Electrode tap disconnection inspection device of battery cell

Abstract

The electrode tab open circuit inspection device of a battery cell according to the present invention comprises: an impedance measuring unit connected to the electrode lead of a battery cell to be inspected and measuring an impedance value according to frequency; and The present invention includes a determination unit that determines whether the battery cell under inspection is disconnected by comparing impedance value data according to frequency of the battery cell under inspection acquired by the impedance measuring unit with a predetermined group of impedance value data according to frequency of normal battery cells in which the electrode tab is not disconnected or battery cells with disconnected electrode tabs. The determination unit selects a predetermined number of impedance value data of normal battery cells or battery cells with disconnected tabs, or normal and disconnected battery cells, that are nearest neighboring to the impedance value data of the battery cell under inspection in a selected specific frequency range, and determines whether the electrode tab of the battery cell under inspection is disconnected according to the type of battery cell that accounts for a larger number among the selected data.

Description

Technology Field

[0001] The present invention relates to an electrode tab disconnection inspection device for non-destructively inspecting an electrode tab of a battery cell. Background Technology

[0003] Recently, rechargeable secondary batteries are being widely used as an energy source for wireless mobile devices. Furthermore, secondary batteries are attracting attention as an energy source for electric vehicles and hybrid electric vehicles, which are being proposed as solutions to address air pollution caused by conventional gasoline and diesel vehicles that use fossil fuels. Consequently, the types of applications utilizing secondary batteries are becoming highly diversified due to their advantages, and it is expected that secondary batteries will be applied to a wider range of fields and products in the future than they are today.

[0004] These secondary batteries are classified into lithium-ion batteries, lithium-ion polymer batteries, and lithium-polymer batteries depending on the composition of the electrodes and electrolytes; among these, the use of lithium-ion polymer batteries is increasing due to their low risk of electrolyte leakage and ease of manufacturing. Generally, secondary batteries are classified according to the shape of the battery case into cylindrical and prismatic batteries, in which the electrode assembly is housed in a cylindrical or prismatic metal can, and pouch-type batteries, in which the electrode assembly is housed in a pouch-type case made of an aluminum laminate sheet. The electrode assembly housed in the battery case is a power generation element capable of charging and discharging, consisting of a positive electrode, a negative electrode, and a separator structure interposed between the positive and negative electrodes. It is further classified into a jelly-roll type, which is wound with a separator interposed between long sheet-type positive and negative electrodes coated with active material, and a stack type, in which multiple positive and negative electrodes of a predetermined size are sequentially stacked with a separator interposed between them.

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

[0006] As described above, an electrode assembly (12) is embedded within the battery case (11) of a pouch-type battery cell (10), and electrode tabs (13) are drawn out from the electrode assembly (12) and welded to electrode leads (14). Since the welds between the electrode tabs and the welds between the electrode tabs and the electrode leads are subjected to forces in various directions during the manufacturing process of the battery cell, a disconnection (15) may occur at one or more of the welded locations. If a disconnection occurs, it may cause defects such as low voltage.

[0007] In order to detect a break in the electrode tab, conventional methods used include applying pressure to the battery cell to measure the change in impedance of the battery cell due to the pressure, as described in Patent Document 1, or physically inspecting the weld location using CT scanning.

[0008] In the technology of Patent Document 1, a pressurizing mechanism is required to separately pressurize the battery cell in order to measure the change in impedance, so it was difficult to apply inspection at the mass production level.

[0009] In addition, since CT scanning takes about 1 minute and 30 seconds to inspect each battery cell, mass production-level inspection was also impossible.

[0010] To overcome the above problem, the applicant developed an electrode tab disconnection method as shown in FIG. 2. That is, a battery cell with a broken tab was detected by comparing the impedance value or the real part resistance value of the impedance of a battery cell under inspection measured in a specific frequency range (e.g., a resonant frequency range) with the impedance value or the real part resistance value of the impedance of a normal battery cell without a broken tab and a battery cell with a broken tab in the same frequency range.

[0011] However, even with the above method, an overlapping region occurred between the impedance value change region of a normal (good) battery cell and the impedance value change region of a tap open (defective) battery cell; and when the impedance value or real part resistance value of the battery cell under inspection fell within this overlapping region, it was difficult to determine whether to classify it as normal or as a tap open.

[0012] In addition, there were issues such as the tap open circuit judgment result varying depending on the resistance value measurement location of the electrode lead.

[0014] Therefore, it is desirable to develop an electrode tab disconnection inspection technology that can more accurately determine whether the electrode tab of a battery cell is disconnected. Prior art literature

[0016] Korean Published Patent Application No. 10-2020-0035594 The problem to be solved

[0017] The present invention was devised to solve the above-mentioned problem and aims to provide a battery cell electrode tab disconnection inspection device capable of more accurately detecting whether the electrode tab of a battery cell is disconnected based on the so-called K-nearest neighbor method (nearest neighbor algorithm).

[0018] In addition, the purpose is to provide a battery cell electrode tab disconnection inspection device capable of accurately determining whether the electrode tab is disconnected based on the resistance value measurement position of the electrode lead. means of solving the problem

[0020] The electrode tab open circuit inspection device of a battery cell according to the present invention comprises: an impedance measuring unit connected to the electrode lead of a battery cell to be inspected and measuring an impedance value according to frequency; and

[0021] The present invention includes a determination unit that determines whether the battery cell under inspection is disconnected by comparing impedance value data according to frequency of the battery cell under inspection acquired by the impedance measuring unit with a predetermined group of impedance value data according to frequency of normal battery cells in which the electrode tab is not disconnected or battery cells with disconnected electrode tabs. The determination unit selects a predetermined number of impedance value data of normal battery cells or battery cells with disconnected tabs, or normal and disconnected battery cells, that are nearest neighboring to the impedance value data of the battery cell under inspection in a selected specific frequency range, and determines whether the electrode tab of the battery cell under inspection is disconnected according to the type of battery cell that accounts for a larger number among the selected data.

[0022] As an example, the selected predetermined number of impedance value data is an odd number of 3 or more.

