DE102021210943B4 - Process for producing a battery cell - Google Patents

Abstract

Method for producing a battery cell, in particular a pouch cell, comprising a number of anode layers (4) and cathode layers (6) as well as intermediate layers (8),
- wherein the anode layers (4) and the cathode layers (6) each have an active material coating (12, 20) and a conductor tab (14, 22),
- wherein at least one through-opening (16) for receiving a guide pin (24) is introduced into the active material coating (12, 20) and/or into the conductor lug (14, 22) in each of the anode layers (4) and the cathode layers (6),
- wherein the anode layers (4) and the cathode layers (6) are stacked alternately on at least one guide pin (24) with an intermediate layer (8) in each case, wherein the at least one guide pin (24) is made of a compressible material,
- wherein the stacked anode layers (4), cathode layers (6) and intermediate layers (8) are joined together to form a cell stack (2),
- wherein the cell stack (2) is inserted together with the at least one guide pin (24) into a cell housing designed as a pouch cell, and
- wherein the guide pin (24) is compressed during an evacuation of the cell housing.

Description

The invention relates to a method for producing a battery cell, in particular a pouch cell, in which a number of anode layers and cathode layers as well as intermediate layers are joined to form a cell stack. The invention further relates to a battery cell with a cell stack.

Motor vehicles that are powered or can be powered electrically or by an electric motor, such as electric, hybrid, plug-in or fuel cell vehicles, usually include an electric motor that can be used to drive one or both vehicle axles. To supply electrical energy, the electric motor is usually connected to an internal (high-voltage) battery as an electrical energy storage device.

Here and in the following, an electrochemical battery is understood to mean a so-called secondary battery of the motor vehicle. In such a (secondary) vehicle battery, the chemical energy that has been used can be restored by means of an electrical charging process. Such vehicle batteries are designed, for example, as electrochemical accumulators, in particular as lithium-ion accumulators.

In order to generate or provide a sufficiently high operating voltage, such vehicle batteries typically have at least one battery module (battery cell module) in which several individual battery cells are connected in a modular manner. Alternatively, a so-called Cell2Pack design is possible, in which the battery cells are connected directly to the vehicle battery, in particular connected in parallel, and are not combined into modules in advance.

Battery cells, for example, have an electrode arrangement which is housed in a cell housing as a casing or sheath and is surrounded by a liquid electrolyte. The cell housing is designed, for example, as a casing with an aluminum composite foil or an aluminum laminate foil, with such flexible or foil-like casings also being referred to as pouch bags or pouch foil casings, and battery cells with such a cell housing also being referred to as pouch cells or soft pack cells.

The electrode arrangement is designed, for example, as an electrode or cell stack that has several anode layers and several cathode layers as electrode layers. The anode layers and the cathode layers are stacked one on top of the other in an alternating stacking direction, with a separator or separator layer being arranged between the anode layers and the cathode layers. The separator causes a physical separation or spacing as well as an electrical insulation of the electrode layers of opposite polarity. The separator or separator layer is permeable to conductive ions of the liquid electrolyte, but an electrical short circuit between the electrodes is avoided.

In order to ensure a long service life and cycle stability of the battery cell, it is necessary that the anode layers and cathode layers, or their active material coatings, are arranged as precisely as possible on top of each other. If this is not the case, increased aging reactions occur. Furthermore, if the electrodes are not stacked precisely, the available active material of the battery cell is not fully utilized, which results in a reduced energy density.

When building cells, an additional guide frame is therefore used, into which the electrode layers and separator layers are placed. However, the guide frame has a detrimental effect on the gravimetric energy density. It must also be ensured that the separator layers always protrude beyond the anode and cathode layers at the edges, despite the guide frame, in order to avoid the risk of an electrical short circuit.

From the DE 10 2016 214 239 A1 , US 7,879,491 B2 , US 2004/0161669 A1 , JP 2015-69812 A , US 9,368,830 B2 , the KR 10 2018 0 019 442 A , and the KR 10 2016 0 004 737 A It is known to provide the electrodes of a battery cell with a through-opening and to stack them on a rigid guide pin during the production of the cell stack.

In the US 2021/0028 433 A1 The electrodes of a battery cell are provided with a through-opening and are stacked on a compressible guide pin during the production of the cell stack.

