High-voltage low-temperature high-power sodium-ion battery electrolyte and preparation method thereof

Abstract

This invention discloses a high-voltage, low-temperature high-power sodium-ion battery electrolyte and its preparation method, belonging to the field of sodium-ion battery electrolyte technology. The electrolyte includes sodium salt, organic solvent, and additives. The additives include a first additive and a second additive. The first additive is a fluorosulfonate, and the second additive is fluorinated benzene. The mass percentage of the additives is 0.2%-6% based on the total mass of the electrolyte. The electrolyte prepared by this invention not only achieves stable cycling under low-temperature conditions but also meets the requirements for stable cycling of O3 and P2 type layered oxide systems at 4.2V, greatly improving energy density and possessing extremely high application value.

Description

Technical Field

[0001] This application relates to the field of sodium-ion battery electrolyte technology, and specifically to a high-voltage, low-temperature, high-power sodium-ion battery electrolyte and its preparation method. Background Technology

[0002] Sodium-ion batteries, as a representative technology of the "post-lithium battery" era, have rapidly gained popularity in the fields of energy storage, start-stop systems, and two-wheeled vehicles in recent years. Their fundamental advantages are mainly the abundance of elements and electrochemical characteristics. The earth's sodium reserves are 420 times that of lithium, and the price is only 1 / 30 of that of lithium, making the price of NaPF6 about 30% lower than that of LiPF6. Moreover, it can be directly switched on existing lithium battery production lines. Sodium ions have a larger radius and a lower desolvation energy barrier than lithium, making them more suitable for high-power, start-stop, and other equipment.

[0003] However, when the ambient temperature drops below -20°C, the shortcomings of sodium electrodes become apparent: due to the significant influence of electrochemical polarization, it becomes extremely difficult for sodium ions to escape from the positive electrode. Furthermore, at low temperatures, Na in the SEI... + The transition energy barrier increases from 0.28 eV to 0.45 eV, and the interface impedance amplifies by 3-4 times, further reducing energy conversion efficiency. When the charging voltage exceeds 4.0 V, sodium batteries again fall into a "high-voltage quagmire." In particular, O3-type layered oxides are prone to phase transitions above 4.0 V, causing the structure to change from the P phase to the O phase, resulting in irreversible capacity loss. In addition, under high voltage, Mn / Ni ions dissolve from the positive electrode and migrate to the negative electrode, catalyzing the organic phase in the SEI film to regenerate Na2CO3 instead of the more stable NaF; after 100 cycles, the SEI film thickness increases from 8 nm to 35 nm, further increasing the ion transition energy barrier.

[0004] Therefore, there is an urgent need to develop a sodium-ion battery electrolyte that combines low temperature, high voltage, and high energy density. Summary of the Invention

[0005] To address the aforementioned issues, the first objective of this application is to provide a high-voltage, low-temperature, high-power sodium-ion battery electrolyte.

[0006] To achieve the above objectives, this application adopts the following technical solution: A high-voltage, low-temperature high-power sodium-ion battery electrolyte, characterized in that it comprises sodium salt, organic solvent, and additives, wherein the additives include a first additive and a second additive, the first additive being a fluorosulfonate and the second additive being fluorinated benzene, and the mass percentage of the additives is 0.2%-6% based on the total mass of the electrolyte.

[0007] Further settings include: The first additive is one or more of sodium fluorosulfonate, lithium fluorosulfonate, and potassium fluorosulfonate. Based on the total mass of the electrolyte: the mass percentage of the first additive is 0.1-3%; the mass percentage of the second additive, fluorinated benzene, is 0.1-3%.

[0008] The sodium salt is a mixture of sodium hexafluorophosphate, sodium difluorosulfonamide, sodium difluorooxalate borate, sodium difluorophosphate, and sodium tetrafluoroborate, and the content of the sodium salt is 0.5 to 1.5 mol / L based on the total volume of the electrolyte.

[0009] The organic solvent is selected from one or more of cyclic carbonates, chain carbonates, carboxylic acid esters, and ether solvents.

[0010] Preferably, the cyclic carbonate is selected from one or more of ethylene carbonate and propylene carbonate.

[0011] Preferably, the chain carbonate is selected from one or more of methyl ethyl carbonate, dimethyl carbonate, and diethyl carbonate.

