Electric powertrain system with multi-module battery pack and inter-module thermal barrier

Abstract

The present invention relates to an electric powertrain system having a multi-module battery pack and an inter-module thermal barrier. A multi-module battery pack includes: a battery tray defining a plurality of battery tray compartments; battery modules each disposed within a corresponding one of the compartments; and a thermal barrier disposed in a predetermined heat transfer path between an adjacent pair of battery modules through the tray. The thermal barrier has a thickness of at least about 1 mm and a thermal conductivity of less than about 4 W / m‑K such that the thermal barrier blocks the heat transfer path to mitigate a thermal runaway event in one of the adjacent pair of battery modules. An electric powertrain system includes a rotating electrical machine having phase leads and an output member, a driven load coupled to the output member, and the multi-module battery pack. A method includes providing the tray, identifying the heat transfer path, and disposing the thermal barrier in the heat transfer path.

Description

Background Art

[0001] High-voltage electrical systems are commonly used to power onboard functions in a variety of mobile and stationary systems. For example, in motor vehicles, rechargeable energy storage systems (RESS) typically include a high-voltage battery pack comprised of a number of interconnected battery modules appropriate for the application. The electrode extensions that comprise the electrochemical cells within each battery module are conductively connected to form the battery pack. The battery pack is configured to provide a direct current (DC) output voltage at a level suitable for powering coupled electrical and / or mechanical loads, where the DC output voltage is determined by the number and electrochemical composition of the battery cells, the specific series or parallel connection used to interconnect the battery modules, and other design factors.

[0002] Particularly in automotive applications, i.e., where the coupled loads include one or more driven wheels, evolving battery technology has enabled the construction of low-profile, multi-module battery packs with high power density. For example, modern battery electric vehicles benefit from flatter, lighter-weight battery packs in which the individual battery modules are supported within a flat battery tray located below the plane of the vehicle's floor pan. The construction and positioning of such battery packs frees up valuable passenger and cargo space within the vehicle that would otherwise be occupied by the battery pack and other power electronics components of the RESS. Summary of the Invention

[0003] Disclosed herein are multi-module battery packs of the type generally described above, electric powertrain systems and motor vehicles employing the same, and methods for constructing the battery packs in a manner that mitigates certain thermal runaway conditions. In various embodiments thereof, the battery pack includes a thermal barrier disposed in or along one or more predetermined heat transfer paths between adjacent battery modules. Different alternative or cooperative embodiments for implementing the thermal barrier include flat adhesive strips of insulating material, spray coatings, fastener / gasket backings, and the like, with possible multi-layer composite embodiments also described herein.

[0004] As understood in the art, thermal runaway is a specific thermodynamic condition or event in which the cell temperature of a given battery cell reaches a threshold temperature, above which the cell temperature will continue to rise in a self-sustaining manner faster than the cell temperature can be regulated, for example, by an onboard cooling system. Above a certain temperature, battery electrodes tend to decompose exothermically as the active material of the battery cell, such as lithium in a typical lithium-based battery, reacts with the surrounding electrolyte material within the battery cell. At higher temperatures, the electrolyte material itself may undergo exothermic reactions, further increasing the cell temperature.

[0005] If thermal runaway occurs within a battery cell positioned in close proximity to another battery cell, the generated heat can quickly spread to adjacent battery cells in an exothermic chain reaction. Similarly, the close proximity of adjacent battery modules in a multi-module battery pack exposes the pack to a higher risk of inter-module thermal runaway, as heat can quickly propagate from one module to another. Therefore, the present solution aims to isolate thermal runaway events within a given battery module by strategically placing thermal insulation materials, i.e., the aforementioned thermal barriers, in a multi-module battery pack according to the present disclosure.

[0006] According to an exemplary embodiment, the multi-module battery pack described herein includes a battery tray, a plurality of battery modules, and a thermal barrier. The battery tray defines a plurality of battery tray compartments. Each respective battery module is disposed within a corresponding battery tray compartment. With respect to the thermal barrier, the component is disposed in one or more heat transfer paths that exist through the battery tray, i.e., between an adjacent pair of battery modules. In this particular embodiment, the thermal barrier as contemplated herein has a thickness of at least approximately 1 millimeter (mm) and a thermal conductivity of less than approximately 4 watts per meter Kelvin (W / mK). The thermal barrier is thus configured to block the heat transfer path to thereby mitigate a thermal runaway event in one of the adjacent pair of battery modules.

[0007] The battery tray may include a transverse inner wall arranged orthogonally relative to a longitudinal outer wall of the battery tray to define the plurality of battery tray compartments, for example, as an approximate grid of rectangular battery tray compartments. In such an embodiment, the predetermined heat transfer path includes a surface of the transverse inner wall.

[0008] Each respective battery module may include a module tab connected to a respective one of the transverse inner walls via a fastener. In this particular configuration, the predetermined heat transfer path passes through the module tab and the fastener connected thereto. In some embodiments, each fastener may comprise a flat / planar annular gasket disposed on one of the transverse inner walls. In this case, the thermal barrier may be disposed between the gasket and the transverse inner wall.

[0009] In one possible embodiment, the thermal barrier may coat the gasket or its surface and / or may be integrally formed therewith.

[0010] In some embodiments, the thermal barrier is configured as an elongated strip adhered or otherwise attached to the transverse inner wall adjacent the gasket.The elongated strip may define a recess configured to receive a threaded fastener therein.

[0011] In one possible configuration, the thermal barrier may include a refractory ceramic material having a thermal conductivity of less than about 4 W / mK.

