Characterization of thermal behaviors of electrochemical double layer capacitors (EDLCs) with aqueous and organic electrolytes

The temperature dependent electrochemical properties of electrochemical double layer capacitors (EDLCs) assembled with two representative electrolytes, aqueous (H2SO4) and organic (Et4NBF4/PC), were investigated using a specified characterization procedure and interpreted by means of a recently developed equivalent circuit model. Over an operating temperature range between −30 °C and 60 °C, these parameters were characterized using the cyclic voltammetry (CV), galvanostatic charging/discharging measurements and electrochemical impedance spectroscopy (EIS). Based on experimental results, the correlations between internal resistance/capacitance and temperature were quantified. Moreover, the temperature dependency of impedances was analyzed through simulations of the EIS data by the equivalent circuit model which takes into account the important roles of the electrolyte properties, diffusion and interfacial processes within EDLCs. The simulated resistances were then utilized to discuss about the energy barriers of kinetic reactions and diffusion and to address the performance discrepancies of the two electrolytes.