A lithium battery tape adhesive and its synthesis method

Abstract

This invention discloses a lithium battery tape adhesive and its synthesis method, belonging to the technical field of adhesives for lithium batteries. It comprises: at least one oligomer containing acrylate groups; at least one oligomer containing epoxy groups; a reactive silicone-fluorine block copolymer oligomer, the end groups of which contain acrylate double bonds capable of participating in UV curing, and its main chain simultaneously containing polysiloxane segments and fluorinated polyacrylate segments; a photoradical initiator; and a latent epoxy curing agent. The reactive silicone-fluorine block copolymer oligomer is a polydimethylsiloxane-polyhexafluorobutyl methacrylate block copolymer (PDMS-b-PFMA), wherein at least one end of the block copolymer is chemically modified to introduce acrylate double bonds. The reactive silicone-fluorine block copolymer oligomer is prepared by atom transfer radical polymerization (ATRP). This method achieves rapid curing while imparting excellent electrolyte resistance and high-temperature stability to the adhesive, realizing a synergistic optimization of both properties.

Description

Technical Field

[0001] This invention belongs to the technical field of adhesives for lithium batteries, specifically relating to a lithium battery tape adhesive and its synthesis method. Background Technology

[0002] In the manufacturing process of lithium batteries, a large amount of tape is used to fix and protect components such as cells, electrodes, tabs and insulating sheets. The adhesive layer in the tape needs to be immersed in electrolyte containing carbonate solvent and LiPF6 for a long time, and must withstand the temperature changes and mechanical stress generated by battery charging and discharging. Therefore, stringent requirements are placed on the adhesive's resistance to electrolyte, high temperature non-residue performance and electrochemical stability.

[0003] Currently, commercially available lithium battery tapes generally use acrylic pressure-sensitive adhesives. The core problem lies in the difficulty of simultaneously achieving both curing efficiency and electrolyte resistance. On the one hand, traditional thermosetting systems have slow curing speeds, with curing cycles typically lasting tens of hours, severely restricting production efficiency. On the other hand, conventional acrylic pressure-sensitive adhesives are prone to swelling and decreased cohesive strength after being immersed in high-temperature electrolytes, leading to a significant decrease in peel strength or even dissolution of the adhesive layer. Residual adhesive is also more likely to occur at high temperatures.

[0004] To improve electrolyte resistance, existing technologies attempt to introduce silicon- or fluorine-containing components. For example, some methods introduce silicon- or fluorine-containing powders through physical blending, but physical blends suffer from poor storage stability and phase separation, making it difficult to maintain uniform performance over long-term use. Other methods use silane coupling agents to modify inorganic fillers in situ, but this approach cannot form stable chemical bonds in the polymer network, limiting its improvement in electrolyte resistance. Furthermore, solvent-free and low-VOC emissions are common goals in the pressure-sensitive adhesive field, but for lithium-ion battery tape adhesives, achieving rapid curing while maintaining reliable adhesion in electrolyte and high-temperature environments remains the primary technical challenge.

[0005] Therefore, in order to address the above-mentioned technical problems, it is necessary to provide a lithium battery tape adhesive and a method for synthesizing the same. Summary of the Invention

[0006] The purpose of this invention is to provide a lithium battery tape adhesive and its synthesis method, which uses reactive silicone-fluorine block copolymer oligomers to participate in the crosslinking network through chemical bonding, thereby achieving rapid curing while endowing the adhesive with excellent electrolyte resistance and high temperature stability.

[0007] To achieve the above objectives, a specific embodiment of the present invention provides the following technical solution: A lithium battery tape adhesive, comprising: At least one oligomer containing an acrylate group; At least one oligomer containing an epoxy group; Reactive silicone-fluorine block copolymer oligomers have end groups containing acrylate double bonds that can participate in UV curing, and their main chain contains both polysiloxane segments and fluorinated polyacrylate segments. Photoradical initiators; Latent epoxy curing agent.

