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

Abstract

The present invention relates to an apparatus for detecting internal defects in a battery cell, comprising: a TDR (Time Domain Reflectometry) module for applying an electric pulse to the inside of the battery cell, detecting a reflected wave of the electric pulse, and comparing a measurement waveform generated by the detection with a reference waveform to detect the presence or absence of a defect, and a signal line electrically connecting the TDR module to an electrode lead of the battery cell, the electric pulse being propagated along a longitudinal direction of the battery cell. The present invention also relates to a method for detecting internal defects in a battery cell.

Description

[Technical Field]

[0001] The present invention relates to an apparatus and method for detecting internal defects in battery cells using TDR.

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

[0003] This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0115841, filed on August 31, 2021, and all contents disclosed in the documents of that Korean patent application are incorporated herein by reference. [Background technology]

[0004] In recent years, rechargeable secondary batteries have been widely used as energy sources for wireless mobile devices. Secondary batteries are also attracting attention as energy sources for electric vehicles and hybrid electric vehicles, which are being proposed as a solution to address air pollution caused by existing gasoline and diesel vehicles that use fossil fuels. Therefore, the types of applications using secondary batteries are becoming increasingly diverse due to the advantages of secondary batteries, and secondary batteries are expected to be applied to more fields and products in the future.

[0005] These secondary batteries can be classified into lithium ion batteries, lithium ion polymer batteries, and lithium polymer batteries depending on the structure of the electrodes and electrolyte. Among these, lithium ion polymer batteries are increasingly being used because they are less likely to leak electrolyte and are easier to manufacture.

[0006] Generally, secondary batteries are classified into cylindrical batteries and prismatic batteries, in which an electrode assembly is housed in a cylindrical or prismatic metal can, and pouch-type batteries, in which an electrode assembly is housed in a pouch-type case made of an aluminum laminate sheet, depending on the shape of the battery case. The electrode assembly housed in the battery case is a chargeable and dischargeable power generating element having a positive electrode, a negative electrode, and a separator structure interposed between the positive and negative electrodes. It is classified into a jelly roll type, in which a long sheet-like positive electrode and a negative electrode coated with an active material are wound up with a separator interposed between them, and a stack type, in which a number of positive electrodes and a negative electrodes of a predetermined size are stacked in sequence with a separator interposed between them.

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

[0008] Meanwhile, the electrode assembly has an electrode tab formed on one side for connecting the battery cell to the outside, and an electrode lead is welded to the electrode tab, which is extended to the outside of the battery case.

[0009] However, various defects may occur in the battery cell during the electrode manufacturing process and the electrode assembly assembly process.

[0010] Specifically, cracks and disconnections may occur in the electrode tab due to differences in elongation between the coated and uncoated portions, physical external forces due to welding, etc. In addition, various defects may occur at various positions, such as poor welding between the electrode tab and the electrode lead, cracks at the boundary between the coated and uncoated portions that occur during the electrode tab formation process, dendrite growth that causes internal short circuits, and damage to the separator that may occur during the assembly process.

[0011] When defects such as those described above occur, the performance of the assembled battery module or battery pack containing them is significantly reduced, which is why it is important to detect them (defective battery cells) in advance and distinguish them from normal battery cells. Conventional non-destructive testing methods include CT testing, X-ray testing, and eddy current testing. However, while these conventional methods are capable of detecting internal defects, they require a certain amount of testing time, are very inefficient in terms of processing, and have low testing accuracy.

[0012] Therefore, there is a need for technology development that can quickly and accurately detect battery cells with internal defects in a non-destructive manner during actual mass production. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] Japanese Patent Application Publication No. 2020-165859 Summary of the Invention [Problem to be solved by the invention]

[0014] The present invention has been made to solve the above problems, and an object of the present invention is to provide an apparatus and method for detecting internal defects in battery cells that can quickly and accurately detect various internal defects in battery cells during actual mass production. [Means for solving the problem]

[0015] The device for detecting internal defects in a battery cell according to the present invention relates to a battery cell having a structure in which an electrode assembly having at least one electrode tab formed on one or both sides thereof is housed in a battery case, and the electrode tabs are connected to electrode leads extending to the outside of the battery case. The device includes a TDR (Time Domain Reflectometry) module that applies an electric pulse to the inside of the battery cell, senses a reflected wave of the electric pulse, and compares a measured waveform generated by the measurement with a reference waveform to detect the presence or absence of a defect, and signal lines that electrically connect the TDR module to the electrode leads of the battery cell, and the electric pulse is applied along the longitudinal direction of the battery cell.

