Apparatus and method for detecting internal defects in battery cells using tdr

Abstract

This technology relates to an apparatus for detecting internal defects in a battery cell, the apparatus comprising: a time-domain reflectometer (TDR) module configured to apply an electrical pulse to the battery cell and compare a reference waveform with a measurement waveform generated by the reflected wave of the detected electrical pulse to determine whether a defect has occurred; and a signal line configured to electrically connect the TDR module to the electrode leads of the battery cell, wherein the electrical pulse is applied in the longitudinal direction of the battery cell. This technology also relates to a method for detecting internal defects in a battery cell.

Description

Technical Field

[0001] This invention relates to an apparatus and method for detecting internal defects in a single battery cell using a time domain reflectometry (TDR).

[0002] More specifically, the present invention relates to an apparatus and method for detecting internal defects in a battery cell, which can use TDR to quickly and accurately detect defects that may occur in various internal regions of the battery cell.

[0003] This application claims priority based on Korean Patent Application No. 10-2021-0115841, filed on August 31, 2021, the entire contents of which are incorporated herein by reference. Background Technology

[0004] Recently, rechargeable batteries have been widely used as an energy source for wireless mobile devices. Furthermore, rechargeable batteries are gaining attention as an energy source for electric vehicles, hybrid electric vehicles, and other applications that have been introduced as a solution to air pollution caused by existing gasoline and diesel vehicles using fossil fuels. Therefore, due to the advantages of rechargeable batteries, their applications are diversifying, and they are expected to be used in even more fields and products in the future.

[0005] Based on the composition of the electrodes and electrolyte, secondary batteries can be classified into lithium-ion batteries, lithium-ion polymer batteries, lithium polymer batteries, etc. Among these batteries, the use of lithium-ion polymer batteries, which are less prone to electrolyte leakage and are easy to manufacture, is increasing.

[0006] Generally, secondary batteries are classified into cylindrical or prismatic batteries and pouch batteries based on the shape of their casing. In cylindrical or prismatic batteries, the electrode assembly is housed in a cylindrical or polygonal metal can. In pouch batteries, the electrode assembly is housed in a pouch-shaped casing of aluminum laminated sheets. The electrode assembly included in the battery casing is a rechargeable and dischargeable power-generating device, comprising a positive electrode, a negative electrode, and a separator between the positive and negative electrodes. Electrode assemblies are classified into jelly roll type and stacked type. The jelly roll type is formed by winding a long sheet coated with active material, with a separator inserted between the positive and negative electrodes, to obtain the structure. In the stacked type, positive and negative electrodes, each having a certain size, are stacked sequentially, with a separator inserted between them.

[0007] The positive and negative electrodes are formed by applying a positive electrode slurry containing a positive electrode active material to a positive electrode current collector, applying a negative electrode slurry containing a negative electrode active material to a negative electrode current collector, and drying and rolling the resulting structure.

[0008] Simultaneously, electrode terminals are formed on one side of the electrode assembly to connect the battery cells to the outside, and electrode leads are soldered to the electrode terminals. The electrode leads are then pulled outside the battery casing.

[0009] However, various defects may occur in the battery cells during the manufacturing of the electrodes and the assembly of the electrode assemblies.

[0010] Specifically, breakage may occur in the electrode tabs due to differences in elongation between the coated and uncoated portions, physical forces applied during welding, etc. Furthermore, various defects may occur in different locations, such as poor welding between the electrode tabs and electrode leads, breakage at the boundary between the uncoated and coated portions during the formation of the electrode tabs, dendrite growth leading to internal short circuits, and damage to the separators during the assembly process.

[0011] When such defects occur, significant performance degradation can occur during the assembly of defective battery modules or battery packs. Therefore, early defect detection to distinguish defective battery cells from normal ones is crucial. In the prior art, non-destructive testing methods such as computed tomography (CT), X-ray inspection, and eddy current testing are used. However, while these methods can detect internal defects, they are time-consuming, resulting in low processing efficiency and low inspection accuracy.

[0012] Therefore, there is a need to develop a technology that can quickly and accurately inspect battery cells with internal defects using a non-destructive method during actual large-scale production.

[0013] [Existing Technical Documents]

[0014] [Patent Literature]

[0015] Japanese Patent Publication No. 2020-165859 Summary of the Invention

[0016] [Technical Issues]

[0017] To address the aforementioned problems, this invention aims to provide an apparatus and method for detecting internal defects in battery cells, which can quickly and accurately detect various internal defects in battery cells during actual mass production.

