Encapsulating Sb atoms in highly conductive Cu-S frameworks for fast and robust sodium storage

Sodium ion batteries (SIBs) currently lack sufficient anode materials that simultaneously demonstrate exceptional capacity, durability under prolonged cycling, and rapid charging capabilities. Antimony (Sb) has emerged as an attractive alloy-based anode candidate due to its notable theoretical capacity, nevertheless grappling with significant challenges including substantial structural deformation during operation and sluggish ion transport kinetics. Herein, we atomically disperse Sb into open Cu-S frameworks with high cyclic stability and good conductivity. In-situ and ex-situ analyses reveal the multistep reversible reaction processes during the charging (formation of Cu₃SbS₄) and discharging (precipitation of fracture-resistant Na₃Sb in the ionic-conductive Na_xCu₂S₂/Na₂S matrix) processes. As a result, the thoughtfully engineered Cu₃SbS₄ anode, without requiring additional carbon compositing, attains a high reversible specific capacity of 597 mAh g⁻¹ at a 0.3 C rate. It also maintains approximately 95% capacity retention even at 15 C after 4300 cycles. The assembled Cu₃SbS₄||Na₃V₂(PO₄)₃ full cell achieves 10 C high rate performance and demonstrates excellent cycling stability of ∼94.0% capacity retention after 200 cycles. Our approach to material design might offer a novel method for creating durable, high-capacity, and high-rate anode materials for sodium-ion batteries.