WO-2026092310-A1 - ELECTROLYTE SOLUTION AND SECONDARY BATTERY

Abstract

An electrolyte solution and a secondary battery. The electrolyte solution comprises a solvent, an additive, and an electrolyte, wherein the solvent comprises a fluorinated solvent, the fluorinated solvent comprises a fluorinated ethylene carbonate and a fluorinated chain ester, and the fluorinated chain ester comprises a compound represented by formula I and a compound represented by formula II, wherein R 2 and R 4 are each independently selected from fluorine-substituted C1-C6 alkyl groups, and R 1 and R 3 are each independently selected from C1-C6 alkyl groups; the mass ratio of the fluorinated ethylene carbonate to the fluorinated chain ester is 1:(0.33-4), the mass ratio of the compound represented by formula I to the compound represented by formula II is 1:(0.33-3), and based on the mass of the electrolyte solution, the mass percentage of the fluorinated solvent is 20% to 80%; the additive comprises tetravinylsilane, and based on the mass of the electrolyte solution, the mass percentage of the tetravinylsilane is M, where 0.02%≤M≤3%. The fluorinated ethylene carbonate, the compound represented by formula I, the compound represented by formula II, and the tetravinylsilane act synergistically so that the electrolyte solution has appropriate viscosity and higher oxidation resistance, while also improving the negative impact of defluorination of the fluorinated solvent on a positive electrode, thereby improving the high-temperature cycling performance and high-temperature storage performance of the secondary battery in high-voltage conditions.

Inventors

• CAI, Wanqian
• XIE, Tian
• YU, Chaochen

Assignees

• 广州天赐高新材料股份有限公司

Dates

Publication Date

20260507

Application Date

20251024

Priority Date

20241030

Claims (11)

1. An electrolyte comprising a solvent, an additive, and an electrolyte, wherein the solvent comprises a fluorinated solvent, the fluorinated solvent comprising fluoroethylene carbonate and fluorinated chain esters, and the fluorinated chain esters comprising at least one compound of Formula I and at least one compound of Formula II. R2 and R4 are each independently selected from fluorine-substituted C1-C6 alkyl groups, and R1 and R3 are each independently selected from C1-C6 alkyl groups. The mass ratio of the fluoroethylene carbonate to the fluorochain ester is 1:(0.33-4), the mass ratio of the compound shown in Formula I to the compound shown in Formula II is 1:(0.33-3), and the mass percentage of the fluorosolvent is 20% to 80% based on the mass of the electrolyte. The additive includes tetraethylenesilane, and the mass percentage of the tetraethylenesilane is M, based on the mass of the electrolyte, where 0.02% ≤ M ≤ 3%.
2. The electrolyte according to claim 1, wherein the electrolyte satisfies at least one of the following conditions: (1) The compound shown in Formula I has 4 to 6 carbon atoms and 3 to 5 fluorine atoms; (2) The compound shown in Formula II has 4 to 6 carbon atoms and 2 to 4 fluorine atoms.
3. The electrolyte according to claim 1, wherein the compound represented by formula I is selected from at least one of the following compounds: The compound represented by Formula II is selected from at least one of the following compounds:
4. The electrolyte according to any one of claims 1 to 3, wherein the electrolyte satisfies at least one of the following conditions: (1) Based on the mass of the electrolyte, the mass percentage of the fluoroethylene carbonate is A, 10% ≤ A ≤ 40%; (2) Based on the mass of the electrolyte, the mass percentage of the compound shown in Formula I is B, where 5% ≤ B ≤ 20%; (3) Based on the mass of the electrolyte, the mass percentage of the compound shown in Formula II is C, where 5% ≤ C ≤ 30%.
5. The electrolyte according to any one of claims 1 to 3, wherein the electrolyte satisfies at least one of the following conditions: (1) Based on the mass of the electrolyte, the mass percentage of the fluoroethylene carbonate is A, 10% ≤ A ≤ 30%; (2) Based on the mass of the electrolyte, the mass percentage of the compound shown in Formula I is B, 10% ≤ B ≤ 20%; (3) Based on the mass of the electrolyte, the mass percentage of the compound shown in Formula II is C, 10% ≤ C ≤ 30%; (4) Based on the mass of the electrolyte, the mass percentage of the fluorinated solvent is 40% to 60%; (5) The mass ratio of the fluoroethylene carbonate to the fluorochain ester is 1:(1-3), and the mass ratio of the compound shown in Formula I to the compound shown in Formula II is 1:(1-3).
6. The electrolyte according to any one of claims 1 to 3, wherein the solvent comprises a non-fluorinated solvent selected from at least one of ethylene carbonate, propylene carbonate, γ-butyrolactone, phenyl acetate, 1,4-butylsulfonate lactone, methyl ethyl carbonate, diethyl carbonate, methyl propyl carbonate, methyl formate, ethyl acetate, methyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, and ethylene glycol dimethyl ether.
7. The electrolyte according to any one of claims 1 to 3, wherein the additive comprises an auxiliary additive selected from 1,3-propanesulfonate lactone, vinyl sulfate, and compounds of formula III: Wherein, based on the mass of the electrolyte, the mass percentage of the auxiliary additive is N, where 0.1% ≤ N ≤ 5%.
8. The electrolyte according to claim 7, wherein 0.01 ≤ M/N ≤ 10.
9. The electrolyte according to claim 7, wherein the electrolyte satisfies at least one of the following conditions: (1) 1% ≤ M ≤ 2%; (2) 0.5% ≤ N ≤ 2%; (3) 0.5 ≤ M/N ≤ 4.
10. A secondary battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte according to any one of claims 1 to 9.
11. According to claim 10, the secondary battery, wherein the positive electrode sheet includes a positive current collector and a positive electrode material layer disposed on at least one surface of the positive current collector, the positive electrode material layer includes a positive electrode active material, the positive electrode active material being selected from at least one of lithium cobalt oxide, LiNi _xCo _yMn_zO ₂ , lithium-rich manganese-based materials, lithium nickel manganese oxide, and lithium manganese oxide, wherein 0≤y≤1, 0≤x≤1, 0≤z≤1, and x+y+z＝1.

