A high-safety active defense type composite gel electrolyte, a preparation method and application thereof

Abstract

This invention discloses a high-safety, active-defense composite gel electrolyte, its preparation method, and its application, belonging to the field of solid-state and quasi-solid-state battery materials technology. The composite gel electrolyte possesses a multi-level synergistic structure, comprising: a three-dimensional porous framework of a fluorinated polymer doped with polar inorganic nanoparticles; a polyethylene oxide polymer gel matrix filling the pores of the framework; and core-shell flame-retardant microcapsules embedded in the gel matrix. By constructing a synergistic coupling relationship between the multi-level physical structure and chemical composition, and utilizing the hydrogen bonds and Lewis acid-base interactions between the polar functional groups of the flame-retardant microcapsule shell and the macromolecular chains of the gel matrix, matrix crystallization is effectively suppressed, and interfacial mass transfer kinetics are optimized. Under the condition of introducing large-volume microcapsules, the interfacial charge transfer impedance is significantly reduced. The composite gel electrolyte combines excellent intrinsic mechanical safety, active thermal defense function, and electrochemical performance, and can be applied in solid-state or quasi-solid-state batteries.

Description

Technical Field

[0001] This invention belongs to the field of solid-state and quasi-solid-state battery materials technology, specifically relating to a high-safety active defense composite gel electrolyte, its preparation method, and its application. Background Technology

[0002] The large-scale commercial application of high-energy-density lithium-ion batteries is at the core of the development of power batteries and energy storage technologies. With the increase in the energy density of cathode materials, particle breakage and release of active oxygen are very likely to occur under high-voltage cycling.

[0003] Traditional liquid organic carbonate electrolytes are highly volatile and flammable, and can easily cause catastrophic thermal runaway when batteries are subjected to mechanical abuse or abnormal temperature rise. This is the main challenge that limits their wider application.

[0004] To improve battery safety, traditional methods typically involve introducing liquid flame retardants into the electrolyte; however, reaching an effective flame retardant concentration can lead to a sharp increase in electrolyte viscosity and a drastic decrease in conductivity.

[0005] Meanwhile, these liquid flame retardants are prone to continuous reduction and decomposition on the negative electrode surface, forming a high-resistivity solid electrolyte interface film, which severely degrades the battery's cycle life and electrochemical performance.

[0006] Against this backdrop, gel polymer electrolytes have attracted much attention due to their combination of the intrinsic safety of solid electrolytes and the high ionic conductivity of liquid electrolytes.

[0007] However, existing polymer systems still face technical bottlenecks: for example, simple polymer electrospun membranes have defects such as excessive porosity and insufficient mechanical strength, and cannot effectively resist lithium dendrite penetration.

[0008] On the other hand, the matrix directly cast using conventional polymer materials still has fatal weaknesses such as easy melting and flammability under high temperature environments, and has poor physical stability.

[0009] Existing technologies that add microencapsulated flame retardants are mostly "passive" physical protection by physically coating the membrane surface, which lacks microscopic structural synergy and usually hinders the transport of lithium ions. Summary of the Invention

[0010] Technical problems solved: This application solves the defects of existing technologies, such as excessive porosity and insufficient mechanical strength of simple polymer electrospun diaphragms, which cannot effectively resist lithium dendrite penetration, and the fatal weaknesses of conventional polymer materials directly cast into the matrix, such as easy melting and flammability under high temperature environment and poor physical stability. It provides a high-safety active defense composite gel electrolyte, its preparation method and application. The composite gel electrolyte provided by this invention has a multi-level synergistic structure and is prepared by in-situ casting of a polymer gel matrix containing flame-retardant microcapsules in a porous framework; the three-dimensional porous polymer framework is uniformly doped with polar inorganic nanoparticles; the flame-retardant microcapsules are embedded and distributed in the gel matrix.

[0011] Purpose of the Invention: The purpose of this invention is to provide a high-safety active defense composite gel electrolyte, its preparation method, and its application, overcoming the aforementioned defects of the prior art. This electrolyte can significantly improve the intrinsic mechanical safety and thermal safety protection capabilities of the battery without sacrificing or even optimizing electrochemical performance, achieving active defense against thermal runaway. Through the synergistic coupling design of multi-level physical structure and chemical composition, this invention not only intrinsically eliminates the risk of thermal runaway and optimizes the mass transfer kinetics of the interface, but also achieves active carbonization safety defense of the battery under abnormal conditions.

