Method and device for checking the quality of an electrochemical cell

Abstract

The invention proposes a method for checking the quality of an electrochemical cell (1), having the following method steps: A) providing an electrochemical cell (2); B) positioning the cell (2) between at least two fixing elements (3, 4), the cell preferably being compressed and at least one of the fixing elements (3, 4) being movably mounted; C) making electrical contact with the cell (2) in order to initiate an electrical charging or discharging process of the cell (2); D) measuring at least one position and / or change in position of the movably mounted fixing element (3, 4) based on a change in cell volume during the charging or discharging process; E) determining a cell quality based on the measured position or change in position.

Description

[0001] title

[0002] Method and apparatus for quality testing of an electrochemical cell

[0003] Description

[0004] The invention relates to a method and a device for quality testing of an electrochemical cell.

[0005] Electrochemical cells play a crucial role in a wide range of industrial applications, as they enable the efficient conversion of chemical energy into electrical energy and vice versa. They can be used, for example, as batteries or accumulators in numerous industries, from consumer electronics to electric vehicles and energy storage systems.

[0006] For the reliable use of electrochemical cells, it is necessary to examine their actual properties both during manufacturing and as part of a final quality inspection, and to evaluate whether they meet the required specifications. Quality testing typically involves measuring the capacity or self-discharge rate of a battery cell. However, this only allows for the determination of properties that relate to the entire battery cell and does not provide information about local defects in the battery cell or one of its components. Consequently, production errors affecting only one area or component of the battery cell cannot be immediately detected, and no measures can be taken to improve quality-critical manufacturing steps and thus reduce reject rates.

[0007] The object of the invention is to improve the quality control of electrochemical cells, to facilitate the detection of defective production steps, and to reduce the reject rates in the manufacture of electrochemical cells. This object is achieved by means of a method according to claim 1 and a device according to claim 12. Advantageous embodiments are the subject of dependent claims.

[0008] The method according to the invention serves for the quality testing of an electrochemical cell and comprises the following process steps:

[0009] A) Providing at least one electrochemical cell;

[0010] B) Positioning the electrochemical cell between at least two fixing elements, wherein the cell is preferably compressed and wherein at least one of the fixing elements is movably mounted;

[0011] C) Electrical contacting of the cell to generate an electrical charging or discharging process of the cell;

[0012] D) Measuring at least one position and / or change in position of the movable fixing element as a function of a cell volume change during the charging or discharging process of the electrochemical cell;

[0013] E) Determining cell quality depending on the measured position and / or change in position.

[0014] The method according to the invention is based on the finding that electrochemical cells undergo a change in volume during and, in particular, as a result of their charging and discharging processes. Investigations have shown that quality-relevant characteristics of the electrochemical cell have a significant influence on the extent of the cell volume change during the charging or discharging process, so that, conversely, it is possible to infer the cell quality from the volume change.

[0015] Furthermore, investigations have shown that it is not necessary to characterize the cell volume change directly based on the electrochemical cell and, in particular, on a change in the shape or volume of the cell body. Instead, it is sufficient to determine the position and / or change in position of at least one movable element, referred to here as the fixing element, which may be in direct or indirect contact with the cell body. This is advantageous because the movement of the fixing element due to the cell volume change is limited to a translational displacement and / or a rotational twist of the fixing element, which is easily characterizable. Thus, despite a sometimes geometrically complex deformation of the electrochemical cell resulting from the cell volume change, preferably no deformation of the fixing element occurs, so that this does not need to be evaluated.

[0016] In a simple example, a tilting of the movable fixing element can be attributed to an inhomogeneous change in cell volume, which in turn can be traced back to a corresponding inhomogeneity of electrochemical processes or an inhomogeneous distribution of chemically active material within the cell, particularly within the cell body. In particular, this allows for the spatially resolved determination of a quality defect with respect to the electrochemical cell, especially its dimensions and geometry. Conversely, a translational displacement of the fixing element can indicate comparatively homogeneous electrochemical processes within the cell and a correspondingly uniform distribution of chemically active material.

[0017] The term cell volume change can be understood as any change in the volume of the electrochemical cell. This can include, in particular, a change in the total volume of the cell body and / or its geometry.

