Disconnection checking device for electrode tabs of battery cells

Abstract

The disconnection inspection apparatus for an electrode tab of a battery cell according to the present application includes a measurement unit that measures an impedance value and an impedance angle according to a frequency of a battery cell to be inspected, a calculation unit that calculates a real part resistance value of an impedance according to a frequency of the battery cell to be inspected from the impedance value and the impedance angle, and a determination unit that inspects whether or not an electrode tab of the battery cell to be inspected is disconnected by inspecting a real part resistance value of a real part resistance value domain in a resonance frequency domain of a high-quality battery cell of the same type as the battery cell to be inspected and a real part resistance value of the impedance of the battery cell to be inspected in a frequency range of the same domain as the resonance frequency domain.

Description

Technical Field

[0001] This invention relates to an electrode connector disconnection inspection device for non-destructive inspection of the disconnection of electrode connectors in battery cells.

[0002] This application claims priority to Korean Patent Application No. 10-2021-0142779, filed on October 25, 2021, the entire contents of which are incorporated herein by reference. Background Technology

[0003] Recently, rechargeable and discharging secondary batteries have been widely used as an energy source for wireless mobile devices. Furthermore, secondary batteries have garnered significant attention as an energy source for electric vehicles and hybrid electric vehicles, which have been proposed as a solution to address air pollution caused by existing fossil fuel-powered gasoline and diesel vehicles. Therefore, due to the advantages of secondary batteries, their applications have become more diversified, and it is anticipated that they will be used in even more fields and products than currently are.

[0004] These secondary batteries can be classified according to the composition of their electrodes and electrolytes into lithium-ion batteries, lithium-ion polymer batteries, and lithium polymer batteries. Among these, lithium-ion polymer batteries, which have a low possibility of electrolyte leakage and are easy to manufacture, are increasingly used. Generally, secondary batteries are classified according to the shape of their casings as follows: cylindrical or prismatic batteries in which the electrode assembly is housed in a cylindrical or prismatic metal can; and pouch batteries in which the electrode assembly is housed in a pouch-shaped casing made of aluminum laminate. The electrode assembly housed in the battery casing is a power generation element, each forming a positive electrode, a negative electrode, and a separator placed between the positive and negative electrodes, thus enabling charging and discharging. Furthermore, they are classified as: wound-core type, in which the separator is placed between and wound long sheet-type positive and negative electrodes coated with active material; and stacked type, in which multiple positive and negative electrodes of predetermined dimensions are sequentially stacked and the separator is placed between them.

[0005] Figure 1 This is a schematic diagram illustrating the location where a break occurs in the electrode connector 13 of the pouch cell 10.

[0006] As shown in the figure, an electrode assembly 12 is housed within the battery casing 11 of the pouch-type battery cell 10, and an electrode connector 13 extends from the electrode assembly 12 and is soldered to an electrode lead 14. Because the electrode connector and its soldered portion, as well as the soldered portion of the electrode connector and the electrode lead, are subjected to forces in various directions during the battery cell manufacturing process, a break 15 may occur at one or more of the soldered locations. When a break occurs, it may cause defects such as low voltage.

[0007] To detect the disconnection of electrode connectors, conventional methods, such as those disclosed in Patent Document 1, have been used, such as pressurizing the battery cell to measure the impedance change of the battery cell under pressure or physically inspecting the welding position by CT scan.

[0008] In the technology of Patent Document 1, since a pressurization mechanism is required to pressurize the battery cell individually in order to measure impedance changes, it is difficult to apply to mass production-level inspection.

[0009] In addition, since a CT scan to inspect each battery cell takes about 1 minute and 30 seconds, mass production-level inspection is again not possible.

[0010] To solve the above problems, the applicant has developed the following: Figure 2 The electrode connector disconnection method is shown. That is, a battery cell with a disconnected connector is detected by comparing the impedance value or real resistance value of the battery cell under test measured in a specific frequency domain (e.g., the resonant frequency domain) with the impedance value or real resistance value of a normal battery cell without a disconnected connector and a battery cell with a disconnected connector in the same frequency domain.

[0011] However, even with the methods described above, there will be areas where the impedance value variation areas of normal (defect-free) battery cells and the impedance value variation areas of battery cells with disconnected connectors (defective) overlap. When the impedance value or real resistance value of the battery cell under inspection belongs to this overlapping area, it is difficult to determine whether the situation is normal or disconnected connector.

[0012] Furthermore, the problem is that the determination of the disconnection of the connector varies depending on the impedance measurement location of the electrode lead.

[0013] Therefore, there is a need to develop an electrode connection disconnection inspection technology that can more accurately determine whether the electrode connections of a battery cell are disconnected.

[0014] [Related Technical Documents]

[0015] [Patent Literature]

[0016] Korean Patent Publication No. 10-2020-0035594 Summary of the Invention

[0017] Technical issues

[0018] This invention is designed to solve the above problems and aims to provide a battery cell electrode connector disconnection inspection device that can more accurately detect whether the battery cell electrode connector is disconnected based on the so-called K-nearest neighbor method.

[0019] Furthermore, the present invention relates to an electrode connector disconnection inspection device for battery cells that can accurately determine whether the electrode connector is disconnected even based on the impedance measurement position of the electrode leads.

[0020] Technical solution

[0021] The electrode connector disconnection inspection device for a battery cell according to the present invention includes: an impedance measuring unit connected to the electrode leads of the battery cell to be inspected to measure impedance values ​​according to frequency; and

[0022] The determining unit is configured to compare the frequency-based impedance value data of the battery cell under test acquired by the impedance measurement unit with a predetermined set of frequency-based impedance value data of normal battery cells without disconnected electrode terminals or frequency-based impedance value data of battery cells with disconnected electrode terminals, in order to determine whether the battery cell under test is disconnected. The determining unit selects a predetermined number of impedance value data points that are closest to the impedance value data of the battery cell under test in a selected specific frequency range from normal battery cells, battery cells with disconnected terminals, or both normal battery cells and battery cells with disconnected terminals. The determining unit determines whether the electrode terminals of the battery cell under test are disconnected based on the type of battery cell that occupies the larger number of selected data points.

[0023] As an example, the selected predetermined number of impedance value data points can be an odd number greater than or equal to 3.

