Performance of Manganese Oxide/CNTs Composites as Electrode Materials for Electrochemical Capacitors

Abstract

Nanocrystalline metal oxides can be prepared with large surface area, electrochemical stability, and pseudocapacitive behavior, being able to be used as supercapacitor electrodes. Among the various metal oxides studied, amorphous and hydrated manganese oxide (a-MnO 2 •nH 2 O) is the most promising for supercapacitor electrodes due to the low cost of the raw material. In the present work, amorphous manganese dioxide (a-MnO 2 •nH 2 O) is prepared by chemical co-precipitation of Mn͑VII͒ and Mn͑II͒ in water medium, giving small particles of relatively high surface area. Carbon nanotubes ͑CNTs͒ are proposed as an alternative additive of carbon black for improving the electrical conductivity of the manganese oxide electrodes used to build capacitors. The results demonstrate that CNTs are effective for increasing the capacitance and improving the electrochemical properties of the a-MnO 2 •nH 2 O electrodes which show a better capacitive behavior than with carbon black. This enhancement is due to the high entanglement of CNTs which form a network of open mesopores, allowing the bulk of MnO 2 to be easily reached by the ions. The performance optimization requires a careful control of the electrolyte pH in order to avoid the irreversible reactions Mn͑IV͒ to Mn͑II͒ at the negative electrode and Mn͑IV͒ to Mn͑VII͒ at the positive one.

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.…”

“…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. 33,39,42,48,49 However, there are a number of problems with this approach. Most important is that any addition of nano-conductor reduces the fraction of capacitive material present.…”

An Interconnected Hierarchical Porous Carbon Materials Prepared by Polymer Precursor and Its Application as Electrode in Supercapacitors

“…Moreover, the carbon materials have good power density, good stability and low resistance for supercapacitors. Carbon materials involved activated carbon [14,15], carbon fiber [16,17], carbon nanotubes [18], and porous carbon [19,20], et al…”

“…Moreover, the carbon materials have good power density, good stability and low resistance for supercapacitors. Carbon materials involved activated carbon [14,15], carbon fiber [16,17], carbon nanotubes [18], and porous carbon [19,20], et alIn this paper, an interconnected hierarchical porous carbon (IHPC) was prepared by the polyHIPE and carbonation method based on phenolic-formaldehyde resin for supercapacitors. Structural and morphological characterizations of IHPC were carried out using field emission scanning electron microscopy (SEM), Capacitive behavior of IHPC was investigated by cyclic voltammetry and galvanostatic charge-discharge in 2 M KOH aqueous solution.…”

Composite Electrodes Made from Carbon Cloth as Supercapacitor Material and Manganese and Cobalt Oxide as Battery One

“…If the scaffold is made from a carbonaceous material or any other active electrode material, it can provide a capacitance in addition to the capacitance of the deposited oxide. [12][13][14][15][16][17][18][19][20][21][22][23][24][25] The preparation of MnO 2 · xH 2 O by a chemical route, usually from KMnO 4 , involves reduction "in situ" of Mn 7+ to Mn 4+ which can be favored by the presence of carbon. The preparation by an electrochemical route has been tried from several Mn precursors, e.g.…”