WO2023087735A1 - 一种新型交联隔膜及其制备方法、电池及电子设备 - Google Patents

一种新型交联隔膜及其制备方法、电池及电子设备 Download PDF

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WO2023087735A1
WO2023087735A1 PCT/CN2022/103584 CN2022103584W WO2023087735A1 WO 2023087735 A1 WO2023087735 A1 WO 2023087735A1 CN 2022103584 W CN2022103584 W CN 2022103584W WO 2023087735 A1 WO2023087735 A1 WO 2023087735A1
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linked
cross
diaphragm
separator
coating
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PCT/CN2022/103584
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English (en)
French (fr)
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邱长泉
李堃
彭锟
宫晓明
蔡裕宏
虞少波
庄志
程跃
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苏州捷力新能源材料有限公司
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Publication of WO2023087735A1 publication Critical patent/WO2023087735A1/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
    • H01M50/449—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
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/26—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof by elimination of a solid phase from a macromolecular composition or article, e.g. leaching out
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/36—After-treatment
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/36—After-treatment
    • C08J9/365—Coating
    • 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
    • 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
    • H01M50/431—Inorganic material
    • H01M50/434—Ceramics
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2351/00—Characterised by the use of graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Derivatives of such polymers
    • C08J2351/06—Characterised by the use of graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Derivatives of such polymers grafted on to homopolymers or copolymers of aliphatic hydrocarbons containing only one carbon-to-carbon double bond
    • 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 application relates to the field of battery diaphragms, in particular to a novel cross-linked diaphragm, a preparation method thereof, batteries and electronic equipment.
  • Lithium-ion batteries are currently commercialized and widely used secondary power sources.
  • the separator is a porous, electrochemically inert medium between the positive and negative electrodes that does not participate in electrochemical reactions but is critical to the safety performance of the cell.
  • the polyolefin separators commonly used today may have some drawbacks.
  • the poor ductility of the separator may cause the separator to be punctured when the cell is mechanically abused.
  • Another example is that the closed cell temperature of the separator is high, so when the cell is overheated, it is difficult to cut off the electrochemical pathway.
  • the rupture temperature of the separator is low, so that the separator will melt when the cell is overheated.
  • the above-mentioned defects can easily lead to damage of the separator and the formation of a short circuit point between the positive and negative electrodes, thereby causing potential safety hazards.
  • the present application provides a novel cross-linked separator and its preparation method, battery and electronic equipment to partially or completely improve or even solve the problems of poor mechanical and heat resistance of battery separators in the related art.
  • the application provides a novel cross-linked diaphragm, including a UV cross-linked upper surface layer, a core layer, and a UV cross-linked lower surface layer; the UV cross-linked upper surface layer and/or the UV cross-linked lower surface layer include a cross-linking agent and a light
  • the initiator comprises a polyolefin composition in the core layer; the thickness of the novel cross-linked diaphragm is 0.5-12 ⁇ m; the sum of the thicknesses of the ultraviolet cross-linked upper surface layer and the ultraviolet cross-linked lower surface layer is 20%-80% of the thickness of the novel cross-linked diaphragm %;
  • the rupture temperature of the new cross-linked membrane is 191-215°C.
  • the crosslinking agent is a bifunctional or multifunctional monomer with an ethylenic double bond, including at least one of the following: 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, divinylbenzene, bis Maleate diacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, triallyl isocyanurate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, and dipentaerythritol Hexaacrylate.
  • the photoinitiator is a free radical polymerization photoinitiator or a cationic polymerization photoinitiator, including at least one of the following: benzoin, benzoin dimethyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin butyl ether, diphenyl ethyl ketone , ⁇ , ⁇ -Dimethoxy- ⁇ -phenylacetophenone, ⁇ , ⁇ -diethoxyacetophenone, ⁇ -hydroxyalkylphenone, ⁇ -aminoalkylphenone, aroylphosphine oxidation Bisbenzoylphenylphosphine oxide, benzophenone, 2,4-dihydroxybenzophenone, Michler's ketone, thiopropoxythioxanthone, isopropylthioxanthone, di Aryliodonium salts, triaryliodonium salts, alkyliodonium
  • the core layer includes a polyolefin composition
  • the polyolefin composition includes first polyethylene and second polyethylene.
  • the first polyethylene and the second polyethylene are selected from any one of the following: polyethylene, polyethylene-propylene copolymer, derivatives of polyethylene-propylene copolymer, polyethylene-butene copolymer, polyethylene- Butene copolymer derivatives, polyethylene-hexene copolymers, polyethylene-hexene copolymer derivatives, polyethylene-octene copolymers, polyethylene-octene copolymer derivatives, polystyrene- Ethylene-styrene copolymers, derivatives of polystyrene-ethylene-styrene copolymers, polystyrene-ethylene-butylene-styrene copolymers, derivatives of polystyrene-ethylene-butylene-styrene copolymers Polyethylene-hydrogenated
  • the polyolefin composition also includes polypropylene or its derivatives.
  • the enthalpy ⁇ Hm of polypropylene or its derivatives is 55-85 J/g, and the density is ⁇ 0.9 g/cm 3 .
  • the viscosity average molecular weight of the polyolefin composition is between 30 ⁇ 10 4 and 1000 ⁇ 10 4 . Further, the viscosity average molecular weight of the polyolefin composition is between 110 ⁇ 10 4 and 500 ⁇ 10 4 .
  • the core layer also includes polyolefin emulsion.
  • the novel cross-linked separator satisfies at least one of the following: both transverse and longitudinal elongation ⁇ 120%; both transverse and longitudinal tensile modulus ⁇ 2000MPa; ratio of longitudinal tensile modulus to transverse tensile modulus ⁇ 0.9; At 120°C, both transverse and longitudinal thermal shrinkage rates are ⁇ 1.8%; porosity is 20%-85%; puncture strength is 650-1400gf; transverse and longitudinal tensile strengths are both ⁇ 2000kgf/cm 2 ; air permeability is ⁇ 172s/100cc/ 5 ⁇ m.
  • the bidirectional elongation at break of the novel cross-linked separator is preferably 120% or less, more preferably 50-120%, and even more preferably 80-120%. It should be noted that within a certain range, appropriately increasing the bidirectional elongation at break of the new cross-linked separator will help reduce the safety problems caused by the expansion and contraction of the battery winding body during charging and discharging (the bidirectional fracture of the new cross-linked separator The elongation may be, for example, 50% or more).
  • the bi-directional elongation at break of the new cross-linked diaphragm is conducive to improving the mechanical strength and thermal stability of the new cross-linked diaphragm (the bi-directional elongation at break of the new cross-linked diaphragm can be, for example, less than 120%) .
  • the longitudinal and transverse tensile strength of the new cross-linked diaphragm is ⁇ 2000kgf/cm 2 , preferably, the longitudinal and transverse tensile strength of the novel cross-linked diaphragm is greater than or equal to 3000kgf/cm 2 ; preferably, the longitudinal and transverse tensile strength of the novel cross-linked diaphragm Strength ⁇ 4000kgf/cm 2 ; preferably, the longitudinal and transverse tensile strength of the novel cross-linked separator ⁇ 4500kgf/cm 2 .
  • the ratio of longitudinal/transverse tensile strength of the novel cross-linked separator is preferably 0.9 or more, preferably 0.96-1.16.
  • the longitudinal and transverse tensile modulus of the novel cross-linked separator is ⁇ 3000Mpa.
  • the longitudinal and transverse tensile modulus of the new cross-linked diaphragm ⁇ 3500Mpa; more preferably, the longitudinal and transverse tensile modulus of the novel cross-linked diaphragm ⁇ 4000Mpa; most preferably, the longitudinal and transverse modulus of the novel cross-linked diaphragm)
  • Tensile modulus ⁇ 4500Mpa Tensile modulus ⁇ 4500Mpa.
  • the ratio of longitudinal/transverse tensile modulus of the novel cross-linked separator is preferably 0.9-1.2, preferably 0.91-1.1. Increasing the tensile modulus of the separator is beneficial to winding the battery core with the separator and processing the coating on the separator.
  • the puncture strength of the novel cross-linked separator is preferably 400-1400 gf, preferably 500-1400 gf, preferably 600-1400 gf, preferably 650-1400 gf. It should be noted that improving the puncture strength of the new cross-linked separator is conducive to improving the safety of the new cross-linked separator, and is conducive to winding the battery core and processing the coating.
  • the thickness of the novel cross-linked separator provided in this example is 0.5-12 ⁇ m, preferably 1-9 ⁇ m, more preferably 5-6 ⁇ m. It should be noted that within a certain range, appropriately reducing the thickness of the new cross-linked separator will not only help to improve the ion transmission efficiency in the battery cell, but also help to improve the energy density of the battery (for example, the thickness is less than 9 ⁇ m). Moreover, within a certain range, appropriately increasing the thickness of the new cross-linked separator will help reduce the self-discharge inside the battery cell, help to improve the isolation ability of the new cross-linked separator, and then help to improve battery safety (for example, the thickness is more than 3 ⁇ m ). Further, the sum of the thicknesses of the ultraviolet crosslinking upper surface layer and the ultraviolet crosslinking lower surface layer is 20% to 75% of the thickness of the novel crosslinking membrane.
  • the closed cell temperature of the novel cross-linked separator is 95-150°C, preferably 95-121°C, more preferably 140-142°C. It should be noted that within a certain range, appropriately increasing the closed-cell temperature of the new cross-linked separator will help prevent the battery from melting during normal use, thereby improving the thermal stability of the battery (closed-cell temperature above 140°C). Within a certain range, appropriately reducing the closed cell temperature of the new cross-linked separator is beneficial to improve the safety of the battery (the closed cell temperature of the new cross-linked separator is below 150°C, preferably below 142°C).
  • the rupture temperature of the novel cross-linked membrane is 191-215°C, preferably 209-215°C. It should be noted that appropriately increasing the membrane rupture temperature of the new cross-linked separator is conducive to improving the safety of the battery under high temperature conditions (for example, in an abnormal thermal environment, the membrane rupture temperature is preferably above 209°C). Further, the difference between the closed cell temperature and the membrane rupture temperature is between 49°C and 103°C.
  • the air permeability of the novel cross-linked membrane is preferably 100-172 s/100 cc, more preferably 150-172 s/100 cc, still more preferably 150-163 s/100 cc, still more preferably 150-155 s/100 cc. It should be noted that within a certain range, appropriately increasing the air permeability of the new cross-linked separator is beneficial to reduce the self-discharge failure rate (for example, the air permeability is above 100s/100cc). Within a certain range, appropriately reducing the air permeability of the new cross-linked separator is conducive to improving the transmission efficiency of ions in the cell (for example, the air permeability is below 172s/100cc).
  • crosslinking density of the novel crosslinked separator is 12-72%.
  • the porosity of the novel cross-linked membrane is preferably 20%-30%.
  • the coating includes one or more of organic coating, inorganic coating and organic/inorganic composite coating.
  • the inorganic coating includes ceramic coating.
  • the ceramic coating includes at least one of the following: aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, zinc oxide, barium oxide, magnesium oxide, beryllium oxide, calcium oxide, thorium oxide, aluminum nitride, titanium nitride, boehmite , apatite, aluminum hydroxide, magnesium hydroxide, barium sulfate, boron nitride, silicon carbide, silicon nitride, cubic boron nitride, hexagonal boron nitride, mesoporous molecular sieves (MCM-41, SBA-15) and layer of pearl mica.
  • the organic coating includes at least one of the following: polyvinylidene fluoride coating, vinylidene fluoride-hexafluoropropylene copolymer coating, polystyrene coating, aramid fiber coating, polyacrylate or its modification coating, polyester coating, polyarylate coating, polyacrylonitrile coating, aramid coating, polyimide coating, polyethersulfone coating, polysulfone coating, polyetherketone coating layer, polyetherimide coating, polybenzimidazole coating and polydopamine.
  • the organic/inorganic composite coating can be prepared by mixing the above-mentioned inorganic coating with an organic coating.
  • the application provides a method for preparing a novel cross-linked diaphragm, comprising the following steps:
  • the polyolefin composition in S1 includes one or more of polyethylene, polyethylene copolymer, polypropylene and polypropylene derivatives with different viscosity-average molecular weights. Further, the selection of the polyolefin composition such as the first polyethylene and the second polyethylene will not be repeated here. Further, the polyolefin composition also includes polypropylene or its derivatives.
  • the enthalpy ⁇ Hm of polypropylene or its derivatives is 55-85 J/g, more preferably in the range of 60-80 J/g; the density is preferably 0.9 g/cm 3 or more, more preferably 0.91 g/cm 3 or more.
  • the polyethylene and its derivatives in the polyolefin composition can be blended with polypropylene and its derivatives, and the polypropylene can be interspersed in the polyethylene to form relatively fine crystals instead of forming large platelets. This is conducive to improving the comprehensive performance of the new cross-linked separator.
  • By optimizing the enthalpy ⁇ Hm of polypropylene it is beneficial to improve the thermal stability of polyolefin microporous membrane and the compatibility with polyethylene materials.
  • the density of polyethylene is preferably 0.85-0.99 g/cm 3 ; more preferably 0.91-0.97 g/cm 3 , and still more preferably 0.92-0.95 g/cm 3 .
  • the compatibility of polyethylene with polypropylene can be changed (when the polyolefin composition described below contains polypropylene).
  • optimizing the density of polyethylene is also conducive to optimizing the degree of delamination of polyethylene or polypropylene.
  • polyethylene Due to the different viscosity average molecular weight, polyethylene has different strength and extensibility, and can have good toughness and processability. Therefore, a separator with a certain degree of crosslinking prepared by polyethylene, crosslinking agent and photoinitiator can have relatively high elongation, excellent strength and thermal stability at the same time. Screening polyethylene with a suitable viscosity-average molecular weight can balance the risk of reduced elongation due to crosslinking.
  • Increasing the proportion of the cross-linking agent in the polyolefin composition of the new cross-linked diaphragm will help reduce the possibility of uneven ultraviolet radiation of the new cross-linked diaphragm, reduce the number of melt crystal points in the new cross-linked diaphragm, and help Improve the quality of a new type of cross-linked separator. Moreover, it is also beneficial to increase the membrane rupture temperature of the novel crosslinked membrane.
  • polyethylene with a relatively high viscosity-average molecular weight can be cut and interspersed between polypropylene molecular chains, which is beneficial to improve the incompatibility of polyethylene and polypropylene.
  • relatively consistent phase separation characteristics can be formed, which is beneficial to prevent excessive deviation of the thickness of the separator.
  • a cobalt source or an electron accelerator is used for pre-irradiation.
  • Pre-irradiation is to use an electron accelerator to irradiate the polyolefin composition material with low dose before mixing and extruding, so that macromolecules such as polyethylene in the polyolefin composition will generate a small amount of free radicals under the action of high-energy radiation.
  • the originally stable polyolefin chain ends can be activated, so that it can be quickly cross-linked under extremely short exposure to ultraviolet light, thereby controlling and deepening the degree of cross-linking;
  • this method can reduce processing difficulty, shorten the subsequent UV crosslinking time, control the degree of crosslinking, improve production efficiency, improve mechanical properties and membrane rupture temperature.
  • the raw material mixture of S2 also includes a polyolefin emulsion, which is a polyethylene wax emulsion with a solid content of 10% to 70%; the melting point of solid particles is 80 to 135°C, preferably 80 to 120°C, Preferably 80-90°C, preferably 110-120°C.
  • the selection of the melting point of solid particles is related to the closed cell temperature.
  • the upper limit should preferably be lower than the melting point of different polyolefin separators.
  • the upper limit is preferably 135°C. Therefore, when the polyolefin separator is UHMWPE, its melting point is around 135°C. At this time, the melting point is preferably low.
  • the coating formed by the polymer emulsion at 135°C can have a closed cell temperature lower than that of the PE separator, improving the overall safety performance of the battery.
  • Other temperatures depend on the different polyolefin materials and the preference when lowering the closed cell temperature of the separator is desired.
  • the raw material mixture of S2 may also include at least one of the following: antioxidants: such as phenols, amines, phosphites or thiodipropionates, etc.; stabilizers: such as sodium stearate, hard Calcium stearate, magnesium stearate or zinc stearate, etc.; antistatic agent, radiation light absorber, light stabilizer, nucleating agent or inorganic particles, etc.
  • the raw material mixture of S2 may also include thermoplastic resins other than polyolefin.
  • the raw material mixture of S2 may also include at least one of the following: linear low-density polyethylene, branched polyethylene, polymethyl methacrylate, polyvinylidene fluoride, or polyacrylonitrile.
  • the area after biaxial stretching is 10 to 50 times the area before biaxial stretching.
  • the weight of the crosslinking agent is between 1 and 20 parts, and the weight of the photoinitiator is between 0.1 and 2 parts.
  • the weight of crosslinking agent is more preferably between 1 ⁇ 15 parts, more preferably between 1 ⁇ 10 parts, more preferably between 1 ⁇ 2 parts, most preferably between 1 ⁇ 1.5 parts;
  • the weight is more preferably between 0.5 and 1.5 parts, more preferably between 0.7 and 1.2 parts.
  • appropriately reducing the proportion of the cross-linking agent in the raw material mixture of the new cross-linked diaphragm is conducive to further improving the polyolefin microporous membrane.
  • Cross-linking efficiency and reduced processing difficulty is conducive to further improving the polyolefin microporous membrane.
  • appropriately increasing the proportion of the crosslinking agent in the raw material mixture is beneficial to reduce the insufficient crosslinking density of the new crosslinked diaphragm possibility, which is conducive to improving the mechanical properties of the novel crosslinked separator.
  • the low-ratio stretching is 1-3 times stretching, and the stretching temperature of the low-ratio stretching is 105-135° C.; the retraction ratio of the retraction operation is between 0.5-10%.
  • the wavelength range of the ultraviolet rays in S5 is between 230-350nm; the ultraviolet radiation time in S5 is 0.2-1s; the ultraviolet radiation power in S5 is 1-4Kw.
  • the purpose of the present application is to provide a battery including a positive electrode, a negative electrode, an electrolyte and the novel cross-linked separator provided in the first aspect or the second aspect.
  • the purpose of this application is to provide an electronic device, including a housing, a display screen housed in the housing, a circuit board assembly, and the battery provided in the third aspect; the battery supplies power to the display screen and the circuit board assembly .
  • the beneficial effects of the present application include: combining the polyolefin composition with a cross-linking agent and a photoinitiator in a specific way can form a new type of cross-linked membrane with high toughness, ultra-high membrane rupture temperature and high puncture strength; according to tests, the present invention
  • the novel cross-linked membrane with a thickness of 5-6 ⁇ m provided by the application can have a membrane rupture temperature of 191-215°C and a closed cell temperature of 95-121°C.
  • the new crosslinked separator of the present application has a relatively high membrane rupture temperature and a large safety range of 49-103°C.
  • the novel cross-linked separator provided by the application is beneficial to improving the mechanical abuse resistance and thermal abuse resistance of the battery, thereby improving the safety of electronic equipment and mobile devices containing the battery.
  • Figure 1 is a schematic structural view of the novel cross-linked membrane provided by the present application.
  • a diaphragm can include a diaphragm substrate and a diaphragm coating.
  • Base separator It can refer to the polyolefin microporous membrane part of the diaphragm.
  • the separator substrate can be used alone in the cell.
  • the separator base material can provide the aforementioned porosity and the aforementioned insulating properties.
  • the novel cross-linked diaphragm described in this application is the diaphragm substrate.
  • Separator coating layer Can refer to a thin layer attached to a separator substrate.
  • the separator coating can be attached to the separator substrate by means of additive manufacturing.
  • the separator coating can be used to enhance the performance of the separator, such as improving the heat resistance and adhesion of the separator.
  • the core core or cell
  • a cell can include positive and negative electrodes.
  • Heat Abuse It can refer to the abuse of the battery in terms of heat (or high temperature).
  • a hot box can be used to test the battery cell for thermal abuse (such as using a high temperature ( ⁇ 130°C) to bake the battery cell).
  • Mechanical abuse (Machenical ab ⁇ se): It can refer to the mechanical abuse of the battery. Cells can be tested for mechanical abuse using needle penetration tests, impact tests, etc.
