Method and system for detecting the peel strength of a current collector

Abstract

The present disclosure provides a method and system for detecting the peel strength of a current collector, the method comprising: providing a current collector to be detected; pasting a first test film on the surface of a first metal layer and a second test film on the surface of a second metal layer to obtain a sample to be detected; preliminarily peeling the first test film on the sample to be detected and reserving a detection part; fixing the sample to be detected on a peeling table; peeling the detection part by using a tension machine to obtain peel strength data; and the length of the first test film is greater than the length of the second test film. The present disclosure provides a method for detecting the peel strength of a current collector, which can obtain the bonding force value between the substrate and the metal layer by using the method for detecting the peel strength of the present disclosure, and reduces the incomplete peeling condition during the peeling process. By completely peeling, the accurate bonding force value is obtained. The detection method of the present disclosure is also suitable for various specifications and models of copper-aluminum and other metal composite current collectors, and has wide applicability.

Description

A method and system for detecting the peel strength of current collectors. Technical Field

[0001] This disclosure relates to the field of lithium-ion battery technology, and more specifically, to a method and system for detecting the peel strength of current collectors. Background Technology

[0002] Lithium-ion batteries typically consist of several parts, including a positive electrode, a negative electrode, a separator, an electrolyte, and a packaging shell. The two most important parts are the positive and negative electrodes. During manufacturing, the positive and negative electrodes are made by uniformly mixing active materials, conductive agents, and binders, and then coating them onto electron current collectors based on Al and Cu foils, respectively. During charging and discharging, to maintain the electroneutrality of the material system, the insertion and extraction of Li ions in the active materials are accompanied by the gain and loss of electrons. Li ion migration occurs between the positive and negative electrodes, within the separator, and in the electrolyte. Electron migration relies on the active materials and conductive agents to transfer electrons to the electron current collector, which then transfers them to the external circuit and reaches the other electrode. Therefore, the electron transport rate between the active materials of the positive and negative electrodes and the electron current collector largely determines the overall kinetic performance of the battery.

[0003] Current related technologies, such as the tape traction test which uses pressure-sensitive adhesive tape, can only roughly determine the bonding force between the metal layer and the substrate, or between the metal layers in a composite current collector, without specific experimental results. There is currently very little research on the bonding effect between the metal and metal layers in composite current collectors, and no mature and effective method for detecting the bonding effect between the metal and metal layers in composite current collectors is yet available. Summary of the Invention

[0004] The purpose of this disclosure is to provide a method and system for detecting the peel strength of current collectors, which can solve at least one of the aforementioned technical problems. The specific solution is as follows:

[0005] According to a specific embodiment of this disclosure, in a first aspect, this disclosure provides a method for detecting the peel strength of a current collector, wherein the current collector includes a first metal layer, a substrate, and a second metal layer stacked sequentially, comprising: providing a current collector to be tested; attaching a first test film to the surface of the first metal layer of the current collector to be tested, and attaching a second test film to the surface of the second metal layer of the current collector to be tested, to obtain a test strip; performing preliminary peeling of the first test film on the test strip, leaving a detection portion; fixing one end of the second test film on the test strip to a peeling table; and using a tensile testing machine to peel the detection portion to obtain peel strength data; wherein the length of the first test film along the peeling direction is greater than the length of the second test film along the peeling direction.

[0006] Optionally, the step of attaching a first test membrane to the first metal layer of the current collector to be tested and attaching a second test membrane to the second metal layer of the current collector to be tested to obtain a test strip includes: baking the adhesive surface of the first test membrane; attaching the adhesive surface to the first metal layer; baking the adhesive surface of the second test membrane; attaching the adhesive surface to the second metal layer; and obtaining a test strip.

[0007] Optionally, a tensile testing machine is used to peel off the detection part to obtain peel strength data, including: testing the peeled-off first metal layer and the substrate on the peeling table to determine whether the peeling is complete; if the peeling is complete, peel strength data is obtained.

[0008] Optionally, detecting the peeled-off first metal layer and the substrate on the peeling stage to determine whether the peeling is complete includes: observing whether there are light-transmitting points on the adhesive surface of the peeled-off first test film; if there are light-transmitting points, it is determined that the peeling is incomplete; testing whether the substrate is conductive; if it is conductive, it is determined that the peeling is excessive or incomplete.

[0009] Optionally, attaching a first test film to the surface of the first metal layer of the current collector to be tested and attaching a second test film to the surface of the second metal layer of the current collector to be tested to obtain test strips includes: cutting the current collector to be tested with the first test film and the second test film attached to it to obtain multiple test strips.

[0010] Optionally, the length of the second test membrane along the peeling direction is less than the length of the test strip along the peeling direction.

[0011] Optionally, the second test membrane is adhered to the second metal layer on the side near the peeling start end.

[0012] Optionally, fixing one end of the second test film of the test strip to the peeling stage includes: attaching double-sided tape to the peeling stage; attaching the second test film to the double-sided tape; wherein the double-sided tape partially overlaps with the test film, and the double-sided tape is attached to the side of the second test film away from the peeling start end.

