WO2024048183A1 - 二次電池用負極、二次電池、及び二次電池用負極の製造方法 - Google Patents

二次電池用負極、二次電池、及び二次電池用負極の製造方法 Download PDF

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WO2024048183A1
WO2024048183A1 PCT/JP2023/028248 JP2023028248W WO2024048183A1 WO 2024048183 A1 WO2024048183 A1 WO 2024048183A1 JP 2023028248 W JP2023028248 W JP 2023028248W WO 2024048183 A1 WO2024048183 A1 WO 2024048183A1
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negative electrode
secondary battery
mass
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active material
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French (fr)
Japanese (ja)
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明宏 谷口
薫 井上
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Panasonic Intellectual Property Management Co Ltd
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Panasonic Intellectual Property Management Co Ltd
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Priority to CN202380060423.XA priority Critical patent/CN119731797A/zh
Priority to EP23859952.6A priority patent/EP4583191A4/en
Priority to JP2024544058A priority patent/JPWO2024048183A1/ja
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
    • 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
    • H01M4/04—Processes of manufacture in general
    • H01M4/0471—Processes of manufacture in general involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis
    • 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
    • H01M4/1395—Processes of manufacture of electrodes based on metals, Si 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
    • H01M4/362—Composites
    • H01M4/364—Composites as mixtures
    • 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
    • H01M4/386—Silicon or alloys based on silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present disclosure relates to a negative electrode for a secondary battery, a secondary battery, and a method for manufacturing a negative electrode for a secondary battery.
  • Si-based materials are attracting attention as materials that can increase the capacity of batteries.
  • the Si-based material is a material that can electrochemically absorb and release lithium ions, and can be charged and discharged with a much larger capacity than carbon materials such as graphite.
  • Patent Document 1 discloses a negative electrode active material for a lithium ion secondary battery containing a Si-based material represented by SiOx (0 ⁇ x ⁇ 2) and a carbon material, A negative electrode active material for a lithium ion secondary battery is disclosed, which is characterized in that the active material has voids inside.
  • Patent Document 2 discloses a negative electrode for a lithium ion secondary battery having a current collector and a negative electrode active material layer laminated on the current collector, the negative electrode active material layer being , a silicon oxide (Si-based material) represented by SiOx (0.3 ⁇ x ⁇ 1.6), and a particulate conductor containing a metal element, and in the negative electrode active material layer.
  • the front part located on the opposite side of the current collector is a negative electrode for lithium ion secondary battery containing a larger amount of the conductor than the inner part located on the current collector side in the negative electrode active material layer.
  • a method for producing a current collector comprising an acidic resin and a silicon oxide represented by SiOx (0.3 ⁇ x ⁇ 1.6), which is laminated on the current collector.
  • a method for producing a negative electrode for a lithium ion secondary battery comprises a heating step of heating the negative electrode intermediate at a temperature, and a removing step of removing the metal layer after the heating step.
  • Si-based materials can increase the capacity of secondary batteries, they pose a problem of swelling of the negative electrode, and improvements are desired.
  • an object of the present disclosure is to provide a negative electrode for a secondary battery, a secondary battery, and a method for manufacturing a negative electrode for a secondary battery that can suppress expansion of the negative electrode.
  • a negative electrode for a secondary battery that is one aspect of the present disclosure includes a negative electrode current collector and a negative electrode composite material layer disposed on the negative electrode current collector, and the negative electrode composite material layer includes a carbon material and a Si
  • the pore size distribution of the negative electrode composite material layer which has a negative electrode active material and a binder containing a system material, has two peak values R1 and R2, measured by mercury porosimetry, and the peak value R1 is 0. .5 ⁇ m or more and 1.5 ⁇ m or less, and the peak value R2 is 2 ⁇ m or more and 10 ⁇ m or less, and the content of the binder contained in the negative electrode composite layer is 4 ⁇ m or more with respect to the total mass of the negative electrode active material. % by mass or more.
  • a secondary battery that is one aspect of the present disclosure is characterized by comprising the negative electrode for a secondary battery.
  • a method for manufacturing a negative electrode for a secondary battery includes applying a negative electrode paste including a negative electrode active material including a carbon material and a Si-based material, a binder, and a pore-forming material to a negative electrode current collector.