[0018] [Technical Solution]

[0019] The present invention provides an apparatus for detecting internal defects in a battery cell, the battery cell having the following structure: an electrode assembly including at least one electrode terminal on one or both sides is housed in a battery casing, and at least one battery terminal is connected to an electrode lead pulled out from the battery casing. The apparatus includes: a time domain reflectometer (TDR) module configured to apply an electrical pulse to the battery cell and compare a reference waveform with a measurement waveform generated by detecting the reflected wave of the electrical pulse to determine whether a defect has occurred; and a signal line configured to electrically connect the TDR module to the electrode lead of the battery cell, wherein the electrical pulse is applied in the longitudinal direction of the battery cell.

[0020] For example, a TDR module may include: an electrical pulse generator configured to generate an electrical pulse to be applied to a battery cell; a reflected wave detector configured to detect the reflected wave of the electrical pulse; and a determiner configured to generate a measurement waveform based on the reflected wave of the electrical pulse detected by the reflected wave detector, compare the measurement waveform with a reference waveform, and determine that a defect has occurred when there is an offset between the measurement waveform and the reference waveform.

[0021] When the rate of change of the impedance represented by the measured waveform compared to the reference waveform is greater than 10%, it can be determined that there is an offset indicating the presence of a defect.

[0022] The measured waveform generated for each region of the battery cell in the longitudinal direction can be compared with a reference waveform to determine whether a defect has occurred in each region of the battery cell.

[0023] In this case, the area of ​​a battery cell may include a welded portion between the electrode leads and electrode tabs of the battery cell joined by welding, an electrode tab portion on which the electrode tabs are positioned, a coated portion coated with electrode active material, and a boundary portion serving as the boundary area between the electrode tab portion and the coated portion.

[0024] Specifically, the reference waveform can be a measurement waveform generated by applying an electrical pulse to a normal battery cell and detecting the reflected wave of the electrical pulse.

[0025] As a specific example, the TDR module may include: a first TDR module configured to apply an electrical pulse signal via a first electrode lead; and a second TDR module configured to sequentially apply electrical pulse signals via a second electrode lead, and the signal line may include: a first signal line configured to electrically connect the first electrode lead to the first TDR module; and a second signal line configured to electrically connect the second electrode lead to the second TDR module.

[0026] For example, the device may further include a grounding wire configured to electrically connect the grounding surface on which the battery cells are arranged to the TDR module.

[0027] As a specific example, a single battery cell can be arranged to be parallel to the grounded surface in the longitudinal direction.

[0028] The device may further include a fixing member configured to fix the electrode leads of the battery cell.

[0029] The present invention also provides a method for detecting internal defects in a single battery cell.

[0030] The method for detecting internal defects in a battery cell includes: applying an electrical pulse to the battery cell via a time-domain reflectometer (TDR) module through a signal line electrically connected to the electrode leads of the battery cell; generating a measurement waveform by the TDR module by detecting the reflected wave generated as the electrical pulse propagates in the longitudinal direction of the battery cell via the signal line; and detecting whether a defect has occurred by comparing the measurement waveform generated by the TDR module with a reference waveform.

[0031] In this context, detecting whether a defect has occurred may include determining that a defect has occurred when there is an offset between the measured waveform and the reference waveform.

[0032] Furthermore, the TDR module can compare the measured waveform generated for each region of the battery cell in the longitudinal direction with a reference waveform to determine whether a defect has occurred in each region of the battery cell. In this case, the region of the battery cell may include the welded portion between the electrode leads and electrode tabs of the battery cell joined by welding, the electrode tab portion on which the electrode tabs are positioned, the coated portion coated with electrode active material, and the boundary portion serving as the boundary region between the electrode tab portion and the coated portion.

[0033] As a specific example, the method may further include: applying an electrical pulse to the battery cell via a signal line connected to the electrode leads of a normal battery cell using a TDR module; generating a measurement waveform by detecting the reflected wave generated when the electrical pulse propagates in the longitudinal direction of the battery cell via the signal line using the TDR module; and setting the measurement waveform as a reference waveform.

[0034] [Beneficial Effects]

[0035] According to the present invention, in actual mass production, a time domain reflectometer (TDR) can be used to quickly and accurately detect various internal defects of a battery cell without disassembling the battery cell.

[0036] Furthermore, according to the present invention, inspections can be performed rapidly during the manufacturing process of battery cells, and internal defects in battery cells can be quickly detected during the recycling or reuse of finished battery cells that have been used for a certain period of time. Therefore, in order to recycle battery cells, it is convenient to determine whether to reuse the battery cells by quickly inspecting for defects. Attached Figure Description

[0037] Figure 1 This is a cross-sectional view of the structure of a typical battery cell.

[0038] Figure 2 This is a schematic diagram illustrating an apparatus and measurement waveform for detecting internal defects in a battery cell according to an embodiment of the present invention.

