Patent ID: 8993646
Filing Date: 2015-03-31
Classification: B01D,H01M,Y02E

Abstract:
1. A method of making a porous polymer separator that, in a lithium ion battery, is sandwiched between a negative electrode and a positive electrode to provide an electrically insulative physical barrier that mechanically separates the two electrodes, the method comprising: preparing a single phase polymer solution that includes a polymer material dissolved in a miscible mixture of a real polymer solvent and a polymer non-solvent, the single phase polymer solution having an elevated temperature above room temperature that facilitates solvation of the polymer material in the miscible mixture of the real polymer solvent and the polymer non-solvent, the polymer non-solvent being selected from the group consisting of water, a C1-C6 aliphatic alcohol, acetone, and mixtures thereof; forming a film from the single phase polymer solution that has a thickness of up to about 150 μm; cooling the film from the elevated temperature to phase-separate the polymer material into a solid polymer precipitate; exposing the solid polymer precipitate to additional polymer non-solvent to remove, by solvent exchange, the real polymer solvent from the solid polymer precipitate; and drying the solid polymer precipitate to remove the polymer non-solvent and any residual of the real polymer solvent from the solid polymer precipitate to form a polymer matrix having opposed major face surfaces and defining a network of pore openings that traverses the polymer matrix and fluidly connects the major face surfaces.