Two-Dimensional Tin Disulfide Nanosheets for Enhanced Sodium Storage

Sodium-ion batteries (SIBs) are considered as complementary alternatives to lithium-ion batteries for grid energy storage due to the abundance of sodium. However, low capacity, poor rate capability, and cycling stability of existing anodes significantly hinder the practical applications of SIBs. Herein, ultrathin two-dimensional SnS₂ nanosheets (3-4 nm in thickness) are synthesized via a facile refluxing process toward enhanced sodium storage. The SnS₂ nanosheets exhibit a high apparent diffusion coefficient of Na⁺ and fast sodiation/desodiation reaction kinetics. In half-cells, the nanosheets deliver a high reversible capacity of 733 mAh g^-1 at 0.1 A g^-1, which still remains up to 435 mAh g^-1 at 2 A g^-1. The cell has a high capacity retention of 647 mA h g^-1 during the 50th cycle at 0.1 A g^-1, which is by far the best for SnS₂, suggesting that nanosheet morphology is beneficial to improve cycling stability in addition to rate capability. The SnS₂ nanosheets also show encouraging performance in a full cell with a Na₃V₂(PO₄)₃ cathode. In addition, the sodium storage mechanism is investigated by ex situ XRD coupled with high-resolution TEM. The high specific capacity, good rate capability, and cycling durability suggest that SnS₂ nanosheets have great potential working as anodes for high-performance SIBs.