In-situ polymer solid electrolyte and preparation method and application thereof

Abstract

The present invention provides a battery additive having a structure wherein X is a polymerizable active group selected from substituted or unsubstituted C2-C6 alkenyl chains, and X is an alkyl group selected from substituted or unsubstituted C2-C6 alkenyl chains. The substituent groups are selected from one or more of halogen atoms, hydroxyl, amino, carboxyl, ester groups, acylamino, acyloxy, nitryl, cyano, ether oxy, phosphate groups, phosphite groups, sulfonate groups, sulfonyl, sulfoxide groups, sulfydryl and silane groups, Y <-> is ionic liquid anions, n is an integer of 1-6, a is an integer of 0-4, and b is an integer of 0-4. According to the invention, through the design of specific functional groups, synergic enhancement of functions such as relatively fast lithium ion transmission and interface stability is realized; an in-situ curing technology is adopted to modify an interface after direct polymerization between a lithium negative electrode and a lithium positive electrode, so that a stable solid electrolyte interface layer is constructed, the solid-solid contact compatibility is improved, the interface impedance is reduced, an efficient ion transmission path is created, and the electrochemical comprehensive performance of the battery is improved.

Description

Technical Field

[0001] This invention relates to the field of solid electrolyte technology for lithium-ion batteries, specifically to an in-situ polymer solid electrolyte, its preparation method, and its application. Background Technology

[0002] Lithium metal batteries (LIBs) occupy an indispensable position in many energy storage devices due to their high energy density, long cycle life, and light weight. Safety issues such as leakage and even explosion during charging / discharging of liquid electrolytes have spurred the emerging development of solid polymer solid electrolytes (SPEs). However, the relatively low conductivity of SPEs limits their application. Polyionic liquids (PILs), possessing both the unique properties of ionic liquids (ILs) (high designability, high ionic conductivity, and a wide electrochemical stability window) and the inherent properties of polymers (mechanical stability, flexibility, and processability), have been used as a "revolutionary" polymer matrix for SPEs. However, existing polyionic liquid-based solid electrolytes (PIL-SPEs) still face the following key bottlenecks.

[0003] 1. Low room temperature ionic conductivity: Due to the properties of ionic liquids, PIL-SPEs have improved room temperature ionic conductivity compared to traditional solid polymer solid electrolytes. However, compared to the state before polymerization, the glass transition temperature (Tg) is significantly increased, which restricts the creep of molecular chain segments, resulting in a decrease in conductivity and limiting its performance in practical applications.

[0004] 2. Lower lithium ion content (Li) + Migration number: the complexing unit on the polymer chain segment and Li + The coordination ability of Li is crucial. Traditional polymer segments - Li + Excessive interaction between them often limits Li + The complexation and decoupling process of Li is not conducive to the complexation and decoupling process of Li. + Rapid diffusion dynamics.

[0005] 3. Interface compatibility needs improvement: There is an interfacial ion transfer barrier between the polyionic liquid-based solid electrolyte and the electrode, resulting in a large interfacial impedance, which affects the battery cycle life.

[0006] Therefore, the present invention aims to develop a solid electrolyte interface layer with good compatibility, low interfacial impedance, efficient ion transport pathway, and stability, which improves the overall electrochemical performance of the battery. Summary of the Invention

[0007] This invention addresses the problems of low ionic conductivity, low lithium-ion transference number, and poor interfacial stability in polymer solid electrolytes obtained through in-situ polymerization of ionic liquid monomers in existing technologies. It provides a novel battery additive. Starting with molecular structure design, a novel battery additive containing ether-oxygen bonds is designed and synthesized. This additive achieves synergistic enhancement of functions such as faster lithium-ion transport and interfacial stability through specific functional groups. By employing in-situ curing technology to directly polymerize between the lithium anode and cathode and then modifying the interface, a stable solid electrolyte interface layer is constructed. This improves the compatibility of the solid-solid contact, reduces interfacial impedance, creates an efficient ion transport pathway, and enhances the overall electrochemical performance of the battery.

[0008] This invention is achieved through the following technical solution: In a first aspect, the present invention provides a battery additive having a structure as shown in Formula 1.

[0009] Wherein X is a polymerizable active group, the polymerizable active group being selected from substituted or unsubstituted C2-C6 alkenyl chains, and the substituted group being selected from one or more of halogen atoms, hydroxyl groups, amino groups, carboxyl groups, ester groups, amide groups, acyloxy groups, nitro groups, cyano groups, etheroxy groups, phosphate ester groups, phosphite ester groups, sulfonate groups, sulfonyl groups, sulfoxide groups, mercapto groups, and silane groups. - For ionic liquid anions, n is an integer from 1 to 6, a is an integer from 0 to 4, and b is an integer from 0 to 4.

[0010] When a is 0 and b is 0, it indicates that the oxygen atom is directly connected to the alkyl chain linked to the ionic liquid anion, and the battery additive has the structure of Formula 2 as follows:

[0011] This invention provides a battery additive with polymerizable active groups on the N-position side chain of its imidazole cation. These groups can form a three-dimensional cross-linked polymer network through in-situ UV curing or thermal polymerization. This network constitutes the mechanical framework of the electrolyte, endowing it with excellent mechanical strength, dimensional stability, and interfacial adhesion to electrodes. This design not only effectively inhibits lithium dendrite growth and improves safety but also provides a core material basis for manufacturing thin, flexible, all-solid-state lithium-ion batteries. Furthermore, innovatively, two groups containing ether oxygen bonds are introduced at one end of the alkyl straight chain in the ionic liquid anionic group. The length of the ether oxygen bond-containing groups is limited by the number of groups a and b, and the number of groups n is also limited. This balances the improvement of lithium-ion migration and transport capabilities in the polymer solid-state electrolyte with the stability of the polymer solid-state electrolyte, thus enhancing interfacial compatibility. One end of the polymer is connected to two groups containing ether oxygen bonds. Due to the lithiophilicity of ether oxygen bonds, the dissociation of lithium salt is enhanced, increasing ionic conductivity and lithium ion transference number. It can also improve the electrochemical window of imidazole polyionic liquids to a certain extent. Setting the number of ether oxygen bonds to two avoids the problem of limited improvement in lithium ion migration capacity due to insufficient ether oxygen bonds, and also avoids the problem of excessive dissociation of lithium salt due to excessive ether oxygen bonds, which leads to an increase in side reactions during battery cycling. The value of n affects the polymerization ability of polymer monomers and the mechanical properties of the final polymer. This invention limits n to this range, effectively avoiding the problem of excessively short chain length due to too small n, which makes the anionic groups too compact during polymerization, resulting in significant steric hindrance effect and seriously hindering the polymerization reaction efficiency and final degree of polymerization of ionic liquid monomers. At the same time, it also avoids the problem of excessively long chain length due to too large n, which may cause excessive chain segment entanglement, crystallization or adverse phase separation, thereby weakening the rigidity of the crosslinked polymer network and reducing the overall mechanical strength. The values ​​of a and b are limited to a narrow range of 0 to 4. At this range, the distance between the ether oxygen bond and the alkyl straight chain is relatively short, resulting in a higher degree of lithium salt dissociation. Based on the above, the mechanical stability and lithium-ion transport capacity of the polymer solid electrolyte are balanced.

