Outer Sphere Electron Transfer Enabling High-Voltage Aqueous Electrolytes

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Aqueous electrolytes in metal-ion batteries are limited by a low voltage window (1.23 V) and side reactions like hydrogen evolution.
• These limitations hinder the potential of safe and low-cost aqueous batteries.

Purpose of the Study:

• To develop a high-voltage aqueous electrolyte for enhanced safety and energy density in metal-ion batteries.
• To investigate the mechanism of outer sphere electron transfer for inhibiting water reactivity.

Main Methods:

• Introduction of catechol (CAT) into aqueous electrolytes.
• Investigation of outer sphere electron transfer mechanism using Zn-ion battery model.
• Electrochemical characterization of Zn//Zn symmetric and Zn//V2O5 full batteries.

Main Results:

• Achieved an expanded electrochemical window of 3.24 V by inhibiting water reactivity.
• Demonstrated outer sphere electron transfer mechanism involving catechol and Zn2+-H2O solvation shells.
• Zn//V2O5 full batteries exhibited high energy density (~380 W h kg-1) and excellent cycling stability (92% retention over 3000 cycles).
• Zn//Zn symmetric batteries achieved a lifespan of 4000 hours.

Conclusions:

• Outer sphere electron transfer strategy effectively enables high-voltage aqueous electrolytes.
• This approach significantly improves the performance of aqueous zinc-ion batteries.
• Paves the way for designing next-generation high-voltage aqueous energy storage systems.