Hybrid composite systems for battery pack enclosures with improved thermal performance

Abstract

A hybrid material housing for a battery pack is provided to mitigate or minimize thermal runaway propagation. The housing includes a composite structure that houses the battery pack and optionally includes a polymer matrix selected from the group consisting of epoxy resins, phenolic resins, polyesters, vinyl esters, and combinations thereof and a reinforcing material selected from the group consisting of glass fibers, carbon fibers, basalt fibers, aramid KEVLAR® fibers, and combinations thereof. A metal layer is disposed along an outer surface of the composite structure, which includes aluminum, steel, stainless steel, alloys, and combinations thereof. In a first mode, the metal layer contacts the composite structure, and in a second mode after exposure to a thermal load greater than or equal to about 500°C, the metal layer at least partially delaminates from the outer surface and forms an insulating air gap to define a thermal barrier. Methods of forming the hybrid material housing are also provided.

Description

Technical Field

[0001] This invention relates to a hybrid composite material system for battery pack housings with improved thermal performance. Background Technology

[0002] This section provides background information relating to this disclosure, which is not necessarily prior art.

[0003] This disclosure relates to a casing or cover for an electrochemical cell / cell pack that provides a thermal barrier to reduce or minimize thermal runaway propagation events.

[0004] Advanced energy storage devices and systems are needed to meet the energy and / or power requirements of various products, including automotive products such as start-stop systems (e.g., 12V start-stop systems), battery auxiliary systems, hybrid electric vehicles (“HEVs”), and electric vehicles (“EVs”). Lithium-ion electrochemistry, or battery packs, typically comprises multiple cells electrically connected in a stack to increase total output. Specifically, battery pack cells may include alternating positive and negative electrodes and separators disposed therebetween to define the stack. These battery pack cells thus form battery pack modules. These modules can be assembled into battery packs, which are housed in a casing or battery pack housing or cover.

[0005] To reduce weight and improve weight efficiency, the battery pack casing or cover can be formed from reinforced composite materials instead of metal. However, it would be advantageous if the casing had a thermal barrier or self-extinguishing behavior to prevent the combustion of the reinforced composite material during a thermal runaway propagation (TRP) event. Summary of the Invention

[0006] This section provides a general overview of this disclosure and is not a full disclosure of its complete scope or all its features.

[0007] This disclosure relates to a hybrid material housing for a battery pack used to mitigate or minimize the propagation of thermal runaway. In some aspects, the housing includes a composite structure defining an inner surface and an outer surface. The composite structure includes a polymer matrix and a reinforcing material distributed therein, and the composite structure has a first coefficient of thermal expansion. The hybrid material housing also includes a metal layer disposed along the outer surface of the composite structure. In a first operating mode, the metal layer contacts the composite structure. In a second operating mode, after exposure to a thermal load greater than or equal to about 500°C, the metal layer at least partially delaminates from the outer surface and forms an insulating air gap to define a thermal barrier.

[0008] In one aspect, the metal layer comprises materials selected from steel, stainless steel, aluminum, alloys, and combinations thereof.

[0009] In one aspect, the metal layer has a thickness greater than or equal to about 0.02 mm and less than or equal to about 0.5 mm. The composite structure has a thickness greater than or equal to about 1.5 mm and less than or equal to about 4 mm.

[0010] In one aspect, the polymer matrix is ​​selected from epoxy resin, phenolic resin, polyester, vinyl ester and combinations thereof, and the reinforcing material is selected from glass fiber, carbon fiber, basalt fiber, aramid fiber and combinations thereof.

[0011] In one aspect, the reinforcing material is present in the composite structure at a volume percentage greater than or equal to about 25% to less than or equal to about 70% by volume, and the polymer matrix is ​​present in the composite structure at a volume percentage greater than or equal to about 30% to less than or equal to about 75% by volume.

[0012] In one aspect, the composite structure further comprises: (i) at least one thermal barrier material distributed within a polymer matrix, (ii) at least one surface layer comprising a thermal barrier material distributed therein, or (i) and (ii).

[0013] In a further aspect, at least one thermal barrier material is selected from: expanded graphite, ammonium polyphosphate (APP), alumina trihydrate (ATH), and combinations thereof.

[0014] In a further aspect, the composite structure includes (i) at least one thermal barrier material distributed within a polymer matrix. The at least one thermal barrier material is present in the composite structure at a weight percentage greater than or equal to about 3% by weight and less than or equal to about 30% by weight.

[0015] In one aspect, the metal layer includes a coating comprising a thermal barrier material.

[0016] In a further aspect, the coating comprises expanded graphite.

[0017] In one aspect, the hybrid material housing further includes an adhesive disposed between the outer surface of the composite structure and the metal layer. The adhesive has a ductility value of greater than or equal to about 2% and less than or equal to about 20% at temperatures above about 200°C.

[0018] In one aspect, the hybrid material housing further includes an adhesive disposed between the outer surface of the composite structure and the metal layer.

[0019] In a further aspect, the adhesive comprises expanded graphite.

[0020] This disclosure also relates to a hybrid material housing for a battery pack used to mitigate or minimize the propagation of thermal runaway. The hybrid material housing includes a composite structure defining an inner and an outer surface. The composite structure comprises a polymer matrix selected from epoxy resins, phenolic resins, polyesters, vinyl esters, and combinations thereof, and a reinforcing material selected from glass fibers, carbon fibers, basalt fibers, aramid fibers, and combinations thereof distributed within the polymer matrix. The hybrid material housing also includes a metal layer disposed along the outer surface of the composite structure. The metal layer is selected from aluminum, steel, stainless steel, alloys, and combinations thereof. In a first operating mode, the metal layer contacts the composite structure. In a second operating mode, after exposure to a thermal load greater than or equal to about 500°C, the metal layer at least partially delaminates from the outer surface and forms an insulating air gap to define a thermal barrier. Furthermore, in the second operating mode, the composite structure remains intact and free of any openings.

