THE ELECTROCHEMICAL CHARGE DISCHARGE PROPERTIES OF ZR-CR-NI HYDROGEN STORAGE ALLOYS

Zr(CrxNi1-x)(2)(0.15 less than or equal to x less than or equal to 0.6 5) alloys were prepared by are melting in an argon atmosphere. Through X-ray diffraction, the main crystal structure of the alloys was found to change from Laves phase cubic C15 to hexagonal C14 as the Cr-to-Ni ratio increased, and lattice parameters and hydrogen absorption capac ities were mainly determined by the Cr content. The alloy Zr(Cr0.35Ni0 .65)(2), which was mainly of C15 Laves phase structure, was found to h ave maximum electrochemical discharge capacity of 305 mA h g(-1) at 29 8 K. The activation behaviors of Zr-Cr-Ni-based hydride electrodes wer e also studied. Fine alloy powders,especially those pulverized by cycl ing in hydrogen gas and where the electrodes were pre-treated with HF- H2O2 solution, were highly activated. As both Zr and Cr have a high re sistance against alkaline solution, it is reasonable for Zr-Cr-Ni allo y electrodes to have durable cycle lives. The chemical valence states and composition of electrode surfaces were also analyzed with X-ray ph otoelectron spectroscopy before and after charge-discharge cycling. An obvious variation in the Zr3d(5/2) peak position before and after cyc ling was detected. The discrepancy is ascribed to the chemical environ ment differences of Zr atom in primordial and activated surface layers .