<p>Temperature variations significantly affect the performance and safety of lithium-ion batteries (LIBs), particularly under extreme conditions and high charge/discharge rates. Uneven heat generation, limited heat dissipation, and residual energy accumulation exacerbate thermal effects, leading to capacity degradation, reduced efficiency, and safety hazards. Addressing these challenges requires a multiscale understanding of the thermal behavior of LIBs. This review provides an integrated, multiscale perspective on battery thermal safety, spanning material-level design, cell-level modeling and state estimation, and system-level thermal management. We first examine the fundamental thermal mechanisms and modeling approaches governing heat generation, transport, and accumulation across varying operating conditions at the cell level. We then explore material-level strategies to mitigate low-temperature degradation and enhance high-temperature stability, enabling reliable all-climate operation. Building on these insights, we assess system-level thermal management approaches, including internal and external preheating, as well as active and passive cooling methods. Particular attention is given to immersion cooling, which offers superior heat dissipation, improved temperature uniformity, and enhanced safety. We comprehensively review immersion cooling technologies, including system configurations, fluid selection, operational parameters, and recent advances in both single-phase and two-phase cooling. By bridging physical mechanisms, modeling frameworks, and engineering solutions across scales, this review highlights key challenges, identifies critical research gaps, and outlines future directions for achieving adaptive and robust thermal safety in LIBs. The insights provided aim to support the development of safer, more reliable, and thermally resilient LIB systems for transportation and large-scale energy storage applications.</p> Graphical abstract <p></p>