Scanning Tunneling Microscopy and Medium Energy Ion Scattering Spectrometry of Spinel Structure of Li4Ti5O12 Surface

Abstract

Spinel lithium titanate (Li4Ti5O12) is one of the promising anode materials for high-performance lithium-ion batteries (LIBs). It is crucial to investigate atomistic structures of Li4Ti5O12 surfaces to understand the phenomena at the LTO/electrolyte interfaces such as CO2-gas generation which greatly affects the performance and safety of LIBs. By applying scanning tunneling microscopy (STM) and medium energy ion scattering (MEIS) to a Li4Ti5O12 (111) film prepared from a TiO2 wafer, we found that there exists two kinds of Li-terminated (111) terraces bounded by steps with different heights. In the major terraces, the top hexagonal Li layer is stacked above the oxygen layer, while the top Li layer is stacked above the Ti-Li layer in the minor terraces. The relative stability between the two surface structures seems to depend on the atmosphere due to different stoichiometry, which is a possible origin of CO2 generation via redox interaction with electrolyte molecules.