[0013] Optionally, it also includes: pre-treating the test strip to remove air between the first test membrane, the current collector to be tested, and the second test membrane.

[0014] According to a specific embodiment of the present disclosure, in a second aspect, the present disclosure provides a system for detecting the peel strength of a current collector, which is used to detect the peel strength of a current collector using the detection method described in any of the above technical solutions.

[0015] Compared with the prior art, the above-described solutions of this disclosure have at least the following beneficial effects:

[0016] This disclosure provides a method for testing the peel strength of current collectors. This method allows for the determination of the bonding force between the substrate and the metal layer, and reduces the likelihood of incomplete peeling. Accurate bonding force values ​​are obtained by measuring complete peeling. This testing method is also applicable to various specifications and models of copper-aluminum and other metal composite current collectors, demonstrating broad applicability. Attached Figure Description

[0017] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure. It is obvious that the drawings described below are merely some embodiments of this disclosure, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. In the drawings:

[0018] Figure 1 shows a flowchart of a method for detecting the peel strength of a current collector according to an embodiment of the present disclosure.

[0019] Figure 2 shows a schematic diagram of the current collector fixing method for detecting the peel strength of the current collector according to an embodiment of the present disclosure.

[0020] Figure 3 shows an enlarged schematic diagram of region A in Figure 2.

[0021] Figure 4 shows a trend graph of peel strength data when a universal tensile testing machine is used to peel the testing part according to an embodiment of the present disclosure.

[0022] Figure label:

[0023] 100: Peeling stage; 200: Double-sided adhesive; 310: First test membrane; 320: Second test membrane; 410: First metal layer; 420: Second metal layer; 430: Substrate; 500: Easy-tear strip; 600: Peeling start end.

[0024] The arrows in Figure 2 indicate the peeling direction.

[0025] In Figure 4, the vertical axis represents the tensile force exerted by the universal tensile testing machine on the testing part, in N; the horizontal axis represents the displacement length exerted by the universal tensile testing machine on the testing part, in mm. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this disclosure clearer, the disclosure will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this disclosure, and not all of them. Based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0027] The terminology used in the embodiments of this disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of this disclosure. The singular forms “a,” “the,” and “the” as used in the embodiments of this disclosure and the appended claims are also intended to include the plural forms, and “multiple” generally includes at least two unless the context clearly indicates otherwise.

[0028] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0029] Currently, two methods are used to peel off current collectors. One method involves using pressure-sensitive adhesive tape to adhere the two metal layers of the current collector, then fixing the non-test side (the side with the second metal layer in this disclosure) to the peeling stage using double-sided adhesive, and finally manually or mechanically peeling off the test side (the side with the first metal layer in this disclosure). The other method involves using pressure-sensitive adhesive tape to adhere to the test surface, then fixing the non-test side to the peeling stage using double-sided adhesive, and finally manually or mechanically peeling off the test side (the side with the first metal layer in this disclosure). However, these current peeling methods are prone to damaging the first metal layer during the peeling process, leaving parts of the first metal layer remaining on the substrate surface; they may also peel off the first metal layer along with the substrate; and they may cause the second metal layer to separate from the pressure-sensitive adhesive tape or double-sided adhesive, resulting in incomplete peeling. Furthermore, the peeling results rely entirely on visual or microscopic observation, without specific data for reference. In the field of composite current collector testing, especially in bonding strength testing, the preparation methods are complex, making it difficult to draw timely and effective conclusions. During the steel plate test, the peeling effect is unstable. The data obtained is usually the force value between the steel plate and the double-sided adhesive, rather than the force between the first metal layer and the substrate.

[0030] The optional embodiments of this disclosure are described in detail below with reference to the accompanying drawings.

[0031] According to a specific embodiment of this disclosure, in a first aspect, this disclosure provides a method for detecting the peel strength of a current collector. The current collector may include a first metal layer 410, a substrate 430, and a second metal layer 420 stacked sequentially. The method may include: providing a current collector to be tested; attaching a first test film 310 to the surface of the first metal layer 410 of the current collector to be tested, and attaching a second test film 320 to the surface of the second metal layer 420 of the current collector to be tested, to obtain a test strip; performing preliminary peeling of the first test film 310 on the test strip, leaving a detection portion; fixing one end of the second test film 320 of the test strip to a peeling table 100; using a tensile testing machine to peel the detection portion to obtain peel strength data; wherein, the length of the first test film 310 along the peeling direction is greater than the length of the second test film 320 along the peeling direction.

[0032] This disclosure provides a method for testing the peel strength of current collectors. This method allows for the determination of the bonding force between the substrate 430 and the metal layer, and reduces the likelihood of incomplete peeling. A precise bonding force value is obtained by measuring the complete peel. This testing method is also applicable to various specifications and models of copper-aluminum and other metal composite current collectors, demonstrating broad applicability. Furthermore, the method provided by this disclosure offers a short preparation time, enabling timely and effective determination of bonding performance.

