Battery cell electrode tab disconnection inspection device

Abstract

The battery cell electrode tab break inspection device of the present invention includes a measurement unit that measures an impedance value and impedance angle corresponding to the frequency of a target battery cell, a calculation unit that calculates a real part resistance value of the impedance corresponding to the frequency of the target battery cell from the impedance value and impedance angle, and a determination unit that inspects the presence or absence of an electrode tab break of the target battery cell by comparing the real part resistance value of a real part resistance value range band in a resonance frequency range band of a good battery cell of the same type as the target battery cell with the real part resistance value of the impedance of the target battery cell in the frequency range of the same range band as the resonance frequency range band.

Description

[Technical field]

[0001] The present invention relates to an electrode tab disconnection inspection device for non-destructively inspecting electrode tabs of battery cells for disconnections.

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0142779 dated October 25, 2021, and all contents disclosed in the documents of that Korean patent application are incorporated herein by reference. [Background technology]

[0003] In recent years, rechargeable secondary batteries have been widely used as energy sources for wireless mobile devices. Secondary batteries are also attracting attention as energy sources for electric vehicles and hybrid electric vehicles, which have been proposed as a solution to address air pollution caused by existing gasoline and diesel vehicles that use fossil fuels. Therefore, the types of applications that use secondary batteries are becoming increasingly diverse due to the advantages of secondary batteries, and secondary batteries are expected to be applied to many more fields and products in the future.

[0004] Such secondary batteries may be classified into lithium ion batteries, lithium ion polymer batteries, lithium polymer batteries, etc. according to the configuration of the electrodes and electrolyte, and among them, the use of lithium ion polymer batteries, which are less likely to leak electrolyte and are easy to manufacture, is increasing. In general, secondary batteries are classified into cylindrical batteries and prismatic batteries in which an electrode assembly is housed in a cylindrical or prismatic metal can, and pouch-type batteries in which an electrode assembly is housed in a pouch-type case of an aluminum laminate sheet, according to the shape of the battery case. The electrode assembly housed in the battery case is a chargeable and dischargeable power generating element having a positive electrode, a negative electrode, and a separator structure interposed between the positive electrode and the negative electrode, and is classified into a jelly roll type in which a separator is interposed between a long sheet-like positive electrode and a negative electrode coated with an active material and wound up, and a stack type in which a number of positive electrodes and negative electrodes of a predetermined size are stacked in sequence with a separator interposed between them.

[0005] FIG. 1 is a schematic diagram showing a location where a break occurs in an electrode tab 13 of a pouch-type battery cell 10.

[0006] As shown in the figure, an electrode assembly 12 is built into a battery case 11 of a pouch-type battery cell 10, and an electrode tab 13 is extended from the electrode assembly 12 and welded to an electrode lead 14. The welds between the electrode tabs and between the electrode tabs and electrode leads are subjected to forces in various directions during the manufacturing process of the battery cell, so that breaks 15 may occur at one or various welded points. If a break occurs, it may cause defects such as low voltage.

[0007] In order to detect breaks in the electrode tabs, a method has been used in which pressure is applied to a battery cell and a change in impedance of the battery cell due to the pressure is measured, as in Patent Document 1, or a method of physically inspecting the welded parts using CT scans.

[0008] The technology of Patent Document 1 requires a separate pressure device for applying pressure to the battery cell in order to measure the impedance change, making it difficult to apply the technology to mass production level testing.

[0009] In addition, CT scans take about one minute and a half to inspect each battery cell, so mass-production level inspections were also not possible.

[0010] In order to overcome the above problems, the applicant has developed a method for breaking electrode tabs as shown in Fig. 2. That is, battery cells with broken tabs are detected by comparing the impedance value or the resistance value of the real part of the impedance of a test battery cell measured in a specific frequency range (for example, the resonant frequency range) with the impedance values ​​or the resistance value of the real part of the impedance in the same frequency range of normal battery cells without broken tabs and battery cells with broken tabs.

[0011] However, even with the above method, there are regions where the impedance value change region of a normal (good) battery cell and the impedance value change region of a broken tab (defective) battery cell overlap, and if the impedance value or real part resistance value of the battery cell being tested falls within this overlap region, it is difficult to determine whether to judge it as normal or as having a broken tab.

[0012] Furthermore, there was a problem in that the results of the determination of tab breakage differed depending on the impedance measurement position of the electrode lead.

[0013] Therefore, there is a need for the development of an electrode tab break inspection technique that can more accurately determine whether or not the electrode tab of a battery cell is broken. [Prior art documents] [Patent documents]

[0014] [Patent Document 1] Korean Patent Publication No. 10-2020-0035594 Summary of the Invention [Problem to be solved by the invention]

[0015] The present invention has been devised to solve the above-mentioned problems, and is a so-called K-nearest neighbors law( Nearby The objective of the present invention is to provide an inspection device for detecting breaks in electrode tabs of battery cells that can more accurately detect the presence or absence of breaks in the electrode tabs of battery cells based on a test result (test result detection algorithm).

[0016] Another object of the present invention is to provide an inspection device for detecting breaks in electrode tabs of a battery cell that can accurately determine the presence or absence of breaks in the electrode tabs according to the impedance measurement position of the electrode lead. [Means for solving the problem]

[0017] The battery cell electrode tab disconnection inspection device according to the present invention comprises: an impedance measuring unit that is connected to an electrode lead of an inspection target battery cell and measures an impedance value according to a frequency; a determination unit that compares the impedance value data corresponding to the frequency of the test target battery cell acquired by the impedance measurement unit with a predetermined group of impedance value data corresponding to the frequency of a normal battery cell in which an electrode tab is not disconnected or a tab disconnected battery cell in which an electrode tab is disconnected, and determines whether or not the test target battery cell is disconnected, and the determination unit determines whether or not the test target battery cell is disconnected by comparing the impedance value data of the test target battery cell in a selected specific frequency range. and nearby (nearest neighboring) A predetermined number of impedance value data of normal battery cells and / or battery cells with broken tabs are selected, and the presence or absence of a broken electrode tab of the battery cell being inspected is determined according to the type of battery cells that account for a greater number of the selected data.

