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5373392 
Journal Article 
Solid Polymer Electrolytes for Lithium Metal Battery via Thermally Induced Cationic Ring-Opening Polymerization (CROP) with an Insight into the Reaction Mechanism 
Nair, JR; Shaji, I; Ehteshami, N; Thum, A; Diddens, D; Heuer, A; Winter, M 
2019 
Yes 
Chemistry of Materials
ISSN: 0897-4756
EISSN: 1520-5002 
31 
9 
3118-3133 
WOS:000468242300007 
We report the synthesis of solid polymer electrolytes (SPEs) using a thermally induced and a lithium salt catalyzed cationic ring-opening polymerization (CROP) technique. A synergistic approach using two salts such as lithium tetrafluoroborate-LiBF4 and lithium bis(trifluoromethane sulfonyl)imide-LiTFSI has assured a complete monomer to polymer conversion and fast reaction kinetics during the CROP process. The initiation mechanism of lithium salt induced CROP is elucidated using molecular dynamic simulation, quantum chemical calculation, real-time FT Raman spectroscopy, nuclear magnetic resonance spectroscopy, X-ray photoelectron spectroscopy, and thermogravim-etry mass spectrometry analysis techniques. The cross-linked 3D network of ethylene oxide based SPE is prepared without the use of any solvents or external catalysts. In particular, a mixture of poly(ethylene glycol) diglycidyl ether, LiBF4, and LiTFSI in appropriate proportions after a baking process produced a freestanding, flexible, and nontacky film. The synthesized SPEs exhibit low glass transition temperature (< -50 degrees C), high ionic conductivity (>0.1 mS cm(-1)), and excellent oxidation stability (>5.5 V vs Li/Li+). The SPE is polymerized directly onto a carbon-coated LiFePO4 cathode film and successfully cycled in a lithium metal battery configuration at 40 and 60 degrees C. As evidence, the SPE is galvanostatically cycled against a high-voltage LiNi1/3Mn1/3Co1/3O2 cathode, and the preliminary results indicated exciting characteristics in terms of specific capacity and Coulombic efficiency.