Direct electrolyte gelling via battery separator composition and structure

Abstract

The capability of directly gelling an electrolyte within a lithium ion (or similar type) battery cell through the reaction of the electrolyte solution with a present battery separator is provided. Such a procedure results generally from the presence of suitable nanofibers within the battery separator structure that exhibit the potential for swelling in the presence of a suitable electrolyte formulation. In this manner, the capability of providing an entrenched gel within the battery separator for longer term viability and electrical generation is possible without externally gelling the electrolyte prior to battery cell introduction. The method of use of such a resultant battery, as well as the battery including such an automatic gelling battery separator/electrolyte combination, are also encompassed within this invention.

What is claimed is: 
     
         1 . A rechargeable lithium ion battery comprising a battery separator and an electrolyte:
 wherein said electrolyte comprises solvents; and   wherein said battery separator consists of a single layer of fabric comprising microfibers exhibiting a minimum width of 3000 nm and nanofibers exhibiting a maximum width of 1000 nm, wherein at least some of said nanofibers exhibit gelation upon contact with said solvents of said electrolyte and wherein said microfibers do not swell and remain dimensionally stable without exhibiting warping and/or melting subsequent to fabrication and upon contact with said electrolyte, wherein said single layer of fabric exhibits a maximum thickness of 100 micrometers; wherein said single layer of fabric exhibits a mean flow pore size of at most 0.80 micrometers; wherein said microfibers exhibit an average length of less than 50 mm, said average length further being at least 5 times the average length of said nanofibers, and wherein said microfibers form a mesh and said nanofibers fill within the interstices of said microfibers.   
     
     
         2 . The battery of  claim 1  wherein said nanofibers present within said single layer of fabric of said separator exhibit an average diameter of at most 700 nm. 
     
     
         3 . The battery of  claim 1  wherein said separator exhibits MD tensile strengths and CD tensile strengths that are substantially the same.