In-situ polymerization of PEG350mA and PEG200diA is attempted to prepare solid-state polymer electrolytes (SPEs) for Li-ion Batteries. Effects of composition and LiClO4 content on properties and performances of the SPEs are investigated by TG, EIS. The role of cross-linking and lithium salt in the IPN type SPEs is investigated by DSC and FT-IR analysis. The IPNs-LiClO4 SPEs show ionic conductivity of 1.5 x 10(-5) S cm(-1) at ambient temperature and applicable thermal stability under 270 degrees C. A Li/SPEs/LiCoO2 coin cell shows acceptable charge/discharge performance. This paves an effective way to develop SPEs for lithium ion batteries. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.003207jes] All rights reserved.