[0016] For example, the TDR module may include an electric pulse generator that generates an electric pulse to be applied to the inside of the battery cell, a reflected wave sensor that senses a reflected wave of the electric pulse, and a determination unit that generates a measurement waveform using the reflected wave of the electric pulse sensed by the reflected wave sensor, compares the measurement waveform with a reference waveform, and determines that a defect has occurred if an offset occurs.

[0017] When the rate of change in impedance shown by the measured waveform compared to the reference waveform is 10% or more, it can be determined as an offset of defect occurrence.

[0018] Meanwhile, the presence or absence of a defect in each region of the battery cell may be detected by comparing the measurement waveform generated for each region of the battery cell divided along the length of the battery cell with a reference waveform.

[0019] In this case, the region of the battery cell includes a welded portion, which is the region where the electrode tab and electrode lead of the battery cell are joined by welding, an electrode tab portion where the electrode tab is located, a ground portion, which is the region where the electrode active material is applied, and a boundary portion, which is the boundary region between the electrode tab portion and the ground portion.

[0020] Specifically, the reference waveform may be a measurement waveform generated by applying an electric pulse to the inside of a normal battery cell and sensing the reflected wave.

[0021] As a specific example, the TDR module includes a first TDR module that applies an electrical pulse signal through a first electrode lead and a second TDR module that sequentially applies an electrical pulse signal through a second electrode lead, and the signal line includes a first signal line that electrically connects the first electrode lead and the first TDR module, and a second signal line that electrically connects the second electrode lead and the second TDR module.

[0022] For example, the battery pack may further include a ground line electrically connecting the TDR module to a ground plane on which the battery cells are disposed.

[0023] As a specific example, the battery cells may be arranged longitudinally parallel to the ground plane.

[0024] As another example, the battery pack may further include a fixing member for fixing the electrode lead of the battery cell.

[0025] The present invention also provides a method for detecting internal defects in a battery cell.

[0026] The method for detecting an internal defect in a battery cell according to the present invention includes the steps of: applying an electric pulse to the inside of the battery cell by a TDR module through a signal line electrically connected to an electrode lead of the battery cell; detecting a reflected wave generated as the electric pulse propagates along a longitudinal direction of the battery cell by the TDR module through the signal line, and generating a measurement waveform; and comparing the measurement waveform generated by the TDR module with a reference waveform to detect whether a defect has occurred.

[0027] At this time, in the stage of detecting whether or not a defect has occurred, if the TDR module compares the measured waveform with the reference waveform and an offset occurs, it can be determined that a defect has occurred.

[0028] For example, the TDR module may compare a measured waveform generated for each region of the battery cell divided along the longitudinal direction of the battery cell with a reference waveform to determine whether a defect has occurred for each region. In this case, the battery cell region may include a welded portion where an electrode tab and an electrode lead of the battery cell are welded together, an electrode tab portion where the electrode tab is located, a land portion where an electrode active material is applied, and a boundary portion between the electrode tab and the land portion.

[0029] As a specific example, the method may further include the steps of: applying an electric pulse to the inside of the battery cell by the TDR module through a signal line connected to the electrode lead of the normal battery cell; receiving a reflected wave generated as the electric pulse propagates along the longitudinal direction of the normal battery cell by the TDR module through the signal line to generate a measurement waveform; and setting the measurement waveform as a reference waveform. [Effects of the Invention]

[0030] The present invention provides an advantage that various internal defects of battery cells can be detected quickly and accurately using time domain reflectometry (TDR) without disassembling the battery cells during actual mass production.

[0031] Furthermore, according to the present invention, not only can rapid inspection be performed during the manufacturing stage of battery cells, but also internal defects of battery cells can be rapidly inspected during the recycling or reuse stage, in which completed battery cells are reused after a certain period of use. Therefore, when recycling battery cells, defects in battery cells can be quickly identified and it can be easily determined whether or not to reuse them. [Brief explanation of the drawings]

[0032] [Figure 1] FIG. 1 is a cross-sectional view showing the structure of a typical battery cell. [Figure 2] 1 is a schematic diagram showing an internal defect detection device for a battery cell according to an embodiment of the present invention and a measured waveform. FIG. [Figure 3]FIG. 1 is a block diagram showing the configuration of a TDR module according to an embodiment of the present invention. [Figure 4a] 10A and 10B are schematic diagrams showing an internal defect detection device for a battery cell according to another embodiment of the present invention and measured waveforms. [Figure 4b] 10A and 10B are schematic diagrams showing an internal defect detection device for a battery cell according to another embodiment of the present invention and measured waveforms. [Figure 5] 1 is a flowchart showing the steps of a method for detecting an internal defect in a battery cell according to an embodiment of the present invention. [Figure 6a] 3 is a graph showing a measured waveform generated by the battery cell internal defect detection device according to the embodiment of FIG. 2. [Figure 6b] 3 is a graph showing a measurement waveform generated by the battery cell internal defect detection device according to the embodiment of FIG. 2. [Figure 6c] 3 is a graph showing a measurement waveform generated by the battery cell internal defect detection device according to the embodiment of FIG. 2. [Figure 6d] 3 is a graph showing a measurement waveform generated by the battery cell internal defect detection device according to the embodiment of FIG. 2. DETAILED DESCRIPTION OF THE INVENTION

[0033] The present invention will be described in detail below. Before that, the terms and words used in the specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted as meanings and concepts that correspond to the technical idea of ​​the present invention based on the principle that the inventor can appropriately define the concepts of terms in order to best describe his own invention.

