The mechanisms by which ions are transported through polymer electrolytes are poorly understood. Structural information should greatly aid in the determination of such mechanisms and the optimization of the electrolyte properties. Ionic conductivity, however, predominates in amorphous polymer-salt phases, and characterization of amorphous solvate structures is difficult. The task is simplified by comparisons with crystalline poly(ethylene oxide) (PEO)-salt phases, but the structural determination of such phases is also difficult because single crystals have not been available. Here, it is demonstrated that single crystals of PEO-lithium salt phases may be prepared and characterized using low molecular weight PEO.