Method for detecting micro-short circuits, test stand, and production line

Abstract

A method for detecting a soft short circuit in an electrode assembly (14) comprises the following steps: First, an electrode assembly (14) having at least one anode and at least one cathode is provided, and a separator having a porosity is inserted between each anode and cathode. Then, the impedance of the electrode assembly (14) is measured, and the measured impedance is compared with a reference value. If the measured impedance deviates from the reference value, a soft short circuit is detected. The electrode assembly (14) is not laminated, and the impedance is measured before introducing the electrolyte and installing the electrode assembly (14) in a galvanic cell. The present invention further relates to a test stand and a manufacturing line.

Description

[Technical Field]

[0001] The present invention relates to a method, test stand and production line for detecting microscopic shorts in electrode assemblies. [Background technology]

[0002] Hereinafter, the term "lithium ion battery" is used synonymously with all common names in the prior art for galvanic elements and cells containing lithium, such as lithium battery, lithium cell, lithium ion cell, lithium polymer cell, lithium ion battery cell, and lithium ion storage battery. This particularly includes rechargeable batteries (secondary batteries). The terms "battery" and "electrochemical cell" are also used synonymously with the terms "lithium ion battery" and "lithium ion cell." The lithium ion battery may also be, for example, a ceramic-based or polymer-based solid-state battery.

[0003] An electrode assembly is an arrangement of at least two different electrodes, at least one positive electrode (cathode) and at least one negative electrode (anode), each containing at least one active material and, optionally, additives such as electrode binders and conductive additives.

[0004] A separator is placed between each cathode and anode to provide electrical and mechanical insulation, but the separator is permeable to ions, such as lithium ions in lithium-ion batteries.

[0005] In the manufacture of galvanic devices such as lithium-ion batteries, the electrode assembly and separator are packed into a housing filled with an electrolyte, which allows ions to migrate through the separator when the galvanic device is charged or discharged.

[0006] A general description of lithium-ion technology can be found in Chapter 9 (Lithium-ion cell, author Thomas Woehrle) of the "Handbuch Lithium-Ionen-Batterien" (editor Reiner Korthauer, Springer, 2013) and Chapter 9 (Lithium-ion cell, author Thomas Woehrle) of the book "Lithium-Ion Batteries: Basics and Applications" (editor Reiner Korthauer, Springer, 2018).

[0007] During the manufacture of a galvanic element (electrical element), it is necessary to ensure that at least one cathode and at least one anode are separated by a separator. If the separator is damaged or not positioned correctly, a so-called microcircuit, i.e. an internal short circuit between the cathode and the anode, can occur. In this case, the galvanic element cannot be used and must be discarded.

[0008] In the prior art, the so-called "HiPot test" is used to detect such micro-short circuits. In the HiPot test, a very high voltage of approximately 500 volts is applied to the electrodes of the electrode / separator assembly or galvanic cell being tested. If the separator assembly is misaligned or mechanically damaged, and the separator does not provide sufficient insulation, a current will flow through the separator at these very high voltages, which can be detected, also known as a voltage drop. In this case, a galvanic cell failure is assumed. If the electrode / separator assembly fails the HiPot test, it is discarded and not processed further.

[0009] Modern galvanic devices, especially lithium-ion batteries, increasingly use so-called "nonwoven" separators. These separators are largely open-porous nonwovens, meaning they have pores that extend along a single axis at least partially through the entire thickness of the separator. Therefore, angular or labyrinthine pore structures are present to a small extent, if at all, and at least not exclusively. Such nonwoven separators are commercially available and are made from chemically, mechanically, and electrochemically stable fibers, such as polyester (DE 102009002680 A1) or polyamide (US 7112389 B1).

[0010] When such open-porosity separators are used, conventional HiPot testing has shown that even if the separator is not damaged and is properly positioned, it often detects micro-shorts. Therefore, there is a need for an alternative test method that can reliably detect micro-shorts even when open-porosity stable separators are used.