[0012] As a further embodiment, in the battery additive, X is a C2~C4 alkenyl chain, n is an integer from 2 to 4, a is an integer from 0 to 3, b is an integer from 0 to 3, and a=b.

[0013] This invention further limits the types of X in battery additives and the values ​​of n, a, and b, while specifying that a and b have the same value. In this case, the N-position side chain of the imidazole cation has a shorter alkenyl side chain, further reducing steric hindrance during polymerization, improving polymerization efficiency, and indirectly optimizing the degree of polymerization of the resulting polymer. The two ether-containing oxygen-bonded groups connected to one end of the alkyl chain are further optimized to have chains of the same length, resulting in a more balanced force distribution and higher molecular regularity. This symmetrical structure helps to form a more uniform microenvironment in the polymer network, not only further promoting efficient lithium-ion transport but also enhancing the stability of the polymer backbone. When a and b are equal, the overall spatial conformation and electron cloud distribution of the anionic groups are more symmetrical, reducing the risk of side reactions caused by uneven local polarity or steric hindrance, thereby improving the long-term compatibility and cycle stability of the electrolyte-electrode interface. Further limiting n to the range of 2-4 achieves a further balance between polymerization activity and the final material's mechanical properties. Within this range, the carbon chain length provides sufficient flexibility to ensure monomer mobility and conversion rate during polymerization, guaranteeing the formation of a dense and complete cross-linked network. Simultaneously, it maintains necessary rigidity, effectively preventing a decrease in mechanical strength due to excessively long and soft chain segments. This allows the prepared polymer solid electrolyte to meet both the compatibility requirements for solid-solid contact with the electrode and the requirements for the toughness and support of the battery material. By keeping values ​​of a and b equal and limiting them to 0-3, excessively long flexible chains can weaken the overall rigidity of the polymer network. Furthermore, excessively long groups containing ether oxygen bonds can prevent excessive dissociation of lithium salts and more intense side reactions with the lithium metal anode, thereby further improving lithium-ion transport, the compatibility and stability of the polymer solid electrolyte-electrode interface, and comprehensively enhancing the overall performance of the battery.

[0014] As a further embodiment, in the battery additive, X is a C2~C3 alkenyl chain, n is an integer from 2 to 3, a is an integer from 0 to 2, b is an integer from 0 to 2, and a=b.

[0015] As a further embodiment, the ionic liquid anion includes one of the following: halogen anion, nitrate anion, carbonate anion, acetate anion, phosphate anion, pyrophosphate anion, perchlorate anion, trifluoromethanesulfonate anion, tetrafluoroborate anion, hexafluorophosphate anion, oxaloborate anion, oxalate anion, borate anion, sulfonate anion, bis(trifluoromethanesulfonyl)imide anion, and bis(fluorosulfonyl)imide anion.

[0016] As a further preferred embodiment, the ionic liquid anion is one of bis(trifluoromethanesulfonyl)imide anion or bis(fluorosulfonyl)imide anion.

[0017] Secondly, the present invention also provides a method for preparing a battery additive, comprising the following steps: S1: Compound 1 (as shown in Formula 3) with a polymerizable active group X attached to the N-position side chain and compound 2 (as shown in Formula 4) are mixed evenly in solution at a molar ratio of (1~1.2):1, and then heated to 70℃~90℃. After reacting for 36~60h, the first product is obtained. Z in compound 2 is selected from any one of halogen atoms, hydroxyl groups, and amino groups.

[0018] The general reaction formula for S1 is shown in Formula 5:

[0019] S2: Dissolve the first product in water, and add the anion Y containing the ionic liquid. - The first lithium salt, wherein the molar ratio of the first product to the first lithium salt is 1:(0.8~1.2), is reacted at room temperature for 8~16 h to obtain an additive for battery use; The general reaction formula for S2 is shown in Formula 6:

[0020] In the mixed solution of S1, the first solvent for dissolving compound 1 and compound 2 is not specifically limited. Those skilled in the art can select a solvent that can dissolve the solutes and does not chemically react with the solutes as needed. For example, it can be selected from any one of ethyl acetate, pure water, n-hexane, and ethanol.

[0021] As a further embodiment, the method for preparing the battery additive includes the following steps: S1: Compound 1 (as shown in Formula 3) with a polymerizable active group X attached to the N-position side chain and compound 2 (as shown in Formula 4) are mixed evenly in solution at a molar ratio of (1~1.2):1, and then heated to 75℃~85℃. After reacting for 40~56h, the first product is obtained. Z in compound 2 is selected from any one of halogen atoms, hydroxyl groups, and amino groups. S2: Dissolve the first product in water, and add the anion Y containing the ionic liquid. - The first lithium salt, wherein the molar ratio of the first product to the first lithium salt is 1:(0.8~1.2), is reacted at room temperature for 8~16 h to obtain an additive for battery use.

[0022] Thirdly, the present invention also provides a polymer solid electrolyte membrane, wherein the raw materials of the polymer solid electrolyte membrane include battery additives prepared by the preparation methods of the first aspect battery additive or the second aspect battery additive, and also include a second lithium salt, a crosslinking agent, an initiator and a base film.

[0023] Fourthly, the present invention also provides a method for preparing a polymer solid electrolyte membrane, comprising the following steps: S1: The battery additive of the first aspect or the battery additive prepared by the method of the second aspect is mixed evenly with the second lithium salt, crosslinking agent, and initiator in a second solvent to prepare a precursor solution; wherein the mass percentage of the second lithium salt added is 5~50wt% of the battery additive, the mass percentage of the crosslinking agent added is 0.5~5wt% of the battery additive, and the mass percentage of the initiator added is 0.2~5wt% of the battery additive;

[0024] S2: The precursor solution prepared in S1 is dropped into the base membrane to fully impregnate it. After the solvent evaporates, the precursor solution is polymerized by heating or ultraviolet light to obtain a polymer solid electrolyte membrane.

[0025] The present invention employs in-situ polymerization, a simple and effective strategy. The core of in-situ polymerization is to formulate low-viscosity monomers, lithium salts, initiators, and other components to form a homogeneous precursor solution. This solution contains small molecules with good fluidity and wettability, which can fully wet the electrode and fill the electrode pores before polymerization. This ensures good contact between the solid electrolyte formed after polymerization and the electrode, significantly reducing the impedance between the electrode and the electrolyte, improving ion transport efficiency, and enhancing the battery's capacity and cycle performance.

