Patent Publication Number: US-2022223972-A1

Title: Battery pack including vent gas passageway

Description:
TECHNICAL FIELD 
     This disclosure relates to a battery assembly of an electrified vehicle, and in particular to a battery pack with a vent gas passageway. 
     BACKGROUND 
     The need to reduce automotive fuel consumption and emissions is well known. Therefore, vehicles are being developed that reduce or completely eliminate reliance on internal combustion engines. Electrified vehicles are one type of vehicle being developed for this purpose. 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 an internal combustion engine to propel the vehicle. 
     A high voltage battery pack typically powers the electric machines and other electrical loads of the electrified vehicle. The battery pack includes a plurality of battery cells and various other battery internal components that support electric propulsion of electrified vehicles. 
     SUMMARY 
     A battery assembly for an electrified vehicle according to an exemplary aspect of the present disclosure incudes, among other things, a battery array having a plurality of battery cells. Each of the battery cells includes a vent configured to release vent gas from a respective one of the battery cells. Further, the battery assembly includes an enclosure assembly surrounding the battery array, and a vent gas passageway within the enclosure assembly. The vent gas passageway includes a plurality of inlet ports, and each of the inlet ports is substantially aligned with a respective one of the vents. 
     In a further non-limiting embodiment of the foregoing battery assembly, the inlet ports are provided by frangible sections of a structure. 
     In a further non-limiting embodiment of any of the foregoing battery assemblies, the vent gas passageway is bound within a plate assembly arranged above the battery cells. 
     In a further non-limiting embodiment of any of the foregoing battery assemblies, the plate assembly includes a first plate and a second plate, the second plate is arranged between the first plate and the vents, and the vent gas passageway is at least partially bound by the first and second plates. 
     In a further non-limiting embodiment of any of the foregoing battery assemblies, the inlet ports are provided by the second plate. 
     In a further non-limiting embodiment of any of the foregoing battery assemblies, the second plate includes a plurality of frangible sections, and each frangible section provides one of the inlet ports. 
     In a further non-limiting embodiment of any of the foregoing battery assemblies, the second plate includes a plurality of notches providing each frangible section. 
     In a further non-limiting embodiment of any of the foregoing battery assemblies, each frangible section is configured to at least partially separate from a remainder of the second plate in response to a thermal event. 
     In a further non-limiting embodiment of any of the foregoing battery assemblies, the vents of the battery cells are adjacent an upper surface of the battery cells, and the second plate is spaced-apart above the upper surfaces of the battery cells. 
     In a further non-limiting embodiment of any of the foregoing battery assemblies, the vent gas passageways provides a circuitous passageway between the inlet ports and an outlet port of the vent gas passageway. 
     In a further non-limiting embodiment of any of the foregoing battery assemblies, the vent gas passageway includes a first section and a second section, and the vent gas passageway is configured such that vent gas entering the vent gas passageway from one or more of the inlet ports flows into either the first section or the second section. 
     In a further non-limiting embodiment of any of the foregoing battery assemblies, a central divider within the vent gas passageway and adjacent the inlet ports directs vent gas entering the vent gas passageway from one or more of the inlet ports into one of the first and second sections. 
     In a further non-limiting embodiment of any of the foregoing battery assemblies, the first and second sections are each configured as a serpentine flow channel. 
     In a further non-limiting embodiment of any of the foregoing battery assemblies, the first and second sections are defined by projections between the first plate and the second plate. 
     In a further non-limiting embodiment of any of the foregoing battery assemblies, the vents of the battery cells are configured to release the vent gas in a thermal event. 
     An electrified vehicle according to an exemplary aspect of the present disclosure includes, among other things, an electric machine configured to propel the electrified vehicle and a battery assembly configured to deliver power to the electric machine. The battery assembly includes a battery array having a plurality of battery cells. Each of the battery cells includes a vent configured to release vent gases from a respective one of the battery cells. The battery assembly further includes an enclosure assembly surrounding the battery array. Further, the battery assembly includes a vent gas passageway within the enclosure assembly. The vent gas passageway includes plurality of inlet ports, and each of the inlet ports is substantially aligned with a respective one of the vents. 
