Redox Mechanisms and Migration Tendencies in Earth-Abundant 0.7Li2MnO3·0.3LiFeO2 Cathodes: Coupling Spin-Resolved X-ray Absorption Near Edge and X-ray Absorption Fine Structure Spectroscopies

Chun Yuen Kwok; Subhadip Mallick; Christopher J. Pollock; Arturo Gutierrez; Marm Dixit; Jason R. Croy; Mahalingam Balasubramanian

doi:10.1021/acs.chemmater.3c02111

Redox Mechanisms and Migration Tendencies in Earth-Abundant 0.7Li₂MnO₃·0.3LiFeO₂ Cathodes: Coupling Spin-Resolved X-ray Absorption Near Edge and X-ray Absorption Fine Structure Spectroscopies

Chun Yuen Kwok, Subhadip Mallick, Christopher J. Pollock, Arturo Gutierrez, Marm Dixit, Jason R. Croy, Mahalingam Balasubramanian

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Abstract

We report the use of iron 1s3p resonant X-ray emission processes to conduct spin-selective, high-energy resolution fluorescence detected X-ray absorption near-edge spectroscopy (HERFD-XANES) on an iron-containing, lithium- and manganese-rich, fully earth-abundant cathode material, Li_1.3Mn_0.5Fe_0.2O₂ (0.7Li₂MnO₃·0.3LiFeO₂). Coupling this technique with conventional Mn K-edge XANES and detailed extended X-ray absorption fine structure (EXAFS) analysis from both the Mn and Fe vantage points, we gain fundamental insights into the redox processes and migration tendencies of transition metals in this cathode material at the bulk level. We show that during the first charge, Fe³⁺ undergoes oxidation to form Fe⁴⁺ prior to the activation plateau. Toward the end of activation, a significant fraction of the iron is present as tetrahedral Fe³⁺. This observation reveals that iron migration from octahedral to tetrahedral sites and iron reduction are initiated during activation. Upon first discharge from the activated state, a continuous and overlapping reduction of both Fe and Mn is observed, with Fe largely restored back as an octahedrally coordinated Fe³⁺. The manganese local environment gradually changes to a distorted cooperative Jahn-Teller Mn³⁺ structure during discharge, with the clear presence of two Mn-O as well as two Mn-Mn correlation distances at 2.0 V. The significant reduction of manganese in the very first discharge is distinctly different from that seen in typical nickel-based lithium-manganese-rich materials but is similar to that observed for pure Li₂MnO₃. These findings shed light on key structure-property correlations in the cathode material and point to a causative relationship between the redox mechanisms as well as structural changes endured by the material and relatively poor performance during extended electrochemical cycling.

Original language	English
Pages (from-to)	300-312
Number of pages	13
Journal	Chemistry of Materials
Volume	36
Issue number	1
DOIs	https://doi.org/10.1021/acs.chemmater.3c02111
State	Published - Jan 9 2024

Funding

Support from the Vehicle Technologies Office of the U.S. Department of Energy (DOE), particularly from the Earth-abundant Cathode Active Materials (EaCAM) consortium, Tien Duong, Tina Chen, and Brian Cunningham, is gratefully acknowledged. This research is conducted at Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for DOE under contract DE-AC05-00OR22725 and Argonne National Laboratory, managed by UChicago Argonne, LLC, for DOE under DE-AC02-06CH11357. This research used resources of the Advanced Photon Source, a DOE Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory and the Center for High-Energy X-ray Sciences (CHEXS), which is supported by the National Science Foundation (BIO, ENG, and MPS Directorates) under award DMR-1829070.

