Electrolyte-resistant adhesive and adhesive tape using the same

Abstract

The application provides a kind of electrolyte-resistant glue, according to mass fraction, electrolyte-resistant glue includes 50-70 parts of main resin, 20-50 parts of tackifying resin, 0-5 parts of crosslinking agent;The main resin includes ethylene-propylene-diene rubber, the ethylene content in ethylene-propylene-diene rubber is 50%-65%, the content of ethylidene norbornene in ethylene-propylene-diene rubber is 0.2%-1.5%.The electrolyte-resistant glue provided by the application contains ethylene-propylene-diene rubber, the introduction of ethylene-propylene-diene rubber can effectively improve the electrolyte resistance of glue and the flexibility of glue layer formed by the electrolyte-resistant glue, based on the application of ethylene-propylene-diene rubber, by controlling the ethylene content and ENB content of ethylene-propylene-diene rubber, the glue layer formed by the electrolyte-resistant glue can achieve higher bonding force.

Description

Technical Field

[0001] The present invention belongs to the technical field of adhesive materials, and in particular relates to an electrolyte-resistant glue and an adhesive tape using the same. Background Art

[0002] Lithium batteries boast high operating voltage, high energy density, low self-discharge, multiple recyclable cycles, long service life, and environmental friendliness. They are widely used in mobile phones, automobiles, laptops, and other applications. During the production and assembly of lithium batteries, lithium battery tape plays a significant role in their safety. Lithium battery tape is typically used for insulation and securing electrode windings, cell terminations, and electrode sheets during the production and assembly process. This requires the tape to possess certain initial tack, sustained tack, high-temperature resistance, and electrolyte corrosion resistance.

[0003] In recent years, the lithium battery assembly industry has seen a significant demand for lithium battery tape with improved electrolyte durability. During the assembly process and subsequent applications, lithium battery tape comes into direct contact with the electrolyte. This requires the tape to withstand long-term immersion in the electrolyte without losing its adhesiveness or dissolving impurities that could contaminate the electrolyte. Existing tapes experience varying degrees of decreased adhesion after electrolyte immersion, failing to effectively improve or resolve the electrolyte durability issue.

[0004] EPDM (Ethylene Propylene Diene Monomer) is a copolymer of ethylene, propylene, and a small amount of non-conjugated diene. It is a type of ethylene propylene rubber, represented by EPDM (Ethylene Propylene Diene Monomer). Because its main chain is composed of chemically stable saturated hydrocarbons, with unsaturated double bonds only in the side chains, it has excellent aging resistance, including ozone resistance, heat resistance, and weather resistance. It is widely used in automotive parts, building waterproofing materials, wire and cable sheathing, heat-resistant hoses, tapes, automotive seals, and other fields. However, EPDM has low surface energy, poor adhesion, and is prone to debonding and loss of adhesion, which limits its application in the tape field. Summary of the Invention

[0005] In order to improve the electrolyte resistance of adhesive tape products suitable for lithium batteries, the present invention provides an electrolyte-resistant glue and an adhesive tape using the same.

[0006] According to a first aspect of the present invention, an electrolyte-resistant glue is provided. The electrolyte-resistant glue comprises, by weight, 50 to 70 parts of a main resin, 20 to 50 parts of a tackifying resin, and 0 to 5 parts of a crosslinking agent. The main resin comprises EPDM rubber, the ethylene content of the EPDM rubber being 50% to 65%, and the ethylidene norbornene (ENB) content of the EPDM rubber being 0.2% to 1.5%. The electrolyte-resistant glue provided by the present invention contains EPDM rubber. The introduction of EPDM rubber can effectively improve the electrolyte resistance of the glue and the flexibility of the adhesive layer formed by the electrolyte-resistant glue. Based on the application of EPDM rubber, by regulating the ethylene content and ENB content of the EPDM rubber, the adhesive layer formed by the electrolyte-resistant glue can achieve higher adhesion. Based on the above content, the tape product made of the electrolyte-resistant glue provided by the present invention is suitable for the preparation and processing of lithium-ion battery products. The adhesive layer structure formed by the above-mentioned electrolyte-resistant glue can still maintain excellent viscosity and structural stability even if it is immersed in electrolyte for a long time. It can reliably fix the battery structural components to which it is applied, and will not dissolve byproducts that affect the normal operation of the battery.

[0007] Preferably, the tackifying resin comprises hydrogenated petroleum resin. For a glue formula containing EPDM rubber, further utilizing hydrogenated petroleum resin in combination with EPDM rubber can better enhance the adhesive force of the glue layer formed by the glue.

[0008] Preferably, the softening point of the hydrogenated petroleum resin is 100°C to 150°C.

[0009] Preferably, the main resin further comprises modified EPDM rubber, wherein the modified groups grafted onto the modified EPDM rubber include at least one of hydroxyl, carboxyl, epoxy, and maleic anhydride. By modifying the EPDM rubber, the bonding effect of the EPDM rubber can be effectively improved.

[0010] Preferably, the grafting rate of the modified EPDM rubber is 0.5% to 2%.