[0018] It is also conceivable that the change in cell volume may be localized, particularly within a specific region of the cell body. Specifically, the change in cell volume may include cell elongation and / or cell compression, which can occur particularly locally.

[0019] The term "position," measured in process step D), can be understood synonymously with a translational and / or rotational position of the movable fixing element. A change in position can accordingly be understood synonymously with a translational and / or rotational change in the position of the movable fixing element.

[0020] The invention is not fundamentally limited to the type of electrochemical process used.

[0021] The process is carried out in the cell. In particular, it can be electrochemical.

[0022] The cell may be a liquid electrolyte cell or a solid-state cell. Studies have shown that the cell volume change described above occurs in principle in all industrially available cells and can be taken into account for a quality assessment of the cell in question.

[0023] The invention is not limited to the design of the fixing elements. It is particularly within the scope of the invention that the fixing elements are either made in one piece or in multiple parts. The fixing elements can, in principle, be made of any material, as long as they preferably have a significantly higher stiffness and / or strength than the electrochemical cell. In particular, the fixing elements can be made of metal, for example aluminum, or plastic.

[0024] It is essential that at least one of the fixing elements is movably mounted. A movable mounting, as defined in the invention, can include the adjustability of the respective fixing element relative to the other fixing element or to another component of the device or electrochemical cell used. It is also within the scope of the invention that the at least two fixing elements are each movably mounted, so that a change in cell volume can affect the adjustment of both fixing elements, and this is measured, particularly in process step D).

[0025] Electrical contacting of the electrochemical cell to generate the electrical charging or discharging process can occur at virtually any time during or after the electrochemical cell's manufacture. Preferably, the process is carried out after cell assembly. Advantages arise when the process is performed during the so-called formation and / or aging and / or end-of-line testing of the cell. In particular, the electrochemical cell is contacted at its electrodes, especially at the electrical contacts.

[0026] In one possible implementation of the inventive method during the formation of the electrochemical cell, the cell is subjected to initial formation after its assembly. This includes several electrical charging and discharging cycles, which can be carried out over several days. Preferred cycle rates are up to one-twentieth of an ampere of the nominal capacity (C / 20) of the electrochemical cell. By applying a comparatively low current rate, the electrochemical cell is protected, while irreversible initial activation or passivation processes can take place. In conventional lithium-ion battery cells, for example, the solid electrolyte interphase (SEI) is formed. This protects the anode from further damage caused by contact with an electrolyte.The formation of organic material within the SEI (Single Electrode Interconnect) by the electrolyte and inorganic material by the electrode creates a solid layer that causes the battery cell to expand and can lead to the cell volume change measurable at the movable fixing element. In addition to the solid components of the SEI, gas also forms at the contact points between the electrode and electrolyte, which can likewise contribute to the cell volume change. In particular, by performing process step E), the spatially resolved distribution of chemically active components within the electrochemical cell, and especially the homogeneity of this distribution, can be determined. Additionally or alternatively, the spatially resolved gas distribution within the electrochemical cell can also be determined.

[0027] It is also conceivable that the inventive method is carried out during end-of-line testing, in which the electrochemical cell undergoes a plurality of charge and discharge cycles, during which, for example, a cell capacity is determined. Investigations have also shown during this phase of cell manufacturing that a change in cell volume occurs, which can be determined in order to draw spatially resolved conclusions about the cell quality, in particular about material distribution or local defects within the cell.

[0028] Measuring the position and / or change in position of the movable fixing element can be done in virtually any way. In particular, the measured position can be an absolute position and / or its change in a stationary and / or device-fixed coordinate system. It is also conceivable that the measured position is a relative position and / or its change, for example, relative to a previously measured position and / or another technical component, especially relative to the other fixing element and / or the measuring device used. Compared to a method in which the cell volume change is determined directly at the cell body, measuring the position and / or change in position of the movable fixing element is simplified in both execution and evaluation.In particular, at least one displacement sensor or distance sensor can be used to determine the position and / or change in position, which interacts metrologically with at least the movable fixing element. Specifically, the measuring device can be arranged on the side of the other fixing element facing the movable fixing element.

