WO2024212526A1 - 隔膜及其制备方法、电池和用电装置 - Google Patents

隔膜及其制备方法、电池和用电装置 Download PDF

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Publication number
WO2024212526A1
WO2024212526A1 PCT/CN2023/133380 CN2023133380W WO2024212526A1 WO 2024212526 A1 WO2024212526 A1 WO 2024212526A1 CN 2023133380 W CN2023133380 W CN 2023133380W WO 2024212526 A1 WO2024212526 A1 WO 2024212526A1
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WIPO (PCT)
Prior art keywords
organic binder
diaphragm
base film
battery
polymer base
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PCT/CN2023/133380
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English (en)
French (fr)
Inventor
李�权
杨建瑞
孙成栋
欧阳楚英
黄思应
王耀辉
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Contemporary Amperex Technology Co Ltd
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Contemporary Amperex Technology Co Ltd
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Priority to EP23932797.6A priority Critical patent/EP4632928A4/en
Publication of WO2024212526A1 publication Critical patent/WO2024212526A1/zh
Priority to US19/269,056 priority patent/US20250343326A1/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • 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
    • H01M50/46—Separators, membranes or diaphragms characterised by their combination with electrodes
    • 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
    • H01M50/403—Manufacturing processes of separators, membranes or diaphragms
    • H01M50/406—Moulding; Embossing; Cutting
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • H01M50/417—Polyolefins
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • H01M50/426—Fluorocarbon polymers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/411—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
    • H01M50/46—Separators, membranes or diaphragms characterised by their combination with electrodes
    • H01M50/461—Separators, membranes or diaphragms characterised by their combination with electrodes with adhesive layers between electrodes and separators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • H01M50/491—Porosity
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • H01M50/494—Tensile strength
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application belongs to the technical field of battery materials, and specifically relates to a diaphragm and a preparation method thereof, a battery and an electrical device.
  • Battery separator film also known as battery diaphragm, is one of the core materials in batteries.
  • the diaphragm is located between the positive and negative electrodes of the battery. Its main function is to separate the positive and negative active materials of the battery to prevent the two electrodes from contacting and short-circuiting. At the same time, it allows the current-carrying ions in the electrolyte to pass through to form a charge and discharge circuit, which has an important impact on battery safety and cost.
  • a polymer adhesive layer is generally sprayed on the surface of the base film of the diaphragm to enhance the adhesion between the diaphragm and the electrode sheet.
  • diaphragms have poor heat resistance and are unstable, and the preparation process is cumbersome and costly.
  • the present application provides a diaphragm and a preparation method thereof, a battery and an electrical device, aiming to solve the technical problem of how to improve the comprehensive performance of the diaphragm at low cost.
  • an embodiment of the present application provides a membrane, comprising a polymer base film and an organic binder dispersed in the polymer base film, wherein ends of molecular chains of some of the organic binder are exposed on a surface of the polymer base film.
  • a self-adhesive diaphragm is formed by dispersing an organic binder in a polymer-based film material.
  • the diaphragm provided in the embodiment of the present application can enhance the mechanical strength of the polymer-based film based on the adhesion of the organic binder in the polymer-based film material, and the organic binder in the diaphragm is not easy to fall off, thereby improving the overall heat resistance and stability of the diaphragm; at the same time, because the thickness of the organic binder dispersed in the polymer-based film material is lower than that of the diaphragm sprayed on the surface, it is more convenient to use.
  • Such a diaphragm can be used in a battery to further improve the energy density and cycle life of the battery.
  • the substrate of the polymer-based film includes at least one of a polyolefin-based material, a fluoropolymer-based material, a polyester-based material, polyetheretherketone, polyimide, cellulose, and cellulose ester.
  • Using at least one of polyolefin materials, fluorine-containing polymer materials, polyester materials, polyetheretherketone, polyimide, cellulose and cellulose ester as the main polymer material of the diaphragm substrate not only has good insulation properties, but also can form a microporous structure, so that the diaphragm can have the air permeability and porosity required by the industry, thereby providing a good migration channel for the ions of the electrolyte and making the battery operate stably and efficiently.
  • the polyolefin material includes at least one of polyethylene and polypropylene; or,
  • the fluorine-containing polymer material includes at least one of polytetrafluoroethylene, polyvinyl fluoride and polyvinylidene fluoride; or,
  • the polyester-based material includes at least one of polyethylene terephthalate and polyurethane.
  • Polyethylene (PE) and polypropylene (PP) have the characteristics of low price, excellent mechanical properties and high electrochemical stability, and are widely used in commercial applications.
  • Polytetrafluoroethylene (PTFE), polyvinyl fluoride (PVF) and polyvinylidene fluoride (PVDF) have good polarity and dielectric constant, which can greatly improve the lyophilicity of the diaphragm.
  • Polyethylene terephthalate has good Resistant to electrolyte corrosion, polyurethane has good wear resistance.
  • the organic binder includes at least one of polyvinylidene fluoride, polyacrylate, acrylic acid, carboxymethyl cellulose, polyimide, ethylene-vinyl acetate copolymer, polyurethane, maleic anhydride, and ethylene acrylic acid copolymer.
  • the above-mentioned organic binder materials have good adhesion and can be dispersed in the polymer-based film material to form a self-adhesive membrane.
  • the molecular weight of the organic binder is 0.01 ten thousand Da to 1.2 million Da, and the molecular weight of the substrate of the polymer-based film is 50 thousand Da to 4 million Da.
  • the organic binder with a molecular weight of 0.01 Da to 1.2 million Da has good adhesion, and the base material of the polymer base film with a molecular weight of 50,000 Da to 4 million Da has good mechanical strength.
  • the molecular weight of the organic binder is 10,000 Da to 1,000,000 Da
  • the molecular weight of the substrate of the polymer-based film is 300,000 Da to 2,000,000 Da.
  • the organic binder with a molecular weight of 10,000 Da to 1,000,000 Da can be well dispersed in the polymer base membrane with a molecular weight of 300,000 Da to 2,000,000 Da, so that the adhesion of the organic binder can be well exerted and it is not easy to fall off, which can further improve the overall heat resistance and stability of the diaphragm.
  • the organic binder and the polymer base film are of different base materials.
  • the organic binder is the same as the polymerization monomer of the polymer base film, and the molecular weight of the organic binder is smaller than the molecular weight of the base material of the polymer base film.
  • the organic binder and the polymer-based membrane are of different types of substrates, such an organic binder dispersed in the polymer-based membrane makes the overall heat resistance of the diaphragm better.
  • the organic binder and the polymer-based membrane are of the same type of polymerization monomer, the organic binder and the substrate have good compatibility, and the molecular weight of the organic binder is less than the molecular weight of the substrate of the polymer-based membrane, thereby maintaining the adhesion of the organic binder and the mechanical strength of the polymer-based membrane.
  • Such an organic binder and substrate can form a self-adhesive diaphragm with better compatibility.
  • the organic binder is evenly dispersed in the substrate, which can make the diaphragm have a good thermal closure function, thereby reducing the risk of thermal runaway and further improving the safety of the diaphragm.
  • the organic binder is the same as the polymer monomer of the polymer base film, the organic binder includes polyvinylidene fluoride with a molecular weight of 300,000 Da to 1,000,000 Da, and the substrate of the polymer base film includes polyvinylidene fluoride with a molecular weight of 1,000,000 Da to 2,000,000 Da.
  • the organic binder and the polymer base film substrate are formed by combining the polyvinylidene fluoride with different molecular weights.
  • the diaphragm material formed by such a combination of materials has good compatibility.
  • the organic binder includes polyvinylidene fluoride having a molecular weight of 400,000 Da to 750,000 Da
  • the substrate of the polymer-based film includes polyvinylidene fluoride having a molecular weight of 1.2 million Da to 1.7 million Da.
  • the diaphragm material formed by such a combination of materials has better comprehensive effects on adhesion and compatibility.
  • the mass ratio of the polymer base film to the organic binder is 10:(0.01-6).
  • the organic binder is dispersed in the polymer base film according to the mass ratio of the polymer base film to the organic binder of 10:(0.01-6) to form a diaphragm. Under this mass ratio condition, the diaphragm can maintain a self-adhesive type and have good heat resistance and stability.
  • the mass ratio of the polymer base film to the organic binder is 10:(0.1-5).
  • Dispersing the organic binder in the polymer base film to form a diaphragm according to the mass ratio of the polymer base film to the organic binder is 10: (0.1-5), which can improve the overall heat resistance and stability of the diaphragm and the structural stability of the battery.
  • the thickness of the separator is 1 ⁇ m to 12 ⁇ m.
  • the organic binder is dispersed in the polymer base film to form a diaphragm with a thickness of 1 ⁇ m to 12 ⁇ m. Due to the bonding effect of the organic binder, the diaphragm still has good mechanical strength at this thickness. At the same time, the low-thickness diaphragm used in the battery can significantly improve the battery energy density.
  • the thickness of the separator is 3 ⁇ m to 6 ⁇ m.
  • an embodiment of the present application provides a method for preparing the above-mentioned diaphragm, comprising the following steps:
  • the mixed material is melt-extruded and then stretched to obtain a diaphragm.
  • the organic binder and the polymer-based film substrate are mixed, melt-extruded and stretched to obtain a diaphragm with a microporous structure.
  • This preparation method of integrating the organic binder and the substrate into a film not only has a simple process and low preparation cost, but also can obtain a self-adhesive diaphragm with excellent heat resistance and stability, thereby improving the energy density and cycle life of the battery.
  • the temperature of the melt extrusion is 200-300°C.
  • the temperature of 200-300° C. can make the mixture of the organic binder and the polymer-based film substrate form a viscous mixture that is uniformly mixed and has good fluidity, so as to facilitate subsequent stretching into a film.
  • the temperature of the stretching process is 100-120°C.
  • the stretching ratio of the stretching process is 10 to 300 times.
  • the melt-extruded material in a viscous flow state is stretched at a stretching ratio of 10 to 300 times to form a diaphragm with a microporous structure.
  • the stretching process includes biaxial stretching with a stretching ratio of 100 to 200 times.
  • Biaxial stretching with a stretching ratio of 100 to 200 times can better control the porosity of the diaphragm and ensure uniform pore distribution.
  • an embodiment of the present application provides a battery, comprising a positive electrode sheet, a negative electrode sheet, and a separator disposed between the positive electrode sheet and the negative electrode sheet, wherein the separator is the separator provided in the first aspect of the embodiment of the present application and/or the separator prepared by the preparation method provided in the second aspect of the embodiment of the present application.
  • the diaphragm By using the diaphragm provided by the first aspect of the embodiment of the present application and/or the diaphragm prepared by the preparation method provided by the second aspect of the embodiment of the present application in a battery, the diaphragm can bond the positive electrode and the negative electrode of the battery together, thereby reducing the spatial activity of the battery electrode and shortening the distance between the positive and negative electrodes. Based on the good heat resistance and stability of the overall diaphragm and its low thickness, the battery has good energy density and cycle life.
  • the adhesion between the separator and the positive electrode sheet or the negative electrode sheet is greater than or equal to 1.0 N/m.
  • the bonding force with the positive electrode sheet or the negative electrode sheet can be greater than or equal to 1.0 N/m, thus stabilizing the structure of the battery.
  • the battery is a secondary battery.
  • Such secondary batteries have high energy density and good cycle life characteristics and can be used as power batteries or power sources for energy storage systems.
  • an embodiment of the present application provides an electrical device, comprising the battery provided in the third aspect of the embodiment of the present application.
  • such an electrical device has a wide range of applicable environments, a long service life, and can work for a longer period of time.
  • FIG2 is a schematic flow chart of a method for preparing a diaphragm according to an embodiment of the present application
  • FIG3 is a schematic structural diagram of an implementation manner of a secondary battery in an embodiment of the present application.
  • FIG4 is an exploded schematic diagram of the secondary battery shown in FIG3 ;
  • FIG5 is a schematic structural diagram of an implementation scheme of a battery module according to an embodiment of the present application.
  • FIG6 is a schematic structural diagram of an implementation scheme of a battery pack according to an embodiment of the present application.
  • FIG7 is a schematic diagram of the exploded structure of the battery pack shown in FIG6 ;
  • FIG. 8 is a schematic diagram of an embodiment of an electrical device including a battery according to an embodiment of the present application as a power source.
  • the term "and/or" is only a description of the association relationship of the associated objects, indicating that there may be three relationships.
  • a and/or B can represent: A exists alone, A and B exist at the same time, and B exists alone.
  • the character "/" in this article generally indicates that the associated objects before and after are in an "or" relationship.
  • the term “multiple” refers to more than two (including two).
  • “Group” refers to two or more groups (including two groups), “multiple pieces” refers to two or more pieces (including two pieces).
  • “At least one” refers to more than one kind (including one, two, three, etc.).
  • the separator is a microporous membrane used to separate the positive and negative electrodes, and is a polymer functional material with a nano-scale microporous structure.
  • the main function of the separator is to separate the positive and negative active materials of the battery to reduce the risk of short circuit due to contact between the two electrodes, while allowing electrolyte ions to pass through.
  • the performance of the separator determines the interface structure and internal resistance of the battery, and directly affects the capacity, cycle and safety performance of the battery. In practical applications, technicians generally modify and modify the separator.
  • the organic bonding layer is combined with the surface of the diaphragm in a whole layer, which not only increases the overall thickness of the diaphragm, thereby affecting the energy density of the battery, but also its viscosity is easily reduced after multiple cycles of charge and discharge, making the organic bonding layer easy to fall off from the surface of the diaphragm, thereby affecting the stability of its bonding.