  • the coating film is heat-treated to decompose and vaporize the pore-forming material, and the negative electrode a second step of forming a material layer, and the pore size distribution of the negative electrode composite material layer measured by mercury intrusion method has two peak values R1 and R2, and the peak value R1 is 0.
  • the peak value R2 is 2 ⁇ m or more and 10 ⁇ m or less
  • the content of the binder contained in the negative electrode paste is 4% by mass with respect to the total mass of the negative electrode active material. It is characterized by the above.
  • a negative electrode for a secondary battery it is possible to provide a negative electrode for a secondary battery, a secondary battery, and a method for manufacturing a negative electrode for a secondary battery that can suppress expansion of the negative electrode.
  • FIG. 1 is a cross-sectional view of a secondary battery that is an example of an embodiment.
  • a negative electrode for a secondary battery that is one aspect of the present disclosure includes a negative electrode current collector and a negative electrode composite material layer disposed on the negative electrode current collector, and the negative electrode composite material layer includes a carbon material and a Si
  • the pore size distribution of the negative electrode composite material layer which has a negative electrode active material and a binder containing a system material, has two peak values R1 and R2, measured by mercury porosimetry, and the peak value R1 is 0. .5 ⁇ m or more and 1.5 ⁇ m or less, and the peak value R2 is 2 ⁇ m or more and 10 ⁇ m or less, and the content of the binder contained in the negative electrode composite layer is 4 ⁇ m or more with respect to the total mass of the negative electrode active material. % by mass or more.
  • the negative electrode composite material layer in which the two peak values (R1, R2) in the pore size distribution satisfy the above range voids are formed that are optimal for absorbing the expansion and contraction of the Si-based material due to charging and discharging. It is presumed that this suppresses the expansion of the negative electrode. Furthermore, it is presumed that when the content of the binder satisfies the above range, a sufficient amount of the binder adheres to the Si-based material is ensured, so that swelling of the negative electrode is further suppressed.
  • a pore-forming material is used when manufacturing the negative electrode for a secondary battery of the present disclosure, but since the binder also adheres to the pore-forming material, if the binder content is low, the Si-based material It becomes difficult to ensure a sufficient amount of binder adheres to the surface. Note that the pore-forming material decomposes and vaporizes and disappears during the heat treatment during negative electrode manufacturing, so the binder attached to the pore-forming material becomes isolated and has little effect on suppressing the expansion of the negative electrode. It is presumed that.
  • FIG. 1 is a cross-sectional view of a secondary battery that is an example of an embodiment.
  • the secondary battery 10 shown in FIG. 1 includes a wound-type electrode body 14 in which a positive electrode 11 and a negative electrode 12 are wound with a separator 13 in between, a non-aqueous electrolyte, and a non-aqueous electrolyte arranged above and below the electrode body 14, respectively. It includes insulating plates 18 and 19 and a battery case 15 that accommodates the above members.
  • the battery case 15 includes a case body 16 having a cylindrical shape with a bottom and a sealing body 17 that closes an opening of the case body 16.
  • the wound type electrode body 14 other forms of electrode bodies may be applied, such as a laminated type electrode body in which positive electrodes and negative electrodes are alternately laminated with separators interposed therebetween.
  • the battery case 15 include a metal case having a cylindrical shape, a square shape, a coin shape, a button shape, etc., a resin case formed by laminating resin sheets (so-called laminate type), and the like.
  • the nonaqueous electrolyte is, for example, an electrolyte that has lithium ion conductivity, and may be a liquid electrolyte (electrolyte solution) or a solid electrolyte.
  • the liquid electrolyte includes, for example, a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent.
  • the negative electrode composite material layer in which the two peak values (R1, R2) in the pore size distribution satisfy the above range has voids that are optimal for improving the permeability of the electrolyte. It is presumed that the use of an electrolytic solution further suppresses the expansion of the negative electrode.
  • non-aqueous solvents used include esters, ethers, nitriles, amides, and mixed solvents of two or more of these.
  • nonaqueous solvents examples include ethylene carbonate (EC), ethylmethyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and mixed solvents thereof.
  • the non-aqueous solvent may contain a halogen-substituted product (for example, fluoroethylene carbonate) in which at least a portion of hydrogen in these solvents is replaced with a halogen atom such as fluorine.
  • a lithium salt such as LiPF 6 is used as the electrolyte salt.
