PI base material adhesive film for lithium battery and preparation method of PI base material adhesive film

Abstract

The invention discloses a PI base material adhesive film for a lithium battery and a preparation method thereof. The PI base material adhesive film sequentially comprises a first pressure-sensitive adhesive film layer, a modified PI base material layer and a second pressure-sensitive adhesive film layer from top to bottom, the modified PI base material layer is prepared from the following raw materials: fluorine-containing polyimide resin, a coupling agent, a nano reinforcing material and hyperbranched polyurethane containing amino; the first pressure-sensitive adhesive film layer and the second pressure-sensitive adhesive film layer are mutually independently prepared from the following components: hyperbranched unsaturated resin, 10-(4-vinyl phenyl)-10H-phenoxazine, 1, 3-bis (ethylene oxide methyl)-5-(2-propenyl)-1, 3, 5-triazine-2, 4, 6 (1H, 3H, 5H)-triketone, methyl vinyl di (butanone oxime) silane, 3, 3 '-diamino-4, 4'-diamino-1, 3, 5-triazine-2, 4, 6 (1H, 3H, 5H)-1, 3, 5-triazine-2, 4, 6 (1H, 3H, 5H)-1, 3, 5-triazine-2, 4, 6 (1H, 3H, 5H)-1, 3, the adhesive is prepared from 4, 4 '-difluorodiphenyl sulfone, a curing agent, a solvent and a solvent type acrylate pressure-sensitive adhesive. The adhesive film is good in cohesiveness, good in high-temperature and high-humidity resistance, sufficient in flexibility and excellent in electrolyte tolerance.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery packaging materials, and in particular to a PI substrate adhesive film for lithium batteries and a preparation method thereof. Background Art

[0002] With the increasing global emphasis on environmental protection and sustainable development, the new energy industry has experienced rapid growth. As a key component of the new energy sector, lithium batteries, with their high energy density and long cycle life, are widely used in a wide range of fields, including electric vehicles, energy storage systems, and portable electronic devices. It is worth noting that the effectiveness of lithium battery applications depends largely on the packaging process, the quality of which directly affects the safety, stability, and service life of the battery, and is crucial to the healthy development of the entire new energy industry chain.

[0003] In lithium-ion battery packaging, the secure connection between the inner core and the outer aluminum-plastic film is crucial. A stable and reliable securement method prevents the inner core from swaying within the film, thus avoiding friction-induced damage to the core and electrode short circuits. While currently used adhesive films can achieve a certain degree of securement, their performance deteriorates rapidly under extreme conditions such as high-temperature cycling and high humidity. Furthermore, conventional adhesive films lack chemical compatibility with the aluminum-plastic film and the inner core material, leading to debonding and delamination after long-term use, seriously impacting the lifespan and safety of lithium-ion batteries. Polyimide (PI) materials, with their excellent heat resistance, chemical stability, and mechanical properties, hold great promise for application in lithium-ion batteries. However, preparing them into the adhesive film used to secure the lithium-ion battery core to the aluminum-plastic film presents numerous challenges. For one thing, existing manufacturing processes struggle to form a strong chemical bond between the PI film, the aluminum-plastic film, and the core material, resulting in suboptimal securing. Furthermore, the PI film's lack of flexibility and conformability prevents it from tightly fitting the complex shapes of the core, limiting its application in lithium-ion battery packaging.

[0004] It can be seen that the development of a PI-based adhesive film for lithium batteries with good bonding properties, excellent high temperature and high humidity resistance, sufficient flexibility and conformability, and excellent electrolyte tolerance and its preparation method meets market demand, has broad market value and application prospects, and is of great significance to promoting the development of the field of adhesive films for lithium batteries. Summary of the Invention

[0005] The main purpose of the present invention is to provide a PI substrate film for lithium batteries with good bonding performance, excellent high temperature and high humidity resistance, sufficient flexibility and conformability, and excellent electrolyte tolerance, and a preparation method thereof.

