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Thermodynamics and kinetics of defects in Li2S

Moradabadi, Ashkan and Kaghazchi, Payam (2016):
Thermodynamics and kinetics of defects in Li2S.
In: Applied Physics Letters, p. 213906, 108, (21), ISSN 0003-6951, [Online-Edition: http://dx.doi.org/10.1063/1.4952434],
[Article]

Abstract

Li2S is the final product of lithiation of sulfur cathodes in lithium-sulfur (Li-S) batteries. In this work, we study formation and diffusion of defects in Li2S. It is found that for a wide range of voltages (referenced to metal Li) between 0.17 V and 2.01 V, positively charged interstitial Li (Li+) is the most favorable defect type with a fixed formation energy of 1.02 eV. The formation energy of negatively charged Li vacancy V(Li,-) is also constant, and it is only 0.13 eV higher than that of Li+. For a narrow range of voltages between 0.00 V and 0.17 V, the formation energy of neutral S vacancy is the lowest and it decreases with decreasing the cell voltage. The energy barrier for Li+ diffusion (0.45 eV), which takes place via an exchange mechanism, is 0.18 eV higher than that for V(Li,-) (0.27 eV), which takes place via a single vacancy hopping. Considering formation energies and diffusion barriers, we find that ionic conductivity in Li2S is due to both Li+ and V(Li,-), but the latter mechanism being slightly more favorable.

Item Type: Article
Erschienen: 2016
Creators: Moradabadi, Ashkan and Kaghazchi, Payam
Title: Thermodynamics and kinetics of defects in Li2S
Language: English
Abstract:

Li2S is the final product of lithiation of sulfur cathodes in lithium-sulfur (Li-S) batteries. In this work, we study formation and diffusion of defects in Li2S. It is found that for a wide range of voltages (referenced to metal Li) between 0.17 V and 2.01 V, positively charged interstitial Li (Li+) is the most favorable defect type with a fixed formation energy of 1.02 eV. The formation energy of negatively charged Li vacancy V(Li,-) is also constant, and it is only 0.13 eV higher than that of Li+. For a narrow range of voltages between 0.00 V and 0.17 V, the formation energy of neutral S vacancy is the lowest and it decreases with decreasing the cell voltage. The energy barrier for Li+ diffusion (0.45 eV), which takes place via an exchange mechanism, is 0.18 eV higher than that for V(Li,-) (0.27 eV), which takes place via a single vacancy hopping. Considering formation energies and diffusion barriers, we find that ionic conductivity in Li2S is due to both Li+ and V(Li,-), but the latter mechanism being slightly more favorable.

Journal or Publication Title: Applied Physics Letters
Volume: 108
Number: 21
Divisions: 11 Department of Materials and Earth Sciences
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences > Material Science > Materials Modelling
Zentrale Einrichtungen > University IT-Service and Computing Centre (HRZ) > Hochleistungsrechner
Zentrale Einrichtungen > University IT-Service and Computing Centre (HRZ)
Zentrale Einrichtungen
Date Deposited: 31 May 2016 07:29
Official URL: http://dx.doi.org/10.1063/1.4952434
Identification Number: doi:10.1063/1.4952434
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