Fluorinated chitosan composite solid electrolyte membrane, preparation method and application thereof

Abstract

This invention discloses a fluorinated chitosan composite solid electrolyte membrane, its preparation method, and its application, belonging to the field of solid-state battery technology. The electrolyte membrane comprises a fluorinated chitosan matrix, LLZTO filler modified with the silane coupling agent KH-550, a lithium salt, and a crosslinking agent PEGDE. The preparation method includes: firstly, preparing fluorinated chitosan with different degrees of fluorination through reaction; secondly, surface-modifying LLZTO powder using KH-550; and finally, mixing and dissolving the above components with the lithium salt and crosslinking agent, casting to form a membrane, and performing interface engineering treatment. This invention utilizes the strong electron-withdrawing effect of fluorinated chitosan and the KH-550-modified LLZTO to construct a highly efficient lithium-ion transport channel, significantly improving the ionic conductivity and mechanical toughness of the electrolyte membrane, effectively suppressing lithium dendrite growth, and greatly improving the cycle stability and safety of solid-state batteries.

Description

Technical Field

[0001] This invention belongs to the technical field, and particularly relates to a fluorinated chitosan composite solid electrolyte membrane, its preparation method, and its application. Background Technology

[0002] With the rapid development of new energy vehicles and portable electronic devices, the demand for high-energy-density and high-safety energy storage devices is becoming increasingly urgent. Traditional lithium-ion batteries use flammable organic liquid electrolytes, posing safety hazards such as leakage, combustion, and even explosion, and their energy density is approaching its theoretical limit. All-solid-state lithium batteries use non-flammable solid electrolytes instead of liquid electrolytes, offering advantages such as intrinsic safety, high energy density, and a wide electrochemical window, and are considered key to next-generation energy storage technology.

[0003] Polymer solid electrolytes have attracted much attention due to their excellent flexibility, ease of processing, and interfacial contact properties. Chitosan, as a natural biopolymer, has advantages such as wide availability and good biocompatibility; however, its low room-temperature ionic conductivity and insufficient mechanical strength limit its direct application. Furthermore, while the introduction of inorganic fillers (such as LLZTO) can improve performance, the poor interfacial compatibility between inorganic fillers and the polymer matrix leads to agglomeration, hindering ion transport. Simultaneously, the instability of the lithium anode-electrolyte interface and the growth of lithium dendrites are also key issues that urgently need to be addressed. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a fluorinated chitosan composite solid electrolyte membrane, its preparation method, and its application.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for preparing a fluorinated chitosan composite solid electrolyte membrane includes the following steps:

[0007] (1) Under the protection of an inert gas, chitosan was dissolved in an organic solvent and swollen. Triethylamine was added and perfluoro anhydride was added dropwise at low temperature to carry out the reaction. After precipitation, washing, purification and drying, fluorinated chitosan was obtained.

[0008] (2) Dissolve the silane coupling agent KH-550 in an alcohol solvent and hydrolyze it. Add LLZTO powder to carry out a surface modification reaction. After separation, washing and drying, KH-550 modified LLZTO is obtained.

[0009] (3) Dissolve the fluorinated chitosan obtained in step (1), the KH-550 modified LLZTO obtained in step (2), lithium salt and crosslinking agent in a solvent, mix them evenly and then cast them into a film, and dry them to obtain a base film.

[0010] (4) Interface treatment: A LiPON layer is deposited by magnetron sputtering on the surface of the base film, and then hot-pressed to densify and coated with a polydopamine layer to obtain the fluorinated chitosan composite solid electrolyte membrane.

[0011] Optionally, the perfluoro anhydride mentioned in step (1) is selected from any one or more of trifluoroacetic anhydride, perfluorobutyric anhydride, or perfluorooctanoic anhydride;

[0012] The organic solvent is selected from polar aprotic solvents, preferably dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP), acetonitrile (CH3CN), and tetrahydrofuran (THF).

[0013] The inert gas is selected from nitrogen or argon;

[0014] Chitosan swells in organic solvents for 2-4 hours;

[0015] The ratio of the added triethylamine to the chitosan is 0.36-2.5 mL : 1.00 g;

[0016] The reaction time for adding perfluoro anhydride was 56 hours.

[0017] Optionally, the molar ratio of chitosan to perfluoro anhydride is 1:(0.1-0.7, based on the glucosamine units in chitosan.

[0018] Optionally, the extraction agent used in the purification process is diethyl ether or tetrahydrofuran.

[0019] Optionally, the LLZTO powder described in step (2) is vacuum dried at 120-150℃ before use;

[0020] The alcohol solvent is selected from anhydrous ethanol.

[0021] Optionally, the surface modification reaction is carried out under conditions of pH 4-5.

[0022] Furthermore, the surface modification reaction conditions are: reacting at 50-80℃ for 6-12 hours.

[0023] Optionally, in step (3), the mass ratio of fluorinated chitosan, KH-550 modified LLZTO, lithium salt and crosslinking agent is 35:35:20:10.

[0024] The lithium salt is selected from any one or more commonly used lithium salts in lithium-ion battery electrolytes, preferably lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium dioxolane borate (LiBOB), lithium difluorooxolane borate (LiDFOB), lithium bis(trifluoromethanesulfonyl)imide (LiFSI), lithium bis(fluorosulfonyl)imide (LiTFSI), or lithium difluorophosphate (LiPO2F2).

[0025] The crosslinking agent is selected from PEGDE with a number average molecular weight range of 400-2000.

[0026] Optionally, the process parameters for magnetron sputtering deposition of the LiPON layer in step (4) are: power 200-400W, Ar:N2 gas flow ratio of 1:1, and vacuum degree <5×10 -3 Pa;

[0027] The hot-pressing densification method is as follows: hot-pressing at 100℃ for 5-10 minutes to densify;

[0028] The method for coating the polydopamine is as follows: after hot pressing densification treatment, a polydopamine layer with a thickness of 50-80 nm is coated on the surface.

[0029] A fluorinated chitosan composite solid electrolyte membrane prepared by the above preparation method.

