WO2023226291A1

WO2023226291A1 - Aluminum-plastic composite film for lithium-ion battery and preparation method therefor

Info

Publication number: WO2023226291A1
Application number: PCT/CN2022/127126
Authority: WO
Inventors: 廖秀连; 戴晓兵; 井光辉
Original assignee: 珠海市赛纬电子材料股份有限公司; 江西省盛纬材料有限公司
Priority date: 2022-05-27
Filing date: 2022-10-24
Publication date: 2023-11-30
Also published as: CN114889249B; CN114889249A

Abstract

An aluminum-plastic composite film for a lithium-ion battery, and a preparation method therefor. The aluminum-plastic composite film comprises an aluminum foil layer, and a heat sealing layer and a protective layer which are located on two sides of the aluminum foil layer, wherein a coating is provided on the outer surface of the protective layer, the coating is prepared by drying a paint, and the paint comprises a polyol solvent, an erucamide emulsion, cyclohexane, a polyacrylonitrile emulsion, modified epoxy resin, a surfactant, and an additive. By adopting the aluminum-plastic composite film, when an electrolyte of the lithium-ion battery boils, the surface of the battery can be rapidly cooled, the risk probability of ignition or explosion of the battery is reduced, the smoothness of the surface of the film material can be improved, and the improvement of the punch forming performance is facilitated. The heat dissipation and the smoothness of the aluminum-plastic composite film are improved, good punch forming performance and encapsulation are guaranteed, and good heat dissipation and punch forming performance complement each other in the aspect of battery safety.

Description

Aluminum-plastic composite film for lithium-ion batteries and preparation method thereof

Technical field

The present application relates to the technical field of lithium battery packaging, and more specifically to an aluminum-plastic composite film for lithium-ion batteries and a preparation method thereof.

Background technique

The common structure of aluminum-plastic composite film for soft-pack lithium-ion batteries is a three-layer structure, with an outer nylon layer, an aluminum foil core layer, and an inner polypropylene layer. In the process of making the battery, the aluminum-plastic composite film goes through processes such as packaging, liquid injection, formation, and second sealing. The electrolyte resistance and safety performance must also be considered during use. Therefore, the aluminum-plastic composite film needs to ensure lithium ions. The safety of the battery must also take into account its packaging performance and other production processes.

As a packaging material for polymer soft-packed lithium-ion batteries, aluminum-plastic composite film not only has the characteristics of thinness, but also has more outstanding safety performance compared to aluminum-shell batteries and polymer soft-packed lithium-ion batteries. When the electrolyte in the battery begins to The aluminum-plastic film will naturally bulge or rupture when boiling and will not explode. However, many batteries on the market still have fire accidents. In order to further improve the safety of the aluminum-plastic composite film, Chinese patent 201921105750. It can better transfer heat evenly from the inside of the lithium battery to the entire battery surface of the lithium battery to avoid local overheating or heat accumulation problems. It can well improve the high temperature resistance performance of the lithium battery and effectively improve the safety performance of the lithium battery. However, this coating is not conducive to the deep formability and packaging process of aluminum-plastic composite films to a certain extent.

Therefore, it needs to be improved to solve the above problems.

Application content

In order to overcome the shortcomings of the prior art, the purpose of this application is to provide an aluminum-plastic composite film for lithium-ion batteries and a preparation method thereof. Using the aluminum-plastic composite film, when the electrolyte of the lithium-ion battery boils, the surface of the battery can be Rapid cooling reduces the risk of battery fire or explosion, and improves the smoothness of the membrane surface, helping to improve the deep forming performance. It not only improves the heat dissipation and smoothness of the aluminum-plastic composite film, but also ensures good punching formability and encapsulation, so that good heat dissipation and punching formability complement each other in terms of battery safety.

In order to achieve the above purpose, this application discloses an aluminum-plastic composite film for lithium-ion batteries, which includes an aluminum foil layer and a heat sealing layer and a protective layer located on both sides of the aluminum foil layer. The outer surface of the protective layer is provided with a coating. The coating is prepared by drying paint, which includes polyol solvent, erucamide emulsion, cyclohexane, polyacrylonitrile emulsion, modified epoxy resin, surfactants and auxiliaries.

Compared with the prior art, the aluminum-plastic composite film for lithium-ion batteries of the present application is provided with a coating on the outer surface of the protective layer. The coating is prepared by drying the coating. In particular, the raw materials for preparing the coating include erucamide emulsion and polyacrylonitrile. Emulsion, modified epoxy resin, surfactant, aluminum-plastic composite film made of these materials can quickly cool the battery surface when the electrolyte of the lithium-ion battery boils, reducing the risk of battery fire or explosion, and can improve The smoothness of the membrane material surface helps improve the punching and forming performance. It not only improves the heat dissipation and smoothness of the aluminum-plastic composite film, but also ensures good punching formability and encapsulation, so that good heat dissipation and punching formability complement each other in terms of battery safety.

