Cosolvent Electrolyte Design for High-Voltage Aqueous Zinc-Sulfur Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Aqueous zinc-sulfur batteries (AZSBs) present cost-effective and safe energy storage solutions.
• Severe cell polarization remains a significant challenge hindering AZSB performance.

Purpose of the Study:

• To enhance the sulfur cathode conversion reaction in AZSBs using a cosolvent.
• To investigate the impact of N,N-diethylformamide (DEF) on electrolyte properties and electrochemical performance.

Main Methods:

• Introduction of N,N-diethylformamide (DEF) as a cosolvent in ZnSO4 electrolyte.
• Electrochemical characterization to assess charge transfer kinetics and cell polarization.
• Computational analysis (HOMO-LUMO gap) and machine learning for design principles.

Main Results:

• The cosolvent electrolyte ([Zn(H2O)5DEF]2+) exhibits a reduced HOMO-LUMO gap (0.74 eV) facilitating faster kinetics.
• DEF weakens the S-S bond through electron injection, enhancing sulfur conductivity.
• Achieved an elevated discharge plateau (0.8 V) and reduced polarization (0.32 V) in AZSBs.

Conclusions:

• DEF cosolvent effectively mitigates polarization and boosts performance in AZSBs.
• Design principles for cosolvent electrolytes, including donor number and HOMO energy, are identified.
• This approach offers a pathway for developing high-performance aqueous zinc-sulfur batteries.