Surface reconstruction driven by low oxygen chemical potential sintering: unlocking superior material properties

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• O3-type layered oxides are promising cathodes for sodium-ion batteries due to high capacity and ease of synthesis.
• Increasing operating voltage is key for practical capacity, but high-voltage reactions degrade performance.
• Interfacial instability between cathode and electrolyte is a major challenge for high-voltage sodium-ion batteries.

Purpose of the Study:

• To develop a surface modification strategy for O3-type layered oxide cathodes to enhance interfacial stability at high voltages.
• To improve the practical capacity and long-term cyclability of sodium-ion batteries.

Main Methods:

• Low oxygen chemical potential (LOCP) sintering strategy to modify cathode surfaces.
• Structural and chemical characterization of modified cathode materials.
• Electrochemical performance testing in pouch full-cells.
• Mechanistic studies including DFT calculations to understand surface transformations.

Main Results:

• LOCP sintering created Ti-rich surfaces with enhanced interfacial stability.
• The optimized cathode delivered 146.7 mA h g^-1 initial capacity with 85.6% retention after 500 cycles.
• LOCP sintering induced surface oxygen vacancies, promoting Ti migration and Mn reduction, leading to structural phase transitions.

Conclusions:

• LOCP sintering is an effective surface engineering strategy for O3-type layered oxide cathodes.
• The developed method significantly improves interfacial stability and electrochemical cyclability for high-voltage sodium-ion batteries.
• Understanding the atomic-scale mechanisms provides insights for designing advanced sodium-ion battery materials.