[0011] DE 10207070 A1 discloses a method for manufacturing a galvanic element. In this method, individual cells intended to form a cell stack for a galvanic element are first checked as a minimum unit by impedance measurement. A non-destructive, 100% inspection is possible. Laminated cells are used as individual cells for this test. In such laminated cells, known from EP 1261048 B1, for example, the individual components, i.e., electrodes, conductors (arrestors), and separators, are firmly and permanently connected to one another, e.g., by plastic, and cannot be separated non-destructively. This method demonstrates the possibility of measuring impedance even without an electrolyte, since lamination residues ensure sufficient contact between the electrodes and separators, allowing a finite impedance to be measured. However, this method is therefore only suitable for stacked cells or electrode / separator stacks consisting of several stacked cells. In such laminated cells, it is not possible to create electrode coils without dangerous damage. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] DE102009002680A1 [Patent Document 2] US7112389B1 [Patent Document 3] DE10207070A1 [Non-patent literature]

[0013] [Non-Patent Document 1] "Handbuch Lithium-Ionen-Batterien" (editor Reiner Korthauer, Springer, 2013), Kapitel 9, (Lithium-ion cell, author Thomas Woehrle [Non-patent document 2] “Lithium-Ion Batteries: Basics and Applications” (editor Reiner Korthauer, Springer, 2018), Kapitel 9, (Lithium-ion cell, author Thomas Woehrle) Summary of the Invention [Problem to be solved by the invention]

[0014] The object of the present invention is to provide further possibilities for reliably detecting micro-short circuits in electrode assemblies. [Means for solving the problem]

[0015] According to the present invention, this problem is solved by a method for detecting micro-short circuits in an electrode assembly, which method includes the following steps: first, the electrode assembly includes at least one anode and at least one cathode, with an open porous separator interposed between each anode and cathode; then, the impedance of the electrode assembly is measured and compared with a reference value; if the measured impedance deviates from the reference value, a short circuit is detected; the electrode assembly is not laminated, and the impedance measurement is performed before introducing the electrolyte and attaching the electrode assembly to a galvanic element.

[0016] According to the present invention, no laminated electrodes or cells are used, i.e., the anode, cathode and separator are not rigidly connected but rather loosely overlap each other, and the bonding of the components is therefore ensured solely by the static friction of the individual parts of the electrode assembly.

[0017] The inventors have found that even in this case, a finite impedance can be measured before the electrode assembly is placed in the galvanic element, particularly before the electrolyte is filled, and thereby a minute short circuit in the electrode assembly can be reliably detected. This is surprising because, since the electrodes and separators are not connected, there are gaps and air inclusions that generate very high interfacial resistance, which would be expected to result in an infinitely large and unmeasurable impedance value. Furthermore, there is no residue from the lamination process, such as residual moisture, and therefore the corresponding conductivity is obtained.

[0018] A secondary positive aspect of the present invention is the fact that assemblies in which the nonwoven separator is not laminated can be reliably tested and approved for micro-short circuits. As a result, micro-short circuit testing does not necessarily require lamination of the nonwoven separator, which is prone to the adverse effects of lamination, especially exposure to high pressures and temperatures.

[0019] However, because at least one separator has open porosity, it is still possible to measure a finite impedance. The inventors recognized that, unlike conventional HiPoT testing, the imperfect electrical insulation of such separators can be advantageously utilized under the conditions of impedance measurement. The voltage required for impedance measurement is lower than that required for HiPoT testing, reducing the energy required and the cost of the test procedure. In conventional HiPoT testing, the incomplete electrical insulation through the open porosity of the separator leads to voltage breakdown.

[0020] The reference value can be determined in advance using an electrode assembly with accurate function. For example, the average value of the impedance measured in the past using an electrode assembly with accurate function can be used as the reference value. Alternatively, the reference value can be simply set to the lower or upper limit of a range of known impedance values. Electrode area: approximately 1800 mm 2 For a bilayer cell with a thickness of approximately 500 μm, a reference value of the order of approximately 40 kΩ can be expected when measured with an AC voltage of approximately 1 kHz. 2 For large area PHEV1 winding cells, a standard range of 80-120mΩ can be expected.

[0021] According to the invention, a statistical evaluation of past impedance measurements of known electrode assemblies can also be performed in order to define a measurement range within which the measured impedance value lies when the electrode assembly is functioning. In this variant, the reference value is a reference range.

[0022] According to the present invention, impedance measurements are performed before the electrode assembly is installed in the housing, particularly before the housing is filled with electrolyte. Thus, the method according to the present invention makes it possible to check the electrode assembly even before further processing. This allows for early detection and sorting of defects in the electrode assembly and mechanical damage to the separator, etc. This reduces the number of rejected products in the production of galvanic cells and reduces production costs. Furthermore, it also makes it easier to detect small internal short circuits during the cell's life in application, improving cell reliability.

