Fluorine-Substituted Halide Solid Electrolytes with Enhanced Stability toward the Lithium Metal

Priya Ganesan; Mervyn Soans; Musa Ali Cambaz; Ramon Zimmermanns; Ritambhara Gond; Stefan Fuchs; Yang Hu; Sebastian Baumgart; Mohsen Sotoudeh; Dominik Stepien; Helge Stein; Axel Groß; Dominic Bresser; Alberto Varzi; Maximilian Fichtner

doi:10.1021/acsami.3c03513

Fluorine-Substituted Halide Solid Electrolytes with Enhanced Stability toward the Lithium Metal

ACS Appl Mater Interfaces. 2023 Aug 16;15(32):38391-38402. doi: 10.1021/acsami.3c03513. Epub 2023 Aug 1.

Authors

Priya Ganesan^{1

2}, Mervyn Soans^{1

2}, Musa Ali Cambaz^{1

2}, Ramon Zimmermanns², Ritambhara Gond³, Stefan Fuchs², Yang Hu^{1

2}, Sebastian Baumgart⁴, Mohsen Sotoudeh⁴, Dominik Stepien^{1

2}, Helge Stein², Axel Groß^{1

4}, Dominic Bresser^{1

2}, Alberto Varzi^{1

2}, Maximilian Fichtner^{1

2}

Affiliations

¹ Helmholtz Institute Ulm (HIU), Helmholtzstrasse 11, 89081 Ulm, Germany.
² Karlsruhe Institute of Technology (KIT), P.O. Box 3640, 76021 Karlsruhe, Germany.
³ Department of Chemistry-Ångström Laboratory, Uppsala University, P.O. Box 538, 751 21 Uppsala, Sweden.
⁴ Institute of Theoretical Chemistry, Ulm University, Oberberghof 7, 89081 Ulm, Germany.

PMID: 37527285
PMCID: PMC10437042 (available on 2024-08-01)
DOI: 10.1021/acsami.3c03513

Abstract

The high ionic conductivity and good oxidation stability of halide-based solid electrolytes evoke strong interest in this class of materials. Nonetheless, the superior oxidative stability compared to sulfides comes at the expense of limited stability toward reduction and instability against metallic lithium anodes, which hinders their practical use. In this context, the gradual fluorination of Li₂ZrCl_6-xF_x (0 ≤ x ≤ 1.2) is proposed to enhance the stability toward lithium-metal anodes. The mechanochemically synthesized fluorine-substituted compounds show the expected distorted local structure (M2-M3 site disorder) and significant change in the overall Li-ion migration barrier. Theoretical calculations reveal an approximate minimum energy path for Li₂ZrCl_6-xF_x (x = 0 and 0.5) with an increase in the Li⁺ migration energy barrier for Li₂ZrCl_5.5F_0.5 in comparison to Li₂ZrCl₆. However, it is found that the fluorine-substituted compound exhibits substantially lower polarization after 800 h of lithium stripping and plating owing to enhanced interfacial stability against the lithium metal, as revealed by density functional theory and ex situ X-ray photoelectron spectroscopy, thanks to the formation of a fluorine-rich passivating interphase.

Keywords: Li2ZrCl6; battery; fluorine substitution; lithium metal; solid electrolyte.