Binder for battery as well as preparation method and application of binder

Abstract

The raw materials of the binder comprise acrylonitrile, acrylate and ionic liquid, and the general formula of the ionic liquid is shown in the specification, or logP is more than or equal to-8 and less than or equal to-2; the mass ratio of the acrylonitrile to the acrylic ester to the ionic liquid is (40-70): (22-52): (5-12), and X is selected from one of a C2-C3 terminal alkenyl group, a C3-C4 terminal acryloyloxy group and a C3-C4 terminal acrylamide group; y < + > and Y '< + > are independently selected from one of ionic liquid cationic groups; z-and Z '-are respectively and independently selected from one of ionic liquid anion groups, R is selected from one of C1-C3 alkyl groups, R' is selected from one of C1-C3 substituted or unsubstituted alkane groups, alkoxy groups and ester groups, n is an integer of 1-5, and the battery binder with high ionic conductivity, interfacial compatibility, excellent binding performance and mechanical strength is obtained.

Description

Technical Field

[0001] This invention relates to the field of solid-state battery binder technology, and more specifically to a battery binder and its application. Background Technology

[0002] With the rapid development of electric vehicles, portable electronic devices, and energy storage systems, the lithium-ion battery market has expanded rapidly, and high-energy-density, high-safety lithium-ion batteries have become a research focus. Traditional liquid lithium-ion batteries use organic liquid electrolytes and polyolefin separators, which pose safety hazards such as leakage, combustion, and even explosion. To address this challenge, more and more research is dedicated to improving battery safety performance through material system innovation. Solid-state batteries use solid electrolytes to replace liquid electrolytes, which is expected to fundamentally solve safety issues and potentially achieve higher energy density and cycle life, achieving a better balance between flame retardancy, thermal stability, and electrochemical compatibility. Among various solid electrolytes, ionic liquids are considered one of the most promising electrolyte materials due to their high ionic conductivity, wide electrochemical window, low volatility, and high thermal stability.

[0003] However, directly applying ionic liquid polymers to solid-state battery systems faces a series of key technological bottlenecks. First, polymerization of ionic liquids typically leads to a significant decrease in ion migration capacity, with ionic conductivity dropping by several orders of magnitude compared to before polymerization. Although copolymerization, plasticization, or the introduction of cross-linking structures can adjust their mechanical properties to some extent, the trade-off between ionic conductivity, adhesion, and mechanical strength remains difficult to overcome. In existing technologies, they are often compounded with conventional polymer binders (such as polyvinylidene fluoride (PVDF), polyethylene oxide (PEO), or styrene-butadiene rubber (SBR), which improves film formation and adhesion, but introduces new problems: on the one hand, most traditional binders are ionic insulators or low-ionic conductors, and their large-scale addition significantly reduces the overall ionic conductivity of the electrolyte, leading to increased internal resistance and decreased rate performance; on the other hand, the compatibility between ionic liquids and these binders is often limited, easily resulting in phase separation or increased interfacial impedance, affecting the continuity of ion transport and reducing the stability of the electrode-electrolyte interface, thus leading to decreased cycle performance. In addition to the aforementioned compatibility and conductivity loss issues, there are also problems such as uneven component distribution and interfacial debonding under long-term cycling or temperature changes, which seriously affect the cycle stability and safety of the battery. The interfacial contact between the electrode active material and the ionic liquid-binder system is also difficult to maintain consistently, leading to a decrease in charge transport efficiency.

[0004] Therefore, existing solid-state battery systems using ionic liquid polymerization often struggle to simultaneously achieve high ionic conductivity, good interfacial compatibility, excellent bonding performance, and sufficient mechanical strength. Developing a novel polymer solid binder material that can balance these key properties is an urgent need to drive the practical application of ionic liquid-based solid-state batteries. This invention aims to develop a battery binder that simultaneously achieves continuous and efficient ion transport channels, interfacial chemical compatibility with electrode materials, strong adhesion to current collectors and active materials, and mechanical toughness to resist volume changes during charge and discharge. This will comprehensively improve the overall electrochemical performance and reliability of lithium-ion batteries, especially solid-state batteries. Summary of the Invention

[0005] This invention addresses the problem in existing technologies where commonly used binders for solid-state battery systems using ionic liquid polymerization often fail to simultaneously achieve high ionic conductivity, good interfacial compatibility, excellent bonding performance, and sufficient mechanical structural strength. This invention innovatively provides a battery binder and its preparation method. The binder innovatively uses acrylonitrile and acrylate as raw materials, along with an ionic liquid possessing a specific water / octanol partition coefficient range and structural characteristics. Under the action of an initiator, the ionic liquid is polymerized with a polymer substrate formed from two matrix raw materials with strong ionic conductivity. This process, involving chemical bonding and microstructural composite of the ionic liquid, acrylonitrile, and acrylate, forms a battery binder with a three-dimensional ionic network structure. While maintaining the high ionic conductivity of the ionic liquid, this invention endows the polymer material with excellent film-forming properties, bonding strength, and interfacial stability, thus providing a battery binder and its preparation method that effectively solves the technical problem of performance imbalance when ionic liquid polymers are used in solid-state batteries.

[0006] This invention is achieved through the following technical solution: This invention provides a battery binder, the raw materials of which include acrylonitrile, acrylate and ionic liquid, wherein the general formula of the ionic liquid is shown in formula (1) or formula (2), and the ionic liquid satisfies -8≤logP≤-2; wherein the mass ratio of acrylonitrile, acrylate and ionic liquid is (40~70):(22~52):(5~12); ; In the formulas (1) and (2), X is selected from one of the terminal alkenyl group of C2 to C3, the terminal acryloxy group of C3 to C4, and the terminal acrylamide group of C3 to C4. In equations (1) and (2), Y + and Y' + Each is independently selected from one of the cationic groups in the ionic liquid; In equations (1) and (2), Z - and Z' - Each is independently selected from one of the anionic groups in the ionic liquid; In formula (1), R is selected from one of the C1-C3 alkyl groups; R' in formulas (1) and (2) is selected from one of the following: substituted or unsubstituted alkane groups of C1 to C3, substituted or unsubstituted alkoxy groups of C1 to C3, and substituted or unsubstituted ester groups of C1 to C3. The substituted group is selected from one or more of the following active groups: thioether group (-S-), thiooxy group (-SO-, -S=O), mercapto group (-SH), boron hydrogen group (-BH4), boronoxy group (-BO-), nitrile group (-CN), amino group (-NH2), imino group (-NH-), nitrate group (-NO3), nitro group (-NO2), ketone carbonyl group (-C(=O)-), hydroxyl group (-OH), phosphorooxy group (-P=O, -PO-), acryloyloxy group (CH2=CH-COO-). n is an integer from 1 to 5.

