Toward High-Performance Mg-S Batteries via a Copper Phosphide Modified Separator.

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Magnesium-sulfur (Mg-S) batteries offer high energy density and low cost potential.
• The shuttle effect from magnesium polysulfide dissolution limits Mg-S battery performance and safety.

Purpose of the Study:

• To develop a novel separator to mitigate the shuttle effect in Mg-S batteries.
• To enhance the stability and cycle life of Mg-S cells.

Main Methods:

• Coating a copper phosphide (Cu3P) confined in a carbon matrix onto a polypropylene membrane.
• Utilizing Density Functional Theory (DFT) calculations, polysulfide permeability tests, and post-mortem analysis.

Main Results:

• The Cu3P-modified separator effectively adsorbs polysulfides and catalyzes S and Mg2+ conversion.
• Demonstrated high specific capacity (449 mAh g-1 at 0.1 C) and fast charge/discharge rates (249 mAh g-1 at 1.0 C).
• Achieved long cycle life (500 cycles at 0.5 C) and stable operation at elevated temperatures.

Conclusions:

• The bifunctional separator successfully suppresses the shuttle effect in Mg-S batteries.
• Cu3P modification enhances electrolyte wettability, thermal stability, and reversibility of Mg-S cells.
• This approach paves the way for practical and high-performance Mg-S battery applications.