Issue 35, 2014

Identifying pseudocapacitance of Fe2O3 in an ionic liquid and its application in asymmetric supercapacitors

Abstract

Pseudocapacitance is commonly associated with surface or near-surface reversible redox reactions, as observed with transition metal oxides in alkaline aqueous electrolytes. Here, we demonstrate that pseudocapacitive behavior of Fe2O3 can occur in a 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4) ionic liquid (IL), and it is closely related to the chemical state variation between Fe3+ and Fe2+ on the surface of a Fe2O3 electrode during the charging/discharging process. By taking advantage of such pseudocapacitance, we prepared a promising electrode material, i.e., graphene nanosheet-supported Fe2O3 nanoparticles (denoted as Fe2O3@GNS), and then built high-performance asymmetric supercapacitors (ASs) using Fe2O3@GNS as the battery-type electrode material, commercial activated carbon (AC)/or activated polyaniline-derived carbon nanorods (denoted as APDC) as the capacitor-type electrode material, and EMIMBF4 IL as the electrolyte. The as-made ASs are able to work reversibly in a full operation voltage region of 0–4 V and exhibit very high energy density. Especially, the AS of Fe2O3@GNS//APDC achieves an extremely high energy density of 177 W h kg−1 and shows a superior combination of high energy and power density (the energy density still remains 62.4 W h kg−1 even at a high power density of 8 kW kg−1).

Graphical abstract: Identifying pseudocapacitance of Fe2O3 in an ionic liquid and its application in asymmetric supercapacitors

Supplementary files

Article information

Article type
Paper
Submitted
23 Apr 2014
Accepted
01 Jul 2014
First published
01 Jul 2014

J. Mater. Chem. A, 2014,2, 14550-14556

Author version available

Identifying pseudocapacitance of Fe2O3 in an ionic liquid and its application in asymmetric supercapacitors

S. Sun, J. Lang, R. Wang, L. Kong, X. Li and X. Yan, J. Mater. Chem. A, 2014, 2, 14550 DOI: 10.1039/C4TA02026J

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