A flame-retardant, dendrite-inhibiting sandwich separator prepared by electrospinning for high-performance and safety lithium batteries

As the "safety switch" of lithium batteries, the separator controls the electrochemical performance and safety performance of lithium batteries. However, highly flammable and easy to induce lithium dendrite generation of commercial polyolefin pose a huge safety hazard for current commercial lithium-ion batteries. Therefore, developing a flame-retardant, lithium dendrite-inhibiting separator can achieve further leap in the lithium battery industry. A "sandwich" separator (SPS-B) is designed by integrating silk fibroin (SF), decabromodiphenyl ethane, and polyvinyl alcohol through electrospinning. SPS-B shows excellent flame-retardant properties through a free radical trapping mechanism. Moreover, the SPS-B demonstrated satisfactory capability of suppressing lithium dendrites by constructing Li3N-SEI with high ionic conductivity and high strength, and the secondary structure beta-sheets of SF can inhibit the "tip effect" of lithium dendrites, which enables efficient lithium plating/stripping in Li//Li and Li//Cu cells. In addition, the enhanced porosity, electrolyte affinity of SPS-B promotes excellent electrochemical performance with enhanced discharge capacity and reduced concentration polarization. Finally, fire risk of soft-pack batteries are evaluated by continuous external heating. Compared with commercial separator, soft-pack batteries with SPS-B show much lower heat release rate, peak temperature and flue gas release rate, further confirming the effectiveness of SPS-B in reducing fire risk. Overall, the SPS-B provides a satisfactory way to develop high-performance and superior safety lithium batteries.