[0034] As used throughout the present specification, the terms "comprise" and "have" are intended to specify the presence of any feature, number, step, operation, component, part, or combination thereof stated in the specification, and should be understood as not precluding the presence or possible addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0035] Furthermore, when a layer, film, region, plate, or other part is described as being "on" another part, this includes not only the case where it is "directly on top" of the other part, but also the case where there is another part in between. Conversely, when a layer, film, region, plate, or other part is described as being "under" another part, this includes not only the case where it is "directly below" the other part, but also the case where there is another part in between. Furthermore, in the specification of the present invention, being "located on" can include not only the case where it is located at the top, but also the case where it is located at the bottom.

[0036] Meanwhile, in this application, the "longitudinal direction" of a battery cell means the direction in which the electrode tabs are pulled out, and the "width direction" means the direction perpendicular to the longitudinal direction.

[0037] The device for detecting internal defects in a battery cell according to the present invention includes a battery cell having a structure in which an electrode assembly having at least one electrode tab formed on one or both sides thereof is housed in a battery case, and the electrode tabs are connected to electrode leads extending to the outside of the battery case. The device includes: a TDR (Time Domain Reflectometry) module that applies an electric pulse to the inside of the battery cell, senses a reflected wave of the electric pulse, and compares a generated measured waveform with a reference waveform to detect the presence or absence of a defect; and signal lines that electrically connect the TDR module to the electrode leads of the battery cell, and the electric pulse is applied along the longitudinal direction of the battery cell.

[0038] As described above, conventional methods for detecting internal defects in battery cells require a certain amount of inspection time, are very inefficient in the process, and do not have high inspection accuracy, making them difficult to apply to actual processes.

[0039] Therefore, the present invention is characterized by using a TDR module that can detect internal defects of a battery cell based on a measurement waveform generated by applying an electric pulse through an electrode lead of the battery cell and sensing the reflected wave of the electric pulse. Furthermore, since the electric pulse propagates along the length of the battery cell, it is possible to detect internal defects in various regions of the battery cell divided along the length of the battery cell.

[0040] The principle behind the TDR module's defect detection is that an electrical pulse traveling along the length of a battery cell is reflected when it reaches a point inside the battery cell where an impedance change occurs. If a battery cell has an internal defect, the impedance change appears differently, which changes the point at which the reflected wave from the electrical pulse occurs and the time it arrives. By comparing these points to measure the impedance over time from the reflected wave, the presence and location of a defect in the battery cell can be determined.

[0041] The detailed configuration of the present invention will now be described in more detail with reference to the accompanying drawings and embodiments. Similar reference numerals are used for similar components throughout the drawings. In the accompanying drawings, the dimensions of structures are exaggerated for clarity. Terms such as "first" and "second" may be used to describe various components, but these components should not be limited by these terms. These terms are used only to distinguish one component from another. For example, a first component may be referred to as a "second component," and similarly, a second component may be referred to as a "first component," without departing from the scope of the present invention. A singular term includes a plural term unless the context clearly indicates otherwise.

[0042] The present invention will be described in detail below.

[0043] (First embodiment) FIG. 1 is a cross-sectional view showing the structure of a typical battery cell.

[0044] 1, a battery cell 1 has a structure in which an electrode assembly 20 having at least one electrode tab 30, 40 formed on one or both sides thereof is housed in a battery case 10, and the electrode tabs 30, 40 are connected to electrode leads 31, 41 extending out of the battery case 10. For example, the electrode leads 31, 41 include a positive electrode lead 31 and a negative electrode lead 41, and the positive electrode lead 31 and the negative electrode lead 41 may be extended in opposite directions from the battery case 10, but the structure is not limited thereto. The electrode assembly and its constituent elements are known to those skilled in the art, and therefore a detailed description thereof will be omitted.

[0045] Fig. 2 is a schematic diagram showing the battery cell internal defect detection device 100 and measured waveforms according to the first embodiment of the present invention, and Fig. 3 is a block diagram showing the configuration of a TDR module 110 according to the first embodiment of the present invention.

