Electrolyte-resistant and high-adhesiveness termination adhesive tape and preparation method thereof

Abstract

The invention relates to the technical field of termination adhesive tapes, and particularly discloses an electrolyte-resistant and high-adhesiveness termination adhesive tape and a preparation method thereof, and the termination adhesive tape sequentially comprises a base material and an acrylic pressure-sensitive adhesive coated on one side of the base material. The termination adhesive tape disclosed by the invention has the advantages of good mechanical property, excellent electrolyte resistance and high bonding strength, and is specially used for edge sealing and bottom insulation protection and fixation of lithium ion batteries, steel shells and soft package battery cells.

Description

Technical Field

[0001] The invention relates to the technical field of termination tapes, and particularly discloses an electrolyte-resistant, highly adhesive termination tape and a preparation method thereof. Background Art

[0002] Lithium-ion batteries are high-performance batteries widely used in portable electronic products. During the assembly and production process, specialized termination tapes are typically used to secure, insulate, and protect the termination points of lithium-ion battery cells. Termination tape is a specialized insulating and securing material specifically designed for the termination points of lithium-ion battery cells. As a specialized pressure-sensitive adhesive, in addition to its performance characteristics, it also has specific requirements for substrate selection, adhesion, and chemical resistance. This is because in high-energy-density lithium-ion batteries, the termination tape is exposed to the high-voltage electrolyte within the battery for extended periods of time. Therefore, the termination tape's resistance needs to be further improved.

[0003] The invention patent with publication number CN114057929A discloses a voltage-resistant and electrolyte-resistant termination tape and a copolymer used for the termination tape. The termination tape includes a base film, specifically a polyethylene terephthalate film, and a voltage-resistant and electrolyte-resistant adhesive attached to the base film. The termination tape disclosed in the invention is cross-linked with a specifically prepared copolymer, a hydroxyl-containing elastomer, and a polyfunctional isocyanate curing agent to form an interpenetrating network three-dimensional cross-linked structure. The resulting adhesive not only maintains the good adhesion of the polyacrylate system, but also exhibits excellent voltage resistance and electrolyte resistance, and can be used in high-energy-density lithium-ion batteries.

[0004] However, the termination tape is generally thick, which may affect the energy density of the lithium battery to a certain extent. When the polyethylene terephthalate film is used as the substrate, its adhesion performance after being resistant to electrolyte may decrease and it is easy to warp, which may have a potential impact on battery performance and safety. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention discloses an electrolyte-resistant, highly adhesive termination tape and its preparation method. The termination tape disclosed in the present invention exhibits excellent mechanical properties, excellent electrolyte resistance, and high bonding strength. It is specifically designed for insulating and securing the edges and bottoms of lithium-ion batteries, steel-cased batteries, and soft-pack battery cells.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] In one aspect, the present invention provides an electrolyte-resistant, highly adhesive termination tape, which comprises, in sequence, a substrate and an acrylic pressure-sensitive adhesive coated on one side of the substrate.

[0008] In some embodiments of the present invention, the substrate is a modified polyethylene terephthalate layer with a thickness of 15 to 20 μm.

[0009] In some embodiments of the present invention, the modified polyethylene terephthalate layer is prepared as follows:

[0010] (1) mica powder and 1,3-bis(3-aminopropyl)1,1,3,3-tetramethyldisiloxane were mixed and added into toluene, the temperature was raised to 65-75°C, ultrasonically dispersed for 20-40 minutes, and filtered and washed to obtain modified mica powder;

[0011] (2) The modified mica powder of step (1) is mixed with ethylene glycol, and ultrasonically dispersed for 10 to 30 minutes, and then terephthalic acid and antimony acetate are added, and an inert atmosphere is introduced, and the temperature is raised to 230 to 260° C. for reaction for 1 to 3 hours, and excess ethylene glycol is removed, and the temperature is further raised to 260 to 300° C. for reaction for 1 to 2 hours. After the reaction is completed, the modified polyethylene terephthalate layer is obtained by stranding, pelletizing, pre-crystallization, drying, melt extrusion, biaxial stretching and heat setting.

