Solid Polymer Electrolytes, 2. Preparation and Ionic Conductivity of Solid Polymer Electrolytes Based on Segmented Polysiloxane-Modified Polyurethane

Abstract

Segmented polyurethanes (PSEU) were synthesized from polydimethylsiloxane diol (PSi) mixed with poly(ethylene glycol) (PEG) in different ratios as soft segment, 4,4′-diphenylmethane diisocyanate as hard segment, and ethylene glycol as chain extender. FT-IR, NMR, and thermal analysis were used to characterize the structure and morphology of these copolymers. These copolymers were then swollen in a LiClO4 /PC liquid electrolyte solution to obtain gel-like polymer electrolytes. The Li+ ions are more effectively adsorbed in the microphase of PEG, however, the existence of polysiloxane significantly improves the property of solvent resistance. Then, impedance spectroscopy was used to investigate the conductivity of these polymers electrolytes as a function of the content of LiClO4/PC liquid electrolyte. The ionic conductivity of these systems reaches an order of 2.33×10–3 S·cm–1 at 80°C and 5.9×10–4 S·cm–1 at 25°C, respectively, where the films with the increase of 50 wt.-% immersed in 1 M LiClO4 /PC are homogenous and exhibit good mechanical properties. The correlation between the structure and the ion-conducting behavior of these copolymers was interpreted by the results of DSC in the presence or absence of Li+.