A Chlorine-Free Electrolyte Based on Non-nucleophilic Magnesium Bis(diisopropyl)amide and Ionic Liquid for Rechargeable Magnesium Batteries

Wen Ren; Di Wu; Yanna NuLi; Xuan Zhang; Jun Yang; Jiulin Wang

doi:10.1021/acsami.1c06669

A Chlorine-Free Electrolyte Based on Non-nucleophilic Magnesium Bis(diisopropyl)amide and Ionic Liquid for Rechargeable Magnesium Batteries

ACS Appl Mater Interfaces. 2021 Jul 21;13(28):32957-32967. doi: 10.1021/acsami.1c06669. Epub 2021 Jul 9.

Authors

Wen Ren¹, Di Wu¹, Yanna NuLi¹, Xuan Zhang¹, Jun Yang¹, Jiulin Wang^{1

2}

Affiliations

¹ School of Chemistry and Chemical Engineering, Shanghai Electrochemical Energy Devices Research Center, Shanghai Jiao Tong University, Shanghai 200240, P. R. China.
² College of Chemistry, Zhengzhou University, Henan 450001, P.R. China.

PMID: 34241994
DOI: 10.1021/acsami.1c06669

Abstract

The electrolyte based on magnesium bis(diisopropyl)amide (MBA), a low-cost and non-nucleophilic organic magnesium salt, is proposed to be an admirable alternative for rechargeable magnesium batteries but suffers from limited ionic conductivity and an inferior electrochemical window in the commonly used ether solvents. In this work, the 1-butyl-1-methylpiperidinium bis(trifluoromethyl sulfonyl)imide (PP₁₄TFSI) ionic liquid as the cosolvent of tetrahydrofuran (THF) in chlorine-free MBA-based electrolytes has been first demonstrated to remarkably improve the ionic conductivity and broaden the oxidative stable potential (2.2 V vs Mg/Mg²⁺) on stainless steel. Reversible Mg electrochemical plating/stripping with a low overpotential below 200 mV and ca. 90% Coulombic efficiency are obtained. The current density of Mg plating/stripping is increased 238 times after the addition of PP₁₄TFSI, where the mechanism of competitive coordination of TFSI^- making an easier Mg plating/stripping is proposed theoretically. The MBA-2AlF₃ electrolyte with a ratio-optimized THF/PP₁₄TFSI cosolvent exhibits good compatibility with the Mo₆S₈ cathode. Furthermore, the Se@pPAN|Mg full cell exhibits an initial capacity of 447.8 mAh g^-1 and as low as ∼0.66% capacity decay per cycle for more than 70 cycles at 0.2 C with the synergy of LiTFSI additives. The facile modification strategy of ionic liquid in the MBA-based electrolyte sheds inspiring light on exploring non-nucleophilic and chlorine-free electrolytes for practical rechargeable magnesium batteries.

Keywords: chlorine-free; electrochemistry; electrolyte; ionic liquid; magnesium batteries; non-nucleophilic.