The structure and electrochemical performance of spherical Al-substituted α-Ni(OH)2 for alkaline rechargeable batteries

Spherical Al-substituted α-Ni(OH)2 for alkaline rechargeable batteries was prepared by a complexation-coprecipitation method. The morphology and structure of the samples were characterized by SEM, XRD and Raman spectroscopy. Their electrochemical performance including charge–discharge behavior, diffusion coefficient of proton (DH+), stability in strong alkaline solution and cycle life was also investigated. The results showed that the Al-substituted α-Ni(OH)2 prepared by this method manifests perfect spherical shape and the specific discharge capacity of the sample with 18.3 mol% Al reaches 477 mAh g−1 when the pH value of synthesis solution is 11.75. The interlayer distance, the oxygen evolution potential and the half discharge potential of the sample increase greatly with the increase of Al content. Compared with β-Ni(OH)2 without Al substitution, there are large amounts of proton defects in Al-substituted α-Ni(OH)2 which increases the diffusion coefficient of proton (DH+) measured by current pulse relaxation (CPR). The Al-substituted α-Ni(OH)2 sample shows an excellent structural stability during ageing treatment in 6 M KOH solution and the loss of Al can be neglected.