Prismatic battery cell and method for manufacturing a cell housing for such a battery cell

Abstract

Prismatic battery cell with a cuboid cell housing (1) having two flat walls (3) opposite each other in a transverse direction (y) of the housing, wherein the two flat walls (3) are connected to side walls (5) opposite each other in the longitudinal direction (x) of the housing and to bottom and top walls (7, 9) opposite each other in the vertical direction (z) of the housing, wherein the cell housing (1) is extended on one or both sides with a housing pocket (21) which defines a cavity (17), and wherein the cavity (17) is filled with air or at least partially filled with a functional material (25), characterized in that the cavity (17) of the housing pocket (21) is open on both sides in the longitudinal direction (x) or in the vertical direction (z) of the housing, so that the cavity can be permeated by cooling air or other coolant or can be easily fitted with the functional material (25) during manufacturing.

Description

[0001] The invention relates to a prismatic battery cell according to the preamble of claim 1 and to a method for manufacturing a cell housing for such a battery cell according to claim 7.

[0002] In a cell assembly for a high-voltage battery system known from the prior art, prismatic lithium-ion battery cells are stacked one behind the other in the stacking direction under mechanical preload. Depending on the cell chemistry, either elastic intermediate layers as compliant compression pads or strips (1 to 2 mm) are placed between the battery cells to compensate for swelling forces over charging cycles and aging. Alternatively, significantly thicker (2 to 5 mm) anti-propagation pads are placed between the battery cells to thermally isolate neighboring cells in the event of thermal runaway in one battery cell and also to compensate for swelling forces over charging cycles and aging. Such cell intermediate pads are based on aerogel / ceramic fleece mats or on silicone foams laminated in plastic films.

[0003] In current technology, the cell intermediate pads are kept as individual components that are positioned between the battery cells during the stacking process. Consequently, the manufacturing process for producing the cell assembly is both component-intensive and technically complex.

[0004] From DE 10 2022 104 370 A1, a battery cell unit is known, comprising a battery cell, a cell housing, and a cell chemistry unit arranged within the cell housing. The battery cell unit is assigned a first width in a first direction, at least in a specific operating position. The battery cell unit has at least one first functional layer that is at least partially compressible in the first direction. This first functional layer is fixedly arranged relative to the battery cell and adjacent to the cell chemistry unit with respect to the first direction. It is designed to compensate for any expansion of the cell chemistry unit in the first direction, ensuring that the battery cell unit does not exceed its assigned first width in the specific operating position.From DE 10 2021 208 931 A1, a battery cell is known that comprises a prismatically shaped battery cell housing and at least one electrode unit, which is received in the prismatically shaped battery cell housing. A space is provided between the prismatically shaped battery cell housing and the at least one electrode unit, which is at least partially filled with a filler element. From DE 20 2019 101 373 U1, a battery rack for receiving a lithium-ion battery module comprising prismatic lithium-ion cells is known. The battery rack has a housing providing a receiving space for the battery module, which is open at the end face, and comprises a base, a top, and two side parts connecting the base to the top. The battery rack also has a partition plate that is spaced apart from the top, leaving a gap.

[0005] A battery cell of this type is known from CN 218975561 U. Further battery cells are known from DE 10 2021 208 931 A1, GB 1 428 132 A and DE 10 2019 211 093 A1.

[0006] The object of the invention is to provide a preferably prismatic battery cell that exhibits increased functionality compared to the prior art. In particular, the component complexity and manufacturing effort for producing a cell assembly consisting of stacked battery cells are to be reduced.

[0007] The problem is solved by the features of claim 1 or 7. Preferred embodiments of the invention are disclosed in the dependent claims.

[0008] The invention relates to a prismatic battery cell with a cell housing, in particular a cuboid shape. The cell housing has two flat walls opposite each other in a transverse direction. The two flat walls are connected to side walls opposite each other in the longitudinal direction of the housing, as well as to bottom and top walls opposite each other in the vertical direction of the housing. According to the invention, the cell housing is extended on one or both sides, in a single piece and made of a single material, with a housing pocket. The housing pocket defines a cavity. This cavity can preferably be at least partially filled with a functional material, such as a functional foam or a flame-retardant material. Alternatively, the cavity can also remain unfilled. The housing pocket integrated into the cell housing can perform the function of a conventional cell spacer pad within the cell assembly.Unlike conventional cell spacer pads, the housing pocket is made of a single material and integrated as a single piece into the cell housing of the battery cell, which greatly reduces the component effort and manufacturing effort required to produce a cell assembly.

