Interphase Self-Optimization Enables Stable Magnesium Anode in Hydrogel Electrolyte

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Magnesium (Mg) metal is a cost-effective anode for high-energy aqueous batteries.
• Mg anodes suffer from severe corrosion and passivation, limiting their practical application.
• Existing strategies to mitigate these issues have limited effectiveness or sacrifice active metal.

Purpose of the Study:

• To develop a stable and efficient Mg anode for aqueous batteries.
• To address the challenges of corrosion and surface passivation in Mg anodes.
• To enable long-term cycling stability in Mg-based energy storage systems.

Main Methods:

• Formulation of a hydrogel electrolyte containing a tridentate chelant and MgCl2.
• Investigation of the anode-electrolyte interface dynamics.
• Testing of Mg anode performance in symmetric cells and hybrid cells with different cathodes.

Main Results:

• A self-optimized, dynamic, Mg2+-conductive interphase (magnesium oxychloride) was formed on the Mg anode surface.
• The hydrogel electrolyte mitigated parasitic reactions and enabled complete conversion of MgO byproduct.
• Reversible Mg plating/stripping was achieved for over 600 hours in symmetric cells.
• Hybrid cells demonstrated stable cycling for up to 500 cycles with 69% capacity retention.

Conclusions:

• The developed hydrogel electrolyte effectively stabilizes the Mg anode by forming a dynamic interphase.
• This approach overcomes the limitations of previous strategies for Mg anode protection.
• The findings pave the way for high-energy, cost-effective, and stable aqueous magnesium batteries.