WO2023053626A1 - 非水電解質二次電池 - Google Patents

非水電解質二次電池 Download PDF

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Publication number
WO2023053626A1
WO2023053626A1 PCT/JP2022/025261 JP2022025261W WO2023053626A1 WO 2023053626 A1 WO2023053626 A1 WO 2023053626A1 JP 2022025261 W JP2022025261 W JP 2022025261W WO 2023053626 A1 WO2023053626 A1 WO 2023053626A1
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positive electrode
mixture layer
electrode mixture
conductive agent
aqueous electrolyte
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French (fr)
Japanese (ja)
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正嗣 青谷
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Sanyo Electric Co Ltd
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Sanyo Electric Co Ltd
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Priority to EP22875505.4A priority Critical patent/EP4411853A4/en
Priority to CN202280063234.3A priority patent/CN117957665A/zh
Priority to JP2023550374A priority patent/JPWO2023053626A1/ja
Priority to US18/693,322 priority patent/US20240396047A1/en
Publication of WO2023053626A1 publication Critical patent/WO2023053626A1/ja
Anticipated expiration legal-status Critical
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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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • 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
    • 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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • 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 non-aqueous electrolyte secondary batteries.
  • the positive electrode of a non-aqueous electrolyte secondary battery has a positive electrode current collector made of metal and a positive electrode mixture layer formed on the surface of the positive electrode current collector.
  • the positive electrode mixture layer contains, in addition to the positive electrode active material, which is the main component, a conductive agent interposed between the positive electrode active materials to form a conductive path.
  • Patent Documents 1 to 3 disclose techniques for changing the content of the conductive agent in the thickness direction of the positive electrode mixture layer.
  • acetylene black, carbon black, etc. which have a relatively small average particle size, are used as the conductive agent in order to increase the packing density of the positive electrode mixture layer and improve the battery capacity.
  • increasing the thickness of the positive electrode mixture layer has been studied.
  • the packing density of the positive electrode mixture layer is increased, the permeability of the electrolytic solution into the positive electrode mixture layer tends to decrease, and the cycle characteristics tend to deteriorate. Become.
  • the techniques disclosed in Patent Documents 1 to 3 do not examine the influence of the average particle size of the conductive agent on the cycle characteristics, and there is still room for improvement.
  • An object of the present disclosure is to provide a non-aqueous electrolyte secondary battery with high capacity and improved cycle characteristics.
  • a non-aqueous electrolyte secondary battery that is one aspect of the present disclosure includes a positive electrode, a negative electrode, a separator that separates the positive electrode and the negative electrode from each other, and a non-aqueous electrolyte. It has a first positive electrode mixture layer formed on the surface of the electric body and a second positive electrode mixture layer formed on the surface of the first positive electrode mixture layer, and the second positive electrode mixture layer has an average particle diameter contains a second conductive agent having a diameter of 0.5 ⁇ m to 15 ⁇ m, and the first positive electrode mixture layer contains the first conductive agent having an average particle size smaller than that of the second conductive agent.
  • non-aqueous electrolyte secondary battery According to the non-aqueous electrolyte secondary battery according to the present disclosure, it is possible to improve battery capacity and cycle characteristics.
  • FIG. 1 is an axial cross-sectional view of a non-aqueous electrolyte secondary battery that is an example of an embodiment
  • FIG. 1 is a cross-sectional view of a positive electrode that is an example of an embodiment
  • FIG. 1 is a cross-sectional view of a positive electrode that is an example of an embodiment
  • a cylindrical battery in which a wound electrode body is housed in a cylindrical outer body is exemplified, but the outer body is not limited to a cylindrical shape, and may be, for example, rectangular, coin-shaped, etc. It may be of a pouch type composed of a laminate sheet including a metal layer and a resin layer. Further, the electrode body may be a laminated electrode body in which a plurality of positive electrodes and a plurality of negative electrodes are alternately laminated with separators interposed therebetween. Further, in this specification, the description of "numerical value (A) to numerical value (B)" means numerical value (A) or more and numerical value (B) or less.