[0030] Optionally, the thickness of the fluorinated chitosan composite solid electrolyte membrane is 30-50 μm.

[0031] A solid-state battery includes a positive electrode, a negative electrode, and a fluorinated chitosan composite solid electrolyte membrane disposed between the positive electrode and the negative electrode;

[0032] The positive electrode comprises: active material (NCM811), conductive carbon black, solid electrolyte and Al current collector, and is prepared by wet coating.

[0033] The negative electrode is a lithium foil coated with an 80 nm polydopamine layer.

[0034] Compared with the prior art, the present invention has the following advantages and technical effects:

[0035] This invention significantly improves the ionic conductivity, mechanical properties, and battery cycle life of an electrolyte by constructing a fluorinated chitosan composite solid-state electrolyte membrane. Specifically, this invention utilizes LLZTO inorganic filler modified with KH-550 to effectively construct a rapid lithium-ion transport channel, resulting in a substantial increase in ionic conductivity. Simultaneously, the introduced fluorinated chitosan not only optimizes ion transport coordination through the coating effect of fluorinated segments but also significantly enhances the material's mechanical toughness and flexibility, exhibiting a marked improvement in elongation at break compared to traditional materials such as unfluorinated chitosan and PVDF. Furthermore, this electrolyte system demonstrates excellent electrochemical stability, effectively passivating the lithium metal anode and inhibiting lithium dendrite growth, thereby significantly improving the cycle performance and safety of solid-state batteries. Attached Figure Description

[0036] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0037] Figure 1 This is a schematic diagram of a solid electrolyte structure; where 1 is a three-dimensional polymer network composite solid electrolyte membrane formed based on fluorinated chitosan; 2 is a LiPON layer deposited by magnetron sputtering; and 3 is a polydopamine layer.

[0038] Figure 2 This is a schematic diagram of a solid-state battery structure; 1 is a three-dimensional polymer network composite solid electrolyte membrane based on fluorinated chitosan; 2 is a LiPON layer deposited by magnetron sputtering; 3 is a polydopamine layer; 4 is an NCM positive electrode; 5 is a positive electrode current collector (aluminum foil); 6 is a lithium metal negative electrode.

[0039] Figure 3 This is a schematic diagram of the lithium-ion transport mechanism in a composite solid electrolyte (fluorinated chain segments in fluorinated chitosan are coated with LLZTO (modified by KH-550), and PEO (polyethylene oxide) segments transport lithium ions); where 7 is the polymer segment formed by PEGDE; 8 is a three-dimensional polymer network with chitosan as the backbone; 9 is the fluorinated segment; 10 is KH-550@LLZTO; and 11 is the formed lithium-ion transport channel;

[0040] Figure 4 This is a graph showing the cycle performance of a solid-state battery.

[0041] Figure 5 This is a process flow diagram for the fabrication of a solid-state battery based on a fluorinated chitosan composite solid electrolyte membrane.

[0042] Figure 6a) is a SEM image of the solid-state battery with added fluorinated chitosan in Example 10 after 400 cycles; b) is a SEM image of the solid-state battery with added non-fluorinated chitosan in Comparative Example 3 after 400 cycles. Detailed Implementation

[0043] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0044] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0045] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0046] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0047] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0048] Unless otherwise specified, "room temperature" in this invention refers to 20-30℃.

[0049] All raw materials used in this invention were purchased from the market.

[0050] The technical solution of the present invention will be further illustrated by the following embodiments.

[0051] Example 1

[0052] A process for preparing fluorinated chitosan includes the following steps:

[0053] S1. Under a dry inert gas atmosphere (nitrogen or argon), add 1.00 g of dried chitosan (~6.2 mmol as glucosamine units; degree of deacetylation >90%, molecular weight >100,000) to a dry 100 mL three-necked flask. Slowly add 50 mL of anhydrous DMF, start stirring and slowly heat to 65 °C, continuing stirring for about 2 hours until the chitosan is basically swollen and dispersed. Then cool the system to 0-5 °C (using a circulating low-temperature water bath).

[0054] S2. While stirring, slowly inject dry triethylamine (2.5 mL, ~18 mmol) into the reaction flask, keeping the system temperature below 5°C.

[0055] S3. Slowly add trifluoroacetic anhydride (0.612 mL, ~4.4 mmol, which is 0.7 equivalent of chitosan amino) dropwise to the above reactants, controlling the dropping rate to keep the reaction temperature at 5°C. The dropping process takes about 30 minutes.

[0056] S4. After the addition is complete, remove the water bath and allow the reaction solution to naturally warm to room temperature. Stir the reaction at this temperature for 8 hours. Then, place the reaction flask in an oil bath and slowly raise the temperature to 65°C. Stir the reaction at this temperature in the dark for 48 hours.

[0057] S5. After cooling the reaction solution to room temperature, slowly add it dropwise to 500 mL of pre-cooled methanol / water mixture while stirring vigorously. This step will cause the product to precipitate. Collect the solid product by filtering through a Buchner funnel or a glass frit funnel. Wash the solid at least three times with a large amount of methanol (approximately 100 mL each time) to remove most of the DMF and adsorbed impurities.

[0058] S6. Place the crude product into the filter paper cassette of a Soxhlet extractor. Extract continuously for 24 hours using diethyl ether or tetrahydrofuran as the extraction solvent. This step effectively removes residual perfluoroacetic anhydride, perfluoroacetic acid, and other small molecule impurities. After extraction, air-dry the product in a fume hood, then transfer it to a vacuum drying oven and vacuum dry at 45°C to constant weight to obtain purified fluorinated chitosan solid Ch-F3@0.7.

[0059] Note: ① In step S3 above, by controlling the amount of trifluoroacetic anhydride added (e.g., 0.087 mL, 0.1 equivalent; 0.262 mL, 0.3 equivalent; 0.435 mL, 0.5 equivalent), fluorinated chitosan solids with corresponding different degrees of fluorination (Ch-F3@0.1; Ch-F3@0.3; Ch-F3@0.5) are finally obtained.

