A battery pack, a battery module, a battery cell and a method for producing a battery cell

Abstract

A battery module (22) comprising at least two battery cells (12), each with a base area (14), which corresponds to a hexagonally flattened circle, and a lateral area (16), which comprises six flattened zones (18) predetermined by the base area (14), and two of the at least two battery cells (12) are in contact with one another via one of the flattened zones (18) of their lateral areas (16), wherein the battery cells (12) are arranged such that the two flattened zones (18) in contact are arranged congruently in a honeycomb pattern. The contact area between the flattened zones may be built by an adhesive or sheet covering the battery cells. The lateral areas of the battery cells may be used as a terminal possibly a positive contact and / or made of aluminium or possibly a negative contact and / or made of stainless steel. An insulation layer (20) may be arranged between two of the battery cells possibly as part of a cooling system. The battery cell may be built with a jelly roll design. The method of producing shape of the cell may be applying pressure to the lateral area of the battery cell housing.

Description

FIELD OF THE INVENTION

[0001] The present invention relates to the field of battery packs for a battery, which is configured as a traction battery for a motor vehicle, and therefore the present invention also relates to the field of automobiles. Furthermore, the present invention relates to a battery cell for the battery module of the battery pack and a method for producing said battery cells. BACKGROUND INFORMATION

[0002] For battery packs, which are often combined into one battery, cylindrical battery cells are an attractive form factor as they can integrate chemistry comprising high energy density. Cylindrical cells such as 21700, 45800 or another diameter and length are round, and therefore only by using adhesive the battery cells can be connected to each other to resemble a structure comparable to a honeycomb. The challenge for a battery or a battery pack lies in module and pack integration.

[0003] However, using cylindrical cells such an assembly does not take full advantage of the metal strength of the battery cell can, but is dependent to a considerable extent on the properties of the adhesive. On the other hand. A hexagonal cell shape may increase pack density and improve mechanical properties of a cell block. However, hexagonal or honeycomb shaped battery cells are very difficult to make therefore they are expensive and difficult to produce. SUMMARY OF THE INVENTION

[0004] It is an object of the present invention to provide a battery module for a battery pack, a battery cell for said battery module and a method of producing a battery cell, by which the electrical density and the mechanical stability compared to a battery module and a battery pack using conventional cells could be easily improved.

[0005] A battery pack, a battery module, a battery cell, and a method according to the invention solve this object. Advantageous embodiments are presented in the dependent claims, the description, and the drawings.

[0006] A first aspect of the present invention relates to a battery module for a battery pack comprising at least two battery cells, one of which comprises a base area, which corresponds to a hexagonally flattened circle, and a lateral area, which comprises six flattened zones determined by the base area, and wherein two of the at least two battery cells are in at least indirect contact with one another via one of the flattened zones of their lateral areas, wherein the battery cells are arranged such that two flattened zones in contact are arranged congruently, so that the mechanical stability of the battery module and the honeycomb arrangement of the battery cells are configured by the contact.

[0007] In other words, the battery cell comprises a base area, which has a shape in between a cylindrical and hexagonal shape so the battery cell has a hexagonal shape with rounded corners or a cylindrical shape with flattened zones.

[0008] The battery module consists of at least two battery cells and may be used to build a battery pack for a battery electric vehicle, in particular a traction battery of the vehicle. Therefore, the battery pack is, in particular, used to supply energy to an electric drive train for the battery electric vehicle.

[0009] Each of the at least two battery cells could be built based on a jelly roll design, where the sidewalls or the walls of the housing form the lateral area. In this design, an insulating sheet is laid down, then a thin layer of an anode material is laid down, a separator layer is applied, and a cathode material is layered on top. This sandwich is then rolled up and inserted into a hollow cylinder casing.

