A solid-state electrolyte with high ionic conductivity and a method of preparing the same

Abstract

The application belongs to the field of lithium ion battery materials, and particularly relates to a solid-state electrolyte with high ionic conductivity and a preparation method thereof. The electrolyte is composed of fluorinated cyclic carbonate grafted polyionic liquid as a polymer matrix, lithium lanthanum zirconium oxide supported on a nano graphene skeleton as an ion conductive reinforcing filler, and double fluorosulfonyl imide lithium, polypropylene carbonate and nanocellulose fiber. The preparation comprises dissolving the fluorinated cyclic carbonate grafted polyionic liquid and the lithium lanthanum zirconium oxide supported on the nano graphene skeleton in anhydrous acetonitrile to form a solution, adding fillers, lithium salt and cellulose fiber to form a slurry, and then coating, drying and hot pressing. The application constructs multi-level ion transmission channels in the electrolyte, has the characteristics of high ionic conductivity, wide electrochemical window and excellent interface stability, can effectively inhibit lithium dendrite growth, and can improve the safety performance and cycle life of the battery. The preparation process is simple, the cost is low, and the application is suitable for large-scale production.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium ion battery materials, and particularly relates to a solid-state electrolyte with high ionic conductivity and a preparation method thereof. BACKGROUND

[0002] With the rapid development of electrochemical energy storage technology, traditional liquid lithium ion batteries have gradually been difficult to meet the growing demand for high energy density and high safety. The inherent volatility, flammability and easy leakage of liquid electrolyte have become a key bottleneck restricting the further development of battery technology. Under this background, all-solid-state lithium batteries are considered as the key development direction of the next generation of energy storage technology because they fundamentally solve the safety problem and are expected to achieve higher energy density. As the core component of all-solid-state batteries, the performance of solid-state electrolyte directly determines the overall performance of the battery. The current research on solid-state electrolyte system is mainly divided into three categories: polymer electrolyte, inorganic ceramic electrolyte and composite electrolyte.

[0003] The polymer electrolyte is represented by polyethylene oxide-based system, which has good flexibility and interface contact with the electrode, but its room temperature ionic conductivity is generally low, and it is easy to crystallize during battery operation, which leads to performance degradation and seriously limits the practical application. Inorganic ceramic electrolyte includes garnet type, perovskite type and novel sulfide type, among which garnet type lithium lanthanum zirconium oxygen material exhibits a wide electrochemical window and good lithium metal stability, but its inherent brittleness and high grain boundary resistance bring challenges to large-scale production and application; although sulfide electrolyte has excellent ionic conduction capacity, it is extremely sensitive to environmental humidity, has harsh synthesis conditions and high cost, and also has problems in interface compatibility with electrode materials. Composite electrolyte attempts to combine the advantages of polymer and inorganic materials, and builds an ionic conduction network by dispersing ceramic fillers in the polymer matrix, but the fillers in the traditional composite system are easy to agglomerate, and the ion transmission resistance at the phase interface is large, which makes it difficult to achieve ideal synergistic effect.

[0004] The main challenges of current solid-state electrolyte technology include: insufficient room temperature ionic conductivity which restricts the battery rate performance; poor interface stability with lithium metal negative electrode which leads to short cycle life; mechanical strength and electrochemical stability of electrolyte material are difficult to balance; complex preparation process leads to high cost. In particular, the existing electrolyte material is difficult to meet the practical requirements in terms of ionic conduction efficiency, interface compatibility, mechanical strength and thermal stability. Although researchers have made some progress through element doping, interface modification and structure design, fundamental innovation is still needed in material system design and preparation process to develop new solid-state electrolyte with high ionic conductivity, excellent interface stability and good mechanical properties, so as to promote the commercialization process of all-solid-state battery technology. SUMMARY

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a solid electrolyte with high ionic conductivity and a method for preparing the same.

[0006] In a first aspect, the present invention provides a method for preparing a solid electrolyte with high ionic conductivity, comprising the steps of:

[0007] S1. Dissolve the fluorinated cyclic carbonate-grafted polyionic liquid and polypropylene carbonate in anhydrous acetonitrile and mechanically stir to form a polymer solution.

[0008] S2. Add lithium lanthanum zirconium oxide and lithium bisfluorosulfonyl imide loaded with a nano-graphene framework to a polymer solution, and disperse by ultrasonication to form a slurry; add nanocellulose fibers, and stir at high speed to obtain a viscous paste; coat the viscous paste on both sides of a porous polypropylene membrane, and dry under vacuum.

[0009] S3. Hot pressing using a hot press.

[0010] In this invention, the formation of a high-ionic-conductivity solid electrolyte is based on a multi-component interfacial coupling and ion transport channel construction mechanism. The imidazole cations in the fluorinated cyclic carbonate-grafted polyionic liquid dissociate with the lithium bis(fluorosulfonyl)imide anions through electrostatic interactions, releasing free lithium ions. The ether oxygen atoms of the polypropylene carbonate further coordinate with the lithium ions, lowering the energy barrier for polymer chain movement and forming a continuous-phase ion transport pathway. Lithium lanthanum zirconium oxide supported on a graphene nanoframework serves as the active filler. The zirconium atoms on its surface interact with the fluorinated segments in the polyionic liquid via Lewis acid-base interactions, reducing interfacial impedance. Simultaneously, the two-dimensional structure of the graphene framework extends within the polymer matrix through π-π stacking, forming a three-dimensional ion-electron hybrid conduction network. The hydroxyl groups of the nanocellulose fibers form hydrogen bonds with the polymer matrix, enhancing mechanical strength. The fiber network and the grain boundaries of the lithium lanthanum zirconium oxide together construct multi-scale channels, promoting lithium-ion interfacial hopping transport. During hot pressing, the components achieve densification through dynamic interfacial rearrangement, ultimately forming a solid electrolyte system with multiple functions including rapid ion conduction, interfacial stability, and dendrite suppression.

[0011] As a preferred technical solution of the present invention, in step S2, the high-speed homogenization stirring time is 2-4 hours; the vacuum drying temperature is 48-52℃.

[0012] As a preferred embodiment of the present invention, in step S3, the hot pressing time at 78-82°C is 5-10 min; the hot pressing temperature is 78-82°C.

