Effect of unequal load of carbon xerogel in electrodes on the electrochemical performance of asymmetric supercapacitors
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This paper investigates the electrochemical performance of asymmetric supercapacitors in an environmentally friendly aqueous electrolyte (1.0 mol L−1 sodium sulfate solution). The asymmetric configuration is based on the use of a highly porous carbon xerogel as active material in both the positive and negative electrodes, but the carbon xerogel loading in each electrode has been substantially modified. This configuration leads to an increase in the operational voltage window up to values of 1.8 V and consequently to a higher specific capacitance (200 F g−1) and energy density (~25 Wh kg−1). Four different mass ratios were employed (1, 1.5, 2 and 3), and the electrochemical response of the cells was evaluated by means of cyclic voltammetry, galvanostatic charge–discharge and impedance spectroscopy. The results demonstrate that the optimal carbon mass ratio in the electrodes is about 2.0 because in these conditions the devices are able to operate with a maximum cell voltage of 1.8 V and with a high electrical efficiency.
KeywordsCarbon xerogel electrodes Asymmetric configuration Electrode loading High voltage Aqueous electrolyte
The authors of INCAR-CSIC would like to acknowledge the financial support provided by the Ministerio de Economía y Competitividad (Ref. MAT-2011-23733 and IPT-2012-0689-420000). The authors of CNR-ITAE acknowledge the financial support provided by Ministero dello Sviluppo Economico within the framework of ‘Accordo ti programma CNR-MSE’, project ‘Sistema electtrochimici per l′accumulo dell′energia’). The COST Organization (COST Action MP1004: Hybrid Energy Storage Devices and Systems for Mobile and Stationary Applications) is also greatefully acknowledged. E.G. Calvo also thanks Ficyt (Spain) for a predoctoral research grant.
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