Multi-morphological carbon cross-linked composite enhances the high-rate performance and ultra-long cycling stability of Na3Fe2(PO4)(P2O7) cathode

Abstract

Sodium-ion batteries (SIBs) have emerged as a promising complement to lithium-ion counterparts, owing to their advantages of abundant resources, low cost, and high safety. Among the polyanion-type cathode materials, Na₃Fe₂(PO₄)(P₂O₇) (NFPP) has garnered significant attention due to its stable three-dimensional framework and environmentally friendly characteristics. However, its inherent low electronic conductivity has hindered practical application. This work presents a modification strategy to address this limitation. By constructing a three-dimensional continuous conductive network within the NFPP composite material (NFPP@C/CNT-rGO) through the integration of carbon nanotubes (CNT), reduced graphene oxide (rGO), and amorphous carbon coating, the electronic conductivity is significantly enhanced, and sodium-ion diffusion sites are optimized. Electrochemical evaluation demonstrates that the NFPP@C/CNT-rGO half-cell delivers a reversible capacity of 113.3 mAh g⁻¹ at 0.1 C, with a capacity retention rate of 70.7% after 6000 cycles at a high rate of 10 C, while maintaining a stable Coulombic efficiency close to 100%. Notably, at 20 C, the capacity reaches 70.2 mAh g⁻¹, far surpassing that of NFPP@C. Furthermore, the assembled NFPP@C/CNT-rGO || HC full cell exhibits a capacity retention rate of 78.4% after 300 cycles at 1 C, validating the material’s practical application potential. This study introduces a novel approach to enhance the performance of iron-based polyanion cathodes in sodium-ion batteries by constructing carbon conductive networks with multi-morphological structures, thereby paving the way for the practical application of sodium-ion batteries.