Electrolyte membrane and preparation method, lithium battery

Abstract

The application provides an electrolyte film, a preparation method and a lithium battery. The electrolyte film comprises a polymer electrolyte, the polymer electrolyte is a polyionic liquid, and the polymerization degree is 80-100. The polymer electrolyte in the electrolyte film provided by the application has a cross-linked network structure and a good polymerization degree, so that the electrolyte film has good mechanical strength and structural stability. Meanwhile, as a polyionic liquid, the polymer electrolyte has good compatibility with an ionic liquid, can improve the conductivity of the electrolyte film, realizes the balance of mechanical properties and conductivity, and improves the comprehensive performance of the battery in safety and electrical performance and the like.

Description

Technical Field

[0001] This application belongs to the field of lithium battery technology, specifically relating to an electrolyte membrane and its preparation method, and a lithium battery. Background Technology

[0002] In the lithium battery industry, the gel / semi-solid system composed of polymer electrolytes and liquid electrolytes is a product that seeks a balance between safety, ionic conductivity, and processing feasibility. As a transition to solid electrolytes, compared to pure solid polymers, it significantly improves ionic conductivity, ensures better rate performance and temperature adaptability, and has good compatibility with existing battery manufacturing processes. However, because flammable liquid electrolytes still exist, this gel / semi-solid system composed of polymer electrolytes and liquid electrolytes has not completely eliminated the safety hazards posed by liquid electrolytes.

[0003] The presence of ionic liquids significantly improves safety performance; however, incompatibility exists between ionic liquids and polymers, leading to interfacial reactions that cause incompatibility in the mechanical properties and conductivity of the electrolyte membrane. Therefore, providing an electrolyte membrane compatible with ionic liquids is a problem that needs to be solved. Summary of the Invention

[0004] The purpose of this application is to provide an electrolyte membrane and its preparation method, as well as a lithium battery, in order to solve the problem that existing electrolyte membranes are not compatible with ionic liquids, resulting in the inability to achieve a balance between mechanical properties and electrical conductivity.

[0005] The first embodiment of this application provides an electrolyte membrane, including a polymer electrolyte, the structure of which is shown in Formula I:

[0006] Formula I; In the formula, R1 is selected from any one of -CH2-CH2-, -CH2-C2H4-, and -CH2-C3H6-; R2 is selected from any one of vinyl, propenyl, or butenyl; M is selected from N-methylimidazolium ion, Br - I - TFSI - and FSI - Any one of them; In the formula, n = 80~100.

[0007] In some embodiments, the tensile strength of the electrolyte membrane is 3-5 MPa, and the conductivity of the electrolyte membrane is 1-2 × 10⁻⁶ MPa. -4 S / m.

[0008] The second embodiment of this application provides a method for preparing an electrolyte membrane, used to prepare the electrolyte membrane in any of the above embodiments, comprising the following steps: An imidazole precursor is provided to undergo a halogenation reaction with a halide containing an unsaturated bond to obtain an imidazole halide, which is then exchanged with a lithium salt to obtain an imidazole ionic liquid. A photoinitiator was added to the imidazole ionic liquid, and the mixture was irradiated to obtain a polymer electrolyte.

[0009] In some embodiments, the molar ratio of the imidazole precursor to the halide with unsaturated bonds is 1:1 to 1.2.

[0010] In some embodiments, the molar ratio of the imidazole halide to the lithium salt is 1:1 to 1.2.

[0011] In some embodiments, the amount of photoinitiator added is 0.05 to 0.1% of the mass of the imidazole ionic liquid.

[0012] In some embodiments, the irradiation step further includes: The imidazole ionic liquid and the photoinitiator are irradiated with ultraviolet light to polymerize the imidazole ionic liquid.

[0013] In some embodiments, the intensity of the ultraviolet light irradiation is 700~1000 mW / cm². 2 The illumination time is 5-10 minutes.

[0014] In some embodiments, the imidazole precursor includes at least one of 1-vinylimidazole, 1-propenylimidazole, 1-butenylimidazole, and 1-isopropenylimidazole.

[0015] In some embodiments, the halides with unsaturated bonds include at least one of bromopropylene compounds, bromoethylene compounds, and bromobutene compounds.

[0016] In some embodiments, the lithium salt includes at least one of lithium bis(trifluoromethanesulfonyl)imide and lithium bis(fluorosulfonyl)imide.

