Dual-Carbon Synergistic Strategy Enabling SbPO₄@MFC/rGO Composites With Hierarchical Conduction Network for High-Performance Sodium-Ion Batteries

Antimony-based anodes have emerged as up-and-coming alloy-type anode materials for sodium-ion batteries (SIBs), owing to their high theoretical capacity and excellent electrical conductivity. However, they still suffer from severe issues such as substantial volume expansion during the sodiation-desodiation process. The novel antimony phosphate/carbon composites are designed through a multi-composited strategy in this work. The exceptional electrochemical performance of the synthesized phosphate/carbon composites arises from the synergistic combination of the unique physicochemical properties of antimony phosphate, the structural flexibility and high electrical conductivity of graphene oxide (GO), and the advantageous features of melamine-resin-derived nitrogen-doped porous carbon. For instance, the SbPO₄@MFC/rGO-0.6 still maintains a high reversible discharge capacity of 201.6 mAh g⁻¹, after 2000 cycles at a high current density of 2.0 A g⁻¹. Density functional theory (DFT) calculations demonstrate that the optimized electronic structure of SbPO₄@MFC/rGO enhances the interfacial interactions between antimony phosphate and the nitrogen-doped carbon matrix, thereby increasing the binding ability of the matrix with Na⁺. Furthermore, the SbPO₄@MFC/rGO-0.6//Na₃V₂(PO₄)₃ full cell can manifest a high energy density of 168.2 Wh kg⁻¹. In particular, SbPO₄@MFC/rGO-0.6//Na₃V₂(PO₄)₃ delivers an energy density of 103.2 Wh kg⁻¹ while maintaining the high power density of 794.1 W kg⁻¹.