Stabilizing Li/electrolyte interface with a transplantable protective layer based on nanoscale LiF domains

Although Li metal has been regarded as one of the most promising anode materials, an unstable Li/electrolyte interface during the cycling process seriously limits its practical application in rechargeable batteries. Herein, we report a transplantable LiF-rich layer (TLL) that can suppress the side reactions between electrolyte and lithium metal. This peelable layer cross-linked by nanoscale LiF domains is obtained by electrochemically reducing NiF₂ electrodes and could be used to protect Li metal anodes. Cu-Li cells using the TLL protection can operate for more than 300 cycles with a Coulombic efficiency as high as ~ 98% in carbonate-based electrolytes. In Li-LiFePO₄ cells, lithium metal with a TLL still looks shiny after 1000 cycles (~ 6 months) in contrast to the black surface of bare lithium foil after ~ 500 cycles (~ 3 months). These results clearly demonstrate that the TLL could greatly limit the side reactions between lithium metal and the carbonate-based electrolytes, and may enable long-term stable operation of Li metal batteries.