WO2025225626A1 - Séparateur pour batterie secondaire à électrolyte non aqueux - Google Patents

Séparateur pour batterie secondaire à électrolyte non aqueux

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Publication number
WO2025225626A1
WO2025225626A1 PCT/JP2025/015642 JP2025015642W WO2025225626A1 WO 2025225626 A1 WO2025225626 A1 WO 2025225626A1 JP 2025015642 W JP2025015642 W JP 2025015642W WO 2025225626 A1 WO2025225626 A1 WO 2025225626A1
Authority
WO
WIPO (PCT)
Prior art keywords
resin particles
separator
electrolyte secondary
secondary battery
mpa
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
PCT/JP2025/015642
Other languages
English (en)
Japanese (ja)
Inventor
将平 楠本
圭衣子 加藤
祐 荻原
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Zeon Corp
Panasonic Energy Co Ltd
Original Assignee
Zeon Corp
Panasonic Energy Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Zeon Corp, Panasonic Energy Co Ltd filed Critical Zeon Corp
Publication of WO2025225626A1 publication Critical patent/WO2025225626A1/fr
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

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Classifications

    • 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
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • 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
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • H01M50/42—Acrylic resins
    • 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
    • H01M50/431—Inorganic material
    • H01M50/434—Ceramics
    • 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
    • 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
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
    • H01M50/457—Separators, membranes or diaphragms characterised by the material having a layered structure comprising three or more layers
    • 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
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • 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

  • This disclosure relates to a separator for a non-aqueous electrolyte secondary battery.
  • non-aqueous electrolyte secondary batteries have become widely used as high-power, high-energy density secondary batteries. These batteries include an electrode assembly having a positive electrode, a negative electrode, and a separator disposed between the positive and negative electrodes, a non-aqueous electrolyte, and an exterior housing that houses these components. The separator separates the positive and negative electrodes while retaining the non-aqueous electrolyte.
  • Patent Document 1 discloses a separator for non-aqueous electrolyte secondary batteries in which a functional layer containing heat-resistant fine particles and resin particles is provided on the surface of a substrate layer made of a porous membrane, with the aim of improving adhesion at low temperatures.
  • a separator for a non-aqueous electrolyte secondary battery is characterized in that resin particles are present on at least one surface, and the resin particles have a 20% compressive strength of 35 MPa or more and 100 MPa or less, and a volume-based particle size (D50) of 4.0 ⁇ m or more and 20.0 ⁇ m or less.
  • the separator for a non-aqueous electrolyte secondary battery which is one aspect of the present disclosure, can provide a non-aqueous electrolyte secondary battery that reduces battery resistance while improving charge-discharge cycle characteristics.
  • FIG. 1 is a longitudinal cross-sectional view of a nonaqueous electrolyte secondary battery according to an embodiment of the present invention
  • FIG. 2 is a cross-sectional view of a separator according to an embodiment.
  • FIG. 3 is a cross-sectional view of a separator according to another embodiment.
  • FIG. 10 is a diagram for explaining a method for evaluating deformation of an electrode plate.
  • separators with resin particles disposed on their surface are known in the prior art. By disposing resin particles on the surface of the separator, an uneven structure is formed on the surface of the separator, and when the separator is incorporated into a non-aqueous electrolyte secondary battery, gaps are created between the electrode plates and the separator. This reduces the internal stress applied to the electrode plates when they expand and contract during charge and discharge, for example, and makes it possible to suppress deformation of the electrode plates.
  • deformation of the electrode plates refers to bending of at least a portion of the electrode plates.
  • separators with resin particles disposed on their surface are used in non-aqueous electrolyte secondary batteries, new issues arise: increased battery resistance and reduced charge and discharge cycle characteristics.
  • the inventors therefore conducted further research and found that by using a separator with resin particles on its surface that have a 20% compressive strength of 35 MPa or more and 100 MPa or less and a volume-based particle size (D50) of 4.0 ⁇ m or more and 20.0 ⁇ m or less, deformation of the resin particles contained in the separator is suppressed, and an increase in battery resistance and a deterioration in charge-discharge cycle characteristics are suppressed.
  • the 20% compressive strength of resin particles refers to the pressure required to compress the resin particles by 20% of their particle size, and can be measured using the method described below.
  • a cylindrical battery in which a wound electrode assembly 14 is housed in a cylindrical, bottomed exterior body 16 is exemplified as a nonaqueous electrolyte secondary battery, but the battery exterior body is not limited to a cylindrical exterior body.
  • the nonaqueous electrolyte secondary battery according to the present disclosure may be, for example, a prismatic battery with a prismatic exterior body, a coin battery with a coin-shaped exterior body, or a pouch-type battery with an exterior body composed of a laminate sheet including a metal layer and a resin layer.
  • the electrode assembly is not limited to a wound type, but may also be a stacked type electrode assembly in which multiple positive electrodes and multiple negative electrodes are alternately stacked with separators interposed between them.
  • the design of the nonaqueous electrolyte secondary battery according to the present disclosure is not limited to the design of the exemplified nonaqueous electrolyte secondary battery, and known nonaqueous electrolyte secondary battery designs may also be applied.
  • the nonaqueous electrolyte secondary battery 10 includes a wound electrode assembly 14, a nonaqueous electrolyte, and an exterior body 16 that houses the electrode assembly 14 and the nonaqueous electrolyte.
  • the electrode assembly 14 includes a positive electrode 11, a negative electrode 12, and a separator 13, and has a wound structure in which the positive electrode 11 and the negative electrode 12 are spirally wound with the separator 13 interposed therebetween.
  • the exterior body 16 is a cylindrical metal container with a bottom and an opening on one axial side, and the opening of the exterior body 16 is closed by a sealing body 17.
  • the sealing body 17 side of the battery will be referred to as the top, and the bottom side of the exterior body 16 will be referred to as the bottom.
  • the positive electrode 11, negative electrode 12, and separator 13 that make up the electrode body 14 are all rectangular, elongated bodies that are spirally wound longitudinally and stacked alternately in the radial direction of the electrode body 14.