[0009] In this cell assembly, a number of battery cells are stacked one behind the other in a single stacking direction under mechanical preload. The casing pockets lie within the force path created by this mechanical preload. Accordingly, the casing pocket can act as a compression pad within the cell stack, compensating for volume expansion of the battery cells due to swelling or aging. Furthermore, the casing pocket can be designed to be elastically compliant, if necessary by adjusting the wall thickness.

[0010] For example, a housing pocket in a cell stack can act as a spacer between adjacent battery cells. Alternatively and / or additionally, the housing pocket can act as a stiffening element, increasing the component rigidity of the battery cell housing. Furthermore, the housing pocket, especially when filled with air, can act as thermal insulation between adjacent battery cells in the cell stack.

[0011] In a specific embodiment, the housing pocket can be realized as follows: At least one of the two flat walls of the cell housing can be double-walled, with an inner wall defining the interior of the cell housing and an outer wall spaced apart, for example, in the transverse direction of the housing, across the cavity. The inner wall and the outer wall can be essentially congruent and, in particular, have the same wall height (in the vertical direction of the housing) and the same wall width (in the longitudinal direction of the housing). To further enhance functionality, the air-filled cavity of the housing pocket can be designed to allow coolant flow. According to the invention, the cavity of the housing pocket is open on both sides in the longitudinal direction of the housing, allowing coolant, such as cooling air, to flow through it, for example, by forced convection.According to the invention, the inner wall of the housing pocket defines the interior of the cell housing, which is hermetically sealed to the outside, in particular against the housing pocket, via the inner wall.

[0012] In another embodiment, the cavity can be subdivided into partial cavities by means of at least one supporting rib. The supporting rib can be attached to either the inner or outer wall of the housing pocket. The partial cavities can be filled with various functional materials. For example, the supporting rib can increase the component stiffness of the battery cell in the transverse direction of the housing, where the mechanical preload in the cell stack acts.

[0013] From a process engineering perspective, it is simple if the cell housing is manufactured using extrusion, particularly aluminum extrusion. In this case, a cell housing intermediate can be cut to length from an extruded profile in a first process step. The bottom and top walls, the flat walls, and the housing pocket are integrated into the cell housing intermediate in a single piece, all made of the same material. In a subsequent second process step, the interior of the cell housing can be fitted with an electrode / separator assembly. Finally, in a third process step, the side walls can be mounted as separate components onto the still open sides of the cell housing intermediate, thus completing the cell housing.

[0014] As an alternative to extrusion, the cell housing can also be manufactured using a folding process. This involves first providing a flat sheet metal blank that, when unfolded, contains the housing walls. The sheet metal blank is then folded into the cell housing using a forming process. In another alternative process, the housing walls of the cell housing can be provided as individual components that are joined together by welding to form the cell housing. For example, the housing pocket can be prefabricated as a separate component. This separate housing pocket can then be attached to the cell housing or the intermediate cell housing component using a joining process, particularly welding.

[0015] In another embodiment, the housing pocket projects beyond a cell housing top wall and / or a cell housing bottom wall by an excess, such that the wall height of the housing pocket is greater than the wall height of the cell housing inner wall. Furthermore, in one embodiment, the cell housing can have a housing pocket whose cavity is not open in the longitudinal direction of the housing, but rather in the vertical direction of the housing on both sides, i.e., upwards and downwards.

[0016] As mentioned above, the cell housing intermediate can be folded from a sheet metal blank, which is folded in a meandering pattern around parallel axes. These axes form the longitudinal edges of the housing. The meandering fold separates the cell housing interior from the cavity of the housing pocket via the inner wall. The end edges of the sheet metal blank, which run parallel to the longitudinal edges of the housing, can each be welded to the inner wall. Finally, the lid assemblies, which are provided as separate components, are mounted onto the still-open sides of the cell housing intermediate, thus completing the cell housing.

