Punch hole inspection device using punch and die and punch hole inspection method using the same

Abstract

The present invention relates to a pinhole inspection device using a punch and a die, which is capable of inspecting defects or damages, particularly pinholes or microcracks, caused by forming, immediately after forming is completed using a punch, and a pinhole inspection method using the same.

Description

Technical Field

[0001] This application claims the benefit of priority to Korean Patent Application No. 2020-0155805, filed on November 19, 2020, the entire disclosure of which is incorporated herein by reference.

[0002] This invention relates to a punch pin hole inspection device using a punch and a die, and a method for inspecting punch pin holes using such a device. In particular, this invention relates to a punch pin hole inspection device using a punch and a die, capable of immediately inspecting defects or damage caused by forming when a pouch-shaped battery casing is formed using a punch and a die, and a method for inspecting punch pin holes using such a device. Background Technology

[0003] The demand for secondary batteries, used as energy sources for mobile devices and electric vehicles, has increased dramatically. In particular, there is a high demand for lithium-ion secondary batteries with high energy density and high discharge voltage.

[0004] Based on their shape and materials, lithium-ion batteries can be categorized into cylindrical batteries made of metal, prismatic batteries made of metal, and pouch batteries made of laminated sheets. Pouch batteries offer advantages such as high energy density per unit weight due to their highly integrated stacking, low manufacturing cost, and easy deformability. Therefore, pouch batteries are used in a variety of devices.

[0005] For pouch-type secondary batteries, a laminate comprising an outer coating, a metal barrier layer, and an inner adhesive layer is formed to serve as the battery casing. Electrode assemblies, along with the electrolyte, are housed within a containment formed within the laminate, and this containment is hermetically sealed, thereby manufacturing the pouch-type secondary battery.

[0006] To form the laminate for the electrode assembly housing, a deep drawing method is used. This method involves placing the laminate on a die, fixing it in place, and pressing it down with a punch while the laminate is held in place by a retainer. However, during deep drawing, due to the limited softness of the laminate and the friction between the punch and the laminate, defects or damage such as pinholes or cracks may form in the outer coating or metal barrier layer of the laminate.

[0007] Even if the surface roughness of the punch contacting the laminate is drastically reduced to prevent such external defects, it is still difficult to prevent the formation of external defects on the laminate due to friction caused by repeated punching. In particular, when the thickness of the laminate, especially the thickness of the metal barrier layer, is small, the formability of the laminate decreases, making it easier for pinholes or cracks to form.

[0008] Shells with defects such as pinholes must be removed through sorting; however, microscale pinholes that are difficult to see with the naked eye are not easily detected.

[0009] Patent Document 1 relates to a method for manufacturing a hot-pressed product and a hot-pressed product, wherein a pressure member having a mold, a blank holder, and a punch is used to hot-press a surface-treated steel sheet with a zinc-nickel plating formed on the surface of a base steel sheet for manufacturing a hot-pressed product. The edge of the surface-treated steel sheet, heated to a temperature between the Ac3 phase transformation point and 1000°C, is cooled to a temperature of 550°C to 400°C at a cooling rate of 100°C / s while positioned between the mold and the blank holder. Pressing begins when the edge temperature reaches 550°C to 400°C, and the pressed body is held at the dead center of the pressing bottom while positioned within the pressure member, allowing the pressed body to cool rapidly after pressing.

[0010] Patent Document 1 discloses a method for detecting the formation of microcracks during hot pressing using a punch and a mold. Unlike this invention, it uses a scanning electron microscope to inspect the cross-section of the pressed product. As in Patent Document 1, inspecting the cross-section of the pressed product using a visual method is too time-consuming, and therefore this method is not suitable for mass production of laminates for pouch batteries.

[0011] Patent Document 2 relates to an apparatus for detecting pinholes in the manufacture of aramid film. Patent Document 2 discloses a method in which electrodes are positioned on opposite surfaces of a continuously conveyed film, a voltage is applied, and a current is detected to check for pinholes forming on the film. Patent Document 2 applies to materials continuously conveyed in rolls, such as films or fibers, which differs from the method according to the present invention, where a voltage is applied between a punch and a die after the pressed body is completed, without movement of the punch.

