Thermal runaway barrier product with new encapsulation

Abstract

A thermal runaway barrier for slowing down a thermal runaway event within a battery assembly. The thermal runaway barrier consisting essentially of at least one thermal insulation layer and at least one polymeric layer covering all external surfaces of the at least one thermal insulation layer such that the at least one thermal insulation layer is essentially encapsulated by the at least one polymeric layer. Methods to make such thermal runaway barrier articles are also provided.

Description

[0001] THERMAL RUNAWAY BARRIER PRODUCT WITH NEW ENCAPSULATION

[0002] The present disclosure relates to a barrier with a new encapsulation for at slowing down a thermal runaway event within a battery assembly, e.g., like a battery assembly used in an electric vehicle. In one embodiment, the barrier with a new encapsulation at least significantly slows down a thermal runaway event. Furthermore, the present disclosure relates to a method for encapsulating a barrier for significantly slowing down a thermal runaway event with at least one polymeric film.

[0003] BACKGROUND

[0004] Electric motors used in electric or hybrid vehicles (e.g., automobiles) are powered, at least in part, by batteries. Lithium ion batteries are typically used in such applications, and they are available in three forms: prismatic cells, pouch cells or cylindrical-shaped cells. These batteries are disposed within the vehicle compactly to save space. Sometimes one or more of the battery cells or battery modules experience a thermal runaway event, which can result in many if not all of the battery cells or battery modules overheating and being destroyed. There is a desire in the industry to prevent, stop or at least significantly slowing down such a thermal runaway event.

[0005] The industry has developed a number of thermal barrier elements, which require multiple layers of various inorganic materials to perform such a function (see, e.g., U.S. Patent No. 8,541 ,126B2).

[0006] The background description provided here is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.

[0007] SUMMARY

[0008] The present inventors have discovered that suitable thermal barrier elements can be used without the need for multiple layers of inorganic nonmetallic materials.

[0009] In one aspect of the present disclosure, a thermal runaway barrier is provided that is operatively adapted for being disposed between battery cells of a battery assembly and for at least significantly slowing down a thermal runaway event within the battery assembly. In a preferred embodiment, the thermal runaway barrier consists of or consists essentially of a single-layer of a nonwoven fibrous thermal insulation comprising a fiber matrix of inorganic fibers, thermally insulative inorganic particles dispersed within the fiber matrix, and a binder dispersed within the fiber matrix so as to hold together the fiber matrix. In other embodiments, the thermal runaway barrier may comprise other layers in addition to the layer of a nonwoven fibrous thermal insulation. An optional organic encapsulation layer may also be included for encapsulating the single-layer of nonwoven fibrous thermal insulation.

[0010] In another aspect of the present disclosure, 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 runaway barriers according to the present disclosure. The battery cells are lined up in a row or stack, with one thermal runaway barrier being disposed between each pair of adjacent battery cells, or between a pre-determined number of battery cells (e.g., after every third battery cell), or between battery modules.

[0011] In a further aspect of the present disclosure, a method is provided for making a thermal runaway barrier according to the present disclosure, where the method comprises forming the layer of nonwoven fibrous thermal insulation using a wet-laid process or dry-laid process.

[0012] The above summary is not intended to describe each disclosed embodiment or every implementation of the present disclosure. The description that follows more particularly exemplifies illustrative embodiments. In several places throughout the application, guidance is provided through lists of examples, which examples can be used in various combinations. In each instance, the recited list serves only as a representative group and should not be interpreted as an exclusive list.

[0013] DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

[0014] In describing preferred embodiments of the disclosure, specific terminology is used for the sake of clarity. This disclosure, however, is not intended to be limited to the specific terms so selected, and each term so selected includes all technical equivalents that operate similarly.

[0015] As used herein, the terms “preferred” and “preferably” refer to embodiments described herein that can afford certain benefits, under certain circumstances. However, 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 and is not intended to exclude other embodiments from the scope of the disclosure.

[0016] 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 may include one or more of the components and equivalents thereof known to those skilled in the art. Further, the term “and / or” means one or all the listed elements or a combination of any two or more of the listed elements.

[0017] It is noted that the term “comprises” and variations thereof do not have a limiting meaning where these terms appear in the accompanying description. Moreover, “a,” “an,” “the,” “at least one,” and “one or more” are used interchangeably herein. Relative terms such as left, right, forward, rearward, top, bottom, side, upper, lower, horizontal, vertical, and the like may be used herein and, if so, are from the perspective observed in the drawing. These terms are used only to simplify the description, however, and not to limit the scope of the disclosure in any way.

[0018] Reference throughout this specification to “one embodiment,” “certain embodiments,” “one or more embodiments” or “an embodiment” means that a particular feature, structure, material, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. Thus, the appearances of the phrases such as “in one or more embodiments,” “in certain embodiments,” “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily referring to the same embodiment of the disclosure. Where applicable, trade designations are set out in all uppercase letters.

[0019] 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 an affliction means preventing, treating, or both treating and preventing further afflictions).

[0020] As used herein, the term “or” is generally employed in its sense including “and / or” unless the content clearly dictates otherwise.

[0021] Also herein, the recitations of numerical ranges by endpoints include all numbers subsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.).