     In a further non-limiting embodiment of the foregoing electrified vehicle, the vent gas passageway is at least partially bound within a plate assembly arranged above the battery cells, the plate assembly includes a first plate and a second plate, and the second plate is arranged between the first plate and the vents. 
     In a further non-limiting embodiment of any of the foregoing electrified vehicles, the second plate includes a plurality of frangible sections, each frangible section provides one of the inlet ports, and each frangible section is configured to at least partially separate from a remainder of the second plate in response to a thermal event. 
     In a further non-limiting embodiment of any of the foregoing electrified vehicles, the vent gas passageway provides a circuitous passageway between the inlet ports and an outlet port of the vent gas passageway. 
     In a further non-limiting embodiment of any of the foregoing electrified vehicles, the circuitous passageway includes two serpentine flow channels. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  schematically illustrates an example powertrain of an electrified vehicle. 
         FIG. 2  is a perspective, exploded view of an example battery assembly. 
         FIG. 3  is a perspective, assembled view of the example battery assembly. 
         FIG. 4  is a perspective, exploded view of another example battery assembly including separators between adjacent battery cells. 
         FIG. 5  is a sectional, side view of a portion of the battery assembly of  FIG. 4  taken along line  5 - 5  from  FIG. 6 . 
         FIG. 6  is a sectional, top view of another portion of the battery assembly of  FIG. 4  taken along line  6 - 6  from  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION 
     This disclosure relates to a battery assembly of an electrified vehicle, and in particular to a battery pack with a vent gas passageway. An example battery assembly includes a battery array having a plurality of battery cells. Each of the battery cells includes a vent configured to release vent gas from a respective one of the battery cells. Further, the battery assembly includes an enclosure assembly surrounding the battery array, and a vent gas passageway within the enclosure assembly. The vent gas passageway includes a plurality of inlet ports, and each of the inlet ports is substantially aligned with a respective one of the vents. Among other benefits, which will be appreciated from the below description, the disclosed arrangement mitigates thermal events, protects the enclosure of the battery assembly, and reduces if not eliminates any discharge of debris, particles, and/or liquid droplets that may be suspended in vent gases. 
       FIG. 1  schematically illustrates a powertrain  10  for an electrified vehicle  12  (“vehicle  12 ”). Although depicted as a hybrid electric vehicle (HEV), it should be understood that the concepts described herein are not limited to HEVs and could extend to other electrified vehicles, including, but not limited to, plug-in hybrid electric vehicles (PHEVs) and battery electric vehicles (BEVs). 
     In one embodiment, the powertrain  10  is a power-split powertrain system that employs a first drive system and a second drive system. The first drive system includes a combination of an engine  14  and a generator  18  (i.e., a first electric machine). The second drive system includes at least a motor  22  (i.e., a second electric machine), the generator  18 , and a battery assembly  24 . In this example, the second drive system is considered an electric drive system of the powertrain  10 . The first and second drive systems generate torque to drive one or more sets of vehicle drive wheels  28  of the vehicle  12 . Although a power-split configuration is shown, this disclosure extends to any hybrid or electric vehicle including full hybrids, parallel hybrids, series hybrids, mild hybrids or micro hybrids. 
     The engine  14 , which in one embodiment is an internal combustion engine, and the generator  18  may be connected through a power transfer unit  30 , such as a planetary gear set. Of course, other types of power transfer units, including other gear sets and transmissions, may be used to connect the engine  14  to the generator  18 . In one non-limiting embodiment, the power transfer unit  30  is a planetary gear set that includes a ring gear  32 , a sun gear  34 , and a carrier assembly  36 . 
