Comparative Evaluation of Ionic Transport Mechanisms in Solid-State Electrolytes

Regents Of The University Of Michigan - Ann Arbor, Ann Arbor MI

Investigators

Abstract

NON-TECHNICAL DESCRPTION: A key aspect towards achieving batteries with energy and power densities that are competitive with fossil fuel is to develop solid-state electrolytes for use as the membrane that separates the anode and cathode. The most important property of this membrane, which facilitates the electrochemical process associated with energy conversion, is to exhibit high ionic conductivity. This issue is why current battery technologies rely on liquid electrolytes. Solid-state electrolytes allow for a more compact form factor, safer operation, and better longevity of batteries, but their ionic conductivity must be improved. To accomplish this goal, various schools of thought and types of materials, including inorganic glasses, fine-grained ceramics, and composites containing an organic plasticizer are being pursued. To date, much of this work has been done by trial and error. In the present project, the optimal materials design criteria for solid-state electrolytes are identified through a comparative study that involves a series of carefully conceived experiments and atomistic computer simulations. This research reveals the underlying fundamental relationships between materials structure, their mechanical properties, and ionic conductivities, including the development of improved theoretical models for the interpretation of experimental findings, which are capable of predicting the optimal materials design for desired performance characteristics. TECHNICAL DETAILS: Solid-state battery electrolytes are key to the advancement of green renewable energy storage technologies. In this research, the materials design criteria are being developed for solid-state electrolytes that exhibit the required high transport rates and transference numbers for small charge carrier cations. Additionally, these electrolytes must maintain a mechanical rigidity sufficient to suppress lithium dendrite growth and safely separate electrodes in self-supporting device structures, and possess an electrochemical stability range wide enough to accommodate large electrode potential differences. The current scope of materials design concepts encompasses materials from crystalline to amorphous, and from inorganic to organic, and with this research the most effective approach is being identified. To this end, the decisive ionic transport mechanisms are systematically isolated by formulating a series of prototype materials systems, each one selectively exposing the influence on the cation mobility that specific structural features within the major materials types have, including interfacial structures in polycrystalline ceramics, plasticizer phases in hybrid organic-inorganic composites, and engineered defects in ion-exchanged oxide glasses. These experiments are coupled with extensive atomistic simulations to interpret experimental findings and to develop theoretical models that facilitate a reliable and transferrable design strategy for solid-state electrolytes. Undergraduate and graduate students, as well as postdoctoral fellows are engaged in research that provides training in both computational and experimental methods of investigation, and that advances the National Materials Genome Initiative mandate through the development of computational tools for predictive materials design. The PI is establishing a bridge program to attract students graduating with a Masters degree from Minority-Serving Institutions (MSIs) with terminal programs, into Doctoral programs at the University of Michigan. He also helps organize the High School Teachers Materials Camp sponsored by ASM International and hosted by his department since 2002.