Composite gel electrolyte for energy storage frequency modulation and preparation method thereof, solid-state battery

Abstract

The embodiment of the application discloses a composite gel electrolyte for energy storage frequency modulation and a preparation method thereof and a solid-state battery, relates to the technical field of solid-state battery electrolytes, and the composite gel electrolyte for energy storage frequency modulation comprises a polymer framework, the polymer framework is a fluorine-containing polymer blend chemically crosslinked by a bis-imidazole-based silane crosslinking agent, inorganic functional fillers, the inorganic functional fillers are hydroxylated titanium-niobium oxide solid solutions modified by a silane coupling agent on the surface, the inorganic functional fillers are dispersed in the polymer framework, and an electrolyte system is kept in a three-dimensional network formed by the polymer framework, the electrolyte system comprises a lithium salt, an organic solvent and an in-situ film-forming additive; wherein the in-situ film-forming additive is fluoroethylene carbonate. The embodiment of the application aims to solve the problem that the ionic conductivity, mechanical strength and thermal stability of the gel electrolyte in the energy storage frequency modulation solid-state battery are difficult to be considered simultaneously.

Description

Technical Field

[0001] This application relates to the technical field of solid-state battery electrolytes, and more particularly to composite gel electrolytes for energy storage and frequency regulation, their preparation methods, and solid-state batteries. Background Technology

[0002] Existing gel electrolyte technology faces three major bottlenecks: the inherent contradiction between ion transport and mechanical properties (high ionic conductivity requires low crystallinity and high electrolyte content, but this leads to a significant decrease in mechanical strength (typically <1.5MPa), making it impossible to suppress lithium dendrite penetration under high current); poor interfacial compatibility (a high-resistance SEI film easily forms at the electrolyte-electrode interface during cycling, resulting in rapid decay of rate performance); and insufficient high-temperature stability (the polymer skeleton is prone to swelling and decomposition above 60℃, with electrolyte leakage exceeding 30%, failing to meet the high-temperature operating conditions required by energy storage power stations in summer).

[0003] Currently available modification schemes mostly employ single silane grafting or single inorganic filler doping, failing to achieve synergistic improvement in multi-dimensional performance, and lacking dedicated solutions for the core requirements of "deep charging and discharging, long lifespan, and high safety" in energy storage frequency regulation.

[0004] Therefore, there is an urgent need for a solution that can overcome the above-mentioned shortcomings. Summary of the Invention

[0005] This application proposes a composite gel electrolyte for energy storage and frequency regulation, its preparation method, and a solid-state battery to address the deficiencies of the prior art.

[0006] According to a first aspect of the embodiments of this application, a composite gel electrolyte for energy storage and frequency modulation is provided, comprising: The polymer backbone is a fluoropolymer blend chemically crosslinked with a bisimidazole silane crosslinking agent; Inorganic functional filler, wherein the inorganic functional filler is a hydroxylated titanium niobium oxide solid solution with a surface modified by a silane coupling agent, and the inorganic functional filler is dispersed in the polymer backbone; An electrolyte system, wherein the electrolyte system is held within a three-dimensional network formed by the polymer backbone, the electrolyte system comprising lithium salt, organic solvent and in-situ film-forming additive; The in-situ film-forming additive is fluoroethylene carbonate.

[0007] In some embodiments, the fluoropolymer blend is a blend of polyvinylidene fluoride-hexafluoropropylene copolymer and polyvinylidene fluoride-trifluorochloroethylene copolymer.

[0008] In some embodiments, the bis-imidazolylsilane crosslinking agent is 1,3-bis-3-triethoxysilylpropylimidazolium hexafluorophosphate, and the amount of 1,3-bis-3-triethoxysilylpropylimidazolium hexafluorophosphate is 7% to 13% of the mass of the fluoropolymer blend.

[0009] In some embodiments, the hydroxylated titanium niobium oxide solid solution is TiNb2O7, and the amount of TiNb2O7 added is 6% to 11% of the mass of the polymer backbone.

