Electrochemical Properties of Gel Copolymer-Electrolyte Based on Phosphonium Ionic Liquid

Abstract

Noble Poly (lithium 2-acrylamido-2-methyl propane sulfonate) and its copolymer withN-vinyl formamide based on trihexyl (tetradecyl) phosphonium acetate [(C6H13)3 P (C14H29)CH3COO; P66614 CH3COO) and trihexyl (tetradecyl)phosphonium bis(trifluoromethane sulfonyl) amide([(C6H13)3P(C14H29)] [TFSA];P66614TFSA) were prepared and analyzed to determine their characteristicsand properties. The ionic conductivity of a copolymer based P66614TFSA ionic liquidsystem exhibits a higher conductivity (8.9 × 10-5Scm-1) than that of a copolymer basedP66614CH3COO system (1.57 × 10-5Scm-1). The charge on the TFSA anion is spread very diffuselythrough the S-N-S core and particularly in the trifluoromethane groups, and this diffusionresults in a decreased interaction between the cation and the anion. The viscosity of P66614TFSA(39 cP at 343 K) and P66614CH3COO (124 cP at 343 K), which is very hydrophobic, was fairlyhigh. High viscosity leads to a slow rate of diffusion of redox species. The ionic conductivityof copolymer of a phosphonium ionic liquid system also exhibits higher conductivity than thatof a homopolymer system. Phosphonium ionic liquids were thermally stable at temperatures upto 400oC