Battery cell for an electrical energy storage device of a motor vehicle that is at least partially electrically powered, electrical energy storage device and motor vehicle

Abstract

The invention relates to a battery cell (4) for an electrical energy storage device (2) of an at least partially electrically powered motor vehicle (1), comprising at least one battery cell housing (5), wherein a multilayer electrode stack (7) is arranged in an interior space (6) of the battery cell housing (5), characterized in that at least one layer (8-16) of the electrode stack (7), which faces an inner wall (21, 22) of the battery cell housing (5), has a reduced height. The invention further relates to an electrical energy storage device (2) and a motor vehicle (1).

Description

[0001] The following invention relates to a battery cell for an electrical energy storage device, in particular for an at least partially electrically powered motor vehicle, comprising at least one battery cell housing, wherein a multilayer electrode stack is arranged in an interior of the battery cell housing. Furthermore, the invention relates to an electrical energy storage device and a motor vehicle with an electrical energy storage device.

[0002] High-voltage batteries for electric vehicles currently predominantly use so-called lithium-ion cells in various packaging forms, such as round cells, prismatic cells (CANs), or pouch cells. The invention relates in particular to prismatic cells with foils in wound or stacked technology and to corresponding round cells, but is not limited to these types of battery cells.

[0003] Electrochemical processes cause the volume of the foil coil / foil stack / foil roll to increase. This increase in volume is also known as swelling. A defined pressure on the battery cell is necessary to enable controlled cell swelling. Uncontrolled swelling, as well as completely suppressed swelling, leads to a reduced service life.

[0004] A homogeneous pressure distribution with a defined pressure is therefore one of several basic requirements for an optimal service life and performance of a battery cell.

[0005] In current prismatic cells, the foil coil / stack / roll is inserted into a deep-drawn or otherwise manufactured housing made of aluminum, for example. The coil / stack rests against two sides of the housing over a large area. These contact surfaces are usually the large contact surfaces of the cells that are adjacent to the adjacent cell. In round cells, the outer layer of the roll rests against the cylindrical outer wall, usually made of sheet metal, of the round cell.

[0006] A disadvantage of current designs is that the rigidity of the housing means that the homogeneous swelling and coil / stack are counteracted by an inhomogeneous counterforce. In prismatic cells, as well as round cells, the edge areas of the housing's contact surface are connected to the side walls, and in round cells to the lid and base, and thus exert relatively high counterforces. The central area of ​​the contact surface is more elastic and exerts significantly lower counterforces. This results in an inhomogeneous force distribution across the surface, which leads to highly inhomogeneous swelling behavior of the coil / stack / roll. Inhomogeneous swelling behavior inevitably leads to different aging behavior within the cell, which means that the possible minimum aging behavior and the maximum possible performance of the battery cell are not fully utilized.

[0007] It is particularly disadvantageous if the permissible maximum pressures are exceeded in the affected area of ​​the stack, causing permanent damage to the active material and rendering this area unusable as an active material. Another disadvantage is that the high swelling forces in the edge areas can lead to a tearing of the CAN, i.e., the housing.

[0008] DE 10 2020 213 364 A1 discloses a battery cell, in particular a lithium-ion battery cell, with an electrode unit and a battery cell housing, wherein the battery cell housing is cylindrical.

[0009] WO 2010 / 105790 discloses an electrode stack comprising at least a cathode, an anode, and a separator with electrolyte. The cathode, anode, and separator are each plate-shaped. The surface area of ​​the separator is at least as large as the surface area of ​​the cathode and / or the anode. The plate-shaped elements of the electrode stack are at least partially connected to one another by fixing means.

[0010] CH 694 715 A5 describes a lithium flat cell, consisting of a first housing part for receiving a first thin-film electrode, a second housing part for receiving a second thin-film electrode and a separator arranged between the thin-film electrodes, wherein the housing parts are formed from electrically conductive foils, the separator has insulating sealing and adhesive material in the region of the contact points of the two housing parts and the two housing parts are connected to the separator by means of the sealing and adhesive material and through the separator to form a closed housing.