[0007] Where n is Y + With Y' + The chain length of the carbon chain between them; the Y + and Y' + The same or different groups can be selected, said Z - and Z' - The same or different functional groups can be selected; where logP is the water / octanol partition coefficient, defined as the logarithm of the ratio of the concentration of the ionic liquid in octanol to the concentration of the ionic liquid in water when the ionic liquid reaches equilibrium in the water / octanol extraction system.

[0008] This invention addresses the common problem in existing solid-state battery systems using ionic liquid polymerization and commonly employed binder systems that struggle to simultaneously achieve high ionic conductivity, good interfacial compatibility, excellent bonding performance, and sufficient mechanical structural strength. This invention innovatively proposes a battery binder that uses acrylonitrile and acrylate as matrix raw materials. It considers that acrylonitrile, after polymerization, can form a rigid structure with supporting properties and possesses certain chemical stability, while acrylate combines flexible segments to form a substrate with viscoelasticity and flexibility after polymerization. This combination of raw materials establishes a substrate with excellent bonding performance and interfacial compatibility. Furthermore, this invention specifies that the ionic liquid is a dual-cationic ionic liquid monomer with specific chemical structural characteristics, achieving a synergistic improvement in high ionic conductivity and thermal stability. This invention, by selecting a combination of characteristics with a lower water / octanol partition coefficient (logP ≤ -5.5), achieves better compatibility with the substrate formed by the polymerization of acrylonitrile and acrylate, and simultaneously exhibits stronger bonding with the active groups on the substrate. This allows for better polymerization of the aforementioned materials, resulting in a battery binder with superior interfacial compatibility. Specifically, the structure of the ionic liquid defined in this invention, along with its logP value, enables stronger intermolecular forces, such as hydrogen bonds and dipole interactions, between its molecular structure and the polar groups in the polymer substrate. This significantly enhances the dispersion uniformity and binding strength of the ionic liquid in the acrylonitrile and acrylate substrate. This characteristic effectively suppresses local aggregation or phase separation of the ionic liquid, ensuring the continuity and stability of the ion transport channel. Furthermore, by optimizing the interfacial chemical environment, the migration barrier of lithium ions at the electrode / electrolyte interface is reduced, further improving the overall ionic conductivity. Through the synergistic effect of the aforementioned ionic liquid, acrylonitrile, and acrylate, the battery binder provided by this invention is a multifunctional synergistic binder material that integrates high ionic conductivity, excellent bonding performance, and structural stability. This results in a battery binder and its preparation method that effectively solves the technical problem of performance imbalance when ionic liquid polymers are used in solid-state batteries. It is particularly suitable for preparing lithium-ion batteries with high safety, high ionic conductivity, and high cycle performance, meeting the urgent needs of lithium-ion batteries for high performance and high safety.

[0009] As a further option, the acrylate is selected from one or more alkyl acrylates with a C12 or lower.

[0010] As an example, the alkyl acrylates with a C12 or lower number include one or more compounds such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, and methyl methacrylate.

[0011] As a further embodiment, n in the ionic liquid is 2 to 4, and the ionic liquid satisfies -6 ≤ logP ≤ -2.

[0012] This invention further optimizes the length of the carbon chain between the two dications in the ionic liquid, while also optimizing the logP range of the ionic liquid. This length provides sufficient chain flexibility and mobility, facilitating the "jump" conduction of lithium ions between adjacent cation sites, thus optimizing ion transport kinetics. It also avoids the excessive rigidity and steric hindrance caused by excessively short chains, or the excessive chain entanglement that might occur with excessively long chains, affecting further polymerization on the polymer matrix network formed by acrylonitrile and acrylate in this invention, thus impacting polymerization integrity and mechanical strength. This optimization allows the ionic liquid monomer to form a moderately flexible microenvironment within the polymer backbone after polymerization, which is conducive to ion migration. Furthermore, optimizing the logP value of the ionic liquid to be within the range of -6 to -2 further balances its compatibility with the polymer matrix and its own electrochemistry. When the logP value is within this range, it ensures better compatibility with acrylonitrile-acrylate polymer substrates rich in polar groups (-CN, -COOR). This allows for uniform dispersion and tight bonding at the molecular level through strong hydrogen bonds and dipole interactions, effectively preventing phase separation and further achieving a balance between high ionic conductivity and a stable interface. Therefore, combining an optimal n of 2~4 with logP limited to -6~-2 represents a synergistic optimization from two dimensions: molecular structural flexibility and interfacial compatibility.

[0013] As a further preferred embodiment, n in the ionic liquid is 2 to 3, and the ionic liquid satisfies -4 ≤ logP ≤ -2.

[0014] As a further option, Y in equation (1) or equation (2) + Y' + Each is independently selected from one of the following: a nitrogen-containing cyclic ionic liquid cationic group, a quaternary ammonium cationic group containing a branched substituent, or a quaternary phosphorus cationic group containing a branched substituent, wherein the branched substituent is selected from C1 to C3 alkyl groups.

[0015] As a further embodiment, the nitrogen-containing cyclic ionic liquid cationic group is selected from one of imidazole cationic groups, pyridine cationic groups, pyrrole cationic groups, and piperidine cationic groups.

[0016] The imidazole cationic group, pyridine cationic group, pyrrole cationic group, and piperidine cationic group can be an imidazole group, pyridine group, pyrrole group, or piperidine group, or an imidazole group, pyridine group, pyrrole group, or piperidine group with substituents on its nitrogen-containing ring structure. In this case, the substituents can be selected from C1 to C3 alkyl groups.

[0017] As a further option, X in formulas (1) and (2) is selected from vinyl, propylene, allyl, and acryloyloxy.

[0018] As a further preferred embodiment, Y in equations (1) and (2) + and Y' + Selected from the same ionic liquid cationic groups.

[0019] As a further preferred embodiment, R' is selected from one of C1-C3 alkane groups or C1-C3 alkane groups substituted with acryloyloxy (CH2=CH-COO-).

