Metal–Organic Frameworks Enabled High-Performance Separators for Safety-Reinforced Lithium Ion Battery

Separators in lithium ion batteries (LIBs) play critical roles in offering ion-conducting routes and preventing the occurrence of internal short circuit. Here, a novel strategy to improve the thermal and cyclic stabilities of polypropylene (PP) separator is demonstrated. The PP separator surface is fully covered by a thin layer of zeolitic imidazolate framework-67 (ZIF-67) to form PP–ZIF-67 composite separator, which boosts cell performance better than the pure PP separator through a direct coating method. For example, the PP separator coated with ZIF-67 samples synthesized in methanol (CH3OH) greatly enhanced the cell's capacity retention (61.5%) compared with the cell that used pure PP separator (0.0%) after 100 cycles at a high temperature of 55 °C. Our results also show that the battery performance is affected by ZIF-67 samples that are synthesized in different solvents, implying that the battery performance may be further enhanced by optimizing the ZIF-67 structures. The proposed strategy paves a new avenue for achieving high-safety LIBs in this work.