Systems and methods for mitigating heat spread within traction battery arrays

Abstract

Battery arrays are provided for traction battery packs. An exemplary battery array may include one or more internal compartments. Each compartment may contain a non-conductive coolant to mitigate or even prevent heat propagation from one cell to another. A compartment air gap may provide a vent path for venting battery venting byproducts during a battery thermal event.

Description

FIELD OF TECHNOLOGY

[0001] This disclosure relates generally to traction battery packs, and more particularly to systems and methods for mitigating heat propagation within a traction battery array during battery thermal events. GENERAL STATE OF THE ART

[0002] Electrified vehicles include a traction battery pack to supply power to the vehicle's electric machines and other electrical devices. The traction battery pack contains a variety of battery cells and various other internal components that support the electric vehicle's propulsion. SUMMARY

[0003] A battery array for a traction battery pack according to an exemplary aspect of the present disclosure includes, among other things, an outer array housing, a cell stack housed within the outer array housing, a compartment extending between the outer array housing and the cell stack, and a non-conductive coolant contained within the compartment and configured to limit heat propagation across the cell stack during a battery thermal event.

[0004] In another non-limiting embodiment of the foregoing battery array, the compartment extends between a top surface of the cell stack and an inner surface of a top plate of the outer array housing.

[0005] In a further non-limiting embodiment of either of the foregoing two battery arrays, the non-conductive coolant is disposed in direct contact with a plurality of battery cells of the cell stack, but does not directly contact the top plate.

[0006] In a further non-limiting embodiment of any of the foregoing battery arrays, the non-conductive coolant is contained within a fluid-filled portion of the compartment. The compartment further includes an air gap portion above the fluid-filled portion.

[0007] In a further non-limiting embodiment of any of the foregoing battery arrays, a slotted plate provides a physical interface between the fluid-filled portion and the air gap portion.

[0008] In a further non-limiting embodiment of any of the foregoing battery arrays, the slotted plate includes a plurality of through-holes.

[0009] In a further non-limiting embodiment of any of the foregoing battery arrays, the air gap portion is an open space extending from the fluid-filled portion to an inner surface of a plate of the outer array housing.

[0010] In a further non-limiting embodiment of any of the foregoing battery arrays, the plate is a top plate of the outer array housing.

[0011] In a further non-limiting embodiment of any of the foregoing battery arrays, the air gap portion provides a vent path for venting battery venting byproducts during the battery thermal event.

[0012] In a further non-limiting embodiment of any of the foregoing battery arrays, the non-conductive coolant is a dielectric fluid.

[0013] A battery array for a traction battery pack according to another exemplary aspect of the present disclosure includes, among other things, an outer array housing, a cell stack housed within the outer array housing, a compartment extending between the outer array housing and the cell stack, and a slotted plate positioned to divide the compartment between a fluid-filled portion and an air gap portion.

[0014] In another non-limiting embodiment of the foregoing battery array, a non-conductive coolant is contained within the fluid-filled portion and configured to limit heat propagation across the cell stack during a battery thermal event.

[0015] In a further non-limiting embodiment of either of the foregoing two battery arrays, the non-conductive coolant is a dielectric fluid.

[0016] In a further non-limiting embodiment of any of the foregoing battery arrays, the compartment extends between a top surface of the cell stack and an inner surface of a top plate of the outer array housing.

[0017] In a further non-limiting embodiment of any of the foregoing battery arrays, a non-conductive coolant is disposed in direct contact with a plurality of battery cells of the cell stack, but does not directly contact the top plate.

[0018] In a further non-limiting embodiment of any of the foregoing battery arrays, the slotted plate provides a physical interface between the fluid-filled portion and the air gap portion and includes a plurality of through-holes.

[0019] In a further non-limiting embodiment of any of the foregoing battery arrays, the air gap portion is an open space extending from the fluid-filled portion to an inner surface of a plate of the outer array housing.

[0020] In a further non-limiting embodiment of any of the foregoing battery arrays, the plate is a top plate of the outer array housing.

[0021] In a further non-limiting embodiment of any of the foregoing battery arrays, the air gap portion provides a venting path for venting battery venting byproducts during a battery thermal event of the battery array.

