Battery cell thermal runaway barrier

Abstract

A thermal runaway barrier for at least significantly slowing a thermal runaway event in a battery cell assembly, the thermal runaway barrier consisting essentially of a single layer of nonwoven fibrous insulation including a fibrous matrix of inorganic fibers, insulating inorganic particles dispersed within the fibrous matrix, and a binder dispersed within the fibrous matrix to hold the fibrous matrix together. An optional organic encapsulation layer may also be used to encapsulate the nonwoven fibrous insulation.

Description

[Technical Field]

[0001] The present invention relates to a barrier for at least significantly slowing down a thermal runaway event in a battery assembly, such as, for example, a battery assembly used in an electric vehicle. [Background technology]

[0002] Electric motors used in electric or hybrid vehicles (e.g., automobiles) are at least partially powered by batteries. Lithium-ion batteries are typically used in such applications and are available in three forms: prismatic cells, pouch cells, or cylindrical cells. These batteries are compactly arranged within the vehicle to save space. In some cases, a thermal runaway event may occur in one or more of the battery cells or battery modules, causing many, if not all, of the battery cells or battery modules to overheat and be destroyed. There is a desire in the industry to prevent, stop, or at least significantly slow down such thermal runaway events.

[0003] The industry has developed several thermal barrier elements that require multiple layers of various inorganic materials to perform such a function (see, for example, US Pat. No. 8,541,126 B2).

[0004] The description of the background art provided herein is intended to provide a general context for the present disclosure. To the extent described in this background art section, the inventors' work described therein, as well as aspects of the description that would not otherwise qualify as prior art at the time of filing, are not admitted, expressly or implicitly, to be prior art to the present disclosure. Summary of the Invention

[0005] The present inventors have discovered that suitable thermal barrier elements can be used without the need for multiple layers of inorganic, non-metallic materials.

[0006] In one aspect of the present invention, a thermal runaway barrier is provided that is disposed between battery cells of a battery assembly and is operatively adapted to at least significantly slow a thermal runaway event within the battery assembly. The thermal runaway barrier consists of, or consists essentially of, a monolayer of nonwoven fibrous insulation including a fibrous matrix of inorganic fibers, insulating inorganic particles dispersed within the fibrous matrix, and a binder dispersed within the fibrous matrix to hold the fibrous matrix together. An optional organic encapsulation layer may also be included to encapsulate the monolayer of nonwoven fibrous insulation.

[0007] In another aspect of the present invention, a battery cell module or assembly for an electric vehicle is provided. The battery cell module or assembly includes a plurality of battery cells disposed within a housing and a plurality of thermal runaway barriers according to the present invention. The battery cells are arranged in a row or stack with one thermal runaway barrier disposed between each pair of adjacent battery cells, or between a predetermined number of battery cells (e.g., after every third battery cell), or between battery modules.

[0008] In a further aspect of the invention, there is provided a method of manufacturing a thermal runaway barrier according to the invention, the method comprising forming a layer of nonwoven fibrous insulation using a wet or dry process.

[0009] The above summary of the present invention is not intended to describe each disclosed embodiment or every implementation of the present invention. The following description more particularly exemplifies exemplary embodiments. In several places throughout this application, guidance is provided by listing examples, which examples can be used in various combinations. In each instance, the recited items serve only as a representative group and should not be interpreted as an exclusive listing. [Brief explanation of the drawings]

[0010] Descriptions corresponding to the included drawings may be within the scope of this specification. [Figure 1]FIG. 1 is a schematic end view of a fiber matrix layer and optional encapsulation layer that may be used in a thermal runaway barrier application. [Figure 2] FIG. 1 is a schematic side view of a battery module of battery cells having a thermal runaway barrier disposed between adjacent battery cells. [Figure 3] FIG. 1 is a schematic top view of a battery pack of battery modules with thermal runaway barriers placed between adjacent battery modules and / or on top of the battery modules. [Figure 4] FIG. 1 is a photographic perspective view of a thermal runaway barrier encapsulated with an adhesive-backed organic polymer layer having a release liner and an expanding gas outlet / notch. [Figure 5] FIG. 1 is a schematic side view of a dry process for fabricating a battery cell thermal runaway barrier, according to one embodiment of the present invention. [Figure 6] FIG. 1 is a cross-sectional view of an embodiment of a thermal runaway barrier showing multiple inflation gas vent holes formed through the encapsulating film, according to one embodiment of the present invention. [Figure 7] FIG. 10 is a cross-sectional view of another embodiment of a thermal runaway barrier illustrating a plurality of inflation gas vents in the form of notches formed through the encapsulating film according to another embodiment of the present invention. [Figure 8] 10A-10C are top views of additional embodiments of thermal runaway barriers having two different types of inflation gas vent holes formed through the encapsulation film. DETAILED DESCRIPTION OF THE INVENTION

[0011] In describing preferred embodiments of the present invention, specific terminology is used for the sake of clarity, however, the present invention is not intended to be limited to the specific terminology so selected, and each term so selected includes all technical equivalents that operate in a similar manner.

[0012] As used herein, the terms "preferred" and "preferably" refer to embodiments described herein that may offer certain advantages, under certain circumstances, although other embodiments may also be preferred, under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, or is intended to exclude other embodiments from the scope of the invention.

[0013] As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to an element preceded by "a" or "the" may include one or more of the element and equivalents thereof known to those skilled in the art. Furthermore, the term "and / or" means one or all listed elements or a combination of any two or more of the listed elements.

[0014] It should be noted that the term "comprises" and variations thereof do not have a limiting meaning when these terms appear in the accompanying description. Furthermore, "a," "an," "the," "at least one," and "one or more" are used interchangeably herein. Relative terms such as left, right, front, rear, top, bottom, side, above, below, horizontal, vertical, etc. may be used herein, and when so, are from the perspective as viewed in the drawings. However, these terms are used merely for ease of description and in no way limit the scope of the present invention.

[0015] Throughout this specification, reference to "one embodiment," "a particular embodiment," "one or more embodiments," or "an embodiment" means that the particular feature, structure, material, or characteristic described with respect to that embodiment is included in at least one embodiment of the invention. Thus, the appearances of phrases such as "in one or more embodiments," "in a particular embodiment," "in one embodiment," or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment of the invention. Where applicable, product names are written in all capital letters.

[0016] The term "and / or" means one or all of the listed elements or a combination of any two or more of the listed elements (e.g., preventing and / or treating pain means preventing, treating, or both treating and preventing further pain).

[0017] As used herein, the term "or" is generally used in its sense including "and / or" unless the context clearly dictates otherwise.

[0018] Also herein, the recitations of numerical ranges by endpoints include all numbers subsumed within that range (eg, 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.).

[0019] "Ambient conditions" means 25°C and a pressure of 101.3 kPa.

[0020] "Average" means number average unless otherwise specified.

[0021] "Continuous" means extending over a single, integrated area along a given layer (a perforated sheet can be continuous).

[0022] "Cure" refers to exposing to any form of radiation, heating, or causing a physical or chemical reaction that results in solidification or an increase in viscosity.

[0023] "Discontinuous" means extending over multiple distinct regions along a given layer, the distinct regions being spaced apart from one another.

[0024] "Size" refers to the longest dimension of a given object or surface.

[0025] "Substantially" means to a significant degree, such as at least an amount of 50%, 60%, 70%, 80%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5%, 99.9%, 99.99%, or 99.999%, or 100%.

[0026] "Thickness" means the distance between opposite surfaces of a single layer or multilayer article.

[0027] Recitation of numerical ranges by endpoints, unless otherwise stated, is by increments according to the precision implied by the endpoints of the specified range and any ranges within that range (e.g., for a range of 1.000 to 5.000, the increment is 0.001; ranges include 1.000, 1.001, 1.002, etc.; 1.100, 1.101, 1.102, etc.; 2.000, 2.001, 2.002, etc.). 02, etc.; 2.100, 2.101, 2.102, etc.; 3.000, 3.001, 3.002, etc.; 3.100, 3.101, 3.102, etc.; 4.000, 4.001, 4.002, etc.; 4.100, 4.101, 4.102, etc.; 5.000, 5.001, 5.002, etc. up to and including 5.999 (including all numbers subsumed within that range).