[0060] ② Accordingly, in step S2 above, the amount of triethylamine added should also be adjusted proportionally for different amounts of trifluoroacetic anhydride (e.g., 0.087 mL, 0.1 equivalent; 0.262 mL, 0.3 equivalent; 0.435 mL, 0.5 equivalent) (corresponding to 0.36 mL; 1.08 mL; 1.8 mL respectively).

[0061] Example 2

[0062] A process for preparing fluorinated chitosan includes the following steps:

[0063] S1. Under a dry inert gas atmosphere (nitrogen or argon), add 1.00 g of dried chitosan (~6.2 mmol as glucosamine units; degree of deacetylation >90%, molecular weight >100,000) to a dry 100 mL three-necked flask. Slowly add 50 mL of anhydrous DMF, start stirring and slowly heat to 65 °C, continuing stirring for about 2 hours until the chitosan is substantially swollen and dispersed. Then cool the system to 0 °C (using a circulating low-temperature water bath).

[0064] S2. While stirring, slowly inject dry triethylamine (2.5 mL, ~18 mmol) into the reaction flask, keeping the system temperature below 5°C.

[0065] S3. Slowly add perfluorobutyric anhydride (1.08 mL, ~4.4 mmol, which is about 0.7 equivalents of chitosan amino) dropwise to the above reactants, controlling the dropping rate to keep the reaction temperature at 5°C. The dropping process takes about 30 minutes.

[0066] S4. After the addition is complete, remove the water bath and allow the reaction solution to naturally warm to room temperature. Stir the reaction at this temperature for 8 hours. Then, place the reaction flask in an oil bath and slowly raise the temperature to 65°C. Stir the reaction at this temperature in the dark for 48 hours.

[0067] S5. After cooling the reaction solution to room temperature, slowly add it dropwise to 500 mL of pre-cooled methanol / water mixture while stirring vigorously. This step will cause the product to precipitate. Collect the solid product by filtering through a Buchner funnel or a glass frit funnel. Wash the solid at least three times with a large amount of methanol (approximately 100 mL each time) to remove most of the DMF and adsorbed impurities.

[0068] S6. Place the crude product into the filter paper cassette of a Soxhlet extractor. Extract continuously for 24 hours using diethyl ether or tetrahydrofuran as the extraction solvent. This step effectively removes residual perfluorobutyric anhydride, perfluorobutyric acid, and other small molecule impurities. After extraction, air-dry the product in a fume hood, then transfer it to a vacuum drying oven and vacuum dry at 45°C to constant weight to obtain purified fluorinated chitosan solid Ch-F7@0.7.

[0069] Note: ① In step S3 above, by controlling the amount of perfluorobutyric anhydride added (e.g., 0.154 mL, 0.1 equivalent; 0.463 mL, 0.3 equivalent; 0.770 mL, 0.5 equivalent), fluorinated chitosan solids with corresponding different degrees of fluorination (Ch-F7@0.1; Ch-F7@0.3; Ch-F7@0.5) are finally obtained.

[0070] ② Accordingly, in step S2 above, the amount of triethylamine added should also be adjusted proportionally (corresponding to: 0.36 mL; 1.08 mL; 1.8 mL) for different amounts of perfluorobutyric anhydride (e.g., 0.154 mL, 0.1 equivalent; 0.463 mL, 0.3 equivalent; 0.770 mL, 0.5 equivalent) for different amounts of perfluorobutyric anhydride added ...

[0071] Example 3

[0072] A process for preparing fluorinated chitosan includes the following steps:

[0073] S1. Under a dry inert gas atmosphere (nitrogen or argon), add 1.00 g of dried chitosan (~6.2 mmol as glucosamine units; degree of deacetylation >90%, molecular weight >100,000) to a dry 100 mL three-necked flask. Slowly add 50 mL of anhydrous DMF, start stirring and slowly heat to 65 °C, continuing stirring for about 2 hours until the chitosan is substantially swollen and dispersed. Then cool the system to 0 °C (using a circulating low-temperature water bath).

[0074] S2. While stirring, slowly inject dry triethylamine (2.5 mL, ~18 mmol) into the reaction flask, keeping the system temperature below 5°C.

[0075] S3. Slowly add perfluorooctanoic anhydride (2.01 mL, ~4.4 mmol, this molar amount is about 0.7 equivalents of chitosan amino) dropwise to the above reactants, controlling the dropping rate to keep the reaction temperature at 5°C. The dropping process takes about 30 minutes.

[0076] S4. After the addition is complete, remove the water bath and allow the reaction solution to naturally warm to room temperature. Stir the reaction at this temperature for 8 hours. Then, place the reaction flask in an oil bath and slowly raise the temperature to 65°C. Stir the reaction at this temperature in the dark for 48 hours.

[0077] S5. After cooling the reaction solution to room temperature, slowly add it dropwise to 500 mL of pre-cooled methanol / water mixture while stirring vigorously. This step will cause the product to precipitate. Collect the solid product by filtering through a Buchner funnel or a glass frit funnel. Wash the solid at least three times with a large amount of methanol (approximately 100 mL each time) to remove most of the DMF and adsorbed impurities.

[0078] S6. Place the crude product into the filter paper cassette of a Soxhlet extractor. Extract continuously for 24 hours using diethyl ether or tetrahydrofuran as the extraction solvent. This step effectively removes residual perfluorooctanoic anhydride, perfluorooctanoic acid, and other small molecule impurities. After extraction, air-dry the product in a fume hood, then transfer it to a vacuum drying oven and vacuum dry at 45°C to constant weight to obtain purified fluorinated chitosan solid Ch-F15@0.7.

[0079] Note: ① In step S3 above, by controlling the amount of perfluorooctanoic anhydride added (e.g., 0.283 mL, 0.1 equivalent; 0.849 mL, 0.3 equivalent; 1.42 mL, 0.5 equivalent), fluorinated chitosan solids with corresponding degrees of fluorination are finally obtained (corresponding to: Ch-F15@0.1; Ch-F15@0.3; Ch-F15@0.5).