  • the solid electrolyte for example, a solid or gel polymer electrolyte, an inorganic solid electrolyte, etc.
  • an inorganic solid electrolyte materials known for use in all-solid lithium ion secondary batteries and the like (for example, oxide-based solid electrolytes, sulfide-based solid electrolytes, halogen-based solid electrolytes, etc.) can be used.
  • the polymer electrolyte includes, for example, a lithium salt and a matrix polymer, or a nonaqueous solvent, a lithium salt, and a matrix polymer.
  • the matrix polymer for example, a polymer material that absorbs a non-aqueous solvent and gels is used. Examples of polymer materials include fluororesins, acrylic resins, polyether resins, and the like. Note that the non-aqueous electrolyte is just one example, and an aqueous electrolyte may be used if applicable.
  • the case body 16 is, for example, a cylindrical metal container with a bottom.
  • a gasket 28 is provided between the case body 16 and the sealing body 17 to ensure airtightness inside the battery.
  • the case main body 16 has an overhanging portion 22 that supports the sealing body 17 and has, for example, a part of a side surface overhanging inward.
  • the projecting portion 22 is preferably formed in an annular shape along the circumferential direction of the case body 16, and supports the sealing body 17 on its upper surface.
  • the sealing body 17 has a structure in which a filter 23, a lower valve body 24, an insulating member 25, an upper valve body 26, and a cap 27 are stacked in order from the electrode body 14 side.
  • Each member constituting the sealing body 17 has, for example, a disk shape or a ring shape, and each member except the insulating member 25 is electrically connected to each other.
  • the lower valve body 24 and the upper valve body 26 are connected to each other at their central portions, and an insulating member 25 is interposed between their respective peripheral portions.
  • the positive electrode lead 20 is connected by welding or the like to the lower surface of the filter 23, which is the bottom plate of the sealing body 17, and the cap 27, which is the top plate of the sealing body 17 and electrically connected to the filter 23, serves as a positive terminal.
  • the negative electrode lead 21 is connected to the bottom inner surface of the case body 16 by welding or the like, and the case body 16 serves as a negative electrode terminal.
  • the positive electrode 11, negative electrode 12, and separator 13 will be explained in detail below.
  • the positive electrode 11 includes a positive electrode current collector and a positive electrode composite material layer disposed on the positive electrode current collector.
  • a metal foil such as aluminum that is stable in the potential range of the positive electrode 11, a film with the metal disposed on the surface, or the like can be used.
  • the positive electrode composite material layer includes, for example, a positive electrode active material, a binder, a conductive material, and the like.
  • the positive electrode 11 can be made by, for example, applying a positive electrode paste containing a positive electrode active material, a binder, a conductive material, etc. to the surface of a positive electrode current collector, drying the coating film, and then rolling the positive electrode mixture layer to form a positive electrode current collector. It can be produced by forming it on both sides of.
  • Examples of the conductive material included in the positive electrode composite layer include carbon materials such as carbon black, acetylene black, Ketjen black, graphite, and carbon nanotubes.
  • Binders included in the positive electrode composite layer include polytetrafluoroethylene (PTFE), fluororesins such as polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide resins, acrylic resins, polyolefin resins, and styrene resins.
  • Examples include cellulose derivatives of butadiene rubber (SBR), carboxymethyl cellulose (CMC) or its salts, polyacrylic acid (PAA) or its salts, polyethylene oxide (PEO), polyvinyl alcohol (PVA), and the like.
  • a lithium transition metal composite oxide or the like is used as the positive electrode active material.
  • Metal elements contained in the lithium transition metal composite oxide include Ni, Co, Mn, Al, B, Mg, Ti, V, Cr, Fe, Cu, Zn, Ga, Sr, Zr, Nb, In, and Sn. , Ta, W, etc. Among these, it is preferable to contain at least one of Ni, Co, and Mn.
  • LiMO2 An example of a suitable lithium transition metal composite oxide is the general formula LiMO2 (M is Ni and X, X is a metal element other than Ni, and the proportion of Ni is the total number of moles of the metal elements other than Li 50 mol % or more and 95 mol % or less of Examples of X in the above formula include Co, Mn, Al, B, Mg, Ti, V, Cr, Fe, Cu, Zn, Ga, Sr, Zr, Nb, In, Sn, Ta, W, etc. .
