Constructing a Size-Controllable Spherical P2-Type Layered Oxides Cathode That Achieves Practicable Sodium-Ion...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• P2-type layered metal oxides are key cathode materials for sodium-ion batteries, offering high voltage and fast sodium-ion diffusion.
• Challenges include limited capacity and poor cycling stability due to phase transformations and structural degradation.

Purpose of the Study:

• To synthesize secondary spherical cathode materials with improved performance for sodium-ion batteries.
• To investigate the relationship between morphology and electrochemical properties.

Main Methods:

• Coprecipitation method to prepare precursors for secondary spherical cathodes.
• Synthesis of P2-type Na0.67Ni0.18Mn0.67Cu0.1Zn0.05O2 with controlled radii.
• Electrochemical testing of half cells and cylindrical cells.
• In situ X-ray diffraction for phase transition analysis.

Main Results:

• Synthesized spherical cathodes exhibit high tap density (1.52 g cm⁻³) and compacted density (3.2 g cm⁻³).
• Half cells show 111.8 mAh g⁻¹ at 0.1 C and 82.64% capacity retention after 1000 cycles at 5 C.
• In situ XRD confirms a reversible P2-OP4 phase transition with minimal volume change (6.96%).
• Cylindrical cells achieve 4.7 Ah capacity with stable cycling over 1000 cycles at 2 C.

Conclusions:

• Secondary spherical morphology enhances cycling stability and electrochemical performance of P2-type cathodes.
• Controlled synthesis via coprecipitation is scalable for industrial production.
• These materials show significant potential for practical sodium-ion battery applications.