WO2021052211A1 - 隔离膜、其制备方法、锂离子二次电池、电池模块、电池包及装置 - Google Patents

隔离膜、其制备方法、锂离子二次电池、电池模块、电池包及装置 Download PDF

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Publication number
WO2021052211A1
WO2021052211A1 PCT/CN2020/113801 CN2020113801W WO2021052211A1 WO 2021052211 A1 WO2021052211 A1 WO 2021052211A1 CN 2020113801 W CN2020113801 W CN 2020113801W WO 2021052211 A1 WO2021052211 A1 WO 2021052211A1
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Prior art keywords
polyimide
functional coating
isolation
battery
membrane
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PCT/CN2020/113801
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English (en)
French (fr)
Inventor
李伟
靳超
史海浩
李谦
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宁德时代新能源科技股份有限公司
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Priority to EP20865882.3A priority Critical patent/EP3975281A4/en
Publication of WO2021052211A1 publication Critical patent/WO2021052211A1/zh
Priority to US17/565,499 priority patent/US20220123436A1/en

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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
    • H01M50/454—Separators, membranes or diaphragms characterised by the material having a layered structure comprising a non-fibrous layer and a fibrous layer superimposed on one another
    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/403—Manufacturing processes of separators, membranes or diaphragms
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • H01M50/42—Acrylic resins
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/411—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
    • H01M50/443—Particulate material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/463—Separators, membranes or diaphragms characterised by their shape
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • 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

  • This application relates to the field of battery technology, in particular to an isolation membrane, a preparation method thereof, a lithium ion secondary battery and a device.
  • the isolation membrane is one of the key internal components, which has an important impact on the overall performance of the lithium-ion battery.
  • Lithium-ion batteries with excellent performance require that the isolation membrane they use not only have the basic performance of ordinary diaphragms, but also have excellent high temperature resistance.
  • the conventional PE separator used in the existing lithium-ion battery has a melting point of 130°C, and when the temperature reaches 150°C, the separator will shrink by more than 30%, which may cause the cathode and anode inside the lithium-ion battery to be There is a big safety hazard.
  • the main means to solve the problem of high temperature resistance of the isolation film is to use CCS (Ceramic Coating Separation, ceramic coating isolation, abbreviation: CCS) such as boehmite slurry to coat the isolation film or use heat-resistant materials to make the isolation film.
  • CCS Ceramic Coating Separation, ceramic coating isolation, abbreviation: CCS
  • boehmite slurry such as boehmite slurry to coat the isolation film or use heat-resistant materials to make the isolation film.
  • the purpose of the present application is to provide an isolation film, a preparation method thereof, a lithium ion secondary battery and a device, so as to improve the high temperature resistance of the isolation film and the thermal safety and stability of the battery and the device.
  • the first aspect of the present application provides an isolation membrane, which includes a porous base film and a functional coating provided on at least one surface of the porous base film.
  • the functional coating includes polyimide nanosheets, polyimide The imide nanosheets are stacked irregularly to form a lamellar loose structure; and the thickness ratio of the functional coating to the porous base film is 0.1-1.0.
  • the isolation film provided by this application contains polyimide in the surface coating of the isolation film. Because polyimide has better high temperature resistance, chemical resistance and electronic insulation, it can significantly improve the isolation film. The thermal stability and chemical stability. On the one hand, the long-term use temperature of the isolation film can be increased to 300°C, and it will not cause the failure of the battery cell when kept at 150°C for 2 hours; the thermal shrinkage resistance of the isolation film has also been significantly improved, in an environment above 180°C The pore structure of the diaphragm can be kept unchanged.
  • polyimide does not swell or dissolve in the electrolyte, and will not have any chemical reaction with the electrolyte and the positive and negative materials, which can ensure the stable operation of the battery during long-term use.
  • the polyimide coating can isolate the internal conduction of electrons between the positive and negative electrodes, prevent the positive and negative electrodes of the battery from being short-circuited, thereby reducing the self-discharge rate of the lithium-ion battery, and effectively improving the safety of the battery.
  • the polyimide used in the functional coating of the isolation film of the present application is a nanosheet material, and the polyimide nanosheets are stacked irregularly to form a laminar loose structure.
  • polyimide nanosheets and the lamellar loose structure formed by stacking have significantly increased physical area and higher toughness, making The functional coating in the present application has the characteristics of larger coverage area per unit weight, smaller effective coating thickness, and lighter weight.
  • the contact area between the sheet structure and the bare film is larger, and the thermal shrinkage resistance is better; and it can more effectively resist the mechanical puncture of the lithium dendrites, avoid micro-short circuits, and improve the safety and cycle performance of the battery.
  • it can more completely isolate the internal conduction of electrons between the positive and negative electrodes, effectively increase the tortuosity of the micropores of the isolation film, and greatly reduce the self-discharge rate of the lithium battery.
  • it can more effectively reduce the weight of the battery and reduce the volume of the battery, indirectly increasing the gram capacity, volume capacity and energy density of the battery.
  • the thickness ratio of the functional coating to the porous base film has a crucial influence on the final performance of the isolation film.
  • the thermal shrinkage performance of the isolation film is improved, the thermal stability of the cell is improved, the puncture resistance of the isolation film is improved, and the safety of the cell is improved; at the same time, with The thickness ratio of the functional coating to the porous base film increases, but the air permeability performance of the isolation film decreases, and the ion transport channel becomes smaller.
  • the thickness ratio of the functional coating and the porous base film in this application is in the range of 0.1 to 1.0, under the comprehensive influence of the thermal shrinkage and air permeability of the isolation film, the thermal stability and safety of the cell, and other properties, The lithium ion secondary battery and device including the separator of the present application can obtain the best performance.
  • the thickness of the porous base film is 2 ⁇ m to 16 ⁇ m, and the thickness of the functional coating is 1 ⁇ m to 10 ⁇ m.
  • the thickness ratio of the functional coating to the porous base film is in the range of 0.1 to 1.0, the thickness of the porous base film and the functional coating can be adjusted within a reasonable range.
  • the average single sheet area of the polyimide nanosheet is 3 ⁇ m 2 -12 ⁇ m 2 .
  • the average single-sheet area of the polyimide nanosheet affects the thermal shrinkage resistance, puncture resistance and air permeability of the isolation film. As the average single-sheet area of the nanosheet increases, the thermal box shrinkage rate of the isolation film decreases and the thermal shrinkage resistance improves; at the same time, the puncture resistance performance is enhanced; but the air permeability will decrease, which can affect the electrolyte The wettability of the isolation membrane.
  • the polyimide nanosheet has a length of 5 ⁇ m to 10 ⁇ m and a width of 1 ⁇ m to 5 ⁇ m.
