Thermal runaway barrier product with new encapsulation

Abstract

A thermal runaway barrier for mitigating thermal runaway events within a battery assembly. The thermal runaway barrier consists essentially of at least one thermal insulation layer and at least one polymer layer covering all outer surfaces of the at least one thermal insulation layer such that the at least one thermal insulation layer pad is essentially encapsulated by the at least one polymer layer. Methods of making such thermal runaway barrier articles are also provided.

Description

[0001] The present disclosure relates to a new - encapsulated barrier for at least slowing down thermal runaway events in a battery assembly (e.g., a battery assembly used in an electric vehicle). In one embodiment, the new - encapsulated barrier at least significantly slows down thermal runaway events. Additionally, the present disclosure relates to a method of using at least one polymer film to encapsulate a barrier for significantly slowing down thermal runaway events. BACKGROUND OF THE INVENTION

[0002] An electric motor used in an electric vehicle or a hybrid vehicle (e.g., an automobile) is at least partially powered by a battery. Lithium - ion batteries are commonly used for such applications and are available in three forms: prismatic cells, pouch cells, or cylindrical cells. These batteries are compactly arranged within the vehicle to save space. Sometimes, one or more of the battery cells or battery modules experience a thermal runaway event, which can cause many (if not all) of the battery cells or battery modules in the battery cell or battery module to overheat and be damaged. The industry desires to prevent, stop, or at least significantly slow down such thermal runaway events.

[0003] The industry has developed many thermal barrier elements that require multiple layers of various inorganic materials to perform such functions (see, for example, U.S. Patent 8,541,126B2).

[0004] The background description provided herein is for the purpose of generally presenting the background of the present disclosure. Within the scope of the description of this background art, the work of the presently named inventors, as well as aspects of the specification that may not otherwise be considered prior art at the time of filing, are not expressly or implicitly admitted as prior art against the present disclosure. SUMMARY OF THE INVENTION

[0005] The inventors have found that suitable thermal barrier elements can be used without multiple layers of inorganic non - metallic materials.

[0006] In one aspect of the present disclosure, a thermal runaway barrier is provided that is operably adapted to be disposed between battery cells of a battery assembly and for at least significantly slowing down thermal runaway events within the battery assembly. In a preferred embodiment, the thermal runaway barrier consists of or consists essentially of a non - woven fiber thermal insulation single layer, the non - woven fiber thermal insulation single layer including a fiber matrix of inorganic fibers, thermal insulation inorganic particles dispersed within the fiber matrix, and a binder dispersed within the fiber matrix to hold the fiber matrix together. In other embodiments, the thermal runaway barrier may further include other layers in addition to the non - woven fiber thermal insulation layer. An optional organic encapsulation layer may also be included for encapsulating the non - woven fiber thermal insulation single layer.

[0007] 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 includes 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 arranged in rows or stacks, and a thermal runaway barrier is provided between each pair of adjacent battery cells, or between a predetermined number of battery cells (e.g., after every three battery cells), or between battery modules.

[0008] In a further aspect of the present disclosure, a method for preparing a thermal runaway barrier according to the present disclosure is provided, wherein the method includes forming a nonwoven fiber thermal insulation layer using a wet-laid process or a dry-laid process.

[0009] The foregoing summary is not intended to describe every disclosed embodiment or every implementation of the present disclosure. The following description more specifically illustrates exemplary embodiments. Throughout this application, guidance is provided through lists of examples, which can be used in various combinations. In each case, the recited lists are only used as representative groups and should not be construed as exclusive lists. Detailed Description

[0010] In describing the preferred embodiments of the present disclosure, specific terms will be used for clarity. However, the present disclosure is not intended to be limited to the particular terms so selected, and each such selected term includes all technical equivalents that perform a similar function.

[0011] As used herein, the terms "preferred" and "preferably" refer to the embodiments described herein that may provide certain benefits in certain circumstances. However, in the same or other circumstances, other embodiments may also be preferred. Additionally, the recitation of one or more preferred embodiments does not imply that other embodiments are not available and is not intended to exclude other embodiments from the scope of the present disclosure.

[0012] As used herein and in the appended claims, unless the context clearly dictates otherwise, the singular forms "a" and "the" include plural referents. Thus, for example, reference to "a" or "the" component may include one or more components known to those skilled in the art or their equivalents. Additionally, the term "and / or" means one or all of the listed elements or any combination of two or more of the listed elements.

[0013] Note that the term "comprising" and its variants do not have a limiting meaning when they appear in the appended specification. In addition, "a", "an", "the", "at least one", and "one or more" are used interchangeably herein. Relative terms such as left, right, forward, backward, top, bottom, side, upper, lower, horizontal, vertical, etc. may be used herein, and if so, they are from the perspective observed in the drawings. However, these terms are only used to simplify the description and do not limit the scope of the present disclosure in any way.

