Double-layer capacitance of waste coffee ground activated carbons in an organic electrolyte

Using ZnCl(2) activation we prepared a series of carbon electrodes from waste coffee grounds to study the effect of mesopores on double-layer capacitance in a tetraethyl ammonium tetrafluoroborate/acetonitrile electrolyte. The activated carbon with the largest mesopore volume achieved an energy density of 34 Wh kg(-1) at low current loads, and significantly retained an energy density of 16.5 Wh kg(-1) and specific capacitance of more than 100 F g(-1) at fast charge-discharge rates (20 A g(-1)). The effect of mesopores on capacitance at fast charge-discharge rates is discussed. (C) 2009 Elsevier B.V. All rights reserved.