Solid electrolyte membrane and preparation method, lithium ion battery

Abstract

This application discloses a solid electrolyte membrane, a method for preparing the same, and a lithium-ion battery, relating to the field of battery technology. In an embodiment of the present application, a polymer membrane is provided on at least one side of the electrolyte membrane body, and the polymer membrane includes poly(vinylidene fluoride-chlorotrifluoroethylene) and a lithium salt dispersed in the poly(vinylidene fluoride-chlorotrifluoroethylene), with a mass ratio of poly(vinylidene fluoride-chlorotrifluoroethylene) to lithium salt of (0.5 to 2):(0.5 to 2), thereby enabling a battery having the solid electrolyte membrane of the embodiment of the present application to have low impedance, high ionic conductivity, and high cycling performance.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a solid electrolyte membrane and a preparation method thereof, and a lithium-ion battery. Background Art

[0002] Lithium-ion batteries, with their long cycle life and high energy density, have become one of the most important energy storage devices in our daily lives. In recent years, the rapid development of electric vehicles has placed higher demands on battery energy density and safety. All-solid-state lithium metal batteries replace flammable liquid electrolytes with solid electrolytes and use lithium metal, which has a higher theoretical specific capacity, as the negative electrode. These batteries offer advantages such as high safety and high energy density, making research on them of great significance.

[0003] In the field of all-solid-state batteries, the interfacial contact between the electrolyte and the lithium anode has long been a concern. This loose contact can lead to a series of serious consequences, one of which is the accelerated growth of lithium dendrites. The appearance of lithium dendrites can further damage the electrolyte membrane and even cause a short circuit between the positive and negative electrodes, ultimately resulting in poor battery cycling performance and even a short circuit, posing a serious safety hazard. Summary of the Invention

[0004] In view of this, the first aspect of the present application provides a solid electrolyte membrane, which includes a stacked electrolyte membrane body and a polymer membrane arranged on at least one side of the electrolyte membrane body; wherein the polymer membrane includes poly(vinylidene fluoride-chlorotrifluoroethylene) and lithium salt dispersed in the poly(vinylidene fluoride-chlorotrifluoroethylene), and the mass ratio of poly(vinylidene fluoride-chlorotrifluoroethylene):lithium salt is (0.5 to 2):(0.5 to 2).

[0005] In some embodiments of the present application, the polymer film is bonded to the electrolyte membrane body via the poly(vinylidene fluoride-chlorotrifluoroethylene); and / or

[0006] The polymer film further comprises a solvent; and / or

[0007] The electrolyte membrane body is an alkaline membrane; and / or

[0008] The polymer membrane also includes an ionic liquid, and the mass ratio of the poly(vinylidene fluoride-chlorotrifluoroethylene): the lithium salt: the ionic liquid is (0.5 to 2): (0.5 to 2): (0.5 to 2.5).

[0009] In some embodiments of the present application, the poly (vinylidene fluoride - chlorotrifluoroethylene) : the lithium salt : the ionic liquid is (0.9 to 1.1): (0.9 to 1.1): (0.9 to 2.5); and / or

[0010] The mass content of the solvent in the polymer film is 5% to 10%.

[0011] In some embodiments of the present application, the polymer membrane and the electrolyte membrane body form an integral structure.

[0012] In some embodiments of the present application, the solvent is an organic solvent.

[0013] In some embodiments of the present application, the thickness of the polymer film is 5 μm to 10 μm.

[0014] In some embodiments of the present application, the lithium salt is selected from LiCl, LiBr, LiI, LiFSI, LiBF4, LiClO4, LiAlO4, LiAlCl4, LiPF6, LiSbF6, LiAsF6, LiB 10 Cl 10 , one or more of LiBOB, LiCF3SO3, LiTFSI, LiCH3SO3, LiCF3CO2, LiCH3CO2 and LiBETI.

[0015] In some embodiments of the present application, the ionic liquid comprises an organic cation and an organic or inorganic anion; the organic cation includes at least one of a pyridinium cation, a piperidinium cation, a pyrrolidinium cation, a cation having a pyrroline skeleton, a cation having a pyrrole skeleton, an imidazolium cation, a tetrahydropyrimidinium cation, a dihydropyrimidinium cation, a pyrazolium cation, a pyrazolinium cation, a tetraalkylammonium cation, a trialkylsulfonium cation or a tetraalkylonium cation; and / or

[0016] The organic or inorganic anions include F - 、Cl - Br - , I - 、NO3 - 、(CN)2N - 、BF4 - 、ClO4 - 、RSO3 - RCOO - PF6 - 、(CF3)2PF4 - 、(CF3)3PF3 - 、(CF3)4PF2 - 、(CF3)5PF - 、(CF3)6P - 、(C2F5SO2)2N - 、(CF3SO3)2N -、(CF3SO2)(CF3CO)N - CF3CF2(CF3)2CO - 、(CF3SO2)2CH - 、(SF5)3C - 、(CF3SO2)3C - CF3(CF2)7SO3 - CF3COO - 、C3F7COO - CF3SO3 - 、C4F9SO3 - At least one of .

[0017] A second aspect of the present application provides a method for preparing a solid electrolyte membrane, which is used to prepare the solid electrolyte membrane. The method comprises the following steps:

[0018] A mixed solution is provided, wherein the mixed solution includes poly(vinylidene fluoride-chlorotrifluoroethylene), a lithium salt, and a solvent. Exemplarily, the mixed solution is prepared by dissolving the poly(vinylidene fluoride-chlorotrifluoroethylene) and the lithium salt in the solvent.

[0019] coating the mixed solution on a substrate;

[0020] After removing part of the solvent, a polymer film is obtained;

[0021] The polymer membrane is stacked on at least one side of the electrolyte membrane body. For example, the electrolyte membrane body is laid on the polymer membrane, and a solid electrolyte membrane is obtained by heat treatment.

[0022] In some embodiments of the present application, the heat treatment includes: maintaining the temperature in an oven at 40°C to 70°C for 2 to 10 hours. For example, a substrate (e.g., a glass substrate) containing the electrolyte membrane body is placed in an oven and maintained at 40°C to 70°C for 2 to 10 hours.

[0023] In the step of removing part of the solvent to obtain the polymer film, part of the solvent is removed by heating, and the mass percentage of the solvent in the polymer film obtained after removing part of the solvent is 40% to 60%.

