In-situ N-doped ultrathin MoS2 anchored on N-doped carbon nanotubes skeleton by Mo-N bonds for fast pseudocapacitive sodium storage

As one of the most promising anode materials in sodium ion batteries (SIBs), MoS₂ has been severely hindered its wide application in the field of energy storage due to the low electronic conductivity and severe volume variation during charge/discharge. Herein, we propose and synthesize an innovative structure of ultrathin N-doped MoS₂ nanosheets anchored on hollow N-doped carbon nanotube skeleton by Mo-N bonds (N-MoS₂@NCNT). It is demonstrated that the N atoms decomposed from NH₄⁺ ions after annealing in-situ substitute the basal S atoms in MoS₂ structure to form N-doped MoS₂ (N-MoS₂), which improves the conductivity of the materials. Moreover, the stable Mo-N bonds between N-MoS₂ and carbon skeleton keep the structural integrity of the electrode. With these merits, the N-MoS₂@NCNT electrode shows high reversible capacity of 504.1 mAh g^–1 with the ultrahigh capacity retention of 104.4 % after 100 cycles at 0.1 A g^–1. The structural engineering of in-situ nitrogen doping combined with the tight chemical bonds between active material and carbon can significantly increase the electrochemical performance of MoS₂. This strategy also provides an original idea for the next step of designing high-performance transition metal sulfide/carbon-based composites anodes for SIBs.