[0012] In a non-limiting exemplary embodiment, the battery tray may be constructed of aluminum or another thermally conductive material suitable for the application.

[0013] The thermal barrier in the multi-layer embodiment may be constructed to include a heat absorbing / phase change layer adhered to the surface of the battery pack, a heat reflective layer adhered to the heat absorbing / phase change layer, and a thermal insulation layer adhered to the heat absorbing / phase change layer.

[0014] In an alternative embodiment, the thermal barrier is formed by a composite thermal spray coating applied to one or more surfaces of the battery tray.

[0015] Also disclosed herein is a method for mitigating thermal runaway events in a multi-module battery pack of the type described above. A method according to an exemplary embodiment includes providing a battery tray having a plurality of battery tray compartments and configured to support a plurality of battery modules arranged thereon. When arranged in this manner, a corresponding one of the battery modules is disposed in a corresponding battery tray compartment. In addition, the method includes identifying a heat transfer path, i.e., one or more such paths, through the battery tray between an adjacent pair of battery modules. The method also includes arranging a thermal barrier in the identified heat transfer path between an adjacent pair of battery modules, wherein the thermal barrier has a thickness of at least about 1 mm and a thermal conductivity of less than about 4 W / mK, such that the thermal barrier blocks the heat transfer path.

[0016] This document also discloses an electric powertrain system. In a representative embodiment, the electric powertrain system includes a rotating electric machine, a driven load, and the aforementioned multi-module battery pack. The rotating electric machine, such as an electric propulsion motor, has phase leads and an output member in a non-limiting alternating current (AC) / multi-phase embodiment. The driven load is coupled to and powered by the output member of the rotating electric machine. A power inverter in this AC embodiment of the rotating electric machine is connected to the battery pack and the phase leads. The power inverter is configured to power the rotating electric machine via the battery pack, thereby enabling the rotating electric machine to deliver motor torque to the driven load.

[0017] In this particular embodiment of an electric powertrain system, a multi-module battery pack includes: the aforementioned battery tray; battery modules arranged in their respective battery tray compartments such that a heat transfer path exists between an adjacent pair of battery modules through the battery tray; and a thermal barrier as described in detail herein. The thermal barrier is adhered or otherwise attached to the battery tray and has a thermal conductivity of less than approximately 4 W / mK such that, during a thermal runaway event in one of the adjacent pair of battery modules, the thermal barrier blocks the heat transfer path. In this manner, the thermal barrier mitigates the thermal runaway event.

[0018] The present invention also includes the following technical solutions.

[0019] Solution 1. A multi-module battery pack comprising:

[0020] a battery tray defining a plurality of battery tray compartments;

[0021] a plurality of battery modules, wherein each respective one of the battery modules is disposed within a corresponding one of the battery tray compartments; and

[0022] A thermal barrier is arranged in a predetermined heat transfer path between an adjacent pair of the battery modules through the battery tray, the thermal barrier having a thickness of at least about 1 mm and a thermal conductivity of less than about 4 W / mK, wherein the thermal barrier is configured to block the heat transfer path and thereby mitigate a thermal runaway event in one of the adjacent pair of the battery modules.

[0023] Option 2. A multi-module battery pack according to Option 1, wherein the battery tray includes a plurality of transverse inner walls, the transverse inner walls are arranged orthogonally relative to the longitudinal outer walls to define the plurality of battery tray compartments, and the predetermined heat transfer path includes surfaces of the transverse inner walls.

[0024] Option 3. A multi-module battery pack according to Option 2, wherein each corresponding battery module among the plurality of battery modules includes a set of module tabs connected to a corresponding one of the lateral inner walls via fasteners, and the predetermined heat transfer path passes through the module tabs and the fasteners connected thereto.

[0025] Option 4. The multi-module battery pack according to Option 3, wherein each of the fasteners comprises an annular washer disposed on one of the lateral inner walls, wherein the thermal barrier is arranged between the annular washer and the lateral inner wall.

[0026] Option 5. A multi-module battery pack according to Option 4, wherein the thermal barrier coats the annular gasket or is formed integrally therewith.

[0027] Option 6. The multi-module battery pack of Option 4, wherein the thermal barrier is configured as an elongated strip attached to the lateral inner wall proximate the annular gasket.

[0028] Option 7. The multi-module battery pack of Option 6, wherein the elongated strip defines a recess configured to receive a threaded fastener therein.

[0029] Option 8. The multi-module battery pack of Option 1, wherein the thermal barrier comprises a refractory ceramic material having a thermal conductivity of less than about 4 W / mK.

[0030] Option 9. The multi-module battery pack according to Option 1, wherein the battery tray is made of aluminum.

[0031] Option 10. The multi-module battery pack according to Option 1, wherein the thermal barrier comprises a heat absorption / phase change layer adhered to the battery pack, a heat reflective layer adhered to the heat absorption / phase change layer, and a heat insulating layer adhered to the heat absorption / phase change layer.

[0032] Option 11. The multi-module battery pack of Option 1, wherein the thermal barrier is a composite thermal spray coating applied to one or more surfaces of the battery tray.

[0033] Solution 12. A method for mitigating a thermal runaway event in a battery pack having a plurality of battery modules, the method comprising:

[0034] providing a battery tray having a plurality of battery tray compartments, each of the battery tray compartments being configured to receive therein and support thereon a corresponding one of the battery modules;

[0035] identifying a heat transfer path through the battery tray between an adjacent pair of battery modules; and

[0036] A thermal barrier is disposed in the heat transfer path between the adjacent pair of battery modules, the thermal barrier having a thickness of at least about 1 mm and a thermal conductivity of less than about 4 W / mK such that the thermal barrier blocks the heat transfer path.