[0039] Figure 3 This is a block diagram illustrating the configuration of a time-domain reflectometer (TDR) module according to an embodiment of the present invention.

[0040] Figure 4a and Figure 4b This is a schematic diagram illustrating an apparatus and measurement waveform for detecting internal defects in a battery cell according to another embodiment of the present invention.

[0041] Figure 5 This is a flowchart of a method for detecting internal defects in a battery cell according to an embodiment of the present invention.

[0042] Figures 6a to 6d It is shown that according to Figure 2 A graph of the measurement waveform generated by the apparatus for detecting internal defects in a single battery cell in an embodiment of the invention. Detailed Implementation

[0043] The present invention will be described in detail below. First, the terms or expressions used in this specification and claims should not be construed as limited to their general understanding or as defined in common dictionaries, but should be understood based on the inventors' ability to appropriately define the terms or expressions to best interpret the principles of the invention, according to the meanings and concepts corresponding to the invention.

[0044] It should be understood that the terms “comprising” and / or “including” as used herein specify the presence of the feature, integer, step, operation, element, component or combination thereof, but do not exclude the presence or addition of one or more features, integers, steps, operations, elements, components or combinations thereof.

[0045] It should be understood that when a component such as a layer, film, region, or plate is referred to as being "above" another component, that component is "directly above" that component, or other components are located between those components. It should also be understood that when a component such as a layer, film, region, or plate is referred to as being "below" another component, that component is "directly below" that component, or other components are located between those components. In this specification, it should be understood that when a component is referred to as being "above" another component, that component is either above or below that component.

[0046] As used in this article, the “longitudinal direction” of a battery cell should be understood as the direction in which the electrode terminals are pulled out, and the “width direction” should be understood as the direction perpendicular to the longitudinal direction.

[0047] The present invention provides an apparatus for detecting internal defects in a battery cell. The battery cell has the following structure: an electrode assembly including at least one electrode terminal on one or both sides is housed in a battery casing, and at least one battery terminal is connected to an electrode lead pulled out from the battery casing. The apparatus includes a time domain reflectometer (TDR) module and a signal line. The TDR module is configured to apply an electrical pulse to the battery cell and compare a reference waveform with a measurement waveform generated by detecting the reflected wave of the electrical pulse to determine whether a defect has occurred. The signal line is configured to electrically connect the TDR module and the electrode lead of the battery cell to each other, wherein the electrical pulse is applied in the longitudinal direction of the battery cell.

[0048] As mentioned above, existing methods for detecting internal defects in battery cells are difficult to apply in practice because they require a considerable amount of time to inspect, have low processing efficiency, and are not very accurate.

[0049] In contrast, the present invention is characterized in that the TDR module can apply an electrical pulse through the electrode leads of the battery cell and use the measurement waveform generated by detecting the reflected wave of the electrical pulse to detect internal defects in the battery cell. Because the electrical pulse propagates in the longitudinal direction of the battery cell, internal defects in various regions of the battery cell in the longitudinal direction can be detected.

[0050] The TDR module detects defects based on the following principle: when an electrical pulse propagating in the longitudinal direction of a battery cell reaches a location within the cell where an impedance change occurs, reflection occurs. In other words, when a battery cell has an internal defect, an impedance change occurs differently, thus altering the time point at which the reflected wave is generated from the electrical pulse and the arrival time of the reflected wave. Using this, a measured waveform representing the impedance over time can be derived from the reflected wave, and this measured waveform can be compared with a reference waveform to identify whether a battery cell has a defect and the location of the defect.

[0051] The above-described components of the present invention will now be described in more detail using the accompanying drawings and embodiments. In describing each drawing, similar reference numerals are used for similar elements. In the drawings, the dimensions of the structures are enlarged for clarity. Various components may be described using terms such as "first" and "second," but these components should not be limited by these terms. Terms are used only to distinguish one component from another. For example, a first component may be referred to as a second component without departing from the scope of the invention, and similarly, a second component may be referred to as a first component. As used herein, the singular is intended to include the plural form as well, unless the context clearly specifies otherwise.

[0052] The present invention will now be described in detail.

[0053] [Embodiments of the Invention]

[0054] (First Embodiment)

[0055] Figure 1 This is a cross-sectional view of the structure of a typical battery cell.

[0056] refer to Figure 1 The battery cell 1 has the following structure: an electrode assembly 20, having at least one electrode tab—e.g., electrode tabs 30 and 40—on one or both sides, is housed in a battery casing 10, and the electrode tabs 30 and 40 are connected to electrode leads 31 and 41 that are pulled out from the battery casing 10. For example, electrode leads 31 and 41 include a positive lead 31 and a negative lead 41, and the positive lead 31 and the negative lead 41 can be pulled out from the battery casing 10 in opposite directions, but the structure of electrode leads 31 and 41 is not limited thereto. Electrode assemblies and their components are well known to those skilled in the art, and therefore their detailed description is omitted herein.

