Insulation paste for lithium battery

Abstract

The present invention discloses an insulation paste for a lithium battery, the insulation paste comprises a light-cured resin and a heat-cured resin, the light-cured resin comprises an acrylate oligomer, a vinyl nitrogen heterocyclic active diluent and a photoinitiator, and the heat-cured resin comprises an epoxy resin, an epoxy active diluent and an amine curing agent. The light-cured resin and the heat-cured resin are added into the composition of the insulation paste, an interpenetrating network structure is formed through a photo-thermal dual-curing system, and the crosslinking density is higher. The insulation paste disclosed by the invention not only can improve the initial adhesion and wet adhesion peeling strength with a pole piece and has a relatively good adhesion effect on the pole piece, but also has low swelling and dissolution rates in an electrolyte, is relatively slightly influenced by the electrolyte of a lithium battery, still keeps excellent performance in the electrolyte, and can meet the processing requirements of the lithium battery.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of battery materials, and particularly relates to an insulating glue for lithium batteries. BACKGROUND

[0002] The connection between the pole piece and the pole lug is a key process in battery manufacturing. Common connection methods include ultrasonic welding, resistance welding (spot welding), laser welding, riveting, and gluing. In the conventional lithium battery manufacturing process, the connection between the pole piece and the pole lug is usually achieved by ultrasonic welding or laser welding process. Such welding operation is easy to introduce residues such as burrs, welding slag, welding spots and metal particles, thereby causing the internal resistance of the battery to increase, and even inducing internal short circuit.

[0003] To solve this problem, the common practice at present is to attach a layer of protective tape on the surface of the welding spot after welding to prevent burrs, welding slag and other foreign matters from piercing the separator and to prevent metal debris from falling into the battery to cause short circuit, thereby improving safety. Moreover, ultrasonic welding is used, and after welding is completed, a welding spot is generated on the pole lug; if the height position of the pole lug is not suitable, the pole lug generally needs to be bent, and in this case, short circuit is easy to occur, so the position of the welding and the two surfaces of the bent pole lug need to be pasted with insulating protective tape.

[0004] However, the insulating protective tape is in long-term contact with electrolyte during subsequent battery processing and actual use, and corrosion is inevitable, which causes the tape to fall off or deform, loses adhesion, and the protection function fails, causing electrolyte leakage and unnecessary safety hazards; at the same time, the dissolved adhesive material also pollutes the electrolyte, thereby affecting the cycle rate of the battery. Secondly, the heat resistance of the tape is limited, and it is easy to shrink and deform at high temperature and fail. Thirdly, the tape has a slow pace, a large amount of manual operation, a complex process, and a low production efficiency.

[0005] The use of insulating glue to form an insulating layer can effectively solve the above problems, and has the characteristics of low requirement for equipment and high automation level. At present, the main material of the insulating glue in the lithium battery processing process is mostly acrylate. Acrylate is a raw material widely used in the field of adhesives, and has many advantages such as easy availability, relatively good stability, and simple process. However, the existing acrylate insulating glue is easy to swell in organic solvent electrolyte due to the large polarity of the polymer, thereby losing adhesion, or some components in the adhesive are released into the electrolyte, thereby polluting the electrolyte, reducing the quality, safety and use of the battery. The problems of the battery, and the application of the lithium ion battery is limited.

[0006] For the insulating glue applied to lithium battery processing, the insulating glue has good bonding effect on the pole piece and can maintain long-term performance stability in the extreme lithium battery electrolyte environment. With the continuous improvement of the performance of lithium batteries, the performance of the existing insulating glue is increasingly difficult to meet the performance requirements of lithium batteries. SUMMARY

[0007] In order to solve the problems existing in the existing protective adhesive tape and insulating glue for lithium batteries, the application provides an insulating glue for lithium batteries which can enhance the bonding performance and electrolyte resistance.

[0008] The purpose of the application is achieved by the following technical solutions.

[0009] The application provides an insulating glue for lithium batteries, which comprises a photocuring resin and a thermal curing resin, the photocuring resin comprises an acrylate oligomer, a vinyl nitrogen heterocyclic active diluent and a photoinitiator, and the thermal curing resin comprises an epoxy resin, an epoxy active diluent and an amine curing agent.