[0011] Preferably, the modified group of the modified EPDM rubber includes maleic anhydride. More preferably, the modified EPDM rubber modified with maleic anhydride can further improve the electrolyte resistance of the adhesive layer formed by the glue.

[0012] Preferably, the mass of the EPDM rubber: the mass of the modified EPDM rubber = 90-98: 2-10.

[0013] Preferably, the electrolyte-resistant glue includes 0.1 to 0.5 parts of a cross-linking agent, calculated by weight, and the cross-linking agent includes at least one of amino resin, nitrogen pyridine, and amino resin.

[0014] Preferably, the electrolyte-resistant glue further comprises 0 to 20 parts of a pigment, wherein the pigment comprises at least one of phthalocyanine blue, titanium dioxide, inorganic cobalt blue, and inorganic cobalt green.

[0015] According to a second aspect of the present invention, there is provided an adhesive tape, wherein the adhesive tape is provided with a first adhesive layer, wherein the first surface adhesive layer is made by using the electrolyte-resistant adhesive according to any one of claims 1 to 8.

[0016] Preferably, the adhesive tape further comprises a first substrate layer, a swelling and loss of adhesion layer, a second substrate layer and a second adhesive layer, and the first adhesive layer, the first substrate layer, the swelling and loss of adhesion layer, the second substrate layer and the second adhesive layer are compounded in sequence.

[0017] Specific embodiment

[0018] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0019] Example 1

[0020] Calculated by mass, the formula for preparing the electrolyte glue in this embodiment is: 60 parts of main resin, 35 parts of tackifying resin, and 0.3 parts of cross-linking agent; in the electrolyte glue formula used in this embodiment, ethylene propylene diene monomer rubber with ENB as the third monomer is used as the main resin, HM-1000 hydrogenated petroleum resin with a softening point of 100°C is used as the tackifying resin, and nitrogen pyridine is used as the cross-linking agent.

[0021] Based on the above basic formula, this example uses the chemical composition of EPDM as a variable to set up different treatment groups, numbered as Treatment Group 1-1, Treatment Group 1-2, and Treatment Group 1-3. The EPDM used in each treatment group was prepared using the Ziegler-Natta catalyst method. The materials used in the preparation process are: propylene, ethylene, and ENB as the reaction monomers, a Ziegler-Natta vanadium-aluminum catalyst system (VOCl3-1 / 2Al2EtCl3) as the catalyst, and n-hexane as the reaction solvent. The reaction monomers undergo a synthesis reaction under the action of the catalyst, wherein: the polymerization temperature is 40-60°C, the reaction pressure is 2.0-2.5 MPa, the polymerization time is 30 minutes, and the reaction heat is used to adiabatically heat the reactor. The amount of reaction monomer is determined based on the ethylene content, ENB content, and propylene content of the target product EPDM. The polymerization temperature and reaction pressure are adaptively adjusted within the above range based on the actual reaction conditions and the ethylene content, ENB content, and propylene content of the target product. The chemical composition of the EPDM rubber prepared in each treatment group is shown in Table 1. The remainder after deducting the ethylene content and ENB content is the propylene content.

[0022] Table 1. Chemical composition of EPDM rubber obtained in each treatment group of Example 1

[0023] Group Ethylene content ENB content Treatment group 1-1 50％ 1.5％ Treatment Group 1-2 65％ 0.2％ Treatment groups 1-3 60％ 1％

[0024] The electrolyte-resistant glue of each treatment group was prepared as follows: materials were prepared according to the electrolyte-resistant glue formula used in this embodiment, and related materials were mixed and dispersed in water to prepare electrolyte-resistant glue with a solid content of 30 wt%.

[0025] Comparative Example 1

[0026] In this comparative example, glue samples were prepared using the same method as in Example 1. The formula used to prepare the glue samples differed only from the electrolyte-resistant glue formula used in each treatment group in Example 1 in the chemical composition of the EPDM rubber. Otherwise, the other materials and their proportions in the two formulas were identical. Using the EPDM rubber component as a variable, this comparative example set up different comparative groups, numbered Comparative Group 1-1, Comparative Group 1-2, Comparative Group 1-3, Comparative Group 1-4, Comparative Group 1-5, Comparative Group 1-6, Comparative Group 1-7, and Comparative Group 1-8. Each of these comparative groups was prepared using the method for preparing EPDM rubber in Example 1. The amounts of monomers used were determined based on the ethylene, ENB, and propylene contents of the target product, EPDM rubber. The polymerization reaction temperature and reaction pressure were adjusted within the ranges provided in Example 1 based on the actual reaction conditions and the ethylene, ENB, and propylene contents of the target product. The chemical composition of the EPDM rubber prepared in each treatment group is shown in Table 2. The remainder after deducting the ethylene content and ENB content is the propylene content.

[0027] Table 2. Chemical composition of EPDM rubber obtained in each comparison group of Comparative Example 1

[0028] Group Ethylene content ENB content Comparison group 1-1 45％ 0.1％ Comparison group 1-2 60％ 0.1％ Comparison groups 1-3 70％ 0.1％ Comparison groups 1-4 45％ 2％ Comparison groups 1-5 60％ 2％ Comparison groups 1-6 70％ 2％ Comparison groups 1-7 45％ 1％ Comparison groups 1-8 70％ 1％

[0029] The glue samples of each comparative group were prepared as follows: materials were prepared according to the glue sample formula used in this comparative example, and the relevant materials were mixed and dispersed in water to prepare glue samples with a solid content of 30 wt%.