[0012] The specific technical solution is as follows: A high-safety active defense composite gel electrolyte, wherein the composite gel electrolyte has a multi-level synergistic structure, specifically including: A three-dimensional porous polymer framework, wherein the three-dimensional porous polymer framework is formed by interwoven fluoropolymer nanofibers, and polar inorganic nanoparticles are uniformly doped in its fiber network. A polymer gel matrix comprising polyethylene oxide polymers and lithium salts, wherein the polymer gel matrix is ​​cast in situ and continuously fills the pores of the three-dimensional porous polymer framework to form quasi-solid-state ion transport channels. And a set of flame-retardant microcapsules embedded in the polymer gel matrix, wherein the flame-retardant microcapsules have a core-shell structure, the core material being a phosphorus- and / or nitrogen-containing polymer flame-retardant compound, and the shell material being a cross-linked resin containing polar functional groups. The polar functional groups on the surface of the flame-retardant microcapsule shell material have hydrogen bonds and Lewis acid-base interactions with the macromolecular chains of the polyethylene oxide polymer, resulting in a relative crystallinity of the composite gel electrolyte between 20% and 45%, which actively induces the matrix to dehydrate and char prematurely in the early stage of abnormal temperature rise.

[0013] Further, the fluoropolymer is selected from one or more combinations of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), vinylidene fluoride-chlorotrifluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, fluorinated ethylene propylene, ethylene tetrafluoroethylene copolymer, and ethylene trichlorofluoroethylene copolymer; the polar inorganic nanoparticles are selected from one or more combinations of magnesium oxide (MgO), aluminum oxide (Al2O3), silicon dioxide (SiO2), zinc oxide, zirconium oxide, calcium carbonate, and barium titanate; in the three-dimensional porous polymer framework, the mass percentage of the polar inorganic nanoparticles is 5%-15%.

[0014] Furthermore, in the polymer gel matrix, the molar ratio of the ethylene oxide EO unit of the polyethylene oxide polymer to the lithium ions dissociated from the lithium salt is 12:1 to 20:1.

[0015] Furthermore, the core material of the flame-retardant microcapsule is selected from one or more of phosphate esters, phosphites, organophosphates, phosphorus and nitrogen compounds, red phosphorus, piperazine pyrophosphate, ammonium polyphosphate, polyphosphazene, melamine cyanurate, melamine polyphosphate, monocyanamide, dicyandiamide, aluminum hydroxide, magnesium hydroxide, and zinc borate; the shell material is selected from one or more of melamine-formaldehyde resin, urea-formaldehyde resin, phenolic resin, melamine resin, polyurethane resin, epoxy resin, polyacrylate resin, and polyurea.

[0016] Furthermore, the surface contact angle of the composite gel electrolyte is between 20° and 50° when tested with commercial liquid carbonate electrolyte; and the interfacial charge transfer impedance of the composite gel electrolyte in the AC impedance test (EIS) is less than 200Ω.

[0017] This application also discloses a method for preparing any of the above-mentioned high-safety active defense composite gel electrolytes, specifically including the following steps: Step 1, skeleton formation: According to the mass ratio, 1.5-2.0 parts of fluoropolymer and 0.1-0.5 parts of polar inorganic nanoparticles are dispersed in 16-16.5 parts of solvent to prepare spinning solution; a high voltage electrostatic field is applied by an electrostatic generator to carry out continuous electrospinning to obtain a three-dimensional porous polymer skeleton with macropores. The second step is precursor preparation: According to the mass ratio, 1-1.5 parts of polyethylene oxide polymer and 0.35-0.4 parts of lithium salt are dissolved in 8-12 parts of solvent system to obtain a basic polymer solution; 0.1-0.3 parts of pre-prepared flame-retardant microcapsules are added to the basic polymer solution, and the mixture is stirred to allow the functional groups on the surface of the microcapsules to combine with the polymer segments, thereby obtaining a composite gel precursor slurry that remains in suspension; The third step is in-situ film formation: the composite gel precursor slurry is uniformly cast onto the three-dimensional porous polymer framework to wet the pores of the framework; then the residual solvent is removed under vacuum heating to solidify the gel matrix, thus obtaining the composite gel electrolyte.