[0026] As a further embodiment, the base membrane is a high-porosity base membrane with a porosity of 60% to 90% and a pore size of 200 to 500 nm.

[0027] This invention further selects a high-porosity base membrane as the self-supporting membrane for the polymer solid electrolyte, providing mechanical support for the electrolyte membrane. Its internal pores are fibrous and continuous, and the structure of the base membrane itself does not affect lithium-ion transport within the electrolyte. This invention also further limits the porosity and pore size of the high-porosity base membrane, which better enables sufficient and rapid wetting of the precursor solution and ensures a tight bond between the three-dimensional network structure formed after polymerization and the base membrane framework. On the one hand, limiting the porosity of the base membrane to 60%~90% provides sufficient pore space and capillary force during the precursor solution drop addition stage, promoting uniform solution distribution and complete filling of the base membrane, thereby forming a continuous, defect-free ion transport network after polymerization. If the porosity is too low, the solution cannot fully wet the membrane, potentially leading to uneven electrolyte distribution and increased interfacial resistance. If the porosity is too high, although it is beneficial for solution filling, it may weaken the mechanical support strength of the base membrane, affecting the overall mechanical properties of the electrolyte membrane. This invention further limits the pore size to 200-500 nm, based on a comprehensive consideration of interfacial contact area, lithium-ion transport path, and lithium dendrite suppression capability. A pore size within this range provides a large specific surface area, significantly enhancing the solid-solid contact between the polymerized electrolyte and the substrate membrane framework, effectively reducing interfacial impedance. Simultaneously, the moderate and continuous pore size facilitates uniform and rapid lithium-ion migration within the electrolyte, avoiding transport bottlenecks caused by excessively small pore sizes or uneven lithium-ion distribution caused by excessively large pore sizes. Furthermore, this pore structure provides a certain physical constraint on lithium dendrite growth, synergizing with the mechanical strength of the polymer itself to further improve battery safety performance.

[0028] As a further embodiment, the method for preparing the polymer solid electrolyte membrane includes the following steps: S1: The battery additive of the first aspect or the battery additive prepared by the preparation method of the second aspect is mixed evenly with the second lithium salt, crosslinking agent and initiator in the second solvent to prepare a precursor solution; wherein the mass percentage of the second lithium salt added is 10~40wt% of the battery additive, the mass percentage of the crosslinking agent added is 1~3wt% of the battery additive, and the mass percentage of the initiator added is 0.5~3wt% of the battery additive; S2: The precursor solution prepared in S1 is dropped into a high-porosity base membrane to fully wet it. After the solvent evaporates, the precursor solution is polymerized by heating or ultraviolet light to obtain a polymer solid electrolyte membrane. The porosity of the high-porosity base membrane is 60%~90%, and the pore size of the high-porosity base membrane is 200~500 nm.

[0029] This invention further optimizes the mass ratio of each component in the precursor solution, which is further adapted to the high-porosity base membrane defined in this invention. The precursor solution is dropped into the high-porosity base membrane. After the solvent evaporates, the solute in the precursor solution can be completely filled in the high-porosity base membrane. The precursor is polymerized by heating or ultraviolet light irradiation, resulting in a polymer solid electrolyte membrane with high pore filling rate and a dense polymer layer on the surface. This avoids a series of problems caused by improper component ratio, such as uneven wetting, incomplete polymerization, decreased mechanical properties, and increased interfacial impedance. It achieves a better balance between monomer polymerization efficiency, ion transport performance, and the final mechanical strength of the electrolyte membrane.

[0030] As a further preferred embodiment, the method for evaporating the solvent in S2 can be achieved by heating under negative pressure to evaporate the solvent, with a heating temperature of 50~70℃ and a heating time of 4~6h.

[0031] This invention can further utilize a high-porosity base membrane as a self-supporting membrane, while using heating and negative pressure to uniformly and densely fill the precursor solution into the base membrane. After filling, the porosity is greatly reduced, and then in-situ polymerization is carried out, which has good interfacial contact and further reduces the interfacial impedance to a certain extent.

[0032] As a further embodiment, the method for preparing the polymer solid electrolyte membrane includes the following steps: S1: The battery additive of the first aspect or the battery additive prepared by the preparation method of the second aspect is mixed evenly with the second lithium salt, crosslinking agent and initiator in the second solvent to prepare a precursor solution; wherein the mass percentage of the second lithium salt added is 10~40wt% of the battery additive, the mass percentage of the crosslinking agent added is 1~3wt% of the battery additive, and the mass percentage of the initiator added is 0.5~3wt% of the battery additive; S2: The precursor solution prepared in S1 is dropped into a high-porosity base membrane to fully impregnate it. The solvent is evaporated by heating under negative pressure at a temperature of 50-70°C for 4-6 hours. Then, the precursor solution is polymerized by heating or ultraviolet irradiation to obtain a polymer solid electrolyte membrane. The porosity of the high-porosity base membrane is 60%-90%, and the pore size of the high-porosity base membrane is 200-500 nm.

[0033] This invention further combines the solvent evaporation method under heating negative pressure with an optimized high-porosity base film and a precisely proportioned precursor solution. This allows the precursor solution to completely occupy the large specific surface area and complex pores of the base film. After solvent removal, the precursor solution and the base film skeleton are tightly bonded, laying a solid foundation for subsequent photocuring or thermal polymerization reactions. The resulting polymer solid electrolyte membrane has a complete three-dimensional ion transport network, reduced interfacial impedance, excellent mechanical integrity, and good interfacial contact, effectively suppressing the growth of lithium dendrites and thus comprehensively improving the electrochemical performance of the all-solid-state battery.

[0034] As a further embodiment, the second lithium salt includes one or more of lithium phosphate, lithium arsenate, lithium borate, lithium sulfonyl salt, lithium sulfonate, and lithium perchlorate.

[0035] As a further option, the initiator is selected from one or more of thermal initiators or photoinitiators.

[0036] As a further embodiment, the crosslinking agent includes one or more of acrylate compounds, acrylamide compounds, and acrylate alcohol compounds.

[0037] As a further preferred embodiment, the thermal initiator is selected from one or more of azobisisobutyronitrile, azobisisoheptanenitrile, and azobiscyclohexylformitrile.

[0038] As a further preferred embodiment, the photoinitiator is selected from TPO photoinitiator or 819 photoinitiator.

[0039] As a further preferred embodiment, the photoinitiator is 819 photoinitiator.

[0040] As a further preferred embodiment, the lithium phosphate salt includes lithium hexafluorophosphate, lithium tetrafluorophosphate, and lithium difluorophosphate.

[0041] As a further preferred embodiment, the lithium arsenate salt includes lithium hexafluoroarsenate.

[0042] As a further preferred embodiment, the lithium borate salt includes lithium tetrafluoroborate, lithium dioxalate borate, and lithium difluorooxalate borate.

