WO2023123205A1 - 隔离膜及其制备方法以及包含该隔离膜的二次电池和用电装置 - Google Patents

隔离膜及其制备方法以及包含该隔离膜的二次电池和用电装置 Download PDF

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Publication number
WO2023123205A1
WO2023123205A1 PCT/CN2021/143069 CN2021143069W WO2023123205A1 WO 2023123205 A1 WO2023123205 A1 WO 2023123205A1 CN 2021143069 W CN2021143069 W CN 2021143069W WO 2023123205 A1 WO2023123205 A1 WO 2023123205A1
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Prior art keywords
pressure
separator
optionally
methacrylate
organic particles
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PCT/CN2021/143069
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English (en)
French (fr)
Inventor
洪海艺
杨建瑞
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Contemporary Amperex Technology Co Ltd
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Contemporary Amperex Technology Co Ltd
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Priority to EP21964985.2A priority Critical patent/EP4239780A4/en
Priority to CN202180096158.1A priority patent/CN117063343A/zh
Priority to PCT/CN2021/143069 priority patent/WO2023123205A1/zh
Priority to US18/327,269 priority patent/US20230307786A1/en
Publication of WO2023123205A1 publication Critical patent/WO2023123205A1/zh
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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
    • 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • H01M50/403—Manufacturing processes of separators, membranes or diaphragms
    • 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
    • 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
    • H01M50/417—Polyolefins
    • 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
    • H01M50/426—Fluorocarbon polymers
    • 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
    • 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
    • H01M50/491—Porosity
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the technical field of batteries, in particular to a separator, a preparation method thereof, a secondary battery and an electrical device including the separator.
  • the separator is a soft material, in order to facilitate the high-efficiency use and mid-way transportation of electrochemical devices, the Usually, a round reel is used as the carrier, and under the action of a certain force, it is wound into a roll on it. At this time, the isolation film layer is in close contact with the layer and there is a certain pressure. If the melting point of the DSC on the isolation film is too low It often causes the diaphragm layers to bond together, which is not conducive to the high-speed compounding of subsequent pole pieces and separators.
  • the present application was made in view of the above problems, and an object of the present application is to provide a pressure-sensitive separator, a method for producing the same, and a secondary battery including the pressure-sensitive separator. Further, the purpose of the present application is to provide an electric device including the secondary battery.
  • the first aspect of the present application provides an isolation membrane, which is a pressure-sensitive isolation membrane, and the isolation membrane may include: a porous isolation membrane substrate and coating on at least one surface of the isolation membrane substrate A pressure-sensitive coating comprising 40-90wt% of the first organic particles and 10-20wt% of the pressure-sensitive adhesive polymer, and optional 0-50wt% of the second organic particles; wherein the pressure
  • the sensitive binder polymer may include a binder polymer and a plasticizer.
  • the release film has good pressure-sensitive properties, and its adhesive force is below 0.23N/m under the action of ⁇ 1MPa, especially below 0.1N/m, so it can avoid the layer and layer of the release film during winding and storage.
  • the bonding between the layers it can have obvious bonding effect with the pole piece under the pressure of ⁇ 2MPa, so when using the separator to prepare the battery, the pole piece can be separated from the pole piece under normal temperature and appropriate pressure.
  • the membrane fits tightly.
  • the mass ratio of the adhesive polymer and the plasticizer included in the pressure-sensitive adhesive polymer may be (4-19):1, optionally (4-11): 1.
  • the relative content of the plasticizer included in the pressure-sensitive adhesive polymer is within the above-mentioned range, which can ensure that the pole piece and the separator can obtain greater adhesion under a certain pressure, and will not cause resistance of the separator. increase, the cycle performance of the secondary battery decreases.
  • the pressure-sensitive adhesive polymer can be a core-shell structure, and both the inner core and the outer shell of the core-shell structure can include an adhesive polymer and a plasticizer, wherein the inner core structure
  • the mass ratio of adhesive polymer and plasticizer described in can be (2-5): 1, can be optionally (3-4): 1, and described adhesive polymer and plasticizer in shell structure
  • the mass ratio of the agent can be (6-10):1, optionally (7-9):1.
  • Both the core and the shell of the core-shell structure are mainly composed of adhesive polymers and plasticizers, which can further improve the pressure-sensitive performance of the pressure-sensitive adhesive polymer, thereby further improving the dynamic performance of the separator.
  • a portion of the plasticizer is grafted onto the binder polymer.
  • at least 5 wt% of the plasticizer is grafted onto the binder polymer, based on the weight of the plasticizer.
  • the average particle size of the pressure-sensitive adhesive polymer may be 0.5-3.0 ⁇ m, optionally 0.8-2.0 ⁇ m.
  • the pressure-sensitive adhesive polymer of suitable particle size facilitates its uniform distribution on the first organic particle or both the first organic particle and the second organic particle, and helps its inner core and outer shell to contact with the pole under a certain pressure. The play of sheet bonding and the effective improvement of the resistance of the separator.
  • the DSC melting point of the pressure-sensitive adhesive polymer can be -50°C-100°C, optionally -45°C-60°C; when the pressure-sensitive adhesive polymer The melting point of DSC is within the above range, which can ensure the adhesive force at normal temperature, and avoid the excessive adhesion of 1MPa, which will cause the separation film to be rolled and bonded; Chip bonding is weak, which is not conducive to cell shaping.
  • the binder polymer may comprise at least one of the first monomers, at least one of the second monomers, at least one of the third monomers and the reaction A copolymer formed by copolymerization of at least one reactive monomer mixture in the type dispersant:
  • the first monomer its melting point is generally higher than 80°C, and may include acrylic acid, methacrylic acid, methyl methacrylate, tert-butyl methacrylate, isobornyl methacrylate, methylol acrylamide, acrylamide, Styrene, acrylonitrile;
  • the second monomer its melting point generally does not exceed 80°C, and may include C4-C22 alkyl acrylate, isobutyl acrylate, isooctyl acrylate, tert-butyl acrylate, 2-ethylhexyl acrylate (isooctyl ), cyclohexyl acrylate, ethyl methacrylate, isobutyl methacrylate, 2-ethylhexyl methacrylate, n-hexyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, 2-Hydroxyethyl acrylate, 2-Hydroxypropyl acrylate, Ethylene urea ethyl methacrylate, Dicyclopentene ethoxy methacrylate, Tetrahydrofuryl methacrylate, Trifluoroethyl methacrylate , dimethylaminoethyl me
  • the third monomer is a cross-linking monomer, containing at least one of hydroxyl, amino, and double bonds, and may include 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, and glycidyl acrylate , glycidyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriisopropoxysilane, ⁇ -methacryloxypropyltrimethoxysilane, N-methylolacrylamide, N-butoxymethyl(meth)acrylamide, diacetoneacrylamide (DAAM), ethyl methacrylate acetoacetate Ester (AAEM), divinylbenzene, epoxy resin with an epoxy value of 0.35-0.50, divinylbenzene;
  • Reactive dispersant it may include polyvinyl alcohol, polypropylene alcohol, polypropylene glycol, polyethylene glycol, polyvinyl acid alcohol.
  • the degree of alcoholysis of these reactive dispersants is ⁇ 85%, and the average degree of polymerization is 400-2000; preferably, the degree of alcoholysis is ⁇ 88%, and the average degree of polymerization is 500-1600.
  • the binder polymer comprises at least one of the above-mentioned first monomers, at least one of the second monomers, at least one of the third monomers and at least one of the reactive dispersants
  • a reactive monomer mixture is copolymerized to form a copolymer, it can ensure proper swelling and bonding of the adhesive polymer, and ensure that the pressure-sensitive adhesive polymer has suitable swelling, pressure sensitivity and bonding performance, while having a suitable modulus of elasticity to ensure the shaping effect, dynamic performance and safety performance of the battery.
  • the plasticizer can be selected from one or more of the following: glycerin C4-C10 alkyl diether or monoether, glycerin C4-C10 carboxylic acid monoester or diester, propylene glycol C4- C10 alkyl monoether, glycerin.
  • the average thickness of the pressure-sensitive coating may be 2-20 ⁇ m, optionally 2-15 ⁇ m.
  • the average particle size of the first organic particles may be 5-30 ⁇ m, optionally 5-20 ⁇ m. Therefore, the first organic particles have a larger average particle size. On the one hand, it can increase the effective contact area between the pole piece and the separator, thereby greatly improving the bonding effect between the pole piece and the separator; on the other hand, it can prevent these organic particles from penetrating into the In the pores formed on the base of the isolation membrane, there are relatively large voids in the large size, so it can also solve the problem of poor air permeability of the isolation membrane, and reduce the possibility of small particles blocking the pores of the isolation membrane to avoid internal resistance. increased risk. In addition, since the first organic particles have a relatively large average particle size and have a certain compressibility, when they exist at the corner of the battery cell, they can effectively provide a stress release space for the corner.
  • the DSC melting point of the first organic particle can be -50°C-200°C, optionally -40°C-160°C, the DSC melting point of the first organic particle is within the above range, and can withstand Swelled by the electrolyte, on the one hand, it will not consume too much electrolyte, and the residual monomer is not easy to be bubbled out by the electrolyte to block the diaphragm, thereby affecting the dynamic performance of the battery cell. On the other hand, the adhesion between the separator and the pole piece will not be greatly reduced, and the pole piece is not easily damaged by the first organic particles, resulting in a decrease in safety performance.
  • the weight average molecular weight of the first organic particles may be 300 ⁇ 10 3 g/mol-800 ⁇ 10 3 g/mol, optionally 400 ⁇ 10 3 g/mol-650 ⁇ 10 3 g /mol.
  • the weight-average molecular weight of the first organic particles is within the above range, which can ensure proper swelling of the first organic particles and proper adhesion to the pole piece.
  • the first organic particles may be one or more polymers containing one or more groups selected from the group consisting of halogen, phenyl, epoxy, cyano, ester and amido group.
  • the first organic particle can be at least one selected from the following: a homopolymer or a copolymer of fluorine-containing alkenyl monomer units, a homopolymer or a copolymer of olefin-based monomer units, Homopolymers or copolymers of unsaturated nitrile monomer units, homopolymers or copolymers of alkylene oxide monomer units, dimers, homopolymers or copolymers of monosaccharide monomer units, and the above-mentioned Modification compound of each homopolymer or copolymer.
  • the fluorine-containing alkenyl monomer unit can be selected from one of vinylidene fluoride, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, tetrafluoroethylene, hexafluoropropylene or derivatives thereof species or several.
  • the olefin-based monomer unit may be selected from one or more of ethylene, propylene, butadiene, isoprene, styrene or derivatives thereof.
  • the unsaturated nitrile monomer unit can be selected from one or more of acrylonitrile, methacrylonitrile or derivatives thereof.
  • the alkylene oxide monomer units may be selected from one or more of ethylene oxide, propylene oxide or derivatives thereof.
  • the monosaccharide monomer unit may be selected from glucose or its derivatives.
  • the first organic particle can be at least one selected from the following: polyvinylidene fluoride, polyvinylidene fluoride, polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride -co-trichloroethylene, polystyrene-co-methyl methacrylate, polystyrene-co-butyl acrylate, polymethyl methacrylate, polyacrylonitrile, polyvinyl acetate, polyethylene-co- Vinyl acetate, polyimide, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose and cyanoethyl sucrose.
  • the first organic particle can be at least one selected from the following: polyvinylidene fluoride-co-hexafluoropropylene, polystyrene-co-butyl acrylate, polyperfluoroethylene, Polyvinylidene fluoride, polyvinylidene fluoride-co-trichloroethylene.
  • the first organic particle When the first organic particle is selected from the above materials, it has proper swelling and proper bonding with the pole piece. It can achieve proper binding force with the pressure-sensitive binder polymer, and at the same time make the pressure-sensitive binder polymer dispersed evenly on it, so as to ensure the bonding and dynamic performance.
  • the mass ratio of the first organic particles to the second organic particles may be (1-4):1, optionally (1.5-2.5):1.
  • the mass ratio of the first organic particles to the second organic particles is within the above range, the wettability and distribution uniformity of the electrolyte can be effectively improved, and the high-temperature storage performance of the battery can be further improved.
  • the average particle size of the first organic particles is relatively large, usually designed as secondary particles, while the average particle size of the second organic particles is relatively small, usually designed as primary particles, between the first organic particles and the second organic particles Under the joint action of the particles, the bonding force between the separator and the electrode sheet can be enhanced, and at the same time, the separator can be further effectively ensured to have a moderate and non-uniform pore structure.
  • the average particle diameter of the second organic particles may be 0.5-10 ⁇ m, optionally 2-8 ⁇ m.
  • the DSC melting point of the second organic particle can be -30-100°C, optionally -30-70°C, the DSC melting point of the second organic particle is within the above range, and can withstand electrolysis Liquid swelling, on the one hand, will not consume too much electrolyte, and the residual monomer is not easy to be bubbled out by the electrolyte to block the diaphragm, thus affecting the dynamic performance of the battery cell.
  • the adhesion between the separator and the pole piece will not be greatly reduced, and the pole piece is not easily damaged by the second organic particles, resulting in a decrease in safety performance.
  • the weight average molecular weight of the second organic particles may be 10 ⁇ 10 3 g/mol-100 ⁇ 10 3 g/mol, optionally 20 ⁇ 10 3 g/mol-80 ⁇ 10 3 g /mol.
  • the weight-average molecular weight of the second organic particles is within the above-mentioned range, which can ensure that the second organic particles have relatively suitable swelling and relatively suitable adhesion with the pole piece.
  • the second organic particle is one or more polymers containing one or more groups selected from the following groups: phenyl, epoxy, cyano, ester, hydroxyl, carboxyl , sulfonyl ester group and pyrrolidone group.
  • the second organic particle may be at least one selected from the following: a homopolymer or a copolymer of an acrylic monomer unit, a homopolymer or a copolymer of an acrylic monomer unit, and not Homopolymer or copolymer of saturated nitrile monomer unit, homopolymer or copolymer of ethylenic monomer unit, homopolymer or copolymer of styrene monomer unit, homopolymer of epoxy monomer unit Compounds or copolymers, polyurethane compounds, rubber compounds, dimers, homopolymers or copolymers of monosaccharide monomer units, and modified compounds of the above-mentioned homopolymers or copolymers.
  • the acrylate monomer unit can be selected from methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, methyl methacrylate, butyl methacrylate, isooctyl methacrylate One or more of esters or their derivatives.
  • the acrylic monomer unit may be selected from one or more of acrylic acid, methacrylic acid or derivatives thereof.
  • the unsaturated nitrile monomer unit can be selected from one or more of acrylonitrile, methacrylonitrile or derivatives thereof.
  • the ethylenic monomer unit may be selected from one or more of ethylene, vinyl acetate, butadiene or derivatives thereof.
  • the styrenic monomer unit may be selected from one or more of styrene, methylstyrene or derivatives thereof.
  • the epoxy monomer unit can be selected from one or more of ethylene oxide, propylene oxide or derivatives thereof.
  • the monosaccharide monomer unit may be selected from glucose or derivatives thereof.
  • the second organic particle is at least one selected from the group consisting of polymethylmethacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, polyethylene-co-vinyl acetate, Polystyrene-co-methyl methacrylate, polystyrene-co-butyl acrylate, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan Polysaccharide, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxymethyl cellulose, acrylonitrile-styrene-butadiene copolymer, styrene-butyl acrylate- Isooctyl acrylate copolymer and polyimide.
  • the second organic particle When the second organic particle is selected from the above substances, it has proper swelling and proper bonding with the pole piece. It can achieve proper binding force with the pressure-sensitive binder polymer, and at the same time make the pressure-sensitive binder polymer dispersed evenly on it, so as to ensure the bonding and dynamic performance.
  • the isolation membrane matrix may have a porosity of 10-95%, a pore diameter of 20-60 nm, and a thickness of 3-12 ⁇ m, optionally 5-9 ⁇ m.
  • porosity of the separator substrate is within the above range, the balance between the kinetics and safety performance of the secondary battery can be achieved; when the thickness of the separator substrate is within the above range, the balance between the energy density and safety performance of the secondary battery can be achieved .
  • the separator base includes one or more films or nonwovens selected from the following: polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate Glycol ester, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole , polyethersulfone, polyphenylene ether, cycloolefin copolymer, polyphenylene sulfide and polyethylene naphthalene.
  • films or nonwovens selected from the following: polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate Glycol ester, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole , polyethersulfone, polyphenylene ether, cycloolefin
  • the second aspect of the present application provides the preparation method of the separator of the first aspect of the present application, which comprises the following steps:
  • step S2) adding a pressure-sensitive adhesive polymer to the first polymer solution obtained in step S1), and mixing to form a second polymer solution;
  • step S3 Optionally, adding second organic particles to the second polymer solution obtained in step S2), and mixing to form a third polymer solution;
  • step S4) coating the second polymer solution obtained in step S2) or the third polymer solution obtained in step S3) on at least one surface of a porous separator substrate, and drying to obtain a separator;
  • the separator includes a pressure-sensitive coating formed on at least one surface of the separator substrate, which includes 40-90 wt% of the first organic particles and 10-20 wt% of the pressure-sensitive adhesive polymer, and optionally 0-50 wt% of second organic particles; wherein the pressure sensitive binder polymer comprises a binder polymer and a plasticizer.
  • the third aspect of the present application provides a secondary battery, which includes a positive electrode sheet, a negative electrode sheet, a separator spaced between the positive electrode sheet and the negative electrode sheet, and an electrolyte, wherein the separator is provided in the first aspect of the present application.
  • the separator or the separator prepared by the method provided in the second aspect of the present application.
  • a fourth aspect of the present application provides an electrical device, which includes a secondary battery selected from the third aspect of the present application.
  • the pressure-sensitive isolation membrane provided by the present application includes a porous isolation membrane substrate and a pressure-sensitive coating coated on at least one surface of the isolation membrane substrate, the coating includes 40-90wt% of the first organic particles and 10-20 wt% of a pressure-sensitive adhesive polymer, and optionally 0-50 wt% of second organic particles, and wherein the pressure-sensitive adhesive polymer may include an adhesive polymer and a plasticized agent, which can make the separator have good ion-conducting ability and adhesive performance under normal temperature conditions, and its resistance under normal temperature conditions is below 1.32 ⁇ , especially below 1.1 ⁇ , and it will not occur under the pressure of ⁇ 1MPa. Adhesive effect, under the pressure of ⁇ 2MPa, it can have obvious adhesive effect with the pole piece.
  • the pole piece of the electrochemical device and the separator can be closely bonded at room temperature, which can avoid the misalignment of the pole piece and the separator of the electrochemical device during the production transfer process, thereby ensuring the structural stability of the electrochemical device And it can ensure the group margin and shell-in quality of the prepared battery cells, thereby improving the battery shaping performance, safety performance and dynamic performance, and can also omit the tunnel furnace and the second process in the traditional battery production process Composite process, so it can save production space and production time, and reduce energy consumption, thereby increasing production capacity.
  • the separator provided by the present invention will not be bonded together during winding and storage, which is convenient for subsequent use in the preparation of electric cells.
  • FIG. 1 is a schematic diagram of a secondary battery provided in an embodiment of the present application.
  • Fig. 2 is a schematic diagram of a battery module provided by an embodiment of the present application.
  • Fig. 3 is a schematic diagram of a battery pack provided by an embodiment of the present application.
  • FIG. 4 is an exploded view of FIG. 3 .
  • Fig. 5 is a schematic diagram of an electrical device provided by an embodiment of the present application.
  • Fig. 6 shows a photo of the topography of the pressure-sensitive coating of the isolation membrane prepared in Example 13 of the present application.
  • ranges disclosed herein are defined in terms of lower and upper limits, and a given range is defined by selecting a lower limit and an upper limit that define the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive and may be combined arbitrarily, ie any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are contemplated. Additionally, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, the following ranges are all expected: 1-3, 1-4, 1-5, 2- 3, 2-4 and 2-5.
  • the numerical range "a-b” represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers.
  • the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article, and "0-5" is only an abbreviated representation of the combination of these values.
  • a certain parameter is an integer ⁇ 2
  • the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed in sequence, and may also include steps (b) and (a) performed in sequence.
  • steps (c) means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c) , may also include steps (a), (c) and (b), may also include steps (c), (a) and (b) and so on.
  • the “comprising” and “comprising” mentioned in this application mean open or closed.
  • the “comprising” and “comprising” may mean that other components not listed may be included or included, or only listed components may be included or included.
  • the term "or” is inclusive unless otherwise stated.
  • the phrase "A or B” means “A, B, or both A and B.” More specifically, the condition "A or B” is satisfied by either of the following: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists) ; or both A and B are true (or exist).
  • an adhesive coating is currently applied on the separator, and in the first compounding of the pole piece of the electrochemical device and the separator, preloading is usually carried out under an appropriate pressure to ensure the electrode of the electrochemical device.
  • preloading is usually carried out under an appropriate pressure to ensure the electrode of the electrochemical device.
  • the pole piece and the separator have a proper bonding effect, and in order to ensure the margin of the cell group and the high efficiency of the case, the pole piece and the separator of the electrochemical device often need to be baked in a tunnel furnace at 80-100 ° C ⁇ After 700s, pressure is applied to make the pole piece of the electrochemical device closely adhere to the separator. Such a process needs to occupy a large amount of production space and production time, making it difficult to increase production capacity.
  • the adhesive coating on the separator uses an adhesive material with a very low softening point.
  • the isolation film usually uses a circular roll as the carrier, and is wound on it under the action of a certain force.
  • the isolation film layer is in close contact with the layer and there is a certain pressure. If the softening point of the contact material is too low, it will often cause the layers of the isolation film to bond together, which is not conducive to the high-speed compounding of the subsequent pole piece and the isolation film.
  • the present application provides a secondary battery with good safety performance and dynamic performance.
