Physical and electrolytic properties of different cyclic carbonates as solvents for electric double-layer capacitors

Abstract

Propylene carbonate (PC) is commonly used as a single solvent for electric double-layer capacitors (EDLCs). Trimethylene carbonate (TMC) and PC are isomeric with each other: structural isomerism, which is especially called metamerism. TMC has a six-membered ring and is solid below 48°C. The relative permittivity of a PC-TMC equimolar binary mixture was highest in the four systems of solvents: PC-TMC > PC-ethylene carbonate (EC) > PC > buthylene carbonate (BC). Despite the lower ionic conductivity, the use of a tetraethylammonium tetrafluoroborate (TEABF4) solution in PC-TMC increased gravimetric capacitance of a coin cell. TMC may weaken solvation of electrolyte ions, and the electrolyte ions can closely approach the electrode in a compact double layer. © The Electrochemical Society of Japan, All rights reserved.