Preferably, in parts by weight, the coating includes 10-20 parts of polyol solvent, 30-40 parts of erucamide emulsion, 10-20 parts of cyclohexane, and 10-20 parts of polyacrylonitrile. Emulsion, 10-20 parts of modified epoxy resin, 0.5-1 part of surfactant and 0.5-1 part of additives.

Preferably, the modified epoxy resin is prepared by modifying epoxy resin with a toughening agent.

Preferably, the surfactant is selected from polyether-modified polydimethylsiloxane.

Preferably, the polyol solvent is selected from at least one of ethylene glycol, glycerol, and pentaerythritol.

Preferably, the thickness of the coating is 0.5-1.5 μm.

Preferably, the heat sealing layer is selected from polypropylene film, and the protective layer is selected from nylon film.

Preferably, the preparation method of the coating is as follows:

(1) Add the polyol and the erucamide emulsion into the reaction device, stir and heat up to 50-150°C;

(2) Add the cyclohexane, the polyacrylonitrile emulsion and the auxiliary agent, and continue stirring;

(3) Add the surfactant, continue stirring, wait until the reaction is completed, and cool to obtain a semi-finished paint product;

(4) Mix and stir the semi-finished paint, the modified epoxy resin and the cyclohexane evenly to obtain a paint.

This application also provides a method for preparing the above-mentioned aluminum-plastic composite film for lithium-ion batteries, including the steps:

Provide aluminum foil layer;

A heat sealing layer is provided on one side of the aluminum foil layer;

A protective layer is provided on the other side of the aluminum foil layer;

Coat paint on the outer surface of the protective layer and dry at 70-95°C to form a coating.

Preferably, the viscosity of the coating is 300-400Cp.

Detailed ways

In order to describe in detail the technical content, structural features, achieved objectives and effects of the present application, they will be described in detail below in conjunction with the embodiments.

This application provides an aluminum-plastic composite film for lithium-ion batteries, which includes an aluminum foil layer and a heat sealing layer and a protective layer located on both sides of the aluminum foil layer. The outer surface of the protective layer is provided with a coating, and the coating is made by drying the coating. Obtained, the coating includes polyol solvent, erucamide emulsion, cyclohexane, polyacrylonitrile emulsion, modified epoxy resin, surfactant and auxiliaries.

Among them, the heat sealing layer is polypropylene film (CPP), and multi-layer cast polypropylene film is preferred. Preferably, the peak melting point of the multi-layer cast polypropylene film is 165°C and the melting range is 145-165°C, which can improve the packaging strength and make the aluminum-plastic composite film have higher safety performance.

It can be understood that the protective layer is a nylon film, an adhesive layer is provided between the protective layer and the aluminum foil layer, an adhesive layer is provided between the heat sealing layer and the aluminum foil layer, and the coating is located outside the protective layer. On the surface, the coating has the characteristics of heat dissipation and improving the smoothness of the film layer, and is conducive to improving the deep forming performance and packaging process.

In a preferred embodiment, in parts by weight, the coating includes 10-20 parts of polyol solvent, 30-40 parts of erucamide emulsion, 10-20 parts of cyclohexane, 10-20 parts of Polyacrylonitrile emulsion, 10-20 parts of modified epoxy resin, 0.5-1 part of surfactant and 0.5-1 part of additives. Among them, the polyol solvent can be but not limited to 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, and 20 parts; the erucamide emulsion can be but not limited to 30 parts, 32 parts, 34 parts, 36 parts, 38 parts parts, 40 parts; cyclohexane can be but not limited to 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, 20 parts; polyacrylonitrile emulsion can be but not limited to 10 parts, 12 parts, 14 parts, 16 parts parts, 18 parts, 20 parts; modified epoxy resin can be but not limited to 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, 20 parts; surfactant can be but not limited to 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1.0 parts; additives can be but not limited to 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1.0 parts.

In a preferred embodiment, the modified epoxy resin is prepared by modifying epoxy resin with a toughening agent. It should be noted that because epoxy resin has benzene ring and heterocyclic functional groups, the molecular chain is less flexible, and has a higher cross-linked structure that is not easily deformed. After curing, it is generally strong in rigidity, insufficient in toughness, and has poor bonding strength and punching depth. Poor formability is not conducive to deep forming of aluminum-plastic composite films. Modified epoxy resin is obtained by modifying epoxy resin with a toughening agent. It has good flexibility and can significantly improve the deep-drawing of aluminum-plastic composite films. forming. Specifically, the modified epoxy resin can be at least one of HEXION EPON 58006, ADEKA resin EP-4000, Miki Group SM716, M172, and Yuanshu BPA-PO, but is not limited to this.

