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.