Synthesis of hollow HC-Ni0.96S@MXene/C nanobox as advanced anode for lithium-ion and sodium-ion battery

In this study, a hybrid composite of MXene loaded with carbon-coated Ni 0.96 S hollow nanobox (shortened as HC-Ni 0.96 S@MXene/C) is successfully synthesized. The micro-structure of HC-Ni 0.96 S@MXene/C is further analyzed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) with EDS mappings. The results reveal that ∼550 nm Ni 0.96 S nanobox with ∼60 nm shell is effectively loaded on MXene nanosheets and encapsulated by a thin carbon layer. When evaluated as advanced anode for lithium-ion batteries (LIBs), HC-Ni 0.96 S@MXene/C achieves a specific capacity of 810.9 mAh g - 1 at 0.1 A g - 1 and remains 455.6 mAh g - 1 at 0.5 A g -1 after 200 cycles. Moreover, in sodium-ion batteries (SIBs), HC-Ni 0.96 S@MXene/C anode delivers 416.5 mAh g - 1 at 0.05 A g - 1 and maintains 201.4 mAh g - 1 at 0.5 A g - 1 after 400 cycles. Additionally, the HC-Ni 0.96 S@MXene/C anode demonstrates higher pseudo-capacitance effects of 81.6 and 92.5 % at a scanning rate of 1 mV s - 1 in LIBs and SIBs respectively. Moreover, the higher pseudo-capacitance effects in SIBs are according with the facts that the ionic diffusion coefficients of Na ions ( D Na +  = 4.6 ∼ 40.6 × 10 -11 (discharge) and 1.7 ∼ 127.8 × 10 -11 (charge) cm 2 /s) are larger than those of Li ions ( D Li +  = 1.1 ∼ 19.6 × 10 -11 (discharge) and 0.82 ∼ 32.6 × 10 -11 (charge) cm 2 /s) for HC-Ni 0.96 S@MXene/C anode. The excellent electrochemical performances of HC-Ni 0.96 S@MXene/C should be assigned to hollow Ni 0.96 S structure, carbon coating and conductive MXene nanosheets, which collectively alleviate volume changes during cycling, enhance electronic conductivity and accelerate ion diffusion respectively. This strategy of synthesizing HC-Ni 0.96 S@MXene/C may provide a guidance for designing advanced LIBs/SIBs anodes in the near future.