[0028] The term "polymer" is understood to include polymers, copolymers (e.g., polymers formed using two or more different monomers), oligomers, and combinations thereof, as well as polymers, oligomers, or copolymers that may be formed in miscible blends.

[0029] The following examples have been selected solely to further illustrate the features, advantages, and other details of the present invention, but it should be expressly understood that, while the examples serve this purpose, the particular materials and amounts used, as well as other conditions and details, should not be construed in any manner that would unduly limit the scope of the invention.

[0030] Referring to Figure 1, a fibrous matrix layer 10 useful for thermal runaway barrier applications contains nonwoven inorganic (i.e., non-metallic) or other heat-resistant fibrous insulating material, thermally insulating ceramic or other non-metallic inorganic particles, and an organic or inorganic binder. As used herein, non-metallic means not a metal or metal alloy. Optionally, the fibrous matrix layer 10 is encapsulated with an organic polymer layer 12.

[0031] 2, an exemplary battery module 20 includes an assembly of battery cells 22 and multiple thermal runaway barriers 24. Each thermal runaway barrier 24 is in the form of a single fiber matrix layer 10, with or without an encapsulant 12, and can be made from the exemplary materials described herein. The thermal runaway barriers 24 can be disposed between adjacent battery cells 22, between groups of cells 22, or both, at one or more locations throughout the battery module 20. Typically, the battery module 20 is mounted on a cooling plate 26 and a tray 28.

[0032] 3 , an exemplary battery pack 30 includes multiple battery modules 20, each of which may have its own cooling plate 26 and tray 28, or all of the modules 20 may share the same cooling plate 26 and tray 28. A thermal runaway barrier 24 formed from the exemplary materials described herein may be disposed between one or more or all of the adjacent battery modules 20, on one or more or all of the battery modules 20 (see reference numeral 24′), or any combination of both. The thermal runaway barrier 24 may also be sized to cover the top of all of the battery modules 20.

[0033] 4, an exemplary thermal runaway barrier 24 includes a single fibrous matrix layer (not shown) encapsulated with organic polymer layers 12 that cover both sides and the periphery of the fibrous matrix layer. In one embodiment, opposing major surfaces of the encapsulation layer 12 are coated with an adhesive (e.g., a pressure-sensitive adhesive) protected by corresponding release liners 14 and 16. The encapsulation layer 12 preferably includes one or more vents or openings 18 (e.g., in the form of notches) that allow air (e.g., hot air) or other gases to escape from the interior of the encapsulation body 12, rather than causing the encapsulation body 12 to swell and expand like a balloon, for example, when the air trapped within the encapsulation body 12 is heated to high temperatures (e.g., when the temperature of one or more of the adjacent battery cells 20 increases).

[0034] Referring to FIG. 5 , conventional dry manufacturing equipment and processes can be used to manufacture the thermal runaway barrier 20 according to the present invention. Examples of such equipment and processes can be found described in U.S. Pat. Nos. 9,580,848 (Henderson et al.), 9,475,034 (Vincent et al.), 7,491,354 (Anderson), and 6,808,664 (Falk et al.). Such equipment may include a chamber or forming box 40 with multiple feeder inlets, including an inlet 42 for feeding any desired combination of fibers, binders, and particles into the box 40, and multiple inlets 44, 44′, and 44″ for feeding any desired number or type of filler material into the box 40. After the fibers are combined and compounded with other raw materials, the resulting nonwoven fibrous material 45 is placed on a belt 46, which conveys the material 45 through a baking oven 47, where at least the binder is cured so that the fibrous material 45 can be further processed. The resulting nonwoven fibrous material 45 is then placed on a belt 46. The cured nonwoven fibrous material 45' is then die-cut, laser-cut, water-jet-cut, or otherwise processed into individual nonwoven fibrous layers 10 (not shown), which are then each processed at encapsulation station 48, for example, by laminating a polymer film 12 (not shown) to both sides of each layer 10. An optional hot melt or pressure-sensitive adhesive may be applied to one or both sides of the encapsulant 12 at corresponding spray stations 49 and 49'. A protective release liner (not shown) may then be applied to each adhesive surface.

[0035] 6, one embodiment of a thermal runaway barrier 24 according to the present invention includes one or more vent holes 52 formed through one or both layers of the encapsulating film 12. The vent holes 52 can have any desired shape (e.g., circular, rectangular, oval, etc.), and preferably the vent holes 52 are formed through a portion of the film 12 that is beyond the perimeter of the encapsulating fibrous layer 10 but still within the perimeter of the encapsulation 12, and also provide a path for inflation gas (e.g., air) to escape from the space containing the fibrous layer 10. The number, size, and location of these vent holes 52 can be varied as desired.

[0036] 7, another embodiment of a thermal runaway barrier 24 according to the present invention includes two vent holes 54, each in the form of a notch formed through the encapsulating film 12. The vent holes 54 can have any desired shape (e.g., semicircular, rectangular, semi-elliptical, etc.), and preferably the notches 54 are formed through a portion of the film 12 that lies beyond the perimeter of the encapsulating fibrous layer 10 and past the perimeter of the encapsulating body 12, and also provide a path for inflation gas (e.g., air) to escape from the space containing the fibrous layer 10. The number, size, and location of these notches 54 can be varied as desired.

[0037] Referring to FIG. 8, an additional embodiment of a thermal runaway barrier 24 according to the present invention includes two different types of vent holes 52 and 54 formed through the enclosure 12, similar to those described above with respect to FIGS. 6 and 7.

[0038] [Table 1]

[0039] Test Method High temperature / low temperature test 1 (HCST1) In an MTS Insight 5 kN tensile testing machine (obtained from MTS Insight, Eden Prairie, MN, United States), the lower platen was heated to 600 °C and the sample was placed on it. The upper platen, with an embedded thermocouple, was lowered so that the distance between the two platens was 1.6 mm. The temperature rise of the cold side was recorded (continuously) versus time until it reached 900 seconds (15 minutes).

[0040] High Temperature / Low Temperature Test 2 (HCST2) In a 10 kN tensile testing machine (obtained from ZWICKROELL, Ulm, Germany), the upper platen was heated to 600°C, and the sample was placed on a lower platen with an embedded thermocouple set at ambient temperature. A heat shield was used to cover the sample, ensuring that the sample was kept at ambient temperature. The heat shield was then removed, and the upper platen was lowered while maintaining a pressure of 1 MPa. The time required for the sample to reach a temperature of 150°C (302°F), designated t(150°C), was recorded.

[0041] shear strength The method of ASTM 273C 273M was followed. A shear rate of 5 min was used.

[0042] Thermal Conductivity Test Thermal conductivity measurements were obtained using a Thermal Constants Analyzer, model TPS 2500S, obtained from Hot Disk® AB (Goteborg, Sweden). Measurements were performed by selecting the Isotropic / Bulk (Type I) module within the software. Measurements were performed using a 3.2 mm diameter Kapton 5465 sensor (Hot Disk®). As specified in the manual, the lateral dimensions of the sample should be 1.5–2.0 times the radius of the sensor. Additionally, the sample thickness should be equal to or greater than the radius of the sensor. To ensure the thickness was sufficiently greater than the radius of the sensor, 3–4 layers of sample were stacked on either side of the sensor, and a small pressure was applied to ensure all layers were in contact with each other.

[0043] The specified parameters were 1) measurement time in seconds, and 2) heating power in mW. The sample temperature was entered as ambient room temperature. The measurement was then performed as defined in the TPS manual.

