Corresponding Author

Song-lin ZUO(zslnl@njfu.com.cn)


In order to improve the electrochemical capacitive properties and to apply coconut shell activated carbon (AC) serving as electrode materials in ionic liquid (IL)-based supercapacitor (SC), the coconut shell AC material was re-activated using a steam as an activating agent in this work, forming a secondary AC (W-AC). The results showed that the specific capacitance of the W-AC electrode was much larger than that of the raw activated carbon electrode (R-AC) in 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM]BF4). The electrochemical techniques including cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) measurement, and electrochemical impedance spectroscopy (EIS) were used to systematically study the capacitive properties of W-AC electrode in a series of ILs composed of different cations and anions. The electrochemical performances of the W-AC electrode using different ILs as electrolytes varied because of the different ion diameters, liquid viscosities and ionic conductivities for various ILs. Among them, the IL electrolytes composed of EMIM+, BMIM+ and BF4-, TFSI- were found to be most suitable for W-AC electrode. The specific capacitance of W-AC electrode reached 153 F•g-1 in [EMIM]BF4 IL electrolyte, and the as–assembled SCs could achieve a high energy density of 57 Wh•kg-1 with a potential window of 3.5 V in [BMIM]BF4. These results may provide valuable information for selecting appropriate ionic liquids and designing high-performance supercapacitors to meet different needs.

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