Method for testing interface bonding strength in composite current collector

Abstract

The invention provides a method for testing the interface bonding strength in a composite current collector, and belongs to the technical field of secondary battery manufacturing. The test method comprises the following steps: S1, taking a sample of the composite current collector, and obtaining the mass M1 of the sample; s2, the sample is immersed in a solvent and subjected to ultrasonic treatment, and the mass M2 of the sample after ultrasonic treatment is obtained; s3, the residual rate beta of the sample is calculated, the calculation formula is that beta = M2 / M1 * 100%, and beta serves as the evaluation index of the interface bonding strength in the composite current collector, the test method can be compatible with samples of various shapes and sizes, meanwhile, the test result has good consistency, and in addition, the test result is accurate. The test result can truly reflect the interface bonding strength of the composite current collector in the actual operation process.

Description

Technical Field

[0001] The present application relates to the technical field of secondary battery manufacturing, and in particular to a method for testing the interface bonding strength in a composite current collector. Background Art

[0002] At present, composite current collectors have attracted wide attention due to their high safety, high energy density and low cost. Composite current collectors are usually composed of a base film layer and a conductive layer located on the surface of the base film layer. The interfacial bonding strength between the functional layers directly affects the specific application of the composite current collector in the battery. Specifically, if the interfacial bonding strength is poor, the composite current collector may have the following problems during application: (1) During the slurry coating process, the composite current collector may crack or break under the action of tension; (2) During the pole piece rolling process, the conductive layer may delaminate under the high compaction design of the pole piece; (3) During the charge and discharge cycle of the battery cell, especially in the high silicon system, the expansion and contraction of the battery cell is more serious, and long-term charge and discharge cycles can easily cause the bonding failure between the conductive layer and the base film layer. Therefore, it is particularly important to accurately detect the interfacial bonding strength in the composite current collector.

[0003] At present, the methods commonly used to evaluate the interfacial bonding strength of composite film materials are mainly 90° peeling method and 180° peeling method. Among them, the 180° peeling method is the most commonly used method, but it has the following problems: (1) The samples to be tested usually need to have fixed specifications or style requirements, and there is a problem of cumbersome sample preparation; (2) The test results are easily affected by the test conditions (such as the width of the sample to be tested, the peeling speed, the stretching distance, and the adhesive force of the tape itself), resulting in poor consistency of the test results; (3) The peeling angle is relatively fixed, while the material may involve different angles and directions in actual use, making it difficult to truly reflect the interfacial bonding strength of the sample. Due to the above-mentioned many defects of the existing test methods, it is urgently needed to develop a more advantageous test method for the interfacial bonding strength of composite current collectors. Summary of the invention

[0004] The purpose of the present application is to provide a test method for the interfacial bonding strength in a composite current collector, which is compatible with samples of various shapes and sizes. At the same time, the test results have good consistency. In addition, the test results can more realistically reflect the interfacial bonding strength of the composite current collector during actual operation.

[0005] The embodiment of the present application is implemented as follows:

[0006] In the first aspect, an embodiment of the present application provides a method for testing the interface bonding strength in a composite current collector, wherein the composite current collector includes a base film layer and a conductive layer located on the surface of the base film layer, and the testing method includes the following steps: S1 takes a sample of the composite current collector to obtain the mass M1 of the sample; S2 immerses the sample in a solvent and performs ultrasonic treatment to obtain the mass M2 of the sample after ultrasonic treatment; S3 calculates the residual rate β of the sample, wherein the calculation formula is β=M2 / M1×100%, and β is used as an evaluation index of the interface bonding strength in the composite current collector.

