In-situ construction of Li-Ag/LiF composite layer for long cycled all-solid-state Li metal battery

All-solid-state lithium batteries employing sulfide solid electrolyte are promising candidates for next generation lithium batteries. Nevertheless, the unstable interface of sulfide solid electrolyte and Li metal has limited the lifespan of sulfide solid state lithium metal batteries. Herein, a composite protection layer composed of Li-Ag/LiF (LAF) is formed on Li metal surface by the in-situ reaction of silver-fluoride (AgF) and Li metal to solve the instability issue of the Li6PS5Cl/Lithium interface. The Li-Ag particles act as nucleation sites for Li deposition and LiF can avoid the growth of lithium dendrites. The density function theory (DFT) calculation results show the lithiophilic of Li-Ag alloys and high interfacial energy of LiF/Li6PS5Cl interface, proving the superiority of the LAF protection layer. The critical current density of the Li-LAF/ Li6PS5Cl/ LAF-Li symmetric battery is 1.6 mA cm-2 and the battery achieved a long lifespan of over 3000 h at 0.1 mA cm-2 and 0.1mAh cm-2 at room temperature. In addition, a high discharge capacity of 139.1mAh/g is obtained in the LiNbO3@LiCoO2/ Li6PS5Cl/ LAF-Li full cell. This work provides a feasible strategy for the interface modification of sulfide all-solid-state Li metal batteries.