Adhesive tape with multi-layer structure and secondary battery applying adhesive tape

Abstract

The utility model discloses an adhesive tape with a multi-layer structure. The adhesive tape comprises a first adhesive layer, a first base material layer, a functional layer, a second base material layer and a second adhesive layer which are compounded in sequence, the functional layer meets the condition that after the functional layer is soaked in an organic acid ester solution at 85 DEG C for 4 hours, the retention rate of stripping force between the functional layer and the first base material layer and between the functional layer and the second base material layer does not exceed 80%; the thickness of the functional layer is 0.1 [mu] m-3 [mu] m. The utility model further discloses a secondary battery which comprises a battery cell, a packaging film / packaging shell and the multi-layer structure adhesive tape, the packaging film / packaging shell wraps the battery cell, and the multi-layer structure adhesive tape is attached between the battery cell and the packaging film. When the battery is formed, the functional layer is soaked in an electrolyte to swell, and the viscosity is quickly reduced or completely lost, so that the first base material layer and the second base material layer on the two sides of the functional layer are loosened. Through the structural design mode, when the secondary battery attached with the multi-layer structure adhesive tape falls off, the first base material layer is attached to the battery cell through the first adhesive layer, the second base material layer is attached to the packaging film / packaging shell through the second adhesive layer, and the battery cell is not subjected to the dragging action force of the packaging film / packaging shell when falling off; therefore, the phenomena of edge breakage, tearing or aluminum foil tearing and the like of the bonding surface of the battery cell are avoided, and the anti-falling performance of the secondary battery is improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of adhesive tape, especially to a multilayer structure adhesive tape and secondary battery using the same. BACKGROUND

[0002] Lithium ion batteries have the characteristics of high working voltage, high energy density, small self-discharge, multiple cycle use, long service life and high environmental protection, and are widely used in mobile phones, automobiles, notebooks and other fields. In the existing lithium ion battery products, the battery pole group and the battery pole group outer packaging film are generally bonded by double-sided adhesive tape to achieve relative fixation. Generally speaking, the battery pole group outer packaging film mainly selects aluminum plastic film, and the bonding surface of the battery pole group is aluminum foil or polyethylene diaphragm. The toughness and strength of the aluminum plastic film are obviously higher than those of the bonding surface of the battery pole group. Therefore, during the falling process of the lithium ion battery product, the pulling force exerted by the aluminum plastic film on the double-sided adhesive tape is greater than the pulling force exerted by the bonding surface of the battery pole group on the double-sided adhesive tape. The difference between the above-mentioned pulling forces easily leads to the edge collapse and tearing of the side of the double-sided adhesive tape bonded to the bonding surface of the battery pole group. In more stringent drop tests, there is even an aluminum foil tearing phenomenon, which adversely affects the drop resistance of the lithium ion battery.

[0003] With the development of science and technology, the requirements for lithium ion batteries in various fields are becoming higher and higher. The stability and safety of lithium ion batteries are the performance indicators that the industry focuses on. The drop resistance of lithium ion batteries determines the stability and safety of lithium ion batteries. Improving the drop resistance of lithium ion batteries has a significant effect on further optimizing the stability and safety of lithium ion batteries. SUMMARY

[0004] In order to improve the drop resistance of the secondary battery, the utility model provides a multilayer structure adhesive tape and secondary battery using the same.

[0005] According to the first aspect of the utility model, a multilayer structure adhesive tape is provided, which comprises a first adhesive layer, a first substrate layer, a functional layer, a second substrate layer and a second adhesive layer which are sequentially compounded. The functional layer satisfies that the peel strength retention rate between the functional layer and the first substrate layer and the second substrate layer is not more than 80% after being soaked in an organic acid ester solution at 85℃ for 4 hours. The thickness of the functional layer is 0.1-3μm.

