Vacancy-Enabled O3 Phase Stabilization for Manganese-Rich Layered Sodium Cathodes

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Manganese-rich layered oxides are promising low-cost, high-capacity cathode materials for sodium-ion batteries.
• Existing P2 phase materials often exhibit rapid capacity degradation, limiting their practical application.

Purpose of the Study:

• To develop a stable O3 phase sodium cathode from a Li and Mn-rich layered material.
• To investigate the role of transition metal and oxygen vacancies in enhancing electrochemical performance.

Main Methods:

• Synthesis of a Li and Mn-rich layered material.
• Electrochemical exchange of sodium and lithium ions.
• Characterization of phase stability and electrochemical cycling.

Main Results:

• The developed material primarily maintains the O3 phase during cycling, exhibiting a full sodiation capacity of approximately 220 mAh g⁻¹.
• Achieved a specific capacity of ~160 mAh g⁻¹ between 2-3.8 V with over 86% capacity retention after 250 cycles.
• Pre-formed vacancies facilitate reversible transition metal migration, creating metastable states that prevent O3-P3 phase transitions.

Conclusions:

• The novel O3 phase cathode demonstrates enhanced stability and capacity retention for sodium-ion batteries.
• The engineered vacancies and resulting phase stabilization are key to overcoming the limitations of traditional P2 phase materials.