  • polyimide nanosheets with length and width within the above range have a larger coverage area per unit weight, a smaller effective coating thickness, and a lighter weight. specialty.
  • the thickness of the polyamide nanosheets is 100 nm to 300 nm.
  • the thickness of the polyimide nanosheet also affects the thermal shrinkage resistance, puncture resistance, and air permeability of the isolation film. As the thickness of the nanosheets increases, the heat box shrinkage rate of the isolation membrane is reduced and the puncture resistance is also improved, but the air permeability decreases, which can affect the infiltration of the electrolyte to the isolation membrane.
  • the functional coating further includes a binder; the binder includes polyfluoroolefin, polyacrylate, polyacrylic, polyurethane, silicone, epoxy, cellulose-derived One or more types of binders.
  • the choice of the above-mentioned adhesive can improve the adhesion of the functional coating.
  • the mass percentage of the binder in the functional coating is 5% to 40%; the mass percentage of the polyimide nanosheets in the functional coating is 60% to 95% .
  • the content of the binder in the functional coating also affects the thermal shrinkage resistance, air permeability, and puncture resistance of the isolation film. As the binder content increases, the hot box shrinkage rate of the isolation membrane is reduced and the puncture resistance is also improved, but the air permeability decreases, which can affect the wettability of the electrolyte to the isolation membrane.
  • the porous base film is selected from polyolefin-based base films, preferably one of polypropylene film, polyethylene film, and polyethylene-propylene copolymer film.
  • the porous base film has good physical stability, mechanical strength, air tightness, high transparency and gloss, toughness and wear resistance.
  • the second aspect of the application provides a method for preparing the isolation film in the first aspect of the application, which includes: (1) mixing polyimide nanosheets, a binder, and deionized water to obtain polyimide nanosheets (2) Coating the aqueous dispersion of polyimide nanosheets on at least one surface of the porous base film to form a functional coating.
  • the thickness ratio of the functional coating to the porous base film is 0.1-1.0, and drying , That is, the isolation film is obtained.
  • the third aspect of the present application provides a lithium ion secondary battery, which includes a positive pole piece, a negative pole piece, a separator separated between the positive pole piece and the negative pole piece, an electrolyte, and the separator is the present application
  • the isolation membrane in the first aspect is the present application.
  • a fourth aspect of the present application provides a battery module, which includes the above-mentioned lithium-ion secondary battery.
  • the lithium-ion secondary battery includes a positive pole piece, a negative pole piece, and is spaced between the positive pole piece and the negative pole piece.
  • the separation membrane, electrolyte, and separation membrane are the separation membrane in the first aspect of the application.
  • a fifth aspect of the present application provides a battery pack including the above-mentioned battery module.
  • the fifth aspect of the present application provides a device including the lithium ion secondary battery of the third aspect of the present application.
  • the battery modules, battery packs, and devices provided by the present application include the lithium ion secondary battery of the present application, and therefore have at least the same or similar beneficial effects.
  • the embodiments of the present application provide an isolation film, which includes a porous base film and a functional coating provided on at least one surface of the porous base film, the functional coating It includes polyimide nanosheets, the polyimide nanosheets are stacked irregularly to form a laminar loose structure; and the thickness ratio of the functional coating to the porous base film is 0.1-1.0.
  • the thermal stability and chemical stability of the isolation film can be improved.
  • the long-term use temperature of the isolation film can be increased to 300°C, and it will not cause the failure of the battery cell if it is kept at 150°C for 2 hours; the thermal shrinkage resistance of the isolation film has been significantly improved, and it can be used in an environment above 180°C. Keep the pore structure of the diaphragm unchanged.
  • polyimide does not swell or dissolve in the electrolyte, and will not have any chemical reaction with the electrolyte and the positive and negative materials, which can ensure the stable operation of the battery during long-term use.
  • the polyimide coating can isolate the internal conduction of electrons between the positive and negative electrodes, prevent the positive and negative electrodes of the battery from being short-circuited, thereby reducing the self-discharge rate of the lithium-ion battery, and effectively improving the safety of the battery.
  • the polyimide used in the functional coating of the isolation film provided in the embodiments of the present application is a nanosheet material, and the polyimide nanosheets are stacked irregularly to form a laminar loose structure.
  • polyimide nanosheets and their stacked laminar loose structure have significantly increased physical area and high toughness, making the present application
  • the functional coatings in the product have the characteristics of larger coverage area per unit weight, smaller effective coating thickness and lighter weight.
  • the contact area between the sheet structure and the bare film is larger, and the thermal shrinkage resistance is better; and it can more effectively resist the mechanical puncture of the lithium dendrites, avoid micro-short circuits, and improve the safety and cycle performance of the battery.
  • it can more completely isolate the internal conduction of electrons between the positive and negative electrodes, effectively increase the tortuosity of the micropores of the isolation film, and greatly reduce the self-discharge rate of the lithium battery.
  • it can also effectively reduce the weight of the battery and reduce the volume of the battery, indirectly increasing the gram capacity, volume capacity and energy density of the battery.
  • the thickness ratio of the functional coating to the porous base film has a crucial influence on the final performance of the isolation film.
  • the thermal shrinkage performance of the isolation film is improved, the thermal stability of the cell is improved, the puncture resistance of the isolation film is improved, and the safety of the cell is improved; at the same time, with The thickness ratio of the functional coating to the porous base film increases, but the air permeability performance of the isolation film decreases, and the ion transport channel becomes smaller.
  • the thickness ratio of the functional coating to the porous base film is in the range of 0.1 to 1.0, under the comprehensive influence of the thermal shrinkage and air permeability of the isolation film, the thermal stability and safety of the cell, the application is included.
  • the best performance can be obtained from the lithium ion secondary battery and device of the separator.
  • the porous base film has a thickness of 2 micrometers ( ⁇ m) to 16 ⁇ m
  • the functional coating has a thickness of 1 ⁇ m to 10 ⁇ m.
  • the thickness ratio of the functional coating to the porous base film is in the range of 0.1 to 1.0, the thickness of the porous base film and the functional coating can be adjusted within a reasonable range.
  • the conventional porous base membrane in the field has a thickness of 2 ⁇ m to 16 ⁇ m.
  • the thickness of the functional coating in the embodiments of the present application is preferably in the range of 1 ⁇ m to 10 ⁇ m.
  • the average single sheet area of the polyimide nanosheet is 3 square micrometers ( ⁇ m 2 ) to 12 ⁇ m 2 .
  • the average single-sheet area of the polyimide nanosheet affects the thermal shrinkage resistance, puncture resistance and air permeability of the isolation film. As the average single-sheet area of the nanosheet increases, the thermal box shrinkage rate of the isolation film decreases and the thermal shrinkage resistance improves; at the same time, the puncture resistance performance is enhanced; but the air permeability will decrease, which can affect the electrolyte The wettability of the isolation membrane. Therefore, the average monolithic area of the polyimide nanosheets in the present application is within the preferred range of 3 ⁇ m 2 to 12 ⁇ m 2. As an example, the average monolithic area of the polyimide nanosheets can also be 4 ⁇ m 2 ⁇ 12 ⁇ m 2 .