[0006] In the multilayer structure adhesive tape, the functional layer is designed as a tacky-loss adhesive layer structure which has a rapid tackiness reduction or a complete tackiness loss under the immersion of electrolyte. When the multilayer structure adhesive tape is attached between the electrode core and the packaging film (such as an aluminum plastic film) / packaging shell (such as a steel shell) of a secondary battery using an organic acid ester solvent as electrolyte, the electrode core and the packaging film / packaging shell are attached by the first adhesive layer and the second adhesive layer respectively, and the functional layer swells and has a rapid tackiness reduction or a complete tackiness loss due to the immersion of electrolyte during the formation of the battery, so that the first substrate layer and the second substrate layer on both sides of the functional layer are released. More specifically, when the electrolyte is immersed, the functional layer swells, and when the swelling ratio reaches a certain degree, the peeling force between the functional layer and the first substrate layer and between the functional layer and the second substrate layer decreases significantly, resulting in the release between each other.

[0007] Further, the functional layer is designed based on the peeling force retention rate between the functional layer and the first substrate layer and the second substrate layer before and after swelling and the thickness of the functional layer, which can ensure that the tacky-loss layer can provide sufficient bonding force to the first substrate layer and the second substrate layer, maintain the storage stability of the multilayer structure adhesive tape, and also ensure that the functional layer can fully lose tackiness after being immersed in electrolyte using an organic acid ester solvent. Based on this, when the secondary battery attached with the multilayer structure adhesive tape falls, the first substrate layer is attached to the electrode core through the first adhesive layer, and the second substrate layer is attached to the packaging film / packaging shell through the second adhesive layer. Since the first substrate layer and the second substrate layer are released, the force of the electrode core on the first substrate layer and the force of the packaging film / packaging shell on the second substrate layer do not interfere with each other, and the electrode core is not affected by the pulling force of the packaging film / packaging shell when falling, thereby avoiding the phenomena of edge collapse, tearing or aluminum foil tearing of the bonding surface of the electrode core and the multilayer structure adhesive tape, and improving the drop resistance of the secondary battery.

[0008] Preferably, the functional layer satisfies that the 180° peeling force between the functional layer and the first substrate layer and between the functional layer and the second substrate layer is not more than 0.03 N / mm after being immersed in an organic acid ester solution at 85℃ for 4 hours.

[0009] Preferably, the first adhesive layer is a pressure-sensitive adhesive layer.

[0010] Preferably, the 180° peeling force between the first adhesive layer and the first substrate layer is not less than 0.03 N / mm.

[0011] Through the above structural design, when the swelling ratio of the functional layer reaches a certain degree, the peeling force between the functional layer and the first substrate layer decreases significantly and is released, but the peeling force between the first adhesive layer and the first substrate layer remains good to ensure that the two are still stably attached. Thus, the battery cell is not subjected to the pulling force of the packaging film / packaging shell due to the release of the first substrate layer and the functional layer, and the first substrate layer can still be attached to the surface of the battery cell through the first adhesive layer. Further, for the U-shaped adhesive method, the U-shaped first substrate layer can also support the battery cell to a certain extent.

[0012] Preferably, the 180° peeling force between the first adhesive layer and the first substrate layer is not less than 0.05 N / mm.

[0013] Preferably, the thickness of the first adhesive layer is 2-4 μm. The thickness of the first adhesive layer can be 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, etc., but is not limited to the listed values, and other values not listed in this range are also applicable.

[0014] Preferably, the second adhesive layer is a heat-sensitive adhesive layer.

[0015] Preferably, after heat pressing, the 180° peeling force between the second adhesive layer and the first substrate layer is not less than 0.1 N / mm.

[0016] Through the above structural design, when the swelling ratio of the functional layer reaches a certain degree, the peeling force between the functional layer and the second substrate layer decreases significantly and is released, but the peeling force between the second adhesive layer and the second substrate layer remains good to ensure that the two are still stably attached. Thus, the packaging film / packaging shell does not exert a pulling force on the battery cell due to the release of the second substrate layer and the functional layer, and the second substrate layer can still be attached to the surface of the packaging film through the second adhesive layer.

[0017] Preferably, the thickness of the second adhesive layer is 3-6 μm. The thickness of the second adhesive layer can be 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, etc., but is not limited to the listed values, and other values not listed in this range are also applicable.

[0018] Preferably, the first substrate layer and the second substrate layer are independently selected from a PET (polyethylene terephthalate) film or a PI (polyimide) film or a PP (polypropylene) film.