[0008] In one or more embodiments of the present invention, the reactive silicone-fluorine block copolymer oligomer is a polydimethylsiloxane-polyhexafluorobutyl methacrylate block copolymer (PDMS-b-PFMA), wherein at least one end of the block copolymer is chemically modified to introduce acrylate double bonds.

[0009] In one or more embodiments of the present invention, the reactive silicone-fluorine block copolymer oligomer is prepared by atom transfer radical polymerization (ATRP), comprising: using a brominated ester derivative of monohydroxyl-terminated polydimethylsiloxane as a macromolecular initiator to initiate the polymerization of hexafluorobutyl methacrylate to obtain a PDMS-b-PFMA diblock copolymer, and then introducing acrylate double bonds through end-group modification.

[0010] In one or more embodiments of the present invention, the oligomer containing acrylate groups is polyurethane acrylate, the oligomer containing epoxy groups is epoxy acrylate; and the adhesive is a solvent-free system.

[0011] In one or more embodiments of the present invention, the content of each component, by weight, is as follows: 40-55 parts of polyurethane acrylate; 10-20 parts epoxy acrylate; 15-25 parts reactive diluent; 5-15 parts of reactive silicone-fluorine block copolymer oligomer; 1-3 parts of photoradical initiator; Latent epoxy curing agent: 1-4 parts; 1-5 parts of nano-silica.

[0012] A method for preparing the lithium battery tape adhesive described above includes the following steps: (1) Providing the reactive silicone-fluorine block copolymer oligomer; (2) Under light-protected conditions, oligomers containing acrylate groups, oligomers containing epoxy groups, reactive diluents, reactive silicone-fluorine block copolymer oligomers and nanofillers are mixed evenly, and then photoradical initiators and latent epoxy curing agents are added. Vacuum degassing is performed to obtain adhesive. (3) Apply the adhesive to the substrate; (4) Expose the coating layer to UV irradiation to induce free radical polymerization and achieve preliminary shaping; (5) Heat the UV-irradiated coating layer to cause the epoxy groups to undergo a cross-linking reaction under the action of a latent curing agent, thus completing the deep curing.

[0013] In one or more embodiments of the present invention, the method for preparing the reactive silicone-fluorine block copolymer oligomer in step (1) includes: Starting with hydroxyl-terminated polydimethylsiloxane, it is converted into a brominated ester macromolecular initiator. In the presence of a catalyst, hexafluorobutyl methacrylate is used as a monomer to obtain a PDMS-b-PFMA diblock copolymer via ATRP reaction. Subsequently, acrylate double bonds are introduced at the polymer ends to obtain the final product.

[0014] A lithium battery tape includes a substrate and an adhesive layer attached to the substrate, the adhesive layer being formed by dual curing of the lithium battery tape adhesive described above through UV irradiation and heating.

[0015] In one or more embodiments of the present invention, the substrate is a polyethylene terephthalate (PET) film or a polyimide (PI) film.

[0016] In one or more embodiments of the present invention, the adhesive or tape is used to bond and fix the cell assembly in an environment where the lithium battery is in contact with the electrolyte.

[0017] Compared with existing technologies, the lithium battery tape adhesive and its synthesis method of the present invention, in which the photoradical initiator and the latent epoxy curing agent work synergistically, allow the surface to dry and set within seconds of UV irradiation, and heat treatment activates deep crosslinking of the epoxy, shortening the curing cycle from tens of hours in traditional thermosetting systems to minutes. The reactive silicone-fluorine block copolymer oligomer participates in the crosslinking network through chemical bonding, enabling the adhesive to maintain high peel strength and leave no residue after long-term immersion in high-temperature electrolyte. The dual curing mechanism, combined with the chemical modification of the reactive silicone-fluorine block copolymer oligomer, achieves rapid curing while endowing the adhesive with excellent electrolyte resistance and high-temperature stability, realizing the synergistic optimization of the two properties. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1This is a schematic diagram of the preparation method of the lithium battery tape adhesive and the tape manufacturing process of the present invention.

