Permeable characteristics of surface film deposited on LiMn2O4 positive electrode revealed by redox-active indicator

Herein, the ferrocene redox indicator-based surface film characteristics of spinel lithium manganese oxide (LMO) were evaluated. The pre-cycling of spinel LMO generated a film on the LMO surface. The surface film deposited on LMO surface suppresses further electrolyte decomposition, while the penetration of approximately 0.7 nm-sized redox indicator is not prevented. The facile self-discharge of LMO and regeneration current from the ferrocenium molecule was observed from the redox indicator in a specifically designed four-electrode cell. From this electrochemical behavior, a small-sized HF molecule attack on the LMO surface through a carbonate-based electrolyte-derived film is defined; hence, the prevention of small-sized molecules into the deposited surface film is crucial for the enhancement of LiMn2O4-based lithium-ion batteries.This work was supported by grants from the National Research Foundation of Korea (2019R1A2C1004694) and the Industrial Technological Innovation Program of the Korea Evaluation Institute of Industrial Technology (KEIT) granted fnancial resource from the Ministry of Trade, Industry & Energy, Republic of Korea (20004954). In addition, this paper was supported by the Konkuk University Researcher Fund in 2020