N,P,S-Codoped Hierarchically Porous Carbon Spheres with Well-Balanced Gravimetric/Volumetric Capacitance for Supercapacitors

Due to the wide application of carbon-based materials in supercapacitors, the concern of volumetric capacitance becomes increasingly important. In this work, the N,P,S-codoped hierarchically porous carbon spheres (N,P,S-HCS) have been rationally designed and originally fabricated using the silica colloids as hard templates, polyaniline as carbon and nitrogen sources, phytic acid as phosphorus sources, and ammonium persulfate as sulfur sources. Both high volumetric and gravimetric capacitance can be achieved. The as-prepared N,P,S-HCS shows the highest specific capacitance of 274 F g–1 and 219 F cm–3 at a current density of 0.5 A g–1, which reveals a superior performance. Moreover, the cycling ability of the N,P,S-HCS can be maintained over 95% to the initial capacitance at a high current density of 10 A g–1 for 10 000 charge–discharge cycles. This is mainly contributed to the uniform doping of N, P, and S as well as the hierarchically porous structure of the N,P,S-HCS. Finally, we assemble it into the all-solid-state symmetric supercapacitors with high energy and power densities of 3.4 W h L–1 with 804 W L–1, respectively. The N,P,S-codoped hierarchically porous carbon spheres with high density show both good volumetric and gravimetric capacitance, which make it a promising material for supercapacitors in practical applications. The present investigations may develop a new direction for the design of carbon materials for a good balance of both high gravimetric and volumetric capacitance.