Pyrrolidium‐ and Imidazolium‐Based Ionic Liquids and Electrolytes with Flexible Oligoether Anions

A new class of fluorine‐free ionic liquids (ILs) and electrolytes based on aliphatic flexible oligoether anions, 2‐(2‐methoxyethoxy)acetate (MEA) and 2‐[2‐(2‐methoxyethoxy)ethoxy]acetate (MEEA), coupled with pyrrolidinium and imidazolium cations is introduced. For the ILs with MEEA anions, Li + conducting electrolytes are created by doping the ILs with 30 mol % of LiMEEA. The structural flexibility of the oligoether functionality in the anion results in glass transition temperatures ( T g ) as low as −60 °C for the neat ILs and the electrolytes. The imidazolium‐based ILs and electrolytes reveal better thermal stabilities but higher T g and lower electrochemical stabilities than the corresponding pyrrolidinium‐based analogues. All neat ILs show comparable transport properties for the cations and these decrease by the addition of lithium salt – the pyrrolidinium‐based electrolyte being affected the most.