[0010] Further, the mass ratio of the photocuring resin and the thermal curing resin is 1: (1-3).

[0011] Further, in the photocuring resin, the mass ratio of the acrylate oligomer, the vinyl nitrogen heterocyclic active diluent and the photoinitiator is (60-80):(20-40):(2-5).

[0012] Further, in the thermal curing resin, the mass ratio of the epoxy resin, the epoxy active diluent and the amine curing agent is (50-70):(15-30):(15-30).

[0013] Further, the viscosity of the photocuring resin is 3000-8000 cp.

[0014] Further, the viscosity of the thermal curing resin is 2000-7000 cp.

[0015] Further, the crosslinking degree of the insulating glue after photocuring and thermal curing is 40%-70%.

[0016] Further, the vinyl nitrogen heterocyclic active diluent comprises at least one of 2-vinylpyridine, 3-vinylpyridine, 4-vinylpyridine, 2-vinylpyrazine, 2-vinylpyrimidine, 2-vinylquinoline, 3-vinylquinoline, 4-vinylquinoline, 1-vinylisoquinoline and 2-vinylquinoxaline.

[0017] Further, the acrylate oligomer comprises an epoxy acrylate polymer and / or a polyurethane acrylate polymer.

[0018] Further, the mass ratio of the epoxy acrylate polymer to the polyurethane acrylate polymer is (3-4):1.

[0019] Further, the photoinitiator comprises at least one of diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, 1-hydroxycyclohexyl phenyl ketone, phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide, benzoin dimethyl ether, 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropanone, 2-isopropylthioxanthone, benzophenone, and 2-ethylanthraquinone.

[0020] Further, the epoxy resin comprises an aliphatic epoxy resin and / or a cycloaliphatic epoxy resin.

[0021] Further, the mass ratio of the aliphatic epoxy resin to the cycloaliphatic epoxy resin is (3-4):1.

[0022] Further, the epoxy active diluent comprises at least one of polypropylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, and 1,6-hexanediol diglycidyl ether.

[0023] Further, the amine curing agent comprises at least one of isophorone diamine, 1,3-cyclohexanedimethylamine, m-xylylenediamine, diaminodiphenyl sulfone, and polyamide 650.

[0024] Compared with the prior art, the present application has the following beneficial effects.

[0025] In the present application, the light curing resin and the heat curing resin are added to the insulating glue composition, and an interpenetrating network structure is formed through a light-heat dual curing system, and the crosslinking density is higher. The light curing realizes rapid shaping, accurate assembly and avoids flowing, and solves the problems of production efficiency and initial shape retention; the heat curing realizes the final performance enhancement, complete reaction and stress release, and solves the problem of long-term reliability of the product.

[0026] The use of the vinyl nitrogen heterocyclic active diluent in the light curing resin and the use of the amine curing agent in the heat curing resin can significantly improve the peeling strength of the insulating glue and the pole piece, and the bonding strength is high. Moreover, the use of the amine curing agent in the heat curing system makes the crosslinking density after curing high, thereby improving the electrolyte resistance; the introduction of the vinyl nitrogen heterocyclic active diluent in the light curing resin makes the vinyl nitrogen heterocyclic active diluent have good anti-swelling property, and the interpenetrating network structure formed after the light-heat curing can reduce the dissolution rate, the swelling and dissolution rate in the electrolyte are low, thereby improving the electrolyte resistance.

[0027] The insulating adhesive of the present invention can not only improve the initial adhesion and wet peel strength with the electrode, and has a good bonding effect on the electrode, but also has a low swelling rate and dissolution rate in the electrolyte, is less affected by the lithium battery electrolyte, and still maintains excellent performance in the electrolyte, which can meet the requirements of lithium battery processing. Detailed Implementation

[0028] To make the technical problems solved, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the embodiments described herein are only some, not all, of the embodiments of this invention, and are merely illustrative and not intended to limit the invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the protection scope of this invention.

