||Block copolymer electrolytes based on poly(ethylene oxide) (PEO) have been regarded as promising materials for solid electrolytes of lithium ion batteries, attributed to the good lithium salt-solvating ability of PEO chains and their high ionic conductivity. However, long-standing challenge of PEO-based electrolytes is inherent crystallinity of PEO, causing drastic reduction in ionic conductivity at room temperature. In here, we suggest a new methodology to modulate PEO crystallinity in block copolymers by embedding end-group functionalized low molecular weight PEO homopolymers. It has been found that the ionic conductivity and morphology of the resultant blends are highly dependent on the type of end groups in PEO homopolymers at the same blend ratio. The results indicated that intermolecular interactions in the PEO phases of blends can be largely modulated by the end-group in PEO homopolymers, thereby significantly affecting thermal and ion transport properties of blend electrolytes.