  • the preparation of the organic bonding layer on the surface of the diaphragm by spraying is a relatively complicated operation process, which is easy to increase the equipment cost and process steps.
  • the embodiment of the present application designs a new self-adhesive diaphragm, which includes a polymer base film and an organic binder dispersed in the polymer base film.
  • the organic binder is added to the polymer base film material to form a self-adhesive isolation film.
  • the heat resistance and stability of the diaphragm as a whole can be improved.
  • Such a diaphragm film forming process is simple, and it can be used in a battery to significantly improve the energy density and cycle life of the battery. Therefore, the following technical solution is proposed.
  • an embodiment of the present application provides a separator, as shown in FIG1 , comprising: a polymer base film 11 and an organic binder 12.
  • the organic binder 12 is dispersed in the polymer base film 11, and at the same time, some molecular chain ends of the organic binder 12 are exposed on the surface of the polymer base film 11.
  • the polymer base film 11 may be a base film formed by a polymer substrate of a separator. Using the polymer substrate as the main material of the separator may be made into a microporous membrane, which may meet the mechanical properties and electrochemical properties required of a battery separator.
  • the organic binder 12 is an organic material additive with bonding properties, which is used to enhance the adhesion between the separator and the electrode to improve the dynamic performance of the battery.
  • the mechanical strength of the polymer base film 11 is enhanced.
  • some of the molecular chain ends of the organic binder 12 are exposed on the surface of the polymer base film 11 to impart adhesion to the surface of the polymer base film 11, thereby forming a self-adhesive diaphragm, wherein the surface of the polymer base film 11 exposed by the molecular chain ends of the organic binder 12 includes a relative upper surface and a lower surface, so that the diaphragm can bond the positive electrode sheet and the negative electrode sheet at the same time in the battery.
  • the embodiment of the present application forms a self-adhesive diaphragm by dispersing the organic binder 12 in the polymer base film 11 material.
  • the mechanical strength of the polymer base film 11 can be enhanced from the inside of the diaphragm based on the adhesiveness of the organic binder 12 dispersed in the polymer base film 11 material, and the organic binder in the diaphragm is not easy to fall off, so such a diaphragm has good heat resistance and stability.
  • the organic binder 12 of the diaphragm provided in the embodiment of the present application is dispersed in the polymer base film 12, and the overall thickness of the diaphragm is lower. When used in a battery, the energy density and cycle life of the battery can be further improved.
  • the substrate of the polymer base film 11 in the separator may be at least one of polyolefin materials, fluorine-containing polymer materials, polyester materials, polyetheretherketone, polyimide, cellulose and cellulose ester.
  • the separator substrate generally has good chemical and thermal stability, appropriate porosity and pore size, and good mechanical strength.
  • Polyolefin materials, fluorinated polymer materials, polyester materials, polyetheretherketone, polyimide, cellulose, and cellulose ester not only have good insulation, but also can form a microporous structure, which can make the separator have the air permeability and porosity required by the industry, thereby providing a good migration channel for the ions of the electrolyte, so that the battery can operate stably and efficiently. Therefore, the above materials can be used as the main polymer material of the separator substrate.
  • a separator with a certain air permeability and porosity can be formed so as to be used in a secondary battery.
  • the air permeability parameter is the Gurley number, which is the time required for a certain volume of gas to pass through a certain area of a membrane under certain pressure conditions.
  • Gurley number is the time required for a certain volume of gas to pass through a certain area of a membrane under certain pressure conditions.
  • For specific testing, refer to the standard GB/T 36363-2018, which tests the time required for 100cc (cubic centimeter, 1cc 1ml) of air to pass through a membrane with an area of 6.45cm2 under a pressure of 1.21kPa.
  • the air permeability of the diaphragm of the present application can be 100s/100cc to 400s/100cc, including but not limited to typical but non-limiting air permeabilities such as 100s/100cc, 150s/100cc, 200s/100cc, 250s/100cc, 300s/100, 320s/100, 380s/100, 400s/100cc, for example, the air permeability of the diaphragm can be 100s/100cc to 200s/100cc.
  • the porosity is the percentage of the volume of the cavities inside the diaphragm to the total volume of the diaphragm.
  • the test can be carried out with reference to the standard GB/T 36363-2018.
  • the porosity of the diaphragm of the present application can be 25% to 80%, including but not limited to 25%, 30%, 32%, 36%, 38%, 40%, 45%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, 60%, 65%, 68%, 70%, 75%, 78%, 80% and other typical but non-limiting porosities.
  • the porosity of the diaphragm can be 30% to 35%.
  • the substrate of the polymer base film 11 in the diaphragm includes: at least one of polyolefin materials, fluorine-containing polymer materials, polyester materials, polyetheretherketone, polyimide, cellulose and cellulose ester.
  • the polyolefin material can be at least one of polyethylene and polypropylene; polyethylene and polypropylene have the characteristics of low price, excellent mechanical properties and high electrochemical stability.
  • Most of the commercial lithium-ion battery diaphragm products are microporous membranes made of polyolefin materials, and the main raw materials are high molecular weight polyethylene and polypropylene. This type of polyolefin material has the advantages of high strength, good acid and alkali corrosion resistance, and waterproofness.
  • polyethylene can be high-density polyethylene (about 0.94-0.96g/ cm3 ) or low-density polyethylene (about 0.91-0.93g/ cm3 ).
  • Fluorine-containing polymer materials can include at least one of polytetrafluoroethylene, polyvinyl fluoride and polyvinylidene fluoride; fluorine-containing polymer materials have good polarity and dielectric constant. The above-mentioned fluorine-containing polymer materials can be used in batteries to improve the lyophilicity of the separator. Polyvinylidene fluoride is the most widely used.
  • Polyester materials can include polyethylene terephthalate and At least one of polyurethane. Polyethylene terephthalate, a polyester material, has good resistance to electrolyte corrosion, and polyurethane, such as polyurethane, has good wear resistance. Therefore, the type of substrate of the polymer base film 11 can be selected according to actual needs.
  • the organic binder 12 in the diaphragm may specifically include at least one of polyvinylidene fluoride, polyacrylate, acrylic acid, carboxymethyl cellulose, polyimide, ethylene-vinyl acetate copolymer, polyurethane, maleic anhydride and ethylene acrylic acid copolymer.
  • the above-mentioned organic binder 12 materials have good adhesion and can be dispersed in the polymer base film 11 material to form a self-adhesive diaphragm.
  • the molecular weight of the organic binder 12 in the diaphragm formed by the combination of the organic binder 12 and the polymer base film 11, can be 0.01 ten thousand Da to 1.2 million Da, and the molecular weight of the substrate of the polymer base film 11 can be 50,000 Da to 4 million Da.
  • Da stands for Dalton, which is a common unit of molecular weight, and is the algebraic sum of the atomic weights of all atoms in a molecule according to the number of atoms.
  • the molecular weight of the organic binder 12 can be 0.01 Da to 1.2 million Da, and has good adhesion.
  • the molecular weight of the organic binder 12 includes but is not limited to 0.1 Da, 0.5 Da, 10,000 Da, 50,000 Da, 200,000 Da, 300,000 Da, 500,000 Da, 600,000 Da, 800,000 Da, 900,000 Da, 1 million Da, 1.1 million Da, 1.2 million Da and other typical but non-limiting molecular weights, for example, it can be 0.1 Da to 1 million Da.
  • the molecular weight of the substrate of the polymer base membrane 11 is 50,000 Da to 4,000,000 Da, and has good mechanical strength.
  • the molecular weight of the substrate of the polymer base membrane 11 includes but is not limited to 50,000 Da, 100,000 Da, 200,000 Da, 300,000 Da, 500,000 Da, 600,000 Da, 800,000 Da, 900,000 Da, 1,000,000 Da, 1,100,000 Da, 1,200,000 Da, 1,600,000 Da, 2,000,000 Da, 2,200,000 Da, 2,400,000 Da, 2,600,000 Da, 3,000,000 Da, 3,200,000 Da, 3,500,000 Da, 3,800,000 Da, 4,000,000 Da and other typical but non-limiting molecular weights, for example, it can be 300,000 Da to 2,000,000 Da.
  • the molecular weight of the organic binder 12 may be 10,000 Da to 1,000,000 Da, and the molecular weight of the substrate of the polymer base film 11 may be 300,000 Da to 2,000,000 Da.
  • the organic binder 12 with a molecular weight of 10,000 Da to 300,000 Da can be well dispersed in the polymer base film 11 with a molecular weight of 300,000 Da to 2,000,000 Da, so that the adhesion of the organic binder 12 can be well exerted, and it is not easy to fall off, which can further improve the heat resistance and stability of the overall separator.
  • the organic binder 12 in the diaphragm may be the same or different from the type of the substrate of the polymer base film 11.
  • the organic binder 12 is of a different type from the substrate of the polymer base film 12, such an organic binder 11 is dispersed in the polymer base film 12 to make the overall heat resistance of the diaphragm better.
  • the molecular weight of the organic binder 12 is less than the molecular weight of the substrate of the polymer base film 11.
  • the organic binder 12 and the substrate of the polymer base film 11 are of the same type of polymer monomer, the organic binder and the substrate have good compatibility, and at the same time, the molecular weight of the organic binder 12 is less than the molecular weight of the substrate of the polymer base film 11, so that the adhesion of the organic binder 12 and the mechanical strength of the polymer base film 11 can be maintained.
  • Such an organic binder 12 and the substrate of the polymer base film 11 can form a self-adhesive diaphragm with better compatibility.
  • the organic binder 12 is evenly dispersed in the substrate 11, which can make the diaphragm have a good thermal closure function, thereby reducing thermal runaway and further improving the safety of the diaphragm.
  • the organic binder 12 and the polymer base film 11 have the same type of polymer monomer, so that the organic binder 12 with a molecular weight smaller than the molecular weight of the substrate of the polymer base film 11 can be selected for combination.
  • the organic binder 12 can include polyvinylidene fluoride with a molecular weight of 300,000 Da to 1,000,000 Da and the substrate of the polymer base film 11 can include polyvinylidene fluoride with a molecular weight of 1,000,000 Da to 2,000,000 Da for combination; further, the organic binder 12 includes polyvinylidene fluoride with a molecular weight of 400,000 Da to 750,000 Da, and the substrate of the polymer base film 11 includes polyvinylidene fluoride with a molecular weight of 1.2 million Da to 1.7 million Da.
  • the above polyvinylidene fluoride with different molecular weights is combined to form the organic binder 12 and the polymer base film.
  • the substrate of 11 can make the materials in the diaphragm have good compatibility, so the thermal closure performance of the diaphragm is better, thus having better safety; at the same time, such a diaphragm has good compressibility and is easier to compress when assembled in the battery, thereby further improving the energy density of the battery.
  • the mass ratio of the polymer base film 11 and the organic binder 12 in the diaphragm can be 10:(0.01-6).
  • the mass ratio of the polymer base film 11 and the organic binder 12 can be, but not limited to, typical but non-limiting mass ratios such as 10:0.01, 10:0.05, 10:0.1, 10:0.4, 10:0.6, 10:1, 10:2, 10:3, 10:4, 10:5, etc.
  • the organic binder 12 is dispersed in the polymer base film 11 to form a diaphragm according to the mass ratio of the polymer base film 11 and the organic binder 12 being 10:(0.01-6). Under this mass ratio condition, the diaphragm can not only maintain a self-adhesive type, but also have good heat resistance and stability.
  • the mass ratio of the polymer base film 11 to the organic binder 12 in the separator can be 10:(0.1-5). According to the mass ratio of the polymer base film 11 to the organic binder 12 being 10:(0.1-5), dispersing the organic binder 12 in such a ratio in the polymer base film 11 to form a separator can improve the heat resistance, stability, and self-adhesion of the separator as a whole, thereby improving the comprehensive effect of the structural stability of the battery.
  • the thickness of the separator can be 1 ⁇ m to 12 ⁇ m.
  • the thickness of the separator includes but is not limited to typical but non-limiting thicknesses such as 1 ⁇ m, 2 ⁇ m, 3 ⁇ m, 5 ⁇ m, 10 ⁇ m, and 12 ⁇ m, for example, 3 ⁇ m to 6 ⁇ m.
  • the organic binder 12 is dispersed in the polymer base film 11 to form a separator with a thickness of 1 ⁇ m to 12 ⁇ m. Due to the effect of the organic binder, the separator still has good mechanical strength at this thickness, and the thermal shrinkage rate is small. Such a low-thickness separator can be used in a battery to significantly improve the battery energy density.
  • the thickness of the separator may be 3 ⁇ m to 6 ⁇ m.
  • the separator with a thickness of 3 ⁇ m to 6 ⁇ m has good mechanical strength and a good comprehensive effect on improving the battery energy density in the battery.
  • the embodiment of the present application can have good thermal shrinkage and tensile strength by selecting different types of organic binders 12 to be dispersed in different types of polymer base films 11 in a certain mass ratio to form the above-mentioned diaphragm with a thickness of 1 ⁇ m to 12 ⁇ m.
  • the transverse thermal shrinkage of the diaphragm under the conditions of 105°C and 1h can be less than or equal to 2.0%
  • the longitudinal thermal shrinkage under the conditions of 105°C and 1h can be less than or equal to 2.0%.
  • the transverse thermal shrinkage or longitudinal thermal shrinkage of the diaphragm includes but is not limited to typical but non-limiting thermal shrinkages such as 0.1%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, etc.
  • the transverse thermal shrinkage and longitudinal thermal shrinkage under the conditions of 105°C and 1h can be 0.1 to 1.2%.
