WO2024192592A1 - 隔离膜、二次电池和用电装置 - Google Patents

隔离膜、二次电池和用电装置 Download PDF

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Publication number
WO2024192592A1
WO2024192592A1 PCT/CN2023/082335 CN2023082335W WO2024192592A1 WO 2024192592 A1 WO2024192592 A1 WO 2024192592A1 CN 2023082335 W CN2023082335 W CN 2023082335W WO 2024192592 A1 WO2024192592 A1 WO 2024192592A1
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Prior art keywords
porous base
membrane
base membrane
average pore
porous
Prior art date
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Ceased
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PCT/CN2023/082335
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English (en)
French (fr)
Inventor
王兆光
杨建瑞
欧阳楚英
孙成栋
黄思应
穆雪颖
韩崇旺
王耀辉
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Contemporary Amperex Technology Co Ltd
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Contemporary Amperex Technology Co Ltd
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Application filed by Contemporary Amperex Technology Co Ltd filed Critical Contemporary Amperex Technology Co Ltd
Priority to EP23927911.0A priority Critical patent/EP4611155A4/en
Priority to PCT/CN2023/082335 priority patent/WO2024192592A1/zh
Priority to KR1020257014430A priority patent/KR20250081907A/ko
Priority to CN202380045997.XA priority patent/CN119343824A/zh
Priority to JP2025525149A priority patent/JP2025536584A/ja
Publication of WO2024192592A1 publication Critical patent/WO2024192592A1/zh
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B32B27/08—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/32—Layered products comprising a layer of synthetic resin comprising polyolefins
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
    • B32B7/02—Physical, chemical or physicochemical properties
    • B32B7/022—Mechanical properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
    • B32B7/02—Physical, chemical or physicochemical properties
    • B32B7/027—Thermal properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
    • B32B7/04—Interconnection of layers
    • B32B7/12—Interconnection of layers using interposed adhesives or interposed materials with bonding properties
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/04—Construction or manufacture in general
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • H01M50/42—Acrylic resins
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/431—Inorganic material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/443—Particulate material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
    • H01M50/451—Separators, membranes or diaphragms characterised by the material having a layered structure comprising layers of only organic material and layers containing inorganic material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • H01M50/491—Porosity
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2255/00—Coating on the layer surface
    • B32B2255/10—Coating on the layer surface on synthetic resin layer or on natural or synthetic rubber layer
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2255/00—Coating on the layer surface
    • B32B2255/26—Polymeric coating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/70—Other properties
    • B32B2307/724—Permeability to gases, adsorption
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2457/00—Electrical equipment
    • B32B2457/10—Batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application belongs to the technical field of secondary batteries, and specifically relates to an isolation membrane, a secondary battery and an electrical device.
  • Secondary batteries are widely used in various consumer electronic products and electric vehicles due to their outstanding characteristics of light weight, no pollution and no memory effect.
  • the present application provides a separation membrane, aiming to improve the cyclability of secondary batteries.
  • the first aspect of the present application provides an isolation membrane, which includes: a first porous base membrane and a second porous base membrane; the melting point of the first porous base membrane is higher than the melting point of the second porous base membrane; in the cross-section along the thickness direction of the isolation membrane, the average pore area of the first porous base membrane is greater than the average pore area of the second porous base membrane.
  • the isolation membrane with a specific structure in the present application can not only improve the heat resistance, but also improve the air permeability.
  • the two base membranes adopt the specific average pore area design scheme of the present application the pore blockage caused by the physical lamination in the isolation membrane preparation process is effectively reduced, thereby improving the air permeability of the isolation membrane and maintaining the continuity and effectiveness of ion transmission.
  • the isolation membrane can also have good puncture performance, so that the two can achieve an optimal balance, thereby improving the battery cycle performance.
  • the ratio of the average pore area of the first porous substrate membrane to the average pore area of the second porous substrate membrane is 1.05-10, and can be optionally 1.5-3.5.
  • the separator can have better air permeability, which is conducive to the penetration of lithium ions.
  • the average pore area of the second porous substrate is relatively small relative to the average pore area of the first porous substrate.
  • the smaller the average pore area the more the fiber filaments of the second porous substrate occupy the spatial structure of the substrate, the greater the strength of the substrate, and the more it can resist lithium dendrites. Therefore, the separator can have both air permeability and mechanical strength, thereby improving the reliability and cycle performance of the separator.
  • the ratio of the average pore area of the first porous substrate to the average pore area of the second porous substrate is 1.5-3.5, the air permeability and mechanical strength of the separator can be further improved, thereby further improving the reliability and cycle performance of the separator.
  • the average pore area of the first porous substrate is 0.0001 ⁇ m 2 -0.5 ⁇ m 2 , optionally 0.01 ⁇ m 2 -0.3 ⁇ m 2 ; and/or the average pore area of the second porous substrate is 0.0001 ⁇ m 2 -0.4 ⁇ m 2 , optionally 0.01 ⁇ m 2 -0.25 ⁇ m 2 .
  • the separator can have both air permeability and mechanical strength, thereby improving the reliability and cycle performance of the separator.
  • the air permeability and mechanical strength of the separator can be further improved, thereby further improving the reliability and cycle performance of the separator.
  • the average pore size of the first porous substrate membrane is greater than the average pore size of the second porous substrate membrane; optionally, the average pore size of the first porous substrate membrane is 100nm-2000nm, and more optionally 100nm-350nm; optionally, the average pore size of the second porous substrate membrane is 100nm-2000nm, and more optionally 100nm-300nm.
  • the average pore size of the first porous substrate is 100nm-2000nm, and/or, when the average pore size of the second porous base membrane is 100nm-2000nm, because the average pore size of the two is different, the smaller the average pore size, the smaller the space occupied by the average pore area, the larger the space occupied by the fiber filaments of the base membrane, and the stronger the mechanical strength of the base membrane; on the contrary, the smaller the space occupied by the fiber filaments of the base membrane, the larger the average pore area of the separator, and the better the air permeability.
  • the separator can have both air permeability and mechanical strength, thereby improving the reliability and cycle performance of the separator.
  • the average pore size of the first porous base membrane is 100nm-350nm
  • the average pore size of the second porous base membrane is 100nm-300nm
  • the air permeability and mechanical strength of the separator can be further improved, thereby further improving the reliability and cycle performance of the separator.
  • the porosity of the first porous base membrane is greater than the porosity of the second porous base membrane; optionally, the porosity of the first porous base membrane is 30%-80%, more optionally 35%-60%; and/or, the porosity of the second porous base membrane is 30%-70%, more optionally 35%-50%.
  • the porosity of the first porous base membrane is greater than the porosity of the second porous base membrane, the porosity of the first porous base membrane is 30%-80%, and/or the porosity of the second porous base membrane is 30%-70%, the porosities of the two base membranes are different, indicating that the proportion of the hole structure per unit area is different, that is, the average pore area is different, the porous base membrane with a large average pore area has good air permeability, and the base membrane with a small average pore area has good mechanical strength.
  • the combination of the two can make the isolation membrane have both air permeability and mechanical strength, thereby improving the reliability and cycle performance of the isolation membrane.
  • the air permeability and mechanical strength of the isolation membrane can be further improved, thereby further improving the reliability and cycle performance of the isolation membrane.
  • the separator further includes a porous coating layer, the porous coating layer is disposed between the first porous base film and the second porous base film, and the porous coating layer includes a binder; optionally, the porous coating layer includes a binder and a filler.
  • the separator further includes a porous coating layer, and the porous coating layer includes a binder and a filler, the heat resistance of the separator can be improved, and the reliability of the secondary battery can be improved.
  • the binder includes one or more of polyacrylate, polyacrylic acid, polytetrafluoroethylene, polyvinylidene fluoride, vinylidene fluoride-trichloroethylene copolymer, polyvinyl pyrrolidone, polyvinyl acetate, ethylene-vinyl acetate copolymer, polyethylene oxide, polyarylate, carboxymethyl cellulose, hydroxypropyl cellulose, regenerated cellulose, cellulose acetate, cellulose acetate propionate, cellulose acetate butyrate, polyacrylonitrile, polyvinyl alcohol, polyethylene, polypropylene, starch, and cyanoethyl pullulan.
  • a porous coating is provided between the first porous base film and the second porous base film, and the binder in the porous coating includes the above components, the reliability of the secondary battery can be improved.
  • the filler includes at least one of inorganic particles, organic particles, and organic-metal framework materials.
  • the filler in the porous coating can further improve the heat resistance and mechanical strength of the separator, thereby improving the reliability of the secondary battery.
  • the isolation membrane satisfies at least one of the following (1)-(2): (1) the porosity of the isolation membrane is 30%-70%, and can be optionally 35%-55%; (2) the air permeability of the isolation membrane is 250s/100cc-400s/100cc, and can be optionally 250s/100cc-320s/100cc.
  • the separator can have good heat resistance, air permeability and mechanical strength, thereby improving the reliability and cycle performance of the secondary battery.
  • the second aspect of the present application provides a secondary battery, including a separator according to any of the above schemes.
  • the first porous base membrane with a large average pore area faces the positive electrode
  • the second porous base membrane with a small average pore area faces the negative electrode
  • the second porous base membrane has good mechanical strength, can exert its excellent physical properties, and is not easily punctured by lithium dendrites generated by the negative electrode, which can improve the reliability of the secondary battery.
  • the secondary battery comprises a positive electrode sheet, a negative electrode sheet and a separator of any of the above schemes, the separator is arranged between the positive electrode sheet and the negative electrode sheet, and the second porous base film of the separator faces the negative electrode sheet.
  • the second porous base film with a large average pore area faces the negative electrode sheet, because the second porous base film has better mechanical properties. Strength, can give full play to its excellent physical properties, is not easily punctured by lithium dendrites generated by the negative electrode, and can improve the reliability of the secondary battery.
  • the third aspect of the present application provides an electric device, which includes the secondary battery of the second aspect of the present application.
  • the secondary battery of the electric device adopts the given isolation film, the reliability of the electric device can be improved.
  • the device of the present application includes the secondary battery provided by the present application, it has at least the same advantages as the secondary battery.
  • FIG. 1 is a schematic structural diagram of an isolation membrane according to an embodiment of the present application.
  • FIG. 2 is a schematic structural diagram of another embodiment of the isolation membrane of the present application.
  • FIG. 3 is a schematic diagram of an embodiment of a secondary battery.
  • FIG. 4 is an exploded view of FIG. 3 .
  • FIG. 5 is a schematic diagram of an embodiment of a battery module.
  • FIG. 6 is a schematic diagram of an embodiment of a battery pack.
  • FIG. 7 is an exploded view of FIG. 6 .
  • FIG. 8 is a schematic diagram of an embodiment of a device in which a secondary battery is used as a power source.
  • any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, and any upper limit can be combined with any other upper limit to form an unspecified range.
  • each separately disclosed point or single value can itself be combined as a lower limit or upper limit with any other point or single value or with other lower limits or upper limits to form an unspecified range.
  • the term "or” is inclusive. That is, the phrase “A or (or) B” means “A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B”: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).
  • a secondary battery is a battery that can be recharged to activate the active materials after being discharged and continue to be used.
