An all-solid-state asymmetric device based on a polyaniline hydrogel for a high energy flexible supercapacitor

Abstract

The demand for low cost, flexible energy storage devices with enhanced energy/power density has increased with the rapid development of portable, flexible electronics. Herein, we report on an all-solid-state flexible, high energy density asymmetric supercapacitor (SC) based on a polyaniline (PANI) hydrogel made using a two-component mixing strategy. PANI hydrogel consists of polymeric networks with high levels of hydration and three-dimensional (3D) microstructures, which lead to faster electron and mass transport and offer a large accessible surface area. The 3D design is mechanically robust and flexible with large internal surfaces designed to pull water via capillary action. The design features ensure a strong interaction between the electrode and electrolyte solution for effective charge storage reactions, while at the same time giving the electrode sufficient mechanical flexibility to work under a bent condition. The PANI hydrogel electrode exhibits an excellent electrochemical performance with a specific capacitance of 862 F g⁻¹ at 1 A g⁻¹. Utilizing this nanocomposite as the positive electrode in a PANI//AC asymmetric configuration results in devices with a remarkable performance including good capacitance (261 F g⁻¹ at 1 A g⁻¹), great rate capability (64% capacitance retention), excellent cycle life (18% loss after 5000 cycles), a maximum energy density of 92.7 W h kg⁻¹, and a high power density of 16 kW kg⁻¹. Furthermore, the areal capacitance, areal energy density, volumetric capacitance, and volumetric energy density of the fabricated supercapacitor are 522 mF cm⁻², 0.185 mW h cm⁻², 17.4 F cm⁻³, and 6.16 mW h cm⁻³, respectively. Even under continuous bending and unbending, the device still provides a stable electrochemical performance without noticeable changes. We also demonstrate the promise of these SCs for various applications as we light up a green LED. This excellent performance holds great promise for next-generation flexible electronics.