Solid-state lithium-ion batteries (SSLIBs) become the new generation of devices for energy storage due to better performance and safety. Poly (ethylene oxide) (PEO) based material is an alternative promising candidate for solid electrolytes, while its thermal conductivity is crucial to heat dissipation inside batteries. In this work, we study the thermal conductivity of PEO by molecular dynamics simulation. Interestingly, by enhancing the structure order, thermal conductivity of crystalline PEO is obtained as high as 60 Wm(-1) K-1 at room temperature, which is two orders higher than the value (0.37 Wm(-1) K-1) of amorphous PEO. Moreover, thermal conductivity of crystalline PEO shows a significant stepped negative temperature dependence, which is attributed to the temperature-induced morphology change. Our study offers useful insights into the fundamental mechanisms that govern the thermal conductivity of PEO but not hinder the ionic transport, which can be used for the thermal management and further optimization of high-performance SSLIBs. (C) 2019 Elsevier Ltd. All rights reserved.