A kind of highly-crystalline solid polymer electrolytes, based on the alpha-PEO-urea-LiTFSI ternary complex, is introduced here. The introduction of LiTFSI into alpha-PEO-urea inclusion compound has not changed the crystalline structure of the inclusion compound. Furthermore, the ionic conductivity of this alpha-PEO-urea-LiTFSI ternary complex has reached up to 6.03 x 10(-5) S cm(-1) at 303 K, where the highest conductivity of the reported highly-crystalline polymer electrolyte is only 1.58 x 10(-7) S cm(-1) for PEO6/LiAsF6. Our investigation might motivate further research on the different kinds of highly-crystalline polymer electrolytes based on the inclusion complexes. (C) 2016 Elsevier Ltd. All rights reserved.