A low-solubility perfluorogel electrolyte with dynamic stress self-repairing function, a preparation method and application thereof

Abstract

The application provides a low-solubility perfluorogel electrolyte with a dynamic stress self-repairing function, a preparation method and application thereof, and the pre-polymerized electrolyte comprises monomers, a cross-linking agent, an initiator, a solvent, a diluent and a lithium salt; the monomers are selected from at least one of fluorine-containing acrylate compounds and at least one of trimethyl-terminated acrylamide compounds, the cross-linking agent is selected from one or more of compounds containing at least three acrylate groups, the initiator is selected from one or more of azo compounds, the solvent is selected from one or more of linear ether solvents containing a double ether bond, and the diluent is selected from one or more of single ether compounds with fluorine-containing alkyl groups at both ends. The pre-polymerized electrolyte prepared by the application inhibits polysulfide shuttle effect, dissipates volume expansion stress and repairs interface micro-damage at the same time. The pre-polymerized electrolyte significantly improves the cycle stability, coulombic efficiency and capacity retention rate of a lithium-sulfur battery.

Description

Technical Field

[0001] This invention relates to the field of lithium-sulfur battery gel electrolyte technology, and in particular to a low-solubility perfluorinated gel electrolyte prepolymer electrolyte with dynamic stress self-healing function, its preparation method and application. Background Technology

[0002] Lithium-sulfur batteries are characterized by their extremely high theoretical specific capacity (1672 mAh g). -1 ) and energy density (2600 Wh kg) -1 Sulfur-based conversion cathodes are considered one of the most promising development directions in the next generation of high-energy secondary battery systems. However, the commercialization of sulfur-based conversion cathodes has long been limited by a series of scientific problems arising from their complex multi-electron redox reaction mechanism.

[0003] In typical ether-based electrolyte systems, sulfur cathodes follow a solid-liquid-solid conversion pathway. Specifically, during discharge, cyclic S8 elemental, FeS2, Fe2S8, and other sulfur-based conversion cathode materials, after lithiation, generate higher-order lithium polysulfides (Li2S) that are readily soluble in the electrolyte. n (4≤n≤8). During battery charging and discharging, these long-chain polysulfides, as intermediate products, are highly soluble in conventional electrolytes. Under the influence of concentration gradients, they migrate across the separator to the lithium anode, react with lithium metal, undergo parasitic reactions, and are reduced to lower-order polysulfides. These polysulfides then diffuse back to the cathode and are oxidized again, forming the so-called "shuttle effect." This effect directly leads to two serious consequences: first, the continuous irreversible loss of active material, resulting in reduced coulombic efficiency and rapid capacity decay; second, the reaction of dissolved polysulfides with the lithium anode leads to corrosion and passivation of the anode interface, severely degrading the battery's cycle life. Furthermore, sulfur-based conversion cathode materials such as S8 elemental, FeS2, and Fe2S8 undergo significant volume changes during the conversion reaction, exhibiting up to 80% volume expansion during charging and discharging, which easily leads to cracking or even pulverization and detachment of the cathode material. This further exacerbates the damage to the electrode structure and slows down the reaction kinetics.

[0004] To address these challenges, researchers have proposed various strategies. One approach involves adding bisphenol A phthalocyanine epoxy derivatives to carbonate electrolytes to inhibit polysulfide migration through adsorption. Another approach involves adding unsaturated additives such as tetrahydrofuran acrylate and hexafluorobutyl methacrylate to form gel electrolytes through thermally initiated in-situ polymerization. However, carbonate electrolytes are prone to spontaneous irreversible reactions with polysulfides, leading to the loss of active materials, failure of the solid-phase conversion mechanism, and subsequent degradation of electrochemical performance.

[0005] Therefore, the key to overcoming the current technological bottleneck lies in how to inhibit the dissolution of polysulfides at the source and endow the electrode system with dynamic repair capabilities to cope with volume changes without losing active materials or sacrificing energy density. Summary of the Invention

[0006] This invention addresses the polysulfide shuttle effect and volume expansion problems of sulfur-based conversion cathodes in existing lithium-sulfur batteries by providing a low-solubility perfluorinated gel electrolyte prepolymer with dynamic stress self-healing capabilities. This invention utilizes the low dielectric constant of the fluorinated components to inhibit polysulfide dissolution, while simultaneously achieving self-healing through hydrogen bonding between the sterically hindered amide groups and the sulfur-based conversion cathode. A monoether compound with fluorinated alkyl ends is used as a diluent, which does not participate in the solvation structure, thereby reducing electrolyte viscosity and establishing a locally high-concentration system. Furthermore, the fluorinated alkyl ends can co-construct a dynamic fluorinated protective layer with the fluorinated acrylate compounds in the monomer, thus maintaining good contact at the electrode / electrolyte interface. Therefore, while effectively inhibiting polysulfide dissolution and shuttle, this invention endows the electrode system with dynamic stress buffering and self-healing capabilities to cope with repeated volume expansion and contraction. Specifically, the in-situ polymerized gel electrolyte constructed in this invention significantly weakens the solubilization effect of the electrolyte on polar polysulfide intermediates by introducing high-fluoride segments, utilizing their low dielectric constant. This reduces the solubility of polysulfides in the electrolyte bulk from a thermodynamic perspective, fundamentally suppressing the shuttle effect. Simultaneously, the sterically hindered amide groups introduced into the gel network backbone can form reversible physical cross-linking points between polymer chains. Based on the dynamic breaking and recombination mechanism of multiple hydrogen bonds, the electrolyte layer can adaptively deform and rebond when microcracks or interfacial detachment occur due to volume changes in the electrode material, repairing interfacial contact failures in real time and maintaining stable lithium-ion transport channels. This integrated design not only solves the key problem of sulfide-based conversion cathode active material loss but also significantly improves the mechanical stability of the electrode structure through dynamic stress dissipation, thereby greatly extending the battery's cycle life and improving its coulombic efficiency. It provides a gel electrolyte solution with both dissolution suppression and dynamic self-repair functions for the practical application of high-energy-density lithium metal secondary batteries.

[0007] This invention is achieved through the following technical solution: In a first aspect, the present invention provides a low-solubility perfluorinated gel electrolyte prepolymerized electrolyte with dynamic stress self-healing function, the low-solubility perfluorinated gel electrolyte prepolymerized electrolyte comprising monomer, crosslinking agent, initiator, solvent, diluent and lithium salt; The monomer is selected from at least one of fluorinated acrylate compounds and at least one of trimethyl-terminated acrylamide compounds; the crosslinking agent is selected from one or more compounds containing at least three acrylate groups; the initiator is selected from one or more azo compounds; the solvent is selected from one or more linear ether solvents containing diether bonds; and the diluent is selected from one or more monoether compounds with fluorinated alkyl ends.

[0008] This invention innovatively provides an in-situ polymerized gel electrolyte prepolymerized electrolyte with dynamic self-healing properties and low polysulfide solubility, particularly suitable for sulfur-based conversion cathode systems (such as S, FeS2, Fe2S8, etc.) in lithium-sulfur batteries. By introducing monomers containing specific functional groups, crosslinking agents, initiators, solvents, diluents, and other components into the prepolymerized electrolyte, a three-dimensional network gel is formed inside the battery. On the one hand, this invention utilizes fluorinated functional groups to reduce the dielectric constant of acrylate monomers to inhibit polysulfide dissolution. On the other hand, it utilizes the hydrogen bonding between the amide groups in acrylamide compounds and the sulfur-based conversion cathode to achieve self-healing function, thereby maintaining good contact at the electrode / electrolyte interface. Furthermore, by introducing sterically hindered trimethyl substituents into the ends of acrylamide monomers, the low solubility of the polymer network for polysulfides is maintained. Meanwhile, the locally high concentration of prepolymerized electrolyte obtained by using the solvent and specific fluorinated alkyl monoether compounds as diluents in this invention has a plasticizing effect, which significantly reduces the solubility of polysulfides while maintaining high lithium-ion conductivity of the electrolyte.

[0009] The above strategy, on the one hand, utilizes the physical confinement effect of gel electrolytes and their chemical interaction with sulfur species to significantly reduce the solubility of polysulfides in electrolytes; on the other hand, its dynamic cross-linking network endows the system with self-healing properties, which can promptly heal micro-damage at the electrode / electrolyte interface caused by volume expansion. At this point, without losing active materials or sacrificing energy density, it can both inhibit the dissolution of polysulfides from the root and endow the electrode system with dynamic repair capabilities to cope with volume changes, providing a new solution for achieving stable and efficient solid-phase conversion sulfur cathodes, and obtaining a prepolymerized electrolyte with both high coulombic efficiency and high cycle capacity retention.