[0022] “Ambient conditions” means at 25°C and 101.3 kPa pressure.

[0023] “Average” means number average, unless otherwise specified.

[0024] “Continuous” means extending across a single, unified area along a given layer (a perforated sheet can be continuous);

[0025] “Cure” refers to exposing to radiation in any form, heating, or allowing to undergo a physical or chemical reaction that results in hardening or an increase in viscosity.

[0026] “Discontinuous” means extending across a plurality of discrete areas along a given layer, where the discrete areas are spaced apart from each other;

[0027] “Size” refers to the longest dimension of a given object or surface.

[0028] “Substantially” means to a significant degree, 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%.

[0029] “Thickness” means the distance between opposing sides of a layer or multilayered article. The recitation of numerical ranges by endpoints includes all numbers subsumed within that range in increments commensurate with the degree of accuracy indicated by the end points of the specified range (e.g., for a range of from 1.000 to 5.000, the increments will be 0.001, and the range will 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) and any range within that range, unless expressly indicated otherwise.

[0030] The term “polymer” will 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 in a miscible blend.

[0031] The reduction of inorganic fiber or particle shedding is significant, when the amount of inorganic fibers or particles lost is less than 10%, 5% or 1% by weight percent of the original fiber or particle content of the layer of nonwoven fibrous thermal insulation. Preferably, the amount of inorganic fibers or particles lost is less than 5% by weight percent of the original fiber or particle content of the layer of nonwoven fibrous thermal insulation. The thinner the organic encapsulation layer (i.e. , the lower the organic content of the barrier) the better the hot / cold test results.

[0032] The present thermal runaway barrier may also be used between battery modules or assemblies.

[0033] Inorganic binders, organic binders, or a combination of both can be useful according to the present disclosure. An example of an inorganic binder useful in both dry-laid or wet-laid fiber processing can include particles of silicone that convert to fusible silica when heated. An organic-inorganic hybrid binder may also be useful such as, e.g., WACKER® MQ 803 TF, which is a co-hydrolysis product of tetra-alkoxy silane (Q unit) and trimethyl-alkoxy silane (M unit). The chemical structure of WACKER® MQ 803 TF can be seen as a three dimensional network of polysilicic acid units which are end-blocked with trimethylsilyl groups. Some residual ethoxy and hydroxy functions are present. The average molecular weight can be exactly controlled by the ratio of M and Q units. This ratio approx, is 0.67 for WACKER® MQ 803 TF.

[0034] Exemplary binder fibers include the use of bicomponent core-sheath polymeric fibers in a dry-laid process. In a wet-laid process, ethylene vinyl acetate latex dispersion binder, bicomponent core-sheath polymeric fibers, or a combination of both can be used. When a polymeric binder fiber is used, the binder can be activated by heating and compressing the nonwoven fibrous thermal insulation material. A combination of organic and inorganic binders can also be used.

[0035] As used herein, the term “consisting only of” indicates that the claimed thermal runaway barrier only encompasses structures with only the recited elements and no other elements. As used herein, the term “consisting essentially of” indicates that the claimed thermal runaway barrier is able to exhibit 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 present inventive thermal runaway barrier does not need to include another layer of other thermal insulation material (e.g., a woven fabric or nonwoven structure of inorganic fibers). Therefore, with the “consisting essentially of’ language, if a third party thermal runaway barrier (e.g., of a competitor) includes all of the features / elements in a claim of the present disclosure, as well as one or more additional features / elements (e.g., an additional layer of inorganic fibers) not recited in the claim, that third party thermal runaway barrier is considered covered by the claim, if the additional feature / element does not determine whether the desired thermal insulation properties will be exhibited by the thermal runaway barrier.

[0036] As used herein, the term “inorganic” refers to ceramic or otherwise nonmetallic (i.e. , not a metal, metal alloy, or metal composite) inorganic material.

[0037] A “thermal runaway” is an event when a battery cell experiences an exothermic chain reaction causing the phenomenon of an uncontrollable temperature rise of the battery cell. The exothermic chain reaction may be caused, for example, by over-heating of the battery cell, over-voltage of the battery cell, and mechanical puncture of the battery cell, among other reasons.

[0038] A “thermal propagation” is when a battery cell thermal runaway causes the remaining battery cells in a battery pack or system to undergo the thermal runaway phenomenon.

[0039] A “thermal runaway event” refers to the overheating of one battery cell, in a container of battery cells, causing a chain reaction of adjacent battery cells overheating, and potentially exploding or catching fire, until the number of overheated battery cells reaches a critical point of propagation resulting in all or more than half of the battery cells in the module or assembly of modules being destroyed. Factors that can cause a battery cell to overheat include: physical damage, applying over voltage, overheating (internal battery cell shorting).