[0010] The present invention is based on the finding that the hexagonal cell shape may be difficult to manufacture and, if the battery module is built with cylindrical cells, the structure stability may rely on the adhesive used to combine the cells. A hexagonal cell shape may increase pack density and improve mechanical properties of the cellblock. Additionally, a honeycomb shape may be difficult to produce, as the winding of the electrodes into a jelly roll creates a cylindrical insert.

[0011] With the battery pack according to the present invention said shape change of the base area is proposed that can be easily achieved in different ways. Before inserting, the casing and the jelly roll may be pre-shaped slightly, more near the bottom and less at the end where the jelly roll is inserted, so that there is no buckling in the bottom area. Another option is to build the cell in a cylindrical form and shape after insertion, even after adding a lid and / or after filling it with electrolyte.

[0012] The housing shape change may have a positive mechanical property impact on the final block of cells or the battery module for the battery pack. A housing shape change towards a hexagonal shape may lead to more improvements that are mechanical. One main advantage of this present invention is that the manufacturing process of the jelly roll may not change. The proposed deformation to the jelly roll may not require a change in the winding process and may maintain said performance. The proposed deformation may be determined and adjusted between 0.5% and 5% of the diameter on each of the six sides of the hexagonal shape to produce the modified shape.

[0013] Alternatively, one might use square or other shapes, which may yield different benefits.

[0014] According to an embodiment of the present invention a contact area between the flattened zones, which are in contact, is built by an adhesive and / or a sheet, in particular, a top or bottom sheet, such as a thin plate, covering the at least two battery cells is used. The sheet may be fixed, for example, by the adhesive on the sides to build the base area perpendicular to the lateral area.

[0015] In another embodiment of the present invention, the lateral area of the at least two battery cells are used each as a terminal and therefore as an electric contact for electrically connecting the battery cells.

[0016] In yet another embodiment of the present invention, at least one of the lateral areas used as a terminal is configured as a positive contact and / or made of aluminum.

[0017] In still another embodiment of the present invention, at least one of the lateral areas used as a terminal is configured as a negative contact and / or made of stainless steel.

[0018] According to another embodiment of the present invention, an insulation layer is arranged between two of the at least two battery cells.

[0019] In a further embodiment of the present invention, the insulation area is part of a cooling system.

[0020] A second aspect of the present invention relates to a battery cell for a battery module according to the first aspect of the present invention comprising a base area which corresponds to a hexagonally flattened circle, and a lateral area which comprises six flattened zones to be determined by the base area and the battery cell built with a jelly roll design.

[0021] Advantageous embodiments of the battery module and the battery pack are to be regarded as advantageous embodiments of the battery cell and vice versa.

[0022] A third aspect of the present invention relates to a method for producing a battery cell according to the second aspect of the present invention in which, after forming a cylindrical jelly roll, the six flattened zones and thus the base area, which corresponds to hexagonally flattened circles, are built by applying pressure to the lateral area.

[0023] Advantageous embodiments of the battery module and of the battery pack and the battery cell of the battery module are to be regarded as advantageous embodiments of the method for producing the battery cell and vice versa.

[0024] According to an embodiment of the present invention, the jelly roll is placed in a housing after the pressure has been applied to the lateral area.

[0025] Further advantages, features, and details of the present invention derive from the following description of preferred embodiments as well as from the drawing. The features and feature combinations previously mentioned in the description as well as the features and feature combinations mentioned in the following description of the figures and / or shown in the figures alone can be employed not only in the respectively indicated combination but also in any other combination or taken alone without leaving the scope of the invention. BRIEF DESCRIPTION OF THE DRAWING

[0026] The novel features and characteristic of the disclosure are set forth in the appended claims. The accompanying drawings, which are incorporated in and constitute a part of this present disclosure, illustrate exemplary embodiments and, together with the description, serve to explain the disclosed principles. The same numbers are used throughout the figures to reference like features and components. Some embodiments of system and / or methods in accordance with embodiments of the present subject matter are now described below, by way of example only, and with reference to the accompanying figures.