Funders	Funder number
National Science Foundation	DMR-1829070
U.S. Department of Energy	DE-AC05-00OR22725
Office of Science
Argonne National Laboratory	DE-AC02-06CH11357

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Kwok, C. Y., Mallick, S., Pollock, C. J., Gutierrez, A., Dixit, M., Croy, J. R., & Balasubramanian, M. (2024). Redox Mechanisms and Migration Tendencies in Earth-Abundant 0.7Li₂MnO₃·0.3LiFeO₂ Cathodes: Coupling Spin-Resolved X-ray Absorption Near Edge and X-ray Absorption Fine Structure Spectroscopies. Chemistry of Materials, 36(1), 300-312. https://doi.org/10.1021/acs.chemmater.3c02111

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title = "Redox Mechanisms and Migration Tendencies in Earth-Abundant 0.7Li2MnO3·0.3LiFeO2 Cathodes: Coupling Spin-Resolved X-ray Absorption Near Edge and X-ray Absorption Fine Structure Spectroscopies",

abstract = "We report the use of iron 1s3p resonant X-ray emission processes to conduct spin-selective, high-energy resolution fluorescence detected X-ray absorption near-edge spectroscopy (HERFD-XANES) on an iron-containing, lithium- and manganese-rich, fully earth-abundant cathode material, Li1.3Mn0.5Fe0.2O2 (0.7Li2MnO3·0.3LiFeO2). Coupling this technique with conventional Mn K-edge XANES and detailed extended X-ray absorption fine structure (EXAFS) analysis from both the Mn and Fe vantage points, we gain fundamental insights into the redox processes and migration tendencies of transition metals in this cathode material at the bulk level. We show that during the first charge, Fe3+ undergoes oxidation to form Fe4+ prior to the activation plateau. Toward the end of activation, a significant fraction of the iron is present as tetrahedral Fe3+. This observation reveals that iron migration from octahedral to tetrahedral sites and iron reduction are initiated during activation. Upon first discharge from the activated state, a continuous and overlapping reduction of both Fe and Mn is observed, with Fe largely restored back as an octahedrally coordinated Fe3+. The manganese local environment gradually changes to a distorted cooperative Jahn-Teller Mn3+ structure during discharge, with the clear presence of two Mn-O as well as two Mn-Mn correlation distances at 2.0 V. The significant reduction of manganese in the very first discharge is distinctly different from that seen in typical nickel-based lithium-manganese-rich materials but is similar to that observed for pure Li2MnO3. These findings shed light on key structure-property correlations in the cathode material and point to a causative relationship between the redox mechanisms as well as structural changes endured by the material and relatively poor performance during extended electrochemical cycling.",

author = "Kwok, {Chun Yuen} and Subhadip Mallick and Pollock, {Christopher J.} and Arturo Gutierrez and Marm Dixit and Croy, {Jason R.} and Mahalingam Balasubramanian",

note = "Publisher Copyright: {\textcopyright} 2023 American Chemical Society.",

year = "2024",

month = jan,

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doi = "10.1021/acs.chemmater.3c02111",

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Kwok, CY, Mallick, S, Pollock, CJ, Gutierrez, A, Dixit, M, Croy, JR & Balasubramanian, M 2024, 'Redox Mechanisms and Migration Tendencies in Earth-Abundant 0.7Li₂MnO₃·0.3LiFeO₂ Cathodes: Coupling Spin-Resolved X-ray Absorption Near Edge and X-ray Absorption Fine Structure Spectroscopies', Chemistry of Materials, vol. 36, no. 1, pp. 300-312. https://doi.org/10.1021/acs.chemmater.3c02111

Redox Mechanisms and Migration Tendencies in Earth-Abundant 0.7Li₂MnO₃·0.3LiFeO₂ Cathodes: Coupling Spin-Resolved X-ray Absorption Near Edge and X-ray Absorption Fine Structure Spectroscopies. / Kwok, Chun Yuen; Mallick, Subhadip; Pollock, Christopher J. et al.
In: Chemistry of Materials, Vol. 36, No. 1, 09.01.2024, p. 300-312.

Research output: Contribution to journal › Article › peer-review

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T1 - Redox Mechanisms and Migration Tendencies in Earth-Abundant 0.7Li2MnO3·0.3LiFeO2 Cathodes

T2 - Coupling Spin-Resolved X-ray Absorption Near Edge and X-ray Absorption Fine Structure Spectroscopies

AU - Kwok, Chun Yuen

AU - Mallick, Subhadip

AU - Pollock, Christopher J.

