WO2024197491A1 - 复合隔离膜、二次电池和用电装置 - Google Patents

复合隔离膜、二次电池和用电装置 Download PDF

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Publication number
WO2024197491A1
WO2024197491A1 PCT/CN2023/083895 CN2023083895W WO2024197491A1 WO 2024197491 A1 WO2024197491 A1 WO 2024197491A1 CN 2023083895 W CN2023083895 W CN 2023083895W WO 2024197491 A1 WO2024197491 A1 WO 2024197491A1
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Prior art keywords
sodium
battery
composite
negative electrode
polymer coating
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PCT/CN2023/083895
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English (en)
French (fr)
Inventor
官英杰
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Contemporary Amperex Technology Co Ltd
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Contemporary Amperex Technology Co Ltd
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Priority to EP23929093.5A priority Critical patent/EP4611156A4/en
Priority to PCT/CN2023/083895 priority patent/WO2024197491A1/zh
Priority to CN202380056589.4A priority patent/CN119768964A/zh
Publication of WO2024197491A1 publication Critical patent/WO2024197491A1/zh
Priority to US19/280,128 priority patent/US20250357624A1/en
Anticipated expiration legal-status Critical
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0569—Liquid materials characterised by the solvents
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/665—Composites
    • H01M4/667—Composites in the form of layers, e.g. coatings
    • 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
    • H01M50/429—Natural polymers
    • H01M50/4295—Natural cotton, cellulose or wood
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/054—Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the technical field of secondary batteries, and in particular to a composite isolation membrane, a secondary battery and an electrical device.
  • secondary batteries have been widely used in energy storage power systems such as hydropower, thermal, wind and solar power stations, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields.
  • the present application is made in view of the above-mentioned problems, and its purpose is to provide a composite isolation membrane comprising a polymer coating, which is beneficial to reduce the contact between the metal deposited on the current collector and the electrolyte, thereby reducing the side reaction between the metal and the electrolyte and improving the cycle performance and storage performance of the battery.
  • a composite isolation membrane including an isolation membrane substrate and a polymer coating located on one side of the isolation membrane substrate, wherein the sodium ion conductivity of the composite isolation membrane is 0.3 mS/cm to 1 mS/cm.
  • the sodium metal phase in the negative electrode can be effectively protected, the side reaction between the electrolyte and the metal can be reduced, and the battery's cycle performance and storage performance can be improved.
  • the polymer coating with high sodium ion conductivity can effectively change the transmission mode of sodium ions between the electrolyte and the electrode, and reduce the free electrolyte solvent on the surface of the electrode through solid phase transmission, thereby reducing the side reaction between the electrolyte and the electrode.
  • the polymer coating is used during the battery assembly process. The elastic compression covers the surface of the electrode, and under the action of mechanical force, further reduces the contact between the sodium metal phase in the negative electrode and the electrolyte, protects the sodium metal phase, and improves the cycle performance and storage performance of the battery.
  • the polymer coating includes at least one of a polymer containing sodium carboxylate groups and/or sodium sulfonate groups, the polymer being conductive to metallic sodium ions.
  • Polymers containing sodium carboxylate groups and/or sodium sulfonate groups can conduct sodium ions, and polymer coatings containing sodium carboxylate groups and/or sodium sulfonate groups can remove solvents from solvated sodium ions during sodium ion conduction, reduce free electrolyte solvents on the interface between sodium metal and the isolation membrane, thereby reducing side reactions between the electrolyte and metallic sodium and improving the cycle performance and storage performance of the battery.
  • the polymer includes one or more of sodium carboxymethyl cellulose, sodium polyacrylate, sodium alginate, sodium perfluorosulfonic acid resin, sodium polymethacrylate and sodium polystyrene sulfonate, and optionally includes one or more of sodium carboxymethyl cellulose and sodium alginate.
  • the polymer coatings containing the above polymers all have high sodium ion conductivity, and by changing the solvation structure of sodium ions in the electrolyte, the free electrolyte solvent on the interface between the sodium metal and the separator is reduced, thereby reducing the side reaction between the electrolyte and the metallic sodium, and improving the cycle performance and storage performance of the battery.
  • the polymer containing sodium carboxymethyl cellulose or sodium alginate is conducive to further improving the cycle performance and storage performance of the battery.
  • the thickness of the polymer coating is 15 nm to 1500 nm, and can be optionally 50 nm to 1000 nm.
  • Controlling the thickness of the polymer coating to 15nm to 1500nm can avoid or reduce the insufficient protection of the polymer coating on the sodium metal phase in the negative electrode due to too thin a thickness, and can also avoid or reduce the increase in the internal resistance of the battery due to too thick a thickness, thereby having an adverse effect on the battery. Further controlling the thickness of the polymer coating to 50nm to 1000nm is conducive to further improving the cycle performance and storage performance of the battery.
  • the polymer coating further comprises a surfactant additive, wherein the surfactant additive comprises one or more of sodium dodecyl sulfate, sodium poly(dipropylene glycol) sulfonate and polyethylene glycol, and optionally sodium poly(dipropylene glycol) sulfonate.
  • the surfactant additive comprises one or more of sodium dodecyl sulfate, sodium poly(dipropylene glycol) sulfonate and polyethylene glycol, and optionally sodium poly(dipropylene glycol) sulfonate.
  • the addition of surface additives is beneficial to improve the wetting between polymer coating and sodium metal properties, so that sodium ions can be more evenly deposited on the surface of the negative electrode current collector, reducing the generation of sodium dendrites and avoiding internal short circuit of the battery. It is also beneficial to improve the cycle performance and storage performance of the sodium metal battery.
  • the mass content of the surfactant additive is 0.05% to 5%, and optionally 0.2% to 3%.
  • Controlling the mass content of the surfactant additive to 0.05% to 5% can avoid or reduce the technical effect of not achieving the improvement of the wettability between the polymer coating and the sodium metal due to the low mass content of the surfactant additive, and can also avoid or reduce the increase in battery impedance due to the high mass content of the surfactant additive, thereby causing a decrease in battery performance. Further controlling the mass content of the surfactant additive to 0.2% to 3% is conducive to further improving the cycle performance and storage performance of the battery.
  • the polymer coating further comprises a reinforcing component, which comprises one or more of polyvinylidene fluoride, styrene-butadiene copolymer, polyimide, polyacrylonitrile, polyacrylamide, polymethyl methacrylate, nitrile rubber and polyurethane, and optionally comprises styrene-butadiene copolymer.
  • a reinforcing component comprises one or more of polyvinylidene fluoride, styrene-butadiene copolymer, polyimide, polyacrylonitrile, polyacrylamide, polymethyl methacrylate, nitrile rubber and polyurethane, and optionally comprises styrene-butadiene copolymer.
  • Adding reinforcing components to the polymer coating is beneficial to improving the mechanical strength and flexibility of the composite diaphragm membrane, and expanding the application of the composite isolation membrane.
  • the mass content of the reinforcing component is 0.01% to 50%, and optionally 0.05% to 10%.
  • Controlling the mass content of the reinforcing component to 0.01% to 50% can avoid or reduce the effect of failing to improve the performance of the composite separator due to the low mass content of the reinforcing component, and can also avoid or reduce the increase in battery impedance due to the high mass content of the reinforcing component, thereby causing a decrease in battery performance. Further controlling the mass content of the reinforcing component to 0.05% to 10% is conducive to further improving the cycle performance and storage performance of the battery.
  • the separator substrate includes one or more of polyethylene, polypropylene, polyester, cellulose, polyimide, polyamide, spandex fiber and aramid fiber, and optionally includes polyethylene.
  • the sources of isolation membrane substrates are wide, and all of the above isolation membrane substrates can be used in combination with polymer coatings to improve battery performance.
  • the second aspect of the present application provides a secondary battery, comprising a negative electrode plate, an electrolyte And the composite isolation membrane described in the first aspect, the polymer coating is located on the negative electrode plate side.
  • the composite isolation membrane located on the side of the polymer negative electrode plate can effectively protect the sodium metal phase in the negative electrode plate, reduce the side reaction between the electrolyte and metallic sodium, and improve the electrochemical performance of the battery.
  • the secondary battery is a negative electrode-free sodium secondary battery.
  • the electrolyte includes an ether solvent
  • the ether solvent includes one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyltetrahydrofuran, diphenyl ether and crown ether, and optionally includes one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether.
  • Ether solvents have better molecular anti-reduction properties, can promote the formation of a stable solid electrolyte interface on the surface of sodium metal, and reduce side reactions during battery cycling.
  • the combination of composite isolation membranes and ether solvents can simultaneously achieve the protection of the polymer coating on the sodium metal phase in the negative electrode plate and the formation of a stable solid electrolyte interface, greatly reducing the occurrence of side reactions and improving battery performance.
  • Ether solvents including one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether are beneficial to further improve the cycling performance and storage performance of the battery.
  • the negative electrode plate includes a negative electrode current collector and a primer layer disposed on at least one surface of the negative electrode current collector, and the primer layer includes one or more of carbon nanotubes, graphite, graphene, silver composite carbon nanoparticles, and tin composite carbon nanoparticles.
  • the above-mentioned base coating not only has excellent conductivity, but also facilitates the uniform deposition of metal ions on the surface of the current collector, thereby improving the coulombic efficiency and cycle performance of the battery.
  • the surface density of the primer layer is 0.5 g/m 2 to 35 g/m 2 .
  • the undercoat layer with a surface density of 0.5 g/m 2 to 35 g/m 2 is beneficial to the uniform distribution of nucleation sites in the negative electrode-free secondary battery, promotes the uniform deposition of metals, and does not affect the transmission behavior of electrons.
  • the primer layer has a thickness of 0.2 ⁇ m to 50 ⁇ m.
  • Controlling the thickness of the primer layer to 0.2 ⁇ m to 50 ⁇ m can provide anode-free secondary batteries. Providing sufficient nucleation sites is conducive to the uniform deposition of metal ions and inhibits dendrites.
  • a third aspect of the present application provides an electrical device, comprising the secondary battery of the second aspect of the present application.
  • FIG1 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • FIG2 is an exploded view of the secondary battery of one embodiment of the present application shown in FIG1 ;
  • FIG3 is a schematic diagram of a battery module according to an embodiment of the present application.
  • FIG4 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG5 is an exploded view of the battery pack according to an embodiment of the present application shown in FIG4 ;
  • FIG. 6 is a schematic diagram of an electric device using a secondary battery as a power source according to an embodiment of the present application.
  • ranges are defined in the form of lower limits and upper limits, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of the particular range. Ranges defined in this manner can be inclusive or exclusive of the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also expected.
  • the numerical range "ab” represents an abbreviation of any real number combination between a and b, where a and b are real numbers.
