WO2018209282A1

WO2018209282A1 - Vent plug for a battery module

Info

Publication number: WO2018209282A1
Application number: PCT/US2018/032393
Authority: WO
Inventors: Ken Nakayama; Nicholas E. Elison; Richard M. Dekeuster
Original assignee: Johnson Controls Technology Company
Priority date: 2017-05-12
Filing date: 2018-05-11
Publication date: 2018-11-15

Abstract

A vent plug (64) attaches to (plugs) a vent port (62) of a lithium ion battery module (28), and is configured to be situated within a vent hose (122) associated with a vehicle (10) or other system in which the battery module (28) is utilized. The vent plug (64) is designed to operate to release the internal pressure of the battery module (28) via the vent port (62) once the internal pressure reaches a threshold.

Description

VENT PLUG FOR A BATTERY MODULE

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority from and the benefit of U.S. Provisional Application Serial No. 62/505,840, filed May 12, 2017, entitled "Controlled Release Pressure Vent Plug and Hose Connection Port Design," which is hereby incorporated by reference in its entirety for all purposes.

BACKGROUND

[0002] The present disclosure relates generally to the field of batteries and battery modules. More specifically, the present disclosure relates to vent configurations for a battery module.

[0003] This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.

[0004] A vehicle that uses one or more battery systems for providing all or a portion of the motive power for the vehicle can be referred to as an xEV, where the term "xEV" is defined herein to include all of the following vehicles, or any variations or combinations thereof, that use electric power for all or a portion of their vehicular motive force. For example, xEVs include electric vehicles (EVs) that utilize electric power for all motive force. As will be appreciated by those skilled in the art, hybrid electric vehicles (HEVs), also considered xEVs, combine an internal combustion engine propulsion system and a battery-powered electric propulsion system, such as 48 Volt (V) or 130V systems. The term HEV may include any variation of a hybrid electric vehicle. For example, full hybrid systems (FHEVs) may provide motive and other electrical power to the vehicle using one or more electric motors, using only an internal combustion engine, or using both. In contrast, mild hybrid systems (MHEVs) disable the internal combustion engine when the vehicle is idling and utilize a battery system to continue powering the air conditioning unit, radio, or other electronics, as well as to restart the engine when propulsion is desired. The mild hybrid system may also apply some level of power assist, during acceleration for example, to supplement the internal combustion engine. Mild hybrids are typically 96V to 130V and recover braking energy through a belt or crank integrated starter generator. Further, a micro- hybrid electric vehicle (mHEV) also uses a "Stop-Start" system similar to the mild hybrids, but the micro-hybrid systems of a mHEV may or may not supply power assist to the internal combustion engine and operates at a voltage below 60V. For the purposes of the present discussion, it should be noted that mHEVs typically do not technically use electric power provided directly to the crankshaft or transmission for any portion of the motive force of the vehicle, but an mHEV may still be considered as an xEV since it does use electric power to supplement a vehicle's power needs when the vehicle is idling with internal combustion engine disabled and recovers braking energy through an integrated starter generator. In addition, a plug-in electric vehicle (PEV) is any vehicle that can be charged from an external source of electricity, such as wall sockets, and the energy stored in the rechargeable battery packs drives or contributes to drive the wheels. PEVs are a subcategory of EVs that include all-electric or battery electric vehicles (BEVs), plug-in hybrid electric vehicles (PHEVs), and electric vehicle conversions of hybrid electric vehicles and conventional internal combustion engine vehicles.

[0005] xEVs as described above may provide a number of advantages as compared to more traditional gas-powered vehicles using only internal combustion engines and traditional electrical systems, which are typically 12V systems powered by a lead acid battery. For example, xEVs may produce fewer undesirable emission products and may exhibit greater fuel efficiency as compared to traditional internal combustion vehicles and, in some cases, such xEVs may eliminate the use of gasoline entirely, as is the case of certain types of EVs or PEVs.

[0006] As technology continues to evolve, there is a need to provide improved power sources, particularly battery modules, for such vehicles. For example, in traditional configurations, battery modules may include a vent mechanism for venting gases from an inside of the battery module. The vent mechanism may enable venting in response to a pressure increase in the inside of the battery module (e.g., a pressure increase exceeding a venting pressure threshold of the battery module). Certain venting mechanisms for battery modules may be complex, and may not provide sufficient flow out of the battery module during a venting situation. Further, certain vents may not provide a sufficient level of sealing of the battery module from the external environment. Accordingly, it is now recognized that improved venting mechanisms for battery modules are desired.

SUMMARY

[0007] A summary of certain embodiments disclosed herein is set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of certain embodiments and that these aspects are not intended to limit the scope of this disclosure. Indeed, this disclosure may encompass a variety of aspects that may not be set forth below.

[0008] The present disclosure relates to a lithium ion battery module having a battery module housing. A vent port extends from the battery module housing and has a vent opening to allow battery cell effluent to escape the battery module housing. A vent plug is disposed within the vent port, and the vent plug includes a stem portion and a coupling portion. The stem portion maintains alignment of the vent plug within the vent port, and the coupling portion forms a seal against the vent port.