[0018] As an example, the selected predetermined number of impedance value data is an odd number equal to or greater than 3.

[0019] As another example, the selected specific frequency range may be a frequency range in which the impedance value data of the normal and open-tab battery cells do not overlap with each other or the overlapping area is the smallest.

[0020] Specifically, if the selected data contains more data about normal battery cells, the battery cell being inspected is determined to be a normal battery cell, and if the selected data contains more data about open-tab battery cells, the battery cell being inspected is determined to be a open-tab battery cell.

[0021] The predetermined impedance value data group according to the frequency of the normal battery cells and the open-tab battery cells is K-nearest neighbors The data may be a set of data that has been iteratively trained using a K-nearest neighbor algorithm.

[0022] As another example of the present invention, the electrode tab disconnection inspection device includes a multi-probe unit having a plurality of probes corresponding to a plurality of measurement points of an electrode lead provided on a battery cell to be inspected, each probe being electrically connected alternately to each measurement point; an impedance measuring unit connected to each probe of the multi-probe unit and measuring an impedance value according to a frequency for each measurement point of the electrode lead; and a determination unit that determines whether or not the battery cell to be inspected has a disconnection by comparing impedance value data according to the frequency of the battery cell to be inspected acquired by the impedance measuring unit with a predetermined impedance value data group according to the frequencies of good battery cells whose electrode tabs are not disconnected and defective battery cells whose electrode tabs are disconnected, and the determination unit determines whether or not the battery cell to be inspected has a disconnection by comparing the impedance value data of the battery cell to be inspected in a selected specific frequency range for each measurement point of the electrode lead. Nearby A predetermined number of impedance value data of normal battery cells and / or battery cells with broken tabs are selected, and the presence or absence of breakage of the electrode tabs connected to each measurement point of the electrode lead is determined according to the type of battery cells that occupy a greater number of the selected data.

[0023] As an example, the selected predetermined number of impedance value data is an odd number equal to or greater than three.

[0024] As another example, the selected specific frequency range may be a frequency range in which the impedance value data of the normal and open-tab battery cells do not overlap with each other or the overlapping area is the smallest.

[0025] Specifically, if the selected data contains a greater number of data items of normal battery cells, it is determined that the electrode tab connected to the measurement point of the electrode lead is not disconnected, and if the selected data contains a greater number of data items of disconnected battery cells, it is determined that the electrode tab connected to the measurement point of the electrode lead is disconnected.

[0026] As an example, the predetermined impedance value data group according to the frequency of the normal battery cells and the open-tab battery cells is as follows: K-nearest neighbors The data may be a set of data that has been iteratively trained using a K-nearest neighbor algorithm.

[0027] For example, the electrode tab breakage inspection device may further include a switching relay box that alternately electrically connects the probes of the multi-probe unit to each measurement point, and a control unit that controls the switching relay box.

[0028] Specifically, the multi-probe unit is connected to at least one of the positive and negative leads of the battery cell, which have different polarities, and with a probe connected to one measurement point of one of the positive and negative leads, the impedance value can be measured alternately at multiple measurement points of the other of the positive and negative leads.

[0029] As an example, the measurement points on the positive and negative leads may be positioned equidistant from the ends of the leads or the case of the battery cell.

[0030] The electrode tab breakage inspection device can determine whether or not the electrode tabs of all battery cells being inspected are broken by combining the determination result of whether or not the electrode tabs are broken at a plurality of measurement points of one of the positive and negative electrode leads among the electrode leads, with the determination result of whether or not the electrode tabs are broken at a plurality of measurement points of another of the positive and negative electrode leads among the electrode leads.

[0031] As another example, the determination unit may additionally determine whether or not the electrode tab of the test target battery cell is broken based on the rate of change of impedance value corresponding to each measurement point of the electrode lead, and may compare the additional determination result with the combined determination result of the presence or absence of a break to determine whether or not the electrode tab of the test target battery cell is finally broken. Effect of the Invention

[0032] According to the present invention, even if it is unclear whether a battery cell is normal or has an open tab, K-nearest neighbors An algorithm can be applied to accurately detect broken electrode tabs of battery cells.

[0033] In addition, by detecting the presence or absence of breakage in the electrode tabs according to the impedance measurement positions of the electrode leads, it is possible to more accurately determine the presence or absence of breakage in the electrode tabs of all the battery cells.

[0034] In addition, the present invention not only enables rapid and accurate inspection during the battery cell manufacturing stage, but also enables rapid and accurate inspection of battery cell defects (presence or absence of breakage of electrode tabs) during the recycling or reuse stage in which completed battery cells are reused after a certain period of use. Therefore, when recycling battery cells, it is possible to accurately identify defects in the battery cells and easily determine whether or not to reuse them. [Brief description of the drawings]

[0035] [Figure 1] 1 is a schematic diagram showing a location where a break occurs in an electrode tab of a pouch-type battery cell. [Diagram 2] 4 is a graph showing the principle of detecting disconnection of an electrode tab of a battery cell using an impedance value or a real part resistance value proposed by the present applicant. [Diagram 3] 1 is a schematic diagram of an electrode tab inspection device for a battery cell according to an embodiment of the present invention. [Figure 4] FIG. 1 is a schematic diagram illustrating the principle of the K-nearest neighbors algorithm. [Diagram 5] 1 is a flowchart showing the data learning process using the K-nearest neighbor algorithm. [Figure 6] FIG. 13 is a schematic diagram of an electrode tab inspection device for a battery cell according to another embodiment of the present invention. [Figure 7] 10 is a schematic diagram showing an example of measuring impedance values ​​according to measurement points on electrode leads of a battery cell; FIG. [Figure 8]7 is a flowchart showing an example of a process for detecting the presence or absence of disconnection in a battery cell using the battery cell electrode tab inspection device of the embodiment in FIG. 6. [Figure 9] 13 is a graph showing the results of determining whether or not there is a break in the impedance value when the impedance value of the negative electrode lead is measured at a fixed measurement point and the impedance value of the positive electrode lead is measured at a different measurement point. [Figure 10] 13 is a graph showing the results of determining whether or not there is a break in the impedance value when the impedance value of the negative electrode lead is measured at a fixed measurement point and the impedance value of the positive electrode lead is measured at a different measurement point. [Figure 11] 10 is a schematic diagram showing the rate of change in impedance value according to the measurement location of a normal battery cell and a battery cell with a broken tab. FIG. [Figure 12] 7 is a flowchart showing another example of detecting the presence or absence of disconnection in a battery cell using the battery cell electrode tab inspection device of the embodiment in FIG. 6. [Figure 13] 13 is another schematic diagram showing the rate of change in impedance value depending on the measurement location of a normal battery cell and a battery cell with a broken tab. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] The present invention will be described in detail below. Before that, the terms and words used in the specification and claims should not be interpreted limitedly to their ordinary or dictionary meanings, but should be interpreted as meanings and concepts that are consistent with the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concepts of the terms in order to best describe his own invention.

