Patent Publication Number: US-2022231351-A1

Title: Battery assembly with multi-function structural assembly

Description:
RELATED APPLICATIONS 
     This application is a continuation of prior U.S. application Ser. No. 14/716,092, filed May 19, 2015, the entirety of which is herein incorporated by reference. 
    
    
     TECHNICAL FIELD 
     This disclosure relates to a battery assembly for an electrified vehicle. The battery assembly includes a structural assembly configured to retain, enclose and/or thermally manage a plurality of battery cells. 
     BACKGROUND 
     The need to reduce automotive fuel consumption and emissions is well known. Therefore, vehicles are being developed that either 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 one or more battery powered electric machines. Conventional motor vehicles, by contrast, rely exclusively on the internal combustion engine to propel the vehicle. 
     High voltage battery assemblies are employed to power the electric machines of electrified vehicles. The battery assemblies include cell stacks constructed of a plurality of battery cells. An array structure binds the battery cells of each cell stack. A separate enclosure assembly houses and seals the battery cells from the exterior environment. Yet another separate structure, typically configured as a cold plate, is commonly positioned in contact with the battery cells to thermally manage the heat generated by the cells. 
     SUMMARY 
     A battery assembly according to an exemplary aspect of the present disclosure includes, among other things, a first cell stack including a plurality of battery cells and a structural assembly including a first pocket sized and shaped to receive the first cell stack. The structural assembly is configured to assert a compressive load on the first cell stack and at least partially enclose the first cell stack. 
     In a further non-limiting embodiment of the foregoing battery assembly, the plurality of battery cells are individual cells disposed side-by-side and unbound relative to one another. 
     In a further non-limiting embodiment of either of the foregoing battery assemblies, each of the plurality of battery cells is contiguous with at least one wall of the structural assembly. 
     In a further non-limiting embodiment of any of the foregoing battery assemblies, a second cell stack is received within a second pocket of the structural assembly. 
     In a further non-limiting embodiment of any of the foregoing battery assemblies, a wall of the structural assembly separates the first pocket from the second pocket. 
     In a further non-limiting embodiment of any of the foregoing battery assemblies, the structural assembly includes a plurality of walls that are joined together. 
     In a further non-limiting embodiment of any of the foregoing battery assemblies, at least one of the plurality of walls includes a channel configured to communicate a fluid to thermally condition the plurality of battery cells. 
     In a further non-limiting embodiment of any of the foregoing battery assemblies, a bus bar module is positioned over top of the first cell stack. 
     In a further non-limiting embodiment of any of the foregoing battery assemblies, a base is positioned at a bottom of the structural assembly and a cover is positioned at a top of the structural assembly. 
     In a further non-limiting embodiment of any of the foregoing battery assemblies, a resilient envelope is disposed around an entire perimeter of the structural assembly. 
     A battery assembly according to another exemplary aspect of the present disclosure includes, among other things, a cell stack and a structural assembly at least partially surrounding the cell stack, the structural assembly including a plurality of walls each including at least one channel configured to communicate a fluid to thermally condition the cell stack. 
     In a further non-limiting embodiment of the foregoing battery assembly, the structural assembly includes a first wall having a first channel of a first cross-sectional area and a second wall having a second channel of a second cross-sectional area greater than the first cross-section area. 
     In a further non-limiting embodiment of either of the foregoing battery assemblies, the cell stack includes a plurality of battery cells that are unbound to one another prior to insertion into a pocket of the structural assembly. 
     In a further non-limiting embodiment of any of the foregoing battery assemblies, the structural assembly is configured to assert a compressive load on the cell stack after insertion of the cell stack into the pocket. 
     In a further non-limiting embodiment of any of the foregoing battery assemblies, the structural assembly is configured in a figure-eight shape. 
     A method according to another exemplary aspect of the present disclosure includes, among other things, compressing a cell stack of a battery assembly and inserting the cell stack into a pocket of a structural assembly. The cell stack is unbound prior to insertion into the pocket and the structural assembly is configured to apply a compressive load against the cell stack after insertion into the pocket. 
     In a further non-limiting embodiment of the foregoing method, the compressing step includes disposing a plurality of battery cells of the cell stack between opposing end spacers and applying a force to the cell stack at the opposing end spacers. 
     In a further non-limiting embodiment of either of the foregoing methods, the structural assembly is configured to at least partially enclose the cell stack. 
     In a further non-limiting embodiment of any of the foregoing methods, the structural assembly is configured to thermally manage a plurality of battery cells of the cell stack. 
