Systems and Methods for Conducting Battery Heat Using Pouch Cells

The present disclosure relates to apparatuses for conducting battery heat comprising an active material positioned between a first cover portion and second cover portion, each portion comprising a thermal conductive material and protection material connected to the thermal conductive material. Also included are systems for conducting heat includes a plurality of pouch cells each comprising an active material positioned between a first cover portion and second cover portion and a plurality of frames, at least one frame positioned between each of the plurality of pouch cells. Finally included are methods, for assembling a pouch cell structure for use in conducting battery heat, comprising constructing a pouch cell assembly by alternating a sequence of pouch cells and frames; positioning a first contact edge of each of pouch cell proximal to a first heat sink and a second contact edge of each pouch cells proximal to a second heat sink opposite the first contact edge; and connecting the first heat sink to the first contact edge of each of the plurality of pouch cells and connecting the second heat sink to the second contact edge of each of the plurality of pouch cells.

TECHNICAL FIELD

The present technology relates to thermal conduction associated with vehicle batteries. More specifically, the present technology relates to accomplishing desired thermal conduction using concurrent pouch cell materials and extended pouch cell edges.

BACKGROUND

Thermal energy (i.e., heat) can be dissipated or conducted using a pouch cell. A pouch cell is an electrode assembly containing electrode lead tabs that carry the positive and negative terminals to the outside of a sealed, flexible case or pouch. Pouch cells are lightweight and flexible in nature, due to an absence of metal casing, and are preferred to cylindrical cells for certain applications.

Heat transfer using pouch cells have a wide array of application including grid energy storage, computer hardware, and vehicle batteries.

Attempts have been made to reduce the weight of pouch cells without altering dissipation or conduction properties. One attempt has been to reduce the thickness of the pouch cell by reducing the number of layers within the electrode assembly. Although reducing the number of layers within the electrode assembly reduces the thickness of the pouch cell, the solution also reduces heat transfer through the pouch cell because heat transfer through an electrode assembly is directly related to the number of electrode layers.

Additionally, this solution does not consider altering the cover material of the pouch cell to include a conductive layer that conduct heat, which will exist as a result of reducing the number of layers within the electrode assembly.

According to another technique, more heat may be propagated by the pouch cell combined with a heat sink. When joining the pouch cell with the heat sink, sufficiency of thermal contact between the two is critical. Ways to ensure robust thermal contact between the pouch cell and the heat sink have included using thermal paste or conductive tape. Shortcomings of using this technique include unwanted additional mass of the paste or tape and possible weakening of the thermal contact by wearing away of the paste/tape over an extended time.

SUMMARY

Given the aforementioned deficiencies, a need exists for systems and methods that efficiently enhance conduction of thermal energy using a pouch cell.

The present disclosure relates to systems and methods for implementing a thermal conduction apparatus. The systems and methods satisfy the aforementioned need using conductive materials and protective materials within a pouch cell cover. The systems and methods also form robust thermal contact between the pouch cell and at least one heat sink.

In operation, conduction of heat occurs through the edges of the pouch cell and the pouch cell cover including concurrent layered materials. Additionally, heat transfer occurs through the robust contact connecting the pouch cell to the at least one heat sink.

Included in the present technology are apparatuses for conducting heat includes a pouch cell containing an active material positioned between a first cover portion and second cover portion, each portion comprising a thermal conductive material and protection material connected to the thermal conductive material. Additionally, the first cover portion is connected to the second cover portion at a first contact edge and at a second contact edge opposite the first contact edge.

Also included is in the present technology are systems for conducting heat includes a plurality of pouch cells each comprising an active material positioned between a first cover portion and second cover portion and a plurality of frames, at least one frame positioned between each of the plurality of pouch cells.

In some embodiments, the protection material may be located on each side of the thermal conductive material.

In some embodiments, the first and second cover portions also contain barrier material adjacent to the protection material of both the first and second cover portions. Within some specific embodiments, the barrier material is located adjacent an outer surface exposed to atmosphere.

