Tailoring Unconventional Cyanogen Defect in High-Entropy Prussian Blue Cathode Material for Advanced Sodium-Ion...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• High-entropy Prussian blue analogues (PBAs) show promise as cathode materials for sodium-ion batteries (SIBs).
• However, inherent defects in the [Fe(CN)₆]^4- structure limit electrochemical performance and phase stability.

Purpose of the Study:

• To engineer cyanide (CN^-) vacancies in high-entropy PBAs to enhance SIB cathode performance.
• To investigate the impact of tailored defects on structural stability, electrochemical kinetics, and Na-ion storage mechanisms.

Main Methods:

• Synthesis of a novel high-entropy PBA (HE-Cu-PA) using a phytic acid (PA) assisted coprecipitation method.
• Characterization of the material's structure, composition, and electrochemical properties.
• Comparative analysis with PA-free and other high-entropy PBA compositions.

Main Results:

• The HE-Cu-PA material exhibits tailored CN^- defects, creating adaptive coordination sites and promoting electronic delocalization.
• This leads to enhanced structural stability, suppressed phase transitions (monoclinic ↔ cubic ↔ tetragonal), and a zero-strain mechanism.
• Achieved high initial capacity (117.6 mAh·g^-1), superior rate capability, and an ultra-long cycle life (>6000 cycles) with minimal decay (0.0085% per cycle).
• Demonstrated potential in quasi-solid-state SIB full batteries with high energy density (338.0 Wh·kg^-1) and long cycle life (>4000 cycles).

Conclusions:

• Tailoring CN^- vacancies in high-entropy PBAs is an effective strategy to overcome limitations in SIB cathodes.
• The HE-Cu-PA material demonstrates exceptional electrochemical performance and stability, making it a viable candidate for advanced SIBs.
• The findings pave the way for developing high-performance, long-lasting sodium-ion energy storage systems.