In-situ nanoencapsulated core-shell silica/polyvinylidene difluoride separators: Synergistically enhance the safety of lithium metal batteries

Regarding the safety risks caused by the high-temperature contraction and melting of traditional polyolefin separators in lithium metal batteries, an in-situ nanoencapsulated silica/polyvinylidene fluoride (ISE-SiO 2 /PVDF) composite separator with core-shell structure was prepared by electrospinning coupled low-temperature hydrolysis technology. The design uses PVDF fiber as the core, and the surface is uniformly coated with the thermally stable SiO 2 nanolayer in situ. The SiO 2 cladding synergistically strengthens the tensile strength of the separator (0.6 MPa → 2.2 MPa). At the same time, the excellent heat/oxygen barrier properties of SiO 2 are used to greatly enhance thermal stability (shrinkage rate at 150 °C, ISE-SiO 2 /PVDF: ∼0%, PE: ∼62%) and flame retardancy (touching the flame without burning), and build a thermal runaway barrier. More importantly, the inherent strong lithium ion affinity of SiO 2 not only induces the formation of low-energy barrier and highly ordered lithium ion transport channels (t Li+ = 0.45, σ = 1.04 mS cm −1 ), but also provides uniformly distributed lithium nucleation sites, which synergistically promotes the uniform deposition of lithium ions and may efficiently inhibits the uncontrollable growth of lithium dendrites. The Li||Li battery based on ISE-SiO 2 /PVDF separator can undergo stable cycling for more than 250 times under the conditions of 1 mA cm −2 /1 mAh cm −2 . The assembled LiCoO 2 (active material load: 10.9 mg)||Li battery can also be stably cycled more than 300 times, and still maintains a capacity retention rate of 58.79% (PE is 36.16%) at a high current density of 5C. This in-situ nanopackaging strategy cleverly combines organic flexibility and inorganic functionality, providing a new efficient way to develop high-safety and high-performance lithium metal battery separators. • The prepared ISE-SiO 2 /PVDF separator realizes the fine compounding of organic and inorganic phases at the nanoscale. • The SiO 2 layer improves flame retardancy and electrochemical properties, eliminating the defects of traditional separators. • The ISE-SiO 2 /PVDF separator offers a practical solution to the safety and longevity of lithium metal batteries.