Alternating Edge- and Face-Sharing Octahedra with Partial Super-Exchange Enabling High-Voltage Layered Cathodes

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Traditional O3-type layered oxides exhibit poor structural stability during high-voltage operation due to edge-sharing octahedra.
• Cobalt (Co) migration is a key factor limiting the performance and lifespan of these cathode materials.
• Developing stable layered oxide structures is crucial for advancing high-energy-density batteries.

Purpose of the Study:

• To design and synthesize a novel, structurally stable edge-sharing coplanar (ESC) O2-type layered oxide cathode.
• To investigate the impact of the ESC configuration on suppressing transition metal migration and enhancing structural integrity.
• To optimize Ni content for improved high-voltage cycling performance and lithium-ion diffusion.

Main Methods:

• Synthesis of a novel ESC O2-type layered oxide structure.
• Characterization of structural stability and Co migration suppression.
• Electrochemical testing, including high-voltage cycling performance and capacity retention.
• Analysis of Ni-O-TM super-exchange interactions and their effect on Li-ion diffusion.

Main Results:

• The ESC configuration effectively suppresses Co migration and enhances intrinsic structural stability.
• Modified ESC cathodes demonstrate high discharge capacity (247 mAh g⁻¹) and excellent capacity retention (79% at 1 C after 100 cycles).
• Optimal Ni content expands unit-cell volume, reducing Li-ion diffusion activation energy, but excess Ni obstructs Li-ion pathways.

Conclusions:

• The edge-sharing coplanar (ESC) O2-type layered structure offers a promising strategy for developing stable high-voltage cathode materials.
• Regulating the local coordination environment is key to achieving high performance in layered oxide cathodes.
• This work provides insights into the role of Ni content and its impact on electrochemical performance in ESC cathodes.