Synergetic role of Li+ during Mg electrodeposition/dissolution in borohydride diglyme electrolyte solution: Voltammetric stripping behaviors on a pt microelectrode indicative of Mg-Li alloying and facilitated dissolution

Jinho Chang, Richard T. Haasch, Jinwoo Kim, Timothy Spila, Paul V. Braun, Andrew A. Gewirth, Ralph G. Nuzzo

Research output: Contribution to journalArticle

31 Citations (Scopus)

Abstract

We describe a voltammetric and spectroscopic study of Mg electrodeposition/dissolution (MgDep/Dis) in borohydride diglyme electrolyte solution containing Li+ carried out on a Pt ultramicroelectrode (UME, r = 5 μm). The data reveal Li+ cation facilitation that has not been previously recognized in studies made using macroelectrodes. While a single broad, asymmetric stripping peak is expected following MgDep on a Pt macroelectrode in 0.1 M Mg(BH4)2 + 1.5 M LiBH4 diglyme solution on a Pt UME, the stripping reveals three resolved oxidation peaks, suggesting that MgDep/Dis consists of not only a Mg/Mg2+ redox reaction but also contributions from Mg-Li alloying/dissolution reaction processes. Detailed XPS, SIMS, ICP, and XRD studies were performed that confirm the importance of Mg-Li alloy formation processes, the nature of which is dependent on the reduction potential used during the MgDep step. Based on the electrochemical and surface analysis data, we propose an electrochemical mechanism for MgDep/Dis in a borohydride diglyme electrolyte solution that, in the presence of 1.5 M Li+ ions, proceeds as follows: (1) Mg2+ + 2e- ⇌ Mg; (2) (1 - x)Mg2+ + xLi+ + (2 - x)e- ⇌ Mg(1-x)Lix, 0 < x ≤ ≤ and (3) (1 - y)Mg2+ + yLi+ + (2 - y)e- ⇌ Mg(1-y)Liy, 0.02 < y ≤ 0.09. Most significantly, we find that the potential-dependent MgDep/Dis kinetics are enhanced as the concentration of the LiBH4 in the diglyme electrolyte is increased, a result reflecting the facilitating influences of reduced uncompensated resistance and the enhanced electro-reduction kinetics of Mg2+ due to Mg-Li alloy formation.

Original languageEnglish
Pages (from-to)2494-2502
Number of pages9
JournalACS Applied Materials and Interfaces
Volume7
Issue number4
DOIs
StatePublished - 2015 Feb 4

Fingerprint

Borohydrides
Microelectrodes
Alloying
Electrodeposition
Electrolytes
Dissolution
Kinetics
Redox reactions
Surface analysis
Secondary ion mass spectrometry
Cations
X ray photoelectron spectroscopy
Positive ions
diglyme
Ions
Oxidation

Keywords

  • Mg electrodeposition/dissolution
  • Mg rechargeable battery
  • Mg-Li alloy
  • Pt microelectrode
  • magnesium borohydride
  • stripping peak

Cite this

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title = "Synergetic role of Li+ during Mg electrodeposition/dissolution in borohydride diglyme electrolyte solution: Voltammetric stripping behaviors on a pt microelectrode indicative of Mg-Li alloying and facilitated dissolution",
abstract = "We describe a voltammetric and spectroscopic study of Mg electrodeposition/dissolution (MgDep/Dis) in borohydride diglyme electrolyte solution containing Li+ carried out on a Pt ultramicroelectrode (UME, r = 5 μm). The data reveal Li+ cation facilitation that has not been previously recognized in studies made using macroelectrodes. While a single broad, asymmetric stripping peak is expected following MgDep on a Pt macroelectrode in 0.1 M Mg(BH4)2 + 1.5 M LiBH4 diglyme solution on a Pt UME, the stripping reveals three resolved oxidation peaks, suggesting that MgDep/Dis consists of not only a Mg/Mg2+ redox reaction but also contributions from Mg-Li alloying/dissolution reaction processes. Detailed XPS, SIMS, ICP, and XRD studies were performed that confirm the importance of Mg-Li alloy formation processes, the nature of which is dependent on the reduction potential used during the MgDep step. Based on the electrochemical and surface analysis data, we propose an electrochemical mechanism for MgDep/Dis in a borohydride diglyme electrolyte solution that, in the presence of 1.5 M Li+ ions, proceeds as follows: (1) Mg2+ + 2e- ⇌ Mg; (2) (1 - x)Mg2+ + xLi+ + (2 - x)e- ⇌ Mg(1-x)Lix, 0 < x ≤ ≤ and (3) (1 - y)Mg2+ + yLi+ + (2 - y)e- ⇌ Mg(1-y)Liy, 0.02 < y ≤ 0.09. Most significantly, we find that the potential-dependent MgDep/Dis kinetics are enhanced as the concentration of the LiBH4 in the diglyme electrolyte is increased, a result reflecting the facilitating influences of reduced uncompensated resistance and the enhanced electro-reduction kinetics of Mg2+ due to Mg-Li alloy formation.",
keywords = "Mg electrodeposition/dissolution, Mg rechargeable battery, Mg-Li alloy, Pt microelectrode, magnesium borohydride, stripping peak",
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Synergetic role of Li+ during Mg electrodeposition/dissolution in borohydride diglyme electrolyte solution : Voltammetric stripping behaviors on a pt microelectrode indicative of Mg-Li alloying and facilitated dissolution. / Chang, Jinho; Haasch, Richard T.; Kim, Jinwoo; Spila, Timothy; Braun, Paul V.; Gewirth, Andrew A.; Nuzzo, Ralph G.

