Unveiling the First Nucleation and Growth Steps of Inorganic Solid Electrolyte Interphase Components
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2018 American Chemical Society. The complexity of the solid electrolyte interphase (SEI) in lithium-ion batteries with graphitic electrodes has triggered extensive research efforts because of its crucial role on the lifetime of the battery. The SEI layer is composed of organic and inorganic species, resultant from the electrolyte decomposition at the electrode-electrolyte interface upon the first cycles of the battery. A stable SEI layer is essential to maintain the chemical and mechanical stability of the electrode as well as the electrochemical stability of the electrolyte in order to prevent further irreversible capacity loss. This work uses computational crystal structure prediction genetic evolutionary algorithms to simulate the nucleation, growth, and aggregation of the inorganic products forming the SEI mosaic film. In depth investigation of the growth mechanisms of LiF and Li2CO3 starting from the first nucleation seeds is undertaken. The cluster-stacking and layer-by-layer SEI growth on the graphite surface as well as near-shore SEI layer cluster aggregation growth mode are shown to be strongly dependent on the electrode degree of lithiation and nature of surface termination groups. Comparison among the various growth modes suggests that the most likely scenario is a mixed mode: small clusters may be formed in near-shore locations and migrate toward the surface during cycling, while nucleation and growth at the surface may also exist. This mixed mode of growth is consistent with a heterogeneous "mosaic" SEI picture suggested in the literature.