Thermoelectric GNP-Integrated MoS2/S Cathodes for Mg-S Batteries with a Li2CO3-Modified Halogen-Free Electrolyte

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Magnesium-sulfur (Mg-S) batteries offer high theoretical energy density but face challenges like sluggish Mg2+ transport and interfacial instability.
• Polysulfide shuttling and poor cycling stability hinder practical applications of Mg-S batteries.

Purpose of the Study:

• To investigate the effect of Li2CO3-modified halogen-free electrolytes on Mg-S battery performance.
• To evaluate the Mg2+ transport properties and interfacial compatibility of the modified electrolyte with a MoS2/sulfur/graphene nanoplatelet cathode.

Main Methods:

• A Li2CO3-modified Mg(NO3)2 electrolyte in ACN/G4 solvent was prepared and characterized.
• Symmetric Mg cells were used to assess Mg plating/stripping behavior and interfacial compatibility.
• Full Mg-S cells with a MoS2/S/GNP composite cathode were galvanostatically cycled to evaluate electrochemical performance.

Main Results:

• The modified electrolyte showed a ~17% increase in ionic conductivity and an enhanced Mg2+ transference number (0.867).
• Improved Mg plating/stripping stability and reduced polarization were observed in symmetric cells.
• Full cells exhibited rapid capacity fading, increased charge-transfer resistance, and decreased Mg2+ diffusion, indicating persistent transport and interfacial limitations.

Conclusions:

• Li2CO3 modification improves Mg2+ transport and interfacial behavior in halogen-free electrolytes for Mg-S batteries.
• These electrolyte enhancements are insufficient to overcome the inherent degradation mechanisms limiting the long-term performance of Mg-S batteries.
• Further research is needed to address fundamental challenges in electrolyte-cathode interactions and material stability for advanced Mg-S battery development.