Engineering Se/N Co‐Doped Hard CNTs with Localized Electron Configuration for Superior Potassium Storage

Abstract The earth‐abundant hard carbons have drawn great concentration as potassium‐ion batteries (KIBs) anode materials because of their richer K‐storage sites and wider interlayer distance versus graphite, but suffer from a low electrochemical reversibility. Herein, the novel Se/N co‐doped hard‐carbon nanotubes (h‐CNTs) with localized electron configuration are demonstrated by creating unique NSeC covalent bonds stemmed from the precise doping of Se atoms into carbon edges and the subsequent bonding with pyrrole‐N. The strong electron‐donating ability of Se atoms on d‐orbital provides abundant free electrons to effectively relieve charge polarization of pyrrole‐N‐C bonds, which contributes to balance the K‐ion adsorption/desorption, therefore greatly boosting reversible K‐ion storage capacity. After filtering into self‐standing anodes with weights of 1.5–12.4 mg cm⁻², all of them deliver a high reversible gravimetric capacity of 341 ± 4 mAh g⁻¹ at 0.2 A g⁻¹ and a linear increasing areal capacity to 4.06 mAh cm⁻². The self‐standing anode can still maintain 209 mAh g⁻¹ at 8.0 A g⁻¹ (93.3% retention) for a long period of 2000 cycles with a constant Se/N content.