Nanophase nickel hydroxide composites doped with several metal ions (such as Al³⁺, Zr³⁺, Co²⁺ and Zn²⁺) were prepared using low temperature solid-state reaction and organic liquid-phase reaction.The cyclic voltammetry experiments show that there is a certain relation between reduction peak potential (E_R) of the sample and the ratio of the doped ion charge (z) to radius (r), i.e.the larger the z/r value of doped metal ion, the more positive the reduction peak potential of the sample.An experimental formula can be summarized as: E_R1-1000(A₁-A₂)+100sgn(-)=E_R2.The dependence of E_R on z/r and the effect of surfactant PEG on samples were presented.Owing to the valence of the metal ions in the active material being high, nickel-based layered double hydroxides (Ni-NLDH) are prone to become isostructural α-nickel hydroxide, which causes the more positive reduction peak potential.Additionally, the reduction peak potentials of the samples are also affected by surfactant PEG coordinated to the doped metal ions.

Key words: nano-Ni(OH)₂, cyclic voltammetry, reduction potential(ER), the ratio of charge to radius(z/r)