[0020] Figure 2 The graph shows a comparison of the peel strength retention rates of the tapes obtained in Examples 1-3 and Comparative Examples 1-2 after immersion in an electrolyte at 85°C for 24 hours and 168 hours. Detailed Implementation

[0021] To enable those skilled in the art to better understand the technical solutions in this disclosure, the technical solutions in the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments in this disclosure, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this disclosure.

[0022] Synthesis Example 1: Preparation of reactive silicone-fluorine block copolymer oligomer (PDMS-b-PFMA-AC); Preparation of the macromolecular initiator PDMS-Br: 50 g of hydroxyl-terminated polydimethylsiloxane was dissolved in 200 mL of anhydrous tetrahydrofuran, and 8.0 mL of triethylamine was added. The mixture was cooled to 0 °C in an ice bath. Under nitrogen protection, 6.5 mL of 2-bromoisobutyryl bromide was slowly added dropwise. After the addition was complete, the mixture was allowed to rise to room temperature and reacted for 24 hours. The triethylamine hydrochloride was removed by filtration. The filtrate was concentrated by rotary evaporation and then added dropwise to a methanol / water (volume ratio 1:1) mixed solvent to precipitate the precipitate. The precipitate was dried under vacuum at 40 °C to constant weight to obtain the brominated ester-terminated PDMS macromolecular initiator (PDMS-Br).

[0023] ATRP polymerization: 20 g PDMS-Br, 25 mL hexafluorobutyl methacrylate, 0.12 g CuBr, 0.36 mL N,N,N',N',N''-pentamethyldiethylenetriamine (PMDETA), and 30 mL anisole were added to a dry Schlenk flask. After deoxygenation through three cycles of liquid nitrogen freezing-vacuuming-thawing, the flask was sealed and placed in an 80°C oil bath with stirring for 8 hours. After the reaction was completed, the copper catalyst was removed by passing the reaction solution through a neutral alumina short column. The filtrate was collected, concentrated, and then precipitated by adding it dropwise to methanol / water (volume ratio 1:1). The precipitate was then dried under vacuum to obtain the PDMS-b-PFMA diblock copolymer. According to GPC analysis, Mn≈12000 g / mol and molecular weight distribution PDI=1.25.

[0024] Terminal acrylate esterification: 10 g of the above PDMS-b-PFMA was dissolved in 50 mL of anhydrous dichloromethane, and 0.8 mL of acryloyl chloride and 1.5 mL of triethylamine were added. The mixture was stirred at room temperature for 12 hours. The reaction solution was washed successively with saturated sodium bicarbonate solution and deionized water. The organic phase was dried with anhydrous magnesium sulfate and concentrated. It was precipitated in n-hexane and dried under vacuum to obtain a reactive silicone-fluorine block copolymer oligomer with terminal acrylate double bonds, denoted as SFL-1. The presence of acrylate double bonds was confirmed by proton nuclear magnetic resonance spectroscopy.

[0025] Example 1: A lithium battery tape adhesive, and a lithium battery tape prepared from the adhesive: By weight, 50 parts of polyurethane acrylate, 15 parts of epoxy acrylate and 20 parts of reactive diluent isobornyl acrylate (IBOA) were mixed evenly, 10 parts of SFL-1 obtained from Synthesis Example 1 and 3 parts of nano silica were added, and the mixture was dispersed at high speed at 1500 rpm for 30 minutes, and then ground with a three-roll mill until the fineness was less than 10 μm; under light-protected conditions, 2 parts of photoinitiator TPO and 3 parts of latent epoxy curing agent dicyandiamide were added, with an average particle size of 5 μm, and the mixture was stirred for 15 minutes and degassed under vacuum to obtain the adhesive composition.

[0026] The obtained adhesive composition was coated onto a 38 μm thick PET film, with the coating thickness controlled at 75 μm. An irradiation energy of 1200 mJ / cm² was used at a wavelength of 385 nm. 2 Irradiate with a UV-LED light source for 3 seconds to initially set the adhesive layer; then place it in a 100℃ oven for 8 minutes to fully crosslink the epoxy groups, and then roll it up to obtain the lithium battery tape.

