Investigation of Cathode Electrolyte Interphase Layer in V 2 O 5 Li-ion Battery Cathodes: Time and Potential Effects

Basic understanding of surface reactions on the Li ion battery electrodes is of great importance as the interphase layers formed on the electrode surface due to the decomposition of electrolyte, during the initial battery cycles affects the safety, cycling life and performance of lithium-ion batteries. The effects of time, potential and cycling rate on the formation of cathode electrolyte interphases (CEIs) have been investigated on a V 2 O 5 intercalation cathode by X-ray photoelectron spectroscopy (XPS). CEI layer on V 2 O 5 based cathode is mainly composed of Li-alkyl carbonates (ROCO 2 Li), Li 2 CO 3 , LiF and some C−O, C=O species such as polyethylene oxide type compounds, Li-alkoxides (R−CH2OLi) and oxalates. Formation of CEI on cathode takes place during the discharge cycle while a partial dissolution/removal has been observed in the charging cycle. Removal of CEI species during the charging cycle could be ascribed to the puckering of V 2 O 5 layers due to de-lithiation process. The formation and dissolution of LiF, ROCO 2 Li and other species has been observed until ≈215 ± 10 h, this may indicate that the decomposition of electrolyte is taking place till several cycles, which is an undesirable phenomenon in LIBs. CEI formation has shown a dependence on lower discharge potential, time and cycling rate.