[0009] The present disclosure also relates to a vent plug for a lithium ion battery module. The vent plug includes a coupling portion comprising an annular wall configured to be disposed within a vent port of the lithium ion battery module. The coupling portion is configured to form a seal against an internal surface of the vent port. A stem portion extends from the coupling portion and has an elongated annular wall having an outer diameter that is smaller than the outer diameter of the coupling portion such that an outer profile of the vent plug has a stepped geometry. [0010] The present disclosure also relates to a battery system having a battery module housing; a plurality of lithium ion battery cells disposed in the housing; a vent port extending through the battery module housing and providing a pathway for the escape of vented cell effluent to escape from the battery module housing; and a vent plug disposed within the vent port. The vent plug includes a coupling portion and a stem portion, and the coupling portion includes a securement feature securing the vent plug in the vent port. The vent plug is configured to be dislodged from the vent port when a pressure within the battery module housing exceeds a threshold corresponding to a total vent of cell effluent from at least one lithium ion battery cell of the plurality of lithium ion battery cells.

DRAWINGS

[0011] Various aspects of this disclosure may be better understood upon reading the following detailed description and upon reference to the drawings in which:

[0012] FIG. 1 is a perspective view of a vehicle having a battery system configured in accordance with present embodiments to provide power for various components of the vehicle;

[0013] FIG. 2 is a cutaway schematic view of an embodiment of the vehicle and the battery system of FIG. 1;

[0014] FIG. 3 is a perspective view of an embodiment of the battery system of FIG. 1, in accordance with an embodiment of the present approach;

[0015] FIG. 4 is a perspective view of an embodiment of a vent plug, in accordance with an embodiment of the present approach;

[0016] FIG. 5 is a cross-section of an embodiment of the vent plug of FIG. 4, in accordance with an embodiment of the present approach;

[0017] FIG. 6 is a cross-sectional side elevation view of the vent plug of FIGS. 4 and 5 being installed into a vent port of a battery module, in accordance with an embodiment of the present approach; [0018] FIG. 7 is a cross-sectional side elevation view of the vent plug and vent port of FIG. 6 after installation, the vent plug maintaining a seal within the vent port at an internal pressure of the battery module below a threshold, in accordance with an embodiment of the present approach;

[0019] FIG. 8 is a cross-sectional side elevation view of an embodiment of the vent plug and vent port of FIG. 7 after the vent plug has been dislodged from the vent port in response to an internal pressure of the battery module being above a threshold, in accordance with an embodiment of the present approach;

[0020] FIG. 9 is perspective view of an embodiment of the vent plug having an O- ring for sealing within the vent port, in accordance with an embodiment of the present approach; and

[0021] FIG. 10 is a cross-sectional perspective view of the vent plug of FIG. 9, in accordance with an embodiment of the present approach.

DETAILED DESCRIPTION

[0022] One or more specific embodiments will be described below. In an effort to provide a concise description of these embodiments, not all features of an actual implementation are described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.

[0023] The battery systems described herein may be used to provide power to various types of electric vehicles (xEVs) and other high voltage energy storage/expending applications (e.g., electrical grid power storage systems). Such battery systems may include one or more battery modules, each battery module having a number of battery cells (e.g., lithium-ion (Li-ion) electrochemical cells) arranged and electrically interconnected to provide particular voltages and/or currents useful to power, for example, one or more components of an xEV. As another example, battery modules in accordance with present embodiments may be incorporated with or provide power to stationary power systems (e.g., non-automotive systems).

[0024] Based on the advantages over traditional gas-power vehicles, manufacturers, which generally produce traditional gas-powered vehicles, may desire to utilize improved vehicle technologies (e.g., regenerative braking technology) within their vehicle lines. Often, these manufacturers may utilize one of their traditional vehicle platforms as a starting point. Accordingly, since traditional gas-powered vehicles are designed to utilize 12 volt battery systems, a 12 volt lithium ion battery may be used to supplement a 12 volt lead-acid battery. More specifically, the 12 volt lithium ion battery may be used to more efficiently capture electrical energy generated during regenerative braking and subsequently supply electrical energy to power the vehicle's electrical system.

[0025] As advancements occur with vehicle technologies, high voltage electrical devices requiring voltage higher than 12 volts may also be included in the vehicle's electrical system. For example, the lithium ion battery may supply electrical energy to an electric motor in a mild-hybrid vehicle. Often, these higher voltage electrical devices utilize voltage greater than 12 volts, for example, up to 48 volts. Accordingly, in some embodiments, the output voltage of a 12 volt lithium ion battery may be boosted using a DC-DC converter to supply power to the high voltage devices. Additionally or alternatively, a 48 volt lithium ion battery may be used to supplement a 12 volt lead- acid battery. More specifically, the 48 volt lithium ion battery may be used to more efficiently capture electrical energy generated during regenerative braking and subsequently supply electrical energy to power the high voltage devices.

[0026] Thus, the design choice regarding whether to utilize a 12 volt lithium ion battery or a 48 volt lithium ion battery may depend directly on the electrical devices included in a particular vehicle. Nevertheless, although the voltage characteristics may differ, the operational principles of a 12 volt lithium ion battery and a 48 volt lithium ion battery are generally similar. More specifically, as described above, both may be used to capture electrical energy during regenerative braking and subsequently supply electrical energy to power electrical devices in the vehicle.