[0019] Preferably, the thickness of the multi-layer structure adhesive tape is 8-25 μm. The thickness of the multi-layer structure adhesive tape can be 8 μm, 11 μm, 14 μm, 17 μm, 20 μm, 23 μm, 26 μm, 29 μm, 33 μm, etc., but is not limited to the listed values, and other values not listed in this range are also applicable.

[0020] According to the second aspect of the utility model, a secondary battery is provided, which comprises a battery cell, a packaging film / packaging shell and the multilayer structure adhesive tape as above, the packaging film / packaging shell wraps the battery cell, and the multilayer structure adhesive tape is attached between the battery cell and the packaging film.

[0021] Preferably, the battery cell comprises a first surface and a second surface arranged oppositely, the multilayer structure adhesive tape is attached at the edge position of the battery cell, and the first adhesive layer simultaneously adheres to the first surface and the second surface, so that the multilayer structure adhesive tape forms a U-shaped wrapping around the edge of the battery cell.

[0022] In the above-mentioned secondary battery, the multilayer structure adhesive tape is continuously attached to the first surface and the second surface of the battery cell at the edge position of the battery cell and forms a U-shaped wrapping, and when the battery is formed, the second adhesive layer of the multilayer structure adhesive tape attached to the surface of the battery cell releases adhesion after heat pressing, so as to be bonded to the packaging film / packaging shell. The functional layer swells and loses adhesion after being soaked in electrolyte when the battery is formed, causing the first substrate layer and the second substrate layer on both sides to be loose, and the first substrate layer can still be bonded to the surface of the battery cell through the first adhesive layer. The multilayer structure adhesive tape forms a U-shaped limiting structure at the edge of the battery cell, which can better support and buffer the falling process of the battery cell, prevent the phenomenon of edge collapse, tearing or aluminum foil tearing of the aluminum-plastic film and aluminum foil due to the difference in traction force of the double-sided adhesive tape, improve the anti-falling performance of the battery cell, and further prevent the occurrence of battery short circuit and fire.

[0023] In summary, compared with the method of attaching double-sided adhesive tape to the battery cell in the traditional lithium ion battery, the multilayer structure adhesive tape of the present application forms a U-shaped wrapping around the edge of the battery cell and is continuously attached to the first surface and the second surface of the battery cell, which can simultaneously play the dual roles of adhering to the packaging film / packaging shell and fixing the battery cell, thereby achieving the purposes of reducing the adhesive process and improving the production efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 It is a schematic diagram of the interlayer structure of the multilayer structure adhesive tape of the utility model;

[0025] Figure 2 It is a schematic diagram of the structure of the secondary battery of Preparation Example 1;

[0026] Figure 3 It is a schematic diagram of the structure of the secondary battery of Preparation Example 2;

[0027] Figure 4 It is another schematic diagram of the structure of the secondary battery of Preparation Example 2;

[0028] Figure 5 It is a schematic diagram of the multilayer structure adhesive tape forming a U-shaped wrapping around the edge of the battery cell in the secondary battery of Preparation Example 2.

[0029] In the drawings, the meanings of the reference signs are as follows:

[0030] 1, cell; 11, first surface; 12, second surface;

[0031] 2, multilayer structure adhesive tape; 21, first adhesive layer; 22, first substrate layer; 23, functional layer; 24, second substrate layer; 25, second adhesive layer;

[0032] 3, protective adhesive tape. DETAILED DESCRIPTION

[0033] In order to better understand and implement, the technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the drawings in the embodiments of the present application.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terminology used in the description of the present application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application.

[0035] Example 1

[0036] Referring to Figure 1 As shown in the figure, the multilayer structure adhesive tape 2 of the present embodiment comprises a first adhesive layer 21, a first substrate layer 22, a functional layer 23, a second substrate layer 24, and a second adhesive layer 25, which are sequentially compounded. Among them, the first adhesive layer 21 and the second adhesive layer 25 have excellent electrolyte resistance, and will not dissolve and can maintain strong adhesion under long-term immersion in electrolyte. The functional layer 23 swells under the immersion of electrolyte, and when the swelling ratio reaches a certain degree, the peeling force between the functional layer 23 and the first substrate layer 22 and between the functional layer 23 and the second substrate layer 24 decreases significantly, resulting in mutual release.

