Supercapacitors (SCs) have generated significant interest due to their advantages including lightweight, rapid charge-discharge, good rate capability and high cyclic stability. Electrodes are one of the most important factors influencing the performance of SCs. MXene is a promising candidate for supercapacitor electrodes, which is a relatively new material with formula Mn+1XnTx, where M is a transitional metal, X stands for C or N, and Tx is surface terminations. Due to its multi-layered structure, high surface area and rich redox chemistry, good electrochemical performance can be expected. To further enhance the conductivity of the MXene electrodes, multi-walled carbon nanotubes (MCNT) were applied as the conducting additive. The as-fabricated composite electrodes showed reduced resistance and enhanced electrochemical performance. Advanced co-dispersants such as cationic celestine blue (CCB) and anionic catechol violet (ACV) were employed to improve the dispersion of components. CCB and ACV can adsorb strongly on the MXene and MCNT surface to form a homogenous suspension and thus improve the mixing between them. Another advanced dispersant 3,4,5-trihydroxybenzamide (THB) also showed adsorption on both MXene and MCNT particles, favored their dispersive mixing and improved electrochemical performance.
Iron oxides are promising materials for negative electrodes for supercapacitors. The attempt to combine highly capacitive Fe3O4 with MXene-MCNT composites proved the synergistic effect of individual components. Investigation of Zn-doped FeOOH as high active mass loading anode with MCNT as conducting additive allowed for enhanced performance. Zn-Fe double hydroxide materials are promising for the fabrication of advanced supercapacitor electrodes. A safe and neutral Na2SO4 electrolyte was was beneficial for the development of asymmetric devices with enlarged voltage window. For cathodes working in an overlapping window with Zn-FeOOH anode, polypyrrole coated carbon nanotube electrode was fabricated with a comparable capacitance. The advanced dopant eriochrome cyanine R (ECR) allowed for the uniform thickness of PPy coating on MCNT and enhanced charge transfer between PPy and MCNT was achieved. Enhanced capacitive properties of cathodes and anodes at high active mass loading working in complimentary voltage windows allowed for fabrication of high-performance supercapacitor, which was a promising device for practical applications. / Thesis / Doctor of Philosophy (PhD) / To reduce the consumption of fossil fuel and meet the surging demand of electric energy, intensive attention has been drawn to new energy storage device, such as capacitors, batteries and supercapacitors. Owing to their higher energy density compared with conventional capacitors and higher power density compared with batteries, supercapacitors are attracting tremendous research interest. The advantages of supercapacitors are fast charge-discharge rate, high power and energy density and excellent cyclic stability.
The objective of this work was to fabricate high-performance supercapacitor devices based on the development of advanced electrode materials. MXene and Fe-based composite materials were synthesized by conceptually new colloidal approach and some efficient dispersants were developed during the process. The enlarged voltage window and superior performance were recorded for asymmetric supercapacitors. The results presented in this work showed much more promising performance compared with that reported in the literature and paved the way for future research.
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/27386 |
| Date | January 2022 |
| Creators | Liang, Wenyu |
| Contributors | Zhitomirsky, Igor, Materials Science and Engineering |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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