Fumed silica surfaces were chemically modified to form single-ion conductors by attaching lithium-exchanged anionic groups (lithium 2-acrylamido-2-methyl-1-propanesulfonate, LiAMPS) to surface methacrylates on Degussa R711 fumed silica (abbreviated as R711-pLiAMPS). Surface lithium-ion contents varying from 0.7 to 9.1 nm(-2) were synthesized. Conductivity and transference number measurements were conducted on nanocomposite electrolytes containing polyethylene glycol dimethyl ether (PEGdm) + R711-pLiAMPS. A maximum room-temperature conductivity of 4.5 x 10(-6) S cm(-1) was obtained at a surface Li+ content of 4.2 nm(-2) and a Li:O mole ratio of 1:100 (15.8 wt % filler) with a Li+ transference number of 0.59. A maximum Li+ transference number of 0.78 was achieved at a surface Li+ surface content of 4.2 nm(-2) and a Li:O mole ratio of 1:20 (48.5 wt % filler) with a conductivity of 2.2 x 10(-6) S cm(-1). Adding lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) to the samples enhances room-temperature conductivity by more than two orders of magnitude while still maintaining a relatively high Li+ transference number. (C) 2004 The Electrochemical Society.