[0018] Further, the solvent is one or more selected from deionized water, ethanol, isopropanol, acetone, tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, and acetonitrile.

[0019] Furthermore, in the first step, the positive voltage of the applied high-voltage electrostatic field is +20kV to +30kV, and the negative voltage is -500V to -1500V; the ambient temperature for continuous electrospinning is controlled between 40℃ and 50℃.

[0020] Furthermore, in the third step, the temperature of the vacuum heating environment is controlled between 50°C and 60°C.

[0021] This application also discloses the application of any of the above-mentioned high-safety active defense composite gel electrolytes in lithium metal batteries, solid / quasi-solid-state lithium-ion power batteries and energy storage batteries. The solid / quasi-solid-state lithium-ion power battery is a high-energy intrinsically safe solid or quasi-solid-state lithium-ion battery, including a positive electrode, a negative electrode and an electrolyte layer disposed between the positive electrode and the negative electrode. The electrolyte layer adopts the high-safety active defense composite gel electrolyte as described in any one of claims 1 to 5.

[0022] Explanation of principle: In this application, the mass percentage of additives in the gel matrix is ​​controlled within a reasonable range. Synergistic fusion is achieved through hydrogen bonds and Lewis acid-base interactions between the polar functional groups on the surface of the microcapsule shell and the macromolecular chains of the matrix. Thanks to this steric hindrance effect, the relative crystallinity of the composite gel electrolyte can be effectively controlled in the range of 20%-45%, which greatly broadens the ion channels in the amorphous region.

[0023] The present invention has the following beneficial effects: (1) Constructing an intrinsic physical safety barrier. The present invention, through the three-dimensional nesting design of a flexible inorganic / organic hybrid framework and a soft gel matrix, endows the electrolyte layer with excellent thermophysical stability. (2) Overcoming the bottleneck of electrochemical performance loss and achieving unexpected technical effects. According to conventional knowledge in the field, introducing a large number of micron-sized solid flame-retardant microcapsules into a polymer gel matrix will inevitably severely hinder the movement of polymer chain segments, block ion transport channels, and drastically worsen the contact impedance of the electrode interface. However, this invention, through specific microstructure design, cleverly utilizes the hydrogen bonds and Lewis acid-base strong interactions between the polar shell of the microcapsules (such as oxygen- and nitrogen-containing functional groups) and the gel matrix to stimulate a significant structural synergistic effect. This multi-level synergy not only did not lead to channel blockage, but also unexpectedly inhibited the intrinsic crystallization of the polymer matrix, successfully constructing a continuous and abundant high-speed The conductive network, and more importantly, the polar synergistic effect greatly optimizes the hydrophilicity of the interface, resulting in an anomalous cliff-like decrease in the interfacial charge transfer impedance under high pressure conditions. Comparative experiments have confirmed that the composite gel electrolyte prepared in the example has a contact angle with the electrolyte as low as 36.1°-39.2° and an extremely low interfacial impedance (170-188Ω). In contrast, the comparative example without polar microcapsules has a contact angle increased to 52.3° and an impedance as high as 540Ω. This anomalous physicochemical phenomenon of "introducing a large volume of foreign matter but reducing impedance in the opposite direction" is a miracle that cannot be easily pieced together and deduced by existing conventional physical blending techniques, achieving excellent technical effects that those skilled in the art could not have predicted. (3) Establish an active carbonization defense mechanism. By introducing core-shell structure flame-retardant microcapsules, the microcapsules can be sensitively broken in the early stage of micro-short circuit or abnormal temperature rise inside the battery. The capsule core material releases phosphorus / nitrogen flame-retardant substances, which catalyze the polymer matrix to undergo dehydration and cross-linking carbonization reaction in advance. The active chemical blocking strategy of "pre-carbonization" replaces the traditional passive physical heat absorption, and a high safety defense line is built in all weather. Attached Figure Description