  • the polyimide nanosheet has a length of 5 ⁇ m-10 ⁇ m and a width of 1 ⁇ m-5 ⁇ m.
  • polyimide nanosheets with length and width within the above range have a larger coverage area per unit weight, a smaller effective coating thickness, and a lighter weight. specialty.
  • the contact area between the sheet structure and the bare film is larger, and the thermal shrinkage resistance is better; and it can more effectively resist the mechanical puncture of the lithium dendrites, avoid micro-short circuits, and improve the safety and cycle performance of the battery.
  • the sheet structure can more completely isolate the internal conduction of electrons between the positive and negative electrodes, effectively increase the tortuosity of the micropores of the isolation film, and greatly reduce the self-discharge rate of the lithium battery. At the same time, it can also more effectively reduce the weight of the battery and reduce the volume of the battery, indirectly increasing the gram capacity, volume capacity and energy density of the battery.
  • the thickness of the polyimide nanosheets is 100 nanometers (nm) to 300 nm.
  • the thickness of the polyimide nanosheet also affects the thermal shrinkage resistance, puncture resistance, and air permeability of the isolation film. As the thickness of the nanosheets increases, the heat box shrinkage rate of the isolation membrane is reduced and the puncture resistance is also improved, but the air permeability decreases, which can affect the infiltration of the electrolyte to the isolation membrane. Therefore, the thickness of the polyimide nanosheets in the present application is within a preferred range of 100 nm to 300 nm.
  • the functional coating further includes a binder; the binder includes polyfluoroolefin, polyacrylate, polyacrylic, polyurethane, silicone, epoxy, and fiber One or more of the element-derived binders.
  • the mass percentage of the binder in the functional coating is 5%-40%; the mass percentage of the polyimide nanosheets in the functional coating It is 60%-95%.
  • the content of the binder in the functional coating also affects the thermal shrinkage resistance, air permeability, and puncture resistance of the isolation film. As the binder content increases, the hot box shrinkage rate of the isolation membrane is reduced and the puncture resistance is also improved, but the air permeability decreases, which can affect the wettability of the electrolyte to the isolation membrane. Therefore, in the embodiments of the present application, the mass percentage of the binder in the functional coating is within a preferred range of 5%-40%.
  • the porous base film is selected from polyolefin-based base films.
  • it may be selected from one of polypropylene films, polyethylene films, and polyethylene-propylene copolymer films.
  • the embodiments of the present application provide a method for preparing the aforementioned isolation film, which includes: (1) mixing a polyimide nanosheet, a binder, and deionized water to obtain a polyimide Aqueous dispersion of nanosheets; wherein the mass percentage of the polyimide nanosheets and the binder is 6%-50%, and the balance is deionized water. (2) Coating the polyimide nanosheet aqueous dispersion on at least one surface of the porous base film to form a functional coating, and the thickness ratio of the functional coating to the porous base film is 0.1-1.0, After drying, an isolation film is obtained.
  • the formulation of the aqueous dispersion of polyimide nanosheets is adjusted to make the formed dispersion have very good stability, and the stable slurry is coated by coating technology After drying on the bare film, a functional coating that is naturally stacked to form a laminar loose structure can be obtained.
  • the embodiments of the present application also provide a lithium ion secondary battery, which includes a positive pole piece, a negative pole piece, and is spaced between the positive pole piece and the negative pole piece.
  • the isolation membrane, electrolyte, the isolation membrane is the isolation membrane provided in the first aspect of the embodiments of the application.
  • a fourth aspect of the present application provides a battery module, which includes the above-mentioned lithium-ion secondary battery.
  • the lithium-ion secondary battery includes a positive pole piece, a negative pole piece, and is spaced between the positive pole piece and the negative pole piece.
  • the separation membrane, electrolyte, and separation membrane are the separation membrane in the first aspect of the application.
  • a fifth aspect of the present application provides a battery pack including the above-mentioned battery module.
  • the embodiments of the present application further provide a device including the lithium ion secondary battery provided in the third aspect of the embodiments of the present application.
  • the embodiment of the present application also provides a battery module including the lithium ion secondary battery as a unit cell and a battery pack including the battery module.
  • the battery pack can be used as a power source for medium or large devices that require high temperature stability, long cycle life, and high rate characteristics.
  • Examples of these medium or large devices include, but are not limited to: electric tools driven by electric motors; electric vehicles (EV), hybrid electric vehicles (HEV), and plug-in hybrid electric vehicles ( Plug in hybrid electric vehicle (referred to as PHEV); electric two-wheeled vehicles such as electric bicycles and electric scooters; electric golf carts; and systems for storing electricity.
  • EV electric vehicles
  • HEV hybrid electric vehicles
  • PHEV plug-in hybrid electric vehicles
  • electric two-wheeled vehicles such as electric bicycles and electric scooters
  • electric golf carts and systems for storing electricity.
  • the isolation film, the preparation method thereof, the lithium ion secondary battery and the device provided in the embodiments of the present application are further described. It should be understood that these embodiments are only used to illustrate the application and not to limit the scope of the application.
  • the total mass percentage content in the polyimide nanosheets ranges from 6% to 50%, wherein the ratio of the polyimide nanosheets to the binder is 5-40:60-95.
  • the aqueous dispersion of polyimide nanosheets is coated on both surfaces of the polyolefin base film by the coating equipment commonly used in the art to form a functional coating.
  • the thickness of the functional coating and the porous base film The ratio is 0.1 to 1.0, and it is dried at 60°C to 80°C to obtain an isolation film.
  • the positive active material lithium cobalt oxide, conductive agent conductive carbon, and binder poly (vinylidene fluoride) (PVDF) are mixed uniformly at a mass ratio of 96:2:2 to prepare lithium ions with a certain viscosity Battery cathode slurry.
  • the negative electrode active material graphite and silicon (Si) powder mixture (wherein, the mass percentage of Si powder is 50%), negative electrode binder styrene butadiene rubber, negative electrode conductive agent conductive carbon black (Super P) according to the mass ratio of 92 : Mix and disperse in a ratio of 3:5 with the solvent N-methylpyrrolidone (NMP) to make a negative electrode slurry, and coat the negative electrode slurry evenly on the negative electrode set according to the coating amount of 130mg/1540mm 2
  • NMP solvent N-methylpyrrolidone
  • the volume ratio of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate is 1:2:1 to obtain electrolysis. liquid.
