Patent Application
20150221995
The present disclosure relates to a pouch-type battery cell with integrated cooling features.
The emergence and utilization of pouch-type Li-ion cells in energy storage applications presents a new paradigm in battery pack system engineering, especially in the design of the device for thermal management. Service life of a pouch-type battery can be shortened due to swelling of the pouch used to encapsulate the active region of the cell. High humidity and high temperature degrades the active region of the cell. Control of the temperature of the battery cell may be important for cell longevity.
In one embodiment, a pouch-type battery cell includes a cell electrode having a cell side and a thermally conductive pouch contacting the cell side. The thermally conductive pouch includes a metal layer having a plurality of topographic features and the features are configured to increase the effective surface area of the pouch. A cover arrangement is included to direct coolant over the pouch.
In another embodiment, a pouch-type battery cell is provided with at least one cell electrode having a cell side that includes a plurality of topographic features formed thereon. The features are configured to increase an effective surface area of the cell side. A thermally conductive pouch is embossed onto the topographic features of the cell electrode. A cover arrangement is included to direct coolant over the topographic features.
In still another embodiment, a vehicle comprising a traction battery including a plurality of pouch-type cells stacked to form an array is provided. Each of the cells includes a thermally conductive pouch having a plurality of topographic features that are configured to increase the effective surface area of the cell. A cooling arrangement is interleaved with the cells and configured to direct coolant over the topographic features to cool the battery.
As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.
The current state of the art thermal management for pouch-type cell uses additional hardware, such as plastic fixtures, cold plates, and compression mounts to help regulate cell temperatures and battery array structure temperature. These designs increase system complexity, cost, weight and yield. The need exists for a simplified system structure with reduced part count and to improve production assembly process speeds. The reduced part count decreases the potential failures that can occur, as does limiting the number of connections and interfaces to the thermal system. As the pouch-type battery cell technology matures and improves, there is ample opportunity to integrate production of cells with cooling features on the cell itself, within the existing structure. There remains a need for simplified cooling for pouch-type battery cells and embodiments of the present invention address this problem by providing integrated surface topographies on existing pouch cell components. Integrating the cooling into existing components reduces part counts, improves manufacturing yield and reduces complexity. It eliminates the need for a cold plate component and associated failure modes. The integrated surface topographies can be designed as cooling path features to enhance thermal heat transfer and cooling. A cooling manifold provides coolant to the features on the pouch which directly cools the pouch cell and its battery cell components. The features can be on one or both sides of the pouch cell, thus enabling designs for single or dual sided cooling. The features are initially fabricated into the surface of the outer electrode of the battery cell or fabricated within the structural component of the pouch itself. The feature is transferred to the thin outer polymer of the pouch during assembly of the pouch. Coolant fluid flows in direct contact with the pouch without penetration into the electrically active regions of the cell. Such integrated cooling features enable direct cooling of the pouch cell surface and eliminate the need for a cold plate component.
In a first embodiment, the cooling path features are located within the pouch by modification to the structural component employed as pouch cell enclosure material. This is done by preforming the topographic features onto the structural element of the pouch enclosure, such as by stamping or embossing. The structural component of the pouch may be a metal such as aluminum, or other thermally conductive moisture sealing material. The featured pouch structural component is covered by thin polymer layers on each side. Referring now to
Integrating the features into an external pouch case provides an opportunity to integrate the topographic features during processing of a laminated polymer/aluminum/polymer pouch case. The aluminum layer is modified by a technique such as stamping, embossing or etching prior to polymer deposition. The aluminum materials in a typical pouch-type cell can be 40-50 microns thick. Some changes to pre- and post-processed thickness of the aluminum layer may be necessary in this embodiment. Additionally, metals other than aluminum may be used as a structural pouch material such as stainless steel or copper or reinforced materials that can be formed into flexible sheets.
In another embodiment, one or both of the outer-most electrodes within the cell itself have topographic features. The topographic features are resolved upon the surface of the pouch-type cell once the pouch enclosure material is vacuum sealed to enclose the active cell components.
An advantage may be that direct cooling on the surface of the pouch cell reduces the thermal resistance of heat dissipation paths from the coolant to the active cell region that is internal to the battery cell. This enhances the local heat transfer coefficient and more effectively cools the cell. Another advantage may be that by integrating cooling features directly to individual cells, the traditional cold plate components for cell thermal management are eliminated. This simplified thermal management design, utilizing existing components, allows for pack and system level designs that are simple to assemble. The number of potential failures is not increased due to additional components and assembly process steps.
Certain embodiments exploit the results of water intrusion studies showing that a high quality seal and encapsulation of the active cell materials prevent coolant penetration into the cell. Additional surface treatment, however, may be employed to ensure the required performance. Surface treatments to further limit moisture ingress could include a wax or other coating to create a hydrophobic layer. This wax, or coating or treatment would cover the cooling features in a thin layer such that the thermal conduction of heat is not compromised.
Referring now to
Direct cooling of the active cells within the array is contained via the pouch surface with integrated features 36, a cover 34 and a gasket or seal 38 creating a coolant manifold 31. The cover 34, in addition to providing an enclosure to hold the cooling fluid in contact with the features 36, additionally serves to align the cells. An array of cells is stacked, located side-by-side, or other orientations, and needs to be aligned, for example in height, side-by-side or with the electrode tabs, etc. The cooling manifold cover accomplishes this alignment since the cell is mated to the manifold wall. Further, the array of cells is compressed by integrating an interlock clip from the cooling manifold cover to a next cooling manifold cover, repeating depending on the number of cells in electrical communication. End plate compression techniques can be employed at the farther ends of the array to further homogenize cell-to-manifold surface mating.
Certain embodiments may allow for a variety of integrated cooling feature designs based upon performance targets and design boundary conditions. The cell features establish a path of cooling fluid through the cooling manifold resulting in a pressure drop across each unit based on feature design and complexity. Multiple cells, each with cooling manifolds, may be arranged in an array. Multiple arrays, or modules, make up a battery pack. An array of cells may consist of individual cooling manifolds with inlet and outlet ports connected to establish a coolant loop.
In one embodiment, the geometry of the features is chosen so that the coolant flow is moved across the cell from side to side by linear features, as shown in
A refinement of this embodiment is shown in
In a further refinement,
A method of forming the pouch-type cell in which the integrated cooling features are within the structural component of the pouch is shown in
Referring now to
While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.