[0014] References throughout this specification to "one embodiment", "certain embodiments", "one or more embodiments", or "an embodiment" mean that a particular feature, structure, material, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. Thus, the phrases (such as "in one or more embodiments", "in certain embodiments", "in one embodiment", or "in an embodiment") that appear multiple times throughout this specification do not necessarily refer to the same embodiment of the present disclosure. Where applicable, trade names are listed in all capital letters.

[0015] 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 distress means preventing, treating, or both preventing and treating further distress).

[0016] As used herein, the term "or" is generally used in its sense that includes "and / or" unless the context clearly indicates otherwise.

[0017] In addition, herein, a numerical range expressed by endpoints includes all the values contained within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.).

[0018] "Environmental conditions" mean at a pressure of 25 °C and 101.3 kPa.

[0019] Unless otherwise specified, "average" means arithmetic mean.

[0020] "Continuous" means extending across a single unified region along a given layer (a perforated sheet can be continuous);

[0021] "Curing" means exposure to radiation in any form, heating, or subjecting it to a physical or chemical reaction that results in hardening or an increase in viscosity.

[0022] "Discontinuous" means extending across multiple discrete regions along a given layer, where these discrete regions are spaced apart from each other;

[0023] "Size" refers to the longest dimension of a given object or surface.

[0024] "Substantially" means to a significant degree, such as 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%.

[0025] "Thickness" means the distance between opposite sides of a layer or multi-layer article.

[0026] A numerical range expressed by endpoints includes all numbers included in the range with increments commensurate with the accuracy indicated by the endpoints of the specified range (e.g., for a range from 1.000 to 5.000, the increment 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 otherwise expressly specified.

[0027] The term "polymer" should 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 form miscible blends.

[0028] 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 fiber thermal insulation layer, the reduction in inorganic fiber or particle shedding is significant. Preferably, the amount of inorganic fiber or particle loss is less than 5 wt% of the original fiber or particle content of the nonwoven fiber thermal insulation layer. The thinner the organic encapsulation layer (i.e., the lower the organic content of the barrier), the better the thermal test results / cold test results.

[0029] The thermal runaway barrier of the present invention can also be used between battery modules or components.

[0030] According to the present disclosure, an inorganic binder, an organic binder, or a combination of both can be useful. Examples of inorganic binders that can be used in dry-laid or wet-laid fiber processing can include silicone particles that convert to fusible silica upon heating. Organic-inorganic hybrid binders are also useful, such as, for example MQ 803TF, which is a co-hydrolysis product of tetraalkoxysilane (Q unit) and trimethylalkoxysilane (M unit). The chemical structure of MQ 803TF can be regarded as a three-dimensional network of polysilicate units, which are capped by trimethylsilyl groups. There are some residual ethoxy functional and hydroxy functional groups. The average molecular weight can be precisely controlled by the ratio of M units and Q units. This ratio is about 0.67 for MQ 803TF.

[0031] Exemplary binder fibers include bicomponent core-sheath type polymer fibers used in dry-laid processes. In wet-laid processes, ethylene vinyl acetate latex dispersion binders, bicomponent core-sheath type polymer fibers, or a combination of both can be used. When using polymer binder fibers, the binder can be activated by heating and compressing the nonwoven fiber thermal insulation material. Combinations of organic and inorganic binders can also be used.

[0032] As used herein, the term "consisting of" indicates that the claimed thermal runaway barrier only covers structures that have only the stated elements and no other elements.

[0033] As used herein, the term "consisting essentially of" indicates that the claimed thermal runaway barrier is capable of exhibiting the desired thermal insulation characteristics by using only the stated features / elements, without an additional layer of thermal insulation material. For example, the thermal runaway barrier of the present invention does not need to include another layer of other thermal insulation materials (e.g., a woven fabric or nonwoven structure of inorganic fibers). Thus, with respect to the "consisting essentially of" language, if a third-party thermal runaway barrier (e.g., a competitor's) includes all of the features / elements in the claims of this disclosure, as well as one or more additional features / elements not recited in the claims (e.g., an additional layer of inorganic fibers), and if that additional feature / element does not determine whether the thermal runaway barrier will exhibit the desired thermal insulation characteristics, then that third-party thermal runaway barrier is considered to be covered by the claims.

[0034] As used herein, the term "inorganic" refers to ceramic or otherwise non-metallic (i.e., not a metal, metal alloy, or metal composite) inorganic materials.

[0035] "Thermal runaway" is an event where a cell undergoes an exothermic chain reaction that causes an uncontrollable temperature rise in the cell. Among other reasons, the exothermic chain reaction can be caused, for example, by overheating of the cell, overvoltage of the cell, and mechanical puncture of the cell.

[0036] "Thermal propagation" is when thermal runaway of a cell causes the remaining cells in a battery pack or system to undergo thermal runaway phenomena.