[0023] The galvanic element is in particular a lithium-ion battery.

[0024] In one variation, a micro-short is detected only if the measured impedance deviates from a reference value by more than a predetermined tolerance, which can be selected to be, for example, ±15% deviation from the reference value.

[0025] The tolerance range can be determined, as well as a reference value, by pre-measuring the impedance of a properly functioning electrode assembly. In particular, the tolerance range can be used to account for production-related variations without yet having an undue adverse effect on the proper functioning of the electrode assembly.

[0026] If the reference value is only an upper or lower limit, the tolerance can be a deviation by a predetermined percentage above the upper limit or below the lower limit, for example, a deviation of 5% above the upper limit or below the lower limit.

[0027] If the reference value is a mean value determined from a statistical analysis of past measurements, the tolerance range can be a predetermined multiple of the standard deviation of the measurements around the reference value. The at least one separator is, in particular, a nonwoven fabric or paper. Preferably, the separator is, in particular, a "nonwoven" separator. Such separators may be made from plastic fibers obtained by extrusion from a polymer melt or other known fiber manufacturing processes. The fibers used may be continuous fibers to form a nonwoven fabric or staple fibers. A nonwoven separator at least partially made from a biopolymer is known from DE 10 2014 205 234 A.

[0028] The nonwoven fabric used as the separator can be formed as an oriented or randomly woven fabric. Known processes, particularly dry-laid processes, aerodynamic processes such as melt-blown processes and spunbonding processes, wet-laid processes, and extrusion processes, can all be used to manufacture the nonwoven fabric. The nonwoven fabric can be mechanically, chemically, or thermally bonded by known methods. In particular, the production of a nonwoven fabric separator from plastic fibers does not require complex additional processing steps, such as fiber structuring. The nonwoven fabric separator can improve the mechanical, chemical, electrochemical, and thermal stability of the electrode assembly.

[0029] Furthermore, at least one separator may include fibers of a plastic selected from the group consisting of polyimide, polyester, aramid, copolymers, and mixtures thereof. Separators using fibers made of these plastics have improved melting temperatures and puncture resistance, particularly compared to polyethylene and polypropylene, improving the separator's temperature resistance and reliability. Furthermore, these plastics can be extruded from a polymer melt using known processes.

[0030] In particular, the separator has a thickness in the range of 8 to 25 μm, preferably 10 to 15 μm. Using such a thin separator, a galvanic element comprising an electrode assembly according to the present invention can achieve high specific energy and energy density. With thin separators, the HiPot test is particularly likely to show a false positive for a fines short circuit, making the method according to the present invention particularly advantageous as an alternative.

[0031] The method according to the invention can be applied to very small pouch cells with an electrode area of ​​2 x 4 cm, as well as to large area PHEV1 cells with an electrode area of ​​up to 15 x 480 cm (Wound PHEV1 cells) and more. Thus, in one variant, at least one cathode and at least one anode are at least 800 mm 2 , preferably at least 5,000 mm 2 , and more preferably at least 7,000 mm 2 , at least 8,000 mm 2 or at least 10,000 mm 2 The electrode area may be

[0032] The electrode area is 800mm 2 ~800,000mm 2 range, especially 5,000mm 2 ~20,000mm 2 or 7,200 mm 2 ~16,200mm 2 The electrode of the electrode assembly may therefore be an electrode with a relatively large area. The method according to the present invention is also suitable for such an electrode surface.

[0033] The dimensions of the electrode are, for example, in the range of 100×50 mm to 200×100 mm, particularly 120×60 mm to 180×90 mm.

[0034] In particular, the electrode assembly includes at least five anodes and at least five cathodes, preferably at least eight anodes and at least eight cathodes. In other words, the method of the present invention can be accurately used with electrode assemblies having a large number of individual electrodes, each of which is not yet firmly connected to one another and / or impregnated with electrolyte. This allows for at least partial re-isolation of loosely connected electrode assemblies when a micro-short circuit is detected by the method of the present invention. This allows for identifying defects in the cathode, cathode, or separator, and allows for the reuse of other components of the electrode assembly.

[0035] In a further variant, preferably used in the mass production of lithium batteries, individual bilayer cells having exactly one cathode and exactly one anode can be tested with the method according to the invention before the bilayer cells are assembled into a stack, and any bilayer cells found to be defective can be sorted and discarded.

