Electrochemical performances of four lanthanum transition-metal complex oxides

As novel negative electrode materials for alkaline batteries, the electrochemical properties of four lanthanum transition-metal (La-TM) complex oxides LaTiO3, LaVO4, LaCrO3 and LaMnO3 were investigated. X-ray diffraction (XRD) and scanning electron microscope (SEM) were employed to characterize their microstructures. All the La-TM oxides were made up of single phases. Electrochemical measurements showed that the maximum discharge capacities of LaTiO3, LaVO4, LaCrO3, and LaMnO3 electrodes at 303 K were 367, 187, 318, and 278 mAh/g, respectively. X-ray photoelectron spectroscopy (XPS) and XRD Rietveld analysis were carried out to discuss the electrochemical reaction mechanism. Electrode kinetics was studied by electrochemical impedance spectrum (EIS). The results showed that the maximum discharge capacity was directly related to the charge-transfer resistance (Rct) of La-TM oxide electrode. The cyclic properties of the four oxides should be further improved and the discharge capacity of LaMnO3 (about 96 mAh/g) was the highest after 10th charge/discharge cycles.