[0012] Patent document 3 relates to a workability evaluation device and a workability evaluation method, including a punch having a multi-branched protrusion with three or more branches, a die having a recess that mates with the protrusion and a planar portion surrounding the recess, and a pressing plate having a pressing plate side portion that is almost parallel to the planar portion of the die, and inserting the target material to be pressed between the planar portion of the die and the pressing plate side portion.

[0013] Patent Document 3 discloses a method for detecting changes, cracks, or damage to the pressed body during the pressing process using a punch and die. This differs from the basic mechanism of the present invention, which measures current, in that a marker is transferred to the target material to be pressed, images are captured using a CCD camera before and after processing based on each marker, and the distance between these markers before and after processing is measured to calculate the change. Because Patent Document 3 uses visual materials, it is difficult to apply to laminates with high reflectivity, and the visual analysis is performed over the entire area, making rapid detection impossible.

[0014] Patent document 4 relates to a method for detecting an abnormality in a thin plate pressing device, wherein when the thin plate is pressed by the relative movement between the punch and the die, at least one of the punch and the die is a pressure element to be measured, and the elastic deformation that occurs in the pressure element to be measured by pressing, as measured by a deformation measuring device mounted on the pressure element to be measured, is greater than or less than a predetermined range, thereby determining that the pressing is abnormal.

[0015] The difference between Patent Document 4 and the measurement mechanism of this invention lies in that, in order to detect the deformation of the punch, a measuring device such as a piezoelectric element or a strain gauge is provided in the punch. Patent Document 4 is for metallic materials such as vehicle plates, and when this document is applied to devices that use electric current, it may not be distinguishable based on whether there is an anomaly.

[0016] An effective method for inspecting pinholes that is also suitable for the characteristics of laminates used in battery casings has not yet been proposed.

[0017] Korean patent application No. 2016-0130831 (November 14, 2016) (“Patent Document 1”)

[0018] International patent application No. 1999-008853 (February 25, 1999) (“Patent Document 2”)

[0019] Japanese patent application No. 2016-144824 (August 12, 2016) (“Patent Document 3”)

[0020] Japanese patent application No. 2008-264849 (November 6, 2008) (“Patent Document 4”) Summary of the Invention

[0021] Technical issues

[0022] The present invention was made in view of the above-mentioned problems. The object of the present invention is to provide a punch hole inspection device using a punch and a die, and a punch hole inspection method using the device. When the laminate is formed into a pouch battery casing using a punch and a die, the punch hole inspection device can immediately inspect for defects or damage caused by forming, especially pinholes or microcracks, immediately after the forming is completed.

[0023] Technical solution

[0024] To achieve the above objectives, the present invention provides a battery casing forming apparatus, the apparatus comprising: a punch configured to press a laminate to form a battery casing; a mold having a receiving portion sized to correspond to an electrode assembly receiving portion to be formed by the punch; a retainer configured to fix the outer edge of the laminate; and a current measuring unit configured to measure the current between the punch and the mold.

[0025] The punch and the die can form an electrode, and when the laminate is disposed between the punch and the die, the current detection unit can apply a voltage to measure its current value.

[0026] When a laminate is used, the punch and the die must be electrically insulated from each other. In this case, it is preferable that the punch and the retainer are also insulated from each other.

[0027] To prevent direct contact between the punch and the laminate, a conductive elastic spacer can be added below the punch. The conductive elastic spacer can be made of conductive elastic rubber material. The conductive elastic spacer can be fixed to the lower part of the side surface of the retainer. Liquid lubricant can be added to the space defined by the conductive elastic spacer and the retainer. In this case, the lubricant must be conductive.

[0028] Furthermore, the present invention provides a method for inspecting the punch holes in a battery casing formed using a battery casing forming apparatus. The punch hole inspection method includes the following steps: S1) placing a laminate on a mold; S2) fixing the laminate to the mold using a retainer; S3) pressing the elastic separator and the laminate using a punch; and S4) measuring the current while applying a voltage between the punch and the mold.

[0029] In step S4), the current can be measured while the voltage is changing.

[0030] The step of measuring impedance while applying alternating current can be used instead of step S4 of measuring current while applying voltage.

[0031] The step S4, which measures the current while applying the voltage, can be replaced by applying a voltage between the metal barrier layer of the laminate and the punch to measure the current, and applying a voltage between the metal barrier layer of the laminate and the mold to measure the current.