[0024] As another example, the selected specific frequency range can be the frequency range in which the impedance data points of normal battery cells and disconnected battery cells do not overlap or have the smallest overlapping area.

[0025] Specifically, a battery cell under inspection can be identified as a normal battery cell when the data of a normal battery cell occupies a large number of the selected data points, and a battery cell with a disconnected connector can be identified as a disconnected connector battery cell when the data of a disconnected connector battery cell occupies a large number of the selected data points.

[0026] Furthermore, the data set of predetermined impedance values ​​based on frequency for normal battery cells and disconnected battery cells can be a data set repeatedly learned through the K nearest neighbor algorithm.

[0027] As another example of the present invention, an electrode connector disconnection inspection device includes: a multi-probe unit comprising a plurality of probes corresponding to a plurality of measurement positions of an electrode lead disposed in a battery cell to be inspected, wherein each probe is alternately and electrically connected to each measurement position; an impedance measurement unit connected to each probe of the multi-probe unit to measure an impedance value according to frequency for each measurement position of the electrode lead; and a determination unit configured to compare the impedance value data of the battery cell to be inspected according to frequency acquired by the impedance measurement unit with a predetermined set of impedance value data according to frequency of a defective battery cell without a disconnected electrode lead or a defective battery cell with a disconnected electrode lead, to determine whether the battery cell to be inspected is disconnected, wherein, for each measurement position of the electrode lead, the determination unit selects a predetermined number of impedance value data points that are nearest neighbors to the impedance value data of the battery cell to be inspected in a selected specific frequency range for a normal battery cell, a battery cell with a disconnected electrode lead, or both a normal battery cell and a battery cell with a disconnected electrode lead, and determines whether the electrode lead connected to the measurement position of the electrode lead is disconnected based on the type of battery cell occupying the larger number of selected data points.

[0028] As an example, the selected predetermined number of impedance value data points can be an odd number greater than or equal to 3.

[0029] As another example, the selected specific frequency range can be the frequency range in which the impedance data points of normal battery cells and disconnected battery cells do not overlap or have the smallest overlapping area.

[0030] Specifically, the electrode connector at the corresponding measurement position connected to the electrode lead can be determined to be not disconnected when the data of the normal battery cell occupies a large number of the selected data points, and can be determined to be disconnected when the data of the disconnected battery cell occupies a large number of the selected data points.

[0031] As an example, a set of data on the predetermined impedance values ​​of normal battery cells and disconnected battery cells based on frequency can be a set of data repeatedly learned through the K-nearest neighbor algorithm.

[0032] As an example, the electrode connector disconnection inspection device may also include: a switching relay box configured to alternately connect each probe of the multi-probe section to each measurement position; and a controller configured to control the switching relay box.

[0033] Specifically, the multi-probe unit can be connected to at least one of the positive and negative leads of the battery cell, and with the probe connected to a measurement position of one of the positive and negative leads, the impedance value can be measured alternately at multiple measurement positions of the other of the positive and negative leads.

[0034] As an example, the measurement position of each of the positive and negative leads can be located at equal intervals, starting from the housing of the battery cell or the end of each lead.

[0035] The electrode connector disconnection inspection device can combine the results of whether the electrode connector is disconnected related to multiple measurement positions of one of the positive and negative leads in the electrode leads with the results of whether the electrode connector is disconnected related to multiple measurement positions of the other of the positive and negative leads in the electrode leads to determine whether all electrode connectors of the battery cell under inspection are disconnected.

[0036] As another example, the determination unit can additionally determine whether the electrode connector of the battery cell under inspection is disconnected based on the rate of change of the impedance value at each measurement location of the electrode lead, and compare the additional determination result with the combined result of whether a disconnection exists to finally determine whether the electrode connector of the battery cell under inspection is disconnected.

[0037] Technical effect

[0038] According to the present invention, even if it is not obvious whether the battery cell is a normal battery cell or a battery cell with a disconnected connector, the disconnection of the electrode connector of the battery cell can be accurately detected by applying the K nearest neighbor algorithm.

[0039] Furthermore, by detecting whether the electrode connectors are disconnected based on the impedance measurement location of the electrode leads, it is possible to more accurately determine whether all electrode connectors of the battery cell are disconnected.

[0040] Furthermore, according to the present invention, not only can rapid and accurate inspections be performed during the manufacturing of battery cells, but also rapid and accurate inspections can be performed on battery cells in reuse or recycling operations where battery cells have been used for a predetermined period of time and then reused to identify defects (such as disconnected electrode connections). Therefore, defects in battery cells can be quickly identified during the recycling of battery cells to determine whether they can be reused. Attached Figure Description

[0041] Figure 1 This is a schematic diagram illustrating the location of a break in the electrode connector of a pouch cell.

[0042] Figure 2 This is a graph illustrating the principle of using impedance values ​​or real resistance values ​​to detect the disconnection of electrode terminals in a battery cell, as proposed by the applicant.

[0043] Figure 3 This is a schematic diagram of a battery cell electrode connector disconnection inspection device according to an embodiment of the present invention.

[0044] Figure 4This is a schematic diagram used to describe the principle of the K-nearest neighbor algorithm.

[0045] Figure 5 This is a flowchart illustrating the data learning process based on the K-nearest neighbor algorithm.

[0046] Figure 6 This is a schematic diagram of a battery cell electrode connector disconnection inspection device according to another embodiment of the present invention.

[0047] Figure 7 This is a schematic diagram illustrating an example of measuring impedance values ​​based on the measurement positions of the electrode leads of a battery cell.

[0048] Figure 8 This is an example of use. Figure 6 The flowchart illustrates an example of the process by which a battery cell electrode connector disconnection detection device detects whether a battery cell is disconnected in an embodiment of the present invention.

[0049] Figure 9 and Figure 10 This is a graph illustrating the determination of whether there is a disconnect when measuring the impedance value by fixing the measurement position of the negative lead and changing the measurement position of the positive lead.

[0050] Figure 11 This is a schematic diagram illustrating the rate of change of impedance values ​​of a normal battery cell and a disconnected battery cell according to the measurement location.

[0051] Figure 12 This is an example of use. Figure 6 The flowchart shows another example of the electrode connector inspection device for the battery cell in this embodiment detecting whether the battery cell is disconnected.