[0044] The results were analyzed by clicking "Calculate" in the software and selecting the "Standard Analysis" option. After the measurement, the software displayed several graphs, including a "Transient" graph and a "Residual" graph. The transient graph displays the temperature rise of the sensor during sample heating, up to a maximum of 200 points. The first pass to analyze the results began with point 10 and included all points up to point 200 of the transient. If the residual graph did not appear to be a random distribution of points, a smaller subset of data points was used for analysis. This was done by trimming points from the beginning and end of the measurement. As a general rule, if fewer than 50 points were used in the analysis, the results were unreliable. In addition to meeting the quality of the residual plot, several other numerical requirements were established, including the "Probe Depth (PD)," "Temperature Rise (TI)," "Total to Characteristic Time (TCT)," and "Mean Deviation (MD)" as specified in the manual. For these specifications, the PD must be less than the sample thickness, the TI must be between 0.4K and 4.0K, the TCT must be between 0.33 and 1.0, and the MD must be 10-4 or better. If these five criteria were not met, the heating power and measurement time were adjusted. The setup was repeated until an accurate measurement was obtained. Precision was defined as meeting all numerical requirements stated in the manual. The thermal conductivity value in W / m K was measured and recorded for the test sample.

[0045] Examples 1 to 8 (EX1 to EX8) and Comparative Examples 1 to 2 (CE1 to CE2) For Examples 1, 3, and 5-7, the staple fiber combinations by weight percent (as identified in Table 2) were weighed and premixed by hand before being placed on a feed belt. The fibrous material was processed (i.e., top-fed) through an airlaid machine such as that disclosed in U.S. Pat. No. 7,491,354, in which the fibers are opened and dispersed in an air stream before being collected on a screen belt. Details of such airlaid machine equipment and methods for using such equipment in forming airlaid webs can be found in U.S. Pat. Nos. 9,580,848 (Henderson et al.), 9,475,034 (Vincent et al.), 7,491,354 (Anderson), and 6,808,664 (Falk et al.). The filler by weight percent (as identified in Table 2) was top- or side-fed into the chamber or forming box of the airlaid machine. A positive displacement feeder coupled with an air driven horn was used to uniformly distribute the filler over the web. The sample was then fed into a forced air convection oven at 290°F (143.3°C) at a speed of 1.1 m / min.

[0046] For Examples 2 and 4, the process described in Example 1 of U.S. Patent No. 5,869,010 (Langer) was followed. Samples were assembled containing the fibers and fillers in the weight percentages specified in Table 2, rather than the materials specified in U.S. Patent No. 5,869,010.

[0047] For Example 8, Example A of U.S. Pat. No. 9,399,864 (Samanta et al.) was followed, with the noted modifications. An aerogel slurry was prepared by adding 400 grams of Barlox 12 (available from Lonza Group, Basel, Switzerland) to 379 liters (110°F) of water. The slurry was mixed. 200 grams of Foamaster 111 (available from BASF Group, Ludwigshafen, Germany) was added and the slurry was mixed. EAF68 was added at a weight percent (as specified in Table 2) and mixed. AG was then added at a weight percent (as specified in Table 2) and mixed. The slurry was mixed for 15 minutes, and 200 grams of MOJO MP 9307C was added and mixed. A fiber slurry was prepared by adding 717 grams of Microstrand 110X-481 (obtained from John Manville, Denver, CO, United States) to 600 gallons of water. The slurry was pulped for 60 seconds at 500 rpm. T255 was added at a weight percent (as specified in Table 2), and the slurry was pulped for 30 seconds at 500 rpm. An additional 300 gallons of water was added to the slurry. 200 gallons of the fiber slurry was mixed with 100 gallons of the aerogel slurry and SW+ at a weight percent (as specified in Table 2). The combined slurries were processed through a papermaking machine.

[0048] [Table 2]

[0049] These samples were subjected to the HCST1 test and the results are shown in Table 3.

[0050] [Table 3]

[0051] Examples 9 to 34 (EX9 to EX34) and Comparative Examples 3 to 8 (CE3 to CE8) The "General Procedure for Preparing Fibrous Sheet" described in U.S. Patent Application Publication No. 2010 / 0115900 was followed, with the substitutions of materials shown in Table 4. Tap water (3 liters, 18°C) and 60 grams (g) of inorganic fibers washed to a shot content of less than 50 weight percent were added to a GT800 classic blender (obtained from Rotor Lips Ltd, Uetendorf, Switzerland). The blender was operated at low speed for 5 seconds. The resulting slurry was rinsed with 1 liter of tap water (18°C) in a RW16 mixing vessel equipped with a paddle mixer (obtained from IKA-Werke GmbH, Staufen, Germany). The slurry was further diluted with 1 liter of tap water (18°C). The diluted slurry was mixed at medium speed to keep the solids suspended. Antifoaming agent (obtained from Henkel, Edison, NJ, under the trade designation "FOAMASTER 111" (0.3 g)) and ethylene-vinyl acetate terpolymer latex (obtained from Air Products, under the trade designation "AIRFLEX 600BP" (6.0 g, 55 wt.% solids)) were added. Flocculant was added dropwise in the amount shown in Table 4. Then, insulating particles were added as shown in Table 4. The mixer speed was increased, and mixing continued for 1 to 5 minutes. The paddle mixer was removed, and the slurry was poured into a 20 cm x 20 cm (8 in x 8 in) sheet former (obtained from Williams Apparatus Co, Watertown, NY, United States) and drained. The surface of the drained sheet was rolled with a rolling pin to remove excess water. The sheet was then pressed between blotter paper at a surface pressure of 90 to 97 kPa (13 to 14 psi) for 5 minutes. The sheets were then dried in a forced air oven at 150°C for 10-15 minutes and allowed to equilibrate overnight exposed to ambient air. The thickness and basis weight of the samples were measured at a constant pressure of 4.9 kPa and are recorded in Table 5. For Examples 15-25 (EX15-EX25), the vermiculite material used in these samples was either preheated to permanently pre-expand the vermiculite prior to use in preparing the samples, or post-heated after preparation to permanently post-expand the vermiculite at the specified time and temperature conditions.For EX21, the vermiculite was preheated at 300°C for 6 hours before the sample was assembled. For EX22 and EX23, after the sample was assembled, the vermiculite was heated at 450°C for 30 minutes. For EX24, the vermiculite was preheated at 500°C for 30 minutes before the sample was assembled. For EX25, EX33, and EX34, the vermiculite in the sample was preheated at 1000°C for 30 minutes before the sample was assembled.

[0052] [Table 4]

[0053] These samples were subjected to the HCST2 test and the results are shown in Table 5.

[0054] [Table 5]

[0055] Example 35 (EX35) PP was laminated onto the sample assembled in Example 5. Both sides of the hand sample were hot-pressed at 132°C (270°F) and 200 kPa. The edges were manually sealed using an impulse sealer at 149°C (300°F), heated for 2 seconds, and cooled for 10 seconds, all steps performed under a compressive force of 524 kPa (76 psi) pressure. The thickness of the PP film was 0.02 mm (1 mil). The 600 gsm samples were subjected to shear strength testing, the results of which are shown in Table 6.

[0056] Example 36 (EX36) Hot melt adhesive H2345 was applied to the samples of Example 35 using a Nordson Altablue Grid Melter equipped with a 6 inch meltblown adhesive die. The adhesive was heated to 380°F (193°C) and sprayed onto the web at 30 psi air pressure and a pump speed of 20 RPM. The 600 gsm samples were subjected to shear strength testing, the results of which are shown in Table 6.

[0057] Example 37 (EX37) FB was spray coated onto the sample assembled in Example 35 using an ACCUSPRAY ONE spray gun system with PPS obtained from 3M Company (St. Paul, MN, United States). One side of the hand sample was spray coated, then flipped over and coated on the other side. The 600 gsm samples were subjected to shear strength testing, the results of which are shown in Table 6.

[0058] Example 38 (EX38) An adhesive was prepared by dissolving PKHH phenoxy resin (obtained from Gabriel Performance Products, Akron, OH, United States) in a 50% solution of methyl ethyl ketone (MEK). The MEK was allowed to evaporate for an additional 60 minutes at room temperature. Two coatings of adhesive were applied to one side of a 0.076 mm (3 mil) PET film (obtained from DuPont, Wilmington, DE, United States). Two coatings of adhesive were applied to one side of another 0.076 mm (3 mil) PET film. The adhesive coating thickness was 0.036 mm (1.4 mil). The adhesive-coated PET sample films were placed on the top and bottom of the sample assembled in Example 5. The 600 gsm samples were subjected to shear strength testing, the results of which are shown in Table 6.

