Effects of various annealing conditions on (Nd, Mg, Zr)(Ni, Al, Co)3.74 metal hydride alloys

Abstract

Annealing Nd-only AB3.74 metal hydride alloy was found to effectively increase composition homogeneity, main A2B7 phase abundance, and both gaseous phase and electrochemical hydrogen storage capacities, as well as to facilitate activation, and improve battery high-rate performance, charge retention, and cycle life. As the phase abundance of the main A2B7 phase increases in the alloy with higher annealing temperatures, the general electrochemical performance improves. Extending the annealing period from 5 to 16h further increases the A2B7 phase abundance, but deteriorates the high-rate dischargeability due to the reduction of AB5 catalytic phase.