  • the numerical range "0-5" means that all real numbers between "0-5" have been listed in this document, and "0-5" is just an abbreviation of these numerical combinations.
  • a parameter is expressed as an integer ⁇ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.
  • the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially.
  • the method may further include step (c), which means that step (c) may be added to the method in any order.
  • the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.
  • the “include” and “comprising” mentioned in this application represent open-ended or closed-ended expressions.
  • the “include” and “comprising” may represent that other components not listed may also be included or only the listed components may be included or only the listed components may be included.
  • the term "or” is inclusive.
  • the phrase “A 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).
  • Metal secondary batteries are secondary batteries that use metal materials (such as lithium, sodium, magnesium, potassium and other metals) as negative electrodes.
  • the metal materials on the negative electrode current collector can be pre-deposited on the current collector surface as negative electrode active materials, or can be deposited in situ on the current collector surface during the charge and discharge process. That is, metal secondary batteries include sodium batteries, lithium batteries, Magnesium batteries, potassium batteries, etc. also include negative electrode-free batteries.
  • the negative electrode sheet in the negative electrode-free battery uses a negative electrode current collector and does not contain negative electrode active materials. During the first charge and discharge process, metal ions are deposited in situ on the negative electrode current collector.
  • the present application proposes a composite isolation membrane including an isolation membrane substrate and a polymer coating located on one side of the isolation membrane substrate.
  • the sodium ion conductivity of the composite isolation membrane is 0.3 mS/cm to 1 mS/cm.
  • the polymer coating protects the sodium metal by reducing the contact between the sodium metal and the electrolyte, thereby reducing the side reactions between the sodium metal and the electrolyte.
  • the polymer coating is located between the negative electrode plate and the separator substrate, and the polymer coating can conduct metal ions.
  • the sodium metal ions diffuse from the positive electrode plate side to the negative electrode plate side, and are deposited on the negative electrode current collector or the negative electrode bottom coating through the polymer coating.
  • the sodium metal loses electrons and desorbs from the negative electrode plate in the form of sodium metal ions and diffuses to the positive electrode plate side through the polymer coating.
  • one side of the separator substrate refers to one side of the surface of the separator substrate.
  • the sodium metal phase in the negative electrode plate can be effectively protected, the side reaction between the electrolyte and the metal can be reduced, and the cycle performance and storage performance of the battery can be improved.
  • the polymer coating with high sodium ion conductivity can effectively change the transmission mode of sodium ions between the electrolyte and the plate, and reduce the free electrolyte solvent on the surface of the plate through solid phase transmission, thereby reducing the side reaction between the electrolyte and the plate.
  • the polymer coating is elastically compressed and covered on the surface of the plate during the battery assembly process, and the contact between the sodium metal phase in the negative electrode plate and the electrolyte is further reduced under the action of mechanical force, thereby protecting the sodium metal phase and improving the cycle performance and storage performance of the battery.
  • the polymer coating is in direct contact with the surface of the barrier film substrate.
  • the polymer coating and the separator substrate have one or more coating.
  • the polymer coating includes at least one of a polymer containing sodium carboxylate groups and/or sodium sulfonate groups, which polymer is conductive to metallic sodium ions.
  • the polymer coating includes a polymer containing sodium carboxylate groups.
  • the polymer coating includes a polymer containing sodium sulfonate groups.
  • the polymer coating includes a polymer containing sodium carboxylate groups and sodium sulfonate groups.
  • Polymers containing sodium carboxylate groups and/or sodium sulfonate groups can conduct sodium ions, and polymer coatings containing sodium carboxylate groups and/or sodium sulfonate groups can change the solvation structure of sodium ions in the electrolyte, reduce the free electrolyte solvent on the interface between sodium metal and the isolation membrane, thereby reducing the side reaction between the electrolyte and metallic sodium, and improving the cycle performance and storage performance of the battery.
  • the polymer includes one or more of sodium carboxymethyl cellulose, sodium polyacrylate, sodium alginate, sodium perfluorosulfonic acid resin, sodium polymethacrylate and sodium polystyrene sulfonate, and optionally includes one or more of sodium carboxymethyl cellulose and sodium alginate.
  • the polymer comprises sodium carboxymethylcellulose. In some embodiments, the polymer comprises sodium alginate. In some embodiments, the polymer comprises sodium carboxymethylcellulose and sodium alginate. In some embodiments, the polymer comprises sodium polyacrylate. In some embodiments, the polymer comprises sodium perfluorosulfonic acid resin.
  • the polymer coatings containing the above polymers all have high sodium ion conductivity, and by changing the solvation structure of sodium ions in the electrolyte, the free electrolyte solvent on the interface between the sodium metal and the separator is reduced, thereby reducing the side reaction between the electrolyte and the metallic sodium, and improving the cycle performance and storage performance of the battery.
  • the polymer containing sodium carboxymethyl cellulose or sodium alginate is conducive to further improving the cycle performance and storage performance of the battery.
  • the thickness of the polymer coating is 15nm to 1500nm, and can be 50nm to 1000nm. In some embodiments, the thickness of the polymer coating can be 15nm, 50nm, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, 550nm, 600nm, 650nm, 700nm, 750nm, 800nm, 850nm, 900nm, 950nm, 1000nm, 1150nm, 1200nm, 1300nm, 1400nm, 1500nm, 1600nm, 1700nm, 1800nm, 1900nm, 2000nm, 2100nm, 2200nm, 2300nm, 2400nm, 2500nm, 2600nm, 2700nm, 2800nm, 2900nm, 3000nm, 3500nm, 3500nm, 3600nm, 3700nm, 3800nm, 3000
  • Controlling the thickness of the polymer coating to 15nm to 1500nm can avoid or reduce the insufficient protection of the polymer coating on the sodium metal phase in the negative electrode due to too thin a thickness, and can also avoid or reduce the increase in the internal resistance of the battery due to too thick a thickness, thereby having an adverse effect on the battery. Further controlling the thickness of the polymer coating to 50nm to 1000nm is conducive to further improving the cycle performance and storage performance of the battery.
  • the polymer coating further comprises a surfactant additive, the surfactant additive comprising one or more of sodium dodecyl sulfate, sodium poly(dipropylene glycol) sulfonate and polyethylene glycol, and optionally sodium poly(dipropylene glycol) sulfonate.
  • a surfactant additive comprising one or more of sodium dodecyl sulfate, sodium poly(dipropylene glycol) sulfonate and polyethylene glycol, and optionally sodium poly(dipropylene glycol) sulfonate.
  • surfactant additives is beneficial to improving the wettability between the polymer coating and sodium metal, so that sodium ions can be more evenly deposited on the surface of the negative electrode current collector, reducing the formation of sodium dendrites and avoiding internal short circuits in the battery. It is also beneficial to improve the cycle performance and storage performance of sodium metal batteries.
  • the mass content of the surfactant additive is 0.05% to 5%, and can be 0.2% to 3%. In some embodiments, based on the total mass of the polymer coating, the mass content of the surfactant additive can be 0.05%, 0.1%, 0.15%, 0.2%, 0.4%, 0.5%, 0.6%, 0.8%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5%, or a value in the range consisting of any two of the above points.
  • Controlling the mass content of the surfactant additive to 0.05% to 5% can avoid or reduce the technical effect of not achieving the improvement of the wettability between the polymer coating and the sodium metal due to the low mass content of the surfactant additive, and can also avoid or reduce the increase in battery impedance due to the high mass content of the surfactant additive, thereby causing a decrease in battery performance. Further controlling the mass content of the surfactant additive to 0.2% to 3% is conducive to further improving the cycle performance and storage performance of the battery.
  • the polymer coating further comprises a reinforcing component, the reinforcing component comprising one or more of polyvinylidene fluoride, styrene-butadiene copolymer, polyimide, polyacrylonitrile, polyacrylamide, polymethyl methacrylate, nitrile rubber and polyurethane, optionally comprising styrene-butadiene copolymer.
  • a reinforcing component comprising one or more of polyvinylidene fluoride, styrene-butadiene copolymer, polyimide, polyacrylonitrile, polyacrylamide, polymethyl methacrylate, nitrile rubber and polyurethane, optionally comprising styrene-butadiene copolymer.
  • Adding reinforcing components to the polymer coating is beneficial to improving the mechanical strength and flexibility of the composite diaphragm membrane and expanding the application of the composite isolation membrane.
  • the mass content of the reinforcing component is 0.01% to 50%, and can be 0.05% to 10%. In some embodiments, based on the total mass of the polymer coating, the mass content of the reinforcing component can be 0.01%, 0.05%, 0.1%, 0.5%, 1%, 2%, 4%, 5%, 6%, 8%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or a value in the range consisting of any two of the above points.
  • Controlling the mass content of the reinforcing component to 0.01% to 50% can avoid or reduce the effect of failing to improve the performance of the composite separator due to the low mass content of the reinforcing component, and can also avoid or reduce the increase in battery impedance due to the high mass content of the reinforcing component, thereby causing a decrease in battery performance. Further controlling the mass content of the reinforcing component to 0.05% to 10% is conducive to further improving the cycle performance and storage performance of the battery.
  • the separator substrate includes one or more of polyethylene, polypropylene, polyester, cellulose, polyimide, polyamide, spandex fiber, and aramid fiber, optionally including polyethylene.
  • the separator substrate comprises polyethylene. In some embodiments, the separator substrate comprises polypropylene. In some embodiments, the separator substrate comprises polyamide. In some embodiments, the separator substrate comprises aramid fibers.
  • the sources of isolation membrane substrates are wide, and all of the above isolation membrane substrates can be used in combination with polymer coatings to improve battery performance.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer formed on at least a portion of the surface of the positive electrode current collector.
  • the positive electrode active material layer includes a positive electrode active material.
  • the positive electrode active material may include at least one of a layered transition metal oxide, a polyanionic compound and a Prussian blue compound.
  • the transition metal in the layered transition metal oxide may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce.
  • the layered transition metal oxide is, for example, NaxMO2 , wherein M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, and 0 ⁇ x ⁇ 1.
  • the polyanionic compound may be a compound having metal ions, transition metal ions and tetrahedral (YO 4 ) n- anion units.
  • the metal ions may be selected from sodium ions, lithium ions, potassium ions and zinc ions;
  • the transition metal may be selected from at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce;
  • Y may be selected from at least one of P, S and Si; and n represents the valence state of (YO 4 ) n- .
  • the Prussian blue compound may be a compound having sodium ions, transition metal ions and cyanide ions (CN-).
  • the transition metal may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce.
  • the Prussian blue compound is, for example, Na a Me b Me' c (CN) 6 , wherein Me and Me' are each independently at least one of Ni, Cu, Fe, Mn, Co and Zn, 0 ⁇ a ⁇ 2, 0 ⁇ b ⁇ 1, 0 ⁇ c ⁇ 1.