[0029] This invention provides an insulating adhesive for lithium batteries, the insulating adhesive comprising a photocurable resin and a thermocurable resin, the photocurable resin comprising acrylate oligomers, vinyl nitrogen heterocyclic reactive diluents and photoinitiators, and the thermocurable resin comprising epoxy resins, epoxy reactive diluents and amine curing agents.

[0030] This invention utilizes a vinyl-acid heterocyclic reactive diluent in the photocurable resin and an amine curing agent in the thermocurable resin. By leveraging the strong Lewis acid-base interaction between nitrogen atoms and metals, the peel strength and adhesion strength between the insulating adhesive and the electrode are significantly improved. Furthermore, the use of an amine curing agent in the thermocurable system results in a high crosslinking density after curing, thereby improving electrolyte resistance. The introduction of the vinyl-acid heterocyclic reactive diluent into the photocurable resin provides good anti-swelling properties; the interpenetrating network structure formed after photo- and thermo-curing reduces the dissolution rate, resulting in low swelling and dissolution rates in the electrolyte, thus improving electrolyte resistance. In application, the insulating adhesive can be directly applied to the interface between the tab and the electrode to achieve its insulating effect. Rapid pre-curing via photocuring followed by complete curing via thermo-curing, combined with the short curing times of both processes, results in a faster cycle time compared to tape application, improving production efficiency.

[0031] In some specific embodiments, the mass ratio of the photocurable resin to the thermocurable resin is 1:(1~3). Specifically, the mass ratio of the photocurable resin to the thermocurable resin can be 1:1, 1:1.2, 1:1.5, 1:1.8, 1:2, 1:2.3, 1:2.6, 1:2.8, or 1:3, etc. By adjusting the mass ratio of the photocurable resin to the thermocurable resin within a suitable range, both the peel strength with the substrate and the resistance to electrolytes can be improved; the relatively larger amount of thermocurable resin mainly improves the peel strength after curing.

[0032] In some specific embodiments, the mass ratio of the acrylate oligomer, vinyl azirionic reactive diluent, and photoinitiator in the photocurable resin is (60~80):(20~40):(2~5); specifically, the mass ratio of the acrylate oligomer, vinyl azirionic reactive diluent, and photoinitiator can be 60:21:2, 60:25:3, 60:40:3, 60:35:5, 65... Varieties such as 65:20:2, 65:25:3, 65:30:5, 65:33:2, 65:40:4, 70:20:3, 70:25:5, 70:27:3, 70:35:4, 70:40:4, 75:20:5, 75:22:3, 70:30:4, 75:40:5, 78:20:2, 80:20:2, 80:30:3, 80:40:5, etc. can be adjusted. By adjusting the vinyl nitrogen heterocyclic reactive diluent in the photocurable resin within a suitable range, swelling and dissolution rates can be reduced, thereby improving electrolyte resistance.

[0033] In some specific embodiments, the mass ratio of epoxy resin, epoxy reactive diluent, and amine curing agent in the thermosetting resin is (50~70):(15~30):(15~30); specifically, the mass ratio of epoxy resin, epoxy reactive diluent, and amine curing agent can be 50:15:35, 50:20:30, 50:25:25, 50:30:20, 55:15:30, 55:20:25, 55:25:20, 55:30:15, 60:15:25, 60:20:20, 60:25:15, 65:15:20, 65:20:15, 70:15:15, etc. By adjusting the amine curing agent in the thermosetting resin to a suitable range, the peel strength and electrolyte resistance can be improved.

[0034] In some specific embodiments, the viscosity of the photocurable resin is 3000~8000 cp, and / or the viscosity of the thermocurable resin is 2000~7000 cp. No additional additives or solvents are needed; by mixing the components of the photocurable / thermocurable resins disclosed in this invention at the specified mass ratio, photocurable and thermocurable resins of the corresponding viscosities can be obtained.

[0035] In some specific embodiments, the degree of crosslinking of the insulating adhesive after photothermal curing is 40% to 70%. This invention adds photocurable resin and thermocurable resin to the insulating adhesive composition, and simultaneously adjusts the components and their proportions. Through a photothermal dual-curing system, an interpenetrating network structure is formed, resulting in a high crosslinking density of the insulating adhesive after photothermal curing.

