Unveiling the role of MoS2 hollow nanospheres on lignite-based carbon for enhanced sodium-ion battery performance

Abstract

The two-dimensional (2D) layered material molybdenum disulfide (MoS₂) exhibits a special Mo-S-Mo sandwich structure with a rather large spacing, making it a promising candidate as an anode material for sodium storage applications. Unfortunately, the practical applications are limited by their intrinsically low electrical conductivity, significant volume alteration and severe particle agglomeration. In this study, we designed a new two-step solvothermal strategy to synthesize ultrathin nanosheet-assembled MoS₂ hollow nanospheres strongly located on lignite-based carbon (MoS₂/C) without any template. The ultrathin nanosheets assembled into hollow structures mitigated the volume changes of MoS₂ during the (dis)charge cycles, facilitated Na⁺ diffusion, and reduced the migration energy barrier within MoS₂. Lignite-based C enhances the electrical conductivity of MoS₂, prevents its aggregation, and alleviates mechanical stress during repeated (dis)charging. The resultant hollow spherical MoS₂/C composite exhibits outstanding cyclability and rate performance when used as an anode in sodium-ion batteries, as it delivers a high specific capacity of 515.8 mAh g⁻¹ after 1000 cycles at 1.0 A g⁻¹, with a 94.34% capacity retention rate. Even at a high current density of 20 A g⁻¹, a capacity of 431 mAh g⁻¹ can still be obtained after 2000 cycles. In particular, the initial Coulombic efficiency of the MoS₂ anode is markedly enhanced by the incorporation of lignite-based C.

Graphical abstract