A covalent organic framework-inorganic ceramic high-conductive composite solid-state electrolyte, a preparation method and application thereof

Abstract

This invention belongs to the field of solid-state electrolyte technology, and discloses a covalent organic framework-inorganic ceramic high-conductivity composite solid-state electrolyte, its preparation method, and its application. The method involves dissolving fluorinated long-chain monomers benzoyl hydrazine and 1,3,5-tricarboxyphenylbenzene in a mixed solvent of mesitylene and o-dichlorobenzene, adding lithium aluminum germanium phosphate ceramic powder, ultrasonically mixing, and then reacting with acetic acid as a catalyst at 110–130°C for 60–90 h under liquid nitrogen freezing, vacuum, and flame sealing. The product is then washed with acetone, tetrahydrofuran, and N,N-dimethylformamide, dried, and mixed with lithium salt to obtain the solid-state electrolyte. This electrolyte, through in-situ coating of the ceramic surface with a fluorinated covalent organic framework, significantly improves interfacial contact and enhances mechanical strength to suppress lithium dendrite penetration. The fluorinated long-chain functional groups weaken the electrostatic forces between ions, promote lithium salt dissociation, increase ionic conductivity and transference number, induce uniform lithium deposition, and improve the cycle stability and high-nickel cathode compatibility of solid-state batteries.

Description

Technical Field

[0001] This invention relates to the field of solid electrolyte technology, and in particular to a covalent organic framework-inorganic ceramic high conductivity composite solid electrolyte, its preparation method and application. Background Technology

[0002] Liquid lithium-ion batteries, due to the flammability and leakage risks of their organic liquid electrolytes, pose a significant safety hazard under conditions such as overcharging, short circuits, or mechanical abuse, severely limiting their further application in electric vehicles and large-scale energy storage. In contrast, solid-state batteries, which use solid electrolytes instead of liquid electrolytes and separators, not only fundamentally eliminate the safety risks of electrolyte leakage and combustion but also allow for the use of high-voltage positive electrodes and metallic lithium anodes, significantly improving battery energy density. Therefore, they are considered an ideal choice for next-generation electrochemical energy storage devices. Consequently, the development of high-performance solid-state electrolytes has become a core focus in this field.

[0003] Based on material properties, typical solid-state electrolytes are mainly classified into four categories: sulfides, oxides, halides, and polymers. Among them, polymer solid-state electrolytes have become a research hotspot in recent years due to their excellent flexibility, good processability, and ease of functionalization. Covalent organic framework (COF) materials are a class of crystalline porous organic macromolecules formed by covalently connecting different organic structural units. Due to their regular and ordered one-dimensional pore structure, designable chemical composition, and excellent stability, they are increasingly used as the framework material for polymer solid-state electrolytes. However, polymer electrolytes, represented by COF, generally have two shortcomings: First, there is a strong coordination interaction between lithium ions and the polymer framework and anions, resulting in difficulty in lithium ion dissociation and a limited number of freely migrating charge carriers, leading to low ionic conductivity and ion transference number; second, the mechanical rigidity of pure COF materials is insufficient, making it difficult to effectively suppress the puncture growth of lithium dendrites during long-term charge-discharge cycles, posing a risk of internal short circuits in the battery. These problems ultimately lead to solid-state batteries assembled with such electrolytes failing to meet practical requirements in terms of capacity retention and cycle stability.

[0004] Meanwhile, NASICON-type inorganic ceramic solid electrolytes, represented by lithium aluminum germanium phosphate (LAGP), possess high room-temperature ionic conductivity and excellent mechanical strength, theoretically capable of effectively suppressing lithium dendrite penetration. However, inorganic ceramic electrolytes face a significant bottleneck in practical applications—the inherent rigidity of their particles and the severe solid-solid interface contact defects between the electrolyte and the electrode result in enormous interfacial impedance, severely hindering lithium-ion cross-interface transport.

