Innovative Energy Storage Smart Windows Relying on Mild Aqueous Zn/MnO₂ Battery Chemistry

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Rechargeable aqueous Zn/MnO2 batteries offer a good performance/cost ratio.
• Their operating principle involves reversible electrodeposition reactions at the anode and cathode.
• Applying this to transparent conductive windows for smart devices is an unexplored area.

Purpose of the Study:

• To develop an innovative bifunctional smart window with combined electrochromic and charge storage properties.
• To demonstrate the proof-of-concept for such a device using Zn/MnO2 chemistry.
• To explore different device architectures for optimal performance.

Main Methods:

• Utilized a mild buffered aqueous electrolyte for the Zn/MnO2 system.
• Employed transparent nanostructured ITO cathodes for MnO2 electrodeposition.
• Used flat transparent FTO anodes for zinc metal electrodeposition.
• Investigated different device architectures, including a face-to-face configuration.

Main Results:

• Achieved high MnO2 loading (555 mA h m-2) with excellent cycling stability (99.5% CE over 200 cycles).
• Obtained significant energy density (860 mA h m-2) when coupled with a zinc metal anode.
• Demonstrated reversible zinc metal electrodeposition (≈280 mA h m-2, >95% CE over 50 cycles).
• Successfully integrated electrochromic and energy storage functions into a single smart window.

Conclusions:

• The developed bifunctional smart window successfully combines electrochromic and charge storage functionalities.
• This work presents the first dual-tinting energy storage smart window based on Zn/MnO2 chemistry.
• The optimized face-to-face architecture enhances the device's overall performance.