The improved electrochemical properties of novel La–Mg–Ni-based hydrogen storage composites

Abstract

In the present study, a novel alloy composite has been synthesized by ball milling nonstoichiometric AB3-type La0.7Mg0.3Ni3.5 alloy with Ti0.17Zr0.08V0.35Cr0.1Ni0.3 alloy in order to improve the cyclic stability and other electrochemical properties of La0.7Mg0.3Ni3.5 alloy electrode. The phase structure, morphology and electrochemical performances of the composite have been investigated systematically. From X-ray diffraction (XRD) patterns, it can be found that the La0.7Mg0.3Ni3.5 and Ti0.17Zr0.08V0.35Cr0.1Ni0.3 alloys still retain their respective phase structures in the composite. Electrochemical studies show that the cyclic stability of the composite electrode is noticeably improved after 100 charge–discharge cycles in comparison with single La0.7Mg0.3Ni3.5 alloy electrode due to enhanced anti-corrosion performance in the alkaline electrolyte. The discharge capacity retention rate C100/Cmax of composite electrode is 62.3%, which is much higher than that of the La0.7Mg0.3Ni3.5 alloy electrode, although the maximum discharge capacity of the former decreases moderately. Both electrochemical impedance spectra (EIS) and linear polarization (LP) studies indicate that the electrochemical kinetics of the composite electrode is also improved. The charge-transfer resistance (Rct), the polarization resistance (Rp) and the exchange current density (I0) of the composite electrode are 160.2 mΩ, 129.5 mΩ and 201.6 mA/g, respectively, which are superior to those of the La0.7Mg0.3Ni3.5 alloy electrode.