  • the separator 13 isolates the positive electrode 11 and negative electrode 12 from each other. Two separators 13 are arranged, for example, sandwiching the positive electrode 11.
  • the electrode body 14 includes a positive electrode lead 20 connected to the positive electrode 11 by welding or the like, and a negative electrode lead 21 connected to the negative electrode 12 by welding or the like.
  • the longitudinal direction of the positive electrode 11 and negative electrode 12 is the winding direction
  • the lateral direction of the positive electrode 11 and negative electrode 12 is the axial direction.
  • the lateral end faces of the positive electrode 11 and negative electrode 12 form the axial end faces of the electrode body 14.
  • the non-aqueous electrolyte has ionic conductivity (e.g., lithium ion conductivity).
  • the non-aqueous electrolyte may be a liquid electrolyte (electrolytic solution) or a solid electrolyte.
  • the liquid electrolyte contains a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent.
  • non-aqueous solvents include esters, ethers, nitriles, amides, and mixed solvents of two or more of these.
  • non-aqueous solvents include ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and mixed solvents of these.
  • the non-aqueous solvent may contain a halogen-substituted solvent (e.g., fluoroethylene carbonate) in which at least a portion of the hydrogen atoms of these solvents are replaced with halogen atoms such as fluorine.
  • a halogen-substituted solvent e.g., fluoroethylene carbonate
  • the electrolyte salt may be, for example, a lithium salt such as LiPF6 .
  • the solid electrolyte for example, a solid or gel-like polymer electrolyte, an inorganic solid electrolyte, etc. is used.
  • the polymer electrolyte includes, for example, a lithium salt and a matrix polymer, or a non-aqueous solvent, a lithium salt, and a matrix polymer.
  • the matrix polymer for example, a polymer material that absorbs the non-aqueous solvent and gels is used.
  • the polymer material for example, fluororesin, acrylic resin, polyether resin, etc. is used.
  • the inorganic solid electrolyte for example, a material known in all-solid-state lithium-ion secondary batteries (for example, oxide-based solid electrolytes, sulfide-based solid electrolytes, halide-based solid electrolytes, etc.) is used.
  • a material known in all-solid-state lithium-ion secondary batteries for example, oxide-based solid electrolytes, sulfide-based solid electrolytes, halide-based solid electrolytes, etc.
  • Insulating plates 18 and 19 are arranged above and below the electrode body 14.
  • the positive electrode lead 20 passes through a through hole in the insulating plate 18 and extends toward the sealing body 17, while the negative electrode lead 21 passes outside the insulating plate 19 and extends toward the bottom side of the exterior body 16.
  • the positive electrode lead 20 is connected to the underside of the internal terminal plate 23 of the sealing body 17 by welding or the like, and the cap 27, which is the top plate of the sealing body 17 and is electrically connected to the internal terminal plate 23, serves as the positive electrode terminal.
  • the negative electrode lead 21 is connected to the inner surface of the bottom of the exterior body 16 by welding or the like, and the exterior body 16 serves as the negative electrode terminal.
  • a gasket 28 is provided between the exterior body 16 and the sealing body 17 to ensure airtightness inside the battery.
  • the exterior body 16 has a grooved portion 22 formed on its side surface that protrudes inward and supports the sealing body 17.
  • the grooved portion 22 is preferably formed in an annular shape along the circumferential direction of the exterior body 16, and supports the sealing body 17 on its top surface.
  • the sealing body 17 is fixed to the top of the exterior body 16 by the grooved portion 22 and the open end of the exterior body 16 that is crimped to the sealing body 17.
  • the sealing body 17 has a structure in which, from the electrode body 14 side, an internal terminal plate 23, a lower valve body 24, an insulating member 25, an upper valve body 26, and a cap 27 are layered.
  • Each member constituting the sealing body 17 has, for example, a disk or ring shape, and all members except for the insulating member 25 are electrically connected to each other.
  • the lower valve body 24 and the upper valve body 26 are connected at their respective centers, with the insulating member 25 interposed between their respective peripheral edges.
  • the positive electrode 11, negative electrode 12, and separator 13 that make up the electrode assembly 14 will be described in detail below, with particular reference to the separator 13.
  • the positive electrode 11 has a positive electrode core 30 and a positive electrode mixture layer 31 formed on the positive electrode core 30.
  • the positive electrode core 30 can be a foil of a metal, such as aluminum or an aluminum alloy, that is stable within the potential range of the positive electrode 11, or a film with such a metal disposed on the surface.
  • the positive electrode mixture layer 31 contains a positive electrode active material, a conductive agent, and a binder.
  • the positive electrode 11 can be produced, for example, by applying a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, a binder, and the like onto the positive electrode core 30, drying the coating, and then compressing it to form the positive electrode mixture layer 31 on both sides of the positive electrode core 30.
  • the positive electrode mixture layer 31 contains particulate lithium metal composite oxide as the positive electrode active material.
  • the lithium metal composite oxide is a composite oxide containing metal elements such as Co, Mn, Ni, and Al in addition to Li.
  • the metal element constituting the lithium metal composite oxide is, for example, at least one selected from Mg, Al, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Y, Zr, Sn, Sb, W, Pb, and Bi. It is particularly preferable to contain at least one selected from Co, Ni, Al, and Mn.
  • suitable composite oxides include lithium metal composite oxides containing Ni, Co, and Mn, and lithium metal composite oxides containing Ni, Co, and Al.
  • Examples of conductive agents contained in the positive electrode mixture layer 31 include carbon black such as acetylene black and ketjen black, graphite, carbon nanotubes (CNT), carbon nanofibers, graphene, and other carbon materials.
  • Examples of binders contained in the positive electrode mixture layer 31 include fluorine-containing resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyimide, acrylic resin, polyolefin, and the like. Furthermore, these resins may be used in combination with carboxymethyl cellulose (CMC) or its salt, polyethylene oxide (PEO), and the like.
  • the negative electrode 12 has a negative electrode core 40 and a negative electrode mixture layer 41 formed on the negative electrode core 40.
  • the negative electrode core 40 can be a foil of a metal, such as copper or a copper alloy, that is stable within the potential range of the negative electrode 12, or a film with such a metal disposed on the surface.
