Apparatus and method for assembling a battery stack

Abstract

An apparatus for assembling a battery stack (7), particularly a fuel cell stack, comprises a handling device (2) including a gripper (6), and a positioning and pressing system (10) formed for compressing a partially completed battery stack (7). The positioning and pressing system (10) includes a lift device (11) provided for accommodating a battery stack (7) at any stage of manufacturing, and a lateral fixing device (12) above the lift device (11) which is constructed from a plurality of modules (13, 14), the modules (13, 14) provided vertically and horizontally for mounting the battery stack (7), and which are adjustable and locatable in both directions.

Description

Technical Field

[0001] The present invention relates to a method for assembling a battery laminate, particularly a laminate of an electrochemical battery, such as a fuel cell laminate. Furthermore, the present invention relates to an apparatus suitable for implementing such an assembly method.

Background Art

[0002] Patent Document 1 discloses an assembly apparatus for laminating a fuel cell laminate. Using this assembly apparatus, a fuel cell laminate alternately combined from a membrane electrode assembly and a bipolar plate is laminated in the vertical direction. The known assembly apparatus has a substantially rectangular parallelepiped-shaped assembly space, and the assembly space is divided by a plurality of vertically oriented placement bars. The placement bars are movable in the horizontal direction, and there is a problem in positioning the membrane electrode assembly and the bipolar plate relative to each other during lamination.

[0003] From Patent Document 2, a system for assembling and compressing a fuel cell laminate is known. This system includes a fuel cell laminate housing and a press having a number of press pins that act on the compression of the fuel cell laminate, and the fuel cell laminate is produced in the fuel cell laminate housing by laminating fuel cell components together.

[0004] The apparatus for automatically laminating a fuel cell laminate described in Patent Document 3 is provided to apply pressure to the laminated fuel cell and further includes a rotatable pressurizing element. The automatic lamination apparatus is further said to be able to detect defective parts and inspect the airtightness of the laminate body.

[0005] Various compression systems for fuel cell laminates are described in Patent Document 4 and Patent Document 5. In this case, fastening bands or strip-shaped holding means connected to the end plates of the battery laminate are provided to compress the fuel cell laminate.

[0006] Patent Document 6 proposes encapsulation for assembling a fuel cell stack, which involves biasing and sealing the fuel cell assembly in the direction of fuel cell stacking.

[0007] The fuel cell stack assembly apparatus described in Patent Document 7 includes a magnet system portion that extends perpendicularly to the base of the assembly apparatus and attracts a plurality of fuel cell units. In this case, the magnet system portion engages with grooves or notches of the fuel cell elements.

[0008] The apparatus described in Patent Document 8 utilizes a robot to handle the battery plate. In this case, the orientation of the battery components can be detected using sensors.

[0009] Further apparatus and methods for handling components of electrochemical systems are known from Patent Documents 9, 10, and 11. In the last mentioned case, a bonding element is provided to tightly bind the compressed battery stack. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] German Patent Application Publication No. 102016220173 Specification [Patent Document 2] German Patent Application Publication No. 102017100362 [Patent Document 3] German Patent Application Publication No. 102015220399 Specification [Patent Document 4] German Patent Application Publication No. 102020127917 Specification [Patent Document 5] German Patent Application Publication No. 102021112699 Specification [Patent Document 6] German Patent Application Publication No. 102018119633 Specification [Patent Document 7] German Utility Model Specification No. 202020105427 [Patent Document 8] U.S. Patent Application Publication No. 2020 / 0091542 [Patent Document 9] China Utility Model No. 207265167 Specification [Patent Document 10] Chinese Patent Application Publication No. 107706438 Specification [Patent Document 11] Chinese Patent Application Publication No. 113036200 Specification [Overview of the project] [Problems that the invention aims to solve]

[0011] The object of the present invention is to achieve progress over the above-mentioned prior art in the manufacture of battery stacks, particularly fuel cell stacks, and to obtain a particularly favorable ratio between assembly cost and process safety. [Means for solving the problem]

[0012] The problem is solved by the present invention with an apparatus suitable for assembling battery stacks, particularly electrochemical battery stacks, having the features of claim 1. Similarly, the problem is solved by the method for assembling battery stacks, particularly fuel cell stacks, as described in claim 8. In relation to the assembly method, the embodiments and advantages of the present invention described below also apply similarly to assembly apparatuses, and vice versa.

