Fluffy-Like Cation-Exchanged Prussian Blue Analogues for Sodium-Ion Battery Cathodes

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Prussian blue (PB) and its analogues are cost-effective cathode materials for sodium-ion batteries (SIBs).
• Structural instability and capacity decay during cycling limit the performance of PB-based SIB cathodes.

Purpose of the Study:

• To enhance the cycling stability of Prussian blue cathodes for SIBs.
• To investigate the effect of nickel (Ni) ion substitution in PB on electrochemical performance.
• To develop a facile method for fabricating high-quality PB cathodes.

Main Methods:

• Cationic solution immersion to replace iron (Fe) sites with Ni ions in PB, creating fluffy-like PB-Ni.
• Tuning Ni content by varying soaking time in NiCl2 solution.
• In situ X-ray diffraction (XRD) to characterize structural transformations during cycling.

Main Results:

• PB-Ni-1d (1-day soaking) demonstrated an initial capacity of 114.2 mA h g⁻¹ at 50 mA g⁻¹.
• PB-Ni-1d achieved stable cycling of 800 cycles at 300 mA g⁻¹.
• In situ XRD confirmed reversible phase transformation and minimal volume variation, with the outer nickel hexacyanoferrate layer maintaining cubic phase for structural integrity.

Conclusions:

• Nickel substitution in PB effectively improves cycling stability for sodium storage in SIBs.
• The cation-exchange strategy is a viable approach for fabricating high-performance PB cathodes.
• PB-Ni-1d exhibits superior electrochemical performance and structural stability, making it a promising cathode material for advanced SIBs.