Patent ID: 12241866

DETAILED DESCRIPTION

Hereinafter, embodiments of the disclosed technology, in which the foregoing problems are specifically solved, will be described with reference to the accompanying drawings. In describing the embodiments, like names and like numerals may be used to refer to like elements, and repetitive descriptions thereof will be avoided.

Referring toFIGS.1A and1B, a non-destructive inspection method for inspecting a pouch-type secondary battery according to one or more embodiments of the disclosed technology may use a non-destructive inspection process to accurately detect a crack condition and a weld condition of a region of electrode tabs12placed inside the pouch14without an error in the process of manufacturing a secondary battery10, thereby largely increasing the yield of a secondary battery10.

The secondary battery10to be inspected is not limited to a stack-pouch-type secondary battery10, but may include any secondary battery having various structures and shapes. For the convenience of description, the stack-pouch-type secondary battery10including a stack-type electrode assembly11and a pouch14will be described below by way of example.

FIG.3is a flowchart of a secondary battery manufacturing method to describe a non-destructive inspection method for a pouch-type secondary battery according to one or more embodiments of the disclosed technology. For the purpose of illustration,FIG.3is described with reference toFIG.4-FIG.7.

Referring toFIGS.1A,1B, and3, the non-destructive inspection method for inspecting the pouch-type secondary battery according to these embodiments may include a first crack condition inspecting operation S110, a second crack condition inspecting operation S120, and a weld condition inspecting operation S130.

The first crack condition inspecting operation S110may be performed after the electrode tab pre-welding process S12, and may refer to an operation in which a first crack condition of the electrode tabs12is inspected by measuring the first crack condition of the electrode tabs12, which may occur during the electrode tab pre-welding process S12, and comparing a measured first crack-condition measurement signal and a preset first crack-condition reference signal.

In some embodiments, the electrode tab pre-welding process S12performed before the first crack condition inspecting operation S110refers to a process of pre-welding and aligning a plurality of electrode tabs12extended from the electrode assembly11manufactured in advance through the electrode assembly manufacturing process S11. For example, the plurality of electrode tabs12extended from the negative or positive electrode plates of the electrode assembly11are pre-welded W1and aligned by ultrasonic waves or a laser. The plurality of electrode tabs12are bent through the electrode tab pre-welding process S12, so that pre-welded free ends thereof can be stacked. Thus, a first crack may occur in the area of the electrode tabs12bent and stacked through the electrode tab pre-welding process S12.

In the first crack condition inspecting operation S110, the first crack-condition measurement signal for the area of the electrode tabs12may be obtained while relatively moving the secondary battery to be inspected or a non-contact sensor. The non-contact sensor employed herein may include a reflective eddy current sensor. Referring toFIG.4, a reflective eddy current sensor21may include a transmitter and a receiver contactlessly disposed at one side of the secondary battery10, in which the transmitter transmits a transmission signal to the electrode tabs12and the receiver receives a reflection signal CS1reflected from the electrode tabs12. For example, the reflection signal CS1varied depending on the first crack condition present in the electrode tabs12while the transmission signal is reflected from the electrode tabs12may be the first crack-condition measurement signal.

The inspection for the crack condition is to inspect cracks present outside the electrode tabs12, and therefore the reflective eddy current sensor21for receiving the reflection signal CS1reflected from the electrode tabs12may be used in the crack condition inspecting operation.

A measurement area CA1of the first crack-condition measurement signal obtained in the first crack condition inspecting operation S110may be the entire area of the electrode tabs12. For example, from one end connected to and bent from the electrode assembly11to the free ends pre-welded W1and stacked. In some embodiments, the measurement area CA1of the first crack-condition measurement signal may be a partial area of the pre-welded W1and stacked free ends of the electrode tabs12. The measurement area CA1of the first crack-condition measurement signal may be varied depending on the types and specifications of reflective eddy current sensors to be used. For example, the first crack-condition measurement signal for the entire area of the electrode tabs12may be obtained at once by scanning once with the reflective eddy current sensor having a relatively wide inspection area, or the first crack-condition measurement signal for the entire area of the electrode tabs12may be obtained several times by scanning several times with the reflective eddy current sensor having a relatively narrow inspection area.

In some embodiments, when the first crack-condition measurement signal is measured in the first crack condition inspecting operation S110, the first crack condition for the area of the electrode tabs12can be inspected by comparing the measured first crack-condition measurement signal and the preset first crack-condition reference signal. The first crack-condition reference signal may refer to a reference signal measured in the electrode tabs12having no cracks after the pre-welding W1. For example, when the first crack-condition measurement signal is out of an allowable error range from the first crack-condition reference signal, those electrode tabs12may be determined as defective products due to the crack. In some embodiments, when the first crack-condition measurement signal is within the allowable error range from the first crack-condition reference signal, those electrode tabs12are determined as normal products. In some embodiments, only the non-defective electrode tabs can be moved on to the next process (e.g., electrode tabs main-welding process S13).