  • Elongation It can also be called the elongation at break, which can refer to the percentage of the length increment when the diaphragm is broken relative to the initial length. Specifically, a tensile test can be performed on the diaphragm under specific conditions, and when the diaphragm is just broken, the increase in the length of the diaphragm divided by the initial length of the diaphragm can be used to characterize the elongation. The larger the elongation value, the less likely the diaphragm will be broken and the better the elongation.
  • the elongation can be divided into longitudinal (MD, ie along the long side of the separator) elongation and transverse (TD, perpendicular to MD, ie along the short side of the separator) elongation.
  • Tensile modulus (Tensile mod ⁇ l ⁇ s): It can refer to the tensile strength under certain stretching conditions, that is, the ratio of the force per unit length required by the diaphragm along the stretching direction to the cross-sectional area of the diaphragm. Tensile modulus can be divided into longitudinal (MD, ie along the long side direction of the separator) tensile modulus and transverse direction (TD, perpendicular to MD, ie along the short side direction of the separator) tensile modulus.
  • MD longitudinal
  • TD transverse direction
  • Tensile strength It can refer to the critical strength value of the plastic deformation of the diaphragm, which can characterize the maximum bearing capacity of the diaphragm under uniform stretching conditions.
  • the tensile strength may refer to the stress obtained by dividing the maximum load force borne by the diaphragm by the initial cross-sectional area of the diaphragm when the diaphragm is just pulled off.
  • the tensile strength is divided into longitudinal (MD, ie along the long side direction of the separator) tensile strength and transverse direction (TD, perpendicular to MD, ie along the short side direction of the separator) tensile strength.
  • Puncture strength P ⁇ nct ⁇ re strength
  • Heat shrinkage It can refer to the size change of the diaphragm before and after heating in the longitudinal/transverse direction (longitudinal MD, that is, along the long side of the diaphragm; transverse TD, perpendicular to MD, that is, along the short side of the diaphragm) Rate.
  • the test method of thermal shrinkage rate may include: measuring the size of the diaphragm in the longitudinal/transverse (MD/TD) direction; placing a diaphragm with a certain size in the longitudinal/transverse (MD/TD) direction in an incubator; Oven to a specific temperature; measure the dimension of the separator in the longitudinal/transverse (MD/TD) direction after heating.
  • Viscosity-average Molec ⁇ lar Weight It can be one of the common expressions of polymer molecular weight. Polymers may have polydispersity and polymer molecular weight generally refers to the average molecular weight of the polymer. Various types of average molecular weights can be obtained by various molecular weight average methods. The molecular weight of the polymer detected by the dilute solution viscosity method may be the viscosity average molecular weight. Molecular weight distribution (distrib ⁇ tion of molec ⁇ lar weight): the ratio of weight average molecular weight to number average molecular weight or the ratio of viscosity average molecular weight to weight average molecular weight.
  • Porosity It can refer to the percentage of the pore volume in the diaphragm to the total volume of the diaphragm.
  • the porosity P satisfies: Where V can be the total volume of the diaphragm, m can be the mass of the diaphragm, and ⁇ can be the skeleton density (or true density) of the diaphragm.
  • Air permeability (G ⁇ rley): It can refer to the degree to which the membrane allows gas to pass through. The air permeability can be obtained by measuring the time required for a unit volume of gas (100cc) to pass through the membrane at a specific pressure (0.05MPa).
  • Hole size It can refer to the diameter of the through hole in the diaphragm. The pore size is measured by a pore size analyzer.
  • Crystallinity It can be obtained by differential scanning calorimetry (DSC) test.
  • the crystallinity of the polyolefin diaphragm can be obtained by the following method: calculate the melting endothermic curve of the polyolefin diaphragm during the process from the beginning of heating to the generation of heat transition enthalpy, and obtain the melting enthalpy value (in joules (J)); The melting enthalpy value was divided by the mass (g) of the sample to obtain the mass-normalized melting enthalpy ( ⁇ Hs) of the polyolefin separator.
  • the mass-normalized enthalpy of fusion ( ⁇ Hs) was then divided by the enthalpy of fusion ( ⁇ Hf) of 100% crystalline polyolefin to obtain the crystallinity X (%) of the polyolefin separator.
  • Closure temperature (Obt ⁇ rator temperat ⁇ re): It can refer to the temperature at which the diaphragm begins to melt and block a part of the previously formed pores during the heating process.
  • Membrane rupture temperature (R ⁇ pt ⁇ re temperat ⁇ re): It can refer to the temperature at which the diaphragm melts to a certain extent and ruptures to cause a partial or comprehensive short circuit.
  • the specific embodiment of the present application provides a separator substrate (namely, a novel cross-linked separator, and the separator substrates hereinafter all refer to the novel cross-linked separator).
  • the membrane substrate can be a microporous membrane, comprising a polyolefin composition.
  • the separator substrate may include a polyolefin composition, a crosslinking agent and a photoinitiator, wherein the crosslinking agent cannot be crosslinked by thermal radiation.
  • the diaphragm substrate may be a porous insulating material. The pores on the diaphragm substrate can pass through lithium ions (the pores on the diaphragm substrate can be the transmission channels of lithium ions).
  • the separator substrate may include, for example, a polyolefin-based material.
  • the membrane substrate may also be referred to as a polyolefin porous membrane substrate.
  • Polyolefin-based materials provide the separator with chemical inertness, electrochemical inertness, porosity, electronic insulation, etc.
  • the separator substrate as the main component of the separator, needs to have properties such as high ductility, high membrane rupture temperature, and low cell closure temperature.
  • Polyolefinic materials may include polyethylene, for example.
  • polyethylene Due to the different viscosity average molecular weight, polyethylene has different strength and extensibility, and can have good toughness and processability. Therefore, a separator with a certain degree of crosslinking prepared by polyethylene containing a crosslinking agent and a photoinitiator can have relatively high elongation, excellent strength and thermal stability at the same time. Screening polyethylene with a suitable viscosity-average molecular weight can balance the risk of reduced elongation due to crosslinking.
  • the polyolefin composition comprises at least one of the following: polyethylene, polyethylene-propylene copolymers, derivatives of polyethylene-propylene copolymers, polyethylene-butene copolymers, polyethylene-butene Derivatives of copolymers, polyethylene-hexene copolymers, derivatives of polyethylene-hexene copolymers, polyethylene-octene copolymers, derivatives of polyethylene-octene copolymers, polystyrene-ethylene- Styrene copolymers, derivatives of polystyrene-ethylene-styrene copolymers, polystyrene-ethylene-butylene-styrene copolymers, derivatives of polystyrene-ethylene-butylene-styrene copolymers, Polyethylene-hydrogenated oligocyclopentadiene, derivatives of polyethylene-hydrogenated oligocyclopentadiene, polyethylene-hydrogenated
  • copolymers may have problems such as unstable film formation and difficult control of molecular weight distribution.
  • the propylene copolymer may comprise ethylene-propylene block copolymers and/or random copolymers.
  • the proportion of the ethylene-propylene block copolymer in the propylene copolymer is higher than that of the random copolymer in the propylene copolymer. Possible reasons may include that the melting point of ethylene-propylene block copolymers is generally higher than that of random copolymers.
  • the separator may also include a separator coating.
  • the diaphragm coating can be attached to one side or both sides of the diaphragm substrate to facilitate the properties of the diaphragm such as high ductility, high membrane rupture temperature, and low cell closure temperature.
  • the membrane coating can also have other properties, such as relatively high adhesion and the like.
  • the separator coating may include one or more of organic coatings, inorganic coatings, and organic-inorganic composite coatings.
  • Inorganic coatings may include ceramic coatings.
  • the ceramic coating may comprise at least one of the following: alumina, silica, titania, zirconia, beryllium oxide, calcium oxide, thorium oxide, aluminum nitride, titanium nitride, boehmite, apatite, aluminum hydroxide , magnesium hydroxide, barium sulfate, boron nitride, silicon carbide, silicon nitride, cubic boron nitride, hexagonal boron nitride, graphene, mesoporous molecular sieves, etc.
  • the organic coating may include at least one of the following: polyvinylidene fluoride coating, vinylidene fluoride-hexafluoropropylene copolymer coating, polystyrene coating, polyacrylate or its modified coating, polyester coating layer, polyarylate coating, polyacrylonitrile coating, aramid coating, polyimide coating, polyethersulfone coating, polysulfone coating, polyetherketone coating, polyetherimide coating and polybenzimidazole.
  • the organic-inorganic composite coating can be prepared by mixing the above-mentioned inorganic coating with an organic coating.
  • the specific embodiment of the present application also provides a lithium ion secondary battery.
  • the core components of the lithium-ion secondary battery may include positive electrode material, negative electrode material, electrolyte, separator, and corresponding communication accessories and circuits.
  • the positive electrode material and the negative electrode material can deintercalate lithium ions to realize energy storage and release.
  • the electrolyte solution can be a transport carrier for lithium ions between the positive electrode material and the negative electrode material.
  • the positive electrode material and the negative electrode material are the main energy storage parts of the lithium-ion secondary battery, which can reflect the energy density, cycle performance and safety performance of the battery cell.
  • the separator is permeable to lithium ions, but the separator itself is not conductive, so the separator can separate the positive electrode material and the negative electrode material to prevent short circuit between the positive electrode material and the negative electrode material.
  • the positive electrode material may include a positive electrode collector and a positive electrode active material disposed on the positive electrode collector.
  • Positive electrode active materials include but are not limited to lithium composite metal oxides (such as nickel-cobalt lithium manganate, etc.), polyanionic lithium compounds LiMx(PO 4 ) y (M is Ni, Co, Mn, Fe, Ti, V, 0 ⁇ x ⁇ 5, 0 ⁇ y ⁇ 5), etc.
  • the negative electrode material may include a negative electrode current collector and a negative electrode active material disposed on the negative electrode current collector.
  • Negative electrode active materials include but are not limited to at least one of the following: lithium metal, lithium alloy, lithium titanate, natural/artificial graphite, MCMB, amorphous carbon, carbon fiber, carbon nanotube, hard carbon, soft carbon, graphene, graphite oxide alkenes, silicon, silicon-carbon compounds, silicon-oxygen compounds, and silicon-metal compounds.
  • the performance of the separator itself should be conducive to the good charge and discharge performance of the lithium-ion secondary battery. For example, in order to stably and reliably separate the cathode material from the anode material, the separator should have a certain strength and ductility to avoid being punctured, that is, the separator should have a certain resistance to mechanical abuse.
  • the lithium-ion secondary battery itself may generate heat.
  • the separator should also have relatively high stability, that is, the separator should have certain heat resistance or heat abuse resistance.
  • the rupture temperature of the diaphragm can be relatively high, and it is not easy to melt when the cell is overheated.
  • the closed cell temperature of the separator can be relatively low, and the electrochemical pathway between the positive electrode material and the negative electrode material can be relatively easily cut off by the separator when the cell is overheated.
  • the diaphragms in the specific embodiments of the present application all adopt the novel cross-linked diaphragm provided by the present application.
  • the specific embodiment of the present application also provides an electronic device, which can be a terminal consumer product or a 3C electronic product, such as a mobile phone, a mobile power supply, a portable computer, an e-reader, a computer, a digital camera, a vehicle-mounted device, a wearable device, an earphone, etc. .
  • the electronic device is a mobile phone as an example for description.
  • a mobile phone includes a housing, a display, and a circuit board assembly.
  • the housing includes a frame and a rear cover.
  • a bezel wraps around the perimeter of the display and around the perimeter of the back cover.
  • the cavity formed between the display screen, frame, and rear cover can be used to place circuit board components.
  • both the display screen and the circuit board assembly can be disposed on the housing.
  • the handset may also include a power supply for powering circuit board components.
  • the power supply can be a lithium electronic secondary battery, and the novel cross-linked diaphragm provided by the application is used in the battery.
  • Pre-irradiate the polyolefin composition and the irradiation dose is 0.1-1 Mrad to obtain a pre-irradiated polyolefin composition
  • Pre-irradiate the polyolefin composition containing a porogen The mixture of crosslinking agent, photoinitiator and polyethylene wax emulsion is mixed and extruded from a screw extruder to form a gel sheet.
  • polyethylene wax emulsion polyethylene wax emulsion
  • cross-linking agent cross-linking agent
  • photoinitiator for the description of the polyolefin composition, polyethylene wax emulsion, cross-linking agent and photoinitiator, reference can be made to the description above, so there is no need to repeat them here.
  • Step (2) is described in detail below.
  • Step (2) may be referred to as an extrusion casting process for short.
  • the extrusion casting process can specifically be that the mixture containing the polyolefin composition, crosslinking agent, photoinitiator, and pore forming agent is kneaded, extruded, and cast by a screw extruder, and cooled to form a gel sheet. process.
  • the mixture may be mixed by a counter-current mixer, twin-shaft blade mixer, twin-pot mixer, or the like.
  • the mixture may be kneaded at high temperature by a single-screw extruder or a twin-screw extruder.
  • a twin-screw extruder is preferred when the viscosity-average molecular weight of the polyolefin composition is below 500 ⁇ 10 4 .
  • the temperature of the extruder is 150-300°C, preferably 160-260°C, preferably 170-230°C.
  • the temperature of the extruder is beneficial to improve the melting and plasticizing efficiency (the temperature of the extruder is preferably above 150°C, more preferably above 160°C, and even more preferably above 170°C). Lowering the temperature of the extruder helps to prevent the oxidative decomposition of the polyolefin composition, photoinitiator and crosslinking agent mixture (the temperature of the extruder is preferably below 300°C, more preferably below 260°C, further preferably below 230°C ).
  • the method of forming the cast sheet may be, for example, a calendering method, a free bonding method, or the like.
  • the thickness of the gel sheet is preferably 200 to 700 ⁇ m, more preferably 250 to 550 ⁇ m. It should be noted that increasing the thickness of the gel sheet is beneficial to increase the mechanical strength of the separator substrate (the thickness of the gel sheet is preferably 200 ⁇ m or more, more preferably 250 ⁇ m or more). Reducing the thickness of the gel sheet is beneficial to increase the crosslinking density of the separator substrate during ultraviolet light irradiation (the thickness of the gel sheet is preferably less than 700 ⁇ m, more preferably less than 550 ⁇ m).
  • the high-temperature melt casting cooling method may be, for example, air cooling, water cooling, oil cooling, direct contact cooling methods such as bringing the cast sheet into contact with a cooling roll. From the perspective of controlling the thickness of the gel sheet and improving the uniformity of the separator substrate, the embodiment of the present application preferably adopts a cooling roller contact cooling method.
  • the purpose of adding porogen to polyolefin composition, crosslinking agent and photoinitiator mixture is to improve the plasticity of polyolefin mixture.
  • the pore-forming agent may include at least one of the following: hydrocarbon organic solvents (such as paraffin wax, etc.), 2-ethylhexyl phthalate, dibutyl phthalate, alkyl sulfonate, phthalate Butylbenzyl formate, diisononyl phthalate.
  • the embodiment of the present application is preferably liquid paraffin.
  • the porogen can be miscible with the polyolefin composition in any ratio (ie, form a homogeneous organic solvent).
  • the proportion of the polyolefin composition, crosslinking agent and photoinitiator in the mixture is preferably 10-50 parts, more preferably 12-30 parts, and even more preferably 15-25 parts. It should be noted that increasing the proportion of the polyolefin composition in the polyolefin composition, crosslinking agent and photoinitiator is conducive to improving its moldability and processability (the proportion of the polyolefin composition can be, for example, 15 parts above). Reducing the proportion of the polyolefin composition in the polyolefin composition, crosslinking agent and photoinitiator is conducive to improving its porosity (the proportion of the polyolefin composition can be, for example, 95 parts or less).
  • the proportion of the pore forming agent in the mixture is preferably 50-90 parts, more preferably 75-85 parts. Adding a pore forming agent in the mixture is not only beneficial to improving the plasticizing ability of the polyolefin composition, but also beneficial to providing a relatively complete pore structure.
  • the mixture also includes inorganic particles.
  • Inorganic particles can be a pore former.
  • inorganic particles are used in step (2), and at least part of the inorganic particles are removed in the final product, it is beneficial to obtain a relatively high porosity, thereby improving ion transmission efficiency.
  • the way to remove the inorganic particles may be, for example, to use a liquid that can dissolve the inorganic particles. If inorganic particles are used in step (2), and at least part of the inorganic particles are retained in the final finished product, it is beneficial to improve the stability of the diaphragm substrate (such as improving the mechanical properties, heat resistance, etc.) of the diaphragm substrate and extremely properties (that is, to improve the affinity between the separator substrate and the electrolyte).
  • the inorganic particles may include, for example, at least one of the following: aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, zinc oxide, barium oxide, magnesium oxide, beryllium oxide, calcium oxide, thorium oxide, aluminum nitride, titanium nitride, boehmite Stone, apatite, aluminum hydroxide, magnesium hydroxide, barium sulfate, boron nitride, silicon carbide, silicon nitride, cubic boron nitride, hexagonal boron nitride.
  • the size of the inorganic particles can affect the uniformity of mixing.
  • the particle size of the inorganic particles is preferably within a range of 5 to 300 nm, more preferably within a range of 10 to 100 nm, and preferably within a range of 20 to 50 nm.
  • the mixture may also include antioxidants.
  • antioxidants can be added to the mixture. That is, the mixture containing polyolefin composition, crosslinking agent, photoinitiator and antioxidant is kneaded and extruded in a screw extruder.
  • the proportion of the antioxidant in the mixture is preferably 0.1-5 parts, more preferably 0.2-2 parts.
  • Step (3) may be referred to simply as a stretching process.
  • the stretching step may be a step of biaxially stretching the gel sheet.
  • the method of biaxial stretching can be, for example, asynchronous stretching (using the sequential biaxial stretching of speed difference roller stretching machine and guide rail chain tenter combination, that is, stretching on the first axis first, and then stretching on the second axis Stretching upwards), synchronous stretching (simultaneous stretching by using a biaxial tenter, that is, stretching in the first axial direction and the second axial direction at the same time).
  • asynchronous stretching using the sequential biaxial stretching of speed difference roller stretching machine and guide rail chain tenter combination, that is, stretching on the first axis first, and then stretching on the second axis Stretching upwards
  • synchronous stretching simultaneous stretching by using a biaxial tenter, that is, stretching in the first axial direction and the second axial direction at the same time.
  • Asynchronous stretching is beneficial to improve the efficiency of stretch forming.
  • the area ratio in the stretching process is 10 to 200 times, preferably 20 to 70 times. It should be noted that reducing the surface ratio in the stretching process is beneficial to increase the elongation of the separator substrate (eg, less than 50 times). Increasing the surface ratio of the stretching process is beneficial to increasing the porosity or pore transmittance, and is beneficial to improving the thickness consistency of the diaphragm substrate (eg, more than 10 times).
  • the stretching temperature in the stretching process should be selected with reference to the solid content of the polyolefin composition (the solid content may be the mass percentage of the remaining part of the polyolefin composition after drying under specified conditions to the total amount).
  • the stretching temperature in the stretching step is 60 to 110°C, preferably 63 to 108°C, preferably 65 to 106°C. It should be noted that within a certain range, appropriately increasing the stretching temperature in the stretching process (for example, above 60°C) is beneficial to prevent cold stretching caused by too low stretching temperature, which in turn causes insufficient activation of molecular chains (that is, the degree of curing relatively large) resulting in a relatively large stress concentration. Within a certain range, appropriately lowering the stretching temperature in the stretching process (for example, below 110° C.) is conducive to improving the pore structure of the separator.
  • Step (4) may be referred to simply as a porogen removal process.
  • the step of removing the pore-forming agent may specifically remove the pore-forming agent in the gel sheet through an extractant.
  • the extractant can dissolve the pore-forming agent (the extractant can be a good solvent for the pore-forming agent), but is incompatible with the polyolefin material (ie, the extractant cannot dissolve the polyolefin material).
  • the extractant may include, for example, at least one of the following: halogenated hydrocarbons (such as dichloromethane, n-hexane, cyclohexane, etc.), acetone, tetrahydrofuran, ethanol, N-methylpyrrolidone, and the like.
  • the extractant is preferably dichloromethane.
  • the method for removing the pore-forming agent may be immersing the gel sheet in the extractant, or spraying the gel sheet with the extractant to extract the plasticizer, and finally drying the extracted gel sheet.