In a preferred embodiment, the polyol solvent is selected from at least one of ethylene glycol, glycerol, and pentaerythritol. The polyol solvent can dissolve the erucamide emulsion well.

In a preferred embodiment, erucic acid amide is stirred and dissolved in an alcoholic solvent at 50-100°C to prepare an erucic acid amide emulsion. The erucic acid amide emulsion has good slippery properties and can improve the smoothness of the film surface. , conducive to heat sealing.

In a preferred embodiment, polyacrylonitrile powder is dissolved in dimethylformamide polar organic solvent to obtain polyacrylonitrile emulsion. The polyacrylonitrile emulsion has good thermal conductivity and is conducive to heat sealing.

In a preferred embodiment, the surfactant is selected from polyether-modified polydimethylsiloxane, which can both reduce surface tension and increase surface slippery, so that the coating has good leveling and recoatability. properties; it can also prevent the formation of Bernard vortices and improve the wettability of the substrate.

In a preferred embodiment, the auxiliary agents can be defoaming agents, smoothing agents, adhesion promoters, leveling agents, etc., but are not limited thereto.

In a preferred embodiment, the thickness of the coating is 0.5-1.5 μm. For example, the thickness of the coating can be but not limited to 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.1 μm, 1.2 μm, 1.3μm, 1.4μm, 1.5μm. When coating, if the coating thickness is too thick, on the one hand, the curing time is too long, and it takes a long time to dry completely, resulting in low efficiency; on the other hand, if the coating thickness is too thick, it is easy to generate large internal stress, and the coating is prone to drying, cracking, and adhesion. Problems such as poor strength and poor packaging of the inner layer of the aluminum-plastic composite film may cause battery leakage, causing battery corrosion or even explosion. When the thickness of the coating is too thin, it will not protect the electrolyte when it boils in the battery.

This application also provides a preparation method for the above coating, as follows:

(1) Add polyol and erucamide emulsion into the reaction device, stir and heat up to 50-150°C;

(2) Add cyclohexane, polyacrylonitrile emulsion and additives, and continue stirring;

(3) Add surfactant, continue stirring, wait until the reaction is completed, and cool to obtain a semi-finished paint product;

(4) Mix the semi-finished product of the paint with the modified epoxy resin and cyclohexane and stir evenly to obtain the paint.

This application also provides a method for preparing an aluminum-plastic composite film for lithium-ion batteries, including the steps:

Provide aluminum foil layer;

There is a heat sealing layer on one side of the aluminum foil layer;

There is a protective layer on the other side of the aluminum foil layer;

Apply paint on the outer surface of the protective layer and dry at 70-95°C to form a coating.

In a preferred embodiment, the viscosity of the coating is 300-400Cp. For example, the viscosity may be but not limited to 300Cp, 320Cp, 340Cp, 360Cp, 380Cp, or 400Cp. When the viscosity is too high, the fluidity becomes poor, the coating cannot evenly cover the outer layer of the aluminum-plastic composite film, and the heat transfer efficiency is inconsistent. The preparation process of the aluminum-plastic composite film is prone to uneven heating and poor uniformity. When applied to batteries, battery problems are prone to occur. Defects such as leakage or poor packaging.

The present application will be further described below through specific examples.

Example 1

A method for preparing aluminum-plastic composite film for lithium-ion batteries, including the steps:

(1) Use a multi-layer polypropylene film with a melting point of 160°C and a melting range of 145-165°C. After the inner layer of adhesive is combined with the aluminum foil, the semi-finished product P/Al is obtained. The P/Al semi-finished product and the nylon film are separated by an outer layer. The layers of adhesive are compounded to obtain P/Al/N finished products;

(2) The preparation method of coating is as follows:

2.1 Add 15 parts of ethylene glycol and 30 parts of erucamide emulsion into the reaction device, stir at 100r/min and raise the temperature to 90°C;

2.2 During the stirring process, slowly add 10 parts of cyclohexane, 15 parts of polyacrylonitrile emulsion, and 0.5 parts of BYK-4509. After continuing to stir for 0.5 hours, add 0.5 parts of polyether modified polydimethylsiloxane (Cathayhua Rong Chemical New Materials Co., Ltd.), continue stirring for 0.5 hours,

2.3 After the reaction is completed, cool to normal temperature to obtain the semi-finished paint;

2.4 Mix the semi-finished paint with 10 parts of modified epoxy resin (HEXION EPON 58006) and 5 parts of cyclohexane and stir evenly to obtain the paint;

(3) Coat the above coating on the surface of the nylon film of the P/Al/N finished product, and dry it at a temperature of 90°C and a vehicle speed of 25m/min to obtain a coating with a dry film thickness of 1.0 μm, thereby preparing the present invention. Application for aluminum-plastic composite film.

