(418b) Understanding the Nanostructure and Performance of Alumina Atomic Layer Deposited Films on a Layered Cathode Oxide Surface Using Molecular Dynamics Simulation
AIChE Annual Meeting
2022
2022 Annual Meeting
Topical Conference: Material Interfaces as Energy Solutions
Interfacial Systems for Energy Application: Modeling and Simulation
Tuesday, November 15, 2022 - 3:48pm to 4:06pm
Specifically, we studied alumina (Al2O3) deposition in contact with a layered cathode oxide (e.g., LiCoO2 or other NMCs) without specific chemical modifications (such as hydration or carbonation products), and we modeled the trimethylaluminum (TMA)/water ALD chemistry with the cathode oxide surface after complete reaction. IFF in the 12-6 Lennard Jones form was used to model both the alumina and the layered cathode oxide. Using molecular dynamics simulations, we studied the structure, energy, and lithium distribution for zero to six monolayers of Al2O3: including multiple initial structures and annealing protocols to sample the configuration space and various degrees of simulated X-Ray crystallinity of the ALD films.
We find alumina films containing two to three monolayers exhibit favorable binding energies to the layered cathode oxide surface and optimum lithium availability on the exterior of the alumina film. Alumina layer numbers outside of two to three layers are thermodynamically less favorable. Generally, the more thermodynamically stable thin film-cathode interfaces possess lower alumina film crystallinities with the exception of two layers, which is highly crystalline, while thicker films are more crystalline. The lithium density profiles through the films show that the lithium exists on either side of thin Al2O3 films while the lithium becomes increasingly incorporated in the bulk of thicker films.
These atomic scale findings help explain experimental data showing two to four alumina ALD cycles yield a maximum discharge capacity and longer cycling stability compared to the uncoated NMC oxide surfaces.