Multi-Impurity Scavenging Separator for Lithium-Ion Batteries with Enhanced High-Temperature Performance

With the increasing demand for high-energy lithium-ion batteries, Ni-rich cathodes are considered as a key component for post lithium-ion batteries (LIBs). However, their practical applications are hindered by their limitations, such as microcracking, transition metal dissolution, and electrolyte decomposition at the cathode surface, which causes an increase in cell resistance. These problems are accelerated by the parasitic reaction of impurities such as H₂O, HF, and transition metal (TM) during cycling, leading to the battery failure. In this regard, removing impurities (H₂O, HF, TM) from the electrolytes is one of the ways to enhance the battery performance. In this work, we fabricated a grafted polyacrylonitrile membrane with zeolite (GPANZ) as a multi-scavenging functional separator to improve the cycling characteristics of LIBs. The GPANZ consisted of H₂O and HF-removing functional zeolite and TM chelate functional polyethyleneimine (PEI), effectively captured various impurities. The obtained GPANZ exhibited excellent physical/electrochemical properties and was applied to the lithium-ion cell composed of graphite anode and NCM811 cathode. The cell with GPANZ showed improved cycle life and structural stability of the electrode compared to the cell with a conventional polyethylene separator after 55 ^oC cycling. Our results highlight the necessity of removing impurities to ensure battery performance and provide new insights for designing functional separators in LIBs.