[0037] A "thermal runaway event" refers to a chain reaction in which one cell in a cell container overheats, causing adjacent cells to overheat, and may explode or catch fire until the number of overheated cells reaches the critical point of propagation, resulting in the destruction of all or more than half of the cells in the module or components of the module. Factors that cause a cell to overheat include physical damage, application of overvoltage, and overheating (internal short circuit of the cell).

[0038] As the energy density of the cell increases, the temperature at which the cell begins to fail (e.g., from at least loss of its efficiency or inability to operate to ignition, combustion, or explosion) decreases. Similarly, as the energy density of the cell decreases, the temperature at which the cell begins to fail increases. For example, as the temperature rises in a controlled ramp, when the temperature reaches about 120°C to 130°C, NMC811 type cells tend to begin to fail or even explode, while when the temperature reaches about 180°C, NMC622 type cells begin to fail or even explode. For cells with lower energy density (e.g., NMC532 type cells and NMC433 type cells), the corresponding temperature is higher. For physically larger cells or when the temperature rises rapidly, heat diffusion through the 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 cell begins to fail or explode to be slightly higher. A thermal runaway barrier of the present disclosure may be required to prevent adjacent cells from reaching a temperature in the range of about 130°C to about 150°C.

[0039] As used herein, "preventing" a thermal runaway event means preventing the overheating of a single cell from causing the overheating of adjacent cells to that single cell. The barrier is considered to prevent a thermal runaway event when the adjacent cells do not reach a temperature above 130°C, 135°C, 140°C, 145°C, or 150°C.

[0040] As used herein, "stopping" a thermal runaway event means that the overheating of a cell only causes adjacent cells (i.e., three, two, or even only one cell on either side of the overheated cell) to overheat, and the remaining cells in the battery module or component do not overheat.

[0041] As used herein, "slowing down" a thermal runaway event means that the thermal runaway event is slowed down for at least long enough to allow a person adjacent to the battery module or component (e.g., an occupant inside the passenger compartment of an electric vehicle) to escape to a safe distance away from the battery module or component before being injured by the thermal runaway event. Once a cell fails (e.g., catches fire or overheats to the extent that it cannot operate properly) and there is a thermal barrier between the cells, the time for any adjacent cell 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.

[0042] The inorganic particles can be solid, hollow, or contain multiple voids. Such particles can include, for example, particles of unexpanded intumescent materials, irreversibly or permanently expanded expandable materials (such as intumescent materials), diatomaceous earth, inorganic aerogel materials, porous ceramic (such as silica) materials, irreversibly or permanently expanded perlite minerals, hollow ceramics, or other forms of inorganic (such as glass) microspheres, etc. Such inorganic particles containing voids, such as those found in irreversibly or permanently expanded vermiculite, are particularly desirable. Irreversibly or permanently expanded perlite mineral particles also contain voids, but perlite minerals are harder than vermiculite minerals and are less easily compressible. Silica-based and other aerogel particles also contain voids.

[0043] As used herein, irreversibly or permanently expanded expandable particles (such as particles of intumescent materials, such as vermiculite minerals and perlite minerals) refer to particles that have been heated to a temperature and for a time such that the particles are irreversibly or permanently expanded to at least 10% and at most 100% of their expandability, or pre-expanded before being used to form a thermal runaway barrier, or post-expanded after being incorporated into a nonwoven fiber thermal insulation monolayer.

[0044] Intumescent particles (such as vermiculite particles) can be permanently expanded by overheating the particles beyond the reversible point (e.g., for vermiculite, in the range of about 350 °C to about 1000 °C). Such permanently expanded intumescent particles (such as vermiculite particles) can have an expanded accordion or worm-like structure, which is more likely to break into smaller particles due to its elongated geometry, lower density, and lower mechanical stability compared to the same particles in their unexpanded state. As the heating temperature increases, the degree of permanent expansion of the particles increases (i.e., the particles can become larger and / or longer). It may also be desirable to use vermiculite that has been permanently expanded by a chemical treatment method (see, for example, "Chemical Exfoliation of Vermiculite and the Production of Colloidal Dispersions", G.F. Walker, W.G. Garrett, (Science) April 21, 1967: Vol. 156, No. 3773, pp. 385 - 387, DOI: 10.1126 / science.156.3773.385; and https: / / science.sciencemag.org / content / 156 / 3773 / 385.abstract).

[0045] Because they are more likely to split in their expanded state, it is desirable for the expandable particles to undergo post-expansion after the unexpanded expandable particles have been incorporated into the nonwoven fiber thermal insulation. Even with gentle processing to keep them from splitting substantially, it is believed that incorporating pre-expanded expandable particles into the nonwoven fiber thermal insulation can still cause the expanded particles to become oriented in the plane of the insulation (i.e., the x-axis, y-axis, and / or between them). For example, for pre-expanded vermiculite particles, the elongated particles can become generally aligned with the fibers in the longitudinal or downstream direction (i.e., the y-axis) of the nonwoven fiber thermal insulation rather than in the thickness direction (i.e., the z-axis).

