Abstract:
Double-layer capacitors were prepared by using activated carbon (1 939.4 m2/g) derived from petroleum coke as electrode and using 1 mol/L Et4NBF4/PC, Et4NBF4/AN, Bu4NBF4/PC and Bu4NBF4/AN as electrolytes, respectively. Their electrochemical performances were carried out through galvanostatic charge-discharge, cyclic voltammograms, and impedance spectroscopy measurements. The highest specific capacitance was obtained in Et4NBF4/PC system at low current loading. For Et4NBF4/AN, the least ionic transfer and diffusion resistance led to an excellent capacitance retention property. For Bu4NBF4, due to the larger solvated ion diameter and higher ion transfer resistance, the capacitive performances were inferior to those of Et4NBF4 in terms of specific capacitance and power density. In addition, owing to an excellent electric conductivity of AN, Et4NBF4/AN exhibited the best frequency response performance with the descant sequence of knee frequency Et4NBF4/AN>Bu4NBF4/AN>Et4NBF4/PC>Bu4NBF4/PC. Compared with Et4NBF4/PC system, Et4NBF4/AN is more suitable as electrolytes in high power output.