Abstract
Nickel hydroxide is widely used as an active material for hybrid supercapacitors. The most electrochemically active is a-Ni(OH) 2 , synthesized using template homogeneous precipitation. In order to achieve maximum characteristics, it was necessary to study the influence of the template concentration on structural, surface and electrochemical properties of Ni(OH) 2 samples. For this purpose, Ni(OH) 2 samples were prepared using template homogeneous precipitation, with Culminal C8564 (template) concentrations of 0 %, 0.5 %, 1 %, 2 %, 3 % and 4 %. Structural properties of the samples were studied by means of X-ray diffraction analysis, size and particle morphology – by means of Scanning Electron Microscopy, the electrochemical characteristic – galvanostatic charge-discharge cycling in the supercapacitor regime. It has been demonstrated that an increase of the template concentration to 0.2 % leads to a decrease of crystallinity and particle size. However, a further decrease of concentration leads to increase of crystallinity and aggregation of nickel hydroxide particles. The influence of the template concentration on the electrochemical properties is different for different concentration ranges. At low template concentrations (below 0.2 %), the specific capacity of the samples is almost independent of cycling current density. The optimal concentration for this range is 0.1 %, with the maximum specific capacity of 499 F/g. Nickel hydroxide prepared with 0.1 % of Culminal C8564, is recommended for use at low and medium current densities (below 80 mA/cm 2 ). At high template concentrations (0.3–0.5 %), the specific capacity increases significantly with an increase of current density. The optimal concentration for the ranges was 0.4 %, with the maximum specific capacity of 525 F/g. Nickel hydroxide samples prepared with 0.4 % of Culminal C8564, is recommended for use in high-speed supercapacitors with high discharge current densities (120 mA/cm 2 and above).
Highlights
Supercapacitors are the most modern chemical power sources
The nickel oxide electrode with Ni(OH)2 as an active material is used as a Faradic electrode for hybrid supercapacitors
It has been found that increasing concentration of a template to 0.2 % leads to a decrease of crystallinity, while it increases with further increase of the template concentration
Summary
Supercapacitors are the most modern chemical power sources. Supercapacitors are widely used for starting electrical engines of cars, pump stations and other devices. Supercapacitors are used as starter chemical power sources for internal combustion engines, uninterruptible power supply units for computers and other devices. The electrochemical process at the Faradic electrode of supercapacitor occurs in a thin surface layer of active material. There are special requirements [1, 2] to the specific surface area, crystal structure and electrochemical activity of Faradic electrode active material. The active material must be composed of nanoand submicron-sized particles with the high specific surface area. The nickel oxide electrode with Ni(OH) as an active material is used as a Faradic electrode for hybrid supercapacitors. The α-Ni(OH) possesses significantly higher electrochemical characteristics than β-Ni(OH) and can be used more efficiently in hybrid supercapacitors. The development and optimization of synthesis methods for preparation of highly electrochemically active α-Ni(OH) are relevant problems
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