Density Functional Theory Study of Ethylene Carbonate Adsorption on the (0001) Surface of Aluminum Oxide α-Al2O3

Brian Ramogayana; David Santos-Carballal; Khomotso P Maenetja; Nora H de Leeuw; Phuti E Ngoepe

doi:10.1021/acsomega.1c03771

Density Functional Theory Study of Ethylene Carbonate Adsorption on the (0001) Surface of Aluminum Oxide α-Al₂O₃

ACS Omega. 2021 Oct 29;6(44):29577-29587. doi: 10.1021/acsomega.1c03771. eCollection 2021 Nov 9.

Authors

Brian Ramogayana¹, David Santos-Carballal^{2

3}, Khomotso P Maenetja¹, Nora H de Leeuw^{2

3

4}, Phuti E Ngoepe¹

Affiliations

¹ Materials Modelling Centre, School of Physical and Mineral Sciences, University of Limpopo, Private Bag x1106, Sovenga 0727, South Africa.
² School of Chemistry, University of Leeds, Leeds LS2 9JT, U.K.
³ School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, U.K.
⁴ Department of Earth Sciences, Utrecht University, Princetonlaan 8a, Utrecht 3584 CB, The Netherlands.

Abstract

Surface coating is one of the techniques used to improve the electrochemical performance and enhance the resistance against decomposition of cathode materials in lithium-ion batteries. Despite several experimental studies addressing the surface coating of secondary Li-ion batteries using α-Al₂O₃, the reactivity of the material toward the electrolyte components is not yet fully understood. Here, we have employed calculations based on the density functional theory to investigate the adsorption of the organic solvent ethylene carbonate (EC) on the major α-Al₂O₃(0001) surface. During adsorption of a single EC molecule, it was found that it prefers to bind parallel to the surface through its carboxyl oxygen. As the surface coverage (θ) was increased up to a monolayer, we observed larger adsorption energies per EC molecule (E _ads/N _EC) for parallel interactions and a reduction for perpendicular interactions. We also noted that increasing the surface coverage with both parallel and perpendicularly interacting EC molecules led to a decrease of the surface free energies and hence increased stability of the α-Al₂O₃(0001) surface. Despite the larger E _ads/N _EC observed when the molecule was placed parallel to the surface, minimal charge transfer was calculated for single EC interactions and at higher surface coverages. The simulated scanning tunneling microscopy images are also presented for a clean corundum α-Al₂O₃ surface and after adsorption with different coverages of parallel and perpendicularly placed EC molecules.