Rechargeable Mg batteries based on a Ag₂S conversion cathode with fast solid-state Mg²⁺ diffusion kinetics

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Rechargeable magnesium (Mg) batteries offer safe, large-scale energy storage due to low-cost, non-dendritic Mg anodes.
• Developing high-performance cathodes remains a significant hurdle for Mg battery advancement.

Purpose of the Study:

• To establish a high-performance rechargeable Mg battery using a silver sulfide (Ag2S) conversion cathode.
• To investigate the electrochemical mechanism and performance of the Ag2S cathode.

Main Methods:

• Electrochemical measurements (capacity, rate capability, cyclability).
• Material characterization using X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), and X-ray Photoelectron Spectroscopy (XPS).

Main Results:

• The Ag2S cathode achieved a reversible capacity of 120 mA h g⁻¹ at 50 mA g⁻¹ and 70 mA h g⁻¹ at 500 mA g⁻¹.
• Demonstrated outstanding long-term cyclability exceeding 400 cycles.
• Identified a two-stage magnesiation mechanism involving intercalation and conversion reactions with high Mg²⁺ diffusion coefficients.

Conclusions:

• The Ag2S conversion cathode offers a promising solution for high-performance rechargeable Mg batteries.
• High Mg²⁺ diffusion coefficients explain the superior electrochemical performance.
• This study provides insights for designing effective conversion cathodes using soft anions and transition metal cations.