Advances in thermal stable separators and solid electrolytes for high-temperature lithium-ion batteries

Nowadays, lithium-ion batteries (LIBs) are widely used in electric vehicles and grid energy storage. However, they are plagued by safety issues such as fires and explosions. Furthermore, as the application range of LIBs expands, there is a growing demand for batteries that can endure high temperatures. However, traditional polyolefin separators present poor thermal stability, and liquid electrolytes containing organic solvents are highly volatile, flammable, and prone to leakage. These disadvantages diminish the cell performances and safety of LIBs working at high temperatures. Therefore, developing separators or electrolytes with high safety and thermal stability is of great significance for achieving of high-temperature LIBs. Here, we analyze the factors that cause lithium batteries to fail in high temperatures. The recent research and development of thermally stable separators (the high-temperature resistant modification for commercial separators, novel polymer separators and inorganic separators) and solid electrolytes (inorganic ceramic electrolytes, solid polymer electrolytes and composite solid electrolytes) in recent years are reviewed. Finally, we summarize the challenges and bottlenecks associated with these advanced separators, solid electrolytes and provide recommendations. This review is anticipated to provide valuable insights into designing highly thermally stable separators and solid electrolytes for the next generation of high-temperature LIBs.