  • a secondary battery includes a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte.
  • active ions are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet.
  • the separator is arranged between the positive electrode sheet and the negative electrode sheet to play a role of isolation.
  • the electrolyte plays a role of conducting ions between the positive electrode sheet and the negative electrode sheet.
  • an embodiment of the present application provides a separator 10 , including: a first porous base membrane 11 and a second porous base membrane 12 ,
  • the melting point of the first porous substrate 11 is higher than that of the second porous substrate 12 .
  • the average pore area of the first porous substrate 11 is larger than that of the second porous substrate 12 .
  • the average pore area of the porous base membrane refers to the ratio of the total pore area of the porous base membrane to the number of pores in the porous base membrane in a cross section along the thickness direction of the separator.
  • the inventors have discovered through extensive research that the isolation membrane with a specific structure of the present application can not only improve heat resistance, but also improve air permeability.
  • the two base membranes adopt the specific average pore area design of the present application, the pore blockage caused by physical lamination in the isolation membrane preparation process is effectively reduced, thereby improving the air permeability of the isolation membrane, maintaining the continuity and effectiveness of ion transmission, and at the same time allowing the isolation membrane to have good puncture performance, so that the two can achieve an optimal balance, thereby improving the cycle performance of the battery.
  • the inventors have found through in-depth research that when the isolation membrane of the present application satisfies the above conditions and optionally satisfies one or more of the following conditions, the performance of the secondary battery can be further improved.
  • the material of the first porous base membrane and the second porous base membrane there is no particular restriction on the material of the first porous base membrane and the second porous base membrane, and any known base membrane with good chemical stability and mechanical stability can be selected.
  • the materials of the first porous base membrane and the second porous base membrane of the isolation membrane are the same or different.
  • the first porous base membrane and the second porous base membrane can be selected from one or more of polyolefin, polyether, polyetheretherketone, polyethylene terephthalate, polyimide, polytetrafluoroethylene, polytetrafluorovinylidene fluoride, polyvinyl alcohol, glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the melting points of the first porous base membrane and the second porous base membrane can be tested using equipment and methods known in the art.
  • differential scanning calorimetry can be used for determination.
  • the determination can be carried out according to the following method: take 4-6 mg of the sample to be tested, place it in the sample chamber of the differential scanning calorimeter, and increase the temperature from 25°C to 400°C at a heating rate of 10°C/min to obtain the melting endothermic curve of the sample. The temperature corresponding to the peak of the curve is the melting point of the sample.
  • the ratio of the average pore area of the first porous substrate to the average pore area of the second porous substrate is 1.05-10, for example, it can be 1.05, 1.2, 1.3, 1.4, 1.5, 2, 2.3, 2.55, 3, 3.1, 3.3, 3.5, 3.7, 4, 4.5, 5, 5.3, 6, 7, 8, 8.5, 9, 9.5, 10 or a range consisting of any two of the above values.
  • it can be 1.05-2.5, 1.05-3.5, 3-6, 4-7, 5-9, 1.05-10, 7-10, 8-10, 9-10, etc.
  • the ratio of the average pore area of the first porous substrate to the average pore area of the second porous substrate is 1.05-10.
  • the ratio of the average pore area of the first porous substrate to the average pore area of the second porous substrate is 1.5-3.5, for example, 1.5, 1.7, 1.9, 2, 2.1, 2.3, 2.5, 2.7, 3, 3.1, 3.3, 3.5 or a range consisting of any two of the above values. For example, 1.5-2.5, 1.5-3.3, 2-3, 2.5-3.5, etc.
  • the separator can have better air permeability, which is conducive to the penetration of lithium ions.
  • the average pore area of the second porous substrate is relatively small relative to the average pore area of the first porous substrate.
  • the smaller the average pore area the more the fiber filaments of the second porous substrate occupy the spatial structure of the substrate, the greater the strength of the substrate, and the more it can resist lithium dendrites. Therefore, the separator can have both air permeability and mechanical strength, thereby improving the reliability and cycle performance of the separator.
  • the ratio of the average pore area of the first porous substrate to the average pore area of the second porous substrate is 1.5-3.5, the air permeability and mechanical strength of the separator can be further improved, thereby further improving the reliability and cycle performance of the separator.
  • the average pore area of the first porous base membrane is 0.0001 ⁇ m 2 -0.5 ⁇ m 2 , for example, 0.0001 ⁇ m 2 , 0.0005 ⁇ m 2 , 0.001 ⁇ m 2 , 0.005 ⁇ m 2 , 0.01 ⁇ m 2 , 0.05 ⁇ m 2 , 0.1 ⁇ m 2 , 0.2 ⁇ m 2 , 0.3 ⁇ m 2 , 0.4 ⁇ m 2 , 0.5 ⁇ m 2 or a range consisting of any two of the above values.
  • the average pore area of the first porous substrate is 0.01 ⁇ m 2 -0.3 ⁇ m 2 .
  • the average pore area of the second porous substrate is 0.0001 ⁇ m 2 -0.4 ⁇ m 2 , for example, 0.0001 ⁇ m 2 , 0.0005 ⁇ m 2 , 0.001 ⁇ m 2 , 0.005 ⁇ m 2 , 0.01 ⁇ m 2 , 0.05 ⁇ m 2 , 0.1 ⁇ m 2 , 0.2 ⁇ m 2 , 0.25 ⁇ m 2 , 0.3 ⁇ m 2 , 0.4 ⁇ m 2 or a range consisting of any two of the above values.
  • the second porous base membrane has an average pore area of 0.01 ⁇ m 2 -0.25 ⁇ m 2 .
  • the separator can have both heat resistance, air permeability and mechanical strength, thereby improving the reliability and cycle performance of the separator.
  • the heat resistance, air permeability and mechanical strength of the separator can be further improved, thereby further improving the reliability and cycle performance of the separator.
  • the cross-sectional image of the isolation membrane is an image along the thickness direction of the isolation membrane.
  • a certain size (e.g., 15 mm ⁇ 15 mm) of the isolation membrane sample to be tested can be cut out from any area of the isolation membrane, and the isolation membrane cross section can be obtained by cutting with an ion beam polisher (e.g., Hitachi Arblade 5000) under freezing conditions (e.g., -80°C); referring to JY/T010-1996, a scanning electron microscope (e.g., Sigma 300 scanning electron microscope of ZEISS, Germany) is used to scan and obtain a SEM image of the isolation membrane cross section (the magnification can be 1000 to 30,000 times); an image processing detection system (e.g., Yihong isolation membrane detection system 2022-0408) is used to obtain the average pore area of the porous base membrane using a multi-segment binarization method.
  • an ion beam polisher e.g., Hitachi Arblade 5000
  • freezing conditions e
  • the test sample When using an ion beam polisher for cutting, the test sample can be wrapped with copper foil or aluminum foil before cutting. When obtaining a SEM image of the isolation film cross section, the test sample can be subjected to gold spraying.
  • the pore area data of the first porous base membrane and the second porous base membrane of the isolation membrane can be obtained respectively, and then the average pore area of the first porous base membrane and the second porous base membrane of the isolation membrane can be obtained respectively through the Mintab software.
  • the ratio of the total pore area of the first porous base membrane of the isolation membrane to the number of pores in the first porous base membrane is the average pore area of the first porous base membrane
  • the ratio of the total pore area of the second porous base membrane of the isolation membrane to the number of pores in the second porous base membrane is the average pore area of the second porous base membrane.
  • the average pore size of the first porous substrate is greater than the average pore size of the second porous substrate, and the average pore size of the first porous substrate is 100nm-2000nm, for example, it can be 100nm, 200nm, 250nm, 300nm, 350nm, 500nm, 700nm, 900nm, 1000nm, 1250nm, 1500nm, 1700nm, 1800nm, 1900nm, 2000nm or a range composed of any two of the above values.
  • the average pore size of the first porous substrate is 100nm-350nm.
  • the average pore size of the second porous substrate is 100nm-2000nm, for example, 100nm, 200nm, 220nm, 250nm, 300nm, 350nm, 500nm, 550nm, 700nm, 900nm, 1000nm, 1250nm, 1500nm, 1700nm, 1800nm, 1900nm, 2000nm or a range consisting of any two of the above values.
  • the average pore size of the first porous substrate is 100nm-300nm.
  • the average pore size of the first porous base membrane is 100nm-2000nm, and/or the average pore size of the second porous base membrane is 100nm-2000nm, because the average pore sizes of the two are different, the smaller the average pore size, the smaller the space occupied by the average pore area, the larger the space occupied by the fiber filaments of the base membrane, and the stronger the mechanical strength of the base membrane; on the contrary, the smaller the space occupied by the fiber filaments of the base membrane, the larger the average pore area of the separator, and the better the air permeability.
  • the separator can have both air permeability and mechanical strength, thereby improving the reliability and cycle performance of the separator.
  • the average pore size of the first porous base membrane is 100nm-350nm
  • the average pore size of the second porous base membrane is 100nm-300nm
  • the air permeability and mechanical strength of the separator can be further improved, thereby further improving the reliability and cycle performance of the separator.
  • the average pore size has a meaning known in the art and can be tested using methods known in the art.
  • a mercury porosimeter can be used to test the pore size with reference to GB/T 21650.1-2008.
  • the porosity of the first porous base membrane is greater than the porosity of the second porous base membrane.
  • the porosity of the first porous base membrane is 30%-80%, for example, 30%, 35%, 38%, 40%, 50%, 55%, 60%, 70%, 75%, 80% or a range consisting of any two of the above values.
  • it can be 30%-40%, 35%-60%, 50%-70%, 75%-80%, etc.
  • the porosity of the first porous substrate is 35%-60%.
  • the porosity of the second porous substrate is 30%-70%, for example, it can be 30%, 35%, 40%, 45%, 50%, 60%, 65%, 70% or a range consisting of any two of the above values. For example, it can be 30%-40%, 35%-50%, 50%-60%, 65%-70%, etc. In some embodiments, the porosity of the second porous substrate is 35%-50%.
  • the porosity of the first porous base membrane is 30%-80%, and/or the porosity of the second porous base membrane is 30%-70%
  • the porosities of the two base membranes are different, indicating that the proportion of the hole structure per unit area is different, that is, the average pore area is different.
  • the porous base membrane with a large average pore area has good air permeability, and the base membrane with a small average pore area has good mechanical strength.
  • the combination of the two can make the isolation membrane have both air permeability and mechanical strength, thereby improving the reliability and cycle performance of the isolation membrane.
  • the air permeability and mechanical strength of the isolation membrane can be further improved, thereby further improving the reliability and cycle performance of the isolation membrane.
  • porosity is a well-known meaning in the art and can be tested using methods known in the art.
  • a mercury intrusion instrument can be used to test the porosity with reference to GB/T 21650.1-2008.
  • a porous coating layer 13 may be further provided between the first porous base film 11 and the second porous base film 12, and the porous coating layer 13 is provided between the first porous base film 11 and the second porous base film 12.
  • the porous coating layer 13 includes a binder.
  • the porous coating layer 13 may include a binder and a filler.
  • the first porous base film and the second porous base film can be directly compounded by hot pressing.