[0010] As a further embodiment, the fluorinated acrylate compound in the monomer is selected from one or more of the following formula 1, wherein m is an integer from 0 to 4, R1 is selected from fluorinated C1 to C3 alkyl groups with ≥5 fluorine atoms, and R2 is selected from hydrogen atoms or C1 to C3 alkyl groups. The acrylamide compound in the monomer is selected from one or more of the following Formula 2, where n is an integer from 0 to 4, and R3 is selected from hydrogen atoms or C1 to C3 alkyl groups; The monoether compounds with fluorinated alkyl ends are selected from one or more of the structures of Formula 3, wherein R4 and R5 are each independently selected from fluorinated C1~C3 alkyl groups and have ≥3 fluorine atoms. In the low-solubility perfluorinated gel electrolyte prepolymer electrolyte with dynamic stress self-healing function, the mass ratio of fluorinated acrylate compounds to acrylamide compounds in the monomer is (70~85):(5~20). .

[0011] Specifically, when m=0, the acrylic acid group in the fluorinated acrylate compound of the monomer is directly connected to the R1 group; when n=0, the acrylamide group in the acrylamide compound of the monomer is directly connected to the tert-butyl group.

[0012] This invention further defines the structures of fluorinated acrylate compounds, acrylamide compounds, and diluents in the monomers, and limits the mass ratio of fluorinated acrylate compounds to acrylamide compounds in the monomers in the low-solubility perfluorinated gel electrolyte prepolymer electrolyte with dynamic stress self-healing function. By precisely controlling the ratio of the two within the range of (70~85):(5~20), a synergistic optimization design with a high-fluorinated skeleton as the main body and a dynamic hydrogen bond network as the functional unit is achieved. At the same time, through precise control of molecular structure, the synergistic optimization of the dynamic reversible hydrogen bond network formed by the fluorinated hydrophobic segments connecting acrylic groups and the acrylamide structure containing terminal trimethyl groups is achieved. While ensuring an extreme inhibition effect on polysulfide dissolution, the system is endowed with efficient self-healing ability. The high-concentration system is further stabilized and plasticized by the diluent containing a high number of fluorine atoms, which together improves the structural stability of the material. On the one hand, for the fluorinated acrylate compounds described in Formula 1, their structural feature is that the acrylate group is located via -(CH2). m - The linker arm is connected to a highly fluorinated alkyl group R1. R1 is selected from fluorinated C1-C3 alkyl groups with ≥5 fluorine atoms, ensuring a high and suitable fluorine atom density and extremely low polarizability in the fluorinated segments. This allows for the formation of stable, low-polarity microregions within the polymer backbone, thermodynamically reducing the solubility of polar polysulfide intermediates. Simultaneously, the adjustable number of m groups in the linker arm (m) within the range of 0-4 provides a degree of flexibility to the molecular structure: when m is small, the highly fluorinated segments are tightly connected to the polymer backbone, forming a more rigid fluorinated shielding layer; when m increases, the mobility of the fluorinated segments is enhanced, further improving the blocking efficiency of the fluorinated regions against polysulfide diffusion during gel network formation. Optimization of the m value ensures both low solubility and mechanical flexibility of the polymer backbone. The innovation of the acrylamide compounds described in Formula 2 lies in the tunable -(CH2) linking of the amide functional group with a sterically hindered tert-butyl group having a terminal trimethyl structure. n - Connecting arms are combined. The tert-butyl group, as a typical sterically hindered substituent, plays multiple functions at the molecular level: First, its large stereostructure effectively shields adjacent amide groups, significantly reducing the chemical affinity of polar amide functional groups for polysulfide molecules without disrupting the hydrogen bonding ability between amide groups, thus avoiding polysulfide dissolution problems that may be caused by the introduction of the amide structure; second, the rigid structure of the tert-butyl group increases the local rigidity of the polymer chain segments, which helps to improve the mechanical stability of the gel skeleton. The tunability of the connecting arm length n in the range of 0~4 provides a means to regulate the dynamic characteristics of the hydrogen bond network: when n=0, the tert-butyl group is directly connected to the nitrogen atom of the amide, and the steric shielding effect on the amide group is most significant. At the same time, the rigid connection between the amide group and the polymer backbone is conducive to the formation of a more ordered hydrogen bond cross-linking network; as n increases, the degree of freedom of movement of the amide group increases, allowing for more effective energy dissipation through conformational adjustment under stress, while the dissociation and recombination kinetics of hydrogen bonds are optimized, improving self-repair efficiency; The diluent, characterized by low viscosity, high fluorine content, and excellent chemical stability, plays multiple key roles in the prepolymerized electrolyte: First, its biether structure endows it with good compatibility with solvents, while its double-terminated fluorinated alkyl groups give it extremely low dielectric constant and lithium-phobic and fluorine-loving properties, thus preventing it from participating in the solvation structure of lithium ions. This helps to form a localized high-concentration electrolyte region at the electrode interface, reducing the dissolution of polysulfides at the source. Second, the presence of fluorinated alkyl groups makes it tend to accumulate on the cathode surface, constructing a dynamic fluorination physical barrier that effectively blocks the diffusion of polysulfides into the electrolyte bulk. Finally, during electrochemical cycling, the fluorinated diluent participates in the film-forming reaction at the electrode / electrolyte interface, inducing the formation of a stable solid electrolyte interface layer rich in LiF. This interface layer has good mechanical strength and flexibility, and can adapt to the volume changes of the sulfur cathode during charging and discharging, preventing interface failure. The fluorinated polymer backbone formed by the polymerization of fluorinated acrylate monomers provides the inherent low solubility of polysulfides, and the fluorinated diluent further enhances this property. Its enrichment at the interface, together with the fluorinated backbone, constructs a multi-layered fluorinated shielding system, inhibiting polysulfide shuttle from both thermodynamic and kinetic perspectives. At the same time, acrylamide monomers endow the gel network with self-healing ability through dynamic hydrogen bonding, while the LiF-rich interface layer induced by the fluorinated diluent enhances the mechanical stability of the interface from an inorganic perspective. The synergy of the two makes the gel electrolyte have both excellent self-healing performance and stable interface structure, which can promptly repair microcracks caused by volume expansion during battery cycling and maintain a continuous inhibition effect on polysulfides. On the other hand, this invention limits the mass ratio of fluorinated acrylate to acrylamide compound to (70~85):(5~20), where the high proportion of fluorinated components constructs a rigid, low-polarity framework, providing the system with an inherent and primary inhibition mechanism against polysulfides; while a certain proportion of amide introduces uniformly dispersed dynamic crosslinking points, endowing the system with stress buffering and self-healing capabilities in response to volume changes. This mass ratio allows the gel electrolyte to maintain effective barrier properties against polysulfides for a long period while preserving the integrity of the interface during repeated expansion and contraction of the electrode volume, thus forming an integrated solution to the dual challenges of shuttle effect and volume expansion. Through the above structural design and formulation optimization, this invention achieves the synergistic effect of the fluorinated component and the amide component: the low-polarity framework constructed by the fluorinated acrylate provides the system with the inherent low solubility characteristics for polysulfides; while the acrylamide compounds, through the design of tunable linkers and sterically hindered substituents, endow the system with a dynamically reversible hydrogen-bonded cross-linking network while maintaining low solubility characteristics. The precise combination of the two at the molecular level and the systematic control of the linker length enable the prepared gel electrolyte to simultaneously satisfy the effective inhibition of polysulfide dissolution and the dynamic dissipation and self-repair of volume expansion stress, providing a multi-faceted solution to the dual challenges of shuttle effect and volume expansion faced by sulfur-based conversion cathodes.

[0013] As a further embodiment, the fluorinated acrylate compound in the monomer is selected from one or more of Formula 1, wherein m is an integer of 1 to 2, R1 is selected from fluorinated C1 to C2 fluoroalkyl groups with ≥5 fluorine atoms, and R2 is selected from one of C1 to C2 alkyl groups. The acrylamide compound in the monomer is selected from one or more of Formula 2, wherein n is an integer from 0 to 2, and R3 is selected from one of C1 to C2 alkyl groups.