[0037] Specifically, in the present embodiment:

[0038] (1) PET film with a thickness of 2 μm is used as the first substrate layer 22 and the second substrate layer 24.

[0039] (2) SEBS pressure sensitive adhesive is used as the adhesive for forming the first adhesive layer 21, and other existing electrolyte resistant pressure sensitive adhesives can also be used to form the first adhesive layer 21 in actual application.

[0040] (3) Polyacrylic resin type swelling release adhesive is used as the adhesive for forming the functional layer 23, and other existing swelling release adhesives that can quickly release after absorbing electrolyte can be used to form the functional layer 23 in actual application.

[0041] (4) The SEBS heat-sensitive adhesive is used as the adhesive for forming the second adhesive layer 25. In practical applications, other existing electrolyte-resistant heat-sensitive adhesives can also be used to form the second adhesive layer 25.

[0042] Based on the above material information, the multilayer structure adhesive tape is prepared according to the following process:

[0043] The adhesive for forming the first adhesive layer 21 is coated on the surface of the release film by a coating process to form the first adhesive layer 21, and the thickness of the first adhesive layer 21 is 3 μm. Then, the first substrate layer 22 is attached to the side of the first adhesive layer 21 away from the release film. The adhesive for forming the functional layer 23 is coated on the surface of the first substrate layer 22 away from the first adhesive layer 21 to form the functional layer 23, and the thickness of the functional layer 23 is 0.5 μm. Then, the second substrate layer 24 is attached to the surface of the functional layer 23. The adhesive for forming the second adhesive layer 25 is coated on the side of the second substrate layer 24 away from the functional layer 23 to form the second adhesive layer 25, and the thickness of the second adhesive layer 25 is 5 μm. Thus, the multilayer structure adhesive tape is obtained.

[0044] Through the above structural design, when the secondary battery with the multilayer structure adhesive tape falls, the first substrate layer 22 is attached to the battery cell through the first adhesive layer 21, and the second substrate layer 24 is attached to the packaging film / packaging shell through the second adhesive layer 25. Since the first substrate layer 22 and the second substrate layer 24 are loose, the force of the battery cell on the first substrate layer 22 and the force of the packaging film / packaging shell on the second substrate layer 24 do not interfere with each other. When the battery cell falls, it is not subject to the pulling force of the packaging film, thereby avoiding the phenomenon of edge collapse, tearing or aluminum foil tearing of the bonding surface of the battery cell and the multilayer structure adhesive tape, and improving the drop resistance of the secondary battery.

[0045] Example 2

[0046] This example refers to the preparation of the multilayer structure adhesive tape according to Example 1, and the difference between this example and Example 1 is that the thermoplastic polyurethane swellable adhesive is used as the adhesive for forming the functional layer 23 in this example, and the thickness of the functional layer 23 formed thereby is 1 μm. Except for the above difference, the other materials used for preparing the multilayer structure adhesive tape and the related preparation process of this example are consistent with those of Example 1.

[0047] Example 3

[0048] This example refers to the preparation of the multilayer structure adhesive tape according to Example 1, and the difference between this example and Example 1 is that the polybutylene succinate swellable adhesive is used as the adhesive for forming the functional layer 23 in this example, and the thickness of the functional layer 23 formed thereby is 3 μm. Except for the above difference, the other materials used for preparing the multilayer structure adhesive tape and the related preparation process of this example are consistent with those of Example 1.

[0049] Comparative Example 1

[0050] The comparative example 1 prepared the multilayer structure adhesive tape according to the example 1, with the difference that the thickness of the functional layer 23 formed in the comparative example 1 was 3.5 μm. Except for the above difference, the materials used to prepare the multilayer structure adhesive tape and the related preparation process of the comparative example 1 were consistent with the example 1.

[0051] Comparative example 2

[0052] The comparative example 2 prepared the multilayer structure adhesive tape according to the example 2, with the difference that the thickness of the functional layer 23 formed in the comparative example 2 was 3.5 μm. Except for the above difference, the materials used to prepare the multilayer structure adhesive tape and the related preparation process of the comparative example 2 were consistent with the example 2.

