Reactivity of VC Electrolyte at Li-Metal Electrode: New Insights on SEI Initial Formation from Density Functional Embedding Theory

Abstract

The metallic lithium (Li) represents the most promising anode material among the next generation of solid-state lithium batteries [1]. An efficient strategy to achieve durable and effective Li-anode batteries is by engineering the solid-electrolyte interphase (SEI) with purposely designed molecules.To this aim, the vinylene carbonate (VC) is one of the most used additives in conventional electrolytes. Some recent experiments proved that the VC promotes the formation of a stable and protective SEI layer between Li metal and electrolyte [2, 3]. Unless the well-known SEI composition, it is difficult to control the VC reactivity, that involves dissociation and polymerization at the electrode surface. Therefore, to dissect these tangled processes, here we present new atomistic insights on VC-Lithium SEI formation via first-principles calculations by Density Functional Embedding Theory (DFET) [4, 5]. Such approach has potentialities for modeling complex reactions at hybrid interfaces in electrocatalysis: it is well suited to combine the best feasible approaches for molecular species (in this case, hybrid HF-DFT for VC molecules and derivatives) and for Li metal electrode (semi-local GGA density functional).Our results highlight different VC dissociation pathways, with formation of reactive radical species and localized cluster of Li2O and Li2CO3. The use of hybrid-DFT-in-DFT embedding is crucial for obtaning energy barriers and qualtitative results in agreement with experiments [3]. Overall, the energetics and structural features of these intermediates improve the current understanding of SEI formation process and can be exploited to drive the reactions toward the desired interfacial properties.[1] J. Janek, W. G. Zeier, Nat Energy 1 (2016) 16141.[2] A. L. Michan et al. Chem. Mater. 28 (2016) 8149.[3] Y. Kamikawa, K. Amezawa, K. Terada, J. Phys. Chem. C 124 (2020) 19937[4] C. Huang, M. Pavone, E. A. Carter, J. Chem. Phys. 134 (2011) 154110[5] C. Huang, A.B. Muñoz-García, M. Pavone, J. Chem. Phys. 145 (2016) 244103