[0024] In the step of obtaining a solid electrolyte membrane by heat treatment, the mass percentage of the solvent in the polymer membrane in the solid electrolyte membrane is 5% to 10%, that is, after the heat treatment, the mass percentage of the solvent in the polymer membrane to the mass percentage of the polymer membrane is 5% to 10%.

[0025] The step of providing a mixed solution comprises: adding an ionic liquid and a lithium salt into a solvent, and mixing and stirring the mixture to obtain a mixed solution.

[0026] In some embodiments of the present application, the coating has a thickness of 5 μm to 10 μm; and / or

[0027] The lithium salt is selected from LiCl, LiBr, LiI, LiFSI, LiBF4, LiClO4, LiAlO4, LiAlCl4, LiPF6, LiSbF6, LiAsF6, LiB 10 Cl 10 , LiBOB (LiB (C2O4) 2), LiCF3SO3, LiTFSI (LiN (SO2CF3) 2), LiCH3SO3, LiCF3CO2, LiCH3CO2 and LiBETI (LiN (SO2CF2CF3) 2) one or more; and / or

[0028] The ionic liquid comprises an organic cation and an organic or inorganic anion; the organic cation may include at least one of a pyridinium cation, a piperidinium cation, a pyrrolidinium cation, a cation having a pyrroline skeleton, a cation having a pyrrole skeleton, an imidazolium cation, a tetrahydropyrimidinium cation, a dihydropyrimidinium cation, a pyrazolium cation, a pyrazolinium cation, a tetraalkylammonium cation, a trialkylsulfonium cation or a tetraalkylonium cation; and / or

[0029] The organic or inorganic anion may include F - 、Cl - Br - , I - 、NO3 - 、(CN)2N - 、BF4 - 、ClO4 - 、RSO3 - RCOO - PF6 - 、(CF3)2PF4 - 、(CF3)3PF3 - 、(CF3)4PF2 - 、(CF3)5PF - 、(CF3)6P - 、(C2F5SO2)2N - 、(CF3SO3)2N - 、(CF3SO2)(CF3CO)N - CF3CF2(CF3)2CO - 、(CF3SO2)2CH - 、(SF5)3C - 、(CF3SO2)3C - CF3(CF2)7SO3 -CF3COO - 、C3F7COO - CF3SO3 - 、C4F9SO3 - At least one of;

[0030] The mass ratio of the poly(vinylidene fluoride-chlorotrifluoroethylene) to the mixed solution is 10% to 20%; and / or

[0031] The mass ratio of the solvent to the mixed solution is 40% to 60%.

[0032] A third aspect of the present application provides a lithium-ion battery, which includes a positive electrode, a negative electrode, and the solid electrolyte membrane or the solid electrolyte membrane obtained by the preparation method.

[0033] Beneficial effects:

[0034] In an embodiment of the present application, a polymer membrane is arranged on at least one side of the electrolyte membrane body. The polymer membrane includes poly(vinylidene fluoride-chlorotrifluoroethylene) and a lithium salt dispersed in the poly(vinylidene fluoride-chlorotrifluoroethylene). Calculated by mass ratio, the poly(vinylidene fluoride-chlorotrifluoroethylene): lithium salt is (0.5 to 2): (0.5 to 2), so that the battery having the solid electrolyte membrane in the embodiment of the present application has lower impedance and higher ionic conductivity, and the battery having the solid electrolyte membrane has higher cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0036] Figure 1 This is an electron microscope image of a cross section of the solid electrolyte membrane obtained in Example 1 of the present application at 1000 times magnification;

[0037] Figure 2 This is an electron microscope image of a cross section of the solid electrolyte membrane obtained in Example 1 of the present application, magnified 2000 times;

[0038] Figure 3 This is an impedance test diagram of a battery assembled with the solid electrolyte membrane obtained in Example 1 of the present application;

[0039] Figure 4 This is an impedance test diagram of a battery assembled with the solid electrolyte membrane obtained in Comparative Example 4 of the present application. DETAILED DESCRIPTION

[0040] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of this application. In addition, it should be understood that the specific embodiments described herein are only used to illustrate and explain the present application and are not used to limit the present application.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used herein in the specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0042] In this application, unless otherwise indicated, directional terms such as "upper" and "lower" generally refer to the upper and lower positions of a device in actual use or operation, specifically in the drawing directions of the accompanying drawings; whereas "inner" and "outer" refer to the outline of the device. Furthermore, in the description of this application, the term "including" means "including but not limited to." Terms such as first, second, and third are used merely as labels and do not impose numerical requirements or establish a sequence.

[0043] In this application, "and / or" describes the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural.

[0044] In this application, "at least one" means one or more, and "plurality" means two or more. "One or more," "at least one of the following," or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c" or "at least one of a, b, and c" can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can each be single or plural.

[0045] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity and should not be understood as a hard limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numbers within the range. For example, the description of a range from 1 to 6 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which applies regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0046] Lithium-ion batteries, with their long cycle life and high energy density, have become one of the most important energy storage devices in our daily lives. In recent years, the rapid development of electric vehicles has placed higher demands on battery energy density and safety. All-solid-state lithium metal batteries replace flammable liquid electrolytes with solid electrolytes and use lithium metal, which has a higher theoretical specific capacity, as the negative electrode. These batteries offer advantages such as high safety and high energy density, making research on them of great significance.

[0047] In the field of all-solid-state batteries, the interfacial contact between the electrolyte and the lithium anode has long been a concern. This loose contact can lead to a series of serious consequences, one of which is the accelerated growth of lithium dendrites. The appearance of lithium dendrites can further damage the electrolyte membrane and even cause a short circuit between the positive and negative electrodes, ultimately resulting in poor battery cycling performance and even a short circuit, posing a serious safety hazard.

[0048] In view of this, a first aspect of an embodiment of the present application provides a solid electrolyte membrane, which includes a stacked electrolyte membrane body and a polymer membrane, and the polymer membrane is arranged on at least one side of the electrolyte membrane body; wherein the polymer membrane includes poly(vinylidene fluoride-chlorotrifluoroethylene) and a lithium salt dispersed in the poly(vinylidene fluoride-chlorotrifluoroethylene), and the mass ratio of poly(vinylidene fluoride-chlorotrifluoroethylene): lithium salt is (0.5 to 2): (0.5 to 2).