  • a secondary battery typically includes a positive pole piece, a negative pole piece, an electrolyte, and a separator.
  • active ions are intercalated and extracted back and forth between the positive and negative electrodes.
  • the electrolyte plays the role of conducting ions between the positive pole piece and the negative pole piece.
  • the separator is arranged between the positive pole piece and the negative pole piece, which mainly plays a role in preventing the short circuit of the positive and negative poles, and at the same time allows ions to pass through.
  • the positive electrode sheet includes a positive electrode collector and a positive electrode membrane disposed on at least one surface of the positive electrode collector and including a positive electrode active material.
  • the positive current collector has two opposing surfaces in its own thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposing surfaces of the positive current collector.
  • the positive current collector can be made of a material with good electrical conductivity and mechanical strength.
  • the positive current collector may be aluminum foil.
  • the present application does not specifically limit the specific type of positive electrode active material, and materials known in the art that can be used for the positive electrode of secondary batteries can be used, and those skilled in the art can choose according to actual needs.
  • the secondary battery provided by the present invention may be a lithium ion secondary battery.
  • the positive active material may include positive active materials known in the art for batteries.
  • the positive electrode active material may include at least one of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds.
  • the present application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials of batteries can also be used.
  • lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO 2 ), lithium nickel oxides (such as LiNiO 2 ), lithium manganese oxides (such as LiMnO 2 , LiMn 2 O 4 ), lithium Nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1/3 Co 1/3 Mn 1/3 O 2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (also abbreviated as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (also abbreviated as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (also abbreviated as NCM 622 ), LiNi At least one of 0.8 Co 0.1 Mn 0.1 O 2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi
  • the olivine structure contains Examples of lithium phosphates may include, but are not limited to, lithium iron phosphate (such as LiFePO 4 (also may be abbreviated as LFP)), composite materials of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), lithium manganese phosphate and carbon At least one of a composite material, lithium manganese iron phosphate, and a composite material of lithium manganese iron phosphate and carbon.
  • lithium iron phosphate such as LiFePO 4 (also may be abbreviated as LFP)
  • composite materials of lithium iron phosphate and carbon such as LiMnPO 4
  • LiMnPO 4 lithium manganese phosphate and carbon
  • the positive electrode film may optionally include a binder.
  • the type of adhesive is not specifically limited, and those skilled in the art can select according to actual needs.
  • the adhesive used for the positive electrode membrane may include one or more of polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE).
  • a conductive agent is optionally included in the positive electrode film.
  • the type of conductive agent is not specifically limited, and those skilled in the art can select according to actual needs.
  • the conductive agent used for the positive electrode membrane may include one or more of graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the step of preparing a positive electrode sheet using a positive active material may include: dispersing the positive active material, a binder, and an optional conductive agent in a solvent, the solvent may be N-methylpyrrolidone, and Stir evenly under the action of a mixer to obtain positive electrode slurry; evenly coat the positive electrode slurry on the aluminum foil of the positive electrode collector, dry it at room temperature, transfer it to an oven for drying, and then perform cold pressing and slitting to obtain positive electrode sheets.
  • the negative electrode sheet includes a negative electrode collector and a negative electrode film arranged on at least one surface of the negative electrode collector.
  • the negative electrode current collector has two opposing surfaces in its own thickness direction, and the negative electrode membrane layer is disposed on any one or both of the two opposing surfaces of the negative electrode current collector.
  • the negative electrode current collector can be made of a material with good electrical conductivity and mechanical strength, which can conduct electricity and collect current.
  • copper foil may be used as the negative electrode current collector.
  • the negative electrode diaphragm includes negative electrode active materials
  • the step of preparing negative electrode pole sheets using the negative electrode active materials may include: dispersing the negative electrode active materials, binders, and optional thickeners and conductive agents in a solvent, and the solvent may be deionized water to form a uniform negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet is obtained.
  • the present application does not specifically limit the specific type of the negative electrode active material, and the negative electrode sheet may optionally include the negative electrode active material that can be used for the negative electrode of the secondary battery.
  • the negative electrode active material can be one or more of graphite materials (such as artificial graphite, natural graphite), mesophase microcarbon spheres (abbreviated as MCMB), hard carbon, soft carbon, silicon-based materials, and tin-based materials.
  • the adhesive can be selected from polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), styrene-butadiene rubber (SBR), sodium alginate ( One or more of SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • PAA polyacrylic acid
  • PAAS sodium polyacrylate
  • PAM polyacrylamide
  • PVA polyvinyl alcohol
  • SBR styrene-butadiene rubber
  • SA sodium alginate
  • PMAA polymethacrylic acid
  • CMCS carboxymethyl chitosan
  • the thickener may be sodium carboxymethylcellulose (CMC-Na).
  • the conductive agent used for the negative electrode sheet can be selected from one of graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers or several.
  • the electrolyte plays the role of conducting ions between the positive pole piece and the negative pole piece.
  • the present application has no specific limitation on the type of electrolyte, which can be selected according to requirements.
  • electrolytes can be liquid, gel or all solid.
  • the electrolyte is an electrolytic solution.
  • the electrolytic solution includes electrolyte salts and solvents.
  • the electrolyte salt may be selected from LiPF 6 (lithium hexafluorophosphate), LiBF 4 (lithium tetrafluoroborate), LiClO 4 (lithium perchlorate), LiAsF 6 (lithium hexafluoroarsenate), LiFSI (difluorosulfonate Lithium imide), LiTFSI (lithium bistrifluoromethanesulfonyl imide), LiTFS (lithium trifluoromethanesulfonate), LiDFOB (lithium difluorooxalate borate), LiBOB (lithium dioxalate borate), LiPO 2 F 2 One or more of (lithium difluorophosphate), LiDFOP (lithium difluorooxalatephosphate) and LiTFOP (lithium tetrafluorooxalatephosphate).
  • LiPF 6 lithium hexafluorophosphate
  • LiBF 4 lithium tetrafluoroborate
  • the solvent may be selected from ethylene carbonate (EC), propylene carbonate (PC), ethylmethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), Dipropyl Carbonate (DPC), Methyl Propyl Carbonate (MPC), Ethyl Propyl Carbonate (EPC), Butylene Carbonate (BC), Fluoroethylene Carbonate (FEC), Methyl Formate (MF), Methyl Acetate Esters (MA), Ethyl Acetate (EA), Propyl Acetate (PA), Methyl Propionate (MP), Ethyl Propionate (EP), Propyl Propionate (PP), Methyl Butyrate (MB) , ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS) and diethyl sul
  • EC
  • additives are optionally included in the electrolyte.
  • additives can include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain performances of batteries, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and additives that improve battery low-temperature performance. Additives etc.
  • Secondary batteries using electrolytes and some secondary batteries using semi-solid electrolytes also include separators.
  • the separator is arranged between the positive pole piece and the negative pole piece to play the role of isolation.
  • the separator can use the pressure-sensitive separator provided by the application, and the separator has good ion-conducting ability and bonding performance under normal temperature conditions, and its resistance under normal temperature conditions is Below 1.32 ⁇ , especially below 1.1 ⁇ , the adhesion force under the action of ⁇ 1MPa is below 0.23N/m, especially below 0.1N/m, and the adhesion force with the pole piece under the action of ⁇ 2MPa is 0.34N /m or more, especially 0.50 N/m or more, more especially 0.60 N/m or more.
  • the separator and its preparation method will be described in detail below.
  • the isolation membrane provided by the present application may include: a porous isolation membrane substrate and a pressure-sensitive coating coated on at least one surface of the isolation membrane substrate, which includes 40-90wt% of the first organic particles and 10-20wt% A pressure-sensitive adhesive polymer, and optionally 0-50 wt% of second organic particles; wherein the pressure-sensitive adhesive polymer may include an adhesive polymer and a plasticizer.
  • the present inventors have noticed through extensive research that when at least one surface of a porous separator substrate is coated with a first organic particle comprising 40-90 wt% and a pressure-sensitive adhesive polymer of 10-20 wt%, and When the optional pressure-sensitive coating of 0-50wt% of the second organic particles is used to prepare the isolation membrane, a pressure-sensitive isolation membrane with good ion-conducting ability and adhesive performance under normal temperature conditions can be obtained, wherein the pressure-sensitive
  • the adhesive polymer may include an adhesive polymer and a plasticizer, and the combination of the two can make the pressure-sensitive adhesive polymer have good pressure-sensitive properties, and further make the release film have good pressure-sensitive properties, so that Its adhesive force is below 0.23N/m under the action of ⁇ 1MPa, especially below 0.1N/m, so it can avoid the bonding between the layers of the separator during winding and storage, and make it Under the action of ⁇ 2MPa pressure, it can have obvious bonding effect with the pole piece.
  • the pole piece and the separator can be tightly bonded under normal temperature conditions and appropriate pressure. On the one hand, it can Avoid the misalignment between the pole piece and the separator, which will cause the cell to be scrapped, affect the performance of the cell, and cause safety risks.
  • the tunnel furnace and the second composite process in the traditional cell production process can be omitted, thereby saving Production space and production time, and reduce energy consumption, significantly increase the production capacity of the cell production, and at the same time can improve the shaping performance, safety performance and dynamic performance of the cell, and then improve the secondary battery containing the cell, and the secondary battery containing the secondary cell. The safety performance and dynamic performance of the electric device of the battery.
  • the mass ratio of the adhesive polymer and the plasticizer included in the pressure-sensitive adhesive polymer may be (4-19):1, optionally (4-11): 1.
  • the relative content of the plasticizer included in the pressure-sensitive adhesive polymer is within the above-mentioned range, which can ensure that the pole piece and the separator obtain greater adhesion without increasing the resistance of the separator. cycle performance is degraded.
  • the plasticizer content can adopt the instrument model STA449F3 thermogravimetric analyzer of Japan Shimadzu Corporation.
  • the test method is as follows: Take about 10 mg of pressure-sensitive adhesive polymer solid, record the original mass as M0, raise the temperature to 200°C, record the mass as M1, and the content of plasticizer is M1-M0, the viscosity
  • the content of the mixture polymer is M0-(M1-M0).
  • the test conditions are set as follows: temperature range -100-400°C, nitrogen atmosphere, 10°C/min.
  • the pressure-sensitive adhesive polymer can be a core-shell structure, and both the inner core and the outer shell of the core-shell structure can include an adhesive polymer and a plasticizer, wherein in the inner core structure
  • the mass ratio of the binder polymer and the plasticizer can be (2-5): 1, optionally (3-4): 1, and the binder polymer and the plasticizer in the shell structure
  • the mass ratio can be (6-10):1, optionally (7-9):1.
  • the core and shell of the core-shell structure are composed of adhesive polymer and plasticizer, which can further improve the pressure-sensitive performance of the pressure-sensitive adhesive polymer, thereby further improving the dynamic performance of the isolation film.
  • the pressure-sensitive adhesive polymer contains a plasticizer, and under a certain pressure (for example, under 1-2MPa), the plasticizer can quickly migrate to the adhesive polymer and the main material of the isolation film. In between, plasticize the binder polymer to stretch its molecular chain, and generate intermolecular hydrogen with the binder such as SBR in the negative pole piece, the thickener of CMC, and the binder in the positive pole piece such as PVDF Bonding effect and enhance the interface wetting, enhance the riveting effect between the two interfaces. Under the action of ⁇ 2MPa, the core structure is crushed, and the plasticizer in the core is released, which can further enhance the above effects.
  • a certain pressure for example, under 1-2MPa
  • a portion of the plasticizer is grafted onto the binder polymer.
  • at least 5 wt% of the plasticizer is grafted onto the binder polymer, based on the weight of the plasticizer.
  • the separation film and the pole piece can form the effect of "broken wire connection", which can improve the durability of bonding at room temperature, reduce rebound, and further Ensure that there will not be too much plasticizer migrating to the electrolyte during the cycle, affecting the performance of the battery.
  • the grafting rate can be detected by the infrared test method, specifically: each test of the adhesive polymer, the plasticizer, and the pressure-sensitive adhesive polymer obtains its Fourier transform infrared spectrum, and in the pressure-sensitive adhesive At the position of 1500-1700cm -1 of the agent polymer, a peak different from that of the adhesive polymer and the individual plasticizer appears, the peak represents the grafted plasticizer, and the area under the peak represents the grafted plasticizer The amount of grafting plasticizer can be calculated from this.
  • the average particle size of the pressure-sensitive adhesive polymer may be 0.5-3.0 ⁇ m, optionally 0.8-2.0 ⁇ m.
  • the pressure-sensitive binder polymer with a suitable average particle size helps it to be evenly distributed on the first or second organic particles, helps to play its inner core and outer shell and pole piece bonding under a certain pressure, and to Effective improvement of the resistance of the isolation film.
  • the average particle size of the pressure-sensitive adhesive polymer can be measured by using a laser particle size analyzer (such as Malvern Master Size 3000) with reference to the standard GB/T 19077.1-2016.
  • a laser particle size analyzer such as Malvern Master Size 3000
  • the DSC melting point of the pressure-sensitive adhesive polymer may be -50°C-100°C, optionally -45°C-60°C; when the pressure-sensitive adhesive polymer The melting point of DSC is within the above range, which can ensure the adhesive force at normal temperature, and avoid the excessive adhesion of 1MPa, which will cause the separation film to be rolled and bonded; Chip bonding is weak, which is not conducive to cell shaping.
  • the binder polymer comprises at least one of the first monomers, at least one of the second monomers, at least one of the third monomers and reactive A copolymer formed by copolymerization of a reactive monomer mixture of at least one of the dispersants:
  • the first monomer its melting point is generally higher than 80°C, and may include acrylic acid, methacrylic acid, methyl methacrylate, tert-butyl methacrylate, isobornyl methacrylate, methylol acrylamide, acrylamide, Styrene, acrylonitrile;
  • the second monomer its melting point generally does not exceed 80°C, and may include C4-C22 alkyl acrylate, isobutyl acrylate, isooctyl acrylate, tert-butyl acrylate, 2-ethylhexyl acrylate (isooctyl ), cyclohexyl acrylate, ethyl methacrylate, isobutyl methacrylate, 2-ethylhexyl methacrylate, n-hexyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, 2-Hydroxyethyl acrylate, 2-Hydroxypropyl acrylate, Ethylene urea ethyl methacrylate, Dicyclopentene ethoxy methacrylate, Tetrahydrofuryl methacrylate, Trifluoroethyl methacrylate , dimethylaminoethyl me
  • the third monomer is a cross-linking monomer, containing at least one of hydroxyl, amino, and double bonds, and may include 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, and glycidyl acrylate , glycidyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriisopropoxysilane, ⁇ -methacryloxypropyltrimethoxysilane, N-methylolacrylamide, N-butoxymethyl(meth)acrylamide, diacetoneacrylamide (DAAM), ethyl methacrylate acetoacetate Ester (AAEM), divinylbenzene, epoxy resin with an epoxy value of 0.35-0.50, divinylbenzene;
  • Reactive dispersant when synthesizing the pressure-sensitive adhesive polymer, it plays the role of dispersing while copolymerizing with the above-mentioned first monomer, second monomer and third monomer, and may include polyvinyl alcohol, Polypropylene alcohol, polypropylene glycol, polyethylene glycol, polyvinyl alcohol.
  • the degree of alcoholysis of these reactive dispersants is ⁇ 85%, and the average degree of polymerization is 400-2000; preferably, the degree of alcoholysis is ⁇ 88%, and the average degree of polymerization is 500-1600.
  • the binder polymer comprises at least one of the above-mentioned first monomers, at least one of the second monomers, at least one of the third monomers and at least one of the reactive dispersants
  • a reactive monomer mixture is copolymerized to form a copolymer, it can ensure proper swelling and bonding of the adhesive polymer, and ensure that the pressure-sensitive adhesive polymer has suitable swelling, pressure sensitivity and bonding performance, while having a suitable modulus of elasticity to ensure the shaping effect, dynamic performance and safety performance of the battery.
  • the plasticizer can be selected from one or more of the following: glycerin C4-C10 alkyl diether or monoether, glycerin C4-C10 carboxylic acid monoester or diester, propylene glycol C4- C10 alkyl monoether, glycerin.
  • the pressure-sensitive adhesive polymer can be synthesized according to the following synthesis method, including the following steps:
  • a solvent such as deionized water
  • sequentially add 0.1-1% mass fraction (it is relative to the reaction monomer mixture added when synthesizing the pressure-sensitive adhesive polymer (comprising the first monomer,
  • a solvent such as deion
  • the second step add 1-4% mass fraction of stabilizer to the first mixed liquid, such as at least one selected from the following: polyethylene oxide, allyl polyether sulfate, methylene succinic acid ( itaconic acid), styrenesulfonic acid, sodium vinylsulfonate, sodium nanocellulose;
  • the homogenizer speed is controlled at 6000-8000r/min, such as 6500r/min for mixing, and the time is 20-60min, such as 30min, mixing
  • the reaction temperature is 20-60°C, such as 45°C, to obtain the second mixed solution;
  • water-based initiator in the second mixed solution, such as at least one selected from the following: sodium bicarbonate, benzoyl peroxide, lauroyl peroxide, cumene Hydrogen peroxide, tert-butyl hydroperoxide, di-tert-butyl peroxide, dicumyl peroxide, tert-butyl peroxybenzoate, tert-butyl peroxy-tert-butyl valerate, methyl ethyl ketone peroxide, ring peroxide Hexanone diisopropyl peroxydicarbonate, dicyclohexyl peroxydicarbonate, potassium persulfate, sodium persulfate, ammonium persulfate, azobisisobutyronitrile, azobisisoheptanonitrile.
  • water-based initiator such as at least one selected from the following: sodium bicarbonate, benzoyl peroxide, lauroyl peroxide, cumene Hydro
  • the speed of the homogenizer is controlled at 8000-12000r/min, such as 8000r/min for mixing, and the time is 20-60min, such as 30min.
  • the reaction temperature is 60-80°C, such as 72°C, to obtain the third mixed liquid.
  • the 4th step under the condition that the homogenizer rotating speed is 100-1000r/min, such as 400r/min, gradually evenly add (control in 60min and just finish dripping) 35%-45% mass fraction of Reacting the monomer mixture, the reaction time is 80-100min, such as 80min, to obtain the fourth mixture.
  • the fifth step is to continue the reaction of the fourth mixture under the condition that the reaction temperature is 80-90°C, such as 84°C; the speed of the homogenizer is 12000-18000r/min, such as 15000r/min, and the time is 120-240min, such as 180min , to obtain the fifth mixture.
  • the sixth step is to add 10-20% mass fraction of plasticizer, such as glycerin, to the fifth mixture, and control the reaction temperature to 80-90°C, such as 84°C; the speed of the homogenizer is controlled to 12000-18000r/min, such as 15000r/min, the reaction time is 120-240min, such as 180min, to obtain the sixth mixture.
  • plasticizer such as glycerin
  • 0.05-0.5% by mass of an aqueous initiator such as ammonium persulfate-sodium bicarbonate
  • the speed of the homogenizer is controlled at 8000-12000r/min, such as 8000r/min, and the time is 20-60 minutes, such as 30 minutes.
  • the reaction temperature is 60-80°C, such as 72°C, to obtain a seventh mixture.
  • the eighth step under the condition that the speed of the homogenizer is 100-1000r/min, such as 400r/min, gradually and uniformly dropwise (controlling at 60min just finished dropping) the reaction of 30%-40% mass fraction in the seventh mixture
  • the reaction time is 100-160 minutes, such as 120 minutes, to obtain the eighth mixture.
  • the ninth step add 5-20% mass fraction of plasticizer, such as glycerin, to the eighth mixture, and control the reaction temperature to 80-90°C, such as 84°C; the speed of the homogenizer is 12000-18000r/min, such as 15000r /min, the time is 120-240min, such as 180min, to obtain the ninth mixture.
  • plasticizer such as glycerin
  • the temperature of the ninth mixture is lowered to below 50° C., and the material is filtered out to obtain a pressure-sensitive adhesive polymer with a core-shell structure.
  • Those skilled in the art can also refer to the above method (omit the seventh to ninth steps, and change the mass fraction of the added plasticizer and reactive monomer mixture accordingly) to synthesize a pressure-sensitive adhesive polymer with a non-core-shell structure.
  • the average thickness of the pressure-sensitive coating may be 2-20 ⁇ m, optionally 2-15 ⁇ m.
  • the average particle size of the first organic particles may be 5-30 ⁇ m, optionally 5-20 ⁇ m.
  • the average particle diameter of the first organic particles can be measured with reference to the standard GB/T 19077.1-2016 using a laser particle size analyzer (such as Malvern Master Size 3000).
  • a laser particle size analyzer such as Malvern Master Size 3000.
  • the bonding effect of the membrane can prevent these organic particles from penetrating into the pores formed on the isolation membrane substrate, and at the same time, there are relatively large gaps in the large size, so it can also solve the problem of poor air permeability of the isolation membrane and reduce The possibility of small particles blocking the pores of the isolation membrane avoids the risk of increased internal resistance.
  • the separator and the pole piece since the corners will not be recombined during the cell manufacturing process (especially for square shell batteries), the separator and the pole piece here are not bonded, and the separator cannot effectively transfer to the surroundings to release the accumulated stress of the pole piece. ; and the characteristics of the cell module's own structure of the prismatic battery will cause the corners to be supported, and the stress caused by the expansion of the pole piece is difficult to release.
  • the pole piece will break, and then puncture the separator, causing a serious safety risk.
  • the first organic particles have a relatively large average particle size and have a certain compressibility, when they exist at the corner of the cell, they can effectively provide a stress release space for the corner.
  • the DSC melting point of the first organic particles can be -50°C-200°C, optionally -40°C-160°C, the DSC melting point of the first organic particles is within the above range, and can withstand Swelled by the electrolyte, on the one hand, it will not consume too much electrolyte, and the residual monomer is not easy to be bubbled out by the electrolyte to block the diaphragm, thereby affecting the dynamic performance of the battery cell. On the other hand, the adhesion between the separator and the pole piece will not be greatly reduced, and the pole piece is not easily damaged by the first organic particles, resulting in a decrease in safety performance.
