Unblocking Oxygen Charge Compensation for Stabilized High-Voltage Structure in P2-Type Sodium-Ion Cathode

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Layered transition-metal oxides are excellent hosts for lithium-ion batteries due to oxygen charge compensation.
• Extending the cycle life of sodium-ion batteries requires enabling similar charge compensation in sodium layered oxides.

Purpose of the Study:

• To investigate a Ti/Mg co-doping strategy for P2-Na2/3Ni1/3Mn2/3O2 cathode material.
• To activate charge compensation via hybridized O 2p–TM 3d covalent bonds in sodium layered oxides.

Main Methods:

• Co-doping a P2-Na2/3Ni1/3Mn2/3O2 cathode material with Titanium (Ti) and Magnesium (Mg).
• Investigating the resulting charge compensation mechanisms and structural evolution during charging.

Main Results:

• The Ti/Mg co-doping strategy successfully activated charge compensation through O 2p–TM 3d covalent bonds.
• Interlayer O–O electrostatic repulsion was weakened, leading to a moderate solid-solution-type structural evolution instead of P2-O2 contraction.
• The cycling stability of the codoped cathode material was significantly improved compared to the pristine sample.

Conclusions:

• This study presents a novel approach for optimizing sodium layered cathodes through rational structural design and electrochemical coupling.
• The findings offer a promising strategy for enhancing the performance and cycle life of sodium-ion batteries.