An apparatus for detecting defects of a battery cell

Abstract

A defect detection device for a battery cell according to one embodiment of the present invention comprises: a current application jig for fixing the electrode lead of the battery cell by applying pressure; and a conductive plate disposed on one surface of the battery cell at a position corresponding to the electrode of the battery cell, wherein the conductive plate comprises a main body having the same shape as the electrode of the battery cell and a uniform thickness, and a reverse current of opposite polarity to the current applied to the battery cell is applied to the conductive plate, and the sum of the magnetic fields induced from the current and the reverse current, respectively, is measured to detect an uncancelled magnetic field appearing at the defect site of the battery cell, thereby detecting the defect site of the battery cell.

Description

Technology Field

[0001] Cross-citation with related application(s)

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0183577 filed on December 23, 2022, and all contents disclosed in the document of said Korean patent application are incorporated herein as part of this specification.

[0003] The present invention relates to a battery cell defect detection device and a battery cell defect detection method, and more specifically, to a device and a battery cell defect detection method that detect the location of a defect in a battery cell using magnetic field interference and cancellation. Background Technology

[0004] X-ray CT, a conventional non-contact, non-destructive analysis method for battery cells, requires a long analysis time, making real-time analysis of various defect causes impossible. Furthermore, while research has been conducted to analyze defects by visualizing internal current distributions to overcome the limitations of X-ray CT, measuring induced magnetic fields via MRI guidance has faced difficulties in achieving high resolution due to the inability of electromagnetic waves to penetrate the battery and the presence of ferromagnetic materials within the battery.

[0005] Accordingly, research has been conducted to detect defects by introducing Magnetic Field Imaging (MFI) technology through changes in the magnetic field generated during the charging and discharging of battery cells. However, this magnetic field imaging technology faces limitations in detecting minute magnetic field changes at the sub-micro T level in images, such as noise caused by the sensitivity of magnetic field sensors or when high currents are applied. Additionally, there is a limitation in that it is time-consuming due to the need for additional data processing, such as comparing the average magnetic field strength of normal and defective cells across different sections.

[0006] FIG. 1 illustrates a battery cell defect detection device according to the prior art. The electrode leads (12) of a battery cell (10) are connected to a pair of current application jigs (1). Current is applied to the current wires (2) connected to each of the current application jigs (1). Accordingly, current flows through the battery cell (10). The magnetic field induced by the current flowing through the battery cell (10) is visualized by magnetic field imaging (MFI). However, according to this prior art, there is no significant difference visible to the naked eye between the magnetic field image of a normal battery cell and the magnetic field image of a battery cell in which a defect has occurred in the electrode plate (11a), such as due to folding of the electrode plate (11a). FIG. 7 shows a magnetic field image according to the prior art. In FIG. 7, no distinct difference is shown between (a) the case of a normal cell and (b) the case of an electrode folding defect cell. It took a considerable amount of time to read this at a fine scale level, and in some cases, it was difficult to read.

[0007] Therefore, an improved detection device capable of rapidly and accurately detecting defects in battery cells is required. The problem to be solved

[0008] The present invention provides a device for detecting defects in a battery cell and a method for detecting defects in a battery cell. The purpose of the invention is to provide a device that rapidly and accurately detects defects in a battery cell by utilizing magnetic field interference and cancellation, particularly among devices that apply magnetic field imaging techniques.

[0009] However, the problems that the embodiments of the present invention aim to solve are not limited to the problems described above and can be expanded in various ways within the scope of the technical ideas included in the present invention. means of solving the problem

[0010] A defect detection device for a battery cell according to one embodiment of the present invention comprises: a current application jig for fixing the electrode lead of a battery cell by applying pressure; and a conductive plate disposed on one surface of the battery cell at a position corresponding to the electrode of the battery cell, wherein the conductive plate comprises: a main body having the same shape as the electrode of the battery cell and having a uniform thickness, and a reverse current of opposite polarity to the current applied to the battery cell is applied to the conductive plate, and the sum of the magnetic fields induced from the current and the reverse current, respectively, is measured to detect an uncancelled magnetic field appearing at a defect site of the battery cell, thereby detecting a defect site of the battery cell.

[0011] In the normal part of the battery cell, the magnetic field induced by the current and the magnetic field induced by the reverse current cancel each other out, so the sum of the magnetic fields is not detected, and in the defective part of the battery cell, the magnetic field that is not canceled out can be detected.

[0012] The reverse current applied to the above-mentioned conductive plate can flow in the opposite direction with substantially the same magnitude as the current applied to the above-mentioned battery cell.

[0013] It may further include a magnetic field measuring unit positioned at a predetermined distance from the large surface area of ​​the battery cell.

[0014] The reverse current applied to the conductive plate flows in the opposite direction to the current applied to the battery cell, and when the distance of the conductive plate from the magnetic field measuring unit is smaller than the distance of the battery cell from the magnetic field measuring unit, the magnitude of the reverse current is equal to or smaller than the magnitude of the current applied to the battery cell to compensate for the change in the strength of the induced magnetic field corresponding to the distance difference, and when the distance of the conductive plate from the magnetic field measuring unit is greater than the distance of the battery cell from the magnetic field measuring unit, the magnitude of the reverse current may be equal to or larger than the magnitude of the current applied to the battery cell to compensate for the change in the strength of the induced magnetic field corresponding to the distance difference.