  • the negative electrode mixture layer 41 contains a negative electrode active material, a binder, and, if necessary, a conductive agent.
  • the negative electrode 12 can be produced by applying a negative electrode mixture slurry containing the negative electrode active material and the binder to the surface of the negative electrode core 40, drying the coating, and then compressing it to form the negative electrode mixture layer 41 on both sides of the negative electrode core 40.
  • the negative electrode mixture layer 41 preferably contains a carbon material and a silicon-containing material as the negative electrode active material.
  • a silicon-containing material makes it easier to achieve a high capacity for the nonaqueous electrolyte secondary battery 10.
  • the negative electrode mixture layer 41 may use, as the negative electrode active material, a material containing at least one of an element that alloys with Li, such as Sn, and a material containing this element.
  • the content of the silicon-containing material is preferably 10% by mass or more of the total mass of the negative electrode active material, more preferably 12% by mass or more, and even more preferably 15% by mass or more.
  • silicon-containing materials undergo greater volumetric changes during charge and discharge than carbon materials. Therefore, when a silicon-containing material is included as the negative electrode active material, compressive stress is applied by separator 13 during charge and discharge, making resin particles 52 (see Figure 2) more likely to undergo compressive deformation. Therefore, the effects of the present disclosure are more pronounced when a silicon-containing material is included as the negative electrode active material.
  • the upper limit of the content of the silicon-containing material is, for example, 50% by mass of the total mass of the negative electrode active material.
  • the carbon material that functions as the negative electrode active material is, for example, at least one selected from the group consisting of natural graphite, artificial graphite, soft carbon, and hard carbon.
  • at least artificial graphite such as massive artificial graphite (MAG) and graphitized mesophase carbon microbeads (MCMB), natural graphite such as flake graphite, massive graphite, and amorphous graphite, or a mixture of these.
  • the volume-based D50 of the carbon material is, for example, 1 ⁇ m or more and 30 ⁇ m or less, and preferably 5 ⁇ m or more and 25 ⁇ m or less.
  • the silicon-containing material may be any material that contains Si, and examples include silicon alloys, silicon compounds, and composite materials containing Si. Of these, composite materials containing Si are preferred.
  • the D50 of composite materials is generally smaller than the D50 of graphite.
  • the volume-based D50 of composite materials is, for example, 1 ⁇ m or more and 15 ⁇ m or less. Note that one type of silicon-containing material may be used alone, or two or more types may be used in combination.
  • a suitable silicon-containing material is a composite particle containing an ion-conducting phase, a Si phase dispersed in the ion-conducting phase, and a conductive layer covering the surface of the ion-conducting phase.
  • the ion-conducting phase is, for example, at least one selected from the group consisting of a silicate phase, an amorphous carbon phase, a silicide phase, and a silicon oxide phase.
  • the Si phase is formed by dispersing Si in the form of fine particles.
  • the ion-conducting phase is a continuous phase composed of a collection of particles finer than the Si phase.
  • the conductive layer is composed of a material with higher conductivity than the ion-conducting phase, and forms a good conductive path within the negative electrode mixture layer 41.
  • An example of a suitable Si-containing composite material is a composite particle having a sea-island structure in which fine Si particles are substantially uniformly dispersed in an amorphous silicon oxide phase, and which is generally represented by the general formula SiO x (0 ⁇ x ⁇ 2).
  • the silicon oxide may be primarily composed of silicon dioxide.
  • the oxygen content ratio (x) to Si is, for example, 0.5 ⁇ x ⁇ 2.0, preferably 0.8 ⁇ x ⁇ 1.5.
  • the binder contained in the negative electrode mixture layer 41 can be fluorine-containing resin, PAN, polyimide, acrylic resin, polyolefin, etc., but styrene butadiene rubber (SBR) is preferred.
  • the negative electrode mixture layer 41 preferably contains CMC or a salt thereof, polyacrylic acid (PAA) or a salt thereof, polyvinyl alcohol (PVA), etc. Among these, it is preferable to use a combination of SBR with CMC or a salt thereof, PAA or a salt thereof, etc.
  • the negative electrode mixture layer 41 may also contain a conductive agent such as CNT.
  • [Separator] 2 is a diagram schematically illustrating a portion of a cross section of the separator 13.
  • the separator 13 includes, for example, a base layer 50, a heat-resistant layer 51 disposed on one surface of the base layer 50, and resin particles 52 disposed on the surface of the heat-resistant layer 51.
  • the surface of the separator 13 on which the heat-resistant layer 51 is disposed will be referred to as a first surface 13A
  • the surface opposite the first surface 13A will be referred to as a second surface 13B.
  • the first surface 13A faces the positive electrode 11
  • the second surface 13B faces the negative electrode 12.
  • the second surface 13B of the separator 13 may face the positive electrode 11.
  • the porosity of the separator 13 is, for example, 30% or more and 70% or less.
  • the porosity of the separator 13 is determined by the porosity of the substrate layer 50.
  • the substrate layer 50 may be, for example, a porous sheet that is ion permeable and insulating. Specific examples of porous sheets include microporous thin films, woven fabrics, and nonwoven fabrics.
  • the material of the substrate layer 50 is not particularly limited, but examples include polyethylene, polypropylene, polyethylene- ⁇ -olefin copolymers and other polyolefins, 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 multi-layer 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 heat-resistant layer 51 contains, for example, inorganic particles.
  • the thickness of the heat-resistant layer 51 is preferably smaller than the thickness of the base layer 50, for example, 0.5 ⁇ m or more and 5 ⁇ m or less.
  • the heat-resistant layer 51 may be provided on both sides of the base layer 50, but from the standpoint of productivity, etc., it is preferable that it be provided on one side of the base layer 50.
  • the inorganic particles contained in the heat-resistant layer 51 are composed of insulating inorganic compounds that are resistant to melting and decomposition when the battery overheats.
  • examples of inorganic particles include metal oxide particles, metal nitride particles, metal fluoride particles, and metal carbide particles.