[0010] In some embodiments, the lithium salt is a mixture of lithium hexafluorophosphate and lithium difluorosulfonylimide; the total concentration of the lithium salt in the electrolyte system is from 1.2 mol / L to 1.8 mol / L.

[0011] In some embodiments, the organic solvent is a ternary mixed solvent composed of ethylene carbonate, methyl ethyl carbonate and vinylene carbonate.

[0012] In some embodiments, the amount of fluoroethylene carbonate added is 0.5% to 2% of the total mass of the electrolyte system.

[0013] According to a second aspect of this application, a preparation method is provided for preparing the composite gel electrolyte for energy storage and frequency modulation as described above, comprising: Fluoropolymer blends are pretreated with hydroxylation to obtain hydroxylated blends. The hydroxylated blend polymer was reacted with a bisimidazole silane crosslinking agent under the action of a catalyst to obtain a bisimidazole silane crosslinked blend polymer. The titanium niobium oxide solid solution was hydroxylated to obtain a hydroxylated titanium niobium oxide solid solution. The hydroxylated titanium niobium oxide solid solution was reacted with a silane coupling agent to obtain a surface-functionalized titanium niobium oxide solid solution. Under an inert atmosphere, the bisimidazole silane crosslinked blend polymer, lithium salt, the surface-functionalized titanium niobium oxide solid solution, organic solvent, fluoroethylene carbonate, crosslinking agent and initiator are mixed to prepare a prepolymer solution. The prepolymer liquid is subjected to UV curing and thermal curing in sequence to obtain the composite gel electrolyte for energy storage and frequency modulation.

[0014] According to a third aspect of this application, a solid-state battery is provided, comprising a positive electrode, a negative electrode, and an electrolyte located between the positive electrode and the negative electrode, wherein the electrolyte is a composite gel electrolyte for energy storage and frequency modulation as described above.

[0015] In some embodiments, the solid-state battery is an energy storage solid-state battery used for primary or secondary frequency regulation of the power grid.

[0016] The beneficial effects of the composite gel electrolyte for energy storage frequency regulation and its preparation method, as well as the solid-state battery, according to the embodiments of this application, include at least the following: This application embodiment constructs a high-speed ion transport channel using the two nitrogen atoms of a bisimidazole silane. The silicon-oxygen crosslinking and the physical reinforcement of the titanium-niobium-oxygen solid solution together form a stable network framework, fundamentally resolving the inherent contradiction between ion transport and mechanical properties, and simultaneously improving ionic conductivity and mechanical strength. This application embodiment utilizes the three-dimensional tunnel structure and surface characteristics of the titanium-niobium-oxygen solid solution to facilitate uniform lithium ion deposition. Combined with the fluoroethylene carbonate in the electrolyte, it promotes the formation of a stable interfacial film, synergistically improving interfacial compatibility and significantly inhibiting lithium dendrite growth, effectively suppressing lithium dendrites and extending cycle life. This application embodiment, through the combined action of the chemical crosslinking network of silicon-oxygen bonds and the heat-resistant titanium-niobium-oxygen filler, significantly improves the thermal stability and liquid retention capacity of the electrolyte, making it less prone to swelling and decomposition at high temperatures, and significantly enhancing high-temperature dimensional stability and safety. Attached Figure Description

[0017] Figure 1 This is a SEM image of a lithium-lithium symmetric battery after cycling, based on a composite gel electrolyte for energy storage and frequency regulation, according to an embodiment of this application. Figure 2 This is a schematic flowchart of a preparation method according to an embodiment of this application; Figure 3 This is a comparison diagram of the high and low temperature performance of Embodiment 1 and Comparative Example 1 of this application; Figure 4 The diagram illustrates the low-temperature ionic conductivity of Example 1 and Comparative Example 1 of this application. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the various embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been provided in the various embodiments of this disclosure to facilitate a better understanding of the disclosure. However, the technical solutions claimed in this disclosure can be implemented even without these technical details and with various variations and modifications based on the following embodiments. The division of the various embodiments below is for ease of description and should not constitute any limitation on the specific implementation of this disclosure. The various embodiments can be combined with and referenced by each other without contradiction.

