Exploring Wet SEI Layer Dynamics and Stability in Lithium-Ion Batteries Through Salt Concentration: An Ab-Initio Molecular Dynamics and Machine Learning Study

The Solid-Electrolyte Interphase (SEI) layer plays a key role in the performance and longevity of lithium-ion batteries (LiBs) (1), with its stability being crucial for efficient reversible operation of LiBs. This study focuses on the dynamics of the 'wet SEI' – an inorganic layer in contact with electrolyte solution (2), comprising components such as lithium fluoride (LiF), lithium oxide (Li₂O), and lithium carbonate (Li₂CO₃). A combination of <i>ab-initio</i> molecular dynamics (AIMD) simulations and machine learning models is employed to identify a 'goldilocks' salt concentration that optimizes the stability of the SEI layer, a critical factor in enhancing battery performance.<br/><br/>The study provides a comprehensive analysis of the interaction dynamics of LiF, Li₂O, and Li₂CO₃ in various electrolyte environments. The changes in cluster stability, surface area, and bond dynamics are explored, particularly focusing on the effects of varying salt concentrations on these parameters. The goal is to characterize an optimal salt concentration that yields an ideal inorganic SEI layer, enhancing the layer's protective qualities and improving overall battery safety and efficiency.<br/><br/>The findings of this study are significant for advancing the understanding of wet SEI layer formation and its optimization in LiBs. The implications of achieving an optimal SEI layer are profound, potentially leading to batteries with higher energy density, longer cycle life, and improved safety profiles.<br/><br/>References<br/>(1) A. Wang, S. Kadam, H. Li, S. Shi, Y. Qi, Review on modeling of the anode solid electrolyte interphase (SEI) for lithium-ion batteries, npj Computational Materials, 4 (2018) 15.<br/><br/>(2) S. Perez Beltran, P.B. Balbuena, SEI formation mechanisms and Li+ dissolution in lithium metal anodes: Impact of the electrolyte composition and the electrolyte-to-anode ratio, Journal of Power Sources, 551 (2022) 232203.