  • the negative electrode 12 includes a negative electrode current collector and a negative electrode composite material layer disposed on the negative electrode current collector.
  • a metal foil such as copper that is stable in the potential range of the negative electrode 12, a film with the metal disposed on the surface, or the like can be used.
  • the negative electrode composite material layer contains a negative electrode active material and a binder, and may also contain a conductive material and the like.
  • the negative electrode active material includes a carbon material and a Si-based material. Note that the negative electrode active material may include, in addition to carbon materials and Si-based materials, a substance that can reversibly insert and release lithium ions. Examples of the conductive material include the same ones as in the case of the positive electrode 11.
  • the pore size distribution of the negative electrode composite layer measured by mercury intrusion method has two peak values R1 and R2.
  • the peak value R1 is 0.5 ⁇ m or more and 1.5 ⁇ m or less
  • the peak value R2 is 2 ⁇ m or more and 10 ⁇ m or less.
  • mercury intrusion method mercury is pressurized to infiltrate the pores of a solid sample, and the diameter and volume of the pores are calculated from the pressure applied to the mercury and the amount of mercury injected into the pores. .
  • the diameter D of the pore can be calculated from the pressure P, the contact angle ⁇ of mercury, and the surface tension ⁇ of mercury according to the following formula. It will be done.
  • the pore size distribution measured by mercury porosimetry is a graph in which the Log differential pore volume (cm 3 /g) is plotted against the average pore size ( ⁇ m) in the section of each measurement point, and the horizontal axis is The pore diameter is ( ⁇ m), and the vertical axis is the Log differential pore volume (cm 3 /g).
  • the peak value in the pore size distribution means the pore size at the apex of the peak in the pore size distribution.
  • the peak value R1 may be 0.5 ⁇ m or more and 1.5 ⁇ m or less, but is preferably 0.8 ⁇ m or more and 1.2 ⁇ m or less, for example. If the peak value R1 is less than 0.5 ⁇ m, there are many small voids between the particles in the negative electrode composite layer, so for example, the permeability of the electrolyte decreases, making it difficult to increase the capacity of the secondary battery. I can't. Furthermore, if the peak value R1 is more than 1.5 ⁇ m (less than 2 ⁇ m), for example, the density of the negative electrode active material decreases, making it impossible to increase the capacity of the secondary battery.
  • the peak value R2 may be 2 ⁇ m or more and 10 ⁇ m or less, but preferably, for example, 4 ⁇ m or more and 8 ⁇ m or less. If the peak value R2 is less than 2 ⁇ m, for example, there are few voids in the negative electrode composite material layer that can absorb the expansion and contraction of the Si-based material due to charging and discharging, so that expansion of the negative electrode cannot be suppressed. Furthermore, if the peak value R2 is 10 ⁇ m or more, for example, there are many large voids in the negative electrode composite layer, so the density of the negative electrode active material decreases, making it impossible to increase the capacity of the secondary battery.
  • Pore size distribution measurement by mercury intrusion method is performed on the negative electrode composite layer before initial charging. For example, using a measurement sample obtained by punching out a secondary battery negative electrode into a predetermined shape before initial charging, the pore size distribution of the negative electrode composite layer of the measurement sample is measured by mercury porosimetry. It can be carried out. Note that the measurement sample only needs to have at least a negative electrode composite material layer on its surface, and may have other structures such as a negative electrode current collector.
  • Measurement of pore size distribution by mercury porosimetry can be performed using, for example, an apparatus such as the Autopore IV9500 series manufactured by Micromeltics.
  • a measurement sample is sealed in a sample container under an inert atmosphere, mercury is injected into the sample container, and pressure is applied to the mercury.
  • the pressure applied to the mercury is adjusted as appropriate depending on the size of the pores that the measurement sample may have, and is not particularly limited, for example, from 0.5 psi (3.4 kPa) to 60,000 psi (413,400 kPa). It is preferable to measure while changing the pressure because the pore diameter can be measured over a wide range.
  • the Si-based material contained in the negative electrode active material is not particularly limited as long as it can reversibly absorb and release ions such as lithium ions, and includes, for example, Si particles, Si-containing alloy particles, Si compound particles, etc. can be mentioned. These may be used alone or in combination of two or more types.
  • Si particles can be obtained by a gas phase method or by pulverizing silicon chips, but any method produced can be used.
