Highly Uniform Anodically Deposited Film of MnO2 Nanoflakes on Carbon Fibers for Flexible and Wearable Fiber-Shaped Supercapacitors

A highly uniform porous film of MnO2 was deposited on carbon fiber by anodic electrodeposition for the fabrication of high-performance electrodes in wearable supercapacitors (SCs) application. The effects of potentiostatic and galvanostatic electrodeposition and the deposition time were investigated. The morphology, crystalline structure, and chemical composition of the obtained fiber-shaped samples were analyzed by field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The charge storage performance of the carbon fibers@MnO2 composite electrode coupled to a gel-like polymeric electrolyte was investigated by cyclic voltammetry and galvanostatic charge-discharge measurements. The specific capacitance of the optimized carbon fiber@MnO2 composite electrodes could reach up to 62 F g-1 corresponding to 23 mF cm-1 in PVA/NaCl gel-polymer electrolyte, i.e., the highest capacitance value ever reported for fiber-shaped SCs. Finally, the stability and the flexibility of the device were studied, and the results indicate exceptional capacitance retention and superior stability of the device subjected to bending even at high angles up to 150°.