[0059] [Table 6]

[0060] Examples 39 to 40 (EX39 to EX40) Using the materials specified in Table 7, samples were assembled using the procedures described in Examples 9-16. The thickness and basis weight of the samples were measured at a constant pressure of 4.9 kPa and are recorded in Table 8. These samples were subjected to the HCST2 test, the results of which are shown in Table 8.

[0061] [Table 7]

[0062] [Table 8]

[0063] Examples 41 to 57 (EX41 to EX57) A combination of staple fibers by basis weight (as specified in Table 9) was weighed and processed through an airlaid processor. Details of the equipment and its use in forming airlaid webs are described in U.S. Patents 9,580,848 (Henderson et al.), 9,475,034 (Vincent et al.), 7,491,354 (Anderson), and 6,808,664 (Falk et al.). The combined staple fibers were then processed again through an airlaid processor, and fumed silica filler was fed directly into the chamber of the airlaid processor by basis weight (as specified in Table 2). A screw feeder was used to uniformly distribute the filler throughout the web. The web was then fed into a forced air convection oven at 300°F (148.89°C) at speeds of 0.25 m / min and 1.5 m / min. Sample thicknesses ranged from 0.5 to 15 mm.

[0064] The web was then densified to a specific gap thickness using a hot press. Polytetrafluoroethylene (PTFE)-coated fiberglass fabric sheets (obtained from McMaster-Carr, Elmhurst, IL, United States) were placed on both sides of the sample, and the sample was placed between two hot plates maintained at a temperature of 300°F (148.89°C). Pressure was applied for 30 to 120 seconds to activate the bicomponent fibers (T255). The densified sample was then immediately placed under pressure between two plates maintained at room temperature for 30 to 120 seconds to set the web to the desired thickness.

[0065] [Table 9]

[0066] These samples were subjected to the HCST2 test and the results are shown in Table 10. The actual thickness of the samples was measured by removing the fiberglass fabric sheet according to ASTM D5736-95. The plate pressure was calibrated to 0.002 psi (13.790 Pascals).

[0067] [Table 10]

[0068] The densities of the 1000 gsm samples (designated EX48-EX53) containing 40% fumed silica were calculated by dividing the actual basis weight (gsm) by the actual thickness (mm). The densities and cold side temperatures recorded after 3600 seconds of HSCT2 testing for EX48-EX53 are shown in Table 11. The table is organized in ascending order of measured cold side temperatures.

[0069] [Table 11]

[0070] Thermal conductivity tests were performed and the results are shown in Table 12.

[0071] [Table 12]

[0072] Surprisingly, it has been found that fumed silica has a higher thermal conductivity than silica aerogel. A nonwoven fibrous insulation (i.e., a fiber matrix) without fumed silica particles will have a lower thermal conductivity than the same fiber matrix containing fumed silica particles.

[0073] Additional Embodiments Battery Cell Thermal Runaway Barrier Embodiments 1. A thermal runaway barrier operably adapted (i.e., designed, configured, shaped, and / or dimensioned) or otherwise suitable for placement between adjacent battery cells (e.g., prismatic or pouch-shaped battery cells) of a battery module or assembly (i.e., a series of battery cells stacked in a row), such as those used to power an electric motor (e.g., those used in electric or hybrid vehicles), to prevent, stop, or at least significantly slow down a thermal runaway event within the battery module or assembly or between adjacent battery modules or assemblies, a fibrous matrix of ceramic or other non-metallic (i.e., not metal, metal alloy, or metal composite) inorganic fibers, insulating ceramic or other non-metallic (i.e., not metal, metal alloy, or metal composite) inorganic particles dispersed within the fibrous matrix, uniformly, evenly, entirely, or otherwise throughout, or to the extent permitted by the manufacturing process (e.g., in both dry and wet processes, there may be some settling of particles to the bottom of the mat), and a single layer of dry-laid or wet-laid nonwoven fibrous insulation (e.g., in the form of a mat, sheet, strip, or three-dimensional thin-walled structure) that includes an organic or inorganic binder (e.g., an organic or inorganic adhesive binder, organic or inorganic binder fibers that are needle-punched, stitched, or otherwise mechanically entangled in the fibrous matrix to hold the fibrous matrix together, etc.) dispersed therein to bind the inorganic filler particles and inorganic fibers together or otherwise hold the fibrous matrix together at least long enough to withstand the required degree of handling (e.g., during the encapsulation process) prior to placement between the battery cells; A thermal runaway barrier consisting essentially of, or consisting only of, an optional organic (e.g., polymer, paper, etc.) encapsulating layer (e.g., one layer or multiple opposing sandwich layers, each layer in the form of a film, coating, organic fiber nonwoven or woven fabric, etc.) that encapsulates all, a majority, or a portion of at least one or both major surfaces of a monolayer of nonwoven fibrous insulation, and preferably also all, a majority, or a portion of the peripheral edges of the monolayer of nonwoven fibrous insulation, to prevent or significantly reduce shedding or loss of inorganic fibers or particles from the encapsulated monolayer of nonwoven fibrous insulation.

[0074] A reduction in shedding of inorganic fibers or particles is significant if the number of lost inorganic fibers or particles is less than 10%, less than 5%, or less than 1% by weight of the original fiber or particle content of the layer of nonwoven fibrous insulation. The thinner the organic encapsulation layer (i.e., the lower the organic content of the barrier), the better the results of the high / low temperature test.

[0075] The thermal runaway barrier of the present invention may also be used between battery modules or assemblies.

[0076] Inorganic binders, organic binders, or a combination of both may be useful in accordance with the present invention, including, for example, those disclosed in U.S. Pat. No. 8,834,759. Examples of inorganic binders useful in both dry and wet fiber processing include silicone particles that convert to fusible silica when heated. Organic-inorganic hybrid binders, such as WACKER® MQ 803 TF, which is the cohydrolysis product of tetraalkoxysilane (Q units) and trimethylalkoxysilane (M units), may also be useful. The chemical structure of WACKER® MQ 803 TF can be viewed as a three-dimensional network of polysilicic acid units end-capped with trimethylsilyl groups. Some residual ethoxy and hydroxy functional groups are present. The average molecular weight can be precisely controlled by the ratio of M to Q units, which for WACKER® MQ 803 TF is approximately 0.67.

[0077] Exemplary binder fibers include the use of bicomponent core-sheath polymer fibers in dry processes. Wet processes can use ethylene vinyl acetate latex dispersion binders, bicomponent core-sheath polymer fibers, or a combination of both. When polymer binder fibers are used, the binder can be activated by heating and compressing the nonwoven fibrous insulation material. A combination of organic and inorganic binders can also be used.

[0078] As used herein, the term "consisting only of" indicates that the claimed thermal runaway barrier includes only structures having the recited elements.

[0079] As used herein, the term "consisting essentially of" indicates that the claimed thermal runaway barrier can exhibit the desired thermal insulating properties by using only the recited features / elements, without the need for additional layers of insulating material. For example, the thermal runaway barrier of the present invention need not include a separate layer of other insulating material (e.g., a woven or nonwoven structure of inorganic fibers). Thus, the term "consisting essentially of" means that if a third-party thermal runaway barrier (e.g., a competitor's) includes all of the claimed features / elements of the present invention and one or more additional features / elements not recited in the claim (e.g., an additional layer of inorganic fibers), the third-party thermal runaway barrier would be considered within the claim if the additional features / elements do not determine whether the thermal runaway barrier exhibits the desired thermal insulating properties.

[0080] As used herein, the term "inorganic" refers to a ceramic or other non-metallic (ie, not a metal, metal alloy, or metal composite) inorganic material.

[0081] "Thermal runaway" refers to a phenomenon in which a battery cell undergoes a heat chain reaction, causing the temperature of the battery cell to rise uncontrollably. Heat chain reactions can be caused by, for example, overheating of the battery cell, overvoltage of the battery cell, or mechanical puncture of the battery cell.

[0082] "Heat propagation" refers to when the thermal runaway of a battery cell causes the remaining battery cells in the battery pack or system to experience thermal runaway phenomena.