[0015] The above magnetic field measurement unit may be a magnetic field imaging (MFI) device.

[0016] The above-mentioned conductive plate may be positioned such that it coincides with the large area of ​​the electrode when viewed from the top surface, and may be positioned parallel to the large area of ​​the electrode when viewed from the side.

[0017] The types of defects detected above may include at least one of a folded portion of the electrode plate of the battery cell, a disconnected portion of the electrode plate, a portion where the electrode active material is unevenly applied to the retaining portion of the electrode plate, a disconnected portion of the electrode lead or electrode tab of the battery cell, and a portion where the stacked electrode plates are misaligned.

[0018] The above-mentioned conductive plate includes a pair of connecting portions protruding from the main body of the conductive plate so as to be positioned at a location corresponding to the electrode lead of the battery cell, and the connecting portions are formed integrally with the main body, have the same thickness as the main body, and are made of the same material, and the reverse current can be applied to the main body through the connecting portions.

[0019] In the above battery cell, a positive lead is disposed at one end of the two ends in the longitudinal direction and a negative lead is disposed at the other end, and one of the connecting parts may be disposed at each of the two ends in the longitudinal direction of the above conductive plate.

[0020] In the above battery cell, both a positive lead and a negative lead are disposed at one end of the battery cell, and both of the above pair of connecting parts may be disposed at one end of the main body of the conductive plate corresponding to the one end of the battery cell.

[0021] The above-mentioned conductive plate may be made of an electrically conductive material.

[0022] The current application jig may further include a current application member having electrical conductivity that presses the electrode lead, and may include a current wire connected to the current application member to apply current to the battery cell.

[0023] It may further include an insulating plate placed below the above conductive plate.

[0024] A method for detecting a defect in a battery cell according to one embodiment of the present invention comprises: a step of applying a reverse current having opposite polarity to the current applied to the battery cell to a conductive plate while applying a current to the battery cell; a step of measuring the sum of magnetic fields induced from the current and the reverse current, respectively; and a step of detecting a defect in the battery cell by detecting an uncancelled magnetic field appearing at a defect in the battery cell, wherein the conductive plate comprises: a main body having the same shape as the electrode of the battery cell and a uniform thickness, and may be disposed on one surface of the battery cell at a position corresponding to the electrode of the battery cell.

[0025] In the normal part of the battery cell, the magnetic field induced by the current and the magnetic field induced by the reverse current cancel each other out, so the sum of the magnetic fields is not detected, and in the defective part of the battery cell, the magnetic field that is not canceled out can be detected.

[0026] The reverse current applied to the above-mentioned conductive plate can flow in the opposite direction with substantially the same magnitude as the current applied to the above-mentioned battery cell.

[0027] A magnetic field measuring unit for measuring the sum of the magnetic fields is positioned at a predetermined distance from the large area of ​​the battery cell, and when the distance of the conductive plate from the magnetic field measuring unit is smaller than the distance of the battery cell from the magnetic field measuring unit, the magnitude of the reverse current is equal to or smaller than the magnitude of the current applied to the battery cell to compensate for the change in the strength of the induced magnetic field corresponding to the distance difference, and when the distance of the conductive plate from the magnetic field measuring unit is greater than the distance of the battery cell from the magnetic field measuring unit, the magnitude of the reverse current may be equal to or larger than the magnitude of the current applied to the battery cell to compensate for the change in the strength of the induced magnetic field corresponding to the distance difference.

[0028] The above-mentioned conductive plate may be positioned such that it coincides with the large area of ​​the electrode when viewed from the top surface, and may be positioned parallel to the large area of ​​the electrode when viewed from the side.

[0029] The types of defects detected above may include at least one of a folded portion of the electrode plate of the battery cell, a disconnected portion of the electrode plate, a portion where the electrode active material is unevenly applied to the retaining portion of the electrode plate, a disconnected portion of the electrode lead or electrode tab of the battery cell, and a portion where the stacked electrode plates are misaligned. Effects of the invention

[0030] According to the present invention, in detecting defects in a battery cell by applying a magnetic field imaging technique, defects in the battery cell can be detected quickly and accurately, particularly by utilizing magnetic field interference and cancellation. Furthermore, reliability regarding the quality of the battery cell produced accordingly can also be ensured.

[0031] The effects of the present invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art from the description in the claims. Brief explanation of the drawing

[0032] FIG. 1 illustrates a battery cell defect detection device according to the prior art. FIG. 2 schematically illustrates a defect detection device for a battery cell according to one embodiment of the present invention. FIG. 3 shows a conductive plate included in the defect detection device of the battery cell of FIG. 2 and placed under the battery cell. Figure 4 illustrates a modified example of Figure 3. Figure 5 schematically illustrates the case where a part of the electrode plate of Figure 3 is folded. Figure 6 shows a magnetic field image measured by the defect detection device of the battery cell of Figure 2. Figure 7 shows a magnetic field image according to a comparative example corresponding to the prior art. Figure 8 is a graph showing the magnetic field strength according to the position of the battery cell in the embodiment of Figure 6. Figure 9 shows a graph of the magnetic field strength according to the position of the battery cell in the comparative example of Figure 7. FIG. 10 is a flowchart of a method for detecting defects in a battery cell according to one embodiment of the present invention. Specific details for implementing the invention

[0033] Hereinafter, embodiments disclosed in this specification will be described in detail with reference to the attached drawings, provided that identical or similar components are given identical or similar reference numerals and redundant descriptions thereof will be omitted.