[0030] Comparative Example 2

[0031] In this comparative example, glue samples were prepared with reference to Example 1. Based on the differences in the formulas used to prepare the glue samples, different comparative groups were set up in this comparative example, which were numbered as comparative group 2-1, comparative group 2-2, and comparative group 2-3, respectively. The formulas and related operations for preparing the glue samples in the above comparative groups are as follows.

[0032] (1) Comparative group 2-1

[0033] The formula for preparing the glue sample of the comparison group 2-1 is: 60 parts of the main resin, 35 parts of the tackifying resin, and 0.3 parts of the cross-linking agent; in the glue sample formula used in the comparison group 2-1, the ethylene propylene diene monomer rubber whose third monomer is dicyclopentadiene (DCPD) is used as the main resin, and the types of the tackifying resin and the cross-linking agent used are the same as those in Example 1.

[0034] The EPDM rubber used in Comparative Group 2-1 was prepared using the process described in Example 1. Unlike Example 1, DCPD was used instead of ENB as the reaction monomer for the EPDM rubber. The amounts of the reaction monomers used were determined based on the ethylene, DCPD, and propylene contents of the target EPDM rubber. The polymerization temperature and pressure were adjusted within the ranges provided in Example 1 based on the actual reaction conditions and the ethylene, DCPD, and propylene contents of the target product. The chemical composition of the EPDM rubber produced in Comparative Group 2-1 was 60% ethylene and 1% DCPD, with the remainder after deducting the ethylene and DCPD contents being propylene.

[0035] The materials were prepared according to the glue sample formula used in this comparative group, and the relevant materials were mixed and dispersed in water to prepare a glue sample with a solid content of 30 wt%.

[0036] (2) Comparative group 2-2

[0037] The formula for preparing the glue sample in comparison group 2-2 is: 60 parts of main resin, 35 parts of tackifying resin, and 0.3 parts of cross-linking agent; in the glue sample formula used in comparison group 2-2, ethylene propylene rubber is used as the main resin, and the types of tackifying resin and cross-linking agent used are the same as those in Example 1.

[0038] The EPDM rubber used in Comparative Group 2-2 was prepared using the Ziegler-Natta catalyst method. The following materials were used: propylene and ethylene as the monomers, a Ziegler-Natta vanadium-aluminum catalyst system (VOCl₃-1 / 2Al₂EtCl₃) was used as the catalyst, and n-hexane was used as the reaction solvent. The monomers underwent a synthesis reaction under the action of the catalyst, with a polymerization temperature of 30-60°C, a reaction pressure of 0.4-0.8 MPa, and a polymerization time of 30 minutes. The heat of the reaction was used to adiabatically heat the reactor. The amount of monomers used was determined based on the ethylene and propylene contents of the target product, the EPDM rubber. The polymerization temperature and pressure were adjusted within the above ranges based on the actual reaction conditions and the ethylene and propylene contents of the target product. The chemical composition of the EPDM rubber produced in Comparative Group 2-2 was 60% ethylene, with the remainder after deducting the ethylene content being propylene.

[0039] The materials were prepared according to the glue sample formula used in this comparative group, and the relevant materials were mixed and dispersed in water to prepare a glue sample with a solid content of 30 wt%.

[0040] (3) Comparative group 2-3

[0041] The formula for preparing the glue sample of the comparison group 2-3 is: 60 parts of the main resin, 35 parts of the tackifying resin, and 0.3 parts of the cross-linking agent; in the glue sample formula used in the comparison group 2-2, hydrogenated sick ethylene-polyisoprene-styrene block copolymer (SEPS) is used as the main resin, and the types of the tackifying resin and the cross-linking agent used are the same as those in Example 1.

[0042] The materials were prepared according to the glue sample formula used in this comparative group, and the relevant materials were mixed and dispersed in water to prepare a glue sample with a solid content of 30 wt%.

[0043] Test Example 1

[0044] 1. Test subjects

[0045] The glues prepared in Example 1, Comparative Example 1 and Comparative Example 2 were used as test objects.

[0046] 2. Make samples

[0047] Use the glue to be tested to make a tape sample according to the following procedures:

[0048] A silicon release film was used as a base film, and the test object was coated on the film surface of the silicon release film. A 2 μm thick PET film was then laminated on the glue coating. The glue was dried to form a pressure-sensitive adhesive layer to obtain the tape sample of this test example.

[0049] 3. Peel force test

[0050] (1) Peel force test before immersion in electrolyte

[0051] S1. At 23±2°C and 50±5% RH, apply the pressure-sensitive adhesive layer of the tape sample to the copper foil.

[0052] S2. Then, affix 5000NS tape and a steel plate in sequence on the side of the copper foil facing away from the tape sample, and affix 5000NS tape as a traction tape on the side of the tape sample facing away from the copper foil.

