Microstructure Regulation of O3/P3 Biphasic Layered Oxide Cathodes for Stable and Fast-Charging Sodium-Ion Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• O3-type sodium cathodes show promise for energy storage but suffer from phase transition and stability issues at high voltages.
• Precise phase/microstructure regulation for these cathodes remains a challenge for practical applications.

Purpose of the Study:

• To propose a biphasic engineering strategy for layered oxide cathodes to improve performance in sodium-ion batteries.
• To investigate the effect of iron content on phase composition and electrochemical properties.

Main Methods:

• Synthesized Na_0.67Mn_0.4Co_0.3-xCu_0.15Li_0.15Fe_xO₂ (NMCCLF) layered oxide cathodes with controlled iron content.
• Integrated O3 and P3 phases to create a biphasic cathode structure.
• Evaluated electrochemical performance, including capacity, cycling stability, and rate capability, particularly at high voltage (4.5 V).

Main Results:

• The optimized O3/P3 biphasic cathode exhibited expanded interlayer spacing, accelerated Na⁺ diffusion, and increased oxygen vacancy concentration.
• Demonstrated a continuous and gentle phase transition process, leading to superior electrochemical stability at high voltages.
• Achieved a reversible capacity of 151.6 mAh g^-1 at 0.1C with 93.91% retention after 200 cycles at 1C, and retained 60 mAh g^-1 at 10C.

Conclusions:

• The biphasic engineering strategy effectively regulates phase composition and microstructure for enhanced sodium-ion battery cathodes.
• The optimized O3/P3 biphasic cathodes offer high structural stability and excellent fast-charging performance.
• This approach provides valuable insights for designing advanced layered oxide cathodes for high-performance sodium-ion batteries.