Electrochemical behaviors of a V3TiNi0.56Hf0.24 alloy electrode during charge–discharge cycling

The electrochemical behaviors of a V3TiNi0.56Hf0.24 alloy electrode during charge–discharge cycling have been studied. It is found that the main and secondary phases of the V3TiNi0.56Hf0.24 alloy transform, respectively, to a dihydride of (V,M)H2 and a C14 phase hydride of (Ti,Hf)(V,Ni)2Hx during the charging process of the alloy electrode. When the electrode is discharged to −0.7 V versus Hg/HgO, both the reaction of (V,M)H2 to (V,M)H and the reaction of (Ti,Hf)(V,Ni)2Hx to (Ti,Hf)(V,Ni)2 takes place. During further discharging from −0.7 to −0.5 V, a strong dissolution reaction of vanadium and an incomplete dehydriding reaction of (V,M)H to β(V,M) occurs simultaneously. The strong dissolution of vanadium in KOH electrolyte solution seriously leads to the deterioration of the alloy.