Improved method for cell stack fabrication by uniform thermal activation of adhesives

Abstract

The present invention relates to a method for manufacturing a cell stack, in particular for an electrochemical storage device, in which at least an anode electrode, a separator layer, and a cathode electrode are repeatedly stacked, folded, or wound on top of each other, at least one layer is coated on one or both sides with a heat-activatable adhesive or at least one layer is provided with an adhesive, the conductive layers, in particular the anode electrode and / or the cathode electrode, are electromagnetically and / or electrically heated, the adhesive is heat-activated by heating the conductive layers, and the anode electrode, separator layer, and cathode electrode are bonded to each other to form a cell stack. The present invention also relates to a device for manufacturing a cell stack, and to an electrochemical storage device with at least one cell stack.

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a cell stack, in particular for an electrochemical storage device, in which at least an anode electrode, a separator layer, and a cathode electrode are repeatedly stacked, folded, or wound on top of each other. Furthermore, the present invention relates to a device for manufacturing a cell stack, and to an electrochemical storage device with at least one cell stack.

[0002] In the manufacture of electrochemical storage devices such as lithium-ion batteries, several alternating layers of anodes, cathodes, and separators are typically arranged in the form of a cell stack. These layers are coated with a heat-activatable adhesive and then bonded together using heat and force. For this purpose, the layers are placed between two heated plates that act on the layers.

[0003] However, heating the layers of the cell stack via a heating plate results in a non-uniform temperature distribution along the height or thickness of the cell stack. Uniform bonding between the layers of the cell stack and bonding of all layers of the cell stack using a heat-activatable adhesive cannot be guaranteed due to the non-uniform temperature distribution. Furthermore, complete heating of all layers of the cell stack is delayed by the insulating and heat-insulating properties of the separator layers, thereby limiting the output of the system in manufacturing the cell stack.

[0004] It is known to accelerate the bonding process by pressing the layers of the cell stack together with greater force or applying higher temperatures to the layers during heating, however, such measures can have a detrimental effect on the material properties of the cell components or individual layers of the cell stack.

[0005] The present invention therefore aims to create a method for manufacturing a cell stack, in particular for an electrochemical storage device, which allows for a fast and uniform joining of the layers of the cell stack. This object is solved by the features specified in claim 1. Further advantageous embodiments of the invention are part of the dependent claims.

[0006] According to one aspect of the present invention, a method for manufacturing a cell stack is provided. In particular, the cell stack is provided for an electrochemical storage device such as a lithium-ion cell. Such a cell stack includes a plurality of anode electrodes, separator layers, and cathode electrodes, which are repeatedly stacked, folded, or wound on top of each other. Further layers, for example, including graphite or other materials, can be provided.

[0007] The anode electrode can be made of, for example, a copper foil or a copper carrier foil covered on one or both sides with an anode substrate, and the cathode electrode can be made of, for example, an aluminum foil or an aluminum carrier foil covered on one or both sides with a cathode substrate.

[0008] For simplicity, additional possible layers common in the field of lithium-ion batteries will not be further described. Adhesive layers may be used or certain layers may be pre-applied with adhesive to form a unitary or one-piece cell stack. For example, the separator layer may be coated on one or both sides with a heat-activatable adhesive or may be pre-applied with adhesive.

[0009] After the anode electrode, separator layer, and cathode electrode are positioned, the conductive layers, particularly the copper and aluminum foils of the anode electrode and / or cathode electrode and / or additional layers or grids, are heated electromagnetically and / or electrically. In contrast to conventional techniques in which a heat source is pressed against the cell stack from the outside and heat slowly spreads from the outside to the inside, in this case, heat is generated directly in all conductive layers of the cell stack. This eliminates time-consuming and uneven heat conduction. Heating the anode electrode and / or cathode electrode directly or immediately heat-activates the adhesive of each separator layer. Heat-activating the adhesive bonds the anode electrode, separator layer, and cathode electrode to each other, forming a one-piece cell stack. This completes the exemplary cell stack.

[0010] Depending on the design and requirements of the method, additional processing steps such as electrical connection of contact lugs, adjustment of final dimensions, application of coatings or packaging, placement of positioning aids, etc. may be performed subsequent to or as part of the method.

