Strategy of manipulating La/Ce ratio to develop metal hydride electrode with excellent capacity even at −40 °C

Abstract

Metal hydride electrodes have been widely used in Ni/MH batteries, but their low-temperature discharge (LTD) performance restricts practical application. Herein, we propose a facile strategy for tuning the La/Ce ratio to prepare metal hydride electrodes for ultra-low-temperature Ni/MH batteries. The enthalpy shifts in the positive direction with a decrease in the La/Ce ratio and the thermodynamic stability decreases. Moreover, the resultant enhanced charge transfer and proton diffusion endows the electrode with impressive kinetics at −40 °C. One novel candidate, namely, La0.55Ce0.37M electrode presents the highest reported capacity of 317.3 mAh g−1 (0.2C) and the highest discharge specific capacity of 27.2 mAh g−1 (1C) even at −40 °C. A commercial-grade AAA nickel-metal hydride battery concomitantly presents the specific capacity of 71 and 456 mAh at a large current of 1000 mA at −40 and −20 °C, respectively. The excellent LTD performance indicates the suitability of this strategy for developing advanced ultra-low-temperature Ni/MH batteries.