EFFECTS OF ELECTRODE COMPACTING ADDITIVES ON THE CYCLE LIFE AND HIGH-RATE DISCHARGEABILITY OF ZR(V0.25NI0.75)2 METAL HYDRIDE ELECTRODES IN ALKALINE-SOLUTION

Materials used as a compacting agent in the production of metal hydride electrodes influence the electrode performance, e.g. cycle life and high rate dischargeability. We have tested several metal hydride electrodes compacted with different metal powders: copper, nickel, cobalt and gold as well as platinum on carbon. The hydrogen storage material of all these electrodes was ZrV0.5Ni1.5. The compacted electrodes were cycled in a 6 M KOH electrolyte. Electrodes using nickel as compacting powder showed the best activation, while copper compacted electrodes showed the best cyclic stability. The ratio of compacting material to the active material is also important as it affects the internal resistance of the electrode. This is especially true for an alloy to binder ratio higher than 25 wt.%. Cobalt shows a partly reversible reaction at the standard potential of -0.83 V vs. the Hg/HgO/OH- reference electrode; it can therefore increase the capacity of the cobalt compacted electrode.