Method for testing wet adhesive force of diaphragm
By directly preparing the separator and electrode sheet after they have been soaked in electrolyte as an electrode assembly and then conducting a peel strength test, the problem of complex and unstable wet adhesion performance evaluation of the separator and electrode sheet in the prior art has been solved, and the effects of simplifying the process, reducing costs and improving stability have been achieved.
Patent Information
- Application Number
- CN202511547360.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-27
- Publication Date
- 2026-01-23
AI Technical Summary
Existing technologies for evaluating the wet adhesion performance of lithium-ion battery separators and electrodes are complex, time-consuming, and yield unstable results, making it impossible to systematically evaluate the interface performance of the separator-electrode after immersion in electrolyte.
The separator and electrode sheet after being impregnated with electrolyte are directly prepared as electrode components. The wet adhesion force is evaluated by peel strength test, which simplifies the test process, reduces variable factors, and simulates the wet adhesion performance in the battery cell.
It simplifies the testing process, shortens the testing cycle, reduces costs, improves the stability and repeatability of the test, and enables better evaluation of the wet adhesion performance of the separator in the battery cell.
Smart Images
Figure CN121384783A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of diaphragm performance testing technology, and more specifically to a method for testing the wet adhesion of diaphragms. Background Technology
[0002] Lithium-ion batteries are among the most widely used rechargeable batteries. A lithium-ion battery is a rechargeable battery that uses lithium ions as the charge carrier. Charging and discharging are achieved through the insertion and extraction of lithium ions between the positive and negative electrodes. It has advantages such as high energy density and long cycle life. A lithium-ion battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator.
[0003] In lithium-ion battery manufacturing, the adhesion force (also known as peel force) between the separator and the electrode is a key parameter affecting battery performance and safety. Currently, the adhesion force between the separator and the electrode is usually tested in the absence of electrolyte, which cannot systematically evaluate the separator-electrode interface performance (also known as wet adhesion performance) after immersion in electrolyte. Existing wet adhesion performance testing involves stacking or winding the positive / negative electrode and separator into a cell according to actual battery manufacturing processes, adding electrolyte to fully immerse the cell, applying pressure, and finally disassembling the electrode assembly for testing. This method is complex, cumbersome, and time-consuming. Furthermore, the test results obtained using this method vary considerably and cannot accurately characterize the wet adhesion performance of the separator. Summary of the Invention
[0004] This application provides a test method for the wet adhesion of a diaphragm, which can improve the accuracy and efficiency of the wet adhesion performance test of the diaphragm, and has the advantages of good stability and repeatability.
[0005] This application provides a method for testing the wet adhesion of a diaphragm, the steps of which include: The diaphragm and the electrode are respectively immersed in a container containing electrolyte, so that the diaphragm and the electrode are completely wetted in the electrolyte; The diaphragm and the electrode sheet, after being soaked in the electrolyte, are stacked in sequence to assemble an electrode assembly; The electrode assembly is subjected to a peel strength test to obtain the wet adhesion between the diaphragm and the electrode sheet.
[0006] In some optional embodiments, immersing the diaphragm and the electrode in a container filled with electrolyte, so that the diaphragm and the electrode are completely immersed in the electrolyte, includes sealing the container after immersing the diaphragm and the electrode in the electrolyte.
[0007] In some optional embodiments, immersing the diaphragm and the electrode in a container of electrolyte to completely wet the diaphragm and the electrode includes immersing the diaphragm and the electrode in the electrolyte for a preset time to allow the electrolyte to fully penetrate and fill the diaphragm and the space between the diaphragm and the electrode.
[0008] In some optional embodiments, the preset time is 0h-24h.
[0009] In some alternative embodiments, the step of sequentially stacking the separator and the electrode after it has been wetted in the electrolyte to assemble an electrode assembly includes assembling the separator and the electrode by hot pressing.
[0010] In some optional embodiments, the hot pressing method satisfies at least one of the following conditions (1)-(3): (1) The pressing temperature of the hot pressing method is in the range of 25℃-100℃; (2) The pressing pressure of the hot pressing method is in the range of 0.5MPa-10MPa; (3) The pressing time of the hot pressing method is 0.5min-10min.