[0012] Preferably, the carboxylic acid ester is selected from one or more of methyl acetate, ethyl acetate, ethyl propionate and propyl propionate.

[0013] Preferably, the ether solvent is selected from one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether.

[0014] In addition to the first and second additives, the additives may also include one or more of the following: fluoroethylene carbonate, 1,3-propyl sulfonyl lactone, vinyl sulfate, vinylene carbonate, methanedisulfonate, tris(trimethylsilyl)phosphate, etc. Particularly preferred, the following additive configurations can achieve better results: The additive is preferably a mixture of fluoroethylene carbonate, 1,3-propylsulfonate lactone, ethylene sulfate, vinylene carbonate, sodium fluorosulfonate, and fluorinated benzene, with the following content based on the total mass of the electrolyte: 1% fluoroethylene carbonate, 0.5% 1,3-propylsulfonate lactone, 1% ethylene sulfate, 0.2% vinylene carbonate, 1% sodium fluorosulfonate, and 1% fluorinated benzene.

[0015] The additive is preferably a mixture of fluoroethylene carbonate, 1,3-propylsulfonate lactone, ethylene sulfate, methylene disulfonate, sodium fluorosulfonate, and fluorinated benzene, with the following content based on the total mass of the electrolyte: 1% fluoroethylene carbonate, 0.5% 1,3-propylsulfonate lactone, 1% ethylene sulfate, 0.2% methylene disulfonate, 1.5% sodium fluorosulfonate, and 2% fluorinated benzene.

[0016] The additive is preferably a mixture of fluoroethylene carbonate, 1,3-propylsulfonate lactone, vinyl sulfate, tris(trimethylsilyl)phosphate, and fluorinated benzene, with the following content based on the total mass of the electrolyte: 1% fluoroethylene carbonate, 0.5% 1,3-propylsulfonate lactone, 1% vinyl sulfate, 0.2% tris(trimethylsilyl)phosphate, 2% sodium fluorosulfonate, and 2% fluorinated benzene.

[0017] The second aspect of this application is to provide a method for preparing a high-voltage, low-temperature high-power sodium-ion battery electrolyte, comprising the following steps: in a glove box filled with argon gas and with a water content of less than 1 ppm, an organic solvent is cooled to below 15°C, sodium salt is added, and after shaking to dissolve, a liquid salt solution is obtained; additives are added to the liquid salt solution to obtain a high-voltage, low-temperature high-power sodium-ion battery electrolyte.

[0018] The third objective of this application is to provide a high-voltage, low-temperature, high-power sodium-ion battery electrolyte for use in sodium-ion batteries, characterized in that: the high-voltage, low-temperature, and high-energy-density sodium-ion battery electrolyte is suitable for sodium-ion batteries operating at -20℃ to 25℃ and with a voltage of 2-4.2V.

[0019] Preferably, the sodium-ion battery has an O3-type or P2-type layered oxide as the positive electrode, a hard carbon material as the negative electrode, and a high-pressure, low-temperature, and high-energy-density sodium-ion battery electrolyte.

[0020] Furthermore, the applicant discovered that adjusting the composition and content of organic solvents and additives in the high-voltage, low-temperature, high-power sodium-ion battery electrolyte of this application, and applying them to sodium-ion batteries with layered oxygen O3 and layered oxygen P2 systems respectively, results in better technical performance, specifically: When applied to sodium-ion batteries with O3-type sodium-ion layered oxide cathode material, the electrolyte composition is as follows: the organic solvent is propylene carbonate, methyl ethyl carbonate, and ethyl acetate in a volume ratio of 1.0:1.0:0.5; the amount of sodium salt added based on the total volume of the electrolyte is: 0.8 mol / L sodium hexafluorophosphate, 0.1 mol / L sodium difluorosulfonyl imide, 0.05 mol / L sodium difluorooxalate borate, and 0.05 mol / L sodium difluorophosphate; the amount of additives added based on the total mass of the electrolyte is: 1% fluoroethylene carbonate, 0.5% 1,3-propylsulfonate lactone, 1% vinyl sulfate, 0.2% vinylene carbonate, 1% sodium fluorosulfonate, and 1% fluorinated benzene.