  • the positive electrode active material layer may further include a conductive agent to improve the conductivity of the positive electrode.
  • the conductive agent may be selected from one or more of Super P, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphite, graphene and carbon nanofibers.
  • the positive electrode current collector may be a conductive carbon sheet, a metal foil, a carbon-coated metal foil, a porous metal plate or a composite current collector.
  • the conductive carbon material of the conductive carbon sheet may be selected from one or more of Super P, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphite, graphene and carbon nanofibers
  • the metal material of the metal foil, the carbon-coated metal foil and the porous metal plate may be independently selected from at least one of copper, aluminum, nickel and stainless steel
  • the composite current collector may be a composite current collector formed by a metal foil and a polymer base film.
  • the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.
  • a solvent such as N-methylpyrrolidone
  • the negative electrode sheet may only include a negative electrode current collector without including a negative electrode active material.
  • the negative electrode sheet may also be formed by pre-depositing a metal phase on the negative electrode current collector.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate.
  • the composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PET polyethylene terephthalate
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the negative electrode plate includes a negative electrode current collector and a primer layer disposed on at least one surface of the negative electrode current collector, and the primer layer includes one or more of carbon nanotubes, graphite, graphene, carbon black, aluminum oxide, silver composite carbon nanoparticles, and tin composite carbon nanoparticles.
  • carbon nanotube refers to a seamless hollow cylinder formed by rolling up a single or multiple layers of graphene, with a tube diameter of less than 100nm and a tube length of more than 100nm.
  • carbon nanotubes include but are not limited to single-walled carbon nanotubes and/or multi-walled carbon nanotubes.
  • the above-mentioned base coating layer not only has excellent conductivity, but also facilitates the uniform deposition of metal ions on the surface of the current collector, thereby improving the cycle performance and safety of the battery.
  • the surface density of the primer layer is 0.5 g/m 2 to 35 g/m 2 .
  • the surface density of the primer layer can be 0.5 g/ m2 , 1 g/ m2 , 2 g/ m2 , 3 g/ m2 , 4 g/ m2 , 5 g/ m2 , 10 g/ m2 , 15 g/ m2 , 20 g/ m2 , 25 g/ m2 , 30 g/ m2 , 35 g/ m2 , or a value in a range consisting of any two of the above points.
  • the undercoat layer with a surface density of 5 g/m 2 to 50 g/m 2 is conducive to the uniform distribution of nucleation sites and promotes the uniform deposition of metals, while not affecting the transmission behavior of electrons.
  • the thickness of the primer layer is 0.2 ⁇ m to 50 ⁇ m.
  • the thickness of the primer layer may be 0.5 ⁇ m, 1 ⁇ m, 1.5 ⁇ m, 2 ⁇ m, 5 ⁇ m, 10 ⁇ m, 15 ⁇ m, 20 ⁇ m, 25 ⁇ m, 30 ⁇ m, 35 ⁇ m, 40 ⁇ m, 45 ⁇ m, 50 ⁇ m, or a value in a range consisting of any two of the above points.
  • the thickness of the primer layer is controlled to be 2 ⁇ m to 100 ⁇ m, which can provide enough nucleation sites.
  • the dots are beneficial to the uniform deposition of metal ions and inhibit dendrites.
  • the electrolyte plays the role of conducting ions between the positive electrode and the negative electrode.
  • the present application has no specific restrictions on the type of electrolyte, which can be selected according to needs.
  • the electrolyte can be liquid, gel or all-solid.
  • the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.
  • the electrolyte salt may be selected from at least one of sodium hexafluorophosphate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, sodium trifluoromethanesulfonate, sodium tetrafluoroborate, sodium difluorophosphate, sodium perchlorate, and sodium chloride.
  • the electrolyte comprises an ester solvent
  • the ester solvent comprises at least one selected from ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, propylene carbonate, methyl acetate, ethyl propionate, and fluoroethylene carbonate.
  • the electrolyte contains an ether solvent
  • the ether solvent includes one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyltetrahydrofuran, diphenyl ether and crown ether, and optionally includes one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether.
  • Ether solvents have better molecular anti-reduction properties, can promote the formation of a stable solid electrolyte interface on the surface of sodium metal, and reduce side reactions during battery cycling.
  • the combination of composite isolation membranes and ether solvents can simultaneously achieve the protection of the polymer coating on the sodium metal phase in the negative electrode plate and the formation of a stable solid electrolyte interface, greatly reducing the occurrence of side reactions and improving battery performance.
  • Ether solvents including one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether are beneficial to further improve the cycling performance and storage performance of the battery.
  • the electrolyte may further include additives, such as 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 or low temperature performance, etc.
  • additives such as 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 or low temperature performance, etc.
  • a secondary battery includes a negative electrode plate, an electrolyte, and a composite separator in some embodiments.
  • FIG. 1 is a square-structured battery cell 5 as an example
  • FIG. 2 is an exploded view of the battery cell 5 .
  • the secondary battery further includes a positive electrode sheet.
  • the secondary battery includes at least one of a lithium battery and a sodium battery.
  • the secondary battery includes at least one of a potassium battery, a magnesium battery, and a zinc battery.
  • the secondary battery is a negative electrode-free sodium battery.
  • the negative electrode-free sodium secondary battery which only contains the negative electrode current collector.
  • the sodium ions obtain electrons on the cathode side and deposit metallic sodium on the surface of the current collector to form a sodium metal phase.
  • the metallic sodium can be converted into sodium ions and return to the positive electrode to achieve cyclic charge and discharge.
  • the negative electrode-free sodium secondary battery can achieve higher energy density because it is not limited by the negative electrode material.
  • it can shorten the battery production cycle, reduce the manufacturing cost of the battery, and greatly improve production efficiency.
  • the CB value of the negative electrode-free sodium secondary battery is less than or equal to 0.1.
  • the CB value is the unit area capacity of the negative electrode plate in the secondary battery divided by the unit area capacity of the positive electrode plate. Since the negative electrode-free battery does not contain negative electrode active materials, the unit area capacity of the negative electrode plate is small, and the CB value of the secondary battery is less than or equal to 0.1.
  • 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 enclose a receiving cavity.
  • the shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity.
  • the positive electrode sheet, the negative electrode sheet and the isolation film can form an electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is encapsulated in the receiving cavity.
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.
  • secondary batteries may be assembled into a battery module.
  • the number of secondary batteries contained in the battery module may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery module.
  • FIG3 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 receiving space, and the plurality of secondary batteries 5 are received in the receiving space.
  • the battery modules described above may also be assembled into a battery pack.
  • the battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.
  • FIG4 and FIG5 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.
  • an electric device comprising at least one of a secondary battery of any embodiment, a battery module of any embodiment, or a battery pack of any embodiment.
  • the electrical device includes at least one of the secondary battery, battery module, or battery pack provided in the present application.
  • the secondary battery, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device.
  • the electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.
  • a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.
  • Fig. 6 is an example of an electric device.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.
  • a battery pack or a battery module may be used.
  • the device may be a mobile phone, a tablet computer, a notebook computer, etc.
  • a device is usually required to be light and thin, and a secondary battery may be used as a power source.
  • CMC carboxymethyl cellulose
  • 10wt% polyvinylidene fluoride binder was fully dissolved in N-methylpyrrolidone, and then 10wt% carbon black conductive agent and 80wt% Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 positive electrode active material were added and stirred and mixed uniformly to obtain positive electrode slurry.
  • the slurry was evenly coated on the surface of the current collector aluminum foil to prepare a positive electrode film layer, and then transferred to a vacuum drying oven for complete drying. The dried pole piece was rolled and punched to obtain a positive electrode piece.
  • Aluminum foil is used as the negative electrode current collector for slitting and die-cutting to prepare negative electrode sheets without a negative electrode film layer.
  • sodium hexafluorophosphate NaPF 6 was dissolved in an organic solvent, ethylene glycol dimethyl ether (DME), and stirred evenly to obtain an electrolyte with a sodium salt concentration of 1 mol/L.
  • DME ethylene glycol dimethyl ether
  • the positive electrode sheet, the composite separator, and the negative electrode sheet are stacked in order, the composite separator is between the positive and negative electrode sheets to play an isolating role, and the polymer coating in the composite separator is located on the negative electrode sheet side, the bare cell is welded with a pole ear, and the bare cell is placed in an aluminum-plastic film, and baked at 80°C to remove water, and then the electrolyte is injected and sealed to obtain an uncharged battery.
  • the uncharged battery is then subjected to the processes of static, hot and cold pressing, formation, shaping, and capacity testing in sequence to obtain the negative-electrode-free sodium secondary battery product of Example 1.
  • CMC carboxymethyl cellulose
  • sodium polydisulfide propane sulfonate are dissolved in deionized water to obtain a polymer slurry.
  • the polymer slurry is evenly coated on one surface of a polyethylene (PE) isolation film substrate using a scraper to prepare a polymer coating, which is then transferred to a vacuum drying oven for drying, drying, and slitting to obtain a composite isolation film.
  • the thickness of the polymer coating is 200 nm, and the mass content of sodium polydisulfide propane sulfonate is 0.5% based on the total mass of the polymer coating.
  • the sodium ion conductivity of the composite isolation film is 0.53 mS/cm.
  • 10wt% polyvinylidene fluoride binder was fully dissolved in N-methylpyrrolidone, and then 10wt% carbon black conductive agent and 80wt% Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 positive electrode active material were added and stirred and mixed uniformly to obtain positive electrode slurry.
  • the slurry was evenly coated on the surface of the current collector aluminum foil to prepare a positive electrode film layer, and then transferred to a vacuum drying oven for complete drying. The dried pole piece was rolled and punched to obtain a positive electrode piece.
  • Aluminum foil is used as the negative electrode current collector for slitting and die-cutting to prepare negative electrode sheets without a negative electrode film layer.
  • the positive electrode sheet, the composite separator, and the negative electrode sheet are stacked in order, the composite separator is between the positive and negative electrode sheets to play an isolating role, and the polymer coating in the composite separator is located on the negative electrode sheet side, the bare cell is welded with a pole ear, and the bare cell is placed in an aluminum-plastic film, and baked at 80°C to remove water, and then the electrolyte is injected and sealed to obtain an uncharged battery.
  • the uncharged battery is then subjected to the processes of static, hot and cold pressing, formation, shaping, and capacity testing in sequence to obtain the negative-electrode-free sodium secondary battery product of Example 2.
  • the preparation methods of the batteries of Examples 3 to 24 are similar to those of the battery of Example 2, but the preparation parameters of the composite isolation membrane and the secondary battery are adjusted. The specific parameters are shown in Tables 1 and 2.
  • CMC carboxymethyl cellulose
  • sodium polydisulfide propane sulfonate are dissolved in deionized water to obtain a polymer slurry.
