Silicon-based anode lithium-ion battery electrolyte

Abstract

The invention provides silicon-based anode lithium-ion battery electrolyte which comprises an organic solvent, lithium salt, a film formation additive and a function additive, wherein the film formation additive comprises fluoro carbonic ester and tri-(pentafluorophenyl)borane, and the additive amounts of fluoro carbonic ester and tri-(pentafluorophenyl)borane respectively take 1%-15% and 0.1%-5% of the total mass of the electrolyte. According to the electrolyte, a stable, uniform and flexible SEI (solid electrolyte interface) film is formed on the surface of a silicon-based anode and can endure volume expansion of the silicon-based anode in repeated charging and discharging processes, so that the cycle performance of a battery is enhanced.

Description

[0001] 【Technical field】 [0002] The invention belongs to the technical field of lithium ion batteries, and in particular relates to an electrolyte solution for a silicon-based negative electrode lithium ion battery. [0003] 【Background technique】 [0004] Silicon-based materials are currently the anode materials for lithium-ion batteries with the highest gram capacity. The stress caused by the large volume expansion and contraction during the lithium-deintercalation process causes a large number of microcracks in the anode, resulting in a large number of microcracks between the active material and the gap between the active material and the current collector. Poor inter-contact, which causes the peeling of the active material and the collapse of the structure, leads to a decrease in conductivity and an increase in the internal resistance of the battery. Therefore, silicon-based negative electrode lithium-ion batteries have problems such as low initial Coulombic efficiency, po...

AI Technical Summary

Problems solved by technology

FEC can form a uniform and stable SEI (Solid Electrolyte Interface) film on the surface of the negative electrode, but it has poor temperature resistance and is easy to decompose at high temperature; and if the amount of FEC added is insufficient, it will also lead to performance degradation at the end of the cycle

The SEI film formed by VC on the surface of the negative electrode is relatively thick, and more lithium and film-forming additives are consumed during the film-forming process, resulting in a low initial Coulombic efficiency of the battery, and the excessive thickness of the film also increases the battery impedance and affects the rate performance.

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