[0052] Figure 13 This is another schematic diagram illustrating the rate of change of impedance values ​​of a normal battery cell and a disconnected battery cell according to the measurement location. Detailed Implementation

[0053] The invention will be described in detail below. Prior to this, the terms and words used in this specification and claims should not be construed as limited to ordinary or dictionary terms, but rather should be interpreted as having meanings and concepts consistent with the technical spirit of the invention, based on the principle that the inventors may appropriately define the concepts of terms in order to best describe their invention.

[0054] In this application, it should be understood that terms such as "comprising" and "having" are intended to indicate the presence of the features, quantities, steps, operations, components, parts, or combinations thereof described in the specification, but do not preclude the possibility of the presence or addition of one or more other features, quantities, steps, operations, components, or combinations thereof. Furthermore, when a part such as a layer, membrane, region, plate, etc., is referred to as being "on" another part, this includes not only the case where the part is "directly" on the other part, but also the case where another part exists between them. On the other hand, when a part such as a layer, membrane, region, plate, etc., is referred to as being "below" another part, this includes not only the case where the part is "directly" below the other part, but also the case where another part exists between them. Additionally, in this application, "disposed on" can mean that something is disposed on a lower or upper part.

[0055] Furthermore, in this application, "length direction" refers to the direction in which the electrode leads of the battery cell protrude.

[0056] When Figure 1 As shown, when the electrode connector of the battery cell is disconnected, a change in the impedance value of the battery cell is estimated. Based on this, Patent Document 1 employs a method to detect whether a disconnection exists by applying pressure to the battery cell and measuring the impedance change.

[0057] However, as mentioned above, the present invention aims to detect the presence of a disconnection based on impedance values ​​without applying pressure.

[0058] Furthermore, the present invention aims to accurately detect whether a connector is disconnected, even when the impedance values ​​of a normal battery cell and a battery cell with a disconnected connector overlap.

[0059] (First Implementation)

[0060] The electrode connector disconnection inspection device 100 according to this embodiment includes: an impedance measurement unit 110 connected to the electrode leads 14 and 14' of the battery cell 10 to be inspected to measure impedance values ​​according to frequency; and a determination unit 120 that compares the frequency-based impedance value data of the battery cell 10 to be inspected obtained by the impedance measurement unit 110 with a predetermined set of frequency-based impedance value data of normal battery cells without disconnected electrode connectors, or frequency-based impedance value data of battery cells with disconnected electrode connectors, to determine whether the battery cell 10 to be inspected is disconnected. The determination unit 120 selects a predetermined number of impedance value data points that are closest to the impedance value data of the battery cell 10 to be inspected within a selected specific frequency range, including normal battery cells, battery cells with disconnected connectors, or both normal battery cells and battery cells with disconnected connectors. The determination unit 120 determines whether the electrode connector of the battery cell 10 to be inspected is disconnected based on the type of battery cell that occupies the larger number of selected data points.

[0061] Figure 3 This is a schematic diagram of a battery cell electrode connector disconnection inspection device 100 according to an embodiment of the present invention.

[0062] Battery cell 10 is a pouch-type cell and a so-called bidirectional battery cell in which electrode leads of different polarities extend from both ends of the battery cell in the longitudinal direction. However, the invention is not limited to this, and according to the invention, it is possible to determine whether the electrode connector of a battery cell, which is a unidirectional battery cell in which electrode leads of different polarities extend from the same end of the battery cell, is disconnected.

[0063] The present invention includes an impedance measuring unit 110 connected to the electrode leads of a battery cell 10 to be inspected. The impedance measuring unit 110 can be connected to the electrode leads of the battery cell 10 via a predetermined connecting cable and connecting terminals. Figure 3 In this configuration, electrode leads 14 and 14' are connected to the impedance measurement unit 110 via probe P and wires. The impedance measurement unit 110 can measure the impedance value of the battery cell 10 according to frequency. For example, when a small alternating current (AC) signal with a different frequency is applied using an electrochemical impedance spectroscopy (EIS) measuring device, the impedance value according to frequency can be obtained. In addition to the impedance value according to frequency, the EIS measuring device can also obtain various impedance-related parameters, such as the phase angle of the impedance, the real part of the resistance value, and the imaginary part of the resistance value, through a predetermined algorithm.

[0064] The electrode connector disconnection inspection device 100 of the present invention compares the frequency-based impedance value data of the battery cell 10 to be inspected, which is obtained by the impedance measurement unit 110, with a predetermined set of frequency-based impedance value data of normal battery cells and battery cells with disconnected connectors, to determine whether the battery cell 10 to be inspected is disconnected.

[0065] The electrode connector disconnection inspection device 100 of the present invention conforms to the conventional technique proposed by the applicant for determining the presence of a disconnection based on a comparison of impedance values ​​within a specific frequency range. However, as Figure 2 As shown, traditional methods cannot accurately determine whether the battery cell 10 under inspection is disconnected, corresponding to the overlapping area where the impedance values ​​of the disconnected battery cells overlap with those of the normal battery terminals. Alternatively, even if the impedance value range of the normal battery cell and the impedance value range of the disconnected battery cell are not clearly distinguishable, it is still difficult to determine whether a disconnection exists.

[0066] This invention uses the so-called K-nearest neighbor method (K-nearest neighbor algorithm, or K-NN algorithm for short) to solve the above problems.

[0067] Figure 4This is a schematic diagram used to describe the principle of the K-NN algorithm.

[0068] The K-Nearest Neighbors (K-NN) algorithm is a supervised learning method (a type of machine learning) and can be described as a distance-based classification model. The K-NN algorithm classifies data by referencing the labels of the "K" nearest other data points, and its advantages lie in its simplicity and ease of implementation. Specifically, when triangular and quadrilateral data are located in... Figure 4 When the data is placed on the predetermined coordinate plane, the data type of the circular data can be determined for classification. When the number of nearest data points to the circular data is 3 (i.e., K is 3), the circular data is classified as triangular data. However, when the number of nearest data points is determined to be 5 (K is 5), the circular data is classified as quadrilateral data. Therefore, by setting an appropriate number of K, the data type can be determined even if it is unclear which type the data belongs to.