[0013] The apparatus provided for assembling the battery stack comprises a handling device including grippers suitable for lifting flat objects, for example in the form of vacuum grippers, or a plurality of such grippers, and a positioning and pressing system formed to compress a partially completed battery stack, cooperating with one or more grippers. In this case, the term “compression” does not necessarily mean that the vertical dimensions of the battery stack are significantly reduced at any given point. In any case, the battery stack to be constructed is vertically aligned, which is equivalent to the horizontal alignment of the flat components that will be stacked on top of each other in the battery stack. Placing the battery components horizontally facilitates faster construction of the stack.

[0014] The positioning and pressing system includes a lifting device provided for accommodating a battery stack at any stage of manufacturing, and a lateral fixing device located above the lifting device, which is constructed from multiple modules, the modules being provided vertically and horizontally for positioning the battery stack and being adjustable and positionable in both directions. The fixing device includes multiple modules for gripping various points on the battery stack.

[0015] For example, two modules are available in which the first and second modules are positioned lateral to the battery stack in a mirror-symmetrical manner, i.e., making lateral contact with the battery stack from both sides. Similarly, embodiments are possible in which the fixing device is constructed from three, four, or more modules of the same or different types. At least two modules positioned in a particularly symmetrical arrangement can be repositioned simultaneously or independently of each other.

[0016] The battery stack uses a fixing device formed from a plurality of modules to apply pressure not only immediately after the completion of the battery stack but also during the production of the battery stack, thereby maintaining the shape. This enables not only high - productivity assembly but also high geometric accuracy along with the horizontal alignment of battery components. In particular, the compression of the battery stack during the assembly process prevents the battery components from slipping and shifting within the stack.

[0017] According to a first possible group of embodiments, each of two or more modules of a common multi - part fixing device of the assembly apparatus includes a plurality of fixing elements displaceable in the horizontal direction. The fixing elements are provided not only in the lateral direction but also in the vertical direction to support the bipolar plates arranged in a stacked manner within the battery stack. In this case, the vertical support means inducing a force acting in the vertical direction on the battery stack.

[0018] For example, three or more fixing elements provided to contact each of the bipolar plates arranged in a stacked manner are supported in a common horizontally and vertically adjustable housing using a single spring. The adjustable housing may be assigned to a single gripping device, and the gripping device is formed to grip or release all of the fixing elements in the housing simultaneously as needed.

[0019] Optionally, in addition to the fixing elements displaceable in the horizontal direction, there is a switchable MEA holding part, which is formed to press on a membrane electrode assembly (MEA) above the partially completed battery stack. When a bipolar plate is placed on the MEA, the MEA holding part is stopped.

[0020] According to a possible second group of embodiments, the side modules of the fixing device each have a corner-shaped surrounding gripper, against which the battery stack abuts laterally and simultaneously upward. This results in a clearly simplified configuration of the assembly device compared to a possible first group of embodiments. This configuration is particularly worth considering when the bipolar plate is bent during assembly, as will be explained in more detail below.

[0021] In either of the possible groups of embodiments, the lift device provided for accommodating the battery stack may have three plates arranged horizontally together, namely a base plate, an intermediate plate, and an upper plate provided for accommodating the battery stack. In this case, there may be a pressure measurement system operating between the base plate and the intermediate plate, while the upper plate is vertically displaceably supported on the intermediate plate using a spring. In particular, both lower plates may be punched in any way as long as the intended support function is provided.