[0017] In some embodiments, the photoinitiator includes at least one of benzoin ether, hydroxymethyl acetone, and 1-hydroxycyclohexylphenyl ketone.

[0018] In some embodiments, prior to the step of adding a photoinitiator to the imidazole ionic liquid, the method further includes: An auxiliary imidazole ionic liquid is added to the imidazole ionic liquid to achieve plasticization; The molar ratio of the auxiliary imidazole ionic liquid to the imidazole ionic liquid is (0.5~1):(0.5~1.5).

[0019] In some embodiments, the auxiliary imidazole ionic liquid includes at least one of N-methylimidazolium ionic liquid, bromoimidazolium ionic liquid, iodoimidazolium ionic liquid, TFSI imidazolium ionic liquid and FSI imidazolium ionic liquid.

[0020] The third embodiment of this application provides a lithium battery, including the electrolyte membrane in any of the above embodiments, or including the electrolyte membrane prepared by the preparation method in any of the above embodiments; The lithium battery retains 93-99.5% of its capacity after 200 cycles at 0.1C / 0.1C.

[0021] This application provides an electrolyte membrane, including a polymer electrolyte, which is a polyionic liquid with a degree of polymerization of 80-100. The polymer electrolyte in the electrolyte membrane provided by this application has a cross-linked network structure and a good degree of polymerization, thereby enabling the electrolyte membrane to have good mechanical strength and structural stability. Simultaneously, as a polyionic liquid, it has good compatibility with ionic liquids, which can improve the conductivity of the electrolyte membrane, thus achieving a balance between mechanical properties and conductivity, and improving the overall performance of the battery in terms of safety and electrical performance. Detailed Implementation

[0022] The technical solutions provided in this application will be clearly and completely described below with reference to the embodiments therein. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0023] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a connection that allows for mutual communication; they can refer to a direct connection, an indirect connection through an intermediate medium, or an indirect connection through a pipe or conduit; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances. In the description of this application, "multiple" means two or more, unless otherwise expressly and specifically limited. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more features.

[0024] The compounds of this application can be synthesized via synthetic routes including methods similar to those known in the field of chemistry, particularly with reference to the description contained herein. Starting materials are generally available from commercial sources or can be readily prepared using methods known to those skilled in the art. For illustrative purposes, the reaction schemes described below illustrate possible routes for synthesizing the compounds of this application and key intermediates. For a more detailed description of each reaction step, see the Examples section below. Those skilled in the art will recognize that other suitable starting materials, reagents, and synthetic routes can be used to synthesize the compounds of this application and their various derivatives.

[0025] The following disclosure provides many different embodiments or examples for implementing different structures of this application. To simplify the disclosure of this application, the configuration and arrangement of specific examples are described below. Of course, these are merely examples and are not intended to limit this application.

[0026] When solid polymer electrolytes are compounded with ionic liquids, the presence of polar groups in the polymer molecular chains, coupled with the ionic liquid's composition of cations and anions, can lead to inter-group chemical reactions if the polarity of the polymer does not match the interionic forces of the ionic liquid, resulting in interfacial reactions. Furthermore, the significant differences in the packing density and mobility of polymer chains compared to the molecular size and polarity of ionic liquids make it difficult for them to form effective interactions, easily leading to phase separation and low compatibility. Solid polymer electrolytes, especially those polymerized from single unsaturated bonds, suffer from low degrees of polymerization, and their mechanical properties deteriorate after adsorbing ionic liquids, making it difficult to reconcile mechanical properties and electrical conductivity. This limits the application of polymer electrolyte membranes in lithium-ion batteries.

[0027] The applicant discovered through research that polyionic liquids obtained by ionic liquid polymerization have a natural compatibility with ionic liquids. Therefore, polyionic liquids obtained by ionic liquid polymerization and ionic liquid composites can be used as electrolyte membranes. While ensuring conductivity, the batteries also perform well in cycle tests, resulting in excellent battery performance.

[0028] The first embodiment of this application provides an electrolyte membrane, including a polymer electrolyte, the structure of which is shown in Formula I:

[0029] Formula I; In the formula, R1 is selected from any one of -CH2-CH2-, -CH2-C2H4-, and -CH2-C3H6-; R2 is selected from any one of vinyl, propenyl, or butenyl; M is selected from N-methylimidazolium ion, Br - I - TFSI - and FSI -Any one of them; In the formula, n = 80~100.

