Epitaxial Growth of Nanostructured Li₂ Se on Lithium Metal for All Solid-State Batteries

Lithium is considered to be the ultimate anode material for high energy-density rechargeable batteries. Recent emerging technologies of all solid-state batteries based on sulfide-based electrolytes raise hope for the practical use of lithium, as it is likely to suppress lithium dendrite growth. However, such devices suffer from undesirable side reactions and a degradation of electrochemical performance. In this work, nanostructured Li₂ Se epitaxially grown on Li metal by chemical vapor deposition are investigated as a protective layer. By adjusting reaction time and cooling rate, a morphology of as-prepared Li₂ Se is controlled, resulting in nanoparticles, nanorods, or nanowalls with a dominant (220) plane parallel to the (110) plane of the Li metal substrate. Uniaxial pressing the layers under a pressure of 50 MPa for a cell preparation transforms more compact and denser. Dual compatibility of the Li₂ Se layers with strong chemical bonds to Li metal and uniform physical contact to a Li₆ PS₅ Csulfide electrolyte prevents undesirable side reactions and enables a homogeneous charge transfer at the interface upon cycling. As a result, a full cell coupled with a LiCoO₂ -based cathode shows significantly enhanced electrochemical performance and demonstrates the practical use of Li anodes with Li₂ Se layers for all solid-state battery applications.