COMPOSITE ELECTROLYTES PREPARED FROM FUMED SILICA, POLYETHYLENE OXIDEOLIGOMERS, AND LITHIUM SALK

The conductivity of solution electrolytes containing lithium salts (im ide and triflate anions), poly(ethylene glycol), and mono- and dimethy l-terminated poly(ethylene glycol) (Mw 200 to 400), and their correspo nding composite electrolytes containing fumed-silica particulates (0 t o 20 weight percent) are reported. At room temperature the ionic condu ctivity is as high as 1.5 x 10(-3) S cm(-1) for the composites studied , and they exhibit a gel-like consistency but flow under shear. The el ectrochemical stability of the composites and compatibility with lithi um metal were also examined. A large potential window (similar to 5.5 V) was found for Li imide-based electrolytes. The passive film formed on lithium in contact with the composite electrolyte is relatively mor e stable and less resistive than that formed in contact with the paren t solution electrolyte. Considering the additional advantages of proce ssability and low volatility, these composites should be good candidat e electrolytes for lithium and lithium ion batteries.