Effect of Ni on electrochemical and hydrogen storage properties of V-rich body-centered-cubic solid solution alloys

Abstract V-rich solid solution alloys are potential candidates for Ni-MH x negative electrodes and hydrogen sorbing materials. Mechanical alloying (MA) is used in this paper to produce Ti 0.5 V 1.5−x Ni x nanocrystalline alloys (x = 0, 0.1, 0.2, 0.3). A SPEX 8000 M mill is used. The aim of this work is to study the effect of chemical modification by Ni on hydrogen sorption/desorption and electrochemical properties of V-rich body-centered-cubic (BCC) alloys. Presented measurements results show formation of BCC phase after 14 h of MA. The nanocrystallinety of obtained materials is confirmed by high resolution transmission electron microscopy images. MA alloys are tested by a Sievert's device at near room temperature. Partial substitution of V by Ni causes improved hydrogenation kinetics, reduced hysteresis and increased hydrogenation/dehydrogenation reversibility. Observed properties are mainly due to differences in structures of studied materials. Electrochemical studies on chemically modified V-rich alloys show that capacity retaining rate and discharge capacity increase with higher Ni content in the material.