An aqueous electrolyte of the widest potential window and its superior capability for capacitors.
A saturated aqueous solution of sodium perchlorate (SSPAS) was found to be electrochemically superior, because the potential window is remarkably wide to be approximately 3.2 V in terms of a cyclic voltammetry. Such a wide potential window has never been reported in any aqueous solutions, and this finding would be of historical significance for aqueous electrolyte to overcome its weak point that the potential window is narrow. In proof of this fact, the capability of SSPAS was examined for the electrolyte of capacitors. Galvanostatic charge-discharge measurements showed that a graphite-based capacitor containing SSPAS as an electrolyte was stable within 5% deviation for the 10,000 times repetition at the operating voltage of 3.2 V without generating any gas. The SSPAS worked also as a functional electrolyte in the presence of an activated carbon and metal oxides in order to increase an energy density. Indeed, in an asymmetric capacitor containing MnO2and Fe3O4mixtures in the positive and negative electrodes, respectively, the energy density enlarged to be 36.3 Whkg-1, which belongs to the largest value in capacitors. Similar electrochemical behaviour was also confirmed in saturated aqueous solutions of other alkali and alkaline earth metal perchlorate salts.
Qualtec Co. Ltd., 4-230 Sambo-cho, Sakai, Osaka, 590-0906, Japan.|Laboratory for Advanced Nuclear Energy, Institute of Innovative Research, Tokyo Institute of Technology O-okayama, Meguro-ku, Tokyo 152-8550, Japan.
Hiroshi
H
Tomiyasu
Qualtec Co. Ltd., 4-230 Sambo-cho, Sakai, Osaka, 590-0906, Japan.
Hirokazu
H
Shikata
Laboratory for Advanced Nuclear Energy, Institute of Innovative Research, Tokyo Institute of Technology O-okayama, Meguro-ku, Tokyo 152-8550, Japan.
Koichiro
K
Takao
School of Engineering, Tokai University, Kitakaname, Hiratsuka 259-1292, Japan.
Noriko
N
Asanuma
Faculty of Engineering, Shinshu University, 4-17-1, Wakasato 380-8553, Japan.
Seiichi
S
Taruta
Qualtec Co. Ltd., 4-230 Sambo-cho, Sakai, Osaka, 590-0906, Japan.
Yoon-Yul
YY
Park