[0021] When applied to sodium-ion batteries with P2-type sodium-ion layered oxide cathode material, the electrolyte composition is as follows: the organic solvent is ethylene carbonate, propylene carbonate, methyl ethyl carbonate, and ethyl acetate in a volume ratio of 1.0:1.0:1.0:1.0; the amount of sodium salts, based on the total volume of the electrolyte, is: 0.6 mol / L sodium hexafluorophosphate, 0.2 mol / L sodium difluorosulfonyl imide, 0.1 mol / L sodium difluorooxalate borate, and 0.1 mol / L sodium difluorophosphate; the amount of additives, based on the total mass of the electrolyte, is: 1% fluoroethylene carbonate, 0.5% 1,3-propylsulfonyl lactone, 1% ethylene sulfate, 0.2% methanedisulfonate, 1.5% sodium fluorosulfonate, and 2% fluorinated benzene.

[0022] The beneficial effects of this application are as follows: This application provides a high-power sodium-ion battery electrolyte that combines high voltage and low temperature, which can not only cycle stably at low temperatures, but also achieve stable cycling at 4.2V, greatly improving the energy density.

[0023] The raw materials used in this application are inexpensive and suitable for large-scale production.

[0024] (3) Through further experiments, the applicant discovered that by adjusting the composition and content of organic solvents and additives for different cathode materials (O3 type layered oxide, P2 type layered oxide), the resulting high-voltage and low-temperature high-power sodium-ion battery electrolyte can overcome the high-voltage constraint in a low-temperature environment and make up for the defect of irreversible capacity loss caused by phase change of layered oxides under high pressure, thus possessing extremely high application value. Attached Figure Description

[0025] Figure 1 The cycling performance of the O3-type sodium-oxygen ion batteries prepared in Examples 6-10 and Comparative Examples 4-6 at 25°C and 2-4.2V is shown.

[0026] Figure 2 The cycling performance of the P2-type sodium-oxygen ion batteries prepared in Examples 11-15 and Comparative Examples 7-9 at 25°C and 2-4.2V is shown.

[0027] Figure 3 The cycling performance of the O3-type sodium-oxygen ion batteries prepared in Examples 6-10 and Comparative Examples 4-6 at -20°C and 2-4.2V is shown.

[0028] Figure 4 The cycling performance of the P2-type sodium-oxygen ion batteries prepared in Examples 11-15 and Comparative Examples 7-9 at -20°C and 2-4.2V is shown.

[0029] Figure 5The room temperature and low temperature pulse discharge performance of the O3-type sodium-oxygen ion batteries prepared in Examples 6-10 and Comparative Examples 4-6 are shown. Detailed Implementation

[0030] 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.

[0031] Example 1

[0032] In a glove box filled with argon and containing less than 1 ppm of water, propylene carbonate, methyl ethyl carbonate, and ethyl acetate 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. Based on the total volume of the electrolyte, 0.8 mol / L sodium hexafluorophosphate, 0.1 mol / L sodium difluorosulfonamide, 0.05 mol / L sodium difluorooxalate borate, and 0.05 mol / L sodium difluorophosphate were added. After shaking to dissolve, a liquid salt solution was obtained. Additives were added to the liquid salt solution, and after mixing, a high-voltage, low-temperature high-power sodium-ion battery electrolyte was obtained. The amount of additives, based on the total mass of the electrolyte, was: 1% fluoroethylene carbonate, 0.5% 1,3-propylsulfonate lactone, 1% vinyl sulfate, 0.2% vinylene carbonate, 1% sodium fluorosulfonate, and 1% fluorinated benzene.

[0033] Example 2

[0034] In a glove box filled with argon and containing less than 1 ppm of water, propylene carbonate, methyl ethyl carbonate, and ethyl acetate 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. Based on the total volume of the electrolyte, 0.8 mol / L sodium hexafluorophosphate, 0.1 mol / L sodium difluorosulfonyl imide, 0.05 mol / L sodium difluorooxalate borate, and 0.05 mol / L sodium difluorophosphate were added. After shaking to dissolve, a liquid salt solution was obtained. Additives were added to the liquid salt solution, and after mixing, a high-voltage, low-temperature high-power sodium-ion battery electrolyte was obtained. The amount of additives, based on the total mass of the electrolyte, was: 1% fluoroethylene carbonate, 0.5% 1,3-propylsulfonyl lactone, 1% vinyl sulfate, 0.2% vinylene carbonate, 1.5% sodium fluorosulfonate, and 1% fluorinated benzene.

