Use of Silk Fibroin Material Composites for Green, Flexible Supercapacitors

Within the context of seeking eco-friendly and readily available materials for energy storage, there is a pressing demand for energy storage solutions that employ environmentally sustainable, high-performance, and adaptable constituents. Specifically, such materials are essential for use in wearable technology, smart sensors, and implantable medical devices, whereas, more broadly, their use plays a pivotal role in shaping their efficiency and ecological footprint. Here, we demonstrate an entirely biopolymer-based supercapacitor with a remarkable performance, achieving a capacitance greater than 0.2 F cm^-2 at a charge-discharge current of 10 mA cm^-2 with 94% capacitance retention after 20,000 cycles. The supercapacitor is composed of three distinct silk fibroin (SF) composite materials, namely, photo-cross-linkable SF (Sil-MA) hydrogel, SF-polydopamine (SF-PDA), and SF bioplastic, to create a gel electrolyte, electrode binder, and encapsulation, respectively. Together, these elements form a mechanically and electrochemically robust skeleton for biofriendly energy storage devices. Moreover, these biomaterial-based supercapacitor devices show stretchability, flexibility, and compressibility while maintaining their electrochemical performance. The biomaterials and fabrication techniques presented can serve as a foundation for investigating various aqueous electrochemical energy storage systems, especially for emerging applications in wearable electronics and environmentally friendly material systems.