Diaphragm, secondary battery and electric device

Abstract

The invention relates to the technical field of batteries, in particular to a diaphragm. The separator according to the present application comprises a base film and a coating layer, the coating layer containing a fluorine-containing polymer, the fluorine-containing polymer having good thermal stability and being capable of promoting the generation of a stable solid electrolyte interface (SEI) film. The battery using the diaphragm has good cycle performance and high-temperature storage performance.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a diaphragm, and a secondary battery and an electrical device using the diaphragm. Background Art

[0002] Secondary batteries have the advantages of high energy density, long service life, and wide operating voltage range, and have been widely used in various fields. With the popularization of secondary batteries, users have put forward higher requirements for the performance of secondary batteries. The core components of batteries generally include positive electrodes, negative electrodes, separators, and electrolytes. The separator can isolate the positive and negative electrodes, preventing the electrons in the battery from passing freely, while allowing the ions in the electrolyte to pass freely between the positive and negative electrodes, which has an important impact on the battery performance. Therefore, it is necessary to continuously research and develop new separators. Summary of the invention

[0003] The present invention aims to provide a diaphragm, which can help a battery produce a solid electrolyte interface (SEI) film rich in LiF, and the diaphragm has good heat resistance and can improve the storage performance and cycle performance of a lithium battery.

[0004] In a first aspect of the present invention, a diaphragm is provided, the diaphragm comprises a base film and a coating, the coating comprises a fluorine-containing polymer, the general formula of the polymer is shown in Formula I:

[0005]

[0006] Where n is an integer, ranging from 50 to 1000;

[0007] At least one of X1, X2 and X3 is F; R is polyepoxy or substituted polyepoxy;

[0008] The structure of polyepoxy vinyl is shown in Formula II:

[0009] -CH 2 -[-CH 2 -O-]- m (Formula II),

[0010] Wherein, m is an integer ranging from 1 to 40.

[0011] When the diaphragm is used in a battery, it can help the battery produce a LiF-rich SEI film. The fluorine-containing polymer itself has good thermal stability, and its decomposition temperature at high temperature is 250°C, which can improve the thermal stability of the diaphragm.

[0012] In some embodiments, n is in the range of 100 to 500. In some embodiments, m is in the range of 5 to 20. Controlling the chain length of the fluorinated polymer and the poly(ethylene oxide) group within a suitable range can increase the mobility of lithium ions in the lithium battery, thereby improving its storage performance and kinetic performance.

[0013] In some embodiments, X1, X2 and X3 are all F. The increase in the degree of fluorination of the polymer monomer can promote the formation of a LiF-rich SEI film.

[0014] In some embodiments, the substituted poly(ethylene oxide) group is a poly(ethylene oxide) group substituted with a halogen element.

[0015] In some embodiments, the substituted polyoxyethylene groups are polyoxyethylene groups substituted with one or more functional groups selected from -OH, -COOH, and -NH2.

[0016] In some embodiments, the mass proportion of the polymer in the coating is 2%-8%. In some embodiments, further, the mass proportion of the polymer in the coating is 3%-5%. Controlling the mass proportion of the polymer in the coating can further improve the cycle performance and high temperature storage performance of the battery.

[0017] A second aspect of the present invention provides a battery.

[0018] In some embodiments, the battery includes the above-described separator.

[0019] According to a third aspect of the present invention, an electrical device is provided.

[0020] In some embodiments, the electrical device includes the battery described above.

[0021] The present invention provides a diaphragm containing a fluorine-containing polymer, wherein the fluorine-containing polymer has good thermal stability and can help the battery to generate a LiF-rich SEI film, thereby improving the cycle performance and high-temperature storage performance of the battery. DETAILED DESCRIPTION

[0022] In order to make the technical solution of the present application clearer and easier to understand, the specific implementation methods of the present application are described in detail below, but unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of actually the same structure may be omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the following description is provided for those skilled in the art to fully understand the present application and is not intended to limit the subject matter described in the claims.

