Defect-Regulated Cubic Prussian Blue Analog Cathodes With Exceptional Stability for Potassium-Ion Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Prussian blue analogs (PBAs) are promising for high-energy potassium-ion batteries (PIBs).
• Crystal degradation leads to capacity fading in PBAs, hindering their development.
• Developing stable, high-performance cathodes is crucial for advancing PIBs.

Purpose of the Study:

• To develop a generalizable strategy for enhancing Fe-based PBAs as scalable, high-energy PIB cathodes.
• To address crystal-degradation-driven capacity fading in PBAs.
• To improve K+ storage capacity and cycling stability.

Main Methods:

• A structure-defect-dual-regulation strategy was employed using Fe-based PBAs.
• Cation vacancies were deliberately introduced at Fe3+ sites in cubic PB lattices.
• Potassium ions were inserted at interstitial sites to balance charge and stabilize the framework.

Main Results:

• The strategy yielded a low-anion-defect cubic structure, enhancing K+ storage and framework stability.
• Suppressed K+ insertion/extraction distortion and preserved Fe redox activity.
• Achieved a high reversible capacity of 124.5 mAh g-1 and 84.9% retention after 800 cycles.

Conclusions:

• The developed strategy effectively mitigates lattice strain and enhances conductivity and ion diffusion.
• The optimized PBA cathode demonstrates durable dual-site redox activity and long-term cycling stability.
• This approach offers a viable pathway for scalable, high-energy PIB cathodes.