Ionothermal Synthesis of Graphene-Based Hierarchically Porous Carbon for High-Energy Supercapacitors with Ionic Liquid Electrolyte

• Published in: Electrochimica acta Vol. 241; pp. 124 - 131
• Main Authors: Hao, Xiao-Feng, Yan, Yang, Gao, Li-Guo, Mu, Wen-Sheng, Hao, Ce
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.07.2017
• Subjects: ionic liquids; ionothermal synthesis; Nanoporous carbon; supercapacitors; ionothermal synthesis; ionic liquids; Nanoporous carbon; supercapacitors
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2017.04.128

Electrochemical double layer capacitors (EDLCs), storing charges by electrostatic attraction of electrolyte ions to the surface of charged electrodes, require an improved energy density to broaden their applications. Here a high-energy-density EDLC is reported by employing ionic liquids not only as the solvent for material synthesis but also as electrolyte. Graphene-based hierarchically porous carbon (GPC) are synthesized via ionothermal method, and exhibits high specific capacitance of 313Fg−1 and 212Fg−1 at a current density of 0.5Ag−1 in aqueous and ionic liquid electrolytes, respectively. The obtained GPC electrode retains about 94.2% of the initial capacitance after 10000 charge/discharge cycles at a current density of 2Ag−1 in aqueous electrolyte, strongly reflecting an excellent long-term cycling stability and rate capability of the electrode. A promoted energy density of 90.4W h kg−1 can be obtained with neat ionic liquid electrolyte, which is about 8 times higher than that with aqueous electrolyte. The ionothermal process guarantees the acquisition of the hierarchical porous structure and high surface area, while the ionic liquid electrolyte assures a broader operating voltage, which both helps to increase the energy density of EDLCs.