[0049] In an embodiment of the present application, a polymer membrane is arranged on at least one side of the electrolyte membrane body, and the polymer membrane includes poly(vinylidene fluoride-chlorotrifluoroethylene) and a lithium salt dispersed in the poly(vinylidene fluoride-chlorotrifluoroethylene). The mass ratio of poly(vinylidene fluoride-chlorotrifluoroethylene): lithium salt is (0.5 to 2): (0.5 to 2), so that the battery having the solid electrolyte membrane in the embodiment of the present application has lower impedance and cycle performance.

[0050] When the solid electrolyte membrane in the embodiment of the present application is used in a lithium metal battery, the polymer membrane can be disposed between the electrolyte membrane body and the lithium negative electrode. The polymer can enhance the contact between the electrolyte membrane body and the lithium negative electrode, making them closer, thereby effectively reducing the possibility of lithium dendrite growth. At the same time, this polymer membrane can also prevent the formation of lithium dendrites, thereby helping to form a stable and good solid electrolyte interface layer (SEI), thereby improving the safety of the battery. The polymer membrane includes a certain amount of lithium salt, so that the battery with the solid electrolyte membrane in the embodiment of the present application has low impedance and cycle performance.

[0051] In addition, the polymer film includes poly(vinylidene fluoride-chlorotrifluoroethylene), so that the polymer film has excellent chemical corrosion resistance and wear resistance.

[0052] For example, the raw materials for preparing the polymer film may contain 0.5 parts, 1 parts, 1.5 parts, and 2 parts of poly(vinylidene fluoride-chlorotrifluoroethylene) by weight. Correspondingly, the raw materials for preparing the polymer film may contain 0.5 parts, 1 parts, 1.5 parts, and 2 parts of lithium salt.

[0053] In some embodiments of the present application, the molecular weight of poly(vinylidene fluoride-chlorotrifluoroethylene) is 400,000 to 500,000. Exemplarily, the molecular weight of the poly(vinylidene fluoride-chlorotrifluoroethylene) is about 450,000.

[0054] In some embodiments of the present application, the mass content of vinylidene fluoride in poly(vinylidene fluoride-chlorotrifluoroethylene) is 75% to 85%, and the mass content of chlorotrifluoroethylene is 15% to 25%. For example, the mass content of vinylidene fluoride in poly(vinylidene fluoride-chlorotrifluoroethylene) is about 80%, and the mass content of chlorotrifluoroethylene is about 20%.

[0055] In some embodiments of the present application, the polymer membrane is bonded to the electrolyte membrane body via the poly(vinylidene fluoride-chlorotrifluoroethylene). This can also be understood as the polymer membrane being bonded to the electrolyte membrane body via its own adhesion. Furthermore, the polymer membrane is bonded to the electrolyte membrane body via the poly(vinylidene fluoride-chlorotrifluoroethylene) to form an integral structure.

[0056] Exemplarily, the polymer film further includes a solvent, which can also be understood as the polymer film being a wet film. It should be noted that a wet polymer film refers to a film containing a certain solvent. The wet polymer film is relatively soft and has strong adhesion properties, and can adhere to the electrolyte membrane body through its own adhesion. Exemplarily, the mass content of the solvent in the polymer film is 5% to 10%. For example, the mass content of the solvent in the polymer film is 5%, 6%, 7%, 8%, 9%, 10%, or a range between any two of the above values.

[0057] Specifically, a polymer wet film with a relatively high solvent content can be prepared first, then laid on the electrolyte membrane body, and then the solvent in the wet film can be partially removed to obtain a polymer membrane. In this way, the polymer wet film with a relatively high solvent content can be reacted in situ on the electrolyte membrane body to form a polymer membrane, thereby achieving better bonding between the electrolyte membrane body and the polymer membrane interface and a tighter interface connection. This is conducive to further ensuring that the battery with the solid electrolyte membrane in the embodiment of the present application has lower impedance and cycle performance.

[0058] Furthermore, the polymer membrane and the electrolyte membrane body form an integral structure. For example, the polymer membrane is formed in situ on the electrolyte membrane body, thereby forming an integral structure. This facilitates further lowering impedance and cycling performance of batteries incorporating the solid electrolyte membrane of the present embodiment.

[0059] Furthermore, the polymer film has a thickness of 5 μm to 10 μm. Exemplarily, the polymer film has a thickness of 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, or any range between any two of the aforementioned values. It should be noted that if the polymer film thickness is too low, for example, less than 5 μm, it can make it difficult to remove the wet film from the previous steps of polymer film preparation, leading to greater process complexity. If the thickness is too high, for example, greater than 10 μm, it can easily lead to an increased volume of the solid electrolyte membrane.

[0060] Specifically, the solvent in the polymer film can be an organic solvent such as DMF, NMP, TFE, acetone, etc.

[0061] In some embodiments of the present application, the electrolyte membrane is an alkaline membrane. Exemplarily, the electrolyte membrane is composed of LLZO (lithium lanthanum zirconium oxide) and PTFE (polytetrafluoroethylene). By mass, LLZO accounts for 80%-99.9% of the electrolyte membrane, and PTFE accounts for 20%-0.01% of the electrolyte membrane. It should be noted that the electrolyte membrane is an alkaline membrane. Poly(vinylidene fluoride-chlorotrifluoroethylene) undergoes a defluorination reaction in an alkaline environment, thereby increasing the adhesion of the polymer membrane and the bonding between the polymer membrane and the electrolyte membrane. This further improves the ionic conductivity of the solid electrolyte membrane and the performance of batteries incorporating the solid electrolyte membrane.

[0062] In some embodiments of the present application, the side of the electrolyte membrane body bonded to the polymer membrane has a plurality of micropores.

[0063] Furthermore, the porosity of the electrolyte membrane body is 3% to 5%. For example, the porosity of the electrolyte membrane body is 3%, 3.5%, 4%, 4.5%, 5%, or a range between any two of the above values.