[0030] It is understood that the value of n represents the degree of polymerization of the polymer electrolyte. The value of n can be any value from 80, 82, 84, 86, 88, 90, 92, 94, 96, 100, or any value within a range of any two values. The polymer electrolyte in the electrolyte membrane provided in this application has a cross-linked network structure and a good degree of polymerization. A higher degree of polymerization results in longer polymer molecular chains and tighter entanglement, making the formed electrolyte membrane less prone to cracking, stretching, or deformation. It can withstand the volume expansion of the electrodes during long-term cycling, avoiding the problem of gel membrane collapse. Simultaneously, as a polyionic liquid, it has good compatibility with ionic liquids, which can improve the conductivity of the electrolyte membrane, thereby achieving a balance between mechanical properties and conductivity, and improving the overall performance of the battery in terms of safety and electrical performance.

[0031] In some embodiments, the tensile strength of the electrolyte membrane is 3~5 MPa, and the conductivity of the electrolyte membrane is 1~2 × 10⁻⁶ MPa. - 4 S / m.

[0032] It is understandable that the tensile strength of the electrolyte membrane can be any value from 3MPa, 3.5MPa, 4MPa, 4.5MPa, and 5MPa, or a value within any range of two values, and the conductivity of the electrolyte membrane can be 1×10⁻⁶. -4 S / m, 1.2×10 -4 S / m, 1.4×10 -4 S / m, 1.6×10 -4 S / m, 1.8×10 -4 S / m, 2×10 -4 Any value or any two values ​​of S / m are considered. When the tensile strength and conductivity of the electrolyte membrane meet the above range, the mechanical strength and conductivity of the electrolyte membrane can meet the requirements of lithium batteries in different application scenarios.

[0033] The second embodiment of this application provides a method for preparing an electrolyte membrane, used to prepare the electrolyte membrane in any of the above embodiments, comprising the following steps: An imidazole precursor is provided to undergo a halogenation reaction with a halide containing an unsaturated bond to obtain an imidazole halide, which is then exchanged with a lithium salt to obtain an imidazole ionic liquid. A polymer electrolyte is obtained by adding a photoinitiator to an imidazole ionic liquid and then irradiating it.

[0034] It is understandable that, since imidazole precursors themselves contain unsaturated bonds, the imidazole halides obtained after reacting with halides containing unsaturated bonds have at least two unsaturated bonds. After exchanging with lithium salts, the resulting imidazole ionic liquids can undergo self-crosslinking during the polymerization reaction, thereby forming a crosslinked network structure, giving the polymer electrolyte ideal mechanical properties. On the other hand, photo-initiated polymerization differs from traditional polymerization reactions in that it produces a large number of byproducts, involves a complicated preparation process, and poses environmental hazards. The photo-initiated polymerization process used in this application is simple and can give the final polymer electrolyte a high degree of polymerization, while reducing the reaction time and improving efficiency.

[0035] In some embodiments, the molar ratio of the imidazole precursor to the halide with unsaturated bonds is 1:1 to 1.2.

[0036] Understandably, the molar ratio of the imidazole precursor to the halide with unsaturated bonds can be any value from 1:1, 1:1.1, 1:1.2, or any value within a range of any two. When the molar ratio of the imidazole precursor to the halide with unsaturated bonds meets the above-mentioned range, the imidazole group in the imidazole precursor can react completely, resulting in a highly efficient halogenation reaction while avoiding side reactions.

[0037] In some embodiments, the molar ratio of imidazole halide to lithium salt is 1:1 to 1.2.

[0038] It is understandable that the molar ratio of imidazole halide to lithium salt can be any value from 1:1, 1:1.1, 1:1.2, or any value within a range of any two values. When the molar ratio of imidazole halide to lithium salt meets the above range, the imidazole halide can react completely, the exchange reaction has high efficiency, and side reactions are avoided.

[0039] In some embodiments, the amount of photoinitiator added is 0.05 to 0.1% of the mass of the imidazole ionic liquid.

[0040] It is understandable that the percentage of photoinitiator added to the mass of imidazole ionic liquid can be any value or a range between any two of the following: 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, and 0.1%. When the amount of photoinitiator added meets the above range, the photo-initiated polymerization reaction can be initiated with high efficiency, while avoiding residual impurities caused by excessive photoinitiator affecting the electrochemical stability of the electrolyte membrane, thus achieving a balance between polymerization efficiency and product performance.