[0006] To achieve the above objectives, the present invention provides a PI substrate adhesive film for lithium batteries, which comprises, from top to bottom, a first pressure-sensitive adhesive film layer, a modified PI substrate layer, and a second pressure-sensitive adhesive film layer; the modified PI substrate layer comprises the following raw materials in parts by mass: 65-85 parts of a fluorinated polyimide resin, 3-5 parts of a coupling agent, 10-15 parts of a nano-reinforced material, and 10-15 parts of a hyperbranched polyurethane containing an amino group; the first pressure-sensitive adhesive film layer and the second pressure-sensitive adhesive film layer are independently made of the following components in percentage by mass: hyperbranched unsaturated The composition comprises 8-12wt% of a resin, 2-4wt% of 10-(4-vinylphenyl)-10H-phenoxazine, 4-6wt% of 1,3-bis(oxiranylmethyl)-5-(2-propenyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 3-5wt% of methylvinylbis(butanone oxime)silane, 1-3wt% of 3,3'-diamino-4,4'-difluorodiphenyl sulfone, 0.1-0.3wt% of a curing agent, 10-20wt% of a solvent, and the balance being a solvent-based acrylic pressure-sensitive adhesive.

[0007] Preferably, the solvent-based acrylate pressure-sensitive adhesive is Henkel-129A solvent-based acrylate pressure-sensitive adhesive.

[0008] Preferably, the solvent is ethyl acetate; and the curing agent is azobisisobutyronitrile.

[0009] Preferably, the hyperbranched unsaturated resin is hyperbranched unsaturated resin Hyper U102.

[0010] Preferably, there is no special requirement for the source of the amino-containing hyperbranched polyurethane. In one embodiment of the present invention, the amino-containing hyperbranched polyurethane is prepared according to the method of Example 1 of the Chinese invention patent with authorization announcement number CN104693405B; the nano-reinforcement material is nano-mica powder; and the average particle size of the nano-mica powder is 10-80 nm.

[0011] Preferably, the coupling agent is at least one of silane coupling agent KH550, silane coupling agent KH560, and silane coupling agent KH570; the brand of the fluorine-containing polyimide resin is DS512, which is provided by Shandong Huaxia Shenzhou New Materials Co., Ltd.

[0012] Another object of the present invention is to provide a method for preparing the PI substrate film for lithium batteries, comprising the following steps: Step S1, dissolving the dried fluorinated polyimide resin in dimethylacetamide, stirring at 70-90° C. for 4-6 hours until completely dissolved, to obtain a fluorinated polyimide resin solution; then sequentially adding a coupling agent, a nano-reinforcement material, and a hyperbranched polyurethane containing an amino group, and continuing stirring for 3-5 hours to form a uniform spinning solution; preparing the spinning solution into a nanofiber membrane using electrospinning technology; and hot-pressing the obtained nanofiber membrane to form a modified PI substrate layer; Step S2: After uniformly mixing the components of the first pressure-sensitive adhesive film layer and the second pressure-sensitive adhesive film layer, a first pressure-sensitive adhesive and a second pressure-sensitive adhesive are obtained; the first pressure-sensitive adhesive and the second pressure-sensitive adhesive are uniformly coated on the upper and lower surfaces of the modified PI substrate layer by a roller coating method; the coated adhesive film is cured at 70-80° C. for 1-2 hours to crosslink and cure the pressure-sensitive adhesive layer to form a PI substrate adhesive film for lithium batteries.

[0013] Preferably, the process parameters of the electrospinning in step S1 are: spinning voltage of 15-20 kV, spinning distance of 10-15 cm, and receiving speed of 5-10 m / min.

[0014] Preferably, the temperature of the hot pressing treatment in step S1 is 150-160° C., the pressure is 5-10 MPa, and the time is 1-2 hours.

[0015] Preferably, the thickness of the modified PI substrate layer is 20-30 μm; the thickness of the first pressure-sensitive adhesive film layer is 5-10 μm; and the thickness of the second pressure-sensitive adhesive film layer is 5-10 μm.

[0016] Due to the application of the above technical solution, the present invention has the following beneficial effects: (1) The method for preparing the PI substrate adhesive film for lithium batteries disclosed in the present invention has a simple process, convenient operation and control, low dependence on equipment, high preparation efficiency and finished product qualification rate, is suitable for large-scale industrial production, and has high promotion and application value.

[0017] (2) The PI-based adhesive film for lithium batteries disclosed in the present invention comprises, from top to bottom, a first pressure-sensitive adhesive film layer, a modified PI substrate layer, and a second pressure-sensitive adhesive film layer. By optimizing the formulations of the modified PI substrate layer and the pressure-sensitive adhesive film layer and employing a specific preparation process, a strong chemical bond is formed between the layers of the adhesive film of the present invention, effectively preventing interlayer separation. In a volume change test simulating the battery's charge and discharge process, the film layers remained tightly bonded, ensuring battery stability.