[0036] In some specific embodiments, the vinyl nitrogen heterocyclic active diluent includes at least one of 2-vinylpyridine, 3-vinylpyridine, 4-vinylpyridine, 2-vinylpyrazine, 2-vinylpyrimidine, 2-vinylquinoline, 3-vinylquinoline, 4-vinylquinoline, 1-vinylisoquinoline, and 2-vinylquinoxaline.

[0037] In some specific embodiments, the acrylate oligomers include epoxy acrylate polymers and / or polyurethane acrylate polymers; preferably, the acrylate oligomers include a mixture of epoxy acrylate polymers and polyurethane acrylate polymers. The mass ratio of the epoxy acrylate polymer to the polyurethane acrylate polymer is (3~4):1. A slightly higher proportion of epoxy acrylate polymer can reduce the swelling and dissolution rate, thereby improving electrolyte resistance.

[0038] More specifically, epoxy acrylate polymers include AgiSyn 1030, YC3380, YC1181, CT-3100A, and Changxing 6270. Polyurethane acrylate polymers include AgiSyn 271, CN983, CN9178, CN8893, and Laromer LR9004.

[0039] In some specific embodiments, the photoinitiator includes at least one selected from diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, 1-hydroxycyclohexyl benzophenone, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, benzoyl dimethyl ether, 2-methyl-1-(4-methylthiophenyl)2-morpholino-1-propanone, 2-isopropylthioxanthraphenone, benzophenone, and 2-ethylanthraquinone.

[0040] In some specific embodiments, the epoxy resin includes aliphatic epoxy resin and / or alicyclic epoxy resin; preferably, the epoxy resin includes a mixture of aliphatic epoxy resin and alicyclic epoxy resin. The mass ratio of aliphatic epoxy resin to alicyclic epoxy resin is (3~4):1, with a slightly higher proportion of aliphatic epoxy resin, which can improve the electrolyte resistance after curing.

[0041] More specifically, the aliphatic epoxy resin includes at least one of bisphenol A epoxy resin E-51, bisphenol A epoxy resin E-44, bisphenol F epoxy resin YDF-161, bisphenol F epoxy resin YDF-162, bisphenol F epoxy resin YDF-165, and bisphenol S epoxy resin CER-3000; the alicyclic epoxy resin includes at least one of 3,4-epoxycyclohexylcarboxylic acid-3',4'-epoxycyclohexylmethyl ester, bis((3,4-epoxycyclohexyl)methyl)adipate, poly[(2-epoxyethylene)-1,2-cyclohexanediol]2-ethyl-2-(hydroxymethyl)-1,3-propanediol ether (3:1), 3,4-epoxycyclohexylmethyl methacrylate, and vinyl cyclohexene dioxide.

[0042] In some specific embodiments, the epoxy reactive diluent includes at least one of polypropylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, and 1,6-hexanediol diglycidyl ether.

[0043] In some specific embodiments, the amine curing agent includes at least one selected from isophorone diamine, 1,3-cyclohexanedimethylamine, m-phenylenediamine, diaminodiphenyl sulfone, and polyamide 650. These amine curing agents can improve peel strength and electrolyte resistance.

[0044] The present invention relates to a method for preparing insulating adhesive for lithium batteries: First, light-curing resin and thermosetting resin are prepared separately. The raw materials required for light-curing resin are mixed evenly at room temperature in the absence of light according to the mass ratio to obtain light-curing resin, which is then stored in the absence of light for later use. The raw materials required for thermosetting resin are mixed evenly at room temperature according to the mass ratio to obtain thermosetting resin, which is then stored for later use. Then, the prepared light-curing resin and thermosetting resin are mixed thoroughly at room temperature according to the mass ratio, and vacuum defoaming is performed to obtain insulating adhesive.

[0045] The specific embodiments of the present invention will be further explained and described below through examples and comparative examples.

[0046] Unless otherwise specified, all reagents, materials, and instruments used in the following description are conventional reagents, materials, and instruments, all of which are commercially available. The reagents involved can also be synthesized using conventional synthetic methods. Unless otherwise specified, the methods in the examples are conventional methods in the art.