[0027] Accordingly, to simplify the following discussion, the present techniques will be described in relation to a battery system with a 12 volt lithium ion battery and a 12 volt lead-acid battery. However, one of ordinary skill in art is able to adapt the present techniques to other battery systems, such as a battery system with a 48 volt lithium ion battery and a 12 volt lead-acid battery.

[0028] The present disclosure relates to batteries and battery modules. More specifically, the present disclosure relates to a vent plug for a battery module that enables a pressure to be substantially maintained within a battery module housing during normal operation (e.g., when a pressure within the battery module housing is less than a threshold level), while also being configured to enable a significant pressure release from within the battery module housing should the pressure in the battery module housing quickly rise above a threshold level. Particular embodiments are directed to lithium ion battery modules that may be used in vehicular contexts (e.g., hybrid electric vehicles) as well as other energy storage/expending applications (e.g., energy storage for an electrical grid).

[0029] With the preceding in mind, the present disclosure describes an improved vent for a battery module. Lithium ion battery systems, such as those used in automotive applications, must be sealed from the external environment. The external environment can otherwise cause contamination, such as water and salt spray ingress that can lead to corrosion and failure of battery functionality. The vent plug of the present disclosure attaches to (plugs) a vent port of a lithium ion battery module, and is configured to be situated within a vent hose associated with a vehicle or other system in which the battery module is utilized. The vent plug is designed to operate to release the internal pressure of the battery module via the vent port once the internal pressure reaches a threshold level. For example, in a situation where one or more battery cells in the battery module vent cell effluent, the vent plug releases from the vent port at a set pressure so that the vent passage is open for controlled release of the effluent. Specifically, the vent plug releases the cell effluent without affecting the structural integrity and seal integrity of the battery housing. The effluent may be directed into a vehicle hose connected to the vent port so that the effluent can be directed to a predetermined location, which may also thereby prevent accidental release of vent gas into controlled environment like the passenger compartment and trunk. The specific geometrical shape of the vent plug may be configured such that the vent plug lodges into the vehicle hose in a position where the vent plug allows cell effluent to continue to travel through and out of the hose.

[0030] Typical batteries do not have a plug that seals, and the interior of such batteries can be subject to external environment influence. Typical check valves require more complex mechanical assembly and are not always effective to create a seal and provide free flowing opening when needed. Example designs of vent plugs configured in accordance with the present disclosure are set forth below.

[0031] To help illustrate, FIG. 1 is a perspective view of an embodiment of a vehicle 10, which may utilize a regenerative braking system. Although the following discussion is presented in relation to vehicles with regenerative braking systems, the techniques described herein are adaptable to other vehicles that capture/store electrical energy with a battery, which may include electric-powered and gas-powered vehicles.

[0032] As discussed above, it would be desirable for a battery system 12 to be largely compatible with traditional vehicle designs. Accordingly, the battery system 12 may be placed in a location in the vehicle 10 that would have housed a traditional battery system. For example, as illustrated, the vehicle 10 may include the battery system 12 positioned similarly to a lead-acid battery of a typical combustion-engine vehicle (e.g., under the hood of the vehicle 10). Furthermore, as will be described in more detail below, the battery system 12 may be positioned to facilitate managing temperature of the battery system 12. For example, in some embodiments, positioning a battery system 12 under the hood of the vehicle 10 may enable an air duct to channel airflow over the battery system 12 and cool the battery system 12. [0033] A more detailed view of the battery system 12 is described in FIG. 2. As depicted, the battery system 12 includes an energy storage component 14 coupled to an ignition system 16, an alternator 18, a vehicle console 20, and optionally to an electric motor 22. Generally, the energy storage component 14 may capture/store electrical energy generated in the vehicle 10 and output electrical energy to power electrical devices in the vehicle 10.

[0034] In other words, the battery system 12 may supply power to components of the vehicle's electrical system, which may include radiator cooling fans, climate control systems, electric power steering systems, active suspension systems, auto park systems, electric oil pumps, electric super/turbochargers, electric water pumps, heated windscreen/defrosters, window lift motors, vanity lights, tire pressure monitoring systems, sunroof motor controls, power seats, alarm systems, infotainment systems, navigation features, lane departure warning systems, electric parking brakes, external lights, or any combination thereof. Illustratively, in the depicted embodiment, the energy storage component 14 supplies power to the vehicle console 20, a display 21 within the vehicle, and the ignition system 16, which may be used to start (e.g., crank) an internal combustion engine 24.

[0035] Additionally, the energy storage component 14 may capture electrical energy generated by the alternator 18 and/or the electric motor 22. In some embodiments, the alternator 18 may generate electrical energy while the internal combustion engine 24 is running. More specifically, the alternator 18 may convert the mechanical energy produced by the rotation of the internal combustion engine 24 into electrical energy. Additionally or altematively, when the vehicle 10 includes an electric motor 22, the electric motor 22 may generate electrical energy by converting mechanical energy produced by the movement of the vehicle 10 (e.g., rotation of the wheels) into electrical energy. Thus, in some embodiments, the energy storage component 14 may capture electrical energy generated by the alternator 18 and/or the electric motor 22 during regenerative braking. As such, the alternator 18 and/or the electric motor 22 are generally referred to herein as a regenerative braking system. [0036] To facilitate capturing and supplying electric energy, the energy storage component 14 may be electrically coupled to the vehicle's electric system via a bus 26. For example, the bus 26 may enable the energy storage component 14 to receive electrical energy generated by the alternator 18 and/or the electric motor 22. Additionally, the bus 26 may enable the energy storage component 14 to output electrical energy to the ignition system 16 and/or the vehicle console 20. Accordingly, when a 12 volt battery system 12 is used, the bus 26 may carry electrical power typically between 8-18 volts.

