Highly Connective Spongy Polyimide Separators Blended with Inorganic Whiskers for High-Performance Lithium-Ion Batteries

A robust flame-retardant separator was fabricated by a nonsolvent-induced phase separation method incorporating polyimide with silicon nitride (Si 3 N 4 ) whiskers. Compared with powder-blended separators, whisker-blended separators not only suppressed the agglomeration of fillers but also improved the internal connectivity of the separator. These advantages were conducive to boosting Li ions and improving the cycling stability. The whisker-blended separator exhibited a high heat endurance in air (400 °C for 1 h). Cells assembled with this separator exhibited a high initial discharge capacity (152 mA h g –1 ), an enhanced capacity retention of 79.4% (120 mA h g –1 ), and a high Coulombic efficiency of 97.5% after 300 cycles.