An alternative for the anode materials of nickel metal hydride batteries: an AB3-type La0.6Gd0.2Mg0.2Ni2.6Co0.3Al0.1 hydrogen storage alloy

Abstract

In order to satisfy the demand for the cyclic stability of commercial Ni-MH anodes, a PuNi₃-type La_0.6Gd_0.2Mg_0.2Ni_2.6Co_0.3Al_0.1 alloy with excellent overall electrochemical properties was prepared by annealing the as-cast alloy sample at different temperatures for a week. The alloy had the highest PuNi₃-type content of 86.9 wt% (1073 K), which offered a capacity retention of 69.6% after 100 cycles. However, 23.7 wt% PuNi₃ type phase of the alloy constantly converted into the Ce₂Ni₇ type phase within a temperature increase of 50 °C, which improved the capacity retention by 12.1% under the same discharge capacity. We found that the addition of Gd did not change the stacked [LaMgNi₄]/[LaNi₅] superlattice and it maintained the structural stability of the crystal as well as its anti-corrosion, which is also a key factor to improve cyclic stability. These findings imply that alloys with both PuNi₃-type and Ce₂Ni₇-type multiphase structures can be considered as a new choice for hydrogen storage.