활성탄분말(BP-20)에 전도성 개량제(Super P, VGCF 및 AB)를 혼합하고 결합제로 전극의 유연성을 갖게 하는 P(VdF-co-HFP)와 전극의 기계적 강도를 높이기 위하여 가교 결합력이 우수하고 분산제인 PVP를 사용하여 전극을 제조하였다. 활성탄, 전도성 개량제(Super P)및 혼합결합제(P(VdF-co-HFP) : PVP = 1 : 3]의 비율은 90:5.5 wt.%로 단위셀 전극을 제조했을 때 전기화학적 특성이 가장 우수하였으며, 전도성 개량제를 첨가함으로써 전기도도 향상과 충전밀도를 높여 내부저항이 감소됨을 확인할 수 있었다. 임피던스 측정결과 전도성 개량제를 첨가한 경우 등가직렬저항이 작아지며, 전극과 전해질의 계면에서 전하전이속도가 빠르고 RC 시간상수가 작아져 전류가 정상상태에 빨리 도달하여 급속충전이 가능하다는 것을 알 수 있었다. 전도성 개량제가 첨가된 경우 단위셀의 자기방전은 이온흡착에 의하여 충전되는 EDLC의 특성상 초기 전해액 내 이온 농도의 확산과정에 의하여 지배되었고, 전기이중층을 통한 누설전류에 의한 자기방전은 전극물질에 상관없이 일정하였다. 2.3 V/230 F급 EDLC는 방전전류에 상관없이 IR drop에 의한 내부저항(DC-ESR)이 일정하기 때문에 순간 정전시 보조전원 등과 같은 산업안전용으로 적용이 가능할 것으로 판단되었다.

Electrodes were fabricated based on activated carbon powder BP-20, conducting agent such as Super P, vapor grown carbon fiber (VGCF) and acetylene black (AB), and the mixed binders of flexible poly-(vinylidenefluoride-co-hexafluoropropylene) [P(VdF-co-HFP)] and cross-linking dispersion agent of polyvinylpyrrolidone(PVP) to increase mechanical strength. In the electrode fabrication of unit cell, it was ascertained that electrochemical characteristics were greatly increased with 90 wt.% of BP-20, 5 wt.% of Super P and 5 wt.% of mixed binder [P(VdF-co-HFP): PVP=7:3]. Also electric conductivity was increased and internal resistance was decreased with addition of conducting agent. According to impedance measurement of the electrode with the addition of conducting agent, we found that it was possible to charge rapidly due to the fast steady-state current convergence caused by low equivalent series resistance (AC-ESR), fast charge transfer rate at interface between electrode and electrolyte and low RC time constant. The self-discharge of unit cell showed that diffusion process was controlled by the ion concentration difference of initial electrolyte due to the characteristics of electric double layer capacitor (EDLC) charged by ion adsorption in the beginning, but this by current leakage through the double-layer at the electrode/electrolyte interface had a minor effect and voltages of curves were remained constant regardless of electrode material. We found that the 2.3 V/230 F grade EDLC would be applied to industrial safety usage such as uninterrupted power supply (UPS) because of the constant DC-ESR by IR drop regardless of discharge current.

Conducting Agent Super P Electric Double Layer Capacitor Supercapacitor Mixed Binder

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