[0012] In some embodiments of the present invention, in step (1), the mass ratio of the mica powder to 1,3-bis(3-aminopropyl)1,1,3,3-tetramethyldisiloxane is 1:(0.02-0.08).

[0013] In some embodiments of the present invention, in step (2), the mass ratio of the modified mica powder, ethylene glycol and terephthalic acid is (0.01-0.05): (0.5-0.7):1.

[0014] The present invention pre-modifies mica powder, grafts siloxane segments onto it, and then reacts it with ethylene glycol and terephthalic acid for esterification and polycondensation. This improves the compatibility between the mica powder and the polymer and increases the conformability of the film after molding. Furthermore, the modified mica powder absorbs heat energy during decomposition of the modified polyethylene terephthalate layer when participating in polymerization to obtain the modified polyethylene terephthalate layer. As the modified mica powder is evenly dispersed in the film, the penetration path of the electrolyte or corrosive gas is further increased, thereby increasing its diffusion time, improving the barrier performance of the film, and ensuring the stability of the film. The addition of the modified mica powder also provides more attachment points for the acrylic pressure-sensitive adhesive, further increasing the adhesive performance of the termination tape after electrolyte aging.

[0015] In some embodiments of the present invention, the acrylic pressure-sensitive adhesive comprises the following raw materials in parts by weight: 60 to 80 parts of polyacrylic acid resin, 10 to 15 parts of modified tackifying resin, 1 to 2 parts of green ink, and 2 to 8 parts of curing agent.

[0016] In some embodiments of the present invention, the modified tackifying resin is prepared as follows:

[0017] The tackifying resin and toluene are mixed, heated to 100-120° C., and N-cyclohexyl-γ-aminopropylmethyldimethoxysilane is added under stirring, followed by a catalyst. The modified tackifying resin is obtained after reacting for 2-3 hours.

[0018] In some embodiments of the present invention, the mass ratio of the tackifying resin to N-cyclohexyl-γ-aminopropylmethyldimethoxysilane is 1:(0.02-0.05).

[0019] Preferably, the mass ratio of the tackifying resin to N-cyclohexyl-γ-aminopropylmethyldimethoxysilane is 1:0.035.

[0020] In some embodiments of the present invention, the coating thickness of the acrylic pressure-sensitive adhesive is 10 to 15 μm.

[0021] Preferably, the preparation steps of the acrylic pressure-sensitive adhesive are as follows:

[0022] The modified tackifying resin and the green ink are mixed and stirred, and then polyacrylic acid resin is added and mixed evenly, and a curing agent is added and stirred to obtain the acrylic pressure-sensitive adhesive.

[0023] By modifying the tackifying resin, the present invention not only increases the initial tack of the termination tape, but also further improves the electrolyte resistance and bonding strength of the termination tape, significantly enhancing the stability of the termination tape. This may be because the polar and cyclohexyl-containing side chains introduced into the modified tackifying resin increase the entanglement density, further enhancing the cohesion and adhesion of the acrylic pressure-sensitive adhesive. Furthermore, during the cross-linking molding process of the acrylic pressure-sensitive adhesive, the cross-linking density is further increased, further enhancing the stability of the acrylic pressure-sensitive adhesive layer and effectively preventing electrolyte penetration. Furthermore, the side chains introduced at a specific ratio avoid the potential loss of stability caused by excessive entanglement.

[0024] Another aspect of the present invention provides a method for preparing an electrolyte-resistant, highly adhesive termination tape, comprising the following steps:

[0025] One side of the modified polyethylene terephthalate layer is corona treated to obtain a substrate surface, and an acrylic pressure-sensitive adhesive is coated on the substrate surface. The substrate surface is dried at 70-110°C for 8-12 minutes for curing, and then aged at 50-60°C for 8-15 days. After cooling, the tape is rolled up and cut to obtain a termination tape.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The termination tape disclosed in the present invention has the advantages of good mechanical properties, excellent electrolyte resistance and high bonding strength, and is specially used for the insulation protection and fixation of the edges and bottoms of lithium-ion batteries, steel shells and soft-pack battery cells.

