Decoupling shell thickness and heteroatom doping in hollow carbon spheres for mechanistic control of charge storage

Abstract

Electrochemical supercapacitors must simultaneously deliver high power density, long life, and rising volumetric energy, yet converting surface area rich carbons into compact, fast, and durable electrodes remains nontrivial. Hollow spherical structures have been extensively studied for their application as supercapacitor electrode materials due to their large specific surface area, regular morphology, and numerous modification sites. This work focuses on the precise control of the shell layer thickness of hollow carbon spheres (HCS) while introducing nitrogen atoms via a one-step method to further enhance the material’s volumetric active material density. The resulting HCS-N-1 exhibits an excellent specific capacitance of 381 F g^-1 at 1 A g^-1 in a three-electrode system, and maintains an astonishing capacitance retention rate of 97.45% after 20,000 cycles at 10 A g^-1. The assembled symmetric supercapacitor (SSC) exhibits an preeminent energy density of 32.5 Wh kg^-1 at a particularly excellent power density of 2463 W kg^-1, with only an 8.41% energy decay after 20,000 charge-discharge cycles. These impressive electrochemical properties highlight the strategic insights provided by this work for the structural design of high-performance hollow spherical carbon materials.