Method for improving stability of SEI membrane of lithium ion battery

Abstract

The invention discloses a method for improving the stability of an SEI membrane of a lithium ion battery. The method comprises the following steps: S1, firstly, keeping a lithium ion battery cell, an electrolyte solvent and an electrolyte added with a lithium salt and a VC stabilizer at a constant temperature for later use; S2, weighing the lithium ion battery cell, and putting the battery cell into a vacuum system with the vacuum degree of -0.08 to -0.1 Mpa; S3, injecting the electrolyte into the battery cell which is kept in vacuum, and standing for 10 seconds; s4, breaking vacuum, and filling inert gas for pressurization; s5, vacuumizing again, the vacuum keeping time being 95 s, and continuously conducting the operation for three cycles; and S6, calculating the actual liquid absorption amount m'' of the battery, wherein m''=m'-m. The method has the advantages that the addition of the VC additive is beneficial to improving the discharge platform of the lithium ion battery, and when the content of VC is 1%, the improvement is most obvious, and the retention rate of the battery capacity is optimal at the moment. In addition, due to the addition of VC, the high-temperature cycle life of the lithium ion battery is remarkably prolonged, and the low-temperature discharge performance and the low-temperature capacity retention rate also reach the optimal level.

Description

technical field [0001] The invention relates to the field of ion batteries, in particular to a method for improving the stability of an SEI film of a lithium ion battery. Background technique [0002] With the advancement of science and technology, batteries are widely used in various fields such as mobile communications, electric vehicles, and energy storage, covering almost all areas of our production, life, and scientific research. Especially in recent years, with the rapid development of new energy vehicles at home and abroad, the demand for batteries is increasing, and the performance requirements for batteries are also getting higher and higher. As a representative of new energy materials, lithium-ion batteries have attracted more and more attention for their performances such as charging, discharging and cycling. [0003] The electrolyte is an important part of the lithium-ion battery, which plays the role of transporting and conducting current between the positive a...

AI Technical Summary

Problems solved by technology

[0006] In the prior art, most of the additives used in industrial SEI film formation are compounds with high reduction and decomposition potentials. They can decompose before other solvent components of the electrolyte during the first charge and discharge process, and form an SEI film on the surface of the negative electrode. The most commonly used additives are EC (ethylene carbonate) and PC (propylene carbonate), but due to their high inertness, the improvement effect on electrolyte film formation is not obvious enough, and the performance of ion batteries has not been greatly improved. Therefore, It is urgent to study a method to improve the stability of the SEI film of lithium-ion batteries to solve the above-mentioned problems.

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