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

Annealing Nd-only AB(3.74) metal hydride alloy was found to effectively increase composition homogeneity, main A(2)B(7) 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 A(2)B(7) phase increases in the alloy with higher annealing temperatures, the general electrochemical performance improves. Extending the annealing period from 5 to 16 h further increases the A(2)B(7) phase abundance, but deteriorates the high-rate dischargeability due to the reduction of AB(5) catalytic phase. (C) 2013 Elsevier B.V. All rights reserved.