WO2024181189A1 - 円筒形二次電池 - Google Patents

円筒形二次電池 Download PDF

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Publication number
WO2024181189A1
WO2024181189A1 PCT/JP2024/005662 JP2024005662W WO2024181189A1 WO 2024181189 A1 WO2024181189 A1 WO 2024181189A1 JP 2024005662 W JP2024005662 W JP 2024005662W WO 2024181189 A1 WO2024181189 A1 WO 2024181189A1
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Prior art keywords
positive electrode
region
exposed portion
secondary battery
negative electrode
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PCT/JP2024/005662
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English (en)
French (fr)
Japanese (ja)
Inventor
駿介 安田
祐 石黒
優輝 西中
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Panasonic Energy Co Ltd
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Panasonic Energy Co Ltd
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Priority to CN202480013596.0A priority Critical patent/CN120642102A/zh
Priority to JP2025503784A priority patent/JPWO2024181189A1/ja
Publication of WO2024181189A1 publication Critical patent/WO2024181189A1/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
    • H01M10/058—Construction or manufacture
    • H01M10/0587—Construction or manufacture of accumulators having only wound construction elements, i.e. wound positive electrodes, wound negative electrodes and wound separators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/443—Particulate material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
    • H01M50/451—Separators, membranes or diaphragms characterised by the material having a layered structure comprising layers of only organic material and layers containing inorganic material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/463—Separators, membranes or diaphragms characterised by their shape
    • 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
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • This disclosure relates to cylindrical secondary batteries.
  • a cylindrical secondary battery is a battery in which an electrode body, in which a positive electrode and a negative electrode are wound with a separator interposed therebetween, is housed in a cylindrical outer can.
  • the positive electrode and the negative electrode each have a current collector and a mixture layer arranged on the surface of the current collector, and the mixture layer contains an active material that can reversibly absorb and release Li ions.
  • An exposed portion is formed on the surface of the electrode where the current collector is exposed, and a tab is connected to the exposed portion for connecting the electrode and the battery terminal.
  • Patent Document 1 discloses a technology in which multiple exposed portions are formed on an electrode and a tab is connected to each of the exposed portions, with the aim of suppressing heat generation at the tab connection portion and improving current collection. In the electrode disclosed in Patent Document 1, an exposed portion is formed over the entire width direction.
  • the objective of this disclosure is to provide a cylindrical secondary battery that suppresses peeling of the composite layer after charge/discharge cycles.
  • a cylindrical secondary battery comprises an electrode assembly in which a positive electrode and a negative electrode are wound with a separator interposed therebetween, a non-aqueous electrolyte, and a cylindrical exterior can that contains the electrode assembly and the non-aqueous electrolyte, the positive electrode has a positive electrode current collector and a positive electrode mixture layer disposed on the surface of the positive electrode current collector, and a plurality of positive electrode exposed portions where the positive electrode current collector is exposed are disposed on the surface of the positive electrode, and the positive electrode exposed portions are in contact with only one of both ends in the width direction of the positive electrode, and the separator has a substrate layer and a filler layer disposed on the surface of the substrate layer that faces the positive electrode.
  • the filler layer contains resin particles and has convex portions formed by the resin particles, and the surface of the positive electrode is divided into a region where the positive electrode exposed portion is arranged and a region where the positive electrode exposed portion is not arranged adjacent to the region where the positive electrode exposed portion is arranged in the width direction, and the surface of the separator is divided into a first region facing the region where the positive electrode exposed portion is arranged and a second region facing the region where the positive electrode exposed portion is not arranged, the area ratio S1 of the area of the convex portions in the first region is larger than the area ratio S2 of the area of the convex portions in the second region.
  • the cylindrical secondary battery according to the present disclosure can suppress peeling of the mixture layer after charge/discharge cycles. This improves the safety of the cylindrical secondary battery.
  • 1 is a longitudinal sectional view of a cylindrical secondary battery according to an embodiment of the present invention
  • 2 is a front view showing a positive electrode and a negative electrode constituting an electrode body provided in the cylindrical secondary battery of FIG. 1 in a developed state
  • 3 is a cross-sectional view for explaining the arrangement of a positive electrode, a negative electrode, and a separator that constitute the electrode assembly shown in FIG. 2.
