Hybrid supercapacitors (SC) with nickel hydroxide electrode are widely used as a primary or backup power sources for electrovehicles and vehicles with hybrid engine, for starting of the different types of electric motor, as a UPS for computer systems, medicine and other equipment, residences and offices, etc. SC are charged and discharged with high currents, therefor electrochemical processes are situated on the surface and in the thin surface layer of particles. Therefor requirements for Ni(OH)2 include high specific surface and optimal crystallinity. Two-stage high-temperature synthesis of nickel hydroxide with high specific capacity has been proposed by us  with following scheme: «Ni(ClO4)2» – «SYNTHESIS» (24 hour, 140°С) – «Na2NiO2» – «HYDROLYSIS» (24 hour, 170°С – hot, 20°С – cold) – Ni(OH)2.
The main aim of these investigation is to optimize of the duration of hydrolysis for obtaining of Ni(OH)2 with high specific capacities. To achieve of this aim hydrolysis duration were proposed as 6, 12, 18 и 24 hour. Obtained samples have been characterized by XRD, SEM, DSC, DTA, voltammogramm and galvanostatic charge-discharge cycling. Specific capacities have been calculated from discharge curves for two mode: full discharge to stable potential and discharge to potential 0 V.
It was shown that for the series of duration of sodium nickelate hydrolysis “6 hour – 12 hour – 18 hour – 24 hour”, there is maximum of specific capacities for 12 and 18 hour. Samples have significantly decreasing capacities, it was correlated with increasing crystallinity and stability of these samples. Maximum specific capacities are: for samples of cold hydrolysis – 138.2 mА∙h/g и 1280.2 F/g (10 mА/sm2), 111.8 mА∙h/g и 358.6 F/g (120 mА/sm2), for samples of hot hydrolysis – 34.6 mА∙h/g и 583.0 F/g (10 mА/sm2), 36.7 mА∙h/g и 303.7 F/g (120 mА/sm2)
Figure 1 – Specific capacities of samples, obtained under different hydrolysis duration (at current density 10 и 120 mА/sm2)