[0022] Optionally, a distance measurement device formed for measuring the distance between the upper plate and the intermediate plate is provided. From the knowledge of the characteristics of the spring described above, the distance measurement device can also be used for pressure measurement, and as a result, redundancy in force measurement is provided together with the pressure measurement system located below on the base plate.

[0023] The method for assembling the battery stack is characterized in that the battery stack, which includes bipolar plates and membrane electrode assemblies arranged horizontally and parallel together during the construction phase, is already subjected to pressure during its fabrication. This is achieved by applying a vertically downward pressure to the battery stack, which is still incomplete at this manufacturing phase, in addition to the gravity of the battery components, after each additional bipolar plate has been placed. This pressure pushes the battery stack downward as a whole, compressing the springs located below the battery stack and supporting it, which is referred to as an overpressure state. After the overpressure that occurs during the assembly of the battery stack, the vertically downward pressure is reduced, and as a result, the battery stack is lifted somewhat again by the springs. Finally, in the subsequent state in which the springs are at least partially expanded, at least the upper bipolar plates are fixed vertically and laterally while maintaining some of the downward pressure.

[0024] The springs that are compressed during overpressure are positioned between height-adjustable plates, particularly by the method described above, and are formed, for example, as coil springs or leaf springs. Similarly, pneumatic supports are also considered. In any case, the lift system that allows for height adjustment of the plates can utilize force measurements, length measurements, or a combination of force measurements and geometric measurements for readjustment.

[0025] A variation of the first method intends for the bipolar plates to be alternately placed on the battery stack in a completely flat state, similar to the membrane electrode assemblies.

[0026] According to an alternative modification, at least the bipolar plate is placed on the battery stack while a force is applied to it in a curved state and directed vertically downward. The central region of the bipolar plate is then pressed against the battery stack, and while maintaining the pressure, the entire bipolar plate is subsequently deformed back to its original flat shape and comes into contact with the battery stack.

[0027] An advantage of the present invention lies, in particular, in that the battery stack, i.e., the stack itself, is already consistently compressed during its fabrication. This advantage is obtained regardless of the type of battery, e.g., fuel cell or electrolytic cell. Tilting the stack during assembly is unnecessary in any case. Depending on the embodiment of the positioning and pressing system that prevents the stack components from slipping and shifting during assembly, the stack components can be aligned not only with their outer shape but also with respect to internal structures, e.g., active regions. Assembly of the final aligned stack components is particularly advantageous when it would no longer be possible to subsequently move components for adjustment purposes. Such limitation of post-adjustability may be provided, for example, by sealing, e.g., silicone sealing within the battery stack.

[0028] Two embodiments of the present invention will be described in more detail below with reference to the drawings. Some of the drawings are only roughly illustrated. [Brief explanation of the drawing]

[0029] [Figure 1] This is a diagram of a first embodiment of an apparatus for assembling a stack of electrochemical cells. [Figure 2] This is a schematic cross-sectional view of a second embodiment of an apparatus for assembling a battery stack in a first operating state. [Figure 3] Figure 2 shows the second operating state of the assembly apparatus. [Modes for carrying out the invention]

[0030] The following description applies to both embodiments unless otherwise stated. Parts that correspond to each other or act in principle equivalently are given the same reference numerals in all figures.

[0031] The manufacturing equipment, denoted by reference numeral 1 as a whole, is formed as a device for assembling a battery stack 7, i.e., a fuel cell stack. The manufacturing equipment 1, i.e., the assembly device, includes a handling device 2 for lifting and positioning the flat fuel cell components to be assembled. The handling device 2 incorporates a support element 3 and a movable element 4, the movable element 4 may be the arm of an articulated arm robot (not shown). Although not shown, the handling device 2 may also include a linearly movable element 4.

[0032] Elements 3 and 4 support a gripper 6 of a known design in principle, such as a vacuum gripper. Alternatively, the gripper 6 may utilize other physical principles such as adhesion or magnetism. A position sensing system 5, which is specifically shown only in Figure 1 but is also present in the embodiments described in Figures 2 and 3, is configured in this specification to detect the positioning of an object relative to the vacuum gripper 6. In addition to the position sensing system 5 shown in Figure 1, a positionally fixed position sensing device may be available, although it is not shown.