  • multiple positive electrode tabs may be provided to improve the current collection at the positive electrode.
  • the area of the positive electrode exposed portion for connecting the positive electrode tab is as small as possible. Therefore, a configuration is conceivable in which the positive electrode exposed portion is not formed over the entire width direction of the positive electrode, but is formed only in the vicinity of the portion where the positive electrode tab is connected.
  • peeling of the mixture layer is likely to occur at the end on the side where the exposed portion of the positive electrode is formed due to charge and discharge cycles.
  • FIG. 1 is a longitudinal cross-sectional view of a cylindrical secondary battery 10 (hereinafter, secondary battery 10) that is an example of an embodiment.
  • secondary battery 10 an electrode body 14 and a non-aqueous electrolyte (not shown) are housed in an outer can 15.
  • the sealing body 16 side will be referred to as the "top” and the bottom side of the outer can 15 as the "bottom”.
  • 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 positive electrode 11, the negative electrode 12, and the separator 13 are all long strip-shaped bodies, and are alternately stacked in the radial direction of the electrode body 14 by being wound in a spiral shape.
  • the separator 13 is formed with dimensions slightly larger than the positive electrode 11 and the negative electrode 12, and two of them are arranged to sandwich the positive electrode 11.
  • non-aqueous solvent (organic solvent) of the non-aqueous electrolyte carbonates, lactones, ethers, ketones, esters, etc. can be used, and these solvents can be used by mixing two or more.
  • a mixed solvent containing a cyclic carbonate and a chain carbonate For example, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), etc. can be used as the cyclic carbonate, and dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), etc. can be used as the chain carbonate.
  • electrolyte salt of the non-aqueous electrolyte LiPF 6 , LiBF 4 , LiCF 3 SO 3 , etc., and mixtures thereof can be used.
  • the amount of electrolyte salt dissolved in the non-aqueous solvent can be, for example, 0.5 mol/L or more and 2.0 mol/L or less.
  • the sealing body 16 seals the opening at the top of the outer can 15, sealing the inside of the secondary battery 10.
  • Insulating plates 17 and 18 are provided above and below the electrode body 14.
  • the positive electrode tab 19 extends vertically through the through hole of the insulating plate 17 and connects the filter 22, which is the bottom plate of the sealing body 16, to the positive electrode 11 included in the electrode body 14. This connects the positive electrode 11 to the sealing body 16, and in the secondary battery 10, the cap 26, which is the top plate of the sealing body 16 electrically connected to the filter 22, becomes the positive electrode terminal.
  • the positive electrode tab 19 is, for example, an aluminum tab.
  • the negative electrode tab 20 extends through the through hole of the insulating plate 18 to the bottom side of the outer can 15 and is welded to the inner surface of the bottom of the outer can 15. This connects the negative electrode 12 to the outer can 15, and in the secondary battery 10, the outer can 15 becomes the negative electrode terminal.
  • the negative electrode tab 20 is, for example, a nickel tab.
  • the number of positive electrode tabs 19 led out from the electrode body 14 is not particularly limited.
  • the current collection of the positive electrode 11 is improved, and the output characteristics of the secondary battery 10 can be improved.
  • the number of positive electrode tabs 19 is preferably 3 to 10, and more preferably 3 to 8.
  • the three or more positive electrode tabs 19 led out from the electrode body 14 may be directly connected to the sealing body 16, or may be connected to the sealing body 16 via a known current collecting member.
  • the negative electrode tab 20 is led out from the vicinity of the inner end of the negative electrode 12 and connected to the outer can 15.
  • the position of the negative electrode tab 20 is not limited to the example shown in FIG. 1.
  • the negative electrode tab 20 may be provided only near the outer end of the negative electrode 12, or may be provided near both the inner end and the outer end of the negative electrode 12.
  • the negative electrode exposed portion 44 may be formed at the outer end of the negative electrode 12 and brought into contact with the inner circumferential surface of the outer can 15, thereby electrically connecting the outer end of the negative electrode 12 to the outer can 15 without using the negative electrode tab 20.
