An Electrochemical Impedance Spectroscopy Study on the Effects of the Surface- and Solution-Based Mechanisms in Li-O2Cells

Kristian Bastholm Knudsen, Tejs Vegge, Bryan D. McCloskey, Johan Hjelm

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The maximum discharge capacity in non-aqueous Li-O2 batteries has been limited to a fraction of its theoretical value, largely due to a conformal deposition of Li2O2 on the cathode surface. However, it has recently been established that additives that increase the shielding of either O2 or Li+ will activate the formation of toroidal shaped Li2O2, thereby dramatically increasing cell capacity. Here we apply porous electrode theory to electrochemical impedance measured at the Li-O2 cathode to investigate changes in the surface- and ionic resistance within the pores under conditions where either the surface-mechanism or the solution-mechanism is favored. Our experimental observations show that (i) an additional charge transfer process is observed in the impedance spectrum where the solution-based mechanism is favored; (ii) that the changes in the ionic resistance in the cathode during discharge (related to Li2O2 build up) is much greater in cells where the solution-based mechanism is activated and can qualitatively determine the extent of discharge product deposited within the pores of the cathode versus the deposition extent at the electrode/electrolyte interface; and (iii) that the observed “sudden-death” during discharge is a consequence of the increasing charge transfer resistance regardless of whether Li2O2 forms predominantly through either the surface- or solution-based mechanism.
Original languageEnglish
JournalJournal of the Electrochemical Society
Issue number9
Pages (from-to)A2065-A2071
Number of pages7
Publication statusPublished - 2016

Bibliographical note

© The Author(s) 2016. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY,, which permits unrestricted reuse of the work in any medium, provided the original work is properly cited.


  • Battery
  • Capacitance
  • Electrochemical impedance spectroscopy
  • Impedance
  • Li-air
  • Li-O2
  • Li2O2
  • Oxygen reduction
  • Pore clogging


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