Development of a 2,3-dichloro-1,4-naphthoquinone/polyvinyl alcohol composite material and its application in all-solid-state flexible supercapacitors

Reducing the loss of active components in electrode materials is an important goal of electrode design and material optimization for electrochemical energy storage devices. All-solid-state devices have rapidly developed in recent years, maintaining high energy density while offering a certain level of safety. Meanwhile, as a new kind of alternatives in active components, organic active small molecules have a significant advantage, such as a wide range, less difficult preparation by solvent method and low cost. In this study, a flexible frame with rich hydroxyl groups (polyvinyl alcohol, PVA) bondage electrochemically active small molecule (2,3-dichloro-1,4- naphthoquinone, DNQ) acting by hydrogen bonding and nano-conductive sheets (reduced graphene oxide, rGO) as electron transfer agent in the hydrogel electrode (DNQ/rGO/PVA-2) has been successfully built. The electrode demonstrated good flexibility and an area sensitivity of 618.2 mF/cm 2 at the current density of 1 mA/cm 2 . After 10,000 charge/discharge cycles, it still maintained 91.1 % stability. The SEM images and XPS analysis after cycling test indicated that the designed structure is stable and effective. An all-solid-state flexible symmetric supercapacitor was assembled using the layer-stacked assembly method. It has an energy density of 49.5 μWh/cm 2 and does not significant capacitance loss when bent at different angles. The DNQ/rGO/PVA-2 hydrogel synthesized exhibits excellent electrochemical and mechanical properties, making it an ideal candidate for flexible supercapacitors.