Device for detecting defects of battery cell

Abstract

An apparatus for detecting a defect of a battery cell according to an embodiment of the present disclosure includes: a current applying jig that presses and fixes an electrode lead of the battery cell; and a conductive plate provided on one surface of the battery cell at a position corresponding to the electrode of the battery cell, in which the conductive plate includes a main body having the same shape as the electrode of the battery cell and having a uniform thickness, a reverse current having a polarity opposite to that of the current applied to the battery cell is applied to the conductive plate, and wherein a sum of magnetic fields derived from the current and the reverse current is measured to detect an uncancelled magnetic field occurring at a defective portion of the battery cell, thereby detecting the defective portion of the battery cell.

Description

Technical Field

[0001] Cross - Reference to Related Applications

[0002] This application claims the benefit of Korean Patent Application No. 10 - 2022 - 0183577, filed on December 23, 2022, and Korean Patent Application No. 10 - 2023 - 0187696, filed on December 20, 2023, in the Korean Intellectual Property Office, the disclosures of which are incorporated herein by reference in their entireties.

[0003] The present disclosure relates to an apparatus and a method for detecting a defect in a battery cell, and more particularly, to an apparatus and a method for detecting a defect in a battery cell, which use magnetic field interference and cancellation to detect the position of a defect in a battery cell. Background Art

[0004] X - ray CT, as a conventional non - contact and non - destructive analysis method for battery cells, requires a long analysis time, making it impossible to perform real - time analysis of various defects. In addition, to address the drawbacks of such X - ray CT analysis, research has been conducted to analyze defects by visualizing the current distribution inside the battery. However, when measuring the induced magnetic field guided by MRI, electromagnetic waves cannot penetrate the battery cell, and it is also difficult to obtain high resolution due to the ferromagnetic materials contained in the battery.

[0005] Therefore, recently, research has been conducted to introduce magnetic field imaging (MFI) technology to detect defects through changes in the magnetic field formed during charging and discharging of a battery cell. However, such magnetic field imaging technology has limitations in detecting noise caused by the sensitivity of magnetic field sensors and in detecting minute changes in the magnetic field at the sub - micro T level in images when high current is applied. Additionally, there are limitations in that additional data processing, such as comparing the average magnetic field intensity of each section between a normal cell and a defective cell, is required, which takes time.

[0006] Figure 1 An apparatus for detecting a defect in a battery cell according to the prior art is shown. The electrode leads 12 of the battery cell 10 are connected to a pair of current application clamps 1. Current is applied to the current transmission lines 2 connected to each of the current application clamps in the current application clamps 1. Thus, current flows through the battery cell 10. Magnetic field imaging (MFI) is used to visualize the magnetic field induced by the current flowing through the battery cell 10. However, according to such prior art, for example, due to the folding of the electrode plate 11a, there is no significant difference between the magnetic field image of a normal battery cell and the magnetic field image of a battery cell in which a defect appears when observed with the naked eye. Figure 7 A magnetic field image according to the prior art is shown. In Figure 7Among them, no obvious difference was observed between (a) a normal monomer and (b) a defective monomer having a folded electrode. Reading this at a fine scale level takes a considerable amount of time, or in some cases, it is difficult to read.

[0007] Therefore, there is a need to develop an improved detection device capable of quickly and accurately detecting defects in battery monomers. Summary of the Invention

[0008] Technical Problem

[0009] An object of the present disclosure is to provide a device for detecting defects in battery monomers and a method for detecting defects in battery monomers. Specifically, among devices applying magnetic field imaging technology, a device that particularly uses magnetic field interference and cancellation to quickly and accurately detect defects in battery monomers is provided.

[0010] However, the technical problems to be solved by the embodiments of the present disclosure are not limited to the above problems, and can be extended in various ways within the scope of the technical ideas included in the present disclosure.

[0011] Technical Solution

[0012] According to an embodiment of the present disclosure, there is provided a device for detecting defects in battery monomers, the device including: a current application clamp that presses and fixes the electrode leads of a battery monomer; and a conductive plate that is disposed on one surface of the battery monomer at a position corresponding to the electrode of the battery monomer, wherein the conductive plate includes a main body having the same shape as the electrode of the battery monomer and having a uniform thickness, wherein a reverse current having a polarity opposite to that of the current applied to the battery monomer is applied to the conductive plate, and wherein the sum of the magnetic fields derived from the current and the reverse current is measured to detect an un-cancelled magnetic field that appears at a defective part of the battery monomer, thereby detecting the defective part of the battery monomer.

[0013] At a normal part of the battery monomer, the magnetic field derived from the current and the magnetic field derived from the reverse current cancel each other out, such that the sum of the magnetic fields may not be detected, and at a defective part of the battery monomer, an un-cancelled magnetic field can be detected.

[0014] The reverse current applied to the conductive plate may have substantially the same magnitude as the current applied to the battery monomer and flow in the opposite direction.

