Ascorbic Acid‐Assisted Synthesis of Mesoporous Sodium Vanadium Phosphate Nanoparticles with Highly sp 2 ‐Coordinated Carbon Coatings as Efficient Cathode Materials for Rechargeable Sodium‐Ion Batteries

Herein, mesoporous sodium vanadium phosphate nanoparticles with highly sp 2 ‐coordinated carbon coatings (meso‐Na 3 V 2 (PO 4 ) 3 /C) were successfully synthesized as efficient cathode material for rechargeable sodium‐ion batteries by using ascorbic acid as both the reductant and carbon source, followed by calcination at 750 °C in an argon atmosphere. Their crystalline structure, morphology, surface area, chemical composition, carbon nature and amount were systematically explored. Following electrochemical measurements, the resultant meso‐Na 3 V 2 (PO 4 ) 3 /C not only delivered good reversible capacity (98 mAh g −1 at 0.1 A g −1 ) and superior rate capability (63 mAh g −1 at 1 A g −1 ) but also exhibited comparable cycling performance (capacity retention: ≈74 % at 450 cycles at 0.4 A g −1 ). Moreover, the symmetrical sodium‐ion full cell with excellent reversibility and cycling stability was also achieved (capacity retention: 92.2 % at 0.1 A g −1 with 99.5 % coulombic efficiency after 100 cycles). These attributes are ascribed to the distinctive mesostructure for facile sodium‐ion insertion/extraction and their continuous sp 2 ‐coordinated carbon coatings, which facilitate electronic conduction.