Electrolyte containing silicon-based lithium salt, preparation method and application thereof
By introducing the silicon-based lithium salt additive lithium trimethylsilyl acetate into lithium-ion batteries, the problem of electrolyte solidification at low temperatures has been solved, enabling the batteries to operate normally and safely in low-temperature environments.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- XIAMEN INST OF RARE EARTH MATERIALS
- Filing Date
- 2022-09-29
- Publication Date
- 2026-05-29
AI Technical Summary
Lithium-ion batteries experience a sharp decline in performance at low temperatures, leading to capacity degradation and safety hazards, which limits their application in extreme environments.
Silicon-based lithium salts, especially trimethylsilyl acetate, are used as electrolyte additives to improve the fluidity of the electrolyte at low temperatures.
It effectively improves the low-temperature performance of the electrolyte, ensuring that the battery can still work normally at low temperatures, avoiding lithium plating on the negative electrode, and improving the low-temperature discharge capacity and safety of the battery.
Smart Images
Figure CN116525936B_ABST
Abstract
Description
Technical Field
[0001] This application relates to a silicon-based lithium salt electrolyte, its preparation method and application, belonging to the field of electrolyte additive technology. Background Technology
[0002] Lithium-ion batteries are widely used in automotive power and grid energy storage due to their advantages such as long cycle life, high specific capacity, and small size. The basic components of a lithium-ion battery include a positive electrode, a negative electrode, a separator, and an electrolyte. The electrolyte is composed of lithium salt, solvent, and additives. The traditional lithium salt is LiPF6, the solvent is a mixture of organic solvents such as ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (DEC), and the additives are vinylene carbonate (VC) and fluoroethylene carbonate (FEC). Different electrolyte compositions result in significant differences in lithium-ion battery performance. Especially at low temperatures, the increased viscosity or even solidification of the electrolyte and the decrease in conductivity can lead to a sharp decline in lithium-ion battery performance, causing the battery to fail to discharge at low temperatures. More seriously, low-temperature charging easily leads to lithium plating on the negative electrode, causing not only a rapid decrease in battery capacity but also serious safety hazards. In northern my country, the cold winter weather directly limits the promotion of new energy vehicles, which directly affects my country's energy strategy. Therefore, developing low-temperature electrolytes is beneficial for broadening the application range of lithium-ion batteries and improving their application value in extreme environments. Summary of the Invention
[0003] To address the aforementioned issues, this application provides a silicon-based lithium salt as an electrolyte additive and introduces it into conventional electrolytes to increase the fluidity of the electrolyte at low temperatures, thereby effectively improving the low-temperature performance of conventional electrolytes.
[0004] According to one aspect of this application, a silicon-based lithium salt electrolyte is provided, comprising a lithium salt, an additive, and a solvent, wherein the additive is lithium trimethylsilyl acetate.
[0005] Optionally, the mass ratio of the lithium salt, additives and solvent is 1:0.1 to 1:2 to 6.
[0006] Optionally, the lithium salt is selected from at least one of lithium hexafluorophosphate and lithium tetrafluorophosphate.
[0007] Optionally, the solvent is selected from at least one of carbonate solvent mixtures and carboxylic acid ester solvent mixtures.
[0008] Optionally, the carbonate mixed solvent is selected from at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, and ethyl methyl carbonate.
[0009] Optionally, the carboxylic acid ester mixed solvent is selected from at least one of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, and methyl butyrate.
[0010] According to another aspect of this application, a method for preparing an electrolyte is provided, wherein raw materials containing lithium salt, additives, and solvent are stirred under an inactive atmosphere, wherein the additive is lithium trimethylsilyl acetate.
[0011] Optionally, the stirring conditions are: a rotation speed of 200 to 600 rpm and a stirring time of 24 to 48 hours.
[0012] Optionally, the inactive atmosphere is selected from at least one of argon, helium, and nitrogen.
[0013] Optionally, the concentration of the lithium salt is 0.5 to 3 mol / L.
[0014] Optionally, the concentration of the lithium salt is selected from any value or a range between two values from 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, and 3 mol / L.
[0015] Optionally, the additive accounts for 0.1% to 10% of the mass of the electrolyte.
[0016] Optionally, the mass of the additive accounts for any value or a range between two values from 0.1%, 1%, 2.5%, 5%, and 10% of the electrolyte.
[0017] Optionally, the preparation method of the lithium trimethylsilyl acetate is as follows:
[0018] 1) Add trimethylsilyl acetic acid solution to lithium compound solution, adjust the pH of the mixture to 5-8 and stir to obtain reaction solution A;
[0019] 2) Centrifuge reaction solution A, take supernatant B, freeze dry, and grind to obtain trimethylsilyl acetate lithium.
[0020] Optionally, the reaction conditions are: temperature 50–80°C, time 0.5–2 h;
[0021] Optionally, the temperature of the reaction is selected from any value or a range between two values of 50°C, 60°C, 65°C, 70°C, and 80°C.
