Electrochemical studies of the nickel-based hydroxide electrode for the oxygen evolution reaction and coulombic efficiency of the electrode

Abstract

Nickel hydroxide, Ni(OH)2 electrode material has been used as a positive electrode in commercial alkaline secondary batteries for more than 100 years. This is because Ni(OH)2 has a good high rate discharge ability performance, wide operation and storage temperature range and relatively low. However, the Ni(OH)2 positive electrode exhibits poor performance which results from (i) competitive reactions of the oxidation of the active material and evolution of oxygen. (ii) The reduced charge acceptance of Ni(OH)2 positive electrode is suspected to be related to a relatively long distance between Ni(OH)2 particles and the nearest portion of the substrate. In this study, electrodes are prepared using β-Ni(OH)2 powder as the active electrode material, hot-pressed onto a nickel mesh current collector. The Ni2+ in the compound β-Ni (OH)2 material is partially substituted with Co2+ and Al3+ metals and the performance of as-prepared materials are optimized and examined. XRD, FTIR, TG-DTA, SEM/ EDS, and ICP confirms the formation of the expected compositions. The samples with 5 wt.% Co2+, and 10 wt. % Al3+ metals are found to be the optimal composition with promising electrochemical activities. The modification of Ni(OH)2 by the partial substitution of Co2+ and Al3+ metals for Ni2+ shows some effect on the redox peaks of Ni(OH)2 and the oxygen evolution reaction (OER). E.g. the onset for oxidation of the active material is significantly improved with partial substitution of Ni2+ by Co2+. On the other hand partial substitution of Ni2+ with Al3+ moves the onset of electrode oxidation to higher potential. In addition, the partial substitution of 10 wt.% Al3+ metal improves both discharge capacity (from 128 mAh/g to 170 mAh/g), and the coulombic efficiency (from 87% to 93%) of the β-Ni(OH)2 electrode.