Interfacial Oxygen Locking via Gradient Structural Design: A Route to Air-Stable and High-Performance Sodium Layered...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Sodium-ion batteries are promising for sustainable energy due to abundant sodium resources.
• Key challenges include moisture sensitivity, poor kinetics, phase degradation, and oxygen loss from layered oxides.

Purpose of the Study:

• To mitigate oxygen loss and interfacial issues in O3-type layered oxides for sodium-ion batteries.
• To enhance the stability and electrochemical performance of sodium-ion battery materials through surface modification.

Main Methods:

• Nonaqueous solvent-assisted ion exchange to create a calcium (Ca)-gradient and sodium (Na)-deficient surface on O3-type layered oxides.
• Experimental analysis and computational calculations to verify the surface architecture's effects.
• Incorporation of calcium into the alkali metal layer of Na_1-xNi_0.33Fe_0.33Mn_0.33O₂.

Main Results:

• The Ca-gradient and Na-deficient surface architecture effectively reduced anionic redox contribution and oxygen release.
• Calcium incorporation improved electrical conductivity and moisture stability.
• Stabilized transition metal ions at high states-of-charge, leading to excellent cycling stability (97.4% capacity retention over 300 cycles) and rate capability (166.9 mAh g^-1 at 0.1 C, 93.9 mAh g^-1 at 10 C).

Conclusions:

• Surface engineering via gradient lattice reconstruction is a viable strategy to enhance sodium-ion battery performance.
• Mechanistic insights into mitigating oxygen loss and improving interfacial stability were provided.
• Developed calcium-doped sodium-ion battery materials show potential for efficient and durable energy storage systems.