[0005] In summary, designing a solid electrolyte material that combines high ionic conductivity, high ion transport number, excellent interfacial contact performance, and sufficient mechanical strength to overcome the respective defects of insufficient rigidity and difficulty in ion dissociation of polymer electrolytes and high interfacial impedance of inorganic ceramic electrolytes is a key technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] To address the problems of poor interfacial contact and high interfacial impedance in inorganic ceramic solid electrolytes, as well as the lithium dendrite puncture problem caused by low ionic conductivity and ion transference number and insufficient mechanical rigidity in polymer solid electrolytes, this invention provides a covalent organic framework-inorganic ceramic composite solid electrolyte, its preparation method, and its application.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for preparing a covalent organic framework-inorganic ceramic composite solid electrolyte, comprising the following steps: S1. Dissolve the fluorinated long-chain monomer benzoyl hydrazide and 1,3,5-triformylphenylbenzene in a mixed solvent, and add the inorganic ceramic germanium aluminum lithium phosphate, and mix evenly by ultrasonication; the mixed solvent is a mixture of mesitylene and o-dichlorobenzene; 1,3,5-tris(p-formylphenyl)benzene (which can be simply referred to as 1,3,5-triformylphenylbenzene in this article); S2. After complete dissolution, add acetic acid as a catalyst to obtain a mixed solution; S3. Freeze the mixed solution with liquid nitrogen, then evacuate the reaction tube and seal it with a flame seal. React at 110℃~130℃ for 60~90h to obtain the reactant. In this invention, the combined operation of liquid nitrogen freezing, vacuuming, and flame sealing is a key process condition to ensure the high crystallinity and uniform in-situ coating of covalent organic framework materials on the inorganic ceramic surface. Liquid nitrogen freezing prevents monomers from reacting prematurely before sealing, ensuring synchronous initiation of reaction sites, and avoiding tube bursting due to solvent thermal expansion during sealing. Flame sealing provides an absolutely static micro-reaction environment that is completely sealed, leak-free, requires no mid-process gas exchange, and has no pressure fluctuations for a reaction cycle of 60–90 hours. This is a necessary condition for COF nucleation and ordered growth. Conventional screw-sealing or dynamic pressure maintenance systems, due to the presence of minor leaks and pressure fluctuations, cannot provide the same stable growth environment and are not suitable for this invention.

[0008] S4. After separation of reactants, powder is obtained and then washed alternately with acetone, tetrahydrofuran and N,N-dimethylformamide. The washed powder is dried to obtain a covalent organic framework-inorganic ceramic composite material. S5. The covalent organic framework-inorganic ceramic composite material is mixed with lithium salt to obtain a solid electrolyte.

[0009] As a preferred technical solution, in step S1, the fluorinated long-chain monomer phthalic acid hydrazide is 2,5-bis((3,3,4,4,5,5,6,6,6-nonafluorohexyl)oxy)terephthalic acid hydrazide; the molar ratio of the fluorinated long-chain monomer phthalic acid hydrazide to 1,3,5-tricarboxyphenylbenzene is 1.2 to 1.8:1; the mass ratio of the total mass of the fluorinated long-chain monomer phthalic acid hydrazide and 1,3,5-tricarboxyphenylbenzene to the mass of lithium germanium aluminum phosphate is 0.8 to 1.2:1; and the volume ratio of mesitylene to o-dichlorobenzene is 1.5 to 2.5:1.

[0010] As a preferred technical solution, in step S2, the concentration of the acetic acid solution is 6 mol / L, and the volume ratio of the acetic acid solution to the mixed solvent is 1:10 to 30.

[0011] As a preferred technical solution, in step S5, the mass ratio of the covalent organic framework-inorganic ceramic composite material to the lithium salt is 1.5 to 2.5:1; the lithium salt is lithium bis(trifluoromethanesulfonyl)imide.

[0012] As a preferred technical solution, in step S5, the covalent organic framework-inorganic ceramic composite material is mixed with lithium salt, ethanol is added, the mixture is stirred at room temperature for 8 to 16 hours, and then vacuum dried at 80 to 120°C to obtain a solid electrolyte.

[0013] Secondly, the present invention also provides a covalent organic framework-inorganic ceramic composite solid electrolyte prepared by the above preparation method.