  • the hot pressing compounding process if the temperature is too high, the porosity will be small and the air permeability will be poor; if the temperature is too low, the first porous base film and the second porous base film will not be firmly bonded. Therefore, it is necessary to adjust a suitable hot pressing temperature.
  • the hot pressing temperature is 20°C-50°C.
  • the binder includes one or more of polyacrylate, polyacrylic acid, polytetrafluoroethylene, polyvinylidene fluoride, vinylidene fluoride-trichloroethylene copolymer, polyvinyl pyrrolidone, polyvinyl acetate, ethylene-vinyl acetate copolymer, polyethylene oxide, polyarylate, carboxymethyl cellulose, hydroxypropyl cellulose, regenerated cellulose, cellulose acetate, cellulose acetate propionate, cellulose acetate butyrate, polyacrylonitrile, polyvinyl alcohol, polyethylene, polypropylene, starch, and cyanoethyl amylopectin.
  • the heat resistance and mechanical strength of the isolation membrane can be further improved, thereby improving the reliability of the secondary battery.
  • carboxymethyl cellulose can be used as a thickener to adjust the viscosity of the slurry.
  • the filler includes at least one of inorganic particles, organic particles, and organic-metal framework materials.
  • the inorganic particles include one or more of inorganic particles having a dielectric constant of 5 or more, inorganic particles having ion conductivity but not storing ions, and inorganic particles capable of undergoing electrochemical reactions.
  • the inorganic particles having a dielectric constant of 5 or more may include at least one of boehmite, aluminum oxide, zinc oxide, silicon oxide, titanium oxide, zirconium oxide, barium oxide, calcium oxide, magnesium oxide, nickel oxide, tin oxide, cerium oxide, yttrium oxide, hafnium oxide, aluminum hydroxide, magnesium hydroxide, silicon carbide, boron carbide, aluminum nitride, silicon nitride, boron nitride, magnesium fluoride, calcium fluoride, barium fluoride, barium sulfate, magnesium aluminum silicate, lithium magnesium silicate, sodium magnesium silicate, bentonite, hectorite, zirconium titanate, barium titanate, Pb(Zr,Ti )O3 (abbreviated as PZT), Pb1- mLamZr1 - nTinO3 ( abbreviated as PLZT, 0 ⁇ m ⁇ 1, 0 ⁇ n ⁇ 1),
  • the modification of each inorganic particle can be chemical modification and/or physical modification.
  • the chemical modification includes coupling agent modification (e.g., silane coupling agent, titanate coupling agent, etc.), surfactant modification, polymer grafting modification, etc.
  • the physical modification can be mechanical force dispersion, ultrasonic dispersion, high energy treatment, etc.
  • the modification can reduce the agglomeration of inorganic particles, thereby making the adhesive layer have a more stable and uniform structure; in addition, by selecting a special The coupling agent, surfactant or polymer with a certain functional group is used to modify the inorganic particles, which also helps to improve the wetting and retention properties of the adhesive layer to the electrolyte and improve the adhesion of the adhesive layer to the first porous base membrane and the second porous base membrane.
  • the inorganic particles having ion conductivity but not storing ions may include Li3PO4 , lithium titanium phosphate Lix1Tiy1 ( PO4 ) 3 , lithium aluminum titanium phosphate Lix2Aly2Tiz1 ( PO4 ) 3 , ( LiAlTiP) x3Oy3 type glass, lithium lanthanum titanate Lix4Lay4TiO3 , lithium germanium thiophosphate Lix5Gey5Pz2Sw , lithium nitride Lix6Ny6 , SiS2 type glass Lix7Siy7Sz3 and P2S5 type glass Lix8Py8S At least one of z4 , 0 ⁇ x1 ⁇ 2, 0 ⁇ y1 ⁇ 3, 0 ⁇ x2 ⁇ 2, 0 ⁇ y2 ⁇ 1, 0 ⁇ z1 ⁇ 3, 0 ⁇ x3 ⁇ 4, 0 ⁇ y3 ⁇ 13, 0 ⁇ x4 ⁇ 2, 0 ⁇ y4 ⁇ 3, 0 ⁇ x5 ⁇ 4,
  • the inorganic particles capable of undergoing an electrochemical reaction may include at least one of lithium-containing transition metal oxides, lithium-containing phosphates, carbon-based materials, silicon-based materials, tin-based materials, and lithium-titanium compounds.
  • the organic particles may include one or more of polycarbonate, polythiophene, polypyridine, polystyrene, polyacrylic wax, polyethylene, polypropylene, cellulose, a cellulose modifier (e.g., carboxymethyl cellulose), melamine resin, phenolic resin, polyester (e.g., polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate), silicone resin, polyimide, polyamideimide, polyaramid, polyphenylene sulfide, polysulfone, polyethersulfone, polyetheretherketone, polyaryletherketone, a copolymer of butyl acrylate and ethyl methacrylate (e.g., a cross-linked polymer of butyl acrylate and ethyl methacrylate).
  • polycarbonate polythiophene
  • polypyridine polystyrene
  • polyacrylic wax polyethylene
  • polypropylene cellulose
  • cellulose
  • the organic-metal framework material may include one or more of a nitrogen-containing heterocyclic ligand building structure, an organic carboxylic acid ligand building structure, and a nitrogen-oxygen mixed ligand building structure.
  • the content of the binder may be greater than or equal to 10%, optionally 10%-30%, based on the total weight of the adhesive layer.
  • the content of the filler may be less than or equal to 90%, optionally 40%-90%, 60%-80%, based on the total weight of the adhesive layer.
  • the coating may further include a dispersant, such as carboxymethyl cellulose, to adjust the viscosity of the coating slurry and improve the quality and uniformity of the coating.
  • a dispersant such as carboxymethyl cellulose
  • the content of the dispersant may be less than or equal to 25%, optionally less than or equal to 20%, based on the total weight of the adhesive layer.
  • the filler in the porous coating layer can further improve the heat resistance and mechanical strength of the isolation membrane, thereby improving the reliability of the secondary battery.
  • the isolation membrane satisfies at least one of the following (1)-(2): (1) the porosity of the isolation membrane is 30%-70%, and can be optionally 35%-55%; (2) the air permeability of the isolation membrane is 250s/100cc-400s/100cc, and can be optionally 250s/100cc-320s/100cc.
  • the separator can have good heat resistance, air permeability and mechanical strength, thereby improving the reliability and cycle performance of the secondary battery.
  • the second aspect of the present application provides a secondary battery, including a separator according to any of the above schemes.
  • the first porous base membrane with a large average pore area faces the positive electrode
  • the second porous base membrane with a small average pore area faces the negative electrode
  • the second porous base membrane has good mechanical strength, can exert its excellent physical properties, and is not easily punctured by lithium dendrites generated by the negative electrode, which can improve the reliability of the secondary battery.
  • the secondary battery comprises a positive electrode sheet, a negative electrode sheet and a separator according to any of the above schemes, the separator is arranged between the positive electrode sheet and the negative electrode sheet, and the second porous base film of the separator faces the negative electrode sheet.
  • the isolation membrane is given, the second porous base membrane with a large average pore area faces the negative electrode plate. Because the second porous base membrane has good mechanical strength, it can exert its excellent physical properties and is not easily punctured by lithium dendrites generated by the negative electrode, which can improve the reliability of the secondary battery.
  • the positive electrode plate generally includes a positive electrode current collector and a positive electrode film layer disposed on the positive electrode current collector, wherein the positive electrode film layer includes a positive electrode active material.
  • the positive electrode current collector may be a conventional metal foil or a composite current collector (a metal material may be disposed on a polymer substrate to form a composite current collector).
  • the positive electrode current collector may be an aluminum foil.
  • the specific type of the positive electrode active material is not limited, and any active material known in the art that can be used for the positive electrode of a secondary battery can be used, and those skilled in the art can select it according to actual needs.
  • the positive electrode active material may include, but is not limited to, one or more of lithium transition metal oxides, lithium-containing phosphates with an olivine structure and their respective modified compounds.
  • lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide and their modified compounds.
  • lithium-containing phosphates with an olivine structure may include, but are not limited to, one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, a composite material of lithium iron manganese phosphate and carbon and their modified compounds. These materials can all be obtained commercially.
  • the modified compounds of the above materials may be doping-modified and/or surface-coated modified materials.
  • the positive electrode film layer usually optionally includes a binder, a conductive agent and other optional auxiliary agents.
  • the conductive agent can be one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, conductive carbon black (Super P, SP), graphene and carbon nanofibers.
  • the binder can be one or more of Polymerized Styrene Butadiene Rubber (SBR), water-based acrylic resin, Polyvinylidene Difluoride (PVDF), Polytetrafluoroethylene (PTFE), Ethylene-vinyl Acetate Copolymer (EVA), Polyacrylic Acid (PAA), Carboxymethyl Cellulose (CMC), Polyvinyl Alcohol (PVA) and Polyvinyl Butyral (PVB).
  • SBR Polymerized Styrene Butadiene Rubber
  • PVDF Polyvinylidene Difluoride
  • PTFE Polytetrafluoroethylene
  • EVA Ethylene-vinyl Acetate Copolymer
  • PAA Polyacrylic Acid
  • CMC Carboxymethyl Cellulose
  • PVA Polyvinyl Alcohol
  • PVB Polyvinyl Butyral
  • the negative electrode plate generally includes a negative electrode current collector and a negative electrode film layer disposed on the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.
  • the negative electrode current collector may be a conventional metal foil or a composite current collector (for example, a metal material may be disposed on a polymer substrate to form a composite current collector).
  • the negative electrode current collector may be a copper foil.
  • the negative electrode active material is not limited, and active materials known in the art that can be used for the negative electrode of a secondary battery can be used, and those skilled in the art can choose according to actual needs.
  • the negative electrode active material may include, but is not limited to, one or more of artificial graphite, natural graphite, hard carbon, soft carbon, silicon-based materials and tin-based materials.
  • the silicon-based material can be selected from one or more of elemental silicon, silicon oxide compounds (such as silicon monoxide), silicon-carbon composites, silicon-nitrogen composites, and silicon alloys.
  • the tin-based material can be selected from one or more of elemental tin, tin oxide compounds, and tin alloys. These materials can all be obtained commercially.
  • the negative electrode active material may include a silicon-based material.
  • the negative electrode film layer usually optionally includes a binder, a conductive agent and other optional auxiliary agents.
  • the conductive agent may be one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the binder can be one or more of styrene-butadiene rubber (SBR), water-based acrylic resin, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyvinyl alcohol (PVA) and polyvinyl butyral (PVB).
  • SBR styrene-butadiene rubber
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • EVA ethylene-vinyl acetate copolymer
  • PVA polyvinyl alcohol
  • PVB polyvinyl butyral
  • thickeners and dispersants e.g., sodium carboxymethylcellulose, CMC-Na
  • PTC thermistor materials e.g., PTC thermistor materials
  • the secondary battery may include an electrolyte that conducts ions between the positive electrode and the negative electrode.
  • the electrolyte may include an electrolyte salt and a solvent.