  • the outer can 15 is a cylindrical metal container with a bottom that is open on one axial side.
  • a gasket 27 is provided between the outer can 15 and the sealing body 16 to ensure airtightness inside the secondary battery 10.
  • the outer can 15 has a grooved portion 21 that supports the sealing body 16, formed, for example, by pressing the side portion from the outside.
  • the grooved portion 21 is preferably formed in an annular shape along the circumferential direction of the outer can 15, and supports the sealing body 16 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 this order from the electrode body 14 side.
  • Each member constituting the sealing body 16 has, for example, a disk or ring shape, and each member except 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 respective centers, and the insulating member 24 is interposed between their respective peripheral edges. If the internal pressure of the battery increases due to abnormal heat generation, for example, the lower valve body 23 breaks, which causes the upper valve body 25 to swell toward the cap 26 and separate from the lower valve body 23, cutting off the electrical connection between them. If the internal pressure increases further, the upper valve body 25 breaks, and gas is discharged from the opening 26a of the cap 26.
  • FIG. 2 is a front view showing the positive electrode 11 and the negative electrode 12 constituting the electrode body 14 of the secondary battery 10 of FIG. 1 in an expanded state.
  • the negative electrode 12 is generally formed to have dimensions slightly larger than the positive electrode 11 in order to prevent lithium precipitation. In other words, the negative electrode 12 is formed to be longer in the longitudinal and transverse directions than the positive electrode 11.
  • the positive electrode 11 has a positive electrode current collector 30 and a positive electrode mixture layer 32 arranged on the surface of the positive electrode current collector 30.
  • a plurality of positive electrode exposed portions 34 where the positive electrode current collector 30 is exposed are arranged on the surface of the positive electrode 11, and the positive electrode exposed portion 34 contacts only one end 11a of both ends in the width direction of the positive electrode 11. In other words, the positive electrode exposed portion 34 does not extend to the other end 11b in the width direction of the positive electrode 11.
  • the positive electrode mixture layer 32 exists between the positive electrode exposed portions 34, so that the area of the positive electrode mixture layer 32 is increased and the battery capacity of the secondary battery 10 is improved.
  • one of the positive electrode tabs 19 is connected to each of the positive electrode exposed portions 34, so that the current collecting ability of the positive electrode 11 is improved and the output characteristics of the secondary battery 10 are improved.
  • the positive electrode current collector 30 can be a foil of a metal such as aluminum that is stable in the potential range of the positive electrode, or a film with the metal disposed on the surface.
  • the thickness of the positive electrode current collector 30 is, for example, 10 ⁇ m or more and 30 ⁇ m or less.
  • the positive electrode mixture layer 32 is preferably formed on both sides of the positive electrode current collector 30.
  • the thickness of the positive electrode mixture layer 32 is, for example, 10 ⁇ m or more and 150 ⁇ m or less on one side of the positive electrode current collector 30.
  • the positive electrode mixture layer 32 contains, for example, a positive electrode active material, a conductive agent, and a binder.
  • the positive electrode can be produced, for example, by applying a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, a binder, etc. to both sides of the positive electrode current collector 30, drying the coating, and then rolling the coating using a roller or the like.
  • the positive electrode active material contained in the positive electrode mixture layer can be, for example, a lithium transition metal composite oxide containing a transition metal element such as Co, Mn, or Ni.
  • lithium transition metal composite oxides include LixCoO2 , LixNiO2 , LixMnO2 , LixCoyNi1 - yO2 , LixCoyM1 - yOz , LixNi1 - yMyOz , LixMn2O4 , LixMn2 - yMyO4 , LiMPO4 , and Li2MPO4F
  • M is at least one of Na, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu , Zn , Al, Cr , Pb, Sb, and B; 0 ⁇ x ⁇ 1.2, 0 ⁇ y ⁇ 0.9, and 2.0 ⁇ z ⁇ 2.3). These may be used alone or in combination of two or more kinds.
  • the positive electrode active material preferably contains a lithium nickel composite oxide, in that it is possible to increase the capacity of the secondary battery 10.