[0034] The suffixes "part" and / or "part" for components used in the following description are assigned or used interchangeably solely for the ease of drafting the specification and do not inherently possess distinct meanings or roles. Furthermore, terms such as "…part," "…part," etc., as described in the specification refer to a unit that processes at least one function or operation, which may be implemented in hardware, software, or a combination of hardware and software.

[0035] In addition, when describing the embodiments disclosed in this specification, if it is determined that a detailed description of related prior art may obscure the essence of the embodiments disclosed in this specification, such detailed description is omitted. Furthermore, the attached drawings are intended only to facilitate understanding of the embodiments disclosed in this specification, and the technical concept disclosed in this specification is not limited by the attached drawings; it should be understood that the drawings include all modifications, equivalents, and substitutions that fall within the spirit and technical scope of the invention.

[0036] In this application, terms such as "comprising" 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.

[0038] Hereinafter, a defect detection device (100) for a battery cell according to one embodiment of the present invention will be described.

[0039] FIG. 2 schematically illustrates a defect detection device (100) for a battery cell according to one embodiment of the present invention. FIG. 3 illustrates a conductive plate included in the defect detection device for a battery cell of FIG. 2 and disposed below the battery cell. FIG. 4 illustrates a modified example of FIG. 3.

[0041] An example is given in which electrode leads (12) are provided at each end of the battery cell (10).

[0042] A defect detection device (100) for a battery cell includes a current application jig (110) connected to an electrode lead (12) of a battery cell (10) to apply current to the electrode lead (12). A current application jig (110) may be provided for each electrode lead (12). The current application jig (110) includes a current application member (111) that contacts the electrode lead (12) and presses the electrode lead (12). The bottom surface of the current application member (111) may be, for example, flat. Additionally, the current application member (111) is made of a material with excellent electrical conductivity so that current can flow to the electrode lead (12) through the current application member (111).

[0043] There are no special restrictions on the shape structure of the current application member (111), and it is sufficient to have a connection structure capable of conducting current to the electrode lead (12) and capable of applying current uniformly across the width of the electrode lead (12). Examples of a connection structure capable of conducting current include a connection structure of a current wire clip and a bolt fastening structure of a wire harness. In addition, if the width of the electrode lead (12) is wide while the width of the current application member (111) is relatively narrow, an uneven current flow distribution pattern may be observed in the electrode lead (12) and / or the electrode tab portion. Accordingly, it is preferable that the width of the current application member (111) be equal to or greater than the width of the electrode lead (12). If necessary, the current application member (111) may also press and fix the electrode lead (12).

[0044] The upper surface of the current application member (111) includes a fixing member (112) that can fix the current application member (111) by pressing it. For example, the fixing member (112) includes an electrically insulating handle, and the lower end of the handle includes a screw-shaped support. The end of the support can contact the upper surface of the current application member (111) to fix the current application member (111). After positioning the electrode lead (12) on the bottom surface of the current application member (111), the handle of the fixing member (112) is rotated to fix the current application member (111) to the end of the support.

[0045] A current wire (120) is connected to a current application member (111), and the current applied from the current wire (120) is applied to an electrode lead (12) through the electrically conductive current application member (111). The current wire (120) may be, for example, an electrically conductive wire, and more specifically, a wire. The current wire (120) includes a positive connection and a negative connection. The current application member (111) may further include a plate-shaped electrically conductive member (112a) extending outwardly, and the current wire (120) may be connected to the electrically conductive member (112a).

[0046] Meanwhile, according to one embodiment of the present invention, a defect detection device (100) for a battery cell includes a conductive plate (130). The conductive plate (130) is in the shape of a plate and is electrically conductive, and can be placed on one surface of the battery cell (10) at a position corresponding to the electrode of the battery cell. Referring to FIGS. 2 and 3, the conductive plate (130) includes a plate-shaped main body (131) and a pair of electrically conductive connecting parts (132) capable of applying reverse current to the main body (131). The conductive plate (130) is an electrically conductive material, and it is sufficient if it is made of a material that has high electrical conductivity and allows current to flow, and, for example, may be made of a conventional conductor material such as copper, iron, or aluminum.

[0047] The main body (131) is a razor. That is, it has a plate shape. More specifically, the main body (131) has a flat shape overall. This is to ensure that the reverse current flows evenly throughout the main body (131), as will be described later, so that the magnetic field is induced uniformly.