[0043] As a further preferred embodiment, the sulfonyl lithium salt includes lithium bis(trifluoromethylsulfonyl)imide and lithium bis(fluorosulfonyl)imide.

[0044] As a further preferred embodiment, the lithium sulfonate salt includes lithium trifluoromethanesulfonate, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(fluorosulfonyl)imide.

[0045] As a further preferred embodiment, the acrylate compound includes ethoxylated trimethylolpropane triacrylate and trimethylolpropane triacrylate.

[0046] As a further preferred embodiment, the acrylamide compound includes N,N-methylenebisacrylamide.

[0047] As a further preferred embodiment, the acrylate compound includes diethylene glycol dimethacrylate.

[0048] As a further option, the second solvent is selected from one or more of N-methylpyrrolidone (NMP), dimethyl ethylene glycol (DME), and acetonitrile.

[0049] As a further preferred embodiment, the second solvent is dimethyl ethylene glycol (DME).

[0050] As a further preferred embodiment, the base membrane is selected from one of high-porosity PE base membrane, high-porosity PEO base membrane, high-porosity PAN base membrane, and high-porosity PTFE base membrane.

[0051] As one preferred embodiment, the method for preparing the polymer solid electrolyte membrane includes the following steps: S1: The battery additive of the first aspect or the battery additive prepared by the second aspect method is mixed evenly with the second lithium salt, crosslinking agent and thermal initiator in DME solvent to prepare a precursor solution; wherein the mass percentage of the second lithium salt added is 10~40wt% of the battery additive, the mass percentage of the crosslinking agent added is 1~3wt% of the polymer monomer, and the mass percentage of the initiator added is 0.5~3wt% of the polymer monomer; S2: The precursor solution prepared in S1 is dropped into a high-porosity PE base membrane. The solvent is evaporated by heating under negative pressure at a temperature of 50-70°C for 4-6 hours. After the solvent evaporates, the precursor solution is polymerized by heating at a temperature of 50-70°C for 12-36 hours. A polymer solid electrolyte membrane is obtained. The porosity of the high-porosity base membrane is 60%-85%, and the pore size is 200-300 nm.

[0052] As another preferred embodiment, the method for preparing the polymer solid electrolyte membrane includes the following steps: S1: The battery additive of the first aspect or the battery additive prepared by the second aspect method is mixed evenly with the second lithium salt, crosslinking agent and 819 photoinitiator in DME solvent to prepare a precursor solution; wherein the mass percentage of the second lithium salt added is 10~40wt% of the battery additive, the mass percentage of the crosslinking agent added is 1~3wt% of the polymer monomer, and the mass percentage of the initiator added is 0.5~3wt% of the polymer monomer; S2: The precursor solution obtained in S1 is dropwise added to a high-porosity PE base membrane. The solvent is evaporated by heating under negative pressure at a temperature of 50-70°C for 4-6 hours. After solvent evaporation, the precursor solution is polymerized by ultraviolet (UV) irradiation at a power of 20-40W, a wavelength of 300-400nm, and a polymerization time of 70-100s, resulting in a polymer solid electrolyte membrane. The high-porosity base membrane has a porosity of 60%-85% and a pore size of 200-300nm.

[0053] Fifthly, the present invention also provides a lithium metal solid-state battery, comprising the polymer solid-state electrolyte membrane described in the third aspect or the polymer solid-state electrolyte membrane prepared by the preparation method described in the fourth aspect.

[0054] The features and beneficial effects of this invention are as follows: In light of the current research status and development trends of polyionic liquid-based polymer solid electrolytes, this invention aims to further develop novel functional polyionic liquid-based polymer solid electrolytes for high-safety lithium metal solid batteries. Compared with existing technologies, this invention has at least the following advantages: (1) Starting from molecular structure design, this invention designs and synthesizes a novel battery additive containing ether oxygen bonds, and achieves synergistic enhancement of functions such as faster lithium-ion transport and interface stability through specific functional groups (ether oxygen bonds); (2) The polymer solid electrolyte disclosed in this invention uses a self-supporting membrane with high porosity and is uniformly and densely filled in the base membrane by heating and negative pressure. While having excellent electrochemical performance, it can also take into account certain mechanical properties. This invention utilizes in-situ solidification technology to directly polymerize between lithium anodes and cathodes and then modify the interface to construct a solid electrolyte interface (SEI) layer. This improves the compatibility of solid-solid contacts, reduces interfacial impedance, creates efficient ion transport pathways, and enhances the electrochemical performance of the battery. Attached Figure Description

[0055] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0056] Figure 1 The diagram shows the structure, hydrogen NMR spectrum, and carbon NMR spectrum of the battery additive prepared in Example 1.

[0057] Figure 2 The diagram shows the discharge specific capacity and coulombic efficiency of the LFP||Li battery assembled in Example 1 at room temperature.

[0058] Figure 3 This is a battery charge / discharge curve diagram for Example 1.

[0059] Figure 4 The lithium-ion transport numbers are for the polymer solid electrolytes of Example 1 and Comparative Example 2. Detailed Implementation

[0060] 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.

[0061] As a specific example of the implementation of this invention, detailed cases are provided below: Example 1: 17.2 g of 1-vinylimidazol, 25 g of 4-chlorobutyral dimethyl acetal, and 40 g of ethyl acetate were added to a round-bottom flask. After stirring thoroughly, the mixture was heated to 80°C and reacted for 48 h to obtain a pale yellow liquid first product. The first product was filtered and repeatedly washed. The washed product 1 was dissolved in water, and a first lithium salt (molar ratio of first product to first lithium salt was 1.1:1) was added. After ion exchange at room temperature for 12 h, a brownish-red liquid was obtained. After repeated washing and rotary evaporation, the battery additive was obtained. Its structural formula and NMR spectrum characterization are as follows. Figure 1 As shown in Figure 7, the reaction process follows the formula:

[0062] The precursor solution is prepared by mixing the battery additive, 20 wt% LiTFSI (by mass of the battery additive), 1 wt% 819 photoinitiator (by mass of the battery additive), 3 wt% ethoxylated trimethylolpropane triacrylate (by mass of the battery additive), and an appropriate amount of DME solvent (40 μL of DME is added for every 0.1 g of LiTFSI) to form a precursor solution.

[0063] A positive electrode sheet was prepared using LFP as the positive electrode material and lithium (Li) as the negative electrode material. The positive electrode shell, positive electrode sheet, 50% of the total amount of precursor solution, a high-porosity PE base film (with a pore size of 260 nm and a porosity of approximately 80%), and another 50% of the total amount of precursor solution were sequentially stacked. The precursor solution was drop-added onto both sides of the high-porosity base film and into the positive electrode sheet to achieve full wetting. The process was completed under vacuum negative pressure (10... -4 pa~ 10 -7 Under the condition of (pa), heating to 60℃ for 5h allows the solvent to evaporate while helping the precursor to better fill the high-porosity base film and positive electrode. The uniform and dense filling of the precursor into the base film is verified by mercury intrusion porosimetry, SEM and EDS. After curing at a UV power of 30W, UV wavelength of 365nm and UV polymerization time of 90s, lithium sheet, gasket, spring sheet and negative electrode shell are placed in sequence to assemble a lithium metal solid battery.

