Epitaxially Grown Lattice-Coherent Surface Enabling Superior Mechanical Integrity for High-Voltage LiCoO₂ Cathode

Area of Science:

• Materials Science
• Electrochemistry
• Solid-state Chemistry

Background:

• High-energy-density cathodes are crucial for advanced batteries.
• High-voltage operation of lithium cobalt oxide (LiCoO2) above 4.55V leads to structural and interfacial instability.
• This instability causes mechanical failure and significant capacity decay.

Purpose of the Study:

• To enhance the structural and interfacial stability of high-voltage LiCoO2.
• To enable stable operation of LiCoO2 at voltages of 4.6V and beyond.
• To explore surface engineering as a strategy for improving LiCoO2 performance.

Main Methods:

• Thermally driven element interdiffusion was employed to create a surface modification.
• A Co-containing Li-rich phase was epitaxially grown on the LiCoO2 surface.
• The structural integrity and electrochemical performance of the modified LiCoO2 were evaluated.

Main Results:

• A highly durable, lattice-coherent Li-rich phase was successfully grown on the LiCoO2 surface.
• Adverse side reactions, irreversible phase transitions, and lattice oxygen loss were significantly inhibited.
• The modified LiCoO2 exhibited excellent cycling stability and additional capacity at 4.6V and 4.7V.

Conclusions:

• Surface engineering via epitaxial growth of a Li-rich phase effectively enhances the mechanical integrity of high-voltage LiCoO2.
• This approach mitigates degradation pathways, enabling stable high-voltage operation.
• The developed surface modification strategy offers a promising route for next-generation high-energy-density cathode materials.