[0048] Additionally, the main body (131) of the conductive plate (130) has the same shape as one side of the main body (11) of the battery cell (10). More precisely, it has the same shape as the electrode plate (11a) of the battery cell (10). For reference, in the present invention, the electrode of the battery cell (10) is a concept that includes the electrode plate (11a), the electrode tab, and the electrode lead (12).

[0049] FIGS. 3 and 4 illustrate a case where the electrode plate (11a) of the battery cell (10) and the main body (131) of the conductive plate (130) have the same shape. The main body (131) is provided such that the length (L) and width (W) of the electrode plate (11a) and the main body (131) of the conductive plate (130) are equal to each other.

[0050] Additionally, when viewed from above, the main body (131) of the conductive plate (130) may be positioned at the same location as the electrode plate (11a) of the battery cell (10). Additionally, when viewed from the side, the conductive plate (130) (the main body (131) of the conductive plate (130)) may be positioned parallel to the electrode plate (11a) of the battery cell (10).

[0051] If the electrode plate (11a) is wrapped with the outer material of the battery cell (10), for example, the position of the conductive plate (130) is finely adjusted to find a point where the magnetic field is completely canceled out and a clear image is produced, and then the alignment with the electrode plate (11a) is adjusted, and the defect can be detected by focusing on measuring the magnetic field detected at the defect area.

[0052] At this time, the main body (131) of the conductive plate (130) is positioned at the same location as the electrode plate (11a) of the battery cell (10), and when a reverse current (i.e., a current density of substantially the same size with opposite polarity) flowing in the opposite direction with substantially the same magnitude (current density) as the current flowing in the electrode plate (11a) of the battery cell (10) is applied to the conductive plate (130), the magnetic field induced from the current flowing in the electrode plate (11a) of the battery cell (10) and the magnetic field induced from the reverse current applied to the conductive plate (130) are canceled out. That is, the magnitude of the magnetic field induced from the current flowing in the electrode plate (11a) of the battery cell (10) and the magnetic field induced from the reverse current applied to the conductive plate (130) are the same, but they are generated in opposite directions.

[0053] That is, in the case of a normal cell, the magnetic field induced by the current flowing through the electrode plate (11a) of the battery cell (10) and the magnetic field induced by the reverse current applied to the conductive plate (130) cancel each other out, so when visualized by magnetic field imaging (MFI), the magnetic field is not detected as shown on the left side of Fig. 6 (Fig. 6(a)). Even if it is detected, it is detected within an acceptable level of the error range.

[0054] When the battery cell (10) is somewhat thick, due to the difference in distance from the conductive plate (130) placed below the battery cell (10), when measuring the magnetic field at a magnetic field measuring unit (not shown) placed near the battery cell (10), an error may occur in the magnitude of the magnetic field induced by the current flowing through the electrode plate (11a) of the battery cell (10) and the magnetic field induced by the reverse current applied to the conductive plate (130). To reduce this error, the magnitude of the reverse current applied to the conductive plate (130) may be further increased or decreased. For reference, through experiments, it was confirmed that the magnitude of the induced magnetic field is proportional to the amount of current and decreases linearly with distance.

[0055] That is, due to the thickness of the battery cell (10), there may be a difference between the distance from the magnetic field measuring unit of the conductive plate (130) and the distance from the magnetic field measuring unit of the battery cell (10). Accordingly, it is necessary to correct for the change in the strength of the induced magnetic field (difference value) corresponding to this difference in distance.

[0056] For reference, the magnetic field measuring unit may be located on the upper surface of the battery cell (10) or on the lower surface of the battery cell (10) based on the large area of ​​the battery cell (10) in FIG. 2. The magnetic field measuring unit is a magnetic field imaging (MFI) device, and it is sufficient if it is capable of measuring and imaging the induced magnetic field to measure defects in the battery cell (10) in the manner described in the present invention.

[0057] More specifically, when a conductive plate (130) is placed on the surface of the battery cell (10) facing the magnetic field measuring unit (for example, in the example of FIG. 2, where the magnetic field measuring unit is positioned on the battery cell (10) and the conductive plate (130) is also placed on the upper surface of the battery cell (10), if the magnitude of the reverse current applied to the conductive plate (130) is equal to or smaller than the magnitude of the current applied to the battery cell (10), the difference in the magnitude of the magnetic field due to the difference in distance between the battery cell (10) and the conductive plate (130) caused by the thickness of the battery cell (10) is corrected.

[0058] Conversely, when a conductive plate (130) is placed on the opposite side of the battery cell (10) facing the magnetic field measuring unit (for example, in the example of FIG. 2, where the magnetic field measuring unit is located on the battery cell (10) and the conductive plate (130) is placed on the lower surface of the battery cell (10), if the magnitude of the reverse current applied to the conductive plate (130) is equal to or greater than the magnitude of the current applied to the battery cell (10), the difference in the magnitude of the magnetic field due to the difference in distance between the battery cell (10) and the conductive plate (130) caused by the thickness of the battery cell (10) is corrected.

[0059] In other words, when the distance from the magnetic field measuring unit of the conductive plate (130) is smaller than the distance from the magnetic field measuring unit of the battery cell (10), the magnitude of the reverse current applied to the conductive plate (130) to correct the change in the strength of the induced magnetic field corresponding to the distance difference is equal to or smaller than the magnitude of the current applied to the battery cell (10). To elaborate, when the change in the strength of the induced magnetic field corresponding to the distance difference is within the error range, the magnitude of the reverse current and the magnitude of the current may be the same.

