PREPARATION AND CHARACTERIZATION OF CROSS-LINKED COMPOSITE POLYMER ELECTROLYTES

Cross-linkable composite electrolytes were prepared from poly(ethylene glycol) dimethyl ether (PEGDME)-500, LiClO4, fumed silica, and 10 wt % methyl, butyl, or octyl methacrylate. The silicas used were chemical ly modified by attaching methacrylate groups to the silica surface thr ough Cs and Cs tethers. Before cross-linking, the electrolytes were th ixotropic and had ionic conductivities of >2 x 10(-4) S/cm. After ultr aviolet (UV)-induced cross-linking, the electrolytes were rubbery and dimensionally stable, and the conductivities were unchanged. Conductiv ity, extraction, and thermal analysis data all support a model where t he added methacrylate monomer and growing polymer chains phase separat e from the electrolyte phase during photopolymerization to yield a met hacrylate-rich silica/polymer phase and little or no polymer in the PE GDME-500 phase. Thus, the mechanical properties of the composite elect rolyte and its ionic conductivity are decoupled and can be optimized i ndependently.