Poly(ethylene oxide)(PEO)-based solid polymer electrolytes(SPEs) are promising materials for lithium-ion batteries owing to their chemical stability and interfacial compatibility. However, residual O–H groups in PEO can induce side reactions with cathodes and hinder lithium-ion transport. In this study, sulfur- and oxygen-containing monomers were introduced to overcome intrinsic limitations of PEO-based SPEs. Sulfur-containing polymers were synthesized and applied as polymer electrolytes with lithium salts. The incorporation of sulfur moieties is expected to enhance thermal stability by increasing intermolecular interaction energy of C–S bonds, leading to a higher glass transition temperature. In addition, the larger atomic radius and longer bond length of sulfur compared to oxygen may increase free volume and facilitate lithium-ion migration. The polymer structure was confirmed by FT-IR and 1H NMR spectroscopy. Thermal and electrochemical properties were evaluated.