Abstract
Electrified interfaces are critical to the performance of energy systems and often demonstrate substantial complexity under operating conditions. A nanoscale understanding of the interfacial microenvironment, i.e., the solid-electrolyte interphase (SEI), in lithium-mediated nitrogen reduction (Li-N2R) is key for realizing efficient ammonia (NH3) production. Herein, we used time-resolved neutron reflectometry (NR) to observe SEI formation under Li-N2R conditions. We found that the LiBF4-based electrolyte provided a substantially more well-defined SEI layer than previous SEI NR interrogations that used LiClO4, highlighting the underlying chemistry that dictates electrolyte design and enabling new NR-based studies. Using in situ NR, we found that the LiBF4-derived SEI under Li-N2R conditions comprises a thick, diffuse outer layer and a thin, compact inner layer at low current cycling (<2 mA/cm2), revealing a structure which ex situ studies have not been able to probe. Increased current cycling and sustained current cycling led to the merging of the layers into a single-layer SEI. We used isotope contrast methods with d6-EtOH and d8-THF to drive time-resolved tracking of SEI growth at low current cycling, revealing that the proton donor modifies the inner layer, and the solvent modifies the outer layer. Li dendritic growth was observed in the absence of a proton donor. Neutron absorption also indicated the presence of boron in the SEI, underscoring the value of neutron-based interrogation. Our results inform Li-based systems and reaction microenvironments, and these methods can be applied broadly to interfacial energy technologies.
| Original language | English |
|---|---|
| Pages (from-to) | 12469-12480 |
| Number of pages | 12 |
| Journal | Journal of the American Chemical Society |
| Volume | 147 |
| Issue number | 15 |
| DOIs | |
| State | Published - Apr 16 2025 |
Funding
V.A.N., P.B., N.H.D., J.B.V.M., I.C., and T.F.J. acknowledge funding from the Villum Fonden (V-SUSTAIN grant 9455). V.A.N. was supported under the National Science Foundation Graduate Research Fellowship Program under grant no. DGE-1656518 and the Camille and Henry Dreyfus Foundation. S.W.L., I.R.A., W.L.W., A.C.N., W.A.T., and T.F.J. acknowledge support from the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division, Catalysis Science Program through the SUNCAT Center for Interface Science and Catalysis for ICP-MS method development and neutron reflectometry-compatible electrochemical cell design. This research was performed at the Spallation Neutron Source, a Department of Energy (DOE) Office of Science User Facility operated by ORNL, which is managed by UT-Battelle LLC for DOE under Contract DE-AC05-00OR22725. The beam time was allocated to the Liquid Reflectometer on proposal number IPTS-30384. NMR measurements were supported by the NIH High-End Instrumentation grant (1 S10 OD028697-01) and conducted at Stanford University. Part of this work was performed at the Stanford Nano Shared Facilities (SNSF), supported by the National Science Foundation under award no. ECCS-2026822. This research was performed in part at the nano@Stanford laboratories, which are supported by the National Science Foundation, part of the National Nanotechnology Coordinated Infrastructure under award no. ECCS-2026822. We thank Dr. Hanyu Wang, Professor Matteo Cargnello, and Dr. Eric McShane for their helpful conversations. M.D. would like to thank Dr. Andrew Caruana, Dr. Christy Kinane, and Dr. Brian Maranville for their input on nested sampling.