[0083] A "thermal runaway event" refers to the overheating of one battery cell within a battery cell enclosure, causing a chain reaction of overheating of adjacent battery cells until the number of overheated battery cells reaches a critical point of propagation, destroying all or more than half of the battery cells within a module or assembly of modules, potentially resulting in an explosion or fire. Factors that can cause battery cell overheating include physical damage, the application of excessive voltage, and overheating (internal short circuit of a battery cell).

[0084] As the energy density of a battery cell increases, the temperature at which the battery cell begins to malfunction (e.g., at least loses its efficiency or ceases to function before catching fire, burning, or exploding) decreases. Similarly, as the energy density of a battery cell decreases, the temperature at which the battery cell begins to malfunction increases. For example, with a controlled temperature increase, NMC811-type battery cells tend to begin to malfunction or even explode when temperatures reach approximately 120°C to 130°C, while NMC622-type battery cells begin to malfunction or even explode when temperatures reach approximately 180°C. The corresponding temperature is higher for battery cells with lower energy densities (e.g., NMC532 and NMC433-type battery cells). When physically larger battery cells are used or when temperatures increase rapidly, it may take longer for the local temperature to reach a critical point due to heat diffusion through the battery cell. It is believed that this heat diffusion effect may somewhat increase the actual temperature at which the battery cell begins to malfunction or explode. It may be desirable for the thermal runaway barrier of the present invention to prevent adjacent cells from reaching temperatures in the range of about 130°C to about 150°C.

[0085] As used herein, "preventing" a thermal runaway event refers to preventing overheating of a single battery cell from causing overheating of battery cells adjacent to the single battery cell. A barrier is considered to prevent a thermal runaway event if the adjacent battery cells do not exceed 130°C, 135°C, 140°C, 145°C, or 150°C.

[0086] As used herein, "terminating" a thermal runaway event refers to overheating of a battery cell causing only adjacent battery cells (i.e., battery cells three, two, or one cell away on either side of the overheating battery cell) to overheat, and not the remaining battery cells in the battery module or assembly.

[0087] As used herein, "slowing down" a thermal runaway event refers to delaying the thermal runaway event at least long enough so that personnel adjacent to the battery module or assembly (e.g., occupants in the passenger compartment of an electric vehicle) can escape to a safe distance from the battery module or assembly before being injured by the thermal runaway event. If a battery cell malfunctions (e.g., catches fire or overheats to the point of not functioning) and a thermal barrier is placed between the battery cells, the time for any adjacent battery cell to propagate the malfunction (e.g., catches fire or overheats) is at least greater than 5 minutes, preferably greater than 10 minutes, or even greater than 20 minutes.

[0088] Inorganic particles may be solid, hollow, or contain multiple voids. Such particles may include, for example, particles of non-expanding expandable materials, irreversibly or permanently expanded expandable materials (e.g., expandable materials), diatomaceous earth, inorganic aerogel materials, porous ceramic (e.g., silica) materials, irreversibly or permanently expanded perlite minerals, hollow ceramics, or other inorganic (e.g., glass) microspheres. Particularly desirable are inorganic particles containing voids, such as those found in irreversibly or permanently expanded vermiculite. Particles of irreversibly or permanently expanded perlite minerals also contain voids, but perlite minerals are harder and less compressible than vermiculite minerals. Silica-based and other aerogel particles also contain voids.

[0089] As used herein, irreversibly or permanently expanded expandable particles (e.g., particles of intumescent materials such as vermiculite and perlite minerals) refer to particles that have been heated to a temperature and for a time such that they irreversibly or permanently expand by at least 10% and up to 100% of their expansion capacity, either by being pre-expanded before being used to form a thermal runaway barrier, or by being post-expanded after being incorporated into a monolayer of nonwoven fibrous insulation.

[0090] Expandable particles (e.g., vermiculite particles) can be permanently expanded by heating the particles beyond the point of reversibility (e.g., in the range of about 350°C to about 1000°C for vermiculite). Such permanently expanded expandable particles (e.g., vermiculite particles) may have an expanded accordion- or worm-like structure that is elongated, less dense, and less mechanically stable than the same particles in an unexpanded state, making them more susceptible to breaking down into smaller particles. As the heating temperature increases, the degree of permanent expansion of the particles increases (i.e., the particles may become larger and / or longer). It may also be desirable to use vermiculite that has been permanently expanded by chemical treatment methods (see, e.g., "Chemical Exfoliation of Vermiculite and the Production of Colloidal Dispersions," G.F. Walker, W.G. Garrett, Science 1967 April 21: Volume 156, Edition 3773, Pages 385-387, DOI: 10.1126 / science.156.3773.385; and https: / / science.sciencemag.org / content / 156 / 3773 / 385.abstract).

[0091] Because the expanded state is more susceptible to degradation, it may be desirable to post-expand the intumescent particles after they have been incorporated into the nonwoven fibrous insulation. Even if gentle processing is used to avoid substantial degradation, it is believed that incorporating pre-expanded intumescent particles into the nonwoven fibrous insulation may still result in the intumescent particles becoming oriented in the plane of the insulation (i.e., the x-axis, y-axis, and / or therebetween). For example, in pre-expanded vermiculite particles, the elongated particles may become generally aligned with the fibers in the longitudinal or downstream direction (i.e., the y-axis) rather than through the thickness of the nonwoven fibrous insulation (i.e., the z-axis).

[0092] In contrast, when they are post-expanded (i.e., after a nonwoven fibrous insulation is made with unexpanded intumescent particles), the expanded intumescent particles are not primarily oriented within the plane of the insulation. Unexpanded intumescent particles typically have a more uniform structural shape (i.e., an aspect ratio closer to 1) compared to the same particles in the expanded state. This more uniform structural shape is believed to be less affected by fiber alignment during the formation of the nonwoven fibrous insulation. As a result, post-expanded intumescent particles are more likely to be isotropically oriented within the nonwoven fibrous insulation. For example, in post-expanded vermiculite particles, the elongated particles may be aligned in the thickness direction (i.e., z-axis), in-plane (i.e., x-axis, y-axis, and / or between them), or off-axis. This difference in orientation between pre-expanded and post-expanded particles is believed to be caused by the unexpanded particles having a more uniform structural shape than that exhibited in the expanded state.

[0093] 2. The thermal runaway barrier of embodiment 1, wherein the layer of nonwoven fibrous insulation contains inorganic fibers in an amount ranging from a low of about 15-19% by weight to a high of about 70, 75, 80, 85, or 90% by weight of the layer of nonwoven fibrous insulation.

[0094] 3. A thermal runaway barrier according to embodiment 1 or 2, wherein the layer of nonwoven fibrous insulation contains fiber shot in an amount ranging from about 3% by weight to about 60% by weight of the amount of inorganic fibers in the layer of nonwoven fibrous insulation.

[0095] In one embodiment, when no insulating particles are added, the inorganic fiber content is 95.2% by weight dry and 95.5% by weight wet. At the lowest level of insulating particle (e.g., aerogel particle) loading, the inorganic fiber content is 72% by weight for both dry and wet. In the case of dry-laid nonwoven fibrous insulation, the fibers are opened (i.e., the bulk fibers are separated and de-densified), which may remove some shot. In the case of wet-laid nonwoven fibrous insulation, the fibers are wet-cleaned, which removes more shot than is removed by the dry-laid opening process. Uncleaned SuperWool Plus from Morgan has approximately 40% shot, and the actual fibrous material content in nonwoven fibrous insulation is 19-43%. It may be desirable for nonwoven fibrous insulation to have a fiber content ranging from about 10% to about 80%. Lower amounts of fiber require higher amounts of organic binder. Other additives (e.g., flame retardant materials, heat-absorbing materials, infrared-reflecting materials, etc.) may also be included.

[0096] 4. The thermal runaway barrier of any one of embodiments 1-3, wherein the layer of nonwoven fibrous insulation contains insulating inorganic particles in an amount ranging from as low as about 10%, 15%, 20%, 25%, 30%, or 35% to as high as about 40%, 45%, 50%, 55%, or 60% by weight of the layer of nonwoven fibrous insulation. For example, a particle content as high as 60% can be achieved using a dry process, and a particle content as high as 50% can be achieved using a wet process.

