Density functional theory (DFT) is employed to research three carbon tubes (CNTs), SWCNT, N-NiCNT, and N-CoCNT. The first two structures synthesized by other groups and N-NiCNT has better sodium storage properties as sodium-ion battery (SIB) anode than SWCNT, the last one is a designed structure. Here, the intrinsic cause why N-NiCNT has better performance than SWCNT has been located at molecular and atomic levels, meanwhile the potential of N-CoCNT as anode candidate is predicted. The researched properties that determine the electrochemical performances involve in structure stability, frontier molecular orbital, partial density of state analysis, and sodiation barrier comparison. The results indicate that the lower sodiation barrier, expanding transfer space, more stable structure stability of N-NiCNT should be responsible for its better sodium storage performance, which consists with the experimental results. In addition, the designed N-CoCNT anode is a promising candidate as SIB anode owing to better stability, lower barrier, and strong N-Co interaction than N-NiCNT

Tingting Xu, Xiaohua Xie, Huisheng Huang and Xinwei Zhao