Improved thermal barrier elasticity

Abstract

A thermal barrier having improved compression performance and methods of making such articles are disclosed. A thermal barrier article comprising: at least one non-woven fibrous thermal insulation layer comprising: (a) a fibrous matrix of inorganic fibers; (b) a plurality of thermally insulating inorganic particles dispersed within the fibrous matrix; (c) a binder dispersed within the fibrous matrix so as to hold the fibrous matrix together; and (d) a plurality of compressible organic particles dispersed within the fibrous matrix. The thermal barrier may be used in a battery assembly.

Description

[0001] The present invention relates to a barrier for at least substantially mitigating thermal runaway events within a battery assembly, such as a battery assembly used in an electric vehicle. The barrier described herein comprises compressible organic particles and exhibits improved elasticity. Further, the present invention relates to a method of producing the barrier. BACKGROUND

[0002] Electric motors used in electric or hybrid vehicles, for example, automobiles, are powered at least in part by batteries. Lithium ion batteries are commonly used in such applications. These batteries are compactly arranged within the vehicle to save space. Typically, lithium ion batteries comprise battery modules or assemblies consisting of individual battery cells. In unfortunate circumstances, these batteries can experience a thermal runaway condition in which one battery cell fails due to various reasons and generates a large amount of heat. The heat can be transferred to adjacent functioning battery cells and cause them to fail. The heat can also initiate a fire. In such a situation, the entire battery module can catch fire due to the propagation of heat, ultimately engulfing the vehicle, posing a safety hazard to the vehicle, its occupants, and the environment surrounding the vehicle. Global regulatory bodies are moving towards implementing a regulation that will require battery manufacturers to isolate the failed battery cell, thereby avoiding the spread of heat to adjacent battery cells, and provide a certain amount of time for the occupants of the vehicle to evacuate the vehicle. One strategy to meet these requirements is to use a thermal barrier between the battery cells that can delay the propagation of thermal runaway.

[0003] The thermal barrier also needs to provide cushioning characteristics during normal use of the battery module. The thermal barrier needs to be tightly fitted between the battery cells and occupy the gap between the battery cells. In other words, the thermal barrier needs to exert a certain pressure on the battery cells. Complicating matters further is that permanent swelling of the battery cells occurs as the battery cells age, which means that the gap between the cells decreases during the service life of the battery cells. In other words, the thermal barrier needs to meet the beginning of life (BOL) and end of life (EOL) pressures exerted by the battery cells when placed between the battery cells. If the pressure exerted by the thermal barrier is lower than the required pressure, the thermal barrier does not fit tightly. If the pressure exerted by the thermal barrier is higher than the required pressure, the battery cells can fail.

[0004] Patent publications WO 2022 / 024076 Al, WO 2022 / 024078 Al and WO 2022 / 024085 Al propose nonwoven webs in which a low thermal conductivity filler (such as aerogel and fumed silica) is dispersed, such nonwoven webs can be used as thermal barriers to prevent heat from a failing battery cell from spreading to other parts of the battery module. The disclosed materials comprise a matrix of inorganic fibers and have thermal stability at the temperature of a thermal runaway condition. A drawback of such nonwoven web based thermal barriers is that their compression profile does not meet the cushioning requirements. Typically, they meet the BOL or EOL pressure requirements, but not both. If the thermal barrier meets the BOL pressure, the pressure exerted by the web at EOL is higher than required. If the thermal barrier meets the EOL pressure, the pressure exerted by the web at BOL is lower than required. In other words, the compression curve needs to be flatter. Therefore, there is a need to improve the compression performance of nonwoven web based thermal barriers. SUMMARY

[0005] There is a need for a thermal barrier that has thermal stability at the temperature of a thermal runaway condition and has improved compression performance.

[0006] In one aspect, a thermal barrier is provided that is operably adapted to be disposed between battery cells of a battery assembly and to at least substantially mitigate a thermal runaway event within the battery assembly. The thermal barrier comprises a nonwoven fibrous thermal insulation layer comprising a fibrous matrix of inorganic fibers, thermally insulating inorganic particles and compressible organic particles dispersed within the fibrous matrix, and a binder dispersed within the fibrous matrix so as to hold the fibrous matrix together. Thus, the thermal barrier as described herein exhibits a certain and improved elasticity. An optional organic encapsulation layer can also be included for encapsulating the nonwoven fibrous thermal insulation layer.

[0007] In another aspect, a battery cell module or assembly for an electric vehicle is provided. The battery cell module or assembly comprises a plurality of battery cells disposed in a housing and a plurality of thermal barriers according to the present invention. The battery cells are arranged in rows or stacks, with one thermal 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, a method for preparing a thermal barrier according to the present invention is provided, wherein the method comprises forming a nonwoven fibrous thermal insulation layer using a wet-laid process or a dry-laid process.

[0009] The above summary of the application is not intended to describe each disclosed embodiment or every implementation thereof. The following description more particularly exemplifies the illustrative embodiments. At various places in the present application, guidance is provided through lists of examples. For each list of examples, indications are provided for multiple ways to choose items from the set of examples to produce desired types of example combinations. The list is not intended to be exhaustive or limiting. BRIEF DESCRIPTION OF DRAWINGS

[0010] The present disclosure is explained in greater detail in terms of a few preferred embodiments on the basis of the drawings in which

[0011] Figure 1 is a schematic end view of a thermal barrier as disclosed herein;

[0012] Figure 2 is a schematic end view of a battery cell module as disclosed herein, with a thermal barrier as disclosed herein disposed between adjacent battery cells;

[0013] Figure 3 is a schematic top view of a battery pack of a battery cell module as disclosed herein, with a thermal barrier placed between adjacent battery modules and / or on top of the battery modules;

[0014] Figure 4 is a photographic perspective view of a thermal barrier as disclosed herein, encapsulated with an adhesive-backed organic polymer layer having a release liner and an expanded gas outlet / notch; and

[0015] Figure 5 is a schematic side view of a dry-laying process for manufacturing a thermal barrier as disclosed herein according to one embodiment of the present disclosure. DETAILED DESCRIPTION

[0016] In describing the preferred embodiment of the application specific terminology will be resorted to. Such terminology, however, is used merely for convenience and, accordingly, is not intended to limit the scope of the present application. Each term, as used herein, should be read expansively and not in a limited sense.

[0017] As used herein, the terms "preferred" and "preferably" refer to embodiments described herein that can provide certain benefits under certain circumstances. However, other embodiments can also be preferred under the same or other circumstances. Additionally, the recitation of one or more preferred embodiments does not suggest that other embodiments are not useful, and is not intended to exclude other embodiments from the scope of the application.

[0018] As used herein and in the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a” or “the” component can include one or more components or equivalents thereof known to those skilled in the art. In addition, the term “and / or” means one or all of the listed elements or a combination of any two or more of the listed elements.

[0019] It is noted that the terms “comprises” and variations thereof do not have a limiting meaning and are used in their open-ended sense to include the terms “consisting essentially of” and “consisting of.”

[0020] As used herein, the term “consisting of’ indicates that the thermal barrier claimed is covered by the structure having only the elements recited.

[0021] As used herein, the term “consisting essentially of’ indicates that the thermal barrier claimed is capable of exhibiting the desired thermal insulation properties by using only the recited features / elements, without the need for additional layers of thermal insulation material. For example, the thermal barrier of the present invention does not need to include another layer of other thermal insulation material (e.g., a woven or nonwoven structure of inorganic fibers). Thus, with respect to the expression “consisting essentially of’, if a third party thermal barrier (e.g., of a competitor) includes all the features / elements recited in the claims of the present invention, as well as one or more additional features / elements not recited in the claims (e.g., an additional layer of inorganic fibers), the third party thermal barrier is considered to be covered by the claims if the additional features / elements do not determine whether the thermal barrier will exhibit the desired thermal insulation and compression properties.

[0022] Relative terms such as top, bottom, side, upper, lower, horizontal, vertical, and the like can be used herein to describe one element’s or feature’s relationship to another element or feature as the case can be in the drawings. These terms are used herein merely to simplify descriptions, and are not meant to limit the scope of the present invention in any way.

[0023] References throughout this specification to “one implementation,” “certain implementations,” “one or more implementations” or “implementation” mean that a particular feature, structure, material, or characteristic being described is included in at least one implementation of the present invention. Thus, the appearances of the phrases, such as “in one or more implementations,” “in certain implementations,” “in one implementation,” or “in an implementation” in various places throughout this specification are not necessarily referring to the same implementation of the present invention.

[0024] As used herein, the term “or” is generally employed in its sense of “and / or” unless the context clearly indicates otherwise.

[0025] Also herein, a numerical range expressed by endpoints includes all numbers subsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.).

[0026] "ambient conditions" means at 25 °C and a pressure of 101.3 kPa.

[0027] "average" means arithmetic, unless otherwise indicated.

[0028] "solidify" means to expose to radiation in any form, heat, or to subject it to a physical or chemical reaction that results in hardening or an increase in viscosity.

[0029] "size" means the longest dimension of a given object or surface.

[0030] "substantially" means to a significant extent, as in an amount of at least 50%, 60%, 70%, 80%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5%, 99.9%, 99.99%, or 99.999%, or 100%.

[0031] "thickness" means the distance between opposite sides of a layer or multi-layer article.

[0032] A numerical range expressed by endpoints includes all numbers subsumed within that range with increments commensurate with the accuracy indicated by the endpoints of the recited range (e.g., for a range from 1.000 to 5.000, the increment would be 0.001 and the range would include 1.000, 1.001, 1.002, etc., 1.100, 1.101, 1.102, etc., 2.000, 2.001, 2.002, 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 5.999) as well as any range subsumed within that range, unless explicitly indicated otherwise.