[0080] ② Accordingly, in step S2 above, the amount of triethylamine added should be adjusted proportionally for different amounts of perfluorooctanoic anhydride (e.g., 0.283 mL, 0.1 equivalent; 0.849 mL, 0.3 equivalent; 1.42 mL, 0.5 equivalent) (corresponding to: 0.36 mL; 1.08 mL; 1.8 mL).

[0081] Example 4

[0082] LLZTO was surface modified using KH-550, and the specific preparation process is as follows:

[0083] S1. Place LLZTO powder (Aldrich-934720, particle size 1-2μm) in a vacuum drying oven and dry at 140℃ for 12 hours to completely remove physically adsorbed water and possible trace amounts of Li2CO3. Grind appropriately and sieve (400 mesh sieve), then store in a vacuum desiccator.

[0084] S2. Dissolve KH-550 in anhydrous ethanol to form a 3wt% solution and stir vigorously with a magnetic stirrer. Then slowly add acetic acid solution (2.5wt%) to adjust the pH of the solution to 4.5. The resulting reaction solution is reacted at 35°C for 4 hours.

[0085] S3. Slowly add the LLZTO powder prepared in S1 to the KH-550 hydrolysis solution prepared in S2, and stir vigorously with a magnetic stirrer. React at 70°C for 12 hours.

[0086] S4. After the reaction is complete, the mixture is vacuum filtered to separate the modified LLZTO solid. The precipitate is washed repeatedly with anhydrous ethanol 5 times, and then placed in a vacuum drying oven and dried at 65°C for 24 hours. Finally, the modified KH-550@LLZTO powder is stored in a vacuum desiccator.

[0087] Example 5

[0088] A method for preparing a fluorinated chitosan composite solid electrolyte membrane (e.g.) Figure 5 (S2-S5), including the following steps:

[0089] (1) Formula

[0090] 35 wt% fluorinated chitosan (Ch-F3@0.1), 35 wt% KH-550@LLZTO, 20 wt% LiFSI, 10 wt% PEGDE (Mn=2000).

[0091] (2) Process

[0092] S1. Base film forming:

[0093] 35 wt% fluorinated chitosan (Ch-F3@0.1), 35 wt% KH-550@LLZTO, 20 wt% LiFSI lithium salt, and 10 wt% PEGDE (Mn=2000) were dissolved in NMP solvent and cast into a 30 μm base film.

[0094] S2. Interface Engineering:

[0095] Magnetron sputtering deposition of LiPON layers (power 350 W, Ar:N2=1:1, vacuum degree <5×10⁻⁶) -3 Pa, thickness approximately 30 nm);

[0096] S3. Post-processing:

[0097] Densification is achieved by hot pressing at 100℃ for 5 minutes, followed by coating the surface with an 80nm polydopamine layer to enhance electrode interface stability.

[0098] Example 6

[0099] A method for preparing a fluorinated chitosan composite solid electrolyte membrane includes the following steps:

[0100] (1) Formula

[0101] 35 wt% fluorinated chitosan (Ch-F3@0.3), 35 wt% KH-550@LLZTO, 20 wt% LiFSI, 10 wt% PEGDE (Mn=2000).

[0102] (2) Process

[0103] S1. Base film forming:

[0104] 35 wt% fluorinated chitosan (Ch-F3@0.3), 35 wt% KH-550@LLZTO, 20 wt% LiFSI lithium salt, and 10 wt% PEGDE (Mn=2000) were dissolved in NMP solvent and cast into a base film of about 30 μm.

[0105] S2. Interface Engineering:

[0106] Magnetron sputtering deposition of LiPON layers (power 350 W, Ar:N2=1:1, vacuum degree <5×10⁻⁶) -3 Pa, thickness approximately 30 nm);

[0107] S3. Post-processing:

[0108] Densification is achieved by hot pressing at 100℃ for 5 minutes, followed by coating the surface with an 80nm polydopamine layer to enhance electrode interface stability.

[0109] Example 7

[0110] A method for preparing a fluorinated chitosan composite solid electrolyte membrane includes the following steps:

[0111] (1) Formula

[0112] 35 wt% fluorinated chitosan (Ch-F3@0.5), 35 wt% KH-550@LLZTO, 20 wt% LiFSI, 10 wt% PEGDE (Mn=2000).

[0113] (2) Process

[0114] S1. Base film forming:

[0115] 35 wt% degraded chitosan (Ch-F3@0.5), 35 wt% KH-550@LLZTO, 20 wt% LiFSI lithium salt, and 10 wt% PEGDE (Mn=2000) were dissolved in NMP solvent and cast into a base film of about 30 μm.

[0116] S2. Interface Engineering:

[0117] Magnetron sputtering deposition of LiPON layers (power 350 W, Ar:N2=1:1, vacuum degree <5×10⁻⁶)-3 Pa, thickness approximately 30 nm);

[0118] S3. Post-processing:

[0119] Densification is achieved by hot pressing at 100℃ for 5 minutes, followed by coating the surface with an 80nm polydopamine layer to enhance electrode interface stability.

[0120] Example 8

[0121] A method for preparing a fluorinated chitosan composite solid electrolyte membrane includes the following steps:

[0122] (1) Formula

[0123] 35 wt% fluorinated chitosan (Ch-F3@0.7), 35 wt% KH-550@LLZTO, 20 wt% LiFSI, 10 wt% PEGDE (Mn=2000).

[0124] (2) Process

[0125] S1. Base film forming:

[0126] 35 wt% fluorinated chitosan (Ch-F3@0.7), 35 wt% KH-550@LLZTO, 20 wt% LiFSI lithium salt, and 10 wt% PEGDE (Mn=2000) were dissolved in NMP solvent and cast into a base film of about 30 μm.

[0127] S2. Interface Engineering:

[0128] Magnetron sputtering deposition of LiPON layers (power 350 W, Ar:N2=1:1, vacuum degree <5×10⁻⁶) -3 Pa, thickness approximately 30 nm);

[0129] S3. Post-processing:

[0130] Densification is achieved by hot pressing at 100℃ for 5 minutes, followed by coating the surface with an 80nm polydopamine layer to enhance electrode interface stability.

