Effect of activated carbon xerogel pore size on the capacitance performance of ionic liquid electrolytes

Abstract

The use of ionic liquid (IL) electrolytes promises to improve the energy density of electrochemical capacitors (ECs) by allowing for operation at higher voltages. Several studies have also shown that the pore size distribution of materials used to produce electrodes is an important factor in determining EC performance. In this research the capacitative, energy and power performance of ILs 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF(4)), 1-ethyl-3-methylimidazolium dicyanamide (EMImN(CN)(2)), 1,2-dimethyl-3-propylimidazolium bis(trifluoromethylsulfonyl)imide (DMPImTFSI), and 1-butyl-3-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate (BMPyT(F5Et)PF3) were studied and compared with the commercially utilised organic electrolyte 1M tetraethylammonium tetrafluoroborate solution in anhydrous propylene carbonate (Et4NBF4-PC 1 M). To assess the effect of pore size on IL performance, controlled porosity carbons were produced from phenolic resins activated in CO2. The carbon samples were characterised by nitrogen adsorption-desorption at 77 K and the relevant electrochemical behaviour was characterised by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. The best capacitance performance was obtained for the activated carbon xerogel with average pore diameter 3.5 nm, whereas the optimum rate performance was obtained for the activated carbon xerogel with average pore diameter 6 nm. When combined in an EC with IL electrolyte EMImBF(4) a specific capacitance of 210 F g(-1) was obtained for activated carbon sample with average pore diameter 3.5 nm at an operating voltage of 3 V. The activated carbon sample with average pore diameter 6 nm allowed for maximum capacitance retention of approximately 70% at 64 mA cm(-2)

Ionic liquid based EDLCs: influence of carbon porosity on electrochemical performance

“…23,38,39 The polycondensation of an aqueous solution of resorcinol, R (Aldrich, 99%) with formaldehyde, F (Aldrich, 37wt.%, stabilised with 10-15wt.% methanol) was catalysed by the addition of sodium carbonate, C (Aldrich, Na 2 CO 3 , >99.5%). R/F molar ratio was kept at 0.5 and R/W was 0.10gcm -³. R/C ratios of 200, 40 250, 300 and 350 were used to control the pore characteristics of the resultant gels.…”

“…33 It has been proposed that the inclusion of ether bonds results in increased specific capacitances in EDLCs using mesoporous carbon electrodes by adding a degree of flexibility into the anion and alteration of the charge density. 34 Therefore to explore As a substantial number of reports have shown that the pore characteristics of electrodes strongly influence the performance of EDLCs, 22,28,[35][36][37][38] we also compare 30 the behaviour of these ILs when combined with electrodes of differing average pore size (d) in the small mesopore range (i.e. 2<d<10nm).…”

Enhanced electron transfer mediated detection of hydrogen peroxide using a silver nanoparticle–reduced graphene oxide–polyaniline fabricated electrochemical sensor

“…The development of nanoscience and nanotechnology has offered new avenues for the application of carbon-based nonmaterial such as graphene, 10 carbon nanotube, 11 porous carbon 12 etc. in electrochemical analysis.…”

Supercapacitors based on highly dispersed polypyrrole-reduced graphene oxide composite with a folded surface

“…The fast growth of portable electronic devices and electric vehicles stimulates the increasing demand for high-energy storage resources in recent years [1][2][3]. Supercapacitors, also known as ultracapacitors or electrochemical capacitors, have attracted considerable attention due to their higher power density than batteries and higher energy density than traditional dielectric capacitors [4][5][6][7][8].…”