[0032] In step S4), a uniform distance is maintained between the punch and the die. This means that, with the laminate positioned between the punch and the die, all positions of the punch and the die are evenly spaced from each other. Only when the punch and the die are evenly spaced from each other is it possible to check for abnormalities by observing the current flow throughout the entire area.

[0033] In step S4), it can be determined whether a pinhole has formed based on whether current is flowing. At this time, when the current flows at a voltage lower than the reference voltage, the abnormality of the pinhole can be determined.

[0034] Furthermore, the present invention can provide all possible combinations of the above-described solutions.

[0035] Beneficial effects

[0036] As can be clearly seen from the above description, in this invention, a current detection unit configured to measure the current between the punch and the die is used to measure the current, thereby allowing for immediate inspection of defects or damage caused by forming, particularly pinholes or microcracks, after the punch forming is completed.

[0037] In this invention, two electrodes, namely the punch and the die, are provided to be spaced at the same distance from the entire surface of the laminate, which has a three-dimensional rather than planar shape, and an electric current is applied immediately after forming, thereby enabling uniform inspection of the entire surface of the formed laminate.

[0038] Furthermore, in this invention, to prevent direct contact between the punch and the laminate, a conductive elastic spacer is disposed below the punch, thereby preventing excessive mechanical stress caused by the punch from being transferred to the laminate. Additionally, current is measured in a stress-free state, thus avoiding measurement errors.

[0039] In this invention, the electrode assembly receiving portion is formed by molding a conductive elastic separator between the laminate and the punch, thereby preventing direct contact between the punch and the laminate and thus minimizing the stick-slip effect occurring on the surface of the punch and the surface of the laminate.

[0040] In addition, adding a liquid lubricant between the punch and the conductive elastic spacer can reduce the friction between the punch and the laminate.

[0041] Furthermore, the addition of the liquid lubricant and conductive elastic separator expands the stretching area of ​​the laminate, thereby preventing the laminate from being locally overstretched and thus becoming thinner.

[0042] Furthermore, when using the battery casing forming apparatus and method according to the present invention, even when using laminates with the same thickness, the electrode assembly receiving portion can be formed more deeply, thereby increasing the capacity of the battery cell and improving the energy density of the battery cell. Attached Figure Description

[0043] Figure 1 a)-b) are cross-sectional views of a traditional battery casing forming device.

[0044] Figure 2 a)-b) are cross-sectional views of the battery casing forming apparatus according to the first embodiment of the present invention.

[0045] Figure 3 a)-b) are cross-sectional views of the battery casing forming apparatus according to the second embodiment of the present invention.

[0046] Figure 4 This is a cross-sectional view of a battery casing forming apparatus according to a third embodiment of the present invention.

[0047] Figure 5 a)-d) show cross-sectional views of the battery casing forming apparatus according to the first embodiment of the present invention, arranged in the order of operation. Detailed Implementation

[0048] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, enabling those skilled in the art to readily implement these preferred embodiments. However, in describing the working principle of the preferred embodiments of the present invention, detailed descriptions of known functions and structures incorporated herein may obscure the subject matter of the invention, and such descriptions will be omitted.

[0049] Furthermore, the same reference numerals will be used throughout the accompanying drawings to denote parts that perform similar functions or operations. Where one part is referred to as being connected to another part throughout the application, that one part may be directly connected to the other part, and also indirectly connected to the other part via the other part. Moreover, including an element does not imply the exclusion of other elements, but rather means that those elements may be further included, unless otherwise stated.

[0050] Furthermore, unless otherwise specified, the description of elements by limitation or addition can be applied to all inventions and does not limit any particular invention.

[0051] Furthermore, in the specification of this invention and the claims of this application, unless otherwise stated, the singular form is intended to include the plural form.

[0052] Furthermore, in the specification of this invention and the claims of this application, unless otherwise stated, "or" includes "and". Therefore, "including A or B" refers to three cases: including A, including B, and including both A and B.

[0053] The laminate used as the casing of a pouch cell is essentially an insulator. Typically, a laminate comprising an outer coating, a metal barrier layer, and an inner adhesive layer exhibits insulating properties. However, during its forming process, defects or damage, such as pinholes or cracks, can form in the outer coating or metal barrier layer of the laminate, thereby degrading its insulating properties.