[0064] In some embodiments of the present application, the raw materials for preparing the polymer membrane also include an ionic liquid. The weight ratio of poly(vinylidene fluoride-chlorotrifluoroethylene): lithium salt: ionic liquid is (0.5 to 2): (0.5 to 2): (0.5 to 2.5). Furthermore, the weight ratio of poly(vinylidene fluoride-chlorotrifluoroethylene): lithium salt: ionic liquid is (0.9 to 1.1): (0.9 to 1.1): (0.9 to 2.5). In this embodiment, adding a certain amount of ionic liquid to the polymer membrane further reduces the impedance of the battery and improves the cycle performance of the battery.

[0065] It should be noted that in the present application, adding lithium salt to the polymer membrane is beneficial to improving the ionic conductivity of the solid electrolyte membrane (or polymer membrane), and the specific type of lithium salt is not limited.

[0066] In some embodiments of the present application, the lithium salt is selected from LiCl, LiBr, LiI, LiFSI, LiBF4, LiClO4, LiAlO4, LiAlCl4, LiPF6, LiSbF6, LiAsF6, LiB 10 Cl 10 , LiBOB (LiB (C2O4) 2), LiCF3SO3, LiTFSI (LiN (SO2CF3) 2), LiCH3SO3, LiCF3CO2, LiCH3CO2 and LiBETI (LiN (SO2CF2CF3) 2) one or more.

[0067] Specifically, in some embodiments of the present application, the lithium salt is selected from lithium bis(fluorosulfonyl)imide (LiFSI). For another example, in other embodiments of the present application, the lithium salt is selected from lithium bis(trifluoromethanesulfonyl)imide (LiN(SO2CF3)2). For another example, in other embodiments of the present application, the lithium salt is selected from lithium perchlorate (LiClO4). For another example, in other embodiments of the present application, the lithium salt is selected from lithium bis(fluorosulfonyl)imide (LiFSI) and lithium perchlorate (LiClO4). It should be noted that compared with the lithium salt selected from lithium perchlorate (LiClO4), the lithium salt selected from lithium bis(fluorosulfonyl)imide (LiFSI) and / or lithium bis(trifluoromethanesulfonyl)imide (LiN(SO2CF3)2) has higher safety performance.

[0068] It should be noted that ionic liquids are compounds containing organic cations and organic or inorganic anions. In this application, the addition of ionic liquids to polymer membranes helps improve the stability and electrochemical performance of the solid electrolyte membrane, improves battery safety and cycle performance, and reduces battery impedance. There are no particular restrictions on the types of cations and anions contained in the ionic liquid.

[0069] For example, the cations contained in the ionic liquid may include at least one of a pyridinium cation, a piperidinium cation, a pyrrolidinium cation, a cation having a pyrroline skeleton, a cation having a pyrrole skeleton, an imidazolium cation, a tetrahydropyrimidinium cation, a dihydropyrimidinium cation, a pyrazolium cation, a pyrazolinium cation, a tetraalkylammonium cation, a trialkylsulfonium cation, or a tetraalkylonium cation.

[0070] The anions contained in the ionic liquid may include F - 、Cl - Br - , I - 、NO3 - 、(CN)2N - 、BF4 - 、ClO4 - 、RSO3 - (wherein R is an alkyl group having 1 to 9 carbon atoms or a phenyl group), RCOO - (wherein R is an alkyl group or a phenyl group having 1 to 9 carbon atoms), PF6 - 、(CF3)2PF4 - 、(CF3)3PF3 - 、(CF3)4PF2 - 、(CF3)5PF - 、(CF3)6P - 、(C2F5SO2)2N - 、(CF3SO3)2N - 、(CF3SO2)(CF3CO)N - CF3CF2(CF3)2CO - 、(CF3SO2)2CH - 、(SF5)3C - 、(CF3SO2)3C - CF3(CF2)7SO3 - CF3COO - 、C3F7COO - CF3SO3 - or C4F9SO3 - .

[0071] Specifically, the ionic liquid may include, but is not limited to, 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide, 1-methyl-1-propylpyrrolidinium bis(trifluorosulfonyl)imide, 1-butyl-2,3-dimethylimidazolium chloride (BMMImCl), Pyr13TFSI, and Pyr14TFSI.

[0072] In some embodiments of the present application, the electrolyte membrane body includes at least one of a doped or undoped LLZO oxide ceramic solid electrolyte, a doped or undoped sulfide solid electrolyte, and a doped or undoped halide solid electrolyte.

[0073] A second aspect of an embodiment of the present application provides a method for preparing a solid electrolyte membrane, comprising the following steps:

[0074] S10 provides a mixed solution; wherein the mixed solution includes poly(vinylidene fluoride-chlorotrifluoroethylene), a lithium salt, and a solvent, and the poly(vinylidene fluoride-chlorotrifluoroethylene) and the lithium salt are dissolved in the solvent.

[0075] Specifically, the ionic liquid and the lithium salt are added to the solvent, and mixed and stirred uniformly to obtain a mixed solution.

[0076] Exemplarily, the mass ratio of poly(vinylidene fluoride-chlorotrifluoroethylene) to the mixed solution is 10% to 20%. It is understood that if the mass ratio of poly(vinylidene fluoride-chlorotrifluoroethylene) to the mixed solution is too low, the solution system may not form a complete film during knife coating, or the film may be uneven, resulting in the film being difficult to peel off from the glass plate. If the mass ratio of poly(vinylidene fluoride-chlorotrifluoroethylene) to the mixed solution is too high, the poly(vinylidene fluoride-chlorotrifluoroethylene) may not be completely dissolved in the solvent.

[0077] It should be noted that the stirring speed and stirring time are not limited, and only need to allow the ionic liquid and lithium salt to be dissolved in the solvent. For example, the process can be carried out at room temperature.

[0078] S20: coating the mixed solution on a substrate, and removing part of the solvent to obtain a polymer wet film.

[0079] It should be noted that to avoid chemical reactions between the substrate and the wet polymer film and to facilitate separation of the polymer film from the substrate in subsequent processes, the substrate may be a glass substrate. Of course, in other embodiments of this application, the substrate may also be other substrates (e.g., a silicon substrate), without limitation. Unless otherwise specified, the following descriptions will use a glass substrate as an example.

[0080] Specifically, the mixed solution can be coated on a glass substrate by a coating machine, and then the glass substrate coated with the mixed solution is placed in an oven to remove part of the solvent to obtain a polymer wet film.

