High Volumetric Energy Density Asymmetric Fibrous Supercapacitors with Coaxial Structure Based on Graphene/MnO2 Hybrid Fibers

Abstract

In order to improve the performance of the fibrous supercapacitors to be more suitable for practical application, we prepared graphene/MnO2 hybrid fibers by doping MnO2 nanorods into graphene fibers through a simple wet spinning method, in which MnO2 act as the pseudocapacitive materials. This hybrid fiber electrode shows a wide potential window of −0.2–1 V and a high volume specific capacitance of 473 F cm−3. Based on these hybrid fibers, we fabricated asymmetric fibrous supercapacitors with coaxial structure. In the coaxial device, the internal electrode is graphene/MnO2 hybrid fiber, while the external electrode is graphene coated by dip coating method. The volume specific capacitance and the volumetric energy density of the coaxial device reaches up to 24 F cm−3 and 8.44 mWh cm−3, respectively, 200 % higher than these of the twisting device. The coaxial structure had not only decreased the charge transfer resistance between the two electrodes, but also increased the volume utilization rate of the devices. Therefore, this type of high volumetric energy density asymmetric fibrous supercapacitors has a wide range of applications in portable and flexible electronics and intelligent fabrics.