[0011] In some optional embodiments, the process of stacking the diaphragm and the electrode in sequence after they have been wetted in the electrolyte to assemble an electrode assembly further includes providing an isolation layer on both the side of the diaphragm facing away from the electrode and the side of the electrode facing away from the diaphragm.
[0012] In some alternative embodiments, the insulating layer includes a Teflon sheet, release paper, plain paper, coated paper, or cardboard.
[0013] In some alternative embodiments, the peel strength test of the electrode assembly includes using a pressure-sensitive tape peel test method.
[0014] In some alternative embodiments, when performing peel strength tests on the electrode assemblies, at least two data points are tested for each electrode assembly.
[0015] The beneficial effects of this application are as follows: Electrodes and separators, after being impregnated with electrolyte, are directly fabricated as electrode assemblies. Then, peel strength tests are performed on these electrode assemblies to characterize the wet adhesion between the separator and the electrode. This eliminates the need to fabricate the electrode and separator into a battery cell and then disassemble the electrode assembly for testing. It avoids the entire battery cell production process and disassembly, simplifying the testing process, significantly shortening the testing cycle, and reducing costs. The operation is simple, and due to the reduction in testing processes, fewer variable factors are introduced. Process parameters such as those for the electrode and separator can be fixed individually, and only the target variable can be changed to directly evaluate the impact of a single variable on the test results. This avoids the influence of battery cell fabrication process variables on the test results, thereby improving the stability and repeatability of the test structure and better simulating the wet adhesion performance of the separator in the battery cell. Attached Figure Description
[0016] Figure 1 This is a schematic flowchart of a method for testing the wet adhesion of a diaphragm in one embodiment. Detailed Implementation
[0017] The present application will now be described in further detail with reference to the accompanying drawings and specific embodiments. Similar elements in different embodiments are referred to by related similar element reference numerals. In the following embodiments, many details are described to facilitate a better understanding of the present application. However, those skilled in the art will readily recognize that some features may be omitted in different situations, or may be replaced by other elements, materials, or methods. In some cases, certain operations related to the present application are not shown or described in the specification. This is to avoid obscuring the core parts of the present application with excessive description. For those skilled in the art, detailed description of these related operations is not necessary; they can fully understand the related operations based on the description in the specification and general technical knowledge in the art.
[0018] Furthermore, the features, operations, or characteristics described in the specification can be combined in any suitable manner to form various embodiments, and the operational steps involved in each embodiment can also be rearranged or adjusted in a manner that is obvious to those skilled in the art. Therefore, the specification and drawings are only for clearly describing a particular embodiment and do not imply that they represent the necessary components and / or order.
[0019] The serial numbers assigned to components in this document, such as "first" and "second," are used only to distinguish the described objects and have no sequential or technical meaning. The terms "connection" and "linkage" used in this application, unless otherwise specified, include both direct and indirect connections (linkages).
[0020] The separator is an important component in a battery. It is placed between the positive and negative electrodes to enable ion transport and migration, allowing the battery to function properly.
[0021] In lithium-ion battery manufacturing, the adhesion force (also known as peel force) between the separator and the electrode is a key parameter affecting battery performance and safety. Currently, the adhesion force between the separator and the electrode is usually tested in the absence of electrolyte, which cannot systematically evaluate the interface performance (also known as wet adhesion performance) of the separator-electrode after immersion in electrolyte. Existing wet adhesion performance testing involves stacking or winding the positive or negative electrode and the separator into a cell according to the actual battery manufacturing process, adding electrolyte to fully immerse the cell, applying pressure, and finally disassembling the electrode assembly (including the separator and electrode) from the cell for testing. This method involves first preparing the cell and then disassembling the electrode assembly as a test sample. This process is complex, cumbersome, and time-consuming, affecting the efficiency of separator wet adhesion force testing. Furthermore, the preparation of this test sample involves many variables (such as the process parameters for cell pressurization and the process parameters for disassembling the electrode assembly), which not only increases the workload but also leads to significant differences in test results, affecting the stability of the test results.
