Chemical and structural design of inorganic-organic layers for stabilized Li anodes

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This project will generate fundamental knowledge and identify design principles for developing improved battery anodes based on lithium metal. This knowledge is critical for enabling rechargeable high energy density lithium electrode batteries for electric vehicle-based transportation and for compact storage of renewably generated electricity. This work will advance understanding of how this active material forms beneficial, ionically-conductive material films that have the potential to impart improved stability, cycling efficiency and lifetime. The insights developed in this work can be used to design new fabrication procedures and improved interfaces for lithium anodes with higher degrees of stability, which is currently a key issue with this technology. This work could lead to lighter, longer-lasting and more compact transportation batteries, which supports improved national energy sustainability, reduced air pollution, and a potential path to more widespread electric vehicle adoption. The educational and outreach plans will leverage and add to existing programs at the Massachusetts Institute of Technology to benefit K-12 students and improve public literacy related to energy storage, batteries and electrochemistry within the Cambridge and Greater Boston areas. This project specifically entails development of new educational materials and teaching modules to support public school science teachers in teaching energy conversion and storage concepts, and workshops to be hosted on MIT campus in collaboration with the MIT Edgerton Center and MIT Museum. The PI also plans inclusion of Greater Boston community college students in summer research.The rechargeable Li electrode is an essential element of the most promising, "beyond Li-ion" advanced battery chemistries. However, Li electrodes do not currently cycle with acceptable Coulombic efficiency, safety, or lifetime. This project investigates how oxide and fluoride gases interact with Li metal, and impart chemical, morphological, and electrochemical properties favorable to formation of an artificial solid electrolyte interphase (SEI). This research includes systematic studies of Li reactions with gases that yield ionic compounds on the Li surface, allowing for independent tuning and study of the formed inorganic interface. By exploring three gases that are projected to yield a comprehensive set of distinct inorganic-layer compositions, this work will contribute new fundamental understanding of how the SEI chemical, structural and electronic properties govern performance, and identify optimized inorganic-layer chemistries that can drive future additive development and optimization. The major tasks that comprise the research plan are: (1) Determine the chemical and structural properties of films formed when fresh Li reacts in gas environments, using X-ray Photoelectron Spectroscopy, Fourier-Transform Infrared Spectroscopy, electron microscopy and thermal/microstructural modeling; (2) Perform cycling measurements and quantify key electrochemical metrics of Coulombic efficiency, cycle life, and short-circuit time; (3) Measure the physical and electrochemical properties of the reactant gas, including reaction kinetics, transport parameters, and electrochemical activity within battery environments, which are relevant to SEI-healing processes; (4) Probe the feasibility and mechanisms of healing reactions using these gases. This effort will contribute new knowledge of how gas molecules decompose in far-from-equilibrium reactions at the surface of a Li electrode, and how this reactivity can be exploited to develop optimized interphases for improved efficiency and cycle life.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.