Abstract: High energy ball milling(HEBM) method was applied to synthesize nickel hydroxide with and without partial substitution for Ni²⁺ sites by such metallic ions as Al³⁺, Al³⁺Zn²⁺ and Al³⁺Zn²⁺Co²⁺. The morphologies, structures, composition and thermal stability of the prepared powders were studied by SEM, XRD, FTIR and TG. The results reveal that all the synthesized Ni(OH)₂ particles agglomerate in sub-micron sizes and the non-substituted Ni(OH)₂ is composed of beta phase with a crystal interlayer distance of 4.64 Å, while the Al³⁺, Al³⁺Zn²⁺, Al³⁺Zn²⁺Co²⁺ substituted products are composed of alpha phase with 8.03 Å crystal interlayer space. Absorbed water molecule is found in all the synthesized Ni(OH)₂ and the non-substituted particles are more thermally stable than substituted α-Ni(OH)₂. The absorption peaks of inserted crystal anions of CO₃^2-  and SO₂4- are detected for metallic ion substituted α-Ni(OH)₂. The specific capacity of Al³⁺ substituted Ni(OH)₂ is 325 mA∙h/g, 5 mA∙h/g higher than Al³⁺Zn²⁺ substituted and non-substituted Ni(OH)₂, but 25 mA∙h/g greater than Al³⁺Zn²⁺Co²⁺ substituted Ni(OH)₂. The electrochemical mechanism of synthesized Ni(OH)₂ electrodes is discussed by EIS spectrum and Al³⁺ substituted Ni(OH)₂ electrode shows a high electrochemical cyclic stability.

Key words: nickel hydroxide; Ni(OH)₂ electrodes; high energy ball milling; metallic ion substitution