[0037] Option 13. The method according to Option 12, further comprising:

[0038] arranging the plurality of battery modules on the battery tray; and

[0039] The plurality of battery modules are fastened to the battery tray to thereby construct the battery pack.

[0040] Solution 14. The method according to solution 13, further comprising:

[0041] An annular gasket is coated or integrally formed with the thermal barrier, wherein securing the plurality of battery modules to the battery tray includes positioning the annular gasket in the heat transfer path.

[0042] Option 15. The method of Option 12, wherein arranging the thermal barrier in the heat transfer path comprises applying a refractory ceramic to a surface of the battery tray, the refractory ceramic having a thermal conductivity of less than about 4 W / mK and a thickness of at least about 1 mm.

[0043] Option 16. The method of Option 12, wherein arranging the thermal barrier in the heat transfer path comprises spraying the thermal barrier directly onto an outer surface of the battery tray.

[0044] Option 17. The method according to Option 12, further comprising:

[0045] forming the thermal barrier into a multi-layer strip, including forming each of a heat absorbing / phase change layer adhered to the battery tray, a heat reflective layer adhered to the heat absorbing / phase change layer, and a heat insulating layer adhered to the heat absorbing / phase change layer; and

[0046] The multi-layer strip is attached to an outer surface of the battery tray.

[0047] Solution 18. An electric powertrain system comprising:

[0048] a rotating electrical machine having phase leads and an output member;

[0049] a driven load coupled to and powered by the output member of the rotating electrical machine;

[0050] A multi-module battery pack having:

[0051] Battery tray;

[0052] a plurality of battery modules, each arranged in a corresponding battery tray compartment of the battery tray such that a heat transfer path exists between an adjacent pair of the battery modules through the battery tray; and

[0053] a thermal barrier attached to the battery tray and having a thermal conductivity of less than about 4 W / mK, such that the thermal barrier is configured to block the heat transfer path during a thermal runaway event of one of the adjacent pair of battery modules to thereby mitigate the thermal runaway event; and

[0054] A power inverter module is connected to the multi-module battery pack and the phase leads of the rotating electric machine, wherein the power inverter module is configured to power the rotating electric machine via the multi-module battery pack to thereby deliver electric machine torque to the driven load.

[0055] Option 19. An electric powertrain system according to Option 18, wherein the battery tray includes a plurality of transverse inner walls, which are arranged orthogonally relative to the longitudinal outer walls to define a plurality of battery tray compartments, the predetermined heat transfer path includes the surface of the transverse inner walls, and each corresponding battery module among the plurality of battery modules includes a set of module tabs connected to a corresponding one of the transverse inner walls via fasteners, so that the predetermined heat transfer path passes through the module tabs and the fasteners connected thereto.

[0056] Option 20. The electric powertrain system of Option 19, further comprising:

[0057] a plurality of gaskets coated with or integrally formed from said thermal barrier; and

[0058] A plurality of threaded fasteners are each engaged with or integrally formed with a corresponding one of the washers and are configured to secure the plurality of battery modules to the battery tray, wherein the threaded fasteners are configured to secure the plurality of battery modules to the battery tray along the lateral inner wall.

[0059] The above summary does not represent every embodiment or every aspect of the present disclosure. The above features and advantages, as well as other possible features and advantages, will be apparent from the following detailed description of the embodiments and best modes for carrying out the present disclosure when taken in conjunction with the accompanying drawings and the appended claims. Furthermore, the present disclosure expressly encompasses all combinations and subcombinations of the elements and features presented above and below. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 is a schematic diagram of an exemplary motor vehicle having a multi-module battery pack supported by a planar battery tray and a thermal barrier configured to block one or more heat transfer paths during a thermal runaway event in a battery module of the battery pack.

[0061] Figure 2 Can be used as Figure 1 A plan view of a representative battery tray and battery modules of a portion of a motor vehicle is shown in FIG.

[0062] Figure 3 yes Figure 1 A partial perspective view of a portion of a battery pack shown in , depicting adjacent battery modules and the heat transfer paths therebetween.

[0063] Figure 4 is a partial perspective view of a battery tray with representative heat concentrations and possible heat transfer paths during a thermal runaway event.

[0064] Figure 5 yes Figure 1 A partial perspective view of a portion of a battery pack.

[0065] Figure 6 is a perspective view of an annular gasket having a thermal barrier as described herein.

[0066] Figure 7 is a schematic diagram of a multi-layer embodiment of a thermal barrier according to one aspect of the present disclosure.

[0067] Representative embodiments of the present disclosure are shown by way of non-limiting example in the accompanying drawings and are described in more detail below. However, the novel aspects of the present disclosure are not limited to the specific forms shown in the above-listed drawings. Rather, the present disclosure is intended to extend to modifications, equivalents, combinations, and alternatives that fall within the scope of the present disclosure, such as those covered by the appended claims. DETAILED DESCRIPTION

[0068] The present disclosure is susceptible of embodiments in many different forms. Representative examples of the present disclosure are shown in the accompanying drawings and described in detail herein as non-limiting examples of the disclosed principles. For this reason, elements and limitations described in the Abstract, Background, Summary, and Detailed Description sections but not explicitly recited in the claims should not be incorporated, individually or collectively, into the claims by implication, inference, or otherwise.

