Boosting Battery Safety by Mitigating Thermal‐Induced Crosstalk with a Bi‐Continuous Separator

Abstract Lithium‐ion batteries are taking center stage in the environmental revolution through the ever‐growing adoption of electric vehicles. However, safety issues derived from battery thermal runaway remain a prominent challenge. In this work, a bi‐continuous separator (Bi‐Sep) via micro‐gravure and phase inversion techniques is developed. The proposed nonshrinkage separator exhibits a nanoporous morphology and a super‐stretchable property, thus effectively blocking both internal short circuits and chemical crosstalk between electrodes at thermal abusive temperatures. Besides its considerable performance at normal conditions, the LiNi_0.6Co_0.2Mn_0.2O₂/graphite pouch cell assembled with the Bi‐Sep separator presents superior sustainability at an elevated temperature of 60 °C. Moreover, the cell using this Bi‐Sep separator achieves an extremely high level of survivability under thermal abusive conditions. This work concludes that engineering the porous structure and thermomechanical properties of a separator, rather than simply improving its heat‐resistance, is of significant importance for the development of safe batteries.