  • the transverse tensile strength of the diaphragm is greater than or equal to 700kg/ cm2
  • the longitudinal tensile strength is greater than or equal to 1000kg/ cm2 .
  • the transverse tensile strength of the diaphragm includes but is not limited to 700kg/ cm2 , 800kg/ cm2 , 1000kg/ cm2 , 1200kg/ cm2 , 1500kg/ cm2 , 2000kg/ cm2 , 2500kg/ cm2 , 3000kg/ cm2 , 3500kg/ cm2 , 4000kg/ cm2 , 4500kg/ cm2 and the like typical but non-limiting tensile strengths
  • the longitudinal tensile strength of the diaphragm includes but is not limited to 1000kg/ cm2 , 1200kg/ cm2 , 1500kg/ cm2 , 2000kg/ cm2 , 2500kg/ cm2 , 3000kg/ cm2 , 3500kg/cm2, 4000kg/ cm2 , 4500kg /cm2.
  • Typical but non-limiting tensile strengths are as follows: 2 , for example, the tensile strength of the separator in the transverse direction is 1000-4000 kg/cm 2 , and the tensile strength in the longitudinal direction is 1200-4000 kg/cm 2 .
  • the present invention provides a method for preparing a diaphragm. As shown in FIG2 , the method for preparing a diaphragm comprises the following steps:
  • the organic binder and the base material of the polymer base film are mixed, melt-extruded, and stretched to obtain a diaphragm with a microporous structure.
  • the raw material is mixed into the substrate of the polymer-based film to form an integrated film to obtain a self-adhesive diaphragm, which simplifies the process steps of adhering the diaphragm to the electrode.
  • the preparation method of integrating the organic binder and the substrate into a film not only has a simple process and low preparation cost, but also can obtain a self-adhesive diaphragm with excellent heat resistance and stability, thereby improving the energy density and cycle life of the battery.
  • the diaphragm prepared in the embodiment of the present application When used in a battery, it has good adhesion to the electrode and can improve the dynamic performance of the battery.
  • the substrate of the polymer-based film can be mixed with the organic binder in a mass ratio of 10: (1 to 5).
  • the substrate of the polymer-based film can be at least one of polyolefin materials, fluorine-containing polymer materials, polyester materials, polyetheretherketone, polyimide, cellulose and cellulose ester.
  • the polyolefin material can be at least one of polyethylene and polypropylene; the fluorine-containing polymer material can be at least one of polytetrafluoroethylene, polyvinyl fluoride and polyvinylidene fluoride; the polyester material can be at least one of polyethylene terephthalate and polyurethane.
  • the specific type of the organic binder can be the same as or different from the type of the substrate of the polymer-based film.
  • the organic binder can specifically include at least one of polyvinylidene fluoride, polyacrylate, acrylic acid, carboxymethyl cellulose, polyimide, ethylene-vinyl acetate copolymer, polyurethane, maleic anhydride and ethylene acrylic acid copolymer.
  • the molecular weight of the organic binder may be 0.01 ten thousand Da to 1.2 million Da, and the molecular weight of the substrate of the polymer base film may be 50 thousand Da to 4 million Da.
  • the melt extrusion temperature when the mixed material is melt extruded is 200-300°C.
  • the melting point of the substrate of the polymer-based film can be 130-400°C, and there are different melting points according to different types of substrates, such as 130°C, 150°C, 200°C, 250°C, 300°C, etc., and specifically 130-190°C, etc.;
  • the melting point of the organic binder can be 100-200°C, and there are different melting points according to different types of organic binders, such as 100°C, 120°C, 150°C, 180°C, 200°C, etc., and specifically 100-150°C, etc.
  • the embodiment of the present application can form a mixture of the organic binder and the polymer-based film substrate into a viscous flow mixture that is uniformly mixed and has good fluidity by melt extrusion at a temperature of 200-300°C, so as to be stretched into a film later.
  • the melt extrusion temperature of the mixture includes but is not limited to typical but non-limiting temperatures such as 200°C, 220°C, 250°C, 260°C, and 300°C.
  • the stretching temperature of the stretching treatment after the mixture is melt-extruded is 100-120°C.
  • the temperature of the molten extrusion material at 200-300°C is reduced to 100-120°C for stretching. Stretching at such a temperature can peel off the crystal interface of the molten material to form a porous structure membrane.
  • the stretching treatment temperature includes but is not limited to typical but non-limiting temperatures such as 100°C, 105°C, 110°C, 105°C, and 120°C.
  • the stretching ratio of the mixed material after melt extrusion is 10 to 300 times.
  • the molten extruded material in the viscous flow state is stretched at a stretching ratio of 10 to 300 times to form a diaphragm of a hard elastic material having a microporous structure.
  • the stretching ratio of the stretching process includes but is not limited to typical but non-limiting stretching ratios such as 10 times, 50 times, 80 times, 100 times, 150 times, 180 times, 200 times, 250 times, and 300 times.
  • the stretching treatment can be a biaxial stretching treatment, for example, the temperature of the molten extrusion material at 200-300°C is reduced to 100-120°C for cooling biaxial stretching with a stretching ratio of 100-200 times. Under such conditions, the porosity of the diaphragm can be better controlled and the pores can be evenly distributed.
  • an embodiment of the present application provides a battery, comprising a positive electrode sheet, a negative electrode sheet, and a separator disposed between the positive electrode sheet and the negative electrode sheet, wherein the separator is the separator provided in the first aspect of the embodiment of the present application and/or the separator prepared by the preparation method provided in the second aspect of the embodiment of the present application.
  • the diaphragm prepared by the method is used in the battery, so that the diaphragm can bond the positive and negative electrodes of the battery together, thereby reducing the spatial activity of the battery electrodes and shortening the distance between the positive and negative electrodes. Based on the good heat resistance and stability of the diaphragm as a whole and its low thickness, the battery has good energy density and cycle life.
  • the bonding strength between the separator in the battery and the positive electrode sheet or the negative electrode sheet is greater than or equal to 1.0N/m.
  • the bonding strength of the separator under this condition has good bonding properties.
  • the bonding strength with the positive electrode or the negative electrode can be greater than or equal to 1N, thus making the battery structure more stable.
  • the battery is a secondary battery.
  • the secondary battery may be an ion battery or a sodium ion battery, etc.
  • Such a secondary battery has high energy density and good cycle life characteristics, and can be used as a power battery or a power source for an energy storage system.
  • a secondary battery includes a positive electrode, a negative electrode, an electrolyte and a separator.
  • active ions are embedded and removed back and forth between the positive electrode and the negative electrode.
  • the electrolyte plays the role of conducting ions between the positive electrode and the negative electrode.
  • the separator is set between the positive electrode and the negative electrode, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing ions to pass through.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode active layer bonded to the positive electrode current collector, wherein the positive electrode active layer contains a positive electrode active material, and when the secondary battery is a lithium ion battery, the positive electrode active material is a lithium-containing material, and when the secondary battery is a sodium ion battery, the positive electrode active material is a sodium-containing material.
  • the current collector of the positive electrode sheet is also called the positive electrode current collector, and a metal foil or a composite current collector may be used.
  • a metal foil aluminum foil may be used.
  • the composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base.
  • the composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate such as polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.
  • the positive electrode active layer may also optionally include a binder.
  • the binder may include at least one of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • the positive electrode active layer may also optionally include a conductive agent.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the negative electrode sheet includes a negative electrode current collector and a positive electrode active layer bonded to the negative electrode current collector.
  • the negative electrode active layer contains a negative electrode active material, and the negative electrode active material can be a negative electrode active material for batteries known in the art.
  • the negative electrode active material can include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate.
  • the current collector of the negative electrode sheet is also called the negative electrode current collector, and the negative electrode current collector may be a metal foil or a composite current collector.
  • the metal foil a copper foil may be used.
  • 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 polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.
  • the negative electrode active layer may also optionally include a binder.
  • the binder may be selected from at least one of styrene-butadiene rubber, polyacrylic acid, sodium polyacrylate, polyacrylamide, polyvinyl alcohol, sodium alginate, polymethacrylic acid and carboxymethyl chitosan.
  • the negative electrode active layer may also optionally include a conductive agent.
  • the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the negative electrode active layer may also optionally include other additives, such as a thickener (such as sodium carboxymethyl cellulose) and the like.
  • the electrolyte plays the role of conducting ions between the positive electrode sheet and the negative electrode sheet.
  • the embodiment of the present application has no specific restrictions on the type of electrolyte, which can be selected according to demand.
  • the electrolyte can be liquid, gel or all-solid.
  • the electrolyte adopts an electrolyte.
  • the electrolyte includes an electrolyte salt and a solvent.
  • the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl imide), lithium bis(trifluoromethanesulfonyl imide), lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium difluorobis(oxalate phosphate) and lithium tetrafluorooxalate phosphate.
  • the corresponding electrolyte salt is replaced with a sodium salt.
  • the solvent in the electrolyte can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.
  • the electrolyte may also optionally include additives.
  • the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain properties of the battery, such as additives that improve the overcharge performance of the battery, additives that improve the high or low temperature performance of the battery, etc.
  • the secondary battery of the present application may include any one of a battery cell, a battery module, and a battery pack.
  • a battery cell refers to a battery housing and a battery cell encapsulated in the battery housing. There is no particular limitation on the shape of the battery cell, which may be cylindrical, square, or any other shape.
  • a battery cell 20 with a square structure is shown in FIG. 3 .
  • the outer packaging of the battery cell 20 may include a shell 21 and a top cover assembly 22.
  • the shell 21 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 21 has an opening connected to the receiving cavity, and the top cover assembly 22 is used to cover the opening to close the receiving cavity.
  • the positive electrode, diaphragm and negative electrode sheet contained in the secondary battery of the embodiment of the present application can form an electrode assembly 23 through a winding process and/or a lamination process.
  • the electrode assembly 23 is encapsulated in the receiving cavity.
  • the electrolyte is infiltrated in the electrode assembly 23.
  • the number of electrode assemblies 23 contained in the battery cell 20 may be one or more, which can be adjusted according to actual needs.
  • the positive electrode, the separator, the negative electrode sheet and the electrolyte can be assembled to form the battery cell 20.
  • the positive electrode, the separator and the negative electrode sheet can be formed into an electrode assembly 23 through a winding process or a lamination process, and the electrode assembly 23 is placed in an outer package, dried and injected with electrolyte, and then vacuum packaged, left to stand, formed, shaped and other processes are performed to obtain the battery cell 20.
  • the battery module is assembled from the battery cells 20 , that is, it may contain a plurality of the battery cells 20 , and the specific number can be adjusted according to the application and capacity of the battery module.
  • FIG5 is a schematic diagram of a battery module 30 as an example.
  • a plurality of battery cells 20 may be arranged in sequence along the length direction of the battery module 30. Of course, they may also be arranged in any other manner. Further, the plurality of battery cells 20 may be fixed by fasteners.
  • the battery module 30 may further include a housing having a storage space, in which a plurality of battery cells 20 are stored.
  • a battery pack is assembled from the above battery cells 20, that is, it may contain a plurality of battery cells 20, wherein a plurality of the battery cells 20 may be assembled into the above battery module 30.
  • the specific number of battery cells 20 or battery modules 30 contained in the battery pack may be adjusted according to the application and capacity of the battery pack.
  • FIG6 and FIG7 are schematic diagrams of a battery pack 40 as an example.
  • the battery pack 40 may include a battery box and a plurality of battery modules 30 disposed in the battery box.
  • the battery box includes an upper box body 41 and a lower box body 42.
  • the box body 41 is used to cover the lower box body 42 and form a closed space for accommodating the battery module 30.
  • a plurality of battery modules 30 can be arranged in the battery box in any manner.
  • the present application also provides an electric device, which includes the battery of the above-mentioned application.
  • the battery can be used as a power source for the electric device, or as an energy storage unit for the electric device. Therefore, the electric device of the present application has a long standby or battery life, and has good stability and safety.
  • the electrical device may be, but is not limited to, a mobile device (such as a mobile phone, a laptop computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc.
  • a mobile device such as a mobile phone, a laptop computer, etc.
  • an electric vehicle such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.
  • an electric train such as a ship and a satellite, an energy storage system, etc.
  • the electrical device may select a secondary battery, a battery module or a battery pack according to its use requirements.
  • FIG8 is a schematic diagram of an electric device as an example.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.
  • a battery pack or a battery module can be used.
  • the electric device can be a mobile phone, a tablet computer, a laptop computer, etc.
  • the electric device is usually required to be thin and light, and a secondary battery can be used as a power source.
  • a diaphragm comprises a polymer base film and an organic binder dispersed in the polymer base film; wherein the organic binder is polyvinylidene fluoride with a molecular weight of 500,000 Da, the substrate of the polymer base film is polypropylene with a molecular weight of 330,000 Da, and the mass ratio of the polymer base film to the organic binder is 10:1.
  • the organic binder is polyvinylidene fluoride with a molecular weight of 500,000 Da
  • the substrate of the polymer base film is polypropylene with a molecular weight of 330,000 Da
  • the mass ratio of the polymer base film to the organic binder is 10:1.
  • the preparation method of the diaphragm comprises the following steps:
  • S12 The mixed material is melt-extruded at 210° C., and then stretched at 120° C. at a stretching ratio of 200 times to obtain a diaphragm with a thickness of 5 ⁇ m.
  • a diaphragm comprises a polymer base film and an organic binder dispersed in the polymer base film; wherein the organic binder is polyvinylidene fluoride with a molecular weight of 500,000 Da, the substrate of the polymer base film is polypropylene with a molecular weight of 330,000 Da, and the mass ratio of the polymer base film to the organic binder is 10:1.