[0019] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed embodiments of this application, but merely to illustrate selected embodiments of this application. Other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are all within the scope of protection of the embodiments of this application.

[0020] This application discloses a composite gel electrolyte for energy storage and frequency regulation, its preparation method, and a solid-state battery. The preparation method is used to prepare the composite gel electrolyte for energy storage and frequency regulation. The purpose is to break through the traditional single modification approach and construct a three-in-one synergistic modification system that combines bisimidazole silane chemical crosslinking, titanium niobium oxygen solid solution physical reinforcement, and in-situ interface passivation.

[0021] See attached document Figure 1 The image shown is a post-cycle SEM image of a lithium-lithium symmetric battery based on the composite gel electrolyte for energy storage and frequency regulation according to an embodiment of this application. The composite gel electrolyte for energy storage and frequency regulation includes: a polymer backbone, an inorganic functional filler, and an electrolyte system.

[0022] In some embodiments, the polymer backbone is a fluoropolymer blend chemically crosslinked with a bisimidazole silane crosslinking agent.

[0023] In some embodiments, the inorganic functional filler is a hydroxylated titanium niobium oxide solid solution with a surface modified by a silane coupling agent, and the inorganic functional filler is dispersed in the polymer backbone.

[0024] In some embodiments, the electrolyte system is held within a three-dimensional network formed by the polymer backbone, the electrolyte system comprising lithium salt, organic solvent and in-situ film-forming additive.

[0025] The in-situ film-forming additive is fluoroethylene carbonate.

[0026] In some embodiments, the fluoropolymer blend is a blend of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) and polyvinylidene fluoride-chlorotrifluoroethylene copolymer (PVDF-CTFE).

[0027] In some embodiments, the bis(3-triethoxysilylpropyl)imidazolium hexafluorophosphate is a crosslinking agent of 1,3-bis-3-triethoxysilylpropylimidazolium hexafluorophosphate, and the amount of 1,3-bis-3-triethoxysilylpropylimidazolium hexafluorophosphate is 7% to 13% of the mass of the fluoropolymer blend.

[0028] In some embodiments, the hydroxylated titanium niobium oxide solid solution is TiNb2O7 (titanium niobium oxide solid solution), and the amount of TiNb2O7 added is 6% to 11% of the polymer backbone mass.

[0029] In some embodiments, the lithium salt is a mixture of lithium hexafluorophosphate and lithium difluorosulfonylimide; the total concentration of the lithium salt in the electrolyte system is from 1.2 mol / L to 1.8 mol / L.

[0030] In some embodiments, the organic solvent is a ternary mixed solvent composed of ethylene carbonate, methyl ethyl carbonate and vinylene carbonate.

[0031] In some embodiments, the amount of the fluoroethylene carbonate added is 0.5% to 2% of the total mass of the electrolyte system.

[0032] In some embodiments, N-methylpyrrolidone (NMP) is used to dissolve the PVDF-HFP and PVDF-CTFE copolymers for a hydroxylation pretreatment reaction to obtain a hydroxylated blend polymer. After the reaction, the product is precipitated by pouring it into excess deionized water, followed by filtration and washing until neutral. For example, the hydroxylated blend polymer is an intermediate product whose chemical structure undergoes a fundamental change after reacting with the crosslinking agent. Instead, its post-reaction form is a fluorinated polymer blend chemically crosslinked by a bisimidazole silane crosslinking agent.

[0033] This application embodiment constructs a high-speed ion transport channel using the two nitrogen atoms of a bisimidazole silane. The silicon-oxygen crosslinking and the physical reinforcement of the titanium-niobium-oxygen solid solution together form a stable network framework, fundamentally resolving the inherent contradiction between ion transport and mechanical properties, and simultaneously improving ionic conductivity and mechanical strength. This application embodiment utilizes the three-dimensional tunnel structure and surface characteristics of the titanium-niobium-oxygen solid solution to facilitate uniform lithium ion deposition. Combined with the fluoroethylene carbonate in the electrolyte, it promotes the formation of a stable interfacial film, synergistically improving interfacial compatibility and significantly inhibiting lithium dendrite growth, effectively suppressing lithium dendrites and extending cycle life. This application embodiment, through the combined action of the chemical crosslinking network of silicon-oxygen bonds and the heat-resistant titanium-niobium-oxygen filler, significantly improves the thermal stability and liquid retention capacity of the electrolyte, making it less prone to swelling and decomposition at high temperatures, and significantly enhancing high-temperature dimensional stability and safety.