[0021] In one aspect, the composite structure further comprises: (i) at least one thermal barrier material distributed within a polymer matrix, (ii) at least one surface layer comprising the thermal barrier material distributed therein, or (i) and (ii).

[0022] In a further aspect, the at least one thermal barrier material is selected from: expanded graphite, ammonium polyphosphate (APP), alumina trihydrate (ATH), and combinations thereof.

[0023] In one aspect, the composite structure comprises (i) at least one thermal barrier material distributed within a polymer matrix. The at least one thermal barrier material is present in the composite structure at a concentration greater than or equal to about 3% by weight and less than or equal to about 30% by weight.

[0024] In one aspect, the metal layer comprises a coating containing expanded graphite.

[0025] In one aspect, the hybrid material housing further includes an adhesive disposed between the outer surface of the composite structure and the metal layer. The adhesive (i) has a ductility value greater than or equal to about 2% and less than or equal to about 20% at temperatures above about 200°C.

[0026] This disclosure further relates to a method for forming a hybrid material shell for a battery pack used to mitigate or minimize the propagation of thermal runaway. The method includes disposing a metal layer into a cavity of a mold. The method further includes disposing a reinforcing material and a polymer or polymer precursor adjacent to the metal layer into the cavity of the mold. The polymer or precursor is cured to form a composite material comprising a polymer matrix having the reinforcing material disposed therein. The mold is opened to remove the hybrid material shell of the battery pack, which includes a composite structure formed of the composite material and has an integrally formed metal layer adjacent thereto.

[0027] In one aspect, after the reinforcing material is applied, the method further includes at least one of the following: heating the mold and applying pressure to the mold to compress it.

[0028] The present invention discloses the following solutions: Option 1. A hybrid material housing for a battery pack used to mitigate or minimize thermal runaway propagation, the housing comprising: A composite structure defining an inner surface and an outer surface, wherein the composite structure comprises a polymer matrix and reinforcing materials distributed therein, and the composite structure has a first coefficient of thermal expansion; and A metal layer disposed along the outer surface of the composite structure, wherein in a first operating mode the metal layer contacts the composite structure, and in a second operating mode after exposure to a heat load greater than or equal to about 500°C, the metal layer at least partially separates from the outer surface layer and forms an insulating air gap to define a thermal barrier.

[0029] Option 2. The hybrid material shell according to Option 1, wherein the metal layer comprises a material selected from steel, stainless steel, aluminum, alloys and combinations thereof.

[0030] Option 3. The hybrid material shell according to Option 1, wherein the metal layer has a thickness greater than or equal to about 0.02 mm to less than or equal to about 0.5 mm, and the composite structure has a thickness greater than or equal to about 1.5 mm to less than or equal to about 4 mm.

[0031] Option 4. The hybrid material shell according to Option 1, wherein the polymer matrix is ​​selected from: epoxy resin, phenolic resin, polyester, vinyl ester and combinations thereof, and the reinforcing material is selected from: glass fiber, carbon fiber, basalt fiber, aramid fiber and combinations thereof.

[0032] Option 5. The hybrid material shell according to Option 1, wherein the reinforcing material is present in the composite structure at a concentration greater than or equal to about 25% by volume to less than or equal to about 70% by volume, and the polymer matrix is ​​present in the composite structure at a concentration greater than or equal to about 30% by volume to less than or equal to about 75% by volume.

[0033] Option 6. The hybrid material shell according to Option 1, wherein the composite structure further comprises: (i) at least one thermal barrier material distributed within the polymer matrix, (ii) at least one surface layer comprising the thermal barrier material distributed therein, or (i) and (ii).

[0034] Option 7. The hybrid material shell according to Option 6, wherein the at least one thermal barrier material is selected from: expanded graphite, ammonium polyphosphate (APP), alumina trihydrate (ATH), and combinations thereof.

[0035] Option 8. The hybrid material shell according to Option 6, wherein the composite structure comprises (i) at least one thermal barrier material distributed within the polymer matrix, wherein the at least one thermal barrier material is present in the composite structure at a weight greater than or equal to about 3% by weight and less than or equal to about 30% by weight.

[0036] Option 9. The hybrid material shell according to Option 1, wherein the metal layer includes a coating comprising a thermal barrier material.

[0037] Option 10. The hybrid material shell according to Option 9, wherein the coating comprises expanded graphite.

[0038] Option 11. The hybrid material shell according to Option 1, further comprising an adhesive disposed between the outer surface of the composite structure and the metal layer, wherein the adhesive has a ductility value of greater than or equal to about 2% and less than or equal to about 20% at a temperature above about 200°C.

[0039] Option 12. The hybrid material shell according to Option 1, further comprising an adhesive disposed between the outer surface of the composite structure and the metal layer, wherein the adhesive comprises expanded graphite.

[0040] Option 13. A hybrid material housing for a battery pack used to mitigate or minimize thermal runaway propagation, the housing comprising: A composite structure defining an inner and outer surface, wherein the composite structure comprises a polymer matrix selected from epoxy resins, phenolic resins, polyesters, vinyl esters, and combinations thereof, and a reinforcing material selected from glass fibers, carbon fibers, basalt fibers, aramid fibers, and combinations thereof distributed within the polymer matrix; and A metal layer disposed along the outer surface of the composite structure, wherein the metal layer is selected from aluminum, steel, stainless steel, alloys and combinations thereof, wherein in a first operating mode the metal layer contacts the composite structure, and in a second operating mode after exposure to a heat load greater than or equal to about 500°C, the metal layer at least partially separates from the outer surface layer and forms an insulating air gap to define a thermal barrier, and the composite structure remains intact without any openings.