  • the volumetric particle size (D50) of the inorganic particles is, for example, 0.05 ⁇ m or more and 2 ⁇ m or less.
  • the volumetric particle size (D50) of the inorganic particles refers to the particle size at which the cumulative frequency of the smallest particle size in the volumetric particle size distribution is 50%, also known as the median diameter.
  • the particle size distribution of the inorganic particles can be measured using a laser diffraction particle size distribution analyzer (e.g., the MT3000II manufactured by Microtrac-Bell) with water as the dispersion medium.
  • the volumetric particle size (D50) of the inorganic particles is a value measured before the separator 13 is incorporated into the nonaqueous electrolyte secondary battery 10.
  • 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.
  • 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 ), or minerals such as barium titanate ( BaTiO3 ) and strontium titanate ( SrTiO3 ). 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 str
  • the content of inorganic particles in the heat-resistant layer 51 is, for example, 45% by mass or more and 95% by mass or less, preferably 50% by mass or more and 95% by mass or less, and more preferably 55% by mass or more and 95% by mass or less, relative to the total mass of the heat-resistant layer 51.
  • the heat-resistant layer 51 may contain a binder.
  • the binder contained in the heat-resistant layer 51 is preferably a polymeric material, such as fluororesins such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE), polyimide resins, polyamide resins, acrylic resins, polyolefin 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 types.
  • fluororesins such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE)
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • polyimide resins polyamide resins
  • the resin particles 52 have a 20% compressive strength of 35 MPa or more, preferably 37 MPa or more, and more preferably 39 MPa or more.
  • the 20% compressive strength of the resin particles 52 By setting the 20% compressive strength of the resin particles 52 to 35 MPa or more, compressive deformation of the resin particles 52 is suppressed.
  • the resin particles 52 have a 20% compressive strength of 100 MPa or less.
  • the 20% compressive strength of the resin particles 52 exceeds 100 MPa, the amount of deformation of the resin particles 52 becomes too small, so the stress that the electrode plate receives from the resin particles 52 during charge and discharge increases, and the internal stress applied to the electrode plate may actually increase. As a result, the electrode plate deforms, which is likely to cause an increase in battery resistance and a deterioration in charge-discharge cycle characteristics.
  • the 20% compressive strength of the resin particles 52 is preferably 65 MPa or less, more preferably 55 MPa or less. In this case, the stress that the electrode plate receives from the resin particles 52 during charge and discharge can be reduced, and deformation of the electrode plate can be sufficiently suppressed.
  • the 20% compressive strength of the resin particles 52 is 35 MPa or more and 100 MPa or less, preferably 35 MPa or more and 65 MPa or less, and more preferably 35 MPa or more and 55 MPa or less.
  • the resin particles 52 may contain resin particles 52 having a 20% compressive strength of less than 35 MPa or more than 100 MPa, but the resin particles 52 are primarily composed of resin particles 52 having a 20% compressive strength of 35 MPa or more and 100 MPa or less.
  • the term "main component" refers to the component that accounts for the largest mass proportion in the resin particles 52.
  • Test temperature room temperature (25°C)
  • Upper pressure indenter Flat indenter with a diameter of 50 ⁇ m (material: diamond)
  • Lower pressure plate SKS flat plate Measurement mode: Compression test Test load: Minimum 10mN, maximum 50mN Load speed: minimum 0.178 mN/sec, maximum 0.221 mN/sec Displacement full scale: 20 ⁇ m
  • the resin particles 52 have a volumetric particle size (D50) of 4.0 ⁇ m or more, and preferably 5.0 ⁇ m or more. If the resin particles 52 have a volumetric particle size (D50) of 4.0 ⁇ m or more, the internal stress applied to the electrode plate when it expands and contracts during charging and discharging is alleviated, thereby suppressing deformation of the electrode plate. Furthermore, the resin particles 52 have a volumetric particle size (D50) of 20.0 ⁇ m or less, and preferably 10.0 ⁇ m or less.
  • the resin particles 52 have a volumetric particle size (D50) of 20.0 ⁇ m or less, clogging of the separator 13 is suppressed, and an increase in battery resistance and a deterioration in charge-discharge cycle characteristics are suppressed. Therefore, the resin particles 52 have a volumetric particle size (D50) of 4.0 ⁇ m or more, and preferably 20.0 ⁇ m or less, and preferably 5.0 ⁇ m or more, and 10.0 ⁇ m or less.
  • the volumetric particle size (D50) of the resin particles 52 like the volumetric particle size (D50) of inorganic particles, refers to the particle size at which the cumulative frequency of the smallest particle size in the volumetric particle size distribution is 50%, and is also called the median diameter.
  • the particle size distribution of the resin particles 52 can be measured using a laser diffraction particle size distribution analyzer (e.g., the MT3000II manufactured by Microtrac-Bell) with water as the dispersion medium.
  • the volumetric particle size (D50) of the resin particles 52 is a value measured before the separator 13 is incorporated into the nonaqueous electrolyte secondary battery 10.
  • the glass transition temperature of the resin particles 52 is preferably 100°C or higher, more preferably 120°C or higher, and even more preferably 140°C or higher. In this case, it becomes easier to increase the 20% compressive strength of the resin particles 52, and the effects of the present disclosure are more pronounced. In other words, if the glass transition temperature of the resin particles 52 is less than 100°C, it becomes difficult to achieve a 20% compressive strength of the resin particles 52 of 35 MPa or higher.
  • the upper limit of the glass transition temperature of the resin particles 52 is, for example, 250°C.
  • the glass transition temperature of the resin particles 52 can be determined using a differential scanning calorimetry (e.g., an EXSTAR DSC6220 manufactured by SII NanoTechnology). Specifically, the resin particles 52 are weighed into an aluminum pan, and measurements are performed under the conditions specified in JIS Z 8703 using the differential scanning calorimetry (DSC) with an empty aluminum pan as a reference, within a measurement temperature range of -100°C to 200°C, at a heating rate of 10°C/min, to obtain a differential scanning calorimetry (DSC) curve.
