Dynamic thermo-responsive polythiourethane–urethane coatings for enhanced energy storage safety

Energy storage systems demand advanced safety concepts capable of a rapid thermal response to early detect thermal runaway events. However, conventional safety techniques often lack reliability, upscalability, and ease of application. This study aims to develop and characterize thermo-responsive polymers which selectively release volatile tracer molecules at defined temperatures. The polymer design relies on polythiourethane–urethanes formed by the reaction of a polyol containing dynamic disulfide groups across isocyanates partly blocked with low-molecular weight thiols. The liberation of the thiols by a thermally triggered deblocking reaction is evidenced by various thermal characterization methods and is monitored with a metal oxide (MOx) sensor test setup to assess real-case safety applicability for batteries. Once activated, the polymer can be reprocessed by thermoforming and recovers its function (ability to release thiols at a defined temperature) by removing the coating, dissolving it in solvent and reacting the composition with additional isocyanates and thiols. These recovery experiments demonstrate the successful re-introduction of the thermally liberated thiol. In addition, the dynamic disulfide bonds facilitate material recovery during reprocessing and preservation of mechanical integrity over multiple cycles as demonstrated by DMA and stress relaxation experiments. The developed dynamic and thermo-responsive polythiourethane–urethane polymers exhibit reliable performance, along with improved recoverability of the gas release function. Thus, these findings provide a foundation for the next generation of advanced and sustainable polymer coatings for safer energy storage systems. • Preparation of thermo-responsive polymers which release volatile thiols • Thermal liberation of the thiols is monitored by MOx sensors • Dynamic disulfide bonds promote reprocessing by thermoform process • Successful re-introduction of the released thiol is demonstrated • Possible application as coatings for safer energy storage systems