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 Ni-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 phases to a greater or lesser extent. It was found by X-ray diffractometry and electron probe microanalysis that the black and white phases were assignable to V-based solid solution and TiNi-based and traces of Ti,Ni-based alloys, respectively. Their pressure composition isotherms suggested that TiV2.1Ni0.3 alloy had potentiality of high discharge capacity (1055 mAh g(-1)). The maximum discharge capacity of the TiV2.1Ni0.3 alloy observed in charge-discharge cycle tests was 540 mAh g(-1) at the discharge current density of 25 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 black and white phases in the TiV2.1Ni0.3 alloy form the most appropriate network which facilitates the hydrogen absorption and desorption. (C) 2000 The Electrochemical Society. S0013-4651(99)10-005-3. All rights reserved.