[0069] The determining unit 120 of this invention selects a predetermined number of impedance values ​​that are nearest neighbors to the impedance value data of the battery cell to be inspected, including normal battery cells, battery cells with disconnected connectors, and both normal battery cells and battery cells with disconnected connectors. Based on the type of battery cell occupying the larger number of selected data points, it determines whether the electrode connector of the battery cell 10 to be inspected is disconnected. In this specification, "nearest neighbor" does not necessarily mean a single data point that is the nearest neighbor. That is, the meaning of "nearest neighbor" in this invention corresponds to the concept of "nearest neighbor" in the K-NN algorithm, and refers to selecting multiple (K) data points that are "nearest neighbors" to a specific data point when K data points are selected around that specific data point.

[0070] Based on Figure 4 In the example description, for instance, triangular data can be considered as impedance value data of a disconnected battery cell, while quadrilateral data can be considered as impedance value data of a normal battery cell. When the impedance value data of a specific frequency of the battery cell 10 to be inspected is considered as circular data, it can be determined according to... Figure 4The type of circular data (whether it's a dashed circle or a solid circle) determines whether the connector of the battery cell 10 under inspection is disconnected. That is, when K is set to 5, the impedance value data (circular data) of the battery cell 10 under inspection can be considered as the impedance value data (quadrilateral data) of a normal battery cell, therefore the battery cell 10 under inspection is determined to be a normal battery cell that is not disconnected. Furthermore, the battery cell 10 under inspection is determined to be a normal battery cell when the data of a normal battery cell constitutes a large proportion of the selected nearest neighbor data points. In other words, when K is 5 and the three nearest neighbor data points to the impedance value data of the battery cell 10 under inspection are data points of a normal battery cell, and two of them are data points of a battery cell with a disconnected connector, the corresponding battery cell 10 under inspection is determined to be a normal battery cell.

[0071] On the other hand, when the data of the battery cell with disconnected connectors constitutes a large number of the selected nearest neighbor data points, the battery cell 10 under inspection is identified as a battery cell with disconnected connectors. That is, when K is 5 and the three nearest neighbor data points to the impedance value data of the battery cell 10 under inspection are data points of a battery cell with disconnected connectors and two data points of a normal battery cell, the corresponding battery cell 10 under inspection is identified as a battery cell with disconnected connectors.

[0072] Same as above, such as Figure 2 As shown, when comparing impedance values ​​using the K-NN algorithm, even if the impedance values ​​of normal battery cells and disconnected battery cells overlap, it is possible to determine whether a disconnection exists. In other words, by selecting a predetermined number of impedance value data points using the K-NN algorithm with an appropriate K value, the number of any nearest data points can be determined. Therefore, even when... Figure 2 As shown, when impedance values ​​overlap as a whole, the type of adjacent battery cells that occupy a larger number of impedance value data points relative to the corresponding battery cell can also be determined.

[0073] Furthermore, in this invention, the impedance value is a concept that includes not only the total impedance value with real and imaginary components but also the real resistance value Rs. That is, when the impedance phase angle and impedance value are known according to the relationship R = Z cosθ, since the real resistance value can be obtained and can also be expressed as an impedance value, it is possible to detect whether there is an open circuit even using the resistance value of the real components. Therefore, the impedance value data using the K-NN algorithm of this invention includes real resistance value data.

[0074] Furthermore, preferably, the predetermined number of impedance data points (i.e., K values) selected to determine whether the electrode connector is disconnected is an odd number greater than or equal to 3. When K is 1, the discrimination power is low, and when K is an even number, it is difficult to determine where the battery cell 10 under inspection belongs when the number of most recent data points is the same (e.g., 2:2). Therefore, the K value can be an odd number such as 3, 5, 7, or 9. However, when the K value is too large, the discrimination power is also reduced, so a K value that is not too large should be selected. Preferably, a K value of 3 or 5 is good.

[0075] Furthermore, the impedance values ​​compared to determine whether the electrode connector is disconnected can be values ​​within a specific frequency range.

[0076] Reference Figure 2 Depending on the frequency, there are regions where the impedance region of a normal battery cell (defect-free region) and the impedance region of a battery cell with a disconnected connector (defect region) are relatively clearly distinguishable. However, there are also regions where the overlap is too large and therefore difficult to compare with the data of the battery cell 10 under inspection. This wide overlap region mainly occurs in the low-frequency domain. Furthermore, since the location or size of the overlap region can vary depending on the type, physical properties, and internal state of the battery cell, an appropriate frequency range should be selected based on the battery cell.

[0077] Therefore, a specific frequency range is selected to determine whether the electrode connector is disconnected.

[0078] This refers to the frequency range in which the impedance data points of normal battery cells and disconnected battery cells do not overlap or have the smallest overlapping area.

[0079] Refer again Figure 3 As described above, the determination unit 120 of the present invention determines whether the connector of the battery cell 10 to be inspected is open according to the K-NN algorithm. Furthermore, the predetermined impedance value data set of normal battery cells and battery cells with open connectors, which is compared with the impedance value data of the battery cell 10 to be inspected, is also a data set obtained through repeated learning according to the K-NN algorithm. This data set is stored in a storage unit 130 such as a predetermined database, and the determination unit 120 can determine whether the connector of the battery cell is open by comparing it with the data set in the storage unit 130. Figure 3 As shown, the storage unit 130 may be provided as a server or database (DB) separate from the determination unit 120. Alternatively, the storage unit 130 may be included in the determination unit 120 as a memory. The determination unit 120 may be a predetermined computing device in which software implementing the K-NN algorithm is embedded.

[0080] Figure 5 This is a flowchart illustrating an example of the data learning process based on the K-nearest neighbor algorithm.

[0081] For example, a predetermined number of battery cells in which the connectors of the positive or negative electrodes are artificially disconnected are manufactured, and a predetermined number of battery cells (e.g., 100 battery cells) for creating a data set can be prepared by mixing the disconnected battery cells with normal battery cells of the same type. By randomly selecting 80% of the battery cells from the total number of cells (e.g., 80 battery cells) and measuring the impedance data of the selected battery cells, the frequency-based impedance data of the normal battery cells and the disconnected battery cells are learned and set as a predetermined data set for comparison (S1).

[0082] By measuring the impedance values ​​of the remaining 20% ​​of battery cells (e.g., 20 battery cells) and using the K-NN algorithm to compare the remaining 20% ​​of battery cells with the data set of the comparison object, it is possible to predict whether each battery cell in the remaining 20% ​​of battery cells will disconnect a predetermined number of times (S2).

