Nitrogen-Doped Carbon Nanotubes with Large Interplanar Distances toward Fast Potassium Storage

One of the main challenges potassium-ion batteries (PIBs) face is the lack of structurally stable anodes with high reactivity and fast kinetics for reversible potassium insertion/extraction. Herein, nitrogen-doped carbon nanotubes (N-CNTs) are synthesized using a straightforward method assisted by a Co-based catalyst. The as-synthesized N-CNTs possess interlayer distances up to 0.38 nm and nitrogen-doping content of 2.2 at.%. Compared to the undoped CNTs (U-CNTs), N-CNTs exhibit a promising initial specific capacity of 568 mAh g-1 at 0.1 A g-1, as well as excellent long-term cycling performance of 104, 82, and 76 mAh g-1 at a high current of 0.5, 1, and 2 A g-1 for 500 cycles. The cyclic voltammetry (CV) measurements reveal the potassium storage mechanism of N-CNTs, which combines the major capacitive mechanisms and the secondary diffusion, and successfully avoids inconspicuous voltage plateau. The kinetic analysis of the galvanostatic intermittent titration technique and ex situ X-ray photoelectron spectroscopy spectra show fast reaction kinetics and low side effects and degradation for the N-CNTs anodes during the potassiation/de-potassiation process. This study provides a straightforward method to synthesize heteroatom-doped carbonaceous anode materials and achieves superior electrochemical properties with cost-effectiveness and material sustainability. Nitrogen-doped carbon nanotubes (N-CNTs) are directly synthesized by a Co-based catalyst, possessing interlayer distances up to 0.38 nm and nitrogen-doping content of 2.2 at.%. N-CNTs electrodes combine the major capacitive mechanisms and the secondary diffusion and successfully avoid inconspicuous voltage plateau. N-CNTs exhibit fast reaction kinetics and low side effects and degradation.image