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Hollow carbon nanospheres with developed porous structure and retained N doping for facilitated electrochemical energy storage.

Development of high porous carbons with abundant surface functionalities and well-defined nanostructure is of significance for many important electrochemical energy storage systems. However, porous carbons suffer from a compromise between porosity, doped functionalities and nanostructure that has thus far restricted their performances. Here we report the design of highly porous, nitrogen-enriched hollow carbon nanospheres (PN-HCNs) by an interfacial copolymerization strategy followed by NH3-assisted carbonization, and further demonstrate their significance and effectiveness in enhancing the electrochemical performances. PN-HCN simultaneously delivers large surface area (1237 m2 g-1) and high N functionalities (6.25 at%) with a remarkable efficiency of surface area increase to N loss ratio enabled by NH3 treatment, and meanwhile inherits the hollow nanospherical structure. Accordingly, owing to the enhanced surface area and remained N doping, the prepared PN-HCN demonstrates outstanding electrochemical performances as host cathode in lithium-sulfur batteries, including a near-to-theoretical capacity of 1620 mAh g-1, high-rate capability, and good cycling stability (789 mAh g-1 at 0.5 C after 200 cycles). These results are superior to those of HCN without NH3 treatment. Also, PN-HCN exhibits superior capacitances (203 F g-1) and fast ion transport ability in supercapacitors. Our finding shows the simultaneous achievement of both highly porous structures and sufficient N functionalities towards high-performance applications.