  • FIG. 1 is an axial cross-sectional view of a cylindrical secondary battery 10 that is an example of an embodiment.
  • an electrode body 14 and a non-aqueous electrolyte (not shown) are housed in an exterior body 15 .
  • the electrode body 14 has a wound structure in which the positive electrode 11 and the negative electrode 12 are wound with the separator 13 interposed therebetween.
  • the sealing member 16 side will be referred to as "upper”
  • the bottom side of the outer package 15 will be referred to as "lower”.
  • the inside of the secondary battery 10 is hermetically sealed by closing the upper open end of the exterior body 15 with the sealing body 16 .
  • Insulating plates 17 and 18 are provided above and below the electrode body 14, respectively.
  • the positive electrode lead 19 extends upward through the through hole of the insulating plate 17 and is welded to the lower surface of the filter 22 which is the bottom plate of the sealing member 16 .
  • the cap 26, which is the top plate of the sealing member 16 electrically connected to the filter 22, serves as a positive electrode terminal.
  • the negative electrode lead 20 extends through the outside of the insulating plate 18 to the bottom side of the exterior body 15 and is welded to the bottom inner surface of the exterior body 15 .
  • the exterior body 15 becomes a negative electrode terminal.
  • the exterior body 15 is, for example, a bottomed cylindrical metal exterior can.
  • a gasket 27 is provided between the exterior body 15 and the sealing body 16 to ensure hermetic sealing of the inside of the secondary battery 10 .
  • the exterior body 15 has, for example, a grooved portion 21 formed by pressing the side portion from the outside.
  • the grooved portion 21 is preferably annularly formed along the circumferential direction of the exterior body 15 and supports the sealing body 16 via a gasket 27 on its upper surface.
  • the sealing body 16 has a filter 22, a lower valve body 23, an insulating member 24, an upper valve body 25, and a cap 26 which are stacked in order from the electrode body 14 side.
  • Each member constituting the sealing member 16 has, for example, a disk shape or a ring shape, and each member other than the insulating member 24 is electrically connected to each other.
  • the lower valve body 23 and the upper valve body 25 are connected to each other at their central portions, and an insulating member 24 is interposed between their peripheral edge portions.
  • the positive electrode 11, the negative electrode 12, the separator 13, and the non-aqueous electrolyte that constitute the secondary battery 10 will be described in detail below, particularly the positive electrode 11.
  • FIG. 2 is a cross-sectional view of the positive electrode 11 that is an example of the embodiment.
  • the positive electrode 11 includes a positive electrode current collector 30, a first positive electrode mixture layer 32 formed on the surface of the positive electrode current collector 30, and a second positive electrode mixture layer formed on the surface of the first positive electrode mixture layer 32. 34.
  • the first positive electrode mixture layer 32 and the second positive electrode mixture layer 34 may be collectively referred to as a positive electrode mixture layer 36 .
  • the positive electrode current collector 30 a foil of a metal such as aluminum that is stable in the potential range of the positive electrode, a film having the metal on the surface layer, or the like can be used.
  • the thickness of the positive electrode current collector 30 is, for example, 10 ⁇ m to 30 ⁇ m.
  • the positive electrode mixture layers 36 are preferably formed on both sides of the positive electrode current collector 30 .
  • the thickness of the positive electrode mixture layer 36 on one side of the positive electrode current collector 30 is preferably 50 ⁇ m to 200 ⁇ m, more preferably 70 ⁇ m to 150 ⁇ m.
  • the positive electrode mixture layer 36 contains, for example, a positive electrode active material, a conductive agent, and a binder.
  • positive electrode active materials include lithium-containing composite oxides containing transition metal elements such as Co, Mn, and Ni.
  • a positive electrode active material may be used individually by 1 type, and may be used in mixture of multiple types.
  • the positive electrode active material contained in the first positive electrode mixture layer 32 and the positive electrode active material contained in the second positive electrode mixture layer 34 may be different from each other, but are preferably the same.
