<p>The rapid deployment of LIBs in electric vehicles, portable electronics, and grid storage has intensified concerns regarding TR (TR). Conventional safety strategies including thermal management systems and shutdown separators, often respond only after significant heat accumulation, limiting their effectiveness in early-stage hazard mitigation. This review explores thermo-responsive nanohydrogels as a new class of internal thermal fuse materials capable of autonomously interrupting failure progression at its onset. These nanostructured polymer networks exhibit temperature-triggered transitions in volume, porosity, conductivity, and interfacial properties, enabling dynamic regulation of ion transport, electrolyte behaviour, and heat flow within battery systems. Integration pathways at the separator, electrolyte and module levels are critically evaluated. Unlike previous reviews that broadly discuss hydrogels, smart polymers, or gel electrolytes in batteries, this review specifically focuses on thermo-responsive nanohydrogels as internal thermal-fuse materials and evaluates them from a battery safety and process-safety perspective. Quantitative examples demonstrate that hydrogel-based systems can significantly delay TR, reduce peak temperatures, and improve cycling stability under abusive conditions. Overall, this review positions thermo-responsive nanohydrogels as multifunctional, adaptive safety components that bridge material design and process-safety engineering, offering a promising pathway toward intrinsically safer next-generation batteries.</p>