[0024] Figure 1 This is a flowchart illustrating the preparation process of the multi-level structured composite gel electrolyte described in this invention. Figure 2 The images show the scanning electron microscope (SEM) microstructures of the different stages of the system of this invention. (a) is a morphology of the spinning skeleton of pure fluorinated polymer, (b) is a morphology of the composite skeleton doped with inorganic particles, (c) is a morphology of the composite film after casting polymer gel, and (d) is a morphology of the final composite gel electrolyte with embedded flame-retardant microcapsules. Figure 3 This is a comparison chart showing the surface contact angle test results of the composite gel electrolyte of this invention with the liquid electrolyte. Figure 4 The AC impedance spectrum of a half-cell equipped with the composite gel electrolyte of the present invention; Figure 5The thermogravimetric-thermal stability verification curves are shown, where (a) is the TG-DTG curve of the pure fluorinated polymer skeleton and (b) is the TG-DTG curve of the composite skeleton doped with polar inorganic nanoparticles. Detailed Implementation

[0025] The preferred embodiments of the present invention will be described in detail below with reference to the examples. It should be understood that the following examples are given for illustrative purposes only and are not intended to limit the scope of the present invention. Those skilled in the art can make various modifications and substitutions to the present invention without departing from the spirit and purpose of the present invention.

[0026] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0027] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0028] It should be noted that the precise point values ​​in the following specific embodiments provide substantial legal and scientific support for the physical substances; the performance parameter tests involved in this invention all follow the following standard methods: the relative crystallinity is calculated by measuring the endothermic enthalpy using a differential scanning calorimeter at a heating rate of 10°C / min; the surface contact angle is obtained by testing at room temperature (25°C) using a commercial carbonate-based mixed electrolyte as the droplet liquid.

[0029] Example 1: A method for preparing a high-safety active defense composite gel electrolyte, specifically including the following steps: Step 1, framework formation: Dissolve 1.5 g of polyvinylidene fluoride in a mixed solvent of 15 g of N,N-dimethylformamide and acetone, add 0.15 g of nano-magnesium oxide (10% of the mass of polyvinylidene fluoride), and stir magnetically at room temperature until completely dissolved to obtain a homogeneous spinning solution. Inject the spinning solution into a syringe with a stainless steel needle, apply a positive voltage of +25 kV and a negative voltage of -1050 V for electrospinning, maintain the ambient temperature at 45 °C, and obtain a three-dimensional porous polymer framework with macroscopic pores; Step 2, Precursor Preparation: In an argon-protected glove box, 1.0 g of polyethylene oxide and 0.4 g of lithium bis(trifluoromethanesulfonyl)imide were dissolved in 10 g of acetonitrile, maintaining the molar ratio of ethylene oxide units to lithium ions precisely at 16:1, and stirred until completely dissolved; then 0.2 g of pre-synthesized flame-retardant microcapsules (core material is piperazine pyrophosphate, shell material is melamine-formaldehyde resin) were added, and the mixture was ultrasonically dispersed to form a stable, non-agglomerated composite slurry; Step 3, Composite Molding: The composite gel precursor slurry is uniformly cast onto the three-dimensional porous polymer framework to impregnate the pores of the framework; it is then dried in a vacuum oven at 55°C to completely remove residual acetonitrile solvent, allowing the gel matrix to solidify. After curing and peeling, a high-safety active defense composite gel electrolyte film is obtained.

[0030] Example 2: A method for preparing a high-safety active defense composite gel electrolyte, specifically including the following steps: Step 1, skeleton formation: Dissolve 1.5 g of vinylidene fluoride-hexafluoropropylene copolymer in 15 g of mixed solvent, add 0.075 g of nano alumina (accounting for 5% of the copolymer mass), stir evenly at room temperature, inject into a syringe with a stainless steel needle, apply a +20kV positive voltage and a -500V negative voltage for electrospinning, maintain the ambient temperature at 40℃, and collect to obtain a three-dimensional porous polymer skeleton; Step 2, Precursor preparation: In an argon-protected glove box, 1.0 g of polyethylene oxide and 0.53 g of lithium bis(trifluoromethanesulfonyl)imide were dissolved in 10 g of acetonitrile, maintaining a molar ratio of ethylene oxide units to lithium ions of 12:1, and stirred until completely dissolved; then 0.2 g of pre-synthesized flame-retardant microcapsules (core material is ammonium polyphosphate, shell material is urea-formaldehyde resin) were added, and the mixture was ultrasonically dispersed to form a composite slurry; Step 3, Composite molding: The above porous skeleton is placed in a mold and the composite slurry is poured evenly. It is then placed in a vacuum oven at 50°C to dry completely to remove the residual acetonitrile solvent. After curing and peeling, a composite gel electrolyte film is obtained.

