Synthesis and characterization of spherical nonstoichiometric Ni(OH)x (x = 2.03–2.10) as electrode materials

The spherical nonstoichiometric Ni(OH)x (x = 2.03–2.10), as a new positive electrode material for Ni/MH batteries, are synthesized by spherical β-Ni(OH)2 surface modified with chemically oxidized NiOOH nanoparticles. The average nickel oxidation state, microstructure and morphology of the spherical nonstoichiometric Ni(OH)x are investigated by complexometric titration, X-ray diffraction (XRD), scamming electron microscopy (SEM) and transmission electron microscopy (TEM). It is demonstrated that the NiOOH with a flaky-like morphology are dispersed randomly on the surface of the spherical β-Ni(OH)2. The effect of NiOOH on the electrochemical performance of spherical nonstoichiometric Ni(OH)x is studied by galvanostatic charge–discharge experiments and cyclic voltammetry. Compared with the spherical β-Ni(OH)2, the spherical nonstoichiometric Ni(OH)x (x = 2.05) has an enhanced discharge capacity (300 mAh g−1 at 0.2 C), higher discharge potential plateau and superior cycle stability. The existence of chemically oxidized NiOOH nanoparticles in the nickel electrode contributes great effect on the improvement of electrochemical performance.