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Issue 11, 2012
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Exploring the large voltage range of carbon/carbon supercapacitors in aqueous lithium sulfate electrolyte

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Abstract

This study investigates the large voltage range of symmetric carbon/carbon capacitors in environmentally friendly aqueous lithium sulfate electrolyte. A high over-potential related to the hydrogen sorption mechanism at the negative electrode contributes usefully to enhance the operating voltage up to 1.9 V with an excellent stability during 10 000 charge/discharge cycles. Such a voltage value is two times higher than the values generally demonstrated with symmetric carbon/carbon capacitors in conventional aqueous media, while avoiding the disadvantages of the corrosive properties of acidic and basic electrolytes. Temperature programmed desorption analysis of the electrodes after long-term cycling gives the evidence that the maximum voltage is essentially limited by an irreversible electro-oxidation process at the positive electrode. If the potential of the positive electrode goes beyond a given value during cell operation, a massive electro-oxidation of carbon leads to a further deleterious increase of the maximum potential of the electrode and an increase of electrode resistance resulting in a decrease of capacitance. Inconvenience can be sidestepped by performing a controlled chemical oxidation of the carbon surface using hydrogen peroxide. As a consequence, the maximum potential of the electrode remains stable during operation of the cell at 1.9 V, and the system can be charged/discharged during 10 000 cycles with very moderate loss of capacitance or increase of resistance.

Graphical abstract: Exploring the large voltage range of carbon/carbon supercapacitors in aqueous lithium sulfate electrolyte

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Article information


Submitted
20 May 2012
Accepted
31 Aug 2012
First published
31 Aug 2012

Energy Environ. Sci., 2012,5, 9611-9617
Article type
Paper

Exploring the large voltage range of carbon/carbon supercapacitors in aqueous lithium sulfate electrolyte

Q. Gao, L. Demarconnay, E. Raymundo-Piñero and F. Béguin, Energy Environ. Sci., 2012, 5, 9611
DOI: 10.1039/C2EE22284A

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