Effect of vanadium substitution in C14 Laves phase alloys for NiMH battery application

• Published in: Journal of alloys and compounds 2009-01, Vol.468 (1), p.482-492
• Main Authors: Young, K., Fetcenko, M.A., Li, F., Ouchi, T., Koch, J.
• Format: Article
• Language: English
• Subjects: Alternative fuels. Production and utilization; Applied sciences; Electrochemical reactions; Energy; Exact sciences and technology; Fuels; Hydrogen; Hydrogen absorbing materials; Metal hydride; Transition metal alloys and compounds
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2008.01.033

Vanadium, as the most important B-site modifier in (Zr,Ti)Ni 2-based Laves phase alloy, was studied to optimize the performance of nickel metal hydride batteries. As the amount of V-substitution for Ni increases, the total hydrogen storage capacity increases, while the reversible hydrogen storage capacity decreases due to the formation of a stable hydride. Lattice constants increase with higher vanadium contents indicating the majority of vanadium atoms reside in the B-site. Broader X-ray diffraction peaks and higher pressure–concentration isotherm slope factors indicate a higher degree of disorder for alloys with a higher V-content. In the study of a series of alloys with various V, Ni, Ti, Zr contents (while maintaining a constant value of electronegativity), all alloys exhibit similar pressure–concentration isotherms and half-cell characteristics. The sealed NiMH battery performance indicates that in the pure C14 alloy family, low-vanadium alloys (12–13 at.%) are more favorable in regards to peak power stability, charge retention, and cycle life.