  • the lithium nickel composite oxide include Li x NiO 2 , Li x Co y Ni 1-y O 2 , and Li x Ni 1-y M y O z (M is at least one of Na, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb, and B; 0 ⁇ x ⁇ 1.2, 0 ⁇ y ⁇ 0.9, and 2.0 ⁇ z ⁇ 2.3).
  • M is at least one of Na, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb, and B; 0 ⁇ x ⁇ 1.2, 0 ⁇ y ⁇ 0.9, and 2.0 ⁇ z ⁇ 2.3).
  • Conductive agents contained in the positive electrode mixture layer include, for example, carbon-based particles such as carbon black (CB), acetylene black (AB), ketjen black, carbon nanotubes (CNT), graphene, and graphite. These may be used alone or in combination of two or more types.
  • Binders contained in the positive electrode mixture layer include, for example, fluorine-based resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyimide-based resins, acrylic-based resins, and polyolefin-based resins. These may be used alone or in combination of two or more types.
  • fluorine-based resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyimide-based resins, acrylic-based resins, and polyolefin-based resins. These may be used alone or in combination of two or more types.
  • the surface of the positive electrode 11 can be divided into a positive electrode exposed portion arrangement region 38 in which the positive electrode exposed portion 34 is arranged, and a positive electrode exposed portion non-arrangement region 39 adjacent to the positive electrode exposed portion arrangement region 38 in the width direction.
  • the positive electrode exposed portion arrangement region 38 and the positive electrode exposed portion non-arrangement region 39 both extend in the longitudinal direction.
  • the ratio of the width direction length of the positive electrode exposed portion arrangement region 38 to the width direction length of the positive electrode exposed portion non-arrangement region 39 is preferably 1:1 to 1:10, and more preferably 1:2 to 1:8.
  • the positive electrode exposed portion arrangement region 38 Since the positive electrode exposed portion arrangement region 38 has a thin positive electrode exposed portion 34, it is subjected to smaller pressure in the radial direction of the electrode body than the positive electrode exposed portion non-arrangement region 39, and the amount of movement associated with charging and discharging is larger, so peeling of the positive electrode mixture layer 32 is likely to occur. As described below, by adjusting the arrangement of the resin particles 54 on the surface of the separator 13 facing the positive electrode 11, the difference in the amount of movement between the positive electrode exposed portion arrangement region 38 and the positive electrode exposed portion non-arrangement region 39 during charging and discharging can be reduced, thereby suppressing peeling of the positive electrode mixture layer 32.
  • the negative electrode 12 has a negative electrode current collector 40 and a negative electrode mixture layer 42 disposed on the surface of the negative electrode current collector 40.
  • the negative electrode 12 has a negative electrode exposed portion 44 where the negative electrode current collector 40 is exposed, for example, at the end of the inner winding in the longitudinal direction, and the negative electrode tab 20 is connected to the negative electrode exposed portion 44.
  • the negative electrode current collector can be a foil of a metal such as copper that is stable in the potential range of the negative electrode, or a film with the metal disposed on the surface.
  • the thickness of the negative electrode current collector is, for example, 5 ⁇ m or more and 30 ⁇ m or less.
  • the negative electrode mixture layer is preferably formed on both sides of the negative electrode current collector.
  • the thickness of the negative electrode mixture layer is, for example, 10 ⁇ m or more and 150 ⁇ m or less 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 can be produced, for example, by applying a negative electrode mixture slurry containing a negative electrode active material, a binder, etc. to both sides of the negative electrode current collector, drying the coating, and then rolling the coating using a roller or the like.
  • 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 generally carbon materials such as graphite are used.
  • the graphite may be any of natural graphite such as flake graphite, lump graphite, and earthy graphite, lump artificial graphite, and artificial graphite such as graphitized mesophase carbon microbeads.
  • the negative electrode active material may be a metal that alloys with Li, such as Si or Sn, a metal compound containing Si or Sn, or a lithium titanium composite oxide.
  • a Si-containing compound represented by SiOx (0.5 ⁇ x ⁇ 1.6) or a Si-containing compound in which fine particles of Si are dispersed in a lithium silicate phase represented by Li2ySiO (2+y) (0 ⁇ y ⁇ 2) may be used in combination with graphite.