[0053] S3. Then use a Kejian tensile tester to clamp the steel plate and the traction tape respectively to perform a peeling force test. The peeling speed is 50mm / min and the peeling angle is 180°. Record the peeling force data and take the average value of a 60mm section after the reading stabilizes (if a severe jagged curve appears, take the average value of the maximum value of the curve every 10mm after stabilization). The judgment standard is the average value of 5 parallel samples.

[0054] (2) Peel strength test after immersion in electrolyte

[0055] S1. At 23±2°C and 50±5% RH, apply the pressure-sensitive adhesive layer of the tape sample to the copper foil.

[0056] S2. The composite structure formed by bonding the copper foil and the tape sample is then immersed in an electrolyte at a temperature of 85±1°C for 4 hours. The components of the electrolyte used are as follows: the mass content of lithium salt (1 mol / L LiPF6) is 12.5%, and the mass content of the organic solvent is 87.5%: calculated by mass ratio, in the organic solvent, ethylene carbonate: propylene carbonate: diethyl carbonate: ethyl propionate = 30:10:30:30.

[0057] S3. After the immersion is completed, the composite structure is removed from the electrolyte.

[0058] S4. Return the test environment to 23±2°C and 50±5% RH. Apply 5000NS tape and a steel plate to the side of the copper foil facing away from the tape sample. Apply 5000NS tape as a traction tape to the side of the tape sample facing away from the copper foil.

[0059] S5. Then use a Kejian tensile tester to clamp the steel plate and the traction tape respectively to perform a peeling force test. The peeling speed is 50mm / min and the peeling angle is 180°. Record the peeling force data and take the average value of a 60mm section after the reading stabilizes (if a severe jagged curve appears, take the average value of the maximum value of the curve every 10mm after stabilization). The judgment standard is the average value of 5 parallel samples.

[0060] The calculation method for the peeling force retention rate before and after the electrolyte is as follows:

[0061]

[0062] 4. Test Results

[0063] The test results are shown in Table 3. Among the tape samples in this test example, those made with the glue of each treatment group in Example 1 achieved higher peel force retention before and after electrolyte soaking, compared to those made with the glue of each control group in Comparative Examples 1 and 2. The main resin used in the electrolyte-resistant glue of each treatment group in Example 1 was EPDM resin, and the chemical composition of the EPDM rubber used was consistent with an ethylene content of 50% to 65% and an ENB content of 0.2% to 1.5%. The test results show that, in the peeling force test set in this test example, the tape samples prepared using the glue of each treatment group in Example 1 meet the peeling force requirement of >0.05N / mm before and after soaking in electrolyte, and the peeling force retention rate before and after soaking in electrolyte reaches more than 40%. This shows that the glue prepared in Example 1 not only has good adhesion but also has good electrolyte resistance. When the pressure-sensitive tapes made from the glue of each treatment group in Example 1 are used in lithium battery products, these pressure-sensitive tapes can be tightly adhered to the surface of the battery cell before and after soaking in electrolyte.

[0064] The glues prepared in the treatment groups of Example 1 were compared with the glues prepared in the control groups of Comparative Example 1. The difference lies in the chemical composition of the EPDM rubber used as the main resin. As described above, the chemical composition of the EPDM rubber used in Example 1 all met the requirements of an ethylene content of 50% to 65% and an ENB content of 0.2% to 1.5%. Using these as a reference, in Comparative Example 1, the EPDM rubber used in Control Groups 1-1, 1-4, and 1-7 had a lower ethylene content, while the EPDM rubber used in Control Groups 1-3, 1-6, and 1-8 had a higher ethylene content. The EPDM rubber used in Control Groups 1-1, 1-2, and 1-3 had a lower ENB content, while the EPDM rubber used in Control Groups 1-4, 1-5, and 1-6 had a higher ENB content. The test results show that the peel force of the adhesive tape samples made from the glues in the above-mentioned comparative groups decreased significantly before and after being immersed in the electrolyte, indicating that these glues have poor electrolyte resistance. The above test results show that in the glue formula using EPDM rubber as the main resin, the chemical composition of the EPDM resin plays a significant role in affecting the electrolyte resistance of the glue. Based on the basic glue formula used in Example 1 and Comparative Example 1, when EPDM rubber with a chemical composition that meets the requirements of ethylene content of 50% to 65% and ENB content of 0.2% to 1.5% is selected as the main resin, the glue can have good electrolyte resistance. When EPDM rubber with a chemical composition that does not meet the above characteristics is selected as the main resin, the glue's electrolyte resistance will be significantly deteriorated, making it difficult to meet the performance requirements of electrolyte resistance.

