Towards a High-Performance Tin Anode for Practical Sodium-Ion Batteries

This study investigates the performance and structural stability of commercial micron-sized tin (Sn) particles as anode active material for sodium-ion batteries. Despite undergoing significant volume change during cycling, the Sn anode demonstrates stable capacity retention over 450 cycles in Sn/Na half-cells with an ether-based electrolyte. Initially fragmented Sn particles restructure into uniformly dispersed 1-micron sized spheres within the first 50 cycles. The restructuring process is hypothesized to result from the interplay between fragmentation and particle coalescence, preventing further pulverization. In the case of incomplete (de)sodiation, the voltage profile gradually evolves over cycling which suggests the development of an inhomogeneous morphology within the Sn electrode. To assess Na inventory loss during restructuring, a limited-inventory protocol was developed for Sn/Na cells, resulting in 95% of capacity retention over 100 cycles. Full NFPP/Sn coin cells only show 84% capacity retention after 100 cycles, which suggests additional parasitic reactions. An in situ pressure measurement was performed on a multi-layer NFPP/Sn pouch cell to monitor the stack pressure change. These results highlight the potential of Sn anodes and emphasize the need to address issues related to parasitic reactions and electrode volume expansion for their successful integration into practical sodium-ion batteries.