[0018] (3) The PI substrate adhesive film for lithium batteries disclosed in the present invention, the modified PI substrate layer comprises the following raw materials in parts by mass: 65-85 parts of fluorinated polyimide resin, 3-5 parts of coupling agent, 10-15 parts of nano-reinforced material, and 10-15 parts of hyperbranched polyurethane containing amino group; the first pressure-sensitive adhesive film layer and the second pressure-sensitive adhesive film layer are independently made of the following components in percentage by mass: 8-12 wt% of hyperbranched unsaturated resin, 10-(4-vinyl)-1-ol The composition comprises 2-4wt% of phenyl)-10H-phenoxazine, 4-6wt% of 1,3-bis(oxiranylmethyl)-5-(2-propenyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 3-5wt% of methylvinylbis(butanone oxime)silane, 1-3wt% of 3,3'-diamino-4,4'-difluorodiphenylsulfone, 0.1-0.3wt% of curing agent, and 10-20wt% of solvent. The remainder is a solvent-based acrylic pressure-sensitive adhesive. The interaction of these raw materials results in a PI substrate film with excellent bonding properties, high temperature and humidity resistance, sufficient flexibility and conformability, and excellent electrolyte tolerance. Phenoxazine, triazone, oxime silane, difluorodiphenyl sulfone and hyperbranched structures are introduced into the pressure-sensitive adhesive film at the same time. These structures, under the influence of multiple effects such as electronic effect, steric effect and conjugation effect, make the prepared adhesive film have better resistance to moisture and heat aging, better electrolyte tolerance and longer service life.

[0019] (4) The present invention discloses a PI substrate adhesive film for lithium batteries. The modified PI substrate layer is modified by blending a nano-reinforcement material and a hyperbranched polyurethane containing an amino group. The introduction of the hyperbranched polyurethane containing an amino group imparts good flexibility to the adhesive film. At the same time, the addition of the nano-reinforcement material significantly improves the mechanical strength of the adhesive film. The carbamate groups contained in the hyperbranched polyurethane containing an amino group can form hydrogen bonds with carbonyl groups, imine groups, etc. on the PI molecular chain, thereby enhancing intermolecular forces and significantly improving compatibility with PI. The introduced amino groups can undergo an epoxy ring-opening reaction with the epoxy groups in the pressure-sensitive adhesive film layer, thereby enhancing the adhesion between the layers and thereby improving the structural stability of the adhesive film.

[0020] (5) The PI substrate adhesive film for lithium batteries disclosed in the present invention has better bonding performance, better high temperature and high humidity resistance, greater flexibility and adhesion, better electrolyte tolerance and longer service life through the reasonable selection of preparation process parameters. DETAILED DESCRIPTION

[0021] The following description is intended to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are merely examples, and those skilled in the art may conceive of other obvious variations. Example 1

[0022] A PI substrate adhesive film for a lithium battery, comprising, from top to bottom, a first pressure-sensitive adhesive film layer, a modified PI substrate layer, and a second pressure-sensitive adhesive film layer; the modified PI substrate layer is made of the following raw materials in parts by mass: 65 parts of a fluorinated polyimide resin, 3 parts of a coupling agent, 10 parts of a nano-reinforced material, and 10 parts of a hyperbranched polyurethane containing an amino group; the first pressure-sensitive adhesive film layer and the second pressure-sensitive adhesive film layer are independently made of the following components in percentage by mass: 8 parts of a hyperbranched unsaturated resin; wt%, 10-(4-vinylphenyl)-10H-phenoxazine 2wt%, 1,3-bis(oxiranylmethyl)-5-(2-propenyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione 4wt%, methylvinylbis(butanone oxime)silane 3wt%, 3,3'-diamino-4,4'-difluorodiphenyl sulfone 1wt%, curing agent 0.1wt%, solvent 10wt%, and the balance is solvent-based acrylic pressure-sensitive adhesive.

[0023] The solvent-based acrylic pressure-sensitive adhesive is Henkel-129A solvent-based acrylic pressure-sensitive adhesive; the solvent is ethyl acetate; the curing agent is azobisisobutyronitrile; the hyperbranched unsaturated resin is the hyperbranched unsaturated resin HyperU102; the amino-containing hyperbranched polyurethane is prepared according to the method of Example 1 of the Chinese invention patent with authorization announcement number CN104693405B; the nano-reinforcement material is nano-mica powder; the average particle size of the nano-mica powder is 10 nm; the coupling agent is silane coupling agent KH550; the brand of the fluorinated polyimide resin is DS512, provided by Shandong Huaxia Shenzhou New Materials Co., Ltd.

