Alumina/phenolphthalein polyetherketone ceramic composite polypropylene separator film for lithium ion power batteries

One way to obtain the lithium ion power battery with better safety performance was to increase the thermal shrinkage resistance of the separator at higher temperature. Phenolphthalein polyetherketone (PEK-C) is a polymer that can withstand high temperature to about 230 °C. Here, we developed a new Al₂O₃ coated composite polypropylene (PP) separator with PEK-C as binder. The coating layer was formed on the surface of the PP separator and both ceramic particles and binder did not infiltrated into the separator along the thickness direction. The composite separator with 4 μm coating layer provided balanced permeability and thermal shrinkage properties. The composite separator was stable at the electrochemical window for lithium ion battery. The coin cells with composite separator showed better charge/discharge performance than that of the cells with the PP separator. It seemed that the composite separator was helpful for high current density discharge. Also, the battery safety performance test had verified that the Al₂O₃ coated composite separator with PEK-C as binder had truly improved the safety performance of the coin cells. So, the newly developed Al₂O₃ coated composite PP separator was a promising safety product for lithium ion power batteries with high energy density.