[0033] Figure 1 shows a flowchart of a method for detecting the peel strength of a current collector according to an embodiment of the present disclosure.

[0034] As shown in Figure 1, in some embodiments, the method for detecting the peel strength of the current collector includes at least the following steps:

[0035] S100, provides the current collector to be tested.

[0036] S200: A first test film is attached to the surface of the first metal layer of the current collector to be tested, and a second test film is attached to the surface of the second metal layer of the current collector to be tested, to obtain the test strip.

[0037] S300: Initially peel off the first test film on the test strip and leave a detection section.

[0038] S400: Fix one end of the second test membrane of the test strip to the peeling stage.

[0039] S500. The detection part is peeled using a tensile testing machine to obtain peel strength data.

[0040] In step S200, the first metal layer 410 is the test surface, and the first test film 310 is adhered to the surface of the first metal layer 410. During the peel test, the first test film 310 adheres to the first metal layer 410. When the first test film 310 is peeled off, the first test film 310 also adheres to the first metal layer 410, thereby peeling the first metal layer 410 off the substrate 430. The second metal layer 420 is a non-test surface, and the second test film 320 is adhered to the surface of the second metal layer 420. Having test films adhered to both sides of the current collector under test makes the subsequent peel strength data more accurate. This prevents the current collector under test from having a test film adhered to one side and the other side being a free end, which would affect the accuracy of the peel strength data.

[0041] It should be noted that this disclosure employs a structure where the length of the first test membrane 310 is greater than the length of the second test membrane 320, thereby reducing the possibility of incomplete peeling during the peeling process. A precise bonding force value is obtained by observing the completely peeled state.

[0042] In step S300, the first test membrane 310 can be initially peeled off manually, separating the first test membrane 310 from the side near the peeling start end. This facilitates subsequent peeling of the detection section using a tensile testing machine. The end effector of the tensile testing machine helps to fix the first test membrane 310. The reserved detection section is the part peeled off using the tensile testing machine, and some data will be collected as peel strength data.

[0043] In step S400, the test strip after preliminary peeling is fixed on the peeling table. An adhesive can be used to attach the non-test side (i.e. the side with the first test film 320) to the peeling table so that it can be peeled off using the tensile testing machine later.

[0044] In step S500, a tensile testing machine is used to peel the detection part at a uniform speed to obtain peel strength data. The peel strength data can directly and intuitively reflect the bonding state between the first metal layer 410 and the substrate 430, determine its bonding force, and digitize the bonding force data that relies on empirical analysis in related technologies, making it convenient for comparison and recording.

[0045] In some embodiments, step S200 may include:

[0046] S210. Bake the adhesive surface of the first test film.

[0047] S220. Adhere the adhesive surface to the first metal layer.

[0048] S230. Bake the adhesive surface of the second test film.

[0049] S240. Adhere the adhesive surface to the second metal layer.

[0050] S260, Obtain the test spline.

[0051] In steps S220-S260, this disclosure uses a thermosensitive material as an adhesive between the test membranes (the first test membrane 310 and the second test membrane 320) and the metal layers (the first metal layer 410 and the first metal layer 420). The adhesiveness of the thermosensitive test membranes is baked out, facilitating adhesion to the surface of the metal layer of the current collector to be tested. During the baking process, the adhesive side is held upwards to prevent it from contacting the oven and sticking.

[0052] In some embodiments, step S500 may include:

[0053] S510. Inspect the first metal layer that has been peeled off and the substrate on the peeling stage to determine whether the peeling is complete.

[0054] S520. If the peeling is complete, obtain the peel strength data.

[0055] In steps S510-S520, this disclosure requires data on the force that causes the first metal layer 410 to separate from the substrate 430, i.e., the bonding force between the first metal layer 410 and the substrate 430. If the peeling is incomplete, the measured peel strength data will also be inaccurate, as it includes the force that causes the first metal layer 410 to break, the force that causes the substrate 430 to break, or the bonding force between the second metal layer 420 and the substrate 430. Therefore, before using the measured peel strength data, the accuracy of the measured peel strength data is verified by checking whether the peeling is complete.

[0056] In some embodiments, step S510 may include:

[0057] S511. Observe whether there are light-transmitting points on the adhesive surface of the first test film that has been peeled off; if there are light-transmitting points, it is determined that the peeling is incomplete.

[0058] S512. Test whether the substrate is conductive; if it is conductive, determine whether the peeling is excessive or incomplete.

[0059] In step S511, this disclosure observes whether there are light-transmitting points on the adhesive surface 310 of the first test film that has been peeled off; if there are light-transmitting points, it proves that the first metal layer 410 is damaged, and part of the first metal layer 410 is still on the substrate 430. The peel strength data obtained includes the force that damaged the first metal layer 410; therefore, when there are light-transmitting points, the peel strength data obtained is inaccurate and cannot be used.

