Preparation method and application of high-performance electrolyte for composite sodium iron phosphate
By constructing an inorganic-organic composite SEI membrane using trifluoromethanesulfonate and acesulfame potassium in a composite sodium iron phosphate electrolyte, the problems of low energy density and poor conductivity in the electrolyte were solved, and the high-performance battery cycle stability and conductivity were improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ZHEJIANG NATRIUM ENERGY CO LTD
- Filing Date
- 2026-05-27
- Publication Date
- 2026-07-31
AI Technical Summary
Existing composite sodium iron phosphate electrolytes suffer from low energy density and poor conductivity, making it difficult to significantly improve them. Furthermore, traditional film-forming additives such as 1,3-propanesulfonate lactone are either toxic or expensive, resulting in low material capacity utilization.
Trifluoromethanesulfonate and acesulfame potassium were used as film-forming additives to construct an inorganic-organic composite SEI membrane, which optimized the stability of the electrode-electrolyte interface and improved conductivity and service life.
It improves the capacity retention and cycle performance of composite sodium iron phosphate batteries, forms a dense SEI film, and improves conductivity and high-temperature stability.
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Figure CN122494812A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of sodium-ion battery electrolyte technology, and specifically to a method for preparing and applying a high-performance electrolyte for composite sodium iron phosphate. Background Technology
[0002] Sodium-ion batteries have become a dark horse in the new energy market due to their abundant resources, low desolvation energy, and excellent cycle performance, attracting favor in the energy storage and power sectors. Compared to layered oxides, composite sodium iron phosphate (NFPP) among polyanionic materials has developed more rapidly. NFPP's three-dimensional ion channel structure has higher stability, and its cycle life can exceed 10,000 cycles, far superior to materials used in lithium batteries and layered oxides. Furthermore, the polyanionic framework (PO4-P2O7) has a strong covalent bond network, suppressing structural collapse and oxygen release at high temperatures and avoiding the risk of thermal runaway. However, NFPP also has some drawbacks, such as low energy density and poor conductivity. The low energy density is mainly due to its specific capacity and low voltage plateau, making it difficult to improve. Significant improvements in electrolytes are also difficult to achieve. On the other hand, conductivity can be optimized by constructing inorganic-organic composite SEI films in the electrolyte, and by adding film-forming additives to improve the stability of the electrode-electrolyte interface.
[0003] Organic sulfonates and sulfur-containing polymers generated by the electrochemical reduction of sulfonate groups are the organic components of SEI films. Furthermore, the sulfonate groups have low reduction potentials, allowing them to preferentially form films at both the positive and negative electrodes, effectively suppressing electrolyte decomposition and gas generation. Commonly used sulfonates include 1,3-propanesulfonolactone (PS) and 1,3-propylenesulfonolactone (PST). However, PS undergoes direct alkylation, exhibiting genotoxicity and carcinogenicity. PST is expensive, and its thicker film formation can lead to lower capacity utilization in NFPP materials with inherently poor conductivity. Summary of the Invention
[0004] To address the aforementioned issues, this application provides a high-performance electrolyte for composite sodium iron phosphate with high capacity retention and good cycle performance.
[0005] To achieve the above objectives, this application adopts the following technical solution: A high-performance electrolyte for composite sodium iron phosphate comprises a sodium salt, an organic solvent, and a film-forming additive, wherein the film-forming additive comprises at least trifluoromethanesulfonate and acesulfame potassium; the film-forming additive has a mass content of 0.1%-4% in the electrolyte based on the total mass of the electrolyte.
[0006] This application provides a high-performance electrolyte for composite sodium iron phosphate, which uses trifluoromethanesulfonate and acesulfame potassium as a combined additive. The electrolyte containing this additive can form an inorganic-organic composite SEI film on the positive and negative electrode sides, which can effectively suppress electrolyte side reactions and storage gas generation, improve the conductivity and service life of NFPP material, and thus prepare a sodium-ion battery with high capacity retention and good cycle performance.
[0007] Further settings include: The trifluoromethanesulfonate is selected from one or more of aluminum trifluoromethanesulfonate, zinc trifluoromethanesulfonate, ferric trifluoromethanesulfonate, and sodium trifluoromethanesulfonate; preferably, the mass content of the trifluoromethanesulfonate is 0.1%-2% based on the total mass of the electrolyte.