[0011] According to a further aspect of the present invention, a device for manufacturing a cell stack is provided. The device is adapted to perform the method according to the present invention. For this purpose, the device can have a receiving space for receiving at least one bundle of layers to be bonded to each other to form the cell stack. Furthermore, at least one heat source capable of inducing heat electromagnetically or electrically in the conductive layers of the bundle is provided. Depending on the design of the device, a pressing device with a lower tool and an upper tool can be used to exert a pressing force on the layers. A control unit can be used to control and regulate the generation of heat and the application of pressing force by the pressing device, for example based on measurement data from sensors.

[0012] According to a further aspect of the present invention, an electrochemical storage device is provided. The electrochemical storage device has at least one cell housing and can be designed as a battery cell based on, for example, lithium-ion technology. At least one cell stack manufactured according to the method of the present invention is arranged in the cell housing. The cell stack manufactured by the method of the present invention is not limited to lithium-ion technology and can therefore be used with many different electrochemical cells that require a one-piece cell stack with many layers.

[0013] By dissipating heat internally to thermally activate the adhesive, the adhesive can be heated for a shorter time before it develops its adhesive properties. Furthermore, by directing heat into the conductive layers, a more uniform temperature profile can be achieved across the cell stack, not just along its thickness, but also laterally or within its layers. Due to the uniform temperature profile within the cell stack, the outer layers are not thermally stressed or are stressed less than the inner layers. Therefore, adverse changes in the material properties of the cell stack layers can be prevented.

[0014] The heat-activatable adhesive may be designed, for example, as a polyurethane-based hot melt adhesive that cures below a temperature threshold and becomes tacky or adhesive above the temperature threshold. Alternatively, the heat-activatable adhesive may be a two-component adhesive with a heat-activatable curing agent. The curing agent liquefies as the temperature increases and can then react with the resin. For example, the heat-activatable adhesive may be designed as PVDF (polyvinylidene fluoride).

[0015] The conductive layers of the cell stack can be heated particularly efficiently when at least one magnetic coil is disposed adjacent to the anode and / or cathode electrodes. The magnetic coil is controlled to generate a time-varying magnetic field that inductively heats the anode and / or cathode electrodes. In particular, components of the anode and / or cathode electrodes that have high electrical conductivity are heated. For example, such components can be copper foil and aluminum foil.

[0016] Depending on the size of the cell stack, the use of several magnetic coils may be advantageous to generate uniform induction of eddy currents in the conductive layers. The anode and / or cathode electrodes typically have aluminum and copper carrier foils embedded in or bonded to the corresponding anode and cathode substrates. Due to their high electrical conductivity, the aluminum and copper carrier foils can be inductively heated particularly quickly and efficiently.

[0017] Preferably, the magnetic field direction of the coil can be perpendicular to the plane of the layer or parallel to the surface normal. Therefore, according to Maxwell's third equation, resulting eddy currents can be induced in the conductive layers as a result of the time-varying magnetic field. However, induced eddy currents represent a power loss, which has the effect of heating the individual foils of the anode and cathode electrodes. Eddy currents are preferably induced in all conductive layers of the cell stack according to the magnitude of the change in the magnetic field over time.

[0018] According to a further exemplary embodiment, the anode and / or cathode electrodes, particularly copper and aluminum foils, are electrically contacted at at least two contact locations by at least one current source and subjected to a constant or varying current to cause heating of the anode and / or cathode electrodes by Joule heating. By this alternative or additional means, the conductive layer can be heated by direct application of current and the resulting generation of power loss to thermally activate the adhesive.

[0019] According to a further embodiment, the anode electrode, the cathode electrode, and the separator layer are positioned in a pressing device. Preferably, the anode electrode, the cathode electrode, and the separator layer are pressed together by the pressing device with a constant or time-varying force while or after the adhesive of the separator layer is thermally activated. The application of the pressing force of the pressing device can ensure the final bonding result. By varying the pressing force over time, the adhesive properties of the adhesive can be controlled particularly precisely.

[0020] The cell stack can be heated particularly uniformly if the anode and / or cathode electrodes are inductively heated by at least two magnetic coils integrated into the upper and / or lower tooling of the pressing device, for example by inducing eddy currents in the copper and aluminum foils of the respective electrodes.

[0021] According to a further exemplary embodiment, the device comprises a guide device for guiding the magnetic field generated by the magnetic coil in at least a specific region, the magnetic field being guided via an upper section of the guide device on the upper tool, a lower section of the guide device on the lower tool, and two lateral sections of the guide device. The guide device or each section of the guide device can, for example, form an outer section of a coil core or magnetic core used to guide external magnetic field lines. The magnetic field lines generated directly by the magnetic coil can flow through the layers of the cell stack and be deflected or guided to the outside of the cell stack via the sections of the guide device.

