Electrolyte Reactivity in the Double Layer in Mg Batteries: An Interface Potential-Dependent DFT Study

Area of Science:

• Electrochemistry
• Materials Science
• Computational Chemistry

Background:

• Magnesium-metal batteries offer high energy density but face challenges with electrolyte stability.
• Electrolyte degradation is a primary limitation hindering the practical application of Mg-metal batteries.

Purpose of the Study:

• To investigate the electrochemical degradation mechanisms of solvent-based electrolytes for Mg-metal batteries.
• To understand electrolyte decomposition pathways and their impact on Mg-metal battery performance.
• To develop a theoretical framework for predicting and improving electrolyte stability.

Main Methods:

• Utilized grand canonical density functional theory (DFT) to model electrolyte behavior.
• Analyzed electrochemical reactions within the double layer region.
• Determined the thermodynamic stability of electrolytes and Mg deposition.

Main Results:

• Identified significant electrolyte reactivity in the double layer, independent of direct Mg-surface contact.
• Showed that dimethoxyethane (DME) and ethylene carbonate (EC) thermodynamically decompose before Mg2+/Mg0 reduction.
• Defined an extended operation potential window (OPW) enabling Mg deposition beyond thermodynamic limits.

Conclusions:

• Electrolyte decomposition in the double layer is a critical factor in Mg-battery failure.
• The developed potential-dependent DFT approach accurately predicts degradation products and mechanisms.
• This methodology provides guidelines for designing stable electrolytes for multivalent batteries and energy storage devices.