Abstract:
A battery cell according to an exemplary aspect of the present disclosure includes, among other things, a can assembly, an electrode assembly housed inside the can assembly and a venting system including a vent port and at least one of a vent tube inside the can assembly or a spacer plate mounted between the vent port and the electrode assembly.

Description:
TECHNICAL FIELD 
       [0001]    This disclosure relates to the venting of battery cells of an electrified vehicle battery pack. 
       BACKGROUND 
       [0002]    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 currently being developed for this purpose. In general, electrified vehicles differ from conventional motor vehicles because they are selectively driven by one or more battery powered electric machines. Conventional motor vehicles, by contrast, rely exclusively on the internal combustion engine to drive the vehicle. 
         [0003]    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 that store electric energy. From time to time, gaseous byproducts may be released by the battery cells, such as caused by encounters with off-normal conditions or environments. The battery cells may therefore include vents that allow the gaseous byproducts to escape from the interiors of the battery cells. 
       SUMMARY 
       [0004]    A battery cell according to an exemplary aspect of the present disclosure includes, among other things, a can assembly, an electrode assembly housed inside the can assembly and a venting system including a vent port and at least one of a vent tube inside the can assembly or a spacer plate mounted between the vent port and the electrode assembly. 
         [0005]    In a further non-limiting embodiment of the foregoing battery cell, the can assembly includes a casing and a top plate. 
         [0006]    In a further non-limiting embodiment of either of the foregoing battery cells, the vent tube is attached to an interior wall of the casing. 
         [0007]    In a further non-limiting embodiment of any of the foregoing battery cells, the vent tube is secured within a corner of the casing. 
         [0008]    In a further non-limiting embodiment of any of the foregoing battery cells, the vent tube includes a first height that is less than a second height of a wall of the casing. 
         [0009]    In a further non-limiting embodiment of any of the foregoing battery cells, the vent port is disposed in the top plate. 
         [0010]    In a further non-limiting embodiment of any of the foregoing battery cells, the vent tube establishes a flow pathway between different portions of the can assembly. 
         [0011]    In a further non-limiting embodiment of any of the foregoing battery cells, a plurality of vent tubes are mounted inside the can assembly and each establishing a flow pathway configured to communicate gaseous byproducts toward the vent port. 
         [0012]    In a further non-limiting embodiment of any of the foregoing battery cells, the spacer plate is mounted to an underside of a top plate of the can assembly. 
         [0013]    In a further non-limiting embodiment of any of the foregoing battery cells, the spacer plate is an arched sheet of material. 
         [0014]    In a further non-limiting embodiment of any of the foregoing battery cells, at least one of the vent tube and the spacer plate includes a plurality of perforations. 
         [0015]    In a further non-limiting embodiment of any of the foregoing battery cells, the venting system includes both of the vent tube and the spacer plate. 
         [0016]    A battery pack according to another exemplary aspect of the present disclosure includes, among other things, a battery assembly that includes a plurality of battery cells. Each battery cell of the plurality of battery cells includes a venting system comprising a vent tube configured to establish a first flow pathway for communicating gaseous byproducts inside the battery cell and a spacer plate configured to establish a second flow pathway for communicating the gaseous byproducts. 
         [0017]    In a further non-limiting embodiment of the foregoing battery pack, the venting system includes a vent port. 
         [0018]    In a further non-limiting embodiment of either of the foregoing battery packs, the spacer plate is disposed between the vent port and an electrode assembly of the battery cell. 
         [0019]    In a further non-limiting embodiment of any of the foregoing battery packs, each of the plurality of battery cells includes a can assembly including a casing and a top plate. 
         [0020]    In a further non-limiting embodiment of any of the foregoing battery packs, the vent tube is disposed in a corner of the casing. 
         [0021]    In a further non-limiting embodiment of any of the foregoing battery packs, the first flow pathway is a vertical flow pathway and the second flow pathway is a lateral flow pathway. 
         [0022]    In a further non-limiting embodiment of any of the foregoing battery packs, at least one of the vent tube and the spacer plate includes a plurality of perforations. 
         [0023]    In a further non-limiting embodiment of any of the foregoing battery packs, the vent tube is a hollow cylinder and the spacer plate is an arched sheet of material. 
         [0024]    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. 
         [0025]    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 
         [0026]      FIG. 1  schematically illustrates a powertrain of an electrified vehicle. 
           [0027]      FIG. 2  illustrates a battery cell for use within a battery pack of an electrified vehicle. 
           [0028]      FIG. 3  illustrates the internal components of the battery cell of  FIG. 2 . 
           [0029]      FIGS. 4A, 4B, 4C, 4D and 4E  illustrate battery cell venting systems that include vent tubes. 
           [0030]      FIG. 4F  illustrates an exemplary vent tube of a battery cell venting system. 
           [0031]      FIG. 5  illustrates a battery cell venting system according to another embodiment of this disclosure. 