  • alloy particles containing Si include alloys containing Si and a metal selected from an alkali metal, an alkaline earth metal, a transition metal, a rare earth metal, or a combination thereof.
  • the Si compound particles include, for example, Si compound particles having a silicate phase and Si particles dispersed in the silicate phase, and Si compound particles having a silicon oxide phase and Si particles dispersed in the silicon oxide phase.
  • Examples include compound particles, Si compound particles having a carbon phase and Si particles dispersed in the carbon phase. Among these, Si compound particles having a silicate phase and Si particles dispersed in the silicate phase, and Si compound particles having a carbon phase and the Preferred are Si compound particles having Si particles dispersed in a carbon phase.
  • the silicate phase contains, for example, at least one element selected from lithium, sodium, potassium, rubidium, cesium, francium, beryllium, magnesium, calcium, strontium, barium, and radium because of its high lithium ion conductivity. It is preferable to include.
  • the silicate phase is preferably a silicate phase containing lithium (hereinafter sometimes referred to as lithium silicate phase) from the viewpoint of high lithium ion conductivity.
  • Si compound particles in which Si particles are dispersed in a silicon oxide phase are, for example, represented by the general formula SiO x (preferably in the range of 0 ⁇ x ⁇ 2, more preferably in the range of 0.5 ⁇ x ⁇ 1.6). be done.
  • Si compound particles in which Si particles are dispersed in a carbon phase have, for example, the general formula SixC1y (0 ⁇ x ⁇ 1 and 0 ⁇ y ⁇ 1, preferably 0.3 ⁇ x ⁇ 0.45 and 0.7 ⁇ The range of y ⁇ 0.55 is more preferable).
  • a conductive film made of a highly conductive material is formed on the surface of the particles of the Si-based material.
  • the conductive film include a carbon film, a metal film, and a metal compound film, but a carbon film is preferable from the viewpoint of electrochemical stability.
  • the carbon film can be formed, for example, by a CVD method using acetylene, methane, etc., or by a method of mixing coal pitch, petroleum pitch, phenol resin, etc. with a silicon-based active material and subjecting the mixture to heat treatment.
  • a conductive film may be formed by fixing a conductive filler such as carbon black to the particle surface of the Si-based material using a binder.
  • the content of the Si-based material is preferably 30% by mass or more based on the total mass of the negative electrode active material, for example, from the viewpoint of increasing the capacity of the secondary battery.
  • the content of the Si-based material should be 30% by mass or more and 60% by mass or less based on the total mass of the negative electrode active material. It is preferably at least 35% by mass and at most 55% by mass.
  • the average particle size of the Si-based material is preferably 4 ⁇ m or more, for example, in order to suppress deterioration of charge-discharge cycle characteristics due to side reactions with the non-aqueous electrolyte. Furthermore, in terms of suppressing the deterioration of the charge/discharge cycle characteristics and further suppressing the swelling of the negative electrode, the average particle size of the Si-based material is preferably, for example, 4 ⁇ m or more and 12 ⁇ m or less, and 6 ⁇ m or more and 10 ⁇ m or less. is more preferable.
  • the carbon material contained in the negative electrode active material includes, for example, conventionally known carbon materials used as negative electrode active materials of secondary batteries.
  • Graphite such as natural graphite such as flaky graphite, massive graphite, and earthy graphite, and artificial graphite such as massive artificial graphite (MAG) and graphitized mesophase carbon microbeads (MCMB) is preferable.
  • MAG massive artificial graphite
  • MCMB graphitized mesophase carbon microbeads
  • the average particle size of the carbon material is preferably 10 ⁇ m or more and 25 ⁇ m or less, and more preferably 12 ⁇ m or more and 20 ⁇ m or less, for example, in order to further suppress swelling of the negative electrode.
  • the average particle size of each material is the volume average particle size D50 where the volume integrated value is 50% in the particle size distribution obtained by laser diffraction scattering method.
  • the content of the carbon material is, for example, preferably 40% by mass or more and 70% by mass or less, and more preferably 45% by mass or more and 65% by mass or less, based on the total mass of the negative electrode active material.
  • the binders included in the negative electrode composite layer include fluororesins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide resins, acrylic resins, Examples include polyolefin resins, styrene-butadiene rubber (SBR), cellulose derivatives of carboxymethylcellulose (CMC) or its salts, polyacrylic acid (PAA) or its salts, polyethylene oxide (PEO), polyvinyl alcohol (PVA), and the like.