[0028] (2) The present invention pre-modifies mica powder, grafts siloxane segments onto it, and then participates in esterification and polycondensation reactions with ethylene glycol and terephthalic acid. On the one hand, the compatibility of mica powder with polymers is improved, and the conformability of the film after molding is increased. On the other hand, the penetration path of electrolyte or corrosive gas is increased, the diffusion time is increased, the barrier performance of the film is increased, and the stability of the film is improved. The addition of modified mica powder also increases the attachment points of acrylic pressure-sensitive adhesive, further increasing the bonding performance after electrolyte aging.

[0029] (3) The present invention improves the initial tack of the termination tape while further improving the electrolyte resistance and bonding strength of the termination tape by modifying the tackifying resin. The stability of the termination tape is greatly improved, and the problem of decreased stability that may be caused by excessive entanglement of the acrylic pressure-sensitive adhesive system is avoided. DETAILED DESCRIPTION

[0030] The present invention will be described below in conjunction with specific embodiments. It should be noted that the following examples are illustrative of the present invention and are intended only to illustrate the present invention and are not intended to limit the present invention. Other combinations and various modifications within the scope of the present invention may be made without departing from the spirit or scope of the present invention.

[0031] Unless otherwise specified, the reagents used below can be easily obtained from commercial companies.

[0032] Unless otherwise specified, the particle size of the mica powder used below is 5-10 μm, commercially available polyethylene terephthalate was purchased from Dongguan Baojia Plastic Co., Ltd., n-butanol etherified melamine formaldehyde resin was purchased from Shanghai Xinhua Resin Co., Ltd., C5 petroleum resin was purchased from Dongguang County Jinda Chemical Co., Ltd., and polyacrylic acid resin was purchased from Hubei Dali Chemical Co., Ltd.

[0033] Unless otherwise specified, the post-processing steps of "filtration", "washing", "stranding", "granulation" and "corona treatment" used below are routine operations for those skilled in the art and can be selected according to actual operations.

[0034] Preparation Example 1

[0035] The preparation steps of the modified polyethylene terephthalate layer are as follows:

[0036] (1) 5 g of mica powder and 0.25 g of 1,3-bis(3-aminopropyl)1,1,3,3-tetramethyldisiloxane were mixed and dispersed in 20 mL of toluene, heated to 70 °C, and ultrasonically treated for 30 min. The modified mica powder was obtained by filtration and washing.

[0037] (2) 3 g of modified mica powder and 60 mL of ethylene glycol were mixed and ultrasonically dispersed to obtain a dispersion of the modified mica powder. 100 g of terephthalic acid and 0.08 g of antimony acetate were then added, and a nitrogen atmosphere was introduced. The temperature was raised to 245 ° C for reaction for 2 h, and excess ethylene glycol was removed. The temperature was raised to 280 ° C for reaction for 1.5 h for polycondensation. After the reaction was completed, the mixture was stretched and pelletized, and then pre-crystallized and dried at 160 ° C. It was melt-extruded at 270 ° C, cooled, and then stretched 3.5 times in the transverse direction and 3 times in the longitudinal direction in a drying tunnel at 90 ° C. Finally, it was heat-set at 220 ° C to obtain a modified polyethylene terephthalate layer.

[0038] Preparation Example 2

[0039] The preparation steps of the modified polyethylene terephthalate layer are the same as those of Preparation Example 1, except that in step (1), the amount of 1,3-bis(3-aminopropyl)1,1,3,3-tetramethyldisiloxane added is 0.45 g.

[0040] Preparation Example 3

[0041] The preparation steps of the modified polyethylene terephthalate layer are the same as those of Preparation Example 1, except that the amount of modified mica powder added in step (2) is 6 g.

[0042] Preparation Example 4

[0043] The preparation steps of the modified tackifying resin are as follows:

[0044] Mix 10 g of C5 petroleum resin and 20 mL of toluene, heat to 110°C, add 0.35 g of N-cyclohexyl-γ-aminopropylmethyldimethoxysilane while stirring, and then add 0.05 mL of 11.9 mol / L concentrated hydrochloric acid. After reacting for 2.5 hours, the modified tackifying resin is obtained.

