Hydrogen absorption and hydride electrode behaviour of the Laves phase ZrV1.5-xCrxNi1.5

The substitution of chromium for vanadium in ZrV1.5-xCrxNi1.5 leads to a cubic C15 phase as the main phase with a low content of the secondary phase Zr7Ni10. The lattice parameters suggest a complex redistribution of V, Ni or Cr between the B and A sites of the Laves phase AB(2), which does not depend only on the Cr content. The pressure-composition isotherms show sloping plateaux, alloy hydrogen contents between 3.35 and 4.25 H/mol and desorption enthalpies of Delta H = 41.8-50.2 kJ/mol H-2 at constant H concentration (1.8 H/mol). Discharge capacities of between 113 and 222 mAh/g have been obtained for the hydride electrodes at a 160 mA/g discharge current; for the Cr-substituted alloys the discharge capacities increase with x. (C) 1999 Elsevier Science S.A. All rights reserved.