 0.25 mA. Then, the charge was paused for 30 minutes. Next, a constant current discharge was performed at a current of 2.5 mA until the circuit voltage reached 4.6 V, then switched to constant voltage discharge when the circuit voltage reached 4.6 V, and continued discharging until the current value reached 0.25 mA.
This charge/discharge cycle was repeated 500 times, and the cycle characteristics were calculated using the following formula.
Capacity retention rate=discharge capacity at 500th cycle/discharge capacity at 1st cycle
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　本開示によれば、二次電池の充放電を繰り返しても金属質物の膨張劣化が起こりにくい二次電池用負極であって、その二次電池用負極を用いた二次電池において、容量と充放電効率とサイクル特性が、それぞれ向上する二次電池用負極を提供することができる。
　本開示の二次電池用負極は、リチウムイオン二次電池の負極に使用することができる。 According to the present disclosure, it is possible to provide a negative electrode for a secondary battery in which expansion and deterioration of the metallic material is unlikely to occur even when the secondary battery is repeatedly charged and discharged, and in a secondary battery using the negative electrode for a secondary battery, the capacity, charge and discharge efficiency, and cycle characteristics are all improved.
The negative electrode for secondary batteries of the present disclosure can be used as the negative electrode of lithium ion secondary batteries.
　　１　　集電層
　　Ａ　　炭素粒子
　　Ａ１　球状黒鉛
　　Ａ２　板状黒鉛
　　Ｂ　　ケイ素粒子
　　２　　複合層
　　Ｃ　　結着剤
　　Ｄ　　空隙
　　３　　二次電池用負極
　　４　　二次電池用正極
　　５　　電解質
　　６　　セパレータ
　　７　　リチウムイオン REFERENCE SIGNS LIST 1 Current collecting layer A Carbon particles A1 Spherical graphite A2 Plate-like graphite B Silicon particles 2 Composite layer C Binder D Void 3 Negative electrode for secondary battery 4 Positive electrode for secondary battery 5 Electrolyte 6 Separator 7 Lithium ion

Claims (8)

