Sugar-based polymers for renewable, degradable, and efficient battery electrolytes James Runge 1,2 , Prof. Frank Marken 1,2 , Prof. Antoine Buchard 1,2 1 Department of Chemistry, University of Bath, UK, 2 Unversity of Bath Institute for Sustainability, UK Traditional lithium-ion batteries (LIBs) possess several issues regarding their safety, performance and sustainability owing to their use of liquid electrolytes based upon organic solvents. Consequently, there is growing interest in replacing the liquid electrolyte with a solid-state counterpart as a strategy to mitigate these flaws. Solid polymer electrolytes (SPEs) have gained considerable attention as alternative electrolyte materials for LIBs due to their low cost of manufacture, greater mechanical strength, and solvent-free nature 1 . The “gold standard” material for SPE applications is poly(ethylene oxide) (PEO) owing to its high ionic conductivity ( ca. 10 -3 S cm -1 at 70 °C). However, PEO-based SPEs possess several shortcomings which restrict their practical application including limited ambient temperature ionic conductivity, poor mechanical strength at elevated temperatures ( T m of PEO = 60-65 °C), high crystallinity and low lithium-ion transference numbers (≤ 0.2) 2 . Furthermore, there concerns regarding the sustainability of PEO as it is fossil-fuel derived. Therefore, it is necessary to design alternative host materials which can replace PEO to advance the field of SPEs for the next generation of rechargeable LIBs 3 . The objectives of the work that will be presented is to develop high performance alternative SPE materials derived from renewable feedstocks. A platform of functionalisable sugar-derived polymers has been developed which contain a high oxygen content to promote coordination and dissolution of lithium salts. The structure and properties can be easily varied to explore a wide chemical space (e.g. glass transition temperature ( T g ) crystallinity, pendant functional groups, and crosslinked networks). Finally, these sugar-based polymers are non-toxic and can exhibit (bio)degradability which could facilitate the recycling of battery technologies and the recovery of precious elements involved in their manufacture. Our group has recently reported a novel bio-derived SPE based upon a cross-linked polyester derived from D-xylose and fatty acid derivatives which exhibited ionic conductivity in the region of 10 -5 S cm -1 at 60 °C 4,5 . This presentation details the synthesis of a novel monomer platform derived from D-xylose and fatty acids containing an oxazolidine-2-thione (OZT) moiety and its co- polymerisation with dithiols. The resulting alternating copolymers are amenable to further post-polymerisation functionalisation reactions with alkyl halides which can be exploited to tailor the properties towards producing efficient battery electrolytes. Finally, initial electrochemical characterisation of the produced SPE materials will be reported.
Figure 1: Schematic representation of routes towards novel functionalised polymers and SPE materials. References
1. V. Bocharova and A. P. Sokolov , Macromolecules , 2020, 53, 4141-4157. 2. Z Xue, D. He, and X. Xie, J . Mater. Chem. A , 2015, 3, 19218-19253.
3. J. Mindemark, M. J. Lacey, T. Bowden and D. Brandell, Prog. Polym. Sci. , 2018, 81, 114-143. 4. M. Piccini, D. J. Leak, C. J. Chuck, and A. Buchard, Polym . Chem ., 2020, 11, 2681-2691. 5. M. Oshinowo, J. R. Runge, M. Piccini, F. Marken, and A. Buchard, J. Mater. Chem. A. , 2022, 10, 6796-6808.
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