Flexible and freestanding PANI: PSS/CNF nanopaper electrodes with enhanced electrochemical performance for supercapacitors

With the fast-expanding markets of portable and wearable electronics, the development of sustainable, cost-effective, and flexible electrodes for energy storage applications is critical. Herein, a flexible, freestanding, binder-free polyaniline: poly (sodium 4-styrene sulfonate)/cellulose nanopaper (PANI: PSS/CNP) electrode was prepared using an in situ polymerization with a facile vacuum filtration approach. The low-cost and environmentally friendly nanocellulose with a three-dimensional (3D) hierarchical porous structure was chosen as the substrate that not only reduced the production cost but also improved the electrolyte absorption, flexibility, and mechanical strength for PANI: PSS/CNP. The freestanding and binder-free structure simplifying the preparation process and increasing the mass loading of the active material in the electrode was beneficial to maximizing electrode utilization. Due to the effective combination of cellulose and PANI: PSS complex, PANI: PSS/CNP electrode exhibited high specific capacitance (2.56 F/cm2) with excellent cycling stability (81.5% capacitance retention, 8000 cycles), mechanical strength, conductance stability, and flexibility. A symmetric supercapacitor device was constructed with PANI: PSS/CNP electrodes, showing outstanding areal specific capacitance (460 mF/cm2) and high energy density (40.9 μWh/cm2). Our work offers a novel and economical approach for the future production of sustainable, low-cost, and energy-efficient flexible electrode materials.