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

Abstract

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 boronassisted 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 10,000 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.