[0046] 2, the device 100 for detecting internal defects in a battery cell according to the present invention includes a TDR module 110 that applies an electric pulse to the inside of the battery cell and detects a reflected wave of the electric pulse to generate a measurement waveform, comparing the measurement waveform with a reference waveform, to detect whether or not a defect has occurred, for a battery cell having a structure in which an electrode assembly 20 having at least one electrode tab 30, 40 formed on each side is housed in a battery case 10, and the electrode tabs 30, 40 are connected to electrode leads 31, 41 extending to the outside of the battery case 10, and a signal line 120 that electrically connects the TDR module 110 to the electrode lead 31 of the battery cell. At this time, the electric pulse propagates along the length of the battery cell, generating a reflected wave.

[0047] 2 illustrates a case where the TDR module 110 applies an electrical pulse signal via the positive electrode lead 31. However, the TDR module can also apply an electrical pulse signal via the negative electrode lead 41, in which case the TDR module is electrically connected to the negative electrode lead 41 via a signal line.

[0048] The TDR module 110 generates an electric pulse and generates a measurement waveform through a reflected wave to detect the presence or absence of a defect.

[0049] Specifically, referring to FIG. 3, the TDR module 110 includes an electric pulse generator 111 that generates an electric pulse to be applied to the inside of the battery cell, a reflected wave sensor 112 that senses a reflected wave of the electric pulse, and a determination unit 113 that generates a measurement waveform using the reflected wave of the electric pulse sensed by the reflected wave sensor 112, compares the measurement waveform with a reference waveform, and determines that a defect has occurred if an offset occurs.

[0050] More specifically, the electric pulse generator 111 may generate an electric pulse at a predetermined time interval and apply it to the inside of the battery cell. The predetermined time interval may be the time it takes for the electric pulse to travel to and from the defect location of the battery cell to be checked. For example, to detect the presence or absence of defects in the entire area along the longitudinal direction of the battery cell, the predetermined time interval may be the time it takes for the electric pulse to travel from the TDR module 110 that applies the electric pulse to the negative lead 41 to which the TDR module 110 is not connected.

[0051] The reflected wave sensor 112 can detect a reflected wave that is reflected by various internal components of the battery cell as the electric pulse signal applied by the electric pulse generator 111 propagates along the length of the battery cell. That is, by measuring the reflected wave of the electric pulse, it is possible to identify a change in impedance value that occurs when the electric pulse applied by the TDR module 110 to the inside of the battery cell travels back and forth inside the battery cell.

[0052] The determination unit 113 generates a measurement waveform based on the reflected wave of the electrical pulse detected by the reflected wave sensor 112. The measurement waveform represents the impedance of the reflected signal of the electrical pulse as a value corresponding to the passage of time. A measurement waveform can be generated with time on the horizontal axis and impedance on the vertical axis. The measurement waveform shown in FIG. 2 is also represented by an impedance Z value corresponding to the passage of time.

[0053] Furthermore, the determination unit 113 can determine that a defect has occurred when an offset occurs by comparing the generated measured waveform with a reference waveform. In this case, an offset occurs when the measured waveform and the reference waveform do not match, meaning that the rate of change in impedance of the measured waveform compared to the reference waveform is 10% or more.

[0054] The reference waveform may be a measurement waveform generated by applying an electric pulse to a normal battery cell and sensing a reflected wave of the electric pulse. A measurement waveform is generated for a target battery cell in the same manner as for a normal battery cell, and compared with the reference waveform to determine that a defect has occurred if an offset occurs.

[0055] As described above, to detect defects throughout the entire length of the battery cell, an electrical pulse was applied from the TDR module 110, which applied the electrical pulse, to the negative electrode lead 41, to which the TDR module 110 was not connected, with a predetermined time interval corresponding to the time it took for the pulse to travel back and forth. As a result, as shown in FIG. 2 , measurement waveforms were generated for each region of the battery cell divided along the length of the battery cell. The battery cell region includes a welded portion a, where the electrode tab 30 and the electrode lead 31 of the battery cell are welded together; an electrode tab portion b, where the electrode tab 30 is located; a land portion d, where the electrode active material is applied; and a boundary portion c, where the electrode tab portion and the land portion are located. In this case, the measurement waveforms generated for each region of the battery cell can be compared with a reference waveform to detect defects for each region of the battery cell. That is, the region of the battery cell where an offset occurs can be identified, and not only the presence or absence of a defect but also the location of the defect can be determined.

[0056] The signal line 120 serves to electrically connect the TDR module 110 and the battery cell via the electrode lead 31. Specifically, an electric pulse generated by the electric pulse generator 111 of the TDR module 110 passes through the signal line 120 and is applied to the inside of the electric cell via the electrode lead 31 of the battery cell. In addition, a reflected wave generated inside the battery cell from the applied electric pulse also passes through the electrode lead 31 of the battery cell and the signal line 120 in sequence, and is transmitted to the reflected wave sensor 112 of the TDR module 110.