[0027] Example 2: The composition and process are basically the same as in Example 1, except that the amount of reactive silicone-fluorine oligomer SFL-1 is increased to 15 parts, the amount of polyurethane acrylate is adjusted to 45 parts, and the amount of reactive diluent IBOA is adjusted to 25 parts; the substrate is changed to a 25 μm thick PI film, and the coating thickness is 50 μm. The UV irradiation energy is 800 mJ / cm². 2 The heat treatment conditions are 120℃ for 5 minutes.

[0028] Example 3: The components and process are basically the same as in Example 1, except that: the amount of SFL-1 is 5 parts, and 5 parts of hexafluorobutyl methacrylate (FMA) are added as an active diluent to replace an equal amount of IBOA, and the amount of polyurethane acrylate is adjusted to 48 parts; the latent curing agent is replaced with 4 parts of modified imidazole, and the heating curing conditions are 100℃×10 minutes.

[0029] Comparative Example 1: No reactive silicone-fluorine block copolymer oligomer SFL-1 was added, the amount of polyurethane acrylate was increased to 60 parts, IBOA was adjusted to 25 parts, and other components and processes were the same as in Example 1.

[0030] Comparative Example 2: SFL-1 was replaced with an equal amount of non-reactive silicone-fluorine physical blend, namely a mixture of 5 parts of non-reactive PDMS with Mn≈3000 and no acrylate end groups and 5 parts of polyhexafluorobutyl methacrylate homopolymer with Mn≈8000 and no reactive end groups. The remaining components and processes were the same as in Example 1.

[0031] Performance testing: The tapes obtained in each embodiment and comparative example were subjected to the following tests, and the results are listed in Table 1: Peel strength and electrolyte resistance tests: Cut the tape into 25mm wide strips, attach them to a SUS304 stainless steel plate, and roll them back and forth once with a 2kg rubber roller; immerse them in 1M LiPF6 electrolyte (EC:DMC:EMC=1:1:1 volume ratio) at 85℃ for 24h and 168h respectively, remove and wipe dry, and use a universal tensile testing machine at a speed of 300mm / min to test the 180° peel strength, and calculate the peel strength retention rate.

[0032] High-temperature adhesive residue test: Apply the tape to the SUS304 board and place it in an oven at 130℃ and 180℃ for 1 hour respectively. After cooling to room temperature, manually peel off the tape and visually observe whether there is any adhesive residue on the surface of the board.

[0033] Gel content: Weigh the cured gel layer, wrap it with a 200-mesh stainless steel mesh, extract it in ethyl acetate using Soxhlet extraction for 48 hours, dry it, weigh it, and calculate the percentage of insoluble matter.

[0034] Electrochemical stability: Cyclic voltammetry was used with a scan range of 2.5V-4.2V and a scan rate of 1mV / s to observe for redox impurities.

[0035] Table 1 Performance Test Results

[0036] From Table 1 and Figure 2 As can be seen, the tapes of Examples 1-3 maintained excellent peel strength after rigorous electrolyte immersion tests, with a retention rate of over 83% after 168 hours. In contrast, Comparative Example 1, lacking reactive silicone oligomers, and Comparative Example 2, which was only physically blended, showed extremely severe peel strength degradation, with a retention rate of less than 30%. The tapes of the Examples peeled off without residue at 180°C, demonstrating excellent cohesiveness and heat resistance. At the same time, the high gel content indicates a dense dual-curing network, and the electrochemical inertness meets the requirements for battery applications.

[0037] The above results fully demonstrate that the present invention, through the introduction of chemical bonding of reactive silicone-fluorine block copolymer oligomers and the synergistic effect of UV light-heat dual curing mechanism, achieves rapid curing while greatly improving the electrolyte resistance and high temperature stability of the adhesive, thus realizing the synergistic optimization of the two properties.