  • binder contained in the positive electrode mixture layer 36 examples include fluorine-based resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyimide-based resins, acrylic-based resins, polyolefin-based resins and the like. These may be used individually by 1 type, and may be used in combination of 2 or more types.
  • the binder contained in the first positive electrode mixture layer 32 and the binder contained in the second positive electrode mixture layer 34 may be different from each other, but are preferably the same.
  • Examples of the conductive agent contained in the positive electrode mixture layer 36 include carbon-based particles such as acetylene black, furnace black, ketjen black, and graphite. These may be used alone or in combination of two or more.
  • the conductive agent contained in the positive electrode mixture layer 36 is different between the first positive electrode mixture layer 32 and the second positive electrode mixture layer 34 . That is, the first positive electrode mixture layer 32 contains the first conductive agent, and the second positive electrode mixture layer 34 contains the second conductive agent.
  • the first positive electrode mixture layer 32 may contain a conductive agent other than the first conductive agent, and the second positive electrode mixture layer 34 may contain a conductive agent other than the second conductive agent, as long as the object of the present disclosure is not impaired. agent.
  • the average particle size of the second conductive agent is 0.5 ⁇ m to 15 ⁇ m, preferably 1 ⁇ m to 10 ⁇ m, more preferably 3 ⁇ m to 9 ⁇ m. This improves the permeability of the electrolytic solution and improves the cycle characteristics. In particular, in high-rate charge/discharge, the improvement in cycle characteristics is remarkable.
  • the average particle size means a volume-based median size (D50). D50 means a particle size at which the cumulative frequency is 50% from the smaller particle size in the volume-based particle size distribution, and is also called median diameter.
  • the particle size distributions of the first conductive agent and the second conductive agent can be measured using a laser diffraction particle size distribution analyzer (eg MT3000II manufactured by Microtrack Bell Co., Ltd.) using water as a dispersion medium.
  • the average particle size of the first conductive agent is smaller than that of the second conductive agent. Thereby, the battery capacity can be improved.
  • the average particle size of the second conductive agent is preferably 1 nm to 500 nm, more preferably 5 nm to 100 nm, particularly preferably 10 nm to 50 nm.
  • the ratio of the average particle size of the first conductive agent to the average particle size of the second conductive agent is preferably 50 to 300, more preferably. is 100-200.
  • the second conductive agent may be graphite.
  • Graphite used as the second conductive agent may be any of natural graphite such as flake graphite, massive graphite, earthy graphite, etc., artificial graphite such as massive artificial graphite, and graphitized mesophase carbon microbeads, and is natural graphite. is preferred.
  • the first conductive agent may be one or more of acetylene black, furnace black, or ketjen black, preferably acetylene black.
  • the thickness ratio between the first positive electrode mixture layer 32 and the second positive electrode mixture layer 34 is preferably 90:10 to 10:90, more preferably 75:25 to 25:75. This makes it possible to achieve both high capacity and improved cycle characteristics.
  • the battery capacity can be increased by increasing the thickness of the first positive electrode mixture layer 32 .
  • Cycle characteristics can be improved by increasing the thickness of the second positive electrode mixture layer 34 .
  • the content of the first conductive agent is preferably 0.1 to 5 parts by mass, more preferably is 0.5 parts by mass to 3 parts by mass.
  • the content of the second conductive agent is preferably 0.1 to 5 parts by mass, More preferably, it is 0.5 parts by mass to 3 parts by mass.
  • the content of the first conductive agent in the first positive electrode mixture layer 32 and the content of the second conductive agent in the second positive electrode mixture layer 34 may differ from each other, but are preferably the same.
  • the method for producing the positive electrode 11 is not particularly limited, but for example, a first positive electrode mixture slurry containing a positive electrode active material, a first conductive agent, and a binder, a positive electrode active material, a second conductive agent, and a binder
  • the first positive electrode mixture slurry was applied to both surfaces of the positive electrode current collector 30 and dried, and the second positive electrode mixture slurry was applied and dried thereon. After that, by rolling the coating film with a rolling roller, the positive electrode 11 having a positive electrode mixture layer having a two-layer structure as shown in FIG. 2 can be manufactured. Further, after applying the first positive electrode mixture slurry, the second positive electrode mixture slurry may be applied thereon without drying, and then dried.