[0060] In step S511, this disclosure tests whether the substrate 430 is conductive. If the substrate 430 is conductive, it proves that the first metal layer 410 is damaged or has not been peeled off, and all or part of the first metal layer 410 is still on the substrate 430. If the first metal layer 410 and the substrate 430 are peeled off together, the substrate 430 that should be on the peeling table 100 will not exist. When testing whether the substrate is conductive, what is actually being tested is the second metal layer 420, which is conductive. Therefore, testing the substrate 430 on the peeling table 100 can also determine that the obtained peel strength data is inaccurate.

[0061] In practical applications, during the peeling process, there is a possibility that the entire current collector may be peeled off. In this case, the adhesive surface of the peeled-off first test membrane 310 has no light-transmitting points, and the substrate 430 is not conductive. It should be noted that in this disclosure, the length of the first test membrane 310 along the peeling direction is greater than the length of the second test membrane 320 along the peeling direction. When pasted onto the current collector to be tested, this structure can, to a certain extent, prevent the first metal layer 410 and the substrate 430 from being peeled off together during the peeling process, essentially eliminating the possibility of the entire current collector being peeled off.

[0062] In some embodiments, step S200 may include:

[0063] S250. Cut the current collector to be tested, after the first test film and the second test film are pasted on, to obtain multiple test strips.

[0064] In step S250, multiple test strips are cut from the same test sample, and peeling data tests are performed on each test strip. The obtained data are averaged, which reduces errors and improves accuracy. Furthermore, test strips that are not completely peeled can be removed, preventing the need for retesting if only one sample is tested and the peeling is incomplete.

[0065] In practical applications, the peel strength data is the average value of the data after complete peeling.

[0066] In some embodiments, step S200 may further include:

[0067] S241. Pre-treat the current collector to be tested after the first test membrane and the second test membrane have been pasted on.

[0068] S242. The pretreated current collector to be tested is subjected to flat plate hot pressing.

[0069] In step S241, the pretreatment may include: rolling, which removes air between the first test film 310, the current collector to be tested, and the second test film 320. This prevents air from causing poor adhesion and incomplete peeling.

[0070] In step S242, the air gaps left after pretreatment are filled by hot pressing with a flat plate. Hot pressing softens the first test film 310 and the second test film 320, allowing them to adhere better to the surfaces of the first metal layer 410 and the second metal layer 420.

[0071] In some embodiments, the hot-pressing temperature of the plate is 60-100℃, the hot-pressing pressure is 0.2-0.6MPa, and the hot-pressing time is 5-8s.

[0072] In a preferred embodiment, the hot-pressing temperature of the plate is 70-90°C, the hot-pressing pressure is 0.2-0.3 MPa, and the hot-pressing time is 5-6 seconds.

[0073] In some embodiments, step S400 may include:

[0074] S410. Apply double-sided tape to the peeling table 100.

[0075] S420. Adhere the second test film to the double-sided tape.

[0076] The double-sided adhesive partially overlaps with the test membrane, and the double-sided adhesive is adhered to the side of the second test membrane away from the peeling start end.

[0077] In some embodiments, step S400 may further include:

[0078] The stripping table 100 is cleaned by using anhydrous alcohol and a lint-free cloth to clean its surface.

[0079] In some embodiments, the first test membrane 310 can be one or more of a hot melt film, a thermosensitive film, a hot-pressed hot melt film, and a hot-pressed thermosensitive film. The thermosensitive film is a uniformly coated high-performance special thermosensitive adhesive, exhibiting high peel strength, good initial tack, excellent cohesion, and good weather resistance. The pressure-sensitive adhesive uses either polyacrylate or polyvinyl ether as a substrate, requiring a uniform substrate with low elasticity and good solvent wettability.

[0080] In some embodiments, the adhesive surface of the first release film may be one or more of EAA (ethylene acrylate copolymer), epoxy resin, styrene, silicone, PU (polyurethane), and polyolefin systems.

[0081] In some embodiments, the substrate 430 of the first release film is one or more of PET (polyethylene terephthalate), BOPP (biaxially oriented polypropylene film), PI (polyimide), and BOPET (biaxially oriented polyester film).

[0082] In some embodiments, the second test film 320 may be one or more of a hot melt film, a thermosensitive film, a hot-pressed hot melt film, and a hot-pressed thermosensitive film.

[0083] In some embodiments, the adhesive surface of the second release film can be one or more of EAA, epoxy resin, styrene, silicone, PU polyurethane, and polyolefin systems.

[0084] In some embodiments, the length of the first test membrane 310 along the peeling direction is twice the length of the second test membrane 320 along the peeling direction. If the second test membrane 320 is too short, it will not adhere firmly and may separate during peeling; if it is too long, it will affect the test length of the tensile testing machine.

[0085] In some embodiments, the initial peel length is 10-20 mm, preferably 5-10 mm. This separates the first test membrane 310 from the side closest to the peel initiation end, facilitating subsequent peeling of the detection section using a tensile testing machine. The end effector of the tensile testing machine helps to fix the first test membrane 310. 10-20 mm is the length of the test membrane that the tensile testing machine can hold.

