Indole-based conjugated macromolecules as a redox-mediated electrolyte for an ultrahigh power supercapacitor
Xiong, T ; Lee, W.S.V ; Chen, L ; Tan, T.L ; Huang, X ; Xue, J
Chen, L
Tan, T.L
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Abstract
Balancing energy density and power density has been a critical challenge since the inception of supercapacitors. Introducing redox-active additives in the supporting electrolyte has been shown to increase the energy density, however the power density and cycling stability are severely hampered in the process. Herein, an extensively conjugated indole-based macromolecule consisting of 5,6-dihydroxyindole/5,6-quinoneindole motifs, prepared by electrochemical polymerization of dopamine under acidic conditions, was employed as a redox-active additive. By utilizing the conjugation effect, the HOMO-LUMO gap (HLG) of the extensively conjugated indole-based macromolecule was reduced to ca. 2.08 eV, which enhanced the electronic transfer kinetics, in turn improving the power density and reversibility of redox reactions. When coupled with a porous honeycomb-like carbon (PHC) electrode, the assembled supercapacitor delivered an excellent rate performance with a high specific capacitance of 205 F g-1 at 1000 A g-1. This work reports one of the highest power densities recorded at 153 kW kg-1 for redox-mediated electrolyte systems with a respectable energy density of 8.8 W h kg-1. In addition to an excellent cycling stability of 97.1% capacitance retention after 20000 charge/discharge cycles, the conjugation degree has to be considered when engineering the redox-active electrolyte so as to improve the power density and stability. © The Royal Society of Chemistry 2017.
Keywords
Additives, Capacitance, Carbon, Electrolytes, Electrolytic capacitors, Macromolecules, Polycyclic aromatic hydrocarbons, Supercapacitor, Capacitance retention, Charge/discharge cycle, Conjugation effects, Critical challenges, Electrolyte systems, Electronic transfers, High specific capacitances, Supporting electrolyte, Redox reactions, additive, chemical compound, electrochemical method, electrolyte, electron, equipment, performance assessment, polymerization, reaction kinetics, redox conditions
Source Title
Energy and Environmental Science
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Date
2017
DOI
10.1039/c7ee02584j
Type
Article