Carbon-Modified NASICON Na₄FeV(PO₄)₃ Cathode with Enhanced Kinetics for High-Performance Sodium-Ion Batteries

Na superionic conductor (NASICON) structured materials are promising cathode materials due to their high sodium diffusivity and thermostability. However, the limited specific capacity and poor reaction kinetics are key issues. In this work, a uniform reactive site network is successfully applied in Na4FeV(PO4)3 by carbon modification. We demonstrate that the NASICON structure of Na4FeV(PO4)3 is capable of delivering a high capacity of 156 mA h g–1 in the voltage range of 2.0–4.4 V. Phase transition determined by ex situ X-ray diffraction (XRD) indicates that the reaction is highly reversible during Na+ insertion/extraction. Notably, a high-mass-loading electrode (6.2 mg cm–2) is also fabricated, which displays decent performance due to the rational design of carbon networks. This work is of great significance for developing high-volumetric energy density sodium-ion batteries (SIBs).