[0047] Example 1

[0048] 1) Preparation of UV-curable resin

[0049] Weigh 2 grams of photoinitiator diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide and place it in an opaque beaker. Add 20 grams of vinyl nitrogen heterocyclic reactive diluent 2-vinylpyridine and stir at room temperature for 20 minutes until the photoinitiator is fully dissolved in the diluent. Then add 78 grams of polyurethane acrylate AgiSyn 271 and stir in the dark for 1 hour to ensure that the three are fully mixed and homogeneous, thus obtaining a light-cured resin. Store in the dark for later use.

[0050] 2) Preparation of thermosetting resin

[0051] Weigh 70g of bisphenol A epoxy resin E-51 and place it in a beaker. Add 15g of epoxy reactive diluent diethylene glycol diglycidyl ether and 15g of amine curing agent m-phenylenediamine. Stir at room temperature for 2 hours to ensure thorough mixing of the three components, and obtain a thermosetting resin for later use.

[0052] 3) Preparation of insulating adhesive for lithium batteries

[0053] Take 50 grams each of the prepared photocurable resin and thermocurable resin, stir at room temperature for 2 hours to ensure thorough mixing, and then defoam under vacuum to obtain the insulating adhesive.

[0054] Example 2

[0055] The photocurable resin, thermocurable resin, and insulating adhesive were prepared according to the steps of Example 1. The main differences between this example and Example 1 are: 1) The raw materials used in the preparation of the photocurable resin are different: 2 grams of 1-hydroxycyclohexyl phenyl ketone, 20 grams of 2-vinylpyrazine, and 78 grams of epoxy acrylate polymer AgiSyn 1030; 2) The raw materials used in the preparation of the thermocurable resin are different: 70 grams of bis((3,4-epoxycyclohexyl)methyl) adipate, 15 grams of polypropylene glycol diglycidyl ether, and 15 grams of isophorone diamine; the rest are the same as in Example 1.

[0056] Example 3

[0057] The photocurable resin, thermocurable resin, and insulating adhesive were prepared according to the steps of Example 1. The main differences between this example and Example 1 are: 1) The raw materials and their amounts used in the preparation of the photocurable resin are different: 2 grams of 1-hydroxycyclohexyl phenyl ketone, 20 grams of 2-vinylpyrazine, 60 grams of epoxy acrylate polymer AgiSyn 1030, and 18 grams of polyurethane acrylate AgiSyn 271; 2) The raw materials used in the preparation of the thermocurable resin are different: 55 grams of bisphenol A epoxy resin E-51, 15 grams of bis((3,4-epoxycyclohexyl)methyl) adipate, 15 grams of polypropylene glycol diglycidyl ether, and 15 grams of isophorone diamine; 3) In the insulating adhesive, the photocurable resin is 40 grams and the thermocurable resin is 60 grams.

[0058] Example 4

[0059] The photocurable resin, thermocurable resin, and insulating adhesive were prepared according to the steps of Example 1. The main differences between this example and Example 1 are: 1) The raw materials and their amounts used in the preparation of the photocurable resin are different: 5 grams of 1-hydroxycyclohexyl phenyl ketone, 30 grams of 2-vinylpyrazine, 50 grams of epoxy acrylate polymer AgiSyn 1030, and 15 grams of polyurethane acrylate AgiSyn 271; 2) The raw materials used in the preparation of the thermocurable resin are different: 45 grams of bisphenol A epoxy resin E-51, 15 grams of bis((3,4-epoxycyclohexyl)methyl) adipate, 20 grams of polypropylene glycol diglycidyl ether, and 20 grams of 1,3-cyclohexanedimethylamine; 3) In the insulating adhesive, the photocurable resin is 25 grams and the thermocurable resin is 75 grams.

[0060] Example 5

[0061] The photocurable resin, thermocurable resin, and insulating adhesive were prepared according to the steps of Example 1. The main differences between this example and Example 1 are: 1) The raw materials and their amounts used in the preparation of the photocurable resin are different: 5 grams of 2-isopropylthioxanthone, 30 grams of 2-vinylpyrazine, and 65 grams of epoxy acrylate polymer AgiSyn 1030; 2) The raw materials used in the preparation of the thermocurable resin are different: 60 grams of bis((3,4-epoxycyclohexyl)methyl)adipate, 20 grams of polypropylene glycol diglycidyl ether, and 20 grams of diaminodiphenyl sulfone; 3) In the insulating adhesive, the photocurable resin is 35 grams and the thermocurable resin is 65 grams.