In other embodiments, the first and second contact edges each contain a curvilinear section located at a juncture created by the first and second cover and the active material. In some embodiments, the curvilinear sections of the first and second contact edges connect respectively to a first and second heat sink.

Finally, included in the present technology are methods, for assembling a pouch cell structure for use in conducting battery heat, comprising constructing a pouch cell assembly by alternating a sequence of pouch cells and frames; positioning a first contact edge of each of pouch cell proximal to a first heat sink and a second contact edge of each pouch cells proximal to a second heat sink opposite the first contact edge; and connecting the first heat sink to the first contact edge of each of the plurality of pouch cells and connecting the second heat sink to the second contact edge of each of the plurality of pouch cells.

In these methods, at least one frame is located adjacent a first cover portion of a pouch cell and another frame is located adjacent a second cover portion of the same pouch cell.

In some embodiments, the connecting further comprises compressing the pouch cell assembly through uniform contact perpendicular to the top of the pouch cell assembly.

In other embodiments, the connecting further comprises bending the first contact edge and second contact edge of each pouch cell to a position perpendicular to the top of the pouch cell assembly.

In other embodiments, the connecting further comprises adhering the first and second contact edges of each pouch cell respectively to a first buffer and a second buffer.

In yet other embodiments, the connecting further comprises encircling a restraint around a perimeter formed by the pouch assembly and the first and second heat sinks located on either side of the pouch assembly.

In yet other embodiments, the connecting further comprises contouring a contact surface on the first and second heat sinks, such that the distance to connect the respective first and second contact edges of each pouch cells and the respective first and second sinks is decreased.

Other aspects of the present technology will be in part apparent and in part pointed out hereinafter.

DETAILED DESCRIPTION

As required, detailed embodiments of the present disclosure are disclosed herein. The disclosed embodiments are merely examples that may be embodied in various and alternative forms, and combinations thereof. As used herein, for example, exemplary, illustrative, and similar terms, refer expansively to embodiments that serve as an illustration, specimen, model or pattern.

Descriptions are to be considered broadly, within the spirit of the description. For example, references to connections between any two parts herein are intended to encompass the two parts being connected directly or indirectly to each other. As another example, a single component described herein, such as in connection with one or more functions, is to be interpreted to cover embodiments in which more than one component is used instead to perform the function(s). And vice versa—i.e., descriptions of multiple components herein in connection with one or more functions are to be interpreted to cover embodiments in which a single component performs the function(s).

In some instances, well-known components, systems, materials or methods have not been described in detail in order to avoid obscuring the present disclosure. Specific structural and functional details disclosed herein are therefore not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present disclosure.

While the present technology is described primarily in connection with a vehicle in the form of an automobile, it is contemplated that the technology can be implemented in connection with other vehicles, such as marine craft and air craft.

While the technology is described primarily in connection with vehicle batteries, the technology is not limited to use with vehicle batteries. Other applications include cooling batteries used in grid energy storage and non-vehicle computers, as just two examples.

I. OVERVIEW OF THE POUCH CELL—FIGS.1AND2

FIG. 1is a perspective view of a pouch cell100. The pouch cell100includes a pouch cell cover110and an active pouch cell material115(seen in callout ofFIG. 1). The pouch cell100also includes pouch cell contact edges120,130and closure edges140,150.

The active material115of the pouch cell100is located behind the material of the cover110. The active material115is a conductive material configured and arranged to conduct heat from the battery—e.g., vehicle battery, via a set of electrode leads in connection with an active material. More specifically, the active material115is a cell assembly in which a positive electrode180, at least one separator185(e.g., an electrolyte), and a negative electrode190are stacked or wound to form the cell assembly. A positive electrode lead160and a negative electrode lead170are attached to the positive electrode180and the negative electrode190, respectively, and extend from the pouch closure edge150for connection with the vehicle battery.

The active material115is coated with a current collector195, e.g., a thin Al or Cu plate made of aluminum, copper, or other conducing material, and attached to the electrode leads160,170. Note that additional configurations of electrode cell assemblies known within the art may be practiced in accordance with the present technology.