  • the positive pole piece, the negative pole piece, and the separator film spaced between the positive pole piece and the negative pole piece are wound and assembled; the electrolyte is injected to make a lithium ion secondary battery.
  • the separators and lithium ion secondary batteries of Examples 1 to 23 of the present application were prepared according to the above methods.
  • the detailed parameters of the separators and lithium ion secondary batteries prepared in each embodiment are shown in Table 1.
  • this application also provides the separation membranes and lithium ion secondary batteries prepared in Comparative Examples 1 to 8, and compares the technical effects of the separation membranes and lithium ion secondary batteries prepared in Examples 1 to 23.
  • the isolation film provided by Comparative Example 1 does not have a functional coating; the isolation film provided by Comparative Example 2 has a functional coating, but the functional coating contains polyimide polymer and a binder; the isolation film provided by Comparative Example 3
  • the isolation film also has a functional coating, but the functional coating contains polyimide nanofibers and a binder.
  • the isolation membranes provided by Comparative Examples 4 to 8 have functional coatings, and the functional coatings contain polyimide nanosheets and a binder, but the thickness ratio of the functional coating to the porous base film is not in the range of 0.1 to 1.0 .
  • the detailed parameters of Comparative Examples 1-8 are also shown in Table 1.
  • S shrinkage rate
  • L1 length in TD direction before shrinking
  • L2 length in TD direction after shrinking.
  • the VW Volks Wagenwerk, Volkswagen, abbreviation: VW
  • the temperature rise rate of 1 minute is increased to 80°C for 16 hours; the temperature is increased to 120°C at the same rate of 2°C/min for 2 hours; the temperature is increased to 150°C at the same rate of 2°C/min for 2 hours.
  • the air permeability of the isolation membrane refers to the degree to which an object or medium allows gas to pass. Under a stable pressure, a certain volume of gas (25 cubic centimeter (cubic centimeter, abbreviation: cc) ⁇ 300cc) flows through a specific area of the sample The time required.
  • the air permeability tester with the product code name Gurley 4110N produced in the United States is used to test and detect the air permeability of the isolation film.
  • Detection method Measure the time required for 100cc of air to pass through a diaphragm with a circular area of 3 inches in diameter under a high pressure of 4.88 inches of water column, in seconds (s).
  • the level of the anti-needle strength of the isolation membrane is expressed by the maximum force generated during the process of piercing the sample to be tested-piercing force.
  • the product code name is Sansi Zongheng UTM6104 series electronic universal testing machine to test the anti-needling strength of the isolation film.
  • Detection method cut 5 specimen diaphragms, set the test speed 100mm/min, specimen name, test times and other parameter information on the equipment control software, click the test operation to get the puncture force value of the specimen, and take the average of the results.