[0023] As another example, the selected specific frequency range may be a frequency range in which the impedance value data of the normal and tapped open-circuit battery cells do not overlap with each other, or the overlapping area is the smallest.

[0024] Specifically, if the data of normal battery cells accounts for a larger number among the selected data, the battery cell to be inspected is determined to be a normal battery cell, and if the data of battery cells with broken tabs accounts for a larger number among the selected data, the battery cell to be inspected is determined to be a battery cell with broken tabs.

[0025] In addition, the data set of predetermined impedance values ​​according to the frequency of the above normal battery cells and tap-disconnected battery cells may be a data set that has been repeatedly learned by the K-nearest neighbor algorithm.

[0026] As another example of the present invention, the electrode tab open circuit inspection device comprises: a multi-probe unit having a plurality of probes corresponding to a plurality of measurement points of an electrode lead provided in a battery cell to be inspected, wherein each probe is electrically connected alternately to each measurement point; and an impedance measurement unit connected to each probe of the multi-probe unit to measure impedance values ​​according to frequency for each measurement point of the electrode lead. The invention includes a determination unit that determines whether the battery cell under inspection is disconnected by comparing the impedance value data according to the frequency of the battery cell under inspection acquired by the impedance measuring unit with a predetermined group of impedance value data according to the frequency of good battery cells in which the electrode tab is not disconnected and defective battery cells in which the electrode tab is disconnected. The determination unit is characterized by selecting, for each measurement point of the electrode lead, the impedance value data of the battery cell under inspection in a selected specific frequency range and a predetermined number of impedance value data of the nearest neighboring normal battery cells, battery cells with a disconnected tab, or normal and disconnected battery cells, and determining whether the electrode tab connected to each measurement point of the electrode lead is disconnected according to the type of battery cell that accounts for a larger number among the selected data.

[0027] As an example, the selected predetermined number of impedance value data is an odd number of 3 or more.

[0028] As another example, the selected specific frequency range may be a frequency range in which the impedance value data of the normal and tapped open-circuit battery cells do not overlap with each other, or the overlapping area is the smallest.

[0029] Specifically, if the data of normal battery cells accounts for a larger number among the selected data, the electrode tab connected to the corresponding measurement point of the electrode lead is determined not to be disconnected, and if the data of disconnected battery cells accounts for a larger number among the selected data, the electrode tab connected to the corresponding measurement point of the electrode lead is determined to be disconnected.

[0030] As an example, a data set of predetermined impedance values ​​according to the frequency of the above normal battery cells and tapped open-circuit battery cells may be a data set that has been repeatedly learned by the K-nearest neighbor algorithm.

[0031] As an example, the electrode tab open circuit inspection device may further include a switching relay box that alternately electrically connects the probes of the multi-probe unit to each measurement location; and a control unit that controls the switching relay box.

[0032] Specifically, the multi-probe unit is connected to at least one of the positive lead and negative lead of the battery cell having different polarities, and with a probe connected to one measurement point of one of the positive lead and negative lead, the impedance values ​​can be measured alternately for a plurality of measurement points of the other lead of the positive lead and negative lead.

[0033] As an example, each measurement point of the positive lead and the negative lead may be located at equal intervals from the end of each lead or the case of the battery cell.

[0034] The above electrode tab open circuit inspection device can determine whether the electrode tab of the entire battery cell being inspected is open circuit by combining the determination result of whether the electrode tab is open circuit regarding multiple measurement points of one of the positive lead and negative lead among the electrode leads, and the determination result of whether the electrode tab is open circuit regarding multiple measurement points of the other of the positive lead and negative lead among the electrode leads.

[0035] As another example, the judgment unit may additionally determine whether the electrode tab of the battery cell under inspection is disconnected based on the rate of change of the impedance value according to each measurement point of the electrode lead, and determine whether the electrode tab of the battery cell under inspection is finally disconnected by comparing the additional judgment result with the combined determination result. Effects of the invention

[0037] According to the present invention, even when it is unclear whether a battery cell is normal or has a broken tab, the electrode tab of the battery cell can be accurately detected by applying the K-nearest neighbor algorithm.

[0038] In addition, by detecting whether the electrode tab is disconnected based on the measurement location of the electrode lead's impedance value, it is possible to more accurately determine whether the electrode tab of the entire battery cell is disconnected. Brief explanation of the drawing

[0040] Figure 1 is a schematic diagram showing the location where a disconnection occurs in the electrode tab of a pouch-type battery cell. FIG. 2 is a graph showing the principle of detecting an open circuit in an electrode tab of a battery cell using an impedance value or a real part resistance value proposed by the applicant. FIG. 3 is a schematic diagram of an electrode tab inspection device for a battery cell according to one embodiment of the present invention. Figure 4 is a schematic diagram explaining the principle of the K-nearest neighbor algorithm. Figure 5 is a flowchart showing the data learning process according to the K-nearest neighbor algorithm. FIG. 6 is a schematic diagram of an electrode tab inspection device for a battery cell according to another embodiment of the present invention. FIG. 7 is a schematic diagram showing an example of measuring impedance values ​​according to the measurement location of the electrode lead of a battery cell. FIG. 8 is a flowchart showing an example of a process for detecting whether a battery cell is disconnected using an electrode tab inspection device of the battery cell of the embodiment of FIG. 6. Figures 9 and 10 are graphs showing the results of determining whether there is an open circuit when the measurement point of the impedance value of the negative lead is fixed and the measurement point of the positive lead is varied to measure the impedance value. Figure 11 is a schematic diagram showing the rate of change of impedance values ​​according to measurement locations of a normal battery cell and a tap-open battery cell. FIG. 12 is a flowchart showing another example of detecting whether a battery cell is disconnected using an electrode tab inspection device of the battery cell of the embodiment of FIG. 6. Figure 13 is another schematic diagram showing the rate of change of impedance values ​​according to measurement locations of a normal battery cell and a tap-open battery cell. Specific details for implementing the invention

[0041] The present invention will be described in detail below. Prior to this, terms or words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings. Instead, based on the principle that the inventor may appropriately define the concepts of terms to best describe their invention, they must be interpreted in a meaning and concept consistent with the technical spirit of the present invention.