  • Step (5) may be referred to as a cross-linking process for short.
  • Ultraviolet radiation crosslinking specifically refers to irradiating the film with high-energy ultraviolet rays under certain temperature conditions, activating the crosslinking agent under the catalytic conditions of the photoinitiator, and causing the irradiated layer to produce chemical three-dimensional network crosslinking.
  • the irradiated light may include high-energy ultraviolet light having a wavelength range below 350nm.
  • the crosslinking agent may include, for example, at least one of the following: 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, divinylbenzene, bismaleic acid diacrylate, trimethylolpropane triacrylate ester, trimethylolpropane trimethacrylate, triallyl isocyanurate, pentaerythritol triacrylate, pentaerythritol tetraacrylate and dipentaerythritol hexaacrylate, etc.; Initiators and cationic polymerization photoinitiators, such as benzoin and its derivatives (benzoin, benzoin dimethyl ether, benzoin ethyl ether, benzoin isopropyl ether or benzoin butyl ether), benzils (diphenyl ethyl ketone, ⁇ , ⁇ -dimethoxy- ⁇ -phenylacetophenone), alkyl
  • polyethylene in the case of adding a photoinitiator, polyethylene is converted into an excited state after absorbing ultraviolet energy, and hydrogen abstraction is generated on the polyethylene chain to generate free radicals.
  • it is an infusible material, which loses its fluidity, its heat resistance is significantly improved, and its dimensional stability at high temperature is good. Due to the chemical chain bridges between the molecular chains, the physical and mechanical properties are improved, especially the tensile strength, stiffness, wear resistance, creep resistance and high temperature dimensional stability, and the corresponding elongation at break decreases.
  • the molecular chains of the cross-linked part are restricted, they can also vibrate slightly near the original position to offset the impact energy, so the impact strength is also increased accordingly.
  • the surface layer of the polyethylene separator can be cross-linked, while the closed-cell performance of the inner layer polyethylene is retained.
  • the thickness of the cross-linked layer can be controlled.
  • reducing the wavelength of ultraviolet radiation is beneficial to further improve the crosslinking efficiency of the polyolefin microporous membrane. Moreover, it is also beneficial to prevent wrinkling and creep of the diaphragm base material, and is beneficial to increase the tensile modulus of the diaphragm base material.
  • Step (6) can be referred to as a heat setting process for short.
  • the heat setting process can refer to the low-magnification stretching and retraction operations on the gel sheet under certain temperature conditions to release the stress accumulated in the gel sheet in the previous process, which is conducive to improving the gel sheet. thermal stability.
  • Low-ratio stretching that is, stretching in the heat setting process specifically refers to stretching with a stretching ratio of 3.0 times or less. It should be noted that reducing the stretching ratio in the heat setting process is beneficial to improve the elongation properties of the gel sheet (the stretching ratio in the heat setting step is preferably 2.5 times or less, more preferably 2 times or less). Increasing the stretching ratio in the heat setting process is beneficial to improve the pore structure of the gel sheet (the stretching ratio in the heat setting process is preferably more than 1 time, more preferably more than 1.2 times).
  • the stretching temperature (setting temperature) of the low-ratio stretching is 105 to 135°C, preferably 105 to 130°C, more preferably 108 to 129°C. It should be noted that lowering the stretching temperature in the heat setting process is beneficial to reduce the crystallinity of the gel sheet (the stretching temperature in the heat setting process is preferably below 135° C.). Increasing the stretching temperature in the heat setting process is beneficial to prevent stress concentration and microcracks in the gel sheet (the stretching temperature in the heat setting process is preferably 105° C. or higher).
  • the retracting operation may specifically refer to relaxing the gel sheet by retracting the track, so that the gel sheet is relaxed or in a semi-free state. Reducing the retraction ratio of the retraction operation helps to prevent excessive relaxation, and then helps to increase the pores of the gel sheet, which helps to improve the transmission efficiency of ions (the retraction ratio of the retraction operation is preferably below 10%, more preferably 4.5% or less, more preferably 3% or less).
  • Improving the retraction ratio of the retraction operation is beneficial to reduce the internal stress of the gel sheet and improve the heat shrinkage of the gel sheet (heat shrinkage can refer to the shrinkage phenomenon that occurs under the action of diaphragm stress at high temperature) (retraction operation
  • the shrinkage ratio is 0.5% or more, preferably 1% or more).
  • Step (7) may specifically include rolling and cutting the gel sheet.
  • step (7) the separator substrate or separator provided in the embodiment of the present application can be obtained.
  • the execution sequence and execution times of the above steps (1) to (7) may not be limited.
  • the execution order may be: (1), (2), (3), (4), (5), (6), (7).
  • Executing step (3) before step (4) is conducive to perfecting the pore structure of the diaphragm and improving the mechanical strength of the diaphragm.
  • the execution sequence may be: (1), (2), (4), (3), (5), (6), (7).
  • the execution order may be: (1), (2), (4), (3), (6), (5), (7).
  • Step (3) i.e. stretching process
  • step (4) i.e. removal of porogen process
  • the specific embodiment of the present application also provides a method for manufacturing a lithium ion battery.
  • the principle is that the novel cross-linked separator provided by the application is arranged between the positive electrode material and the negative electrode material (for example, assemble in the order of positive electrode material-diaphragm-negative electrode material or negative electrode material-diaphragm-positive electrode material); The layered parts of the separator, the negative electrode material are wound to obtain a wound body; the wound body is loaded into the battery case; and the electrolyte is injected.
  • the positive electrode material can be obtained in the following manner: a positive electrode active material (such as lithium cobaltate), a conductive agent (such as conductive carbon black, S ⁇ per-P, SP), a binder (such as polyvinylidene fluoride ), mixed in a solvent (such as N-methylpyrrolidone) at a mass ratio of 97:1.5:1.5 to form a positive electrode slurry; through coating equipment, the positive electrode slurry is evenly coated on both sides of the plate (such as aluminum foil); The positive electrode slurry on the plate is dried in an oven to remove the solvent; the positive electrode material on the plate is cold-pressed, stripped, and lug-welded.
  • a positive electrode active material such as lithium cobaltate
  • a conductive agent such as conductive carbon black, S ⁇ per-P, SP
  • a binder such as polyvinylidene fluoride
  • the negative electrode material can be obtained in the following manner: negative electrode active material (such as artificial graphite), thickener (such as carboxymethyl cellulose), binder (such as styrene-butadiene rubber), with 97: The mass ratio of 1.3:1.7 is mixed in a solvent (such as deionized water) to form a negative electrode slurry; through the coating equipment, the negative electrode slurry is evenly coated on both sides of the plate (such as copper foil); The negative electrode slurry is dried to remove the solvent; the negative electrode material on the plate is cold-pressed, stripped, and tab-welded.
  • negative electrode active material such as artificial graphite
  • thickener such as carboxymethyl cellulose
  • binder such as styrene-butadiene rubber
  • the separator can be obtained by coating a separator coating on the surface of the separator substrate.
  • the thickness of the membrane coating may be, for example, 0.5 ⁇ m-10 ⁇ m.
  • the membrane coating may include an inorganic coating (such as a ceramic coating) and an organic coating (such as an oily PVDF coating) disposed on the inorganic coating.
  • the ceramic coating is beneficial to improve the heat resistance of the separator.
  • PVDF coating has a certain bonding performance, which can improve the bonding force between the separator and the positive electrode material (or between the separator and the negative electrode material), so that the separator can be more closely bonded to the positive electrode material or the negative electrode material, thereby improving the battery life.
  • Separator coatings can include organic coatings or hybrid coatings, which are directly coated on the surface of the separator substrate.
  • the above-mentioned positive electrode material, separator and negative electrode material are wound together to make a bare cell.
  • the storage capacity of the bare cell can reach 3.8Ah, for example, and the working voltage of the bare cell can be 3.0-4.43V.
  • the finished lithium-ion battery can be made by encapsulating, baking, injecting liquid, forming and other processes on the bare cell.
  • a. Sampling Dissolve the polyolefin material completely in organic solvents such as decahydronaphthalene and tetrahydrofuran, and prepare a solution with a concentration of 0.5-1.5 mg/mL. Let it stand at room temperature for a period of time without ultrasonication, and filter it with a semi-permeable membrane.
  • GPC gel permeation chromatography
  • Data processing Draw the distribution curve of viscosity and viscosity average molecular weight, which can read the molecular weight distribution.
  • multiple tests can be performed on the polyolefin material, and the arithmetic mean value can be calculated (the calculation of the arithmetic mean value is beneficial to reduce the difference caused by the measurement system).
  • Method 1 a. Sampling: Take a sample of 1 ⁇ 10 3 mm 2 from the diaphragm (the area of the sample can also be ⁇ 1.5 ⁇ 10 3 mm 2 ), and the number of test points depends on the condition of the diaphragm (usually not less than 10 points). b. Test: Under the condition of 23 ⁇ 2°C, the test is carried out by the ultra-thickness measuring instrument. c. Data processing: the measured value of the thickness of each test point, and take the arithmetic mean value.
  • Method 2 a. Sampling: For products with a width of less than 200mm: determine a point every 40 ⁇ 5mm along the longitudinal direction, the number of test points is not less than 10, and the number of test points can be determined according to the width of the diaphragm. Less than 20mm; for products with a width ⁇ 200mm: determine a point every 80 ⁇ 5mm along the transverse direction, the number of test points is not less than 10, the number of test points can be determined according to the width of the diaphragm, and the distance between the starting point of the measurement and the edge is not less than 20mm.
  • b. Test Test each test point with a thickness measuring instrument at 23 ⁇ 2°C. The diameter of the measuring surface should be between 2.5 and 10mm, and the load applied to the sample on the measuring surface should be between 0.5 and 1.0N. between.
  • Data processing take the arithmetic mean value of the measured thickness of each test point.
  • Method 1 a. Sampling: cut a 1 ⁇ 10 4 mm 2 sample from the diaphragm. b. Test: The porosity is measured by the density method. c. Data processing. The overall porosity P of the sample can be calculated by the following formula:
  • m can be the mass of the sample (for example, obtained by an analytical balance)
  • skeleton density ⁇ can be the material true density of the sample
  • V can be the volume of the sample.
  • Method 2 a. Sampling: Cut a rectangular sample with a 237 ⁇ 170mm plate sampler. When cutting the sample, it should be as far away from the edge of the diaphragm as possible (for example, more than 50mm from the edge of the diaphragm).
  • Test The porosity is measured by the density method, including measuring n (n can be greater than or equal to 9) points of the sample, and the n points can be distributed in an equidistant lattice.
  • Data processing the porosity Pi of each point can be calculated by the following formula:
  • m i is the mass of each point
  • ⁇ is the skeleton density of the sample (can be calculated according to the material ratio)
  • Vi is the total volume of each point (can be calculated according to the length, width and thickness of the sample) ;
  • the overall porosity P of the sample can be calculated by the following formula:
  • Method 1 a. Sampling: Take a sample with a diameter ⁇ 28mm from the diaphragm.
  • Test Test according to the method specified in the standard JIS P8117-2009. It may include: setting the pressure of the cylinder-driven pressure reducing valve to 0.25MPa, the test pressure to 0.05MPa, and selecting "JIS" as the test standard.
  • Data processing randomly cut 6 samples from the full width of the diaphragm, respectively record the air resistance value of each sample and calculate the arithmetic mean value of each sample.
  • Method 2 a. Sampling: Cut 6 square samples with a 100 ⁇ 100mm type plate sampler. When cutting the sample, it should be as far away from the edge of the diaphragm as possible (for example, more than 50mm from the edge of the diaphragm). Each sample is evenly distributed on the membrane (that is, the full width of the membrane is evenly divided to obtain 6 areas, and one sample is cut in each area of the 6 areas).
  • b. Test Test according to the method specified in the standard JIS P8117-2009. Set the pressure of the cylinder-driven pressure reducing valve to 0.25MPa, the test pressure to 0.05MPa, and select "JIS" as the test standard.
  • Data processing record the air resistance value of each sample separately, and calculate the arithmetic mean value of the air resistance values of these 6 samples.
  • Method 1 a. Sampling: Take a sample with a diameter ⁇ 45 mm from the microporous membrane. b. Test: fix the sample on the fixture in the center, the test needle is spherical with a diameter of 1mm (the material is sapphire), ensure that the sample extends to or exceeds the edge of the clamping disc in all directions, and confirm that the sample is completely fixed on the ring fixture on, no slippage. During the test, the diaphragm is punctured, and the speed of the machine is set at 300 ⁇ 10mm/min until the punctured ball completely breaks the sample, and the puncture resistance is the maximum force recorded during the test. c. Data processing: randomly cut 6 samples from the full width, record the puncture strength values of each sample respectively, and calculate the arithmetic mean value of the puncture strength values of each sample.
  • Method 2 a. Sampling: Cut 6 rectangular samples with a 237 ⁇ 170mm type plate sampler. When cutting the sample, it should be as far away from the edge of the diaphragm as possible (for example, more than 50mm from the edge of the diaphragm). Each sample is evenly distributed on the membrane (that is, the full width of the membrane is evenly divided to obtain 6 areas, and one sample is cut in each area of the 6 areas).
  • Test Test according to the method specified in the standard ASTMD4833-07.
  • the test needle is a spherical needle with a diameter of 1mm (the material is sapphire); fix the sample on the fixture in the center, ensure that the sample extends to or exceeds the edge of the clamping disc in all directions, and confirm that the sample is completely fixed on the ring fixture. There is no slipping phenomenon; during the test, the speed of the machine is set at 300 ⁇ 10mm/min, and the diaphragm is punctured until the test needle completely breaks the sample; the puncture resistance is the maximum force recorded during the test.
  • Data processing record the puncture strength of each sample separately, and calculate the arithmetic mean value of the puncture strength of these 6 samples.
  • Method 1 On the overall width sample, cut the diaphragm according to the MD and TD directions respectively, and obtain multiple strip-shaped samples with a length ⁇ 50 mm and a width of about 15 ⁇ 0.1 mm (testing for MD , then the width of the sample can be along the TD direction of the diaphragm, and the length of the sample can be along the MD direction of the diaphragm; to test TD, the width of the sample can be along the MD direction of the diaphragm, and the length of the sample can be along the TD direction of the diaphragm).
  • Test Use a stretching machine to stretch, the distance between the clamps can be 100 ⁇ 5mm, until the sample is broken, and the stretching speed can be 100 ⁇ 1mm/min.
  • Data processing record the tensile strength and elongation of each sample respectively.
  • Method 2 a. Sampling: Cut 6 rectangular samples with a 237 ⁇ 170mm type plate sampler. When cutting the sample, it should be as far away from the edge of the diaphragm as possible (for example, more than 50mm from the edge of the diaphragm). Each sample is evenly distributed on the diaphragm (that is, along the MD and TD directions of the diaphragm, the entire width of the diaphragm is evenly separated to obtain 6 regions, and one sample is cut in each region of the 6 regions). Afterwards, a strip-shaped sample with a length ⁇ 150 mm and a width 15 ⁇ 0.1 mm is cut by a sampler. b. Test: measure according to the method stipulated in GB/T1040.3-2006.
  • the distance between the clamps may be 100 ⁇ 5mm, and the stretching speed may be 100 ⁇ 1mm/min.
  • Data processing record the tensile strength and elongation of each sample separately, and calculate the arithmetic mean value of these 6 samples.
  • Method 1 On the overall width sample, cut the diaphragm according to the MD and TD directions respectively, and obtain multiple strip-shaped samples with a length ⁇ 50 mm and a width of about 15 ⁇ 0.1 mm (testing for MD , then the width of the sample can be along the TD direction of the diaphragm, and the length of the sample can be along the MD direction of the diaphragm; to test TD, the width of the sample can be along the MD direction of the diaphragm, and the length of the sample can be along the TD direction of the diaphragm).
  • the distance between the clamps can be 100 ⁇ 5mm, the stretching speed can be 25 ⁇ 1mm/min, the strain at the starting point can be set to 0.05%, and the strain at the end point can be set to 0.5%.
  • the tensile modulus can be calculated by the regression slope method, and the value of the tensile modulus can be equal to the least squares regression linear fitting of the stress-strain curve in the range of 0.05%-0.25% strain The slope, the unit is Mpa (refer to GB/T 1040.1-2018).
  • Method 2 a. Sampling: Cut 6 rectangular samples with a 237 ⁇ 170mm type plate sampler. When cutting the sample, it should be as far away from the edge of the diaphragm as possible (for example, more than 50mm from the edge of the diaphragm). Each sample is evenly distributed on the diaphragm (that is, along the MD and TD directions of the diaphragm, the entire width of the diaphragm is evenly separated to obtain 6 regions, and one sample is cut in each region of the 6 regions). Afterwards, cut a strip sample with a length ⁇ 150mm and a width 15 ⁇ 0.mm by a sampler. b.
  • the distance between the clamps can be 100 ⁇ 5mm, the stretching speed can be 25 ⁇ 1mm/min, the strain at the starting point can be set to 0.05%, and the strain at the end point can be set to 0.5%.
  • the tensile modulus can be calculated by the regression slope method, and the value of the tensile modulus can be equal to the least squares regression linear fitting of the stress-strain curve in the range of 0.05%-0.25% strain The slope, the unit is Mpa (refer to GB/T 1040.1-2018).
  • a. Sampling Take a circular sample with a diameter of 15mm with corresponding tools, and then use tweezers to soak the sample in a glass dish filled with test solution.
  • Test test by bubble point method. Put the sample into the sample cover, and test according to the standard ASTM F316-2011, according to the operation steps of the pore size analyzer. Compressed air can be used at low pressure, the pressure can be 80psi; low-purity nitrogen can be used at high pressure, the pressure can be ⁇ 350psi.
  • Data processing According to the test results, export the test report of the pore size and pore size distribution of the sample.
  • a. Sampling Randomly cut 6 samples from the full width. The specific sampling of each sample can include: cutting 100mm along the MD direction of the diaphragm; when the TD direction of the diaphragm is greater than 100mm, the length of the test sample in the TD direction can be 100mm; when the TD direction of the microporous membrane is less than 100mm , the length of the test sample in the TD direction can be based on actual conditions. b.
  • Test Mark the vertical and horizontal marks of the sample, measure and record the vertical and horizontal dimensions of each sample; heat the electric thermostat to 120°C; place the sample flat in the paper jacket layer, and the sample has no folds, Wrinkling, adhesion, etc.; put the paper sleeve with the sample (for example, 10 layers) into the middle of the constant temperature oven (for example, the opening time does not exceed 3s); heat the sample to 120 °C, the heating time is 1h; take out the sample and cool it to room temperature, and measure the longitudinal length and transverse length. c.
  • Test use differential scanning calorimeter (DSC), and test under N 2 atmosphere, raise the temperature to within 30°C above the melting point of polyolefin at 10°C/min for the first time, keep it warm for 3min, and obtain polyolefin Raise the crystallinity once, then lower the temperature at 10°C/min to ⁇ 40°C and keep it for 3 minutes, and then raise the temperature at 10°C/min for the second time to within 30°C above the melting point of polyolefin to obtain the crystallinity of polyolefin at the second temperature rise, And read the melting point temperature directly.
  • DSC differential scanning calorimeter
  • Data processing Calculate the area under the melting endothermic curve (from the beginning of the heating cycle to the generation of heat transition enthalpy) (that is, integrate the melting endothermic curve) to obtain the melting enthalpy value in joules (J); the melting enthalpy The value is divided by the sample mass (g) to obtain the mass-normalized enthalpy of fusion ( ⁇ Hs) of the sample.
  • a. Sampling Take 5 power conversion system (pcs) batteries from each group, and mark the central position of the battery cells.
  • Data processing Observe the experimental phenomenon, if there is no fire or explosion after acupuncture, it is judged as passed.
  • a. Sampling Take 5pcs batteries from each group.
  • b. Test At 25 ⁇ 3°C, charge the cell to a limit voltage of 4.43V with a constant current of 1.2A, and then charge at a constant voltage of 4.43V until the current decreases to 0.025C; -Test within 24 hours; through the convection method or circulating hot air box, the battery core is heated from the initial temperature of 25 ⁇ 3°C, and the temperature change rate can be 5 ⁇ 2°C/min; after the temperature rises to 130 ⁇ 2°C, it will keep 30min.