[0017] In a further process sequence for manufacturing a cell housing intermediate, a cell housing intermediate can be cut to length from an extruded profile produced in an extrusion process in a first process step. In cross-section, the cell housing intermediate can be U-shaped with a bottom wall and lateral housing pockets or flat walls extending upwards from it. At this stage of the process, the two lateral housing pockets or flat walls are still spread apart laterally. Furthermore, the two housing pockets or flat walls can be capped at the top with cover wall ribs that project inwards at right angles. A loading opening is formed between the two cover wall ribs, through which the electrode / separator assembly is inserted into the interior of the cell housing in a placement process. This is followed by a forming step in which the two housing pockets or flat walls are then formed.The flat sidewalls are moved towards each other using joining forces, bringing the cover wall webs into weldable contact. In a final welding process, the two cover wall webs can be welded together to form the cell housing intermediate. Subsequently, the lid assemblies, which are provided as separate components, are mounted onto the still open sides of the cell housing intermediate, thus completing the cell housing.

[0018] Exemplary embodiments of the invention are described below with reference to the accompanying figures. These show: Fig. Figures 1 to 7d show different views of the battery cell according to the invention; as well as Fig. 8a to 11c further embodiments of the invention.

[0019] In the Fig. Figure 1 shows a prismatic battery cell in isolation. Its cuboid cell housing 1 has two flat walls 3 opposite each other in a transverse direction y. The two flat walls 3 are connected to side walls or cover assemblies 5 opposite each other in the longitudinal direction x of the housing, and to bottom and top walls 7, 9 opposite each other in the vertical direction z of the housing. Each of the cover assemblies 5 consists of a cell terminal 11 and a cover plate 13.

[0020] The one in Fig. The right-hand flat wall of the cell housing 1 is double-walled, consisting of an inner wall 15 that defines the interior of the cell housing and an outer wall 19 that is spaced from the inner wall 15 in the transverse direction y of the housing by a cavity 17. This creates a housing pocket 21 whose cavity 17 is open on both sides in the longitudinal direction x of the housing. The inner wall 15 and the outer wall 19 of the housing pocket 21 are congruent and have the same wall height Δz and the same wall width Δy.

[0021] The provision of the housing pocket 21 increases the functionality of the cell housing 1. For example, the air-filled housing pocket 21 acts as a spacer or as a thermal insulation element between adjacent battery cells of a cell assembly or cell stack 23, as used in the Fig. Figure 2 shows that cell assembly 23 contains a number of battery cells that are identical in construction to those shown in the Fig. The battery cells shown in 1 are arranged one behind the other in a stacking direction and with mechanical preload F in the stacking direction. V The housing pockets 21 of the battery cells installed in the cell assembly 23 are subjected to the force path of the mechanical preload F. V The housing pockets 21 are positioned. Furthermore, they are designed to be sufficiently elastic and flexible. The housing pockets 21 can therefore act as compression pads, compensating for volume expansion of the battery cells due to swelling or aging. Additionally, the housing pockets 21 of the battery cells can be cooled with coolant, e.g., cooling air, to cool the cell stack 23.

[0022] Alternatively, in the Fig. Figure 3 shows a cell stack 23 in which the cavity 17 of the housing pockets 21 is each filled with a flame-retardant material 25. In this case, the housing pockets 21 act both as spacers and as flame guards in the event of thermal runaway of one of the battery cells.

[0023] In the Fig. Figure 4 shows another cell stack 23, which is essentially identical in construction to the one in the Fig. The cell cluster shown in section 3 is structured as 23. In contrast to the Fig. 3 are in the Fig. 4 The housing pockets 21 of the battery cells stacked in the cell assembly 23 are filled with air, while an additional cell spacer pad 27 is positioned between each battery cell as a separate housing component. The air-filled housing pockets 21 act as thermal insulation elements and compression pads, while the cell spacer pads 27 act as flame retardants.

[0024] Based on the Fig. Figure 5 below describes a manufacturing process for producing the cell housing 1. In a first process step, a cell housing intermediate 29 is cut from an extruded profile 31, which has been produced in an extrusion process. The cell housing intermediate 29 incorporates the bottom and top walls 7, 9, the two flat walls 3, and the housing pocket 21 in a single piece and made of a uniform material. In a second process step (not shown), the interior of the cell housing intermediate 29 is coated with a (only in the Fig. 10, Fig. 11b and Fig. The electrode / separator assembly 37 (shown in Figure 11c) is assembled. Subsequently, the cover assemblies 5, which are provided as separate components, are mounted onto the still open housing sides of the cell housing intermediate 29, thus completing the cell housing 1.

