Density Functional Theory Study of Redox Potential Shifts in LixMnyFe1-yPO4 Battery Electrodes

Research output: Contribution to journalJournal article – Annual report year: 2019Researchpeer-review

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Density Functional Theory Study of Redox Potential Shifts in LixMnyFe1-yPO4 Battery Electrodes. / Loftager, Simon; Schougaard, Steen Brian ; Vegge, Tejs; García Lastra, Juan Maria.

In: The Journal of Physical Chemistry Part C, Vol. 123, No. 1, 2019, p. 102-109.

Research output: Contribution to journalJournal article – Annual report year: 2019Researchpeer-review

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@article{c027cd9515ad43c6b017856eb168945c,
title = "Density Functional Theory Study of Redox Potential Shifts in LixMnyFe1-yPO4 Battery Electrodes",
abstract = "Olivine-structured LiMPO4 materials (M = Mn, Fe, Co, Ni, or mixtures) exhibit higher redox potentials than their layer oxide counterparts. This is due to the so-called inductive effect in the former, where the inner P–O bonds in the phosphate units make the M–O bond weaker than in the latter. A strategy to further increase the redox potentials in the olivines is to mix two metals. Along these lines, Kobayashi et al. have shown experimentally that Mn2+–Mn3+ and Fe2+–Fe3+ redox potentials approximately shift 0.1 V upon full substitution of Fe by Mn in LixMnyFe1–yPO4. Here, through density functional theory calculations, we found that the average metal–oxygen bond lengths (M = Mn, Fe) increase with increasing Mn content, resulting in a decrease in the covalency of the transition-metal–oxygen interaction. The decrease in the covalency can be linked with good qualitative agreement to the experimentally observed M2+–M3+ voltage-plateau positive shift. Finally, the impact of the Mn-content-dependent voltage plateaus and unit-cell volume on the energy densities of the active compound is discussed.",
author = "Simon Loftager and Schougaard, {Steen Brian} and Tejs Vegge and {Garc{\'i}a Lastra}, {Juan Maria}",
year = "2019",
doi = "10.1021/acs.jpcc.8b09167",
language = "English",
volume = "123",
pages = "102--109",
journal = "The Journal of Physical Chemistry Part C",
issn = "1932-7447",
publisher = "American Chemical Society",
number = "1",

}

RIS

TY - JOUR

T1 - Density Functional Theory Study of Redox Potential Shifts in LixMnyFe1-yPO4 Battery Electrodes

AU - Loftager, Simon

AU - Schougaard, Steen Brian

AU - Vegge, Tejs

AU - García Lastra, Juan Maria

PY - 2019

Y1 - 2019

N2 - Olivine-structured LiMPO4 materials (M = Mn, Fe, Co, Ni, or mixtures) exhibit higher redox potentials than their layer oxide counterparts. This is due to the so-called inductive effect in the former, where the inner P–O bonds in the phosphate units make the M–O bond weaker than in the latter. A strategy to further increase the redox potentials in the olivines is to mix two metals. Along these lines, Kobayashi et al. have shown experimentally that Mn2+–Mn3+ and Fe2+–Fe3+ redox potentials approximately shift 0.1 V upon full substitution of Fe by Mn in LixMnyFe1–yPO4. Here, through density functional theory calculations, we found that the average metal–oxygen bond lengths (M = Mn, Fe) increase with increasing Mn content, resulting in a decrease in the covalency of the transition-metal–oxygen interaction. The decrease in the covalency can be linked with good qualitative agreement to the experimentally observed M2+–M3+ voltage-plateau positive shift. Finally, the impact of the Mn-content-dependent voltage plateaus and unit-cell volume on the energy densities of the active compound is discussed.

AB - Olivine-structured LiMPO4 materials (M = Mn, Fe, Co, Ni, or mixtures) exhibit higher redox potentials than their layer oxide counterparts. This is due to the so-called inductive effect in the former, where the inner P–O bonds in the phosphate units make the M–O bond weaker than in the latter. A strategy to further increase the redox potentials in the olivines is to mix two metals. Along these lines, Kobayashi et al. have shown experimentally that Mn2+–Mn3+ and Fe2+–Fe3+ redox potentials approximately shift 0.1 V upon full substitution of Fe by Mn in LixMnyFe1–yPO4. Here, through density functional theory calculations, we found that the average metal–oxygen bond lengths (M = Mn, Fe) increase with increasing Mn content, resulting in a decrease in the covalency of the transition-metal–oxygen interaction. The decrease in the covalency can be linked with good qualitative agreement to the experimentally observed M2+–M3+ voltage-plateau positive shift. Finally, the impact of the Mn-content-dependent voltage plateaus and unit-cell volume on the energy densities of the active compound is discussed.

U2 - 10.1021/acs.jpcc.8b09167

DO - 10.1021/acs.jpcc.8b09167

M3 - Journal article

VL - 123

SP - 102

EP - 109

JO - The Journal of Physical Chemistry Part C

JF - The Journal of Physical Chemistry Part C

SN - 1932-7447

IS - 1

ER -