  • the organic binder is polyvinylidene fluoride with a molecular weight of 500,000 Da
  • the substrate of the polymer base film is polypropylene with a molecular weight of 330,000 Da
  • the mass ratio of the polymer base film to the organic binder is 10:1.
  • the preparation method of the diaphragm comprises the following steps:
  • the mixed material is melt-extruded at 210° C., and then stretched at 120° C. at a stretching ratio of 500 to obtain a diaphragm with a thickness of 1 um.
  • a diaphragm comprises a polymer base film and an organic binder dispersed in the polymer base film; wherein the organic binder is polyvinylidene fluoride with a molecular weight of 500,000 Da, the substrate of the polymer base film is polypropylene with a molecular weight of 330,000 Da, and the mass ratio of the polymer base film to the organic binder is 10:1.
  • the organic binder is polyvinylidene fluoride with a molecular weight of 500,000 Da
  • the substrate of the polymer base film is polypropylene with a molecular weight of 330,000 Da
  • the mass ratio of the polymer base film to the organic binder is 10:1.
  • the preparation method of the diaphragm comprises the following steps:
  • the mixed material is melt-extruded at 210° C., and then stretched at 120° C. at a stretching ratio of 80 to obtain a diaphragm with a thickness of 12 ⁇ m.
  • a diaphragm comprises a polymer base film and an organic binder dispersed in the polymer base film; wherein the organic binder is polyvinylidene fluoride with a molecular weight of 500,000 Da, the substrate of the polymer base film is polypropylene with a molecular weight of 330,000 Da, and the mass ratio of the polymer base film to the organic binder is 10:5.
  • the organic binder is polyvinylidene fluoride with a molecular weight of 500,000 Da
  • the substrate of the polymer base film is polypropylene with a molecular weight of 330,000 Da
  • the mass ratio of the polymer base film to the organic binder is 10:5.
  • the preparation method of the diaphragm comprises the following steps:
  • a diaphragm comprises a polymer base film and an organic binder dispersed in the polymer base film; wherein the organic binder is polyvinylidene fluoride with a molecular weight of 600,000 Da, the substrate of the polymer base film is polypropylene with a molecular weight of 330,000 Da, and the mass ratio of the polymer base film to the organic binder is 10:1.
  • the organic binder is polyvinylidene fluoride with a molecular weight of 600,000 Da
  • the substrate of the polymer base film is polypropylene with a molecular weight of 330,000 Da
  • the mass ratio of the polymer base film to the organic binder is 10:1.
  • the preparation method of the diaphragm comprises the following steps:
  • S12 The mixed material is melt-extruded at 210° C., and then stretched at 120° C. at a stretching ratio of 200 to obtain a diaphragm with a thickness of 5 ⁇ m.
  • a diaphragm comprises a polymer base film and an organic binder dispersed in the polymer base film; wherein the organic binder is carboxymethyl cellulose with a molecular weight of 10,000 Da, the substrate of the polymer base film is polypropylene with a molecular weight of 330,000 Da, and the mass ratio of the polymer base film to the organic binder is 10:1.
  • the preparation method of the diaphragm comprises the following steps:
  • S12 The mixed material is melt-extruded at 210° C., and then stretched at 120° C. at a stretching ratio of 200 times to obtain a diaphragm with a thickness of 5 ⁇ m.
  • a diaphragm comprises a polymer base film and an organic binder dispersed in the polymer base film; wherein the organic binder is polyvinylidene fluoride with a molecular weight of 500,000 Da, the substrate of the polymer base film is polyvinylidene fluoride with a molecular weight of 1.2 million Da, and the mass ratio of the polymer base film to the organic binder is 10:1.
  • the preparation method of the diaphragm comprises the following steps:
  • S12 The mixed material is melt-extruded at 210° C., and then stretched at 120° C. at a stretching ratio of 200 times to obtain a diaphragm with a thickness of 5 ⁇ m.
  • a diaphragm includes a polymer base film and an organic binder layer sprayed on the surface of the polymer base film, wherein the polymer base film has a thickness of 5 ⁇ m and the organic binder layer has a thickness of 2 ⁇ m.
  • the base material of the polymer base film is polypropylene with a molecular weight of 330,000 Da
  • the binder of the organic binder layer is polyvinylidene fluoride with a molecular weight of 500,000 Da.
  • the mass ratio is 10:1.
  • a diaphragm includes a polymer base film and an organic binder layer sprayed on the surface of the polymer base film, wherein the polymer base film has a thickness of 5 ⁇ m and the organic binder layer has a thickness of 2 ⁇ m.
  • the base material of the polymer base film is polypropylene with a molecular weight of 330,000 Da
  • the binder of the organic binder layer is polyvinylidene fluoride with a molecular weight of 500,000 Da
  • the mass ratio of the polymer base film to the organic binder layer is 10:5.
  • a diaphragm includes a polymer base film and an organic binder layer sprayed on the surface of the polymer base film, the polymer base film has a thickness of 5um, and the organic binder layer has a thickness of 2 ⁇ m.
  • the base material of the polymer base film is polypropylene with a molecular weight of 330,000Da
  • the binder of the organic binder layer is polyvinylidene fluoride with a molecular weight of 600,000Da
  • the mass ratio of the polymer base film to the organic binder layer is 10:1.
  • a diaphragm includes a polymer base film and an organic binder layer sprayed on the surface of the polymer base film, the polymer base film has a thickness of 5um, and the organic binder layer has a thickness of 2 ⁇ m.
  • the base material of the polymer base film is polyvinylidene fluoride with a molecular weight of 1.2 million Da
  • the binder of the organic binder layer is polyvinylidene fluoride with a molecular weight of 500,000 Da
  • the mass ratio of the polymer base film to the organic binder layer is 10:1.
  • a secondary battery cell comprises a battery cell formed by a positive electrode sheet, a separator and a negative electrode sheet, and also comprises an electrolyte.
  • the separator is the separator provided in Example A1.
  • the preparation method of the secondary battery cell comprises:
  • Preparation of positive electrode sheet Using methyl pyrrolidone (NMP) as solvent, LiNi 0.8 Co 0.1 Mn 0.1 O 2 , carbon nanotubes (CNT) and binder (PVDF) are mixed in a mass ratio of 97:2:1 to prepare a positive electrode slurry with a solid content of 80%; the positive electrode slurry is evenly coated on aluminum foil, double-sided coating is performed, and after sufficient drying, cold pressing and slitting, a positive electrode sheet is obtained as a positive electrode.
  • NMP methyl pyrrolidone
  • CNT carbon nanotubes
  • PVDF binder
  • Preparation of negative electrode sheet Using water as solvent, artificial graphite, conductive agent SP, dispersant (CMC), and binder (SBR) are mixed in a mass ratio of 96:1:1:2 to prepare a negative electrode slurry with a solid content of 58%; the positive electrode slurry is evenly coated on the aluminum foil, double-sided coating is performed, and after sufficient drying, cold pressing, and slitting, the negative electrode sheet is obtained as the negative electrode.
  • Electrolyte At room temperature, ethylene carbonate (EC)/diethyl carbonate (DEC) were mixed in a volume ratio of 1:1, and LiPF 6 was added to the mixed solution to obtain a solution with a concentration of 1 mol/L as the electrolyte;
  • EC ethylene carbonate
  • DEC diethyl carbonate
  • Secondary battery assembly In a low-humidity constant temperature room, the positive and negative electrode sheets prepared as above are stacked and wound in the order of "positive electrode-diaphragm-negative electrode” to form a bare cell, and then filled with electrolyte to assemble into a lithium-ion secondary battery.
  • the present embodiment B1 to embodiment B7 and comparative examples B1 to comparative examples B4 respectively provide a secondary battery cell, each of which includes a battery cell formed by a positive electrode sheet, a separator and a negative electrode sheet, and also includes an electrolyte.
  • the separators of embodiments B1 to embodiment B7 and comparative examples B1 to comparative examples B4 correspond to the separators provided by embodiments A1 to embodiment A7 and comparative examples A1 to comparative examples A4 respectively.
  • the separator in the above embodiment A1 is used as the separator in the battery cell of the secondary battery embodiment B1
  • the separator in the embodiment A2 is used as the separator in the battery cell of the secondary battery embodiment B2
  • the separator in comparative example A4 is used as the separator in the battery cell of the battery comparative example B4.
  • Sample preparation Place the separator on the positive/negative electrode sheet, press at 7 tons pressure for 30 seconds at 60/75/95°C to obtain the test sample.
  • Test The test sample is firmly bonded to the test metal fixture, the diaphragm and the pole piece are peeled off at 180 degrees, and the force value data is recorded as the bonding force with the pole piece.
  • the air permeability, transverse tensile strength (MD), and longitudinal tensile strength (TD) of the isolation membrane have well-known meanings in the art, and can be tested using the standard GB/T 36363-2018 known in the art.
  • Sample preparation The prepared diaphragm was punched into samples with a width of 50 mm and a length of 100 mm using a punching machine. Five parallel samples were placed on A4 paper and fixed. The A4 paper containing the samples was then placed on corrugated paper with a thickness of 1 mm to 5 mm.
  • Sample test Place the A4 paper on the corrugated paper into a blast oven, set the temperature of the blast oven to 250°C, and start timing after the temperature reaches the set temperature and stabilizes for 30 minutes. After the set time (1 hour in this application) is reached, measure the length and width of the diaphragm, and mark the values as a and b respectively.
  • Diaphragm porosity test method Use mercury intrusion meter to test according to GB/T 21650.1-2008.
  • Example A7 of the present application uses polyvinylidene fluoride of different molecular weights as a binder and substrate, and its adhesion, mechanical strength and thermal stability are the best.
  • the secondary battery prepared in the embodiment and the comparative example is charged at a constant current of 1C to a charge cut-off voltage V1, then charged at a constant voltage to a current ⁇ 0.05C, left to stand for 5 minutes, and then discharged at a constant current of 0.33C to a discharge cut-off voltage V2, left to stand for 5 minutes.
  • This is a charge and discharge cycle.
  • the battery is tested for cyclic charge and discharge according to this method until the battery capacity decays to 80%. The number of cycles at this time is the cycle life of the battery at 25°C.
  • the secondary batteries prepared in the examples and comparative examples were charged at a constant current of 1C to a charging cut-off voltage V1, and then charged at a constant voltage to a current ⁇ 0.05C. After standing for 5 minutes, the battery capacity was tested.
  • the battery capacity ⁇ the voltage at this time / the weight of the battery cell is the energy density of the battery.
  • the secondary batteries of Examples B1-B7 of the present application use the diaphragm unique to the present application, and their energy density and cycle life are better than those of the comparative example. Moreover, under the same other conditions, the thicker the thickness of the secondary battery diaphragm of Example B3, the better the battery cycle life, and the lower the thickness of the secondary battery diaphragm of Example B2, the better the battery energy density. Under the same thickness conditions, the secondary battery diaphragm of Example B7 uses polyvinylidene fluoride of different molecular weights as a binder and substrate, and its energy density and cycle life are the best.