  • the electrolyte salt can be selected from one or more of lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium bisfluorosulfonyl imide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium bisoxalatoborate (LiBOB), lithium difluorophosphate (LiPO 2 F 2 ), lithium difluorobisoxalatophosphate (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP).
  • LiPF 6 lithium hexafluorophosphate
  • LiBF 4 lithium perchlor
  • the solvent can be selected from ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF) , methyl acetate (Methyl Acetate, MA), ethyl acetate (Ethyl Acetate, EA), propyl acetate (n-Propyl Acetate, PA), methyl propionate (Methyl Propionate, MP), ethyl propionate (Ethyl Propanoate, EP), propyl propionate (n-Propyl Propionate, PP), methyl butyrate (Methyl Butyrate MB), ethyl butyrate (Ethyl butyrate
  • the electrolyte further includes additives, such as additives that may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high temperature performance, and additives that improve battery low temperature performance.
  • additives such as additives that may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high temperature performance, and additives that improve battery low temperature performance.
  • the first porous base membrane with a large average pore area faces the positive electrode plate
  • the second porous base membrane with a small average pore area faces the negative electrode plate. Because the second porous base membrane has good mechanical strength and can exert its excellent physical properties, it is not easily punctured by lithium dendrites generated by the negative electrode, thereby improving the reliability of the secondary battery.
  • FIG3 is a secondary battery 5 of a square structure as an example.
  • the secondary battery may include an outer package for packaging a positive electrode sheet, a negative electrode sheet, and an electrolyte.
  • the first porous base film of the separator faces the positive electrode sheet.
  • the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell.
  • the outer packaging of the secondary battery can also be a soft package, such as a bag-type soft package.
  • the material of the soft package can be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).
  • the outer package may include a shell 51 and a cover plate 53.
  • the shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate are enclosed to form a receiving cavity.
  • the shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can A cover is disposed on the opening to close the accommodating cavity.
  • the positive electrode sheet, the separator, the negative electrode sheet and the electrolyte can be assembled to form a secondary battery.
  • the positive electrode sheet, the separator, and the negative electrode sheet can be formed into an electrode assembly through a winding process and/or a lamination process, and the electrode assembly is placed in an outer package, and the electrolyte is injected after drying. After vacuum packaging, standing, forming, shaping and other processes, a battery cell is obtained.
  • Multiple battery cells can also be further connected in series, in parallel or in mixed connection to form a battery module.
  • Multiple battery modules can also be connected in series, in parallel or in mixed connection to form a battery pack. In some embodiments, multiple battery cells can also directly form a battery pack.
  • FIG5 is a battery module 4 as an example.
  • a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the plurality of secondary batteries 5 may be fixed by fasteners.
  • the battery module 4 may further include a housing having a housing space in which the plurality of secondary batteries 5 are housed.
  • the battery modules described above may also be assembled into a battery pack, and the number of battery modules contained in the battery pack may be adjusted according to the application and capacity of the battery pack.
  • FIG6 and FIG7 are battery packs 1 as an example.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box.
  • the battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 can be covered on the lower box body 3 to form a closed space for accommodating the battery modules 4.
  • the plurality of battery modules 4 can be arranged in the battery box in any manner.
  • the present application also provides an electrical device, which includes the secondary battery of the present application.
  • the battery cell, battery module or battery pack can be used as a power source for the device, or as an energy storage unit for the device.
  • the device can be, but is not limited to, a mobile device (such as a mobile phone, a laptop computer), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck), an electric train, a ship and a satellite, and an energy storage system.
  • the device can select a battery cell, a battery module or a battery pack according to its usage requirements.
  • FIG8 is an example of an electric device.
  • the electric device may be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.
  • a battery pack or a battery module may be used.
  • the electric device may be a mobile phone, a tablet computer, or a notebook computer.
  • the electric device is usually required to be thin and light, and a battery cell may be used as a power source.
  • the device of the present application includes the secondary battery provided by the present application, it has at least the same advantages as the secondary battery.
  • a first porous base membrane and a second porous base membrane are provided.
  • the first porous base membrane meets the following requirements: the material is polypropylene (PP), the thickness is 6 ⁇ m, and the average pore area S1 is 0.0025 ⁇ m 2 .
  • the second porous base membrane meets the following requirements: the material is polyethylene (PE), the thickness is 4 ⁇ m, and the average pore area S2 is 0.0023 ⁇ m 2 .
  • the ratio of the average pore area S1 of the first porous substrate to the average pore area S2 of the second porous substrate is 1.09.
  • Preparing coating slurry Preparing coating slurry: Mix the binder polyacrylate and the fillers alumina particles and carboxymethyl cellulose in a ratio of 1:4:1 in an appropriate amount of solvent deionized water to prepare a coating slurry.
  • step (3) The coating slurry of step (2) is applied on one side of the second porous base membrane of step (1) to form a coating layer.
  • step (3) hot-pressing the first porous base membrane and the coated second porous base membrane of step (3) to obtain a separator, wherein the coating layer is between the first porous base membrane and the second porous base membrane.
  • the preparation method of the isolation membrane 2-11 is similar to that of the isolation membrane 1, except that the average pore area of the first porous base membrane or the second porous base membrane is adjusted, as shown in Table 1.
  • the other preparation methods are consistent with the preparation method of the isolation membrane of Example 1.
  • the isolation membrane 1 prepared by the above method was subjected to relevant performance tests, and the specific results are shown in Table 1.
  • the positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811), the conductive agent carbon black (SuperP), and the binder polyvinylidene fluoride (PVDF) are uniformly mixed in a proper amount of solvent N-methylpyrrolidone (NMP) at a mass ratio of 96.2:2.7:1.1 to obtain a positive electrode slurry, and the positive electrode slurry is coated on a positive electrode current collector aluminum foil, and the positive electrode sheet is obtained through drying, cold pressing, slitting, and cutting processes.
  • NMP solvent N-methylpyrrolidone
  • the negative electrode active material artificial graphite, the conductive agent carbon black (SuperP), the binder styrene-butadiene rubber (SBR) and sodium carboxymethyl cellulose (CMC-Na) are mixed uniformly in a proper amount of solvent deionized water at a mass ratio of 96.4:0.7:1.8:1.1 to obtain a negative electrode slurry, and the negative electrode slurry is coated on the negative electrode current collector copper foil, and the negative electrode sheet is obtained through the processes of drying, cold pressing, slitting and cutting.
  • the isolation film adopts the isolation film 1 prepared above.
  • Ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed at a mass ratio of 30:70 to obtain an organic solvent, and fully dried electrolyte salt LiPF 6 is dissolved in the mixed solvent, the concentration of the electrolyte salt is 1.0 mol/L, and the mixture is evenly mixed to obtain an electrolyte solution.
  • the positive electrode sheet, the separator, and the negative electrode sheet are stacked in order, so that the separator is placed between the positive electrode sheet and the negative electrode sheet to play an isolating role, and then they are wound to obtain an electrode assembly; the electrode assembly is placed in an outer package, and the prepared electrolyte is injected into the dried secondary battery. After vacuum packaging, standing, formation, and shaping processes, a secondary battery is obtained.
  • the air permeability of the isolation membrane has a well-known meaning in the art and can be measured by methods known in the art. For example, it can be tested with reference to the standard GB/T 36363-2018.
  • the secondary batteries prepared in the examples and comparative examples were charged at a constant current rate of 1C to a charge cut-off voltage V1, then charged at a constant voltage to a current ⁇ 0.05C, left to stand for 5 min, and then discharged at a constant current rate of 0.33C to a discharge cut-off voltage V2, left to stand for 5 min.
  • This is one charge and discharge cycle.
  • the number of cycles at this time is the cycle life of the battery at 25°C.
  • the separators used satisfy that the melting point of the first porous base membrane is higher than the melting point of the second porous base membrane, and the average pore area of the first porous base membrane is larger than the average pore area of the second porous base membrane, so that the prepared battery has better cycle performance and higher reliability.
  • the separator used in Comparative Example 1 does not meet the design of this application, so that the cycle performance of the prepared battery is poor.

