<p>Dual-ion batteries have got significant attention in recent years due to their efficient ion insertion mechanism, abundant electrode material options, and chemical stability, showcasing advantages such as high operating voltage, low cost, and enhanced safety. Organic electrode materials are often used in dual-ion batteries due to their designability and high theoretical capacity. However, the compatibility between organic electrode materials and current collectors affects the cycling and capacity performance of dual-ion batteries. In this paper, a novel thin film structure of sulfuric acid-doped polyaniline composite copper oxide is electropolymerized on the surface of copper foil current collector. The synergistic effect of electropolymerization-driven oxidation and copper oxide templating facilitates the formation of doped polyaniline nanoparticles, transforming the polymer into long-range ordered crystalline structures with a particle size of 10&#xa0;nm. Because of the crystalline nanostructure of doped polyaniline and copper oxide, there is an interface change between the anode and active material during charge–discharge cycles, reducing the internal charge transfer resistance from 112 to 40 Ω. While the dual-ion battery shows a significant improvement at high rates, experiments show that the dual-ion battery still retains a capacity of 44 mAh g⁻¹ after 2000 cycles at 5 C, with a capacity retention rate of 69.7%, but the capacity of dual-ion battery without the modification current collectors is only 12 mAh g⁻¹ after 2000 cycles at 5 C. The paper discusses the mechanism of the smallest size composite polyaniline material and the influence mechanisms on the performance of dual-ion batteries.</p> Graphical Abstract <p></p>