[0045] Preparation Example 5

[0046] The preparation steps of the modified tackifying resin are the same as those of Preparation Example 4, except that the amount of N-cyclohexyl-γ-aminopropylmethyldimethoxysilane added is 0.6 g.

[0047] Preparation Example 6

[0048] The preparation steps of acrylic pressure-sensitive adhesive are as follows:

[0049] 12.5 g of modified tackifying resin and 1.5 g of green ink were mixed and stirred, and then 70 g of polyacrylic acid resin was added and mixed evenly. 5 g of n-butanol etherified melamine formaldehyde resin was added and stirred to obtain acrylic pressure-sensitive adhesive.

[0050] The modified tackifying resin used was obtained from Preparation Example 4.

[0051] Preparation Example 7

[0052] The preparation steps of acrylic pressure-sensitive adhesive are as follows:

[0053] Mix 10g of modified tackifying resin and 1g of green ink, add 60g of polyacrylic acid resin, mix evenly, add 2g of n-butanol etherified melamine formaldehyde resin, and stir to obtain acrylic pressure-sensitive adhesive.

[0054] The modified tackifying resin used was obtained from Preparation Example 4.

[0055] Preparation Example 8

[0056] The preparation steps of acrylic pressure-sensitive adhesive are as follows:

[0057] 15 g of modified tackifying resin and 2 g of green ink were mixed and stirred, and then 80 g of polyacrylic acid resin was added and mixed evenly. 8 g of n-butanol etherified melamine formaldehyde resin was added and stirred to obtain acrylic pressure-sensitive adhesive.

[0058] The modified tackifying resin used was obtained from Preparation Example 4.

[0059] Preparation Example 9

[0060] The preparation steps of the acrylic pressure-sensitive adhesive are the same as those in Preparation Example 6, except that the modified tackifying resin used is obtained from Preparation Example 5.

[0061] Preparation Example 10

[0062] The preparation steps of the acrylic pressure-sensitive adhesive were the same as those in Preparation Example 6, except that an equal amount of C5 petroleum resin was used to replace the modified tackifying resin obtained in Preparation Example 4.

[0063] Unless otherwise specified, the thickness of the modified polyethylene terephthalate layer used below is 18 μm, and the coating thickness of the acrylic pressure-sensitive adhesive used below is 12 μm.

[0064] Example 1

[0065] A method for preparing an electrolyte-resistant, highly adhesive termination tape comprises the following steps:

[0066] One side of the modified polyethylene terephthalate layer is corona treated to obtain a substrate surface, and an acrylic pressure-sensitive adhesive is coated on the substrate surface. The substrate surface is dried at 90°C for 10 minutes to cure, and then aged at 55°C for 12 days. After cooling, the tape is rolled up and cut to obtain a termination tape.

[0067] The modified polyethylene terephthalate layer used in this example is obtained from Preparation Example 1, and the acrylic pressure-sensitive adhesive used is obtained from Preparation Example 6.

[0068] Example 2

[0069] A method for preparing an electrolyte-resistant, highly adhesive termination tape comprises the following steps:

[0070] One side of the modified polyethylene terephthalate layer is corona treated to obtain a substrate surface, and an acrylic pressure-sensitive adhesive is coated on the substrate surface. The substrate surface is dried at 110°C for 8 minutes to cure, and then aged at 60°C for 8 days. After cooling, the tape is rolled up and cut to obtain a termination tape.

[0071] The modified polyethylene terephthalate layer used in this example is obtained from Preparation Example 2, and the acrylic pressure-sensitive adhesive used is obtained from Preparation Example 7.

[0072] Example 3

[0073] A method for preparing an electrolyte-resistant, highly adhesive termination tape comprises the following steps:

[0074] One side of the modified polyethylene terephthalate layer is corona treated to obtain a substrate surface, and an acrylic pressure-sensitive adhesive is coated on the substrate surface. The substrate surface is dried at 70°C for 12 minutes to cure, and then aged at 50°C for 15 days. After cooling, the tape is rolled up and cut to obtain a termination tape.