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Abstract

本申请提供一种隔离膜，其包括：第一多孔基膜和第二多孔基膜，第一多孔基膜的熔点高于第二多孔基膜的熔点；在沿隔离膜厚度方向的截面中，第一多孔基膜的平均孔面积大于第二多孔基膜的平均孔面积。可以使隔离膜兼具透气性和机械强度，从而提高隔离膜的可靠性和循环性能。

Description

隔离膜、二次电池和用电装置 技术领域
本申请属于二次电池技术领域，具体涉及一种隔离膜、二次电池和用电装置。
背景技术
二次电池因具有重量轻、无污染、无记忆效应突出特点，被广泛应用于各类消费类电子产品和电动车辆中。
随着新能源行业的不断发展，用户对二次电池提出了更高的使用需求。
因此，如何使二次电池具有更好的循环性是目前亟待解决的问题。
发明内容
鉴于背景技术中存在的技术问题，本申请提供一种隔离膜，旨在提高二次电池的循环性。
为了实现上述目的，本申请的第一方面提供一种隔离膜，其包括：第一多孔基膜和第二多孔基膜；第一多孔基膜的熔点高于第二多孔基膜的熔点；在沿隔离膜厚度方向的截面中，第一多孔基膜的平均孔面积大于第二多孔基膜的平均孔面积。
相对于现有技术，本申请至少包括如下的有益效果：
本申请特定结构的隔离膜不仅可以改善耐热性能，还可以改善透气性，当两个基膜采用本申请特定的平均孔面积设计方案时，有效降低由隔离膜制备工艺中的物理层压造成的孔隙堵塞，从而改善隔离膜的透气性能，保持离子传输的连续性及有效性，同时还可以使隔离膜兼顾较好的穿刺性能，使得二者能达到最优平衡，从而改善电池的循环性能。
在本申请任意实施方式中，第一多孔基膜的平均孔面积与第二多孔基膜的平均孔面积之比为1.05-10，可选为1.5-3.5。
当第一多孔基膜的平均孔面积与第二多孔基膜的平均孔面积之比为1.05-10时，可以使隔离膜拥有更好的透气性，有利于锂离子的透过，第二多孔基膜的平均孔面积相对于第一多孔基膜的平均孔面积相对较小，平均孔面积相对越小，则第二多孔基膜的纤维丝占据基膜的空间结构越多，基膜的强度越大，越能抵抗锂枝晶，因此，可以使隔离膜兼具透气性和机械强度，从而提高隔离膜的可靠性和循环性能。当第一多孔基膜的平均孔面积与第二多孔基膜的平均孔面积之比为1.5-3.5时，可以进一步改善隔离膜的透气性和机械强度，从而进一步提高隔离膜的可靠性和循环性能。
在本申请任意实施方式中，第一多孔基膜的平均孔面积为0.0001μm2-0.5μm2，可选为0.01μm2-0.3μm2；和/或，第二多孔基膜的平均孔面积为0.0001μm2-0.4μm2，可选为0.01μm2-0.25μm2。
当第一多孔基膜的平均孔面积为0.0001μm2-0.5μm2，和/或，第二多孔基膜的平均孔面积为0.0001μm2-0.4μm2时，因为第一多孔基膜和第二多孔基膜的平均孔面积不同，可以使隔离膜兼具透气性和机械强度，从而提高隔离膜的可靠性和循环性能。当第一多孔基膜的平均孔面积为0.01μm2-0.3μm2，和/或，第二多孔基膜的平均孔面积为0.01μm2-0.25μm2时，可以进一步改善隔离膜的透气性和机械强度，从而进一步提高隔离膜的可靠性和循环性能。
在本申请任意实施方式中，第一多孔基膜的平均孔径大于第二多孔基膜的平均孔径；可选地，第一多孔基膜的平均孔径为100nm-2000nm，更可选为100nm-350nm；可选地，第二多孔基膜的平均孔径为100nm-2000nm，更可选为100nm-300nm。
当第一多孔基膜的平均孔径大于第二多孔基膜的平均孔径，第一多孔基膜的平均孔径为 100nm-2000nm，和/或，第二多孔基膜的平均孔径为100nm-2000nm时，因为两者的平均孔径不同，平均孔径越小，平均孔面积占据的空间越小，基膜的纤维丝占用的空间越大，基膜的机械强度越强；相反，基膜的纤维丝占用的空间越小隔离膜，隔离膜的平均孔面积越大，透气性越好。因此，可以使隔离膜兼具透气性和机械强度，从而提高隔离膜的可靠性和循环性能。当第一多孔基膜的平均孔径为100nm-350nm，和/或，第二多孔基膜的平均孔径为100nm-300nm时，可以进一步改善隔离膜的透气性和机械强度，从而进一步提高隔离膜的可靠性和循环性能。
在本申请任意实施方式中，第一多孔基膜的孔隙率大于第二多孔基膜的孔隙率；可选地，第一多孔基膜的孔隙率为30％-80％，更可选为35％-60％；和/或，第二多孔基膜的孔隙率为30％-70％，更可选为35％-50％。
当第一多孔基膜的孔隙率大于第二多孔基膜的孔隙率，第一多孔基膜的孔隙率为30％-80％，和/或，第二多孔基膜的孔隙率为30％-70％时，两个基膜的孔隙率不同，表示单位面积内孔洞结构占据的比例不同，即平均孔面积大小不同，平均孔面积大的多孔基膜透气性好，平均孔面积小的基膜机械强度好，两者复合可以使隔离膜兼具透气性和机械强度，从而提高隔离膜的可靠性和循环性能。当第一多孔基膜的孔隙率为35％-60％，和/或，第二多孔基膜的孔隙率为35％-50％时，可以进一步改善隔离膜的透气性和机械强度，从而进一步提高隔离膜的可靠性和循环性能。
在本申请任意实施方式中，隔离膜还包括多孔涂层，多孔涂层设置在第一多孔基膜和第二多孔基膜之间，多孔涂层包括粘结剂；可选地，多孔涂层包括粘结剂和填充物。当隔离膜还包括多孔涂层，多孔涂层包括粘结剂和填充物时，能改善隔离膜的耐热性，提高二次电池的可靠性。
在本申请任意实施方式中，粘结剂包括聚丙烯酸酯、聚丙烯酸、聚四氟乙烯、聚偏氟乙烯、偏氟乙烯-三氯乙烯共聚物、聚乙烯吡咯烷酮、聚乙酸乙烯酯、乙烯-乙酸乙烯酯共聚物、聚环氧乙烷、聚芳酯、羧甲基纤维素、羟丙基纤维素、再生纤维素、乙酸纤维素、乙酸丙酸纤维素、乙酸丁酸纤维素、聚丙烯腈、聚乙烯醇、聚乙烯、聚丙烯、淀粉、氰基乙基支链淀粉中的一种或几种。当第一多孔基膜和第二多孔基膜之间设置有多孔涂层，且多孔涂层中的粘结剂包括以上组分时，能够提高二次电池的可靠性。
在本申请任意实施方式中，填充物包括无机颗粒、有机颗粒、有机-金属框架材料中的至少一种。当第一多孔基膜和第二多孔基膜之间设置有多孔涂层，且多孔涂层中的填充物包括上述无机颗粒、有机颗粒、有机-金属框架材料中的至少一种时，多孔涂层中的填充物可以使隔离膜的耐热性和机械强度得到进一步的改善，从而可以提高二次电池的可靠性。
在本申请任意实施方式中，隔离膜满足下述(1)-(2)中的至少一项：(1)隔离膜的孔隙率为30％-70％，可选为35％-55％；(2)隔离膜的透气度为250s/100cc-400s/100cc，可选为250s/100cc-320s/100cc。
当隔离膜在上述特征中至少一项满足所给的范围时，可使得隔离膜兼具良好的耐热性能、透气性和机械强度，从而可以提高二次电池的可靠性和循环性能。
本申请的第二方面提供一种二次电池，包括以上任一方案的隔离膜。当二次电池采用所给的隔离膜时，平均孔面积大的第一多孔基膜朝向正极极片，从而平均孔面积小的第二多孔基膜朝向负极极片，因为第二多孔基膜有较好的机械强度，可发挥其优异的物理性能，不易被负极产生的锂枝晶刺破，可提高二次电池的可靠性。
在本申请任意实施方式中，二次电池包括正极极片、负极极片和以上任一方案的隔离膜，隔离膜设置在正极极片和负极极片之间，隔离膜的第二多孔基膜朝向负极极片。当二次电池采用所给的隔离膜时，平均孔面积大的第二多孔基膜朝向负极极片，因为第二多孔基膜有较好的机械 强度，可发挥其优异的物理性能，不易被负极产生的锂枝晶刺破，可提高二次电池的可靠性。
本申请的第三方面提供一种用电装置，其包括本申请第二方面的二次电池。当用电装置的二次电池采用所给的隔离膜时，可提高用电装置的可靠性。
由于本申请的装置包括本申请提供的二次电池，因而至少具有与二次电池相同的优势。
附图说明
为了更清楚地说明本申请的技术方案，下面将对本申请中所使用的附图作简单介绍。显而易见地，下面所描述的附图仅仅是本申请的一些实施方式，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据附图获得其他的附图。
图1是本申请隔离膜的一实施方式的结构示意图。
图2是本申请隔离膜的另一实施方式的结构示意图。
图3是二次电池的一实施方式的示意图。
图4是图3的分解图。
图5是电池模块的一实施方式的示意图。
图6是电池包的一实施方式的示意图。
图7是图6的分解图。
图8是二次电池用作电源的装置的一实施方式的示意图。
具体实施方式
下面结合具体实施方式，进一步阐述本申请。应理解，这些具体实施方式仅用于说明本申请而不用于限制本申请的范围。
为了简明，本文仅具体地公开了一些数值范围。然而，任意下限可以与任意上限组合形成未明确记载的范围；以及任意下限可以与其它下限组合形成未明确记载的范围，同样任意上限可以与任意其它上限组合形成未明确记载的范围。此外，每个单独公开的点或单个数值自身可以作为下限或上限与任意其它点或单个数值组合或与其它下限或上限组合形成未明确记载的范围。
在本文的描述中，除非另有说明，术语“或(or)”是包括性的。也就是说，短语“A或(or)B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。
在本文的描述中，需要说明的是，除非另有说明，“以上”、“以下”为包括本数，“一种或几种”中“几种”的含义是两种及两种以上。
除非另有说明，本申请中使用的术语具有本领域技术人员通常所理解的公知含义。除非另有说明，本申请中提到的各参数的数值可以用本领域常用的各种测量方法进行测量(例如，可以按照在本申请的实施例中给出的方法进行测试)。
二次电池
二次电池，是指在电池放电后可通过充电的方式使活性材料激活而继续使用的电池。
通常情况下，二次电池包括正极极片、负极极片、隔离膜及电解质。在电池充放电过程中，活性离子在正极极片和负极极片之间往返嵌入和脱出。隔离膜设置在正极极片和负极极片之间，起到隔离的作用。电解质在正极极片和负极极片之间起到传导离子的作用。
[隔离膜]
参阅图1，本申请实施例提供一种隔离膜10，包括：第一多孔基膜11和第二多孔基膜12， 第一多孔基膜11的熔点高于所述第二多孔基膜12的熔点，在沿隔离膜厚度方向的截面中，第一多孔基膜11的平均孔面积大于第二多孔基膜12的平均孔面积。
本申请中，多孔基膜的平均孔面积是指沿隔离膜厚度方向的截面中，多孔基膜的总孔面积与多孔基膜中的孔数量的比值。
不希望限于任何理论，发明人经大量研究发现，本申请特定结构的隔离膜不仅可以改善耐热性能，还可以改善透气性，当两个基膜采用本申请特定的平均孔面积设计方案时，有效降低由隔离膜制备工艺中的物理层压造成的孔隙堵塞，从而改善隔离膜的透气性能，保持离子传输的连续性及有效性，同时还可以使隔离膜兼顾较好的穿刺性能，使得二者能达到最优平衡，从而改善电池的循环性能。
本发明人经深入研究发现，当本申请的隔离膜在满足上述条件的基础上，若更可选地满足下述条件中的一个或几个时，可以进一步改善二次电池的性能。
对第一多孔基膜和第二多孔基膜的材质没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的基膜。隔离膜的第一多孔基膜、第二多孔基膜的材料相同或不同。在一些实施方式中，第一多孔基膜和第二多孔基膜可以选自聚烯烃、聚醚、聚醚醚酮、对苯二甲酸乙二醇酯、聚酰亚胺、聚四氟乙烯、聚偏四氟乙烯、聚乙烯醇、玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的一种或几种。
