Solid-State\nPrecursor Impregnation for Enhanced Capacitance\nin Hierarchical Flexible Poly(3,4-Ethylenedioxythiophene) Supercapacitors

Abstract

Increasing\ncapacitance and energy density is a major challenge\nin developing supercapacitors for flexible portable electronics. A\nthick electrode with a high mass loading of active electronic material\nleads to high areal capacitance; however, the higher the loading,\nthe higher the mechanical stiffness and ion diffusion resistance,\nthereby hampering development of flexible supercapacitors. Here, we\nshow a chemical strategy that leads to a hierarchical electrode structure\nproducing devices with both an exceedingly high areal capacitance\nand superior flexibility. We utilize α-Fe₂O₃ particles as an oxidant precursor for controlling oxidative radical\npolymerization of the conducting polymer poly­(3,4-ethylenedioxythiophene)\n(PEDOT) from the vapor phase. Our approach impregnates carbon cloth\nwith α-Fe₂O₃ particles prior to monomer\nvapor exposure, resulting in state-of-the-art flexible nanofibrillar\nPEDOT supercapacitors possessing high areal capacitance (2243 mF/cm² for two-electrode <i>vs</i> 6210 mF/cm² for three-electrode) and high areal energy density (412 μWh/cm²).