[0015] The device for detecting defects in battery monomers may further include a magnetic field measurement unit that is disposed at a predetermined distance from a large area of the battery monomer.

[0016] The reverse current applied to the conductive plate flows in a direction opposite to the current applied to the battery cell; when the distance between the conductive plate and the magnetic field measurement unit is less than the distance between the battery cell and the magnetic field measurement unit, the magnitude of the reverse current can be equal to or less than the magnitude of the current applied to the battery cell in order to correct for the change in the intensity of the induced magnetic field corresponding to the distance difference; and when the distance between the conductive plate and the magnetic field measurement unit is greater than the distance between the battery cell and the magnetic field measurement unit, the magnitude of the reverse current can be equal to or greater than the magnitude of the current applied to the battery cell to correct for the change in the intensity of the induced magnetic field corresponding to the distance difference.

[0017] The magnetic field measurement unit can be a magnetic field imaging (MFI) device.

[0018] The conductive plate can be arranged to match the large area of the electrode when viewed from the top surface and can be arranged to be parallel to the large area of the electrode when viewed from the side surface.

[0019] The types of defects detected above can include at least one of the following: 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 coated 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.

[0020] The conductive plate includes a pair of connecting members that protrude from the main body of the conductive plate so as to be arranged at positions corresponding to the electrode leads of the battery cell. The connecting members are integrally formed 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 members.

[0021] The battery cell can be configured such that the positive electrode lead is arranged at one end of the two ends in the longitudinal direction, and the negative electrode lead is arranged at the other end, and the connecting members can be arranged at both ends of the conductive plate one by one in the longitudinal direction.

[0022] The battery cell is configured such that both the positive electrode lead and the negative electrode lead can be arranged at one end of the battery cell, and the pair of connecting members can be all arranged on one end of the main body of the conductive plate corresponding to one end of the battery cell.

[0023] The conductive plate can be made of a conductive material.

[0024] The current application jig includes a current application member that presses the electrode lead and has conductivity, and can also include a current transmission wire connected to the current application member for applying current to the battery cell.

[0025] The device for detecting defects of the battery cell can also include an insulating plate arranged below the conductive plate.

[0026] According to another embodiment of the present disclosure, a method for detecting a defect of a battery cell is provided. The method includes the following steps: while applying a current to the battery cell, applying a reverse current having a polarity opposite to that of the current applied to the battery cell to a conductive plate; measuring the sum of magnetic fields respectively derived from the current and the reverse current; and detecting an un-cancelled magnetic field that appears at a defective part of the battery cell, thereby detecting the defective part of the battery cell. The conductive plate includes a main body having the same shape as the electrode of the battery cell and having a uniform thickness, and can be disposed on one surface of the battery cell at a position corresponding to the electrode of the battery cell.

[0027] At a normal part of the battery cell, the magnetic field derived from the current and the magnetic field derived from the reverse current cancel each other out, such that the sum of the magnetic fields may not be detected. And at a defective part of the battery cell, an un-cancelled magnetic field can be detected.

[0028] The reverse current applied to the conductive plate may have substantially the same magnitude as the current applied to the battery cell and flow in the opposite direction.

[0029] The magnetic field measurement unit for measuring the sum of the magnetic fields is disposed at a predetermined distance from a large area of the battery cell; when the distance between the conductive plate and the magnetic field measurement unit is less than the distance between the battery cell and the magnetic field measurement unit, the magnitude of the reverse current may be equal to or less than the magnitude of the current applied to the battery cell, so as to correct the change in the intensity of the induced magnetic field corresponding to the distance difference; and when the distance between the conductive plate and the magnetic field measurement unit is greater than the distance between the battery cell and the magnetic field measurement unit, the magnitude of the reverse current is equal to or greater than the magnitude of the current applied to the battery cell, to correct the change in the intensity of the induced magnetic field corresponding to the distance difference.

[0030] The conductive plate may be disposed to match a large area of the electrode when viewed from the top surface, and may be disposed parallel to the large area of the electrode when viewed from the side surface.

[0031] The types of the detected defects may include at least one of the following: a folded part of the electrode plate of the battery cell, a disconnected part of the electrode plate, a part where the electrode active material is unevenly applied to the coated part of the electrode plate, a disconnected part of the electrode lead or electrode tab of the battery cell, and a part where the stacked electrode plates are misaligned.

[0032] Advantageous Effects

[0033] According to the present disclosure, when applying magnetic field imaging technology to detect defects in a battery cell, magnetic field interference and cancellation can be particularly utilized to quickly and accurately detect defects in the battery cell. In addition, the reliability of the quality of the battery cell thus produced can be ensured.

[0034] The effects that can be obtained from the present disclosure are not limited to the above effects, and additional other effects not mentioned herein will be clearly understood by those skilled in the art from the description of the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Shows an apparatus for detecting defects in battery cells according to the prior art.

[0036] Figure 2 Schematically shows an apparatus for detecting defects in battery cells according to an embodiment of the present disclosure.