[0014] Thirdly, the present invention also provides a solid electrolyte membrane comprising the above-mentioned covalent organic framework-inorganic ceramic composite solid electrolyte and PTFE dispersion.

[0015] Fourthly, the present invention also provides a method for preparing the above-mentioned solid electrolyte membrane, comprising the following steps: compounding the solid electrolyte with a PTFE (polytetrafluoroethylene) dispersion, obtaining an electrolyte membrane by roller pressing, immersing the electrolyte membrane in a lithium salt solvent for activation and drying, thereby obtaining the final product.

[0016] As a preferred technical solution, the PTFE concentration in the PTFE dispersion is 40%–80%, and the amount of PTFE dispersion used is 0.5%–5% of the mass of the solid electrolyte; the lithium salt solvent is lithium bis(trifluoromethanesulfonyl)imide dissolved in propylene carbonate, with a concentration of 0.5–2 mol / L and an activation time of 12–24 h; the drying temperature is 80–120 °C, and the drying time is 8–24 h.

[0017] Fifthly, the present invention also provides a solid-state battery comprising the above-described solid electrolyte membrane.

[0018] The reaction mechanism of the covalent organic framework-inorganic ceramic composite solid electrolyte of this invention is as follows: A fluorinated long-chain monomer, benzoyl hydrazine, with two reaction sites and a strong electron-withdrawing fluorine group as a special modified functional group, is selected and reacted with 1,3,5-tricarboxyphenylbenzene, which has three reaction sites, to synthesize a covalent organic framework material (FF-COF, see [link to invention]) with a two-dimensional hexagonal network structure via a solvothermal method. Figure 11 Simultaneously, in-situ growth technology was used to synthesize and grow FF-COF on the surface of lithium aluminum germanium phosphate (LAGP) ceramic powder, ultimately achieving effective coating of LAGP particles with FF-COF to form FF-COF@LAGP composite material.

[0019] The nonafluorohexyl segment in the fluorinated long-chain monomer benzodiazepine possesses a large number of lone pairs of electrons, creating an electron-rich environment on the inner walls of the pores in the prepared COF material. This effectively weakens the electrostatic interaction between lithium ions and anions, promotes lithium salt dissociation, and increases the lithium ion transference number. Simultaneously, the numerous one-dimensional ordered ion channels provided by the COF material can induce uniform deposition of lithium ions on the electrode surface, inhibiting the formation and growth of lithium dendrites. Its two-dimensional flexible extended structure increases the effective contact area between the electrolyte and the electrode, significantly reducing interfacial impedance. Furthermore, the fluorinated sites can form a stable interfacial passivation layer (LiF) with lithium ions, further improving interfacial stability and battery cycle life.

[0020] In-situ growth of COF on the inorganic ceramic LAGP surface resulted in a core-shell morphology of COF encapsulating LAGP, effectively improving the poor interfacial contact between inorganic ceramic particles and between the electrolyte and the electrode. It also compensated for the inherent rigidity of pure COF materials and their susceptibility to lithium dendrite penetration. The introduction of inorganic ceramic LAGP also reduced the overall synthesis cost of the material.

[0021] Compared with the prior art, the beneficial effects of the present invention are: (1) By in-situ growth of fluorine-containing COF on the surface of LAGP, an organic-inorganic composite solid electrolyte was successfully constructed, which significantly improved the interfacial contact of LAGP and effectively enhanced the mechanical strength of the composite solid electrolyte. (2) The long-chain fluorine-containing functional groups modified in the COF backbone make the pores an electron-rich environment, effectively weakening the electrostatic interaction between anions and cations, promoting lithium ion dissociation, and improving ionic conductivity and ion transference number. (3) COF materials have a highly ordered crystalline structure and contain a large number of one-dimensional nano-ion channels, which can induce uniform deposition of lithium ions, significantly inhibit the formation and growth of lithium dendrites, and promote the formation of a stable interface layer. (4) The ionic conductivity of the composite solid electrolyte of the present invention can reach 4.48 × 10⁻⁶ after testing. -3 The electrochemical window is 5.45 V, the ion transference number is 0.64, and the lithium-symmetric cell operates at 0.2 mA / cm. 2 Under stable cycling conditions, it can cycle for more than 2,500 hours. The solid-state battery assembled with lithium iron phosphate cathode has an initial discharge specific capacity of 160 mAh / g at 1C rate, and the capacity retention rate can still reach 90% after 900 cycles. Attached Figure Description