  • c. Data processing Observe the experimental phenomenon, if there is no fire or explosion after heating up, it is judged as passed.
  • a. Sampling Take 5pcs batteries from each group.
  • b. Test At 25 ⁇ 3°C, charge the battery to a limit voltage of 4.43V according to a constant current of 1.2A, and then charge at a constant voltage of 4.43V until the current decreases to 0.025C; after fully charged, charge the battery at 12- Test within 24 hours; heat the battery from the initial temperature of 25 ⁇ 3°C by means of convection or circulating hot air box, and the temperature change rate can be 5 ⁇ 2°C/min; keep the temperature for 30 minutes after rising to 140 ⁇ 2°C.
  • Data processing Observe the experimental phenomenon, if there is no fire or explosion after heating up, it is judged as passed.
  • Method 1 The mass ratio before and after decalin dissolves the separator is the percentage of cross-linked layer thickness; Method 2: The ratio of the increased value of tensile strength after cross-linking to the increased value of fully cross-linked tensile strength is the percentage of cross-linked layer thickness.
  • Embodiment 1 provides a novel cross-linked diaphragm (hereinafter referred to as the diaphragm substrate).
  • Separator substrates include polyethylene, crosslinkers, photoinitiators and antioxidants.
  • polyethylene with a viscosity-average molecular weight of 110 ⁇ 10 4 accounts for 100 parts by weight in the diaphragm base material;
  • the crosslinking agent is triallyl isocyanurate, and the proportion in the diaphragm base material is 1 part by weight;
  • the photoinitiator is benzophenone, and the proportion in the diaphragm base material is 0.7 parts by weight;
  • the antioxidant is 3-(3,5-di-tert-butyl-4-hydroxyphenyl) isooctyl acrylic acid
  • the proportion of ester and antioxidant in the separator base material is 0.3 parts by weight.
  • the separator substrate provided in Example 1 was prepared by the following preparation method:
  • Step (1) pre-irradiate the high molecular weight polyethylene with a cobalt source or an electron accelerator to obtain pre-irradiated high molecular weight polyethylene (the specific parameters of the radiation dose are shown in Tables 1-4).
  • Step (2) using a twin-shaft blade mixer, the above-mentioned polyethylene, triallyl isocyanurate, benzophenone and 3-(3,5-di-tert-butyl-4-hydroxybenzene Base) isooctyl acrylate is premixed to obtain a premix; feed nitrogen into the feeder and the twin-screw extruder in advance, and then the premix is sent into the twin-screw extruder through the feeder;
  • Step (3) setting the gel sheet in an asynchronous stretching machine for biaxial stretching (specific parameters are shown in Tables 1-4).
  • Step (4) extracting the stretched gel sheet with dichloromethane to remove the liquid paraffin in step (2).
  • Step (5) subjecting the extracted gel sheet to high-energy ultraviolet radiation (specific parameters are shown in Tables 1-4).
  • Step (6) heat-setting the gel sheet after ultraviolet crosslinking (specific parameters are shown in Tables 1-4).
  • Step (7) continuously cutting and winding the heat-set gel sheet.
  • the separator provided in Example 2 includes a separator substrate and a separator coating.
  • the raw materials of the diaphragm base material are the same as in Example 1 except that the proportion of the crosslinking agent in the diaphragm base material is 1.5 parts.
  • Diaphragm coatings are heat-resistant coatings and bond coatings.
  • the heat-resistant coating is Al 2 O 3 .
  • the bond coat is oil-based PVDF.
  • the membrane provided in Example 2 can be obtained through steps (1)-step (7) and step (8) in Example 1. In step (8), a membrane coating is provided on the rolled gel sheet (ie, the membrane substrate).
  • step (8) may include: sending the diaphragm base material into the coating device, adopting a micro-gravure roll coating method, coating a heat-resistant coating on the diaphragm base material (that is, performing a coating); The thermally coated diaphragm is sent into the drying oven, and the diaphragm is dried with hot air (that is, one-time drying); the oily system micro-gravure roller coating method is used to coat the surface of the diaphragm coated with heat-resistant coating. layer (i.e. secondary coating; send the diaphragm containing the adhesive coating into a drying oven, and dry the diaphragm with hot air (i.e. perform secondary drying); put the (secondary) dried diaphragm into the winding The device is rolled up to obtain the finished diaphragm.
  • a micro-gravure roll coating method coating a heat-resistant coating on the diaphragm base material (that is, performing a coating)
  • the thermally coated diaphragm is sent into
  • the separator provided in Example 3 includes a separator substrate and a separator coating.
  • the raw materials of the diaphragm substrate are the same as those in Example 2 except that the proportion of the crosslinking agent in the diaphragm substrate is 2.0 parts.
  • Diaphragm coating is Al 2 O 3 heat-resistant coating and oily PVDF bonding coating.
  • the separator provided in Example 4 includes a separator substrate and a separator coating.
  • the raw material selection and ratio of the diaphragm substrate are the same as in Example 2.
  • Diaphragm coating is Al 2 O 3 heat-resistant coating and oily PVDF bonding coating.
  • the manufacturing method and specific parameters of the diaphragm provided in Example 4 can refer to Example 2 and Table 1, and will not be repeated here.
  • the separator provided in Example 5 includes a separator substrate and a separator coating.
  • the raw material selection and ratio of the diaphragm substrate are the same as in Example 2.
  • Diaphragm coating is Al 2 O 3 heat-resistant coating and oily PVDF bonding coating.
  • the manufacturing method and other specific parameters of the diaphragm provided in Example 5 can refer to Example 2 and Table 1, and will not be repeated here.
  • the separator provided in Example 6 includes a separator substrate and a separator coating.
  • the raw material selection and ratio of the diaphragm substrate are the same as in Example 2.
  • Diaphragm coating is Al 2 O 3 heat-resistant coating and oily PVDF bonding coating.
  • the manufacturing method and other specific parameters of the diaphragm provided in Example 6 can refer to Example 2 and Table 1, and will not be repeated here. It should be noted that, in Example 6, a heat-resistant coating on one side and a water system PVDF micro-gravure roll coating are used.
  • the membrane provided by Example 7 includes a membrane substrate.
  • the raw materials of the diaphragm base material are the same as those in Example 2, except that polyethylene wax emulsion with a solid particle melting point of 110-120° C. is added.
  • Diaphragm coating is Al 2 O 3 heat-resistant coating and oily PVDF bonding coating.
  • the membrane provided in Example 8 includes a membrane substrate and a membrane coating.
  • the raw materials of the diaphragm base material are the same as those in Example 2, except that polyethylene wax emulsion with a solid particle melting point of 110-120° C. is added.
  • Diaphragm coating is Al 2 O 3 heat-resistant coating and oily PVDF bonding coating. The manufacturing method and other specific parameters of the diaphragm provided in Example 8 can refer to Example 2 and Table 2, and will not be repeated here.
  • the membrane provided in Example 9 includes a membrane substrate and a membrane coating.
  • the raw materials of the diaphragm base material are the same as those in Example 2, except that polyethylene wax emulsion with a solid particle melting point of 110-120° C. is added.
  • Diaphragm coatings are heat-resistant coatings and bond coatings.
  • the heat-resistant coating is Al 2 O 3 .
  • the bond coat is oil-based PVDF.
  • the membrane provided in Example 10 includes a membrane substrate and a membrane coating.
  • the raw materials of the diaphragm substrate are the same as those in Example 2, except that polyethylene wax emulsion with a melting point of solid particles of 110-120° C. is added.
  • the bond coat is oil-based PVDF.
  • the manufacturing method and other specific parameters of the diaphragm provided in Example 10 can refer to Example 2 and Table 2, and will not be repeated here. It should be noted that the specific processing parameters of Example 10 are different from those of Example 2 (for example, including polymer solid content, etc.).
  • the membrane provided in Example 11 includes a membrane substrate and a membrane coating.
  • the raw materials of the diaphragm base material are the same as those in Example 2, except that polyethylene wax emulsion with a solid particle melting point of 110-120° C. is added.
  • Diaphragm coatings are heat-resistant coatings and bond coatings.
  • the heat-resistant coating is Al 2 O 3 .
  • the bond coat is oil-based PVDF.
  • the membrane provided in Example 12 includes a membrane substrate and a membrane coating. Except that the raw material of the diaphragm substrate is selected to add polyethylene wax emulsion with a melting point of solid particles of 110-120° C., other selections and diaphragm coating are the same as in Example 2.
