Synthesis, characterization, and electrochemical performances of alpha nickel hydroxide by coprecipitating Sn2+

Abstract

Sn-substituted α-Ni(OH)2 for Ni-MH battery is prepared by supersonic coprecipitating method, using NiSO4 as nickel ion source and SnSO4 as doping material. The crystal structure and morphology of the samples were characterized with X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM). The results demonstrate that the crystal structure of all samples changes from α/β mixed phase to pure α phase and the interlayer spacing becomes larger with more Sn2+ substitution for Ni2+, while the agglomeration particle size decreases initially and then increases. The electrochemical performances of the prepared nickel hydroxide were characterized by cyclic voltammetry (CV) and charge-discharge tests. The results reveal that 15 % Sn-substituted α-Ni(OH)2 has best electrochemical performance, such as best reaction reversibility, highest proton diffusion coefficient, the maximum discharge capacity (303.6 mAh/g at 0.2 C), and the maximum capacity retention (maintaining 90.5 % after 30 cycles at 0.2 C).