[0014] This invention further optimizes the molecular structure parameters of fluorinated acrylate compounds and acrylamide compounds in the monomers. By optimizing the length of the connecting chain, the length of the fluorinated alkyl chain of the fluorinated acrylate compound, and the alkyl substituents of the side chains of the two monomers to a better range, the comprehensive performance of the gel electrolyte is precisely controlled. At this time, the synergistic effect of each structural parameter enables the polymer network to achieve a better balance between polysulfide barrier capability, dynamic self-healing efficiency, and ion transport performance.

[0015] As a further embodiment, in the low-solubility perfluorinated gel electrolyte prepolymerized electrolyte with dynamic stress self-healing function, the monomer and crosslinking agent account for 5~30 wt% of the prepolymerized electrolyte by mass, the mass ratio of the monomer to the crosslinking agent is (1~9):1, the initiator accounts for 0.1~2 wt% of the prepolymerized electrolyte by mass, the volume ratio of the solvent to the diluent is 1:(0.5~3), and the concentration of the lithium salt in the prepolymerized electrolyte is 1.0~2.0 mol / L.

[0016] This invention further optimizes the proportions of each component in the prepolymerized electrolyte. By systematically controlling the total content of monomers and crosslinking agents, the mass ratio of monomers to crosslinking agents, the initiator content, the solvent-to-diluent ratio, and the lithium salt concentration, a better balance between polysulfide barrier capacity and self-healing performance is achieved in the gel electrolyte. At this point, the parameters work synergistically. Since both the monomers and crosslinking agents contain acrylate groups, the total amount and ratio of monomers and crosslinking agents determine the skeletal density of the gel network, which in turn affects the retention capacity of the solvent / diluent and the lithium-ion transport pathway. The appropriate addition of the initiator ensures the formation of a well-organized network. The solvent-to-diluent ratio directly regulates the microscopic solvation structure of the electrolyte, and together with the lithium salt concentration, determines the ionic conductivity and the effect of inhibiting polysulfide dissolution. Through the synergistic optimization of these multi-dimensional parameters, the prepolymerized electrolyte prepared by this invention, after in-situ polymerization inside the battery, can form a gel electrolyte with both strong polysulfide barrier capacity and dynamic self-healing function. Together, they ensured the cycle stability and coulombic efficiency of the battery, providing further assurance for achieving long-term cycle stability of sulfur-based conversion cathodes.

[0017] Secondly, the present invention also provides a method for preparing the low-solubility perfluorinated gel electrolyte prepolymerized electrolyte with dynamic stress self-healing function as described in the first aspect, comprising the following steps: S1: Add lithium salt to solvent, stir thoroughly until clear, add diluent, and continue stirring until clear to obtain local high-concentration electrolyte, wherein the concentration of lithium salt in local high-concentration electrolyte is 0.5~2.5 mol / L; S2: Fluorinated acrylate compounds, trimethyl-terminated acrylamide compounds, crosslinking agents, and initiators are added to a local high-concentration electrolyte according to the target mass ratio, and the mixture is stirred evenly to obtain a prepolymerized electrolyte.

[0018] As a further preferred embodiment, the mass ratio of the fluorinated acrylate compound to the trimethyl-terminated acrylamide compound is (70~85):(5~20), the mass ratio of the monomer containing the fluorinated acrylate compound and the trimethyl-terminated acrylamide compound to the crosslinking agent is (1~9):1, and the amount of monomer and crosslinking agent added to the prepolymerization electrolyte is 5~30 wt%. The amount of initiator added to the prepolymerization electrolyte is 0.1~2 wt%.

[0019] Thirdly, the present invention also provides the application of the low-solubility perfluorinated gel electrolyte prepolymerized electrolyte with dynamic stress self-healing function in lithium-ion batteries, wherein the lithium-ion batteries include lithium-sulfur batteries.

[0020] The features and beneficial effects of this invention are as follows: In this invention, the fluorinated acrylate component contains a fluoroalkyl branched structure, which, when introduced, can form a low-polarity local microenvironment within the polymer network. Due to the extremely low electronic polarizability of fluorine atoms, the fluorinated segments significantly reduce the overall dielectric constant of the polymer backbone, thereby weakening the interaction between the gel electrolyte and polar polysulfide intermediates (such as Li₂S). xThe design effectively suppresses the dissolution behavior of polysulfides in the electrolyte phase from a thermodynamic perspective. Furthermore, it increases the diffusion barrier of polysulfide ions through the steric hindrance effect of the fluorinated segments, reducing their migration rate in the electrolyte and thus mitigating the problem of active material loss caused by the "shuttle effect" at its root. Acrylamide-like compounds introduced into the system play a crucial role in dynamic mechanical response. The amide groups (-CONH-) in these compounds can form reversible weak hydrogen bond interactions with other polar functional groups in the polymer network (such as the CF bond in fluorinated acrylates, carbonyl C=O, etc.). When the sulfur-based conversion cathode (such as FeS2) undergoes severe volume expansion due to the conversion reaction during charging and discharging, the resulting internal stress first acts on these hydrogen bond crosslinking points. Since the bond energy of hydrogen bonds is much lower than that of covalent bonds, hydrogen bonds preferentially dissociate under stress, dissipating most of the mechanical energy through a "sacrificial bond" mechanism, thereby avoiding irreversible breakage of the polymer backbone due to stress concentration. Once the stress is released, the dissociated hydrogen bonds can spontaneously recombine under thermodynamic drive, allowing the damaged interface structure to be dynamically repaired. This process endows the gel electrolyte layer with excellent stress buffering and self-healing capabilities, ensuring that the electrode particles maintain good contact with the electrolyte even after repeated volume changes, thus guaranteeing the integrity of the lithium-ion transport pathway. The acrylamide-based compounds used in this invention further achieve effective shielding of the polarity of the amide groups by introducing sterically hindered substituents (such as tert-butyl, adamantyl, and sterically hindered aryl groups). This molecular design has a dual function: on the one hand, the steric shielding effect of the sterically hindered groups reduces the affinity of the polar amide groups for polysulfide molecules without impairing hydrogen bond formation, avoiding the problem of accelerated polysulfide dissolution that may be caused by the introduction of the amide structure; on the other hand, the presence of sterically hindered substituents increases the rigidity of the polymer chain segments, further enhancing the mechanical stability of the gel skeleton and helping to maintain structural integrity during long-term cycling.

[0021] In summary, this invention, through the synergistic design of fluorine-containing components and shielding amide components, combined with the solvent and diluent system of this invention, successfully constructs a perfluorinated gel electrolyte that can both inhibit the dissolution and migration of polysulfides and achieve stress dissipation and self-repair through a dynamic hydrogen bond network. This provides an integrated solution to address the two core challenges of shuttle effect and volume expansion faced by sulfur-based conversion cathodes. Attached Figure Description

[0022] 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.

[0023] Figure 1 The graphs show the cycling performance of Li-FeS2 batteries prepared using prepolymerized electrolytes in Examples 1, 4, and Comparative Example 1. Detailed Implementation

[0024] 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.

[0025] This invention addresses the polysulfide shuttle effect and volume expansion problems of sulfur-based conversion cathodes in existing lithium-sulfur batteries by providing a low-solubility perfluorinated gel electrolyte prepolymer with dynamic stress self-healing capabilities. This invention utilizes the low dielectric constant of the fluorinated components to inhibit polysulfide dissolution, while simultaneously achieving self-healing through hydrogen bonding between the sterically hindered amide groups and the sulfur-based conversion cathode. A monoether compound with fluorinated alkyl ends is used as a diluent, which does not participate in the solvation structure, thereby reducing electrolyte viscosity and establishing a locally high-concentration system. Furthermore, the fluorinated alkyl ends can co-construct a dynamic fluorinated protective layer with the fluorinated acrylate compounds in the monomer, thus maintaining good contact at the electrode / electrolyte interface. Therefore, while effectively inhibiting polysulfide dissolution and shuttle, this invention endows the electrode system with dynamic stress buffering and self-healing capabilities to cope with repeated volume expansion and contraction. Specifically, the in-situ polymerized gel electrolyte constructed in this invention significantly weakens the solubilization effect of the electrolyte on polar polysulfide intermediates by introducing high-fluoride segments, utilizing their low dielectric constant. This reduces the solubility of polysulfides in the electrolyte bulk from a thermodynamic perspective, fundamentally suppressing the shuttle effect. Simultaneously, the sterically hindered amide groups introduced into the gel network backbone can form reversible physical cross-linking points between polymer chains. Based on the dynamic breaking and recombination mechanism of multiple hydrogen bonds, the electrolyte layer can adaptively deform and rebond when microcracks or interfacial detachment occur due to volume changes in the electrode material, repairing interfacial contact failures in real time and maintaining stable lithium-ion transport channels. This integrated design not only solves the key problem of sulfide-based conversion cathode active material loss but also significantly improves the mechanical stability of the electrode structure through dynamic stress dissipation, thereby greatly extending the battery's cycle life and improving its coulombic efficiency. It provides a gel electrolyte solution with both dissolution suppression and dynamic self-repair functions for the practical application of high-energy-density lithium metal secondary batteries.

