Surface Bromination of Lithium‐Metal Anode for High Cyclic Efficiency

Abstract Lithium‐metal batteries suffer from short cycle life and poor safety due to uncontrolled dendrite growth at Li anodes. An advanced solid‐electrolyte interphase (SEI) with homogeneous chemical composition and physical structure holds great promise to address the issues. Herein, a new surface bromination approach is proposed for stabilizing SEI of Li anode via a scalable dip‐coating method. A lithium bromide‐enriched SEI is readily created on Li metal from chemical passivation by bromooctane. In‐situ optical microscopy reveals the crucial role of LiBr in inhibiting dendritic Li growth. The mechanistic investigations suggest the crystal facet (111) of LiBr provides high adsorption energy and low diffusion barriers for Li⁺ ions. The incorporation of LiBr into SEI guarantees the stable cycling of Li irrespective of with ether or carbonate electrolytes, and the SEI is endurable at extremely low or high temperatures. The symmetric cell of the LiBr modified Li delivers a long lifespan of 2400 h with an overpotential less than 15 mV at 0.5 mA cm^‐2, 1 mAh cm^‐2. When paired with commercial cathodes, decent cycling retention and rate capability are available as well. This work demonstrates a feasible strategy for the development of stable Li‐metal batteries.