ELECTRICAL, THERMAL AND NMR INVESTIGATION OF COMPOSITE SOLID ELECTROLYTES BASED ON PEO, LII AND HIGH-SURFACE-AREA INORGANIC OXIDES

High salt concentration polymer composite electrolytes, containing pol y(ethylene oxide) (PEO), LII and nanoscale Al2O3 Or MgO and, in some c ases, ethylene carbonate (EC) and poly(methyl methacrylate) (PMMA), we re investigate by electrical conductivity, differential scanning calor imetry (DSC) and both wide-line and high resolution solid state Li-7 N MR. The high resolution NMR spectrum of a sample with a PEO:Li ratio o f 3:2 is consistent with at least two Li environments, one solvated by the polymer and one in small ionic clusters. A correlation between th e observed change in Li environment at elevated temperature and a sudd en increase in conductivity is suggested. All results demonstrate that the conduction mechanism in concentrated composite electrolytes is; s ignificantly different than in more dilute polymer electrolytes, in wh ich the ion transport process is associated with polymer segmental mot ion. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.