[0022] Figure 1 The image shows the XRD pattern of the FF-COF@LAGP-based electrolyte of Example 2 of this invention. Figure 2 This is the solid-state carbon NMR spectrum of FF-COF in Example 2 of the present invention; Figure 3 This is a transmission electron microscope (TEM) image of the FF-COF@LAGP-based electrolyte from Example 2 of the present invention. Figure 4 This is a thermogravimetric failure curve of the FF-COF material in Example 2 of the present invention under nitrogen atmosphere. Figure 5 This is a graph showing the ionic conductivity of the FF-COF@LAGP-based electrolyte in Example 2 of the present invention. Figure 6 This is an electrochemical window diagram of the FF-COF@LAGP-based electrolyte of Example 2 of the present invention; Figure 7 This is an ion transport number diagram of the FF-COF@LAGP-based electrolyte of Example 2 of the present invention; Figure 8 This is a cycle performance diagram of the lithium symmetric battery prepared by the FF-COF@LAGP-based electrolyte in Example 2 of the present invention; Figure 9 The image shows the cycle performance of the solid-state battery prepared by matching the FF-COF@LAGP-based electrolyte with the lithium iron phosphate cathode in Example 2 of this invention. Figure 10 The above are charge-discharge curves of the solid-state battery prepared by matching FF-COF@LAGP-based electrolyte with lithium iron phosphate cathode in Example 2 of this invention under different cycles. Figure 11 This is a schematic diagram of the covalent organic framework material described in this invention. Detailed Implementation

[0023] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below with reference to specific embodiments.

[0024] Unless otherwise specified, the raw materials, reagents and instruments used in the following examples can be purchased through conventional commercial channels, and the operating steps used are all conventional operations in the art.

[0025] Example 1

[0026] A method for preparing a covalent organic framework-inorganic ceramic highly conductive composite solid electrolyte includes the following steps: S1. Dissolve the fluorinated long-chain monomer benzoyl hydrazide and 1,3,5-tricarboxyphenylbenzene in a mixed solvent of mesitylene and o-dichlorobenzene at a molar ratio of 3:2. The volume ratio of mesitylene to o-dichlorobenzene in the mixed solvent is 1:1. Then add lithium aluminum germanium phosphate ceramic at a mass ratio of 1:1. The mixed solvent should be able to cover all the solid powder. S2. Sonicate the mixture in step S1 for 10 min until it is completely dissolved, then add 6 mol / L acetic acid as a catalyst to obtain a mixed solution. The volume ratio of the acetic acid to the mixed solvent is 1:20. S3. Freeze the mixed solution in step S2 with liquid nitrogen. After freezing, evacuate the reaction tube and seal it with a flame seal. React at 120°C for 72 hours to obtain the reactants. S4. After separation of the reactants, a light yellow powder was obtained. The powder was washed alternately with acetone, tetrahydrofuran and N,N-dimethylformamide. The washed powder was dried to obtain a covalent organic framework-inorganic ceramic high conductivity composite material. The powder was washed three times with acetone, tetrahydrofuran and N,N-dimethylformamide, 50 mL each time. S5. Mix FF-COF@LAGP material with lithium salt to obtain a solid electrolyte. The lithium salt is LiTFSI. Mix covalent organic framework and lithium salt in a mass ratio of 2:1, add ethanol, stir at room temperature for 12 hours, and finally vacuum dry at 100℃ to obtain a solid electrolyte.