  • Binders contained in the negative electrode mixture layer include, for example, styrene butadiene rubber (SBR), nitrile butadiene rubber (NBR), carboxymethyl cellulose (CMC) or its salts, polyacrylic acid (PAA) or its salts (PAA-Na, PAA-K, etc., or it may be a partially neutralized salt), polyvinyl alcohol (PVA), etc. These may be used alone or in combination of two or more types.
  • SBR styrene butadiene rubber
  • NBR nitrile butadiene rubber
  • CMC carboxymethyl cellulose
  • PAA polyacrylic acid
  • PAA-Na polyacrylic acid
  • PAA-K polyvinyl alcohol
  • PVA polyvinyl alcohol
  • FIG. 3 is a cross-sectional view for explaining the arrangement of the positive electrode 11, the negative electrode 12, and the separator 13 that constitute the electrode body 14 shown in FIG. 2.
  • the separator 13 has a base layer 50 and a filler layer 52 disposed on the surface of the base layer 50 facing the positive electrode 11.
  • the filler layer 52 is disposed on only one side of the base layer 50, with the filler layer 52 facing the positive electrode 11 and the base layer 50 facing the negative electrode 12.
  • the form of the separator 13 is not limited to the example shown in FIG. 3, and the filler layer 52 may be disposed on both sides of the base layer 50.
  • the substrate layer 50 for example, a porous sheet having ion permeability and insulating properties is used.
  • porous sheets include a microporous thin film, a woven fabric, and a nonwoven fabric.
  • the material of the substrate layer 50 is not particularly limited, but examples include polyolefins such as polyethylene, polypropylene, copolymers of polyethylene and ⁇ -olefin, acrylic resins, polystyrene, polyester, cellulose, polyimide, polyphenylene sulfide, polyether ether ketone, and fluororesins.
  • the substrate layer 50 may have a single layer structure or a multilayer structure.
  • the thickness of the substrate layer 50 is preferably 3 ⁇ m or more and 20 ⁇ m or less, and more preferably 5 ⁇ m or more and 15 ⁇ m or less.
  • the filler layer 52 contains resin particles 54, inorganic particles, and a binder.
  • the filler layer 52 also has protrusions 56 formed by the resin particles 54, and the protrusions 56 protrude from an inorganic particle layer 57 of the filler layer 52 that is formed by the inorganic particles and the binder.
  • Examples of inorganic particles include metal oxide particles, metal nitride particles, metal fluoride particles, and metal carbide particles.
  • metal oxide particles include aluminum oxide, titanium oxide, magnesium oxide, zirconium oxide, nickel oxide, silicon oxide, and manganese oxide.
  • metal nitride particles include titanium nitride, boron nitride, aluminum nitride, magnesium nitride, and silicon nitride.
  • Examples of metal fluoride particles include aluminum fluoride, lithium fluoride, sodium fluoride, magnesium fluoride, calcium fluoride, and barium fluoride.
  • metal carbide particles include silicon carbide, boron carbide, titanium carbide, and tungsten carbide.
  • the inorganic particles may be porous aluminosilicates such as zeolite ( M2 /nO.Al2O3.xSiO2.yH2O , where M is a metal element, n is the valence of M, x ⁇ 2, y ⁇ 0), layered silicates such as talc ( Mg3Si4O10 (OH) 2 ), minerals such as barium titanate ( BaTiO3 ) and strontium titanate ( SrTiO3 ), etc. These may be used alone or in combination of two or more.
  • zeolite M2 /nO.Al2O3.xSiO2.yH2O , where M is a metal element, n is the valence of M, x ⁇ 2, y ⁇ 0
  • layered silicates such as talc ( Mg3Si4O10 (OH) 2 )
  • minerals such as barium titanate ( BaTiO3 ) and strontium titanate ( SrTi
  • the binder is preferably a polymer material, and examples of the binder include fluorine-based resins such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE), polyimide-based resins, polyamide-based resins, acrylic resins, polyolefin-based resins, styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR), carboxymethyl cellulose (CMC) or a salt thereof, polyacrylic acid (PAA) or a salt thereof, polyvinyl alcohol (PVA), etc. These may be used alone or in combination of two or more kinds.