[0041] In some embodiments, the irradiation step further includes: Irradiate imidazole ionic liquids and photoinitiators with ultraviolet light to polymerize the imidazole ionic liquids.

[0042] In some embodiments, the intensity of ultraviolet light irradiation is 700~1000 mW / cm². 2 The illumination time is 5-10 minutes.

[0043] It is understandable that ultraviolet light can quickly activate photoinitiators, promoting the efficient cross-linking polymerization of imidazole ionic liquids. Using ultraviolet light to initiate the polymerization of imidazole ionic liquids results in mild reaction conditions that are easy to precisely control, effectively shortening the reaction cycle and improving preparation efficiency.

[0044] The intensity of ultraviolet light can be taken as 700 mW / cm². 2 750mW / cm 2 800mW / cm 2 850mW / cm 2 900mW / cm 2 950mW / cm 2 1000mW / cm 2 The irradiation time can be any value or any two values ​​within the range specified in the text. The irradiation time can be any value or any two values ​​within the range of 5 min, 6 min, 7 min, 8 min, 9 min, and 10 min. When the irradiation intensity meets the above range and duration, the polyionic liquid can fully polymerize and achieve an ideal degree of polymerization. Simultaneously, mild and appropriate irradiation conditions can ensure the uniformity of the polymer electrolyte structure, reduce intramembrane defects, and thus further improve the mechanical stability and electrochemical consistency of the electrolyte membrane.

[0045] In some embodiments, the imidazole precursor includes at least one of 1-vinylimidazole, 1-propenylimidazole, 1-butenylimidazole, and 1-isopropenylimidazole.

[0046] In some embodiments, the halides with unsaturated bonds include at least one of brominated propene compounds, brominated ethylene compounds, and brominated butene compounds.

[0047] In some embodiments, the lithium salt includes at least one of lithium bis(trifluoromethanesulfonyl)imide and lithium bis(fluorosulfonyl)imide.

[0048] In some embodiments, the photoinitiator includes at least one of benzoin ether, hydroxymethyl acetone, and 1-hydroxycyclohexylphenyl ketone.

[0049] In some embodiments, prior to the step of adding a photoinitiator to the imidazole ionic liquid, the method further includes: Adding an auxiliary imidazole ionic liquid to imidazole ionic liquids can achieve plasticization. The molar ratio of auxiliary imidazole ionic liquid to imidazole ionic liquid is (0.5~1):(0.5~1.5).

[0050] Understandably, assisted imidazole ionic liquids can be used as plasticizers. Ionic liquids composed only of anions and cations have extremely high ionic conductivity and extremely low vapor pressure, which prevents them from exhibiting the flammability of traditional organic solvents, thus making them a good alternative to electrolytes.

[0051] In some embodiments, the auxiliary imidazole ionic liquid includes at least one of N-methylimidazolium ionic liquid, bromoimidazolium ionic liquid, iodoimidazolium ionic liquid, TFSI imidazolium ionic liquid and FSI imidazolium ionic liquid.

[0052] The third embodiment of this application provides a lithium battery, including the electrolyte membrane in any of the above embodiments, or including the electrolyte membrane prepared by the preparation method in any of the above embodiments; Among them, the lithium battery retains 93~99.5% of its capacity after 200 cycles at 0.1C / 0.1C.

[0053] The electrolyte membrane, its preparation method, and the lithium battery provided in this application are described below with reference to specific embodiments: Example 1 This embodiment provides an electrolyte membrane, which is prepared through the following steps: 1) Preparation of ionic liquid: 2.35g of 1-vinylimidazolium and 3.63g of bromopropene were mixed and subjected to bromination to obtain imidazolium bromide, which was then subjected to exchange reaction with 7.17g of LiTFSI to obtain ionic liquid; 2) Polymerization to form a film: The prepared ionic liquid is mixed with N-methylimidazolium ionic liquid, 70 mg of benzoin ether is added, and the mixture is subjected to ultraviolet light to polymerize and obtain a transparent polymer electrolyte membrane containing the polyionic liquid 1-vinyl-3-propenylimidazolium-bis(trifluoromethanesulfonylimide) lithium.