[0060] Conversely, if the distance from the magnetic field measuring unit of the conductive plate (130) is greater than the distance from the magnetic field measuring unit of the battery cell (10), the magnitude of the reverse current applied to the conductive plate (130) to correct for the change in the strength of the induced magnetic field corresponding to the distance difference is equal to or greater than the magnitude of the current applied to the battery cell (10). Furthermore, if the change in the strength of the induced magnetic field corresponding to the distance difference is within the error range, the magnitude of the reverse current and the magnitude of the current may be the same.

[0061] Meanwhile, if there is a defect in the electrode plate (11a) of the battery cell (10), such as in the case of folding of the electrode plate (11a), the reverse current flows uniformly throughout the main body (131) of the conductive plate (130), and thus the magnetic field induced therefrom is also uniformly. However, the magnitude of the induced magnetic field changes in the area where there is a defect in the electrode plate (11a) of the battery cell (10). For example, the surface of the current collector is exposed in the part where the electrode plate (11a) is folded, and a significant decrease in the magnetic field is observed in that part due to the absence of the electrode plate (11a) and the active material. In addition, in the area where the electrode plate (11a) active material is not properly coated on the retaining part of the electrode plate (11a) sheet, the amount of current decreases, and the magnitude of the induced magnetic field becomes smaller. Accordingly, the magnetic field induced in the area where there is a defect in the electrode plate (11a) of the battery cell (10) is not completely canceled out by the magnetic field in the opposite direction applied from the current flowing uniformly throughout the conductive plate (130). Accordingly, when measured by a magnetic field measuring unit (not shown) placed near the battery cell (10), as shown on the right side of FIG. 6 (Fig. 6(b)), a magnetic field that is not canceled out compared to a normal area is clearly detected in the defective area of ​​the electrode plate (11a) of the battery cell (10). Therefore, compared to conventional technology, the defective area of ​​the electrode plate (11a) of the battery cell (10) can be detected quickly and accurately.

[0062] The connecting portion (132) of the conductive plate (130) includes a positive electrode and a negative electrode. The connecting portion (132) of the conductive plate (130) may be positioned at a location corresponding to the positive lead and negative lead of the battery cell (10). That is, when viewed from above, the connecting portion (132) of the conductive plate (130) may be provided at the same location as the positive lead and negative lead of the battery cell (10). Additionally, the connecting portion (132) may be formed integrally with the main body (131) or combined with the main body (133). The shape of the connecting portion (132) is not limited to that shown in FIGS. 2 and FIGS. 3, and it is sufficient if it allows current to flow through the main body (131).

[0063] In some cases, the connecting part (132) may also be in the shape of a plate having the same thickness as the main body (131) and may be made of the same material as the main body (131).

[0064] The defect detection device (100) of the battery cell may additionally include an insulating plate (140) placed below the conductive plate (130). The insulating plate (140) may be, for example, in the shape of a plate with thickness, or may be an insulating film. The insulating plate (140) has electrical insulation properties and prevents a short circuit of the conductive plate (130) or the battery cell (10).

[0066] Additionally, a magnetic field measuring unit (not shown) may be positioned near the battery cell (10) at a predetermined distance from the battery cell (10). The magnetic field measuring unit measures the total magnetic field in which the magnetic field induced by the current flowing through the battery cell (10) and the magnetic field induced by the reverse current flowing through the conductive plate (130) interfere with or cancel each other out. That is, since the magnetic field induced by the current flowing through the battery cell (10) and the magnetic field induced by the reverse current flowing through the conductive plate (130) are each induced in opposite directions, the total magnetic field has a result value in which the induced magnetic fields in opposite directions cancel each other out or interfere with each other.

[0067] The embodiment of FIG. 6 shows a magnetic field image when the magnetic field measuring unit is positioned on the battery cell (10), that is, on the Z-axis (height direction of the battery cell (10)). However, the present invention is not limited thereto, and the magnetic field measuring unit may be positioned on the front or rear of the battery cell (10), that is, on the X-axis (length direction of the battery cell (10)), or on both sides of the battery cell (10), that is, on the Y-axis (width direction of the battery cell (10)) to measure the Y-axis component of the induced magnetic field.

[0068] Additionally, the magnetic field measuring unit may be a conventional magnetic field measuring unit. For example, it may be a magnetic field imaging device that applies magnetic field imaging (MFI) technology. However, the present invention is not limited thereto, and any measuring unit capable of detecting a magnetic field and indicating the location of a defect in the battery cell (10) is sufficient.