[0065] The adhesives produced from the treatment groups of Example 1 were compared with the adhesives produced from the control groups of Comparative Example 2. The main resin used differed in the type of base resin. Treatment groups 1-3 used EPDM rubber with ENB as the third monomer, while control group 2-1 used EPDM rubber with DCPD as the third monomer. Control group 2-2 used EPDM rubber without a third monomer, while control group 2-3 used SEPS as the main resin. While the base resin used in control group 2-1 was also EPDM rubber, and both had equivalent ethylene and third monomer contents, the adhesive tape samples produced using these two materials exhibited significant differences in electrolytic resistance. Based on this premise, the adhesive tape sample containing EPDM rubber with ENB as the third monomer exhibited superior electrolyte resistance. In addition to treatment groups 1-3, the electrolyte resistance of glue samples prepared using the glues of treatment groups 1-1 and 1-2 was also superior to that of glue samples prepared using the glue of comparison group 2-1. This demonstrates that, compared to glues using EPDM rubber with a third monomer of DCPD, glues formulated using EPDM rubber with a chemical composition satisfying an ethylene content of 50% to 65% and an ENB content of 0.2% to 1.5% exhibit superior electrolyte resistance. Furthermore, a comparison of the main resin materials used in comparison groups 2-2 and 2-3 with those of the treatment groups in Example 1 reveals that glues formulated using EPDM rubber with a chemical composition satisfying an ethylene content of 50% to 65% and an ENB content of 0.2% to 1.5% exhibit superior electrolyte resistance.

[0066] Table 3. Peel force test results of Test Example 1

[0067]

[0068] Example 2

[0069] This example prepared glue samples with reference to Example 1. The formula for preparing the electrolyte glue in this example is: 60 parts of a main resin, 35 parts of a tackifying resin, and 0.3 parts of a crosslinking agent. The electrolyte glue formula used in this example uses the EPDM rubber prepared in Treatment Groups 1-3 of Example 1 as the main resin, and nitrogen pyridine as the crosslinking agent. This example uses the type of tackifying resin used in the formula as a variable, setting up different treatment groups, numbered as Treatment Group 2-1 and Treatment Group 2-2. The electrolyte formulas used in these treatment groups differ from those used in Treatment Groups 1-3 of Example 1 only in that each treatment group uses a different type of tackifying resin to replace the tackifying resin used in the electrolyte formula of Treatment Groups 1-3 of Example 1 by equal weight. The tackifying resins used in each treatment group of Example 2 are shown in Table 4. For ease of comparison, the tackifying resins used in Treatment Groups 1-3 of Example 1 are also included in Table 4.

[0070] Table 4. Tackifying resins used in each treatment group of Example 2

[0071] Group Tackifying resin Treatment groups 1-3 HM-1000 hydrogenated petroleum resin with a softening point of 100°C Treatment group 2-1 HM-1000 hydrogenated rosin resin with a softening point of 100°C Treatment group 2-2 HM-1000 hydrogenated terpene resin with a softening point of 100°C

[0072] The electrolyte-resistant glue of each treatment group was prepared as follows: materials were prepared according to the electrolyte-resistant glue formula used in this embodiment, and related materials were mixed and dispersed in water to prepare electrolyte-resistant glue with a solid content of 30 wt%.

[0073] Comparative Example 3

[0074] This comparative example refers to the comparative group 2-3 of comparative example 2 to prepare glue samples. The formula for preparing the electrolyte glue in this comparative example is: 60 parts of the main resin, 35 parts of the tackifying resin, and 0.3 parts of the cross-linking agent. In the electrolyte glue formula used in this embodiment, the SEPS used in the comparative group 2-3 of comparative example 2 is used as the main resin, and nitrogen pyridine is used as the cross-linking agent. This comparative example uses the type of tackifying resin used in the formula as a variable, and sets different comparative groups, numbered as comparative group 3-1 and comparative group 3-2. The electrolyte formula used in each comparative group is compared with the electrolyte formula used in the comparative group 2-3 of comparative example 2, except that each comparative group uses a different type of tackifying resin to replace the tackifying resin used in the electrolyte formula of comparative group 2-3 of comparative example 2 in equal mass. The tackifying resin used in each comparative group of comparative example 3 is shown in Table 5. For ease of comparison, the tackifying resin used in comparative group 2-3 of comparative example 2 is also included in Table 5.

[0075] Table 5. Tackifying resins used in each comparison group of Comparative Example 3

[0076] Group Tackifying resin Comparison group 2-3 HM-1000 hydrogenated petroleum resin with a softening point of 100°C Comparative group 3-1 HM-1000 hydrogenated rosin resin with a softening point of 100°C Comparative group 3-2 HM-1000 hydrogenated terpene resin with a softening point of 100°C

[0077] The glue samples of each comparative group were prepared as follows: materials were prepared according to the electrolyte-resistant glue formula used in this comparative example, and the relevant materials were mixed and dispersed in water to prepare glue samples with a solid content of 30 wt%.

[0078] Test Example 2

[0079] 1. Test subjects

[0080] The glues prepared in Example 2 and Comparative Example 3 were used as test objects.

[0081] 2. Make samples

[0082] Using the glue to be tested, a tape sample was prepared according to the following procedure:

[0083] A silicon release film was used as a base film, and the test object was coated on the film surface of the silicon release film. A 2 μm thick PET film was then laminated on the glue coating. The glue was dried to form a pressure-sensitive adhesive layer to obtain the tape sample of this test example.

[0084] 3. Peel force test

[0085] The relevant processing of the peeling force test is the same as the peeling force test in Test Example 1.