[0020] As a further preferred embodiment, Y in equation (1) or equation (2) + and Y' + X is one of the quaternary ammonium cationic groups containing branched substituents, X in formula (1) and formula (2) is acryloyloxy, and n in the ionic liquid is 2~3, satisfying -4≤logP≤-2.

[0021] As a further embodiment, the anionic group of the ionic liquid includes one or more of the following: halide anion, tetrafluoroborate anion, hexafluorophosphate anion, carbonate anion, phosphate anion, pyrophosphate anion, perchlorate anion, sulfonamide anion, oxaloborate anion, sulfonate anion, acetate anion, sulfate anion, nitrate anion, oxalate anion, and borate anion.

[0022] As a further preferred embodiment, the Z - and Z' - Each is independently selected from one or more of the following: halide anion, phosphate anion, perchlorate anion, sulfonamide anion, oxalate-borate anion, and sulfonate anion.

[0023] As a further preferred embodiment, Z - and Z' - Both are sulfonamide anions.

[0024] As a further embodiment, in the raw materials of the battery binder, the mass ratio of acrylonitrile, acrylate and ionic liquid is (50~60):(32~42):(7~9).

[0025] This invention can further optimize the raw materials of battery binders. On the one hand, based on the different properties of acrylonitrile and acrylate, the polymerization of acrylonitrile provides a rigid structure and chemical stability for battery binders; while the polymerization of acrylate enhances the adhesion and flexibility of the material. This invention further balances the amount of acrylonitrile and acrylate, thus further balancing the structural strength and bonding performance of the material. On this basis, the total mass ratio of acrylonitrile and acrylate to the mass ratio of ionic liquid is also further optimized. At this point, a sufficient binder substrate is obtained. On this substrate, appropriate ionic liquid polymerization can improve the ionic conductivity while further ensuring the bonding performance and structural strength of the material.

[0026] As a further embodiment, the raw materials for the battery binder also include an initiator, wherein the mass of the initiator is 0.1% to 5% of the mass of acrylonitrile.

[0027] As an example, the initiator includes one or more thermal initiators such as benzoyl peroxide, azobisisobutyronitrile, and azobisisoheptanenitrile.

[0028] As a further preferred embodiment, the initiator has a mass of 0.5% to 2% of the mass of acrylonitrile.

[0029] This invention further specifies that the battery binder also includes an initiator, and also limits the amount of initiator used. Based on the above, by precisely controlling the amount of initiator added, the molecular weight and degree of polymerization of the initial polymer substrate can be effectively regulated, thereby laying a controllable foundation for the subsequent bonding of ionic liquids and the formation of network structures, and avoiding problems such as uneven product performance and poor stability caused by polymerization reactions that are too fast or too slow.

[0030] The present invention also provides a method for preparing a battery binder, comprising the following steps: S1: Mix acrylonitrile and acrylate in a polymerization solvent according to the target mass ratio, heat to 60~80℃, add initiator, and react for 3~5 hours; S2: Add the ionic liquid to the product of S1 according to the target mass ratio, and react at 60~80℃ for 12~36 h to obtain the battery binder.

[0031] As a further embodiment, the polymerization solvent is selected from one or more of dimethylformamide, dimethyl sulfoxide, and dimethylacetamide, and the concentration of acrylonitrile in the polymerization solvent is 200~400g / L.

[0032] As a further embodiment, the method for preparing the battery binder includes the following steps: S1: Mix acrylonitrile and acrylate in a polymerization solvent according to the target mass ratio, purge with nitrogen to remove oxygen for 20-40 minutes, heat to 60-80℃ under nitrogen protection, add initiator, and react for 3-5 hours; S2: Add the ionic liquid to the product of S1 according to the target mass ratio, react at 60~80℃ for 12~36 h, cool to room temperature, add dropwise to deionized water, stir, and dry to obtain the battery binder.

[0033] As a further embodiment, the method for preparing the ionic liquid includes the following steps: S1: Ion exchange: In a first solvent, an ionic liquid cation consisting of a halide anion B- and an ionic liquid cation Y' with a halogenated C-substituted alkyl chain is exchanged. + Compound I (as shown in Formula 3) and including ionic liquid anionic groups Z - First alkali metal salt A + Z - Mixing yields a liquid containing the desired ionic liquid cation group Y'. + A monocationic ionic liquid, wherein A + It is one of the metal cations; ; The general reaction formula for S1 is as follows, as shown in formula (4): ; S2: Quaternization reaction or quaternization reaction: In the second solvent, the monocationic ionic liquid prepared in S1 and compound II (as shown in formula (5)) are heated to obtain a dicationic ionic liquid; wherein, the structural formula of compound II contains X and ionic liquid group Y; the general formula of S2 is as follows, as shown in formula (6) or formula (7). ; ; ; S3: Ion exchange: In a third solvent, the aforementioned dual-cationic ionic liquid and the ionic liquid anion group Z' are exchanged. - The second alkali metal salt A' + Z' - The battery additive is obtained by mixing, wherein A' + It is one of the metal cations; the general reaction formula of S3 is as follows, such as formula (8) or formula (9); ; .

[0034] As a further embodiment, the method for preparing the ionic liquid includes the following steps: S1: Ion exchange: Compound I and an alkali metal salt are stirred and washed in a first solvent to obtain a cation group Y' containing the desired ionic liquid. + Monocationic ionic liquids; S2: Quaternization reaction: In the second solvent, the monocationic ionic liquid prepared in S1 and compound II are heated under reflux and washed to obtain a dicationic ionic liquid; S3: Ion exchange: In a third solvent, the aforementioned dicationic ionic liquid and alkali metal salt are stirred and washed to obtain a Z'-containing solution. - The ionic liquid.

[0035] As a further embodiment, in S1 and S3, the stirring temperature is 20~45 ℃ and the stirring time is 1~4 h; in S2, the heating and reflux temperature is 0~90 ℃ and the reflux time is 1~72 h.

[0036] As a further embodiment, the first solvent and the third solvent are each independently selected from one of deionized water, methanol, ethanol, isopropanol, acetonitrile, and acetone, and the second solvent is selected from one of ethyl acetate, butyl acetate, isopropyl acetate, tetrahydrofuran, diethyl ether, methyl tert-butyl ether, toluene, dichloromethane, and chloroform.

[0037] As a further preferred embodiment, both the first solvent and the third solvent are deionized water, and the second solvent is ethyl acetate.