[0022] The sections of the guide device may be in conductive contact or may be spaced apart. Furthermore, the sections of the guide device may be made of a ferromagnetic metal alloy. In order to reduce eddy current losses in the guide device, the sections of the guide device may be manufactured in the form of a sheet metal package. This measure allows the magnetic return to be controlled and makes the operation of the magnetic coil particularly energy-efficient.

[0023] Depending on the design, the sections of the guiding device can be cooled by air or liquid, and similarly, the at least one magnetic coil can be air or liquid cooled.

[0024] The device for manufacturing a cell stack can be designed to be particularly flexible if the magnetic field generated by at least one magnetic coil is guided through two side sections of a guide device, which are arranged in a pressing direction between the upper and lower sections of the guide device or arranged laterally adjacent to the upper and lower sections of the guide device. Such an arrangement of the guide device sections allows for flexible insertion of the cell stack into the receiving space. For example, the upper tool with the upper section or the side sections can be removed to place a bundle of layers in the receiving space to manufacture the cell stack and remove the cell stack from the receiving space after the bonding process.

[0025] According to a further embodiment, the temperature is measured by a temperature measuring device during thermal activation of the adhesive along at least one anode layer and / or cathode layer. The use of the temperature measuring device and its corresponding connection to a control unit allows for precise control of heating within the conductive layers of the cell stack. Thus, at least one magnetic coil can be controlled and monitored based on the measurement data determined by the temperature measuring device.

[0026] The temperature measuring device can be implemented in a particularly versatile manner if the temperature is measured directly by at least one thermoelement and / or measuring resistor of the temperature measuring device. In an alternative embodiment, the temperature is measured indirectly by measuring the conductivity of at least one anode and / or cathode layer by the temperature measuring device. This allows a particularly accurate temperature determination along the entire width or length of the layer.

[0027] Hereinafter, some embodiments of the present invention will be described in more detail with reference to the drawings. [Brief explanation of the drawings]

[0028] [Figure 1] 1 shows a schematic cross-sectional view of a device for manufacturing a cell stack to illustrate a method according to one embodiment of the present invention. [Figure 2] FIG. 10 shows a schematic cross-sectional view of a device for manufacturing a cell stack according to a second embodiment. [Figure 3] FIG. 10 shows a schematic cross-sectional view of a device for manufacturing a cell stack according to a third embodiment. [Figure 4] FIG. 1 shows a schematic cross-sectional view of an electrochemical storage device with a cell stack. [Figure 5] FIG. 5 shows a schematic detailed view of the cross section shown in FIG. 4 to illustrate the configuration of the cell stack.

[0029] In the drawings, identical reference numbers indicate the same elements or structural components. The sizes and relative positions of the illustrated elements are not necessarily drawn to scale, and some of these elements are shown in an exaggerated position for clarity. Furthermore, the particular shapes of the illustrated elements are not intended to convey any information regarding the actual shape of the individual elements, but have been selected solely for ease of recognition in the figures.

[0030] 1 shows a schematic cross-sectional view of a device 10 for manufacturing a cell stack 100 to illustrate a method according to one embodiment of the present invention. The device 10 is shown according to a first embodiment.

[0031] The cell stack 100 to be manufactured by this method is particularly intended for an electrochemical storage device 200, such as a lithium-ion cell, as shown in Figure 4. In the illustrated embodiment, such a cell stack 100 comprises a plurality of anode electrodes 101, separator layers 103, and cathode electrodes 102, which are repeatedly stacked, folded, or wound on top of each other.

[0032] Adhesive layers (not shown) may be used or certain layers may be pre-applied with adhesive to form a unitary or one-piece cell stack 100. For example, separator layer 103 may be coated or wetted with a heat-activatable adhesive on one or both sides. Depending on the method configuration, any of layers 101, 102, 103 may be provided with a heat-activatable adhesive. The use of adhesive with separator layer 103 serves to illustrate the method herein.

[0033] In a first step of the method, the layers 101, 102, 103 of the cell stack 100 are placed in the receiving space 11 of the device 10. Each layer 101, 102, 103 is aligned with respect to each other and may be temporarily protected from unintentional sliding by clamps, scaffolding, or the receiving space 11. Each layer 101, 102, 103 of the cell stack 100 is shown in detail in FIG. 4 by way of example.