[0086] In some embodiments, the step of attaching a first test membrane 310 to the first metal layer 410 of the current collector to be tested and attaching a second test membrane 320 to the second metal layer 420 of the current collector to be tested to obtain a test strip may include: baking the adhesive surface of the first test membrane 310; attaching the adhesive surface to the first metal layer 410; baking the adhesive surface of the second test membrane 320; attaching the adhesive surface to the second metal layer 420; and obtaining the test strip. This disclosure uses a thermosensitive material as the adhesive between the test membranes (the first test membrane 310 and the second test membrane 320) and the metal layers (the first metal layer 410 and the first metal layer 420), baking to develop the adhesiveness of the thermosensitive test membrane, facilitating adhesion to the surface of the metal layer of the current collector to be tested. During the baking process, the adhesive surface is kept upwards to prevent the adhesive surface from contacting the oven and sticking.

[0087] In some embodiments, a forced-air oven is used to bake the adhesive surfaces of the first test membrane 310 and the second test membrane 320. The baking temperature is 60-100℃, preferably 70-90℃; the baking time is 5-20 seconds, preferably 8-10 seconds. Baking develops the adhesiveness of the thermal test membrane, facilitating its adhesion to the metal layer surface of the current collector to be tested. During baking, the adhesive surface is kept upwards to prevent it from sticking to the oven.

[0088] In some embodiments, using a tensile testing machine to peel off the detection part to obtain peel strength data may include: detecting the peeled-off first metal layer 410 and the substrate 430 on the peeling table 100 to determine whether the peeling is complete; if the peeling is complete, obtaining peel strength data.

[0089] In some embodiments, detecting the peeled first metal layer 410 and the substrate 430 on the peeling stage 100 to determine whether the peeling is complete may include: observing whether there are light-transmitting points on the adhesive surface of the peeled first test film 310; if there are light-transmitting points, it is determined that the peeling is incomplete; testing whether the substrate 430 is conductive; if it is conductive, it is determined that the peeling is excessive or incomplete.

[0090] In some embodiments, if it is determined that the peeling is excessive or incomplete, the obtained peeling strength data is discarded.

[0091] In some embodiments, after peeling, a four-probe test can be used to test whether the substrate 430 is conductive or has resistance. First, the four-probe resistance tester has high precision. It can measure with an accuracy of up to 0.01%, which is much higher than the accuracy of traditional resistance testers. This ensures accurate measurement, reduces measurement errors, and improves measurement accuracy. Second, the four-probe resistance tester has high-speed measurement capabilities. It can measure resistance values ​​in a short time, meeting the needs of rapid measurement. This increases measurement speed and efficiency. Furthermore, the four-probe resistance tester has an automatic adjustment function. It can automatically adjust the measurement accuracy according to changes in the resistance value, making the measurement more accurate. Finally, the four-probe resistance tester is simple and easy to use. Its operation is simple and easy to perform, requiring no professional technical knowledge. This saves operation time and improves operational efficiency.

[0092] In some embodiments, the pre-peeling speed is 30-80 mm / min, preferably 50-60 mm / min; the peeling speed is 100-300 mm / min. It should be noted that the pre-peeling speed is a force applied before the working load is applied to enhance the reliability and tightness of the connection, preventing gaps or relative slippage between the connectors after loading; that is, the pre-peeling speed is the speed at which a pre-tensioning force is applied to the tensile testing machine, and after reaching the pre-tensioning force, it is converted into the test speed. The peeling speed is the test speed, i.e., the speed during peeling.

[0093] In some embodiments, the judgment criterion is that the test result error of multiple test strips is within 0.5N / 15mm. If the test error is exceeded, the test strips need to be retested until the sample error is guaranteed to be within 0.5N, and the average value of multiple strips is taken as the test result.

[0094] In some embodiments, after the multiple test strips are obtained by cutting, the stripping of the detection section by all the test strips is completed within a first time.

[0095] In some embodiments, the first time is 1 minute.

[0096] In some embodiments, the tensile testing machine is set to use the last 10-30 mm of data as the peel strength data.

[0097] In a preferred embodiment, the tensile testing machine sets the last 20-25 mm of data as the peel strength data.

[0098] In some embodiments, attaching a first test membrane 310 to the surface of the first metal layer 410 of the current collector to be tested and attaching a second test membrane 320 to the surface of the second metal layer 420 of the current collector to be tested, obtaining the test strip may include: cutting the current collector to be tested with the first test membrane 310 and the second test membrane 320 attached thereon to obtain multiple test strips.

[0099] In some embodiments, the length of the second test membrane 320 along the peeling direction is less than the length of the test strip along the peeling direction.

[0100] In some embodiments, the second test membrane 320 is adhered to the second metal layer 420 on the side near the peeling start end 600.

