Spray-On Reduced Graphene Oxide-Poly(vinyl alcohol) Supercapacitors for Flexible Energy and Power

Flexible and mechanically robust energy storage devices, such as capacitors, are future enablers of the next generation of structural energy and power, flexible electronics, and biometrics. These concepts require that the capacitor be seamlessly integrated into the device in a scalable process, while still maintaining mechanical and electrochemical properties. The challenge is that ease-of-processing, mechanical, and electrochemical properties are not mutually exclusive. Spraying allows for fast manufacture, but producing an ink amenable to spraying is challenging because of aggregation of the electroactive materials in the dispersion, resulting in poor performance. Here, sprayable, flexible supercapacitor electrodes are demonstrated containing reduced graphene oxide (rGO), poly(vinyl alcohol) (PVA), and carbon black achieved via high-throughput air-brushing process from aqueous media. The spray processing, mechanical properties, and electrochemical performance of various compositions of rGO, PVA, and carbon black are explored. rGO sheets provide capacitive energy storage, PVA facilitates air-brushing, and carbon black bridges rGO sheets to form electronic pathways. Due to the good combination of mechanical and electrochemical properties, a flexible supercapacitor shows steady capacitance retention after several bending cycles. This spray-on three-component composite electrode balances electrochemical and mechanical properties, which is otherwise difficult to realize for compact brick and mortar structures, especially from airbrushing.