[0027] The drawing shows in:

[0028] Fig. 1 a symmetrical top view of a battery cell for a battery module for a battery pack;

[0029] Fig. 2 a top view of a battery module for a battery pack comprising at least two of the battery cells of Fig. 1.

[0030] In the figures, the same reference signs indicate the same elements or elements having the same function. DETAILED DESCRIPTION

[0031] In the present document, the word "exemplary" is used herein to mean "serving as an example, instance, or illustration". Any embodiment or implementation of the present subject matter described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.

[0032] While the present disclosure is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawing and will be described in detail below. It should be understood, however, that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternatives falling within the scope of the disclosure.

[0033] The terms “comprises”, “comprising”, or any other variations thereof, are intended to cover a non-exclusive inclusion so that a setup, device or method that comprises a list of components or steps does not include only those components or steps but may include other components or steps not expressly listed or inherent to such setup or device or method. In other words, one or more elements in a system or apparatus preceded by “comprises” or “comprise” does not or do not, without more constraints, preclude the existence of other elements or additional elements in the system or method.

[0034] In the following detailed description of the embodiment of the present disclosure, reference is made to the accompanying drawing that forms part hereof, and in which is shown by way of illustration a specific embodiment in which the disclosure may be practiced. This embodiment is described in sufficient detail to enable those skilled in the art to practice the disclosure, and it is to be understood that other embodiments may be utilized and that changes may be made without departing from the scope of the present disclosure. The following description is, therefore, not to be taken in a limiting sense.

[0035] Fig. 1 shows a battery cell 12 for a battery module 22 of a battery pack 10 shown in Fig. 2. The battery cell 12 comprises a base area 14 which corresponds to a hexagonally flattened circle and a lateral area 16 which comprises six flattened zones 18 predetermined by the base area 14.

[0036] In Fig. 1, the line with the long dashes shows a hexagonal shape and the line with the short dashes shows a cylindrical shape so that in Fig. 1 one can easily see the difference between a classical cylindrical or hexagonal shape and the modified shape for the inventive base area 14, which may be built by a hexagonally flattened circle.

[0037] Fig. 2 shows the battery module 22 of the battery pack 10 comprising at least two of the battery cells 12 shown in Fig. 1 where two of the at least two battery cells 12 are in contact with one another via one of the flattened zones 18 of the lateral area 16 wherein the battery cells 12 are arranged such that two flattened zones 18 in contact are arranged congruently, which means the flattened zones 18 are completely in contact with each other so that the mechanical stability of the battery pack 10 and the honeycomb-like arrangement of the battery cells 12 are configured by the contact of the flattened zones 18.

[0038] The lateral area 16 may be built by a can in which a jelly roll is placed, which builds the “battery” part of the battery cell 12. Since jelly rolls swell during formation and cycle life, there may be no pressure needed for insertion of the jelly roll into the honeycomb-like cell housing for the modified shape of the battery cell 12.

[0039] Battery packs like the battery pack 10 are large structures of smaller components the battery modules 22 which include the battery cells 12. The battery pack 10 may be optimized for weight and strength, in particular, if used in batteries such as traction batteries for electric vehicles. Honeycomb-like structures are known for a good weight to strength ratio.

[0040] To achieve a structure similar to a honeycomb with a cylindrical cell, such as 21700 or 46800 in the state of the art, may be connected by using adhesive between the battery cells 12. However, such an assembly may rely on the properties of the adhesive instead of the cell cans metal strength.

[0041] The cylindrical jelly roll cell may be deformed without having a major impact on performance because the laminates used for a jelly roll are flexible. In one method of manufacturing the battery cell 12, the jelly roll may be formed in a known manner and after the jelly roll is formed, pressure may be applied to the lateral area, for example by a press, resulting in the formation of the six flattened zones 18 and thus the base area 14, which corresponds to the hexagonal flattened circle. It is proposed to manufacture the battery cell 12 in a form that is between a cylindrical and honeycomb shape, as the modified shape may significantly reduce adhesive use by significantly increasing mechanical strength of the battery cells 12 for the battery module 22 and battery pack 10.

