Improved electrochemical performance of BCC alloy by Ni addition and surface modification with AB5 alloy

The hydrogen storage and electrochemical properties of the Ti0.32Mn0.22Cr0.1V0.28Nix (x = 0, 0.05, 0.15, 0.2) alloys were investigated. XRD results revealed that the addition of Ni resulted in the formation of C14 Laves phase. With the increasing Ni content, the lattice parameter a of BCC phase and the lattice parameter a and c of C14 Laves phase decreased. The Ni addition reduced the hydrogen absorption/desorption capacities at gas solid reaction, but improved the electrochemical discharge capacity significantly. The maximum discharge capacity of 392 mAh g-1 was obtained for the Ti0.32Mn0.22Cr0.1V0.28Ni0.15 alloy. Cycling measurement revealed that the discharge capacity of the Ti0.32Mn0.22Cr0.1V0.28Ni0.15 alloy degraded with the increasing cycle number, decreasing to 63% of the maximum discharge capacity after 100 cycles. Further improvement on the activation and cycle life of this alloy can be achieved by surface modification with 20 wt.% LaNi3.55Co0.75Mn0.4Al0.3 addition.