[0037] Additionally, as depicted, the energy storage component 14 may include multiple battery modules. For example, in the depicted embodiment, the energy storage component 14 includes a lead acid (e.g., a first) battery module 28 in accordance with present embodiments, and a lithium ion (e.g., a second) battery module 30, where each battery module 28, 30 includes one or more battery cells. In other embodiments, the energy storage component 14 may include any number of battery modules. Additionally, although the first battery module 28 and the second battery module 30 are depicted adjacent to one another, they may be positioned in different areas around the vehicle. For example, the second battery module 30 may be positioned in or about the interior of the vehicle 10 while the first battery module 28 may be positioned under the hood of the vehicle 10.

[0038] In some embodiments, the energy storage component 14 may include multiple battery modules to utilize multiple different battery chemistries. For example, the first battery module 28 may utilize a lead-acid battery chemistry and the second battery module 30 may utilize a lithium ion battery chemistry. In such an embodiment, the performance of the battery system 12 may be improved since the lithium ion battery chemistry generally has a higher coulombic efficiency and/or a higher power charge acceptance rate (e.g., higher maximum charge current or charge voltage) than the lead- acid battery chemistry. As such, the capture, storage, and/or distribution efficiency of the battery system 12 may be improved.

[0039] To facilitate controlling the capturing and storing of electrical energy, the battery system 12 may additionally include a control module 32. More specifically, the control module 32 may control operations of components in the battery system 12, such as relays (e.g., switches) within energy storage component 14, the alternator 18, and/or the electric motor 22. For example, the control module 32 may regulate amount of electrical energy captured/supplied by each battery module 28 or 30 (e.g., to de-rate and re-rate the battery system 12), perform load balancing between the battery modules 28 and 30, determine a state of charge of each battery module 28 or 30, determine temperature of each battery module 28 or 30, determine a predicted temperature trajectory of either battery module 28 and 30, determine predicted life span of either battery module 28 or 30, determine fuel economy contribution by either battery module 28 or 30, determine an effective resistance of each battery module 28 or 30, control magnitude of voltage or current output by the alternator 18 and/or the electric motor 22, and the like.

[0040] Accordingly, the control module (e.g., unit) 32 may include one or more processors 34 and one or more memories 36. More specifically, the one or more processors 34 may include one or more application specific integrated circuits (ASICs), one or more field programmable gate arrays (FPGAs), one or more general purpose processors, or any combination thereof. Generally, the processor 34 may perform computer-readable instructions related to the processes described herein. Additionally, the processor 34 may be a fixed-point processor or a floating-point processor.

[0041] Additionally, the one or more memories 36 may include volatile memory, such as random access memory (RAM), and/or non-volatile memory, such as read-only memory (ROM), optical drives, hard disc drives, or solid-state drives. In some embodiments, the control module 32 may include portions of a vehicle control unit (VCU) and/or a separate battery control module. Additionally, as depicted, the control module 32 may be included separate from the energy storage component 14, such as a standalone module. In other embodiments, the battery management system (BMS) may be included within the energy storage component 14.

[0042] In certain embodiments, the control module 32 or the processor 34 may receive data from various sensors 38 disposed within and/or around the energy storage component 14. The sensors 38 may include a variety of sensors for measuring current, voltage, temperature, and the like regarding the battery module 28 or 30. After receiving data from the sensors 38, the processor 34 may convert raw data into estimations of parameters of the battery modules 28 and 30. As such, the processor 34 may render the raw data into data that may provide an operator of the vehicle 10 with valuable information pertaining to operations of the battery system 12, and the information pertaining to the operations of the battery system 12 may be displayed on the display 21. The display 21 may display various images generated by device 10, such as a GUI for an operating system or image data (including still images and video data). The display 21 may be any suitable type of display, such as a liquid crystal display (LCD), plasma display, or an organic light emitting diode (OLED) display, for example. Additionally, the display 21 may include a touch-sensitive element that may provide inputs to the adjust parameters of the control module 32 or data processed by the processor 34.

[0043] The energy storage component 14 may have dimensions comparable to those of a typical lead-acid battery to limit modifications to the vehicle 10 design to accommodate the battery system 12. For example, the energy storage component 14 may be of similar dimensions to an H6 battery, which may be approximately 13.9 inches x 6.8 inches x 7.5 inches. As depicted, the energy storage component 14 may be included within a single continuous housing. In other embodiments, the energy storage component 14 may include multiple housings coupled together (e.g., a first housing including the first battery 28 and a second housing including the second battery 30). In still other embodiments, as mentioned above, the energy storage component 14 may include the first battery module 28 located under the hood of the vehicle 10, and the second battery module 30 may be located within the interior of the vehicle 10.

