In situ construction of High-safety and Non-flammable polyimide “Ceramic” Lithium-ion battery separator via SiO2 Nano-Encapsulation

For the purpose of the needs of high-safety energy storage devices, we report a new type of high-performance core–shell structure PI/SiO2 inorganic–organic composite separator. This polymer separator has good flame retardant, strong mechanical properties, high thermal stability and high ion transmission efficiency. Unlike traditional ceramic modified separators, this hybrid separator is achieved by in situ nano-encapsulation hydrolysis. As a precursor of SiO2, Tetrabutyl orthosilicate (TBOS) is selected to coat on PI nanofibers surface, which endows a high retention rate of hydrolyzed silica and a dense/uniform coating. Due to the formation of silica nanoshell, the PI/SiO2 nanofiber separator shows an ultra-high 73.69 MPa tensile strength, a contact angle of only 6.8° and great thermal stability at 378 °C. The NCM811 half-cell equipped with composite separator shows a great capacity of 146 mAh·g−1 at 5C, which is much better than the battery using original PI separator and Celgard-2400 separator. It is worth nothing that the battery with PI/SiO2 separator exhibits superior cycle stability with little energy weaken during 100 cycles. This research provides a new strategy for preparing high-performance non-flammable organic–inorganic composite separators.