Composite separators for internal thermal management in rechargeable lithium batteries: A review

Separators are thin microporous membranes that allow lithium-ion (Li+) transport across interfaces and through electrolyte, have a vital role in maintaining stable performance and safety of lithium batteries. However, conventional separators for rechargeable lithium batteries suffer from temperature-induced shrinkage, poor wettability, and low tensile stability, resulting in poor battery performance, short battery life, and safety hazards. To address these issues, it is crucial to address these challenges in engineering separators to meet the requirements of next-generation energy storage systems. Herein, we first discuss fundamental properties and requirements of separators for rechargeable lithium batteries. From the scientific societies, therefore, various physical and chemical modifications have been made to conventional separators, resulting in functional composite separators. This review summarizes and discusses how composite separators manage internal thermal safety in rechargeable lithium batteries, along with other benefits, including Li+ conductivity, structural integrity, wettability, better rate capability, and suppression of crossover.