Dual-Functional Lanthanum Doping: Stabilizing Cathodes by Simultaneously Mitigating Na⁺/Vacancy Ordering and Oxygen...

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• P2-type layered oxides (Na_xLi_yMn_1-yO₂) are promising sodium-ion battery cathodes due to high capacity from anionic redox.
• Challenges include Na⁺/vacancy ordering and irreversible oxygen release, limiting rate capability and stability.

Purpose of the Study:

• To investigate the effect of trace lanthanum (La) doping on P2-Na_0.6Li_0.2Mn_0.8O₂ cathode performance.
• To elucidate the mechanisms behind La's influence on sodium-ion distribution, oxygen stability, and electrochemical properties.

Main Methods:

• Synthesis of La-doped P2-type layered oxides.
• Electrochemical testing (cycling, rate capability).
• In situ/ex situ characterization and theoretical calculations.

Main Results:

• La doping altered Na⁺ distribution and suppressed Na⁺/vacancy ordering.
• High La-O bond energy stabilized lattice oxygen, preventing irreversible oxygen release.
• Optimized La-doped cathode (LM-La0.04) showed high capacity (193.5 mAh g^-1 at 0.2 C) and excellent rate performance (86.8 mAh g^-1 at 10 C).
• Remarkable capacity retention during long-term cycling was observed.

Conclusions:

• Trace La doping is an effective strategy to enhance the electrochemical performance of P2-type layered oxide cathodes.
• Lanthanum improves structural integrity and redox reversibility by stabilizing oxygen and modifying sodium-ion dynamics.
• This work offers a viable doping approach for developing high-energy, stable anion-redox cathode materials for sodium-ion batteries.