Fabrication of SnS₂/Mn₂SnS₄/Carbon Heterostructures for Sodium-Ion Batteries with High Initial Coulombic Efficiency and Cycling Stability

SnS₂ has been extensive studied as an anode material for sodium storage owing to its high theoretical specific capacity, whereas the unsatisfied initial Coulombic efficiency (ICE) caused by the partial irreversible conversion reaction during the charge/discharge process is one of the critical issues that hamper its practical applications. Hence, heterostructured SnS₂/Mn₂SnS₄/carbon nanoboxes (SMS/C NBs) have been developed by a facial wet-chemical method and utilized as the anode material of sodium ion batteries. SMS/C NBs can deliver an initial capacity of 841.2 mAh g^-1 with high ICE of 90.8%, excellent rate capability (752.3, 604.7, 570.1, 546.9, 519.7, and 488.7 mAh g^-1 at the current rate of 0.1, 0.5, 1.0, 2.0, 5.0, and 10.0 A g^-1, respectively), and long cycling stability (522.5 mAh g^-1 at 5.0 A g^-1 after 500 cycles). The existence of SnS₂/Mn₂SnS₄ heterojunctions can effectively stabilize the reaction products Sn and Na₂S, greatly prevent the coarsening of nanosized Sn⁰, and enhance reversible conversion--alloying reaction, which play a key role in improving the ICE and extending the cycling performance. Moreover, the heterostructured SMS coupled with the interacting carbon network provides efficient channels for electrons and Na⁺ diffusion, resulting in an excellent rate performance.