[0101] In some embodiments, fixing one end of the second test membrane 320 of the test strip to the peeling stage 100 may include: attaching double-sided adhesive 200 to the peeling stage 100; attaching the second test membrane 320 to the double-sided adhesive 200; wherein the double-sided adhesive 200 partially overlaps with the test membrane, and the double-sided adhesive 200 is attached to the side of the second test membrane 320 away from the peeling start end 600.

[0102] In some embodiments, the method for detecting the peel strength of the current collector may further include: pre-treating the test strip to remove air between the first test membrane 310, the current collector to be tested, and the second test membrane 320.

[0103] In some embodiments, attaching the double-sided adhesive 200 to the peeling table 100 may include: rolling the double-sided adhesive 200 attached to the peeling table 100 to make the double-sided adhesive 200 adhere more firmly to the peeling table 100.

[0104] In some embodiments, the length of the double-sided adhesive 200 along the peeling direction is 40-70 mm. The length of the double-sided adhesive 200 needs to be shorter than the length of the first test film 310 along the peeling direction, and it cannot be too short, otherwise it will not be able to simultaneously adhere the second test film 310 and the second metal layer 420.

[0105] In some embodiments, the pretreatment may include: rolling.

[0106] In some embodiments, the number of rolling cycles is 3-5. Too many rolling cycles may damage the current collector under test, while too few cycles may not be enough to purge air.

[0107] The pretreatment process removes air from between the first test membrane 310, the current collector to be tested, and the second test membrane 320.

[0108] In some embodiments, the method for detecting the peel strength of the current collector may further include: hot pressing the pretreated current collector to be tested onto a flat plate.

[0109] The air gaps after pretreatment are filled by hot pressing on a flat plate. Hot pressing softens the first test membrane 310 and the second test membrane 320, allowing them to adhere better to the surfaces of the first metal layer 410 and the second metal layer 420.

[0110] In some embodiments, the current collector to be tested is wrapped before hot pressing to prevent it from sticking to the hot press and causing sample damage.

[0111] In some embodiments, the method for detecting the peel strength of the current collector may further include: providing an easy-tear strip 500 on the side of the first test film 310 of the test strip near the peel initiation end 600. By providing the easy-tear strip 500, a certain force-bearing portion is provided, facilitating peeling.

[0112] In some embodiments, the easy-tear strip 500 is the portion of the first test film 310 that extends beyond the first metal layer 410 at the peeling start point. That is, the projection of the first metal layer 410 onto the first test film 310 is within the range of the first test film 310, but the projection of the first test film 310 onto the first metal layer 410 extends beyond the range of the first metal layer 410 near the peeling start point. By leaving the easy-tear strip 500 in place when attaching the first test film 310, peeling is convenient and eliminates the need for subsequent additional installations, making it simple and convenient.

[0113] In some embodiments, the method for detecting the peel strength of the current collector may further include: providing an easy-tear strip 500 on the side of the second test film 320 of the test strip near the peel initiation end 600. By providing the easy-tear strip 500, a certain force-bearing portion is provided, facilitating peeling.

[0114] In some embodiments, the easy-tear strip 500 is the portion of the second test film 320 that extends beyond the second metal layer 420 at the peeling start point. That is, the projection of the second metal layer 420 onto the second test film 320 is within the range of the second test film 320, while the projection of the second test film 320 onto the second metal layer 420 extends beyond the range of the second metal layer 420 near the peeling start point. By leaving the easy-tear strip 500 in place when attaching the second test film 320, peeling is convenient and eliminates the need for subsequent additional installations, making it simple and convenient.

[0115] In some embodiments, the thickness of the first test membrane 310 can be 20-80 micrometers. If the first test membrane 310 is too thick, the final data obtained will be inaccurate, as part of the force of the tensile testing machine will be used for the deformation of the first test membrane 310; if the first test membrane 310 is too thin, it is easy to damage the first test membrane 310 during peeling, resulting in peeling failure.

[0116] In a preferred embodiment, the thickness of the first test membrane 310 is 30-50 micrometers.

[0117] In some embodiments, the thickness of the second test membrane 320 can be 20-80 micrometers.

[0118] In a preferred embodiment, the thickness of the second test membrane 320 is 30-50 micrometers. If the second test membrane 320 is too thick, the final data will be inaccurate, as part of the force of the tensile testing machine will be used for the deformation of the second test membrane 320; if the second test membrane 320 is too thin, it is easy to damage the second test membrane 320 during peeling, resulting in peeling failure.

[0119] Figure 2 shows a schematic diagram of the current collector fixing process in a method for detecting the peel strength of the current collector according to an embodiment of the present disclosure. Figure 3 shows an enlarged schematic diagram of region A in Figure 2.

