Lithium-ion batteries (LIBs) are extensively examined and employed as the predominant power source for electric vehicles, attributable to their remarkable efficiency and energy density. Nonetheless, despite the accelerating global consumption of LIBs, thermal safety remains a significant concern. This paper conducts a comprehensive analysis of the thermal safety challenges associated with LIBs, focusing on the thermal behavior of LIBs, incidents of thermal runaway, and the safety protocols implemented at both the cell and battery pack levels. The initial segment of the discourse addresses the mechanisms of heat generation within LIBs, elaborating on the processes of heat production, dissipation, and retention within a cell. Subsequently, the principal factors contributing to thermal runaway, which may culminate in catastrophic failures, are identified and summarized within the investigation. These factors encompass internal short circuits, overcharging, and mechanical impairments.