Regulating Interfacial Kinetics of Mg Metal Anode by Introducing Thiourea Additives to Halogen-Free Electrolyte

Area of Science:

• Electrochemistry
• Materials Science

Background:

• Magnesium-sulfur (Mg-S) batteries offer high theoretical energy density.
• Interfacial kinetics at the magnesium (Mg) metal anode are critical for Mg-S battery performance.
• Stabilizing the Mg-electrolyte interface and improving Mg²⁺ transport are key challenges.

Purpose of the Study:

• To investigate the effect of thiourea (TU) additives on the Mg-electrolyte interface in halogen-free electrolytes (HFEs).
• To enhance Mg²⁺ transport and electrochemical performance of Mg-S batteries.
• To elucidate the mechanism of TU in regulating interfacial kinetics.

Main Methods:

• Addition of thiourea (TU) to a Mg(NO₃)₂·6H₂O based halogen-free electrolyte.
• Electrochemical characterization including ionic conductivity and transference number measurements.
• Assembly and testing of Mg-S coin cells.
• Surface analysis using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS).

Main Results:

• Optimized TU content (0.05-0.2 g per 1.5 g salt) improved ion mobility and ionic conductivity.
• The transference number increased to 0.81 with TU modification.
• TU-modified electrolytes resulted in higher initial discharge capacity (880 mAh g^-1) and improved cycling stability.
• Reduced polysulfide diffusion was observed in TU-modified systems.
• Characterization confirmed the formation of a more uniform and stable interfacial layer on the Mg anode.

Conclusions:

• Thiourea (TU) effectively regulates interfacial kinetics at the Mg anode in halogen-free electrolytes.
• Electrolyte engineering with TU additives offers a promising strategy to enhance Mg-S battery performance.
• The study demonstrates a simple yet effective method for stabilizing the Mg-electrolyte interface.