  • the weight average molecular weight of the first organic particles may be 300 ⁇ 10 3 g/mol-800 ⁇ 10 3 g/mol, optionally 400 ⁇ 10 3 g/mol-650 ⁇ 10 3 g /mol.
  • the weight-average molecular weight of the first organic particles is within the above range, which can ensure proper swelling of the first organic particles and proper adhesion to the pole piece.
  • too much weight average molecular weight will cause too little swelling, which is not conducive to the replenishment of electrolyte in the later stage of the cell cycle, affecting the performance of the battery cell, and at the same time, too large a weight average molecular weight will cause the modulus of the first organic particles to be too large , direct pressure damage to the pole piece, affecting the safety performance of the battery cell.
  • the weight-average molecular weight is too small and the swelling is too large, a large amount of residual monomers of the first organic particles will dissolve under the action of the electrolyte to increase the resistance of the separator, and deteriorate the electrolyte to affect the kinetic performance of the battery cell.
  • the weight average molecular weight is measured by Tosoh Corporation HLC-8320GPC gel permeation chromatography (SuperMultiporeHZ series semi-micro SEC column, standard product is polystyrene) to measure the weight average molecular weight (Mw).
  • the test method is as follows: 2 mg of the polymer powder to be tested is dissolved in 2 mL of DMF solvent dedicated to GPC, and then 2.5 ⁇ L is injected for testing. The parameters are set as follows: pump flow rate: 5 mL/min; injection volume: 100 ⁇ L; temperature control range: 60 °C; data acquisition frequency: 100 Hz.
  • the first organic particles may be one or more polymers containing one or more groups selected from the group consisting of halogen, phenyl, epoxy, cyano, ester and amido group.
  • the first organic particle may be at least one selected from the following: a homopolymer or a copolymer of fluorine-containing alkenyl monomer units, a homopolymer or copolymer of olefin-based monomer units, Homopolymers or copolymers of unsaturated nitrile monomer units, homopolymers or copolymers of alkylene oxide monomer units, dimers, homopolymers or copolymers of monosaccharide monomer units, and the above-mentioned Modification compound of each homopolymer or copolymer.
  • the fluorine-containing alkenyl monomer unit can be selected from one of vinylidene fluoride, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, tetrafluoroethylene, hexafluoropropylene or derivatives thereof species or several.
  • the olefin-based monomer unit may be selected from one or more of ethylene, propylene, butadiene, isoprene, styrene or derivatives thereof.
  • the unsaturated nitrile monomer unit may be selected from one or more of acrylonitrile, methacrylonitrile or derivatives thereof.
  • the alkylene oxide monomer unit may be selected from one or more of ethylene oxide, propylene oxide or derivatives thereof.
  • the monosaccharide monomer unit may be selected from glucose or its derivatives.
  • the first organic particles can be at least one selected from the following: polyvinylidene fluoride, polyvinylidene fluoride, polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride -co-trichloroethylene, polystyrene-co-methyl methacrylate, polystyrene-co-butyl acrylate, polymethyl methacrylate, polyacrylonitrile, polyvinyl acetate, polyethylene-co- Vinyl acetate, polyimide, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose and cyanoethyl sucrose.
  • the first organic particle can be at least one selected from the following: polyvinylidene fluoride-co-hexafluoropropylene, polystyrene-co-butyl acrylate, polyperfluoroethylene, Polyvinylidene fluoride, polyvinylidene fluoride-co-trichloroethylene.
  • the first organic particle When the first organic particle is selected from the above materials, it has proper swelling and proper bonding with the pole piece. It can achieve proper bonding force with the pressure-sensitive adhesive polymer, and at the same time make the pressure-sensitive adhesive polymer dispersed evenly on it, ensuring the bonding and dynamic performance.
  • the mass ratio of the first organic particles to the second organic particles may be (1-4):1, optionally (1.5-2.5):1.
  • the mass ratio of the first organic particle to the second organic particle is within the above range, the wettability and uniformity of the electrolyte can be effectively improved, and the high-temperature storage performance of the battery can be further improved; especially, when the battery is in use, if In the case of penetration by foreign matter, the second organic particles can instantly wrap the foreign matter and the exposed copper or aluminum foil to form the first polymer insulating layer, which effectively reduces the probability of short circuit between the positive and negative electrodes and improves the safety performance of the battery , as the temperature around the foreign matter rises, the first organic particles will form a stronger second polymer insulating layer around the first polymer insulating layer, thereby further improving the safety performance of the battery.
  • the average particle size of the second organic particles may be 0.5-10 ⁇ m, optionally 2-8 ⁇ m.
  • the average particle size of the second organic particle can be measured with reference to the standard GB/T 19077.1-2016 using a laser particle size analyzer (such as Malvern Master Size 3000).
  • a laser particle size analyzer such as Malvern Master Size 3000.
  • the first and second organic particles can form a large-area adhesive film structure, which can reduce or block the ion transmission channel and prevent further contact between the positive electrode and the negative electrode. , to delay the thermal runaway of the battery, so that the battery can further obtain good safety performance.
  • the average particle size of the first organic particles is relatively large, usually designed as secondary particles, while the average particle size of the second organic particles is relatively small, usually designed as primary particles, between the first organic particles and the second organic particles Under the joint action of the particles, the bonding force between the separator and the electrode sheet can be enhanced, and at the same time, the separator can be further effectively ensured to have a moderate and non-uniform pore structure.
  • the first organic particles are secondary particles, which can help to form a uniform coating interface, and can effectively improve the tab dislocation problem during the preparation of battery cells.
  • Organic particles are primary particles, and it is not easy to form a large-area film structure between particles, so the pores will not be blocked, which can further improve the rate performance and safety performance of the battery.
  • the DSC melting point of the second organic particles may be -30-100°C, optionally -30-70°C.
  • the DSC melting point of the second organic particles may be -30-100°C, optionally -30-70°C.
  • the DSC melting point of the second organic particles can withstand The swelling of the electrolyte, on the one hand, does not consume too much electrolyte, and the residual monomer is not easy to be bubbled out by the electrolyte to block the diaphragm, thereby affecting the dynamic performance of the battery cell.
  • the adhesion between the separator and the pole piece will not be greatly reduced, and the pole piece is not easily damaged by the second organic particles, resulting in a decrease in safety performance.
  • DSC melting point is meaning known in the art, can measure with instrument and method known in the art, for example, can be the DSC melting point tester of DSC 200F3 by the instrument model of German NETZSC company.
  • the testing method is as follows: about 10 mg of sample is taken for testing.
  • the test conditions are set as follows: temperature range: -100-200°C, nitrogen atmosphere, 10°C/min. When the temperature is raised for the first time, the temperature corresponding to the absorption peak is the corresponding DSC melting point.
  • the weight average molecular weight of the second organic particles may be 10 ⁇ 10 3 g/mol-100 ⁇ 10 3 g/mol, optionally 20 ⁇ 10 3 g/mol-80 ⁇ 10 3 g /mol.
  • the weight-average molecular weight of the second organic particles is within the above-mentioned range, which can ensure that the second organic particles have relatively suitable swelling and relatively suitable adhesion with the pole piece.
  • too much weight average molecular weight will cause too small swelling, which is not conducive to the replenishment of electrolyte in the later stage of the cell cycle, affecting the performance of the cell, and at the same time, too large a weight average molecular weight will cause the modulus of the second organic particle to be too large , direct pressure damage to the pole piece, affecting the safety performance of the battery cell.
  • the test method of the weight average molecular weight of the second organic particles is the same as the test method of the first organic particle weight average molecular weight.
  • the second organic particles are one or more polymers containing one or more groups selected from the following groups: phenyl, epoxy, cyano, ester, hydroxyl, carboxyl , sulfonyl ester group and pyrrolidone group.
  • the second organic particle may be at least one selected from the following: a homopolymer or a copolymer of an acrylic monomer unit, a homopolymer or a copolymer of an acrylic monomer unit, and not Homopolymer or copolymer of saturated nitrile monomer unit, homopolymer or copolymer of ethylenic monomer unit, homopolymer or copolymer of styrene monomer unit, homopolymer of epoxy monomer unit Compounds or copolymers, polyurethane compounds, rubber compounds, dimers, homopolymers or copolymers of monosaccharide monomer units, and modified compounds of the above-mentioned homopolymers or copolymers.
  • the acrylate monomer unit can be selected from methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, methyl methacrylate, butyl methacrylate, isooctyl methacrylate One or more of esters or their derivatives.
  • the acrylic monomer unit may be selected from one or more of acrylic acid, methacrylic acid or derivatives thereof.
  • the unsaturated nitrile monomer unit may be selected from one or more of acrylonitrile, methacrylonitrile or derivatives thereof.
  • the ethylenic monomer unit may be selected from one or more of ethylene, vinyl acetate, butadiene or derivatives thereof.
  • the styrenic monomer units may be selected from one or more of styrene, methylstyrene or derivatives thereof.
  • the epoxy monomer unit can be selected from one or more of ethylene oxide, propylene oxide or derivatives thereof.
  • the monosaccharide monomer unit may be selected from glucose or its derivatives.
  • the second organic particle is at least one selected from the group consisting of polymethylmethacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, polyethylene-co-vinyl acetate, Polystyrene-co-methyl methacrylate, polystyrene-co-butyl acrylate, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan Polysaccharide, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxymethyl cellulose, acrylonitrile-styrene-butadiene copolymer, styrene-butyl acrylate- Isooctyl acrylate copolymer and polyimide.
  • the second organic particle When the second organic particle is selected from the above substances, it has proper swelling and proper bonding with the pole piece. It can achieve proper bonding force with the pressure-sensitive adhesive polymer, and at the same time make the pressure-sensitive adhesive polymer dispersed evenly on it, ensuring the bonding and dynamic performance.
  • the isolation membrane matrix may have a porosity of 10-95%, a pore diameter of 20-60 nm, and a thickness of 3-12 ⁇ m, optionally 5-9 ⁇ m.
  • porosity of the separator substrate is within the above range, the balance between the kinetics and safety performance of the secondary battery can be achieved; when the thickness of the separator substrate is within the above range, the balance between the energy density and safety performance of the secondary battery can be achieved .
  • the separator base may include one or more films or nonwovens selected from the following: polyethylene, polypropylene, polyethylene terephthalate, polyethylene terephthalate Butanediol ester, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzo Imidazole, polyethersulfone, polyphenylene ether, cycloolefin copolymer, polyphenylene sulfide, and polyethylene naphthalene.
  • films or nonwovens selected from the following: polyethylene, polypropylene, polyethylene terephthalate, polyethylene terephthalate Butanediol ester, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzo Imidazole, polyethersulfone, polyphenylene ether,
  • the present application also provides a preparation method of the isolation film, which comprises the following steps:
  • step S2) adding a pressure-sensitive adhesive polymer to the first polymer solution obtained in step S1), and mixing to form a second polymer solution;
  • step S3 Optionally, adding second organic particles to the second polymer solution obtained in step S2), and mixing to form a third polymer solution;
  • step S4) coating the second polymer solution obtained in step S2) or the third polymer solution obtained in step S3) on at least one surface of a porous separator substrate, and drying to obtain a separator;
  • the separator includes a pressure-sensitive coating formed on at least one surface of the separator substrate, which includes 40-90 wt% of the first organic particles and 10-20 wt% of the pressure-sensitive adhesive polymer, and optionally 0-50 wt% of second organic particles; wherein the pressure sensitive binder polymer comprises a binder polymer and a plasticizer.
  • non-limiting examples of dispersants used in step S1) may include acrylates (such as BYK grade 22136), branched alcohol polyethers (such as Dow grade TMN-6), polyethylene glycol tris Methyl nonyl ether.
  • Non-limiting examples of solvents used in step S1) may include acetone, tetrahydrofuran, dichloromethane, chloroform, dimethylformamide, N-methyl-2-pyrrolidone, cyclohexane, water or mixtures thereof.
  • non-limiting examples of coating methods used in step S4) may include dip coating, die coating, roll coating, comma coating, spin coating, or combinations thereof .
  • the coating weight on one side after drying may be 0.42-0.52 g/m 2 .
  • the secondary battery may include an outer package for encapsulating a positive electrode tab, a negative electrode tab, a separator, and an electrolyte.
  • the positive pole piece, the negative pole piece and the separator can be laminated or wound to form a stacked structure cell or a wound structure cell, and the cell is packaged in the outer package; the electrolyte can be electrolyte, and the electrolyte can be infiltrated in the cell.
  • the number of cells in the secondary battery can be one or several, and can be adjusted according to requirements.
  • the outer package of the secondary battery may be a soft bag, such as a pouch-type soft bag.
  • the material of the soft bag can be plastic, such as one or more of polypropylene PP, polybutylene terephthalate PBT, polybutylene succinate PBS, etc. can be included.
  • the outer package of the secondary battery may also be a hard case, such as an aluminum case.
  • the positive pole piece, the negative pole piece and the separator can be made into an electrode assembly through a winding process or a lamination process.
  • FIG. 1 shows a secondary battery 5 with a square structure as an example.
  • the secondary battery provided by the present invention can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.
  • FIG. 2 is a battery module 4 as an example.
  • a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4 .
  • the plurality of secondary batteries 5 may be fixed by fasteners.
  • the battery module 4 may further include a case having a housing space in which a plurality of secondary batteries 5 are accommodated.
  • battery modules assembled from secondary batteries can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box.
  • the battery box includes an upper box body 2 and a lower box body 3 , the upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery module 4 .
  • Multiple battery modules 4 can be arranged in the battery box in any manner.
  • the present application also provides an electric device, the electric device includes the secondary battery provided by the present application, and the secondary battery provides power for the electric device.
  • the electric device can be, but not limited to, mobile devices (such as mobile phones, notebook computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.
  • the electric device can select a secondary battery, a battery module or a battery pack according to its usage requirements.
  • FIG. 5 is an example of an electrical device.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.
  • a battery pack or a battery module may be used.
  • the electric device may be a mobile phone, a tablet computer, a notebook computer, and the like.
  • the electrical device is usually required to be light and thin, and a secondary battery can be used as a power source.
  • the first organic particle polyvinylidene fluoride-co-hexafluoropropylene (wherein, based on the weight of vinylidene fluoride (VDF) monomer and hexafluoropropylene (HFP) monomer, HFP monomer accounts for about 9 %), the weight average molecular weight is about 600 ⁇ 10 3 g/mol, the average particle size is about 7 ⁇ m, and the DSC melting point is about 150°C) and dispersant (BYK-22136) are added to water to form the first polymer solution;
  • the pressure-sensitive adhesive polymer (the glass transition temperature of which is about 10 ° C, the average particle size is about 1.1 ⁇ m, including the adhesive polymer and plasticizer at a mass ratio of 5:1 (wherein the relative Based on the weight of the plasticizer, about 8 wt% of the plasticizer is grafted on the binder polymer) and some deionized water, where the binder polymer is 30% isobutyl acrylate + 25% isooctyl acrylate +5% methacrylic acid-2-hydroxypropyl ester+15% styrene+22% acrylonitrile+3% polyvinyl alcohol copolymer, the plasticizer is glycerin) add step 2) in the first polymer solution that obtains, Mixing to form a second polymer solution with a solid content of 12 wt%, wherein the mass ratio of the first organic particles to the pressure-sensitive adhesive polymer is 85:15;
  • the second polymer solution with a solid content of 12wt% obtained in step 3) is used as an aqueous coating slurry, and is coated on one surface of the isolation film substrate by spin spraying, and after drying, the isolation film is obtained.
  • membrane The prepared separator includes a separator substrate, and a pressure-sensitive coating coated on one surface of the separator substrate, the pressure-sensitive coating has a thickness of about 3 ⁇ m, and includes a first organic particle and a mass ratio of 85:15.
  • a pressure-sensitive adhesive polymer, and the pressure-sensitive adhesive polymer includes an adhesive polymer and a plasticizer in a mass ratio of 5:1 (wherein, with respect to the weight of the plasticizer, about 8 wt % plasticizer grafted onto the binder polymer).
  • the active material LiNi 1/3 Mn 1/3 Co 1/3 O 2 , the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) are mixed in the solvent N-methylpyrrolidone at a weight ratio of 94:3:3 After fully stirring and mixing uniformly, a positive electrode slurry is obtained, which is coated on an Al foil, dried, and cold-pressed to obtain a positive electrode sheet.
  • the loading capacity of the positive electrode active material on the positive electrode sheet is 0.32g/1540.25mm 2 , and the density is 3.45g/cm 3 .
  • Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 3:5:2, and then LiPF 6 was uniformly dissolved in the above solution to obtain an electrolyte.
  • the concentration of LiPF 6 is 1 mol/L.
  • the separators prepared in each embodiment or comparative example were used as separators for electric cores.
  • the separator is in the middle of the positive and negative poles to play the role of isolation, and wind up to get the bare cell.
  • What needs to be added is that if the coating of the separator is single-sided, the coated side faces the cathode (that is, the positive electrode sheet) side.
  • the testing process is as follows:
  • the testing process is as follows:
  • Isolation film preparation Cut each test isolation film into samples of the same size (45.3mm*33.7mm), place the samples at 60°C and bake for at least 4 hours, then quickly transfer to 25°C Reserve in a clean glove box;
  • Symmetrical battery-confined Pocket bag (symmetrical battery-confined aluminum-plastic bag (aluminum-plastic bag is a general commodity composed of polypropylene and aluminum foil for soft-pack batteries)) Preparation: use Cu Foil to Cu Foil (copper foil For copper foil) A blank symmetrical cell assembled as a current collector. The localization of the Pocket bag is realized by punching holes in the middle of the green glue. Pocket bags need to be baked at 60°C for at least 4 hours before use, and then quickly transferred to a 25°C class 100 clean glove box as described in (1) above for use;
  • the French Bio-Logic VMP3 electrochemical workstation is used, the voltage is ⁇ 5V, the current is ⁇ 400mA, and the current accuracy is 0.1%*100 ⁇ A.
  • the measurement conditions of the EIS are set to a voltage frequency of 1MHz-1kHz, the disturbance voltage is set to 5MV, and the pressure of the fixture is controlled at 0.7MPa.
  • the mass ratio of the first organic particle to the pressure-sensitive adhesive polymer in the pressure-sensitive coating of the isolation film prepared in Example 2 is 90:10.
  • the mass ratio of the first organic particle to the pressure-sensitive adhesive polymer in the pressure-sensitive coating of the isolation film prepared in Example 3 is 80:20.
  • the adhesive polymer in the pressure-sensitive adhesive polymer used in Example 4 is 30% isobutyl acrylate + 25% isooctyl acrylate + 5% 2-hydroxypropyl acrylate + 15% styrene + 22% acrylamide + 3% polyethylene glycol copolymer, plasticizer is glycerin.
  • the adhesive polymer in the pressure sensitive adhesive polymer used in Example 5 is 30% cyclohexyl acrylate + 25% tetrahydrofuryl methacrylate + 5% -2-hydroxypropyl methacrylate + 15% Styrene + 22% acrylonitrile + 3% polyethylene glycol copolymer, plasticizer is glycerin.
  • the adhesive polymer in the pressure sensitive adhesive polymer used in Example 6 was 30% cyclohexyl acrylate + 25% tetrahydrofuryl methacrylate + 5% divinylbenzene + 15% styrene + 22% Acrylonitrile + 3% polyethylene glycol copolymer, plasticizer is glycerin.
  • the adhesive polymer in the pressure sensitive adhesive polymer used in Example 7 was 30% isobutyl acrylate + 25% isooctyl acrylate + 5% divinylbenzene + 15% styrene + 22% propylene Nitrile + 3% polyvinyl alcohol copolymer, plasticizer is glycerin.
  • the adhesive polymer in the pressure sensitive adhesive polymer used in Example 8 was 30% isobutyl acrylate + 25% isooctyl acrylate + 5% 2-hydroxypropyl methacrylate + 15% benzene Ethylene + 22% acrylonitrile + 3% polyvinyl alcohol copolymer, plasticizer is glycerol C4-C10 alkyl diether.
  • the adhesive polymer in the pressure sensitive adhesive polymer used in Example 9 was 30% isobutyl acrylate + 25% isooctyl acrylate + 5% 2-hydroxypropyl methacrylate + 15% benzene Ethylene + 22% acrylonitrile + 3% polyvinyl alcohol copolymer, plasticizer is propylene glycol C4-C10 alkyl monoether.
  • the grafting of plasticizer in the pressure sensitive adhesive polymer used in Example 10 was 5 wt%.
  • the grafting of plasticizer in the pressure sensitive adhesive polymer used in Example 11 was 3 wt%.
  • the grafting of the plasticizer in the pressure-sensitive adhesive polymer used in Example 12 was 0 wt%, that is, there was no grafting of the plasticizer.