[0022] Optionally, the reaction time is selected from any value or a range between two values from 0.5h, 1h, 1.25h, 1.75h, and 2h.
[0023] Optionally, the freeze-drying temperature is -20 to -60°C.
[0024] Optionally, the freeze-drying temperature is selected from any value or a range between two values from -20℃, -30℃, -40℃, -50℃, and -60℃.
[0025] Optionally, the lithium compound is selected from at least one of lithium hydroxide, lithium chloride, lithium sulfate, lithium carbonate, and lithium phosphate.
[0026] Optionally, the concentration of the lithium compound solution is 0.5–3 mol / L.
[0027] Optionally, the concentration of the lithium compound solution is selected from any value or a range between two values from 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, and 3 mol / L.
[0028] Optionally, the concentration of the trimethylsilyl acetic acid solution is 0.5–3 mol / L.
[0029] Optionally, the concentration of the trimethylsilyl acetic acid solution is selected from any value or a range between two values from 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, and 3 mol / L.
[0030] According to another aspect of this application, a button cell battery pack is provided, wherein the electrolyte is selected from the electrolyte described above or an electrolyte prepared according to the method described above.
[0031] As a specific application, the electrolyte provides a button cell assembly method in which the positive electrode shell, positive electrode plate, separator, negative electrode plate, gasket, spring, and negative electrode shell are assembled in sequence in an argon-filled glove box. Before encapsulation, 100 μm of the electrolyte prepared by the above method is added.
[0032] The cathode materials include lithium nickel cobalt manganese oxide, lithium phosphate, lithium manganese oxide, and lithium cobalt oxide.
[0033] Negative electrode materials include graphite, silicon, silicon-carbon, and lithium titanate.
[0034] The beneficial effects that this application can produce include:
[0035] 1) The silicon-based lithium salt electrolyte provided in this application uses trimethylsilyl acetate as an electrolyte additive, which effectively improves the fluidity of traditional electrolytes at low temperatures, thereby improving the low-temperature performance of the electrolyte. Attached Figure Description
[0036] Figure 1 The XRD pattern of lithium trimethylsilyl acetate in Example 1 of this application;
[0037] Figure 2 The infrared image of lithium trimethylsilyl acetate in Example 1 of this application;
[0038] Figure 3 This is a schematic diagram showing the state of the electrolyte in Example 1 and Comparative Example 1 of this application at -40°C.
[0039] Figure 4 The above are charge-discharge curves of the batteries of Example 1 and Comparative Example 1 of this application at 0.2C under conditions of 25°C and -40°C.
[0040] Figure 5 This is the overall flowchart of Embodiment 1 of this application. Detailed Implementation
[0041] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.
[0042] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.
[0043] The analysis method in the embodiments of this application is as follows:
[0044] XRD patterns of lithium trimethylsilyl acetate were obtained using an X-ray diffractometer and analyzed.
[0045] The infrared spectrum of lithium trimethylsilyl acetate was obtained using Fourier transform infrared spectroscopy diffractometer for analysis;
[0046] The battery was tested by discharging it at a rate of 0.2C at -40°C in a constant temperature chamber.
[0047] Example 1
[0048] pass Figure 5 As can be seen, the overall process of synthesizing silicon-based lithium salt additives, preparing electrolytes, and testing batteries in this embodiment is as follows:
[0049] 1) Synthesis method of silicon-based lithium salt additive: 10 mL of 1 M lithium hydroxide solution was placed in a water bath at 60 °C, and 10 mL of 1 M trimethylsilylacetic acid solution was slowly added dropwise to adjust the pH to 7. The mixture was stirred for 1 h to obtain reaction solution A. The supernatant B of reaction solution A was centrifuged and freeze-dried at -40 °C and ground to obtain lithium trimethylsilylacetic acid.
[0050] The XRD pattern and infrared spectrum of the prepared trimethylsilyl acetate are as follows: Figure 1 and Figure 2 As shown, according to Figure 1It can be seen that the main phase peak of lithium trimethylsilyl acetate does not coincide with the main phase peaks of both trimethylsilyl acetate and lithium hydroxide, suggesting that the synthesis of lithium trimethylsilyl acetate was successful. Meanwhile, based on... Figure 2 It can be known that the range is 2500-3300cm -1 Within the wavelength range, the peak intensity of lithium trimethylsilyl acetate showed a significant change relative to trimethylsilylacetic acid – a stretching change of the COOH group, further indicating the successful synthesis of lithium trimethylsilyl acetate.
[0051] 2) Electrolyte preparation method: Prepare the solvent according to the volume ratio EC:DMC:DEC = 3:4:3. Add lithium salt LiPF6 and additive lithium trimethylsilyl acetate to the solvent. The concentration of LiPF6 in the solvent is 1M, and the mass fraction of lithium trimethylsilyl acetate in the solvent is 1wt%. Stir at 200 rpm for 24 hours at room temperature for later use.
