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.
N1 - Publisher Copyright:
© 2015 American Chemical Society.
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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U2 - 10.1021/am507375t
DO - 10.1021/am507375t
M3 - Article
C2 - 25562374
AN - SCOPUS:84922454556
SN - 1944-8244
VL - 7
SP - 2494
EP - 2502
JO - ACS Applied Materials and Interfaces
JF - ACS Applied Materials and Interfaces
IS - 4
ER -