Nonaqueous electrolyte for secondary lithium ion battery

Abstract

The invention relates to the technical field of lithium ion batteries, in particular to a nonaqueous electrolyte for a secondary lithium ion battery, which is prepared by adopting an organic solvent containing at least one cyclic carbonate and one linear carbonate, wherein the cyclic carbonate comprises ethylene carbonate (EC) and propylene carbonate (PC), the linear carbonate comprises ethyl methyl carbonate (EMC), diethyl carbonate (DEC) or a solvent system formed by any of the EMC and the DEC, and lithium hexaflourophosphate is used as the electrolyte. The nonaqueous electrolyte is characterized in that nitriles (NC-R-CN) are simultaneously added, wherein R is alkyl, C is 2-6, vinylene carbonate (VC), fluoroethylene carbonate (FEC) and 1,3-propane sultone (PS) are used as additives, and the weight percents of all additives are regulated. A battery adopting the nonaqueous electrolyte has excellent high-temperature property and circulating property.

Description

Technical field [0001] The present invention relates to the technical field of lithium ion batteries, in particular to an electrolyte for non-aqueous secondary lithium batteries. Background technique [0002] With the popularization of electronic products in people's daily life, lithium-ion batteries have been widely used in civil power sources due to their environmental protection, high energy density, light weight, and safety advantages. At the same time, users have put forward higher and higher requirements for battery energy density, usage time, and ambient temperature. [0003] At present, the electrolyte for non-aqueous lithium secondary batteries usually uses organic solvents containing cyclic carbonate and a linear carbonate. Cyclic carbonates include ethylene carbonate (EC), propylene carbonate (PC), and linear carbonate. The ester includes a solvent system composed of ethyl methyl carbonate (EMC), diethyl carbonate (DEC) or any of them, with lithium hexafluorophosphate a...

AI Technical Summary

Problems solved by technology

For example, adding nitrile (NC-R-CN) additives alone in the electrolyte additives can improve the high-temperature storage performance of the battery, but it will affect the capacity of the battery; if adding vinylene carbonate (VC) additives alone in the electrolyte additives , improve the high-temperature cycle performance of the battery, but the low-temperature cycle performance is poor; for example, adding a fluoroethylene carbonate (FEC) additive to the electrolyte additive alone can prolong the cycle life of the battery, but the battery will be flattened when stored at high temperature; Adding 1,3-propane sultone (PS) additive alone in the electrolyte additive can improve the high-temperature cycle performance of the battery, but the low-temperature performance is deteriorated; such as US 7078132, adding additives FB and VC to improve its high-temperature cycle performance, but there is a risk of lithium precipitation at low temperature

[0004] In the development of batteries with increased energy density, lithium cobalt oxide (LiCoO 2 ), the negative electrode generally uses high-graphitization graphite material, but it is difficult to match the high-graphitization graphite material to the electrolyte to achieve the best effects of high-temperature storage performance, low-temperature performance and cycle performance at the same time, and there are usually problems such as high-temperature storage gas and cycle life. In order to solve the above problems, some solutions have been proposed for the electrolyte

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