  • the first organic particle polyvinylidene fluoride-co-hexafluoropropylene (wherein, based on the weight of vinylidene fluoride (VDF) monomer and hexafluoropropylene (HFP) monomer, HFP monomer accounts for about 9 %), the weight average molecular weight is about 600 ⁇ 10 3 g/mol, the average particle size is about 7 ⁇ m, and the DSC melting point is about 150°C) and dispersant (BYK-22136) are added to water to form the first polymer solution;
  • the pressure-sensitive adhesive polymer (its DSC melting point is about 10°C, and its average particle size is about 1.1 ⁇ m, including adhesive polymer and plasticizer at a mass ratio of 5:1 (wherein relative to the plasticizer The weight of the plasticizer, about 8wt% of the plasticizer is grafted on the binder polymer) and some deionized water, wherein the binder polymer is 30% isobutyl acrylate+25% isooctyl acrylate+5 % methacrylic acid-2-hydroxypropyl ester+15% styrene+22% acrylonitrile+3% polyvinyl alcohol copolymer, plasticizer is glycerin) add step 2) in the first polymer solution that obtains, mix with Forming a second polymer solution with a solid content of 12% by weight;
  • step 3 Add second organic particles (30% styrene-50% butyl acrylate-20% isooctyl acrylate to the second polymer solution obtained in step 3), with an average particle size of 4 ⁇ m and a DSC melting point of about 55° C. ), so that the mass ratio of the first organic particles and the second organic particles is 65:20, mixed to form a third polymer solution with a solid content of 12%, wherein the organic particles (including the first organic particles with a mass ratio of 65:20 Particle and the second organic particle) and the mass ratio of pressure-sensitive adhesive polymer is 85:15;
  • the third polymer solution with a solid content of 12wt% obtained in step 4) is used as an aqueous coating slurry, and is coated on one surface of the isolation film substrate by spin spraying, and after drying, the isolation film is obtained.
  • membrane The prepared separator includes a separator substrate, and a pressure-sensitive coating coated on one surface of the separator substrate, the pressure-sensitive coating has a thickness of about 3 ⁇ m, and includes organic particles (including a first organic particle and a second organic particle at a mass ratio of 65:20) and a pressure-sensitive adhesive polymer, and the pressure-sensitive adhesive polymer includes an adhesive polymer with a mass ratio of 5:1 and a plasticizer (wherein about 8% by weight of the plasticizer is grafted onto the binder polymer relative to the weight of the plasticizer).
  • FIG. 6 the morphology of the pressure-sensitive coating of the diaphragm prepared in this embodiment is shown.
  • the mass ratio of the organic particles and the pressure-sensitive adhesive polymer in the pressure-sensitive coating of the separator prepared in Example 14 is 85:15, wherein the mass ratio of the first organic particles and the second organic particles in the organic particles is 75 :10.
  • the mass ratio of the organic particles and the pressure-sensitive adhesive polymer in the pressure-sensitive coating of the separator prepared in Example 15 is 90:10, wherein the mass ratio of the first organic particles and the second organic particles in the organic particles is 65 :25.
  • the mass ratio of the first organic particle to the pressure-sensitive adhesive polymer in the pressure-sensitive coating of the isolation film prepared in Comparative Example 1 was 91:9.
  • the mass ratio of the first organic particle to the pressure-sensitive adhesive polymer in the pressure-sensitive coating of the isolation film prepared in Comparative Example 2 was 74:26.
  • Example 1 The same as Example 1 except that the pressure sensitive adhesive polymer described in Example 1 was not used. specifically:
  • the release film prepared in Comparative Example 3 only uses the binder polymer without plasticizer, and the mass ratio of the first organic particles and the binder polymer in the pressure-sensitive coating of the prepared release film is 85:15 .
  • the separator prepared in Comparative Example 4 only used plasticizer without binder polymer, and the mass ratio of the first organic particles and the plasticizer in the pressure-sensitive coating of the prepared separator was 85:15.
  • the prepared separator can avoid the bonding between the layers of the separator during winding and storage, and when the separator is used to prepare the battery, the pole piece and the separator can be tightly bonded under normal temperature conditions. Bonding, on the one hand, can avoid the dislocation between the pole piece and the separator, which will cause the cell to be scrapped, affect the performance of the cell, and cause safety risks. On the other hand, it can omit the tunnel furnace and the second process in the traditional cell production process. Composite technology can save production space and production time, reduce energy consumption, significantly increase the production capacity of battery cells, and improve battery shaping performance, safety performance and dynamic performance.
  • the grafting of the plasticizer in the pressure-sensitive adhesive polymer is conducive to reducing the resistance of the separator, and is conducive to improving the cycle performance of the secondary battery prepared by the separator, especially It is more beneficial to obtain a separator with lower resistance and a secondary battery with better cycle performance when the grafting rate of the plasticizer in the pressure-sensitive adhesive polymer is more than 5 wt%. From the results of Comparative Examples 1-2, it can be seen that when more or less pressure-sensitive adhesive polymers are used, the resistance of the separator will be significantly increased, and the cycle performance of the secondary battery will be significantly deteriorated.
  • the particle size of the first organic particles used in Example 16 was about 3 ⁇ m, and the thickness of the pressure-sensitive coating was about 0.8 ⁇ m.
  • the particle size of the first organic particles used in Example 17 is about 5 ⁇ m, and the thickness of the pressure-sensitive coating is about 2 ⁇ m.
  • the particle size of the first organic particles used in Example 18 is about 20 ⁇ m, and the thickness of the pressure-sensitive coating is about 15 ⁇ m.
  • the particle size of the first organic particles used in Example 19 is about 30 ⁇ m, and the thickness of the pressure-sensitive coating is about 20 ⁇ m.
  • the particle size of the first organic particles used in Example 20 is about 36 ⁇ m, and the thickness of the pressure-sensitive coating is about 22 ⁇ m.
  • Example 2 The same as Example 1 except that the particle size of the pressure-sensitive adhesive polymer is different. specifically:
  • the particle size of the pressure-sensitive adhesive polymer used in Example 21 was about 0.3 ⁇ m.
  • the particle size of the pressure-sensitive adhesive polymer used in Example 22 was about 0.5 ⁇ m.
  • the particle size of the pressure-sensitive adhesive polymer used in Example 23 was about 0.8 ⁇ m.
  • the particle size of the pressure-sensitive adhesive polymer used in Example 24 was about 1.0 ⁇ m.
  • the particle size of the pressure-sensitive adhesive polymer used in Example 25 was about 2.0 ⁇ m.
  • the particle size of the pressure-sensitive adhesive polymer used in Example 26 was about 3.0 ⁇ m.
  • the particle size of the pressure-sensitive adhesive polymer used in Example 27 was about 3.5 ⁇ m.
  • the pressure-sensitive adhesive polymer used in Example 28 included the adhesive polymer and the plasticizer in a mass ratio of about 3:1.
  • the pressure-sensitive adhesive polymer used in Example 29 included the adhesive polymer and the plasticizer in a mass ratio of about 4:1.
  • the mass ratio of the adhesive polymer and the plasticizer included in the pressure-sensitive adhesive polymer used in Example 30 was about 11:1.
  • the mass ratio of the adhesive polymer and the plasticizer included in the pressure-sensitive adhesive polymer used in Example 31 was about 19:1.
  • the pressure-sensitive adhesive polymer used in Example 32 included the adhesive polymer and the plasticizer in a mass ratio of about 21:1.
  • the particle size of the second organic particles used in Example 33 is about 0.3 ⁇ m, and the thickness of the pressure-sensitive coating is about 3 ⁇ m.
  • the particle size of the second organic particles used in Example 34 is about 0.5 ⁇ m, and the thickness of the pressure-sensitive coating is about 3 ⁇ m.
  • the particle size of the second organic particles used in Example 35 is about 2 ⁇ m, and the thickness of the pressure-sensitive coating is about 3 ⁇ m.
  • the particle size of the second organic particles used in Example 36 is about 8 ⁇ m, and the thickness of the pressure-sensitive coating is about 4 ⁇ m.
  • the particle size of the second organic particles used in Example 37 is about 10 ⁇ m, and the thickness of the pressure-sensitive coating is about 6 ⁇ m.
  • the particle size of the second organic particles used in Example 38 is about 12 ⁇ m, and the thickness of the pressure-sensitive coating is about 10 ⁇ m.
  • Table 2 The performance of the separator prepared in Examples 16-38 and the cycle performance test results of the secondary battery prepared by the separator
  • Examples 16-20 are changed by changing the particle diameter of the first organic particles
  • Examples 21-27 are changed by changing the particle size of the pressure-sensitive adhesive polymer
  • Examples 28-32 are changed by changing the pressure
  • the mass ratio of the adhesive polymer and the plasticizer included in the sensitive adhesive polymer, and the particle size of the second organic particles in Examples 33-38, the prepared separators all have good high viscosity at room temperature.