  • fluororesins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide resins, acrylic resins
  • SBR styrene-butadiene rubber
  • CMC carboxymethylcellulose
  • PAA polyacrylic acid
  • PEO polyethylene oxide
  • PVA polyvinyl alcohol
  • the binder is selected from the group consisting of styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC) or a salt thereof, polyacrylic acid (PAA) or a salt thereof, in terms of further suppressing swelling of the negative electrode. It is preferable to include at least one kind of.
  • the content of the binder may be 4% by mass or more, preferably 6% by mass or more, and more preferably 8% by mass, based on the total mass of the negative electrode active material, in order to suppress swelling of the negative electrode. That's all.
  • the upper limit of the binder content may be, for example, 20% by mass or less, or 15% by mass or less, based on the total mass of the negative electrode active material, from the viewpoint of energy density of the battery.
  • the negative electrode 12 is prepared by applying a negative electrode paste containing a negative electrode active material containing a carbon material and a Si-based material, a pore-forming material, and a binder to a negative electrode current collector to form a coating film, and then applying the coating film.
  • the method includes a first step of rolling, and a second step of heat-treating the coating film after the first step to decompose and vaporize the pore-forming material to form a negative electrode composite layer.
  • the pore-forming material By heat-treating the coating film, the pore-forming material is decomposed and vaporized (e.g., by sublimation), and the pore-forming material is released from within the coating film. , relatively large voids are formed.
  • the pore distribution of the negative electrode composite layer has a peak value R1 of 0.5 ⁇ m or more and 1.5 ⁇ m or less, and a peak value R1 of 2 ⁇ m or more and 10 ⁇ m or less. It has R2.
  • the pore distribution of the negative electrode composite layer usually has only a peak value R1 of 0.5 ⁇ m or more and 1.5 ⁇ m or less.
  • the content of the binder contained in the negative electrode paste may be 4% by mass or more based on the total mass of the negative electrode active material in terms of suppressing swelling of the negative electrode, but preferably 6% by mass or more, and more Preferably it is 8% by mass or more.
  • the upper limit of the content of the binder contained in the negative electrode paste may be, for example, 20% by mass or less, or 15% by mass or less.
  • the heat treatment temperature is not particularly limited as long as it is a temperature at which the pore-forming material decomposes and vaporizes.
  • the heat treatment time may be 5 hours or more as long as sufficient time is ensured for the pore-forming material in the coating film to decompose and vaporize.
  • the pore-forming material known materials can be used. Examples of the pore-forming material include metal oxalates, camphor, naphthalene, and the like. Further, as the pore-forming material, for example, dicarboxylic acids such as fumaric acid, malonic acid, and malic acid may be used. It is preferable that the average particle size of the pore-forming material is, for example, 2 ⁇ m or more and 10 ⁇ m or less. By setting the average particle size of the pore-forming material within the above range, it becomes easy to control the peak value R2 in the pore size distribution of the negative electrode composite layer to a range of 2 ⁇ m or more and 10 ⁇ m or less.
  • the average particle size of each material used for the negative electrode active material, adjusting the viscosity of the negative electrode paste by adding a solvent, etc., adjusting the heat treatment time and temperature may be controlled by adjusting the linear pressure during coating rolling.
  • raw materials such as the negative electrode active material, pore-forming material, and binder are mixed using, for example, cutter mills, pin mills, bead mills, fine particle composite equipment (between a specially shaped rotor that rotates at high speed inside a tank and a collision plate).
  • cutter mills pin mills
  • bead mills fine particle composite equipment (between a specially shaped rotor that rotates at high speed inside a tank and a collision plate).
  • kneading machines such as granulators, twin-screw extrusion kneaders, and planetary mixers.
  • a slit die coater for example, a reverse roll coater, a lip coater, a blade coater, a knife coater, a gravure coater, a dip coater, etc. are used.
  • the heating and drying temperature is preferably a temperature at which the pore-forming material does not decompose and vaporize, but a part of the pore-forming material may decompose and vaporize due to heating and drying.
  • the coating film may be rolled several times using, for example, a roll press machine at a predetermined linear pressure until the coating film reaches a predetermined thickness.
