Engineered Nanostructured Li₂Se on Lithium Metal Anodes for Enhancing Energy Density in All-Solid-State Lithium Metal Batteries

Lithium metal is regarded as the ideal anode material for high-energy-density rechargeable batteries. Recent progress in all-solid-state batteries using sulfide-based electrolytes has renewed optimism for the practical application of lithium anodes, as they are likely to inhibit dendrite formation. However, these anodes still face challenges such as unwanted side reactions and the deterioration of electrochemical performance. In this study, we introduce nanostructured Li₂Se protective layers, epitaxially grown on Li metal via a chemical vapor deposition (CVD) process. The Li₂Se layers are composed of nanoparticles, nanorods, and nanowalls, depending on reaction time and cooling rate. When subjected to 50 MPa pressure, the Li₂Se grains are compressed, creating a more compact and dense layer. This Li₂Se protective layer, with strong physical and chemical bonding to both the Li metal and solid electrolyte, mitigates unstable side reactions and promotes uniform charge distribution between the Li metal and the solid electrolyte during cycling. A full cell paired with a LiCoO₂-based cathode demonstrates significantly improved electrochemical performance, suggesting the potential for practical application of Li anodes with Li₂Se protective layers in high-energy-density solid-state lithium metal batteries.