CN-115101815-B - Electrolyte and lithium ion battery

Abstract

The invention discloses an electrolyte and a lithium ion battery. The electrolyte comprises a mixed solvent of fluorocarbonate and linear carbonate, lithium salt, an additive and a stabilizer. Wherein the mass part ratio of the fluorocarbonate to the linear carbonate in the mixed solvent is 1 (1-5). The electrolyte provided by the invention has good thermal stability, and the defect that the cyclic carbonate is easy to decompose at high temperature is overcome. The lithium ion battery assembled by using the electrolyte provided by the invention has better high-temperature storage performance, and the gas yield of the assembled lithium ion battery at a high temperature is obviously reduced. The safety performance of the assembled lithium ion battery is greatly improved, the heat-resistant temperature is up to 160 ℃, in addition, the battery also has better cycle performance, and the capacity retention rate can still reach more than 94% when the battery is cycled to 600 circles under the current density of 1 ℃.

Inventors

• WANG FALI

Assignees

• 联动天翼新能源有限公司

Dates

Publication Date

20260508

Application Date

20220318

Claims (6)

1. 1. The electrolyte is characterized by comprising the following components in percentage by mass: 1) 78-82% of a solvent; 2) 3-4% of an additive; 3) 13-17% of lithium salt; 4) 0.1-3% of a stabilizer; The solvent consists of fluorocarbonate and linear carbonate, wherein the mass ratio of the fluorocarbonate to the linear carbonate in the solvent is 1:((60.4/26) -5); the stabilizer comprises one or more of N, N' -diisopropylcarbodiimide, N-diisopropylethylamine, 4-imidazole formaldehyde and 1-methylimidazole; the additive comprises one or more of ethoxy pentafluoroethylene triphosphazene, trifluoro ethoxy pentafluoroethylene triphosphazene and phenoxy pentafluoroethylene triphosphazene.
2. 2. The electrolyte according to claim 1, wherein the fluorocarbonate comprises one or more of fluoroethylene carbonate, fluoropropylene carbonate, difluoroethylene carbonate, difluoropropylene carbonate, 2-trifluoroethyl carbonate and 4-trifluoromethyl ethylene carbonate, and the linear carbonate comprises one or more of methylethyl carbonate, dimethyl carbonate, diethyl carbonate and methylpropyl carbonate.
3. 3. The electrolyte according to claim 1, wherein the lithium salt comprises one or more of lithium hexafluorophosphate, lithium difluorosulfonimide salt, lithium difluorooxalato borate and lithium dioxaato borate.
4. 4. The method for preparing the electrolyte according to any one of claims 1 to 3, which is characterized by comprising the step of mixing the components to obtain the electrolyte.
5. 5. A lithium ion battery, characterized in that the electrolyte used in the lithium ion battery is the electrolyte described in any one of claims 1 to 3.
6. 6. The lithium ion battery of claim 5, wherein the lithium ion battery comprises a lithium cobalt oxide lithium ion battery, a lithium iron phosphate lithium ion battery, a lithium manganate lithium ion battery, and a lithium nickel cobalt manganate lithium ion battery.

Description

Electrolyte and lithium ion battery Technical Field The invention belongs to the technical field of lithium ion batteries, and particularly relates to an electrolyte and a lithium ion battery. Background In order to cope with the problems of increasingly serious environmental pollution and energy crisis, people are continuously rising in the call for green energy. Among them, lithium ion secondary batteries are widely used in various portable electrons with their longer operating life, higher operating voltage and energy density, and lower environmental pollution. The adoption of the high-nickel ternary cathode material to match with the graphite composite anode material with high silicon content is one of important means for improving the energy density of the battery. However, as the nickel content increases, the safety and stability of the battery are greatly reduced, and as the use content of the silicon anode increases, the cycle performance and high temperature performance of the battery are gradually reduced. Among the major impediments limiting the development of high nickel ternary cathode materials is the rapid oxidative decomposition of the electrolyte at high voltages and temperatures. For this reason, researchers have made extensive studies to develop a number of novel electrolyte systems, such as high concentration, sulfone and nitrile electrolytes, and the like. Although the novel electrolyte system obviously improves the compatibility of the electrolyte with the positive electrode under high voltage, most of the systems can not simultaneously meet the requirements of high-temperature storage and safety performance of the lithium ion battery. Therefore, there is a strong need to develop an electrolyte so that the electrolyte can improve the cycle performance of a battery and also can improve the high-temperature storage performance and the safety performance of the battery when being used for a high-voltage cathode material. Disclosure of Invention The present invention aims to solve at least one of the technical problems in the prior art described above. Therefore, the invention provides the electrolyte and the lithium ion battery, wherein the electrolyte comprises the mixed solvent of the fluorocarbonate and the linear carbonate, the lithium salt, the additive and the stabilizer, the defect that the carbonate solvent is easy to decompose at high temperature is overcome, and the thermal stability of the electrolyte is improved. The lithium ion battery assembled by using the electrolyte has better high-temperature storage performance, the gas production rate is greatly reduced, and in addition, the electrolyte improves the safety performance and the cycle performance of the assembled lithium ion battery. In a first aspect of the invention, an electrolyte is provided that includes a solvent, a lithium salt, an additive, and a stabilizer. According to an aspect of the invention, in some embodiments of the invention, the solvent comprises a fluorocarbonate and a linear carbonate. In some preferred embodiments of the present invention, the mass part ratio of the fluorocarbonate and the linear carbonate in the solvent is 1 (1-5). In some preferred embodiments of the present invention, the electrolyte contains 75-85% by mass of solvent. In some preferred embodiments of the present invention, the electrolyte contains 2-5% by mass of additives. In some preferred embodiments of the present invention, the electrolyte contains 10-20% by mass of lithium salt. In some preferred embodiments of the present invention, the electrolyte contains 0.05-5% by mass of stabilizer. In some more preferred embodiments of the present invention, the electrolyte contains 78-82% by mass of solvent. In some more preferred embodiments of the present invention, the electrolyte contains 3-4% by mass of additives. In some more preferred embodiments of the present invention, the electrolyte contains 13-17% by mass of lithium salt. In some more preferred embodiments of the present invention, the electrolyte contains 0.1-3% by mass of stabilizer. In some preferred embodiments of the present invention, the fluorocarbonate comprises one or more of fluoroethylene carbonate, propylene carbonate, bis-fluoroethylene carbonate, bis-fluoropropylene carbonate, 2-trifluoroethyl carbonate and 4-trifluoromethyl ethylene carbonate. In some preferred embodiments of the present invention, the linear carbonate comprises one or more of methyl ethyl carbonate, dimethyl carbonate, diethyl carbonate and methyl propyl carbonate. In some preferred embodiments of the invention, the additive comprises one or more of ethoxy pentafluoroethylene triphosphazene, trifluoroethoxy pentafluoroethylene triphosphazene, and phenoxy pentafluoroethylene triphosphazene. In some preferred embodiments of the present invention, the lithium salt comprises one or more of lithium hexafluorophosphate, lithium difluorosulfonimide salt, lithium difluorooxalato borate and lithi