The invention is based on the object of specifying a particularly suitable method for producing a battery cell. In particular, the aim is to achieve the simplest and most reliable alignment and positioning of the electrode and separator layers during stacking, with as little or as little reduction in the gravimetric energy density as possible. The invention is also based on the object to specify a particularly suitable battery cell.

With regard to the method, the object is achieved according to the invention with the features of claim 1 and with regard to the battery cell with the features of claim 7. Advantageous embodiments and further developments are the subject of the subclaims. The advantages and embodiments mentioned with regard to the method can also be transferred to the battery cell and vice versa.

The method according to the invention is intended for producing a battery cell, in particular for a pouch cell or soft bag cell, and is suitable and designed for this purpose. The method can be used both for producing liquid cells, i.e. battery cells with a liquid electrolyte, and for producing solid-state cells, i.e. battery cells with a solid-state electrolyte. The battery cell is designed as a lithium-ion cell, for example. The battery cell has a number of anode layers and cathode layers as well as intermediate layers. In the case of a liquid cell, the intermediate layers are designed in particular as separator layers, whereby in the case of a solid-state cell, the intermediate layers are designed in particular as solid-state electrolyte layers.

The following statements refer in particular to liquid cells, but can also be applied to solid-state cells.

The electrode layers, i.e. the anode layers and the cathode layers, have an electrically conductive (metal) foil as a current conductor and an active material coating applied to it. The foil can be coated as a substrate on one or both sides with the active material, for example. The electrode material is designed as an anode material or cathode material, with an anode layer in particular using a copper foil with an anode active material applied to it, and a cathode layer in particular using an aluminum foil with a cathode active material. The electrode layers have an uncoated or uncoated edge region of the foil, i.e. an edge-side foil region which is not provided with the active material coating. This edge region forms an associated conductor flag (current collector) for contacting the electrode layers. Due to the foil-like design, the electrode layers and separator layers are also referred to below as electrode sheets and separator sheets.

According to the method, at least one through-opening (guide hole) is made in the active material coating and/or in the conductor tab in each of the electrode layers. The conjunction "and/or" is to be understood here and in the following in such a way that the features linked by means of this conjunction can be designed both together and as alternatives to one another.

The through-openings are preferably closed on the circumference or on all sides. In other words, the through-openings are designed as holes or recesses. For example, the through-openings are made in the electrode layers by punching or laser cutting. The through-openings are intended, suitable and designed to accommodate a guide pin. For example, a number of through-openings, i.e. at least two through-openings, preferably exactly two through-openings, are made in each of the electrode layers.

According to the invention, at least one guide pin is provided on which the anode layers and the cathode layers are alternately stacked with a separator layer in between. A guide pin is to be understood in particular as a bolt-shaped, pin-shaped, pin-shaped or (circular) cylindrical body which extends along a stacking direction and onto which the electrode layers are placed, plugged or threaded by means of the through-openings. The guide pin thus passes through the through-openings of the stacked electrode layers during the stacking process. In particular, the electrode layers are held in a form-fitting manner on the guide pin by the through-openings, so that a reliable and structurally simple alignment and positioning of the electrode layers is ensured during stacking.

The stacked anode layers, cathode layers and separator layers are then joined together to form a cell stack. The (cell) stack height of the cell stack essentially corresponds to the height of at least one guide pin. For example, after the layers have been placed on the guide pin, the cell stack is fixed or joined with an adhesive tape or by means of lamination, and thus secured against relative slipping of the layers. This creates a particularly suitable method for producing a battery cell. In particular, this ensures a particularly high stacking accuracy when stacking the cell stack without the use of a guide frame.

In a conceivable further development not according to the invention, the cell stack is released or lifted off the at least one guide pin and inserted into a cell housing without guide pins. The at least one guide pin thus serves exclusively as a stacking aid for stacking the cell stack.

According to the invention, the cell stack is inserted into a cell housing together with the at least one guide pin. The cell stack is therefore installed in the cell housing including the guide pin. The guide pin is made of a compressible material, with the cell housing being designed, for example, as a pouch film, in particular as a plastic-aluminum composite film. According to the invention, the guide pin is designed to be compressible in such a way that the guide pin is compressed when the pouch film or the cell housing is evacuated, i.e. pressed together or compressed along the stack direction or pin longitudinal direction. This additionally fixes the position of the electrode layers.