[0070] Meanwhile, the types of defects of the battery cell (10) that can be detected according to the embodiments of the present invention are not limited to those described above, and various types of defects can be detected. For instance, in addition to the folding of the electrode plate (11a) described above, the disconnection of the electrode plate (11a) (e.g., perforation or tearing), and the defect in the coating of the electrode active material on the retaining portion of the electrode plate (11a), the disconnection of the electrode tab or electrode lead can also be detected. In this case, the connecting portion (132) of the conductive plate (130) has the same shape as the electrode tab or electrode lead, and the disconnection of the electrode tab or electrode lead can be effectively detected when the main body (131) of the conductive plate (130) and the connecting portion (132) are formed integrally and have the same thickness and flatness. Alternatively, misalignment of a plurality of electrode plates (11a) stacked inside the battery cell (10) can also be detected. As much as the electrode plates (11a) are misaligned, there is a change in the magnetic field induced from the current applied to the battery cell (10) in the misaligned area, and if this is offset by the uniform magnetic field induced from the reverse current applied to the conductive plate (130), the changed magnetic field in the misaligned area is clearly detected.

[0072] In the embodiments of FIGS. 2 and 3 described above, a device for detecting defects in a battery cell (10) was described in which a positive lead and a negative lead are provided separately at each end of the battery cell (10). However, the present invention is not limited thereto and can be modified and changed to suit the environment in which the present invention is implemented.

[0073] For example, referring to FIG. 4, when both a positive lead and a negative lead are provided at one end of the battery cell (10), the connection part (132) of the conductive plate (130) may be implemented by placing it at a position corresponding to the positive lead and the negative lead of the battery cell (10). That is, when viewed from above, if the connection part (132) of the conductive plate (130) is provided at the same position as the positive lead and the negative lead of the battery cell (10), then the current flowing through the electrode plate (11a) of the battery cell (10) and the reverse current flowing through the main body (131) of the conductive plate (130) are only opposite in direction, but the flow pattern is substantially the same, so the magnetic fields cancel each other out, making it easy to detect defects in the battery cell (10).

[0075] For reference, the dotted lines shown between the electrode plate (11a) and the electrode lead (12) of the battery cell (10) in FIGS. 3 and 4, and between the main body (131) and the connecting part (132) of the conductive plate (130), do not represent folded parts, but are indicated as dotted lines to clearly distinguish between each component. Also, note that the electrode tab is not separately distinguished in the part labeled as the electrode lead (12).

[0077] FIG. 5 schematically illustrates the case where a portion of the electrode plate (11a) of FIG. 2 and FIG. 3 is folded. FIG. 6 shows a magnetic field image measured by a defect detection device (100) of the battery cell of FIG. 2. FIG. 7 shows a magnetic field image according to a comparative example (prior art). In FIG. 6 and FIG. 7, (a) on the left shows the case of a normal cell, and (b) on the right shows the case of an electrode-folded defective cell.

[0078] The measurement conditions in the embodiment of FIG. 6 and the embodiment of FIG. 7 are the same and are as follows.

[0079] - Charging current: 260 mA

[0080] - z-distance: 3 mm (distance between the battery cell and the measuring unit)

[0081] - Measurement speed: 100 mm / min

[0082] - 3rd scan mean data

[0083] - Image resolution: 2.5 * 0.0646 mm 2

[0084] In addition, in the embodiment of FIG. 6, as described above, a charging current of the same magnitude is applied to the conductive plate (130), but a current in the opposite direction to the current applied to the battery cell (10) is applied.

[0085] It can be seen that a change in the magnetic field is clearly visible in the magnetic field image of Fig. 6(b), that is, on the right side of Fig. 6, corresponding to the folded portion (P) of the electrode plate (11a) of Fig. 5. On the other hand, in Fig. 7 according to the comparative example, no distinct difference is shown between (a) the case of a normal cell and (b) the case of an electrode fold defect cell, so it can be seen that there are limitations in clearly determining the location of the defect visually.

[0086] FIG. 8 is a graph showing the magnetic field strength according to the position of the battery cell (10) in the embodiment of FIG. 6. FIG. 9 is a graph showing the magnetic field strength according to the position of the battery cell (10) in the comparative example of FIG. 7. In the graph of FIG. 8 according to the embodiment of FIG. 6, the difference in the measured magnetic field strength between the defective cell with folded electrodes and the normal cell is clearly visible in the defective area. On the other hand, in the graph of FIG. 9 according to the embodiment of FIG. 7, the defect is not clearly visible because the trend of the graph regarding the magnetic field strength measured between the defective cell with folded electrodes and the normal cell is similar.

[0088] Hereinafter, a method for detecting defects in a battery cell according to one embodiment of the present invention will be described.

[0089] FIG. 10 is a flowchart of a method for detecting defects in a battery cell according to one embodiment of the present invention.

[0090] Referring to FIG. 10, a method for detecting a defect in a battery cell comprises the steps of: applying a current to the battery cell while applying a reverse current of opposite polarity to the current applied to the battery cell to a conductive plate (S110); measuring the sum of magnetic fields induced from the current applied to the battery cell and the reverse current applied to the conductive plate, respectively (S120); and detecting a defect in the battery cell by detecting an uncancelled magnetic field appearing at a defect in the battery cell (S130).

[0091] As described above in FIGS. 2 to 4, the conductive plate (130) is a plate-shaped plate that can be placed on one side of the battery cell (10) at a position corresponding to the electrode of the battery cell (10) and has electrical conductivity. When viewed from the top surface, the conductive plate (130) is placed to coincide with the large area of ​​the electrode of the battery cell (10), and when viewed from the side, it is placed parallel to the large area of ​​the electrode of the battery cell (10).