[0008] The acesulfame potassium salt is selected from one or more combinations of potassium acesulfame potassium, sodium acesulfame potassium, and lithium acesulfame potassium; preferably, the mass content of acesulfame potassium salt is 0.1%-2% based on the total mass of the electrolyte.
[0009] In addition to trifluoromethanesulfonate and acesulfame potassium, the film-forming additive may also include other additives selected from one or more of ethylene carbonate, vinylene carbonate, tris(trimethylsilane)phosphite, vinyl sulfate, mannitol vinyl sulfate, maleic anhydride, citrate anhydride, diethylene glycol anhydride, adiponitrile, and trifluoromethanesulfonate anhydride. Preferably, based on the total mass of the electrolyte, the mass content of the other additives in the electrolyte is 0.1%-5%.
[0010] The sodium salt is selected from one or more of sodium hexafluorophosphate, sodium difluorosulfonamide, sodium difluorooxalate borate, sodium difluorophosphate, and sodium tetrafluorooxalate borate.
[0011] The organic solvent is selected from one or more of cyclic carbonates, chain carbonates, carboxylic acid esters, and ether solvents.
[0012] The cyclic carbonate is selected from one or more of ethylene carbonate and propylene carbonate.
[0013] The chain carbonate is selected from one or more of methyl ethyl carbonate, methyl propyl carbonate, dimethyl carbonate, and diethyl carbonate.
[0014] The carboxylic acid ester is selected from one or more of ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, and propyl propionate.
[0015] The ether solvent is selected from one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, and triethylene glycol dimethyl ether.
[0016] The second aspect of this application is to provide a high-performance electrolyte for composite sodium iron phosphate, comprising the following steps: in a glove box filled with argon and with a water content of less than 1 ppm, cooling an organic solvent to below 15°C, adding sodium salt, shaking to dissolve and obtain a liquid salt solution, and adding a film-forming additive to the liquid salt solution to obtain a high-performance electrolyte for composite sodium iron phosphate.
[0017] The third aspect of this application is to provide an application of a high-performance electrolyte for composite sodium iron phosphate in the preparation of sodium-ion batteries, characterized in that: the positive electrode is composite sodium iron phosphate, the negative electrode is hard carbon material, and the electrolyte is a high-performance electrolyte for composite sodium iron phosphate.
[0018] Compared with the prior art, the technical advantages of this application are as follows: The trifluoromethanesulfonate and acesulfame potassium salt combination selected in this application constitutes a film-forming additive. The fluorine in the trifluoromethanesulfonate additive can improve antioxidant performance, low-temperature performance, and film formation, while the sulfonic acid group can generate organic sulfonates. The sodium acesulfame potassium salt (such as sodium acesulfame) can effectively form a film. The sodium ions in sodium acesulfame potassium can combine with the fluorine in trifluoromethanesulfonate to generate sodium fluoride, forming an inorganic membrane component. By constructing an organic-inorganic composite SEI membrane, the conductivity of NFPP can be effectively improved, thereby improving the capacity retention and cycle performance of sodium-ion batteries. Attached Figure Description
[0019] Figure 1 The diagram shows the capacity retention rate of the electrolytes prepared for the examples and comparative examples at 25°C and 1C / 1C charge / discharge.
[0020] Figure 2 The diagram shows the capacity retention rate of the electrolytes prepared for the examples and comparative examples at 45°C and 1C / 1C charge / discharge. Detailed Implementation
[0021] The present application will be further explained below with reference to the accompanying drawings and embodiments. Unless otherwise specified, the raw materials and reagents used in the following embodiments are all known in the art or commercially available products.
[0022] Example 1
[0023] In a glove box filled with argon and containing less than 1 ppm of water, propylene carbonate, ethyl methyl carbonate, and diethyl carbonate were mixed uniformly at a volume ratio of 1.0:1.0:1.0. The mixture was then placed in a cold trap and cooled to below 15°C. 0.9 mol / L sodium hexafluorophosphate, 0.1 mol / L sodium difluorosulfonamide, 0.05 mol / L sodium difluorooxalate borate, and 0.1 mol / L sodium difluorophosphate were added. After shaking to dissolve the solids, a liquid salt solution was obtained. Film-forming additives were added to the liquid salt solution, based on the total mass of the electrolyte, consisting of: 1% fluoroethylene carbonate, 0.5% vinyl sulfate, 0.4% vinylene carbonate, 0.5% sodium acesulfame potassium, and 0.5% aluminum trifluoromethanesulfonate, to obtain a high-performance electrolyte for NFPP.