第一多孔基膜和第二多孔基膜的熔点可以采用本领域已知的设备和方法进行测试。例如，可采用差示扫描量热法进行测定。具体可参考标准GB/T 19466.3-2004。作为示例，可按照如下方法进行测定：取4-6mg待测样品，置于差示扫描量热仪的样品室，温度从25℃升温至400℃，升温速率为10℃/min，得到样品的熔融吸热曲线，曲线峰值对应的温度为样品的熔点。
在本申请任意实施方式中，第一多孔基膜的平均孔面积与第二多孔基膜的平均孔面积之比为1.05-10，例如，可以为1.05，1.2，1.3，1.4，1.5，2，2.3，2.55，3，3.1，3.3，3.5，3.7，4，4.5，5，5.3，6，7，8，8.5，9，9.5，10或是上述任意两个数值组成的范围。例如，可以为1.05-2.5，1.05-3.5，3-6，4-7，5-9，1.05-10，7-10，8-10，9-10等。在一些实施例中，第一多孔基膜的平均孔面积与第二多孔基膜的平均孔面积之比为1.05-10。可选地，第一多孔基膜的平均孔面积与第二多孔基膜的平均孔面积之比为1.5-3.5，例如，可以为1.5，1.7，1.9，2，2.1，2.3，2.5，2.7，3，3.1，3.3，3.5或是上述任意两个数值组成的范围。例如，可以为1.5-2.5，1.5-3.3，2-3，2.5-3.5等。
当第一多孔基膜的平均孔面积与第二多孔基膜的平均孔面积之比为1.05-10时，可以使隔离膜拥有更好的透气性，有利于锂离子的透过，第二多孔基膜的平均孔面积相对于第一多孔基膜的平均孔面积相对较小，平均孔面积相对越小，则第二多孔基膜的纤维丝占据基膜的空间结构越多，基膜的强度越大，越能抵抗锂枝晶，因此，可以使隔离膜兼具透气性和机械强度，从而提高隔离膜的可靠性和循环性能。当第一多孔基膜的平均孔面积与第二多孔基膜的平均孔面积之比为1.5-3.5时，可以进一步改善隔离膜的透气性和机械强度，从而进一步提高隔离膜的可靠性和循环性能。
在本申请任意实施方式中，第一多孔基膜的平均孔面积为0.0001μm2-0.5μm2，例如，可以为0.0001μm2，0.0005μm2，0.001μm2，0.005μm2，0.01μm2，0.05μm2，0.1μm2，0.2μm2，0.3μm2，0.4μm2，0.5μm2或是上述任意两个数值组成的范围。例如，可以为0.0001μm2-0.01μm2，0.01μm2-0.3μm2，0.05μm2-0.4μm2，0.1μm2-0.5μm2等。在一些实施例中，第一多孔基膜的平均孔面积为0.01μm2-0.3μm2。第二多孔基膜的平均孔面积为0.0001μm2-0.4μm2，例如，可以为0.0001μm2，0.0005μm2，0.001μm2，0.005μm2，0.01μm2，0.05μm2，0.1μm2，0.2μm2，0.25μm2，0.3μm2，0.4μm2或是上述任意两个数值组成的范围。例如，可以为0.0001μm2-0.01μm2，0.01μm2-0.25μm2，0.05μm2-0.4μm2，0.1μm2-0.4μm2 等。在一些实施例中，第二多孔基膜的平均孔面积为0.01μm2-0.25μm2。
当第一多孔基膜的平均孔面积为0.0001μm2-0.5μm2，和/或，第二多孔基膜的平均孔面积为0.0001μm2-0.4μm2时，因为第一多孔基膜和第二多孔基膜的平均孔面积不同，可以使隔离膜兼具耐热性、透气性和机械强度，从而提高隔离膜的可靠性和循环性能。当第一多孔基膜的平均孔面积为0.01μm2-0.3μm2，和/或，第二多孔基膜的平均孔面积为0.01μm2-0.25μm2，时，可以进一步改善隔离膜的耐热性、透气性和机械强度，从而进一步提高隔离膜的可靠性和循环性能。
在本申请中，隔离膜的截面图像为沿隔离膜的厚度方向的图像。可以从隔离膜中任选一区域裁切出一定尺寸(例如15mm×15mm)的待测隔离膜样品，通过离子束抛光仪(例如日立Arblade 5000)在冷冻条件下(例如-80℃)切割获得隔离膜横截面；参考JY/T010-1996，使用扫描电子显微镜(例如德国ZEISS公司的Sigma 300型扫描电子显微镜)扫描获得隔离膜截面的SEM图(放大倍数可为1000倍至30000倍)；使用图像处理检测系统(例如易鸿隔离膜检测系统2022-0408)利用多段二值化方法获取多孔基膜的平均孔面积。
在使用离子束抛光仪进行切割时，可以将测试样品用铜箔或铝箔包裹后进行切割处理。在获得隔离膜截面的SEM图时，可以对测试样品进行喷金处理。
使用图像处理检测系统，可以分别获得隔离膜的第一多孔基膜和第二多孔基膜的孔面积数据，然后可以通过Mintab软件，分别获得隔离膜的第一多孔基膜和第二多孔基膜的平均孔面积。其中，隔离膜的第一多孔基膜的总孔面积与第一多孔基膜中的孔数量的比值即为第一多孔基膜的平均孔面积，隔离膜的第二多孔基膜的总孔面积与第二多孔基膜中的孔数量的比值即为第二多孔基膜的平均孔面积。
在本申请任意实施方式中，第一多孔基膜的平均孔径大于第二多孔基膜的平均孔径，第一多孔基膜的平均孔径为100nm-2000nm，例如，可以为100nm，200nm，250nm，300nm，350nm，500nm，700nm，900nm，1000nm，1250nm，1500nm，1700nm，1800nm，1900nm，2000nm或是上述任意两个数值组成的范围。例如，可以为100nm-350nm，200nm-900nm，300nm-1000nm，500nm-1500nm，1000nm-1800nm，1250nm-2000nm等。在一些实施例中，第一多孔基膜的平均孔径为100nm-350nm。第二多孔基膜的平均孔径为100nm-2000nm，例如，可以为100nm，200nm，220nm，250nm，300nm，350nm，500nm，550nm，700nm，900nm，1000nm，1250nm，1500nm，1700nm，1800nm，1900nm，2000nm或是上述任意两个数值组成的范围。例如，可以为100nm-350nm，250nm-700nm，300nm-1000nm，500nm-1000nm，1000nm-1800nm，1250nm-2000nm等。在一些实施例中，第一多孔基膜的平均孔径为100nm-300nm。
当第一多孔基膜的平均孔径大于第二多孔基膜的平均孔径，第一多孔基膜的平均孔径为100nm-2000nm，和/或，第二多孔基膜的平均孔径为100nm-2000nm时，因为两者的平均孔径不同，平均孔径越小，平均孔面积占据的空间越小，基膜的纤维丝占用的空间越大，基膜的机械强度越强；相反，基膜的纤维丝占用的空间越小，隔离膜的平均孔面积越大，透气性越好。因此，可以使隔离膜兼具透气性和机械强度，从而提高隔离膜的可靠性和循环性能。当第一多孔基膜的平均孔径为100nm-350nm，和/或，第二多孔基膜的平均孔径为100nm-300nm时，可以进一步改善隔离膜的透气性和机械强度，从而进一步提高隔离膜的可靠性和循环性能。
根据一些实施例，平均孔径为本领域公知的含义，可以采用本领域已知的方法测试。例如，可以采用压汞仪，参考GB/T 21650.1-2008进行测试。
在本申请任意实施方式中，第一多孔基膜的孔隙率大于第二多孔基膜的孔隙率，可选地，第一多孔基膜的孔隙率为30％-80％，例如，可以为30％，35％，38％，40％，50％，55％，60％，70％， 75％，80％或是上述任意两个数值组成的范围。例如，可以为30％-40％，35％-60％，50％-70％，75％-80％等。在一些实施例中，第一多孔基膜的孔隙率为35％-60％。第二多孔基膜的孔隙率为30％-70％，例如，可以为30％，35％，40％，45％，50％，60％，65％，70％或是上述任意两个数值组成的范围。例如，可以为30％-40％，35％-50％，50％-60％，65％-70％等。在一些实施例中，第二多孔基膜的孔隙率为35％-50％。
当第一多孔基膜的孔隙率为30％-80％，和/或，第二多孔基膜的孔隙率为30％-70％时，两个基膜的孔隙率不同，表示单位面积内孔洞结构占据的比例不同，即平均孔面积大小不同，平均孔面积大的多孔基膜透气性好，平均孔面积小的基膜机械强度好，两者复合可以使隔离膜兼具透气性和机械强度，从而提高隔离膜的可靠性和循环性能。当第一多孔基膜的孔隙率为35％-60％，和/或，第二多孔基膜的孔隙率为35％-50％时，可以进一步改善隔离膜的透气性和机械强度，从而进一步提高隔离膜的可靠性和循环性能。
根据一些实施例，孔隙率为本领域公知的含义，可以采用本领域已知的方法测试。例如，可以采用压汞仪，参考GB/T 21650.1-2008进行测试。
参阅图2，在本申请任意实施方式中，第一多孔基膜11和第二多孔基膜12之间还可以设置有多孔涂层13，多孔涂层13设置在第一多孔基膜11和第二多孔基膜12之间。多孔涂层13包括粘结剂。可选地，多孔涂层13可以包括粘结剂和填充物。当第一多孔基膜和第二多孔基膜之间设置有多孔涂层13时，多孔涂层13包括粘结剂和填充物时，不仅能削弱过热压复合过程中的工艺缺陷，同时，能够进一步改善隔离膜的耐热性和机械强度，从而提高二次电池的可靠性。
第一多孔基膜和第二多孔基膜可以直接通过热压方式复合，在热压方式复合的过程中，如果温度过高，将导致孔隙率小、透气性差；如果温度过低，将导致第一多孔基膜和第二多孔基膜粘接不牢，因此，需要调节合适的热压温度。可选地，热压温度在20℃-50℃。
在本申请任意实施方式中，粘结剂包括聚丙烯酸酯、聚丙烯酸、聚四氟乙烯、聚偏氟乙烯、偏氟乙烯-三氯乙烯共聚物、聚乙烯吡咯烷酮、聚乙酸乙烯酯、乙烯-乙酸乙烯酯共聚物、聚环氧乙烷、聚芳酯、羧甲基纤维素、羟丙基纤维素、再生纤维素、乙酸纤维素、乙酸丙酸纤维素、乙酸丁酸纤维素、聚丙烯腈、聚乙烯醇、聚乙烯、聚丙烯、淀粉、氰基乙基支链淀粉中的一种或几种。当第一多孔基膜11和第二多孔基膜12之间设置有多孔涂层13，且多孔涂层13中的粘结剂包括以上组分时，能够进一步改善隔离膜的耐热性和机械强度，从而可以提高二次电池的可靠性。在一些实施例中，可以使用羧甲基纤维素作为增稠剂来调节浆料的粘度。
在本申请任意实施方式中，填充物包括无机颗粒、有机颗粒、有机-金属框架材料中的至少一种。
可选地，所述无机颗粒包括具有5以上介电常数的无机颗粒、具有离子传导性但不储存离子的无机颗粒和能够发生电化学反应的无机颗粒中的一种或多种。
可选地，所述具有5以上介电常数的无机颗粒可包括勃姆石、氧化铝、氧化锌、氧化硅、氧化钛、氧化锆、氧化钡、氧化钙、氧化镁、氧化镍、氧化锡、氧化铈、氧化钇、氧化铪、氢氧化铝、氢氧化镁、碳化硅、碳化硼、氮化铝、氮化硅、氮化硼、氟化镁、氟化钙、氟化钡、硫酸钡、硅酸镁铝、硅酸镁锂、硅酸镁钠、膨润土、水辉石、钛酸锆、钛酸钡、Pb(Zr,Ti)O3(简写为PZT)、Pb1-mLamZr1-nTinO3(简写为PLZT，0＜m＜1，0＜n＜1)、Pb(Mg3Nb2/3)O3-PbTiO3(简写为PMN-PT)、及其各自的改性无机颗粒中的至少一种。可选地，各无机颗粒的改性方式可为化学改性和/或物理改性。所述化学改性方式包括偶联剂改性(例如采用硅烷偶联剂、钛酸酯偶联剂等)、表面活性剂改性、聚合物接枝改性等。所述物理改性方式可为机械力分散、超声分散、高能处理等。通过改性处理能够减少无机颗粒的团聚，由此能使粘接层具有更稳定和更均一的结构；此外，通过选择具有特 定官能团的偶联剂、表面活性剂或聚合物以改性无机颗粒，还有助于提升粘接层对电解液的浸润和保持特性、提升粘接层对第一多孔基膜、第二多孔基膜的粘结性。