  • separator 13 for example, a porous sheet having ion permeability and insulation properties is used. Specific examples of porous sheets include microporous thin films, woven fabrics, and nonwoven fabrics. Suitable materials for the separator 13 include polyolefins such as polyethylene and polypropylene, cellulose, and the like. The separator 13 may have either a single layer structure or a laminated structure. A heat-resistant layer or the like may be formed on the surface of the separator.
  • Example 1 [Preparation of negative electrode] Graphite particles with an average particle size of 17 ⁇ m and a Si-based material with an average particle size of 8 ⁇ m in which Si particles are dispersed in a carbon phase were mixed at a mass ratio of 50:50. This mixture was used as a negative electrode active material. 100 parts by mass of negative electrode active material, 2 parts by mass of carboxymethyl cellulose (CMC) as a binder, 2 parts by mass of styrene-butadiene rubber (SBR) as a binder, 1 part by mass of multi-walled carbon nanotubes, fumaric acid (average particle size 6 ⁇ m). 12.5 parts by mass were mixed and mixed with arbitrary water to prepare a negative electrode paste.
  • CMC carboxymethyl cellulose
  • SBR styrene-butadiene rubber
  • This negative electrode paste was applied to both sides of a negative electrode current collector made of copper foil, the coating film was dried, and then the coating film was rolled with a rolling roller. Thereafter, the coating film was heat-treated at 200° C. for 5 hours to produce a negative electrode in which negative electrode composite layers were formed on both sides of the negative electrode current collector.
  • the pore size distribution of the negative electrode composite layer was measured by mercury intrusion method, and as a result, two peak values R1 and R2 were shown, the peak value R1 was 1 ⁇ m, and the peak value R2 was 6 ⁇ m. .
  • N- A positive electrode paste was prepared by adding methyl-2-pyrrolidone (NMP). This negative electrode paste was applied to both sides of an aluminum foil, the coating film was dried, and then the coating film was rolled with a rolling roller to produce a positive electrode in which a positive electrode mixture layer was formed on both sides of the positive electrode current collector.
  • NMP methyl-2-pyrrolidone
  • a non-aqueous electrolyte was prepared by dissolving LiPF 6 at a concentration of 1 mol/L in a mixed solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed at a mass ratio of 1:3.
  • EC ethylene carbonate
  • EMC ethyl methyl carbonate
  • a positive electrode and a negative electrode were laminated so as to face each other with a polyolefin separator in between, and this was wound to produce an electrode body.
  • the electrode body was housed in a bottomed cylindrical battery case body, and after the non-aqueous electrolyte was injected, the opening of the battery case body was sealed with a gasket and a sealing body to prepare a test cell.
  • Example 2 A test cell was produced in the same manner as in Example 1, except that in producing the negative electrode, 4 parts by mass of carboxymethyl cellulose (CMC) and 4 parts by mass of styrene-butadiene rubber (SBR) were used.
  • CMC carboxymethyl cellulose
  • SBR styrene-butadiene rubber
  • the pore size distribution of the negative electrode composite layer was measured by mercury porosimetry, and the results showed two peak values R1 and R2, with the peak value R1 being 1 ⁇ m and the peak value R2 being 6 ⁇ m. Ta.
  • Example 3 A test cell was produced in the same manner as in Example 1, except that in producing the negative electrode, 5 parts by mass of carboxymethyl cellulose (CMC) and 5 parts by mass of styrene-butadiene rubber (SBR) were used.
  • CMC carboxymethyl cellulose
  • SBR styrene-butadiene rubber
  • the pore size distribution of the negative electrode composite layer was measured by mercury intrusion method, and as a result, two peak values R1 and R2 were shown, the peak value R1 was 1 ⁇ m, and the peak value R2 was 6 ⁇ m. Ta.
  • ⁇ Comparative example 1> A test cell was produced in the same manner as in Example 1, except that in producing the negative electrode, 1.5 parts by mass of carboxymethyl cellulose (CMC) and 1.5 parts by mass of styrene-butadiene rubber (SBR) were used.
  • CMC carboxymethyl cellulose
  • SBR styrene-butadiene rubber
  • the pore size distribution of the negative electrode composite layer was measured by mercury porosimetry, and as a result, two peak values R1 and R2 were observed, with the peak value R1 being 1 ⁇ m and the peak value R2 being 6 ⁇ m. Ta.