[0064] Example 2: The only difference from Example 1 is that the PE high-porosity base film with a porosity of about 80% and an average pore size of about 260 nm is replaced with a PE high-porosity base film with a porosity of about 90% and an average pore size of about 500 nm. The rest of the composition, preparation method, battery assembly and testing method are the same as in Example 1.

[0065] Example 3: The only difference from Example 1 is that the content of the second lithium salt is changed from 20wt% LiTFSI to 30wt% LiTFSI. The rest of the composition, preparation method, battery assembly and testing method are the same as in Example 1.

[0066] Example 4: The only difference from Example 1 is that the content of the second lithium salt is changed from 20wt% LiTFSI to 10wt% LiTFSI. The rest of the composition, preparation method, battery assembly and testing method are the same as in Example 1.

[0067] Example 5: The only difference from Example 1 is that a precursor solution was prepared by uniformly mixing battery additives, 5 wt% LiTFSI (by weight of the battery additives), 0.2 wt% 819 photoinitiator (by weight of the battery additives), 0.5 wt% crosslinking agent ethoxylated trimethylolpropane triacrylate (by weight of the battery additives), and an appropriate amount of DME solvent (40 μL of DME for every 0.1 g of LiTFSI). The remaining components, preparation methods, battery assembly, and testing methods are the same as in Example 1.

[0068] Example 6: The only difference from Example 1 is that a precursor solution is prepared by uniformly mixing battery additives, 50 wt% LiTFSI (by weight of battery additives), 5 wt% 819 photoinitiator (by weight of battery additives), 5 wt% ethoxylated trimethylolpropane triacrylate (by weight of battery additives), and an appropriate amount of DME solvent (40 μL of DME for every 0.1 g of LiTFSI). The remaining components, preparation methods, battery assembly, and testing methods are the same as in Example 1.

[0069] Example 7: The only difference from Example 1 is that compound 1 is replaced with a compound of formula 8. The rest of the composition, preparation method, battery assembly and testing method are the same as in Example 1.

[0070]

[0071] Example 8: The only difference from Example 1 is that compound 1 is replaced with a compound of formula 9. The rest of the composition, preparation method, battery assembly and testing method are the same as in Example 1.

[0072]

[0073] Example 9: The only difference from Example 1 is that compound 2 is replaced with a compound of formula 10. The rest of the composition, preparation method, battery assembly and testing method are the same as in Example 1.

[0074]

[0075] Example 10: The only difference from Example 1 is that compound 2 is replaced with a compound of formula 11. The rest of the composition, preparation method, battery assembly and testing method are the same as in Example 1.

[0076]

[0077] Example 11: The only difference from Example 1 is that compound 2 is replaced with a compound of formula 12. The rest of the composition, preparation method, battery assembly and testing method are the same as in Example 1.

[0078]

[0079] Example 12: The only difference from Example 1 is that 17.2 g of 1-vinylimidazol, 25 g of 4-chlorobutyral dimethyl acetal, and 40 g of ethyl acetate were added to a round-bottom flask. After stirring thoroughly, the mixture was heated to 70°C and reacted for 36 h to obtain a pale yellow liquid first product. The remaining composition, preparation method, battery assembly, and testing methods were the same as in Example 1.

[0080] Example 13: The only difference from Example 1 is that the solvent evaporation conditions of 60°C, 5h, and vacuum pressure are replaced with heating at only 60°C without vacuum pressure treatment. All other components, preparation methods, battery assembly, and testing methods are the same as in Example 1.

[0081] Example 14: The only difference from Example 1 is that the PE high-porosity base film with a porosity of about 80% and an average pore size of about 260 nm is replaced with a PE base film with a porosity of about 55% and an average pore size of about 180 nm. The rest of the composition, preparation method, battery assembly and testing method are the same as in Example 1.

[0082] Example 15: The only difference from Example 1 is that the 819 photoinitiator is replaced with the thermal initiator azobisisobutyronitrile (AIBN). The precursor solution is polymerized by heating at 60°C for 24 hours. All other components, preparation methods, battery assembly, and testing methods are the same as in Example 1.

[0083] Example 16: The only difference from Example 1 is that the second solvent DME added to the polymer precursor solution is replaced with acetonitrile. The rest of the composition, preparation method, battery assembly and testing method are the same as in Example 1.

[0084] Example 17: The only difference from Example 1 is that the photoinitiator in the precursor is replaced by photoinitiator tpo instead of photoinitiator 819. The rest of the composition, preparation method, battery assembly and testing method are the same as in Example 1.

[0085] Comparative Example 1: The only difference from Example 1 is that the polyionic liquid monomer is [VMIM]TFSI, which lacks the ether oxygen bond of the monomer prepared in Example 1.

[0086] Comparative Example 2: The only difference from Example 1 is that no crosslinking agent was added to the polymer precursor. The rest of the composition, preparation method, battery assembly and testing method are the same as in Example 1.

[0087] Comparative Example 3: The only difference from Example 1 is that no solvent was added to the polymer precursor solution. The rest of the composition, preparation method, battery assembly and testing methods are the same as those in Example 1.

[0088] Comparative Example 4: The only difference from Example 1 is that compound 2 is replaced with a compound of Formula 13. The rest of the composition, preparation method, battery assembly and testing method are the same as in Example 1.

[0089]

[0090] Comparative Example 5: The only difference from Example 1 is that compound 2 is replaced with a compound of Formula 14. The rest of the composition, preparation method, battery assembly and testing method are the same as in Example 1.

[0091]

[0092] After the batteries of Examples 1 to 17 and Comparative Examples 1 to 5 were assembled, the following tests were performed respectively: (1) Ionic conductivity test: The ionic conductivity of pure liquids can be directly tested using a conductivity analyzer. The conductivity analyzer uses electrodes to introduce current into the substance being tested, and simultaneously measures the current intensity passing through the substance. By utilizing the movement behavior of ions in an electric field, it reflects the strength of the substance's conductivity. The impedance of the SS||SS battery is tested using an electrochemical workstation, and then the specific ionic conductivity is calculated using σ=L / (R·S), where L is the actual distance between the two electrodes and S is the effective contact area.

[0093] (2) The filling effect and density of the precursor are judged by measuring the pore size and porosity of the PE high-porosity base film and the positive electrode by mercury intrusion porosimetry.

[0094] (3) Battery first-cycle discharge capacity test method: By assembling LFP||Li batteries (the areal loading of the electrode is 2.3 mgcm) -2 The battery was placed in a battery test chamber at 25℃, 45℃, and 60℃ for charge-discharge cycle testing. The test voltage range was 2.5V~4.0V, and the test rate was 3 activations at 0.05C and 0.1C cycles.

