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

Abstract

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.