[0011] The object of the present invention is to provide a battery cell, an electrical energy storage device and a motor vehicle by means of which swelling within the battery cell can be improved and homogenized.

[0012] This object is achieved by a battery cell, an electrical energy storage device, and a motor vehicle according to the independent patent claims. Advantageous embodiments are specified in the subclaims.

[0013] One aspect of the invention relates to a battery cell for an electrical energy storage device of an at least partially electrically operated motor vehicle, comprising at least one battery cell housing, wherein a multi-layer electrode stack is arranged in an interior space of the battery cell housing.

[0014] It is provided that at least one layer of the electrode stack, which faces an inner wall of the battery cell housing, has a reduced height extension.

[0015] In particular, the objective of the invention described here is to reduce the thickness of the so-called active material or electrode stack in the edge regions of the battery cell housing. Due to the reduced material in the edge regions, swelling does not lead to exceeding the permissible maximum pressures / surface pressures over the lifetime. The coil / stack / roll, and especially the electrode stack, thus ages more homogeneously.

[0016] In particular, this has the advantage of ensuring a homogeneous pressure distribution across the active surface of the coil / stack / roll. The permissible maximum pressure is not exceeded. Furthermore, due to the homogeneous pressure distribution, an extended service life can be expected. The more homogeneous pressure distribution and the lower material stress in the battery cell housing and at the weld seams that connect the battery cell housing and the corresponding cover also increase the service life. Furthermore, a more homogeneous current density distribution, a lower tendency towards lithium plating, lower temperature development, and reduced outgassing behavior can be achieved. Any gas that is produced collects in the center of the stack, and the gas can be "expelled" towards the edge area via increased surface pressure within the center.

[0017] The technical implementation is ideally carried out using FEM (finite element method) methods and swell range calculations from virtual testing. This ensures that the maximum permissible pressures on the stack are not exceeded over its service life.

[0018] In particular, the battery cell can be designed as a lithium-ion battery cell. However, the invention is also applicable to other types of battery cells.

[0019] The intended use of the battery cell is preferably in a motor vehicle, but is not limited to this area. Thus, the invention can be applied to any battery cell.

[0020] According to an advantageous embodiment, the electrode stack is designed as a prismatic winding. In particular, this allows for the provision of a prismatic battery cell.

[0021] It is also advantageous if the electrode stack is designed as a jelly roll. In other words, the battery cell housing can be designed, in particular, as a round cell. Thus, a round cell can also be provided.

[0022] A further advantageous embodiment provides for the electrode stack to be designed as an electrode stack, in other words, as stacked layers. This allows, for example, prismatic cells with a stack as well as pouch cells with a stack, especially with a corresponding additional housing, to be improved.

[0023] A further advantageous embodiment provides that at least one middle layer of the electrode stack extends the total height of the interior. In particular, this means that the middle layer of the electrode stack has a maximum height extension within the interior. Height refers, in particular, to the height between a lower cover element and an upper cover element of the battery cell.

[0024] In particular, several middle layers can have the maximum height of the electrode stack. Only the outer layers are provided with a reduced height. In particular, the reduction in the heights of the layers can, for example, be implemented in stages.

[0025] It is further advantageous if the electrode stack is angled, in particular trapezoidal, at least at one end region of the electrode stack. This makes it easy to provide an electrode stack that can then, for example, be wound or rolled accordingly and, at the same time, be provided with a reduced height at the outer layers.

[0026] It is also advantageous if a separator film is additionally formed between the layers with a reduced height, particularly between the outer layers of the electrode stack. In particular, the separator film can thus also be provided with a reduced height, which further reduces the swelling pressure at the edge regions.

[0027] According to a further advantageous embodiment, a separator film is formed between the layers with a non-reduced height. Thus, the separator film can be provided between the layers with little effort.

[0028] A further aspect of the invention relates to an electrical energy storage device with at least one battery cell according to the preceding aspect. The electrical battery storage device can be designed, for example, as a traction battery of a motor vehicle.