  • fluorine-based resins such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE)
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • polyimide-based resins polyamide-based resins
  • acrylic resins polyo
  • Examples of materials for the resin particles 54 include acrylic resins made of ethylenically unsaturated carboxylic acid alkyl esters such as methyl acrylate, butyl acrylate, ethyl acrylate, and 2-ethylhexyl acrylate; resins made of cyano-group-containing ethylenically unsaturated monomers such as acrylonitrile; and resins made of ethylenically unsaturated carboxylic acids and their salts such as acrylic acid, methacrylic acid, and maleic acid.
  • the resin particles 54 have adhesive properties with the positive electrode 11, and in the secondary battery 10, the resin particles 54 are preferably adhered to the positive electrode. By adhering the resin particles 54 to the positive electrode 11, movement of the positive electrode 11 due to charging and discharging is suppressed, and the effect of suppressing peeling of the positive electrode mixture layer 32 becomes more pronounced.
  • the resin particles 54 exhibit adhesive properties with respect to the positive electrode 11, for example, when a non-aqueous electrolyte is held.
  • the area ratio S1 of the area of the convex portion 56 in the first region 58 is larger than the area ratio S2 of the area of the convex portion 56 in the second region 59.
  • S1 is preferably 2% or more and 20% or less, more preferably 4% or more and 16% or less.
  • S2 is preferably 0% or more and 10% or less, more preferably 0% or more and 8% or less.
  • S2/S1 obtained by dividing S2 by S1, satisfies 0 ⁇ S2/S1 ⁇ 1, preferably 0 ⁇ S2/S1 ⁇ 0.5, and more preferably 0 ⁇ S2/S1 ⁇ 0.25.
  • the average particle size (D50) of the resin particles 54 contained in the first region 58 can be made larger than the D50 of the resin particles 54 contained in the first region 58, so that S1>S2 can be satisfied.
  • the average particle size (D50) of the resin particles 54 contained in the first region 58 and the second region 59 can be made substantially the same, while the number of the resin particles 54 contained in the first region 58 can be made larger than the number of the resin particles 54 contained in the second region 59, so that S1>S2 can be satisfied.
  • the D50 of the resin particles used when manufacturing the separator 13 is, for example, 1 ⁇ m or more and 10 ⁇ m or less.
  • the average particle size (D50) means the particle size at which the cumulative frequency is 50% from the smallest particle size in the volume-based particle size distribution, and is also called the median diameter.
  • the particle size distribution of the resin particles is measured by dispersing them in a dispersion medium using a laser diffraction particle size distribution measuring device (e.g., MT3000II, manufactured by Microtrack Bell).
  • the average particle area of the convex portion 56 in the first region 58 is larger than the average particle area of the convex portion 56 in the second region 59.
  • the average particle area of the convex portion 56 in the first region 58 is, for example, 500 ⁇ m 2 or more and 2000 ⁇ m 2 or less
  • the average particle area of the convex portion 56 in the second region 59 is, for example, 0 ⁇ m 2 or more and 1500 ⁇ m 2 or less.
  • the average particle area is the area per resin particle measured using the separator 13 removed from the secondary battery 10 after the charge/discharge cycle.
  • the surface of the filler layer 52 is observed with a scanning electron microscope (for example, SU8220 manufactured by Hitachi High-Tech Corporation), and the average value of the areas of 30 convex portions 56 in each of the first region 58 and the second region 59 is taken as the average particle area.
  • a scanning electron microscope for example, SU8220 manufactured by Hitachi High-Tech Corporation
  • Example> [Preparation of positive electrode]
  • the positive electrode active material aluminum-containing lithium nickel cobalt oxide represented by LiNi 0.88 Co 0.09 Al 0.03 O 2 was used. 100 parts by mass of the positive electrode active material, 1 part by mass of acetylene black (AB), and 0.9 parts by mass of polyvinylidene fluoride (PVDF) were mixed, and an appropriate amount of N-methyl-2-pyrrolidone (NMP) was added to prepare a positive electrode mixture slurry. Next, the positive electrode mixture slurry was applied to both sides of a belt-shaped positive electrode collector made of aluminum foil having a thickness of 15 ⁇ m so that eight positive electrode exposed parts were formed. As shown in the example in FIG.
