Stabilizing the Layer-Structured Oxide Cathode by Modulating the Oxygen Redox Activity for Sodium Ion Batteries.

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Layer-structured oxides are promising cathodes for sodium-ion batteries (SIBs) due to anionic redox activity.
• However, excessive oxygen redox reactions cause irreversible oxygen release, degrading cycling stability.

Purpose of the Study:

• To enhance the cycling stability and electrochemical performance of O3-NaNi0.3Mn0.5Cu0.1Ti0.05W0.05O2 cathodes.
• To investigate the role of sulfur ion doping in suppressing oxygen loss and improving reversibility.

Main Methods:

• High-temperature quenching was used to introduce sulfur ions into the O3-NaNi0.3Mn0.5Cu0.1Ti0.05W0.05O2 structure.
• Electrochemical characterization, including cycling tests and rate capability measurements, was performed.
• Structural analysis focused on the formation of stable S-O covalent bonds.

Main Results:

• A novel Na2S-modified O3/P2-NaNi0.3Mn0.5Cu0.1Ti0.05W0.05O2 composite was successfully synthesized.
• The modified cathode exhibited a high reversible capacity of 173.1 mAh g-1 between 1.5-4.3 V at 0.1 C.
• Excellent cycling stability was achieved with 81.5% capacity retention after 120 cycles at 1 C, along with good rate capability.

Conclusions:

• Sulfur ion doping effectively enhances the reversibility of oxidation-reduction reactions and suppresses lattice oxygen loss.
• The stable S-O covalent bonds play a crucial role in inhibiting oxygen release.
• The Na2S-modified composite demonstrates significant potential as a high-performance cathode material for SIBs.