[0095] (4) Capacity retention (10 cycles): By assembling LFP|Li cells (the areal loading of the electrode is 2.3 mg cm⁻¹) -2 The battery was placed in a battery test chamber at 25℃, 45℃, and 60℃ for charge-discharge cycle testing. The test voltage range was 2.5 V to 4.0 V, and the test rate was 3 activations at 0.05C and 0.1C cycles.

[0096] Table 1 shows the performance test data of Examples 1-17 and Comparative Examples 1-5. It compares the polymer precursor solutions of different examples and comparative examples in the filling of PE high-porosity base film and positive electrode sheet, and the ionic conductivity of their assembled SS||SS batteries, the first discharge specific capacity of LFP||Li batteries, and the capacity retention rate after 50 cycles.

[0097] The method for assembling SS||SS batteries is as follows: the positive electrode shell, gasket, 1 / 2 precursor solution, high porosity base film, and 1 / 2 precursor solution are stacked sequentially. Under vacuum negative pressure, the mixture is heated to 60°C for 5 hours to allow the solvent to evaporate. The ultraviolet power is 30W, the ultraviolet wavelength is 365nm, and the ultraviolet polymerization time is 90s. After curing, the gasket, spring sheet, and negative electrode shell are placed sequentially to assemble the SS||SS battery.

[0098]

[0099] As can be seen from the comparison between Examples 1-17 and Comparative Examples 1-5, this invention addresses the problems of low ionic conductivity, lithium-ion transference number, and poor interfacial stability in polymer solid electrolytes obtained by in-situ polymerization of ionic liquid monomers in existing technologies. It provides a novel battery additive. Starting from molecular structure design, a novel battery additive containing ether-oxygen bonds was designed and synthesized. Through specific functional groups, it achieves synergistic enhancement of functions such as faster lithium-ion transport and interfacial stability. Using in-situ curing technology, direct polymerization is performed between the lithium anode and cathode, followed by interface modification to construct a stable solid electrolyte interface layer. This improves the compatibility of solid-solid contacts, reduces interfacial impedance, and creates an efficient ion transport pathway. Compared to the comparative examples of polymer solid electrolytes prepared without using the ionic liquid monomers specified in this invention, this invention significantly improves the room temperature ionic conductivity of the polymer solid electrolyte, while also improving the first-cycle discharge specific capacity and cycle performance of the battery, thus enhancing the overall electrochemical performance of the battery.

[0100] Figure 2 The discharge specific capacity and coulombic efficiency of the LFP||Li battery assembled in Example 1 are shown at room temperature. It can be found that the polyionic liquid-based solid electrolyte of the present invention can enable the battery to exhibit high discharge specific capacity (≥140 mAh / g), high average coulombic efficiency (≥99.9%), and high capacity retention (≥96% capacity retention after 50 cycles).

[0101] Figure 3 The charge-discharge curves of the battery in Example 1 show that it also exhibits a small increase in polarization voltage, indicating excellent electrochemical stability. These results fully demonstrate that the polyionic liquid-based solid electrolyte of the present invention has good electrode compatibility, ensuring long-term cycle stability and high coulombic efficiency of the battery.

[0102] By comparing Example 1 and Comparative Example 1, it was found that the present invention designs and synthesizes a novel battery additive containing ether oxygen bonds. Through specific functional groups, multiple groups containing ether oxygen bonds are introduced to achieve synergistic enhancement of functions such as faster lithium-ion transport and interface stability. After direct polymerization between the lithium anode and cathode using in-situ curing technology, the interface is modified to construct a stable solid electrolyte interface layer, improve the compatibility of solid-solid contact, reduce interface impedance, create an efficient ion transport pathway, and improve the overall electrochemical performance of the battery.

[0103] By comparing Example 1 and Comparative Example 2, it was found that the crosslinking agent used in this invention can polymerize to form a more stable crosslinked network structure, reducing residual monomers caused by insufficient polymerization and significantly avoiding irreversible side reactions between residual monomers and the electrode. Furthermore, this invention selects acrylate compounds, acrylamide compounds, and acrylate alcohol compounds as crosslinking agents, which contain a large number of C=O bonds, thus improving the lithium-ion transference number to a certain extent. Figure 4 As shown, the lithium-ion transference number (0.69 eV) of the polymer solid electrolyte of the present invention is significantly higher than that of the polymer without crosslinking agent in Comparative Example 2 (0.46 eV), and the assembled battery has higher capacity utilization and capacity retention, indicating that it can effectively improve the cycle stability of the battery.

[0104] By comparing Examples 1, 16, and 3, it can be found that the addition of a volatile second solvent in this invention not only helps the precursor solution to mix uniformly, but also helps the precursor to fill better into the base film and the positive electrode. Furthermore, this invention further reveals that DME solvent, compared to acetonitrile solvent, more easily forms a more stable anion-dominated solvation structure, thereby constructing a more protective SEI film. Moreover, its higher chemical stability makes the harm from trace residues far less than that from acetonitrile.

[0105] Comparing Example 1 and Comparative Examples 4-5, it can be seen that the N-position side chain of the imidazole cation in this invention has polymerizable active groups, which can form a three-dimensional cross-linked polymer network through in-situ UV curing or thermal polymerization. This forms the mechanical framework of the electrolyte, endowing it with excellent mechanical strength, dimensional stability, and interfacial adhesion to the electrode. This design not only effectively inhibits the growth of lithium dendrites and improves safety, but also provides a core material basis for manufacturing thin, flexible, all-solid-state lithium-ion batteries. Based on the above, two groups containing ether oxygen bonds are innovatively introduced into the anionic group of the ionic liquid at one end of the alkyl straight chain. Due to the lithiophilicity of the ether oxygen bond, the dissociation of the lithium salt is enhanced, increasing ionic conductivity and lithium-ion transference number. It can also, to a certain extent, improve the electrochemical window of the imidazole ionic liquid, avoiding the limited improvement in lithium-ion migration capacity due to insufficient ether oxygen bonds, and also avoiding the problem of excessive dissociation of the lithium salt due to excessive ether oxygen bonds, which leads to increased side reactions during battery cycling. At this point, the ether oxygen bonds are distributed on the two groups at one end of the alkyl straight chain, resulting in a higher degree of lithium salt dissociation. Based on the above, the mechanical stability of the polymer solid electrolyte and the lithium-ion transport capability are balanced.

[0106] By comparing Example 1 and Example 2, it can be seen that the present invention further optimizes the pore size and porosity of the high-porosity base film, so that the precursor fills the base film in a suitable proportion. While constructing a complete three-dimensional network of polymer solid electrolyte, it avoids the overall mechanical strength from deteriorating after polymerization. Under external pressure or impact, it is more prone to distortion and cracking, resulting in uneven deposition of lithium ions on the electrode surface, which may lead to lithium dendrite growth and seriously threaten the safety and cycle life of the battery.