[0033] The term "polymer" shall be 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 can be formed into miscible blends.

[0034] The thermal barrier is operably adapted (i.e., designed, configured, shaped, and / or dimensioned) or otherwise adapted to be disposed between adjacent battery cells (i.e., a series of battery cells stacked in a row) of a battery module or assembly, such as a battery module or assembly used to power an electric motor (e.g., as used in an electric or hybrid vehicle).

[0035] The thermal barrier as disclosed herein can prevent, stop, or can at least significantly slow down a thermal runaway event within or between adjacent battery modules or assemblies.

[0036] “Thermal runaway” is a phenomenon when a battery cell experiences a chain reaction of heat release that leads to an uncontrolled temperature rise of the battery cell. The chain reaction of heat release can be caused by, among other things, overheating of the battery cell, overvoltage of the battery cell, and mechanical puncture of the battery cell.

[0037] “Thermal propagation” is a phenomenon when a battery cell thermal runaway causes the remaining battery cells in the battery module or assembly to experience a thermal runaway phenomenon.

[0038] “Thermal runaway event” refers to one battery cell in a battery module or assembly of battery cells overheating, leading to a chain reaction of overheating of adjacent battery cells, and possibly exploding or catching fire until the number of overheated battery cells reaches a critical point of propagation, leading to all or more than half of the battery cells in the module or assembly of modules being destroyed. Factors that lead to overheating of the battery cells include: physical damage, application of overvoltage, overheating (internal short circuit of the battery cell).

[0039] As the energy density of the battery cell increases, the temperature at which the battery cell begins to fail (e.g., from at least losing its efficiency or not working to igniting, burning, or exploding) decreases. Likewise, as the energy density of the battery cell decreases, the temperature at which the battery cell begins to fail increases. For example, NMC811 type battery cells tend to begin to fail or even explode when the temperature reaches about 120°C to 130°C, while NMC622 type battery cells begin to fail or even explode when the temperature reaches about 180°C, as the temperature is ramped up in a controlled manner. For battery cells with lower energy density (e.g., NMC532 type battery cells and NMC433 type battery cells), the corresponding temperature is higher. For physically larger battery cells or when the temperature is ramped up quickly, the heat diffusion through the battery cell can cause the local temperature to take longer to reach the critical point. It is believed that this heat diffusion effect can cause the actual temperature at which the battery cell begins to fail explosively to be slightly higher. It can be desirable for the thermal barrier of the present disclosure to prevent adjacent battery cells from reaching a temperature in the range of about 130°C to about 150°C.

[0040] As used herein, to "prevent" a thermal runaway event means to prevent overheating of a single battery cell from causing overheating of battery cells adjacent to that single battery cell. The thermal barrier is considered to prevent a thermal runaway event when the adjacent battery cells do not reach above 130°C, 135°C, 140°C, 145°C, or 150°C.

[0041] As used herein, to "stop" a thermal runaway event means that the overheating of a battery cell only causes overheating of adjacent battery cells (i.e., three, two, or even just one battery cell on either side of the overheating battery cell), and the remaining battery cells in the battery module or assembly do not overheat.

[0042] As used herein, to "slow down" a thermal runaway event means that the thermal runaway event is slowed down for at least long enough to allow personnel adjacent to the battery module or assembly (e.g., occupants inside an electric vehicle passenger compartment) to escape to a safe distance away from the battery module or assembly before being harmed by the thermal runaway event. Once a battery cell fails (e.g., catches fire or overheats to the point of not functioning properly) and there is a thermal barrier between the battery cells, the time for any adjacent battery cells to propagate the failure (e.g., catch fire or overheat) is at least greater than 5 minutes, and preferably greater than 10 minutes or even 20 minutes or more.

[0043] The thermal barrier of the present disclosure involves a nonwoven fibrous thermal insulation material comprising: (a) a fibrous matrix of inorganic fibers; (b) a plurality of thermally insulating inorganic particles dispersed within the fibrous matrix; (c) a plurality of compressible organic particles dispersed within the fibrous matrix, and (c) a binder dispersed within the fibrous matrix so as to hold the fibrous matrix together.

[0044] The thermal barrier as disclosed herein comprises a nonwoven fibrous thermal insulation layer comprising a fibrous matrix of inorganic fibers. The thermal barrier can comprise only one or more nonwoven fibrous thermal insulation layers comprising a fibrous matrix of inorganic fibers. The nonwoven fibrous thermal insulation material can be dry-laid or wet-laid. The nonwoven fibrous thermal insulation material can be in the form of a mat, a sheet, a strip, or a three-dimensional thin-walled structure.

[0045] As used herein, the term "inorganic" means a ceramic or otherwise non-metallic (i.e., not a metal, metal alloy, or metal composite) inorganic material.

[0046] The inorganic fibers generally have an average aspect ratio, i.e., average length to diameter ratio, of greater than 2500. The average aspect ratio of the inorganic fibers can be from greater than 2500 up to 70,000, or from greater than 2500 up to 50,000, or from 3000 to 70,000, or from 3000 to 50,000, or from 5000 to 70,000, or from 5000 to 50,000, or from 8000 to 70,000, or from 8000 to 50,000. The average aspect ratio of the inorganic fibers can also be greater than 70,000.

[0047] The average aspect ratio is measured by measuring the length and diameter of individual fibers on a scanning electron micrograph and calculating the aspect ratio, i.e., the ratio of length to diameter. The aspect ratio of 50 individual fibers is determined and the average is calculated.

[0048] The inorganic fibers can have a diameter of 1 pm to 20 pm. The inorganic fibers can have a length of 1 mm to 400 mm or more.

[0049] The inorganic fibers of the fibrous matrix can be selected from the group of fibers consisting of alkaline earth silicate fibers, refractory ceramic fibers (RCF), polycrystalline wool (PCW) fibers, basalt fibers, glass fibers, silica fibers, and combinations thereof. Glass fibers and silica fibers generally contain no or only nominal flocks. PCW generally contains up to 5% flocks, while alkaline earth silicate (AES) fibers contain up to 60% flocks when uncleaned and as little as 10% to 30% minimum flocks when cleaned. Flocks consist of spherical particles that do not transform into fibers in the manufacturing process.

[0050] The nonwoven fibrous thermal insulation layer can include inorganic fibers in an amount ranging from 15 wt% to 90 wt%, or from 15 wt% to 70 wt%, or from 20 wt% to 90 wt%, or from 20 wt% to 80 wt%, or from 20 wt% to 70 wt%, or from 30 wt% to 60 wt%, or from 35 wt% to 55 wt%, based on the total weight of the nonwoven fibrous thermal insulation.

[0051] The nonwoven fibrous thermal insulation layer of the thermal barrier disclosed herein includes a plurality of thermally insulative inorganic particles and a plurality of compressible organic particles dispersed within a fibrous matrix.

[0052] The plurality of particles can be uniformly, consistently, substantially, or otherwise dispersed throughout the fibrous matrix, or dispersed in the fibrous matrix to the extent permitted by the manufacturing process (e.g., in dry-laid and wet-laid processes, the particles can have a small amount of settling on the bottom of the mat).

[0053] The thermally insulating inorganic particles can include particles selected from the group consisting of inorganic aerogels, xerogels, hollow or porous ceramic microspheres, unexpanded vermiculite, irreversibly or permanently expanded vermiculite, fumed silica, other forms of porous silica, irreversibly or permanently expanded or unexpanded perlite, pumice, irreversibly or permanently expanded clays, diatomaceous earth, titanium dioxide, zirconium oxide, and combinations thereof. The inorganic particles can be solid, hollow, or include a plurality of voids. Such particles can include, for example, unexpanded intumescent particles, irreversibly or permanently expanded expandable materials (e.g., intumescent materials), diatomaceous earth, inorganic aerogel materials, porous ceramic (e.g., silica) materials, irreversibly or permanently expanded perlite minerals, hollow ceramic or other forms of inorganic (e.g., glass) microspheres, and the like. Such void-containing inorganic particles, such as those found in irreversibly or permanently expanded vermiculite, are particularly desirable. Irreversibly or permanently expanded perlite mineral particles also include voids, but the perlite mineral is harder and less compressible than the vermiculite mineral. Silica-based and other aerogel particles also include voids.

[0054] Particles of fumed silica can have a specific surface area in the range of about 100 m2 / g up to about 400 m2 / g. 2 / g up to about 400 m2 / g. 2 / g up to about 400 m2 / g.

[0055] As used herein, irreversibly or permanently expanded expandable particles (e.g., particles of intumescent materials such as vermiculite minerals and perlite minerals) refer to particles that have been heated to a temperature and time such that the particles irreversibly or permanently expand to at least 10% and up to 100% of their expandability, or pre-expanded prior to being incorporated into the thermal barrier, or post-expanded after being incorporated into the nonwoven fibrous thermal insulation.

[0056] Expanded particles (e.g., vermiculite particles) can be permanently expanded by superheating the particles beyond the reversible point (e.g., for vermiculite, in the range of about 350 °C to about 1000 °C). Such permanently expanded expanded particles (e.g., vermiculite particles) can have an expanded accordion or worm-like structure that is more susceptible to breaking into smaller particles due to its elongated geometry, lower density, and lower mechanical stability compared to the same particle in its unexpanded state. The degree of permanent expansion of the particles increases (i.e., the particles can become larger and / or longer) as the temperature of the heating increases. It can also be desirable to use vermiculite that has been permanently expanded through a chemical treatment process (see, e.g., “Chemical Exfoliation of Vermiculite and the Production of Colloidal Dispersions,” G. F. Walker, W. G. Garrett, Science, April 21, 1967: Volume 156, Issue 3773, Pages 385-387).

