Electrolyte-resistant glue and adhesive tape using same

Abstract

The invention provides electrolyte-resistant glue which comprises the following components in parts by mass: 50-70 parts of matrix resin, 20-50 parts of tackifying resin and 0-5 parts of a cross-linking agent, the matrix resin comprises ethylene-propylene-diene monomer rubber, the ethylene content in the ethylene-propylene-diene monomer rubber is 50%-65%, and the ethylidene norbornene content in the ethylene-propylene-diene monomer rubber is 0.2%-1.5%. The electrolyte-resistant glue provided by the invention contains the ethylene-propylene-diene monomer, the introduction of the ethylene-propylene-diene monomer can effectively improve the electrolyte resistance of the glue and the flexibility of a glue layer formed by the electrolyte-resistant glue, and based on the application of the ethylene-propylene-diene monomer, the ethylene content and the ENB content of the ethylene-propylene-diene monomer are regulated and controlled, so that the electrolyte resistance of the glue is improved. And a glue layer formed by the electrolyte-resistant glue can achieve higher binding power.

Description

Technical Field

[0001] The 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 have the characteristics of high operating voltage, high energy density, low self-discharge, multiple cycles, long service life, and high environmental protection. They are widely used in mobile phones, automobiles, notebooks and other fields. In the production and assembly process of lithium batteries, lithium battery tape has an important impact on the safety performance of lithium batteries. Lithium battery tape is generally used for insulation and fixed protection of electrode windings, cell terminations, and pole pieces during the production and assembly of lithium batteries. This requires that lithium battery tape needs to have certain initial adhesion, sustained adhesion, high temperature resistance, and electrolyte corrosion resistance.

[0003] In recent years, the lithium battery assembly field has a great demand for the electrolyte durability of lithium battery tape. During the lithium battery assembly process and in later applications, the lithium battery tape will directly contact the electrolyte, which requires the tape to withstand long-term immersion in the electrolyte without losing its viscosity and dissolving impurities to pollute the electrolyte. The existing tapes will have varying degrees of decreased adhesion after being immersed in the electrolyte, which fails to improve or solve the problem of electrolyte durability of lithium battery tapes.

[0004] EPDM is a copolymer of ethylene, propylene and a small amount of non-conjugated dienes. 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 and only contains unsaturated double bonds in the side chains, it has excellent aging resistance such as ozone resistance, heat resistance, and weather resistance. It has been widely used in automotive parts, waterproof materials for construction, wire and cable sheaths, heat-resistant hoses, tapes, automotive seals and other fields. However, EPDM has low surface energy, poor viscosity, and is easy to debond and lose adhesion, which limits the application of EPDM in the field of tapes. Summary of the invention

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

[0006] According to the first aspect of the present invention, there is provided an electrolyte-resistant glue, which comprises 50-70 parts of a main resin, 20-50 parts of a tackifying resin, and 0-5 parts of a cross-linking agent, calculated by weight; the main resin comprises ethylene propylene diene monomer rubber, the ethylene content in the ethylene propylene diene monomer rubber is 50%-65%, and the ethylidene norbornene (abbreviated as ENB) content in the ethylene propylene diene monomer rubber is 0.2%-1.5%. The electrolyte-resistant glue provided by the present invention contains ethylene propylene diene monomer rubber, and the introduction of ethylene propylene diene monomer 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 ethylene propylene diene monomer rubber, by regulating the ethylene content and ENB content of the ethylene propylene diene monomer rubber, the adhesive layer formed by the electrolyte-resistant glue can achieve a higher bonding force. 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 includes hydrogenated petroleum resin. For a glue formula containing EPDM rubber, further using hydrogenated petroleum resin and EPDM rubber together can better improve the bonding 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 also includes modified EPDM rubber, and the modified groups grafted into 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 groups of the modified EPDM rubber is 0.5% to 2%.

[0011] Preferably, the modified group of the modified EPDM rubber includes maleic anhydride. The modified EPDM rubber modified with maleic anhydride is further preferred, which can further improve the electrolyte resistance of the glue layer formed by the glue.

