Facilitating Sodium-Ion Diffusion in Fe-Doped Co₃O₄ for High-Rate Performance

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Cobalt oxide (Co3O4) is a promising anode material for sodium-ion batteries (SIBs) due to its high theoretical capacity.
• However, low conductivity and poor rate performance hinder the practical application of Co3O4 in SIBs.

Purpose of the Study:

• To enhance the electrochemical performance of Co3O4 anodes for SIBs.
• To investigate the effect of iron (Fe) doping on the structure and properties of Co3O4 nanoparticles.

Main Methods:

• Co-precipitation doping strategy to synthesize iron-doped Co3O4 nanoparticles (FexCo3-xO4 NPs).
• Experimental characterization and theoretical calculations to confirm Fe doping sites and analyze structural changes.
• Electrochemical testing of FexCo3-xO4 NPs as anodes in SIBs, including rate capability and cycling stability tests.
• Assembly and testing of a Na-ion full cell using FexCo3-xO4 NPs.

Main Results:

• Fe doping at octahedral sites within the spinel structure of Co3O4 was confirmed.
• Fe doping led to a decreased bandgap and enlarged ion transport spacing, facilitating electron and Na-ion transport.
• The FexCo3-xO4 NPs exhibited an impressive rate capability of 402.9 mAh g⁻¹ at 3 A g⁻¹.
• Remarkable cycling stability was achieved, maintaining 786.2 mAh g⁻¹ after 500 cycles at 0.5 A g⁻¹ with no capacity fading.
• A Na-ion full cell demonstrated a discharge capacity of 105 mAh g⁻¹ with stable cycling.

Conclusions:

• Fe doping is a critical factor in enhancing the rate performance and cycling stability of Co3O4 anodes for SIBs.
• The enhanced performance is attributed to improved electron and ion transport facilitated by Fe doping.
• This study offers valuable insights into designing high-rate electrodes and presents a promising approach for advanced sodium anodes.