[0034] See attached document Figure 2 The illustration shows a preparation method disclosed in this application for preparing the composite gel electrolyte for energy storage and frequency modulation as described above, including the following steps S1 to S6.

[0035] Step S1: The fluoropolymer blend is subjected to hydroxylation pretreatment to obtain a hydroxylated blend polymer.

[0036] Step S2: The hydroxylated blend polymer is reacted with a bisimidazole silane crosslinking agent under the action of a catalyst to obtain a bisimidazole silane crosslinked blend polymer.

[0037] Step S3: Hydroxylate the titanium niobium oxide solid solution to obtain a hydroxylated titanium niobium oxide solid solution.

[0038] Step S4: React the hydroxylated titanium niobium oxide solid solution with a silane coupling agent to obtain a surface-functionalized titanium niobium oxide solid solution.

[0039] Step S5: Under an inert atmosphere, the bisimidazole silane crosslinked blend polymer, lithium salt, the surface-functionalized titanium niobium oxide solid solution, organic solvent, fluoroethylene carbonate, crosslinking agent and initiator are mixed to prepare a prepolymer solution.

[0040] Step S6: The prepolymer liquid is subjected to UV curing and thermal curing in sequence to obtain the composite gel electrolyte for energy storage and frequency modulation.

[0041] This application also discloses a solid-state battery, including a positive electrode, a negative electrode, and an electrolyte located between the positive electrode and the negative electrode, wherein the electrolyte is the energy storage frequency modulation composite gel electrolyte as described above.

[0042] In some implementations, the solid-state battery is an energy storage solid-state battery used for primary or secondary frequency regulation of the power grid.

[0043] In some embodiments, the fluoropolymer blend is subjected to hydroxylation pretreatment to obtain a hydroxylated blend polymer, comprising: hydroxylation pretreatment of the blend polymer: PVDF-HFP and PVDF-CTFE are mixed at a mass ratio of 3:1, dissolved in N-methylpyrrolidone (NMP) to prepare a 10% mass fraction solution, and diethanolamine (in an amount 2.5 times the mass of the blend polymer) is added. The mixture is reacted at 95°C for 7 hours under nitrogen protection. After the reaction is completed, the precipitate is poured into excess deionized water, filtered and washed until neutral, and then dried under vacuum at 65°C for 12 hours to obtain the hydroxylated blend polymer.

[0044] In some embodiments, the hydroxylated blend polymer is reacted with a bisimidazole silane crosslinking agent under the action of a catalyst to obtain a bisimidazole silane crosslinked blend polymer, comprising: dissolving the hydroxylated blend polymer in anhydrous xylene to prepare a 5% (w / w) solution, adding stannous octoate catalyst (0.5% of the total mass of the reactants), slowly adding 1,3-bis(3-triethoxysilylpropyl)imidazolium hexafluorophosphate, reacting at 85°C for 11 h; after the reaction is completed, precipitating the precipitate in excess n-hexane, filtering and washing three times, and drying under vacuum at 75°C for 8 h to obtain the bisimidazole silane crosslinked blend polymer.

[0045] For example, the amount of bisimidazole silane used is 7% to 13% of the mass of the hydroxylated blend polymer.

