Thermal runaway prevention through scalable fabrication of safety reinforced layer in practical Li-ion batteries.

Integrating safety features to cut off excessive current during accidental internal short circuits in Li-ion batteries (LIBs) can reduce the risk of thermal runaway. However, making this concept practical requires overcoming challenges in both material development and scalable manufacturing. Here, we demonstrate the roll-to-roll production of a safety reinforced layer (SRL) on current collectors at a rate of 5 km per day. The SRL, made of molecularly engineered polythiophene (PTh) and carbon additives, interrupts current flow during voltage drops or overheating without adversely affecting battery performance. Impact testing on 3.4-Ah pouch cells shows that the SRL reduces battery explosions from 63% to 10%. This work underscores the potential of integrating material science with manufacturing technology to enhance battery safety.