[0042] In this application, terms such as "comprising" or "having" are intended to specify the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof. Furthermore, when a part such as a layer, film, region, or plate is described as being "on" another part, this includes not only cases where it is "immediately above" the other part, but also cases 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 cases where it is "immediately below" the other part, but also cases where there is another part in between. Additionally, in this application, being placed "on" may include cases where it is placed on the lower part as well as on the upper part.

[0043] Meanwhile, in this application, "length direction" refers to the direction in which the electrode lead of the battery cell protrudes.

[0045] It is presumed that if the electrode tab of a battery cell is disconnected as shown in Fig. 1, there will be a change in the impedance value of the battery cell. Based on this, Patent Document 1 adopts a method of detecting whether the connection is broken by applying pressure to the battery cell and measuring the change in impedance.

[0046] However, as described above, the present invention aims to detect whether a wire is disconnected based on the impedance value without applying pressure.

[0047] In addition, it is intended to accurately detect whether the tab is disconnected even when the impedance values ​​of a normal battery cell and a battery cell with a disconnected tab overlap.

[0049] (First embodiment)

[0050] The electrode tab open circuit inspection device (100) of the present embodiment includes an impedance measuring unit (110) connected to the electrode leads (14, 14') of the battery cell (10) to be inspected, which measures an impedance value according to frequency; The invention includes a determination unit (120) that determines whether the battery cell (10) to be tested is disconnected by comparing the impedance value data according to the frequency of the battery cell (10) to be tested, obtained by the impedance measuring unit (110), with a predetermined group of impedance value data according to the frequency of normal battery cells in which the electrode tab is not disconnected or battery cells with a disconnected electrode tab. The determination unit (120) is characterized by selecting a predetermined number of impedance value data of normal battery cells or battery cells with a disconnected tab or normal and disconnected tabs that are nearest neighboring to the impedance value data of the battery cell (10) to be tested in a selected specific frequency range, and determining whether the electrode tab of the battery cell (10) to be tested is disconnected according to the type of battery cell that occupies a larger number among the selected data.

[0051] FIG. 3 is a schematic diagram of an electrode tab inspection device (100) of a battery cell according to one embodiment of the present invention.

[0052] The above battery cell (10) is a pouch-type cell and is a so-called bidirectional battery cell in which electrode leads of different polarities are derived from each of the longitudinal ends of the battery cell. However, it is not limited to this, and the present invention can determine whether the electrode tab is disconnected using a unidirectional battery cell in which electrode leads of different polarities are derived from the same end of the battery cell.

[0053] The present invention includes an impedance measuring unit (110) connected to the electrode lead of a battery cell (10) to be tested. The impedance measuring unit (110) may be connected to the electrode lead of the battery cell (10) by means of a predetermined connecting cable and a connection terminal. In FIG. 3, the electrode lead (14, 14') and the impedance measuring unit (110) are connected by a probe (P) and a wire. The impedance measuring unit (110) can measure the impedance value of the battery cell (10) according to frequency. As the impedance measuring unit (110), for example, an EIS (Electrochemical Impedance Spectroscopy) measuring instrument can be used to obtain an impedance value according to frequency by applying a minute AC signal of a different frequency. In addition to the impedance value, the EIS measuring instrument can obtain various parameters related to the impedance value, such as the impedance phase angle, real part resistance value, and imaginary part resistance value through predetermined calculations, according to frequency.

[0054] The electrode tab disconnection inspection device (100) of the present invention determines whether the battery cell (10) to be inspected is disconnected by comparing the impedance value data according to the frequency of the battery cell (10) to be inspected, obtained by the impedance measuring device (110), with the group of impedance value data according to the frequency of a predetermined normal battery cell and a battery cell with a disconnected tab.

[0055] The inspection device (100) of the present invention is in line with the technology for determining whether a wire is broken by comparing impedance values ​​in a specific frequency range proposed by the present applicant. However, as shown in FIG. 2, the conventional method could not accurately determine whether a wire is broken for a battery cell (10) to be inspected that corresponds to an overlap area where the impedance values ​​of a normal battery cell and a battery cell with a broken tab overlap. Alternatively, it was difficult to determine whether a wire is broken even when it is unclear whether it falls within the range of impedance values ​​of a normal battery cell or the range of impedance values ​​of a battery cell with a broken tab.

[0056] The present invention resolves the above problem by using the so-called K-nearest neighbor method (K-nearest neighbor algorithm, abbreviated as K-NN algorithm).

[0057] Figure 4 is a schematic diagram explaining the principle of the K-NN algorithm.

[0058] The K-Nearest Neighbor algorithm, abbreviated as K-NN, is a type of supervised learning, a form of machine learning, and can be described as a distance-based classification analysis model. The K-NN algorithm classifies data by referencing the labels of 'K' other data points that are close to the data point; it has the advantage of being simple and easy to implement. Specifically, as shown in Figure 4, when triangle data and square data are located on a predetermined coordinate plane, it is possible to determine which data point the circular data should be classified to belong to. If the number of data points closest to the circular data is determined to be 3 (i.e., K=3), the circular data is classified to belong to the triangle data. However, if the number of data points closest to the circular data is determined to be 5 (K=5), the circular data is classified to belong to the square data. Therefore, by setting an appropriate number of K, it becomes possible to determine the type of data even when it is unclear which type of data it belongs to.

[0059] The determination unit (120) of the present invention selects a predetermined number of impedance values ​​of normal battery cells or battery cells with a tab disconnection or normal and battery cells with a tab disconnection that are closest neighbors to the impedance value data of the battery cell to be inspected, and determines whether the electrode tab of the battery cell (10) to be inspected is disconnected according to the type of battery cell that occupies a larger number among the selected data. In this specification, "closest neighbor" does not necessarily mean a single data that is closest neighbor. That is, the meaning of "closest neighbor" in the present invention corresponds to the concept of "closest neighbor" in the K-NN algorithm, meaning that when K data are selected around a specific data, a plurality (K) of data that are "closest neighbors" to the specific data are selected.

