New electrolyte membranes for Li-based cells: Methacrylic polymers encompassing pyrrolidinium-based ionic liquid by single step photo-polymerisation

• Published in: Journal of membrane science Vol. 423-424; pp. 459 - 467
• Main Authors: Gerbaldi, C., Nair, Jijeesh R., Ferrari, S., Chiappone, A., Meligrana, G., Zanarini, S., Mustarelli, P., Penazzi, N., Bongiovanni, R.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.12.2012
• Subjects: ambient temperature; artificial membranes; batteries; electrochemistry; electrodes; electrolytes; ionic liquids; lithium; Lithium battery; Methacrylate; Photo-polymerisation; Polymer electrolyte membrane; polymers; Pyrrolidinium; Room temperature ionic liquid; Polymer electrolyte membrane; Lithium battery; Photo-polymerisation; Room temperature ionic liquid; Pyrrolidinium; Methacrylate
• ISSN: 0376-7388; 1873-3123
• DOI: 10.1016/j.memsci.2012.08.057

We demonstrate herein the application of an in situ single-step free radical photo-polymerisation process to incorporate room temperature ionic liquids (RTILs) into polymer membranes to be used as quasi-solid electrolytes in lithium-based batteries. The membranes are prepared by UV irradiating a mixture of photo-curable dimethacrylic oligomers and a proper radical photo-initiator along with a large quantity (i.e., 60wt%) of ether-functionalized pyrrolidinium-imide ionic liquid (PYRA1201TFSI) and LiTFSI lithium salt. Stable and flexible polymer films with homogeneous nature are easily produced: they combine the advantages of polymer electrolytes swollen by conventional organic liquid electrolytes with the non-flammability, high thermal and electrochemical stability typical of RTILs. Appreciable ionic conductivity values (0.1–1mScm−1) and good overall electrochemical performances are obtained in a wide temperature range. The polymer electrolyte membranes are tested in lab-scale cells using LiFePO4 as the cathode and Li metal as the anode. Good charge/discharge capacities, Coulombic efficiency close to unity, and low capacity loss at medium C-rates during preliminary cycling are obtained. These interesting properties highlight that such green and safe electrolyte systems could become a strong contender in the field of thin and flexible Li-based power sources. ► Methacrylic polymer electrolyte encompassing pyrrolidinium-based RTIL for Li cells. ► Fast in situ single-step photopolymerisation to incorporate the ionic liquid. ► High ionic conductivity, stability and safety features in a wide temperature range. ► Good cyclability and stable performances in real battery configuration.