Apparatus and method for checking the disconnection of electrode terminals in battery cells

Abstract

The device for checking the disconnection of electrode connectors for battery cells according to the present invention includes: a measuring unit that measures an impedance value and an impedance angle according to the frequency of the battery cell to be checked; a calculating unit that calculates the real part resistance value of the impedance according to the frequency of the battery cell to be checked based on the impedance value and the impedance angle; and a determining unit that checks whether the electrode connector of the battery cell to be checked is disconnected by comparing the real resistance value of a good quality battery cell of the same type as the battery cell to be checked within a range of real resistance values ​​in the resonant frequency range with the real resistance value of the impedance of the battery cell to be checked within the same frequency range as the resonant frequency range.

Description

Technical Field

[0001] The present invention relates to an apparatus and method for inspecting the disconnection of electrode connectors in a battery cell, for non-destructive inspection of the disconnection of electrode connectors in a target battery cell.

[0002] This application claims priority to Korean Patent Application No. 10-2021-0104021, filed on August 6, 2021, the entire contents of which are incorporated herein by reference. Background Technology

[0003] Recently, rechargeable and discharging batteries have been widely used as energy sources for wireless mobile devices. Furthermore, as an energy source for electric vehicles, hybrid electric vehicles, and the like, rechargeable batteries have attracted attention, being proposed as a solution to air pollution from existing gasoline and diesel vehicles that use fossil fuels. Therefore, due to the advantages of rechargeable batteries, their applications have diversified, and in the future, they are expected to be used in even more fields and products.

[0004] Such secondary batteries can be classified into lithium-ion batteries, lithium-ion polymer batteries, and lithium polymer batteries based on the composition of their electrodes and electrolytes. Among these, the use of lithium-ion polymer batteries, which have a low possibility of electrolyte leakage and are easy to manufacture, is increasing. Secondary batteries are typically classified according to the shape of their battery casings, including cylindrical and prismatic batteries where the electrode assembly is housed in a cylindrical or prismatic metal can, and pouch batteries where the electrode assembly is housed in a pouch-shaped casing formed of aluminum laminated sheets. The electrode assembly housed in the battery casing is formed into a structure including a positive electrode, a negative electrode, and a separator inserted between the positive and negative electrodes. It is a power-generating element capable of charging and discharging and is classified into gel roll type and stacked type. In the gel roll type, the separator is inserted between the positive and negative electrodes, which are coated with active material and have an elongated sheet shape, and is wound up. In the stacked type, multiple positive and negative electrodes of predetermined dimensions are sequentially stacked with the separator inserted between them.

[0005] Figure 1 This is a schematic diagram showing the disconnected position of the electrode connector 13 of the pouch cell 10.

[0006] As shown in the figure, the electrode assembly 12 is installed in the battery casing 11 of the pouch cell 10, and the electrode connector 13 is removed from the electrode assembly 12 and soldered to the electrode lead 14. Because the soldered portions of the electrode connectors and the soldered portions of the electrode connectors and the electrode leads receive forces in various directions during the manufacturing process of the battery cell, breakage may occur at one or more of the soldered portions. When breakage occurs, it may lead to defects such as low voltage.

[0007] To detect the disconnection of the electrode connector, conventional methods, such as those described in Patent Document 1, have been used, such as pressing the battery cell and measuring the impedance change based on the pressing, or physically inspecting the weld position by capturing computed tomography (CT) images.

[0008] In the technology of Patent Document 1, since a separate pressing device is required to press the battery cell to measure the impedance change, it is difficult to apply the method to mass production level inspection.

[0009] Furthermore, in the case of taking CT images, it is impossible to perform large-scale production-level inspections because it takes approximately 1 minute and 30 seconds to inspect each battery cell.

[0010] Therefore, there is a need to develop a battery cell electrode connector disconnection inspection technology, in which the battery cell is not pressed and does not require a long inspection period, and can be performed quickly at a large-scale production level.

[0011] [Primary Technology]

[0012] [Patent Literature]

[0013] Korean Patent Publication No. 10-2020-0035594 Summary of the Invention

[0014] Technical issues

[0015] The purpose of this invention is to provide an apparatus and method for checking the disconnection of electrode connectors in battery cells, which can detect the disconnection of electrode connectors in a short time.

[0016] Technical solution

[0017] According to the present invention, an apparatus for checking the disconnection of electrode connectors of a battery cell includes: a measuring unit that measures an impedance value and an impedance angle according to the frequency of the target battery cell; a calculation unit that calculates the real part resistance value of the impedance according to the frequency of the target battery cell based on the impedance value and the impedance angle; and a determining unit that determines whether the electrode connector of the battery cell is disconnected by comparing the real part resistance value of a good battery cell of the same type as the target battery cell within a resonant frequency range with the real part resistance value of the impedance of the target battery cell within a frequency range equal to the resonant frequency range.

[0018] As an example, when the real part resistance value of the impedance of the target battery cell in the same frequency range as the resonant frequency range is greater than the real part resistance value of the good battery cell in the resonant frequency range, the determining unit can determine that the electrode connector of the target battery cell is disconnected.

[0019] As an example, the measuring unit could be an electrochemical impedance spectroscopy (EIS) instrument.