[0022] This application provides a method for testing the wet adhesion of a separator. The testing steps include directly preparing an electrode assembly from an electrode sheet and a separator after impregnation with electrolyte, and then performing a peel strength test on the electrode assembly to characterize the wet adhesion between the separator and the electrode sheet. This method eliminates the need to prepare the electrode sheet and separator into a battery cell and then disassemble the electrode assembly for testing. It avoids the need for the complete battery cell production process (such as electrolyte injection, encapsulation, formation, and aging) and disassembly, simplifying the testing process, significantly shortening the testing cycle, and reducing costs. The method is easy to operate, and due to the reduction in testing processes, fewer variable factors are introduced. Parameters such as electrode sheet (e.g., type of active material, coating thickness, compaction density) and separator (e.g., material, pore size, thickness) can be fixed individually, and only the target variable (e.g., amount of binder, separator coating type) can be changed. This allows for direct evaluation of the impact of a single variable on the test results, avoiding the influence of battery cell manufacturing process variables on the test results. This improves the stability and repeatability of the test structure, better simulating the wet adhesion performance of the separator in the battery cell. The test method of this application can be used to simulate the wet adhesion performance of secondary battery cells such as lithium-ion batteries and sodium-ion batteries.
[0023] Please see Figure 1 The steps of the test method for the wet adhesion of the diaphragm include: S101: Place the diaphragm and the electrode in a container filled with electrolyte, so that the diaphragm and the electrode are completely immersed in the electrolyte.
[0024] In some embodiments, the diaphragm and the electrode can be placed simultaneously in the same container filled with electrolyte, and the electrolyte level is higher than the top of the diaphragm and the electrode, so that the diaphragm and the electrode are completely immersed in the electrolyte, thereby ensuring that the diaphragm and the electrode are in full contact with the electrolyte.
[0025] In some embodiments, after the diaphragm and electrode are immersed in the electrolyte, the container is sealed to prevent electrolyte evaporation or contamination. For example, plastic wrap or other airtight and liquid-impermeable materials are used to seal the openings of the container that come into contact with the outside environment, preventing electrolyte evaporation or contamination during immersion and thus avoiding affecting the accuracy of the test results.
[0026] In some embodiments, the diaphragm and the electrode are immersed in the electrolyte for a preset time, so that the electrolyte can fully penetrate and fill the pores of the diaphragm and the surface and internal structure of the electrode.
[0027] In some embodiments, the preset time is 0h-24h. For example, the preset time can be 1min-24h. Specifically, the preset time can be 1min, 30min, 1h, 2h, 4h, 6h, 8h, 10h, 12h, 14h, 16h, 18h, 20h, 22h, or 24h, or any two of the above values. Because the diaphragm and electrode are easily wetted by the electrolyte, during testing, the diaphragm and electrode can be placed in the container and immediately removed, i.e., almost no soaking; this soaking time can then be counted as 0h.
[0028] S102: Stack the diaphragm and electrode sheet soaked in electrolyte in step S101 in sequence to assemble an electrode assembly.
[0029] In some embodiments, the separator and electrode are stacked and assembled by hot pressing to simulate the actual bonding state of the battery electrode assembly. Specifically, a certain temperature and pressure are applied to the electrode and separator using a hot press, and after a certain pressing time, the separator and electrode are bonded together to form an electrode assembly. During hot pressing, the hot pressing parameters (including pressing temperature, pressing pressure, and pressing time) can be changed to test the peel strength between the separator and electrode under different conditions. This can also be used to verify the adaptability of the test method of this application, that is, to verify whether the test method is suitable for various cell manufacturing parameters by changing the hot pressing parameters.
[0030] In some embodiments, the pressing temperature of the hot pressing method is 25°C-100°C. For example, the pressing temperature can be 25°C, 50°C, 75°C or 100°C, or any two of the above values.
[0031] In some embodiments, the pressing pressure of the hot pressing method is 0.5MPa-10MPa. For example, the pressing pressure can be 0.5MPa, 1MPa, 2MPa, 3MPa, 4MPa, 5MPa, 6MPa, 7MPa, 8MPa, 9MPa or 10MPa, or any two of the above values.
