Structure and properties of POSS-(PMMA46)8 impregnated commercial polypropylene separator

In order to improve the safety and reduce interface impedance of lithium-ion batteries, the star-shaped polyhedral POSS-poly(methyl methacrylate) (POSS-(PMMA46)8), which has both excellent heat resistance and good compatibility with the polymer material, was selected as a modifier to modify the separator of commercial polypropylene (PP) by the method of impregnation. The micromorphology of the composite separator was studied by scanning electron microscope (SEM). The mechanical property of the separator was measured by a tensile tester. The thermal stability of the separator was studied at a high temperature. The wettability of the separator was tested by a contact angle tester. The AC impedance was used to obtain the bulk impedance of the composite separator and then its ionic conductivity was studied. The electrochemical stability of the separator was measured by linear sweep voltammetry (LSV). The results show that when the mass fraction of POSS-(PMMA46)8 is 40%, the pore distribution of the composite membrane is homogeneous, and the wettability is the best. The tensile strength is 5.34 times that of the original film, and the thermo-stability is ideal at 160℃/1h. The conductivity of the composite membrane is 1.35×10-3 S/cm. The interface resistance between the composite separator and the electrode is reduced from 743Ω to 152Ω, and which is 79.5% higher than that of the original film; for Li/Separator/LiFePO4 cell, the charge-discharge cycling stability is better and the battery capacity at low magnification is comparable to commercial PP separator.