[0040] As the energy density of a battery cell increases, the temperature at which the battery cell starts to malfunction (e.g., from at least losing its efficiency or failing to function up to igniting, burning or exploding) decreases. Likewise, as the energy density of the battery cell decreases, the temperature at which the battery cell starts to malfunction increases. For example, with a controlled ramping up of the temperature, NMC811 type battery cells tend to start malfunctioning or even blow up when the temperature reaches around 120°C to 130°C, while NMC622 type battery cells start to malfunction or even blow up when they reach a temperature of around 180°C. The corresponding temperature is higher for battery cells with lower energy densities (e.g., NMC532 and NMC433 type battery cells). With physically larger battery cells or when the temperature is rapidly increased, thermal diffusion through the battery cell can result in the localized temperature taking longer to get up to the critical point. It is believed that this thermal diffusion effect can cause the actual temperature at which the battery cell starts to malfunction or blow up to be somewhat higher. It can be desirable for the thermal runaway barrier of the present disclosure to prevent an adjacent battery from reaching a temperature in the range of from about 130°C up to about 150°C.

[0041] As used herein, “preventing” a thermal runaway event refers to preventing the overheating of a single battery cell from causing the overheating of battery cells that are adjacent to the single battery cell. The barrier is considered to prevent a thermal runaway event, when adjacent battery cells do not reach above 130°C, 135°C, 140°C, 145°C or 150°C.

[0042] As used herein, “stopping” a thermal runaway event refers to the overheating of a battery cell only causing adjacent battery cells (i.e. , three, two or even only one battery cell away on either side of the overheating battery cell) to overheat and the remaining battery cells in the battery module or assembly do not overheat.

[0043] As used herein, “slowing down” a thermal runaway event refers to the thermal runaway event being slowed down at least long enough to allow personnel adjacent to the battery module or assembly (e.g., an occupant inside of an electric vehicle passenger compartment) to escape to a safe distance away from the battery module or assembly, before being injured by the thermal runaway event. Once a battery cell malfunctions (e.g., is on fire or overheats to the point of not functioning) and a thermal barrier is in place between battery cells, the time for any adjacent battery cells to propagate the malfunction (e.g., catching fire or overheating) is at least more than 5 minutes, and preferably more than 10 minutes or even 20 minutes.

[0044] The inorganic particles can be solid, hollow or contain multiple voids. Such particles can include, e.g., particles of unexpanded intumescent material, irreversibly or permanently expanded expandable materials (e.g., intumescent material), diatomaceous earth, inorganic aerogel material, porous ceramic (e.g., silica) material, irreversibly or permanently expanded perlite mineral, hollow ceramic or otherwise inorganic (e.g., glass) microspheres, etc. Such inorganic particles that contain voids such as, e.g., those found in irreversibly or permanently expanded vermiculite are particularly desirable. Particles of irreversibly or permanently expanded perlite mineral also contain voids, but perlite mineral is harder and less compressible than vermiculite mineral. Silica-based and other aerogel particles also contain voids.

[0045] As used herein, an irreversibly or permanently expanded expandable particle (e.g., particle of intumescent material such as vermiculite and perlite mineral) refers to a particle that has been heated to a temperature and for a time that causes the particle to irreversibly or permanently expand to at least 10% and up to 100% of its expandability, either by being preexpanded before being used to form the thermal runaway barrier, or post-expanded after it is incorporated into the single layer of nonwoven fibrous thermal insulation.

[0046] Intumescent particles (e.g., vermiculite particles) can be permanently expanded by overheating the particles to beyond the point of reversibility (e.g., in the range of from about 350°C up to about 1000°C for vermiculite). Such a permanently expanded intumescent particle (e.g., vermiculite particle) can have an expanded accordion or worm-like structure that is easier to break apart into smaller particles, compared to the same particle in its unexpanded state, because of its elongated geometry, lower density and lower mechanical stability. As the heating temperature increases, the degree of permanent expansion of the particle increases (i.e. , the particles can get larger and / or longer). It may also be desirable to use vermiculite that has been permanently expanded by a chemical treatment method (see, e.g., “Chemical Exfoliation of Vermiculite and the Production of Colloidal Dispersions”, G.F. Walker, W.G. Garrett, Science 21Apr1967: Vol. 156, Issue 3773, pp. 385-387, DOI: 10.1126 / science. 156.3773.385; and https: / / science.sciencemag.org / content / 156 / 3773 / 385.abstract).

[0047] Because they are easier to break apart in their expanded state, it can be desirable to post-expand the intumescent particles, after the unexpanded intumescent particles have been incorporated into the nonwoven fibrous thermal insulation. Even if gentle processing is employed so as not to substantially break them apart, it is believed that incorporating preexpanded intumescent particles into the nonwoven fibrous thermal insulation can still result in the expanded particles becoming oriented into the plane (i.e., x-axis, y-axis, and / or therebetween) of the insulation. For example, with pre-expanded vermiculite particles, the elongated particles can become generally aligned with the fibers in the longitudinal or downstream direction (i.e., y-axis), rather than in the thickness direction (i.e., z-axis), of the nonwoven fibrous thermal insulation.

[0048] In contrast, when they are post-expanded (i.e., after the nonwoven fibrous thermal insulation is made with unexpanded intumescent particles), the expanded intumescent particles are not oriented primarily in the plane of the insulation. Unexpanded intumescent particles typically have a more uniform structural geometry (i.e., have an aspect ratio closer to 1) compared to the same particles in its expanded state. It is believed that this more uniform structural geometry is less likely to be influenced by the alignment of the fibers during the formation of the nonwoven fibrous thermal insulation. As a result, the post-expanded intumescent 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., z-axis), in plane (i.e., x-axis, y-axis, and / or therebetween), or off-axis thereof. It is believed this difference between the orientation of pre-expanded particles versus post-expanded particles is caused by the unexpanded particles having a more uniform structural geometry than that exhibited while in their expanded state. Exemplary Embodiments (items)

[0049] The following items will serve to illustrate preferred embodiments of the present disclosure. It is understood, however, that they serve illustrative purposes and are not to be construed in a manner that would unduly limit the scope of this disclosure.