[0057] Because they are more susceptible to breaking in their expanded state, it can be desirable for expanded particles to post-expand after the unexpanded expanded particles have been incorporated into the nonwoven fibrous thermal insulation. Even with mild processing to leave them substantially unbroken, it is believed that incorporating pre-expanded expanded particles into nonwoven fibrous thermal insulation can still result in the expanded particles becoming oriented into the plane of the insulation (i.e., the x-axis, y-axis, and / or therebetween). For example, with pre-expanded vermiculite particles, the elongated particles can become generally aligned with the fibers in the machine direction or downstream direction (i.e., the y-axis) of the nonwoven fibrous thermal insulation, rather than in the thickness direction (i.e., the z-axis).

[0058] In contrast, when they post-expand (i.e., after the nonwoven fibrous thermal insulation is prepared with unexpanded expanded particles), the expanded expanded particles are not primarily oriented in the plane of the insulation. The unexpanded expanded particles generally have a more uniform structural geometry (i.e., have an aspect ratio closer to 1) compared to the same particles in their expanded state. It is believed that this more uniform structural geometry is less likely to be affected by inorganic fiber alignment during the formation of the nonwoven fibrous thermal insulation. As a result, the post-expanded expanded particles are more likely to be oriented isotropically within the nonwoven fibrous thermal insulation. For example, with post-expanded vermiculite particles, the elongated particles can become aligned in the thickness direction (i.e., the z-axis), in-plane (i.e., the x-axis, y-axis, and / or therebetween), or off-axis thereof. It is believed that this difference between the orientation of pre-expanded particles and post-expanded particles is caused by the unexpanded particles having a more uniform structural geometry than when in their expanded state.

[0059] The nonwoven fibrous thermal insulation layer can include thermal insulation particles in an amount of at least 10 wt.%, or at least 15 wt.%, or at least 20 wt.%, or at least 25 wt.%, or at least 30 wt.%, or at least 35 wt.%, based on the total weight of the nonwoven fibrous thermal insulation. The nonwoven fibrous thermal insulation layer can include thermal insulation particles in an amount of at most 40 wt.%, or at most 45 wt.%, or at most 50 wt.%, or at most 55 wt.%, or at most 60 wt.%, based on the total weight of the nonwoven fibrous thermal insulation. For example, particle contents of up to 60 wt.% can be obtained using dry-laid processes, and particle contents of up to 50 wt.% can be obtained using wet-laid processes. The nonwoven fibrous thermal insulation layer can include a plurality of thermal insulation inorganic particles in an amount of 10 wt.% to 60 wt.%, based on the total weight of the nonwoven fibrous thermal insulation.

[0060] The nonwoven thermal insulation layer of the thermal barrier disclosed herein includes a binder dispersed within the fibrous matrix so as to hold the fibrous matrix together. The binder can be an organic or inorganic binder, such as an organic or inorganic adhesive-type binder, organic or inorganic binder fibers that are needled, stitched, or otherwise mechanically entangled into the fibrous matrix so as to hold the fibrous matrix together. The binder can be uniformly, consistently, substantially, or otherwise dispersed throughout the fibrous matrix, or as permitted by the manufacturing process, so as to bind the inorganic fibers and thermal insulation particles, and compressible organic particles together, or otherwise hold the fibrous matrix together for the desired length of time, at least to withstand the operational strength required prior to installation between battery cells (e.g., during the encapsulation process).

[0061] In accordance with the present disclosure, inorganic binders, organic binders, or a combination of both can be useful, and can include, for example, those disclosed in U.S. Patent No. 8,834,759. An example of an inorganic binder that can be used in dry-laid or wet-laid fiber processing can include silicon resin particles that convert to fusable silica upon heating. Organic-inorganic hybrid binders are also useful, such as, for example, those sold under the trade name “Wacker MQ 803TF,” which is a co-hydrolyzate of tetraalkoxysilane (Q units) and trimethylalkoxysilane (M units). The chemical structure of Wacker MQ 803TF can be thought of as a three-dimensional network of polysilicic acid units that are terminated by trimethylsilyl groups. There is some residual ethoxy functionality and hydroxyl functionality. The average molecular weight can be precisely controlled by the ratio of M units to Q units. The ratio is approximately 0.67 for Wacker MQ 803TF.

[0062] The binder dispersed within the fibrous matrix can be in the form of polymeric fibers. Advantageously, the binder can be in the form of bicomponent core-shell polymeric fibers, such as core-shell polyester fiber / polyethylene fiber. The polymeric fiber binder does not lose its fibrous form during the process of making the thermal barrier.

[0063] Exemplary binder fibers include the use of bicomponent core-shell polymeric fibers in dry-laid processes. In wet-laid processes, ethylene vinyl acetate latex dispersion binders, bicomponent core-shell polymeric fibers, or a combination of both can be used. When polymeric binder fibers are used, the binder can be activated by heating and compressing the nonwoven fibrous thermal insulation material. Combinations of organic and inorganic binders can also be used.

[0064] The organic binder for the thermal barrier disclosed herein can be in the form of polymeric fibers (e.g., PE / PET, PET, FRPET, such as those available under the trade designation “T255” from Trevira), dry polymeric powders (e.g., LDPE, polyamide, epoxy powder (available under the trade designations “3M Scotchcast 265,” “3M Scotchkote 6258” from 3M CO., St. Paul, MN), or liquid binders (e.g., acrylic latex, ethylene vinyl acetate (EAF68) latex, silicone, polyurethane, etc.).

[0065] The nonwoven fibrous thermal insulation layer can include the binder in an amount of at least 2.5 wt.%, at least 3.0 wt.%, at least 4.0 wt.%, at least 4.5 wt.%, at least 5.0 wt.%, at least 5.5 wt.%, at least 6.0 wt.%, or at least 6.5 wt.%, based on the total weight of the nonwoven fibrous thermal insulation. The nonwoven fibrous thermal insulation layer can include the binder in an amount of at most 7.0 wt.%, at most 7.5 wt.%, at most 8.0 wt.%, at most 8.5 wt.%, at most 9.0 wt.%, at most 9.5 wt.%, at most 10 wt.%, at most 15 wt.%, or at most 20 wt.%, based on the total weight of the nonwoven fibrous thermal insulation. The nonwoven fibrous thermal insulation layer can include the binder in an amount of 2.5 wt.% to 15 wt.%, or 2.5 wt.% to 20 wt.%, based on the total weight of the nonwoven fibrous thermal insulation.

[0066] The nonwoven fibrous thermal insulation layer of the thermal barrier disclosed herein further comprises a plurality of compressible organic particles dispersed within the fibrous matrix.

[0067] The compressible organic particles can be selected from hollow organic microspheres or solid organic microspheres. Exemplary compressible organic particles include expanded microspheres, rubber particles, foam particles, silicone particles, polyurethane particles, styrene block copolymer particles, and any combinations and mixtures thereof.

[0068] In some embodiments, the compressible organic particles are selected from hollow organic microspheres, preferably from expandable hollow organic microspheres and expanded hollow organic microspheres. Generally, hollow organic microspheres comprise a thermoplastic polymer shell and a core comprising a liquid or a gas. Expandable organic microspheres are activated at a temperature at which the thermoplastic polymer shell softens and the core expands. The expansion of the core liquid results in the expansion of the entire microsphere, i.e. an increase in its volume. The polymer shell preferably contains a thermoplastic shell component comprising a compound selected from acrylonitrile, methacrylonitrile, polyesters, polyurethanes, poly(meth)acrylates, polyethylenes, polystyrenes, and any combinations and mixtures thereof. The core preferably comprises a liquid selected from organic liquids such as pentane, hexane, heptane, octane, nonane and decane and their halogenated derivatives, and a gas selected from methane, propane, nitrogen, noble gases, and any combinations thereof. Expanded hollow organic microspheres preferably exhibit a density in the range of about 0.001 g / cc to about 0.1 g / cc (grams per cubic centimeter), preferably about 0.002 g / cc to 0.08 g / cc, and more preferably about 0.003 g / cc to about 0.06 g / cc. Expanded hollow organic microspheres exhibit a particle size mode (peak) in the range of about 10 micrometers to about 300 micrometers, preferably about 20 micrometers to about 250 micrometers, more preferably about 30 micrometers to about 200 micrometers.

[0069] Furthermore, it was found to be advantageous to disperse the hollow microspheres in a mixture in the production process of the thermal barrier article according to the present application. This has at least the advantage of an improved particle processability and / or an improved process safety, since small organic particles are known to form flammable mixtures with air. Preferably, the mixture for dispersing the hollow microspheres is selected from inorganic materials, organic resins, inorganic liquids such as water, organic liquids preferably selected from oils such as mineral oil, natural oil and synthetic oil, alcohols such as polyvinyl alcohol, and any combinations and mixtures thereof. The organic resins can be selected from epoxy resins, polyester resins, polyurethane resins, polycarbonate resins, polyether resins, ethylene vinyl acetate resins, and any combinations thereof.

[0070] In some embodiments, the foam particles are selected from silicone foam particles, polyurethane foam particles, rubber foam particles, polyolefin foam particles such as polypropylene, polystyrene foam particles, thermoset foam particles, polyether sulfone foam particles or other organic foam particles, and mixtures thereof.

