Enhancing the Supercapacitor Performance of Graphene/MnO₂ Nanostructured Electrodes by Conductive Wrapping

Abstract

MnO2 is considered one of the most promising pseudocapactive materials for high-performance supercapacitors given its high theoretical specific capacitance, low-cost, environmental benignity, and natural abundance. However, MnO2 electrodes often suffer from poor electronic and ionic conductivities, resulting in their limited performance in power density and cycling. Here we developed a "conductive wrapping" method to greatly improve the supercapacitor performance of graphene/MnO2-based nanostructured electrodes. By three-dimensional (3D) conductive wrapping of graphene/MnO2 nanostructures with carbon nanotubes or conducting polymer, specific capacitance of the electrodes (considering total mass of active materials) has substantially increased by ∼20% and ∼45%, respectively, with values as high as ∼380 F/g achieved. Moreover, these ternary composite electrodes have also exhibited excellent cycling performance with >95% capacitance retention over 3000 cycles. This 3D conductive wrapping approach represents an exciting direction for enhancing the device performance of metal oxide-based electrochemical supercapacitors and can be generalized for designing next-generation high-performance energy storage devices.

MnOx/carbon nanotube/reduced graphene oxide nanohybrids as high-performance supercapacitor electrodes

“…13 However, despite a few examples of MnO x reported recently, 14 most previous studies simply denoted the synthesized Mn oxides as MnO 2 with few or no structural investigations. [15][16][17] The integration of MnO x into supercapacitor electrodes with binders is also challenging because of the non-uniform particle size, poor electrical conductivity and structural instability of MnO x . In addition, MnO x was mainly synthesized by methods involving hazardous chemicals, strong acids and high-temperature thermal annealing, with the controllability, scalability and reliability of these methods remaining unclear.…”

Effect of Percolation on the Capacitance of Supercapacitor Electrodes Prepared from Composites of Manganese Dioxide Nanoplatelets and Carbon Nanotubes

“…30,39,[42][43][44][45][46] It is worth noting that such an approach is straightforward when using solution processing techniques. 6,47 Numerous researchers have shown that this strategy can result in increased capacitance by facilitating transport of charge from redox sites to the external circuit.…”

Significantly enhanced energy density of magnetite/polypyrrole nanocomposite capacitors at high rates by low magnetic fields

“…In addition, the utilization efficiency of electrode materials will be severely compromised at higher rates, and only relatively large pores can be entered by counter ions [39]. To solve the issue, great efforts have been dedicated to fabricating nanostructured electrode materials with larger specific surface area [40] or shorter diffusion path [41]. Unfortunately, there exist still some problems, like the increased undesirable reactions at the electrode/electrolyte interface due to the high specific surface area, and reduced electrical conductivities compared to those of their bulk counterparts due to the shortened electron mean free path arising predominantly from the surface scattering in the nanomaterials [42].…”