2, Georgia Institute of Technology, Atlanta, Georgia, United States
Conducting polymers (CPs) have been extensively investigated as prospective charge-storage materials for electrochemical capacitors. However, the methods typically used to fabricate CP-based electrodes (e.g., electrodeposition for 2D thin-film electrodes or solution-based synthesis followed by processing into composite-electrode formulations) severely limit their footprint-normalized capacity and rate performance, hindering their technological relevance. As an alternative, Reynolds and co-workers recently developed synthetic methods that yield gram-scale quantities of solution-processable CPs based on ProDOT and EDOT.[i],[ii] The ability to solubilize these CP variants makes them amenable to incorporation into advanced 3D electrode architectures. We demonstrate scalable solution-based deposition methods to incorporate these CPs as conformal thin films at loadings of ≥ 30 wt.% throughout macroscopically thick 3D carbon-paper electrodes. The resulting 3D electrode design maintains the inherently fast charge-storage kinetics of the CP, yet greatly enhances the footprint-normalized capacitance by a factor of 120, from 0.4 mF cm-2 for the 2D thin film to 48 mF cm-2 for the 3D electrode. To demonstrate the technological relevance of these CP-3D carbon paper electrodes, we assess their rate-dependent capacitance/capacity, self-discharge, and cycle life in two terminal devices.
[i]. Ponder Jr., J. F.; Österholm, A. M.; Reynolds, J. R. “Designing a Soluble PEDOT Analogue without Surfactants or Dispersants,” Macromolecules 49, 2106 (2016).
[ii]. Österholm, A. M.; Ponder Jr., J. F.; Kerszulis, J. A.; Reynolds, J. R., “Solution Processed PEDOT Analogues in Electrochemical Supercapacitors,” ACS Appl. Mater. Interfaces 8, 13492 (2016).