  • Lithium-ion charging and discharging equipment use the product code name of Xinwei mobile power product dedicated tester to charge and discharge the battery repeatedly until the capacity attenuation rate reaches 80%.
  • the battery capacity above is 70 ampere hours (Ah), and the battery is repeatedly charged and discharged. The core is charged and discharged.
  • the capacity of the cell decays to 56Ah, stop the test and record the number of repeated charging and discharging, which is the cycle performance data of the cell.
  • Table 1 below shows the detailed parameters and test results of the separators and lithium ion secondary batteries provided in Examples 1-23 and Comparative Examples 1-8:
  • the surface of the isolation film provided in Examples 1-23 is additionally provided with a functional coating including polyimide nanosheets, and the thickness ratio of the functional coating to the base film is in the range of 0.1-1.0.
  • the isolation membranes provided by Comparative Examples 1 to 3 are respectively without additional functional coatings and additional polyimide polymer materials or polyimide nanofibers on the surface.
  • the performance of the separators provided by Comparative Examples 1 to 3 and the battery cycle performance are significantly inferior to those of Examples 1 to 23.
  • the isolation film in Comparative Examples 4-8 is added with a functional coating including polyimide nanosheets
  • the thickness ratio of the functional coating including polyimide nanosheets to the base film is not in the range of 0.1 to 1.0
  • the performance and battery cycle performance of the separator film provided by Comparative Examples 4 to 8 have been significantly reduced. It can be seen that when the thickness ratio of the functional coating and the porous base film is in the range of 0.1 to 1.0, the thermal shrinkage of the separator film Under the combined influence of many performances such as performance and gas permeability, cell thermal stability and safety, the isolation membrane and electrochemical device can obtain the best performance.

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Abstract

本申请实施例提供一种隔离膜、其制备方法、锂离子二次电池、电池模块、电池包及装置。本申请所提供的隔离膜包括多孔基膜及设于多孔基膜至少一个表面上的功能涂层，该功能涂层包括聚酰亚胺纳米片，所述聚酰亚胺纳米片不规则堆积形成片层状疏松结构；且功能涂层与多孔基膜的厚度比为0.1～1.0。本申请同时也提供上述隔离膜的制备方法及包含上述隔离膜的锂离子二次电池及装置。

Description

隔离膜、其制备方法、锂离子二次电池、电池模块、电池包及装置
相关申请的交叉引用
本申请要求享有于2019年09月17日提交的名称为“隔离膜、其制备方法、锂离子二次电池及装置”的中国专利申请201910874822.5的优先权，该申请的全部内容通过引用并入本文中。
技术领域
本申请涉及电池技术领域，特别是涉及一种隔离膜、其制备方法、锂离子二次电池及装置。
背景技术
在锂离子电池结构中，隔离膜是关键的内层组件之一，对锂离子电池的综合性能具有重要影响。性能优异的锂离子电池要求其使用的隔离膜不但具有普通隔膜的基本性能，还应具有优异的耐高温性能。现有的锂离子电池中所使用的常规PE隔离膜的熔点为130℃，而当温度达到150℃时，隔膜将收缩30％以上，可能造成锂离子电池内部的阴阳极短接，给电池带来很大的安全隐患。
目前，解决隔离膜耐高温问题的主要手段是使用CCS(Ceramic Coating Separation，陶瓷涂层隔离，简称：CCS)例如勃母石浆料对隔离膜进行涂布或者使用耐热材料制成隔离膜。然而，CCS生产过程中存在结块的问题，使得涂布CCS的隔离膜出现颗粒，热压时容易刺破隔离膜，且勃母石的比重较大，会降低锂离子电池的重量能量密度。此外，也未能寻 找到其他耐热效果好、开发成熟且价格合理的隔离膜材料。
发明内容
鉴于背景技术中存在的问题，本申请的目的在于提供一种隔离膜、其制备方法、锂离子二次电池及装置，以提高隔离膜的耐高温性能以及电池和装置的热安全稳定性。
为了达到上述目的，本申请的第一方面提供了一种隔离膜，其包括多孔基膜及设于多孔基膜至少一个表面上的功能涂层，功能涂层包括聚酰亚胺纳米片，聚酰亚胺纳米片不规则堆积形成片层状疏松结构；且功能涂层与多孔基膜的厚度比为0.1～1.0。
