Reversible Intercalation of Al-Ions in Poly(3,4-Ethylenedioxythiophene): Poly(4-Styrenesulfonate) Electrode for Aqueous Electrochemical Capacitors with High Energy Density

Due to the high capacity of the three-electron redox mechanism, Al-ions-based energy-storage devices have the potential to provide a viable solution to meet the growing demand for powering electronic products. However, discovering suitable electrode materials for reversible insertion of Al ions remains a difficult task. Herein, it is reported that a classical conductive polymeric material poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) can perform the reversible Al-ions intercalation for aqueous electrochemical capacitors. The as-prepared PEDOT:PSS film on a carbon cloth composite electrode exhibits a large magnitude of faradaic currents and sharp redox peaks in cyclic voltammetry (CV) curves in aluminum sulfate electrolyte, and delivers a high capacitance of 269 F g⁻¹ (78 mAh g⁻¹). Diffusion-controlled Al-ions intercalation/deintercalation as the charge-storage mechanism is demonstrated here, which is not observed in other ions-based electrolytes (H⁺, Mg²⁺, Li⁺, Na⁺). An asymmetric electrochemical capacitor based on Al ions, composed of such an electrode and activated carbon electrode is assembled and displays a high energy density of 41.6 Wh kg⁻¹ at a power density of 0.24 kW kg⁻¹, demonstrating a promising aqueous electrochemical capacitor with an advanced energy density via polyvalent ions intercalation.