     The generator  18  can be driven by the engine  14  through the power transfer unit  30  to convert kinetic energy to electrical energy. The generator  18  can alternatively function as a motor to convert electrical energy into kinetic energy, thereby outputting torque to a shaft  38  connected to the power transfer unit  30 . Because the generator  18  is operatively connected to the engine  14 , the speed of the engine  14  can be controlled by the generator  18 . 
     The ring gear  32  of the power transfer unit  30  may be connected to a shaft  40 , which is connected to vehicle drive wheels  28  through a second power transfer unit  44 . The second power transfer unit  44  may include a gear set having a plurality of gears  46 . Other power transfer units may also be suitable. The gears  46  transfer torque from the engine  14  to a differential  48  to ultimately provide traction to the vehicle drive wheels  28 . The differential  48  may include a plurality of gears that enable the transfer of torque to the vehicle drive wheels  28 . In one embodiment, the second power transfer unit  44  is mechanically coupled to an axle  50  through the differential  48  to distribute torque to the vehicle drive wheels  28 . 
     The motor  22  can also be employed to drive the vehicle drive wheels  28  by outputting torque to a shaft  52  that is also connected to the second power transfer unit  44 . In one embodiment, the motor  22  and the generator  18  cooperate as part of a regenerative braking system in which both the motor  22  and the generator  18  can be employed as motors to output torque. For example, the motor  22  and the generator  18  can each output electrical power to the battery assembly  24 . 
     The battery assembly  24  is an exemplary electrified vehicle battery. The battery assembly  24  may be a high voltage traction battery pack that includes a plurality of battery arrays  25 , or other groupings of battery cells, capable of outputting electrical power to operate the motor  22 , the generator  18 , and/or other electrical loads of the vehicle  12 . 
     An example battery array  25  is shown in  FIG. 2 , and includes a single battery array with a plurality of battery cells. This disclosure is not limited to battery packs with one battery array and extends to battery packs with one or more battery arrays. Other types of energy storage devices and/or output devices can also be used to electrically power the vehicle  12 . 
     In one non-limiting embodiment, the vehicle  12  has two basic operating modes. The vehicle  12  may operate in an Electric Vehicle (EV) mode where the motor  22  is used (generally without assistance from the engine  14 ) for vehicle propulsion, thereby depleting the battery assembly  24  state of charge up to its maximum allowable discharging rate under certain driving patterns/cycles. The EV mode is an example of a charge depleting mode of operation for the vehicle  12 . During EV mode, the state of charge of the battery assembly  24  may increase in some circumstances, for example due to a period of regenerative braking. The engine  14  is generally OFF under a default EV mode but could be operated as necessary based on a vehicle system state or as permitted by the operator. 
     The vehicle  12  may additionally operate in a Hybrid (HEV) mode in which the engine  14  and the motor  22  are both used for vehicle propulsion. The HEV mode is an example of a charge sustaining mode of operation for the vehicle  12 . During the HEV mode, the vehicle  12  may reduce the motor  22  propulsion usage in order to maintain the state of charge of the battery assembly  24  at a constant or approximately constant level by increasing the engine  14  propulsion usage. The vehicle  12  may be operated in other operating modes in addition to the EV and HEV modes within the scope of this disclosure. 
       FIG. 2  illustrates additional detail of the battery assembly  24  in an exploded view.  FIG. 3  illustrates the same battery assembly  24  in an assembled state. With joint reference to  FIGS. 2 and 3 , the battery assembly  24  includes one battery array  56  configured to supply electrical power to various vehicle components. The battery assembly  24  could include additional battery arrays, however. 
     The battery array  56  includes a plurality of battery cells  58  that are stacked side-by-side along a span length (i.e., the largest dimension) of the battery array  56 . Although not shown in the schematic depiction of  FIG. 2 , the battery cells  58  may be electrically connected to one another using busbar assemblies. In one embodiment, the battery cells  58  are prismatic, lithium-ion cells. However, battery cells having other geometries (cylindrical, pouch, etc.) and/or other chemistries (nickel-metal hydride, lead-acid, etc.) could alternatively be utilized within the scope of this disclosure. 
