Improved capacity of redox-active functional carbon cathodes by dimension reduction for hybrid supercapacitorsElectronic supplementary information (ESI) available. See DOI: 10.1039/c7ta10881h

• Main Authors: Liu, Tianyuan, Lee, Byeongyong, Lee, Michael J, Park, Jinho, Chen, Zhongming, Noda, Suguru, Lee, Seung Woo
• Format: Article
• Language: English
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/c7ta10881h

Hybrid supercapacitors, which combine the advantages of supercapacitors and rechargeable batteries, have the potential to meet the demands of both high-energy and -power in electrochemical energy storage systems. However, the energy density of the hybrid supercapacitors has been limited because of the low capacity of the activated carbon cathode. Here we introduce a high-capacity carbon cathode containing plenty of oxygen functional groups that are redox-active towards both Li- and Na-ions. This functional carbon has an ultra-thin two-dimensional structure that has significant advantages in utilizing the redox reactions. The functional carbon cathode can exhibit very high capacities of ∼250 mA h g −1 in Li-cells and ∼210 mA h g −1 in Na-cells. A hybrid supercapacitor consisting of the two-dimensional functional carbon cathode with a commercial level loading density of ∼9.3 mg cm −2 and a Si-based anode delivers a high-energy density of ∼182 W h kg −1 at a high-power density of 1 kW kg −1 . Two-dimensional functional carbon electrodes prepared by hydrothermal carbonization of glucose with a graphene oxide template can deliver high capacities of 250 mA h g −1 in Li-cells and 210 mA h g −1 in Na-cells.