[0037] Figure 3 Shows a conductive plate included in the Figure 2 apparatus for detecting defects in battery cells and disposed below the battery cell.

[0038] Figure 4 Shows Figure 3 a modification of.

[0039] Figure 5 Schematically shows Figure 3 a case where a part of the electrode plate is folded.

[0040] Figure 6 Shows a magnetic field image measured in the Figure 2 apparatus for detecting defects in battery cells.

[0041] Figure 7 Shows a magnetic field image according to a comparative example corresponding to the prior art.

[0042] Figure 8 Graphically shows Figure 6 the intensity of the magnetic field caused by the position of the battery cell in the embodiment of.

[0043] Figure 9 Graphically shows Figure 7 the intensity of the magnetic field caused by the position of the battery cell in the comparative example of.

[0044] Figure 10 Is a flowchart of a method for detecting defects in battery cells according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0045] Hereinafter, embodiments disclosed in the present specification will be described in detail with reference to the drawings. However, the same or similar elements are assigned the same reference numerals regardless of the reference numerals, and redundant descriptions thereof will be omitted.

[0046] In the following description, the suffixes "member" and / or "component" of the elements used are assigned or used only for the ease of description in the specification, and the suffixes themselves do not have a meaning or function to distinguish from each other. In addition, terms such as "member...", "component..." described in the specification mean a unit for performing at least one function or operation, which may be embodied by hardware, by software, or by a combination of hardware and software.

[0047] In the following description of the present disclosure, when the detailed description of known functions and configurations incorporated herein may obscure the subject matter of the present disclosure, the detailed description will be omitted. In addition, the drawings are only for easily understanding the embodiments disclosed in this specification. However, the technical ideas disclosed herein are not limited by the drawings and should be construed to include all variations, equivalents, and alternatives included within the spirit and scope of the present disclosure.

[0048] In this specification, terms such as "comprising" or "having" are intended to indicate that the features, numbers, steps, operations, components, parts, or combinations thereof described in the specification exist, but it should be understood that this does not exclude the existence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0049] Now, a device 100 for detecting defects of battery cells according to an embodiment of the present disclosure will be described.

[0050] Figure 2 Schematically shown is a device 100 for detecting defects of battery cells according to an embodiment of the present disclosure. Figure 3 Shown is included in a device for detecting Figure 2 defects of battery cells and is a conductive plate disposed below the battery cell. Figure 4 Shown is Figure 3 a modification of

[0051] As an example, the case where the electrode leads 12 are disposed at both ends of the battery cell 10 will be described.

[0052] The device 100 for detecting defects of battery cells includes a current application jig 110 connected to the electrode leads 12 of the battery cell 10 and applying current to the electrode leads 12. The current application jig 110 may be provided for each electrode lead 12 one by one. The current application jig 110 includes a current application member 111 that contacts and presses the electrode lead 12. For example, the bottom surface of the current application member 111 may be flat. In addition, the current application member 111 is made of a material having excellent electrical conductivity such that current can flow through the current application member 111 to the electrode lead 12.

[0053] The shape and structure of the current application member 111 are not particularly limited, and it can be used as long as it has a connection structure capable of conducting electricity to the electrode lead 12 and can uniformly apply current across the width of the electrode lead 12. Examples of the connection structure capable of conducting electricity may include a connection structure for a current conductor clip, a bolt fastening structure for a wire harness, etc. Additionally, if the width of the current application member 111 is relatively narrow while the width of the electrode lead 12 is wide, an uneven current distribution pattern may be observed at the electrode lead 12 and / or the electrode tab portion. Thus, preferably, the width of the current application member 111 is equal to or greater than the width of the electrode lead 12. If necessary, the current application member 111 can press and fix the electrode lead 12.

[0054] The upper surface of the current application member 111 includes a fixing member 112 that can press and fix the current application member 111. For example, the fastening member 112 includes an electrically insulating handle, and the lower end of the handle includes a screw-shaped support member. The end of the support member can contact the upper surface of the current application member 111 and fix the current application member 111. After positioning the electrode lead 12 on the bottom surface of the current application member 111, the current application member 111 is fixed to the end of the support portion by rotating the handle of the fixing member 112.

[0055] The current transmission line 120 is connected to the current application member 111, and the current applied from the current transmission line 120 is applied to the electrode lead 12 through the conductive current application member 111. The current transmission line 120 can be, for example, a transmission line having conductivity, and more specifically, it can be an electric wire. The current transmission line 120 includes a positive connection part and a negative connection part. The current application member 111 may also include a plate-shaped conductive member 112a extending outward, and the current transmission line 120 can be connected to the conductive member 112a.

