Effect of Charge Non-Uniformity on the Lithium Dendrites and Improvement by the LiF Interfacial Layer

All-solid-state lithium metal batteries with high safety and high energy density have received widespread attention. However, the development of solid-state electrolytes (SSEs) is limited by the growth of lithium dendrites. In this paper, by using density functional theory, we investigated the charge density distribution uniformity of the neutral systems and the system with excess electrons on the surface of cubic Li7La3Zr2O12 (c-LLZO). Our results show that the surface of c-LLZO can be easily occupied by excess electrons and its charge density distribution is uneven, which causes lithium ions to aggregate in areas with higher charge density and reduce to metallic lithium and eventually results in the lithium dendrite formation. We also found that the use of a LiF buffer layer can make the charge density distribution near the interface layer more uniform, thereby inhibiting the growth of lithium dendrites. Such theoretical results well explain the role of LiF in SSEs and offer a promising way to prevent the lithium dendrite formation.