[0024] Example 2
[0025] In a glove box filled with argon and containing less than 1 ppm of water, propylene carbonate, ethyl methyl carbonate, and diethyl carbonate were mixed uniformly at a volume ratio of 1.0:1.0:0.5 and placed in a cold trap to cool to below 15°C. Then, 0.8 mol / L sodium hexafluorophosphate, 0.2 mol / L sodium difluorosulfonamide, 0.05 mol / L sodium difluorooxalate borate, and 0.1 mol / L sodium difluorophosphate were added. After shaking to dissolve, a liquid salt solution was obtained. Film-forming additives were added to the liquid salt solution, based on the total mass of the electrolyte, namely: 1% fluoroethylene carbonate, 0.5% vinyl sulfate, 0.4% vinylene carbonate, 0.5% acesulfame potassium, and 0.5% ferric trifluoromethanesulfonate, to obtain a high-performance electrolyte for NFPP.
[0026] Example 3
[0027] In a glove box filled with argon and containing less than 1 ppm of water, ethylene carbonate, methyl ethyl carbonate, and diethyl carbonate were mixed uniformly at a volume ratio of 1.0:1.0:1.0 and placed in a cold trap to cool to below 15°C. Then, 0.8 mol / L sodium hexafluorophosphate, 0.2 mol / L sodium difluorosulfonamide, 0.1 mol / L sodium difluorooxalate borate, and 0.1 mol / L sodium difluorophosphate were added. After shaking to dissolve, a liquid salt solution was obtained. Film-forming additives were added to the liquid salt solution, based on the total mass of the electrolyte, namely: 2% fluoroethylene carbonate, 1% ethylene sulfate, 0.2% vinylene carbonate, 0.5% sodium acesulfame potassium, and 0.5% aluminum trifluoromethanesulfonate, to obtain a high-performance electrolyte for NFPP.
[0028] Example 4
[0029] In a glove box filled with argon and containing less than 1 ppm of water, propylene carbonate and ethyl methyl carbonate were mixed uniformly at a volume ratio of 1.0:1.0 and placed in a cold trap to cool to below 15°C. Then, 0.9 mol / L sodium hexafluorophosphate, 0.2 mol / L sodium difluorosulfonamide, 0.05 mol / L sodium difluorooxalate borate, and 0.1 mol / L sodium difluorophosphate were added. After shaking to dissolve, a liquid salt solution was obtained. Film-forming additives were added to the liquid salt solution, based on the total mass of the electrolyte, namely: 1% fluoroethylene carbonate, 0.5% vinyl sulfate, 0.4% vinylene carbonate, 0.5% sodium acesulfame potassium, and 0.5% zinc trifluoromethanesulfonate, to obtain a high-performance electrolyte for NFPP.
[0030] Example 5
[0031] In a glove box filled with argon and containing less than 1 ppm of water, propylene carbonate, ethyl methyl carbonate, and dimethyl carbonate were mixed uniformly at a volume ratio of 1.5:1.0:1.0 and placed in a cold trap to cool to below 15°C. 1 mol / L sodium hexafluorophosphate, 0.2 mol / L sodium difluorosulfonamide, 0.1 mol / L sodium difluorooxalate borate, and 0.05 mol / L sodium difluorophosphate were added. After shaking to dissolve, a liquid salt solution was obtained. Film-forming additives were added to the liquid salt solution, based on the total mass of the electrolyte, namely: 1% fluoroethylene carbonate, 1% ethylene sulfate, 0.6% vinylene carbonate, 0.4% sodium acesulfame potassium, and 0.6% aluminum trifluoromethanesulfonate, to obtain a high-performance electrolyte for NFPP.
[0032] The high-performance electrolytes for NFPP prepared in Examples 1-5 were applied to sodium-ion batteries (NFPP type), and their electrochemical performance was tested as shown in Examples 6-10.