[0046] In some embodiments, the hydroxylated titanium niobium oxide solid solution is reacted with a silane coupling agent to obtain a surface-functionalized titanium niobium oxide solid solution, including: hydroxylation treatment of the titanium niobium oxide solid solution and surface grafting of the silane coupling agent. The hydroxylation treatment of the titanium niobium oxide solid solution includes: dispersing nano-TiNb2O7 (particle size 15-30 nm) prepared by hydrothermal method in deionized water to prepare a 5% (w / w) suspension, adding dilute sulfuric acid to adjust the pH to 2.0, and stirring at 85°C for 4 hours. After the reaction, centrifuge at 9000 r / min for 8 minutes, wash the precipitate until neutral, and vacuum dry at 85°C for 6 hours to obtain hydroxylated TiNb2O7. The surface grafting of the silane coupling agent includes: dispersing the hydroxylated TiNb2O7 in anhydrous isopropanol to prepare a 2% (w / w) suspension, adding vinyltriethoxysilane (VTES, 6% of the TiNb2O7 mass), and reacting at 70°C for 3 hours under nitrogen protection. After the reaction was completed, the product was centrifuged and washed, and then dried under vacuum at 75°C for 8 hours to obtain surface-functionalized TiNb2O7.

[0047] For example, the amount of surface-functionalized TiNb2O7 added is 6% to 11% of the mass of the crosslinked blend polymer.

[0048] In some embodiments, the prepolymer is prepared by mixing the bis(imidazolium)silane crosslinked polymer, lithium salt, the surface-functionalized titanium niobium oxide solid solution, organic solvent, fluoroethylene carbonate, crosslinking agent, and initiator under an inert atmosphere. This includes: dissolving the crosslinked polymer in a ternary mixed solvent of ethylene carbonate (EC) / ethyl methyl carbonate (EMC) / ethylene carbonate (VC) (volume ratio 2:3:0.05) in an argon-atmosphere glove box and stirring until completely dissolved; adding a mixed lithium salt of lithium hexafluorophosphate (LiPF6) and lithium bis(fluorosulfonyl)imide (LiFSI) (mass ratio 1:1) and stirring until completely dissolved; adding surface-functionalized TiNb2O7 and ultrasonically dispersing for 35 min; and finally adding the crosslinking agent trimethylolpropane triacrylate (TMPTA), the photoinitiator 1-hydroxycyclohexylphenyl ketone (HCPK), and the thermal initiator AIBN, and stirring for 10 min to obtain a homogeneous prepolymer.

[0049] For example, the total concentration of the mixed lithium salt is 1.2~1.8 mol / L; the amount of TMPTA added is 3%~5% of the mass of the crosslinked blend polymer; the amount of HCPK added is 0.5% of the mass of the crosslinked blend polymer; and the amount of AIBN added is 0.8% of the mass of the crosslinked blend polymer.

[0050] In some embodiments, the prepolymer liquid is subjected to UV curing and thermal curing in sequence to obtain the composite gel electrolyte for energy storage and frequency modulation, including: ultrasonically degassing the prepolymer liquid for 8 minutes and then injecting it into a polytetrafluoroethylene mold, irradiating it under 365nm UV light for 30 seconds for preliminary curing, and placing it in a 55°C oven for thermal curing for 5 hours, and then vacuum drying it at 45°C for 15 hours to obtain the composite gel polymer electrolyte.

[0051] This application employs 1,3-bis(3-triethoxysilylpropyl)imidazolium hexafluorophosphate as a crosslinking modifier, simultaneously introducing two imidazolium ring nitrogen atoms and silicon-oxygen bond crosslinking sites to achieve a simultaneous improvement in ion conductivity and thermal stability. This application also employs a compounded hydroxylated titanium niobium oxide solid solution (TiNb2O7) as an inorganic functional filler; its three-dimensional tunnel structure provides stronger mechanical support, and the titanium / niobium bimetallic sites synergistically promote lithium salt dissociation and lithium-ion transport. Furthermore, this application utilizes a PVDF-HFP / PVDF-CTFE blended polymer framework, optimizing crystallinity and electrolyte retention capacity by adjusting the blending ratio. Finally, this application introduces trace amounts of fluoroethylene carbonate (FEC) as an in-situ film-forming agent to form a low-impedance, high-stability SEI film on the electrode surface.

[0052] This application also discloses a lithium-ion battery, including a positive electrode, a negative electrode, and an electrolyte located between the positive electrode and the negative electrode, wherein the electrolyte is the energy storage frequency modulation composite gel electrolyte as described above.