[0007] In the above technical scheme, before ultrasonic treatment, the mass M1 of the composite current collector sample is obtained, and after ultrasonic treatment, the mass M2 of the sample is obtained, and then the residual rate β of the sample is calculated according to the above formula to obtain the size of the interfacial bonding strength in the composite current collector. This test method has many advantages. First, since the sample is directly placed in a solvent for ultrasonic treatment, it can be applied to samples of various shapes and sizes, thereby simplifying the sample preparation process; second, the composite current collector is also under solvent conditions in the battery, and the ultrasonic treatment of the sample in the solvent can more realistically reflect the interfacial bonding strength of the composite current collector during actual operation, so as to better guide the application of the composite current collector in the battery; third, the entire test process does not involve external parameters such as peeling speed, stretching distance, and the adhesive force of the tape itself, so that the test results have good consistency.

[0008] In some optional embodiments, during the ultrasonic treatment step, the sample is immersed in the solvent in a vertical state.

[0009] In the above technical solution, the sample is immersed in the solvent in a vertical state during the ultrasonic treatment, so that the conductive layers on both sides of the base film layer can be more fully exposed to the solvent, so that the conductive layer can be more easily peeled off from the base film layer under the action of ultrasonic waves.

[0010] In some optional embodiments, the solvent is selected from at least one of ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate and propylene carbonate.

[0011] In the above technical scheme, the above types of solvents are all relatively commonly used solvents in electrolytes and account for a relatively large volume proportion. The samples are ultrasonically treated in the above types of solvents, which is more in line with the actual application conditions of the composite current collector, so that the test results can better guide the application of the composite current collector in batteries.

[0012] In some optional embodiments, before calculating the residual rate β, a step of obtaining the mass M0 of the base film layer in the sample is also included, and the calculation formula of the residual rate β is β=(M2-M0) / (M1-M0)×100%.

[0013] In the above technical scheme, before calculating the residual rate β, it also includes the step of obtaining the mass M0 of the base film layer in the sample, and adjusting the calculation formula of the residual rate β to β = (M2-M0) / (M1-M0) × 100%. When the test results of different samples are relatively close, M1 and M2 are simultaneously subtracted from M0 to calculate the residual rate β, which can make the numerical result of the residual rate β larger, thereby facilitating the comparison of the interface bonding strength between different samples.

[0014] In some optional embodiments, the step of obtaining M0 includes: acid-dissolving, washing and drying the sample after ultrasonic treatment in sequence to obtain a base film layer, and weighing the mass of the base film layer to obtain M0.

[0015] In the above technical scheme, the sample after ultrasonic treatment is acid-dissolved, cleaned and dried in sequence to obtain the base film layer and based on this, the mass M0 of the base film layer is obtained. This acquisition method has the advantage of being easy to implement. At the same time, it can also more thoroughly peel off the conductive layer from the base film layer so as to obtain M0 more accurately.

[0016] In some alternative embodiments, there are multiple samples.

[0017] In the above technical solution, multiple samples are provided so that M1 and M2 can be obtained by calculating the average mass. The average mass can more truly and accurately reflect the mass of the sample at different stages, so that the test results have higher consistency.

[0018] In some optional embodiments, in the ultrasonic treatment step: the multiple samples are immersed in the solvent in a vertical state, and the multiple samples are ultrasonically treated synchronously by the same ultrasonic device.

[0019] In the above technical solution, multiple samples are ultrasonically processed synchronously by the same ultrasonic device, so that the test conditions of each sample are relatively close, which helps to improve the consistency of the test results.

[0020] In some optional embodiments, the plurality of samples are distributed in the ultrasonic device at circumferential intervals, and the distances from the ultrasonic source of the ultrasonic device to the plurality of samples are the same.

[0021] In the above technical solution, the intensity of the ultrasonic waves received by samples at different positions is slightly different. The distance between the ultrasonic source and each sample is set to be the same so that the test conditions of each sample are closer, which helps to further improve the consistency of the test results.

[0022] In some optional embodiments, the samples are disc-shaped samples with a diameter of 2 to 4 cm, and the ultrasound source is located at the intersection of the central axes of the multiple samples (ie, the conductive layer side of each sample faces the ultrasound source).

