Effect of Thickness and Surface Decoration of Lithium-Metal Electrodes for Lithium-Metal Batteries
Authors: Stan Marian Cristian , Kolek Martin , Börner Markus , Liebenau Dominik , Schappacher Falko , Bieker Peter , Winter Martin 
Published: February 2020

Lithium-metal batteries (LMBs) regained recently increased interest as potential next-generation battery technology besides the lithium ion technology (LIB).[1,2] This originates in the promised enhanced energy density of such batteries when lithium-metal is considered as anode material and also because of the variety of compatible cathode materials, e.g. high voltage lithium transition metal oxide, sulfur and oxygen cathodes. Nevertheless, in laboratory conditions, it is generally accepted that the amount of lithium-metal anode active materials exceeding balanced capacity levels for cathode and anode which are required in practical cells. Such an imbalance is resulting in reduced energy density values. An oversized lithium-metal anode is actually needed due to the heterogeneous lithium electrodeposition and electrodissolution behavior, which results in poor cycling performance, low Coulombic efficiencies, continuous formation of the solid electrolyte interphase (SEI), electrolyte consumption, loss of active material, corrosion and formation of high surface area lithium (HSAL) that leads to dendritic lithium deposits.[3,4] In order to minimize the existing capacity gap between the lithium-metal anode and the cathode materials, thin lithium-metal electrodes (with reduced excess capacity) are required. It has been reported that the amount of capacity used in lithium-metal electrodes has also an effect on the quality (morphology) of the lithium deposits.[5]

The surface composition of the lithium-metal electrodes can be adjusted by thinning the surface native film[6] while the interphase to the electrolyte can be tuned by means of an artificial-SEI. The latter approach focuses on creating an artificial-SEI that is able to homogenize the flux of Li-ions during the electrodeposition process resulting in stabilized and enhanced electrochemical performances. In this work, we would like to present the effect that the thickness of the lithium-metal electrodes and artificial-SEI on such electrodes has on the cycling performances of lithium-metal cells. Furthermore, the effect of the different areal capacities, from laboratory grade (>150 µm) to thin lithium foil (<30 µm), and with additional artificial-SEI on the thermal stability of such cells (CR 2032) is also evaluated.

Acknowledgements:

The work presented here is funded through the Europeans Union's Horizon 2020 research and innovation programme under the Grant Agreement No. 666221 within the HELIS project. The authors also acknowledge the German Federal Ministry of Research and Education (BMBF) for the funding of the project MEET Hi-EnD II (FKZ 03XP0084A).

References:

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[2] R. Schmuch, R. Wagner, G. Hörpel, T. Placke, M. Winter, Nature Energy, 2018, 3, 267–278.

[3] W. Xu, J. Wang, F. Ding, X. Chen, E. Nasybulin, Y. Zhang, J.-G. Zhang, Energy & Environmental Science, 2014, 7, 513–537.

[4] M. Winter, Zeitschrift fuer Physikalische Chemie, 2009, 223, 1395–1406.

[5] S. Jiao, J. Zheng, Q. Li, X. Li, M.H. Engelhard, R. Cao, J.-G. Zhang, W. Xu, Joule, 2018, 2, 110–124.

[6] J. Becking, A. Gröbmeyer, M. Kolek, U. Rodehorst, S. Schulze, M. Winter, P. Bieker, M.C. Stan, Advanced Materials Interfaces, 2017, 4, 1700166.