Entropy-Tailored Fast-Charging Sodium Layered Cathodes

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• O3-type layered transition metal oxides are promising cathode materials for sodium-ion batteries, offering high energy density.
• The structural transition between octahedral (O-type) and prismatic (P-type) phases during cycling impacts sodium-ion mobility and battery lifespan.

Purpose of the Study:

• To investigate the relationship between O-P transitions, oxygen behavior, and sodium-ion kinetics in O3-type cathodes.
• To develop an entropy-tailored approach to enhance structural transitions and improve battery performance.

Main Methods:

• Compositionally versatile, entropy-tailored approach.
• In situ high-energy synchrotron X-ray diffraction (HEXRD) to study structural transitions.
• X-ray absorption spectroscopy (XAS) and theoretical analyses to confirm structural and chemical stability.

Main Results:

• Promoted preferred O-P transitions with enhanced sodium-ion migration.
• Mitigated irreversible oxygen loss and suppressed transition metal migration and surface reconstruction.
• Achieved high rate capability (88.7 mAh g⁻¹ at 20 C) and prolonged cycle life (74.3% retention after 1000 cycles).

Conclusions:

• The entropy-tailored strategy effectively enhances sodium-ion kinetics and structural stability in O3-type cathodes.
• This work provides a deeper understanding of structure-property relationships for advanced layered cathode materials.
• The findings broaden the prospects for fabricating high-power-density sodium-ion battery electrodes.