Recent Advances in Innovative Polymer Electrolytes based on Poly(ionic liquid)s

This article reviews the general strategies for the design of innovative polymer electrolytes using poly(ionic liquid)s. First, we review the properties of poly(ionic liquid)s as solid polymer electrolytes (SPEs). The different factors that affect the bulk ionic conductivity of poly(ionic liquid)s are discussed such as chemical nature of the cation, anion, the spacer, the polymer backbone and its glass transition temperature, the purity and water content. Special attention is given to the optimization of both the ionic monomer chemical structure and macromolecular architecture to achieve the highest possible polymer ionic conductivity (≈10−5 S/cm at 25 °C). Secondly, the preparation of gel type polymer electrolytes, named “ion gels”, based on ionic liquids and poly(ionic liquid)s is discussed in terms of preparation methods and composition. Due to the presence of free ions, such ion gels provide higher ionic conductivity (10−2 − 10−3 S/cm at 25 ºC) than SPEs. Finally, the actual applications of innovative polymer electrolytes based on poly(ionic liquid)s are summarized and their advantages are discussed.