[0037] The terms "comprise" and "have" used in this application are intended to specify the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, and should be understood as not precluding the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof. In addition, when a part such as a layer, film, region, or plate is described as being "on" another part, this includes not only the case where it is "directly on" the other part, but also the case where there is another part in between. Conversely, when a part such as a layer, film, region, or plate is described as being "under" another part, this includes not only the case where it is "directly under" the other part, but also the case where there is another part in between. In addition, in this application, being "on" may include not only the case where it is located on the top, but also the case where it is located on the bottom.

[0038] Meanwhile, in this application, the term "longitudinal direction" refers to the direction in which the electrode leads of the battery cell protrude.

[0039] It is presumed that if the electrode tab of a battery cell is disconnected as shown in Figure 1, there will be a change in the impedance value of the battery cell. Based on this, Patent Document 1 adopts a method of applying pressure to the battery cell and measuring the impedance change to detect the presence or absence of a disconnection.

[0040] However, as described above, the present invention is intended to detect the presence or absence of a disconnection based on the impedance value without applying pressure.

[0041] Also, even when the impedance values ​​of a normal battery cell and a battery cell with a broken tab overlap, the presence or absence of a broken tab can be accurately detected.

[0042] (First embodiment) The electrode tab disconnection inspection device 100 of this embodiment includes an impedance measurement unit 110 that is connected to the electrode leads 14, 14' of the battery cell 10 under inspection and measures an impedance value according to frequency, and a determination unit 120 that compares the impedance value data according to frequency of the battery cell 10 under inspection acquired by the impedance measurement unit 110 with a predetermined impedance value data group according to frequency of a normal battery cell in which the electrode tab is not disconnected or a tab disconnected battery cell in which the electrode tab is disconnected to determine whether or not the battery cell 10 under inspection is disconnected. The determination unit 120 determines the presence or absence of a disconnection in the battery cell 10 under inspection by comparing the impedance value data of the battery cell 10 under inspection in a selected specific frequency range with a predetermined impedance value data group according to frequency of a normal battery cell in which the electrode tab is not disconnected or a tab disconnected battery cell in which the electrode tab is disconnected. and nearby The method is characterized in that a predetermined number of impedance value data of normal battery cells and / or battery cells with broken tabs is selected, and the presence or absence of a broken electrode tab of the test target battery cell 10 is determined according to the type of battery cell that accounts for the largest number of the selected data.

[0043] FIG. 3 is a schematic diagram of an electrode tab inspection device 100 for a battery cell according to one embodiment of the present invention.

[0044] The battery cell 10 is a pouch-type cell, a so-called bidirectional battery cell in which electrode leads of different polarities are led out from both ends of the battery cell in the longitudinal direction. However, this is not limited to this, and the presence or absence of electrode tab breakage can also be determined in a unidirectional battery cell in which electrode leads of different polarities are led out from the same end of the battery cell.

[0045] The present invention includes an impedance measuring unit 110 connected to the electrode lead of the battery cell 10 to be inspected. The impedance measuring unit 110 can be connected to the electrode lead of the battery cell 10 by a predetermined connecting cable and a connection terminal. In FIG. 3, the electrode leads 14, 14' and the impedance measuring unit 110 are connected by a probe P and a conductor. The impedance measuring unit 110 can measure the impedance value of the battery cell 10 according to the frequency. When a minute AC signal with a different frequency is applied by, for example, an EIS (Electrochemical Impedance Spectroscopy) measuring device as the impedance measuring unit 110, an impedance value according to the frequency can be obtained. In addition to the impedance value, the EIS measuring device can obtain various parameters related to the impedance according to the frequency, such as the phase angle of the impedance, the real part resistance value, the imaginary part resistance value through a predetermined calculation.

[0046] The electrode tab open circuit inspection device 100 of the present invention compares the impedance value data according to the frequency of the inspected battery cell 10 acquired by the impedance measuring instrument 110 with a group of impedance value data according to the frequencies of predetermined normal battery cells and battery cells with open tabs to determine whether or not the inspected battery cell 10 is open.

[0047] The inspection device 100 of the present invention is in line with a conventional technique proposed by the present applicant for determining the presence or absence of an open circuit by comparing impedance values ​​in a specific frequency range. However, as shown in Fig. 2, the conventional method was unable to accurately determine the presence or absence of an open circuit for a test target battery cell 10 that falls in an overlapping region where the impedance values ​​of a normal battery cell and a battery cell with an open tab overlap. Also, it was difficult to determine the presence or absence of an open circuit when it was unclear whether the impedance value range of the battery cell was that of a normal battery cell or that of a battery cell with an open tab.

[0048] The present invention relates to a so-called K-nearest neighbors law( K-nearest neighborsThis method solves the above problems by using the K-nearest neighbor algorithm (abbreviated as K-NN algorithm).

[0049] FIG. 4 is a schematic diagram illustrating the principle of the K-NN algorithm.

[0050] K-nearest neighbors The K-NN algorithm, or K-NN algorithm for short, is a type of supervised learning, which is a type of machine learning, and can be considered a distance-based classification analysis model. The K-NN algorithm classifies data by referring to the labels of "K" different data that are close to the data, and has the advantage of being a simple algorithm and easy to implement. Specifically, when triangular data and rectangular data are located on a certain coordinate plane as shown in FIG. 4, it can determine which data the circular data should belong to. If the number of data closest to the circular data is determined to be three (i.e., K=3), the circular data is classified as belonging to triangular data. However, if the number of data closest to the circular data is determined to be five (K=5), the circular data is classified as belonging to rectangular data. Therefore, by setting an appropriate number of K, it is possible to determine the type of data even when it is unclear which type of data it belongs to.

