The electrochemical properties of hydrogen storage Zr-based Laves phase alloys

Abstract

Zr-based Laves phase alloys Zr(MnCrVNi)2 were designed by means of the orthogonal method, and the electrochemical properties of the alloy electrodes were investigated. It was found that the maximum discharge capacity reached 343 mA h g−1, the discharge capacity ratio at a discharge rate of 200-50 mA g−1 was more than 80%, the number of activation cycles is less than 13 and the self-discharge ratio after 2 weeks varied between 16.1 and 53.1%. X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray analysis tests showed that the as-cast Zr-based Laves phase alloy consisted of at least eight phases. The major cubic C15-type Laves phase coexisted with the hexagonal C14-type Laves phase, orthorhombic Zr7Ni10 phase, tetragonal, Zr9Ni11 phase and a few other phases. X-ray photoelectron spectroscopy proved that Zr and Mn were richer in the outer layer of the Zr-based Laves phase hydride electrode; Ni and Cr were deficient on the surface of the electrode. After 540 charging-discharging cycles, the discharge capacities of the Zr-based Laves phase hydride electrodes decreased by 20–30%. This was mainly caused by the formation of oxides at the surface of the electrodes.