Theoretical calculation study on the electrochemical properties of lithium halide-based artificial SEI films for lithium metal anodes

All solid-state lithium-metal batteries (ASSLMBs) have significant advantages, such as high safety and high energy density, and the solid electrolyte interface (SEI) film between the internal lithium metal anode and the solid electrolyte plays an important role. However, spontaneously formed SEI film has poor stability, leading to a decrease in the Coulombic efficiency of the cell and a shorter cycle lifetime. As a result, the research and development of artificial SEI films have become one of the hot topics in the field of lithium batteries. In this paper, the electrochemical properties of lithium halide-based artificial SEI films (LiF, LiCl, LiBr, LiI) were studied by density functional theory based on first principles. Firstly, the structural stabilities, mechanical properties, and electronic insulation of SEI films were analyzed and compared. Subsequently, the adsorption and migration behavior of lithium ions (Li+) on these surfaces were investigated, starting from the stable surface structures of SEI films. Based on this, the interface structures of SEI film/lithium metal were constructed by matching lattice, and their interface bonding strength and charge distribution were explored. Additionally, the inhibitory ability of SEI films on lithium dendrite growth was examined. LiF has the most stable bulk and surface structures, as well as a stable interface structure with lithium metal. Furthermore, it possesses the best mechanical properties, electronic insulation, and the ability to inhibit the growth of lithium dendrites. It can be seen that LiF is a suitable artificial SEI film for lithium metal anodes.