[0041] Scheme 14. The hybrid material shell according to Scheme 13, wherein the composite structure further comprises: (i) at least one thermal barrier material distributed within the polymer matrix, (ii) at least one surface layer comprising the thermal barrier material distributed therein, or (i) and (ii).

[0042] Option 15. The hybrid material shell according to Option 14, wherein the at least one thermal barrier material is selected from: expanded graphite, ammonium polyphosphate (APP), alumina trihydrate (ATH), and combinations thereof.

[0043] Option 16. The hybrid material shell according to Option 13, wherein the composite structure comprises (i) at least one thermal barrier material distributed within the polymer matrix, wherein the at least one thermal barrier material is present in the composite structure at a weight greater than or equal to about 3% by weight and less than or equal to about 30% by weight.

[0044] Option 17. The hybrid material shell according to Option 13, wherein the metal layer comprises a coating containing expanded graphite.

[0045] Option 18. The hybrid material housing according to Option 13, further comprising an adhesive disposed between the outer surface of the composite structure and the metal layer, wherein the adhesive (i) has a ductility value of greater than or equal to about 2% and less than or equal to about 20% at a temperature above about 200°C.

[0046] Option 19. A method for forming a hybrid material casing for mitigating or minimizing the propagation of thermal runaway in a battery pack, the method comprising: The metal layer is placed into the cavity of the mold; The reinforcing material and polymer or polymer precursor are disposed adjacent to the metal layer in the cavity of the mold; The polymer or polymer precursor is cured to form a composite material comprising a polymer matrix having reinforcing materials disposed therein; and The mold is opened to remove a hybrid material shell for the battery pack, which includes a composite structure formed of the composite material and has an adjacent integrally formed metal layer.

[0047] Option 20. The method according to Option 19, wherein after setting the reinforcing material, the method further comprises at least one of: heating the mold and applying pressure to the mold to compress it.

[0048] Further applicability will become apparent from the description provided herein. The description and specific examples in this invention are intended to be illustrative only and are not intended to limit the scope of this disclosure. Attached Figure Description

[0049] The accompanying drawings described herein are for illustrative purposes only and not for all possible embodiments, and are not intended to limit the scope of this disclosure.

[0050] Figure 1It is a perspective view of an example of a composite battery pack cover or housing having a battery pack containing various components disposed therein.

[0051] Figure 2A-2B This disclosure shows a hybrid material shell for a battery pack with a composite structure and a metal layer, prepared according to certain aspects of this disclosure, for mitigating or minimizing the propagation of thermal runaway. Figure 2A In the first working mode and in Figure 2B A perspective view of the second operating mode, in which a metal layer separates from the composite structure layer in a selected area to form a thermal barrier.

[0052] Figure 3 The diagram shows a side cross-sectional view of a hybrid material shell of a battery pack having a composite structure and a metal layer, prepared according to certain aspects of this disclosure, for mitigating or minimizing the propagation of thermal runaway, in a first operating mode, and then exposed to a heat source in the form of a test torch flame to transition to a second operating mode, wherein the metal layer separates from the composite structure layer in selected areas to form a thermal barrier.

[0053] Figure 4 Showing a side cross-sectional view of yet another variation of the hybrid material casing for mitigating or minimizing thermal runaway propagation of a battery pack according to certain aspects of this disclosure, wherein a coating having a thermal barrier material is disposed on a metal layer to intersect with the composite structure.

[0054] Throughout the several views in the accompanying drawings, the corresponding reference numerals refer to the respective components. Detailed Implementation

[0055] Exemplary embodiments are provided to make this disclosure complete and to fully communicate its scope to those skilled in the art. Numerous specific details, such as examples of specific compositions, components, apparatuses, and methods, are set forth to provide a full understanding of embodiments of this disclosure. It will be apparent to those skilled in the art that specific details are not required, that exemplary embodiments may be presented in many different forms, and that none of them should be construed as limiting the scope of this disclosure. In some exemplary embodiments, well-known methods, well-known apparatus structures, and well-known techniques are not described in detail.

[0056] The terminology used herein is for the purpose of describing particular exemplary embodiments only and is not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “the” are intended to include the plural forms as used herein. The terms “comprising,” “including,” “covering,” and “having” are concurrent and thus specify the presence of the stated features, elements, compositions, steps, integers, operations, and / or components, but do not exclude the presence or inclusion of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. Although the open-ended term “comprising” should be understood as a non-limiting term used to describe and claim the various embodiments described herein, in some respects it may be understood alternatively to more restrictive and limiting terms such as “consisting of” or “substantially consisting of.” Thus, for any given embodiment recounting a composition, material, component, element, feature, integer, operation, and / or method step, this disclosure also specifically includes embodiments consisting of or substantially consisting of such recounted compositions, materials, components, elements, features, integers, operations, and / or method steps. In the case of “consisting of…”, the alternative embodiments exclude any additional compositions, materials, components, elements, features, integers, operating and / or method steps. In the case of “essentially composed of…”, any additional compositions, materials, components, elements, features, integers, operating and / or method steps that substantially affect the essential and novel characteristics are excluded from such embodiments. However, any compositions, materials, components, elements, features, integers, operating and / or method steps that do not substantially affect the essential and novel characteristics may be included in the embodiments.

[0057] Any methods, procedures, and operations described herein should not be construed as requiring them to be performed in a specific order as discussed or illustrated, unless explicitly stated otherwise. It should also be understood that additional or alternative steps may be used unless otherwise stated.

[0058] When a component, element, or layer is mentioned as being “on,” “engaged,” “connected,” or “coupled” to another component or layer, it may be directly engaged, connected, or coupled to the other component, element, or layer, or an intermediary element or layer may be present. In contrast, when an element is mentioned as being “directly on,” “directly engaged,” “directly connected,” or “directly coupled” to another component or layer, an intermediary element or layer may not be present. Other terms used to describe relationships between elements should be interpreted similarly (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and / or” includes any and all combinations of one or more of the related enumerations.

