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Aim of investigation is to study the possibility of activating a promising Ni(OH) 2 , prepared using two-step high-temperature synthesis, by adding 3%, 5% and 10% (mol.) Al 3+ to Ni 2+ . For describing the intercalation of Al 3+ into hydroxide structure, "Separate-Solid-Liquid-Solid" mechanism, which included the formation of separate Al-containing phase on synthesis stage, and incorporation of Al 3+ into Ni(OH) 2 or formation of surface compounds during hydrolysis stage, has been proposed. EDX analysis of precursor confirmed the formation of separate Al-containing phases. By means of PXRD, EDX, SEM, TEM revealed realization of both ways of Al 3+ incorporation: at high amounts of Al 3+ (5% and 10% mol.), predominantly surface compounds are formed with distorted and altered particle shape and appearance of "core-shell" particles. At low amounts of Al 3+ (3% mol.), permeably doping occurs, with partial intercalation of Al 3+ into the nickel hydroxide structure. Based on CVA and GCDC results, Al 3+ acts as a poison upon the formation of surface compounds have been found. Upon doping of hot hydrolysis samples with aluminum, sample activation was observed, which resulted in an increase of specific capacity by 1.99 times, from 569 Fg −1 (pure Ni(OH) 2 ) to 1112 Fg −1 .

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