[0086] 4. Test Results

[0087] The test results are shown in Table 6. For ease of comparison, the relevant test results of Example 1, Treatment Groups 1-3, and Comparative Example 2, Comparative Group 2-3, in Test Example 1 are also included in Table 6. In the glue formula using EPDM rubber as the main resin, the tackifying resin is combined with the EPDM rubber to ensure that the glue has excellent bonding properties. Comparing Treatment Groups 1-3, 2-1, and 2-2, the main resins used in the three are exactly the same, all of which are EPDM rubber with ENB as the third monomer. However, the glue formula using hydrogenated petroleum resin as the tackifying resin has the highest peel force retention rate before and after electrolyte soaking. This shows that for the glue formula using EPDM rubber with ENB as the third monomer as the main resin, combining hydrogenated petroleum resin as the tackifying resin component in the formula can improve its electrolyte resistance while ensuring the bonding properties of the pressure-sensitive adhesive tape formed by the glue. However, in the electrolyte formulas of comparison groups 2-3, 3-1, and 3-2, the main resin used is SEPS. For the tape samples made using this type of glue, changing the type of thickening resin in the glue formula is difficult to effectively improve its electrolyte resistance.

[0088] Table 6. Peel force test results of Test Example 2

[0089]

[0090] Example 3

[0091] 1. Preparation of modified EPDM rubber

[0092] (1) Hydroxyl modified EPDM rubber

[0093] The EPDM rubber obtained in treatment groups 1-3 of Example 1 was used as a raw material, and a hydroxyl-modified ternary rubber was prepared according to the method provided in CN115386021A. The grafting rate of hydroxyl groups was 1%.

[0094] (2) Maleic anhydride modified EPDM rubber

[0095] The EPDM rubber prepared in treatment groups 1-3 of Example 1 was used as a raw material, and maleic anhydride-modified ternary rubber was prepared according to the method provided in CN118638273A. The grafting rate of maleic anhydride was 1%.

[0096] (3) Epoxy modified EPDM rubber

[0097] The EPDM rubber prepared in treatment groups 1-3 of Example 1 was used as a raw material, and referring to the method provided in "The Effect of Epoxidized EPDM Rubber on the Structure and Properties of PBT" (Liu Bo, Wu Wei; "China Plastics", April 2018, Vol. 32, No. 4), an epoxy-modified ternary rubber was prepared, and the grafting rate of the epoxy group was 1%.

[0098] 2. Prepare electrolyte-resistant glue

[0099] The formula for preparing the electrolyte-resistant glue in this embodiment is: 60 parts of the main resin, 35 parts of the tackifying resin, and 0.3 parts of the cross-linking agent. In the electrolyte glue formula used in this embodiment, the main resin is composed of the EPDM rubber prepared by treatment groups 1-3 of Example 1 and the modified EPDM rubber prepared therefrom in a mass ratio of ternary modified EPDM rubber: modified EPDM rubber = 95:5, HM-1000 hydrogenated petroleum resin with a softening point of 100°C is used as the tackifying resin, and nitrogen pyridine is used as the cross-linking agent. In this example, the type of modified EPDM rubber used in the formulation was used as a variable, and different treatment groups were set up, numbered as Treatment Group 3-1, Treatment Group 3-2, and Treatment Group 3-3. The electrolyte formulations used in these treatment groups differed from those used in Treatment Groups 1-3 of Example 1 only in that each treatment group used a different type of modified EPDM rubber in combination with unmodified EPDM rubber as the main resin in the electrolyte formulation. The modified EPDM rubber used in each treatment group of Example 3 is shown in Table 7.

[0100] Table 7. Tackifying resins used in each treatment group of Example 3

[0101] Group Main resin composition (mass ratio) Treatment group 3-1 EPDM rubber: hydroxyl modified EPDM rubber = 95:5 Treatment group 3-2 EPDM rubber: maleic anhydride modified EPDM rubber = 95:5 Treatment group 3-3 EPDM rubber: epoxy modified EPDM rubber = 95:5

[0102] The electrolyte-resistant glue of each treatment group was prepared as follows: materials were prepared according to the electrolyte-resistant glue formula used in this embodiment, and related materials were mixed and dispersed in water to prepare electrolyte-resistant glue with a solid content of 30 wt%.

[0103] Test Example 3

[0104] 1. Test subjects

[0105] The glue prepared in Example 3 was used as the test object.

[0106] 2. Make samples

[0107] Using the glue to be tested, a tape sample was prepared according to the following procedure:

[0108] A silicon release film was used as a base film, and the test object was coated on the film surface of the silicon release film. A 2 μm thick PET film was then laminated on the glue coating. The glue was dried to form a pressure-sensitive adhesive layer to obtain the tape sample of this test example.

[0109] 3. Peel force test

[0110] The relevant processing of the peeling force test is the same as the peeling force test in Test Example 1.

[0111] 4. Test Results

[0112] The test results are shown in Table 8. For ease of comparison, the relevant test results of Treatment Groups 1-3 in Example 1 in Test Example 1 are also included in Table 8. In this test example, the main resin in the glue formulations involved all included unmodified EPDM rubber, and the unmodified EPDM rubber had the same chemical composition. For comparison, using Treatment Groups 1-3 as a comparison, the glue formulations of Treatment Groups 3-1, 3-2, and 3-3 contained not only unmodified EPDM rubber but also EPDM rubber modified with different groups. Compared to the glue samples prepared using the glues of Treatment Groups 1-3, the combination of modified EPDM rubber and unmodified EPDM rubber can simultaneously improve the bonding performance and electrolyte resistance of the glue and the pressure-sensitive adhesive tape prepared using it.