[0056] Meanwhile, according to an embodiment of the present disclosure, the device 100 for detecting defects of a battery cell includes a conductive plate 130. The conductive plate 130 has a plate shape that can be disposed on one surface of the battery cell 10 at a position corresponding to the electrode of the battery cell, and has conductivity. Refer to Figure 2 and Figure 3 , the conductive plate 130 includes a plate-shaped main body 131 and a pair of conductive connection parts 132 that can apply a reverse current to the main body 131. The conductive plate 130 is a conductive material, and it is sufficient that it is made of a material having high conductivity and allowing current to flow, and for example, it can be made of ordinary conductive wire materials such as copper, iron, and aluminum.

[0057] The main body 131 is a surface line. That is, it has a plate shape. More specifically, the main body 131 has a flat shape as a whole. This is to ensure that the reverse current flows uniformly through the main body 131 and the magnetic field is uniformly induced, as will be described later.

[0058] In addition, the main body 131 of the conductive plate 130 has the same shape as one surface of the main body 11 of the battery cell 10. More specifically, it has the same shape as the electrode plate 11a of the battery cell 10. For reference, in the present disclosure, the electrode of the battery cell 10 is a concept including the electrode plate 11a, the electrode tab, and the electrode lead 12.

[0059] Figure 3 and Figure 4 The 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 is shown. The main body 131 is arranged such that the length L and the width W of the electrode plate 11a and the main body 131 of the conductive plate 130 are equal to each other.

[0060] In addition, when viewed from above, the main body 131 of the conductive plate 130 can be arranged at the same position as the electrode plate 11a of the battery cell 10. In addition, when viewed from the side, the conductive plate 130 (the main body 131 of the conductive plate 130) can be arranged parallel to the electrode plate 11a of the battery cell 10.

[0061] If the electrode plate 11a is wrapped by the external material of the battery cell 10, for example, when finely adjusting the position of the conductive plate 130, it is found that the magnetic field is completely canceled to show a clear image as a whole and the point aligned with the electrode plate, and the magnetic field detected at the defective part is measured intensively, thereby detecting the defect.

[0062] At this time, the main body 131 of the conductive plate 130 is arranged at the same position as the electrode plate 11a of the battery cell 10, and when a reverse current having substantially the same magnitude (current density) as the current flowing through the electrode plate 11a of the battery cell 10 and flowing in the opposite direction (that is, having opposite polarities and substantially the same magnitude of current density) is applied to the conductive plate 130, the magnetic field induced from the current flowing through the electrode plate 11a of the battery cell 10 and the magnetic field induced from the reverse current applied to the conductive plate 130 cancel each other out. That is, the magnetic field induced from the current flowing through the electrode plate 11a of the battery cell 10 and the magnetic field induced from the reverse current applied to the conductive plate 130 have the same magnitude, but are generated in opposite directions.

[0063] That is, in the case of a normal cell, the magnetic field induced by the current flowing through the electrode plate 11a of the cell 10 and the magnetic field induced by the reverse current applied to the conductive plate 130 cancel each other out. Therefore, when visualized using magnetic field imaging (MFI), no magnetic field is detected, as shown on the left side of Figure 6 ( Figure 6 (a)). Even if it is detected, it is detected within an acceptable level of the error range.

[0064] If the cell 10 is slightly thicker due to the distance difference from the conductive plate 130 provided below the cell 10, when measuring the magnetic field using a magnetic field measurement unit (not shown) provided near the cell 10, an error may occur in the magnitudes of the magnetic field induced by the current flowing through the electrode plate 11a of the 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 can 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.

[0065] That is, due to the thickness of the cell 10, there may be a difference between the distance between the conductive plate 130 and the magnetic field measurement unit and the distance between the cell 10 and the magnetic field measurement unit. Therefore, it is necessary to correct the change (difference) in the intensity of the induced magnetic field corresponding to this distance difference.

[0066] For reference, based on Figure 2 the large area of the cell 10 in, the magnetic field measurement unit can be located on the upper surface of the cell 10 or can be located on a surface lower than the cell 10. The magnetic field measurement unit is a magnetic field imaging (MFI) device, and it can be used if it can measure and image the induced magnetic field and measure defects in the cell 10 by the method described in the present disclosure.

[0067] More specifically, when the conductive plate 130 is provided on the surface of the cell 10 facing the magnetic field measurement unit, for example, in the example of Figure 2 , when the magnetic field measurement unit is located on the cell 10 and the conductive plate 130 is also provided on the upper surface of the cell 10, if the magnitude of the reverse current applied to the conductive plate 130 is equal to or less than the magnitude of the current applied to the cell 10, the difference in the magnitude of the magnetic field caused by the distance deviation between the cell 10 and the conductive plate 130 due to the thickness of the cell 10 is corrected.

[0068] Conversely, when the conductive plate 130 is provided on the surface opposite to the surface of the cell 10 facing the magnetic field measurement unit, for example, in Figure 2In the example, when the magnetic field measurement unit is located on the battery cell 10 and the conductive plate 130 is disposed 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 caused by the distance deviation due to the thickness of the battery cell 10 between the battery cell 10 and the conductive plate 130 is corrected.