  • the positive electrode exposed parts were made to contact only one end in the width direction of the positive electrode. After drying this coating film, it was rolled and cut to a predetermined electrode plate size to prepare a positive electrode in which a positive electrode mixture layer was formed on both sides of the positive electrode collector.
  • the ratio of the widthwise length of the positive electrode exposed portion arrangement region to the widthwise length of the positive electrode exposed portion non-arrangement region was 1 : 5. Thereafter, an aluminum positive electrode tab was welded to each of the three positive electrode exposed portions.
  • a negative electrode mixture slurry 95 parts by mass of graphite, 5 parts by mass of Si oxide (SiO), 1 part by mass of sodium carboxymethylcellulose (CMC-Na), and 1 part by mass of styrene butadiene rubber (SBR) were mixed, and an appropriate amount of water was added to prepare a negative electrode mixture slurry.
  • the negative electrode mixture slurry was applied to both sides of a strip-shaped negative electrode current collector made of copper foil with a thickness of 8 ⁇ m, dried, rolled, and cut to a predetermined electrode plate size to prepare a negative electrode in which a negative electrode mixture layer was formed on both sides of the negative electrode current collector.
  • a negative electrode exposed portion in which no mixture layer was present and the current collector surface was exposed was provided at the inner end of the negative electrode, and a nickel negative electrode tab was welded to the negative electrode exposed portion.
  • Alumina ( ⁇ -Al 2 O 3 ) particles as inorganic particles with an average particle size (D50) of 0.7 ⁇ m, acrylic resin particles as resin particles with a D50 of 4 ⁇ m, and an acrylic acid ester-based binder emulsion were mixed in a solid content mass ratio of 100:2:3, and then an appropriate amount of water was added so that the solid content concentration became 10 mass % to prepare a first dispersion.
  • a second dispersion was prepared in the same manner as the first dispersion, except that the amount of the acrylic resin particles added was changed from 2 parts by mass to 1 part by mass.
  • a 12 ⁇ m-thick porous polyethylene substrate was used as the substrate layer.
  • a first dispersion was applied to a first region facing the region where the positive electrode exposed portion was located, and a second dispersion was applied to a second region facing the region where the positive electrode exposed portion was not located.
  • the coating was then dried by heating in an oven at 50°C for 4 hours, forming a filler layer in which acrylic resin particles protruded from the surface of a 3 ⁇ m-thick inorganic particle layer formed by the binder.
  • a non-aqueous electrolyte was prepared by adding 5 parts by mass of vinylene carbonate (VC) to 100 parts by mass of a mixed solvent prepared by mixing ethylene carbonate (EC) and dimethyl carbonate (DMC) in a volume ratio of 3:7, and dissolving lithium hexafluorophosphate (LiPF 6 ) in the mixed solvent at a concentration of 1.5 mol/L.
  • VC vinylene carbonate
  • EC ethylene carbonate
  • DMC dimethyl carbonate
  • a wound electrode body was produced by spirally winding the positive and negative electrodes with a separator between them. At this time, the filler layer of the separator was made to face the positive electrode. Insulating plates were placed on the top and bottom of the electrode body, respectively, and the electrode body was housed in an outer can.
  • the negative electrode tab was welded to the bottom of a cylindrical outer can with a bottom, and the positive electrode tab was welded to a sealing member. After injecting a non-aqueous electrolyte into the outer can, the opening of the outer can was sealed with a sealing member via a gasket, and a cylindrical secondary battery was produced.
  • Example 2 A secondary battery was produced and evaluated in the same manner as in Example 1, except that in the preparation of the separator, the amount of the acrylic resin particles added in the first dispersion was changed from 2 parts by mass to 1 part by mass, and the amount of the acrylic resin particles added in the second dispersion was changed from 1 part by mass to 0.5 parts by mass.