     In a further non-limiting embodiment of any of the foregoing methods, the method includes sealing the cell stack of the battery assembly relative to an exterior environment after the inserting step. 
     The embodiments, examples and alternatives of the preceding paragraphs, the claims, or the following description and drawings, including any of their various aspects or respective individual features, may be taken independently or in any combination. Features described in connection with one embodiment are applicable to all embodiments, unless such features are incompatible. 
     The various features and advantages of this disclosure will become apparent to those skilled in the art from the following detailed description. The drawings that accompany the detailed description can be briefly described as follows. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  schematically illustrates a powertrain of an electrified vehicle. 
         FIG. 2  is a cross-sectional view of a battery assembly according to a first embodiment of this disclosure. 
         FIG. 3  is an exploded view of a structural assembly of a battery assembly. 
         FIG. 4  is an exploded view of selected portions of a battery assembly. 
         FIGS. 5A and 5B  illustrate additional configurations of a structural assembly of a battery assembly. 
         FIGS. 6A and 6B  illustrate additional features of the battery assembly of  FIG. 4 . 
         FIG. 7  illustrates a battery assembly according to another embodiment of this disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     This disclosure details a battery assembly for an electrified vehicle. The battery assembly may include one or more cell stacks each having a plurality of individual battery cells positioned adjacent to one another. A structural assembly of the battery assembly includes pockets that are sized and shaped to receive the cell stacks. In some embodiments, the structural assembly is configured to assert a compressive load against each cell stack and at least partially enclose the cell stacks. In other embodiments, the structure assembly is configured to thermally condition the battery cells of each cell stack. The multi-function structural assembly reduces the number and size of the components of the battery assembly, substantially eliminates conventional array retention components, and substantially eliminates threaded fastener connections to render a near zero air volume battery assembly. These and other features are discussed in greater detail in the following paragraphs of this detailed description. 
       FIG. 1  schematically illustrates a powertrain  10  for an electrified vehicle  12 . Although depicted as a hybrid electric vehicle (HEV), it should be understood that the concepts described herein are not limited to HEV&#39;s and could extend to other electrified vehicles, including, but not limited to, plug-in hybrid electric vehicles (PHEV&#39;s), battery electric vehicles (BEV&#39;s) and fuel cell vehicles. 
     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 electrified 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 include a high voltage traction battery pack that includes a plurality of battery cells capable of outputting electrical power to operate the motor  22  and the generator  18 , among other components. Other types of energy storage devices and/or output devices can also be used to electrically power the electrified vehicle  12 . 
     In one non-limiting embodiment, the electrified vehicle  12  has two basic operating modes. The electrified 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 electrified 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 electrified 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 electrified vehicle  12 . During the HEV mode, the electrified 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. The electrified 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 a battery assembly  24  that could be employed within an electrified vehicle. For example, the battery assembly  24  could be employed within the electrified vehicle  12  of  FIG. 1 . The battery assembly  24  includes a plurality of battery cells  58  for supplying electrical power to various components of the electrified vehicle  12 . Although a specific number of battery cells  58  are illustrated in the various Figures of this disclosure, the battery assembly  24  could include any amount of cells. In other words, this disclosure is not limited to the specific configuration shown in  FIG. 2 . 
     The battery cells  58  may be stacked side-by-side relative to one another (into the page in the cross-sectional view of  FIG. 2 ) to construct one or more cell stacks  62  (i.e., groupings of battery cells). In one embodiment, the battery assembly  24  includes two cell stacks  62 . However, the battery assembly  24  could include a single cell stack  62  or multiple cell stacks  62  within the scope of this disclosure. 
     In one embodiment, the battery cells  58  are prismatic, lithium-ion cells. However, battery cells having other geometries (cylindrical, pouch, etc.) and/or chemistries (nickel-metal hydride, lead-acid, etc.) could alternatively be utilized within the scope of this disclosure. 
     The battery assembly  24  may additionally include a multi-function structural assembly  64 . For example, the structural assembly  64  may be configured to apply a compressive load against the cell stacks  62 , at least partially enclose and seal the cell stacks  62 , support and separate the cell stacks  62  from one another, and thermally manage the battery cells  58  of each cell stack  62 . These functions are discussed in greater detail below. 
     A base  66  may be attached to a bottom of the structural assembly  64  and a cover  68  may be attached to the top of the structural assembly  64 . The structural assembly  64 , the base  66  and the cover  68  combine to enclose the cell stacks  62  such that the cell stacks  62  are substantially sealed from an exterior environment EX. 