[0025] In the Fig. Figure 6 shows the battery cell according to the invention in a further embodiment. In contrast to the Fig. 1 is in the Fig. 6 The battery cell is equipped on both sides in the transverse direction y of the housing with a housing pocket 21. Accordingly, the two flat walls 3 are each double-walled with an inner wall 15, an outer wall 19 and an intermediate cavity 17.

[0026] In the Fig. Figures 7a to 7d show different versions of the cell housing 1. Fig. 7a The cell housing 1 has a housing pocket 21 on both sides in the transverse housing direction y, as is also the case in the Fig. 6 is the case. The same applies to the one in the Fig. 7b shown cell casing 1. As can be seen from the Fig. As can be seen from Figure 7b, the outer walls 19 of the two casing pockets 21 close off in the casing vertical direction z upwards and downwards with rounded ends which are attached to the upper and lower ends of the cell casing inner wall 15.

[0027] In the Fig. 7c shows that the cell housing 1 is formed on one side in the transverse direction y with a housing pocket 21. The cavity 17 of the housing pocket 21 is divided into two separate partial cavities by a support rib 33. These can optionally be filled with different filling material.

[0028] In the Fig. In section 7d, the cell housing 1 is also formed on one side with a housing pocket 21. Its cavity 17 is subdivided into a total of four partial cavities by means of support webs 33. The support webs 33 can increase the component stiffness of the cell housing 1 in the transverse housing direction y, in which the mechanical preload F V It acts in cell group 33.

[0029] In the Fig. 8a and Fig. Section 8b shows further embodiments. Their structure and function essentially correspond to the structure and function of the preceding embodiments. In the Fig. 8a is analogous to Fig. 6 The battery cell is equipped on both sides in the transverse direction y of the housing with a housing pocket 21. In contrast to the Fig. 6 stand out in the Fig. 8a the two housing pockets 21 the cell housing top wall 9 by an excess, so that the wall height Δz2 of the housing pockets 21 is dimensioned larger than the wall height Δz1 of the cell housing inner wall 15. The same also applies to the embodiment of the Fig. 8b, in which the two housing pockets 21 project beyond both the cell housing top wall 9 and the cell housing bottom wall 7 by an excess.

[0030] The one in Fig. The cell housing shown in 9 has - analogous to the embodiment of the Fig. 1 - only on its right side of the casing a case pocket 21. In contrast to the Fig. However, 1 is in the Fig. 9 the cavity 17 of the case pocket 21 is not open in the longitudinal direction x of the case, but rather in the vertical direction z of the case on both sides, that is to the top and to the bottom.

[0031] In the Fig. 10 is a cell housing intermediate 29 made from a folded sheet metal blank, which is folded in a meandering pattern around mutually parallel folding axes F in a folding process. The folding axes F form in the Fig. 10 the longitudinal edges of the casing running in the longitudinal direction x. Due to the meandering folding, the cell casing interior, in which in the Fig. 10 an electrode / separator arrangement 37 is inserted, separated from the cavity 17 of the housing pocket 21 by the inner wall 15. The end edges 39 of the sheet metal blank, which run parallel to the longitudinal edges of the housing, can each be welded to the inner wall 15 in a welding process. Subsequently, the cover assemblies 5, which are provided as separate components, are mounted onto the still open housing sides of the cell housing intermediate product 29, thus completing the cell housing 1.

