Ionic liquid surfactant-derived carbon micro/nanostructures toward application of supercapacitors

Abstract

N-Doped mesoporous hollow carbon spheres (MHCSs) with different inner structures have attracted increasing attention in energy storage devices due to their low density and high electrical conductivity. Herein, vesicles formed by the molecular self-assembly of the ionic liquid surfactant derived from its unique properties (e.g. lower charge density and π–π interaction between the polar heads) are employed as soft templates to synthesize two kinds of uniform MHCSs (e.g. mesoporous hollow carbon spheres and core–shell structured carbon nanospheres) with high nitrogen (N) doping and various inner layouts including hollow, yolk–shell and Momordica grosvenori-like structures. The elaborate tailoring in the architectures of full sized MHCSs (55 nm–2 μm) endows them with welcome features as electrode materials for symmetrical supercapacitors. In particular, the representative sample of as-prepared N-doped MHCSs exhibits excellent electric double-layer capacitor performance with an electrochemical specific capacitance (308 F g⁻¹ at 0.2 A g⁻¹), superb capacitance retentions (233 F g⁻¹ at 20 A g⁻¹ and 174 F g⁻¹ at 100 A g⁻¹), and high cycling stability (85% capacitance retention at 10 A g⁻¹ after 5000 cycles) in a 6 M KOH electrolyte. The full-sized carbon spheres with tunable architectures are expected to find more applications in catalysis, adsorption, biomedicine and energy storage and conversion devices.