[0071] In some embodiments, the compressible organic particles have an average particle size of at least 1 pm, 5 pm, 10 pm, 20 pm, 50 pm, 75 pm, or even 100 pm. In some embodiments, the compressible organic particles have an average particle size of at most 25 pm, 50 pm, 100 pm, 200 pm, 250 pm, 400 pm, 500 pm, 750 pm, 1 mm, 2 mm, 5 mm, or even 10 mm. The average particle size can be measured using techniques known in the art, including laser diffraction, optical microscopy, or sieving. In some embodiments, the compressible organic particles have a particle size of at most 10 mm, and can be from 1 pm to 10 mm, or from 10 pm to 10 mm, or from 100 pm to 10 mm, or from 1 mm to 10 mm, as measured by sieving analysis. In some embodiments, the compressible organic particles have a median particle size (d 50 ) of from 1 pm up to 500 pm, or from 1 pm up to 250 pm. The median particle size (d 50 ) can be measured by laser diffraction.

[0072] The compressible organic particles can be spherical or irregularly shaped or any other shape.

[0073] The nonwoven fibrous thermal insulation layer can include the compressible organic particles in an amount of from 1 wt% to 50 wt%, or from 3 wt% to 30 wt%, or from 3 wt% to 25 wt%, or from 3 wt% to 20 wt%, based on the total weight of the nonwoven fibrous thermal insulation. In some embodiments, the nonwoven fibrous thermal insulation layer includes at least 1 wt%, 2 wt%, 3 wt%, 5 wt%, 10 wt%, 15 wt%, or even 20 wt% of the compressible organic particles. In some embodiments, the nonwoven fibrous thermal insulation layer includes at most 50 wt%, 40 wt%, 35 wt%, 30 wt%, 25 wt%, 20 wt%, 15 wt%, or even 10 wt% of the compressible organic particles. Generally, the amount of compressible organic particles used in the nonwoven fibrous thermal insulation layer will strike a balance between providing the desired compression properties and minimizing the flammability and / or thermal conductivity of the article. In some embodiments, the nonwoven fibrous thermal insulation layer can include the compressible organic particles in an amount of from 3 wt% to 20 wt%, based on the total weight of the nonwoven fibrous thermal insulation.

[0074] By compressible organic particles, it is meant organic particles that can be compressed to some extent (i.e., to a smaller size) and that ideally return to their original size when the compression force is removed. It is believed that this behavior creates the elasticity of the thermal barrier article. That is, if a compression force applied to one of the major surfaces compresses the article to a compressed or thinner state, it will (ideally) return to its original thickness or a thickness close to its original thickness.

[0075] The thermal barriers disclosed herein exhibit a lower pressure than a thermal barrier comprising a nonwoven fibrous thermal insulation layer of the same composition but without the addition of compressible organic particles (assuming the samples have the same thickness and / or basis weight). The thermal barriers disclosed herein exhibit a pressure that is at least 10%, or at least 15%, or at least 20%, or at least 25%, or at least 30%, or at least 35%, or at least 40%, or at least 45%, or at least 50% lower than a thermal barrier comprising a nonwoven fibrous thermal insulation layer of the same composition but without the addition of compressible organic particles in the installed (i.e., compressed) state. The thermal barriers disclosed herein exhibit a pressure that is at most 60% lower than a thermal barrier comprising a nonwoven fibrous thermal insulation layer of the same composition but without the addition of compressible organic particles. This reduction in the pressure exhibited by the thermal barriers can be observed when measuring the pressure exhibited by the thermal barriers disclosed herein and the thermal barriers without the addition of compressible organic particles at the same relative axial compression and the same sample thickness of the uncompressed and compressed thermal barriers, i.e., when measuring the pressure exhibited by the thermal barriers disclosed herein and the thermal barriers without the addition of compressible organic particles at the same gap.

[0076] In some embodiments, the initial compression performance of the thermal barrier articles of the present disclosure can be tested, where the nonwoven fibrous thermal insulation layer is placed between two platens and a load is applied and the relaxation pressure is measured based on a given gap size. In some embodiments, the addition of the compressible organic particles reduces the pressure by at least 20%, 25%, 30%, 35%, or even 40% relative to a control (i.e., the same material without the compressible organic particles), depending on the gap size used, e.g., such as described in Compression Performance Test Method 1.

[0077] Typically in use, the thermal barrier articles are exposed to repeated load cycles. For example, modern lithium-ion batteries or battery cells often exhibit a “breathing effect” when being charged and discharged, i.e., the battery cell expands in volume when being charged and contracts in volume when being discharged. Over the lifetime of the battery, the battery cell undergoes multiple charge and discharge cycles and this can also change the volume of the battery over the lifetime of the battery. That is, the battery cell can contract or expand in volume over its lifetime. The elastic properties of the articles according to the present invention are advantageous as the articles are typically disposed between the battery cells and need to conform to the dimensions of the battery cells during operation, i.e., during charging and discharging. With the elastic properties described herein, the articles according to the present invention are able to conform to the dimensions of the battery cell over the lifetime of the battery cell, while not suffering any degradation of its other advantageous properties, in particular the ability to possess when a thermal runaway event occurs.

[0078] The expansion and contraction of battery cells as described herein and their effect on thermal barriers can be simulated by cyclic compression testing, such as those described in the methods section.

[0079] In one example, a thermal barrier article is repeatedly compressed and released using a cyclic test such as described in Compression Performance Test Method 2, and the minimum pressure is reported. The pressure at compression is recorded as Pmax, while the pressure after release is recorded as Pmin. It has been found that, in some embodiments, thermal barrier articles having a minimum pressure peak Pmin above a certain level are particularly advantageous for the applications described herein. Thus, in some embodiments, it is preferred that a thermal barrier according to the present application exhibits a minimum pressure peak Pmin of at least 20 kPa, 25 kPa, 30 kPa, 40 kPa, or even 50 kPa, as determined according to the tests described in the experimental section. In some embodiments, a thermal barrier article according to the present disclosure has a percent recovery (i.e., Pmin / applied pressure) of at least 10%, 15%, 20%, 25%, 30%, 40%, 50%, 60%, 70%, or even 80%.

[0080] When a thermal barrier article is subjected to a cyclic test, the initial life pressure (e.g., the pressure at cycle 1) and the end-of-life pressure (e.g., the pressure at cycle 1000) can be detected. In some embodiments, when a thermal barrier article of the present disclosure is tested, the change in pressure at the end of life delta (delta end-of-life) is less than 1000 kPa, 750 kPa, 500 kPa, or even 400 kPa. The change in pressure at the end of life delta is determined by subtracting Pmin from Pmax at the last cycle. In general, it is advantageous to have a lower change in pressure at the end of life delta, however the value should be at least higher than 50 kPa.

[0081] In another example, a cyclic test such as described in Compression Performance Test Method 3 is applied. As described above, a thermal barrier material needs to not only satisfy the pressure applied at the beginning of the compression test (i.e., initial life), but also the pressure required at the end of the compression test (i.e., end of life). When reporting the results of this test method, the initial life pressure is recorded as Pmin at the first test cycle, and the end of life pressure is recorded as Pmax at the last test cycle. In some embodiments, thermal barriers of the present disclosure have improved initial life and end of life performance. For example, in some embodiments, a thermal barrier article of the present disclosure has an initial life pressure of at least 25 kPa, 30 kPa, 40 kPa, 50 kPa, 75 kPa, 100 kPa, 500 kPa, or even 100 kPa. In some embodiments, a thermal barrier article of the present disclosure has an end of life pressure of at most 2000 kPa, 1800 kPa, or even 1600 kPa.

[0082] The thermal barrier exhibits pressure on adjacent battery cells in the installed (i.e., compressed) state. The compressible organic particles included in the nonwoven fibrous thermal insulation layer of the thermal barrier disclosed herein have a function of affecting the compression performance of the thermal barrier, and can also be referred to as “compression performance-affecting particles.” This means that the compressibility of the thermal barrier is stronger due to the addition of the compressible organic particles, or in other words, the thermal barrier can be compressed to a higher degree with a smaller pressure applied to the thermal barrier. This also means that the pressure exerted by the thermal barrier on adjacent battery cells in the installed (i.e., compressed) state is reduced compared to a thermal barrier that does not include compressible organic particles. Due to the improved compressibility, the thermal barrier is able to meet the compression requirements at the early and late stages of life when placed between battery cells.

[0083] The thermal barrier materials of the present disclosure should have thermal stability at the temperature of the thermal runaway condition, and therefore, in some embodiments, the amount of organic material present in the thermal barrier can be less than 50 wt%, 45 wt%, 40 wt%, 35 wt%, 30 wt%, 25 wt%, 20 wt%, or even 15 wt%.

[0084] In general, to be a qualified thermal barrier material, the nonwoven fibrous thermal insulation material of the present disclosure should pass the flammability test. For example, the UL-94 standard (current at the time of filing this application), Safety Standard for Flammability of Plastic Materials for Parts in Devices and Appliances, determines by testing whether a material tends to extinguish or spread a flame after the test specimen has been ignited. The UL-94 standard has been harmonized with IEC 60707, 60695-11-10, and 60695-11-20, and ISO 9772 and 9773. Briefly, a 75 mm x 150 mm sample is exposed to a 2 cm, 50 W tirrel burner flame ignition source. The test sample is placed vertically above the flame, and the test flame impinges the bottom of the sample. For each sample, the extinguishing time is measured and a V rating is assigned. The V rating is a measure of extinguishment without the sample burning to the top clamp or dripping of molten material that could ignite a cotton indicator. The ratings are shown in Table 1 below.

