Fabrication and Performance of PET-ceramic Separators

Ceramic-coating separators were prepared with poly(ethylene terephthalate) (PET) nonwoven membrane as the substrate. Different particle sizes and variable ratios of SiO2 and Al2O3 were coated on the PET surface by dip coating technology, using PVDF-HFP as the binder. The separators took advantage of both kinds of ceramic particles, so that the big pores of PET were filled more effectively. Surface morphology, porosity, electrolyte wettability, thermal stability, ionic conductivity, and electrochemical impedance spectroscope (EIS) of composite separators with different ratios of SiO2 to Al2O3 were systematically investigated, and separators with ratio of SiO2/Al2O3=3/7 showed superior performance. Electrochemical properties of MCMB /LiNi1/3Co1/3Mn1/3O2 2025-type coin cells assembled by the ceramic separators with ratio of SiO2/Al2O3=3/7 were also tested, as compared with commercialized PP separators. The results demonstrated that the ceramic separators performed with 93.9% capacity retention after 100 cycles and capacity of 82.7 mAh/g at 10C rate, better than PP separators.