[0057] Figure 2 This is a schematic diagram illustrating an apparatus 100 for detecting internal defects in a battery cell according to a first embodiment of the present invention and a measurement waveform. Figure 3 This is a block diagram illustrating the configuration of a TDR module according to a first embodiment of the present invention.

[0058] refer to Figure 2The apparatus 100 for detecting internal defects in a battery cell according to the present invention includes: a TDR module 110 for applying an electrical pulse to the battery cell and comparing a measured waveform generated by detecting the reflected wave of the electrical pulse with a reference waveform to determine whether a defect has occurred; and a signal line 120 for electrically connecting the TDR module 110 to an electrode lead 31 of the battery cell, wherein the battery cell has the following structure: an electrode assembly 20, including at least one electrode tab—e.g., electrode tabs 30 and 40—on both sides thereof, is housed in a battery casing 10, and the electrode tabs 30 and 40 are connected to electrode leads 31 and 41 pulled out from the battery casing 10. In this case, a reflected wave occurs as the electrical pulse propagates in the longitudinal direction of the battery cell.

[0059] Figure 2 The diagram shows the TDR module 110 applying an electrical pulse signal via electrode lead 31, which serves as the positive lead. However, the TDR module 110 can also apply an electrical pulse signal via electrode lead 41, which serves as the negative lead, and in this case, the TDR module 110 is electrically connected to the negative lead 41 via a signal line.

[0060] The TDR module 110 generates an electrical pulse and produces a measurement waveform based on the reflected wave of the electrical pulse to detect whether a defect has occurred.

[0061] Specifically, refer to Figure 3 The TDR module 110 includes: an electrical pulse generator 111 for generating an electrical pulse to be applied to a battery cell; a reflected wave detector 112 for detecting the reflected wave of the electrical pulse; and a determiner 113 for generating a measurement waveform based on the reflected wave of the electrical pulse detected by the reflected wave detector 112, comparing the measurement waveform with a reference waveform, and determining that a defect has occurred when the comparison result indicates that there is an offset.

[0062] More specifically, the electrical pulse generator 111 can generate electrical pulses and apply them to the battery cells at regular time intervals. The time interval can be defined as the time required for the electrical pulse to travel to and return from the defect location of the battery cell to be inspected. For example, to detect defects in all areas of the battery cell in the longitudinal direction, the time interval can be defined as the time required for the electrical pulse to propagate between the TDR module 110 where the electrical pulse is applied and the unconnected negative lead 41 of the TDR module 110.

[0063] As the electrical pulse signal supplied from the electrical pulse generator 111 propagates in the longitudinal direction of the battery cell, the reflected wave detector 112 can detect reflected waves from various internal components of the battery cell. In other words, by measuring the reflected waves of the electrical pulse, the impedance changes generated as the electrical pulse applied to the battery cell through the TDR module 110 propagates back and forth within the battery cell can be examined.

[0064] Determiner 113 generates a measurement waveform based on the reflected wave of the electrical pulse detected by reflected wave detector 112. The measurement waveform represents the impedance of the reflected signal of the electrical pulse over time. The measurement waveform can be represented by plotting time on the horizontal axis and impedance on the vertical axis. Figure 2 The measured waveform shown represents the impedance over time.

[0065] Determiner 113 can compare the generated measured waveform with a reference waveform and determine that a defect has occurred when there is an offset between the measured waveform and the reference waveform. In this case, it can be understood that when an offset exists, the measured waveform and the reference waveform are mismatched, and the rate of change of the impedance of the measured waveform compared with the reference waveform is greater than 10%.

[0066] The reference waveform can be a measurement waveform generated by applying an electrical pulse to a normal battery cell and detecting the reflected wave of the pulse. When the measurement waveform of the battery cell under test is generated in the same manner as that of a normal battery cell, and the result of comparing the measurement waveform with the reference waveform indicates a deviation, a defect is determined to have occurred.

[0067] As described above, in order to detect defects in all areas of a battery cell in the longitudinal direction, an electrical pulse is applied by setting the time interval to the time required for the electrical pulse to propagate between the TDR module 110 where the pulse is applied and the unconnected negative lead 41 of the TDR module, and then back to the TDR module 110. Therefore, as... Figure 2 As shown, measurement waveforms can be generated for each region of a battery cell in the longitudinal direction. The regions of the battery cell include: a welded portion a between the electrode leads 31 and electrode tabs 30 joined by welding; a tab portion b on which the electrode tabs 30 are positioned; a coated portion d coated with electrode active material; and a boundary portion c serving as the boundary between tab portion b and coated portion d. In this case, the measurement waveforms generated for each region of the battery cell can be compared with a reference waveform to detect whether a defect has occurred in each region of the battery cell. That is, because regions of the battery cell that have experienced displacement can be examined, not only can the presence of a defect be detected, but also the location of the defect can be determined.