[0113] Table 8. Peel force test results statistics of Test Example 3

[0114]

[0115] Example 4

[0116] In this embodiment, the cross-linking agent used in the preparation of the electrolyte-resistant glue formula is used as a variable to set different treatment groups. Three treatment groups are set and numbered as treatment group 4-1, treatment group 4-2, and treatment group 4-3 respectively.

[0117] The electrolyte-resistant glue formulations used in Treatment Groups 4-1 and 4-2 were: 60 parts main resin, 35 parts tackifying resin, and 0.3 parts crosslinking agent. The main resin composition in these treatment groups was identical to that used in Treatment Group 3-2 of Example 3, with HM-1000 hydrogenated petroleum resin with a softening point of 100°C serving as the tackifying resin. The electrolyte formulations used in Treatment Groups 4-1 and 4-2 differed only from that used in Treatment Group 3-2 of Example 3, with each treatment group replacing the nitrogen-containing pyridine in the electrolyte formulation used in Treatment Group 3-2 of Example 3 with equal amounts of different materials.

[0118] The formula for preparing electrolyte-resistant glue in treatment group 4-3 is: 60 parts of main resin and 35 parts of tackifying resin; in the electrolyte glue formula used in the above treatment group, the composition of the main resin is the same as the component composition of the main resin used in treatment group 3-2 of Example 3, and HM-1000 hydrogenated petroleum resin with a softening point of 100°C is used as the tackifying resin.

[0119] The cross-linking agents used in the electrolyte-resistant glue formulations of each treatment group in Example 4 are specifically shown in Table 9. For ease of comparison, the cross-linking agents used in treatment group 3-2 in Example 3 are also included in Table 9.

[0120] Table 9. Cross-linking agents used in each treatment group of Example 4

[0121] Group crosslinking agent Treatment group 3-2 Nitrous pyridine Treatment group 4-1 amino resin Treatment group 4-2 Isocyanates Treatment group 4-3 none

[0122] The electrolyte-resistant glue of each treatment group was prepared as follows: materials were prepared according to the electrolyte-resistant glue formula used in this embodiment, and related materials were mixed and dispersed in water to prepare electrolyte-resistant glue with a solid content of 30 wt%.

[0123] Test Example 4

[0124] 1. Test subjects

[0125] The glue prepared in Example 4 was used as the test object.

[0126] 2. Make samples

[0127] Using the glue to be tested, a tape sample was prepared according to the following procedure:

[0128] A silicon release film was used as a base film, and the test object was coated on the film surface of the silicon release film. A 2 μm thick PET film was then laminated on the glue coating. The glue was dried to form a pressure-sensitive adhesive layer to obtain the tape sample of this test example.

[0129] 3. Peel force test

[0130] The relevant processing of the peeling force test is the same as the peeling force test in Test Example 1.

[0131] 4. Test Results

[0132] The test results are shown in Table 10. For ease of comparison, the relevant test results for Treatment Group 3-2 in Example 3, as tested in Test Example 3, are also included in Table 10. The glue formulations used in this test example differed in their crosslinker components. The glue formulation used in Treatment Group 4-3 did not contain a crosslinker, while the glue formulations used in Treatment Groups 3-2, 4-1, and 4-2 all contained a crosslinker. The peel force retention data for the glue in Treatment Group 4-3 before and after electrolyte soaking showed that its electrolyte resistance was superior to that of the glues produced in all the control groups set forth in Comparative Examples 1, 2, and 3. This demonstrates that for glue formulations containing EPDM rubber in the main resin with a chemical composition of 50% to 65% ethylene content and 0.2% to 1.5% ENB, even without the use of a crosslinker, the glue can achieve excellent bonding and electrolyte resistance. On this basis, introducing a cross-linking agent into the formula can further improve the electrolyte resistance of the glue. This can be verified by comparing the peeling force retention data before and after the electrolyte soaking of the glue of treatment group 4-3 with treatment group 3-2, treatment group 4-1, and treatment group 4-2 in this test example.

[0133] Table 10. Peel force test results of Test Example 4

[0134]

[0135] Preparation Example

[0136] In this preparation example, the glues prepared from treatment groups 1-3 of Example 1, treatment groups 3-2 of Example 3, and treatment groups 4-3 of Example 4 were used to further prepare multi-layer structural adhesive tapes.

[0137] The multi-layer structural adhesive tape is composed of a release film, a first adhesive layer, a first base material layer, a swelling and adhesion-losing layer, a second base material layer, and a second adhesive layer which are compounded in sequence.

[0138] In this preparation example:

[0139] (1) PET films with a thickness of 2 μm were used as the first substrate layer and the second substrate layer.

[0140] (2) The glues prepared from treatment groups 1-3 of Example 1, treatment groups 3-2 of Example 3, and treatment groups 4-3 of Example 4 were respectively used to form the first glue layer.

