Patent Publication Number: US-2023137044-A1

Title: Traction battery pack enclosure assemblies with integrated thermal barrier systems

Description:
TECHNICAL FIELD 
     This disclosure relates generally to electrified vehicle traction battery packs, and more particularly to traction battery pack enclosure assemblies that include integrated thermal barrier systems for mitigating the effects of battery thermal events. 
     BACKGROUND 
     Electrified vehicles are designed to reduce or completely eliminate reliance on internal combustion engines. In general, electrified vehicles differ from conventional motor vehicles because they are selectively driven by battery powered electric machines. Conventional motor vehicles, by contrast, rely exclusively on the internal combustion engine to propel the vehicle. 
     A high voltage traction battery pack typically powers the electric machines and other electrical loads of the electrified vehicle. The traction battery pack includes a plurality of battery cells and various other battery internal components that support the electric propulsion of electrified vehicles. 
     SUMMARY 
     A battery pack according to an exemplary aspect of the present disclosure includes, among other things, an enclosure assembly, a first battery array housed within the enclosure assembly, and a second battery array housed within the enclosure assembly. The enclosure assembly includes a thermal barrier system adapted to minimize thermal propagation within an interior of the enclosure assembly during a battery thermal event. The thermal barrier system includes a bifurcation structure that extends between the first battery array and the second battery array. 
     In a further non-limiting embodiment of the foregoing battery pack, the enclosure assembly includes a tray and a cover. The thermal battery system protrudes from an inner surface of the cover. 
     In a further non-limiting embodiment of either of the foregoing battery packs, the bifurcation structure isolates a first portion of the interior where the first battery array resides from a second portion of the interior where the second battery array resides. 
     In a further non-limiting embodiment of any of the foregoing battery packs, the bifurcation structure includes an outer foam layer that is received in abutting contact with a mounting structure that extends between the first battery array and the second battery array. 
     In a further non-limiting embodiment of any of the foregoing battery packs, the outer foam layer is received in abutting contact with an upper platform of the mounting structure. 
     In a further non-limiting embodiment of any of the foregoing battery packs, the bifurcation structure straddles a mounting structure that extends between the first battery array and the second battery array. 
     In a further non-limiting embodiment of any of the foregoing battery packs, the thermal barrier system includes a canopy structure arranged to cover at least a portion of a bus bar assembly that electrically couples the first and second battery arrays. 
     In a further non-limiting embodiment of any of the foregoing battery packs, the canopy structure includes a first arm that is arranged to cover a first portion of the bus bar assembly and a second arm that is arranged to cover a second portion of the bus bar assembly. 
     In a further non-limiting embodiment of any of the foregoing battery packs, the first arm includes a first angled tip portion that is angled toward the first battery array and a second angled tip portion that is angled toward the second battery array. 
     In a further non-limiting embodiment of any of the foregoing battery packs, the first angled tip portion includes a first outer foam layer that is received in abutting contact with an upper surface of the first battery array, and the second angled tip portion includes a second outer foam layer that is received in abutting contact with an upper surface of the second battery array. 
     A battery pack according to another exemplary aspect of the present disclosure includes, among other things, an enclosure assembly, a first battery array housed within the enclosure assembly, a second battery array housed within the enclosure assembly, and a bus bar assembly configured to electrically couple the first and second battery arrays. The enclosure assembly includes a thermal barrier system adapted to minimize thermal propagation within an interior of the enclosure assembly during a battery thermal event. The thermal barrier system includes a canopy structure arranged to cover at least a portion of the bus bar assembly. 
     In a further non-limiting embodiment of the foregoing battery pack, the enclosure assembly includes a tray and a cover. The thermal battery system protrudes from an inner surface of the cover. 
     In a further non-limiting embodiment of either of the foregoing battery packs, the canopy structure includes a first arm that is arranged to cover a first portion of the bus bar assembly and a second arm that is arranged to cover a second portion of the bus bar assembly. 
     In a further non-limiting embodiment of any of the foregoing battery packs, the first arm includes a first angled tip portion that is angled toward the first battery array and a second angled tip portion that is angled toward the second battery array. 
     In a further non-limiting embodiment of any of the foregoing battery packs, the first angled tip portion includes a first outer foam layer that is received in abutting contact with an upper surface of the first battery array, and the second angled tip portion includes a second outer foam layer that is received in abutting contact with an upper surface of the second battery array. 