The second crack condition inspecting operation S120may be performed after the electrode tab main-welding process S13, and may refer to an operation in which a second crack condition of the electrode tabs12may be inspected by measuring the second crack condition of the electrode tabs12, which may occur during the electrode tab main-welding process S13, and comparing a measured second crack-condition measurement signal and a preset second crack-condition reference signal.

In some embodiments, the electrode tab main-welding process S13performed before the second crack condition inspecting operation S120refers to a process of main-welding and connecting an electrode lead13to the pre-welded electrode tabs12. For example, the electrode lead13is main-welded W2and connected to the plurality of electrode tabs12by ultrasonic waves or a laser. Thus, a second crack may occur in the area of the electrode tabs12through the electrode tab main-welding process S13.

The second crack condition inspecting operation S120may be substantially the same as the foregoing first crack condition inspecting operation S110. For example, the second crack-condition measurement signal for the area of the electrode tabs12may be obtained while relatively moving the secondary battery to be inspected or a non-contact sensor. The non-contact sensor employed herein may include a reflective eddy current sensor. Referring toFIG.5, a reflective eddy current sensor22may include a transmitter and a receiver contactlessly disposed at one side of the secondary battery10, in which the transmitter transmits a transmission signal to the electrode tabs12and the receiver receives a reflection signal CS2reflected from the electrode tabs12. For example, the reflection signal CS2varied depending on the second crack condition present in the electrode tabs12while the transmission signal is reflected from the electrode tabs12may be the second crack-condition measurement signal. The reflective eddy current sensor22used in the second crack condition inspecting operation S120may be the same as the reflective eddy current sensor21used in the first crack condition inspecting operation S110.

A measurement area CA2of the second crack-condition measurement signal obtained in the second crack condition inspecting operation S120may also be the entire area of the electrode tabs12, for example, from one end connected to and bent from the electrode assembly11to the free ends main-welded W2. Of course, the measurement area CA2of the second crack-condition measurement signal may be a partial area of the main-welded W2free ends of the electrode tabs12. The second crack-condition measurement signal for the entire area of the electrode tabs12may be obtained at once by scanning once with the reflective eddy current sensor having a relatively wide inspection area, or the second crack-condition measurement signal for the entire area of the electrode tabs12may be obtained several times by scanning several times with the reflective eddy current sensor having a relatively narrow inspection area.

When the second crack-condition measurement signal is measured in the second crack condition inspecting operation S120, the second crack condition for the area of the electrode tabs12is inspected by comparing the measured second crack-condition measurement signal and the preset second crack-condition reference signal. The second crack-condition reference signal can refer to a reference signal measured in the electrode tabs12having no cracks after the main-welding W2. For example, when the second crack-condition measurement signal is out of an allowable error range from the second crack-condition reference signal, those electrode tabs12may be determined as defective products due to the crack. In some embodiments, when the second crack-condition measurement signal is within the allowable error range from the second crack-condition reference signal, those electrode tabs12are determined as normal products. In some embodiments, only the passed electrode tabs are moved on to the next process.

The weld condition inspecting operation S130may be performed after the electrode tab main-welding process S13, and may refer to an operation in which a weld condition of the electrode tabs12may be inspected by measuring the weld condition of the electrode tabs12, and comparing a measured weld-condition measurement signal and a preset weld-condition reference signal. Here, the weld condition may refer to weld strength.

In some embodiments, the weld condition inspecting operation S130may be performed following the foregoing second crack condition inspecting operation S120, prior to the second crack condition inspecting operation S120, or simultaneously with the second crack condition inspecting operation S120.

The weld condition inspecting operation S130may obtain the weld-condition measurement signal for the area of the electrode tabs12while relatively moving the secondary battery to be inspected or the non-contact sensor. The non-contact sensor used herein may include a transmissive eddy current sensor. Referring toFIG.6, a transmissive eddy current sensor23may include a transmitter contactlessly disposed at one side of the secondary battery10, and a receiver contactlessly disposed at the other side of the secondary battery10, in which the transmitter transmits a transmission signal toward the electrode tabs12and the receiver receives a transmission signal WS transmitted through the electrode tabs12. For example, the transmission signal WS can be varied depending on the weld strength of the welded portions W1and W2of the electrode tabs12while the transmission signal passes through the electrode tabs12may be the weld-condition measurement signal.

