ORIGINAL PAPER Highly ionic conducting methacrylic-based gel-polymer electrolytes by UV-curing technique C. Gerbaldi Æ J. R. Nair Æ G. Meligrana Æ R. Bongiovanni Æ S. Bodoardo Æ N. Penazzi Received: 7 October 2008 / Accepted: 20 January 2009 / Published online: 10 February 2009 Ó Springer Science+Business Media B.V. 2009 Abstract Today, special interest is focused on polymer systems showing high ionic conductivity at ambient and/or sub ambient temperatures, since they find unique practical applications, such as separators in high power, versatile, rechargeable Li-based batteries. Thermo-set membranes prepared by free radical photo polymerisation (UV-curing) could be an interesting alternative to existing polymer electrolytes. In the present paper, we report the application of this technique to the synthesis of gel-polymer mem- branes which can be used as electrolytes for lithium battery application. These membranes are prepared by mixing a dimethacrylic (BEMA) and/or a diacrylic monomer (PEGDA), a methacrylic reactive diluent (PEGMA) and a radical photo-initiator with the in situ addition of a EC/DEC solution. The above mixtures are UV irradiated to obtain transparent, flexible, easy to handle gel-polymer films. The gel-polymer electrolytes (GPEs) are then pre- pared by swelling these membranes in different liquid electrolytes. The results obtained indicate some superior and satisfactory performances in terms of ionic conduc- tivity at ambient temperature for various GPEs prepared with different lithium salt solutions. The relevance of these features in view of practical application is here demon- strated by the response of lithium cells based on prepared GPEs. Keywords UV-curing Á Acrylate Á Methacrylate Á Gel-polymer electrolyte Á Ionic conductivity Á Lithium polymer cell 1 Introduction The development of advanced materials for energy storage and conversion has been receiving wide attention to meet the rising demand for clean energy technologies. In par- ticular, a large effort is being devoted towards the improvement of specific properties of electrochemical devices such as rechargeable lithium-based batteries, in view of their possible application in the automotive field. Beyond the others, rechargeable lithium polymer bat- teries, which are generally formed by a lithium metal anode, a polymer electrolyte separator and a metal oxide cathode capable of reversibly intercalating/de-intercalating Li ? ions, represent an excellent choice for electrochemical power sources characterized by high energy and/or power densities, good cyclability, reliability and safety [1–3]. Although a commercial reality, these power sources are still the object of intense R&D aiming to improve their performances for high-end applications [4, 5]. High per- forming innovative materials are fundamental for all the three main components of the cell, i.e. anode, cathode and electrolyte. The electrode materials need to have high capacity and durability, while the electrolyte should be a membrane capable of high ionic conductivity even at ambient temperature, with good mechanical and interfacial properties and stable performances. In all cases, the materials must be low cost, ecologically friendly and safe. In line with this tendency, in the recent years our research group carried out a systematic investigation on those materials which appear particularly promising for the C. Gerbaldi (&) Á J. R. Nair Á G. Meligrana Á R. Bongiovanni Á S. Bodoardo Á N. Penazzi Department of Materials Science and Chemical Engineering, Politecnico di Torino, C.so Duca degli Abruzzi 24, 10129 Turin, Italy e-mail: claudio.gerbaldi@polito.it 123 J Appl Electrochem (2009) 39:2199–2207 DOI 10.1007/s10800-009-9805-6