[0023] In the above technical solution, the circular sheet samples in the above diameter range are used for testing, which has the advantages of convenient sampling and subsequent experimental operations. At the same time, the conductive layer side of each sample is set to face the ultrasonic source, which can improve the ultrasonic stripping effect.

[0024] In some optional embodiments, the thickness of the base film layer is 1 to 10 μm, and the thickness of the conductive layer is 0.1 to 2 μm.

[0025] In the above technical solution, the thickness of the base film layer and the conductive layer in the composite current collector are respectively limited within the above ranges, so that the conductive layer can be effectively peeled off from the base film layer by ultrasonic treatment.

[0026] In some optional embodiments, in the ultrasonic treatment step, the ultrasonic power is 100-500 W, and the ultrasonic time is 1-10 min.

[0027] In the above technical solution, for the composite current collector, the ultrasonic power and ultrasonic time in the ultrasonic treatment are limited to the above ranges, respectively, so that the conductive layer is easily separated from the base film layer and the base film is not easily damaged. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0029] Figure 1 A flow chart of a method for testing the interfacial bonding strength in a composite current collector provided in an embodiment of the present application;

[0030] Figure 2 A schematic diagram of the distribution of multiple samples in an ultrasonic device provided in an embodiment of the present application.

[0031] Icon: Ultrasonic device-10; Ultrasonic source-11; Container-20; Sample-30. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0033] It should be noted that “and / or” in this application, such as “Feature 1 and / or Feature 2”, refers to the three situations of “Feature 1” alone, “Feature 2” alone, or “Feature 1” plus “Feature 2”.

[0034] In addition, in the description of the present application, unless otherwise specified, the meaning of "multiple" in "one or more" refers to two or more; the range of "value a ~ value b" includes the two end values ​​"a" and "b", and the "unit" in "value a ~ value b + unit of measurement" represents the "unit of measurement" of both "value a" and "value b".

[0035] The following is a detailed description of a method for testing the interfacial bonding strength in a composite current collector in an embodiment of the present application.

[0036] In the first aspect, an embodiment of the present application provides a method for testing the interface bonding strength in a composite current collector, wherein the composite current collector includes a base film layer and a conductive layer located on the surface of the base film layer, and the testing method includes the following steps: S1 takes a sample of the composite current collector to obtain the mass M1 of the sample; S2 immerses the sample in a solvent and performs ultrasonic treatment to obtain the mass M2 of the sample after ultrasonic treatment; S3 calculates the residual rate β of the sample, wherein the calculation formula is β=M2 / M1×100%, and β is used as an evaluation index of the interface bonding strength in the composite current collector.

[0037] In this application, before ultrasonic treatment, the mass M1 of the composite current collector sample is obtained, and the mass M2 of the sample is obtained after ultrasonic treatment. Then, the residual rate β of the sample is calculated according to the above formula to obtain the size of the interfacial bonding strength in the composite current collector. This test method has many advantages. First, since the sample is directly placed in a solvent for ultrasonic treatment, it can be applied to samples of various shapes and sizes, thereby simplifying the sample preparation process; second, the composite current collector is also under solvent conditions in the battery, and the ultrasonic treatment of the sample in the solvent can more realistically reflect the interfacial bonding strength of the composite current collector during actual operation, so as to better guide the application of the composite current collector in the battery; third, the entire test process does not involve external parameters such as peeling speed, stretching distance, and the adhesive force of the tape itself, so that the test results have better consistency.

[0038] It should be noted that the structural form of the composite current collector and the corresponding preparation method are not limited. As long as the composite current collector is available in the art, it can be tested using the method provided in the embodiments of the present application.

[0039] As an example, during the ultrasonic treatment step, the sample is immersed in the solvent in a vertical state.

[0040] In this embodiment, the sample is immersed in the solvent in a vertical state during the ultrasonic treatment, so that the conductive layers on both sides of the base film layer can be more fully exposed to the solvent, so that the conductive layers can be more easily peeled off from the base film layer under the action of ultrasonic waves.