首先，本申请所提供的隔离膜，在隔离膜表面涂层中含有聚酰亚胺成份，由于聚酰亚胺具有较佳的耐高温性、耐化学性和电子绝缘性，可显著提高隔离膜的热稳定性和化学稳定性。一方面，隔离膜的长期使用温度可提高至300℃，在150℃环境中保温2小时不会引起电芯的失效；隔离膜的抗热收缩特性也得到明显的提高，在180℃以上环境中可保持隔膜的孔结构不变。另一方面，聚酰亚胺在电解液中不溶胀、不溶解，不会与电解液、正负极材料发生任何化学反应，可确保电池在长期使用过程中稳定运行。再一方面，聚酰亚胺涂层可隔绝电子在正负极间的内传导，防止电池的正负极短接，从而降低锂离子电池的自放电率，有效提高电池的安全性。
在一些示例性实施例中，本申请的隔离膜功能涂层中所采用的聚酰亚胺为纳米片材料，且聚酰亚胺纳米片不规则堆积形成片层状疏松结构。相对于聚酰亚胺高分子材料或聚酰亚胺纳米纤维而言，聚酰亚胺纳米片及堆积所形成的片层状疏松结构，具有显著增大的物理面积和更高的韧性，使得本申请中的功能涂层具有单位重量覆盖面积更大、有效涂覆厚度更 小、重量更轻的特点。一方面，片状结构与裸膜的接触面积更大，抗热收缩性更优；且能更有效地抵档锂枝晶的机械穿刺，避免微短路，提升电池的安全性和循环性能。另一方面，可更完全地隔绝电子在正负极间的内传导，有效增加隔离膜微孔的曲折度，大幅度降低锂电池的自放电率。再一方面，还可更有效减轻电池的重量并缩小电池的体积，间接地提高电池的克容量、体积容量和能量密度。
更重要的是，申请人发现，功能涂层与多孔基膜的厚度比对于隔离膜的最终性能具有至关重要的影响。随着功能涂层与多孔基膜的厚度比增加，隔离膜的热收缩性能得到提高、电芯热稳定性提高，隔离膜的抗穿刺性能提高、电芯安全性提高；于此同时，随着功能涂层与多孔基膜的厚度比增加，隔离膜的透气度性能却发生降低，离子传输通道变小。当本申请中的功能涂层与多孔基膜的厚度比在0.1～1.0的范围内，在隔离膜的热收缩性和透气性、电芯热稳定性和安全性等诸多性能的综合影响下，包含了本申请的隔离膜的锂离子二次电池及装置可获得最佳性能。
在一些示例性实施例中，多孔基膜的厚度为2μm～16μm，功能涂层的厚度为1μm～10μm。在符合功能涂层与多孔基膜的厚度比在0.1～1.0的范围内的前提下，可以在合理范围内调整多孔基膜和功能涂层的厚度。
在一些示例性实施例中，聚酰亚胺纳米片的平均单片面积为3μm 2～12μm 2。聚酰亚胺纳米片的平均单片面积影响隔离膜的抗热收缩性、抗穿刺性和透气度。随着纳米片平均单片面积的增大，隔离膜的热箱收缩率随之降低、抗热收缩性得到提高；同时，抗穿刺性能得到增强；但透气度会降低，从而可影响电解液对隔离膜的浸润性。
在一些示例性实施例中，聚酰亚胺纳米片的长为5μm～10μm、宽为1μm～5μm。长、宽在上述范围内的聚酰亚胺纳米片，相对于聚酰亚胺纳米纤维或聚酰亚胺纳米纤维线，具有单位重量覆盖面积更大、有效涂 覆厚度更小、重量更轻的特点。
在一些示例性实施例中，聚酰胺纳米片的厚度为100nm～300nm。聚酰亚胺纳米片的厚度也影响隔离膜的抗热收缩性、抗穿刺性、透气性。随着纳米片厚度的增加，隔离膜的热箱收缩率随之降低、抗穿刺性也得到提高，但是透气度降低，从而可影响电解液对隔离膜的浸润性。
在一些示例性实施例中，功能涂层还包括粘结剂；粘结剂包括聚氟烯烃类、聚丙烯酸酯类、聚丙烯酸类、聚氨酯类、硅树脂类、环氧树脂类、纤维素衍生类粘结剂中的一种或多种。选用上述粘接剂可以提高功能涂层的粘结性。
在一些示例性实施例中，粘结剂在功能涂层中的质量百分含量为5％～40％；聚酰亚胺纳米片在功能涂层中的质量百分含量为60％～95％。功能涂层中粘结剂的含量也对隔离膜的抗热收缩性、透气性、抗穿刺性产生影响。随着粘结剂含量的增加，隔离膜的热箱收缩率随之降低、抗穿刺性也得到提高，但是透气度降低，从而可影响电解液对隔离膜的浸润性。
在一些示例性实施例中，多孔基膜选自聚烯烃类基膜，优选自聚丙烯膜、聚乙烯膜和聚乙稀-丙烯共聚物膜中的一种。上述多孔基膜物理稳定性、机械强度、气密性较好，透明度和光泽度较高，坚韧耐磨。
本申请的第二方面提供了本申请的第一方面中的隔离膜的制备方法，包括：(1)将聚酰亚胺纳米片、粘结剂和去离子水混合，得到聚酰亚胺纳米片水性分散液；(2)将聚酰亚胺纳米片水性分散液涂覆在多孔基膜至少一个表面上，形成功能涂层，功能涂层与多孔基膜的厚度比为0.1～1.0，干燥，即得到隔离膜。
本申请的第三方面提供了一种锂离子二次电池，其包括正极极片、负极极片、间隔于正极极片和负极极片之间的隔离膜、电解液，隔离膜为本申请的第一方面中的隔离膜。
本申请的第四方面提供了一种电池模块，该电池模块包括上述的锂离子二次电池，锂离子二次电池包括正极极片、负极极片、间隔于正极极片和负极极片之间的隔离膜、电解液，隔离膜为本申请的第一方面中的隔离膜。
本申请的第五方面提供了一种电池包，该电池包包括上述的电池模块。
本申请的第五方面提供了一种装置，该装置包含本申请第三方面的锂离子二次电池。
本申请提供的电池模块、电池包和装置包括本申请的锂离子二次电池，因而至少具有相同或类似的有益效果。
具体实施方式
下面结合附图和实施例对本申请的实施方式作进一步详细描述。以下实施例的详细描述和附图用于示例性地说明本申请的原理，但不能用来限制本申请的范围，即本申请不限于所描述的实施例。
在本申请的描述中，需要说明的是，除非另有说明，“多个”的含义是两个以上；术语“上”、“下”、“左”、“右”、“内”、“外”等指示的方位或位置关系仅是为了便于描述本申请和简化描述，而不是指示或暗示所指的装置或元件必须具有特定的方位、以特定的方位构造和操作，因此不能理解为对本申请的限制。此外，术语“第一”、“第二”、“第三”等仅用于描述目的，而不能理解为指示或暗示相对重要性。“垂直”并不是严格意义上的垂直，而是在误差允许范围之内。“平行”并不是严格意义上的平行，而是在误差允许范围之内。
下述描述中出现的方位词均为图中示出的方向，并不是对本申请的具体结构进行限定。在本申请的描述中，还需要说明的是，除非另有明确 的规定和限定，术语“安装”、“相连”、“连接”应做广义理解，例如，可以是固定连接，也可以是可拆卸连接，或一体地连接；可以是直接相连，也可以通过中间媒介间接相连。对于本领域的普通技术人员而言，可视具体情况理解上述术语在本申请中的具体含义。
根据本申请实施例的第一方面，本申请的实施例提供一种隔离膜，该隔离膜包括多孔基膜及设于所述多孔基膜至少一个表面上的功能涂层，所述功能涂层包括聚酰亚胺纳米片，所述聚酰亚胺纳米片不规则堆积形成片层状疏松结构；且所述功能涂层与所述多孔基膜的厚度比为0.1～1.0。
由于聚酰亚胺具有较佳的耐高温性、耐化学性和电子绝缘性，可提高隔离膜的热稳定性和化学稳定性。一方面，隔离膜的长期使用温度可提高至300℃，在150℃环境中保温2小时不会引起电芯的失效；隔离膜的抗热收缩特性得到显著提高，在180℃以上的环境中可保持隔膜的孔结构不变。另一方面，聚酰亚胺在电解液中不溶胀、不溶解，不会与电解液、正负极材料发生任何化学反应，可确保电池在长期使用过程中稳定运行。再一方面，聚酰亚胺涂层可隔绝电子在正负极间的内传导，防止电池的正负极短接，从而降低锂离子电池的自放电率，有效提高电池的安全性。
在一些实施例中，本申请实施例提供的隔离膜功能涂层中所采用的聚酰亚胺为纳米片材料，且聚酰亚胺纳米片不规则堆积形成片层状疏松结构。相对于聚酰亚胺高分子材料或聚酰亚胺纳米纤维而言，聚酰亚胺纳米片及其堆积形成的片层状疏松结构，具有显著增大的物理面积和高韧性，使得本申请中的功能涂层具有单位重量覆盖面积更大、有效涂覆厚度更小、重量更轻的特点。一方面，片状结构与裸膜的接触面积更大，抗热收缩性更优；且能更有效地抵档锂枝晶的机械穿刺，避免微短路，提升电池的安全性和循环性能。另一方面，可更完全地隔绝电子在正负极间的内传导，有效增加隔离膜微孔的曲折度，大幅度降低锂电池的自放电率。再一 方面，还可有效减轻电池的重量并缩小电池的体积，间接地提高电池的克容量、体积容量和能量密度。
