Minimizing the confinement effect of micropores to optimize the capacitive performance of carbon materials

The specific capacitance of carbon-based supercapacitors is limited by the micropore confinement effect of porous carbon. To address this issue, a nitrogen-doped carbon material was synthesised in situ in air atmosphere using Zn-MOF and molten salt as the precursor and etching sealant, respectively. Molten ions encapsulated within carbon structures prevent the agglomeration of carbon microcrystals and serve as templates, leading to the formation of a two-dimensional carbon sheet structure with abundant mesopores and micropores. Electrochemical tests and calculations have indicated that the two-dimensional sheet structure and its abundant mesopores accelerate electrolyte ion transport, minimise micropore confinement effects and enhance active site utilisation. Symmetric supercapacitors with potassium hydroxide as the electrolyte exhibit an energy density of 18 Wh kg ⁻¹, while those with lithium sulfate as the electrolyte exhibit an energy density of 34 Wh kg ⁻¹, which is critical for the applications of carbon material in supercapacitors.