Phosphorus-transfer-induced self-healing of carbon layers for precise modulation of hard carbon defects and closed pores

Hard carbon (HC) is a promising anode material for sodium-ion batteries. However, the precise design of closed-pore structures and the control of carbon defects remain key bottlenecks in the development of polymer-derived hard carbon. Based on this, this paper proposes a phosphorus (P)-transfer-induced carbon layer self-healing strategy, achieving synergistic optimization of closed-pore structures and carbon defects. Through a pre-oxidation-mediated transfer pathway of boundary phosphorus (P–O–C) to carbon matrix phosphorus (P–C), radical competitive reactions are triggered during pyrolysis, transforming thick and short disordered carbon layers into thin and long pseudo-graphitic carbon layers. This strategy constructs abundant and uniformly distributed small-sized closed pores (0.76 nm) in the carbon matrix while converting irregular edge carbon defects into intrinsic carbon defects. The synergistic optimization of both promotes the formation of fluorine-rich solid electrolyte interface components, significantly enhancing Na⁺ transport kinetics. The optimized hard carbon exhibits a reversible specific capacity of up to 429.0 mAh g⁻¹, an initial coulombic efficiency (ICE) of up to 89.44 %, and excellent cycling performance at a current density of 5 A g⁻¹, enabling 10000 cycles. This study provides a new approach for the development of high-performance polymer-derived hard carbon materials.