Publications Details

Reversible Electrochemical Interface of Mg Metal and Conventional Electrolyte Enabled by Intermediate Adsorption

Wang, Hui; Feng, Xuefei; Chen, Ying; Liu, Yi-Sheng; Han, Kee S.; Zhou, Mingxia; Engelhard, Mark H.; Murugesan, Vijayakumar; Assary, Rajeev S.; Liu, Tianbiao L.; Henderson, Wesley; Nie, Zimin; Gu, Meng; Xiao, Jie; Wang, Chongmin; Persson, Kristin; Mei, Donghai; Zhang, Ji-Guang; T, Muellerkarl; Guo, Jinghua; Zavadil, Kevin R.; Shao, Yuyan; Liu, Jun

Conventional 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. In this paper, we report that, through tuning a conventional electrolyte—Mg(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.