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Insights into surficial processes of pristine and coated magnesium anodes in magnesium-sulfur batteries

Häcker, Joachim and Rommel, Tobias and Wagner, Norbert and Friedrich, Kaspar Andreas (2021) Insights into surficial processes of pristine and coated magnesium anodes in magnesium-sulfur batteries. 12th Electrochemical Impedance Analysis (EIA), 29.-30. Nov. 2021, Online.

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The electrochemical couple of magnesium and sulfur represents a promising high-energy battery system with improved sustainability due to higher abundance and better recyclability of the raw materials. Furthermore, the Mg-S battery offers improved safety as magnesium exhibits a lower tendency to form dendrites compared to lithium metal. However, in contrast to Li, magnesium metal is prone to be passivated by surface layers, e.g. a solid electrolyte interphase (SEI), comprising electrolyte decomposition products like MgF2 and MgO, but also sulfur compounds like MgSO4 and MgS [1]. Latter originates in sulfur species (S8 and Sx2-) being dissolute at the sulfur composite cathode and diffuse to the Mg anode surface. The passivation character of the SEI is due to the sluggish diffusion of Mg2+ ions in most solid materials caused by its large charge density. A promising approach to overcome this issue is the implication of an ex situ prepared surface layer with sufficient Mg ion conductivity, a so-called artificial SEI [2,3]. To gain insights into the surficial processes of pristine and artificial-SEI-coated Mg anodes, electrochemical impedance spectroscopy (EIS) was applied. To distinguish between stripping and plating in symmetrical Mg-Mg cells and to exclude the impedance response of the sulfur cathode in full Mg-S cells, half-cell EIS measurements are performed by the use of a magnesium metal reference ring electrode. By analyzing the distribution of relaxation times (DRT), Nyquist, Bode and f-Im plots, the number of present processes was determined and suitable equivalent circuits (EC) were defined. Comparing EIS spectra at open-cell voltage (OCV), different current densities and states of charge (SOC), the processes are assigned to the Mg/Mg2+ charge transfer and the SEI diffusion. Furthermore, the porous nature of the artificial SEI is identified and a high-ohmic adsorption layer was found to be present during extended non-current conditions.

Item URL in elib:https://elib.dlr.de/145165/
Document Type:Conference or Workshop Item (Speech)
Title:Insights into surficial processes of pristine and coated magnesium anodes in magnesium-sulfur batteries
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Häcker, JoachimJoachim.Haecker (at) dlr.dehttps://orcid.org/0000-0003-2031-9898
Rommel, Tobiast.rommel (at) dlr.dehttps://orcid.org/0000-0001-8945-4444
Wagner, NorbertNorbert.Wagner (at) dlr.dehttps://orcid.org/0000-0002-2596-8689
Friedrich, Kaspar AndreasAndreas.Friedrich (at) dlr.deUNSPECIFIED
Date:30 November 2021
Refereed publication:Yes
Open Access:Yes
Gold Open Access:No
In ISI Web of Science:No
Keywords:Magnesium-Schwefel Batterie, Magnesium-Sulfur, Artificial SEI, Electrochemical Impedance Spectroscopy, EIS
Event Title:12th Electrochemical Impedance Analysis (EIA)
Event Location:Online
Event Type:international Conference
Event Dates:29.-30. Nov. 2021
HGF - Research field:Energy
HGF - Program:Materials and Technologies for the Energy Transition
HGF - Program Themes:Electrochemical Energy Storage
DLR - Research area:Energy
DLR - Program:E SP - Energy Storage
DLR - Research theme (Project):E - Electrochemical Storage
Location: Stuttgart
Institutes and Institutions:Institute of Engineering Thermodynamics > Electrochemical Energy Technology
Deposited By: Häcker, Joachim
Deposited On:06 Dec 2021 18:38
Last Modified:01 Aug 2022 03:00

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