An investigation on the structural and electrochemical properties of La0.7Mg0.3(Ni0.85Co0.15)x (x=3.15-3.80) hydrogen storage electrode alloys

In this paper, the structural and electrochemical properties of the La0.7Mg0.3(Ni0.85Co0.15)x (x = 3.15, 3.30, 3.50, 3.65, 3.80) hydrogen storage electrode alloys have been studied systematically. From the XRD analyses, each alloy of this series is composed of the LaNi3 phase and the LaNi5 phase, and the phase abundance of each phase varies with the degree of non-stoichiometry x and determines the hydrogen absorption capacity of the alloy. The electrochemical studies show that as *y increases the maximum discharge capacity first increases from 365.7 mAh/g (x = 3.15) to 398.4 mAh/g (x = 3.50) and then decreases to 328.5 mAh/g (x = 3.80). Moreover, as x increases from 3.15 to 3.80, the high rate dischargeability (HRD), the exchange current density (I0), the limiting current density (IL) and the diffusion coefficient (D), of the alloy electrodes all increase first and then decrease.