The active material115of the pouch cell may contain any material that conducts heat including but not limited to lithium cobalt oxide, lithium manganese dioxide, and/or lithium iron phosphate.

The active material115of the pouch cell is commonly contained by an outer layer. More specifically, the active material115is in one embodiment contained by the cover110of the pouch cell100.

The cover110of the pouch cell100in one embodiment includes a sheet (or multiple sheets) of material sealed on its side/sides—e.g., sealed at each of the four sides of the active material115of the pouch cell shown inFIG. 1. The function of the cover110is to protect and contain the active material115of the pouch cell100. Additionally, the cover110of the pouch cell100is intended to conduct heat from the vehicle battery. As such, the cover110in some embodiments comprises materials having both protecting properties as well as heat-conducting properties.

As to not unnecessarily increase mass of the pouch cell100, the cover110is in one embodiment designed as a thin layer. For example, a layer of pouch cell cover110may be between approximately 1% and approximately 5% of an overall thickness of the pouch cell100.

Further details concerning the structure and composition of the cover of the pouch cell are described below in association withFIGS. 2 and 3.

In one embodiment, the contact edges120,130and the closure edges140,150are created by first placing the active material115between sheets of the pouch cell cover110. When the sheets of the cover110surround the active material115, the portions of the cover110not in contact with the active material115are cohesively connected (e.g., adhered) to create a seal around the active material115. The seal created by the layers of cover110in turn creates the four edges, i.e., contact edges120,130and the closure edges140,150. Closure edge150attaches a positive electrode lead160and a negative electrode lead,170to the active material115and secures in position the electrode leads160,170.

The closure edges140,150seal the pouch cell100at the edges, containing the active material115. The contact edges120,130similarly contain the active material115through sealing the pouch cell100.

The contact edges120,130function additionally to connect the pouch cell100with one or more heat sinks (shownFIG. 2andFIG. 4). In the contemplated embodiment, the heat sinks are connected to pouch cell100, alternatively, in addition to, or by way of the contact edges120,130.

Adequate connection between the contact edges120,130and the heat sinks is vital for conducting heat as desired from the vehicle battery to a cooling system contained within the heat sinks, which dissipate the heat transferred by the contact edges120,130.

To promote the role of the contact edges120,130to connect the pouch cell100to the heat sinks, the contact edges120,130in one embodiment each has a greater width than widths of the closure edges140,150, especially in embodiments in which the closure edges do not perform such an adhering function. More specifically, a contact edge width125is greater in width than the closure edge width145.

Further details concerning structure of the pouch cell contact edges are described in association withFIG. 2.

FIG. 2is a side view of a pouch cell structure200. The pouch cell structure200is in turn part of a pouch cell assembly, shown inFIG. 4. The pouch cell structure200includes a pouch cell220and pouch cell edges. In some embodiments the pouch cell220, specifically an active material224and a pouch cell cover228, are similar in function and character to the pouch cell100and its components described in association withFIG. 1. In other embodiments, the pouch cell220includes additional features to enhance thermal contact between the pouch cell220and heat sinks260,270.

Similar to the pouch cell cover110described inFIG. 1, a pouch cell cover228in some embodiments includes sheets of material configured and arranged to encase and protect an active material224as well as to conduct heat from the vehicle battery. For these purposes, the cover228of the pouch cell220may include materials having protecting properties as well as heat-conducting properties. Further details concerning composition of the cover are described in association withFIG. 3.

As described inFIG. 1, sheets of the cover228seal to create four edges along the perimeter of the pouch cell structure200, specifically two contact edges and two closure edges. The pouch cell structure200, illustrates contact edges230,240as well as a closure edge235. The second closure edge (not illustrated) is located on the opposite side of the closure edge235. The closure edge235and the second closure edge exist to ensure the active material224is contained within the sheets of the cover228. In addition to containing the active material224, the contact edges230,240connect the pouch cell structure200to a heat sink260and a heat sink270where heat is removed from the pouch cell structure200.

