Mixed-dimensional van der Waals heterostructure of Bi2S3 nanorods and SnS2 nanosheets bridged with N-doped carbon interlayer for enhanced sodium-ion batteries

Heterostructure engineering offers significant potential to advance the energy storage capabilities of sodium-ion batteries (SIBs). The typical presence of rich surface states in nanosemiconductors, however, introduces substantial surface barriers that impede surface conductivity, thereby limiting the performance of batteries. Herein, we developed a mix-dimensional van der Waals heterostructure (Bi₂S₃@NC/SnS₂@NC) by synthesizing p-type SnS₂ nanosheets on n-type Bi₂S₃ nanorods, bridged with an ultrathin nitrogen-doped carbon (NC) layer. This structure served as an anode, improving electrochemical performance through additional redox reaction sites and a porous structure that supports electrolyte flow and Na⁺ transport. This reduces mechanical stress during charging cycles, maintaining structural integrity. Most critically, theoretical and experimental analyses show that the NC layer passivates interface states, enhancing the built-in electrical field and reducing electron and Na⁺ transport resistance, thereby boosting redox activity. Consequently, the Bi₂S₃@NC/SnS₂@NC anode exhibits a high specific capacity of 290 mAh g⁻¹ after 1400 cycles at 5 A g⁻¹, and 233.6 mAh g⁻¹ at a high rate of 10 A g⁻¹. In full-cell setups with Na₃V₂(PO₄)₃ cathodes, it can maintain 461.4 mAh g⁻¹ after 100 cycles at 0.1 A g⁻¹. This work demonstrates the crucial role of heterostructure engineering in advancing efficient energy storage solutions.