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• The N-doped carbon nanotubes (N-CLNTs) were prepared through the carbonization of PANI nanotubes. • The N-CLNTs possesses 3D interconnected networks with unique 1D tubular structure. • The N-CLNTs-700 exhibits excellent cycling stability. • The excellent performance of N-CLNTs-700 attribute to multiple synergistic effects. Potassium-ion batteries (PIBs), as an inexpensive alternative to lithium-ion batteries (LIBs), have attracted significant attention for large-scale energy storage owing to their high capacity and low cost. The polyaniline (PANI) is a promising carbon source for high-performance PIBs anodes because of its diversity of morphologies and high N content. However, the PANI-derived carbon is rarely utilized as PIBs anode. Herein, the cross-linked porous N-doped carbon nanotubes (N-CLNTs) were prepared through the carbonization of PANI nanotubes. By adjusting the carbonization temperature, the N-CLNTs with different N content were designed to systematically elaborate on the effect of the N-doping on the electrochemical properties for PIB anodes. Owing to the synergistic effect of the high N-5/N-6 content and unique 1D tubular structure, the N-CLNTs-700 delivers a reversible capacity of 261 mAh g−1 at 0.05 A g−1 after 150 cycles and can still remain 168 mAh g−1 at 2 A g−1 over 3000 cycles. These results shed light on the design of carbon materials to efficiently enhance the electrochemical performance of PIBs. [ABSTRACT FROM AUTHOR]

Potassium-ion batteries (PIBs) are in the spotlight as a possible alternative to lithium-ion batteries. Graphitic carbons are promising anode materials for PIBs due to their low-plateau potential that is beneficial for the realization of high-voltage full cells. However, inferior cycling stability hinders their practical application. Herein, highly graphitized carbon nanofibers (HG-CNFs) as a free-standing electrode are served as the anode for PIBs. The HG-CNFs exhibits a reversible capacity of 200 mAh g−1 at the plateau potential below 0.2 V (76% of total capacity) and superior rate performance with a depotassiation capacity of 226 mAh g−1 at 35 C. Moreover, the capacity decay of HG-CNFs is less than 0.008% per cycle during 400 cycles, which is superior to those of most other graphitic carbons. The excellent electrochemical performance of HG-CNFs is attributed to its merits of free-standing fibrous networks and graphitic structure with rational defects that alleviate the volume expansion incurred by K+ intercalation. • Highly graphitized carbon nanofibers as a free-standing electrode was prepared. • The interconnected networks improve the integrity and buffer the volume expansion. • The HG-CNFs exhibits a capacity of 200 mAh g−1 at the plateau potential below 0.2 V. • The HG-CNFs shows outstanding cycling performance in K-ion half-cells. [ABSTRACT FROM AUTHOR]