Chemistry, Impedance, and Morphology Evolution in Solid Electrolyte Interphase Films during Formation in Lithium Ion Batteries

The solid electrolyte interphase (SEI) forms during the initial cycles in lithium ion batteries and evolves throughout the battery life. By protecting the electrode and passing lithium ions, the SEI plays an important role in the performance and degradation of lithium ion batteries. Identifying how the SEI forms and evolves during battery cycling helps us understand and mitigate battery degradation. In this work, we address the SEI chemical and electrochemical evolution during its formation process and provide a correlation between these properties. It is found that the SEI chemistry, not just its thickness, has a distinct influence on its impedance, which may ultimately impact the battery performance.