Stabilizing the Bulk Lattice and Passivating the Interface/Surface via an In Situ Constructed Dual-Layer Modified for...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• O3-type layered oxides are promising for sodium-ion batteries (SIBs) but face challenges like phase transitions and degradation.
• Existing modifications often fail to address bulk instability and adhesion issues.

Purpose of the Study:

• To develop a novel dual-layer modification for O3-type layered oxide cathodes to enhance SIB performance.
• To improve structural stability, ionic conductivity, and resistance to degradation.

Main Methods:

• An in situ AlPO4/Na3xAl1-xPO4 dual-layer coating was constructed on NNFM via liquid-phase mixing and high-temperature sintering.
• The modified cathode (AC-NNFM) was tested in SIBs and full pouch cells.

Main Results:

• The inner Na3xAl1-xPO4 layer stabilized the bulk structure and facilitated Na+ transport.
• The outer AlPO4 layer acted as a protective barrier against moisture, CO2, and transition metal dissolution.
• The modified cathode retained 85.8% capacity after 300 cycles at 1C and showed excellent high-temperature stability.
• Full cells exhibited improved capacity retention and reduced temperature rise.

Conclusions:

• A synergistic bulk-anchoring and interface-passivation strategy was demonstrated for advanced SIB cathode design.
• The dual-layer modification effectively addresses key degradation mechanisms in O3-type layered oxides.
• This approach offers a promising pathway for developing high-performance and durable sodium-ion batteries.