The development of high-performance flexible batteries is imperative for several contemporary applications including flexible electronics, wearable sensors and implantable medical devices. However, traditional organic liquid-based electrolytes are not ideal for flexible batteries due to their inherent safety and stability issues. In this study, a non-volatile, non-flammable and safe ionic liquid (IL)-based polymer electrolyte film with solid-like feature is fabricated and incorporated in a flexible lithium ion battery. The ionic liquid is 1-Ethyl-3-methylimidazolium dicyanamide (EMIMDCA) and the polymer is composed of poly(vinylidene fluoride-co-hexafluoropropene) (PVDF-HFP). The electrolyte exhibits good thermal stability (i.e. no weight loss up to 300 degrees C) and relatively high ionic conductivity (6 x 10(-4) S cm(-1)). The flexible thin-film lithium ion battery based on solid-like electrolyte film is encapsulated using a thermal lamination process and demonstrates excellent electrochemical performance, in both flat and bent configurations. (C) 2015 Elsevier B.V. All rights reserved.