In situ formation of lithiophilic Li22Sn5 alloy and high Li-ion conductive Li2S/Li2Se via metal chalcogenide SnSSe for dendrite-free Li metal anodes

Abstract

Lithium metal has gained extensive attention as the most ideal candidate for next-generation battery anode owing to the ultrahigh specific capacity and the lowest electrochemical potential. However, uncontrollable dendrite growth and huge volume variation extremely restrict the future deployment of lithium metal batteries. Herein, we report metal chalcogenide SnSSe with unique nanoplate stacking structure as a robust substrate for stable Li metal anode. During the initial Li plating process, lithiophilic Li22Sn5 alloy and Li2S/Li2Se sites are obtained via in-situ electrochemical reaction of Li metal and SnSSe. Density functional theory (DFT) calculation demonstrates that the formed Li2S/Li2Se achieves low Li diffusion energy barrier, ensuring rapid Li+ migration. Li22Sn5 alloy provides strong nucleation sites, promoting uniform Li nucleation. Furthermore, in-situ optical microscopy analysis suggests that the synthesized effect fundamentally inhibits lithium dendrite growth. Consequently, SnSSe modified Cu foil delivered an ultralow nucleation overpotential, superior cycling stability with 450 cycles (Coulombic efficiency, >98%), and excellent plating/stripping behavior over 2200 h at 0.5 mA cm−2. Moreover, the brilliant reversible cycles and rate capability were also realized in Li@SnSSe//LiFePO4 (LFP) full cell, shedding light on the feasibility of SnSSe for stable and dendrite-free lithium metal anode.