  • the manufacturing method and specific parameters of the diaphragm provided in Example 12 can refer to Example 11 and Table 2, so it is not necessary to repeat them in detail here.
  • Examples 13-15 provided a membrane comprising a membrane substrate and a membrane coating.
  • the raw material selection and proportion of the diaphragm substrate are the same as in Example 2.
  • the diaphragm coating is an Al 2 O 3 heat-resistant coating and an oily PVDF bond coating.
  • the manufacturing method and specific parameters of the diaphragm provided in Examples 13-15 can refer to Example 11 and Table 3, and will not be repeated here.
  • Examples 16-18 provide a membrane comprising a membrane substrate and a membrane coating. Except that the raw material of the diaphragm base material is selected to add polyethylene wax emulsion whose melting point of solid particles is 80-90° C., other selections and diaphragm coating are the same as in Example 2.
  • the manufacturing methods and parameters of the diaphragms provided in Examples 16-18 can refer to Example 11 and Table 4, and will not be repeated here.
  • the separator provided in Comparative Examples 1-3 includes a separator substrate and a separator coating.
  • the separator provided in Comparative Example 1 was polyethylene with a viscosity average molecular weight of 110 ⁇ 10 4 .
  • the diaphragm provided in Comparative Example 1 was obtained by the following method:
  • Step (1) using a twin-shaft blade mixer, the polyethylene is pre-feeded with nitrogen inside the feeder and the twin-screw extruder, and then the polyethylene is sent into the twin-screw extruder through the feeder;
  • the oil pump preheats the liquid paraffin (the preheating temperature of the liquid paraffin is 40°C.
  • Step (2) setting the gel sheet in an asynchronous stretching machine for biaxial stretching (specific parameters are shown in Table 1).
  • Step (3) extracting the stretched gel sheet with dichloromethane to remove the liquid paraffin in step (1).
  • Step (4) heat-setting the gel sheet after ultraviolet crosslinking (specific parameters are shown in Table 1).
  • Step (5) cutting and winding the heat-set gel sheet.
  • Diaphragm coating is Al 2 O heat-resistant coating and oily PVDF bonding coating.
  • the manufacturing method and specific parameters of the diaphragms provided in Comparative Examples 2-6 can refer to Comparative Example 1 and Table 3, and will not be repeated here.
  • the separator provided in Comparative Examples 7-9 includes a separator substrate and a separator coating.
  • the raw material selection, ratio and diaphragm coating of the diaphragm base material are the same as those in Comparative Example 1.
  • the manufacturing method and specific parameters of the diaphragms provided in Comparative Examples 7-9 can refer to Example 11 and Table 4, and no further details are necessary here.
  • the wavelength of ultraviolet light has a crucial effect on the crosslinking density.
  • the longer the wavelength of ultraviolet light the stronger the radiation ability and the more energy it carries, but the weaker the penetration ability, it can only affect the surface of the diaphragm.
  • the core layer of the diaphragm is not cross-linked, and the smaller the cross-linking density of the diaphragm is, it is difficult to increase the cross-linking density of the diaphragm, and the high-temperature thermal stability of the diaphragm is poor.
  • the core layer still retains the low melting point performance of polyolefin, so the low-temperature closed cell temperature of the separator is relatively low.
  • Example 12 From Examples 6-7 and Example 12, it can be seen that the coating process of the separator (such as adjusting the coating material, system and other conditions) can affect the performance index of the battery cell of the separator and improve the consistency of the performance of the separator.
  • the coating process of the separator (such as adjusting the coating material, system and other conditions) can affect the performance index of the battery cell of the separator and improve the consistency of the performance of the separator.
  • the crosslinking density of the separator increases significantly with the increase of the irradiation time, and the crosslinking density of the separator can be controlled by controlling the irradiation time. At the same time, it is also beneficial to improve the mechanical properties and thermal stability of the separator. However, the closed cell temperature of the separator also increases, which is not conducive to the safety performance of the battery.
  • the novel cross-linked membrane with a thickness of 5-6 ⁇ m can have a membrane rupture temperature of 191-236° C. and a cell-closing temperature of 95-121° C.
  • the membrane provided by the embodiment of the present application has a relatively high membrane rupture temperature and a relatively wide closed-pore membrane rupture platform.
  • the separator has a relatively high tensile modulus and tensile strength, which is beneficial to the processing of the separator in the cell process (for example, it is beneficial to avoid edge protrusion, winding deviation, bending, and wrinkling due to high elongation characteristics. and other issues) and the acupuncture pass rate of the battery.
  • the separator provided by the application is beneficial to improve the mechanical abuse resistance and thermal abuse resistance of the battery, and its comprehensive performance is very excellent.
  • the thickness of the new cross-linked separator of this application is 5-6 ⁇ m.
  • the so-called crosslinking agent ratio in the present application refers to the ratio of the weight part of the crosslinking agent to the weight part of the polyolefin composition.

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Abstract

本申请涉及电池隔膜领域，具体公开了一种新型交联隔膜及其制备方法、电池及电子设备。新型交联隔膜包括紫外交联上表层、芯层和紫外交联下表层；紫外交联上表层和/或紫外交联下表层中包括交联剂和光引发剂；芯层中包括聚烯烃组合物；新型交联隔膜的厚度为0.5～12μm；紫外交联上表层与紫外交联下表层的厚度之和为新型交联隔膜的厚度的20％～80％；新型交联隔膜的破膜温度为191～215℃。将聚烯烃组合物与交联剂和光引发剂以特定方式组合，可以形成具有高韧性、超高破膜温度以及高穿刺强度的新型交联隔膜，并且具有相对较高的拉伸模量和拉伸强度，利于隔膜在电芯工艺中的加工。本申请提供的新型交联隔膜有利于提高电池的耐机械滥用和耐热滥用性能。

Description

一种新型交联隔膜及其制备方法、电池及电子设备
本申请要求申请号为202111356632.8、申请日为2021年11月16日以及专利名称为“一种新型交联隔膜及其制备方法，电池及电子设备”的专利申请文件的优先权。
技术领域
本申请涉及电池隔膜领域，具体涉及一种新型交联隔膜及其制备方法、电池及电子设备。
背景技术
锂离子电池是目前商业化且广泛使用的二次电源。在锂离子电池中，隔膜是介于正极和负极之间的多孔、电化学惰性介质，其不参与电化学反应，但对电芯的安全性能至关重要。目前常用的聚烯烃隔膜可能存在一些缺陷。例如，隔膜的延展性不佳，在电芯被机械滥用时，可能导致隔膜被刺破。又如，隔膜的闭孔温度高，从而在电芯过热时，电化学通路较难被切断。又如，隔膜的破膜温度低，使得在电芯过热时隔膜发生熔化。上述缺陷容易导致隔膜破损、在正极和负极之间形成短路点，进而引发安全隐患。
申请内容
基于上述的不足，本申请提供了一种新型交联隔膜及其制备方法、电池及电子设备，以部分或全部地改善、甚至解决相关技术中电池隔膜耐机械性能和耐热性能差的问题。
为达到上述目的，本申请的技术方案是这样实现的：
在第一方面，本申请提供一种新型交联隔膜，包括紫外交联上表层、芯层、紫外交联下表层；紫外交联上表层和/或紫外交联下表层中包括交联剂和光引发剂，芯层中包括聚烯烃组合物；新型交联隔膜的厚度为0.5～12μm；紫外交联上表层与紫外交联下表层的厚度之和为新型交联隔膜的厚度的20％～80％；新型交联隔膜的破膜温度为191～215℃。
交联剂为带有烯类双键的双官能团或多官能团单体，包括以下至少一种：1,6-己二醇二丙烯酸酯、新戊二醇二丙烯酸酯、二乙烯基苯、双马来酸二丙烯酸酯、三羟甲基丙烷三丙烯酸酯、三羟甲基丙烷三甲基丙烯酸酯、三烯丙基异三聚氰酸酯、季戊四醇三丙烯酸酯、季戊四醇四丙烯酸酯和二季戊四醇六丙烯酸酯。
进一步地，光引发剂为自由基聚合光引发剂或阳离子聚合光引发剂，包括以下至少一种：安息香、安息香双甲醚、安息香乙醚、安息香异丙醚、安息香丁醚、二苯基乙酮、α,α-二甲氧基-α-苯基苯乙酮、α,α-二乙氧基苯乙酮、α-羟烷基苯酮、α-胺烷基苯酮、芳酰基膦氧化物、双苯甲酰基苯基氧化膦、二苯甲酮、2,4-二羟基二苯甲酮、米蚩酮、硫代丙氧基硫杂蒽酮、异丙基硫杂蒽酮、二芳基碘鎓盐、三芳基碘鎓盐、烷基碘鎓盐和异丙苯茂铁六氟磷酸盐。
芯层包括聚烯烃组合物，进一步地，聚烯烃组合物包括第一聚乙烯和第二聚乙烯。其中，第一聚乙烯和第二聚乙烯均选自以下任意一种：聚乙烯、聚乙烯-丙烯共聚物、聚乙烯-丙烯共聚物的衍生物、聚乙烯-丁烯共聚物、聚乙烯-丁烯共聚物的衍生物、聚乙烯-己烯共聚物、聚乙烯-己烯共聚物的衍生物、聚乙烯-辛烯共聚物、聚乙烯-辛烯共聚物的衍生物、聚苯乙烯-乙烯-苯乙烯共聚物、聚苯乙烯-乙烯-苯乙烯共聚物的衍生物、聚苯乙烯-乙烯-丁烯-苯乙烯共聚物、聚苯乙烯-乙烯-丁烯-苯乙烯共聚物的衍生物、聚乙烯-氢化寡环戊二烯、聚乙烯-氢化寡环戊二烯的衍生物、聚氧化乙烯、聚氧化乙烯的衍生物、聚戊烯-乙烯共聚物、聚戊烯-乙烯共聚物的衍生物、聚己烯-乙烯共聚物、聚己烯-乙烯共聚物的衍生物、聚甲基戊烯-乙烯共聚物以及聚甲基戊烯-乙烯共聚物的衍生物。
进一步地，聚烯烃组合物还包括聚丙烯或其衍生物。其中，聚丙烯或其衍生物的热焓△Hm为55～85J/g，密度≥0.9g/cm 3。
进一步地，聚烯烃组合物的粘均分子量在30×10 4～1000×10 4之间。进一步地，聚烯烃组合物的粘均分子量在110×10 4～500×10 4之间。
进一步地，芯层还包括聚聚烯烃类乳液。
进一步地，新型交联隔膜满足以下至少一种：横向和纵向延伸率均≤120％；横向和纵向拉伸模量均≥2000MPa；纵向拉伸模量与横向拉伸模量的比值≥0.9；120℃下横向和纵向热收缩率均≤1.8％；孔隙率为20％～85％；穿刺强度为650～1400gf；横向和纵向拉伸强度均≥2000kgf/cm 2；透气度≤172s/100cc/5μm。
进一步地，新型交联隔膜的双向断裂伸长率优选为120％以下，更优选为50～120％，进一步优选为80～ 120％。需要说明的是，在一定范围内，适当提高新型交联隔膜的双向断裂伸长率，有利于减少因电池卷绕体在充放电时膨胀收缩而引起的安全问题(新型交联隔膜的双向断裂伸长率例如可以为50％以上)。在一定范围内，适当降低新型交联隔膜的双向断裂伸长率，有利于提升新型交联隔膜的机械强度、热稳定性(新型交联隔膜的双向断裂伸长率例如可以为120％以下)。
新型交联隔膜的纵向和横向拉伸强度≥2000kgf/cm 2，优选的，新型交联隔膜的纵向和横向拉伸强度≥3000kgf/cm 2；优选的，新型交联隔膜的纵向和横向拉伸强度≥4000kgf/cm 2；优选的，新型交联隔膜的纵向和横向拉伸强度≥4500kgf/cm 2。
新型交联隔膜的纵向/横向拉伸强度的比值优选为0.9以上，优选为0.96～1.16。新型交联隔膜的纵向和横向拉伸模量≥3000Mpa。优选的，新型交联隔膜的纵向和横向拉伸模量≥3500Mpa；更优选的，新型交联隔膜的纵向和横向拉伸模量≥4000Mpa；最优选的，新型交联隔膜的纵向和横向)拉伸模量≥4500Mpa。
新型交联隔膜的纵向/横向拉伸模量的比值优选为0.9～1.2，优选为0.91～1.1。提高隔膜的拉伸模量，有利于利用隔膜卷绕电芯和在隔膜上加工涂层。
新型交联隔膜的穿刺强度优选为400～1400gf，优选为500～1400gf，优选为600～1400gf，优选为650～1400gf。需要说明的是，提高新型交联隔膜的穿刺强度，有利于提升新型交联隔膜的安全性，且有利于卷绕电芯和加工涂层。
本示例提供的新型交联隔膜的厚度为0.5～12μm，优选为1～9μm，进一步优选为5～6μm。需要说明的是，在一定范围内，适当降低新型交联隔膜的厚度，不仅有利于提高离子在电芯内的传输效率，还有利于提高电池的能量密度(例如厚度为9μm以下)。并且，在一定范围内，适当提高新型交联隔膜的厚度，有利于减少电芯内部的自放电，有利于提升新型交联隔膜的隔离能力，进而有利于提升电池安全性(例如厚度为3μm以上)。进一步地，紫外交联上表层与紫外交联下表层的厚度之和为新型交联隔膜的厚度的20％～75％。
新型交联隔膜的闭孔温度为95～150℃，优选为95～121℃，再优选140～142℃。需要说明的是，在一定范围内，适当提高新型交联隔膜的闭孔温度，有利于防止电池在正常使用过程中融化，进而有利于提升电池的热稳定性能(闭孔温度140℃以上)。在一定范围内，适当降低新型交联隔膜的闭孔温度，有利于提升电池的安全性(新型交联隔膜的闭孔温度为150℃以下优选为142℃以下)。
新型交联隔膜的破膜温度为191～215℃，优选为209～215℃。需要说明的是，适当提高新型交联隔膜的破膜温度，有利于提升电池在高温条件下的安全性(例如，在热异常环境下，破膜温度优选为209℃以上)。进一步地，闭孔温度与破膜温度之间的差值介于49～103℃之间。
新型交联隔膜的透气度优选为100～172s/100cc，更优选为150～172s/100cc，进一步优选为150～163s/100cc，更进一步优选为150～155s/100cc。需要说明的是，在一定范围内，适当提高新型交联隔膜的透气度，有利于降低自放电不良率(例如透气度为100s/100cc以上)。在一定范围内，适当降低新型交联隔膜的透气度，有利于提高离子在电芯内的传输效率(例如透气度为172s/100cc以下)。
进一步地，新型交联隔膜的交联密度为12～72％。
进一步地，新型交联隔膜的孔隙率优选为20％～30％。