[0024] A method for preparing the PI substrate film for lithium batteries comprises the following steps: Step S1, dissolving the dried fluorinated polyimide resin in dimethylacetamide and stirring at 70° C. for 4 hours until completely dissolved to obtain a fluorinated polyimide resin solution; then sequentially adding a coupling agent, a nano-reinforcement material, and a hyperbranched polyurethane containing an amino group, and continuing stirring for 3 hours to form a uniform spinning solution; preparing the spinning solution into a nanofiber membrane using electrospinning technology; and hot-pressing the obtained nanofiber membrane to form a modified PI substrate layer; Step S2: After uniformly mixing the components of the first pressure-sensitive adhesive film layer and the second pressure-sensitive adhesive film layer, a first pressure-sensitive adhesive and a second pressure-sensitive adhesive are obtained; the first pressure-sensitive adhesive and the second pressure-sensitive adhesive are uniformly coated on the upper and lower surfaces of the modified PI substrate layer by a roller coating method; the coated adhesive film is cured at 70°C for 1 hour to crosslink and cure the pressure-sensitive adhesive layer to form a PI substrate adhesive film for lithium batteries.

[0025] The process parameters of the electrospinning in step S1 are: spinning voltage of 15 kV, spinning distance of 10 cm, and receiving speed of 5 m / min; the temperature of the hot pressing treatment in step S1 is 150°C, the pressure is 5 MPa, and the time is 1 hour; the thickness of the modified PI substrate layer is 20 μm; the thickness of the first pressure-sensitive adhesive film layer is 5 μm; and the thickness of the second pressure-sensitive adhesive film layer is 5 μm. Example 2

[0026] A PI substrate adhesive film for a lithium battery, comprising, from top to bottom, a first pressure-sensitive adhesive film layer, a modified PI substrate layer, and a second pressure-sensitive adhesive film layer; the modified PI substrate layer is made of the following raw materials in parts by mass: 70 parts of a fluorinated polyimide resin, 3.5 parts of a coupling agent, 11 parts of a nano-reinforced material, and 12 parts of a hyperbranched polyurethane containing an amino group; the first pressure-sensitive adhesive film layer and the second pressure-sensitive adhesive film layer are independently made of the following components in percentage by mass: 9wt% of a hyperbranched unsaturated resin, 10-(4-vinylphenyl)-10H-phenoxazine 2.5wt%, 1,3-bis(oxiranylmethyl)-5-(2-propenyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione 4.5wt%, methylvinylbis(butanone oxime)silane 3.5wt%, 3,3'-diamino-4,4'-difluorodiphenyl sulfone 1.5wt%, curing agent 0.15wt%, solvent 13wt%, and the remainder is solvent-based acrylic pressure-sensitive adhesive.

[0027] The solvent-based acrylic pressure-sensitive adhesive is Henkel-129A solvent-based acrylic pressure-sensitive adhesive; the solvent is ethyl acetate; the curing agent is azobisisobutyronitrile; the hyperbranched unsaturated resin is the hyperbranched unsaturated resin HyperU102; the amino-containing hyperbranched polyurethane is prepared according to the method of Example 1 of the Chinese invention patent with authorization announcement number CN104693405B; the nano-reinforcement material is nano-mica powder; the average particle size of the nano-mica powder is 30 nm; the coupling agent is silane coupling agent KH560; the brand of the fluorinated polyimide resin is DS512, provided by Shandong Huaxia Shenzhou New Materials Co., Ltd.

[0028] A method for preparing the PI substrate film for lithium batteries comprises the following steps: Step S1, dissolving the dried fluorinated polyimide resin in dimethylacetamide, stirring at 75° C. for 4.5 hours until completely dissolved, to obtain a fluorinated polyimide resin solution; then sequentially adding a coupling agent, a nano-reinforcement material, and a hyperbranched polyurethane containing an amino group, and continuing stirring for 3.5 hours to form a uniform spinning solution; preparing the spinning solution into a nanofiber membrane using electrospinning technology; and hot-pressing the obtained nanofiber membrane to form a modified PI substrate layer; Step S2: After uniformly mixing the components of the first pressure-sensitive adhesive film layer and the second pressure-sensitive adhesive film layer, a first pressure-sensitive adhesive and a second pressure-sensitive adhesive are obtained; the first pressure-sensitive adhesive and the second pressure-sensitive adhesive are uniformly coated on the upper and lower surfaces of the modified PI substrate layer by a roller coating method; the coated adhesive film is cured at 73° C. for 1.2 hours to crosslink and cure the pressure-sensitive adhesive layer to form a PI substrate adhesive film for lithium batteries.

