A method for testing the transverse peel force of a coating on a separator

Abstract

The application provides a coated diaphragm coating lateral peeling force test method, which tests the sum of the longitudinal peeling force and the lateral peeling force of the coated diaphragm coating and the longitudinal peeling force of the coating, subtracts the longitudinal peeling force from the sum of the lateral peeling force and the longitudinal peeling force, and obtains the lateral peeling force of the coating. The application provides a test method for the lateral peeling force of the coating, which provides technical support for evaluating the powder dropping and cracking of the coating.

Description

Technical Field

[0001] This invention relates to the field of diaphragm coating testing technology, and in particular to a method for testing the lateral peel force of a coated diaphragm. Background Technology

[0002] In recent years, the use of lithium batteries has been increasing, not only because they are environmentally friendly, but also because they have advantages such as high energy storage and long lifespan. A lithium battery consists of four parts: the positive electrode, the negative electrode, the separator, and the electrolyte. The separator, located between the positive and negative electrodes, acts as an isolation barrier, allowing only lithium ions to pass through while blocking negative ions, thus preventing short circuits. However, the separator itself has poor heat resistance, so a heat-resistant layer needs to be coated on it. Performance evaluation of the heat-resistant layer often includes assessing whether the coating cracks, its wettability, and the amount of powder shedding. Powder shedding is generally characterized by peel strength. When the peel strength is too low, powder easily sheds during coating and lithium battery processing, compromising its heat resistance. Therefore, evaluating the peel strength performance of the coated separator is crucial.

[0003] In current tests of diaphragm coating peel strength, the general procedure is to attach adhesive tape to the diaphragm coating, with the tape width being smaller than the diaphragm width, and then apply tensile force to peel the diaphragm to test the peel strength. Figure 1 People often consider the peel force at this point as the peel force between the coating and the base film (i.e., longitudinal peel force, reflecting whether the coating and the diaphragm can adhere stably; when the longitudinal peel force is too small, the entire coating will detach from the diaphragm), ignoring the fact that a certain peel force is also required for the coating to tear apart (i.e., transverse peel force, reflecting whether the coatings are tightly bonded and the amount of powder falling off the coating surface; when the transverse peel force is too small, cracks easily form between the coatings, and powder easily falls off the coating surface). In reality, the peel force measured by the above method is the sum of the transverse and longitudinal peel forces. Because the transverse peel force is not considered, the peel force, which is actually the sum of the transverse and longitudinal peel forces, is directly considered as the peel force between the diaphragm coating and the base film. Current technology has not yet provided a method for testing the transverse peel force of the diaphragm coating.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] This invention verifies the existence of lateral peel force in the coated diaphragm coating and provides a test method for it, offering technical support for evaluating coating powdering and cracking properties.

[0006] The purpose of this invention is to provide a method for testing the lateral peel force of a coated diaphragm.

[0007] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0008] This invention provides a method for testing the lateral peel force of a coated diaphragm, comprising the following steps:

[0009] (1) Fix one side of the base film of the coated diaphragm sample A onto the test plate; attach a peeling tape in the center of the coated side of the coated diaphragm sample A, the width of the peeling tape being smaller than the width of the coated diaphragm sample A; apply a pulling force to the peeling tape to peel off the coating, and test the peeling force F1 of the coating;

[0010] (2) Take another coated diaphragm sample B from the same coated diaphragm, fix one side of the base film of the coated diaphragm sample B to the test plate; stick a peeling tape on the coated side of the coated diaphragm sample B, the width of the peeling tape being equal to the width of the coated diaphragm sample B; apply a pulling force to the peeling tape to peel off the coating, and test the peeling force F2 of the coating.

[0011] (3) Calculate the lateral peel force F of the membrane coating. 横向 = (F1-F2) / 2;

[0012] Alternatively, it may include the following steps:

[0013] (1') Fix one side of the base film of the coated diaphragm sample A onto the test plate; attach a peeling tape along one side of the long side of the coated diaphragm sample A, the width of the peeling tape being smaller than the width of the coated diaphragm sample A; apply a pulling force to the peeling tape to peel off the coating, and test the peeling force F3 of the coating.

[0014] (2') Take another coated diaphragm sample B from the same coated diaphragm, fix one side of the base film of the coated diaphragm sample B to the test plate; stick a release tape on the coated side of the coated diaphragm sample B, the width of the release tape being equal to the width of the coated diaphragm sample B; apply a tensile force to the release tape to peel off the coating, and test the peel force F2 of the coating.

[0015] (3') Calculate the lateral peel force F of the membrane coating. 横向 =F3-F2;

[0016] The order of steps (1) and (2) can be interchanged; the order of steps (1') and (2') can be interchanged.

