  High-entropy alloys (HEAs) and their corresponding high-entropy hydrides are
new potential candidates for negative electrode materials of nickel-metal
hydride (Ni-MH) batteries. This study investigates the cyclic electrochemical
hydrogen storage performance of two AB-type HEAs (A: hydride-forming elements,
B: non-hydride-forming elements) in Ni-MH batteries. TiV2ZrCrMnFeNi with a
dual-phase structure shows a fast activation and a low charge transfer
impedance with a discharge capacity of 150 mAhg-1, while TiV1.5Zr1.5CrMnFeNi
with a single phase shows a slow activation and a capacity of only 60 mAhg-1.
The better electrochemical performance of TiV2ZrCrMnFeNi was attributed to its
higher vanadium/zirconium ratio and abundant interphase boundaries, which act
as hydrogen paths and heterogeneous hydride nucleation sites. These results
suggest the high potential of dual-phase HEAs as new active electrode materials
for Ni-MH batteries.