[0069] In other words, when the distance between the conductive plate 130 and the magnetic field measurement unit is less than the distance between the battery cell 10 and the magnetic field measurement unit, the magnitude of the reverse current applied to the conductive plate 130 is equal to or less than the magnitude of the current applied to the battery cell 10 in order to correct the change in the intensity of the induced magnetic field corresponding to the distance difference. More specifically, if the change in the intensity 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.

[0070] On the contrary, when the distance between the conductive plate 130 and the magnetic field measurement unit is greater than the distance between the battery cell 10 and the magnetic field measurement unit, 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 in order to correct the change in the intensity of the induced magnetic field corresponding to the distance difference. More specifically, if the change in the intensity 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.

[0071] On the other hand, if there are defects in the electrode plate 11a of the battery cell 10, such as folding of the electrode plate 11a, the reverse current uniformly flows through the main body 131 of the conductive plate 130, so that the induced magnetic field as a whole is also uniform. However, the magnitude of the induced magnetic field changes in the portion where the electrode plate 11a of the battery cell 10 has a defect. For example, the surface of the current collector is exposed at the folded portion of the electrode plate 11a, and in this portion, a significant decrease in the magnetic field occurs due to the absence of the electrode plate 11a and the active material. In addition, the amount of current decreases in the portion where the active material of the electrode plate 11a is not properly applied to the coated portion of the electrode plate 11a, and the magnitude of the induced magnetic field decreases. As a result, the magnetic field induced in the defective portion of the electrode plate 11a of the battery cell 10 is not completely canceled out by the magnetic field in the opposite direction applied by the current flowing uniformly across the conductive plate 130. Therefore, when measured by a magnetic field measurement unit (not shown) placed near the battery cell 10, an uncanceled magnetic field is clearly detected in the defective portion of the electrode plate 11a of the battery cell 10 compared to the normal portion, as shown on the right side of Figure 6 ( Figure 6 (b)). Therefore, compared with the prior art, defective portions in the electrode plate 11a of the battery cell 10 can be detected quickly and accurately.

[0072] The connection member 132 of the conductive plate 130 includes a positive electrode member and a negative electrode member. The connection member 132 of the conductive plate 130 may be disposed at positions corresponding to the positive electrode lead and the negative electrode lead of the battery cell 10. That is, when viewed from above, the connection member 132 of the conductive plate 130 may be disposed at the same positions as the positive electrode lead and the negative electrode lead of the battery cell 10. In addition, the connection member 132 may be integrally formed with the main body 131 or may be coupled to the main body 133. The shape of the connection member 132 is not limited to Figure 2 and Figure 3 the shapes shown in, and may be any shape that allows current to flow through the main body 131.

[0073] In some cases, the connection member 132 may also have a plate shape having the same thickness as the main body 131 and may be made of the same material as the main body 131.

[0074] The device 100 for detecting a defect of the battery cell may further include an insulating plate 140 disposed below the conductive plate 130. For example, the insulating plate 140 may have a thick plate shape or may be an insulating film. The insulating plate 140 has electrical insulation properties and prevents the conductive plate 130 or the battery cell 10 from short-circuiting.

[0075] In addition, a magnetic field measurement unit (not shown) may be disposed near the battery cell 10 and spaced apart from the battery cell 10 by a predetermined distance. The magnetic field measurement unit measures the total magnetic field in which the magnetic field induced from the current flowing through the battery cell 10 and the magnetic field induced from the reverse current flowing through the conductive plate 130 interfere with or cancel each other. That is, regarding the sum of the magnetic field induced from the current flowing through the battery cell 10 and the magnetic field induced from the reverse current flowing through the conductive plate 130, since the induced magnetic fields are in opposite directions, the total magnetic field has a value as a result of the induced magnetic fields in opposite directions canceling or interfering with each other.

[0076] Figure 6 The embodiment of shows a magnetic field image when the magnetic field measurement unit is disposed on the battery cell 10 - that is, when it is disposed on the Z-axis (in the height direction of the battery cell 10). However, the present disclosure is not limited thereto, and the magnetic field measurement unit is disposed on the front side or the rear side of the battery cell 10, that is, on the X-axis (in the longitudinal direction of the battery cell 10), or is disposed on both sides of the battery cell 10, that is, on the Y-axis (in the width direction of the battery cell 10), and thus the Y-axis component of the induced magnetic field can also be measured.

[0077] In addition, a general magnetic field measurement unit can be applied as the magnetic field measurement unit. For example, it can be a magnetic field imaging device using magnetic field imaging (MFI) technology. However, the present disclosure is not limited thereto, and it is sufficient that it is a measurement unit capable of detecting a magnetic field and indicating the position of a defect in the battery cell 10.

