Date of Award
The electrochemical supercapacitors (ESs) are an emerging technology that promises to play an important role in meeting the demands of automotive and electronic industry. A notable improvement in ES performance has been achieved through recent advances in understanding charge storage mechanisms and the development of advanced nanostructured materials, such as nanostructured MnO2 and composites.
The anodic electrophoretic deposition (EPD) method has been developed for the fabrication of MnO2 and composite MnO2-multiwalled carbon nanotubes (MWCNTs) films. The problem of low stability of MnO2 suspensions was addressed by the development of new dispersing agents. Benzoic acid and phenolic molecules, such as 3,4-dihydroxybenzoic acid, 3,4-dihydroxyphenylacetic, 3,4-dihydroxyhydrocinnamic acid, 3,4,5-trihydroxybenzoic acid, salicylic acid, 2,3,4-trihydroxybenzoic acid, aurintricarboxylic acid and aurintricarboxylic acid ammonium salt were investigated as additives for the dispersion and charging of MnO2 nanoparticles. The adsorption of the organic molecules on the MnO2 nanoparticles involved the interaction of COOH groups and OH groups with Mn atoms on the particle surfaces and complexation. The results showed that adjacent OH groups, as well as adjacent OH and COOH groups bonded to the aromatic ring of the phenolic molecules enabled enhanced adsorption of the organic molecules. It was found that EPD of MnO2 and MWCNTs can be achieved using 3,4-dihydroxybenzoic acid, 2,3,4-trihydroxybenzoic acid, and aurintricarboxylic acid as a common dispersants and charging additives.
Aurintricarboxylic acid ammonium salt provided a charge required for efficient dispersion and EPD of MWCNTs and graphene.
New dispersion methods allowed the formation of composite electrodes by colloidal techniques, such as EPD or slurry impregnation of MnO2 and MWCNTs into advanced current collectors, such as porous nickel foam and nickel plaque. The composite electrodes showed excellent capacitive performance with large material loading in 0.5 M Na2SO4 electrolyte. MnO2 and MWCNTs can form a porous network, which is beneficial for the electrolyte access to the active materials. The effect of the MWCNTs concentration, scan rate and electrodes type on the capacitive behaviour was discussed. It was found that the addition of MWCNTs can improve the capacitive performance of MnO2 electrodes and reduced equivalent series resistance.
Ata, Mustafa Sami, "Advanced Materials and Fabrication Methods for Electrochemical Supercapacitors" (2012). Open Access Dissertations and Theses. Paper 7597.
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