High-performance Na3.12Fe2.44(P2O7)2 cathode materials with three-dimensional porous structure for sodium-ion batteries

Sodium-ion batteries (SIBs) are the highly promising rechargeable batteries for large-scale energy storage systems, offering advantages such as low cost, high safety and fast charging capabilities. Important research work on SIBs has focused on exploring high-performance electrode materials and their mechanism in depth. With benefits of low cost, good thermal stability and small volume strain, Na 3.12 Fe 2.44 (P 2 O 7 ) 2 (NFPO) is a potential cathode material. However, the inherent poor conductivity of the material leads to polarization, consequently compromising electrochemical reversibility. Therefore, we synthesized NFPO composites with porous structure (P-NFPO) by sol-gel method which exhibited excellent electrochemical performance. The diffusion path of sodium ions during charging and discharging can be effectively shortened by the three-dimensional pore structure, which also promotes electrolyte penetration and absorbs volume expansion. P-NFPO exhibits a reversible specific capacity of 108.13 mAh g −1 at the rate of 0.1 C. Additionally, NFPO exhibits superb long-term cyclability and rate capability. Its specific capacity was found to be 95.94 mAh g −1 at a current density of 1 C. Impressively, even after 400 cycles at a rate of 5 C, it retains 95.1 % of its initial capacity, maintaining a reversible specific capacity of 74.6 mAh g −1 . Furthermore, when operated at 0.2 C, the P-NFPO//hard carbon full cell demonstrates a reversible capacity of 100.9 mAh g −1 . This study presents new ideas for modified cathode materials and promotes the practical application of cathode materials.