Six-electron-conversion selenium cathodes stabilized by dead-selenium revitalizer for aqueous zinc batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Aqueous zinc batteries offer safe and sustainable large-scale energy storage.
• Limited energy density in current aqueous zinc batteries necessitates advanced cathode materials.
• High-capacity cathodes with elevated redox potentials are crucial for improving energy density.

Purpose of the Study:

• To develop a high-capacity, stable cathode for aqueous zinc batteries.
• To investigate a reversible six-electron-conversion selenium (Se) cathode.
• To enhance the performance of zinc-selenium (Zn-Se) cells using a bromide/polybromide (Br-/Br_n^-) redox couple.

Main Methods:

• Fabrication of a zinc-selenium (Zn-Se) cell utilizing a selenium (Se) cathode in a ZnCl₂-based hydrogel electrolyte.
• Incorporation of bromide salt as an electrolyte additive to introduce the Br-/Br_n^- redox couple.
• Electrochemical characterization, including cycling stability tests and capacity measurements.

Main Results:

• The Br-/Br_n^- redox couple effectively revitalizes passivated zinc anodes by reacting with dead Se, regenerating active Se for the cathode.
• Cycling stability was significantly improved, with the Zn-Se cell maintaining 1246.8 mAh g_Se^-1 after 50 cycles.
• The cell achieved a high specific capacity of 2077.6 mAh g_Se^-1 and a specific energy of 404.2 Wh kg^-1.

Conclusions:

• The developed selenium cathode with a bromide/polybromide redox additive demonstrates enhanced cycling stability and high energy density for aqueous zinc batteries.
• The Br-/Br_n^- redox couple effectively mitigates Se passivation on the zinc anode, a key challenge in Zn-Se battery performance.
• This approach presents a promising strategy for advancing high-performance and sustainable aqueous zinc energy storage systems.