  • the adhesion force with the cathode electrode is above 0.56N/m under the action of ⁇ 2MPa, and the adhesion with the electrode under the action of ⁇ 1MPa
  • the relay force is all below 0.23N/m; the secondary batteries prepared using the separators prepared in each embodiment also have good cycle performance, and their capacity retention rates at 25°C and 45°C are all above 70%.
  • the particle size of the first organic particles used is in the range of 5-30 ⁇ m, and/or the particle size of the pressure-sensitive binder polymer is in the range of 0.5-3 ⁇ m, and/or the pressure-sensitive binder polymer
  • the mass ratio of the binder polymer and the plasticizer included in the compound is in the range of (4-19):1, and/or the particle size of the second organic particles is in the range of 0.5-10 ⁇ m, it is more effective to impart isolation
  • the film has good room temperature, high adhesive performance and ion-conducting ability.
  • the pressure-sensitive adhesive polymer used is a pressure-sensitive adhesive polymer with a core-shell structure
  • the rest is the same as that of Example 1.
  • Both the inner core and the outer shell of the pressure-sensitive adhesive polymer of the core-shell structure include the adhesive polymer and the plasticizer, and the inner core and the outer shell of the pressure-sensitive adhesive polymer used in Examples 39-47
  • the mass ratio of the binder polymer to the plasticizer is specifically shown in Table 3 below.
  • Table 3 Mass ratio of adhesive polymer to plasticizer in inner core and outer shell of pressure sensitive adhesive polymer used in Examples 39-47
  • the capacity retention rate is above 89%.
  • the mass ratio of the adhesive polymer and the plasticizer in the core structure of the pressure-sensitive adhesive polymer of the core-shell structure is (3-4):1, the adhesive polymer and the plasticizer in the shell structure Under the condition that the mass ratio of the plasticizer is (7-9):1, it can further effectively endow the separator with high adhesive performance and ion-conducting ability at room temperature, and the resistance of the obtained separator is lower, all below 0.8 ⁇
  • the adhesion force to the cathode electrode is above 1.23N/m
  • the adhesion force to the anode electrode is above 1.1N/m
  • the adhesion force to the electrode is above 0.1 under the action of ⁇ 1MPa.
  • N/m or less; the cycle performance of secondary batteries prepared from these separators is also better, and the capacity retention rates at 25°C and 45°C are both above 91%.
  • the present application is not limited to the above-mentioned embodiments.
  • the above-mentioned embodiments are merely examples, and within the scope of the technical solutions of the present application, embodiments that have substantially the same configuration as the technical idea and exert the same effects are included in the technical scope of the present application.
  • various modifications conceivable by those skilled in the art are added to the embodiments, and other forms constructed by combining some components in the embodiments are also included in the scope of the present application. .

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Abstract

本申请提供了一种隔离膜及其制备方法以及包含该隔离膜的二次电池和用电装置。其中所述隔离膜包括：多孔的隔离膜基体和涂布在所述隔离膜基体的至少一个表面上的压力敏感涂层，该压力敏感涂层包括40-90wt％的第一有机颗粒和10-20wt％的压力敏感型粘合剂聚合物，和任选的0-50wt％的第二有机颗粒；且其中所述压力敏感型粘合剂聚合物包括粘合剂聚合物和增塑剂。本发明提供的隔离膜在常温下具有良好的导离子能力和粘接性能，其在≤1MPa的压力作用下不会发生粘接作用，而在≥2MPa压力作用下会明显发生粘接作用，能够明显改善电化学器件结构稳定性和离子传导。

Description

隔离膜及其制备方法以及包含该隔离膜的二次电池和用电装置 技术领域
本申请涉及电池技术领域，尤其涉及一种隔离膜及其制备方法以及包含该隔离膜的二次电池和用电装置。
背景技术
在电化学器件的电芯制造过程中，极片与隔离膜在转移过程中不可避免的会发生错位，轻则会导致极片互相接触导致干电芯报废，重则极片在满充后打皱严重影响动力学性能，并降低电芯安全性能。因此目前会在隔离膜上涂敷粘接涂层，并且在电化学器件的极片与隔离膜的第一道复合中，通常会在适当的压力作用下进行预压，保证电化学器件的极片与隔离膜在进入下一道工序前有一定粘接，但是由于生产效率的要求，此时的压力及作用时间都不能满足电化学器件的极片与隔离膜达到适当的粘接。
为了解决上述问题，隔离膜上的粘接涂层使用DSC熔点很低的粘接物质时，需要考虑如下难题：隔离膜是软物质，为了方便电化学器件的高效率使用及中途运输，隔离膜通常是以圆型卷筒为载体，在一定力的作用下，在其上卷绕成卷，此时隔离膜层与层紧密接触且有一定的压力作用，如果隔离膜上的DSC熔点过低常常会导致隔膜层与层之间粘接在一起，不利于后续极片与隔离膜的高速复合。
发明内容
本申请是鉴于上述课题而进行的，其目的在于，提供一种压力敏感型隔离膜及其制备方法，以及包含该压力敏感型隔离膜的二次电池。进一步地，本申请的目的还在于提供包含该二次电池的用电装置。
为了实现上述目的，本申请的第一方面提供一种隔离膜，其为压力敏感型隔离膜，该隔离膜可包括：多孔的隔离膜基体和涂布在所述隔离膜基体的至少一个表面上的压力敏感涂层，其包括40-90wt％的第一有机颗粒和10-20wt％的压力敏感型粘合剂聚合物，和任选的0-50wt％的第二有机颗粒；其中所述压力敏感型粘合剂聚合物可包括粘合剂聚合物和增塑剂。该隔离膜具有良好的压敏特性，其在≤1MPa作用下粘接力在0.23N/m以下，尤其是在0.1N/m以下，因此可以避免隔离膜在收卷及存储过程中的层与层之间的粘接， 其在≥2MPa压力作用下能够与极片发生明显的粘接作用，因此在使用该隔离膜制备电芯时，在常温条件，适当压力下即可将极片与隔离膜紧密贴合。
在一些实施方式中，所述压力敏感型粘合剂聚合物中包括的粘合剂聚合物和增塑剂的质量比可为(4-19):1，可选为(4-11):1。压力敏感型粘合剂聚合物中包括的增塑剂的相对含量在上述范围内，能够保证极片与隔离膜在一定压力作用下获得较大的粘接力，并且不会导致隔离膜的电阻增加，二次电池的循环性能下降。
在一些实施方式中，所述压力敏感型粘合剂聚合物可为核壳结构，在所述核壳结构的内核和外壳中均可包括粘合剂聚合物和增塑剂，其中在内核结构中所述粘合剂聚合物和增塑剂的质量比可为(2-5):1，可选为(3-4):1，在外壳结构中所述粘合剂聚合物和增塑剂的质量比可为(6-10):1，可选为(7-9):1。核壳结构的内核与外壳都主要是由粘合剂聚合物和增塑剂组成，可以进一步提高压力敏感型粘合剂聚合物的压敏性能，从而进一步提升隔离膜的动力学性能。
在一些实施方式中，一部分所述增塑剂接枝在所述粘合剂聚合物上。可选地，基于所述增塑剂的重量，至少5wt％的增塑剂接枝在所述粘合剂聚合物上。当一部分所述增塑剂接枝在所述粘合剂聚合物上时，能够防止增塑剂在循环过程中大量迁移到电解液中，消耗电解液的多种功能添加剂，增加隔离膜电阻值，影响电芯的动力学性能。
在一些实施方式中，所述压力敏感型粘合剂聚合物的平均粒径可为0.5-3.0μm，可选为0.8-2.0μm。合适粒径的压力敏感型粘合剂聚合物有助于其在第一有机颗粒或者第一有机颗粒和第二有机颗粒两者上均匀分布，有助于在一定压力下其内核和外壳与极片粘接的发挥，及对隔离膜阻值的有效改进。
在一些实施方式中，所述压力敏感型粘合剂聚合物的DSC熔点可为-50℃-100℃，可选为-45℃-60℃；当所述压力敏感型粘合剂聚合物的DSC熔点在上述范围内，能够保证在常温下的粘结力，避免在1MPa下粘接力过大造成隔离膜收卷粘接；同时避免在常温2MPa下粘接力过小造成隔离膜与极片粘接较弱，不利于电芯整形。
在一些实施方式中，所述粘合剂聚合物可包括由包含以下的第一单体中的至少一种、第二单体中的至少一种、第三单体中的至少一种和反应型分散剂中的至少一种的反应单体混合物共聚形成的共聚物：
第一单体：其熔点一般高于80℃，可包括丙烯酸、甲基丙烯酸、甲基丙烯酸甲酯、甲基丙烯酸叔丁酯、甲基丙烯酸异冰片酯、羟甲基丙烯酰胺、丙烯酰胺、苯乙烯、丙烯腈；
第二单体：其熔点一般不超过80℃，可包括丙烯酸C4-C22烷基酯、丙烯酸异丁酯、丙烯酸异辛酯、丙烯酸叔丁酯、丙烯酸-2-乙基己酯(异辛酯)、丙烯酸环己酯、甲基丙烯酸乙酯、甲基丙烯酸异丁酯、甲基丙烯酸-2-乙基己酯、甲基丙烯酸正己酯、甲基丙烯酸环己酯、甲基丙烯酸苄酯、丙烯酸-2-羟乙酯、丙烯酸-2-羟丙酯、甲基丙烯酸亚乙基脲乙酯、甲基丙烯酸双环戊烯乙氧基酯、甲基丙烯酸四氢呋喃酯、甲基丙烯酸三氟乙酯、甲基丙烯酸二甲氨基乙酯、甲基丙烯酸二乙氨基乙酯、甲基丙烯酸亚乙基脲乙酯、甲基丙烯酸丙烯酯、甲基丙烯酸双环戊烯乙氧基酯、甲基丙烯酸四氢呋喃酯、甲基丙烯酸三氟乙酯；
第三单体：其为交联单体，含有羟基、氨基、双键中的至少一个，可包括甲基丙烯酸-2-羟乙酯、甲基丙烯酸-2-羟丙酯、丙烯酸缩水甘油酯、甲基丙烯酸缩水甘油酯、甲基丙烯酸二甲氨基乙酯、甲基丙烯酸二乙氨基乙酯、乙烯基三甲氧基硅烷、乙烯基三乙氧基硅烷、乙烯基三异丙氧基硅烷、γ-甲基丙烯酰氧基丙基三甲氧基硅烷、N-羟甲基丙烯酰胺、N-丁氧甲基(甲基)丙烯酰胺、二丙酮丙烯酰胺(DAAM)、甲基丙烯酸乙酰乙酸乙酯(AAEM)、二乙烯基苯、环氧值在0.35-0.50的环氧树脂、二乙烯苯；
反应型分散剂：其可包括聚乙烯醇、聚丙烯醇、聚丙烯乙二醇、聚乙二醇、聚乙烯酸醇。可选地，这些反应型分散剂的醇解度≥85％，平均聚合度400-2000；优选醇解度≥88％，平均聚合度500-1600。
当所述粘合剂聚合物包括由包含上述的第一单体中的至少一种、第二单体中的至少一种、第三单体中的至少一种和反应型分散剂中的至少一种的反应单体混合物共聚形成的共聚物时，能够确保所述粘合剂聚合物合适的溶胀和粘接，保证压力敏感型粘结剂聚合物有适合的溶胀、压敏性和粘接性能，同时有合适的弹性模量，保证电芯的整形效果、动力学性能和安全性能。
在一些实施方式中，所述增塑剂可选自以下中的一种或几种：甘油C4-C10烷基二醚或者单醚、甘油C4-C10羧酸单酯或者二酯、丙二醇C4-C10烷基单醚、甘油。
在一些实施方式中，所述压力敏感涂层的平均厚度可为2-20μm，可选为 2-15μm。
在一些实施方式中，所述第一有机颗粒的平均粒径可为5-30μm，可选为5-20μm。由此第一有机颗粒具有较大的平均粒径，一方面可以增加极片和隔离膜的有效接触面积，进而大幅提升极片和隔离膜的粘接作用；另一方面可以避免这些有机颗粒渗入在隔离膜基体上形成的孔中，同时大尺寸存在相对较大的空隙，因此还可以解决隔离膜的透气性差的问题，并降低了小颗粒堵住隔离膜孔洞的可能性，避免造成内阻增加的风险。另外，由于第一有机颗粒具有较大的平均粒径，有一定的压缩能力，当其存在于电芯拐角处时可以有效提供拐角的应力释放空间。
在一些实施方式中，所述第一有机颗粒的DSC熔点可为-50℃-200℃，可选为-40℃-160℃，所述第一有机颗粒的DSC熔点在上述范围内，能够耐受电解液溶胀，一方面，不会消耗过多电解液，残留单体不易被电解液泡出堵住隔膜，从而影响电芯的动力学性能。另一方面，不会导致隔离膜与极片的粘接大幅下降，并且极片不易被第一有机颗粒压损导致安全性能下降。
在一些实施方式中，所述第一有机颗粒的重均分子量可为300×10 3g/mol-800×10 3g/mol，可选为400×10 3g/mol-650×10 3g/mol。所述第一有机颗粒的重均分子量在上述范围内，可以保证第一有机颗粒有比较合适的溶胀以及与极片有比较合适的粘接力。在一些实施方式中，所述第一有机颗粒可为包含一种或几种选自以下的基团的一种或几种聚合物：卤素、苯基、环氧基、氰基、酯基和酰胺基。
在一些实施方式中，所述第一有机颗粒可为选自以下的至少一种：含氟烯基单体单元的均聚物或共聚物，烯烃基单体单元的均聚物或共聚物，不饱和腈类单体单元的均聚物或共聚物，环氧烷类单体单元的均聚物或共聚物，单糖类单体单元的二聚物、均聚物或共聚物，以及上述各均聚物或共聚物的改性化合物。
在一些实施方式中，所述含氟烯基单体单元可选自二氟乙烯、偏二氟乙烯、三氟乙烯、三氟氯乙烯、四氟乙烯、六氟丙烯或其衍生物中的一种或几种。
在一些实施方式中，所述烯烃基单体单元可选自乙烯、丙烯、丁二烯、异戊二烯、苯乙烯或其衍生物中的一种或几种。
在一些实施方式中，所述不饱和腈类单体单元可选自丙烯腈、甲基丙烯腈或其衍生物中的一种或几种。
在一些实施方式中，所述环氧烷类单体单元可选自环氧乙烷、环氧丙烷或其衍生物中的一种或几种。
在一些实施方式中，所述单糖类单体单元可选自葡萄糖或其衍生物。
在一些实施方式中，所述第一有机颗粒可为选自以下的至少一种：聚全氟乙烯、聚偏二氟乙烯、聚偏二氟乙烯-共-六氟丙烯、聚偏二氟乙烯-共-三氯乙烯、聚苯乙烯-共-甲基丙烯酸甲酯、聚苯乙烯-共-丙烯酸丁酯、聚甲基丙烯酸甲酯、聚丙烯腈、聚乙酸乙烯酯、聚乙烯-共-乙酸乙烯酯、聚酰亚胺、聚环氧乙烷、乙酸纤维素、乙酸丁酸纤维素、乙酸丙酸纤维素、氰基乙基普鲁兰、氰基乙基聚乙烯醇、氰基乙基纤维素和氰基乙基蔗糖。
在一些实施方式中，所述第一有机颗粒可为选自以下中的至少一种：聚偏二氟乙烯-共-六氟丙烯、聚苯乙烯-共-丙烯酸丁酯、聚全氟乙烯、聚偏二氟乙烯、聚偏二氟乙烯-共-三氯乙烯。
第一有机颗粒选自上述物质时，其具有合适溶胀，并且与极片有合适的粘接。能够实现与压力敏感型粘结剂聚合物有适当的结合力，同时使在其上的压力敏感型粘结剂聚合物分散均匀，保证了粘接和动力学性能。
在一些实施方式中，所述第一有机颗粒和第二有机颗粒的质量比可为(1-4):1，可选为(1.5-2.5):1。当第一有机颗粒和第二有机颗粒的质量比在上述范围内时，可以有效提高电解液的浸润性及分布均匀性，进一步改善电池的高温存储性能。其中第一有机颗粒的平均粒径相对较大，通常被设计成二次颗粒，而第二有机颗粒的平均粒径相对较小，通常被设计成一次颗粒，在第一有机颗粒和第二有机颗粒的共同作用下，可以在增强隔离膜与电极极片之间粘结力的同时，进一步有效保证隔离膜具有适度且不均匀的孔隙结构。
在一些实施方式中，所述第二有机颗粒的平均粒径可为0.5-10μm，可选为2-8μm。
在一些实施方式中，所述第二有机颗粒的DSC熔点可为-30-100℃，可选为-30-70℃，所述第二有机颗粒的DSC熔点在上述范围内，能够耐受电解液溶胀，一方面，不会消耗过多电解液，残留单体不易被电解液泡出堵住隔膜，从而影响电芯的动力学性能。另一方面，不会导致隔离膜与极片的粘接大幅下降，并且极片不易被第二有机颗粒压损导致安全性能下降。
在一些实施方式中，所述第二有机颗粒的重均分子量可为10×10 3g/mol-100×10 3g/mol，可选为20×10 3g/mol-80×10 3g/mol。所述第二有机颗 粒的重均分子量在上述范围内，可以保证第二有机颗粒有比较合适的溶胀以及与极片有比较合适的粘接力。
在一些实施方式中，所述第二有机颗粒为包含一种或几种选自以下的基团的一种或几种聚合物：苯基、环氧基、氰基、酯基、羟基、羧基、磺酰酯基和吡咯烷酮基。
在一些实施方式中，所述第二有机颗粒可为选自以下的至少一种：丙烯酸酯类单体单元的均聚物或共聚物，丙烯酸类单体单元的均聚物或共聚物，不饱和腈类单体单元的均聚物或共聚物，烯类单体单元的均聚物或共聚物，苯乙烯类单体单元的均聚物或共聚物，环氧类单体单元的均聚物或共聚物，聚氨酯类化合物，橡胶类化合物，单糖类单体单元的二聚物、均聚物或共聚物，以及上述各均聚物或共聚物的改性化合物。
在一些实施方式中，所述丙烯酸酯类单体单元可选自丙烯酸甲酯、丙烯酸乙酯、丙烯酸丙酯、丙烯酸丁酯、甲基丙烯酸甲酯、甲基丙烯酸丁酯、甲基丙烯酸异辛酯或其衍生物中的一种或几种。
在一些实施方式中，所述丙烯酸类单体单元可以选自丙烯酸、甲基丙烯酸或其衍生物中的一种或几种。
在一些实施方式中，所述不饱和腈类单体单元可选自丙烯腈、甲基丙烯腈或其衍生物中的一种或几种。
在一些实施方式中，所述烯类单体单元可以选自乙烯、乙酸乙烯酯、丁二烯或其衍生物中的一种或几种。
在一些实施方式中，所述苯乙烯类单体单元可选自苯乙烯、甲基苯乙烯或其衍生物中的一种或几种。
在一些实施方式中，所述环氧类单体单元可选自环氧乙烷、环氧丙烷或其衍生物中的一种或几种。
在一些实施方式中，单糖类单体单元可选自葡萄糖或其衍生物。
在一些实施方式中，所述第二有机颗粒为选自以下的至少一种：聚甲基丙烯酸甲酯、聚丙烯腈、聚乙烯吡咯烷酮、聚乙酸乙烯酯、聚乙烯-共-乙酸乙烯酯、聚苯乙烯-共-甲基丙烯酸甲酯、聚苯乙烯-共-丙烯酸丁酯、聚环氧乙烷、乙酸纤维素、乙酸丁酸纤维素、乙酸丙酸纤维素、氰乙基普鲁兰多糖、氰乙基聚乙烯醇、氰乙基纤维素、氰乙基蔗糖、普鲁兰多糖、羧甲基纤维素、丙 烯腈-苯乙烯-丁二烯共聚物、苯乙烯-丙烯酸丁酯-丙烯酸异辛酯共聚物和聚酰亚胺。
第二有机颗粒选自上述物质时，其具有合适溶胀，并且与极片有合适的粘接。能够实现与压力敏感型粘结剂聚合物有适当的结合力，同时使在其上的压力敏感型粘结剂聚合物分散均匀，保证了粘接和动力学性能。
在一些实施方式中，所述隔离膜基体的孔隙率可为10-95％，孔径可为20-60nm，厚度可为3-12μm，可选为5-9μm。当隔离膜基体的孔隙率在上述范围内时，可实现二次电池动力学和安全性能的平衡；当隔离膜基体的厚度在上述范围内时，可实现二次电池能量密度和安全性能的平衡。
在一些实施方式中，所述隔离膜基体包括选自以下的一种或几种的膜或非织造物：聚乙烯、聚丙烯、聚对苯二甲酸乙二醇酯、聚对苯二甲酸丁二醇酯、聚酯、聚缩醛、聚酰胺、聚碳酸酯、聚酰亚胺、聚醚醚酮、聚芳基醚酮、聚醚酰亚胺、聚酰胺酰亚胺、聚苯并咪唑、聚醚砜、聚苯醚、环烯烃共聚物、聚苯硫醚和聚乙烯萘。
本申请的第二方面提供了本申请的第一方面的隔离膜的制备方法，其包括以下步骤：
S1)将第一有机颗粒和分散剂加入溶剂中以形成第一聚合物溶液；
S2)将压力敏感型粘合剂聚合物加入步骤S1)得到的第一聚合物溶液中，混合以形成第二聚合物溶液；
S3)任选地，在步骤S2)得到的第二聚合物溶液中加入第二有机颗粒，混合以形成第三聚合物溶液；和
S4)将步骤S2)得到的第二聚合物溶液或步骤S3)得到的第三聚合物溶液涂布到多孔的隔离膜基体的至少一个表面上，干燥后得到隔离膜；
其中所述隔离膜包括在所述隔离膜基体的至少一个表面上形成的压力敏感涂层，其包括40-90wt％的第一有机颗粒和10-20wt％的压力敏感型粘合剂聚合物，和任选的0-50wt％的第二有机颗粒；其中所述压力敏感型粘合剂聚合物包括粘合剂聚合物和增塑剂。
本申请的第三方面提供一种二次电池，其包括正极片、负极片、间隔于正极片和负极片之间的隔离膜，以及电解液，其中所述隔离膜为本申请第一方面提供的隔离膜或本申请第二方面提供的方法制备的隔离膜。
本申请的第四方面提供一种用电装置，其包括选自本申请的第三方面提供的二次电池。
有益效果