[0033] Example 6
[0034] Using the high-performance NFPP electrolyte prepared in Example 1, with NFPP sodium-ion cathode material as the positive electrode and hard carbon material as the negative electrode, dry cells were fabricated by stacking. After electrolyte injection, high-temperature aging, secondary electrolyte injection, and sealing, a single-cell soft-pack battery with a capacity of 0.7Ah was successfully fabricated. Parameter settings: After capacity testing, the cells were activated at room temperature by cycling three times at 0.2C. They were then charged and discharged at 25℃ and 45℃ with a current of 1C / 1C, respectively, with a charge / discharge voltage range of 1.5-3.5V.
[0035] Example 7
[0036] The electrolyte prepared in Example 2 was injected, and the operation steps were the same as in Example 6.
[0037] Example 8
[0038] The electrolyte prepared in Example 3 was injected, and the operation steps were the same as in Example 6.
[0039] Example 9
[0040] The electrolyte prepared in Example 4 was injected, and the operation steps were the same as in Example 6.
[0041] Example 10
[0042] The electrolyte prepared in Example 5 was injected, and the operation steps were the same as in Example 6.
[0043] Comparative Example 1 In a glove box filled with argon and containing less than 1 ppm of water, propylene carbonate, methyl ethyl carbonate, and diethyl carbonate were mixed uniformly in a volume ratio of 1.0:1.0:1.0 and placed in a cold trap to cool to below 15°C. Then, 0.9 mol / L sodium hexafluorophosphate, 0.1 mol / L sodium difluorosulfonamide, 0.05 mol / L sodium difluorooxalate borate, and 0.1 mol / L sodium difluorophosphate were added. After shaking to dissolve, a liquid salt solution was obtained. Additives were added to the liquid salt solution, based on the total mass of the electrolyte, namely: 1% fluoroethylene carbonate, 0.5% vinyl sulfate, and 0.4% vinylene carbonate, to obtain the electrolyte.
[0044] Comparative Example 2 In a glove box filled with argon and containing less than 1 ppm of water, propylene carbonate, methyl ethyl carbonate, and diethyl carbonate were mixed uniformly in a volume ratio of 1.0:1.0:1.0 and placed in a cold trap to cool to below 15°C. Then, 0.9 mol / L sodium hexafluorophosphate, 0.1 mol / L sodium difluorosulfonamide, 0.05 mol / L sodium difluorooxalate borate, and 0.1 mol / L sodium difluorophosphate were added. After shaking to dissolve, a liquid salt solution was obtained. Additives were added to the liquid salt solution, based on the total mass of the electrolyte, namely: 1% fluoroethylene carbonate, 0.5% vinyl sulfate, 0.4% vinylene carbonate, and 1% 1,3-propanesulfonate lactone, to obtain the electrolyte.
[0045] Comparative Example 3 In a glove box filled with argon and containing less than 1 ppm of water, propylene carbonate, methyl ethyl carbonate, and diethyl carbonate were mixed uniformly at a volume ratio of 1.0:1.0:1.0. The mixture was then placed in a cold trap and cooled to below 15°C. 0.9 mol / L sodium hexafluorophosphate, 0.1 mol / L sodium difluorosulfonamide, 0.05 mol / L sodium difluorooxalate borate, and 0.1 mol / L sodium difluorophosphate were added. After shaking to dissolve the mixture, a liquid salt solution was obtained. Additives were added to the liquid salt solution, based on the total mass of the electrolyte: 1% fluoroethylene carbonate, 0.5% vinyl sulfate, 0.4% vinylene carbonate, and 1% 1,3-propylene sulfonate lactone, to obtain the electrolyte.
[0046] Comparative Example 4 In a glove box filled with argon and containing less than 1 ppm of water, propylene carbonate, ethyl methyl carbonate, and diethyl carbonate were mixed uniformly at a volume ratio of 1.0:1.0:1.0. The mixture was then placed in a cold trap and cooled to below 15°C. 0.9 mol / L sodium hexafluorophosphate, 0.1 mol / L sodium difluorosulfonamide, 0.05 mol / L sodium difluorooxalate borate, and 0.1 mol / L sodium difluorophosphate were added. After shaking to dissolve the solids, a liquid salt solution was obtained. Additives were added to the liquid salt solution based on the total mass of the electrolyte: 1% fluoroethylene carbonate, 0.5% vinyl sulfate, 0.4% vinylene carbonate, and 0.5% aluminum trifluoromethanesulfonate, to obtain the electrolyte for NFPP.