In: ACS Applied Materials and Interfaces, Vol. 7, No. 4, 04.02.2015, p. 2494-2502.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Synergetic role of Li+ during Mg electrodeposition/dissolution in borohydride diglyme electrolyte solution

T2 - Voltammetric stripping behaviors on a pt microelectrode indicative of Mg-Li alloying and facilitated dissolution

AU - Chang, Jinho

AU - Haasch, Richard T.

AU - Kim, Jinwoo

AU - Spila, Timothy

AU - Braun, Paul V.

AU - Gewirth, Andrew A.

AU - Nuzzo, Ralph G.

PY - 2015/2/4

Y1 - 2015/2/4

N2 - We describe a voltammetric and spectroscopic study of Mg electrodeposition/dissolution (MgDep/Dis) in borohydride diglyme electrolyte solution containing Li+ carried out on a Pt ultramicroelectrode (UME, r = 5 μm). The data reveal Li+ cation facilitation that has not been previously recognized in studies made using macroelectrodes. While a single broad, asymmetric stripping peak is expected following MgDep on a Pt macroelectrode in 0.1 M Mg(BH4)2 + 1.5 M LiBH4 diglyme solution on a Pt UME, the stripping reveals three resolved oxidation peaks, suggesting that MgDep/Dis consists of not only a Mg/Mg2+ redox reaction but also contributions from Mg-Li alloying/dissolution reaction processes. Detailed XPS, SIMS, ICP, and XRD studies were performed that confirm the importance of Mg-Li alloy formation processes, the nature of which is dependent on the reduction potential used during the MgDep step. Based on the electrochemical and surface analysis data, we propose an electrochemical mechanism for MgDep/Dis in a borohydride diglyme electrolyte solution that, in the presence of 1.5 M Li+ ions, proceeds as follows: (1) Mg2+ + 2e- ⇌ Mg; (2) (1 - x)Mg2+ + xLi+ + (2 - x)e- ⇌ Mg(1-x)Lix, 0 < x ≤ ≤ and (3) (1 - y)Mg2+ + yLi+ + (2 - y)e- ⇌ Mg(1-y)Liy, 0.02 < y ≤ 0.09. Most significantly, we find that the potential-dependent MgDep/Dis kinetics are enhanced as the concentration of the LiBH4 in the diglyme electrolyte is increased, a result reflecting the facilitating influences of reduced uncompensated resistance and the enhanced electro-reduction kinetics of Mg2+ due to Mg-Li alloy formation.

AB - We describe a voltammetric and spectroscopic study of Mg electrodeposition/dissolution (MgDep/Dis) in borohydride diglyme electrolyte solution containing Li+ carried out on a Pt ultramicroelectrode (UME, r = 5 μm). The data reveal Li+ cation facilitation that has not been previously recognized in studies made using macroelectrodes. While a single broad, asymmetric stripping peak is expected following MgDep on a Pt macroelectrode in 0.1 M Mg(BH4)2 + 1.5 M LiBH4 diglyme solution on a Pt UME, the stripping reveals three resolved oxidation peaks, suggesting that MgDep/Dis consists of not only a Mg/Mg2+ redox reaction but also contributions from Mg-Li alloying/dissolution reaction processes. Detailed XPS, SIMS, ICP, and XRD studies were performed that confirm the importance of Mg-Li alloy formation processes, the nature of which is dependent on the reduction potential used during the MgDep step. Based on the electrochemical and surface analysis data, we propose an electrochemical mechanism for MgDep/Dis in a borohydride diglyme electrolyte solution that, in the presence of 1.5 M Li+ ions, proceeds as follows: (1) Mg2+ + 2e- ⇌ Mg; (2) (1 - x)Mg2+ + xLi+ + (2 - x)e- ⇌ Mg(1-x)Lix, 0 < x ≤ ≤ and (3) (1 - y)Mg2+ + yLi+ + (2 - y)e- ⇌ Mg(1-y)Liy, 0.02 < y ≤ 0.09. Most significantly, we find that the potential-dependent MgDep/Dis kinetics are enhanced as the concentration of the LiBH4 in the diglyme electrolyte is increased, a result reflecting the facilitating influences of reduced uncompensated resistance and the enhanced electro-reduction kinetics of Mg2+ due to Mg-Li alloy formation.

KW - Mg electrodeposition/dissolution

KW - Mg rechargeable battery

KW - Mg-Li alloy

KW - Pt microelectrode

KW - magnesium borohydride

KW - stripping peak

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