Direct Conversion of Fe 2 O 3 to 3D Nanofibrillar PEDOT Microsupercapacitors

Microsupercapacitors (mu SCs) are attractive electrochemical energy storage devices serving as alternatives to batteries in miniaturized portable electronics owing to high-power density and extended cycling stability. Current state-of-the-art microfabrication strategies are limited by costly steps producing materials with structural defects that lead to low energy density. This paper introduces an electrode engineering platform that combines conventional microfabrication and polymerization from the vapor phase producing 3D mu SCs of the conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT). A sputtered Fe2O3 precursor layer enables deposition of a 250 nm thick polymer coating comprised of a high packing density of vertically aligned PEDOT nanofibers possessing exceptional electrical conductivity (3580 S cm(-1)). The 3D mu SCs exhibit state-of-the-art volumetric energy density (16.1 mWh cm(-3)) as well as areal (21.3 mF cm(-2)) and volumetric (400 F cm(-3)) capacitances in 1 m H2SO4 aqueous electrolyte. These figures of merit represent the highest values among conducting polymer-based mu SCs. Electrochemical performance is controlled by investigating coating thickness, gap distance, fractal geometry, and gel electrolyte (1 m H2SO4/polyvinyl alcohol). The quasisolid-state mu SCs exhibit extended rate capability (50 V s(-1)), retain 94% of original capacitance after 10 000 cycles and remain thermally stable up to 60 degrees C.