Synergistic interaction between redox-active electrolyte and binder-free functionalized carbon for ultrahigh supercapacitor performance

Abstract

Development of supercapacitors with high-energy density and high-power density is a tremendous challenge. Although the use of conductive carbon materials is promising, other methods are needed to reach high cyclability, which cannot be achieved by fully utilizing the surface-oxygen redox reactions of carbon. Here we introduce an effective strategy that utilizes Cu 2+ reduction with carbon-oxygen surface groups of the binder-free electrode in a new redox-active electrolyte. We report a 10-fold increase in the voltammetric capacitance (4,700 F g-1) compared with conventional electrolyte. We measured galvanostatic capacitances of 1,335 F g-1 with a retention of 99.4% after 5,000 cycles at 60 A g-1 in a three-electrode cell and 1,010 F g-1 in a two-electrode cell. This improvement is attributed to the synergistic effects between surface-oxygen molecules and electrolyte ions as well as the low charge transfer resistance (0.04 Ω) of the binder-free porous electrode. Our strategy provides a versatile method for designing new energy storage devices and is promising for the development of high-performance supercapacitors for large-scale applications. © 2013 Macmillan Publishers Limited.