Synthesis of Polyimide-PEO Copolymers: Toward thermally stable solid polymer electrolytes for Lithium-Metal batteries
Timofey I. Kolesnikov, Dominik Voll, Fabian Jeschull, Patrick Théato
Abstract
The rapid pace of technological advancement in field of electric vehicles and need in sustainable energy sources calls for new, high-performance energy storage technologies. Lithium metal batteries (LMBs) based on solid polymer electrolyte represent a promising battery technology to increase energy density of conventional batteries while enhancing safety, eliminating dendrite formation, and providing mechanical flexibility. In this study, we developed novel polyimide-poly(ethylene oxide) (PI-PEO) copolymers and employed them as solid polymer electrolytes for LMBs. Copolymers with 5, 15, and 30 mol% of PEO-containing diamine were synthesized by reacting with aromatic dianhydride and diamine, using a facile and eco-friendly method in a benzoic acid melt. Chemical structures were confirmed using NMR and IR spectroscopy. Glass transition temperatures varied from 24 °C to 195 °C, increasing with a decrease in the PEO/PI moiety ratio. All copolymers demonstrated good thermal stability up to T5% > 345 °C with a two-step degradation and favorable mechanical properties below the glass transition temperature, as observed by DMA measurements. Solid polymer electrolytes with 70 wt% of LiTFSI exhibited an ionic conductivity of 1.4 × 10−4 S cm−1 at 70 °C, with a transference number of 0.7. The polymer electrolyte exhibited non-flammable properties and the potential for utilization in lithium metal batteries, indicating the promising application of these new polymers for high-safety battery systems.