Polypropylene separators (PP) are widely used in lithium-ion batteries due to good electrochemical stability and low cost. However, PP separators are prone to thermal shrinkage at high temperatures, resulting in short circuit of positive and negative electrode contacts and thermal runaway. In this work, a waterborne core-shell emulsion binder rich in carboxyl and ester groups with both strength and adhesion is designed and coated with alumina (Al