A series of (La, Mg)Ni2.8Co0.5 metal hydride alloys was studied in order to understand the effects of partial Al-substitution for Co on the alloy's structure, gaseous phase hydrogen storage properties, and electrochemical performance. The alloys were characterized by X-ray diffraction, scanning electron microscopy, X-ray energy dispersive spectroscopy, pressure-concentration-temperature characterization, half-cell electrochemical tests, and sealed full-cell tests. After an annealing process at 960 degrees C for 5 h, the main matrix of the Al-free base alloy shifted from AB(3) phase into an A(2)B(7) phase. Annealed alloy samples incorporating Al promoted the AB(5) phase over the A(2)B(7) phase. The annealing treatment (AB(3) to A(2)B(7)) increased the gaseous phase hydrogen storage capacity and lowered the plateau pressure and hysteresis in the absorption desorption isotherms. The addition of Al in the annealed samples (A(2)B(7) to AB(5)) decreased gaseous phase hydrogen storage and electrochemical capacities, decreased high rate dischargeability, but increased cycle stability. Continuous pulverization of the metal hydride alloy at the negative electrode appeared to be the main failure mode of this series of alloys despite the lower starting rate of pulverization when compared to commercially available AB(5) alloys. (C) 2015 Elsevier B.V. All rights reserved.