Effect of ball-milling time on the electrochemical properties of La–Mg–Ni-based hydrogen storage composite alloys

In the present study, the effect of ball-milling time on the structure and the overall electrochemical properties of the novel La–Mg–Ni-based hydrogen storage composite alloys was investigated systematically. It is found that, from the results of X-ray diffraction (XRD) and scanning electron microscopy (SEM), the composite alloy is formed after ball milling the homogenous mixture of both La0.7Mg0.3Ni3.5 alloy and Ti0.17Zr0.8V0.35Cr0.1Ni0.3 alloy for different times. In these composite alloys, both La0.7Mg0.3Ni3.5 and Ti0.17Zr0.8V0.35Cr0.1Ni0.3 alloys basically maintain their respective original phase structures. The electrochemical studies show that the cyclic life of the composite alloy electrodes is improved with increasing ball-milling time, especially for the sample ball-milled for 120 min. After 100 charge–discharge cycles, the capacity retention rate C 100 / C max increases from 62.4% (30 min) to 80.3% (120 min), which can be ascribed to the enhanced anti-corrosion performance of electrode in KOH solution. Moreover, the electrochemical impedance spectra (EIS) and linear polarization (LP) measurements indicate that the kinetics of electrochemical hydrogen reaction is also improved with the increase of ball-milling time.