Preparation and electrochemical properties of La0.4Sr0.6FeO3 as negative electrode of Ni/MH batteries

Perovskite-type oxide La0.4Sr0.6FeO3 powder was prepared by a stearic acid combustion method, and its phase structure, kinetic characteristics, and electrochemical properties were systematically investigated as the negative electrode for Ni/MH batteries. X-ray diffraction (XRD) shows that the as-prepared powder consists of a single phase with rhombohedral structure. After 20 cycles, perovskite-type structure still remains in the electrode sample. The electrochemical test shows that the reaction at the La0.4Sr0.6FeO3 electrode is reversible. With an increase in temperature from 298 K to 333 K, its initial discharge capacities increase from 153.4 mA h g−1 to 502.6 mA h g−1 at 31.25 mA g−1, and from 56.0 mA h g−1 to 279.6 mA h g−1 at 125 mA g−1, respectively. At a discharge current density of 125 mA g−1, its capacities keep steady at about 80.0 mA h g−1, 195 mA h g−1 and 370 mA h g−1 at 298 K, 313 K and 333 K, respectively. Both the exchange current density and the proton diffusion coefficient of the La0.4Sr0.6FeO3 oxide electrode also increase with temperature in a manner similar to the discharge capacity.