[0060] To explain based on the example in Fig. 4, for instance, the triangular data can be considered as the impedance value data of the battery cells with broken tabs, and the square data as the impedance value data of the normal battery cells. If the impedance value data of a specific frequency of the battery cell (10) under inspection is considered as circular data, the presence of broken tabs in the battery cell (10) under inspection can be determined based on whether it falls within the category of the dotted or solid circle in Fig. 4. That is, when K is set to 5, the impedance value data (circular data) of the battery cell (10) under inspection can be viewed as the impedance value data (square data) of the normal battery cells, and thus the battery cell (10) under inspection is determined to be a normal battery cell that is not broken. Furthermore, if the data of normal battery cells accounts for a larger number among the data selected as the closest neighbors, the battery cell (10) under inspection is determined to be a normal battery cell. That is, if K=5 and among the data closest to the impedance value data of the battery cell (10) to be tested, 3 are normal battery cells and 2 are tap-open battery cells, then the battery cell (10) to be tested is determined to be a normal battery cell.

[0061] Conversely, if the data of tap-disconnected battery cells among the selected nearest neighbor data accounts for a larger number, the battery cell (10) to be inspected is determined to be a tap-disconnected battery cell. That is, if K=5 and among the data closest neighbors to the impedance value data of the battery cell (10) to be inspected, 3 are tap-disconnected battery cells and 2 are normal battery cells, then the battery cell (10) to be inspected is determined to be a tap-disconnected battery cell.

[0062] In this way, by comparing impedance values ​​according to the K-NN algorithm, it is possible to determine whether there is a disconnection even when the impedance values ​​of normal and tap-disconnected battery cells overlap as shown in FIG. 2. That is, by selecting an appropriate K value according to the K-NN algorithm and selecting a predetermined number of impedance value data, the number of nearest data can be determined for any data. Therefore, even when the impedance values ​​overlap overall as shown in FIG. 2, it is possible to determine the type of adjacent battery cell that occupies a larger number of impedance value data for the corresponding battery cell.

[0063] Meanwhile, in the present invention, the impedance value is a concept that includes not only the total impedance value having real and imaginary components, but also the real resistance value (Rs). That is, if the impedance phase angle and the impedance value are known according to the relationship R = Z COSθ, the real resistance value can be calculated, and since the real resistance value can also be expressed as an impedance value, the presence of an open circuit can be detected using the resistance value of the real component. Therefore, the impedance value data to which the K-NN algorithm of the present invention is applied also includes the real resistance value data.

[0064] In addition, it is preferable that the number of impedance value data, i.e., the K value, selected to determine whether the electrode tab is disconnected is an odd number of 3 or more. If K is 1, the discriminative power decreases, and if K is an even number, it is difficult to determine which category the battery cell (10) under inspection belongs to when the number of nearest data is, for example, 2 to 2. Therefore, it is preferable that the K value be an odd number such as 3, 5, 7, or 9. However, if the K value becomes too large, the discriminative power of the judgment also decreases, so a K value that is not too large must be selected. Preferably, a K value of 3 or 5 is good.

[0065] In addition, the impedance value data used to determine whether the electrode tab is open can be a value within a specific frequency range.

[0066] Referring to FIG. 2, there are areas where the impedance region of a normal battery cell (good zone) and the impedance region of a battery cell with a broken tab (defective zone) are relatively clearly distinguished depending on the frequency, but there are also areas where the overlap zone is too large to be compared with the data of the battery cell (10) being inspected. Such extensive overlap zones mainly occur in the low frequency range. In addition, since the location or size of the overlap zone may vary depending on the type, physical properties, and internal condition of the battery cell, an appropriate frequency range must be selected according to the battery cell.

[0067] Therefore, the specific frequency range selected to determine whether the electrode tab is open refers to the 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.

[0068] Referring again to FIG. 3, it can be seen that the judgment unit (120) of the present invention determines whether the tab of the battery cell (10) under inspection is disconnected by the K-NN algorithm as described above. Meanwhile, a predetermined impedance value data group of normal and disconnected battery cells, which is compared with the impedance value data of the battery cell (10) under inspection, is also a data group obtained by iterative learning by the K-NN algorithm. This data group is stored in a storage unit (130), such as a predetermined database, and the judgment unit (120) can determine whether the tab of the battery cell is disconnected by comparing it with the data group of the storage unit (130). As shown in FIG. 3, the storage unit (130) may be provided as a separate server or DB from the judgment unit (120). Alternatively, it may be included in the judgment unit (120) as a memory-type storage unit. The judgment unit (120) may be a predetermined computing device with software in which the K-NN algorithm is implemented.

[0070] Figure 5 is a flowchart showing an example of a data learning process according to the K-nearest neighbor algorithm.

[0071] For example, a predetermined number of battery cells with the positive or negative tabs artificially disconnected can be produced, and normal battery cells of the same type can be mixed with these disconnected tab battery cells to prepare a predetermined number (e.g., 100) of battery cells for creating a data group. 80% (e.g., 80) of the battery cells in this group are randomly selected, and the impedance value data of the selected battery cells is measured to learn the impedance value data according to frequency of the normal battery cells and the disconnected tab battery cells, thereby forming a predetermined data group for comparison (S1).

[0072] The impedance values ​​of the remaining 20% ​​(e.g., 20) of battery cells are measured and compared with the data set of comparison targets using the K-NN algorithm to predict whether each of the 20% of battery cells is disconnected a predetermined number of times (S3).

[0073] Next, the predicted result is verified against whether the actual normal and tap-open battery cell is a valid cell (S3).

[0074] Cell ID Predicted recovery Recovery predicted by single line Recovery predicted to be normal Actual battery cell 11360 25th 0 25 Normal battery cell 11361 17th episode 0 17 Normal battery cell 22464 23rd episode 23 0 Tab open circuit battery cell 22465 23rd episode 23 0 Tab open circuit battery cell

[0075] 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 based on the impedance value data set of 80% of the selected battery cells in the population, the tap disconnection status can be predicted with 100% accuracy. Of course, depending on which data set is selected, the prediction result may not be 100% but may have other accuracy levels such as 90% or 95%. In this way, data with verified accuracy is updated as training data for predicting tap disconnection.

