Recent progress in advanced separators for lithium-ion batteries (LIBs) is reviewed, highlighting three main types: modified polymeric separators, composite separators, and inorganic separators. The current state-of-the-art LIBs face challenges such as low energy density, limited durability, and safety concerns, which cannot be solved solely by improving electrodes. Separators, a critical component, influence battery electrochemical properties and safety without participating in electrochemical reactions. Developing innovative separators is essential for designing more sustainable and reliable energy storage systems. Advanced separators have become an important research area in both laboratories and industries. Lithium-ion batteries have become crucial for the electric vehicle (EV) revolution and are considered one of the most impressive successes in modern electrochemistry. The global market for LIBs is expected to grow significantly, reaching about $56 billion in 2024 and $253 billion by 2030. The separator is a key component that isolates the electrodes, prevents direct contact, and allows lithium ion passage. It also ensures safe battery operation. However, in exceptional cases, such as accidents or misuse, damage to the separator can lead to electrode contact, causing chemical reactions and potential fires or explosions. Therefore, advanced separators with enhanced requirements such as chemical stability, wettability, thermal stability, mechanical strength, and porosity are needed. Recent research has focused on the design and development of advanced separators for cutting-edge LIBs, shifting from morphology control to multifunctionality. The traditional preparation methods of separators include dry- and wet-processed stretching methods. The dry method includes uniaxial and biaxial stretching, while the wet method involves phase separation. The wet method allows better control of pore size and porosity but requires solvents, which may lead to pollution and increased costs. The early market for battery separators was dominated by Japan, South Korea, and the USA. As the leading company, the development of advanced separators continues to be an important research direction.Recent progress in advanced separators for lithium-ion batteries (LIBs) is reviewed, highlighting three main types: modified polymeric separators, composite separators, and inorganic separators. The current state-of-the-art LIBs face challenges such as low energy density, limited durability, and safety concerns, which cannot be solved solely by improving electrodes. Separators, a critical component, influence battery electrochemical properties and safety without participating in electrochemical reactions. Developing innovative separators is essential for designing more sustainable and reliable energy storage systems. Advanced separators have become an important research area in both laboratories and industries. Lithium-ion batteries have become crucial for the electric vehicle (EV) revolution and are considered one of the most impressive successes in modern electrochemistry. The global market for LIBs is expected to grow significantly, reaching about $56 billion in 2024 and $253 billion by 2030. The separator is a key component that isolates the electrodes, prevents direct contact, and allows lithium ion passage. It also ensures safe battery operation. However, in exceptional cases, such as accidents or misuse, damage to the separator can lead to electrode contact, causing chemical reactions and potential fires or explosions. Therefore, advanced separators with enhanced requirements such as chemical stability, wettability, thermal stability, mechanical strength, and porosity are needed. Recent research has focused on the design and development of advanced separators for cutting-edge LIBs, shifting from morphology control to multifunctionality. The traditional preparation methods of separators include dry- and wet-processed stretching methods. The dry method includes uniaxial and biaxial stretching, while the wet method involves phase separation. The wet method allows better control of pore size and porosity but requires solvents, which may lead to pollution and increased costs. The early market for battery separators was dominated by Japan, South Korea, and the USA. As the leading company, the development of advanced separators continues to be an important research direction.