     An enclosure assembly  60  surrounds the battery array  56 . The enclosure assembly  60  includes a bottom wall  62 , left and right side walls  64 ,  66 , end walls  68 ,  70 , and a top wall  72 . The enclosure assembly  60  surrounds an interior  74  (i.e., area inside the walls  62 ,  64 ,  66 ,  68 ,  70 ,  72 ) of the enclosure assembly  60 , which houses the battery array  56  and any other components of the battery assembly  24 . The enclosure assembly  60  may take any size, shape or configuration, and is not limited to the specific configuration of  FIG. 2 . Further, the adjacent parts of the enclosure assembly  60  are connected together. In order to provide an air and water-tight seal, one or more gaskets and/or seals may fill the space at an interface between the mating surfaces of the parts of the enclosure assembly  60 . 
     During operation of the electrified vehicle  12 , the battery cells  58  and internal components of the battery assembly  24  can experience a rare event known as thermal runaway during certain battery thermal events (e.g., overcharging, overheating, etc.). Further, in such conditions, the battery cells  58  may vent gases into the interior  74  of the enclosure assembly  60 . The vent gases may be caused by an applied force or a thermal event, and can either cause or exacerbate an existing thermal event. The vent gases expelled by the battery cells  58  may include a gaseous byproduct including gas and debris, such as relatively small, solid particles and/or liquid droplets suspended in the gas. In this disclosure, reference to “gas” or “vent gas” is inclusive of any debris, particles, and/or droplets suspended in that gas, unless specifically indicated. 
     In  FIG. 2 , adjacent battery cells  58  directly contact one another. This disclosure extends to other arrangements, such as in  FIG. 4 , in which there is a separator  76  between each adjacent battery cell  58 . The separators  76  may be made of thermally insulated material such as aerogel or mica. The quantities of battery cells  58  and separators  76  in  FIGS. 2 and 4  are exemplary. 
     In both examples, the battery cells  58  each include a vent port  78  (“vent  78 ”) adjacent an upper surface  79  of the battery cell  58 . The vents  78  are configured to release vent gases from the interior of the battery cells  58  when the battery cells  58  become relatively hot and/or experience an increase in pressure, such as during a thermal event. The vents  78  are configured to open when an internal pressure of the battery cell  58  exceeds a threshold, which is 400 kPa in one example. 
     In this disclosure, the battery assembly  24  further includes a plate assembly  80  which is arranged in the enclosure assembly  60  and at least partially defines a vent gas passageway  82 , as generally shown in  FIG. 5 . The plate assembly  80  includes a first plate  84  and second plate  86 . The first plate  84  is a top plate and is arranged adjacent the top wall  72 . In a particular example, the first plate  84  is directly attached to the top wall  72 . The second plate  86  is spaced-apart from the first plate  84  in a direction toward the bottom wall  62  such that a vertical space exists between the first and second plates  84 ,  86 , which provides the vent gas passageway  82 . In particular, a majority of the first plate  84  lies in a plane that is spaced-apart vertically from a plane containing a majority of the second plate  86 . When the first plate  84  includes projections, as discussed below relative to  FIG. 6 , the second plate  86  may contact those projections. Still, the main portions of the first and second plates  84 ,  86 , namely everything but the projections, are spaced-apart from one another to provide the vent gas passageway  82 . 
     In an example of this disclosure, the first and second plates  84 ,  86  are made of a material with a relatively low thermal conductivity, a relatively low breakdown voltage, a relatively high flexural modulus, and a relatively high tensile strength. In a particular example, the first and second plates  84 ,  86  are made of a material that exhibits a thermal conductivity less than 0.3 W/m*K (Watts per meter-Kelvin), a breakdown voltage less than 20 kV, a flexural modulus of 120 MPa, and a tensile strength of 1800 MPa. Example materials for the first and second plates  84 ,  86  include mica and fiber glass. The materials of the first and second plates  84 ,  86  may also be both electrically and thermally insulated. 