     In a further non-limiting embodiment of any of the foregoing battery packs, the thermal barrier system includes a bifurcation structure that extends between the first battery array and the second battery array. 
     In a further non-limiting embodiment of any of the foregoing battery packs, the bifurcation structure isolates a first portion of the interior where the first battery array resides from a second portion of the interior where the second battery array resides. 
     In a further non-limiting embodiment of any of the foregoing battery packs, the bifurcation structure includes an outer foam layer that is received in abutting contact with a mounting structure that extends between the first battery array and the second battery array. 
     In a further non-limiting embodiment of any of the foregoing battery packs, the outer foam layer is received in abutting contact with an upper platform of the mounting structure. 
     In a further non-limiting embodiment of any of the foregoing battery packs, the bifurcation structure straddles a mounting structure that extends between the first battery array and the second battery array. 
     The embodiments, examples, and alternatives of the preceding paragraphs, the claims, or the following description and drawings, including any of their various aspects or respective individual features, may be taken independently or in any combination. Features described in connection with one embodiment are applicable to all embodiments, unless such features are incompatible. 
     The various features and advantages of this disclosure will become apparent to those skilled in the art from the following detailed description. The drawings that accompany the detailed description can be briefly described as follows. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    schematically illustrates a powertrain of an electrified vehicle. 
         FIG.  2    is a cross-sectional view of an exemplary traction battery pack that includes a thermal barrier system. 
         FIG.  3    is a cross-sectional view of another exemplary traction battery pack that includes a thermal barrier system. 
     
    
    
     DETAILED DESCRIPTION 
     This disclosure details exemplary traction battery pack designs for use in electrified vehicles. An exemplary traction battery pack may include a thermal barrier system adapted for mitigating thermal propagation inside of the traction battery pack during battery thermal events. The thermal barrier system may include features such as a bifurcation structure and/or a canopy structure. The bifurcation structure is adapted for substantially isolating a first portion of an enclosure interior where a first battery internal component (e.g., a first battery array) resides from a second portion of the enclosure interior where a second battery internal component (e.g., a second battery array) resides, and the canopy structure is adapted for protecting a bus bar assembly of the traction battery pack. These and other features are discussed in greater detail in the following paragraphs of this detailed description. 
       FIG.  1    schematically illustrates a powertrain  10  of an electrified vehicle  12 . In an embodiment, the electrified vehicle  12  is a battery electric vehicle (BEV). However, it should be understood that 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. Although not shown in this exemplary embodiment, the electrified vehicle  12  could be equipped with an internal combustion engine that can be employed either alone or in combination with other energy sources to propel the electrified vehicle  12 . 
     In the illustrated embodiment, the electrified vehicle  12  is a full electric vehicle propelled solely through electric power, such as by an electric machine  14 , without any assistance from an internal combustion engine. The electric machine  14  may operate as an electric motor, an electric generator, or both. The electric machine  14  receives electrical power and provides a rotational output torque. The electric machine  14  may be connected to a gearbox  16  for adjusting the output torque and speed of the electric machine  14  by a predetermined gear ratio. The gearbox  16  is connected to a set of drive wheels  18  by an output shaft  20 . 
     A voltage bus  22  electrically connects the electric machine  14  to a traction battery pack  24  through an inverter  26 , which can also be referred to as an inverter system controller (ISC). The electric machine  14 , the gearbox  16 , and the inverter  26  may be collectively referred to as a transmission  28  of the electrified vehicle  12 . 
     The traction battery pack  24  is an exemplary electrified vehicle battery. The traction battery pack  24  may be a high voltage traction battery pack that includes one or more battery arrays  25  (i.e., battery assemblies or groupings of battery cells) capable of outputting electrical power to operate the electric machine  14  and/or other electrical loads of the electrified vehicle  12 . Other types of energy storage devices and/or output devices can also be used to electrically power the electrified vehicle  12 . 
     The one or more battery arrays  25  of the traction battery pack  24  may include a plurality of battery cells  32  that store energy for powering various electrical loads of the electrified vehicle  12 . The traction battery pack  24  could employ any number of battery cells  32  within the scope of this disclosure. Accordingly, this disclosure should not be limited to the exact configuration shown in  FIG.  1   . 
