Effects of surface and bulk modifications on electrochemical and physicochemical characteristics of MgNi alloys

Effects of partial substitution of Mg in MgNi with both Ti and V and subsequent surface modification by ball-milling with graphite on electrochemical and physicochemical characteristics of amorphous MgNi alloys were investigated. It was found from thermogravimetry (TG) that hydrogen desorbability of the MgNi alloys was improved by either partial substitution with both Ti and V or surface modification with graphite, and that the combination of the partial substitution and the subsequent surface modification enhanced the hydrogen desorbability further. In charge-discharge cycle tests, the partial substitution with Ti and V or surface modification with graphite suppressed the decay of discharge capacity with increasing cycle number. Mg0.9Ti0.06V0.04Ni alloy modified with graphite exhibited further improved cycle performance as compared with either unmodified Mg0.9Ti0.06V0.04Ni alloy or MgNi alloy modified with graphite. These results indicate that modification of both bulk and surface of the MgNi alloys is very effective in improving hydrogen desorbability and charge-discharge cycle performance of the alloys. (C) 2002 Elsevier Science B.V. All rights reserved.