CeO₂-modified P2-Na-Co-Mn-O cathode with enhanced sodium storage characteristics

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Layered oxide cathodes are crucial for sodium-ion batteries.
• Improving cycling stability and dynamic properties is essential for practical applications.
• P2-Na_0.67Co_0.25Mn_0.75O₂ is a promising cathode material but suffers from poor cycling stability.

Purpose of the Study:

• To enhance the cycling stability and dynamic properties of P2-Na_0.67Co_0.25Mn_0.75O₂ cathodes.
• To investigate the effect of cerium dioxide (CeO₂) surface modification on cathode performance.
• To understand the mechanism behind the performance enhancement.

Main Methods:

• Solid-state synthesis of CeO₂-modified P2-Na_0.67Co_0.25Mn_0.75O₂.
• Characterization using X-ray photoelectron spectra, X-ray diffraction, and Raman spectra.
• Electrochemical testing including cycling performance and capacity retention measurements.

Main Results:

• CeO₂ surface modification did not alter the P2-structure or the oxidation states of Co and Mn.
• A small amount of Ce⁴⁺ was reduced to Ce³⁺, with some Ce ions entering the P2-oxide surface lattice.
• The 2.00 wt% CeO₂-modified cathode delivered a maximum discharge capacity of 135.93 mA h g^-1 with 91.96% retention after 100 cycles.
• The pristine cathode showed a lower capacity (116.14 mA h g^-1) and poor retention (25.96% after 100 cycles).

Conclusions:

• CeO₂ surface modification significantly improves the cycling stability and kinetic properties of P2-type oxide cathodes.
• The enhancement is attributed to improved electric conductivity and sodium ion diffusivity.
• This surface modification strategy offers a viable route for developing high-performance sodium-ion batteries.