The inspection for the weld condition is to inspect the weld strength or the like between the electrode tab12and the electrode tab12, and a connecting portion between the electrode tabs12and the electrode lead13, such as the weld strength or the like inside the electrode tabs12, and therefore the reflective sensor cannot detect the weld condition. Therefore, the weld condition inspecting operation may employ the transmissive eddy current sensor23that receives the transmission signal WS passed through the electrode tabs12.

In some embodiments, because the transmissive eddy current sensor23receives the transmission signal WS passed through the electrode tabs12, the received measurement signal may include not only the weld-condition measurement signal but also the crack-condition measurement signal. Therefore, it may be difficult to accurately determine through the received transmission signal WS whether the defect is caused by the crack condition or the weld condition.

This deficiency can be resolved by the disclosed technology according to one or more embodiments as disclosed herein. For example, the electrode tabs12determined to be defective in terms of the crack condition are filtered out in advance by the first crack condition inspecting operation S110and the second crack condition inspecting operation S120, and the weld condition inspecting operation S130can be performed for the electrode tabs12determined to be passed in terms of the crack condition. Therefore, the transmission signal WS received in the transmissive eddy current sensor23may include information about the weld condition.

A measurement area WA of the weld-condition measurement signal obtained in the weld condition inspecting operation S130may also be the entire area of the electrode tabs12. In some embodiments, the measurement area WA of the weld-condition measurement signal may be a partial area of the free ends having the welded portions W1and W2of the electrode tabs12. The weld-condition measurement signal for the entire area of the electrode tabs12may be obtained at once by scanning once with the reflective eddy current sensor having a relatively wide inspection area, or the weld-condition measurement signal for the entire area of the electrode tabs12may be obtained several times by scanning several times with the reflective eddy current sensor having a relatively narrow inspection area.

When the weld-condition measurement signal is measured in the weld condition inspecting operation S130, the weld condition for the area of the electrode tabs12may be inspected by comparing the measured weld-condition measurement signal and the preset weld-condition reference signal. The weld-condition reference signal may refer to a reference signal measured in the state that the welded portions W1and W2connecting the electrode tabs12and the electrode lead13have appropriate weld strength. For example, when the weld-condition measurement signal is out of an allowable error range from the weld-condition reference signal, those electrode tabs12are determined to have a defective weld condition. In some embodiments, when the weld-condition measurement signal is within the allowable error range from the weld-condition reference signal, those electrode tabs12are determined to have a normal weld condition. Only the passed electrode tabs are moved on to the next process.

FIG.8Aillustrates a comparison between a weld-condition reference signal and a weld-condition measurement signal measured in normally welded electrode tabs at the weld condition inspecting operation, according to embodiments.FIG.8Billustrates an example of weld-condition measurement signal (WMS) and weld-condition reference signal (WSS). For the purpose of illustration,FIGS.8A and8Bare described with reference toFIG.3.

When the welded portion W of the electrode tabs12is measured in the weld condition inspecting operation S130while relatively moving the secondary battery to be inspected or the eddy current sensor in the direction of D1as shown inFIG.8A, the WMS for each position of the welded portion W of the electrode tabs12is obtained as shown inFIG.8B. In some embodiments, the electrode tabs12are determined to have a normal weld condition when the WMS matches the WSS.

FIG.9Aillustrates an example of a comparison between a weld-condition reference signal and a weld-condition measurement signal measured in defectively welded electrode tabs (defects in weld strength) at the weld condition inspecting operation, according to embodiments.FIG.9Billustrates an example of weld-condition measurement signal (WMS) and weld-condition reference signal (WSS) with an allowable error range (OKS1), a central value (WSSc), and an central value (WMSc) of the WMS. For the purpose of illustration,FIGS.9A and9Bare described with reference toFIG.3.

As shown inFIGS.9A and9B, in the weld condition inspecting operation S130, it may be determined whether there is a defect in the weld strength of the welded portion W of the electrode tabs12, by comparing the WSSc on a center line CL of the WSS and the WMSc on the CL of the WMS. For example, when the WMSc of the WMS is within the OKS1from the WSSc of the WSS, the electrode tabs12can be determined to have normal weld strength. As shown therein, when the WMSc of the WMS is out of the OKS1from the WSSc of the WSS, the electrode tabs12can be determined to have defective weld strength.

FIG.10Aillustrates an example of comparison between a weld-condition reference signal and a weld-condition measurement signal measured in defectively welded electrode tabs (defects due to asymmetric weld strength) at the weld condition inspecting operation, according to embodiments.FIG.10Billustrates an example of weld-condition measurement signals (WMS, WMS1, WMS2) and weld-condition reference signal (WSS) with an allowable error range (OKS2). For the purpose of illustration,FIGS.10A and10Bare described with reference toFIG.3.

