Photo-cured polymer electrolyte membranes for energy storage and conversion systems

Polymer electrolytes represent the ultimate in terms of desirable properties for the next-generation of safe and efficient energy storage and production devices. They promise an all-solid-state construction, a wide variety of shapes and sizes, lightweight, low-cost of fabrication, high safety and high energy density. In this communication, we present a summary of our recent and most interesting results regarding the synthesis, physico-chemical and electrochemical characterization of polymer electrolyte membranes based on different monomers/oligomers (methacrylic and/or ethylene oxide based) with several kinds of additives, salts, plasticizers and fillers. The crosslinking produced by UV irradiation allows the incorporation of higher amount of RTIL (e.g., imidazolium, pyrrolidinium, etc.) and/or tetraethylene glycol dimethyl ether (tetraglyme) with lithium salt (based on TFSI anion), leading to a material with remarkable homogeneity and robustness. The UV-cured PEO-based polymer network is able to efficiently hold the RTIL without any leakage. Tensile analysis confirmed that the membranes exhibit improved Young’s modulus for systems encompassing >50 wt.% of RTIL. The SPE showed the thermal stability up to 375 °C under inert conditions, and such a remarkable result is particularly interesting for application in Li-ion batteries with increased safety. The SPE exhibited excellent ionic conductivity (> 5x10–4 S cm–1 at 25 °C), electrochemical stability (>5V vs. Li+/Li), and excellent interfacial stability towards the lithium metal electrode. The ability to resist the lithium dendrite nucleation and growth was tested by galvanostatic polarization studies. Noteworthy, the samples showed resistance at current intensities > 0.1 mA cm-2. The lab-scale Li-polymer cells assembled showed stable charge/discharge characteristics without any capacity fading (>140 mAh g1) at various current rates and temperatures. The PE membrane after some modifications were also tested in dye-sensitized solar cells (DSSCs). Different bio-based additives (e.g., nanocellulose) are considered in order to improve mechanical, interfacial and electrochemical properties. The introduction of iodine/iodide-based redox mediator in the polymer matrix assured the functioning of a lab-scale test cell with conversion efficiency exceeding 6% at 1 sun. The overall results achieved on such systems demonstrate that, compared to other techniques, UV curing is a versatile method, easy to be scaled-up at an industrial level due to its easiness and rapidity in processing. It can open up promising perspectives in obtaining innovative electrolytes with high flexibility, well suited for flexible and/or non-planar electronics application.