本申请所提供的压力敏感型隔离膜包括多孔的隔离膜基体和涂布在所述隔离膜基体的至少一个表面上的压力敏感涂层，该涂层包括40-90wt％的第一有机颗粒和10-20wt％的压力敏感型粘合剂聚合物，和任选的0-50wt％的第二有机颗粒，且其中所述压力敏感型粘合剂聚合物可包括粘合剂聚合物和增塑剂，能够使得该隔离膜在常温条件下具有良好的导离子能力和粘接性能，其常温条件下的电阻为1.32Ω以下，尤其在1.1Ω以下，并且在≤1MPa的压力作用下不会发生粘接作用，在≥2MPa压力作用下能够与极片发生明显的粘接作用。因此，一方面，在常温下即可将电化学器件的极片与隔离膜紧密贴合，可以避免电化学器件极片与隔离膜在生产转移过程中发生错位，进而保证电化学器件的结构稳定性，并且可以保证制备的电芯的群裕度及入壳优率，从而提升电芯整形性能、安全性能和动力学性能，而且还可以省略传统电芯生产工艺中的隧道炉及第二道复合工序，因此可以节约生产空间和生产时间，并降低能耗，从而提升产能。另一方面，本发明提供的隔离膜在收卷及存储过程中不会粘接在一起，方便后续在电芯制备中使用。
附图说明
为了更清楚地说明本申请实施例的技术方案，下面将对本申请实施例中所需要使用的附图作简单地介绍，显而易见地，下面所描述的附图仅仅是本申请的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据附图获得其他的附图。
图1是本申请实施例提供的一种二次电池的示意图。
图2是本申请实施例提供的一种电池模块的示意图。
图3是本申请实施例提供的一种电池包的示意图。
图4是图3的分解图。
图5是本申请实施例提供的一种用电装置的示意图。
图6示出了本申请实施例13制备的隔离膜的压力敏感涂层的形貌照片。
其中，附图标记说明如下：
1、电池包；
2、上箱体；
3、下箱体；
4、电池模块；
5、二次电池。
具体实施方式
以下，适当地参照附图详细说明具体公开了本申请的隔离膜及其制备方法、二次电池和用电装置的实施方式。但是会有省略不必要的详细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，附图及以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-5。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有技术特征以及可选技术特征可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，所述方法包括步骤(a)和(b)，表示所述方法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，所述提到所述方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到所述方法，例如，所述方法可以包括步骤(a)、(b)和(c)，也可包括步骤(a)、(c)和(b)，也可 以包括步骤(c)、(a)和(b)等。
如果没有特别的说明，本申请所提到的“包括”和“包含”表示开放式，也可以是封闭式。例如，所述“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分，也可以仅包括或包含列出的组分。
如果没有特别的说明，在本申请中，术语“或”是包括性的。举例来说，短语“A或B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。
在本文的描述中，需要说明的是，除非另有说明，“以上”、“以下”为包含本数，“一种或几种”中“几种”的含义是两种或两种以上。
【二次电池】
二次电池因其具有高能量密度、便于携带、无记忆效应、环境友好等优势，成为用电装置的电源优选项。二次电池中隔离膜是保证电池安全性能的重要部分，然而，一方面，在电化学器件的电芯制造过程中，极片与隔离膜在生产转移过程中不可避免的会发生错位，轻则会导致极片互相接触导致干电芯报废，重则极片在满充后打皱严重影响动力学性能，并降低电芯安全性能。因此目前会在隔离膜上涂敷粘接涂层，并且在电化学器件的极片与隔离膜的第一道复合中，通常会在适当的压力作用下进行预压，保证电化学器件的极片与隔离膜在进入下一道工序前有一定粘接，但是由于生产效率的要求，且考虑到大压力会使主材结构劣化，因此，此时的压力及作用时间都不能满足电化学器件的极片与隔离膜达到适当的粘接效果，并且为了保证电芯群裕度及入壳优率，电化学器件的极片与隔离膜常常还需要在80-100℃的隧道炉中烘烤≥700s后施加压力，让电化学器件的极片与隔离膜紧密贴合。这样的工艺需要占用大量的生产空间及生产时间，造成产能提升困难。另一方面，为了解决上述问题，隔离膜上的粘接涂层使用软化点很低的粘接物质，需要考虑如下难题：隔离膜是软物质，为了方便电化学器件的高效率使用及中途运输，隔离膜通常是以圆型卷筒为载体，在一定力的作用下，在其上卷绕成卷，此时隔离膜层与层紧密接触且有一定的压力作用，如果隔离膜上的粘接物质软化点过低常常会导致隔离膜层与层之间粘接在一起，不利于后续极片与隔离膜的高速复合。
本申请提供一种二次电池，该二次电池具有良好的安全性能和动力学性 能。
通常情况下，二次电池包括正极极片、负极极片、电解质和隔离膜。在电池充电过程中，活性离子在正极极片和负极极片之间往返嵌入和脱出。电解质在正极极片和负极极片之间起到传导离子的作用。隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使离子通过。
[正极极片]
正极极片包括正极集流体以及设置在正极集流体至少一个表面上且包括正极活性材料的正极膜片。作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极膜片层设置在正极集流体相对的两个表面中的任意一者或两者上。
正极集流体可以采用具有良好导电性及机械强度的材质。在一些实施例中，正极集流体可以采用为铝箔。
本申请对正极活性材料的具体种类不做具体限制，可以采用本领域已知的能够用于二次电池正极的材料，本领域技术人员可以根据实际需求进行选择。
在一些实施例中，本发明提供的二次电池可以为锂离子二次电池。正极活性材料可包含本领域公知的用于电池的正极活性材料。例如，正极活性材料可以包含以下材料中的至少一种：橄榄石结构的含锂磷酸盐、锂过渡金属氧化物及其各自的改性化合物。但本申请并不限定于这些材料，还可以使用其他可被用作电池正极活性材料的传统材料。其中，锂过渡金属氧化物的示例可包括但不限于锂钴氧化物(如LiCoO 2)、锂镍氧化物(如LiNiO 2)、锂锰氧化物(如LiMnO 2、LiMn 2O 4)、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物(如LiNi 1/3Co 1/3Mn 1/3O 2(也可以简称为NCM 333)、LiNi 0.5Co 0.2Mn 0.3O 2(也可以简称为NCM 523)、LiNi 0.5Co 0.25Mn 0.25O 2(也可以简称为NCM 211)、LiNi 0.6Co 0.2Mn 0.2O 2(也可以简称为NCM 622)、LiNi 0.8Co 0.1Mn 0.1O 2(也可以简称为NCM 811)、锂镍钴铝氧化物(如LiNi 0.85Co 0.15Al 0.05O 2)及其改性化合物等中的至少一种。橄榄石结构的含锂磷酸盐的示例可包括但不限于磷酸铁锂(如LiFePO 4(也可以简称为LFP))、磷酸铁锂与碳的复合材料、磷酸锰锂(如LiMnPO 4)、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料中的至少一种。
在一些实施例中，正极膜片中还可选地包括粘接剂。对粘接剂的种类不 做具体限制，本领域技术人员可以根据实际需求进行选择。作为示例，用于正极膜片的粘接剂可包括聚偏氟乙烯(PVDF)和聚四氟乙烯(PTFE)中的一种或几种。
在一些实施例中，正极膜片中还可选地包括导电剂。对导电剂的种类不做具体限制，本领域技术人员可以根据实际需求进行选择。作为示例，用于正极膜片的导电剂可包括石墨、超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的一种或几种。
在一些实施例中，采用正极活性材料制备正极极片的步骤可以包括：将正极活性材料、粘结剂、以及可选的导电剂分散于溶剂中，溶剂可以是N-甲基吡咯烷酮，在真空搅拌机的作用下搅拌均匀获得正极浆料；将正极浆料均匀涂覆于正极集流体铝箔上，在室温晒干后转移至烘箱中干燥，然后进行冷压、分切得到正极极片。
[负极极片]
负极极片包括负极集流体以及设置在负极集流体至少一个表面上的负极膜片。作为示例，负极集流体具有在其自身厚度方向相对的两个表面，负极膜片层设置在负极集流体相对的两个表面中的任意一者或两者上。
负极集流体可以采用具有良好导电性及机械强度的材质，起导电和集流的作用。在一些实施例中，负极集流体可以采用铜箔。
负极膜片包括负极活性材料，采用负极活性材料制备负极极片的步骤可以包括：将负极活性材料、粘接剂、以及可选的增稠剂和导电剂分散于溶剂中，溶剂可以是去离子水，形成均匀的负极浆料；将负极浆料涂覆在负极集流体上，经烘干、冷压等工序后，得到负极极片。
在一些实施例中，本申请对负极活性材料的具体种类不做具体限制，负极极片可选的包括可用于二次电池负极的负极活性材料。负极活性材料可以是石墨材料(如人造石墨、天然石墨)、中间相微碳球(简写为MCMB)、硬碳、软碳、硅基材料、锡基材料中的一种或几种。
在一些实施例中，粘接剂可以选自聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、丁苯橡胶(SBR)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的一种或几种。
在一些实施例中，增稠剂可以是羧甲基纤维素钠(CMC-Na)。
在一些实施例中，用于负极极片的导电剂可以选自石墨、超导碳、乙炔 黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯和碳纳米纤维中的一种或几种。
[电解质]
电解质在正极极片和负极极片之间起到传导离子的作用。本申请对电解质的种类没有具体的限制，可根据需求进行选择。例如，电解质可以是液态的、凝胶态的或全固态的。
在一些实施例中，电解质采用电解液。电解液包括电解质盐和溶剂。
在一些实施例中，电解质盐可选自LiPF 6(六氟磷酸锂)、LiBF 4(四氟硼酸锂)、LiClO 4(高氯酸锂)、LiAsF 6(六氟砷酸锂)、LiFSI(双氟磺酰亚胺锂)、LiTFSI(双三氟甲磺酰亚胺锂)、LiTFS(三氟甲磺酸锂)、LiDFOB(二氟草酸硼酸锂)、LiBOB(二草酸硼酸锂)、LiPO 2F 2(二氟磷酸锂)、LiDFOP(二氟二草酸磷酸锂)及LiTFOP(四氟草酸磷酸锂)中的一种或几种。
在一些实施例中，溶剂可选自碳酸亚乙酯(EC)、碳酸亚丙酯(PC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸亚丁酯(BC)、氟代碳酸亚乙酯(FEC)、甲酸甲酯(MF)、乙酸甲酯(MA)、乙酸乙酯(EA)、乙酸丙酯(PA)、丙酸甲酯(MP)、丙酸乙酯(EP)、丙酸丙酯(PP)、丁酸甲酯(MB)、丁酸乙酯(EB)、1,4-丁内酯(GBL)、环丁砜(SF)、二甲砜(MSM)、甲乙砜(EMS)及二乙砜(ESE)中的一种或几种。
在一些实施例中，电解液中还可选地包括添加剂。例如添加剂可以包括负极成膜添加剂，也可以包括正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温性能的添加剂、改善电池低温性能的添加剂等。
[隔离膜]
采用电解液的二次电池、以及一些采用半固态电解质的二次电池中，还包括隔离膜。隔离膜设置在正极极片和负极极片之间起到隔离的作用。
在本申请提供的二次电池中，隔离膜可以使用本申请提供的压力敏感型隔离膜，该隔离膜在常温条件下具有良好的导离子能力和粘接性能，其在常温条件下的电阻为1.32Ω以下，尤其在1.1Ω以下，在≤1MPa作用下的粘接力为0.23N/m以下，尤其是在0.1N/m以下，在≥2MPa作用下与极片的粘接力为0.34N/m以上，尤其是在0.50N/m以上，更尤其在0.60N/m以上。以下将详细描述该隔离膜及其制备方法。
隔离膜
本申请提供的隔离膜可包括：多孔的隔离膜基体和涂布在所述隔离膜基体的至少一个表面上的压力敏感涂层，其包括40-90wt％的第一有机颗粒和10-20wt％的压力敏感型粘合剂聚合物，和任选的0-50wt％的第二有机颗粒；其中所述压力敏感型粘合剂聚合物可包括粘合剂聚合物和增塑剂。
本发明人通过大量的研究注意到，当在多孔的隔离膜基体的至少一个表面上涂布包括40-90wt％的第一有机颗粒和10-20wt％的压力敏感型粘合剂聚合物，和任选的0-50wt％的第二有机颗粒的压力敏感涂层来制备隔离膜时，可以获得在常温条件下具有良好的导离子能力和粘接性能的压力敏感型隔离膜，其中压力敏感型粘合剂聚合物可包括粘合剂聚合物和增塑剂，两者共同作用可使得压力敏感型粘合剂聚合物具有良好的压敏特性，进一步使得隔离膜具有良好的压敏特性，使其在≤1MPa作用下粘接力在0.23N/m以下，尤其是在0.1N/m以下，因此可以避免隔离膜在收卷及存储过程中的层与层之间的粘接，以及使其在≥2MPa压力作用下能够与极片发生明显的粘接作用，因此在使用该隔离膜制备电芯时，在常温条件、适当压力下即可将极片与隔离膜紧密贴合，一方面可以避免极片和隔离膜之间发生错位而造成电芯报废、影响电芯性能和产生安全风险，另一方面可以省略传统的电芯生产工艺中的隧道炉及第二道复合工艺，进而可以节约生产空间和生产时间，并降低能耗，明显提升电芯生产的产能，同时可以提升电芯整形性能、安全性能和动力学性能，进而提升包含该电芯的二次电池，以及包含该二次电池的用电装置的安全性能和动力学性能。
在一些实施例中，所述压力敏感型粘合剂聚合物中包括的粘合剂聚合物和增塑剂的质量比可为(4-19):1，可选为(4-11):1。压力敏感型粘合剂聚合物中包括的增塑剂的相对含量在上述范围内，能够保证极片与隔离膜获得较大的粘接力，并且不会导致隔离膜的电阻增加，二次电池的循环性能下降。
其中，增塑剂含量可以采用日本岛津株式会社的仪器型号STA449F3热重分析仪。作为具体的示例，测试方法如下：取约10mg压力敏感型粘合剂聚合物固体，原始质量记为M0，升温至200℃，质量记为M1，增塑剂的含量即为M1-M0，粘合剂聚合物的含量为M0-(M1-M0)。测试条件设置为：温度范围-100-400℃，氮气氛围，10℃/min。
在一些实施例中，所述压力敏感型粘合剂聚合物可为核壳结构，在该核壳结构的内核和外壳中均可包括粘合剂聚合物和增塑剂，其中在内核结构中 所述粘合剂聚合物和增塑剂的质量比可为(2-5):1，可选为(3-4):1，在外壳结构中所述粘合剂聚合物和增塑剂的质量比可为(6-10):1，可选为(7-9):1。核壳结构的内核与外壳都是由粘合剂聚合物和增塑剂组成，可以进一步提高压力敏感型粘合剂聚合物的压敏性能，从而进一步提升隔离膜的动力学性能。另一方面，在压力敏感型粘合剂聚合物中包含增塑剂，在一定的压力作用下(例如1-2MPa下)，增塑剂可以快速迁移到粘合剂聚合物和隔离膜主材料之间，增塑粘合剂聚合物，使其分子链舒展，与负极极片中的例如SBR类粘接剂、CMC的增稠剂、正极极片中的粘接剂例如PVDF发生分子间氢键作用并提升界面润湿，增强两个界面间的铆合作用。在≥2MPa作用下核结构被压碎，核中的增塑剂释放，可以进一步提升以上作用。
在一些实施例中，一部分所述增塑剂接枝在所述粘合剂聚合物上。可选地，基于所述增塑剂的重量，至少5wt％的增塑剂接枝在所述粘合剂聚合物上。当一部分所述增塑剂接枝在所述粘合剂聚合物上时，能够防止增塑剂在循环过程中大量迁移到电解液中，消耗电解液的多种功能添加剂，增加隔离膜电阻值，影响电芯的动力学性能。其中当至少5wt％的增塑剂接枝在粘合剂聚合物主链时，隔离膜和极片可以形成“藕断丝连”的作用，进而可以提升常温粘合的持久性，降低反弹，同时可进一步保证不会有过多增塑剂在循环过程迁移到电解液，影响电芯性能。其中接枝率可以通过红外测试方法检测，具体为：对粘合剂聚合物、增塑剂、压力敏感型粘合剂聚合物各测试获得其傅里叶红外谱图，在压力敏感型粘合剂聚合物1500-1700cm -1的位置出现一个有别于粘合剂聚合物和单独的增塑剂的峰，该峰即表示接枝的增塑剂，峰下面积表示接枝的增塑剂的量，由此可计算获得增塑剂的接枝率。
在一些实施例中，所述压力敏感型粘合剂聚合物的平均粒径可为0.5-3.0μm，可选为0.8-2.0μm。合适平均粒径的压力敏感型粘合剂聚合物有助于其在第一或者第二有机颗粒上均匀分布，有助于在一定压力下其内核和外壳与极片粘接的发挥，及对隔离膜阻值的有效改进。
其中，压力敏感型粘合剂聚合物的平均粒径可以参照标准GB/T 19077.1-2016，使用激光粒度分析仪(如Malvern Master Size 3000)测定。
在一些实施例中，所述压力敏感型粘合剂聚合物的DSC熔点可为-50℃-100℃，可选为-45℃-60℃；当所述压力敏感型粘合剂聚合物的DSC熔点在上述范围内，能够保证在常温下的粘结力，避免在1MPa下粘接力过大造成 隔离膜收卷粘接；同时避免在常温2MPa下粘接力过小造成隔离膜与极片粘接较弱，不利于电芯整形。
在一些实施例中，所述粘合剂聚合物包括由包含以下的第一单体中的至少一种、第二单体中的至少一种、第三单体中的至少一种和反应型分散剂中的至少一种的反应单体混合物共聚形成的共聚物：
第一单体：其熔点一般高于80℃，可包括丙烯酸、甲基丙烯酸、甲基丙烯酸甲酯、甲基丙烯酸叔丁酯、甲基丙烯酸异冰片酯、羟甲基丙烯酰胺、丙烯酰胺、苯乙烯、丙烯腈；
第二单体：其熔点一般不超过80℃，可包括丙烯酸C4-C22烷基酯、丙烯酸异丁酯、丙烯酸异辛酯、丙烯酸叔丁酯、丙烯酸-2-乙基己酯(异辛酯)、丙烯酸环己酯、甲基丙烯酸乙酯、甲基丙烯酸异丁酯、甲基丙烯酸-2-乙基己酯、甲基丙烯酸正己酯、甲基丙烯酸环己酯、甲基丙烯酸苄酯、丙烯酸-2-羟乙酯、丙烯酸-2-羟丙酯、甲基丙烯酸亚乙基脲乙酯、甲基丙烯酸双环戊烯乙氧基酯、甲基丙烯酸四氢呋喃酯、甲基丙烯酸三氟乙酯、甲基丙烯酸二甲氨基乙酯、甲基丙烯酸二乙氨基乙酯、甲基丙烯酸亚乙基脲乙酯、甲基丙烯酸丙烯酯、甲基丙烯酸双环戊烯乙氧基酯、甲基丙烯酸四氢呋喃酯、甲基丙烯酸三氟乙酯；
第三单体：其为交联单体，含有羟基、氨基、双键中的至少一个，可包括甲基丙烯酸-2-羟乙酯、甲基丙烯酸-2-羟丙酯、丙烯酸缩水甘油酯、甲基丙烯酸缩水甘油酯、甲基丙烯酸二甲氨基乙酯、甲基丙烯酸二乙氨基乙酯、乙烯基三甲氧基硅烷、乙烯基三乙氧基硅烷、乙烯基三异丙氧基硅烷、γ-甲基丙烯酰氧基丙基三甲氧基硅烷、N-羟甲基丙烯酰胺、N-丁氧甲基(甲基)丙烯酰胺、二丙酮丙烯酰胺(DAAM)、甲基丙烯酸乙酰乙酸乙酯(AAEM)、二乙烯基苯、环氧值在0.35-0.50的环氧树脂、二乙烯苯；
反应型分散剂：其在合成压力敏感型粘合剂聚合物时，与上述的第一单体、第二单体和第三单体边共聚边起到分散的作用，可包括聚乙烯醇、聚丙烯醇、聚丙烯乙二醇、聚乙二醇、聚乙烯酸醇。可选地，这些反应型分散剂的醇解度≥85％，平均聚合度400-2000；优选醇解度≥88％，平均聚合度500-1600。
当所述粘合剂聚合物包括由包含上述的第一单体中的至少一种、第二单体中的至少一种、第三单体中的至少一种和反应型分散剂中的至少一种的反 应单体混合物共聚形成的共聚物时，能够确保所述粘合剂聚合物合适的溶胀和粘接，保证压力敏感型粘结剂聚合物有适合的溶胀、压敏性和粘接性能，同时有合适的弹性模量，保证电芯的整形效果、动力学性能和安全性能。
在一些实施例中，所述增塑剂可选自以下中的一种或几种：甘油C4-C10烷基二醚或者单醚、甘油C4-C10羧酸单酯或者二酯、丙二醇C4-C10烷基单醚、甘油。
在一些实施例中，压力敏感型粘合剂聚合物可以按照以下合成方法合成，包括以下步骤：
第一步，在溶剂(例如去离子水)中，依次加入0.1-1％质量分数(其相对于在合成压力敏感型粘合剂聚合物时加入的反应单体混合物(包含第一单体、第二单体、第三单体和反应型分散剂)、助剂(包括乳化剂、稳定剂、水性引发剂)和增塑剂的总重量，下同)的乳化剂(例如烯丙基磺酸盐)，2-3％质量分数、数均分子量≤1000，熔点在0-30℃的低聚物(例如甲基丙烯酸十八烷基酯)，均质机转速控制在8000-12000r/min，如10000r/min进行分散，分散时间可为20-60min，如50min，分散反应温度为20-40℃，如25℃，获得第一混合液。
第二步，向第一混合液中加入1-4％质量分数的稳定剂，如选自以下中的至少一种：聚氧化乙烯、烯丙基聚醚硫酸盐、亚甲基丁二酸(衣康酸)、苯乙烯磺酸、乙烯基磺酸钠、纳米纤维素钠；均质机转速控制在6000-8000r/min，比如6500r/min进行混合，时间为20-60min，如30min，混合反应温度为20-60℃，如45℃，获得第二混合液；
第三步，向第二混合液中加入0.05-0.5％质量分数的水性引发剂，如选自以下中的至少一种：碳酸氢钠、过氧化苯甲酰、过氧化月桂酰、异丙苯过氧化氢、叔丁基过氧化氢、过氧化二叔丁基、过氧化二异丙苯、过氧化苯甲酸叔丁酯、过氧化叔戊酸叔丁基酯、过氧化甲乙酮、过氧化环己酮过氧化二碳酸二异丙酯、过氧化二碳酸二环己酯、过硫酸钾、过硫酸钠、过硫酸铵、偶氮二异丁腈、偶氮二异庚腈。均质机转速控制在8000-12000r/min，比如8000r/min进行混合，时间20-60min，如30min。反应温度60-80℃，如72℃，获得第三混合液。
第四步，在均质机转速为100-1000r/min，如400r/min的条件下，逐步向第三混合液中均匀滴加(控制在60min刚好滴完)35％-45％质量分数的反 应单体混合物，反应时间80-100min，如80min，获得第四混合物。
第五步，将第四混合物在反应温度为80-90℃，如84℃；均质机转速为12000-18000r/min，如15000r/min的条件下继续反应，时间为120-240min，如180min，获得第五混合物。
第六步，向第五混合物中加入10-20％质量分数的增塑剂，如甘油，反应温度控制为80-90℃，如84℃；均质机转速控制为12000-18000r/min，如15000r/min，反应时间为120-240min，如180min，获得第六混合物。
第七步，向第六混合物中加入0.05-0.5％质量分数的水性引发剂，如过硫酸铵-碳酸氢钠。均质机转速控制为8000-12000r/min，如8000r/min，时间为20-60分钟，如30分钟。反应温度为60-80℃，如72℃，获得第七混合物。
第八步，在均质机转速为100-1000r/min，如400r/min的条件下，向第七混合物中逐步均匀滴加(控制在60min刚好滴完)30％-40％质量分数的反应单体混合物，反应时间为100-160min，如120min，获得第八混合物。
第九步，向第八混合物中加入5-20％质量分数的增塑剂，如甘油，控制反应温度为80-90℃，如84℃；均质机转速为12000-18000r/min，如15000r/min，时间为120-240min，如180min，获得第九混合物。
第十步，将第九混合物的温度降至50℃以下，过滤出料，即得核壳结构的压力敏感型粘合剂聚合物。本领域技术人员也可以参照上述方法(省略第七至第九步，并相应改变添加的增塑剂和反应单体混合物的质量分数)合成获得非核壳结构的压力敏感型粘合剂聚合物。