[0038] It will be apparent to those skilled in the art that this disclosure is not limited to the details of the exemplary embodiments described above, and that this disclosure can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of this disclosure is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within this disclosure. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0039] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A lithium battery tape adhesive, characterized in that, Include: At least one oligomer containing an acrylate group; At least one oligomer containing an epoxy group; Reactive silicone-fluorine block copolymer oligomers have end groups containing acrylate double bonds that can participate in UV curing, and their main chain contains both polysiloxane segments and fluorinated polyacrylate segments. Photoradical initiators; Latent epoxy curing agent.

2. The lithium battery tape adhesive according to claim 1, characterized in that, The reactive siloxane block copolymer oligomer is a polydimethylsiloxane-polyhexafluorobutyl methacrylate block copolymer (PDMS-b-PFMA), in which at least one end of the block copolymer is chemically modified to introduce acrylate double bonds.

3. The lithium battery tape adhesive according to claim 2, characterized in that, The reactive silane-fluorine block copolymer oligomer is prepared by atom transfer radical polymerization (ATRP), which includes: using a bromoester derivative of monohydroxyl-terminated polydimethylsiloxane as a macromolecular initiator to initiate the polymerization of hexafluorobutyl methacrylate to obtain a PDMS-b-PFMA diblock copolymer, and then introducing acrylate double bonds through end-group modification.

4. The lithium battery tape adhesive according to claim 1, characterized in that, The oligomer containing acrylate groups is a polyurethane acrylate, and the oligomer containing epoxy groups is an epoxy acrylate; and the adhesive is a solvent-free system.

5. The lithium battery tape adhesive according to claim 4, characterized in that, The content of each component, by weight, is as follows: 40-55 parts of polyurethane acrylate; 10-20 parts epoxy acrylate; 15-25 parts reactive diluent; 5-15 parts of reactive silicone-fluorine block copolymer oligomer; 1-3 parts of photoradical initiator; 1-4 parts of latent epoxy curing agent; 1-5 parts of nano-silica.

6. A method for preparing the lithium battery tape adhesive of claim 1, characterized in that, Includes the following steps: (1) Providing the reactive silicone-fluorine block copolymer oligomer; (2) Under light-protected conditions, oligomers containing acrylate groups, oligomers containing epoxy groups, reactive diluents, reactive silicone-fluorine block copolymer oligomers and nanofillers are mixed evenly, and then photoradical initiators and latent epoxy curing agents are added. Vacuum degassing is performed to obtain adhesive. (3) Apply the adhesive to the substrate; (4) Expose the coating layer to UV irradiation to induce free radical polymerization and achieve preliminary shaping; (5) Heat the UV-irradiated coating layer to cause the epoxy groups to undergo a cross-linking reaction under the action of a latent curing agent, thus completing the deep curing.

7. The method according to claim 6, characterized in that, The preparation method of the reactive silicone-fluorine block copolymer oligomer in step (1) includes: Starting with hydroxyl-terminated polydimethylsiloxane, it is converted into a brominated ester macromolecular initiator. In the presence of a catalyst, hexafluorobutyl methacrylate is used as a monomer to obtain a PDMS-b-PFMA diblock copolymer via ATRP reaction. Subsequently, acrylate double bonds are introduced at the polymer ends to obtain the final product.

8. A lithium battery tape, comprising a substrate and an adhesive layer attached to the substrate, characterized in that, The adhesive layer is formed by dual curing of the lithium battery tape adhesive of claim 1 through UV irradiation and heating.

9. The lithium battery tape according to claim 8, characterized in that, The substrate is a polyethylene terephthalate (PET) film or a polyimide (PI) film.

10. The application of the lithium battery tape adhesive according to claim 1 or the lithium battery tape according to claim 8 in fixing lithium battery cells, characterized in that, The adhesive or tape is used to bond and fix the cell assembly in an environment where it comes into contact with the electrolyte inside the lithium battery.

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