Pinning Effect Enhanced Structural Stability toward a Zero-Strain Layered Cathode for Sodium-Ion Batteries.

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Layered oxides are promising cathode materials for sodium-ion batteries due to high capacity.
• These materials often suffer from structural instability during cycling, limiting their practical application.

Purpose of the Study:

• To introduce a pinning effect strategy to enhance the structural stability of layered sodium-ion battery cathodes.
• To investigate the influence of transition metal occupancy on the Na-site for improved electrochemical performance.

Main Methods:

• Synthesis of Na_0.67Mn_0.5Co_0.5-xFe_xO₂ layered oxides with varying Fe doping concentrations (0%, 2.5%, 7.3%).
• Electrochemical characterization including cycling performance and rate capability tests.
• Structural analysis to evaluate volume variation and ion diffusion pathways.

Main Results:

• Optimal Fe³⁺ occupancy (2.5%) at the Na-site effectively pinned the layered structure, reducing slab sliding.
• Achieved ultra-low volume variation (0.6%) and maintained efficient 2D Na-ion diffusion channels.
• The optimized Na_0.67Mn_0.5Co_0.4Fe_0.1O₂ cathode demonstrated excellent cycle stability (>1000 cycles) and rate capability (up to 10 C).

Conclusions:

• The pinning effect strategy significantly improves the structural and electrochemical stability of layered oxide cathodes.
• Controlled Fe doping provides effective pinning points, enhancing sodium-ion battery performance.
• This approach offers a promising route for developing high-performance sodium-ion batteries.