[0046] Conversely, when they undergo post-expansion (i.e., after preparing the nonwoven fiber thermal insulation with unexpanded expandable particles), the expanded expandable particles are not primarily oriented in the plane of the insulation. The unexpanded expandable particles typically have a more uniform structural geometry (i.e., a closer aspect ratio 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 fiber alignment during the formation of the nonwoven fiber thermal insulation. As a result, the post-expanded expandable particles are more likely to be oriented isotropically within the nonwoven fiber thermal insulation. For example, with respect to 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 between them), or in an off-axis direction. It is believed that this difference in orientation between the pre-expanded particles and the post-expanded particles is caused by the unexpanded particles having a more uniform structural geometry than when in their expanded state.

[0047] Exemplary Embodiment (Project)

[0048] The following items will be used to illustrate the preferred embodiments of the present disclosure. However, it should be understood that although they are for illustrative purposes, none of the specific details are to be construed in a manner that unduly limits the scope of the present disclosure.

[0049] 1. A thermal runaway barrier article, the thermal runaway barrier article comprising:

[0050] (a) at least one thermal insulation layer; and

[0051] at least one polymer layer that covers all outer surfaces of the at least one thermal insulation layer such that the at least one thermal insulation layer pad is encapsulated by the at least one polymer layer;

[0052] wherein the at least one polymer layer is heat-shrinkable.

[0053] 2. A thermal runaway barrier article, the thermal runaway barrier article comprising:

[0054] (a) at least one thermal insulation layer; and

[0055] At least one polymer layer that covers all outer surfaces of the at least one thermal insulation layer such that the at least one thermal insulation layer pad is encapsulated by the at least one polymer layer;

[0056] Wherein the at least one polymer layer wraps the thermal insulation layer at an angle in two directions and includes at least one sealed area.

[0057] 3. A thermal runaway barrier article, the thermal runaway barrier article comprising:

[0058] (a) At least one thermal insulation layer); and

[0059] (b) At least one polymer layer that covers all outer surfaces of the at least one thermal insulation layer such that the at least one thermal insulation layer pad is encapsulated by the at least one polymer layer;

[0060] Wherein the at least one polymer layer wraps the at least one thermal insulation layer in one direction and includes at least two sealed areas.

[0061] 4. The thermal runaway barrier article according to any one of the preceding items, wherein the at least one polymer film comprises at least one polymer material selected from polyolefins, polyvinyl chloride, ethylene-vinyl acetate copolymers, preferably selected from polyolefins.

[0062] 5. The thermal runaway barrier article according to item 4, wherein the polyolefin is selected from low density polyethylene (LDPE), linear low density polyethylene (LLDPE), and high density polyethylene (HDPE).

[0063] 6. The thermal runaway barrier article according to any one of the preceding items, wherein the polymer film forms a sealed bag including sealed areas on four sides, on three sides, or on two sides.

[0064] 7. The thermal runaway barrier article according to item 6, wherein the polymer film forms a sealed bag including heat-sealed areas on two sides, preferably wherein the sealed bag further includes a seal at the center of the bag.

[0065] 8. The thermal runaway barrier according to any one of the preceding items, wherein the at least one sealed area is a lap joint or a peel joint.

[0066] 9. 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 ultrasonic welding area, or an adhesive seal.

[0067] 10. The thermal runaway barrier article according to any one of the preceding items, wherein the at least one polymer layer is wound by a horizontal form-fill-seal process (HFFS) or a vertical form-fill-seal process (VFFS), preferably by a vertical form-fill-seal process (VFFS).

[0068] 11. The thermal runaway barrier article according to any one of the preceding items, wherein the at least one polymer layer includes perforations and / or ventilation holes. Each layer may have at least one ventilation hole formed through the layer, and the at least one ventilation hole is positioned and sized to allow the expanding gas (e.g., air) contained within the thermal runaway barrier to escape from the organic encapsulation such that 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 is heated (e.g., during normal operation or overheating of an adjacent battery cell), the structural integrity of the organic encapsulation layer remains intact (i.e., the nonwoven fiber thermal insulation layer remains fully, mostly, or at least significantly encapsulated by the organic encapsulation layer). Each ventilation hole may be in a rectangular shape, a circular shape, an oval shape, or any other desired shape or a combination thereof. One or more or each ventilation hole may be in the form of a notch protruding from the side edge of the encapsulation towards the center of the thermal runaway barrier. Alternatively, one or more or each ventilation hole may be formed inside the side edge of the encapsulation and adjacent to the nonwoven thermal insulation. Additionally, one or more or each ventilation hole may be formed through the encapsulation layer only on one side of the nonwoven fiber thermal insulation. It may also be desirable for each ventilation hole to be in the form of a plurality of small perforations that are grouped together (e.g., like a sieve, a strainer, or a filter) to provide a desired outlet opening area. The thermal runaway barrier has a top edge, a bottom edge, and opposite side edges, and the at least one ventilation hole may be positioned along the perimeter of one or two opposite side edges.