[0085] Table 1. UL94 Classification (V-Rating)

[0086] UL 94 Classification V-0 V-1 V-2 Time for burning to stop 10 seconds 30 seconds 30 seconds Allowable dripping of burning material (ignition of cotton ball) No No Yes Sample completely burned No No No

[0087] The nonwoven fibrous thermal insulation layer can have an installed (i.e., compressed) thickness in the range of 0.5 mm up to 20.0 mm. In particular, the installed (i.e., compressed) thickness can be in the range of 0.5 mm up to 2.5 mm, where the lower limit can be 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, or 1.5 mm, and the upper limit can be 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 be in the range of 5 mm up to 20 mm, where the lower limit can be about 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, or 12 mm, and the upper limit can be about 13 mm, 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, 19 mm, or 20 mm. In some applications, the installed thickness can be in the range of 10 mm up to 20 mm, where the lower limit can be about 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, or 15 mm, and the upper limit can be about 15 mm, 16 mm, 17 mm, 18 mm, 19 mm, or 20 mm. In some applications, the installed thickness can even be as high as 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 the nonwoven fibrous thermal insulation layer is almost always less than its uninstalled (i.e., uncompressed) thickness. Measurements of the performance of the thermal barrier are made when it is in its installed (i.e., compressed) state.

[0088] The uninstalled (i.e., uncompressed) thickness of the nonwoven fibrous thermal insulation layer can range from 1.0 mm up to 8.0 mm, where the lower limit can be 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, 3.1 mm, 3.2 mm, 3.3 mm, 3.4 mm, or 3.5 mm, and the upper limit can 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 thermal insulation layer is always greater than its installed thickness.

[0089] The weight per square meter of the nonwoven fibrous thermal insulation layer can range from 100 g / m2 2 up to 2000 g / m2 2 . Depending on the composition of the thermal barrier, for a gap between adjacent battery cells ranging from about 0.75 mm up to about 1.25 mm, a weight per square meter ranging from about 100 g / m2 2 (e.g., 150 g / m2 2 , 200 g / m2 2 , or even 250 g / m2 2 ) to about 400 g / m2 2 (e.g., 300 g / m2 2 , 350 g / m2 2 ) can be desirable. Depending on the composition of the thermal barrier, for a gap between adjacent battery cells ranging from about 0.75 mm up to about 2.5 mm, a weight per square meter ranging from about 300 g / m2 2 up to about 550 g / m2 2 may also be desirable. For a gap between adjacent battery cells ranging from about 2.5 mm up to 8.0 mm, a weight per square meter ranging from about 600 g / m2 2 up to about 2000 g / m2 2 (e.g., 650 g / m2 2 , 700 g / m2 2 , 750 g / m2 2 , 800 g / m2 2 , 900 g / m2 2 , 950 g / m2 2 , 1000 g / m2 2 , 1050 g / m22 , 1100 g / m 2 , 1150 g / m 2 , 1200 g / m 2 , 1250 g / m 2 , 1300 g / m 2 , 1350 g / m 2 , 1400 g / m 2 , 1450 g / m 2 , 1500 g / m 2 , 1600 g / m 2 , 1700 g / m 2 , 1750 g / m 2 , 1800 g / m 2 , 1900 g / m 2 , or 2000 g / m 2 ).

[0090] The thermal barrier disclosed herein can optionally further comprise an organic encapsulation layer encapsulating the nonwoven fibrous thermal insulation layer. The optional organic encapsulation layer can be a polymeric layer or a paper layer. The organic encapsulation layer can be, for example, one or more opposing sandwich layers, with each layer being in the form of a film, a coating, an organic fibrous nonwoven or woven. The organic encapsulation layer can enclose or otherwise encapsulate all, most or a portion of at least one or both major faces, and preferably also all, most or a portion of the perimeter edges of the nonwoven fibrous thermal insulation layer, to prevent or substantially reduce the shedding or loss of fibers or particles from the encapsulated nonwoven fibrous thermal insulation layer.

[0091] The thermal barrier disclosed herein can optionally further comprise an inorganic encapsulation layer encapsulating the nonwoven fibrous thermal insulation layer. The optional inorganic encapsulation layer can be, for example, a 25 g / m 2 to 80 g / m 2 of glass fiber woven. The inorganic encapsulation layer can be, for example, one or more opposing sandwich layers, with each layer being in the form of an inorganic coating or fibrous nonwoven or woven. The inorganic encapsulation layer can enclose or otherwise encapsulate all, most or a portion of at least one or both major faces, and preferably also all, most or a portion of the perimeter edges of the nonwoven fibrous thermal insulation layer, to prevent or substantially reduce the shedding or loss of fibers or particles from the encapsulated nonwoven fibrous thermal insulation layer.

[0092] The reduction in shedding of inorganic fibers or particles is substantial when the amount of inorganic fiber or particle loss is less than 10 wt%, 5 wt% or 1 wt% of the original fiber or particle content of the nonwoven fibrous thermal insulation layer. The thinner the organic encapsulation layer (i.e. the lower the organic content of the barrier), the better the hot test results / cold test results.

[0093] The thermal barrier can be provided as a thermal barrier assembly comprising a plurality of the thermal barriers disclosed herein, wherein the plurality of thermal barriers are (a) provided in a stack in a container (e.g., a paperboard or other box), (b) provided end-to-end in series, with one major face of each thermal barrier adhered to a major adhesive surface of a length of single- or double-sided tape (when double-sided tape is used, the opposing major adhesive surface of the tape can be protected by a release liner), or (c) provided end-to-end in series in the form of a tape, with one or more nonwoven fibrous thermal insulation layers of each thermal barrier provided end-to-end and sandwiched or otherwise enclosed between two opposing lengths of organic (e.g., polymeric) enclosure layers (e.g., in the form of two opposing films, coatings, fibrous fabrics, etc.).

[0094] Also disclosed herein are methods of making the thermal barriers disclosed herein, the methods comprising:

[0095] forming the nonwoven fibrous thermal insulation layer using a wet-laid process or a dry-laid process;

[0096] providing a plurality of thermally insulating inorganic particles;

[0097] providing a plurality of compressible organic particles; and

[0098] providing a plurality of compressible organic particles; and

[0099] providing a plurality of compressible organic particles; and

[0100] The process steps for forming the nonwoven fibrous thermal insulation layer using a wet-laid process or a dry-laid process include

[0101] providing an inorganic fiber;

[0102] providing a binder; and

[0103] mixing the inorganic fiber and the binder.

[0104] The inorganic fiber, the binder, and the plurality of particles for use in the thermal barrier as described above can be used to manufacture the thermal barriers disclosed herein.

[0105] Referring to Figure 1 , a nonwoven fibrous thermal insulation layer 10 is shown, the nonwoven fibrous thermal insulation layer comprising an inorganic fiber matrix, a binder, and a plurality of particles. Optionally, the nonwoven fibrous thermal insulation layer 10 is enclosed using an organic or inorganic layer 12.

[0106] Referring to Figure 2Exemplary battery cell module 20 includes a plurality of battery cells 22 and a plurality of thermal barriers 24. Each thermal barrier 24 can be in the form of one or more nonwoven fibrous thermal insulation layers 10, with or without an encapsulation layer 12, and can be made from the exemplary materials described herein. At one or more locations throughout battery cell module 20, thermal barriers 24 can be disposed between adjacent battery cells 22, between groups of cells 22, or both. Typically, battery cell module 20 rests above a cooling plate 26 and a tray 28.

[0107] Referring to Figure 3 Exemplary battery pack 30 includes a plurality of battery cell modules 20, which can each have its own cooling plate 26 and tray 28, or all of the modules 20 can share the same cooling plate 26 and tray 28. Thermal barriers 24 formed from the exemplary materials described herein can be disposed between one or more or all adjacent battery cell modules 20, on top of one or more or all battery cell modules 20 (see reference numeral 24'), or any combination of both. The size of the individual or multiple thermal barriers 24 can also be set to cover the top of all of the battery cell modules 20.

[0108] Referring to Figure 4 Exemplary thermal barrier 24 includes one or more fibrous matrix layers (not shown) encapsulated with a layer 12 that covers both sides and the perimeter edges of the one or more nonwoven fibrous thermal insulation layers. In one embodiment, the major opposing faces of encapsulation layer 12 are coated with an adhesive (e.g., a pressure sensitive adhesive) protected by corresponding release liners 14 and 16. Preferably, encapsulation layer 12 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 encapsulation layer 12, preventing the encapsulation layer from swelling and bulging like a balloon, for example, when air trapped in encapsulation layer 12 is heated to an elevated temperature (e.g., when the temperature of one or more adjacent battery cells 20 is elevated).

[0109] Referring to Figure 5Conventional dry-laid manufacturing equipment and processes can be used to manufacture the thermal barriers disclosed herein. Embodiments of such equipment and processes can be found in U.S. Patent 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 can include a chamber or forming box 40 having multiple feeder inlets, including an inlet 42 for feeding a desired combination of matrix fibers (inorganic fibers) and binder into the box 40, and multiple inlets 44, 44', and 44" for feeding thermal insulation particles and compressible organic particles into the box 40. After the fibers are combined and mixed with the other ingredients, the resulting nonwoven fibrous material 45 is deposited onto a belt 46 that carries the material 45 into, through, and out of a baking oven 47 in which the binder is cured at least so that the fibrous material 45 can be further processed. The resulting 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 processed at an encapsulation station 48, for example by laminating a polymeric film 12 (not shown) to opposite sides of the single layer 10 or a stack of two or more layers 10. An optional hot melt or pressure sensitive adhesive can be applied to one or both sides of the encapsulation 12 at corresponding spray stations 49 and 49'. Protective release liners (not shown) can then be applied to each adhesive surface.

