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Title: Degradation Mechanisms of Magnesium Metal Anodes in Electrolytes Based on (CF 3SO 2) 2N at High Current Densities

The energy density of rechargeable batteries utilizing metals as anodes surpasses that of Li ion batteries, which employ carbon instead. Among possible metals, magnesium represents a potential alternative to the conventional choice, lithium, in terms of storage density, safety,stability, and cost. However, a major obstacle for metal-based batteries is the identification of electrolytes that show reversible deposition/dissolution of the metal anode and support reversible intercalation of ions into a cathode. Traditional Grignard-based Mg electrolytes are excellent with respect to the reversible deposition of Mg, but their limited anodic stability and compatibility with oxide cathodes hinder their applicability in Mg batteries with higher voltage. Non-Grignard electrolytes, which consist of ethereal solutions of magnesium(II) bis(trifluoromethanesulfonyl)imide (Mg(TFSI) 2), remain fairly stable near the potential of Mg deposition. The slight reactivity of these electrolytes toward Mg metal can be remedied by the addition of surface-protecting agents, such as MgCl 2. Hence, ethereal solutions of Mg(TFSI) 2 salt with MgCl 2 as an additive have been suggested as a representative non-Grignard Mg electrolyte. In this work, the degradation mechanisms of a Mg metal anode in the TFSI-based electrolyte were studied using a current density of 1 mA cm -2 and an areal capacity of ~0.4more » mAh cm -2, which is close to those used in practical applications. The degradation mechanisms identified include the corrosion of Mg metal, which causes the loss of electronic pathways and mechanical integrity, the nonuniform deposition of Mg, and the decomposition of TFSI - anions. This study not only represents an assessment of the behavior of Mg metal anodes at practical current density and areal capacity but also details the outcomes of interfacial passivation, which was detected by simple cyclic voltammetry experiments. This study also points out the absolute absence of any passivation at the electrode-electrolyte interface for the premise of developing electrolytes compatible with a metal anode.« less
 [1] ; ORCiD logo [2] ;  [3] ;  [1] ;  [1] ;  [2] ; ORCiD logo [2] ; ORCiD logo [1]
  1. Univ. of Illinois, Chicago, IL (United States). Dept. of Chemistry; Argonne National Lab. (ANL), Argonne, IL (United States). Joint Center for Energy Storage Research (JCESR)
  2. Argonne National Lab. (ANL), Argonne, IL (United States). Joint Center for Energy Storage Research (JCESR); Argonne National Lab. (ANL), Argonne, IL (United States). Chemical Sciences and Engineering Division
  3. Univ. of Illinois, Chicago, IL (United States). Dept. of Chemistry
Publication Date:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Additional Journal Information:
Journal Volume: 33; Journal Issue: 37; Journal ID: ISSN 0743-7463
American Chemical Society
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
25 ENERGY STORAGE; metal anode
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