[0023] If not otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution. If not otherwise specified, the "includes", "comprising", "having" and any variations thereof mentioned in the present application are intended to cover non-exclusive inclusions. For example, the "includes" and "comprising" may mean that other components not listed may also be included or contained, or only the listed components may be included or contained.

[0024] If not specifically stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0025] If not otherwise specified, in this application, the terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. If not otherwise specified, in this application, the term "multiple" refers to more than two (including two), similarly, "multiple groups" refers to more than two (including two), and "multiple pieces" refers to more than two (including two).

[0026] Unless otherwise specified, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or position relationship are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the embodiments of the present application.

[0027] The "range" disclosed in this application is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of the particular range. The range defined in this way can be inclusive or exclusive of the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. In this application, unless otherwise specified, the numerical range "ab" represents any real number between a and b, and abbreviations of their combinations, where a and b are both real numbers. For example, 2%-8% means that any real number between 2% and 8% has been disclosed, as well as any combination therebetween.

[0028] For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to specific circumstances.

[0029] The embodiments of the present application provide a diaphragm containing a fluorine-containing polymer. A battery using the diaphragm can improve high-temperature storage performance and dynamic performance.

[0030] [Isolation film]

[0031] In some embodiments, the secondary battery further includes a separator. The separator includes a coating and a base film. The present application has no particular restrictions on the type of the separator base film, and any known porous base film with good chemical stability and mechanical stability can be selected.

[0032] In some embodiments, the material of the base film can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The base film can be a single-layer film or a multi-layer composite film, without particular limitation. When the base film is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0033] The general structural formula of the polymer in the coating is shown in Formula I:

[0034]

[0035] The prepared fluorine-containing polymer is a polymer in which X1, X2 and X3 are all F, the chain length n of the polymer main body is 50, R is an unsubstituted polyvinyl epoxy group, and the chain length m of the polyvinyl epoxy group is 17.

[0036] Preparation of the polymer: under a nitrogen atmosphere at -40°C, diethylene glycol methyl vinyl ether and trifluorochloroethylene (molar ratio of 3:2) are added to anhydrous ether. Azobisisobutyronitrile is added to the above solution (the mass ratio of the catalyst to the original solution is 2:100). The solution is deoxygenated by freezing-pumping-heating and thawing three times. After deoxygenation, photocatalysis is carried out under a 30W ultraviolet lamp. The chain length of the polymer is controlled by gel permeation chromatography (GPC). The photocatalyzed solution is cooled and concentrated under vacuum to obtain a concentrate. The concentrate is dissolved in chloroform and added dropwise to anhydrous ether under stirring, filtered and vacuum dried to obtain the product. The product is a polymer in which X1, X2, and X3 are all F, the polymer chain length n is 50, R is an unsubstituted polyepoxy vinyl group, and the polyepoxy vinyl chain length m is 17.

[0037] Preparation of diaphragm: The preparation of diaphragm can adopt conventional methods in the art. For example, 84% polyvinylidene fluoride, 12% polyacrylonitrile, and 4% of the above fluorine-containing polymer are dissolved in deionized water at 25°C, with a solid content of 15%. The base film is a 12um PP isolation film. The above materials are sprayed on the surface of the base film.

[0038] [Positive electrode]

[0039] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer includes a positive electrode active material.

[0040] As a non-limiting example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode active material layer is coated on any one or both of the two opposite surfaces of the positive electrode current collector.

