High Surface Area Graphene-Based Materials for Electrochemical Energy Storage

We present an overview of work in the Ruoff group on graphene-based and graphene-derived materials in energy storage systems (EES). With high electrical conductivity and surface area, graphene-based materials are being intensively studied as electrode material or support material in ultracapacitors and batteries. Graphene-based materials with different physicochemical properties have been studied including chemically reduced graphene oxide,[1] thermally reduced graphene oxide,[2] microwave exfoliated graphite oxide (MEGO),[3] and activated microwave-expanded graphite oxide (‘a-MEGO’).[4] Our recent work based on a highly porous graphene-derived carbon material showed that extremely high specific surface area can be obtained by an activation process, which allows for extensive formation of an electrochemical double layer (EDL) and a high gravimetric capacitance in a symmetric ultracapacitor. In addition, activated graphene-based materials showed significantly improved performance in terms of energy density approaching that of conventional lead-acid batteries.[4, 5] Other studies of highly porous graphene-derived materials in EES including Li-ion capacitors and Li-S batteries will also be presented, along with current efforts in our group on graphene-based and graphene–derived materials for electrical energy storage. REFERENCES 1. Stoller, M.D., et al., Graphene-Based Ultracapacitors. Nano Letters, 2008. 8 (10): p. 3498-3502. 2. Zhu, Y.W., et al., Exfoliation of Graphite Oxide in Propylene Carbonate and Thermal Reduction of the Resulting Graphene Oxide Platelets. ACS Nano, 2010. 4 (2): p. 1227-1233. 3. Zhu, Y.W., et al., Microwave assisted exfoliation and reduction of graphite oxide for ultracapacitors. Carbon, 2010. 48 (7): p. 2118-2122. 4. Zhu, Y.W., et al., Carbon-Based Supercapacitors Produced by Activation of Graphene. Science, 2011. 332 (6037): p. 1537-1541. 5. Kim, T., et al., Activated graphene-based carbons as supercapacitor electrodes with macro- and mesopores. ACS Nano, 2013. 7 (8): p. 6899-905.