  • Example 2 A test cell was prepared in the same manner as in Example 1, except that in the preparation of the negative electrode, carboxymethyl cellulose (CMC) was changed to 0.5 parts by mass, and styrene-butadiene rubber (SBR) was changed to 0.5 parts by mass.
  • CMC carboxymethyl cellulose
  • SBR styrene-butadiene rubber
  • the pore size distribution of the negative electrode composite material layer was measured by mercury porosimetry, and the results showed two peak values R1 and R2, with the peak value R1 being 1 ⁇ m and the peak value R2 being 6 ⁇ m. Ta.
  • Example 3 A test cell was produced in the same manner as in Example 1, except that fumaric acid having an average particle size of 1 ⁇ m was used in producing the negative electrode.
  • the pore size distribution of the negative electrode composite layer was measured by mercury intrusion method, and as a result, one peak value R1 was shown, and the peak value R1 was 1 ⁇ m.
  • the swelling ratio of the negative electrode was less than 125%.
  • the swelling ratio of the negative electrode was 125% or more. That is, in a negative electrode composite material layer having a negative electrode active material containing a carbon material and a Si-based material and a binder, the pore size distribution measured by the mercury intrusion method has two peak values R1 and R2, and the peak value R1 is 0.5 ⁇ m or more and 1.5 ⁇ m or less, the peak value R2 is 2 ⁇ m or more and 10 ⁇ m or less, and the content of the binder is 4% by mass or more based on the total mass of the negative electrode active material. By using this, it becomes possible to suppress the expansion of the negative electrode.
  • [Additional notes] (1) comprising a negative electrode current collector and a negative electrode composite material layer disposed on the negative electrode current collector,
  • the negative electrode composite material layer has a negative electrode active material and a binder containing a carbon material and a Si-based material,
  • the pore size distribution of the negative electrode composite layer measured by mercury porosimetry has two peak values R1 and R2,
  • the peak value R1 is 0.5 ⁇ m or more and 1.5 ⁇ m or less
  • the peak value R2 is 2 ⁇ m or more and 10 ⁇ m or less
  • a negative electrode for a secondary battery wherein the content of the binder contained in the negative electrode composite layer is 4% by mass or more based on the total mass of the negative electrode active material.
  • the content of the Si-based material is 30% by mass or more based on the total mass of the negative electrode active material.
  • a secondary battery comprising the negative electrode for a secondary battery according to any one of (1) to (9) above.
  • a negative electrode paste containing a negative electrode active material including a carbon material and a Si-based material, a binder, and a pore-forming material is applied to a negative electrode current collector to create a coating film, and then the coating film is rolled.
  • the first step After the first step, a second step of heat-treating the coating film to decompose and vaporize the pore-forming material to form a negative electrode composite layer,
  • the pore size distribution of the negative electrode composite layer measured by mercury porosimetry has two peak values R1 and R2,
  • the peak value R1 is 0.5 ⁇ m or more and 1.5 ⁇ m or less
  • the peak value R2 is 2 ⁇ m or more and 10 ⁇ m or less
  • a method for producing a negative electrode for a secondary battery wherein the content of the binder contained in the negative electrode paste is 4% by mass or more based on the total mass of the negative electrode active material.

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PCT/JP2023/028248 2022-08-29 2023-08-02 二次電池用負極、二次電池、及び二次電池用負極の製造方法 Ceased WO2024048183A1 (ja)

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EP23859952.6A EP4583191A4 (en) 2022-08-29 2023-08-02 NEGATIVE ELECTRODE FOR SECONDARY BATTERIES, SECONDARY BATTERY AND METHOD FOR PRODUCING NEGATIVE ELECTRODE FOR SECONDARY BATTERIES
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JP2013219059A (ja) 2013-07-30 2013-10-24 Sumitomo Bakelite Co Ltd リチウムイオン二次電池用負極活物質、リチウムイオン二次電池用負極合剤、リチウムイオン二次電池用負極、及びリチウムイオン二次電池
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JP2013219059A (ja) 2013-07-30 2013-10-24 Sumitomo Bakelite Co Ltd リチウムイオン二次電池用負極活物質、リチウムイオン二次電池用負極合剤、リチウムイオン二次電池用負極、及びリチウムイオン二次電池
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