Solid electrolyte interphases (SEI) enable the Li-ion intercalation chemistries to operate reversibly beyond the thermodynamic stability limits of non-aqueous electrolytes. The chemical building blocks of SEI mainly come from solvents decomposition products. Exceptions arise, when salt anion are reduction-labile, or when salt concentration exceeds certain thresholds, where anion starts to participate in the interphasial chemistry. In those latter cases, unusually high F-content were often found in the interphases, and unexpected benefits from such intrephasial chemistries arose. However, high F-content in interphases were not always welcomed, thus, the morphology and structure of interphases should play an equally important role as their chemical compositions.
In this work, we explore the different manners that interphases could be fluorinated via the electrolyte sources, and the various battery chemistries that could benefit from such fluorination.