[0017] Step (1)

[0018] In this step, the base film side of the diaphragm sample to be tested is first fixed on the test plate; then, a release tape is pasted in the center of the coating side of the diaphragm sample; and then a pulling force is applied to the release tape to peel off the coating and test the peel force of the coating.

[0019] The coated separator can be any battery separator with a coating layer known in the art, and there are no particular limitations on the coating layer, such as ceramic coating layer, polymer coating layer, etc.; there are also no particular limitations on the base film, which can be any material known in the art that can be used for battery separators or a separator prepared by any existing method.

[0020] The test plate can be any base plate known in the art that facilitates the attachment of test samples. The material of the test plate can be stainless steel, glass, plastic, ceramic or metal, such as stainless steel plate, glass slide, plastic plate, ceramic plate or metal plate.

[0021] In some embodiments, the base film side of the diaphragm sample is fixed to the test plate with double-sided tape. That is, the double-sided tape is first pasted on the test plate, the double-sided tape paper layer is peeled off, and the base film side of the diaphragm sample is attached to the upper surface of the double-sided tape.

[0022] There are no special restrictions on the size of the test plate and the coated diaphragm sample. Preferably, the width of the coated diaphragm sample is less than or equal to the width of the test plate and greater than or equal to the width of the double-sided tape. The length of the coated diaphragm sample is less than or equal to or greater than the length of the test plate (the part that is longer than the length of the test plate can be folded to the back of the test plate).

[0023] In some embodiments, the test plate is 10-20cm × 1-9cm in size, for example, 15cm × 5cm. The coated diaphragm sample is 10-20cm × 1-5cm in size, for example, 15cm × 3cm.

[0024] A strip of release tape, narrower than the width of the diaphragm sample, is centered on the coated side of the diaphragm sample. If the width of the release tape is narrower than the width of the diaphragm sample, the length of the release tape is equal to or greater than the length of the test plate (the excess portion is folded towards the back of the test plate).

[0025] In some implementations, the size of the release tape is 10-20cm × 1-3cm, for example, 15cm × 1.9cm.

[0026] The release tape can be any tape known in the art that can be used for peel force testing, such as 3M release tape.

[0027] In some implementations, after the release tape is applied, a rubber roller is used to roll back and forth naturally on the release tape. The width of the rubber roller can be 1-9cm, for example 5cm, and the weight of the rubber roller can be 1-5kg, for example 2kg.

[0028] Apply a tensile force to the peeling tape to peel off the coating, and test the peeling force of the coating at this time, which is recorded as F1.

[0029] There are no particular restrictions on the peeling method; any peeling method known in the art for testing peel force can be used, such as peeling with a clamp. There are no particular restrictions on the method for testing peel force; instruments commonly used in the art for testing peel force can be used, such as an electric tensile testing machine to test the peel force of the coating.

[0030] There are no particular restrictions on the peel angle; it can be any angle commonly used in peel force testing, with a preferred peel angle of 90-180°, for example, 180°.

[0031] A peel angle of 180° means that the direction of the tensile force applied to the test sample is parallel to the reference plane, with the plane where the test plate is located as the reference plane; a peel angle of 90° means that the direction of the tensile force applied to the test sample is perpendicular to the reference plane, with the plane where the test plate is located as the reference plane.

[0032] In some embodiments, after applying the release tape, the coating and the adhesive side of the release tape can be peeled off at a distance (e.g., 10-20 mm) and then folded in the opposite direction to form a free end. The folding angle is 90-180°, for example, 180°. One end of the test plate is clamped on the upper clamp (left clamp), and the free end of the release tape is clamped on the lower clamp (right clamp). Then, the electric tensile testing machine is started to perform the test.

[0033] In some implementations, step (1) specifically includes:

[0034] 1A: Take a stainless steel plate that is 15cm long and 5cm wide. Stick a double-sided tape that is 15cm long and 3cm wide in the center of the stainless steel plate, with the length and width corresponding to the stainless steel plate. Peel off the double-sided tape.

[0035] 1B: Take a coated diaphragm sample with a length of 15cm and a width of 3cm. Attach the base film side of the coated diaphragm sample to the upper surface of the double-sided adhesive, with the coated film side facing up. The length and width of the coated diaphragm sample should be aligned with the length and width of the double-sided adhesive.

[0036] 1C: Take a piece of 3M release adhesive that is 15cm long and 1.9cm wide, with the adhesive layer tightly attached to the coating layer, and place the 3M release adhesive in the center of the coated diaphragm sample;

[0037] 1D: Roll the 3M release adhesive back and forth naturally 3 times using a rubber roller. The roller is 5cm wide and weighs 2kg.

[0038] 1E: Using the 180° peel method, the peel force of the coating is tested with an electric tensile testing machine and denoted as F1. At this time, F1 = F 纵向 +2×F 横向 .

