Abstract
The physico-chemical performance of the novel anode LaGaO3 for Ni/MH accumulators was studied using the electrochemical impedance spectroscopy (EIS) method during cycling. The measured EIS data of the perovskite oxide are fitted according to the proposed equivalent circuit representing various processes involved in the mechanism of hydrogenation/dehydrogenation reactions of the oxide. Different kinetic elements such as current density I0$$ {I}_0 $$, charge transfer resistance Rct$$ {R}_{\mathrm{ct}} $$, hydrogen transfer resistance Rht$$ {R}_{\mathrm{ht}} $$, double layer capacitance Cdl$$ {C}_{\mathrm{dl}} $$, and mass hydrogen diffusion Y0$$ {Y}_0 $$ were estimated under cycling. The EIS results relieved that current density I0$$ {I}_0 $$ of the oxide increases quickly during the activation process and its maximum value is obtained at the second cycle (377.67 mA g(-1)). The degradation of the charge transfer rate of the oxide after activation can be ascribed to the corrosion of the electrode/electrolyte interface. The variation of the Warburg impedance Y0$$ {Y}_0 $$ could be attributed to the change in the morphological and the structure of the working electrode over cycling. The EIS analysis relieved that electrochemical behavior of the oxide is controlled by the charge-transfer rate and the modification of the electrode surface.