Relation between ionic conductivity and solubility of CO2 in pressurized solid polymer electrolytes

The isothermal conductivity and solubility of CO2 in amorphous poly(oligo-oxyethylene glycol methacrylate) (PMEO)−LiX (X = N(SO2CF3)2, CF3SO3, LiClO4, BF4, and Br) electrolytes at CO2 pressures between 0.1 and 20 MPa were measured by an in-situ impedance unit consisting of a supercritical CO2 extraction system and an original high-pressure reactor. Solubility was estimated from the gravimetric change at desorption procedure (CO2-out), which is based on the Fickian diffusion of CO2 molecules in polymer. The relation between the conductivity in CO2 and qt=0 (the amount of saturated CO2 in 1 g of a sample) is discussed as a function of pressure. The conductivity in pressurized CO2 increases linearly with increasing qt=0 due to the decrease in Tg and the effect on qt=0 of fluorine atoms in the anion; there is the Lewis acid−base interaction between CO2 molecules and dissociated anions. The LiTFSI electrolyte had the highest qt=0, more than 0.35, and the conductivity at 20 MPa was 17 times higher than that at ...