[0075] The modified polyethylene terephthalate layer used in this example is obtained from Preparation Example 3, and the acrylic pressure-sensitive adhesive used is obtained from Preparation Example 8.

[0076] Example 4

[0077] A termination tape with electrolyte resistance and high adhesion and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that the modified polyethylene terephthalate layer used is obtained from Preparation Example 2.

[0078] Example 5

[0079] A termination tape with electrolyte resistance and high adhesion and a preparation method thereof. The specific implementation manner is the same as that of Example 1, except that the modified polyethylene terephthalate layer used is obtained from Preparation Example 3.

[0080] Example 6

[0081] A termination tape with electrolyte resistance and high adhesion and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that the acrylic pressure-sensitive adhesive used is obtained from Preparation Example 9.

[0082] Example 7

[0083] A termination tape with electrolyte resistance and high adhesion and a preparation method thereof. The difference lies in that commercially available polyethylene terephthalate is pre-crystallized and dried at 160°C, melt-extruded at 270°C, cooled, and then stretched 3.5 times in the transverse direction and 3 times in the longitudinal direction in a drying tunnel at 90°C. Finally, it is heat-set at 220°C and then replaced with an equal amount of the modified polyethylene terephthalate layer.

[0084] Example 8

[0085] A termination tape with electrolyte resistance and high adhesion and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that the acrylic pressure-sensitive adhesive used is obtained from Preparation Example 10.

[0086] Performance Testing

[0087] The termination tapes obtained in Examples 1-8 were subjected to the following performance tests. The specific test results are shown in Table 1:

[0088] (1) Mechanical properties test: The tensile strength and elongation at break of the pressure-sensitive adhesive tape were tested using a universal tensile testing machine produced by INSTRON. The test environment was room temperature, the sample size was 150 mm × 15 mm, the effective test length was 100 mm, and the test speed was 10 mm / min.

[0089] (2) Adhesion performance test: 180° peel strength was tested according to GB / T2792-2014 standard using a peel force tester (peel rate of 300 mm / min), which is the initial peel strength;

[0090] (3) Electrolyte resistance performance test: After laminating the aluminum foil, immerse it in an electrolyte (the mass ratio of the electrolyte is as follows: EC / PC / DEC / EP=30 / 10 / 30 / 30, and the mass ratio of 1 mol / L LiPF6 lithium salt is calculated as 12.5 wt%) at 85°C (the mass ratio of the termination tape and the electrolyte is 1:60) for 24 hours. Refer to the performance test (2) for a 180° peel strength test, which is the post-electrolyte peel strength, and then calculate the peel force retention rate (peel force retention rate = (post-electrolyte peel strength / initial peel strength)*100%).

[0091] Table 1

[0092]

[0093] As can be seen from Table 1, the termination tapes provided in Examples 1 to 3 of the present invention have good mechanical properties, excellent electrolyte resistance and good bonding strength.

[0094] By comparing Example 4 and Example 5 with Example 1, it can be seen that when the addition amounts of 1,3-bis(3-aminopropyl)1,1,3,3-tetramethyldisiloxane and modified mica powder in the preparation of the modified polyethylene terephthalate layer are changed respectively, the mechanical properties, electrolyte resistance and bonding strength of the termination tape will all decrease to varying degrees.

[0095] By comparing Example 6 with Example 1, it can be seen that when the amount of N-cyclohexyl-γ-aminopropylmethyldimethoxysilane added in the preparation of the modified tackifying resin used in the preparation of the acrylic pressure-sensitive adhesive is changed, the adhesion of the acrylic pressure-sensitive adhesive will be reduced and the cross-linking density of the acrylic pressure-sensitive adhesive during cross-linking molding will be affected, thereby affecting the bonding strength and electrolyte resistance of the termination tape.

[0096] By comparing Example 7 with Example 1, it can be seen that when the modified polyethylene terephthalate layer is replaced by an equal amount of commercially available polyethylene terephthalate, the electrolyte resistance and bonding strength of the termination tape are reduced, and the mechanical properties are also affected to a certain extent, possibly due to the lack of penetration paths and attachment points provided by the modified mica powder.