[0041] In other possible implementations, the sample may be immersed in the solvent in a horizontal state or in an inclined state, and the specific state may be adaptively adjusted according to actual needs.

[0042] It should be noted that the type of solvent is not limited and can be adaptively adjusted in combination with the actual application conditions of the composite current collector.

[0043] As an example, the solvent is selected from at least one of ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate and propylene carbonate.

[0044] In this embodiment, the above-mentioned types of solvents are all relatively commonly used solvents in the electrolyte and account for a relatively large volume proportion. The samples are ultrasonically treated in the above-mentioned types of solvents, which is more in line with the actual application conditions of the composite current collector, so that the test results can better guide the application of the composite current collector in the battery.

[0045] In other possible implementations, the solvent may also be at least one of water, ethanol and N-methylpyrrolidone.

[0046] As an example, before calculating the residual rate β, a step of obtaining the mass M0 of the base film layer in the sample is also included, and the calculation formula of the residual rate β is β=(M2-M0) / (M1-M0)×100%.

[0047] In this embodiment, before calculating the residual rate β, the step of obtaining the mass M0 of the base film layer in the sample is also included, and the calculation formula of the residual rate β is adjusted to β = (M2-M0) / (M1-M0) × 100%. When the test results of different samples are relatively close, M1 and M2 are simultaneously subtracted from M0 to calculate the residual rate β, which can make the numerical result of the residual rate β larger, thereby facilitating the comparison of the interface bonding strength between different samples.

[0048] It should be noted that there is no limitation on the method of obtaining M0. For example, the separate base film layer may be directly weighed; or the conductive layer on the sample may be completely removed to obtain a separate base film layer, and then the base film layer may be weighed.

[0049] As an example, the steps of obtaining M0 include: acid-dissolving, washing and drying the sample after ultrasonic treatment in sequence to obtain a base film layer, and weighing the mass of the base film layer to obtain M0.

[0050] In this embodiment, the sample after ultrasonic treatment is successively acid-dissolved, cleaned and dried to obtain the base film layer and based on this, the mass M0 of the base film layer is obtained. This acquisition method has the advantage of being easy to implement. At the same time, it can also more thoroughly peel off the conductive layer from the base film layer so as to obtain M0 more accurately.

[0051] In other possible implementations, the mass M0 of the base membrane layer may also be obtained by increasing the ultrasonic power and the ultrasonic time.

[0052] As an example, there are multiple samples.

[0053] In this embodiment, a plurality of samples are provided so that M1 and M2 can be obtained by calculating the average mass. The average mass can more truly and accurately reflect the mass of the sample at different stages, so that the test results have higher consistency.

[0054] It should be noted that the number of samples is not limited, for example, it can be 2, 3 or 4, and can be adaptively adjusted according to actual needs.

[0055] As an example, in the ultrasonic treatment step: multiple samples are immersed in the solvent in a vertical state, and the multiple samples are ultrasonically treated synchronously by the same ultrasonic device.

[0056] In this embodiment, multiple samples are ultrasonically processed synchronously by the same ultrasonic device, so that the test conditions of each sample are relatively close, which helps to improve the consistency of the test results.

[0057] In other possible implementations, multiple samples may be ultrasonically processed simultaneously in different ultrasonic devices, or multiple samples may be ultrasonically processed sequentially in the same ultrasonic device.

[0058] As an example, the multiple samples are distributed in the ultrasonic device at circumferential intervals, and the distances from the ultrasonic source of the ultrasonic device to the multiple samples are the same.

[0059] In this embodiment, the intensity of the ultrasonic waves received by samples at different positions is slightly different, and the distances from the ultrasonic source to each sample are set to be the same so that the test conditions of each sample are closer, which helps to further improve the consistency of the test results.

[0060] As an example, the sample is a disc-shaped sample with a diameter of 2 to 4 cm (for example, but not limited to, any point value of 2 cm, 2.5 cm, 3 cm, 3.5 cm and 4 cm in diameter or a range of values ​​between any two of them), and the ultrasonic source is located at the intersection of the central axes of the multiple samples (that is, the conductive layer side of each sample is facing the ultrasonic source).

