Manganese Oxide/Carbon Aerogel Composite: an Outstanding Supercapacitor Electrode Material

Abstract

Manganese oxide/carbon aerogel composite electrodes are prepared by a self‐limiting anodic‐electrochemical deposition of manganese oxide into a binder‐enriched carbon aerogel layer, drop‐cast on a graphite substrate, using 0.1 M Mn(CH3COO)2·4H2O as the electrolyte. Manganese oxide grows in the form of thin nanofibers along the backbone of the carbon aerogel, leaving adequate working space for the electrolyte and enabling a fuller extent of the utilization of the manganese oxide to make the composite an outstanding supercapacitor electrode material. The manganese oxide is determined to be Mn3O4 with the Raman spectroscopy and high‐resolution transmission electron microscopy. The rectangularity of the cyclic‐voltammogram loops of the composite electrode is excellent and remains that way for scan rates up to a very‐high value of 500 mV s−1, indicating extremely good redox reversibility and cycle efficiency. At a scan rate of 25 mV s−1, the specific capacitance, as measured in 0.5 M Na2SO4 for a potential window of 0.1–0.9 V vs. Ag/AgCl, reaches a maximum value of 503 F g−1 and experiences only a negligible decay of less than 1% at the 6000th cycle, implying an extraordinary cycling stability. The cycling efficiency is as high as 98% at a current density of 8 A g−1 cm−2, showing an almost‐ideal capacitive behavior. The power density reaches 48.5 kW kg−1 and the energy density 21.6 W h kg−1 at a scan rate of 500 mV s−1, well above the specifications of current state‐of‐the‐art supercapacitors.

Fast Supercapacitors Based on Graphene‐Bridged V2O3/VOx Core–Shell Nanostructure Electrodes with a Power Density of 1 MW kg−1

“…It is very exciting to notice from Figure 4 b that the fabricated supercapacitors based on graphene-bridged V 2 O 3 /VO x core-shell nanocomposite structure can work at a rate as high as 50 V s −1 . This rate is 1-2 orders higher than typically reported 0.1-1 V s -1 rates of oxide pseudocapacitive ECs, [ 23,28,31 ] and is higher even than conventional active carbon-based EDLCs. The rate of our ECs is approaching ultrahigh-power micrometer-sized EDLCs based on onion-like carbon [ 42 ] or perpendicularly-oriented graphene, [ 6 ] but with much higher capacitance and energy density.…”

“…We report synthesis of such composite nanostructure using a facile solvothermal method followed by hydrogen thermal processing. The fabricated coin cell-type supercapacitor exhibited a C-D rate as high as 50 V s -1 , which is 1-2 orders higher than typically reported 0.1-1 V s -1 rates of oxide pseudocapacitive ECs, [ 23,28,31 ] and is also higher than conventional active carbon-based EDLCs. Increasing the energy density using the pseudocapacitance effect and at the same time obtaining extremely high C-D rate will enable such ECs to compete with batteries and conventional electrolytic capacitors in a number of applications.…”

High-performance flexible solid-state supercapacitors based on MnO2-decorated nanocarbon electrodes

“…Supercapacitors can be classied into two types, electrical double-layer capacitors and pseudocapacitors, in terms of charge storage mechanisms. 26 Carbon materials 16,27 are promising electrode materials for electrical double-layer capacitors, which have high power density and long cycle life but suffer from relatively low capacitance. Transition metal oxides have been studied as pseudocapacitor electrodes because of their much higher capacitances as compared to carbon materials.…”

“…Up to now, a number of exible manganese oxide/carbon hybrid structures have been investigated for supercapacitors by depositing manganese oxides onto various carbon materials. 26,[28][29][30][31] In those studies, however, the electrochemical performance of manganese oxide/carbon hybrid electrodes was not studied for nonliquid electrolytes, which are more suitable for exible and solid-state devices. Recently, Yuan et al have fabricated exible solid-state supercapacitors based on MnO 2 /carbon hybrid electrodes and phosphoric acid-polyvinyl alcohol (H 3 PO 4 -PVA) gel electrolyte, which provide an energy density of 4.8 W h À1 kg À1 .…”

“…For electrodeposition of functional materials, mesopores can reduce pore blocking during the deposition process. 20,26 The CNT/CNO lms with large SSA and high conductivity were used as the backbone for the electrodeposition of MnO 2 . The electrodeposition of MnO 2 was conducted in a solution containing 0.02 M MnSO 4 and 0.2 M Na 2 SO 4 .…”