[0034] The receiving space 11 of the device is designed to receive at least one bundle of layers 101, 102, 103 that are intended to be joined to one another to form a cell stack 100. Furthermore, at least one heat source 20, 21 is provided, which is able to induce heat electromagnetically (heat source 20) and / or electrically (heat source 21) in the conductive layers 101, 102 of the bundle. Thus, after the layers 101, 102, 103 have been provided, the conductive layers 101, 102, which in the illustrated embodiment are designed as anode electrodes 101 and / or cathode electrodes 102, are heated electromagnetically and / or electrically in a further step of the method.

[0035] In the illustrated embodiment example, the device 10 comprises a pressing device 30 with a lower tool 31 and an upper tool 32 for exerting a pressing force F on the layers 101, 102, 103. A control unit 40 is used to control and regulate the generation of heat by the heat sources 20, 21 and the application of the pressing force by the pressing device 30, for example based on measurement data from sensors. A temperature measuring device 41 is shown schematically for directly or indirectly determining the temperature of the layers 101, 102, 103. The temperature measuring device 41 can use thermal and / or electrical sensors to measure the temperature of the layers 101, 102, 103. The thermal sensor can determine the temperature based on direct contact with the layers 101, 102, 103 or based on non-contact measurement, for example by recording infrared radiation.

[0036] To provide uniform heating of the conductive layers 101, 102, the control unit 40 can control the two magnetic coils 20 to generate a time-varying magnetic field B that inductively heats the anode electrode 101 and / or the cathode electrode 102. The resulting magnetic field lines of the magnetic field B are shown by arrows in Figures 1, 2, and 3.

[0037] Alternatively or additionally, the anode electrode 101 and / or the cathode electrode 102 may be electrically contacted at at least two contact locations by at least one current source 21 and exposed to a constant or varying current to cause heating of the anode electrode 101 and / or the cathode electrode 102 by Joule heating. The current source 21 may also be controllable by the control unit 40.

[0038] Heating the anode electrode 101 and / or the cathode electrode 102 directly or immediately heat-activates the adhesive of the respective separator layer 103. Due to the heat activation of the adhesive, the anode electrode 101, the separator layer 103, and the cathode electrode 102 are bonded to each other to form a one-piece cell stack 100. This step completes the cell stack 100. Depending on the design and requirements of the method, additional processing steps such as electrical connection of contact lugs, final dimension adjustment, application of coatings or packaging, placement of positioning aids, etc. may be performed subsequent to or as part of the method.

[0039] 2 shows a schematic cross-sectional view of a device 10 for manufacturing a cell stack 100 according to a second embodiment. In contrast to the example embodiment shown in FIG. 1, here the device 10 is shown with a guiding device 50 for guiding the magnetic field B generated by the magnetic coil 20 at least in certain regions. For this purpose, the guiding device 50 has an upper section 51, a lower section 52 and two lateral sections 53.

[0040] The upper section 51 is assembled into the upper tool 31 of the pressing device 30. The lower section 52 is assembled into the lower tool 32 of the pressing device 30. The lateral sections 53 of the guiding device 50 are positioned laterally adjacent to the upper and lower sections 51, 52 and form a substantially closed loop for the magnetic return flow. In the example embodiment shown, the receiving space 11 is arranged centrally within this loop.

[0041] In the illustrated example embodiment, the lateral sections 53 are disposed between the upper section 51 and the lower section 52 along the thickness or height direction H, which corresponds to the contact pressure direction in the illustrated example embodiment.

[0042] 3 shows a schematic cross-sectional view of a manufacturing device 10 for a cell stack 100 according to a third embodiment. In contrast to the device 10 shown in FIG. 2, the lateral sections 53 of the guide device 50 are offset laterally along the lateral direction L relative to the upper section 51 and the lower section 52. This allows the upper tool 31 and the lower tool 32 to move freely along the height direction H relative to the lateral sections 32.

[0043] For ease of understanding, the control unit 40 and the temperature measuring device 41 are not shown in FIGS.

[0044] 4 shows a schematic cross-sectional view of an electrochemical storage device 200 with a one-piece cell stack 100. The electrochemical storage device 200 has a cell housing 201 and can be designed, for example, as a battery cell based on lithium-ion technology. At least one one-piece cell stack 100 manufactured according to the method of the present invention is arranged in the cell housing 201. The cell stack 100 is electrically contacted on both sides, for example, by poles 202, 203.

