Battery cell thermal runaway barrier

Abstract

A thermal runaway barrier for at least significantly slowing down a thermal runaway event within a battery assembly. The thermal runaway barrier includes a layer of a nonwoven fibrous thermal insulation comprising a fiber matrix of inorganic fibers, thermally insulative inorganic particles of fumed silica dispersed within the fiber matrix, and a binder dispersed within the fiber matrix so as to hold together the fiber matrix. An optional organic encapsulation layer may also be used to encapsulate the nonwoven fibrous thermal insulation.

1 . A thermal runaway barrier operatively adapted for being disposed between battery cells of a battery assembly and for at least significantly slowing down a thermal runaway event within the battery assembly, said thermal runaway barrier comprising:
 a layer of a nonwoven fibrous thermal insulation comprising a fiber matrix of inorganic fibers;   thermally insulative inorganic particles of fumed silica material dispersed within the fiber matrix, and a binder dispersed within the fiber matrix so as to hold together the fiber matrix;   an optional organic encapsulation layer enclosing the layer of nonwoven fibrous thermal insulation; and   an optional inorganic encapsulation layer enclosing the layer of nonwoven fibrous thermal insulation.   
     
     
         2 . The thermal runaway barrier according to  claim 1 , wherein the particles of fumed silica have a surface area in the range of from about 100 m 2 /g up to about 400 m 2 /g. 
     
     
         3 . The thermal runaway barrier according to  claim 1 , wherein the layer of nonwoven fibrous thermal insulation contains an amount of fiber shot in the range of from about 3% up to about 60% by weight of the amount of inorganic fibers in the layer of nonwoven fibrous thermal insulation. 
     
     
         4 . The thermal runaway barrier according to  claim 1 , wherein the layer of nonwoven fibrous thermal insulation contains an amount of thermally insulative inorganic particles in the range of from as low as about 10% up to as high as about 60%, by weight of the layer of nonwoven fibrous thermal insulation. 
     
     
         5 . The thermal runaway barrier according to  claim 1 , wherein the layer of nonwoven fibrous thermal insulation contains an amount of organic binder in the range of from as low as about 2.5% up to as high as about 10.0%, by weight of the layer of nonwoven fibrous thermal insulation. 
     
     
         6 . The thermal runaway barrier according to  claim 1 , wherein the layer of nonwoven fibrous thermal insulation has an installed thickness in the range of from about 0.5 mm up to less than 5.0 mm. 
     
     
         7 . The thermal runaway barrier according to  claim 1 , wherein the layer of nonwoven fibrous thermal insulation has a basis weight in the range of from as low as about 250 g/m 2  and up to as high as about 1000 g/m 2 . 
     
     
         8 . The thermal runaway barrier according to  claim 1 , wherein the layer of nonwoven fibrous thermal insulation has an uncompressed basis weight in the range of from about 250 g/m 2  up to about 400 g/m 2 . 
     
     
         9 . The thermal runaway barrier according to  claim 1 , wherein the thermally insulative inorganic particles further comprise particles of one or any combination of the materials selected from the group consisting of inorganic aerogel, xerogel, hollow or porous ceramic microspheres, unexpanded vermiculite, irreversibly or permanently expanded vermiculite, otherwise porous silica, irreversibly or permanently expanded perlite, unexpanded perlite, pumicite, expanded clay, diatomaceous earth, titania and zirconia. 
     
     
         10 . The thermal runaway barrier according to  claim 1 , wherein the layer of nonwoven fibrous thermal insulation is encapsulated by the organic encapsulation layer. 
     
     
         11 . The thermal runaway barrier according to  claim 10 , wherein the organic encapsulation layer has at least one vent hole formed therethrough that is located and sized to allow gas contained within the thermal runaway barrier to escape from the organic encapsulation, such that the structural integrity of the organic encapsulation layer is kept intact, during a thermal runaway event. 
     
     
         12 . The thermal runaway barrier according to  claim 10 , wherein the thermal runaway barrier has a top edge, a bottom edge and opposite side edges, and the at least one vent hole is located along the periphery of one or both opposite side edges. 
     
     
         13 . The thermal runaway barrier according to  claim 10 , wherein the at least one vent hole provides an exit opening through the organic encapsulation layer having an opening area in the range of from about 2 mm 2  up to about 15 mm 2 . 
     
     
         14 . The thermal runaway barrier according to  claim 10 , wherein the layer of nonwoven fibrous thermal insulation has a peripheral edge, and the organic encapsulation layer is sealed around the peripheral edge. 
     
     
         15 . The thermal runaway barrier according to  claim 1 , wherein the layer of nonwoven fibrous thermal insulation passes at least the V-2 level of the UL94 Flammability Test. 
     
     
         16 . The thermal runaway barrier according to  claim 1 , wherein the thermally insulative inorganic particles comprise particles of irreversibly or permanently expanded intumescent material. 
     
     
         17 . The thermal runaway barrier according to  claim 1 , wherein the thermally insulative inorganic particles comprise particles of irreversibly or permanently expanded vermiculite. 
     
     
         18 . The thermal runaway barrier according to  claim 17 , wherein the expanded vermiculite has been irreversibly or permanently expanded in the range of from at least about 10% up to 100% of its expandability. 
     
     
         19 . A battery cell module for an electric vehicle, said battery cell module comprising:
 a plurality of battery cells disposed in a housing; and   a plurality of thermal runaway barriers according to  claim 1 ,   wherein the battery cells are lined up in a row, with one thermal runaway barrier being disposed between each pair of adjacent battery cells.   
     
     
         20 . A method of making the thermal runaway barrier according to  claim 1 , wherein said method comprises:
 forming the layer of nonwoven fibrous thermal insulation using a wet-laid process or dry-laid process.