Contributed Talk  - Thursday, 16 September I 14:40 PM (CEST)

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Beatrice Wolff: "Solid Electrolyte Interface Formation on Lithium Metal Anode Investigated by Nanomechanical Mapping"

Beatrice Wolff ᵃ ᵇ, Florian Hausena, ᵇ
ᵃ Forschungszentrum Jülich GmbH, Institute of Energy and Climate Research, IEK-9, 52425 Jülich, Germany
ᵇ RWTH Aachen University, Institute of Physical Chemistry, Landoltweg 2, 52074 Aachen, Germany

The application of lithium metal as anode material would allow batteries with drastically higher energy densities than current Li-ion batteries based on graphitic materials as anodes. However, the commercialisation of metallic lithium as anode material is currently hindered by two main challenges: On the one hand, lithium metal is thermodynamically unstable with respect to organic electrolytes. The reaction between lithium and the electrolyte consumes both materials causing a decrease in capacity and formation of a self-passivating surface film, the so-called solid electrolyte interphase (SEI) [1]. On the other hand, upon cycling of the battery, lithium deposits unevenly on the surface and forms dendrites of various shapes. This eventually leads to a short circuit of the battery and thus constitutes a significant safety risk.
In this contribution, we address the issue of understanding the formation process and composition of the SEI layer which forms upon reaction of lithium metal with the electrolyte. This understanding is necessary to tackle both challenges described above. Using nanomechanical mapping, we assess the topography as well as mechanical properties such as Young´s modulus and adhesion of the lithium metal surface simultaneously under operating conditions in relevant media. In particular, initial stages and dynamics of the SEI layer formation are probed. We clearly observe changes in the morphology of the evolving SEI layer. Moreover, the evolution of Young´s modulus over time provides interesting insights into the mechanical properties of the SEI layer. In addition, we compare the influence of different approaches of surface preparation as well as electrolyte composition on the SEI formation.

[1] X.-B. Cheng, R. Zhang, C.-Z. Zhao, F. Wei, J.-G. Zhang, Q. Zhang, A Review of Solid Electrolyte Interphases on Lithium Metal Anode, Adv. Sci., 3 (2016) 1500213.