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.

We proposed a Voronoi finite element method to determine the possible intermediate phases of cathode materials of Li-ion batteries. Lithium-vacancy arrangements can be accurately predicted based on Voronoi polyhedra centered on lithium ions. Using this method, we can reproduce the well-known lithium removal processes of LiCoO2 and Li1.2Mn0.54Ni0.13Co0.13O2. Moreover, this method can effectively reduce the number of arrangements that need to be calculated. Our work provides a reasonable and efficient way to investigate the structural evolution of cathode materials during delithiation.