Carbon-Coated MOF-Derived Porous SnPS Core-Shell Structure as Superior Anode for Sodium-Ion Batteries.

Metal thiophosphites have recently emerged as a hot electrode material system for sodium-ion batteries because of their large theoretical capacity. Nevertheless, the sluggish electrochemical reaction kinetics and drastic volume expansion induced by the low conductivity and inherent conversion-alloying reaction mechanism, require urgent resolution. Herein, a distinctive porous core-shell structure, denoted as SnPS@C, is controllably synthesized by synchronously phosphor-sulfurizing resorcinol-formaldehyde-coated tin metal-organic framework cubes. Thanks to the 3D porous structure, the ion diffusion kinetics are accelerated. In addition, SnPS@C features a tough protective carbon layer, which improves the electrochemical activity and reduces the polarization. As expected, the as-prepared SnPS@C electrode exhibits superior electrochemical performance compared to pure SnPS, including excellent rate capability (1342.4 and 731.1 mAh g at 0.1 and 4 A g, respectively), and impressive long-term cycling stability (97.9% capacity retention after 1000 cycles at 1 A g). Moreover, the sodium storage mechanism is thoroughly studied by in-situ and ex-situ characterizations. This work offers an innovative approach to enhance the energy storage performance of metal thiophosphite materials through meticulous structural design, including the introduction of porous characteristics and core-shell structures.