[0020] As a specific example, when a portion of the real resistance value range of the good battery cell within the resonant frequency range overlaps with the change line of the real resistance value of the defective battery cell, or the real resistance value range of the defective battery cell within the same frequency range as the resonant frequency range, the determining unit can check whether the electrode connector of the target battery cell is disconnected by comparing the real resistance value of the good battery cell within the real resistance value range, including or excluding the overlapping change line or range, with the real resistance value of the target battery cell.

[0021] As another example, the determining unit can determine the real resistance value within the real resistance range of the good battery cell based on frequency data and real resistance value data within the resonant frequency range of the good battery cell, and compare the real resistance value within the real resistance range of the good battery cell with the real resistance value of the target battery cell to determine whether the electrode connector of the target battery cell is disconnected.

[0022] Furthermore, the device for checking the disconnection of the electrode terminals of the battery cells may also include a storage unit storing information relating to at least one of the resonant frequency range of the plurality of battery cells, the range of real resistance values ​​of the good battery cells within the resonant frequency range, and the correlation between the real resistance values ​​within the resonant frequency range and the frequency.

[0023] According to another aspect of the present invention, a method for checking the disconnection of electrode connectors of a battery cell includes the following steps: measuring an impedance value and an impedance angle according to the frequency of the target battery cell; calculating the real part resistance value of the impedance according to the frequency of the target battery cell based on the impedance value and the impedance angle; and determining whether the electrode connector of the target battery cell is disconnected by comparing the real part resistance value of a good battery cell of the same type as the target battery cell within a resonant frequency range with the real part resistance value of the impedance of the target battery cell within a frequency range equal to the resonant frequency range.

[0024] The resonant frequency range of the good battery cell can be the range of frequencies at which the imaginary part of the measured impedance value of each of the plurality of good battery cells changes from a positive (+) value to a negative (-) value.

[0025] As an example, the method may include the following steps: obtaining a real resistance value line of the good product impedance of each good battery cell by connecting the real resistance values ​​of each good battery cell at frequencies within the resonant frequency range; and setting the real resistance value region adjacent to the real resistance value line of the good product impedance of the good battery cell as the real resistance value range within the resonant frequency range of the good battery cell.

[0026] Specifically, the determination step may include: determining the target battery cell as a defective product when the real part resistance value of the impedance of the target battery cell in the same frequency range as the resonant frequency range is greater than the real part resistance value of the region of the real part resistance value of the good battery cell; and determining the target battery cell as a good product when the real part resistance value of the impedance of the target battery cell in the same frequency range as the resonant frequency range is less than or equal to the range of the real part resistance value of the region of the real part resistance value.

[0027] Alternatively, the determination step may include: comparing the real resistance value of the good battery cell within the real resistance value region at three points—the minimum frequency, the intermediate frequency, and the maximum frequency—with the real resistance value of the target battery cell to determine whether the target battery cell is good or bad.

[0028] As a specific example, the method may include: obtaining a defective product real resistance value line for each battery cell or a defective real resistance value region adjacent to the real resistance value lines of the plurality of defective battery cells by connecting the real resistance values ​​of each of the plurality of defective battery cells with disconnected electrode terminals; and when the defective product real resistance value line or the defective product real resistance value region overlaps with the real resistance value region of the good battery cell, setting the range including or excluding the overlapping area or line as the real resistance value range of the good battery cell, to determine whether the battery cell is good or bad.

[0029] As another example, the method may include: deriving the correlation between the real resistance value and the frequency within the resonant frequency range from frequency data and real resistance value data within the resonant frequency range of the plurality of good battery cells; and setting the real resistance value range within the resonant frequency range based on the derived correlation with the real resistance value range within the resonant frequency range of the good battery cells.

[0030] As an example, the determining step may include: determining the target battery cell as a defective product when the real part of the impedance of the target battery cell in the same frequency range as the resonant frequency range is greater than the real part of the impedance of the good battery cell in the same frequency range based on the correlation; and determining the target battery cell as a good product when the real part of the impedance of the target battery cell in the same frequency range as the resonant frequency range is less than the real part of the impedance of the good battery cell in the same frequency range based on the correlation.

[0031] As another example, the determination step may include: determining whether the battery cell is good or bad by comparing the real resistance values ​​of a good product expressed according to the correlation at three points—the minimum frequency, the middle frequency, and the maximum frequency—with the real resistance values ​​of the target battery cell at the three frequencies.

[0032] The determination step may include: determining the target battery cell as a defective product when the real part resistance value of the impedance of the target battery cell in the same frequency range as the resonant frequency range is greater than the real part resistance value based on the correlation in the resonant frequency range of the good battery cell by a predetermined range or more.

[0033] Beneficial effects

[0034] According to the present invention, since the disconnection of electrode connectors can be quickly checked, large-scale production-level inspection can be performed. Furthermore, the disconnection inspection of the present invention can prevent defective battery cells from being shipped.

[0035] Furthermore, according to the present invention, defects (disconnection of electrode connectors) in the target battery cell can be quickly inspected not only during the battery cell manufacturing stage but also during the recycling or reuse stage, where the finished battery cell is reused after a certain period of use. Therefore, when the battery cell is recycled, it can be easily determined whether the battery should be used by quickly inspecting for defects. Attached Figure Description

[0036] Figure 1 This is a schematic diagram showing the location where the electrode connector of a pouch cell is disconnected.