[0110] An example of a "wet-laid" process that can be used to manufacture thermal barriers as disclosed herein is described in the Examples of U.S. Patent No. 6,458,418, which is incorporated herein by reference in its entirety. In this wet-laid process, the thermal barrier can be made using at least one dilute (ideally no more than 5 wt% solids) aqueous slurry containing inorganic fibers, binder, and thermal insulation particles, and compressible organic particles, by depositing the aqueous slurry onto a permeable substrate such as a screen or "wire" of a papermaking machine; partially dewatering the slurry by gravity and / or vacuum; and then pressing to increase density (e.g., using a press roll). The thermal barrier is then fully dried with a heated roll.

[0111] Also disclosed herein are battery cell modules for electric vehicles, the battery cell modules comprising:

[0112] a plurality of battery cells disposed in a housing; and

[0113] a plurality of thermal barriers as disclosed herein,

[0114] wherein one thermal barrier is disposed between each pair of adjacent battery cells.

[0115] A plurality of battery cell modules can be included in a battery pack.

[0116] The following items will serve to illustrate preferred embodiments of the present application. It should be understood, however, that they are set forth for purposes of illustration only, and are not to be construed in any way to restrict the scope of the application.

[0117] Item 1 : A thermal barrier article comprising

[0118] (i) at least one nonwoven fibrous thermal insulation layer comprising

[0119] (a) a fibrous matrix of inorganic fibers;

[0120] (b) a plurality of thermally insulative inorganic particles dispersed within the fibrous matrix;

[0121] (c) a binder dispersed within the fibrous matrix so as to hold the fibrous matrix together; and

[0122] (d) a plurality of compressible organic particles dispersed within the fibrous matrix; and

[0123] (ii) optionally, at least one organic encapsulation layer encapsulating the at least one nonwoven fibrous thermal insulation layer.

[0124] Item 2: The thermal barrier article of item 1, wherein the addition of the compressible organic particles results in at least a 20% reduction in pressure experienced by the thermal barrier article compared to the same thermal barrier article without the compressible organic particles.

[0125] Item 3: The thermal barrier article of item 1 or item 2, wherein the thermal barrier exhibits a minimum pressure peak P(min) of at least 25 kPa, preferably at least 30 kPa, still more preferably at least 40 kPa, even more preferably at least 50 kPa in Compression Performance Test 2, as determined according to the test described in the Experimental Section.

[0126] Item 4: The thermal barrier article of any of the preceding items, wherein the at least one nonwoven fibrous thermal insulation layer comprises an amount of thermally insulative inorganic particles ranging from as low as about 10 wt% up to as high as about 60 wt% of the nonwoven fibrous thermal insulation layer.

[0127] Item 5: The thermal barrier of any of the preceding items, wherein the at least one nonwoven fibrous thermal insulation layer comprises an amount of binder ranging from as low as about 2.5 wt% up to as high as about 10.0 wt% of the nonwoven fibrous thermal insulation layer.

[0128] Item 6: The thermal barrier according to any of the preceding items, wherein the at least one nonwoven fibrous thermal insulation layer comprises an amount of compressible organic particles ranging from as low as about 0.5 wt.% up to as high as about 20 wt.%, preferably from about 0.8 wt.% up to as high as about 15 wt.%, and more preferably from about 1 wt.% up to as high as about 10 wt.% of the at least one nonwoven fibrous thermal insulation layer.

[0129] Item 7: The thermal barrier according to any of the preceding items, wherein the compressible organic particles are selected from the group consisting of expanded microspheres, rubber particles, foam particles, silicone particles, polyurethane particles, styrene block copolymer particles, and any combination and mixture thereof.

[0130] Item 8: The thermal barrier according to item 7, wherein the compressible organic particles are selected from hollow organic microspheres, preferably from expandable hollow organic microspheres and expanded hollow organic microspheres.

[0131] Item 9: The thermal barrier according to item 8, wherein the hollow organic microspheres comprise a polymeric shell and a core comprising a liquid or a gas.

[0132] Item 10: The thermal barrier according to item 9, wherein the polymeric shell contains a thermoplastic shell component comprising a compound selected from the group consisting of acrylonitrile, methacrylonitrile, polyesters, polyurethanes, poly(meth)acrylates, polyethylenes, polystyrenes, and any combination and mixture thereof.

[0133] Item 11 : The thermal barrier according to item 9 or item 10, wherein the core comprises a liquid selected from organic liquids such as pentane, hexane, heptane, octane, nonane, and decane and their halogenated derivatives, and a gas selected from methane, propane, nitrogen, noble gases, and any combination thereof.

[0134] Item 12: The thermal barrier according to item 7, wherein the foam particles comprise silicone foam particles, polyurethane foam particles, rubber foam particles, polyolefin foam particles such as polypropylene, polystyrene foam particles, thermoset foam particles, polyether sulfone foam particles, or other organic foam particles, or mixtures thereof.

[0135] Item 13: The thermal barrier according to any of the preceding items, wherein the compressible organic particles are dispersed within a matrix selected from the group consisting of inorganic materials, organic resins, inorganic liquids such as water, organic liquids preferably selected from oils such as mineral oil, natural oils, and synthetic oils, alcohols such as polyvinyl alcohol, and any combination and mixture thereof.

[0136] Item 14: The thermal barrier of item 13, wherein the organic resin is selected from the group consisting of epoxy resins, polyester resins, polyurethane resins, polycarbonate resins, polyether resins, ethylene vinyl acetate resins, and any combination thereof.

[0137] Item 15: The thermal barrier of any of the preceding items, wherein the thermal barrier exhibits an initial life pressure of at least 25 kPa and a terminal life pressure of at most 2000 kPa.

[0138] Item 16: The thermal barrier of any of the preceding items, wherein the nonwoven fibrous thermal insulation layer has an installed thickness in the range of from about 0.5 mm up to less than 20 mm, preferably from about 1 mm up to less than about 17 mm, more preferably from about 2 mm up to less than about 15 mm.

[0139] Item 17: The thermal barrier of any of the preceding items, wherein the nonwoven fibrous thermal insulation layer has a basis weight in the range of from as low as about 100 g / m2 2 up to as high as about 5000 g / m2 2 , preferably from about 200 g / m2 2 up to as high as about 4000 g / m2 2 , and more preferably from about 300 g / m2 2 up to as high as about 3000 g / m2 2 .

[0140] Item 18: The thermal barrier of any of the preceding items, wherein the nonwoven fibrous thermal insulation layer has an uncompressed basis weight in the range of from about 100 g / m2 2 up to about 3000 g / m2 2 , preferably from about 200 g / m2 2 up to about 2500 g / m2 2 , and more preferably from about 300 g / m2 2 up to about 2000 g / m2 2 .

[0141] Item 19: The thermal barrier of any of the preceding items, wherein the thermally insulative inorganic particles comprise particles of one or any combination of materials selected from the group consisting of inorganic aerogels, xerogels, hollow or porous ceramic microspheres, unexpanded vermiculite, irreversibly or permanently expanded vermiculite, fumed silica, other forms of porous silica, irreversibly or permanently expanded or unexpanded perlite, pumice, irreversibly or permanently expanded clays, diatomaceous earth, titanium dioxide, and zirconium oxide.

[0142] Item 20: The thermal barrier of any of the preceding items, wherein the nonwoven fibrous thermal insulation layer is encapsulated by the organic encapsulation layer.

[0143] Item 21: The thermal barrier according to Item 20, wherein the organic encapsulation layer further comprises a nonwoven layer.

[0144] Project 22: A thermal barrier according to any one of the preceding projects, wherein the organic encapsulation layer has at least one vent formed through the organic encapsulation layer, the at least one vent being positioned and sized to allow gas contained within the thermal barrier to escape from the organic encapsulation layer, such that the structural integrity of the organic encapsulation layer is maintained during a thermal runaway event.

[0145] Item 23: A thermal barrier according to any one of Items 20 to 22, wherein the thermal barrier has a top edge, a bottom edge, and opposing side edges, and the at least one vent, such as a slit or cavity, is positioned along the periphery of one or both opposing side edges. Each layer may have at least one vent formed through the layer, the at least one vent being positioned and sized to allow expanding gas (e.g., air) contained within the thermal barrier to escape from the organic encapsulation, such that when the thermal barrier is compressed during the assembly of the battery cell module (e.g., a stack of battery cells), or when the thermal barrier is heated (e.g., during normal operation or overheating of the adjacent battery cells), the structural integrity of the organic encapsulation layer is maintained (i.e., the nonwoven fiber thermal insulation layer remains fully, mostly, or at least significantly encapsulated by the organic encapsulation layer). Each vent may be rectangular, circular, elliptical, or any other desired shape or combination thereof. One or more or each vent may be in the form of a notch projecting from the side edge of the encapsulation toward the center of the thermal barrier. Alternatively, one or more vents may be formed inside the side edge of the encapsulation and adjacent to the nonwoven thermal insulation. Furthermore, one or more vents may be formed only on one side of the nonwoven thermal insulation through the encapsulation layer. It may also be necessary for each vent to be in the form of multiple small perforations, which are clustered together (e.g., like a screen, sieve, or filter) to provide a desired outlet opening area. The thermal barrier has a top edge, a bottom edge, and opposing side edges, and the at least one vent may be positioned along the periphery of one or two opposing side edges.

[0146] Item 24: A thermal barrier according to any one of Items 22 to 23, wherein the at least one vent provides an outlet opening through the organic encapsulation layer, the outlet opening having a diameter of approximately 2 mm. 2 Up to about 15mm 2 The opening area within the range. It is conceivable that it may be necessary to have any specific area within the range, or any narrower range within the range.

[0147] Item 25: The thermal barrier according to item 24, wherein the at least one vent hole provides an exit opening through the organic encapsulation layer, the exit opening having an opening area in the range of about 2 square millimeters to at most about 15 square millimeters.