[0092] The reverse current applied to the conductive plate (130) flows in the opposite direction with substantially the same magnitude as the current applied to the battery cell (10).

[0093] In the normal portion of the battery cell (10), the magnetic field induced by the current applied to the battery cell (10) and the magnetic field induced by the reverse current applied to the conductive plate (130) cancel each other out, so the sum of the magnetic fields is not detected.

[0094] On the other hand, at the defective part of the battery cell, since the magnitude of the current applied to the battery cell (10) and the magnitude of the reverse current applied to the conductive plate (130) are different, the magnetic field induced from the current applied to the battery cell (10) and the magnetic field induced from the reverse current applied to the conductive plate (130) are not completely canceled out, so the uncanceled magnetic field is detected.

[0095] As described above, the magnetic field measuring unit is positioned at a predetermined distance from the large surface area of ​​the battery cell (10). At this time, due to the thickness of the battery cell (10), there may be a difference between the distance from the magnetic field measuring unit of the conductive plate (130) and the distance from the magnetic field measuring unit of the battery cell (10). Accordingly, it is necessary to correct for the change in the strength of the induced magnetic field (difference value) corresponding to this difference in distance.

[0096] More specifically, when the distance from the magnetic field measuring unit of the conductive plate (130) is smaller than the distance from the magnetic field measuring unit of the battery cell (10), the magnitude of the reverse current applied to the conductive plate (130) to correct the change in the strength of the induced magnetic field corresponding to the distance difference is equal to or smaller than the magnitude of the current applied to the battery cell (10). Furthermore, when the change in the strength of the induced magnetic field corresponding to the distance difference is within the error range, the magnitude of the reverse current and the magnitude of the current may be the same.

[0097] On the other hand, if the distance from the magnetic field measuring unit of the conductive plate (130) is greater than the distance from the magnetic field measuring unit of the battery cell (10), the magnitude of the reverse current applied to the conductive plate (130) to correct the change in the strength of the induced magnetic field corresponding to the distance difference is equal to or greater than the magnitude of the current applied to the battery cell (10). To elaborate, if the change in the strength of the induced magnetic field corresponding to the distance difference is within the error range, the magnitude of the reverse current and the magnitude of the current may be the same.

[0098] The type of defect detected by the defect detection method of the battery cell includes at least one of the following: a folded portion of the electrode plate (11a) of the battery cell (10), a disconnected portion of the electrode plate (11a), a portion where the electrode active material is unevenly applied to the retaining portion of the electrode plate (11a), a disconnected portion of the electrode lead (12) or electrode tab of the battery cell (10), and a portion where the stacked electrode plate (11a) is misaligned.

[0099] A more detailed description of the method for detecting defects in a battery cell overlaps with the description of the battery cell defect detection device described in FIGS. 2 to 9, so refer to FIGS. 2 to 9.

[0101] When a defect in a battery cell (10) is detected using the battery cell defect detection device (100) and the battery cell defect detection method according to the present invention, the defect area can be detected quickly compared to the prior art. At the same time, the defect area can be accurately identified and detected. Accordingly, reliability regarding the quality of the produced battery cell can also be ensured.

[0103] Although preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention as defined in the following claims also fall within the scope of the present invention. Explanation of the symbols

[0104] 10: Battery cell 11: Main body 11a: Electrode plate 12: Electrode Lead 100: Battery cell defect detection device 110: Current application jig 111: Current application component 112: Fixed member 120: Current wire 130: Challenge Board 131: Main body 132: Connection 140: Insulating plate

