Development of Highly Efficient Prussian Blue Cathode Materials for Sodium Ion Batteries Guided by In-situ/Operando 57Fe Mössbauer Characterization Techniques

Sodium ion batteries (SIBs) have the advantages of extensive resources, and low cost, making them one of the preferred new energy storage techniques suitable for medium and low-speed electric vehicles and large-scale energy storage field. Prussian blue analogues (PBAs) as cathode materials for SIBs have high ion transfer velocity and high theoretical specific capacity due to their large metal organic frameworks. However, the defects and water inside the PBAs structure induce to a fragile skeleton of the materials, which would lead to unsatisfying electrochemical performance in the practical application. Furthermore, it’s still challenging to apply various in-situ/operando characterizations to explore the working mechanisms of SIBs. This review introduces three kinds of new Prussian blue cathode materials with high performance separately synthesized by the new strategies of high temperature drying, calcination and heterogeneous combination to regulate the crystal phase and composition of Prussian blue and its analogues; advanced in-situ/operando characterizations mainly including ⁵⁷Fe Mössbauer spectroscopy, X-ray diffraction, X-ray absorption spectroscopy, and theoretical calculations are carried out to reveal the charging/discharging process, capacity degradation mechanism and sodium storage mechanism of SIBs.

Key Words: Sodium ion battery, Prussian blue analogues cathode, Operando characterization, Sodium storage mechanism, Capacity degradation mechanism