Studies\non Tubular MnO₂‑Core/Carbon\nNanofiber-Shell Electrodes for Electrochemical Capacitors

Abstract

The goal of this study is to design\nhollow carbon nanofibers containing\nMnO₂ (PPMMn), in which the pores of the carbon nanofiber\nsurface are utilized for ion diffusion to facilitate rapid MnO₂ surface redox reactions. Electrochemical performance is optimized\nby controlling the growth of MnO₂ on the inner or outer\nsurfaces of carbon nanofibers by varying MnCl₂ contents.\nAccessible specific surface areas and the hollow structure of PPMMn\ncomposites provide more active sites and internal spaces to enable\nelectrolyte ion access. The energy storage capabilities of PPMMn in\nthe assembled symmetrical supercapacitors provide excellent capacitive\nbehavior with a maximum specific capacitance of 254 F g^–1, a maximum energy density of 32 Wh kg^–1, and long-term\ncycling stability (96% of the initial capacitance after 10,000 cycles).\nIn addition, the cyclic voltammetry curves are nearly overlapped for\nthe PPMMn electrode in a flat or bent state, and the PPMMn-based devices\nassembled in series successfully lit a commercial light-emitting diode.\nThe study shows that PPMMn electrodes have excellent flexibilities\nand mechanical strengths and broad prospects in the energy storage\nfield.