Performance of Non-foam Type Nickel Electrode Using Surface-coated Ni(OH)₂ for Nickel-metal Hydride Battery

Abstract

New paste-type positive electrodes with Ni- or Co(OH)2-coated Ni(OH)2 for nickel/metal-hydride (Ni/MH) battery were prepared using low-cost punching metal as substrate. Their charge-discharge properties were evaluated using non-sealed battery. Electrodes with Ni- and Co(OH)2-coated Ni(OH)2 showed higher discharge capacity than those with Ni and CoO as conductive agents, respectively. SEM observation and resistance of these Ni(OH)2 materials suggest formation of fine conductive network by homogeneous Ni and Co(OH)2 coating. The capacities of these coated electrodes faded by 25% after 50 charge-discharge cycles. Their swelling rate during cycles was larger than those of the conventional Ni-foam electrodes, and the cycle degradation was mainly attributable to decrease in current collectivity by the swelling. Sealed battery with Co(OH)2-coated Ni(OH)2 showed utilization efficiency of 77% (vs. 0.2 C) at 3 C rate, which was comparable to that of conventional Ni-foam electrode.