[0035] Example 3

[0036] In a glove box filled with argon and containing less than 1 ppm of water, propylene carbonate, methyl ethyl carbonate, and ethyl acetate 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. Based on the total volume of the electrolyte, 0.8 mol / L sodium hexafluorophosphate, 0.1 mol / L sodium difluorosulfonyl imide, 0.05 mol / L sodium difluorooxalate borate, and 0.05 mol / L sodium difluorophosphate were added. After shaking to dissolve, a liquid salt solution was obtained. Additives were added to the liquid salt solution, and after mixing, a high-voltage, low-temperature high-power sodium-ion battery electrolyte was obtained. The amount of additives, based on the total mass of the electrolyte, was: 1% fluoroethylene carbonate, 0.5% 1,3-propylsulfonyl lactone, 1% vinyl sulfate, 0.2% vinylene carbonate, 1.5% sodium fluorosulfonate, and 2% fluorinated benzene.

[0037] Example 4

[0038] In a glove box filled with argon and containing less than 1 ppm of water, propylene carbonate, methyl ethyl carbonate, and ethyl acetate were mixed uniformly at a volume ratio of 1.0:1.0:0.5. The mixture was then placed in a cold trap and cooled to below 15°C. Based on the total volume of the electrolyte, 0.6 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. Additives were added to the liquid salt solution, and after mixing, a high-voltage, low-temperature high-power sodium-ion battery electrolyte was obtained. The amount of additives, based on the total mass of the electrolyte, was: 1% fluoroethylene carbonate, 0.5% 1,3-propylsulfonyl lactone, 1% vinyl sulfate, 2% sodium fluorosulfonate, and 2% fluorinated benzene.

[0039] Example 5

[0040] In a glove box filled with argon and containing less than 1 ppm of water, propylene carbonate, methyl ethyl carbonate, and ethyl acetate 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. Based on the total volume of the electrolyte, 1.0 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. Additives were added to the liquid salt solution, and after mixing, a high-voltage, low-temperature high-power sodium-ion battery electrolyte was obtained. The amount of additives, based on the total mass of the electrolyte, was: 1% fluoroethylene carbonate, 0.5% 1,3-propylsulfonyl lactone, 1% vinyl sulfate, 2.5% sodium fluorosulfonate, and 2.5% fluorinated benzene.

[0041] Comparative Example 1 In a glove box filled with argon and containing less than 1 ppm of water, propylene carbonate, methyl ethyl carbonate, and ethyl acetate 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. Based on the total volume of the electrolyte, 0.8 mol / L sodium hexafluorophosphate, 0.1 mol / L sodium difluorosulfonamide, 0.05 mol / L sodium difluorooxalate borate, and 0.05 mol / L sodium difluorophosphate were added. After shaking to dissolve, a liquid salt solution was obtained. Additives were added to the liquid salt solution, and after mixing, a sodium-ion battery electrolyte was obtained. The amount of additives, based on the total mass of the electrolyte, was: 1% fluoroethylene carbonate, 0.5% 1,3-propylsulfonyl lactone, 1% vinyl sulfate, 0.2% vinylene carbonate, and 1.5% sodium fluorosulfonate.

[0042] Comparative Example 2 In a glove box filled with argon and containing less than 1 ppm of water, propylene carbonate, methyl ethyl carbonate, and ethyl acetate 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. Based on the total volume of the electrolyte, 0.8 mol / L sodium hexafluorophosphate, 0.1 mol / L sodium difluorosulfonyl imide, 0.05 mol / L sodium difluorooxalate borate, and 0.05 mol / L sodium difluorophosphate were added. After shaking to dissolve, a liquid salt solution was obtained. Additives were added to the liquid salt solution, and after mixing, a sodium-ion battery electrolyte was obtained. The amount of additives, based on the total mass of the electrolyte, was: 1% fluoroethylene carbonate, 0.5% 1,3-propylsulfonyl lactone, 1% vinyl sulfate, 0.2% vinylene carbonate, and 1.5% fluorinated benzene.