[0061] In this embodiment, the circular sheet samples in the above diameter range are used for testing, which has the advantages of convenient sampling and facilitating subsequent experimental operations. At the same time, the conductive layer side of each sample is set to face the ultrasonic source, which can improve the ultrasonic stripping effect.

[0062] In other possible implementations, the shape of the sample may also be a square, a rectangle, a triangle, an ellipse, etc., which may be adaptively adjusted according to actual needs.

[0063] It should be noted that there is no limitation on the implementation method of immersing the sample in a solvent for ultrasonic treatment. For example, the solvent may be contained in an ultrasonic device, and then the sample may be directly immersed in the solvent for ultrasonic treatment. Alternatively, the sample may be placed in a separate container containing a solvent, and then the container may be transferred to an ultrasonic device (wherein the medium in the ultrasonic device is water) for ultrasonic treatment. In the embodiment of the present application, the latter is taken as an example, which can reduce the amount of non-aqueous solvent used.

[0064] As an example, the thickness of the base film layer is 1 to 10 μm, for example but not limited to the thickness of any point value among 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm and 10 μm, or the range value between any two thereof; the thickness of the conductive layer is 0.1 to 2 μm, for example but not limited to the thickness of any point value among 0.1 μm, 0.5 μm, 1 μm, 1.5 μm and 2 μm, or the range value between any two thereof.

[0065] In this embodiment, the thickness of the base film layer and the conductive layer in the composite current collector are respectively limited to the above ranges, so that the conductive layer can be effectively peeled off from the base film layer by ultrasonic treatment.

[0066] As an example, in the ultrasonic treatment step, the ultrasonic power is 100-500 W, for example but not limited to any one of 100 W, 200 W, 300 W, 400 W and 500 W or a range between any two of them; the ultrasonic time is 1-10 min, for example but not limited to any one of 1 min, 2 min, 4 min, 6 min, 8 min and 10 min or a range between any two of them.

[0067] In this embodiment, for the composite current collector, the ultrasonic power and ultrasonic time in the ultrasonic treatment are respectively limited to the above ranges, so that the conductive layer is easily separated from the base film layer and the base film is not easily damaged.

[0068] It should be noted that any process or step not specifically described or limited in the test process may be set according to conventional selection in the art.

[0069] As an example, a flow chart of a method for testing the interfacial bonding strength in a composite current collector is shown in Figure 1 .

[0070] In order to better understand the technical solution, a distribution diagram of multiple samples in an ultrasonic device is used for auxiliary explanation. For details, please refer to Figure 2 , wherein four samples 30 are respectively located in a container 20 and immersed in a solvent, the four containers 20 are circumferentially spaced and distributed in the same ultrasonic device 10 , and the ultrasonic source 11 of the ultrasonic device 10 is located at the center of the four containers 20 .

[0071] The features and performance of the present application are further described in detail below in conjunction with the embodiments.

[0072] Example 1

[0073] The present application provides a method for testing the interfacial bonding strength in a composite current collector, comprising the following steps:

[0074] S1 provides a composite current collector, which includes a PET base film layer and a Cu conductive layer located on the surface of the base film layer, wherein the base film layer has a thickness of 5 μm and the conductive layer has a thickness of 1 μm; four discs with a diameter of 3 cm are cut from random areas of the composite current collector, and the average mass is obtained after weighing to obtain M1 (18.72 mg).

[0075] S2 divides the four samples in S1 into Figure 2 The distribution method shown is set up, wherein the solvent in the container and the medium in the ultrasonic device are both water, and the sample is immersed in the solvent in a vertical state; then the four samples are ultrasonically treated simultaneously, wherein the ultrasonic power is 200 W and the ultrasonic time is 5 min; after the ultrasonic treatment, the four samples are washed with distilled water in turn and dried at 60°C, and the average mass is calculated after weighing to obtain M2 (17.39 mg).