[0036] Furthermore, the galvanic element may be a cell stack or a cell coil. Since the individual electrodes of the electrode assembly according to the present invention are not yet connected to each other, and in particular laminated individual cells are not used, the method according to the present invention can be used not only for cell stacks but also for cell coils. In this way, it is also possible to reliably identify the cell coil by impedance measurement, in contrast to using stacked individual single cells.

[0037] Impedance measurements can be performed using AC current or voltage at frequencies between 500 Hz and 1.5 kHz, especially at 1 kHz, which allows for both shorter measurement times and higher reliability of impedance measurements.

[0038] The impedance can be measured using the real and imaginary parts of the impedance and / or the absolute value of the impedance, i.e. the phase sensitive and / or absolute value of the impedance can be used.

[0039] The object of the present invention is further achieved by a test stand for verifying electrode assemblies, which is arranged to carry out the method described above.

[0040] In particular, the test stand can be integrated into a production line, for example a manufacturing plant, for producing galvanic elements.

[0041] In particular, the test stand includes a sensor module having contacts for contacting the conductive flags of the electrode assembly.

[0042] The test stand can further include a memory module and an evaluation module. The memory module can store a history of measured impedance values ​​to enable statistical evaluation based on the stored values, for example to determine a reference range for impedance measurements. Reference values ​​and tolerance ranges can also be stored in the memory module. The evaluation module can compare the impedance measured by the sensor module with the reference values.

[0043] Additionally, the test stand can be equipped with a communication module and configured to exchange data with other components on the production line. In this way, any micro-shorts detected can be reported to other devices on the production line, allowing the defective electrode assemblies to be sorted or further processed.

[0044] The invention is further solved by a production line equipped with a test stand of the above type. [Brief explanation of the drawings]

[0045] Further advantages and features of the present invention will become apparent from the following description and drawings of exemplary embodiments, which are not intended to be understood in a limiting sense, in which: FIG. 1 is a diagrammatic view of a test stand according to the invention in a production line according to the invention; FIG. 2 is a block diagram of the method according to the invention. DETAILED DESCRIPTION OF THE INVENTION

[0046] FIG. 1 shows a portion of a manufacturing line 10 for manufacturing galvanic elements.

[0047] The manufacturing line 10 consists of a conveyor belt 12 on which a plurality of electrode assemblies 14 are disposed.

[0048] The electrode assembly 14 includes at least one anode, at least one cathode, and a separator between each anode and cathode, which are loosely arranged relative to one another, and the electrode assembly 14 includes the same number of cathodes and anodes.

[0049] In the embodiment shown, each of the electrode assemblies 14 includes at least 50 cathodes and at least 50 anodes, preferably at least 80 cathodes and at least 80 anodes, forming the electrode assemblies 14 as cell stacks, although in principle the electrode assemblies 14 could also be cell coils.

[0050] Each electrode assembly 14 has a cathode conductor flag 16 and an anode conductor flag 18. The cathode conductor flag 16 or the anode conductor flag 18 is designed as a collection of individual conductors of the cathodes or anodes, so that all cathodes can be electrically contacted via the cathode conductor flag 16, and all anodes of each electrode assembly 14 can be electrically contacted via the anode conductor flag 18.

[0051] The cathode and the anode each have at least one active material.

[0052] In principle, all materials known in the art can be used as the cathode active material (positive electrode active material), such as LiCoO2, lithium-nickel-cobalt-manganese compounds (abbreviated as NCM or NMC), lithium-nickel-cobalt-aluminum-oxide (NCA), lithium-iron phosphate, and other olivine compounds, as well as lithium manganese oxide spinels (LMO). Also usable are so-called over-lithium-ion layered oxides (OLO).

[0053] The cathode active material may also contain a mixture of two or more of the lithium-containing compounds described above.

[0054] In the embodiment shown, the cathode active material is NMC622 (LiNi 0.6 Mn 0.2 Co 0.2 O2).

[0055] Additionally, the cathode active material may further comprise additives, such as carbon or carbon-containing compounds, particularly conductive carbon black, graphite, carbon nanotubes (CNTs), and / or graphene, etc. Such additives can function as conductivity modifiers to enhance electrical conductivity within the electrode.

[0056] The cathode may further comprise a binder (electrode binder) that holds the active material and, optionally, the conductive material (such as conductive carbon black) together and further binds them to the current collector foil. The electrode binder may be selected from the group consisting of polyvinylidene fluoride (PVdF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), polyethylene oxide (PEO), polytetrafluoroethylene (PTFE), polyacrylate, styrene butadiene rubber (SBR), polyvinylpyrrolidone (PVP), carboxymethyl cellulose (CMC), and mixtures and copolymers thereof.

