IONIC-CONDUCTIVITY AND LI-7 NMR-STUDY OF SOLID POLYMER ELECTROLYTES BASED ON POLYETHERURETHANE COPOLYMER NETWORKS

Abstract

Crosslinked polyetherurethane (PEU) copolymer networks consisting of the low molecular weight poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) segments with an aliphatic diisocyanate were synthesized and complexed with a LiClO4 salt to form solid polymer electrolytes. The ionic conductivities of these samples were measured as a function of PEO composition at various temperatures. And a solid Li-7 NMR relaxation technique was used as a means of understanding the local environments and dynamics of the lithium ions in the polymer electrolytes. The difference in spin-spin relaxation times (T2) between two spectral components enabled to their separation, and thus we could monitor the mobile Li+ ion concentration and its motion as a function of PEO composition and temperature.