[0120] As shown in Figures 2 and 3, it is clearly visible from the angles of Figures 2 and 3 that the length of the first test membrane 310 along the peeling direction is greater than the length of the second test membrane 320 along the peeling direction, and the length of the second test membrane 320 along the peeling direction is less than the length of the test strip along the peeling direction. The second test membrane 320 is adhered to the second metal layer 420 on the side near the peeling start end 600. The double-sided adhesive 200 partially overlaps with the second test membrane 320, and is adhered to the side of the second test membrane 320 away from the peeling start end 600. The double-sided adhesive 200 can simultaneously adhere to the second test membrane 320 and the second metal layer 420. The overlapping portion of the second test membrane 320 away from the peeling start end 600 and the double-sided adhesive 200 forms a transition zone, which prevents the second metal layer 420 from separating from the second test membrane 320 during the peeling process, improving the peeling success rate; after peeling beyond the transition zone, the peeling becomes more stable. Example

[0121] The system provides a current collector to be tested, a first test membrane 310, and a second test membrane 320. Both the first test membrane 310 and the second test membrane 320 are thermal membranes. The first test membrane 310 has a length of 160 mm along the peeling direction, and the second test membrane 320 has a length of 80 mm along the peeling direction. Both the first test membrane 310 and the second test membrane 320 have a thickness of 40 micrometers and a width of 60 mm. The current collector to be tested has a length of 155 mm (with a 5 mm easy-tear strip 500 reserved) and a width of 60 mm.

[0122] The adhesive surfaces of the first test membrane 310 and the second test membrane 320 are baked in an oven at 80 degrees Celsius for 9 seconds. The baked adhesive surface of the first test membrane 310 is then adhered to the surface of the first metal layer 410; the baked adhesive surface of the second test membrane 320 is then adhered to the surface of the second metal layer 420. Easy-tear strips 500 are left at the peeling start point 600 on both the first test membrane 310 and the second test membrane 320. The easy-tear strips 500 are 5 mm long and 60 mm wide, the same as those on the first and second test membranes 310 and 320, respectively. The test sample is then obtained.

[0123] The sample to be tested was rolled 5 times using a roller press, then wrapped with A4 paper, and then hot-pressed with a flatbed hot press at a temperature of 80 degrees Celsius, a pressure of 0.5 MPa, and a time of 4 seconds.

[0124] The sample to be tested was cut using a sampling knife along the peeling direction, with a width of 15 mm, to obtain three test strips of the same size (sample 1, sample 2, and sample 3).

[0125] Manually perform preliminary peeling on samples 1-3, with a peeling length of 20 mm, leaving a 130 mm long detection section.

[0126] Clean the 100 sides of the peeling table with anhydrous alcohol and a lint-free cloth.

[0127] Take a piece of double-sided adhesive tape 200 with a length of 70 mm and a width of 15 mm, and stick one side of the double-sided adhesive tape 200 onto the cleaned peeling table 100. Use a pressure roller to press the double-sided adhesive tape 200 five times.

[0128] The side of the second test film 320 of samples 1-3 away from the adhesive surface is adhered to the double-sided adhesive 200, with one end of the double-sided adhesive 200 aligned with the side of the second test film 320 away from the peel start end 600. The test strips are then rolled 5 times using a pressure roller.

[0129] The testing section was peeled using a universal tensile testing machine. The working width of the universal tensile testing machine was 15 mm, and the pre-peeling speed was 50 mm / min.

[0130] After the peeling is completed, the first metal layer 410 that has been peeled off and the substrate 430 on the peeling table 100 are inspected to determine that the peeling is complete and peeling strength data is obtained.

[0131] The first metal layer 410 peeled off from samples 1-3 and the substrate 430 on the peeling stage 100 are tested to determine whether the peeling is complete. The peeling data of the last 25 mm is taken to obtain the peeling strength data.

[0132] Figure 4 shows a trend graph of peel strength data when a universal tensile testing machine is used to peel the testing part according to an embodiment of the present disclosure.

[0133] As shown in Figure 4, the first segment shows the peel strength data trend before the transition zone, the second segment shows the peel strength data trend of the detection unit in the transition zone, and the third segment shows the peel strength data trend after the transition zone. By setting the transition zone, the separation of the second metal layer 420 from the second test film 320 is avoided during the peeling process, thus improving the peeling success rate; after peeling beyond the transition zone, the peeling becomes more stable.

[0134] Experimental results:

[0135] Using the peel strength test method of the current collector disclosed herein, with a hot pressing temperature of 70-90℃, a pressure of 0.2-0.6 MPa, and a time of 5-8 s, the obtained peel strength data is 6.642 N / 15 mm;

[0136] The hot-pressing temperature was 140-160℃, the pressure was 0.2-0.6 MPa, and the time was 5-8 seconds. The resulting peel strength data was 7.838 N / 15 mm.

[0137] Therefore, it can be concluded that a temperature of 140-160℃, a pressure of 10-15MPa, and a time of 45-90 minutes will increase the bonding force between the current collector metal layer and the substrate 430.

[0138] Taking a pressure of 10-15MPa as an example, the hot pressing temperature is between 70-90℃ and 5-8s. The resulting peel strength data is 7.334N / 15mm. Moreover, the peel success rate is reduced. Due to excessive pressure, the adhesive surface of the thermosensitive film and the current collector are damaged, making it unsuitable for current collector testing.

