Insights into Spontaneous Solid Electrolyte Interphase Formation at Magnesium Metal Anode Surface from Ab Initio Molecular Dynamics Simulations

Garvit Agarwal; Jason D Howard; Venkateshkumar Prabhakaran; Grant E Johnson; Vijayakumar Murugesan; Karl T Mueller; Larry A Curtiss; Rajeev S Assary

doi:10.1021/acsami.1c07864

Insights into Spontaneous Solid Electrolyte Interphase Formation at Magnesium Metal Anode Surface from Ab Initio Molecular Dynamics Simulations

ACS Appl Mater Interfaces. 2021 Aug 18;13(32):38816-38825. doi: 10.1021/acsami.1c07864. Epub 2021 Aug 6.

Authors

Garvit Agarwal^{1

2}, Jason D Howard^{1

2}, Venkateshkumar Prabhakaran^{2

3}, Grant E Johnson^{2

3}, Vijayakumar Murugesan^{2

3}, Karl T Mueller^{2

3}, Larry A Curtiss^{1

2}, Rajeev S Assary^{1

2}

Affiliations

¹ Materials Science Division, Argonne National Laboratory, Lemont, Illinois 60439, United States.
² Joint Center for Energy Storage Research (JCESR), Argonne National Laboratory, Lemont, Illinois 60439, United States.
³ Pacific Northwest National Laboratory, Richland, Washington 99352, United States.

PMID: 34362250
DOI: 10.1021/acsami.1c07864

Abstract

Spontaneous chemical reactivity at multivalent (Mg, Ca, Zn, Al) electrode surfaces is critical to solid electrolyte interphase (SEI) formation, and hence, directly affects the longevity of batteries. Here, we report an investigation of the reactivity of 0.5 M Mg(TFSI)₂ in 1,2-dimethoxyethane (DME) solvent at a Mg(0001) surface using ab initio molecular dynamics (AIMD) simulations and detailed Bader charge analysis. Based on the simulations, the initial degradation reactions of the electrolyte strongly depend on the structure of the Mg(TFSI)₂ species near the anode surface. At the surface, the dissociation of Mg(TFSI)₂ species occurs via cleavage of the N-S bond for the solvent separated ion pair (SSIP) and via cleavage of the C-S bond for the contact ion pair (CIP) configuration. In the case of the CIP, both TFSI anions undergo spontaneous bond dissociation reactions to form atomic O, C, S, F, and N species adsorbed on the surface of the Mg anode. These products indicate that the initial SEI layer formed on the surface of the pristine Mg anode consists of a complex mixture of multiple components such as oxides, carbides, sulfides, fluorides, and nitrides. We believe that the atomic-level insights gained from these simulations will lay the groundwork for the rational design of tailored and functional interphases that are critical for the success of multivalent battery technology.

Keywords: Mg-battery; ab initio molecular dynamics; density functional theory; interfacial reactivity; reaction mechanisms; solid-electrode interphase (SEI).