[0078] Meanwhile, the types of defects of the battery cell 10 that can be detected according to the embodiments of the present disclosure are not limited to those described above, and various types of defects can be detected. For example, in addition to the folding of the electrode plate 11a, the disconnection of the electrode plate 11a (e.g., perforation or tearing, etc.), and the defective application of the electrode active material on the coated portion of the electrode plate 11a as described above, the disconnection point of the electrode tab or the electrode lead can also be detected. In this case, the connecting member 132 of the conductive plate 130 has the same shape as the electrode tab or the electrode lead, and when the main body 131 and the connecting member 132 of the conductive plate 130 are integrally formed and have the same thickness and the same flatness, the disconnection point of the electrode tab or the electrode lead can be effectively detected. Alternatively, the misalignment of the plurality of electrode plates 11a stacked inside the battery cell 10 can also be detected. Due to the misalignment of the electrode plates 11a, the magnetic field induced before applying current to the battery cell 10 at the misaligned portion changes, and if this is canceled out by the uniform magnetic field induced from the reverse current applied to the conductive plate 130, the changed magnetic field can be clearly detected in the misaligned portion.

[0079] In the above Figure 2 and Figure 3 embodiments, a device for detecting defects of the battery cell 10 when the positive lead and the negative lead are separately provided at both ends of the battery cell 10 is described. However, the present disclosure is not limited thereto, and it can be modified and changed to match the environment in which the present invention is implemented.

[0080] For example, referring to Figure 4 , when both the positive lead and the negative lead are provided at one end of the battery cell 10, it can also be achieved by placing the connecting member 132 of the conductive plate 130 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 connecting member 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, 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 only have opposite directions, and the flow patterns are basically the same, so that the magnetic fields cancel each other out, and the defects in the battery cell 10 can be easily detected.

[0081] For reference, in Figure 3 and Figure 4In , the dashed lines shown between the electrode plate 11a and the electrode lead 12 of the battery cell 10 and between the main body 131 and the connecting member 132 of the conductive plate 130 do not mean folding portions, but are indicated as dashed lines to clarify the division between each component. Additionally, it should be noted that the electrode tab is not separately divided in the portion marked as the electrode lead 12.

[0082] Figure 5 is schematically shown Figure 2 and Figure 3 a case where a part of the electrode plate 11a is folded. Figure 6 shows the Figure 2 magnetic field image measured by the device 100 for detecting defects of the battery cell. Figure 7 shows the magnetic field image according to the comparative example (prior art). In Figure 6 and Figure 7 , (a) the case of a normal cell is shown on the left, and (b) the case of a cell with an electrical folding defect is shown on the right.

[0083] Figure 6 The measurement conditions in the embodiments of Figure 7 and

[0084] - Charging current: 260 mA

[0085] - z distance: 3 mm (distance between the battery cell and the measurement unit)

[0086] - Measurement speed: 100 mm / min

[0087] - Third scan mean data

[0088] - Image resolution: 2.5 * 0.0646 mm

[0089] Additionally, in the embodiments of Figure 6 , as described above, a charging current of the same magnitude is applied to the conductive plate 130, but a current in the direction opposite to the current applied to the battery cell 10 is applied.

[0090] It can be seen that a change in the magnetic field clearly appears in Figure 6 the magnetic field image on the right side of Figure 6 , that is, in Figure 5 (b), so as to coincide with the partially folded portion (P) of the electrode plate 11a in Figure 7 . On the other hand, in according to the comparative example, no obvious difference is seen between (a) the case of a normal cell and (b) the case of a defective cell with a folded electrode. Therefore, it can be seen that there are limitations in visually clearly distinguishing the location of the defect.

[0091] Figure 8 Graphically shows Figure 6 the intensity of the magnetic field caused by the position of the battery cell 10 in the embodiment of Figure 9 Graphically shows Figure 7 the intensity of the magnetic field caused by the position of the battery cell 10 in the comparative example of Figure 6 In the embodiment according to Figure 8 In the graph of Figure 7 in the embodiment according to Figure 9 the difference in the intensity of the magnetic field measured between the defective cell with the folded electrode and the normal cell clearly appears at the defective site. On the other hand, in the graph of

[0092] Next, a method for detecting a defect of a battery cell according to an embodiment of the present disclosure will be described.

[0093] Figure 10 is a flowchart of a method for detecting a defect of a battery cell according to an embodiment of the present disclosure.

[0094] Referring to Figure 10 , a method for detecting a defect of a battery cell includes: step (S110) of applying a reverse current having a polarity opposite to that of the current applied to the battery cell to the conductive plate while applying a current to the battery cell; step (S120) of measuring the sum of the magnetic fields derived from the current applied to the battery cell and the reverse current applied to the conductive plate; and step (S130) of detecting the un-canceled magnetic field that appears at the defective site of the battery cell, thereby detecting the defective site of the battery cell.

[0095] As described above with reference to Figures 2 to 4 , the conductive plate 130 has a plate shape that can be placed on one surface of the battery cell 10 at a position corresponding to the electrode of the battery cell 10 and has conductivity. The conductive plate 130 is arranged to match the large area of the electrode of the battery cell 10 when viewed from the top surface, and is arranged to be parallel to the large area of the electrode of the battery cell 10 when viewed from the side surface.