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

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

[0014] Preferably, the electrolyte-resistant glue further comprises 0 to 20 parts of a pigment, and 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 embodiments of a part of the present invention, rather than all 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 embodiment uses the chemical composition of EPDM as a variable to set different treatment groups, which are numbered as treatment group 1-1, treatment group 1-2, and treatment group 1-3. The EPDM used in each treatment group is prepared by the Ziegler-Natta catalyst method, and the materials used in the preparation process are: the reaction monomers are propylene, ethylene, and ENB, the Ziegler-Natta vanadium-aluminum catalyst system (VOCl3-1 / 2Al2EtCl3) is used as a catalyst, and n-hexane is used as a reaction solvent. The reaction monomers are allowed to undergo a synthetic reaction under the action of the catalyst, wherein: the polymerization reaction temperature is 40-60°C, the reaction pressure is 2.0-2.5MPa, the polymerization time is 30min, and the reaction heat is used for adiabatic heating of the reactor. The amount of reaction monomers taken is determined based on the ethylene content, ENB content, and propylene content in the target product EPDM. The polymerization reaction temperature and reaction pressure are based on the actual reaction conditions and the ethylene content, ENB content, and propylene content in the target product, and are adaptively adjusted within the above range. 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 the 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 method for preparing electrolyte-resistant glue in each treatment group is as follows: prepare materials according to the electrolyte-resistant glue formula composition adopted in this embodiment, mix the relevant materials and disperse them in water to prepare electrolyte-resistant glue with a solid content of 30wt%.

[0025] Comparative Example 1

[0026] This comparative example prepares glue samples with reference to Example 1. The difference between the formula used to prepare the glue samples in this comparative example and the electrolyte-resistant glue formula used in each treatment group of Example 1 is that the chemical composition of the EPDM rubber is different. Apart from this, the other materials and material ratios in the two formulas are exactly the same. Taking the component composition of the EPDM rubber as a variable, this comparative example sets different comparative groups, which are numbered as 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. The above comparative groups prepare EPDM rubber with reference to the method for preparing EPDM rubber in Example 1. The amount of reaction monomers used is determined based on the ethylene content, ENB content, and propylene content in the target product EPDM rubber. The polymerization reaction temperature and reaction pressure are based on the actual reaction conditions and the ethylene content, ENB content, and propylene content in the target product, and are adaptively adjusted within the range provided in Example 1. 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 the 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 Group 1-3 70％ 0.1％ Comparison Group 1-4 45％ 2％ Comparison Group 1-5 60％ 2％ Comparison Group 1-6 70％ 2％ Comparison Group 1-7 45％ 1％ Comparison Group 1-8 70％ 1％

[0029] The method for preparing glue samples in each comparative group is as follows: prepare materials according to the glue sample formula composition adopted in this comparative example, mix the relevant materials and disperse them in water to prepare glue samples with a solid content of 30wt%.

[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 the comparative group 2-1 was prepared by referring to the process for preparing the EPDM rubber in Example 1. The difference from Example 1 is that the comparative group 2-1 uses DCPD instead of ENB as the reaction monomer for preparing the EPDM rubber, and the amount of the reaction monomer is determined based on the ethylene content, DCPD content, and propylene content in the target product EPDM rubber. The polymerization temperature and reaction pressure are adaptively adjusted within the range provided in Example 1 based on the actual reaction conditions and the ethylene content, DCPD content, and propylene content in the target product. The chemical composition of the EPDM rubber obtained in the comparative group 2-1 is 60% ethylene content and 1% DCPD content, and the remainder after deducting the ethylene content and DCPD content is the propylene content.

[0035] The materials were prepared according to the glue sample formula used in this comparison 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 of the comparison group 2-2 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, ethylene propylene rubber 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.

[0038] The ethylene-propylene rubber used in the comparative group 2-2 is prepared by the Ziegler-Natta catalyst method. The materials used in the preparation process are: the reaction monomers are propylene and ethylene, the Ziegler-Natta vanadium-aluminum catalyst system (VOCl3-1 / 2Al2EtCl3) is used as the catalyst, and n-hexane is used as the reaction solvent. The reaction monomers are allowed to undergo a synthetic reaction under the action of the catalyst, wherein: the polymerization reaction temperature is 30-60°C, the reaction pressure is 0.4-0.8MPa, the polymerization time is 30min, and the reaction heat is used for adiabatic heating of the reactor. The amount of the reaction monomer is determined based on the ethylene content and propylene content in the target product ethylene-propylene rubber. The polymerization reaction temperature and reaction pressure are based on the actual reaction conditions and the ethylene content and propylene content in the target product, and are adaptively adjusted within the above range. The chemical composition of the ethylene-propylene rubber obtained in the comparative group 2-2 is 60% ethylene content, and the remainder after deducting the ethylene content is the propylene content.