[0041] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. 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 base layer. The composite current collector may be obtained by forming a metal material on a polymer material substrate. In the positive electrode current collector, non-limiting examples of the metal material may include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. In the positive electrode current collector, non-limiting examples of the polymer material substrate may include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0042] In some embodiments, the positive electrode active material may adopt a positive electrode active material for a battery known in the art. As a non-limiting example, the positive electrode active material may include one or more of the following materials: a lithium-containing phosphate with an olivine structure, a lithium transition metal oxide, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, examples of lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxide (such as LiCoO2), lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their modified compounds. Non-limiting examples of lithium-containing phosphates with an olivine structure may include, but are not limited to, one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon. Non-limiting examples of lithium cobalt oxides may include LiCoO2; non-limiting examples of lithium nickel oxides may include LiNiO2; non-limiting examples of lithium manganese oxides may include LiMnO2, LiMn2O4, etc.; non-limiting examples of lithium nickel cobalt manganese oxides may include LiNi1 / 3Co1 / 3Mn1 / 3O2 (also referred to as NCM333), LiNi0.5Co0.2Mn0.3O2 (also referred to as NCM523), LiNi0.5Co0.25Mn0.25O2 (also referred to as NCM211), LiNi0.6Co0.2Mn0.2O2 (also referred to as NCM622), LiNi0.8Co0.1Mn0.1O2 (also referred to as NCM811), etc. Non-limiting examples of lithium nickel cobalt aluminum oxides may include LiNi0.85Co0.15Al0.05O2. New materials obtained by appropriate modification of the listed positive electrode active materials also fall within the scope of positive electrode active materials. The aforementioned appropriate modification refers to acceptable modification methods for positive electrode active materials, and a non-limiting example is coating modification.

[0043] In some embodiments, the positive electrode active material layer may also optionally include a binder. As a non-limiting example, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0044] In some embodiments, the positive electrode active material layer may further optionally include a conductive agent. As non-limiting examples, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0045] In some embodiments, the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent to form a positive electrode slurry; the positive electrode slurry is coated on at least one side of the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained. The surface of the positive electrode collector coated with the positive electrode slurry can be on a single surface of the positive electrode collector or on both surfaces of the positive electrode collector. The surface of the positive electrode collector coated with the positive electrode slurry can be on a single surface of the positive electrode collector or on both surfaces of the positive electrode collector.

[0046] [Negative electrode]

[0047] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

[0048] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

[0049] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, 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 a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0050] In some embodiments, the negative electrode active material may adopt the negative electrode active material for the battery known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0051] In some embodiments, the negative electrode film layer may further include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).

[0052] In some embodiments, the negative electrode film layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0053] In some embodiments, the negative electrode film layer may further include other additives, such as a thickener. Optionally, the thickener may be sodium carboxymethyl cellulose.

[0054] In some embodiments, the negative electrode sheet can be prepared by the following method: the above components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder, etc. are dispersed in a solvent to form a negative electrode slurry. Optionally, the solvent can be deionized water; the negative electrode slurry is coated on the negative electrode collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0055] [Electrolyte]

[0056] The electrolyte plays the role of conducting ions between the positive electrode plate and the negative electrode plate. In some embodiments of the present application, the electrolyte includes an electrolyte salt and a solvent. In some embodiments, 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 difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate and lithium tetrafluorooxalatophosphate.

[0057] In some embodiments, the solvent 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.

[0058] In some embodiments, the electrolyte may further include additives. Optionally, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.

[0059] [Secondary battery]

[0060] Some embodiments of the present application provide a secondary battery. The secondary battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator. During the battery charge and discharge process, active ions are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays the role of conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is arranged between the positive electrode sheet and the negative electrode sheet, mainly playing the role of preventing the positive and negative electrodes from short-circuiting, while allowing ions to pass through. The secondary battery of some embodiments of the present application can be assembled using the following method.

[0061] Positive electrode sheet: The positive electrode active materials lithium iron phosphate, polyvinylidene fluoride (PVDF), conductive carbon black (SP), and carbon nanotubes (CNT) are dissolved in N-methylpyrrolidone (NMP) in a weight ratio of 94%: 2.5%: 3%: 0.5%, coated on aluminum foil, and then dried, rolled, and cut into positive electrode sheets.

[0062] Negative electrode sheet: add graphite, conductive carbon black (Super P), carbon nanotubes (CNT), styrene-butadiene rubber (SBR), and sodium carboxymethyl cellulose (CMC Na) in a weight ratio of 95%: 1.2%: 0.5%: 2.1%: 1.2% into deionized water and stir evenly to prepare a negative electrode slurry. Evenly coat the prepared negative electrode slurry on the carbon-coated copper foil of the negative electrode current collector, and prepare a negative electrode sheet after drying and rolling.