[0026] This invention is achieved through the following technical solution: In a first aspect, the present invention provides a low-solubility perfluorinated gel electrolyte prepolymerized electrolyte with dynamic stress self-healing function, the low-solubility perfluorinated gel electrolyte prepolymerized electrolyte comprising monomer, crosslinking agent, initiator, solvent, diluent and lithium salt; The monomer is selected from at least one of fluorinated acrylate compounds and at least one of trimethyl-terminated acrylamide compounds; the crosslinking agent is selected from one or more compounds containing at least three acrylate groups; the initiator is selected from one or more azo compounds; the solvent is selected from one or more linear ether solvents containing diether bonds; and the diluent is selected from one or more monoether compounds with fluorinated alkyl ends.

[0027] As a further embodiment, the fluorinated acrylate compound in the monomer is selected from one or more of the following formula 1, wherein m is an integer from 0 to 4, R1 is selected from fluorinated C1 to C3 alkyl groups with ≥5 fluorine atoms, and R2 is selected from hydrogen atoms or C1 to C3 alkyl groups. The acrylamide compound in the monomer is selected from one or more of the following Formula 2, where n is an integer from 0 to 4, and R3 is selected from hydrogen atoms or C1 to C3 alkyl groups; The monoether compounds with fluorinated alkyl ends are selected from one or more of the structures of Formula 3, wherein R4 and R5 are each independently selected from fluorinated C1-C3 alkyl groups and have ≥3 fluorine atoms. In the low-solubility perfluorinated gel electrolyte prepolymer electrolyte with dynamic stress self-healing function, the mass ratio of fluorinated acrylate compounds to acrylamide compounds in the monomer is (70~85):(5~20). .

[0028] Specifically, when m=0, the acrylic acid group in the fluorinated acrylate compound of the monomer is directly connected to the R1 group; when n=0, the acrylamide group in the acrylamide compound of the monomer is directly connected to the tert-butyl group.

[0029] As a further embodiment, the fluorinated acrylate compound in the monomer is selected from one or more of Formula 1, wherein m is an integer of 1 to 2, R1 is selected from fluorinated C1 to C2 fluorinated alkyl groups with ≥5 fluorine atoms, and R2 is selected from one of C1 to C2 alkyl groups. The acrylamide compound in the monomer is selected from one or more of Formula 2, wherein n is an integer from 0 to 2, and R3 is selected from one of C1 to C2 alkyl groups.

[0030] As a further embodiment, in the low-solubility perfluorinated gel electrolyte prepolymerized electrolyte with dynamic stress self-healing function, the monomer and crosslinking agent account for 5~30 wt% of the prepolymerized electrolyte by mass, the mass ratio of the monomer to the crosslinking agent is (1~9):1, the initiator accounts for 0.1~2 wt% of the prepolymerized electrolyte by mass, the volume ratio of the solvent to the diluent is 1:(0.5~3), and the concentration of the lithium salt in the prepolymerized electrolyte is 1.0~2.0 mol / L.

[0031] As a further embodiment, in the low-solubility perfluorinated gel electrolyte prepolymerized electrolyte with dynamic stress self-healing function, the monomer and crosslinking agent account for 7~15 wt% of the prepolymerized electrolyte by mass, the mass ratio of the monomer to the crosslinking agent is (4~6):1, the initiator accounts for 0.1~0.3 wt% of the prepolymerized electrolyte by mass, the volume ratio of the solvent to the diluent is 1:(1.5~2.5), and the concentration of the lithium salt in the prepolymerized electrolyte is 1.4~1.6 mol / L.

[0032] As a further embodiment, the lithium salt includes one or more of the following: lithium fluoride phosphate, lithium fluoride arsenate, lithium fluoride borate, lithium fluoride sulfonylimide, lithium fluoride sulfonate, and lithium fluoride perchlorate.

[0033] As a further preferred embodiment, the fluorinated lithium phosphate salt includes lithium hexafluorophosphate, lithium tetrafluorophosphate, and lithium difluorophosphate.

[0034] As a further preferred embodiment, the fluorinated lithium arsenate salt includes lithium hexafluoroarsenate.

[0035] As a further preferred embodiment, the fluorinated lithium borate salt includes lithium tetrafluoroborate, lithium dioxalate borate, and lithium difluorooxalate borate.

[0036] As a further preferred embodiment, the fluorinated sulfonyl imide lithium salt includes lithium bis(trifluoromethylsulfonyl imide) and lithium bis(fluorosulfonyl imide).

[0037] As a further preferred embodiment, the fluorinated lithium sulfonate salt includes lithium trifluoromethyl sulfonate.

[0038] As a further preferred embodiment, the lithium salt is selected from either fluorosulfonylimide lithium salt or fluorosulfonate lithium salt.

[0039] The present invention further preferably uses either a lithium salt containing fluorosulfonylimide or a lithium salt containing fluorosulfonate. By further optimizing the anionic structure of the lithium salt, a deep fit is achieved with the low-solubility perfluorinated gel electrolyte network and locally high-concentration electrolyte system with dynamic stress self-healing function constructed in this invention. Both the anions of the lithium salt containing fluorosulfonylimide and the lithium salt containing fluorosulfonate contain fluorine atoms, exhibiting good compatibility with the low-polarity fluorinated framework constructed from fluorinated acrylates. This helps to form uniform ion transport channels in the gel network, avoiding a decrease in ionic conductivity due to phase separation. Simultaneously, the sulfonylimide or sulfonic acid anions can form weak hydrogen bonds or dipole-dipole interactions with the amide groups of acrylamide compounds in the monomer. This reversible physical cross-linking enhances the mechanical stability of the gel network to a certain extent without affecting the dynamic dissociation and recombination of hydrogen bonds under stress, maintaining the high efficiency of the self-healing function. Therefore, a significant synergistic enhancement effect is exhibited in terms of polysulfide inhibition, interface stability, and lithium-ion transport kinetics.

[0040] As an example, the solvent includes one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, 1,3-dimethoxybutane, 1,1-diethoxyethane, and 1,2-dimethoxypropane.

[0041] As an example, the diluent includes one or more of bis(2,2,2-trifluoroethyl) ether, 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.

[0042] As an example, the crosslinking agent includes one or more of pentaerythritol tetraacrylate, trimethylolpropane triacrylate, and dipentaerythritol hexaacrylate.

[0043] As an example, the fluorinated acrylate compounds in the monomer include one or more of methyl hexafluorobutyl acrylate, hexafluorobutyl acrylate, tetrafluoropropyl acrylate, tetrafluorobutyl methacrylate, perfluorohexylpropyl acrylate, and tridecafluorooctyl acrylate.

[0044] As an example, the acrylamide compounds in the monomer include one or more of N-tert-butyl methacrylate and N-tert-octyl acrylamide.

[0045] As an example, the azo compounds include one or more of azobisisobutyronitrile, azobisisoheptanenitrile, azobisisovalerate, dimethyl azobisisobutyrate, azoisobutylcyanoformamide, and azobisimidazolinylpropane.

[0046] As a further preferred embodiment, in the low-solubility perfluorinated gel electrolyte prepolymer electrolyte with dynamic stress self-healing function, the monomers are hexafluorobutyl methacrylate and N-tert-butylmethacrylamide, the crosslinking agent is pentaerythritol tetraacrylate, the solvent is 1,2-dimethoxypropane (DMP), the diluent is 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE), the initiator is azobisisobutyronitrile (AIBN), and the lithium salt is lithium bisfluorosulfonylimide (LiFSI). The volume ratio of solvent to diluent is 1:2, the concentration of lithium salt in the prepolymerization electrolyte is 1.5 mol / L, the mass ratio of monomer to crosslinking agent is 5:1, and the amount of monomer and crosslinking agent added in the prepolymerization electrolyte is 10 wt%. The amount of initiator added in the prepolymerization electrolyte is 0.2 wt%.