[0054] On the other hand, when the laminate is not abnormal, its insulation properties are maintained. Therefore, whether the laminate is abnormal can be determined by measuring its insulation properties. In cases where the degree or size of defects or damage such as pinholes or cracks is small, a distinct current will only be generated when a high voltage is applied between two electrodes spaced evenly apart.

[0055] The formed laminate has a three-dimensional rather than planar shape. Therefore, for accurate detection, the two electrodes must be set at the same distance from each other across the entire surface of the formed laminate.

[0056] In many cases, the punches and dies used for forming are made of metal and have the same shape as the laminate being formed. Therefore, this invention was developed with the consideration of accurately detecting any abnormalities across the entire surface of the formed laminate when the punches and dies are used as electrodes.

[0057] In the following, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0058] Figure 2 a)-b) are cross-sectional views of the battery casing forming apparatus 200 according to the first embodiment of the present invention.

[0059] Reference Figure 2a)-b) The battery casing forming apparatus 200 according to the first embodiment of the present invention includes: a punch 210 configured to press a laminate 205 to form a battery casing; a mold 220 having a receiving portion corresponding to the size of the electrode assembly receiving portion formed by the punch 210; a retainer 230 configured to fix the outer edge of the laminate 205; and a current measuring unit A configured to measure the current between the punch 210 and the mold 220.

[0060] The punch 210 and the die 220 constitute electrodes, and the current measuring unit A is connected to its electrode terminals a and b. When the laminate 205 is disposed between the punch 210 and the die 220, a voltage can be applied to measure its current value. Although the current measuring unit A is... Figure 2 a)-b) to Figure 5 The current measuring unit may be simply shown in a)-d), but may include a part configured to apply a DC voltage and an ammeter configured to measure the current flowing between a and b after the voltage is applied, or may measure the impedance between a and b after an AC voltage is applied.

[0061] When the laminate 205 is provided, the punch 210 and the die 220 must be electrically insulated from each other. Preferably, the punch 210 and the holder 230 are also insulated from each other. This is because, under normal circumstances, whether the insulated laminate 205 is abnormal is measured based on the current amplitude, but when the punch 210 and the die 220 are electrically connected, it is difficult to determine whether the laminate 205 is abnormal. Furthermore, if neither the punch 210 nor the holder 230 is insulated, the punch 210 and the die 220 can be electrically connected to each other due to contact between the punch 210 and the holder 230, and also due to contact between the die 220 and the holder 230. Preferably, the punch 210 and the holder 230 are electrically insulated from each other.

[0062] Figure 2 a) Shows the state before the laminate 205 is pressed using the punch 210. Figure 2 b) shows the state after pressing. In this invention, the current or impedance between electrode terminals a and b can be measured immediately after pressing or forming is completed, thereby immediately determining whether the formed laminate 205 is abnormal.

[0063] The formed laminate 205 has a three-dimensional rather than planar shape. Therefore, for accurate detection, a punch 210 and a die 220 with two electrode terminals a and b are used, and the punch 210 and the die 220 are set at the same distance from the entire surface of the formed laminate 205, thereby obtaining highly accurate results.

[0064] Figure 3a)-b) are cross-sectional views of the battery casing forming apparatus 300 according to the second embodiment of the present invention. Figure 3 The battery casing forming apparatus 300 in a)-b) is formed by adding a conductive elastic separator 335 to... Figure 2 a)-b) are constructed using the battery casing forming apparatus 200 according to the first embodiment of the present invention.

[0065] To prevent direct contact between the punch 310 and the laminate 305, a conductive elastic partition 335 can be added below the punch 310, and the conductive elastic partition 335 can be made of conductive elastic rubber material. The conductive elastic partition 335 can be fixed to the lower part of the side surface of the retainer 330. Liquid lubricant can be added to the space defined by the conductive elastic partition 335 and the retainer 330. At this time, the liquid lubricant must be conductive.

[0066] The liquid lubricant significantly reduces the friction between the punch and the conductive elastic separator, allowing the surfaces of the conductive elastic separator and the punch to slide very smoothly relative to each other.

[0067] As a result, the area of ​​the laminate stretched by the punch increases, thus reducing the average elongation of the stretched area. For example, the thickness of the laminate in the stretched state can be 70% or more of the thickness of the laminate before stretching.