[0051] The determination unit 120 of the present invention determines the impedance value data of the test target battery cell. and nearby A predetermined number of impedance values ​​of normal battery cells and / or battery cells with broken tabs are selected, and the presence or absence of breaks in the electrode tabs of the battery cells 10 to be inspected is judged according to the type of battery cells that account for the greater number of the selected data. Nearby " is not necessarily the most Close to It does not mean one piece of data. Nearby " means the " of the K-NN algorithm. Nearby This corresponds to the concept of ", and when K pieces of data are selected around a specific data, the specific data has " Nearby " of This means that multiple (K) pieces of data are selected.

[0052] To explain based on the example of Figure 4, for example, the triangular data can be regarded as the impedance value data of a battery cell with a broken tab, and the square data as the impedance value data of a normal battery cell. If the impedance value data of a specific frequency of the battery cell 10 under test is regarded as circular data, the presence or absence of a broken tab of the battery cell 10 under test can be determined based on whether it falls within the category of the dotted or solid circle in Figure 4. In other words, when K is 5, the impedance value data (circular data) of the battery cell 10 under test can be regarded as the impedance value data (square data) of a normal battery cell, and therefore the battery cell 10 under test is determined to be a normal battery cell with no broken wires. In addition, Nearby If the number of normal battery cell data items is larger than the number of normal battery cell data items selected to be tested, the test target battery cell 10 is determined to be a normal battery cell. Nearby If three of the data are normal battery cells and two are broken tab battery cells, the test target battery cell 10 is determined to be a normal battery cell.

[0053] Conversely, the selected Nearby If the number of data items related to the battery cell with an open tab is larger than the number of data items related to the battery cell with an open tab, the battery cell 10 to be inspected is determined to be a battery cell with an open tab. Nearby If three of the data are for a battery cell with an open tab and two are for a normal battery cell, the test target battery cell 10 is determined to be a battery cell with an open tab.

[0054] In this way, by comparing impedance values ​​according to the K-NN algorithm, it is possible to determine the presence or absence of an open circuit even when the impedance values ​​of normal and open-tab battery cells overlap as shown in Figure 2. In other words, by selecting an appropriate K value according to the K-NN algorithm and selecting a predetermined number of impedance value data, it is possible to determine the number of nearest neighbor data for any data. Therefore, even when the impedance values ​​overlap overall as shown in Figure 2, it is possible to determine the type of adjacent battery cell that occupies the largest number of impedance value data for the corresponding battery cell.

[0055] Meanwhile, in the present invention, the impedance value is a concept including not only the total impedance value having real and imaginary components, but also the real part resistance value (Rs). That is, if the impedance phase angle and the impedance value are known according to the relationship of R=Z COSθ, the real part resistance value can be obtained, and since the real part resistance value can also be expressed as an impedance value, the presence or absence of a disconnection can be detected from the resistance value of the real part component. Therefore, the impedance value data to which the K-NN algorithm of the present invention is applied includes the above-mentioned real part resistance value data.

[0056] In addition, it is preferable that the predetermined number of impedance value data selected to determine whether or not the electrode tab is broken, i.e., the K value, is an odd number equal to or greater than 3. If K is 1, the discrimination power decreases, and if the K value is an even number, it is difficult to determine to which battery cell 10 to be inspected belongs when the number of nearest neighbor data is the same, for example, 2:2. Therefore, it is preferable that the K value is an odd number such as 3, 5, 7, or 9. However, if the K value is too large, the discrimination power of the judgment also decreases, so a K value that is not too large must be selected. A K value of 3 or 5 is preferable.

[0057] Furthermore, the impedance value data compared to determine whether or not the electrode tab is broken may be a value in a specific frequency range.

[0058] 2, there are some regions where the impedance region of a normal battery cell (good zone) and the impedance region of a battery cell with a broken tab (bad zone) are relatively clearly separated according to frequency, but there are also regions where the overlap zone is too large to make comparison with the data of the battery cell 10 being inspected. Such wide overlap zones mainly occur in the low frequency region. In addition, since the position and size of the overlap zone may vary depending on the type, physical properties, and internal state of the battery cell, an appropriate frequency range must be selected for each battery cell.

[0059] Therefore, the specific frequency range selected to determine whether or not an electrode tab is broken refers to a frequency range in which the impedance value data of the normal and open-tab battery cells do not overlap with each other or in which the overlapping area is the smallest.

[0060] Referring again to FIG. 3, it can be seen that the determination unit 120 of the present invention determines whether or not the tab of the battery cell 10 to be inspected is broken by the K-NN algorithm as described above. Meanwhile, the predetermined impedance value data group of normal and open-tab battery cells to be compared with the impedance value data of the battery cell 10 to be inspected is also a data group obtained by repeated learning by the K-NN algorithm. Such a data group is stored in a storage unit 130 such as a predetermined database, and the determination unit 120 can determine whether or not the tab of the battery cell is broken by comparing with the data group of the storage unit 130. As shown in FIG. 3, the storage unit 130 can be provided in the form of a server or DB separate from the determination unit 120. Alternatively, it can be included in the determination unit 120 as a memory-type storage unit. The determination unit 120 can be a predetermined computing device having software in which the K-NN algorithm is implemented.

[0061] Figure 5 shows K-nearest neighbors 1 is a flowchart illustrating an example of a data learning process using an algorithm.

[0062] For example, a predetermined number of battery cells may be prepared by artificially breaking the positive or negative tabs, and a predetermined number (e.g., 100) of battery cells may be prepared as a population for creating a data group by mixing these broken-tab battery cells with normal battery cells of the same type. Of the battery cells in this population, 80% (e.g., 80) of the battery cells may be randomly selected, the impedance value data of the selected battery cells may be measured, and the impedance value data according to the frequency of the normal battery cells and the broken-tab battery cells may be learned to create a predetermined data group to be compared (S1).

