Analyzing the Li-Al-O Interphase of Atomic Layer-Deposited Al₂O₃ Films on Layered Oxide Cathodes Using Atomistic...

Area of Science:

• Materials Science
• Electrochemistry
• Computational Chemistry

Background:

• Alumina surface coatings enhance layered oxide cathode performance in lithium-ion batteries.
• Atomic Layer Deposition (ALD) creates ultrathin alumina films (<2 nm) beneficial for LiNiMnCoO2 materials.
• The atomic structure and Li-Al-O product formation at the interface are not well understood.

Purpose of the Study:

• To quantify the nanostructure of amorphous alumina films on LiCoO2 using molecular dynamics simulations.
• To investigate the Li-Al-O interphase formation and atomic arrangements at the interface.
• To provide insights into the structure-property relationships of ALD alumina coatings.

Main Methods:

• Molecular dynamics simulations of amorphous alumina films on the (0001) LiCoO2 surface.
• Calculation of elemental mass density profiles to determine interphase thickness.
• Analysis of Al coordination numbers to understand short-range order.

Main Results:

• The Li-Al-O interphase extends approximately 2 nm from the LiCoO2 surface.
• Layering of Al and O atoms observed at the interface up to ~1.5 nm.
• Significant amounts of octahedral [6]Al found at the interface, alongside tetrahedral [4]Al.

Conclusions:

• ALD alumina forms a pseudomorphic Li-Al-O overlayer that approximates the LiCoO2 lattice.
• Thicker films transition to a bulk amorphous alumina structure.
• Findings are applicable to other layered LiNiMnCoO2 materials, informing the use of ALD alumina coatings.