Uniaxially oriented carbon monoliths as supercapacitor electrodes

Cylindrical carbon monoliths of 7 mm in diameter and certain heights (1 2 3 4 and 5 mm) are studied as model electrodes for supercapacitors The monoliths show a narrow microporous structure with average micropore size of 0 73 nm and specific surface area of 1086 m(2) g(-1) The monoliths show straight walls and channels both arranged along the cylinder axis The former account for a remarkable electrical conductivity (6 5 S cm(-1) at room temperature) The latter allow a rapid ionic transport between the electrolyte bulk and the carbon walls and account for a high specific capacitance at high current density The cell capacitance and resistance increase lineally with the monolith height according to C = (1 78 +/- 0 06)h and ESR = (0 08 +/- 0 01)h + (1 67 +/- 0 04) respectively The contribution of the electrolyte resistance monolith resistance and monolith/collector resistance to ESR is discussed The cell response time or constant tune increases with the monolith height but according to a power dependence tau = (4 5 +/- 0 2)h((1 01 +/- 0 03)) The carbon of the monoliths show in KOH electrolyte a specific capacitance of 150 Fg(-1) and a capacitance per sui face area of 14 mu F cm(-2) (C) 2010 Elsevier Ltd All rights reserved