           [0032]      FIG. 6  illustrates a battery cell venting system according to yet another embodiment of this disclosure. 
           [0033]      FIG. 7  illustrates a battery cell venting system according to yet another embodiment of this disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0034]    This disclosure describes a venting system for venting gaseous byproducts that may accumulate inside battery cells of an electrified vehicle battery pack. An exemplary battery cell includes a can assembly, an electrode assembly housed inside the can assembly, and a venting system for venting the gaseous byproducts. The venting system may include a vent port and either a vent tube inside the can assembly or a spacer plate mounted between the vent port and the electrode assembly. In some embodiments, the venting system includes both the vent tube and the spacer plate. The proposed venting systems of this disclosure provide multiple flow pathways within the battery cell for facilitating venting of the gaseous byproducts. These and other features are discussed in greater detail in the following paragraphs of this detailed description. 
         [0035]      FIG. 1  schematically illustrates a powertrain  10  of an electrified vehicle  12 . Although depicted as a battery electric vehicle (BEV), it should be understood that the concepts described herein are not limited to BEV&#39;s and could extend to other electrified vehicles, including but not limited to, plug-in hybrid electric vehicles (PHEV&#39;s) or full hybrid electric vehicles (FHEV). Therefore, although not shown in this 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 . 
         [0036]    In one non-limiting embodiment, the electrified vehicle  12  is a full electric vehicle propelled solely through electric power supplied by an electric machine  14  without 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 power. 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 high voltage bus  22  electrically connects the electric machine  14  to a battery pack  24  through an inverter  26 . The electric machine  14 , the gearbox  16 , and the inverter  26  may collectively be referred to as a transmission  28 . 
         [0037]    The battery pack  24  is an exemplary electrified vehicle battery. The battery pack  24  may be a high voltage traction battery pack that includes a plurality of battery assemblies  25  (i.e., battery arrays 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 power the electrified vehicle  12 . 
         [0038]    The electrified vehicle  12  may also include a charging system  30  for charging the energy storage devices (e.g., battery cells) of the battery pack  24 . The charging system  30  may be connected to an external power source (not shown) for receiving and distributing power. The charging system  30  may also be equipped with power electronics for converting AC power received from the external power supply to DC power for charging the energy storage devices of the battery pack  24 . The charging system  30  may also accommodate one or more conventional voltage sources from the external power supply (e.g., 110 volt, 220 volt, etc.). 
         [0039]    The powertrain  10  of  FIG. 1  is shown schematically 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. 
         [0040]      FIGS. 2 and 3  illustrate an exemplary battery cell  56  that may be employed within an electrified vehicle battery pack, such as the battery pack  24  of the electrified vehicle  12  of  FIG. 1 , for example. The battery cell  56  stores electrical energy for powering various electrical loads of the electrified vehicle  12 . The battery pack  24  could employ any number of battery cells  56 . For example, a plurality of the battery cells  56  may be stacked side by side along a longitudinal axis to construct a grouping of battery cells  56 , sometimes referred to as a “cell stack” or “module.” The battery pack  24  could also include multiple individual groupings of the battery cells  56 . 
         [0041]    In one non-limiting embodiment, the battery cell  56  is a prismatic, lithium-ion cell. However, battery cells having other geometries (cylindrical, pouch, etc.), other chemistries (nickel-metal hydride, etc.), or both, could also benefit from the teachings of the disclosure. 
         [0042]    The exemplary battery cell  56  includes a can assembly  58  and an electrode assembly  60  housed inside the can assembly  58 . In one non-limiting embodiment, the can assembly  58  includes a casing  62  and a top plate  64 . The casing  62  includes a plurality of walls  66  that define an interior  68  for housing the electrode assembly  60 . The top plate  64  of the can assembly  58  may be mounted to the casing  62 . In one non-limiting embodiment, the top plate  64  is welded to the casing  62 . The top plate  64  includes terminals  70  (e.g., one positive terminal and one negative terminal). Current collector bars  72  (see  FIG. 3 ) are connected between the terminals  70  and current-collecting foil surfaces of the electrode assembly  60  within the interior  68  of the casing  62  (see  FIG. 3 ). The addition of an electrolyte (e.g., liquid, gel or solid) allows ionic current flow between the active materials of each electrode. 
         [0043]    The electrode assembly  60 , sometimes referred to as a jelly roll, is formed by winding a positive electrode (e.g., a cathode) with an active coating, a negative electrode (e.g., an anode) with an active coating, and a separator inserted between the positive electrode and the negative electrode. The electrode assembly  60  may be wound about either a vertical or horizontal axis. Electrical current flows to and from the active materials of the positive and negative electrodes. The circuit is completed by ionic flow between the electrodes, as supported by the electrolyte. 