[0097] By comparing Example 8 with Example 1, it can be seen that when the acrylic pressure-sensitive adhesive prepared by using C5 petroleum resin as a tackifying resin replaces the acrylic pressure-sensitive adhesive used in equal amounts, its insufficient cohesion in the system will lead to a decrease in the bonding strength of the termination tape before and after electrolyte resistance, and the electrolyte resistance performance of the termination tape will also deteriorate.

[0098] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment, it is not intended to limit the present invention. Any technician familiar with the present profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A termination tape having electrolyte resistance and high adhesion, characterized in that: The termination tape comprises a substrate and an acrylic pressure-sensitive adhesive coated on one side of the substrate.

2. The electrolyte-resistant, highly adhesive termination tape according to claim 1, characterized in that The substrate is a modified polyethylene terephthalate layer with a thickness of 15 to 20 μm.

3. The electrolyte-resistant, highly adhesive termination tape according to claim 2, characterized in that The steps for preparing the modified polyethylene terephthalate layer are as follows: (1) mica powder and 1,3-bis(3-aminopropyl)1,1,3,3-tetramethyldisiloxane were mixed and added into toluene, the temperature was raised to 65-75°C, ultrasonically dispersed for 20-40 minutes, and filtered and washed to obtain modified mica powder; (2) The modified mica powder of step (1) is mixed with ethylene glycol, and ultrasonically dispersed for 10 to 30 minutes, and then terephthalic acid and antimony acetate are added, and an inert atmosphere is introduced, and the temperature is raised to 230 to 260° C. for reaction for 1 to 3 hours, and excess ethylene glycol is removed, and the temperature is further raised to 260 to 300° C. for reaction for 1 to 2 hours. After the reaction is completed, the modified polyethylene terephthalate layer is obtained by stranding, pelletizing, pre-crystallization, drying, melt extrusion, biaxial stretching and heat setting.

4. The electrolyte-resistant, highly adhesive termination tape according to claim 3, characterized in that In step (1), the mass ratio of the mica powder to 1,3-bis(3-aminopropyl)1,1,3,3-tetramethyldisiloxane is 1:(0.02-0.08).

5. The electrolyte-resistant, highly adhesive termination tape according to claim 3, characterized in that In step (2), the mass ratio of the modified mica powder, ethylene glycol and terephthalic acid is (0.01-0.05): (0.5-0.7):

1.

6. The electrolyte-resistant, highly adhesive termination tape according to claim 1, characterized in that The acrylic pressure-sensitive adhesive comprises the following raw materials in parts by weight: 60 to 80 parts of polyacrylic acid resin, 10 to 15 parts of modified tackifying resin, 1 to 2 parts of ink, and 2 to 8 parts of curing agent.

7. The electrolyte-resistant, highly adhesive termination tape according to claim 6, characterized in that The preparation steps of the modified tackifying resin are as follows: The tackifying resin and toluene are mixed, heated to 100-120° C., and N-cyclohexyl-γ-aminopropylmethyldimethoxysilane is added under stirring, followed by a catalyst. The modified tackifying resin is obtained after reacting for 2-3 hours.

8. The electrolyte-resistant, highly adhesive termination tape according to claim 7, characterized in that The mass ratio of the tackifying resin to N-cyclohexyl-γ-aminopropylmethyldimethoxysilane is 1:(0.02-0.05).

9. The electrolyte-resistant, highly adhesive termination tape according to claim 1, characterized in that The coating thickness of the acrylic pressure-sensitive adhesive is 10 to 15 μm.

10. A method for preparing the electrolyte-resistant, highly adhesive termination tape according to any one of claims 1 to 9, characterized in that: The following steps are involved: One side of the modified polyethylene terephthalate layer is corona treated to obtain a substrate surface, an acrylic pressure-sensitive adhesive is coated on the substrate surface, dried at 70-110° C. for 8-12 minutes to cure, and then aged at 50-60° C. for 8-15 days. After cooling, the tape is rolled up and cut to obtain the termination tape.

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