Microsized Sn as Advanced Anodes in Glyme-Based Electrolyte for Na-Ion Batteries

An experiment was conducted to demonstrate that glyme-based electrolytes enable high reversible capacity of Sn anode for Na-ion batteries. The improvement in the stability mainly relies on the formation of protecting films which prevent the formation of insulating domains of active materials. Moreover, the Na-Sn phases during electrochemical alloying are examined through in situ XRD characterization to clarify several intermediate phases such as amorphous NaSn. In particular, a new polymorph of Na9Sn4is found and its crystal structure is analyzed by synchrotron X-ray diffraction. Finally, prototype full cells using Sn anode and NVP cathode are assembled. They demonstrate the great advantages of using Sn instead of hard carbon as anodes since enhancements of 19% and 61% increase in gravimetric and volumetric energy densities, respectively, can be achieved.