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Multi-element-doped α-Ni(OH) was prepared by an ultrasonic-assisted co-precipitation method. The crystal structures and morphologies of the prepared samples were characterized by x-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy, respectively. The results showed that the interlayer spacings of all samples were larger than that of pure α-Ni(OH) and that the structural stability became better with increases in the number of doped elements and the doped ratio. The electrochemical performances of the prepared samples, including cyclic voltammetry, electrochemical impedance spectroscopy and charge-discharge tests, were also analyzed. The results indicated that Al/Yb/Co/Mn-doped α-Ni(OH) had better electrochemical reversibility, lower charge-transfer resistance, a larger proton diffusion coefficient (8.47 × 10 cm/s) and a higher discharge capacity (288.2 mAh g at 0.5 °C) than Al/Co/Mn-doped α-Ni(OH) due to the synergistic effect of the doped elements. [ABSTRACT FROM AUTHOR]

Alpha nickel hydroxide has better performance than commercial beta nickel hydroxide. However, the main defect is that α-phase is easily transformed to β-phase Ni(OH) 2 upon aging in a strong alkaline solution. The different effects of the doping cations Al 3+ , Yb 3+ and Co 2+ on the chemical composition, morphology, structure and electrochemical properties of Ni(OH) 2 are studied, with the same doping ratio. The results demonstrate that the synergistic effect of the ternary doping samples is better than the binary. The Al-Yb-Co-Ni(OH) 2 exhibits excellent structural stability, which can stay the pure α-phase in strong alkaline solutions over 60 days. The CV measurements demonstrate that the relevant electrode has the highest proton diffusion coefficient, indicating a higher electrochemical activity and faster reaction kinetics due to the fast ionic transportation. Moreover, the above electrode has the higher charge efficiency, better reversibility and cycle stability. [ABSTRACT FROM AUTHOR]

The multi-element doped alpha nickel hydroxide has been prepared by supersonic co-precipitation method. Three kinds of samples A, B and C are prepared by chemically coprecipitating Ni/Al, Ni/Al/Mn and Ni/Al/Mn/Yb, respectively. Inductively coupled plasma atomic emission spectroscopy (ICP-AES), Particle size distribution (PSD) measurement, X-ray diffraction (XRD), scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FT-IR) are used to characterize the physical properties of the synthesized α-Ni(OH) 2 samples, such as chemical composition, morphology, structural stability of the crystal. The results show that all samples are nano-sized materials and the interlayer spacing becomes larger and the structural stability becomes better with the increase of doped elements and doped ratio. The prepared alpha nickel hydroxide samples are added into micro-sized beta nickel hydroxide to form biphase electrode materials for Ni-MH battery. The electrochemical characterization of the biphase electrodes, including cyclic voltammetry (CV) and charge/discharge test, are also performed. The results demonstrate that the biphase electrode with sample C exhibits better electrochemical reversibility and cyclic stability, higher charge efficient and discharge potential, larger proton diffusion coefficient (5.81 × 10 −12 cm 2 s −1 ) and discharge capacity (309.0 mAh g −1 ). Hence, it indicates that all doped elements can produce the synergic effect and further improve the electrochemical properties of the alpha nickel hydroxide. [ABSTRACT FROM AUTHOR]