An efficient in situ electrochemical method to boost the performance of sodium vanadium phosphate cathodes by conductive polymer coating

This study evaluates the impact of in situ electropolymerized poly(3,4-ethylenedioxythiophene) (PEDOT) coatings on Na 3 V 2 (PO 4 ) 3 (NVP) cathodes for sodium-ion batteries (SIB). Pristine bare and carbon-coated NVP samples served as both starting materials and references to highlight the effect of the electropolymerized coating. Successful PEDOT in situ electropolymerization was confirmed through SEM, Raman spectroscopy, and DSC, while X-ray diffraction demonstrated the preservation of the NVP crystalline structure. Electrochemical characterization revealed that PEDOT coating enhances electronic conductivity and Na + -ion transport kinetics. The carbon-coated NVP sample with in situ electropolymerized PEDOT coating delivered superior capacity (150 mAh·g −1 at C/10), excellent rate capability (60 mAh·g −1 at 10C), and capacity retention of 88% after 100 cycles at 1C (105 mAh·g −1 ). EIS revealed that PEDOT coating reduces charge-transfer resistance and stabilizes the electrode-electrolyte interface, thereby supporting improved long-term performance. These results confirm that in situ electropolymerized PEDOT provides an effective conductive and protective coating for NVP cathodes. Compared with conventional approaches such as chemical polymerization, integrating in situ carbon formation with a conformal in situ electrochemical PEDOT coating establishes a highly interconnected conductive network. This synergistic architecture significantly enhances sodium-ion storage performance by improving electrical conductivity, facilitating charge transfer, and promoting structural stability during cycling. • In situ electropolymerized PEDOT coating enhanced cathode for sodium-ion batteries. • PEDOT coating significantly boosted capacity beyond conventional carbon coatings. • Carbon and PEDOT form a synergistic conductive network for better energy storage. • The optimized material delivered high capacity and stable cycling.