title: Passivation Dynamics in the Anisotropic Deposition and Stripping of Bulk Magnesium Electrodes During Electrochemical Cycling.
abstract: Although rechargeable magnesium (Mg) batteries show promise for use as a next generation technology for high-density energy storage, little is known about the Mg anode solid electrolyte interphase and its implications for the performance and durability of a Mg-based battery. We explore in this report passivation effects engendered during the electrochemical cycling of a bulk Mg anode, characterizing their influences during metal deposition and dissolution in a simple, nonaqueous, Grignard electrolyte solution (ethylmagnesium bromide, EtMgBr, in tetrahydrofuran). Scanning electron microscopy images of Mg foil working electrodes after electrochemical polarization to dissolution potentials show the formation of corrosion pits. The pit densities so evidenced are markedly potential-dependent. When the Mg working electrode is cycled both potentiostatically and galvanostatically in EtMgBr these pits, formed due to passive layer breakdown, act as the foci for subsequent electrochemical activity. Detailed microscopy, diffraction, and spectroscopic data show that further passivation and corrosion results in the anisotropic stripping of the Mg {0001} plane, leaving thin oxide-comprising passivated side wall structures that demark the {0001} fiber texture of the etched Mg grains. Upon long-term cycling, oxide side walls formed due to the pronounced crystallographic anisotropy of the anodic stripping processes, leading to complex overlay anisotropic, columnar structures, exceeding 50 μm in height. The passive responses mediating the growth of these structures appear to be an intrinsic feature of the electrochemical growth and dissolution of Mg using this electrolyte.
authors.forename: David J
authors.initials: DJ
authors.lastname: Wetzel
authors.forename: Marvin A
authors.initials: MA
authors.lastname: Malone
authors.forename: Richard T
authors.initials: RT
authors.lastname: Haasch
authors.forename: Yifei
authors.initials: Y
authors.lastname: Meng
authors.affiliation: Fakultät für Physik, Universität Bielefeld , Universitätsstr.25, D-33615 Bielefeld, Germany.
authors.forename: Henning
authors.initials: H
authors.lastname: Vieker
authors.affiliation: Sandia National Laboratories , Albuquerque, New Mexico 87185, United States.
authors.forename: Nathan T
authors.initials: NT
authors.lastname: Hahn
authors.affiliation: Fakultät für Physik, Universität Bielefeld , Universitätsstr.25, D-33615 Bielefeld, Germany.
authors.forename: Armin
authors.initials: A
authors.lastname: Gölzhäuser
authors.forename: Jian-Min
authors.initials: JM
authors.lastname: Zuo
authors.affiliation: Sandia National Laboratories , Albuquerque, New Mexico 87185, United States.
authors.forename: Kevin R
authors.initials: KR
authors.lastname: Zavadil
authors.forename: Andrew A
authors.initials: AA
authors.lastname: Gewirth
authors.forename: Ralph G
authors.initials: RG
authors.lastname: Nuzzo
keywords: columnar growth; corrosion; magnesium anode; passivation; rechargeable magnesium battery