[0044] FIG. 3 is a perspective view of an embodiment of the lithium ion battery module 28 that includes a first battery module terminal 50 and a second battery module terminal 52. The battery module terminals 50, 52 are disposed on a battery module housing 54 and are electrically coupled to one or more battery cells disposed within a cavity of the housing 54. As such, a load or a power supply may be coupled to the battery module terminals 50, 52, such that the lithium ion battery module 28 supplies and/or receives electrical power. As shown in the illustrated embodiment of FIG. 3, the cavity of the housing 54 is sealed via a cover 56. In some embodiments, the cover 56 is secured to the housing 54 via a weld (e.g., a laser weld), fasteners, another suitable technique, or a combination thereof.

[0045] While the housing 54 is generally sealed (e.g., substantially air tight), there may be a number of potential leak paths that may be sealed using additional methods. For example, regions where the terminals 50, 52 and a signal connector barrel 58 extend through the housing 54 may represent leak paths that utilize additional features (e.g., mechanical features) to provide additional sealing. In this respect, the lithium ion battery module 28 also includes a vent path extending from its battery cells, which are internal to the housing 54, and out of the housing 54 via a vent opening 60, which may be an opening positioned at the end of a vent passage defined by a vent port 62 (e.g., a barbed fitting or hose barb). The vent opening 60 thus represents an opening in the housing 54 that can potentially allow the ingress of moisture via the external environment.

[0046] A vent plug 64 configured in accordance with the present disclosure may be seated within the vent opening 60 and against internal surfaces of the vent port 62 defining the vent passage. As illustrated in FIG. 3, the vent plug 64 is installed in the vent opening 60 a manner where the vent plug 64 is aligned with the vent port 62 along a common longitudinal axis 66. The vent plug 64 may be sized and shaped so as to have an interference fit within the vent opening 60 to effectively seal the housing 54 from the external environment. Further, the vent plug 64 may be made from materials selected to provide an appropriate degree of flexibility or rigidity and surface contact with the surfaces of the vent port 62. The vent plug 64, therefore, is designed to be positioned within the vent port 62 to create a seal via an interference fit. The strength of this seal may be determined by the materials of the vent plug 64, and its sizing relative to the size of the vent opening 60. In this way, the vent plug 64 is configured to be dislodged from the vent opening 60 once an internal pressure of the lithium ion battery module 28 reaches a threshold level due, for example, to a predetermined amount of venting by the battery cells internal to the module. Various features of the vent plug 64 are described in further detail with respect to FIGS. 4-9. [0047] When installed in the vehicle 10, the vent port 62 interfaces with a vent hose or similar feature of the vehicle 10 to allow for a sealed vent path that extends from the internal cavity of the lithium ion battery module 28, through the vent passage defined by the vent port 62, and into a vent hose of the vehicle 10. The vent hose of the vehicle 10 may lead to a predetermined location internal or external to the vehicle 10 where battery cell effluent can be discharged. As shown, the vent port 62 may be a barbed fitting including an elongated portion 68 having an annular protrusion 70. The elongated portion 68 allows for a vehicle vent hose to be installed over the vent port 62, and the annular protrusion 70 allows for a tight interference fit to be created between the vent port 62 and the vehicle hose.

[0048] As shown in FIGS. 4-10, there may be different designs for the vent plug 64, though they generally include certain similar features. FIGS. 4-8 depict a first embodiment of the vent plug 64. As shown in the illustrated embodiment of FIG. 4, the vent plug 64 includes a larger annular portion and a smaller, elongated annular portion extending from the larger annular portion. Generally, the larger annular portion directly contacts the housing portions defining the vent opening 60 (e.g., the internal surfaces of the vent port 62).

[0049] To facilitate discussion, the smaller, elongated annular portion is referred to as a stem portion 80, and the larger annular portion is referred to as a coupling portion 82. The stem portion 80 may be configured to extend into the opening 60 of the battery module housing 54. The coupling portion 82 may include a securement feature 84, which in the illustrated embodiment is an outer surface 86 of the coupling portion 82 but can additionally or alternatively include other features such as an O-ring (e.g., as shown in FIGS. 9 and 10), another friction fit component, a weld between the coupling portion 82 and the opening 60, an adhesive, or any combination thereof.

[0050] FIG. 5 is a cross-sectional perspective view taken along a longitudinal axis 90 of the vent plug 64. The stem portion 80, as noted, is configured to extend within the vent opening 60, and generally has a smaller outer diameter (noted in FIG. 5 as ODs) than an outer diameter of the coupling portion 82 (noted in FIG. 5 as ODc). The stem portion 80 has a first end 92 that forms a distal end 94 of the vent plug 64, which is shown as being closed. An opposite, second end 96 of the stem portion 80 transitions into the coupling portion 82, which terminates in a proximal end 98 of the vent plug 64, which is shown as being open-ended (e.g., is hollow). The outer diameter ODs may be substantially the same along the length of the stem portion 80, or may, as shown, change along the length of the stem portion 80. Specifically, as shown, the ODs increases from the first end 92 to the second end 96 such that the stem portion 80 is tapered. In this respect, because the stem portion 80 extends from the coupling portion 82, and the stem portion 80 has an outer diameter that is smaller than the outer diameter of the coupling portion, an outer profile of the vent plug 64 has a stepped geometry. This stepped geometry may be beneficial for handling and to allow for more controlled venting situations, as discussed herein.

