Tailoring thickness of conformal conducting polymer decorated aligned carbon nanotube electrodes for energy storage

Aligned Carbon nanotubes (A-CNT) based electrodes have emerged as high-performance elements in electric energy storage and conversion devices. Morphological tailoring of conformal coatings of poly(ethylenedioxythiophene) (PEDOT) conductive polymer (CP) on the A-CNT scaffold is demonstrated by controlling CP thickness at the nm scale. Results show that the CP nano-films dominate the electrode capacitance in a supercapacitor application, contributing as much as 10x (pseudo)capacitance over the electric double layer of pristine A-CNT due to volumetric vs. surface charge storage. Comparison to theoretical ion mobilities shows that the conformal CP films have active sites at ∼30% doping, indicating the CP quality is similar to thin films on flat substrates and that all these sites are accessed at all CP thickness values (up to 10 nm PEDOT thickness) and do not limit the rate of ion transport in and out of the CP film volume. Supercapacitor electrodes fabricated from these novel morphology-controlled nanostructured composites provide a new route towards high-performance next generation energy storage devices. Nanometer-thickness conducting polymer films are conformally deposited on aligned arrays of carbon nanotubes, and their quality assessed vs. flat substrates via ion storage experiments in a supercapacitor electrode configuration. Time-dependent behavior shows that ion diffusion in the thin (nm-scale control) conformal films is not rate limiting.