The contact edges230,240may include additional conductive material such as foil or sealing film to enhance the sheets of material within the cover228. These additional conductive materials may also be used to extend the contact edge230,240to a width greater than the original width.

The initial orientation of the contact edges230,240, prior to the attachment of the heat sinks260,270, is on a linear plane parallel to the linear plane of the closure edge235. However, when heat sinks260,270are attached, the final orientation of the contact edges230,240is on a plane that is perpendicular to the closure edge235. This perpendicular orientation will allow substantial contact with the heat sinks260,270. Therefore, the width of the contact edges230,240, such as the width125described inFIG. 1, should be such that the contact edges230,240may fold to create a perpendicular orientation. For example, the contact edges230,240may have a width approximately between 1 and 100 millimeters, depending on the pouch cell structure200.

Properly connection of the contact edges230,240to the heat sinks260,270, is a critical purpose of the pouch cell structure200. Options to improve connection, and thus improve thermal contact, include among others: using frames to secure the position of the pouch cell220, curvilinear sections within the contact edges230,240; using buffers280,290within the pouch cell structure200; using a thermal adhesive295on the heat sinks260,270.

In some embodiments, the pouch cell220is secured by frames210,212. The frame210may be positioned adjacent to a surface created by a sheet of the cover228on one side of the pouch cell220, and the frame212may be positioned adjacent to a surface created by a sheet of the cover228on the opposite side of the pouch cell220. Both frames210,212serve to securely position the pouch cell220. In these embodiments, the frame212also serve as the point of contact between the contact edge230and heat sinks260as well as the point of contact between the contact edge240and the heat sink270.

In certain embodiments, the frames210,212may include a cutout within the frame molding that facilitates the automatic bending of the contact edges230,240. Automatic bending creates an orientation of the contact edges230,240that is in close proximity to a plane perpendicular to the linear plane of the closure edge235. When the contact edges230,240have an orientation that near the desired perpendicular plane, connection to the heat sinks260,270becomes easier.

Further qualities and characteristics of support frames such as frames210,212are well known in the art and will not be described in further detail.

In some embodiments, the contact edges230,240include curvilinear sections235and245, respectively. The curvilinear sections235and245create ridges within the contact edges230,240. Ridges provide the contact edges230,240the ability to stretch and bend during expansion and contraction of the pouch cell structure200. The ability of the curvilinear sections235and245to stretch and bend reduces the amount of stress experienced by the remaining portion the contact edges230,240, which may prevent reduced thermal contact over time between the contact edges230,240and the heat sinks260,270.

In some embodiments, the pouch cell structure200may include buffers280,290between the frame and the contact edge. The buffers280,290create uniform contact between the contact edges230,240and the heat sinks260,270. The buffers280,290improve thermal contact by increasing contact pressure between the pouch cell structure200and the heat sinks260,270. Since the thermal conductivity between the contact edge230,240and the heat sinks260,270depends on the contact pressure, higher and uniform contact pressure will increase the heat flow by increased heat conduction.

The buffer280is located between the frame212and the contact edge230, and improves contact between the heat sink260and the contact edge230. Similarly, the buffer290is located between frame212and the contact edge240and creates improved contact between the heat sink270and the contact edge240. The buffers280,290allow a uniform contact to be created between the contact edges230,240and their respective heat sinks260,270. The buffers280,290also ensure adherence between contact edges230,240, and their respective heat sinks260,270to improve the heat transfer from the pouch cell structure200to the heat sinks260,270. Contact buffers, such as the buffers280,290, may be made of any insulating material such as rubber, silicone, or other polymers known in the art.

In addition to curvilinear sections and buffers, the heat sinks260,270may include a thermal adhesive295to improve contact with the pouch cell structure200. The thermal adhesive295would be applied to the surface of the heat sinks260,270that are connected to the contact edges230,240, e.g., contact surfaces268and278respectively. Thermal adhesives such as thermal paste/epoxy or conductive tape are used throughout the art to improve contact and heat transfer between items.