[0148] Item 26: The thermal barrier according to any one of items 22 to 25, wherein the organic encapsulation layer comprises at least one polymeric layer.

[0149] Item 27: The thermal barrier according to item 26, wherein the at least one polymeric layer is heat-shrinkable, or wherein the at least one polymeric layer is wrapped around the thermal insulation layer at an angle in two directions and comprises at least one sealing region, or wherein the at least one polymeric layer is wrapped around the at least one thermal insulation layer in one direction and comprises at least two sealing regions.

[0150] Item 28: The thermal barrier according to any one of items 26 to 27, wherein the at least one polymeric film comprises at least one polymeric material selected from the group consisting of polyolefins, polyvinyl chloride, ethylene-vinyl acetate copolymers, preferably from polyolefins.

[0151] Item 29: The thermal barrier according to item 27, wherein the at least one sealing region is a heat-sealed region, an ultrasonic welded region or an adhesive seal.

[0152] Item 30: The thermal barrier according to item 27, wherein the at least one polymeric layer is wound in a horizontal form-fill-seal process (HFFS) or in a vertical form-fill-seal process (VFFS), preferably in a vertical form-fill-seal process (VFFS).

[0153] Item 31 : The thermal barrier according to any one of the preceding items, wherein the nonwoven fibrous thermal insulation layer passes at least the V-2 rating of the UL94 flammability test.

[0154] Item 32: A battery cell module for an electric vehicle, the battery cell module comprising:

[0155] (A) a plurality of battery cells disposed in a housing; and

[0156] (B) a plurality of thermal barriers according to any one of items 1 to 31 ; wherein the battery cells are arranged in rows, with one thermal barrier disposed between each pair of adjacent battery cells.

[0157] Item 33: The battery cell module according to item 32, wherein the battery cell module is a lithium-ion battery cell module.

[0158] Item 34: A method of making a thermal barrier according to any one of items 1 to 31, wherein the method comprises forming the nonwoven fibrous thermal insulation layer using a wet-laid process or a dry-laid process.

[0159] Item 35: The method according to item 34, further comprising: providing thermal insulation inorganic particles made entirely of unexpanded intumescent particles (e.g., unexpanded vermiculite particles or unexpanded perlite particles), made mostly of the unexpanded intumescent particles, or comprising at least the unexpanded intumescent particles; providing compressible organic particles selected from the group consisting of intumescent microspheres, rubber particles, foam particles, silicone particles, polyurethane particles, styrene block co-polymer particles, and any combination and mixture thereof; disposing the thermal insulation inorganic particles and the compressible organic particles to be distributed uniformly or consistently throughout or within the nonwoven fibrous thermal insulation layer; and heating the unexpanded intumescent particles and the compressible organic particles to a temperature and time that irreversibly or permanently expands the unexpanded intumescent particles and optionally the compressible organic particles, wherein the heating occurs before or after disposing the thermal insulation inorganic particles and / or the compressible organic particles within the nonwoven fibrous thermal insulation layer.

[0160] Item 36: The method according to item 35, wherein the heating irreversibly or permanently expands the unexpanded intumescent particles and optionally the compressible organic particles, such as the expandable hollow microspheres, to a range of at least about 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90% to at most 100% of their expandability.

[0161] Item 37: Use of a thermal barrier according to any one of items 1 to 31 for at least slowing the propagation of a thermal runaway event in a battery.

[0162] Item 38: The use according to item 37, wherein the battery is a lithium-ion battery.

[0163] Item 39: The use according to item 38, wherein the lithium-ion battery is contained in a vehicle, such as a car, a bus, a train, a boat, or an airplane.

[0164] Item 40: Use of a thermal barrier according to any one of items 1 to 31 in the manufacture of a lithium-ion battery.

[0165] Examples

[0166] All parts, percentages, ratios, etc. in the examples and the rest of the specification are by weight, unless otherwise indicated or readily apparent from the context.

[0167] The following abbreviations are used in the following examples: cm = centimeter, g = gram, gsm = grams per square meter, °C = degrees Celsius, in = inch, lbf = pound force, kgf = kilogram force, kPa = kilopascal, m = meter, min = minute, pm = micrometer, mm = millimeter, MPa = megapascal, N = Newton, sec = second, and W = watt.

[0168] Material Table

[0169]

[0170]

[0171] Test Methods

[0172] Compressive Property Test Method 1 :

[0173] The compression performance of the sample was tested by placing a two inch (50.8 mm) diameter sample having an 8 mm height between two platens on a load frame (MTS Alliance RT / 50 load frame). The top platen was slowly moved downward until the force reached 10 N. This position was marked as the free height of the sample. The top platen was then moved downward at a rate of 25 mm / min until the gap between the platens was 5.0 mm. The pressure was recorded and noted as the peak pressure at 5.0 mm. The sample was held at this gap for 300 seconds. The pressure was recorded at the end of 300 seconds and this pressure was recorded as the relaxation pressure at 5.0 mm. The top platen was then moved further downward to 4.5 mm and the measurement of peak pressure and relaxation pressure was repeated as described above. Such pressures were recorded at the following gaps (in mm): 5.0, 4.5, 4.0, 3.5, 3.0, 2.5, 2.0, 1.5, and 1.0. The relaxation pressure was plotted as a function of gap.

[0174] Compressive Property Test Method 2 (Cycling)

[0175] A tensile tester (purchased from ZwickRoell GmbH & Co. KG, Ulm, Germany) was used to test the compression performance of the sample in compression mode. The test sample had a diameter of 50.8 mm and a thickness of more than 3 mm. The test was performed at about 23 °C. The upper platen of the tester was moved at a rate of 25 mm / min until a maximum force of 300 kPa was reached. After allowing the gap to relax for 15 seconds at 300 kPa, the gap was held at the same position for 300 seconds. The initial thickness defined in this way was taken as the sample thickness. Next, the upper platen was moved up and down for 1000 cycles, holding the gap for 5 seconds at each maximum and minimum peak of each cycle.

[0176] The first gap cycle starts with a 12.5% amplitude at a rate of 1 mm / min for a full load / unload cycle. The amplitude is stepped down to 12.5% / 2 = 6.25% from cycle 1 to cycle 1000.

[0177] The simulation module assembles a lithium ion battery cell with a state of charge (SOC) of 30% at the start, and the gap is closed by 70% of the amplitude to reach a fully charged battery state with a SOC of 100%. In the next step, the upper table moves up and stops at the full breathing amplitude with a SOC of 0%. Thus, the second gap starts with a gap that is larger than the starting thickness.

[0178] Furthermore, the open gap at a SOC of 0% and the closed gap at a SOC of 100% are stepped down by 25% in each cycle, reaching 75% of the starting gap at cycle 1000.

[0179] The compression force (in kPa) of each max and min peak of each cycle is recorded. The lowest pressure recorded throughout the test is recorded as the minimum pressure peak, Pmin.

[0180] In some embodiments, the percent recovery is recorded, which is calculated as (Pmin / 300 kPa) x 100. In some embodiments, Pmax and Pmin at cycle 1000, which cycle is designated as the end of life (EOL) cycle, are also recorded. Pmin is subtracted from Pmax, and the result is recorded as ΔEOL.

[0181] Compressive Property Test Method 3 (Cycling)

[0182] The compression performance of the samples was tested by placing a four inch by four inch (101.6 mm) square sample having a height of up to 1 inch (25.4 mm) between two platens on a load frame (Model 5969, available from Instron, Norwood, MA). The top platen was moved downward until the gap between the surfaces reached 3.5 mm. This position was marked as the starting height of the sample, and this state was held for one hour to allow stress relaxation. The top platen was then moved downward at a rate of 1 pm / s for 0.5 mm until the gap between the platens was 3 mm, and this position was again held for one hour. The top platen was then moved upward at a rate of 1 pm / s for 0.4 mm until the gap was 3.4 mm, and this state was again held for one hour. The compression-decompression cycle of “move downward 0.5 mm, hold for one hour, move upward 0.4 mm, hold for one hour” was repeated until the pressure reached 3 MPa, or the gap configuration was 1.6 mm, whichever occurred first. The resulting compression pressure was recorded by the pressure sensor of the device throughout the test. The performance of the sample was then gauged according to the minimum pressure detected, referred to as the beginning of life (BOL) pressure, and, where applicable, the pressure measured when the sample gap was 1.8 mm, referred to as the end of life (EOL) pressure.

[0183] Basis Weight Determination Method :

[0184] Two inch (50.8 mm) diameter samples having an 8 mm height were weighed on a top loading balance and the weight was divided by the area of the sample. The basis weight of all samples was in the range of 1050 g / m 2 to 1370 g / m 2 .

[0185] General Method for Preparing Thermal Barriers :

[0186] The short fiber weight percent combinations (shown in the table below) were weighed and pre-mixed by hand before being placed on the feed belt. The fibrous material was processed through an air-laid processor (i.e., fed from the top) as disclosed in U.S. Patent No. 7,491,354, where the fibers are opened and dispersed into an air stream and then collected on a screen belt. Details of such air-laid (or dry-laid) processing equipment and methods of forming air-laid webs using such equipment can be found in U.S. Patent 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 fillers (i.e., insulating inorganic particles and compressible organic particles) were fed into the chamber or forming box of the air-laid processor from the top or side in a weight amount. A volumetric feeder coupled with a pneumatic horn was used to distribute the fillers uniformly into the web. The sample was then run through a forced air convection oven at 143.3 °C (290 °F) at a speed of 1.1 m / min to activate the binder and bond the web together.

[0187] Densification Treatment of Prepared Meshes

[0188] The above web was densified to a specified height using a hot press with a gap set at the specified height.

