The electrochemical performances of Ti-V-based hydrogen storage composite electrodes prepared by ball milling method

In order to overcome the inherent disadvantages of Ti-V-based hydrogen storage alloys, such as poor activation behavior and low high-rate dischargeability, the novel composites Ti0.17Zr0.08V0.35Cr0.1Ni0.3-x wt.% La0.7Mg0.3Ni2.75Co0.75 (x = 0, 5, 10 and 20) were successfully synthesized by ball milling method in the present study. And the structure and overall electrochemical properties of as-prepared composites are investigated systemically. The electrochemical studies show that the maximum discharge capacity of the composite electrodes displays no variation with the increase of La0.7Mg0.3Ni2.75Co0.75 content, whereas the high-rate dischargeability (HRD) and the activation behavior are distinctly improved with increasing x. The electrochemical hydrogen kinetics of composite electrodes is also studied by means of electrochemical impedance spectroscopy (EIS), linear polarization (LP), anodic polarization (AP) and potential-step measurements. It is found that the charge-transfer reaction resistance Rct is decreased with increasing the amount of La0.7Mg0.3Ni2.75Co0.75 while exchange current density I0, limiting current density IL and hydrogen diffusion coefficient D are all increased with increasing the amount of La0.7Mg0.3Ni2.75Co0.75. These results suggest that the formation of composite with La0.7Mg0.3Ni2.75Co0.75 alloy is a promising strategy for improving the HRD, activation behavior and electrochemical kinetics of Ti-V-based alloy electrodes.