[0051] As noted above, the stem portion 80 is hollow, and has an internal diameter IDs. The IDs of the stem portion 80 may follow the ODs, for example to maintain a constant thickness of a wall 100 of the stem portion 80. Maintaining a constant wall thickness may be beneficial to ensure reproducible manufacture (e.g., molding) of the stem portion 80 of the vent plug 64. Indeed, it should be noted that in certain embodiments, the wall 100 forms the outer profile of the vent plug 64. In certain of these embodiments, the wall 100 is a constant thickness throughout the outer profile.

[0052] As also shown, the coupling portion 82 is hollow. In a similar manner as set forth above with respect to the stem portion 80, a wall 102 of the coupling portion 82 may be of a substantially constant thickness. The thickness of the wall 102 may be chosen for ease of manufacture, but may also affect the flexibility of the coupling portion 82 to provide for a more stable interference fit within the vent opening 60. In the illustrated embodiment, the outer surface 86 of the coupling portion 82 is oriented substantially parallel to the longitudinal axis 90 of the vent plug 64, and is therefore not tapered. However, in other embodiments, the outer surface 86 may be angled such that the coupling portion 82 is tapered outwardly (diverging away from the longitudinal axis 90) in a direction from the distal end 94 to the proximal end 98. In still further embodiments, the outer surface 86 may be angled such that the coupling portion 82 is tapered inwardly (converging the longitudinal axis 90) in the direction from the distal end 94 to the proximal end 98. The angle of the outer surface 86 may be adjusted, for example during design processes, by adjusting an internal angle 104 between an internal face 106 of the coupling portion 82 that is oriented transverse to the longitudinal direction 90, and an internal surface 108 located on an opposing side of the wall 102 relative to the outer surface 86.

[0053] The illustrated vent plug 64 also includes an internal transition 110 from the stem portion 80 to the coupling portion 82. The internal transition 110 may be formed by an angled internal surface 112 separating the second end 96 of the stem portion 80 and the internal face 106 of the coupling portion 82. In certain embodiments, the internal transition 110 may be provided to maintain ease of manufacture (e.g., for purposes of a constant wall thickness), may represent a joint between distinct stem portion 80 and coupling portion 82 pieces, or may be used to provide an additional degree of flexibility for the vent plug 64. For instance, the internal transition 110 may allow some degree of deformation between the stem portion 80 and the coupling portion 82.

[0054] As set forth above with respect to FIG. 3 and as also shown in FIG. 6, the vent plug 64 is inserted into the vent opening 60 along the common longitudinal axis 66 in an orientation where the stem portion 80 provides proper alignment of the vent plug 64 with the vent port 62. Specifically, the elongated nature of the stem portion 80 prevents rotation of the vent plug 64 within the vent port 62. Preventing rotation in this manner helps ensure that the vent plug 64 maintains a seal, rather than rotating to an orientation where fluids (e.g., air, water) can easily bypass the vent plug 64. Thus, the overall length of the vent plug 64 (from the distal end 94 to the proximal end 98) may be at least equal to, or greater than, an internal diameter IDv of the vent port 62.

[0055] The stem portion 80 may also be useful for manufacturing processes used to assemble the lithium ion battery module 28. For example, the stem portion 80 provides a handling surface for manipulating (e.g., via an automated tool) the vent plug 64, for example to facilitate loading into a machine.

[0056] As noted, the vent plug 64 fits into the vent opening 60, and interference creates a friction force that internal pressure forces caused by cell venting must overcome to push out the vent plug 64. Accordingly, the tightness of the fitment may determine the level of intemal pressure required to push out the vent plug 64. The tightness of this fit may be determined, for example, by a combination of material selection and the sizing of the vent plug 64 relative to the size of the opening 60. In this respect, the cross-sectional elevation view shown in FIG. 6 demonstrates the relationship of the intemal diameter IDv of the vent opening 60 and the outer diameter ODc of the vent plug 64.

[0057] As shown, the outer diameter ODc of the vent plug 64 is larger than the internal diameter IDv of the vent opening 60. Thus, when the vent plug 64 is inserted into the vent opening 60, the outer surface 86 of the coupling portion 82 of the vent plug 64 contacts an intemal surface 120 of the vent port 62, thereby creating an interference fit. By way of non-limiting example, the outer diameter ODc of the vent plug 64 may be between 0% and 10% larger (e.g., between 0.1% and 10%, such as between 7% and 8%) than the internal diameter IDv of the vent opening 60. The degree by which outer diameter ODc of the vent plug 64 is oversized relative to the internal diameter IDv of the vent opening 60 may, at least in part, determine the internal pressure that the vent plug 64 is able to withstand before being dislodged from the vent opening 60.

[0058] Manipulating a coefficient of friction between the outer surface 86 of the coupling portion 82 of the vent plug 64 and the internal surface 120 of the vent port 62 also, at least in part, determine the internal pressure that the vent plug 64 is able to withstand before being dislodged from the vent opening 60. There may be a number of approaches for manipulating the coefficient of friction. For example, the material construction of the vent plug 64 may be selected to have a coefficient of friction against a material of the internal surface 120 of the vent port 62 that provides a sufficient amount of resistance to movement so as to maintain a seal at the vent opening 60 until a threshold internal pressure is reached within the lithium ion battery module 28.

