Thermal Stability and Ionic Conductivity of High-Temperature Proton Conducting Ionic Liquid−Polymer Composite Electrolyte Membranes for Fuel Cell Applications

The current technology of polymer electrolyte membrane fuel cells (PEMFCs) is based on perfluorosulfonic acid (PFSA) polymer membranes operating at a typical temperature of 80°C. Important key issues and limitations of PFSA based PEMFCs include hydration levels, CO poisoning, and hydrogen. To overcome these limitations, high temperature polymer electrolyte membranes (PEMs) for operation above 120°C are under development. This review encompasses the high temperature PEMs operating above 100°C, focusing on ionic liquids (ILs), as well as the ionic conductivities (ICs) and thermal stabilities (TSs) of IL-polymer composite membranes. The best IL-polymer composite membranes with the maximum available ICs and high TSs are discussed. The effect of casting methods on the ICs and TSs of IL-polymer composite membranes is also presented. The IL-polymer composite membrane increases the ionic mobility of charge transport by creating an ordered network of ionic domains in the PEMs.