  • the negative electrode 12 has a negative electrode current collector and a negative electrode mixture layer formed on the surface of the negative electrode current collector.
  • a foil of a metal such as copper that is stable in the potential range of the negative electrode, a film having the metal on the surface layer, or the like can be used.
  • the thickness of the negative electrode current collector is, for example, 5 ⁇ m to 30 ⁇ m.
  • the negative electrode mixture layers are preferably formed on both sides of the negative electrode current collector.
  • the thickness of the negative electrode mixture layer is, for example, 10 ⁇ m to 150 ⁇ m on one side of the negative electrode current collector.
  • the negative electrode mixture layer contains, for example, a negative electrode active material and a binder.
  • the negative electrode is produced, for example, by applying a negative electrode mixture slurry containing a negative electrode active material, a binder, etc. on both sides of a negative electrode current collector, drying the coating film, and then rolling the coating film using a roller or the like. can be made.
  • the negative electrode active material contained in the negative electrode mixture layer is not particularly limited as long as it can reversibly absorb and release lithium ions, and carbon materials such as graphite are generally used.
  • Graphite may be any of natural graphite such as flaky graphite, massive graphite and earthy graphite, artificial graphite such as massive artificial graphite and graphitized mesophase carbon microbeads.
  • a metal alloyed with Li such as Si or Sn, a metal compound containing Si, Sn or the like, a lithium-titanium composite oxide, or the like may be used.
  • Si-containing compound represented by SiO x (0.5 ⁇ x ⁇ 1.6) or a lithium silicate phase represented by Li 2y SiO (2+y) (0 ⁇ y ⁇ 2) contains fine particles of Si.
  • a dispersed Si-containing compound or the like may be used in combination with graphite.
  • binder contained in the negative electrode mixture layer examples include styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR), carboxymethylcellulose (CMC) or salts thereof, polyacrylic acid (PAA) or salts thereof (PAA -Na, PAA-K, and partially neutralized salts), polyvinyl alcohol (PVA), and the like. These may be used individually by 1 type, and may be used in combination of 2 or more types.
  • the separator 13 separates the positive electrode 11 and the negative electrode 12 from each other.
  • a porous sheet or the like having ion permeability and insulation is used as the separator 13.
  • porous sheets include microporous membranes, woven fabrics, and non-woven fabrics.
  • Suitable materials for the separator include olefin resins such as polyethylene and polypropylene, and cellulose.
  • the separator 13 may be a laminate having a cellulose fiber layer and a thermoplastic resin fiber layer such as an olefin resin.
  • a multilayer separator including a polyethylene layer and a polypropylene layer may be used, and a separator 13 having a surface coated with a material such as aramid resin or ceramic may be used.
  • a non-aqueous electrolyte is, for example, an electrolytic solution containing a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent.
  • non-aqueous solvents examples include esters, ethers, nitriles such as acetonitrile, amides such as dimethylformamide, and mixed solvents of two or more thereof.
  • the non-aqueous solvent may contain a halogen-substituted product obtained by substituting at least part of the hydrogen atoms of these solvents with halogen atoms such as fluorine.
  • halogen-substituted compounds include fluorinated cyclic carbonates such as fluoroethylene carbonate (FEC), fluorinated chain carbonates, and fluorinated chain carboxylates such as methyl fluoropropionate (FMP).
  • FEC fluoroethylene carbonate
  • FMP fluorinated chain carboxylates
  • esters examples include cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC) and butylene carbonate, dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), methyl propyl carbonate. , Ethyl propyl carbonate, Methyl isopropyl carbonate, and other chain carbonates; ⁇ -Butyrolactone (GBL), ⁇ -Valerolactone (GVL), and other cyclic carboxylic acid esters; ), chain carboxylic acid esters such as ethyl propionate, and the like.
  • cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC) and butylene carbonate, dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), methyl propyl carbonate.