[0097] 5. The thermal runaway barrier of any one of embodiments 1-4, wherein the layer of nonwoven fibrous insulation contains an amount of organic binder ranging from as low as about 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 5.5%, 6.0%, or 6.5% by weight of the layer of nonwoven fibrous insulation to as high as about 7.0%, 7.5%, 8.0%, 8.5%, 9.0%, 9.5%, or 10.0% by weight of the layer of nonwoven fibrous insulation.

[0098] 6. The thermal runaway barrier of any one of embodiments 1 to 5, wherein the layer of nonwoven fibrous insulation has an installed (i.e., compressed) thickness in the range of about 0.5 mm to less than 5.0 mm. In particular, the installed (i.e., compressed) thickness can be in the range of about 0.5 mm to about 2.5 mm, with a lower limit of about 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, and an upper limit of about 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2.0 mm, 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm, or 2.5 mm. In some applications, the installed thickness can even be as high as less than about 2.6 mm, 2.7 mm, 2.8 mm, 2.9 mm, 3.0 mm, 3.1 mm, 3.2 mm, 3.3 mm, 3.4 mm, 3.5 mm, 3.6 mm, 3.7 mm, 3.8 mm, 3.9 mm, 4.0 mm, 4.1 mm, 4.2 mm, 4.3 mm, 4.4 mm, 4.5 mm, 4.6 mm, 4.7 mm, 4.8 mm, 4.9 mm, or 5.0 mm. The installed thickness of a layer of nonwoven fibrous insulation is almost always less than its uninstalled (i.e., uncompressed) thickness. Thermal runaway barrier performance is measured when in its installed (i.e., compressed) state.

[0099] 7. The layer of nonwoven fibrous insulation has an uninstalled (i.e., uncompressed) thickness in the range of about 1.0 mm to 8.0 mm, with the lower limits being about 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2.0 mm, 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm, 2.5 mm, 2.6 mm, 2.7 mm, 2.8 mm, 2.9 mm, 3.0 mm 7.0 mm, 7.5 mm, or 8.0 mm. The thermal runaway barrier of any one of embodiments 1-6, wherein the thickness of the nonwoven fibrous insulation layer may be about 4.0 mm, 4.1 mm, 4.2 mm, 4.3 mm, 4.4 mm, 4.5 mm, 4.6 mm, 4.7 mm, 4.8 mm, 4.9 mm, 5.0 mm, 5.5 mm, 6.0 mm, 6.5 mm, 7.0 mm, 7.5 mm, or 8.0 mm. The uncompressed thickness of the nonwoven fibrous insulation layer is almost always greater than its installed thickness.

[0100] 8. The layer of nonwoven fiber insulation is approximately 250 g / m 2 from a low value of about 1000 g / m 2 The thermal runaway barrier of any one of embodiments 1-7, having a basis weight ranging from about 250 g / m2 to as high as about 250 g / m2 for gaps between adjacent battery cells ranging from about 0.75 mm to about 1.25 mm, depending on the composition of the thermal runaway barrier. 2 ~about 400g / m 2 (e.g., 300g / m 2 , 350g / m 2 Depending on the thermal runaway barrier composition, a basis weight of about 300 g / m may be desirable for gaps between adjacent battery cells ranging from about 0.75 mm to about 2.5 mm, and up to about 2 ~about 550g / m 2 It may also be desirable for the gap between adjacent battery cells to be in the range of about 2.5 mm to less than 5.0 mm, with a basis weight of about 600 g / m 2 ~About 1000g / m 2 (For example, about 650 g / m 2 , 700g / m 2 , 750g / m 2 , 800g / m 2 , 850g / m 2 , 900g / m 2 , 950g / m 2 , or 1000g / m 2 Desired results are achieved with a thermal runaway barrier using insulating inorganic particles of irreversibly or permanently expanded vermiculite, where the nonwoven fibrous insulation is about 450 g / m² for gaps ranging from about 1.50 mm to about 2.5 mm. 2 or 550 g / m 2 The sheet has a basis weight of .

[0101] In one embodiment, the insulating inorganic particles are particles of irreversibly or permanently expanded vermiculite, and the layer of nonwoven fibrous insulation is 450 g / m² for a gap installed between adjacent battery cells ranging from about 1.50 mm to about 2.5 mm. 2In another embodiment, the insulating inorganic particles are particles of irreversibly or permanently expanded vermiculite, and the layer of nonwoven fibrous insulation has a basis weight of 550 g / m for gaps installed between adjacent battery cells ranging from about 1.50 mm to about 2.5 mm. 2 The sheet has a basis weight of .

[0102] 9. The layer of nonwoven fiber insulation is approximately 250 g / m 2 ~about 400g / m 2 9. The thermal runaway barrier of any one of embodiments 1-8, having a basis weight in the range of

[0103] In certain embodiments, for example, when the insulating inorganic particles are vermiculite and the gap is about 1 mm, the thickness is about 300 g / m 2 ~400g / m 2 When aerogel particles are used and the gap is about 1 mm, a basis weight in the range of about 250 g / m 2 A basis weight of about 800 g / m2 may also be desirable. 2 ~About 1000g / m 2 In some cases, a basis weight in the range of

[0104] 10. The insulating inorganic particles may be inorganic (e.g., titania, zirconia, and / or silica) aerogels, xerogels, hollow or porous ceramic (e.g., glass, alumina, etc.) microspheres (e.g., bubbles, foam spheres, beads, etc.), unexpanded vermiculite, irreversibly or permanently expanded vermiculite (i.e., vermiculite heated to a temperature and for a time that causes the vermiculite particles to irreversibly or permanently expand to at least 10% to 100% of their expansion capacity, either by pre-expansion before being used to form a barrier or by post-expansion after becoming a monolayer of nonwoven fibrous insulation), fumed vermiculite, or the like. 10. The thermal runaway barrier of any one of embodiments 1-9, made from, or at least comprising, particles of one or any combination of materials selected from the group consisting of mud silica and other porous silica, irreversibly or permanently expanded perlite (i.e., perlite that has been heated to a temperature and for a time that causes the perlite particles to irreversibly or permanently expand to at least 10% to 100% of their expansion capacity, either by pre-expansion before being used to form a barrier or by post-expansion after becoming a monolayer of nonwoven fibrous insulation), unexpanded perlite, pumice, irreversibly or permanently expanded clay, diatomaceous earth, titania, and zirconia.

[0105] Expanded clays are lightweight particles or aggregates that can be made by heating clay to approximately 1,200°C (2,190°F) in a rotary kiln. The resulting gases expand the clay through thousands of tiny bubbles that form during heating, creating a honeycomb structure. Expanded clays can have a roughly round or potato shape due to their circular motion in the kiln and are available in a variety of sizes and densities. Expanded clays are used in the production of lightweight concrete products (see, for example, the website: https: / / www.archiexpo.com / architecture-design-manufacturer / expanded-clay-aggregate-concrete-23000.html) and other applications. Expanded clays are most commonly known by the brand names LECA (an acronym for Lightly Expanded Clay Aggregates) or LIAPOR (Porous Lias Clay), and are also known as Hydroton and the non-proprietary terms fired clay pebbles, grow rocks, expanded clay, or hydrocones, which are small spheres of clay that have been baked and expanded (see, for example, the website: https: / / www.sciencedirect.com / topics / engineering / expanded-clay-aggregate).

[0106] 11. The thermal runaway barrier of any one of embodiments 1-10, wherein the inorganic fibers of the fiber matrix are selected from the group of fibers consisting of alkaline earth silicate fibers, refractory ceramic fibers (RCF), polycrystalline wool (PCW) fibers, basalt fibers, glass fibers, and silicate fibers. Glass and silica fibers typically contain no particles or only a small amount of shot particles. PCW typically contains up to 5% shot particles, while alkaline earth silicate (AES) fibers contain up to 60% shot particles when unwashed and as low as about 10-30% shot particles when washed.

