Preparation of Yb-substituted α-Ni(OH)2 and its physicochemical properties

• Yb substituted α-nickel hydroxide was prepared by ultrasonic-assisted precipitation.
• The electrode for 1.44 wt.% Yb has the highest capacity of 295.1 mAh/g at 0.2 C.
• EDS spectrum was tested to show that Yb distributing in the lattice of α-Ni(OH)2 uniformly.
• The FWHM of peaks were marked to show the directional growth of the crystallite.

Nano-sized Yb-substituted α-Ni(OH)2 was synthesized by ultrasonic-assisted precipitation, using nickel sulfate as nickel source and Yb(NO3)3⋅5H2O as doping material. The crystal structure, morphology, and particle size distribution of the sample were characterized with X-ray diffraction (XRD), infrared spectroscopy, transmission electron microscope (TEM), scanning electron microscope (SEM), high resolution transmission electron microscopy (HRTEM), and laser particle size analyzer (PSD). The results indicate that the samples are anisotropic polycrystalline α-Ni(OH)2 with particle size of 50–200 nm, and the particle size increases with Yb-doping. The synthesized samples were tested in Ni-MH battery. The specific capacity increases initially and then decreases with increasing Yb-doping ratio with the maximum discharge capacity of 295.1 mAh/g at 0.2 C, which is 60 mAh/g higher than the micro-sized spherical nickel electrode. At the same time, the prepared material has lower charging voltage, higher discharge voltage plateau, and better cycle performance.

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