[0029] The process parameters of the electrospinning in step S1 are: spinning voltage of 17 kV, spinning distance of 12 cm, and receiving speed of 7 m / min; the temperature of the hot pressing treatment in step S1 is 153°C, the pressure is 7 MPa, and the time is 1.3 hours; the thickness of the modified PI substrate layer is 20 μm; the thickness of the first pressure-sensitive adhesive film layer is 5 μm; and the thickness of the second pressure-sensitive adhesive film layer is 5 μm. Example 3

[0030] A PI substrate adhesive film for a lithium battery, comprising, from top to bottom, a first pressure-sensitive adhesive film layer, a modified PI substrate layer, and a second pressure-sensitive adhesive film layer; the modified PI substrate layer is made of the following raw materials in parts by mass: 75 parts of a fluorinated polyimide resin, 4 parts of a coupling agent, 13 parts of a nano-reinforced material, and 13 parts of a hyperbranched polyurethane containing an amino group; the first pressure-sensitive adhesive film layer and the second pressure-sensitive adhesive film layer are independently made of the following components in parts by mass: 10 parts of a hyperbranched unsaturated resin; wt%, 10-(4-vinylphenyl)-10H-phenoxazine 3wt%, 1,3-bis(oxiranylmethyl)-5-(2-propenyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione 5wt%, methylvinylbis(butanone oxime)silane 4wt%, 3,3'-diamino-4,4'-difluorodiphenyl sulfone 2wt%, curing agent 0.2wt%, solvent 15wt%, and the balance is solvent-based acrylic pressure-sensitive adhesive.

[0031] The solvent-based acrylic pressure-sensitive adhesive is Henkel-129A solvent-based acrylic pressure-sensitive adhesive; the solvent is ethyl acetate; the curing agent is azobisisobutyronitrile; the hyperbranched unsaturated resin is the hyperbranched unsaturated resin HyperU102; the amino-containing hyperbranched polyurethane is prepared according to the method of Example 1 of the Chinese invention patent with authorization announcement number CN104693405B; the nano-reinforcement material is nano-mica powder; the average particle size of the nano-mica powder is 50 nm; the coupling agent is silane coupling agent KH570; the brand of the fluorinated polyimide resin is DS512, provided by Shandong Huaxia Shenzhou New Materials Co., Ltd.

[0032] A method for preparing the PI substrate film for lithium batteries comprises the following steps: Step S1, dissolving the dried fluorinated polyimide resin in dimethylacetamide and stirring at 80° C. for 5 hours until completely dissolved to obtain a fluorinated polyimide resin solution; then sequentially adding a coupling agent, a nano-reinforcement material, and a hyperbranched polyurethane containing an amino group, and continuing stirring for 4 hours to form a uniform spinning solution; preparing the spinning solution into a nanofiber membrane using electrospinning technology; and hot-pressing the obtained nanofiber membrane to form a modified PI substrate layer; Step S2: After the components of the first pressure-sensitive adhesive film layer and the second pressure-sensitive adhesive film layer are mixed evenly, a first pressure-sensitive adhesive and a second pressure-sensitive adhesive are obtained; the first pressure-sensitive adhesive and the second pressure-sensitive adhesive are evenly coated on the upper and lower surfaces of the modified PI substrate layer by a roller coating method; the coated film is cured at 75° C. for 1.5 hours to crosslink and cure the pressure-sensitive adhesive layer to form a PI substrate film for lithium batteries.

[0033] The process parameters of the electrospinning in step S1 are: spinning voltage of 18 kV, spinning distance of 13 cm, and receiving speed of 7.5 m / min; the temperature of the hot pressing treatment in step S1 is 155 ° C, the pressure is 8 MPa, and the time is 1.5 hours; the thickness of the modified PI substrate layer is 20 μm; the thickness of the first pressure-sensitive adhesive film layer is 5 μm; the thickness of the second pressure-sensitive adhesive film layer is 5 μm. Example 4

