Conductivity and viscosity of liquid and gel electrolytes based on LiClO4, LiN(CF3SO2)2 and PMMA

Liquid electrolytes comprising lithium salts of the type LiX (X = N(CF3SO2)(2), ClO4) dissolved in an aprotic solvent PC and a binary mixture of PC and EC show sigma(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 sigma(25) value, retaining the liquid-like behaviour with sigma(25(max)) similar to 10(-3) S cm(-1). The small sigma(25) decline in contrast to the dramatic eta(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). (C) 2002 Elsevier Science B.V. All rights reserved.