Li ion conductors based on laponite/poly(ethylene oxide) composites

Synthesis and characterization of single-ion conducting poly(ethylene oxide) (PEO)/Li-laponite nanocomposites are reported. The amount of PEO that can be intercalated into laponite, a synthetic hectorite with high surface area, ranges from about 0.7 g/g Li-laponite when the polymer average molecular weight is 1000 or above, to about 1 g/g for oligomers of average molecular weight 500. The interlayer spacing increases from al,out 10 Angstrom in the dry clay to 20-24 Angstrom in the nanocomposites, depending upon polymer molecular weight,;and the average particle size increases proportionally, but is still in the sub-micron range. AC impedance measurements on the clear, slightly brittle, self-supporting films indicate that the nanocomposite conductivity is greatly enhanced over that of the dry clay. A maximum of about 10(-6) S/cm at 80 degrees C is obtained for materials containing a slight excess of polymer, and conductivities of nanocomposites containing PEO were generally higher than that of those containing oxymethylene-linked polyethylene glycols (amorphous PEOs). Suggestions for further improving conductivity and mechanical properties of these novel materials are presented. (C) 1998 Published by Elsevier Science B.V. All rights reserved.