     The vertical space between the first and second plates  84 ,  86  is set such that vent gases can flow through the vent gas passageway  82  while also starving the vent gases of oxygen within the vent gas passageway  82 , which serves to prevent furtherance of a thermal event. Adjusting the vertical space between the first and second plates  84 ,  86  changes the volume of the vent gas passageway  82 . The precise vertical space between the first and second plates  84 ,  86  is set during a manufacturing process based on a chemistry of the battery cells  58 , and in turn an expected chemistry of the vent gases. Further, the arrangement of walls  62 ,  64 ,  66 ,  68 ,  70 ,  72  is also set such that the volume of the interior  74  prevents the furtherance of a thermal event, based on the expected chemistry of the vent gases. Other factors may be considered when setting the vertical space between the first and second plates  84 ,  86  and the size of the interior  74 . Such factors include the characteristics of the cell chemistry relative to high heats and pressures, the altitude at which the electrified vehicle  12  is most likely to be used, the nitrogen concentration in air, the expected nitrogen concentration in a particular location within the battery assembly  24  after or during a thermal event, etc. 
     Fluid, namely vent gas, is configured to flow along the vent gas passageway  82  from an inlet to an outlet. In this example, the vent gas passageway  82  includes a plurality of inlets and a plurality of outlets. The vent gas passageway  82  is vertically bound by the first and second plates  84 ,  86 , and is bound at the ends and on the sides by walls  64 ,  66 ,  68 ,  70 , in this example. 
     In this disclosure, the inlets to the vent gas passageway  82  are provided by inlet ports  88  formed in the second plate  86 . In  FIG. 5 , three inlet ports  88 A- 88 C are shown. The inlet ports  88 A- 88 C are frangible sections of the second plate  86  vertically aligned with the vents  78 . The frangible sections are formed by providing notches  90  in the second plate. While notches are mentioned as a technique for forming the frangible sections, the frangible sections could be formed in another manner. In normal operating conditions, the frangible sections may be relatively indistinguishable from a remainder of the second plate  86 . However, the frangible sections are intentionally weakened such that they will at least partially separate from the remainder of the second plate  86  in response to relatively high pressures, such as those associated with vent gases released from the vents  78  in a thermal event. In an example, the frangible sections are configured to at least partially separate when exposed to pressures of 400 kPa or greater. 
     Regarding the vertical alignment of the inlet ports  88  relative to the vents  78 , with reference to the inlet port  88 B and the corresponding vent  78 , a vertical line X passes through both the inlet port  88 B and the vent  78 . The vertical line X in this example is parallel to a direction of gravity. Further, when viewed from above (such as from the perspective of the first plate  84 ), the inlet port  88 B at least partially overlaps the vent  78 . In this example, the inlet port  88 B fully overlaps the vent  78 . Specifically, the inlet port  88 B is of a larger area than the vent  78  and the two are arranged such that when viewed in the direction of the line X from the perspective of the first plate  84 , the area of the vent  78  is fully within the area of the inlet port  88 B. The other inlet ports  88 A,  88 C and corresponding vents  78  are aligned in a similar manner. Further, while the second plate  86  does not contact the vents  78 , the second plate  86  is spaced-apart vertically from the vents  78  by a relatively small distance D such that a vast majority of vent gas is directed into the vent gas passageway  82 . 
     In this disclosure, with reference to  FIG. 6 , outlets  92 ,  94  of the vent gas passageway  82  are illustrated schematically. The outlets  92 ,  94  may be provided by one-way valves permitting egress but not ingress of fluid. The outlets  92 ,  94  may be formed in or adjacent the left and right side walls  64 ,  66 , as examples. The outlets  92 ,  94  may be formed elsewhere, such as in the top wall  72  as an alternative to or in addition to the left and right side walls  64 ,  66 . 