[0050] 1. A thermal runaway barrier article, comprising

[0051] (a) at least one thermal insulation layer; and at least one polymeric layer covering all external surfaces of the at least one thermal insulation layer such that the at least one thermal insulation layer mat is encapsulated by the at least one polymeric layer; wherein the at least one polymeric layer is heat-shrunk.

[0052] 2. A thermal runaway barrier article, comprising

[0053] (a) at least one thermal insulation layer; and at least one polymeric layer covering all external surfaces of the at least one thermal insulation layer such that the at least one thermal insulation layer mat is encapsulated by the at least one polymeric layer; wherein the at least one polymeric layer is wrapped around the thermal insulation layer in two directions at an angle and comprises at least one sealed area.

[0054] 3. A thermal runaway barrier article, comprising

[0055] (a) at least one thermal insulation layer); and

[0056] (b) at least one polymeric layer covering all external surfaces of the at least one thermal insulation layer such that the at least one thermal insulation layer mat is encapsulated by the at least one polymeric layer; 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 sealed areas.

[0057] 4. The thermal runaway barrier article according to any one of the preceding items, wherein the at least one polymeric film comprises at least one polymeric material selected from polyolefins, polyvinylchloride, ethylene-vinyl acetate copolymer, preferably from polyolefins.

[0058] 5. The thermal runaway barrier article according to item 4, wherein the polyolefins are selected from low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and high-density polyethylene (HDPE).

[0059] 6. The thermal runaway barrier article according to any one of the preceding items, wherein the polymeric film forms a sealed pouch comprising sealed areas on four sides, on three sides, or on two sides. The thermal runaway barrier article according to item 6, wherein the polymeric film forms a sealed pouch comprising heat-sealed areas on two sides, preferably wherein the sealed pouch further comprises a seal in the center of the pouch. The thermal runaway barrier according to any one of the preceding items, wherein the at least one sealed area is a lap seam or a peel seam. The thermal runaway barrier article according to any one of the preceding items, wherein the at least one sealed area is a heat-sealed area, an ultrasonically welded area, or an adhesively bonded seal. The thermal runaway barrier article according to any one of the preceding items, wherein the at least one polymer layer is wound in a horizontal form fill seal procedure (HFFS) or in a vertical form fill seal procedure (VFFS), preferably in a vertical form fill seal procedure (VFFS). The thermal runaway barrier article according to any one of the preceding items, wherein the at least one polymer layer comprises perforations and / or vent holes. Each layer may have at least one vent hole formed therethrough that is located 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 is kept intact (i.e. , the layer of nonwoven fibrous thermal insulation remains completely, mostly or at least significantly encapsulated by the organic encapsulation layer), when the thermal runaway barrier is compressed during the assembly of the battery cell module (e.g., a stack of battery cells) or when the thermal runaway barrier heats up (e.g., during the normal operation or overheating of the adjacent battery cells). Each vent hole can be in the shape of a rectangle, circle, oval or any other shape desired or combination thereof. One or more or each vent hole can be in the form of a notch that projects from a side edge of the encapsulation towards the center of the thermal runaway barrier Alternatively, one or more or each vent hole can be formed interior of the side edge of the encapsulation and adjacent to the nonwoven thermal insulation In addition, one or more or each vent hole can be formed through the encapsulation layer on only one side of the nonwoven fibrous thermal insulation. It can also be desirable for each vent hole to be in the form of a plurality of small perforation, that are clustered together (e.g., like a screen, sieve or colander) to provide the desired exit opening area. The thermal runaway barrier has a top edge, a bottom edge and opposite side edges, and the at least one vent hole may be located along the periphery of one or both opposite side edges.

[0060] The at least one vent hole may provide an exit opening through the organic encapsulation layer having an opening area in the range of from about 2 mm2up to about 15 mm2. It is contemplated that any particular area within this range, or any narrower range within this range, could be desirable.

[0061] 12. The thermal runaway barrier article according to any one of the preceding items, wherein the article further comprises at least non-woven layer.

[0062] 13. The thermal runaway barrier article according to any one of the preceding items, wherein, the at least one non-woven layer constitutes the at least one polymeric layer or is located between the at least one polymeric layer and the at least one thermal insulation layer.

[0063] 14. The thermal runaway barrier article according to item 13, wherein the at least one non-woven layer comprises at least one non-woven fabric.

[0064] 15. The thermal runaway barrier article according to any one of items 12 to 14, wherein the at least one non-woven layer comprises at least one melt-blown non-woven material and / or spunbond non-woven material.

[0065] 16. The thermal runaway barrier article according to any one of items 12 to 15, wherein the at least one non-woven layer further comprises a filter material such as a charged material, such as a PPS active carbon filter material.