[0037] Figure 2 This is a diagram showing an example of a Nyquist plot of a battery cell.

[0038] Figure 3 It is a graph showing the impedance values ​​on the complex plane.

[0039] Figure 4 This is a schematic diagram illustrating an apparatus for checking the disconnection of the electrode connectors of the battery cell of the present invention.

[0040] Figure 5 This is a flowchart illustrating the process of setting a good range of real resistance values ​​for a battery cell for the method of checking the disconnection of electrode terminals in the battery cell according to the present invention.

[0041] Figure 6 This is a diagram illustrating the process of obtaining a range of real resistance values ​​and determining whether a battery cell is good or bad, according to a method for checking the disconnection of an electrode connector based on an embodiment of the present invention.

[0042] Figure 7 This is a diagram illustrating the process of obtaining a range of real resistance values ​​and determining whether a battery cell is in good condition, according to another embodiment of the present invention, a method for checking the disconnection of electrode connectors. Detailed Implementation

[0043] The invention will now be described in detail. First, the terms and words used in this specification and claims should not be construed as limited to their dictionary meanings or significance, but should be interpreted based on the inventor's appropriate definition of the concepts of the terms in order to best describe the invention, through meanings and concepts consistent with the technical scope of the invention.

[0044] In this application, it should be understood that terms such as "comprising" or "having" are intended to indicate the presence of the features, quantities, steps, operations, components, parts, or combinations thereof described in the specification, and they do not preclude the possibility of the presence or addition of one or more other features or quantities, steps or operations, components, parts, or combinations thereof. Furthermore, when a portion (e.g., a layer, membrane, region, plate, etc.) is referred to as "above another portion," this includes not only the case where the portion is "directly above another portion," but also the case where the other portion is located between them. On the other hand, when a portion (e.g., a layer, membrane, region, plate, etc.) is referred to as "below another portion," this includes not only the case where the portion is "directly below another portion," but also the case where the other portion is located between them. Additionally, in this application, "above" can include both bottom and top.

[0045] Meanwhile, in this specification, "longitudinal" refers to the direction in which the electrode leads of the battery cell protrude.

[0046] When the electrode terminals of the battery cell are like Figure 1 When the circuit is disconnected, the impedance value of the battery cell is estimated to change. Based on this, Patent Document 1 employs a method to detect whether a disconnection has occurred by pressing the battery cell and measuring the impedance change.

[0047] However, as stated above, the present invention aims to detect whether a disconnection has occurred based on impedance without applying pressure. Even when impedance changes due to a disconnection, since impedance is a value that changes according to frequency, a frequency should be specified for testing whether a disconnection has occurred based on impedance.

[0048] The resonant frequency is the frequency at which the reactance component of the impedance is zero. That is, the resonant frequency is the frequency at which the imaginary component of the impedance is zero. The resonant frequency of a battery cell is not 100% identical, but varies depending on the shape, chemical composition, and type of the battery cell. Therefore, the resonant frequency of a battery cell is a parameter indicating its characteristics or physical properties. Thus, the inventors predicted that changes in the physical properties of a battery cell could be observed by measuring the impedance at the resonant frequency. The disconnection of the electrode terminals of a battery cell can also be an example of a change in physical properties. The starting point of this invention is that when the impedance value of a good battery cell with intact electrode terminals at the resonant frequency is obtained, the disconnection of the electrode terminals can be quickly and easily checked by comparing this impedance value with the impedance value of the target battery cell under inspection.

[0049] Figure 2 This is an example graph showing the Nyquist plot of a battery cell. When small AC signals of different frequencies are applied to a specific battery cell using an impedance measurement device (such as an electrochemical impedance spectroscopy (EIS) instrument), a plot like this can be obtained. Figure 2The Nyquist plot is shown. However, although the actual points measured by the EIS instrument are limited to the number of frequencies, appropriate curve fitting can be used to obtain plots such as... Figure 2 The diagram shown illustrates this. In this case, the resonant frequency is the frequency at which the imaginary part of the impedance is zero. That is, when measuring the impedance of a battery cell using an EIS instrument, the frequency at which the imaginary part of the impedance changes from a positive (+) value to a negative (-) value (or vice versa) is the resonant frequency. Figure 2 In this context, the impedance Rs is the impedance at the resonant frequency, i.e., the real part of the resistance.

[0050] Figure 3 It is a graph showing the impedance values ​​as presented in the complex plane. For example... Figure 3 As shown, the real resistance Rs of the impedance is expressed as |Z|cosθ. The premise of this invention is to obtain the range of resonant frequencies (resonant frequency range) of a good battery cell and extract the range of real resistance values ​​of the good battery cell within the resonant frequency range. With this resistance value data for a good product, when the real resistance value of the target battery cell 10 is obtained according to its frequency and compared with the real resistance value of a good product within the same frequency range (resonant frequency range), defective products (i.e., battery cells with disconnections in the electrode terminals) can be easily detected.

[0051] The present invention will be described in detail below.

[0052] Figure 4 This is a schematic diagram illustrating the device of the present invention for checking the disconnection of electrode connectors in a battery cell.