[0038] As a further option, the cation A in the first alkali metal salt and the second alkali metal salt... + and A' + Each is independently selected from one or more metal cations such as lithium ion, sodium ion, zinc ion, potassium ion, magnesium ion, and calcium ion. A in the first alkali metal salt... + and A' in the second alkali metal salt + You can choose the same or different metal cations.

[0039] As a further option, the halogenated group C in compound I is selected from either a chlorinated group or a brominated group.

[0040] As a further option, the halogen anion B in compound I - It is selected from either chloride anion or bromide anion.

[0041] The present invention also provides a lithium-ion battery, comprising the battery binder or a battery binder prepared by the method for preparing the battery binder.

[0042] Preferably, the lithium-ion battery is an all-solid-state battery.

[0043] The features and beneficial effects of this invention are as follows: (1) This invention innovatively combines the rigid structure of acrylonitrile with the flexible segments of acrylate, and ionic liquid monomers with specific dicationic structures and specific logP values ​​at the molecular level. This design, through chemical copolymerization, constructs an integrated structure of a "rigid and flexible" polymer skeleton and a continuous, uniform three-dimensional ion transport network at the microscopic level, fundamentally solving the inherent contradiction between ionic conductivity, mechanical strength and interfacial adhesion, and achieving functional complementarity and synergistic performance improvement of the three raw materials.

[0044] (2) This invention effectively suppresses ionic liquid leakage or phase separation caused by traditional physical blending by selecting a specific structured dual-cationic ionic liquid and copolymerizing it into a polymer network. The selected ionic liquid itself has high ionic conductivity potential and a wide electrochemical window, and its relatively low logP value ensures excellent compatibility with the polymer substrate, forming a continuous, low-resistance lithium-ion transport channel. This allows the prepared binder to function as both a binder component and a highly efficient solid electrolyte host in the solid-state battery system, endowing the full battery with excellent electrochemical performance.

[0045] (3) By limiting the acrylonitrile and acrylate in the polymer substrate during the intermediate preparation process, the polar functional groups (-CN, -COOR) of the polymer can generate strong hydrogen bonds, dipole-dipole interactions, etc. with the ionic liquid. The polymerized material significantly enhances the interfacial bonding force and chemical compatibility between the binder and the electrode active material and current collector. This strong interfacial interaction can effectively buffer the volume change during the charge and discharge process, reduce interfacial side reactions, and significantly reduce interfacial impedance, thereby greatly improving the ionic conductivity and cycle life of the battery.

[0046] (4) The acrylonitrile specified in this invention can form rigid segments after polymerization, providing sufficient mechanical support strength and dimensional stability for the material, while the flexible segments of acrylate endow the material with good viscoelasticity and flexibility. This substrate, combined with a uniformly dispersed ionic liquid network, results in a battery binder that has both high bonding strength and good toughness, effectively suppressing cracks and structural collapse caused by the volume expansion / contraction of the active material during cycling, and ensuring the long-term integrity of the electrode structure.

[0047] (5) The preparation method of the present invention is simple and controllable, easy to scale up, and the reaction conditions are mild, requiring no complex equipment. By using a stepwise polymerization strategy, a polymer substrate with controllable performance is first formed, and then a functionalized ionic liquid is introduced for copolymerization, which ensures the designability of the product structure and batch stability, and has good prospects for industrial scale-up.

[0048] In summary, this invention, through innovative material system and molecular structure design, provides a battery binder that can simultaneously satisfy high ionic conductivity, excellent interfacial performance, strong mechanical adhesion, and outstanding safety. It provides a key material solution for developing next-generation solid-state lithium batteries with high performance, high energy density, and high safety, and has significant theoretical and practical value. Detailed Implementation

[0049] To facilitate understanding of the present invention, a more comprehensive description of the present invention will be given below, and embodiments of the present invention will be provided, but this does not limit the scope of the present invention.

[0050] As a specific example of the implementation of this invention, detailed cases are provided below.

[0051] Example 1: The preparation method of the battery binder in this example includes the following steps: (1) Take 20 g of (4-bromobutyl)trimethylammonium bromide, 25 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and 50 g of deionized water into a beaker and stir at 25 °C for 2 h. Wash the lower layer solution three times with 50 mL of deionized water to obtain a single cation ionic liquid after ion exchange. (2) Take 20 g of the monocationic ionic liquid obtained in step (1) and 15 g of dimethylaminoethyl acrylate and dissolve them in 50 mL of ethyl acetate. After stirring and refluxing at 75 °C for 24 h, wash three times with 50 mL of ethyl acetate to obtain the dicationic ionic liquid. (3) Take 20 g of the bis-cationic ionic liquid obtained in step (2), 20 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and 50 g of deionized water into a beaker and stir at 25 °C for 2 h. Wash the lower layer solution three times with 50 mL of deionized water to obtain ionic liquid S1. The ionic liquid S1 in this embodiment has the following structure: ; (4) In a three-necked flask equipped with a stir bar, a condenser and a nitrogen inlet tube, add 30 g of acrylonitrile, 16 g of ethyl acrylate and 92 mL of DMF as solvent, and purge with nitrogen for 30 minutes to remove oxygen. Under nitrogen protection, heat the reaction system to 70°C, add 0.25 g of initiator AIBN, and stir continuously for 4 hours. (5) Under a nitrogen atmosphere, take 4g of the ionic liquid S1 obtained in step (3) and add it to the flask in step (4). Keep the temperature at 70℃ and continue the reaction for 24 hours. (6) After the reaction is complete, the viscous reaction solution is cooled to room temperature and then slowly added dropwise to 400 mL of vigorously stirred deionized water. A white flocculent precipitate is formed, which, after drying, yields a white powdery battery binder.

[0052] The differences between Examples 2 to 7 lie in the different contents of acrylonitrile, the different contents of different ionic liquid monomer types, and the differences in adhesive performance resulting from the selection of different types of acrylate monomers.

[0053] Example 2: The difference from Example 1 is that the ratio of acrylonitrile to ethyl acrylate in step (4) is different. The ratio of acrylonitrile to ethyl acrylate is adjusted to 40%:52%. In a three-necked flask equipped with a stir bar, a condenser, and a nitrogen inlet tube, 20 g of acrylonitrile, 26 g of ethyl acrylate, and 92 mL of DMF are added as solvent. Nitrogen gas is purged for 30 minutes to remove oxygen. Under nitrogen protection, the reaction system is heated to 70°C, and 0.25 g of initiator AIBN is added. The reaction is stirred continuously for 4 hours. The remaining steps and conditions are the same as in Example 1.

