High-temperature electrochemical performance of low-cost La–Ni–Fe based hydrogen storage alloys with different preparation methods.

In order to optimize the microstructure and high temperature electrochemical performances of low-cost AB 5 -type Ml(NiMnAl) 4.2 Co 0.3 Fe 0.5 hydrogen storage electrode alloys, four different preparation methods including normal solidification (NS), normal solidification and 900 °C heat treatment (NS + HT), rapid solidification (RS), rapid solidification and 900 °C heat treatment (RS + HT) were adopted in this work. All alloys exhibit CaCu 5 type hexagonal structure and there is a small amount of A 2 B 7 phase in NS + HT and RS + HT alloys. It is found the using of HT process can decrease the hydrogen equilibrium plateau pressure, the plateau slope and hysteresis at 40, 60 and 80 °C. The NS + HT and RS + HT alloys also possess better activation, high rate discharge performance, larger discharge capacity, but poor cycling performance due to the existence of A 2 B 7 phase which can accelerate dissolution of Ni, Mn and Fe elements in KOH alkaline electrolyte. The RS process can make alloy exhibit the best cycling performance especially at 60 °C. [ABSTRACT FROM AUTHOR]