Optimization of a Novel Non-Flammable Solid Polymer Electrolyte for Lithium Metal Batteries
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- Nowadays, a worldwide move is occurring to switch from fossil fuels to renewable energy. The automotive sector is contributing to this change by moving to electric vehicles. To make this transition possible, the most viable and appropriate solution is the use of solid-state batteries. These batteries include a lithium metal anode allowing higher battery performance. To form all-solid batteries, a solid electrolyte and a catholyte are mandatory. This project mainly focuses on solid polymer electrolytes with a perspective to use them for hybrid solid electrolytes in the future. A second part focuses on catholyte formation. This research is based on the use of copolymers formed by 3 different monomers: MAPC1, MACyCB and B-PEGMA. Each monomer is selected for specific characteristics, MAPC1 for its fire-retardant properties, MACyCB for its good ionic conductivity and B-PEGMA for its mechanical properties. This study focuses on the electrochemical and thermal properties of these copolymers. For the electrolyte study, we first demonstrated that boronate (B-PEGMA) and cyclocarbonate (MACyCB) containing copolymers loaded with LiTFSI gave the best ionic conductivity of 10-5 S.cm-1 at 60°C. Secondly, we were able to determine that the best molar ratio polymer: lithium salt was 1:2. Finally, over a range of 4 different lithium salts, LiFSI gave the best conductivity with 10-4 S.cm-1 at 60°C. The catholyte study determined the optimum weight percentage of each component: 15% carbon black, 40% NMC and 45% polymer and salt with the ratio 1:1 (polymer:Li) with copolymers containing 10-20% boronate, 50-60% cyclocarbonate and 20-30% phosphonate.