[0053] Test example 1

[0054] 1. Test object

[0055] The multilayer structure adhesives prepared in the examples 1-3 and the comparative examples 1-2 were taken as the test objects.

[0056] 2. Peeling force test

[0057] (1) Peeling force test before soaking in electrolyte:

[0058] S1. The test object was laid on a steel plate with the second adhesive layer 25 facing the steel plate, and a copper foil was attached to the surface of the first adhesive layer 21 of the test object, and then the composite structure formed by the copper foil, the test object and the steel plate was hot-pressed at a temperature of 85°C, a pressure of 600 kg and a time of 30 minutes.

[0059] S2. The test environment was again restored to 23±2°C and 50±5% RH, and then 5000NS adhesive tape and a steel plate were attached to the side of the composite structure opposite to the test object.

[0060] S3. Then the steel plates on both sides of the test object were clamped with a Kejian tensile tester for peeling force test, with a peeling speed of 50 mm / min and a peeling angle of 180°, and the peeling force data was recorded, and the average value of a length of 60 mm after the reading was stable was taken (if a serious jagged curve appeared, the average value of the maximum value of every 10 mm after the curve was stable was taken), and the average value of 5 parallel samples was taken as the determination standard.

[0061] (2) Peeling force test after soaking in electrolyte:

[0062] S1. The test object was laid on a steel plate with the second adhesive layer 25 facing the steel plate in an environment of 23±2℃ and 50±5% RH, and a copper foil was attached to the surface of the first adhesive layer 21 of the test object, and then the composite structure of the copper foil, the test object and the steel plate was hot-pressed at a temperature of 85℃, a pressure of 600kg and for a time of 30 minutes.

[0063] S2. The composite structure was then immersed in an electrolyte at a temperature of 85±1℃ for a time of 4 hours, and the electrolyte had the following composition: 12.5% by mass of lithium salt (1 mol / L LiPF6) and 87.5% by mass of organic solvent, and the organic solvent had a mass ratio of ethylene carbonate: propylene carbonate: diethyl carbonate: ethyl propionate = 30:10:30:30.

[0064] S3. After the immersion, the composite structure was removed from the electrolyte.

[0065] S4. The test environment was again restored to 23±2℃ and 50±5% RH, and then a 5000NS adhesive tape and a steel plate were attached to the side of the copper foil of the composite structure opposite to the test object.

[0066] S5. Then, a KJ- 1 1 1 tensile tester was used to clamp the steel plates on the two sides of the test object to test the peeling force, the peeling speed was 50mm / min and the peeling angle was 180°, and the peeling force data was recorded, and the average value of a length of 60mm after the reading was stable was taken (if a serious jagged curve appeared, the average value of the maximum value of the curve every 10mm after the curve was stable was taken), and the average value of 5 parallel samples was taken as the determination standard.

[0067] The calculation method of the peeling force retention rate before and after the electrolyte immersion was as follows:

[0068]

[0069] 3. Test results

[0070] The test results of the test example are shown in Table 1. From the test results, it can be seen that the multi-layer structured adhesive tapes prepared in Examples 1-3 have a rapid decrease in the peeling force between the functional layer 23 and the first substrate layer 22 and the second substrate layer 24 after being immersed in the electrolyte, so that the first substrate layer 22 and the second substrate layer 24 are prone to be detached, especially the multi-layer structured adhesive tape provided in Example 1, after being immersed in the electrolyte, the first substrate layer 22 and the second substrate layer 24 are basically in a detached state. The multi-layer structured adhesive tapes provided in Comparative Examples 1 and 2 have a significantly increased bonding force of the functional layer 23 due to the thick thickness of the functional layer 23, and after being immersed in the electrolyte, the peeling force between the functional layer 23 and the first substrate layer 22 and the second substrate layer 24 also decreases significantly, and the peeling force retention rate is difficult to decrease to less than 80% of the peeling force before being immersed in the electrolyte. Thus, after being immersed in the electrolyte, the multi-layer structured adhesive tapes provided in Comparative Examples 1 and 2 can still rely on the force provided by the functional layer 23 to maintain the compactness between the first substrate layer 22 and the second substrate layer 24.