[0052] Where EC stands for ethylene carbonate;
[0053] DMC stands for dimethyl carbonate.
[0054] DEC stands for methyl ethyl carbonate.
[0055] 3) Low-temperature performance test method for electrolyte: Lithium nickel cobalt manganese oxide was used as the positive electrode and graphite as the negative electrode to assemble the battery, and the electrolyte from step 2 of Example 1 was added. The battery was discharged at a rate of 0.2C at -40℃.
[0056] Comparative Example 1
[0057] A battery was assembled using lithium nickel cobalt manganese oxide as the positive electrode and graphite as the negative electrode. A 1M LiPF6EC:DMC:DEC ratio of 3:4:3 was used as the base electrolyte. The battery was discharged at a rate of 0.2C at -40℃.
[0058] The electrolyte prepared in Example 1 and the electrolyte in Comparative Example 1 are in the following states at -40°C: Figure 3 As shown, through Figure 3 It can be seen that the electrolyte in Example 1 with added silicon-based lithium salt remains a flowing liquid at -40°C, while the electrolyte in Comparative Example 1 without added silicon-based lithium salt has solidified at -40°C. Therefore, it can be concluded that adding trimethylsilyl lithium acetate to the electrolyte can effectively improve the fluidity of the electrolyte at low temperatures.
[0059] The batteries from Example 1 and Comparative Example 1 were discharged at -40°C at a rate of 0.2C. The data obtained are as follows: Figure 4 As shown, through Figure 4It can be seen that the discharge capacity of Example 1 remains at around 100 mAh / g at -40℃, while the discharge capacity of Comparative Example 1 drops sharply to 30 mAh / g at -40℃. Furthermore, the discharge capacities of both are essentially the same at room temperature (25℃), indicating that silicon-based lithium sources are beneficial for improving the low-temperature performance of the battery without affecting its room-temperature performance.
[0060] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.
Claims
1. An electrolyte containing a silicon-based lithium salt, characterized in that, Includes lithium salts, additives, and solvents; The additive is lithium trimethylsilyl acetate.
2. The electrolyte according to claim 1, characterized in that, The mass ratio of the lithium salt, additives and solvent is 1:0.1~1:2~6.
3. The electrolyte according to claim 1, characterized in that, The lithium salt is selected from at least one of lithium hexafluorophosphate and lithium tetrafluorophosphate.
4. The electrolyte according to claim 1, characterized in that, The solvent is selected from at least one of carbonate solvent mixtures and carboxylic acid ester solvent mixtures.
5. The electrolyte according to claim 4, characterized in that, The carbonate mixed solvent is selected from at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, and ethyl methyl carbonate.
6. The electrolyte according to claim 4, characterized in that, The carboxylic acid ester mixed solvent is selected from at least one of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, and methyl butyrate.
7. A method for preparing the electrolyte according to any one of claims 1 to 6, characterized in that, Includes the following steps: Under an inactive atmosphere, the raw materials containing lithium salt, additives, and solvents are stirred. The additive is lithium trimethylsilyl acetate.
8. The preparation method according to claim 7, characterized in that, The stirring conditions are: 200~600 rpm, 24~48 h.
9. The preparation method according to claim 7, characterized in that, The inactive atmosphere is selected from at least one of argon, helium, and nitrogen.
10. The preparation method according to claim 7, characterized in that, The concentration of the lithium salt is 0.5~3 mol / L.
11. The preparation method according to claim 7, characterized in that, The additive accounts for 0.1 to 10% of the mass of the electrolyte.
12. The preparation method according to claim 7, characterized in that, The preparation method of the trimethylsilyl acetate lithium is as follows: 1) Add trimethylsilyl acetic acid solution to lithium compound solution, adjust the pH of the mixture to 5-8 and stir to obtain reaction solution A; 2) Centrifuge reaction solution A, freeze-dry the supernatant B, and grind it to obtain lithium trimethylsilyl acetate.
13. The preparation method according to claim 12, characterized in that, The reaction conditions are: temperature 50~80℃, time 0.5~2h.
14. The preparation method according to claim 12, characterized in that, The freeze-drying temperature is -20 to -60°C.
15. The preparation method according to claim 12, characterized in that, The lithium compound is selected from at least one of lithium hydroxide, lithium chloride, lithium sulfate, lithium carbonate, and lithium phosphate.
16. The preparation method according to claim 12, characterized in that, The concentration of the lithium compound solution is 0.5~3 mol / L.
17. The preparation method according to claim 12, characterized in that, The concentration of the trimethylsilyl acetic acid solution is 0.5~3 mol / L.
18. A button cell battery pack, characterized in that, The electrolyte is the electrolyte of silicon-based lithium salt according to any one of claims 1 to 6 or the electrolyte of silicon-based lithium salt obtained by the preparation method according to any one of claims 7 to 17.