Recent progress of fiber-shaped asymmetric supercapacitors

Asymmetric designed supercapacitors usually couple two different electrodes with a Faradaic or battery-type electrode as the energy source role and a non-faradaic (or electric double-layer) electrode as the power source in one configuration, and thus can operate in much wider potential windows than that of the symmetrical design, thus potentially leading to a substantial increase in the energy density. Here, we focused on the recent progresses and advances of fiber-shaped asymmetric supercapacitors (FASCs) with respect to their electrode materials, design and configuration. Firstly, capacitive and pseudocapacitive materials, such as carbon materials, conductive polymers and metal oxides/sulfides/nitrides, are comprehensively discussed with the scope of their working potential ranges, proper electrolytes and working principles. Then the progresses to date on the FASCs including the device design, electrode fabrication and electrochemical performance of the FASCs are summarized. Finally, a short conclusion is made, combining with the future perspectives in this rapid developing area.