Confined pyrolysis for direct conversion of solid resin spheres into yolk–shell carbon spheres for supercapacitor

Abstract

Yolk–shell carbon spheres (YCS) have been widely used in many fields due to their abundant electron transport paths, high ion-accessibility and surface area as well as excellent mechanical properties. However, up to the present, the preparation of yolk–shell carbon spheres with tunable structures has always been a challenge. Herein, the direct conversion of solid resin spheres into YCS is achieved by a facile confined pyrolysis strategy. A silica shell with different degrees of openness is built on the surface of a solid resin sphere to form a confined nanospace, in which the volatile gases generated in the process of pyrolysis are deposited, forming a tunable yolk–shell structure. The results show that the YCS samples prepared in a relatively compact confined environment (YCS-C) have a thinner shell, higher surface area and richer porous structure. As electrode materials for supercapacitors, YCS-C show an excellent specific capacitance of 330 F g⁻¹ at 0.5 A g⁻¹ and outstanding stability with 88.5% initial capacity retention after 10 000 cyclic tests, making them promising candidates for high-performance energy storage devices.