Activation mechanism of conventional electrolytes with amine solvents: Species evolution and hydride-containing interphase formation

Key Words:MG METAL; MAGNESIUM; DEPOSITION; BATTERIES; GROWTH

Abstract:Rechargeable magnesium (Mg)-metal batteries have brought great expect to overcome the safety and energy density concerns of typical lithium-ion batteries. However, interfacial passivation of the Mg-metal anode impairs the reversible Mg plating/stripping chemistries, resulting in low Coulombic efficiency and large overpotential. In this work, a facile isobutylamine (IBA)-assisted activation strategy has been proposed and the fundamental mechanism has been unveiled in a specific way of evolving active species and forming MgH2-based solid-electrolyte interphase. After introducing IBA into a typical electrolyte of magnesium bis(trifluoromethanesulfonyl) imide (Mg(TFSI)(2)) in diglyme (G2) solvents, electrolyte species of [Mg2 (IBA)(5)](2 ) and protonated amine-based cations of [(IBA)H]( ) have been detected by nuclear magnetic resonance and mass spectra. This not only indicates direct solvation of IBA toward Mg2 but also suggests its ionization, which is central to mitigating the decomposition of G2 and TFSI anions by forming neutrally charged [(IBAH( ))(TFSI-)](0) and other complex ions. A series of experiments, including cryogenic-electron microscopy, D2O titration-mass spectra, and time of flight secondary ion mass spectrometry results, reveal a thin, non-passivated, and MgH2-containing interphase on the Mg-metal anode. Besides, uniform and dendrite-free Mg electrodeposits have been revealed in composite electrolytes. Benefiting from the activation effects of IBA, the composite electrolyte displays superior electrochemical performance (overpotential is approximately 0.16 V versus 2.00 V for conventional electrolyte; Coulombic efficiency is above 90% versus <10% for conventional electrolyte). This work offers a fresh direction to advanced electrolyte design for next-generation rechargeable batteries.(c) 2024 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

Volume:98

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Translation or Not:no