Does aluminum and niobium substitution for nickel actually improve the electrochemical performance of Mg₂ Ni?

In the present investigation, Mg₆₇ Ni_(33–x) Nb₁ Al _x ( x = 0, 1, 3 and 5 wt%) hydrogen storage alloys were synthesized using high energy ball milling technique. Ball milled powders were subjected to various characterization techniques viz., X-ray diffraction, Scanning electron microscopy with an Energy-dispersive X-ray spectroscopy (EDS) and Transmission electron microscopy. Effect of Al and Nb substitution on the inter-planar shift and its corresponding implications on lattice strain, crystallite size and unit cell volume of Mg₂ Ni compound were also discussed. Activation energy of the milled powders was calculated using Kissinger analysis. Mg₆₇ Ni₃₃ powder exhibit lower activation energy than others. Cyclic voltammetry, electrochemical impedance spectroscopy and charge–discharge studies were done on the developed electrode materials. Increasing Al substitution for Mg increases the cycling stability of electrode materials from 68 (x = 0) to 77% (x = 5).