Electrochemical performance of multiphase nickel hydroxide

Abstract

The high density nano-crystalline multiphase nickel hydroxide containing at least three doping elements was synthesized and its electrochemical characteristics were studied. The electrochemical behavior of the high density spherical multiphases α-Ni(OH) 2 were also investigated. The results show that the structure of the material is a mixed phase of α-Ni(OH) 2 and β-Ni(OH) 2, which has a the same stabilized structure as α-Ni(OH) 2 during long-term charge/discharge process. High density spherical multiphases α-Ni(OH) 2 have a much better redox reversibility, a much lower oxidation potential of Ni(II) than the corresponding oxidation state in the case of β-Ni(OH) 2, and a much higher reduction potential. They exchange one electron during electrochemical reaction and have a higher proton diffusion coefficient. The mechanism of the electrode reaction is proton diffusion, and the proton diffusion coefficient is 5.67×10 −10 cm 2/s. Moreover, they reveal a higher discharge capacity than β-Ni(OH) 2/β-NiOOH because they exchange one electron per nickel atom during charge/discharge process.