[0053] The electrode connector disconnection inspection device 100 for battery cell 10 according to the present invention includes: a measuring unit 110 that measures the impedance value and impedance angle according to the frequency of the target battery cell 10; a calculation unit 120 that calculates the real resistance value Rs of the impedance according to the frequency of the target battery cell 10 based on the impedance value and impedance angle; and a determining unit that determines whether the electrode connector of the target battery cell 10 is disconnected by comparing the real resistance value Rs of a good battery cell of the same type as the target battery cell 10 within the resonant frequency range with the real resistance value Rs of the impedance of the target battery cell 10 within the same frequency range as the resonant frequency range.

[0054] The electrode connector disconnection inspection device 100 of the present invention includes a measuring unit 110. The measuring unit 110 can be an EIS instrument. According to the EIS instrument, impedance parameters at various frequencies can be obtained as described above. For example, impedance Z, reactance X, impedance angle θ, voltage, temperature, etc. can be obtained. In addition, the resonant frequency, which is the frequency at which the sign of the reactance (which is the imaginary part of the resistance) changes, can also be checked. The measuring unit 110 can measure the impedance value and impedance angle according to the frequency of the target battery cell 10 being inspected.

[0055] Furthermore, the electrode connector disconnection inspection device 100 of the present invention includes a calculation unit 120, which calculates the real resistance value Rs of the impedance at the frequency of the target battery cell 10 under inspection based on the impedance value and the impedance angle. When the impedance Z and the impedance angle θ are known, the real resistance value Rs can be obtained through the above equation Rs=|Z|cosθ. That is, multiple real resistance values ​​Rs can be obtained according to the frequency variation.

[0056] This invention includes a determining unit that compares the real resistance value Rs of the impedance of the target battery cell 10 to the real resistance value Rs of a good battery cell within the resonant frequency range. The range of real resistance values ​​for good products within the resonant frequency range of good battery cells of the same type as the target battery cell 10 has been pre-obtained using an EIS instrument. The setting of the range of real resistance values ​​for good products will be described below in conjunction with the method of disconnecting the electrode terminals for inspecting battery cells according to this invention.

[0057] To check if the electrode connector is disconnected, a real resistance value Rs is selected from the real resistance values ​​Rs of the target battery cell 10 within the same frequency range as that of a good battery cell. Since the target battery cell 10 is the same type of battery cell as the good product, its resonant frequency is likely to be within the resonant frequency range of the good product. However, depending on the internal state of the battery cell, the resonant frequency of the target battery cell 10 may not be within the resonant frequency range. However, in this invention, since the real resistance value data of the good product verified by multiple good battery cells is compared with the real resistance value data of the target battery cell 10, the resonant frequency of the target battery cell 10 does not necessarily have to be within the resonant frequency range of the good product. That is, when measuring the frequency of the target battery cell 10, if the frequency range of the target battery cell 10 is the same as the resonant frequency range of a good product, this frequency range is acceptable. Furthermore, by comparing the real resistance value Rs of the target battery cell 10 within this frequency range with the real resistance value range of a good product, it can be quickly determined whether the electrode connector of the target battery cell 10 is disconnected. In this case, since only the real resistance value of the target battery cell 10 within a specific frequency range measured by the EIS instrument is compared with a preset real resistance value range of a good product, it is not necessary to press the battery cell. Therefore, whether the battery cell is disconnected can be easily checked by an algorithm or calculation program that uses the measurement unit 110 to perform the measurement, the calculation unit 120 to calculate the real resistance value Rs, and the determination unit 130 to perform the comparison. In this respect, since the electrode connector disconnection inspection device 100 of the present invention can perform inspections quickly at a level applicable to mass production, the electrode connector disconnection inspection device 100 is highly advantageous for factory automation.

[0058] As a specific example, there are instances where a portion of the real resistance value range of a good battery cell within its resonant frequency range overlaps with the real resistance value range of a defective battery cell within the same frequency range as its resonant frequency range, or where the variation line of the real resistance value range of the defective battery cell overlaps. In other words, the real resistance value range of a good product is not necessarily completely distinguishable from the real resistance value Rs of a defective product. This overlap between the real resistance value ranges of good and defective products becomes significant in the low-frequency range, as described below. However, as will be described below, the overlap is much smaller within the resonant frequency range, which is why the real resistance Rs within the resonant frequency range is compared.

[0059] The determining unit 130 can check whether the electrode connector of the target battery cell 10 is broken by comparing the real resistance value Rs within a range of real resistance values ​​that includes overlapping change lines or does not include overlapping ranges of good battery cells with the real resistance value Rs of the target battery cell 10. For example, in the case of battery cells in fields with strict quality standards and very high safety requirements, the breakage is checked by comparing only the range of real resistance values ​​of good products (which does not include the range overlapping with the resistance value range or real resistance value change lines of defective products) with the real resistance value Rs of the target battery cell 10. In this case, although a battery cell with good quality can be considered a defective product and discarded, when safety is given priority, a battery cell with overlapping real resistance values ​​Rs is also considered a defective product.

