Mingda Tao

Microstructure and electrochemical properties of LaNi4–xFeMnx (x=0–0.8) hydrogen storage alloys

Abstract In order to reduce the cost of LaNi 5 based hydrogen storage alloys, effect of substitution of Mn for Ni on structural and electrochemical properties of LaNi 4– x FeMn x ( x =0–0.8) hydrogen storage alloys was studied systematically. X-ray diffraction (XRD) and scanning electron microscope (SEM) showed that LaNi 5 and La 2 Ni 7 phases were invariably present in all alloy samples, and when x ≥0.4, (Fe, Ni) phase was observed. Electrochemical studies revealed that the discharge capacity reached a maximum value of 306.4 mAh/g when x =0.2 and the cycling stability decreased with the increase of x . With the increase of Mn content, hydrogen diffusion coefficient decreased, whereas high rate discharge-ability (HRD) and exchange current density first increased slowly when x ≤0.2 and then decreased markedly when x =0.8, indicating that electrochemical reaction on the surface of alloy electrodes had strong influence on kinetic property.

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.

Hydrogen-induced amorphization in LaNi3–xMnx compounds

Abstract Effects of Mn content on the hydrogen-induced amorphization of LaNi 3– x Mn x ( x =0.0, 0.1, 0.3 and 0.5) hydrogen storage alloys were studied systematically. All the alloys were prepared using a rapid quenching and annealing method. As the charging time increased, the hydrogen-induced amorphization occurred gradually in all the compounds for the first cycle. During the discharge process, discharge potential plateau was not observed in LaNi 3 . As Mn content increased, however, structural changes were inhibited partly, and a plateau evolved gradually in the discharge curves.