Understanding of the ion transport in blended TPU-PEO polymer electrolytes

Abstract Fast and easily scalable solvent-free extrusion of polymer electrolytes would represent significant progress in the development of environmentally friendly solid alkali-ion and alkali-metal batteries. In this study, we compare cast and extruded solid polymer electrolytes composed of lithium bis(trifluoromethanesulfonyl)imide salt of varying content dissolved in host matrix of polyurethane and polyethylene oxide . The electrolytes were characterized by means of differential scanning calorimetry, infrared spectroscopy, AC impedance, broad-band spectroscopy, and one-dimensional 7 Li and 19 F nuclear magnetic resonance. Analysis of the FTIR spectra showed that both polymers can coordinate lithium cations by ethylene oxide (EO) and amine (NH) electron donating groups. The interactions between Li + and each polymer affect phase transition behavior, conductivity, and ion self-diffusion coefficients. Contrary to our expectations, it was found that unidirectional annealing, which was assumed to be induced by the extrusion process, does not alter out-of-plane ionic conductivity. Moreover, the bulk conductivity of extruded blended polymer electrolyte with 1:15 Li:EO ratio is more than twice that of its cast counterpart over the entire temperature range studied.