Example 2

(2) The preparation method of coating is as follows:

2.1 Add 20 parts of ethylene glycol and 40 parts of erucamide emulsion into the reaction device, stir at 100r/min and raise the temperature to 120°C;

2.2 During the stirring process, slowly add 10 parts of cyclohexane, 10 parts of polyacrylonitrile emulsion, and 1 part of BYK-4509. After continuing to stir for 0.5 hours, add 0.5 parts of polyether modified polydimethylsiloxane (Cathayhua Rong Chemical New Materials Co., Ltd.), continue stirring for 0.5 hours,

2.4 Mix the semi-finished paint with 15 parts of modified epoxy resin (ADEKA resin EP-4000) and 5 parts of cyclohexane and stir evenly to obtain the paint;

(3) Coat the above coating on the surface of the nylon film of the P/Al/N finished product, and dry it at a temperature of 90°C and a vehicle speed of 25m/min to obtain a coating with a dry film thickness of 0.5 μm, thereby preparing the present invention. Application for aluminum-plastic composite film.

Example 3

(2) The preparation method of coating is as follows:

2.1 Add 10 parts of ethylene glycol and 35 parts of erucamide emulsion into the reaction device, stir at 100r/min and raise the temperature to 80°C;

2.2 During the stirring process, slowly add 10 parts of cyclohexane, 20 parts of polyacrylonitrile emulsion, and 0.5 parts of BYK-4509. After continuing to stir for 0.5 hours, add 1 part of polyether modified polydimethylsiloxane (Cathayhua Rong Chemical New Materials Co., Ltd.), continue stirring for 0.5 hours,

2.4 Mix the semi-finished paint with 10 parts of modified epoxy resin (Miki Group SM716) and 10 parts of cyclohexane and stir evenly to obtain the paint;

(3) Coat the above coating on the surface of the nylon film of the P/Al/N finished product, and dry it at a temperature of 90°C and a vehicle speed of 25m/min to obtain a coating with a dry film thickness of 1.5 μm, thereby preparing the present invention. Application for aluminum-plastic composite film.

Comparative example 1

Comparative Example 1 is basically the same as Example 1, except that in step 2.4, Comparative Example 1 uses epoxy resin WSR618 (E-51), while Example 1 uses modified epoxy resin (HEXION EPON 58006), and the rest are the same. .

Comparative example 2

Comparative Example 2 is basically the same as Example 1, except that Comparative Example 2 does not contain erucic acid amide emulsion in the coating preparation, while Example 1 uses erucic acid amide emulsion, and the rest are the same.

Comparative example 3

Comparative Example 3 is basically the same as Example 1, except that Comparative Example 3 does not contain polyacrylonitrile emulsion in the preparation of the coating, while Example 1 uses polyacrylonitrile emulsion, and the rest are the same.

Comparative example 4

Comparative Example 4 is basically the same as Example 1, except that Comparative Example 4 does not contain polyether-modified polydimethylsiloxane in the preparation of the coating, while Example 1 uses polyether-modified polydimethylsiloxane. , the rest are the same.

Comparative example 5

Comparative Example 5 is basically the same as Example 1, except that the thickness of the coating in Comparative Example 5 is 2.0 μm, while the thickness of the coating in Example 1 is 1.0 μm, and the rest are the same.

Comparative example 6

Comparative Example 6 is basically the same as Example 1, except that the thickness of the coating in Comparative Example 6 is 0.2 μm, while the thickness of the coating in Example 1 is 1.0 μm, and the rest are the same.

Comparative example 7

Comparative Example 7 is basically the same as Example 1, except that Comparative Example 7 does not contain a coating, while Example 1 contains a coating, and the rest are the same.

Comparative example 8

Comparative Example 8 is basically the same as Example 1, except that Comparative Example 8 uses a multi-layer polypropylene film with a melting point of 185°C and a melting range of 165-190°C, while Example 1 uses a multilayer polypropylene film with a melting point of 160°C and a melting range of 145°C. -165°C multi-layer polypropylene film, all else being the same.

