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 Zn²⁺ 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^-1 even at a high current density of 15 A g^-1, significantly outperforming conventional potassium vanadate-based cathodes. To investigate the electrochemical behavior, overpotential and Zn²⁺ diffusion coefficient (D_Zn²⁺) were systematically evaluated as a function of synthesis time. The results revealed a substantial reduction in overpotential and a notable increase in D_Zn²⁺, reaching 3.86 × 10^-10 cm² s^-1, nearly double that of pristine potassium vanadate. This improvement is attributed to the synergistic effects of PEDOT intercalation and oxygen vacancy engineering, which optimize Zn²⁺ 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.