[0043] Comparative Example 3 In a glove box filled with argon and containing less than 1 ppm of water, propylene carbonate, methyl ethyl carbonate, and ethyl acetate 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. Based on the total volume of the electrolyte, 0.8 mol / L sodium hexafluorophosphate, 0.1 mol / L sodium difluorosulfonamide, 0.05 mol / L sodium difluorooxalate borate, and 0.05 mol / L sodium difluorophosphate were added. After shaking to dissolve, a liquid salt solution was obtained. Additives were added to the liquid salt solution, and after mixing, a sodium-ion battery electrolyte was obtained. The amount of additives, based on the total mass of the electrolyte, was: 1% fluoroethylene carbonate, 0.5% 1,3-propylsulfonate lactone, 1% vinyl sulfate, and 0.2% vinylene carbonate.

[0044] Performance testing: The performance of the high-voltage, low-temperature, high-power sodium-ion battery electrolytes prepared in Examples 1-5 in sodium-ion batteries (O3-type oxygen layer) was investigated, as shown in Examples 6-10.

[0045] Example 6

[0046] Using the electrolyte prepared in Example 1, with O3-type sodium ion layered oxide as the positive electrode material 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 0.95Ah was completed. Parameter settings: After capacity testing, the cells were cyclically charged three times at 0.1C at room temperature, and then placed in environmental chambers at different temperatures for charge-discharge cycle tests. Constant current charge-discharge was performed at 1C at 25℃ and at 0.2C at -20℃, with a charge-discharge voltage range of 2.0-4.2V.

[0047] Example 7

[0048] The operation steps are the same as in Example 6, except that the electrolyte prepared in Example 2 is used for injection.

[0049] Example 8

[0050] The operation steps are the same as in Example 6, except that the electrolyte prepared in Example 3 is used for injection.

[0051] Example 9

[0052] The operation steps are the same as in Example 6, except that the electrolyte prepared in Example 4 is used for injection.

[0053] Example 10

[0054] The operation steps are the same as in Example 6, except that the electrolyte prepared in Example 5 is used for injection.

[0055] The performance of the sodium-ion battery electrolytes prepared in Comparative Examples 1-3 in sodium-ion batteries (O3-type oxygen layer) was investigated, as shown in Comparative Examples 4-6.

[0056] Comparative Example 4 Using the electrolyte prepared in Comparative Example 1, with O3-type sodium ion layered oxide as the positive electrode material and hard carbon material as the negative electrode, dry cells were fabricated through stacking. After electrolyte injection, high-temperature aging, secondary electrolyte injection, and sealing, a single-cell soft-pack battery with a capacity of 0.95Ah was successfully fabricated. Parameter settings: After capacity testing, the cells were cycled three times at 0.1C at room temperature, and then placed in environmental chambers at different temperatures for charge-discharge cycle tests. Constant current charge-discharge was performed at 1C at 25℃ and at 0.2C at -20℃, with a charge-discharge voltage range of 2.0-4.2V.

[0057] Comparative Example 5 The operation steps are the same as those in Comparative Example 4, except that the electrolyte prepared in Comparative Example 2 is used for injection.

[0058] Comparative Example 6 The operation steps are the same as those in Comparative Example 4, except that the electrolyte prepared in Comparative Example 3 is used for injection.

[0059] Test results and analysis: The experimental data of sodium-ion batteries (type 03 layered oxygen) assembled in Examples 6-10 and Comparative Examples 4-6 were statistically analyzed, such as... Figure 1 , Figure 3 , Figure 5 As shown: (1) The high voltage performance of the batteries in Examples 6-10 after adding sodium fluorosulfonate and fluorinated benzene was improved compared with that of the battery in Comparative Example 6 without adding sodium fluorosulfonate or fluorinated benzene.

[0060] (2) Compared with Comparative Examples 4 and 5, which used electrolytes with only sodium fluorosulfonate or fluorinated benzene, the electrolyte using both sodium fluorosulfonate and fluorinated benzene showed better performance. Example 8 exhibited the best performance in room temperature cycling, mainly due to the synergistic effect of sodium fluorosulfonate and fluorinated benzene at certain addition levels. Specifically, sodium fluorosulfonate, as an impedance-reducing additive, produces a thinner and denser SEI film, and its desolvation barrier is lower, making its intrinsic properties more favorable for low-temperature performance. Fluorinated benzene, as a fluorinated solvent, not only optimizes high-voltage performance but also reduces electrolyte viscosity, further enhancing the transport capacity of sodium ions in the electrolyte liquid phase.