[0039] The materials were prepared according to the glue sample formula used in this comparison 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 comparison 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] Using the glue to be tested, make a tape sample according to the following operation:

[0048] A silicon release film was used as a base film, the test object was coated on the film surface of the silicon release film, and then a PET film with a thickness of 2 μm was attached to the glue coating, and 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. In an environment of 23±2℃ and 50±5%RH, adhere the copper foil with the pressure-sensitive adhesive layer of the tape sample.

[0052] S2. Then, 5000NS tape and steel plate are sequentially attached to the side of the copper foil facing away from the tape sample, and 5000NS tape is attached to the side of the tape sample facing away from the copper foil as a traction tape.

[0053] S3. Then use Kejian tensile gauge to clamp the steel plate and traction tape respectively for 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 of 5 parallel samples.

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

[0055] S1. In an environment of 23±2℃ and 50±5%RH, adhere the copper foil with the pressure-sensitive adhesive layer of the tape sample.

[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 taken out from the electrolyte.

[0058] S4. Restore the test environment to 23±2℃, 50±5%RH, and stick 5000NS tape and steel plate on the side of the copper foil facing away from the tape sample in sequence, and stick 5000NS tape on the side of the tape sample facing away from the copper foil as a traction tape.

[0059] S5. Then use Kejian tensile gauge to clamp the steel plate and traction tape respectively for 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 of 5 parallel samples.

[0060] The calculation method of 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. In the tape samples of this test example, compared with the tape samples made with the glue of each comparison group of Comparative Example 1 and Comparative Example 2, the tape samples made with the glue of each treatment group of Example 1 can achieve a higher peeling force retention rate before and after the electrolyte is soaked. The main resin of the electrolyte-resistant glue prepared in each treatment group of Example 1 is EPDM resin, and the chemical composition of the EPDM rubber used meets the requirements of 50% to 65% ethylene content and 0.2% to 1.5% ENB content. The test results show that, in the peeling force test set in this test example, the tape samples prepared by using the glue of each treatment group in Example 1 satisfy the peeling force>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 of the glue of each treatment group in Example 1 are used in lithium battery products, these pressure-sensitive tapes can be tightly attached to the surface of the battery cell before and after soaking in electrolyte.

[0064] The glue obtained from each treatment group of Example 1 was compared with the glue obtained from each comparison group of Comparative Example 1. The difference was the chemical composition of the EPDM rubber as the main resin. As mentioned above, the chemical composition of the EPDM rubber used in Example 1 all met the requirements of ethylene content of 50% to 65% and ENB content of 0.2% to 1.5%. With this as a reference, in Comparative Example 1, the ethylene content in the EPDM rubber used in Comparative Groups 1-1, 1-4, and 1-7 was relatively low, the ethylene content in the EPDM rubber used in Comparative Groups 1-3, 1-6, and 1-8 was relatively high, the ENB content in the EPDM rubber used in Comparative Groups 1-1, 1-2, and 1-3 was relatively low, and the ENB content in the EPDM rubber used in Comparative Groups 1-4, 1-5, and 1-6 was relatively high. From the test results, it can be seen that the measured peeling force of the adhesive tape samples made of the glue of the above-mentioned comparison groups has significantly decreased before and after being immersed in the electrolyte, that is, the electrolyte resistance of these glues is not good. The above test results show that in the glue formula that also uses EPDM rubber as the main resin, the chemical composition of EPDM resin plays an important role in affecting the electrolyte resistance of the glue. Based on the basic glue formula used in Example 1 and Comparative Example 1, when the chemical composition of EPDM rubber with an ethylene content of 50% to 65% and an ENB content of 0.2% to 1.5% is selected as the main resin, the glue can have good electrolyte resistance. When the chemical composition of EPDM rubber that does not meet the above characteristics is selected as the main resin, the electrolyte resistance of the glue will be significantly deteriorated, and it is difficult to meet the performance requirements of electrolyte resistance.

