Method for producing a battery cell housing, battery cell housing, battery and use of the battery

Abstract

The invention relates to a method for producing a battery cell housing (1), to a battery cell housing (1), to a battery and to the use thereof. A metal sheet with two sheet edges (9, 10) is provided as starting material, a material tapering is made in the metal sheet as predetermined breaking point (12), and the metal sheet is shaped to form a three-dimensional body such that the two sheet edges (9, 10) abut one another. Then the two abutting sheet edges (9, 10) are fixedly interconnected.

Description

[0001] Method for producing a housing of a battery cell, housing of a battery cell, battery and use of the battery

[0002] The invention relates to a method for producing a housing of a battery cell, a housing of a battery cell, a battery and the use thereof.

[0003] In batteries, especially lithium-ion batteries, thermal runaway must be reliably prevented. Thermal runaway is a self-reinforcing, heat-generating process that can occur, for example, due to inadequate cooling or exogenous shocks such as accidents and the associated mechanical damage. Thermal runaway can lead to fire or explosion. Without safety mechanisms, the battery will burst uncontrollably.

[0004] Various safety mechanisms are known from the prior art to prevent the uncontrolled bursting of batteries. For example, AT 518 161 B1 discloses a battery with a plurality of battery cells arranged in a housing. In order to prevent infection of neighboring undamaged battery cells in the event of thermal runaway of a defective battery cell, at least two battery cells arranged in a row in a stacking direction are arranged in the housing so that they can be moved in the stacking direction. Two neighboring battery cells can be thermally insulated by a - preferably intumescent - protective material above a predetermined temperature. The protective material is arranged between neighboring battery cells in such a way that the neighboring battery cells can be moved away from each other in the stacking direction into a fire protection position by the protective material.This protection requires additional installation space and requires intumescent material.

[0005] CN 217 848 163 U describes an explosion-proof assembly for a battery enclosure with a circular vent in one of the enclosure walls. The enclosure wall is covered by a plastic plate that covers an outlet opening. The plastic plate has weakened areas and is bolted to the enclosure wall and sealed with a sealing ring. Explosion protection with such a safety valve is relatively complex and requires many individual parts. Another safety valve is disclosed in JP-H11250885 A. It is constructed in such a way that a thin metal section is formed in a part of the enclosure so that the gas in the enclosure is released by rupturing the thin section when the internal pressure in the enclosure becomes equal to or higher than a predetermined value (relief pressure), thereby reducing the internal pressure in the enclosure. The metal plate is welded, and during welding, heat can be transferred to the thin part of the safety valve.As a result, the thin part of the safety valve, which has been work-hardened, is difficult to adjust to a specific valve opening pressure.

[0006] To solve this problem, US 2012 / 0 114 988 A1 proposes a battery housing with a housing cover. The cover has an elliptical recessed area in which a V-shaped break groove is located. To prevent the heat generated during welding of the housing from adversely affecting the safety valve, the recessed area is flanked by slots opposite the break groove, which are intended to impair heat transfer. The production of a housing with such a housing cover is still comparatively complex.

[0007] Object of the invention

[0008] The object of the present invention is to propose a method for producing a housing for a battery cell that avoids the aforementioned disadvantages. Furthermore, the object of the invention is to provide a housing for a battery cell, to create a battery with such a battery cell, and to demonstrate a use.

[0009] The objects are achieved by a method according to claim 1, by a use according to claim 10 and by devices of claims 5 and 9. Advantageous embodiments are the subject of the dependent claims. Advantages and embodiments described in connection with the method also apply mutatis mutandis to the devices and conversely, advantages and embodiments described in connection with the devices also apply mutatis mutandis to the methods. The housing according to the invention is produced from sheet metal. For this purpose, a strip material can first be cut to length. The sheet metal strip (bare) formed from the semi-finished product can be coated. The sheet metal strip is an essentially two-dimensional structure and has two opposite sheet metal edges. The sheet metal strip is cold-formed, with two sheet metal edges facing one another after cold forming and then being firmly connected to one another. The connection is preferably made by means of a material bond.Before the sheet edges are firmly connected, the sheet is provided with a material taper as a predetermined breaking point.

[0010] The manufacturing of the housing according to the invention is particularly simple because the predetermined breaking point can be created using the same process steps used to form the sheet metal strip. This eliminates the need for additional components and eliminates the need for machining different sides of the sheet metal strip, simplifying tooling and handling. Finally, only a single (linear) weld seam is required, eliminating the need to reposition the housing blank and thus enabling short cycle times.

[0011] The material taper is preferably introduced by embossing into the preferably still flat sheet metal. This allows it to be introduced directly during the production of the cell housing, avoiding the use of a separate component. Particularly preferred, but not necessarily, the material taper is created during the production of the cell housing by forming, so that it does not require an additional, non-process step. The material taper can take the form of a longitudinal groove and represents a weakening of the housing, forming a predetermined breaking point. It thus represents a burst contour.

