High-Entropy Co-Free O3-Type Layered Oxyfluoride: A Promising Air-Stable Cathode for Sodium-Ion Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Sodium-ion batteries (SIBs) are gaining traction as a sustainable alternative to lithium-ion batteries due to resource availability.
• Developing high-performance cathode materials is crucial for advancing SIB technology.

Purpose of the Study:

• To synthesize and characterize a novel cobalt-free, high-entropy oxyfluoride cathode for SIBs.
• To investigate the impact of high-entropy composition and lithium incorporation on electrochemical performance and structural stability.

Main Methods:

• High-entropy synthesis approach to create a multi-element single-phase cathode.
• Electrochemical testing (cycling performance, capacity measurements) within a specific voltage window.
• In situ and ex situ diffraction studies to analyze structural changes during cycling.

Main Results:

• Achieved reversible capacities of 109 mAh g⁻¹ (2-4 V) and 144 mAh g⁻¹ (2-4.3 V) in initial cycles.
• Demonstrated significant improvements in cycling stability and air stability.
• Confirmed suppression of complex phase transitions via diffraction studies, attributed to the high-entropy strategy.

Conclusions:

• The high-entropy approach is effective in developing stable, high-capacity cobalt-free cathodes for sodium-ion batteries.
• Oxyfluoride composition and lithium incorporation enhance configurational entropy, structural stability, and electrochemical kinetics.
• This work provides a strong foundation for future research into high-entropy materials for advanced energy storage solutions.