Superionicity: A new path for polymer electrolytes
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Rachel A. Segalman, Ph.D
University of California Santa Barbara
Abstract: Superionicity: A new path for polymer electrolytes
While polymer electrolytes hold the promise of improving safety and mechanical durability of electrochemical devices, most suffer from relatively low ionic conductivities especially at ambient temperature. Long-range Li-ion transport in most solid polymeric electrolytes occurs via a vehicular mechanism that couples polymer segmental dynamics to electrolyte performance. Consequently, the majority of successful polymer electrolyte candidate materials are extensively plasticized, representing a tradeoff between desirable mechanical properties and electrochemical functionality. Polymeric ionic liquids (PILs) capable of conducting multivalent ions are based on transient metal-ligand coordination interactions and the conductivity is related to both the segmental motion of the backbone and the lifetime of the metal-ligand bond. In this talk we demonstrate zwitterionic polymers based on PILs that exhibit superionic conductivity -- a mechanism of transport far more weakly coupled to backbone mobility due to the availability of strategically placed free volume elements in the structure. These materials demonstrate high Lithium ion conductivities (10-3 S/cm) and cation transport numbers (t+=0.67) despite their modest glass transition temperatures (0-25°C).
Rachel A. Segalman received her B.S. from the University of Texas at Austin and Ph.D from the University of California, Santa Barbara. She was a postdoctoral fellow at the Université Louis Pasteur before joining the faculty of UC Berkeley and Lawrence Berkeley National Laboratories from 2004-2014. During a portion of this time she also served as the Materials Science Division Director at Lawrence Berkeley National Laboratories. In 2014, she moved to UC Santa Barbara to be the Kramer Professor of Chemical Engineering and Materials and became Department Chair of Chemical Engineering in 2015. In 2018 she also became the Schlinger Distinguished Chair of Chemical Engineering and the Associate Director of the UT/UCSB/LBL EFRC: Center for Materials for Water and Energy Systems. She is the co-editor of the Annual Reviews of Chemical and Biomolecular Engineering and an associate editor of ACS Macro Letters. Segalman’s group works on controlling the structure and thermodynamics of functional polymers for energy applications including polymeric ionic liquids and semiconducting and bioinspired polymers. Among other awards, Segalman received the Journal of Polymer Science Innovation Award, the Dillon Medal from the American Physical Society, the Presidential Early Career Award in Science and Engineering, is an Alfred P. Sloan Fellow and a Camille Dreyfus Teacher Scholar. She is also a Fellow of the American Physical Society and was elected to the American Academy of Arts and Sciences and the National Academy of Engineering.
Statement of Technical Interest: Expertise includes controlling the hierarchical structure and thermodynamics of energy-relevant polymers including polymeric ionic liquids and semiconducting and bioinspired polymers. This includes a desire to understand the molecular-scale design rules and synthesis that lead to self-assembly and mesoscale architectures that then control macroscopic transport properties. We seek to understand the role of monomer sequence and specific interactions, as well as chain shape, on self-assembly in polymers whose architecture is determined by a desired functionality rather than classical Gaussian chain statistics. We then bridge into understanding how these same structural features affect energy relevant properties such as ionic, thermal, or electronic conductivity and surface activity. Applications of relevance include battery electrolytes and binders, organic thermoelectrics, semiconducting polymer devices, separation membranes, and bioinspired polymers for applications ranging from anti-fouling coatings to photoresists.