[0054] Example 2 This embodiment provides an electrolyte membrane, which is prepared through the following steps: 1) Preparation of ionic liquid: 2.82g of 1-vinylimidazolium was mixed with 3.63g of bromopropene and subjected to bromination to obtain imidazolium bromide, which was then subjected to exchange reaction with 7.17g of LiTFSI to obtain ionic liquid; 2) Polymerization to form a film: The prepared ionic liquid is mixed with N-methylimidazolium ionic liquid, 70 mg of benzoin ether is added, and the mixture is subjected to ultraviolet light to polymerize and obtain a transparent polymer electrolyte membrane containing the polyionic liquid 1-vinyl-3-propenylimidazolium-bis(trifluoromethanesulfonylimide) lithium.

[0055] Example 3 This embodiment provides an electrolyte membrane, which is prepared through the following steps: 1) Preparation of ionic liquid: 2.35g of 1-vinylimidazolium and 3.02g of bromopropene were mixed and subjected to bromination to obtain imidazolium bromide, which was then subjected to exchange reaction with 7.17g of LiTFSI to obtain ionic liquid; 2) Polymerization to form a film: The prepared ionic liquid is mixed with N-methylimidazolium ionic liquid, 70 mg of benzoin ether is added, and the mixture is subjected to ultraviolet light to polymerize and obtain a transparent polymer electrolyte membrane containing the polyionic liquid 1-vinyl-3-propenylimidazolium-bis(trifluoromethanesulfonylimide) lithium.

[0056] Example 4 This embodiment provides an electrolyte membrane, which is prepared through the following steps: 1) Preparation of ionic liquid: 2.35g of 1-vinylimidazolium and 3.63g of bromopropene were mixed and subjected to bromination to obtain imidazolium bromide, which was then subjected to exchange reaction with 7.17g of LiTFSI to obtain ionic liquid; 2) Polymerization to form a film: The prepared ionic liquid is mixed with N-methylimidazolium ionic liquid, 35 mg of benzoin ether is added, and the mixture is subjected to ultraviolet light to polymerize and obtain a transparent polymer electrolyte membrane containing the polyionic liquid 1-vinyl-3-propenylimidazolium-bis(trifluoromethanesulfonylimide) lithium.

[0057] Example 5 This embodiment provides an electrolyte membrane, which is prepared through the following steps: 1) Preparation of ionic liquid: 2.35g of 1-vinylimidazolium and 3.63g of bromopropene were mixed and subjected to bromination to obtain imidazolium bromide, which was then subjected to exchange reaction with 7.17g of LiTFSI to obtain ionic liquid; 2) Polymerization to form a film: The prepared ionic liquid is mixed with N-methylimidazolium ionic liquid, 140 mg of benzoin ether is added, and the mixture is subjected to ultraviolet light to polymerize and obtain a transparent polymer electrolyte membrane containing the polyionic liquid 1-vinyl-3-propenylimidazolium-bis(trifluoromethanesulfonylimide) lithium.

[0058] Example 6 This embodiment provides an electrolyte membrane, which is prepared through the following steps: 1) Preparation of ionic liquid: 2.35g of 1-vinylimidazolium and 3.63g of bromopropene were mixed and subjected to bromination to obtain imidazolium bromide, which was then subjected to exchange reaction with 7.17g of LiTFSI to obtain ionic liquid; 2) Polymerization to form a film: The prepared ionic liquid is mixed with N-methylimidazolium ionic liquid, 140 mg of benzoin ether is added, and the mixture is subjected to ultraviolet light to polymerize and obtain a transparent polymer electrolyte membrane containing the polyionic liquid 1-vinyl-3-propenylimidazolium-bis(trifluoromethanesulfonylimide) lithium.

[0059] Example 7 This embodiment provides an electrolyte membrane, which is prepared through the following steps: 1) Preparation of ionic liquid: 2.35g of 1-vinylimidazolium and 3.63g of bromopropene were mixed and subjected to bromination to obtain imidazolium bromide, which was then subjected to exchange reaction with 7.17g of LiTFSI to obtain ionic liquid; 2) Polymerization to form a film: The prepared ionic liquid is mixed with N-methylimidazolium ionic liquid, 140 mg of benzoin ether is added, and the mixture is subjected to ultraviolet light to polymerize and obtain a transparent polymer electrolyte membrane containing the polyionic liquid 1-vinyl-3-propenylimidazolium-bis(trifluoromethanesulfonylimide) lithium.