     In an embodiment, the battery cells  32  are lithium-ion cells. However, other cell chemistries (nickel-metal hydride, lead-acid, etc.) could alternatively be utilized within the scope of this disclosure. 
     In another embodiment, the battery cells  32  are cylindrical or prismatic battery cells. However, other cell geometries could alternatively be utilized within the scope of this disclosure. 
     An enclosure assembly  34  may house the battery arrays  25  of the traction battery pack  24 . The enclosure assembly  34  may include any size, shape, and configuration within the scope of this disclosure. 
     The electrified vehicle  12  may also include a charging system  30  for charging the energy storage devices (e.g., the battery cells  32 ) of the traction battery pack  24 . The charging system  30  may include charging components that are located both onboard the electrified vehicle  12  (e.g. vehicle charge port assembly, etc.) and external to the electrified vehicle  12  (e.g., electric vehicle supply equipment (EVSE), etc.). The charging system  30  can be connected to an external power source (e.g., a grid power source) for receiving and distributing power received from the external power source throughout the electrified vehicle  12 . 
     The powertrain  10  depicted by  FIG.  1    is highly schematic and is not intended to limit this disclosure. Various additional components could alternatively or additionally be employed by the powertrain  10  within the scope of this disclosure. 
     During operation of the electrified vehicle  12 , the battery cells  32  and other internal components of the traction battery pack  24  can experience a rare event known as thermal runaway during certain battery thermal events (e.g., overcharging, overdischarging, overheating, etc.). Further, in such conditions, the battery cells  32  may vent gases and/or other effluents into the interior of the enclosure assembly  34 . The vent gases may be caused by an applied force or a thermal event, and can either cause or exacerbate an existing battery thermal event. A relatively significant amount of heat can be generated during battery thermal events, and if not contained, the generated heat can cascade to other battery internal components, thereby accelerating thermal runaway. This disclosure is therefore directed to traction battery pack designs that incorporate thermal barrier systems for mitigating thermal propagation within the interior of the traction battery pack when battery thermal events occur. 
       FIG.  2    illustrates in cross-section a traction battery pack  24  that may be employed within an electrified vehicle. For example, the traction battery pack  24  could be employed as part of the powertrain  10  of the electrified vehicle  12  of  FIG.  1   . 
     The enclosure assembly  34  of the traction battery pack  24  may be a sealed enclosure that includes a tray  36 , a cover  38 , and a seal  40 . The seal  40  may be disposed between the tray  36  and the cover  38  for sealing an interface  42  therebetween. The seal  40  may be a press-in-place seal, a foam seal, a curable seal, or any other type of seal suitable for sealing the interface  42  of the enclosure assembly  34 . 
     The tray  36  and the cover  38  may be constructed of metallic materials, polymer-based materials, textile materials, or any combination of these materials. In an exemplary embodiment, the cover  38  is constructed of polymer-based materials and the tray  36  is constructed of metallic materials. The cover  38  may therefore include a different material makeup than the tray  36 . 
     Once the cover  38  is secured to the tray  36 , the enclosure assembly  34  may establish an interior  44  for holding battery arrays and other battery internal components (not shown in  FIG.  3    for simplicity) of the traction battery pack  24 . The interior  44  may be established by inner walls/surfaces of both the tray  36  and the cover  38 . 
     In the illustrated embodiment, the traction battery pack  24  includes a first battery array  25 A and a second battery array  25 B housed within the interior  44 . Although the traction battery pack  24  of  FIG.  2    is depicted as having a two battery arrays, the traction battery pack  24  could include a greater number of battery arrays within the scope of this disclosure. Although not shown, one or more battery internal components (e.g., bussed electrical center (BEC), battery electric control module (BECM), etc.) could additionally be housed within the interior  44 . 
     The first battery array  25 A and the second battery array  25 B may be positioned atop the tray  36 . The cover  38  may then be received over the first and second battery arrays  25 A,  25 B and mounted to the tray  36  to assemble the enclosure assembly  34 . 