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Abstract

本申请公开了一种隔膜及其制备方法、电池和用电装置。隔膜包括聚合物基膜和分散在聚合物基膜中的有机粘结剂，部分有机粘结剂的分子链末端露出聚合物基膜的表面。本申请通过将有机粘结剂分散在聚合物基膜材料中形成一种自粘型隔膜，利用聚合物基膜材料内的有机粘结剂的粘结性可以增强聚合物基膜的力学强度，提高隔膜整体的耐热性和稳定性；同时，有机粘结剂分散在聚合物基膜材料中比喷涂在表面的隔膜厚度更低，可以进一步提高电池的能量密度和循环寿命。

Description

隔膜及其制备方法、电池和用电装置
本申请要求于2023年04月11日在中国专利局提交的、申请号为202310385807.0、发明名称为“隔膜及其制备方法、电池和用电装置”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请属于电池材料技术领域，具体涉及一种隔膜及其制备方法、电池和用电装置。
背景技术
电池隔离膜(battery separator film，BSF)又称电池隔膜，是电池中的核心材料之一。隔膜位于电池的正极和负极之间，主要作用是将电池的正、负极活性物质分隔开以防止两极接触而短路，同时允许电解液中的载流离子通过，形成充放电回路，对电池安全性和成本有重要影响。
为了提高电池的动力学性能，一般在隔膜的基膜表面喷涂聚合物粘结层以增强隔膜与电极片的粘接，但这样的隔膜耐热性差、不稳定，而且制备工艺流程繁琐，成本高。
发明内容
鉴于上述问题，本申请提供一种隔膜及其制备方法、电池和用电装置，旨在解决如何低成本地提高隔膜综合性能的技术问题。
第一方面，本申请实施例提供一种隔膜，包括聚合物基膜和分散在聚合物基膜中的有机粘结剂，部分有机粘结剂的分子链末端露出聚合物基膜的表面。
通过将有机粘结剂分散在聚合物基膜材料中形成一种自粘型隔膜，对比喷涂在聚合物基膜表面，本申请实施例提供的隔膜基于聚合物基膜材料内的有机粘结剂的粘结性可以增强聚合物基膜的力学强度，而且隔膜内的有机粘结剂不易脱落，从而提高了隔膜整体的耐热性和稳定性；同时，因有机粘结剂分散在聚合物基膜材料中比喷涂在表面的隔膜厚度更低，使用更方便，这样的隔膜用在电池中可以进一步提高电池的能量密度和循环寿命。
在一些实施例中，聚合物基膜的基材包括聚烯烃类材料、含氟聚合物类材料、聚酯类材料、聚醚醚酮、聚酰亚胺、纤维素和纤维素酯中的至少一种。
将聚烯烃类材料、含氟聚合物类材料、聚酯类材料、聚醚醚酮、聚酰亚胺、纤维素和纤维素酯中至少一种用作隔膜基材的主体聚合物材料，不仅绝缘性好，而且可以形成微孔结构，可以使隔膜具备行业所需要的透气度和孔隙率，从而为电解液的离子提供良好的迁移通道，使电池稳定高效运行。
在一些实施例中，聚烯烃类材料包括聚乙烯和聚丙烯中的至少一种；或者，
含氟聚合物类材料包括聚四氟乙烯、聚氟乙烯和聚偏氟乙烯中的至少一种；或者，
聚酯类材料包括聚对苯二甲酸乙二醇酯和聚氨酯中的至少一种。
聚乙烯(PE)和聚丙烯(PP)具有价格低、机械性能优良和电化学稳定性高的特点，商业应用广泛。聚四氟乙烯(PTFE)、聚氟乙烯(PVF)和聚偏氟乙烯(PVDF)具有很好的极性和介电常数，可以很好地提高隔膜的亲液性。聚对苯二甲酸乙二醇酯具有很好的 耐电解液腐蚀性，聚氨酯具有很好的耐磨性。
在一些实施例中，有机粘结剂包括聚偏氟乙烯、聚丙烯酸酯、丙烯酸、羧甲基纤维素、聚酰亚胺、乙烯-醋酸乙烯共聚物、聚氨酯、马来酸酐和乙烯丙烯酸共聚物中的至少一种。
上述种类的有机粘结剂材料具有很好的粘结性，可以分散在聚合物基膜材料中形成自粘型隔膜。
在一些实施例中，有机粘结剂的分子量为0.01万Da～120万Da，聚合物基膜的基材分子量为5万Da～400万Da。
分子量为0.01万Da～120万Da的有机粘结剂具有很好的粘结性，分子量为5万Da～400万Da的聚合物基膜的基材具有很好的力学强度。
在一些实施例中，有机粘结剂的分子量为0.1万Da～100万Da，聚合物基膜的基材分子量为30万Da～200万Da。
分子量为0.1万Da～100万Da的有机粘结剂可以很好地分散在分子量为30万Da～200万Da的聚合物基膜中，从而可以很好地发挥有机粘结剂的粘结性，同时不易脱落，可以进一步提高隔膜整体的耐热性和稳定性。
在一些实施例中，有机粘结剂与聚合物基膜的基材种类不同；或者
有机粘结剂与聚合物基膜的聚合单体相同，且有机粘结剂的分子量小于聚合物基膜的基材的分子量。
一方面，如有机粘结剂与聚合物基膜的基材种类不同，这样的有机粘结剂分散在聚合物基膜中使隔膜整体耐热性更好。另一方面，如有机粘结剂与聚合物基膜的聚合单体种类相同，此时有机粘结剂和基材具有很好的相容性，同时有机粘结剂的分子量小于聚合物基膜的基材的分子量，从而可以保持有机粘结剂的粘结性以及聚合物基膜的力学强度。这样的有机粘结剂和基材搭配可以形成相容性更好的自粘型隔膜，有机粘结剂均匀分散在基材中可以使隔膜具有很好的热闭孔功能，从而降低热失控风险，可以进一步提高隔膜的安全性。
在一些实施例中，有机粘结剂与聚合物基膜的聚合单体相同，有机粘结剂包括分子量为30万Da～100万Da的聚偏氟乙烯，聚合物基膜的基材包括分子量为100万Da～200万Da的聚偏氟乙烯。
利用上述不同分子量的聚偏氟乙烯搭配形成有机粘结剂和聚合物基膜的基材，这样的搭配材料形成的隔膜材料具有很好的相容性。
在一实施例中，有机粘结剂包括分子量为40万Da～75万Da的聚偏氟乙烯，聚合物基膜的基材包括分子量为120万Da～170万Da的聚偏氟乙烯。
这样的搭配材料形成的隔膜材料粘结性和相容性综合效果更佳。
在一些实施例中，聚合物基膜和有机粘结剂的质量比为10：(0.01～6)。
按照聚合物基膜和有机粘结剂的质量比为10：(0.01～6)将有机粘结剂分散在聚合物基膜形成隔膜，该质量比例条件下可以使隔膜保持自粘型，同时具有较好的耐热性和稳定性。
在一些实施例中，聚合物基膜和有机粘结剂的质量比为10：(0.1～5)。
按照聚合物基膜和有机粘结剂的质量比为10：(0.1～5)将有机粘结剂分散在聚合物基膜形成隔膜，可以使隔膜整体的耐热性、稳定性以及对电池的结构稳定性提升综合效果好。
在一些实施例中，隔膜的厚度为1μm～12μm。
有机粘结剂分散在聚合物基膜中形成厚度为1μm～12μm的隔膜，因有机粘结剂的粘结作用，该厚度下仍然具有很好的力学强度，同时该低厚度的隔膜用于电池中可以显著提高电池能量密度。
在一些实施例中，隔膜的厚度3μm～6μm。
厚度为3μm～6μm的隔膜力学强度和能量密度的综合效果好。
第二方面，本申请实施例提供一种上述隔膜的制备方法，包括以下步骤：
将有机粘结剂和聚合物基膜的基材混合，得到混合料；
将混合料熔融挤出，然后拉伸处理，得到隔膜。
通过采用干法拉伸致孔技术，将有机粘结剂和聚合物基膜的基材混合熔融挤出、拉伸得到具有微孔结构的隔膜，这样的将有机粘结剂和基材一体成膜的制备方法，不仅工艺简单、制备成本低，而且可以得到具有很好的耐热性和稳定性的自粘型隔膜，从而可以提高电池的能量密度和循环寿命。
在一些实施例中，熔融挤出的温度为200～300℃。
200～300℃的温度可以使有机粘结剂和聚合物基膜基材的混合料形成混合均匀、且具有较好流动性的粘流态混合料，以便后续拉伸成膜。
在一些实施例中，拉伸处理的温度为100～120℃。
将200～300℃的熔融挤出物料温度降至100～120℃进行拉伸处理，在这样的温度下拉伸可以使熔融材料结晶界面剥离形成多孔结构的隔膜。
在一些实施例中，拉伸处理的拉伸倍率为10～300倍。
粘流态下的熔融挤出材料通过10～300倍的拉伸倍率进行拉伸，可以形成具有微孔结构的隔膜。
在一些实施例中，拉伸处理包括拉伸倍率为100～200倍的双向拉伸。
100～200倍的拉伸倍率进行双向拉伸，可以较好地控制隔膜的孔隙率，同时孔隙分布均匀。
第三方面，本申请实施例提供一种电池，包括正极片、负极片和置于正极片与负极片之间的隔膜，隔膜为本申请实施例第一方面提供的隔膜和/或本申请实施例第二方面提供的制备方法制备得到的隔膜。
通过将本申请实施例第一方面提供的隔膜和/或本申请实施例第二方面提供的制备方法制备得到的隔膜用在电池中，这样隔膜可以将电池的正极片和负极片粘结在一起，从而减少了电池极片的空间活度，拉近了正、负极之间的距离，基于隔膜整体的耐热性和稳定性好、厚度低，从而使电池具有很好的能量密度和循环寿命。
在一些实施例中，在95℃、7MPa、10s的热压条件下，隔膜与正极片或负极片的粘接力大于等于1.0N/m。
利用自粘型的隔膜的高粘结性，可以与正极片或负极片的粘接力大于等于1.0N/m，这样使电池的结构稳定。
在一些实施例中，电池为二次电池。
这样的二次电池具有高能量密度和良好的循环寿命特性，可以用作动力电池或者储能系统电源。
第四方面，本申请实施例提供一种用电装置，包括本申请实施例第三方面提供的电池。
通过采用本申请实施例第三方面提供的电池，这样的用电装置适用环境广，使用寿命长，可以更长久地进行工作。
上述说明仅是本申请技术方案的概述，为了能够更清楚了解本申请的技术手段，而可依照说明书的内容予以实施，并且为了让本申请的上述和其它目的、特征和优点能够更明显易懂，以下特举本申请的具体实施方式。
附图说明
通过阅读对下文优选实施方式的详细描述，各种其他的优点和益处对于本领域普通技术人员将变得清楚明了。附图仅用于示出优选实施方式的目的，而并不认为是对本申请的限制。而且在全部附图中，用相同的附图标号表示相同的部件。在附图中：
图1是本申请实施例的隔膜的膜层结构示意图；
图2是本申请实施例的隔膜的制备方法流程示意图；
图3为本申请实施例二次电池的一实施方式的结构示意图；
图4为图3所示二次电池的分解示意图；
图5为本申请实施例电池模块的一实施方式结构示意图；
图6为本申请实施例电池包的一实施方式结构示意图；
图7为图6所示电池包的分解结构示意图；
图8为包含本申请实施例电池作为电源的用电装置的一实施方式的示意图。
附图标记说明：
11-聚合物基膜；12-有机粘结剂；20-电池单体；21-壳体；22-顶盖组件；23-电极组件；
30-电池模块；40-电池包；41-上箱体；42-下箱体。
具体实施方式
下面将结合附图对本申请技术方案的实施例进行详细的描述。以下实施例仅用于更加清楚地说明本申请的技术方案，因此只作为示例，而不能以此来限制本申请的保护范围。
除非另有定义，本文所使用的所有的技术和科学术语与属于本申请的技术领域的技术人员通常理解的含义相同；本文中所使用的术语只是为了描述具体的实施例的目的，不是旨在于限制本申请；本申请的说明书和权利要求书及上述附图说明中的术语“包括”和“具有”以及它们的任何变形，意图在于覆盖不排他的包含。
在本申请实施例的描述中，技术术语“第一”“第二”等仅用于区别不同对象，而不能理解为指示或暗示相对重要性或者隐含指明所指示的技术特征的数量、特定顺序或主次关系。在本申请实施例的描述中，“多个”的含义是两个以上，除非另有明确具体的限定。
在本文中提及“实施例”意味着，结合实施例描述的特定特征、结构或特性可以包含在本申请的至少一个实施例中。在说明书中的各个位置出现该短语并不一定均是指相同的实施例，也不是与其它实施例互斥的独立的或备选的实施例。本领域技术人员显式地和隐式地理解的是，本文所描述的实施例可以与其它实施例相结合。
在本申请实施例的描述中，术语“和/或”仅仅是一种描述关联对象的关联关系，表示可以存在三种关系，例如A和/或B，可以表示：单独存在A，同时存在A和B，单独存在B这三种情况。另外，本文中字符“/”，一般表示前后关联对象是一种“或”的关系。
在本申请实施例的描述中，术语“多个”指的是两个以上(包括两个)，同理，“多 组”指的是两组以上(包括两组)，“多片”指的是两片以上(包括两片)。“至少一种”指的是一种以上(包括一种、两种、三种等)。
在本申请实施例的描述中，技术术语“中心”“纵向”“横向”“长度”“宽度”“厚度”“上”“下”“前”“后”“左”“右”“竖直”“水平”“顶”“底”“内”“外”“顺时针”“逆时针”“轴向”“径向”“周向”等指示的方位或位置关系为基于附图所示的方位或位置关系，仅是为了便于描述本申请实施例和简化描述，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实施例的限制。
在本申请实施例的描述中，除非另有明确的规定和限定，技术术语“安装”“相连”“连接”“固定”等术语应做广义理解，例如，可以是固定连接，也可以是可拆卸连接，或成一体；也可以是机械连接，也可以是电连接；可以是直接相连，也可以通过中间媒介间接相连，可以是两个元件内部的连通或两个元件的相互作用关系。对于本领域的普通技术人员而言，可以根据具体情况理解上述术语在本申请实施例中的具体含义。
