Tunable LiZn‐Intermetallic Coating Thickness on Lithium Metal and Its Effect on Morphology and Performance in Lithium Metal Batteries

Abstract

Lithium metal batteries are promising next‐generation rechargeable batteries with high energy density. However, the high reactivity of lithium metal leads to an undesirable growth of high surface area lithium during electrodeposition and ‐dissolution and remains a key challenge that must be addressed to enable commercialization. Modification of the Li metal surface to obtain protective coatings is a common method to overcome these challenges. In this study, the influence of the thickness of an intermetallic coating on Li metal is investigated after application by means of thermal evaporation. In addition, the relevance of pre‐treatments in reducing the native layer thickness and surface roughness by roll‐pressing Li metal prior to coating is demonstrated. Morphological analyses are performed on cross‐sections prepared under cryogenic conditions to investigate the origin of high surface area lithium growth and coating cracks after electrodeposition and ‐dissolution processes. The results obtained support the conclusion that the exclusive combination of roll‐pressed Li metal foil followed by coating reduces overvoltage and improves cycle life at elevated current densities.