Microscopic Analysis of the Mechanical Stability of an SEI Layer Structure Depending on the FEC Additive Concentration in Na-Ion Batteries: Maximum Appearance in Vickers Hardness at Lower FEC Concentrations

Amine Bouibes; Nisrine Sakaki; Masataka Nagaoka

doi:10.1021/acsomega.2c06224

Microscopic Analysis of the Mechanical Stability of an SEI Layer Structure Depending on the FEC Additive Concentration in Na-Ion Batteries: Maximum Appearance in Vickers Hardness at Lower FEC Concentrations

ACS Omega. 2023 May 1;8(19):16570-16578. doi: 10.1021/acsomega.2c06224. eCollection 2023 May 16.

Authors

Amine Bouibes^{1

2}, Nisrine Sakaki¹, Masataka Nagaoka^{1

2

3}

Affiliations

¹ Graduate School of Informatics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan.
² Elements Strategy Initiative for Catalysts and Batteries (ESICB), Kyoto University, Kyodai Katsura, Nishikyo-ku, Kyoto 615-8520, Japan.
³ Future Value Creation Research Center, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan.

Abstract

The stability of the solid electrolyte interphase (SEI) layer during the charging-discharging cycles is reasonably related to its microscopic elasticity. For the first time, it was theoretically revealed that each component of the elastic moduli takes a maximum at an optimal concentration of 1.0 vol % of fluoroethylene carbonate (FEC) for the SEI layer formed in the FEC-added NaPF₆/PC-based electrolyte. The elastic constants indicated that the SEI layer formed at lower FEC concentrations is more resistant to tensile and shear deformations. The optimal hardness is sensitive in the lower FEC concentrations although it simply decreases as the FEC concentration increases. This is due to the formation of a denser SEI structure with small cavities in the lower concentrations. The results are excellently consistent with the experimental one, justifying the microscopic understanding of the FEC additive effect on the mechanical stability of the SEI layers designed through the Red Moon simulation.