[0047] This invention further optimizes the types and proportions of components in a low-solubility perfluorinated gel electrolyte prepolymer with dynamic stress self-healing function. In this prepolymer, a high concentration of lithium difluorosulfonylimide (LiFSI) dissolves in the solvent, significantly reducing the solvent's solubility for polysulfides. The ether solvent DMP, due to its low polarity, avoids harmful side reactions between the solvent and metallic lithium and polysulfides. The diluent TTE hardly participates in the solvation structure, thus reducing the electrolyte viscosity. The monomers hexafluorobutyl methacrylate and N-tert-butylmethacrylamide, possessing unsaturated double bonds, polymerize with the crosslinking agent pentaerythritol tetraacrylate, which also has multiple unsaturated double bonds, under the catalysis of the thermal initiator AIBN, to form a uniform three-dimensional polymer network. This electrolyte effectively inhibits the dissolution and shuttle of polysulfides, adapts to the volume deformation of the cathode material, improves the cycle stability and energy density of this type of battery, extends battery life, and enhances overall performance.

[0048] Secondly, the present invention also provides a method for preparing the low-solubility perfluorinated gel electrolyte prepolymerized electrolyte with dynamic stress self-healing function, comprising the following steps: S1: Add lithium salt to solvent, stir thoroughly until clear, add diluent, and continue stirring until clear to obtain local high-concentration electrolyte, wherein the concentration of lithium salt in local high-concentration electrolyte is 0.5~2.5 mol / L; S2: Fluorinated acrylate compounds, trimethyl-terminated acrylamide compounds, crosslinking agents, and initiators are added to a local high-concentration electrolyte according to the target mass ratio, and the mixture is stirred evenly to obtain a prepolymerized electrolyte.

[0049] As a further preferred embodiment, the mass ratio of the fluorinated acrylate compound to the trimethyl-terminated acrylamide compound is (70~85):(5~20), the mass ratio of the monomer containing the fluorinated acrylate compound and the trimethyl-terminated acrylamide compound to the crosslinking agent is (1~9):1, and the amount of monomer and crosslinking agent added to the prepolymerization electrolyte is 5~30 wt%. The amount of initiator added to the prepolymerization electrolyte is 0.1~2 wt%.

[0050] As an example, the preparation method of the low-solubility perfluorinated gel electrolyte prepolymerized electrolyte with dynamic stress self-healing function includes the following steps: S1: Weigh 841.8 mg of lithium salt LiFSI and add it to 1 mL of solvent 1,2-dimethoxypropane (DMP). Stir until the lithium salt dissolves to obtain a homogeneous and clear solution. Then add 2 mL of diluent 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) and continue stirring until homogeneous and clear to obtain a locally high-concentration electrolyte. S2: Weigh 449 mg of the locally high-concentration electrolyte obtained in step 1, add 40 mg of hexafluorobutyl methacrylate monomer, 5 mg of N-tert-butylmethacrylamide monomer, and 5 mg of pentaerythritol tetraacrylate crosslinking agent, and add 1 mg of azobisisobutyronitrile (AIBN) initiator. Stir until homogeneous to obtain the prepolymerized electrolyte. The mass ratio of hexafluorobutyl methacrylate, N-tert-butylmethacrylate, pentaerythritol tetraacrylate, and azobisisobutyronitrile (AIBN) initiator is 80:10:10:2, and the amount of monomer and crosslinking agent added is 10 wt% of the prepolymerized electrolyte.

[0051] Thirdly, the present invention also provides the application of the low-solubility perfluorinated gel electrolyte prepolymerized electrolyte with dynamic stress self-healing function in lithium-ion batteries, wherein the lithium-ion batteries include lithium-sulfur batteries.

[0052] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0053] The chemical raw materials used in the following examples and comparative examples are all prior art and commercially available. The experimental apparatus and testing equipment used in the following examples and comparative examples are all conventional equipment in the art, and there are no special requirements or limitations.

[0054] As a specific example of the implementation of this invention, detailed cases are provided below: Example 1: Step 1: Weigh 841.8 mg of lithium bis(fluorosulfonyl)imide (LiFSI) and add it to 1 mL of solvent 1,2-dimethoxypropane (DMP). Stir until the lithium salt dissolves to obtain a homogeneous and clear solution. Then add 2 mL of diluent 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) and continue stirring until homogeneous and clear to obtain a locally high-concentration electrolyte. Step 2: Weigh 449 mg of the locally high-concentration electrolyte obtained in Step 1, add 40 mg of hexafluorobutyl methacrylate monomer, 5 mg of N-tert-butylmethacrylamide monomer, and 5 mg of pentaerythritol tetraacrylate crosslinking agent, and add 1 mg of azobisisobutyronitrile (AIBN) initiator. Stir until homogeneous to obtain the prepolymerized electrolyte. The mass ratio of hexafluorobutyl methacrylate, N-tert-butylmethacrylate, pentaerythritol tetraacrylate, and azobisisobutyronitrile (AIBN) initiator is 80:10:10:2, and the amount of monomer and crosslinking agent added is 10 wt% of the prepolymerized electrolyte.

[0055] Example 2: Compared with Example 1, the difference is that the mass ratio of hexafluorobutyl methacrylate monomer to N-tert-butylmethacrylamide monomer added to the prepolymerized electrolyte is 85:5, and the rest is the same as Example 1; Specifically, in step 2, the amount of hexafluorobutyl methacrylate monomer added is 42.5 mg, and the amount of N-tert-butylmethacrylamide monomer added is 2.5 mg.

[0056] Example 3: Compared with Example 1, the difference is that the mass ratio of hexafluorobutyl methacrylate monomer to N-tert-butylmethacrylamide monomer added to the prepolymerized electrolyte is 70:20, and the rest is the same as Example 1; Specifically, in step 2, the amount of hexafluorobutyl methacrylate monomer added is 35 mg, and the amount of N-tert-butylmethacrylamide monomer added is 10 mg.

[0057] Example 4: Compared with Example 1, the difference is that the monomer hexafluorobutyl methacrylate added to the prepolymer electrolyte is replaced with tetrafluoropropyl acrylate.

[0058] Example 5: Compared with Example 1, the difference is that the monomer N-tert-butylmethacrylamide added to the prepolymer electrolyte is replaced with N-tert-octylacrylamide.

[0059] Example 6: Compared with Example 1, the difference is that the monomer hexafluorobutyl methacrylate added to the prepolymer electrolyte is replaced with perfluorohexylpropyl acrylate.

[0060] Example 7: Compared with Example 1, the difference is that the monomer hexafluorobutyl methacrylate added to the prepolymer electrolyte is replaced with tridecafluorooctyl acrylate.

[0061] Example 8: The difference from Example 1 is that the lithium salt in the prepolymerized electrolyte is lithium tetrafluoroborate.

[0062] Example 9: Compared with Example 1, the difference is that the crosslinking agent in the prepolymer electrolyte is trimethylolpropane triacrylate.

[0063] Example 10: Compared with Example 1, the difference is that the monomer hexafluorobutyl methacrylate added to the prepolymer electrolyte is replaced with 4,4,5,5,6,6,6-heptafluoroacrylate.

[0064] Example 11: Compared with Example 1, the difference is that the monomer N-tert-butylmethacrylamide added to the prepolymer electrolyte is replaced with N-(4,4-dimethylpentyl)acrylamide.

[0065] Example 12: Compared with Example 1, the difference lies in the amount of each component used: Specifically, step 1: Weigh 280.6 mg of lithium salt LiFSI, add it to 1 mL of solvent DMP, stir until the lithium salt dissolves, and obtain a uniform and clear solution. Then add 0.5 mL of diluent TTE and continue stirring until a uniform and clear state is obtained to obtain a locally high-concentration electrolyte. Step 2: Weigh 474.5 mg of the locally high-concentration electrolyte obtained in Step 1, add 11.1 mg of hexafluorobutyl methacrylate monomer, 1.4 mg of N-tert-butylmethacrylamide monomer, and 12.5 mg of pentaerythritol tetraacrylate crosslinking agent, and add 0.5 mg of AIBN initiator. Stir until homogeneous to obtain the prepolymerized electrolyte. The mass ratio of hexafluorobutyl methacrylate, N-tert-butylmethacrylate, pentaerythritol tetraacrylate, and AIBN initiator is 44.4:5.6:50:0.02, and the amount of monomer and crosslinking agent added is 5 wt% of the prepolymerized electrolyte.