Other embodiments can include a mechanical means of attaching the contact edges230,240to the heat sinks260,270. The mechanical means can be used for independent attachment or in conjunction with the thermal adhesive295. Mechanical means can include but are not limited to clips, such as wire-form or flat spring, spacers, or push pins.

FIG. 3is a cross sectional view of the cover material included in a cover assembly300. The cover assembly300includes successive layers of conductive material to conduct heat as well as protection material to shield the conductive material. The cover assembly300has an inner surface360, which is adjacent to an active material115(shown in the call out ofFIG. 1), and an outer surface370, which is adjacent to the atmosphere, e.g., air between one pouch cell and the next pouch cell within a multi pouch cell assembly, as described inFIG. 4.

The cover assembly300includes a conductive layer320, which provides additional conduction as heat flows from the active material to the atmosphere. A first conduction occurs within the active material. As heat flows through the inner surface360, to the cover material assembly300, a second conduction of heat occurs due to the conductive layer320. Finally, heat is dissipated when it is delivered to a heat sink (not shown inFIG. 3).

For maximum heat distribution a single conductive layer is suggested, however, multiple conductive layers may be used to achieve the same rate of heat distribution.

The conductive layer320may have a thermal conductivity (K) approximately between 200 W/m/K and 500 W/m/K. For example, the conductive material may include materials such as but not limited to aluminum (K≈200 W/m/K), copper (K≈300 W/m/K), graphite (K≈400 W/m/K). Additional material properties such as heat capacity, thermal conductivity, and thermal expansion may be used in selecting a conductive material.

The thickness of the conductive layer320is typically inversely proportional to the thermal properties of the conductive material. More specifically, as the thermal conductivity coefficient increases, the required thickness of the conductive layer320decreases. Therefore, the thickness of the conductive layer320may vary depending on the conductive material used.

The thickness of the conductive layer320should be such that efficient heat conduction occurs. This heat conduction can be measured through the change in temperature (ΔT) or other quantitative factor. For example, when striving for a ΔT of 5° C., if aluminum is the conductive material, the thickness of the conductive material may be between 30 microns and 50 microns. However, if copper is the conductive material in the same scenario, the thickness of the conductive material may only need to be between 20 and 40 microns. As the desired ΔT changes for different applications, so does the thickness of the conductive layer320.

In addition to the conductive layer320, the cover material assembly300includes protection layers310and330. The protection layers310and330are connected to either side of the conductive layer320through a bonding layer340. The bonding layer340can be any means of bonding that is known in the art such as but not limited to thermoset polymers, thermoplastic material, solvent-cast adhesive, or glue. In certain embodiments, the bonding layer340of the protection layers310and330to the conductive layer320may occur through heat fusion.

The protection layers310and330may be made of the same material or differing materials. Materials for the protection layers310and320may include, but are not limited to, polypropylene (PP), polyvinyl chloride (PVC), high density polyethylene (HDPE), polyamide (PA) nylon, or other similar materials.

The thickness of the protection layers310,330may be dependent on the material used. However, the protection layer310may likely have a greater thickness than the protection layer330due to the fact that the protection layer310is directly adjacent to the inner surface360, which receives heat transfer from the active material of the pouch cell.

As an example, if the conductive layer320has a thickness of 50 microns, the protection layer310would be approximately between 100 and 150 microns. Additionally, the protection layer330would be approximately between 25 and 75 microns.

In certain embodiments, the cover material assembly300may include a barrier layer350. The barrier layer350would serve as additional protection by preventing penetration of the pouch cell structure. The barrier layer350would separate the protection layer330from the outer surface370. Since the barrier layer350serves as a blockade, the thickness of the barrier layer350would be likely be less than the conductive layer320. The barrier layer350may be made from materials including but not limited polyethylene terephthalate (PET) and Polybutylene terephthalate (PBT).

