The aim of this paper is the comparison of structural, morphological and electrical properties of thermally extended graphite synthesized by chemical oxidation of graphite with sulfur of nitric acids at all other same conditions. Thermal treatments of graphite intercalation compounds were performed at a temperature of 600°C on the air for 10 min but additional annealing in temperature range of 100-600oC for 1 hour was done. The obtained materials were characterized by XRD, Raman spectroscopy and impedance spectroscopy. The evolution of structural ordering of thermally extended graphite samples at increasing of annealing temperature was traced. It was determined that the additional annealing allows to control the electrical conductivity and structural disordering degree of extended graphite samples that is useful for preparation of efficient current collectors for electrochemical capacitors.
A simple and effective hydrothermal synthesis of spherical α-Ni(OH)2 particles and α-Ni(OH)2/carbon composites was proposed. The mechanism of ultrafine α-Ni(OH)2 phase forming and correlations between synthesis conditions, morphology, electrical conductivity were analyzed. It was found that carbon nanoparticles form an electric conductive cover on nickel hydroxide microparticles during synthesis which increases overall electronic conductivity of the composite material. α-Ni(OH)2 and α-Ni(OH)2/C samples were tested as electrodes for hybrid supercapacitors. It was found that carbon coverings stabilize α-Ni(OH)2 phase in the alkaline medium. The comparison of the influence of laser irradiation and ultrasonic treatment on the electrochemical performance of the obtained materials was made.
The paper reveals the results of electrochemical studies of activated nanoporous carbon material (NPC) as an electrode material for electrochemical capacitors (EC), the charge of which is accumulated in an electrical double layer (EDL). NPC material has been obtained from raw material of plant origin (hemp shives) by thermochemical activation using phosphoric acid. It has been established that there is an optimal ratio between the amount of acid and precursor based on plant biomass that is equal to 0.75:1. The specific surface area of the obtained NPCwas ~ 2000 m2/g, and the maximum specific capacitance of EC models based on them was ~ 113 F/g. At the same time, the contribution of the EDL capacitance to the total capacitance is 60-80 %.
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