[0081] In some embodiments of the present application, the glass substrate coated with the mixed solution is placed in an oven and kept warm at a temperature of 50° C. to 80° C. for 2 to 30 minutes.

[0082] Exemplarily, the mass ratio of the solvent in the polymer wet film is 40% to 60%. It should be noted that if the mass ratio of the solvent is too low (e.g., below 40%), poor adhesion can occur, and the polymer wet film can easily separate from the electrolyte membrane during the subsequent heat treatment to remove some of the solvent. If the mass ratio of the solvent is too high (e.g., above 60%), the reaction between the polymer wet film and the electrolyte membrane can be too intense, affecting the subsequent overall performance of the membrane.

[0083] Specifically, the glass substrate coated with the mixed solution was placed in an oven at 60° C. for 5 minutes.

[0084] S30: laying the electrolyte membrane body on the polymer wet membrane, and obtaining a solid electrolyte membrane through heating treatment.

[0085] Specifically, after the heating treatment, the polymer wet film loses part of the solvent and forms a polymer membrane, and the electrolyte membrane body and the polymer membrane form an integrated structure.

[0086] In some embodiments of the present application, a substrate (e.g., a glass substrate) containing the electrolyte membrane is placed in an oven and maintained at a temperature of 50°C to 80°C for 2 to 10 hours. It should be noted that the mass percentage of the solvent in the polymer membrane obtained after this step is 5% to 10%. This allows the solvent to be primarily present in a complexed state in the polymer membrane, which is beneficial for further improving the performance of batteries containing the solid electrolyte membrane.

[0087] Specifically, the glass substrate coated with the mixed solution was placed in an oven at 60 degrees for 4 hours.

[0088] It should be noted that the solid electrolyte membrane prepared by the preparation process of the embodiment of the present application is beneficial to improving the contact area between the polymer membrane and the electrolyte membrane body and the bonding force at the interface, which is beneficial to avoiding the problem of loose contact between the polymer membrane and the solid electrolyte membrane body, so that the battery with the solid electrolyte membrane in the embodiment of the present application has lower impedance and cycle performance.

[0089] It should be noted that the solvent in this application is not limited, as long as it can dissolve poly(vinylidene fluoride-chlorotrifluoroethylene) and lithium salt and is easily removed after film formation. Exemplary solvents include but are not limited to N,N-dimethylformamide.

[0090] In some embodiments of the present application, the thickness of the polymer wet film is 5 μm to 10 μm.

[0091] In some embodiments of the present application, the polymer membrane further comprises an ionic liquid. The weight ratio of poly(vinylidene fluoride-chlorotrifluoroethylene): lithium salt: ionic liquid is (0.5 to 2): (0.5 to 2): (0.5 to 2.5). Furthermore, the weight ratio of poly(vinylidene fluoride-chlorotrifluoroethylene): lithium salt: ionic liquid is (0.9 to 1.1): (0.9 to 1.1): (0.9 to 2.5). In this embodiment, the addition of a certain amount of ionic liquid to the polymer membrane further reduces the impedance of the battery and improves the cycle performance of the battery.

[0092] It should be noted that in the present application, adding lithium salt to the polymer membrane is beneficial to improving the ionic conductivity of the solid electrolyte membrane, and the specific type of lithium salt is not limited.

[0093] In some embodiments of the present application, the lithium salt is selected from LiCl, LiBr, LiI, LiFSI, LiBF4, LiClO4, LiAlO4, LiAlCl4, LiPF6, LiSbF6, LiAsF6, LiB 10 Cl 10 , LiBOB (LiB (C2O4) 2), LiCF3SO3, LiTFSI (LiN (SO2CF3) 2), LiCH3SO3, LiCF3CO2, LiCH3CO2 and LiBETI (LiN (SO2CF2CF3) 2) one or more.

[0094] Specifically, in some embodiments of the present application, the lithium salt is selected from lithium bis(fluorosulfonyl)imide (LiFSI). For another example, in other embodiments of the present application, the lithium salt is selected from lithium bis(trifluoromethanesulfonyl)imide (LiN(SO2CF3)2). For another example, in other embodiments of the present application, the lithium salt is selected from lithium perchlorate (LiClO4). For another example, in other embodiments of the present application, the lithium salt is selected from lithium bis(fluorosulfonyl)imide (LiFSI) and lithium perchlorate (LiClO4). It should be noted that compared with the lithium salt selected from lithium perchlorate (LiClO4), the lithium salt selected from lithium bis(fluorosulfonyl)imide (LiFSI) and / or lithium bis(trifluoromethanesulfonyl)imide (LiN(SO2CF3)2) has higher safety performance.

[0095] It should be noted that ionic liquids are compounds containing organic cations and organic or inorganic anions. In this application, the addition of ionic liquids to polymer membranes is beneficial for improving the ionic conductivity of the solid electrolyte membrane, enhancing battery safety and cycle performance, and reducing battery impedance. There are no particular restrictions on the types of cations and anions contained in the ionic liquid.

[0096] For example, the cation contained in the ionic liquid may include a pyridinium cation, a piperidinium cation, a pyrrolidinium cation, a cation having a pyrroline skeleton, a cation having a pyrrole skeleton, an imidazolium cation, a tetrahydropyrimidinium cation, a dihydropyrimidinium cation, a pyrazolium cation, a pyrazolinium cation, a tetraalkylammonium cation, a trialkylsulfonium cation, or a tetraalkylonium cation.

[0097] The anions contained in the ionic liquid may include F - 、Cl - Br - , I - 、NO3 - 、(CN)2N - 、BF4 - 、ClO4 - 、RSO3 - (wherein R is an alkyl group having 1 to 9 carbon atoms or a phenyl group), RCOO - (wherein R is an alkyl group or a phenyl group having 1 to 9 carbon atoms), PF6 - 、(CF3)2PF4 - 、(CF3)3PF3 - 、(CF3)4PF2 - 、(CF3)5PF - 、(CF3)6P - 、(C2F5SO2)2N - 、(CF3SO3)2N - 、(CF3SO2)(CF3CO)N - CF3CF2(CF3)2CO - 、(CF3SO2)2CH - 、(SF5)3C - 、(CF3SO2)3C - CF3(CF2)7SO3 - CF3COO - 、C3F7COO - CF3SO3 - or C4F9SO3 - .

