Electrolyte and lithium ion battery comprising same

Abstract

The invention relates to the technical field of lithium ion batteries, particularly relates to electrolyte and a lithium ion battery comprising the same. The electrolyte disclosed by the invention comprises lithium salt, an organic solvent and an additive A, wherein the additive A comprises silane compounds containing cyano groups and dinitrile compounds containing ether bonds; the additive A can be used for improving the rate capability and low-temperature discharge performance of the battery under a high voltage, thereby improving the service life of the lithium ion battery. The electrolyte disclosed by the invention further comprises an additive B which is one or more of ether compounds, nitrile compounds, cyclic ester compounds containing S=O double bonds, cyclic carbonate compounds containing C-C unsaturated bonds and compounds containing imido groups. The lithium ion battery comprising the electrolyte can achieve the objective of high voltage and the highest normal working voltage can be improved to 4.4V-5.0V; in addition, the cycle performance of the lithium ion battery is excellent and the capacity retention ratios during charging and discharging can be both high.

Description

technical field [0001] The invention relates to the technical field of lithium ion batteries, in particular to an electrolyte and a lithium ion battery including the electrolyte. Background technique [0002] In recent years, with the rapid development of smart electronic products, higher requirements have been placed on 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 material increases and the stability decreases, which leads to the electrochemical oxidation reaction of the non-aqueous electrolyte on the surface of the positive electrode, and then decomposes to generate gas. At the same time, ...

AI Technical Summary

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 the battery, which in turn will reduce the rate and cycle performance of the battery.

The prior art has disclosed a class of siliconitrile compounds containing oligoethylene oxide units as electrolyte additives or co-solvents, and developed electrolyte materials with the advantages of strong oxidation resistance, large dielectric constant, and high thermal safety, although This type of compound can form an SEI film on the surface of graphite to prevent PC from damaging the graphite electrode. However, its structure contains oligomeric ether chains. During the battery reaction, the ether chains are easily broken, which affects the stability of the SEI film, resulting in battery failure. Reduced service life

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