Ultralarge interlayer distance and C,N-codoping enable superior sodium storage capabilities of MoS₂ nanoonions

Sodium-ion batteries have emerged as a desired alternative to lithium-ion batteries (LIBs) on account of their low cost, good safety, and large reserves of sodium in the earth's crust. The sodium storage capabilities of batteries significatnly depend on the structure and composition of electrode materials. Herein, a new type of C,N-codoped MoS₂ nanoonions with ultralarge interlayer spacing of 1.16 nm has been successfully fabricated by vapor phase sulfuration of the as-prepared PPy-PMo₁₂ precursor at an optimized vulcanization temperature. More importantly, the delicate internal nanostructure has been directly observed via electron tomography (ET) technique and 3D reconstruction. Thanks to the structure and composition merits, the resulting anode materials of C/N-MoS₂-800 delivers remarkable sodium storage properties. The reversible capacity retains 617.7 mA h g⁻¹ at 100 mA g⁻¹ after 200 cycles. The electrochemical kinetic analysis and density functional theory (DFT) calculations further comfirm that the expanded interlayer distance and C,N-codoping of MoS₂ nanosheets promote the superior Na⁺ intercalation/deintercalation kinetics. In turn, the resulted pseudocapacitance-dominated electrochemical behavior also enables the superior rate capability.