Constraining Interlayer Slipping in P2-Type Layered Oxides with Oxygen Redox by Constructing Strong Covalent Bonds

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Lattice oxygen redox (LOR) in P2-type layered oxides offers high energy density for sodium-ion batteries.
• However, LOR can cause structural distortion and irreversible phase transitions, degrading performance.

Purpose of the Study:

• To replace the detrimental OP4 phase with a stable Z phase in P2-type layered oxides.
• To enhance the electrochemical performance of sodium-ion battery cathodes by introducing antimony (Sb).

Main Methods:

• Substitution of transition metal (TM) layers with Sb in P2-type oxides.
• Analysis of phase transitions and structural stability.
• Electrochemical testing of half and full cells.

Main Results:

• Sb introduction promotes a Z phase transition, suppressing OP4 phase formation.
• The Z phase transition reduces structural strain and lowers Na+ diffusion barriers.
• Sb-substituted oxides exhibit excellent kinetics, rate capability (79 mAh g-1 at 1 A g-1), and high energy density (487 Wh kg-1).

Conclusions:

• Replacing OP4 with Z phase via Sb substitution is a viable strategy for stable, high-energy sodium-ion battery cathodes.
• This approach mitigates LOR-induced degradation, paving the way for practical applications.