[0076] In addition, to increase the accuracy of the data set, this data learning process can be repeated, for example, 100 times to obtain a control data set for a more reliable and accurate K-NN algorithm (S4).

[0078] (Second embodiment)

[0079] The electrode tab open circuit inspection device (200) of the present embodiment comprises: a plurality of probes (P1, P2, P3) corresponding to a plurality of measurement points of electrode leads (14, 14') provided in a battery cell (10) to be inspected, wherein each probe (P1, P2, P3) is electrically connected alternately to each measurement point; and an impedance measurement unit (210) connected to each probe (P1, P2, P3) of the multi-probe unit (240) to measure impedance values ​​according to frequency for each measurement point of the electrode lead. The invention includes a determination unit (220) that determines whether the battery cell (10) to be inspected is disconnected by comparing the impedance value data according to the frequency of the battery cell (10) to be inspected, obtained by the impedance measuring unit (210), with a predetermined group of impedance value data according to the frequency of good battery cells in which the electrode tab is not disconnected and defective battery cells in which the electrode tab is disconnected. The determination unit (220) is characterized by selecting, for each measurement point of the electrode lead, the impedance value data of the battery cell (10) to be inspected in a selected specific frequency range and a predetermined number of impedance value data of the nearest neighboring normal battery cells or battery cells with a disconnected tab, or normal and disconnected battery cells, and determining whether the electrode tab connected to each measurement point of the electrode lead is disconnected according to the type of battery cell that occupies a larger number among the selected data.

[0080] FIG. 6 is a schematic diagram of an electrode tab inspection device (200) of a battery cell according to the second embodiment.

[0081] The electrode tab inspection device (200) of the present embodiment is equipped with a multi-probe unit (240). The multi-probe unit (240) is equipped with a plurality of probes (P1, P2, P3) at positions corresponding to a plurality of measurement points of electrode leads provided at both ends in the longitudinal direction of a pouch-type battery cell. As shown in FIG. 1, the electrode leads are connected to a plurality of tab bundles. Even if a disconnection occurs in a specific tab, a tab at another location may be normal, and if the impedance value is measured at the location of the electrode lead connected to such normal tab, the value can be measured as the impedance value of a normal battery cell. Therefore, there may be cases where a defective battery cell is shipped to the market after measuring the impedance value at only one measurement point of the electrode lead.

[0082] In order to prevent the above-mentioned case, the invention of the present embodiment is equipped with a multi-probe unit (240) to measure impedance values ​​at multiple locations of the electrode lead using multiple probes (P1, P2, P3). However, the impedance values ​​are not measured all at once using multiple probes (P1, P2, P3); instead, each probe (P1, P2, P3) is electrically connected alternately to each measurement location to enable sequential measurement of the impedance values ​​at specific locations.

[0083] In addition, the inspection device (200) of the present invention includes an impedance measuring unit (210) connected to each probe (P1, P2, P3) of the multi-probe unit (240) to measure impedance values ​​according to frequency for each measurement location of the electrode leads (14, 14'). An EIS measuring instrument (210) may be used as the impedance measuring unit (210). Since the impedance measuring unit (210) has been sufficiently explained in the first embodiment, a detailed description thereof is omitted in this embodiment.

[0084] The determination unit (220) of this embodiment can also determine whether the electrode tab is disconnected for each measurement point of the electrode lead (14, 14') by the K-NN algorithm, as in the first embodiment. Unlike the first embodiment, this embodiment is equipped with a plurality of probes (P1, P2, P3) that are electrically connected alternately to each measurement point, so the K-NN algorithm can be applied to each measurement point. Accordingly, this embodiment can determine whether the electrode lead is normal or disconnected by comparing it with a predetermined impedance value data group according to the frequency of normal or disconnected battery cells for each measurement point of the electrode lead. In this case, for an equivalent comparison, the predetermined impedance value data group that is compared with the impedance value measured at a specific location of the electrode lead (14, 14') must also be measured at the same location as the specific location of the electrode lead.

[0085] In addition, the number of impedance value data selected to determine the nearest neighbor is an odd number of 3 or more, which is the same as in the first embodiment. Also, for each measurement location, the frequency of the group of impedance value data that is compared with the impedance value data to be tested must be selected within a range where the impedance value data of normal and tap-open battery cells do not overlap as much as possible, just as in the first embodiment.

[0086] By means of the K-NN algorithm, the determination of whether the electrode tab at each measurement location of this embodiment is disconnected is performed as follows.

[0087] For the impedance values ​​measured at each measurement point, if the data of normal battery cells among the selected nearest neighbor data accounts for a larger number, the electrode tab connected to the corresponding measurement point of the electrode lead is determined not to be disconnected.

[0088] For the impedance values ​​measured at each measurement point, if the data of battery cells with disconnected tabs among the selected nearest neighbor data accounts for a larger number, the electrode tab connected to the corresponding measurement point of the electrode lead is determined to be disconnected.

[0089] In this case, the data set of predetermined impedance values ​​according to the frequency of the contrasting normal battery cells and tap-open battery cells is also a data set that has been repeatedly learned by the K-NN algorithm as shown in Fig. 5.

[0090] These data groups are stored in a storage unit (230), such as a database, and the judgment unit (220) can determine whether the battery cell's tab is disconnected by comparing it with the data groups in the storage unit (230). As shown in FIG. 6, the storage unit (230) may be provided as a separate server or DB from the judgment unit (220). Alternatively, it may be included in the judgment unit (220) as a memory-type storage unit. The judgment unit (220) may be a certain computing device with embedded software in which a K-NN algorithm is implemented.

[0091] In order to alternately electrically connect the above-mentioned plurality of probes (P1, P2, P3) to each measurement point, the electrode tab open circuit inspection device (200) of the present embodiment may be equipped with a switching relay box (250). The switching relay box (250) is connected to each probe (P1, P2, P3) of the multi-probe unit (240) by a circuit and is equipped with a switch or relay (SW) that electrically switches and electrically connects each probe (P1, P2, P3). Since such an electrical relay mechanism is commonly known, a description thereof will be omitted. When the above-mentioned multi-probe unit (240) is connected to at least one of the positive lead and negative lead (14, 14') of the battery cell having different polarities, the impedance values ​​for each of the plurality of measurement points at each lead can be measured by the EIS meter (210).

