Examining Electrolyte Compatibility on Polymorphic MnO₂ Cathodes for Room-Temperature Rechargeable Magnesium...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Rechargeable magnesium batteries are explored as alternatives to lithium-ion batteries due to magnesium's abundance and high energy density.
• Practical application of magnesium batteries with oxide cathodes and magnesium anodes at room temperature remains limited.

Purpose of the Study:

• To compare the electrochemical performance and interfacial behavior of various MnO2 cathode polymorphs in two distinct electrolytes.
• To identify challenges and opportunities for developing stable room-temperature magnesium batteries.

Main Methods:

• Investigated nanorod-like α-MnO2 and λ-MnO2 cathodes.
• Tested two electrolytes: Mg[TFSA]2/G3 and Mg[Al(hfip)4]2/G3.
• Evaluated discharge capacities, magnesium anode reversibility, and electrode/electrolyte interfacial stability.

Main Results:

• Mg[TFSA]2/G3 showed capacities up to 100 mA h g-1 but suffered from magnesium anode passivation.
• Mg[Al(hfip)4]2/G3 enabled reversible magnesium deposition/dissolution but induced side reactions at the MnO2 cathode.
• Side reactions involving MnO2 and electrolyte species, rather than Mg2+ intercalation, were observed, leading to cathode degradation.

Conclusions:

• Electrolyte selection significantly influences magnesium battery performance and stability.
• Improving the interfacial stability between oxide cathodes and electrolytes is crucial for practical rechargeable magnesium batteries.
• Further research is needed to overcome passivation and side reaction issues for viable magnesium battery technology.