Electrospun polyimide@organic-montmorillonite composite separator with enhanced mechanical and thermal performances for high-safety lithium-ion battery

The separator is a critical component in improving the safety and charge–discharge property of lithium-ion batteries (LIBs). However, the poor heat resistance and flame retardancy of commercial polyolefin separators easily increase the risk of short circuit and thermal runaway, thus affecting the safety, service life, and charge–discharge performance of LIBs. Herein, polyimide (PI) separators containing organic montmorillonite (OMMT) are prepared by electrospinning. Compared with the commercial Celgard 2500 separator, the prepared PI/OMMT composite separator exhibited outstanding electrolyte wettability, superior thermal dimensional stability up to 250 °C, good flame retardancy, wider electrochemical stability window (5.0 V), and higher ionic conductivity (0.77 mS cm−1). Moreover, the coin cells with the PI@OMMT separator still have a discharge capacity of 131 mAh g−1 and a capacity retention rate of 97% after 100 cycles at 1c, much higher than that of Celgard 2500 Separator (107 mAh g−1 and 80%). These excellent features make it a promising candidate for LIBs separators with high electrochemical performance and safety.Graphical abstract