Self-Confined Semi-Conversion Reaction Endowing an Ultra-Long Life Aqueous Cu-Cu₂Se Battery.

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Aqueous rechargeable metal-selenium batteries offer high capacity and safety for large-scale energy storage.
• Se-based materials face challenges like volume expansion and poor conductivity, limiting performance.

Purpose of the Study:

• To address the limitations of Se-based materials in aqueous batteries.
• To propose and validate a novel self-confined semi-conversion reaction mechanism for enhanced electrochemical performance.

Main Methods:

• In situ X-ray diffraction and ex situ transmission electron microscopy to verify the reaction mechanism.
• Multi-technique analysis including in situ electrochemical impedance spectroscopy, relaxation time distribution, and cyclic voltammetry.

Main Results:

• Demonstrated a self-confined semi-conversion reaction (Cu2Se↔CuSe) with high crystallinity and reversible stress changes.
• Achieved high initial reversible capacity (230.5 mAh g-1) and exceptional cycling stability (100% retention after 15,000 cycles).
• Identified pseudocapacitive contribution and minimized charge transfer resistance as key performance factors.

Conclusions:

• The proposed mechanism significantly improves the cycling performance of aqueous copper-selenium batteries.
• Provides new design principles for high-performance aqueous copper-based batteries.
• Highlights the potential of these batteries for next-generation energy storage.