Abstract
An electric double layer capacitor (EDLC) uses an electric double layer (EDL) in an electrolytic solution. Owing to the extremely small thickness of the EDL, the EDL has huge capacitance. The EDLC is expected to store a large amount of electric energy. This paper reports on the behavior of ions in the EDL. The purpose of the present study is to analyze the behavior of ions in the EDL. For this purpose, capacitance of the EDL in 1 and 5 wt.% NaCl solution at room and low temperature was observed. The NaCl solution was frozen using liquid nitrogen (LN2) while the EDL was formed by voltage application. Afterwards, the discharge current was measured when the frozen NaCl solution melted. The following results were obtained. 1. The capacitance of the frozen EDL by slow cooling is approximately five times larger than that of the EDL at room temperature. 2. The EDL is kept in the frozen NaCl solution after short-circuiting. 3. The capacitance of the frozen EDL by slow cooling is larger than that of the EDL by rapid cooling.