[0039] Step (2)

[0040] In this step, another coated diaphragm sample from the same coated diaphragm is taken and the base film side is fixed on the test plate; then, a release tape is pasted on the coating side of the coated diaphragm sample; and then a pulling force is applied to the release tape to peel off the coating and test the peel force of the coating.

[0041] The description of the test plate here is the same as in step (1).

[0042] In some embodiments, the base film side of the diaphragm sample is fixed to the test plate with double-sided tape. That is, the double-sided tape is first pasted on the test plate, the double-sided tape paper layer is peeled off, and the base film side of the diaphragm sample is attached to the upper surface of the double-sided tape.

[0043] There are no special restrictions on the size of the test plate and the coated diaphragm sample. Preferably, the width of the coated diaphragm sample is less than or equal to the width of the test plate and greater than or equal to the width of the double-sided tape. The length of the coated diaphragm sample is less than or equal to or greater than the length of the test plate (the part that is longer than the length of the test plate can be folded to the back of the test plate).

[0044] In some embodiments, the test plate is 10-20cm × 1-9cm in size, for example, 15cm × 5cm. The coated diaphragm sample is 10-20cm × 1-3cm in size, for example, 15cm × 1.9cm.

[0045] Apply a release tape of the same width as the diaphragm sample to the coated side of the diaphragm sample. If the width of the release tape is equal to the width of the diaphragm sample, the length of the release tape should be equal to or greater than the length of the test plate (the excess portion should be folded towards the back of the test plate).

[0046] In some implementations, the size of the release tape is 10-20cm × 1-3cm, for example, 15cm × 1.9cm.

[0047] The release tape can be any tape known in the art that can be used for peel force testing, such as 3M release tape.

[0048] In some implementations, after the release tape is applied, a rubber roller is used to roll back and forth naturally on the release tape. The width of the rubber roller can be 1-9cm, for example 5cm, and the weight of the rubber roller can be 1-5kg, for example 2kg.

[0049] Apply tension to the peeling tape to peel off the coating, and test the peeling force of the coating at this time, which is recorded as F2.

[0050] The peeling method here is the same as in step (1), and the same test conditions are maintained for steps (1) and (2).

[0051] In some implementations, step (2) specifically includes:

[0052] 2A: Take another stainless steel plate with a length of 15cm and a width of 5cm. Stick a double-sided tape with a length of 15cm and a width of 1.9cm in the center of the stainless steel plate, with the length and width corresponding to the stainless steel plate. Peel off the double-sided tape.

[0053] 2B: Take a coated diaphragm sample with a length of 15cm and a width of 1.9cm. Attach the base film side of the coated diaphragm sample to the upper surface of the double-sided adhesive, with the coated film side facing up. The length and width of the coated diaphragm sample should be aligned with the length and width of the double-sided adhesive.

[0054] 2C: Take a 15cm long × 1.9cm wide piece of 3M release adhesive, with the adhesive layer tightly attached to the coating layer, and the length and width of the 3M release adhesive should be aligned with the length and width of the coated diaphragm sample.

[0055] 2D: Roll the 3M release adhesive back and forth naturally 3 times using a rubber roller. The roller is 5cm wide and weighs 2kg.

[0056] 2E: Using the 180° peel method, the peel force of the coating is tested with an electric tensile testing machine and denoted as F2. At this time, F2 = F 纵向 .

[0057] Step (3)

[0058] In this step, the sum of the transverse peel force and longitudinal peel force (F1) tested in step (1) is subtracted from the longitudinal peel force (F2) tested in step (2) to obtain the transverse peel force of the diaphragm coating. In step (1), the coating is torn apart by the part that is stuck to the tape and the part that is not stuck. The force of this tearing is the transverse peel force. Since the situation is the same on both sides of the tape, dividing by 2 gives the single transverse peel force.

[0059] Step (1')

[0060] In this step, the base film side of the diaphragm sample to be tested is first fixed on the test plate; then, a release tape is pasted along the long side of the coating side of the diaphragm sample; and then a pulling force is applied to the release tape to peel off the coating and test the peel force of the coating.

[0061] The coated separator can be any battery separator with a coating layer known in the art, and there are no particular limitations on the coating layer, such as ceramic coating layer, polymer coating layer, etc.; there are also no particular limitations on the base film, which can be any material known in the art that can be used for battery separators or a separator prepared by any existing method.

[0062] The test plate can be any base plate known in the art that facilitates the attachment of test samples. The material of the test plate can be stainless steel, glass, plastic, ceramic or metal, such as stainless steel plate, glass slide, plastic plate, ceramic plate or metal plate.

[0063] In some embodiments, the base film side of the diaphragm sample is fixed to the test plate with double-sided tape. That is, the double-sided tape is first pasted on the test plate, the double-sided tape paper layer is peeled off, and the base film side of the diaphragm sample is attached to the upper surface of the double-sided tape.