[0096] The reverse current applied to the conductive plate 130 has substantially the same magnitude as the current applied to the battery cell 10 and flows in the opposite direction.

[0097] At a normal part of the battery cell 10, 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 cancel each other out, such that the total magnetic field is not detected.

[0098] On the other hand, at a defective part of the battery cell, the magnitudes of the current applied to the battery cell 10 and the reverse current applied to the conductive plate 130 are different, and thus, 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, and the un-canceled magnetic field is detected.

[0099] As described above, the magnetic field measurement unit is provided at a predetermined distance from a large 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 between the conductive plate 130 and the magnetic field measurement unit and the distance between the battery cell 10 and the magnetic field measurement unit. Therefore, it is necessary to correct the change (difference) in the intensity of the induced magnetic field corresponding to this distance difference.

[0100] More specifically, when the distance between the conductive plate 130 and the magnetic field measurement unit is less than the distance between the battery cell 10 and the magnetic field measurement unit, the magnitude of the reverse current is equal to or less than the magnitude of the current applied to the conductive plate 130 in order to correct the change in the intensity of the induced magnetic field corresponding to the distance difference. More specifically, if the change in the intensity 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 can be the same.

[0101] On the other hand, when the distance between the conductive plate 130 and the magnetic field measurement unit is greater than the distance between the battery cell 10 and the magnetic field measurement unit, 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 in order to correct the change in the intensity of the induced magnetic field corresponding to the distance difference. More specifically, if the change in the intensity 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 can be the same.

[0102] The types of defects of the battery cell include at least one of the following: a folded part of the electrode plate 11a of the battery cell 10, a disconnected part of the electrode plate 11a, a part where the electrode active material is unevenly applied to the coated part of the electrode plate 11a, a disconnected part of the electrode lead 12 or the electrode tab of the battery cell 10, and a part where the stacked electrode plates 11a are misaligned.

[0103] In addition, a more detailed description of the method for detecting defects of the battery cell overlaps with the description of the device for detecting defects of the battery cell described above in Figures 2 to 9 and thus, reference is made to those described above with reference to Figures 2 to 9 described.

[0104] When detecting the defects of the battery cell 10 by using the device 100 for detecting the defects of the battery cell and the method for detecting the defects of the battery cell according to the present disclosure, compared with the prior art, the defective part can be detected quickly. At the same time, the defective part can be determined more accurately. Thereby, the reliability of the quality of the produced battery cells can be ensured.

[0105] Although the present invention has been described in detail above with reference to the preferred embodiments of the present invention, those skilled in the art will recognize that the scope of the present disclosure is not limited thereto, and various modifications and improvements can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined in the appended claims and their equivalents.

[0106] [Description of Reference Numerals]

[0107] 10: Battery cell

[0108] 11: Main body

[0109] 11a: Electrode plate

[0110] 12: Electrode lead

[0111] 100: Device for detecting the defects of the battery cell

[0112] 110: Current application clamp

[0113] 111: Current application member

[0114] 112: Fixing member

[0115] 120: Conductive wire

[0116] 130: Conductive plate

[0117] 131: Main body

[0118] 132: Connection member

[0119] 140: Insulating plate

Claims

1. A device for detecting defects in a battery cell, comprising: A current application clamp that presses and fixes the electrode leads of the battery cell; And A conductive plate that is disposed on one surface of the battery cell at a position corresponding to the electrode of the battery cell, Wherein the conductive plate includes a main body having the same shape as the electrode of the battery cell and having a uniform thickness, Wherein a reverse current having a polarity opposite to that of the current applied to the battery cell is applied to the conductive plate, and Wherein the sum of the magnetic fields derived from the current and the reverse current is measured to detect an uncompensated magnetic field that appears at a defective portion of the battery cell, thereby detecting the defective portion of the battery cell.

2. The device for detecting defects in a battery cell according to claim 1, wherein: At a normal portion of the battery cell, the magnetic field derived from the current and the magnetic field derived from the reverse current cancel each other out, such that the sum of the magnetic fields is not detected, and At the defective portion of the battery cell, an uncompensated magnetic field is detected.

3. The device for detecting defects in a battery cell according to claim 1, wherein: The reverse current applied to the conductive plate has substantially the same magnitude as the current applied to the battery cell and flows in the opposite direction.

4. The device for detecting defects in a battery cell according to claim 1, Further comprising a magnetic field measurement unit that is disposed at a predetermined distance from a large area of the battery cell.