[0029] Furthermore, the invention also relates to a motor vehicle with at least one electrical energy storage device according to the preceding aspect. The motor vehicle is designed, in particular, as an at least partially electrically powered motor vehicle or as a fully electrically powered motor vehicle.

[0030] Advantageous embodiments of the battery cell are to be regarded as advantageous embodiments of the electrical energy storage device and of the motor vehicle.

[0031] An electrical energy store within the meaning of the invention comprises at least one and in particular a plurality of electrically conductively interconnected battery cells, wherein such a battery cell preferably provides a voltage in the range of 3.5 to 4.0 volts. Such a battery cell can be designed, for example, as a prismatic cell, a pouch cell or a round cell. The battery is preferably configured as a so-called high-voltage battery, which is designed to provide an electrical voltage in the range of more than 60 volts, in particular in the range of several hundred volts. Such a high-voltage battery can be arranged in a motor vehicle, where it can supply an electrical consumer, in particular a drive motor, with electrical energy.

[0032] Further features of the invention emerge from the claims, the figures and the description of the figures. The features and combinations of features mentioned above in the description as well as the features and combinations of features mentioned below in the description of the figures and / or shown in the figures can be encompassed by the invention not only in the respectively specified combination, but also in other combinations. In particular, the invention can also encompass embodiments and combinations of features that do not have all the features of an originally formulated claim. Furthermore, the invention can encompass embodiments and combinations of features that go beyond the combinations of features set out in the backreferences to the claims or deviate from them.

[0033] Showing: Fig. 1 a schematic side view of an embodiment of a motor vehicle with an embodiment of an electrical energy storage device with an embodiment of a battery cell; Fig. 2 a schematic sectional view of an embodiment of a battery cell; Fig. 3 a schematic side view according to a pressure behavior within a battery cell.

[0034] The invention is explained in more detail below using specific embodiments and associated schematic drawings. In the figures, identical or functionally equivalent elements may be provided with the same reference numerals. The description of identical or functionally equivalent elements may not necessarily be repeated for different figures.

[0035] Fig. 1 shows a schematic side view of an embodiment of a motor vehicle 1. The motor vehicle 1 is designed in particular as an at least partially electrically operated motor vehicle 1 or as a fully electric motor vehicle 1. The motor vehicle 1 has at least one electrical energy storage device 2. The electrical energy storage device 2 can, for example, provide electrical energy for a traction motor 3 of the motor vehicle 1. The electrical energy storage device 2 has at least one battery cell 4, in particular a plurality of battery cells 4. The battery cells 4 can be designed as round cells, prismatic cells or even as pouch cells.

[0036] Fig. 2 shows a schematic perspective view of an embodiment of a battery cell 4. In the following exemplary embodiment, the battery cell 4 is illustrated in particular as a prismatic battery cell 4. The battery cell 4 has in particular a housing 5. The housing 5 in turn forms an interior space 6, wherein an electrode stack 7 is formed in the interior space 6, wherein the electrode stack 7 has a plurality of layers 8 to 16. In the following exemplary embodiment, the electrode stack 7 can thus be designed in particular as an electrode stack or as an electrode winding. The different layers 8 to 16 are designed in particular, for example, as cathodes, anodes or separators.

[0037] As in the Fig. 2, the battery cell 4 has a predetermined height H. Furthermore, the battery cell 4 is divided into three regions, in particular a first region 17, which is located in the region of a cover 18 of the battery cell 4, a second region 19, which in particular represents a central region of the battery cell 4, and a third region 20, which is formed at a lower region of the battery cell 4.

[0038] Increased pressure may occur during swelling, particularly in the first area 17 and the third area 20.

[0039] In particular, in order to achieve a homogeneous swelling pressure within the battery cell 4, it is proposed according to the invention that at least one layer 8, 16 of the electrode stack 7, which faces an inner wall 21, 22 of the housing 5, has a reduced height extension, in particular in the direction of H.