[0069] The at least one ventilation hole may provide an outlet opening through the organic encapsulation layer, and the outlet opening has an opening area in the range of about 2 mm 2 to at most about 15 mm 2 . It is contemplated that any specific area within this range, or any narrower range within this range, may be required.

[0070] 12. The thermal runaway barrier article according to any one of the preceding items, wherein the article further includes at least a nonwoven layer.

[0071] 13. The thermal runaway barrier article according to any one of the preceding items, wherein the at least one nonwoven layer constitutes the at least one polymer layer, or is located between the at least one polymer layer and the at least one thermal insulation layer.

[0072] 14. The thermal runaway barrier article according to item 13, wherein the at least one nonwoven layer comprises at least one nonwoven fabric.

[0073] 15. The thermal runaway barrier article according to any one of items 12 to 14, wherein the at least one nonwoven layer comprises at least one meltblown nonwoven material and / or spunbond nonwoven material.

[0074] 16. The thermal runaway barrier article according to any one of items 12 to 15, wherein the at least one nonwoven layer further comprises a filter material, such as an electrically charged material, such as a PPS activated carbon filter material.

[0075] 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.

[0076] 18. The thermal runaway barrier article according to any one of the preceding items, wherein the at least thermally shrunk polymer layer is obtained by thermally shrinking at least one heat-shrinkable polymer film.

[0077] 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 flame retardant material, at least one colorant, at least one conductive material, and any combination and mixture thereof.

[0078] 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 ceramic fiber mats and nonwoven ceramic fiber mats, preferably from nonwoven ceramic fiber mats. The inorganic fibers of the fiber matrix are optionally selected from the group consisting of: alkaline earth silicate fibers, refractory ceramic fibers (RCF), polycrystalline wool (PCW) fibers, basalt fibers, glass fibers, and silicate fibers. Glass fibers and silica fibers typically do not contain any or only contain nominal particulates. PCW typically contains up to 5% particulates, while alkaline earth silicate (AES) fibers contain up to 60% particulates when uncleaned and as low as about 10% - 30% minimum particulates when cleaned.

[0079] 21. 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 thermal insulation particles dispersed within the fiber matrix.

[0080] 22. The thermal runaway barrier article according to item 21, wherein the thermal insulation particles are selected from inorganic thermal insulation particles.

[0081] 23. The thermal runaway barrier article according to item 22, wherein the thermally insulating inorganic particles comprise particles of one or any combination of materials selected from the group consisting of: inorganic aerogels, xerogels, hollow ceramic microspheres 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 clay, diatomaceous earth, titanium dioxide, and zirconium oxide.

[0082] 24. The thermal runaway barrier article according to any one of the preceding items, wherein the at least one ceramic fiber mat comprises thermally insulating particles in an amount in the range of 10 wt% to 60 wt% based on the total weight of the at least one ceramic fiber mat.

[0083] 25. The thermal runaway barrier article according to any one of the preceding items, wherein the installed thickness of the at least one thermal insulation layer ranges from about 0.5 mm to at most less than 5.0 mm. The installed (i.e., compressed) thickness of the nonwoven fiber thermal insulation layer can range from about 0.5 mm to at most less than 5.0 mm. Specifically, the installed (i.e., compressed) thickness can range from about 0.5 mm to at most 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 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 less than 5.0 mm. The installed thickness of the nonwoven fiber thermal insulation layer 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) state. The uninstalled (i.e., uncompressed) thickness of the nonwoven fiber thermal insulation layer can range from about 1.0 mm to at most 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 fiber thermal insulation layer is almost always greater than its installed thickness.

[0084] 26. The thermal runaway barrier article according to any one of the preceding items, wherein the at least one thermal insulation layer exhibits from 250 g / m 2 to 1000 g / m 2basis weight in the range of. For example, in certain embodiments, when the thermally insulating inorganic particles are vermiculite and the gap is about 1 mm, a basis weight of about 300 g / m 2 to up to 400 g / m 2 basis weight in the range of. When using aerogel particles and the gap is about 1 mm, a basis weight of about 250 g / m 2 may also be required. When the gap is about 2.0 mm, a basis weight in the range of about 800 g / m 2 to up to about 1000 g / m 2 may be desired. The nonwoven fiber thermal insulation layer has a basis weight in the range of as low as about 250 g / m 2 up to as high as about 1000 g / m 2 basis weight in the range of. Depending on the composition of the thermal runaway barrier, for a gap between adjacent battery cells in the range from about 0.75 mm to up to about 1.25 mm, a basis weight in the range of about 250 g / m 2 to about 400 g / m 2 (e.g., 300 g / m 2 , 350 g / m 2 ) may be required. Depending on the composition of the thermal runaway barrier, for a gap between adjacent battery cells in the range of about 0.75 mm to about 2.5 mm, a basis weight in the range of about 300 g / m 2 to up to about 550 g / m 2 may be required, and for a gap between adjacent battery cells in the range of about 2.5 mm to up to less than 5.0 mm, a basis weight in the range of about 600 g / m 2 to up to about 1000 g / m 2 may be required (e.g., about 650 g / m 2 , 700 g / m 2 , 750 g / m 2 , 800 g / m 2 , 850 g / m 2 , 900 g / m 2 , 950 g / m 2 or 1000 g / m 2 ). A thermal runaway barrier using thermally insulating inorganic particles of irreversible or permanently expanded vermiculite has achieved the desired results, where for a gap in the range of 1.50 mm to up to about 2.5 mm, the basis weight of the nonwoven fiber thermal insulation is about 450 g / m 2 or 550 g / m 2 .