在节能减排的时代背景下，新能源技术发展迅猛，其中以电池技术的研究突破和应用最为显著。在离子电池如锂离子电池中，电池隔膜是重要的部件之一。隔膜是一种用于隔开正极和负极的微孔膜，是具有纳米级微孔结构的高分子功能材料。隔膜的主要作用是将电池的正、负极活性物质分隔开以降低两极接触而短路的风险，同时允许电解质离子通过。隔膜的性能决定着电池的界面结构、内阻等，直接影响着电池的容量、循环以及电池的安全性能。在实际应用中，技术人员一般会对隔膜进行改性与修饰。
为了提高电池的动力学性能，市场上有通过在隔膜表面喷涂有机粘结层以增强隔膜与极片的粘结性的改性方案。但是，喷涂得到的隔膜的表面有机粘结层耐热性较差，因电池在充放电过程中会释放热量，尤其在短路或过充电的时候，会有大量热量放出，当温度升高的时候，隔膜表面的有机粘结层的低耐热性影响隔膜的隔离作用。同时，有机粘结层以整层的方式结合在隔膜表面，不仅增加了隔膜整体的厚度，从而影响电池能量密度，而且电池多次循环充放电后其粘性容易降低使得有机粘结层容易从隔膜表面脱落，从而影响其结合的稳定性。另外，采用喷涂的方式在隔膜表面制备有机粘结层，操作过程较为复杂，容易增加设备成本和工艺流程步骤。
基于以上考虑，为了克服隔膜表面喷涂有机粘结层的缺陷，本申请实施例设计出一种自粘型的新型隔膜，该隔膜包括聚合物基膜和分散在聚合物基膜中的有机粘结剂。利用有机粘结剂加入到聚合物基膜材料中形成自粘型隔离膜，基于聚合物基膜材料内的有机粘结剂的粘结性，从而可以提高隔膜整体的耐热性和稳定性，这样的隔膜成膜工艺简单，用在电池中可以显著提高电池的能量密度和循环寿命。由此提出了如下技术方案。
隔膜
第一方面，本申请实施例提供一种隔膜，如图1所示，包括：聚合物基膜11和有机粘结剂12。有机粘结剂12分散在聚合物基膜11中，同时，有部分有机粘结剂12的分子链末端露出聚合物基膜11的表面。
聚合物基膜11可以是由隔膜的聚合物基材形成的基膜，使用聚合物基材作为隔膜的主体材料可以制成微孔膜，可以满足电池隔膜所需要的力学性能以及电化学性能等。
有机粘结剂12是具有粘结性能的有机材料助剂，用于增强隔膜和极片的粘接性以提高电池的动力学性能。本申请实施例的隔膜中，有机粘结剂12分散在聚合物基膜11中增 强聚合物基膜11的力学强度，同时，有部分有机粘结剂12的分子链末端露出聚合物基膜11的表面赋予聚合物基膜11表面的粘结性，形成一种自粘型隔膜，其中有机粘结剂12的分子链末端露出聚合物基膜11的表面包括相对的上表面和下表面，从而使隔膜在电池中可以同时粘结正极片和负极片。
本申请实施例通过将有机粘结剂12分散在聚合物基膜11材料中形成一种自粘型隔膜，基于聚合物基膜11材料内分散的有机粘结剂12的粘结性可以从隔膜内部增强聚合物基膜11的力学强度，而且隔膜内的有机粘结剂不易脱落，因此这样的隔膜具有很好的耐热性和稳定性。对比目前喷涂在聚合物基膜11表面形成粘结层的方式，本申请实施例提供的隔膜的有机粘结剂12分散在聚合物基膜12内，隔膜整体厚度更低，用在电池中可以进一步提高电池的能量密度和循环寿命。
一些实施例中，隔膜中聚合物基膜11的基材可以是包括聚烯烃类材料、含氟聚合物类材料、聚酯类材料、聚醚醚酮、聚酰亚胺、纤维素和纤维素酯中的至少一种。
隔膜基材一般可以有良好的化学和热稳定性、适当的孔隙率和孔径以及良好的机械强度。聚烯烃类材料、含氟聚合物类材料、聚酯类材料、聚醚醚酮、聚酰亚胺、纤维素和纤维素酯不仅绝缘性好，而且可以形成微孔结构，可以使隔膜具备行业所需要的透气度和孔隙率，从而为电解液的离子提供良好的迁移通道，使电池稳定高效运行，因此上述材料可以用作隔膜基材的主体聚合物材料。
具体地，本申请实施例的隔膜中，通过上述聚合物基膜11的基材和有机粘结剂12的种类、比例选择可以形成具有一定的透气度和孔隙率的隔膜，以便用在二次电池中。
透气度的参数选用Gurley数，即一定体积的气体，在一定压力条件下通过一定面积的隔膜所需要的时间。具体可以参照标准GB/T 36363-2018进行测试，通过测试在1.21kPa压力下、100cc(cubic centimeter，1cc＝1ml)空气通过面积为6.45cm2隔膜所需要的时间。示范例中，经测试本申请的隔膜的透气度可以为100s/100cc～400s/100cc，包括但不仅仅为100s/100cc、150s/100cc、200s/100cc、250s/100cc、300s/100、320s/100、380s/100、400s/100cc等典型但非限制性的透气度，例如隔膜的透气度可以为100s/100cc～200s/100cc。
孔隙率即为隔膜内部空穴的体积占隔膜总体积的百分率。具体可以参照标准GB/T 36363-2018进行测试，示范例中，经测试本申请的隔膜的孔隙率可以为25％～80％，包括但不仅仅为25％、30％、32％、36％、38％、40％、45％、46％、48％、50％、52％、54％、56％、58％、60％、65％、68％、70％、75％、78％、80％等典型但非限制性的孔隙率，例如隔膜的孔隙率可以为30％～35％。
一些实施例中，隔膜中聚合物基膜11的基材包括：聚烯烃类材料、含氟聚合物类材料和、聚酯类材料、聚醚醚酮、聚酰亚胺、纤维素和纤维素酯中的至少一种。其中，(1)聚烯烃类材料可以是包括聚乙烯和聚丙烯中的至少一种；聚乙烯和聚丙烯具有价格低、机械性能优良和电化学稳定性高的特点，商品化的锂离子电池隔膜产品多为聚烯烃类材料制备的微孔膜，主要原料为高分子量的聚乙烯和聚丙烯，这类聚烯烃材料具有强度高、耐酸碱腐蚀性好、防水等优点，其工业制备成熟，商业应用广泛。进一步地，聚乙烯可以是高密度聚乙烯(约0.94～0.96g/cm3)或低密度聚乙烯(约0.91～0.93g/cm3)。(2)含氟聚合物类材料可以是包括聚四氟乙烯、聚氟乙烯和聚偏氟乙烯中的至少一种；含氟聚合物类材料具有很好的极性和介电常数，上述含氟聚合物类材料用于电池中可以很好地提高隔膜的亲液性，以聚偏氟乙烯应用最广。(3)聚酯类材料可以是包括聚对苯二甲酸乙二醇酯和 聚氨酯中的至少一种。聚对苯二甲酸乙二醇酯这种聚酯类材料具有很好的耐电解液腐蚀性，聚氨酯如聚氨基甲酸酯具有很好的耐磨性。因此，可以根据实际需要，对聚合物基膜11的基材种类进行选择。
在一些实施例中，隔膜中的有机粘结剂12具体可以包括聚偏氟乙烯、聚丙烯酸酯、丙烯酸、羧甲基纤维素、聚酰亚胺、乙烯-醋酸乙烯共聚物、聚氨酯、马来酸酐和乙烯丙烯酸共聚物中的至少一种。上述种类的有机粘结剂12材料具有很好的粘结性，可以分散在聚合物基膜11材料中形成自粘型隔膜。
在一些实施例中，上述有机粘结剂12和聚合物基膜12材料种类搭配形成的隔膜中，有机粘结剂12的分子量可以为0.01万Da～120万Da，聚合物基膜11的基材分子量可以为5万Da～400万Da。
Da全称道尔顿(Dalton)，是分子量常用单位，是将分子中所有原子按个数求原子量的代数和。有机粘结剂12的分子量可以为0.01万Da～120万Da，具有很好的粘结性，示范例中，有机粘结剂12的分子量包括但不仅仅为0.1万Da、0.5万Da、1万Da、5万Da、20万Da、30万Da、50万Da、60万Da、80万Da、90万Da、100万Da、110万Da、120万Da等典型但非限制性的分子量，例如可以为0.1万Da～100万Da。聚合物基膜11的基材分子量为5万Da～400万Da，具有很好的力学强度，示范例中，聚合物基膜11的基材分子量包括但不仅仅为5万Da、10万Da、20万Da、30万Da、50万Da、60万Da、80万Da、90万Da、100万Da、110万Da、120万Da、160万Da、200万Da、220万Da、240万Da、260万Da、300万Da、320万Da、350万Da、380万Da、400万Da等典型但非限制性的分子量，例如可以为30万Da～200万Da。
在一些实施例中，有机粘结剂12的分子量可以为0.1万Da～100万Da，聚合物基膜11的基材分子量可以为30万Da～200万Da。分子量为0.1万Da～30万Da的有机粘结剂12可以很好地分散在分子量为30万Da～200万Da的聚合物基膜11中，从而可以很好地发挥有机粘结剂12的粘结性，同时不易脱落，可以进一步提高隔膜整体的耐热性和稳定性。
在一些实施例中，隔膜中的有机粘结剂12与聚合物基膜11的基材种类可以相同或不同。例如，如有机粘结剂12与聚合物基膜12的基材种类不同，这样的有机粘结剂11分散在聚合物基膜12中使隔膜整体耐热性更好。当有机粘结剂11与聚合物基膜12的基材的聚合单体种类相同，则有机粘结剂12的分子量小于聚合物基膜11的基材的分子量。因有机粘结剂12与聚合物基膜11的基材聚合单体种类相同，有机粘结剂和基材具有很好的相容性，同时有机粘结剂12的分子量小于聚合物基膜11的基材的分子量，从而可以保持有机粘结剂12的粘结性以及聚合物基膜11的力学强度，这样的有机粘结剂12和聚合物基膜11的基材搭配可以形成相容性更好的自粘型隔膜，有机粘结剂12均匀分散在基材11中可以使隔膜具有很好的热闭孔功能，从而降低热失控，进一步提高隔膜的安全性。
在一些实施例中，有机粘结剂12与聚合物基膜11的聚合单体种类相同，这样可以选用分子量小于聚合物基膜11的基材分子量的有机粘结剂12进行搭配。例如，可以选用有机粘结剂12包括分子量为30万Da～100万Da的聚偏氟乙烯和聚合物基膜11的基材包括分子量为100万Da～200万Da的聚偏氟乙烯进行搭配；进一步地，有机粘结剂12包括分子量为40万Da～75万Da的聚偏氟乙烯，聚合物基膜11的基材包括分子量为120万Da～170万Da的聚偏氟乙烯。上述不同分子量的聚偏氟乙烯搭配形成有机粘结剂12和聚合物基膜 11的基材，可以使隔膜中的材料具有很好的相容性，因而隔膜热闭孔性能更佳，从而具有更好的安全性；同时，这样的隔膜具有很好的压缩性，用在电池中组装时更容易压缩，从而可以进一步提高电池的能量密度。
一些实施例中，隔膜中的聚合物基膜11和有机粘结剂12的质量比可以为10：(0.01～6)。示范例中，聚合物基膜11和有机粘结剂12的质量比可以但不仅仅为10：0.01、10：0.05、10：0.1、10：0.4、10：0.6、10：1、10：2、10：3、10：4、10：5等典型但非限制性的质量比。本申请实施例通过按照聚合物基膜11和有机粘结剂12的质量比为10：(0.01～6)，将有机粘结剂12分散在聚合物基膜11形成隔膜，该质量比例条件下不仅可以使隔膜保持自粘型，同时具有较好的耐热性和稳定性。
一些实施例中，隔膜中的聚合物基膜11和有机粘结剂12的质量比可以为10：(0.1～5)。按照聚合物基膜11和有机粘结剂12的质量比为10：(0.1～5)，将这样比例的有机粘结剂12分散在聚合物基膜11形成隔膜，可以使隔膜整体的耐热性、稳定性、以及自粘性从而提升电池的结构稳定性的综合效果好。
在一些实施例中，隔膜的厚度可以为1μm～12μm。示范例中，隔膜的厚度包括但不仅仅为1μm、2μm、3μm、5μm、10μm、12μm等典型但非限制性的厚度，例如可以为3μm～6μm。有机粘结剂12分散在聚合物基膜11中形成厚度为1μm～12μm的隔膜，因有机粘结剂作用，该厚度下仍然具有很好的力学强度，同时热收缩率小，这样的低厚度的隔膜用于电池中可以显著提高电池能量密度。
在一些实施例中，隔膜的厚度可以为3μm～6μm。厚度为3μm～6μm的隔膜力学强度，以及在电池中对电池能量密度提升作用的综合效果好。
具体地，本申请实施例通过选用不同种类的有机粘结剂12以一定质量比例分散在不同种类聚合物基膜11中形成上述厚度为1μm～12μm的隔膜可以具有很好的热收缩率和拉伸强度。例如，(1)隔膜在105℃、1h的条件下横向热收缩率可以小于或等于2.0％，在105℃、1h的条件下纵向热收缩率可以小于或等于2.0％。示范例中，隔膜的横向热收缩率或纵向热收缩率包括但不仅仅为0.1％、0.5％、0.8％、1％、1.2％、1.5％、1.8％、2％等典型但非限制性的热收缩率，例如在105℃、1h的条件下横向热收缩率和纵向热收缩率可以为0.1～1.2％。(2)隔膜的横向拉伸强度大于或等于700kg/cm2，纵向拉伸强度大于或等于1000kg/cm2。示范例中，隔膜的横向拉伸强度包括但不仅仅为700kg/cm2、800kg/cm2、1000kg/cm2、1200kg/cm2、1500kg/cm2、2000kg/cm2、2500kg/cm2、3000kg/cm2、3500kg/cm2、4000kg/cm2、4500kg/cm2等典型但非限制性的拉伸强度，隔膜的纵向拉伸强度包括但不仅仅为1000kg/cm2、1200kg/cm2、1500kg/cm2、2000kg/cm2、2500kg/cm2、3000kg/cm2、3500kg/cm2、4000kg/cm2、4500kg/cm2等典型但非限制性的拉伸强度，例如，隔膜的横向拉伸强度为1000～4000kg/cm2，纵向拉伸强度为1200～4000kg/cm2。
隔膜的制备方法
第二方面，本申请实施例提供一种隔膜的制备方法。如图2所示，隔膜的制备方法包括以下步骤：
S01：将有机粘结剂和聚合物基膜的基材混合，得到混合料；
S02：将混合料熔融挤出，然后拉伸处理，得到隔膜。
