Lithium ion battery electrolyte used at low temperature

Abstract

The invention discloses a lithium ion battery electrolyte used at low temperature. The electrolyte comprises a lithium salt, an additive and a non-aqueous organic solvent, wherein the lithium salt is a composite lithium salt of a phosphoric acid lithium salt, a sulfimide lithium salt and a boric acid lithium salt, the additive is selected from fluoroethylene carbonate and ethoxy(pentafluoro)cyclotriphosphazene, and the non-aqueous organic solvent comprises a carbonic ester solvent and a linear carboxylic ester solvent. By matching the linear carboxylic ester solvent with low freezing point and low viscosity with the carbonic ester solvent, the viscosity of the electrolyte is reduced, the interfacial compatibility of the solvent and a graphite negative electrode is maintained, meanwhile, a lithium salt system is adjusted, the low-temperature lithium ion conductivity of the electrolyte is improved, and the low-temperature rate performance of a lithium ion battery is improved; in addition, various additives are added, so that a stable interfacial film is formed, and the low-temperature cycle and rate performance of the lithium ion battery are improved.

Description

technical field [0001] The invention belongs to the technical field of lithium-ion battery electrolytes, and in particular relates to a low-temperature lithium-ion battery electrolyte. Background technique [0002] As one of the most successful chemical energy storage batteries today, lithium-ion batteries have the characteristics of high nominal voltage, high specific energy, long cycle life, no memory effect, etc., and are environmentally friendly and pollution-free. Their footprints are not only found in consumer electronics products , and expanded into the field of electric vehicles. However, such a lithium-ion battery with such excellent performance is very sensitive to temperature. Low temperature will cause the electrical performance of the lithium-ion battery to decline, and even make the lithium-ion battery unusable. During low-temperature charging, especially when low-temperature and high-rate charging, lithium metal will precipitate and deposit on the negative el...

AI Technical Summary

Problems solved by technology

However, such a lithium-ion battery with such excellent performance is very sensitive to temperature. Low temperature will cause the electrical performance of the lithium-ion battery to decline, and even make the lithium-ion battery unusable.

During low-temperature charging, especially when low-temperature and high-rate charging, lithium metal will precipitate and deposit on the negative electrode, and the deposited metal lithium will easily react irreversibly with the electrolyte to consume a large amount of electrolyte, and at the same time further increase the thickness of the SEI film, resulting in battery The impedance of the surface film of the negative electrode will further increase, and the polarization of the battery will increase again, which will greatly damage the low temperature performance, cycle life and safety performance of the battery.