[0047] Comparative Example 5 In a glove box filled with argon and containing less than 1 ppm of water, propylene carbonate, methyl ethyl carbonate, and diethyl carbonate were mixed uniformly at a volume ratio of 1.0:1.0:1.0. The mixture was then placed in a cold trap and cooled to below 15°C. 0.9 mol / L sodium hexafluorophosphate, 0.1 mol / L sodium difluorosulfonamide, 0.05 mol / L sodium difluorooxalate borate, and 0.1 mol / L sodium difluorophosphate were added. After shaking to dissolve the solids, a liquid salt solution was obtained. Additives were added to the liquid salt solution based on the total mass of the electrolyte: 1% fluoroethylene carbonate, 0.5% vinyl sulfate, 0.4% vinylene carbonate, and 0.5% sodium acesulfame potassium, to obtain the electrolyte for NFPP.
[0048] The electrolytes prepared in Comparative Examples 1-5 were applied to sodium-ion batteries (NFPP type), and their electrochemical performance was tested as shown in Comparative Examples 6-10.
[0049] Comparative Example 6 Using the electrolyte prepared in Comparative Example 1, with NFPP type sodium ion positive electrode material as the positive electrode and hard carbon material as the negative electrode, dry cells were fabricated by stacking. After electrolyte injection, high-temperature aging, secondary electrolyte injection, and sealing, a single-cell soft-pack battery with a capacity of 0.7Ah was successfully fabricated. Parameter settings: After capacity testing, the cells were activated at room temperature by cycling three times at 0.2C. Then, they were charged and discharged at 25℃ and 45℃ with a current of 1C / 1C, respectively, with a charge / discharge voltage range of 1.5-3.5V.
[0050] Comparative Example 7 The electrolyte prepared in Comparative Example 2 was injected, and the operation steps were the same as those in Comparative Example 6.
[0051] Comparative Example 8 The electrolyte prepared in Comparative Example 3 was injected, and the operation steps were the same as those in Comparative Example 6.
[0052] Comparative Example 9 The electrolyte prepared in Comparative Example 4 was injected, and the operation steps were the same as those in Comparative Example 6.
[0053] Comparative Example 10 The electrolyte prepared in Comparative Example 5 was injected, and the operation steps were the same as those in Comparative Example 6.
[0054] Performance testing: The batteries assembled in Examples 6-10 and Comparative Examples 6-10 were charged and discharged at 25°C and 45°C respectively with a current of 1C / 1C, and the charge / discharge voltage range was 1.5-3.5V. The test results are as follows. Figure 1 , Figure 2 As shown: 1. Comparing Examples 6-10, it can be seen that Example 6 exhibits the best performance. This is mainly attributed to the presence of sodium ions in sodium acesulfame potassium, which not only optimizes film formation but also optimizes solvation sheath formation and reduces desolvation energy, while potassium ions themselves lack solvation energy regulation. Furthermore, aluminum trifluoromethanesulfonate has a dehydration and acid-suppressing effect compared to other trifluoromethanesulfonates. Al ions are strong Lewis acids and preferentially coordinate with trace amounts of water in the electrolyte, weakening the decomposition of sodium salts such as NaPF6 / NaBF4 by water and inhibiting the generation of HF and acidic impurities through hydrolysis. Therefore, it can maximize its performance advantages.
[0055] 2. Comparing the electrolytes of Examples 6-10 with those of Comparative Examples 6-8, it can be seen that the combined use of trifluoromethanesulfonate and acesulfame potassium salt exhibits superior performance compared to the traditional 1,3-propanesulfonate lactone and 1,3-acrylate sulfonate lactone. This is because the electrolyte prepared using trifluoromethanesulfonate and acesulfame potassium salt forms a thinner and denser film with lower impedance, resulting in higher capacity retention during room temperature cycling. Furthermore, the SEI film is more stable and less prone to decomposition under high-temperature conditions, demonstrating more stable high-temperature performance.
