Understanding the Role of Commercial Separators and Their Reactivity toward LiPF ₆ on the Failure Mechanism of High?Voltage NCM523 || Graphite Lithium Ion Cells

NCM523 || graphite lithium ion cells operated at 4.5 V are prone to an early “rollover” failure, due electrode cross-talk, that is, transition metal (TM = Mn, Ni, and Co) dissolution from deposition graphite, subsequent formation of Li dendrites, and, in the worst case, generation (micro-)short-circuits by dendrites growing cathode. Here, impact different separators on high-voltage performance is elucidated focusing separators’ structural properties (e.g., membrane vs fiber) their reactivity toward LiPF6 ceramic-coated separators). First, separator architecture has a major cycle life. Fiber-structured can prevent failure more homogeneous TMs thus, hindering penetration In contrast, porous membrane-structured cannot cell inhomogeneous TM deposits/Li dendrites. Second, it demonstrated types (Boehmite (?-AlO(OH)) ?-Al2O3) exhibit reactivities LiPF6. While ?-Al2O3 shows minor LiPF6, ?-AlO(OH) coating leads situ beneficial difluorophosphate anion high amounts decomposition, which significantly improves