WO2024095810A1 - 二次電池用負極、二次電池及びその製造方法 - Google Patents

二次電池用負極、二次電池及びその製造方法 Download PDF

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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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secondary battery
graphite
negative electrode
composite layer
silicon particles
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French (fr)
Japanese (ja)
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祐輔 久野
和倫 岡野
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Kyocera Corp
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Kyocera Corp
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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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PCT/JP2023/038216 2022-10-31 2023-10-23 二次電池用負極、二次電池及びその製造方法 Ceased WO2024095810A1 (ja)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH11238505A (ja) * 1997-12-16 1999-08-31 Matsushita Electric Ind Co Ltd 非水電解液二次電池およびその負極と負極の製造法
JPH11354126A (ja) * 1998-06-09 1999-12-24 Matsushita Electric Ind Co Ltd 非水電解液二次電池用負極およびそれを用いた電池
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 (ja) * 1997-12-16 1999-08-31 Matsushita Electric Ind Co Ltd 非水電解液二次電池およびその負極と負極の製造法
JPH11354126A (ja) * 1998-06-09 1999-12-24 Matsushita Electric Ind Co Ltd 非水電解液二次電池用負極およびそれを用いた電池
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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