[0092] Additionally, a control unit may be provided to control the switching relay box (250) so that each of the probes (P1, P2, P3) are alternately connected to each measurement location. The control unit may be separate from the judgment unit (220) or may include the judgment unit (220) as shown in FIG. 6. In the latter case, the control unit may be a control computer equipped with a judgment unit (220) having software that implements the K-NN algorithm.

[0093] In FIG. 6, impedance values ​​are measured at three measurement points for each electrode lead. However, the number of measurement points may be two, four, five, or more as needed. In FIG. 6, R and L refer to the right and left sides of the electrode lead. In particular, open circuits frequently occur in the tabs adjacent to both sides of the electrode lead. Taking this into account, the embodiment of FIG. 6 shows that impedance values ​​are measured at the R and L sections, which are the sides of the electrode lead. It is preferable that the measurement points be set according to the same standard. For example, if measurement points are set parallel at the same interval relative to the ends of each lead (14, 14') or the battery cell case, impedance values ​​can be measured and compared for each measurement point under relatively equal conditions.

[0094] In the switching relay box (250) of FIG. 6, the dotted line indicates that the switch (SW) is not connected, and the solid line indicates that the switch (SW) is connected. Accordingly, FIG. 6 shows that both the positive lead and the negative lead (14, 14') measure the impedance value at the measurement point at the R position. By switching the relay box (250), the impedance value at other measurement points can also be measured.

[0095] When measuring impedance values ​​at multiple locations of a single electrode lead, the measurement locations of other electrode leads need to be fixed. This is because it is necessary to objectively compare whether the tap is open at multiple locations of a single electrode lead. FIG. 7 is a schematic diagram illustrating such a measurement setup. Referring to FIG. 7, the measurement location of the right electrode lead (14') (e.g., negative electrode lead) is fixed at a single central location, and the measurement locations of the left electrode lead (14) (e.g., positive electrode lead) are set at two locations, R and L, to alternately measure impedance values. By doing so, it is possible to objectively compare whether the tap is open at location R of the positive electrode lead (14) and whether the tap is open at location L, and if an open circuit is detected at either location, the battery cell is determined to be a battery cell with an open tap. In FIG. 7, for convenience of illustration, only one probe is shown to indicate that the measurement location of the right electrode lead (14') is fixed at one location. However, as shown in FIG. 6, it is obvious that only one probe can be electrically connected to the corresponding measurement point by switching. Conversely to FIG. 7, the measurement point of the positive lead (14) on the left can be fixed to one central point, and the impedance value can be measured for two points, R and L, of the negative lead (14') on the right to detect whether the tab connected to the negative lead is disconnected. In this way, the probes (P1, P2, P3) of the multi-probe unit (240) are alternately electrically connected to each measurement point of the electrode lead to measure the impedance value, and the battery cell (10) to be inspected is determined to be a normal battery cell only when the impedance value of each measurement point corresponds to the impedance value of a normal battery cell, and is determined to be a battery cell with a disconnected tab if the impedance value of any one point corresponds to the impedance value of a battery cell with a disconnected tab.

[0096] FIG. 8 is a flowchart showing an example of a process for detecting whether a battery cell is disconnected using an electrode tab inspection device of the battery cell of the embodiment of FIG. 6.

[0097] First, impedance value data of multiple electrode leads is obtained by the impedance measuring unit (210).

[0098] For example, as shown in FIG. 7, the measurement position of the negative lead (14') is fixed, and impedance value data at L and R points of the positive lead (14) is acquired. Next, the measurement position of the positive lead (14) is fixed, and impedance value data at L and R points of the negative lead (14') is acquired (A1).

[0099] Next, the impedance value data for each location and the group of contrast impedance value data for the same location learned by, for example, the K-NN algorithm are compared by the nearest neighbor algorithm to detect a tap open circuit at the location (A2).

[0100] In this case, even if a disconnection is not detected at a specific location, a disconnection may be detected at another location. Therefore, since combining the results of disconnection detection at multiple locations can reduce the number of cases where a tap disconnection is not detected, the detection results of each measured location are combined to detect the disconnection (A3).

[0101] Finally, based on the combined detection results, it is possible to determine whether the entire battery cell is disconnected (A4).

[0102] Table 2 below shows the detection of electrode tab disconnection in the entire battery cell (10) to be inspected by combining the results of determining whether the electrode tab is disconnected at multiple measurement points (R, L) of the positive lead (14) and the results of determining whether the electrode tab is disconnected at multiple measurement points (R, L) of the negative lead (14').

[0103] Selected frequency range: 160~100Hz (analysis of 2 measurement points) / K=5 Test conditions K-NN Judgment Results 1+2 / 3+4 combination result 1. 27 normal products VS 27 positively disconnected wires (Cathode lead position fixed + Positive lead L measured) Not detected: 3 1 not detected 2. 27 Normal Products VS 27 Positively Illegible Products (Cathode Lead Position Fixed + Positive Lead R Measured) Not detected: 4 3. 27 normal products VS 27 with open cathode (positive lead position fixed + negative lead L measured) Not detected: 3 1 not detected 4. 27 normal products VS 27 with open cathode (positive lead position fixed + negative lead R measured) Not detected: 4

[0104] FIGS. 9 and 10 are graphs showing the results of determining whether a wire is disconnected when the measurement point of the impedance value of the negative lead (14') is fixed and the measurement point of the positive lead (14) is varied. That is, FIGS. 9 and 10 show that the number of undetected wires is reduced by the combination of the judgment results in cases 1 and 2 of Table 2.