  • the polymer slurry is evenly coated on one surface of a polyethylene (PE) isolation film substrate using a scraper to prepare a polymer coating, which is then transferred to a vacuum drying oven for drying, drying, and slitting to obtain a composite isolation film.
  • the thickness of the polymer coating is 200 nm, and the mass content of sodium polydisulfide propane sulfonate is 0.5% based on the total mass of the polymer coating.
  • the sodium ion conductivity of the composite isolation film is 0.53 mS/cm.
  • 10wt% polyvinylidene fluoride binder was fully dissolved in N-methylpyrrolidone, and then 10wt% carbon black conductive agent and 80wt% Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 positive electrode active material were added and stirred and mixed evenly to obtain positive electrode slurry.
  • the slurry was evenly coated on the surface of the current collector aluminum foil to prepare a positive electrode film layer, and then transferred to a vacuum drying oven for complete drying.
  • the dried pole piece was rolled and punched to obtain a positive electrode piece.
  • sodium hexafluorophosphate NaPF 6 was dissolved in an organic solvent, ethylene glycol dimethyl ether (DME), and stirred evenly to obtain an electrolyte with a sodium salt concentration of 1 mol/L.
  • DME ethylene glycol dimethyl ether
  • the positive electrode sheet, the composite separator, and the negative electrode sheet are stacked in order, the composite separator is between the positive and negative electrode sheets to play an isolating role, and the polymer coating in the composite separator is located on the negative electrode sheet side, the bare cell is welded with a pole ear, and the bare cell is placed in an aluminum-plastic film, and baked at 80°C to remove water, and then the electrolyte is injected and sealed to obtain an uncharged battery.
  • the uncharged battery is then subjected to the processes of static, hot and cold pressing, formation, shaping, and capacity testing in sequence to obtain the sodium secondary battery product of Example 25.
  • the preparation method of the battery of Example 26 is similar to that of the battery of Example 25, but the primer layer on the negative electrode current collector is adjusted.
  • the specific parameters are shown in Tables 1 and 2.
  • the battery preparation method in Comparative Example 1 is basically similar to that in Example 1, but the composite isolation membrane only includes an isolation membrane substrate and does not include a polymer coating.
  • the specific parameters are shown in Tables 1 and 2.
  • the preparation method of the battery of Comparative Example 2 is similar to that of the battery of Comparative Example 1, but the type of solvent in the electrolyte is adjusted.
  • the specific parameters are shown in Tables 1 and 2.
  • PVDF polyvinylidene fluoride
  • 10wt% polyvinylidene fluoride binder was fully dissolved in N-methylpyrrolidone, and then 10wt% carbon black conductive agent and 80wt% Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 positive electrode active material were added and stirred and mixed evenly to obtain positive electrode slurry.
  • the slurry was evenly coated on the surface of the current collector aluminum foil to prepare a positive electrode film layer, and then transferred to a vacuum drying oven for complete drying.
  • the dried pole piece was rolled and punched to obtain a positive electrode piece.
  • the aluminum foil current collector is cut and die-cut to prepare a negative electrode sheet without a negative electrode film layer.
  • sodium hexafluorophosphate NaPF 6 was dissolved in an organic solvent, ethylene glycol dimethyl ether (DME), and stirred evenly to obtain an electrolyte with a sodium salt concentration of 1.0 mol/L.
  • DME ethylene glycol dimethyl ether
  • the positive electrode sheet, the composite separator, and the negative electrode sheet are stacked in order, the composite separator is between the positive and negative electrode sheets to play an isolating role, and the polymer coating in the composite separator is located on the negative electrode sheet side, the bare cell is welded with a pole ear, and the bare cell is placed in an aluminum-plastic film, and baked at 80°C to remove water, and then the electrolyte is injected and sealed to obtain an uncharged battery.
  • the uncharged battery is then subjected to the processes of static, hot and cold pressing, formation, shaping, capacity testing, etc., to obtain the negative-electrode-free sodium secondary battery product of Comparative Example 3.
  • the preparation method of the battery of Comparative Example 4 is similar to that of the battery of Comparative Example 3, but the type of solvent in the electrolyte is adjusted.
  • the specific parameters are shown in Tables 1 and 2.
  • Example 1 a symmetrical battery is used to test the sodium ion conductivity of the composite isolation membrane.
  • the preparation process of the symmetrical battery is similar to that of the battery in Example 1, except that the negative electrode plate is coated with a hard carbon material, and the battery is stacked in a manner that the negative electrode plate, the isolation membrane, Negative electrode sheet.
  • the impedance of the battery was tested using the French Bio-Logic VMP3B electrochemical workstation to obtain the bulk resistance of the composite isolation membrane.