[0107] By comparing Examples 1, 3, 4 and Examples 5-6, it can be seen that when the lithium salt ratio is 10-30 wt% of the polyionic liquid monomer, the ionic conductivity is higher. This may be because it avoids the problem that a high lithium salt content in the precursor solution leads to a high viscosity of the polymer precursor solution, which prevents the polymer precursor solution from filling the pores of the base film well. It also avoids the problem that a low lithium salt content in the polymer precursor solution results in a smaller effective current.

[0108] By comparing Examples 1, 7, and 9 with Examples 8, 10, and 11, it can be seen that the present invention further limits the type of X and the values ​​of n, a, and b in the battery additive, and limits a and b to the same value. In this case, the N-position side chain of the imidazole cation has a shorter alkenyl side chain, further reducing steric hindrance during polymerization and improving polymerization efficiency, while indirectly optimizing the degree of polymerization of the polymer formed after polymerization. The two ether-containing oxygen bond groups connected to one end of the alkyl chain are further optimized to have chains of the same length, resulting in a more balanced force distribution and higher molecular regularity. This symmetrical structure helps to form a more uniform microenvironment in the polymer network, which not only further promotes the efficient transport of lithium ions but also enhances the stability of the polymer skeleton. When a and b are equal, the overall spatial conformation and electron cloud distribution of the anionic groups are more symmetrical, which reduces the risk of side reactions caused by uneven local polarity or steric hindrance, thereby improving the long-term compatibility and cycle stability of the electrolyte-electrode interface. By further limiting n to the range of 2-4, a further balance was achieved between polymerization activity and the final material's mechanical properties. The carbon chain length within this range provides sufficient flexibility to ensure monomer mobility and conversion rate during polymerization, guaranteeing the formation of a dense and complete cross-linked network; it also maintains necessary rigidity, effectively preventing a decrease in mechanical strength due to excessively long and soft chain segments. This allows the prepared polymer solid electrolyte to meet both the compatibility requirements for solid-solid contact with the electrode and the requirements for the battery material's toughness and support. Keeping a and b equal while limiting their values ​​to 0-3 avoids the possibility that excessively long flexible chains might weaken the overall rigidity of the polymer network. This further avoids the possibility that excessively long groups containing ether oxygen bonds might cause excessive dissociation of lithium salts and more intense side reactions with the lithium metal anode, thereby further improving lithium-ion transport, the compatibility and stability of the polymer solid electrolyte-electrode interface, and comprehensively enhancing the battery's overall performance.

[0109] A comparison of Examples 1 and 7 and 9 shows that the present invention further restricts the N-position side chain of the imidazole cation to have a shorter alkenyl side chain, further reducing steric hindrance during polymerization and improving polymerization efficiency, while indirectly optimizing the degree of polymerization of the polymer formed after polymerization; further restricting n to the range of 2 to 3 achieves a further balance between polymerization activity and the final material mechanical properties. The carbon chain length within this range provides sufficient flexibility to ensure the monomer's mobility and conversion rate during polymerization, ensuring the formation of a dense and complete cross-linked network; it also maintains necessary rigidity, effectively preventing a decrease in mechanical strength due to excessively long and soft chain segments. This allows the prepared polymer solid electrolyte to meet both the compatibility requirements for solid-solid contact with the electrode and the requirements for the toughness and support of the battery material. Limiting the values ​​of a and b to 0~2 avoids the possibility that excessively long flexible chains may weaken the overall rigidity of the polymer network. This further avoids the possibility that excessively long groups containing ether oxygen bonds may cause excessive dissociation of lithium salts and more intense side reactions with lithium metal anodes. As a result, the lithium-ion transport of the battery, the compatibility and stability of the polymer solid electrolyte and electrode interface are further improved, and the overall performance of the battery is comprehensively enhanced.

[0110] By comparing Example 1 and Example 12, it can be seen that the present invention further optimizes the reaction temperature and time between compound 1 and compound 2, achieving a more complete reaction and improving the synthesis efficiency of battery additives.

[0111] By comparing Examples 1 and 5-6, and Examples 13-14, it can be seen that the present invention further combines the solvent evaporation method of heating under negative pressure with the optimized high-porosity base film and the precisely proportioned precursor solution. This can further enable the precursor solution to completely occupy the large specific surface area and complex channels of the base film. After the solvent is removed, the precursor solution and the base film skeleton are tightly bonded, laying a solid foundation for subsequent photocuring or thermal polymerization reactions. The resulting polymer solid electrolyte membrane has a complete three-dimensional ion transport network, reduces interfacial impedance, has excellent mechanical integrity, and good cross-sectional contact, which can effectively suppress the growth of lithium dendrites, thereby comprehensively improving the electrochemical performance of the all-solid-state battery.

[0112] By comparing Example 1 and Example 17, it can be seen that when photoinitiator 819 is replaced with TPO, because the free radical generation efficiency of photoinitiator 819 is higher than that of photoinitiator TPO, under the same initiator content and light exposure time, Example 1 can form a structure with higher degree of polymerization and more complete crosslinking network, reducing the occurrence of side reactions of residual monomers, and is more beneficial to ionic conductivity and interface stability.

[0113] In summary, addressing the problems of low room-temperature ionic conductivity, low lithium-ion transference number, poor interfacial contact, and poor processability in existing polymer solid electrolytes, a polyionic liquid-based polymer solid electrolyte has been invented. Due to limitations in current solid electrolyte preparation methods, it is impossible to achieve a comprehensive performance combining excellent mechanical strength, high ionic conductivity, strong processability, and industrialization potential. This invention polymerizes polyionic liquid monomers with specific functional groups to form a solid electrolyte, combining the intrinsic advantages of ionic liquids (non-flammability, structural tunability, electrochemical and thermal stability) with the easy processing and excellent flexibility of polymers, showing great potential in solid-state lithium metal batteries. Furthermore, using a high-porosity base film as a support, and employing volatile solvents, the precursor solution can be uniformly and densely filled into the base film and electrode, improving room-temperature ionic conductivity to a certain extent while maintaining a certain level of mechanical strength. Simultaneously, the use of UV-cured semi-in-situ polymerization further improves its interfacial compatibility and safety compared to traditional assembly methods. Based on these innovations, a polyionic liquid-based polymer solid electrolyte with comprehensive performance has been invented.

