We report a new class of polymer electrolytes that exhibit high Li+-ionic conductivity and thermal stability up to 200 degrees C. The polymer electrolyte consists of a solvate ionic liquid ([Li(G4)][TFSA]), comprising an equimolar mixture of lithium bis(trifluoromethanesulfonyl)amide (Li[TFSA]) and tetraglyme (G4), and a well-defined ABA-triblock copolymer, polystyrene-b-poly(methyl methacrylate)-b-polystyrene (PSt-b-PMMA-b-PSt, SMS). The electrolyte is formed by the self-assembly of SMS, where the solvatophobic PSt segments serves as physical cross-linking points, and the solvatophilic PMMA segment with preferentially dissolved [Li(G4)][TFSA] forms ion-conduction paths. In the electrolyte, the preservation of the complex cation [Li(G4)](+) in the PMMA phase was demonstrated by pulsed-field gradient spinecho (PGSE) NMR, Raman spectra, and thermogravimetric analysis. Because of the preservation of [Li(G4)](+), which hinders the direct interaction of Li+ with the polymer segment and the coupling of the ionic transport from the segmental motion, the room temperature ionic conductivity of the electrolyte reached an appreciable level (10(4)10(3) S cm(1)).