[0107] 12. The thermal runaway barrier of any one of the preceding embodiments, wherein the organic binder is in the form of a polymer fiber (e.g., PE / PET, PET, FRPET), a dry polymer powder (e.g., LDPE, polyamide, epoxy resin powder (3M SCOTCHCAST 265, 3M SCOTCHKOTE 6258)), or a liquid binder (e.g., acyl latex, ethylene vinyl acetate (EAF68) latex, silicone, polyurethane, etc.).

[0108] 13. The thermal runaway barrier of any one of embodiments 1-12, wherein the layer of nonwoven fibrous insulation is encapsulated by an organic encapsulation layer.

[0109] 14. A thermal runaway barrier as described in embodiment 13, wherein the organic encapsulation layer has at least one vent hole formed therethrough, the vent hole being positioned and sized to allow expanding gas (e.g., air) contained within the thermal runaway barrier to escape from the organic encapsulation, such that the structural integrity of the organic encapsulation layer remains intact (i.e., the layer of nonwoven fibrous insulation remains completely, mostly, or at least significantly encapsulated by the organic encapsulation layer) when the thermal runaway barrier is compressed during assembly of a battery cell module (e.g., a stack of battery cells) or when the thermal runaway barrier is heated (e.g., during normal operation or upon overheating of an adjacent battery cell). Each vent hole may be rectangular (see, e.g., FIG. 8), circular, oval, or any other shape desired, or a combination thereof. One or more or each vent hole may be in the shape of a notch protruding from a side edge of the encapsulation toward the center of the thermal runaway barrier (see, e.g., left vent 54 in FIG. 8 and vent 54 in FIG. 7). Alternatively, the or each vent hole can be formed inside the side edge of the encapsulant, adjacent to the nonwoven insulation (see, e.g., right vent hole 52 in FIG. 8 and vent hole 52 in FIG. 6). Additionally, the or each vent hole can be formed through the encapsulation layer on only one side (see right vent hole 52 in FIG. 6) or both sides (see left vent hole 52 in FIG. 6) of the nonwoven fibrous insulation. It may also be desirable for each vent hole to be in the form of a plurality of small perforations clustered together (e.g., as in a screen, sieve, or colander) to provide a desired outlet opening area.

[0110] 15. A thermal runaway barrier as described in embodiment 13 or 14, wherein the thermal runaway barrier has an upper edge, a lower edge, and opposing side edges, and at least one vent hole is located along the periphery of one or both opposing side edges.

[0111] 16. At least one ventilation hole must be approximately 2 mm 2 ~about 15mm 216. The thermal runaway barrier of any one of embodiments 13-15, providing an exit opening through the organic encapsulation layer having an open area in the range of: It is contemplated that any specific range within this range, or any narrower range within this range, may be desirable.

[0112] 17. The thermal runaway barrier of any one of embodiments 13-16, wherein the organic encapsulation layer is in the form of a continuous layer, a discontinuous layer (e.g., having perforations, through-holes, or porosity that allow gas to pass through the organic layer), or a combination of both. In addition, the organic layer can be in the form of an organic (e.g., polymer) film, a scrim, a woven or nonwoven fabric, an adhesive (e.g., a thermoplastic or hot-melt adhesive) layer, or a combination thereof. One example of an organic layer is a polymer film (e.g., a copolyester polymer film).

[0113] 18. The thermal runaway barrier of any one of embodiments 13 to 17, wherein the organic encapsulation layer is a calendered layer, a hot melt coated layer, a spray coated layer, a dip coated layer, or a laminated layer (e.g., by using a pressure sensitive adhesive or other adhesive).

[0114] 19. A thermal runaway barrier according to any one of embodiments 13-18, wherein the layer of nonwoven fibrous insulation has a periphery and the organic encapsulation layer is sealed around the periphery.

[0115] 20. A thermal runaway barrier according to any one of the preceding embodiments, wherein the layer of nonwoven fiber insulation passes the following UL94 flammability test at least at level V-2 or V-1, preferably V-0.

[0116] Flammability Test Testing was performed using the UL 94 standard, i.e., the Standard for Flammability Safety Testing of Plastic Materials for Equipment and Appliance Parts. UL 94 is a flammability standard for plastics published by Underwriters Laboratories, USA. This standard determines whether a material tends to extinguish or spread the flame when a test specimen ignites. The UL-94 standard is harmonized with IEC 60707, 60695-11-10, and 60695-11-20, and ISO 9772 and 9773. 75 mm x 150 mm specimens were exposed to a 2 cm, 50 W tirrel burner flame ignition source. The test specimen was positioned vertically above the flame, with the test flame hitting the bottom of the specimen. The time to extinguishment was measured for each specimen, and a V rating was assigned. As shown in Table 1 below, the V rating is a measure of the time it takes for the sample to extinguish without burning to the top of the clamp or dropping molten material that ignites the cotton indicator.

[0117] [Table 13]

[0118] 21. The thermal runaway barrier of any one of embodiments 1-20, wherein the insulating inorganic particles are made from or at least comprise particles of an irreversibly or permanently expanded expandable material (e.g., an intumescent material).

[0119] 22. The thermal runaway barrier of embodiment 21, wherein the insulating inorganic particles are made from, or at least comprise, particles of an expanded intumescent material that have been irreversibly or permanently expanded in the range of at least about 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90% to 100% of their expansion capacity.

[0120] 23. The thermal runaway barrier of any one of embodiments 1 to 20, wherein the insulating inorganic particles are made from or at least comprise irreversibly or permanently expanded particles (e.g., vermiculite particles).

[0121] 24. The thermal runaway barrier of embodiment 23, wherein the expanded particles (e.g., vermiculite particles) are irreversibly or permanently expanded in the range of at least about 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90% to 100% of their expansion capacity.

[0122] 25. The thermal runaway barrier of any one of embodiments 1-24, wherein the insulating inorganic particles further comprise particles of at least fumed silica.

[0123] 26. Fumed silica particles are approximately 100 m 2 / g~about 400m 2 26. The thermal runaway barrier of embodiment 25, having a surface area in the range of 1 / g.

[0124] 27. A thermal runaway barrier assembly comprising a plurality of thermal runaway barriers according to any one of embodiments 1 to 26, wherein the plurality of thermal runaway barriers are provided (a) in the form of a stack within a container (e.g., a cardboard or other box); (b) arranged end-to-end in series, with one major surface of each thermal runaway barrier adhered to a major adhesive surface of a length of double-sided or single-sided adhesive tape (where double-sided adhesive tape is used, the opposite major adhesive surface of the tape may be protected by a release liner); or (c) arranged end-to-end in series in the form of a tape, with a single layer of nonwoven fibrous insulation of each thermal runaway barrier arranged end-to-end and sandwiched or otherwise encapsulated between two opposing lengths of organic (e.g., polymeric) encapsulation layers (e.g., in the form of two opposing films, coatings, etc.).

[0125] Battery Cell Module Embodiments 28. a plurality of battery cells disposed within a housing; A plurality of thermal runaway barriers according to any one of embodiments 1 to 27, A battery cell module or assembly for an electric vehicle in which the battery cells are arranged in a row or stack with one thermal runaway barrier disposed between each pair of adjacent battery cells or between a predetermined number of battery cells.

[0126] Methods of Manufacturing Embodiments of Battery Cell Thermal Runaway Barriers 29. A method of making a thermal runaway barrier according to any one of embodiments 1 to 27, comprising forming a layer of nonwoven fibrous insulation using a wet process or a dry process.

[0127] 30. providing insulating inorganic particles that are made entirely of, predominantly made of, or at least include, non-expanded intumescent particles (e.g., non-expanded vermiculite particles or non-expanded perlite particles); disposing insulating inorganic particles so as to be uniformly or evenly distributed throughout or within the layer of nonwoven fibrous insulation; heating the unexpanded expandable particles to a temperature and for a time that irreversibly or permanently expands the unexpanded expandable particles; 30. The method of embodiment 29, wherein the heating occurs before or after the insulating inorganic particles are disposed within the layer of nonwoven fibrous insulation.