[0063] Electrolyte: The lithium salt used is lithium hexafluorophosphate (LiPF6), and the solution is prepared with a concentration of 1 M. The solvent is a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) in a weight ratio of 1:1:1.

[0064] Battery assembly: The prepared negative electrode sheet, positive electrode sheet and separator are stacked, and the battery is made through processes such as winding, packaging, liquid injection and formation.

[0065] The present application also provides an electrical device, which includes a secondary battery provided by the present application. The secondary battery can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device can include mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, etc. Among them, the mobile device can be a mobile phone, a laptop computer, etc.; the electric vehicle can be a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric truck, etc.

[0066] [Storage performance test]

[0067] The storage performance of the battery can be characterized by the capacity retention rate after being stored at a certain temperature for a certain period of time. The capacity retention rate can be measured through a 60°C storage test. Specifically, in a 25°C environment, in the 2.0V-4.2V voltage range, the battery is charged at a 1C constant current, and the first capacity is calibrated after full charge. Then, after being stored in an environment of 60±2°C for 90 days, the capacity is calibrated again, and the ratio of the capacity to the first capacity is the capacity retention rate.

[0068] [Cyclic performance test]

[0069] The cycle performance of the battery can be characterized by the capacity retention rate after a certain number of cycles. For example, the capacity retention rate of 800 cycles at 25°C is tested. Specifically, the battery charge and discharge voltage range is 2.0V-4.2V. When charging, the battery is charged to 4.2V at a 3C constant current, and then charged to 0.05C at a constant voltage. When discharging, the battery is discharged to 2.0V at a 3C constant current. The first discharge capacity is marked as C1, and the next discharge after charging is recorded as C2, and so on. The 800th discharge capacity is recorded as C800. The capacity retention rate of 800 cycles is C800 / C1*100%.

[0070] [Discharge resistance detection]

[0071] Discharge resistance (Direct Current Resistance, DCR) can characterize the dynamic performance of the battery. Discharge resistance is also called battery internal resistance. The smaller the battery internal resistance, the better the dynamic performance of the battery. Optionally, a 10s discharge resistance (Direct Current Resistance, DCR) test is performed at 25°C. The battery's charge and discharge voltage range is 2.0V-4.2V. Fully charge the battery using the 1C constant current charging method, adjust its state of charge (State of Charge, SOC) to 50%, then place it at -10°C for 12h, discharge it at 10C for 10s, and record the discharge resistance.

[0072] [Material Detection]

[0073] The molecular weight of the polymer was detected by gel permeation chromatography (GPC), and the polymer chain length n and m were detected. The battery separator coating material was dissolved in deuterated chloroform CDCl3, and characterized by nuclear magnetic resonance (NMR) for 1H and 19F, and the peak position and peak height in the H spectrum and F spectrum were determined to confirm the type and content of the polymer.

[0074] The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If the technology, method or condition is not specifically indicated in the specification, it shall be carried out according to the technology or condition described in the literature in this field or according to the product specification. The reagents or instruments used are conventional products that can be obtained commercially if they are not specifically indicated.

[0075] Example

[0076] Example 1

[0077] Polymer synthesis: The synthesis was carried out according to the synthesis method in the above specific embodiment.

[0078] Diaphragm: prepared according to the preparation method in the above specific embodiment.

[0079] Secondary battery: According to the operation method in the above specific embodiment, prepare the positive electrode, the negative electrode, the electrolyte, and assemble the secondary battery.

[0080] Examples 2 to 5, Comparative Example 1 and Comparative Example 2 are basically the same as Example 1, except that the length n of the chain segments of the polymer main body is different, and the others are the same. See the table below for details.

[0081] Examples 6 to 10 are basically the same as Example 3, except that the value of the polyoxyethylene chain length m in the polymer is different, and the others are the same. See the table below for details.

[0082] Embodiments 11 to 13 are basically the same as Embodiment 3, except that the number of fluorine atoms in the polymer main body is different, and the others are the same.