[0068] For example, at least one substance selected from the group consisting of the following can be used as a liquid lubricant: hydrocarbon-based oils, such as liquid paraffin, greases, mineral and vegetable oils, emulsified oils, demulsifiers, pour point depressants, viscosity modifiers, defoamers, mineral oils (including pure mineral oils or pure mineral oils with additives), fatty oils (including animal and vegetable oils), mixtures of mineral and fatty oils, and synthetic oils. Ionic materials or ionic liquids may be added to ensure conductivity.

[0069] As mentioned above, the use of liquid lubricant can prevent localized stretching of the laminate.

[0070] If the laminate and the punch are in direct contact, slippage is unlikely to occur due to friction between their surfaces. As a result, the area of ​​the laminate that is stretched becomes narrower, so only a localized area of ​​the laminate is stretched. In particular, since the portion of the laminate that becomes the sidewall of the electrode assembly housing is primarily stretched when the laminate is formed into a battery casing, the thickness of this portion is excessively reduced, making the battery casing susceptible to damage.

[0071] As mentioned above, since stick-slip can easily occur on the surface of the laminate and the surface of the punch, the laminate can be locally overstretched, which may increase the defect rate of battery casing forming.

[0072] In this invention, with the conductive elastic partition 335 positioned between the laminate 305 and the punch 310, the punch 310 presses down on the laminate 305, thus the surfaces of the laminate 305 and the punch 310 do not directly contact each other. Therefore, this solves the common problem of scratches on the laminate caused by an uneven surface of the punch or by foreign matter introduced between the punch and the laminate.

[0073] However, preferably, the elastic separator is made of a conductive material for measuring current. If the elastic separator is not made of a conductive material, a very high voltage must be applied to measure the current, which is very dangerous for the person performing the measurement. Therefore, preferably, the elastic separator is conductive. Conductive elastic separators can be manufactured by mixing common separators made of elastic resin or rubber materials with a conductive polymer.

[0074] Since the conductive elastic separator 335 is fixed to the retainer 330, the conductive elastic separator 335 can be stably fixed to the retainer 330 when the laminate 305 is pressed with the punch 310.

[0075] Figure 4 This is a cross-sectional view of a battery casing forming apparatus 400 according to a third embodiment of the present invention.

[0076] The battery casing forming apparatus 400 differs from the battery casing forming apparatus 200 according to the first embodiment in that a voltage is applied between the metal barrier layer 403 of the laminate 405 and the punch 410 to measure the current, and a voltage is applied between the metal barrier layer 403 of the laminate 405 and the mold 420 to measure the current.

[0077] When using the battery casing forming apparatus 400 according to the third embodiment of the present invention to measure whether the laminate 405 is abnormal, it is possible to accurately detect which surface of the laminate 405 is damaged, that is, which of the outer coating layer 402 and the inner adhesive layer 404 is damaged, thereby enabling a fine inspection of whether the apparatus is abnormal.

[0078] In step S4, which measures current while applying voltage, voltage can be applied between the metal barrier layer of the laminate and the punch to measure current, and voltage can also be applied between the metal barrier layer of the laminate and the mold to measure current.

[0079] In the first, second, and third embodiments of the present invention, only the characteristic components are emphasized, therefore these embodiments can be combined with each other. For example, the second and third embodiments can be combined with each other.

[0080] Figure 5 a)-d) show cross-sectional views of the battery casing forming apparatus according to the first embodiment of the present invention, arranged in the order of operation. In addition to the first embodiment, Figure 5 The order of a)-d) can also be applied equivalently to the second embodiment, the third embodiment, or a combination of these embodiments.

[0081] The method for inspecting the punch holes of a battery casing formed using a battery casing forming apparatus includes the following steps: S1) Step of setting the laminate 205 on the mold 220 (see...) Figure 5 a)); S2) The step of securing the laminate 205 to the mold 220 using the retainer 230 (see...) Figure 5 b)); S3) Step of pressing the laminate 205 with punch 210 (see...) Figure 5 c)); and S4) the steps of applying voltage between punch 210 and die 220 while measuring current.