In an advantageous embodiment, the at least one through-opening is introduced into the active material coating of the electrode layers, with a corresponding through-opening being introduced into each of the separator layers. In addition to the electrode layers, the separator layers arranged between them are also stacked on the guide pin. This ensures a particularly high positional accuracy of the separator layers in the cell stack.

In an expedient further development, the through-openings of the separator layers have a smaller diameter than the through-openings of the electrode layers. In other words, the separator through-openings are designed to be slightly smaller than the electrode through-openings, for example, in order to avoid an electrical short circuit between the stacked electrode layers.

In a suitable design, the active material coating is essentially rectangular, with two through-openings being made in diametrically opposite corner areas of the active material coating. The arrangement of the through-openings or the corresponding guide pins enables particularly stable and twist-proof stacking.

In a preferred embodiment, the at least one through-opening is made in the conductor tabs of the electrode layers. This ensures a particularly high energy density of the battery cell, since no active material is cut out. Preferably, the anode layers are stacked on a first guide pin and the cathode layers on a second guide pin. This means that the perforated conductor tabs of the electrode layers are placed or threaded onto different guide pins, so that the risk of a short circuit is advantageously and easily avoided.

In a conceivable embodiment, two through-openings arranged at a distance from one another are introduced into the conductor tabs of the anode layers and the cathode layers, so that reliable protection against twisting is realized.

In a design with only one through-opening per conductor flag, an additional guide bar is preferably provided for the stacking process to align the conductor flags or electrode layers. Alternatively, it is conceivable, for example, that the through-opening and the guide pin have a polygonal geometry or cross-sectional shape. For example, the guide pin and the through-opening have a quadrangular, in particular a square or rectangular, cross-sectional shape. This means that the through-opening, and thus the conductor flag, can be placed on the guide pin reliably and without twisting.

For example, the conductor tabs of the anode layers and cathode layers are arranged on a common side of the cell stack. This results in a particularly compact arrangement.

The battery cell according to the invention is designed in particular as a pouch cell for a vehicle battery. The battery cell is produced using a method described above, wherein the battery cell has a cell stack with a number of anode layers and cathode layers as well as separator layers, which are stacked alternately. The electrode layers each have at least one through-opening for receiving a guide pin in the active material coating and/or in the conductor tab. This creates a particularly suitable battery cell.

• 1 in Draufsicht eine Anodenschicht in einer ersten Ausführungsform,
• 2 in Draufsicht eine Kathodenschicht in einer ersten Ausführungsform,
• 3 in Draufsicht eine Separatorschicht in einer ersten Ausführungsform,
• 4 in Draufsicht einen Zellstapel gemäß der ersten Ausführungsform,
• 5 in Perspektive den Zellstapel gemäß der ersten Ausführungsform mit zwei Führungsstiften,
• 6 in Draufsicht eine Anodenschicht in einer zweiten Ausführungsform,
• 7 in Draufsicht eine Kathodenschicht in einer zweiten Ausführungsform,
• 8 in Draufsicht eine Separatorschicht in einer zweiten Ausführungsform,
• 9 in Draufsicht einen Zellstapel gemäß der zweiten Ausführungsform,
• 10 in Perspektive den Zellstapel gemäß der zweiten Ausführungsform mit zwei Führungsstiften und einer Führungsleiste,
• 11 in Draufsicht eine Anodenschicht in einer dritten Ausführungsform,
• 12 in Draufsicht eine Kathodenschicht in einer dritten Ausführungsform,
• 13 in Draufsicht eine Separatorschicht in einer dritten Ausführungsform,
• 14 in Draufsicht einen Zellstapel gemäß der dritten Ausführungsform, und
• 15 in Perspektive den Zellstapel gemäß der dritten Ausführungsform mit vier Führungsstiften.

In the following, embodiments of the invention are explained in more detail with reference to a drawing. In schematic and simplified representations:

• 1 in plan view an anode layer in a first embodiment,
• 2 in plan view a cathode layer in a first embodiment,
• 3 in plan view a separator layer in a first embodiment,
• 4 in plan view a cell stack according to the first embodiment,
• 5 in perspective the cell stack according to the first embodiment with two guide pins,
• 6 in plan view an anode layer in a second embodiment,
• 7 in plan view a cathode layer in a second embodiment,
• 8 in plan view a separator layer in a second embodiment,
• 9 in plan view a cell stack according to the second embodiment,
• 10 in perspective the cell stack according to the second embodiment with two guide pins and a guide bar,
• 11 in plan view an anode layer in a third embodiment,
• 12 in plan view a cathode layer in a third embodiment,
• 13 in plan view a separator layer in a third embodiment,
• 14 in plan view a cell stack according to the third embodiment, and
• 15 in perspective the cell stack according to the third embodiment with four guide pins.