[0131] Example 9

[0132] A method for preparing a fluorinated chitosan composite solid electrolyte membrane includes the following steps:

[0133] (1) Formula

[0134] 35 wt% fluorinated chitosan (Ch-F7@0.1), 35 wt% KH-550@LLZTO, 20 wt% LiFSI, 10 wt% PEGDE (Mn=2000).

[0135] (2) Process

[0136] S1. Base film forming:

[0137] 35 wt% fluorinated chitosan (Ch-F7@0.1), 35 wt% KH-550@LLZTO, 20 wt% LiFSI lithium salt, and 10 wt% PEGDE (Mn=2000) were dissolved in NMP solvent and cast into a base film of about 30 μm.

[0138] S2. Interface Engineering:

[0139] Magnetron sputtering deposition of LiPON layers (power 350 W, Ar:N2=1:1, vacuum degree <5×10⁻⁶) -3 Pa, thickness approximately 30 nm);

[0140] S3. Post-processing:

[0141] Densification is achieved by hot pressing at 100℃ for 5 minutes, followed by coating the surface with an 80nm polydopamine layer to enhance electrode interface stability.

[0142] Example 10

[0143] A method for preparing a fluorinated chitosan composite solid electrolyte membrane includes the following steps:

[0144] (1) Formula

[0145] 35 wt% fluorinated chitosan (Ch-F7@0.3), 35 wt% KH-550@LLZTO, 20 wt% LiFSI, 10 wt% PEGDE (Mn=2000).

[0146] (2) Process

[0147] S1. Base film forming:

[0148] 35 wt% degraded chitosan (Ch-F7@0.3), 35 wt% KH-550@LLZTO, 20 wt% LiFSI lithium salt, and 10 wt% PEGDE (Mn=2000) were dissolved in NMP solvent and cast into a base film of about 30 μm.

[0149] S2. Interface Engineering:

[0150] Magnetron sputtering deposition of LiPON layers (power 350 W, Ar:N2=1:1, vacuum degree <5×10⁻⁶) -3 Pa, thickness approximately 30 nm);

[0151] S3. Post-processing:

[0152] Densification is achieved by hot pressing at 100℃ for 5 minutes, followed by coating the surface with an 80nm polydopamine layer to enhance electrode interface stability.

[0153] Example 11

[0154] A method for preparing a fluorinated chitosan composite solid electrolyte membrane includes the following steps:

[0155] (1) Formula

[0156] 35 wt% fluorinated chitosan (Ch-F7@0.5), 35 wt% KH-550@LLZTO, 20 wt% LiFSI, 10 wt% PEGDE (Mn=2000).

[0157] (2) Process

[0158] S1. Base film forming:

[0159] 35 wt% degraded chitosan (Ch-F7@0.5), 35 wt% KH-550@LLZTO, 20 wt% LiFSI lithium salt, and 10 wt% PEGDE (Mn=2000) were dissolved in NMP solvent and cast into a base film of about 30 μm.

[0160] S2. Interface Engineering:

[0161] Magnetron sputtering deposition of LiPON layers (power 350 W, Ar:N2=1:1, vacuum degree <5×10⁻⁶) -3 Pa, thickness approximately 30 nm);

[0162] S3. Post-processing:

[0163] Densification is achieved by hot pressing at 100℃ for 5 minutes, followed by coating the surface with an 80nm polydopamine layer to enhance electrode interface stability.

[0164] Example 12

[0165] A method for preparing a fluorinated chitosan composite solid electrolyte membrane includes the following steps:

[0166] (1) Formula

[0167] 35 wt% fluorinated chitosan (Ch-F7@0.7), 35 wt% KH-550@LLZTO, 20 wt% LiFSI, 10 wt% PEGDE (Mn=2000).

[0168] (2) Process

[0169] S1. Base film forming:

[0170] 35 wt% degraded chitosan (Ch-F7@0.7), 35 wt% KH-550@LLZTO, 20 wt% LiFSI lithium salt, and 10 wt% PEGDE (Mn=2000) were dissolved in NMP solvent and cast into a base film of about 30 μm.

[0171] S2. Interface Engineering:

[0172] Magnetron sputtering deposition of LiPON layers (power 350 W, Ar:N2=1:1, vacuum degree <5×10⁻⁶) -3 Pa, thickness approximately 30 nm);

[0173] S3. Post-processing:

[0174] Densification is achieved by hot pressing at 100℃ for 5 minutes, followed by coating the surface with an 80nm polydopamine layer to enhance electrode interface stability.

[0175] Example 13

[0176] A method for preparing a fluorinated chitosan composite solid electrolyte membrane includes the following steps:

[0177] (1) Formula

[0178] 35 wt% fluorinated chitosan (Ch-F15@0.1), 35 wt% KH-550@LLZTO, 20 wt% LiFSI, 10 wt% PEGDE (Mn=2000).

[0179] (2) Process

[0180] S1. Base film forming:

[0181] 35 wt% degraded chitosan (Ch-F157@0.1), 35 wt% KH-550@LLZTO, 20 wt% LiFSI lithium salt, and 10 wt% PEGDE (Mn=2000) were dissolved in NMP solvent and cast into a base film of about 30 μm.

[0182] S2. Interface Engineering:

[0183] Magnetron sputtering deposition of LiPON layers (power 350 W, Ar:N2=1:1, vacuum degree <5×10⁻⁶) -3 Pa, thickness approximately 30 nm);

[0184] S3. Post-processing:

[0185] Densification is achieved by hot pressing at 100℃ for 5 minutes, followed by coating the surface with an 80nm polydopamine layer to enhance electrode interface stability.

[0186] Example 14

[0187] A method for preparing a fluorinated chitosan composite solid electrolyte membrane includes the following steps:

[0188] (1) Formula

[0189] 35 wt% fluorinated chitosan (Ch-F15@0.3), 35 wt% KH-550@LLZTO, 20 wt% LiFSI, 10 wt% PEGDE (Mn=2000).

[0190] (2) Process

[0191] S1. Base film forming:

[0192] 35 wt% degraded chitosan (Ch-F15@0.3), 35 wt% KH-550@LLZTO, 20 wt% LiFSI lithium salt, and 10 wt% PEGDE (Mn=2000) were dissolved in NMP solvent and cast into a base film of about 30 μm.