[0065] The glue obtained from each treatment group of Example 1 is compared with the glue obtained from each comparison group of Comparative Example 2. The difference lies in the type of main resin. The main resin used in treatment group 1-3 is EPDM rubber with ENB as the third monomer, the main resin used in comparison group 2-1 is EPDM rubber with DCPD as the third monomer, the main resin used in comparison group 2-2 is EPDM rubber without the third monomer, and the main resin used in comparison group 2-3 is SEPS. Compared with the EPDM rubber used in treatment group 1-3, although the main resin used in comparison group 2-1 is also EPDM rubber, and the ethylene content and the third monomer content of the two are equal, the tape samples prepared by the two respectively show obvious differences in electrolytic resistance. Based on the above premise, the tape sample containing EPDM rubber with ENB as the third monomer in the component composition has better electrolyte resistance. In addition to treatment groups 1-3, the electrolyte resistance measured by the glue samples made from the glue of treatment groups 1-1 and 1-2 is also better than the electrolyte resistance of the glue samples made from the glue of comparison group 2-1. This shows that, compared with the glue using EPDM rubber with the third monomer being DCPD, the glue prepared with EPDM rubber having a chemical composition satisfying an ethylene content of 50% to 65% and an ENB content of 0.2% to 1.5% has an advantage in electrolyte resistance. In addition, the material types of the main resins used in comparison groups 2-2 and 2-3 are compared with the treatment groups in Example 1. Similarly, the following conclusion can be drawn that the glue prepared with EPDM rubber having a chemical composition satisfying an ethylene content of 50% to 65% and an ENB content of 0.2% to 1.5% has an advantage in electrolyte resistance.

[0066] Table 3. Statistics of peel force test results of test example 1

[0067]

[0068] Example 2

[0069] This embodiment prepares glue samples with reference to Example 1. The formula used in this embodiment for preparing electrolyte glue 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, the EPDM rubber prepared by treatment groups 1-3 in Example 1 is used as the main resin, and nitrogen pyridine is used as the cross-linking agent. This embodiment uses the type of tackifying resin used in the formula as a variable, and sets different treatment groups, which are numbered as treatment group 2-1 and treatment group 2-2 respectively. The electrolyte formula used by the above treatment groups is compared with the electrolyte formula used by treatment groups 1-3 in Example 1, and the difference is only that each treatment group uses different types of tackifying resins to replace the tackifying resin used in the electrolyte formula of treatment groups 1-3 in Example 1 in equal quality. The tackifying resin used by each treatment group in Example 2 is specifically shown in Table 4. For the convenience of comparison, the tackifying resin used by treatment groups 1-3 in Example 1 is also loaded in Table 4.

[0070] Table 4. Tackifying resins used in each treatment group in 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 method for preparing electrolyte-resistant glue in each treatment group is as follows: prepare materials according to the electrolyte-resistant glue formula composition adopted in this embodiment, mix the relevant materials and disperse them in water to prepare electrolyte-resistant glue with a solid content of 30wt%.

[0073] Comparative Example 3

[0074] This comparative example refers to comparative example 2 and comparative group 2-3 to prepare glue samples. The formula used in this comparative example to prepare electrolyte glue 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, SEPS used in comparative group 2-3 in 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, which are numbered as comparative group 3-1 and comparative group 3-2 respectively. The electrolyte formula used in each comparative group is compared with the electrolyte formula used in comparative group 2-3 of comparative example 2, and the difference is only that each comparative group uses different types of tackifying resins to replace the tackifying resin used in the electrolyte formula of comparative group 2-3 of comparative example 2 in equal quality. The tackifying resin used in each comparative group of comparative example 3 is specifically shown in Table 5. For the convenience of comparison, the tackifying resin used in comparative group 2-3 of comparative example 2 is also loaded in Table 5.

[0075] Table 5. Tackifying resin 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 Comparison group 3-1 HM-1000 hydrogenated rosin resin with a softening point of 100°C Comparison group 3-2 HM-1000 hydrogenated terpene resin with a softening point of 100°C

[0077] The method of preparing glue samples in each comparison group is as follows: prepare materials according to the electrolyte-resistant glue formula composition adopted in this comparative example, mix the relevant materials and disperse them in water to prepare glue samples with a solid content of 30wt%.

[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 is prepared according to the following operation:

[0083] A silicon release film was used as a base film, the test object was coated on the film surface of the silicon release film, and then a PET film with a thickness of 2 μm was attached to the glue coating, and 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 peel force test is the same as the peel force test in Test Example 1.