[0069] For the purposes of the present description, unless otherwise stated, the use of the singular includes the plural and vice versa, the terms "and" and "or" shall be both conjunctions and disjunctive conjunctions, both "any" and "all" shall mean "any and all," and the terms "including," "comprising," "containing," "having," and the like shall mean "including but not limited to." In addition, approximate terms such as "approximately," "almost," "substantially," "roughly," and "approximately" may be used herein in the sense of "at, close to, or nearly at," or "within ±5% thereof," or "within an acceptable manufacturing tolerance," or a logical combination thereof.

[0070] Referring to the drawings, wherein like reference numerals refer to like parts, Figure 1 A motor vehicle 10 is schematically depicted having an electric powertrain system 11 that includes a multi-module battery pack 16. As described herein, the battery pack 16 is constructed using one or more thermal barriers 55, each of which is disposed in or along one or more predetermined heat transfer paths within the battery pack 16. The presence of the thermal barriers 55 is intended to help mitigate inter-module thermal runaway events as described below.

[0071] The motor vehicle 10 in the exemplary configuration shown includes a vehicle body 12 and a set of wheels 14, the latter of which serve as driven loads. Figure 11 and described below is a representative battery electric vehicle, but is not limited thereto. That is, those skilled in the art will appreciate that the present teachings can be advantageously applied in a wide range of electrified systems, such as, but not limited to, hybrid electric vehicles, propeller-driven rail or air vehicles such as ships, trains, and rotary or fixed-wing aircraft, battery-powered robots, and various other mobile platforms in which electrical energy is drawn from or stored in the constituent electrochemical cells (not shown) of the battery pack 16. Similarly, the present teachings can be extended to stationary systems, such as power plants, cranes, and conveyor systems, in which the electric powertrain system 11 actively powers driven loads other than the illustrated wheels 14.

[0072] exist Figure 1 In the non-limiting exemplary embodiment of the present invention, the electric powertrain system 11 includes a power inverter 20 and a rotating electric machine 18. The power inverter 20, commonly referred to in the art as a traction power inverter module or TPIM, is electrically connected to the positive (+) and negative (-) rails of a direct current (DC) voltage bus 25. As shown, the DC link capacitor (C L ) 21 may be arranged across the positive and negative rails. As part of a power inverter 20, upper and lower semiconductor switches 22, such as MOSFETs, or alternatively, IGBTs, thyristors, power diodes, or another application-suitable switch configuration with controlled binary ON / conducting and OFF / non-conducting states, are shown to respectively connect the positive rail (upper semiconductor switch 22) and the negative rail (lower semiconductor switch 22) to the stator phase windings 19 of the rotating electrical machine 18.

[0073] The multi-module battery pack 16 contemplated herein includes a plurality of battery modules 16M. As is understood in the art, such a multi-unit, multi-module configuration assembles the battery pack 16 from a number of battery modules 16M suitable for the application, wherein Figure 1 The nominal number and arrangement of cells are illustrative of the present teachings and are not intended to be limiting. Within a given battery module 16M, the individual battery cells are conductively coupled together, for example, by laser welding or ultrasonic welding. Each battery module 16M is conductively interconnected in a series or parallel arrangement to provide a specific battery output voltage.

[0074] During propulsion applications, the DC input voltage from the multi-module battery pack 16 is provided to the power inverter 20 and thereby converted into a multi-phase / alternating current (AC) output voltage. Thereafter, the AC output voltage from the power inverter 20 is used to power the electric machine 18, which ultimately results in rotation of its output member 180. The resulting torque (arrow T) is then O ) is transferred to one or more wheels 14, while in other embodiments driven loads other than wheels 14 are possible.

[0075] As generally mentioned above, thermal runaway is an undesirable condition or thermodynamic event that may result when a battery cell temperature reaches a threshold temperature, above which the battery cell temperature continues to rise. The rise in battery cell temperature occurs faster than the battery cell temperature can be effectively regulated, for example, using an onboard cooling system (not shown). When a thermal runaway event occurs within a given battery module 16M that is positioned immediately adjacent to an adjacent battery module 16M, such as the one described below, Figure 3 As shown in FIG1 , the heat from a thermal runaway event can spread rapidly between the adjacent battery modules 16M- 1 and 16M- 2 . Figure 1 This is schematically represented by block arrow 24 .

[0076] Therefore, the following reference Figure 2-6 The solution described herein is intended to isolate and contain thermal runaway locally within a specific battery module 16M of a multi-module battery pack 16. Figure 2 This desired result is achieved by placing insulating materials at or along strategic locations of the heat transfer device to form the above-mentioned thermal barrier 55. In this way, the thermal barrier 55 purposefully blocks a predetermined or identified heat transfer path.

[0077] refer to Figure 2 ,exist Figure 1 In one possible embodiment of the multi-module battery pack 16 shown in , which is shown with the outer shell removed for clarity and simplicity of illustration, the individual battery modules 16M are arranged on a battery tray 30 constructed of a thermally conductive material, which is typically a lightweight and structurally supportive material. As used herein, "thermal conductivity" with respect to the battery tray 30 encompasses materials having a thermal conductivity of approximately 50-100 W / mK or more at 20-25°C. In an exemplary configuration, for example, the battery tray 30 is constructed of aluminum and, therefore, has a thermal conductivity of approximately 200 W / mK or more at the aforementioned reference condition of 20-25°C.