[0061] The performance of the high-voltage, low-temperature, high-power sodium-ion battery electrolytes prepared in Examples 1-5 in sodium-ion batteries (P2 type layered oxygen) was investigated, as shown in Examples 11-15.

[0062] Example 11

[0063] Using the electrolyte prepared in Example 1, with P2-type sodium ion layered oxide as the positive electrode material 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 cyclically charged three times at 0.1C at room temperature, and then placed in environmental chambers at different temperatures for charge-discharge cycle tests. Constant current charge-discharge was performed at 1C at 25℃ and at 0.2C at -20℃, with a charge-discharge voltage range of 2.0-4.2V.

[0064] Example 12

[0065] The operation steps are the same as in Example 11, except that the electrolyte prepared in Example 2 is used for injection.

[0066] Example 13

[0067] The operation steps are the same as in Example 11, except that the electrolyte prepared in Example 3 is used for injection.

[0068] Example 14

[0069] The operation steps are the same as in Example 11, except that the electrolyte prepared in Example 4 is used for injection.

[0070] Example 15

[0071] The operation steps are the same as in Example 11, except that the electrolyte prepared in Example 5 is used for injection.

[0072] The performance of the sodium-ion battery electrolytes prepared in Comparative Examples 1-3 in sodium-ion batteries (P2 type layered oxygen) was investigated, as shown in Comparative Examples 7-9.

[0073] Comparative Example 7 Using the electrolyte prepared in Comparative Example 1, and employing P2-type sodium-ion layered oxide positive electrode material and hard carbon material negative electrode, dry cells were fabricated through 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 cyclically charged three times at 0.1C at room temperature, and then subjected to charge-discharge cycle tests in environmental chambers at different temperatures. Constant current charge-discharge was performed at 1C at 25℃ and at 0.2C at -20℃, with a charge-discharge voltage range of 1.5-4.2V.

[0074] Comparative Example 8 The operation steps are the same as in Example 7, except that the electrolyte prepared in Comparative Example 2 is used for injection.

[0075] Comparative Example 9 The operation steps are the same as in Example 8, except that the electrolyte prepared in Comparative Example 3 is used for injection.

[0076] Test results and analysis: (1) The experimental data of sodium-ion batteries (P2 type oxygen layer) in Examples 11-15 were statistically analyzed, such as... Figure 2 , Figure 4 As shown, the addition of sodium fluorosulfonate and fluorinated benzene to the electrolyte significantly improves the performance of the P2-type laminar oxygen system. Fluorine in fluorinated benzene has extremely high electronegativity, which can significantly reduce the HOMO level of the solvent and improve its antioxidant properties. Sodium fluorosulfonate is also more beneficial for low-temperature performance. Even though the P2-type laminar oxygen system has a high phase transition potential, the organic combination of sodium fluorosulfonate and fluorinated benzene can significantly optimize its performance.

[0077] (2) Statistical analysis was performed on the experimental data of sodium-ion batteries (P2 type oxygen layer) in proportions 7-9, such as... Figure 2 , Figure 4As shown, the example in which neither sodium fluorosulfonate nor fluorinated benzene was added to the P2-type layered oxide exhibited the worst performance, indicating that conventional electrolytes have poor oxidation and polarization resistance under high pressure or low temperature, failing to meet the requirements of specific applications. Examples with the addition of sodium fluorosulfonate or fluorinated benzene significantly improved this. Data shows that fluorinated benzene provides a more significant improvement in high-pressure performance, while the low-temperature performance of both is relatively similar, indicating that both improve low-temperature performance. The example using a combination of sodium fluorosulfonate and fluorinated benzene showed the best performance.

[0078] 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-voltage, low-temperature high-power sodium-ion battery electrolyte, characterized in that, It includes sodium salt, organic solvent, and additives. The additives include a first additive and a second additive. The first additive is a fluorosulfonate, and the second additive is fluorinated benzene. The mass percentage of the additives is 0.2%-6% based on the total mass of the electrolyte.