[0064] There are no special restrictions on the size of the test plate and the coated diaphragm sample. Preferably, the width of the coated diaphragm sample is less than or equal to the width of the test plate and greater than or equal to the width of the double-sided tape. The length of the coated diaphragm sample is less than or equal to or greater than the length of the test plate (the part that is longer than the length of the test plate can be folded to the back of the test plate).

[0065] In some embodiments, the test plate is 10-20cm × 1-9cm in size, for example, 15cm × 5cm. The coated diaphragm sample is 10-20cm × 1-5cm in size, for example, 15cm × 2.5cm.

[0066] A strip of release tape with a width smaller than that of the diaphragm sample is attached to the long side of the coated side of the diaphragm sample. If the width of the release tape is smaller than that of the diaphragm sample, the length of the release tape is equal to or greater than the length of the test plate (the excess part is folded towards the back of the test plate).

[0067] In some implementations, the size of the release tape is 10-20cm × 1-3cm, for example, 15cm × 1.9cm.

[0068] The release tape can be any tape known in the art that can be used for peel force testing, such as 3M release tape.

[0069] In some implementations, after the release tape is applied, a rubber roller is used to roll back and forth naturally on the release tape. The width of the rubber roller can be 1-9cm, for example 5cm, and the weight of the rubber roller can be 1-5kg, for example 2kg.

[0070] Apply tension to the peeling tape to peel off the coating, and test the peeling force of the coating at this time, which is recorded as F3.

[0071] There are no particular restrictions on the peeling method; any peeling method known in the art for testing peel force can be used, such as peeling with a clamp. There are no particular restrictions on the method for testing peel force; instruments commonly used in the art for testing peel force can be used, such as an electric tensile testing machine to test the peel force of the coating.

[0072] There are no particular restrictions on the peel angle; it can be any angle commonly used in peel force testing, with a preferred peel angle of 90-180°, for example, 180°.

[0073] A peel angle of 180° means that the direction of the tensile force applied to the test sample is parallel to the reference plane, with the plane where the test plate is located as the reference plane; a peel angle of 90° means that the direction of the tensile force applied to the test sample is perpendicular to the reference plane, with the plane where the test plate is located as the reference plane.

[0074] In some embodiments, after applying the release tape, the coating and the adhesive side of the release tape can be peeled off at a distance (e.g., 10-20 mm) and then folded in the opposite direction to form a free end. The folding angle is 90-180°, for example, 180°. One end of the test plate is clamped on the upper clamp (left clamp), and the free end of the release tape is clamped on the lower clamp (right clamp). Then, the electric tensile testing machine is started to perform the test.

[0075] In some implementations, step (1') specifically includes:

[0076] 1'A: Take a stainless steel plate that is 15cm long and 5cm wide. Stick a piece of double-sided tape that is 15cm long and 2.5cm wide in the center of the stainless steel plate, with the length and width corresponding to the stainless steel plate. Peel off the double-sided tape.

[0077] 1'B: Take a coated diaphragm sample with a length of 15cm and a width of 2.5cm. Attach the base film side of the coated diaphragm sample to the upper surface of the double-sided adhesive, with the coated film side facing up. The length and width of the coated diaphragm sample should be aligned with the length and width of the double-sided adhesive.

[0078] 1'C: Take a piece of 3M release adhesive that is 15cm long and 1.9cm wide, with the adhesive layer tightly attached to the coating layer, and the long side of the 3M release adhesive aligned with the long side of the coated diaphragm sample.

[0079] 1'D: Roll the 3M release adhesive back and forth naturally 3 times using a rubber roller. The roller is 5cm wide and weighs 2kg.

[0080] 1'E: Using the 180° peel method, the peel force of the coating is tested with an electric tensile testing machine and denoted as F3. At this time, F3 = F 纵向 +F 横向 .

[0081] Step (2')

[0082] The relevant description of step (2) is the same as that of step (2).

[0083] Step (3')

[0084] In this step, the sum of the lateral peel force and longitudinal peel force (F1) tested in step (1') is subtracted from the longitudinal peel force (F2) tested in step (2') to obtain the lateral peel force of the membrane coating.

[0085] Beneficial effects:

[0086] This invention confirms the existence of lateral peel force between coatings of a diaphragm. By testing the sum of longitudinal and lateral peel forces of the coating and the longitudinal peel force, the lateral peel force is obtained, providing a test method for the lateral peel force of the coating and providing technical support for evaluating coating powdering, cracking, etc.

[0087] The present invention has been described in detail above; however, the above embodiments are merely illustrative in nature and are not intended to limit the invention. Furthermore, this document is not limited to the foregoing prior art or the invention itself, or to any theory described in the following embodiments.