通过采用干法拉伸致孔技术，将有机粘结剂和聚合物基膜的基材混合熔融挤出、拉伸得到具有微孔结构的隔膜。本申请实施例的隔膜的制备方法，将有机粘结剂从隔膜制备的 原料端中就混进聚合物基膜的基材中一体成膜得到自粘型隔膜，简化了能与电极粘附隔膜的工艺步骤，这样将有机粘结剂和基材一体成膜的制备方法，不仅工艺简单、制备成本低，而且可以得到具有很好的耐热性和稳定性的自粘型隔膜，从而可以提高电池的能量密度和循环寿命。
本申请实施例制备得到的隔膜用于电池中时，与电极具有很好的粘接性，可以提升电池的动力学性能。
S01：有机粘结剂和聚合物基膜的基材具体种类和比例上文已详细阐述。具体地，聚合物基膜的基材可以和有机粘结剂以质量比为10：(1～5)混合。而聚合物基膜的基材可以是包括聚烯烃类材料、含氟聚合物类材料、聚酯类材料、聚醚醚酮、聚酰亚胺、纤维素和纤维素酯中的至少一种。其中，聚烯烃类材料可以是包括聚乙烯和聚丙烯中的至少一种；含氟聚合物类材料可以是包括聚四氟乙烯、聚氟乙烯和聚偏氟乙烯中的至少一种；聚酯类材料可以是包括聚对苯二甲酸乙二醇酯和聚氨酯中的至少一种。有机粘结剂具体种类可以和聚合物基膜的基材种类相同或不同。有机粘结剂具体可以包括聚偏氟乙烯、聚丙烯酸酯、丙烯酸、羧甲基纤维素、聚酰亚胺、乙烯-醋酸乙烯共聚物、聚氨酯、马来酸酐和乙烯丙烯酸共聚物中的至少一种。有机粘结剂的分子量可以为0.01万Da～120万Da，聚合物基膜的基材分子量可以为5万Da～400万Da。
S02：一些实施例中，将混合料熔融挤出时的熔融挤出温度为200～300℃。
聚合物基膜的基材的熔点可以为130～400℃，根据基材种类不同有不同熔点，如可以是130℃、150℃、200℃、250℃、300℃等，具体可以是130～190℃等；有机粘结剂的熔点可以为100～200℃，根据不同有机粘结剂种类不同有不同熔点，如可以是100℃、120℃、150℃、180℃、200℃等，具体可以是100～150℃等。而本申请实施例通过在200～300℃的温度下进行熔融挤出，可以使有机粘结剂和聚合物基膜基材的混合料形成混合均匀、且具有较好流动性的粘流态混合料，以便后续拉伸成膜。示范例中，混合料熔融挤出温度包括但不仅仅为200℃、220℃、250℃、260℃、300℃等典型但非限制性的温度。
一些实施例中，将混合料熔融挤出后的拉伸处理的拉伸温度为100～120℃。
将200～300℃的熔融挤出物料温度降至100～120℃进行拉伸处理，在这样的温度下拉伸可以使熔融材料结晶界面剥离形成多孔结构的隔膜。示范例中，拉伸处理温度包括但不仅仅为100℃、105℃、110℃、105℃、120℃等典型但非限制性的温度。
一些实施例中，将混合料熔融挤出后的拉伸处理的拉伸倍率为10～300倍。
粘流态下的熔融挤出材料通过10～300倍的拉伸倍率进行拉伸，可以形成具有微孔结构的硬弹性体材料的隔膜。示范例中，拉伸处理的拉伸倍率包括但不仅仅为10倍、50倍、80倍、100倍、150倍、180倍、200倍、250倍、300倍等典型但非限制性的拉伸倍率。
一些实施例中，拉伸处理可以是双向拉伸处理，例如，将200～300℃的熔融挤出物料温度降至100～120℃进行拉伸倍率为100～200倍的冷却双向拉伸，这样的条件下可以较好地控制隔膜的孔隙率，而且孔隙可以均匀分布。
二次电池
第三方面，本申请实施例提供一种电池，包括正极片、负极片和置于正极片与负极片之间的隔膜，隔膜为本申请实施例第一方面提供的隔膜和/或本申请实施例第二方面提供的制备方法制备得到的隔膜。
通过将本申请实施例第一方面提供的隔膜和/或本申请实施例第二方面提供的制备方 法制备得到的隔膜用在电池中，这样隔膜可以将电池的正极片和负极片粘结在一起，从而减少了电池极片的空间活度，拉近了正、负极之间的距离，基于隔膜整体的耐热性和稳定性好、厚度低，从而使电池具有很好的能量密度和循环寿命。
一些实施例中，在95℃、7MPa、10s的热压条件下，电池中的隔膜与正极片或负极片的粘接力大于等于1.0N/m。该条件下的隔膜粘结强度具有很好的粘结性，利用自粘型的隔膜的高粘结性，可以与正极或负极的粘接力大于等于1N，这样使电池的结构更稳定。
一些实施例中，电池为二次电池。示范例中，二次电池可以是离子电池或钠离子电池等，这样的二次电池具有高能量密度和良好的循环寿命特性，可以用作动力电池或者储能系统电源。
通常情况下，二次电池包括正极片、负极片、电解质和隔膜。在电池充放电过程中，活性离子在正极片和负极片之间往返嵌入和脱出。电解质在正极片和负极片之间起到传导离子的作用。隔膜设置在正极片和负极片之间，主要起到防止正负极短路的作用，同时可以使离子通过。
在一些实施方式中，正极片包括正极集流体和结合在正极集流体上的正极活性层。其中，正极活性层含有正极活性材料，二次电池为锂离子电池时，正极活性材料为含锂材料，二次电池为钠离子电池时，正极活性材料为含钠材料。
在一些实施方式中，正极片的集流体又称正极集流体，可采用金属箔片或复合集流体。例如，作为金属箔片，可采用铝箔。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层至少一个表面上的金属层。复合集流体可通过将金属材料(铝、铝合金、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、聚对苯二甲酸乙二醇酯、聚对苯二甲酸丁二醇酯、聚苯乙烯、聚乙烯等的基材上而形成。
在一些实施方式中，正极活性层还可选地包括粘结剂。作为示例，粘结剂可以包括聚偏氟乙烯、聚四氟乙烯、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物及含氟丙烯酸酯树脂中的至少一种。进一步地，正极活性层还可选地包括导电剂。作为示例，导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，负极片包括负极集流体和结合在负极极集流体上的正极活性层。其中，负极活性层含有负极活性材料，负极活性材料可采用本领域公知的用于电池的负极活性材料。作为示例，负极活性材料可包括人造石墨、天然石墨、软炭、硬炭、硅基材料、锡基材料和钛酸锂等中至少一种。
在一些实施方式中，负极片的集流体又称负极集流体，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、聚对苯二甲酸乙二醇酯、聚对苯二甲酸丁二醇酯、聚苯乙烯、聚乙烯等的基材上而形成。
在一些实施方式中，负极活性层还可选地包括粘结剂。粘结剂可选自丁苯橡胶、聚丙烯酸、聚丙烯酸钠、聚丙烯酰胺、聚乙烯醇、海藻酸钠、聚甲基丙烯酸及羧甲基壳聚糖中的至少一种。进一步地，负极活性层还可选地包括导电剂。导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。负极活性层还可选地包括其他助剂，例如增稠剂(如羧甲基纤维素钠)等。
电解质在正极片和负极片之间起到传导离子的作用。本申请实施例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。对于二次电池为锂离子电池，电解质盐可选自六氟磷酸锂、四氟硼酸锂、高氯酸锂、六氟砷酸锂、双氟磺酰亚胺锂、双三氟甲磺酰亚胺锂、三氟甲磺酸锂、二氟磷酸锂、二氟草酸硼酸锂、二氟二草酸磷酸锂及四氟草酸磷酸锂中的至少一种。对于二次电池为钠离子电池，相应的电解质盐换成钠盐。
在一些实施方式中，电解液中的溶剂可选自碳酸亚乙酯、碳酸亚丙酯、碳酸甲乙酯、碳酸二乙酯、碳酸二甲酯、碳酸二丙酯、碳酸甲丙酯、碳酸乙丙酯、碳酸亚丁酯、氟代碳酸亚乙酯、甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丁酸甲酯、丁酸乙酯、1,4-丁内酯、环丁砜、二甲砜、甲乙砜及二乙砜中的至少一种。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。
一些实施例中，本申请实施例二次电池可以包括电池单体、电池模块、电池包中的任一种。其中，电池单体是指包括电池壳体和封装于该电池壳体内的电芯。电池单体的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。如图3所示的方形结构的电池单体20。
在一些实施例中，如图4所示，电池单体20的外包装可包括壳体21和顶盖组件22。壳体21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21具有与容纳腔连通的开口，顶盖组件22用于盖设开口，以封闭容纳腔。本申请实施例二次电池所含的正极、隔膜和负极片可经卷绕工艺和/或叠片工艺形成电极组件23。电极组件23封装于容纳腔。电解液浸润于电极组件23中。电池单体20所含电极组件23的数量可以为一个或多个，可以根据实际需求来调节。
电池单体20的制备方法是公知的。在一些实施例中，可将正极、隔膜和负极片和电解液组装形成电池单体20。作为示例，可将正极、隔膜和负极片经卷绕工艺或叠片工艺形成电极组件23，将电极组件23置于外包装中，烘干后注入电解液，经过真空封装、静置、化成、整形等工序，得到电池单体20。
电池模块是指由该电池单体20组装而成，也即是可以含有多个该电池单体20，具体数量可根据电池模块的应用和容量来调节。
一些实施例中，图5是作为一个示例的电池模块30的示意图。如图5所示，在电池模块30中，多个电池单体20可以是沿电池模块30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电池单体20进行固定。
可选地，电池模块30还可以包括具有容纳空间的外壳，多个电池单体20容纳于该容纳空间。电池包是指由上文电池单体20组装而成，也即是可以含有多个电池单体20，其中，多个该电池单体20可以组装成上文电池模块30。电池包所含的电池单体20或电池模块30具体数量可根据电池包的应用和容量进行调节。
如实施例中，图6和图7是作为一个示例的电池包40的示意图。在电池包40中可以包括电池箱和设置于电池箱中的多个电池模块30。电池箱包括上箱体41和下箱体42，上 箱体41用于盖设下箱体42，并形成用于容纳电池模块30的封闭空间。多个电池模块30可以按照任意的方式排布于电池箱中。
用电装置
第四方面，本申请实施例还提供一种用电装置，用电装置包括上文本申请实施例电池。电池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。因此本申请实施例用电装置待机或续航时间长，稳定性和安全性好。
用电装置可以但不限于是移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等。该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8是作为一个示例的用电装置的示意图。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高功率和高能量密度的需求，可以采用电池包或电池模块。作为另一个示例的用电装置可以是手机、平板电脑、笔记本电脑等。该用电装置通常要求轻薄化，可以采用二次电池作为电源。
实施例
以下，说明本申请的实施例。下面描述的实施例是示例性的，仅用于解释本申请，而不能理解为对本申请的限制。实施例中未注明具体技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品。
1.隔膜及其制备方法实施例
实施例A1
一种隔膜，包括聚合物基膜和分散在聚合物基膜中的有机粘结剂；其中，有机粘结剂是分子量为50万Da的聚偏氟乙烯，聚合物基膜的基材是分子量为33万Da的聚丙烯，聚合物基膜和有机粘结剂的质量比为10：1。
隔膜的制备方法包括如下步骤：
S11：将基材与有机粘结剂以10：1的质量比混合，得到混合料；
S12：将混合料于210℃熔融挤出，然后在120℃条件下以200倍拉伸倍率进行拉伸处理，得到厚度为5um的隔膜。
实施例A2
一种隔膜，包括聚合物基膜和分散在聚合物基膜中的有机粘结剂；其中，有机粘结剂是分子量为50万Da的聚偏氟乙烯，聚合物基膜的基材是分子量为33万Da的聚丙烯，聚合物基膜和有机粘结剂的质量比为10：1。
隔膜的制备方法包括如下步骤：
S11：将基材与有机粘结剂以10：1的质量比混合，得到混合料；
S12：将混合料于210℃熔融挤出，然后在120℃条件下以500拉伸倍率进行拉伸处理，得到厚度为1um的隔膜。
实施例A3
一种隔膜，包括聚合物基膜和分散在聚合物基膜中的有机粘结剂；其中，有机粘结剂是分子量为50万Da的聚偏氟乙烯，聚合物基膜的基材是分子量为33万Da的聚丙烯，聚合物基膜和有机粘结剂的质量比为10：1。
隔膜的制备方法包括如下步骤：
S11：将基材与有机粘结剂以10：1的质量比混合，得到混合料；
S12：将混合料于210℃熔融挤出，然后在120℃条件下以80拉伸倍率进行拉伸处理，得到厚度为12um的隔膜。
实施例A4