[0098] Specifically, the ionic liquid may include, but is not limited to, 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide, 1-methyl-1-propylpyrrolidinium bis(trifluorosulfonyl)imide, 1-butyl-2,3-dimethylimidazolium chloride (BMMImCl), Pyr13TFSI, Pyr14TFSI, and EMIMTFSI.

[0099] In some embodiments of the present application, the electrolyte membrane body includes at least one of a doped or undoped LLZO oxide ceramic solid electrolyte, a doped or undoped sulfide solid electrolyte, and a doped or undoped halide solid electrolyte.

[0100] For ease of understanding, the solid electrolyte membrane in this application is further described below in conjunction with specific embodiments and experimental test results.

[0101] Example 1

[0102] (1) Preparation of mixed solution: P(VDF-TrFE) (poly(vinylidene fluoride-chlorotrifluoroethylene), weight average molecular weight of about 450,000, mass ratio of vinylidene fluoride to chlorotrifluoroethylene of about 4:1), 1-butyl-2,3-dimethylimidazolium chloride and lithium bis(fluorosulfonyl)imide were mixed in a mass ratio of 1:1:1, added to N,N-dimethylformamide, and stirred at room temperature for 12 hours to form a uniform mixed solution.

[0103] (2) Preparation of polymer film: The mixed solution obtained in step (1) is coated on a glass substrate by a coating machine and placed in a 60-degree oven for a certain period of time to obtain a polymer wet film with a thickness of 10 μm and a solvent content of 50%.

[0104] (3) The solid electrolyte membrane is evenly spread on the polymer wet film, and then the glass substrate with the solid electrolyte membrane is placed in a 60-degree oven for 4 hours to obtain a solid electrolyte membrane. The thickness of the solid electrolyte membrane is about 50 microns, and the mass content of the solvent in the polymer membrane is 5% to 10%. The electron microscope image of a cross section of the solid electrolyte membrane is as follows: Figure 1 and Figure 2 shown.

[0105] Example 2

[0106] The difference from Example 1 is that 1-butyl-2,3-dimethylimidazolium chloride is not added in the preparation step of the mixed solution.

[0107] (1) Preparation of mixed solution: P(VDF-TrFE) and lithium bis(fluorosulfonyl)imide were mixed in a mass ratio of 1:1, added to N,N-dimethylformamide, and stirred at room temperature for 12 hours to form a uniform mixed solution.

[0108] Example 3

[0109] The difference from Example 1 is that in the step of preparing the mixed solution, the mass ratio of P(VDF-TrFE), 1-butyl-2,3-dimethylimidazolium chloride and lithium bis(fluorosulfonyl)imide is 1:2:1. The details are as follows:

[0110] (1) Preparation of mixed solution: P(VDF-TrFE), 1-butyl-2,3-dimethylimidazolium chloride and lithium bis(fluorosulfonyl)imide were mixed in a mass ratio of 1:2:1, added to N,N-dimethylformamide, and stirred at room temperature for 12 hours to form a uniform mixed solution.

[0111] Example 4

[0112] The difference from Example 1 is that in the step of preparing the mixed solution, the mass ratio of P(VDF-TrFE), 1-butyl-2,3-dimethylimidazolium chloride and lithium bis(fluorosulfonyl)imide is 1:1:2. The details are as follows:

[0113] (1) Preparation of mixed solution: P(VDF-TrFE), 1-butyl-2,3-dimethylimidazolium chloride and lithium bis(fluorosulfonyl)imide were mixed in a mass ratio of 1:1:2, added to N,N-dimethylformamide, and stirred at room temperature for 12 hours to form a uniform mixed solution.

[0114] Example 5

[0115] The difference from Example 1 is that in the step of preparing the mixed solution, Pyr13TFSI replaces 1-butyl-2,3-dimethylimidazolium chloride. The details are as follows:

[0116] (1) Preparation of mixed solution: P(VDF-TrFE), Pyr13TFSI and lithium bis(fluorosulfonyl)imide were mixed in a mass ratio of 1:1:1, added to N,N-dimethylformamide, and stirred at room temperature for 12 hours to form a uniform mixed solution.

[0117] Example 6

[0118] The difference from Example 1 is that in the step of preparing the mixed solution, EMIMTFSI replaces 1-butyl-2,3-dimethylimidazolium chloride. The details are as follows:

[0119] (1) Preparation of mixed solution: P(VDF-TrFE), EMIMTFSI and lithium bis(fluorosulfonyl)imide were mixed in a mass ratio of 1:1:1, added to N,N-dimethylformamide, and stirred at room temperature for 12 hours to form a uniform mixed solution.

[0120] Example 7

[0121] The difference from Example 1 is that in the step of preparing the mixed solution, lithium bis(trifluoromethanesulfonyl imide) replaces lithium bis(fluorosulfonyl imide). The details are as follows:

[0122] (1) Preparation of mixed solution: P(VDF-TrFE), 1-butyl-2,3-dimethylimidazolium chloride and lithium bis(trifluoromethanesulfonyl)imide were mixed in a mass ratio of 1:1:1, added to N,N-dimethylformamide, and stirred at room temperature for 12 hours to form a uniform mixed solution.

[0123] Example 8

[0124] The difference from Example 1 is that in the step of preparing the mixed solution, lithium perchlorate replaces lithium bis(fluorosulfonyl)imide. The details are as follows:

[0125] (1) Preparation of mixed solution: P(VDF-TrFE), 1-butyl-2,3-dimethylimidazolium chloride and lithium perchlorate were mixed in a mass ratio of 1:1:1, added to N,N-dimethylformamide, and stirred at room temperature for 12 hours to form a uniform mixed solution.

[0126] Example 9

[0127] The difference from Example 1 is that in the step of preparing the polymer film, the holding time is changed so that the residual solvent content of the wet polymer film is 60%.

[0128] Example 10

[0129] The difference from Example 1 is that in the step of preparing the polymer film, the holding time is changed so that the residual solvent content of the wet polymer film is 40%.

[0130] Comparative Example 1

[0131] The difference from Example 1 is that lithium bis(fluorosulfonyl)imide is not added in the step of preparing the mixed solution.

[0132] Comparative Example 2

[0133] The difference from Example 1 is that in the step of preparing the mixed solution, PVDF replaces poly(vinylidene fluoride-chlorotrifluoroethylene).

