A Four-Electron Sulfur Electrode Hosting a Cu²⁺ /Cu⁺ Redox Charge Carrier

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Elemental sulfur cathodes offer high theoretical capacity but suffer from low conductivity and polysulfide shuttling.
• Developing efficient charge carriers and stable electrode structures is crucial for unlocking sulfur's potential in batteries.

Purpose of the Study:

• To investigate a novel copper-sulfur (Cu-S) electrode utilizing Cu2+ as a charge carrier for high-performance electrochemical energy storage.
• To characterize the electrochemical behavior, capacity, voltage, polarization, and cycling stability of the Cu-S electrode.

Main Methods:

• Electrochemical synthesis and characterization of the Cu-S electrode.
• Analysis of the four-electron sulfur electrode reaction (S↔CuS↔Cu2S).
• Testing in a hybrid cell with a Zn metal anode and anion-exchange membrane separator.

Main Results:

• Achieved a specific capacity of 3044 mAh g−1 (sulfur mass) or 609 mAh g−1 (Cu2S mass).
• Demonstrated a high potential of 0.5 V vs. SHE, low polarization (0.05 V), and 1200 cycles with 72% capacity retention at 12.5 A g−1.
• Hybrid cell delivered 1.15 V average discharge voltage and 547 Wh kg−1 specific energy, with stable cycling over 110 cycles.

Conclusions:

• The Cu-S electrode exhibits excellent electrochemical performance, including high capacity, low polarization, and superior cycling stability.
• The Cu-S cathode is a viable option for high-energy-density battery applications, particularly in hybrid cell configurations.