[0027] S6. The solid electrolyte and PTFE dispersion are combined and rolled to obtain an electrolyte membrane. The electrolyte membrane is then activated by immersing it in a lithium salt solvent and dried. The PTFE concentration in the PTFE dispersion is 60%, and the amount of PTFE dispersion is 1% of the mass of the solid electrolyte. The lithium salt solvent is LiTFSI dissolved in propylene carbonate, with a concentration of 1 mol / L, and the activation time is 12 h. The drying temperature is 100℃, and the drying time is 12 h.

[0028] S7. The electrolyte membrane is used to prepare button cells or solid-state cells.

[0029] Example 2

[0030] 58.2 mg of the fluorinated long-chain monomer phthalohydrazide (2,5-bis((3,3,4,4,5,5,6,6,6-nonafluorohexyl)oxy)terephthalohydrazide), 19.8 mg of 1,3,5-tricarboxyphenylbenzene, and 78 mg of lithium aluminum germanium phosphate (LAGP) were added to 3 mL of a mixed solvent of mesitylene and o-dichlorobenzene (2 mL mesitylene and 1 mL o-dichlorobenzene), and the mixture was sonicated for 10 min.

[0031] 0.2 mL of acetic acid solution (6 mol / L) was added to the sonicated solution to obtain a mixed solution, which was then transferred to a Pyrex glass reaction tube. The reaction tube was immersed in liquid nitrogen for rapid freezing until the material was completely solidified. This prevented premature monomer reaction and ensured safe sealing. After freezing, a vacuum was applied to remove air and moisture from the tube, and the tube was then sealed by flame melting under continuous vacuum. This combined operation created a completely closed, absolutely oxygen-free, anhydrous, and undisturbed static microreaction environment for the subsequent 72-hour reaction. This is the key guarantee for FF-COF to achieve uniform in-situ coating on the LAGP surface with high crystallinity, which cannot be provided by other sealing methods.

[0032] The tube was broken, and the solid powder was collected by filtration or centrifugation. The powder was then washed alternately with acetone, tetrahydrofuran, and N,N-dimethylformamide, and dried at 100°C for 12 hours. This yielded the FF-COF@LAGP material.

[0033] like Figure 1 As shown in the XRD test data, the highly crystalline peaks of the COF material synthesis are clearly visible, while the characteristic peaks of the LAGP material are still somewhat retained. Figure 2 As shown, the peak with a chemical shift of approximately 160° in the solid-state carbon NMR spectrum represents a C=N bond, indicating the feasibility of this method for preparing COF materials. TEM images of the FF-COF@LAGP material are shown below. Figure 3 As shown, it can be clearly seen that the COF material was successfully grown in situ on the LAGP surface and successfully coated on the LAGP surface, proving that this synthesis method is effective.

[0034] A solid electrolyte was obtained by mixing FF-COF@LAGP material with a lithium salt. The lithium salt was LiTFSI. FF-COF@LAGP material and lithium salt were mixed at a mass ratio of 2:1, ethanol was added, and the mixture was stirred at room temperature for 12 hours. Finally, the mixture was vacuum dried at 100°C to obtain the solid electrolyte.

[0035] A solid electrolyte and a PTFE dispersion were combined and rolled to obtain an electrolyte membrane. The electrolyte membrane was then activated by immersing it in a lithium salt solvent and dried. The PTFE dispersion had a PTFE concentration of 60% and was used at 1% of the mass of the solid electrolyte. The lithium salt solvent was LiTFSI dissolved in propylene carbonate at a concentration of 1 mol / L, and the activation time was 12 h. The drying temperature was 100℃, and the drying time was 12 h.

[0036] like Figure 4 As shown, the FF-COF material was gradually heated under a nitrogen atmosphere to obtain a weight loss curve. At 350℃, the material exhibited significant structural deformation, which severely affected the material's performance and ultimately led to the material's decomposition and failure. This test determined the highest temperature that the material could withstand.

