Multiple nano-sized a-Ni（OH）2was synthesized by ultrasonic-assisted precipitation under different conditions. The crystal structure and particle size distribution of the sample were characterized with X-ray diffraction（XRD）, infrared spectroscopy, and laser particle size analyzer（PSA）. The results show that the samples are anisotropic polycrystalline of a and b Ni（OH）2, and the ratio of a and b changes with the difference of nickel source, resulting in the largest ratio of a-Ni（OH）2using nickel nitrate as reactant. Larger amount of Na2CO3is conducive to the formation of a-Ni（OH）2; while the resultant phases are all b with the same conditions but no doping. The results of PSD indicate that the samples are about 100–120 nm in size, and the sample with nickel sulfate as nickel source has the minimum particle size. The three ions of nickel source appear in the absorption peaks in the Fourier transform infrared spectrum showing that the ions change the crystal structure of Ni（OH）2. EDS testing shows that Y and anion distribute in the lattice of aNi（OH）2uniformly.
Qing-Sheng XuYan-Juan ZhuLiang-Guo HuangJie LuoZhong-Ju ZhangCheng-Cheng MiaoHu Ye
The nano-nickel hydroxide samples were prepared by means of ultrasonic-assisted precipitation and the impact of source/doping element/buffer on the structure of Ni（OH）： was studied. The results of XRD, IR and TEM testing clearly revealed that larger anionic radius of the nickel sources or the buffer solution was conducive to the formation of α-Ni（OH）2. The proportion of α-Ni（OH）： samples doped with two elements was larger than that doped with single element. Additionally, speciation, valence as well as the radius of doping ions can directly affect the phase of Ni（OH）2.
Nanometer Cu singly doped and Cu/Al co-doped nickel hydroxides were synthesized by ultrasonic-assisted precipitation method. Their crystal structure, particle size, morphology, tap density and electrochemical performance were investigated. The results show that the samples have a-phase structure with narrow particle size distribution. Cu singly doped nano-Ni（OH）2 contains irregular particles, while Cu/Al co-doped nano-Ni（OH）2 displays a quasi-spherical shape and has a relatively higher tap density. Composite electrodes were prepared by mixing 8% （mass fraction） nanometer samples with commercial micro-size spherical nickel. The charge/discharge test and cyclic voltammetry results indicate that the electrochemical performance of Cu/Al co-doped nano-Ni（OH）2 is better than that of Cu singly doped nano-Ni（OH）2, the former＇s discharge capacity reaches 330 mA.h/g at 0.2C, 12 mA.h/g and 91 mA.h/g larger than that of Cu singly doped sample and pure spherical nickel electrode, respectively. Moreover, the proton diffusion coefficient of Cu/Al co-doped sample is 52.3% larger than that of Cu singly doped sample.
