Abstract With the deep commercialization of lithium‐ion batteries (LIBs), the market has put forward higher requirements for their energy density, safety, and lifespan. The separator, as a key component of the physical barrier that hinders short circuits, offers numerous opportunities for enhancing cell performance by compensating the drawbacks of the cathode/anode or providing innovative functions. To date, considerable efforts have been devoted to the exploration of advanced separators, aiming at overcoming the challenges faced by LIBs. This review first outlines the fundamental requirements and preparation techniques of separators to guide the meticulous design. Then, the critical roles of the separator in the cathode and anode are summarized, accompanied by up‐to‐date progress, challenges, and potential improvement strategies. Additionally, this work emphasizes the roles of the separator in achieving high thermal safety performance in batteries and classifies its functions. Finally, an outlook on future research directions is provided to inspire the design and commercialization of separators. This review aims to deepen the understanding of the roles of separators and foster the development of separator‐derived strategies for addressing issues in the field of energy storage.
Liu et al. (2025) studied this question.