The influence of copper and carbon black on electrochemical behavior of nickel positive electrode

Abstract

Nickel hydroxide is used as an active material in positive electrodes of secondary alkaline batteries. In alkaline batteries, the capacity of the negative electrode is greater than that of the positive electrode, hence the cell capacity is limited by the positive electrode. The practical capacity of the Ni(OH) 2 positive electrode depends on the efficiency of the conductive network connecting the Ni(OH) 2 particles with the current collector. In this study, hot-pressed-type electrodes were prepared using fiber-like β-Ni(OH) 2 powder as the active material on a nickel mesh as a current collector. The effect of carbon black as a conductive network for Ni(OH) 2 active material and the partial substitution of Cu(OH) 2 for β-Ni(OH) 2 material on the electrode performance, are examined. The carbon black powder addition improves the utilization of the active material; however it lead to a decrease in stability of the electrode. The partial substitution of Cu(OH) 2 for β-Ni(OH) 2 significantly improves the coulombic efficiency of the β-Ni(OH) 2 active material and it also increases the specific discharge capacity and enhance the stability of the electrode. These findings showed that the copper modified β-Ni(OH) 2 electrodes possessed an improved specific capacity and stability and thus may be recognized as a promising hybrid material for battery electrode applications. • The β-phase Ni(OH) 2 is formed when hydrothermal treatment is applied. • Carbon black improves specific discharge capacity but not stability. • Cu 2+ substitution improves both capacity and stability.