     The battery assembly  24  may additionally include one or more bus bar modules  70 . The bus bar modules  70  may be located above each cell stack  62  and are adapted to electrically connect the battery cells  58  of each cell stack  62 . In one embodiment, the bus bar modules  70  are disposed between the cell stacks  62  and the cover  68 . 
       FIG. 3 , with continued reference to  FIG. 2 , illustrates a non-limiting embodiment of the structural assembly  64  of the battery assembly  24 . The structural assembly  64  includes a plurality of walls  72 . The walls  72  may be extruded, cast, molded or manufactured using some other known technique. In one embodiment, the walls  72  are made of aluminum, although other materials are also contemplated within the scope of this disclosure. The plurality of walls  72  may be formed into a desired size and shape and joined together, such as by welding, to construct the rigid structural assembly  64 . In one non-limiting embodiment, the walls  72  are joined together to establish a figure-eight shaped design capable of receiving two cell stacks  62  (see  FIG. 4 ). However, other designs are also contemplated, including but not limited to designs in which the structural assembly  64  is configured to receive a single cell stack  62  (see  FIG. 5A ) or multiple cell stacks  62  (see  FIG. 5B ). 
     Each of the plurality of walls  72  may optionally include one or more channels  74  that extend inside the walls  72 . In one embodiment, the channels  74  are openings (which may be machined, cast, formed, punched, extruded, etc.) formed either partially or entirely through the walls  72 . Other manufacturing techniques could be utilized to form the channels  74 . A fluid F may be communicated inside the channels  74  to thermally condition the battery cells  58  of each cell stack  62 . The fluid F may be a liquid, such as refrigerant, water, or ethylene glycol mixture, or a gas, such as air. 
     The channels  74  can be configured in different sizes and shapes to help meter and balance the flow of the fluid F through the walls  72 . The size and shape of each channel  74  and the total number of channels  74  provided are not intended to limit this disclosure. Depending on the design of the structural assembly  64 , the fluid F may flow linearly within the channels  74  of one wall  72  and may turn at a right angle to flow into other walls  72 . In the illustrated embodiment, the channels  74 -C of the center wall  72 -C include a greater cross-sectional area than the channels  74  of the other walls  72  because the center wall  72 -C is positioned between two cell stacks  62  and will therefore require more fluid to achieve similar heat flux capabilities between the adjacent cell stacks  62 . 
     The structural assembly  64  may additionally include an inlet cap  76  and an outlet cap  78 . The inlet cap  76  and the outlet cap  78  may be connected to at least one of the walls  72  to provide an inlet and an outlet for receiving and expelling the fluid F. The inlet cap  76  and the outlet cap  78  may be sized to receive a sufficient amount of the fluid F to feed the other walls  72  and expel the fluid F from the walls  72 . The walls  72  that receive the inlet cap  76  and the outlet cap  78  may also include additional end caps  80  for closing-off the channels  74  so the fluid F can only exit the structural assembly  64  via the outlet cap  78 . 
       FIGS. 4, 6A and 6B  schematically illustrate assembly of the battery assembly  24 . Referring first to  FIG. 3 , the battery cells  58  of a first cell stack  62 A may optionally be disposed between end spacers  82 . Although not shown, additional spacers may optionally be positioned between each battery cell  58  to provide electrical isolation between the adjacent battery cells  58  of the first cell stack  62 A. At this stage of the assembly, the battery cells  58  are unbound relative to one another by mechanical fastening devices such as threaded fasteners, brackets, plates and/or straps. 
     The battery cells  58  of the first cell stack  62  may be compressed, such as with tooling (not shown). In one embodiment, the battery cells  58  are compressed enough to lift and manipulate the first cell stack  62 A without the battery cells  58  dropping out by applying a force F at each end spacer  82 . The compressed first cell stack  62 A is then inserted into a first pocket  84 A of the structural assembly  64 . The first cell stack  62 A may be slightly over-compressed such that it fits into the first pocket  84 A. Once the first cell stack  62  is received within the first pocket  84 A, the walls  72  of the structural assembly  64  exert a compressive load on the first cell stack  62 A and at least partially enclose the first cell stack  62 A. The battery cells  58  are contiguous with at least one of the walls  72  of the structural assembly  64  once received within the first pocket  84 A (see  FIG. 6A ). The end spacers  82  may include slots  86  that can be engaged by tooling for lifting and manipulating the first cell stack  62 A. The slots  86  may be filled after the tooling has inserted the cell stack  62 A and been removed in order to support the battery cells  58  in a more uniform manner and promote a more uniform opportunity for heat transfer at all portions of the battery cells  58  and the walls  72 . The end spacers  82  may be made of a material having a relatively low co-efficient of friction that facilitates sliding against the walls  72  for simplifying insertion of the first cell stack  62 A into the first pocket  84 A of the structural assembly  64 . In one non-limiting embodiment, the end spacers  82  are made of ultrahigh molecular weight polypropylene (UHMWPP). 
