Effects of Mo substitution for Ni on the microstructure and property of V-based hydrogen storage alloys

Yanwei Tong,Lin Deng

doi:10.1051/matecconf/20166303001

Abstract

In order to study the property the V-based hydrogen storage alloys, Ni in the alloys was partially substituted by Mo. The V 2 Ti 0.5 Cr 0.5 Ni 1-x Mo x (x=0.02-0.08) hydrogen storage alloys were prepared by induction melting, and the effects of Mo content on the microstructure and electrochemical property were investigated systematically. The results show that the alloys mainly consist of a V-based solid solution phase with a BCC structure and a TiNi-based secondary phase. The electrochemical measurements indicate that with increasing the content of Mo, the maximum discharge capacity, the cycle stability and high rate discharge ability is increased first and then decreased.

Highlights

Hydrogen storage alloys used as negative electrode materials in Ni/MH secondary batteries are extensively studied in the past decades and a series of metal hydride electrode materials have been discovered, such as rareearth-based AB5-type alloys [1], AB3-type rare-earthbased alloys [2], AB2-type Laves phase alloys [3], Mgbased alloys [4], and V-based solid solution alloys [5,6]
Some researchers have studied the influence of Mo additive in AB5-type alloys [13,14], but the research of influence of Mo additive in V -based hydrogen storage alloys is seldom
It displays that all of the alloy samples are mainly composed of two distinct crystallographic phases: the 3-D interpenetrating phase is the TiNi-based phase, and the dendritic phase is the V-based solid solution phase

Summary

Introduction

Hydrogen storage alloys used as negative electrode materials in Ni/MH secondary batteries are extensively studied in the past decades and a series of metal hydride electrode materials have been discovered, such as rareearth-based AB5-type alloys [1], AB3-type rare-earthbased alloys [2], AB2-type Laves phase alloys [3], Mgbased alloys [4], and V-based solid solution alloys [5,6]. As one kind of metal-based hydrogen storage alloys, Vbased solid solution alloys have exhibited highly attractive properties for practical application because of their higher hydrogen storage capacity and lower hydrogen absorption/desorption temperature [7,8,9]. The V-based hydrogen storage alloy exhibited poor charge-discharge cycle stability because of the dissolution of the V constituent in the electrolyte. In order to improve the cycle stability of this type of alloy, the investigations of the element substitution and additive [10-12] were conducted. We prepared V2Ti0.5Cr0.5Ni1-xMox (x=0.02-0.08) alloys in which Mo was partially substitution for Ni, in order to improve the chargedischarge cycle stability of V2Ti0.5Cr0.5Ni alloy. The electrochemical property was performed on LAND battery testing instrument using a tri-electrode system consisting of a working electrode (MH electrode), a sintered Ni(OH)2/NiOOH counter electrode with excessive capacity and a reference electrode (Hg/HgO, OH-). The electrode was charged for 6 h at a constant current density (100 mA/g) followed by 5 min resting time and discharge at a constant current density (60 mA/g) to a cutoff potential of -0.6 V at 303 K

Alloy structure characteristic a Corresponding author

Discharge capacity and cycle stability

High rate discharge ability

Conclusions