[0042] The mechanical impact of the planes of the battery cells 12 planes may be analyzed and improved. For the battery module 22, the battery cells 12 may be attached to each other with some amount of adhesive. If housings for the battery cells 12 are on the same electrical potential in the battery module’s 22 electrical wiring schematic, the adhesive may be electrically conductive.

[0043] Often many battery cells 12 are connected electrically in parallel. The insulation layer 20 may be used in a plane form as an electrically insulating layer adjacent to the lateral areas of neighboring cells 12 where the potential changes to connect the battery cells 12. The insulation layer 20 may be part of a cooling system of the battery pack 10 with one or more battery modules 22.

[0044] If battery cells 12 are manufactured with a particular polarity, the manufacturing process may not include the insulating areas such as the insulation layer 20 and may alternate the polarity between cell blocks to produce a series connection of parallel batter cells 12. For example, battery cells 12 with a positive terminal on the housing may require an aluminum housing or aluminum coated housing and battery cells 12 with negative terminal on the housing may require stainless steel.

[0045] Top and bottom of such a honeycomb-like structure formed by the battery cells 12 shown in Fig. 2 may be produced with a flat thin sheet material to gain additional mechanical stiffness and strength. This may be accomplished easily by attaching a lightweight thin sheet on top and bottom of the battery cell 12. The sheets may also be part of the cooling system of the battery pack 10.

[0046] With the battery cell 12, the battery module 22, and the battery pack 10, the modified shape of a cylindrical cell with honeycomb features is provided. Reference Signs 10 battery pack 12 battery cell 14 base area 16 lateral area 18 flattened zone 20 insulation layer 22 battery module

Claims

1. A battery module (22) of a battery pack (10) comprising at least two battery cells (12), each with a base area (14), which corresponds to a hexagonally flattened circle, and a lateral area (16), which comprises six flattened zones (18) predetermined by the base area (14), and wherein two of the at least two battery cells (12) are in contact with one another via one of the flattened zones (18) of their lateral areas (16), wherein the battery cells (12) are arranged such that the two flattened zones (18) in contact are arranged congruently so that a mechanical stability of the battery module (22) and a honeycomb arrangement of the battery cells (12) are configured by the contact.

2. The battery module (22) according to claim 1, characterized in thata contact area between the flattened zones (18), which are in contact, is built by an adhesive and / or a sheet covering the at least two battery cells (12) is used.

3. The battery module (22) according to claim 1 or 2, characterized in thatthe lateral areas (16) of the at least two battery cells (12) are used each as a terminal.

4. The battery module (22) according to claim 3, characterized in thatat least one of the lateral areas (16) used as a terminal is configured as a positive contact and / or made of aluminum.

5. The battery module (22) according to claim 3 or 4, characterized in thatat least one of the lateral areas (16) used as a terminal is configured as a negative contact and / or made of stainless steel.

6. The battery module (22) according to any one of the preceding claims, characterized in thatan insulation layer (20) is arranged between two of the at least two battery cells (12).

7. The battery module (22) according to claim 6, characterized in thatthe insulation layer (20) is part of a cooling system.

8. A battery cell (12) for a battery module (22) according to any one of the preceding claims comprising a base area (14), which corresponds to a hexagonally flattened circle, and a lateral area (16), which comprises six flattened zones (18) predetermined by the base area (14) whereby the battery cell (12) is built with a jelly roll design.

9. A method for producing a battery cell (12) according to claim 8, in which, after forming a cylindrical jelly roll, the six flattened zones (18) and thus the base area (14), which corresponds to a hexagonally flattened circle, are built by applying pressure to the lateral area (16).

10. The method according to claim 9, characterized in thatthe jelly roll is placed in a housing after applying the pressure to the lateral area (16).

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