[0029] Within the scope of the invention, cell quality can be determined using a model that specifies a relationship between the position and / or change in position of the at least one fixation element and cell elongation, and / or a relationship between the position and / or change in position of the at least one fixation element and cell quality. The model can be a mathematical model developed based on experimental or simulation-based investigations. Additionally or alternatively, the model can be based on an analytically determined relationship between a change in cell volume and / or a cell property. It is also within the scope of the invention for the model to be based on artificial intelligence and to specify at least one of the aforementioned relationships.

[0030] In a preferred further development, the electrochemical cell provided in process step A) is a flat cell. The two fixing elements are each essentially planar and clamp the electrochemical cell in process step B).

[0031] The aforementioned further development is based on the understanding that quality-relevant properties of an electrochemical cell, particularly in the case of flat cells, have a significant influence on cell volume changes. Within the scope of this advantageous further development, a flat cell can be considered a type of electrochemical cell that extends essentially flat along a main plane. Specifically, this can be a pouch cell or a prismatic cell, which are common industrial forms of flat cells. The planar design of the two fixing elements makes it easy to align the cell body between them and fix it in place for the process.

[0032] In an advantageous further development, the cell body is aligned, at least in process step D), with a main extension plane essentially parallel to a direction of gravity.

[0033] According to the aforementioned refinement, the cell body is positioned essentially upright for the purpose of carrying out the procedure. This allows a gas pocket, which can form, for example, in liquid electrolyte cells, to accumulate at an upper edge of the cell due to a density difference compared to the other materials inside the cell, and to be spatially separated from the other materials, especially the electrolyte. This makes it possible to take the influence of the gas pocket on the cell volume change into account through measurement and, in particular, to compensate for it during computational analysis.

[0034] In an advantageous further development, in process step B) the movable fixing element is pressed against the cell body with a contact force.

[0035] Unlike an arrangement where the fixing elements are moved into a defined position to clamp the cell body, the embodiment described above provides for a defined clamping force to be exerted on the cell body. Such clamping of the electrochemical cell ensures that any change in cell volume is directly transmitted to the movable fixing element. This allows even comparatively small changes in cell volume to be measured, particularly when the fixing element moves less than 1 micrometer, especially during tilting and / or translational adjustment. It is particularly advantageous if the clamping force is adjustable. This makes it possible to determine the extent of the cell volume change against resistance, thus preferably allowing the setting of a minimum required cell extension force.This can be used to measure only those cell volume changes that result from exceeding a minimum internal pressure. Any actuator can be used to apply the contact force, and it can be force-controlled.

[0036] In an advantageous embodiment, the movable fixing element is mounted so that it is spatially free to move relative to the other fixing element. This includes, in particular, rotational tilting and / or translational displacement of the movable fixing element. In process step D), any tilting and / or axial positional change of the movable fixing element relative to the other fixing element is measured.

[0037] The further development described above is based on the understanding that the change in position of the movable fixing element can occur in the form of a tilting and / or axial position change, each of which can be assigned to a specific cell quality. A tilting of the movable fixing element can be considered a rotation of the fixing element around at least one tilting axis, which runs orthogonally to an axis along which the fixing elements are arranged. An axial position change can be considered a change in distance along an axis along which the two fixing elements are arranged.

[0038] In particular, in process step D), a rotational tilting and a translational displacement of the movable fixing element can occur simultaneously as a result of the cell volume change. Specifically, a pivot bearing can be designed between the movable fixing element and an actuator, by means of which the clamping force is applied, enabling tilting of the movable fixing element. Translational displacement of the movable fixing element can occur along an adjustment axis of the actuator and can be guided by the actuator. This eliminates the need for additional axial guidance of the movable fixing element.

[0039] The actuator's contact force, exerted against the movable fixing element, presses the element against the electrochemical cell and maintains contact with the cell body even during tilting and / or translational displacement. This enables reliable measurement of cell volume changes.

[0040] In an advantageous embodiment, the movable fixing element is subjected to a clamping force by means of a fluidic working cylinder. The movable fixing element and the working cylinder can be tilted relative to each other by means of two detachable and correspondingly designed spherical elements. Additionally or alternatively, the movable fixing element is axially adjustable along an adjustment axis of the fluidic working cylinder.