[0031] Example 3: A method for preparing a high-safety active defense composite gel electrolyte, comprising the following preparation steps: Step 1, skeleton forming: Add 0.225 g of nano silica (accounting for 15% of the mass of polytetrafluoroethylene) to a 1.5 g polytetrafluoroethylene solution system, stir evenly at room temperature, and inject into a syringe with a stainless steel needle. Apply a positive voltage of +30kV and a negative voltage of -1500V to perform electrospinning. Maintain the ambient temperature at 50℃ and collect to obtain a three-dimensional porous polymer skeleton. Step 2, Precursor Preparation: In an argon-protected glove box, 1.0 g of polyethylene oxide and 0.32 g of lithium bis(trifluoromethanesulfonyl)imide were dissolved in 10 g of acetonitrile and stirred until completely dissolved, maintaining a molar ratio of ethylene oxide units to lithium ions of 20:1; then 0.2 g of pre-synthesized flame-retardant microcapsules (core material is piperazine pyrophosphate, shell material is polyurethane resin) were added and ultrasonically dispersed to form a composite slurry; Step 3, in-situ film formation: The above porous skeleton is placed in a mold and the composite slurry is uniformly poured in. It is then placed in a vacuum oven at 60°C to dry completely to remove the residual acetonitrile solvent. After curing and peeling, a composite gel electrolyte film is obtained.

[0032] Comparative Example 1: A method for preparing a composite gel electrolyte, comprising the following preparation steps: Step 1, skeleton forming: Dissolve polyvinylidene fluoride in a mixed solvent, add 10% of the mass of polyvinylidene fluoride nano magnesium oxide, stir evenly, and then perform electrospinning to obtain a three-dimensional porous polymer skeleton. Step 2, Precursor preparation: Dissolve polyethylene oxide and lithium bis(trifluoromethanesulfonyl)imide in acetonitrile, maintaining the molar ratio of ethylene oxide units to lithium ions at 16:1. Then, directly add bare piperazine pyrophosphate powder that is not coated with polar crosslinking resin, and disperse it by ultrasonication to form a slurry. Step 3, Composite molding: The above porous skeleton is placed in a mold and the slurry is poured evenly. It is then placed in a vacuum oven at 55°C to dry and remove residual solvent. After curing and peeling, a composite gel electrolyte film is obtained.

[0033] Comparative Example 2, a method for preparing a composite gel electrolyte, comprising the following preparation steps: Step 1, Precursor preparation: Dissolve polyethylene oxide and lithium bis(trifluoromethanesulfonyl)imide in acetonitrile, maintaining the molar ratio of ethylene oxide units to lithium ions at 16:1. Then add flame-retardant microcapsules (core material is piperazine pyrophosphate, shell material is melamine-formaldehyde resin), and disperse by ultrasonication to form a stable suspended composite slurry. Step 2, Composite molding: The polymer slurry containing flame-retardant microcapsules prepared above is uniformly cast onto a flat polytetrafluoroethylene plate, dried in a vacuum oven at 55°C to remove residual solvent, and then peeled off to obtain a pure polymer composite film supported by a non-woven skeleton.

[0034] Summary of performance evaluation and test data: To clearly demonstrate the influence of multi-level physical structure and chemical ratio on the final performance of composite gel electrolyte, and to prove the rationality of the scope of protection claimed by the present invention, the following table summarizes the key preparation parameters and core performance test results of Examples 1 to 3 and Comparative Examples 1 to 2.

