Optimization design of MnO2-based fiber supercapacitors with diverse crystal structures

With the rapid development of electronic science and technology, the demand for portable and flexible energy supply strategies become urgent. Fiber supercapacitors attract extensive attention due to their lightweight, fast charge-discharge and excellent safety, which can be considered as potential energy storage devices to power electronic watches and the human motion monitoring system. MnO 2 shows high theoretical specific capacity, excellent physical/chemical stability and environmental friendliness, showing a broad application prospect as electrochemical active materials. This work proposes an optimal design strategy for MnO 2 -based fiber supercapacitors: β-MnO 2 and γ-MnO 2 are chosen as electrochemical active materials respectively, and the fiber electrode as well as fiber supercapacitors are fabricated via coaxial wet spinning. According to the results, γ-MnO 2 fiber supercapacitor presents the maximum C L of 0.86 μF/cm, E L of 9.65 10 −5  μWh/cm and P L of 0.33 μW/cm. After 10,000 charge/discharge cycles, the fiber supercapacitor can maintain the high level of consistency, demonstrating excellent long-term reliability. Furthermore, the electrochemical performance of the obtained fiber supercapacitors is almost unaffected in bending or knotting situations, indicating outstanding mechanical strength as well as flexibility. This work provides an effective basis for reliable design of fiber supercapacitors and promotes their application in flexible smart wearable field in the future.