Citric Acid‐Assisted Sol–Gel Synthesis of K ₃ V ₃ (PO ₄ ) ₄ : Regulating Its Pore Structure and Pseudocapacitive Sodium‐Ion Storage

ABSTRACT Sodium‐ion batteries (SIBs) are promising for large‐scale energy storage, but the large ionic radius of Na + restricts their transport kinetics. Polyanionic K 3 V 3 (PO 4 ) 4 (KVP) is an attractive cathode material owing to its stable crystal structure and excellent cycling performance, yet it suffers from metal ion segregation, particle agglomeration, and poor pore structure regulation during synthesis. Herein, a sol–gel method was employed to optimize KVP preparation. Adjusting the stoichiometric ratio of citric acid suppressed ion segregation, while optimizing the sintering temperature balanced crystallinity and porosity. Prepared with 2 mmol citric acid and sintered at 800°C, the optimized KVP2 exhibits excellent crystallinity, a uniform porous structure, and homogeneously distributed K, V, and P elements. Electrochemical tests reveal a pseudocapacitance‐dominated charge storage mechanism (81% pseudocapacitive contribution at 1 mV s −1 ). KVP2 delivers an initial discharge capacity of 64.7 mAh g −1 at 10 mA g −1 and retains 82.3% capacity after 500 cycles at 100 mA g −1 . This work effectively enhances the kinetics and structural stability of KVP via citric acid regulation and sintering optimization, providing a novel strategy for designing high‐performance polyanionic cathodes and promoting SIB industrialization.