[0022] In a further non-limiting embodiment of any of the foregoing battery arrays, the vent path extends through a through-hole of the slotted plate.

[0023] The embodiments, examples, and alternatives of the preceding paragraphs, the claims, or the following description and drawings, including their various aspects or respective individual features, may be used independently of one another or in any combination. Features described in connection with one embodiment are applicable to all embodiments, unless such features are incompatible.

[0024] The various features and advantages of this disclosure will become apparent to those skilled in the art from the following detailed description. The drawings accompanying the detailed description may be briefly described as follows. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 shows a schematic diagram of an electrified vehicle. Fig. Figure 2 illustrates a battery array of a traction battery pack. Fig. 3 is a cross-sectional view through section 3-3 of Fig. 2. Fig. 4 illustrates selected portions of another exemplary battery array for a traction battery pack. DETAILED DESCRIPTION

[0025] This disclosure describes in detail battery arrays for traction battery packs. An exemplary battery array may include one or more internal compartments. Each compartment may contain a non-conductive coolant to mitigate or even prevent heat propagation from one cell to another. An air gap of the compartment may provide a vent path for venting battery venting byproducts during a battery thermal event. These and other features are discussed in more detail in the following paragraphs of this detailed description.

[0026] Fig. 1 schematically illustrates an electrified vehicle 10. The electrified vehicle 10 may include any type of electrified powertrain. In one embodiment, the electrified vehicle 10 is a battery electric vehicle (BEV). However, the concepts described herein are not limited to BEVs and could extend to other electrified vehicles, including, but not limited to, hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), fuel cell vehicles, etc. Therefore, although not specifically illustrated in the exemplary embodiment, the powertrain of the electrified vehicle 10 could be equipped with an internal combustion engine, which can be used either alone or in combination with other power sources to propel the electrified vehicle 10.

[0027] In the illustrated embodiment, the electrified vehicle 10 is depicted as an automobile. However, the electrified vehicle 10 could alternatively be a sport utility vehicle (SUV), a van, a pickup truck, or any other vehicle configuration. Although a specific relationship of the components is illustrated in the figures of this disclosure, the illustrations are not intended to limit this disclosure. The placement and orientation of the various components of the electrified vehicle 10 are shown schematically and could vary within the scope of this disclosure. Furthermore, the various figures accompanying this disclosure are not necessarily drawn to scale, and some features may be exaggerated or minimized to highlight certain details of a particular component or system.

[0028] In one embodiment, the electrified vehicle 10 is an all-electric vehicle powered solely by electric power, such as one or more electric machines 12, without any assistance from an internal combustion engine. The electric machine 12 may operate as an electric motor, an electric generator, or both. The electric machine 12 receives electric power and may convert the electric power into torque to drive one or more wheels 14 of the electrified vehicle 10.

[0029] A voltage bus 16 may electrically couple the electric machine 12 to a traction battery pack 18. The traction battery pack 18 is an exemplary battery of an electrified vehicle. The traction battery pack 18 may be a high-voltage traction battery pack assembly including a plurality of battery cell groupings capable of outputting electrical power to power the electric machine 12 and / or other electrical loads of the electrified vehicle 10. Alternatively or additionally, other types of energy storage devices and / or output devices could also be used to supply electrical power to the electrified vehicle 10.

[0030] The traction battery pack 18 may be attached to an underbody 20 of the electrified vehicle 10. However, the traction battery pack 18 could be located elsewhere on the electrified vehicle 10 within the scope of this disclosure.

[0031] The Fig. 2 and Fig. 3 illustrate an exemplary battery bank 22 for a traction battery pack, such as the traction battery pack 18 of Fig. 1. One or more battery arrays having a configuration similar to that described in Fig. 2-3, could be installed within the traction battery pack 18.

[0032] The battery array 22 may include a plurality of battery cells 24 (they Fig. 3). In one embodiment, the battery cells 24 are lithium-ion pouch cells. However, within the scope of this disclosure, battery cells having other geometries (cylindrical, prismatic, etc.) and / or chemistries (nickel-metal hydride, lead-acid, etc.) could alternatively be used. The total number of battery cells 24 provided within the battery array 22 may vary and is not intended to limit this disclosure.