[0060] On the other hand, in battery cells where relatively high quality standards and relatively high safety are not required, from the perspective of product productivity, the presence of disconnections is checked by considering all products with good real resistance values ​​Rs within the overlapping range as belonging to the good product range. In this case, although it is possible to identify defective battery cells that have disconnected as good products, productivity and safety are weighted and compared, and this possibility is accepted.

[0061] On the other hand, the determining unit 130 can check whether the electrode connector of the target battery cell 10 is disconnected by comparing the real resistance value Rs in the real resistance value range of the good battery cell, derived from the correlation between frequency data and real resonance value data within the resonant frequency range of the good battery cell, with the real resistance value Rs of the target battery cell 10. For example, multiple real resistance value data can be obtained for multiple frequencies of each good battery. In this case, when the frequency data and impedance value data are plotted on a coordinate plane, several scattered data points will be displayed. For example, linear regression analysis can be used to obtain the correlation between the frequency data and the real resistance value data. When such a correlation is obtained, a function or correlation can be derived within the resonant frequency range of multiple battery cells. Then, since the real resistance value range of the good product according to a single correlation is compared with the real resistance value range of the target battery cell, it is possible to check whether a disconnection has occurred more quickly and accurately. A more detailed description of the method for checking the disconnection of the electrode connector according to the present invention will be provided.

[0062] The electrode connector disconnection inspection device 100 of the present invention may further include a storage unit 140, which stores information relating to at least one of the following: the resonant frequency range of a plurality of battery cells, the range of real resistance values ​​of good battery cells within the resonant frequency range, and the correlation between the frequency and the real resistance value Rs within the resonant frequency range. Figure 4 As shown, the storage unit 140 can be provided in conjunction with the determination unit 130 (see [reference]). Figure 4 A) A separate server or database (DB) type. Alternatively, storage unit 131 may be included in determining unit 130 as a type of storage (see [link]). Figure 4 B).

[0063] like Figure 4 As shown, a disconnection can be quickly checked by using the measurement unit 110 to measure the impedance value and impedance angle according to the frequency of the target battery cell 10, using the calculation unit 120 to calculate the real resistance value Rs according to the frequency from these values, and using the determination unit 130 to compare the real resistance value Rs in the resonant frequency range of the good battery cell with the real resistance value Rs of the target battery cell 10 in the same frequency range. Each of the calculation unit 120 and the determination unit 130 can be a computing device implemented in hardware, including a computing device (such as a central processing unit (CPU) or a microcontroller unit (MCU)) and a storage device (such as a hard disk), using predetermined software, and the calculation unit 120 and the determination unit 130 are configured to communicate with each other. Furthermore, according to an embodiment, the calculation unit 120 and the determination unit 130 can also be implemented as a single processor.

[0064] The following describes a method for checking the disconnection of electrode connectors in a battery cell, according to the present invention.

[0065] The method of the present invention for checking the disconnection of electrode connectors includes: measuring an impedance value and an impedance angle according to the frequency of the target battery cell; calculating a real resistance value Rs of the impedance according to the frequency of the target battery cell based on the impedance value and the impedance angle; and determining whether the electrode connector of the target battery is disconnected by comparing a real resistance value within a resonant frequency range of a good battery cell of the same type as the target battery cell with a real resistance value of the impedance of the target battery cell within a frequency range equal to the resonant frequency range.

[0066] First, such as Figure 2 As shown, when the target battery cell is connected to the measurement unit 110, such as an EIS instrument, the impedance value and impedance angle are measured according to the frequency of the target battery. As described above, since the EIS instrument can measure various parameters related to impedance, it can measure both impedance value and impedance angle.

[0067] Next, the real part resistance value Rs of the impedance at the frequency of the target battery cell being inspected is calculated based on the impedance value and impedance angle. For example, the calculation unit 120 equipped with a predetermined calculation program can... Figure 3 The predetermined equation shown mechanically and automatically calculates the real part resistance value Rs of the impedance based on the frequency of the target battery cell being inspected.

[0068] Finally, by comparing the real resistance value Rs of a good battery cell of the same type as the target battery cell with the real resistance value Rs of the impedance of the target battery cell in the same frequency range as the resonant frequency range, it is determined whether the electrode connection of the target battery is disconnected.

[0069] In this determination, the real resistance value Rs of a good battery cell of the same type as the target battery cell is compared with the real resistance value of the target battery cell within its resonant frequency range. Therefore, information related to the resonant frequency range of the good battery cell and information related to the real resistance value range of the good product within its resonant frequency range are required. Furthermore, the method for determining whether a disconnection has occurred may differ slightly depending on the type of good product real resistance value range obtained.

[0070] This information should be obtained before inspecting the target battery cell. The following will describe the acquisition of this information and the methods used to check for disconnections, or the methods for determining this information.

[0071] Figure 5 This is a flowchart illustrating the process of setting a good range of real resistance values ​​for a battery cell for the method of checking the disconnection of electrode terminals in the battery cell according to the present invention.

[0072] First, while changing the frequency, measure the impedance and impedance angle of multiple good battery cells (with the electrode connections of the battery cells not disconnected). As mentioned above, this process can be performed using an EIS instrument. Thus, the aforementioned impedance parameters can be obtained.

