Solid-state high-resolution C-13 NMR studies are carried out on a series of PEO/LiCF3SO3 complexes with different EO/Li molar ratios at room temperature. The obtained spectra clearly show that there are four phases, namely the crystalline PEO, the amorphous PEO, the PEO3:LiCF3SO3 crystalline complex and the PEO3:LiCF3SO3 amorphous complex, coexisting in the samples with EO/Li molar ratios larger than 3. The solid-state C-13 NMR spectrum of the PEO3:LiCF3SO3 crystalline complex exhibits six peaks with high resolution at room temperature, while the previously reported C-13 NMR spectra showed only one peak. These six peaks are assigned with the combination of the C-13 dipolar-INADEQUATE and the two-dimensional exchange spectra. Moreover, remarkable helical jumps of PEO segments are demonstrated to exist in the crystalline complex. Our study paves the way towards a better understanding of the phase structures and subsequently the conduction mechanism of PEO-based solid polymer electrolytes. (C) 2012 Elsevier Ltd. All rights reserved.