[0012] In an alternative embodiment, the material taper is introduced into the cell casing by scoring or engraving. By machining the material taper in this way, the opening pressure of the casing can be precisely adjusted. In one embodiment, only cold forming techniques are required to produce the casing before the sheet ends are finally joined. Cold forming techniques that are particularly envisaged include embossing, deep drawing, punching, and bending. This ensures optimal use of the material, as there is virtually no waste. By omitting machining processes, it can be ensured that the casing's interior is not contaminated, thus potentially eliminating the need for cleaning and deburring.

[0013] The housing is thus manufactured from a single circuit board, with the remaining separation point subsequently joined. Preferably, the separation point is positioned opposite the predetermined breaking point. This maximum distance ensures that the heat generated by welding the separation point has minimal impact on the predetermined breaking point.

[0014] The process is generally suitable for producing housings for round cells, but is primarily intended for prismatic cells. The sheet metal strip is formed in such a way that it ultimately describes the envelope of a cuboid (surface area) without the two end walls, i.e., a cuboid open on both ends. The edges of the cuboid can be rounded for process-related reasons. The body thus formed is also referred to as a square tube.

[0015] Preferably, two ends of the sheet metal formed into a square tube are connected to each other by a weld. The weld can be a weld seam or one or more spot welds. Particularly preferably, the predetermined breaking point and the weld are located on different side surfaces of the square tube.

[0016] The predetermined breaking point can be designed as a longitudinal groove. In one embodiment, it runs parallel to the length of the square tube. It is advantageous if it is spaced from the end faces. This ensures that the housing does not accidentally burst anywhere along its entire length. This not only keeps any material escaping away from the end walls, so that their connection is subjected to less stress, but also allows the material to be collected in a common chamber that can extend across several battery cells. The width of the chamber can be limited to the length of the predetermined breaking points, and its volume can be adjusted to the total number of battery cells to be secured.

[0017] Preferably, the longitudinal groove extends over 10% to 30% of the distance between the end faces of the housing.

[0018] The two opposite open end faces of the housing can be subsequently closed with sheet-metal end caps—i.e., after the sheet metal has been formed and the two ends of the sheet metal have been welded together to form a shell—so that the battery cell can be formed into a pressure chamber. Accordingly, the end caps can also be integrally bonded to the housing. The battery cell thus comprises at least the shell and the parts that close the interior of the can shell, in particular the end caps. The end caps can have a thicker wall than the shell. The end caps preferably contain the battery cell's electrical contacts.

[0019] Preferably, the jacket has a substantially constant wall thickness of 0.2 to 1 mm, preferably 0.25 to 0.8 mm, particularly preferably 0.3 to 0.5 mm.

[0020] A coating can be applied to the outer surface of the casing, at least in certain areas. The coating is intended for electrical insulation of the housing. The housing is provided with a coating or prepared for it as a single part or subassembly, i.e., before the sheet metal is formed into the housing. Processes such as anodizing, coating, painting, gluing, etching, blasting, embossing, brushing, or the like are suitable for this purpose. The coating is preferably a UV varnish.

[0021] For reasons of readability, the invention has been described using a single battery cell. The corresponding embodiments preferably refer to all battery cells arranged in the battery, with the battery cells being arranged side by side in a so-called stack in the battery housing. The battery cells can be immersion-cooled, i.e., they can be surrounded by a dielectric immersion fluid at least in some areas for immersion temperature control in the battery housing.

[0022] In order to achieve an optionally desired preload of the battery cells, especially during commissioning or in new condition, elastic elements, such as disc springs, can be used at the ends of the battery cell rows to preload the stack.

[0023] The battery assembly can be used in a variety of applications, particularly in cars, trucks, buses, construction vehicles, machinery, or marine applications. The battery assembly can also be understood as a battery pack with multiple battery cells. The battery assembly is, in particular, a lithium-ion accumulator.

[0024] Short description of the drawings

[0025] Further measures improving the invention are described in more detail below together with the description of preferred embodiments of the invention with reference to the figures, wherein identical or similar components are provided with the same reference numerals.

[0026] Figure 1 is a perspective partial view of a battery cell according to the invention in a first embodiment,

[0027] Figure 2 is a simplified perspective view of a second battery cell according to the invention,

[0028] Figure 3 is a perspective partial view of a battery cell according to the invention in a third embodiment,

[0029] Figure 4a is a schematic representation of a first embodiment of a predetermined breaking point and Figure 4b is a schematic representation of a second embodiment of a predetermined breaking point.

[0030] Detailed description of the drawings

[0031] Figure 1 shows at least a partial view of a housing 1 for a battery cell for a motor vehicle (not shown here). Preferably, several battery cells with similar housings 1 form a battery.

