Oxidization of fluid-like Li metal with inherent LiLi2O interface from simulation insights

The oxidization of pure Li is rarely discussed, but substantially important in the design and optimization, especially the failure mechanism of Li metal anode for rechargeable batteries. In this context, the Li metal and inherent LiLi2O interface after oxidization are examined using first principles calculations. The results demonstrated that in Li itself, the Li ion exhibits a fluid-like transport feature, especially in the vacancy-assisted migration. The fresh Li surface can be oxidized quickly in air with a thick cover (mainly Li oxides), and an inherent LiLi2O interface is, therefore, introduced. With the lowest surface energy, the Li (111) plane is revealed with a strong capability of adsorbing O and N atoms to form the distorted XLi6 (X = O, N, etc.) octahedra in the outmost surface layers. Although the Li ion migrates fast in Li itself, the LiLi2O interface shows a sluggish Li diffusion kinetic in Li2O side. This ultimately leads to the Li diffusion prefers to go along the interface boundary in Li side, which loosens the LiLi2O interface structure to result in the exfoliation of surface metastable Li2O spontaneously during electrochemical cycles in Li-metal batteries.