[0141] (3) The formula for forming the swelling and adhesion-losing layer consists of 80 wt.% of EVA and 20 wt.% of HM-1000 hydrogenated petroleum resin with a softening point of 100°C.

[0142] (4) The formula for forming the second adhesive layer consists of 60 wt.% of SEBS and 40 wt.% of HM-1000 hydrogenated petroleum resin with a softening point of 100°C.

[0143] Based on the above material information, a multilayer structural tape was prepared according to the following process:

[0144] A coating process is adopted to coat glue for forming a first adhesive layer on the surface of a release film to form the first adhesive layer; then a first substrate layer is attached to the side of the first adhesive layer away from the release film; glue for forming a swelling and losing adhesion layer is coated on the surface of the first substrate layer away from the first adhesive layer to form the swelling and losing adhesion layer; then a second substrate layer is attached to the surface of the swelling and losing adhesion layer; glue for forming a second adhesive layer is coated on the side of the second substrate layer away from the swelling and losing adhesion layer to form the second adhesive layer, thereby obtaining a multi-layer structural tape.

[0145] Test Example 5

[0146] 1. Test subjects

[0147] The multilayer structured adhesive tape prepared in the preparation example was used as a test object.

[0148] 2. Make samples

[0149] The separator, negative electrode sheet, separator, and positive electrode sheet are stacked and wound together to form a battery cell. This is then hot-pressed with aluminum-plastic film and then subjected to drying, liquid injection, and formation steps to form a lithium battery sample. The first layer of multi-layer structural tape is adhered to the surface of the battery cell, while the inner surface of the aluminum-plastic film is adhered to the second layer of the multi-layer structural tape.

[0150] In addition, in the electrolyte used, the mass content of lithium salt (1 mol / L LiPF6) is 12.5%, and the mass content of organic solvent is 87.5%: calculated according to the mass ratio, ethylene carbonate: propylene carbonate: diethyl carbonate: ethyl propionate in the organic solvent = 30:10:30:30.

[0151] 3. Lithium battery drop test

[0152] The six sides and four corners of the lithium battery sample are placed facing the ground, and then the lithium battery sample is dropped vertically from a height of 1.8m. After the drop test, the lithium battery voltage is tested. If the voltage change is less than 60mV, it is judged to have passed, otherwise it has failed. If the battery smokes and catches fire, it is judged to have failed. The lithium battery drop test pass rate of lithium battery samples made using the same test object is calculated as follows:

[0153]

[0154] 4. Test Results

[0155] The test results of this test are shown in Table 11. From the test results, it can be seen that the lithium battery samples tested in this test example all have excellent anti-drop performance.

[0156] Table 11. Lithium battery drop test results of Test Example 5

[0157] Glue sources for making multi-layer structural tapes Lithium battery drop test pass rate Example 1 Treatment Groups 1-3 100％ Example 3 Treatment Group 3-2 100％ Example 4 Treatment Group 4-3 100％

[0158] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents, but these modifications or replacements are all within the scope of protection of the present invention.

Claims

1. An electrolyte-resistant glue, characterized by: Calculated by weight, the electrolyte-resistant glue includes 50-70 parts of main resin, 20-50 parts of tackifying resin, and 0.1-0.5 parts of cross-linking agent; The main resin includes EPDM rubber, the ethylene content in the EPDM rubber is 50% to 65%, and the ethylidene norbornene content in the EPDM rubber is 0.2% to 1.5%; The cross-linking agent includes at least one of amino resin, nitrogen pyridine and isocyanate.

2. The electrolyte-resistant glue according to claim 1, characterized in that: The tackifying resin includes hydrogenated petroleum resin.

3. The electrolyte-resistant glue according to claim 1, wherein: The main resin further comprises modified EPDM rubber, and the modified groups grafted onto the modified EPDM rubber comprise at least one of hydroxyl, carboxyl, epoxy and maleic anhydride.

4. The electrolyte-resistant glue according to claim 3, characterized in that: The modified group grafting rate of the modified EPDM rubber is 0.5% to 2%.

5. The electrolyte-resistant glue according to claim 3, characterized in that: The modifying group of the modified EPDM rubber includes maleic anhydride.

6. The electrolyte-resistant glue according to claim 3, characterized in that: The mass of the EPDM rubber: the mass of the modified EPDM rubber = 90-98: 2-10.

7. The electrolyte-resistant glue according to claim 1, wherein: The electrolyte-resistant glue further includes a pigment, and the pigment includes at least one of phthalocyanine blue, titanium dioxide, inorganic cobalt blue, and inorganic cobalt green.

8. An adhesive tape, characterized in that: The adhesive tape is provided with a first adhesive layer, and the first adhesive layer is made using the electrolyte-resistant adhesive according to any one of claims 1 to 7.

9. The adhesive tape according to claim 8, wherein: The adhesive tape further includes a first substrate layer, a swelling and loss of adhesion layer, a second substrate layer and a second adhesive layer, wherein the first adhesive layer, the first substrate layer, the swelling and loss of adhesion layer, the second substrate layer and the second adhesive layer are compounded in sequence.

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