[0013] As a preferred embodiment of the present invention, the preparation method of the fluorinated cyclic carbonate grafted polyionic liquid includes: A1, under argon protection, dissolving 1-vinyl-3-ethylimidazolium bromide and 4-((2,2,3,3,4,4,5,5,6,6-decafluorohexyloxy)methyl)-1,3-dioxolane-2-one methacrylate in anhydrous acetonitrile, adding it to a reactor and stirring until completely dissolved; then adding azobisisobutyronitrile and refluxing at 68-72°C to obtain a crude product; A2, precipitating the crude product in diethyl ether to obtain an intermediate; dissolving the intermediate in a mixed solvent of deionized water and acetone, adding lithium bis(trifluoromethanesulfonyl)imide for anion exchange, stirring at room temperature; separating the organic phase and washing with deionized water until neutral, and vacuum drying.

[0014] As a preferred embodiment of the present invention, the preparation steps of 4-((2,2,3,3,4,4,5,5,6,6-decafluorohexyloxy)methyl)-1,3-dioxolane-2-one methacrylate include: firstly, adding 0.1 mol of glycerol and 0.13 mol of dimethyl carbonate to a 250 mL three-necked flask containing 0.5 g of potassium carbonate, stirring and refluxing at 90 °C for 5 h; after the reaction is completed, cooling the reaction solution to 25 °C, adding 50 mL of deionized water, and using 3 × 50 mL dimethyl carbonate solution... Extracted with chloromethane, the organic phases were combined and dried over anhydrous magnesium sulfate for 8 h. After filtration, the solvent was removed by rotary evaporation to obtain 4-(hydroxymethyl)-1,3-dioxolane-2-one. Then, 4-(hydroxymethyl)-1,3-dioxolane-2-one was dissolved in 100 mL of dichloromethane, cooled to 0 °C in an ice-water bath, and 0.12 mol of thionyl chloride was slowly added dropwise. After the addition was completed, the temperature was raised to 25 °C and reacted for 4 h. The solvent and excess thionyl chloride were removed by rotary evaporation to obtain the 4-(chloromethyl)-1,3-dioxolane-2-one intermediate. Subsequently, 0.095 mol of 1H,1H,6H,6H-perfluorohexane-1,6-diol was dissolved in 150 mL of anhydrous acetonitrile, and 0.114 mol of sodium hydride (60% dispersed in mineral oil) was added. The mixture was stirred at 0 °C for 30 min to generate the sodium alkoxide. Then, the 4-(chloromethyl)-1,3-dioxolane-2-one intermediate obtained in the previous step was added, and the mixture was heated to 80 °C for 10 h under nitrogen protection. After the reaction was completed, the reaction solution was cooled to 20 °C, and the solid was removed by filtration. The filtrate was concentrated by rotary evaporation to obtain a fluorinated cyclic carbonate intermediate. Finally, this intermediate was dissolved in 100 mL of tetrahydrofuran and cooled to... A mixed solution consisting of 0.11 mol methacryloyl chloride and 0.12 mol triethylamine was slowly added dropwise at 2℃ over a period of 1 h. The reaction was then continued at 2℃ for 14 h. After the reaction was completed, the reaction solution was poured into 200 mL of ice water and extracted with 3 × 80 mL ethyl acetate. The combined organic phases were washed twice each with 5% sodium bicarbonate solution and saturated brine. The organic phase was dried over anhydrous sodium sulfate for 12 h and then filtered. The filtrate was concentrated by rotary evaporation and finally purified by silica gel column chromatography. The eluent was a mixed solvent of petroleum ether / ethyl acetate in a volume ratio of 3:1. The target component was collected, and the solvent was removed by rotary evaporation to obtain the final product.

[0015] As a preferred embodiment of the present invention, the 1H,1H,6H,6H-perfluorohexane-1,6-diol was purchased from Beijing Naphthene Biochemical Technology Co., Ltd.

[0016] In this invention, the preparation of fluorinated cyclic carbonate-grafted polyionic liquids is based on a synergistic reaction mechanism of free radical copolymerization and anion exchange. Under argon protection, the vinyl group in 1-vinyl-3-ethylimidazolium bromide and the methacrylate group in 4-((2,2,3,3,4,4,5,5,6,6-decafluorohexyloxy)methyl)-1,3-dioxolane-2-one methacrylate form a covalently linked main chain structure through the breaking and recombination of carbon-carbon double bonds, initiated by free radicals generated from the thermal decomposition of azobisisobutyronitrile. The cyclic carbonate unit of the fluorinated monomer coordinates with lithium ions through its carbonyl oxygen atom, promoting the dissociation of lithium salt, while the long-chain fluorinated alkyl group forms a hydrophobic layer on the polymer surface through self-assembly, enhancing interfacial stability. Subsequently, during the anion exchange process, bromide ions undergo a displacement reaction with the bulky anion in lithium bis(trifluoromethanesulfonyl)imide, and the phase transfer is promoted by a mixed solvent of acetone and water, ultimately forming a polyionic liquid framework with high ion mobility. In this process, the synergistic effect of the fluorinated segments and cyclic carbonates not only broadens the electrochemical window, but also inhibits the occurrence of side reactions by inducing the formation of a stable lithium fluoride layer at the electrode interface.

[0017] As a preferred embodiment of the present invention, in step A1, the mass ratio of 1-vinyl-3-ethylimidazolium bromide to 4-((2,2,3,3,4,4,5,5,6,6-decafluorohexyloxy)methyl)-1,3-dioxolane-2-one methacrylate is 1:(0.8-1.5); the reflux reaction time at 68-72°C is 24-30 h.

[0018] As a preferred embodiment of the present invention, in step A2, the stirring time at room temperature is 12-14 hours.

[0019] As a preferred technical solution of the present invention, the preparation method of lithium lanthanum zirconium oxide supported on the nano-graphene framework includes: B1, dispersing graphene oxide in a mixed solvent of ethanol and water, ultrasonically treating it to form a dispersion; adding lithium nitrate, lanthanum nitrate and zirconium oxychloride, and stirring; then adding a methanol solution of tetrabutylammonium hydroxide as a precipitant, and continuously stirring at 58-62°C to form a gel; B2, vacuum drying the gel at 78-82°C, grinding it into a fine powder, placing the fine powder in a tube furnace, and pre-sintering it at 500-600°C under an argon atmosphere, and then sintering it at 1000-1100°C.