[0066] Example 13: The difference from Example 1 is the amount of each component used. Specifically, step 1: Weigh 1496.6 mg of lithium salt LiFSI, add it to 1 mL of solvent DMP, stir until the lithium salt dissolves, and obtain a uniform and clear solution. Then add 3 mL of diluent TTE and continue stirring until a uniform and clear state is reached to obtain a locally high-concentration electrolyte. Step 2: Weigh 340 mg of the locally high-concentration electrolyte obtained in Step 1, add 120 mg of hexafluorobutyl methacrylate monomer, 15 mg of N-tert-butylmethacrylamide monomer, and 15 mg of pentaerythritol tetraacrylate crosslinking agent, and add 10 mg of initiator AIBN. Stir until homogeneous to obtain the prepolymerized electrolyte. The mass ratio of hexafluorobutyl methacrylate, N-tert-butylmethacrylate, pentaerythritol tetraacrylate, and initiator AIBN is 80:10:10:6.7, and the amount of monomer and polymer added is 30 wt% of the electrolyte.

[0067] Example 14: Compared with Example 1, the difference lies in the amount of each component used; Specifically, step 1: Weigh 654.7 mg of lithium salt LiFSI, add it to 1 mL of solvent DMP, stir until the lithium salt dissolves, and obtain a uniform and clear solution. Then add 1.5 mL of diluent TTE and continue stirring until a uniform and clear state is obtained to obtain a locally high-concentration electrolyte. Step 2: Weigh 464.5 mg of the locally high-concentration electrolyte obtained in Step 1, add 25 mg of hexafluorobutyl methacrylate monomer, 3 mg of N-tert-butylmethacrylamide monomer, and 7 mg of pentaerythritol tetraacrylate crosslinking agent, and add 0.5 mg of initiator AIBN. Stir until homogeneous to obtain the prepolymerized electrolyte. The mass ratio of hexafluorobutyl methacrylate, N-tert-butylmethacrylate, pentaerythritol tetraacrylate, and initiator AIBN is 71.4:8.6:20:1.4, and the amount of monomer and polymer added is 7 wt% of the electrolyte.

[0068] Example 15: Compared with Example 1, the difference lies in the amount of each component used; Specifically, step 1: Weigh 1047.6 mg of lithium salt LiFSI, add it to 1 mL of solvent DMP, stir until the lithium salt dissolves, and obtain a uniform and clear solution. Then add 2.5 mL of diluent TTE and continue stirring until a uniform and clear state is obtained to obtain a locally high-concentration electrolyte. Step 2: Weigh 423.5 mg of the locally high-concentration electrolyte obtained in Step 1, add 57.2 mg of hexafluorobutyl methacrylate monomer, 7.1 mg of N-tert-butylmethacrylamide monomer, and 10.7 mg of pentaerythritol tetraacrylate crosslinking agent, and add 1.5 mg of AIBN initiator. After stirring evenly, a prepolymerized electrolyte is obtained. The mass ratio of hexafluorobutyl methacrylate, N-tert-butylmethacrylate, pentaerythritol tetraacrylate, and initiator AIBN is 76.4:9.5:14.3:2, and the amount of monomer and polymer added is 15 wt% of the electrolyte.

[0069] Comparative Example 1: Compared with Example 1, the difference is that the monomer hexafluorobutyl methacrylate added to the prepolymer electrolyte is replaced with butyl acrylate.

[0070] Comparative Example 2: Compared with Example 1, the difference is that the monomer N-tert-butylmethacrylamide added to the prepolymer electrolyte is replaced with acrylamide.

[0071] Comparative Example 3: Compared with Example 1, the difference is that only the monomer hexafluorobutyl methacrylate is added to the prepolymer electrolyte, and the mass ratio of the monomer hexafluorobutyl methacrylate to the crosslinking agent pentaerythritol tetraacrylate is 90:10.

[0072] Comparative Example 4: Compared with Example 1, the difference is that the monomer N-tert-butylmethacrylamide added to the prepolymer electrolyte is replaced with N-isopropylacrylamide.

[0073] Comparative Example 5: Compared with Example 1, the difference is that the monomer N-tert-butylmethacrylamide added to the prepolymer electrolyte is replaced with N-benzylacrylamide.

[0074] Comparative Example 6: Compared with Example 1, the difference is that the monomer N-tert-butylmethacrylamide added to the prepolymer electrolyte is replaced with N-(2-ethylhexyl)acrylamide.

[0075] Comparative Example 7: The difference from Example 1 is that the solvent is tetrahydrofuran.

[0076] Comparative Example 8: The difference from Example 1 is that the diluent is heptafluoro-1-methoxypropane.

[0077] Lithium-sulfur batteries were prepared using the prepolymerized electrolytes obtained in Examples 1-15 and Comparative Examples 1-8 above. Step 1: Preparation of FeS2 cathode: Weigh out 320 mg of FeS2, 32 mg of Super P conductive carbon black, 40 mg of polyacrylic acid, and 8 mg of carbon nanotubes, grind them for 10 min, mix them evenly, then pour in 4 mL of deionized water, and stir with a homogenizer for 20 min to obtain a uniform positive electrode slurry. Then, coat the obtained slurry evenly on aluminum foil, dry it in a 60℃ forced-air oven for 2 h, and then transfer it to an 80℃ vacuum oven for vacuum drying for 12 h. Cut the dried FeS2 positive electrode into appropriate sizes for later use.

[0078] Step 2: Assemble the CR-2032 button cell battery: Place the FeS2 electrode sheet obtained in step 1 into the center of the positive electrode shell, take 25 μL of prepolymerized electrolyte and drop it onto the positive electrode sheet, then place a 19 mm diameter polypropylene separator, add another 25 μL of prepolymerized electrolyte, and place a 200 μm lithium metal sheet on top, aligning it with the center of the positive electrode sheet. Subsequently, place stainless steel gaskets and spring sheets in sequence, and finally place the battery into a press to pressurize and seal it.

[0079] Step 3: Heating the battery to construct an in-situ polymerized gel electrolyte: After the battery obtained in step 2 is left to stand for 12 hours, it is heated at 60°C for 3 hours to initiate in-situ polymerization of the electrolyte.

[0080] The polymer electrolytes or batteries prepared in Examples 1-15 and Comparative Examples 1-8 were tested according to the following methods: The specific capacity, coulombic efficiency, and cycle capacity retention were obtained after 300 cycles at 25°C and a 1C rate. Specific data are shown in Table 1 below. Table 1

[0081] As can be seen from the comparison of Examples 1-15 and Comparative Examples 1-8, the low-solubility perfluorinated gel electrolyte prepolymer electrolyte with dynamic stress self-healing function constructed in this invention exhibits significant technical advantages in suppressing polysulfide shuttle effect, buffering electrode volume expansion, maintaining interface stability, and improving battery cycle life through systematic optimization of the structure, ratio, and process conditions of each component.

[0082] As can be seen from the comparison between Example 1 and Comparative Example 1, as Figure 1 As shown, when the fluorinated monomer hexafluorobutyl methacrylate was replaced with fluorine-free butyl acrylate, the battery's capacity retention was in a failed state after 300 cycles at 1C rate, with an initial specific capacity of only 614 mAh / g and a significantly degraded average coulombic efficiency. This indicates that the introduction of fluorinated segments is crucial; the extremely low polarizability of fluorine atoms endows the polymer backbone with low-polarity microregions, fundamentally weakening its ability to solubilize polysulfide intermediates. Example 1 used hexafluorobutyl methacrylate, which has a moderate fluorine atom density, forming a continuous and stable fluorinated shielding layer in the polymer network, effectively inhibiting the dissolution and shuttle of polysulfides, thereby achieving an initial specific capacity of 759 mAh / g and a 300-cycle capacity retention of 77.1%.