[0056] Comparing Examples 6-10 with Comparative Examples 9 and 10, it can be seen that: although the performance of using trifluoromethanesulfonate and acesulfame potassium alone is improved compared with 1,3-propanesulfonate lactone and 1,3-acrylate sulfonate lactone, the cycle performance is still relatively poor; however, the cycle performance is significantly improved when trifluoromethanesulfonate and acesulfame potassium are used in combination. This is attributed to the synergistic effect between trifluoromethanesulfonate and acesulfame potassium, which greatly optimizes the interface and improves the film stability. Even though the SEI film may decompose at high temperatures, it still exhibits good electrochemical performance.
[0057] The above description is merely a preferred embodiment of this application and is used to illustrate this application. It does not limit the implementation of this application in any way. Therefore, equivalent substitutions, improvements, and modifications made without departing from the principles of this application are still included within the scope of the claims of this application.
Claims
1. A high performance electrolyte for composite sodium iron phosphate, characterized by: It comprises a sodium salt, an organic solvent, and a film-forming additive, wherein the film-forming additive includes at least trifluoromethanesulfonate and acesulfame potassium; the film-forming additive has a mass content of 0.1%-4% in the electrolyte based on the total mass of the electrolyte.
2. A high performance electrolyte for composite sodium ferric phosphate according to claim 1, characterized by: The trifluoromethanesulfonate is selected from one or more of aluminum trifluoromethanesulfonate, zinc trifluoromethanesulfonate, ferric trifluoromethanesulfonate, and sodium trifluoromethanesulfonate, and the mass content of the trifluoromethanesulfonate is 0.1%-2% based on the total mass of the electrolyte.
3. A high performance electrolyte for composite sodium ferric phosphate according to claim 1, characterized by: The acesulfame potassium salt is selected from one or more of potassium acesulfame potassium, sodium acesulfame potassium, and lithium acesulfame potassium, and the mass content of acesulfame potassium salt is 0.1%-2% based on the total mass of the electrolyte.
4. The high performance electrolyte for composite sodium ferric phosphate according to claim 1, characterized by: In addition to trifluoromethanesulfonate and acesulfame potassium, the film-forming additives also include other additives: the other additives are selected from one or more of ethylene carbonate, vinylene carbonate, tris(trimethylsilane)phosphite, vinyl sulfate, mannitol vinyl sulfate, maleic anhydride, citrate anhydride, diethylene glycol anhydride, adiponitrile, and trifluoromethanesulfonate anhydride. Based on the total mass of the electrolyte, the mass content of the other additives in the electrolyte is 0.1%-5%.
5. The high performance electrolyte for composite sodium ferric phosphate according to claim 1, characterized by: The sodium salt is selected from one or more of sodium hexafluorophosphate, sodium difluorosulfonamide, sodium difluorooxalate borate, sodium difluorophosphate, and sodium tetrafluorooxalate borate.
6. The high-performance electrolyte for composite sodium iron phosphate according to claim 1, characterized in that: The organic solvent is selected from one or more of cyclic carbonates, chain carbonates, carboxylic acid esters, and ether solvents.
7. The high-performance electrolyte for composite sodium iron phosphate according to claim 1, characterized in that: The cyclic carbonate is selected from one or more of ethylene carbonate and propylene carbonate; the chain carbonate is selected from one or more of methyl ethyl carbonate, methyl propyl carbonate, dimethyl carbonate and diethyl carbonate; the carboxylic acid ester is selected from one or more of ethyl acetate, propyl acetate, methyl propionate, ethyl propionate and propyl propionate; the ether solvent is selected from one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether and triethylene glycol dimethyl ether.
8. A method for preparing a high-performance electrolyte for composite sodium iron phosphate as described in claim 1, characterized in that: Includes the following steps: In a glove box filled with argon and with a water content of less than 1 ppm, the organic solvent was cooled to below 15°C, sodium salt was added, and the solution was shaken to dissolve it, resulting in a liquid salt solution. A film-forming additive was then added to the liquid salt solution to obtain a high-performance electrolyte for composite sodium iron phosphate.
9. The application of the high-performance electrolyte for composite sodium iron phosphate as described in claim 1 in the preparation of sodium-ion batteries.
10. The application of the high-performance electrolyte for composite sodium iron phosphate according to claim 9 in the preparation of sodium-ion batteries, characterized in that: The positive electrode of the sodium-ion battery is composite sodium iron phosphate, the negative electrode is hard carbon material, and the electrolyte is a high-performance electrolyte for composite sodium iron phosphate.