[0040] The Fig. 2 shows in particular that the reduced height extension extends, for example, in the first area 17 and in the third area 20. Furthermore, the Fig. 2, several of the layers 8 to 16 have a reduced height extension. In the following exemplary embodiment, in particular, layers 8, 9, 10, and 11 can have a reduced height extension. Furthermore, layers 13, 14, 15, and 16 also have a reduced height extension. Only the middle layer 12 has a maximum height extension. This is, of course, to be understood purely as an example. It is also possible for several middle layers to have a maximum height extension. In particular, it is further shown that the height extension of the individual layers is gradually increased from the outer layers 8, 16 to the maximum height H, up to the middle layer 12.

[0041] In particular, the Fig. 2, that in the first region 17, an area with recessed anodes / cathodes is provided to prevent excessive swelling pressure. This is also observed in the third region 20.

[0042] In particular, the Fig. 2, for example, in an electrode stack 7 as an electrode stack, the corresponding edge layers of the electrode stack are made gradually smaller in order to reduce the stack thickness at the edge regions, particularly in the first region 17 and the third region 20. Corresponding separator films can, but do not have to, be made smaller.

[0043] For prismatic cells with a coil and round cells with a roll, for example, the last turns of the coil can be reduced in width on both sides, forming a triangular or trapezoidal shape. This reduces the thickness of the active material at the end faces of the coil or roll.

[0044] The stack can be reduced in the inner layers. Furthermore, the stack can be reduced gradually or in a single step. The anode or cathode foil can be trimmed in a rectangular shape or in any desired shape. Furthermore, trimming can occur all around the stack or only on specific sides.

[0045] Fig. 3 again shows a pressure / height diagram according to a pressure distribution within the battery cell 4, as shown in the Fig.2. Corresponding arrows 23 represent pressures over the height H purely by way of example. Furthermore, a line for an average pressure 24 is shown. Due to the reduction of the height H at the first region 17 and third region 20, the swelling pressure remains below a predetermined threshold value 25. Corresponding triangles 26 schematically illustrate how the swelling pressure would be recorded within the battery cell 4 without reducing the height H. LIST OF REFERENCE SYMBOLS: 1 motor vehicle 2 electrical energy storage 3 Traction motor 4 battery cells 5 housings 6 Interior 7 electrode stacks 8 layer 9 layer 10 layers 11 shift 12 layer 13 shift 14 shift 15 shift 16 shift 17 first area 18 lids 19 second area 20 third area 21 Interior wall 22 Interior wall 23 Arrow 24 medium pressure 25 Threshold 26 Triangle H Height P pressure QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2020 213 364 A1

[0008] WO 2010 / 105790

[0009] CH 694 715 A5

[0010]

Claims

[1] Battery cell (4) for an electrical energy storage device (2) of an at least partially electrically operated motor vehicle (1), with at least one battery cell housing (5), wherein a multi-layer electrode stack (7) is arranged in an interior space (6) of the battery cell housing (5), characterized by , that at least one layer (8 - 16) of the electrode stack (7), which faces an inner wall (21, 22) of the battery cell housing (5), has a reduced height extension. [2] Battery cell (4) according to claim 1, characterized by , that the electrode stack (7) is designed as a prismatic winding. [3] Battery cell (4) according to claim 1, characterized by , that the electrode stack (7) is designed as a jelly roll. [4] Battery cell (4) according to claim 1, characterized by , that the electrode stack (7) is designed as an electrode stack. [5] Battery cell (4) according to one of the preceding claims, characterized by , that at least one middle layer (8 - 16) of the electrode stack (7) extends over a total height of the interior space (6). [6] Battery cell (4) according to one of the preceding claims, characterized by , that the electrode stack (7) is angled, in particular trapezoidal, at least at one end region of the electrode stack (7). [7] Battery cell (4) according to one of the preceding claims, characterized by , that a separator film between the layers (8 - 16) is additionally formed with a reduced height (H), in particular between the outer layers (8 - 16) of the electrode stack (7). [8] Battery cell (4) according to one of claims 1 to 6, characterized by , that a separator film is formed between the layers (8 - 16) with a non-reduced height (H). [9] Electrical energy storage device (2) with at least one battery cell (4) according to one of claims 1 to 8. [10] Motor vehicle (1) with at least one electrical energy storage device (2) according to claim 9.

Images