No abstract

Cobalt oxyhydroxide coat on the surface of nickel hydroxide particles is finished employing a simple ball milling process. The structure, morphology, and surface composition of the coated Ni(OH) 2 particles is characterized by using X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy tests. The results show that numerous strip-like particles of a mixture of Ni(OH) 2 and CoOOH aggregate on the surface of the Ni(OH) 2 particles, and a structure of b-Ni(OH) 2 is preserved. Compared to the Ni(OH) 2 electrodes with a mixed CoO additive, the electrochemical activity of the electrodes with ball milled CoOOH coat can be improved as shown by using electrochemical impedance spectroscopy test, thus resulting in charge-discharge and cycle life performance improvement of the electrodes.

In this article,cobalt additives are introduced into nickel hydroxide electrodes by two incorporation methods-co-precipitated cobalt hydroxide during the nickel hydroxide synthesis or post-added CoO with nickel hydroxide. The results of X-ray diffraction, cyclic voltammetry, electrochemical impedance spectroscopy, and charge-discharge tests indicate that (i) the diffraction peaks show a decrease in intensity and increase in the half peak breadths for Ni(OH) 2 with co-precipitated cobalt hydroxide; (ii) the electrochemical activity of nickel hydroxide can be improved by both incorporated cobalt and the effects of post-added CoO are more notable; (iii) CoOOH derived from post-added CoO is not stable in the KOH electrolyte when the potential of the Ni(OH) 2 electrode is lowered and its reduction product may be inactive, thus results in an irreversible capacity loss of nickel-metalhydride battery after over-discharge-state storage.