[0083] Examples 14 to 17 are basically the same as Example 3, except that the polyoxyethylene groups in the polymer are substituted differently, and the rest are the same. See the table below for details.

[0084] Examples 18 to 22 are basically the same as Example 3, except that the mass percentage of the polymer in the coating is different, and the others are the same. See the table below for details.

[0085] Table 1 Specific experimental parameters and performance of secondary batteries of Examples 1-22 and Comparative Examples 1-3

[0086]

[0087]

[0088] The present invention provides a diaphragm, wherein the diaphragm coating material contains the polymer provided by the present invention, the chain length n of the polymer main body is in the range of 50-1000; at least one of X1, X2 and X3 is F; R is polyepoxyethylene or substituted polyepoxyethylene; the chain length m of the polyepoxyethylene is in the range of 1-40. When the diaphragm is used in a battery, it can help the battery to produce a LiF-rich SEI film, and the fluorine-containing polymer itself has good thermal stability, and the temperature at which it starts to decompose at high temperature is 250°C, which can improve the thermal stability of the diaphragm.

[0089] Examples 1 to 5, Comparative Examples 1 and 2, can illustrate that when the segment length n of the fluorine-containing polymer body in the diaphragm coating is in the range of 50-1000, which can be selected as 50-500, 50-200, 50-100, 200-500 or 250-500, the corresponding battery has good cycle performance and high temperature storage performance.

[0090] Examples 6 to 10 illustrate that when the segment length m of the polyoxyethylene group in the polymer is in the range of 1-40, and can be selected in the range of 1-20, 1-17, 1-5, 5-17 or 17-40, the corresponding battery has good cycle performance and high temperature storage performance.

[0091] Examples 11 to 13 illustrate that as the proportion of fluorine in the polymer monomer increases, when X1, X2 and X3 are all F, the battery containing the fluorine-containing polymer separator has better storage performance and cycle performance.

[0092] Examples 14 to 17 illustrate that after the poly(ethylene oxide) groups in the polymer are replaced with different functional groups, the performance of the battery containing the polymer is roughly the same as that before the replacement, with a storage capacity retention rate between 89.3% and 94%, and a cycle capacity retention rate between 94.5% and 97%.

[0093] Examples 18 to 22 illustrate that when the mass proportion of the fluorine-containing polymer in the coating is controlled in the range of 2%-8%, which can be optionally in the range of 2%-5%, 2%-4% or 3%-5%, the battery can have good storage capacity retention rate and cycle capacity retention rate.

[0094] The present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and the same effect as the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A diaphragm, It is characterized in that It includes a base film and a coating; the coating includes a fluorine-containing polymer, and the general formula of the fluorine-containing polymer is shown in Formula I: Where n is an integer, ranging from 50 to 1000; At least one of X1, X2 and X3 is F; R is polyepoxy or substituted polyepoxy; The structure of the polyepoxy vinyl group is shown in Formula II: -CH 2 -[-CH 2 -O-]- m (Formula II), Wherein, m is an integer ranging from 1 to 40.

2. The diaphragm according to claim 1, It is characterized in that The value range of n is: 100-500.

3. The diaphragm according to any one of claims 1 to 2, It is characterized in that The value range of m is: 5-20.

4. The diaphragm according to any one of claims 1 to 3, It is characterized in that Said X1, X2 and X3 are all F.

5. The diaphragm according to any one of claims 1 to 4, It is characterized in that The substituted polyepoxy vinyl group is a polyepoxy vinyl group substituted with a halogen element.

6. The diaphragm according to any one of claims 1 to 5, It is characterized in that The substituted polyepoxyethylene group is a polyepoxyethylene group substituted with -OH, -COOH or -NH2.

7. The diaphragm according to any one of claims 1 to 6, It is characterized in that The mass percentage of the fluorine-containing polymer in the coating is 2%-8%, and can be optionally 3%-5%.

8. A battery, It is characterized in that The diaphragm comprises the diaphragm according to any one of claims 1 to 7.

9. An electrical device, It is characterized in that Comprising the battery as claimed in claim 8.

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