[0134] Comparative Example 3

[0135] The difference from Example 1 is that in the step of preparing the polymer wet film, the holding time is changed so that the residual solvent content of the polymer wet film is 80%.

[0136] Comparative Example 4

[0137] The difference from Example 1 is that in the step of preparing the polymer wet film, the holding time is changed so that the residual solvent content of the polymer wet film is 0, thereby obtaining a dry polymer film.

[0138] (1) Preparation of mixed solution: P(VDF-TrFE), 1-butyl-2,3-dimethylimidazolium chloride and lithium bis(fluorosulfonyl)imide were mixed in a mass ratio of 1:1:1, added to N,N-dimethylformamide, and stirred at room temperature for 12 hours to form a uniform mixed solution.

[0139] (2) Preparation of polymer: The mixed solution obtained in step (1) was coated on a glass substrate by a coating machine and placed in an oven at 60 degrees for 8 hours to obtain a dry polymer film.

[0140] (3) Spread the electrolyte membrane evenly on the dry polymer membrane for use.

[0141] Preparation of test cells

[0142] The solid electrolyte membranes prepared in Examples 1 to 10 and Comparative Examples 1 to 4 were separated from the glass substrate and then assembled with the lithium negative electrode and the positive electrode to obtain button batteries. 2 The battery cycle performance was tested under 0.33C charging and 1C discharging conditions.

[0143] Experimental testing

[0144] Ionic conductivity test:

[0145] The solid electrolyte membranes prepared in Examples 1 to 10 and Comparative Examples 1 to 4 were assembled into steel sheet to steel sheet button cells, and the impedance values ​​were tested at 25°C. The ionic conductivity was calculated.

[0146] Cyclic performance test:

[0147] The battery was charged at 25°C at a constant current and constant voltage of 0.33C to 4.2V, and then discharged at a constant current of 1C to 3.0V. This constituted one cycle.

[0148] Battery impedance test:

[0149] The impedance of a coin cell battery composed of lithium anode / electrolyte / NCM811 cathode was tested at 25°C using an electrochemical tester.

[0150] Safety corresponds to the number of cycles

[0151] The prepared solid electrolyte membrane was subjected to an ionic conductivity test, and the test results are shown in Table 1. The prepared battery was subjected to a cycle performance and battery impedance test, and the test results are shown in Table 2.

[0152] Table 1

[0153]

[0154] Table 2

[0155]

[0156] It can be seen from Examples 1 to 10 of the present application that the solid electrolyte membrane provided in the embodiments of the present application includes a stacked electrolyte membrane body and a polymer membrane, and the polymer membrane includes poly(vinylidene fluoride-chlorotrifluoroethylene) and a lithium salt dispersed in the poly(vinylidene fluoride-chlorotrifluoroethylene). Calculated by mass ratio, the poly(vinylidene fluoride-chlorotrifluoroethylene): lithium salt is (0.5 to 2): (0.5 to 2), so that the solid electrolyte membrane in the present application has a higher ionic conductivity, and the battery having the solid electrolyte membrane has a higher cycle performance.

[0157] The difference between Example 1 and Comparative Example 1 is that no lithium salt is added to the polymer membrane. Tables 1 and 2 show that adding an appropriate amount of lithium salt to the polymer membrane can improve ionic conductivity and cycling performance. The difference between Example 1 and Comparative Example 2 lies in the different polymer membrane matrix materials. Tables 1 and 2 show that, compared to PVDF, the polymer membrane matrix material of the present application, P(VDF-TrFE), is more conducive to improving the ionic conductivity of the solid electrolyte membrane, and batteries incorporating this solid electrolyte membrane exhibit better cycling performance. Furthermore, as shown in Example 1, Comparative Examples 1, and 2, the P(VDF-TrFE) matrix and the lithium salt dispersed therein produce a synergistic effect in improving ionic conductivity and cycling performance.

[0158] Example 2 differs from Example 1 in that no ionic liquid is added to the raw materials used to prepare the polymer membrane. As can be seen from Tables 1 and 2, the addition of an ionic liquid to the polymer membrane further improves the ionic conductivity and cycling performance of the solid electrolyte. As can be seen from Examples 1 to 4, a ratio of poly(vinylidene fluoride-chlorotrifluoroethylene):lithium salt:ionic liquid of (0.5 to 2):(0.5 to 2):(1 to 2.5) further improves the ionic conductivity and cycling performance of the solid electrolyte membrane in this application.

[0159] The difference between Example 1, Example 9 and Example 10 and Comparative Example 3 and Comparative Example 4 is that the process for preparing the solid electrolyte membrane is different. The solvent content of the polymer membrane in Example 1 is about 50%, the solvent content of the polymer membrane in Example 9 is about 60%, the solvent content of the polymer membrane in Example 10 is about 40%, and the solvent content of the polymer membrane in Comparative Example 3 is about 80%. The polymer membrane prepared in Comparative Example 4 does not include a solvent. It can be seen from Tables 1 and 2 that if the mass percentage of the solvent in the polymer membrane is too high, for example, higher than 80%, there is a problem of being unable to form a membrane. An appropriate amount of solvent in the polymer membrane is beneficial to further improve the ionic conductivity and cycle performance. Figures 1 to 4 It can be seen that the possible reason is that the polymer membrane and the solid electrolyte membrane body prepared in the embodiment of the present application are tightly fitted to form an integrated structure, which is beneficial to reducing impedance and improving battery cycle.

[0160] The above is a detailed introduction to the technical solutions provided in the embodiments of the present application. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method of the present application and its core idea. At the same time, for those skilled in the art, based on the ideas of the present application, there may be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A solid electrolyte membrane, characterized in that The solid electrolyte membrane comprises an electrolyte membrane body and a polymer membrane stacked together, the polymer membrane being disposed on at least one side of the electrolyte membrane body; wherein the polymer membrane comprises poly(vinylidene fluoride-chlorotrifluoroethylene) and a lithium salt dispersed in the poly(vinylidene fluoride-chlorotrifluoroethylene), and the mass ratio of poly(vinylidene fluoride-chlorotrifluoroethylene): lithium salt is (0.5 to 2): (0.5 to 2); The electrolyte membrane body is an alkaline membrane, and the polymer membrane is bonded to the electrolyte membrane body through the poly(vinylidene fluoride-chlorotrifluoroethylene) to form an integrated structure.