[0086] 4. Test Results

[0087] The test results are shown in Table 6. For the convenience of comparison, the relevant test results of the treatment groups 1-3 of Example 1 and the comparison groups 2-3 of Comparative Example 2 in Test Example 1 are also included in Table 6. In the glue formula using EPDM as the main resin, the tackifying resin is matched with the EPDM to ensure that the glue has excellent bonding properties. Comparing the treatment groups 1-3, 2-1 and 2-2, the main resins used by the three are exactly the same, all of which are EPDM with ENB as the third monomer. However, the peeling force retention rate before and after the electrolyte is measured by the glue formula using hydrogenated petroleum resin as the tackifying resin is the highest. This shows that for the glue formula using EPDM with ENB as the third monomer as the main resin, the combination of hydrogenated petroleum resin as the tackifying resin component in the formula can improve its electrolyte resistance while ensuring the bonding performance of the pressure-sensitive 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. Statistics of 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, and the grafting rate of hydroxyl was 1%.

[0094] (2) Maleic anhydride modified EPDM rubber

[0095] The EPDM rubber obtained 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 by 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 electrolyte-resistant 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 adopted 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. This embodiment uses the type of modified EPDM rubber used in the formula as a variable, and sets different treatment groups, which are numbered as treatment group 3-1, treatment group 3-2, and treatment group 3-3. The electrolyte formula used in the above treatment groups is different from the electrolyte formula used in treatment groups 1-3 of Example 1, except that each treatment group uses a different type of modified EPDM rubber and unmodified EPDM rubber as the main resin in the electrolyte formula. The modified EPDM rubber used in each treatment group of Example 3 is specifically 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 method for preparing electrolyte-resistant glue in each treatment group is as follows: prepare materials according to the electrolyte-resistant glue formula composition adopted in this embodiment, mix the relevant materials and disperse them in water to prepare electrolyte-resistant glue with a solid content of 30wt%.

[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 is prepared according to the following operation:

[0108] A silicon release film was used as a base film, the test object was coated on the film surface of the silicon release film, and then a PET film with a thickness of 2 μm was attached to the glue coating, and 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 peel force test is the same as the peel force test in Test Example 1.

[0111] 4. Test Results

[0112] The test results are shown in Table 8. For the convenience of comparison, the relevant test results of treatment groups 1-3 of Example 1 in Test Example 1 are also included in Table 8. In the test objects of this test example, the main resin in the glue formula involved all includes unmodified EPDM rubber, and the chemical composition of the unmodified EPDM rubber is the same. Taking treatment groups 1-3 as a comparison, the glue formulas of treatment groups 3-1, 3-2, and 3-3 contain not only unmodified EPDM rubber, but also EPDM rubber modified by different groups. Compared with the glue samples prepared by using the glue of treatment groups 1-3, the use of modified EPDM rubber and unmodified EPDM rubber can simultaneously improve the bonding performance and electrolyte resistance of the glue and the pressure-sensitive tape prepared by using the glue.

[0113] Table 8. Statistics of peel force test results 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 are numbered as treatment group 4-1, treatment group 4-2, and treatment group 4-3 respectively.

[0117] The formula for preparing electrolyte-resistant glue in treatment group 4-1 and treatment group 4-2 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 the above treatment groups, 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. Compared with the electrolyte formula used in treatment group 3-2 of Example 3, the only difference between the electrolyte formula used in treatment group 4-1 and treatment group 4-2 and the electrolyte formula used in treatment group 3-2 of Example 3 is that each treatment group uses different types of materials of equal mass to replace the nitrogen pyridine in the electrolyte formula used in treatment group 3-2 of Example 3 as a cross-linking agent.

[0118] The formula for preparing electrolyte-resistant glue of treatment group 4-3 is: 60 parts of main resin and 35 parts of tackifying resin; in the electrolyte glue formula adopted by the above-mentioned treatment group, the composition of the main resin is the same as the component composition of the main resin adopted by 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 Pyridine Treatment Group 4-1 Amino resin Treatment Group 4-2 Isocyanate Treatment Group 4-3 none

[0122] The method for preparing electrolyte-resistant glue in each treatment group is as follows: prepare materials according to the electrolyte-resistant glue formula composition adopted in this embodiment, mix the relevant materials and disperse them in water to prepare electrolyte-resistant glue with a solid content of 30wt%.

[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 is prepared according to the following operation:

[0128] A silicon release film was used as a base film, the test object was coated on the film surface of the silicon release film, and then a PET film with a thickness of 2 μm was attached to the glue coating, and 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 peel force test is the same as the peel force test in Test Example 1.

