Ionic liquid-induced tunable N-doped mesoporous carbon spheres for supercapacitors

Abstract

N-Doped mesoporous carbon spheres (N-MCSs) have shown important applications in many fields. Herein, N-MCSs with uniform spherical morphology, adjustable inner structure, and abundant mesoporous are prepared by a feasible co-assembly of an ionic liquid (IL), a silica precursor (tetraethoxysilane (TEOS)) and a carbon precursor (resorcinol/formaldehyde resin (RF)). The IL is used as a template on which TEOS and RF are assembled together through electrostatic interactions to form a spherical shape. Nitrogen in the IL results in N-doping of the carbon framework. Moreover, addition of TEOS can provide rich mesopores and cavity structures for the N-MCSs. The system solvent volume and RF amounts have a direct impact on the structure of the N-MCSs, changing from core–shell to hollow or from core–shell to solid carbon spheres. Different structures in the N-MCSs lead to distinct electrochemical properties as an electrode material. The N-MCSs have a unique core–shell structure, a crumpled surface, appropriate N-doping and a high surface area, which endows them with higher electrochemical properties of 350 F g⁻¹ capacitance at 0.5 A g⁻¹, good rate performance of 77.5% retention in the current density range of 0.5–10 A g⁻¹, and long cycle life with 80.2% of the initial capacity after 10 000 cyclic tests, showing their promising potential to be used as an electrode material in supercapacitors.