A highly conductive composite electrolyte consisting of polymer and room temperature molten fluorohydrogenates

A highly conductive composite electrolyte consisting of poly-2-hydroxyethyl methacrylate and a room temperature molten fluorohydrogenates, EtMeIm(HF)nF (EtMeIm: 1-ethyl-3-methylimidazolium, the averaged number n of the oligomeric anions in the vacuum stable salt is 2.3), has been obtained by a radical reaction method. A transparent gel composite electrolyte is formed when the molar fraction of EtMeIm(HF)nF, N, is in the range of 0.20–0.60. The conductivity of the electrolyte increases as the N increases. The maximum conductivity of 2.3×10−2 S cm−1 is obtained for N=0.60 at 300 K. Like the original salt, this composite electrolyte exhibits an excellent stability in air and does not etch the Pyrex glass. The electrochemical window of the neat salt, ∼3.2 V, is extended to ∼3.5 V for the composite electrolyte.