Engineering Heterostructured Fe-Co-P Arrays for Robust Sodium Storage.

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Transition metal phosphides are promising for sodium ion batteries (SIBs) due to high theoretical capacity.
• Volume fluctuations in phosphides during cycling cause capacity decay, limiting SIB applications.

Purpose of the Study:

• To construct novel heterostructured Fe-Co-P (FeP/Co2P) arrays for enhanced SIB performance.
• To address the capacity decay issue caused by volume changes in metal phosphides.

Main Methods:

• Fabrication of self-supported heterostructured Fe-Co-P arrays.
• Electrochemical performance testing of the fabricated arrays in SIBs.
• Density Functional Theoretical (DFT) calculations to investigate electronic structure and ion transport.

Main Results:

• The heterostructure effectively mitigates volume changes during sodiation/desodiation.
• DFT calculations confirmed a built-in electric field at heterointerfaces, accelerating charge transfer and Na+ ion diffusion.
• The FeP/Co2P heterostructure exhibited higher electrical conductivity compared to individual FeP and Co2P.
• Demonstrated superior performance with high reversible capacities (634 mAh g-1 at 0.2 A g-1 and 239 mAh g-1 at 1 A g-1 after 300 cycles).

Conclusions:

• Heterostructured Fe-Co-P arrays provide a promising anode material for high-performance SIBs.
• The unique heterostructure design enhances electrochemical stability and ion transport.
• This work offers a viable strategy to overcome the limitations of traditional metal phosphides in energy storage devices.