         [0044]    The battery cell  56  may additionally include a venting system  74  for discharging gaseous byproducts from the interior  68 . The gaseous byproducts may be released during a thermal runaway event in which a battery cell  56  heats up faster than the heat can be dissipated, for example. In one non-limiting embodiment, the venting system  74  includes a vent port  76  for discharging the gaseous byproducts. The vent port  76  may be covered with a membrane  78 . During certain conditions, gaseous byproducts released from the electrode assembly  60  may be expelled from the interior  68  by communicating these byproducts through the vent port  76 . 
         [0045]    The exemplary venting system  74  may include various additional features for expelling the gaseous byproducts. The various venting system features discussed below establish multiple flow pathways for expelling the gaseous byproducts from the battery cell  56  and prevent the vent port  76  from becoming blocked. Incorporation of any or all of the exemplary venting features of this disclosure can mitigate pressure build-up inside the battery cell  56  during the rare occurrence of a thermal runaway event. 
         [0046]      FIGS. 4A-4E  illustrate additional features of the venting system  74  of the battery cell  56 . In one non-limiting embodiment, the venting system  74  includes one or more vent tubes  80  that establish flow pathways  85  for directing gaseous byproducts GB (see  FIG. 4A ) along an unobstructed path toward the vent port  76 . The vent tubes  80  may be secured within the interior  68  of the casing  62  of the battery cell  56 . For example, the vent tubes  80  could be welded or brazed to the walls  66  on the interior  68  of the casing  62 . In one non-limiting embodiment, the vent tubes  80  are made of a metallic material. Suitable metallic materials include, but are not limited to, steel and aluminum. 
         [0047]    In another non-limiting embodiment, a height H 1  of the vent tubes  80  is smaller than a height H 2  of each wall  66  of the casing  62  (best shown in  FIG. 4A ). In this way, gaseous byproducts GB that accumulate in the bottom portion of the casing  62  may be freely vertically communicated through the vent tubes  80  toward the top plate  64 , which is typically where the vent port  76  is located. In one non-limiting embodiment, the height H 1  is ⅓ of the height H 2 . In another non-limiting embodiment, the height H 1  is ½ of the height H 2 . 
         [0048]    The vent tubes  80  may optionally be secured at one or more corners  82  of the casing  62 . In one non-limiting embodiment, vent tubes  80  are located within the corners  82  on the same side of the casing  62  (see  FIG. 4B ). In another non-limiting embodiment, vent tubes  80  are disposed within opposite corners  82  of the casing  62  (see  FIG. 4C ). In yet another non-limiting embodiment, vent tubes  80  are positioned at each corner  82  of the casing  62  (see  FIG. 4D ). In still another non-limiting embodiment, the vent tubes  80  are secured to the walls  66  of the casing  62  at locations that are spaced from the corners  82  (see, for example,  FIG. 4E ). 
         [0049]    The vent tubes  80  may embody any size or shape. In one non-limiting embodiment, the vent tubes  80  are configured as hollow cylinders for establishing the flow pathways  85 . In another non-limiting embodiment, the vent tubes  80  include a plurality of perforations  86  (see  FIG. 4F ) for ensuring free flow of the gaseous byproducts GB even if portions of the vent tubes  80  become blocked by solid electrode debris or other debris. 
         [0050]    In another embodiment, shown in  FIG. 5 , the venting system  74  includes a spacer plate  88  for preventing blockage of the vent port  76 . In one non-limiting embodiment, the venting spacer plate  88  is mounted in a gap  90  that extends between the vent port  76  and the electrode assembly  60 . In another non-limiting embodiment, the spacer plate  88  is mounted to an underside  92  of the top plate  64 . The spacer plate  88 , which may be made of a metallic material, may be welded or otherwise secured to any portion of the battery cell  56 . 
         [0051]    The spacer plate  88  is a rigid sub-structure mounted inside the battery cell  56  to ensure the reliable, unobstructed flow of gaseous byproducts toward the vent port  76 . In one non-limiting embodiment, the spacer plate  88  is configured as an arched sheet of material. Other shapes are also contemplated within the scope of this disclosure. 
         [0052]    In yet another non-limiting embodiment, the spacer plate  88  includes a plurality of perforations  94  (see  FIG. 6 ). The perforations  94  ensure the free flow of gaseous byproducts even if portions of the spacer plate  88  become blocked by solid electrode debris or other debris. 
         [0053]    In yet another non-limiting embodiment, shown in  FIG. 7 , the venting system  74  includes both vent tubes  80  and the spacer plate  88 . The vent tubes  80  may establish vertical flow pathways for directing gaseous byproducts toward the vent port  76  (i.e., from the bottom toward the top of the battery cell  56 ), whereas the spacer plate  88  may prevent blockage of the vent port  76  and establish lateral flow pathways for communicating the gaseous byproducts should the electrode assembly  60  expand during a thermal runaway event. 
         [0054]    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. 
         [0055]    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. 
         [0056]    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.