[0063] The impedance values ​​of the remaining 20% ​​(e.g., 20) battery cells are measured and compared with the above-mentioned comparison data group using the K-NN algorithm to predict the presence or absence of an open circuit in each of the 20% of the battery cells a predetermined number of times (S3).

[0064] Next, the predicted results are verified to be consistent with the actual normal and open-tab battery cells (S3).

[0065] [Table 1]

[0066] From Table 1 above, it can be seen that when the K-NN algorithm predicts whether a battery cell with a specific cell ID is normal or disconnected using a set of impedance value data of 80% of the battery cells selected from the population, it is possible to predict the presence or absence of a tab disconnection with 100% accuracy. Of course, depending on which set of data is selected, the prediction result may have other accuracy levels such as 90%, 95%, etc., rather than 100%. In this way, data whose accuracy has been verified is updated as learning data for predicting tab disconnection.

[0067] In addition, in order to improve the accuracy of the data set, such a data learning process may be repeated, for example, 100 times to obtain a more reliable and accurate control data set for the K-NN algorithm (S4).

[0068] Second embodiment The electrode tab disconnection inspection device 200 of this embodiment includes a multi-probe unit 240 that is electrically connected to each of the measurement points of the electrode leads 14, 14' provided on the battery cell 10 to be inspected, and the multi-probe unit 240 is connected to each of the probes P1, P2, P3 of the multi-probe unit 240 to measure an impedance value according to a frequency for each measurement point of the electrode lead, and a determination unit 220 that compares the impedance value data according to the frequency of the battery cell 10 to be inspected acquired by the impedance measurement unit 210 with a predetermined impedance value data group according to the frequency of a good battery cell whose electrode tab is not disconnected and a defective battery cell whose electrode tab is disconnected to determine whether or not the battery cell 10 to be inspected is disconnected. The determination unit 220 determines the presence or absence of a disconnection in the battery cell 10 to be inspected by comparing the impedance value data of the battery cell 10 to be inspected in a selected specific frequency range for each measurement point of the electrode lead. Nearby A predetermined number of impedance value data of normal battery cells, or battery cells with open tabs, or battery cells that are normal and have open tabs are selected, and the presence or absence of a break in the electrode tabs connected to each measurement point of the electrode lead is determined according to the type of battery cells that occupy a greater number of the selected data.

[0069] FIG. 6 is a schematic diagram of a battery cell electrode tab inspection device 200 according to the second embodiment.

[0070] The electrode tab inspection device 200 of the present embodiment includes a multi-probe unit 240. The multi-probe unit 240 includes a plurality of probes P1, P2, and P3 at positions corresponding to a plurality of measurement points of the electrode lead provided at both ends of the longitudinal direction of the pouch-type battery cell. As shown in FIG. 1, the electrode lead is connected to a plurality of tab bundles. Even if a break occurs in a specific tab, tabs at other positions may be normal, and when an impedance value is measured at a position of the electrode lead connected to such a normal tab, the measured value may be measured as the impedance value of a normal battery cell. Therefore, when an impedance value is measured at only one measurement point of the electrode lead, a defective battery cell may be shipped to the market.

[0071] In order to prevent the above-mentioned case, the present invention includes a multi-probe unit 240 that can measure impedance values ​​at multiple positions on the electrode lead using multiple probes P1, P2, and P3. However, the impedance is not measured at once using the multiple probes P1, P2, and P3, but each probe P1, P2, and P3 is electrically connected to each measurement point in turn, so that impedance values ​​at specific positions can be measured sequentially.

[0072] The inspection device 200 of the present invention also includes an impedance measuring unit 210 that is connected to each of the probes P1, P2, P3 of the multi-probe unit 240 and measures an impedance value corresponding to a frequency for each measurement point of the electrode leads 14, 14'. An EIS measuring instrument 210 may be used as the impedance measuring unit 210. The impedance measuring unit 210 has been fully described in the first embodiment, so a detailed description thereof will be omitted in this embodiment.

[0073] The determination unit 220 of this embodiment may determine the presence or absence of breakage of the electrode tabs at each measurement point of the electrode leads 14, 14' using the K-NN algorithm, as in the first embodiment. Unlike the first embodiment, this embodiment includes a plurality of probes P1, P2, and P3 that are electrically connected to each measurement point in turn, and therefore may apply the K-NN algorithm to each measurement point. Therefore, this embodiment may determine the presence or absence of normality or breakage at each measurement point of the electrode leads by comparing with a predetermined impedance value data group corresponding to the frequency of normal or broken tab battery cells. In this case, for an equivalent comparison, the predetermined impedance value data group to be compared with the impedance value measured at a specific position of the electrode leads 14, 14' must also be measured at the same position as the specific position of the electrode leads.

[0074] Also, Nearby As in the first embodiment, the predetermined number of impedance value data selected to determine whether or not a battery cell has an open tab is an odd number equal to or greater than 3. Also, as in the first embodiment, the frequency of the impedance value data group to be compared with the impedance value data of the test subject for each measurement point should be selected in a range in which the impedance value data of normal and open-tab battery cells do not overlap as much as possible.

[0075] In this embodiment, the presence or absence of breakage of the electrode tab at each measurement point is determined by the K-NN algorithm as follows.

[0076] The impedance values ​​measured at each measurement point were selected Nearby If the data of normal battery cells accounts for a larger number of data, it is determined that the electrode tab connected to the corresponding measurement point of the electrode lead is not disconnected.

[0077] The impedance values ​​measured at each measurement point were selected NearbyIf the data for the battery cell with a broken tab accounts for a larger number of pieces of data, it is determined that the electrode tab connected to the corresponding measurement point of the electrode lead is broken.

[0078] In this case, the predetermined impedance value data groups according to the frequencies of the normal battery cells and the broken tab battery cells to be compared are also data groups iteratively learned using the K-NN algorithm as shown in FIG.

