Boron-catalyzed graphitized carbon coating in Na₄Fe₃(PO₄)₂P₂O₇ cathodes boosts reaction kinetics for high-rate and long-cycle sodium-ion batteries

Sodium-ion batteries (SIBs) have emerged as a compelling alternative to lithium-ion batteries (LIBs) for large-scale energy storage applications, primarily due to the natural abundance, low cost, and uniform geographic distribution of sodium resources. Among available cathodes, the polyanionic cathode Na₄Fe₃(PO₄)₂P₂O₇ (NFPP) combines both excellent cycling stability and a high theoretical capacity. However, the intrinsically low electronic conductivity of NFPP, attributable to the insulating nature of its PO₄-linked FeO₆ units, markedly impedes charge-transfer kinetics. Here, we introduce a boron-assisted carbon coating on NFPP (NFPP/B–C), where boron doping generates p-type carriers and enhances carbon graphitization, increasing the conductivity from 4.76 × 10⁻⁴ to 8.4 × 10⁻⁴ S cm⁻¹. As a result, the optimized NFPP/B–C cathode delivers an initial charge capacity of 127.2 mAh g⁻¹ at 0.1C and 89.2 mAh g⁻¹ at 50C, with 91.0% capacity retention over 10000 cycles at 20C. These results establish boron-assisted graphitized carbon coatings as an effective strategy for enabling high-power and durable NFPP cathodes for sodium ion batteries.