Rational design of a hollow porous structure for enhancing diffusion kinetics of K ions in edge-nitrogen doped carbon nanorods
Ping Niu, Yang Yang, Zhiqiang Li, Gaohui Ding, Lingzhi Wei, Yao Ge, Helin Niu, Yulin Min, Fangcai Zheng, Qianwang Chen
Abstract
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.