A High-Capacity Aqueous Rechargeable Supercapacitors Based on Electrochemical Al3+ Intercalation

With a three-electron redox-mechanism-based high capacity, Al-ion-based electrochemical battery capacitor systems are expected to provide high capacity, low cost and high safety to meet the increasing energy demands. However, the reversible insertion of Al3+ into electrode materials remains a difficult project. Here, we demonstrate a new strategy to achieve reversible Al3+ insertion in a classical conductive polymeric material namely PEDOT:PSS, in aluminum sulfate aqueous electrolyte system. The freestanding composite film with a hierarchical porous structure is prepared through vacuum-assisted curing of a mixed dispersion containing PEDOT:PSS on carbon cloth substrate. The as-prepared PEDOT: PSS composite electrode exhibits extremely high capacitances of 265 F/g at the current density of 0.2 A/g, and enhanced electrochemical stability in the aqueous Al ions electrolyte. The PEDOT:PSS electrode sustains more diffusion of Al ions with more electric quantity in the Al3+ electrolyte, compared to in traditional acid electrolyte. It also exhibits a lower charge transfer resistance in the aluminum ion electrolyte, rather than in other cations electrolyte, which helps reduce the polarization at the electrode/electrolyte interface and improved the aluminum ion migration. Furthermore, the PEDOT: PSS electrode and an activated carbon anode are assembled as aqueous rechargeable Al ion electrochemical supercapacitor. The discharge capacity of this system exhibits to be 51 mAh/g at the current density of 100 mA/g and displays a high energy density of 43.2 Wh/Kg at the power density of 265 W/Kg, demonstrating a promising aqueous energy storage device with high performance and low cost.