[0076] S3 dissolves the four samples in S2 in acid (1M nitric acid solution) in turn until the Cu conductive layer is completely stripped off, then washes the four samples in turn with distilled water and dries them at 60°C. After weighing, the average mass is obtained to obtain M0 (4.91 mg).

[0077] S4 calculates the residual rate β of the sample, wherein the calculation formula is β=(M2-M0) / (M1-M0)×100%, and β is used as an evaluation index of the interface bonding strength in the composite current collector.

[0078] Example 2

[0079] The present application provides a method for testing the interfacial bonding strength in a composite current collector, comprising the following steps:

[0080] S1 provides a PET base film layer with a thickness of 5 μm; four discs with a diameter of 3 cm are cut from a random area of ​​the base film layer, and the average mass is calculated after weighing to obtain M0 (4.91 mg).

[0081] S2 provides a composite current collector, which includes a PET base film layer and a Cu conductive layer located on the surface of the base film layer, wherein the base film layer has a thickness of 5 μm and the conductive layer has a thickness of 1 μm; four discs with a diameter of 3 cm are cut from random areas of the composite current collector, and the average mass is obtained after weighing to obtain M1 (18.72 mg).

[0082] S3 takes the four samples in S2 according to Figure 2 The distribution method shown is set up, wherein the solvent in the container and the medium in the ultrasonic device are both water, and the sample is immersed in the solvent in a vertical state; then the four samples are ultrasonically treated simultaneously, wherein the ultrasonic power is 200 W and the ultrasonic time is 5 min; after the ultrasonic treatment, the four samples are washed with distilled water in turn and dried at 60°C, and the average mass is calculated after weighing to obtain M2 (17.39 mg).

[0083] S4 calculates the residual rate β of the sample, wherein the calculation formula is β=(M2-M0) / (M1-M0)×100%, and β is used as an evaluation index of the interface bonding strength in the composite current collector.

[0084] Example 3

[0085] The embodiment of the present application provides a method for testing the interfacial bonding strength in a composite current collector, which differs from Embodiment 1 only in that the solvent in the container is dimethyl carbonate.

[0086] Example 4

[0087] The embodiment of the present application provides a method for testing the interface bonding strength in a composite current collector, which differs from Example 3 only in that the composite current collector includes a PET base film layer, a base layer (made of Cr) located on the surface of the base film layer, and a Cu conductive layer located on the surface of the base layer, wherein the base film layer has a thickness of 5 μm, the base layer has a thickness of 5 nm, and the conductive layer has a thickness of 1 μm.

[0088] Example 5

[0089] The embodiment of the present application provides a method for testing the interfacial bonding strength in a composite current collector, which differs from Embodiment 4 only in that the material of the base film layer is PP.

[0090] In order to better compare the interfacial bonding strength of the composite current collectors in various embodiments, a summary is given here in the form of a table, and please refer to Table 1 for details.

[0091] Table 1

[0092] sample Residual rate β(%) Example 1 90.4 Example 2 90.4 Example 3 75.5 Example 4 85.2 Example 5 32.5

[0093] Referring to Table 1, it can be seen from the test results of Examples 1 and 3 that the interfacial bonding strengths of the composite current collector tested in different solvents are different. Therefore, a solvent commonly used in the electrolyte and with a relatively large volume share is selected as the test solvent, which can more truly reflect the interfacial bonding strength of the composite current collector during actual operation.

[0094] It can be seen from the test results of Examples 4 and 5 that the interface bonding strength obtained by the test in Example 4 is greater than the interface bonding strength obtained by the test in Example 5. The test results are consistent with the theoretical results (the surface polarity of PET material is stronger, and the bonding strength with metal is greater, while the surface polarity of PP material is weaker, and the bonding strength with metal is smaller), proving that the results of the test method provided in the examples of the present application are effective.