Corresponding parts and sizes are always provided with the same reference symbols in all figures.

In the 1 to 5 a first embodiment of a cell stack 2 of a battery cell (not shown in detail) is shown. The cell stack 2 has at least one anode layer 4 and one cathode layer 6 as well as a separator layer as an intermediate layer 8, which are arranged stacked one above the other along a stacking direction.

The in 1 The anode layer (anode sheet) 4 shown has a substantially rectangular copper foil as a substrate 10, to which an active material coating 12 made of an anode active material is applied on both sides, for example. On a short side, an uncoated area of the substrate 10 is designed as a conductor flag (current collector) 14. The cantilever-like conductor flag 14 is arranged offset from a long side. In other words, a section of the substrate 10 is removed on the opposite long side.

In the area of the approximately rectangular active material coating 12, two through-openings 16 are introduced or cut out as guide holes in the anode layer 4, which penetrate the active material coating 12 and the substrate 10. The through-openings 16 are introduced in diametrically opposite corner areas of the active material coating 12.

The 2 shows a corresponding cathode layer (cathode sheet) 6 with an aluminum foil as substrate 18 and a double-sided active material coating 20 made of a cathode active material. On one short side, an uncoated area of the substrate 18 is designed as a conductor flag (current collector) 22. Two through-openings 16 are made in the active material coating 20 and in the substrate 18, which in the stacked state ( 4 , 5 ) are arranged in alignment with the through-openings of the anode layer 4.

When stacked ( 4 , 5 ), the anode layer 4 and the cathode layer 6 are arranged such that the conductor tabs 14, 22 are arranged on a common (stack) side. The conductor tab 22 is designed to correspond to the conductor tab 14 and is arranged offset from the opposite long side, so that the conductor tabs 14 of the anode layers 4 are arranged on one side half and the conductor tabs 22 of the cathode layers 6 are arranged on the other side half of the short side.

In the 3 a separator layer (separator sheet) 8 is shown. The separator layer 8 is introduced in the stacked state as a separating or insulating layer between two adjacent anode layers 4 and cathode layers 6. The separator layer 8 is permeable to conductive ions of a liquid electrolyte of the battery cell. As can be seen in particular in the 4 As can be seen, the separator layer 8 protrudes beyond the active material coatings 12, 20 at the edge, so that reliable and operationally safe insulation is achieved in the stacked state. Two through-openings 16' are made in the separator layer 8, which are arranged in alignment with the through-openings 16 of the anode layer 4 and the cathode layer 6. The through-openings 16' have a smaller diameter than the through-openings 16.

During the manufacture of the battery cell, a number of anode layers 4, cathode layers 6 and separator layers 8 are stacked to form the cell stack 2. To increase the stacking accuracy, in particular for the relative alignment and positioning of the layers 4, 6 and 8, two guides oriented perpendicular to the layers 4, 6, 8 are Guide pins 24 are provided on which the anode layers 4 and the cathode layers 6 are stacked alternately with a separator layer 8 in between. The layers 4, 6, 8 are placed, plugged or threaded onto the guide pins 24 in a form-fitting manner using their respective through-openings 16, 16'. This secures the cell stack 2 against relative slipping of the layers 4, 6, 8 during stacking.

The stacked anode layers 4, cathode layers 6, and separator layers 8 are then joined to form the cell stack 2, for example using an adhesive tape. The (cell) stack height of the finished cell stack 2 essentially corresponds to the height of the guide pins 24.

In this embodiment according to the invention, the guide pins 24 are made of a compressible material and are installed together with the cell stack 2 in a cell housing, in particular in a pouch film. The cell stack 2 is therefore installed in the cell housing including the guide pins 24. The guide pins 24 are designed to be compressible in such a way that the guide pins 24 are compressed when the pouch film or the cell housing is evacuated, i.e. pressed together or compressed along the stack direction or pin longitudinal direction, and thus additionally fix the position of the layers 4, 6, 8.

