The parameters of theaging process of nickel hydroxide in thealkali medium, depending on aging time and presence of cobalt hydroxide additive, have been determined. It was revealed that theaging process is governed by re-crystallization of nickel hydroxide and it also occurs through theordering of crystal lattice defects, including in the direction along (001) plane. It was determined that aging results in a significant decrease of theutilization coefficient of nickel hydroxide. It was also revealed that theaging rate is high initially, but decreases overtime. It was determined that theutilization coefficient for nickel hydroxide with and without cobalt hydroxide had decreased by 37 % and 47 %, respectively, after aging in 4.5МКОНfor 56 days. The mechanism describing thechange of theaverage discharge potential for theaged samples with cobalt hydroxide has been proposed. It is assumed that aging of nickel hydroxide with cobalt hydroxide leads to theformation of a layered double hydroxide film on thesurface of nickel particles.