[0071] In the test objects of the present test, whether or not immersed in the electrolyte, the peeling force between the first adhesive layer 21 and the first substrate layer 22, and the peeling force between the first adhesive layer 21 and the copper foil are not less than 0.03 N / mm, so that before and after being immersed in the electrolyte, the first adhesive layer 21 and the first substrate layer 22, and the surface of the copper foil belonging to the same test object do not have a phenomenon of adhesion loss and falling off. In addition, whether or not immersed in the electrolyte, the peeling force between the second adhesive layer 25 and the second substrate layer 24, and the peeling force between the second adhesive layer 25 and the steel plate are not less than 0.1 N / mm, so that before and after being immersed in the electrolyte, the second adhesive layer 25 and the second substrate layer 24, and the surface of the packaging film / packaging shell belonging to the same test object do not have a phenomenon of adhesion loss and falling off.

[0072] Table 1. Test results of Test Example 1

[0073]

[0074]

[0075] Preparation Example 1

[0076] In the present preparation example, commercially available double-sided adhesive tapes for lithium ion (one side is a pressure-sensitive adhesive layer, and the other side is a heat-sensitive adhesive layer, excluding functional layers with swelling adhesion loss function), multi-layer structured adhesive tapes prepared in Examples 1-3, and multi-layer structured adhesive tapes prepared in Comparative Examples 1-2 are used to prepare secondary batteries.

[0077] Specifically, the secondary battery includes the cell 1, a packaging film wrapping the cell 1, and a protective tape 3 attached between the middle of the surface of the cell 1 and the packaging film. In this production example, the commercially available double-sided adhesive tape for lithium ion, the multi-layered structure adhesive tape produced in Examples 1 to 3, and the multi-layered structure adhesive tape produced in Comparative Examples 1 and 2 were used as the protective tape 3, respectively, and the pressure-sensitive adhesive side of the protective tape 3 was attached to the surface of the cell, and the heat-sensitive adhesive side was attached to the surface of the packaging film. Subsequently, the packaging film was heat-pressed and packaged, and high temperature (85°C) and high pressure were applied to the outer surface of the packaging film to make the heat-sensitive adhesive sticky and adhere to the packaging film. Then, the secondary battery was formed through the steps of drying, liquid injection, and formation.

[0078] Test Example 2

[0079] 1. Test object: The secondary battery produced in Production Example 1 was used as the test object.

[0080] 2. Drop test of secondary battery

[0081] (1) 1.8 m vertical orientation drop test: The six faces and four corners of the test object were respectively oriented toward the ground, and then the test object was vertically dropped from a height of 1.8 m. After the drop test, the test object was tested, and if the voltage change was less than 60 mV, it was determined to pass, otherwise it was determined to fail; if the battery smoked or caught fire, it was determined to fail.

[0082] (2) 2 m vertical orientation drop test: The six faces and four corners of the test object were respectively oriented toward the ground, and then the test object was vertically dropped from a height of 2 m. After the drop test, the lithium battery voltage was tested, and if the voltage change was less than 60 mV, it was determined to pass, otherwise it was determined to fail; if the battery smoked or caught fire, it was determined to fail.

[0083] The pass rate of the lithium battery drop test of the lithium battery samples produced using the same test object was calculated as follows:

[0084]

