Interphase and Penetration Dynamics for Stable Alkali Metal Anodes

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A prosperous society with a sustainable energy future relies on advanced energy storage technologies. While lithium (Li)-ion batteries have changed lives through electronic devices, portable power tools and electric cars, further increasing the state of the art for energy storage has been difficult. One approach is to replace the bulky graphite anode with an ultrathin film of Li metal anode to nearly double the energy density of the battery. However, this type of battery material is subjected to formation of finger-like dendritic growths of lithium metal on the anode. These can grow into the electrolyte and separator components and cause an electrical short circuit that can destroy the battery and present a safety hazard. Suppressing this root cause of electrical short circuits is an urgent need, especially at higher current densities when fast recharge is required for high-capacity next-generation batteries. This fundamental research project addresses the study of formation of the component flaws (e.g. the dendrites and electrode coatings) that cause a potential short circuit and also loss in energy capacity. This project will generate new understanding that will enable superior designs of electrodes that will lead to safer, high energy density batteries. The project will also benefit the education of graduate, undergraduate and K-12 students. A summer program will be establish that will target underrepresented high school age students and high school teachers using engineering concepts of metal-based batteries.This study focuses on the interphase and metal penetration dynamics of lithium, sodium, and potassium metal anodes, investigating (1) how the dynamics of the macroscopic electrode-separator instability will naturally select just a few disparate pores for metal penetration, at low current densities and areal capacities, regardless of the uniformity of deposition; (2) the actual metal growth mechanisms in the selected pores; and (3) the in situ formation dynamics of the SEI microstructures and the impact on the macroscopic and microscopic dynamics in (1) and (2). It is intended to be the first study to establish a quantitative understanding of pore-selection and in-pore growth dynamics during alkali metal penetration through porous separators. Unique transparent capillary cells will be monitored operando under optical microscope. Advanced characterization and imaging technologies at atomic and nanoscales, such as cryo-transmission electron microscopy, will be used to confirm the characteristic lengths of SEI microstructures in the lateral direction. Through the intimately combined experimental and theoretical investigation, a new theoretical framework that can seamlessly connect the domain experiments will be developed to guide the holistic design of stable alkali metal anodes.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.