[0088] Unless otherwise expressly stated, numerical ranges throughout the application include any subranges therein and any numerical values ​​incremented by the smallest subunit of a given value. Unless otherwise expressly stated, numerical values ​​throughout the application represent approximate measures or limitations on the range of embodiments including minor deviations from a given value and having approximately the mentioned value as well as having the mentioned precise value. Except in the detailed description of the working embodiments provided at the end, all numerical values ​​of parameters (e.g., quantities or conditions) in this application (including the appended claims) should in all cases be understood to be modified by the term “approximately,” regardless of whether “approximately” actually precedes the numerical value. “Approximately” indicates that the stated numerical value allows for slight inaccuracies (some close to precision at that value; approximately or reasonably close to the value; approximate). If the inaccuracy provided by “approximately” is not understood in this common sense in the art, then “approximately” as used herein at least indicates a variation that can be produced by common methods of measuring and using these parameters. For example, “approximately” can include variations less than or equal to 10%, less than or equal to 5%, less than or equal to 4%, less than or equal to 3%, less than or equal to 2%, less than or equal to 1%, or less than or equal to 0.5%. Attached Figure Description

[0089] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0090] Figure 1 A schematic diagram of the coating peel force F1 test in Embodiment 1 of the present invention is shown.

[0091] Figure 2 A schematic diagram of the coating peel force F2 test in Embodiment 1 of the present invention is shown.

[0092] Figure 3A schematic diagram of the coating peel force F1 test in Embodiment 1 of the present invention is shown.

[0093] Figure 4 A graph showing the relationship between the lateral peel strength of the coating and the adhesive content in an embodiment of the present invention is shown.

[0094] Illustration: 1-Stainless steel plate; 2-Double-sided adhesive; 3-Base film; 4-Coating layer; 5-Release adhesive. Detailed Implementation

[0095] The present invention will be further described below with reference to the embodiments. It should be noted that the following embodiments are provided for illustrative purposes only and do not constitute a limitation on the scope of protection of the present invention.

[0096] Unless otherwise specified, the raw materials, reagents, and methods used in the embodiments are all conventional raw materials, reagents, and methods in the art.

[0097] The 3M release adhesive is Scotch-3M600 high-grade transparent adhesive (19mm × 32.9m);

[0098] The electric tensile testing machine is the HL990-AL (Standard Version) electric tensile testing machine from Shenzhen Hengsili Measurement Instrument Co., Ltd.

[0099] Example 1

[0100] Preparation of coated diaphragm: 58 parts deionized water, 38.5 parts alumina, and 2 parts carboxymethyl cellulose (CMC) were mixed and dispersed at 1500 rpm for 120 min at room temperature. Then, 0.5 parts styrene-butadiene rubber (SBR) and 1 part wetting agent polyoxyethylene alkyl ether (Aladdin CAS No.: 68439-51-0) were added and stirred at 1000 rpm for 60 min to obtain a well dispersed slurry. The slurry was coated onto the diaphragm using microgravure technology and dried and wound to obtain the finished product. The diaphragm used was a 7μm base film from Jieli, and the coating thickness was 3μm.

[0101] Test method for lateral peel force of diaphragm coating:

[0102] Test coating peel strength F1 (e.g.) Figure 1 As shown):

[0103] Step 1: Take a stainless steel plate 1 with a length of 15cm and a width of 5cm. Stick a double-sided tape 2 with a length of 15cm and a width of 3cm in the center of the stainless steel plate 1, with the length and width corresponding to the stainless steel plate 1. Peel off the paper layer of the double-sided tape 2.

[0104] Step 2: Take the above-mentioned coated diaphragm sample with a length of 15cm and a width of 3cm, attach one side of the base film 3 of the coated diaphragm sample to the upper surface of the double-sided adhesive 2, with the coated side facing up, and the length and width of the coated diaphragm sample are aligned with the length and width of the double-sided adhesive 2.

[0105] Step 3: Take a piece of 3M release adhesive 5 that is 15cm long and 1.9cm wide, and place the adhesive layer tightly against the coating layer 4. Place the 3M release adhesive 5 in the center of the coated diaphragm sample.

[0106] Step 4: Roll the 3M release adhesive 5 back and forth naturally 3 times using a rubber roller. The rubber roller is 5cm wide and weighs 2kg.

[0107] Step 5: Using the 180° peel method, test the peel force of the coating with an electric tensile testing machine, and record it as F1. At this time, F1 = F 纵向 +2×F 横向 ;

[0108] Test coating peel strength F2 (e.g.) Figure 2 As shown):

[0109] Step 6: Take another stainless steel plate 1 with a length of 15cm and a width of 5cm. Stick a double-sided tape 2 with a length of 15cm and a width of 1.9cm in the center of the stainless steel plate 1, with the length and width corresponding to the stainless steel plate 1. Peel off the paper layer of the double-sided tape 2.