[0020] In this invention, the preparation of lithium lanthanum zirconium oxide supported on a nano-graphene framework relies on the template effect of graphene oxide and the crystal nucleation and growth mechanism during high-temperature sintering. In the graphene oxide dispersion, the epoxy and carboxyl groups on its surface bind to metal ions in lithium nitrate, lanthanum nitrate, and zirconium oxychloride through coordination bonds, forming a metal hydroxide gel under the precipitation of tetrabutylammonium hydroxide, which is uniformly anchored on the graphene sheets. During the pre-sintering stage, some oxygen-containing groups of graphene decompose under an argon atmosphere, forming a reduced three-dimensional graphene oxide network, while the metal precursor is transformed into an amorphous oxide. In the subsequent high-temperature sintering stage, lithium lanthanum zirconium oxide undergoes heterogeneous nucleation on the graphene framework surface, growing into cubic phase crystals. The sp² hybrid carbon structure of graphene regulates grain size through interfacial stress, inhibiting excessive grain boundary growth. The continuous graphene network not only provides a low-torsion path for ion transport, but its surface defects also stabilize the oxygen vacancies of lithium lanthanum zirconium oxide through electrostatic interactions, thereby significantly reducing the ion migration activation energy and improving ionic conductivity.

[0021] As a preferred embodiment of the present invention, in step B1, the mass ratio of graphene oxide, lithium nitrate, lanthanum nitrate and zirconium oxychloride is 1:(2-5):(8-15):(3.5-6.5); the stirring time is 12-14h.

[0022] As a preferred embodiment of the present invention, in step B2, the pre-sintering time at 500-600℃ is 2-4 hours; the sintering time at 1000-1100℃ is 4-6 hours.

[0023] In a second aspect, the present invention provides a method for preparing a solid electrolyte with high ionic conductivity, comprising the following raw materials in parts by weight: 30-60 parts of fluorinated cyclic carbonate-grafted polyionic liquid; 10-30 parts of lithium lanthanum zirconium oxide supported on a graphene nanoframework; 5-15 parts of lithium bis(fluorosulfonyl)imide; 20-40 parts of polypropylene carbonate; and 1-5 parts of nanocellulose fibers.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) This invention achieves a significant improvement in the overall performance of solid-state electrolytes through unique material design and innovative preparation processes. First, in terms of electrochemical performance, the synergistic effect of fluorinated cyclic carbonate-grafted polyionic liquid and lithium lanthanum zirconium oxide loaded on a nano-graphene framework constructs a multi-level ion transport channel within the electrolyte. The polyionic liquid framework provides a continuous ion conduction pathway, while the cyclic carbonate units promote lithium salt dissociation through strong coordination with lithium ions, and the lithium lanthanum zirconium oxide filler loaded on the nano-graphene framework forms additional fast lithium ion transport channels. The construction of this multi-scale ion transport network enables the electrolyte to achieve high ionic conductivity at room temperature while maintaining a high lithium ion transference number. In addition, the introduction of fluorinated segments not only broadens the electrochemical window of the electrolyte, enabling it to match high-voltage cathode materials, but also helps to form a stable protective layer at the electrode interface, effectively suppressing the occurrence of side reactions and laying a material foundation for constructing high-energy-density battery systems.

[0026] (2) In terms of interface stability, the solid electrolyte of the present invention exhibits significant advantages. The fluorinated cyclic carbonate structural unit can spontaneously form a uniform solid electrolyte interface film rich in lithium fluoride on the lithium metal surface. This interface film has high ionic conductivity and mechanical strength, which can effectively suppress the growth of lithium dendrites and significantly improve the cycle life and safety performance of the battery. At the same time, the lithium lanthanum zirconium oxide filler supported by the nano-graphene framework forms a stable phase interface with the polymer matrix through strong interaction, which not only improves the dispersibility of the filler but also reduces the interface impedance and promotes the rapid transport of lithium ions at the phase interface. This unique interface design enables the electrolyte and electrode materials to maintain good physical contact and chemical compatibility, maintain a stable interface structure during long-term cycling, effectively alleviate the interface degradation problem during cycling, and provide a reliable guarantee for the long-life operation of all-solid-state batteries.

[0027] (3) In terms of mechanical properties and practical application, this invention achieves a balanced optimization of various properties through the synergistic effect of multiple components. The addition of nanocellulose fibers, along with fluorinated cyclic carbonate-grafted polyionic liquid and polypropylene carbonate, forms a three-dimensional network structure, which significantly enhances the mechanical strength and toughness of the electrolyte, enabling it to effectively resist lithium dendrite puncture while maintaining good flexibility to adapt to changes in electrode volume. The presence of the nanographene framework not only improves the dispersibility of lithium lanthanum zirconium oxide filler but also enhances the thermal and dimensional stability of the electrolyte, allowing it to maintain stable performance over a wide temperature range. From the perspective of the preparation process, the solution casting and hot pressing processes used in this invention are simple and easy to implement, suitable for large-scale production, and have relatively low raw material costs, showing good commercial prospects. This solid electrolyte, which combines high ionic conductivity, excellent interfacial stability, good mechanical properties, and simple preparation, provides important material support for promoting the practical application of all-solid-state lithium batteries. Detailed Implementation

[0028] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0029] The sources of some components in the examples and comparative examples are as follows:

[0030] The polypropylene carbonate was purchased from Shandong Aifu Technology Co., Ltd.

[0031] The lithium bis(fluorosulfonyl)imide was purchased from Jiangsu Huasheng Lithium Battery Materials Co., Ltd.

[0032] The nanocellulose fibers were purchased from Zhejiang Yuewei New Materials Technology Co., Ltd.

[0033] The porous polypropylene diaphragm was purchased from Shenzhen Xingyuan Material Technology Co., Ltd.

[0034] The 1-vinyl-3-ethylimidazolium bromide was purchased from Lanzhou Kaidi Sulfur Chemical Co., Ltd.

[0035] The azobisisobutyronitrile was purchased from Hubei Zhenhua Chemical Co., Ltd.

[0036] The lithium bis(trifluoromethanesulfonyl)imide was purchased from Jiangsu Guotai Chaowei New Materials Co., Ltd.

[0037] The graphene oxide was purchased from Hangzhou Morui Technology Co., Ltd.

[0038] The lithium nitrate was purchased from Sichuan Guoli Lithium Materials Co., Ltd.

[0039] The lanthanum nitrate was purchased from Baotou Sanlong Rare Metals Materials Co., Ltd.

[0040] The zirconium oxychloride was purchased from Zhejiang Oriental Zirconium Industry Technology Co., Ltd.

[0041] The tetrabutylammonium hydroxide was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0042] The tubular furnace was purchased from Hefei Kejing Materials Technology Co., Ltd.