Performance tests were performed on the products prepared in Examples 1-3 and Comparative Examples 1-8. The relevant descriptions are as follows:

Among them, the friction coefficient of the product surface is used to judge its slipperiness. The test method is based on GB10006-88 Determination of friction coefficient of plastic films and diaphragms. The results are shown in Table 1.

Table 1 Slippery test results

Among them, the product safety is judged by the punching depth of the aluminum-plastic composite film and the temperature of the battery surface. The punching depth of the aluminum-plastic composite film is tested with a die machine, and the temperature of the battery surface is bonded with a temperature probe on the battery surface to monitor temperature changes in real time. , the results are shown in Table 2.

Table 2 Plastic composite film punching depth and battery surface temperature test results

Among them, the packaging effect of the aluminum-plastic composite film is judged by the packaging strength. The test is carried out according to the QBT 2358-1998 plastic film packaging bag heat sealing strength test method. The results are shown in Table 3.

Table 3 Aluminum-plastic composite film packaging strength test results

It can be seen from the data in Table 1-3 that compared with Comparative Example 7, Example 1-3 of the present application adds a layer of special coating, so that the aluminum-plastic composite film has good heat dissipation function at high temperatures and can also improve the film quality. The smoothness of the material surface helps improve the punching and forming performance, and good heat dissipation and punching formability complement each other in terms of battery safety. While improving the heat dissipation and smoothness of the aluminum-plastic composite film, it also ensures good deep formability and encapsulation properties of the aluminum-plastic composite film.

Referring to the data of Comparative Examples 1-2 in Table 2, it can be seen that when using epoxy resin without toughener modification or erucamide-free emulsion, the penetration depth is smaller, only 3.5mm.

Referring to the data of Comparative Example 8 in Table 3, it can be seen that when a coating is used, a polypropylene film with a low melting point must be used, otherwise the packaging effect of the aluminum-plastic composite film will be poor.

The above disclosures are only preferred embodiments of the present application. Of course, they cannot be used to limit the scope of rights of the present application. Therefore, equivalent changes made according to the patent scope of the present application are still within the scope of the present application.

Claims

An aluminum-plastic composite film for lithium-ion batteries, including an aluminum foil layer and a heat sealing layer and a protective layer located on both sides of the aluminum foil layer. It is characterized in that the outer surface of the protective layer is provided with a coating, and the coating is composed of The coating is prepared by drying, and the coating includes polyol solvent, erucamide emulsion, cyclohexane, polyacrylonitrile emulsion, modified epoxy resin, surfactant and auxiliaries.
The aluminum-plastic composite film for lithium-ion batteries according to claim 1, wherein the coating includes 10-20 parts by weight of polyol solvent, 30-40 parts of erucamide emulsion, 10 parts by weight, -20 parts of cyclohexane, 10-20 parts of polyacrylonitrile emulsion, 10-20 parts of modified epoxy resin, 0.5-1 part of surfactant and 0.5-1 part of additives.
The aluminum-plastic composite film for lithium-ion batteries according to claim 1, wherein the modified epoxy resin is an epoxy resin modified with a toughening agent.
The aluminum-plastic composite film for lithium-ion batteries according to claim 1, wherein the surfactant is selected from polyether-modified polydimethylsiloxane.
The aluminum-plastic composite film for lithium-ion batteries according to claim 1, wherein the polyol solvent is selected from at least one selected from the group consisting of ethylene glycol, glycerin, and pentaerythritol.
The aluminum-plastic composite film for lithium-ion batteries according to claim 1, wherein the thickness of the coating is 0.5-1.5 μm.
The aluminum-plastic composite film for lithium-ion batteries according to claim 1, wherein the heat sealing layer is selected from polypropylene film, and the protective layer is selected from nylon film.
The aluminum-plastic composite film for lithium-ion batteries according to claim 1, wherein the preparation method of the coating is as follows:

(1) Add the polyol and the erucamide emulsion into the reaction device, stir and heat up to 50-150°C;

(2) Add the cyclohexane, the polyacrylonitrile emulsion and the auxiliary agent, and continue stirring;

(3) Add the surfactant, continue stirring, wait until the reaction is completed, and cool to obtain a semi-finished paint product;

(4) Mix and stir the semi-finished paint, the modified epoxy resin and the cyclohexane evenly to obtain a paint.
A method for preparing an aluminum-plastic composite film for lithium-ion batteries according to any one of claims 1 to 8, characterized in that it includes the steps:

Provide aluminum foil layer;

A heat sealing layer is provided on one side of the aluminum foil layer;

A protective layer is provided on the other side of the aluminum foil layer;

Coat paint on the outer surface of the protective layer and dry at 70-95°C to form a coating.
The preparation method according to claim 9, characterized in that the viscosity of the coating is 300-400Cp.