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 Na 3 V 2 (PO 4 ) 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.