As shown inFIGS.10A and10B, in the weld condition inspecting operation S130, it may be determined whether there is a defect in the weld strength of the welded portion W of the electrode tabs12, by determining whether a left signal area (WMS1) and a right signal area (WMS2) of the weld-condition measurement signal (WMS) are symmetrical with respect to the center line (CL) of the WSS. For example, when a difference value A1between the WSS and the WMS due to the asymmetry between the WMS1and the WMS2is within the range of OKS2from the WSS, the welded portion W of the electrode tabs12may be determined to maintain normal weld strength and symmetry. As shown therein, when the difference value A1between the WSS and the WMS is out of the range of OKS2from the WSS, the welded portion W of the electrode tabs12may be determined to be asymmetric and have defective weld strength. In some embodiments, the difference A1between the WMS and the WSS may be a degree of increasing or decreasing an integral value of the WMS corresponding to the entire areas of the WMS1and the WMS2.

In some embodiments, the non-destructive inspection method for the pouch-type secondary battery according to an embodiment may further include an alignment condition inspecting operation S140.

The alignment condition inspecting operation S140may be performed after the electrode tab main-welding process S13, and may refer to an operation in which an alignment condition of the electrode tabs12is inspected by measuring the alignment condition of the electrode tabs12, and comparing a measured alignment condition measurement signal and a preset alignment condition reference signal.

In some embodiments, the area of the electrode tabs12may have a defective alignment condition such as folding or lifting while undergoing the electrode tab pre-welding process S12and the electrode tab main-welding process S13. For example, a folding area may be formed in a bending area of the electrode tabs12connected to the electrode assembly, and a lifting area may be formed in the welded portions W1and W2.

The alignment condition inspecting operation S140may be performed following the foregoing weld condition inspecting operation S130, prior to the weld condition inspecting operation S130, or simultaneously with the weld condition inspecting operation S130. Further, the alignment condition inspecting operation S140may be performed in substantially the same manner as the weld condition inspecting operation S130. The transmissive eddy current sensor used in the alignment condition inspecting operation S140may be the same sensor as the transmissive eddy current sensor23used in the foregoing weld condition inspecting operation S130.

When the alignment condition measurement signal is measured in the alignment condition inspecting operation S140, the alignment condition such as folding and lifting of the electrode tabs12may be inspected by comparing a measured alignment condition measurement signal and a preset alignment condition reference signal. The alignment condition reference signal refers to a reference signal measured in the electrode tabs12straightly aligned without being folded or lifted after performing the main welding W2. For example, when the alignment condition measurement signal is out of an allowable error range from the alignment condition reference signal, those electrode tabs12may be determined as defective alignment conditions. In some embodiments, when the alignment condition measurement signal is within the allowable error range from the alignment condition reference signal, those electrode tabs12may be determined as normal products. Only the passed electrode tabs are moved on to the next process.

In some embodiments, the non-destructive inspection method for the pouch-type secondary battery may further include a third crack condition inspecting operation S150.

The third crack condition inspecting operation S150may be performed after the packing process S14, and may refer to an operation in which a third crack condition of the electrode tabs12is inspected by measuring a third crack condition of the electrode tabs12, which may occur in the packing process S14, and comparing a measured third crack-condition measurement signal and a preset third crack-condition reference signal.

In some embodiments, the packing process S14performed before the third crack condition inspecting operation S150refers to a process of packing the electrode assembly including the electrode tabs12into the pouch14. For example, the electrode assembly11including the electrode tabs12is accommodated and packed into the pouch14in the state that the electrode lead13is partially exposed to the outside, and an adhering process is then performed using a sealant or the like for sealing between the electrode lead13and the pouch14. Even during the packing process S14, a third crack may occur in the area of the electrode tabs12. For example, during the packing process S14, only the crack may occur without a change in the foregoing weld condition.

The third crack condition inspecting operation S150may be performed in substantially the same manner as the foregoing weld condition inspecting operation S130. For example, the third crack-condition measurement signal for the area of the electrode tabs12may be obtained while relatively moving the secondary battery to be inspected or the non-contact sensor. The non-contact sensor used herein may include a transmissive eddy current sensor. Referring toFIG.7, a transmissive eddy current sensor24may include a transmitter contactlessly disposed at one side of the secondary battery10, and a receiver contactlessly disposed at the other side of the secondary battery10, in which the transmitter transmits a transmission signal toward the electrode tabs12covered with the pouch14, and the receiver receives a transmission signal CS3sequentially transmitted through the pouch14and the electrode tabs12. For example, the transmission signal CS3varied depending on the third crack condition of the electrode tabs12while the transmission signal passes through the pouch14and the electrode tabs12in sequence may be the third crack-condition measurement signal. The transmissive eddy current sensor24used in the third crack condition inspecting operation S150may be the same sensor as the transmissive eddy current sensor23used in the weld condition inspecting operation S130and the alignment condition inspecting operation S140described above.