[0060] Example 8 This embodiment provides an electrolyte membrane, which is prepared through the following steps: 1) Preparation of ionic liquid: 2.35g of 1-vinylimidazolium and 3.63g of bromopropene were mixed and subjected to bromination to obtain imidazolium bromide, which was then subjected to exchange reaction with 7.17g of LiTFSI to obtain ionic liquid; 2) Polymerization to form a film: The prepared ionic liquid is mixed with N-methylimidazolium ionic liquid, 140 mg of benzoin ether is added, and the mixture is subjected to ultraviolet light to polymerize and obtain a transparent polymer electrolyte membrane containing the polyionic liquid 1-vinyl-3-propenylimidazolium-bis(trifluoromethanesulfonylimide) lithium.

[0061] Comparative Example 1 This embodiment provides an electrolyte membrane, which is prepared through the following steps: 1) Preparation of ionic liquid: 4.7g of 1-vinylimidazolium was mixed with 3.63g of bromopropene and subjected to bromination reaction to obtain imidazolium bromide, which was then subjected to exchange reaction with 7.17g of LiTFSI to obtain ionic liquid; 2) Polymerization to form a film: The prepared ionic liquid is mixed with N-methylimidazolium ionic liquid, 140 mg of benzoin ether is added, and the mixture is subjected to ultraviolet light to polymerize and obtain a transparent polymer electrolyte membrane containing the polyionic liquid 1-vinyl-3-propenylimidazolium-bis(trifluoromethanesulfonylimide) lithium.

[0062] Comparative Example 2 This embodiment provides an electrolyte membrane, which is prepared through the following steps: 1) Preparation of ionic liquid: 4.7g of 1-vinylimidazolium was mixed with 7.26g of bromopropene and subjected to bromination reaction to obtain imidazolium bromide, which was then subjected to exchange reaction with 7.17g of LiTFSI to obtain ionic liquid; 2) Polymerization to form a film: The prepared ionic liquid is mixed with N-methylimidazolium ionic liquid, 140 mg of benzoin ether is added, and the mixture is subjected to ultraviolet light to polymerize and obtain a transparent polymer electrolyte membrane containing the polyionic liquid 1-vinyl-3-propenylimidazolium-bis(trifluoromethanesulfonylimide) lithium.

[0063] Comparative Example 3 This embodiment provides an electrolyte membrane, which is prepared through the following steps: 1) Preparation of ionic liquid: 4.7g of 1-vinylimidazolium was mixed with 7.26g of bromopropene and subjected to bromination reaction to obtain imidazolium bromide, which was then subjected to exchange reaction with 7.17g of LiTFSI to obtain ionic liquid; 2) Polymerization to form a film: The prepared ionic liquid is mixed with N-methylimidazolium ionic liquid, 140 mg of benzoin ether is added, and the mixture is subjected to ultraviolet light to polymerize and obtain a transparent polymer electrolyte membrane containing the polyionic liquid 1-vinyl-3-propenylimidazolium-bis(trifluoromethanesulfonylimide) lithium.

[0064] Comparative Example 4 This embodiment provides an electrolyte membrane, which is prepared through the following steps: 1) Preparation of ionic liquid: 4.7g of 1-vinylimidazolium was mixed with 7.26g of bromopropene and subjected to bromination reaction to obtain imidazolium bromide, which was then subjected to exchange reaction with 7.17g of LiTFSI to obtain ionic liquid; 2) Polymerization to form a film: The prepared ionic liquid is mixed with N-methylimidazolium ionic liquid, 140 mg of benzoin ether is added, and the mixture is subjected to ultraviolet light to polymerize and obtain a transparent polymer electrolyte membrane containing the polyionic liquid 1-vinyl-3-propenylimidazolium-bis(trifluoromethanesulfonylimide) lithium.

[0065] The process parameter variables in Examples 1-8 and Comparative Examples 1-4 are shown in Table 1.

[0066] Table 1

[0067] The transparent polymer electrolyte membranes from Examples 1-8 and Comparative Examples 1-4 were assembled to form batteries, and performance tests were performed. The steps are as follows: Button cell assembly: The self-made positive electrode, the purchased lithium negative electrode, and the electrolyte membrane prepared in the above examples and comparative examples are assembled in a glove box to obtain a button cell.

[0068] Conductivity test: Stainless steel sheets are used on both sides to prepare the electrolyte membrane. The impedance of the electrolyte membrane is obtained by EIS test using an electrochemical workstation, and the conductivity is calculated using a formula.