[0131] 4. Test Results

[0132] The test results are shown in Table 10. For the convenience of comparison, the relevant test results of the treatment group 3-2 of Example 3 in Test Example 3 are also included in Table 10. In the test objects of this test example, the difference in the glue formula is the crosslinking agent component. Among them, the glue formula used in the treatment group 4-3 does not contain a crosslinking agent component, while the glue formulas used in the treatment groups 3-2, 4-1, and 4-2 respectively contain a crosslinking agent component. From the peeling force retention data before and after the electrolyte is soaked in the corresponding treatment group 4-3, its electrolyte resistance is better than the electrolyte resistance of the glue prepared by all the comparative groups set in Comparative Examples 1, 2, and 3. It can be shown that for the glue formula containing EPDM rubber with a chemical composition of 50% to 65% ethylene content and 0.2% to 1.5% ENB content in the main resin, even if a crosslinking agent is not used, the glue can achieve good bonding performance and electrolytic 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 immersion of the glues of treatment group 4-3 with those of treatment group 3-2, treatment group 4-1, and treatment group 4-2 in this test example.

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

[0134]

[0135] Preparation Example

[0136] In this preparation example, the glues prepared in treatment groups 1-3 of Example 1, treatment groups 3-2 of Example 3, and treatment groups 4-3 of Example 4 are used to further prepare a multilayer structure adhesive tape.

[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 loss-of-adhesion layer, a second base material layer, and a second adhesive layer which are compounded in sequence.

[0138] In this preparation example:

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

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

[0141] (3) The formula for forming the swelling and debonding layer is composed of 80 wt.% EVA + 20 wt.% 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 + 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 is prepared according to the following process:

[0144] By adopting a coating process, glue for forming a first adhesive layer is coated on the surface of a release film to form the first adhesive layer; then the first substrate layer is attached to the side of the first adhesive layer away from the release film; glue for forming a swollen and unbonded layer is coated on the surface of the first substrate layer away from the first adhesive layer to form the swollen and unbonded layer; then the second substrate layer is attached to the surface of the swollen and unbonded layer; glue for forming a second adhesive layer is coated on the side of the second substrate layer away from the swollen and unbonded 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, which is then hot-pressed and packaged with aluminum-plastic film, and then dried, injected, and formed to form a lithium battery sample. The surface of the battery cell is attached with the first adhesive layer of the multi-layer structural tape, and the inner surface of the aluminum-plastic film is attached with the second adhesive 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 by mass ratio, in the organic solvent, ethylene carbonate: propylene carbonate: diethyl carbonate: ethyl propionate = 30:10:30:30.

[0151] 3. Lithium battery drop test

[0152] The six faces and four corners of the lithium battery sample are respectively 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 be passed, otherwise it is not passed; if the battery smokes and catches fire, it is judged to be not passed. The lithium battery drop test pass rate of lithium battery samples made with 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 of the test objects of 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 rather than to limit the protection scope of the present invention. Although the present invention is described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the technical solutions of the present invention can be modified or equivalently replaced, but these modifications or replacements are all within the protection scope of the present invention.

Claims

1. An electrolyte-resistant glue, characterized in that: Calculated by weight, the electrolyte-resistant glue includes 50-70 parts of main resin, 20-50 parts of tackifying resin, and 0-5 parts of cross-linking agent; The main resin comprises 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%.

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, characterized in that: The main resin also includes modified EPDM rubber, and the modified groups grafted into the modified EPDM rubber include at least one of hydroxyl, carboxyl, epoxy and maleic anhydride.

4. The electrolyte-resistant glue according to claim 3, characterized in that: The grafting rate of the modified groups 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, characterized in that: Calculated by weight, the electrolyte-resistant glue includes 0.1 to 0.5 parts of the cross-linking agent, and the cross-linking agent includes at least one of amino resin, nitrogen pyridine, and isocyanate.

8. The electrolyte-resistant glue according to claim 1, characterized in that: The pigment includes at least one of phthalocyanine blue, titanium dioxide, inorganic cobalt blue and inorganic cobalt green.

9. An adhesive tape, characterized in that: The adhesive tape is provided with a first adhesive layer, and the first surface adhesive layer is made by using the electrolyte-resistant glue as claimed in any one of claims 1 to 8.

10. The adhesive tape according to claim 9, characterized in that: 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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