[0114] The technical features of the embodiments described above can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make modifications, alterations, substitutions, and variations to the above embodiments within the scope of the present invention. Furthermore, without contradiction, those skilled in the art can combine and integrate different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

Claims

1. An additive for a battery, characterized by, having a structure as Formula 1, , wherein X is a polymerizable active group selected from a substituted or unsubstituted C2-C6 alkenyl chain, the substituent group being selected from one or more of a halogen atom, a hydroxyl group, an amino group, a carboxyl group, an ester group, an amide group, an acyloxy group, a nitro group, a cyano group, an ether oxygen group, a phosphate group, a phosphite group, a sulfonate group, a sulfonyl group, a sulfoxide group, a sulfhydryl group, a silyl group, Y - is an ionic liquid anion, n is an integer from 1 to 6, a is an integer from 0 to 4, and b is an integer from 0 to 4.

2. The additive for a battery according to claim 1, characterized by in the battery additive, X is a C2-C4 alkenyl chain, n is an integer of 2-4, a is an integer of 0-3, b is an integer of 0-3, and a=b; Preferably, in the battery additive, X is a C2-C3 alkenyl chain, n is an integer of 2-3, a is an integer of 0-2, b is an integer of 0-2, and a=b.

3. The additive for a battery according to claim 1, characterized by The ionic liquid anion comprises one of halide anion, nitrate anion, carbonate anion, acetate anion, phosphate anion, pyrophosphate anion, perchlorate anion, triflate anion, tetrafluoroborate anion, hexafluorophosphate anion, oxalate borate anion, oxalate anion, borate anion, sulfonate anion, bis(trifluoromethylsulfonyl)imide anion, bis(fluorosulfonyl)imide anion. Preferably, the ionic liquid anion is one of bis(trifluoromethylsulfonyl)imide anion, bis(fluorosulfonyl)imide anion.

4. A method for producing the additive for a battery according to any one of claims 1 to 3, characterized by, having the following steps: S1: mixing compound 1 (such as Formula 3) with a polymerizable active group X connected to the side chain of N position and compound 2 (such as Formula 4) in a solution at a molar ratio of (1-1.2):1, and then heating to 70-90℃, and then reacting for 36-60h to obtain a first product, wherein Z in compound 2 is selected from any one of halogen atom, hydroxyl, amino; , The reaction general formula of S1 is as Formula 5: , S2: dissolving the first product in water, adding a first lithium salt containing the ionic liquid anion Y - at a molar ratio of the first product to the first lithium salt of 1: (0.8-1.2) and reacting at room temperature for 8-16 h to obtain an additive for batteries; The reaction general formula of S2 is as Formula 6, 。 5. The preparation method according to claim 4, characterized in that, The preparation method has the following steps: S1: mixing compound 1 (such as Formula 3) with a polymerizable active group X connected to the side chain of N position and compound 2 (such as Formula 4) in a solution at a molar ratio of (1-1.2):1, and then heating to 75-85℃, and then reacting for 40-56h to obtain a first product, wherein Z in compound 2 is selected from any one of halogen atom, hydroxyl, amino; S2: dissolving the first product in water, adding a first lithium salt containing the ionic liquid anion Y-, and the molar ratio of the first product to the first lithium salt is 1:(0.8-1.2), and then reacting at room temperature for 8-16h to obtain the battery additive.

6. A polymer solid-state electrolyte membrane, characterized by, The raw material of the polymer solid-state electrolyte film comprises the battery additive of any one of claims 1-3 or the battery additive prepared by the preparation method of any one of claims 4-5, and further comprises a second lithium salt, a crosslinking agent, an initiator, and a base film.

7. A method of producing the polymer solid electrolyte film according to claim 6, characterized by, comprising the following steps: S1: mixing the battery additive, a second lithium salt, a crosslinking agent, and an initiator in a second solvent to prepare a precursor solution; wherein the mass percentage of the second lithium salt added is 5-50wt% of the battery additive, the mass percentage of the crosslinking agent added is 0.5-5wt% of the battery additive, and the mass percentage of the initiator added is 0.2-5wt% of the battery additive; S2: dropping the precursor solution prepared in S1 into the base film, fully infiltrating, volatilizing the solvent, and then polymerizing the precursor solution by heating or ultraviolet light to obtain the polymer solid-state electrolyte film.

8. The preparation method according to claim 7, characterized in that, The base film is a high porosity base film, the porosity of the high porosity base film is 60%~90%, and the pore size of the high porosity base film is 200~500nm; Preferably, the preparation method of the polymer solid electrolyte film comprises the following steps: S1: uniformly mix the battery additive of the first aspect or the battery additive prepared by the preparation method of the second aspect, a second lithium salt, a crosslinking agent, and an initiator in a second solvent to prepare a precursor solution; wherein the mass percentage of the second lithium salt added is 10~40wt% of the battery additive, the mass percentage of the crosslinking agent added is 1~3wt% of the battery additive, and the mass percentage of the initiator added is 0.5~3wt% of the battery additive; S2: drop the precursor solution prepared in S1 into a high porosity base film, fully soak, volatilize the solvent, then polymerize the precursor solution by heating or ultraviolet light to obtain a polymer solid electrolyte film; the porosity of the high porosity base film is 60%~90%, and the pore size of the high porosity base film is 200~500nm.

9. The preparation method according to claim 7, characterized in that, The method of volatilizing the solvent in S2 can volatilize the solvent by heating under negative pressure, the heating temperature is 50~70℃, and the heating time is 4~6h; Preferably, the preparation method of the polymer solid electrolyte film comprises the following steps: S1: uniformly mix the battery additive of the first aspect or the battery additive prepared by the preparation method of the second aspect, a second lithium salt, a crosslinking agent, and an initiator in a second solvent to prepare a precursor solution; wherein the mass percentage of the second lithium salt added is 10~40wt% of the battery additive, the mass percentage of the crosslinking agent added is 1~3wt% of the battery additive, and the mass percentage of the initiator added is 0.5~3wt% of the battery additive; S2: drop the precursor solution prepared in S1 into a high porosity base film, fully soak, volatilize the solvent by heating under negative pressure, the heating temperature is 50~70℃, and the heating time is 4~6h, then polymerize the precursor solution by heating or ultraviolet light to obtain a polymer solid electrolyte film; the porosity of the high porosity base film is 60%~90%, and the pore size of the high porosity base film is 200~500nm. Preferably, the second lithium salt includes one or more of lithium phosphate, lithium arsenate, lithium borate, lithium sulfonate, lithium sulfonate, lithium perchlorate; Preferably, the initiator is selected from one or more of thermal initiators or photoinitiators; Preferably, the crosslinking agent includes one or more of acrylate compounds, acrylamide compounds, and acrylic alcohol ester compounds; Preferably, the thermal initiator is selected from one or more of azobisisobutyronitrile, azobisisoheptyl nitrile, and azobiscyclohexyl nitrile; Further preferably, the photoinitiator is a TPO photoinitiator or an 819 photoinitiator; Further preferably, the photoinitiator is an 819 photoinitiator.

10. A lithium metal solid-state battery, characterized by, The polymer solid electrolyte film of claim 6 or the polymer solid electrolyte film prepared by the preparation method of any one of claims 7~9.

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