[0095] Test Example 1

[0096] Consistency test of test results

[0097] Test method:

[0098] The test was repeated 4 times according to the test method of Example 3, and then the average value and relative standard deviation of the residual rate were calculated. At the same time, the composite current collector in Example 3 was subjected to a peeling test using a conventional 180° peeling method (i.e., the control group), wherein the foil width was cut to 20 mm and the peeling speed was 50 mm / min. The test was repeated 4 times, and then the average value and relative standard deviation of the peeling force were calculated. The results are statistically summarized in Table 2.

[0099] Table 2

[0100] sample 1 2 3 4 average value(%) Relative standard deviation (%) Residual rate β(%) 75.5 78.4 76.7 74.3 76.2 2.3 Peel force(N) 0.55 0.46 0.53 0.67 0.55 15.8

[0101] Referring to Table 2, it can be seen from the test results of Example 3 and the control group that the interface bonding strength of the composite current collector is tested by the test method provided in the embodiment of the present application, and the relative standard deviation of the test results is only 2.3%, which is much lower than the relative standard deviation of 15.8% of the test results of the 180° peeling method, proving that the test method provided in the embodiment of the present application has the advantage of better consistency of test results.

[0102] The embodiments described above are part of the embodiments of the present application, rather than all of the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the present application for protection, but merely represents the selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present application.

Claims

1. A method for testing the interfacial bonding strength in a composite current collector, characterized in that: The composite current collector includes a base film layer and a conductive layer located on the surface of the base film layer, and the testing method includes the following steps: S1 takes a sample of the composite current collector and obtains a mass M1 of the sample; S2 immerses the sample in a solvent and performs ultrasonic treatment, obtaining a mass M2 of the sample after the ultrasonic treatment; S3 calculates the residual rate β of the sample, wherein the calculation formula is β=M2 / M1×100%, and uses the β as an evaluation index of the interface bonding strength in the composite current collector.

2. The method for testing the interfacial bonding strength in a composite current collector according to claim 1, characterized in that: In the ultrasonic treatment step, the sample is immersed in the solvent in a vertical state.

3. The method for testing the interfacial bonding strength in a composite current collector according to claim 1, characterized in that: The solvent is selected from at least one of ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate and propylene carbonate.

4. The method for testing the interfacial bonding strength in a composite current collector according to any one of claims 1 to 3, characterized in that: Before calculating the residual rate β, the method further includes obtaining the mass M0 of the base film layer in the sample, and the calculation formula of the residual rate β is β=(M2-M0) / (M1-M0)×100%.

5. The method for testing the interfacial bonding strength in a composite current collector according to claim 4, characterized in that: The step of obtaining the M0 includes: acid dissolving, washing and drying the sample after the ultrasonic treatment in sequence to obtain the base film layer, and weighing the mass of the base film layer to obtain the M0.

6. The method for testing the interfacial bonding strength in a composite current collector according to any one of claims 1 to 3, characterized in that: There are multiple samples.

7. The method for testing the interfacial bonding strength in a composite current collector according to claim 6, characterized in that: In the ultrasonic treatment step: the plurality of samples are immersed in the solvent in a vertical state, and the plurality of samples are subjected to the ultrasonic treatment synchronously by the same ultrasonic device; Optionally, the plurality of samples are distributed in the ultrasonic device at circumferential intervals, and the distances from the ultrasonic source of the ultrasonic device to the plurality of samples are the same.

8. The method for testing the interfacial bonding strength in a composite current collector according to claim 7, characterized in that: The samples are disc-shaped samples with a diameter of 2 to 4 cm, and the ultrasonic source is located at the intersection of the central axes of the samples.

9. The method for testing the interfacial bonding strength in a composite current collector according to claim 8, characterized in that: The thickness of the base film layer is 1-10 μm, and the thickness of the conductive layer is 0.1-2 μm.

10. The method for testing the interfacial bonding strength in a composite current collector according to claim 9, characterized in that: In the ultrasonic treatment step, the ultrasonic power is 100-500W, and the ultrasonic time is 1-10min.

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