[0054] Example 3: The difference from Example 1 is that the ratio of acrylonitrile to ethyl acrylate in step (4) is different. The ratio of acrylonitrile to ethyl acrylate is adjusted to 50%:42%. In a three-necked flask equipped with a stir bar, a condenser, and a nitrogen inlet tube, 25g of acrylonitrile, 21g of ethyl acrylate, and 92mL of DMF are added as solvent. Nitrogen is purged for 30 minutes to remove oxygen. Under nitrogen protection, the reaction system is heated to 70°C, and 0.25g of initiator AIBN is added. The reaction is stirred continuously for 4 hours. The remaining steps and conditions are the same as in Example 1.

[0055] Example 4: The difference from Example 1 is that the ratio of acrylonitrile to ethyl acrylate in step (4) is different. The ratio of acrylonitrile to ethyl acrylate is adjusted to 70%:22%. In a three-necked flask equipped with a stir bar, a condenser, and a nitrogen inlet tube, 35 g of acrylonitrile, 11 g of ethyl acrylate, and 92 mL of DMF are added as solvent. Nitrogen is purged for 30 minutes to remove oxygen. Under nitrogen protection, the reaction system is heated to 70°C, and 0.25 g of initiator AIBN is added. The reaction is stirred continuously for 4 hours. The remaining steps and conditions are the same as in Example 1.

[0056] Example 5: The difference from Example 1 is that in step (4), ethyl acrylate is replaced with methyl acrylate, and the remaining steps and conditions are the same as in Example 1.

[0057] Example 6: The difference from Example 1 is that in step (4), ethyl acrylate is replaced with butyl acrylate, and the remaining steps and conditions are the same as in Example 1.

[0058] Example 7: The difference from Example 1 is that in step (4), ethyl acrylate is replaced with methyl methacrylate, and the remaining steps and conditions are the same as in Example 1.

[0059] Example 8: The difference from Example 1 is that in step (1), the (4-bromobutyl)trimethylammonium bromide monomer is replaced with (4-bromobutyl)trimethylphosphorus bromide, and in step (2), the dimethylaminomethyl acrylate monomer is replaced with 1-vinylimidazolium to obtain polymerizable ionic liquid S2. The remaining steps and conditions are the same as in Example 1. The structure of S2 is as follows:

[0060] Example 9: The difference from Example 1 is that in step (2), the dimethylaminomethyl acrylate monomer is replaced with 1-vinylimidazolium to obtain polymerizable ionic liquid S3. The remaining steps and conditions are the same as in Example 1. The structure of S3 is as follows:

[0061] Example 10: The difference from Example 1 is that the ratio of acrylonitrile, ethyl acrylate and ionic liquid in step (4) is different. The ratio is adjusted to 60:35:5, while the other conditions are exactly the same.

[0062] Example 11: The difference from Example 1 is that the ratio of acrylonitrile, ethyl acrylate and ionic liquid in step (4) is different. The ratio is adjusted to 60:30:10, while other conditions are exactly the same.

[0063] Example 12: The difference from Example 1 is that the ionic liquid is replaced with ionic liquid S4. The difference from Example 1 is that in step (1), 20 g of (2-bromoethyl)triethylammonium bromide, 25 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and 50 g of deionized water are added to a beaker and stirred at 25 °C for 2 h. The lower layer solution is washed three times with 50 mL of deionized water to obtain a single-cation ionic liquid after ion exchange. The remaining steps and conditions are the same as in Example 1. The structure of S4 is as follows:

[0064] Example 13: The difference from Example 1 is that the ionic liquid is replaced with ionic liquid S5. The difference is that the monomer used in step (1) is (1) 20 g of 1,4-dibromoethane and 50 g of dimethylaminomethyl acrylate are dissolved in 50 mL of ethyl acetate, stirred and refluxed at 75 °C for 24 h, and then washed three times with 50 mL of ethyl acetate to obtain a symmetrical dicationic ionic liquid. The other steps are exactly the same as in Example 1; The structure of S5 is as follows:

[0065] Example 14: The difference from Example 1 is that the ionic liquid is replaced with ionic liquid S6. The difference is that in step (1), 20 g of 1,4-dibromobutane and 50 g of dimethylaminomethyl acrylate are dissolved in 50 mL of ethyl acetate, stirred and refluxed at 75 °C for 24 h, and then washed three times with 50 mL of ethyl acetate to obtain a symmetrical dicationic ionic liquid. The other steps are exactly the same as in Example 1. The structure of S6 is as follows:

[0066] Comparative Example 1: (1) In a three-necked flask equipped with a stir bar, a condenser and a nitrogen inlet tube, 30 g of PVDF, 16 g of hexafluoropropylene and 92 mL of DMF were added as solvent, and nitrogen was purged for 30 minutes to remove oxygen. Under nitrogen protection, the reaction system was heated to 70 °C, and 0.25 g of initiator AIBN was added. The reaction was stirred continuously for 4 hours. (2) Under a nitrogen atmosphere, add 4g of hexafluoropropylene to the flask in step (4), maintain the temperature at 70℃ and continue the reaction for 24 hours; (3) After the reaction is complete, the viscous reaction solution is cooled to room temperature and then slowly added dropwise to 400 mL of vigorously stirred deionized water. A white flocculent precipitate is formed, which, after drying, yields a white powdery battery binder.

[0067] Comparative Example 2: The main difference between this comparative example and Example 1 is that no polymerizable ionic liquid S1 is added in step (5), and the reaction is continued for 24 hours under the condition of maintaining the temperature at 70°C.

[0068] Comparative Example 3: The difference from Example 1 is that the ionic liquid is replaced with ionic liquid S7. The difference is that in step (1), 20 g of (4-bromobutyl)(N-(dimethoxyphosphate)methyl)dimethylammonium bromide, 25 g of lithium perchlorate (LiClO4), and 50 g of deionized water are added to a beaker and stirred at 25°C for 2 hours. The lower layer solution is washed three times with 50 mL of deionized water to obtain a single-cation ionic liquid after ion exchange. The other steps are exactly the same as in Example 1. The structure of S7 is as follows:

[0069] Comparative Example 4: The difference from Example 1 is that the ionic liquid is replaced with ionic liquid S8, which is 1-vinyl-3-butylimidazolium bis(trifluoromethanesulfonyl)imide salt; (1) In a three-necked flask equipped with a stir bar, a condenser and a nitrogen inlet tube, add 30 g of acrylonitrile, 16 g of ethyl acrylate and 92 mL of DMF as solvent, and purge with nitrogen for 30 minutes to remove oxygen. Under nitrogen protection, heat the reaction system to 70 °C, add 0.25 g of initiator AIBN, and stir continuously for 4 hours.

