Influence of Sc 3+ on LiMn 2O 4 cathode materials at elevated temperature

Abstract

Sc 3+ -doped lithium manganese oxides were synthesized by solid-state reaction. The influences of doping element on structure, mean valence of manganese, and electrochemical performances were studied by X-ray diffraction (XRD), galvanostatic charge-discharge and cyclic voltammetric tests, and also electrochemical impedance spectroscopy (EIS). XRD tests showed that doped lithium manganese oxides were pure spinel structure without other phases. Redox titration and visible spectrophotometry tests indicated that the mean valence of manganese in doped lithium manganese oxides was higher than that of pure one. LiSc 0.02Mn 1.98O 4 remained 92.9% of the initial specific discharge capacity after 50th cycle at a constant current of 50 m/g, and the reversibility of LiSc 0.02Mn 1.98O 4 was improved in comparison with pure LiMn 2O 4 at 50 °C. EIS indicated that film deposition on spinel particles was suppressed because of Sc 3+ doping, and the charge transfer between the surface film and spinel particles with increasing temperature for Sc 3+ -doped materials became easier as compared with undoped one.