  • DSC differential scanning calorimetry
  • the glass transition temperature can then be determined from the intersection of the baseline immediately before the endothermic peak of the DSC curve where the differential signal (DDSC) is 0.05 mW/min/mg or greater, and the tangent to the DSC curve at the first inflection point that appears after the endothermic peak.
  • DDSC differential signal
  • the 20% compressive strength, volumetric particle size (D50), and glass transition temperature of resin particles 52 can be adjusted by the type and amount of metal hydroxide used in preparing resin particles 52, as well as the preparation method and conditions for resin particles 52. Details of metal hydroxides are described below.
  • examples of the monomer units contained in the resin particles 52 include aromatic monovinyl monomer units, crosslinkable monomer units, and (meth)acrylic acid alkyl ester monomer units.
  • a polymer when a polymer "contains a monomer unit,” it means that "a polymer obtained using that monomer contains structural units derived from the monomer.”
  • (meth)acrylic means acrylic and/or methacrylic.
  • aromatic monovinyl monomers that can form aromatic monovinyl monomer units include, but are not limited to, styrene, ⁇ -methylstyrene, butoxystyrene, vinylnaphthalene, etc., with styrene being preferred. These aromatic monovinyl monomers may be used alone or in combination of two or more in any ratio.
  • Cross-linkable monomers capable of forming cross-linkable monomer units include, for example, polyfunctional monomers having two or more polymerization reactive groups in the monomer.
  • polyfunctional monomers include (meth)acrylic acid allyl ester monomers such as allyl methacrylate; aromatic divinyl monomers such as divinylbenzene and divinylnaphthalene; di(meth)acrylic acid ester monomers such as diethylene glycol dimethacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, and 1,3-butylene glycol diacrylate; tri(meth)acrylic acid ester monomers such as trimethylolpropane trimethacrylate and trimethylolpropane triacrylate; and ethylenically unsaturated monomers containing epoxy groups such as allyl glycidyl ether and glycidyl methacrylate.
  • divinylbenzene is preferred as the aromatic divinyl monomer
  • ethylene glycol dimethacrylate is preferred as the di(meth)acrylic acid ester monomer
  • trimethylolpropane trimethacrylate is preferred as the tri(meth)acrylic acid ester monomer
  • glycidyl methacrylate is preferred as the ethylenically unsaturated monomer containing an epoxy group.
  • crosslinkable monomers may be used alone or in combination of two or more types in any ratio.
  • the crosslinkable monomer unit is at least one type of crosslinkable monomer unit selected from the group consisting of aromatic divinyl monomer units, di(meth)acrylic acid ester monomer units, tri(meth)acrylic acid ester monomer units, and ethylenically unsaturated monomer units containing an epoxy group.
  • the resin particles 52 are preferably composed of particles containing resin particles 52 containing at least one crosslinkable monomer unit selected from the group consisting of aromatic divinyl monomers, di(meth)acrylic acid ester monomer units, tri(meth)acrylic acid ester monomer units, and ethylenically unsaturated monomer units containing epoxy groups; more preferably composed of particles containing resin particles 52 containing at least one crosslinkable monomer unit selected from the group consisting of aromatic divinyl monomer units, di(meth)acrylic acid ester monomer units, and ethylenically unsaturated monomer units containing epoxy groups; even more preferably composed of particles containing resin particles 52 containing both aromatic divinyl monomer units or di(meth)acrylic acid ester monomer units and ethylenically unsaturated monomer units containing epoxy groups; and particularly preferably composed of particles containing both di(meth)acrylic acid ester monomer units and ethylenically unsaturated monomer units containing epoxy groups;
  • the content of crosslinkable monomer units in resin particles 52 is preferably 2% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, and preferably 99% by mass or less, more preferably 75% by mass or less, and even more preferably 50% by mass or less. If the content of crosslinkable monomer units is 2% by mass or more, an increase in battery resistance can be suppressed. Furthermore, if the content of crosslinkable monomer units is 99% by mass or less, a decrease in charge/discharge cycle characteristics can be suppressed.
  • Examples of (meth)acrylic acid alkyl ester monomers that can form (meth)acrylic acid alkyl ester monomer units include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, butyl acrylates such as n-butyl acrylate and t-butyl acrylate, octyl acrylates such as pentyl acrylate, hexyl acrylate, heptyl acrylate, and 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, lauryl acrylate, n-tetradecyl acrylate, and stearyl acrylate.
  • alkyl acrylates examples include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, butyl methacrylates such as n-butyl methacrylate and t-butyl methacrylate, octyl methacrylates such as pentyl methacrylate, hexyl methacrylate, heptyl methacrylate and 2-ethylhexyl methacrylate, and alkyl methacrylates such as nonyl methacrylate, decyl methacrylate, lauryl methacrylate, n-tetradecyl methacrylate and stearyl methacrylate. Among these, n-butyl acrylate, 2-ethylhexyl acrylate and methyl methacrylate are preferred. These alkyl (meth)acrylate monomers may be used alone or in combination of two or more in any ratio.
  • Resin particles 52 can be prepared by polymerizing a monomer composition containing the above-mentioned monomers in an aqueous solvent such as water.
  • an aqueous solvent such as water.
  • the proportion of each monomer in the monomer composition is typically the same as the proportion of each monomer unit in the polymer that constitutes resin particles 52.
  • the polymerization method is not particularly limited, and any of the following methods can be used: suspension polymerization, emulsion polymerization aggregation, pulverization, dissolution suspension, seed polymerization, etc.
  • suspension polymerization is preferred because it allows resin particles 52 to be produced with high productivity.
  • any of the polymerization reactions can be used, such as radical polymerization and living radical polymerization.
  • the monomer composition used to prepare particles containing polymer A can contain other additives such as chain transfer agents, polymerization regulators, polymerization reaction retarders, reactive fluidizing agents, fillers, flame retardants, antioxidants, colorants, etc. in any desired amounts.
  • the monomer composition is dispersed in water, a polymerization initiator is added, and then droplets of the monomer composition are formed.
  • the droplets can be formed, for example, by shearing and stirring the water containing the monomer composition using a disperser such as an emulsifying disperser.
