Modulating the Reactivity of Amine-Based Electrolytes for Stable Rechargeable Magnesium Batteries

Abstract

Despite their advantages complementary to lithium- and sodium-ion batteries, rechargeable magnesium batteries (RMBs) still suffer from multiple limitations that impede their commercialization. Amine-based electrolytes have recently emerged as promising options to overcome the long-standing challenge of sluggish Mg2+ ion transport at the magnesium metal interface; however, their uncontrolled chemical and electrochemical reactivity impairs cycling and calendar life. After screening a range of bidentate methoxyethylamine derivatives, we herein identify aminoacetaldehyde dimethyl acetal (ADMA)─functionalized with a methoxy substituent─as a single electrolyte solvent that achieves an optimal balance between interfacial ionic transport and (electro)chemical stability. These optimal properties are enabled by the concerted modulation of electron donicity and steric hindrance in ADMA. Consequently, the ADMA-based electrolyte delivers stable cycling for Mg||SS half-cells─even under operating protocols incorporating intermittent rest periods─as well as for full-cells paired with Mo6S8 and tellurium cathodes. This study demonstrates that longstanding interfacial issues at the Mg metal anode in RMBs can be resolved through the sophisticated molecular engineering of scalable, bidentate methoxyethylamine electrolyte solvents.