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Yayuan Liu1 Yi Cui1

1, Stanford University, Stanford, California, United States

The physiochemical properties of the solid-electrolyte interphase (SEI), primarily governed by electrolyte composition, have a profound impact on the electrochemical cycling of metallic lithium (Li). Herein, we discovered that the effect of nitrate anions on regulating Li deposition previously known in ether-based electrolytes can be extended to carbonate-based electrolytes, which can dramatically alter the morphology of Li nuclei from dendritic to spherical, albeit extremely limited solubility. The effect can be attributed to the preferential reductive decomposition of nitrate anions during SEI formation that modifies the interfacial environment. And the mechanistic origins behind the phenomenon were investigated based on the structure, ion-transport property and charge transfer kinetics of the modified SEI utilizing advanced characterization techniques such as cryo transmission electron microscopy and ultramicroelectrode. Furthermore, to overcome the solubility barrier, a solubility-mediated sustained release methodology was introduced, in which nitrate anions were encapsulated in porous polymer gel and can be steadily dissolved during battery operation to maintain a high concentration at the electroplating front. As such, effective Li dendrite suppression and remarkably enhanced cycling stability can be achieved in both half- and full-cell configurations in corrosive carbonate electrolytes, significantly outperforming conventional electrolyte additives. The proposed approach is generally applicable in various carbonate-based electrolyte systems and can improve the reversibility of Li metal anode without sacrificing the stability, ionic conductivity, or the cost of electrolytes.

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