Method for improving hydrophilicity and thermal stability of polypropylene lithium-ion battery separator

Aiming at the problem that hydrophilicity and thermal stability of a polypropylene lithium-ion battery separator are poor, the invention provides a method for layer-by-layer self-assembly of polyelectrolyte on the surface of a separator so as to improve the hydrophilicity and thermal stability of the polypropylene lithium-ion battery separator. According to the technical scheme, an aqueous solution polymerization method is adopted for respectively preparing anion polyelectrolyte containing an anion structural unit and cation polyelectrolyte containing a cation structural unit, and a pretreated polypropylene separator is repeatedly and alternately soaked in two polyelectrolyte solutions, so that macromolecule polyelectrolyte is self assembled onto the surface of the polypropylene separator under the action of an electrostatic force; the polypropylene lithium-ion battery separator prepared by adopting the method provided by the invention has high hydrophilicity and thermal stability, a static water contact angl