[0078] exist Figure 2In an exemplary layout of FIG, similarly constructed battery modules 16M are arranged in corresponding module areas, such as M-1 and M-2, extending along the width (W) and length (L) of the battery tray 30. In such an embodiment, the battery tray 30 is constructed as a grid formed by longitudinal outer walls 32 extending along the length L of the battery tray 30 and intersecting equally spaced transverse inner walls 34, where "outer" and "inner" are the relative positions of the walls 32 and 34 with respect to each other. In the illustrated embodiment, the longitudinal middle wall 32* forms the approximate centerline of the battery pack 16, but is otherwise configured to function as one of the longitudinal outer walls 32. The transverse inner wall 34 may correspond to a crossbar of a rechargeable energy storage system (RESS) in a representative automotive application. Thus, the intersecting longitudinal outer walls 32, longitudinal middle walls 32*, and transverse inner walls 34 together define a plurality of battery tray compartments 36, wherein a given battery module 16M is arranged in a corresponding one of the tray compartments 36, each of which is supported from below by a battery tray floor 38 (see FIG. Figure 4 ).

[0079] refer to Figure 3 Due to the close proximity of the battery modules 16M, one or more heat transfer paths (arrows 50 ) exist through the intervening structure of the battery tray 30 . For example, Figure 3 The battery module 16M, labeled 16M-1, is positioned immediately adjacent to another battery module 16M, the latter of which is nominally labeled 16M-2. Battery modules 16M-1 and 16M-2 thus form an adjacent pair of battery modules 16M as used herein. For example, in the event of a thermal runaway event within battery module 16M-1, the generated heat emanating from battery module 16M-1 will tend to propagate along one or more of the heat transfer paths (arrows 50) and into battery module 16M-2, which, absent its own thermal runaway event, will then be at a lower temperature than battery module 16M-1.

[0080] For example, in Figure 2 In the illustrated arrangement, although the battery module 16M is separated from the longitudinal outer wall 32 and the transverse inner wall 34 by a short distance, heat from the battery module 16M-1 will tend to flow into the battery module 16M-1 through the intermediate conductive structure of the battery module 16M, which includes Figure 4 , a battery module floor 38 , a lateral interior wall 34 disposed between the battery modules 16M- 1 and 16M- 2 , and intervening conductive connection hardware.

[0081] In some installation configurations, the battery modules 16M can be securely fastened to the battery tray 30 using fasteners 40, such as threaded screws or bolts constructed of metal. Each battery module 16M, including representative battery modules 16M-1 and 16M-2, can include peripheral module tabs 42 to facilitate assembly of the multi-module battery pack 16. In one possible configuration, the module tabs 42 extend toward a corresponding one of the lateral inner walls 34 of the battery tray 30. The fasteners 40 are then inserted through openings in the module tabs 42 and tightened into place using a torque wrench or hand tool.

[0082] Thus, a heat transfer path 50 exists between an adjacent pair of battery modules 16M through the battery tray 30, including the fasteners 40 and module tabs 42. Consequently, a thermal runaway event occurring in battery module 16M-1 may propagate to battery module 16M-2 or other adjacent battery modules 16M, often rapidly, thereby potentially leading to a pack-wide thermal runaway event. Therefore, placement of a thermal barrier 55 within the heat transfer path 50, as described below, is used to mitigate such events, particularly by isolating the thermal runaway to the initiating battery module 16M, or in this example, to battery module 16M-1.

[0083] Now refer to Figure 4 , showing the above and Figure 2 The battery tray 30 is depicted in FIG, wherein the battery module 16M is removed for clarity. Figure 3 Consistent with the example of FIG1 , during a thermal runaway event within the confines of the battery module 16M-1, the battery tray floor 38 defining the lower portion of the battery tray compartment 36 will tend to heat up as the exothermic reaction within the battery module 16M-1 proceeds. Although the battery module 16M-1 is physically separated from the transverse inner wall 34 by a small air gap that itself provides a degree of thermal insulation, a heat transfer path (arrow 50) extends through the transverse inner wall 34, through which the battery module 16M-1 is heated. Figure 3 Fasteners 40 and module tabs 42. With respect to the medium (MM) and low (LL) temperature regions, Figure 4 The resulting localized high temperature areas (HH) are indicated by heavier shading in FIG. Thus, the thermal barrier 55 in its various embodiments is adhered or otherwise attached to the battery tray 30 , for example, to the upper surface 134 of the lateral inner wall 34 as shown.

[0084] Now refer to Figure 5 and Figure 6 The construction of the thermal barrier 55 and the placement options suitable for the application are described in detail. Figure 5 In the case of an external battery electrical connection 70 shown in a simplified manner, in order to fully alleviate Figure 1To prevent thermal runaway within the multi-module battery pack 16, a thermal barrier 55 can be disposed within one or more heat transfer paths (arrows 50) on the intermediate portion of the battery tray 30. As contemplated herein, the thermal barrier 55 includes one or more materials that collectively provide a low thermal conductivity relative to the material used to construct the battery tray 30. For example, the thermal barrier 55 can have a thermal conductivity of approximately 4 W / mK or less in some embodiments, or less than approximately 2 W / mK in other embodiments, such as when the thermal barrier 55 is composed of a refractory ceramic.

[0085] In order to provide sufficient resilience, the thermal barrier 55 should have a thickness sufficient to withstand the forces applied during assembly, e.g. Figure 3 Fasteners 40 or Figure 5 1 when applying torque to the fastener 140 of the alternative configuration shown in FIG. In some embodiments, a thickness of at least about 1 mm may be sufficient, while increased thickness beyond this point provides additional structural integrity at the expense of possible weight and material cost. Thus, the thermal barrier 55 in its various embodiments is configured to substantially or completely block the heat transfer path (arrow 50) and thereby isolate thermal runaway within the multi-module battery pack 16 due to its unique structure and targeted placement.