  • the test process of the comparative example and other embodiments is the same as above.
  • the test process of the comparative example and other embodiments is the same as above.
  • the storage performance test process is as follows: after the prepared full battery is left to stand for 4 hours at 25°C, the battery is charged to 3.7V at a constant current of 0.33C, then charged at a constant voltage of 3.7V until the current drops to 0.05C, and then discharged to 2.5V at a constant current of 0.33C to obtain an initial discharge capacity D1; after the battery is placed in a constant temperature environment at 25°C for 60 days, the above test steps are repeated to obtain a discharge capacity D2.
  • the capacity retention rate of the battery after 60 days of storage D2/D1 ⁇ 100%.
  • the test process of the comparative example and other embodiments is the same as above.
  • the batteries of the embodiments and comparative examples were prepared according to the above method, and various performance parameters were measured. The results are shown in Tables 1 and 2 below.
  • the composite isolation membrane in Examples 1 to 26 includes an isolation membrane substrate and a polymer coating located on one side of the isolation membrane substrate, and the ion conductivity of the composite isolation membrane is 0.1mS/cm to 6mS/cm. From the comparison between Examples 1 to 23 and Comparative Examples 1 and 4, and Example 24 and Comparative Examples 2 to 3, it can be seen that the polymer coating is provided on one side of the isolation membrane substrate, and the ion conductivity of the composite isolation membrane is controlled to be 0.3mS/cm to 1mS/cm, which is conducive to improving the capacity retention rate and storage performance of the battery after 100 cycles, and broadening the application of the battery.
  • the polymer coating includes a polymer containing a -COONa group or a -SOONa group, which is beneficial to improving the capacity retention rate and storage performance of the battery after 100 cycles.
  • the polymer coating containing a -COONa group is beneficial to further improving the capacity retention rate and storage performance of the battery after 100 cycles.
  • the polymer in the polymer coating includes sodium carboxymethyl cellulose, sodium polyacrylate, sodium alginate or sodium perfluorosulfonic acid resin, which are beneficial to improving the capacity retention rate and storage performance of the battery after 100 cycles.
  • the polymer coating also includes a surfactant additive, and the surfactant additive includes sodium dodecyl sulfate, sodium polydisulfide dipropane sulfonate or polyethylene glycol, which are beneficial to improving the capacity retention rate and storage performance of the battery after 100 cycles.
  • the polymer coating also includes a reinforcing component, and the reinforcing component includes polyvinylidene fluoride or styrene-butadiene copolymer, which is beneficial to further improve the capacity retention rate and storage performance of the battery after 100 cycles.

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Abstract

本申请提供了一种复合隔离膜、二次电池和用电装置。该复合隔离膜包括隔离膜基材和位于隔离膜基材一侧的聚合物涂层，复合隔离膜的钠离子电导率为0.3mS/cm～1mS/cm。该聚合物涂层有利于减少沉积在集流体上的金属与电解液的接触，从而减少金属与电解液之间的副反应，提高电池的循环性能和存储性能。

Description

复合隔离膜、二次电池和用电装置 技术领域
本申请涉及二次电池技术领域，尤其涉及一种复合隔离膜、二次电池和用电装置。
背景技术
近年来，二次电池广泛应用于水力、火力、风力和太阳能电站等储能电源系统，以及电动工具、电动自行车、电动摩托车、电动汽车、军事装备、航空航天等多个领域。
界面稳定性是衡量二次电池的重要指标，极片与电解液之间的副反应会严重影响界面的稳定性，导致电池电化学性能和安全性能的下降，无法满足新一代电化学体系的应用需要。
发明内容
本申请是鉴于上述课题而进行的，其目的在于一种包含聚合物涂层的复合隔离膜，该聚合物涂层有利于减少沉积在集流体上的金属与电解液的接触，从而减少金属与电解液之间的副反应，提高电池的循环性能和存储性能。
本申请的第一方面，提供了一种复合隔离膜包括隔离膜基材和位于所述隔离膜基材一侧的聚合物涂层，所述复合隔离膜的钠离子电导率为0.3mS/cm～1mS/cm。
通过在隔离膜基材的一侧设置钠离子电导率高的聚合物涂层，可以有效地保护负极极片中的钠金属相，减少电解液与金属的副反应，提升电池的循环性能和存储性能。一方面，钠离子电导率高的聚合物涂层可有效改变钠离子在电解液与极片间的传输方式，通过固相传输的方式减少了极片表面游离的电解液溶剂，从而减少电解液与极片的副反应。另一方面，聚合物涂层在电池装配过程中通过 弹性压缩覆盖于极片表面，在机械力的作用下进一步减少负极极片中的钠金属相与电解液的接触，保护钠金属相，提升其电池的循环性能和存储性能。
在任意实施方式中，所述聚合物涂层包括含有羧酸钠基团和/或磺酸钠基团的聚合物中的至少一种，所述聚合物可传导金属钠离子。
含有羧酸钠基团和/或磺酸钠基团的聚合物均可以进行钠离子的传导，且含有羧酸钠基团和/或磺酸钠基团的聚合物涂层均可在进行钠离子传导的过程中使溶剂化结构的钠离子脱除溶剂，减少钠金属与隔离膜之间界面上的游离电解液溶剂，从而减少电解液与金属钠的副反应，提升其电池的循环性能和存储性能。
在任意实施方式中，所述聚合物包括羧甲基纤维素钠、聚丙烯酸钠、海藻酸钠、钠型全氟磺酸树脂、聚甲基丙烯酸钠和聚苯乙烯磺酸钠中的一种或多种，可选地包括羧甲基纤维素钠和海藻酸钠中一种或多种。
包含上述聚合物的聚合物涂层均具有高的钠离子电导率，且通过改变电解液中钠离子的溶剂化结构，减少钠金属与隔离膜之间界面上的游离电解液溶剂，从而减少电解液与金属钠的副反应，提升其电池的循环性能和存储性能。包含羧甲基纤维素钠或海藻酸钠的聚合物有利于进一步提升其电池的循环性能和存储性能。
在任意实施方式中，所述聚合物涂层的厚度为15nm～1500nm，可选为50nm～1000nm。
控制聚合物涂层的厚度为15nm～1500nm，既可避免或减少由于厚度过薄导致聚合物涂层对负极极片中钠金属相的保护不足，也可避免或减少由于厚度过厚而引起电池内阻的增加，从而对电池产生不利的影响。进一步控制聚合物涂层的厚度为50nm～1000nm，有利于进一步提升其电池的循环性能和存储性能。
在任意实施方式中，所述聚合物涂层还包括表面活性添加剂，所述表面活性添加剂包括十二烷基硫酸钠、聚二硫二丙烷磺酸钠和聚乙二醇中的一种或多种，可选地包括聚二硫二丙烷磺酸钠。
表面添加剂的加入有利于提升聚合物涂层与钠金属之间的浸润 性，从而能够使钠离子更均匀的沉积在负极集流体表面，减少钠枝晶的产生，避免电池发生内部短路，同时也有利于提升钠金属电池的循环性能和存储性能。
在任意实施方式中，基于所述聚合物涂层的总质量计，所述表面活性添加剂的质量含量为0.05％～5％，可选为0.2％～3％。
控制表面活性添加剂的质量含量为0.05％～5％，即可避免或减少表面活性添加剂的质量含量过低而导致达不到改善聚合物涂层与钠金属之间浸润性的技术效果，也可避免或减少表面活性添加剂的质量含量过高而导致电池阻抗的增加，从而引起电池性能的下降。进一步控制表面活性添加剂的质量含量为0.2％～3％，有利于进一步提升其电池的循环性能和存储性能。
在任意实施方式中，所述聚合物涂层还包括增强组分，所述增强组分包括聚偏二氟乙烯、苯乙烯-丁二烯共聚物、聚酰亚胺、聚丙烯腈、聚丙烯酰胺、聚甲基丙烯酸甲酯、丁腈橡胶和聚氨酯中的一种或多种，可选地包括苯乙烯-丁二烯共聚物。
在聚合物涂层中添加增强组分，有利于提升复合隔膜膜的机械强度和柔韧性，拓展了复合隔离膜的应用。
在任意实施方式中，基于所述聚合物涂层的总质量计，所述增强组分的质量含量为0.01％～50％，可选为0.05％～10％。
控制增强组分的质量含量为0.01％～50％，即可避免或减少增强组分的质量含量过低而导致达不到提升复合隔离膜性能的效果，也可避免或减少增强组分的质量含量过高而导致电池阻抗的增加，从而引起电池性能的下降。进一步控制增强组分的质量含量为0.05％～10％，有利于进一步提升其电池的循环性能和存储性能。