[0139] After a trial run of 45-90 minutes, with a hot-pressing temperature of 70-90°C and a pressure of 0.2-0.6 MPa, the resulting peel strength data was 7.025 N / 15 mm. During the hot-pressing process, the bonding force increased significantly due to the excessively long hot-pressing time between the adhesive surface of the heat-sensitive film and the current collector.

[0140] Therefore, it can be concluded that a temperature of 140-160℃, a pressure of 10-15MPa, and a time of 45-90 minutes will increase the bonding force between the metal layer of the current collector and the substrate.

[0141] According to a specific embodiment of the present disclosure, in a second aspect, the present disclosure provides a system for detecting the peel strength of a current collector, which is used to detect the peel strength of a current collector using the detection method described in any of the above technical solutions.

[0142] This disclosure aims to protect a method and system for testing the peel strength of a current collector. The method may include: providing a current collector to be tested; attaching a first test film 310 to the surface of a first metal layer 410 of the current collector to be tested, and attaching a second test film 320 to the surface of a second metal layer 420 of the current collector to be tested, to obtain a test strip; initially peeling the first test film 310 on the test strip, leaving a detection portion; fixing one end of the second test film 320 of the test strip to a peeling table 100; peeling the detection portion using a tensile testing machine to obtain peel strength data; wherein, the length of the first test film 310 along the peeling direction is greater than the length of the second test film 320 along the peeling direction. This disclosure provides a method for testing the peel strength of a current collector, which can determine the bonding force between the substrate 430 and the metal layer, and reduces the possibility of incomplete peeling during the peeling process. Accurate bonding force values ​​are obtained through complete peeling. The testing method of this disclosure is also applicable to various specifications and models of copper-aluminum and other metal composite current collectors, and has wide applicability.

[0143] The units described in the embodiments of this disclosure can be implemented in software or in hardware. The name of a unit does not necessarily limit the unit itself; for example, the first acquisition unit can also be described as "a unit that acquires at least two Internet Protocol addresses".

Claims

1. A method for detecting the peel strength of a current collector, wherein the current collector comprises a first metal layer, a substrate, and a second metal layer sequentially stacked, characterized in that, include: Provide the current collector to be tested; A first test film is attached to the surface of the first metal layer of the current collector to be tested, and a second test film is attached to the surface of the second metal layer of the current collector to be tested, to obtain the test strip; The first test membrane on the test strip is initially peeled off, leaving a detection section; one end of the second test membrane on the test strip is fixed on the peeling table; the detection section is peeled off using a tensile testing machine to obtain peel strength data; wherein, the length of the first test membrane along the peeling direction is greater than the length of the second test membrane along the peeling direction.

2. The method for detecting the peel strength of the current collector according to claim 1, characterized in that, The process of attaching a first test film to the surface of the first metal layer of the current collector to be tested, and attaching a second test film to the surface of the second metal layer of the current collector to be tested, to obtain a test strip includes: baking the adhesive surface of the first test film; attaching the adhesive surface to the first metal layer; baking the adhesive surface of the second test film; attaching the adhesive surface to the second metal layer; and obtaining a test strip.

3. The method for detecting the peel strength of the current collector according to claim 1, characterized in that, The peeling strength data is obtained by using a tensile testing machine to peel off the detection part, including: testing the peeled-off first metal layer and the substrate on the peeling table to determine whether the peeling is complete; if the peeling is complete, the peeling strength data is obtained.

4. The method for detecting the peel strength of the current collector according to claim 3, characterized in that, The process of inspecting the first metal layer that has been peeled off and the substrate on the peeling stage to determine whether the peeling is complete includes: observing whether there are light-transmitting points on the adhesive surface of the first test film that has been peeled off; if there are light-transmitting points, it is determined that the peeling is incomplete; testing whether the substrate is conductive; if it is conductive, it is determined that the peeling is excessive or incomplete.

5. The method for detecting the peel strength of the current collector according to claim 1, characterized in that, An easy-tear strip is provided on the side of the first test film of the test strip near the peeling start end.

6. The method for detecting the peel strength of the current collector according to claim 1, characterized in that, The length of the second test membrane along the peeling direction is less than the length of the test strip along the peeling direction.

7. The method for detecting the peel strength of the current collector according to claim 1, characterized in that, The second test membrane is adhered to the second metal layer on the side near the peeling start end.

8. The method for detecting the peel strength of the current collector according to claim 1, characterized in that, Fixing one end of the second test film of the test strip to the peeling stage includes: attaching double-sided tape to the peeling stage; attaching the second test film to the double-sided tape; wherein the double-sided tape partially overlaps with the second test film, and the double-sided tape is attached to the side of the second test film away from the peeling start end.

9. The method for detecting the peel strength of the current collector according to claim 1, characterized in that, Also includes: The test sample is pretreated to remove air between the first test membrane, the current collector to be tested, and the second test membrane.

10. A system for detecting the peel strength of a current collector, characterized in that, It is used to perform peel strength testing on the current collector using the testing method described in any one of claims 1-9.

Images