[0066] 17. The thermal runaway barrier article, wherein the at least one thermal insulation layer comprises at least one fiber mat, preferably at least one inorganic fiber mat, more preferably at least one ceramic fiber mat.

[0067] 18. The thermal runaway barrier article according to any one of the preceding items, wherein the at least heat-shrunk polymeric layer is obtained by heat shrinking at least one heat-shrinkable polymeric film.

[0068] 19. The thermal runaway barrier article according to any one of the preceding items, wherein the at least one heat-shrinkable polymer film further comprises at least one filler material, at least one fire retardant material, at least one colorant, at least one electric conductive material, and any combinations and mixtures thereof.

[0069] 20. The thermal runaway barrier article according to any one of the preceding items, wherein the at least one ceramic fiber mat is selected from woven and non-woven ceramic fiber mats, preferably from non-woven ceramic fiber mats. The inorganic fibers of the fiber matrix may 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 and silicate fiber. Glass fibers and silica fibers typically do not contain any or only nominal shot particles. PCW typically contains a max of 5% shot particles, while alkaline earth silicate (AES) fibers contain up to 60% shot particles when uncleaned and as low as about 10 - 30% minimum shot particles when cleaned). The thermal runaway barrier article according to any one of the preceding items, wherein the at least one ceramic fiber mat comprises a ceramic fiber mat matrix and thermally insulative particles dispersed within the fiber matrix. The thermal runaway barrier article according to item 21 , wherein the thermally insulative particles are selected from inorganic thermally insulative particles. The thermal runaway barrier article according to item 22, wherein the thermally insulative inorganic particles comprise particles of one or any combination of the materials selected from the group consisting of inorganic aerogel, xerogel, hollow or porous ceramic microspheres, unexpanded vermiculite, irreversibly or permanently expanded vermiculite, fumed silica, otherwise porous silica, irreversibly or permanently expanded or unexpanded perlite, pumicite, irreversibly or permanently expanded clay, diatomaceous earth, titania and zirconia. The thermal runaway barrier article according to any one of the preceding items, wherein the at least one ceramic fiber mat comprises the thermally insulative particles in an amount in the range of from 10 wt.-% to 60 wt.-%, based on the total weight of the at least one ceramic fiber mat. The thermal runaway barrier article according to any one of the preceding items, wherein the at least one thermal insulation layer has an installed thickness in the range of from about 0.5 mm up to less than 5.0 mm. The layer of nonwoven fibrous thermal insulation may have an installed (i.e. , compressed) thickness in the range of from about 0.5 mm up to less than 5.0 mm. In particular, the installed (i.e., compressed) thickness can be in the range of from about 0.5 mm up to about 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, 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 may 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,

[0070] 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 less than 5.0 mm. The installed thickness of the layer of nonwoven fibrous thermal insulation is almost always less than its uninstalled (i.e., uncompressed) thickness. The performance of the thermal runaway barrier is measured when it is in its installed (i.e., compressed) condition. The layer of nonwoven fibrous thermal insulation may have an uninstalled (i.e., uncompressed) thickness in the range of from about 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,

[0071] 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 layer of nonwoven fibrous thermal insulation is almost always greater than its installed thickness.

[0072] 26. The thermal runaway barrier article according to any one of the preceding items, wherein the at least one thermal insulation layer exhibits a basis weight in the range of from 250 g / m2to 1000 g / m2. In a particular embodiment, for example, a basis weight in the range of from about 300 g / m2up to 400 g / m2can be desirable, when the thermally insulative inorganic particles are vermiculite and the gap is about 1 mm. A basis weight of about 250 g / m2can also be desirable, when aerogel particles are used and the gap is about 1mm. When the gap is about 2.0 mm, a basis weight in the range of from about 800 g / m2up to about 1000 g / m2may be desirable, the layer of nonwoven fibrous thermal insulation has a basis weight in the range of from as low as about 250 g / m2up to as high as about 1000 g / m2. Depending on the composition of the thermal runaway barrier, it can be desirable for the basis weight to be in the range of from about 250 g / m2to about 400 g / m2(e.g., 300 g / m2, 350 g / m2) for a gap between adjacent battery cells in the range of from about 0.75 mm up to about 1.25 mm. Depending on the composition of the thermal runaway barrier, it can also be desirable for the basis weight to be in the range of from about 300 g / m2up to about 550 g / m2for a gap between adjacent battery cells in the range of from about 0.75 mm to about 2.5 mm. , and up to as high as about, For gaps between adjacent battery cells in the range of from about 2.5 mm up to less than 5.0 mm, it can be desirable for the basis weight to be in the range of from about 600 g / m2up to about 1000 g / m2(e.g., about 650 g / m2, 700 g / m2, 750 g / m2, 800 g / m2, 850 g / m2, 900 g / m2, 950 g / m2or 1000 g / m2). Desirable results have been achieved with thermal runaway barriers using thermally insulative inorganic particles of irreversibly or permanently expanded vermiculite, where the nonwoven fibrous thermal insulation has a basis weight of about 450 g / m2or 550 g / m2for a gap in the range of from about a 1.50 mm up to about 2.5 mm.