可选地，所述具有离子传导性但不储存离子的无机颗粒可包括Li3PO4、磷酸钛锂Lix1Tiy1(PO4)3、磷酸钛铝锂Lix2Aly2Tiz1(PO4)3、(LiAlTiP)x3Oy3型玻璃、钛酸镧锂Lix4Lay4TiO3、硫代磷酸锗锂Lix5Gey5Pz2Sw、氮化锂Lix6Ny6、SiS2型玻璃Lix7Siy7Sz3和P2S5型玻璃Lix8Py8Sz4中的至少一种，0＜x1＜2，0＜y1＜3，0＜x2＜2，0＜y2＜1，0＜z1＜3，0＜x3＜4，0＜y3＜13，0＜x4＜2，0＜y4＜3，0＜x5＜4，0＜y5＜1，0＜z2＜1，0＜w＜5，0＜x6＜4，0＜y6＜2，0＜x7＜3，0＜y7＜2，0＜z3＜4，0＜x8＜3，0＜y8＜3，0＜z4＜7。由此能够进一步提升隔离膜的离子导通率。
可选地，所述能够发生电化学反应的无机颗粒可包括含锂过渡金属氧化物、含锂磷酸盐、碳基材料、硅基材料、锡基材料和锂钛化合物中的至少一种。
可选地，有机颗粒可以包括聚碳酸酯、聚噻吩、聚吡啶、聚苯乙烯、聚丙烯酸蜡、聚乙烯、聚丙烯、纤维素、纤维素改性剂(例如羧基甲基纤维素)、三聚氰胺树脂、酚醛树脂、聚酯(例如聚对苯二甲酸乙二醇酯、聚萘二甲酸乙二醇酯、聚对苯二甲酸丁二醇酯)、有机硅树脂、聚酰亚胺、聚酰胺酰亚胺、聚芳酰胺、聚苯硫醚、聚砜、聚醚砜、聚醚醚酮、聚芳醚酮、丙烯酸丁酯与甲基丙烯酸乙酯的共聚物(例如丙烯酸丁酯与甲基丙烯酸乙酯的交联聚合物)中的一种或多种。
可选地，有机-金属框架材料可以包括含氮杂环类配体构筑结构、有机羧酸类配体构筑结构、含氮氧混合类配体构筑结构中的一种或多种。
在一些实施例中，粘结剂的含量可以大于等于10％，可选为10％-30％，基于粘接层的总重量计。
在一些实施例中，填充物的含量可以小于等于90％，可选为40％-90％，60％-80％，基于粘接层的总重量计。
在一些实施例中，涂层还可以包括分散剂，例如羧甲基纤维素，由此可以调节涂层浆料的粘度，提升涂层的质量和均匀性。
在一些实施例中，分散剂的含量可以小于等于25％，可选为小于等于20％，基于粘接层的总重量计。
当第一多孔基膜和第二多孔基膜之间设置有多孔涂层，且多孔涂层中的填充物包括上述无机颗粒、有机颗粒、有机-金属框架材料中的至少一种时，多孔涂层中的填充物可以使隔离膜的耐热性和机械强度得到进一步的改善，从而可以提高二次电池的可靠性。
在本申请任意实施方式中，隔离膜满足下述(1)-(2)中的至少一项：(1)隔离膜的孔隙率为30％-70％，可选为35％-55％；(2)隔离膜的透气度为250s/100cc-400s/100cc，可选为250s/100cc-320s/100cc。
当隔离膜在上述特征中至少一项满足所给的范围时，可使得隔离膜兼具良好的耐热性能、透气性和机械强度，从而可以提高二次电池的可靠性和循环性能。
本申请的第二方面提供一种二次电池，包括以上任一方案的隔离膜。当二次电池采用所给的隔离膜时，平均孔面积大的第一多孔基膜朝向正极极片，从而平均孔面积小的第二多孔基膜朝向负极极片，因为第二多孔基膜有较好的机械强度，可发挥其优异的物理性能，不易被负极产生的锂枝晶刺破，可提高二次电池的可靠性。
在本申请任意实施方式中，二次电池包括正极极片、负极极片和以上任一方案的隔离膜，隔离膜设置在正极极片和负极极片之间，隔离膜的第二多孔基膜朝向负极极片。当二次电池采用 所给的隔离膜时，平均孔面积大的第二多孔基膜朝向负极极片，因为第二多孔基膜有较好的机械强度，可发挥其优异的物理性能，不易被负极产生的锂枝晶刺破，可提高二次电池的可靠性。
如果没有特别的说明，在隔离膜中所使用的各原料(例如第一多孔基膜、第二多孔基膜、粘结剂、填充物等)均可以通过市购获得。
[正极极片]
在二次电池中，所述正极极片通常包括正极集流体及设置在正极集流体上的正极膜层，所述正极膜层包括正极活性材料。
所述正极集流体可以采用常规金属箔片或复合集流体(可以将金属材料设置在高分子基材上形成复合集流体)。作为示例，正极集流体可以采用铝箔。
所述正极活性材料的具体种类不做限制，可以采用本领域已知的能够用于二次电池正极的活性材料，本领域技术人员可以根据实际需求进行选择。
作为示例，所述正极活性材料可以包括，但不限于，锂过渡金属氧化物，橄榄石结构的含锂磷酸盐及其各自的改性化合物中的一种或几种。锂过渡金属氧化物的示例可包括但不限于锂钴氧化物、锂镍氧化物、锂锰氧化物、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物、锂镍钴铝氧化物及其改性化合物中的一种或几种。橄榄石结构的含锂磷酸盐的示例可包括但不限于磷酸铁锂、磷酸铁锂与碳的复合材料、磷酸锰锂、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料及其改性化合物中的一种或几种。这些材料均可以通过商业途径获得。
上述各材料的改性化合物可以是对材料进行掺杂改性和/或表面包覆改性。
所述正极膜层通常更可选地包括粘结剂、导电剂和其他可选助剂。
作为示例，导电剂可以为超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、导电炭黑(Super P，SP)、石墨烯及碳纳米纤维中一种或几种。
作为示例，粘结剂可以为丁苯橡胶(Polymerized Styrene Butadiene Rubber，SBR)、水性丙烯酸树脂(water-basedacrylicresin)、聚偏二氟乙烯(Polyvinylidene Difluoride，PVDF)、聚四氟乙烯(Polytetrafluoroethylene，PTFE)、乙烯-醋酸乙烯酯共聚物(Ethylene-vinyl Acetate Copolymer，EVA)、聚丙烯酸(Polyacrylic Acid，PAA)、羧甲基纤维素(Carboxymethyl Cellulose，CMC)、聚乙烯醇(Polyvinyl Alcohol,Vinylalcohol Polymer，PVA)及聚乙烯醇缩丁醛(Polyvinyl Butyral，PVB)中的一种或几种。
[负极极片]
在二次电池中，所述负极极片通常包括负极集流体及设置在负极集流体上的负极膜层，所述负极膜层包括负极活性材料。
所述负极集流体可以采用常规金属箔片或复合集流体(例如可以将金属材料设置在高分子基材上形成复合集流体)。作为示例，负极集流体可以采用铜箔。
所述负极活性材料的具体种类不做限制，可以采用本领域已知的能够用于二次电池负极的活性材料，本领域技术人员可以根据实际需求进行选择。作为示例，所述负极活性材料可以包括，但不限于，人造石墨、天然石墨、硬碳、软碳、硅基材料和锡基材料中的一种或几种。所述硅基材料可选自单质硅、硅氧化合物(例如氧化亚硅)、硅碳复合物、硅氮复合物、硅合金中的一种或几种。所述锡基材料可选自单质锡、锡氧化合物、锡合金中的一种或几种。这些材料均可以通过商业途径获得。
在一些实施方式中，为了进一步提高电池的能量密度，所述负极活性材料可以包括硅基材料。
所述负极膜层通常更可选地包括粘结剂、导电剂和其他可选助剂。
作为示例，导电剂可以为超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中一种或几种。
作为示例，粘结剂可以为丁苯橡胶(SBR)、水性丙烯酸树脂(water-basedacrylicresin)、聚偏二氟乙烯(PVDF)、聚四氟乙烯(PTFE)、乙烯-醋酸乙烯酯共聚物(EVA)、聚乙烯醇(PVA)及聚乙烯醇缩丁醛(PVB)中的一种或几种。
作为示例，其他可选助剂可以是增稠及分散剂(例如羧甲基纤维素钠Carboxymethylcellulose Sodium，CMC-Na)、PTC热敏电阻材料。
[电解液]
二次电池可以包括电解液，电解液在正极和负极之间起到传导离子的作用。所述电解液可以包括电解质盐和溶剂。
作为示例，电解质盐可选自六氟磷酸锂(LiPF6)、四氟硼酸锂(LiBF4)、高氯酸锂(LiClO4)、六氟砷酸锂(LiAsF6)、双氟磺酰亚胺锂(LiFSI)、双三氟甲磺酰亚胺锂(LiTFSI)、三氟甲磺酸锂(LiTFS)、二氟草酸硼酸锂(LiDFOB)、二草酸硼酸锂(LiBOB)、二氟磷酸锂(LiPO2F2)、二氟二草酸磷酸锂(LiDFOP)及四氟草酸磷酸锂(LiTFOP)中的一种或几种。
作为示例，所述溶剂可选自碳酸亚乙酯(Ethylene Carbonate，EC)、碳酸亚丙酯(Propylene Carbonate，PC)、碳酸甲乙酯(Methyl Ethyl Carbonate，EMC)、碳酸二乙酯(Diethyl Carbonate，DEC)、碳酸二甲酯(Dimethyl Darbonate，DMC)、碳酸二丙酯(Dipropyl Carbonate，DPC)、碳酸甲丙酯(Methyl Propyl Carbonate，MPC)、碳酸乙丙酯(Diisopropyl Carbonate，EPC)、碳酸亚丁酯(Butylene Carbonate，BC)、氟代碳酸亚乙酯(Fluoroethylene Carbonate，FEC)、甲酸甲酯(Methyl Formate，MF)、乙酸甲酯(Methyl Acetate，MA)、乙酸乙酯(Ethyl Acetate，EA)、乙酸丙酯(n-Propyl Acetate，PA)、丙酸甲酯(Methyl Propionate，MP)、丙酸乙酯(Ethyl Propanoate，EP)、丙酸丙酯(n-Propyl Propionate，PP)、丁酸甲酯(Methyl ButyrateMB)、丁酸乙酯(Ethyl Butyrate，EB)、1,4-丁内酯(1,4-Butyrolactone，GBL)、环丁砜(Tetramethylene Sulfone，SF)、二甲砜(Methyl Sulfone，MSM)、甲乙砜(Methyl Ethyl Sulfone，EMS)及二乙砜(Diethyl Sulfone，ESE)中的一种或几种。
在一些实施方式中，电解液中还包括添加剂。例如添加剂可以包括负极成膜添加剂，也可以包括正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温性能的添加剂、改善电池低温性能的添加剂。
当二次电池采用所给的隔离膜时，平均孔面积大的第一多孔基膜朝向正极极片，从而平均孔面积小的第二多孔基膜朝向负极极片，因为第二多孔基膜有较好的机械强度，可发挥其优异的物理性能，不易被负极产生的锂枝晶刺破，可提高二次电池的可靠性。
本申请实施例对二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。如图3是作为一个示例的方形结构的二次电池5。
