Electrochemical and structural characterization of Ti-V-Ni hydrogen storage alloys with BCC structure

Various Ti-V-Ni hydrogen storage alloys branched from TiV0.9Ni0.5, one of N i-substituted TiV1.4-based alloys, were prepared by an are-melting method. All alloys prepared in this work were composed of both black and white phas es to a greater or lesser extent. It was found by X-ray diffractometry and electron probe microanalysis that the black and white phases were assignabl e to V-based solid solution and TiNi-based and traces of Ti,Ni-based alloys , respectively. Their pressure composition isotherms suggested that TiV2.1N i0.3 alloy had potentiality of high discharge capacity (1055 mAh g(-1)). Th e maximum discharge capacity of the TiV2.1Ni0.3 alloy observed in charge-di scharge cycle tests was 540 mAh g(-1) at the discharge current density of 2 5 mA g(-1), which was the highest value among the Ti-V-Ni alloys with body- centered cubic structure reported until now. This seems to be because the b lack and white phases in the TiV2.1Ni0.3 alloy form the most appropriate ne twork which facilitates the hydrogen absorption and desorption. (C) 2000 Th e Electrochemical Society. S0013-4651(99)10-005-3. All rights reserved.