2. The high-voltage, low-temperature high-power sodium-ion battery electrolyte according to claim 1, characterized in that: The first additive is one or more of sodium fluorosulfonate, lithium fluorosulfonate, and potassium fluorosulfonate, and the mass percentage of fluorosulfonate is 0.1-3% based on the total mass of the electrolyte.

3. The high-voltage and low-temperature high-power sodium-ion battery electrolyte according to claim 1, characterized in that: The second additive, fluorinated benzene, accounts for 0.1-3% of the total mass of the electrolyte.

4. The high-voltage, low-temperature high-power sodium-ion battery electrolyte according to claim 1, characterized in that: The sodium salt is a mixture of sodium hexafluorophosphate, sodium difluorosulfonamide, sodium difluorooxalate borate, sodium difluorophosphate, and sodium tetrafluoroborate, and the amount of sodium salt added is 0.5 to 1.5 mol / L based on the total volume of the electrolyte.

5. The high-voltage, low-temperature high-power sodium-ion battery electrolyte 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.

6. The high-voltage, low-temperature high-power sodium-ion battery electrolyte according to claim 5, 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, dimethyl carbonate and diethyl carbonate; the carboxylic acid ester is selected from one or more of methyl acetate, ethyl acetate, ethyl propionate and propyl propionate; the ether solvent is selected from one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether.

7. The high-voltage, low-temperature high-power sodium-ion battery electrolyte according to claim 1, characterized in that: In addition to the first and second additives, the additives also include other additives selected from one or more of fluoroethylene carbonate, 1,3-propylsulfonyl lactone, ethylene sulfate, vinylene carbonate, methanedisulfonate, and tris(trimethylsilyl)phosphate.

8. A method for preparing a high-voltage, low-temperature high-power sodium-ion battery electrolyte according to any one of claims 1-8, characterized in that, Includes the following steps: In a glove box filled with argon and with a water content of less than 1 ppm, an organic solvent is cooled to below 15°C, sodium salt is added, and the solution is shaken to dissolve it, resulting in a liquid salt solution. Additives are then added to the liquid salt solution to obtain a high-power sodium-ion battery electrolyte with both high voltage and low temperature.

9. The application of a high-voltage, low-temperature, high-power sodium-ion battery electrolyte as described in any one of claims 1-8 in sodium-ion batteries, characterized in that: The sodium-ion battery uses O3-type or P2-type layered oxide as the positive electrode, hard carbon material as the negative electrode, and high-power sodium-ion battery electrolyte with high voltage and low temperature.

10. The application of a high-voltage, low-temperature, high-power sodium-ion battery electrolyte according to claim 9 in sodium-ion batteries, characterized in that: When applied to sodium-ion batteries with O3-type sodium-ion layered oxide as the cathode material, the electrolyte composition is as follows: the organic solvent is propylene carbonate, methyl ethyl carbonate, and ethyl acetate in a volume ratio of 1.0:1.0:0.5; the amount of sodium salt added based on the total volume of the electrolyte is: 0.8 mol / L sodium hexafluorophosphate, 0.1 mol / L sodium difluorosulfonyl imide, 0.05 mol / L sodium difluorooxalate borate, and 0.05 mol / L sodium difluorophosphate; the amount of additives added based on the total mass of the electrolyte is: 1% fluoroethylene carbonate, 0.5% 1,3-propylsulfonate lactone, 1% vinyl sulfate, 0.2% vinylene carbonate, 1% sodium fluorosulfonate, and 1% fluorinated benzene. When applied to sodium-ion batteries with P2-type sodium-ion layered oxide as the cathode material, the electrolyte composition is as follows: the organic solvent is ethylene carbonate, propylene carbonate, methyl ethyl carbonate, and ethyl acetate in a volume ratio of 1.0:1.0:1.0:1.0; the amount of sodium salts, based on the total volume of the electrolyte, is: 0.6 mol / L sodium hexafluorophosphate, 0.2 mol / L sodium difluorosulfonyl imide, 0.1 mol / L sodium difluorooxalate borate, and 0.1 mol / L sodium difluorophosphate; the amount of additives, based on the total mass of the electrolyte, is: 1% fluoroethylene carbonate, 0.5% 1,3-propylsulfonyl lactone, 1% ethylene sulfate, 0.2% methanedisulfonate, 1.5% sodium fluorosulfonate, and 2% fluorinated benzene.

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