Deciphering the Competing Mechanisms of Li Microstructure Formation in Solid Electrolytes with Nuclear Magnetic Resonance Spectroscopy (NMR) and Imaging (MRI)

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PART 1: NON-TECHNICAL SUMMARY This project tackles a critical challenge in battery technology that is widely used daily: the formation of tiny structures, called dendrites, within batteries. These dendrites can cause short circuits, limiting the power and lifespan of solid-state batteries, which are crucial for powering a sustainable energy future. The team aims to understand how these dendrites form and develop mitigating strategies. The research focuses on Li7La3Zr2O12 (LLZO), an important component in solid-state batteries. By using advanced techniques like nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI), the team hopes to uncover the root causes of dendrite formation. This understanding is vital for designing batteries with longer lifespans and higher efficiency.The outcomes of this research will enhance our understanding of battery technology and contribute to developing more efficient and sustainable energy storage solutions, directly benefiting society at large. The project also aims to develop new tools to study a broad range of functional materials, contributing to scientific knowledge in multiple fields. Moreover, it will establish a new course on advanced magnetic resonance techniques and broaden the participation of underrepresented groups in scientific research via several educational and outreach platforms. By addressing the major challenges associated with rechargeable batteries, this project will promote the progress of science and technology and advance the national welfare. PART 2: TECHNICAL SUMMARYLi microstructure formation in solid electrolytes results in battery short circuits, limiting the power density and lifespan of all-solid-state batteries (ASSBs). Unlike extensively studied liquid systems, dendrite formation in solids is complex and challenging to characterize. This project proposes two mechanisms for dendrite formation in solid electrolytes: non-uniform Li plating at the electrode-electrolyte interface (Mechanism 1) and reduction of Li+ ions at grain boundaries within solid electrolytes (Mechanism 2). While Mechanism 1 has been explored using electron and optical microscopy, Mechanism 2 remains less understood due to challenges in noninvasively probing bulk solids. To address this, the proposal employs nuclear magnetic resonance spectroscopy (NMR) and imaging (MRI) techniques. Specifically, the project aims to determine the source of Li dendrites using tracer-exchange NMR, create 3D images of dendrites within solid electrolytes using noninvasive 7Li/6Li MRI, and monitor real-time dendrite formation using in situ NMR and MRI, complemented by electron paramagnetic resonance studies. The chosen material system, Li7La3Zr2O12 (LLZO) and its derivatives represent a prominent oxide-based solid electrolyte with known dendrite formation issues. The research aims to distinguish between the proposed mechanisms and determine the dominant one with spatial and temporal resolution under varied conditions relevant to ASSB electrochemical cycling. Investigations on LLZO derivatives with diverse electronic conductivities will provide insights into the role of electronic conductivity in determining dendrite formation mechanisms and their distribution. The outcomes of this work will contribute to understanding and mitigating dendrite-related challenges, ultimately advancing the development of safer and more efficient solid-state 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.