在任意实施方式中，所述隔离膜基材包括聚乙烯、聚丙烯、聚酯、纤维素、聚酰亚胺、聚酰胺、氨纶纤维和芳纶纤维中的一种或多种，可选地包括聚乙烯。
隔离膜基材的来源广泛，上述隔离膜基材均可与聚合物涂层搭配使用实现电池性能的提升。
本申请的第二方面提供一种二次电池，包括负极极片、电解液 和第一方面所述的复合隔离膜，所述聚合物涂层位于所述负极极片侧。
位于聚合物负极极片侧的复合隔离膜可以有效地保护负极极片中的钠金属相，减少电解液与金属钠的副反应，提升电池的电化学性能。
在任意实施方式中，所述二次电池是无负极钠二次电池。
在任意实施方式中，所述电解液包括醚类溶剂，所述醚类溶剂包括乙二醇二甲醚、乙二醇二乙醚、二乙二醇二甲醚、三乙二醇二甲醚、四乙二醇二甲醚、1,3-二氧戊环、四氢呋喃、甲基四氢呋喃、二苯醚和冠醚中的一种或多种，可选地包括乙二醇二甲醚、乙二醇二乙醚、二乙二醇二甲醚和四乙二醇二甲醚中的一种或多种。
醚类溶剂具有更为优异的分子抗还原性能，能够促进钠金属表面形成稳定的固态电解质界面，减少电池循环过程的副反应。复合隔离膜与醚类溶剂的搭配使用，同时实现聚合物涂层对负极极片中钠金属相的保护，以及稳定固态电解质界面的形成，大大减少副反应的产生，提升电池的性能。包括乙二醇二甲醚、乙二醇二乙醚、二乙二醇二甲醚和四乙二醇二甲醚中的一种或多种的醚类溶剂有利于进一步提升其电池的循环性能和存储性能。
在任意实施方式中，所述负极极片包括负极集流体以及设置在所述负极集流体至少一个表面的底涂层，所述底涂层包括碳纳米管、石墨、石墨烯、银复合碳纳米颗粒、锡复合碳纳米颗粒中的一种或多种。
上述底涂层不仅具有优异的导电性，还有利于金属离子在集流体表面的均匀沉积，提升电池的库伦效率和循环性能。
在任意实施方式中，所述底涂层的面密度为0.5g/m2～35g/m2。
面密度为0.5g/m2～35g/m2的底涂层有利于无负极二次电池中成核位点的均匀分布，促进金属的均匀沉积，同时也不影响电子的传输行为。
在任意实施方式中，所述底涂层的厚度为0.2μm～50μm。
控制底涂层的厚度为0.2μm～50μm，可以为无负极二次电池提 供足够多的成核位点有利于金属离子的均匀沉积，抑制枝晶。
本申请的第三方面提供一种用电装置，包括本申请第二方面的二次电池。
附图说明
图1是本申请一实施方式的二次电池的示意图；
图2是图1所示的本申请一实施方式的二次电池的分解图；
图3是本申请一实施方式的电池模块的示意图；
图4是本申请一实施方式的电池包的示意图；
图5是图4所示的本申请一实施方式的电池包的分解图；
图6是本申请一实施方式的二次电池用作电源的用电装置的示意图。
附图标记说明：
1电池包；2上箱体；3下箱体；4电池模块；5二次电池；51壳
体；52电极组件；53盖板。
具体实施方式
以下，适当地参照附图详细说明具体公开了本申请的复合隔离膜、二次电池和用电装置的实施方式。但是会有省略不必要的详细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，附图及以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5， 则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-5。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有技术特征以及可选技术特征可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，所述方法包括步骤(a)和(b)，表示所述方法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，所述提到所述方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到所述方法，例如，所述方法可以包括步骤(a)、(b)和(c)，也可包括步骤(a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。
如果没有特别的说明，本申请所提到的“包括”和“包含”表示开放式，也可以是封闭式。例如，所述“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分，也可以仅包括或包含列出的组分。
如果没有特别的说明，在本申请中，术语“或”是包括性的。举例来说，短语“A或B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。
金属二次电池是以金属材料(如锂、钠、镁、钾等金属)作为负极的二次电池。负极集流体上的金属材料既可以作为负极活性材料预沉积于集流体表面，也可以在充放电过程中原位沉积于集流体表面，即金属二次电池既包括具有负极活性材料的钠电池、锂电池、 镁电池、钾电池等，也包括无负极电池。无负极电池中的负极极片采用负极集流体，不含有负极活性材料，在首次充放电过程中，金属离子在负极集流体上原位沉积。
金属电池目前存在诸多问题，以无负极钠电池为例，在充放电过程中，金属钠与电解液之间容易发生副反应，消耗了大量钠元素，降低了电池的循环性能和存储性能。
[复合隔离膜]
基于此，本申请提出了一种复合隔离膜包括隔离膜基材和位于隔离膜基材一侧的聚合物涂层，复合隔离膜的钠离子电导率为0.3mS/cm～1mS/cm。
聚合物涂层通过减少钠金属与电解液之间的接触，从而减少钠金属与电解液之间的副反应，实现对钠金属的保护。聚合物涂层位于负极极片和隔离膜基材之间，且聚合物涂层可传导金属离子。充电过程中，钠金属离子从正极极片侧向负极极片侧扩散、且通过聚合物涂层传导沉积到负极集流体或负极底涂层上，放电过程中，钠金属失去电子以钠金属离子形式从负极极片上脱附经聚合物涂层传导向正极极片侧扩散。
在本文中，术语“隔离膜基材的一侧”是指隔离膜基材表面的一侧。
通过在隔离膜基材的一侧设置钠离子电导率高的聚合物涂层，可以有效地保护负极极片中的钠金属相，减少电解液与金属的副反应，提升电池的循环性能和存储性能。一方面，钠离子电导率高的聚合物涂层可有效改变钠离子在电解液与极片间的传输方式，通过固相传输的方式减少了极片表面游离的电解液溶剂，从而减少电解液与极片的副反应。另一方面，聚合物涂层在电池装配过程中通过弹性压缩覆盖于极片表面，在机械力的作用下进一步减少负极极片中的钠金属相与电解液的接触，保护钠金属相，提升其电池的循环性能和存储性能。
在一些实施方式中，聚合物涂层与隔离膜基材表面直接接触。
在一些实施方式中，聚合物涂层与隔离膜基材具有一个或多个 涂层。
在一些实施方式中，聚合物涂层包括含有羧酸钠基团和/或磺酸钠基团的聚合物中的至少一种，所述聚合物可传导金属钠离子。
在一些实施方式中，聚合物涂层包括含有羧酸钠基团的聚合物。
在一些实施方式中，聚合物涂层包括含有磺酸钠基团的聚合物。
在一些实施方式中，聚合物涂层包括含有羧酸钠基团和磺酸钠基团的聚合物。
含有羧酸钠基团和/或磺酸钠基团的聚合物均可以进行钠离子的传导，且含有羧酸钠基团和/或磺酸钠基团的聚合物涂层均可改变电解液中钠离子的溶剂化结构，减少钠金属与隔离膜之间界面上的游离电解液溶剂，从而减少电解液与金属钠的副反应，提升其电池的循环性能和存储性能。
在一些实施方式中，聚合物包括羧甲基纤维素钠、聚丙烯酸钠、海藻酸钠、钠型全氟磺酸树脂、聚甲基丙烯酸钠和聚苯乙烯磺酸钠中的一种或多种，可选地包括羧甲基纤维素钠和海藻酸钠中一种或多种。
在一些实施方式中，聚合物包括羧甲基纤维素钠。在一些实施方式中，聚合物包括海藻酸钠。在一些实施方式中，聚合物包括羧甲基纤维素钠和海藻酸钠。在一些实施方式中，聚合物包括聚丙烯酸钠。在一些实施方式中，聚合物包括钠型全氟磺酸树脂。
包含上述聚合物的聚合物涂层均具有高的钠离子电导率，且通过改变电解液中钠离子的溶剂化结构，减少钠金属与隔离膜之间界面上的游离电解液溶剂，从而减少电解液与金属钠的副反应，提升其电池的循环性能和存储性能。包含羧甲基纤维素钠或海藻酸钠的聚合物有利于进一步提升其电池的循环性能和存储性能。
在一些实施方式中，聚合物涂层的厚度为15nm～1500nm，可选为50nm～1000nm。在一些实施方式中，聚合物涂层的厚度可选为15nm、50nm、100nm、150nm、200nm、250nm、300nm、350nm、400nm、450nm、500nm、550nm、600nm、650nm、700nm、750nm、800nm、850nm、900nm、950nm、1000nm、1150nm、 1200nm、1250nm、1300nm、1350nm、1400nm、1450nm、1500nm、或由上述任意两点构成的范围中的数值。
控制聚合物涂层的厚度为15nm～1500nm，既可避免或减少由于厚度过薄导致聚合物涂层对负极极片中钠金属相的保护不足，也可避免或减少由于厚度过厚而引起电池内阻的增加，从而对电池产生不利的影响。进一步控制聚合物涂层的厚度为50nm～1000nm，有利于进一步提升其电池的循环性能和存储性能。
在一些实施方式中，聚合物涂层还包括表面活性添加剂，表面活性添加剂包括十二烷基硫酸钠、聚二硫二丙烷磺酸钠和聚乙二醇中的一种或多种，可选地包括聚二硫二丙烷磺酸钠。
表面活性添加剂的加入有利于提升聚合物涂层与钠金属之间的浸润性，从而能够使钠离子更均匀的沉积在负极集流体表面，减少钠枝晶的产生，避免电池发生内部短路，同时也有利于提升钠金属电池的循环性能和存储性能。
在一些实施方式中，基于聚合物涂层的总质量计，表面活性添加剂的质量含量为0.05％～5％，可选为0.2％～3％。在一些实施方式中，基于聚合物涂层的总质量计，表面活性添加剂的质量含量可选为0.05％、0.1％、0.15％、0.2％、0.4％、0.5％、0.6％、0.8％、1.0％、1.5％、2.0％、2.5％、3.0％、3.5％、4.0％、4.5％、5％、或由上述任意两点构成的范围中的数值。
控制表面活性添加剂的质量含量为0.05％～5％，即可避免或减少表面活性添加剂的质量含量过低而导致达不到改善聚合物涂层与钠金属之间浸润性的技术效果，也可避免或减少表面活性添加剂的质量含量过高而导致电池阻抗的增加，从而引起电池性能的下降。进一步控制表面活性添加剂的质量含量为0.2％～3％，有利于进一步提升其电池的循环性能和存储性能。
在一些实施方式中，聚合物涂层还包括增强组分，增强组分包括聚偏二氟乙烯、苯乙烯-丁二烯共聚物、聚酰亚胺、聚丙烯腈、聚丙烯酰胺、聚甲基丙烯酸甲酯、丁腈橡胶和聚氨酯中的一种或多种，可选地包括苯乙烯-丁二烯共聚物。
在聚合物涂层中添加增强组分，有利于提升复合隔膜膜的机械强度和柔韧性，拓展了复合隔离膜的应用。
在一些实施方式中，基于聚合物涂层的总质量计，增强组分的质量含量为0.01％～50％，可选为0.05％～10％。在一些实施方式中，基于聚合物涂层的总质量计，增强组分的质量含量可选为0.01％、0.05％、0.1％、0.5％、1％、2％、4％、5％、6％、8％、10％、15％、20％、25％、30％、35％、40％、45％、50％、或由上述任意两点构成的范围中的数值。
控制增强组分的质量含量为0.01％～50％，即可避免或减少增强组分的质量含量过低而导致达不到提升复合隔离膜性能的效果，也可避免或减少增强组分的质量含量过高而导致电池阻抗的增加，从而引起电池性能的下降。进一步控制增强组分的质量含量为0.05％～10％，有利于进一步提升其电池的循环性能和存储性能。
在一些实施方式中，隔离膜基材包括聚乙烯、聚丙烯、聚酯、纤维素、聚酰亚胺、聚酰胺、氨纶纤维和芳纶纤维中的一种或多种，可选地包括聚乙烯。
在一些实施方式中，隔离膜基材包括聚乙烯。在一些实施方式中，隔离膜基材包括聚丙烯。在一些实施方式中，隔离膜基材包括聚酰胺。在一些实施方式中，隔离膜基材包括芳纶纤维。
隔离膜基材的来源广泛，上述隔离膜基材均可与聚合物涂层搭配使用实现电池性能的提升。
[正极极片]
正极极片包括正极集流体及形成于正极集流体的至少部分表面上的正极活性物质层，正极活性物质层包括正极活性物质，正极活性物质可以包括层状过渡金属氧化物、聚阴离子型化合物和普鲁士蓝类化合物中的至少一种。
层状过渡金属氧化物中的过渡金属可以是Mn、Fe、Ni、Co、Cr、Cu、Ti、Zn、V、Zr及Ce中的至少一种。可选的，层状过渡金属氧化物例如为NaxMO2，其中M为Ti、V、Mn、Co、Ni、Fe、Cr及Cu中的一种或几种，0＜x≤1。
聚阴离子型化合物可以是具有金属离子、过渡金属离子及四面体型(YO4)n-阴离子单元的一类化合物。金属离子可选为钠离子、锂离子、钾离子、锌离子的一种；过渡金属可选为Mn、Fe、Ni、Co、Cr、Cu、Ti、Zn、V、Zr及Ce中的至少一种；Y可选为P、S及Si中的至少一种；n表示(YO4)n-的价态。
