Mechanism for Lithium Dendrite Formation in Solid State Electrolytes

University Of Maryland, College Park, College Park MD

Investigators

Abstract

The need to store energy from intermittent renewable energy sources and the ongoing electrification of light-duty vehicle transportation increase the demand for high energy density batteries that have acceptable durability and cost. The utilization of lithium (Li) metal as the battery anode holds great potential to significantly improve the energy density. However, thus far, use of this anode material has been unsuccessful with the conventional liquid electrolytes because of compromised durability and safety issues arising from Li dendrite growth that shorts the battery. Solid electrolytes have been considered as the ideal solution to prevent dendrite growth because of their high mechanical strength. However, recent reports indicate formation of lithium dendrites in Li7La3Zr2O12 (LLZO) solid electrolytes by mechanisms that remain inconclusive. This fundamental research project aims to elucidate the origin of lithium dendrite formation in LLZO solid electrolytes. The scientific insights will be used to design solid electrolytes that result in rechargeable Li batteries with improved energy and power densities and improved lifetime. The interdisciplinary nature of this research will provide training opportunities for researchers at all levels including postdoctoral researcher, graduate and undergraduate students in the fields of electrochemistry, materials sciences and energy. Additional outreach activities include mentoring undergraduates through the Chem-E Car and GEMSTONE programs at the University of Maryland College Park. The overall objective of this fundamental engineering science project is to identify the mechanisms of lithium dendrite formation in LLZO solid electrolytes, and to use these insights to design new solid electrolytes for dendrite-free Li plating at large current densities. The dynamic evolution of depth distribution of Li dendrites in LLZO will be studied using an in-situ neutron depth profile (NDP) technique. A precise three-dimensional lithium distribution in LLZO will be reconstructed using focused ion beam scanning electron microscopy (FIB-SEM). A computational study using first-principle calculation at the atomic scale and electro-chemo-mechanical modeling at the continuum level will be implemented to understand the distribution of lithium dendrites in LLZO. Combining the advantages of NDP (in situ, non-destructive, lithium selective, statistical), FIB-SEM (high-resolution, chemical analysis), and the computation studies at both atomic-level and continuum level, unprecedented information will be obtained on the mechanism of lithium dendrite formation in LLZO. Novel approaches to improve the dendrite suppression capability of LLZO will also be tested based on the new understandings. The fundamental knowledge gained from this project will promote the development of safe, high-energy all-solid-state Li batteries. 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.