[0032] The housing 1 is intended for a prismatic battery cell and has a shell 2 made of sheet metal. The sheet metal from which the housing 1 is formed by forming has a substantially constant thickness of between 0.2 and 1 mm. The shell 2 is cuboid-shaped and has two opposing, wide side surfaces 3, 4 and two perpendicularly arranged, likewise opposing, narrow side surfaces 5, 6. The housing 1 is hollow inside and can be subsequently equipped via the initially open end faces 7, 8 of the housing 1. After the sheet metal has been formed and the ends of the sheet metal have been welded to form the shell 2, the open end faces 7, 8 can be closed by covers (not shown here) which can be welded to the shell 2 in order to form the cell can 4 into a pressure vessel.

[0033] On the outer side of the jacket 2, a coating - not shown in detail here - is arranged at least in some areas, which is designed for electrical insulation and as protection against mechanical stress, for example as a result of vibrations.

[0034] As Figure 2 shows, the shell 2, formed from a previously flat sheet metal strip, has two opposing sheet metal edges 9, 10 after forming. The sheet metal edges 9, 10 are firmly connected to each other by a weld seam 11, wherein the weld seam 11 extends parallel to the longitudinal direction of the side surfaces 5, 6.

[0035] The weld seam 11 is arranged in the second narrow side surface 6 according to Figure 2. On the opposite, first narrow side surface 5, a predetermined breaking point 12 in the form of a material taper is arranged. In the embodiment according to Figure 2, the predetermined breaking point 12 is a longitudinal groove with reduced material thickness, which is spaced from the end faces 7, 8. In the embodiment according to Figure 1, the longitudinal groove extends over the entire length of the narrow side surface 5. The rear region 13 of the groove base, arranged on the inside of the housing 1, does not protrude into the formed cavity 14.

[0036] In the embodiment according to Figure 3, the housing 1 has further grooves 15, 16.

[0037] The further grooves 15, 16 can in turn represent predetermined breaking points, but can also relieve the predetermined breaking point 12 or stiffen the housing 1.

[0038] Finally, Figures 4a and 4b show different shapes of predetermined breaking points 12. The predetermined breaking point 12 shown in Figure 4a is designed as a longitudinal groove, and in the predetermined breaking point 12 shown in Figure 4b, V-shaped recesses adjoin the longitudinal groove, so that the areas adjacent to the longitudinal groove form a flap-like closure. This ensures that a large amount of gas escapes quickly in the event of a burst, thus rapidly reducing the internal pressure.

[0039] List of reference symbols

[0040] 1 housing

[0041] 2 Sheath 3 first, wide side surface

[0042] 4 second, wide side surface

[0043] 5 first, narrow side surface

[0044] 6 second, narrow side surface

[0045] 7 first front side 8 second front side

[0046] 9 first sheet edge

[0047] 10 second sheet edge

[0048] 11 Weld seam

[0049] 12 Predetermined breaking point 13 Rear area

[0050] 14 Cavity

[0051] 15 first, further groove

[0052] 16 second, further groove

Claims

Patent claims 1. A method for producing a housing (1) of a battery cell, characterized in that - a sheet with two sheet edges (9, 10) is provided as starting material, - a material taper is introduced into the sheet as a predetermined breaking point (12) and - the sheet is formed into a three-dimensional body in such a way that the two sheet edges (9, 10) lie against each other and - the two adjacent sheet edges (9, 10) are firmly connected to each other.

2. Method according to claim 1, characterized in that the predetermined breaking point (12) is introduced simultaneously with a forming step of the flat sheet metal into a three-dimensional body.

3. Method according to claim 1 or 2, characterized in that the predetermined breaking point (12) is formed into the sheet metal by forming.

4. Method according to claim 1 or 2, characterized in that the predetermined breaking point (12) is introduced by scoring or engraving.

5. Housing (1) for a prismatic battery cell with a predetermined breaking point (12) for thermal runaway of the battery cell, characterized in that the housing (1) is formed from a sheet metal formed into a square tube and the predetermined breaking point (12) is formed in one piece therewith.

6. Housing according to claim 5, characterized in that the two sheet metal edges (9, 10) of the sheet metal formed into the square tube are connected to one another by a weld (11), wherein the predetermined breaking point (12) and the weld (11) are arranged on different side surfaces (5, 6) of the square tube.

7. Housing according to claim 5, characterized in that the predetermined breaking point (12) is introduced into the sheet metal by forming or by scoring or engraving.

8. Housing according to claims 6 and 7, characterized in that the square tube has two end faces (7, 8) spaced apart by an end face distance, and in that the predetermined breaking point (12) is designed as a longitudinal groove which extends over 10% to 30% of the end face distance and is spaced from both end faces (7, 8).

9. Battery with an arrangement of several battery cells arranged one behind the other in a longitudinal direction, each having a housing (1) according to claims 5 to 8, characterized by a common chamber extending in the longitudinal direction, which covers the predetermined breaking points (12).

10. Use of a battery according to claim 9 as a vehicle battery.

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