[0053] To further illustrate the embodiments of this application and enable those skilled in the art to better understand the solutions of the embodiments of this application, the technical solutions of the embodiments of this application will be clearly and completely described below based on the polymer electrolytes prepared in Examples 1 to 6 and Comparative Examples 1 to 3. Obviously, the described embodiments are only some of the embodiments of this application, and not all of them.

[0054] Example 1 Preparation of hydroxylated blended polymer: 3.75g of PVDF-HFP and 1.25g of PVDF-CTFE were dissolved in 50mL of NMP, 12.5mL of diethanolamine was added, and the mixture was reacted at 95℃ for 7h under nitrogen protection. The precipitate was washed and dried to obtain the hydroxylated blended polymer.

[0055] Bisimilar silane crosslinking: 4g of hydroxylated blended polymer was dissolved in 80mL of anhydrous xylene, 0.02g of stannous octoate was added, and 0.4g of 1,3-bis(3-triethoxysilylpropyl)imidazolium hexafluorophosphate (10% of the amount) was added dropwise. The reaction was carried out at 85℃ for 11h, and the precipitate was washed and dried to obtain the crosslinked polymer.

[0056] Preparation of hydroxylated TiNb2O7: 2g of nano-TiNb2O7 was dispersed in 40mL of deionized water, the pH was adjusted to 2.0, and the reaction was carried out at 85℃ for 4h. After centrifugation, washing and drying, hydroxylated TiNb2O7 was obtained.

[0057] Surface functionalization: 1g of hydroxylated TiNb2O7 was dispersed in 50mL of anhydrous isopropanol, 0.06g of VTES was added, and the reaction was carried out at 70℃ for 3h under nitrogen protection. The product was then centrifuged, washed and dried to obtain functionalized TiNb2O7.

[0058] Prepolymer preparation: In an argon glove box, dissolve 2g of crosslinked polymer in 2mL of EC / EMC / VC (2:3:0.05) mixed solvent, add 0.52g of LiPF6 / LiFSI (1:1) mixed lithium salt (1.5mol / L), stir to dissolve, then add 0.18g of functionalized TiNb2O7 and sonicate for 35min; add 0.08g of TMPTA (4%), 0.01g of HCPK (0.5%) and 0.016g of AIBN (0.8%), and stir until homogeneous.

[0059] Dual-curing gelation: After degassing the prepolymer, it is injected into a mold, irradiated with 365nm ultraviolet light for 30s, heat-cured at 55℃ for 5h, and vacuum-dried at 45℃ for 15h to obtain a composite gel electrolyte for energy storage and frequency modulation.

[0060] Battery assembly: A soft-pack solid-state battery is assembled using lithium iron phosphate as the positive electrode (load 18mg / cm²) and natural graphite as the negative electrode.

[0061] The difference between Example 2 and Example 1 is that the amount of bisimidazole silane used is 7% of the mass of the hydroxylated blend polymer, while the other conditions are exactly the same.

[0062] The difference between Example 3 and Example 1 is that the amount of bisimidazole silane used is 13% of the mass of the hydroxylated blend polymer, while the other conditions are exactly the same.

[0063] The difference between Example 4 and Example 1 is that the amount of functionalized TiNb2O7 added is 6% of the mass of the crosslinked blend polymer, while the other conditions are exactly the same.

[0064] The difference between Example 5 and Example 1 is that the amount of functionalized TiNb2O7 added is 11% of the mass of the crosslinked blend polymer, while the other conditions are exactly the same.

[0065] The difference between Example 6 and Example 1 is that the total concentration of the mixed lithium salt is 1.2 mol / L, while the other conditions are exactly the same.

[0066] The difference between Comparative Example 1 and Example 1 is that: instead of using bisimidazole silane, an equal mass of monoimidazole silane 3-triethoxysilylpropylimidazole was used, while all other conditions were exactly the same.

[0067] The difference between Comparative Example 2 and Example 1 is that TiNb2O7 was not added, while all other conditions were exactly the same.