[0043] Preparation Example 1

[0044] This preparation example provides a preparation step for 4-((2,2,3,3,4,4,5,5,6,6-decafluorohexyloxy)methyl)-1,3-dioxolane-2-one methacrylate, including:

[0045] First, 0.1 mol of glycerol and 0.13 mol of dimethyl carbonate were added to a 250 mL three-necked flask containing 0.5 g of potassium carbonate. The mixture was stirred and refluxed at 90 °C for 5 h. After the reaction was completed, the reaction solution was cooled to 25 °C, 50 mL of deionized water was added, and the mixture was extracted with 3 × 50 mL of dichloromethane. The organic phases were combined and dried over anhydrous magnesium sulfate for 8 h. After filtration, the solvent was removed by rotary evaporation to obtain 4-(hydroxymethyl)-1,3-dioxolane-2-one.

[0046] Then, 4-(hydroxymethyl)-1,3-dioxolane-2-one was dissolved in 100 mL of dichloromethane, cooled to 0 °C in an ice-water bath, and 0.12 mol of thionyl chloride was slowly added dropwise. After the addition was completed, the temperature was raised to 25 °C and reacted for 4 h. The solvent and excess thionyl chloride were removed by rotary evaporation to obtain the 4-(chloromethyl)-1,3-dioxolane-2-one intermediate.

[0047] Subsequently, 0.095 mol of 1H,1H,6H,6H-perfluorohexane-1,6-diol was dissolved in 150 mL of anhydrous acetonitrile, and 0.114 mol of sodium hydride (60% dispersed in mineral oil) was added. The mixture was stirred at 0 °C for 30 min to generate sodium alkoxide. Then, the 4-(chloromethyl)-1,3-dioxolane-2-one intermediate obtained in the previous step was added, and the mixture was heated to 80 °C and reacted for 10 h under nitrogen protection. After the reaction was completed, the reaction solution was cooled to 20 °C, the solid was removed by filtration, and the filtrate was concentrated by rotary evaporation to obtain a fluorinated cyclic carbonate intermediate.

[0048] Finally, the intermediate was dissolved in 100 mL of tetrahydrofuran, cooled to 2 °C, and a mixed solution of 0.11 mol methacryloyl chloride and 0.12 mol triethylamine was slowly added dropwise over a period of 1 h. The reaction was then continued at 2 °C for 14 h. After the reaction was completed, the reaction solution was poured into 200 mL of ice water and extracted with 3 × 80 mL ethyl acetate. The combined organic phases were washed twice each with 5% sodium bicarbonate solution and saturated brine. The organic phase was dried over anhydrous sodium sulfate for 12 h and then filtered. The filtrate was concentrated by rotary evaporation and finally purified by silica gel column chromatography with a 3:1 volume ratio of petroleum ether / ethyl acetate as the eluent. The target component was collected, and the solvent was removed by rotary evaporation to obtain the final product.

[0049] Example 1

[0050] This embodiment provides a preparation step for a solid electrolyte with high ionic conductivity, including:

[0051] First, a fluorinated cyclic carbonate-grafted polyionic liquid was prepared. Under argon protection, 10.0 g of 1-vinyl-3-ethylimidazolium bromide and 12.0 g of 4-((2,2,3,3,4,4,5,5,6,6-decafluorohexyloxy)methyl)-1,3-dioxolane-2-one methacrylate were dissolved in 200 mL of anhydrous acetonitrile. The solution was stirred at 500 rpm for 30 min until completely dissolved. Then, 0.3 g of azobisisobutyronitrile was added, and the mixture was refluxed in an oil bath at 70 °C for 27 h to obtain the desired product. The viscous crude product was slowly poured into 1000 mL of diethyl ether to precipitate. After standing for 2 hours, it was filtered to obtain a white solid intermediate. The intermediate was dissolved in a mixed solvent of 100 mL of deionized water and 100 mL of acetone. 15.0 g of lithium bis(trifluoromethanesulfonyl)imide was added, and anion exchange was carried out by magnetic stirring at 300 rpm for 13 hours at 25 °C. The organic phase was separated, washed with 3 × 100 mL of deionized water until neutral, and dried in a vacuum drying oven at 60 °C for 24 hours to obtain a fluorinated cyclic carbonate-grafted polyionic liquid.

[0052] Then, lithium lanthanum zirconium oxide supported on a nano-graphene framework was prepared. 1.0 g of graphene oxide was dispersed in a mixed solvent of 150 mL ethanol and 150 mL water and ultrasonically treated at 400 W for 4 h to form a uniform dispersion. 3.5 g of lithium nitrate, 11.0 g of lanthanum nitrate and 5.0 g of zirconium oxychloride were added and mechanically stirred at 400 rpm for 13 h at 25 °C. Then, 20 mL of a methanol solution of tetrabutylammonium hydroxide was slowly added dropwise as a precipitant. The mixture was stirred continuously in a 60 °C water bath for 2 h to form a gel. The gel was dried in a vacuum drying oven at 80 °C for 12 h and ground into fine powder with a particle size of less than 50 μm. The fine powder was placed in a tube furnace and pre-sintered at 550 °C for 3 h at a heating rate of 5 °C / min under an argon atmosphere. Then, the temperature was increased to 1050 °C at 10 °C / min and sintered for 5 h. The mixture was naturally cooled to room temperature to obtain lithium lanthanum zirconium oxide supported on a nano-graphene framework.

[0053] Finally, a solid electrolyte with high ionic conductivity was prepared by dissolving 45.0 g of fluorinated cyclic carbonate-grafted polyionic liquid and 25.0 g of polypropylene carbonate in 500 mL of anhydrous acetonitrile. The solution was mechanically stirred at 600 rpm for 6 h at 25 °C to form a homogeneous polymer solution. 20.0 g of lithium lanthanum zirconium oxide supported on a graphene nanoframework and 10.0 g of lithium bis(fluorosulfonyl)imide were added, and the mixture was ultrasonically dispersed at 300 W for 3 h to form a homogeneous slurry. 3.0 g of nanocellulose fibers were added, and the mixture was homogenized at 10,000 rpm for 3 h to obtain a viscous paste. The viscous paste was uniformly coated on both sides of a porous polypropylene membrane with a thickness of 25 μm, and the coating thickness was controlled at 100 μm. The membrane was dried in a vacuum drying oven at 50 °C for 24 h, and then hot-pressed at 80 °C and 10 MPa for 8 min to obtain a solid electrolyte membrane with a thickness of 120 μm. The 4-((2,2,3,3,4,4,5,5,6,6-decafluorohexyloxy)methyl)-1,3-dioxolane-2-one methacrylate of this embodiment is the substance obtained in Preparation Example 1.

