Highly Crystalline Prussian Blue for Kinetics Enhanced Potassium Storage

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Prussian blue analogs (PBAs) are promising cathode materials for potassium-ion batteries (KIBs) due to their open framework structures.
• High crystallinity is crucial for efficient K+ ion migration and storage in PBAs.

Purpose of the Study:

• To synthesize highly crystalline K2Fe[Fe(CN)6] (KFeHCF-E) using a simple coprecipitation method with a chelating agent.
• To evaluate the electrochemical performance of KFeHCF-E as a cathode material in KIBs.

Main Methods:

• Coprecipitation synthesis using ethylenediaminetetraacetic acid dipotassium salt as a chelating agent.
• Electrochemical testing in KIBs, including rate capability and cycling stability.
• Galvanostatic intermittent titration technique (GITT) to determine K+ migration rate.
• In situ X-ray diffraction (XRD) to investigate structural stability.

Main Results:

• The synthesized KFeHCF-E exhibited excellent rate capability and an ultra-long lifespan of 5000 cycles with 61.3% capacity retention at 100 mA g-1.
• The highest K+ migration rate in the bulk phase was determined to be 10-9 cm2 s-1.
• In situ XRD confirmed the robust lattice structure and reversible solid-phase K+ storage mechanism.

Conclusions:

• A simple crystallinity optimization method for PBAs was developed.
• Highly crystalline KFeHCF-E demonstrates superior performance as a cathode material for advanced KIBs.
• This approach offers a pathway for developing high-performance PBAs for energy storage applications.