[0034] A PI substrate adhesive film for a lithium battery, comprising, from top to bottom, a first pressure-sensitive adhesive film layer, a modified PI substrate layer, and a second pressure-sensitive adhesive film layer; the modified PI substrate layer is made of the following raw materials in parts by mass: 80 parts of a fluorinated polyimide resin, 4.5 parts of a coupling agent, 14 parts of a nano-reinforced material, and 14 parts of a hyperbranched polyurethane containing an amino group; the first pressure-sensitive adhesive film layer and the second pressure-sensitive adhesive film layer are independently made of the following components in percentage by mass: 11 wt% of a hyperbranched unsaturated resin; , 10-(4-vinylphenyl)-10H-phenoxazine 3.5wt%, 1,3-bis(oxiranylmethyl)-5-(2-propenyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione 5.5wt%, methylvinylbis(butanone oxime)silane 4.5wt%, 3,3'-diamino-4,4'-difluorodiphenyl sulfone 2.5wt%, curing agent 0.25wt%, solvent 18wt%, and the remainder is solvent-based acrylic pressure-sensitive adhesive.

[0035] The solvent-based acrylic pressure-sensitive adhesive is Henkel-129A solvent-based acrylic pressure-sensitive adhesive; the solvent is ethyl acetate; the curing agent is azobisisobutyronitrile; the hyperbranched unsaturated resin is hyperbranched unsaturated resin HyperU102; the amino-containing hyperbranched polyurethane is prepared according to the method of Example 1 of the Chinese invention patent with authorization announcement number CN104693405B; the nano-reinforcement material is nano-mica powder; the average particle size of the nano-mica powder is 70 nm; the coupling agent is a mixture of silane coupling agent KH550, silane coupling agent KH560, and silane coupling agent KH570 in a mass ratio of 1:2:1; the brand of the fluorinated polyimide resin is DS512, provided by Shandong Huaxia Shenzhou New Materials Co., Ltd.

[0036] A method for preparing the PI substrate film for lithium batteries comprises the following steps: Step S1, dissolving the dried fluorinated polyimide resin in dimethylacetamide, stirring at 70-90° C. for 5.5 hours until completely dissolved, to obtain a fluorinated polyimide resin solution; then sequentially adding a coupling agent, a nano-reinforcement material, and a hyperbranched polyurethane containing an amino group, and continuing stirring for 4.5 hours to form a uniform spinning solution; preparing the spinning solution into a nanofiber membrane using electrospinning technology; and hot-pressing the obtained nanofiber membrane to form a modified PI substrate layer; Step S2: After uniformly mixing the components of the first pressure-sensitive adhesive film layer and the second pressure-sensitive adhesive film layer, a first pressure-sensitive adhesive and a second pressure-sensitive adhesive are obtained; the first pressure-sensitive adhesive and the second pressure-sensitive adhesive are uniformly coated on the upper and lower surfaces of the modified PI substrate layer by a roller coating method; the coated adhesive film is cured at 78° C. for 1.8 hours to crosslink and cure the pressure-sensitive adhesive layer to form a PI substrate adhesive film for lithium batteries.

[0037] The process parameters of the electrospinning in step S1 are: spinning voltage of 19 kV, spinning distance of 14 cm, and receiving speed of 9 m / min; the temperature of the hot pressing treatment in step S1 is 158°C, the pressure is 9 MPa, and the time is 1.9 hours; the thickness of the modified PI substrate layer is 20 μm; the thickness of the first pressure-sensitive adhesive film layer is 5 μm; and the thickness of the second pressure-sensitive adhesive film layer is 5 μm. Example 5

[0038] A PI substrate adhesive film for a lithium battery comprises, from top to bottom, a first pressure-sensitive adhesive film layer, a modified PI substrate layer, and a second pressure-sensitive adhesive film layer; the modified PI substrate layer comprises the following raw materials in parts by mass: 85 parts of a fluorinated polyimide resin, 5 parts of a coupling agent, 15 parts of a nano-reinforced material, and 15 parts of a hyperbranched polyurethane containing an amino group; the first pressure-sensitive adhesive film layer and the second pressure-sensitive adhesive film layer are independently made of the following components in percentage by mass: 12 parts of a hyperbranched unsaturated resin; wt%, 10-(4-vinylphenyl)-10H-phenoxazine 4wt%, 1,3-bis(oxiranylmethyl)-5-(2-propenyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione 6wt%, methylvinylbis(butanone oxime)silane 5wt%, 3,3'-diamino-4,4'-difluorodiphenyl sulfone 3wt%, curing agent 0.3wt%, solvent 20wt%, and the remainder is solvent-based acrylic pressure-sensitive adhesive.

