Microsized Sn-Hard Carbon Composite Anode with Capacities of 583 mAh g ^–1 and 1073 mAh cm ^–3 for Sodium-Ion Batteries

Sodium-ion batteries (SIBs) are applied for large-scale energy storage systems, yet their energy density remains capped by hard carbon (HC) anodes with modest gravimetric and volumetric capacities. Herein, we report an alloying-carbon strategy that applies microsized Sn particles with microsized HC particles to form thick-film anodes. The optimized Sn-HC composite couples the high capacity and compaction density of Sn with the structural robustness of HC, displaying the gravimetric and volumetric capacities of 583 mAh g–1 and 1073 mAh cm–3, an initial Coulombic efficiency of 90.5%, a capacity retention of ∼89.5% after 1000 cycles at 0.5 A g–1, and limited electrode swelling of 33.7%. Coupled with the Na3V2(PO4)3 cathode, the SIB full cell delivers an energy density of 254 Wh kg–1 and high-rate capabilities. Such Sn-HC architecture offers a scalable and industrially relevant route to simultaneously increase the gravimetric and volumetric capacities of anodes for SIBs.