Redesigning Solvation Structure toward Passivation-Free Magnesium Metal Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Rechargeable magnesium metal batteries (RMBs) show promise due to magnesium's high capacity.
• Passivation layer formation on magnesium anodes is a major obstacle to RMB performance.
• Current solutions using halogenide additives compromise electrolyte stability and cathode cyclability.

Purpose of the Study:

• To design a novel electrolyte for RMBs that enables passivation-free magnesium deposition.
• To maintain high anodic stability and cathode compatibility in magnesium-based electrolytes.
• To overcome the limitations of existing electrolytes in RMBs.

Main Methods:

• Introduction of hexa-fluoroisopropyloxy (HFIP-) anion into the Mg2+ solvation structure.
• Creation of a weakly coordinated solvation structure with a [Mg-HFIP]+ contact ion pair.
• Testing of the new electrolyte in Mg||PDI-EDA and Mg||Mo6S8 full cells.

Main Results:

• Achieved passivation-free magnesium deposition.
• Demonstrated high anodic stability and cathode compatibility.
• Mg||PDI-EDA and Mg||Mo6S8 full cells exhibited ~80% capacity retention over 400 and 500 cycles, respectively.
• Significantly improved cyclability compared to simple electrolytes.

Conclusions:

• The developed electrolyte system is highly compatible with RMBs.
• Modifying solvation structure is a viable strategy for creating practical electrolytes for RMBs.
• This work advances the development of high-performance rechargeable magnesium batteries.