[0054] Example 2

[0055] The difference between this embodiment and Example 1 is that, firstly, a fluorinated cyclic carbonate-grafted polyionic liquid is prepared. Under argon protection, 10.0 g of 1-vinyl-3-ethylimidazolium bromide and 8.0 g of 4-((2,2,3,3,4,4,5,5,6,6-decafluorohexyloxy)methyl)-1,3-dioxolane-2-one methacrylate is dissolved in 200 mL of anhydrous acetonitrile, and 0.3 g of azobisisobutyronitrile is added. The mixture is refluxed at 68 °C for 30 h to obtain a crude product. The crude product is precipitated in diethyl ether to obtain an intermediate. The intermediate is dissolved in a mixed solvent of 100 mL of deionized water and 100 mL of acetone, and 15.0 g of lithium bis(trifluoromethanesulfonyl)imide is added for anion exchange. The mixture is stirred at room temperature for 12 h, the organic phase is separated and washed with deionized water until neutral, and then vacuum dried to obtain the fluorinated cyclic carbonate-grafted polyionic liquid.

[0056] Then, lithium lanthanum zirconium oxide supported on a nano-graphene framework was prepared. 1.0 g of graphene oxide was dispersed in a mixed solvent of 150 mL ethanol and 150 mL water and ultrasonically treated for 4 h to form a dispersion. 2.0 g of lithium nitrate, 8.0 g of lanthanum nitrate and 3.5 g of zirconium oxychloride were added and stirred for 12 h. Then, 20 mL of a methanol solution of tetrabutylammonium hydroxide was added dropwise as a precipitant. The mixture was stirred continuously at 58 °C to form a gel. The gel was vacuum dried at 78 °C and ground into a fine powder. The fine powder was placed in a tube furnace and pre-sintered at 500 °C for 4 h under an argon atmosphere. The temperature was then raised to 1000 °C and sintered for 6 h to obtain lithium lanthanum zirconium oxide supported on a nano-graphene framework.

[0057] Finally, a solid electrolyte with high ionic conductivity was prepared by dissolving 30.0 g of fluorinated cyclic carbonate-grafted polyionic liquid and 20.0 g of polypropylene carbonate in 500 mL of anhydrous acetonitrile and mechanically stirring for 6 h to form a polymer solution. 10.0 g of lithium lanthanum zirconium oxide supported on a graphene nanoframework and 5.0 g of lithium bis(fluorosulfonyl)imide were added and ultrasonically dispersed for 3 h to form a slurry. 1.0 g of nanocellulose fiber was added and homogenized at high speed for 2 h to obtain a viscous paste. The viscous paste was coated on both sides of a porous polypropylene membrane and vacuum dried at 48 °C for 24 h. The solid electrolyte was obtained by hot pressing at 78 °C for 10 min using a hot press.

[0058] Example 3

[0059] The difference between this embodiment and Example 1 is that, firstly, a fluorinated cyclic carbonate-grafted polyionic liquid is prepared. Under argon protection, 10.0 g of 1-vinyl-3-ethylimidazolium bromide and 15.0 g of 4-((2,2,3,3,4,4,5,5,6,6-decafluorohexyloxy)methyl)-1,3-dioxolane-2-one methacrylate is dissolved in 200 mL of anhydrous acetonitrile, and 0.3 g of azobisisobutyronitrile is added. The mixture is refluxed at 72 °C for 24 h to obtain a crude product. The crude product is precipitated in diethyl ether to obtain an intermediate. The intermediate is dissolved in a mixed solvent of 100 mL of deionized water and 100 mL of acetone, and 15.0 g of lithium bis(trifluoromethanesulfonyl)imide is added for anion exchange. The mixture is stirred at room temperature for 14 h, the organic phase is separated, and the mixture is washed with deionized water until neutral. The mixture is then vacuum dried to obtain the fluorinated cyclic carbonate-grafted polyionic liquid.

[0060] Then, lithium lanthanum zirconium oxide supported on a nano-graphene framework was prepared. 1.0 g of graphene oxide was dispersed in a mixed solvent of 150 mL ethanol and 150 mL water and ultrasonically treated for 4 h to form a dispersion. 5.0 g of lithium nitrate, 15.0 g of lanthanum nitrate and 6.5 g of zirconium oxychloride were added and stirred for 14 h. Then, 20 mL of a methanol solution of tetrabutylammonium hydroxide was added dropwise as a precipitant. The mixture was stirred continuously at 62 °C to form a gel. The gel was vacuum dried at 82 °C and ground into a fine powder. The fine powder was placed in a tube furnace and pre-sintered at 600 °C for 2 h under an argon atmosphere. The temperature was then raised to 1100 °C and sintered for 4 h to obtain lithium lanthanum zirconium oxide supported on a nano-graphene framework.

[0061] Finally, a solid electrolyte with high ionic conductivity was prepared by dissolving 60.0 g of fluorinated cyclic carbonate-grafted polyionic liquid and 40.0 g of polypropylene carbonate in 500 mL of anhydrous acetonitrile and mechanically stirring for 6 h to form a polymer solution. Then, 30.0 g of lithium lanthanum zirconium oxide supported on a graphene nanoframework and 15.0 g of lithium bis(fluorosulfonyl)imide were added and ultrasonically dispersed for 3 h to form a slurry. Finally, 5.0 g of nanocellulose fibers were added and homogenized at high speed for 4 h to obtain a viscous paste. The viscous paste was coated on both sides of a porous polypropylene membrane and vacuum dried at 52 °C for 24 h. The solid electrolyte was then obtained by hot pressing at 82 °C for 5 min using a hot press.

[0062] Comparative Example 1

[0063] This comparative example provides a preparation procedure for a solid electrolyte with high ionic conductivity, including:

[0064] First, a common polyionic liquid was prepared. 10.0 g of 1-vinyl-3-ethylimidazolium bromide was dissolved in 200 mL of anhydrous acetonitrile under argon protection. The solution was stirred at 500 rpm for 30 min to ensure complete dissolution. 0.3 g of azobisisobutyronitrile was added, and the mixture was refluxed in an oil bath at 70 °C for 27 h to obtain a viscous crude product. The crude product was slowly poured into 1000 mL of diethyl ether to precipitate. After standing for 2 h, the mixture was filtered to obtain a white solid intermediate. This intermediate was dissolved in a mixed solvent of 100 mL of deionized water and 100 mL of acetone. 15.0 g of lithium bis(trifluoromethanesulfonyl)imide was added, and anion exchange was performed by magnetic stirring at 300 rpm for 13 h at 25 °C. The organic phase was separated, washed with 3 × 100 mL of deionized water until neutral, and dried in a vacuum drying oven at 60 °C for 24 h to obtain the common polyionic liquid.

