Activation characteristics of Ml1-xMmx (Ni3.55Co0.75Mn0.4Al0.3) hydrogen storage alloys after surface modification

The surface of multicomponents Ml(1) -(x)Mm(x)(Ni3.55Co0.75Mn0.41Al0.3) (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5) hydrogen storage alloys was impregnated in the vitriol liquor (0.01, 0.02, 0.04 mol (center dot) L-1) for five minutes at room temperature. With the following charge/discharge procedure, I-c = 60 mAh (center dot) g(-1) x 7.5 h, I-d = 60 mAh (center dot) g (-1), the final cutoff voltage was -0.60 V (vs. Hg/HgO), activation characteristics of the alloys with different Ml : Mm ratio were investigated. And the effects on activation characteristics of alloys modified by different surface methods were also investigated. The results indicate that Ml:Mm ratio and different surface modification process have a prominent effect on activation characteristics of the alloys. Activation characteristics and initial discharge capacities of the alloys have a great improvement after surface modification. The effects of activation characteristics are more obvious with the vitriol concentration increasing. The alloy Ml(0.7)Mm(0.3)(Ni3.55Co0.75Mn0.4Al0.3) shows the best activation characteristics and a maximum discharge capacity. With surface modification, the alloy was activated after 2 cycles, and the maximum discharge capacity is 250.1 mAh (center dot) g(-1).