     One of the first and second plates  84 ,  86  may include projections extending between the plates to direct vent gas within the vent gas passageway  82 . In an example, the first plate  84  includes a series of projections  96 A- 96 G, as shown in  FIG. 6 . Each of the projections  96 A- 96 G extends from the first plate  84  to the second plate  86 . A central one of the projections, here central projection  96 D, is arranged above and between the inlet ports  88 A,  88 B,  88 C and serves as a divider directing vent gas to either a first section  98  of the vent gas passageway  82  or a second section  100  of the vent gas passageway  82 . The projections  96 A- 96 G could be provided by structures separate from the first and second plates  84 ,  86 . Those separate structures can then be attached to the first and/or second plates  84 ,  86  by welding or brazing, as examples. 
     The projections  96 A- 96 C and  96 E- 96 G are staggered such that the first and sections  98 ,  100  each define a serpentine flow channel. Specifically, the first section  98  of the vent gas passageway  82  is a serpentine channel defined by the projections  96 A- 96 C and leads from the inlet ports  88 A- 88 C to the outlet  92 . The second section  100  is a serpentine channel defined by the projections  96 E- 96 G and leads from the inlet ports  88 A- 88 C to the outlet  94 . This disclosure is not limited to vent gas passageways with multiple sections or with serpentine flow channels. Rather, this disclosure extends to other circuitous passageways which provide an indirect route from an inlet to an outlet. A benefit of such a configuration is that, during a thermal event, as vent gases flow through the vent gas passageway  82 , any debris, particles, or liquid droplets suspended in the vent gas tend to fall out of the gas and collect in the vent gas passageway  82 , which prevents the discharge of such debris, particles, and/or liquid droplets into the electrified vehicle  12  and/or the surrounding environment. 
     In  FIG. 5 , a thermal event has occurred relative to the middle-most battery cell  58 . As such, vent gas V has been released from the vent  78  and the vent gas V has caused the frangible section defining the inlet port  88 B to at least partially separate from the remainder of the plate  86  such that the vent gas V enters the vent gas passageway  82 . As vent gas V enters the vent gas passageway  82 , it may impinge on the first plate  84 . Further, any particles or droplets or other debris within the vent gas V will also impinge on the first plate  84 . As generally discussed above, the material of the first plate  84  is selected of a relatively high strength material to protect the top wall  72 . Downstream of the inlet port  88 B, the vent gas V splits by interaction with the central projection  96 D and is directed along one of the sections  98 ,  100  to a corresponding one of the outlets  92 ,  94 . As the vent gas V flows along the vent gas passageway  82 , any debris, particles, and/or droplets suspended the vent gas V fall out of the suspension and collect against the upper surface of the second plate  86 . In this regard, the vent gas passageway  82  acts as a filter. Further, since vent gas V was directed into the vent gas passageway  82  as opposed to circulating within the interior  74 , propagation of a thermal event is mitigated. 
     It should be understood that terms such as “about,” “substantially,” and “generally” are not intended to be boundaryless terms, and should be interpreted consistent with the way one skilled in the art would interpret those terms. It should also be understood that directional terms such as “upper,” “top,” “vertical,” “forward,” “rear,” “side,” “above,” “below,” etc., are used herein relative to the normal operational attitude of a vehicle for purposes of explanation only, and should not be deemed limiting. 
     Although the different examples have the specific components shown in the illustrations, embodiments of this disclosure are not limited to those particular combinations. It is possible to use some of the components or features from one of the examples in combination with features or components from another one of the examples. In addition, the various figures accompanying this disclosure are not necessarily to scale, and some features may be exaggerated or minimized to show certain details of a particular component or arrangement. 
     One of ordinary skill in this art would understand that the above-described embodiments are exemplary and non-limiting. That is, modifications of this disclosure would come within the scope of the claims. Accordingly, the following claims should be studied to determine their true scope and content.