[0041] The working cylinder can be designed as a hydraulic or pneumatic actuator, by means of which the clamping force can be exerted on the movable fixing element. The clamping force can preferably be adjusted via pressure control, in particular by means of a pressure reducer. The two correspondingly designed spherical elements can each be considered as cooperating bearing elements, one of which is concave and the other convex, and whose geometries and dimensions are selected such that they can interlock and form a pivot bearing for tilting the movable fixing element. It is preferably possible to disconnect and reconnect the spherical elements as required.In a simple embodiment, one of the cap elements has the shape of a spherical element, the surface of which is partially designed to support a correspondingly shaped spherical shell, which represents the other cap element. Preferably, at least one tilting axis of the movably mounted fixing element runs through one of the cap elements or a geometric center point of a curved surface formed by them.

[0042] It is a beneficial further development that one of the spherical elements has a closed concave surface that corresponds to a convex surface of the other spherical element. It is also conceivable that at least one of the spherical elements is formed by a plurality of partial surfaces, which are specifically designed to meet each other. This reduces the total area in which the spherical elements are in contact with each other when connected, thus also reducing frictional resistance compared to a closed spherical surface.

[0043] In an advantageous further development, the movable fixing element is provided with a force measuring device in the area of ​​a force application point of the contact force, by means of which the contact force is monitored at least during process step D).

[0044] The force transducer enables the measurement of the contact force acting on the movable fixing element during the measurement of its position and / or change of position. In particular, the monitored contact force can be used to control the actuator that applies the contact force to the movable fixing element. This results in advantages regarding the accuracy of the process. Additionally or alternatively, a pressure-sensitive film can be inserted between the movable fixing element and the cell body, allowing the prevailing contact pressure on the electrochemical cell to be measured.

[0045] In an advantageous further development, process step D) is carried out using an optical measuring device.

[0046] The use of the optical measuring device is advantageous because the position and / or change in position of the movable fixing element can be detected without contact. Compared to a measuring method in which the position and / or change in position is detected tactilely, the movement of the movable fixing element is not affected, thus enabling increased accuracy during the execution of process step D).

[0047] In an advantageous embodiment, the optical measuring device comprises at least two optical measuring heads which determine the position and / or the change in position of the movable fixing element at two different measuring positions. The embodiment described above is based on the finding that two measuring heads may be sufficient to determine a tilting of the movable fixing element about a tilting axis and / or translational displacement. In particular, the measuring heads are arranged such that they interact metrologically with two different edge regions of the movable fixing element.This makes it possible to reliably detect a tilting of the fixing element when the tilting of the movable fixing element occurs about a tilting axis that lies between the edge regions of the movable fixing element, particularly in the area of ​​the point of application of the contact force that can be exerted on the movable fixing element. In particular, the optical measuring heads can each be integrated into one of the two fixing elements, especially into the fixing element that is arranged opposite the movable fixing element.

[0048] In an advantageous further development, the optical measuring device has at least three measuring heads which determine the position and / or the change in position of the movable fixing element at three different measuring positions.

[0049] In particular, the measuring heads are arranged such that they interact metrologically with three different edge regions of the movable fixing element. This makes it possible to reliably detect a tilting of the fixing element when it occurs around two tilting axes. The arrangement of preferably at least three single-point sensors allows the movement of the plate in space to be unambiguously characterized.

[0050] Preferably, the optical measuring heads are chromatically confocal single-point sensors, which are arranged, in particular, at uniform intervals along a circumference whose center lies in the area of ​​the point of application of the contact force exerted on the movable fixing element. Chromatically confocal single-point sensors are advantageous for carrying out process step D) because they have a good measuring resolution, which can be below 1 micrometer. Furthermore, they each have a large measuring range, which can be on the order of several millimeters, making it possible to determine cell volume changes over a correspondingly large area. Moreover, such sensors are sufficiently insensitive to the temperature or air pressure fluctuations typically encountered during the testing of electrochemical cells.

[0051] The sensors can be mounted in a position that allows them to be moved relative to the movable fixing element and can be positioned before carrying out process step D) such that the fixing element is located in the measuring range of the sensors during the cell volume change.

[0052] In an advantageous further development, the two fixing elements are connected to each other before process step B) by means of a screw-and-spring connection, which pre-tensions the electrochemical cell at least in process step B) and which is released at the latest after the application of the contact force, in particular by the working cylinder.