  • Ethyl propyl carbonate Methyl isopropyl carbonate
  • ethers examples include 1,3-dioxolane, 4-methyl-1,3-dioxolane, tetrahydrofuran, 2-methyltetrahydrofuran, propylene oxide, 1,2-butylene oxide, 1,3-dioxane, 1,4 -dioxane, 1,3,5-trioxane, furan, 2-methylfuran, 1,8-cineol, cyclic ethers such as crown ether, 1,2-dimethoxyethane, diethyl ether, dipropyl ether, diisopropyl ether, dibutyl ether , dihexyl ether, ethyl vinyl ether, butyl vinyl ether, methyl phenyl ether, ethyl phenyl ether, butyl phenyl ether, pentyl phenyl ether, methoxytoluene, benzyl ethyl ether, diphenyl ether, cycl
  • the electrolyte salt is a lithium salt.
  • lithium salts include LiBF4 , LiClO4 , LiPF6 , LiAsF6 , LiSbF6 , LiAlCl4 , LiSCN, LiCF3SO3 , LiCF3CO2 , Li(P( C2O4 ) F4 ) , LiPF 6-x (C n F 2n+1 ) x (1 ⁇ x ⁇ 6, n is 1 or 2), LiB 10 Cl 10 , LiCl, LiBr, LiI, lithium chloroborane, lithium lower aliphatic carboxylate, Li 2 B 4O7 , borates such as Li (B( C2O4 ) F2 ), LiN( SO2CF3 ) 2 , LiN( C1F2l + 1SO2 )( CmF2m + 1SO2 ) ⁇ l , where m is an integer equal to or greater than 0 ⁇ .
  • Lithium salts may be used singly or in combination. Of these, it is preferable to use LiPF 6 from the viewpoint of ion conductivity, electrochemical stability, and the like.
  • the lithium salt concentration may be, for example, 0.8 mol to 1.8 mol per 1 L of the non-aqueous solvent.
  • Example> [Preparation of positive electrode] Acetylene black (AB) having an average particle size of 35 nm was used as the first conductive agent. LiNi 0.88 Co 0.09 Al 0.03 O 2 Lithium transition metal composite oxide represented by LiNi 0.88 Co 0.09 Al 0.03 O 2, the first conductive agent, and polyvinylidene fluoride (PVDF) were mixed at a weight ratio of 100: 1: 0.9 They were mixed at the same ratio and kneaded while adding N-methylpyrrolidone (NMP) to prepare a first positive electrode mixture slurry.
  • NMP N-methylpyrrolidone
  • the first positive electrode mixture slurry is applied to both sides of a positive electrode current collector made of aluminum foil having a thickness of 15 ⁇ m by a doctor blade method, and the coating film is dried to form a first positive electrode mixture layer (uncompressed state). bottom.
  • Graphite with an average particle size of 6 ⁇ m was used as the second conductive agent.
  • a lithium transition metal composite oxide represented by LiNi 0.88 Co 0.09 Al 0.03 O 2 , a second conductive agent, and PVDF are mixed at a mass ratio of 100:1:0.9, The mixture was kneaded while adding N-methylpyrrolidone (NMP) to prepare a second positive electrode mixture slurry.
  • NMP N-methylpyrrolidone
  • the second positive electrode mixture slurry is applied to both surfaces of the first positive electrode mixture layer by a doctor blade method, and the coating film is dried, thereby covering the entire surface of the first positive electrode mixture layer with the second positive electrode mixture slurry.
  • the layers were laminated.
  • the first positive electrode mixture layer and the second positive electrode mixture layer After rolling the first positive electrode mixture layer and the second positive electrode mixture layer using rollers, they were cut into a predetermined electrode size to prepare a positive electrode. In addition, an exposed portion where the positive electrode current collector was exposed was provided on a part of the positive electrode, and an aluminum positive electrode lead was attached to the exposed portion. After rolling, the packing density of the positive electrode was 3.6 g/cm 3 .
  • the thickness of the positive electrode mixture layer was 100 ⁇ m on one side of the positive electrode current collector.
