This article reviews the PEO-based electrolytes for lithium-ion batteries.Poly(ethylene oxide) (PEO) based materials are widely considered as promising candidates of polymer hosts in solid-state electrolytes for high energy density secondary lithium batteries. They have several specific advantages such as high safety, easy fabrication, low cost, high energy density, good electrochemical stability, and excellent compatibility with lithium salt. However, the typical linear PEO does not reach the production requirement because its insufficient ionic conductivity due to the high crystallinity of the ethylene oxide (EO) chains, which can restrain the ionic transition due to the stiff structure especially at low temperature. The scientists have explored different approaches to reduce the crystallinity hence to improve the ionic conductivity of PEO-based electrolytes, including: blending, modifying and making PEO derivatives etc. This review is focused on surveying the recent developments and issues about PEO-based electrolytes for lithium-ion batteries.