普鲁士蓝类化合物可以是具有钠离子、过渡金属离子及氰根离子(CN-)的一类化合物。过渡金属可以是Mn、Fe、Ni、Co、Cr、Cu、Ti、Zn、V、Zr及Ce中的至少一种。普鲁士蓝类化合物例如为NaaMebMe’c(CN)6，其中Me及Me’各自独立地为Ni、Cu、Fe、Mn、Co及Zn中的至少一种，0＜a≤2，0＜b＜1，0＜c＜1。
正极活性物质层还可以包括导电剂，以改善正极的导电性能。导电剂可选为Super P、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨、石墨烯及碳纳米纤维中的一种或几种。
正极活性物质层还可以包括粘结剂，以将正极活性物质和可选的导电剂牢固地粘结在正极集流体上。粘结剂可选为聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、聚丙烯酸(PAA)、聚乙烯醇(PVA)、乙烯-醋酸乙烯酯共聚物(EVA)、丁苯橡胶(SBR)、羧甲基纤维素(CMC)、海藻酸钠(SA)、聚甲基丙烯酸(PMA)及羧甲基壳聚糖(CMCS)中的至少一种。
正极集流体可以采用导电碳片、金属箔材、涂炭金属箔材、多孔金属板或复合集流体。导电碳片的导电碳材质可选为Super P、炭黑、科琴黑、碳点、碳纳米管、石墨、石墨烯及碳纳米纤维中的一种或几种，金属箔材、涂炭金属箔材和多孔金属板的金属材质各自独立地选自铜、铝、镍及不锈钢中的至少一种，复合集流体可以为金属箔材与高分子基膜复合形成的复合集流体。
在一些实施方式中，可以通过以下方式制备正极极片：将上述用于制备正极极片的组分，例如正极活性材料、导电剂、粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成正极浆料；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，即可得到正极极片。
[负极极片]
负极极片可以仅包括负极集流体，不包含负极活性材料。负极极片也可以在负极集流体上预沉积金属相。
在一些实施方式中，负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铝箔或铜箔。复合集流体可包括高分子材料基层和形成于高分子材料基材至少一个表面上的金属层。复合集流体可通过将金属材料(铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，负极极片包括负极集流体以及设置在负极集流体至少一个表面的底涂层，底涂层包括碳纳米管、石墨、石墨烯、炭黑、氧化铝、银复合碳纳米颗粒、锡复合碳纳米颗粒中的一种或多种。
在本文中，术语“碳纳米管”是指单层或多层石墨烯卷起来形成的无缝空心圆柱体，管径低于100nm，管长超过100nm。作为示例，碳纳米管包括但不限于单壁碳纳米管和/或多壁碳纳米管。
上述底涂层不仅具有优异的导电性，还有利于金属离子在集流体表面的均匀沉积，提升电池的循环性能和安全性。
在一些实施方式中，底涂层的面密度为0.5g/m2～35g/m2。
在一些实施方式中，底涂层的面密度可选为0.5g/m2、1g/m2、2g/m2、3g/m2、4g/m2、5g/m2、10g/m2、15g/m2、20g/m2、25g/m2、30g/m2、35g/m2、或由上述任意两点构成的范围中的数值。
面密度为5g/m2～50g/m2的底涂层有利于成核位点的均匀分布，促进金属的均匀沉积，同时也不影响电子的传输行为。
在一些实施方式中，底涂层的厚度为0.2μm～50μm。
在一些实施方式中，底涂层的厚度可选为0.5μm、1μm、1.5μm、2μm、5μm、10μm、15μm、20μm、25μm、30μm、35μm、40μm、45μm、50μm、或由上述任意两点构成的范围中的数值。
控制底涂层的厚度为2μm～100μm，可以提供足够多的成核位 点有利于金属离子的均匀沉积，抑制枝晶。
[电解质]
电解质在正极极片和负极极片之间起到传导离子的作用。本申请对电解质的种类没有具体的限制，可根据需求进行选择。例如，电解质可以是液态的、凝胶态的或全固态的。
在一些实施方式中，电解质采用电解液。电解液包括电解质盐和溶剂。
在一些实施方式中，电解质盐可选自六氟磷酸钠、双氟磺酰亚胺钠、双三氟甲烷磺酰亚胺钠、三氟甲磺酸钠、四氟硼酸钠、二氟磷酸钠、高氯酸钠、氯化钠中的至少一种。
在一些实施方式中，电解液包含酯类溶剂，酯类溶剂包含选自碳酸乙烯酯、碳酸丙烯酯、碳酸二乙酯、碳酸二甲酯、碳酸甲乙酯、碳酸亚丙酯、醋酸甲酯、丙酸乙酯、氟代乙烯碳酸脂中的的至少一种。
在一些实施方式中，电解液包含醚类溶剂，醚类溶剂包括乙二醇二甲醚、乙二醇二乙醚、二乙二醇二甲醚、三乙二醇二甲醚、四乙二醇二甲醚、1,3-二氧戊环、四氢呋喃、甲基四氢呋喃、二苯醚和冠醚中的一种或多种，可选地包括乙二醇二甲醚、乙二醇二乙醚、二乙二醇二甲醚和四乙二醇二甲醚中的一种或多种。
醚类溶剂具有更为优异的分子抗还原性能，能够促进钠金属表面形成稳定的固态电解质界面，减少电池循环过程的副反应。复合隔离膜与醚类溶剂的搭配使用，同时实现聚合物涂层对负极极片中钠金属相的保护，以及稳定固态电解质界面的形成，大大减少副反应的产生，提升电池的性能。包括乙二醇二甲醚、乙二醇二乙醚、二乙二醇二甲醚和四乙二醇二甲醚中的一种或多种的醚类溶剂有利于进一步提升其电池的循环性能和存储性能。
在一些实施方式中，电解液还可选地包括添加剂。例如添加剂可以包括负极成膜添加剂、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、改善电池高温或低温性能的添加剂等。
[二次电池]
二次电池，包括负极极片、电解液和一些实施方式中的复合隔离膜。
本申请对二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。例如，图1是作为一个示例的方形结构的电池单体5，图2是电池单体5的分解图。
在一些实施方式中，二次电池还包括正极极片。
在一些实施方式中，二次电池包括锂电池、钠电池中的至少一种。
在一些实施方式中，二次电池包括钾电池、镁电池、锌电池中的至少一种。
在一些实施方式中，二次电池为无负极钠电池。
无负极钠二次电池中不预沉积负极活性材料，仅包含负极集流体。首次充电时，钠离子在阴极侧得到电子以金属钠在集流体表面沉积形成钠金属相，放电时，金属钠能够转变为钠离子回到正极，实现循环充放。相比于其他钠二次电池，无负极钠二次电池由于不受负极材料的限制，可以获得更高的能量密度。而且在保持电池高电化学性能的同时，可以缩短电池的生产周期、降低电池的制造成本，极大提高生产效率。
在一些实施方式中，无负极钠二次电池的CB值小于等于0.1。
CB值为二次电池中负极极片的单位面积容量除以正极极片的单位面积容量。由于无负极电池中，不包含负极活性材料，因此负极极片的单位面积容量较小，二次电池的CB值小于等于0.1。
在一些实施方式中，参照图2，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能够盖设于开口，以封闭容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件52。电极组件52封装于容纳腔内。二次电池5所含电极组件52的数量可以为一个或多个，本领域技术人员可根据具体实际需求进行选择。
在一些实施方式中，二次电池可以组装成电池模块，电池模块所含二次电池的数量可以为一个或多个，具体数量本领域技术人员可根据电池模块的应用和容量进行选择。
图3是作为一个示例的电池模块4。参照图3，在电池模块4中，多个二次电池5可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个二次电池5进行固定。
可选地，电池模块4还可以包括具有容纳空间的外壳，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为一个或多个，具体数量本领域技术人员可根据电池包的应用和容量进行选择。
图4和图5是作为一个示例的电池包1。参照图4和图5，在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2能够盖设于下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。
[用电装置]
本申请的一个实施方式中，提供一种用电装置，包括任意实施方式的二次电池、任意实施方式的电池模块或任意实施方式的电池包中的至少一种。
用电装置包括本申请提供的二次电池、电池模块、或电池包中的至少一种。二次电池、电池模块、或电池包可以用作用电装置的电源，也可以用作用电装置的能量存储单元。用电装置可以包括移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等，但不限于此。
作为用电装置，可以根据其使用需求来选择二次电池、电池模块或电池包。
图6是作为一个示例的用电装置。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对二次电池的高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的装置可以是手机、平板电脑、笔记本电脑等。该装置通常要求轻薄化，可以采用二次电池作为电源。
实施例
以下，说明本申请的实施例。下面描述的实施例是示例性的，仅用于解释本申请，而不能理解为对本申请的限制。实施例中未注明具体技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品。
一、制备方法
实施例1
1)复合隔离膜的制备
将羧甲基纤维素钠(CMC)溶解于去离子水中，得到聚合物浆料。采用刮刀将上述聚合物浆料均匀涂布到聚乙烯(PE)隔离膜基材的一个表面上制备聚合物涂层，涂布完成后转移到真空干燥箱中进行干燥，烘干、分切，得到复合隔离膜。聚合物涂层的厚度为200nm，复合隔离膜的钠离子电导率为0.53mS/cm。
2)正极极片的制备
将10wt％聚偏二氟乙烯粘结剂充分溶解于N-甲基吡咯烷酮中，再加入10wt％炭黑导电剂与80wt％Na4Fe3(PO4)2P2O7正极活性材料搅拌混合均匀，得到正极浆料。将浆料均匀涂敷在集流体铝箔表面以制备正极膜层，然后转移到真空干燥箱中完全干燥。将干燥后的极片进行辊压、冲切，得到正极极片。
3)负极极片的制备
采用铝箔作为负极集流体分切、模切，制备无负极膜层的负极极片。
4)电解液
在氩气气氛手套箱中(H2O<0.1ppm，O2<0.1ppm)，将钠盐六氟磷酸钠NaPF6溶解于有机溶剂乙二醇二甲醚(DME)中，搅拌均匀，得到钠盐浓度1mol/L的电解液。
5)电池的制备
将正极极片、复合隔离膜、负极极片按顺序叠好，复合隔离膜处于正、负极片之间起到隔离的作用，且复合隔离膜中的聚合物涂层位于负极极片侧，给裸电芯焊接极耳，并将裸电芯装入铝塑膜中，并在80℃下烘烤除水，随即注入电解液并封口，得到不带电的电池。不带电的电池再依次经过静置、热冷压、化成、整形、容量测试等工序，获得实施例1的无负极钠二次电池产品。
实施例2
1)复合隔离膜的制备
将羧甲基纤维素钠(CMC)和聚二硫二丙烷磺酸钠溶解于去离子水中，得到聚合物浆料。采用刮刀将上述聚合物浆料均匀涂布到聚乙烯(PE)隔离膜基材的一个表面上制备聚合物涂层，涂布完成后转移到真空干燥箱中进行干燥，烘干、分切，得到复合隔离膜。聚合物涂层的厚度为200nm，基于聚合物涂层的总质量计，聚二硫二丙烷磺酸钠的质量含量为0.5％，复合隔离膜的钠离子电导率为0.53mS/cm。
2)正极极片的制备
将10wt％聚偏二氟乙烯粘结剂充分溶解于N-甲基吡咯烷酮中，再加入10wt％炭黑导电剂与80wt％Na4Fe3(PO4)2P2O7正极活性材料搅拌混合均匀，得到正极浆料。将浆料均匀涂敷在集流体铝箔表面以制备正极膜层，然后转移到真空干燥箱中完全干燥。将干燥后的极片进行辊压、冲切，得到正极极片。
3)负极极片的制备
采用铝箔作为负极集流体分切、模切，制备无负极膜层的负极极片。
4)电解液
在氩气气氛手套箱中(H2O<0.1ppm，O2<0.1ppm)，将钠盐六氟 磷酸钠NaPF6溶解于有机溶剂乙二醇二甲醚(DME)中，搅拌均匀，得到钠盐浓度1mol/L的电解液。
5)电池的制备
