Stability of the LiMn2O4 surface in a LiPF6-based non-aqueous electrolyte studied by in-situ atomic force microscopy

Abstract

Investigation of the surface stability of electrode materials in a liquid electrolyte is significantly important for understanding the deterioration of stored Li-ion battery cells. Here, we examined LiMn2O4 surfaces in a LiPF6-based non-aqueous electrolyte by in-situ atomic force microscopy. A LiMn2O4(111) surface sample with a well-defined atomically-flat structure was prepared from a MnO(111) wafer. Although the surfaces of non-exposed or dry-air-exposed samples did not change in a typical electrolyte such as LiPF6 dissolved in propylene carbonate, the surface morphology of an air-exposed sample greatly changed under the same condition. Transmission electron microscopy observation revealed that the surface roughness is increased by the dissolution of one or two atomic layers of LiMn2O4-crystal surfaces in the electrolyte. The adsorbed water on the air-exposed surface is the origin of this phenomenon.