Activation of Zr0.5Ti0.5V0.75Ni1.25 electrodes by hot alkaline solutions

Abstract

Hot alkaline treatment of the multiphase alloy Zr0.5Ti0 5V0 75Ni1 25 results in significant surface corrosion, with at least some of the corrosion products being soluble in the treating solution. The corrosion process generates hydrogen that is largely absorbed by the alloy during treatment, resulting in heterogeneous particle cracking and significant electrochemical discharge capacity (C0) even before the first deliberate charge. The discharge capacity (C1) after the first deliberate charge is significantly increased by hot alkaline treatment. C0 is a direct measure of alloy corrosion during the hot alkaline treatment and should be minimized in practice. C1 is a measure of electrochemical activation rate and should be maximized in practice. Another important parameter is the maximum capacity Cmax The effects of treatment time and temperature, as well as solution (KOH vs. NaOH) on C0, and Cmax are presented, along with some long-time cyclic capacity data.