Electrochemical performance of Zn-substituted Ni(OH)2 for alkaline rechargeable batteries

Zn-substituted Ni(OH)(2) for alkaline rechargeable batteries was prepared by a chemical coprecipitation method. The structures were characterized by X-ray diffraction and scanning electron microscopy, and the electrochemical performance, including charge-discharge behavior, the proton diffusion coefficient (DH+), and the cycle life, was investigated in detail. The results showed that the charge-discharge potentials of Zn-substituted beta-Ni(OH)(2) are much higher than those of Zn-substituted alpha-Ni(OH)(2). For a single alpha (for 30.5-48.4% Zn content) or a single beta (from 0 to 9.3% Zn content) phase in the sample, the discharge potentials increase with the increase of Zn content. However, when there is an alpha and beta phase mixture in the sample, the discharge potential decreases with an increase of Zn content. The DH+ values of Zn 0% and Zn 38.1% samples measured by the current-pulse relaxation method are much lower than those of Zn 9.3% and Zn 19.6% samples. DH+ of all the samples decreases with an increase of the depth of discharge. The effects of different Zn contents on the charge-discharge potentials of the nickel electrodes can be attributed to the differences of the electrochemical and diffusion polarization.