[0065] Then, lithium lanthanum zirconium oxide supported on a nano-graphene framework was prepared. 1.0 g of graphene oxide was dispersed in a mixed solvent of 150 mL ethanol and 150 mL water and ultrasonically treated at 400 W for 4 h to form a uniform dispersion. 3.5 g of lithium nitrate, 11.0 g of lanthanum nitrate and 5.0 g of zirconium oxychloride were added and mechanically stirred at 400 rpm for 13 h at 25 °C. Then, 20 mL of a methanol solution of tetrabutylammonium hydroxide was slowly added dropwise as a precipitant. The mixture was stirred continuously in a 60 °C water bath for 2 h to form a gel. The gel was dried in a vacuum drying oven at 80 °C for 12 h and ground into fine powder with a particle size of less than 50 μm. The fine powder was placed in a tube furnace and pre-sintered at 550 °C for 3 h at a heating rate of 5 °C / min under an argon atmosphere. Then, the temperature was increased to 1050 °C at 10 °C / min and sintered for 5 h. The mixture was naturally cooled to room temperature to obtain lithium lanthanum zirconium oxide supported on a nano-graphene framework.

[0066] Finally, a comparative solid electrolyte was prepared. 45.0 g of ordinary polyionic liquid and 25.0 g of polypropylene carbonate were dissolved in 500 mL of anhydrous acetonitrile. The solution was mechanically stirred at 600 rpm for 6 h at 25 °C to form a homogeneous polymer solution. 20.0 g of lithium lanthanum zirconium oxide supported on a graphene nanoframework and 10.0 g of lithium bis(fluorosulfonyl)imide were added. The mixture was ultrasonically dispersed at 300 W for 3 h to form a homogeneous slurry. 3.0 g of nanocellulose fibers were added, and the mixture was homogenized at 10,000 rpm for 3 h to obtain a viscous paste. The viscous paste was uniformly coated on both sides of a porous polypropylene membrane with a thickness of 25 μm. The coating thickness was controlled at 100 μm. The membrane was dried in a vacuum drying oven at 50 °C for 24 h and then hot-pressed at 80 °C and 10 MPa for 8 min to obtain a comparative solid electrolyte membrane with a thickness of 120 μm.

[0067] Comparative Example 2

[0068] This comparative example provides a preparation procedure for a solid electrolyte with high ionic conductivity, including:

[0069] First, a fluorinated cyclic carbonate-grafted polyionic liquid was prepared by adding 10.0 g of 1-vinyl-3-ethylimidazolium bromide and 12.0 g of... under argon protection. 4-((2,2,3,3,4,4,5,5,6,6-decafluorohexyloxy)methyl)-1,3-dioxolane-2-one methacrylate was dissolved in 200 mL of anhydrous acetonitrile and stirred at 500 rpm for 30 min with a mechanical stirrer until completely dissolved. 0.3 g of azobisisobutyronitrile was added, and the mixture was refluxed in an oil bath at 70 °C for 27 h to obtain a viscous crude product. The crude product was slowly poured into 1000 mL of diethyl ether to precipitate. After standing for 2 h, the mixture was filtered to obtain a white solid intermediate. The intermediate was dissolved in a mixed solvent of 100 mL of deionized water and 100 mL of acetone, and 15.0 g of lithium bis(trifluoromethanesulfonyl)imide was added. The mixture was magnetically stirred at 300 rpm for 13 h at 25 °C for anion exchange. The organic phase was separated, washed with 3 × 100 mL of deionized water until neutral, and dried in a vacuum drying oven at 60 °C for 24 h to obtain a fluorinated cyclic carbonate-grafted polyionic liquid.

[0070] Then, ordinary lithium lanthanum zirconium oxide was prepared by mixing and grinding 3.5g lithium nitrate, 11.0g lanthanum nitrate and 5.0g zirconium oxychloride in a mortar for 1 hour until uniform. The uniformly mixed powder was placed in a muffle furnace and sintered at 1050℃ for 5 hours in an air atmosphere at a heating rate of 5℃ / min. After naturally cooling to room temperature, it was ground to obtain ordinary lithium lanthanum zirconium oxide powder.

[0071] Finally, a comparative solid electrolyte was prepared. 45.0 g of fluorinated cyclic carbonate-grafted polyionic liquid and 25.0 g of polypropylene carbonate were dissolved in 500 mL of anhydrous acetonitrile. The solution was mechanically stirred at 600 rpm for 6 h at 25 °C to form a homogeneous polymer solution. 20.0 g of ordinary lithium lanthanum zirconium oxide and 10.0 g of lithium bis(fluorosulfonyl)imide were added, and the mixture was ultrasonically dispersed at 300 W for 3 h to form a homogeneous slurry. 3.0 g of nanocellulose fibers were added, and the mixture was homogenized at 10000 rpm for 3 h to obtain a viscous paste. The viscous paste was uniformly coated on both sides of a porous polypropylene membrane with a thickness of 25 μm. The coating thickness was controlled at 100 μm. The membrane was dried in a vacuum drying oven at 50 °C for 24 h, and then hot-pressed at 80 °C and 10 MPa for 8 min to obtain a comparative solid electrolyte membrane with a thickness of 120 μm. The 4-((2,2,3,3,4,4,5,5,6,6-decafluorohexyloxy)methyl)-1,3-dioxolane-2-one methacrylate in this comparative example is the substance obtained in Preparation Example 1.

