CN111690132A

CN111690132A - Preparation method of self-repairing polyamide packaging material for lithium battery soft package

Info

Publication number: CN111690132A
Application number: CN202010484399.0A
Authority: CN
Inventors: 徐奕; 杨晶磊; 向勇; 唐先忠; 伍芳
Original assignee: University of Electronic Science and Technology of China
Current assignee: University of Electronic Science and Technology of China
Priority date: 2020-06-01
Filing date: 2020-06-01
Publication date: 2020-09-22

Abstract

The invention discloses a preparation method of a self-repairing polyamide packaging material for a lithium battery soft package, which comprises the following steps: adding diamine, diacid chloride, cosolvent and solvent into a three-neck flask, reacting for more than 15 minutes at 10 ℃ under the protection of nitrogen, repeatedly washing the product with distilled water and ethanol, and drying in a vacuum oven. The test result of the invention shows that compared with the polyamide film without disulfide bonds, the polyamide film containing disulfide bonds not only has excellent mechanical strength, but also has remarkable self-repairing performance, the highest self-repairing performance can reach 92 percent, and the problem that fine cracks are generated in the outer package of the lithium battery in the transportation and use process can be well solved, so that the safety of the lithium battery is further improved, and the service life of the lithium battery is further prolonged.

Description

Preparation method of self-repairing polyamide packaging material for lithium battery soft package

Technical Field

The invention relates to the technical field of aluminum plastic film composite packaging, in particular to a preparation method of a self-repairing polyamide packaging material for a lithium battery soft package.

Background

In recent years, lithium ion batteries have been widely used in the digital electronics field due to their advantages of large capacity, long cycle life, light weight, and no memory effect. The lithium battery is divided into a soft package mode and a hard package mode, and the soft package lithium battery has the advantages of large capacity, light weight, good safety and the like, so that the lithium battery becomes the development direction of the lithium battery. The soft package lithium ion battery adopts an aluminum-plastic composite film similar to a polymer lithium ion battery as a battery shell to replace a steel or aluminum shell of a common lithium ion battery. The aluminum-plastic composite film can be roughly divided into three layers: the inner layer is a bonding layer, and is made of polyethylene or polypropylene materials mostly to play a role in sealing and bonding. The intermediate level is the aluminium foil, can prevent the infiltration of the outside steam of battery, prevents simultaneously that inside electrolyte from oozing. The outer layer is a protective layer, and is made of polyester or nylon materials with high melting point, so that the battery has strong mechanical performance, prevents external force from damaging the battery, and plays a role in protecting the battery. But the plastic-aluminum membrane can make the glue film have tiny crackle in the in-process of bonding and the process or the use of battery equipment, and this kind of craze crack is difficult for detecting, is difficult for carrying out external force and restoreing, and can not change the material, in case the crackle can cause lithium cell life to shorten and the security reduces, causes the service function decline of equipment.

Disclosure of Invention

In view of the above, the present invention provides a method for preparing a self-repairing polyamide packaging material for lithium battery soft packs, wherein dynamic disulfide bonds are introduced into a polyamide (i.e., nylon) film layer material, and a diamine or diacid chloride containing disulfide bonds is subjected to a polycondensation reaction to obtain a disulfide bond-containing polyamide. When the damage and the crack occur, the disulfide bond is uniformly cracked to generate free radicals, and the free radicals are recombined to form the disulfide bond under the mild condition to repair the crack, so that the polyamide film layer material has self-repairability. The material has excellent mechanical properties, and can realize high-efficiency self-repairing at room temperature.

In order to achieve the above purpose, the invention adopts the technical scheme that:

1) under the protection of nitrogen, diamine and cosolvent (LiCl or CaCl) are added into a three-neck flask filled with proper amount of solvent₂) Stirring at normal temperature until the components are dissolved;

2) placing the flask in an ice-water bath, reducing the temperature of the system to be below 10 ℃, slowly adding diacyl chloride into the flask, continuously stirring and reacting for more than 15 minutes, pouring the product into water, filtering, repeatedly washing with distilled water and ethanol for many times, and carrying out vacuum drying after reduced pressure suction filtration;

3) preferably, the diamine is 4,4 '-diaminodiphenyl disulfide, 3' -dithiodipropylamine, hexamethylenediamine;

4) preferably, the diacid chloride is 2,2 '-dithiodibenzoyl chloride, 3' -dithiodipropyl chloride, adipoyl chloride and terephthaloyl chloride;

5) preferably, the solvent is N-methyl pyrrolidone or sulfolane.

Detailed Description

The following example is a description of the steps of the preparation method of the self-repairing polyamide packaging material for the soft package of the lithium battery.

Example 1

40ml of N-methylpyrrolidone and then 0.2% by weight of LiCl or CaCl were added to a 100ml three-necked flask at room temperature₂After stirring and dissolution, 6.21g (0.025mol) of 4, 4' -diaminodiphenyl disulfide was added. Placing the flask in an ice-water bath, reducing the temperature of the system to be below 10 ℃, introducing nitrogen for protection, slowly dropwise adding 4.68g (0.0255mol) of adipoyl chloride, continuing to stir for 15 minutes, stopping, pouring the product into water, filtering, repeatedly washing the obtained precipitate with distilled water and ethanol for multiple times, performing vacuum filtration under reduced pressure, placing the obtained product into a vacuum oven to remove the solvent, and then testing by a conventional method.

