Understanding electrochemical cation insertion into prussian blue from electrode deformation and mass changes

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Prussian blue analogues are promising electrode materials for energy storage.
• Understanding ion insertion mechanisms is crucial for optimizing battery performance.
• Aqueous electrolytes offer a safer and more sustainable alternative for electrochemical devices.

Purpose of the Study:

• To investigate the mechanism of alkali ion insertion into Prussian blue from aqueous electrolytes.
• To correlate ion insertion with structural and mass changes in real-time.
• To identify factors enabling stable electrochemical cycling of Prussian blue.

Main Methods:

• Operando Atomic Force Microscopy (AFM) to observe surface deformation.
• Electrochemical Quartz Crystal Microbalance (EQCM) to monitor mass changes during cycling.
• Electrochemical characterization in aqueous electrolytes.

Main Results:

• Observed coupling between electrical current and rates of deformation and mass change.
• Identified potassium ion (K+) as the only stable cycling alkali ion.
• Attributed K+ stability to its lower hydration energy compared to other alkali ions.
• Demonstrated reversible deformation of the Prussian blue framework upon K+ (de)insertion, irrespective of its open structure.

Conclusions:

• Potassium ion insertion into Prussian blue from aqueous electrolytes is stable due to its lower hydration energy.
• The observed reversible deformation highlights the structural adaptability of Prussian blue.
• These findings provide insights into designing stable Prussian blue-based electrodes for electrochemical applications.