[0053] To ensure precise alignment and easy handling of the electrochemical cell, the two fixing elements can be joined together using the aforementioned screw-and-spring connection. The springs exert a defined force on the electrochemical cell, compressing it. During operation, the screw-and-spring connection is released once the working cylinder has built up the necessary clamping force.

[0054] As explained above, the problem is also solved by a device according to claim 12. The device according to the invention is designed for quality control of an electrochemical cell and comprises two fixing elements which enclose a space provided for receiving the electrochemical cell. At least one of the two fixing elements is movably mounted relative to the other fixing element. Furthermore, the device comprises a measuring device which is designed to detect the position and / or change in position of the movably mounted fixing element when a cell is held in the space during an electrical charging or discharging process in one or more positions.Furthermore, the device includes an evaluation unit which is connected to the measuring device via a signal connection and is designed to determine cell quality depending on the measurable position or change in position of the movable fixing element.

[0055] It is conceivable to combine several devices according to the invention in such a way that several electrochemical cells can be automatically included in the devices and tested for their quality.

[0056] It is within the scope of the invention that the fixing elements are interchangeable. It is also conceivable that the fixing elements are each equipped with one or more temperature sensors, by means of which, in particular, a comprehensive temperature measurement can be carried out. For this purpose, the fixing elements can be provided with one or more bores intended for receiving thermocouples. It is also possible to equip the fixing elements with temperature control elements suitable for cooling or heating the respective fixing element and, in particular, the cell. This allows different temperature levels to be set as needed during quality control and their influence on the cell volume change to be determined.

[0057] As already explained in connection with the method according to the invention, the position and / or change in position of the fixing element can be measured using one or more confocal sensors; however, other types of non-contact distance sensors can also be integrated. Furthermore, it is possible to position one or more pressure sensors between the electrochemical cell and the fixing element. Overall, a large number of different physical quantities can be detected with a single device.

[0058] Furthermore, multiple electrochemical cells can be stacked within the device, allowing their volume changes to be superimposed and simultaneously measured. To differentiate individual cells, they can be individually and sequentially charged or discharged and tested alternately. Another alternative setup involves a cell stack with a plate inserted between each pair of adjacent cells. The position of these plates is measured by distance sensors, enabling the simultaneous measurement of multiple cells.

[0059] In particular, the measuring device, which is designed to detect the position and / or change in position of the movable fixing element of a cell held in the space during an electrical charging or discharging process, can be arranged on the other fixing element. This allows the device to have a simple and compact design overall, eliminating the need for retaining elements to hold the measuring device. Furthermore, such an arrangement has a positive effect on the effects of thermal distortion on the device.

[0060] Preferably, the device according to the invention is suitable for carrying out the method according to the invention or an advantageous further development thereof. In this respect, the descriptions of the method according to the invention apply accordingly with regard to the possible embodiments of the device and the advantages achievable therewith.

[0061] Advantageous embodiments of the invention are explained below with reference to the figures. These show:

[0062] Figure 1 shows a device for quality testing of an electrochemical cell in views a) and b).

[0063] In the production of electrochemical cells, such as rechargeable batteries, it is crucial to ensure they possess the desired properties to prevent malfunctions during operation. One type of quality control, typically performed after the components of such an electrochemical cell have been assembled and known as end-of-line testing, can include determining the cell's capacity. For this purpose, the electrochemical cell is electrically contacted at its electrodes, and its charging and discharging behavior is characterized. However, a disadvantage of such end-of-line testing is that the electrochemical cell's overall quality can only be characterized uniformly, and no conclusions can be drawn about the quality of individual components or specific areas within the cell.

[0064] Figure 1 shows in views a) and b) a device 1 which is designed to carry out a method for quality testing of an electrochemical cell 2 and in particular enables a spatially resolved conclusion about the quality of its components or cell areas.

[0065] As shown in view a), the device 1 has a first fixing element 3 and a second fixing element 4, between which the electrochemical cell 2 is mounted. As explained in detail below, the second fixing element 4 is movably mounted relative to the first fixing element 3.

[0066] The first fixing element 3 is equipped with three distance sensors in a circumferential edge region. These sensors are each designed as optical chromatic confocal measuring sensors 5 and each serves to measure the distance between the first fixing element 3 and the opposite, movably mounted second fixing element 4. For clarity, only one of the chromatic confocal measuring sensors 5 is labeled with a reference symbol.

