Crystal phase, structure stability and electrochemical performance of Co/Cu/Al-substituted nano-sized alpha nickel hydroxide

The single- and multi-element-substituted nano-sized nickel hydroxides have been synthesized by ultrasonic-assisted co-precipitation method. Four kinds of samples a, b, c and d are prepared by chemically co-precipitating Ni/Co, Ni/Cu, Ni/Cu/Co and Ni/Cu/Co/Al, respectively. The crystal structure, morphology and particle size distribution of all samples are characterized by X-ray diffraction, Fourier transform infrared spectroscopy, laser particle size analyzer and electron microscope (TEM, SEM). The results show that the samples are nano-sized Ni(OH)2 and the crystalline phase of samples b, c and d are pure α-Ni(OH)2 phase while sample a is α/β-Ni(OH)2. The electrochemical performance of the prepared samples, including cyclic voltammetry (CV) and charge/discharge tests, are performed. The results demonstrate that the electrode prepared by sample d exhibits better electrochemical reversibility, larger proton diffusion coefficient (2.58 × 10−12 cm2 s−1) and higher discharge capacity (302.39 mAh g−1) due to the synergic effect of all doped elements.