Nonequimolar Eight-Component Design Enables a Medium-Entropy O3/P2 Biphasic Layered Oxide for High-Performance...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Layered oxides, specifically O3- and P2-type, are key cathode materials for sodium-ion batteries (SIBs).
• Their widespread adoption is hindered by single-phase limitations and poor stability, which are not significantly improved by simple doping.

Purpose of the Study:

• To develop a stable and high-performance cathode material for SIBs.
• To overcome the inherent drawbacks of single-phase layered oxides using a novel synthesis strategy.

Main Methods:

• Fabrication of an eight-component, nonequimolar medium-entropy layered oxide cathode (Na0.9NiCuZnMgFeMnTiSn) with an O3/P2 biphasic structure.
• Utilizing electrochemically active elements as dominant constituents and incorporating minor inactive elements to stabilize the structure and enhance kinetics.
• Characterization of the material's structural, electrochemical, and cycling properties.

Main Results:

• The synthesized Na0.9NiCuZnMgFeMnTiSn cathode exhibits a dominant O3 phase (81.1%) with a P2 phase (18.9%).
• It delivers a high reversible capacity of 143.4 mAh g-1 at 10 mA g-1.
• Demonstrates excellent cycling stability (86.0 mAh g-1 after 100 cycles at 200 mA g-1) and rate capability (81.8 mAh g-1 at 300 mA g-1).

Conclusions:

• The nonequimolar medium-entropy strategy effectively stabilizes the O3/P2 biphasic structure, suppressing phase transitions.
• This approach enhances sodium-ion diffusion kinetics and improves overall battery performance.
• The developed cathode material shows significant promise for advanced sodium-ion battery applications.