Constructing high-performance N-doped carbon nanotubes anode by tuning interlayer spacing and the compatibility mechanism with ether electrolyte for sodium-ion batteries

The graphitic carbon nitride (g-C3N4) as a promising high-nitrogen carbon material has attracted abundant attentions in energy storage field. In this work, the N-doped carbon nanotubes (N-CNTs) are synthesized through a facile one-step pyrolysis of g-C3N4 precursor assisting by Ni catalyst. The obtained N-CNTs possess unique one-dimensional (1D) nanotubular structure, high conductivity, suitable N-doping around 8.73 ∼ 14.72 at.% and tunable interlayer distance up to 0.462 nm which can accommodate sufficiently Na+. Serving as anodes for sodium-ion batteries (SIBs), the resultant N-CNTs exhibit a promising specific capacity of 290.3 mAh⋅g−1 at 0.05 A⋅g−1 and superior rate capability of 164.5 mAh⋅g−1 at 10 A⋅g−1, as well as excellent long-term cycling performance at 0.5 A⋅g−1 for 1000 cycles. Further kinetic analysis and ex-situ Raman reveal the sodium storage mechanism of N-CNTs, which simultaneously combines the diffusion and the dominated capacitive mechanisms together. According to the first principles, density functional theory (DFT) calculations from the perspective of atomic structure further demonstrate that the superior electrochemical performance of N-CNTs is attributed to the strong adsorption interaction between Na+ in ether-based electrolyte and pyrrolic N site. This work provides a facile method to synthesize N-doped carbon nanotube with remarkable electrochemical performance, which is a promising nanotube-structured anode material for the practical application of SIBs.