[0083] Next, verify the prediction results and whether the battery cell is indeed a normal battery cell and the battery cell with the connector disconnected (S3).

[0084] [Table 1]

[0085] From Table 1, when the K-NN algorithm predicts whether a battery cell with a specific cell ID is normal or disconnected based on the impedance values ​​of 80% of the selected battery cell population, it can be seen that it can predict whether the electrode connector is disconnected with 100% accuracy. Of course, depending on the selected data set, the prediction result may not have 100% accuracy and can have different accuracies, such as 90%, 95%, etc. As above, updated data with validated accuracy is used as training data for predicting connector disconnection.

[0086] In addition, to improve the accuracy of the data set, the data learning process can be repeated (e.g., 100 times) to obtain a more reliable and accurate comparison data set for the K-NN algorithm (S4).

[0087] (Second Implementation)

[0088] The electrode connector disconnection inspection device 200 according to this embodiment includes: a multi-probe unit 240, which includes a plurality of probes P1, P2, and P3 corresponding to a plurality of measurement positions where electrode leads 14 and 14' are disposed in the battery cell 10 to be inspected, and wherein each probe P1, P2, and P3 is alternately and electrically connected to the respective measurement position; an impedance measurement unit 210, which is connected to each of the probes P1, P2, and P3 of the multi-probe unit 240 to measure an impedance value according to frequency for each measurement position of the electrode lead; and a determination unit 220, which compares the frequency-based impedance value data of the battery cell 10 to be inspected obtained by the impedance measurement unit 210 with the data of the battery cell 10 not disconnected. The determination unit 220 determines whether the battery cell 10 to be inspected is disconnected by using a predetermined set of impedance value data based on frequency for both defective battery cells with disconnected electrode connectors and defective battery cells with disconnected electrode connectors. For each measurement position of the electrode lead, the determination unit 220 selects a predetermined number of impedance value data points that are closest to the impedance value data of the battery cell 10 to be inspected within a selected specific frequency range for normal battery cells, battery cells with disconnected connectors, or both normal battery cells and battery cells with disconnected connectors. The determination unit 220 then determines whether the electrode connector at the measurement position connected to the measurement electrode lead is disconnected based on the type of battery cell that occupies the larger number of selected data points.

[0089] Figure 6 This is a schematic diagram of the electrode connector disconnection inspection device 200 for a battery cell according to the second embodiment.

[0090] The electrode connector disconnection inspection device 200 of this embodiment includes a multi-probe unit 240. The multi-probe unit 240 includes multiple probes P1, P2, and P3, whose positions correspond to multiple measurement positions of the electrode leads disposed at both ends of the pouch cell in the length direction. For example... Figure 1 As shown, electrode leads are connected to multiple electrode connector bundles. Even if a particular connector is disconnected, the connectors at other locations may be normal, and the impedance value can be measured at the location of the electrode lead connected to a normal connector as the impedance value of a normal battery cell. Therefore, if the impedance value is measured only at one measurement location of the electrode lead, defective battery cells may be shipped to the market.

[0091] To prevent the above situation, the invention of this embodiment includes a multi-probe section 240, which allows multiple probes P1, P2, and P3 to be used to measure impedance values ​​at several locations on the electrode leads. However, the impedance is not measured by using multiple probes P1, P2, and P3 at a time, and since probes P1, P2, and P3 are alternately and electrically connected to the measurement locations, the impedance values ​​at specific locations can be measured sequentially.

[0092] Furthermore, the inspection device 200 of the present invention includes an impedance measurement unit 210 connected to the respective probes P1, P2, and P3 of the multi-probe unit 240 to measure impedance values ​​according to frequency at each measurement position of the electrode leads 14 and 14'. An EIS measuring device can be used as the impedance measurement unit 210. Since the impedance measurement unit 210 has been fully described in the first embodiment, its detailed description will be omitted in this embodiment.

[0093] The determination unit 220 in this embodiment can also determine whether the electrode connector is disconnected for each measurement location of electrode leads 14 and 14' using the K-NN algorithm, as shown in the first embodiment. Unlike the first embodiment, since this embodiment includes multiple probes P1, P2, and P3 that are alternately and electrically connected to the measurement locations, the K-NN algorithm can be applied to each measurement location. Therefore, this embodiment can determine whether the battery cell is normal or disconnected by comparing a predetermined impedance value data set based on frequency for each measurement location of the electrode leads with a normal battery cell or a battery cell with a disconnected connector. In this case, to perform the same comparison, the predetermined impedance value data set compared with the impedance values ​​measured at specific locations of electrode leads 14 and 14' should also be measured at the same location as the specific location of the corresponding electrode lead.

[0094] Furthermore, as in the first embodiment, the predetermined number of impedance data points selected to determine the nearest neighbor can be an odd number greater than or equal to 3. Additionally, as in the first embodiment, for each measurement location, the frequency of the impedance data set compared with the impedance data to be checked should be selected from a range in which the impedance data points of normal battery cells and disconnected battery cells overlap as little as possible.

[0095] The following K-NN algorithm is used to determine whether the electrode connector at each measurement location in this embodiment is disconnected.

[0096] When the data points of a normal battery cell occupy a large number of the nearest neighbor data points selected for the impedance value measured at each measurement location, the electrode connectors connected to the corresponding measurement locations of the electrode leads are determined to be not disconnected.

[0097] When the data points of the disconnected battery cell occupy a large number of the nearest neighbor data points selected for the impedance value measured at each measurement location, the electrode connector connected to the corresponding measurement location of the electrode lead is determined to be disconnected.

[0098] In this case, the data set of predetermined impedance values ​​based on frequency for normal battery cells and disconnected battery cells to be compared is also a data set repeatedly learned through the K-NN algorithm, such as... Figure 5 As shown.

[0099] The data set is stored in a storage unit 230, such as a predetermined database, and the determination unit 220 can determine whether the battery cell connector is disconnected by comparing it with the data set in the storage unit 230. Figure 6 As shown, the storage unit 230 can be provided as a server or database separate from the determination unit 220. Alternatively, the storage unit 130 can be included in the determination unit 220 as a memory. The determination unit 220 can be a predetermined computing device with software implementing the K-NN algorithm embedded therein.

