Lithium-ion batteries (LIBs) are critical energy storage technologies, but their safety is a major concern due to the risk of fires and explosions, especially with high energy density. This review summarizes the origins of LIB safety issues and highlights recent advancements in materials design to enhance safety. The thermal runaway process, which leads to fires and explosions, occurs in three stages: overheating, heat accumulation and gas release, and combustion. The first stage is triggered by internal short circuits, such as those caused by dendrite formation, which can be mitigated through improved anode materials and multifunctional electrolytes and separators. The second stage involves exothermic reactions that release oxygen and heat, which can be addressed by using reliable cathode materials with enhanced thermal stability and thermally switchable current collectors. The third stage involves combustion, which can be prevented by using nonflammable electrolytes and flame-retardant additives. The review also discusses the development of solid-state electrolytes and nonflammable liquid electrolytes as potential solutions for safer LIBs. Overall, the focus is on designing materials that can intrinsically improve battery safety, ensuring reliable performance and preventing catastrophic failures.Lithium-ion batteries (LIBs) are critical energy storage technologies, but their safety is a major concern due to the risk of fires and explosions, especially with high energy density. This review summarizes the origins of LIB safety issues and highlights recent advancements in materials design to enhance safety. The thermal runaway process, which leads to fires and explosions, occurs in three stages: overheating, heat accumulation and gas release, and combustion. The first stage is triggered by internal short circuits, such as those caused by dendrite formation, which can be mitigated through improved anode materials and multifunctional electrolytes and separators. The second stage involves exothermic reactions that release oxygen and heat, which can be addressed by using reliable cathode materials with enhanced thermal stability and thermally switchable current collectors. The third stage involves combustion, which can be prevented by using nonflammable electrolytes and flame-retardant additives. The review also discusses the development of solid-state electrolytes and nonflammable liquid electrolytes as potential solutions for safer LIBs. Overall, the focus is on designing materials that can intrinsically improve battery safety, ensuring reliable performance and preventing catastrophic failures.