[0073] In one embodiment, the thermally insulative inorganic particles are particles of irreversibly or permanently expanded vermiculite, and the layer of nonwoven fibrous thermal insulation has a basis weight of 450 g / m2for an installed gap between adjacent battery cells in the range of from about a 1.50 mm up to about 2.5 mm. In another embodiment, the thermally insulative inorganic particles are particles of irreversibly or permanently expanded vermiculite, and the layer of nonwoven fibrous thermal insulation has a basis weight of 550 g / m2for an installed gap between adjacent battery cells in the range of from about a 1.50 mm up to about 2.5 mm 27. The thermal runaway barrier article according to any one of the preceding items, wherein the at least one thermal insulation layer has an uncompressed basis weight in the range of from 250 g / m2to 400 g / m2.

[0074] 28. The thermal runaway barrier article according to any one of the preceding items, wherein the at least one thermal insulative layer further comprises a binder dispersed within the fiber mat.

[0075] 29. The thermal runaway barrier article according to item 28, wherein the at least one binder is selected from organic binders.

[0076] 30. The thermal runaway barrier article according to item 28 or item 29, wherein the at least one organic binder is contained in the at least one thermal insulative layer in an amount in the range of from 2.5 to 10 wt.-%, based on the total weight of the at least one thermal insulative layer.

[0077] 31. The thermal runaway barrier article according to any one of the preceding items, wherein the at least one at least one ceramic fiber mat was wrapped in the at least one heat shrinkable polymeric film prior to heat shrinking.

[0078] 32. The thermal runaway barrier article according to any one of the preceding items, wherein the at least one thermal insulation layer mat is seamless encapsulated by the at least one polymeric layer.

[0079] 33. The thermal runaway barrier article according to any one of the preceding items, wherein the thermal runaway barrier article is a thermal barrier runaway article for a lithium ion battery or a solid state battery, preferably for a lithium ion battery.

[0080] 34. The thermal runaway barrier article according to any one of the preceding items, wherein the at least one thermal insulative layer passes at least the V-2 level of the LIL94 Flammability Test.

[0081] 35. A battery cell module for an electric vehicle, said battery cell module comprising:

[0082] (A) a plurality of battery cells disposed in a housing; and

[0083] (B) a plurality of thermal runaway barriers according to any one of the preceding items; wherein the battery cells a lined up in a row, with one thermal barriers being disposed between each pair of adjacent battery cells.

[0084] 36. The battery cell module according to item 35, wherein the battery cell module is a lithium ion battery cell module.

[0085] 37. A method for producing a thermal runaway barrier comprising the following steps:

[0086] (i) Providing at least one ceramic fiber mat;

[0087] (ii) Applying at polymeric film to the surface of the at least one ceramic fiber mat such that the at least one ceramic fiber mat is encapsulated by the at least one polymeric layer; and (iii) Optionally, applying heat to the polymeric film such as to effectuate heat shrinking of the polymeric film such that the at least one polymeric layer is covering all external surfaces of the ceramic fiber mat.

[0088] 38. The method according to item 37, wherein the at least one polymeric film is at least one heat shrinkable polymeric film.

[0089] 39. The method according to item 38, wherein after step (iii) the at least one ceramic fiber mat is seamless encapsulated by the at least one polymeric layer.

[0090] 40. The method according to item 38 or item 39, wherein the at least one heatshrinkable polymeric film comprises at least one heatshrinkable polymeric material selected from polyolefins, polyvinylchloride, ethylene-vinyl acetate copolymer, preferably from polyolefins.

[0091] 41. The method according to item 40, wherein the polyolefins are selected from low- density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and high- density polyethylene (HDPE).

[0092] 42. The method according to any one of items 37 to 41, wherein applying heat comprises heating in an oven, blowing with hot air, irradiating with heat sources, irradiating with light sources, and any combinations thereof.

[0093] 43. The method according to any one of items 37 to 42, wherein applying the at least one heat shrinkable polymer film in step (ii) comprises wrapping the at least one ceramic fiber mat in the at least one heat shrinkable polymer film or inserting the at least one ceramic fiber mat in a sleeve formed by the at least one heat shrinkable polymer film.

[0094] 44. The method according to any one of items 37 to 43, wherein at least one, at least two, or at least three layers of the heat shrinkable polymer film are applied to the at least one ceramic fiber mat.

[0095] 45. The method according to any one of items 37 to 44, wherein applying the at least one heat shrinkable polymer film to the at least one ceramic fiber mat is carried out by means of automatic or robotic equipment.

[0096] 46. The method according to any one of items 37 to 45, wherein the at least one heat shrinkable polymer film comprises holes and / or perforations.

[0097] 47. The method according to any one of items 37 to 46, wherein in step (iii) pressure and / or a weight load are additionally applied to at least one major surface of the at least one ceramic fiber mat encapsulated by the at least one polymeric layer during applying heat.

[0098] 48. The method according to item 37, wherein step (ii) comprises wrapping the at least one ceramic fiber mat with the at least one polymeric layer in a cross-wise manner in two directions and sealing the polymeric layer in at least one zone such that at least one seam or seal is provided.

[0099] 49. The method according to item 37, wherein step (ii) comprises wrapping the at least one ceramic fiber mat with the at least one polymeric layer in one direction and sealing the polymeric layer in at least one zone such that at least two seams or seals are provided.