  • Example 3 A secondary battery was produced and evaluated in the same manner as in Example 1, except that in the preparation of the separator, the amount of the acrylic resin particles added in the first dispersion was changed from 2 parts by mass to 1 part by mass, and the amount of the acrylic resin particles added in the second dispersion was changed from 1 part by mass to 0.25 parts by mass.
  • Example 4 A secondary battery was produced and evaluated in the same manner as in Example 1, except that in the preparation of the separator, the amount of the acrylic resin particles added in the second dispersion was changed from 1 part by mass to 0.5 parts by mass.
  • Example 5 A secondary battery was produced and evaluated in the same manner as in Example 1, except that in the preparation of the separator, the acrylic resin particles were not added to the second dispersion liquid.
  • Example 2 A secondary battery was produced and evaluated in the same manner as in Example 1, except that in the preparation of the separator, the amount of the acrylic resin particles added in the first dispersion was changed from 2 parts by mass to 0.5 parts by mass, and the amount of the acrylic resin particles added in the second dispersion was changed from 1 part by mass to 0.5 parts by mass.
  • Table 1 The evaluation results of the secondary batteries according to the examples and comparative examples are shown in Table 1.
  • the gap size was evaluated in four stages: less than 10 ⁇ m, 10 ⁇ m to 20 ⁇ m, 20 ⁇ m to 30 ⁇ m, and more than 30 ⁇ m.
  • Table 1 also shows the average particle area of the resin particles contained in the first region and the average particle area of the resin particles contained in the second region, which were measured using the separator removed from the cylindrical secondary battery after the charge-discharge cycle test.
  • Composition 1
  • a cylindrical secondary battery comprising an electrode assembly in which a positive electrode and a negative electrode are wound with a separator interposed therebetween, a non-aqueous electrolyte, and a cylindrical outer can for accommodating the electrode assembly and the non-aqueous electrolyte,
  • the positive electrode has a positive electrode current collector and a positive electrode mixture layer disposed on a surface of the positive electrode current collector, a plurality of positive electrode exposed portions at which the positive electrode current collector is exposed are disposed on a surface of the positive electrode;
  • the positive electrode exposed portion is in contact with only one of both widthwise ends of the positive electrode
  • the separator has a substrate layer and a filler layer disposed on a surface of the substrate layer facing a positive electrode, the filler layer contains resin particles and has protrusions formed by the resin particles;
  • Configuration: 2 2. The cylindrical secondary battery according to claim 1, wherein S1 is 2% or more and 20% or less, and S2 is 0% or more and 10% or less.
  • Configuration: 3 3. The cylindrical secondary battery according to claim 1, wherein an average particle area of the convex portions in the first region is larger than an average particle area of the convex portions in the second region.
  • Configuration: 4 The cylindrical secondary battery according to any one of configurations 1 to 3, wherein the average particle area of the convex portions in the first region is 500 ⁇ m 2 or more and 2000 ⁇ m 2 or less, and the average particle area of the convex portions in the second region is 0 ⁇ m 2 or more and 1500 ⁇ m 2 or less.

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  • Inorganic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Secondary Cells (AREA)
  • Battery Electrode And Active Subsutance (AREA)
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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2021161842A1 (ja) * 2020-02-12 2021-08-19 日本ゼオン株式会社 電気化学素子用積層体及び電気化学素子
WO2022114228A1 (ja) * 2020-11-30 2022-06-02 旭化成株式会社 蓄電デバイス用セパレータ及びこれを含む蓄電デバイス
WO2022224872A1 (ja) * 2021-04-20 2022-10-27 パナソニックＩｐマネジメント株式会社 リチウム二次電池

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2021161842A1 (ja) * 2020-02-12 2021-08-19 日本ゼオン株式会社 電気化学素子用積層体及び電気化学素子
WO2022114228A1 (ja) * 2020-11-30 2022-06-02 旭化成株式会社 蓄電デバイス用セパレータ及びこれを含む蓄電デバイス
WO2022224872A1 (ja) * 2021-04-20 2022-10-27 パナソニックＩｐマネジメント株式会社 リチウム二次電池

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