[0072] Comparative Example 3

[0073] This comparative example provides a preparation procedure for a solid electrolyte with high ionic conductivity, including:

[0074] First, a common polyionic liquid was prepared. 10.0 g of 1-vinyl-3-ethylimidazolium bromide was dissolved in 200 mL of anhydrous acetonitrile under argon protection. The solution was stirred at 500 rpm for 30 min to ensure complete dissolution. 0.3 g of azobisisobutyronitrile was added, and the mixture was refluxed in an oil bath at 70 °C for 27 h to obtain a viscous crude product. The crude product was slowly poured into 1000 mL of diethyl ether to precipitate. After standing for 2 h, the mixture was filtered to obtain a white solid intermediate. This intermediate was dissolved in a mixed solvent of 100 mL of deionized water and 100 mL of acetone. 15.0 g of lithium bis(trifluoromethanesulfonyl)imide was added, and anion exchange was performed by magnetic stirring at 300 rpm for 13 h at 25 °C. The organic phase was separated, washed with 3 × 100 mL of deionized water until neutral, and dried in a vacuum drying oven at 60 °C for 24 h to obtain the common polyionic liquid.

[0075] Then, ordinary lithium lanthanum zirconium oxide was prepared by mixing and grinding 3.5g lithium nitrate, 11.0g lanthanum nitrate and 5.0g zirconium oxychloride in a mortar for 1 hour until uniform. The uniformly mixed powder was placed in a muffle furnace and sintered at 1050℃ for 5 hours in an air atmosphere at a heating rate of 5℃ / min. After naturally cooling to room temperature, it was ground to obtain ordinary lithium lanthanum zirconium oxide powder.

[0076] Finally, a comparative solid electrolyte was prepared. 45.0 g of ordinary polyionic liquid and 25.0 g of polypropylene carbonate were dissolved in 500 mL of anhydrous acetonitrile. The solution was mechanically stirred at 600 rpm for 6 h at 25 °C to form a homogeneous polymer solution. 20.0 g of ordinary lithium lanthanum zirconium oxide and 10.0 g of lithium bis(fluorosulfonyl)imide were added, and the mixture was ultrasonically dispersed at 300 W for 3 h to form a homogeneous slurry. 3.0 g of nanocellulose fiber was added, and the mixture was homogenized at 10000 rpm for 3 h to obtain a viscous paste. The viscous paste was uniformly coated on both sides of a porous polypropylene membrane with a thickness of 25 μm. The coating thickness was controlled at 100 μm. The membrane was dried in a vacuum drying oven at 50 °C for 24 h, and then hot-pressed at 80 °C and 10 MPa for 8 min to obtain a comparative solid electrolyte membrane with a thickness of 120 μm.

[0077] The performance of the high ionic conductivity solid electrolytes obtained in Examples 1-3 and Comparative Examples 1-3 was tested in accordance with national and industry standard testing specifications.

[0078] Ionic conductivity was measured using the AC impedance method. An electrochemical workstation was used with a frequency range of 100 kHz to 0.1 Hz and an amplitude of 5 mV. A solid electrolyte membrane was assembled into a blocking cell (SS|electrolyte|SS, where SS is a stainless steel electrode). Impedance spectra were recorded in a 25°C incubator. The impedance values ​​at the intersection of the high-frequency region and the real axis in the spectrum were combined with the electrolyte membrane thickness and electrode area, using the formula σ = L / (R). bCalculate the ionic conductivity using the formula ×A), where L is the electrolyte thickness and R is the electrolyte thickness. b Let A be the volume resistance and A be the electrode area. Each sample is tested three times and the average value is taken.

[0079] Lithium-ion transport number (LHT) was measured using a potentiostatic polarization method. A Li|electrolyte|Li symmetric cell was assembled, a 10mV DC polarization voltage was applied, and the initial current I0 and steady-state current Is were recorded. Simultaneously, the change in interfacial resistance before and after polarization was measured using AC impedance spectroscopy. The result was calculated using the formula tLi. + The lithium-ion transference number was calculated as Is(ΔV-I0R0) / [I0(ΔV-IsRs)], with a test temperature of 25℃ and a polarization time of 2 hours.

[0080] Linear scanning voltammetry was used to determine the electrochemical window using an electrochemical workstation. A Li|electrolyte|SS cell was assembled, with a scan rate of 0.1 mV / s and a voltage range of 2.5 V to 6.0 V, at a current density exceeding 1 mA / cm². 2 The voltage is the decomposition voltage.

[0081] Tensile strength testing was performed using a universal testing machine. The electrolyte membrane was cut into 100mm×10mm strip samples, the tensile rate was 10mm / min, the maximum load at break was recorded, and the tensile strength was calculated.

[0082] Thermal stability tests were performed using a thermogravimetric analyzer. The temperature was increased from room temperature to 600°C at a rate of 10°C / min under a nitrogen atmosphere, and the temperature at which 5% mass loss occurred was recorded as the thermal decomposition temperature.

[0083] The temperature dependence test of ionic conductivity was carried out in the temperature range of -20℃ to 80℃. The assembled blocking battery was placed in a high and low temperature test chamber, and the impedance was tested after holding it at 20℃ intervals for 1 hour. The ionic conductivity at each temperature was calculated, and the activation energy of ionic conduction was fitted using the Arrhenius formula.

[0084] Cyclic performance testing was performed on assembled NCM622|electrolyte|Li half-cells. The cells were charged and discharged at 25°C at a rate of 0.5C within a voltage range of 2.7V to 4.3V. The discharge capacity of the 100th cycle was recorded, and the capacity retention rate was calculated.

[0085] Interface stability testing was conducted by assembling a Li|electrolyte|Li symmetric battery and performing constant current cycling at a current density of 0.2 mA / cm². Each cycle lasted for 1 hour of charge-discharge, and the voltage-time curve was recorded. Short-circuit time was also observed.

[0086] The performance test data above are shown in Table 1.

[0087] Table 1 Performance Test Results

[0088]

[0089] The test results in Table 1 above clearly show that the comprehensive performance of Examples 1-3 is significantly better than that of Comparative Examples 1-3, which fully demonstrates that the synergistic effect of the two modified compounds, namely the fluorinated cyclic carbonate-grafted polyionic liquid and the lithium lanthanum zirconium oxide supported on the nano-graphene framework, designed in this invention effectively solves the key problems faced by solid electrolyte technology.

[0090] Specifically, Example 1 achieved 1.2 × 10⁻⁶ at room temperature. -3 The high ionic conductivity (S / cm) of Example 1 is nearly an order of magnitude higher than that of Comparative Example 3, while the lithium-ion transference number reaches 0.72, significantly higher than 0.41 in Comparative Example 1 and 0.32 in Comparative Example 3. This indicates that the multi-level ion transport channels constructed through molecular structure design significantly improve lithium-ion conduction efficiency and suppress anion migration. The wide electrochemical window of 5.5V in Example 1 is significantly better than that of 4.8V in Comparative Example 1 and 4.5V in Comparative Example 3, demonstrating that the introduction of the fluorinated cyclic carbonate structure effectively enhances the antioxidant capacity of the electrolyte, enabling it to be matched with high-voltage cathode materials.

