Preparation and Performance of Inorganic Composite Separators for Lithium-ion Battery

Seven kinds of polypropylene (PP) composite separators were prepared by coating PP separators with inorganic particles such as aluminum oxide (Al2O3),barium sulfate (BaSO4), lead zirconate titanate (PZT), titanium dioxide (TiO2), fumed silica R202 (R-SiO2), A380 (A(SiO2)) and precipitated silica (P-SSiO2). The morphology study showed that uniform coating layers were formed on the PP separators. Compared with the bare PP separator, the permeability of the composite separators decreased a little, while the thermal stability improved greatly. The effects of coating layer on the electrochemical stability of the electrolyte were also investigated by linear sweep voltammetry (LSV) and it was found that the coating material didn't deteriorated the performance of the electrolyte. The cycling performance of the cells showed that the capacity of cells increased by more than 20 mAh/g for almost all kinds of composite separators and could retain the advantage at a high discharge rates of 2 C (except for A(SiO2)). However, for the cells with A(SiO2) composite separators, the capacity decayed very rapidly at the rate of 2 C. We attributed the rapid capacity decay to the too large specific surface area and lots of silicon hydroxyls on the surface of A(SiO2), which increased the transport resistance of the lithium ion.