A promising anode candidate for rechargeable nickel metal hydride power battery: An A5B19-type La–Sm–Nd–Mg–Ni–Al-based hydrogen storage alloy

Abstract

Nickel metal hydride rechargeable batteries hold a prominent position in battery-powered electric vehicles market, owing to the noticeable advantages of high-power capability. To promote the utilization of the nickel metal hydride batteries, the anode materials – hydrogen storage alloys, are in the spotlight. Here, we report an A5B19-type La–Sm–Nd–Mg–Ni–Al-based alloy with superior rate performance. The alloy is specifically composed of Pr5Co19-and Ce5Co19-type structures after annealing during which the Ce5Co19-type structure transforms to Pr5Co19-type structure within 900–995 °C. We find that the alloy exhibits desirable rate performance as possessing more Ce5Co19-type structure that the Ce5Co19-type alloy (900 °C) delivers a high discharge capacity of 277.4 mAh g−1 even at 1500 mA g−1 which is 72.4 mAh g−1 higher than the Pr5Co19-type alloy (995 °C). Further exploration reveals the fascinating high rate dischargeability benefitting from the kinetics including the fast charge transfer and speedy hydrogen diffusion. Differing from the pattern of rate performance, the cycling stability of the alloy is enhanced by the growing Pr5Co19-type structure whose capacity retention rate is 89.4% at the 100th cycle. The work will encourage the progress of the nickel metal hydride batteries with superior rate performance and long cycling life.