Development of advanced protic ionic liquid-based electrolytes for energy storage devices

This thesis is dedicated to the development of alternative electrolytes for electrochemical energy storage devices which have become a crucial part of modern society and infrastructure. Conventional electrolytes for supercapacitors or batteries are usually based on a combination of conducting salt and flammable or volatile solvents. Replacing them with inflammable and very low volatile ionic liquids (ILs), molten salts with a melting point below 100 °C, can increase the safety of the devices, which is an imperative for mobile as well as stationary applications. While there are many different types of ILs, the works within this thesis focus on protic ionic liquids (PILs), bearing an available proton in their structure. They have the advantage of an easier, thus often cheaper synthesis as well as the possibility of an additional charge transport mechanism besides conventional vehicular ion transport. Both points address the most often cited drawbacks of ionic liquids, meaning the cost as well as bad transport characteristics, i.e., high viscosity and low ionic conductivity. The implementation of PILs in electrochemical energy storage devices is yet not as advanced compared to their aprotic counterparts. This is related to the presence of an easily reducible, available proton in their structure. Nevertheless, their application in supercapacitors as well as batteries documented in the literature so far show promising results.