在一些实施方式中，二次电池可包括外包装。该外包装用于封装正极极片、负极极片和电解质。隔离膜的所述第一多孔基膜朝向所述正极极片。
在一些实施方式中，二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳。二次电池的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，如可包括聚丙烯(Polypropylene，PP)、聚对苯二甲酸丁二醇酯(Polybutylene Terephthalate，PBT)、聚丁二酸丁二醇酯(Polybutylene Succinate，PBS)中的一种或几种。
在一些实施方式中，参照图4，外包装可包括壳体51和盖板53。其中，壳体51可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的开口，盖板53能 够盖设于所述开口，以封闭所述容纳腔。
本申请的二次电池的制备方法是公知的。在一些实施例中，可将正极极片、隔离膜、负极极片和电解液组装形成二次电池。作为示例，可将正极极片、隔离膜、负极极片经卷绕工艺和/或叠片工艺形成电极组件，将电极组件置于外包装中，烘干后注入电解液，经过真空封装、静置、化成、整形等工序，得到电池单体。多个电池单体还可以进一步经由串联或并联或混联组成电池模块。多个电池模块还可以经由串联或并联或混联形成电池包。在一些实施例中，多个电池单体还可以直接组成电池包。
图5是作为一个示例的电池模块4。参照图5，在电池模块4中，多个二次电池5可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个二次电池5进行固定。
电池模块4还可以包括具有容纳空间的外壳，多个二次电池5容纳于该容纳空间。
在一些实施方式中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量可以根据电池包的应用和容量进行调节。
图6和图7是作为一个示例的电池包1。参照图6和图7，在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2能够盖设于下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。
[装置]
本申请还提供一种用电装置，所述用电装置包括本申请的二次电池。所述电池单体、电池模块或电池包可以作为所述装置的电源，也可以作为所述装置的能量存储单元。所述装置可以但不限于是移动设备(例如手机、笔记本电脑)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车)、电气列车、船舶及卫星、储能系统。
所述装置可以根据其使用需求来选择电池单体、电池模块或电池包。
图8是作为一个示例的用电装置。该用电装置可以为纯电动车、混合动力电动车、或插电式混合动力电动车。为了满足该用电装置对二次电池的高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的用电装置可以是手机、平板电脑、笔记本电脑。该用电装置通常要求轻薄化，可以采用电池单体作为电源。
由于本申请的装置包括本申请提供的二次电池，因而至少具有与二次电池相同的优势。
以下结合实施例进一步说明本申请的有益效果。
为了使本申请实施例所解决的技术问题、技术方案及有益效果更加清楚，以下将结合实施例和附图进行进一步详细说明。显然，所描述的实施例仅仅是本申请一部分实施例，而不是全部的实施例。以下对至少一个示例性实施例的描述实际上仅仅是说明性的，决不作为对本申请及其应用的任何限制。基于本申请中的实施例，本领域普通技术人员在没有付出创造性劳动前提下所获得的所有其他实施例都属于本申请保护的范围。
一、隔离膜的制备
隔离膜1：
(1)提供第一多孔基膜和第二多孔基膜。
第一多孔基膜满足：材质为聚丙烯(PP)，厚度为6μm，平均孔面积S1为0.0025μm2。
第二多孔基膜满足：材质为聚乙烯(Polyethylene，PE)，厚度为4μm，平均孔面积S2为0.0023μm2。
其中，第一多孔基膜的平均孔面积S1与第二多孔基膜的平均孔面积S2之比为1.09。
(2)配制涂层浆料：配制涂层浆料：将粘结剂聚丙烯酸酯和填充物氧化铝颗粒、羧甲基纤维素按照1：4：1比例在适量溶剂去离子水中混合均匀，制成涂层浆料。
(3)将步骤(2)的涂层浆料涂布在步骤(1)的第二多孔基膜的一侧，形成涂层。
(4)将第一多孔基膜与步骤(3)的涂布后的第二多孔基膜进行热压复合，得到隔离膜，其中，涂层在第一多孔基膜和第二多孔基膜之间。
隔离膜2-11的制备方法与隔离膜1相似，不同点在于：调整了第一多孔基膜或第二多孔基膜的平均孔面积，具体详见表1。其他的制备方法均与实施例1的隔离膜的制备方法一致。
对上述方法制备成的隔离膜1进行相关性能测试，具体结果详见表1。
二、电池的制备
实施例1
1、正极极片的制备
将正极活性材料LiNi0.8Co0.1Mn0.1O2(NCM811)、导电剂炭黑(SuperP)、粘结剂聚偏二氟乙烯(PVDF)按质量比96.2:2.7:1.1在适量的溶剂N-甲基吡咯烷酮(N-Methylpyrrolidone，NMP)中混合均匀，得到正极浆料，将正极浆料涂布于正极集流体铝箔上，通过烘干、冷压、分条、裁切工序，得到正极极片。
2、负极极片的制备
将负极活性材料人造石墨、导电剂炭黑(SuperP)、粘结剂丁苯橡胶(SBR)和羧甲基纤维素钠(CMC-Na)按质量比96.4:0.7:1.8:1.1在适量的溶剂去离子水中混合均匀，得到负极浆料，将负极浆料涂布于负极集流体铜箔上，通过烘干、冷压、分条、裁切工序，得到负极极片。
3、隔离膜
隔离膜采用上述制备的隔离膜1。
4、电解液的制备
将碳酸亚乙酯(EC)和碳酸甲乙酯(EMC)按质量比30:70进行混合，得到有机溶剂，将充分干燥的电解质盐LiPF6溶解于上述混合溶剂中，电解质盐的浓度为1.0mol/L，混合均匀后获得电解液。
5、二次电池的制备
将正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正极极片、负极极片之间起到隔离的作用，然后卷绕得到电极组件；将电极组件置于外包装中，将上述制备好的电解液注入到干燥后的二次电池中，经过真空封装、静置、化成、整形工序，获得二次电池。
实施例2-10和对比例1的二次电池与实施例1的二次电池的制备方法相似，不同点在于使用了不同的隔离膜(其中，实施例1-10采用的是隔离膜1-10，对比例1采用的是隔离膜11)，具体详见表1。
三、电池性能测试
1、透气性测试
隔离膜的透气度具有本领域公知的含义，可以采用本领域已知的方法进行测量。例如，均可参照标准GB/T 36363-2018进行测试。
2、电池循环性能(圈)
25℃下，将实施例和对比例制备得到的二次电池以1C倍率恒流充电至充电截止电压V1，之后恒压充电至电流≤0.05C，静置5min，再以0.33C倍率恒流放电至放电截止电压V2，静置5min， 此为一个充放电循环。按照此方法对电池进行循环充放电测试，直至电池容量衰减至80％。此时的循环圈数即为电池在25℃下的循环寿命。
由表1可见，实施例1-10中，采用的隔离膜满足第一多孔基膜的熔点高于第二多孔基膜的熔点，且第一多孔基膜的平均孔面积大于第二多孔基膜的平均孔面积，使得所制备的电池具有较好的循环性能，可靠性更高。而对比例1采用的隔离膜不满足本申请的设计，使得所制备的电池的循环性能较差。
以上所述，仅为本申请的具体实施方式，但本申请的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本申请揭露的技术范围内，可轻易想到各种等效的修改或替换，这些修改或替换都应涵盖在本申请的保护范围之内。因此，本申请的保护范围应以权利要求的保护范围为准。

Claims (12)

  1. 一种隔离膜，包括：第一多孔基膜和第二多孔基膜；所述第一多孔基膜的熔点高于所述第二多孔基膜的熔点；在沿所述隔离膜厚度方向的截面中，所述第一多孔基膜的平均孔面积大于所述第二多孔基膜的平均孔面积。
  2. 如权利要求1所述的隔离膜，其中，所述第一多孔基膜的平均孔面积与所述第二多孔基膜的平均孔面积之比为1.05-10，可选为1.5-3.5。
  3. 如权利要求1或2所述的隔离膜，其中，
    所述第一多孔基膜的平均孔面积为0.0001μm2-0.5μm2，可选为0.01μm2-0.3μm2；和/或，
    所述第二多孔基膜的平均孔面积为0.0001μm2-0.4μm2，可选为0.01μm2-0.25μm2。
  4. 如权利要求1-3任一项所述的隔离膜，其中，
    所述第一多孔基膜的平均孔径大于所述第二多孔基膜的平均孔径；
    可选地，所述第一多孔基膜的平均孔径为100nm-2000nm，更可选为100nm-350nm；
    可选地，所述第二多孔基膜的平均孔径为100nm-2000nm，更可选为100nm-300nm。
  5. 如权利要求1-4任一项所述的隔离膜，其中，
    所述第一多孔基膜的孔隙率大于所述第二多孔基膜的孔隙率；
    可选地，所述第一多孔基膜的孔隙率为30％-80％，更可选为35％-60％；
    可选地，所述第二多孔基膜的孔隙率为30％-70％，更可选为35％-50％。
  6. 如权利要求1-5任一项所述的隔离膜，其中，所述隔离膜还包括多孔涂层，所述多孔涂层设置在所述第一多孔基膜和所述第二多孔基膜之间，所述多孔涂层包括粘结剂；可选地，所述多孔涂层包括粘结剂和填充物。
  7. 如权利要求6所述隔离膜，其中，所述粘结剂包括聚丙烯酸酯、聚丙烯酸、聚四氟乙烯、聚偏氟乙烯、偏氟乙烯-三氯乙烯共聚物、聚乙烯吡咯烷酮、聚乙酸乙烯酯、乙烯-乙酸乙烯酯共聚物、聚环氧乙烷、聚芳酯、羧甲基纤维素、羟丙基纤维素、再生纤维素、乙酸纤维素、乙酸丙酸纤维素、乙酸丁酸纤维素、聚丙烯腈、聚乙烯醇、聚乙烯、聚丙烯、淀粉、氰基乙基支链淀粉中的一种或几种。
  8. 如权利要求6或7任一项所述隔离膜，其中，所述填充物包括无机颗粒、有机颗粒、有机-金属框架材料中的至少一种。
  9. 如权利要求1-8任一项所述隔离膜，其中，所述隔离膜满足下述(1)-(2)中的至少一项：
    所述隔离膜的孔隙率为30％-70％，可选为35％-55％；
    所述隔离膜的透气度为250s/100cc-400s/100cc，可选为250s/100cc-320s/100cc。
  10. 一种二次电池，包括如权利要求1-9任一项所述的隔离膜。
  11. 如权利要求10所述二次电池，其中，包括正极极片、负极极片，所述隔离膜设置在所述正极极片和所述负极极片之间，所述隔离膜的所述第二多孔基膜朝向所述负极极片。
  12. 一种用电装置，包括如权利要求10或11所述的二次电池。
PCT/CN2023/082335 2023-03-17 2023-03-17 隔离膜、二次电池和用电装置 Ceased WO2024192592A1 (zh)

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