α-MnO2 Nanowires and Amino-Modified Reduced Graphene Oxide Hybrid Films for Constructing the Flexible High-Performance Symmetrical Supercapacitors

Abstract

Graphene or its derivates are used as an electrode material for the fabrication of supercapacitors (SCs). However, graphene or its composites readily agglomerate or stack in water, which seriously imparts SC energy efficiency. Presently, we used a new composite using [Formula: see text]-MnO2 nanowires and nitrogen-doped reduced graphene oxide ([Formula: see text]-MnO2/NRGO) for the fabrication of electrodes required in symmetric SCs. Hydrothermally synthesized [Formula: see text]-MnO2 nanowires have a smooth surface, good dispersion, and a high length-to-width ratio. The formation of stable and densely networked structures and the synergy between NRGO and [Formula: see text]-MnO2 nanowires enable the [Formula: see text]-MnO2/NRGO film electrode to show a large area-specific capacitance (386.8[Formula: see text]mF[Formula: see text]cm[Formula: see text]) at 1[Formula: see text]mA[Formula: see text][Formula: see text][Formula: see text]cm[Formula: see text] current density; the capacity retention is 62.4% when the current density increases from 1[Formula: see text]mA[Formula: see text][Formula: see text][Formula: see text]cm[Formula: see text] to 10[Formula: see text]mA[Formula: see text][Formula: see text][Formula: see text]cm[Formula: see text]. The flexible and symmetrical [Formula: see text]-MnO2/NRGO SC was assembled using [Formula: see text]-MnO2/NRGO film electrodes in 1 M Na2SO4 electrolyte with a cellulose paper separator, has good capacitance retention (94%), excellent Coulombic efficiency (99%) after 3000 cycles, and high energy density (28.22[Formula: see text][Formula: see text]Wh[Formula: see text][Formula: see text][Formula: see text]cm[Formula: see text]) at 0.8[Formula: see text]mW[Formula: see text][Formula: see text][Formula: see text]cm[Formula: see text] power density. The [Formula: see text]-MnO2 nanowires/NRGO hybrid film flexible and symmetrical SCs are characterized by high energy storage, good cycle life and Columbic efficiency, which offer promising applications in the portable and wearable electronics industry.