[0085] 3. Test results

[0086] The test results of this test example are shown in Table 2. In the test object of this test example, both the pressure-sensitive adhesive layer and the heat-sensitive adhesive layer of the protective tape 3 have excellent electrolyte resistance, and do not dissolve and can maintain strong adhesion even in the case of long-term immersion in electrolyte. However, the functional layer 23 included in the multi-layer structured tape prepared in Examples 1 to 3 swells due to immersion in electrolyte during formation, and the peeling force between the functional layer 23 and the first substrate layer 22 and the second substrate layer 24 is greatly reduced, and thus the first substrate layer 22 and the second substrate layer 24 on both sides of the functional layer 23 are released. After the battery is formed, the packaging film tightly wraps the electrode 1, and even in the case where the functional layer 23 swells, loses adhesion, and is released from the first substrate layer 22 and the second substrate layer 24, the packaging film still functions to tightly wrap the electrode 1. Since the first substrate layer 22 and the second substrate layer 24 are released from each other, the force of the electrode 1 on the first substrate layer 22 and the force of the packaging film on the second substrate layer 24 do not interfere with each other, and the electrode 1 is not pulled by the packaging film when it falls, thereby preventing the edge of the bonding surface of the electrode 1 and the multi-layer structured tape from being damaged, torn, or the aluminum foil from being torn, and improving the drop resistance of the secondary battery. Based on this, it can be seen from the test results that the secondary batteries using the multi-layer structured tapes prepared in Examples 1 to 3 as the protective tape 3 all have good pass rates in the drop resistance test of this test example, and thus it is shown that the multi-layer structure provided in Examples 1 to 3 can effectively improve the drop resistance of the secondary battery. In addition, as the vertical drop height of the drop resistance test increases, the pass rate of the drop resistance test decreases for the secondary batteries using the same protective tape 3.

[0087] The test object using the commercially available double-sided tape does not include a functional layer that loses adhesion, and thus the electrode and the packaging film are still tightly adhered by the double-sided tape after the battery is formed and formed. Thus, in the drop resistance test, since the outer packaging material is an aluminum plastic film and the bonding surface of the electrode 1 is an aluminum foil or a polyethylene separator, the toughness and strength of the aluminum plastic film are significantly higher than those of the bonding surface of the electrode 1, and thus the pulling force of the aluminum plastic film on the protective tape 3 is greater than the pulling force of the bonding surface of the electrode 1 on the protective tape 3 during the drop of the lithium ion battery product, and the difference between the above pulling forces easily causes the edge of the side of the protective tape 3 adhered to the bonding surface of the electrode 1 to be damaged or torn, and in a more severe drop test, the aluminum foil can be torn, which adversely affects the drop resistance of the lithium ion battery, and thus the vertical drop test pass rate of the test object prepared using the commercially available double-sided tape is significantly low in this test example.

[0088] In addition, the multi-layer structure adhesive tapes prepared in Comparative Example 1 and Comparative Example 2 have the problem of insufficient tack loss, as described above. Therefore, the test objects prepared using the multi-layer structure adhesive tapes still have the compact combination between the first substrate layer 22 and the second substrate layer 24 of the protective adhesive tape 3 after the liquid injection and formation, and the protective adhesive tape 3 is still subjected to the uneven force from the battery cell and the packaging film. Therefore, the vertical orientation drop test passing rate of the test objects prepared using Comparative Example 1 and Comparative Example 2 is obviously low.

[0089] Table 2. Anti-drop test results of the secondary battery prepared in Preparation Example 1

[0090]

[0091]

[0092] Preparation Example 2

[0093] In this preparation example, the multi-layer structure adhesive tape 2 prepared in Embodiment 1-3 is used to prepare a secondary battery.

[0094] Specifically, the secondary battery includes a battery cell 1, a packaging film, and a multi-layer structure adhesive tape 2. The packaging film wraps the battery cell 1, as shown in Figure 3 and Figure 4 The battery cell 1 includes a first surface 11 and a second surface 12 arranged oppositely. The multi-layer structure adhesive tape 2 is attached to the four edge positions of the battery cell 1. The first adhesive layer 21 is attached to the first surface 11 and the second surface 12 at the same time, so that the multi-layer structure adhesive tape 2 is wrapped around the four edges of the battery cell 1 in a U shape. The side of the pressure-sensitive adhesive of the multi-layer structure adhesive tape 2 is attached to the surface of the battery cell, and the side of the heat-sensitive adhesive is attached to the surface of the packaging film, as shown in Figure 5 Subsequently, the packaging film is heat-pressed and packaged. High temperature (85°C) and high pressure are applied to the outer surface of the packaging film, so that the heat-sensitive adhesive generates tack and is bonded to the packaging film. The secondary battery is formed through the steps of drying, liquid injection, and formation. The multi-layer structure adhesive tape 2 is attached between the battery cell 1 and the packaging film and wrapped around the edges of the battery cell 1 in a U shape.