[0033] The battery cells 24 may be stacked side by side along a stack axis to form a grouping of battery cells 24 or a cell stack 26. The cell stack 26 of the battery array 22 may be subgrouped into two or more cell banks. The battery cells 24 may be held in compression relative to one another within the cell stack 26.

[0034] An outer array housing 28 of the battery array 22 may be arranged to substantially surround the battery cells 24 of the cell stack 26. In one embodiment, the outer array housing 28 completely encloses the battery cells 24 of the cell stack 26 and includes a top plate 30, a bottom plate 32, a pair of end plates 34, and a pair of side plates 36. One or more of the top plate 30, the bottom plate 32, the end plates 34, and the side plates 36 may be integrated together as part of a unitary structure. For example, the bottom plate 32 and the end plates 34 could be integrated together to form a unitary array structure that interfaces with the top plate 30. However, other configurations of the outer array housing 28 are possible within the scope of this disclosure.

[0035] With reference now mainly to Fig. 3, one or more compartments 38 may be provided within the battery array 22. Each compartment 38 is an open space extending within the interior of the battery array 22. For example, the compartment 38 may extend between top surfaces 40 of the battery cells 24 of the cell stack 26 and an inner surface 42 of the top plate 30 of the outer array housing 28. However, other arrangements are contemplated within the scope of this disclosure, and therefore, the compartment 38 could alternatively or additionally extend between the cell stack 26 and any of the plates of the outer array housing 28.

[0036] The compartment 38 may be partially filled with a non-conductive coolant 44, thereby dividing the chamber 38 into a fluid-filled portion 46 and an air-gap portion 48. The fluid-filled portion 46 may extend from the top surfaces 40 of the battery cells 24 to the air-gap portion 48, and the air-gap portion 48 may extend into the open space between the non-conductive coolant 44 and the inner surface 42 of the top plate 30. The non-conductive coolant 44 may therefore be in direct contact with the battery cells 24, but is generally not in direct contact with the top plate 30. Among other functions, the air-gap portion 48 may provide an open space to accommodate expansion of the battery cells 24. In other implementations, the compartment 38 may be completely filled with the non-conductive coolant 44.

[0037] The non-conductive coolant 44 may be a dielectric fluid, such as an engineered Novek™ fluid sold by 3M™. However, other non-conductive coolants may be suitable, and the actual chemical composition and design properties (e.g., dielectric constant, maximum dielectric strength, boiling point, etc.) of the non-conductive coolant 44 may vary depending on the environment in which the battery array 22 is to be used.

[0038] Although rare, the battery array 22 could be subjected to a battery thermal event during its operation. A battery thermal event may occur, for example, during overcharge conditions, overdischarge conditions, or other conditions and may cause one or more of the battery cells 24 to emit battery vent byproducts V, which may include gases, vented particulates, and / or other vent byproducts. During such a battery thermal event, the non-conductive coolant 44 contained within the fluid-filled portion 46 of the compartment 38 may substantially reduce or even prevent convective heat transfer from the battery vent byproducts V to the cells, thereby substantially mitigating heat propagation across the cell stack 26.Furthermore, the air gap portion 48 of the compartment 38 may establish a dedicated vent path P for expelling the battery vent byproducts V from the battery array 22 during the battery thermal event. For example, the battery vent byproducts V may be passed through the fluid-filled portion 46 and then flow over the inner surface 42 of the top plate 30 without directly passing over the battery cells 24 as they travel along the vent path P. Although not specifically shown, the battery vent byproducts V may eventually be expelled to a location outside the battery array 22 (e.g., outside the outer array housing 28) after entering the air gap portion 48.

[0039] With reference now to Fig.4, a slotted plate 50 may optionally be disposed within the compartment 38. The slotted plate 50 may be positioned to provide a physical interface between the fluid-filled portion 46 of the compartment 38 containing the non-conductive coolant 44 and the air gap portion 48 of the compartment 38 not containing the non-conductive coolant 44. The slotted plate 50 may be configured to maintain the non-conductive coolant 44 in contact with the battery cells 24. Through-holes 52 may be formed through the slotted plate 50 and may allow the battery venting byproducts V to flow through the slotted plate 50 as they travel along the venting path P during a battery thermal event.