[0086] like Figure 5 As schematically depicted in FIG, the thermal barrier 55 may be implemented as an elongated strip 55S of thermally insulating material, wherein the elongated strip 55S is adhered or otherwise securely attached to the outer surface 134 of the battery tray 30, particularly the lateral inner wall 34 thereof, in close proximity thereto. Figure 3 or Figure 5 Fasteners 40 or 140. For example, in Figure 5 In the embodiment of the present invention, the fastener 140 includes an annular washer 44, which can be integrally formed with the rest of the fastener 140 or as shown in FIG. Figure 6 The individual components depicted in .

[0087] Figure 5 In an embodiment, the thermal barrier 55 may define a set of grooves or recesses 60 configured to receive therein threaded fasteners 40, i.e., threaded shafts (not shown) extending into the battery tray 30. Such recesses 60 may be complementary to similar recesses 160 defined by the module tabs 42, i.e., have a profile, shape, and contour matching that of the recesses 160. Using recesses 60 instead of integrally coating the transverse inner wall 34, or integrally forming the gasket 44 from the material used to construct the thermal barrier 55, may have the benefit of reducing assembly costs. Furthermore, the gasket 44, constructed from a relatively low-cost metal, can be more easily replaced if lost without having to replace the underlying thermal barrier 55, which would not be the case if the gasket 44 were integrally constructed from or coated with the thermal barrier 55.

[0088] Figure 5The annular gasket 44 itself can be considered an intermediary portion of the battery tray 30, attached thereto once properly installed and fastened. In representative embodiments, the thermal barrier 55 can partially or completely coat the gasket 44, or the gasket 44 itself can be constructed from the material of the thermal barrier 55. For example, each gasket 44 can be constructed at least partially from mica, ceramic, or a composite material and installed beneath each module tab 42. The heat transfer path 50 passes directly through the gasket 44 and the fastener 40 disposed therein, or through an alternative fastener 140. Therefore, coating the gasket 44 with the thermal barrier 55, coating the lower surface of the gasket 44, or constructing the gasket 44 entirely from the material of the thermal barrier 55 will help block the heat transfer path (arrow 50).

[0089] Brief Reference Figure 6 , Figure 5 The gasket 44 may be implemented as an annular gasket 240 having an upper surface 240-1, a lower surface 240-2, and a central hole or through hole 75 having a central axis 80. For example, when the gasket 240 is installed, the lower surface 240-2 is adjacent to the battery tray 30, as shown in FIG. Figure 5 The gasket 44 and the thermal barrier 155 may be used alone or in combination Figure 5 The elongated strip 55S is adhered or otherwise attached to the lower surface 240-2.

[0090] In some embodiments, Figure 5 The thermal barrier 55 may also be used to coat the lateral inner walls 34 and upper surface 134, as opposed to the isolated outer surface adjacent only the fasteners 40 or 140 as described above. There are various methods for implementing the thermal barrier 55 to significantly delay heat propagation during a module-to-module / inter-module thermal runaway event. As described above, one such method is to construct the thermal barrier 55 as Figure 5 The elongated strips 55S may be applied to the lateral inner wall 34 during assembly of the multi-module battery pack 16 .

[0091] Alternatively, as Figure 7 As depicted in FIG, the thermal barrier 55 or 155 can be constructed as a multi-layer barrier 255 having a heat absorbing / phase change layer (L1-ABS) 56, a heat reflective layer (L2-REFL) 57 adhered or attached to the heat absorbing / phase change layer 56, and a heat insulating layer (L3-INS) 58 adhered or attached to the heat reflective layer 57. Regarding each of the layers 56, 57, and 58, the heat absorbing / phase change layer 56 can be adhered or attached to a specific portion or surface of the battery tray 30, such as the lateral inner wall 34 as shown, and can be composed of a heat shrinkable material and / or a material containing melt / sublimized particles. Such a construction will produce a porous microstructure when subjected to elevated temperatures.

[0092] Figure 7 The heat reflective layer 57 schematically shown in FIG. 5 may contain reflective particles in some embodiments, or the layer 57 may be composed of a smooth, polished or other finished material to reflect an application-specific amount of incident heat. Figure 7 The effective "top coating" of the multilayer construction can be composed of refractory ceramics, as described above. Materials with a thermal conductivity of about 4 W / mK or less, such as alumina, titania, etc., can be used, down to those materials with a thermal conductivity of less than about 2 W / mK.

[0093] Typically, materials with the lowest thermal conductivity tend to be the most expensive, and therefore, there is a cost-benefit trade-off when selecting an application-appropriate material to implement the present teachings. By way of example and not limitation, exemplary materials for constructing thermal insulation layer 58 include yttria-stabilized zirconia (YSZ), such as Y2O3-ZrO2 or Gd2Zr2O7, TiO2, spinel, Al2O3, and the like. Such materials, and other possible materials, should provide sufficient load-bearing capacity when torque is applied to fastener 40, a property favored by application to a suitable thickness, such as 1 mm or greater.

