Highly Electrochemically-Reversible Mesoporous Na₂ FePO₄ F/C as Cathode Material for High-Performance Sodium-Ion...

As promising cathode materials, iron-based phosphate compounds have attracted wide attention for sodium-ion batteries due to their low cost and safety. Among them, sodium iron fluorophosphate (Na₂ FePO₄ F) is widely noted due to its layered structure and high operating voltage compared with NaFePO₄ . Here, a mesoporous Na₂ FePO₄ F@C (M-NFPF@C) composite derived from mesoporous FePO₄ is synthesized through a facile ball-milling combined calcination method. Benefiting from the mesoporous structure and highly conductive carbon, the M-NFPF@C material exhibits a high reversible capacity of 114 mAh g^-1 at 0.1 C, excellent rate capability (42 mAh g^-1 at 10 C), and good cycling performance (55% retention after 600 cycles at 5 C). The high plateau capacity obtained (>90% of total capacity) not only shows high electrochemical reversibility of the as-prepared M-NFPF@C but also provides high energy density, which mainly originates from its mesoporous structure derived from the mesoporous FePO₄ precursor. The M-NFPF@C serves as a promising cathode material with high performance and low cost for sodium-ion batteries.