[0100] 50. Use of the thermal runaway barrier article according to any one of items 1 to 35 for at least slowing down propagation of thermal runaway events in batteries, preferably for the prevention of thermal runaway events in lithium ion batteries.

[0101] 51. The use according to item 50, wherein the lithium ion battery is comprised in a vehicle such as car, bus, train, ship, or aeroplane.

[0102] 52. Use of the thermal runaway barrier article according to any one of items 1 to 35 in the manufacture of lithium ion batteries.

[0103] EXAMPLES

[0104] The following Examples have been selected merely to further illustrate features, advantages, and other details of the disclosure. It is to be expressly understood, however, that while the Examples serve this purpose, the particular ingredients and amounts used as well as other conditions and details are not to be construed in a manner that would unduly limit the scope of this disclosure.

[0105] Flammability test

[0106] The test was performed using the UL-94 standard, the Standard for safety of Flammability of Plastic Materials for Parts in Devices and Appliances testing. The UL-94 standard is a plastics flammability standard released by Underwriters Laboratories of the United States. The standard determines the material’s tendency to either extinguish or spread the flame once the specimen has been ignited. The UL-94 standard is harmonized with IEC 60707, 60695-11-10 and 60695-11-20 and ISO 9772 and 9773. A 75 mm x 150 mm sample was exposed to a 2 cm, 50W tirrel burner flame ignition source. The test samples were placed vertically above the flame with the test flame impinging on the bottom of the sample. For each sample, the time to extinguish was measured and V ratings are assigned. V ratings are a measure to extinguish along with the sample not burning to the top clamp or dripping molten material which would ignite a cotton indicator, as shown in Table 1 below. Table 1 : LIL94 classification (V rating).

[0107] Example 1 (EX1)

[0108] A thermal runaway barrier mat TRB 2000 from 3M was encapsulated with a polypropylene film having a thickness of about 25 microns in a x-wrap protocol. That is, the mat was wrapped with the film from two sides. Then it was wrapped with the film on the other two sides. After that, heat seals were formed by heating the overlapping films on the back, on the right side and on the left side of the mat. Thus, a thermal runaway barrier mat encapsulated with a polypropylene film and having seals on the back, on the right side and on the left side was obtained.

[0109] The following process settings were used:

[0110] Wrapper speed: 70 pcs / minute

[0111] Heating temperatures: back seal 185 °C, right seal 180 °C, left seal 180 °C.

[0112] Example 2 (EX2)

[0113] A thermal runaway barrier mat TRB 2000 from 3M was encapsulated with a heat-sealable PET film from Mitsubishi company (grade RHS 30 microns, transparent film) in a flow-wrap protocol. That is, the mat was wrapped with the film from two sides. Then, heat seals were formed by heating the overlapping films on the lower side, on the right side and on the left side of the mat. Thus, a thermal runaway barrier mat encapsulated with a polypropylene film and having seals on the lower side, on the right side and on the left side was obtained.

[0114] Example 3 (EX3)

[0115] A thermal runaway barrier mat TRB 2000 from 3M was wrapped in a heat-shrinkable polyolefin film having a thickness of about 15 microns. This assembly was then transferred into a heat shrink tunnel. The following process settings were used: Temperature: 120 °C Sealing time: 6 sec Shrinking time: 4 sec The heat-shrinkable film was heat-shrunken around the mat. Accordingly, a thermal runaway barrier mat encapsulated with a polypropylene film without any additional seams or seals was obtained. The article was well-wrapped and encapsulated, and exhibited some warping due to the shrinkage of the heat-shrinkable film.

[0116] Example 4 (EX4)

[0117] The experiment according to EX3 was repeated, with the difference that the heat-shrinkable polyolefin film exhibited perforations. Accordingly, a thermal runaway barrier mat encapsulated with a polypropylene film without any additional seams or seals was obtained. The article was well-encapsulated, and exhibited less warping than in EX3.

[0118] Example 5 (EX5)

[0119] The experiment according to EX5 was repeated, with the difference that a carton sheet was placed on top of the film-wrapped map during the exposure in the heat shrink tunnel, thereby applying a weight load. Accordingly, a thermal runaway barrier mat encapsulated with a polypropylene film without any additional seams or seals was obtained. The article was well- encapsulated, and exhibited less warping than in EX5.

[0120] Example 6 (EX6)

[0121] The experiment according to EX5 was repeated, with the difference instead of the carton sheet, a metal mesh was placed on top of the film-wrapped article during exposure in the heat shrink tunnel, thereby applying a weight load. Accordingly, a thermal runaway barrier mat encapsulated with a polypropylene film without any additional seams or seals was obtained. The article was well-encapsulated and did not show any warping.

[0122] Example 7 (EX7)

[0123] A thermal runaway barrier mat TRB 2000 from 3M was wrapped in a heat-shrinkable polyolefin film was wrapped with two layers simultaneously, i.e. a first layer of a heat-shrinkable polypropylene film having a thickness of about 15 microns and also having perforations, and a second layer of a non-woven fabric. The non-woven fabric was applied between the TRB mat and under the perforated, heat-shrinkable film. After that, heat shrinking was carried out as described under EX3. The article obtained thereby was well-encapsulated. No shedding of fibers through the perforations of the polymer film was observed.