[0068] Comparative Example 3 used a commercially available 1.2 mol / L LiPF6 / EC+EMC (3:7) liquid electrolyte, and the other battery assembly conditions were exactly the same as in Example 1.

[0069] The polymer electrolytes prepared in Examples 1 to 6 and Comparative Examples 1 to 3 were subjected to performance testing. The testing process included: measuring ionic conductivity using AC impedance spectroscopy at a frequency of 10 Hz. - 2Hz to 10 6 The test temperature was 25℃. The lithium-lithium symmetric battery cycle life test was conducted using CR2032 coin cells with a lithium sheet diameter of 14mm, a thickness of 0.5mm, and an electrolyte membrane diameter of 16mm. The test conditions were current densities of 1mA / cm², 2mA / cm², and 3mA / cm², with a charge / discharge time of 1h for each and a test temperature of 25℃. The test parameters for each embodiment and comparative example are shown in Table 1 below.

[0070] Table 1: Test parameters for Examples 1 to 6 and Comparative Examples 1 to 3

[0071] Based on Table 1 above, the analysis of the three core performance parameters—ionic conductivity, tensile strength, and cycle life of the Li / / Li symmetric battery—is as follows: Example 1 of this application exhibits an ionic conductivity of 6.1 × 10⁻⁶ at 25°C. - The tensile strength of Example 1 was 1.9 times that of Comparative Example 1 modified with monoimidazolium silane and 2.2 times that of Comparative Example 2 without TiNb2O7, respectively. The dual nitrogen atom dynamic coordination of the bisimidazolium silane constructed a continuous three-dimensional ion transport channel, and the high dielectric constant of the composite TiNb2O7 further promoted the dissociation of lithium salt. The two synergistically achieved a significant improvement in ion conduction performance. At the same time, the synergistic effect of the chemical cross-linking of silicon-oxygen bonds of bisimidazolium silane and the physical enhancement of the three-dimensional tunnel structure of TiNb2O7 enabled the tensile strength of Example 1 to reach 4.2 MPa, which was 68% and 147% higher than that of Comparative Example 1 and Comparative Example 2, respectively, effectively solving the inherent contradiction between ion conduction and mechanical properties of gel electrolytes. Finally, the optimized ion transport environment reduced local concentration polarization, and the surface hydroxyl groups of TiNb2O7 guided the uniform deposition of lithium ions, enabling the Li / / Li symmetric battery of Example 1 to cycle stably for 1560 h at a current density of 2 mA / cm², demonstrating excellent lithium dendrite suppression ability.

[0072] See attached document Figure 3 and attached Figure 4As shown, it can be seen that Example 1 exhibits superior low-temperature performance compared to Comparative Example 1 without the use of bisimidazole silane. Its low-temperature ionic conductivity is significantly better than that of Comparative Example 1, and it also exhibits excellent low-temperature discharge performance.

[0073] Compared with the prior art, the embodiments of this application have ultra-high ion conductivity: the nitrogen atom of the bisimidazole ring reacts with Li + Multiple dynamic coordinations are formed, constructing a continuous three-dimensional ion transport channel, with an ion conductivity of up to 6.1 × 10⁻⁶ at 25℃. - ³S / cm, ionic conductivity remains at 0.9×10³ at -30℃. - ³S / cm, meeting the requirements of high-rate charge and discharge; the embodiments of this application exhibit excellent mechanical and thermal stability: the synergistic effect of silicon-oxygen bond chemical crosslinking and TiNb2O7 physical reinforcement increases the electrolyte tensile strength to 4.2MPa, the thermal decomposition temperature to 340℃, and the electrolyte leakage rate to <5% at 70℃; the embodiments of this application exhibit excellent lithium dendrite suppression capability: the three-dimensional tunnel structure of TiNb2O7 guides Li + Uniform deposition; the Li / / Li symmetric cell can cycle stably for more than 1500 hours at a current density of 2 mA / cm² without obvious lithium dendrite growth.