[0085] In one embodiment, the thermally insulating inorganic particles are particles of irreversible or permanently expanded vermiculite, and for an installation gap between adjacent battery cells in the range of from about 1.50 mm to at most about 2.5 mm, the basis weight of the nonwoven fiber thermal insulation layer is 450 g / m 2 In another embodiment, the thermally insulating inorganic particles are particles of irreversible or permanently expanded vermiculite, and for an installation gap between adjacent battery cells in the range of from about 1.50 mm to at most about 2.5 mm, the basis weight of the nonwoven fiber thermal insulation layer is 550 g / m 2

[0086] 27. The thermal runaway barrier article according to any one of the preceding items, wherein the uncompressed basis weight of the at least one thermal insulation layer is in the range of 250 g / m 2 to 400 g / m 2 range.

[0087] 28. The thermal runaway barrier article according to any one of the preceding items, wherein the at least one thermal insulation layer further comprises a binder dispersed within the fiber mat.

[0088] 29. The thermal runaway barrier article according to item 28, wherein the at least one binder is selected from organic binders.

[0089] 30. The thermal runaway barrier article according to item 28 or item 29, wherein the at least one organic binder is included in the at least one thermal insulation layer in an amount in the range of 2.5 wt% to 10 wt% based on the total weight of the at least one thermal insulation layer.

[0090] 31. The thermal runaway barrier article according to any one of the preceding items, wherein the at least one ceramic fiber mat is wrapped in the at least one heat-shrinkable polymer film before heat shrinkage.

[0091] 32. The thermal runaway barrier article according to any one of the preceding items, wherein the at least one thermal insulation layer mat is seamlessly encapsulated by the at least one polymer layer.

[0092] 33. The thermal runaway barrier article according to any one of the preceding items, wherein the thermal runaway barrier article is a thermal runaway barrier article for a lithium-ion battery or a solid-state battery, preferably for a lithium-ion battery.

[0093] 34. The thermal runaway barrier article according to any one of the preceding items, wherein the at least one thermal insulation layer passes at least the V-2 level of the UL94 flammability test.

[0094] 35. A battery cell module for an electric vehicle, the battery cell module comprising:

[0095] (A) A plurality of battery cells, the plurality of battery cells being disposed in a housing; and

[0096] (B) A plurality of thermal runaway barriers according to any one of the preceding items;

[0097] Wherein the battery cells are arranged in rows, and a thermal barrier is provided between each pair of adjacent battery cells.

[0098] 36. The battery cell module according to item 35, wherein the battery cell module is a lithium-ion battery cell module.

[0099] 37. A method for preparing a thermal runaway barrier, the method comprising the following steps:

[0100] (i) Providing at least one ceramic fiber mat;

[0101] (ii) Applying a polymer 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 polymer layer; and

[0102] (iii) Optionally, applying heat to the polymer film to cause thermal shrinkage of the polymer film such that the at least one polymer layer covers all outer surfaces of the ceramic fiber mat.

[0103] 38. The method according to item 37, wherein the at least one polymer film is at least one heat-shrinkable polymer film.

[0104] 39. The method according to item 38, wherein after step (iii), the at least one ceramic fiber mat is seamlessly encapsulated by the at least one polymer layer.

[0105] 40. The method according to item 38 or item 39, wherein the at least one heat-shrinkable polymer film comprises at least one heat-shrinkable polymer material selected from polyolefins, polyvinyl chloride, ethylene-vinyl acetate copolymer, preferably selected from polyolefins.

[0106] 41. The method according to item 40, wherein the polyolefin is selected from low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and high-density polyethylene (HDPE).

[0107] 42. The method according to any one of items 37 to 41, wherein applying heat includes heating in an oven, blowing with hot air, irradiating with a heat source, irradiating with a light source, and any combination thereof.

[0108] 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 into a sleeve formed by the at least one heat-shrinkable polymer film.

[0109] 44. The method according to any one of items 37 to 43, wherein at least one layer, at least two layers or at least three layers of the heat-shrinkable polymer film are applied to the at least one ceramic fiber mat.

[0110] 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 using an automatic or robotic device.

[0111] 46. The method according to any one of items 37 to 45, wherein the at least one heat-shrinkable polymer film comprises pores and / or perforations.

