Ultrafast Electrochemical Growth of Lithiophilic Nano‐Flake Arrays for Stable Lithium Metal Anode

Abstract Lithium dendrites caused by nonuniform Li + flux leads to the capacity fade and short‐circuit hazard of lithium metal batteries. The solid electrolyte interface (SEI) is critical to the uniformity of Li + flux. Here, an ultrafast preparation of uniform and vertical Cu 7 S 4 nano‐flake arrays (Cu 7 S 4 NFAs) on the Cu substrate is reported. These arrays can largely improve the lithiophilicity of the anode and form Li 2 S‐enriched SEI due to the electrochemical reduction of Cu 7 S 4 NFAs with lithium. A further statistical analysis suggests that the SEI, with a higher content of Li 2 S, is more effective to inhibit the formation of lithium dendrites and yields less dead lithium. A quite stable coulombic efficiency of 98.6% can be maintained for 400 cycles at 1 mA cm –2 . Furthermore, at negative to positive electrode capacity ratio of 1.5 (N/P = 1.5), the full battery of Li@Cu 7 S 4 NFAs||S shows 83% capacity retention after 100 cycles at 1 C, much higher than that of Li@Cu||S (33%). The findings demonstrate that high Li 2 S content in the SEI is crucial for the dendrite inhibition to achieve better electrochemical performance.