[0193] S2. Interface Engineering:

[0194] Magnetron sputtering deposition of LiPON layers (power 350 W, Ar:N2=1:1, vacuum degree <5×10⁻⁶) -3 Pa, thickness approximately 30 nm);

[0195] S3. Post-processing:

[0196] Densification is achieved by hot pressing at 100℃ for 5 minutes, followed by coating the surface with an 80nm polydopamine layer to enhance electrode interface stability.

[0197] Example 15

[0198] A method for preparing a fluorinated chitosan composite solid electrolyte membrane includes the following steps:

[0199] (1) Formula

[0200] 35 wt% fluorinated chitosan (Ch-F15@0.5), 35 wt% KH-550@LLZTO, 20 wt% LiFSI, 10 wt% PEGDE (Mn=2000).

[0201] (2) Process

[0202] S1. Base film forming:

[0203] 35 wt% degraded chitosan (Ch-F15@0.5), 35 wt% KH-550@LLZTO, 20 wt% LiFSI lithium salt, and 10 wt% PEGDE (Mn=2000) were dissolved in NMP solvent and cast into a base film of about 30 μm.

[0204] S2. Interface Engineering:

[0205] Magnetron sputtering deposition of LiPON layers (power 350 W, Ar:N2=1:1, vacuum degree <5×10⁻⁶) -3 Pa, thickness approximately 30 nm);

[0206] S3. Post-processing:

[0207] Densification is achieved by hot pressing at 100℃ for 5 minutes, followed by coating the surface with an 80nm polydopamine layer to enhance electrode interface stability.

[0208] Example 16

[0209] A method for preparing a fluorinated chitosan composite solid electrolyte membrane includes the following steps:

[0210] (1) Formula

[0211] 35 wt% fluorinated chitosan (Ch-F15@0.7), 35 wt% KH-550@LLZTO, 20 wt% LiFSI, 10 wt% PEGDE (Mn=2000).

[0212] (2) Process

[0213] S1. Base film forming:

[0214] 35 wt% degraded chitosan (Ch-F15@0.7), 35 wt% KH-550@LLZTO, 20 wt% LiFSI lithium salt, and 10 wt% PEGDE (Mn=2000) were dissolved in NMP solvent and cast into a base film of about 30 μm.

[0215] S2. Interface Engineering:

[0216] Magnetron sputtering deposition of LiPON layers (power 350 W, Ar:N2=1:1, vacuum degree <5×10⁻⁶) -3 Pa, thickness approximately 30 nm);

[0217] S3. Post-processing:

[0218] Densification is achieved by hot pressing at 100℃ for 5 minutes, followed by coating the surface with an 80nm polydopamine layer to enhance electrode interface stability.

[0219] Comparative Example 1

[0220] A method for preparing a fluorinated chitosan composite solid electrolyte membrane, the technical solution of which is the same as that in Example 10, the difference being that PEGDE is not added, and the method includes the following steps:

[0221] (1) Formula

[0222] 45 wt% fluorinated chitosan (Ch-F7@0.3), 35 wt% KH-550@LLZTO, 20 wt% LiFSI.

[0223] (2) Process

[0224] S1. Base film forming:

[0225] 45 wt% degraded chitosan (Ch-F7@0.3), 35 wt% KH-550@LLZTO, and 20 wt% LiFSI lithium salt were dissolved in NMP solvent and cast into a base film of about 30 μm.

[0226] S2. Interface Engineering:

[0227] Magnetron sputtering deposition of LiPON layers (power 350 W, Ar:N2=1:1, vacuum degree <5×10⁻⁶) -3 Pa, thickness approximately 30 nm);

[0228] S3. Post-processing:

[0229] Densification is achieved by hot pressing at 100℃ for 5 minutes, followed by coating the surface with an 80nm polydopamine layer to enhance electrode interface stability.

[0230] Comparative Example 2

[0231] A method for preparing a solid electrolyte membrane, the technical solution is the same as in Example 10, the difference being that: fluorinated chitosan is not added, and PVDF is used instead.

[0232] Includes the following steps:

[0233] (1) Formula

[0234] 45 wt% PVDF, 35 wt% KH-550@LLZTO, 20 wt% LiFSI.

[0235] (2) Process

[0236] S1. Base film forming:

[0237] 45 wt% PVDF, 35 wt% KH-550@LLZTO, and 20 wt% LiFSI lithium salt were dissolved in NMP solvent and cast into a base film of about 30 μm.

[0238] S2. Interface Engineering:

[0239] Magnetron sputtering deposition of LiPON layers (power 350 W, Ar:N2=1:1, vacuum degree <5×10⁻⁶) -3 Pa, thickness approximately 30 nm);

[0240] S3. Post-processing:

[0241] Densification is achieved by hot pressing at 100℃ for 5 minutes, followed by coating the surface with an 80nm polydopamine layer to enhance electrode interface stability.

[0242] Comparative Example 3

[0243] A method for preparing a solid electrolyte membrane, the technical solution is the same as in Example 10, the difference being that: non-fluorinated chitosan is used in place of fluorinated chitosan by mass.

[0244] Includes the following steps:

[0245] (1) Formula

[0246] 35 wt% chitosan (degree of deacetylation greater than 90%, molecular weight > 100,000), 35 wt% KH-550@LLZTO, 20 wt% LiFSI, 10 wt% PEGDE (Mn=2000).

[0247] (2) Process

[0248] S1. Base film forming:

[0249] 35 wt% chitosan (degree of deacetylation greater than 90%, molecular weight > 100,000), 35 wt% KH-550@LLZTO, 20 wt% LiFSI lithium salt, and 10 wt% PEGDE (Mn=2000) were dissolved in NMP solvent and cast into a base film of about 30 μm.

