Effects of additions on AB5-type hydrogen storage alloy in MH–Ni battery application

The AB5-type hydrogen storage alloy of Mm0.3Ml0.7Ni3.55Co0.75Mn0.4Al0.3 were synthesized and mixed with PVA (Polyvinyl Alcohol) or different percentage Ni powder as the test samples. The cycle stabilities of the composites were tested in 6 M KOH electrolyte through electrochemical method. The results indicated that all the samples with Ni powder have better cycle stabilities and flatter discharge voltage platform. The sample of Mm0.3Ml0.7Ni3.55Co0.75Mn0.4Al0.3 + 200 wt.% Ni has the highest capacity conservation rate of 80.5% and the longest discharge time of 5.2 h. The SEM images show that the particle diameters of the alloy decreased by 2 μm and the surface smoothed without sharp edges after adding Ni powder. It can be presumed that adding Ni can improve the cycle stability of the alloy of Mm0.3Ml0.7Ni3.55Co0.75Mn0.4Al0.3 in the alkaline electrolyte and enhance the reaction rate in the charge/discharge cycles.