[0070] (2) Under a nitrogen atmosphere, 4g of the ionic liquid 1-vinyl-3-butylimidazolium bis(trifluoromethanesulfonyl)imide salt was added to the flask in step (1), and the temperature was maintained at 70°C for 24 hours. (3) After the reaction is complete, the viscous reaction solution is cooled to room temperature and then slowly added dropwise to 400 mL of vigorously stirred deionized water. A white flocculent precipitate is formed, which, after drying, yields a white powdery battery binder; The structure of S8 is as follows:

[0071] Fabrication of pouch cells: The binders obtained in Examples 1-14 and Comparative Examples 1-4 were dissolved in NMP solvent at a ratio of lithium nickel cobalt manganese oxide: conductive carbon black: binder = 97:1.5:1.5 to obtain a positive electrode slurry with a solid content of 75%. The positive electrode slurry was coated onto the surface of aluminum foil using a coating machine, and after drying and rolling, a positive electrode sheet was obtained. The binder PAA, SBR, graphite, silicon carbide, conductive carbon black, sodium carboxymethyl cellulose, and water were mixed evenly in a planetary mixer at a mass ratio of 2:1:76:20:1:1:100 to obtain a negative electrode slurry. The negative electrode slurry was coated onto the surface of copper foil using a coating machine, and after drying and rolling, a negative electrode sheet was obtained. A 2Ah pouch cell was assembled in a dry room, and the cell was heated at 55°C for 48 hours.

[0072] The battery binders or pouch cells prepared in Examples 1 to 14 and Comparative Examples 1 to 4 were tested as follows: 1. Battery cycle performance test: Impedance test was performed using an electrochemical workstation. The charge and discharge voltage range was 2~4.5V using a charge and discharge device at 25℃. The battery cycled for two cycles at 0.1C and 100 cycles at 0.5C. The results are shown in Table 1.

[0073] 2. Viscosity of the adhesive: After the adhesive was allowed to stand to eliminate air bubbles, the viscosity was tested using a rotating digital viscometer. A No. 4 rotor was used, and the viscosity was tested at a speed of 60 rpm. The test temperature of the adhesive was 25℃. The results are shown in Table 1.

[0074] 3. Peel strength of the positive electrode sheet: The peel strength of the positive electrode sheet is tested using a mechanical testing machine with a 180° tensile peel method. The specific steps include the following: 1) Take a 3cm wide piece of 3M double-sided tape and stick it parallel to the peeling steel sheet. Then, use a pressure roller to roll it back and forth 5 times at a uniform speed to ensure that the adhesive surface is flat. 2) Cut the positive electrode sheet into small strips (the sample width is consistent with the width of the 3M adhesive), and the length of the positive electrode sheet is about twice the length of the stripped steel sheet; 3) Adhere the material coating area of ​​the positive electrode sheet to the 3M adhesive on the peeling steel sheet, and roll it back and forth 5 times at a uniform speed with a pressure roller; 4) Vertically fix the stripping steel sheet under the test fixture, ensuring it is properly positioned on the left and right and clamped without any lifting. 5) Pull the other end of the positive electrode to be tested perpendicular to the upper clamp, clamp it, and start the tensile testing machine to begin the test. The tensile rate is controlled at 50 mm / min. Take the average value of three tests as the test result. The results are shown in Table 1.

[0075] 4. Ionic Conductivity: The ionic conductivity of the binders provided in all examples and comparative examples was tested, including the following steps: The binder was cast onto a stainless steel electrode (stainless steel disc diameter φ = 1.9 cm) using a solution casting method and dried at 85°C for 12 hours, followed by vacuum drying at 60°C for 24 hours. The thickness of the dried binder was then measured. The stainless steel electrode with the binder was assembled with an equal-area stainless steel counter electrode to form a blocking electrode, which was then assembled into a coin cell. EIS testing was performed. The ionic conductivity of the binder was calculated using the following formula: Ionic Conductivity = L / (R × S), where L is the binder thickness, R is the bulk impedance, and S is the stainless steel area. The results are shown in Table 1.

[0076] In this invention, the water / octanol partition coefficient log P is defined as the logarithm of the ratio of the concentration of the ionic liquid in octanol to its concentration in water when the ionic liquid reaches equilibrium in the water / octanol extraction system. This invention can influence the ion transport efficiency of the battery binder by adjusting the length of the carbon chain between the dicationic groups of the ionic liquid, or by adjusting the type of dicationic groups. A suitable water / octanol partition coefficient log P is for the ionic liquid. The log P value of the ionic liquid in this invention varies due to changes in the aforementioned factors. Further optimization of the water / octanol partition coefficient log P can further improve the ionic conductivity of the battery binder prepared by this invention. Simultaneously, by enhancing the bonding between the ionic liquid and the polymer substrate formed by the polymerization of acrylonitrile and acrylate, the stability and interfacial compatibility of the material are improved while simultaneously increasing the ionic conductivity.

[0077] The performance parameters and test data of Examples 1-14 and Comparative Examples 1-4 are shown in Table 1: Table 1

[0078] This invention successfully constructs a battery binder that combines high ionic conductivity, excellent mechanical bonding strength, and outstanding interfacial stability. By chemically copolymerizing acrylonitrile with a rigid structure, flexible viscoelastic acrylate, and a polymerizable ionic liquid with a specific structure (dual cationic) and hydrophilic properties (low logP value), this invention creatively solves the technical bottleneck of the difficulty in synergistically improving ionic conductivity, adhesion, mechanical strength, and interfacial compatibility in traditional simple physical blending systems of ionic liquid polymers and commonly used binders.