[0094] In another possible embodiment, the thermal barrier 55 of the above-described figures may be applied as a multifunctional / composite thermal spray coating in a single step. For example, the upper surface 134 (134) of the transverse inner wall 34 may be coated using thermal spray techniques of the type understood in the art. Figure 4 ). It is possible that a mask could be used to form discrete / discrete heat blocking areas beneath the module tabs 42, or the entirety of the lateral inner wall 34 could be coated to a desired thickness.

[0095] Since the thermal spray coating process introduces porosity into the discharged material, the increased porosity has the desired effect of reducing the resulting thermal conductivity. In addition, the spray coating can be provided with a roughened surface treatment, for example, by rolling or texturing. The resulting surface roughening will have the effect of reducing the total contact area with the transverse inner wall 34. The reduced contact area will also reduce thermal conductivity in the assembled state. When using refractory ceramics, such materials can be used as such or can be mixed with a low melting point polymer material.

[0096] As will be appreciated by those skilled in the art, the foregoing disclosure is applicable to implementation of Figure 1 The method may include providing a battery tray 30 having battery tray compartments 36. The battery tray 30, as disclosed above, is constructed of a thermally conductive, lightweight material such as aluminum. Each of the battery tray compartments 36 is configured to receive and support a corresponding one of the battery modules 16M therein. Figure 2 and Figure 3 Best shown in .

[0097] The method in this embodiment includes identifying one or more heat transfer paths, wherein Figure 3 and Figure 4 4. Various heat transfer paths (arrows 50) are presented in the figure that are between the battery modules 16M and through the intervening portions of the battery tray 30 and the connecting hardware, such as the fasteners 40. For example, finite element analysis or commercially available or custom thermal simulation and analysis / modeling software applications can be used to identify the most likely heat propagation paths under different simulated thermal runaway conditions, or a user can perform a preliminary analysis of the assembled multi-module battery pack 16 to identify adjacent or interconnecting surfaces through which heat from one of the battery modules 16M may flow.

[0098] After identifying the possible heat transfer paths, the method includes placing a thermal barrier 55 on one or more intervening portions of the battery tray 30 such that the thermal barrier 55 is constructed, i.e., positioned and built to block the heat transfer path during a thermal runaway event. In some embodiments, the method may include placing a plurality of battery modules 16M on the battery tray 30 such that a heat transfer path (arrow 50) is formed between the battery modules 16M through the intervening portions of the battery tray 30 and possible connecting hardware. Placing the thermal barrier 55 may include applying a refractory ceramic to the battery tray 30 as Figure 7 , wherein in a possible embodiment as described above, the refractory ceramic has a thermal conductivity of less than about 4 W / mK and a thickness of at least about 1 mm.

[0099] Arranging the thermal barrier 55 may optionally include spraying the thermal barrier 55 directly onto the battery tray 30. Other embodiments include forming the thermal barrier 55 as a multi-layer elongated strip or annular gasket 44, for example, as a heat absorbing / phase change layer 56, a heat reflecting layer 57 adjacent to the heat absorbing / phase change layer 56, and a heat insulating layer 58 adjacent to the heat absorbing / phase change layer 57, as shown in FIG. Figure 7 Attaching the multi-layer elongated strip or gasket 44 to the outer surface 134 of the battery tray 30 may include securing the gasket 44 to the battery tray 30 using fasteners 40 .

[0100] As will be appreciated by those of ordinary skill in the art in view of the foregoing teachings, the present solution provides for a significant delay in module-to-module heat propagation in a wide variety of stationary or mobile battery applications, including but not limited to Figure 1The exemplary vehicle application depicted in and described herein. Depending on the end use of the multi-module battery pack 16, different embodiments may be used, including constructing the gasket 44 from the material of the thermal barrier 55 or coating the gasket 44 with such material, adhering multiple layers of strips of the thermal barrier 55 to the battery tray 30, or coating the lateral inner wall 34 with the thermal barrier 55 in a spray coating application. For example, by placing the thermal barrier 55 below the module tabs 42, the thermal barrier 55 is positioned to slow the spread of heat between adjacent battery modules 16M. This, in turn, can facilitate the repair and isolation of potential faults. Given the foregoing teachings, those skilled in the art will appreciate these and other benefits.

[0101] The detailed description and drawings or figures support and describe the present teachings, but the scope of the present teachings is limited only by the claims. Although some best modes and other embodiments for carrying out the present teachings have been described in detail, various alternative designs and embodiments exist for practicing the present teachings as defined in the appended claims. Moreover, the present disclosure expressly includes combinations and subcombinations of the elements and features presented above and below.

Claims

1. A multi-module battery pack comprising: a battery tray defining a plurality of battery tray compartments and having a battery tray floor, wherein the battery tray is configured as a grid formed by longitudinal exterior walls extending along a length of the battery tray and intersecting equally spaced transverse interior walls; a plurality of battery modules, wherein each respective one of the battery modules is disposed within a corresponding one of the battery tray compartments and supported from below by the battery tray floor; and a thermal barrier attached to respective upper surfaces of the lateral inner walls and disposed in a predetermined heat transfer path existing between an adjacent pair of the battery modules through the battery tray, the thermal barrier having a thickness of at least about 1 mm and a thermal conductivity of less than about 4 W / mK, wherein the thermal barrier is configured to block the heat transfer path and thereby mitigate a thermal runaway event in one of the adjacent pair of the battery modules, Each corresponding battery module among the plurality of battery modules includes a set of module tabs connected to a corresponding one of the transverse inner walls via fasteners, and the predetermined heat transfer path passes through the module tabs and the fasteners connected thereto.

