The Influence of Conductive Salt Ion Selection on EDLC Electrolyte Characteristics and Carbon-Electrolyte Interaction

Abstract

This study compares several electrolytes for application in electrochemical double layer capacitors (EDLCs), as well as their influence on double layer formation on different activated carbon materials. While propylene carbonate (PC) was used as electrolyte solvent in all cases, the applied conductive salt was varied. A change in conductive salt was found to have a great impact on solubility as well as the electrolytes' ion transport properties. Most importantly the choice of conductive salt strongly influenced the maximum operative potentials of PC based electrolytes, leading to EDLCs exhibiting maximum operative voltages as high as 3.5 V. Furthermore it was found that not only a high operative voltage, but also well adjusted transport properties are needed for an EDLC electrolyte in order to maximize the device's energy and power capabilities. Finally the electrolytes' influence on the capacitance of five activated carbon materials was studied, leading to the conclusion that in order to maximize energy storage in EDLCs, electrolyte and carbon material have to be adjusted one to another.

Characterization of Different Conductive Salts in ACN‐Based Electrolytes for Electrochemical Double‐Layer Capacitors

“…This is very interesting because it has been shown that, on the contrary, the selection of salt has a strong influence on the operating voltage of PC‐based EDLCs . By comparing the operating voltage results with the results of the same conducting salts in PC (which have been obtained under comparable conditions), interesting dissimilarities were observed . On the one hand, Et 4 N + seems to be more stable in ACN (−1.6 V vs. Ag) than in PC (−1.3 V vs. Ag).…”

“…in which E is the cell voltage [V], i is the current [A], t d is the discharge time [s], m am is the active‐material weight of both electrodes [g], and dE / dt is the slope of the discharge curve [mV s −1 ] …”

“…Several investigations have shown that it is not possible to realize high‐voltage devices (>3 V) by using state‐of‐the‐art electrolytes. Therefore, many efforts have been made towards the introduction of novel electrolytes ,…”

“…Recently, we showed that the use of conductive salts as an alternative to Et 4 NBF 4 represents a promising strategy for the realization of high‐voltage PC‐based EDLCs . In fact, EDLCs with operating voltages higher than 3 V are feasible by using these alternative salts in combination with PC.…”

“…In fact, EDLCs with operating voltages higher than 3 V are feasible by using these alternative salts in combination with PC. These EDLCs display higher energy and comparable power with respect to state‐of‐the‐art PC‐based systems …”