[0079] As can be seen from the comparison of Examples 1-15 and Comparative Examples 1-4 in this invention, polymerizing a polymerizable ionic liquid with double bonds into the polymer backbone structure formed by acrylonitrile and acrylate via free radical polymerization significantly improves the ionic conductivity of the binder compared to polymerization without ionic liquid or using other commonly used binders. This improves the solid-solid interface problem in solid-state batteries, while achieving high ionic conductivity, good interfacial compatibility, excellent bonding performance, and sufficient mechanical structural strength. The comparison of Examples 1-15 and Comparative Examples 3-4 shows that the structure of the ionic liquid defined in this invention and its logP value enable stronger intermolecular forces, such as hydrogen bonds and dipole interactions, between its molecular structure and the polar groups in the polymer substrate. This significantly enhances the dispersion uniformity and binding strength of the ionic liquid in the acrylonitrile and acrylate substrate. This characteristic effectively inhibits local aggregation or phase separation of the ionic liquid, ensuring the continuity and stability of the ion transport channel. Furthermore, by optimizing the interfacial chemical environment, the migration barrier of lithium ions at the electrode / electrolyte interface is reduced, further improving the overall ionic conductivity. Under the synergistic effect of the ionic liquid, acrylonitrile, and acrylate, the battery binder provided by the present invention is a multifunctional synergistically improved binder material that integrates high ionic conductivity, excellent bonding performance, and structural stability. Thus, a battery binder and its preparation method are obtained that effectively solve the technical problem of performance imbalance when ionic liquid polymers are used in solid-state batteries.

[0080] A comparison of Examples 1 and 3 with Examples 2, 4, 10, and 11 shows that the present invention further optimizes the mass ratio of acrylonitrile, acrylate, and ionic liquid in the raw materials for preparing battery binders to (50~60):(32~42):(7~9). This further balances the effect of the ionic liquid on improving ionic conductivity and the influence of acrylonitrile monomer and acrylate polymerization on bonding performance and structural strength. Based on the above, a viscosity greater than 5000 mPa·s and a peel strength greater than 11 N / m can be obtained, while also exhibiting a strength greater than 1.2 N / m. 10 -4 The improved ionic conductivity of s.cm, along with the enhanced structural strength and ionic conductivity, enabled this invention to achieve a cycle capacity retention rate of >92.42%.

[0081] Specifically, through comparisons of Examples 1 and 3 and Examples 10 and 11, it was found that simultaneously optimizing the amounts of acrylate and ionic liquid can further balance the bonding performance and ionic conductivity, achieving a synergistic performance improvement. Changing the ionic liquid content significantly affects the ionic conductivity; binders with higher ionic liquid content have higher ionic conductivity, but this leads to a significant decrease in the peel strength of the binder in the electrode. This is mainly because the steric hindrance during the polymerization process of the ionic liquid is greater, affecting the overall degree of polymerization. It is necessary to control the amount of ionic liquid monomer within an optimal range so that the binder can ensure sufficient peel strength and better ionic conductivity, thereby improving the long-term cycle capability of solid-state batteries.

[0082] As can be seen from the comparison of Examples 1 and 3 and Examples 2 and 4, further optimizing the mass ratio of acrylonitrile and acrylate can further balance the peel strength and viscosity of the material. The appropriate viscosity also provides suitable conditions for the polymerization of ionic liquids, and indirectly and synergistically improves the ionic conductivity of the material.

[0083] As can be seen from the comparison of Examples 1 and Examples 5-7, the present invention further optimizes the type of acrylate. When the acrylate of the present invention is ethyl acrylate, it achieves a further balance between adhesive strength, flexibility and molecular chain length, thus exhibiting better overall performance.

[0084] Because methyl acrylate has a moderately long alkyl chain, the polymer matrix formed after its polymerization with acrylonitrile possesses suitable structural strength, and its chain segments exhibit a certain degree of flexibility. This allows for further improvement in the mechanical properties, flexibility, adhesion, and ionic conductivity of the resulting battery binder material. It also avoids the problem of insufficient chain segment flexibility due to excessively short alkyl chains, which leads to a slightly weaker buffering capacity against electrode volume changes. Furthermore, it avoids the problem of excessive flexibility in the polymer product due to longer alkyl chains, which results in reduced peel strength. Compared to Example 7, Example 1 of this invention further reduces the steric hindrance generated by acrylate, making it more active and less sterically hindered in the polymerization reaction. This is beneficial for forming a copolymer matrix with a more regular structure and a more controllable molecular weight distribution with acrylonitrile. This further ensures the uniformity of the final product structure and the stability of its performance.

[0085] By comparing Examples 1 with Examples 8-9, it was found that when the cation in the ionic liquid is a quaternary ammonium cation group containing branched substituents and X is preferably an acryloyloxy group, the acryloyloxy structure is more easily polymerized onto the main structure of the binder, resulting in higher ionic conductivity and better cycle performance of the battery.

[0086] A comparison of Examples 1, 12, 13, and Examples 14-15 revealed that the present invention further optimizes the length of the carbon chain between the two dications in the ionic liquid, while simultaneously optimizing the logP range of the ionic liquid. At this point, the carbon chain length defined by the present invention provides sufficient chain segment flexibility and mobility, facilitating the "jump" conduction of lithium ions between adjacent cation sites, thereby optimizing ion transport kinetics. It also avoids the drawbacks of excessively short chain lengths leading to excessive rigidity and steric hindrance, or excessively long chain lengths potentially causing excessive chain segment entanglement, affecting further polymerization with the acrylonitrile and acrylate polymer substrate network in the present invention, thus impacting polymerization integrity and mechanical strength. This optimization allows the ionic liquid monomer to form a moderately flexible microenvironment within the polymer backbone after polymerization, which is conducive to ion migration. Furthermore, optimizing the logP value of the ionic liquid to be within the range of -6 to -2 further balances its compatibility with the polymer substrate and its own electrochemistry. When the logP value is within this range, it ensures better compatibility with acrylonitrile-acrylate substrates rich in polar groups (-CN, -COOR). This allows for uniform dispersion and tight bonding at the molecular level through strong hydrogen bonds and dipole interactions, effectively preventing phase separation and further achieving a balance between high ionic conductivity and a stable interface. Therefore, combining an optimal n of 2~4 with logP limited to -6~-2 represents a further synergistic optimization from both the perspectives of molecular structural flexibility and interfacial compatibility.

[0087] In summary, this invention, through innovative synergistic design at the molecular level, chemically bonds the rigid support of acrylonitrile, the flexible bonding of acrylate, and a polymerizable ionic liquid with a specific dual-cationic structure and a suitable logP value, successfully constructing a battery binder rich in three-dimensional continuous ion channels. This binder system overcomes the traditional trade-offs between ionic conductivity, mechanical bonding strength, interfacial compatibility, and structural stability, achieving simultaneous optimization and significant improvement of several key performance characteristics. This material solution not only provides a new approach to overcoming the common challenges of high solid-solid interface impedance and poor stability in solid-state batteries, but also lays a crucial material foundation for developing next-generation solid-state lithium batteries with high safety, high energy density, and long cycle life, possessing significant theoretical value and broad prospects for industrial application.