[0059] In total, the sizing and material construction of the vent plug 64 relative to the vent opening 60 may be selected so as to provide a sufficient seal that resists the ingress of moisture into the lithium ion battery module under the expected operating conditions of the module. As an example, normal operating conditions of the lithium ion battery module 28 may include expected operating conditions within the vehicle 10, which may range between -10 °C and 80 °C.

[0060] Further, the sizing and material construction of the vent plug 64 may be selected so as to provide a sufficient seal that resists dislodgement of the vent plug 64 from the vent port until a particular threshold internal pressure of the lithium ion battery module 28 has been reached. By way of further example, the threshold internal pressure may be an expected internal pressure corresponding to a complete release of cell effluent from any one or a combination of the battery cells (e.g., a predetermined number of battery cells) internal to the module 28. The particular number of venting battery cells and corresponding expected internal pressures of the lithium ion battery module 28 may be determined experimentally, may be modeled or calculated, or a combination, to determine an appropriate material and sizing of the vent plug 64 relative to the vent opening 60.

[0061] By way of example, the material of the vent plug 64 may be the same as the material of the vent port 62 (e.g., the same as the housing 54, such as a polypropylene material or similar material), or may be different. In embodiments where the vent plug 64 is made of a different material, the vent plug 64 may be made from a softer or more compliant material compared to the vent port 62. For instance, the vent plug 64 may have a lower Shore hardness value than the vent port 62. Further, in certain embodiments, the walls of the vent plug 64 (and in particular the wall of the coupling portion 82) may be constructed of the same material as the vent port 62, but may be thinner compared to the walls of the vent port 62. In this respect, when the vent plug 64 is inserted into the vent opening 60, hollow portion of the coupling portion 82 may allow the coupling portion 82 to flex under the strain of being placed within the vent port 62 and in response to being compressed against the internal surface 120.

[0062] As shown in FIG. 7, the vent plug 64 is situated within the vent port 62 via an interference fit in which the outer surface 86 is in contact with the internal surface 120. In this embodiment, the friction force created by the interference fit is sufficient to maintain the position of the vent plug 64 within the vent port at a first pressure PI . The first pressure PI is below a threshold pressure corresponding to, for example, an expected internal pressure of the battery module corresponding to a full release of cell effluent from one or more battery cells of the lithium ion battery module 28.

[0063] FIG. 8 depicts the configuration shown in FIG. 7 once the internal pressure of the lithium ion battery module 28 has reached or exceeded the threshold, shown as a second pressure P2. Also shown is a vent hose 122 of the vehicle 10 to which the vent port 62 is attached. As illustrated, the second pressure P2 is generally sufficient to overcome the friction force that maintains the vent plug 64 within the vent opening 60, and causes the vent plug 64 to be dislodged out of the vent opening 60 generally along the common longitudinal axis 66.

[0064] Ejection of the vent plug 64 from the vent port 62 allows internally confined gases to escape the lithium ion battery module 28 via the vent port 62. In the illustrated embodiment, the cell effluent is directed into the vent hose 122, which is configured to direct the cell effluent into a predetermined location. Alternatively, depending on the location of the battery module 28 in the vehicle 10, the vent hose 122 may not be present, and the cell effluent may simply be vented into the surrounding atmosphere.

[0065] While ejection of the vent plug 64 is generally along the longitudinal axis 66, due to the construction of the vent plug 64, specifically the relative geometries of the stem portion 80 and the coupling portion 82, ejection of the vent plug 64 also results in a tumbling action, shown as arrow 124. This tumbling action allows the vent plug 64 to lodge in the vent hose 122 in a position in which fluid (e.g., gas) is still able to pass through the hose 122 (e.g., bypass the vent plug 64).

[0066] It should be noted that while the foregoing description discussed above with respect to FIGS. 4-8 is provided in the context of the outer surface 86 of the vent plug 64 being the securement feature 84, that the description may apply to other vent plug configurations in which the securement feature 84 is different. In this respect, FIGS. 9 and 10 depict an embodiment of the vent plug 64 that uses an O-ring 130 as the securement feature 84 (e.g., as a sealing surface). In some embodiments, the O-ring 130 may be made from a more compliant material than the material of the vent plug 64. By way of non-limiting example, the O-ring 130 may be an ethylene propylene diene monomer (EPDM) rubber, which may maintain compliant properties over a range of temperatures corresponding to typical vehicle battery use. The remainder of the vent plug 64 may be constructed from, for example, a polyolefin (e.g., polyethylene (PE), low density polyethylene (LDPE)), a polycarbonate (PC), or similar material. Indeed, it has been found that the vent plug configuration shown in FIGS. 9 and 10 provides superior sealing performance across a wider range of operating temperatures compared to the vent plug configuration shown in FIGS. 4 and 5.

[0067] As will be appreciated with reference to the cross-sectional perspective view shown in FIG. 10, the vent plug 64 with the O-ring 130 includes many of the same features as described above with respect to FIG. 5. In the illustrated embodiment, the O-ring 130 is positioned in an annular groove 132 of the coupling portion 82. For instance, the annular groove 132 may be positioned so as to place the O-ring 130 between a first shoulder 134 and a second shoulder 136 of the coupling portion.