[0062] Example 6

[0063] The photocurable resin, thermocurable resin, and insulating adhesive were prepared according to the steps of Example 1. The main differences between this example and Example 1 are: 1) The raw materials and their amounts used in the preparation of the photocurable resin are different: 5 grams of benzoyl dimethyl ether, 30 grams of 3-vinylquinoline, and 65 grams of polyurethane acrylate polymer AgiSyn 271; 2) The raw materials used in the preparation of the thermocurable resin are different: 60 grams of bisphenol S epoxy resin CER-3000, 20 grams of polypropylene glycol diglycidyl ether, and 20 grams of isophorone diamine; 3) In the insulating adhesive, the photocurable resin is 30 grams and the thermocurable resin is 70 grams.

[0064] Example 7

[0065] The photocurable resin, thermocurable resin, and insulating adhesive were prepared according to the steps of Example 1. The main differences between this example and Example 1 are: 1) The raw materials and their amounts used in the preparation of the photocurable resin are different: 5 grams of 2-methyl-1-(4-methylthiophenyl)2-morpholino-1-propanone, 25 grams of 2-vinylpyrimidine, and 70 grams of polyurethane acrylate polymer AgiSyn 271; 2) The raw materials used in the preparation of the thermocurable resin are different: 50 grams of bisphenol F epoxy resin YDF-161, 30 grams of polypropylene glycol diglycidyl ether, and 20 grams of polyamide 650; 3) In the insulating adhesive, the photocurable resin is 32 grams and the thermocurable resin is 68 grams.

[0066] Example 8

[0067] The photocurable resin, thermocurable resin, and insulating adhesive were prepared according to the steps of Example 1. The main differences between this example and Example 1 are: 1) The amount of raw materials used in the preparation of the photocurable resin is different: 7 grams of diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, 43 grams of 2-vinylpyridine, and 50 grams of polyurethane acrylate; 2) The amount of raw materials used in the preparation of the thermocurable resin is different: 80 grams of bisphenol A epoxy resin E-51, 10 grams of diethylene glycol diglycidyl ether, and 10 grams of m-phenylenediamine; the rest are the same as in Example 1.

[0068] Example 9

[0069] The photocurable resin, thermocurable resin, and insulating adhesive were prepared according to the steps of Example 1. The main differences between this example and Example 1 are: 1) The amount of raw materials used in the preparation of the photocurable resin is different: 5 grams of diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, 10 grams of 2-vinylpyridine, and 85 grams of polyurethane acrylate; 2) The amount of raw materials used in the preparation of the thermocurable resin is different: 45 grams of bisphenol A epoxy resin E-51, 35 grams of diethylene glycol diglycidyl ether, and 20 grams of m-phenylenediamine; the rest are the same as in Example 1.

[0070] Example 10

[0071] The photocurable resin, thermocurable resin, and insulating adhesive were prepared according to the steps of Example 1. The main difference between this example and Example 1 is that the photocurable resin in the insulating adhesive is 60 grams and the thermocurable resin is 40 grams.

[0072] Comparative Example 1

[0073] This comparative example uses existing acrylic protective tapes.

[0074] Comparative Example 2

[0075] This comparative example uses existing acrylic insulating adhesives.

[0076] Comparative Example 3

[0077] The main difference between this comparative example and Example 1 is that the insulating adhesive does not contain thermosetting resin, and the photocurable resin is prepared according to the steps of Example 1.

[0078] Comparative Example 4

[0079] The main difference between this comparative example and Example 1 is that the insulating adhesive does not contain light-curing resin, and the thermosetting resin is prepared according to the steps of Example 1.

[0080] Comparative Example 5

[0081] The photocurable resin, thermocurable resin, and insulating adhesive were prepared according to the steps of Example 1. The main difference between this comparative example and Example 1 is that the reactive diluent used in the preparation of the photocurable resin is different; it is 1,6-hexanediol diacrylate.