[0105] FIG. 9 shows the results of measuring the real part resistance value R at a total of 21 frequency points within the frequency range of 1 kHz to 0.1 Hz for 27 normal (good) battery cells and 27 battery cells in which L points of the positive lead (14) are disconnected. As illustrated, in the high and low frequency regions, the impedance value data sets of the normal products and the disconnected battery cells overlap, making it difficult to form a comparison data set for determining the quality of the battery cells (10) under inspection. Since there is relatively little overlap between 160 and 100 Hz in FIG. 9, the disconnection status was detected by the K-NN algorithm in this frequency range. For convenience of illustration, the frequency (f)-real part resistance value (R) coordinate data were connected by lines, but as described above, in reality, frequency-real part resistance value data at each of the 21 points were acquired using an EIS measuring instrument (210) and compared using the K-NN algorithm. The detection result of FIG. 9, cell ID. Since this experiment was conducted by acquiring (learning) impedance value data using battery cells that were known in advance to be normal / short-circuited, it was possible to identify battery cells with short circuits that were not detected by the above detection method. As shown in Fig. 9, three short-circuited battery cells with cell IDs 12672, 12684, and 12710 were determined to be good products and were not detected.

[0106] FIG. 10 shows the results of measuring the real part resistance value R at a total of 21 frequency points within the frequency range of 1 kHz to 0.1 Hz for 27 normal (good) battery cells and 27 battery cells in which the R point of the positive lead (14) is disconnected. Similarly, the disconnection status was detected by the K-NN algorithm in the frequency range of 160 to 100 Hz. As a result of the detection, four disconnected battery cells with cell IDs 12710, 12705, 12664, and 12671 were determined to be good and were not detected.

[0107] When the judgment results of Figures 9 and 10 are combined, only the open-circuit battery cell with cell ID 12710 was not detected. That is, as shown in Table 2, when the test results of 1 and 2 above are combined, the open-circuit battery cell that is not detected becomes 1 out of 54, so the accuracy or efficiency of open-circuit detection can be greatly increased.

[0108] In addition, the position of the positive lead (14) is fixed, and the measurement points of the negative lead (14') are divided into L and R to detect whether the tab is disconnected. When the results are determined by combining these, only one battery cell is not detected, similar to FIGS. 9 and 10, so the detection accuracy is also improved.

[0110] Meanwhile, when measuring impedance values ​​at multiple measurement points using a multi-point method as in the present embodiment, the rate of change in impedance values ​​of normal battery cells and battery cells with disconnected tabs appears differently depending on the measurement point.

[0111] Figure 11 is a schematic diagram showing the rate of change of impedance values ​​according to measurement locations of a normal battery cell and a tap-open battery cell.

[0112] Figure 11 shows the rate of change in impedance value according to frequency for each location while fixing the measurement location of the positive lead (P:14) and changing the measurement location of the negative lead (N:14')) to 5 locations.

[0113] As described above, in the case of a normal battery cell, it can be seen that the rate of change in impedance values ​​at five locations is almost similar. However, in the case of a battery cell with a broken tab, it can be seen that the impedance values ​​are generally higher than those of a normal battery cell, and the rates of change are different. In particular, it can be seen that the rate of change in impedance value at location 4, where the broken tab occurred, differs significantly from the rate of change in impedance value at the remaining locations.

[0114] From this, in the present embodiment of the invention, which determines whether a tap is open based on the impedance values ​​of multiple electrode leads, it is determined that if the electrode tap is additionally determined based on the rate of change of impedance values ​​from such multi-point measurement, and if this additional determination result is combined with the determination result of whether a tap is open based on the K-NN method, the tap open detection result can be further improved.

[0115] FIG. 12 is a flowchart showing another example of detecting whether a battery cell is disconnected using an electrode tab inspection device of the battery cell of the embodiment of FIG. 6.

[0116] First, impedance value data for multiple locations of the electrode leads are acquired using the electrode tab inspection device shown in Fig. 6 (B1).

[0117] Next, the impedance value data is compared with a predetermined impedance value data group of a normal battery cell and a tap-open battery cell using the K-NN algorithm to primarily detect whether there is a disconnection at each measurement location (B2). In this case, as shown in FIG. 8, the detection accuracy can be increased by combining the results of determining whether there is a disconnection at multiple locations.

[0118] Next, regarding the electrode lead, the rate of change of impedance value data at multiple locations is compared according to each measurement location to secondarily detect whether each battery cell is disconnected (B3). That is, the detection result of B2 can be verified with the detection result of B3.

[0119] Finally, the final disconnected battery cell can be detected by combining the above first and second detection results. Since the determination of whether a connection is open based on the rate of change of impedance values ​​according to the measurement location differs somewhat in approach from the determination of whether a connection is open based on the above-described K-NN algorithm, the first and second detection results may match or differ in part. If there is a partial difference, additional undetected battery cells can be discovered, thereby increasing the detection accuracy.

[0120] Figure 13 is another schematic diagram showing the rate of change of impedance values ​​according to measurement locations of a normal battery cell and a tap-open battery cell.

[0121] The two lines shown in each graph of Fig. 13 represent the real part resistance values ​​measured according to frequency for L and R points of the positive lead, respectively.

[0122] As described above, the eight normal battery cells above show almost no difference in the rate of change of impedance values ​​depending on the measurement location, whereas the battery cells with open tabs below show a large difference in the rate of change of impedance values ​​depending on the measurement location. From this, it can be seen that the method of measuring impedance values ​​at different measurement locations using a multi-point probing method and detecting open-tab battery cells from the rate of change also shows considerable accuracy.

[0123] Therefore, by checking whether the tab of the battery cell is disconnected through a flow such as that of Fig. 12, the detection accuracy can be further increased.

[0125] The foregoing description is merely an illustrative explanation of the technical concept of the present invention, and those skilled in the art to which the present invention pertains will be able to make various modifications and variations within the scope of the essential characteristics of the present invention. Accordingly, the drawings disclosed in this invention are intended to explain, not limit, the technical concept of the present invention, and the scope of the technical concept of the present invention is not limited by these drawings. The scope of protection of the present invention shall be interpreted by the claims below, and all technical concepts within an equivalent scope shall be interpreted as being included within the scope of rights of the present invention.

