High-voltage aqueous asymmetric pseudocapacitors based on methyl blue-doped polyaniline hydrogels and the derived N/S-codoped carbon aerogels

Abstract

The energy density of aqueous-electrolyte supercapacitors based on nanostructured carbon materials is usually limited by relatively narrow operating voltage window (about 1 V in acid aqueous electrolyte), due to the existence of overpotential. We report a novel N/S-codoped carbon aerogel (NS-CAG) derived from a methyl blue-doped polyaniline hydrogel (MB-PHG) with 3D interconnected supramolecular architecture through polymerization and carbonization. The obtained NS-CAG shows a high active nitrogen content along with simultaneous interlayer expansion, probably attributed to the MB-enabled supramolecular architecture of MB-PHG precursor, in favor of improving its pseudocapacitance and electrolyte ion diffusion. The assembled asymmetric pseudocapacitors based on the graphite fiber-supported NS-CAG and MB-PHG electrodes, can break through the overpotential barrier to an ultrahigh operating voltage window of 2.0 V in 1 M H2SO4, resulting in the excellent energy density of 59.7 Wh kg−1 at 1 kW kg−1. This high-energy asymmetric pseudocapacitor can open up an exciting route to extend the operating voltage window for aqueous-electrolyte energy storage.