Interconnected carbon nanocapsules with high N/S co-doping as stable and high-capacity potassium-ion battery anode

Carbonaceous materials have drawn much attention in potassium-ion batteries (PIBs) due to their low price and superior physicochemical properties. However, the application of carbonaceous materials in PIB anodes is hindered by sluggish kinetics and large volume expansion. Herein, N/S co-doped carbon nanocapsule (NSCN) is constructed for superior K~+storage. The NSCN possesses 3D nanocapsule framework with abundant meso/macropores, which guarantees structural robustness and accelerates ions/electrons transportation. The high-level N/S co-doping in carbon matrix not only generates ample defects and active sites for K~+adsorption, but also expands interlayer distance for facile K~+intercalation/deintercalation. As a result, the NSCN electrode delivers a high reversible capacity (408 m Ah g-1at 0.05 A g-1), outstanding rate capability (149 m Ah g-1at 5 A g-1) and favorable cycle stability (150m Ah g-1at 2 A g-1after 2000 cycles). Ex situ TEM, Raman and XPS measurements demonstrate the excellent stability and reversibility of NSCN electrode during potassiation/depotassiation process. This work provides inspiration for the optimization of energy storage materials by structure and doping engineering.