Solid organic electrolytes

Abstract

Solid, or highly viscous, organic electrolytes consisting of alkylimidazolium cation with alkyl, PEGylated and fluorinated side chains of different molecular weights were synthesized and characterized (cf. chemical structures in Schemes 1 and 2). The PEGylated/fluorinated imidazolium iodide is a solid organic electrolyte that has a conductivity of about 2×10S/cm at 30° C. The ionic conductivity could be significantly increased (1.11×10S/cm at 30° C. and S/cm at 2.88×10at 90° C.) by blending the PEGylated/fluorinated imidazolium iodide with another solid electrolyte, 1-ethyl-3-methylimidazolium iodide (EtMImI). The PEGylated imidazolium iodides synthesized in the present work have conductivities in the range 1.6×10S/cm to 2×10S/cm at 30° C. and viscosities in the range 620 cP to 720 cP at 30° C. The iodide counter ion in the present electrolytes supplies the anion for the I/Iredox mediators for DSSCs. Therefore, the organic electrolytes of the present invention can be used even without the addition of inorganic salts such as LiI or KI. We found that the addition of an organic solid electrolyte, EtMImI, resulted in an increase in the ionic conductivity of the PEGylated/fluorinated imidazolium iodides, whereas the addition of the inorganic LiI led to a decrease in ionic conductivity. All the electrolytes are thermally stable until high temperatures (250° C. to 300° C.).