High‐Performance Polyimide Nanofiber Membrane for Progressive and Safe Lithium‐Ion Batteries Guarded by a Zirconia Armor Layer

Abstract Innovative technologies for the fabrication of separators possessing outstanding properties like superior thermostability, mechanical strength, and ultrahigh flame resistance are imperative for advanced and safe energy storage systems (ESSs). Nevertheless, there are lots of limitations to attain the requirements mentioned above for classic polymeric separators. Herein, to achieve all these goals, we fabricate a zirconia nanoshell@polyimide core formed in situ (ZrO 2 @PI in situ) as a nanofabric membrane via an innovative and convenient strategy to be used as a novel high‐performance flexible ceramic composite separator. Different from traditional ceramic‐coated separators, the in situ ZrO 2 @PI composite separator possesses a shell‐core structure obtained via an in situ absorption complexation and hydrolysis strategy, which endows ultrahigh flame resistance, superior wettability, thermostability, and excellent ionic conductivity. The NCM811 batteries installed with an in situ ZrO 2 @PI nanofabric separator displays the outstanding capacity of 159.0 mAh g −1 at 5 C, far higher than the cells assembled with a PI separator (146.2 mAh g −1 ) or Celgard‐2400 separator (125.1 mAh g −1 ) at the same 5 C. In addition, the cell manifests outstanding cycle performance, for which the capacity retention ratio is 89.4 % after 100 cycles at 1 C. All test results certify the ZrO 2 @PI composite separators formed in situ can be effectively applied in progressive and safe batteries.