V2O5/PEDOT composite cathode for aqueous zinc-ion batteries: electrochemical performance and quantum chemical insights into structure and electronic properties

Abstract

Aqueous zinc-ion batteries (AZIBs) have emerged as a safe and sustainable alternative to lithium-ion systems. Vanadium oxides are considered among the most promising cathode materials due to their high theoretical capacity and low cost. However, the low conductivity and structural degradation of pristine V₂O₅ hinder its practical application. In this work, a V₂O₅/PEDOT composite was synthesized via a simple solution polymerization method and investigated using ZnSO₄ and Zn(CF₃SO₃)₂ electrolytes. The material exhibited high reversible capacities up to 451 mAh·g^− 1 at 0.5 A·g^− 1 in ZnSO₄ and demonstrated comparable performance in both electrolytes at moderate current densities (≤ 2 A·g^− 1). At higher currents, Zn(CF₃SO₃)₂ outperformed ZnSO₄, giving 284 mAh·g^− 1 at 10 A·g^− 1 versus only 76 mAh·g^− 1. ZnSO₄ electrolyte remains attractive for cost-sensitive applications, while Zn(CF₃SO₃)₂ offers significant advantages for high-power zinc-ion batteries. Quantum chemical calculations show that in V₂O₅/PEDOT composites, the degree of polymerization determines the PEDOT-induced modification of the electronic structure. PEDOT preserves the layered V₂O₅ framework but introduces occupied band-gap states, thereby enhancing the composite’s electronic conductivity.