[0039] The solvent-based acrylic pressure-sensitive adhesive is Henkel-129A solvent-based acrylic pressure-sensitive adhesive; the solvent is ethyl acetate; the curing agent is azobisisobutyronitrile; the hyperbranched unsaturated resin is the hyperbranched unsaturated resin HyperU102; the amino-containing hyperbranched polyurethane is prepared according to the method of Example 1 of the Chinese invention patent with authorization announcement number CN104693405B; the nano-reinforcement material is nano-mica powder; the average particle size of the nano-mica powder is 80 nm; the coupling agent is silane coupling agent KH550; the brand of the fluorinated polyimide resin is DS512, provided by Shandong Huaxia Shenzhou New Materials Co., Ltd.

[0040] A method for preparing the PI substrate film for lithium batteries comprises the following steps: Step S1, dissolving the dried fluorinated polyimide resin in dimethylacetamide and stirring at 90° C. for 6 hours until completely dissolved to obtain a fluorinated polyimide resin solution; then sequentially adding a coupling agent, a nano-reinforcement material, and a hyperbranched polyurethane containing an amino group, and continuing stirring for 5 hours to form a uniform spinning solution; preparing the spinning solution into a nanofiber membrane using electrospinning technology; and hot-pressing the obtained nanofiber membrane to form a modified PI substrate layer; Step S2: After uniformly mixing the components of the first pressure-sensitive adhesive film layer and the second pressure-sensitive adhesive film layer, a first pressure-sensitive adhesive and a second pressure-sensitive adhesive are obtained; the first pressure-sensitive adhesive and the second pressure-sensitive adhesive are uniformly coated on the upper and lower surfaces of the modified PI substrate layer by a roller coating method; the coated adhesive film is cured at 80° C. for 2 hours to crosslink and cure the pressure-sensitive adhesive layer to form a PI substrate adhesive film for lithium batteries.

[0041] The process parameters of the electrospinning in step S1 are: spinning voltage of 20 kV, spinning distance of 15 cm, and receiving speed of 10 m / min; the temperature of the hot pressing treatment in step S1 is 160°C, the pressure is 10 MPa, and the time is 2 hours; the thickness of the modified PI substrate layer is 20 μm; the thickness of the first pressure-sensitive adhesive film layer is 5 μm; and the thickness of the second pressure-sensitive adhesive film layer is 5 μm.

[0042] Comparative Example 1 A PI substrate adhesive film for a lithium battery and a preparation method thereof are basically the same as Example 1, except that an equal amount of a fluorinated polyimide resin is used instead of the amino-containing hyperbranched polyurethane, and 10-(4-vinylphenyl)-10H-phenoxazine and methylvinylbis(butanone oxime)silane are not added.

[0043] Comparative Example 2 A PI substrate adhesive film for a lithium battery and a preparation method thereof, which is basically the same as Example 1, except that 1,3-bis(oxiranylmethyl)-5-(2-propenyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione and 3,3'-diamino-4,4'-difluorodiphenyl sulfone are not added.

[0044] In order to further illustrate the beneficial technical effects of the PI substrate films for lithium batteries involved in the embodiments of the present invention, relevant performance tests were conducted on the PI substrate films for lithium batteries involved in Examples 1-5 and Comparative Examples 1-2. The test results are shown in Table 1. The test method is as follows: (1) Peel strength test: Refer to the national standard GB / T 2792-2014 "Test method for peel strength of adhesive tape" to conduct a 180° peel strength test between the adhesive tape and the stainless steel plate.

[0045] (2) Moisture-heat aging resistance test: Place the film in an environment with a temperature of 85°C and a relative humidity of 85% for 1000 hours. After cooling to room temperature, test the 180° peel strength again according to the method in (1) and calculate the retention rate of the 180° peel strength. The larger the value, the better the moisture-heat aging resistance.

[0046] (3) Electrolyte resistance test: Soak the PI substrate film for lithium batteries in each example in an electrolyte with a weight 40 times that of the PI substrate film for lithium batteries for 24 hours; after taking it out, observe whether there is any delamination or bubbling. If there is no obvious change, the electrolyte resistance performance passes, otherwise it fails.

[0047] (4) Flexibility: The flexibility of the film is evaluated by a bending test. The film sample is repeatedly bent 180° to observe whether cracks or debonding occur.

[0048] Table 1 Performance test results of PI substrate film for lithium batteries

[0049] As can be seen from Table 1, the PI substrate film for lithium batteries disclosed in the embodiment of the present invention has better bonding performance and high temperature and humidity resistance than the comparative example product, and is more excellent in flexibility and electrolyte tolerance; the combined use of amino-containing hyperbranched polyurethane, 10-(4-vinylphenyl)-10H-phenoxazine, methylvinylbis(butanone oxime)silane, 1,3-bis(oxiranylmethyl)-5-(2-propenyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione and 3,3'-diamino-4,4'-difluorodiphenyl sulfone is beneficial to improving the above properties.

