Two-Dimensional Mn3O4 Nanowalls Grown on Carbon Fibers as Electrodes for Flexible Supercapacitors.

Abstract

Emerging flexible and wearable electronic devices necessitates the development of fiber-type energy storage devices to power them. Supercapacitors received great attention for applications in flexible and wearable devices due to their scalability, safety, and miniature size. Herein, we report the fabrication of a flexible supercapacitor using manganese(II,III) oxide (Mn3O4) nanowalls (NWs) grown by electrochemical deposition on carbon fiber (CF) as electrode-active material. Here, CF serves as both a substrate for the growth of Mn3O4 NWs and a current collector for making a lightweight supercapacitor. Two-dimensional Mn3O4 NWs were uniformly grown on CF with high surface coverage. A three-dimensional nanostructured electrode is obtained using these individual two-dimensional Mn3O4 NWs. The Mn3O4 NWs grown on CF are characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and Raman spectroscopy. A symmetric sandwich-type supercapacitor is fabricated using two-dimensional Mn3O4 NW electrodes in an aqueous 1 M Na2SO4 electrolyte. The Mn3O4 NW supercapacitor electrode exhibits a specific capacitance of 300.7 F g–1 at a scan rate of 5 mV s–1. The assembled symmetric sandwich-type supercapacitor displayed high flexibility even at a bending angle of 180° without altering its performance. The Mn3O4 NW supercapacitor also displayed a long cycle life of 7500 cycles with 100% capacitance retention.