[0073] Subsequently, the resonant frequency of each battery cell is extracted to derive the resonant frequency range of multiple good battery cells. In this case, the resonant frequency range of a good battery cell is the range of frequencies encompassing the frequency range where the imaginary part of the measured impedance value of each of the multiple good battery cells changes from a positive (+) value to a negative (-) value. Since the resonant frequencies differ slightly even when the battery cell types are the same, the entire resonant frequency range is obtained when the resonant frequency of each of the multiple battery cells is obtained. This is determined as the resonant frequency range of the corresponding good battery cell.

[0074] Next, through Figure 3 The equation calculates the real part of the impedance Rs of multiple good battery cells from the impedance value and impedance angle.

[0075] Furthermore, based on the resonant frequency range and the calculated Rs value, a good range of real resistance values ​​for the battery cell within the resonant frequency range is set.

[0076] Two implementations related to the setting of the real part resistance value range will be described below. The method for checking for disconnection can be changed in each implementation.

[0077] Forms for implementing the present invention

[0078] (First Implementation)

[0079] Figure 6 This is a diagram illustrating the process of obtaining a range of real resistance values ​​and determining whether a battery cell is good or bad, according to a method for checking the disconnection of an electrode connector based on an embodiment of the present invention.

[0080] like Figure 6 As shown, the real resistance value Rs of each good battery cell at a frequency f within the resonant frequency range can be connected to obtain a line representing the real resistance value of the good product impedance for each battery cell. In this embodiment, the real resistance values ​​Rs of ten good battery cells at frequencies f are obtained, and the real resistance values ​​R are connected as a line.

[0081] In this case, the region of real resistance values ​​adjacent to the real resistance value line of a good product impedance of a good battery cell can be the range of real resistance values ​​within the resonant frequency range of the good battery cell. Figure 6 In the diagram, the region of good products is shown at frequency f. However, as described below, at low frequencies, due to the presence of many regions overlapping with the region of real resistance values ​​of defective products, only the range of real resistance values ​​within the resonant frequency range is limited to the range of real resistance values ​​of good products used for disconnection checks.

[0082] In this case, when checking the real resistance value Rs of the target battery cell, the real resistance value within the same frequency range as the resonant frequency range is compared with the real resistance value region of a good battery cell. Figure 6 The real resistance values ​​within the resonant frequency range are compared. If the former is greater than the latter, the target battery cell can be identified as a defective product, and if the former falls within the latter's range or is smaller, the target battery cell can be identified as a good product.

[0083] Alternatively, when determining whether a battery cell is good or bad, the real resistance value Rs of a good battery cell can be compared with the real resistance value Rs of a specific battery cell at three points: the minimum frequency, the middle frequency, and the maximum frequency within the resonant frequency range. That is, since the resonant frequencies of ten good battery cells span a range (resonant frequency range), comparing the real resistance values ​​Rs at a single point within that range may reduce reliability. Therefore, comparing the real resistance values ​​Rs of good battery cells at... Figure 6 The real resistance value Rs at the minimum frequency z, the middle frequency y, and the maximum frequency x within the resonant frequency range is compared with the real resistance value Rs of the target battery cell at three frequency points that are the same as the resonant frequency to determine whether the battery cell is good or bad.

[0084] While ideally the real resistance ranges of good products and defective products should not overlap, in reality, there may be situations such as... Figure 6 The overlapping range is shown. For example, in multiple (five) defective battery cells where all electrode connections are broken, the defective product real resistance value lines for each battery cell or adjacent defective product real resistance value regions of multiple defective battery cells can be obtained by connecting the real resistance values ​​according to the frequency f of the battery cell. Figure 6 As shown, the region of real resistance values ​​in defective products overlaps significantly with the region of good products at low frequencies. However, as shown, within the resonant frequency range, the real resistance values ​​Rs in the region of defective products are relatively clearly distinguishable from those in the region of good products, and only some of the real resistance values ​​Rs in the region of defective products overlap with those in the region of good products. In this case, as described above, the range of good products based on the real resistance value Rs can be determined by weighting and comparing quality standards, safety, and productivity perspectives. Figure 6 As shown in the enlarged diagram, when quality and safety are important, portion B, which excludes the area where the real resistance value line of a defective product or the area where the real resistance value of a defective product overlaps with the area where the real resistance value of a good battery cell overlaps with that of a good battery cell, is excluded. The goodness of the target battery cell is determined by comparing the real resistance value (area) C under portion B with the real resistance value Rs of the target battery cell being inspected. When quality standards are not stringent and productivity is considered, the goodness of the target battery cell is determined by comparing the entire range of real resistance values ​​of a good product, including portion B and the real resistance value (area) C, with the real resistance value Rs of the target battery cell being inspected.

[0085] (Second Implementation)

[0086] Figure 7This is a diagram illustrating the process of obtaining a range of real resistance values ​​and determining whether a battery cell is good or bad, according to another embodiment of the present invention, for checking the disconnection of electrode connectors.

[0087] and Figure 6 Similarly, this embodiment is characterized by simplifying the range of real resistance values ​​of good batteries by using statistical techniques such as regression analysis to simplify disconnection checks, rather than combining the real resistance value lines at the resonant frequencies of individual good battery cells.