[0110] Step 7: Take a diaphragm sample with a length of 15cm and a width of 1.9cm. Attach one side of the base film 3 of the diaphragm sample to the upper surface of the double-sided adhesive 2, with the coated side facing up. The length and width of the diaphragm sample should be aligned with the length and width of the double-sided adhesive 2.

[0111] Step 8: Take a piece of 3M release adhesive 5 that is 15cm long and 1.9cm wide, and place the adhesive layer tightly against the coating layer 4. The length and width of the 3M release adhesive 5 should be aligned with the length and width of the coated diaphragm sample.

[0112] Step 9: Roll the 3M release adhesive 5 back and forth naturally 3 times using a rubber roller. The rubber roller is 5cm wide and weighs 2kg.

[0113] Step 10: Using the 180° peel method, test the peel force of the coating with an electric tensile testing machine, and record it as F2. At this time, F2 = F 纵向 ;

[0114] Step 11: Apply transverse peel force F to the diaphragm sample coating 横向 = (F1-F2) / 2.

[0115] Example 2

[0116] Preparation of coated diaphragm: 57.5 parts deionized water, 38.5 parts alumina, and 2 parts carboxymethyl cellulose (CMC) were mixed and dispersed at 1500 rpm for 120 min at room temperature using a high-speed disperser. Then, 1 part styrene-butadiene rubber (SBR) and 1 part wetting agent polyoxyethylene alkyl ether (Aladdin CAS No.: 68439-51-0) were added and stirred at 1000 rpm for 60 min to obtain a well dispersed slurry. The slurry was coated onto the diaphragm using microgravure technology and dried and wound to obtain the finished product. The diaphragm used was a 7μm base film from Jieli, and the coating thickness was 3μm.

[0117] Lateral peel force test of the coated diaphragm: The peel forces F1 and F2 of the coated diaphragm were tested according to the method in Example 1, and the results were obtained from the formula F 横向 = (F1-F2) / 2, and the lateral peel force of the coated diaphragm can be obtained.

[0118] Example 3

[0119] Separator preparation: 55.5 parts deionized water, 38.5 parts alumina, and 2 parts carboxymethyl cellulose (CMC) were mixed and dispersed at 1500 rpm for 120 min at room temperature using a high-speed disperser. Then, 3 parts styrene-butadiene rubber (SBR) and 1 part wetting agent polyoxyethylene alkyl ether (Aladdin CAS No.: 68439-51-0) were added and stirred at 1000 rpm for 60 min to obtain a well dispersed homogenate. The homogenate was coated onto the separator using microgravure technology, and the finished product was obtained after drying and winding. The separator used a 7μm base film from Jieli and the coating thickness was 3μm.

[0120] Lateral peel force test of the coated diaphragm: The peel forces F1 and F2 of the coated diaphragm were tested according to the method in Example 1, and the results were obtained from the formula F 横向 = (F1-F2) / 2, and the lateral peel force of the coated diaphragm can be obtained.

[0121] Example 4

[0122] Separator preparation: 53.5 parts deionized water, 38.5 parts alumina, and 2 parts carboxymethyl cellulose (CMC) were mixed and dispersed at 1500 rpm for 120 min at room temperature using a high-speed disperser. Then, 5 parts styrene-butadiene rubber (SBR) and 1 part wetting agent polyoxyethylene alkyl ether (Aladdin CAS No.: 68439-51-0) were added and stirred at 1000 rpm for 60 min to obtain a well dispersed slurry. The slurry was coated onto the separator using microgravure technology, and the finished product was obtained after drying and winding. The separator used a 7μm base film from Jieli and the coating thickness was 3μm.

[0123] Lateral peel force test of the coated diaphragm: The peel forces F1 and F2 of the coated diaphragm were tested according to the method in Example 1, and the results were obtained from the formula F 横向= (F1-F2) / 2, and the lateral peel force of the coated diaphragm can be obtained.

[0124] Example 5

[0125] Separator preparation: 50.5 parts deionized water, 38.5 parts alumina, and 2 parts carboxymethyl cellulose (CMC) were mixed and dispersed at 1500 rpm for 120 min at room temperature using a high-speed disperser. Then, 8 parts styrene-butadiene rubber (SBR) and 1 part wetting agent polyoxyethylene alkyl ether (Aladdin CAS No.: 68439-51-0) were added and stirred at 1000 rpm for 60 min to obtain a well dispersed slurry. The slurry was coated onto the separator using microgravure technology, and the finished product was obtained after drying and winding. The separator used a 7μm base film from Jieli and the coating thickness was 3μm.

[0126] Lateral peel force test of the coated diaphragm: The peel forces F1 and F2 of the coated diaphragm were tested according to the method in Example 1, and the results were obtained from the formula F 横向 = (F1-F2) / 2, and the lateral peel force of the coated diaphragm can be obtained.

