Optimizing the Interlayer Spacing of Heteroatom-Doped Carbon Nanofibers toward Ultrahigh Potassium-Storage Performances.

Precise control over the interlayer spacing for K + intercalation is an effective approach to boost the potassium-storage performances in carbonaceous materials. Herein, we first found that the optimal interlayer spacing for K + intercalation is around 0.38 nm for N, O codoped carbon nanofibers (NOCNs), displaying a reversible capacity of 627 mAh g -1 at 0.1 A g -1 after 200 cycles, excellent rate capability (123 mAh g -1 at 20 A g -1 ), and ultrastable cycling stability (262 mAh g -1 at 5 A g -1 after 10 000 cycles). Such good potassium-storage performances have never been reported in carbonaceous materials. The theoretical calculations and electrochemical studies reveal that the optimal interlayer spacing and N, O heteroatom-induced active sites work together to provide an intercalation-adsorption mechanism for storing K + in carbonaceous materials. This work facilitates the understanding of the role of the critical interlayer spacing for K + intercalation in carbonaceous materials.