[0057] Meanwhile, the battery cell is placed on a ground plane 131, and the ground plane 131 is electrically connected to the TDR module 110 by a ground wire 130. The provision of the ground plane 131 and the ground wire 130 can prevent safety issues that may occur if an electric pulse is propagated to the outside of the battery cell instead of the inside due to an unexpected cause. That is, the TDR module 110 can safely apply an electric pulse to the inside of the battery cell.

[0058] In this case, the battery cells may be arranged in a longitudinal direction parallel to the ground surface 131. If the battery cells are not arranged in a longitudinal direction parallel to the ground surface 131, it may be difficult for the TDR module 110 to accurately apply the electrical pulse in the longitudinal direction of the battery cells, making it difficult to generate an accurate measurement waveform. In other words, when the battery cells are arranged in a longitudinal direction parallel to the ground surface 131, the accuracy of internal defect detection in the battery cells can be improved.

[0059] In addition, a fixing member 140 may be further included to fix the electrode leads 31 and 41 of the battery cell, thereby stably fixing the battery cell. As shown in FIG. 2, when a battery cell is placed on a ground surface 131, a space is formed between the ground surface 131 and the electrode leads 31 and 41. Therefore, the positions of the electrode leads 31 and 41 and the battery cell may easily change when the battery cell receives an external impact or an electric pulse is applied. This may result in a disconnection between the battery cell and the TDR module 110. In response to this, a fixing member 140 may be further included to fix the electrode leads 31 and 41 in the space between the ground surface 131 and the electrode leads 31 and 41, thereby preventing the disconnection between the battery cell and the TDR module 110. In other words, stable detection of internal defects in the battery cell is possible. In FIG. 2, the fixing member 140 is illustrated as being provided in the space between the ground surface 131 and the electrode leads 31 and 41, supporting the lower surfaces of the electrode leads 31 and 41. However, the fixing member 140 is not particularly limited as long as it has a shape that can fix the electrode leads 31, 41. For example, it may be provided in a shape that protrudes from the ground surface 131 and supports both side surfaces of the electrode leads 31, 41.

[0060] (Second embodiment) 4a and 4b are schematic diagrams showing a battery cell internal defect detection device 100' and measurement waveforms according to a second embodiment of the present invention. Specifically, FIG. 4a shows a measurement waveform generated by applying an electrical pulse from a first TDR module 110a connected to the positive electrode lead 31 via a first signal line 120a and generating a measurement waveform based on the reflected wave of the electrical pulse. Meanwhile, FIG. 4b shows a measurement waveform generated by applying an electrical pulse from a second TDR module 110b connected to the negative electrode lead 41 via a second signal line 120b and generating a measurement waveform based on the reflected wave of the electrical pulse. The measurement waveforms shown in FIGS. 4a and 4b are expressed as impedance Z values ​​over time.

[0061] The TDR module 110 of the battery cell internal defect detection device 100′ of this embodiment includes a first TDR module 110a that applies an electric pulse via the positive electrode lead 31 and a second TDR module 110b that sequentially applies an electric pulse signal via the negative electrode lead 41, and the signal line 120 includes a first signal line 120a that electrically connects the positive electrode lead 31 and the first TDR module 110a and a second signal line 120b that electrically connects the negative electrode lead 41 and the second TDR module 110b. That is, the present embodiment differs from the first embodiment in that the first TDR module 110a and the second TDR module 110b, which are electrically connected to the positive electrode lead 31 and the negative electrode lead 41 via the first signal line 120a and the second signal line 120b, respectively, sequentially apply electric pulses. In the second embodiment, common components to those of the first embodiment are designated by common reference numerals, and detailed descriptions thereof will be omitted.

[0062] In this embodiment, the TDR device includes not only a first TDR module 110a electrically connected to the positive lead 31 via a first signal line 120a, but also a second TDR module 110b electrically connected to the negative lead 41 via a second signal line 120b. In this case, the first TDR module 110a applies an electrical pulse via the positive lead 31, and then the second TDR module 110b applies an electrical pulse via the negative lead 41. If they are applied simultaneously, the electrical pulse applied by the first TDR module 110a and the electrical pulse applied by the second TDR module 110b may interfere with each other, making it difficult to form an accurate measurement waveform.