[0035] Table 1. Summary of preparation parameters and electrochemical and physical performance test results for the examples and comparative examples. .

[0036] As shown in Table 1 and the relevant electrochemical test results, the relative crystallinity of the composite electrolyte membranes obtained in Examples 1 to 3 was stably controlled within the range of 20%-45%.

[0037] The introduction of polar microcapsules unexpectedly and effectively suppressed matrix crystallization, creating abundant amorphous ion channels. When titrated with commercial liquid electrolyte, the surface contact angle remained within the hydrophilic range of 20°-50°.

[0038] After being assembled into a coin cell, its AC impedance was tested. The interfacial charge transfer impedance was significantly lower than 200Ω, demonstrating excellent ion transport dynamics and perfectly achieving an unexpected synergistic resistance reduction effect.

[0039] In contrast, in Comparative Example 1, due to the use of bare flame retardant powder without polar resin coating, the powder was severely agglomerated in the polymer matrix, exhibiting a macroscopic phase separation state.

[0040] This directly leads to a significant increase in the electrolyte contact angle to over 50°, severely deteriorating the interfacial affinity and causing the interfacial impedance to abnormally soar to over 500Ω, which is simply unable to meet the normal electrochemical operation requirements of high-energy-density batteries.

[0041] Thermal stability and long-cycle electrochemical performance were verified by thermogravimetric analysis and long-cycle assembly test of high-voltage coin cells on the films prepared in Example 1 and Comparative Example 2, respectively.

[0042] Thermogravimetric analysis results show that, thanks to the multi-level synergistic effect of the three-dimensional porous polymer framework and the flame-retardant microcapsules, the peak temperature of the maximum weight loss rate of the composite gel electrolyte in Example 1 is significantly delayed, exhibiting excellent high-temperature dimensional stability and heat resistance.

[0043] Cyclic test results confirmed that the battery in Comparative Example 2 (due to the lack of a three-dimensional porous polymer framework as a physical support barrier) experienced severe polarization in the early stages of cycling due to intensified interfacial side reactions and uneven dendrite deposition, ultimately leading to a precipitous capacity decay failure due to internal short circuits.

[0044] The battery using the multi-level physical and chemical nested structure of Embodiment 1 of the present invention, after undergoing rigorous long-cycle testing, not only maintained stable coulombic efficiency, but also maintained an extremely high level of discharge specific capacity. This comparison directly confirms that the composite multi-level system of the present invention not only has extremely superior intrinsic thermal stability at high temperatures, but also provides excellent electrochemical compatibility and long-life transport barrier.

[0045] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made to the present invention within the spirit and scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A high-safety active defense composite gel electrolyte, characterized in that, The composite gel electrolyte has a multi-level synergistic structure, specifically including: A three-dimensional porous polymer framework, wherein the three-dimensional porous polymer framework is formed by interwoven fluoropolymer nanofibers, and polar inorganic nanoparticles are uniformly doped in its fiber network. A polymer gel matrix comprising polyethylene oxide polymers and lithium salts, wherein the polymer gel matrix is ​​cast in situ and continuously fills the pores of the three-dimensional porous polymer framework to form quasi-solid-state ion transport channels. And a set of flame-retardant microcapsules embedded in the polymer gel matrix, wherein the flame-retardant microcapsules have a core-shell structure, the core material being a phosphorus- and / or nitrogen-containing polymer flame-retardant compound, and the shell material being a cross-linked resin containing polar functional groups. The polar functional groups on the surface of the flame-retardant microcapsule shell material have hydrogen bonds and Lewis acid-base interactions with the macromolecular chains of the polyethylene oxide polymer, resulting in a relative crystallinity of the composite gel electrolyte between 20% and 45%, which actively induces the matrix to dehydrate and char prematurely in the early stage of abnormal temperature rise.

2. The high-safety active defense composite gel electrolyte according to claim 1, characterized in that, The fluoropolymer is selected from one or more combinations of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), vinylidene fluoride-chlorotrifluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, fluorinated ethylene propylene, ethylene tetrafluoroethylene copolymer, and ethylene trichlorofluoroethylene copolymer; the polar inorganic nanoparticles are selected from one or more combinations of magnesium oxide (MgO), aluminum oxide (Al2O3), silicon dioxide (SiO2), zinc oxide, zirconium oxide, calcium carbonate, and barium titanate; the mass percentage of the polar inorganic nanoparticles in the three-dimensional porous polymer framework is 5%-15%.