[0127] The test results of the example are as follows:

[0128] Example glue ratio <![CDATA[F1 N / m]]> <![CDATA[F2 N / m]]> <![CDATA[F 横向 N / m]]> <![CDATA[2F 横向 N / m]]> <![CDATA[F 横向 / F1]]> <![CDATA[2F 横向 / F1]]> Example 1 0.50％ 3.45 3.06 0.20 0.39 5.7％ 11.3％ Example 2 1.00％ 8.98 7.82 0.58 1.16 6.5％ 12.9％ Example 3 3.00％ 36.87 32.69 2.09 4.18 5.7％ 11.3％ Example 4 5.00％ 63.25 57.37 2.94 5.88 4.6％ 9.3％ Example 5 8.00％ 85.43 75.08 5.18 10.35 6.1％ 12.1％

[0129] Note: Adhesive ratio refers to the proportion of adhesive (styrene-butadiene rubber) in the coating formulation.

[0130] Example 6

[0131] The peel strength F3 of the coated diaphragm coatings in Examples 1-5 were tested according to the following methods (e.g., ...). Figure 3 As shown):

[0132] (1) Take another stainless steel plate 1 with a length of 15cm and a width of 5cm. Stick a double-sided tape 2 with a length of 15cm and a width of 1.9cm in the center of the stainless steel plate 1, with the length and width corresponding to the stainless steel plate 1. Peel off the paper layer of the double-sided tape 2.

[0133] (2) Take a coated diaphragm sample with a length of 15cm and a width of 2.5cm. Place one side of the base film 3 of the coated diaphragm sample against the upper surface of the double-sided adhesive 2 with the coated side facing up. The length and width of the coated diaphragm sample should be aligned with the length and width of the double-sided adhesive 2.

[0134] (3) Take a 3M release adhesive 5 with a length of 15cm and a width of 1.9cm. The adhesive layer should be tightly attached to the coating layer 4. The long side of the 3M release adhesive 5 should be aligned with the long side of the coated diaphragm sample.

[0135] (4) Roll the rubber roller back and forth naturally 3 times on the 3M peeling adhesive 5. The width of the rubber roller is 5cm and the weight is 2kg.

[0136] (5) Using the 180° peel method, the peel force of the coating is tested with an electric tensile testing machine and recorded as F3. At this time, F3 = F 纵向 +F' 横向 (F') 横向 =F3-F 纵向 Finally, compare the F values ​​of each sample. 横向 and F' 横向 Are they the same?

[0137] The results are as follows:

[0138] Example <![CDATA[F 横向 N / m]]> <![CDATA[F3 N / m]]> <![CDATA[F' 横向 N / m]]> <![CDATA[F 横向 -F' 横向 ]]> Example 1 0.20 3.27 0.21 -0.01 Example 2 0.58 8.38 0.56 0.02 Example 3 2.09 34.83 2.14 -0.05 Example 4 2.94 60.35 2.98 -0.04 Example 5 5.18 80.21 5.13 0.05

[0139] As can be seen from the data in the examples, the peel force of the coated diaphragm does indeed include both lateral peel force and longitudinal peel force, which is consistent with previous... Figure 1 In the tests, the results are often directly regarded as the peel force between the coating and the base film, while ignoring the fact that the coating and the coating need a certain lateral peel force to be torn apart. According to the test data of this invention, the magnitude of the lateral peel force of the coating accounts for 5% to 6% of the total peel force.

[0140] Figure 4 This is a graph showing the relationship between the lateral peel strength of the coating and the adhesive content. It can be seen that the lateral peel strength of the coating is directly proportional to the adhesive content; as the amount of adhesive increases, the lateral peel strength of the coating gradually increases.

[0141] The test examples show that F 横向 Peeling force and F' 横向 The peel strength test results were essentially the same for both methods, indicating that the method used... Figure 1 and Figure 2 Combining the test results of lateral peel force and the adoption of Figure 2 and Figure 3 The results of the combined lateral peel force tests were basically the same, and the test results of both methods showed the presence of lateral peeling of the coating.

[0142] Application examples

[0143] The main coating material for lithium battery separators is high-temperature resistant material, such as alumina and boehmite. To achieve the development of ultra-thin coatings without reducing the thermal shrinkage performance of the separator, it is often necessary to reduce the particle size of the main material. This can reduce the coating thickness without affecting the unit coating weight, thus ensuring that thermal shrinkage does not deteriorate. However, while the particle size of the main material is reduced, its specific surface area also increases, and the mutual attraction between particles also increases. When the attraction between particles is greater than the lateral peel force of the coating, the coating will crack.