[0040] The exemplary battery arrays of this disclosure include systems and methods for mitigating or even preventing heat propagation inside traction battery arrays of electrified vehicles. The proposed systems may provide numerous advantages over known solutions, including, among other things, presenting a novel configuration that significantly slows or even prevents heat propagation from one cell to another while providing dedicated vent passages for expelling battery venting byproducts during battery thermal events.

[0041] Although the various non-limiting embodiments are illustrated as having specific components or steps, the embodiments of this disclosure are not limited to these particular combinations. It is possible to use some of the components or features from any of the non-limiting embodiments in combination with features or components from any of the other non-limiting embodiments.

[0042] It should be understood that like reference numerals indicate corresponding or similar elements throughout the several views. It should be understood that while a particular component arrangement is disclosed and illustrated in these exemplary embodiments, other arrangements could also benefit from the teachings of this disclosure.

[0043] The foregoing description is intended to be interpreted as illustrative and not in a limiting sense. One of ordinary skill in the art will understand that certain modifications may be encompassed within the scope of the present disclosure. For these reasons, the following claims should be read carefully to determine the true scope and content of this disclosure.

Claims

[1] Battery array for a traction battery pack, comprising: an outer array enclosure; a cell stack housed inside the outer array casing; a compartment extending between the outer array housing and the cell stack; and a non-conductive coolant contained within the compartment and configured to limit heat propagation across the cell stack during a battery thermal event. [2] The battery array of claim 1, wherein the compartment extends between a top surface of the cell stack and an inner surface of a top plate of the outer array housing. [3] The battery array of claim 2, wherein the non-conductive coolant is disposed in direct contact with a plurality of battery cells of the cell stack, but does not directly contact the top plate. [4] A battery array according to any one of the preceding claims, wherein the non-conductive coolant is contained within a fluid-filled portion of the compartment, and wherein the compartment further comprises an air gap portion above the fluid-filled portion. [5] The battery array of claim 4, wherein a slotted plate provides a physical interface between the fluid-filled portion and the air gap portion, and wherein the slotted plate includes a plurality of through-holes. [6] The battery array of claim 4, wherein the air gap portion is an open space extending from the fluid-filled portion to an inner surface of a plate of the outer array housing. [7] The battery array of claim 6, wherein the plate is a top plate of the outer array housing. [8] The battery array of claim 4, wherein the air gap portion provides a vent path for venting battery venting byproducts during the battery thermal event. [9] A battery array according to any one of the preceding claims, wherein the non-conductive coolant is a dielectric fluid. [10] Battery array for a traction battery pack, comprising: an outer array enclosure; a cell stack housed inside the outer array casing; a compartment extending between the outer array housing and the cell stack; and a slotted plate positioned to divide the compartment between a fluid-filled section and an air-gap section. [11] The battery array of claim 10, comprising a non-conductive coolant contained within the fluid-filled portion and configured to limit heat propagation across the cell stack during a battery thermal event, and optionally wherein the non-conductive coolant is a dielectric fluid. [12] The battery array of claim 10 or 11, wherein the compartment extends between a top surface of the cell stack and an inner surface of a top plate of the outer array housing, and optionally wherein a non-conductive coolant is disposed in direct contact with a plurality of battery cells of the cell stack but does not directly contact the top plate. [13] The battery array of any one of claims 10 to 12, wherein the slotted plate provides a physical interface between the fluid-filled portion and the air gap portion and includes a plurality of through-holes. [14] The battery array of any one of claims 10 to 13, wherein the air gap portion is an open space extending from the fluid-filled portion to an inner surface of a plate of the outer array housing, and optionally wherein the plate is a top plate of the outer array housing. [15] The battery array of any one of claims 10 to 14, wherein the air gap portion provides a vent path for venting battery venting byproducts during a battery thermal event of the battery array, and optionally wherein the vent path extends through a through-hole of the slotted plate.

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