进一步地，新型交联隔膜的一侧或两侧上设置有涂层。涂层包括有机涂层、无机涂层和有机/无机复合涂层中的一种或多种。
进一步地，无机涂层包括陶瓷涂层。陶瓷涂层包括以下至少一种：氧化铝，氧化硅，氧化钛，氧化锆，氧化锌，氧化钡，氧化镁，氧化铍，氧化钙，氧化钍，氮化铝，氮化钛，勃母石，磷灰石，氢氧化铝，氢氧化镁，硫酸钡，氮化硼，碳化硅，氮化硅，立方氮化硼，六方氮化硼，介孔分子筛(MCM-41，SBA-15)和珍珠云母层。
进一步地，有机涂层包括以下至少一种：聚偏氟乙烯涂层、偏二氟乙烯-六氟丙烯共聚物涂层、聚苯乙烯涂层、芳纶涂层、聚丙烯酸酯或其改性物涂层、聚酯涂层、聚芳酯涂层、聚丙烯腈涂层、芳香族聚酰胺涂层、聚酰亚胺涂层、聚醚砜涂层、聚砜涂层、聚醚酮涂层、聚醚酰亚胺涂层、聚苯并咪唑涂层和聚多巴胺。
有机/无机复合涂层可以通过上述无机涂层与有机涂层混合制备得到。
在第二方面，本申请提供一种新型交联隔膜的制备方法，包括以下步骤：
S1、将聚烯烃组合物进行预辐照，辐照剂量为0.1～1Mrad，得到预辐照的聚烯烃组合物；S2、将包括有上述预辐照的聚烯烃组合物、交联剂、光引发剂以及成孔剂的原料混合物混合，并从螺杆挤出机挤出，形成凝胶片材；S3、对凝胶片材进行双轴拉伸，后去除凝胶片材中的成孔剂；S4、对凝胶片材进行热定型，热定型包括低倍率拉伸和回缩操作；S5、对凝胶片材进行紫外线照射表层，进行交联；S6、对所述凝胶片材进行收卷、分切，形成新型交联隔膜。
进一步地，S1中聚烯烃组合物包括粘均分子量不同的聚乙烯、聚乙烯共聚物、聚丙烯和聚丙烯衍生物中的一种或多种。进一步地，聚烯烃组合物如第一聚乙烯和第二聚乙烯的选择，此处不再赘述。进一步地，聚烯烃组合物还包括聚丙烯或其衍生物。聚丙烯或其衍生物的热焓△Hm为55～85J/g，更优选为60～80J/g范围内；密度优选为0.9g/cm 3以上，更优选为0.91g/cm 3以上。
聚烯烃组合物中的聚乙烯及其衍生物可以与聚丙烯及其衍生物共混，聚丙烯可以穿插在聚乙烯中，形成相对细密的晶体，而不是形成大的片晶。这有利于提高新型交联隔膜的综合性能。通过优化聚丙烯的热焓△Hm，有利于提高聚烯烃微孔膜耐热稳定性以及与聚乙烯材料的相容性。通过将热焓△Hm在55～85J/g范围内的聚丙烯添加在新型交联隔膜中，有利于提升抗拉强度，改善膜面柔性过高、挺度较低的问题；在裁切或附着涂层的过程中，有利于减少边缘突出、卷绕偏离、弯曲、褶皱等的可能性。
更进一步地，聚乙烯的密度优选为0.85～0.99g/cm 3；更优选为0.91～0.97g/cm 3，进一步优选为0.92～0.95g/cm 3。通过改变聚乙烯的密度，可以改变聚乙烯与聚丙烯的相容性(下述聚烯烃组合物含聚丙烯时)。另外，优化聚乙烯的密度，还有利于优化聚乙烯或聚丙烯的分层程度。
由于粘均分子量不同，聚乙烯有不同的强度和延伸性，可以具有良好的韧性和可加工度。因此，利用聚乙烯、交联剂和光引发剂制备的一定交联度的隔膜，可以同时具备相对高的延伸率、优异的强度和热稳定性。筛选合适粘均分子量的聚乙烯可以平衡因交联产生的延伸率降低的风险。
提高交联剂在新型交联隔膜的聚烯烃组合物中的占比，有利于减少新型交联隔膜紫外辐射不均匀不良的可能性，减少新型交联隔膜内的熔体晶点数量，有利于提高个新型交联隔膜品质。并且，还有利于提高新型交联隔膜的破膜温度。
另外，在高温剪切熔融阶段，具有相对高粘均分子量的聚乙烯可以切割、穿插在聚丙烯分子链之间，有利于改善聚乙烯和聚丙烯不相容的现象。另外，在共混挤出过程中(例如在流延工序中)，可以形成相对一致的相分离特性，有利于防止隔膜厚度偏离程度过大。
进一步地，S1中采用的是钴源或电子加速器进行预辐照。
预辐照是采用电子加速器对聚烯烃组合物材料在混炼挤出之前进行低剂量辐射，使聚烯烃组合物中的例如聚乙烯大分子在辐射高能射线作用下产生较少量自由基。这样既可以使得原本稳定的聚烯烃链端得以活化，使其可以在极短的紫外光曝露下快速交联，进而控制及深化其交联程度；又由于其分子间自由基密度较低在后续加工过程中，包括混炼挤出、拉伸萃取、退火等，又不足以自发交联，避免其熔体粘度上升影响加工性。总的来说，此方法可降低加工难度，缩短后续紫外交联时间，可控交联程度，提高生产效率，提高力学性能及破膜温度。
进一步地，S2的原料混合物中还包括聚烯烃类乳液，聚烯烃类乳液为聚乙烯蜡乳液，固含量在10％～70％；固态颗粒物熔点为80～135℃，优选为80～120℃，优选80～90℃，优选110～120℃。固态颗粒物熔点的选择和闭孔温度有关，上限优选应低于不同聚烯烃隔膜的熔点，例如上限优选135℃时是因此当聚烯烃隔膜为UHMWPE时其熔点在135℃左右，此时优选熔点低于135℃的高分子乳液形成的涂层可以具有低于PE隔膜的闭孔温度，提高电池整体安全性能。其他温度取决于不同的聚烯烃材质以及想要降低隔膜闭孔温度时的优选。
进一步地，S2的原料混合物还可以包括以下至少一种：抗氧剂：如酚类、胺类、亚磷酸酯类或硫代二丙酸酯类等；稳定剂：如硬脂酸钠、硬脂酸钙、硬脂酸镁或硬脂酸锌等；抗静电剂、辐射光吸收剂、光稳定剂、成核剂或无机颗粒等。进一步地，S2的原料混合物还可以包括除聚烯烃以外的热塑性树脂。进一步 地，S2的原料混合物还可以包括以下至少一种：线性低密度聚乙烯、支化聚乙烯、聚甲基丙烯酸甲酯、聚偏氟乙烯或聚丙烯腈等。
进一步地，S2中，双轴拉伸后的面积为双轴拉伸前的面积的10～50倍。
进一步地，按聚烯烃组合物的重量为100份计，交联剂的重量介于1～20份之间，光引发剂的重量介于0.1～2份之间。交联剂的重量更优选为1～15份之间，进一步优选为1～10份之间，更进一步优选为1～2份之间，最优选为1～1.5份之间；光引发剂的重量更优选为介于0.5～1.5份之间，进一步优选为0.7～1.2份之间。在一定范围内，适当降低交联剂在新型交联隔膜的原料混合物中的占比(或提高引发剂在新型交联隔膜的原料混合物中的占比)，有利于进一步提高聚烯烃微孔膜交联效率和降低加工难度。并且，还有利于防止新型交联隔膜起皱、蠕变，有利于提高新型交联隔膜的拉伸模量。在一定范围内，适当提高交联剂在原料混合物中的占比(或降低聚烯烃组合物在新型交联隔膜的原料混合物中的占比)，有利于减少新型交联隔膜交联密度不足的可能性，有利于提高新型交联隔膜的机械性能。并且，还有利于提高新型交联隔膜的破膜温度。
在本申请中，通过优化聚烯烃组合物在原料混合物中的占比，有利于提高新型交联隔膜获得相对好的延伸率、挺度及拉伸模量。
进一步地，S4中，低倍率拉伸为1～3倍的拉伸，低倍率拉伸的拉伸温度为105～135℃；所述回缩操作的回缩比为0.5～10％之间。
进一步地，S5中紫外线的波长范围介于230～350nm之间；S5中紫外线辐射时间为0.2～1s；S5中紫外线辐射功率为1～4Kw。
在第三方面，本申请的目的在于还提供一种电池，包括正极、负极、电解质和第一方面或第二方面提供的新型交联隔膜。
在第四方面，本申请的目的在于还提供一种电子设备，包括壳体、以及收容于壳体内的显示屏、电路板组件和第三方面提供的电池；电池为显示屏和电路板组件供电。
本申请的有益效果包括：将聚烯烃组合物与交联剂和光引发剂以特定方式组合，可以形成具有高韧性、超高破膜温度以及高穿刺强度的新型交联隔膜；根据测试可知，本申请提供的5～6μm厚度的新型交联隔膜可以具有191～215℃的破膜温度，95～121℃的闭孔温度。与未交联聚乙烯组分的隔膜相比，本申请新型交联隔膜具有相对高的破膜温度和极大的49～103℃安全区间。并且具有相对较高的拉伸模量和拉伸强度，这有利于隔膜在电芯工艺中的加工(例如有利于避免因高延伸特性导致的边缘突出、卷绕偏离、弯曲、褶皱等问题)。本申请提供的新型交联隔膜有利于提高电池的耐机械滥用和耐热滥用性能，进而提高含有该电池的电子设备和移动装置的安全性。
附图说明
图1为本申请提供的新型交联隔膜的结构示意图。
附图标记：100-芯层；101-紫外交联上表层；102-紫外交联下表层。
具体实施方式
以下对本申请的具体实施方式进行详细说明。应当理解的是，此处所描述的具体实施方式仅用于说明和解释本申请，并不用于限制本申请。
在介绍本申请实施方式之前，先阐述本申请中出现的技术术语。
隔膜(Separator)：可以指用于分隔电芯正极和负极、防止正负极直接接触而短路的介质。隔膜的基本特性是具有多孔性(可提供离子传输的通道)和绝缘性(防止漏电)。隔膜可以包括隔膜基材和隔膜涂层。隔膜基材(Base separator)：可以指隔膜中的聚烯烃微孔膜部分。隔膜基材可以被单独使用在电芯中。隔膜基材可以提供上述多孔性和上述绝缘性。本申请所述的新型交联隔膜即为隔膜基材。隔膜涂层(Separator coating layer)：可以指附着于隔膜基材上的薄层。隔膜涂层可以通过增材制造的方式附着在隔膜基材上。隔膜涂层可以用于增强隔膜的性能，例如提高隔膜的耐热性、粘接性等。电芯(core或cell)，可以指电池中具有蓄电功能的部分。电芯可以包括正极和负极。
热滥用(Heat abμse)：可以指电芯在热(或高温)方面的滥用。可以使用热箱对电芯进行有关热滥用 的测试(如使用高温(≥130℃)烘烤电芯)。机械滥用(Machenical abμse)：可以指电芯在机械方面的滥用。可以使用针刺测试、撞击测试等对电芯进行有关机械滥用的测试。
延伸率(Elongation)：又可以被称作断裂伸长率，可以指隔膜被拉断时的长度增量相对于初始长度的百分比。具体而言，可以在特定条件下对隔膜进行拉伸测试，在隔膜被刚好被拉断时，隔膜长度的增加量除以隔膜的初始长度可以用于表征延伸率。延伸率的数值越大，意味着隔膜越不容易被拉断，延伸性越好。延伸率可以被划分纵向(MD，即沿隔膜的长边方向)延伸率和横向(TD，相对于MD垂直，即沿隔膜的短边方向)延伸率。
拉伸模量(Tensile modμlμs)：可以指在一定拉伸条件下的抗拉强度，即隔膜沿拉伸方向所需的单位长度力与隔膜截面积之比。拉伸模量可以被划分为纵向(MD，即沿隔膜的长边方向)拉伸模量和横向(TD，相对于MD垂直，即沿隔膜的短边方向)拉伸模量。拉伸强度(Tensile strength)：可以指隔膜塑性变形的临界强度值，可以表征隔膜在均匀拉伸条件下的最大承载能力。拉伸强度可以指，在隔膜被刚好被拉断时，隔膜所承受的最大负载力除以隔膜初始截面积所得的应力。拉伸强度被划分为纵向(MD，即沿隔膜的长边方向)拉伸强度和横向(TD，相对于MD垂直，即沿隔膜的短边方向)拉伸强度。穿刺强度(Pμnctμre strength)：可以指，采用直径为1.0mm的球形钢针以300±10mm/min的速度顶刺隔膜，钢针穿透隔膜所需的力即为隔膜的穿刺强度。
热收缩率(Heat shrinkage)：可以指加热前后隔膜在纵/横(纵向MD，即沿隔膜的长边方向；横向TD，相对于MD垂直，即沿隔膜的短边方向)方向上的尺寸变化率。热收缩率的测试方法可以包括：测量隔膜在纵/横(MD/TD)方向上的尺寸；将在纵/横(MD/TD)方向上具有一定尺寸的隔膜放置在恒温箱中；加热恒温箱至特定温度；测量加热后隔膜在纵/横(MD/TD)方向上的尺寸。
粘均分子量(Viscosity-average Molecμlar Weight)：可以是一种常见的聚合物分子量的表示方法之一。聚合物可以具有多分散性，聚合物分子量通常指聚合物的平均分子量。可以通过多种分子量平均方法，得到多种类型的平均分子量。采用稀溶液粘度法检测得到的聚合物的分子量可以是粘均分子量。分子量分布(distribμtion of molecμlar weight)：重均分子量与数均分子量的比值或者粘均分子量与重均分子量的比值。
孔隙率(Porosity)：可以指隔膜中孔隙体积占隔膜总体积的百分比。孔隙率P满足：
Figure PCTCN2022103584-appb-000001
其中V可以是隔膜的总体积，m可以是隔膜的质量，ρ可以是隔膜的骨架密度(或真密度)。
透气度(Gμrley)：可以指隔膜允许气体通过的程度。透气度可以通过测量单位气体体积(100cc)在特定压力(0.05MPa)下透过隔膜所需时间得到。孔径(Hole size)：可以指隔膜中直通孔的直径。孔径通过孔径分析仪测试得到。
结晶度(Crystallinity)：可以通过差示扫描量热仪(differential scanning calorimetry，DSC)测试得到。聚烯烃隔膜的结晶度可以通过以下方式得到：计算从加热开始到产生热转变焓的过程中，对聚烯烃隔膜的熔化吸热曲线积分，得到熔化焓值(单位为焦耳(J))；将熔化焓值除以样品的质量(g)，得到聚烯烃隔膜的质量归一化熔化焓(△Hs)。然后将质量归一化熔化焓(△Hs)除以100％结晶聚烯烃的熔化焓(△Hf)，获得聚烯烃隔膜的结晶度X(％)。
闭孔温度(Obtμrator temperatμre)：可以指在升温过程中，隔膜开始融化并封堵原先形成的一部分孔隙时的温度。破膜温度(Rμptμre temperatμre)：可以指隔膜融化到一定程度发生破裂导致局部或全面短路时的温度。
本申请的具体实施方式提供一种隔膜基材(即新型交联隔膜，下文中的隔膜基材均指新型交联隔膜)。该隔膜基材可以是微孔膜，包括聚烯烃组合物。具体地，隔膜基材可以包括聚烯烃组合物，交联剂和光引发剂，其中交联剂不能通过热辐射进行交联。隔膜基材可以是一种多孔绝缘材料。隔膜基材上的孔隙可以透过锂离子(隔膜基材上的孔隙可以是锂离子的传输通道)。隔膜基材例如可以包括聚烯烃类材料。隔膜基材还可以被称为聚烯烃多孔隔膜基材。聚烯烃类材料为隔膜提供化学惰性、电化学惰性、多孔性、电子 绝缘性等。另外，根据上文所述的隔膜的性能，隔膜基材作为隔膜的主要组成部分，需要具备高延展性、高破膜温度、低闭孔温度等性能。聚烯烃类材料例如可以包括聚乙烯。
需要说明的是，上述聚烯烃组合物，交联剂和光引发剂的组合有利于优化隔膜基材的机械性能、耐热性能。
由于粘均分子量不同，聚乙烯有不同的强度和延伸性，可以具有良好的韧性和可加工度。因此，聚乙烯包含交联剂和光引发剂制备的一定交联度的隔膜可以同时具备相对高的延伸率、优异的强度和热稳定性。筛选合适粘均分子量的聚乙烯可以平衡因交联产生的延伸率降低的风险。
在某些实施方式中，聚烯烃组合物包括以下至少一种：聚乙烯，聚乙烯-丙烯共聚物、聚乙烯-丙烯共聚物的衍生物、聚乙烯-丁烯共聚物、聚乙烯-丁烯共聚物的衍生物、聚乙烯-己烯共聚物、聚乙烯-己烯共聚物的衍生物、聚乙烯-辛烯共聚物、聚乙烯-辛烯共聚物的衍生物、聚苯乙烯-乙烯-苯乙烯共聚物、聚苯乙烯-乙烯-苯乙烯共聚物的衍生物、聚苯乙烯-乙烯-丁烯-苯乙烯共聚物、聚苯乙烯-乙烯-丁烯-苯乙烯共聚物的衍生物、聚乙烯-氢化寡环戊二烯、聚乙烯-氢化寡环戊二烯的衍生物、聚氧化乙烯、聚氧化乙烯的衍生物、聚戊烯-乙烯共聚物、聚戊烯-乙烯共聚物的衍生物、聚己烯-乙烯共聚物、聚己烯-乙烯共聚物的衍生物、聚甲基戊烯-乙烯共聚物以及聚甲基戊烯-乙烯共聚物的衍生物。
相对于均聚物，共聚物可能会产生成膜不稳定、分子量分布不易控制等问题。
丙烯共聚物可以包含乙烯-丙烯嵌段共聚物和/或无规共聚物。优选地，乙烯-丙烯嵌段共聚物在丙烯共聚物的占比高于无规共聚物在丙烯共聚物的占比。可能的原因可以包括，乙烯-丙烯嵌段共聚物的熔点通常高于无规共聚物的熔点。
在隔膜基材的性能不足或有待提升的情况下，隔膜还可以包括隔膜涂层。隔膜涂层可以附着于隔膜基材一侧或两侧，以有利于隔膜具有高延展性、高破膜温度、低闭孔温度等性能。另外，隔膜涂层还可以具有其他性能，例如具有相对高的粘结性等。
隔膜涂层可包括有机涂层、无机涂层和有机无机复合涂层中的一者或多者。无机涂层可以包括陶瓷涂层。陶瓷涂层可以包括以下至少一种：氧化铝，氧化硅，氧化钛，氧化锆，氧化铍，氧化钙，氧化钍，氮化铝，氮化钛，勃姆石，磷灰石，氢氧化铝，氢氧化镁，硫酸钡，氮化硼，碳化硅，氮化硅，立方氮化硼，六方氮化硼，石墨烯，介孔分子筛等。有机涂层可以包括以下至少一种：聚偏氟乙烯涂层、偏二氟乙烯-六氟丙烯共聚物涂层、聚苯乙烯涂层、聚丙烯酸酯或其改性物涂层、聚酯涂层、聚芳酯涂层、聚丙烯腈涂层、芳香族聚酰胺涂层、聚酰亚胺涂层、聚醚砜涂层、聚砜涂层、聚醚酮涂层、聚醚酰亚胺涂层和聚苯并咪唑。
有机无机复合涂层可以通过上述无机涂层与有机涂层混合制备得到。
本申请具体实施方式还提供一种锂离子二次电池。该锂离子二次电池的核心部件可以包括正极材料、负极材料、电解液、隔膜以及相应的连通辅件和回路。正极材料、负极材料可以脱嵌锂离子，以实现能量的存储和释放。电解液可以是锂离子在正极材料、负极材料之间的传输载体。正极材料、负极材料是锂离子二次电池的主体储能部分，可以体现电芯的能量密度、循环性能及安全性能。隔膜可透过锂离子，但隔膜本身不导电，从而隔膜可以将正极材料和负极材料隔开，以防止正极材料与负极材料之间短路。
正极材料可以包括正极集流体和设置在正极集流体上的正极活性材料。正极活性材料包括但不限于锂的复合金属氧化物(如镍钴锰酸锂等)、聚阴离子锂化合物LiMx(PO 4) y(M为Ni、Co、Mn、Fe、Ti、V，0≤x≤5，0≤y≤5)等。负极材料可以包括负极集流体和设置在负极集流体上的负极活性材料。负极活性材料包括但不限于以下至少一种：金属锂、锂合金、钛酸锂、天然/人造石墨、MCMB、无定型碳、碳纤维、碳纳米管、硬碳、软碳、石墨烯、氧化石墨烯、硅、硅碳化合物、硅氧化合物和硅金属化合物。隔膜本身的性能应当有利于锂离子二次电池实现良好的充放电性能。例如，为了稳定、可靠地将正极材料和负极材料隔开，隔膜应具有一定的强度和延展性，以避免被刺破，即隔膜应当具有一定的耐机械滥用性。又如，在充放电过程中，锂离子二次电池自身可能会发热。在温度较高的情况下，隔膜也应当具有相对高的稳定性，即隔膜应当具有一定的耐热性或耐热滥用性。一方面，隔膜的破膜温度可以相对较高，在电芯过热时也不易发生熔化。另一方面，隔膜的闭孔温度可以相对较低，在电芯过热时，正极材料和负极材料之间的 电化学通路可以相对容易地被隔膜切断。
本申请具体实施方式中的隔膜均采用本申请提供的新型交联隔膜。
本申请具体实施方式还提供一种电子设备，可以是终端消费产品或3C电子产品，如手机、移动电源、便携机、电子阅读器、电脑、数码相机、车载设备、可穿戴设备、耳机等设备。以电子设备是手机为例进行说明。手机包括壳体、显示屏和电路板组件。具体的，壳体包括边框和后盖。边框环绕在显示屏的外周且环绕在后盖的外周。显示屏、边框、后盖之间形成的空腔可以用于放置电路板组件。在一个示例中，显示屏和电路板组件均可以被设置在壳体上。手机还可以包括用于为电路板组件供电的电源。电源是可以锂电子二次电池，电池中使用本申请提供的新型交联隔膜。
本申请具体实施方式还提供一种隔膜基材的制造方法：
(1)将聚烯烃组合物进行预辐照，辐照剂量为0.1～1Mrad，得到预辐照的聚烯烃组合物；(2)将包含有成孔剂、预辐照的聚烯烃组合物、交联剂和光引发剂、聚乙烯蜡乳液的混合物混合，并从螺杆挤出机挤出，形成凝胶片材。
有关聚烯烃组合物、聚乙烯蜡乳液、交联剂和光引发剂的说明可以参照上文说明书中所述，在此就不必再赘述。
以下对步骤(2)进行详细阐述。
步骤(2)可以简称为挤出流延工序。挤出流延工序具体可以是，将包含有聚烯烃组合物、交联剂和光引发剂、成孔剂的混合物通过螺杆挤出机混炼、挤出、流延，冷却形成凝胶片材的工序。
在一个可能的示例中，可以通过逆流混料机、双轴叶片混料机、双锅混料机等对混合物进行混合。
在一个可能的示例中，可以通过单轴螺杆挤出机或双轴螺杆挤出机对混合物进行高温混炼。为获得相对良好的挤出效果，在聚烯烃组合物的粘均分子量500×10 4以下的情况下，优选双轴螺杆挤出机。
挤出机的温度为150～300℃，优选为160～260℃，优选为170～230℃。
需要说明的是，增大挤出机的温度，有利于提高熔融塑化效率(挤出机的温度优选为150℃以上，更优选为160℃以上，进一步优选为170℃以上)。降低挤出机的温度，有利于防止聚烯烃组合物、光引发剂和交联剂混合物氧化分解(挤出机的温度优选为300℃以下，更优选为260℃以下，进一步优选为230℃以下)。
形成铸片的方法例如可以是压延法、自由贴片法等。
凝胶片材的厚度优选为200～700μm，更优选为250～550μm。需要说明的是，提高凝胶片材的厚度，有利于增大隔膜基材的机械强度(凝胶片材厚度优选为200μm以上，更优选为250μm以上)。降低凝胶片材的厚度，有利于提高隔膜基材在紫外光辐照过程中的交联密度(凝胶片材厚度优选为700μm以下，更优选为550μm以下)。
高温熔体流延冷却方法例如可以是风冷、水冷、油冷、使流延片材与冷却辊接触等直接接触降温法。从控制凝胶片材厚度以及提升隔膜基材的均一性的角度考虑，本申请实施方式优选采用冷却辊接触降温的方法。
在聚烯烃组合物、交联剂和光引发剂混合物中添加成孔剂的目的是提升聚烯烃混合物的塑性。成孔剂例如可以包括以下至少一种：烃类有机溶剂(如石蜡等)、邻苯二甲酸-2-乙基己酯、邻苯二甲酸二丁酯、烷基磺酸酯、邻苯二甲酸丁苄酯、邻苯二甲酸二异壬酯。本申请实施方式优选液体石蜡。
可选的，在高温条件下，成孔剂可以与聚烯烃组合物以任意比例互溶(即形成均一相的有机溶剂)。
聚烯烃组合物、交联剂和光引发剂在所述混合物中的占比优选为10～50份，更优选为12～30份，进一步优选为15～25份。需要说明的是，增加聚烯烃组合物在聚烯烃组合物、交联剂和光引发剂中的占比，有利于提高其成模性和可加工性(聚烯烃组合物占比例如可以为15份以上)。降低聚烯烃组合物在聚烯烃组合物、交联剂和光引发剂中的占比，有利于提高其成孔性(聚烯烃组合物占比例如可以为95份以下)。成孔剂在混合物中的占比优选为50～90份，更优选为75～85份。在混合物中添加成孔剂除了有利于提高聚烯烃组合物的塑化能力，还有利于提供相对完整的孔隙结构。
可选的，混合物还包括无机颗粒。无机颗粒可以是一种制孔剂。
如果在步骤(2)中使用无机颗粒，并在最终的成品中去除至少部分该无机颗粒，有利于获得相对高的孔隙率，进而提升离子传输效率。去除无机颗粒的方式例如可以是使用可溶解无机颗粒的液体。如果在步骤(2)中使用无机颗粒，并在最终的成品中保留至少部分该无机颗粒，有利于提高隔膜基材的稳定性(例如提高隔膜基材的机械性能、耐热性能等)和极性(即提高隔膜基材与电解液的亲和力)。
