Reductive Decomposition Reactions of Ethylene Carbonate by Explicit Electron Transfer from Lithium: An eReaxFF Molecular Dynamics Study

(Chemical Equation Presented) A detailed understanding of the mechanism of the formation of the solid electrolyte interphase (SEI) is crucial for designing high-capacity and longer-lifecycle lithium-ion batteries. The anode-side SEI primarily consists of the reductive dissociation products of the electrolyte molecules. Any accurate computational method for studying the reductive decomposition mechanism of electrolyte molecules is required to include an explicit electronic degree of freedom. In this study, we employed our newly developed eReaxFF method to investigate the major reduction reaction pathways of SEI formation with ethylene carbonate (EC) based electrolytes. In the eReaxFF method, electrons are treated explicitly in a pseudoclassical manner. The method has the ability to simulate explicit electrons in a complex reactive environment. Our eReaxFF-predicted results for the EC decomposition reactions are in good agreement with the quantum chemistry data available in the literature. Our molecular dynamics (MD) simulations capture the mechanism of the reduction of the EC molecule due to electron transfer from lithium, ring opening of EC to generate EC^-/Li⁺ radicals, and subsequent radical termination reactions. Our results indicate that the eReaxFF method is a useful tool for large-scale simulations to describe redox reactions occurring at electrode-electrolyte interfaces where quantum-chemistry-based methods are not viable because of their high computational requirements.