Crosslinked Polymer Electrolytes for Safe and High-Performing Lithium-based Batteries

Profoundly ion conducting, self-standing and tack-free ethylene oxide based polymer electrolytes are successfully prepared via a rapid and easily up-scalable free radical polymerization (UV/thermal curing). It can be an interesting alternative to produce polymer electrolytes, being highly advantageous due to its easiness and rapidity in processing, high efficiency and eco-friendliness as the use of solvent is avoided. The crosslinking produced during curing allows the incorporation of high amount of RTIL (e.g., imidazolium, pyrrolidinium) or tetraglyme and lithium salt (TFSI anion), leading to a material with remarkable homogeneity and robustness. The polymer network can efficiently hold plasticizers without leakage. Samples are thermally stable up to 375 °C under inert conditions, which is particularly interesting for application in Li-ion batteries with increased safety. Excellent ionic conductivity (>0.1 mS cm–1 at 25 °C), wide electrochemical stability (> 5 V vs. Li), stable interfacial properties and dendrite nucleation/growth resistance are obtained. The lab-scale Li-polymer cells assembled with different electrode materials (e.g., LiFePO4, Li-rich NMC, LiCoPO4, TiO2) show stable charge/discharge characteristics with limited capacity fading upon very long-term reversible cycling. The overall remarkable performance of the novel polymer electrolytes postulates the possibility of effective implementation in the next generation of safe and durable secondary Li-based polymer batteries working at ambient and/or sub-ambient temperatures.