而且，通过实验得到验证，功能涂层与多孔基膜的厚度比对于隔离膜的最终性能具有至关重要的影响。随着功能涂层与多孔基膜的厚度比增加，隔离膜的热收缩性能得到提高、电芯热稳定性提高，隔离膜的抗穿刺性能提高、电芯安全性提高；于此同时，随着功能涂层与多孔基膜的厚度比增加，隔离膜的透气度性能却发生降低，离子传输通道变小。当功能涂层与多孔基膜的厚度比在0.1～1.0的范围内，在隔离膜的热收缩性和透气性、电芯热稳定性和安全性等诸多性能的综合影响下，包含了本申请的隔离膜的锂离子二次电池及装置可获得最佳性能。
在一些实施例中，所述多孔基膜的厚度为2微米(μm)～16μm，所述功能涂层的厚度为1μm～10μm。在符合功能涂层与多孔基膜的厚度比在0.1～1.0的范围内的前提下，可以在合理范围内调整多孔基膜和功能涂层的厚度。考虑到隔离膜的基本性能，本领域中常规的多孔基膜的厚度为2μm～16μm，在此前提下，本申请实施例中的功能涂层的厚度以1μm～10μm范围内为佳。
在一些实施例中，所述聚酰亚胺纳米片的平均单片面积为3平方微米(μm 2)～12μm 2。聚酰亚胺纳米片的平均单片面积影响隔离膜的抗热收缩性、抗穿刺性和透气度。随着纳米片平均单片面积的增大，隔离膜的热箱收缩率随之降低、抗热收缩性得到提高；同时，抗穿刺性能得到增强；但透气度会降低，从而可影响电解液对隔离膜的浸润性。因而，本申请中的聚酰亚胺纳米片的平均单片面积在3μm 2～12μm 2的较佳范围内，作为一种示例，聚酰亚胺纳米片的平均单片面积也可以为4μm 2～12μm 2。
在一些实施例中，所述聚酰亚胺纳米片的长为5μm～10μm、宽为1μm～5μm。长、宽在上述范围内的聚酰亚胺纳米片，相对于聚酰亚胺纳米 纤维或聚酰亚胺纳米纤维线，具有单位重量覆盖面积更大、有效涂覆厚度更小、重量更轻的特点。一方面，片状结构与裸膜的接触面积更大，抗热收缩性更优；且能更有效地抵档锂枝晶的机械穿刺，避免微短路，提升电池的安全性和循环性能。另一方面，片状结构可更完全地隔绝电子在正负极间的内传导，有效增加隔离膜微孔的曲折度，大幅度降低锂电池的自放电率。同时，也可更有效减轻电池的重量并缩小电池的体积，间接地提高电池的克容量、体积容量和能量密度。
在一些实施例中，所述聚酰亚胺纳米片的厚度为100纳米(nm)～300nm。聚酰亚胺纳米片的厚度也影响隔离膜的抗热收缩性、抗穿刺性、透气性。随着纳米片厚度的增加，隔离膜的热箱收缩率随之降低、抗穿刺性也得到提高，但是透气度降低，从而可影响电解液对隔离膜的浸润性。因而，本申请中的聚酰亚胺纳米片的厚度在100nm～300nm的较佳范围内。
在一些实施例中，所述功能涂层还包括粘结剂；所述粘结剂包括聚氟烯烃类、聚丙烯酸酯类、聚丙烯酸类、聚氨酯类、硅树脂类、环氧树脂类和纤维素衍生类粘结剂中的一种或多种。
在一些实施例中，所述粘结剂在所述功能涂层中的质量百分含量为5％～40％；所述聚酰亚胺纳米片在所述功能涂层中的质量百分含量为60％～95％。功能涂层中粘结剂的含量也对隔离膜的抗热收缩性、透气性、抗穿刺性产生影响。随着粘结剂含量的增加，隔离膜的热箱收缩率随之降低、抗穿刺性也得到提高，但是透气度降低，从而可影响电解液对隔离膜的浸润性。因而，本申请实施例中，粘结剂在功能涂层中的质量百分含量在5％～40％的较佳范围内。
在一些实施例中，所述多孔基膜选自聚烯烃类基膜，示例性的，可选自聚丙烯膜、聚乙烯膜和聚乙稀-丙烯共聚物膜中的一种。
根据本申请实施例的第二方面，本申请实施例提供上述隔离膜的制 备方法，其包括：(1)将聚酰亚胺纳米片、粘结剂和去离子水混合，得到聚酰亚胺纳米片水性分散液；其中，聚酰亚胺纳米片和粘结剂的质量百分含量为6％～50％，余量为去离子水。(2)将所述聚酰亚胺纳米片水性分散液涂覆在多孔基膜至少一个表面上，形成功能涂层，所述功能涂层与所述多孔基膜的厚度比为0.1～1.0，干燥，即得到隔离膜。
本申请实施例提供的上述制备方法中，通过调节聚酰亚胺纳米片水性分散液的配方，使得形成的分散液具有非常好的稳定性，通过涂覆技术将该种稳定的浆料涂覆到裸膜上，烘干，即可得到自然堆积形成片层状疏松结构的功能涂层。
根据本申请实施例的第三方面，本申请的实施例还提供一种锂离子二次电池，其包括正极极片、负极极片、间隔于所述正极极片和所述负极极片之间的隔离膜、电解液，所述隔离膜为本申请实施例第一方面所提供的隔离膜。
本申请的第四方面提供了一种电池模块，该电池模块包括上述的锂离子二次电池，锂离子二次电池包括正极极片、负极极片、间隔于正极极片和负极极片之间的隔离膜、电解液，隔离膜为本申请的第一方面中的隔离膜。
本申请的第五方面提供了一种电池包，该电池包包括上述的电池模块。
根据本申请实施例的第五方面，本申请的实施例还提供一种装置，该装置包含本申请实施例第三方面所提供的锂离子二次电池。
本申请的实施例还提供包含所述锂离子二次电池作为单元电池的电池模块和包含所述电池模块的电池组。
所述电池组可以用作要求高温稳定性、长循环寿命、高倍率特性的中型或大型装置的电源。
这些中型或大型装置的实例包括但不限于：电动马达驱动的电动工具；电动车辆(Electric vehicles，简称：EV)、混合电动车辆(Hybrid electric vehicle，简称：HEV)和插电式混合电动车辆(Plug in hybrid electric vehicle，简称：PHEV)；电动双轮车辆如电动自行车和电动踏板车；电动高尔夫球车；以及用于储存电力的系统。
下面结合一些示例性实施例和对比例，进一步阐述本申请实施例提供的隔离膜、其制备方法、锂离子二次电池及装置。应理解，这些实施例仅用于说明本申请而不用于限制本申请的范围。
实施例1-23
(1)隔离膜的制备
将聚酰亚胺纳米片、粘结剂和去离子水混合，得到聚酰亚胺纳米片水性分散液；其中，聚酰亚胺纳米片和粘结剂在聚酰亚胺纳米片水性分散液中的总质量百分含量范围为6％～50％，其中，聚酰亚胺纳米片和粘结剂的质量份之比为：5～40:60～95。
通过本领域常用的涂覆设备将聚酰亚胺纳米片水性分散液涂覆在聚烯烃类基膜的两个表面上，形成功能涂层，所述功能涂层与所述多孔基膜的厚度比为0.1～1.0，在60℃～80℃下烘干，得到隔离膜。
(2)正极极片的制备
将正极活性物质钴酸锂、导电剂导电碳、粘结剂聚偏氟乙烯(Poly(vinylidene fluoride)，简称：PVDF)按质量比96：2：2混合均匀，制成具有一定粘度的锂离子电池正极浆料。将正极浆料涂布在正极集流体铝箔上，85℃下烘干后冷压，进行切边、裁片、分条，分条后在真空条件、85℃下烘干4小时，焊接极耳，制成正极极片。
(3)负极极片的制备
将负极活性物质石墨与硅(Si)粉的混合物(其中，Si粉的质量百 分含量为50％)、负极粘接剂丁苯橡胶、负极导电剂导电碳黑(Super P)按质量比92:3:5比例混合分散与溶剂N-甲基吡咯烷酮(N-methylpyrrolidone，简称：NMP)中，制成负极浆料，按照130mg/1540mm 2的涂覆量将负极浆料均匀涂覆在负极集流体铜箔的正反两面上，经过85℃烤箱烘干，制得负极极片。
(4)电解液的制备
将六氟磷酸锂溶解于碳酸乙烯酯、碳酸二甲酯及碳酸甲乙酯的混合溶剂中，其中，碳酸乙烯酯，碳酸二甲酯及碳酸甲乙酯的体积比为1：2：1，即得到电解液。
