Fluorination of Ni-Rich Lithium-Ion Battery Cathode Materials by Fluorine Gas: Chemistry, Characterization, and Electrochemical Performance in Full-cells

Ulf Breddemann, Johannes Sicklinger, Florian Schipper, Victoria Davis, Anna Fischer, Korbinian Huber, Evan M. Erickson, Michael Daub, Anke Hoffmann, Christoph Erk, Boris Markovsky, Doron Aurbach, Hubert A. Gasteiger, Ingo Krossing

Research output: Contribution to journalArticlepeer-review

13 Scopus citations

Abstract

The mild fluorination of Ni-rich NCM CAMs (NCM=nickel-cobalt-manganese oxide; CAM=cathode active material) with a few hundred mbar of elementary fluorine gas (F2) at room temperature was systematically studied. The resulting fluorinated CAMs were fully analyzed and compared to the pristine ones. Fluorination at room temperature converts part of the soluble basic species on the CAM-surface into a protecting thin and amorphous LiF film. No formation of a metal fluoride other than LiF was detected. SEM images revealed a smoothened CAM surface upon fluorination, possibly due to the LiF film formation. Apparently due to this protecting, but insulating LiF-film, the fluorinated material has a reduced electrical conductivity in comparison to the pristine material. Yet, all fluorinated Ni-rich NCM CAMs showed a considerably higher press density than the pristine material, which in addition increased with higher fluoride concentrations. In addition, fluorination of the Ni-rich CAMs led to the chemically induced formation of small amounts of water, which according to TGA-MS-measurements can be removed by heating the material to 450 °C for a few hours. Overall, the tested fluorinated NCM 811 samples showed improved electrochemical performance over the pristine samples in full-cells with graphite anodes at 30 °C and 45 °C after 500 cycles. Moreover, the fluorination apparently reduces Mn and Co cross talk from the CAM to the anode active material (AAM) through the electrolyte during charge/discharge.

Original languageEnglish
Pages (from-to)632-645
Number of pages14
JournalBatteries and Supercaps
Volume4
Issue number4
DOIs
StatePublished - Apr 2021

Bibliographical note

Publisher Copyright:
© 2020 The Authors. Batteries & Supercaps published by Wiley-VCH GmbH

Funding

This work was supported by the [Albert-Ludwigs-Universität Freiburg], by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany's Excellence Strategy – EXC-2193/1 – 390951807 and by BASF SE in the Battery Materials Network. The use of the SEM-EDX set up, acquired through the BMBF project EDELKAT (FKZ 03X5524), is gratefully acknowledged. We would like to thank Anita Becherer for support in obtaining SEM-EDX measurements and Mr. Andreas Warmbold for executing the TGA/DTA measurements. Finally, we would also like to thank Hans Beyer for valuable suggestions. Open access funding enabled and organized by Projekt DEAL.

FundersFunder number
BASF
Deutsche ForschungsgemeinschaftEXC-2193/1 – 390951807
Bundesministerium für Bildung und ForschungFKZ 03X5524
Albert-Ludwigs-Universität Freiburg

    Keywords

    • Lithium-ion batteries
    • Ni-rich cathode materials
    • electrochemical testing.
    • fluorine gas
    • mild surface fluorination

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