  • polymerization initiators examples include oil-soluble polymerization initiators such as t-butylperoxy-2-ethylhexanoate and azobisisobutyronitrile.
  • the polymerization initiator may be added after the monomer composition has been dispersed in water and before droplets are formed, or it may be added to the monomer composition before it is dispersed in water.
  • a dispersion stabilizer to the water to form the droplets of the monomer composition.
  • examples of the dispersion stabilizer that can be used include metal hydroxides such as magnesium hydroxide, calcium phosphate, and sodium dodecylbenzenesulfonate.
  • the dispersion stabilizer may be added in the form of a colloidal dispersion in which the dispersion stabilizer is dispersed in water, for example.
  • resin particles 52 are present on the surface of heat-resistant layer 51.
  • resin particles 52 are attached to the surface of heat-resistant layer 51, and the entire resin particles 52 are exposed from heat-resistant layer 51.
  • an uneven structure is formed on the surface of separator 13.
  • separator 13 is incorporated into non-aqueous electrolyte secondary battery 10
  • gaps are formed between positive electrode 11 and separator 13.
  • Resin particles 52 are dispersed, for example, over the entire surface of heat-resistant layer 51.
  • resin particles 52 may be present on second surface 13B instead of or in addition to first surface 13A.
  • some of the resin particles 52 may not be directly attached to the surface of heat-resistant layer 51, but may be attached to the surface of resin particles 52.
  • the ratio of the area where resin particles 52 are present to the entire area of the first surface 13A is preferably 2% or more, more preferably 5% or more, and even more preferably 10% or more. In this case, it is possible to form an appropriately sized uneven structure on the first surface 13A of the separator 13. Furthermore, the ratio of the area where resin particles 52 are present to the entire area of the first surface 13A is preferably 30% or less, more preferably 25% or less, and even more preferably 20% or less. In this case, smooth movement of Li ions is possible within the separator 13, and an increase in battery resistance is suppressed.
  • an example of a suitable range for the ratio of the area where resin particles 52 are present to the entire area of the first surface 13A is 2% or more and 30% or less, more preferably 5% or more and 25% or less, and even more preferably 10% or more and 20% or less.
  • the ratio of the area of the region where the resin particles 52 are present to the entire area of the first surface 13A can be calculated using a laser microscope (for example, a VK-X3000 manufactured by Keyence Corporation).
  • Methods for making resin particles 52 present on the surface of heat-resistant layer 51 include, for example, gravure coating, spraying, bar coating, die coating, knife coating, roll coating, reverse roll coating, screen printing, inkjet printing, lamination, and electrophotography, with gravure coating being preferred.
  • resin particles 52 may be made present on the surface of heat-resistant layer 51 by preparing a liquid composition in which resin particles 52 are dispersed in a dispersion medium, applying the liquid composition to the surface of heat-resistant layer 51, and drying the coating.
  • the resin particles 52 are present on the surface of the heat-resistant layer 51, but the arrangement of the resin particles 52 is not limited to this.
  • a portion of the resin particles 52 may be present inside the heat-resistant layer 51.
  • the resin particles 52 protrude from the heat-resistant layer 51. This allows the resin particles 52 to be present on the surface of the separator 13, forming an uneven structure on the separator surface.
  • the resin particles 52 protrude from the heat-resistant layer 51
  • at least some of the resin particles 52 may not protrude from the heat-resistant layer 51 but may be embedded in the heat-resistant layer 51.
  • the heat-resistant layer 51 containing the resin particles 52 can be produced, for example, by applying a slurry composition containing inorganic particles, resin particles 52, a binder, and a dispersion medium to the surface of the substrate layer 50 and drying the coating.
  • a heat-resistant layer 51 is disposed on one surface of the base layer 50, but the heat-resistant layer 51 does not have to be disposed.
  • the resin particles 52 may be attached directly to the surface of the base layer 50. Even in this case, an uneven structure caused by the resin particles 52 is formed on the surface of the separator 13, and the effects of the present disclosure can be achieved.
  • Example 1 [Preparation of Positive Electrode]
  • the positive electrode active material aluminum-containing lithium nickel cobalt oxide represented by LiNi0.88Co0.09Al0.03O2 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.
  • NMP N-methyl-2-pyrrolidone
  • the positive electrode mixture slurry was applied to both sides of a strip-shaped positive electrode current collector made of aluminum foil with a thickness of 15 ⁇ m, dried, rolled, and cut to a predetermined electrode plate size to produce a positive electrode in which a positive electrode mixture layer was formed on both sides of the positive electrode current collector.
  • a positive electrode exposed portion in which the positive electrode mixture layer was not present and the current collector surface was exposed was provided in the approximate center of the longitudinal direction of the positive electrode, and an aluminum positive electrode lead was welded to the positive electrode exposed portion.
  • a negative electrode mixture slurry 95 parts by mass of graphite, 5 parts by mass of silicon oxide (SiO), 1 part by mass of sodium carboxymethyl cellulose (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 produce 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 the negative electrode mixture layer was not present and the current collector surface was exposed was provided at the inner end of the winding of the negative electrode, and a nickel negative electrode lead was welded to the negative electrode exposed portion.
  • a monomer composition was prepared by mixing 85 parts of styrene as an aromatic monovinyl monomer, 5 parts of glycidyl methacrylate as a crosslinkable monomer, and 10 parts of ethylene glycol dimethacrylate.
  • a colloidal dispersion containing magnesium hydroxide as a metal hydroxide was prepared by gradually adding, with stirring, an aqueous solution prepared by dissolving 7.0 parts of sodium hydroxide in 50 parts of ion-exchanged water to an aqueous solution prepared by dissolving 10.0 parts of magnesium chloride in 200 parts of ion-exchanged water.
  • Resin particles were prepared by suspension polymerization. Specifically, the monomer composition obtained as described above was added to the colloidal dispersion containing magnesium hydroxide, and after further stirring, 3.0 parts of t-butylperoxy-2-ethylhexanoate ("Perbutyl O” manufactured by NOF Corporation) was added as a polymerization initiator to obtain a mixed solution. The resulting mixed solution was subjected to high-shear stirring at 12,000 rpm for 1 minute using an in-line emulsifying disperser ("Cavitron” manufactured by Pacific Machinery Works, Ltd.) to form droplets of the monomer composition in the colloidal dispersion containing magnesium hydroxide.