[0083] A comparison of Example 1 and Comparative Example 2 shows that when the monomer N-tert-butylmethacrylamide is replaced with acrylamide, the amide group in acrylamide is completely exposed in the polymer network due to the lack of the terminal trimethyl structure, thus losing the steric shielding effect of the large hindered group. This structural difference has a significant negative impact on the performance of the gel electrolyte, as the exposed amide group (-CONH2) has strong polarity, which affects the performance of polysulfide intermediates (Li2S). x The chemical affinity of fluorinated acrylates is significantly increased. This affinity, to some extent, offsets the repulsive effect of the low-polarity framework constructed by fluorinated acrylates on polysulfides, leading to the dissolution of some polysulfides in the gel electrolyte and the failure to effectively suppress the shuttle effect. Therefore, the battery continuously loses active material during cycling, resulting in a decrease in coulombic efficiency and rapid capacity decay. Secondly, regarding self-healing function, although acrylamide can still form a physical cross-linked network through hydrogen bonding between amide groups, the lack of rigid support from tert-butyl groups reduces the structural order and mechanical stability of the hydrogen bond network. When the electrode material generates internal stress due to volume expansion, although hydrogen bonds can dissociate and dissipate energy, the network is too loose, resulting in poor recombination efficiency and orientation of hydrogen bonds after stress release, making it difficult to achieve timely and effective repair of micro-damage at the electrode / electrolyte interface.

[0084] A comparison of Example 1 and Comparative Example 3 shows that when only hexafluorobutyl methacrylate monomer is added, due to the lack of acrylamide compounds with dynamic reversible hydrogen bonding, the constructed polymer network is formed solely by covalent cross-linking of fluorinated acrylate and cross-linking agents, and there are no reversible physical cross-linking points in the system. This structural difference significantly affects the mechanical response characteristics and interfacial stability of the gel electrolyte. Regarding interfacial self-healing capabilities, the polymer network of Comparative Example 3 lacks a dynamic hydrogen bond breaking and recombination mechanism, making it unable to achieve real-time repair of microcracks or interfacial detachment. During repeated volume expansion and contraction of the electrode material, micro-damage inevitably occurs at the electrode / electrolyte interface. However, due to the lack of self-healing function in the network, this damage accumulates continuously, ultimately leading to rapid degradation of battery performance.

[0085] As can be seen from Example 1 and Comparative Example 4, when the monomer N-tert-butylmethacrylamide added to the prepolymer electrolyte is replaced with N-isopropylacrylamide, it is similar to N-tert-butylmethacrylate, but the steric hindrance effect is relatively lower than that of tert-butyl, and there is no methylated acrylate, which may improve the solubility of polysulfides.

[0086] As can be seen from the comparison between Example 1 and Comparative Example 5, replacing the monomer N-tert-butylmethacrylamide in the prepolymer electrolyte with N-benzylacrylamide provides a higher steric hindrance effect for the benzene ring, but the polymer is more rigid, which affects ion transport and reduces the first-efficiency.

[0087] As can be seen from the comparison between Example 1 and Comparative Example 6, since the monomer N-tert-butylmethacrylamide is replaced with N-(2-ethylhexyl)acrylamide, it has a large steric hindrance effect, but the side chain length is longer, which affects ion transport, and the first-efficiency is significantly reduced.

[0088] A comparison of Example 1 and Comparative Example 7 shows that when the solvent is replaced with a cyclic ether compound, such as tetrahydrofuran, the microscopic solvation structure of the prepolymerized electrolyte and the final performance of the gel electrolyte undergo fundamental changes due to the significant differences in the solvent's molecular structure and physicochemical properties. Firstly, regarding the formation of a locally high-concentration electrolyte structure, tetrahydrofuran, as a cyclic ether solvent, has a fixed molecular conformation, large steric hindrance, and a high dielectric constant and strong coordination ability. The linear diether molecular chain used in Example 1 is flexible and can adjust its conformation through intramolecular rotation, forming a suitable coordination effect with lithium ions. Simultaneously, it synergistically constructs a unique locally high-concentration environment with the fluorinated diluent, effectively reducing the content of free solvent molecules and thus weakening its solubility for polysulfides. Regarding compatibility with the fluorinated diluent, tetrahydrofuran has poor miscibility with the fluorinated diluent, easily leading to microphase separation and resulting in an inhomogeneous electrolyte system. This inhomogeneity is solidified during subsequent in-situ polymerization, resulting in defective regions in the formed gel network structure. Some regions are enriched with fluorinated segments, while others are enriched with solvent. The solvent-rich regions become channels for the dissolution and shuttle movement of polysulfides, severely weakening the suppression effect of the shuttle effect.

[0089] As can be seen from the comparison between Examples 1 and Examples 2-3, the present invention further defines the structure of the fluorinated acrylate compounds and the acrylamide compounds in the monomer and limits the mass ratio of the fluorinated acrylate compounds to the acrylamide compounds in the monomer in the low-solubility perfluorinated gel electrolyte prepolymer electrolyte with dynamic stress self-healing function. At this time, by precisely controlling the ratio of the two in the range of (70~85):(5~20), a synergistic optimization design with a high fluorinated skeleton as the main body and a dynamic hydrogen bond network as the functional unit is achieved. At the same time, through the precise control of molecular structure, the synergistic optimization of the dynamic reversible hydrogen bond network formed by the fluorinated hydrophobic segments connecting the acrylic groups and the acrylamide structure containing the terminal trimethyl group is achieved. While ensuring an extreme inhibition effect on the dissolution of polysulfides, the system is endowed with a high-efficiency self-healing ability. A comparison of Examples 1 and 4 shows that the present invention further optimizes the number of fluorine atoms in R1 of fluorinated acrylate compounds. Similar to hexafluorobutyl methacrylate, Example 4 has a low degree of fluorination and no methylated acrylates. It has a relatively strong ability to dissolve polysulfides and a relatively low cycle capacity.

[0090] A comparison of Examples 1 and 5 shows that replacing N-tert-butylmethacrylamide with N-tert-octylacrylamide, while maintaining a certain degree of shielding effect on the amide group, has a negative impact on the polymer's network structure and dynamic properties due to the longer alkyl chain and greater steric hindrance of the tert-octyl group compared to the tert-butyl group. The tert-octyl group's long chain introduces excessive flexible components, reducing the overall rigidity and mechanical strength of the polymer network. When the electrode material undergoes volume expansion, the overly soft gel network cannot provide sufficient support, potentially leading to excessive deformation or even structural damage, failing to effectively maintain stable contact at the electrode / electrolyte interface.

[0091] A comparison of Examples 1 and 6-7 shows that, similar to hexafluorobutyl methacrylate, but with a higher degree of fluorination, the excessively long side chains may hinder ion transport. Further optimization of the alkyl chain length and the carbon chain length of the R1 substituent in this invention can further improve the overall performance.

[0092] A comparison of Examples 1 and 8 shows that the present invention further optimizes the lithium salt to LiFSI. By further optimizing the lithium salt anion structure, a deep fit is achieved with the low-solubility perfluorinated gel electrolyte network and locally high-concentration electrolyte system with dynamic stress self-healing function constructed in this invention. The anions of fluorosulfonylimide lithium salt or fluorosulfonate lithium salt both contain fluorine atoms, exhibiting good compatibility with the low-polarity fluorinated framework constructed from fluorinated acrylates. This helps to form uniform ion transport channels in the gel network, avoiding a decrease in ionic conductivity due to phase separation. Simultaneously, the sulfonylimide or sulfonic acid anions can form weak hydrogen bonds or dipole-dipole interactions with the amide groups of acrylamide compounds in the monomer. This reversible physical cross-linking enhances the mechanical stability of the gel network to a certain extent without affecting the dynamic dissociation and recombination of hydrogen bonds under stress, maintaining the high efficiency of the self-healing function. Therefore, it exhibits a significant synergistic enhancement effect in polysulfide suppression, interface stability, and lithium-ion transport kinetics.

[0093] A comparison of Examples 1, 14, 15 and Examples 12-13 shows that the present invention further optimizes the proportions of each component in the prepolymerized electrolyte by systematically controlling the total content of monomers and crosslinking agents, the mass ratio of monomers to crosslinking agents, the initiator content, the ratio of solvent to diluent, and the lithium salt concentration. This achieves a better balance between the polysulfide barrier capacity and self-healing performance of the gel electrolyte. At this point, the parameters work synergistically. Both the monomers and crosslinking agents contain acrylate groups. The total amount and ratio of monomers and crosslinking agents determine the backbone density of the gel network, which in turn affects the retention capacity of the solvent / diluent and the lithium ion transport path. The appropriate addition of the initiator ensures the formation of a regular network. The ratio of solvent to diluent directly controls the microscopic solvation structure of the electrolyte, which, together with the lithium salt concentration, determines the ionic conductivity and the dissolution inhibition effect on polysulfides. Through the synergistic optimization of the aforementioned multi-dimensional parameters, the prepolymerized electrolyte prepared in this invention, after in-situ polymerization inside the battery, can form a gel electrolyte with both strong polysulfide barrier capabilities and dynamic self-healing function. This collectively ensures the battery's cycle stability and coulombic efficiency, providing further assurance for achieving long-term cycle stability of the sulfur-based conversion cathode.

