Protective solid-electrolyte-interphase for dendrite-free stable lithium metal batteries

Lithium (Li) is considered the most promising anode material in Li metal batteries (LMBs) owing to its high theoretical capacity. However, the formation of unstable solid electrolyte interphase (SEI) layer and unexpected Li dendrites growth during electrochemical deposition leads to lower cycling performance and coulombic efficiency with a safety concern, which have hindered the real-world applications of rechargeable LIBs. Here, we develop a facile and efficient approach to overcome these issues. An ultrathin Nickel (Ni) layer (50nm) has been sputtered on the surface of Li chips in a nitrogen environment to obtain a protective artificial SEI layer comprising of Li₃N and Ni₃N. Lithiophilicity, and higher ionic conductivity (4.9×10^-1 mScm^-1) of Li₃N and Ni₃N prevent the direct contact between extensive reactive Li metal and liquid electrolyte, which promote homogeneous deposition of Li, suppression of Li dendrites formation, and improvement of Li-ion diffusion. Besides, Ni performs as an electrical bridge between Li metal electrode and the plated Li, which promotes lowering the impedance. In a symmetrical cell, this artificial SEI layer exhibits a stable voltage profile with excellent plating/striping cycles compared to bare Li anode.