[0068] The vent plug 64 having the O-ring 130 may be inserted into the vent port 62 in generally the same manner as set forth in FIG. 6. Further, the vent plug 64 may operate in a similar manner as set forth with respect to FIGS. 7 and 8. However, in certain embodiments, the O-ring 130 (or similar securement feature 84) may also be configured to become dislodged from the vent plug 64 when the pressure in the battery module housing 54 exceeds the threshold level. In such a situation, the O-ring 130 and the remainder of the vent plug 64 (e.g., a body of the vent plug 64) may separate to create an open vent path for cell effluent to escape from the lithium ion battery module 28.

[0069] While only certain features and embodiments have been illustrated and described, many modifications and changes may occur to those skilled in the art (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters (e.g., temperatures, pressures, etc.), mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the disclosed subj ect matter. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. Furthermore, in an effort to provide a concise description of the exemplary embodiments, all features of an actual implementation may not have been described. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation specific decisions may be made. Such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure, without undue experimentation.

Claims

CLAIMS:

1. A lithium ion battery module, comprising:

a battery module housing;

a vent port extending from the battery module housing and having a vent opening to allow battery cell effluent to escape the battery module housing; and

a vent plug disposed within the vent port, wherein the vent plug comprises a stem portion and a coupling portion, wherein the stem portion maintains alignment of the vent plug within the vent port, and the coupling portion forms a seal against the vent port.

2. The lithium ion battery module of claim 1, wherein the coupling portion of the vent plug has a sealing surface outer diameter that is larger than an internal diameter of the vent port such that the vent plug is secured via an interference fit within the vent port.

3. The lithium ion battery module of claim 1, wherein the stem portion is tapered along its length.

4. The lithium ion battery module of claim 1 , wherein an outer diameter of the coupling portion is larger than an outer diameter of the stem portion.

5. The lithium ion battery module of claim 1, wherein the vent plug is hollow and comprises a wall forming the outer profile of the vent plug, wherein the wall is a constant thickness throughout the outer profile.

6. The lithium ion battery module of claim 1, wherein the coupling portion of the vent plug comprises a securement feature configured to secure the vent plug in the vent port.

7. The lithium ion battery module of claim 6, wherein the securement feature is an outer surface of an annular wall of the coupling portion.

8. The lithium ion battery module of claim 6, wherein the securement feature is an O-ring positioned about an annular wall of the coupling portion.

9. The lithium ion battery module of claim 8, wherein the O-ring is configured to separate from a body of the vent plug when an internal pressure of the lithium ion battery module reaches a threshold, the separation creating a path for cell effluent to escape from the battery module housing, and wherein the threshold corresponds to an expected internal pressure resulting from at least one battery cell of the plurality of battery cells

10. The lithium ion battery module of claim 8, wherein the O-ring is positioned within a groove of the coupling portion, and wherein the O-ring is located between a first shoulder and a second shoulder of the coupling portion.

11. The lithium ion battery module of claim 1, wherein the vent plug is configured to maintain the seal at pressures below a threshold internal pressure of the lithium ion battery.

12. The lithium ion battery module of claim 1, wherein the vent plug is configured to dislodge from the vent port at pressures above a threshold internal pressure of the lithium ion battery.

13. A vent plug for a lithium ion battery module, comprising:

a coupling portion comprising an annular wall configured to be disposed within a vent port of the lithium ion battery module, and wherein the coupling portion is configured to form a seal against an internal surface of the vent port; and

a stem portion extending from the coupling portion and comprising an elongated annular wall having an outer diameter that is smaller than the outer diameter of the coupling portion such that an outer profile of the vent plug has a stepped geometry.

14. The vent plug of claim 13, wherein the outer diameter of the elongated annular wall varies along a length of the stem portion such that the stem portion has a tapered profile.

15. The vent plug of claim 13, wherein the annular wall of the coupling portion is oriented parallel with respect to a longitudinal axis of the vent plug.

16. The vent plug of claim 13, comprising an O-ring positioned about the annular wall.

17. The vent plug of claim 16, wherein the O-ring is positioned within a groove formed in the annular wall.

18. A battery system, comprising:

a battery module housing;

a plurality of lithium ion battery cells disposed in the housing;

a vent port extending through the battery module housing and providing a pathway for the escape of vented cell effluent to escape from the battery module housing; and

a vent plug disposed within the vent port, wherein the vent plug comprises a coupling portion and a stem portion, wherein the coupling portion comprises a securement feature securing the vent plug in the vent port, wherein the vent plug is configured to be dislodged from the vent port when a pressure within the battery module housing exceeds a threshold corresponding to a total vent of cell effluent from at least one lithium ion battery cell of the plurality of lithium ion battery cells.

19. The battery system of claim 17, wherein the securement feature of the vent plug comprises an O-ring positioned about an annular wall of the coupling portion.

20. The battery system of claim 17, wherein the vent plug comprises a stem portion extending from the coupling portion, the stem portion preventing rotation of the coupling portion within the vent port so that the vent plug maintains a seal of the pathway when the internal pressure of the battery module housing is below the threshold.