[0067] In a manner not shown in detail here, the device comprises a total of three measuring sensors 5, which are arranged circumferentially distributed around the first fixing element 3 in a surrounding edge region. This makes it possible to detect any relative position of the second fixing element 4 with respect to the first fixing element 3, which can be a displacement and / or a tilt. It is also possible to detect a change in the relative position. In particular, the tilt can be detected and uniquely characterized not only about one tilt axis, but about two tilt axes. This is facilitated by the three measuring sensors 5, since it is possible to uniquely describe any position of the movable fixing element 4 relative to the first fixing element 3 by means of three measurable distances. It is also conceivable that an absolute position of the second fixing element 4 or a change therein can be determined.The second fixing element 4 can be subjected to a contact force on a side facing away from the first fixing element 3, so that the electrochemical cell 2 arranged between the first and second fixing elements 3 and 4 can be subjected to mechanical pressure and compressed. A pneumatic working cylinder 6 is provided for this purpose, which is mechanically coupled to the second fixing element 4 via its piston rod.

[0068] In addition to its function as an actuator, the pneumatic working cylinder 6 also serves to movably support the second fixing element 4. For this purpose, a convexly shaped bearing ball 7, which has a spherical cap shape in some areas, is arranged at one end face of the lifting rod. The bearing ball 7 is detachably connected to a convexly shaped shell part 8, which has a negative cap shape corresponding to the cap shape of the bearing ball 7. In the assembled state, the bearing ball 7 and the shell part 8 form a pivot bearing, which allows free rotation of the second fixing element 4 relative to the other components of the device 1, in particular the first fixing element 3. The resulting tilting axes, which are oriented in the plane of Figure 1 and orthogonally to it, pass through the pivot bearing formed by the bearing ball 7 and the shell part 8.

[0069] The second fixing element 4 is connected to a load cell 9, which makes it possible to monitor and, if necessary, regulate the contact force exerted by the working cylinder 6. For this purpose, the load cell can be connected to a control system of the working cylinder 6 in a manner not shown in detail.

[0070] The device 1 described above serves, as mentioned above, for quality control of the electrochemical cell 2. For this purpose, the electrochemical cell 2 is electrically contacted at its electrodes in a manner not shown in detail here, so that a charging or discharging process is possible. As investigations have shown, a change in cell volume occurs during the charging or discharging process, which depends on the properties of the electrochemical cell. If the cell 2, clamped by the fixing elements, expands unevenly, particularly at a single point, the fixing element 4 can tilt relative to the fixing element 3 of the device 1, thereby indicating an inhomogeneity in the structure of the cell 2. If, on the other hand, the cell 2 expands uniformly, the air volume in the working cylinder 6 acts like an air spring, and the movable fixing element

[0071] 4 is moved axially in the longitudinal direction of the piston, without any tilting taking place.

[0072] To determine cell quality, the confocal sensors are connected to an evaluation computer 10. This evaluation computer 10 implements an evaluation routine that uses the distance data from the measuring sensors 5 to infer cell quality. For this purpose, the evaluation routine uses a mathematical model, which may have been previously determined experimentally or analytically, and which specifies a relationship between the relative adjustment between the first and second fixing elements 3 and 4, respectively, and the properties of the electrochemical cell 2. Specifically, the evaluation routine processes the distance data in such a way that the quality information is spatially resolved and output with respect to the geometry of the electrochemical cell 2. This is illustrated in view b) of Figure 2.

[0073] Before electrically contacting the electrochemical cell 2 and pressurizing it by means of the working cylinder 6, it is possible, in a manner not shown in detail here, to connect the fixing elements 3 and 4 to each other by means of a screw-spring connection and to pre-tension the electrochemical cell 2.

[0074] It is within the scope of the possible application of the device 1 that it is carried out during any test procedure of an assembled electrochemical cell 2. This includes, in particular, its formation and end-of-line testing. In particular, any other parameter can be determined simultaneously, especially an electric current or an electric voltage during the charging or discharging process of the cell.

