Heterogeneous-Interface-Induced Charge Redistribution Toward Fe-Based Polyanion Cathode for Advanced Sodium-Ion...

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Sodium-ion batteries (SIBs) are promising energy storage devices.
• Na4Fe3(PO4)2P2O7 (NFPP) is a prospective cathode material for SIBs.
• Inactive phase formation (maricite-NaFePO4) and poor conductivity hinder NFPP performance.

Purpose of the Study:

• To develop a high-performance Fe-based polyanionic cathode for SIBs.
• To overcome inactive phase formation and enhance electronic conductivity in NFPP.
• To construct a novel heterostructure in NFPP cathode materials.

Main Methods:

• Fine-tuning the stoichiometric ratio of the Na site to control phase composition.
• Synthesizing NFPP-NFPO heterogeneous composites.
• Utilizing density functional theory (DFT) calculations to analyze interface properties.

Main Results:

• Successfully transformed the inactive maricite-NaFePO4 phase into the active Na2FeP2O7 or NFPP phase.
• Achieved enhanced structural stability and charge transport kinetics via interfacial charge redistribution.
• Demonstrated high discharge specific capacity, ultralong cycle life (71.4% retention after 10,000 cycles at 50 C), and ultrafast rate capability (60.2 mAh g-1 at 200 C).
• Exhibited impressive high-temperature tolerance.

Conclusions:

• Heterogeneous composites can be achieved by manipulating phase composition.
• This approach provides a new strategy for designing high-performance polyanionic cathodes for SIBs.
• The developed NFPP-NFPO material shows significant potential for advanced sodium-ion battery applications.