[0032] In the Fig. Figures 11a to 11c illustrate a further process sequence for the manufacture of a cell housing intermediate product 29. Accordingly, in a first process step ( Fig. 11a) A cell casing intermediate 29 is cut from an extrusion profile produced in an extrusion process. In cross-section, the cell casing intermediate 29 has a U-shaped profile with a bottom wall 7 and lateral casing pockets 21 extending upwards from it. In the Fig. In the cell housing intermediate product 29 shown in Figure 11a, the two housing pockets 20 are spread apart laterally. Furthermore, the two housing pockets 21 are closed at the top by cover wall ribs 41 that project inwards at right angles. A loading opening 43 is formed between the two cover wall ribs 41, through which, in a loading process ( Fig. 11b) the electrode / separator assembly 37 is inserted into the interior of the cell housing. This is followed by a forming step in which the two housing pockets 21 are joined with joining forces F FThe two cover wall webs 41 are moved towards each other, bringing them into weldable contact. In a final welding process, the two cover wall webs 41 are welded together to form the cell housing intermediate 29. Subsequently, the cover assemblies 5, which are provided as separate components, are mounted onto the still open housing sides of the cell housing intermediate 29, thus completing the cell housing 1. Reference symbol list 1 cell casing 3 flat wall 5 Cover assembly 7, 9 Floor and ceiling wall 11 Cell terminal 13 Cover plate 15 Interior wall 17 Cavity 19 Exterior wall 21 Case bag 23 cell cluster 25 Flame retardant material 27 cell interlayer pads 29 Cell casing intermediate 31 Extrusion profile 33 Support bridge 35 cavity 37 Electrode / separator arrangement 39 end edges 41 Deck wall walkway 43 Loading opening F V mechanical preload F Folding axles F F Joining force Δz, Δz1, Δz2 Wall heights

Claims

[1] Prismatic battery cell with a cuboid cell housing (1) having two flat walls (3) opposite each other in a transverse direction (y) of the housing, wherein the two flat walls (3) are connected to side walls (5) opposite each other in the longitudinal direction (x) of the housing and to bottom and top walls (7, 9) opposite each other in the vertical direction (z) of the housing, wherein the cell housing (1) is extended on one or both sides with a housing pocket (21) which defines a cavity (17), and wherein the cavity (17) is filled with air or at least partially filled with a functional material (25), characterized by , that the cavity (17) of the housing pocket (21) is open on both sides in the longitudinal direction (x) or in the vertical direction (z) of the housing, so that the cavity can be permeated by cooling air or other coolant or can be easily fitted with the functional material (25) for manufacturing purposes. [2] Prismatic battery cell according to claim 1, characterized by , that the battery cell is part of a cell stack (23) in which a number of battery cells are arranged in a stacking direction under mechanical preload (F V ) stacked one behind the other. [3] Prismatic battery cell according to claim 2, characterized by , that the housing pocket (21) acts as a spacer between adjacent battery cells in the cell stack (23), and / or that the housing pocket (21) acts as a stiffening element that increases the component stiffness of the cell housing (1) of the battery cell, and / or that the housing pocket (21) acts as thermal insulation between adjacent battery cells in the cell stack (23). [4] Prismatic battery cell according to any one of the preceding claims, characterized by, that to provide the housing pocket (21) at least one of the cell housing walls is double-walled with an inner wall (15) limiting the cell housing interior and an outer wall (19) spaced apart from it via the cavity (17), and that the inner wall (15) hermetically seals the cell housing interior against the housing pocket (21). [5] Prismatic battery cell according to any one of the preceding claims, characterized by , that the inner wall (15) and the outer wall (19) are essentially identical and in particular have the same wall height (Δz) and the same wall width (Δx), or that the inner wall (15) and the outer wall (19) have different wall heights (Δz1, Δz2). [6] Prismatic battery cell according to any one of the preceding claims, characterized by, that the cavity (17) is subdivided into partial cavities by means of at least one support web (33), that the support web (33) is force-transmittingly connected to both the inner wall (15) and the outer wall (19) of the housing pocket (21), and that in particular the partial cavities can be filled with different functional materials (25), and / or that the support web (33) increases the component stiffness of the battery cell in the transverse direction (y) of the housing, in which the mechanical preload (F) v ) in the cell stack (23). [7] Method for manufacturing a cuboid cell housing (1) for a prismatic battery cell according to any one of claims 1 to 6, characterized by , that the cell casing (1) is produced by extrusion. [8] Method according to claim 7, characterized by , that - in a first process step, a cell housing intermediate product (29) is cut to length from an extrusion profile (31) produced during extrusion, and that the bottom and top walls (7, 9), the flat walls (3) and the housing pocket (21) are integrated in the cell housing intermediate product (29) in a single piece and made of a single material, and - in a second process step, the cell housing interior is equipped with an electrode / separator arrangement, and - in a third process step the side walls (5) can be attached as separate components to the still open housing sides of the cell housing intermediate product (29) to form the cell housing (1).

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