CAREER: NMR of the Solid Electrolyte Interphase on Li Metal Anodes

Lithium metal batteries are expected to enable high energy density applications in electrified transportation and grid storage. However, lithium metal components suffer from severe interfacial instabilities, leading to efficiency losses and serious safety concerns. In the region between the negative electrode and the liquid electrolyte, a solid electrolyte interphase (SEI) is produced by the spontaneous breakdown of electrolyte compounds. The SEI in lithium metal batteries is hypothesized to play a key role in lithium deposition but is challenging to assess with traditional materials characterization methods. In this proposal, we use nuclear magnetic resonance (NMR) spectroscopic techniques to create a molecular-level description of the chemical reactions that occur at lithium metal interfaces to ultimately mitigate the formation microstructures for safe and efficient battery operation. This research program is strongly coupled with educational activities to bridge gaps in NMR training through a hands-on 'In Situ NMR of Energy Materials' workshop aimed at local researchers and industry partners. These efforts are complemented with plans to broaden the participation of underrepresented and underprivileged women in undergraduate research through a partnership with the Science Pathways Scholars Program at Barnard (women's college). We will leverage connections within the community to host a TEDx conference to improve NMR education for the general public and generate excitement for aspiring youth and their families by highlighting the use of NMR for vaccine development, energy storage, disease treatment, and the arts.

The objective of this proposal is to use NMR spectroscopy to elucidate the chemical mechanisms underpinning SEI formation and function, and to use that knowledge to achieve the desired smooth Li deposition in Li metal batteries. The key challenge in obtaining this information is that the complex SEI structure evolves during Li deposition/dissolution and is easily disturbed when removed from its native operating environment. In order to overcome these issues, we propose to use a combination of solution and solid-state NMR, together with magnetic resonance imaging (MRI) to provide a comprehensive assessment of the composition, arrangement, and dynamics of the SEI that forms on the surface of Li metal anodes. In situ NMR/MRI provides accurate chemical, spatial, and temporal information on multiphase interfacial phenomena to elucidate the role of electrolyte decomposition, anode/cathode crosstalk, and ion transport on lithium deposition behavior. Assignment of the interfacial chemistries and transport phenomena that dictate the formation of electrochemically inactive Li will allow us to describe, at the molecular-level, chemical mechanisms underpinning low Coulombic efficiency. We will also educate students and industrial researchers on in situ NMR methods using cost-effective electrode fabrication techniques and widely available electrochemical and NMR equipment so that they can go beyond current, 'black box' approaches to collect and analyze data.

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.