Ab Initio Molecular Dynamics with Sequential Electron Addition as a Tool to Find Initial Reductive Solid Electrolyte Interface Formation Reactions

Lithium-ion batteries (LIBs) are an essential building block for modern energy storage. The solid-electrolyte interface (SEI) is an important component of LIBs, which acts as a passivation layer and prevents electrode and electrolyte from further decomposition and, thus, from capacity loss. In this work, we investigated the first steps of SEI formation initiated from commonly used electrolyte compounds ethylene carbonate (EC), diethyl carbonate (DEC), vinylele carbonate (VC), and 1,3-propane sultone (PS). Ab initio molecular dynamics (AIMD) simulations based on density functional theory was used to discover chemical reactions without chemical intuition. In order to simulate the reductive potential at the electrode, electrons are added sequentially to the system, leading to electro-reductive decomposition of the compounds. It was observed that this progressive electron addition leads to the formation of various reaction products, which can act as further reactants in subsequent reactions. Further reaction products were observed, some of which were reactions known from the literature, but also other, energetically less favorable structures were discovered. The molecular structures found in the AIMD simulations agree closely with experimental findings, validating the accuracy and reliability of the herein presented approach of sequentially adding electrons in molecular simulations.