Self-Leveling Electrolyte Enabled Dendrite-Free Lithium Deposition For Safer And Stable Lithium Metal Batteries

Lithium (Li) metal is considered an ideal anode material for future high-energy rechargeable batteries. However, the extremely unstable interfaces between lithium anode and electrolyte induce uncontrollable dendrite formation and low Coulombic efficiency, retarding its practical applications in Li metal batteries (LMB). Herein, we propose a facile and feasible strategy of introducing 12-Crown-4 ether as a leveling additive into the electrolyte to inherently eliminate the self-amplification behavior of dendrite growth. The Li+-additive complexes with low electron-accepting ability are preferentially adsorbed on the initial protuberant tips of Li metal surface, which can effectively regulate the local polarization resistance and improve the current distribution uniformity. Based on this principle, a self-leveling electrolyte comprising fluoroethylene carbonate (FEC) solvent and 12-Crown-4 additive is developed. Dense and dendrite-free Li deposition, as well as enhanced interfacial stability is achieved in such electrolyte, rendering a significantly improved Coulombic efficiency (97.24%) in Li||Cu cells and a superior cycling stability in Li||Li cells. Moreover, a Li metal full-cell with high-loading LiFePO4 cathode (12.5 mg cm-2) retains 98% capacity after 100 cycles at 0.5 C. This self-leveling electrolyte approach opens up new perspective on the mechanistic and methodological aspects for designing safer lithium metal batteries.