[0091] In terms of mechanical properties, the tensile strength of Example 1 (12.5 MPa) is significantly higher than that of Comparative Example 3 (6.8 MPa), indicating that the reinforcing network formed by the nanocellulose fibers and the three-dimensional graphene skeleton effectively improves the mechanical integrity of the electrolyte. Thermal stability tests show that the thermal decomposition temperature of Example 1 reaches 315°C, which is 20-40°C higher than that of the comparative example, confirming the synergistic effect of the fluoropolymer skeleton and inorganic filler on improving thermal stability.

[0092] Regarding interface stability, the lithium symmetric battery of Example 1 has a cycle life of over 2000 hours, while Comparative Example 1 has only 480 hours and Comparative Example 3 has only 220 hours. This is attributed to the fact that the stable interface layer rich in lithium fluoride induced by fluorinated cyclic carbonate on the lithium metal surface and the improved interface contact by the graphene framework jointly inhibited the growth of lithium dendrites.

[0093] In the cycling performance test, Example 1 retained 93.5% of its capacity after 100 cycles, significantly higher than Comparative Example 1's 75.6% and Comparative Example 3's 68.3%, demonstrating the formation of a stable solid-solid interface between the modified electrolyte and the electrode. The ion conduction activation energy test showed that Example 1 was 0.28 eV, significantly lower than the 0.35-0.45 eV of the comparative examples, indicating that the designed ion transport path effectively reduced the lithium-ion migration barrier.

[0094] In summary, this invention, through the synergistic design of two modified compounds, successfully addresses the technical bottlenecks of insufficient ionic conductivity, high interfacial impedance, and the difficulty in balancing mechanical strength and electrochemical stability in solid-state electrolytes. It achieves a balance between high ionic conductivity, excellent interfacial stability, and good mechanical properties, providing an effective material solution for the development of high-safety, high-energy-density all-solid-state lithium batteries.

Claims

1. A method for preparing a solid electrolyte with high ionic conductivity, characterized in that the steps include... include: S1. Dissolve the fluorinated cyclic carbonate-grafted polyionic liquid and polypropylene carbonate in anhydrous acetonitrile and mechanically stir to form a polymer solution. S2. Add lithium lanthanum zirconium oxide and lithium bisfluorosulfonyl imide loaded with a nano-graphene framework to a polymer solution, and disperse by ultrasonication to form a slurry; add nanocellulose fibers, and stir at high speed to obtain a viscous paste; coat the viscous paste on both sides of a porous polypropylene membrane, and dry under vacuum. S3. Hot pressing using a hot press.

2. The method for preparing a solid electrolyte with high ionic conductivity according to claim 1, characterized in that, In step S2, the high-speed homogenization stirring time is 2-4 hours; the vacuum drying temperature is 48-52℃.

3. The method for preparing a solid electrolyte with high ionic conductivity according to claim 1, characterized in that, In step S3, the hot pressing time at 78-82℃ is 5-10 minutes; the hot pressing temperature is 78-82℃.

4. The method for preparing a solid electrolyte with high ionic conductivity according to claim 1, characterized in that, The preparation method of the fluorinated cyclic carbonate-grafted polyionic liquid includes: A1. Under argon protection, 1-vinyl-3-ethylimidazolium bromide and 4-((2,2,3,3,4,4,5,5,6,6-decafluorohexyloxy)methyl)-1,3-dioxolane-2-one methacrylate were dissolved in anhydrous acetonitrile, added to a reactor, and stirred until completely dissolved; then azobisisobutyronitrile was added, and the mixture was refluxed at 68-72°C to obtain the crude product; A2. The crude product was precipitated in diethyl ether to obtain an intermediate; the intermediate was dissolved in a mixed solvent of deionized water and acetone, and lithium bis(trifluoromethanesulfonyl)imide was added for anion exchange while stirring at room temperature; the organic phase was separated and washed with deionized water until neutral, and then dried under vacuum.

5. The method for preparing a solid electrolyte with high ionic conductivity according to claim 4, characterized in that, In step A1, the mass ratio of 1-vinyl-3-ethylimidazolium bromide to 4-((2,2,3,3,4,4,5,5,6,6-decafluorohexyloxy)methyl)-1,3-dioxolane-2-one methacrylate is 1:(0.8-1.5); the reflux reaction is carried out at 68-72℃ for 24-30 h.

6. The method for preparing a solid electrolyte with high ionic conductivity according to claim 4, characterized in that, In step A2, the stirring time at room temperature is 12-14 hours.

7. The method for preparing a solid electrolyte with high ionic conductivity according to claim 1, characterized in that, The preparation method of the lithium lanthanum zirconium oxide supported on the nano-graphene framework includes: B1, dispersing graphene oxide in a mixed solvent of ethanol and water, ultrasonically treating it to form a dispersion; adding lithium nitrate, lanthanum nitrate and zirconium oxychloride, and stirring; then adding a methanol solution of tetrabutylammonium hydroxide as a precipitant, and stirring continuously at 58-62℃ to form a gel; B2, vacuum drying the gel at 78-82℃, grinding it into a fine powder, placing the fine powder in a tube furnace, and pre-sintering it at 500-600℃ under an argon atmosphere, and then sintering it at 1000-1100℃.

8. The method for preparing a solid electrolyte with high ionic conductivity according to claim 7, characterized in that, In step B1, the mass ratio of graphene oxide, lithium nitrate, lanthanum nitrate and zirconium oxychloride is 1:(2-5):(8-15):(3.5-6.5); the stirring time is 12-14h.

9. The method for preparing a solid electrolyte with high ionic conductivity according to claim 7, characterized in that, In step B2, the pre-sintering time at 500-600℃ is 2-4 hours; the sintering time at 1000-1100℃ is 4-6 hours.

10. A solid electrolyte with high ionic conductivity prepared by the method for preparing a solid electrolyte with high ionic conductivity according to any one of claims 1-9, characterized in that, The raw materials include the following parts by weight: 30-60 parts of fluorinated cyclic carbonate grafted polyionic liquid; The nano-graphene framework contains 10-30 parts of lithium lanthanum zirconium oxide, 5-15 parts of lithium bisfluorosulfonyl imide, 20-40 parts of polypropylene carbonate, and 1-5 parts of nanocellulose fibers.

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