[0075] It is conceivable that the components of the device 1 shown in Figure 1 can be replaced with equivalent means. In particular, it is conceivable to use any other force-controlled actuator instead of the working cylinder 6. Robots may be suitable for this purpose in the industrial production of battery cells. It is also conceivable that, instead of the embodiment shown in Figure 1, several cells 1 can be tested simultaneously. For this purpose, they can be arranged in a common plane so that the fixing elements 3 and 4 are each in contact with several cells, and any uneven expansion of the cells can also be determined by measuring the distance between the fixing elements. Likewise, several cells can be stacked and placed between the fixing elements 3 and 4 and subjected to a charging or discharging process at staggered intervals.The expansion of the cells can be determined as a function of time based on the measurable values ​​relating to a tilting or displacement of the movable fixing element.

Claims

Claims 1. Method for quality control of an electrochemical cell (1) comprising the following process steps: A) Providing an electrochemical cell (2); B) Positioning the cell (2) between at least two fixing elements (3, 4), wherein the cell is preferably compressed, and wherein at least one of the fixing elements (3, 4) is movably mounted; C) Electrical contacting of the electrochemical cell (2) to generate an electrical charging or discharging process of the cell (2); D) Measuring at least one position and / or change in position of the movable fixing element (3, 4) as a function of a change in cell volume during the charging or discharging process of the electrochemical cell; E) Determining cell quality depending on the measured position and / or change in position.

2. Method according to claim 1, wherein the electrochemical cell (2) provided in process step A) is a flat cell, in particular a pouch cell or a prismatic cell, and the two fixing elements (3, 4) are each substantially planar and clamp the electrochemical cell (2) in process step B).

3. Method according to claim 2, wherein a cell body of the electrochemical cell (2) is oriented at least in process step D) with a principal extension plane substantially parallel to a direction of gravity.

4. Method according to one of the preceding claims, wherein in process step B) the movable fixing element is pressed against the electrochemical cell with a contact force which is in particular adjustable.

5. The method of claim 4, wherein the movable fixing element (3, 4) is mounted so that it is freely movable relative to the other fixing element (3, 4), in particular so that it can be tilted rotationally and / or displaced translationally, and in process step D) a tilting and / or axial change in position of the movable fixing element (3, 4) relative to the other fixing element (3, 4) is measured.

6. Method according to claim 5, wherein the movable fixing element (3, 4) is subjected to the clamping force by means of a fluidic working cylinder (6), wherein the movable fixing element (3, 4) and the working cylinder (6) are tiltable relative to each other by means of two detachable and corresponding spherical elements (7, 8) and / or wherein the movable fixing element (3, 4) is axially adjustable along an adjustment axis of the fluidic working cylinder (6).

7. Method at least according to claim 4, wherein the movably mounted fixing element (3, 4) is provided with a force measuring device (9) at least in the area of ​​a force application point of the contact force, by means of which the contact force is monitored at least during method step D) and in particular the contact force of the fluidic working cylinder (6) is controlled.

8. Method according to one of the preceding claims, wherein method step D) is carried out by means of an optical measuring device (9).

9. Method according to claim 8, wherein the optical measuring device (9) comprises at least two optical measuring heads, in particular two chromatic confocal sensors, which determine the position and / or the change in position of the movable fixing element (3, 4) at two different measuring positions.

10. Method according to claim 9, wherein the optical measuring device (5) comprises at least three measuring heads, in particular three chromatic confocal sensors, which determine the position and / or the change in position of the movable fixing element (3, 4) at three different measuring positions.

11. Method at least according to claim 4, wherein the two fixing elements are connected to each other before process step B) by means of a screw-and-spring connection, which preloads and in particular compresses the electrochemical cell (2) at least in process step B) and which is released at the latest after the application of the contact force, in particular by the working cylinder (6).

12. Device for quality testing of an electrochemical cell, comprising two fixing elements (3, 4) enclosing a space designed to hold the electrochemical cell (2), wherein at least one of the two fixing elements (3, 4) is movably mounted relative to the other fixing element (3, 4), further comprising a measuring device (5) designed to detect the position and / or change in position of the movably mounted fixing element (3, 4) of a cell (2) held in the space during an electrical charging or discharging process, and an evaluation unit (10) which is connected to the measuring device (5) via a signal and is designed to determine cell quality as a function of the measurable position or change in position of the movably mounted fixing element (3, 4).

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