[0250] S2. Interface Engineering:

[0251] Magnetron sputtering deposition of LiPON layers (power 350 W, Ar:N2=1:1, vacuum degree <5×10⁻⁶) -3 Pa, thickness approximately 30 nm);

[0252] S3. Post-processing:

[0253] Densification is achieved by hot pressing at 100℃ for 5 minutes, followed by coating the surface with an 80nm polydopamine layer to enhance electrode interface stability.

[0254] Comparative Example 4

[0255] A method for preparing a solid electrolyte membrane, the technical solution is the same as in Example 10, the difference being that: LLZTO without KH-550 modification is used in place of KH-550@LLZTO.

[0256] Includes the following steps:

[0257] (1) Formula

[0258] 35 wt% fluorinated chitosan (Ch-F7@0.3), 35 wt% LLZTO, 20 wt% LiFSI, 10 wt% PEGDE (Mn=2000).

[0259] (2) Process

[0260] S1. Base film forming:

[0261] 35 wt% degraded chitosan (Ch-F7@0.3), 35 wt% LLZTO, 20 wt% lithium LiFSI, and 10 wt% PEGDE (Mn=2000) were dissolved in NMP solvent and cast into a base film of about 30 μm.

[0262] S2. Interface Engineering:

[0263] Magnetron sputtering deposition of LiPON layers (power 350 W, Ar:N2=1:1, vacuum degree <5×10⁻⁶) -3 Pa, thickness approximately 30 nm);

[0264] S3. Post-processing:

[0265] Densification is achieved by hot pressing at 100℃ for 5 minutes, followed by coating the surface with an 80nm polydopamine layer to enhance electrode interface stability.

[0266] Comparative Example 5

[0267] A method for preparing a solid electrolyte membrane, the technical solution is the same as in Example 10, the difference being that LLZTO is not added.

[0268] Includes the following steps:

[0269] (1) Formula

[0270] 45 wt% fluorinated chitosan (Ch-F7@0.3), 30 wt% LiFSI, 25 wt% PEGDE (Mn=2000).

[0271] (2) Process

[0272] S1. Base film forming:

[0273] 45 wt% degraded chitosan (Ch-F7@0.3), 30 wt% lithium LiFSI, and 25 wt% PEGDE (Mn=2000) were dissolved in NMP solvent and cast into a base film of about 30 μm.

[0274] S2. Interface Engineering:

[0275] Magnetron sputtering deposition of LiPON layers (power 350 W, Ar:N2=1:1, vacuum degree <5×10⁻⁶)-3 Pa, thickness approximately 30 nm);

[0276] S3. Post-processing:

[0277] Densification is achieved by hot pressing at 100℃ for 5 minutes, followed by coating the surface with an 80nm polydopamine layer to enhance electrode interface stability.

[0278] Example 1: Elongation at break test of solid electrolyte membrane

[0279] Tensile specimens of the adhesive film were prepared according to ASTM standard D638, with five specimens required for each selected strain rate. Tensile tests were conducted under constant temperature and humidity conditions: 25°C, 40%RH. The experimental results are the average of the five sets of test values.

[0280] Table 1 Elongation at break of solid electrolyte membranes

[0281]

[0282] Example 2: Testing of Ionic and Electronic Conductivity of Solid Electrolyte Membranes

[0283] The ionic conductivity of the solid electrolyte membrane was tested according to the standard blocked electrode method (ASTM D257). Specific conditions were: 25°C; the electrolyte membrane was cut into 10 mm diameter discs; lithium metal electrodes were hot-pressed onto both sides of the membrane in a glove box (H2O / O2 < 0.1 ppm); frequency range: 0.1 Hz–1.0 MHz; amplitude: 10 mV. The experimental results are the average of five sets of experimental values.

[0284] The ionic conductivity of the solid electrolyte membrane was tested according to the standard electron-blocking electrode method (J. Electrochem. S℃. Standard Procedure). Specific conditions were as follows: at 25℃, the electrolyte membrane was cut into 10 mm diameter discs and placed in a glove box (H2O / O2 < 0.1 ppm). Lithium and gold metal electrodes were hot-pressed onto both sides of the membrane to form a Li|electrolyte|Au structure. A constant small voltage (0.1-0.5 V) was applied, and the membrane was polarized for a long period (1-24 hours). The current decay curve was recorded until the steady-state electron current was reached. The experimental results are the average of five sets of experimental values.

[0285] Table 2 Ionic conductivity and electronic conductivity of solid electrolyte membranes

[0286]

[0287] As can be seen from the table:

[0288] 1. LLZTO modified with KH-550 provides a faster ion channel (ionic conductivity increased by 4.67 times) compared to LLZTO without KH-550 modification.

[0289] 2. Fluorinated chitosan provides a better ion transport coordination effect compared to non-fluorinated chitosan, improving the efficiency of ion channels (ionic conductivity increased by 7.5 times).

[0290] 3. PEGDE crosslinking improves mechanical toughness (28% elongation at break vs. 3% without addition);

[0291] 4. Fluorinated chitosan helps improve overall mechanical flexibility (28% elongation at break vs 19% with unfluorinated chitosan).

[0292] Example 3: Fabrication and Testing of Solid-State Batteries

[0293] like Figure 5 As shown (corresponding to S6-8 in the figure), the preparation process of a fluorinated chitosan composite solid electrolyte membrane solid battery includes the following steps:

[0294] 1. Preparation of solid-state battery cathode

[0295] Composition: 80 wt% active material (NCM811) + 10 wt% conductive carbon black + 10 wt% solid electrolyte. A positive electrode sheet with a thickness of 80-100 μm is obtained by wet coating with an Al current collector. Positive electrodes with a diameter of 14 mm are punched out (compatible with CR2032 battery cases).

[0296] 2. Solid electrolyte membrane

[0297] Following the method of Example 10, a solid electrolyte membrane with a LiPON layer deposited by magnetron sputtering on one side (for the negative electrode) was prepared, with a total thickness of 30-50 μm. Solid electrolyte membranes (adapted to CR2032 battery cases) with a diameter of 14 mm were then punched.

[0298] 3. Lithium metal anode

[0299] It uses a lithium foil with a thickness of approximately 50 μm and is pre-coated with an 80 nm polydopamine layer. The negative electrode is punched into a 14 mm diameter disc (compatible with CR2032 battery case).

