Microsized Gray Tin as a High-Rate and Long-Life Anode Material for Advanced Sodium-Ion Batteries

Sodium-ion batteries (SIBs) are developed to address the serious concern about the limited resources of lithium. To achieve high energy density, anode materials with a large specific capacity and a low operation voltage are highly desirable. Herein, microsized particles of gray Sn (α-Sn) are explored as an anode material of SIBs for the first time. The distinct structure of α-Sn endows it the reduced volume change, the improved interaction with polymer binders and the in situ formation of amorphous Sn, as supported by in situ XRD, TEM and DFT calculations. Therefore, α-Sn exhibits an excellent electrochemical performance, much better than β-Sn widely used before. Even microsized particles of α-Sn without any treatments deliver a capacity of ∼451 mAh g^-1 after 3500 cycles at 2 A g^-1 or ∼464 mAh g^-1 at 4 A g^-1 in a rate test. The results indicate the promising potential of α-Sn in SIBs.