在一些实施例中，所述压力敏感涂层的平均厚度可为2-20μm，可选为2-15μm。
在一些实施例中，所述第一有机颗粒的平均粒径可为5-30μm，可选为5-20μm。其中，第一有机颗粒的平均粒径可以参照标准GB/T 19077.1-2016，使用激光粒度分析仪(如Malvern Master Size 3000)测定。第一有机颗粒的平均粒径控制为5-30μm时，由此第一有机颗粒具有较大的平均粒径，一方面可以增加极片和隔离膜的有效接触面积，进而大幅提升极片和隔离膜的粘接作用；另一方面可以避免这些有机颗粒渗入在隔离膜基体上形成的孔中，同时大尺寸存在相对较大的空隙，因此还可以解决隔离膜的透气性差的问题，并降低了小颗粒堵住隔离膜孔洞的可能性，避免造成内阻增加的风险。另外，由于电芯制作过程中拐角处不会经过复合(尤其是对于方壳电池)，因此此 处的隔离膜和极片并没有粘接，隔离膜无法有效转移向四周释放极片累积的应力；而且方壳电池的电芯模组自身结构的特点会造成拐角被顶住，极片膨胀形成的应力很难释放。因此如果电池拐角没有足够的空间，当循环到一定程度，即应力大于铜铝箔的延伸率时，极片会断裂，进而刺破隔离膜造成严重的安全风险。而在本发明中，由于第一有机颗粒具有较大的平均粒径，有一定的压缩能力，当其存在于电芯拐角处时可以有效提供拐角的应力释放空间。
在一些实施例中，所述第一有机颗粒的DSC熔点可为-50℃-200℃，可选为-40℃-160℃，所述第一有机颗粒的DSC熔点在上述范围内，能够耐受电解液溶胀，一方面，不会消耗过多电解液，残留单体不易被电解液泡出堵住隔膜，从而影响电芯的动力学性能。另一方面，不会导致隔离膜与极片的粘接大幅下降，并且极片不易被第一有机颗粒压损导致安全性能下降。
在一些实施例中，所述第一有机颗粒的重均分子量可为300×10 3g/mol-800×10 3g/mol，可选为400×10 3g/mol-650×10 3g/mol。
所述第一有机颗粒的重均分子量在上述范围内，可以保证第一有机颗粒有比较合适的溶胀以及与极片有比较合适的粘接力。对于同类型的第一有机颗粒，重均分子量过大会造成溶胀过小，不利于电芯循环后期电解液的补充，影响电芯性能，同时重均分子量过大会造成第一有机颗粒模量过大，直接压损极片，影响电芯安全性能。重均分子量过小，溶胀过大，在电解液作用下第一有机颗粒残留单体大量溶出增加隔离膜电阻，并恶化电解液影响电芯动力学性能。
其中，重均分子量采用日本东曹株式会社HLC-8320GPC凝胶渗透色谱(SuperMultiporeHZ系列半微量SEC柱，标准品为聚苯乙烯)测量重均分子量(Mw)。测试方法如下：将2mg待测聚合物粉末溶解于2mL的GPC专用的DMF溶剂中，然后进样2.5μL，进行测试。参数设置为：泵流量：5mL/min；加注容积：100μL；温度控制范围：60℃；数据采集频率：100Hz。
在一些实施例中，所述第一有机颗粒可为包含一种或几种选自以下的基团的一种或几种聚合物：卤素、苯基、环氧基、氰基、酯基和酰胺基。
在一些实施例中，所述第一有机颗粒可为选自以下的至少一种：含氟烯基单体单元的均聚物或共聚物，烯烃基单体单元的均聚物或共聚物，不饱和腈类单体单元的均聚物或共聚物，环氧烷类单体单元的均聚物或共聚物，单 糖类单体单元的二聚物、均聚物或共聚物，以及上述各均聚物或共聚物的改性化合物。
在一些实施例中，所述含氟烯基单体单元可选自二氟乙烯、偏二氟乙烯、三氟乙烯、三氟氯乙烯、四氟乙烯、六氟丙烯或其衍生物中的一种或几种。
在一些实施例中，所述烯烃基单体单元可选自乙烯、丙烯、丁二烯、异戊二烯、苯乙烯或其衍生物中的一种或几种。
在一些实施例中，所述不饱和腈类单体单元可选自丙烯腈、甲基丙烯腈或其衍生物中的一种或几种。
在一些实施例中，所述环氧烷类单体单元可选自环氧乙烷、环氧丙烷或其衍生物中的一种或几种。
在一些实施例中，所述单糖类单体单元可选自葡萄糖或其衍生物。
在一些实施例中，所述第一有机颗粒可为选自以下的至少一种：聚全氟乙烯、聚偏二氟乙烯、聚偏二氟乙烯-共-六氟丙烯、聚偏二氟乙烯-共-三氯乙烯、聚苯乙烯-共-甲基丙烯酸甲酯、聚苯乙烯-共-丙烯酸丁酯、聚甲基丙烯酸甲酯、聚丙烯腈、聚乙酸乙烯酯、聚乙烯-共-乙酸乙烯酯、聚酰亚胺、聚环氧乙烷、乙酸纤维素、乙酸丁酸纤维素、乙酸丙酸纤维素、氰基乙基普鲁兰、氰基乙基聚乙烯醇、氰基乙基纤维素和氰基乙基蔗糖。
在一些实施例中，所述第一有机颗粒可为选自以下中的至少一种：聚偏二氟乙烯-共-六氟丙烯、聚苯乙烯-共-丙烯酸丁酯、聚全氟乙烯、聚偏二氟乙烯、聚偏二氟乙烯-共-三氯乙烯。
第一有机颗粒选自上述物质时，其具有合适溶胀，并且与极片有合适的粘接。能够实现与压力敏感型粘合剂聚合物有适当的结合力，同时使在其上的压力敏感型粘合剂聚合物分散均匀，保证了粘接和动力学性能。
在一些实施例中，所述第一有机颗粒和第二有机颗粒的质量比可为(1-4):1，可选为(1.5-2.5):1。当第一有机颗粒和第二有机颗粒的质量比在上述范围内时，可以有效提高电解液的浸润性及分布均匀性，进一步改善电池的高温存储性能；特别地，当电池在使用过程中如果遇到异物刺入的情况下，第二有机颗粒可以瞬间将异物和裸露的铜箔或铝箔包裹住，形成第一高分子绝缘层，有效降低正负极发生短路的概率，提高电池的安全性能，随着异物周围温度的升高，第一有机颗粒会在第一高分子绝缘层周围形成更为牢固的第二高分子绝缘层，从而进一步改善电池的安全性能。
在一些实施例中，所述第二有机颗粒的平均粒径可为0.5-10μm，可选为2-8μm。其中，第二有机颗粒的平均粒径可以参照标准GB/T 19077.1-2016，使用激光粒度分析仪(如Malvern Master Size 3000)测定。采用以上粒径范围内的第二有机颗粒时，可以使得二次电池在正常工作时，能够在第一有机颗粒、第二有机颗粒之间进一步形成充足且不均匀分布的空隙，保证离子传输通道的畅通，从而进一步使电池具有良好的循环性能。同时，二次电池处于高温工作(例如电芯发生故障，产生高温)时，第一及第二有机颗粒能够形成大面积的胶膜结构，可以减少或阻隔离子传输通道，防止正极和负极进一步接触，延缓电池的热失控，从而可以进一步使电池获得良好的安全性能。其中第一有机颗粒的平均粒径相对较大，通常被设计成二次颗粒，而第二有机颗粒的平均粒径相对较小，通常被设计成一次颗粒，在第一有机颗粒和第二有机颗粒的共同作用下，可以在增强隔离膜与电极极片之间粘结力的同时，进一步有效保证隔离膜具有适度且不均匀的孔隙结构。另外，一方面，在电池电芯制备过程中，第一有机颗粒为二次颗粒，可有助于形成均匀的涂层界面，可以有效改善电池电芯制备过程中的极耳错位问题，第二有机颗粒为一次颗粒，颗粒与颗粒之间则不容易形成大面积的胶膜结构，因此不会导致孔道被堵，从而可以进一步改善电池的倍率性能和安全性能。
在一些实施例中，所述第二有机颗粒的DSC熔点可为-30-100℃，可选为-30-70℃，当所述第二有机颗粒的DSC熔点在上述范围内，能够耐受电解液溶胀，一方面，不会消耗过多电解液，残留单体不易被电解液泡出堵住隔膜，从而影响电芯的动力学性能。另一方面，不会导致隔离膜与极片的粘接大幅下降，并且极片不易被第二有机颗粒压损导致安全性能下降。
其中，DSC熔点为本领域公知的含义，可以用本领域公知的仪器及方法进行测定，例如，可以是通过德国NETZSC公司的仪器型号为DSC 200F3的DSC熔点测试仪。作为具体的示例，测试方法如下：取约10mg样品进行测试。测试条件设置为：温度范围：-100-200℃，氮气氛围，10℃/min。选取第一次升温时，吸收峰所对应的温度即为相应的DSC熔点。
在一些实施例中，所述第二有机颗粒的重均分子量可为10×10 3g/mol-100×10 3g/mol，可选为20×10 3g/mol-80×10 3g/mol。
所述第二有机颗粒的重均分子量在上述范围内，可以保证第二有机颗粒有比较合适的溶胀以及与极片有比较合适的粘接力。对于同类型的第二有机颗粒，重均分子量过大会造成溶胀过小，不利于电芯循环后期电解液的补充， 影响电芯性能，同时重均分子量过大会造成第二有机颗粒模量过大，直接压损极片，影响电芯安全性能。重均分子量过小，溶胀过大，在电解液作用下第二有机颗粒残留单体大量溶出增加隔离膜电阻，并恶化电解液影响电芯动力学性能。其中，第二有机颗粒的重均分子量的测试方法与第一有机颗粒重均分子量的测试方法相同。
在一些实施例中，所述第二有机颗粒为包含一种或几种选自以下的基团的一种或几种聚合物：苯基、环氧基、氰基、酯基、羟基、羧基、磺酰酯基和吡咯烷酮基。
在一些实施例中，所述第二有机颗粒可为选自以下的至少一种：丙烯酸酯类单体单元的均聚物或共聚物，丙烯酸类单体单元的均聚物或共聚物，不饱和腈类单体单元的均聚物或共聚物，烯类单体单元的均聚物或共聚物，苯乙烯类单体单元的均聚物或共聚物，环氧类单体单元的均聚物或共聚物，聚氨酯类化合物，橡胶类化合物，单糖类单体单元的二聚物、均聚物或共聚物，以及上述各均聚物或共聚物的改性化合物。
在一些实施例中，所述丙烯酸酯类单体单元可选自丙烯酸甲酯、丙烯酸乙酯、丙烯酸丙酯、丙烯酸丁酯、甲基丙烯酸甲酯、甲基丙烯酸丁酯、甲基丙烯酸异辛酯或其衍生物中的一种或几种。
在一些实施例中，所述丙烯酸类单体单元可以选自丙烯酸、甲基丙烯酸或其衍生物中的一种或几种。
在一些实施例中，所述不饱和腈类单体单元可选自丙烯腈、甲基丙烯腈或其衍生物中的一种或几种。
在一些实施例中，所述烯类单体单元可以选自乙烯、乙酸乙烯酯、丁二烯或其衍生物中的一种或几种。
在一些实施例中，所述苯乙烯类单体单元可选自苯乙烯、甲基苯乙烯或其衍生物中的一种或几种。
在一些实施例中，所述环氧类单体单元可选自环氧乙烷、环氧丙烷或其衍生物中的一种或几种。
在一些实施例中，单糖类单体单元可选自葡萄糖或其衍生物。
在一些实施例中，所述第二有机颗粒为选自以下的至少一种：聚甲基丙烯酸甲酯、聚丙烯腈、聚乙烯吡咯烷酮、聚乙酸乙烯酯、聚乙烯-共-乙酸乙烯酯、聚苯乙烯-共-甲基丙烯酸甲酯、聚苯乙烯-共-丙烯酸丁酯、聚环氧乙烷、 乙酸纤维素、乙酸丁酸纤维素、乙酸丙酸纤维素、氰乙基普鲁兰多糖、氰乙基聚乙烯醇、氰乙基纤维素、氰乙基蔗糖、普鲁兰多糖、羧甲基纤维素、丙烯腈-苯乙烯-丁二烯共聚物、苯乙烯-丙烯酸丁酯-丙烯酸异辛酯共聚物和聚酰亚胺。
第二有机颗粒选自上述物质时，其具有合适溶胀，并且与极片有合适的粘接。能够实现与压力敏感型粘合剂聚合物有适当的结合力，同时使在其上的压力敏感型粘合剂聚合物分散均匀，保证了粘接和动力学性能。
在一些实施例中，所述隔离膜基体的孔隙率可为10-95％，孔径可为20-60nm，厚度可为3-12μm，可选为5-9μm。当隔离膜基体的孔隙率在上述范围内时，可实现二次电池动力学和安全性能的平衡；当隔离膜基体的厚度在上述范围内时，可实现二次电池能量密度和安全性能的平衡。
在一些实施例中，所述隔离膜基体可包括选自以下的一种或几种的膜或非织造物：聚乙烯、聚丙烯、聚对苯二甲酸乙二醇酯、聚对苯二甲酸丁二醇酯、聚酯、聚缩醛、聚酰胺、聚碳酸酯、聚酰亚胺、聚醚醚酮、聚芳基醚酮、聚醚酰亚胺、聚酰胺酰亚胺、聚苯并咪唑、聚醚砜、聚苯醚、环烯烃共聚物、聚苯硫醚和聚乙烯萘。
隔离膜的制备方法
本申请还提供了隔离膜的制备方法，其包括以下步骤：
S1)将第一有机颗粒和分散剂加入溶剂中以形成第一聚合物溶液；
S2)将压力敏感型粘合剂聚合物加入步骤S1)得到的第一聚合物溶液中，混合以形成第二聚合物溶液；
S3)任选地，在步骤S2)得到的第二聚合物溶液中加入第二有机颗粒，混合以形成第三聚合物溶液；和
S4)将步骤S2)得到的第二聚合物溶液或步骤S3)得到的第三聚合物溶液涂布到多孔的隔离膜基体的至少一个表面上，干燥后得到隔离膜；
其中所述隔离膜包括在所述隔离膜基体的至少一个表面上形成的压力敏感涂层，其包括40-90wt％的第一有机颗粒和10-20wt％的压力敏感型粘合剂聚合物，和任选的0-50wt％的第二有机颗粒；其中所述压力敏感型粘合剂聚合物包括粘合剂聚合物和增塑剂。
在一些实施例中，步骤S1)中使用的分散剂的非限制性实例可包括丙烯酸酯(如BYK牌号22136)、枝化醇聚醚(如陶氏牌号TMN-6)、聚乙二醇 三甲基壬基醚。步骤S1)中使用的溶剂的非限定性实例可包括丙酮、四氢呋喃、二氯甲烷、氯仿、二甲基甲酰胺、N-甲基-2-吡咯烷酮、环己烷、水或它们的混合物。
在一些实施例中，步骤S4)中使用的涂布方法的非限制性实例可包括浸涂法、模涂法、辊涂法、逗点涂覆法(comma coating)、旋涂或它们的组合。干燥后的单面涂布重量可为0.42-0.52g/m 2。
[外包装]
在一些实施例中，二次电池可以包括外包装，用于封装正极极片、负极极片、隔离膜和电解质。作为一个示例，正极极片、负极极片和隔离膜可经叠片或卷绕形成叠片结构电芯或卷绕结构电芯，电芯封装在外包装内；电解质可采用电解液，电解液浸润于电芯中。二次电池中电芯的数量可以为一个或几个，可以根据需求来调节。
在一些实施例中，二次电池的外包装可以是软包，例如袋式软包。软包的材质可以是塑料，如可包括聚丙烯PP、聚对苯二甲酸丁二醇酯PBT、聚丁二酸丁二醇酯PBS等中的一种或几种。二次电池的外包装也可以是硬壳，例如铝壳等。
在一些实施例中，正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件。
本申请对二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。如图1是作为一个示例的方形结构的二次电池5。
可以将本发明提供的二次电池组装成电池模块，电池模块所含二次电池的数量可以为多个，具体数量可根据电池模块的应用和容量来调节。
图2是作为一个示例的电池模块4。参照图2，在电池模块4中，多个二次电池5可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个二次电池5进行固定。
可选地，电池模块4还可以包括具有容纳空间的壳体，多个二次电池5容纳于该容纳空间。
在本发明中，还可以将由二次电池组装的电池模块组装成电池包，电池包所含电池模块的数量可以根据电池包的应用和容量进行调节。
图3和图4是作为一个示例的电池包1。参照图3和图4，在电池包1中 可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2能够盖设于下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。
【用电装置】
本申请还提供一种用电装置，该用电装置包括本申请提供的二次电池，所述二次电池为所述用电装置提供电源。所述用电装置可以但不限于是移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等。
所述用电装置可以根据其使用需求来选择二次电池、电池模块或电池包。
图5是作为一个示例的用电装置。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对二次电池的高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的用电装置可以是手机、平板电脑、笔记本电脑等。该用电装置通常要求轻薄化，可以采用二次电池作为电源。
实施例
以下，说明本申请的实施例。下面描述的实施例是示例性的，仅用于解释本申请，而不能理解为对本申请的限制。实施例中未注明具体技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品。
实施例1
隔离膜的制备
1)取厚度约为9μm、孔径约为50nm且孔隙率约为38％的聚乙烯微孔膜作为隔离膜基体；
2)将第一有机颗粒(聚偏二氟乙烯-共-六氟丙烯(其中，基于偏二氟乙烯(VDF)单体和六氟丙烯(HFP)单体重量计，HFP单体约占9％)，重均分子量约为600×10 3g/mol，平均粒径约为7μm，DSC熔点约为150℃)和分散剂(BYK-22136)加入水中，形成第一聚合物溶液；
3)将压力敏感型粘合剂聚合物(其玻璃化转变温度约为10℃，平均粒径约为1.1μm，包括质量比为5:1的粘合剂聚合物和增塑剂(其中相对于增塑剂的重量，约8wt％的增塑剂接枝在粘合剂聚合物上)以及若干去离子水，其中 粘合剂聚合物为30％丙烯酸异丁酯+25％丙烯酸异辛酯+5％甲基丙烯酸-2-羟丙酯+15％苯乙烯+22％丙烯腈+3％聚乙烯醇共聚物，增塑剂为甘油)加入步骤2)得到的第一聚合物溶液中，混合以形成固含量为12wt％的第二聚合物溶液，其中所含的第一有机颗粒与压力敏感型粘合剂聚合物的质量比为85:15；
4)将步骤3)获得的固含量为12wt％的第二聚合物溶液作为水性涂层浆料，通过旋喷的方式涂覆在隔离膜基体的一个表面上，烘干后，即制得隔离膜。制备的隔离膜包括隔离膜基体，和在隔离膜基体的一个表面上涂布的压力敏感涂层，该压力敏感涂层的厚度为约3μm，包括质量比为85:15的第一有机颗粒和压力敏感型粘合剂聚合物，且该压力敏感型粘合剂聚合物包括质量比为5:1的粘合剂聚合物和增塑剂(其中相对于增塑剂的重量，约8wt％的增塑剂接枝在粘合剂聚合物上)。
二次电池的制备
将活性物质LiNi 1/3Mn 1/3Co 1/3O 2、导电剂乙炔黑、粘结剂聚偏二氟乙烯(PVDF)按重量比94:3:3在溶剂N-甲基吡咯烷酮中充分搅拌混合均匀后，得到正极浆料，将该浆料涂覆于Al箔上烘干、冷压，得到正极极片。正极极片上正极活性材料的负载量为0.32g/1540.25mm 2，密度为3.45g/cm 3。
将活性物质人造石墨、导电剂乙炔黑、粘结剂丁苯橡胶(SBR)、增稠剂碳甲基纤维素钠(CMC)按照重量比95:2:2:1在溶剂去离子水中充分搅拌混合均匀后，得到负极浆料，将该浆料涂覆于Cu箔上烘干、冷压，得到负极极片。负极极片上石墨的负载量为0.18g/1540.25mm 2，密度为1.65g/cm 3。
将碳酸亚乙酯(EC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)按体积比3:5:2混合，然后将LiPF 6均匀溶解在上述溶液中，得到电解液。该电解液中，LiPF 6的浓度为1mol/L。
以各实施例或对比例制备的隔离膜作为电芯用隔离膜。
将正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正负极中间起到隔离的作用，并卷绕得到裸电芯。将裸电芯置于外包装中，注入电解液并封装即可得到二次电池。需要补充的是，若隔离膜涂层为单面，则涂层面朝向阴极(即正极极片)侧。
隔离膜的粘接性能评估
测试过程如下：
1.选取长为300mm宽为100mm的制备的隔离膜，上述制备的正极极片 和负极极片。
2.将隔离膜上下用纸张包好使用刀模和冲压机冲切成54.2mm*72.5mm的样品。
3.将冲切好的隔离膜样品与正极极片或负极极片整齐叠好，注意隔离膜朝上，上下各垫130mm*130mm大小铁氟龙，把叠好的样品放置在硬纸板的中间，盖上一张150mm*160mm硬纸板。
4.将叠好的样品放入平压机调整压力，调整好气压，压力＝350KG±10KG(相当于约0.87MPa)或压力＝850Kg±10KG(相当于约2.24MPa)，设定T＝25℃，时间设定为15s，进行热压。
5.将热压好的样品使用刀模和冲压机冲切成72.5mm*15mm的小条。
6.将极片的一面通过双面胶贴在钢板上固定，另一面粘接有隔离膜，使用双面胶将宽度为15mm的A4纸条与隔离膜粘连在一起，完成测试样品制作。测试时，将固定极片的钢板固定，而拉力机向上拉动A4纸条，使隔离膜与极片剖离。
7.开启高铁拉力机，依次设置为：粘接力测试、速度50mm/min，起始夹具间距40mm。
8.将测试样品置于夹具之间，将钢板的末端固定在下夹头，将A4纸固定在上夹头。上下端夹头分别用夹具夹紧。
9.点击电脑桌面拉伸的操作界面，将力、位移等清零，然后点击“开始”，进行预拉伸约5mm；预拉伸后，重新将力、位移等清零，开始测试，等测试完后，导出并保存完整数据。
10.每一组至少测量5条测试样品，并且5条测试样品粘接力测试的曲线重复性较好，则进行下一组测试。否则需要再进行测试，直到5条测试样品重复性较好为止。
11.测试完成后，作出粘接强度(N/m)-位移曲线，并计算粘接力大小。
隔离膜的电阻性能评估
测试过程如下：
(1)隔离膜准备：将各待测隔离膜裁成相同的大小的样品(45.3mm*33.7mm)，并将样品放置在60℃的环境下烘烤至少4h，然后迅速转入25℃百级洁净手套箱中备用；
(2)对称电池限域性Pocket袋(对称电池限域性铝塑袋(铝塑袋是软包 电池用的聚丙烯和铝箔复合的通用商品))制备：采用Cu Foil对Cu Foil(铜箔对铜箔)为集流体组装的空白对称电池。该Pocket袋的限域性是通过绿胶中间冲孔实现的。Pocket袋在使用前需放在60℃的环境下烘烤至少4h，然后迅速转入如上文(1)中所述的25℃百级洁净手套箱中备用；
(3)对称电池的组装：以阳极极片为电极，在如上文(1)中所述的手套箱中原位组装5组分别具有不同隔离膜层数(1、2、3、4、5层)的对称电池样品，每组样品有5个平行样；用简易封装机将Pocket袋侧封，移液枪注液(300μL)，底封；
(4)对组装好的对称电池上夹具：将组装好的对称电池放置在如上文(1)中所述的手套箱中过夜，以便让电解液充分浸润隔离膜；次日，上金属夹具，夹具的压力控制在0.7MPa；
(5)测量电化学阻抗谱(EIS)：
测量之前，将具有不同隔离膜层数的对称电池放在高低温箱中25℃恒温半小时，测量设定温度(25℃)下的EIS(如果是低温(例如-25℃-0℃)，恒温的时间可相应延长，如两个小时左右)；
(6)采用法国Bio-Logic VMP3电化学工作站，电压＜5V，电流＜400mA，电流精度：0.1％*100μA。测量时，EIS的测量条件设置为电压频率1MHz-1kHz，扰动电压设置为5MV，夹具的压力控制在0.7MPa。
(7)以EIS数据的实部对负虚部做出散点图，同时要将不同层数和相同层数的平行样的数据画在一张图上，如此得到的EIS图作为EIS原始数据的比较。
(8)将上述(7)获得的EIS图中非第一象限的点剔除，得到新的EIS图。在所述新的EIS图中对第一象限的散点进行线性拟合，得到关联式，令y＝0，可得到x值，即为所需的电解液在隔离膜中的电阻值。依次类推，则可以将测得的EIS数据进行线性拟合处理即可得到不同层数的平行样之间的电阻值。
二次电池的性能评估
循环性能测试：
将制备的二次电池各组取5支，通过以下步骤对二次电池重复进行充电和放电，并计算二次电池在25℃或45℃条件下的循环容量保持率。
在25℃的环境中，进行第一次充电和放电，在0.7C(即2h内完全放掉 理论容量的电流值)的充电电流下进行恒流和恒压充电，直到上限电压为4.4V，然后在0.5C的放电电流下进行恒流放电，直到最终电压为3V，记录首次循环的放电容量；而后进行1000次的充电和放电循环，记录第1000次循环的放电容量。循环容量保持率＝(第1000次循环的放电容量/首次循环的放电容量)×100％。
在45℃的环境中，进行第一次充电和放电，在0.7C(即2h内完全放掉理论容量的电流值)的充电电流下进行恒流和恒压充电，直到上限电压为4.4V，然后在0.5C的放电电流下进行恒流放电，直到最终电压为3V，记录首次循环的放电容量；而后进行1000次的充电和放电循环，记录第1000次循环的放电容量。循环容量保持率＝(第1000次循环的放电容量/首次循环的放电容量)×100％。