[0057] The anode active material (negative electrode active material) can be selected from the group consisting of lithium metal oxides such as lithium titanate, metal oxides such as Fe2O3, ZnO, ZnFe2O4, carbonaceous materials such as graphite, synthetic graphite, natural graphite, graphene, mesocarbon, doped carbon, hard carbon, soft carbon, fullerene, mixtures of silicon and carbon, silicon, silicon suboxide ("SiO"), silicon alloys, lithium alloys, and mixtures thereof. Pure lithium anodes are also possible.

[0058] As the electrode material for the negative electrode, niobium pentoxide, tin alloy, titanium dioxide, titanate, tin dioxide, silicon, etc. can be used.

[0059] In the embodiment shown, the anode active material is graphite.

[0060] In addition to the anode active material, the anode may further include other components and additives, such as a carrier, a binder, a conductivity enhancer, etc. The additional components and additives may be any of the compounds and materials known in the art.

[0061] The separator is an open-porosity "non-woven" separator and can be composed of fibers of a plastic selected from the group consisting of polyimide, polyester, aramid, copolymers and mixtures thereof.

[0062] In the embodiment shown, the separator is a nonwoven fabric formed from polyester fibers.

[0063] The manufacturing line 10 further comprises a test stand 20 according to the present invention for testing the electrode assemblies 14 .

[0064] The test stand 20 includes a sensor module 22 that can electrically contact, by means of contacts 24, the cathode conductor flag 16 and the anode conductor flag 18 of the electrode assembly 14 being tested to perform impedance measurements.

[0065] The test stand 20 further includes a memory module 26 , an evaluation module 28 , and a communication module 30 .

[0066] The following describes a method according to the present invention for detecting micro-shorts in the electrode assembly 14.

[0067] First, the electrode assembly 14 is prepared (step S1 in FIG. 2).

[0068] Conveyor belt 12 is arranged to move electrode assemblies 14 disposed on conveyor belt 12 in the direction indicated by arrow A in FIG.

[0069] Thus, each of the electrode assemblies 14 is guided successively to the level of the above-mentioned test stand 20 so that the cathode conductor flag 16 and the anode conductor flag 18 of the electrode assembly can be electrically contacted by the contacts 24 of the sensor module 22.

[0070] Next, the sensor module 22 measures the impedance of the electrode assembly using an alternating current with a frequency of 1 kHz (step S2 in FIG. 2).

[0071] The measurements are transmitted by the sensor module 22 to a memory module 26, which also stores previously determined reference values.

[0072] The evaluation module 28 then compares the measured value with the reference value contained in the memory module 26. If the measured value deviates from the reference value by more than a predefined tolerance, which is also stored in the memory module 26, then in the illustrated embodiment a micro-short in the electrode assembly 14 is detected (step S3 in FIG. 2).

[0073] In this case, the test stand 20 can communicate with further equipment (not shown) in the production line 10 that sorts out defective electrode assemblies 14 by means of the communication module 30. To this end, the communication module 30 may be arranged for wireless and / or wired communication with the further equipment in the production line 10.

[0074] Table 1 shows a comparison of impedance measurements made in accordance with the present invention with conventional "HiPoT" tests. Electrode assemblies with one cathode, one anode, and one separator were compared.

[0075] Before the first charging with the galvanic element, the electrode assembly is tested using both test methods.

[0076] In the HiPoT test, a high voltage of 500 V is applied to the electrode assembly. If a current flows as a result, the corresponding electrode assembly is determined to have failed.

[0077] As can be seen from Table 1, in the case of the HiPoT test, all 10 electrode assemblies are classified as faulty before electrolyte filling and formation, but the same electrode assemblies are detected as functional by the method according to the present invention by impedance measurements.

[0078] After assembling the electrode assembly into the housing and filling it with electrolyte to form the galvanic element, the electrode assembly was confirmed to function correctly in all cases.

[0079] Therefore, when separators with open porosity are used, the method according to the invention makes it possible to detect fine short circuits earlier and at the same time more reliably than is possible with conventional HiPoT tests.

