Tri-Layer Nonwoven Separator with Thermal Shutdown Function Fabricated through a Facile Papermaking Method for High-Safety Lithium-Ion Battery

Lithium-ion batteries have long been plagued by the safety issue of thermal runaway. Improving the thermal stability and developing the thermal shutdown function of the separators are considered reliable solutions. Therefore, in this work, a tri-layer structured nonwoven separator with a thermal shutdown function has been prepared via the papermaking method. The separator comprises a polyethylene fiber layer, a microfibrillated cellulose fibers layer, and a polyethylene terephthalate nonwoven fabric layer. The polyethylene fiber layer endows the separator with a thermal shutdown function at 135 °C. The middle polyethylene terephthalate nonwoven layer provides support, while the microfibrillated cellulose fibers adjust the pore size. The separators exhibit excellent thermal stability, no shrinkage after heat treatment at 200 °C, and a wide thermal shutdown temperature window, thereby enhancing battery safety. This research provides an approach to fabricating high-safety thermal shutdown separators.