Reversible Cl/Cl^- redox in a spinel Mn₃O₄ electrode

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Halides offer unique anodic redox behavior for charge compensation.
• Irreversible conversion to gaseous halogens limits halide use as charge carriers at room temperature.

Purpose of the Study:

• To investigate reversible halide conversion for charge storage.
• To explore stabilization of converted halogen species within electrode lattices.

Main Methods:

• Electrochemical characterization of Mn3O4 electrodes in concentrated chloride electrolytes.
• In-situ/ex-situ analysis to identify converted chlorine species.
• Computational modeling to understand reaction mechanisms.

Main Results:

• Reversible conversion of chloride ions to near-neutral atomic chlorine species at room temperature.
• Stabilization of atomic chlorine within Zn2+-trapped Mn3O4 structure.
• Identification of polychloride anions (e.g., [Cl3]-, [Cl5]-) as charge carriers.

Conclusions:

• Chloride/chloride redox is the primary mechanism for observed capacity in the Mn3O4 electrode.
• Halogen plating within electrode lattices represents a new charge-storage mechanism.
• This work demonstrates a viable pathway for advanced electrochemical energy storage.