AU - Gutierrez, Arturo

AU - Dixit, Marm

AU - Croy, Jason R.

AU - Balasubramanian, Mahalingam

PY - 2024/1/9

Y1 - 2024/1/9

N2 - We report the use of iron 1s3p resonant X-ray emission processes to conduct spin-selective, high-energy resolution fluorescence detected X-ray absorption near-edge spectroscopy (HERFD-XANES) on an iron-containing, lithium- and manganese-rich, fully earth-abundant cathode material, Li1.3Mn0.5Fe0.2O2 (0.7Li2MnO3·0.3LiFeO2). Coupling this technique with conventional Mn K-edge XANES and detailed extended X-ray absorption fine structure (EXAFS) analysis from both the Mn and Fe vantage points, we gain fundamental insights into the redox processes and migration tendencies of transition metals in this cathode material at the bulk level. We show that during the first charge, Fe3+ undergoes oxidation to form Fe4+ prior to the activation plateau. Toward the end of activation, a significant fraction of the iron is present as tetrahedral Fe3+. This observation reveals that iron migration from octahedral to tetrahedral sites and iron reduction are initiated during activation. Upon first discharge from the activated state, a continuous and overlapping reduction of both Fe and Mn is observed, with Fe largely restored back as an octahedrally coordinated Fe3+. The manganese local environment gradually changes to a distorted cooperative Jahn-Teller Mn3+ structure during discharge, with the clear presence of two Mn-O as well as two Mn-Mn correlation distances at 2.0 V. The significant reduction of manganese in the very first discharge is distinctly different from that seen in typical nickel-based lithium-manganese-rich materials but is similar to that observed for pure Li2MnO3. These findings shed light on key structure-property correlations in the cathode material and point to a causative relationship between the redox mechanisms as well as structural changes endured by the material and relatively poor performance during extended electrochemical cycling.

AB - We report the use of iron 1s3p resonant X-ray emission processes to conduct spin-selective, high-energy resolution fluorescence detected X-ray absorption near-edge spectroscopy (HERFD-XANES) on an iron-containing, lithium- and manganese-rich, fully earth-abundant cathode material, Li1.3Mn0.5Fe0.2O2 (0.7Li2MnO3·0.3LiFeO2). Coupling this technique with conventional Mn K-edge XANES and detailed extended X-ray absorption fine structure (EXAFS) analysis from both the Mn and Fe vantage points, we gain fundamental insights into the redox processes and migration tendencies of transition metals in this cathode material at the bulk level. We show that during the first charge, Fe3+ undergoes oxidation to form Fe4+ prior to the activation plateau. Toward the end of activation, a significant fraction of the iron is present as tetrahedral Fe3+. This observation reveals that iron migration from octahedral to tetrahedral sites and iron reduction are initiated during activation. Upon first discharge from the activated state, a continuous and overlapping reduction of both Fe and Mn is observed, with Fe largely restored back as an octahedrally coordinated Fe3+. The manganese local environment gradually changes to a distorted cooperative Jahn-Teller Mn3+ structure during discharge, with the clear presence of two Mn-O as well as two Mn-Mn correlation distances at 2.0 V. The significant reduction of manganese in the very first discharge is distinctly different from that seen in typical nickel-based lithium-manganese-rich materials but is similar to that observed for pure Li2MnO3. These findings shed light on key structure-property correlations in the cathode material and point to a causative relationship between the redox mechanisms as well as structural changes endured by the material and relatively poor performance during extended electrochemical cycling.

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Redox Mechanisms and Migration Tendencies in Earth-Abundant 0.7Li₂MnO₃·0.3LiFeO₂ Cathodes: Coupling Spin-Resolved X-ray Absorption Near Edge and X-ray Absorption Fine Structure Spectroscopies

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