Gradient Sodium Deficiency Optimization in O3-Type Cathode Materials for Superior Performance and Air Stability

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• O3-type layered oxides are promising for sodium-ion batteries due to synthesis ease and high sodium content.
• Complex phase transitions and poor air stability hinder their practical application.
• Sodium deficiency improves stability but reduces capacity.

Purpose of the Study:

• To develop a hierarchical composition regulation strategy for O3-type layered oxides.
• To achieve radial concentration control of sodium, creating sodium gradients.
• To enhance air stability, electrochemical performance, and cycling stability.

Main Methods:

• Hierarchical composition regulation strategy for radial sodium concentration control.
• Construction of radially distributed sodium gradients in O3-type layered oxides.
• Electrochemical testing including cycling stability and air stability tests.

Main Results:

• The gradient Na content structure alleviates volume changes during O3-P3 phase transition.
• Suppression of Na+/H+ exchange leads to enhanced air stability and kinetic performance.
• The modified cathode shows 93.37% capacity retention after 400 cycles at 5C.
• Maintained 84.9 mAh g-1 capacity after 300 cycles at 1C under humid and CO2-rich conditions, with 77.27% retention.

Conclusions:

• Radial sodium concentration control is a viable strategy for improving O3-type layered oxide cathode materials.
• This approach enhances air stability, electrochemical performance, and cycling stability.
• Contributes to the development of high-performance, air-stable sodium-ion battery cathodes.