[0100] To alternately and electrically connect multiple probes P1, P2, and P3 to measurement positions, the electrode connector disconnection inspection device 200 of this embodiment may include a switching relay box 250. The switching relay box 250 is electrically connected to each probe P1, P2, and P3 of the multi-probe unit 240 and includes a switch (SW) or relay for electrically switching and connecting each probe P1, P2, and P3. Since this relay mechanism is well-known, its description will be omitted. When the multi-probe unit 240 is connected to at least one of the positive lead 14 and the negative lead 14' of a battery cell with different polarities, an EIS measuring device can be used to measure the impedance values ​​associated with multiple measurement positions in each lead.

[0101] Furthermore, a control switching relay box 250 can be provided to allow probes P1, P2, and P3 to be alternately connected to a controller at each measurement position. The controller may be separate from or may include the determination unit 220, such as... Figure 6 As shown. In the latter case, the controller can be a control computer having a determination unit 220 with embedded software implementing the K-NN algorithm.

[0102] exist Figure 6 In this process, the impedance value is measured at each of the three measurement locations on the electrode lead. However, the number of measurement locations can be 2, 4, 5, or more, depending on the requirements. Figure 6 In this context, R and L refer to the left and right sides of the electrode lead. Specifically, the disconnection mainly occurs at the junction adjacent to the two sides of the electrode lead. Considering this, Figure 6 The implementation illustrates measuring impedance values ​​at two side portions R and L of the electrode leads. The measurement locations can be set to the same standard. For example, when the measurement locations are set based on the ends of each of the positive lead 14 and the negative lead 14', or the battery cell housing, being arranged side-by-side at equal intervals, the impedance can be measured and compared under relatively identical conditions for each measurement location.

[0103] exist Figure 6 In the switching relay box 250, dashed lines indicate that switch SW is not connected, while solid lines indicate that switch SW is connected. Therefore, Figure 6 The example illustrates measuring impedance values ​​at the R position of both the positive lead 14 and the negative lead 14′. Impedance values ​​can also be measured at other positions due to the switching of the relay box 250.

[0104] When measuring impedance values ​​at multiple locations on a single electrode lead, it is necessary to fix the measurement locations of the other electrode leads. This is because it allows for an objective comparison of whether the connection is broken at multiple locations on a single electrode lead. Figure 7 This is a schematic diagram illustrating this measurement state. (Refer to...) Figure 7 The impedance value is measured alternately by fixing the measurement position of the right electrode lead 14′ (e.g., the negative lead) at a central position and setting the measurement positions of the left electrode lead 14′ (e.g., the positive lead) at two positions R and L. Therefore, it is possible to objectively compare whether the connector is broken at position R of the positive lead 14′ and whether the connector is broken at position L of the positive lead 14′, and when either position is sensed as broken, the battery cell is determined to be a disconnected battery cell. Figure 7 In this example, for ease of illustration, the measurement position of electrode lead 14′ on the right is fixed in a single location, representing only one probe. However, as... Figure 6 As shown, by switching, only one probe can be electrically connected to the corresponding measurement position. (And...) Figure 7 Conversely, the disconnection of the electrode connector connected to the negative electrode lead can be detected by fixing the measurement position of the positive lead 14 on the left side at a central position and measuring the impedance values ​​at two positions R and L of the negative lead 14' on the right side. As described above, the impedance is measured by alternately and electrically connecting the probes P1, P2, and P3 of the multi-probe section 240 to the measurement positions of the electrode leads. The corresponding battery cell 10 under inspection is determined to be a normal battery cell only if the impedance value at each measurement point corresponds to the impedance value of a normal battery cell, and is determined to be a battery cell with a disconnected connector when the impedance value at a position belongs to a battery cell with a disconnected connector.

[0105] Figure 8 This is an example of use. Figure 6 The flowchart illustrates an example of the process by which a battery cell electrode connector disconnection detection device detects whether a battery cell is disconnected in an embodiment of the present invention.

[0106] First, impedance data at multiple locations of the electrode leads are acquired by the impedance measurement unit 210.

[0107] For example, such as Figure 7As shown, the measurement position of the negative lead 14' is fixed, and the impedance data at positions L and R of the positive lead 14 are obtained. Next, the measurement position of the positive lead 14 is fixed, and the impedance data at positions L and R of the negative lead 14' are obtained (A1).

[0108] Next, the impedance data at each location is compared with a set of comparative impedance data at the same location, for example, learned by the K-NN algorithm, using the nearest neighbor algorithm, to detect a disconnection at the corresponding location (A2).

[0109] In this situation, even if a disconnection is not detected at a specific location, it may still be detected at other locations. Therefore, since the number of cases where a disconnection is not detected can be reduced by combining the disconnection detection results at several locations, a disconnection can be detected by combining the measurement detection results at each location (A3).

[0110] Finally, the combined detection results can be used to determine whether all battery cells are disconnected (A4).

[0111] Table 2 below shows how the disconnection of all electrode connections of the battery cell 10 under inspection is detected by combining the results of whether the electrode connections associated with multiple measurement positions R and L of the positive lead 14 are disconnected with the results of whether the electrode connections associated with multiple measurement positions R and L of the negative lead 14′ are disconnected.

[0112] [Table 2]

[0113] Selected frequency range: 100-160Hz (analysis of 2 measurement locations) / K=5

[0114] Figure 9 and Figure 10 This is a graph illustrating the determination of whether a disconnection exists when measuring impedance by fixing the measurement position of the negative lead 14' and changing the measurement position of the positive lead 14. In other words, Figure 9 and Figure 10 The example illustrates how combining the results of cases 1 and 2 in Table 2 reduced the number of undetected cases.

[0115] Figure 9 The results illustrate the real resistance R measured at 21 points within a frequency range of 1 kHz to 0.1 Hz for 27 normal (defect-free) battery cells and 27 battery cells in which the positive lead 14 is disconnected at position L. As shown, the impedance data sets for normal products and disconnected battery cells overlap in the high-frequency and low-frequency domains, making them difficult to use as a comparative data set for determining whether the battery cell 10 under inspection is normal. Figure 9In this experiment, due to the relatively small overlap between 160Hz and 100Hz, disconnections were detected using the K-NN algorithm within this frequency range. For ease of illustration, the frequency (f)-real resistance R coordinate data points are connected by lines; however, as mentioned above, in practice, frequency-real resistance data at 21 points were acquired using an EIS measurement device and compared using the K-NN algorithm. Since this experiment was performed by pre-acquiring (learning) impedance value data using battery cells known to be either normal cells or disconnected cells, disconnected battery cells that were not detected even by the aforementioned detection methods can be identified. Figure 9 As shown, the three disconnected battery cells with unit IDs 12672, 12684 and 12710 were identified as defect-free battery cells and therefore were not detected.