[0033] Using the handling device 2, a fuel cell stack 7, also abbreviated as a stack, is constructed. The planar components of the stack 7 are bipolar plates 8 and membrane electrode assemblies 9. The fuel cell stack 7, which is being fabricated, is already under pressure during its construction. For this purpose, a positioning and pressing system, numbered 10 as a whole, is provided. A lift device 11 is assigned to the positioning and pressing system 10, and the partially completed stack 7 rests on the lift device 11. Furthermore, the positioning and pressing system 10 has a lateral fixing device, numbered 12 as a whole, which, in this specification, comprises exactly two modules 13, 14, namely, a first module 13 and a second module 14, where modules 13, 14 are formed mirror-symmetrically to each other. In this specification, without limiting generality, the first module 13 is referred to as the left module of the fixing device 12, and the second module 14 is referred to as the right module of the fixing device 12. In a modified embodiment, for example, there are four modules 13 and 14, and these four modules 13 and 14 are located on all four sides of the rectangular stack 7 in the schematic diagram.

[0034] The stack 7 is constructed vertically, meaning that the different components 8 and 9 of the stack 7 are always aligned horizontally when the stack 7 is being constructed. The height of the stack 7 is adjustable using a lift system 15, which is part of a lifting device 11. The lift system 15 is designed to change the height setting of a base plate 16 located below an intermediate plate 18. Between the plates 16 and 18 is a pressure measuring system 17, i.e., a measuring system of a type of scale. Further above the intermediate plate 18 are several springs 19 formed as pressure springs, which support an upper plate 21, also referred to as a housing device, which supports the stack 7 to be assembled. A spacing measuring device 20 operating between the intermediate plate 18 and the upper plate 21 can be used as an additional force measuring device if the properties of the springs 19 are known.

[0035] A linear guide 22 is provided to allow a predetermined linear shift between the intermediate plate 18 and the housing unit 21. An end stopper 35 functions when the housing unit 21 is lifted to its maximum extent from the intermediate plate 18 and therefore from the base plate 16. In plan view, the housing unit 21 matches the dimensions of the components 8 and 9 of the fuel cell stack 7.

[0036] To hold the different components 8 and 9 of the fuel cell stack 7 in place during the fabrication of the fuel cell stack 7, and in this case to apply a force F to the stack 7 in the vertical direction, the above-described fixing device 12 is provided on the one hand, and the MEA holding unit 23 is provided on the other hand. The MEA holding unit 23 is provided solely for contact with the membrane electrode assembly 9 located above in the stack 7. As soon as this membrane electrode assembly 9 is covered by the bipolar plate 8, the MEA holding unit 23 stops. The operating mechanism of the MEA holding unit 23, i.e., the device for holding the membrane electrode assembly 9, is numbered 24.

[0037] Each module 13, 14 of the fixing device 12 has a plurality of displaceable fixing elements 25, in this specification three, in the embodiment shown in Figure 1. A spring 26 acts on each of the fixing elements 25 formed as sliders, displacing the associated fixing element 25 in the direction of the laminate 7. The entire fixing elements 25 and springs 26 of each module 13, 14 are located in a housing 27. A guide device for horizontal shifting of the housing 27 is numbered 28. The guide device 28 is operable using an operating device 29. A gripping device 30 is provided, including a gripping plate 31, to hold the fixing elements 25 in the housing 27. A spring 32 acts on the gripping plate 31 in a vertical gripping direction. In the opposite direction, a tension element 33, operable using an operating device 34, acts.