[0068] Signal line 120 is electrically connected to TDR module 110 and battery cell via electrode lead 31. Specifically, electrical pulses generated by electrical pulse generator 111 of TDR module 110 are applied to battery cell via signal line 120 and then via electrode lead 31 of battery cell. Furthermore, reflected waves generated from the electrical pulses applied to battery cell sequentially pass through electrode lead 31 of battery cell and signal line 120, and are then transmitted to reflected wave detector 112 of TDR module 110.

[0069] Simultaneously, the battery cells are arranged on a grounding surface 131, and the grounding surface 131 and the TDR module 110 are electrically connected to each other via a grounding wire 130. By providing the grounding surface 131 and the grounding wire 130, accidents can be prevented when an electrical pulse propagates to the outside of the battery cell due to unforeseen reasons. In other words, the TDR module 110 can safely apply electrical pulses to the battery cells.

[0070] In this configuration, the battery cells can be arranged parallel to the grounding surface 131 in the longitudinal direction. When the battery cells are not arranged parallel to the grounding surface 131, it is difficult to accurately apply electrical pulses from the TDR module 110 in the longitudinal direction of the battery cells, and therefore, it may be difficult to accurately generate measurement waveforms. In other words, arranging the battery cells parallel to the grounding surface 131 in the longitudinal direction can improve the accuracy of detecting internal defects in the battery cells.

[0071] A fixing member 140 can be further provided to fix the electrode leads 31 and 41 of the battery cell, thereby stably fixing the battery cell. For example... Figure 2 As shown, when the battery cell is arranged on the grounding surface 131, there is a space between the grounding surface 131 and the electrode leads 31 and 41. Therefore, when an external impact or electrical pulse is applied to the battery cell, the positions of the electrode leads 31 and 41 and the battery cell may change. Consequently, the battery cell and the TDR module 110 may become disconnected. Therefore, a fixing member 140 can be further provided in the space between the grounding surface 131 and the electrode leads 31 and 41 to fix the electrode leads 31 and 41, thereby preventing the battery cell and the TDR module 110 from becoming disconnected. That is, internal defects of the battery cell can be detected reliably. Figure 2 In this configuration, a fixing member 140 is provided in the space between the grounding surface 131 and the electrode leads 31 and 41 to support the lower surfaces of the electrode leads 31 and 41. However, the shape of the fixing member 140 is not particularly limited, as long as the electrode leads 31 and 41 can be fixed by the fixing member 140. For example, the fixing member 140 may protrude from the grounding surface 131 to support the opposite side surfaces of each of the electrode leads 31 and 41.

[0072] (Second Embodiment)

[0073] Figure 4a and Figure 4b This is a schematic diagram illustrating an apparatus 100' for detecting internal defects in a battery cell according to a second embodiment of the present invention, and a measurement waveform. Specifically, Figure 4a This illustrates applying an electrical pulse via the first signal line 120a from the first TDR module 110a connected to the positive lead 31, and generating a measurement waveform based on the reflected wave of the electrical pulse. Simultaneously, Figure 4b This illustrates applying an electrical pulse from a second TDR module 110b connected to the negative lead 41 via a second signal line 120b, and generating a measurement waveform based on the reflected wave of the electrical pulse. In this case, Figure 4a and 4b The measured waveforms shown represent the impedance Z over time.

[0074] The second embodiment differs from the first embodiment in that the TDR module 110 of the device 100' for detecting internal defects in a battery cell in this embodiment includes: a first TDR module 110a for applying an electrical pulse through the positive lead 31; a second TDR module 110b for applying an electrical pulse through the negative lead 41; and a signal line 120 including: a first signal line 120a for electrically connecting the positive lead 31 to the first TDR module 110a; and a second signal line 120b for electrically connecting the negative lead 41 to the second TDR module 110b. That is, the second embodiment differs from the first embodiment in that the first TDR module 110a and the second TDR module 110b, respectively electrically connected to the first signal line 120a and the second signal line 120b, sequentially apply electrical pulses to the positive lead 31 and the negative lead 41. In the second embodiment, the same components as in the first embodiment are given the same reference numerals, and their detailed descriptions are omitted herein.

