Collaborative Research: Thermodynamics and Ion Transport in Block Copolymer/Lithium Salt Mixtures

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TECHNICAL SUMMARY:A fundamental study of the interplay between ordered morphology, grain structure, and ionic conductivity in mixtures of block copolymers and lithium salts is proposed. The results of the proposed work have the potential to impact the development of high specific energy batteries with solid electrolytes. The work will focus on mixtures of polystyrene-polyethyleneoxide block copolymers, synthesized by anionic polymerization, and bis-trifluoromethylsulfonimide (LiTFSI), a salt that is often used in batteries containing polymer electrolytes. Small-angle X-ray scattering and depolarized light scattering will be used to determine the nature of the order-disorder and order-order phase transitions in these materials. Conductivity measurements will be made on the same samples as those used in the X-ray and light scattering studies using AC impedance spectroscopy. Measurements will be made over a wide range of block copolymer compositions, salt concentration, temperature, and annealing conditions. NON-TECHNICAL SUMMARY:The fundamental work proposed in this project is motivated by the need to design safe rechargeable batteries for clean energy-related applications such as electric vehicles and stationary energy storage. The proposed nanostructured ion-conducting solid will be used as the electrolyte in a lithium battery. By replacing the flammable liquid electrolyte that is used in current lithium batteries by a solid, one can use higher energy electrodes that, in turn increase the energy density of the battery. The absence of a flammable component makes the battery safe. The co-PIs will use solid-state batteries for demonstrations in their outreach activities involving high school students. Garetz works with the David Packard Center for Technology and Educational Alliances in New York City to mentor local high school students in fields related to technology and research. Balsara works with Math and Science Summer Academy program at Berkeley, and enrichment program which brings students from the Oakland School District to the University of California. The PIs will continue an ongoing collaboration with Professor M. Banaszak at A. Mickiewicz University, Poland on the subject of ion-containing polymers that arose from an NSF-sponsored workshop in Poland.