[0079] Such a group of data is stored in a storage unit 230 such as a predetermined database, and the determination unit 220 can determine whether or not a tab of a battery cell is broken by comparing the group of data in the storage unit 230. As shown in Fig. 6, the storage unit 230 can be provided in the form of a server or DB separate from the determination unit 220. Alternatively, the storage unit 230 can be included in the determination unit 220 as a memory-type storage unit. The determination unit 220 can be a predetermined computing device having software in which the K-NN algorithm is implemented.

[0080] In order to electrically connect the plurality of stacked probes P1, P2, and P3 to each measurement point in turn, the electrode tab disconnection inspection device 200 of the present embodiment may include a switching relay box 250. The switching relay box 250 is connected to each of the probes P1, P2, and P3 of the multi-probe unit 240 by a circuit, and includes a switch or relay SW that electrically switches and electrically connects each of the probes P1, P2, and P3. Such electrical relay devices are generally known, and therefore a description thereof will be omitted. When the multi-probe unit 240 is connected to at least one of the positive and negative leads 14 and 14' of the battery cell having different polarities, the impedance values ​​of the plurality of measurement points in each lead can be measured by the EIS measuring device 210.

[0081] Also, a control unit may be provided to control the switching relay box 250 so that the probes P1, P2, and P3 are alternately connected to the respective measurement points. The control unit may be separate from the determination unit 220 or may include the determination unit 220 as shown in Fig. 6. In the latter case, the control unit may be a control computer including the determination unit 220 in which software implementing the K-NN algorithm is embedded.

[0082] In FIG. 6, impedance values ​​are measured at three measurement points on each electrode lead. However, the number of measurement points may be two, four, five, or more, as necessary. In FIG. 6, R and L refer to the right and left sides of the electrode lead. In particular, breaks often occur at the tabs adjacent to both sides of the electrode lead. In view of this, the embodiment of FIG. 6 shows that impedance values ​​are measured at the R and L parts on both sides of the electrode lead. It is preferable that the measurement points are set to the same standard. For example, if the measurement points are set in a line at the same intervals based on the end of each lead 14, 14' or the case of the battery cell, the impedance can be measured and compared under relatively similar conditions for each measurement point.

[0083] In the switching relay box 250 of Fig. 6, the dashed lines indicate that the switch SW is not connected, and the solid lines indicate that the switch SW is connected. Thus, Fig. 6 shows that both the positive and negative leads 14, 14' measure impedance values ​​at the measurement point at position R. By switching the relay box 250, impedance values ​​at other measurement points can also be measured.

[0084] When measuring impedance values ​​at multiple points on one electrode lead, the measurement points on the other electrode leads must be fixed. This is because it is only in this way that it is possible to objectively compare whether or not there is a tab break at multiple points on one electrode lead. FIG. 7 is a schematic diagram showing such a measurement. Referring to FIG. 7, the measurement point on the right electrode lead 14' (e.g., negative electrode lead) is fixed at one central point, and the measurement points on the left electrode lead 14 (e.g., positive electrode lead) are set at two points, R and L, and impedance values ​​are measured alternately. In this way, it is possible to objectively compare whether or not there is a tab break at point R of the positive electrode lead 14 and whether or not there is a tab break at point L, and if any one of the points is detected as being broken, the battery cell is determined to be a battery cell with a broken tab. In FIG. 7, only one probe is shown to indicate that the measurement point on the right electrode lead 14' is fixed at one point. However, it is of course possible to electrically connect only one probe to the measurement point by switching as in FIG. 6. 7, the measurement point of the positive electrode lead 14 on the left side may be fixed at one central point, and impedance values ​​may be measured at two points, R and L, of the negative electrode lead 14' on the right side to detect whether the tab connected to the negative electrode lead is broken. In this manner, the impedance is measured by alternately connecting the probes P1, P2, and P3 of the multi-probe unit 240 to each measurement point of the electrode lead, and the test subject battery cell 10 is determined to be a normal battery cell only if the impedance values ​​of all the measurement points correspond to the impedance values ​​of a normal battery cell, and is determined to be a battery cell with an open tab if the impedance value of any one point belongs to the impedance value of a battery cell with an open tab.

[0085] FIG. 8 is a flow chart showing an example of a process for detecting the presence or absence of a disconnection in a battery cell using the battery cell electrode tab inspection device of the embodiment shown in FIG.

[0086] First, impedance value data at multiple points on the electrode lead is acquired by the impedance measuring section 210.

[0087] 7, for example, the measurement position of the negative electrode lead 14' is fixed, and impedance value data is obtained at points L and R of the positive electrode lead 14. Next, the measurement position of the positive electrode lead 14 is fixed, and impedance value data is obtained at points L and R of the negative electrode lead 14' (A1).

[0088] Next, the impedance value data for each location is compared with a control impedance value data group at the same location that has been trained using, for example, a K-NN algorithm. Nearby A comparison is made using an algorithm to detect tab breakage at that location (A2).

[0089] In this case, even if a break is not detected at a specific location, it may be detected at other locations. Therefore, by combining the break detection results at multiple locations, the number of cases where a tab break is not detected can be reduced, so the break is detected by combining the detection results at each measured location (A3).

[0090] Finally, based on the combined detection results, it can be determined whether or not all the battery cells are open (A4).

[0091] Table 2 below shows that electrode tab breaks were detected in the entire battery cell 10 that was the subject of the overall inspection by combining the results of determining whether or not there is an electrode tab break at multiple measurement points R, L of the positive electrode lead 14 and the results of determining whether or not there is an electrode tab break at multiple measurement points R, L of the negative electrode lead 14'.

[0092] [Table 2] Selectable frequency range: 160-100Hz (analysis of two measurement points) / K=5

[0093] 9 and 10 are graphs showing the results of determining whether or not there is a disconnection when the impedance value of the negative electrode lead 14' is measured at a fixed measurement point and the impedance value is measured at a different measurement point on the positive electrode lead 14. That is, Figs. 9 and 10 show that the number of undetected pieces was reduced by combining the determination results in cases 1 and 2 in Table 2.