[0082] Comparative Example 6

[0083] The photocurable resin, thermocurable resin, and insulating adhesive were prepared according to the steps of Example 1. The main difference between this comparative example and Example 1 is that the curing agent used in the preparation of the thermocurable resin is 2-methylimidazole.

[0084] Performance testing:

[0085] To better understand the present invention, the insulating adhesives or protective tapes (hereinafter referred to as "samples") prepared in the above embodiments and comparative examples were tested as follows, and the test results are shown in Table 1.

[0086] Sample pretreatment: Using aluminum foil as the substrate, insulating adhesive was applied to the substrate with a scraper, cured with ultraviolet light for 3 seconds, and then heat-cured at 85 degrees Celsius for 1 hour to form a 15 μm thick adhesive film, which is the cured product film. The film was then cut to a size of 20 mm × 100 mm to obtain the treated sample.

[0087] [Initial Adhesion Peel Strength Test] The substrate of the treated sample was fixed on the back plate, and the adhesive film of the sample was peeled off at 180°. The peeling force at 180° was tested, and the peeling speed was 50 mm / min. Three samples were tested for each example and comparative example, and the average value was taken to obtain the peel strength before soaking in liquid, i.e., the initial adhesion peel strength.

[0088] [Wet Adhesion Peel Strength Test] The treated sample was placed in the electrolyte, sealed, and placed in an 85℃ oven for 24 hours. The peel force at 180° was then tested. The peel speed was 50 mm / min. Three samples were tested for each example and comparative example, and the average value was taken to obtain the peel strength after soaking in the electrolyte, i.e., the wet adhesion peel strength.

[0089] [Swelling Rate Test] Take an appropriate amount of the treated sample, and record its mass as M1. Immerse it in the electrolyte and place it in an 85℃ oven for aging for 24 hours. Take out the sample, wipe off the electrolyte on its surface, and weigh it to obtain M2. Calculate the swelling rate according to the formula (M2-M1) / M1×100%.

[0090] [Dissolution Rate Test] Take an appropriate amount of the treated sample, and record its mass as M1. Soak it in the electrolyte, place it in an 85℃ oven, age it for 24 hours, take it out, wipe off the electrolyte on its surface, and dry it at 85℃ for 24 hours. Weigh it to obtain M3. Calculate the dissolution rate according to the formula (M1-M3) / M1×100%.

[0091] Table 1 Test Results

[0092]

[0093] As can be seen from the test results of Examples 1 to 10 in Table 1, the insulating adhesive of the present invention can not only improve the initial adhesion and wet adhesion peel strength with the electrode, and has a good bonding effect on the electrode, but also has a low swelling rate and dissolution rate in the electrolyte, is less affected by the lithium battery electrolyte, and still maintains excellent performance in the electrolyte, which can meet the requirements of lithium battery processing.

[0094] The test results of Examples 1-7 and Examples 8-10 show that the mass ratio of the photocurable resin to the thermocurable resin, the proportion of vinyl nitrogen heterocyclic reactive diluent in the photocurable resin, and the proportion of amine curing agent in the thermocurable resin are all within the scope of this invention, resulting in better performance. After photothermal curing, the initial peel strength of the insulating adhesive on aluminum foil is 0.12-0.24 N / mm, and the peel strength after immersion in electrolyte is 0.06-0.11 N / mm, indicating better adhesion. The swelling rate is less than 8%, and the dissolution rate is less than 5%, showing less influence from the lithium battery electrolyte. A higher proportion of thermocurable resin improves the peel strength. If the proportion of vinyl nitrogen heterocyclic reactive diluent in the photocurable resin and the proportion of amine curing agent in the thermocurable resin are outside the scope of this invention, the peel strength will decrease slightly, and the swelling and dissolution rate in the electrolyte will increase slightly.

[0095] The test results of Examples 1-7 and Comparative Examples 1-2 show that, compared with the prior art, the insulating adhesive of the present invention has better peel strength, significantly reduced swelling and dissolution rate in electrolyte, and is less affected by lithium battery electrolyte.

