Room temperature surface-engineering enabling stability of high-energy-density lithium batteries

Lithium (Li) ion batteries have witnessed a great success in areas ranging from portable electronics to electrical vehicles. Among various materials used for battery anodes, Li metal has been considered as the “Holy Grail” due to the highest theoretical capacity and lowest electrochemical potential. However, unmodified Li metal anode suffers from uncontrolled dendrite growth as well as inherent ultrahigh reactivity. Here we report a facile and universal approach to engineering Li anode by passivating anode surface through reactions with CF_x, which yields a uniform porous LiF layer on the surface of Li metal. Retaining a high theoretical specific capacity of 3680 mAh/g, a marked extension of the cycle life for Li anode after the formation of a LiF surface layer was achieved, and characterization of Li/Li₄Ti₅O₁₂ (LTO) cells with surface-engineered Li anode showed capacity retention of 94.79% after 800 cycles at 2 C, which is much higher than those in the cells with pure Li anode (62.07%). Further, enhanced stability and suppressed overpotential augment after 300 cycles were realized in symmetric cells of surface-engineered Li metal. In addition, Li/S cells with surface-engineered Li anodes also exhibit significantly improved initial columbic efficiency, cyclability, and specific capacity simultaneously. These results suggest that an engineered LiF surface layer would enable an ideal Li metal anode for high-energy-density batteries of the future.