A paste type negative electrode using a MmNi5 based hydrogen storage alloy for a nickel–metal hydride (Ni–MH) battery

Different conducting materials (nickel, copper, cobalt, graphite) were mixed with a MmNi5 type hydrogen storage alloy, and negative electrodes for a nickel–metal hydride(Ni–MH) rechargeable battery were prepared and examined with respect to the discharge capacity of the electrodes. The change in the discharge capacity of the electrodes with different conducting materials was measured as a function of the number of electrochemical charge and discharge cycles. From the measurements, the electrodes with cobalt and graphite were found to yield much higher discharge capacities than those with nickel or cobalt. From a comparative discharge measurements for an electrode composed of only cobalt powder without the alloy and an electrode with a mixture of cobalt and the alloy, an appreciable contribution of the cobalt surface to the enhancement of charge and discharge capacities was found.