Anion-Regulated Solvation Structure and Electrode Interface toward Rechargeable Magnesium Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Developing efficient electrolytes is crucial for rechargeable magnesium batteries (RMBs).
• Single-anion electrolytes often limit the necessary redox properties for fast Mg²⁺ transport.
• Solid/cathode-electrolyte interphase (SEI/CEI) stability is critical for RMB performance.

Purpose of the Study:

• To engineer a chlorine-free, dual-anion electrolyte for enhanced Mg²⁺ transport in RMBs.
• To investigate the role of anion-mediated solvation in stabilizing battery interphases.
• To demonstrate improved electrochemical performance in Mg-based battery systems.

Main Methods:

• Formulation of a dual-anion electrolyte using magnesium bis(trifluoromethanesulfonyl)imide and PP₁₄CF₃SO₃ in diglyme/MOEA solvent.
• Electrochemical characterization of Mg plating/stripping, anode/cathode compatibility, and anodic stability.
• Testing of Mg∥Mg, SS∥Mg, Mo₆S₈∥Mg, and PBAQ∥Mg full cells.

Main Results:

• The dual-anion electrolyte facilitated efficient Mg plating/stripping and cathode compatibility.
• Stabilized Mg-anode SEI and promoted C-N-rich CEI formation due to MOEA interactions.
• Achieved extended lifespan over 2500 h in SS∥Mg cells with 98.1% average Coulombic efficiency.
• Demonstrated excellent rate performance in Mo₆S₈∥Mg cells and 2.8 V operation in PBAQ∥Mg cells with ~70% capacity retention.

Conclusions:

• The proposed dual-anion electrolyte significantly enhances RMB performance through anion-mediated solvation regulation.
• This electrolyte design offers a promising pathway for advanced electrolyte engineering in high-performance RMBs.
• The findings provide critical insights for developing next-generation magnesium-based energy storage devices.