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) show promise for high-energy potassium-ion batteries (PIBs).
• Crystal degradation leads to capacity fading in PBAs, limiting their application.
• Developing stable, high-performance cathodes for PIBs is crucial for next-generation energy storage.

Purpose of the Study:

• To develop a generalizable strategy for enhancing Fe-based PBAs as scalable, high-energy PIB cathodes.
• To address crystal degradation and capacity fading issues in PBAs.
• To improve the electrochemical performance and cycling stability of potassium-ion battery cathodes.

Main Methods:

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

Main Results:

• The strategy yielded a low-anion-defect cubic structure, increasing K⁺ storage capacity.
• The Fe─C octahedral framework was stabilized, suppressing K⁺ insertion/extraction distortion.
• The optimized cathode achieved 124.5 mAh g^-1 at 50 mA g^-1 with 84.9% retention after 800 cycles.

Conclusions:

• The developed strategy effectively enhances the energy density and durability of Fe-based PBAs for PIBs.
• Controlling cation vacancies and crystal structure is key to overcoming capacity fading.
• This approach offers a pathway for scalable, high-performance potassium-ion battery cathodes.