In Situ Construction of Gradient Sulfide/Alloy Interfacial Layer for Stable Solid-State Lithium Metal Batteries

The poor compatibility and sluggish Li⁺ transport kinetics of the Li anodic interface restrict the development of solid-state lithium metal batteries with composite solid electrolytes. Li alloy and sulfide-containing layer exhibits high Li⁺ conductivity and reasonable stability, showing promising application potential in artificial Li anodic interfacial layer. However, it is still challenging to achieve controllable construction of ultrathin sulfide-based interfacial layer on solid electrolytes via a simple method. Here, a facile in-situ film-formation approach by electrochemically covering Sb₂S₃ in the composite electrolyte (SbS@CSE) to sulfide and Li-Sb alloy is proposed. Based on this approach, the construction of gradient Li₂S/Li₃Sb-rich interfacial layer is achieved, which uniformize the interfacial Li⁺ flow and stabilize the Li anodic interface. The correspondent Li/SbS@CSE/Li symmetric cell exhibits an improved critical current density of 0.8 mA cm^-2, and stable cycling for over 1200 h. The all-solid-state Li batteries LiFePO₄/SbS@CSE/Li retain a high capacity retention rate about 90.4% at 60 °C for over 700 cycles at 1 C, showing excellent cycling stability in recent reports on PEO-based composite solid electrolytes.