无机颗粒例如可以包括以下至少一种：氧化铝，氧化硅，氧化钛，氧化锆，氧化锌，氧化钡，氧化镁，氧化铍，氧化钙，氧化钍，氮化铝，氮化钛，勃母石，磷灰石，氢氧化铝，氢氧化镁，硫酸钡，氮化硼，碳化硅，氮化硅，立方氮化硼，六方氮化硼。无机颗粒的尺寸可以影响混炼的均匀性。无机颗粒的粒径优选在5～300nm范围内，更优选为10～100nm范围内，优选为20～50nm范围内。
可选的，混合物还可以包括抗氧化剂。
为了减少聚烯烃组合物、交联剂和光引发剂混合物的氧化分解，可以在混合物中添加抗氧化剂。也就是说，将包含有聚烯烃组合物、交联剂、光引发剂和抗氧化剂的混合物在螺杆挤出机内混炼并挤出。
在一个可能的示例中，优选抗氧化剂在混合物中的占比为0.1～5份，更优选为0.2～2份。
(3)对凝胶片材进行双轴拉伸。
步骤(3)可以简称为拉伸工序。拉伸工序可以是将凝胶片材在双轴方向上进行拉伸的工序。
双轴拉伸的方法例如可以是异步拉伸(采用速差辊拉伸机与导轨链拉幅机组合的顺序双轴拉伸，即先在第一轴向上拉伸，之后在第二轴向上拉伸)、同步拉伸(采用双轴拉幅机同时拉伸，即同时在第一轴向、第二轴向上拉伸)。异步拉伸有利于提高拉伸成型效率。
拉伸工序中的面拉比(横向拉伸比例*纵向拉伸比例，或拉伸后面积/拉伸前面积)为10～200倍，优选为20～70倍。需要说明的是，降低拉伸工序的面拉比，利于提高隔膜基材的延伸率(如50倍以下)。提高拉伸工序的面拉比，利于提高孔隙率或孔隙透过率，利于改善隔膜基材的厚度一致性(如10倍以上)。
拉伸工序中的拉伸温度应参考聚烯烃组合物固含量(固含量可以是聚烯烃组合物在规定条件下烘干后剩余部分占总量的质量百分数)来选择。拉伸工序中的拉伸温度为60～110℃，优选为63～108℃，优选为65～106℃。需要说明的是，在一定的范围内，适当提高拉伸工序中的拉伸温度(例如60℃以上)，有利于防止拉伸温度过低导致冷拉，进而造成分子链活化不够(即固化程度相对较大)而产生相对较大的应力集中。在一定的范围内，适当降低拉伸工序中的拉伸温度(例如110℃以下)，有利于完善隔膜的孔隙结构。
(4)去除凝胶片材中的成孔剂。
步骤(4)可以简称为去除成孔剂工序。去除成孔剂工序具体可以通过萃取剂将凝胶片材中的成孔剂去除。萃取剂可以溶解成孔剂(萃取剂可以是成孔剂的优良溶剂)，而与聚烯烃材料不相容(即萃取剂无法溶解聚烯烃材料)。萃取剂例如可以包括以下至少一种：卤代烃(如二氯甲烷、正己烷、环己烷等)、丙酮、四氢呋喃、乙醇、N-甲基吡咯烷酮等。在本申请实施例中，萃取剂优选为二氯甲烷。
去除成孔剂的方法可以是，将凝胶片材在萃取剂中浸没，或者对凝胶片材喷淋萃取剂，以萃取出增塑剂，最后将萃取后的凝胶片材进行干燥。
(5)紫外光辐照交联。
步骤(5)可以简称为交联工序。紫外光辐照交联具体指，在一定温度条件下，对薄膜进行紫外高能辐照，在光引发剂催化条件下激活交联剂，使辐照层产生化学三维网状交联。辐射光可以包括其波长范围在350nm以下的高能紫外光。交联剂例如可以包括以下至少一种：1,6-己二醇二丙烯酸酯、新戊二醇二丙烯酸酯、二乙烯基苯、双马来酸二丙烯酸酯、三羟甲基丙烷三丙烯酸酯、三羟甲基丙烷三甲基丙烯酸酯、三烯丙基异三聚氰酸酯、季戊四醇三丙烯酸酯、季戊四醇四丙烯酸酯和二季戊四醇六丙烯酸酯等；光引发剂分为自由基聚合光引发剂和阳离子聚合光引发剂，如苯偶姻及衍生物(安息香、安息香双甲醚、安息香乙醚、安息香异丙醚或安息香丁醚)、苯偶酰类(二苯基乙酮、α，α-二甲氧基-α-苯基苯乙酮)、烷基苯酮类(α，α-二乙氧基苯乙酮、α-羟烷基苯酮、α-胺烷基苯酮)、酰基磷氧化物(芳酰基膦氧化物、双苯甲酰基苯基氧化膦)、二苯甲酮类(二苯甲酮、2,4-二羟基二苯甲酮、米蚩酮)、硫杂蒽酮类(硫代丙氧基硫杂蒽酮、异丙基硫杂蒽酮)、二芳基碘鎓盐、三芳基碘鎓盐、烷基碘鎓盐以及异丙苯茂铁六氟磷酸盐等一种或多种。
在本申请的一些实施方式中，聚乙烯在外加光引发剂的情况下，通过吸收紫外线能量后转变为激发态，在聚乙烯链上夺氢产生自由基，添加引发剂加快聚乙烯分子链间的交联，形成三维网状结构的体型大分子。此结构情况下为不熔物，失去流动性，耐热性能明显提高，高温尺寸稳定性好。由于分子链间架起化学链桥，物理力学性能提高，特别是拉伸强度、刚度、耐磨性、耐蠕变性和耐高温尺寸稳定性，相应的断裂伸长率下降。由于交联部分的分子链虽受限制，但还可以在原位置附近作轻微振动以抵消冲击能，故冲击强度也相应提高。
在本申请中，由于紫外线穿透能力差，只能对聚乙烯隔膜表层进行交联，而保留内层聚乙烯的闭孔性能。通过对紫外线波长的控制，进而控制交联层的厚度。
在本申请中，降低紫外辐射光波长有利于进一步提高聚烯烃微孔膜交联效率。并且，还有利于防止隔膜基材起皱、蠕变，有利于提高隔膜基材的拉伸模量。
(6)对凝胶片材进行热定型。
步骤(6)可以简称为热定型工序。热定型工序可以指，在一定温度条件下，对凝胶片材进行低倍率拉伸和回缩操作，以释放凝胶片材在前序工艺中积累的应力，进而有利于改善凝胶片材的热稳定性能。
低倍率拉伸(即热定型工序中的拉伸)具体可以指拉伸比在3.0倍以下的拉伸。需要说明的是，降低热定型工序中的拉伸倍率，有利提高凝胶片材的延伸特性(热定型工序中的拉伸倍率优选为2.5倍以下，更优选为2倍以下)。增大热定型工序中的拉伸倍率，有利完善凝胶片材的孔隙结构(热定型工序中的拉伸倍率优选为1倍以上，更优选为1.2倍以上)。
低倍率拉伸的拉伸温度(定型温度)为105～135℃，优选为105～130℃，进一步优选为108～129℃。需要说明的是，降低热定型工序中的拉伸温度，有利于降低凝胶片材的结晶度(热定型工序中的拉伸温度优选为135℃以下)。增大热定型工序中的拉伸温度，有利于为了防止凝胶片材内产生应力集中和微裂缝(热定型工序中的拉伸温度优选为105℃以上)。
回缩操作具体可以指，通过回缩轨道松弛凝胶片材，使凝胶片材松弛或处于半自由状态。降低回缩操作的回缩比，有利于防止过度松弛，进而有利于增大凝胶片材的孔隙，有利于提高离子的传输效率(回缩操作的回缩比优选为10％以下，更优选为4.5％以下，进一步优选为3％以下)。提高回缩操作的回缩比，有利于降低凝胶片材的内应力，改善凝胶片材的热收缩(热收缩可以指高温下在隔膜应力的作用下发生的收缩现象)(回缩操作的回缩比为0.5％以上，优选为1％以上)。
(7)收卷，分切工序。
步骤(7)具体可以是，对凝胶片材进行收卷、分切。通过步骤(7)，可以得到本申请实施例提供的隔膜基材或隔膜。
本申请的实施方式中可以不限定上述步骤(1)～(7)的执行顺序和执行次数。例如，优选地，执行顺序可以是：(1)、(2)、(3)、(4)、(5)、(6)、(7)。在步骤(4)之前执行步骤(3)，有利于完善隔膜的孔隙结构，提高隔膜的机械强度。又如，执行顺序可以是：(1)、(2)、(4)、(3)、(5)、(6)、(7)。又如，执行顺序可以是：(1)、(2)、(4)、(3)、(6)、(5)、(7)。步骤(3)(即拉伸工序)可以在步骤(4)(即去除成孔剂工序)之前或之后进行，或者与步骤(4)之前的工序同时进行，或者与步骤(4)之后的工序同时进行。
本申请具体实施方式还提供一种锂离子电池的制造方法。其原理是，将本申请提供的新型交联隔膜设置在正极材料、负极材料之间(例如按照正极材料-隔膜-负极材料或者负极材料-隔膜-正极材料的顺序进行装配)；对包含正极材料、隔膜、负极材料的层状部件进行卷绕得到卷绕体；将卷绕体装入电池外壳中；注入电解液。
在一个可能的示例中，正极材料可以通过如下方式得到：将正极活性材料(如钴酸锂)、导电剂(如导电炭黑，Sμper-P，SP)、粘接剂(如聚偏氟乙烯)，以97:1.5:1.5的质量比在溶剂(如N-甲基吡咯烷酮)中混合，形成正极浆料；通过涂布设备，将正极浆料均匀涂布在板材(如铝箔)的两面；通过烘箱对板材上的正极浆料烘干，以去除溶剂；对板材上的正极材料进行冷压、分条、极耳焊接。
在一个可能的示例中，负极材料可以通过如下方式得到：将负极活性材料(如人造石墨)、增稠剂(如 羧甲基纤维素)、粘接剂(如丁苯橡胶)，以97:1.3:1.7的质量比在溶剂(如去离子水)中混合，形成负极浆料；通过涂布设备，将负极浆料均匀涂布在板材(如铜箔)的两面；通过烘箱对板材上的负极浆料烘干，以去除溶剂；对板材上的负极材料进行冷压、分条、极耳焊接。
在一个可能的示例中，隔膜可以通过如下方式得到：在隔膜基材的表面涂覆隔膜涂层。本申请实施方式中，隔膜涂层的厚度例如可以是0.5μm-10μm。
例如，该隔膜涂层可以包括无机涂层(如陶瓷涂层)和设置在无机涂层上的有机涂层(如油性PVDF涂层)。其中，陶瓷涂层有利于可以提高隔膜的耐热性。PVDF涂层具有一定粘结性能，可以提高隔膜与正极材料之间(或隔膜与负极材料之间)的粘结力，使得隔膜可以与正极材料或负极材料粘结地更加紧密，进而提升电芯的硬度、提高电芯的针刺测试的通过率。如果隔膜可以与正极材料或负极材料之间存在粘结空隙，则不利于电芯的硬度，也不利于电芯的针刺测试的通过率。
隔膜涂层可以包括有机涂层或混合涂层，直接涂布在隔膜基材表面。
将上述正极材料、隔膜和负极材料一起进行卷绕，可以制成裸电芯。该裸电芯的蓄电容量例如可以达到3.8Ah，该裸电芯的工作电压可以为3.0-4.43V。
对裸电芯进行封装、烘烤、注液、化成等工序，可以制成锂离子电池成品。
在以下实施例和对比例中，性能参数按照如下方法测定：
1、粘均分子量和分子量分布
a.取样：将聚烯烃材料完全溶解在十氢化萘、四氢呋喃等有机溶剂中，配制成0.5～1.5mg/mL浓度的溶液，室温静置一段时间，不可超声，并采用半透膜过滤。b.测试：在135℃条件下，采用凝胶渗透色谱法(GPC)测定聚烯烃材料的粘度，同根据下列计算公式所得粘度[η]算出粘均分子量Mv：[η]＝6.77×10 -4Mv 0.67。其中，聚丙烯的粘均分子量可以根据下列公式算出：[η]＝1.10×10 -4Mv 0.8。c.数据处理：绘制粘度与粘均分子量的分布曲线，既可以读出分子量分布。可选的，可以对聚烯烃材料进行多次测试，并计算算术平均值(计算算术平均值有利于降低测量系统所带来差异)。
2、膜厚度
方式一：a.取样：从隔膜上截取1×10 3mm 2样品(样品的面积例如还可以≥1.5×10 3mm 2)，测试点数视隔膜情况而定(通常不小于10个点)。b.测试：在23±2℃条件下通过万分厚度测量仪进行测试。c.数据处理：每个测试点的厚度实测值，并取算数平均值。
方式二：a.取样：对于宽度＜200mm的产品：沿纵向方向每隔40±5mm确定一个点，测试点数不小于10个，测试点数可以视隔膜宽度而定，其中，测量起点距边部不小于20mm；对于宽度≥200mm的产品：沿横向方向每隔80±5mm确定一个点，测试点数不小于10个，测试点数可以视隔膜宽度而定，其中，测量起点距边部不小于20mm。b.测试：在23±2℃条件下通过厚度测量仪对每个测试点进行测试，测量面的直径应在2.5～10mm之间，测量面对试样施加的负荷应在0.5～1.0N之间。c.数据处理：每个测试点的厚度实测值并取算数平均值。
3、孔隙率(％)
方式一：a.取样：从隔膜上截取1×10 4mm 2样品。b.测试：采用密度法测量孔隙率。c.数据处理。样本整体的孔隙率P可以通过如下公式计算得到：
Figure PCTCN2022103584-appb-000002
其中，m可以为样品质量(例如通过分析天平得到)，骨架密度ρ可以为样品的材料真密度，V可以为样品的体积。
方式二：a.取样：通过237×170mm型板取样器裁取矩形试样1个。裁样时，应尽可能远离隔膜的边部(如距隔膜边部50mm以上)。b.测试：采用密度法测量孔隙率，包括测量试样的n(n例如可以大于或等于9)个点，这n个点可以呈等距点阵分布。c.数据处理：每个点的孔隙率Pi可以通过如下公式计算得到：
Figure PCTCN2022103584-appb-000003
其中，m i为每个点的质量，ρ为试样的骨架密度(可以根据物料配比 计算得到)，Vi为每个点的总体积(可以根据试样的长度、宽度、厚度计算得到)；
样本整体的孔隙率P可以通过如下公式计算得到：
Figure PCTCN2022103584-appb-000004
4、透气度(s/100cc)
方式一：a.取样：从隔膜上截取直径≥28mm的样品。b.测试：按照标准JIS P8117-2009中规定的方法进行测试。可以包括：设置汽缸驱动减压阀的压强为0.25MPa，测试压为0.05MPa，测试标准选定“JIS”。c.数据处理：在隔膜全幅宽随机裁取6个试样，分别记录各试样的气阻值大小并计算各样品的算术平均值。
方式二：a.取样：通过100×100mm型板取样器裁取方形试样6个。裁样时，应尽可能远离隔膜的边部(如距隔膜边部50mm以上)。每个试样均匀分布在隔膜上(即均分隔膜的全幅宽得到6个区，在这6个区内的每个区内裁取1个试样)。b.测试：按照标准JIS P8117-2009中规定的方法进行测试。设置汽缸驱动减压阀的压强为0.25MPa，测试压为0.05MPa，测试标准选定“JIS”。c.数据处理：分别记录每个试样的气阻值大小，并计算这6个试样的气阻值的算术平均值。
5、穿刺强度
方式一：a.取样：从微孔膜上截取直径≥45mm的样品。b.测试：将样品居中固定在夹具上，测试针头为直径1mm的球形(材质为蓝宝石)，确保试样在各个方向延伸到或者超过夹紧盘的边缘，确认样品完全固定于环状夹具之上，无打滑现象。测试时，对隔膜进行穿刺，机器的速度设定为300±10mm/min，直到穿刺球棒完全使试样破裂，穿刺阻力为测试过程中所记录的最大力。c.数据处理：全幅宽随机裁取6个试样，分别记录各样品穿刺强度值，并计算各样品穿刺强度值的算术平均值。
方式二：a.取样：通过237×170mm型板取样器裁取矩形试样6个。裁样时，应尽可能远离隔膜的边部(如距隔膜边部50mm以上)。每个试样均匀分布在隔膜上(即均分隔膜的全幅宽得到6个区，在这6个区内的每个区内裁取1个试样)。b.测试：按照标准ASTMD4833-07规定的方法进行测试。测试针头为球形针头，直径为1mm(材质为蓝宝石)；将样品居中固定在夹具上，确保试样在各个方向延伸到或者超过夹紧盘的边缘，确认样品完全固定于环状夹具之上，无打滑现象；测试时，机器的速度设定为300±10mm/min，对隔膜进行穿刺，直到测试针头完全使试样破裂；穿刺阻力为测试过程中所记录的最大力。c.数据处理：分别记录每个试样的穿刺强度，并计算这6个试样的穿刺强度的算术平均值。
6、拉伸强度和延伸率
方式一：a.取样：在整体幅宽试样上，分别按照MD和TD方向对隔膜进行裁剪，得到多个长≥50mm、宽约为15±0.1mm的长条形样品(对MD进行测试，则样品的宽度可以沿隔膜的TD方向，样品的长度可以沿隔膜的MD方向；对TD进行测试，则样品的宽度可以沿隔膜的MD方向，样品的长度可以沿隔膜的TD方向)。b.测试：采用拉伸机进行拉伸，夹具间距可以为100±5mm，直至样品被拉断，拉伸速度可以为100±1mm/min。c.数据处理：分别记录每个样品的拉伸强度、延伸率。
方式二：a.取样：通过237×170mm型板取样器裁取矩形试样6个。裁样时，应尽可能远离隔膜的边部(如距隔膜边部50mm以上)。每个试样均匀分布在隔膜上(即沿隔膜的MD、TD方向，均分隔膜的全幅宽，得到6个区，在这6个区内的每个区内裁取1个试样)。之后，通过取样仪裁切长≥150mm，宽15±0.1mm的长条形样本。b.测试：按GB/T1040.3-2006规定的方法进行测量。具体可以包括：夹具间距可以为100±5mm，拉伸速度可以为100±1mm/min。c.数据处理：分别记录每个试样的拉伸强度、延伸率，并计算这6个试样的算术平均值。
7、拉伸模量
方式一：a.取样：在整体幅宽试样上，分别按照MD和TD方向对隔膜进行裁剪，得到多个长≥50mm、宽约为15±0.1mm的长条形样品(对MD进行测试，则样品的宽度可以沿隔膜的TD方向，样品的长度可以沿隔膜的MD方向；对TD进行测试，则样品的宽度可以沿隔膜的MD方向，样品的长度可以沿隔膜的 TD方向)。b.测试：采用拉伸机进行拉伸，夹具间距可以为100±5mm，拉伸速度可以为25±1mm/min，起始点应变可以设置为0.05％，结束点应变可以设置为0.5％。c.数据处理：拉伸模量可以通过回归斜率法计算得到，拉伸模量的值可以等于，在应变为0.05％-0.25％的区间内，应力-应变曲线的最小二乘回归线性拟合的斜率，单位为Mpa(参考GB/T 1040.1-2018)。
方式二：a.取样：通过237×170mm型板取样器裁取矩形试样6个。裁样时，应尽可能远离隔膜的边部(如距隔膜边部50mm以上)。每个试样均匀分布在隔膜上(即沿隔膜的MD、TD方向，均分隔膜的全幅宽，得到6个区，在这6个区内的每个区内裁取1个试样)。之后，通过取样仪裁切长≥150mm，宽15±0.mm的长条形样本。b.测试：采用拉伸机进行拉伸，夹具间距可以为100±5mm，拉伸速度可以为25±1mm/min，起始点应变可以设置为0.05％，结束点应变可以设置为0.5％。c.数据处理：拉伸模量可以通过回归斜率法计算得到，拉伸模量的值可以等于，在应变为0.05％-0.25％的区间内，应力-应变曲线的最小二乘回归线性拟合的斜率，单位为Mpa(参考GB/T 1040.1-2018)。
8、孔径
a.取样：用相应工具取一个直径为15mm的圆形试样，然后用镊子将试样放在装有测试液的玻璃皿中浸润。b.测试：采用泡点法进行测试。把样品放入样品盖中，按标准ASTM F316-2011，根据孔径分析仪的操作步骤进行测试。低压时可以使用压缩空气，压力可以为80psi；高压时可以使用低纯氮气，压力≥350psi。c.数据处理：根据测试结果，导出样品的孔径大小和孔径分布的测试报告。
9、120℃热收缩率
a.取样：全幅宽随机裁取6个试样。每个试样的具体取样可以包括：沿隔膜的MD方向，裁取100mm；当隔膜的TD方向大于100mm时，测试样品在TD方向上的长度可以为100mm；当微孔膜TD方向小于100mm时，测试样品在TD方向上的长度可以以实际为准。b.测试：标记好样品的纵、横向标识，测量并记录每片试样纵横向的尺寸；电热恒温箱加热至120℃；将试样平置于纸夹套层中，试样无折叠、起皱、粘连等情况；将夹有试样的纸套(层数例如可以为10层)平整地放入恒温烘箱中部(开门时间例如不超过3s，)；通过电热恒温箱加热试样至120℃，加热时间为1h；取出试样后冷却至室温，测量纵向长度和横向长度。c.数据处理：计算各个样本的热收缩率：T＝(L0-L)/L0×100％，其中，T可以为试样热收缩率(％)，L0可以为加热前试样的长度(mm)，L可以为加热后试样的长度(mm)，计算样本热收缩率的算术平均值。
10、熔点(℃)及结晶度(％)测量
a.取样：在精度为0.01mg的天平上对隔膜样品称重。隔膜样品的质量应在5mg～10mg之间。平行样品间的质量差应在±2mg之内。b.测试：采用差示扫描量热仪(DSC)，并在N 2氛围下进行测试，以10℃/min第一次升温到聚烯烃的熔点以上30℃以内，保温3min，得到聚烯烃的一次升温结晶度，随后以10℃/min降温到≤40℃并保温3min，再以10℃/min第二次升温到聚烯烃的熔点以上30℃以内，得到聚烯烃的二次升温结晶度，并直接读取熔点温度。c.数据处理：计算熔化吸热曲线(从加热循环开始到产生热转变焓)下的面积(即对熔化吸热曲线进行积分)，获得熔化焓值，单位是焦耳(J)；将熔化焓值除以样品质量(g)，可以得到样品的质量归一化熔化焓(△Hs)。然后可以根据以下公式计算样品的结晶度X(％)：结晶度X(％)＝样品的质量归一化熔化焓(△Hs)/100％结晶聚乙烯的熔化焓(△Hf)×100％，其中，100％结晶聚乙烯的熔化焓(△Hf)＝293.8J/g。
11、针刺测试
a.取样：每组取5储能系统(power conversion system，pcs)电池，并标记电芯的中央位置。b.测试：在25±3℃下，按照1.2A的恒定电流将电芯充电至限制电压4.43V，然后再在4.43V恒压充电，直至电流减小到0.025C；充满电后，在12-24h内进行测试；在25±3℃下，以150mm/s的速度将钢钉刺入电芯中央部分，直至贯穿为止，保持10min后退针。钢钉直径为2.45±0.06mm，长度为45±2.5mm，尖端长度可以在2～4.9mm之间。c.数据处理：观测实验现象，针刺后不起火、不爆炸，判定为通过。
12、130℃热冲击测试
a.取样：每组取5pcs电池。b.测试：在25±3℃下，按照1.2A的恒定电流将电芯充电至限制电压4.43V， 然后再在4.43V恒压充电，直至电流减小到0.025C；充满电后，在12-24h内进行测试；通过对流方式或循环热空气箱，从起始温度25±3℃开始对电芯进行加热，温变率可以为5±2℃/min；升温至130±2℃后保持30min。c.数据处理：观测实验现象，升温后不起火、不爆炸，判定为通过。
13、140℃热冲击测试
a.取样：每组取5pcs电池。b.测试：在25±3℃下，按照1.2A的恒定电流将电池充电至限制电压4.43V，然后再在4.43V恒压充电，直至电流减小到0.025C；充满电后，在12-24h内进行测试；通过对流方式或循环热空气箱，从起始温度25±3℃开始对电池进行加热，温变率可以为5±2℃/min；升温至140±2℃后保持30min。c.数据处理：观测实验现象，升温后不起火、不爆炸，判定为通过。
14、闭孔温度和破膜温度的测试方法
裁取长30mm、宽30mm的隔离膜样品，将其密封在连有正极和负极的金属仓内，然后注入测试用电解液并密封。测试用电解液的制备方法：将锂盐LiPF6与非水有机溶剂(碳酸乙烯酯(EC)∶碳酸二乙酯(DEC)∶碳酸亚丙酯(PC)∶丙酸丙酯(PP)∶碳酸亚乙烯酯(VC))＝20∶30∶20∶28∶2，质量比)按质量比8∶92配制而成的溶液。将金属仓连接电阻记录仪。将金属仓放入200℃烘箱内，记录样品电阻随温度的变化。将样品电阻增加至1000欧姆所对应的温度记为闭孔温度。随温度的升高，将样品电阻重新降为1000欧姆所对应的温度记为破膜温度。
