Fluorine-compensated Na3V2(PO4)2F3 cathode for long-term durable sodium ion batteries

Polyanionic Na 3 V 2 (PO 4 ) 2 F 3 is widely recognized as a promising cathode material for sodium ion batteries due to its high operating voltage. However, two critical challenges hinder its application: the formation of intergrowth structures owing to fluorine loss and the sluggish charge-transfer process resulting from the highly electronegative anions. Herein, Na 3 V 2 (PO 4 ) 2 F 3 with micro-nano structured morphology is obtained via a spray-drying method, which shortens diffusion pathways and enhances Na + transport kinetics. Besides, the fluorine chemistry of the cathode is regulated to optimize the atomic structure and electronic properties, whereby ensuring the formation of [V 2 O 8 F 3 ] bioctahedral framework while improving the electronic conductivity by narrowing the band gap and delocalizing the electron. As a result of optimized Na + /e − transfer kinetics and strengthened framework structure, the fluorine-compensated Na 3 V 2 (PO 4 ) 2 F 3 exhibits outstanding cycling durability (82.8 % capacity retention after 3000 cycles) and high-rate capability (74.7 mAh g −1 at 30 C). Particularly, the Na 3 V 2 (PO 4 ) 2 F 3 cathode exhibits remarkable temperature adaptability to the high environment (60 °C) and cold conditions (−20 °C). Moreover, the Na 3 V 2 (PO 4 ) 2 F 3 ||hard carbon full cell delivers a high energy density (434.9 Wh kg −1 ), further highlighting its great potential as a practical cathode material. This work may support the application of Na 3 V 2 (PO 4 ) 2 F 3 cathode for long-term durable sodium-ion batteries.