[0144] The above research found that the lateral peel force of the coating is directly proportional to the glue ratio. Therefore, in practical applications, while reducing the particle size of the main material, the amount of glue used in the coating should be considered. Selecting a low particle size main material while increasing the glue ratio can prevent the coating from cracking.

[0145] The above embodiments are merely illustrative of the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and substance defined by the claims of the present invention; and such modifications or substitutions are still within the scope defined by the claims of the present invention.

Claims

1. A method for testing the lateral peel force of a coated diaphragm, characterized in that, Includes the following steps: (1) Fix one side of the base film of the coated diaphragm sample A onto the test plate; attach a release tape in the center of the coated side of the coated diaphragm sample A, the width of the release tape being smaller than the width of the coated diaphragm sample A; apply a pulling force to the release tape to peel off the coating, and test the peeling force F1 of the coating; (2) Take another coated diaphragm sample B from the same coated diaphragm and fix one side of the base film of coated diaphragm sample B on the test plate; A release tape is attached to the coated side of the diaphragm sample B, the width of which is equal to the width of the coated diaphragm sample B; a tensile force is applied to the release tape to peel off the coating, and the peel force F2 of the coating is tested. (3) Calculate the lateral peel force F of the diaphragm coating. 横向 = (F1-F2) / 2; Alternatively, it may include the following steps: (1') Fix one side of the base film of the coated diaphragm sample A onto the test plate; attach a peeling tape along one side of the long side of the coated diaphragm sample A, the width of the peeling tape being smaller than the width of the coated diaphragm sample A; apply a pulling force to the peeling tape to peel off the coating, and test the peeling force F3 of the coating. (2') Take another coated diaphragm sample B from the same coated diaphragm, fix one side of the base film of the coated diaphragm sample B to the test plate; stick a peeling tape on the coated side of the coated diaphragm sample B, the width of the peeling tape being equal to the width of the coated diaphragm sample B; apply a pulling force to the peeling tape to peel off the coating, and test the peeling force F2 of the coating. (3') Calculate the lateral peel force F of the diaphragm coating. 横向 =F3-F2; The order of steps (1) and (2) can be interchanged; the order of steps (1') and (2') can be interchanged; The lateral peel force refers to the peel force required to tear the coating apart.

2. The method according to claim 1, characterized in that, In step (1) or step (1'), one side of the base film of the coated diaphragm sample A is fixed to the test plate with double-sided adhesive. In step (2) or step (2'), one side of the base film of the coated diaphragm sample B is fixed to the test plate with double-sided adhesive.

3. The method according to claim 1, characterized in that, In step (1), the size of the test plate is 10-20cm × 1-9cm; the size of the coated diaphragm sample A is 10-20cm × 1-5cm; and the size of the peeling tape is 10-20cm × 1-3cm. In step (1'), the size of the test plate is 10-20cm×1-9cm; the size of the coated diaphragm sample A is 10-20cm×1-5cm; and the size of the peeling tape is 10-20cm×1-3cm.

4. The method according to claim 1, characterized in that, In step (1), the size of the test plate is 15cm × 5cm; the size of the coated diaphragm sample A is 15cm × 3cm; and the size of the peeling tape is 15cm × 1.9cm. In step (1'), the test plate is 15cm×5cm in size; the coated diaphragm sample A is 15cm×2.5cm in size; and the peeling tape is 15cm×1.9cm in size.

5. The method according to claim 1, characterized in that, In step (2) or step (2'), the size of the test plate is 10-20cm×1-9cm; the size of the coated diaphragm sample B is 10-20cm×1-3cm; and the size of the peeling tape is 10-20cm×1-3cm.

6. The method according to claim 1, characterized in that, In step (2) or step (2'), the size of the test plate is 15cm×5cm; the size of the coated diaphragm sample B is 15cm×1.9cm; and the size of the peeling tape is 15cm×1.9cm.

7. The method according to claim 1, characterized in that, In step (1) or step (1'), after applying the release tape to the coated side of the diaphragm sample A, use a roller to roll back and forth naturally on the release tape. In step (2) or step (2'), after applying the release tape to the coated side of the diaphragm sample B, a roller is used to roll back and forth naturally on the release tape.

8. The method according to claim 7, characterized in that, The width of the rubber roller is 1-9cm, and the weight is 1-5kg.

9. The method according to claim 8, characterized in that, The width of the rubber roller is 5cm and its weight is 2kg.

10. The method according to claim 1, characterized in that, In steps (1) and (2), the peeling angle of the peeling coating is 90-180°; In steps (1') and (2'), the peeling angle of the peeling coating is 90-180°.

11. The method according to claim 1, characterized in that, In steps (1) and (2), the peel force of the coating is tested using an electric tensile testing machine; Alternatively, in steps (1') and (2'), an electric tensile testing machine is used to test the peel strength of the coating.

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