[0189] For CE 1 and EX 1-10, the sample was placed between the two hot plates of the hot press, which were held at 300 °F (149 °C) for about 10 minutes. A predetermined amount of pressure was applied for a predetermined amount of time to activate the binder. Following this step, the densified sample was immediately placed between two plates, which were held at a predetermined pressure at room temperature for a predetermined time to lock the web to the desired thickness. The pressure and time during the heating step were adjusted to achieve the desired thickness. For example, to achieve a final thickness of 8 mm, a pressure of 1500 lbf (680 kgf; applied over an area of 250 mm x 100 mm) was used for 1 minute.

[0190] For CE 2 and EX 11-18, the densification process was performed using the same procedure as described above, except that the sample was pressed at 200 °C for 5 minutes. Thickness was not recorded.

[0191] Comparative Example 1 (CE 1) and Examples 1-10 (EX 1-10)

[0192] Articles were prepared following the general method for preparing thermal barriers and the webs prepared were densified using the components shown in Table 2. Compression performance test 1 was performed on these samples and the results are shown in Table 2 below.

[0193] Table 2

[0194]

[0195] *) For a sample with a height of 8 mm, a test gap of 4 mm corresponds to a compression of 50%

[0196] **) For a sample with a height of 8 mm, a test gap of 2 mm corresponds to a compression of 75%

[0197] Comparative Example 2 (CE 2) and Examples 11-12 (EX 11-12)

[0198] Articles were prepared according to the general method for preparing thermal barriers and the prepared webs were densified using the weight percentages of the components as shown in Table 3. The samples were subjected to the Compression Performance Test Method 2 and the results are shown in Table 3.

[0199] Table 3

[0200]

[0201]

[0202] Examples 13-16 (EX 13-16)

[0203] Articles were prepared according to the general method for preparing thermal barriers and the prepared webs were densified using the weight percentages of the components as shown in Table 4. The samples were subjected to the Compression Performance Test Method 2 and the results are shown in Table 4.

[0204] Table 4

[0205] CE 2 EX 13 EX 14 EX 15 EX 16 Ceramic Fibers 50％ 50％ 50％ 50％ 50％ Filler 40％ 40％ 40％ 40％ 40％ Binder 10％ 10％ 10％ 10％ 10％ Dualite U010-185D - 1.5％ 3.0％ 5.6％ 9.6％ Pmin 10 kPa 34 kPa 71 kPa 98 kPa 111 kPa % Recovery 3％ 11％ 24％ 33％ 37％ Pmax at EOL 1151 kPa 928 kPa 754 kPa 682 kPa 681 kPa Pmin at EOL 138 kPa 141 kPa 158 kPa 178 kPa 188 kPa ΔEOL 1013 kPa 787 kPa 596 kPa 504 kPa 493 kPa

[0206] Examples 17-18 (EX 17-18)

[0207] Articles were prepared according to the general method for preparing thermal barriers and the prepared webs were densified using the weight percentages of the components as shown in Table 5. The samples were subjected to the Compression Performance Test Method 2 and the results are shown in Table 5. Note that MB120 is a dispersion of expandable microspheres that expand during processing.

[0208] Table 5

[0209] EX 17 EX 18 Ceramic Fibers 50％ 50％ Filler 40％ 40％ Binder 10％ 10％ MB120 1.4％ 2.7％ Pmin 91 kPa 74 kPa

[0210] Comparative Example 3 (CE 3) and Examples 19-20 (Ex. 19-20)

[0211] Articles were prepared according to the general method for making thermal barriers using the weight percentages of components as shown in Table 6. These materials were processed with a target total basis weight of 1050 gsm. The compression performance test method 3 was performed on the samples and the minimum open gap pressure P(BOL) and the maximum pressure at 1.8 mm gap P(EOL) were determined accordingly. The results for the non-densified samples are shown in Table 6. Some of the samples were subjected to a densification process using a Glenro twin belt compression oven. The webs were subjected to the densification process at 200 °C, 1 m / min with a force of 30,000 N. These densified samples were tested using the cyclic compression test 3 and the average results from the two samples are reported in Table 6.

[0212] Table 6

[0213]

[0214] Various modifications and alterations to this application can be made by those skilled in the art without departing from the spirit and scope of the application. For example, it is believed that microwave heating can be used to irreversibly or permanently expand the particles made from intumescent materials. It is believed that the use of microwave energy, rather than baking in an oven, can result in more uniform expansion of the intumescent particles within the fibrous matrix. Accordingly, the application is not limited to the above-described embodiments, but is intended to be bound by the limitations as set forth in the following claims and any equivalents thereof. The application can be suitably 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 hereby incorporated by reference in their entirety.

Claims

1. A thermal barrier article comprising: at least one nonwoven fibrous thermal insulation layer comprising: (a) a fibrous matrix of inorganic fibers; (b) a plurality of thermally insulative inorganic particles dispersed within the fibrous matrix; (c) a binder dispersed within the fibrous matrix so as to hold the fibrous matrix together; and (d) a plurality of compressible organic particles dispersed within the fibrous matrix.

2. The thermal barrier article of claim 1, which is compressible.

3. The thermal barrier of claim 2, wherein the thermal barrier exhibits a minimum pressure peak P(min) of at least 25 kPa, preferably at least 30 kPa, still more preferably at least 40 kPa, even more preferably at least 50 kPa, as determined according to the tests described in the Experimental Section in Compression Performance Test 2.

4. The thermal barrier of claim 2 or 3, wherein the thermal barrier has a life-early pressure of at least 25 kPa and a life-late pressure of at most 2000 kPa when tested according to Compression Performance Test Method 3.

5. The thermal barrier of any one of claims 2 to 4, wherein the addition of the compressible organic particles reduces the pressure experienced by the thermal barrier article by at least 20% compared to the same thermal barrier article without the compressible organic particles.

6. The thermal barrier of any one of the preceding claims, wherein the at least one nonwoven fibrous thermal insulation layer comprises the compressible organic particles in an amount ranging from as low as about 0.5 wt% up to as high as about 20 wt% of the at least one nonwoven fibrous thermal insulation layer.

7. The thermal barrier of any one of the preceding claims, wherein the compressible organic particles are expanded microspheres, rubber particles, foam particles, silicone particles, polyurethane particles, styrene block co-polymer particles, or any combination or mixture thereof.

8. The thermal barrier of claim 7, wherein the compressible organic particles are hollow organic microspheres.

9. The thermal barrier of claim 7, wherein the foam particles are silicone foam particles, polyurethane foam particles, rubber foam particles, polyolefin foam particles, polystyrene foam particles, thermoset foam particles, polyether sulfone foam particles, or other organic foam particles, or mixtures thereof.

10. The thermal barrier of any one of the preceding claims, wherein the nonwoven fibrous thermal insulation layer has an installed thickness ranging from about 0.5 mm up to less than 20 mm.

11. The thermal barrier of any of the preceding claims, wherein the nonwoven fibrous thermal insulation layer has a basis weight in the range of as low as about 100 g / m 2 up to as high as about 5000 g / m 2 .

12. The thermal barrier of any one of the preceding claims, wherein the thermally insulative inorganic particles comprise particles of one or any combination of materials selected from the group consisting of inorganic aerogels, xerogels, hollow or porous ceramic microspheres, unexpanded vermiculite, irreversibly or permanently expanded vermiculite, fumed silica, other forms of porous silica, irreversibly or permanently expanded or unexpanded perlite, pumice, irreversibly or permanently expanded clays, diatomaceous earth, titanium dioxide, and zirconium oxide, or combinations thereof.

13. The thermal barrier of claim 12, wherein the thermally insulative inorganic particles are fumed silica.

14. The thermal barrier of claim 12, wherein the thermally insulative inorganic particles are inorganic aerogels.

15. The article of any of the preceding claims, wherein the nonwoven fibrous thermal insulation layer comprises the thermally insulative inorganic particles in an amount of at least 10 wt.% and up to 60 wt.%, based on the total weight of the nonwoven fibrous thermal insulation.

16. The article of any of the preceding claims, wherein the binder comprises polyethylene, polyethylene terephthalate, flame-retardant polyethylene terephthalate, epoxy, acrylic polymer, methacrylic polymer, ethylene vinyl acetate, silicone polyurethane, or any combination or mixture thereof.

17. The article of any of the preceding claims, wherein the binder comprises bicomponent core-shell polymer fibers.

18. The article of any of the preceding claims, wherein the compressible organic particles are dispersed within an organic resin.

19. The thermal barrier of any of the preceding claims, wherein the thermal barrier further comprises at least one encapsulation layer, the at least one encapsulation layer encapsulating the at least one nonwoven fibrous thermal insulation layer.

20. The thermal barrier of claim 19, wherein the at least one encapsulation layer is organic.

21. A battery cell module for an electric vehicle, the battery cell module comprising: (A) a plurality of battery cells disposed in a housing; and (B) a plurality of thermal barriers according to any of the preceding claims; wherein the battery cells are arranged in rows, with one thermal barrier disposed between each pair of adjacent battery cells.

22. A method of making a thermal barrier article according to any of claims 1 to 20, the method comprising: forming a nonwoven fibrous thermal insulation layer using a wet-laid process or a dry-laid process; providing a plurality of thermally insulative inorganic particles; disposing the plurality of thermally insulative inorganic particles to be distributed uniformly or consistently throughout or within the nonwoven fibrous thermal insulation layer; providing a plurality of compressible organic particles; disposing the plurality of compressible organic particles to be distributed uniformly or consistently throughout or within the nonwoven fibrous thermal insulation layer; and providing a binder distributed throughout or within the nonwoven fibrous thermal insulation layer to provide the thermal barrier article.

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