[0075] In this embodiment, a second TDR module 110b electrically connected to the negative lead 41 via a second signal line 120b and a first TDR module 110a electrically connected to the positive lead 31 via a first signal line 120a are further provided. In this case, the first TDR module 110a applies an electrical pulse through the positive lead 31, and then the second TDR module 110b sequentially applies an electrical pulse through the negative lead 41. When electrical pulses are applied simultaneously through the first TDR module 110a and the second TDR module 110b, interference occurs between the electrical pulses, making it difficult to accurately generate the measurement waveform.

[0076] Simultaneously, by sequentially applying electrical pulses to both the positive lead 31 and the negative lead 41, measurement waveforms and reference waveforms can be generated for each of all internal regions of the battery cell, and compared to detect the presence of defects. As in the first embodiment, even when an electrical pulse is applied only to the positive lead 31, the pulse propagates to the negative lead 41. However, the pulse may not fully reach the vicinity of the negative lead 41, which is far from the TDR module 110, so the measurement waveform generated based on the reflected wave may not be accurate. Therefore, when an electrical pulse is applied to the negative lead 41 via the second TDR module 110b, accurate measurement waveforms can be generated for all regions of the negative lead. In other words, accurate measurement waveforms can be generated for all internal regions of the battery cell.

[0077] First, as in the first embodiment, an electrical pulse can be applied to the positive electrode lead 31 to detect defects in all regions of the positive electrode along the longitudinal direction of the battery cell. Specifically, as... Figure 4a As shown, defects can be detected in the positive electrode welded portion a1 between the positive electrode terminal piece 30 and the positive electrode lead 31 joined by welding, the positive electrode terminal piece portion b1 on which the positive electrode terminal piece 30 is arranged, the positive electrode coated portion d1 which is a region coated with positive electrode active material, and the positive electrode boundary portion c1 which is the boundary region between the positive electrode terminal piece portion b1 and the positive electrode coated portion d1. Then, an electrical pulse can be applied to the negative electrode lead 41 to detect defects in all regions of the negative electrode in the longitudinal direction of the battery cell. Specifically, as... Figure 4b As shown, defects can be detected in the negative electrode welding portion a2 between the negative electrode connector 40 and the negative electrode lead 41 joined by welding, the negative electrode connector portion b2 on which the negative electrode connector 40 is arranged, the negative electrode coating portion d2 which is a region coated with negative electrode active material, and the negative electrode boundary portion c2 which is a boundary region between the negative electrode connector portion b2 and the negative electrode coating portion d2.

[0078] In this embodiment, the application of an electrical pulse by the first TDR module 110a to the positive terminal and the subsequent application of an electrical pulse by the second TDR module 111b to the negative terminal have been described. However, there is no particular restriction on the order in which the electrical pulses are applied; the electrical pulse can be applied to the negative terminal first, followed by the positive terminal.

[0079] The present invention also provides a method for detecting internal defects in a single battery cell.

[0080] Figure 5 This is a flowchart of a method for detecting internal defects in a battery cell according to an embodiment of the present invention.

[0081] First, a reference waveform is generated as a standard for determining whether a defect has occurred. Specifically, the method may include: applying an electrical pulse to a normal battery cell via a signal line electrically connected to the electrode leads of the normal battery cell using a TDR module (S10); generating a measurement waveform via the signal line by detecting the reflected wave generated as the electrical pulse propagates in the longitudinal direction of the normal battery cell using the TDR module (S20); and setting the measurement waveform as the reference waveform (S30).

[0082] Next, a measurement waveform for the battery cell under test is generated in the same manner as a reference waveform generated relative to a normal battery cell. Specifically, the method may further include: applying an electrical pulse to the battery cell via a signal line electrically connected to the electrode leads of the battery cell using a TDR module (S40); generating a measurement waveform by detecting reflected waves generated as the electrical pulse propagates in the longitudinal direction of the battery cell via the signal line and the TDR module (S50); and comparing the generated measurement waveform with the reference waveform via the TDR module to determine whether a defect has occurred (S60).

[0083] In this case, when detecting whether a defect has occurred, a defect is determined to have occurred when the result of comparing the measured waveform with the reference waveform shows an offset.

[0084] Furthermore, the TDR module compares the measured waveform generated for each region of the battery cell in the longitudinal direction with a reference waveform to determine whether a defect has occurred in each region of the battery cell. The regions of the battery cell may include: the welded portion between the electrode terminals and electrode leads joined by welding; the electrode terminal portion on which the electrode terminals are positioned; the coated portion coated with electrode active material; and the boundary portion serving as the boundary between the electrode terminals and the coated portion.

[0085] Example

[0086] A normal battery cell is manufactured with the following structure: an electrode assembly having a positive terminal on one side and a negative terminal on the other side is housed in a battery casing, and the positive terminal and the negative terminal are respectively connected to a positive lead and a negative lead pulled out from the battery casing.

