Diffusion Mechanisms in the Solid Electrolyte Interphase in Li-Ion Batteries from First Principle Calculation

The understanding of the mechanisms of Li-ion transport and electron leakage through the solid electrolyte interphase (SEI) layer is crucial to enhance the performance of rechargeable Li-ion batteries. Our study was based on a slab model of Li metal covered by Li₂CO₃ with contact with ethylene carbonate (EC) electrolyte. Pure Li metal is an ideal negative electrode for its high capacity and low voltage level. The layer of crystalline Li₂CO₃ was used to mimic the SEI layer, since our recent recognition by TEM that Li₂CO₃ was the component responsible for stabilizing the SEI. The barriers for Li and electron transport under applied voltage will be computed within the framework of DFT and constrained-DFT to understand the mechanism in electrochemical systems. Ab inito molecular dynamics (AIMD) simulations will be performed to explicitly track Li⁺ diffusion pathways. Energy profiles as a function of the electric field during this reduction reaction will be  determined to understand the effects of electric field  on the diffusion barrier.