Anti-freezing aqueous electrolytes for electric double-layer capacitors

Different types of alcohol have been proposed as the anti-freezing additives for aqueous electrolytes in double-layer capacitors (EDLCs). The influence of ion solvation on the capacitive behavior of porous carbon electrode in the anti-freezing aqueous electrolytes has been studied. The low-temperature performance of EDLCs composed of either micro- or meso-porous carbon in these electrolytes has been fully investigated. Deduced from cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge–discharge measurements, it has been discovered that the anti-freezing electrolyte of methanol/water-concentrated NaClO4 possesses low equivalent series resistance at −40 °C. EDLCs using the electrolytes of methanol/water-concentrated NaClO4 solutions deliver improved energy density and power density at the temperature as low as −40 °C.