Fiber-shaped supercapacitors

Fiber-shaped supercapacitors (FSSCs) have attracted extensive attention owing to their potential application in flexible and wearable electronics with the merits of tiny volume, high flexibility and deformability compared to the traditional planar structured supercapacitors. Here, we summarize the recent important development and progress of FSSCs with respect to electrolyte materials, electrode materials, configuration and function. This chapter begins with brief introduction on the device structure. Then flexible gel electrolytes (e.g. aqueous, organic, ionic liquids and redox-active gels) are summarized. Subsequently, the capacitive performance of traditional electrode materials (e.g. carbon materials, conductive polymers, metal oxides etc.) and emerging electrode materials (e.g. MXenes, metal-organic frameworks (MOFs), polyoxometalates (POMs), black phosphorusare (BP) etc.) are introduced. In the next section, electrode substrates (e.g. metal fiber, carbon fiber, cotton fiber etc.) and electrochemical performances of the configured fiber-shaped supercapacitors are summarized. Some practical applications, such as self-healing, stretchable and electrochromic FSSCs are also discussed. Finally, a short conclusion is made, combining with current challenges and potential solutions from device performance to large-scale production in this field.