Short-Chain Polyselenosulfide Copolymers as Cathode Materials for Lithium-Sulfur Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Chemistry

Background:

• Lithium-sulfur (Li-S) batteries offer high theoretical energy density but suffer from poor cycle life due to polysulfide shuttling.
• Sulfur-rich copolymers present a strategy to mitigate these issues compared to pure sulfur (S ₈) cathodes.

Purpose of the Study:

• To investigate novel sulfur-rich polymers with short tetrasulfide (PTS) and selenotrisulfide (PTSeS) bonds as cathode materials for Li-S batteries.
• To evaluate the impact of selenium doping on polymer conductivity and electrochemical performance.
• To demonstrate the effectiveness of short poly(seleno)sulfide chains in suppressing the shuttle effect.

Main Methods:

• Synthesis of sulfur-rich polymers with short tetrasulfide (PTS) and selenotrisulfide (PTSeS) linkages.
• Electrochemical characterization of PTS and PTSeS as cathode materials in Li-S cells.
• Comparative analysis of cycling stability, capacity decay, active material utilization, and rate performance.

Main Results:

• Both PTS and PTSeS effectively suppressed the shuttle effect due to intrinsically short poly(seleno)sulfide bonds.
• Selenium doping in PTSeS significantly enhanced electrical conductivity and improved battery performance.
• PTSeS demonstrated superior active material utilization and high rate performance compared to PTS.
• Both materials exhibited excellent cycling stability with low capacity decay (<0.08% per cycle) over 500 cycles.

Conclusions:

• Short-chain poly(seleno)sulfide polymers are effective cathode materials for Li-S batteries, mitigating polysulfide shuttling.
• Selenium doping is a viable strategy to enhance conductivity and electrochemical performance in sulfur-based cathodes.
• PTSeS shows particular promise for high-performance Li-S batteries due to improved kinetics and utilization.