[0063] On the other hand, by sequentially applying an electric pulse to both the positive electrode lead 31 and the negative electrode lead 41, a measurement waveform and a reference waveform can be generated for the entire internal region of the battery cell, and the presence or absence of defects can be detected by comparing them. Even when an electric pulse is applied only to the positive electrode lead 31, as in the first embodiment, the electric pulse propagates to the negative electrode lead 41. However, the electric pulse may not completely reach the area near the negative electrode lead 41, which is far from the TDR module, and the measurement waveform generated from the reflected wave may be inaccurate. Therefore, when an electric pulse is also applied to the negative electrode lead 41 via the second TDR module 110b, an accurate measurement waveform can be generated for the entire negative electrode area. In other words, an accurate measurement waveform can be generated for the entire internal region of the battery cell.

[0064] First, as in the first embodiment, an electric pulse is applied to the positive electrode lead 31 to detect defects in the entire region of the positive electrode along the longitudinal direction of the battery cell. Specifically, as shown in FIG. 4A, defects can be detected in the positive electrode welded portion a1, which is the region where the positive electrode tab 30 of the battery cell and the positive electrode lead 31 are welded together; the positive electrode tab portion b1 where the positive electrode tab 30 is located; the positive electrode ground portion d1, which is the region where the positive electrode active material is applied; and the positive electrode boundary portion c1, which is the boundary region between the positive electrode tab portion b1 and the positive electrode ground portion d1. Next, an electric pulse is applied to the negative electrode lead 41 to detect defects in the entire region of the negative electrode along the longitudinal direction of the battery cell. Specifically, as shown in FIG. 4b, defects that have occurred in the negative electrode welded portion a2, which is the area where the negative electrode tab 40 and the negative electrode lead 41 of the battery cell are joined by welding, the negative electrode tab portion b2 where the negative electrode tab 40 is located, the negative electrode ground portion d2, which is the area where the negative electrode active material is applied, and the negative electrode boundary portion c2, which is the boundary area between the negative electrode tab portion b2 and the negative electrode ground portion d2, can be detected.

[0065] In this embodiment, the first TDR module 110a first applies an electric pulse to the positive electrode, and then the second TDR module 110b applies an electric pulse to the negative electrode. However, the procedure for applying the electric pulses is not particularly limited, and it is also possible to first apply an electric pulse to the negative electrode and then apply an electric pulse to the positive electrode.

[0066] The present invention also provides a method for detecting internal defects in a battery cell.

[0067] FIG. 5 is a flowchart showing the steps of a method for detecting internal defects in a battery cell according to one embodiment of the present invention.

[0068] The method first generates a reference waveform that serves as a reference for determining whether a defect is detected. Specifically, the method includes step S10 in which a TDR module applies an electric pulse to the inside of a battery cell via a signal line electrically connected to an electrode lead of a normal battery cell, step S20 in which the TDR module senses a reflected wave generated as the electric pulse propagates along the length of the battery cell via the signal line to generate a measurement waveform, and step S30 in which the measurement waveform is set as a reference waveform.

[0069] Next, a measurement waveform of the battery cell to be inspected is generated in the same manner as generating the reference waveform of the normal battery cell. Specifically, the method includes step S40 in which the TDR module applies an electric pulse to the inside of the battery cell to be inspected via a signal line electrically connected to the electrode lead of the battery cell to be inspected, step S50 in which the TDR module senses a reflected wave generated as the electric pulse propagates along the length of the battery cell via the signal line and generates a measurement waveform, and step S60 in which the measurement waveform generated by the TDR module is compared with the reference waveform to detect whether a defect has occurred.

[0070] At this time, in the stage of detecting whether or not a defect has occurred, the TDR module compares the measured waveform with the reference waveform and determines that a defect has occurred if an offset occurs.

[0071] The TDR module compares a measured waveform generated for each region of the battery cell divided along the longitudinal direction of the battery cell with a reference waveform to determine whether or not a defect has occurred in each region of the battery cell. The battery cell region may include a welded portion where an electrode tab and an electrode lead of the battery cell are joined by welding, an electrode tab portion where the electrode tab is located, a land portion where an electrode active material is applied, and a boundary portion between the electrode tab and the land portion.

[0072] (Example) A normal battery cell was manufactured having a structure in which an electrode assembly having a plurality of positive electrode tabs formed on one side and a plurality of negative electrode tabs formed on the other side was housed in a battery case, and the positive electrode tabs and negative electrode tabs were connected to positive electrode leads and negative electrode leads, respectively, that were drawn out to the outside of the battery case.

[0073] (Comparative Example 1) A battery cell was manufactured in the same manner as in the reference example above, except that only some of the positive electrode tabs were welded to the positive electrode lead, creating a defect in the welded portion where the electrode tabs and the electrode lead were welded together.

[0074] (Comparative Example 2) A battery cell was manufactured in the same manner as in the reference example, except that a crack occurred in one or more of the positive electrode tabs by applying an external impact to a positive electrode tab portion where the positive electrode tabs were located.