[0032] In some embodiments, the pressing time of the hot pressing method is 0.5 min to 10 min. For example, the pressing pressure can be 0.5 min, 1 min, 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min or 10 min, or any two of the above values.
[0033] In some embodiments, during the fabrication of the electrode assembly, an isolation layer is provided on both the side of the diaphragm away from the electrode and the side of the electrode away from the diaphragm. The isolation layer is used to prevent the diaphragm or electrode from directly contacting the hot pressing device during the hot pressing process, thereby protecting the electrode and the hot pressing equipment, and ensuring the accuracy and consistency of the adhesion test results.
[0034] In some embodiments, the release layer is a Teflon sheet, release paper, plain paper, coated paper, or cardboard. For example, the release layer can be made of A4 paper (i.e., commonly used A4 paper) made of plain paper, coated paper, cardboard, or other materials. Using A4 paper as the release layer has the advantages of readily available materials and low cost.
[0035] S103: Perform a peel strength test on the electrode assembly to characterize the wet adhesion between the diaphragm and the electrode sheet.
[0036] In some embodiments, the peel strength test adopts the pressure-sensitive adhesive tape peel test method, which is as follows: the pressure-sensitive adhesive tape is attached to the outer surface of the electrode assembly, and the diaphragm is separated from the electrode by peeling off the pressure-sensitive adhesive tape. The change in force during the peeling process is recorded to calculate the peel strength.
[0037] In some embodiments, when performing peel strength tests on electrode assemblies, at least two data points are tested for each electrode assembly. This can also be understood as performing at least two parallel tests on the same electrode assembly, and finally taking the average of the test results as the final characterization data to reduce test errors. For example, three or more parallel tests can be performed on the same electrode assembly.
[0038] The testing method of this application will be further described in detail below with specific embodiments and comparative examples. It should be noted that the embodiments and comparative examples provided in this application are only for further illustration and should not be construed as limiting this application. In these embodiments and comparative examples, unless otherwise specified, the reagents and instruments used are all commercially available, and the experimental operations are all performed in accordance with the product instructions and conventional experimental procedures.
[0039] Example 1
[0040] PVDF (polyvinylidene fluoride) sprayed film (PVDF melting point 140℃-160℃) was cut into 20mm×200mm strips, and the positive electrode was cut into 20mm×80mm strips. They were immersed in electrolyte and completely wetted for 1 minute. They were then stacked and assembled in the manner of A4 paper / separator / electrode / A4 paper. They were pressed at 25℃ and 0.5MPa for 0.5 minutes. The peel strength between the separator and the electrode was then tested using the pressure-sensitive adhesive tape peel test method. Each electrode assembly was tested in parallel three times.
[0041] Examples 2 to 20 Examples 2 to 20 are carried out with reference to Example 1, with differences shown in Table 1. The differences include electrolyte soaking time, pressing temperature, pressing time and pressing pressure of hot pressing method. The specific process parameters of each example are shown in Table 1.
[0042] Table 1 Parameter conditions corresponding to the embodiments Table 1 Parameter conditions corresponding to the embodiments
[0043] Comparative Example 1 The traditional soft-pack battery assembly method is adopted, with positive and negative electrode sheets and separators stacked alternately (coated side facing the positive electrode), and then semi-heat-sealed with aluminum-plastic film. After injecting electrolyte in a glove box, it is completely sealed and pressed at 100℃ and 9.5MPa for 10 minutes. Then the cell is disassembled and the electrode assembly is taken out. The peel strength between the separator and the electrode sheet is tested by the pressure-sensitive adhesive tape peel test method. The electrode assembly is tested in parallel three times.
[0044] The test results are shown in Table 2.
[0045] Table 2. Diaphragm wet adhesion test data
[0046] Examples 1 to 4 compare the wet tack strength of the diaphragm under different pressing temperatures. Since the boiling point of the organic solvent in the electrolyte is around 90°C, there will be electrolyte loss on the surface of the diaphragm and electrode when the pressing temperature is 100°C. Table 2 shows that the wet tack strength increases significantly with increasing pressing temperature.