[0088] That is, such as Figure 6 As shown, frequency and real resistance data for multiple (e.g., 10, 100, or 1000) good battery cells within the resonant frequency range are plotted on a coordinate plane with frequency and real resistance value Rs. In this case, as the number of battery cells increases, the dispersion of data points marked as coordinates may also increase. Based on this data, a relational equation that appropriately reflects the data can be derived with frequency f as the independent variable and real resistance value Rs as the dependent variable. That is, the correlation between multiple data segments can be derived through regression analysis. The relational equation can be one of various functions such as linear functions, quadratic functions, polynomial functions, exponential functions, and logarithmic functions.

[0089] As described above, the correlation between frequencies within the resonant frequency range and the real resistance value Rs is derived, and based on the derived correlation, the region of real resistance values ​​within the resonant frequency range is defined as the range of real resistance values ​​within the resonant frequency range of a good battery cell.

[0090] refer to Figure 7 This shows a correlation between frequency data and real resistance data of ten good battery cells.

[0091] Therefore, when inspecting a target battery cell, if the real resistance value Rs of the target battery cell in the same frequency range as the resonant frequency range is greater than the correlation-based real resistance value of a good battery cell in the same frequency range, the target battery cell can be identified as a defective product. Conversely, if the real resistance value Rs of the target battery cell in the same frequency range as the resonant frequency range is less than the correlation-based real resistance value range of a good battery cell in the same frequency range, the target battery cell can be identified as a good product.

[0092] Specifically, the quality of a target battery cell can be determined by comparing the real resistance values ​​r, q, and p of a good product, which are expressed as correlations at the minimum frequency z, the middle frequency y, and the maximum frequency x within the resonant frequency range, with the real resistance value Rs of a specific battery cell at the three frequency points.

[0093] Alternatively, when determining the defective battery cell, if the real part of the impedance of a particular battery cell in the same frequency range as the resonant frequency range is larger by a predetermined range or more than the correlation-based real part of the impedance of a good battery cell in the same frequency range as the resonant frequency range, the target battery cell can be identified as a defective product. Because regression analysis models multiple data points, errors (residuals and estimated standard errors) inevitably arise between the actual measured data and the data based on the correlation equation. Therefore, when... Figure 7 The real part resistance value of the single functional relationship shown is compared with the real part resistance value of the target battery cell. If the real part resistance value of the target battery cell is larger than the real part resistance value of a good battery cell within the resonant frequency range by a certain range (e.g., a statistically generated error range), the target battery cell can be identified as a defective product. This is similar to excluding good product areas from the range of real part resistance values. Figure 6 The implementation method uses the overlapping real resistance values ​​of the defective product area to determine whether a disconnection has occurred. Therefore, it allows for a more rigorous inspection of whether the battery cell's electrode connections are disconnected.

[0094] As described above, in this invention, it is possible to quickly check whether the electrode connections of a battery cell are disconnected even without pressing the battery cell. That is, by using a conventional impedance meter such as an EIS instrument and predetermined statistical techniques, it is possible to quickly and easily check whether the electrode connections of a battery cell are disconnected simply by comparing them with the real resistance value of a good battery cell.

[0095] Furthermore, according to the present invention, not only can rapid inspection be performed during the battery cell manufacturing stage, but also defects (such as disconnected electrode joints) in the battery cells can be quickly detected during the recycling or reuse stage (when the finished battery cells are reused after a certain period of use). Therefore, when the battery cells are recycled, it can be easily determined whether the battery is still usable by inspecting for defects in the battery cells.

[0096] The above description is merely an example illustrating the technical spirit of the present invention. Those skilled in the art can make various changes, modifications, and substitutions without departing from the essential characteristics of the invention. Therefore, the embodiments disclosed in this invention are considered in a descriptive sense only and not for limiting purposes, and the scope of the invention is not limited by the embodiments. It should be understood that the scope of the invention is defined by the appended claims and includes all modifications and equivalents falling within the scope of the appended claims.

[0097] Furthermore, although directional terms such as up, down, left, right, forward, and backward have been used in this specification, these terms are merely for descriptive convenience, and it is clear that the direction changes depending on the position of the target object or the observer.

[0098] (See attached image labels)

[0099] 10: Battery cells

[0100] 11: Battery casing

[0101] 12: Electrode assembly

[0102] 13: Electrode connector

[0103] 14: Electrode leads

[0104] 15: Disconnect

[0105] 100: Battery cell electrode connector disconnection inspection equipment

[0106] 110: Measurement Department

[0107] 120: Computing Department

[0108] 130: Determining Department

[0109] 131, 140: Storage Department

Claims

1. A device for checking the disconnection of electrode terminals of a battery cell, the device comprising: The measuring unit measures the impedance value and impedance angle based on the frequency of the target battery cell being inspected; The calculation unit calculates the real part of the impedance resistance value based on the impedance value and the impedance angle, according to the frequency of the target battery cell being inspected. as well as The determining unit determines whether the electrode connector of the target battery cell is disconnected by comparing the real resistance value of a good battery cell of the same type as the target battery cell with the real resistance value of the impedance of the target battery cell in the same frequency range as the resonant frequency range.

2. The apparatus according to claim 1, wherein, When the real part resistance value of the impedance of the target battery cell in the same frequency range as the resonant frequency range is greater than the real part resistance value of the good battery cell in the resonant frequency range, the determining unit determines that the electrode connector of the target battery cell is disconnected.

