PerspectiveApplied Physics

Valuing Reversible Energy Storage

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Science  16 Mar 2012:
Vol. 335, Issue 6074, pp. 1312-1313
DOI: 10.1126/science.1219134

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The development of new materials that provide the capability of high-performance energy storage combined with flexibility of fabrication opens up the possibility of a wide range of technological applications. On page 1326 of this issue, El-Kady et al. (1) describe thin and highly flexible electrochemical capacitors (ECs) that were created by means of a very simple and innovative process. Unlike the usual approaches of making thin graphene electrodes that start with a particulate and use roll-coating, screen printing, or ink-jet printing (2), their process involves focusing a low-power laser onto a thin graphene oxide deposit to convert it into graphene. The incorporation of graphene in electrodes created with mechanical processes tends to be in agglomerates that provide little performance advantage over traditional particulate-activated carbon electrodes. El-Kady et al.'s approach also contrasts with plasma-assisted chemical vapor deposition processes that have been used to grow vertically oriented graphene nanosheet electrodes (3). Although graphene structures grown by such methods are well-formed and offer performance advantages over traditional activated carbon materials, they require complicated vacuum process equipment, plus the graphene growth rate is very slow (4). The somewhat simple EC electrode fabrication process reported by El-Kady et al. therefore appears to circumvent many of the difficulties encountered with traditional processes.