     The first and second battery arrays  25 A,  25 B may be received relative to a floor  46  of the tray  36 . The floor  46  may function as a heat exchanger plate or “cold plate” for conducting heat out of the battery cells  32  of the first and second battery arrays  25 A,  25 B. A thermal interface material  48  may be disposed between each of the first and second battery arrays  25 A,  25 B and the floor  46 . The thermal interface material  48  may include an epoxy resin, a silicone based material, a thermal grease, etc. and is designed to increase the thermal conductivity between the first and second battery arrays  25 A,  25 B and the tray  36 . Although shown as being an integrated feature of the tray  36  in this embodiment, a separate “cold plate” structure could be provided between the thermal interface material  48  and the floor  46 . 
     A bus bar assembly  50  may be utilized to electrically couple the first battery array  25 A and the second battery array  25 B. The bus bar assembly  50  may be attached to terminals  52  of the first and second battery arrays  25 A,  25 B and is configured to carry electrical current between the first and second battery arrays  25 A,  25 B for electrically distributing power. 
     The second battery array  25 B may be positioned side-by-side with the first battery array  25 A within the interior  44  of the enclosure assembly  34 . The first battery array  25 A may extend along a first longitudinal axis A 1  (into the page in  FIG.  2   ), and the second battery array  25 B may extend along a second longitudinal axis A 2  (into the page in  FIG.  2   ) that is parallel to the first longitudinal axis A 1 . In an embodiment, the first and second longitudinal axes A 1 , A 2  may extend in a cross-car direction when the traction battery pack  24  is mounted on the electrified vehicle  12 . However, other configurations and orientations of the first and second battery arrays  25 A,  25 B are further contemplated within the scope of this disclosure. 
     A mounting structure  54  may protrude upwardly from the tray  36  and may be disposed at a location of the interior  44  that is axially between the first and second battery arrays  25 A,  25 B. The mounting structure  54  could be any component of the traction battery pack  24 . In an embodiment, the mounting structure  54  is an integral component of the tray  36  of the enclosure assembly  34 . In another embodiment, the mounting structure  54  is a T-bracket that is fixedly mounted to the tray  36  for at least partially separating the first battery array  25 A from the second battery array  25 B. 
     Each of the first and second battery arrays  25 A,  25 B may include a mounting flange  56  that may be fixedly mounted (e.g., bolted, welded, etc.) to the mounting structure  54 . The mounting flange  56  of the first battery array  25 A may be mounted at an opposite side of the mounting structure  54  from the mounting flange  56  of the second battery array  25 B. 
     The traction battery pack  24  may additionally include a thermal barrier system  58  configured for mitigating thermal propagation between the first and second battery arrays  25 A,  25 B during battery thermal events. For example, the thermal barrier system  58  may be configured to block heat, battery cell vent gases, effluents, etc. from being transferred from one of the first battery array  25 A or the second battery array  25 B to the other of the first battery array  25 A or the second battery array  25 B during battery thermal events. 
     In an embodiment, all or portions of the thermal barrier system  58  may be integrated features of the cover  38  of the enclosure assembly  34 . For example, select portions of the thermal barrier system  58  may be molded-in or adhered to an inner surface  60  of the cover  38 . The thermal barrier system  58  may protrude inwardly from the inner surface  60  in a direction toward the floor  46  of the tray  36  (e.g., toward the first and second battery arrays  25 A,  25 B). 
     The thermal barrier system  58  may include a base  62 , a bifurcation structure  64 , and a canopy structure  66 . Although discussed herein individually due to their unique functions, each of the base  62 , the bifurcation structure  64 , and the canopy structure  66  may be integrally formed as unitary, molded construct. 
     The base  62  may protrude inwardly from the inner surface  60  of the cover  38 . The base  62  may be a molded feature of the cover  62  or could be a separate component that is adhered to the inner surface  60  of the cover  38 . 
     The bifurcation structure  64  may protrude further inwardly from the base  62  and may extend to a position that is axially between the first battery array  25 A and the second battery array  25 B. The bifurcation structure  64  may include an outer foam layer  68  that is received in abutting contact with an upper platform  70  of the mounting structure  54 . Therefore, in combination with the mounting structure  54 , the bifurcation structure  64  may substantially isolate a first portion P 1  of the interior  44  where the first battery array  25 A resides from a second portion P 2  of the interior  44  where the second battery array  25 B resides (and vice versa), thereby minimizing thermal propagation during battery thermal events. 