[0075] (Comparative Example 3) A battery cell was fabricated in the same manner as in the reference example, except that a portion of the positive electrode active material located in the boundary region between the positive electrode tab and the positive electrode land portion, which is the region where the positive electrode active material was applied, was removed.

[0076] Comparative Example 4 A battery cell was manufactured in the same manner as in the referenced example, except that a nail was used to pierce the ground portion, which was the area where the positive electrode active material was applied, to create an internal short circuit between the positive electrode and the negative electrode.

[0077] (Experimental example) The measured waveform of a normal battery cell of the example was generated using the battery cell defect detection device of the first embodiment shown in Figure 2 and set as the reference waveform. Measured waveforms of the battery cells of Comparative Examples 1 to 4 were generated using the same method and compared with the reference waveform. At this time, the reference waveform and the measured waveform were expressed as impedance values ​​according to the passage of time.

[0078] 6a shows a comparison of the measured waveform of the battery cell of Comparative Example 1 with a reference waveform using the battery cell defect detection device 100 of the first embodiment. As shown in FIG. 6a, it was confirmed that a measured waveform with an impedance value that differed by 10% or more compared to the reference waveform appeared at welded portion a of the battery cell. This enabled detection of a defect in welded portion a of the battery cell of Comparative Example 1.

[0079] Figure 6b shows a comparison of the measured waveform of the battery cell of Comparative Example 2 with a reference waveform using the battery cell defect detection device 100 of the first embodiment. As shown in Figure 6b, it was confirmed that a measured waveform with an impedance value that differed by 10% or more compared to the reference waveform appeared at electrode tab portion b of the battery cell. This enabled detection of a defect in electrode tab portion b of the battery cell of Comparative Example 2.

[0080] Fig. 6c shows a comparison of the measured waveform of the battery cell of Comparative Example 3 with a reference waveform using the battery cell defect detection device 100 of the first embodiment. As shown in Fig. 6c, it was confirmed that a measured waveform with an impedance value that differed by 10% or more compared to the reference waveform appeared at boundary c of the battery cell. This enabled detection of a defect at boundary c in the battery cell of Comparative Example 3.

[0081] Figure 6d shows a comparison of the measured waveform of the battery cell of Comparative Example 4 with a reference waveform using the battery cell defect detection device 100 of the first embodiment. As shown in Figure 6d, it was confirmed that a measured waveform with an impedance value that differed by 10% or more compared to the reference waveform appeared in the grounded portion d of the battery cell. This enabled us to detect that the battery cell of Comparative Example 4 had a defect in the grounded portion d.

[0082] As described above, according to the present invention, various internal defects of battery cells can be detected quickly and accurately using time domain reflectometry (TDR) without disassembling the battery cells during actual mass production.

[0083] Furthermore, according to the present invention, not only can rapid inspection be performed during the manufacturing stage of battery cells, but also internal defects of battery cells can be rapidly inspected during the recycling or reuse stage, in which completed battery cells are reused after a certain period of use. Therefore, when recycling battery cells, defects in battery cells can be quickly identified and it can be easily determined whether or not to reuse them.

[0084] The above description merely exemplifies the technical concept of the present invention, and various modifications and variations may be made by a person skilled in the art without departing from the essential characteristics of the present invention. Therefore, the drawings disclosed in the present invention are intended to explain, not to limit, the technical concept of the present invention, and the scope of the technical concept of the present invention is not limited by such drawings. The scope of protection of the present invention should be interpreted by the scope of the claims, and all technical concepts within the equivalent range should be interpreted as being included in the scope of the present invention.

[0085] Although terms indicating directions such as up, down, left, right, front, and back are used in this specification, these terms are used for convenience of explanation, and it is obvious that they may change depending on the position of the object in question, the position of the observer, etc. [Explanation of symbols]

[0086] 1: Battery cell 10: Battery case 20: Electrode assembly 30: First electrode tab (positive electrode) 31: First electrode lead 40: Second electrode tab (negative electrode) 41: Second electrode lead 100, 100': Battery cell internal defect detection device 110: TDR module 111: Electrical pulse generator 112:Reflected wave sensor 113: Judgment section 120: Signal line 130: Ground wire 131: Ground plane 140: Fixing member