     Alternatively, the slots  86  may be omitted, thus leaving end spacers  82  as a more continuous sheet. The first cell stack  62 A may be compressed to fit into the pocket  84 A. An independent pusher block may be used to slide the first cell stack  62 A into the pocket  84 A. 
     If the structural assembly  64  includes additional pockets, additional cell stacks  62  may be received therein. For example, as shown in  FIGS. 6A and 6B , a second cell stack  62 B may be inserted into a second pocket  84 B of the structural assembly  64 . 
     Referring now primarily to  FIGS. 6A and 6B , a bus bar module  70  may be positioned over top of each of the first and second cell stacks  62 A,  62 B. In one non-limiting embodiment, the bus bar modules  70  are cubic shaped and are made of a suitable combination of conductive and insulating materials. Each bus bar module  70  may be located above one of the first and second cell stacks  62 A,  62 B and can then attached to the battery cells  58 , such as via welding, to electrically connect the battery cells  58 . In one embodiment, the walls  72  of the structural assembly  64  are sized such that when the first and second cell stacks  62 A,  62 B and the bus bar modules  70  are installed, a flat (or near flat) top surface  88  is provided (see  FIG. 6B ). 
     The base  66  may be attached to the structural assembly  64  either before or after inserting the first and second cell stacks  62 A,  62 B. The cover  68  (see  FIG. 2 ), however, may be attached to the structural assembly  64  after insertion of the contents of the battery assembly  24 . The base  66  and the cover  68  may be structural plates that are joined to the structural assembly  64  in a liquid tight manner such as via welding or adhesion. 
       FIG. 7  illustrates another exemplary battery assembly  124 . In this disclosure, like reference numbers designate like elements where appropriate and reference numerals with the addition of 100 or multiples thereof designate modified elements that are understood to incorporate the same features and benefits of the corresponding original elements. In this exemplary embodiment, the battery assembly  124  includes one or more cell stacks  162 , a structural assembly  164  including a plurality of walls  172 , a bus bar module  170  for each cell stack  162 , and a resilient envelope  190 . 
     In one embodiment, the walls  172  of the structural assembly  164  include flanges  192 . The flanges  192  support and act as depth stops for insertion of the cell stacks  162 . Each wall  172  may include one flange  192  (e.g., at exterior walls) or two flanges  192  (e.g., at interior walls). 
     In another embodiment, the resilient envelope  190  is disposed around an entire perimeter of the battery assembly  124  to resiliently and hermetically seal the battery assembly  124  relative to the exterior environment EX. The resilient envelope  190  may be a polymer such as high density polyethylene (HDPE). Other resilient envelope materials are also contemplated. The resilient envelope  190  may exhibit a relatively thin profile, portions of which may act as a compressible spring. For example, portions of the resilient envelope  190  may include corrugations  199  (here, disposed at the top portion of the resilient envelope  190 ) that are compressible to allow the battery assembly  124  to be press fit against a mounting surface  194 . The battery assembly  124  could then be mounted to the mounting surface  194  using brackets, straps or other fastening devices. In this way, the battery assembly  124  may exhibit zero clearance relative to the mounting surface  194 . 
     The battery assemblies described by this disclosure provide compact designs that leave near zero air spaces inside the assembly. This reduces the amount of air available to expand/contract inside the assembly. Furthermore, the exemplary battery assemblies provide a packaging solution that reduces the number and size of packaging components, substantially eliminates conventional array retention components, and substantially eliminates threaded fastener connections. 
     Although the different non-limiting embodiments are illustrated as having specific components or steps, the embodiments of this disclosure are not limited to those particular combinations. It is possible to use some of the components or features from any of the non-limiting embodiments in combination with features or components from any of the other non-limiting embodiments. 
     It should be understood that like reference numerals identify corresponding or similar elements throughout the several drawings. It should be understood that although a particular component arrangement is disclosed and illustrated in these exemplary embodiments, other arrangements could also benefit from the teachings of this disclosure. 
     The foregoing description shall be interpreted as illustrative and not in any limiting sense. A worker of ordinary skill in the art would understand that certain modifications could come within the scope of this disclosure. For these reasons, the following claims should be studied to determine the true scope and content of this disclosure.