[0300] 4. Battery packaging

[0301] The positive electrode, electrolyte membrane, and negative electrode are stacked in sequence, then hot-pressed at 80°C for 10 min (pressure 10 MPa), and encapsulated using a stainless steel CR2032 battery case to obtain a complete solid-state battery.

[0302] 5. Battery Testing

[0303] 60℃ constant temperature chamber, 0.5C charge / discharge, cutoff voltage range: 2.8-4.3 V.

[0304] Figure 4 For solid-state battery cycle performance testing, Example 10 is a battery prepared using the solid-state electrolyte prepared in Example 10; Comparative Example 3 is a battery prepared using the solid-state electrolyte prepared in Comparative Example 3. Test conditions: 60℃ constant temperature chamber, 0.5C charge / discharge, cutoff voltage range: 2.8-4.3 V. From Figure 4 It can be seen from this:

[0305] In the solid electrolyte system of this invention, the addition of fluorinated chitosan can greatly improve the cycle life of the battery. The cycle performance of the solid battery is improved from poor when non-fluorinated chitosan is added (400 cycles / 69% capacity retention) to better when degraded chitosan is added (400 cycles / 95% capacity retention).

[0306] Figure 6 In Example 10, after 400 cycles, no obvious cracks appeared in the LiPON layer of the solid-state battery with added fluorinated chitosan (a) and the battery capacity remained above 95%; in Example 2, after 400 cycles, most of the LiPON layer of the solid-state battery with added non-fluorinated chitosan showed obvious cracks (comparative Example 3) and the battery capacity dropped sharply.

[0307] In summary, fluorinated chitosan passivates the lithium anode (improving dendrite suppression efficiency by more than 30%). After 400 cycles, most of the LiPON layers in the solid-state battery with non-fluorinated chitosan showed obvious cracks, resulting in a sharp decrease in battery capacity. However, after 400 cycles, no obvious cracks appeared in the LiPON layer of the solid-state battery with fluorinated chitosan.

[0308] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a fluorinated chitosan composite solid electrolyte membrane, characterized by, Includes the following steps: (1) Under the protection of an inert gas, chitosan was dissolved in an organic solvent and swollen. Triethylamine was added and perfluoro anhydride was added dropwise to carry out the reaction. After precipitation, washing, purification and drying, fluorinated chitosan was obtained. (2) Dissolve the silane coupling agent KH-550 in an alcohol solvent and hydrolyze it. Add LLZTO powder to carry out a surface modification reaction. After separation, washing and drying, KH-550 modified LLZTO is obtained. (3) Dissolve the fluorinated chitosan obtained in step (1), the KH-550 modified LLZTO obtained in step (2), lithium salt and crosslinking agent in a solvent, mix them evenly and then cast them into a film, and dry them to obtain a base film. (4) A LiPON layer is deposited by magnetron sputtering on the surface of the base film, and then hot-pressed to densify and coated with a polydopamine layer to obtain the fluorinated chitosan composite solid electrolyte membrane.

2. The method for preparing a fluorinated chitosan composite solid electrolyte membrane according to claim 1, characterized in that, The perfluoro anhydride mentioned in step (1) is selected from any one or more of trifluoroacetic anhydride, perfluorobutyric anhydride, or perfluorooctanoic anhydride; The organic solvent is selected from dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, acetonitrile, or tetrahydrofuran; The inert gas is selected from nitrogen or argon; The chitosan swells in the organic solvent for 2-4 hours. The ratio of the added triethylamine to the chitosan is 0.36-2.5 mL : 1.00 g; The reaction time for adding the perfluoro anhydride was 56 hours.

3. The method for preparing a fluorinated chitosan composite solid electrolyte membrane according to claim 1, characterized in that, Based on the glucosamine units in chitosan, the molar ratio of chitosan to perfluoro anhydride is 1:(0.1-0.7).

4. The method for preparing a fluorinated chitosan composite solid electrolyte membrane according to claim 1, characterized in that, The LLZTO powder described in step (2) is vacuum dried at 120-150℃ before use; The alcohol solvent is selected from anhydrous ethanol.

5. The method for preparing a fluorinated chitosan composite solid electrolyte membrane according to claim 1, characterized in that, The surface modification reaction was carried out under conditions of pH 4-5.

6. The method for preparing a fluorinated chitosan composite solid electrolyte membrane according to claim 5, characterized in that, The surface modification reaction conditions are: reaction at 50-80℃ for 6-12 hours.

7. The method for preparing a fluorinated chitosan composite solid electrolyte membrane according to claim 1, characterized in that, In step (3), the mass ratio of fluorinated chitosan, KH-550 modified LLZTO, lithium salt and crosslinking agent is 35:35:20:10; The lithium salt is selected from lithium hexafluorophosphate, lithium tetrafluoroborate, lithium dioxalate borate, lithium difluorooxalate borate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, or lithium difluorophosphate. The crosslinking agent is selected from PEGDE with a number average molecular weight range of 400-2000.

8. The method for preparing a fluorinated chitosan composite solid electrolyte membrane according to claim 1, characterized in that, The process parameters for depositing the LiPON layer in step (4) are: power 200-400 W, Ar:N2 gas flow ratio 1:1, vacuum degree <5×10 -3 Pa. The hot-pressing densification method is as follows: hot-pressing at 100℃ for 5-10 minutes to densify; The method for coating the polydopamine is as follows: after hot pressing densification treatment, a polydopamine layer with a thickness of 50-80 nm is coated on the surface.

9. A fluorinated chitosan composite solid electrolyte membrane prepared by the preparation method according to any one of claims 1-8, characterized in that, The film thickness is 30-50 μm.

10. A solid-state battery, characterized in that, Includes a positive electrode, a negative electrode, and a fluorinated chitosan composite solid electrolyte membrane as described in claim 9, disposed between the positive and negative electrodes; The positive electrode comprises: an active material, conductive carbon black, a solid electrolyte, and an Al current collector, and is prepared by wet coating. The negative electrode is a lithium foil coated with an 80 nm polydopamine layer.

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