Accessing Mg-Ion Storage in V₂PS₁₀ via Combined Cationic-Anionic Redox with Selective Bond Cleavage

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Magnesium batteries are promising for energy storage due to magnesium's abundance and high energy density potential.
• Development is hindered by a lack of suitable cathodes and slow magnesium ion diffusion kinetics.
• Strong interactions between Mg2+ and host structures impede efficient ion transport.

Purpose of the Study:

• To introduce V2PS10 as a novel positive electrode material for rechargeable magnesium batteries.
• To investigate the mechanism behind fast magnesium ion diffusion in V2PS10.
• To understand the role of combined cationic and anionic redox processes in battery performance.

Main Methods:

• Electrochemical testing to determine cyclable capacity and ion diffusion rates.
• X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) to identify redox mechanisms.
• Maximum entropy method (MEM) analysis, density functional theory (DFT), and projected density of states (PDOS) for structural and electronic characterization.

Main Results:

• V2PS10 achieved a cyclable capacity of 100 mAh g-1 with fast Mg2+ diffusion (7.2 x 10^-11 to 4 x 10^-14 cm2 s-1).
• Fast insertion mechanism attributed to combined V-site cationic redox and (S2)2- site anionic redox via reversible S-S bond cleavage.
• Structural analysis revealed spatially separated cationic and anionic redox processes, facilitating reversible Mg insertion.

Conclusions:

• V2PS10 demonstrates significant potential as a cathode material for high-performance magnesium batteries.
• The unique redox mechanism involving S-S bond cleavage and spatially separated redox sites enables rapid Mg2+ transport.
• Synergistic effects between Mg site occupancy and electron transfer location enhance battery performance.