  • the ratio of the thickness of the first positive electrode mixture layer to the thickness of the second positive electrode mixture layer was 50:50.
  • Negative electrode active material carboxymethyl cellulose (CMC): styrene-butadiene rubber (SBR) were kneaded in water so that the mass ratio was 100:1:1 to prepare a negative electrode mixture slurry.
  • CMC carboxymethyl cellulose
  • SBR styrene-butadiene rubber
  • the negative electrode mixture slurry is applied to both sides of a negative electrode current collector made of copper foil by a doctor blade method, and after drying, the coating film is rolled with a roller and cut into a predetermined electrode size to form a negative electrode. was made.
  • an exposed portion where the surface of the negative electrode current collector was exposed was provided on a part of the negative electrode, and a negative electrode lead made of nickel was attached to the exposed portion.
  • Lithium hexafluorophosphate LiPF 6 was added at a concentration of 1.5 mol/L to a mixed solvent in which ethylene carbonate (EC) and dimethyl carbonate (DMC) were mixed at a volume ratio of 1:3. Dissolved. Furthermore, vinylene carbonate (VC) was dissolved in the mixed solvent at a concentration of 5% by mass to prepare a non-aqueous electrolyte (electrolytic solution).
  • a wound electrode body was produced by spirally winding the positive electrode and the negative electrode through a separator made of a polyethylene film having a thickness of 12 ⁇ m. This electrode body was housed in a bottomed cylindrical outer package, and the negative electrode lead was welded to the bottom of the outer package. Next, the positive electrode lead was welded to the sealing body, and after the non-aqueous electrolyte was injected, the opening of the exterior body was sealed with the sealing body to obtain a secondary battery.
  • a secondary battery was produced in the same manner as in Examples, except that graphite with an average particle size of 6 ⁇ m was used as the first conductive agent and AB with an average particle size of 35 nm was used as the second conductive agent in the production of the positive electrode. and evaluated. After rolling, the packing density of the positive electrode was 3.6 g/cm 3 .
  • ⁇ Comparative Example 2> A secondary battery was fabricated and evaluated in the same manner as in Examples, except that graphite having an average particle size of 6 ⁇ m was used as the first conductive agent in fabricating the positive electrode. After rolling, the packing density of the positive electrode was 3.4 g/cm 3 . Since the average particle size of the first conductive agent in Comparative Example 2 is larger than the average particle size of the first conductive agent in Examples, even if the positive electrode mixture layer is rolled at the same linear pressure, the packing density is lower than that in Examples. is presumed to have decreased.
  • Table 1 shows the evaluation results of the secondary batteries of Examples and Comparative Examples. Table 1 also shows the average particle size of the first conductive agent and the second conductive agent, and the packing density of the positive electrode.
  • the secondary batteries of the examples excellent battery capacity and capacity retention rate are obtained.
  • the secondary batteries of Comparative Examples 1 and 3 in which the second positive electrode mixture layer contains a conductive agent having a small average particle size, are inferior in capacity retention rate to the secondary batteries of Examples.
  • the secondary batteries of Comparative Examples 1 and 3 have a longer liquid absorption time than the secondary batteries of Examples.
  • the secondary battery of Comparative Example 2 in which the first positive electrode mixture layer contains a conductive agent having a large average particle size, is inferior in battery capacity to the secondary batteries of Examples.

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PCT/JP2022/025261 2021-09-28 2022-06-24 非水電解質二次電池 Ceased WO2023053626A1 (ja)

Priority Applications (4)

Application Number Priority Date Filing Date Title
EP22875505.4A EP4411853A4 (en) 2021-09-28 2022-06-24 NON-AQUEOUS ELECTROLYTE SECONDARY BATTERY
CN202280063234.3A CN117957665A (zh) 2021-09-28 2022-06-24 非水电解质二次电池
JP2023550374A JPWO2023053626A1 (https=) 2021-09-28 2022-06-24
US18/693,322 US20240396047A1 (en) 2021-09-28 2022-06-24 Non-aqueous electrolyte secondary battery

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