  • the colloidal dispersion containing magnesium hydroxide, in which droplets of the above monomer composition had formed, was placed in a reactor, heated to 90°C, and polymerized for 5 hours.
  • the resulting dispersion was purified using an evaporator under reduced pressure at 90°C for 2 hours, yielding an aqueous dispersion containing resin particles.
  • a polyethylene porous substrate with a thickness of 12 ⁇ m was used as the substrate layer. Then, alumina ( ⁇ -Al 2 O 3 ) particles as inorganic particles with a particle size (D50) of 0.7 ⁇ m, an acrylic acid ester binder emulsion, and carboxymethyl cellulose as a thickener were mixed in a solid content mass ratio of 100:3:1.5, and then an appropriate amount of water was added to prepare a dispersion so that the solid content concentration was 40 mass%.
  • This dispersion was applied to the entire surface of the porous substrate as the substrate layer using a gravure coater set at a conveying speed of 1.5 m/min and a drying oven temperature of 40 ° C., to prepare a heat-resistant layer with a thickness of 3 ⁇ m containing ⁇ -Al 2 O 3 .
  • the first resin particles, an acrylic ester-based binder emulsion, and carboxymethyl cellulose as a thickener were mixed in a solids mass ratio of 100:10:10, and an appropriate amount of water was added to make the solids concentration 10% by mass to prepare a dispersion.
  • This dispersion was applied to the entire surface of the heat-resistant layer using a gravure coater set at a conveying speed of 4 m/min and a drying oven temperature of 85°C, thereby adhering the first resin particles to the surface of the heat-resistant layer.
  • the first resin particles had a 20% compressive strength of 39.0 MPa, a volume-based particle size (D50) of 5.0 ⁇ m, and a glass transition temperature of 124°C.
  • the first surface of the separator was observed from the surface side using a laser microscope (Keyence Corporation VK-X3000), the ratio of the area where the first resin particles were present to the entire area of the first surface was 10%.
  • 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 of ethylene carbonate (EC) and dimethyl carbonate (DMC) in a volume ratio of 3:7, and dissolving lithium hexafluorophosphate (LiPF 6 ) at a concentration of 1.5 mol/L.
  • VC vinylene carbonate
  • EC ethylene carbonate
  • DMC dimethyl carbonate
  • a wound electrode assembly was fabricated by spirally winding the positive and negative electrodes with a separator interposed therebetween, with the heat-resistant layer of the separator facing the positive electrode. Insulating plates were placed on the top and bottom of the electrode assembly, respectively, and the electrode assembly was housed in an outer can.
  • the negative electrode lead was welded to the bottom of the cylindrical outer can with a bottom, and the positive electrode lead was welded to a sealing member. After pouring the electrolyte into the outer can, the opening of the outer can was sealed with a sealing member via a gasket, completing the fabrication of a nonaqueous electrolyte secondary battery.
  • the test cell was subjected to constant current charging at 0.2 C at a temperature of 25° C. until the battery voltage reached 4.2 V, and then constant voltage charging at 4.2 V until the current value reached 0.02 C. Subsequently, constant current discharging was performed at 1.0 C for 10 seconds, and the battery resistance was calculated by dividing the voltage drop by the current value.
  • the test cell was charged at a constant current of 0.2 C until the battery voltage reached 4.2 V, and then charged at a constant voltage of 4.2 V until the current reached 0.02 C. It was then discharged at a constant current of 0.2 C until the battery voltage reached 2.5 V. This charge-discharge cycle was repeated 200 times, with a 20-minute rest period between each cycle. After 200 cycles, the nonaqueous electrolyte secondary battery was charged at a constant current of 0.2 C until the battery voltage reached 4.2 V, and then charged at a constant voltage of 4.2 V until the current reached 0.02 C, resulting in a charged state.
  • the nonaqueous electrolyte secondary battery in this charged state was observed for a cross section near the center of the winding of the electrode assembly using an X-ray CT scanner (Shimadzu Corporation, SMX-225CT FPD HR). If deformation (bending) of the electrode plate (at least one of the positive electrode and the negative electrode) occurred, the angle ⁇ of electrode plate deformation was confirmed, as shown in FIG. 4 .
  • the degree of deformation of the electrode plates was classified into A, B, and C based on the following evaluation criteria.
  • C Angle ⁇ is 150° or less
  • Example 2 A nonaqueous electrolyte secondary battery was fabricated in the same manner as in Example 1, except that in the preparation of the resin particles, instead of the first resin particles, 70 parts of styrene as an aromatic monovinyl monomer, and 5 parts of glycidyl methacrylate and 25 parts of ethylene glycol dimethacrylate as crosslinkable monomers were mixed to prepare a monomer composition and obtain resin particles (second resin particles).
  • the second resin particles had a 20% compressive strength of 53.3 MPa, a volume-based particle size (D50) of 5.0 ⁇ m, and a glass transition temperature of 164°C. Furthermore, when the first surface of the separator was observed from the surface side using a laser microscope (Keyence Corporation VK-X3000), the ratio of the area of the region where the second resin particles were present to the area of the entire first surface was 10%.
  • Example 3 A nonaqueous electrolyte secondary battery was fabricated in the same manner as in Example 1, except that in the preparation of the resin particles, instead of the first resin particles, 45 parts of styrene as an aromatic monovinyl monomer, and 5 parts of glycidyl methacrylate and 50 parts of ethylene glycol dimethacrylate as crosslinkable monomers were mixed to prepare a monomer composition and obtain resin particles (third resin particles).
  • the third resin particles had a 20% compressive strength of 58.0 MPa, a volume-based particle size (D50) of 5.0 ⁇ m, and a glass transition temperature above the upper limit of the measurement temperature range (>200°C). Furthermore, when the first surface of the separator was observed from the surface side using a laser microscope (Keyence Corporation VK-X3000), the ratio of the area of the region where the third resin particles were present to the area of the entire first surface was 10%.
