Facile Synthesis of Na-Doped MnO₂ Nanosheets on Carbon Nanotube Fibers for Ultrahigh-Energy-Density All-Solid-State Wearable Asymmetric Supercapacitors

Flexible fiber-shaped supercapacitors hold promising potential in the area of portable and wearable electronics. Unfortunately, their general application is hindered by the restricted energy densities due to low operating voltage and small specific surface area. Herein, an all-solid-state fiber-shaped asymmetric supercapacitor (FASC) possessing ultrahigh energy density is reported, in which the positive electrode was designed as Na-doped MnO₂ nanosheets on carbon nanotube fibers (CNTFs) and the negative electrode as MoS₂ nanosheet-coated CNTFs. Owing to the excellent properties of the designed electrodes, our FASCs exhibit a large operating potential window (0-2.2 V), a remarkable specific capacitance (265.4 mF/cm²), as well as an ultrahigh energy density (178.4 μWh/cm²). Moreover, the devices are of outstanding mechanical flexibility.