Battery separators having a low apparent density

Abstract

In some embodiments, a battery separator described herein may comprise a layer having a relatively low apparent density; for example, the density that includes any unoccupied space within the outermost boundaries of the layer may be relatively low. The low apparent density may be attributed to, at least in part, the geometry of the layer. For instance, in some embodiments, the layer may include undulations and/or have at least one non-planar surface (e.g., a corrugated layer; an embossed layer). In some embodiments, a battery comprising a layer having a relatively low apparent density may have desirable properties, including relatively low electrical resistance and/or relatively high capacity. The battery separators described herein may be well suited for a variety of battery types, including lead acid batteries.

What is claimed is: 
     
         1 . A battery separator, comprising:
 a non-woven web comprising:
 a plurality of glass fibers having an average diameter of greater than or equal to about 0.1 microns and less than or equal to about 15 microns, wherein the glass fibers are present in an amount of greater than or equal to about 2 wt. % and less than or equal to about 95 wt. % of the non-woven web; 
 a plurality of synthetic fibers, wherein the synthetic fibers are present in the non-woven web in an amount of greater than or equal to about 1 wt. % and less than or equal to about 80 wt. % of the non-woven web; and 
 a plurality of inorganic particles, wherein the inorganic particles are present in an amount of greater than or equal to about 10 wt. % and less than or equal to about 80 wt. % of the non-woven web, 
 wherein the apparent density of the battery separator is greater than or equal to about 40 g/m 2 /mm and less than or equal to about 250 g/m 2 /mm. 
   
     
     
         2 . A battery separator, comprising:
 a non-woven web comprising:
 a plurality of glass fibers having an average diameter of greater than or equal to about 0.1 microns; 
 a plurality of synthetic fibers, wherein the synthetic fibers are present in an amount of greater than or equal to about 1 wt. % and less than or equal to about 80 wt. % of the non-woven web; and 
 a plurality of inorganic particles, wherein the inorganic particles are present in an amount of greater than or equal to about 10 wt. % and less than or equal to about 80 wt. % of the non-woven web; 
 wherein the non-woven web is corrugated, embossed, pleated, creped, or micrexed. 
   
     
     
         3 . A battery separator, comprising:
 a non-woven web comprising:   a plurality of glass fibers having an average diameter of greater than or equal to about 0.1 microns and less than or equal to about 15 microns,   wherein the non-woven web is embossed.