2. The multi-module battery pack according to claim 1, wherein: The transverse inner walls are arranged orthogonally relative to the longitudinal outer walls to define the plurality of battery tray compartments.

3. The multi-module battery pack according to claim 1, wherein: Each of the fasteners comprises an annular washer disposed on one of the transverse inner walls, wherein the thermal barrier is arranged between the annular washer and the transverse inner wall.

4. The multi-module battery pack according to claim 3, wherein: The thermal barrier coats the annular gasket or is formed integrally therewith.

5. The multi-module battery pack according to claim 3, wherein: The thermal barrier is configured as an elongated strip attached to the transverse inner wall proximate the annular gasket.

6. The multi-module battery pack according to claim 5, wherein: The elongated strip defines a recess configured to receive a threaded fastener therein.

7. The multi-module battery pack according to claim 1, wherein: The thermal barrier comprises a refractory ceramic material having a thermal conductivity of less than about 4 W / mK.

8. The multi-module battery pack according to claim 1, wherein: The battery tray is constructed of aluminum.

9. The multi-module battery pack according to claim 1, wherein: The thermal barrier includes a heat absorption / phase change layer adhered to the battery pack, a heat reflective layer adhered to the heat absorption / phase change layer, and a heat insulating layer adhered to the heat absorption / phase change layer.

10. The multi-module battery pack according to claim 1, wherein: The thermal barrier is a composite thermal spray coating applied to one or more surfaces of the battery tray.

11. A method for mitigating a thermal runaway event in a battery pack having a plurality of battery modules, the method comprising: providing a battery tray having a battery tray floor configured to support the battery modules from below, wherein the battery tray is configured as a grid formed by longitudinal outer walls extending along a length of the battery tray and intersecting equally spaced transverse inner walls, wherein the battery tray defines a plurality of battery tray compartments, each of the battery tray compartments being configured to receive therein and support thereon a respective one of the battery modules; identifying a heat transfer path between an adjacent pair of battery modules through the battery tray; arranging the plurality of battery modules on the battery tray; securing the plurality of battery modules to the battery tray to thereby construct the battery pack, including connecting the plurality of battery modules to a corresponding one of the transverse inner walls via a set of module tabs and fasteners; and A thermal barrier is disposed on a corresponding upper surface of the lateral inner wall in the heat transfer path between the adjacent pair of battery modules, the thermal barrier having a thickness of at least about 1 mm and a thermal conductivity of less than about 4 W / mK, such that the thermal barrier blocks the heat transfer path, wherein the heat transfer path passes through the module tabs and the fasteners connected thereto.

12. The method according to claim 11, further comprising: An annular gasket is coated or integrally formed with the thermal barrier, wherein securing the plurality of battery modules to the battery tray includes positioning the annular gasket in the heat transfer path.

13. The method according to claim 11, wherein Disposing the thermal barrier in the heat transfer path includes applying a refractory ceramic to a surface of the battery tray, the refractory ceramic having a thermal conductivity of less than about 4 W / mK and a thickness of at least about 1 mm.

14. The method according to claim 11, wherein Disposing the thermal barrier in the heat transfer path includes spraying the thermal barrier directly onto an outer surface of the battery tray.

15. The method according to claim 11, further comprising: forming the thermal barrier as a multi-layer strip, including forming each of a heat absorbing / phase change layer adhered to the battery tray, a heat reflective layer adhered to the heat absorbing / phase change layer, and a heat insulating layer adhered to the heat absorbing / phase change layer; and The multi-layer strip is attached to an outer surface of the battery tray.

16. An electric powertrain system comprising: a rotating electrical machine having phase leads and an output member; a driven load coupled to and powered by the output member of the rotating electrical machine; A multi-module battery pack having: a battery tray having a battery tray floor and configured as a grid formed by longitudinal exterior walls extending along the length of the battery tray and intersecting equally spaced transverse interior walls; a plurality of battery modules each arranged in a respective battery tray compartment of the battery tray and supported from below by the battery tray floor such that a heat transfer path exists between an adjacent pair of the battery modules through the battery tray, wherein each respective battery module of the plurality of battery modules includes a set of module tabs connected to a respective one of the transverse inner walls via fasteners; and a thermal barrier attached to a respective upper surface of the lateral inner wall of the battery tray, disposed in a predetermined heat transfer path through the battery tray, and having a thermal conductivity of less than about 4 W / mK, such that the thermal barrier is configured to block the heat transfer path during a thermal runaway event of one of the adjacent pair of battery modules to thereby mitigate the thermal runaway event, wherein the predetermined heat transfer path passes through the module tab and the fastener connected thereto; and A power inverter module is connected to the multi-module battery pack and the phase leads of the rotating electric machine, wherein the power inverter module is configured to power the rotating electric machine via the multi-module battery pack to thereby deliver electric machine torque to the driven load.

17. The electric powertrain system of claim 16, further comprising: a plurality of gaskets coated or integrally formed with said thermal barrier; as well as A plurality of threaded fasteners are each engaged with or integrally formed with a corresponding one of the washers and are configured to secure the plurality of battery modules to the battery tray, wherein the threaded fasteners are configured to secure the plurality of battery modules to the battery tray along the lateral inner wall.

18. The electric powertrain system of claim 17, wherein: The thermal barrier is configured as an elongated strip attached to the transverse inner wall proximate the gasket.

19. The electric powertrain system of claim 18, wherein: The elongated strip defines notches, each notch being configured to receive a corresponding one of the fasteners therein.

20. The electric powertrain system of claim 16, wherein: The battery tray is constructed of aluminum.

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