[0059] Although the terms first, second, third, etc., may be used herein to describe various steps, elements, components, regions, layers, and / or sections, these steps, elements, components, regions, layers, and / or sections should not be limited by these terms unless otherwise stated. These terms may be used only to distinguish one step, element, component, region, layer, or section from another. Unless the context clearly indicates otherwise, terms such as “first,” “second,” and other numerical terms used herein do not imply order or sequence. Therefore, the first step, element, component, region, layer, or section discussed below may be referred to as the second step, element, component, region, layer, or section without departing from the teachings of the exemplary embodiments.

[0060] For ease of description, spatially or temporally relative terms such as “before,” “after,” “inner,” “outer,” “below,” “below,” “lower,” “above,” “upper,” etc., may be used herein to describe the relationship of one element or feature as shown in the accompanying drawings to other elements or features(s). In addition to the orientations shown in the accompanying drawings, spatially or temporally relative terms may be intended to cover different orientations of the apparatus or system during use or operation.

[0061] Throughout this disclosure, numerical values ​​represent approximate measurements or range limits to cover slight deviations from a given value and embodiments that substantially have the mentioned value as well as embodiments that precisely have the mentioned value. Except in the detailed description of the working examples provided at the end, all numerical values ​​of parameters (e.g., quantities or conditions) in this specification (including the appended claims) should be understood to be modified in all cases by the term “about,” regardless of whether “about” actually precedes the numerical value. “About” means that the numerical value allows for a certain degree of slight imprecision (approaching the exact value to a certain extent; substantially or reasonably approximating the value; almost). If the imprecision provided by “about” is not otherwise understood in this ordinary sense in the art, then “about” as used herein refers to at least a deviation that can be caused by ordinary methods of measuring and using such parameters. For example, “about” may include deviations of less than or equal to 5%, optionally less than or equal to 4%, optionally less than or equal to 3%, optionally less than or equal to 2%, optionally less than or equal to 1%, optionally less than or equal to 0.5%, and in some respects optionally less than or equal to 0.1%.

[0062] In addition, the disclosure of the range includes disclosure of all values ​​throughout the range and disclosure of further subdivisions of the range, including disclosure of the endpoints and subranges given by the range.

[0063] Exemplary embodiments will now be described more fully with reference to the accompanying drawings.

[0064] In various respects, this disclosure provides a housing or enclosure for a battery pack to mitigate or minimize the propagation of thermal runaway. The housing is generally understood as a rigid physical structure that houses multiple electrochemical cells to form multiple modules within a battery pack. The housing protects the battery pack and any other internal components from external environmental factors, including external forces. The housing may also be referred to as a cover or enclosure. Notably, the concepts described herein can be used to form other protective structures that enclose other sub-components within the battery pack.

[0065] Figure 1 This illustration shows a non-limiting example of a battery pack housing 20 for a lithium-ion battery pack. The housing has an outer surface 22 and an inner surface 24 facing the internal compartment 26. The housing 20 can be an assembly of discrete components or parts to connect them together to define a protective structure encapsulating the internal components, such as a lower tray cover 28 and an upper battery pack cover 30. This technology envisions that at least the upper battery pack cover 30 is formed of a hybrid material, as further described below.

[0066] The battery pack 32 is housed in the internal compartment 26, which includes one or more battery modules 34 (for illustration purposes, in...). Figure 1 Only a single module is shown, but as those skilled in the art will recognize, multiple modules may actually exist within the battery pack 32. Each battery pack module 34 typically includes multiple battery cells 36 (which may be provided in sub-assemblies of stacks or blocks), which may be housed in frames or other structures within the individual battery pack module 34 to resist external forces or heat. Any number of batteries, blocks, and / or battery pack modules can be selected and connected to the positive or negative source terminals. Batteries, blocks, and battery pack modules can be connected: in series and / or in parallel; in different connection configurations; and can be organized into packs and / or groups. The battery cells 36 and(one or more) modules 34 can be connected via a battery management system (BMS - not shown). Figure 1 The system provides connectivity and control, facilitating the control and management of various aspects of battery pack operation, including power output, voltage, current, temperature, SOX, etc. The battery pack housing 20 thus encloses the battery pack 32, which in turn includes one or more battery pack modules 34, a BMS, and an optional cooling system (not shown). These, along with any other electrical conduits or conventional components such as busbars, circuitry, and terminal sections for external connections to loads and power sources, are contained within the internal compartment 26 of the battery pack housing 20.

[0067] In various respects, this disclosure includes a battery pack housing for mitigating or minimizing thermal runaway propagation (TRP), which can be an uncontrolled, high-temperature thermal event, including conflict or fire. As mentioned herein, such TRP events can be caused by excessive heat loads exceeding the normal operating temperature range. For example, a short circuit within the battery pack can lead to TRP. For example, the heat source or flame source in a thermal runaway propagation event may exceed about 500°C, optionally about 600°C, optionally about 700°C, optionally about 800°C, optionally about 900°C, optionally about 1,000°C, optionally about 1,100°C, and optionally exceed about 1,200°C. The heat source or flame source may originate from the internal compartments of the battery pack housing or module. The housing comprises a composite structure formed of a polymer composite material containing a polymer matrix and reinforcing materials (e.g., multiple particles or fibers) distributed therein. The composite material may therefore have reinforcing materials or fillers in the form of fibers or particles dispersed in the polymer matrix.

[0068] The polymer matrix can be formed from any kind of suitable precursor or resin. For example, thermosetting resins are cured from liquid precursors to form polymers. For thermoplastic polymer matrix materials, the polymer is melted into a liquid state or dissolved in a solvent to form a solution, which is then incorporated with fibers to form a composite material. As a non-limiting example, in some variations, the polymer matrix precursor may include: epoxy resins (in which hydroxyl groups, such as bisphenol A and bisphenol B, react with epichlorohydrin), phenolic resins (phenolic resins can be formed by reacting phenols or substituted phenols with formaldehyde), polyesters, vinyl esters, and combinations thereof.