[0112] 47. The method according to any one of items 37 to 46, wherein in step (iii), during the application of heat, a pressure and / or weight load is additionally applied to at least one major surface of the at least one ceramic fiber mat encapsulated by the at least one polymer layer.

[0113] 48. The method according to item 37, wherein step (ii) comprises wrapping the at least one ceramic fiber mat in two directions in a crosswise manner using the at least one polymer layer and sealing the polymer layer in at least one area so as to provide at least one seam or seal.

[0114] 49. The method according to item 37, wherein step (ii) comprises wrapping the at least one ceramic fiber mat in one direction using the at least one polymer layer and sealing the polymer layer in at least one area so as to provide at least two seams or seals.

[0115] 50. Use of the thermal runaway barrier article according to any one of items 1 to 35 for at least slowing down the propagation of a thermal runaway event in a battery, preferably for preventing a thermal runaway event in a lithium-ion battery.

[0116] 51. The use according to item 50, wherein the lithium-ion battery is included in a vehicle, such as a car, bus, train, ship or aircraft.

[0117] 52. Use of the thermal runaway barrier article according to any one of items 1 to 35 in the manufacture of a lithium-ion battery.

[0118] Example

[0119] The following selected embodiments are only for further illustrating the features, advantages and other details of the present disclosure. However, it should be clearly understood that although these embodiments can serve as examples, the specific components, amounts and other conditions and details used therein should not be understood in a way that unduly limits the scope of the present disclosure.

[0120] Flammability Test

[0121] This test is performed using the UL-94 standard (a standard for the flammability safety of plastic materials in parts of testing equipment and appliances). The UL-94 standard is a plastic flammability standard published by Underwriters Laboratories Inc. in the United States. This standard determines the tendency of a sample to either extinguish or spread the flame after being ignited. The UL-94 standard has been harmonized with IEC 60707, 60695-11-10 and 60695-11-20, as well as ISO 9772 and 9773. A 75 mm × 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 on 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 the extinguishing time in the case where the sample does not burn up to the top clamp or drip molten material that can ignite a cotton indicator, as shown in Table 1 below.

[0122] Table 1: UL94 Classification (V Rating) 。

[0123] UL 94 Classification V-0 V-1 V-2 How long does combustion stop within 10s 30s 30s Allow dripping of burning material (ignite cotton ball) No No Yes The sample burns completely No No No

[0124] Example 1 (EX1)

[0125] A thermal runaway barrier pad TRB 2000 purchased from 3M is encapsulated according to a cross-encapsulation scheme using a polypropylene film with a thickness of about 25 microns. That is, the pad is wrapped with the film from both sides. Then it is wrapped with the film on the other two sides. After that, heat seals are formed by heating the overlapping films on the back, right and left sides of the pad. Thus, a thermal runaway barrier pad encapsulated with a polypropylene film and having seals on the back, right and left sides is obtained.

[0126] The following process settings are used:

[0127] Encapsulator speed: 70 pcs / minute

[0128] Heating temperature: 185 °C for the back seal, 180 °C for the right seal, 180 °C for the left seal.

[0129] Example 2 (EX2)

[0130] The thermal runaway barrier pad TRB 2000 purchased from 3M was encapsulated according to a flow encapsulation scheme using a heat-sealable PET film (grade RHS 30 microns, transparent film) purchased from Mitsubishi company. That is, the pad was wrapped with the film from both sides. Then, heat seals were formed by heating the overlapping film on the lower, right, and left sides of the pad. Thus, a thermal runaway barrier pad encapsulated with a polypropylene film and having seals on the lower, right, and left sides was obtained.

[0131] Example 3 (EX3)

[0132] The thermal runaway barrier pad TRB 2000 purchased from 3M was wrapped in a heat-shrinkable polyolefin film with a thickness of about 15 microns. Then the assembly was transferred to a heat-shrink tunnel. The following process settings were used:

[0133] Temperature: 120 °C

[0134] Sealing time: 6 seconds

[0135] Shrinking time: 4 seconds

[0136] The heat-shrinkable film was heat-shrunk around the pad. Thus, a thermal runaway barrier pad 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.

[0137] Example 4 (EX4)

[0138] The experiment according to EX3 was repeated, with the difference that the heat-shrinkable polyolefin film exhibited perforations. Thus, a thermal runaway barrier pad 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.

[0139] Example 5 (EX5)

[0140] The experiment according to EX5 was repeated, with the difference that during exposure in the heat-shrink tunnel, a cardboard sheet was placed on top of the film-wrapped pad to apply a weight load. Thus, a thermal runaway barrier pad 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.

[0141] Example 6 (EX6)

[0142] Repeat the experiment according to EX5, except that during exposure in the heat shrink tunnel, a metal mesh instead of a carton sheet is placed on top of the film-wrapped article to apply a weight load. Thus, a thermal runaway barrier pad encapsulated with a polypropylene film without any additional seams or seals is obtained. The article is well encapsulated and does not show any warping.

