In-Situ Armoring: A Robust, High-Wettability and Fire-Resistant Hybrid Separator for Advanced and Safe Batteries.

Development of non-flammable separators with excellent properties is in urgent need by next-generation advanced and safe energy storage devices. However, it has been extremely challenging to simultaneously achieve fire-resistance, high mechanical strength, good thermo-mechanical stability and low ion-transport resistance for polymeric separators. Herein, to address all these needs, we report an in-situ formed core-shell silica@ silica-imbedded polyimide (in-situ SiO2 @(PI/SiO2 )) nanofabric as a new high-performance inorganic-organic hybrid separator. Different from conventional ceramics-modified separators, this in-situ SiO2 @(PI/SiO2 ) core-shell separator is realized for the first time via an inverse in-situ hydrolysis process. Benefited from the in-situ formed silica nano-shell, the in-situ SiO2 @(PI/SiO2 ) core-shell separator shows the highest tensile strength of 42 MPa among all reported nanofiber-based separators, excellent wettability to the electrolyte, good thermo-mechanical stability at 300 ºC and fire-resistance. The LiFePO4 half-cell assembled with this hybrid separator showed a high capacity of 139 mA h g-1 @ 5C, which is much higher than that of the battery with the pristine PI separator (126.2 mA h g-1 @ 5C) and Celgard-2400 separator (95.1 mA h g-1 @ 5C). More importantly, the battery showed excellent cycling stability with no capacity decay over 100 cycles at the high temperature of 120 ºC. This study provides a novel method for the fabrication of high-performance and non-flammable polymeric-inorganic hybrid battery separators.