Optimization of the duration and the temperature of synthesis at the two-stage high-temperature synthesis of the nickel hydroxide as an active substance of supercapacitors
A. I. Vepreva, D. V. Nabokov, A. S. Sykchin, Коваленко В. Л. , Коток В. А. , A. A. Burkov, B. A. Ananchenko, S. Deabate, A. Mehdi, J.-L. Bantignies, F. Henn, A. S. Baskevich
Химия и современные технологии
Hybrid supercapacitors (SC) with nickel hydroxide electrode are widely used as primary or backup power sources for electrovehicles and vehicles with a 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 is charged and discharged with high currents, therefor electrochemical processes are situated on the surface and in the thin surface layer of particles. Therefore 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 this investigation is to optimize the duration and the temperature of synthesis for obtaining of Ni(OH)2 with high specific capacities. To achieve this aim synthesis duration were proposed as 6, 12, 18 и 24 hours. Obtained samples have been characterized by XRD, SEM, DSC, DTA, voltammogram and galvanostatic charge-discharge cycling. Specific capacities have been calculated from discharge curves for two modes: full discharge to stable potential and discharge to potential 0 V.
As a result of the investigation, the optimal condition of the stage of sodium nickelate synthesis has been detected. It was shown that under shot duration sodium nickelate and after that nickel hydroxide with “pseudo-single” particle morphology has not formed.