[0116] Figure 10 The results illustrate the measurement of the real resistance R at 21 points within a frequency range of 1 kHz to 0.1 Hz for 27 normal (defect-free) battery cells and 27 battery cells in which the positive lead 14 is disconnected at position R. Disconnection was detected again using the K-NN algorithm within a frequency range of 160 Hz to 100 Hz. Based on the detection results, four disconnected battery cells with cell IDs 12710, 12705, 12664, and 12671 were identified as defect-free battery cells and therefore were not detected.

[0117] When combined Figure 9 and Figure 10 When determining the results, only the disconnected battery cell with cell ID 12710 was not detected. In other words, as shown in Table 2, when combining the test results of 1 and 2, since there is one undetected disconnected battery cell out of 54 battery cells, the accuracy or efficiency of disconnection detection can be greatly improved.

[0118] Furthermore, based on the fixed position of the positive lead 14, and the classification of the measured positions of the negative lead 14′ into L and R to detect whether the connector is disconnected, the determined result is executed through their combination, because as Figure 9 and Figure 10 There is only one undetected disconnected battery cell, thus improving detection accuracy.

[0119] Furthermore, when impedance values ​​are measured at several measurement locations in a multi-point manner as shown in this embodiment, the rate of change of impedance values ​​for normal battery cells and disconnected battery cells varies depending on the measurement location.

[0120] Figure 11 This is a schematic diagram illustrating the rate of change of impedance values ​​of a normal battery cell and a disconnected battery cell according to the measurement location.

[0121] Figure 11 The example illustrates the rate of change of impedance value at each position according to frequency while fixing the measurement position of the positive lead (P: 14) and changing the measurement position of the negative lead (N: 14′) to five.

[0122] As shown in the figure, in the case of a normal battery cell, the rate of change of impedance at the five locations is almost the same. However, in the case of a battery cell with the connector disconnected, the impedance values ​​are generally higher than those of a normal battery cell, and the rates of change are also different. Specifically, the rate of change of impedance at the fourth location, where the connector is disconnected, is significantly different from the rates of change of impedance at the other locations.

[0123] Accordingly, in the present invention which uses impedance values ​​at multiple locations of the electrode leads to determine whether the connector is open, the rate of change of impedance values ​​measured at these multiple points is used to additionally determine whether the electrode connector is open, and when this additional determination result is combined with the determination result of whether the electrode connector is open determined by the K-NN method, it is determined that the connector openness detection result can be further improved.

[0124] Figure 12 This is an example of use. Figure 6 The flowchart shows another example of a battery cell electrode connector disconnection detection device used in the implementation of the method to detect whether a battery cell is disconnected.

[0125] First, use Figure 6 The electrode connector inspection device shown acquires impedance data (B1) at each of multiple locations on the electrode leads.

[0126] Next, the impedance value data is compared with a predetermined set of impedance value data for normal battery cells and disconnected battery cells using the K-NN algorithm to detect whether each measurement location is disconnected for the first time (B2). In this case, as... Figure 8 As shown, the results of determining whether several locations are disconnected can be combined to improve detection accuracy.

[0127] Next, in the corresponding electrode leads, the rate of change of impedance data at multiple locations is compared to detect whether each battery cell is disconnected (B3). In other words, the detection result of B2 can be verified based on the detection result of B3.

[0128] Finally, the final disconnected battery cell can be detected by combining the first and second detection results. Since determining whether a disconnection exists based on the rate of change of impedance at the measurement location is a different method than determining disconnection using the K-NN algorithm described above, the first and second detection results may be the same or partially different. When the first and second detection results are partially different, the detection accuracy can be improved because undetected battery cells can be additionally discovered.

[0129] Figure 13 This is another schematic diagram illustrating the rate of change of impedance values ​​of a normal battery cell and a disconnected battery cell according to the measurement location.

[0130] Figure 13 The two lines shown in the graphs are the measured real part resistance values ​​of the positive lead L and R at various frequencies.

[0131] As shown in the figure, the top eight normal battery cells exhibit slightly different rates of impedance change depending on the measurement position, while the bottom disconnected battery cell shows a significantly different rate of impedance change depending on the measurement position. This demonstrates that the method of measuring impedance by changing the measurement position using a multi-point probing approach and then detecting disconnected battery cells based on the rate of change also shows significant accuracy.

[0132] Therefore, by means of Figure 12 The flowchart shown checks whether the battery cell connectors are disconnected, which can further improve the accuracy of the detection.

[0133] According to the present invention, not only can rapid and accurate inspections be performed during the manufacturing of battery cells, but also rapid and accurate detection can be made of defects (such as disconnected electrode connections) in battery cells that have been used for a predetermined period of time and then reused. Therefore, defects in battery cells can be quickly identified during the recycling process to determine whether the battery cells can be reused.

[0134] The above description is merely an exemplary description of the technical spirit of the present invention, and those skilled in the art can make various modifications and variations without departing from the essential characteristics of the present invention. Therefore, the accompanying drawings disclosed in this invention are provided not to limit but to describe the technical spirit of the invention, and the scope of the technical spirit of the invention is not limited by these drawings. The scope of the invention should be interpreted by the following claims, and should be interpreted as including all technical spirit within the equivalent scope within the scope of the invention.

[0135] In addition, this specification uses directional terms such as up, down, left, right, forward, and backward, but these terms are obviously only for ease of description and can be changed according to the position of the target object, the position of the observer, etc.