5. The device for detecting defects in a battery cell according to claim 4, wherein: The reverse current applied to the conductive plate flows in a direction opposite to that of the current applied to the battery cell, When the distance between the conductive plate and the magnetic field measurement unit is less than the distance between the battery cell and the magnetic field measurement unit, the magnitude of the reverse current is equal to or less than the magnitude of the current applied to the battery cell in order to correct for a change in the intensity of the induced magnetic field corresponding to the distance difference, and When the distance between the conductive plate and the magnetic field measurement unit is greater than the distance between the battery cell and the magnetic field measurement unit, the magnitude of the reverse current is equal to or greater than the magnitude of the current applied to the battery cell to correct for a change in the intensity of the induced magnetic field corresponding to the distance difference.

6. The device for detecting defects in a battery cell according to claim 4, wherein: The magnetic field measurement unit is a magnetic field imaging (MFI) device.

7. The device for detecting defects in a battery cell according to claim 1, wherein: The conductive plate: Is arranged to match a large area of the electrode when viewed from the top surface, and Is arranged to be parallel to a large area of the electrode when viewed from the side surface.

8. The device for detecting defects in a battery cell according to claim 1, wherein: The types of the detected defects include at least one of the following: the folded portion of the electrode plate of the battery cell, the disconnected portion of the electrode plate, the portion where the electrode active material is unevenly applied to the coated portion of the electrode plate, the disconnected portion of the electrode lead or electrode tab of the battery cell, and the misaligned portion of the stacked electrode plates.

9. The device for detecting defects of a battery cell according to claim 1, wherein: The conductive plate includes a pair of connecting members that protrude from the main body of the conductive plate so as to be disposed at positions corresponding to the electrode leads of the battery cell, The connecting members are integrally formed 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 members.

10. The device for detecting defects of a battery cell according to claim 9, wherein: The battery cell is configured such that the positive electrode lead is disposed at one of the two ends in the longitudinal direction, and the negative electrode lead is disposed at the other end, and The connecting members are respectively and successively disposed at both ends of the conductive plate in the longitudinal direction.

11. The device for detecting defects of a battery cell according to claim 9, wherein: The battery cell is configured such that both the positive electrode lead and the negative electrode lead are disposed at one end of the battery cell, and The pair of connecting members are all disposed on one end of the main body of the conductive plate corresponding to the one end of the battery cell.

12. The device for detecting defects of a battery cell according to claim 1, wherein: The conductive plate is made of a conductive material.

13. The device for detecting defects of a battery cell according to claim 1, wherein: The current application clamp includes a current application member that presses the electrode lead and has conductivity, and Further includes a current transmission wire connected to the current application member to apply current to the battery cell.

14. The device for detecting defects of a battery cell according to claim 1, Further includes an insulating plate disposed below the conductive plate.

15. A method for detecting defects of a battery cell, the method comprising the following steps: Applying a reverse current having a polarity opposite to the current applied to the battery cell to the conductive plate while applying current to the battery cell; Measuring the sum of the magnetic fields respectively derived from the current and the reverse current; And Detecting the un-canceled magnetic field that appears at the defective part of the battery cell, thereby detecting the defective part of the battery cell, Wherein, the conductive plate: Includes a main body having the same shape as the electrode of the battery cell and having a uniform thickness, and Is disposed on one surface of the battery cell at a position corresponding to the electrode of the battery cell.

16. The method for detecting defects of a battery cell according to claim 15, wherein: At a normal portion of the battery cell, the magnetic field derived from the current and the magnetic field derived from the reverse current cancel each other out, such that the sum of the magnetic fields is not detected, and at the defective portion of the battery cell, an uncancelled magnetic field is detected.

17. The method for detecting a defect of a battery cell according to claim 15, wherein: the reverse current applied to the conductive plate has substantially the same magnitude as the current applied to the battery cell and flows in the opposite direction.

18. The method for detecting a defect of a battery cell according to claim 15, wherein: the magnetic field measurement unit for measuring the sum of the magnetic fields is disposed at a predetermined distance from a large area of the battery cell, when the distance between the conductive plate and the magnetic field measurement unit is less than the distance between the battery cell and the magnetic field measurement unit, the magnitude of the reverse current is equal to or less than the magnitude of the current applied to the battery cell, so as to correct the change in the intensity of the induced magnetic field corresponding to the distance difference, and when the distance between the conductive plate and the magnetic field measurement unit is greater than the distance between the battery cell and the magnetic field measurement unit, the magnitude of the reverse current is equal to or greater than the magnitude of the current applied to the battery cell, so as to correct the change in the intensity of the induced magnetic field corresponding to the distance difference.

19. The method for detecting a defect of a battery cell according to claim 15, wherein: the conductive plate: is arranged to match a large area of the electrode when viewed from the top surface, and is arranged to be parallel to a large area of the electrode when viewed from the side surface.

20. The method for detecting a defect of a battery cell according to claim 15, wherein: the types of the detected defects include at least one of the following: a folded portion of the electrode plate of the battery cell, a disconnected portion of the electrode plate, a portion where electrode active material is unevenly applied to a coated portion of the electrode plate, a disconnected portion of an electrode lead or an electrode tab of the battery cell, and a portion where stacked electrode plates are misaligned.

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