一种隔膜，包括聚合物基膜和分散在聚合物基膜中的有机粘结剂；其中，有机粘结剂是分子量为50万Da的聚偏氟乙烯，聚合物基膜的基材是分子量为33万Da的聚丙烯，聚合物基膜和有机粘结剂的质量比为10：5。
隔膜的制备方法包括如下步骤：
S21：将基材与有机粘结剂以10：5的质量比混合，得到混合料；
S22：将混合料于210℃熔融挤出，然后在120℃条件下以200倍拉伸倍率进行拉伸处理，得到厚度为5um的隔膜。
实施例A5
一种隔膜，包括聚合物基膜和分散在聚合物基膜中的有机粘结剂；其中，有机粘结剂是分子量为60万Da的聚偏氟乙烯，聚合物基膜的基材是分子量为33万Da的聚丙烯，聚合物基膜和有机粘结剂的质量比为10：1。
隔膜的制备方法包括如下步骤：
S11：将基材与有机粘结剂以10：1的质量比混合，得到混合料；
S12：将混合料于210℃熔融挤出，然后在120℃条件下以200拉伸倍率进行拉伸处理，得到厚度为5um的隔膜。
实施例A6
一种隔膜，包括聚合物基膜和分散在聚合物基膜中的有机粘结剂；其中，有机粘结剂是分子量为1万Da的羧甲基纤维素，聚合物基膜的基材是分子量为33万Da的聚丙烯，聚合物基膜和有机粘结剂的质量比为10：1。
隔膜的制备方法包括如下步骤：
S11：将基材与有机粘结剂以10：1的质量比混合，得到混合料；
S12：将混合料于210℃熔融挤出，然后在120℃条件下以200倍拉伸倍率进行拉伸处理，得到厚度为5um的隔膜。
实施例A7
一种隔膜，包括聚合物基膜和分散在聚合物基膜中的有机粘结剂；其中，有机粘结剂是分子量为50万Da的聚偏氟乙烯，聚合物基膜的基材是分子量为120万Da的聚偏氟乙烯，聚合物基膜和有机粘结剂的质量比为10：1。
隔膜的制备方法包括如下步骤：
S11：将基材与有机粘结剂以10：1的质量比混合，得到混合料；
S12：将混合料于210℃熔融挤出，然后在120℃条件下以200倍拉伸倍率进行拉伸处理，得到厚度为5um的隔膜。
对比例A1
一种隔膜，包括聚合物基膜和喷涂在聚合物基膜表面的有机粘结剂层，聚合物基膜厚度为5um，有机粘结剂层厚度为2μm。聚合物基膜的基材是分子量为33万Da的聚丙烯，有机粘结剂层的粘结剂是分子量为50万Da的聚偏氟乙烯，聚合物基膜和有机粘结剂层的 质量比为10：1。
对比例A2
一种隔膜，包括聚合物基膜和喷涂在聚合物基膜表面的有机粘结剂层，聚合物基膜厚度为5um，有机粘结剂层厚度为2μm。聚合物基膜的基材是分子量为33万Da的聚丙烯，有机粘结剂层的粘结剂是分子量为50万Da的聚偏氟乙烯，聚合物基膜和有机粘结剂层的质量比为10：5。
对比例A3
一种隔膜，包括聚合物基膜和喷涂在聚合物基膜表面的有机粘结剂层，聚合物基膜厚度为5um，有机粘结剂层厚度为2μm。聚合物基膜的基材是分子量为33万Da的聚丙烯，有机粘结剂层的粘结剂是分子量为60万Da的聚偏氟乙烯，聚合物基膜和有机粘结剂层的质量比为10：1。
对比例A4
一种隔膜，包括聚合物基膜和喷涂在聚合物基膜表面的有机粘结剂层，聚合物基膜厚度为5um，有机粘结剂层厚度为2μm。聚合物基膜的基材是分子量为120万Da的聚偏氟乙烯，有机粘结剂层的粘结剂是分子量为50万Da的聚偏氟乙烯，聚合物基膜和有机粘结剂层的质量比为10：1。
2.二次电池单体实施例
实施例B1
二次电池单体，包括正极片、隔膜和负极片形成的电芯，还包括电解液。其中，隔膜为实施例A1提供的隔膜。二次电池单体的制备方法包括：
正极片制备：以甲基吡咯烷酮(NMP)为溶剂，将LiNi0.8Co0.1Mn0.1O2、碳纳米管(CNT)、粘结剂(PVDF)以质量比97：2：1混合，制成固含量为80％的正极浆料；将正极浆料均匀涂覆在铝箔上，进行双面涂布，经充分干燥、冷压、分切后得到正极片作为正电极。
负极片制备：以水为溶剂，将人造石墨、导电剂SP、分散剂(CMC)、粘结剂(SBR)以质量比96：1：1：2混合，制成固含量为58％的负极浆料；将正极浆料均匀涂覆在铝箔上，进行双面涂布，经充分干燥、冷压、分切后得到负极片作为负电极。
电解液：在室温下，将碳酸亚乙酯(EC)/碳酸二乙酯(DEC)按体积比1:1进行混合，在混合溶液加入LiPF6得到浓度为1mol/L的溶液作为电解液；
二次电池组装：在低湿恒温房内用如上制备的正极片、负极片，以“正电极-隔膜-负电极”的顺序叠置、卷绕形成裸电芯，再充入电解液，组装成锂离子二次电池。
实施例B1至实施例B7和对比例B1至对比例B4；
本实施例B1至实施例B7和对比例B1至对比例B4分别提供一种二次电池单体，各二次电池单体包括正极片、隔膜和负极片形成的电芯，还包括电解液。其中，实施例B1至实施例B7和对比例B1至对比例B4的隔膜分别对应为实施例A1至实施例A7和对比例A1至对比例A4提供的隔膜。其中，上文实施例A1中隔膜作为二次电池实施例B1电池电芯中隔膜，实施例A2中隔膜作为二次电池实施例B2电池电芯中隔膜，依次类推，对比例A4中隔膜作为电池对比例B4电池电芯中隔膜。
性能测试
将上述实施例和对比例的隔膜和二次电池单体分别进行测试。
1、隔膜对极片粘接力测试方法
制样：将隔膜置于正/负极片上，60/75/95℃条件下以7吨压力压30s取出成测试样品。
测试：将测试样品与测试金属夹具粘接牢固，隔膜与极片呈180°剥离，记录力值数据为与极片的粘接力。
2、隔膜穿刺强度测试的方法：
用美工刀将隔膜裁成条状，其中条状隔膜的宽度必须大于100mm。将宽度为100mm的试片安装在样膜固定夹环上，然后用直径1.0mm、直径顶端半径为0.5mm的钢针，以(50±5)mm/min的速度去顶刺，读取钢针穿透试片的大负荷。测试一般测3个点，取其算术平均值，测试片数5个以上。隔膜穿刺强度依据标准：GB/T 10004-2008。
3、隔膜透气度、抗拉强度等测试的方法：
隔离膜的透气度、横向拉伸强度(MD)、纵向拉伸强度(TD)均具有本领域公知的含义，可以采用本领域已知的标准GB/T 36363-2018进行测试。
4、隔膜热收缩率测试的方法：
样品制备：将上述制备的隔膜用冲压机冲切成宽度为50mm、长度为100mm的样品，取5个平行样品放置在A4纸上并固定，再将装有样品的A4纸放置在厚度为1mm至5mm的瓦楞纸上。
样品测试：将放置在瓦楞纸上面的A4纸放入鼓风式烘箱，鼓风式烘箱温度设置为250℃，待温度达到设定温度并稳定30分钟后，开始计时，到达设定时间(本申请为1小时)后，测量隔膜的长度和宽度，数值分别标记为a和b。热收缩率计算：纵向(MD)热收缩率＝[(100-a)/100]×100％，横向(TD)热收缩率＝[(50-b)/50]×100％，取5个平行样品的平均值作为测试结果。
5、隔膜孔隙率测试的方法：采用压汞仪参考GB/T 21650.1-2008进行测试。
隔膜的测试结果如表1所示。
表1

由表1中测试结果可知：
本申请的实施例A1-A7的隔膜的极片粘结力、穿刺强调和热收缩率均比对比例A1-A4高，且透气性更好。同时，实施例A1、A4、A5、A7分别依次对比表面喷涂方式的对比例A1-A4，在其他条件相同下，本申请实施例的横向拉伸强度和纵向拉伸强度比对比例喷涂结合方式更高。由此表明，采用本申请实施例自粘型的隔膜具有更好的粘附性、力学强度和热稳定性，同时对基膜孔隙率影响小。而且本申请实施例A7通过用不同分子量的聚偏氟乙烯做粘结剂和基材，其粘附性、力学强度和热稳定性的效果最佳。
6、二次电池单体的循环寿命测试方法：
25℃下，将实施例和对比例制备得到的二次电池以1C倍率恒流充电至充电截止电压V1，之后恒压充电至电流≤0.05C，静置5min，再以0.33C倍率恒流放电至放电截止电压V2，静置5min，此为一个充放电循环。按照此方法对电池进行循环充放电测试，直至电池容量衰减至80％。此时的循环圈数即为电池在25℃下的循环寿命。
7、二次电池单体的能量密度测试方法：
25℃下，将实施例和对比例制备得到的二次电池以1C倍率恒流充电至充电截止电压V1，之后恒压充电至电流≤0.05C，静置5min，测试其电池容量，电池容量×此时电压/电芯重量则为电池的能量密度。
二次电池的测试结果如表2所示。
表2

由表2中测试结果可知：
本申请的实施例B1-B7的二次电池使用本申请特有的隔膜，其能量密度和循环寿命均比对比例好。而且在其他条件相同下，实施例B3的二次电池隔膜厚度越厚，其电池循环寿命越好，实施例B2的二次电池隔膜厚度越低，其电池能量密度越好。而在厚度相同条件下，实施例B7的二次电池隔膜用不同分子量的聚偏氟乙烯做粘结剂和基材，其能量密度和循环寿命的效果最佳。
最后应说明的是：以上各实施例仅用以说明本申请的技术方案，而非对其限制；尽管参照前述各实施例对本申请进行了详细的说明，本领域的普通技术人员应当理解：其依然可以对前述各实施例所记载的技术方案进行修改，或者对其中部分或者全部技术特征进行等同替换；而这些修改或者替换，并不使相应技术方案的本质脱离本申请各实施例技术方案的范围，其均应涵盖在本申请的权利要求和说明书的范围当中。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 (22)

  1. 一种隔膜，其特征在于，包括聚合物基膜和分散在所述聚合物基膜中的有机粘结剂，部分所述有机粘结剂的分子链末端露出所述聚合物基膜的表面。
  2. 如权利要求1所述的隔膜，其特征在于，所述聚合物基膜的基材包括聚烯烃类材料、含氟聚合物类材料、聚酯类材料、聚醚醚酮、聚酰亚胺、纤维素和纤维素酯中的至少一种。
  3. 如权利要求2项所述的隔膜，其特征在于，所述聚烯烃类材料包括聚乙烯和聚丙烯中的至少一种；或者，
    所述含氟聚合物类材料包括聚四氟乙烯、聚氟乙烯和聚偏氟乙烯中的至少一种；或者，
    所述聚酯类材料包括聚对苯二甲酸乙二醇酯和聚氨酯中的至少一种。
  4. 如权利要求1-3任一项所述的隔膜，其特征在于，所述有机粘结剂包括聚偏氟乙烯、聚丙烯酸酯、丙烯酸、羧甲基纤维素、聚酰亚胺、乙烯-醋酸乙烯共聚物、聚氨酯、马来酸酐和乙烯丙烯酸共聚物中的至少一种。
  5. 如权利要求1-4任一项所述的隔膜，其特征在于，所述有机粘结剂的分子量为0.01万Da～120万Da，所述聚合物基膜的基材分子量为5万Da～400万Da。
  6. 如权利要求5所述的隔膜，其特征在于，所述有机粘结剂的分子量为0.1万Da～100万Da，所述聚合物基膜的基材分子量为30万Da～200万Da。
  7. 如权利要求1-6任一项所述的隔膜，其特征在于，所述有机粘结剂与所述聚合物基膜的基材种类不同；或者，
    所述有机粘结剂与所述聚合物基膜的聚合单体相同，且所述有机粘结剂的分子量小于所述聚合物基膜的基材分子量。
  8. 如权利要求7所述的隔膜，其特征在于，所述有机粘结剂与所述聚合物基膜的聚合单体相同，所述有机粘结剂包括分子量为30万Da～100万Da的聚偏氟乙烯，所述聚合物基膜的基材包括分子量为100万Da～200万Da的聚偏氟乙烯。
  9. 如权利要求8所述的隔膜，其特征在于，所述有机粘结剂包括分子量为40万Da～75万Da的聚偏氟乙烯，所述聚合物基膜的基材包括分子量为120万Da～170万Da的聚偏氟乙烯。
  10. 如权利要求1-9任一项所述的隔膜，其特征在于，所述聚合物基膜和所述有机粘结剂的质量比为10：(0.01～6)。
  11. 如权利要求10所述的隔膜，其特征在于，所述聚合物基膜和所述有机粘结剂的质量比为10：(0.1～5)。
  12. 如权利要求1-11任一项所述的隔膜，其特征在于，所述隔膜的厚度为1μm～12μm。
  13. 如权利要求12所述的隔膜，其特征在于，所述隔膜的厚度3μm～6μm。
  14. 一种如权利要求1-13任一项所述的隔膜的制备方法，其特征在于，包括以下步骤：
    将所述有机粘结剂和所述聚合物基膜的基材混合，得到混合料；
    将所述混合料熔融挤出，然后拉伸处理，得到所述隔膜。
  15. 如权利要求14所述的制备方法，其特征在于，所述熔融挤出的温度为200～300℃。
  16. 如权利要求14或15所述的制备方法，其特征在于，所述拉伸处理的温度为100～120℃。
  17. 如权利要求14-16任一项所述的制备方法，其特征在于，所述拉伸处理的拉伸倍率为10～300倍。
  18. 如权利要求17所述的制备方法，其特征在于，所述拉伸处理包括拉伸倍率为100～200倍的双向拉伸。
  19. 一种电池，其特征在于，包括正极片、负极片以及置于所述正极片与所述负极片之间的隔膜，所述隔膜为权利要求1至13任一项所述的隔膜或权利要求14至18任一项所述的制备方法制备得到的隔膜。
  20. 如权利要求19所述的电池，其特征在于，在95℃、7MPa、10s的热压条件下，所述隔膜与所述正极片或所述负极片的粘接力大于或等于1.0N/m。
  21. 根据权利要求19或20所述的电池，其特征在于，所述电池为二次电池。
  22. 一种用电装置，其特征在于，所述用电装置包括如权利要求19至21任一项所述的电池。
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