Repairing Carbon Defects Via Trace Phosphorus Doping for Enhanced Sodium-Ion Storage

Hard carbon (HC) is widely investigated as an anode material for sodium-ion batteries (SIBs), but it suffers from poor rate capability, unsatisfactory cycling stability, and low initial Coulombic efficiency (ICE). Phosphorus doping can improve Na+ storage by enlarging interlayer spacing and introducing active sites, but excessive doping usually generates abundant defects, aggravates side reactions, and hinders ion transport. Herein, we propose a synergistic strategy combining trace phosphorus (P) doping with defect repair to fabricate low-defect “vesicular” P-doped hard carbon (PHC). Controlled P incorporation expands the interlayer spacing, heals structural defects, and reinforces the carbon framework, enabling balanced electrochemical performance without compromising rate capability and cycle life. The optimized PHC-1.5% anode delivers a reversible capacity of 364.98 m Ah g–1, maintains 220 mAh g–1 at 2 A g–1, and retains 63.07% capacity after 5000 cycles. This work provides a simple and scalable route for defect-regulated hard carbon toward advanced SIB applications.