[0080] [Table 1]

[0081] After forming the galvanic element produced by the tested electrode assembly, it was checked whether the cell voltage had further decreased compared to the expected self-discharge after 14 days of rest. All cells previously checked by the method of the present invention showed no voltage drop and were therefore confirmed to be functioning properly. The present invention includes the following items. [Item 1] 1. A method for detecting micro-shorts in an electrode assembly (14), comprising: - providing an electrode assembly (14) having at least one anode and at least one cathode with an open porous separator interposed between each anode and cathode; - measuring the impedance of the electrode assembly (14), and - comparing the measured impedance with a reference value; wherein the electrode assembly (14) is unlaminated and the impedance measurement is performed prior to the introduction of the electrolyte and the placement of the electrode assembly (14) in the galvanic element. [Item 2] Item 10. The method according to item 1, characterized in that a micro-short circuit is detected when the measured impedance deviates from the reference value by more than a predetermined tolerance. [Item 3] 3. The method according to item 1 or 2, characterized in that the separator is a nonwoven fabric, and the separator preferably comprises fibers formed from a plastic selected from the group consisting of polyimide, polyester, aramid, copolymers and mixtures thereof. [Item 4] 4. The method according to any one of items 1 to 3, characterized in that the separator has a thickness in the range of 8 to 25 μm, preferably 10 to 15 μm. [Item 5] At least one cathode and at least one anode are at least 800 mm 2 , preferably at least 5000 mm 2 , more preferably at least 7000 mm 2 , at least 8000mm 2 Or at least 10000mm 2 5. The method according to any one of items 1 to 4, wherein the electrode area is [Item 6] The electrode area is 800 mm 2 ~800,000mm 2 , preferably 5000 mm 2 ~20000mm 2 or 7200mm 2 ~16200mm 2 Item 6. The method according to item 5, wherein the range is [Item 7] 7. The method according to any one of items 1 to 6, characterized in that the electrode assembly (14) has exactly one cathode and one anode with exactly one separator, or the electrode assembly (14) has at least five anodes and at least five cathodes. [Item 8] 8. The method according to any one of items 1 to 7, wherein the electrode assembly (14) is a cell stack or a cell coil. [Item 9] 9. The method according to any one of items 1 to 8, characterized in that an alternating current or an alternating voltage having a frequency in the range of 500 Hz to 1.5 kHz, in particular 1 kHz, is used for measuring the impedance. [Item 10] A test bench for checking an electrode assembly (14), adapted to carry out the method according to any one of items 1 to 9. [Item 11] Item 11. A manufacturing line for a galvanic element including an electrode assembly (14), comprising the test bench (20) according to item 10.

Claims

1. A method for detecting micro-shorts in an electrode assembly (14), comprising: - providing an electrode assembly (14) having at least one anode and at least one cathode with an open porous separator interposed between each anode and cathode; - measuring the impedance of the electrode assembly (14), and - comparing the measured impedance with a reference value, wherein the electrode assembly (14) is unlaminated and the impedance measurement is performed prior to the introduction of the electrolyte and the placement of the electrode assembly (14) in the housing; The method, wherein the separator is a nonwoven fabric, the separator comprising fibers formed from a plastic selected from the group consisting of polyimide, polyester, aramid, and mixtures thereof.

2. 2. The method of claim 1, wherein a micro-short is detected when the measured impedance deviates from a reference value by more than a predetermined tolerance.

3. The method of claim 1 or 2, characterized in that the separator comprises fibers formed from polyester.

4. 4. The method according to claim 1, wherein the separator has a thickness in the range of 8 to 25 μm.

5. 5. The method according to claim 1, wherein the at least one cathode and the at least one anode have an electrode area of ​​at least 800 mm 2 .

6. The electrode area is 800 mm ２ The method according to claim 5, characterized in that the surface area is in the range of 800,000 mm2.

7. 7. The method according to claim 1, wherein the electrode assembly (14) has exactly one cathode and one anode with exactly one separator, or the electrode assembly (14) has at least five anodes and at least five cathodes.

8. The method according to any one of claims 1 to 7, characterized in that the electrode assembly (14) is a cell stack or a cell coil.

9. 9. A method according to claim 1, wherein an alternating current or voltage with a frequency in the range of 500 Hz to 1.5 kHz is used for measuring the impedance.

10. A test bench for checking electrode assemblies (14), adapted to carry out the method according to any one of claims 1 to 9.

11. A manufacturing line for galvanic elements including electrode assemblies (14), comprising the test bench (20) of claim 10.

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