[0045] 5 shows a schematic detailed view of the cross section shown in FIG. 4 to illustrate the configuration of the cell stack 100. The cell stack 100 has a plurality of anode electrodes 101, separator layers 103, and cathode electrodes 102, which are repeatedly stacked, folded, or wound on top of each other and connected to each other by the method already described.

[0046] In the illustrated embodiment, each anode electrode 101 comprises a copper foil 104 or copper carrier foil covered on both sides by an anode substrate 105 .

[0047] Similarly, each cathode electrode 102 comprises an aluminum foil 106 or aluminum carrier foil covered on both sides with a cathode substrate 107 .

[0048] The cell stack 100 is terminated on both sides along the height direction H by anode electrodes 101, and the anode electrodes 101, separator layers 103, and cathode electrodes 102 alternate continuously along the height direction.

Claims

1. 1. A method for manufacturing a cell stack (100), in particular for an electrochemical storage device (200), comprising stacking, folding or winding at least an anode electrode (101), a separator layer (103) and a cathode electrode (102) one on top of the other, at least one layer (101, 102, 103) being coated on one or both sides with a heat-activatable adhesive or at least one layer (101, 102, 103) being provided with an adhesive, heating conductive layers (101, 102), in particular the anode electrode (101) and / or the cathode electrode (102), electromagnetically and / or electrically, and heat-activating the adhesive by heating the conductive layers (101, 102), in particular bonding the anode electrode (101), the separator layer (103) and the cathode electrode (102) to one another to form a one-piece cell stack (100).

2. 2. The method of claim 1, wherein at least one magnetic coil (20) is disposed adjacent to the anode electrode (101) and / or the cathode electrode (102), and the magnetic coil (20) is driven to generate a time-varying magnetic field (B) that inductively heats the anode electrode (101) and / or the cathode electrode (102).

3. 3. The method according to claim 1 or 2, wherein the anode electrode (101) and / or the cathode electrode (102) are electrically contacted at at least two contact locations by at least one current source (20) and are exposed to a constant or varying current to cause heating of the anode electrode (101) and / or the cathode electrode (102) by Joule heating.

4. 4. The method according to claim 1, wherein the anode electrode (101), the cathode electrode (102), and the separator layer (103) are positioned in a pressing device (30), and the anode electrode (101), the cathode electrode (102), and the separator layer (103) are pressed together by the pressing device (30) with a constant or time-varying pressing force (F) during or after the adhesive is thermally activated.

5. 5. The method according to claim 2, wherein the anode electrode (101) and / or the cathode electrode (102) are inductively heated by at least one magnetic coil (20) integrated into an upper tool (31) and / or a lower tool (32) of the pressing device (30).

6. 6. The method according to claim 5, wherein a guide device (50) is provided for guiding the magnetic field (B) generated by the magnetic coil (20) in at least a specific region, and the magnetic field (B) generated by the magnetic coil (20) is guided via an upper section (51) of the guide device (50) on the upper tool (31), via a lower section (52) of the guide device (50) on the lower tool (32), and via two lateral sections (53) of the guide device (50).

7. 7. The method according to claim 6, wherein the magnetic field (B) generated by the at least one magnetic coil (20) is guided through the two lateral sections (53) of the guide device (50), the two lateral sections (53) being arranged between the upper section (51) and the lower section (52) or laterally adjacent to the upper section (51) and the lower section (52) of the guide device (50) in the direction of the pressing force.

8. 8. The method according to any one of claims 1 to 7, wherein during thermal activation of the adhesive along at least one anode layer (101) and / or cathode layer (102), the temperature is measured by a temperature measuring device (41).

9. the temperature is measured directly by at least one thermoelement and / or measuring resistor of the temperature measuring device (41); Alternatively, the temperature is measured indirectly by measuring the conductivity of at least one anode layer (101) and / or cathode layer (102) by the temperature measuring device (41).

9. The method according to any one of claims 1 to 8.

10. A device (10) for manufacturing a cell stack (100), the device (10) being adapted to carry out the method according to any one of claims 1 to 9.

11. 10. An electrochemical storage device (200) comprising at least one cell housing (201) in which at least one cell stack (100) manufactured according to the method of any one of claims 1 to 9 is disposed.

Images