[0082] In the second embodiment with the addition of a conductive elastic separator, in step S3), the punch 210 can simultaneously press the conductive elastic separator and the laminate. In the third embodiment, in step S4 where a voltage is applied while measuring the current, a voltage can be applied between the metal barrier layer of the laminate and the punch to measure the current, and a voltage can also be applied between the metal barrier layer of the laminate and the mold to measure the current.

[0083] Meanwhile, in step S4), the current can be measured while the voltage is changed, or the impedance can be measured while AC is applied.

[0084] In step S4), it is preferable to maintain a uniform distance between the punch and the die. This means that, with the laminate positioned between the punch and the die, the punch and the die are spaced evenly apart at all locations. The reason is that only when the punch and the die are spaced evenly apart can anomalies be detected by current flow throughout the entire area.

[0085] In step S4), it can be determined whether a pinhole is formed based on whether there is current flow, and when the current flows at a voltage lower than the reference voltage, the pinhole abnormality can be determined.

[0086] Those skilled in the art will understand that, based on the above description, various applications and modifications can be made within the scope of this invention.

[0087] (Refer to the labeling explanation)

[0088] 100, 200, 300, 400: Battery casing manufacturing equipment

[0089] 105, 205, 305, 405: Laminated sheets

[0090] 402: Outer coating

[0091] 403: Metal Barrier Layer

[0092] 404: Inner adhesive layer

[0093] 110, 210, 310, 410: Punch

[0094] 120, 220, 320, 420: Mold

[0095] 130, 230, 330, 430: Retaining parts

[0096] 335: Flexible partition

[0097] a, b, c: Electrode terminals

[0098] A: Ammeter

[0099] Industrial applicability

[0100] This invention relates to a punch hole inspection device using a punch and a die, and a punch hole inspection method using such a punch hole inspection device. When the laminate is formed into a pouch-shaped battery casing using a punch and a die, the device can immediately inspect for defects or damage caused by forming, especially pinholes or microcracks, after the forming is completed using the punch. Therefore, this invention has industrial applicability.

Claims

1. A battery casing forming apparatus, comprising: A punch configured to press laminates to form a battery casing; A mold having a receiving portion that corresponds in size to the electrode assembly receiving portion to be formed by the punch; A retainer configured to secure the outer edge of the laminate; A conductive elastic partition located below the punch is configured to prevent direct contact between the punch and the laminate. A current measuring unit is configured to measure the current between the punch and the die. The punch is configured to simultaneously press the conductive elastic separator and the laminate.

2. The battery casing forming apparatus according to claim 1, wherein the punch and the mold constitute an electrode, and in, When the laminate is placed between the punch and the mold, the current detection unit applies a voltage to measure the current value of the laminate.

3. The battery casing forming apparatus according to claim 2, wherein, When the laminate is set, the punch and the mold are electrically insulated from each other.

4. The battery casing forming apparatus according to claim 1, wherein the conductive elastic separator is made of conductive elastic rubber material.

5. The battery casing forming apparatus according to claim 1, wherein the conductive elastic separator is fixed to the lower part of the side surface of the retainer.

6. A method for inspecting pin holes in a battery casing formed using a battery casing forming apparatus according to any one of claims 1 to 5, the method comprising: S1) Place the laminate on the mold; S2) Secure the laminate to the mold using a retainer; S3) Press the laminate using a punch; and S4) Measure the current while applying voltage between the punch and the die.

7. The method for inspecting punch holes according to claim 6, wherein, In step S4), the voltage is changed while the current is measured.

8. The method for inspecting a punch hole according to claim 6, wherein the step of measuring the impedance while applying an alternating current is replaced by the step of measuring the current while applying a voltage (S4).

9. The punch hole inspection method according to claim 6, wherein the steps of applying a voltage between the metal barrier layer of the laminate and the punch to measure the current, and applying a voltage between the metal barrier layer of the laminate and the mold to measure the current, replace the step S4 of measuring the current while applying the voltage.

10. The method for inspecting punch holes according to claim 6, wherein, In step S4), a uniform distance is maintained between the punch and the die.

11. The method for inspecting punch holes according to claim 6, wherein, In step S4), it is determined whether a punch hole is formed based on whether current flows.

12. The method for inspecting punch holes according to claim 11, wherein, The anomaly of the pinhole is identified when the current flows at a voltage lower than the reference voltage.

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