Nitrogen-doped hollow carbon nanoparticles with optimized multiscale nanostructures via dolomite-assisted chemical vapor deposition for high-performance potassium-ion capacitor

Carbon-based materials are considered as promising anode candidates for potassium-ion storage with the key bottlenecks lying in the slow kinetics and huge volume expansion caused by the large size of K+. Herein, nitrogen-doped hollow carbon nanoparticles (NHCP) with optimized multiscale nanostructures are synthesized by a natural template-assisted chemical vapor deposition process. Benefiting from the stacking nanoparticles structure with hierarchical pores, high level of pyridinic-/pyrrolic-N, and enlarged interlayer spacing, the constructed NHCP anode delivers superior K+ storage properties in terms of high reversible capacity (412.7 mAh g−1 at 0.03 A g−1), favorable rate capability, and long cyclic stability. The detailed experimental and computational studies reveal the combined storage mechanism of K+ adsorption and insertion in the multiscale nanostructure of NHCP. To achieve high areal capacities, self-supported NHCP electrodes with high mass loadings (3.41 and 6.23 mg cm−2) were constructed by a vacuum-assisted infiltration process which exhibits greatly improved areal capacities as compared with the traditional slurry coating electrode. The assembled full-carbon potassium-ion capacitor based on NHCP anode exhibits high energy and power densities (168 Wh kg−1 and 9.4 kW kg−1) and a long cycling lifespan (83.9% capacity retention after 10000 cycles at 1.0 A g−1). This work provides a facile fabrication method for porous carbon electrodes with high mass loadings and capacities, which holds the potential for practical application.