[0069] Suitable, non-limiting examples of reinforcing fibers for polymer composites include carbon fibers, glass fibers (e.g., glass or quartz fibers), basalt fibers, and aramid fibers, such as KEVLAR. TM The fiber supplier purchases aramid or para-aramid fibers, and combinations thereof, from DuPont. The fiber can be a single fiber continuously or randomly distributed within a resin matrix, or provided as a fiber mat or fabric with interconnected or contacting fibers. Suitable fibers may include chopped or continuous fibers. In some respects, the fiber can be a relatively short fiber (having a length ≥ about 0.1 mm to ≤ about 10 mm), a relatively long fiber (having a length ≥ about 10 mm to ≤ about 100 mm), or a continuous fiber (having a length ≥ about 100 mm), and may include any combination thereof. Long-length fibers provide a good balance of plasticity / productivity / mechanical properties.

[0070] Fibers within polymer composites can be of random orientation, such as essentially two-dimensional random orientation or oriented in a specific direction (e.g., anisotropy). In some variations, fiber mats, or combinations thereof, with fibers having a high degree of planar or unidirectional orientation, can be used. Alternatively, random fiber mats can be used.

[0071] In some respects, continuous or discontinuous glass fibers can be used in polymer composites. In other respects, continuous or discontinuous carbon fibers can be used in polymer composites, which may have a yield strength of more than or equal to about 4,000 MPa to less than or equal to about 5,000 MPa.

[0072] The reinforcing material (e.g., fiber) may be present in the polymer composite in an amount greater than or equal to about 25 vol% to less than or equal to about 70 vol%, optionally greater than or equal to about 35 vol% to less than or equal to about 60 vol%, wherein the polymer matrix may be present in an amount greater than or equal to about 30 vol% to less than or equal to about 75 vol%, optionally greater than or equal to about 40 vol% to less than or equal to about 70 vol%. In some aspects, the reinforcing material may be uniformly distributed within the polymer matrix.

[0073] Fiber-reinforced composites may further contain other conventional components, including other reinforcing materials, functional fillers or additives, such as organic / inorganic fillers, flame retardants, UV stabilizers, antioxidants, colorants or pigments such as carbon black powder, release agents, softeners, plasticizers, surfactants, etc.

[0074] In one variant, the composite material comprises an epoxy resin having glass and / or carbon fibers distributed therein as reinforcement. In another variant, the composite material comprises a phenolic resin having glass and / or carbon fibers distributed therein as reinforcement. Phenolic resins exhibit high heat resistance and low flammability, which is advantageous when used as a thermal barrier in composite materials according to certain aspects of this disclosure. However, without some modifications contemplated by this teaching, composite materials reinforced with phenolic resin alone may be insufficient to withstand composite burn-through under certain conditions.

[0075] In some other variations, the reinforcement can be a sheet molding compound (SMC), which typically comprises a glass fiber reinforced thermosetting polymer composition. In some aspects, the composite material can be a sheet molding compound (SMC) having multiple fibers impregnated with phenolic resin.

[0076] In other respects, the polymer composite structure may consist of any fiber-reinforced composite material disclosed in U.S. Patent Nos. 9,650,003, 9,592,853 and U.S. Publication No. 2015 / 0108793, each of which is incorporated herein by reference in its entirety.

[0077] According to certain aspects of this disclosure, in addition to including the aforementioned reinforcing materials to provide mechanical strength to the composite material, the composite material may also include one or more thermal barrier materials that enhance thermal barrier properties, such as intumescent or flame-retardant materials. Intumescent materials are generally those materials that swell or increase in volume when exposed to high temperatures, such as flames, which helps to prevent or reduce heat transfer through them. For example, by increasing in volume, intumescent materials can block the oxygen flow required for flame propagation. In some variations, suitable intumescent materials may be expandable graphite. In another variation, flame-retardant materials may be included in the composite material, which similarly helps to slow or inhibit the spread of fire and flame. Suitable flame-retardant materials include ammonium polyphosphate (APP), alumina trihydrate (ATH), and combinations thereof. Therefore, in some aspects, the polymeric material includes a thermal barrier material selected from expandable graphite, ammonium polyphosphate (APP), alumina trihydrate (ATH), and combinations thereof. The thermal barrier material may be incorporated into the polymeric composite material in an amount greater than or equal to about 3% by weight volume fraction to less than or equal to about 30% by weight volume fraction, optionally greater than or equal to about 3% by weight volume fraction to less than or equal to about 20% by weight volume fraction. In this case, when thermal barrier materials are added, the weight volume fraction of the reinforcing fibers will be reduced accordingly. Therefore, the volume fraction of the resin is maintained at the previously specified level, for example, greater than or equal to about 30% to less than or equal to about 75%.

[0078] In other variations, thermal barrier materials may be applied as coatings to one or more surfaces of a composite structure comprising the composite material. For example, thermal barrier materials, such as intumescent materials, may be mixed with an adhesive and applied as a layer to the surface of the composite material to define an intumescent coating. Suitable adhesives may include thermoplastic adhesives, such as polyesters, or thermosetting adhesives, such as epoxy resins.

[0079] In some respects, this disclosure envisions a battery pack casing as an assembly of different materials with different coefficients of thermal expansion, such as Figure 2A-2B And those shown in 3. In this way, as will be further described herein, the assembly creates a strategic separation and / or delamination between different materials (e.g., between the composite structure and the metal surface) during a battery thermal runaway propagation (TRP) event, thereby generating a flame-retardant thermal barrier at the interface, effectively reducing the temperature on the back side of the metal plate or layer.

