Full-Scale Regulation Enabled High-Performance Sodium O3-Type Layered Cathodes

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• O3-type cathodes offer high energy density for sodium-ion batteries but suffer from structural degradation and poor cycling stability.
• Interfacial instability and kinetic limitations at elevated voltages lead to rapid capacity fading and safety concerns.

Purpose of the Study:

• To develop a multifunctional surface-to-bulk modification strategy for O3-NaNi1/3Fe1/3Mn1/3O2 cathodes.
• To enhance the structural integrity, interfacial stability, and sodium-ion diffusion kinetics of the cathode material.
• To improve the overall state of health (SOH) and durability of sodium-ion batteries.

Main Methods:

• In situ formation of a perovskite-type CaZrO3 protective layer on O3-NaNi1/3Fe1/3Mn1/3O2 primary particles.
• Incorporation of Ca2+ and F- into the cathode's ternary lattice to reinforce the structure and facilitate Na+ diffusion.
• Analysis of structural changes, including intergrowth phase transitions (P3-OP2) and mitigation of Jahn-Teller distortion.

Main Results:

• The CaZrO3 layer successfully constructed a stable cathode-electrolyte-interphase, suppressing side reactions and transition metal dissolution.
• Anchored Ca2+ pillars and Zr-O bonds reinforced the TMO6 octahedra, while F- doping facilitated Na+ diffusion.
• Alleviation of lattice strain and restrained migration of Fe4+O6 due to an improved coordination environment.
• The modified cathode (NFM-CZF) exhibited excellent rate capability and retained 83.8% of its capacity after 300 cycles at 2C.

Conclusions:

• Synchronous surface and bulk modification effectively enhances the electrochemical performance and durability of O3-type cathodes.
• The developed strategy provides valuable insights into regulating internal and external structures for high-performance sodium-ion batteries.
• This approach offers a promising pathway for the commercialization of sodium-ion batteries with improved safety and longevity.