Method of forming an electrically conductive, freestanding microporous polymer sheet

Abstract

A freestanding, microporous polymer sheet ( 52, 56 ) is composed of a polymer matrix binding an electrically conductive matrix. The polymer matrix preferably includes UHMWPE, and the electrically conductive matrix is preferably in powder form. The UHMWPE is of a molecular weight that provides sufficient molecular chain entanglement to form a sheet with freestanding characteristics. Multiple microporous sheets ( 30 ) can be wound or stacked in a package filled with an electrolyte to function as electrodes in an energy storage device ( 86 ), such as a battery. Metallic layers ( 81, 83 ) can be applied to the microporous sheets to function as current collectors in such devices.

1 . A coextrusion process for simultaneously producting a unitary electrode assembly composed of anode, cathode, and separator layers formed as a multiple layer web, comprising: 
 introducing into an anode an ultrahigh molecular weight polyolefin, a plasticizer, and an anode active material to form an anode extrudate layer;    introducing into a cathode extruder an ulrahigh molecular weight polyolefin, a plasticizer, and a cathode active material to form a cathode extrudate layer;    introducing into a separator extruder an ultrahigh molecular weight polyolefin, a plasticizer, and an electrically nonconductive material filler to form a separator extrudate layer; and    forming a coherent bond between adjacent ones of the anode, cathode, and separator extrudate layers to form a multiple layer web in which the separator extrudate layer is positioned between anode and cathode extrudate layers.    
     
     
         2 . The method of  claim 1 , in which the forming of a coherent bond comprises coextruding the anode, cathode, and separator extrudate layers.  
     
     
         3 . The method of  claim 1 , in which the forming of a coherent bond comprises laminating together the anode, cathode, and separator extrudate layers.  
     
     
         4 . The method of  claim 1 , further comprising bonding a different one of a pair of current collector layers to each of the anode extrudate layer and the cathode extrudate layer to form an electrochemical cell.