[0069] Cyclic testing: The battery prepared in the third step is tested on the Xinwei test cabinet.

[0070] The test results are shown in Table 2.

[0071] Table 2

[0072] As shown in Table 2, the battery fabricated using the electrolyte membrane obtained by the method provided in this application exhibits relatively ideal performance in terms of conductivity and cycle performance. Comparative Example 1 shows that excessive addition of the imidazole precursor affects the battery's conductivity and cycle performance; Comparative Example 2 shows that excessive addition of the halide affects the battery's conductivity; Comparative Examples 3 and 4 show that when the light intensity exceeds the specified range, it affects both the mechanical strength and electrical properties of the electrolyte membrane, thereby impacting the battery's conductivity and cycle performance.

[0073] The electrolyte membrane and its preparation method, as well as the lithium battery, provided in the embodiments of this application have been described in detail above. Specific examples have been used in this application to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the technical solutions and core ideas of this application. Those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. An electrolyte membrane, characterized in that, It includes a polymer electrolyte, the structure of which is shown in Formula I: Formula I; In the formula, R1 is selected from any one of -CH2-CH2-, -CH2-C2H4-, and -CH2-C3H6-; R2 is selected from any one of vinyl, propenyl, or butenyl; M is selected from N-methylimidazolium ion, Br - I - TFSI - and FSI - Any one of them; n=80~100。 2. The electrolyte membrane according to claim 1, characterized in that, The electrolyte membrane has a tensile strength of 3~5 MPa and an electrical conductivity of 1~2 × 10⁻⁶ MPa. -4 S / m.

3. A method for preparing an electrolyte membrane as described in claim 1 or 2, characterized in that, Includes the following steps: An imidazole precursor is provided to undergo a halogenation reaction with a halide containing an unsaturated bond to obtain an imidazole halide, which is then exchanged with a lithium salt to obtain an imidazole ionic liquid. A photoinitiator was added to the imidazole ionic liquid, and the mixture was irradiated to obtain a polymer electrolyte.

4. The method for preparing the electrolyte membrane according to claim 3, characterized in that, The molar ratio of the imidazole precursor to the unsaturated halide is 1:1 to 1.2; and / or, The molar ratio of the imidazole halide to the lithium salt is 1:1 to 1.2; and / or, The amount of photoinitiator added is 0.05~0.1% of the mass of the imidazole ionic liquid.

5. The method for preparing the electrolyte membrane according to claim 3, characterized in that, The irradiation step further includes: The imidazole ionic liquid and the photoinitiator are irradiated with ultraviolet light to polymerize the imidazole ionic liquid.

6. The method for preparing the electrolyte membrane according to claim 5, characterized in that, The intensity of the ultraviolet light irradiation is 700~1000mW / cm². 2 The illumination time is 5-10 minutes.

7. The method for preparing the electrolyte membrane according to claim 3, characterized in that, The imidazole precursors include at least one of 1-vinylimidazolium, 1-propenylimidazolium, 1-butenylimidazolium, and 1-isopropenylimidazolium; and / or, The halides with unsaturated bonds include at least one of bromopropylene compounds, bromoethylene compounds, and bromobutene compounds; and / or, The lithium salt comprises at least one of lithium bis(trifluoromethanesulfonyl)imide and lithium bis(fluorosulfonyl)imide; and / or, The photoinitiator includes at least one of benzoin ether, hydroxymethyl acetone, and 1-hydroxycyclohexylphenyl ketone.

8. The method for preparing the electrolyte membrane according to claim 3, characterized in that, Before the step of adding the photoinitiator to the imidazole ionic liquid, the method further includes: An auxiliary imidazole ionic liquid is added to the imidazole ionic liquid to achieve plasticization; The molar ratio of the auxiliary imidazole ionic liquid to the imidazole ionic liquid is (0.5~1):(0.5~1.5).

9. The method for preparing the electrolyte membrane according to claim 8, characterized in that, The auxiliary imidazole ionic liquid includes at least one of N-methylimidazolium ionic liquid, bromoimidazolium ionic liquid, iodoimidazolium ionic liquid, TFSI imidazolium ionic liquid and FSI imidazolium ionic liquid.

10. A lithium battery, characterized in that, The electrolyte membrane includes any one of claims 1 to 2, or the electrolyte membrane prepared by any one of claims 3 to 9; The lithium battery retains 93-99.5% of its capacity after 200 cycles at 0.1C / 0.1C.

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