[0080] For example, Figure 2A and 3Assembly 100 includes a composite structure 110 that defines an internal compartment facing the battery pack. Figure 1 The internal compartment 26 shown has an inward first surface 112 and an outward second surface 114. During a TRP event, a heat source may be present in the battery pack and thus originate from the internal compartment. In the assembly 100, the composite structure 110 will therefore be in direct contact with the heat source. This composite structure may be formed from a composite material as described above, comprising a polymer matrix and reinforcing materials distributed therein. The composite structure has a first coefficient of thermal expansion. In some aspects, the first coefficient of thermal expansion (CTE) / first linear coefficient of thermal expansion (CLTE) of the composite structure may be greater than 0 to less than or equal to 10 x 10⁻⁶ in the fiber direction (when the fibers are aligned). -6 And approximately 30 x 10 in the horizontal direction. -6 Up to 50 x 10 -6 Typically, the coefficient of thermal expansion in composite materials depends on orientation, being lower in directions parallel to fiber orientation and higher in those orthogonal to or perpendicular to fiber orientation.

[0081] The thickness of the composite layer can be greater than or equal to about 1.5 mm to less than or equal to about 4 mm. For example, glass or carbon fiber epoxy composites can have a thickness greater than or equal to about 1.5 mm to less than or equal to about 4 mm. Sheet molding compounds having glass or carbon fiber and phenolic resin can have a thickness greater than or equal to about 2.5 mm to less than or equal to about 4 mm.

[0082] Assembly 100 also includes a metal layer 120 disposed along the outward second surface 114 of the composite structure 110 (and thus on the exposed side opposite to the internal compartment of the housing), wherein the metal layer 120 has a second coefficient of thermal expansion (CTE) / linear coefficient of thermal expansion (CLTE) different from the first coefficient of thermal expansion (CLTE). Typically, metallic materials are substantially isotropic in terms of CLTE. According to this teaching, maximizing the CLTE difference between the various components of the composite structure and the metal layer results in strategic delamination of the linear coefficients of thermal expansion of the metal and composite material measured in two orthogonal directions.

[0083] For example, the second CLTE of the metal can be placed side-by-side with and compared to the highest CLTE of the composite structure to obtain the maximum difference in CLTE. For instance, the CLTE difference (Δα) can be calculated in a specific direction using the following equation: Δα = (α mi -α ci), where α is the CLTE in a predetermined direction, i is 1, 2; m is a metal, and c is a composite material. In some aspects, the metal layer may comprise aluminum, steel, stainless steel, and any alloy or combination thereof. The second linear coefficient of thermal expansion (CLTE) of aluminum is 2.1 x 10⁻⁶. -6 Up to 2.4 x 10 -6 The steel CLTE is 1.1 x 10 -6 Up to 1.3 x 10 -6 In this way, the maximum difference between the coefficients of thermal expansion of the various components of the metal and composite material, measured in two orthogonal directions, in various aspects of this technology contributes to the generation of strategic delamination.

[0084] The metal layer can be a foil or a thin layer. The thickness of the metal layer can be greater than or equal to about 0.02 mm to less than or equal to about 0.5 mm. For example, an aluminum layer can have a thickness greater than or equal to about 0.1 mm to less than or equal to about 0.5 mm. A steel layer can have a thickness greater than or equal to about 0.02 mm to less than or equal to about 0.1 mm.

[0085] The metal plate 120 can be bonded to the outward second surface 114 of the composite structure 110 or integrally formed with the composite structure 110. In some respects, although in Figure 3 Not shown, but an adhesive may be used to bond the outward second surface 114 of the composite structure 110 to the metal layer 120. In some variations, the adhesive has low ductility at high temperatures, for example, a ductility value of about 2% to about 20% at temperatures above about 200°C. The adhesive may contain one or more expandable materials, such as expanded graphite as discussed above, which can increase in volume when exposed to excessive heat loads. In this way, the adhesive promotes a desired amount of delamination during thermal events. In some aspects, the adhesive may be an epoxy adhesive or a polyurethane adhesive. Low-ductility adhesives are chosen so that they are prone to failure at elevated temperatures during TRP events. The adhesive may be applied to coat the entire outward second surface 114 or may be applied discontinuously, such as in the form of lines, grids, dots, etc. As will be further described below, in some forming methods, the metal layer may be alternatively disposed in a mold or die, wherein the composite material is molded or formed adjacent to it, such that the two materials form an integral assembly.

[0086] Figure 2A and 3 The assembly 100 is shown in the first operating mode, wherein the metal layer 120 is in contact with the composite structure 110, and Figure 2B and 3 The heat load 130 (such as flame or as shown) on the inward first surface 112 exposed to the adjacent composite structure 110 is displayed. Figure 3As shown, after the torch (which generates the test flame as part of the torch test) is shown, the assembly 100B is in the second operating mode. As described above, the heat load 130 may have a temperature greater than or equal to about 500°C, optionally greater than or equal to about 600°C, optionally greater than or equal to about 700°C, optionally greater than or equal to about 800°C, optionally greater than or equal to about 900°C, optionally greater than or equal to about 1,000°C, optionally greater than or equal to about 1,100°C, and optionally possibly exceeding about 1,200°C. It is worth noting that the setup shown simulates the heat load 130 that may occur within the battery pack casing as it would during battery pack operation and use, such that the heat load / flame 130 first contacts the inward first surface 112 of the composite structure 110.

