Abstract
To obtain a novel negative electrode for nickel-metal hydride rechargeable batteries, perovskite-type oxide LaGaO3 was synthesized by the sol-gel method. The electrochemical properties of the oxide were systematically investigated at different temperatures by using galvanostatic, chronoamperometric, and potentiodynamic polarization methods. We have selected 298, 313, and 328 K as room, intermediate, and high temperatures, respectively. The galvanostatic results showed that the discharge capacity of the oxide LaGaO3 increased with the temperature elevating during the first 3 cycles. This oxide has the highest discharge capacity of about 220 mAh g(-1)at high temperature. For room and intermediate temperatures, we observed that the discharge capacity maintains a constant about of 5 and 13 mAh g(-1) for 298 and 313 K, respectively, when the number of cycles is increased. The electrochemical kinetic analysis indicates that the exchange current density and the hydrogen diffusion coefficient of the oxide LaGaO3 increase with the rise in temperature. The apparent activation energy (E-alpha) for hydrogen diffusion process and the activation energy (Delta H-r*) for charge-transfer reaction of the investigated oxide electrode LaGaO3 are estimated. The calculated values of the E-alpha and Delta H-r* are 117.46 and 105 kJ mol(-1), respectively. The above experimental results indicated that the kinetic properties of the working electrode have been significantly improved by the elevating of the temperature. The best electrochemical performance (faster activation and highest maximum capacity) of the oxide electrode is obtained at high temperature (328 K).