[0128] 31. The method of embodiment 30, wherein the heating is carried out after the insulating inorganic particles are disposed within the layer of nonwoven fibrous insulation.

[0129] 32. The method of embodiment 30 or 31, wherein heating irreversibly or permanently expands the unexpanded expandable particles in the range of at least about 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90% to 100% of their expansion capacity.

[0130] 33. The method of any one of embodiments 30-32, wherein the non-expanded intumescent particles comprise non-expanded vermiculite particles, non-expanded perlite particles, or both.

[0131] 34. providing insulating inorganic particles made entirely from, made predominantly from, or at least including pre-expanded expandable particles (e.g., expanded vermiculite or expanded perlite); disposing the insulating inorganic particles so as to be uniformly or evenly distributed throughout or within the layer of nonwoven fibrous insulation; 30. The method of embodiment 29, wherein the pre-expanded intumescent particles are formed by heating the unexpanded intumescent particles to a temperature and for a time that irreversibly or permanently expands the unexpanded intumescent particles before the insulating inorganic particles are disposed within the layer of nonwoven fibrous insulation.

[0132] 35. The method of embodiment 34, wherein the pre-expanded expandable particles are irreversibly or permanently expanded in the range of at least about 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90% to 100% of their expansion capacity.

[0133] 36. The method of embodiment 34 or 35, wherein the pre-expanded expandable particles comprise pre-expanded vermiculite particles, pre-expanded perlite particles, or both.

[0134] Various modifications and variations of the present invention can be made without departing from the spirit and scope thereof. For example, it is believed that microwave heating can be used to irreversibly or permanently expand particles made from expandable materials. It is also believed that the use of microwave energy, rather than baking in an oven, can more uniformly expand the expandable particles within the fiber matrix. Accordingly, the present invention is not limited to the above, but should be limited by the limitations set forth in any of the following embodiments and their equivalents. The present invention may suitably be practiced in the absence of any element not specifically disclosed herein. All patents and patent applications cited above, including those in the Background section, are incorporated herein by reference in their entirety. In the following, exemplary embodiments are presented. [Item 1] a thermal runaway barrier disposed between battery cells of a battery assembly and operatively adapted to at least significantly slow down a thermal runaway event within said battery assembly, a single layer of nonwoven fibrous insulation comprising a fibrous matrix of inorganic fibers, insulating inorganic particles dispersed within the fibrous matrix, and a binder dispersed within the fibrous matrix to hold the fibrous matrix together; an optional organic encapsulation layer encapsulating said monolayer of nonwoven fibrous insulation. [Item 2] Item 1. The thermal runaway barrier of item 1, wherein the layer of nonwoven fibrous insulation contains fiber shot in an amount ranging from about 3% to about 60% by weight of the amount of inorganic fibers in the layer of nonwoven fibrous insulation. [Item 3] 3. The thermal runaway barrier of claim 1 or 2, wherein the layer of nonwoven fibrous insulation contains insulating inorganic particles in an amount ranging from as low as about 10% to as high as about 60% by weight of the layer of nonwoven fibrous insulation. [Item 4] 4. The thermal runaway barrier of any one of claims 1 to 3, wherein the layer of nonwoven fibrous insulation contains an organic binder in an amount ranging from as low as about 2.5% to as high as about 10.0% by weight of the layer of nonwoven fibrous insulation. [Item 5] 5. The thermal runaway barrier of any one of claims 1 to 4, wherein the layer of nonwoven fibrous insulation has an installed thickness in the range of about 0.5 mm to less than 5.0 mm. [Item 6] The layer of nonwoven fiber insulation has a thickness of about 250 g / m 2 from a low value of about 1000 g / m 2 6. The thermal runaway barrier of any one of items 1 to 5, having a basis weight ranging from 1000 to as high as 10 ... [Item 7] The layer of nonwoven fiber insulation has a thickness of about 250 g / m 2 ~about 400g / m 2 7. The thermal runaway barrier of any one of items 1 to 6, having an uncompressed basis weight in the range of [Item 8] 8. The thermal runaway barrier of any one of items 1 to 7, wherein the insulating inorganic particles comprise particles of one or any combination of materials selected from the group consisting of inorganic aerogel, xerogel, hollow or porous ceramic microspheres, unexpanded vermiculite, irreversibly or permanently expanded vermiculite, fumed silica, other porous silica, irreversibly or permanently expanded or unexpanded perlite, pumice, irreversibly or permanently expanded clay, diatomaceous earth, titania, and zirconia. [Item 9] 9. The thermal runaway barrier of any one of items 1 to 8, wherein the layer of nonwoven fibrous insulation is encapsulated by the organic encapsulation layer. [Item 10] 10. The thermal runaway barrier of claim 9, wherein the organic encapsulation layer has at least one vent hole formed therethrough, the vent hole being positioned 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 remains intact during a thermal runaway event. [Item 11] Item 11. The thermal runaway barrier of item 9 or 10, wherein the thermal runaway barrier has a top edge, a bottom edge, and opposing side edges, and the at least one vent hole is located along the periphery of one or both opposing side edges. [Item 12] The at least one vent hole is about 2 mm 2 ~about 15mm 2 12. The thermal runaway barrier of any one of items 9 to 11, providing an exit opening through the organic encapsulation layer having an opening area in the range of [Item 13] 13. The thermal runaway barrier of any one of items 9 to 12, wherein the layer of nonwoven fibrous insulation has a periphery and the organic encapsulation layer is sealed around the periphery. [Item 14] 14. The thermal runaway barrier of any one of the preceding claims, wherein the layer of nonwoven fiber insulation passes at least the V-2 level of the UL94 flammability test. [Item 15] a plurality of battery cells disposed within a housing; A plurality of thermal runaway barriers according to any one of items 1 to 14, The battery cells are arranged in a row with one thermal runaway barrier disposed between each pair of adjacent battery cells.

Claims

1. a thermal runaway barrier disposed between battery cells of a battery assembly and operatively adapted to at least significantly slow down a thermal runaway event within said battery assembly, a single layer of nonwoven fibrous insulation comprising a fibrous matrix of inorganic fibers, insulating inorganic particles dispersed within the fibrous matrix, and a binder dispersed within the fibrous matrix to hold the fibrous matrix together; an organic encapsulation layer; the layer of nonwoven fibrous insulation is encapsulated by the organic encapsulation layer; the organic encapsulation layer has at least one vent hole formed therethrough, the vent hole being positioned 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 remains intact during a thermal runaway event; Thermal runaway barrier.

2. 10. The thermal runaway barrier of claim 1, wherein the layer of nonwoven fibrous insulation contains fiber shot in an amount ranging from about 3% to about 60% by weight of the amount of inorganic fibers in the layer of nonwoven fibrous insulation.

3. 3. The thermal runaway barrier of claim 1 or 2, wherein the layer of nonwoven fibrous insulation contains insulating inorganic particles in an amount ranging from as low as about 10% to as high as about 60% by weight of the layer of nonwoven fibrous insulation.

4. 4. The thermal runaway barrier of any one of claims 1 to 3, wherein the layer of nonwoven fibrous insulation contains an organic binder in an amount ranging from a low of about 2.5% to a high of about 10.0% by weight of the layer of nonwoven fibrous insulation.

5. The thermal runaway barrier of any one of claims 1 to 4, wherein the layer of nonwoven fibrous insulation has an installed thickness in the range of about 0.5 mm to less than 5.0 mm.

6. The layer of nonwoven fiber insulation has a thickness of about 250 g / m ２ from a low value of about 1000 g / m ２ 6. The thermal runaway barrier of any one of claims 1 to 5, having a basis weight ranging from 0.1 to as high as 0.

1.

7. The layer of nonwoven fiber insulation has a thickness of about 250 g / m ２ ~About 400g / m ２ The thermal runaway barrier of any one of claims 1 to 6, having an uncompressed basis weight in the range of

8. a plurality of battery cells disposed within a housing; a plurality of thermal runaway barriers according to any one of claims 1 to 7; The battery cells are arranged in a row with one thermal runaway barrier disposed between each pair of adjacent battery cells.

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