[0136] (See attached image labels)

[0137] 10: Battery Unit

[0138] 11: Battery casing

[0139] 12: Electrode assembly

[0140] 13: Electrode connector

[0141] 14: Electrode leads

[0142] 15: Disconnected section

[0143] 100: Battery cell electrode connector disconnection inspection equipment

[0144] 110: Impedance Measurement Section

[0145] 120: Confirmation Department

[0146] 130: Storage Department

[0147] P: Probe

[0148] 14 and 14′: Electrode leads

[0149] 200: Battery cell electrode connector disconnection inspection equipment

[0150] 210: Impedance Measurement Section

[0151] 220: Controller (Determination Unit)

[0152] 230: Storage Department

[0153] 240: Multi-probe section

[0154] 250: Switching relay box

[0155] SW: Switch or relay

[0156] P1, P2, P3: Probes based on the measurement position

Claims

1. An electrode connector disconnection inspection device, the electrode connector disconnection inspection device comprising: An impedance measuring unit is connected to the electrode leads of the battery cell to be inspected to measure the impedance value according to the frequency. as well as A determining unit is configured to compare frequency-based impedance value data of the battery cell under inspection acquired by the impedance measurement unit with frequency-based impedance value data of a normal battery cell without a disconnect electrode connector or frequency-based impedance value data of a battery cell with a disconnect electrode connector, in order to determine whether the battery cell under inspection is disconnected. The determining unit selects a predetermined number of impedance value data points that are nearest neighbors to the impedance value data of the battery cell under test within a selected specific frequency range from normal battery cells, battery cells with disconnected connectors, or both normal battery cells and battery cells with disconnected connectors. It then determines whether the electrode connector of the battery cell under test is disconnected based on the type of battery cell that occupies the larger number of selected data points. The data set of predetermined impedance values ​​based on frequency for the normal battery cell and the disconnected battery cell is a data set repeatedly learned by the K nearest neighbor algorithm.

2. The electrode connector disconnection inspection device according to claim 1, wherein, The selected predetermined number of impedance value data points is an odd number greater than or equal to 3.

3. The electrode connector disconnection inspection device according to claim 2, wherein, The selected predetermined number of impedance value data points is 3 or 5.

4. The electrode connector disconnection inspection device according to claim 1, wherein, The selected specific frequency range is the frequency range in which the impedance data points of the normal battery cell and the disconnected battery cell do not overlap or have the smallest overlapping area.

5. The electrode connector disconnection inspection device according to claim 1, wherein, The battery cell to be inspected is identified as a normal battery cell when the data of the normal battery cell occupies a large number of the selected data points, and is identified as a disconnected battery cell when the data of the disconnected battery cell occupies a large number of the selected data points.

6. The electrode connector disconnection inspection device according to claim 1, further comprising a storage unit, wherein the data set is stored in the storage unit, and the determining unit determines whether the connector of the battery cell is disconnected by comparing it with the data set in the storage unit.

7. An electrode connector disconnection inspection device, the electrode connector disconnection inspection device comprising: A multi-probe section, the multi-probe section including multiple probes corresponding to multiple measurement positions of electrode leads disposed in the battery cell to be inspected, wherein each probe is alternately and electrically connected to each measurement position; An impedance measurement unit is connected to each probe of the multi-probe unit to measure the impedance value according to the frequency at each measurement position of the electrode lead; as well as The determining unit is configured to compare the frequency-based impedance value data of the battery cell under inspection acquired by the impedance measurement unit with a predetermined set of frequency-based impedance value data of a defective battery cell without a disconnected electrode connector or a defective battery cell with a disconnected electrode connector, to determine whether the battery cell under inspection is disconnected. Specifically, for each measurement position of the electrode lead, the determining unit selects a predetermined number of impedance value data points that are closest to the impedance value data of the battery cell to be inspected in a selected specific frequency range, for normal battery cells, battery cells with disconnected connectors, or both normal battery cells and battery cells with disconnected connectors, and determines whether the electrode connector connected to the measurement position of the electrode lead is disconnected based on the type of battery cell that occupies the larger number of selected data points.

8. The electrode connector disconnection inspection device according to claim 7, wherein, The selected predetermined number of impedance value data points is an odd number greater than or equal to 3.

9. The electrode connector disconnection inspection device according to claim 8, wherein, The selected predetermined number of impedance value data points is 3 or 5.

10. The electrode connector disconnection inspection device according to claim 7, wherein, The selected specific frequency range is the frequency range in which the impedance data points of the normal battery cell and the disconnected battery cell do not overlap or have the smallest overlapping area.

11. The electrode connector disconnection inspection device according to claim 7, wherein, The electrode connector at the corresponding measurement position connected to the electrode lead is determined to be not disconnected when the data of the normal battery cell occupies a large number of selected data points, and is determined to be disconnected when the data of the disconnected battery cell occupies a large number of selected data points.

12. The electrode connector disconnection inspection device according to claim 7, wherein, The data set of predetermined impedance values ​​based on frequency for the normal battery cell and the disconnected battery cell is a data set repeatedly learned by the K-nearest neighbor algorithm.

13. The electrode connector disconnection inspection device according to claim 7, further comprising: A switching relay box is configured to alternately connect each probe of the multi-probe unit to each measurement position; as well as A controller configured to control the switching relay box.

14. The electrode connector disconnection inspection device according to claim 13, wherein, The multi-probe unit is connected to at least one of the positive and negative leads of the battery cell, and with the probe connected to one of the positive and negative leads at a measurement position, the impedance value is alternately measured at multiple measurement positions of the other of the positive and negative leads.

15. The electrode connector disconnection inspection device according to claim 14, wherein, The measurement position of each of the positive and negative leads is located at equal intervals, starting from the housing of the battery cell or the end of each lead.

16. The electrode connector disconnection inspection device according to claim 7, wherein, The electrode connector disconnection inspection device combines the results of whether the electrode connector is disconnected with the results of whether the electrode connector is disconnected with the results of whether the electrode connector is disconnected with the results of whether the electrode connector is disconnected with the results of whether the electrode connector is disconnected with the results of whether the electrode connector is disconnected with the results of whether the electrode connector is disconnected with the results of whether the electrode connector is disconnected with the results of multiple measurement positions of the positive and negative leads to the electrode leads, in order to determine whether all electrode connectors of the battery cell to be inspected are disconnected.

17. The electrode connector disconnection inspection device according to claim 16, wherein, The determining unit additionally determines whether the electrode connector of the battery cell under inspection is disconnected based on the rate of change of the impedance value at each measurement position of the electrode lead, and compares the additional determining result with the combined determining result of whether a disconnection exists, so as to finally determine whether the electrode connector of the battery cell under inspection is disconnected.

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