[0037] Impedance testing was performed on the aforementioned FF-COF@LAGP composite electrolyte, such as... Figure 5 As shown, based on the impedance and the formula for calculating ionic conductivity, the ionic conductivity of this electrolyte is calculated to be 4.48 × 10⁻⁶. -3 It has a high ionic conductivity (S / cm). For example... Figure 6 The image shows the electrochemical window test of this electrolyte, with a voltage window of 5.45V, indicating high antioxidant capacity. Figure 7 As shown, this electrolyte exhibits an ion transport number of 0.64, demonstrating high ion transport number and selectivity. The FF-COF@LAGP solid-state electrolyte significantly improves ionic conductivity, ion transport number, and broadens the electrochemical reaction window, promoting the development of high-performance solid-state batteries and providing a novel, green, and environmentally friendly synthesis method for covalent organic framework-inorganic ceramic composite materials.

[0038] Comparative Example 1 58.2 mg of the fluorinated long-chain monomer benzoyl hydrazide, 19.8 mg of 1,3,5-tricarboxyphenylbenzene and 78 mg of LAGP were added to a mixed solvent of 3 mL of mesitylene and o-dichlorobenzene (2 mL mesitylene and 1 mL o-dichlorobenzene) according to the distribution of the zeolite dispersion system, and mechanically sonicated for 10 min.

[0039] 0.2 mL of acetic acid solution with a concentration of 6 mol / L was added to the sonicated solution. The reaction tube was frozen with liquid nitrogen, and then sealed by vacuuming and flame sealing. The sealed tube was then reacted at 120°C for 72 h.

[0040] The tube was broken, and the solid powder was collected by filtration or centrifugation. The powder was washed with acetone and tetrahydrofuran and dried at 100°C for 12 hours to obtain FF-COF@LAGP material.

[0041] Comparative Example 2 58.2 mg of the fluorinated long-chain monomer benzoyl hydrazide, 19.8 mg of 1,3,5-tricarboxyphenylbenzene and 78 mg of LAGP were added to 3 mL of a mixed solvent of mesitylene and o-dichlorobenzene (2 mL mesitylene and 1 mL o-dichlorobenzene), and the mixture was subjected to mechanical sonication for 10 min.

[0042] 0.2 mL of acetic acid solution with a concentration of 6 mol / L was added to the ultrasonicated solution, and the tube was sealed by conventional tightening. The sealed tube was then reacted at 120℃ for 72 h.

[0043] The tube was broken, and the solid powder was collected by filtration or centrifugation. The powder was washed with acetone and tetrahydrofuran and dried at 100°C for 12 hours to obtain FF-COF@LAGP material.

[0044] Explanation of the role of Comparative Example 1 and Comparative Example 2 Comparative Example 1 uses a zeolite dispersion system to add LAGP, which differs from Example 2 where LAGP is directly mixed with the monomer for in-situ growth. Comparative Example 2 uses conventional screw sealing instead of flame sealing. These two comparative examples, under different process conditions, demonstrate the crucial role of the in-situ growth technology and flame sealing process employed in this invention for the successful preparation of COF@LAGP composite materials.

[0045] Test Example 1 The COF-LAGP-based composite solid electrolyte membrane obtained in Example 2 was used to assemble a lithium-lithium symmetric button battery and subjected to constant current charge-discharge stable cycle test.

[0046] The preferred symmetrical battery assembly method is to use a 0.5mm steel sheet, followed by a lithium sheet, an electrolyte membrane, and another lithium sheet and steel sheet, pressed together under a pressure of 10MPa to form a symmetrical battery. The battery operates at 0.2 mA / cm². 2 and 0.2 mAh / cm 2 The constant current charge and discharge test was performed under the specified conditions.

[0047] like Figure 8 As shown, the symmetric cell remained stable after 2500 hours of cycling, demonstrating long-term cycling stability of lithium-ion intercalation / deintercalation and effectiveness in suppressing lithium dendrites at the interface.

[0048] Test Example 2 Lithium iron phosphate solid-state battery assembly process: Positive electrode: lithium iron phosphate electrode, loading 3mg / cm³ 2 The process begins with a COF-LAGP-based composite solid electrolyte membrane, followed by a lithium sheet, all pressed together under a pressure of 10 MPa to form a solid-state battery. The battery is then subjected to constant current charge-discharge testing at a high current density of 1C.

