Establishing a Stable Anode-Electrolyte Interface in Mg Batteries by Electrolyte Additive.

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Simple magnesium salts offer stable, conductive electrolytes for next-generation magnesium (Mg) batteries.
• Mg electrolytes face challenges with high charge-transfer resistance at the Mg anode surface due to adsorbed species.
• Understanding and mitigating anode-electrolyte interfacial issues is crucial for full-cell performance.

Purpose of the Study:

• To investigate the effect of anode-electrolyte interfacial properties on Mg battery performance using a model Mg cell.
• To demonstrate how an additive can improve the activation process and overall performance of Mg batteries.
• To provide insights into interfacial phenomena and the tunability of simple-salt Mg electrolytes.

Main Methods:

• Fabrication of a model Mg cell using Mg[B(hfip)₄]₂/DME electrolyte and a Chevrel phase Mo₆S₈ cathode.
• Electrochemical analysis to study cell performance, activation cycles, and rate capability.
• Spectroscopic analysis to investigate the composition and properties of the anode-electrolyte interface and the solid electrolyte interphase (SEI).

Main Results:

• The Mg cell required activation cycles, primarily due to anode-electrolyte interface conditioning.
• Introducing a small amount of Mg(BH₄)₂ additive to the electrolyte boosted the activation process.
• The additive facilitated native oxide removal and promoted SEI formation on the Mg anode, leading to stable capacity from the second cycle.
• The modified electrolyte enabled 600 cycles of reversible cycling and excellent rate capability.

Conclusions:

• Mg(BH₄)₂ additive effectively conditions the Mg anode-electrolyte interface, overcoming initial activation limitations.
• The additive enhances the formation of a stable SEI layer, crucial for long-term battery cycling.
• This study highlights the potential for facile tuning of simple-salt Mg electrolytes to achieve high-performance Mg batteries.