Spatial Charge Storage within Honeycomb-Carbon Frameworks for Ultrafast Supercapacitors with High Energy and Power Densities

Carbon-based supercapacitors store charge through the adsorption of electrolyte ions onto the carbon surface. Therefore, it would be more attractive for the enhanced charge storage if the locations for storing charge can be extended from carbon surface to space. Here, a novel spatial charge storage mechanism based on counterion effect from Fe(CN)₆³⁻ ions bridged by oxygen groups and confined into honeycomb-carbon frameworks is presented, which can provide additionally spatial charge storage for electrical double-layer capacitances in a negative potential region and pseudocapacitances from Fe(CN)₆³⁻/Fe(CN)₆⁴⁻ in a positive potential region. More importantly, an ultrafast supercapacitor based on this novelty carbon can be charged/discharged within 0.7 s to deliver both high specific energy of 15 W h kg⁻¹ and ultrahigh specific power of 79.1 kW kg⁻¹ in 1 m Na₂SO₄ electrolyte, much higher than those of previously reported asymmetric supercapacitors in aqueous electrolytes, as well as excellent cycling stability. These features suggest a new generation of ultrafast asymmetric supercapacitors as novel high-performance energy storage devices.