[0087] Comparison Example 1

[0088] The battery cell is manufactured in the same manner as in the example, except that only a portion of the positive electrode tabs are soldered to the positive electrode lead, which results in damage to the soldered portion between the electrode tabs and the electrode lead that are joined by soldering.

[0089] Comparison Example 2

[0090] The battery cell is manufactured in the same manner as in the example, except that an external impact is applied to the portion of the positive terminal on which the positive terminal is placed, resulting in a crack in at least one positive terminal.

[0091] Comparison Example 3

[0092] The battery cell is manufactured in the same manner as in the example, except that the positive active material applied to the boundary portion is partially removed, which is the boundary between the positive electrode terminal and the positive electrode coating portion coated with the positive active material.

[0093] Comparison Example 4

[0094] The battery cell is manufactured in the same manner as in the example, except that the nail penetrates the coated portion containing the positive electrode active material, thereby causing an internal short circuit between the positive and negative electrodes.

[0095] Experimental Example

[0096] pass Figure 2 The apparatus for detecting defects in a battery cell according to the first embodiment shown generates a measurement waveform of an example normal battery cell and sets it as a reference waveform. Measurement waveforms of the battery cells in comparison examples 1 to 4 are generated in the same manner and compared with the reference waveform. In this case, the reference waveform and the measurement waveform are expressed as impedance over time.

[0097] Figure 6a The diagram shows the result of comparing the measured waveform of a battery cell from Comparison Example 1 with a reference waveform using the apparatus 100 for detecting defects in a battery cell according to the first embodiment. Figure 6a As shown, it can be confirmed that a measured waveform with an impedance more than 10% greater than that of the reference waveform appears at the welded portion a of the battery cell. Therefore, a defect in the welded portion a of the battery cell in Comparative Example 1 is detected.

[0098] Figure 6b The diagram shows the result of comparing the measured waveform of a battery cell from Comparison Example 2 with a reference waveform using the apparatus 100 for detecting defects in a battery cell according to the first embodiment. Figure 6b As shown, it can be confirmed that a measured waveform with an impedance more than 10% greater than that of the reference waveform appears on the electrode terminal portion b of the battery cell. Therefore, a defect was detected in the electrode terminal portion b of the battery cell in Comparative Example 2.

[0099] Figure 6c The diagram shows the result of comparing the measured waveform of a battery cell from Comparison Example 3 with a reference waveform using the apparatus 100 for detecting defects in a battery cell according to the first embodiment. Figure 6cAs shown, it can be confirmed that a measured waveform with an impedance more than 10% greater than that of the reference waveform appears at the boundary portion c of the battery cell. Therefore, a defect in the boundary portion c of the battery cell in Comparative Example 3 is detected.

[0100] Figure 6d The diagram shows the result of comparing the measured waveform of a battery cell from Comparison Example 4 with a reference waveform using the apparatus 100 for detecting defects in a battery cell according to the first embodiment. Figure 6d As shown, it can be confirmed that a measured waveform with an impedance more than 10% greater than that of the reference waveform appears on the coated portion d of the battery cell. Therefore, a defect in the coated portion d of the battery cell in Comparative Example 4 is detected.

[0101] As described above, according to the present invention, in actual mass production, TDR can be used to quickly and accurately detect various internal defects of battery cells without disassembling the battery cells.

[0102] Furthermore, according to the present invention, inspections can be performed rapidly during the manufacturing process of battery cells, and internal defects in battery cells can be quickly detected during recycling or reuse operations of finished battery cells that have been used for a certain period of time. Therefore, in order to recycle battery cells, it is convenient to determine whether to reuse the battery cells by quickly inspecting for defects.

[0103] The above description is merely an example of the technical concept of the present invention. Various modifications and changes can be made by those skilled in the art without departing from the basic characteristics of the invention. Therefore, the accompanying drawings provided herein are not intended to limit the technical concept of the invention, but rather to describe it, and the scope of the technical concept of the invention is not limited by the drawings. The scope of protection of the present invention should be interpreted based on the claims, and all technical concepts within the same scope as the present invention should be interpreted as being included within the scope of the present invention.

[0104] In this specification, terms such as up, down, left, right, front, and back are used for convenience of description only, and it is obvious that these terms may be changed depending on the position of the object or the observer.

[0105] (See attached image labels)

[0106] 1: Battery cell

[0107] 10: Battery casing

[0108] 20: Electrode assembly

[0109] 30: First electrode (positive) connector

[0110] 31: First electrode lead

[0111] 40: Second electrode (negative electrode) connector

[0112] 41: Second electrode lead

[0113] 100, 100': Devices used to detect internal defects in individual battery cells.

