Developing a flame-retardant flexible composite phase change material to realize both temperature control and thermal runaway prevention for lithium-ion battery pack

Exploring a facile solution to controlling the operating temperature within the range between −25 °C and 60 °C and the temperature difference between batteries less than 5 °C as well as preventing thermal runaway for battery packs, is significant, but remains challenging. Herein, a flame-retardant flexible composite phase change material was developed and applied for both the temperature control and thermal runaway prevention of battery packs. Specifically, a flame-retardant coating comprising 70 % polydimethylsiloxane as a binder was first investigated to determine the optimal mass ratio of 3:1 for the blend of expandable graphite and ammonium polyphosphate. The flame-retardant flexible composite phase change material was then produced by applying the optimal coating at a loading of 15 % on a flexible composite phase change material that was obtained from incorporating an ethylene propylene diene monomer with a mass fraction of 40 % into an 80 % paraffin/20 % expanded graphite composite. The flame-retardant flexible CPCM not only exhibited the highest flame-retardant rating of V-0, a significant latent heat capacity and good thermal reliability, but also demonstrated improved thermal conductivity and enhanced mechanical properties in tensile strength, bending, and compression as compared with the uncoated counterpart. The flame-retardant flexible composite phase change material achieves better temperature control performance for a battery pack compared to the material without a flame-retardant coating. Moreover, the flame-retardant flexible composite phase change material effectively prevents thermal runaway propagation within a battery pack. These favorable characteristics demonstrate the considerable potential of the flame-retardant flexible CPCM for battery thermal management in electric vehicles.