FIG. 4is a side view of a pouch cell assembly400containing multiple pouch cell structures. The pouch cell assembly400includes a plurality of frames and a plurality of pouch cell structures. Included in the plurality of pouch cell structures is a pouch cell structure420, which includes contact edges430,440. The contact edges430,440connect to heat sinks460,470, respectively. Similarly, a pouch cell structure422includes contact edges432and442, which connect to heat sinks460,470respectively. The same pouch cell structure exists for all pouch cells within the pouch cell assembly400.

Options to improve connection and thermal contact are similar to the options discussed in association withFIG. 2. These options include the use of frames; the use of curvilinear sections (not shown, see reference numerals235,245inFIG. 2) within the contact edges; the use of buffers (not shown, see reference numerals280,290inFIG. 2); the use of thermal adhesive on the heat sinks (not shown, see reference numeral295inFIG. 2). Each pouch cell may be secured by frames located on either side of the surfaces created by the pouch cells420,422, etc. The frames serve to position the pouch cells and serve as a point of contact between the contact edges430,432, etc. and heat sink460and the contact edges and440,442, etc. and the heat sink470.

The contact edges430,432, etc. and440,442, etc. may include curvilinear sections to allow for the expansion and contraction of pouch cell structure200.

The buffers may be used to create uniform contact between the contact edges, e.g.,430,440, and the heat sinks460,470and would be located between a frame and a contact edge. Note that buffers may be used on all frames regardless of proximity to the contact edges. For example, a buffer would be located between frame410and the contact edge430, and another buffer would be located between the frame410and the contact edge440. For example, buffers may be located between frame414and the contact edges432,442. Additionally, buffers may also be located on frame412to create additional contact surface area for the contact edges430,440.

The thermal adhesive may be the similar to the thermal adhesive295discussed in association withFIG. 2. The thermal adhesive would be applied to the surface of the heat sinks460,470that are connected to the contact surfaces468,478. Thermal adhesives such as thermal paste/epoxy or conductive tape are used throughout the art to improve contact and heat transfer between items.

In some embodiments may include a mechanical means (not shown) of attaching the heat sinks460,470to the pouch cell assembly400. The mechanical means can be used for independent attachment or in conjunction with an adhesive, e.g., the thermal adhesive295. Mechanical means can include but are not limited to clips, such as wire-form or flat spring, spacers, or push pins.

FIG. 5is a perspective view of the pouch cell assembly400after it has been connected to the heat sinks460and470.

Options to improve connection and thermal contact are similar to the options discussed in association withFIGS. 2 and 4. Additionally, as seen inFIG. 5, thermal connection may be improved through encircling a restraint480around the perimeter of the pouch cell assembly400, or creating contoured heat sinks.

The restraint480may be used to increase connection between each of the pouch edges within the pouch cell assembly400and the heat sinks460,470. The restraint480would wrap around the perimeter of the heat sinks460,470with the pouch cell assembly400inserted therebetween, creating points of contact with the exterior surface462on the heat sink460and the exterior surface472on the heat sink470. The restraint480may be any non-conducting material used to secure the overall pouch cell assembly400including but not limited to belts, straps, or cords.

The contoured heat sink would include a convex surface to improve thermal contact during attachment of the heat sinks460,470to the contact edges430,440. The convex section would be along the contact surfaces468and478.

In other embodiments, the exterior surfaces462,472may also be contoured in embodiments that include a restraint480. Contoured heat sink embodiments may also include an insert490to create contact between the restraint480and the heat sink exterior surfaces462and472. The contoured heat sink would secure the contact surfaces468,478to each of the contact edges included within the pouch cell assembly400.

Various embodiments of the present disclosure are disclosed herein. The disclosed embodiments are merely examples that may be embodied in various and alternative forms, and combinations thereof.

The law does not require and it is economically prohibitive to illustrate and teach every possible embodiment of the present technology. Hence, the above-described embodiments are merely exemplary illustrations of implementations set forth for a clear understanding of the principles of the disclosure.

Variations, modifications, and combinations may be made to the above-described embodiments without departing from the scope of the claims. All such variations, modifications, and combinations are included herein by the scope of this disclosure and the following claims.