Improving Cycling Stability of the Lithium Anode by a Spin-Coated High-Purity Li<sub>3</sub>PS<sub>4</sub> Artificial SEI Layer
Hongjiao Wang, Lilin Wu, Xue Bai, Fang Wang, Zhongkuan Luo, Xianghua Zhang, Laurent Calvez, Ping Fan, Bo Fan
Abstract
Controlling the composition and microstructure of the solid electrolyte interphase (SEI) layer is critical to improving the cycling stability of the high-energy-density lithium–metal electrode. It is a quite tricky task to control the properties of the SEI layer which is conventionally formed by the chemical reactions between a Li metal and the additives. Herein, we develop a new route to synthesize a lithium-compatible sol of the sulfide electrolyte Li 3 PS 4, so that a Li 3 PS 4 artificial SEI layer with a controllable nanoscale thickness and high phase purity can be prepared by spin-coating. The layer stabilizes the lithium/electrolyte interface by homogenizing the Li-ion flux, preventing the parasitic reactions, and alleviating concentration polarization. Consequently, a symmetrical cell with the Li 3 PS 4 -modified lithium electrodes can achieve stable lithium plating/stripping for 800 h at a current density of 1 mA cm –2 . The Li–S batteries assembled with the Li 3 PS 4 -protected Li anodes show better capacity retention than their bare Li counterparts, whose average decay rate from the 240th cycle to the 800th cycle is only 0.004%/cycle. In addition, the Li 3 PS 4 layer improves the rate capacity of the batteries, significantly enhancing the capacity from 175 to 682 mA h g –1 at a 2 C rate. The spin-coated Li 3 PS 4 artificial SEI layer provides a new strategy to develop high-performance Li metal batteries.