2. The solid electrolyte membrane according to claim 1, wherein The polymer film further comprises a solvent; and / or The polymer membrane also includes an ionic liquid, and the mass ratio of the poly(vinylidene fluoride-chlorotrifluoroethylene): the lithium salt: the ionic liquid is (0.5 to 2): (0.5 to 2): (0.5 to 2.5).

3. The solid electrolyte membrane according to claim 2, wherein The poly (vinylidene fluoride - chlorotrifluoroethylene) : the lithium salt : the ionic liquid is (0.9 to 1.1): (0.9 to 1.1): (0.9 to 2.5); and / or The mass content of the solvent in the polymer film is 5% to 10%; and / or The solvent is an organic solvent.

4. The solid electrolyte membrane according to any one of claims 1 to 3, wherein The polymer film has a thickness of 5 μm to 10 μm.

5. The solid electrolyte membrane according to claim 4, wherein The lithium salt is selected from LiCl, LiBr, LiI, LiFSI, LiBF4, LiClO4, LiAlO4, LiAlCl4, LiPF6, LiSbF6, LiAsF6, LiB 10 Cl 10 , one or more of LiBOB, LiCF3SO3, LiTFSI, LiCH3SO3, LiCF3CO2, LiCH3CO2 and LiBETI.

6. The solid electrolyte membrane according to claim 2, wherein The ionic liquid comprises an organic cation and an organic or inorganic anion; the organic cation comprises at least one of a pyridinium cation, a piperidinium cation, a pyrrolidinium cation, a cation having a pyrroline skeleton, a cation having a pyrrole skeleton, an imidazolium cation, a tetrahydropyrimidinium cation, a dihydropyrimidinium cation, a pyrazolium cation, a pyrazolinium cation, a tetraalkylammonium cation, a trialkylsulfonium cation or a tetraalkylonium cation.

7. The solid electrolyte membrane according to claim 2, wherein The ionic liquid comprises an organic cation and an organic or inorganic anion; the organic or inorganic anion comprises F - 、Cl - Br - , I - 、NO3 - 、(CN)2N - 、BF4 - 、ClO4 - 、RSO3 - RCOO - PF6 - 、(CF3)2PF4 - 、(CF3)3PF3 - 、(CF3)4PF2 - 、(CF3)5PF - 、(CF3)6P - 、(C2F5SO2)2N - 、(CF3SO3)2N - 、(CF3SO2)(CF3CO)N - CF3CF2(CF3)2CO - 、(CF3SO2)2CH - 、(SF5)3C - 、(CF3SO2)3C - CF3(CF2)7SO3 - CF3COO - 、C3F7COO - CF3SO3 - 、C4F9SO3 - At least one of .

8. A method for preparing a solid electrolyte membrane according to any one of claims 1 to 7, characterized in that: The preparation method comprises the following steps: Providing a mixed solution, wherein the mixed solution is obtained by dissolving poly(vinylidene fluoride-chlorotrifluoroethylene) and a lithium salt in a solvent; coating the mixed solution on a substrate; After removing part of the solvent, a polymer film is obtained; Laminating the polymer membrane on at least one side of the electrolyte membrane body; The solid electrolyte membrane is obtained by heating.

9. The preparation method according to claim 8, wherein The heat treatment comprises: keeping the temperature in an oven at 40° C. to 70° C. for 2 to 10 hours; and / or In the step of removing part of the solvent, the mass percentage of the solvent in the obtained polymer film is 60% to 40% by mass; and / or In the step of heat treatment to obtain a solid electrolyte membrane, the mass percentage of the solvent in the polymer membrane in the solid electrolyte membrane is 5% to 10%; and / or The step of providing a mixed solution comprises: adding an ionic liquid and a lithium salt into a solvent, and mixing and stirring the mixture to obtain a mixed solution.

10. The preparation method according to claim 9, characterized in that In the coating step, the coating thickness of the mixed solution is 5 μm to 10 μm; and / or The lithium salt is selected from LiCl, LiBr, LiI, LiFSI, LiBF4, LiClO4, LiAlO4, LiAlCl4, LiPF6, LiSbF6, LiAsF6, LiB 10 Cl 10 , one or more of LiBOB, LiCF3SO3, LiTFSI, LiCH3SO3, LiCF3CO2, LiCH3CO2 and LiBETI; and / or The mixed solution includes an ionic liquid, which contains an organic cation and an organic or inorganic anion; the organic cation includes at least one of a pyridinium cation, a piperidinium cation, a pyrrolidinium cation, a cation having a pyrroline skeleton, a cation having a pyrrole skeleton, an imidazolium cation, a tetrahydropyrimidinium cation, a dihydropyrimidinium cation, a pyrazolium cation, a pyrazolinium cation, a tetraalkylammonium cation, a trialkylsulfonium cation or a tetraalkylonium cation.

11. The preparation method according to claim 9, wherein The mixed solution includes an ionic liquid, and the ionic liquid includes an organic cation and an organic or inorganic anion; the organic or inorganic anion includes F - 、Cl - Br - , I - 、NO3 - 、(CN)2N - 、BF4 - 、ClO4 - 、RSO3 - RCOO - PF6 - 、(CF3)2PF4 - 、(CF3)3PF3 - 、(CF3)4PF2 - 、(CF3)5PF - 、(CF3)6P - 、(C2F5SO2)2N - 、(CF3SO3)2N - 、(CF3SO2)(CF3CO)N - CF3CF2(CF3)2CO - 、(CF3SO2)2CH - 、(SF5)3C - 、(CF3SO2)3C - CF3(CF2)7SO3 - CF3COO - 、C3F7COO - CF3SO3 - 、C4F9SO3 - At least one of; The mass ratio of the poly(vinylidene fluoride-chlorotrifluoroethylene) to the mixed solution is 10% to 20%; and / or The mass ratio of the solvent to the mixed solution is 40% to 60%.

12. A lithium ion battery, characterized in that: The invention comprises a positive electrode, a negative electrode and the solid electrolyte membrane according to any one of claims 1 to 7 or the solid electrolyte membrane obtained by the preparation method according to any one of claims 8 to 11.

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