In an alternative embodiment not according to the invention, the cell stack 2 is released or lifted off the guide pins 24 and inserted into a cell housing without guide pins 24. The guide pins 24 serve exclusively as a stacking aid when stacking the cell stack 2.

The following is based on the 6 to 10 a second embodiment of the invention is explained in more detail. In this embodiment, a through-opening 16 is made in each of the anode layers 4 and the cathode layers 6, whereby the separator layers 8 are designed without through-openings. The through-opening 16 is made approximately centrally in the respective conductor tab 14, 22. The conductor tabs 14 are placed on one of the guide pins 24 and the conductor tabs 22 on another guide pin 24. In the stacked state, a gap region 26 is formed between the conductor tabs 14, 22. Since only one end-side through-opening 16 is made in each of the layers 4 and 6, an additional guide strip 28 is provided as protection against twisting or slipping during stacking, which is arranged between the conductor tabs 14, 22 in the gap region 26.

Below is a third embodiment based on the 11 to 15 explained in more detail. In this embodiment, the conductor flags 14, 22 are wider and extend essentially over the entire width of the respective substrate 10, 18. The conductor flags 14, 22 are arranged on opposite stack sides, with two through-openings 16 being made in each of the conductor flags 14, 22. Four guide pins 24 are provided for stacking, two each for the conductor flags 14 and two each for the conductor flags 22 ( 15 ).

list of reference symbols

2

cell stack

4

anode layer

6

cathode layer

8

intermediate layer

10

substrate

12

active material coating

14

arrester flags

16, 16`

through-hole

18

substrate

20

active material coating

22

arrester flags

24

guide pin

26

gap area

28

guide rail

Claims (7)

Method for producing a battery cell, in particular a pouch cell, having a number of anode layers (4) and cathode layers (6) as well as intermediate layers (8), - wherein the anode layers (4) and the cathode layers (6) each have an active material coating (12, 20) and a conductor tab (14, 22), - wherein at least one through-opening (16) for receiving a guide pin (24) is introduced into the active material coating (12, 20) and/or into the conductor tab (14, 22) in the anode layers (4) and in the cathode layers (6), - wherein the anode layers (4) and the cathode layers (6) are stacked alternately on at least one guide pin (24) with an intermediate layer (8) in between, wherein the at least one guide pin (24) is made of a compressible material, - wherein the stacked anode layers (4), Cathode layers (6) and intermediate layers (8) are joined together to form a cell stack (2), - wherein the cell stack (2) is inserted together with the at least one guide pin (24) into a cell housing designed as a pouch cell, and - wherein the guide pin (24) is compressed during an evacuation of the cell housing. procedure according to claim 1 , characterized in that the at least one through-opening (16) is introduced into the active material coating (12, 20) of the anode layers (4) and cathode layers (6), wherein a corresponding through-opening (16') is introduced into each intermediate layer (8). procedure according to claim 2 , characterized in that the through-openings (16') of the intermediate layers (8) have a smaller diameter than the through-openings (16) of the anode layers (4) and cathode layers (6). procedure according to claim 2 or 3 , characterized in that the active material coating (12, 20) is substantially rectangular, wherein two through-openings (16) are introduced in diametrically opposite corner regions. Method according to one of the Claims 1 until 4 , characterized in that the at least one through-opening (16) is introduced into the conductor tabs (14, 22) of the anode layers (4) and cathode layers (6), wherein the anode layers (4) are stacked on a first guide pin (24) and the cathode layers (6) are stacked on a second guide pin (24). procedure according to claim 5 , characterized in that two through openings (16) arranged at a distance from one another are introduced into the conductor tabs (14, 22) of the anode layers (4) and the cathode layers (6). Battery cell manufactured by a process according to any of the Claims 1 until 6 , comprising a cell stack (2) with a number of anode layers (4) and cathode layers (6) as well as intermediate layers (8), at least one guide pin (24) made of a compressible material, and a cell housing designed as a pouch cell, - wherein at least one through-opening (16) for receiving a guide pin (24) is introduced into an active material coating (12, 20) and/or into a conductor flag (14, 22) in each of the anode layers (4) and the cathode layers (6), - wherein the anode layers (4) and the cathode layers (6) are stacked alternately on the at least one guide pin (24) with an intermediate layer (8) in between, - wherein the cell stack (2) is inserted into the cell housing together with the at least one guide pin (24), - wherein the cell housing is evacuated, and - wherein the guide pin (24) is compressed.

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