Journal article
An Electrochemical Impedance Spectroscopy Study on the Effects of the Surface- and Solution-Based Mechanisms in Li-O2Cells
Department of Energy Conversion and Storage, Technical University of Denmark1
Atomic Scale Materials Modelling, Department of Energy Conversion and Storage, Technical University of Denmark2
University of California at San Diego3
Applied Electrochemistry, Department of Energy Conversion and Storage, Technical University of Denmark4
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.
Language: | English |
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Publisher: | The Electrochemical Society |
Year: | 2016 |
Pages: | A2065-A2071 |
ISSN: | 19457111 and 00134651 |
Types: | Journal article |
DOI: | 10.1149/2.1111609jes |
ORCIDs: | Knudsen, Kristian Bastholm , Vegge, Tejs and Hjelm, Johan |
Battery Capacitance Electrochemical impedance spectroscopy Impedance Li-O2 Li-air Li2O2 Oxygen reduction Pore clogging