实施例2-3
除了压力敏感涂层中第一有机颗粒和压力敏感型粘合剂聚合物的质量比不同，其余与实施例1相同。具体地：
实施例2中制备的隔离膜的压力敏感涂层中第一有机颗粒和压力敏感型粘合剂聚合物的质量比90:10。
实施例3中制备的隔离膜的压力敏感涂层中第一有机颗粒和压力敏感型粘合剂聚合物的质量比80:20。
实施例4-9
除了使用的压力敏感型粘合剂聚合物中的粘合剂聚合物或增塑剂不同外，其余与实施例1相同。具体地：
实施例4使用的压力敏感型粘合剂聚合物中的粘合剂聚合物为30％丙烯酸异丁酯+25％丙烯酸异辛酯+5％丙烯酸-2-羟丙酯+15％苯乙烯+22％丙烯酰胺+3％聚乙二醇共聚物，增塑剂为甘油。
实施例5使用的压力敏感型粘合剂聚合物中的粘合剂聚合物为30％丙烯酸环己酯+25％甲基丙烯酸四氢呋喃酯+5％甲基丙烯酸-2-羟丙酯+15％苯乙烯+22％丙烯腈+3％聚乙二醇共聚物，增塑剂为甘油。
实施例6使用的压力敏感型粘合剂聚合物中的粘合剂聚合物为30％丙烯酸环己酯+25％甲基丙烯酸四氢呋喃酯+5％二乙烯基苯+15％苯乙烯+22％丙烯腈+3％聚乙二醇共聚物，增塑剂为甘油。
实施例7使用的压力敏感型粘合剂聚合物中的粘合剂聚合物为30％丙烯 酸异丁酯+25％丙烯酸异辛酯+5％二乙烯基苯+15％苯乙烯+22％丙烯腈+3％聚乙烯醇共聚物，增塑剂为甘油。
实施例8使用的压力敏感型粘合剂聚合物中的粘合剂聚合物为30％丙烯酸异丁酯+25％丙烯酸异辛酯+5％甲基丙烯酸-2-羟丙酯+15％苯乙烯+22％丙烯腈+3％聚乙烯醇共聚物，增塑剂为甘油C4-C10烷基二醚。
实施例9使用的压力敏感型粘合剂聚合物中的粘合剂聚合物为30％丙烯酸异丁酯+25％丙烯酸异辛酯+5％甲基丙烯酸-2-羟丙酯+15％苯乙烯+22％丙烯腈+3％聚乙烯醇共聚物，增塑剂为丙二醇C4-C10烷基单醚。
实施例10-12
除了使用的压力敏感型粘合剂聚合物中增塑剂的接枝率不同外，其余与实施例1相同。具体地：
实施例10使用的压力敏感型粘合剂聚合物中增塑剂的接枝为5wt％。
实施例11使用的压力敏感型粘合剂聚合物中增塑剂的接枝为3wt％。
实施例12使用的压力敏感型粘合剂聚合物中增塑剂的接枝为0wt％，即增塑剂无接枝。
实施例13
隔离膜的制备
1)取厚度约为9μm、孔径约为50nm且孔隙率约为38％的聚乙烯微孔膜作为隔离膜基体；
2)将第一有机颗粒(聚偏二氟乙烯-共-六氟丙烯(其中，基于偏二氟乙烯(VDF)单体和六氟丙烯(HFP)单体重量计，HFP单体约占9％)，重均分子量约为600×10 3g/mol，平均粒径约为7μm，DSC熔点约为150℃)和分散剂(BYK-22136)加入水中，形成第一聚合物溶液；
3)将压力敏感型粘合剂聚合物(其DSC熔点约为10℃，平均粒径约为1.1μm，包括质量比为5:1的粘合剂聚合物和增塑剂(其中相对于增塑剂的重量，约8wt％的增塑剂接枝在粘合剂聚合物上)以及若干去离子水，其中粘合剂聚合物为30％丙烯酸异丁酯+25％丙烯酸异辛酯+5％甲基丙烯酸-2-羟丙酯+15％苯乙烯+22％丙烯腈+3％聚乙烯醇共聚物，增塑剂为甘油)加入步骤2)得到的第一聚合物溶液中，混合以形成固含量为12wt％的第二聚合物溶液；
4)向步骤3)获得的第二聚合物溶液中加入第二有机颗粒(30％苯乙烯-50％丙烯酸丁酯-20％丙烯酸异辛酯，平均粒径为4μm，DSC熔点约为55℃)， 使得第一有机颗粒和第二有机颗粒的质量比为65:20，混合以形成固含量为12％的第三聚合物溶液，其中有机颗粒(包括质量比为65:20的第一有机颗粒和第二有机颗粒)与压力敏感型粘合剂聚合物的质量比为85:15；
5)将步骤4)获得的固含量为12wt％的第三聚合物溶液作为水性涂层浆料，通过旋喷的方式涂覆在隔离膜基体的一个表面上，烘干后，即制得隔离膜。制备的隔离膜包括隔离膜基体，和在隔离膜基体的一个表面上涂布的压力敏感涂层，该压力敏感涂层的厚度为约3μm，包括质量比为85:15的有机颗粒(其中包括质量比为65:20的第一有机颗粒和第二有机颗粒)和压力敏感型粘合剂聚合物，且该压力敏感型粘合剂聚合物包括质量比为5:1的粘合剂聚合物和增塑剂(其中相对于增塑剂的重量，约8wt％的增塑剂接枝在粘合剂聚合物上)。如图6所示，示出了该实施例制备的隔膜的压力敏感涂层的形貌。
实施例14-15
除了压力敏感涂层中有机颗粒和压力敏感型粘合剂聚合物的质量比不同，其余与实施例13相同。具体地：
实施例14中制备的隔离膜的压力敏感涂层中有机颗粒和压力敏感型粘合剂聚合物的质量比85:15，其中有机颗粒中第一有机颗粒和第二有机颗粒的质量比为75:10。
实施例15中制备的隔离膜的压力敏感涂层中有机颗粒和压力敏感型粘合剂聚合物的质量比90:10，其中有机颗粒中第一有机颗粒和第二有机颗粒的质量比为65:25。
对比例1-2
除了压力敏感涂层中第一有机颗粒和压力敏感型粘合剂聚合物的质量比不同，其余与实施例1相同。具体地：
对比例1中制备的隔离膜的压力敏感涂层中第一有机颗粒和压力敏感型粘合剂聚合物的质量比91:9。
对比例2中制备的隔离膜的压力敏感涂层中第一有机颗粒和压力敏感型粘合剂聚合物的质量比74:26。
对比例3-4
除了未使用实施例1中描述的压力敏感型粘合剂聚合物外，其余与实施例1相同。具体地：
对比例3中制备的隔离膜仅使用粘合剂聚合物而不含增塑剂，在制备的 隔离膜的压力敏感涂层中第一有机颗粒和粘合剂聚合物的质量比为85:15。
对比例4中制备的隔离膜仅使用增塑剂而不含粘合剂聚合物，在制备的隔离膜的压力敏感涂层中第一有机颗粒和增塑剂的质量比为85:15。
对上述实施例1-15和对比例1-4制备的隔离膜的粘接性能、电阻以及由该隔离膜制备的二次电池的循环性能进行评估，结果如下表1所示。
表1：实施例1-15和对比例1-4制备的隔离膜的性能以及由该隔离膜制备的二次电池的循环性能测试结果
Figure PCTCN2021143069-appb-000001
Figure PCTCN2021143069-appb-000002
由上表1记载的结果可知，在制备隔离膜时使用由粘合剂聚合物和增塑剂制备的压力敏感型粘合剂聚合物，并搭配有机颗粒，能够有效赋予隔离膜常温高粘接性能和导离子能力，在常温条件下，制备的隔离膜的电阻均在1.32Ω以下，在≥2MPa作用下与阴极电极的粘接力均在0.70N/m以上，甚至在1.00N/m以上，与阳极电极的粘接力均在0.50N/m以上，而在≤1MPa作用下与电极的粘接力均在0.1N/m以下。因此制备的隔离膜可以避免隔离膜在收卷及存储过程中的层与层之间的粘接，并且在使用该隔离膜制备电芯时，在常温条件下即可将极片与隔离膜紧密贴合，一方面可以避免极片和隔离膜之间发生错位而造成电芯报废、影响电芯性能和产生安全风险，另一方面可以省略传统的电芯生产工艺中的隧道炉及第二道复合工艺，进而可以节约生产空间和生产时间，并降低能耗，明显提升电芯生产的产能，同时可以提升电芯整形性能、安全性能和动力学性能。由实施例10-12的结果可知，压力敏感型粘合剂聚合物中增塑剂的接枝有利于降低隔离膜的电阻，并有利于提高由隔离膜制备的二次电池的循环性能，尤其是当压力敏感型粘合剂聚合物中增塑剂的接枝率为5wt％以上时，更有利于获得电阻更低的隔离膜以及循环性能更加优良的二次电池。由对比例1-2的结果可知，当使用的压力敏感型粘合剂聚合物较多或较少时，均会导致隔离膜的电阻明显增加，同时显著劣化二次电池的循环性能。由对比例3-4的结果可知，当使用的压力敏感型粘合剂聚合物中仅包括粘合剂聚合物和增塑剂中的一种时，均会导致隔离膜的粘结性能劣化，并劣化二次电池的循环性能，并且当使用的压力敏感型粘合剂聚合物中全部都是增塑剂时，更会导致隔离膜的电阻明显增加，并显著劣化二次电池的循环性能。
实施例16-20
除了第一有机颗粒的粒径不同，以及压力敏感涂层的厚度不同外，其余与实施例1相同。具体地：
实施例16中使用的第一有机颗粒的粒径约为3μm，压力敏感涂层的厚度 约为0.8μm。
实施例17中使用的第一有机颗粒的粒径约为5μm，压力敏感涂层的厚度约为2μm。
实施例18中使用的第一有机颗粒的粒径约为20μm，压力敏感涂层的厚度约为15μm。
实施例19中使用的第一有机颗粒的粒径约为30μm，压力敏感涂层的厚度约为20μm。
实施例20中使用的第一有机颗粒的粒径约为36μm，压力敏感涂层的厚度约为22μm。
实施例21-27
除了压力敏感型粘合剂聚合物的粒径不同外，其余与实施例1相同。具体地：
实施例21使用的压力敏感型粘合剂聚合物的粒径约为0.3μm。
实施例22使用的压力敏感型粘合剂聚合物的粒径约为0.5μm。
实施例23使用的压力敏感型粘合剂聚合物的粒径约为0.8μm。
实施例24使用的压力敏感型粘合剂聚合物的粒径约为1.0μm。
实施例25使用的压力敏感型粘合剂聚合物的粒径约为2.0μm。
实施例26使用的压力敏感型粘合剂聚合物的粒径约为3.0μm。
实施例27使用的压力敏感型粘合剂聚合物的粒径约为3.5μm。
实施例28-32
除了使用的压力敏感型粘合剂聚合物中包括的粘合剂聚合物和增塑剂的质量比不同外，其余与实施例1相同。具体地：
实施例28中使用的压力敏感型粘合剂聚合物中包括的粘合剂聚合物和增塑剂的质量比约为3:1。
实施例29中使用的压力敏感型粘合剂聚合物中包括的粘合剂聚合物和增塑剂的质量比约为4:1。
实施例30中使用的压力敏感型粘合剂聚合物中包括的粘合剂聚合物和增塑剂的质量比约为11:1。
实施例31中使用的压力敏感型粘合剂聚合物中包括的粘合剂聚合物和增塑剂的质量比约为19:1。
实施例32中使用的压力敏感型粘合剂聚合物中包括的粘合剂聚合物和增 塑剂的质量比约为21:1。
实施例33-38
除了使用的第二有机颗粒的粒径不同，以及制备的压力敏感涂层的厚度不同外，其余与实施例14相同。具体地：
实施例33使用的第二有机颗粒的粒径约为0.3μm，压力敏感涂层的厚度约为3μm。
实施例34使用的第二有机颗粒的粒径约为0.5μm，压力敏感涂层的厚度约为3μm。
实施例35使用的第二有机颗粒的粒径约为2μm，压力敏感涂层的厚度约为3μm。
实施例36使用的第二有机颗粒的粒径约为8μm，压力敏感涂层的厚度约为4μm。
实施例37使用的第二有机颗粒的粒径约为10μm，压力敏感涂层的厚度约为6μm。
实施例38使用的第二有机颗粒的粒径约为12μm，压力敏感涂层的厚度约为10μm。
对上述实施例16-38制备的隔离膜的粘接性能、电阻以及由该隔离膜制备的二次电池的循环性能进行评估，结果如下表2所示。
表2：实施例16-38制备的隔离膜的性能以及由该隔离膜制备的二次电池的循环性能测试结果
Figure PCTCN2021143069-appb-000003
Figure PCTCN2021143069-appb-000004
由表2记载的结果可知，实施例16-20通过改变第一有机颗粒的粒径，实施例21-27通过改变压力敏感型粘合剂聚合物的粒径，实施例28-32通过改变压力敏感型粘合剂聚合物中包括的粘合剂聚合物和增塑剂的质量比，以及实施例33-38通过改变第二有机颗粒的粒径，制备的隔离膜均具有良好的常温高粘接性能和导离子能力，在常温条件下，其电阻均在1.3Ω以下，在≥2MPa作用下与阴极电极的粘接力均在0.56N/m以上，而在≤1MPa作用下与电极的粘接力均在0.23N/m以下；利用各实施例制备的隔离膜制备的二次电池也均具有良好的循环性能，其在25℃和45℃条件下的容量保持率均在70％以上。尤其是当使用的第一有机颗粒的粒径在5-30μm范围内，和/或压力敏感型粘合剂聚合物的粒径在0.5-3μm范围内，和/或压力敏感型粘合剂聚合物中包括的粘合剂聚合物和增塑剂的质量比在(4-19):1范围内，和/或第二有机颗粒的粒径在0.5-10μm范围内时，更能够有效赋予隔离膜良好的常温高粘接性能和导离子能力，在常温条件下，其电阻均在1.1Ω以下，在≥2MPa作用下与阴极电极的粘接力均在0.80N/m以上，而在≤1MPa作用下与电极的粘接力均在0.1N/m以下；利用这些隔离膜制备的二次电池也均具有更好的循环性能， 其在25℃和45℃条件下的容量保持率均在80％以上。
实施例39-47
除了使用的压力敏感型粘合剂聚合物为核壳结构的压力敏感型粘合剂聚合物，其余与实施例1相同。在核壳结构的压力敏感型粘合剂聚合物的内核和外壳中均包括粘合剂聚合物和增塑剂，实施例39-47中使用的压力敏感型粘合剂聚合物的内核和外壳中粘合剂聚合物和增塑剂的质量比具体如下表3所示。
对上述实施例39-47制备的隔离膜的粘接性能、电阻以及由该隔离膜制备的二次电池的循环性能进行评估，结果如下表4所示。
表3：实施例39-47中使用的压力敏感型粘合剂聚合物的内核和外壳中粘合剂聚合物和增塑剂的质量比
Figure PCTCN2021143069-appb-000005
表4：实施例39-47制备的隔离膜的性能以及由该隔离膜制备的二次电池的循环性能测试结果
Figure PCTCN2021143069-appb-000006
Figure PCTCN2021143069-appb-000007
由上表4记载的结果可知，在制备隔离膜时使用由粘合剂聚合物和增塑剂制备的为核壳结构的压力敏感型粘合剂聚合物时，能够进一步有效赋予隔离膜常温高粘接性能和导离子能力，获得的隔离膜的电阻均较低，均在0.9Ω以下，在≥2MPa作用下与阴极电极的粘接力均在1.21N/m以上，与阳极电极的粘接力均在0.85N/m以上，而在≤1MPa作用下与电极的粘接力均在0.1N/m以下，并且制备的二次电池均具有良好的循环性能，其在25℃和45℃条件下的容量保持率均在89％以上。尤其是当核壳结构的压力敏感型粘合剂聚合物的内核结构中粘合剂聚合物和增塑剂的质量比为(3-4):1，外壳结构中粘合剂聚合物和增塑剂的质量比为(7-9):1的条件下，更能够进一步有效赋予隔离膜常温高粘接性能和导离子能力，获得的隔离膜的电阻更低，均在0.8Ω以下，并且在≥2MPa作用下与阴极电极的粘接力均在1.23N/m以上，与阳极电极的粘接力均在1.1N/m以上，而在≤1MPa作用下与电极的粘接力均在0.1N/m以下；由这些隔离膜制备的二次电池的循环性能也更好，其在25℃和45℃条件下的容量保持率均在91％以上。
需要说明的是，本申请不限定于上述实施方式。上述实施方式仅为示例，在本申请的技术方案范围内具有与技术思想实质相同的构成、发挥相同作用效果的实施方式均包含在本申请的技术范围内。此外，在不脱离本申请主旨的范围内，对实施方式施加本领域技术人员能够想到的各种变形、将实施方式中的一部分构成要素加以组合而构筑的其它方式也包含在本申请的范围内。

Claims (15)

  1. 一种隔离膜，其包括：
    多孔的隔离膜基体；和
    涂布在所述隔离膜基体的至少一个表面上的压力敏感涂层，其包括40-90wt％的第一有机颗粒和10-20wt％的压力敏感型粘合剂聚合物，和任选的0-50wt％的第二有机颗粒；
    其中所述压力敏感型粘合剂聚合物包括粘合剂聚合物和增塑剂。
  2. 根据权利要求1所述的隔离膜，其中所述压力敏感型粘合剂聚合物中包括的粘合剂聚合物和增塑剂的质量比为(4-19):1，可选为(4-11):1。
  3. 根据权利要求1或2所述的隔离膜，其中所述压力敏感型粘合剂聚合物为核壳结构，在所述核壳结构的内核和外壳均包括粘合剂聚合物和增塑剂，其中在内核结构中所述粘合剂聚合物和增塑剂的质量比为(2-5):1，可选为(3-4):1，在外壳结构中所述粘合剂聚合物和增塑剂的质量比为(6-10):1，可选为(7-9):1。
  4. 根据权利要求1-3中任一项所述的隔离膜，其中一部分所述增塑剂接枝在所述粘合剂聚合物上；
    可选地，基于所述增塑剂的重量，至少5wt％的增塑剂接枝在所述粘合剂聚合物上。
  5. 根据权利要求1-4中任一项所述的隔离膜，其中所述压力敏感型粘合剂聚合物的平均粒径为0.5-3.0μm，可选为0.8-2.0μm；可选地，所述压力敏感型粘合剂聚合物的DSC熔点为-50℃-100℃，可选为-45℃-60℃。
  6. 根据权利要求1-5中任一项所述的隔离膜，其中所述粘合剂聚合物包括由包含以下的第一单体中的至少一种、第二单体中的至少一种、第三单体中的至少一种和反应型分散剂中的至少一种的反应单体混合物共聚形成的共聚物：
    第一单体：包括丙烯酸、甲基丙烯酸、甲基丙烯酸甲酯、甲基丙烯酸叔 丁酯、甲基丙烯酸异冰片酯、羟甲基丙烯酰胺、丙烯酰胺、苯乙烯、丙烯腈；
    第二单体：包括丙烯酸C4-C22烷基酯、丙烯酸异丁酯、丙烯酸异辛酯、丙烯酸叔丁酯、丙烯酸-2-乙基己酯(异辛酯)、丙烯酸环己酯、甲基丙烯酸乙酯、甲基丙烯酸异丁酯、甲基丙烯酸-2-乙基己酯、甲基丙烯酸正己酯、甲基丙烯酸环己酯、甲基丙烯酸苄酯、丙烯酸-2-羟乙酯、丙烯酸-2-羟丙酯、甲基丙烯酸亚乙基脲乙酯、甲基丙烯酸双环戊烯乙氧基酯、甲基丙烯酸四氢呋喃酯、甲基丙烯酸三氟乙酯、甲基丙烯酸二甲氨基乙酯、甲基丙烯酸二乙氨基乙酯、甲基丙烯酸亚乙基脲乙酯、甲基丙烯酸丙烯酯、甲基丙烯酸双环戊烯乙氧基酯、甲基丙烯酸四氢呋喃酯、甲基丙烯酸三氟乙酯；
    第三单体：包括甲基丙烯酸-2-羟乙酯、甲基丙烯酸-2-羟丙酯、丙烯酸缩水甘油酯、甲基丙烯酸缩水甘油酯、甲基丙烯酸二甲氨基乙酯、甲基丙烯酸二乙氨基乙酯、乙烯基三甲氧基硅烷、乙烯基三乙氧基硅烷、乙烯基三异丙氧基硅烷、γ-甲基丙烯酰氧基丙基三甲氧基硅烷、N-羟甲基丙烯酰胺、N-丁氧甲基(甲基)丙烯酰胺、二丙酮丙烯酰胺(DAAM)、甲基丙烯酸乙酰乙酸乙酯(AAEM)、二乙烯基苯、环氧值在0.35-0.50的环氧树脂、二乙烯苯；
    反应型分散剂：包括聚乙烯醇、聚丙烯醇、聚丙烯乙二醇、聚乙二醇、聚乙烯酸醇。
  7. 根据权利要求1-6中任一项所述的隔离膜，其中所述增塑剂选自以下中的一种或几种：甘油C4-C10烷基二醚或者单醚、甘油C4-C10羧酸单酯或者二酯、丙二醇C4-C10烷基单醚、甘油。
  8. 根据权利要求1-7中任一项所述的隔离膜，其中所述压力敏感涂层的平均厚度为2-20μm，可选为2-15μm。
  9. 根据权利要求1-8中任一项所述的隔离膜，其中所述第一有机颗粒的平均粒径为5-30μm，可选为5-20μm；
    可选地，所述第一有机颗粒的DSC熔点为-50℃-200℃，可选为-40℃-160℃；
    可选地，所述第一有机颗粒的重均分子量为300×10 3g/mol-800×10 3g/mol，可选为400×10 3g/mol-650×10 3g/mol；
    可选地，所述第一有机颗粒为包含一种或几种选自以下的基团的一种或几种聚合物：卤素、苯基、环氧基、氰基、酯基和酰胺基；
    可选地，所述第一有机颗粒为选自以下的至少一种：含氟烯基单体单元的均聚物或共聚物，烯烃基单体单元的均聚物或共聚物，不饱和腈类单体单元的均聚物或共聚物，环氧烷类单体单元的均聚物或共聚物，单糖类单体单元的二聚物、均聚物或共聚物，以及上述各均聚物或共聚物的改性化合物；
    进一步可选地，所述第一有机颗粒为选自以下的至少一种：聚全氟乙烯、聚偏二氟乙烯、聚偏二氟乙烯-共-六氟丙烯、聚偏二氟乙烯-共-三氯乙烯、聚苯乙烯-共-甲基丙烯酸甲酯、聚苯乙烯-共-丙烯酸丁酯、聚甲基丙烯酸甲酯、聚丙烯腈、聚乙酸乙烯酯、聚乙烯-共-乙酸乙烯酯、聚酰亚胺、聚环氧乙烷、乙酸纤维素、乙酸丁酸纤维素、乙酸丙酸纤维素、氰基乙基普鲁兰、氰基乙基聚乙烯醇、氰基乙基纤维素和氰基乙基蔗糖；
    更进一步可选地，所述第一有机颗粒为选自以下中的至少一种：聚偏二氟乙烯-共-六氟丙烯、聚苯乙烯-共-丙烯酸丁酯、聚全氟乙烯、聚偏二氟乙烯、聚偏二氟乙烯-共-三氯乙烯。
  10. 根据权利要求1-9中任一项所述的隔离膜，其中所述第一有机颗粒和第二有机颗粒的质量比为(1-4):1，可选为(1.5-2.5):1。
  11. 根据权利要求1-10中任一项所述的隔离膜，其中所述第二有机颗粒的平均粒径为0.5-10μm，可选为2-8μm；
    可选地，所述第二有机颗粒的DSC熔点为-30-100℃，可选为-30-70℃；
    可选地，所述第二有机颗粒的重均分子量为10×10 3g/mol-100×10 3g/mol，可选为20×10 3g/mol-80×10 3g/mol；
    可选地，所述第二有机颗粒为包含一种或几种选自以下的基团的一种或几种聚合物：苯基、环氧基、氰基、酯基、羟基、羧基、磺酰酯基和吡咯烷酮基；
    可选地，所述第二有机颗粒为选自以下的至少一种：丙烯酸酯类单体单元的均聚物或共聚物，丙烯酸类单体单元的均聚物或共聚物，不饱和腈类单体单元的均聚物或共聚物，烯类单体单元的均聚物或共聚物，苯乙烯类单体单元的均聚物或共聚物，环氧类单体单元的均聚物或共聚物，聚氨酯类化合 物，橡胶类化合物，单糖类单体单元的二聚物、均聚物或共聚物，以及上述各均聚物或共聚物的改性化合物；
    进一步可选地，所述第二有机颗粒为选自以下的至少一种：聚甲基丙烯酸甲酯、聚丙烯腈、聚乙烯吡咯烷酮、聚乙酸乙烯酯、聚乙烯-共-乙酸乙烯酯、聚苯乙烯-共-甲基丙烯酸甲酯、聚苯乙烯-共-丙烯酸丁酯、聚环氧乙烷、乙酸纤维素、乙酸丁酸纤维素、乙酸丙酸纤维素、氰乙基普鲁兰多糖、氰乙基聚乙烯醇、氰乙基纤维素、氰乙基蔗糖、普鲁兰多糖、羧甲基纤维素、丙烯腈-苯乙烯-丁二烯共聚物、苯乙烯-丙烯酸丁酯-丙烯酸异辛酯共聚物和聚酰亚胺。
  12. 根据权利要求1-11中任一项所述的隔离膜，其中所述隔离膜基体的孔隙率为10-95％，孔径为20-60nm，厚度为3-12μm，可选为5-9μm；
    可选地，所述隔离膜基体包括选自以下的一种或几种的膜或非织造物：聚乙烯、聚丙烯、聚对苯二甲酸乙二醇酯、聚对苯二甲酸丁二醇酯、聚酯、聚缩醛、聚酰胺、聚碳酸酯、聚酰亚胺、聚醚醚酮、聚芳基醚酮、聚醚酰亚胺、聚酰胺酰亚胺、聚苯并咪唑、聚醚砜、聚苯醚、环烯烃共聚物、聚苯硫醚和聚乙烯萘。
  13. 权利要求1-12中任一项所述的隔离膜的制备方法，其包括以下步骤：
    S1)将第一有机颗粒和分散剂加入溶剂中以形成第一聚合物溶液；
    S2)将压力敏感型粘合剂聚合物加入步骤S1)得到的第一聚合物溶液中，混合以形成第二聚合物溶液；
    S3)任选地，在步骤S2)得到的第二聚合物溶液中加入第二有机颗粒，混合以形成第三聚合物溶液；和
    S4)将步骤S2)得到的第二聚合物溶液或步骤S3)得到的第三聚合物溶液涂布到多孔的隔离膜基体的至少一个表面上，干燥后得到隔离膜；
    其中所述隔离膜包括在所述隔离膜基体的至少一个表面上形成的压力敏感涂层，其包括40-90wt％的第一有机颗粒和10-20wt％的压力敏感型粘合剂聚合物，和任选的0-50wt％的第二有机颗粒；其中所述压力敏感型粘合剂聚合物包括粘合剂聚合物和增塑剂。
  14. 一种二次电池，其包括正极片、负极片、间隔于正极片和负极片之间的隔离膜，以及电解液，其中所述隔离膜为权利要求1-12中任一项所述的隔离膜或权利要求13所述的制备方法获得的隔离膜。
  15. 一种用电装置，其包括选自权利要求14所述的二次电池。
PCT/CN2021/143069 2021-12-30 2021-12-30 隔离膜及其制备方法以及包含该隔离膜的二次电池和用电装置 Ceased WO2023123205A1 (zh)

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