Development of multipurpose ethylene oxide based polymer electrolytes for smart and energy efficient devices

Wide interest is mounting on polymer electrolytes for application in energy efficient devices such as rechargeable batteries, electrochromics and photovoltaics. Solid polymer electrolytes exhibit unique advantages: mechanical integrity, variety of fabrication methods and intimate electrode/electrolyte interfacial properties. They also improve safety along with more compact and lightweight packaging. Since the discovery of ionic conductivity in alkali metal salt complexes of poly(ethylene oxide), PEO, lot of research was devoted on systems containing lithium salts to be used as electrolytes, particularly in Li-based batteries. In this work, highly ionic conducting PEO-based polymer electrolytes, encompassing lithium salts dissolved in Room Temperature Ionic liquids (RTIL), were successfully prepared via rapid hot-press and subsequently cross-linked via UV irradiation. All the prepared materials were thoroughly characterised in terms of their physical, chemical and morphological properties and tested for ionic conductivity, electrochemical stability and cycling performances. The UV-curing process on such materials led to the production of elastic and resistant polymer electrolyte membranes. The degree of PEO crystallinity was greatly reduced down to the amorphous state by addition of lithium salt and RTIL and UV-induced cross-linking process. As a consequence, a noticeably increased ionic conductivity was registered (> 10-4 Scm-1 at RT). The polymer electrolyte demonstrated a very stable interfacial stability versus lithium metal and a very wide electrochemical stability window (0-5.5 V vs. Li). In the presence of such an electrolyte, the laboratory-scale devices showed remarkable performances, only slightly lower than those using liquid electrolyte, respect to which demonstrated a much greater durability. The obtained findings demonstrate that our proposed preparation can provide a new, easy and low cost approach to fabricate polymer electrolytes with remarkable performance for the next generation of advanced flexible energy production and storage devices.