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 beta-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 beta-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 beta-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. (C) 2010 Elsevier B.V. All rights reserved.