Ultracapacitor Technical Support (EDLC System)

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Development of Electric Double Layer Capacitor(EDLC): Electrolyte effects
2007-07-25, Hit : 20939

Ha-Young Lee, S.P. Jeong, D.B. Kim and H. Y. Lee
LS Mtron

Abstract - EDLC

Electric Double Layer Capacitor (EDLC) has shown a lot of outstanding features as an energy storage device although it has lower energy density compared with batteries. For making up for this weak point, researchers have been investigated electrode materials, electrolyte and other components in the whole system. As energy density is proportion to V2, LS Mtron has been especially focusing on the performance of electrolytes to increase a range of operating voltage (V). In this study, the effect of electrolytes on the performance of overall system was evaluated by using symmetric EDLC cell which was prepared by using a commercial activated carbon as an electrode material and acetonitrile as an electrolyte. It was observed from the result of linear sweep voltammetry that triethylmetylammonium tetrafluoroborate (TEMATFB) showed wider stable potential window than tetraethylammonium tetrafluoroborate (TEATFB), a normal electrolyte adapted in a commercial EDLC. And the accelerated performance tests were carried out at 60℃ in charged state with two systems containing TEMATFB and TEATFB, respectively. It is observed that TEMATFB is very effective to reduce the rate of degradation at 3.0V as a function of time compared with TEATFB. These results indicate that an appropriate choice of electrolyte system such as TEMATFB could help to make the reliability of overall system increase.

Experimental - EDLC

1) Half cell test
Linear Sweep Voltammetry was carried out using carbon electrode as a working electrode, Ag wire as a reference electrode and electrolytes which were 1.0M TEATFB and 1.0M
TEMATFB in Acetonitrile.

2) Single cell test
Two kinds of electrolytes above mentioned were used to manufacture 3000F electric double layer capacitors. Basic characteristics such as capacitance and DC resistance were measured as a function of time and voltage with sustaining large EDLCs at charged state,
60℃ (accelerated test).

Results - EDLC

Conclusion - EDLC

◆ TEMATFB has wider stable potential range and less degradation rate than TEATFB.

◆ Rate of capacitance degradation and DC resistance increment have close relationship with the kind of electrolyte at operating voltage, 3.0V. TEMATFB is effective to reduce DC resistance of 3.0V EDLC system. Change of discharged capacitance at high rated current
is making due to increase of IR drop (DC resistance)

◆ It is believed that physical properties of electrolyte after accelerated test is changed compared with initial value at the starting of test, although the capacitance with low rated current discharging doesn’t show big difference as a function of kind of used electrolyte.

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1 Development of Electric Double Layer Capacitor(EDLC): Electr ... 20939

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