Safe, high-energy supercapacitors for transportation

Safety is the main concern for application of electrochemical energy storage/conversion systems in transportation and this is where the ionic liquids (ILs) for their low vapour pressure and high thermal stability come in. In supercapacitors which are systems of high power the use of ILs as electrolytes even permits high cell voltage which is a powerful strategy for their energy increase. This presentation reports on the use of ILs in supercapacitors operating above room temperature with emphasis on the cell configurations, hybrid or asymmetric, that allow to take advantage of the wide electrochemical stability window of these electrolytes. Results of the study on the selection and development of electrode materials in relation to the nature of the IL, which in turn affects their capacitive responses, and thus the capacitance and energy of the supercapacitors, are given and discussed. The mass contribution of the IL electrolyte to specific properties of supercapacitors is also emphasized.