Claims

1. An apparatus for detecting internal defects in a battery cell, the apparatus having a structure in which an electrode assembly having at least one electrode tab formed on one or both sides thereof is housed in a battery case, the electrode tabs being connected to first and second electrode leads extending to the outside of the battery case, a first TDR module that applies a first electric pulse to the battery cell, senses a reflected wave of the first electric pulse, and compares a measurement waveform generated by the measurement with a reference waveform to detect whether a defect has occurred; a second TDR module that applies a second electric pulse to the battery cell after the first electric pulse is applied, and compares a measurement waveform generated by detecting a reflected wave of the second electric pulse with a reference waveform to detect whether a defect has occurred; a first signal line electrically connecting the first TDR module and a first electrode lead of the battery cell; a second signal line electrically connecting the second TDR module and a second electrode lead of the battery cell; a ground surface on which the battery cell is placed; a first ground line connected to the ground plane and the first signal line, electrically connecting the ground plane to the first TDR module; a second ground line connected to the ground plane and the second signal line, electrically connecting the ground plane to the second TDR module; a first fixing member for fixing the first electrode lead of the battery cell in a space between the ground surface and the first electrode lead; and a second fixing member for fixing the second electrode lead of the battery cell in a space between the ground surface and the second electrode lead; The first and second electric pulses are applied along the longitudinal direction of the battery cell.

2. The first TDR module an electric pulse generator that generates an electric pulse to be applied to the interior of the battery cell; a reflected wave sensor that detects a reflected wave of the electrical pulse; a determination unit that generates the measurement waveform using a reflected wave of the electrical pulse sensed by the reflected wave sensor, compares the measurement waveform with a reference waveform, and determines that a defect has occurred if an offset occurs.

3. 3. The battery cell internal defect detection device according to claim 2, wherein a change rate of impedance indicated by the measured waveform compared to the reference waveform is 10% or more, and the change rate is determined to be an offset indicating the occurrence of a defect.

4. 2. The device for detecting internal defects in a battery cell of claim 1, wherein the first TDR module compares measurement waveforms generated for each region of the battery cell divided along a longitudinal direction of the battery cell with the reference waveform to detect whether or not a defect has occurred for each region of the battery cell.

5. 5. The device for detecting internal defects in a battery cell according to claim 4, wherein the region of the battery cell includes a welded portion where an electrode tab and an electrode lead of the battery cell are joined by welding, an electrode tab portion where the electrode tab is located, a ground portion where an electrode active material is applied, and a boundary portion between the electrode tab portion and the ground portion.

6. 6. The device for detecting internal defects in a battery cell according to claim 1, wherein the reference waveform is a measured waveform generated by applying an electric pulse to the inside of a normal battery cell and sensing a reflected wave.

7. The battery cell internal defect detection device according to claim 1 , wherein the battery cell is arranged in parallel with the ground plane in the longitudinal direction.

8. applying a first electrical pulse to the battery cell through a first signal line electrically connecting the first TDR module to a first electrode lead of the battery cell; After the first electrical pulse is applied, the second TDR module applies a second electrical pulse to the inside of the battery cell through a second signal line electrically connecting the second TDR module and a second electrode lead of the battery cell; the first TDR module senses a reflected wave generated when the first electrical pulse propagates along a longitudinal direction of the battery cell through the first signal line, and generates a measurement waveform; the second TDR module senses a reflected wave generated while the second electrical pulse is propagated along a longitudinal direction of the battery cell through the second signal line, and generates a measurement waveform; comparing the measurement waveform generated by the first TDR module with a reference waveform to detect whether a defect occurs; comparing the measurement waveform generated by the second TDR module with a reference waveform to detect whether a defect occurs; a first ground line is provided, the first ground line being connected to a ground plane on which the battery cell is disposed and the first signal line, and electrically connecting the ground plane to the first TDR module; a second ground line is provided, the second ground line being connected to the ground plane and the second signal line, and electrically connecting the ground plane to the second TDR module; a first fixing member for fixing the first electrode lead of the battery cell in a space between the ground surface and the first electrode lead; and a second fixing member for fixing the second electrode lead of the battery cell in a space between the ground surface and the second electrode lead;

9. 9. The method for detecting an internal defect in a battery cell according to claim 8, wherein, in the step of comparing the measurement waveform generated by the first TDR module with a reference waveform to detect whether or not a defect has occurred, the first TDR module compares the measurement waveform with the reference waveform and determines that a defect has occurred if an offset occurs.

10. 10. The method of claim 8, wherein the first TDR module compares a reference waveform with a measurement waveform generated for each region of the battery cell divided along a longitudinal direction of the battery cell to determine whether a defect occurs for each region of the battery cell.

11. 11. The method for detecting internal defects in a battery cell according to claim 10, wherein the region of the battery cell includes a welded portion where an electrode tab and an electrode lead of the battery cell are joined by welding, an electrode tab portion where the electrode tab is located, a land portion where an electrode active material is applied, and a boundary portion where the electrode tab and the land portion are located.

12. The first TDR module applies an electric pulse to the inside of the battery cell through a signal line connected to an electrode lead of a normal battery cell; the first TDR module receives a reflected wave generated when the electrical pulse propagates along a longitudinal direction of a normal battery cell through the signal line, and generates a measurement waveform; The method of claim 8 , further comprising: setting the measured waveform as a reference waveform.

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