[0143] Example 7 (EX7)

[0144] Wrap the thermal runaway barrier pad TRB 2000 purchased from 3M in a heat-shrinkable polyolefin film, using two layers for wrapping, namely a first layer of a heat-shrinkable polypropylene film with a thickness of about 15 microns and also having perforations, and a second layer of a nonwoven fabric. Place the nonwoven fabric between the TRB pads and under the perforated, heat-shrinkable film. Then, perform heat shrinkage as described according to EX3. The article thus obtained is well encapsulated. No fibers are observed to fall off through the perforations of the polymer film.

[0145] Without departing from the spirit and scope of the present disclosure, various modifications and changes can be made to the present disclosure. For example, it is believed that microwave heating can be used for irreversible or permanent expansion of particles prepared from expandable materials. It is believed that using microwave energy, instead of baking in an oven, can result in more uniform expansion of the expandable particles within the fiber matrix. Therefore, the present disclosure is not limited to the above-described embodiments, but is subject to the limitations mentioned in the following embodiments and any equivalents thereof. The present disclosure can be implemented in a suitable manner without any element not specifically disclosed in the present disclosure. All patents and patent applications cited above, including those in the background art section, are hereby incorporated by reference in their entirety.

Claims

1. A thermal runaway barrier article, the thermal runaway barrier article comprises: (a) at least one thermal insulation layer; and (b) at least one polymer layer, the at least one polymer layer covering all outer surfaces of the at least one thermal insulation layer such that at least one thermal insulation layer pad is encapsulated by the at least one polymer layer; wherein the at least one polymer layer is heat - shrinkable, or wherein the at least one polymer layer wraps the thermal insulation layer at an angle in two directions and includes at least one sealing area, or wherein the at least one polymer layer wraps the at least one thermal insulation layer in one direction and includes at least two sealing areas.

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

3. The thermal runaway barrier article according to claim 2, wherein the polyolefin is 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 sealing area is a heat - sealed area, an ultrasonic welding area, or an adhesive seal.

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

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

7. The thermal runaway barrier article according to claim 1, wherein the article further comprises at least one non - woven layer.

8. The thermal runaway barrier article according to claim 7, wherein at least one non - woven layer constitutes the at least one polymer layer, or is located between the at least one polymer layer and the at least one thermal insulation layer.

9. The thermal runaway barrier article according to claim 1, wherein the at least one thermal insulation layer comprises at least one fiber pad, preferably at least one inorganic fiber pad, more preferably at least one ceramic fiber pad.

10. The thermal runaway barrier article according to claim 1, wherein the at least heat - shrinkable polymer layer is obtained by heat - shrinking at least one heat - shrinkable polymer film.

11. The thermal runaway barrier article according to claim 9, wherein the at least one ceramic fiber pad is selected from woven ceramic fiber pads and non - woven ceramic fiber pads, preferably selected from non - woven ceramic fiber pads.

12. The thermal runaway barrier article according to claim 9, wherein the at least one ceramic fiber pad comprises a ceramic fiber pad matrix and thermal insulation particles dispersed within the fiber matrix.

13. The thermal runaway barrier article according to claim 12, wherein the thermally insulating inorganic particles comprise particles of one or any combination of materials selected from the group consisting of inorganic aerogels, xerogels, hollow ceramic microspheres 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 clay, diatomaceous earth, titanium dioxide, and zirconium oxide.

14. 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 runaway barriers according to claim 1; wherein the battery cells are arranged in rows, and wherein a thermal barrier is disposed between each pair of adjacent battery cells.

15. The battery cell module according to claim 14, wherein the battery cell module is a lithium-ion battery cell module.

16. A method for preparing a thermal runaway barrier, the method comprising the steps of: (i) providing at least one ceramic fiber mat; (ii) applying a polymer 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 polymer layer; and (iii) optionally, applying heat to the polymer film to cause thermal shrinkage of the polymer film such that the at least one polymer layer covers all outer surfaces of the ceramic fiber mat.

17. The method according to claim 16, wherein applying heat comprises heating in an oven, blowing hot air, irradiating with a heat source, irradiating with a light source, and any combination thereof.

18. The method according to claim 16, wherein the at least one heat-shrinkable polymer film comprises pores and / or perforations.

19. The method according to claim 16, wherein in step (iii), during the application of heat, a pressure and / or a weight load is additionally applied to at least one major surface of the at least one ceramic fiber mat encapsulated by the at least one polymer layer.

20. The method according to claim 16, wherein step (ii) comprises wrapping the at least one ceramic fiber mat in two directions in a crosswise manner using the at least one polymer layer and sealing the polymer layer in at least one area so as to provide at least one seam or seal, or wherein step (ii) comprises wrapping the at least one ceramic fiber mat in one direction using the at least one polymer layer and sealing the polymer layer in at least one area so as to provide at least two seams or seals.