Issue 11, 2024

Synthesis and performance of binder-free porous carbon electrodes in electrochemical capacitors

Abstract

Porous binder-free carbon electrodes were obtained by impregnating cellulose filter papers with phenolic resin through soft-salt template synthesis and thermal pyrolysis. These self-standing electrodes were used directly in a supercapacitor device. To understand the impacts of filter paper (FP) thickness on carbon filter paper (CFP) morphology, porosity, and surface functionalities, five different materials were examined. The CFP electrode thickness was adjusted linearly with the FP thickness to produce electrodes ranging from 100 to ∼800 μm. As the thickness of the CFP increased, there was an increase in the specific surface area and oxygen-based functionalities. Electrochemical testing in a 1 M KOH aqueous electrolyte demonstrated that electrode thickness played a key role in electrochemical capacitor (EC) performance, i.e., capacitance enhances linearly when the electrode becomes thinner. For low thicknesses (<280 μm), the capacitance and rate capability decreased slightly with increasing thickness; for high thicknesses, the performance drastically degraded despite the high specific surface area and oxygen surface functionalities. This effect was amplified at high regimes, indicating that high electrode thicknesses and fiber diameters limited electrolyte diffusion in the applied synthesis conditions. Thus, the high material porosity was inaccessible to ion adsorption. Consequently, thinner electrodes showed the highest capacitance (197 F g−1 at 0.1 A g−1) and rate capability (81%) values, exceeding those of their traditional binder-electrode counterparts prepared under similar conditions. Finally, for alkali metal hydroxide solutions, 1 M KOH exhibited a cation match with the salt template (KCl), while CsOH achieved additional capacitance retention (88% at 10 A g−1). Complex ion adsorption mechanisms were observed through a quartz crystal microbalance.

Graphical abstract: Synthesis and performance of binder-free porous carbon electrodes in electrochemical capacitors

Supplementary files

Article information

Article type
Paper
Submitted
18 Aug 2023
Accepted
04 Jan 2024
First published
14 Feb 2024
This article is Open Access
Creative Commons BY license

J. Mater. Chem. A, 2024,12, 6412-6425

Synthesis and performance of binder-free porous carbon electrodes in electrochemical capacitors

A. Platek-Mielczarek, A. Beda, K. Fic and C. Matei Ghimbeu, J. Mater. Chem. A, 2024, 12, 6412 DOI: 10.1039/D3TA04971J

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