Patching Solid Electrolyte Interphase via Modulating Anion Decomposition Reactions for Stable Lithium Metal Batteries

Solid electrolyte interphase (SEI) on lithium (Li) metal anodes undergoes repeated rupture and patching during cycles, which induces the formation of inactive Li and the rapid failure of Li metal batteries. The inactive Li compounds used to patch SEI dominate inactive Li for highly reversible Li metal anodes. Herein, patching SEI rapidly by modulating decomposition reactions of bis(fluorosulfonyl)imide anion (FSI^-) in the electrolyte is proposed to decrease the amount of inactive Li compounds. Increasing overpotential of anodes can promote the fast and complete decomposition reactions of FSI^-, which increases the amount of insoluble inorganic components in the decomposition products of one FSI^-. Abundant insoluble inorganic components can build SEI efficiently to avoid the further decomposition of the electrolyte. Then, a protocol is proposed to increase overpotential of anodes by applying a high current density within a short time during the final stage of Li deposition in Li metal batteries. With the proposed protocol, the amount of inactive Li compounds decreases by 62.2%. Furthermore, a prototype pouch cell of 411 Wh kg^-1 achieves 202 stable cycles. This work provides a fresh understanding of SEI formation and inspires a new strategy to stabilize SEI.