[0114] 110: TDR module

[0115] 111: Electrical pulse generator

[0116] 112: Reflected wave detector

[0117] 113: Determiner

[0118] 120: Signal line

[0119] 130: Grounding wire

[0120] 131: Grounding surface

[0121] 140: Fixed component

Claims

1. An apparatus for detecting an internal defect of a battery cell having a structure in which an electrode assembly including at least one electrode tab on one side or both sides thereof is accommodated in a battery case, and the at least one battery tab is connected to an electrode lead wire drawn out from the battery case, the apparatus comprising: a time domain reflectometry (TDR) module configured to apply an electric pulse into the battery cell and compare a reference waveform with a measurement waveform generated by detecting a reflected wave of the electric pulse to determine whether a defect occurs; and a signal line configured to electrically connect the TDR module to the electrode lead wire of the battery cell, wherein the electric pulse is applied in a longitudinal direction of the battery cell, wherein the TDR module comprises: a first TDR module configured to apply an electric pulse signal through a first electrode lead wire; and a second TDR module configured to sequentially apply an electric pulse signal through a second electrode lead wire, and the signal line comprises: a first signal line configured to electrically connect the first electrode lead wire to the first TDR module; and a second signal line configured to electrically connect the second electrode lead wire to the second TDR module.

2. The apparatus of claim 1, wherein, the TDR module comprises: an electric pulse generator configured to generate the electric pulse to be applied into the battery cell; a reflected wave detector configured to detect the reflected wave of the electric pulse; and a determiner configured to generate the measurement waveform from the reflected wave of the electric pulse detected by the reflected wave detector, compare the measurement waveform with the reference waveform, and determine that a defect occurs when a shift occurs between the measurement waveform and the reference waveform.

3. The apparatus of claim 2, wherein, the shift indicating occurrence of a defect is determined when a rate of change of impedance represented by the measurement waveform is 10% or more compared to the reference waveform.

4. The apparatus of claim 1, wherein, the TDR module compares the measurement waveform generated for each region of the battery cell in the longitudinal direction of the battery cell with the reference waveform to determine whether a defect occurs in each region of the battery cell.

5. The apparatus of claim 4, wherein, the regions of the battery cell include a welding portion between the electrode lead wire and the electrode tab of the battery cell joined by welding, an electrode tab portion on which the electrode tab is positioned, a coated portion coated with an electrode active material, and a boundary portion as a boundary region between the electrode tab portion and the coated portion.

6. The apparatus of claim 1, wherein, the reference waveform includes a measurement waveform generated by detecting a reflected wave reflected when the electric pulse is applied into a normal battery cell. 7.The apparatus of claim 1, further comprising a ground line configured to electrically connect a ground surface on which the battery cell is disposed to the TDR module.

8. The apparatus of claim 7, wherein, the battery cell is disposed in parallel with the ground surface in the longitudinal direction. 9.The apparatus of claim 1, further comprising a fixing member configured to fix the electrode lead of the battery cell. 10.A method of detecting an internal defect of a battery cell, comprising: applying, by a time domain reflectometry (TDR) module, an electrical pulse into a battery cell through a signal line electrically connected to an electrode lead of the battery cell; generating, by the TDR module, a measurement waveform by detecting a reflected wave generated as the electrical pulse propagates in a longitudinal direction of the battery cell through the signal line; and detecting whether a defect occurs by comparing the measurement waveform generated by the TDR module with a reference waveform, wherein the applying of the electrical pulse into the battery cell comprises: applying, by a first TDR module, an electrical pulse signal through a first electrode lead, wherein a first signal line is configured to electrically connect the first electrode lead to the first TDR module; and sequentially applying, by a second TDR module, an electrical pulse signal through a second electrode lead, wherein a second signal line is configured to electrically connect the second electrode lead to the second TDR module. The detecting of whether a defect occurs comprises determining that a defect occurs when a shift occurs between the measurement waveform and the reference waveform.

11. The method of claim 10, wherein, The TDR module compares the measurement waveform generated for each region of the battery cell in the longitudinal direction of the battery cell with the reference waveform to determine whether a defect occurs in each region of the battery cell.

12. The method of claim 10, wherein, The regions of the battery cell include a welding portion between the electrode lead and an electrode tab of the battery cell joined by welding, a tab portion on which the electrode tab is positioned, a coated portion coated with an electrode active material, and a boundary portion as a boundary region between the tab portion and the coated portion.

13. The method of claim 12, wherein, 14.The method of claim 10, further comprising: applying, by a TDR module, an electrical pulse into a battery cell through a signal line connected to an electrode lead of the battery cell; generating, by the TDR module, a measurement waveform by detecting a reflected wave generated as the electrical pulse propagates in a longitudinal direction of the battery cell through the signal line; and setting the measurement waveform as the reference waveform. ​ ​

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