[0094] FIG. 9 shows the results of measuring the real part resistance R at a total of 21 points of frequency within a frequency range of 1 kHz to 0.1 Hz for 27 normal (non-defective) battery cells and 27 battery cells with a broken L portion of the positive electrode lead 14. As shown in the figure, in the high and low frequency regions, the impedance value data groups of normal and broken battery cells overlap, making it difficult to use them as a comparison data group for determining the quality of the battery cell 10 to be inspected. In FIG. 9, since there is relatively little overlap between 160 and 100 Hz, the presence or absence of a break was detected by the K-NN algorithm in this frequency range. For convenience of illustration, the coordinate data of frequency f-real part resistance R is connected by a line, but as described above, in reality, frequency-real part resistance data of 21 points was obtained by the EIS measuring device 210 and compared by the K-NN algorithm. This experiment was performed by acquiring (learning) impedance value data using battery cells whose status as normal / open-tab battery cells was known in advance, and therefore it was possible to identify open-tab battery cells that would not have been detected by the above detection method. As shown in Figure 9, three open-tab battery cells with cell IDs 12672, 12684, and 12710 were determined to be non-defective and were not detected.

[0095] Figure 10 shows the results of measuring the real resistance R at a total of 21 frequency points within the frequency range of 1 kHz to 0.1 Hz for 27 normal (non-defective) battery cells and 27 battery cells with a broken portion R of the positive lead 14. In addition, the presence or absence of a broken portion was detected using the K-NN algorithm within the frequency range of 160 to 100 Hz. As a result of the detection, the four broken battery cells with cell IDs 12710, 12705, 12664, and 12671 were determined to be non-defective and not detected.

[0096] 9 and 10, only the open battery cell with cell ID 12710 was not detected. In other words, by combining the test results of 1 and 2 above as shown in Table 2, the number of undetected open battery cells is 1 out of 54, which can greatly increase the accuracy or efficiency of open circuit detection.

[0097] In addition, the position of the positive electrode lead 14 was fixed, and the measurement points of the negative electrode lead 14' were divided into L and R to detect whether the tab was broken or not. As a result of combining these results and judging, only one battery cell was not detected, similar to Figures 9 and 10 above, and the detection accuracy was also improved.

[0098] On the other hand, when impedance values ​​are measured at multiple measurement points using a multipoint method as in this embodiment, the rate of change in impedance values ​​of normal battery cells and battery cells with open tabs differs depending on the measurement point.

[0099] FIG. 11 is a schematic diagram showing the rate of change in impedance value at different measurement points for normal battery cells and battery cells with broken tabs.

[0100] FIG. 11 shows the rate of change in impedance value according to frequency at each location while the measurement location of the positive electrode lead P: 14 is fixed and the measurement location of the negative electrode lead N: 14' is changed to five locations.

[0101] As shown in the figure, in the case of normal battery cells, the impedance change rates at the five locations are almost similar. However, in the case of battery cells with broken tabs, the impedance values ​​are generally larger than those of normal battery cells, and the change rates are also different. In particular, the impedance change rate at location 4, where the broken tab occurred, is significantly different from the impedance change rate at the remaining locations.

[0102] Therefore, in this embodiment of the invention in which the presence or absence of a tab break is determined based on the impedance values ​​at multiple points on the electrode lead, it is believed that the detection result of tab breakage can be further improved by additionally determining the presence or absence of an electrode tab breakage based on the rate of change of the impedance value obtained by such multi-point measurement and combining this additional determination result with the determination result of the presence or absence of a breakage determined by the above-mentioned K-NN method.

[0103] FIG. 12 is a flow chart showing another example of detecting the presence or absence of disconnection in a battery cell using the battery cell electrode tab inspection device of the embodiment in FIG.

[0104] First, impedance value data of a plurality of points of an electrode lead is acquired by the electrode tab inspection device shown in FIG. 6 (B1).

[0105] Next, the impedance value data is compared with a predetermined set of impedance value data for normal battery cells and battery cells with open tabs using a K-NN algorithm to primarily detect whether or not there is an open circuit at each measurement point (B2). In this case, as shown in Figure 8, the detection accuracy can be improved by combining the results of determining whether or not there is an open circuit at multiple points.

[0106] Next, the change rate of impedance value data at a plurality of points in the electrode lead is compared according to each measurement point to secondarily detect the presence or absence of disconnection in each battery cell (B3). That is, the detection result of B3 can be used to verify the detection result of B2.

[0107] Finally, the primary and secondary detection results are combined to finally detect an open battery cell. The determination of the presence or absence of an open circuit based on the rate of change of impedance value according to the measurement location is somewhat different from the determination of the presence or absence of an open circuit using the K-NN algorithm described above, so the primary and secondary detection results may match or may differ in part. If there is a difference in part, additional undetected battery cells may be found, thereby improving the detection accuracy.

[0108] FIG. 13 is another schematic diagram showing the rate of change in impedance value depending on the measurement location of a normal battery cell and a battery cell with a broken tab.

[0109] The two lines in each graph in FIG. 13 are measurements of the real part of the resistance value according to frequency at points L and R of the positive electrode lead.

[0110] As shown in the figure, the impedance value change rate for the top eight normal battery cells is almost the same depending on the measurement location, while the impedance value change rate for the bottom open-tab battery cell is significantly different depending on the measurement location. This shows that the method of detecting open-tab battery cells based on the change rate after measuring impedance values ​​at different measurement locations using the multi-point probing method also shows considerable accuracy.

[0111] Therefore, by inspecting whether or not the tab of the battery cell is broken according to the flow as shown in FIG. 12, the detection accuracy can be improved.

[0112] According to the present invention, not only can a rapid and accurate inspection be performed during the battery cell manufacturing stage, but also defects in the battery cells (presence or absence of breakage of electrode tabs) can be rapidly and accurately inspected during the recycling or reuse stage in which the completed battery cells are reused after being used for a certain period of time. Therefore, when recycling the battery cells, defects in the battery cells can be quickly identified and it can be easily determined whether or not to reuse them.

[0113] The above description is merely illustrative of the technical idea of ​​the present invention, and a person having ordinary knowledge in the technical field to which the present invention belongs may make various modifications and variations without departing from the essential characteristics of the present invention. Therefore, the drawings disclosed in the present invention are for the purpose of explanation, not for the purpose of limiting the technical idea of ​​the present invention, and the scope of the technical idea of ​​the present invention is not limited by such drawings. The scope of protection of the present invention should be interpreted by the claims, and all technical ideas within the equivalent range should be interpreted as being included in the scope of the present invention.

