Fire-Proofing, Mechanic-Reinforcing, Electrostatic-Spinning Strategies Toward Fabricating Porous Separator for Superior and Safer Lithium-Ion Batteries

The extended use of lithium-ion batteries (LIBs) strongly suffers from thermal runaway hazards. The key material of the separator is known to play a crucial role in affecting the safety of the battery. Nevertheless, the influence of separators on the thermal runaway action of batteries has not been extensively studied. In this context, a fireproof, mechanically strong separator is prepared, based on polyimide polyphosphazene (PZS) cross-linked SiO2 (SiO2@PZS@PI), which has high porosity, electrolyte uptake, and ionic conductivity. Moreover, the self-extinguishing time of the designed separator is shortened by 91.9%, without obvious deformation even at 200 °C. In addition, after this separator is assembled into the battery, the time to reach the maximum thermal runaway temperature is delayed by 350 min, whereas the thermal runaway activation energy is increased by 79.7%. Moreover, a lithium deposition/stripping test confirmed the superior ability of the SiO2@PZS@PI separator to inhibit the growth of lithium dendrites. Notably, the replacement of the Celgard separator with the SiO2@PZS@PI separator greatly improved the cycling and rate performance of the battery. This study proposes a design for a high-performance separator, facilitating the design of safer and more effective LIBs.