Ultra-Low Concentration Electrolyte Enabling LiF-Rich SEI and Dense Plating/Stripping Processes for Lithium Metal Batteries.

Abstract

The interface structure of the electrode is closely related to the electrochemical performance of lithium‐metal batteries (LMBs). In particular, a high‐quality solid electrode interface (SEI) and uniform, dense lithium plating/stripping processes play a key role in achieving stable LMBs. Herein, a LiF‐rich SEI and a uniform and dense plating/stripping process of the electrolyte by reducing the electrolyte concentration without changing the solvation structure, thereby avoiding the high cost and poor wetting properties of high‐concentration electrolytes are achieved. The ultra‐low concentration electrolyte with an unchanged Li+ solvation structure can restrain the inhomogeneous diffusion flux of Li+, thereby achieving more uniform lithium deposition and stripping processes while maintaining a LiF‐rich SEI. The LiIICu battery with this electrolyte exhibits enhanced cycling stability for 1000 cycles with a coulombic efficiency of 99% at 1 mA cm–2 and 1 mAh cm–2. For the LiIILiFePO4 pouch cell, the capacity retention values at 0.5 and 1 C are 98.6% and 91.4%, respectively. This study offers a new perspective for the commercial application of low‐cost electrolytes with ultra‐low concentrations and high concentration effects.