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 orthorhornbic 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. (C) 2009 Elsevier Ltd. All rights reserved.

采用硬脂酸燃烧法制备了La(1 - x)SrxFeO3（x = 0.2，0.4）粉末，并对其相结构和电化学性能进行了系统研究。X射线衍射（XRD）分析表明，La(1 - x)SrxFeO3钙钛矿型氧化物分别由单相正交结构（x = 0.2）和三方结构（x = 0.4）组成。电化学测试表明，La(1 - x)SrxFeO3氧化物电极上的反应是可逆的。La(1 - x)SrxFeO3氧化物电极的放电容量随温度升高而增加。在电流密度为31.25 mA g - 1时，随着温度从298 K升高到333 K，其初始放电容量分别从324.4 mA h g - 1增加到543.0 mA h g - 1（当x = 0.2时），从147.0 mA h g - 1增加到501.5 mA h g - 1（当x = 0.4时）。经过20次充放电循环后，它们仍然保持钙钛矿型结构。与放电容量和温度之间的关系类似，电化学动力学分析表明，La(1 - x)SrxFeO3氧化物电极的交换电流密度和质子扩散系数随温度升高而增加。与La0.8Sr0.2FeO3相比，La0.6Sr0.4FeO3电极由于在不同温度下具有更高的循环容量，是一种更有前途的电化学储氢候选材料。（C）2009 Elsevier Ltd.保留所有权利。