[0127] Meanwhile, although terms indicating directions such as up, down, left, right, front, and back have been used in this specification, these terms are used merely for convenience of explanation, and it is obvious that they may vary depending on the location of the object or the position of the observer. Explanation of the symbols

[0129] 10: Battery cell 11: Battery case 12: Electrode assembly 13: Electrode tab 14: Electrode Lead 15: Single line section 100: Battery cell electrode tab open circuit inspection device 110: Impedance measurement section 120: Judgment panel 130: Storage section P: Probe 14,14': Electrode leads 200: Battery cell electrode tab open circuit inspection device 210: Impedance measurement section 220: Control unit (judgment unit) 230: Storage section 240: Multi-probe section 250: Switching relay box SW: Switch or relay P1, P2, P3: Probes according to measurement location

Claims

Claim 1 An impedance measuring unit connected to the electrode lead of a battery cell under inspection to measure an impedance value according to frequency; The invention includes a determination unit that determines whether the battery cell to be inspected is disconnected by comparing the impedance value data according to frequency of the battery cell to be inspected, obtained by the impedance measuring unit, with a predetermined group of impedance value data according to frequency of normal battery cells in which the electrode tab is not disconnected or battery cells with a disconnected electrode tab. The determination unit selects a predetermined number of impedance value data of normal battery cells, battery cells with a disconnected tab, or both normal and disconnected battery cells that are nearest neighboring to the impedance value data of the battery cell to be inspected in a selected specific frequency range, and determines whether the electrode tab of the battery cell to be inspected is disconnected according to the type of battery cell that occupies a larger number among the selected data. If the data of normal battery cells occupies a larger number among the selected data, the battery cell to be inspected is determined to be a normal battery cell, and if the data of battery cells with a disconnected tab occupies a larger number among the selected data, the battery cell to be inspected is determined to be a battery cell with a disconnected tab. The contrasting impedance value data is impedance value data The electrode tab disconnection inspection device is a real part resistance value data excluding the imaginary part resistance value, wherein the judgment unit selects a predetermined number of real part resistance value data and determines whether the electrode tab of the battery cell to be inspected is disconnected according to the type of battery cell that occupies a larger number among the selected data, and the selected specific frequency range is a frequency range in which the real part resistance value data of the normal and tab disconnection battery cells do not overlap with each other, or the overlapping area is the smallest. Claim 2 In claim 1, the electrode tab open circuit inspection device wherein the selected predetermined number of real part resistance value data is an odd number of 3 or more. Claim 3 delete Claim 4 delete Claim 5 In claim 1, the electrode tab open circuit inspection device, wherein the data set of predetermined real part resistance values ​​according to the frequency of the normal battery cells and the tab open circuit battery cells is a data set that is repeatedly learned by the K-nearest neighbor algorithm. Claim 6 A multi-probe unit having a plurality of probes corresponding to a plurality of measurement points of an electrode lead provided in a battery cell to be inspected, wherein each probe is electrically connected alternately to each measurement point; and an impedance measurement unit connected to each probe of the multi-probe unit to measure impedance values ​​according to frequency for each measurement point of the electrode lead; The electrode tab disconnection inspection device comprises a determination unit that determines whether the battery cell to be inspected is disconnected by comparing the impedance value data according to the frequency of the battery cell to be inspected, obtained by the impedance measuring unit, with a predetermined group of impedance value data according to the frequency of good battery cells in which the electrode tab is not disconnected or defective battery cells in which the electrode tab is disconnected. The determination unit selects, for each measurement point of the electrode lead, the impedance value data of the battery cell to be inspected in a selected specific frequency range and a predetermined number of impedance value data of the nearest neighboring normal battery cells or battery cells with a disconnected tab, or normal and battery cells with a disconnected tab, and determines whether the electrode tab connected to each measurement point of the electrode lead is disconnected according to the type of battery cell that occupies a larger number among the selected data. Claim 7 In claim 6, the electrode tab open circuit inspection device wherein the selected predetermined number of impedance value data is an odd number of 3 or more. Claim 8 In claim 6, the selected specific frequency range is an electrode tab open circuit inspection device in which the impedance value data of the normal and tab open circuit battery cells do not overlap with each other, or the overlapping area is the smallest. Claim 9 An electrode tab disconnection inspection device according to claim 6, wherein if the data of normal battery cells among the selected data account for a larger number, the electrode tab connected to the corresponding measurement point of the electrode lead is determined not to be disconnected, and if the data of disconnected battery cells among the selected data account for a larger number, the electrode tab connected to the corresponding measurement point of the electrode lead is determined to be disconnected. Claim 10 In claim 6, the electrode tab open circuit inspection device, wherein the data set of predetermined impedance values ​​according to the frequency of the normal battery cells and the tab open circuit battery cells is a data set that is repeatedly learned by the K-nearest neighbor algorithm. Claim 11 In claim 6, an electrode tab open circuit inspection device further comprising: a switching relay box that alternately electrically connects the probes of the multi-probe unit to each measurement location; and a control unit that controls the switching relay box. Claim 12 An electrode tab open circuit inspection device according to claim 11, wherein the multi-probe unit is connected to at least one of the positive lead and negative lead having different polarities of the battery cell, and the impedance values ​​are alternately measured for a plurality of measurement points of the other lead of the positive lead and negative lead while the probe is connected to one measurement point of one of the positive lead and negative lead. Claim 13 In claim 12, each measurement location of the positive lead and the negative lead is an electrode tab open circuit inspection device located at equal intervals from the end of the positive lead and the end of the negative lead, or from the case of the battery cell. Claim 14 An electrode tab disconnection inspection device according to claim 6, which determines whether the electrode tab is disconnected in all battery cells subject to inspection by combining the determination result of whether the electrode tab is disconnected in relation to multiple measurement points of one of the positive lead and negative lead among the electrode leads, and the determination result of whether the electrode tab is disconnected in relation to multiple measurement points of the other of the positive lead and negative lead among the electrode leads. Claim 15 In claim 14, the above-mentioned judgment unit further determines whether the electrode tab of the battery cell under inspection is disconnected based on the rate of change of impedance values ​​according to each measurement location of the electrode lead, and determines the final disconnection of the electrode tab of the battery cell under inspection by comparing the additional judgment result with the combined determination result.

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