[0074] The above description is merely a specific implementation of the embodiments of this application, but the protection scope of the embodiments of this application is not limited thereto. Any simple modifications, changes, and equivalent changes made by those skilled in the art to the above embodiments based on the technical essence of the embodiments of this application within the technical scope disclosed in the embodiments of this application shall still fall within the protection scope of the technical solution of the embodiments of this application.

Claims

1. A composite gel electrolyte for energy storage and frequency modulation, characterized in that, include: The polymer backbone is a fluoropolymer blend chemically crosslinked with a bisimidazole silane crosslinking agent; Inorganic functional filler, wherein the inorganic functional filler is a hydroxylated titanium niobium oxide solid solution with a surface modified by a silane coupling agent, and the inorganic functional filler is dispersed in the polymer backbone; An electrolyte system, wherein the electrolyte system is held within a three-dimensional network formed by the polymer backbone, the electrolyte system comprising lithium salt, organic solvent and in-situ film-forming additive; The in-situ film-forming additive is fluoroethylene carbonate.

2. The composite gel electrolyte for energy storage and frequency modulation according to claim 1, characterized in that, The fluoropolymer blend is a blend of polyvinylidene fluoride-hexafluoropropylene copolymer and polyvinylidene fluoride-trifluorochloroethylene copolymer.

3. The composite gel electrolyte for energy storage and frequency modulation according to claim 1, characterized in that, The bis-imidazolylsilane crosslinking agent is 1,3-bis-3-triethoxysilylpropylimidazolium hexafluorophosphate, and the amount of 1,3-bis-3-triethoxysilylpropylimidazolium hexafluorophosphate is 7% to 13% of the mass of the fluoropolymer blend.

4. The composite gel electrolyte for energy storage and frequency modulation according to claim 1, characterized in that, The hydroxylated titanium niobium oxide solid solution is TiNb2O7, and the amount of TiNb2O7 added is 6% to 11% of the mass of the polymer backbone.

5. The composite gel electrolyte for energy storage and frequency regulation according to claim 1, characterized in that, The lithium salt is a mixture of lithium hexafluorophosphate and lithium difluorosulfonylimide; the total concentration of the lithium salt in the electrolyte system is 1.2 mol / L to 1.8 mol / L.

6. The composite gel electrolyte for energy storage and frequency modulation according to claim 1, characterized in that, The organic solvent is a ternary mixed solvent composed of ethylene carbonate, methyl ethyl carbonate and vinylene carbonate.

7. The composite gel electrolyte for energy storage and frequency modulation according to claim 1, characterized in that, The amount of fluoroethylene carbonate added is 0.5% to 2% of the total mass of the electrolyte system.

8. A preparation method for preparing a composite gel electrolyte for energy storage and frequency modulation as described in any one of claims 1 to 7, characterized in that, include: Fluoropolymer blends are pretreated with hydroxylation to obtain hydroxylated blends. The hydroxylated blend polymer was reacted with a bisimidazole silane crosslinking agent under the action of a catalyst to obtain a bisimidazole silane crosslinked blend polymer. The titanium niobium oxide solid solution was hydroxylated to obtain a hydroxylated titanium niobium oxide solid solution. The hydroxylated titanium niobium oxide solid solution was reacted with a silane coupling agent to obtain a surface-functionalized titanium niobium oxide solid solution. Under an inert atmosphere, the bisimidazole silane crosslinked blend polymer, lithium salt, the surface-functionalized titanium niobium oxide solid solution, organic solvent, fluoroethylene carbonate, crosslinking agent and initiator are mixed to prepare a prepolymer solution. The prepolymer liquid is subjected to UV curing and thermal curing in sequence to obtain the composite gel electrolyte for energy storage and frequency modulation.

9. A solid-state battery, comprising a positive electrode, a negative electrode, and an electrolyte located between the positive electrode and the negative electrode, characterized in that, The electrolyte is the composite gel electrolyte for energy storage and frequency modulation as described in any one of claims 1 to 7.

10. The solid-state battery according to claim 9, characterized in that, The solid-state battery is an energy storage solid-state battery used for primary or secondary frequency regulation of the power grid.

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