Buffered Fluorination Strategy for Stabilizing Sodium-Rich O3-Type Layered Oxides in High-Humidity Environments for...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• O3-type layered oxides are promising for sodium-ion batteries (SIBs).
• Capacity fade in SIBs is linked to unstable cathode-electrolyte interphase (CEI) and structural degradation during deep desodiation.
• Moisture sensitivity hinders the processability of these cathode materials.

Purpose of the Study:

• To develop a surface engineering strategy for O3-type layered oxide cathodes.
• To mitigate structural collapse and capacity fade caused by moisture and deep desodiation.
• To improve the stability and performance of sodium-ion batteries.

Main Methods:

• A buffered fluorination strategy using Na3FeF6 was applied to engineer oxide surfaces under high humidity.
• Theoretical calculations and experimental analyses were employed to understand the mechanisms.
• The artificial CEI formation and its effects on structural stability were investigated.

Main Results:

• The fluorination strategy effectively mitigated moisture-induced sodium leaching and structural collapse.
• An armor-like artificial CEI was formed, suppressing detrimental phase transitions during deep desodiation.
• Surface fluorination inhibited lattice oxygen mobility, reduced iron dissolution, and alleviated surface lattice distortion.

Conclusions:

• The buffered fluorination strategy enhances the stability and performance of sodium-rich O3-type layered oxides for SIBs.
• This approach offers a viable solution for processing sensitive materials in humid environments.
• The findings extend surface engineering concepts to challenging cathode materials for next-generation energy storage.