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Multistep Reaction Mechanisms in Nonaqueous Lithium–Oxygen Batteries with Redox Mediator : a Model-Based Study

  • Lithium–oxygen cells with nonaqueous electrolyte show high overpotentials during charge, indicating asymmetric charge/discharge reaction mechanisms. We present a kinetic modeling and simulation study of the lithium–oxygen cell cycling behavior. The model includes a multistep reaction mechanism of the cell reaction (2Li + O2 ⇄ Li2O2) forming lithium peroxide by precipitation, coupled to a 1DLithium–oxygen cells with nonaqueous electrolyte show high overpotentials during charge, indicating asymmetric charge/discharge reaction mechanisms. We present a kinetic modeling and simulation study of the lithium–oxygen cell cycling behavior. The model includes a multistep reaction mechanism of the cell reaction (2Li + O2 ⇄ Li2O2) forming lithium peroxide by precipitation, coupled to a 1D porous-electrode transport model. We apply the model to study the asymmetric discharge/charge characteristics and analyze the influence of a redox mediator dissolved homogeneously in the liquid electrolyte. Model predictions are compared to experimental galvanostatic cycling data of cells without and with 2,2,6,6-tetramethylpiperidinyloxyl (TEMPO) as redox mediator. The predicted discharge behavior shows good agreement with the experimental results. A spatiotemporal analysis of species concentrations reveals inhomogeneous distributions of dissolved oxygen and reaction products within the cathode during discharge. The experimentally observed charge overpotentials as well as their reduction by using a redox mediator can be qualitatively reproduced with a partially irreversible reaction mechanism. However, the proposed models fail to reproduce the particular shape of the experimental charge curve with continuously increasing charge overpotential, which implies that part of the reaction mechanism is still open for investigation in future work.show moreshow less

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Metadaten
Author:Daniel Grübl, Benjamin Bergner, Daniel Schröder, Jürgen Janek, Wolfgang G. BesslerORCiDGND
Year of Publication:2016
Language:English
GND Keyword:Lithium-Ionen-Akkumulator; Reaktionsmechanismus; Redoxpotenzial
Parent Title (English):Journal of Physical Chemistry
Volume:120
Issue:43
First Page:24623
Last Page:24636
Document Type:Article (reviewed)
Institutes:Bibliografie
Release Date:2018/01/03
Licence (German):License LogoEs gilt das UrhG
DOI:https://doi.org/10.1021/acs.jpcc.6b07886