Highly Efficient Chlorine Fixation Based on Organic Selenium for 3.7-V Aqueous Batteries

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Aqueous batteries require high-potential cathode materials to improve energy density.
• Chlorine-based batteries offer high redox potential and capacity but suffer from chlorine gas leakage and poor reversibility.

Purpose of the Study:

• To develop a stable and reversible chlorine redox reaction (ClRR) for high-performance aqueous batteries.
• To address the challenges of chlorine gas emission and poor Cl fixation in chlorine-based batteries.

Main Methods:

• Utilized a selenium-based organic molecule, polymerized benzoselenadiazole (poly-PhSe), as a chlorine-anchoring agent.
• Employed chalcogen-halogen coordinating chemistry for atomic-level chlorine fixation.
• Investigated the electrochemical performance of the poly-PhSe electrode with a graphite anode in an aqueous system.

Main Results:

• Achieved highly reversible ClRR with significantly reduced chlorine gas emission.
• Demonstrated a high discharge voltage of 3.7 V (vs. graphite anode) and an average output voltage of 1.79 V.
• Obtained a high discharge capacity of 344 mAh g⁻¹ with 99.1% Coulombic efficiency and 84.6% capacity retention after 850 cycles.
• Pouch cells delivered a record areal capacity of 5.3 mAh cm⁻².

Conclusions:

• Atomic-level chlorine fixation via chalcogen-halogen coordination chemistry enables efficient and reversible ClRR.
• The developed poly-PhSe electrode shows great potential for practical applications in high-performance aqueous batteries.
• This approach provides new insights for designing reversible halogen-based battery systems.