Electrolyte and lithium ion battery

Abstract

The invention provides an electrolyte and a lithium ion battery. The electrolyte comprises a lithium salt, an organic solvent and an additive, wherein the additive comprises a first additive, and the first additive comprises alkyl lithium sulfate and fluoro-ether. By the electrolyte, the storage performance, the cycle property, the rate performance and the low-temperature discharge performance of the lithium ion battery under high temperature and high voltage can be improved, meanwhile, the safety performance of the lithium ion battery is improved, and the service lifetime of the lithium ion battery is prolonged.

Description

technical field [0001] The invention relates to the field of lithium ion batteries, in particular to an electrolyte and a lithium ion battery. Background technique [0002] In recent years, the rapid development of smart electronic products has put forward higher requirements for the battery life of lithium-ion batteries. In order to increase the energy density of lithium-ion batteries, developing high-voltage lithium-ion batteries is one of the effective methods. [0003] At present, lithium-ion batteries with an operating voltage above 4.4V have become a research hotspot for many scientific research institutes and enterprises. However, under high voltage, the oxidation activity of the positive electrode active material increases and the stability decreases, which makes the electrolyte easy to undergo electrochemical oxidation reaction on the surface of the positive electrode, and then decomposes to generate gas. At the same time, the transition metal elements in the posi...

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Problems solved by technology

These additives can form a film on the positive electrode, but it will increase the interfacial impedance, resulting in a decrease in the kinetics of lithium ion migration and diffusion in lithium-ion batteries, which in turn will reduce the rate and cycle performance of lithium-ion batteries.

The Chinese patent document CN105074996A published on November 18, 2015 discloses adding SO 4 Based compounds can improve the electrochemical properties of storage devices at high temperature and high pressure, due to SO 4 The base compound can form a covering film on the positive and negative electrodes at the same time. However, the resistance of the covering film is too small. When it is exposed to high temperature for a long time, the covering film will decompose and cause side reactions in lithium-ion batteries, which poses a safety hazard.

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