Frame-filling C/C composite for high-performance EDLCs with high withstanding voltage

Based on the equation of E = 1/2CV(2), increasing voltage can significantly enhance the energy density of electric double-layer capacitors (EDLCs). However, with the voltage above 2.7 V, the lifespan of EDLCs drops rapidly due to the undesired parasitic processes. To operate at voltage above 2.7 V, a frame-filling C/C composite is prepared by constructing relatively perfect carbon network and reducing the oxygen-containing groups. The as-prepared sample F310-800 exhibits high specific surface area (2626 m(2) g(-1)), adequate e-conductivity (142 S m(-1)), high sp(2)-bonding carbon content (92.6%) and low oxygen content (4.6 wt%). Although totally free of any carbon black, it demonstrates excellent EDLC performances. It can successfully operate at voltage of 3 V in TEABF(4)/PC electrolyte and obtain high gravimetric capacitance (C-g) of 140 F g(-1) and volumetric capacitance (C-v) of 57.4 F cm(-3) at 50 mA g(-1) with rate capacity C-10/0.05 as high as 66%. Additionally, at voltage of 3.5 V in pure EMIMBF4 electrolyte, it achieves ultrahigh C-g of 156 F g(-1) and Cv of 64 F cm(-3) at 50 mA g(-1). Its energy density can reach up to 66.3 Wh kg(-1). Meantime, after 5000 cycles at 2.5 A g(-1), it holds 91.9% of its initial capacitance. (c) 2018 Elsevier Ltd. All rights reserved.