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Reversible Electrochemical Interface of Mg Metal and Conventional Electrolyte Enabled by Intermediate Adsorption
journal contribution
posted on 2019-12-13, 20:36 authored by Hui Wang, Xuefei Feng, Ying Chen, Yi-Sheng Liu, Kee Sung Han, Mingxia Zhou, Mark H. Engelhard, Vijayakumar Murugesan, Rajeev S. Assary, Tianbiao Leo Liu, Wesley Henderson, Zimin Nie, Meng Gu, Jie Xiao, Chongmin Wang, Kristin Persson, Donghai Mei, Ji-Guang Zhang, Karl T. Mueller, Jinghua Guo, Kevin Zavadil, Yuyan Shao, Jun LiuConventional electrolytes made by mixing simple Mg2+ salts and aprotic solvents, analogous to those in Li-ion
batteries,
are incompatible with Mg anodes because Mg metal readily reacts with
such electrolytes, producing a passivation layer that blocks Mg2+ transport. Here, we report that, through tuning a conventional
electrolyteMg(TFSI)2 (TFSI– is
N(SO2CF3)2–)with
an Mg(BH4)2 cosalt, highly reversible Mg plating/stripping
with a high Coulombic efficiency is achieved by neutralizing the first
solvation shell of Mg cationic clusters between Mg2+ and
TFSI– and enhanced reductive stability of free TFSI–. A critical adsorption step between Mg0 atoms and active Mg cation clusters involving BH4– anions is identified to be the key enabler for reversible
Mg plating/stripping through analysis of the distribution of relaxation
times (DRT) from operando electrochemical impedance spectroscopy (EIS),
operando electrochemical X-ray absorption spectroscopy (XAS), nuclear
magnetic resonance (NMR), and density functional theory (DFT) calculations.
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Keywords
BHDRTMg metalMg anodesMg cation clustersoperando electrochemical impedance spectroscopyCoulombic efficiencyIntermediate Adsorptionreductive stabilityTFSIMg cationic clusterspassivation layerDFTCF2 cosaltMg Metalsolvation shellNMRadsorption stepaprotic solventsReversible Electrochemical InterfaceMg 0 atomsXASrelaxation timesConventional Electrolyte EnabledEISLi-ion batteries
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