Rational design of a hollow porous structure for enhancing diffusion kinetics of K ions in edge-nitrogen doped carbon nanorods

The high electrical conductivity makes it possible for one-dimensional (1D) carbon materials to be used as the promising anodes for potassium ion batteries (PIBs), however, the sluggish diffusion kinetics caused by large-sized potassium ions (K⁺) limits their practical applications in energy storage systems. In this work, hollow carbon nanorods were rationally designed as a case to verify the superiority of 1D hollow structure to improve the diffusion kinetics of K⁺. Simultaneously, edge-N (pyridinic-N and pyrrolic-N) atoms were also introduced into 1D hollow carbon structure, which can provide ample active sites and defects in graphitic lattices to adsorb K⁺, providing extra capacitive storage capacity. As expected, the optimized edge-N doped hollow carbon nanorods (ENHCRs) exhibits a high reversible capacity of 544 mAh·g⁻¹ at 0.1 A·g⁻¹ after 200 cycles. Even at 5 A·g⁻¹, it displays a long-term cycling stability with 255 mAh·g⁻¹ over 10,000 cycles. The electrochemical measurements confirm that the hollow structure is favorable to improve the transfer kinetics of K⁺ during cycling. And the theoretical calculations demonstrate that edge-N doping can enhance the local electronegativity of graphitic lattices to adsorb much more K⁺, where edge-N doping synergizes with 1D hollow structure to achieve enhanced K⁺-storage performances.