High-Performance Asymmetric Supercapacitor Based on Graphene Hydrogel and Nanostructured MnO₂

Abstract

We have successfully fabricated an asymmetric supercapacitor with high energy and power densities using graphene hydrogel (GH) with 3D interconnected pores as the negative electrode and vertically aligned MnO(2) nanoplates on nickel foam (MnO(2)-NF) as the positive electrode in a neutral aqueous Na(2)SO(4) electrolyte. Because of the desirable porous structure, high specific capacitance and rate capability of GH and MnO(2)-NF, complementary potential window of the two electrodes, and the elimination of polymer binders and conducting additives, the asymmetric supercapacitor can be cycled reversibly in a wide potential window of 0-2.0 V and exhibits an energy density of 23.2 Wh kg(-1) with a power density of 1.0 kW kg(-1). Energy density of the asymmetric supercapacitor is significantly improved in comparison with those of symmetric supercapacitors based on GH (5.5 Wh kg(-1)) and MnO(2)-NF (6.7 Wh kg(-1)). Even at a high power density of 10.0 kW kg(-1), the asymmetric supercapacitor can deliver a high energy density of 14.9 Wh kg(-1). The asymmetric supercapacitor also presents stable cycling performance with 83.4% capacitance retention after 5000 cycles.

Microwave synthesis: Characterization and electrochemical properties of amorphous activated carbon-MnO2 nanocomposite electrodes

“…As seen from the CV curves (Fig. 4 a), the both electrodes exhibit nearly perfect symmetric rectangular shape which is indicative of ideal capacitors [1], however, there is a distinct difference between the current response in the CV spectra of other synthesis techniques that are available in the literature such as electrodeposition [34], hydrothermal autoclave [35], and reflux [36] for production of diverse Mn carbon based composites; the results obtained using the microwave approach are quite comparable and encouraging taking into account the reduced time for the synthesis of these materials by microwave. Fig.…”

Microwave assisted synthesis of MnO2 on nickel foam-graphene for electrochemical capacitor

“…For example, Yong-Qing Zhao et al recently reported a composite of MnO 2 /graphene/nickel foam using a facile electrochemical deposition strategy [25]. Several studies have attempted to synthesize various graphene/MnO 2 nanocomposite using techniques such as chemical [26 27], microwave irradiation [28], electrodeposition [29][30][31], redox deposition [32] and polymer-assisted chemical reduction [33].…”

α-Fe2O3-Based Core-Shell-Nanorod–Structured Positiveand Negative Electrodes for a High-Performance α-Fe2O3/C//α-Fe2O3/MnOxAsymmetric Supercapacitor

“…8 The energy density of supercapacitors can be enhanced by increasing their capacitance as well as their operating-potential window, which can be achieved more easily with asymmetric supercapacitors (ASCs) than with the symmetric supercapacitors (SSCs) since, with suitable combination of positive and negative electrode materials, the operational potential window as high as 2 V has been achieved even with aqueous electrolytes. 6,[9][10][11][12][13][14] In recent years, efforts have been expended to explore several ASCs with different electrode materials based on redox-active transition-metal oxides, like RuO 2 , 15 SnO 2 , 23 etc., which are not commercially viable owing to their high cost and environmental incompatibility. Accordingly, there is need to explore certain alternative combinations of positive and negative electrode materials to design a high-performance, cost-effective and environmentally benign ASC.…”

“…4,[6][7][8][9][10][11]13,14,19,23,24 Besides MnO 2 suffers from poor electri- * Electrochemical Society Fellow. z E-mail: deb.sarkar1985@gmail.com; akshukla2006@gmail.com; sarma@iisc.ac.in cal conductivity (10 −5 -10 −6 S/cm), which affects the rate capability of the supercapacitors, but this limitation could be circumvented through nanostructured core-shell electrode design.…”