In some embodiments, the third crack condition inspecting operation S150inspects the area of the electrode tabs12covered with the pouch14, and therefore the third crack-condition measurement signal measured after passing through the electrode tabs12with the pouch14the third crack condition inspecting operation S150and the weld-condition measurement signal measured after passing only the electrode tabs12without the pouch14in the weld condition inspecting operation S130basically have similar signal patterns even though the third crack-condition measurement signal and the weld-condition measurement signal are slightly different from each other.

In some embodiments, the third crack-condition measurement signal having a signal pattern similar to the weld-condition measurement signal is obtained in combination with the measurement signals varied depending on the pouch14and the welded portions W1and W2, and therefore only the third crack-condition measurement signal measured in the third crack condition inspecting operation S150is lowly discriminative to be used as a criterion for inspecting a defect caused by the third crack present in the electrode tabs12.

Accordingly, the third crack condition inspecting operation S150according to an embodiment compares the measured third crack-condition measurement signal and the preset third crack-condition reference signal, in which a difference between the weld-condition measurement signal previously measured without the pouch14in the weld condition inspecting operation S130and a newly measured third crack-condition measurement signal is calculated, and the calculated difference and the third crack-condition reference signal are compared, thereby detecting whether the electrode tabs12are defective due to cracks before final shipment. For example, when the difference between the weld-condition measurement signal and the third crack-condition measurement signal is within an allowable error range from the third crack-condition reference signal, the electrode tabs12may be determined as normal products without defects due to cracks. When the difference between the weld-condition measurement signal and the third crack-condition measurement signal is out of the allowable error range from the third crack-condition reference signal, the electrode tabs12may be determined as defective products having cracks.

In some embodiments, the difference between the weld-condition measurement signal and the third crack-condition measurement signal, the third crack-condition reference signal, and the allowable error range may be provided as numerical information.

According to the one or more embodiments of the disclosed technology, the weld-condition measurement signal previously measured in the weld condition inspecting operation S130prior to the third crack condition inspecting operation S150performed following the packing process S14is used, and the difference between the weld-condition measurement signal and the third crack-condition measurement signal is used as a criterion for finally inspecting the crack condition of the electrode tabs12before shipment, thereby accurately detecting a defect in products due to at least one of the crack, alignment, and weld conditions of the electrode tabs12of the secondary battery10to be finally shipped.

In some embodiments, in the third crack condition inspecting operation S150like the weld condition inspecting operation S130showing a similar signal pattern, symmetry of the third cracks formed in the electrode tabs12or a crack condition (partial or complete cracks) is more accurately determined by comparing the central value on the center line of the third crack-condition reference signal and the central value on the center line of the third crack-condition measurement signal, or by determining whether a left signal area and a right signal area of the third crack-condition measurement signal are symmetrical with respect to the center line of the third crack-condition reference signal (seeFIGS.9and10).

As described above, a non-destructive inspection method for a pouch-type secondary battery according to the disclosed technology primarily inspects a crack condition in an area of electrode tabs after an electrode tab pre-welding process, and secondarily inspects a crack condition and a weld condition in the area of the electrode tabs after an electrode tab main-welding process, thereby accurately detecting whether the area of the electrode tabs, of which the welding processes are completed, is defective due to the crack and weld conditions before a packing process, i.e., before being packed into the pouch.

Further, the non-destructive inspection method for the pouch-type secondary battery according to the disclosed technology finally inspects the crack condition present in the area of the electrode tabs covered with the pouch after the packing process, in which the difference calculated between a previously measured weld-condition measurement signal and a newly measured crack-condition measurement signal is used as a criterion for detecting cracks, so that the inspection of the crack condition can be highly discriminative in a crack condition inspecting operation after the packing process, and a defect caused by at least one of the crack, alignment, and weld conditions in the area of the electrode tabs of the secondary battery to be finally shipped is accurately detected without erroneous detection, thereby largely increasing the yield of the secondary battery.

Although a few embodiments of the disclosed technology have been described above with reference to the accompanying drawings, it will be appreciated by those skilled in the art that various changes or modifications can be made without departing from the spirit and scope of the disclosed technology defined in the appended claims.