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

Abstract

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 about 10 Å in the dry clay to 20–24 Å 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°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.