(5)锂离子二次电池的制备
将上述正极极片、负极极片、间隔于正极极片和负极极片之间的隔离膜卷绕组装；注入电解液制成锂离子二次电池。
按照上述方法制备本申请实施例1～23的隔离膜及锂离子二次电池，各实施例制备的隔离膜及锂离子二次电池的详细参数如表1所示。
此外，本申请还提供了对比例1～8制备的隔离膜及锂离子二次电池，将其与实施例1～23中制备的隔离膜及锂离子二次电池的技术效果进行对比。
其中，对比例1提供的隔离膜不具有功能涂层；对比例2提供的隔离膜具有功能涂层，但其功能涂层中包含聚酰亚胺高分子及粘结剂；对比例3提供的隔离膜也具有功能涂层，但其功能涂层中包含聚酰亚胺纳米纤维及粘结剂。对比例4～8提供的隔离膜具有功能涂层，且功能涂层中包含聚酰亚胺纳米片和粘结剂，但是功能涂层与多孔基膜的厚度比并不在0.1～1.0的范围内。对比例1～8的详细参数也如表1所示。
对实施例1～23和对比例1～8中隔离膜及锂离子二次电池的性能参数定义及检测方法如下：
(1)隔离膜热收缩率检测：
隔离膜的热收缩率S是指TD方向(Transverse Direction，垂直于机械方向，简称：TD方向)的长度收缩比例：S＝(L1-L2)/L1。
S:收缩率；L1:收缩前TD方向长度；L2:收缩后TD方向长度。
本申请的实施例中，在产品代号为DHG-9070A DHG系列高温烘箱中，采用VW(Volks Wagenwerk，大众，简称：VW)热箱测试标准，进行隔离膜热收缩率的检测：以2℃/分钟的升温速率升温到80℃，保温16小时；以2℃/分钟的相同速率继续升温到120℃，保温2小时；以2℃/分钟的相同速率继续升温到150℃，保温2小时。
(2)隔离膜透气度检测：
隔离膜的透气度是指：物体或介质允许气体通过的程度，在稳定的压力下，测定一定体积的气体(25立方厘米(cubic centimeter，简称：cc)～300cc)流过特定面积的试样所需的时间。
本申请的实施例中，使用美国生产的产品代号为Gurley 4110N的透气度测试仪测试检测隔离膜的透气度。检测方法：测量100cc空气在4.88英寸水柱高压力下，透过3英寸直径圆形面积隔膜所需的时间，单位为秒(s)。
(3)抗针刺强度检测：
隔离膜的抗针刺强度的高低以刺穿待测试样过程中产生的最大力值——穿刺力表示。
本申请的实施例中，使用产品代号为三思纵横UTM6104系列电子万能试验机测试隔离膜的抗针刺强度。检测方法：裁取5片试样隔膜，设备控制软件上设置试验速度100mm/min、试样名称、试验次数等参数信息，点击试验操作得到试样的穿刺力值，结果取平均值。
(4)电池循环性能测试：
用锂离子充放电设备：使用产品代号为新威移动电源成品专用测试仪对电池重复进行充放电，直至容量衰减率达到80％，如上述电芯容量为70安时(Ah)，重复对电芯进行充放电，当电芯容量衰减至56Ah时，停止测试，记录重复充放电的次数，即为电芯的循环性能数据。
下表1为实施例1～23和对比例1～8中提供的隔离膜及锂离子二次电池的详细参数和测试结果：
表1实施例及对比例的详细参数和测试结果
Figure PCTCN2020113801-appb-000001
从表1数据可以看到：实施例1～23提供的隔离膜表面增设了包括聚酰亚胺纳米片的功能涂层，且功能涂层与基膜的厚度比在0.1～1.0范围内。对比例1～3提供的隔离膜分别为不增设功能涂层、表面增设聚酰亚胺高分子材料或聚酰亚胺纳米纤维。对比例1～3提供的隔离膜的性能以及电池循环性能明显劣于实施例1～23。同时，对比例4～8中的隔离膜虽然增设 了包括聚酰亚胺纳米片的功能涂层，但包括聚酰亚胺纳米片的功能涂层与基膜的厚度比不在0.1～1.0范围内，对比例4～8提供的隔离膜的性能和电池循环性能发生了显著下降，由此可知，当功能涂层与多孔基膜的厚度比在0.1～1.0的范围内，在隔离膜的热收缩性和透气性、电芯热稳定性和安全性等诸多性能的综合影响下，隔离膜及电化学装置可获得最佳性能。
此外，从实施例3、6～11中的数据可以看到，当聚酰亚胺纳米片的平均单片面积在3μm 2～12μm 2的范围内，在隔离膜的多项综合性能影响下的电池循环性能较佳。从实施例3、12～17的数据可以看到，聚酰亚胺纳米片的厚度在100nm～300nm的范围内，在隔离膜的多项综合性能影响下的电池循环性能较佳。从实施例3、18～23的数据可以看到，当粘结剂在功能涂层中的质量百分含量在5％～40％的范围内，在隔离膜的多项综合性能影响下的电池循环性能较佳。
虽然已经参考优选实施例对本申请进行了描述，但在不脱离本申请的范围的情况下，可以对其进行各种改进并且可以用等效物替换其中的部件。尤其是，只要不存在结构冲突，各个实施例中所提到的各项技术特征均可以任意方式组合起来。本申请并不局限于文中公开的特定实施例，而是包括落入权利要求的范围内的所有技术方案。

Claims (13)

  1. 一种隔离膜，包括多孔基膜及设于所述多孔基膜至少一个表面上的功能涂层，其中，
    所述功能涂层包括聚酰亚胺纳米片，所述聚酰亚胺纳米片不规则堆积形成片层状疏松结构；且所述功能涂层与所述多孔基膜的厚度比为0.1～1.0。
  2. 根据权利要求1所述的隔离膜，其中，所述多孔基膜的厚度为2μm～16μm，所述功能涂层的厚度为1μm～10μm。
  3. 根据权利要求1所述的隔离膜，其中，所述聚酰亚胺纳米片的平均单片面积为3μm 2～12μm 2。
  4. 根据权利要求3所述的隔离膜，其中，所述聚酰亚胺纳米片的长为5μm～10μm、宽为1μm～5μm。
  5. 根据权利要求1所述的隔离膜，其中，所述聚酰胺纳米片的厚度为100nm～300nm。
  6. 根据权利要求1所述的隔离膜，其中，所述功能涂层还包括粘结剂；所述粘结剂包括聚氟烯烃类、聚丙烯酸酯类、聚丙烯酸类、聚氨酯类、硅树脂类、环氧树脂类、纤维素衍生类粘结剂中的一种或多种。
  7. 根据权利要求6所述的隔离膜，其中，所述粘结剂在所述功能涂层中的质量百分含量为5％～40％；所述聚酰亚胺纳米片在所述功能涂层中 的质量百分含量为60％～95％。
  8. 根据权利要求1所述的隔离膜，其中，所述多孔基膜选自聚烯烃类基膜，优选自聚丙烯膜、聚乙烯膜和聚乙稀-丙烯共聚物膜中的一种。
  9. 权利要求1-8中任一项所述的隔离膜的制备方法，其中，包括：
    (1)将聚酰亚胺纳米片、粘结剂和去离子水混合，得到聚酰亚胺纳米片水性分散液；
    (2)将所述聚酰亚胺纳米片水性分散液涂覆在多孔基膜至少一个表面上，形成功能涂层，所述功能涂层与所述多孔基膜的厚度比为0.1～1.0，干燥，即得到隔离膜。
  10. 一种锂离子二次电池，包括正极极片、负极极片、间隔于所述正极极片和所述负极极片之间的隔离膜、电解液，其中，所述隔离膜为权利要求1-8中任一项所述的隔离膜。
  11. 一种电池模块，其中，所述电池模块包括权利要求10所述的锂离子二次电池，所述锂离子二次电池包括正极极片、负极极片、间隔于正极极片和负极极片之间的隔离膜、电解液。
  12. 一种电池包，其中，所述电池包包括权利要求11所述的电池模块。
  13. 一种包含权利要求10所述的锂离子二次电池的装置。
PCT/CN2020/113801 2019-09-17 2020-09-07 隔离膜、其制备方法、锂离子二次电池、电池模块、电池包及装置 WO2021052211A1 (zh)

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