Claims

Claim 1 A battery cell defect detection device comprising: a current application jig for fixing the electrode lead of a battery cell by applying pressure; and a conductive plate disposed on a large surface area of ​​the battery cell at a position corresponding to the electrode of the battery cell, wherein the conductive plate comprises: a main body having the same shape as the electrode of the battery cell and a uniform thickness; a reverse current having opposite polarity to the current applied to the battery cell is applied to the conductive plate, and the defect of the battery cell is detected by measuring the sum of the magnetic fields induced from the current and the reverse current, respectively, and detecting an uncancelled magnetic field appearing at the defect of the battery cell. Claim 2 A battery cell defect detection device according to claim 1, wherein in the normal part of the battery cell, the magnetic field induced by the current and the magnetic field induced by the reverse current cancel each other out so that the sum of the magnetic fields is not detected, and in the defective part of the battery cell, the magnetic field that is not canceled out is detected. Claim 3 A defect detection device for a battery cell according to claim 1, wherein the reverse current applied to the conductive plate flows in the opposite direction having substantially the same magnitude as the current applied to the battery cell. Claim 4 A defect detection device for a battery cell according to claim 1, further comprising a magnetic field measuring unit disposed at a predetermined distance from the large area of ​​the battery cell. Claim 5 A defect detection device for a battery cell according to claim 4, wherein the reverse current applied to the conductive plate flows in the opposite direction to the current applied to the battery cell, and when the distance of the conductive plate from the magnetic field measuring unit is smaller than the distance of the battery cell from the magnetic field measuring unit, the magnitude of the reverse current is equal to or smaller than the magnitude of the current applied to the battery cell to compensate for the change in the strength of the induced magnetic field corresponding to the distance difference, and when the distance of the conductive plate from the magnetic field measuring unit is greater than the distance of the battery cell from the magnetic field measuring unit, the magnitude of the reverse current is equal to or larger than the magnitude of the current applied to the battery cell to compensate for the change in the strength of the induced magnetic field corresponding to the distance difference. Claim 6 In paragraph 4, the above magnetic field measurement unit is a magnetic field imaging (MFI) device, a defect detection device for a battery cell. Claim 7 A defect detection device for a battery cell according to claim 1, wherein the conductive plate is positioned to coincide with the large area of ​​the electrode when viewed from the top surface, and is positioned parallel to the large area of ​​the electrode when viewed from the side. Claim 8 A defect detection device for a battery cell according to claim 1, wherein the type of detected defect includes at least one of a folded portion of the electrode plate of the battery cell, a disconnected portion of the electrode plate, a portion where the electrode active material is unevenly applied to the retaining portion of the electrode plate, a disconnected portion of the electrode lead or electrode tab of the battery cell, and a portion where the stacked electrode plates are misaligned. Claim 9 A defect detection device for a battery cell according to claim 1, wherein the conductive plate includes a pair of connecting portions protruding from the main body of the conductive plate so as to be positioned at a location corresponding to the electrode lead of the battery cell, the connecting portions are formed integrally with the main body, have the same thickness as the main body, and are made of the same material, and the reverse current is applied to the main body through the connecting portions. Claim 10 A defect detection device for a battery cell according to claim 9, wherein the battery cell has a positive lead disposed at one end of the two ends in the longitudinal direction and a negative lead disposed at the other end, and the connecting part is disposed at each of the two ends of the conductive plate in the longitudinal direction. Claim 11 A defect detection device for a battery cell according to claim 9, wherein the battery cell has both a positive lead and a negative lead disposed at one end of the battery cell, and both of the pair of connecting parts disposed at one end of the main body of the conductive plate corresponding to the one end of the battery cell. Claim 12 A defect detection device for a battery cell according to claim 1, wherein the conductive plate is made of an electrically conductive material. Claim 13 A defect detection device for a battery cell according to claim 1, wherein the current application jig includes a current application member having electrical conductivity that presses the electrode lead, and further includes a current wire connected to the current application member to apply current to the battery cell. Claim 14 A defect detection device for a battery cell according to claim 1, further comprising an insulating plate disposed below the conductive plate. Claim 15 A method for detecting defects in a battery cell, comprising: a step of applying a reverse current of opposite polarity to the current applied to the battery cell to a conductive plate while applying a current to the battery cell; a step of measuring the sum of magnetic fields induced from the current and the reverse current, respectively; and a step of detecting a defect in the battery cell by detecting an uncancelled magnetic field appearing at a defect in the battery cell, wherein the conductive plate comprises: a main body having the same shape as the electrode of the battery cell and a uniform thickness, and is disposed at a position corresponding to the electrode of the battery cell on a large area of ​​the battery cell. Claim 16 A method for detecting defects in a battery cell according to claim 15, wherein in the normal part of the battery cell, the magnetic field induced by the current and the magnetic field induced by the reverse current cancel each other out so that the sum of the magnetic fields is not detected, and in the defective part of the battery cell, the magnetic field that is not canceled out is detected. Claim 17 A method for detecting defects in a battery cell according to claim 15, wherein the reverse current applied to the conductive plate flows in the opposite direction having substantially the same magnitude as the current applied to the battery cell. Claim 18 A method for detecting defects in a battery cell according to claim 15, wherein a magnetic field measuring unit for measuring the sum of the magnetic fields is disposed at a predetermined distance from the large area of ​​the battery cell, and when the distance of the conductive plate from the magnetic field measuring unit is smaller than the distance of the battery cell from the magnetic field measuring unit, the magnitude of the reverse current is equal to or smaller than the magnitude of the current applied to the battery cell to correct the change in the strength of the induced magnetic field corresponding to the distance difference, and when the distance of the conductive plate from the magnetic field measuring unit is greater than the distance of the battery cell from the magnetic field measuring unit, the magnitude of the reverse current is equal to or larger than the magnitude of the current applied to the battery cell to correct the change in the strength of the induced magnetic field corresponding to the distance difference. Claim 19 A method for detecting defects in a battery cell according to claim 15, wherein the conductive plate is positioned such that it corresponds to the large area of ​​the electrode when viewed from the top surface, and is positioned parallel to the large area of ​​the electrode when viewed from the side. Claim 20 A method for detecting defects in a battery cell according to claim 15, wherein the types of defects detected include at least one of a folded portion of the electrode plate of the battery cell, a disconnected portion of the electrode plate, a portion where the electrode active material is unevenly coated on the retaining portion of the electrode plate, a disconnected portion of the electrode lead or electrode tab of the battery cell, and a portion where the stacked electrode plates are misaligned.

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