[0088] It should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A binder for a battery, characterized by, The raw material of the battery binder comprises acrylonitrile, acrylate and ionic liquid, the general formula of the ionic liquid is shown in formula (1) or formula (2), and the ionic liquid satisfies -8≤logP≤-2; wherein the mass ratio of the acrylonitrile, acrylate and ionic liquid is (40~70):(22~52):(5~12); ； X in the formula (1) and formula (2) is selected from one of C2~C3 terminal alkenyl, C3~C4 terminal acryloxy, C3~C4 terminal acrylamide; Y + and Y' + each independently is selected from one of the ionic liquid cation groups; Z - and Z' - each independently is selected from one of the ionic liquid anion groups; R in the formula (1) is selected from one of C1~C3 alkyl; R' in the formula (1) and formula (2) is selected from one of C1~C3 substituted or unsubstituted alkyl, C1~C3 substituted or unsubstituted alkoxy, C1~C3 substituted or unsubstituted ester group, wherein the substituent group is selected from one or more of active groups containing sulfide group (-S-), sulfoxide group (-S-O-, -S=O), mercapto group (-SH), borohydride group (-BH4), boron oxygen group (-B-O-), nitrile group (-CN), amino group (-NH2), imino group (-NH-), nitric acid group (-NO3), nitro group (-NO2), ketone carbonyl group (-C(=O)-), hydroxyl group (-OH), phosphorus oxygen group (-P=O, -P-O-), acryloxy group (CH2=CH-COO-), etc.; n is an integer of 1~5.

2. The binder for a battery according to claim 1, characterized by The acrylate is selected from one or more of C12 or less alkyl acrylate; Preferably, the acrylate is selected from one or more of methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, methyl methacrylate.

3. The binder for a battery according to claim 1, characterized by n in the ionic liquid is 2~4, and the ionic liquid satisfies -6≤logP≤-2; Preferably, n in the ionic liquid is 2~3, and the ionic liquid satisfies -4≤logP≤-2.

4. The binder for a battery according to claim 1, characterized by Y in the formula (1) or formula (2) + Y' + each independently is selected from one of a nitrogen-containing cyclic ionic liquid cation group, a quaternary ammonium cation group containing a branched substituent, a quaternary phosphorus cation group containing a branched substituent, wherein the branched substituent is selected from C1-C3 alkyl groups; Preferably, the nitrogen-containing cyclic ionic liquid cation group is selected from one of imidazole cation group, pyridine cation group, pyrrole cation group, piperidine cation group; Preferably, X in the formula (1) and formula (2) is selected from one of vinyl, propenyl, allyl, acryloxy; Further preferably, Y + and Y' + are selected from the same ionic liquid cation group; Further preferably, R' is selected from one of C1~C3 alkyl or C1~C3 alkyl substituted with acryloxy group (CH2=CH-COO-).

5. The binder for a battery according to claim 1, characterized by Y in the formula (1) or the formula (2) + and Y' + is one of quaternary ammonium cation groups containing branched substituents, X in the formula (1) and the formula (2) is acryloxy, and n in the ionic liquid is 2-3, satisfying -4≤logP≤-2.

6. The binder for a battery according to claim 1, characterized by In the raw material of the battery binder, the mass ratio of the acrylonitrile, acrylate and ionic liquid is (50~60):(32~42):(7~9); Preferably, the raw material of the battery binder further comprises an initiator, and the mass of the initiator is 0.1%~5% of the mass of the acrylonitrile; Further preferably, the mass of the initiator is 0.5%~2% of the mass of the acrylonitrile.

7. A method of producing the binder for a battery as claimed in any one of claims 1 to 6, characterized by, The method comprises the following steps: S1: mix acrylonitrile and acrylate in a polymerization solvent according to the target mass ratio, heat to 60~80℃, add an initiator, and react for 3~5 hours; S2: adding the ionic liquid into the product of S1 according to a target mass ratio, and reacting at 60-80°C for 12-36 h to obtain the battery binder.

8. The preparation method according to claim 7, characterized in that, The polymerization solvent is selected from one or more of dimethylformamide and dimethyl sulfoxide, and the concentration of the acrylonitrile in the polymerization solvent is 200-400 g / L; Preferably, the battery binder preparation method comprises the following steps: S1: mixing acrylonitrile and acrylate in a polymerization solvent according to a target mass ratio, removing oxygen by nitrogen blowing for 20-40 min, heating to 60-80°C under nitrogen protection, adding an initiator, and reacting for 3-5 h; S2: adding the ionic liquid into the product of S1 according to a target mass ratio, and reacting at 60-80°C for 12-36 h, cooling to room temperature, adding dropwise into deionized water, stirring, drying, and obtaining the battery binder.

9. The preparation method according to claim 7, characterized in that, The preparation method of the ionic liquid comprises the following steps: S1: ion exchange: mixing a compound I (as formula 3) comprising a halide anion B- and an ionic liquid cation group Y' with a first alkali metal salt A comprising an ionic liquid anion group Z + - + Z - in a first solvent, to obtain a mono-cationic ionic liquid comprising the desired ionic liquid cation group Y' + , wherein A + is one of the metal cations;​​ ； The reaction general formula of S1 is as follows, such as formula (4): ； S2: quaternary ammonium reaction or quaternary phosphorus reaction: heating the monocation ionic liquid prepared in S1 and compound II (such as formula (5)) in a second solvent to obtain a dication ionic liquid; wherein the structural formula of compound II contains X and ionic liquid group Y; the reaction general formula of S2 is as follows, such as formula (6) or formula (7): ； ； ； S3: Ion exchange: In a third solvent, the aforementioned dual-cationic ionic liquid and the ionic liquid anion group Z' are exchanged. - The second alkali metal salt A' + Z' - The battery additive is obtained by mixing, wherein A' + It is one of the metal cations; the general reaction formula of S3 is as follows, such as formula (8) or formula (9); ； 。 10. A lithium-ion battery, characterized by, The battery binder prepared by the battery binder preparation method of any one of claims 1-6 or the battery binder preparation method of any one of claims 7-9; Preferably, the lithium ion battery is a full solid-state battery.

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