[0050] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions merely illustrate the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A PI substrate film for lithium batteries, characterized in that: From top to bottom, it includes a first pressure-sensitive adhesive film layer, a modified PI substrate layer, and a second pressure-sensitive adhesive film layer; the modified PI substrate layer is made of the following raw materials in parts by mass: 65-85 parts of fluorinated polyimide resin, 3-5 parts of coupling agent, 10-15 parts of nano-reinforced material, and 10-15 parts of hyperbranched polyurethane containing amino group; the first pressure-sensitive adhesive film layer and the second pressure-sensitive adhesive film layer are independently made of the following components in parts by mass: 8-12wt% of hyperbranched unsaturated resin, 10- The invention relates to a solvent-based acrylic pressure-sensitive adhesive comprising 2-4 wt% of (4-vinylphenyl)-10H-phenoxazine, 4-6 wt% of 1,3-bis(oxiranylmethyl)-5-(2-propenyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 3-5 wt% of methylvinylbis(butanone oxime)silane, 1-3 wt% of 3,3'-diamino-4,4'-difluorodiphenyl sulfone, 0.1-0.3 wt% of a curing agent, and 10-20 wt% of a solvent. The remainder is a solvent-based acrylic pressure-sensitive adhesive.

2. The PI substrate film for lithium batteries according to claim 1, characterized in that: The solvent-based acrylate pressure-sensitive adhesive is Henkel-129A solvent-based acrylate pressure-sensitive adhesive.

3. The PI substrate film for lithium batteries according to claim 1, characterized in that: The solvent is ethyl acetate; the curing agent is azobisisobutyronitrile.

4. The PI substrate film for lithium batteries according to claim 1, wherein The hyperbranched unsaturated resin is the hyperbranched unsaturated resin Hyper U102.

5. The PI substrate film for lithium batteries according to claim 1, characterized in that: The nano-reinforcement material is nano-mica powder; the average particle size of the nano-mica powder is 10-80nm.

6. The PI substrate film for lithium batteries according to claim 1, characterized in that: The coupling agent is at least one of silane coupling agent KH550, silane coupling agent KH560, and silane coupling agent KH570; and the brand of the fluorine-containing polyimide resin is DS512.

7. A method for preparing a PI substrate film for lithium batteries according to any one of claims 1 to 6, characterized in that: The steps include: Step S1, dissolving the dried fluorinated polyimide resin in dimethylacetamide, stirring at 70-90° C. for 4-6 hours until completely dissolved, to obtain a fluorinated polyimide resin solution; then sequentially adding a coupling agent, a nano-reinforcement material, and a hyperbranched polyurethane containing an amino group, and continuing stirring for 3-5 hours to form a uniform spinning solution; preparing the spinning solution into a nanofiber membrane using electrospinning technology; and hot-pressing the obtained nanofiber membrane to form a modified PI substrate layer; Step S2: After uniformly mixing the components of the first pressure-sensitive adhesive film layer and the second pressure-sensitive adhesive film layer, a first pressure-sensitive adhesive and a second pressure-sensitive adhesive are obtained; the first pressure-sensitive adhesive and the second pressure-sensitive adhesive are uniformly coated on the upper and lower surfaces of the modified PI substrate layer by a roller coating method; the coated adhesive film is cured at 70-80° C. for 1-2 hours to crosslink and cure the pressure-sensitive adhesive layer to form a PI substrate adhesive film for lithium batteries.

8. The method for preparing a PI substrate film for a lithium battery according to claim 7, wherein: The process parameters of the electrospinning in step S1 are: spinning voltage of 15-20 kV, spinning distance of 10-15 cm, and receiving speed of 5-10 m / min.

9. The method for preparing a PI substrate film for a lithium battery according to claim 7, wherein: The temperature of the hot pressing treatment in step S1 is 150-160° C., the pressure is 5-10 MPa, and the time is 1-2 hours.

10. The method for preparing a PI substrate film for lithium batteries according to claim 7, characterized in that: The thickness of the modified PI substrate layer is 20-30 μm; the thickness of the first pressure-sensitive adhesive film layer is 5-10 μm; and the thickness of the second pressure-sensitive adhesive film layer is 5-10 μm.

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