15、交联厚度的测试方法
方式一：十氢萘溶解隔膜前后质量比即为交联层厚度百分比；方式二：交联后拉伸强度增加值与完全交联拉伸强度增加值的比值即为交联层厚度百分比。
[实施例1]
实施例1提供一种新型交联隔膜(下称隔膜基材)。隔膜基材包括聚乙烯、交联剂、光引发剂和抗氧化剂。其中，粘均分子量为110×10 4的聚乙烯在隔膜基材中的占比为100重量份；交联剂为三烯丙基异三聚氰酸酯，在隔膜基材中的占比为1重量份；光引发剂为二苯甲酮，在隔膜基材中的占比为0.7重量份；抗氧化剂为3-(3，5-二叔丁基-4-羟基苯基)丙烯酸异辛酯，抗氧化剂在隔膜基材中的占比为0.3重量份。
实施例1提供的隔膜基材通过以下制备方法制得：
步骤(1)、用钴源或电子加速器对高分子量聚乙烯进行预辐照，得到预辐照的高分子量聚乙烯(辐照剂量具体参数如表1～4)。
步骤(2)、使用双轴叶片混料机，将上述聚乙烯、三烯丙基异三聚氰酸酯、二苯甲酮和3-(3，5-二叔丁基-4-羟基苯基)丙烯酸异辛酯进行预混，得到预混物；在给料机和双螺杆挤出机内部预先通入氮气，然后将预混物通过给料机送入双螺杆挤出机；通过送油泵将液体石蜡预热(液体石蜡的预热温度为40℃，其中，液体石蜡在40℃条件下的粘度可以为28-35厘斯，厘斯是一种运动粘度单位，可简称为cst，1cst＝1mm2/s)送入双螺杆挤出机，挤出量控制在75～100㎏；熔融混炼的温度可以为170℃，螺杆转速可以为28r/min(转每分，revolμtions per minμte，rpm)；通过调整送油泵的输送量，使得在混炼过程中的聚乙烯、三烯丙基异三聚氰酸酯和二苯甲酮混合物的固含量为设定值(如表1)。最终得到共混物；通过T型模头挤出共混物，流延冷却，以获得凝胶片材(厚度如表1～4)。
步骤(3)、将凝胶片材设置在异步拉伸机中，进行双轴拉伸(具体参数如表1～4)。步骤(4)、通过二氯甲烷，对拉伸后的凝胶片材进行萃取，以去除步骤(2)中的液体石蜡。步骤(5)、将萃取后的凝胶片进行紫外高能辐照(具体参数如表1～4)。步骤(6)、将紫外交联后的凝胶片材进行热定型(具体参数如表1～4)。步骤(7)、将热定型后的凝胶片材连续地进行分切、收卷。
实施例1的其他具体参数参照下文中的表1。
[实施例2]
实施例2提供的隔膜包括隔膜基材和隔膜涂层。隔膜基材的原料除交联剂在隔膜基材中的占比为1.5份，其他原料选择及占比同实施例1。隔膜涂层为耐热涂层和粘结涂层。耐热涂层为Al 2O 3。粘接涂层为油性PVDF。实施例2提供的隔膜可以通过实施例1中的步骤(1)-步骤(7)以及步骤(8)得到。步骤(8)、在将收卷后的凝胶片材(即隔膜基材)上设置隔膜涂层。
步骤(8)的具体内容可以包括：将隔膜基材送入涂布装置，采用微凹辊涂布方式，在隔膜基材上涂布耐热涂层(即进行一次涂布)；将包含耐热涂层的隔膜送入干燥箱，并采用热风对隔膜进行干燥(即进行一次干燥)；采用油性体系微凹辊涂布的方式，在涂布耐热涂层的隔膜表面涂布粘接涂层(即进行二次涂布；将包含粘接涂层的隔膜送入干燥箱，并采用热风对隔膜进行干燥(即进行二次干燥)；将(二次)干燥后的隔膜放入收卷装置进行收卷，得到隔膜成品。
实施例2的其他具体参数参照下文中的表1。
[实施例3]
实施例3提供的隔膜包括隔膜基材和隔膜涂层。隔膜基材的原料除交联剂在隔膜基材中的占比为2.0份外，其他原料选择及占比与实施例2相同。隔膜涂层为Al 2O 3耐热涂层和油性PVDF粘结涂层。实施例3提供的隔膜的制造方法和其他具体参数可以参照实施例2和表1，在此就不必再详细赘述。
[实施例4]
实施例4提供的隔膜包括隔膜基材和隔膜涂层。隔膜基材的原料选择及占比同实施例2。隔膜涂层为Al 2O 3耐热涂层和油性PVDF粘结涂层。实施例4提供的隔膜的制造方法和具体参数可以参照实施例2和表1，不再赘述。
[实施例5]
实施例5提供的隔膜包括隔膜基材和隔膜涂层。隔膜基材的原料选择及占比同实施例2。隔膜涂层为Al 2O 3耐热涂层和油性PVDF粘结涂层。实施例5提供的隔膜的制造方法和其他具体参数可以参照实施例2和表1，不再赘述。
[实施例6]
实施例6提供的隔膜包括隔膜基材和隔膜涂层。隔膜基材的原料选择及占比同实施例2。隔膜涂层为Al 2O 3耐热涂层和油性PVDF粘结涂层。实施例6提供的隔膜的制造方法和其他具体参数可以参照实施例2和表1，不再赘述。需要说明的是，实施例6中是采用单面耐热涂层及采用水体系PVDF微凹辊涂布的方式。
表1 实施例1-6的具体参数
Figure PCTCN2022103584-appb-000005
Figure PCTCN2022103584-appb-000006
[实施例7]
实施例7提供的隔膜包括隔膜基材。隔膜基材的原料除了选择加入固态颗粒物熔点为110～120℃的聚乙烯蜡乳液外，其余选择与实施例2相同。隔膜涂层为Al 2O 3耐热涂层和油性PVDF粘结涂层。实施例7提供的隔膜的制造方法和其他具体参数可以参照实施例2和表2，在此就不必再详细赘述。
[实施例8]
实施例8提供的隔膜包括隔膜基材和隔膜涂层。隔膜基材的原料除了选择加入固态颗粒物熔点为110～120℃的聚乙烯蜡乳液外，其余选择与实施例2相同。隔膜涂层为Al 2O 3耐热涂层和油性PVDF粘结涂层。 实施例8提供的隔膜的制造方法和其他具体参数可以参照实施例2和表2，不再赘述。
[实施例9]
实施例9提供的隔膜包括隔膜基材和隔膜涂层。隔膜基材的原料除了选择加入固态颗粒物熔点为110～120℃的聚乙烯蜡乳液外，其余选择与实施例2相同。隔膜涂层为耐热涂层和粘结涂层。耐热涂层为Al 2O 3。粘接涂层为油性PVDF。实施例9提供的隔膜的制造方法和其他具体参数可以参照实施例2和表2，在此就不必再详细赘述。需要说明的是，实施例9的具体加工参数与实施例2的具体加工参数不同(例如包括挤出量、凝胶片材厚度和双轴拉伸的拉伸倍率等)。
[实施例10]
实施例10提供的隔膜包括隔膜基材和隔膜涂层。隔膜基材的原料除了选择加入固态颗粒物熔点为110～120℃的聚乙烯蜡乳液外，其余选择和隔膜涂层与实施例2相同。粘接涂层为油性PVDF。实施例10提供的隔膜的制造方法和其他具体参数可以参照实施例2和表2，不再赘述。需要说明的是，实施例10的具体加工参数与实施例2的具体加工参数不同(例如包括聚合物固含量等)。
[实施例11]
实施例11提供的隔膜包括隔膜基材和隔膜涂层。隔膜基材的原料除了选择加入固态颗粒物熔点为110～120℃的聚乙烯蜡乳液外，其余选择与实施例2相同。隔膜涂层为耐热涂层和粘结涂层。耐热涂层为Al 2O 3。粘接涂层为油性PVDF。实施例11提供的隔膜的制造方法和其他具体参数可以参照实施例2和表2，在此就不必再详细赘述。需要说明的是，实施例11的具体加工参数与实施例2的具体加工参数不同(例如包括挤出量、凝胶片材厚度和双轴拉伸的拉伸倍率等)。
[实施例12]
实施例12提供的隔膜包括隔膜基材和隔膜涂层。隔膜基材的原料除了选择加入固态颗粒物熔点为110～120℃的聚乙烯蜡乳液外，其余选择及隔膜涂层与实施例2相同。实施例12提供的隔膜的制造方法和具体参数可以参照实施例11和表2，在此就不必再详细赘述。
表2 实施例7-12的具体参数
Figure PCTCN2022103584-appb-000007
Figure PCTCN2022103584-appb-000008
[实施例13-15]
实施例13-15提供的隔膜包括隔膜基材和隔膜涂层。隔膜基材的原料选择及占比与实施例2相同。隔膜涂层为Al 2O 3耐热涂层和油性PVDF粘结涂层实施例13-15提供的隔膜的制造方法和具体参数可以参照实施例11和表3，不再赘述。
[实施例16-18]
实施例16-18提供的隔膜包括隔膜基材和隔膜涂层。隔膜基材的原料除了选择加入固态颗粒物熔点为80～90℃的聚乙烯蜡乳液外，其余选择及隔膜涂层同实施例2。实施例16-18提供的隔膜的制造方法和参数可以参照实施例11和表4，不再赘述。
[对比例1-3]
对比例1-3提供的隔膜包括隔膜基材和隔膜涂层。对比例1提供的隔膜为粘均分子量为110×10 4的聚乙烯。对比例1提供的隔膜通过以下方法得到：
步骤(1)、使用双轴叶片混料机，将聚乙烯在给料机和双螺杆挤出机内部预先通入氮气，然后将聚乙烯通过给料机送入双螺杆挤出机；通过送油泵将液体石蜡预热(液体石蜡的预热温度为40℃。液体石蜡在40℃条件下的粘度可以为28-35厘斯，厘斯是一种运动粘度单位，可简称为cst，1cst＝1mm2/s)送入双螺杆挤出机，挤出量控制在75～100㎏；熔融混炼的温度可以为170℃，螺杆转速可以为28r/min；通过调整送油泵的输送量，使得在混炼过程中的聚乙烯的固含量为设定值(如表3)。最终得到共混物；通过T型模头挤出共混物，并流延冷却，以获得凝胶片材(凝胶片材的厚度如表3)。步骤(2)、将凝胶片材设置在异步拉伸机中，进行双轴拉伸(具体参数如表1)。步骤(3)、通过二氯甲烷，对拉伸后的凝胶片材进行萃取，以去除步骤(1)中的液体石蜡。步骤(4)、将紫外交联后的凝胶片材进行热定型(具体参数如表 1)。步骤(5)、将热定型后的凝胶片材进行分切、收卷。
对比例1的其他具体参数参照下文中的表3。隔膜涂层为Al 2O耐热涂层和油性PVDF粘结涂层。对比例2-6提供的隔膜的制造方法和具体参数可以参照对比例1和表3，不再赘述。
[对比例7-9]
对比例7-9提供的隔膜包括隔膜基材和隔膜涂层。
隔膜基材的原料选择、占比以及隔膜涂层同对比例1。对比例7-9提供的隔膜的制造方法和具体参数可以参照实施例11和表4，在此就不必再详细赘述。
实施例1-6的5μm隔膜破膜温度均达到175℃以上。
通过实施例1-3可以看出，提高交联剂的比例，有利于提高隔膜交联密度且交联剂的比例大于1.5之后，隔膜交联密度出现拐点；进一步提高交联剂比例，还可能产生熔体塑化不均匀的问题，降低膜面质量，还可能提高隔膜的闭孔温度。这意味着，对于隔膜的综合性能而言，交联剂比例并非越高越好。
通过实施例4-6可以看出，紫外线波长对交联密度有至关重要的作用，紫外线波长越长，辐射能力越强所携带能量越多，但穿透能力越弱，只能对隔膜表面进行交联，隔膜芯层没有交联，隔膜交联密度越小，难以提高隔膜的交联密度，进而隔膜高温热稳定性差。但由于只进行表层浅层次聚烯烃的交联，芯层还保有聚烯烃的低熔点性能，所以隔膜的低温闭孔温度比较低。
通过实施例6-7和实施例12可以看出，隔膜的涂层工艺(如调整涂层材料、体系等条件)可以影响隔膜的电芯性能指标，提高隔膜性能一致性。
通过实施例7-9可以看出，辐射时间的增加，隔膜的交联密度显著增加，可以通过控制辐射时间，进而控制隔膜的交联密度。同时也有利于提高隔膜的机械性性能和热稳定性。但是隔膜的闭孔温度也随之增高，反而不利于电池的安全性能。
通过实施例10-12可以看出，提高高压汞灯的功率可以进一步提高隔膜的交联密度和交联速率，因此可以通过匹配高压汞灯的功率和线速度，从而可以得到合适的隔膜。但随着高压汞灯的功率的提高，汞灯所产生的热量对隔膜外观产生较大的影响，降低隔膜质量。且随着交联密度的提高，隔膜的断裂延伸率急剧下降，进而影响电芯的针刺通过率。
通过将聚烯烃组合物、交联剂、光引发剂按照特定方式混合、采用传统湿法隔膜制造工艺并采用适宜的紫外线进行辐射，实现隔膜表面聚烯烃的交联，而内部芯层可以保持低温闭孔性能，可以形成具有高破膜温度、低闭孔温度、高穿刺强度、高温热稳定性良好的隔膜。
表3 实施例13-15及对比例1-6的具体参数
Figure PCTCN2022103584-appb-000009
Figure PCTCN2022103584-appb-000010
Figure PCTCN2022103584-appb-000011
通过实施例13-15可以看出，提高交联隔膜厚度可以提高隔膜的拉伸强度和延伸率，同时提高隔膜在电芯中热冲击通过率，因此可以通过匹配隔膜的厚度，从而可以得到合适的隔膜应用场景。通过对比例1-3可以看出，常规隔膜在不同厚度情况下，具有相似的闭孔温度，未交联聚乙烯隔膜的闭孔温度在138-141℃之间，破膜温度在150-160℃之间，与实施例相比，通过控制聚乙烯交联密度，可以得到破膜特性优异的隔膜。通过对比例4-6可以看出，交联隔膜不经预辐照的情况下，各力学性能都差于辐照后隔膜但强于未交联基膜。其闭孔温度及破膜温度低于预辐照隔膜且高于未交联基膜。
表4 实施例16-18及对比例7-9的具体参数
Figure PCTCN2022103584-appb-000012
Figure PCTCN2022103584-appb-000013
通过实施例16-18可以看出，提高聚乙烯的分子量可以提高隔膜的拉伸强度和延伸率，同时改善了破膜温度，且分子量越高，交联密度越低，破膜温度越高，因此可以通过匹配聚乙烯的分子量，从而可以得到合适的隔膜应用场景。通过对比例7-9可以看出，不同聚乙烯分子量生产常规隔膜情况下，闭孔温度与分子量高低呈正相关，通过控制聚乙烯交联密度，可以得到破膜特性优异的隔膜。
根据测试可知，本申请提供的5～6μm厚度的新型交联隔膜可以具有191～236℃的破膜温度，95～121℃的闭孔温度。与非交联隔膜相比，本申请实施例提供的隔膜具有相对高的破膜温度，相对较宽的闭孔破膜平台。并且，该隔膜具有相对较高的拉伸模量和拉伸强度，这有利于隔膜在电芯工艺中的加工(例如有利于避免因高延伸特性导致的边缘突出、卷绕偏离、弯曲、褶皱等问题)以及电芯的针刺通过率。本申请提供的隔膜有利于提高电池的耐机械滥用和耐热滥用性能，其综合性能十分优异。
以上涉及到数据表中的数据由于存在保留小数点位数的问题，其相近的数据范围将被合理的保护和支持，例如本申请的新型交联隔膜的厚度为5～6μm等。本申请中所谓交联剂比例为交联剂重量份与聚烯烃组合物重量份的比值。
以上涉及到公知常识的内容不作详细描述，本领域的技术人员能够理解。以上所述仅为本申请的一些具体实施例而已，并不用以限制本申请，凡在本申请的精神和原则之内，所作的任何修改、等同替换、改进等，均应包含在本申请的保护范围之内。本项申请的技术性范围并不局限于说明书上的内容，必须要根据权利要求范围来确定其技术性范围。

Claims (34)

  1. 一种新型交联隔膜，其包括：紫外交联上表层、芯层和紫外交联下表层；所述紫外交联上表层和/或所述紫外交联下表层中包括交联剂和光引发剂；所述芯层中包括聚烯烃组合物；所述新型交联隔膜的厚度为0.5～12μm；所述紫外交联上表层与所述紫外交联下表层的厚度之和为所述新型交联隔膜的厚度的20％～80％；所述新型交联隔膜的破膜温度为191～215℃。
  2. 根据权利要求1所述的新型交联隔膜，其中，所述聚烯烃组合物包括第一聚乙烯和第二聚乙烯，所述第一聚乙烯和所述第二聚乙烯均选自以下任意一种：聚乙烯、聚乙烯-丙烯共聚物、聚乙烯-丙烯共聚物的衍生物、聚乙烯-丁烯共聚物、聚乙烯-丁烯共聚物的衍生物、聚乙烯-己烯共聚物、聚乙烯-己烯共聚物的衍生物、聚乙烯-辛烯共聚物、聚乙烯-辛烯共聚物的衍生物、聚苯乙烯-乙烯-苯乙烯共聚物、聚苯乙烯-乙烯-苯乙烯共聚物的衍生物、聚苯乙烯-乙烯-丁烯-苯乙烯共聚物、聚苯乙烯-乙烯-丁烯-苯乙烯共聚物的衍生物、聚乙烯-氢化寡环戊二烯、聚乙烯-氢化寡环戊二烯的衍生物、聚氧化乙烯、聚氧化乙烯的衍生物、聚戊烯-乙烯共聚物、聚戊烯-乙烯共聚物的衍生物、聚己烯-乙烯共聚物、聚己烯-乙烯共聚物的衍生物、聚甲基戊烯-乙烯共聚物以及聚甲基戊烯-乙烯共聚物的衍生物。
  3. 根据权利要求1所述的新型交联隔膜，其中，所述聚烯烃组合物还包括聚丙烯或其衍生物，所述聚丙烯或其衍生物的热焓△Hm为55～85J/g，密度≥0.9g/cm 3。
  4. 根据权利要求1～3任一项所述的新型交联隔膜，其中，所述芯层中还包括聚烯烃类乳液。
  5. 根据权利要求1所述的新型交联隔膜，其中，所述交联剂为带有烯类双键的双官能团或多官能团单体，包括以下至少一种：1,6-己二醇二丙烯酸酯、新戊二醇二丙烯酸酯、二乙烯基苯、双马来酸二丙烯酸酯、三羟甲基丙烷三丙烯酸酯、三羟甲基丙烷三甲基丙烯酸酯、三烯丙基异三聚氰酸酯、季戊四醇三丙烯酸酯、季戊四醇四丙烯酸酯和二季戊四醇六丙烯酸酯。
  6. 根据权利要求1所述的新型交联隔膜，其中，所述光引发剂为自由基聚合光引发剂或阳离子聚合光引发剂，包括以下至少一种：安息香、安息香双甲醚、安息香乙醚、安息香异丙醚、安息香丁醚、二苯基乙酮、α,α-二甲氧基-α-苯基苯乙酮、α,α-二乙氧基苯乙酮、α-羟烷基苯酮、α-胺烷基苯酮、芳酰基膦氧化物、双苯甲酰基苯基氧化膦、二苯甲酮、2,4-二羟基二苯甲酮、米蚩酮、硫代丙氧基硫杂蒽酮、异丙基硫杂蒽酮、二芳基碘鎓盐、三芳基碘鎓盐、烷基碘鎓盐和异丙苯茂铁六氟磷酸盐。
  7. 根据权利要求1所述的新型交联隔膜，其中，所述新型交联隔膜的厚度为3～9μm；所述紫外交联上表层与所述紫外交联下表层的厚度之和为所述新型交联隔膜的厚度的20％～75％。
  8. 根据权利要求6所述的新型交联隔膜，其中，所述新型交联隔膜的厚度为5～6μm。
  9. 根据权利要求1所述的新型交联隔膜，其中，所述新型交联隔膜的闭孔温度为95～150℃。
  10. 根据权利要求9所述的新型交联隔膜，其中，所述闭孔温度为95～121℃。
  11. 根据权利要求9所述的新型交联隔膜，其中，所述闭孔温度与所述破膜温度的差值介于49～103℃之间。
  12. 根据权利要求1所述的新型交联隔膜，其中，所述新型交联隔膜的交联密度为12～72％。
  13. 根据权利要求1所述的新型交联隔膜，其中，所述新型交联隔膜的透气度为150～155s/100cc。
  14. 根据权利要求1所述的新型交联隔膜，其中，所述新型交联隔膜的横向和纵向延伸率均在80～120％之间。
  15. 根据权利要求1所述的新型交联隔膜，其中，所述新型交联隔膜的横向和纵向拉伸强度均≥2000kgf/cm 2，横向和纵向拉伸模量均≥2000Mpa。
  16. 根据权利要求1所述的新型交联隔膜，其中，所述新型交联隔膜的穿刺强度为650～1400gf。
  17. 根据权利要求1所述的新型交联隔膜，其中，所述新型交联隔膜在120℃下的横向和纵向热收缩率均≤1.8％。
  18. 根据权利要求1所述的新型交联隔膜，其中，所述聚烯烃组合物的粘均分子量在30×10 4～1000×10 4之间。
  19. 根据权利要求1所述的新型交联隔膜，其中，所述新型交联隔膜的一侧或两侧上设置有涂层，所 述涂层包括有机涂层、无机涂层和有机/无机复合涂层中的一种或多种。
  20. 根据权利要求19所述的新型交联隔膜，其中，所述无机涂层包括陶瓷涂层，所述陶瓷涂层包括以下至少一种：氧化铝，氧化硅，氧化钛，氧化锆，氧化锌，氧化钡，氧化镁，氧化铍，氧化钙，氧化钍，氮化铝，氮化钛，勃母石，磷灰石，氢氧化铝，氢氧化镁，硫酸钡，氮化硼，碳化硅，氮化硅，立方氮化硼，六方氮化硼，介孔分子筛和珍珠云母层。
  21. 根据权利要求19所述的新型交联隔膜，其中，所述有机涂层包括以下至少一种：聚偏氟乙烯涂层、偏二氟乙烯-六氟丙烯共聚物涂层、聚苯乙烯涂层、芳纶涂层、聚丙烯酸酯或其改性物涂层、聚酯涂层、聚芳酯涂层、聚丙烯腈涂层、芳香族聚酰胺涂层、聚酰亚胺涂层、聚醚砜涂层、聚砜涂层、聚醚酮涂层、聚醚酰亚胺涂层、聚苯并咪唑涂层和聚多巴胺。
  22. 一种新型交联隔膜的制备方法，其包括以下步骤：
    S1、将聚烯烃组合物进行预辐照，辐照剂量为0.1～1Mrad，得到预辐照的聚烯烃组合物；
    S2、将包括有所述预辐照的聚烯烃组合物、交联剂、光引发剂以及成孔剂的原料混合物混合，并从螺杆挤出机挤出，形成凝胶片材；
    S3、对所述凝胶片材进行双轴拉伸，后去除所述凝胶片材中的成孔剂；
    S4、对所述凝胶片材进行热定型，所述热定型包括低倍率拉伸和回缩操作；
    S5、对所述凝胶片材进行紫外线照射表层，进行交联；
    S6、对所述凝胶片材进行收卷、分切，形成所述新型交联隔膜。
  23. 根据权利要求22所述新型交联隔膜的制备方法，其中，所述S1中，所述聚烯烃组合物包括粘均分子量不同的一种或多种聚乙烯、聚乙烯共聚物、聚丙烯或聚丙烯衍生物。
  24. 根据权利要求22所述新型交联隔膜的制备方法，其中，所述S2中，所述原料混合物还包括聚烯烃类乳液。
  25. 根据权利要求22所述新型交联隔膜的制备方法，其中，按所述聚烯烃组合物的重量为100份计，所述交联剂的重量介于1～1.5份之间，所述光引发剂的重量介于0.7～1.2份之间。
  26. 根据权利要求24所述新型交联隔膜的制备方法，其中，所述聚烯烃类乳液为聚乙烯蜡乳液，其固含量在10％～70％，固态颗粒物熔点为80～120℃。
  27. 根据权利要求22所述新型交联隔膜的制备方法，其中，在所述S1中，采用钴源或电子加速器进行预辐照。
  28. 根据权利要求22所述新型交联隔膜的制备方法，其中，所述S3中，双轴拉伸后的面积为双轴拉伸前的面积的10～50倍。
  29. 根据权利要求22所述新型交联隔膜的制备方法，其中，所述S4中，所述低倍率拉伸为1～3倍的拉伸，所述低倍率拉伸的拉伸温度为105～135℃；所述回缩操作的回缩比为0.5～20％。
  30. 根据权利要求22所述新型交联隔膜的制备方法，其中，所述S5中，紫外线的波长范围介于230～350nm之间。
  31. 根据权利要求22所述新型交联隔膜的制备方法，其中，所述S5中，紫外线辐射时间为0.2～1s。
  32. 根据权利要求22所述新型交联隔膜的制备方法，其中，所述S5中，紫外线辐射功率为1～4Kw。
  33. 一种电池，其包括：正极、负极、电解质，以及权利要求1～21中任一项所述的新型交联隔膜或者根据权利要求22～32任一项所述的新型交联隔膜的制备方法制得的所述新型交联隔膜。
  34. 一种电子设备，其包括：壳体、收容于所述壳体内的显示屏、电路板组件和权利要求33所述的电池；所述电池为所述显示屏和所述电路板组件供电。
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