[0038] The embodiments shown in Figures 2 and 3 differ from the embodiment shown in Figure 1 in that the modules 13 and 14 of the lateral fixing device 12 are substantially more simply formed. In Figures 2 and 3, the functions of modules 13 and 14 are taken over by the surrounding grippers 36, respectively, which not only act as lateral stoppers for the components 8 and 9 of the fuel cell stack 7 but also compress the stack 7 as a whole. The bipolar plate 8 is first received and perfectly horizontally aligned by the vacuum gripper 6, as schematically shown in Figure 2. The same applies to the receiving of the membrane electrode assembly 9 by the handling device 2. In this respect, there is still no difference between the method that can be carried out using the apparatus shown in Figures 2 and 3 and the method that can be carried out using the apparatus shown in Figure 1. Instead of a single vacuum gripper 6, multiple vacuum grippers 6 are available in the case of Figures 2 and 3.

[0039] Following the lifting of the bipolar plate 8, the method specifically shown in Figures 2 and 3 has particular advantages over the method carried out using the manufacturing equipment 1 described in Figure 1. As can be seen from Figure 3, the bipolar plate 8, lifted using a gripper 6, for example a vacuum gripper, is bent before being placed on the stack 7, so that the edges of the bipolar plate 8 are bent upward. In this state, the central region of the bipolar plate 8 is then placed on the stack 7. Subsequently, the bipolar plate 8 is deformed back to its original flat shape by increasing the force F. Once this process is complete, both enclosing grippers 36 grip the stack 7, so that the stack 7 remains in its compressed form. The enclosing grippers 36 are then temporarily released from the stack 7, allowing the next initially bent components 8, 9 to be placed on the fuel cell stack 7.

[0040] In the embodiment shown in Figure 1, as already described, the bipolar plate 8 is not deformed during the construction of the stack 7. When the bipolar plate 8 is to be placed on top of the stack 7, the MEA holding section 23 is opened first. The correct stacking position of the bipolar plate 8 is monitored using the position sensing system 5. After stacking the bipolar plate 8, the bipolar plate 8 remains fixed to the gripper 6 for the time being. Subsequently, the handling device 2 presses the bipolar plate 8 against the stack 7 so that the stack 7 is overpressurized against the spring 19. Compared to the deformation of the spring 19, the deformation of the stack 7 itself in this case is minimal at most. The vertical overpressure, expressed in millimeters, corresponds to the sum of the thickness of the bipolar plate 8 and a predetermined additional path (Zusatzweg) that is substantially less than the thickness of the bipolar plate 8.

[0041] When the overpressure reaches the value of the additional path, no compressive force is generated on the lateral fixing element 25. The displaceable lateral fixing element 25, as can be seen in Figure 1, allows for not only lateral support but also vertical support of the bipolar plate 8. When no vertical force is acting on the fixing element 25, the fixing element 25 is moved laterally away from the stack 7 using the guide device 28 and the operating device 29. Subsequently, the stack 7 is pressed further downward using the handling device 2 until the maximum value of the overpressure is reached. In this state, the fixing element 25 is again in contact with the bipolar plate 8 when the gripping device 30 is open, but is moved precisely around one bipolar plate 8. At this point, the gripping device 30 can be closed again. The settings of the lifting device 11 are updated during the above process, and various measuring devices 17, 20 provide technical redundancy for measurement. When the membrane electrode assembly 9 is placed on the fuel cell stack 7 under construction, the above overpressure does not occur. [Explanation of Symbols]

[0042] 1 Manufacturing equipment 2. Handling equipment 3. Support elements 4 movable elements 5. Location detection system 6. Grippers, Vacuum Grippers 7. Fuel cell stacks 8 Bipolar Plates 9 Membrane electrode assembly, MEA 10 Positioning and Pressing Systems 11. Lifting device 12 Lateral fixation device 13. First module of the fixing device 14. Second module of the fixing device 15 Lift System 16 Base Plate 17 Pressure Measurement System 18 Intermediate plate 19 springs 20 Interval measuring device 21 Upper plate, housing device 22 Linear Guide 23 MEA holding part 24. Operating mechanism of the MEA holding unit 25 Displaceable lateral fixing element 26. Spring acts on fixed element 25. 27 Housing for fixed elements 28 Guide device for horizontal shifting of housing section 27 29 Operating device for guide device 28 30 Gripping device 31 Gripping plate 32. Spring acts on gripping plate 31. 33. Tensile elements, acting against gripping forces. 34. Operating device for manipulating tensile elements 35 End Stopper 36 Enclosed Gripper F force

