Electrochemical properties of La1-xSrxFeO3 (x = 0.2, 0.4) as negative electrode of Ni-MH batteries

La(1-x)SrxFeO3 (x = 0.2,0.4) powders were prepared by a stearic acid combustion method, and their phase structure and electrochemical properties were investigated systematically. X-ray diffraction (XRD) analysis shows that La(1-x)SrxFeO3 perovskite-type oxides consist of single-phase orthorhombic structure (x = 0.2) and rhombohedral one (x = 0.4), respectively. The electrochemical test shows that the reaction at La(1-x)SrxFeO3 oxide electrodes are reversible. The discharge capacities of La(1-x)SrxFeO3 oxide electrodes increase as the temperature rises. With the increase of the temperature from 298 K to 333 K, their initial discharge capacity mounts up from 324.4 mA h g-1 to 543.0 mA h g-1 (when x = 0.2) and from 147.0 mA h g-1 to 501.5 mA h g-1 (when x = 0.4) at the current density of 31.25 mA g-1, respectively. After 20 charge-discharge cycles, they still remain perovskite-type structure. Being similar to the relationship between the discharge capacity and the temperature, the electrochemical kinetic analysis indicates that the exchange current density and proton diffusion coefficient of La(1-x)SrxFeO3 oxide electrodes increase with the increase of the temperature. Compared with La0.8Sr0.2FeO3, La0.6Sr0.4FeO3 electrode is a more promising candidate for electrochemical hydrogen storage because of its higher cycle capacity at various temperatures.