Layered Hierarchical Modification Strategy in P2-Type Oxide Cathodes Enables High-Rate Capability and Long-Term...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• P2-Na_0.67Ni_0.33Mn_0.67O₂ is a common cathode for sodium-ion batteries (SIBs).
• Key challenges include irreversible P2-O2 phase transitions, Na⁺/vacancy ordering, and anion redox reactions.
• These issues limit the electrochemical performance and cycle life of SIBs.

Purpose of the Study:

• To develop a layered hierarchical modification strategy for P2-NaNM cathodes.
• To address critical challenges hindering SIB performance: phase transitions, ion ordering, and anion redox.
• To enhance the structural stability and electrochemical properties of sodium-ion battery cathodes.

Main Methods:

• Incorporation of Fluorine (F) at oxygen sites to improve anion redox reversibility.
• Lithium (Li) substitution in transition metal sites to promote cationic disorder and inhibit Na⁺/vacancy ordering.
• Magnesium (Mg) substitution at sodium sites to mitigate layer repulsion and enhance structural cohesion.

Main Results:

• The optimized P2-Na_0.67Ni_0.25Li_0.08Mn_0.57Mg_0.10O_1.93F_0.07 (Mg-NaNLMF) cathode shows excellent stability.
• Achieved 98.07% capacity retention over 60 cycles at 0.1C and 81.72% after 1000 cycles at 10C.
• Demonstrated enhanced structural integrity and suppressed irreversible phase transitions and redox reactions.

Conclusions:

• A layered hierarchical modification strategy effectively solves critical issues in P2-NaNM cathodes.
• The developed Mg-NaNLMF cathode offers superior electrochemical performance for sodium-ion batteries.
• This approach provides a new paradigm for designing high-performance layered oxide cathodes.