Description

An electrolyte and a secondary battery This application claims priority to Chinese Patent Application No. 202411525371.1, filed on October 30, 2024, entitled "An Electrolyte and a Secondary Battery", the entire contents of which are incorporated herein by reference. Technical Field This application relates to the field of electrochemical technology, and in particular to an electrolyte and a secondary battery. Background Technology Rechargeable batteries (such as lithium-ion batteries) are widely used in electric vehicles and consumer electronics due to their advantages such as high energy density, high output power, long cycle life, and environmental friendliness. As the application scope of rechargeable batteries continues to expand and their usage scenarios become more diverse, the market is placing higher demands on their electrochemical performance. To meet the market's demand for high-capacity batteries, a common technical approach is to increase the upper cutoff voltage. With advancements in materials and technology, people are paying more attention to battery range, portability, and safety, which places even higher demands on battery performance. As a key material in rechargeable batteries, the performance of the electrolyte determines the maximum performance of materials such as the positive electrode, negative electrode, and separator. Generally, to improve the cycle performance of rechargeable batteries, conventional film-forming additives can form a protective interfacial film at the positive and negative electrodes, thereby improving the battery's cycle performance. However, under more demanding operating environments (high temperature, high voltage), conventional electrolytes exhibit poor oxidation resistance, and the byproducts generated from excessive decomposition can damage the interfacial film, rendering its protective function ineffective and affecting the cycle performance of the rechargeable battery. Simultaneously, the oxidation stability of the positive electrode material also deteriorates under harsh operating conditions, leading to increased capacity loss. Therefore, improving the high-temperature cycle performance and high-temperature storage performance of rechargeable batteries under high-voltage conditions has become an urgent problem to be solved. Summary of the Invention The purpose of this application is to provide an electrolyte and a secondary battery to improve the high-temperature cycling performance and high-temperature storage performance of the secondary battery under high-voltage conditions. The specific technical solution is as follows: A first aspect of this application provides an electrolyte comprising a solvent, an additive, and an electrolyte, wherein the solvent comprises a fluorinated solvent, the fluorinated solvent comprising fluoroethylene carbonate and fluorinated chain esters, and the fluorinated chain esters comprising at least one compound of Formula I and at least one compound of Formula II. R2 and R4 are each independently selected from fluorine-substituted C1-C6 alkyl groups, and R1 and R3 are each independently selected from C1-C6 alkyl groups; the mass ratio of the fluorinated ethylene carbonate to the fluorinated chain ester is 1:(0.33-4), the mass ratio of the compound shown in Formula I to the compound shown in Formula II is 1:(0.33-3), and the mass percentage of the fluorinated solvent is 20% to 80% based on the mass of the electrolyte; the additive includes tetraethylenesilane, and the mass percentage of the tetraethylenesilane is M, 0.02% ≤ M ≤ 3% based on the mass of the electrolyte. The second aspect of this application provides a secondary battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte provided in the first aspect of this application. The beneficial effects of this application are: This application provides an electrolyte and a secondary battery. The electrolyte includes a solvent, an additive, and an electrolyte. The solvent includes fluoroethylene carbonate, a compound shown in Formula I, and a compound shown in Formula II. The mass ratio of fluoroethylene carbonate to fluorochain ester is 1:(0.33-4), and the mass ratio of the compound shown in Formula I to the compound shown in Formula II is 1:(0.33-3). Based on the mass of the electrolyte, the mass percentage of the fluorosolvent is 20% to 80%. The additive includes tetraethylenesilane, and based on the mass of the electrolyte, the mass percentage of tetraethylenesilane is M, where 0.02% ≤ M ≤ 3%. Through the above configuration, the fluoroethylene carbonate, the compound shown in Formula I, the compound shown in Formula II, and tetraethylenesilane work synergistically to give the electrolyte a suitable viscosity and high oxidation resistance, while also effectively mitigating the negative impact of defluorination on the positive electrode, thereby improving the high-temperature cycle performance and high-temperature storage performance o