Formation sequence of solid-electrolyte-interphases and impacts on lithium deposition and dissolution on copper: an in-situ atomic force microscopic study

Abstract

Copper is a most widely used substrate for Li deposition and dissolution in lithium metal anodes, which are complicated by the formation of solid-electrolyte-interphases (SEIs) whose physical and chemical properties can affect Li deposition and dissolution significantly. However, initial Li nucleation and growth on bare Cu creates Li nuclei that only partially cover the Cu surface so that SEI formation could proceed not only on Li nuclei but also on the bare region of the Cu surface with different kinetics, which may affect the follow-up processes distinctively. In this paper, we employ in-situ atomic force microscopy (AFM) together with X-ray photoelectron spectroscopy (XPS) to investigate how SEIs formed on Cu surface, without Li participation, and on the surface of growing Li nuclei, with Li participation, affect the components and structures of the SEIs, and how the formation sequence of the two kinds of SEIs along with Li deposition affect subsequent dissolution and re-deposition processes in a pyrrolidinium-based ionic liquid electrolyte containing small amount of water. Nanoscale in-situ AFM observations show that sphere-like Li deposits may have differently conditioned SEI-shells, depending on whether Li nucleation is precedent with formation of the SEI on Cu. Models of integrated-SEI shells and segmented-SEI shells are proposed to respectively describe SEI shells formed on Li nuclei and the SEI shells sequentially-formed on Cu and then on Li nuclei. “Top-dissolution” are observed for both types of shelled Li deposits, but the integrated-SEI shells only show wrinkles which can be recovered upon Li re-deposition while the segmented-SEI shells are apparently top-opened due to mechanical stresses introduced at the junctions of the top regions and become “dead” SEIs which forces subsequent Li nucleation and growth in the interstice of the dead SEIs. Our work provides insights on the impact mechanism of SEIs on Li deposition and dissolution on foreign substrates, and reveals that SEIs could be more influential to Li dissolution and spatial integration of SEI shells on Li deposits is important to improving the reversibility of deposition and dissolution cycling.

Supplementary files

Article information

Article type
Paper
Submitted
12 Jul 2021
Accepted
06 Oct 2021
First published
07 Oct 2021

Faraday Discuss., 2021, Accepted Manuscript

Formation sequence of solid-electrolyte-interphases and impacts on lithium deposition and dissolution on copper: an in-situ atomic force microscopic study

W. Wang, Y. Gu, H. Yan, K. Li, Z. Chen, Q. Wu, C. Kranz, J. Yan and B. Mao, Faraday Discuss., 2021, Accepted Manuscript , DOI: 10.1039/D1FD00043H

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