[0095] Further, compared with the design of the conventional lithium ion battery using the double-sided adhesive tape 3, the multi-layer structure adhesive tape 2 of the present application is wrapped around the edges of the battery cell 1 in a U shape and is continuously attached to the first surface 11 and the second surface 12 of the battery cell. The U-shaped multi-layer structure adhesive tape 2 located at the four edges of the battery cell can simultaneously play the dual roles of adhering the packaging film and fixing the battery cell 1, thereby achieving the purpose of reducing the adhesive application process and improving the production efficiency.

[0096] Test Example 3

[0097] 1. Test object: the secondary battery prepared in Preparation Example 2 is used as the test object.

[0098] 2. Secondary battery drop resistance test

[0099] The operation of the secondary battery drop resistance test in Test Example 2 was kept consistent.

[0100] 3. Test results

[0101] The test results of this test example were compared with the test results of the test objects using the multi-layer structure adhesive provided in Examples 1-3 as the protective adhesive tape in Test Example 2. For the secondary battery using the same kind of multi-layer structure adhesive tape 2, under the test condition that the vertical orientation drop height reached 2m, the secondary battery prepared in Preparation Example 2 could achieve a higher vertical orientation drop test pass rate compared with the secondary battery prepared in Preparation Example 1.

[0102] In the secondary battery prepared in Preparation Example 2, the multi-layer structure adhesive tape 2 wrapped around the edge of the battery cell 1 in a U shape, so that the multi-layer structure adhesive tape 2 formed a U-shaped limiting structure at the edge of the battery cell 1, which could better support and buffer the drop process of the battery cell, further optimize the drop resistance performance of the battery cell 1, and be conducive to achieving better stability and safety of the secondary battery.

[0103] Table 3. Drop resistance test results of the secondary battery prepared in Preparation Example 2

[0104]

[0105] The technical means disclosed in the utility model scheme are not limited to the technical means disclosed in the above-mentioned embodiments, and also include technical solutions composed of any combination of the above technical features. It should be noted that for ordinary skilled persons in the art, without departing from the principles of the utility model, a number of improvements and refinements can be made, and these improvements and refinements are also considered within the protection scope of the utility model.

Claims

1. A multi-layered construction tape, characterized by, The multilayer structure adhesive tape comprises a first adhesive layer, a first substrate layer, a functional layer, a second substrate layer and a second adhesive layer which are sequentially compounded; The functional layer satisfies that the peel strength retention rate between the functional layer and the first substrate layer and the second substrate layer is not more than 80% after being soaked in an organic acid ester solution at 85℃ for 4 hours; The thickness of the functional layer is 0.1-3 μm.

2. The multi-layer construction tape of claim 1, wherein, The functional layer satisfies that the 180° peel strength between the functional layer and the first substrate layer and between the functional layer and the second substrate layer is not more than 0.03 N / mm after being soaked in an organic acid ester solution at 85℃ for 4 hours.

3. The multi-layer construction tape of claim 1, wherein, The peel strength between the first adhesive layer and the first substrate layer is not less than 0.03 N / mm.

4. The multi-layer construction tape of claim 3, wherein, The thickness of the first adhesive layer is 2-4 μm.

5. The multi-layer construction tape of claim 1, wherein, The peel strength between the second adhesive layer and the second substrate layer is not less than 0.1 N / mm.

6. The multi-layer construction tape of claim 5, wherein, The thickness of the second adhesive layer is 3-6 μm.

7. The multi-layer construction tape of claim 1, wherein, The first substrate layer and the second substrate layer are independently selected from PET film or PI film or PP film.

8. The multi-layer construction tape of claim 1, wherein, The thickness of the multilayer structure adhesive tape is 8-25 μm.

9. A secondary battery characterized by comprising: The multilayer structure adhesive tape is attached between the electrode core and the packaging film.

10. The secondary battery according to claim 9, characterized by The electrode core comprises a first surface and a second surface which are oppositely arranged, the multilayer structure adhesive tape is attached at the edge position of the electrode core, and the first adhesive layer is attached to the first surface and the second surface at the same time so that the multilayer structure adhesive tape is U-shapedly wrapped around the edge of the electrode core.

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