Rationally coupling thermal tolerance, thermal conductance, and overheating-response in a separator for safe batteries

Abstract

Batteries with increasing energy density have boosted the development of electric vehicles with longer driving ranges but are also arousing safety concerns, especially thermal runaway, which impede their large-scale application. Herein, guided by electro-chemo-thermal process modeling, we reveal the coupled roles of thermal tolerance, thermal conductance, and overheating-response properties of separators in preventing thermal runaway under abusive harsh conditions. As such, we realize the thermal process intensification by integrating these properties into a thermal managing trilayer separator by sandwiching a thermal tolerant poly(p-phenylene benzobisoxazole) matrix between the mixture layers of thermally conducting boron nitride nanosheets and overheating-responding polyvinylidene fluoride. Compared with commercial separators, such a separator shows much improved safety performance including nonflammability, anti-shrinkage performance at high-temperature (almost zero at 350 °C) and thermal shutdown property, finally doubling the safety-responding window for the battery management system. The strategy of coupling thermal tolerance, conductance, and overheating-response capability in a separator provides a new platform to intensify the thermal management of batteries and paves the way for the application of high-safety and high energy density batteries.