[0087] As described above, after exposure to heat load 130, assembly 100B is in a second operating mode, wherein metal layer 120 is at least partially delaminated from the outward second surface 114 of composite structure 110. In this way, as metal layer 120 separates from the outward second surface 114 in selected areas, for example remaining attached to the outward second surface 114 in certain anchored first regions 132, while separating and delamining in other areas, a plurality of insulating air gaps 134 are defined between the outward second surface 114 of composite structure 110 and metal layer 120 to define a thermal barrier. These plurality of insulating air gaps 134 minimize flame propagation and serve to promote protection of composite structure 110 against burn-through or reaching temperatures that would cause gaps or openings to form in composite structure 110. Furthermore, this flame-retardant thermal barrier at the interface between composite structure 110 and metal layer 120 effectively reduces the temperature on the back surface 140 of the metal layer and absorbs heat from composite structure 110. The delaminated metal layer 120 thus enhances heat dissipation. As described above, in this variant, the strategic mismatch of the coefficient of thermal expansion (CTE) between the composite structure and the metal plate maximizes the separation between the two different materials during battery thermal events to create gaps / delamination, thereby protecting the composite structure and minimizing or preventing it from being burned through (e.g., thermal loads burn the composite material to the point of forming perforations, cracks, or openings).

[0088] The thermal barrier formed by the insulating gap 134 defined between the composite structure 110 and the metal layer 120 provides higher temperature durability than prior art, for example, in some variations it can withstand torches or flames up to 1,200°C. In some prior art, the metal layer facing the interior of the battery pack housing compartment is sacrificial and may melt upon exposure to thermal loads associated with TRP events, rather than forming a thermal barrier with insulating gaps.

[0089] Furthermore, some prior art relies on three or more layers, such as a polymer substrate, one or more individual blanket layers, and a metal foil (facing the internal compartment). Such a metal foil and / or blanket layer acts as a sacrificial layer to protect the polymer structure / substrate, which performs the fire extinguishing function independently. In this art, the composite structure itself can be modified to provide the desired thermal performance even without individual blanket layers. Therefore, the hybrid material housing may be free of any blanket layers. In other variations, the hybrid material housing may be free of any sacrificial layer (except for adhesives that may melt). Furthermore, in some aspects, the battery pack housing may consist substantially of the aforementioned composite structure and metal layers, or of the aforementioned composite structure and metal layers (with or without at least one surface layer comprising a thermal barrier material distributed therein and an optional adhesive layer disposed therebetween). As mentioned above, the metal layers remain present during and after the TRP event.

[0090] Furthermore, in some prior art, gas release relies on hot gases expelled from the battery, which would cause the metal layer to contact the cover layer during a TRP event, making it unpredictable or uncertain whether any air gaps would form. In this embodiment, the metal layer is disposed on the outer side or exterior of the housing, so the expelled gases (e.g., from adhesives or composite structure release) will help form an air gap between the metal layer and the composite material, thereby reliably forming a thermal barrier. Notably, this technology maintains the temperature of the outer surface of the housing opposite the flame or torch during a TRP event, such that the metal layer opposite the flame / torch is at a below-critical temperature, and no holes or openings are formed on the surface of the housing / composite structure facing the flame / torch during the TRP event.

[0091] Other variations of the battery pack casing used to mitigate or minimize thermal runaway propagation may have Figure 2A-2B Assemblies of materials described in the context of 3, but with additional or alternative features. For example, such as Figure 4As shown, assembly 110B includes a composite structure 110 and a metal layer 120 as shown in a first operating mode, but it further modifies the interface 150 between the outward second surface 114 of the composite structure 110 and the metal layer 120 by adding a coating 152 to the metal layer 120 to further separate (not shown) during a thermal event in a second operating mode to form a thermal barrier. The coating 152 may comprise a thermal barrier material such as carbon, silicon carbide (SiC), silicon nitride (Si3N4), or a combination thereof. In other respects, the coating 152 may be applied to either the composite structure 110 or the metal layer 120. For example, a coating 152 comprising an expandable material, such as an expanded graphite layer, may be disposed on the metal layer 120. Alternatively, the coating 152 may comprise an expandable material mixed with a polymer binder and applied to the composite fiber preform to coat the outward second surface 114. It should be noted that coating 152 may be different from the adhesive used, and as mentioned above, if an adhesive is available for bonding metal layer 120 to composite structure 110, it may contain multiple particles of thermal barrier material disposed therein, such as expanded graphite expanded material.

[0092] Methods for forming hybrid material assembly housings for battery packs may include forming composite structures by compression molding, resin transfer molding, or sheet molding compound, as non-limiting examples. The composite structures may be integrally molded or molded as individual components to be joined or coupled together after the molding process.

[0093] In some aspects, a method is provided for forming a hybrid material shell for a battery pack used to mitigate or minimize the propagation of thermal runaway. The method includes depositing a metal layer into a cavity of a mold. The mold may be preheated. The method then further includes depositing a reinforcing material and a polymer or polymer precursor adjacent to the metal layer into the cavity of the mold. Notably, alternatively, the reinforcing material and polymer or polymer precursor may be placed into the mold cavity first, and then the metal layer is placed on the material. The method also includes curing the polymer or polymer precursor (e.g., curing, crosslinking, or cooling molten thermoplastic) to form a composite material comprising a polymer matrix having the reinforcing material disposed therein. The method may further include at least one of: heating the mold and applying pressure to the mold for compression. The mold can then be opened to remove the hybrid material shell of the battery pack, which comprises a composite structure formed of the composite material and has an integrally formed metal layer adjacent thereto.

[0094] In one variation, the composite structure and the metal foil or sheet can be integrally formed in a compression molding or resin transfer molding process. As background, for resin transfer molding (RTM), a dry fiber reinforcement material (in this case, with a metal foil or sheet adjacent to the dry fiber reinforcement material) can be placed in a mold, and resin can be injected into the mold under pressure (e.g., from about 10 psi to about 3,000 psi). The mold can be heated first. Injection molding techniques known in the art can also be used to introduce resin into the reinforcement material, particularly when the reinforcement material contains discontinuous fibers. For example, a precursor containing resin and reinforcement material can be injected or poured into a defined space or mold, and then the precursor can be cured to form a polymer composite material. The term "injection molding" also includes reaction injection molding using thermosetting resins. In one example, the mold can be heated to about 120°C, then the mold can be opened and the reinforcement material (e.g., reinforcing fabric or pad) can be placed in the mold with the metal layer adjacent to it. The mold can then be closed, a vacuum applied, and resin, such as epoxy or phenolic resin, injected into the mold to fill the cavity. The mold can be kept closed at 120°C for 3 minutes. The mold is then opened and the housing assembly is removed.