[0049] like Figure 9As shown, the battery's initial discharge specific capacity at 1 C is 160 mAh / g, and after 900 cycles, the capacity retention rate still reaches 90%, exhibiting high capacity retention. The discharge specific capacity is 144 mAh / g. Figure 10 As shown, the charge-discharge curves of the solid-state battery at different cycles demonstrate that the battery has a high coulombic efficiency and maintains a stable capacity.

[0050] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a covalent organic framework-inorganic ceramic composite solid electrolyte, characterized in that, Includes the following steps: S1. Dissolve the fluorinated long-chain monomer benzoyl hydrazide and 1,3,5-tricarboxyphenylbenzene in a mixed solvent, and add the inorganic ceramic lithium germanium aluminum phosphate, and mix evenly by ultrasonication; the mixed solvent is a mixture of mesitylene and o-dichlorobenzene; S2. After complete dissolution, add acetic acid as a catalyst to obtain a mixed solution; S3. Freeze the mixed solution with liquid nitrogen, then evacuate the reaction tube and seal it with a flame seal. React at 110℃~130℃ for 60~90h to obtain the reactant. S4. After separation of reactants, powder is obtained and then washed alternately with acetone, tetrahydrofuran and N,N-dimethylformamide. The washed powder is dried to obtain a covalent organic framework-inorganic ceramic composite material. S5. The covalent organic framework-inorganic ceramic composite material is mixed with lithium salt to obtain a solid electrolyte.

2. The preparation method according to claim 1, characterized in that: In step S1, the fluorinated long-chain monomer phthalic acid hydrazide is 2,5-bis((3,3,4,4,5,5,6,6,6-nonafluorohexyl)oxy)terephthalic acid hydrazide; the molar ratio of the fluorinated long-chain monomer phthalic acid hydrazide to 1,3,5-tricarboxyphenylbenzene is 1.2–1.8:1; the mass ratio of the total mass of the fluorinated long-chain monomer phthalic acid hydrazide and 1,3,5-tricarboxyphenylbenzene to the mass of lithium germanium aluminum phosphate is 0.8–1.2:1; and the volume ratio of mesitylene to o-dichlorobenzene is 1.5–2.5:

1.

3. The preparation method according to claim 1, characterized in that: In step S2, the concentration of the acetic acid solution is 6 mol / L, and the volume ratio of the acetic acid solution to the mixed solvent is 1:10 to 30.

4. The preparation method according to claim 1, characterized in that: In step S5, the mass ratio of the covalent organic framework-inorganic ceramic composite material to the lithium salt is 1.5 to 2.5:1; the lithium salt is lithium bis(trifluoromethanesulfonyl)imide.

5. The preparation method according to claim 4, characterized in that: In step S5, the covalent organic framework-inorganic ceramic composite material is mixed with lithium salt, ethanol is added, and the mixture is stirred at room temperature for 8 to 16 hours. Then, it is vacuum dried at 80 to 120°C to obtain a solid electrolyte.

6. A covalent organic framework-inorganic ceramic composite solid electrolyte prepared by the preparation method according to any one of claims 1 to 5.

7. A solid electrolyte membrane, characterized in that: Includes the solid electrolyte and PTFE dispersion as described in claim 6.

8. A method for preparing a solid electrolyte membrane as described in claim 7, characterized in that, The process includes the following steps: combining the solid electrolyte with a PTFE dispersion, rolling the mixture to obtain an electrolyte membrane, immersing the electrolyte membrane in a lithium salt solvent for activation, and then drying it to obtain the final product.

9. The preparation method according to claim 8, characterized in that: The PTFE concentration in the PTFE dispersion is 40%–80%, and the amount of PTFE dispersion used is 0.5%–5% of the mass of the solid electrolyte; the lithium salt solvent is lithium bis(trifluoromethanesulfonyl)imide dissolved in propylene carbonate, with a concentration of 0.5–2 mol / L and an activation time of 12–24 h; the drying temperature is 80–120 °C, and the drying time is 8–24 h.

10. A solid-state battery, characterized in that: It includes the solid electrolyte membrane as described in claim 7.

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