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

Using ZnCl2 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.