[0095] Another technique may involve compression molding. In some aspects, the method of compression molding the composite housing assembly may include adding a prepreg of reinforcing material and resin, along with a metal foil or plate disposed adjacent thereto, into a mold. The assembly is then placed in the cavity of the compression mold. In some variations, the compression mold and cavity may optionally be preheated. The assembly is then compression molded by applying or maintaining heat and applying pressure to form a compression-molded solidified polymer assembly. In some aspects, the assembly is retained in the compression mold until the mold cools to a predetermined temperature. The mold may be opened and the composite assembly removed from the cavity.

[0096] In some variations, the composite structure can be pre-formed using typical composite molding processes and then bonded to the metal layer in a post-forming operation. In this method, the composite material and metal foil are placed together, and an adhesive is placed between them. Furthermore, an adhesive jig is used under compression and heat to cure the adhesive and form a bond between the composite material and the metal foil. For example, methods for forming the composite structure of the shell may include compression molding, injection molding, pultrusion, resin transfer molding, molding of sheet molding compounds, autoclave molding, vacuum bagging, and hand layup, as non-limiting examples. Bonding of the metal layer / plate can be achieved by applying the adhesive to at least one surface of the composite structure and / or the metal layer. The adhesive can be applied discontinuously or continuously using techniques known to those skilled in the art. In cases where the adhesive contains a thermal barrier material, the adhesive is mixed with the thermal barrier material and then applied.

[0097] While the hybrid material assemblies for battery pack housings provided by this technology are particularly suitable for components of automobiles or other vehicles (e.g., motorcycles, boats, tractors, buses, motorcycles, trains, mobile homes, campervans, and tanks), they can also be used in a variety of other industrial and applications, including aerospace components, consumer products, devices, buildings (e.g., residences, offices, sheds, warehouses), office equipment and furniture, and industrial equipment machinery, agricultural or farm equipment, or heavy machinery, as non-limiting examples.

[0098] The above description of the embodiments has been provided for illustrative and descriptive purposes. It is not intended to be exhaustive or limiting of this disclosure. The various elements or features of a particular embodiment are generally not limited to that particular embodiment, but are interchangeable and can be used in the selected embodiment, if applicable, even if not explicitly shown or described. It can also be changed in many ways. Such variations should not be considered as a departure from this disclosure, but all such modifications are intended to be included within the scope of this disclosure.

Claims

1. A hybrid material housing for a battery pack used to mitigate or minimize thermal runaway propagation, the housing comprising: A composite structure defining an inner surface and an outer surface, wherein the composite structure comprises a polymer matrix and a reinforcing material distributed therein, and the composite structure has a first coefficient of thermal expansion; and A metal layer disposed along the outer surface of the composite structure, wherein the metal layer has a second coefficient of thermal expansion different from the first coefficient of thermal expansion, wherein in a first operating mode the metal layer contacts the composite structure, and in a second operating mode after exposure to a heat load greater than or equal to 500°C, the metal layer at least partially separates from the outer surface layer and forms an insulating air gap to define a thermal barrier.

2. The hybrid material shell according to claim 1, wherein the metal layer comprises a material selected from steel, stainless steel, aluminum, alloys, and combinations thereof.

3. The hybrid material shell according to claim 1, wherein the metal layer has a thickness of greater than or equal to 0.02 mm and less than or equal to 0.5 mm, and the composite structure has a thickness of greater than or equal to 1.5 mm and less than or equal to 4 mm.

4. The hybrid material shell according to claim 1, wherein the polymer matrix is ​​selected from epoxy resin, phenolic resin, polyester, vinyl ester and combinations thereof, and the reinforcing material is selected from glass fiber, carbon fiber, basalt fiber, aramid fiber and combinations thereof.

5. The hybrid material shell of claim 1, wherein the reinforcing material is present in the composite structure at a concentration of greater than or equal to 25% by volume to less than or equal to 70% by volume, and the polymer matrix is ​​present in the composite structure at a concentration of greater than or equal to 30% by volume to less than or equal to 75% by volume.

6. The hybrid material shell according to claim 1, wherein the composite structure further comprises: (i) at least one thermal barrier material distributed within the polymer matrix, (ii) at least one surface layer comprising the thermal barrier material distributed therein, or (i) and (ii).

7. The hybrid material shell according to claim 6, wherein the at least one thermal barrier material is selected from: expanded graphite, ammonium polyphosphate (APP), alumina trihydrate (ATH), and combinations thereof.

8. The hybrid material shell of claim 6, wherein the composite structure comprises (i) at least one thermal barrier material distributed within the polymer matrix, wherein the at least one thermal barrier material is present in the composite structure at a weight of 3% or more and less than or equal to 30% by weight.

9. The hybrid material housing of claim 1, wherein the metal layer comprises a coating containing a thermal barrier material.

10. The hybrid material shell of claim 9, wherein the coating comprises expanded graphite.

11. The hybrid material shell of claim 1, further comprising an adhesive disposed between the outer surface of the composite structure and the metal layer, wherein the adhesive has a ductility value of greater than or equal to 2% and less than or equal to 20% at a temperature above 200°C.

12. The hybrid material housing according to claim 1, further comprising an adhesive disposed between the outer surface of the composite structure and the metal layer, wherein the adhesive comprises expanded graphite.

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