The solid electrolyte interphase (SEI) generated spontaneously on the surface of lithium anode, is a protective layer to inhibit further reaction of electrolyte with lithium and to prevent the formation of lithium dendrites. The composition and properties of SEI layers determine the cycling performance of lithium batteries to some extent. Here we report a novel solution to optimize the SEI layer by applying an additional alternating current (AC) electric field during the generation of SEI. The application of an AC field enhances the association of anions and cations in the electrolytes, which results in an improved delivery of anions to the surface of lithium anode. The decomposition of anions at the surface leads to the formation of an anion-derived SEI layer containing a mass of LiF and Li₂S particles. The grain boundaries among these particles provide fast diffusion channels for lithium ions, forming a high conductive SEI layer. The optimized composition of SEI layer is confirmed by X-ray photoelectron spectroscopy analysis and electrochemical characterizations. Through this strategy, the cycle performance of lithium batteries is greatly improved, and the stable cycling life of Cu@Li | Li cells and Cu@Li | NMC811 cells increases more than 3 times.

锂负极表面自发生成的固体电解质界面（SEI）是一种保护层，可抑制电解质与锂的进一步反应，防止锂枝晶的形成。SEI层的组成和性能在一定程度上决定了锂电池的循环性能。在这里，我们报告了一种新的解决方案，通过在 SEI 生成期间施加额外的交流 (AC) 电场来优化 SEI 层。交流场的应用增强了电解质中阴离子和阳离子的结合，从而改善了阴离子向锂负极表面的输送。表面阴离子的分解导致形成含有大量 LiF 和 Li _{2的阴离子衍生 SEI 层}S 粒子。这些颗粒之间的晶界为锂离子提供了快速扩散通道，形成了高导电性的 SEI 层。通过 X 射线光电子能谱分析和电化学表征证实了 SEI 层的优化组成。通过这一策略，锂电池的循环性能大大提高，Cu@Li稳定循环寿命| 锂电池和Cu@Li | NMC811细胞增加3倍以上。