     The canopy structure  66  may be a hood-like structure that is arranged to cover at least a portion of the bus bar assembly  50 . The canopy structure  66  may include a first arm  72  that protrudes outwardly in a first direction away from the base  62  for interfacing with the first battery array  25 A, and a second arm  74  that protrudes outwardly in a second, opposite direction away from the base  62  for interfacing with the second battery array  25 B. A first angled tip portion  76  of the first arm  72  may include an outer foam layer  80  that is received in abutting contact with an upper surface  84  of the first battery array  25 A at a location that is slightly outboard of the bus bar assembly  50 , and a second angled tip portion  78  of the second arm  74  may include an outer foam layer  82  that is received in abutting contact with an upper surface  86  of the second battery array  25 B at a location that is slightly outboard of the bus bar assembly  50 . The canopy structure  66  may thus substantially block the transfer of heat and/or cell vent byproducts, gases, effluents, etc. from the first battery array  25 A and/or the second battery array  25  to the bus bar assembly  50 , thereby preventing the likelihood of electrically shorting either of the battery arrays  25 A,  25 B through the bus bar assembly  50 . 
     The cover  38  and the components of the thermal barrier system  58  may be made of a high temperature material. In an embodiment, the cover  38  and the base  62 , the bifurcation structure  64 , and the canopy structure  66  of the thermal barrier system  58  are made of a glass fiber reinforced thermoplastic material that is impregnated with a intumescent material. In another embodiment, the outer foam layers  68 ,  80 , and  82  of the thermal barrier system  58  are made of a silicate-based or polyurethane-based material that includes a high temperature aerogel foam (e.g., silica or metal oxide). The outer foam layers  68 ,  80 ,  82  may be overmolded features of the bifurcation structure  64  and the canopy structure  66 , respectively. Alternatively, the outer foam layers  68 ,  80 ,  82  may be adhered to the bifurcation structure  64  and the canopy structure  66 , respectively. 
       FIG.  3    illustrates in cross-section another exemplary thermal barrier system  158  that can be utilized within the traction battery pack  24 . The thermal barrier system  158  is similar to the thermal barrier system  158  discussed above. However, in this embodiment, the thermal barrier system  158  includes a slightly modified bifurcation structure  164 . The base  62  and the canopy structure  66  of the thermal barrier system  158  are substantially similar to those same components of the thermal barrier system  58  of  FIG.  2    and are therefore not re-discussed here for the sake of brevity. 
     The bifurcation structure  164  of the thermal barrier system  158  may straddle an upper platform  70  of the mounting structure  54 . The bifurcation structure  164  may include a first leg  190  that extends along a first side of the upper platform  70  (e.g., between the first battery array  25 A and the upper platform  70 ), and a second leg  192  that extends along a second side of the upper platform  70  (e.g., between the second battery array  25 B and the upper platform  70 ). 
     The first leg  190  may include an outer foam layer  194  that is received in abutting contact with a mounting flange  56  of the first battery array  25 A, and the second leg  192  may include an outer foam layer  196  that is received in abutting contact with a mounting flange  56  of the second battery array  25 B. Therefore, in combination with the mounting structure  54 , the bifurcation structure  164  may substantially isolate the first portion P 1  of the interior  44  where the first battery array  25 A resides from the second portion P 2  of the interior  44  where the second battery array  25 B resides (and vice versa), thereby minimizing thermal propagation during battery thermal events. 
     The exemplary thermal barrier systems of this disclosure are designed to mitigate array-to-array thermal propagation during battery thermal events for protecting the high voltage components of the traction battery pack. The thermal barrier systems may further provide increased thermal insulation between adjacent battery arrays and therefore reduce the susceptibility of adjacent modules reaching high temperatures during battery thermal events. 
     Although the different non-limiting embodiments are illustrated as having specific components or steps, the embodiments of this disclosure are not limited to those 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. 
     It should be understood that like reference numerals identify corresponding or similar elements throughout the several drawings. It should be understood that although a particular component arrangement is disclosed and illustrated in these exemplary embodiments, other arrangements could also benefit from the teachings of this disclosure. 
     The foregoing description shall be interpreted as illustrative and not in any limiting sense. A worker of ordinary skill in the art would understand that certain modifications could come within the scope of this disclosure. For these reasons, the following claims should be studied to determine the true scope and content of this disclosure.