Claims

1. An apparatus for assembling a battery stack (7), comprising: a handling device (2) having a gripper (6) formed for lifting a flat object; a positioning and pressing system (10), the positioning and pressing system (10) being formed for compressing a partially completed battery stack (7); a lift device (11) provided for housing the battery stack (7) at any stage of manufacturing; and a lateral fixing device (12) above the lift device (11) constructed from a plurality of modules (13, 14), the modules (13, 14) being provided vertically and horizontally for mounting the battery stack (7), and being adjustable and positionable in both directions.

2. The apparatus according to claim 1, wherein each of the modules (13, 14) of the fixing device (12) includes a plurality of horizontally displaceable fixing elements (25), the plurality of fixing elements (25) being provided not only laterally but also vertically to support the bipolar plates (8) arranged in a superimposed configuration.

3. The apparatus according to claim 2, characterized in that at least three overlapping fixed elements (25), each provided to contact a bipolar plate (8), are individually spring-biased and housed in a common housing (27) that is adjustable in the horizontal and vertical directions.

4. The apparatus according to claim 3, characterized in that a single gripping device (30) is assigned to the housing section (27), and the gripping device (30) is formed to simultaneously grip all of the fixed elements (25) present in the housing section (27).

5. The apparatus according to any one of claims 2 to 4, characterized in that, in addition to a horizontally displaceable fixed element (25), there is a switchable MEA holding part (23), the MEA holding part (23) is formed to press against a membrane electrode assembly (9) located above a partially completed battery stack (7).

6. The apparatus according to claim 1, wherein both modules (13, 14) on the sides of the fixing device (12) each have a rectangular enclosed gripper (36), and the battery stack (7) is in contact with the enclosed gripper (36) on the side and simultaneously on the top.

7. The apparatus according to any one of claims 1 to 6, wherein the lifting device (11) comprises three plates (16, 18, 21) arranged in parallel together, namely a base plate (16), an intermediate plate (18), and an upper plate (21) provided for housing the battery stack (7), wherein there is a pressure measuring system (17) operating between the base plate (16) and the intermediate plate (18), the upper plate (21) is supported on the intermediate plate (18) so as to be vertically displaceable using a spring (19), and a spacing measuring device (20) formed for measuring the distance between the upper plate (21) and the intermediate plate (18).

8. A method for assembling a battery stack (7), wherein the battery stack (7), which includes bipolar plates (8) and membrane electrode assemblies (9) arranged together horizontally and parallel to each other during the construction phase, is subjected to pressure during its fabrication by applying vertically downward pressure to the battery stack (7) after each additional bipolar plate (8) has been placed, thereby pushing the battery stack (7) downward as a whole, which represents a process of overpressure in which a spring (19) located below and supporting the battery stack (7) is compressed, after which the vertically downward pressure is reduced, as a result the battery stack (7) is lifted again by the spring (19), and then, in a predetermined expanded state of the spring (19), at least the upper bipolar plates (8) are fixed vertically and laterally while maintaining a portion of the downward pressure.

9. The method according to claim 8, characterized in that the bipolar plate (8) and the membrane electrode assembly (9) are alternately placed on the battery stack (7) in a completely flat state.

10. The method according to claim 8, characterized in that at least the bipolar plate (8) is placed on the battery stack (7) in a curved state, and then the central region of the bipolar plate (8) is pressed onto the battery stack (7), and while maintaining the pressure, the entire bipolar plate (8) is subsequently deformed into its flat shape and comes into contact with the battery stack (7).

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