Oxides free materials for flexible and paper-based supercapacitors

Development in flexible and wearable smart electronics has a great demand for flexible, lightweight, and even stretchable energy storage devices. Flexible batteries and supercapacitors are two conventional powers sources for the continuous operation of flexible and wearable electronic devices. Among these, the flexible supercapacitors play a promising role in flexible and wearable devices owing to their higher power density, comparable volumetric energy density, fast charging/discharging, and exceptionally longer operation lifetimes than batteries. As electrode materials are a crucial component in determining the performance of the supercapacitors, a wide variety of electroactive materials like carbon nanostructures, metal-based compounds, and conducting polymers have been extensively studied and developed. This chapter elaborates on the recent development in oxide-free electrode materials like metal carbide, nitride, phosphides, and chalcogenides for flexible and paper-based supercapacitors. Besides, it discusses the major components like flexible substrates, electrolytes, and various device architectures of the flexible supercapacitors. Finally, summarizes the topic with the current challenges and future perspectives in developing high-performance flexible supercapacitors for the future flexible and wearable electronic appliances.