  1. 　集電層（１）と複合層（２）を含む二次電池用負極（３）であって、
    　前記複合層（２）が、炭素粒子（Ａ）とケイ素粒子（Ｂ）を含み、
    　前記炭素粒子（Ａ）が、球状黒鉛（Ａ１）及び板状黒鉛（Ａ２）を含み、
    　前記複合層（２）の断面ＳＥＭ画像（５０００倍）において、前記ケイ素粒子（Ｂ）の占める割合と空隙（Ｄ）の占める割合の比（ケイ素粒子（Ｂ）：空隙（Ｄ））が、１．０：６．０～１．０：１０．０である、二次電池用負極。     A negative electrode (3) for a secondary battery comprising a current collecting layer (1) and a composite layer (2),
    The composite layer (2) contains carbon particles (A) and silicon particles (B),
    The carbon particles (A) contain spherical graphite (A1) and plate-like graphite (A2),
    In a cross-sectional SEM image (magnification: 5000) of the composite layer (2), the ratio of the proportion of the silicon particles (B) to the proportion of the voids (D) (silicon particles (B):voids (D)) is 1.0:6.0 to 1.0:10.0.
  2. 　前記複合層（２）の断面ＳＥＭ画像（５０００倍）において、前記空隙（Ｄ）の占める割合が、１５．０％～３５．０％である、請求項１に記載の二次電池用負極。 The negative electrode for a secondary battery according to claim 1, wherein the proportion of the voids (D) in a cross-sectional SEM image (5000x) of the composite layer (2) is 15.0% to 35.0%.
  3. 　前記複合層（２）の断面ＳＥＭ画像（５０００倍）において、前記ケイ素粒子（Ｂ）の占める割合が、２．０％～５．０％である、請求項１又は２に記載の二次電池用負極。 The negative electrode for a secondary battery according to claim 1 or 2, wherein the proportion of the silicon particles (B) in a cross-sectional SEM image (5000x) of the composite layer (2) is 2.0% to 5.0%.
  4. 　前記球状黒鉛（Ａ１）と前記板状黒鉛（Ａ２）の質量比（Ａ１：Ａ２）が、６０：４０～９５：５である、請求項１～３の何れかに記載の二次電池用負極。 The negative electrode for a secondary battery according to any one of claims 1 to 3, wherein the mass ratio (A1:A2) of the spherical graphite (A1) to the plate-like graphite (A2) is 60:40 to 95:5.
  5. 　前記球状黒鉛（Ａ１）のメディアン径（ｄ５０）が１０μｍ～３０μｍであり、前記板状黒鉛（Ａ２）のメディアン径（ｄ５０）が５μｍ～４０μｍであり、前記ケイ素粒子（Ｂ）のメディアン径（ｄ５０）が１μｍ以下である、請求項１～４の何れかに記載の二次電池用負極。 The negative electrode for a secondary battery according to any one of claims 1 to 4, wherein the median diameter (d50) of the spherical graphite (A1) is 10 μm to 30 μm, the median diameter (d50) of the plate-like graphite (A2) is 5 μm to 40 μm, and the median diameter (d50) of the silicon particles (B) is 1 μm or less.
  6. 　前記板状黒鉛（Ａ２）が、厚み（Ｚ方向）１～５００ｎｍ及び長さ（Ｘ及びＹ方向）５～４０μｍの形状を有する、請求項１～５の何れかに記載の二次電池用負極。 The negative electrode for a secondary battery according to any one of claims 1 to 5, wherein the plate-like graphite (A2) has a thickness (Z direction) of 1 to 500 nm and a length (X and Y directions) of 5 to 40 μm.
  7. 　請求項１～６のいずれか１項に記載の二次電池用負極（３）と、二次電池用正極（４）と、電解質（５）とを備える、二次電池。 A secondary battery comprising a negative electrode (3) for a secondary battery according to any one of claims 1 to 6, a positive electrode (4) for a secondary battery, and an electrolyte (5).
  8. 　請求項７に記載の二次電池の製造方法であって、
    　前記複合層（２）と前記集電層（１）を重ね合わせて負極材料を得る工程と、
    　前記負極材料に、１ＭＰａ以上の圧力で圧延処理を施して前記二次電池用負極（３）を得る工程を有する、二次電池の製造方法。     A method for producing a secondary battery according to claim 7, comprising the steps of:
    a step of superposing the composite layer (2) and the current collecting layer (1) to obtain a negative electrode material;
    The method for producing a secondary battery includes a step of rolling the negative electrode material at a pressure of 1 MPa or more to obtain the negative electrode for the secondary battery (3).
PCT/JP2023/038216 2022-10-31 2023-10-23 Negative electrode for secondary battery, secondary battery, and method for producing same WO2024095810A1 (en)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH11238505A (en) * 1997-12-16 1999-08-31 Matsushita Electric Ind Co Ltd Nonaqueous electrolyte secondary battery, negative electrode thereof, and manufacture of the negative electrode
JPH11354126A (en) * 1998-06-09 1999-12-24 Matsushita Electric Ind Co Ltd Nonaqueous electrolyte battery negative electrode and battery using it
US20160268591A1 (en) * 2015-03-13 2016-09-15 Samsung Sdi Co., Ltd. Negative electrode for rechargeable lithium battery, method of manufacturing same, and rechargeable lithium battery including same

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH11238505A (en) * 1997-12-16 1999-08-31 Matsushita Electric Ind Co Ltd Nonaqueous electrolyte secondary battery, negative electrode thereof, and manufacture of the negative electrode
JPH11354126A (en) * 1998-06-09 1999-12-24 Matsushita Electric Ind Co Ltd Nonaqueous electrolyte battery negative electrode and battery using it
US20160268591A1 (en) * 2015-03-13 2016-09-15 Samsung Sdi Co., Ltd. Negative electrode for rechargeable lithium battery, method of manufacturing same, and rechargeable lithium battery including same

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