A multi-iodine doped strategy for ionic conductivity enhancement of crown ether functionalized ionic liquids

Abstract

A novel crown ether functionalized ionic liquid has been designed, synthesized and characterized in detail. The thermal properties of the ionic liquid are also investigated. When LiI or MgI₂ is introduced into the ionic liquid at the same concentration of the metal cations, the particular trapping ability of the crown ether to metal cations could effectively reduce the electrostatic interaction between the metal cations and iodide anions to release more iodide anions. Electrochemical impedance analysis reveals that ∼35 fold of ionic conductivity enhancement for the multi-iodine doped ionic liquids can be obviously observed at room temperature. For applications, these multi-iodine doped crown ether functionalized ionic liquids can be used as gel electrolytes for dye-sensitized solar cells, displaying a power conversion efficiency of 3.86% at a simulated AM1.5 solar spectrum illumination at 100 mW cm⁻¹. These preliminary results provide us with a feasible strategy to enhance the ionic conductivity and explore new ionic liquid electrolytes for energy storage and conversion devices.