[0047] Examples 4 to 8 compare the wet adhesion strength of the diaphragm under different pressing pressure conditions. As can be seen from Table 2, the wet adhesion strength gradually increases with the increase of pressing pressure.
[0048] Examples 8 to 13 compare the wet adhesion strength of the diaphragm under different pressing time conditions. As can be seen from Table 2, the wet adhesion strength gradually increases with the increase of pressing time.
[0049] Examples 13 to 20 compare the wet adhesion strength of the diaphragm and electrode under different immersion times in the electrolyte. As can be seen from Table 2, the wet adhesion strength decreases significantly with increasing immersion time. This is because after the diaphragm is immersed in the electrolyte for a long time, organic solvents (such as DMC, EC, etc.) will penetrate the polymer containing high molecular chains in the coating, resulting in polymer swelling. When the swollen diaphragm is hot-pressed, the material rigidity decreases, resulting in lower density or mechanical strength than the un-immersed diaphragm.
[0050] By comparing Examples 4 to 20 with Comparative Example 1, it can be seen that the stability among the multiple test data of this application is good, indicating that the test method of this application can better simulate the wet adhesion performance of the separator in the battery cell.
[0051] The above examples illustrate this application only to aid understanding and are not intended to limit its scope. Those skilled in the art to which this application pertains can make various simple deductions, modifications, or substitutions based on the ideas presented.
Claims
1. A method for testing the wet adhesion of a diaphragm, characterized in that, The steps include: The diaphragm and the electrode are respectively immersed in a container containing electrolyte, so that the diaphragm and the electrode are completely wetted in the electrolyte; The diaphragm and the electrode sheet, after being soaked in the electrolyte, are stacked in sequence to assemble an electrode assembly; The electrode assembly is subjected to a peel strength test to obtain the wet adhesion between the diaphragm and the electrode sheet.
2. The method for testing the wet adhesion of the diaphragm according to claim 1, characterized in that, The step of immersing the diaphragm and the electrode in a container filled with electrolyte, so that the diaphragm and the electrode are completely immersed in the electrolyte, includes sealing the container after immersing the diaphragm and the electrode in the electrolyte.
3. The method for testing the wet adhesion of the diaphragm according to claim 1 or 2, characterized in that, The step of immersing the diaphragm and the electrode in a container filled with electrolyte, so that the diaphragm and the electrode are completely immersed in the electrolyte, includes immersing the diaphragm and the electrode in the electrolyte for a preset time, so that the electrolyte can fully penetrate and fill the diaphragm and the space between the diaphragm and the electrode.
4. The method for testing the wet adhesion of the diaphragm according to claim 3, characterized in that, The preset time is 0h-24h.
5. The method for testing the wet adhesion of a diaphragm according to claim 1, characterized in that, The step of stacking the diaphragm and the electrode sheet sequentially after they have been soaked in the electrolyte to assemble an electrode assembly includes assembling the diaphragm and the electrode sheet by hot pressing.
6. The method for testing the wet adhesion of a diaphragm according to claim 5, characterized in that, The hot pressing method satisfies at least one of the following conditions (1)-(3): (1) The pressing temperature of the hot pressing method is in the range of 25℃-100℃; (2) The pressing pressure of the hot pressing method is in the range of 0.5MPa-10MPa; (3) The pressing time of the hot pressing method is 0.5min-10min.
7. The method for testing the wet adhesion of a diaphragm according to claim 5, characterized in that, The method of stacking the diaphragm and the electrode after it has been soaked in the electrolyte to assemble the electrode assembly further includes providing an isolation layer on the side of the diaphragm away from the electrode and on the side of the electrode away from the diaphragm.
8. The method for testing the wet adhesion of a diaphragm according to claim 7, characterized in that, The isolation layer includes Teflon board, release paper, ordinary paper, coated paper, or cardboard.
9. The method for testing the wet adhesion of a diaphragm according to claim 1, characterized in that, The peel strength test of the electrode assembly includes the use of a pressure-sensitive tape peel test method.
10. The method for testing the wet adhesion of a diaphragm according to claim 9, characterized in that, When performing a peel strength test on the electrode assembly, at least two data points are tested for each electrode assembly.