Precisely engineered hollow carbon spheres with controllable shell thickness, pore-size distribution, and heteroatom doping for high-performance supercapacitors

Hollow carbon spheres (HCSs) attracted increasing attention in the field of supercapacitor materials owing to their unique hollow structure. However, their hollow shells exhibited weak mechanical strength and tended to collapse under high-rate cycling. In this study, a nitrogen/sulfur co-doped hollow carbon sphere (NS-HCS) with tunable shell thickness was synthesized by adjusting the shell thickness and dopant loading. The optimized NS-HCS-1 integrated double-layer and pseudocapacitive storage while retaining the intrinsic high-power characteristics of carbon materials. The appropriate shell thickness enhanced structural durability, whereas N and S doping enriched the pore structure, accelerated ion transport, and provided additional pseudocapacitance, thereby improving electrochemical performance. In a three-electrode system, the material delivered a specific capacitance of 366 F g −1 at 1 A g −1 and retained 98.42 % of its initial capacitance after 20,000 cycles at 15 A g −1 . The assembled symmetric cell achieved a maximum energy density of 34.08 Wh kg −1 and a power density of 570 W kg −1 . This synergistic engineering of shell thickness and heteroatom doping afforded outstanding electrochemical performance, rendering NS-HCS-1 a promising electrode candidate for next-generation supercapacitors.