[0094] In summary, this invention successfully constructs a low-solubility perfluorinated gel electrolyte prepolymer electrolyte with dynamic stress self-healing function by carefully designing a synergistic combination of fluorinated acrylate and trimethyl-terminated acrylamide monomers, combined with specific diether solvents, di-terminated fluorinated alkyl diluents, multifunctional crosslinking agents, and suitable lithium salts and initiators. After in-situ polymerization inside the battery, the prepolymerized electrolyte forms a three-dimensional gel network that fully leverages multiple synergistic effects: the low-polarity microenvironment constructed by fluorinated segments significantly inhibits the dissolution and shuttle of polysulfide intermediates from a thermodynamic perspective, effectively anchoring the active material; the dynamic reversible hydrogen bond network introduced by the sterically hindered acrylamide structure endows the electrolyte layer with excellent stress dissipation and interface self-healing capabilities, enabling real-time healing of microcracks and interface contact failures caused by the massive volume expansion of the sulfur cathode, thereby maintaining the long-term stability of the electrode / electrolyte interface and the integrity of the ion transport pathway; the dual-terminated fluorinated alkyl diluent not only assists in constructing a locally high-concentration electrolyte structure, further enhancing the polysulfide suppression effect, but also participates in the formation of a stable interface layer rich in LiF, synergistically improving interface stability. Through systematic optimization of the molecular structure of each component (such as linker length, number of fluorine atoms, and alkyl substituents) and their ratios (such as the mass ratio of fluorinated monomers to amide monomers, total monomer / crosslinker content, solvent / diluent ratio, and lithium salt concentration), this invention further achieves a better balance among key properties of the gel electrolyte, including polysulfide barrier capability, self-healing efficiency, mechanical stability, and ionic conductivity. Experimental data fully demonstrate that lithium-sulfur batteries (such as Li-FeS2 batteries) assembled using the prepolymerized electrolyte of this invention retain more than 65% of their capacity after 300 cycles at 1C rate, with a specific capacity of up to 730 mAh / g in the first cycle, excellent average coulombic efficiency, and overall electrochemical performance far superior to those of the comparative examples. This invention provides an integrated, efficient, and practical gel electrolyte solution for overcoming the two core challenges of shuttle effect and volume expansion faced by sulfur-based conversion cathodes, significantly improving the cycle stability, coulombic efficiency, and capacity retention of lithium-sulfur batteries. It has significant scientific importance and broad industrial prospects for promoting the practical application of high-energy-density lithium metal secondary batteries.

[0095] 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. A low-solubility perfluorinated gel electrolyte prepolymerized electrolyte with dynamic stress self-healing function, characterized in that, The low-solubility perfluorinated gel electrolyte prepolymer electrolyte comprises monomers, crosslinking agents, initiators, solvents, diluents, and lithium salts; The monomer is selected from at least one of fluorinated acrylate compounds and at least one of trimethyl-terminated acrylamide compounds; the crosslinking agent is selected from one or more compounds containing at least three acrylate groups; the initiator is selected from one or more azo compounds; the solvent is selected from one or more linear ether solvents containing diether bonds; and the diluent is selected from one or more monoether compounds with fluorinated alkyl ends.

2. The low-solubility perfluorinated gel electrolyte prepolymerized electrolyte according to claim 1, characterized in that, The fluorinated acrylate compound in the monomer is selected from one or more of the following formula 1, wherein m is an integer from 0 to 4, R1 is selected from fluorinated C1 to C3 alkyl groups with ≥5 fluorine atoms, and R2 is selected from hydrogen atoms or C1 to C3 alkyl groups. The acrylamide compound in the monomer is selected from one or more of the following Formula 2, where n is an integer from 0 to 4, and R3 is selected from hydrogen atoms or C1 to C3 alkyl groups; The monoether compounds with fluorinated alkyl ends are selected from one or more of the structures of Formula 3, wherein R4 and R5 are each independently selected from fluorinated C1-C3 alkyl groups and have ≥3 fluorine atoms. In the low-solubility perfluorinated gel electrolyte prepolymer electrolyte with dynamic stress self-healing function, the mass ratio of fluorinated acrylate compounds to acrylamide compounds in the monomer is (70~85):(5~20). 。 3. The low-solubility perfluorinated gel electrolyte prepolymerized electrolyte according to claim 1, characterized in that, The fluorinated acrylate compound in the monomer is selected from one or more of Formula 1, wherein m is an integer of 1 to 2, R1 is selected from fluorinated C1 to C2 fluorinated alkyl groups with ≥5 fluorine atoms, and R2 is selected from one of C1 to C2 alkyl groups. The acrylamide compound in the monomer is selected from one or more of Formula 2, wherein n is an integer from 0 to 2, and R3 is selected from one of C1 to C2 alkyl groups.

4. The low-solubility perfluorinated gel electrolyte prepolymerized electrolyte according to claim 1, characterized in that, In the low-solubility perfluorinated gel electrolyte prepolymerization electrolyte with dynamic stress self-healing function, the monomer and crosslinking agent account for 5~30 wt% of the prepolymerization electrolyte by mass, the mass ratio of monomer to crosslinking agent is (1~9):1, the initiator accounts for 0.1~2 wt% of the prepolymerization electrolyte by mass, the volume ratio of solvent to diluent is 1:(0.5~3), and the concentration of lithium salt in the prepolymerization electrolyte is 1.0~2.0 mol / L.

5. The low-solubility perfluorinated gel electrolyte prepolymerized electrolyte according to claim 1, characterized in that, In the low-solubility perfluorinated gel electrolyte prepolymerization electrolyte with dynamic stress self-healing function, the monomer and crosslinking agent account for 7~15 wt% of the prepolymerization electrolyte by mass, the mass ratio of monomer to crosslinking agent is (4~6):1, the initiator accounts for 0.1~0.3 wt% of the prepolymerization electrolyte by mass, the volume ratio of solvent to diluent is 1:(1.5~2.5), and the concentration of lithium salt in the prepolymerization electrolyte is 1.4~1.6 mol / L.

6. The low-solubility perfluorinated gel electrolyte prepolymerized electrolyte according to claim 1, characterized in that, The lithium salt includes one or more of the following: lithium fluoride phosphate, lithium fluoride arsenate, lithium fluoride borate, lithium fluoride sulfonylimide, lithium fluoride sulfonate, and lithium fluoride perchlorate. Preferably, the lithium salt is selected from one or more of fluorosulfonylimide lithium salts or fluorosulfonate lithium salts.

7. The low-solubility perfluorinated gel electrolyte prepolymerized electrolyte according to claim 1, characterized in that, In the low-solubility perfluorinated gel electrolyte prepolymer electrolyte with dynamic stress self-healing function, the monomers are hexafluorobutyl methacrylate and N-tert-butylmethacrylamide, the crosslinking agent is pentaerythritol tetraacrylate, the solvent is 1,2-dimethoxypropane (DMP), the diluent is 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE), the initiator is azobisisobutyronitrile (AIBN), and the lithium salt is lithium bisfluorosulfonylimide (LiFSI). The volume ratio of solvent to diluent is 1:2, the concentration of lithium salt in the prepolymer electrolyte is 1.5 mol / L, the mass ratio of monomer to crosslinking agent is 5:1, the amount of monomer and crosslinking agent added in the prepolymer electrolyte is 10 wt%, and the amount of initiator added in the prepolymer electrolyte is 0.2 wt%.

8. A method for preparing a low-solubility perfluorinated gel electrolyte prepolymerized electrolyte with dynamic stress self-healing function as described in any one of claims 1 to 7, comprising the following steps: S1: Add lithium salt to solvent, stir thoroughly until clear, add diluent, and continue stirring until clear to obtain local high-concentration electrolyte, wherein the concentration of lithium salt in local high-concentration electrolyte is 0.5~2.5 mol / L; S2: Fluorinated acrylate compounds, trimethyl-terminated acrylamide compounds, crosslinking agents, and initiators are added to a local high-concentration electrolyte according to the target mass ratio, and the mixture is stirred evenly to obtain a prepolymerized electrolyte.

9. The application of a low-solubility perfluorinated gel electrolyte prepolymerized electrolyte with dynamic stress self-healing function in lithium-ion batteries, characterized in that, The lithium-ion battery includes a lithium-sulfur battery.

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