Fundamental Understanding of SEI Effects on Li Dendrite Formation and Growth

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Lithium ion batteries are the state-of-the-art choice for powering today's electric and hybrid electric vehicles. The energy density and power capability are limited; new chemistries are needed to increase the performance of the electric vehicle. Replacing the graphite electrodes in the commercialized lithium-ion batteries with lithium metal is expected to boost the energy density of batteries significantly. However, research efforts to use lithium metal electrodes in batteries have failed due to non-uniform deposition of lithium metal during charge and discharge cycles. This project will utilize several state-of-the art computer simulation tools and real-time microscopy techniques to investigate the lithium metal deposition in various battery electrolytes. In particular, the project will address how the by-products of electrolyte reactions with lithium metal affect the growth and morphology of lithium dendrites. The formation of these filaments in the battery shorts the battery causing failure. The results of this project will pave the road for developing high energy density lithium metal batteries. Several venues for integrating research with undergraduate and graduate education and outreach activities at University of Illinois at Chicago (UIC) will occur as a result of this project. Graduate and undergraduate students will be exposed to several advanced microscopy tools and computer simulation packages that will provide a unique set of research experience. Outreach activities are planned to disseminate the results of this study to high school and undergraduate students and motivate them to pursue studies related to electrochemical energy storage technologies. Outreach activities for local high school female and underrepresented students in STEM during the UIC-Mechanical and Industrial Engineering Department Open House and UIC Summer Youth Program will be conducted. Lithium-metal electrodes have the potential to enable lightweight and high energy density batteries for transportation propulsion applications. A major obstacle to achieve this goal remains on the non-uniform deposition of lithium metals that appear in the form of fibrous or dendritic morphology. These lithium dendrites can poke through the electrolyte and separator of batteries and eventually result in electrical short circuit potentially causing fire. Significant research has been conducted to develop prevention mechanisms of Li dendrite growth; however, the progress has been limited due to the lack of fundamental understanding on the formation and growth of the dendrites. The fundamental questions such as how Li dendrites are formed, grown and split under the influence of the solid electrolyte interface (SEI) remain unanswered. The PIs will employ a multi-scale and multi-physics approach using advance experimental and theoretical methods such as in-situ transmission electron microscopy (TEM), in-operando optical microscopy, electrochemical impedance spectroscopy (EIS), density functional theory (DFT) calculations, and phase-field modeling (PFM) to study the growth of Li dendrites under the SEI influence.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.