[0114] In this specification, terms indicating directions such as up, down, left, right, front, and back are used for convenience of explanation, but it is self-evident that these terms may change depending on the position of the object in question, the position of the observer, etc. [Explanation of symbols]

[0115] 10: Battery cell 11: Battery case 12: Electrode assembly 13: Electrode tab 14: Electrode lead 15: Disconnection 100: Electrode tab disconnection inspection device 110: Impedance measurement unit 120: Judgment section 130: Storage unit P: Probe 14, 14': Electrode lead 200: Electrode tab disconnection inspection device 210: Impedance measurement unit 220: Control unit (determination unit) 230: Storage unit 240: Multi-probe section 250: Switching relay box SW: Switch or relay P1, P2, P3: Probes depending on the measurement point

Claims

1. an impedance measuring unit connected to an electrode lead of the test subject battery cell and configured to measure an impedance value according to a frequency; a determination unit that compares the impedance value data corresponding to the frequency of the test target battery cell acquired by the impedance measurement unit with a predetermined group of impedance value data corresponding to the frequency of a normal battery cell in which an electrode tab is not disconnected or a tab disconnected battery cell in which the electrode tab is disconnected, and determines whether or not the test target battery cell is disconnected, an electrode tab open circuit inspection device in which the determination unit selects an odd number of impedance value data, three or more, of the impedance value data of the test target battery cell within a selected specific frequency range and of nearby normal battery cells and / or open tab battery cells, and determines whether or not the electrode tab of the test target battery cell is open depending on whether the data of normal battery cells or the data of open tab battery cells accounts for a greater number of the selected data.

2. 2. The electrode tab disconnection inspection device of claim 1, wherein the selected specific frequency range is a frequency range in which the impedance value data of the normal battery cells and the open-tab battery cells do not overlap with each other or the overlapping area is the smallest.

3. If the number of data items of the normal battery cells is larger than the number of data items of the selected battery cells, the battery cell to be inspected is determined to be a normal battery cell; 3. The electrode tab disconnection inspection device according to claim 1, wherein when a larger number of pieces of data are about battery cells with disconnected tabs among the selected pieces of data, the inspection target battery cell is determined to be a battery cell with a disconnected tab.

4. 3. The electrode tab disconnection inspection device according to claim 1, wherein the predetermined impedance value data groups according to frequencies of normal battery cells and battery cells with disconnected tabs are data groups iteratively learned using a K-nearest neighbor algorithm.

5. a multi-probe unit including a plurality of probes corresponding to a plurality of measurement points of an electrode lead provided on a battery cell to be inspected, each probe being electrically connected to each measurement point in turn; an impedance measuring unit connected to each probe of the multi-probe unit and measuring an impedance value corresponding to a frequency for each measurement point of the electrode lead; a determination unit that determines whether or not the test target battery cell is disconnected by comparing the impedance value data corresponding to the frequency of the test target battery cell acquired by the impedance measurement unit with a predetermined group of impedance value data corresponding to the frequency of a non-defective battery cell whose electrode tab is not disconnected or a defective battery cell whose electrode tab is disconnected, the determination unit selects, for each measurement point on the electrode lead, an odd number of impedance value data (three or more) of the impedance value data of the test target battery cell and nearby normal battery cells and / or battery cells with open tabs in a selected specific frequency range, and determines whether or not there is a break in the electrode tabs connected to each measurement point on the electrode lead depending on whether the data of normal battery cells accounts for a greater number or the data of battery cells with open tabs accounts for a greater number of the selected data.

6. 6. The electrode tab disconnection inspection device of claim 5, wherein the selected specific frequency range is a frequency range in which the impedance value data of the normal battery cells and the open-tab battery cells do not overlap with each other or the overlapping area is the smallest.

7. If the data of the normal battery cells is more than the data of the selected data, it is determined that the electrode tab connected to the corresponding measurement point of the electrode lead is not disconnected; 6. The electrode tab disconnection inspection device according to claim 5, wherein when a larger number of pieces of data on disconnected battery cells are included in the selected data, the electrode tab connected to the corresponding measurement point of the electrode lead is determined to be disconnected.

8. 6. The electrode tab disconnection inspection device according to claim 5, wherein the predetermined impedance value data groups according to the frequencies of the normal battery cells and the disconnected tab battery cells are data groups iteratively learned using a K-nearest neighbor algorithm.

9. a switching relay box for electrically connecting the probes of the multi-probe unit to each measurement point in turn; The electrode tab disconnection inspection device according to claim 5 , further comprising a control unit that controls the switching relay box.

10. The multi-probe unit is connected to at least one of a positive electrode lead and a negative electrode lead having different polarities of the test target battery cell, 10. The electrode tab disconnection inspection device according to claim 9, wherein, in a state where a probe is connected to one measurement point of one of the positive electrode lead and the negative electrode lead, the impedance value is measured alternately for a plurality of measurement points of the other of the positive electrode lead and the negative electrode lead.

11. 11. The electrode tab disconnection inspection device according to claim 10, wherein the measurement points of the positive electrode lead and the negative electrode lead are positioned at equal intervals from an end of each lead or a case of the battery cell to be inspected.

12. A determination result of the presence or absence of breakage of an electrode tab at a plurality of measurement points of one of the positive electrode lead and the negative electrode lead among the electrode leads; and 9. The electrode tab disconnection inspection device according to claim 5, wherein the presence or absence of an electrode tab disconnection of a battery cell to be inspected is determined by combining a determination result of the presence or absence of an electrode tab disconnection for a plurality of measurement points of another one of the positive electrode lead and the negative electrode lead among the electrode leads.

13. 13. The electrode tab disconnection inspection device according to claim 12, wherein the determination unit additionally determines the presence or absence of an electrode tab disconnection of the test target battery cell based on a rate of change in impedance value corresponding to each measurement point of the electrode lead, and determines the presence or absence of an electrode tab disconnection of the test target battery cell by comparing the additional determination result with the combined determination result of the presence or absence of the disconnection.

Images