[0124] This disclosure may take on various modifications and alterations without departing from its spirit and scope. For example, it is believed that microwave heating can be used to irreversibly or permanently expand the particles made from intumescent materials. It is also believed that using microwave energy, rather than baking in an oven, can result in a more uniform expansion of the intumescent particles within the fiber matrix. Accordingly, this disclosure is not limited to the above-described but is to be controlled by the limitations set forth in the following embodiments and any equivalents thereof. This disclosure may 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 incorporated by reference into this document in total.

Claims

What is claimed is:

1. A thermal runaway barrier article, comprising(a) at least one thermal insulation layer; and(b) at least one polymeric layer covering all external surfaces of the at least one thermal insulation layer such that the at least one thermal insulation layer mat is encapsulated by the at least one polymeric layer; wherein the at least one polymeric layer is heat-shrunk, or wherein the at least one polymeric layer is wrapped around the thermal insulation layer in two directions at an angle and comprises at least one sealed area, 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 sealed areas.

2. The thermal runaway barrier article according to claim 1 , wherein the at least one polymeric film comprises at least one polymeric material selected from polyolefins, polyvinylchloride, ethylene-vinyl acetate copolymer, preferably from polyolefins.

3. The thermal runaway barrier article according to claim 2, wherein the polyolefins are selected from low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and high-density polyethylene (HDPE).

4. The thermal runaway barrier article according to claim 1 , wherein the at least one sealed area is a heat-sealed area, an ultrasonically welded area, or an adhesively bonded seal.

5. The thermal runaway barrier article according to claim 1 , wherein the at least one polymer layer is wound in an horizontal form fill seal procedure (HFFS) or in a vertical form fill seal procedure (VFFS), preferably in a vertical form fill seal procedure (VFFS).

6. The thermal runaway barrier article according to claim 1 , wherein the at least one polymer layer comprises perforations and / or vent holes.

7. The thermal runaway barrier article according to claim 1, wherein the article further comprises at least non-woven layer.The thermal runaway barrier article according to claim 7, wherein the at least one non-woven layer constitutes the at least one polymeric layer or is located between the at least one polymeric layer and the at least one thermal insulation layer. The thermal runaway barrier article according to claim 1 , wherein the at least one thermal insulation layer comprises at least one fiber mat, preferably at least one inorganic fiber mat, more preferably at least one ceramic fiber mat. The thermal runaway barrier article according to claim 1 , wherein the at least heat- shrunk polymeric layer is obtained by heat shrinking at least one heat-shrinkable polymeric film. The thermal runaway barrier article according to claim 9, wherein the at least one ceramic fiber mat is selected from woven and non-woven ceramic fiber mats, preferably from non-woven ceramic fiber mats. The thermal runaway barrier article according to claim 9, wherein the at least one ceramic fiber mat comprises a ceramic fiber mat matrix and thermally insulative particles dispersed within the fiber matrix. The thermal runaway barrier article according to claim 12, wherein the thermally insulative inorganic particles comprise particles of one or any combination of the materials selected from the group consisting of inorganic aerogel, xerogel, hollow or porous ceramic microspheres, unexpanded vermiculite, irreversibly or permanently expanded vermiculite, fumed silica, otherwise porous silica, irreversibly or permanently expanded or unexpanded perlite, pumicite, irreversibly or permanently expanded clay, diatomaceous earth, titania and zirconia. A battery cell module for an electric vehicle, said battery cell module comprising:(A) a plurality of battery cells disposed in a housing; and(B) a plurality of thermal runaway barriers according to claim 1; wherein the battery cells a lined up in a row, with one thermal barriers being disposed between each pair of adjacent battery cells. The battery cell module according to claim 14, wherein the battery cell module is a lithium ion battery cell module. A method for producing a thermal runaway barrier comprising the following steps: (i) Providing at least one ceramic fiber mat;(ii) Applying at polymeric film to the surface of the at least one ceramic fiber mat such that the at least one ceramic fiber mat is encapsulated by the at least one polymeric layer; and(iii) Optionally, applying heat to the polymeric film such as to effectuate heat shrinking of the polymeric film such that the at least one polymeric layer is covering all external surfaces of the ceramic fiber mat. The method according to claim 16, wherein applying heat comprises heating in an oven, blowing with hot air, irradiating with heat sources, irradiating with light sources, and any combinations thereof. The method according to claim 16, wherein the at least one heat shrinkable polymer film comprises holes and / or perforations. The method according to claim 16, wherein in step (iii) pressure and / or a weight load are additionally applied to at least one major surface of the at least one ceramic fiber mat encapsulated by the at least one polymeric layer during applying heat. The method according to claim 16, wherein step (ii) comprises wrapping the at least one ceramic fiber mat with the at least one polymeric layer in a cross-wise manner in two directions and sealing the polymeric layer in at least one zone such that at least one seam or seal is provided, or wherein step (ii) comprises wrapping the at least one ceramic fiber mat with the at least one polymeric layer in one direction and sealing the polymeric layer in at least one zone such that at least two seams or seals are provided.

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