Electrochemical performance of a coaxial fiber-shaped asymmetric supercapacitor based on nanostructured MnO^sub 2^/CNT-web paper and Fe^sub 2^O^sub 3^/carbon fiber electrodes

The fiber-shaped supercapacitor is a promising energy storage device in wearable and portable electronics because of its high flexibility, small size, and light weight. However, most of the reported fiber-shaped supercapacitors have exhibited low capacitance and energy density due to the limited surface area between the two fiber electrodes and operating voltage range. Herein, we successfully developed a coaxial fiber-shaped asymmetric supercapacitor (CFASC) made from MnO2/CNT-web paper as a cathode coupled with Fe2O3/carbon fiber as an anode with a high operating voltage of 2.2 V. The prepared CFASC device showed a high volumetric energy density of 0.43 mWh cm−3 at a power density of 0.02 W cm−3, which is comparable to those of previously reported fiber-shaped supercapacitors. Additionally, CFASC exhibited good rate capability, long cycle life, and high volumetric capacitance (0.67 F cm−3) with excellent flexibility. The promising performance of CFASC illustrated its potential for portable and wearable energy storage devices.