TG-MS analysis on thermal decomposable components in the SEI film on Cr2O3 powder anode in Li-ion batteries

Abstract

The thermal decomposable species in the solid electrolyte interphase (SEI) film on Cr2O3 powder anode at different lithiated and delithiated states in the first cycle were analyzed by thermogravimetry and mass spectrometry (TG-MS) technique. The weight loss ratio in a fully lithiated Cr2O3 electrode during TG measurement at 50–500 °C is 8.9 wt%, which is decreased to 1.5 wt% for a fully delithiated Cr2O3 electrode. This indicates that the SEI film on Cr2O3 powder anode is decomposed electrochemically upon delithiation. The main gas products are CH2=CH2, CO2, and CH3-containing volatile species in thermal reaction. They are released step-by-step in four characteristic temperature regions, which were originated mainly from oligomer and polyethylene-oxide-like species, partly from ROCO2Li. It is also observed that the amount of thermal decomposable components in the SEI film on the fully lithiated Cr2O3 powder electrode is much higher than that on graphite and hard carbon anodes, indicating different SEI features of transition metal oxide anodes.