Beyond Separation: Multifunctional Separators in Rechargeable Batteries

With the wide application of high-performance rechargeable batteries in numerous fields, the requirements for batteries are becoming increasingly stringent, which are not limited only to electrochemical performance but also include mechanical properties, safety, sustainability, and intelligence. As a key component of rechargeable batteries, the current separator plays a more important role in enhancing the overall battery performance, beyond the traditional separation function. This review focuses on the modification methods of separators and the design of multifunctional separators. A variety of promising strategies, such as surface functionalization, functional coating, intrinsic modification, and macro-architecture design, are described. The optimization of the multifunctional separator in terms of thermal stability, mechanical strength, sustainability, intelligent detection, and lithium replenishment has also been discussed. In addition, this article points out the current challenges in the research of multifunctional separators and provides suggestions for their future development, which will bring valuable insights to the improvement of battery separators.