材料科学
分离器(采油)
阴极
陶瓷
反应性(心理学)
化学工程
复合材料
电解质
石墨
电极
化学
物理化学
病理
工程类
物理
热力学
替代医学
医学
作者
Sven Klein,Jens Matthies Wrogemann,Stefan van Wickeren,Patrick Harte,Peer Bärmann,Bastian Heidrich,Jakob Michael Hesper,Kristina Borzutzki,Sascha Nowak,Markus Börner,Martin Winter,Johannes Kasnatscheew,Tobias Placke
标识
DOI:10.1002/aenm.202102599
摘要
Abstract NCM523 || graphite lithium ion cells operated at 4.5 V are prone to an early “rollover” failure, due to electrode cross‐talk, that is, transition metal (TM = Mn, Ni, and Co) dissolution from NCM523 and deposition at graphite, subsequent formation of Li metal dendrites, and, in the worst case, generation of (micro‐)short‐circuits by dendrites growing to the cathode. Here, the impact of different separators on the high‐voltage performance of NCM523 || graphite cells is elucidated focusing on the separators’ structural properties (e.g., membrane vs fiber) and their reactivity toward LiPF 6 (e.g., ceramic‐coated separators). First, the separator architecture has a major impact on cycle life. Fiber‐structured separators can prevent the “rollover” failure by a more homogeneous deposition of TMs and formation of Li metal dendrites, thus, hindering penetration of dendrites to the cathode. In contrast, porous membrane‐structured separators cannot prevent the cell failure due to inhomogeneous TM deposits/Li metal dendrites. Second, it is demonstrated that different types of ceramic‐coated separators (Boehmite (γ‐AlO(OH)) vs α‐Al 2 O 3 ) exhibit different reactivities toward LiPF 6 . While α‐Al 2 O 3 shows a minor reactivity toward LiPF 6 , the γ‐AlO(OH) coating leads to in situ formation of the beneficial difluorophosphate anion in high amounts due the high reactivity toward LiPF 6 decomposition, which significantly improves cycle life.
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