[0096] The test results of Examples 1-7 and Comparative Examples 3-4 show that if the insulating adhesive contains only thermosetting resin or light-curing resin, it will also lead to a significant decrease in peel strength, a low bonding strength, a significant increase in swelling rate and dissolution rate in electrolyte, and poor electrolyte resistance.

[0097] The test results of Examples 1-7 and Comparative Examples 5-6 show that: if the reactive diluent used in the photocurable resin is not a vinyl nitrogen heterocyclic reactive diluent, the peel strength is significantly reduced, the adhesive strength is low, the swelling and dissolution rate in the electrolyte is significantly increased, and the electrolyte resistance is poor; if the curing agent of the thermocurable resin is not an amine curing agent, the peel strength is significantly reduced, the adhesive strength is low, the swelling and dissolution rate in the electrolyte is significantly increased, and the electrolyte resistance is poor.

[0098] The present invention has been further described above with reference to specific embodiments. However, it should be understood that the specific description herein should not be construed as limiting the nature and scope of the present invention. Various modifications made to the above embodiments by those skilled in the art after reading this specification are all within the scope of protection of the present invention.

Claims

1. An insulating adhesive for lithium batteries, characterized in that, The insulating adhesive includes a photocurable resin and a thermocurable resin. The photocurable resin includes acrylate oligomers, vinyl nitrogen heterocyclic reactive diluents, and photoinitiators. The thermocurable resin includes epoxy resin, epoxy reactive diluents, and amine curing agents.

2. The insulating adhesive for lithium batteries according to claim 1, characterized in that, The mass ratio of the photocurable resin to the thermocurable resin is 1:(1~3).

3. The insulating adhesive for lithium batteries according to claim 1 or 2, characterized in that, In the photocurable resin, the mass ratio of the acrylate oligomer, the vinyl nitrogen heterocyclic reactive diluent, and the photoinitiator is (60~80):(20~40):(2~5); and / or, In the thermosetting resin, the mass ratio of epoxy resin, epoxy reactive diluent and amine curing agent is (50~70):(15~30):(15~30).

4. The insulating adhesive for lithium batteries according to claim 1, characterized in that, The viscosity of the photocurable resin is 3000~8000 cp; and / or, The viscosity of the thermosetting resin is 2000~7000cp.

5. The insulating adhesive for lithium batteries according to claim 1, characterized in that, The degree of crosslinking of the insulating adhesive after photothermal curing is 40%~70%.

6. The insulating adhesive for lithium batteries according to any one of claims 1 to 5, characterized in that, The vinyl nitrogen heterocyclic reactive diluent includes at least one of 2-vinylpyridine, 3-vinylpyridine, 4-vinylpyridine, 2-vinylpyrazine, 2-vinylpyrimidine, 2-vinylquinoline, 3-vinylquinoline, 4-vinylquinoline, 1-vinylisoquinoline, and 2-vinylquinoxaline.

7. The insulating adhesive for lithium batteries according to any one of claims 1 to 5, characterized in that, The acrylate oligomers include epoxy acrylate polymers and / or polyurethane acrylate polymers; And / or, the mass ratio of the epoxy acrylate polymer to the polyurethane acrylate polymer is (3~4):

1.

8. The insulating adhesive for lithium batteries according to any one of claims 1 to 5, characterized in that, The photoinitiator includes at least one of diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, 1-hydroxycyclohexyl benzophenone, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, benzoyl dimethyl ether, 2-methyl-1-(4-methylthiophenyl)2-morpholino-1-propanone, 2-isopropylthioxanthraphenone, benzophenone, and 2-ethylanthraquinone.

9. The insulating adhesive for lithium batteries according to any one of claims 1 to 5, characterized in that, The epoxy resin includes aliphatic epoxy resin and / or alicyclic epoxy resin; And / or, the mass ratio of the aliphatic epoxy resin to the alicyclic epoxy resin is (3~4):

1.

10. The insulating adhesive for lithium batteries according to any one of claims 1 to 5, characterized in that, The epoxy reactive diluent includes at least one selected from polypropylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, and 1,6-hexanediol diglycidyl ether; and / or, The amine curing agent includes at least one of isophorone diamine, 1,3-cyclohexanedimethylamine, m-phenylenediamine, diaminodiphenyl sulfone, and polyamide 650.

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