Task-Specific Ionic Liquids for Electrochemical Applications

Abstract

Ionic liquids (ILs) have been widely examined as solvents, additives, or catalysts in a variety of applications including organic catalysis [ 1 -5 ], inorganic and materials synthesis [ 6 ], biocatalysis [ 7 -12 ], electrochemistry [ 13 ], pharmaceutical chemistry [ 14 ], polymerization [ 15 , 16 ], and engineering fl uids [ 17 -19 ]. The physicochemical properties of ILs are tunable through a careful selection of a variety of different cations and anions and a rational combination of ion pairs. More interestingly, cations and/or anions can be further functionalized to form so-called task-specifi c ionic liquids (TSILs). The notion of TSILs carrying specifi c functionality tailored for particular applications has proven visionary, and a variety of different functional groups have been grafted onto ILs [ 20 -22 ]. In particular, there is an exponential growth in constructing new TSILs as electrolytes for electrochemical applications. This chapter focuses on a critical discussion of some major types of TSILs and their electrochemical properties and applications. Ether/Thioether-and Hydroxyl/Thiol-Functionalized ILs General Physical PropertiesOur recent review has captured some key physical properties of ether-and alcoholfunctionalized ILs [ 22 ]. The inclusion of alkyloxy or alkyloxyalkyl groups in ILs often lowers the melting points ( T m ) [ 23 -26 ]. Additionally, the lowering of the