Intercalation Pseudocapacitance Boosting Ultrafast Sodium Storage in Prussian Blue Analogs

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Sodium-ion batteries require high rate capability for large-scale energy storage.
• Limitations in Na+ ion kinetics due to large ionic radius and mass hinder conventional electrode performance.
• Diffusion-controlled mechanisms in traditional electrodes present challenges for rapid charging/discharging.

Purpose of the Study:

• To demonstrate a unique intercalation pseudocapacitance in low-vacancy copper hexacyanoferrate.
• To achieve outstanding rate capability in sodium-ion battery electrodes.
• To overcome the limitations of solid-state diffusion in Prussian blue analogs.

Main Methods:

• Synthesis of low-vacancy copper hexacyanoferrate.
• Electrochemical characterization to evaluate rate capability and capacity.
• Analysis of ion diffusion pathways and structural stability during redox reactions.

Main Results:

• Demonstrated unique intercalation pseudocapacitance in low-vacancy copper hexacyanoferrate.
• Achieved outstanding rate capability, with 50% capacity retained at 100 C.
• Observed an unexpected activation of the Cu+/Cu2+ couple, leading to record capacity for this material.
• Reported a capacity of 86 mAh g-1 at 1 C, with 70% achieved at 0°C.

Conclusions:

• Minimizing vacancies in copper hexacyanoferrate creates unhindered Na+ diffusion pathways.
• Elimination of solid-state diffusion limits enhances electrode performance.
• Intercalation pseudocapacitance in Prussian blue analogs offers a promising route for high-rate sodium-ion battery electrodes.