  • Example 1 A non-aqueous electrolyte secondary battery was fabricated in the same manner as in Example 1, except that in the preparation of the separator, resin particles were not attached to the surface of the heat-resistant layer.
  • the 20% compressive strength of the fourth resin particles was 31.7 MPa, the volume-based particle size (D50) was 5.0 ⁇ m, and the glass transition temperature was 61 ° C. Furthermore, when the first surface of the separator was observed from the surface side using a laser microscope (Keyence Corporation VK-X3000), the ratio of the area of the region where the fourth resin particles were present to the area of the entire first surface was 10%.
  • Table 1 shows the evaluation results of the test cells of the examples and comparative examples. Table 1 also shows the 20% compressive strength, volume-based particle size (D50), and glass transition temperature of the resin particles.
  • the battery resistance and capacity retention rate shown in Table 1 are shown relative to the battery resistance and capacity retention rate of the test cell of Comparative Example 1, which are set at 100. A higher battery resistance value indicates a lower resistance, and a higher capacity retention rate value indicates better charge/discharge cycle characteristics.
  • the test cells of the examples had improved battery resistance and capacity retention compared to the test cells of the comparative examples.
  • the test cell of comparative example 1 in which no resin particles were present on the surface of the separator, experienced plate deformation during charge and discharge. This is presumably due to the absence of gaps between the separator and the plate, which increases internal stress when the plate expands.
  • test cell of comparative example 2 in which resin particles with a 20% compressive strength of less than 35 MPa were present on the surface of the separator, did not experience plate deformation, but did experience increased battery resistance and a deterioration in capacity retention. This is presumably due to the resin particles compressing and deforming as the plate expands, causing clogging of the separator.
  • Configuration 1 A separator for a non-aqueous electrolyte secondary battery, the separator having resin particles present on at least one surface thereof, the resin particles having a 20% compressive strength of 35 MPa or more and 100 MPa or less and a volume-based particle size (D50) of 4.0 ⁇ m or more and 20.0 ⁇ m or less.
  • Configuration 2 The separator for a non-aqueous electrolyte secondary battery according to Configuration 1, wherein the resin particles have a volume-based particle size (D50) of 4.0 ⁇ m or more and 10.0 ⁇ m or less.
  • Configuration 3 The separator for a non-aqueous electrolyte secondary battery according to Configuration 1 or 2, wherein the resin particles have a 20% compressive strength of 35 MPa or more and 65 MPa or less.
  • Configuration 4 The separator for a non-aqueous electrolyte secondary battery according to any one of Configurations 1 to 3, wherein the resin particles have a 20% compressive strength of 35 MPa or more and 55 MPa or less.
  • Configuration 5 The separator for a nonaqueous electrolyte secondary battery according to any one of Configurations 1 to 4, wherein the separator has a base layer and a heat-resistant layer disposed on one surface of the base layer, the heat-resistant layer containing inorganic particles, and the resin particles are present in at least one of the interior of the heat-resistant layer, the surface of the heat-resistant layer, and the other surface of the base layer.
  • Configuration 6 The separator for a non-aqueous electrolyte secondary battery according to any one of Configurations 1 to 5, wherein the resin particles have a glass transition temperature of 100° C. or higher.
  • Configuration 7 The separator for a nonaqueous electrolyte secondary battery according to any one of Configurations 1 to 6, wherein, in a surface view of the separator, the surface on which the resin particles are provided has an area in which the resin particles are present that is a ratio of 2% to 30% of the area of the entire surface of the separator.
  • Non-aqueous electrolyte secondary battery 11 Positive electrode, 12 Negative electrode, 13 Separator, 13A First surface, 13B Second surface, 14 Electrode body, 16 Exterior body, 17 Sealing body, 18, 19 Insulating plate, 20 Positive electrode lead, 21 Negative electrode lead, 22 Grooved portion, 23 Internal terminal plate, 24 Lower valve body, 25 Insulating member, 26 Upper valve body, 27 Cap, 28 Gasket, 30 Positive electrode core, 31 Positive electrode mixture layer, 40 Negative electrode core, 41 Negative electrode mixture layer, 50 Base layer, 51 Heat-resistant layer, 52 Resin particles

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Abstract

Un séparateur (13) pour une batterie secondaire à électrolyte non aqueux selon un mode de réalisation de la présente invention est caractérisé en ce que des particules de résine (52) sont présentes sur au moins une surface, et les particules de résine (52) ont une résistance à la compression à 20% valant de 35 à 100 MPa, et un diamètre de particule basé sur le volume (D50) valant de 4,0 à 20,0 µm.
PCT/JP2025/015642 2024-04-26 2025-04-22 Séparateur pour batterie secondaire à électrolyte non aqueux Pending WO2025225626A1 (fr)

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WO2024011356A1 (fr) * 2022-07-11 2024-01-18 宁德时代新能源科技股份有限公司 Séparateur et son procédé de préparation, batterie secondaire, module de batterie, bloc-batterie et dispositif électrique

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WO2020090395A1 (fr) * 2018-10-31 2020-05-07 日本ゼオン株式会社 Composition de couche fonctionnelle de batterie secondaire non aqueuse, couche fonctionnelle de batterie secondaire non aqueuse, séparateur pour batterie secondaire non aqueuse et batterie secondaire non aqueuse
JP2022026936A (ja) * 2020-07-31 2022-02-10 帝人株式会社 非水系二次電池用セパレータ及び非水系二次電池
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WO2023205967A1 (fr) * 2022-04-24 2023-11-02 宁德新能源科技有限公司 Séparateur et dispositif le comprenant
WO2023229161A1 (fr) * 2022-05-26 2023-11-30 주식회사 엘지에너지솔루션 Séparateur contenant une couche de revêtement poreux composite organique/inorganique pour dispositif électrochimique, et dispositif électrochimique le comprenant
WO2024011356A1 (fr) * 2022-07-11 2024-01-18 宁德时代新能源科技股份有限公司 Séparateur et son procédé de préparation, batterie secondaire, module de batterie, bloc-batterie et dispositif électrique

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