3. The apparatus according to claim 1, wherein, The measurement unit includes an electrochemical impedance spectroscopy (EIS) instrument.

4. The apparatus according to claim 1, wherein, When a portion of the real resistance value range of the good battery cell within the resonant frequency range overlaps with the change line of the real resistance value of the defective battery cell, or the real resistance value range of the defective battery cell within the same frequency range as the resonant frequency range, the determining unit checks whether the electrode connector of the target battery cell is disconnected by comparing the real resistance value of the good battery cell within the real resistance value range, including or excluding the overlapping change line or range, with the real resistance value of the target battery cell.

5. The apparatus according to claim 1, wherein the determining unit determines a real resistance value within a real resistance range of the good battery cell based on frequency data within the resonant frequency range of the good battery cell and real resistance value data within the resonant frequency range, and compares the real resistance value within the real resistance range of the good battery cell with the real resistance value of the target battery cell to check whether the electrode connector of the target battery cell is disconnected.

6. The apparatus of claim 1, further comprising a storage unit storing information relating to at least one of the resonant frequency range of the plurality of battery cells, the range of real resistance values ​​of the good battery cell within the resonant frequency range, and the correlation between the real resistance value within the resonant frequency range and the frequency.

7. A method for checking the disconnection of electrode terminals in a battery cell, the method comprising the following steps: The impedance value and impedance angle are measured based on the frequency of the target battery cell being inspected. Calculate the real part of the impedance value based on the impedance value and the impedance angle, according to the frequency of the target battery cell being inspected. as well as The electrode connection of the target battery cell is determined to be disconnected by comparing the real resistance value of a good battery cell of the same type as the target battery cell with the real resistance value of the impedance of the target battery cell in the same frequency range as the resonant frequency range.

8. The method according to claim 7, wherein, The resonant frequency range of the good battery cell is the range of frequencies at which the imaginary part of the impedance value measured for each of the plurality of good battery cells changes from a positive value to a negative value.

9. The method according to claim 8, wherein the method comprises the following steps: By connecting the real resistance values ​​of each good battery cell at frequencies within the resonant frequency range, a line of real resistance values ​​for the good product impedance of each good battery is obtained. as well as The region of real resistance values ​​adjacent to the real resistance value line of the good product impedance of the good battery cell is set as the range of real resistance values ​​within the resonant frequency range of the good battery cell.

10. The method of claim 9, wherein, The determining steps include: When the real resistance value of the target battery cell in the same frequency range as the resonant frequency range is greater than the real resistance value of the good battery cell in the same real resistance range, the target battery cell is determined to be a defective product; and When the real part resistance value of the impedance of the target battery cell in the same frequency range as the resonant frequency range is less than or equal to the range of real resistance values ​​in the real resistance value region, the target battery cell is determined to be a good product.

11. The method according to claim 9, wherein, The determination step includes: comparing each real resistance value in the real resistance value region of the good battery cell with each real resistance value of the target battery cell to determine whether the target battery cell is good or bad by comparing each real resistance value of the target battery cell with each real resistance value of the target battery cell at three points in the resonant frequency range: the minimum frequency, the middle frequency, and the maximum frequency.

12. The method according to claim 9, wherein the method comprises the following steps: By connecting the real resistance values ​​of each of the multiple defective battery cells with disconnected electrode terminals at the frequency, a defective product real resistance value line for each battery cell or a defective real resistance value region adjacent to the real resistance value lines of the multiple defective battery cells is obtained. as well as When the real resistance value line or the real resistance value region of the defective product overlaps with the real resistance value region of the good battery cell, the range including or excluding the overlapping region or line is set as the real resistance value range of the good battery cell to determine whether the battery cell is good or bad.

13. The method according to claim 8, wherein the method comprises the following steps: The correlation between the real resistance value and the frequency within the resonant frequency range is derived from the frequency data and real resistance value data within the resonant frequency range of the plurality of good battery cells; as well as Based on the derived correlation between the real resistance value range within the resonant frequency range of the good battery cell, the real resistance value range within the resonant frequency range is set.

14. The method of claim 13, wherein, The determining steps include: When the real part of the impedance of the target battery cell in the same frequency range as the resonant frequency range is greater than the real part of the impedance of the good battery cell in the same frequency range based on the correlation, the target battery cell is determined to be a defective product; and When the real part resistance value of the impedance of the target battery cell in the same frequency range as the resonant frequency range is less than the real part resistance value range based on the correlation in the resonant frequency range of the good battery cell, the target battery cell is determined to be a good product.

15. The method according to claim 13, wherein, The determination steps include: determining whether the battery cell is good or bad by comparing the real resistance values ​​of a good product expressed according to the correlation at the minimum, middle, and maximum frequencies within the resonant frequency range with the real resistance values ​​of the target battery cell at each of these three frequencies.

16. The method according to claim 13, wherein, The determination step includes: when the real part resistance value of the impedance of the target battery cell in the same frequency range as the resonant frequency range is greater than the real part resistance value of the good battery cell in the resonant frequency range based on the correlation by a predetermined range or more, the target battery cell is determined to be a defective product.

Images