Nanostructured Li₂Se as a Protective Layer for All-Solid-State Lithium Metal Batteries

Lithium metal is considered the ultimate anode material for high-energy rechargeable batteries. Recent advances in all solid-state batteries based on sulfide-based electrolytes are likely to inhibit lithium dendritic growth, raising hopes for practical application of lithium-ion batteries. However, undesirable side effects and poor electrochemical performance can cause difficulties. Here, the nanostructured Li₂Se protective layer was reported here by chemical vapor deposition. The prepared Li₂Se layer consists of nanoparticles, nanorods, and nanowalls with a dominant (220) plane parallel to the (110) plane of the Li metal substrate in terms of reaction time and cooling rate. By adjusting the reaction time and cooling rate, Li₂Se can be controlled as follows. Pressing a layer below 50 MPa will flatten the Li₂Se protective layer and convert it into more compact and denser layers. Li₂Se protective layer with strong physical and chemical bonds to Li metals prevent unstable side reactions and allow uniform charge distribution between Li metals and sulfide-base electrolyte during cycling. Full cell coupled with a LiCoO₂-based cathode significantly improves electrochemical performance and shows the possibility of practical use of Li anode with Li₂Se protective layers for high energy density all solid-state lithium metal batteries.