3. The high-safety active defense composite gel electrolyte according to claim 1, characterized in that, In the polymer gel matrix, the molar ratio of the ethylene oxide EO unit of the polyethylene oxide polymer to the lithium ions dissociated from the lithium salt is 12:1 to 20:

1.

4. The high-safety active defense composite gel electrolyte according to claim 1, characterized in that, The core material of the flame-retardant microcapsule is selected from one or more of the following: phosphate ester, phosphite ester, organophosphate salt, phosphorus nitrogen compound, red phosphorus, piperazine pyrophosphate, ammonium polyphosphate, polyphosphazene, melamine cyanurate, melamine polyphosphate, monocyanamide, dicyandiamide, aluminum hydroxide, magnesium hydroxide, and zinc borate; the shell material is selected from one or more of the following: melamine-formaldehyde resin, urea-formaldehyde resin, phenolic resin, melamine resin, polyurethane resin, epoxy resin, polyacrylate resin, and polyurea.

5. The high-safety active defense composite gel electrolyte according to claim 1, characterized in that, The surface contact angle of the composite gel electrolyte is between 20° and 50° when tested with commercial liquid carbonate electrolyte; and the interfacial charge transfer impedance of the composite gel electrolyte is less than 200Ω in the AC impedance test (EIS).

6. A method for preparing the high-safety active defense composite gel electrolyte according to any one of claims 1-5, characterized in that, Specifically, the steps include the following: Step 1, skeleton formation: According to the mass ratio, 1.5-2.0 parts of fluoropolymer and 0.1-0.5 parts of polar inorganic nanoparticles are dispersed in 16-16.5 parts of solvent to prepare spinning solution; a high voltage electrostatic field is applied by an electrostatic generator to carry out continuous electrospinning to obtain a three-dimensional porous polymer skeleton with macropores. The second step is precursor preparation: According to the mass ratio, 1-1.5 parts of polyethylene oxide polymer and 0.35-0.4 parts of lithium salt are dissolved in 8-12 parts of solvent system to obtain a basic polymer solution; 0.1-0.3 parts of pre-prepared flame-retardant microcapsules are added to the basic polymer solution, and the mixture is stirred to allow the functional groups on the surface of the microcapsules to combine with the polymer segments, thereby obtaining a composite gel precursor slurry that remains in suspension; The third step is in-situ film formation: the composite gel precursor slurry is uniformly cast onto the three-dimensional porous polymer framework to wet the pores of the framework; then the residual solvent is removed under vacuum heating to solidify the gel matrix, thus obtaining the composite gel electrolyte.

7. The preparation method of the high-safety active defense composite gel electrolyte according to claim 6, characterized in that, The solvent is one or more of deionized water, ethanol, isopropanol, acetone, tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, and acetonitrile.

8. The preparation method of the high-safety active defense composite gel electrolyte according to claim 6, characterized in that, In the first step, the positive voltage of the applied high-voltage electrostatic field is +20kV to +30kV, and the negative voltage is -500V to -1500V; the ambient temperature for continuous electrospinning is controlled between 40℃ and 50℃.

9. The preparation method of the high-safety active defense composite gel electrolyte according to claim 6, characterized in that, In the third step, the temperature of the vacuum heating environment is controlled between 50°C and 60°C.

10. The application of the high-safety active defense composite gel electrolyte according to any one of claims 1-5 in lithium metal batteries, solid / quasi-solid-state lithium-ion power batteries, and energy storage batteries, characterized in that: Solid-state / quasi-solid-state lithium-ion power batteries are high-energy-density intrinsically safe solid-state or quasi-solid-state lithium-ion batteries, including a positive electrode, a negative electrode, and an electrolyte layer disposed between the positive electrode and the negative electrode. The electrolyte layer adopts the high-safety active defense composite gel electrolyte as described in any one of claims 1 to 5.

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