Ultrasonic synthesis of conducting polymers intercalated potassium vanadate nanofiber composites as cathode for aqueous zinc-ion batteries.

Aqueous zinc-ion batteries (AZIBs) have gained attention as next-generation energy storage systems due to their safety, cost-effectiveness, and eco-friendliness. However, their commercialization is hindered by the structural instability and low electrochemical performance of cathode materials. Herein, we present poly(3,4-ethylenedioxythiophene) (PEDOT)-intercalated potassium vanadate nanofibers (E-PVNF) with oxygen vacancies, synthesized via a sonochemical method. Oxygen vacancies play a crucial role in facilitating Zn diffusion and charge transport by providing additional ion migration channels and enhancing electronic conductivity. The E-PVNF exhibited a high specific capacity of 182.50mAh g even at a high current density of 15 A g, significantly outperforming conventional potassium vanadate-based cathodes. To investigate the electrochemical behavior, overpotential and Zn diffusion coefficient (D) were systematically evaluated as a function of synthesis time. The results revealed a substantial reduction in overpotential and a notable increase in D, reaching 3.86 × 10 cm s, nearly double that of pristine potassium vanadate. This improvement is attributed to the synergistic effects of PEDOT intercalation and oxygen vacancy engineering, which optimize Zn diffusion pathways and enhance charge transfer. Additionally, while oxygen vacancies facilitate ion and electron transport, they do not directly increase theoretical capacity. This study provides a scalable and effective electrode design strategy for high-performance AZIBs, offering insights into the role of conducting polymer intercalation and oxygen vacancy engineering in improving electrochemical stability and rate capability.