Conductivity and viscosity of liquid and gel electrolytes based on LiClO 4, LiN(CF 3SO 2) 2 and PMMA

Abstract

Liquid electrolytes comprising lithium salts of the type LiX (X=N(CF 3SO 2) 2, ClO 4) dissolved in an aprotic solvent PC and a binary mixture of PC and EC show σ 25(max) of the order of 10 −2 S cm −1. Gel electrolytes synthesized by the incorporation of PMMA up to 25 wt.% in these liquid electrolytes show insignificant changes in the σ 25 value, retaining the liquid-like behaviour with σ 25(max)∼10 −3 S cm −1. The small σ 25 decline in contrast to the dramatic η 25 increase upon PMMA incorporation in liquid electrolytes exemplifies that PMMA plays a nonsolvating, passive role in these systems. The conduction mechanism that persists in liquid electrolytes is apparently preserved in gel electrolytes based on PMMA. Gel electrolytes can be visualized as highly viscous liquid electrolytes encaged in a polymeric matrix as thermal dependence of conductivity and viscosity for liquid and gel electrolytes follow nearly the same trend. PMMA imparts mechanical stability to gels thereby promoting ease of device fabrication. Nominal variance of conductivity over a wide temperature range makes these gel electrolytes ideal candidates for electrochromic windows (ECWs).