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whether LiH is a reaction intermediate in H2 formation or a by-product of the reaction. The observed formation of Li3N, followed by LiNH2 support the previously proposed mechanism of ammonia formation. Overall, this study highlights the crucial role of the SEI layer in limiting proton transport to plated lithium, which is necessary for higher selectivity toward ammonia production. LiF was confirmed as a key component of the SEI layer formed by LiBF4, likely due to its easy formation and ability to reform the SEI layer after cracks appear. Additionally, reaction intermediates related to both ammonia and hydrogen formation were detected and characterized.

is likely undesirable, as it diminishes the protective effects of the SEI layer. However, the decrease in lithium peak intensity slowed after a short time, indicating partial SEI layer reformation. This rapid reformation of the SEI layer in fluorine-containing electrolytes, attributed to the easy formation of LiF, is known to improve the stability of lithium metal batteries. Similarly, in Li-NRR, fast SEI restoration limits the exposure of plated lithium, even after cracks form in the SEI.

The formation of LiH had previously been suggested but not experimentally observed until now. It remains uncertain

PRINCIPAL PUBLICATION AND AUTHORS

Operando investigations of the solid electrolyte interphase in the lithium mediated nitrogen reduction reaction, N.H. Deissler (a), J.B.V. Mygind (a), K. Li (a), V.A. Niemann (b), P. Benedek (b), V. Vinci (c), S. Li (a), X. Fu (a), P.C.K. Vesborg (a), T.F. Jaramillo (b), J. Kibsgaard (a), J. Drnec (c), I. Chorkendorff (a), Energy Environ. Sci. 17, 3482-3492 (2024); https:/doi.org/10.1039/D3EE04235A (a) Department of Physics, Technical University of Denmark, Kongens Lyngby (Denmark) (b) Department of Chemical Engineering, Stanford University, Stanford, California (USA); SUNCAT Center for Interface Science and Catalysis, SLAC National Accelerator Laboratory, Menlo Park, California (USA) (c) ESRF

Fig. 75: a) Temporal evolution of the Li (110) peak intensities for various electrolyte compositions. b) Working electrode potentials measured during the experiments corresponding to the different electrolyte conditions. c) Temporal changes in peak intensities of identified SEI species and reaction intermediates during the experiments.