将正极极片、复合隔离膜、负极极片按顺序叠好，复合隔离膜处于正、负极片之间起到隔离的作用，且复合隔离膜中的聚合物涂层位于负极极片侧，给裸电芯焊接极耳，并将裸电芯装入铝塑膜中，并在80℃下烘烤除水，随即注入电解液并封口，得到不带电的电池。不带电的电池再依次经过静置、热冷压、化成、整形、容量测试等工序，获得实施例2的无负极钠二次电池产品。
实施例3～24
实施例3～24的电池与实施例2的电池制备方法相似，但是调整了复合隔离膜以及二次电池的制备参数，具体参数如表1和表2所示。
实施例25
1)复合隔离膜的制备
将羧甲基纤维素钠(CMC)和聚二硫二丙烷磺酸钠溶解于去离子水中，得到聚合物浆料。采用刮刀将上述聚合物浆料均匀涂布到聚乙烯(PE)隔离膜基材的一个表面上制备聚合物涂层，涂布完成后转移到真空干燥箱中进行干燥，烘干、分切，得到复合隔离膜。聚合物涂层的厚度为200nm，基于聚合物涂层的总质量计，聚二硫二丙烷磺酸钠的质量含量为0.5％，复合隔离膜的钠离子电导率为0.53mS/cm。
2)正极极片的制备
将10wt％聚偏二氟乙烯粘结剂充分溶解于N-甲基吡咯烷酮中，再加入10wt％炭黑导电剂与80wt％Na4Fe3(PO4)2P2O7正极活性材料搅拌混合均匀，得到正极浆料。将浆料均匀涂敷在集流体铝箔表面以制备正极膜层，然后转移到真空干燥箱中完全干燥。将干燥后的极片进行辊压、冲切，得到正极极片。
3)负极极片的制备
称取5g单壁碳纳米管溶解于去离子水中，经超声分散制备成浆 料，将浆料涂布在铝箔负极集流体上以制备底涂层，然后转移到真空干燥箱中完全干燥，随后进行分切、模切，制备无负极结构的负极极片。其中，底涂层的面密度为1g/m2。
4)电解液
在氩气气氛手套箱中(H2O<0.1ppm，O2<0.1ppm)，将钠盐六氟磷酸钠NaPF6溶解于有机溶剂乙二醇二甲醚(DME)中，搅拌均匀，得到钠盐浓度1mol/L的电解液。
5)电池的制备
将正极极片、复合隔离膜、负极极片按顺序叠好，复合隔离膜处于正、负极片之间起到隔离的作用，且复合隔离膜中的聚合物涂层位于负极极片侧，给裸电芯焊接极耳，并将裸电芯装入铝塑膜中，并在80℃下烘烤除水，随即注入电解液并封口，得到不带电的电池。不带电的电池再依次经过静置、热冷压、化成、整形、容量测试等工序，获得实施例25的钠二次电池产品。
实施例26
实施例26的电池与实施例25的电池制备方法相似，但是调整了负极集流体上的底涂层，具体参数如表1和表2所示。
对比例1
对比例1中的电池制备方法与实施例1基本相似，但是复合隔离膜中仅包括隔离膜基材，不包括聚合物涂层，具体参数如表1和表2所示。
对比例2
对比例2的电池与对比例1的电池制备方法相似，但是调整了电解液中溶剂的种类，具体参数如表1和表2所示。
对比例3
1)复合隔离膜的制备
将聚偏氟乙烯(PVDF)溶解于去离子水中，得到聚合物浆料。采用刮刀将上述聚合物浆料均匀涂布到聚乙烯(PE)隔离膜基材的一个表面上制备聚合物涂层，涂布完成后转移到真空干燥箱中进行干燥，烘干、分切，得到复合隔离膜。聚合物涂层的厚度为200nm， 复合隔离膜的钠离子电导率为0.11mS/cm。
2)正极极片的制备
将10wt％聚偏二氟乙烯粘结剂充分溶解于N-甲基吡咯烷酮中，再加入10wt％炭黑导电剂与80wt％Na4Fe3(PO4)2P2O7正极活性材料搅拌混合均匀，得到正极浆料。将浆料均匀涂敷在集流体铝箔表面以制备正极膜层，然后转移到真空干燥箱中完全干燥。将干燥后的极片进行辊压、冲切，得到正极极片。
3)负极极片的制备
将铝箔集流体进行分切、模切，制备得到无负极膜层的负极极片。
4)电解液
在氩气气氛手套箱中(H2O<0.1ppm，O2<0.1ppm)，将钠盐六氟磷酸钠NaPF6溶解于有机溶剂乙二醇二甲醚(DME)中，搅拌均匀，得到钠盐浓度1.0mol/L的电解液。
5)电池的制备
将正极极片、复合隔离膜、负极极片按顺序叠好，复合隔离膜处于正、负极片之间起到隔离的作用，且复合隔离膜中的聚合物涂层位于负极极片侧，给裸电芯焊接极耳，并将裸电芯装入铝塑膜中，并在80℃下烘烤除水，随即注入电解液并封口，得到不带电的电池。不带电的电池再依次经过静置、热冷压、化成、整形、容量测试等工序，获得对比例3的无负极钠二次电池产品。
对比例4
对比例4的电池与对比例3的电池制备方法相似，但是调整了电解液中溶剂的种类，具体参数如表1和表2所示。
二、性能测试
1、复合隔离膜
1)钠离子电导率测试
以实施例1为例，使用对称电池测试复合隔离膜的钠离子电导率。对称电池制备过程与实施例1的电池相似，区别在于，其负极极片涂覆有硬碳材料，同时，电池的堆叠方式为负极极片、隔离膜、 负极极片。钠离子电导率的计算公式为：σ＝l/(K·S)*10，其中σ是复合隔离膜的钠离子电导率，单位为mS/cm；l是一层复合隔离膜的厚度，单位为m；S是测试电池中复合隔离膜的有效面积，单位为m2；K是电解液在一层复合隔离膜的体电阻，单位为Ω。采用法国比奥罗杰BiO-Logic VMP3B电化学工作站测试电池的阻抗，得出复合隔离膜的体电阻。对比例以及其他实施例的测试过程同上。
2、电池性能测试
1)循环性能测试
循环性能测试过程如下：在25℃下，以1C恒定电流充电至3.7V，之后以3.7V恒压充电至电流降到0.05C，再以1C恒定电流放电至2.5V，得到初始容量(C0)；如此反复充放电至第n圈，得钠离子电池循环n圈后的放电容量，记为Cdn。记录循环第100次后电池的过程容量(C100)，循环100圈后的容量保持率＝C100/C1×100％。对比例以及其他实施例的测试过程同上。
2)存储性能测试
存储性能测试过程如下：在25下，将制备的全电池静置4小时后，将电池在0.33C的恒定电流充电至3.7V，之后以3.7V恒压充电至电流降到0.05C，再以0.33C恒定电流放电至2.5V，得到初始放电容量D1；将电池置于25恒温环境中进行存储60天后，重复上述测试步骤，得到放电容量D2。存储60天后电池的容量保持率＝D2/D1×100％。对比例以及其他实施例的测试过程同上。
三、各实施例、对比例测试结果分析
按照上述方法分别制备各实施例和对比例的电池，并测量各项性能参数，结果见下表1和表2。
表1

表2
根据上述结果可知，实施例1～26中的复合隔离膜包括隔离膜基材和位于隔离膜基材一侧的聚合物涂层，复合隔离膜的离子电导率为0.1mS/cm～6mS/cm。从实施例1～23和对比例1、4，实施例24与对比例2～3的的对比可见，在隔离膜基材的一侧设置聚合物涂层，且控制复合隔离膜的离子电导率为0.3mS/cm～1mS/cm，有利于提高其电池循环100圈后的容量保持率和存储性能，拓宽电池的应用。
从实施例1～23和对比例1、4的对比可见，聚合物涂层包括含有-COONa基团或-SOONa基团的聚合物，有利于提高其电池循环100圈后的容量保持率和存储性能。从实施例2、15与对比例14、16的对比可见，相比于聚合物涂层中含有-SOONa基团的聚合物，聚合物涂层中含有-COONa基团，有利于进一步提高其电池循环100圈后的容量保持率和存储性能。
从实施例1～23和对比例1、4的对比可见，聚合物涂层中的聚合物包括羧甲基纤维素钠、聚丙烯酸钠、海藻酸钠或钠型全氟磺酸树脂，均有利于提高其电池循环100圈后的容量保持率和存储性能。
从实施例2～6与实施例7～8的对比可见，控制聚合物涂层的厚度为15nm～1500nm，有利于进一步提高其电池循环100圈后的容量保持率和存储性能。从实施例2、4～5与实施例3、6的对比可见，控制聚合物涂层的厚度为50nm～1000nm，有利于进一步大幅提高其电池循环100圈后的容量保持率和存储性能。
从实施例9～13、17～18与对比例1的对比可见，聚合物涂层还包括表面活性添加剂，且表面活性添加剂包括十二烷基硫酸钠、聚二硫二丙烷磺酸钠或聚乙二醇，均有利于提高其电池循环100圈后的容量保持率和存储性能。
从实施例2、9～13与对比例1的对比可见，控制表面活性添加剂的质量含量为0.05％～5％，有利于提高其电池循环100圈后的容量保持率和存储性能。从实施例2、10～12与实施例9、13的对比可见，控制表面活性添加剂的质量含量为0.2％～3％，有利于进一步提高其电池循环100圈后的容量保持率和存储性能。
从实施例20～21与实施例2的对比可见，聚合物涂层还包括增强组分，增强组分包括聚偏二氟乙烯或苯乙烯-丁二烯共聚物，有利于进一步提高其电池循环100圈后的容量保持率和存储性能。
从实施例2、22～23与实施例24的对比可见，相比于电解液中的溶剂选自碳酸二甲酯，电解液中的溶剂选自乙二醇二甲醚、乙二醇二乙醚或四氢呋喃，更有利于提升其电池循环100圈后的容量保持率和存储性能。从实施例2、22与实施例23的对比可见，相比于电解液中的溶剂选自四氢呋喃，电解液中的溶剂选自乙二醇二甲醚或乙二醇二乙醚，有利于进一步提升其电池循环100圈后的容量保持率和存储性能。
从实施例25～26与实施例2的对比可见，在负极集流体上设置单壁碳纳米管底涂层或石墨烯底涂层，有利于提升其电池循环100圈后的容量保持率和存储性能。
需要说明的是，本申请不限定于上述实施方式。上述实施方式仅为示例，在本申请的技术方案范围内具有与技术思想实质相同的构成、发挥相同作用效果的实施方式均包含在本申请的技术范围内。此外，在不脱离本申请主旨的范围内，对实施方式施加本领域技术人员能够想到的各种变形、将实施方式中的一部分构成要素加以组合而构筑的其它方式也包含在本申请的范围内。

Claims (16)

  1. 一种复合隔离膜，其特征在于，所述复合隔离膜包括隔离膜基材和位于所述隔离膜基材一侧的聚合物涂层，所述复合隔离膜的钠离子电导率为0.3mS/cm～1mS/cm。
  2. 根据权利要求1所述的复合隔离膜，其特征在于，所述聚合物涂层包括含有羧酸钠基团和/或磺酸钠基团的聚合物中的至少一种，所述聚合物可传导金属钠离子。
  3. 根据权利要求1或2所述的复合隔离膜，其特征在于，所述聚合物包括羧甲基纤维素钠、聚丙烯酸钠、海藻酸钠、钠型全氟磺酸树脂、聚甲基丙烯酸钠和聚苯乙烯磺酸钠中的一种或多种，可选地包括羧甲基纤维素钠和海藻酸钠中一种或多种。
  4. 根据权利要求1至3中任一项所述的复合隔离膜，其特征在于，所述聚合物涂层的厚度为15nm～1500nm，可选为50nm～1000nm。
  5. 根据权利要求1至4中任一项所述的复合隔离膜，其特征在于，所述聚合物涂层还包括表面活性添加剂，所述表面活性添加剂包括十二烷基硫酸钠、聚二硫二丙烷磺酸钠和聚乙二醇中的一种或多种，可选地包括聚二硫二丙烷磺酸钠。
  6. 根据权利要求5所述的复合隔离膜，其特征在于，基于所述聚合物涂层的总质量计，所述表面活性添加剂的质量含量为0.05％～5％，可选为0.2％～3％。
  7. 根据权利要求1至6中任一项所述的复合隔离膜，其特征在于，所述聚合物涂层还包括增强组分，所述增强组分包括聚偏二氟 乙烯、苯乙烯-丁二烯共聚物、聚酰亚胺、聚丙烯腈、聚丙烯酰胺、聚甲基丙烯酸甲酯、丁腈橡胶和聚氨酯中的一种或多种，可选地包括苯乙烯-丁二烯共聚物。
  8. 根据权利要求7所述的复合隔离膜，其特征在于，基于所述聚合物涂层的总质量计，所述增强组分的质量含量为0.01％～50％，可选为0.05％～10％。
  9. 根据权利要求1至8中任一项所述的复合隔离膜，其特征在于，所述隔离膜基材包括聚乙烯、聚丙烯、聚酯、纤维素、聚酰亚胺、聚酰胺、氨纶纤维和芳纶纤维中的一种或多种，可选地包括聚乙烯。
  10. 一种钠二次电池，其特征在于，包括负极极片、电解液和权利要求1至9中任一项所述的复合隔离膜，所述复合隔离膜的所述聚合物涂层位于所述负极极片侧。
  11. 根据权利要求10所述的钠二次电池，其特征在于，所述二次电池是无负极钠二次电池。
  12. 根据权利要求10或11所述的钠二次电池，其特征在于，所述电解液包括醚类溶剂，所述醚类溶剂包括乙二醇二甲醚、乙二醇二乙醚、二乙二醇二甲醚、三乙二醇二甲醚、四乙二醇二甲醚、1,3-二氧戊环、四氢呋喃、甲基四氢呋喃、二苯醚和冠醚中的一种或多种，可选地包括乙二醇二甲醚、乙二醇二乙醚、二乙二醇二甲醚和四乙二醇二甲醚中的一种或多种。
  13. 根据权利要求10至12中任一项所述的钠二次电池，其特征在于，所述负极极片包括负极集流体以及设置在所述负极集流体至少一个表面的底涂层，所述底涂层包括碳纳米管、石墨、石墨烯、 银复合碳纳米颗粒、锡复合碳纳米颗粒中的一种或多种。
  14. 根据权利要求13所述的钠二次电池，其特征在于，所述底涂层的面密度为0.5g/m2～35g/m2。
  15. 根据权利要求13或14所述的钠二次电池，其特征在于，所述底涂层的厚度为0.2μm～50μm。
  16. 一种用电装置，其特征在于，包括权利要求10至15中任一项所述的钠二次电池。
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