Example 2 the same procedure as in example 1 was repeated except that the type of the diacid chloride was changed to terephthaloyl chloride, and the specific composition content was as shown in table 1.

Examples 3 and 4 the procedure of example 1 was followed except that the kinds of diamine and diacid chloride were changed, the diamine was 3, 3' -dithiodipropylamine, and the diacid chloride was adipoyl chloride or terephthaloyl chloride, and the specific composition contents were as shown in table 1.

Examples 5 and 6 the procedure of example 1 was followed except that the kinds of diamine and diacid chloride were changed, the diamine was hexamethylenediamine, the diacid chloride was 2,2 '-dithiodibenzoyl chloride or 3, 3' -dithiodipropyl chloride, and the specific composition contents were as shown in table 1.

Comparative example 1

At room temperature, 100ml three-neck roasting40ml of N-methylpyrrolidone are added into a bottle, and then 0.2% wt of LiCl or CaCl is added₂After stirring and dissolving, 4.96g (0.025mol) of 4, 4' -diaminodiphenylmethane was added. Placing the flask in an ice-water bath, reducing the temperature of the system to be below 10 ℃, introducing nitrogen for protection, slowly dropwise adding 4.68g (0.0255mol) of adipoyl chloride, continuing to stir for 15 minutes, stopping, pouring the product into water, filtering, repeatedly washing the obtained precipitate with distilled water and ethanol for multiple times, performing vacuum filtration under reduced pressure, placing the obtained product into a vacuum oven to remove the solvent, and then testing by a conventional method. (comparative example different example 1 in which diamine was changed to 4, 4' -diaminodiphenylmethane containing no disulfide bond)

Comparative example 2

40ml of N-methylpyrrolidone and then 0.2% by weight of LiCl or CaCl were added to a 100ml three-necked flask at room temperature₂After stirring and dissolving, 4.96g (0.025mol) of 4, 4' -diaminodiphenylmethane was added. Placing the flask in an ice-water bath, cooling the system to below 10 ℃, introducing nitrogen for protection, slowly dropwise adding 5.18g (0.0255mol) of terephthaloyl chloride, continuing to stir for 15 minutes, stopping, pouring the product into water, filtering, repeatedly washing the obtained precipitate with distilled water and ethanol for multiple times, performing vacuum filtration, placing in a vacuum oven to remove the solvent, and testing by a conventional method. (comparative example 3 in which diamine was changed to 4, 4' -diaminodiphenylmethane containing no disulfide bond)

Comparative example 3

40ml of N-methylpyrrolidone and then 0.2% by weight of LiCl or CaCl were added to a 100ml three-necked flask at room temperature₂After stirring and dissolving, 2.90g (0.025mol) of hexamethylenediamine was added. Placing the flask in an ice-water bath, reducing the temperature of the system to be below 10 ℃, introducing nitrogen for protection, slowly dropwise adding 4.68g (0.0255mol) of adipoyl chloride, continuing to stir for 15 minutes, stopping, pouring the product into water, filtering, repeatedly washing the obtained precipitate with distilled water and ethanol for multiple times, performing vacuum filtration under reduced pressure, placing the obtained product into a vacuum oven to remove the solvent, and then testing by a conventional method. (comparative example 1 in which diamine was changed to hexamethylenediamine without disulfide bond)

Table one example and comparative components and proportions

The polyamide films of examples 1 to 6 and comparative examples 1 to 3 were compounded with aluminum foil and a polypropylene adhesive to prepare aluminum-plastic film samples.

The aluminum-plastic films prepared by using the polyamide films prepared in examples 1 to 6 and comparative examples 1 to 3 were subjected to a peel strength test and a tensile strength test and the self-repairing efficiency thereof was calculated, and the statistical results are shown in table two:

table two test results of examples and comparative examples

The second table shows that compared with polyamide without disulfide bonds, the polyamide containing disulfide bonds has equivalent or even better mechanical strength and obvious self-repairing performance under mild conditions, can well solve the problem that micro cracks are generated in an outer package of a lithium battery in the transportation or use process, and further improves the use safety and the service life of the lithium battery.

Claims

1. A preparation method of a self-repairing polyamide packaging material for a lithium battery soft package comprises the following steps:

1) aromatic dithio-diamine or aliphatic dithio-diamine and cosolvent (LiCl or CaCl) under nitrogen protection₂) Dissolving in solvent, slowly adding diacyl chloride in ice water bath (below 10 deg.C), and reacting for more than 15 min;

2) pouring the reactant obtained in the above steps into water, filtering, repeatedly washing with distilled water and ethanol for several times, carrying out vacuum filtration, and drying in a vacuum oven.

2. The preparation method of the self-repairing polyamide packaging material for the soft package of the lithium battery, according to claim 1, is characterized in that: the diamine is at least one of 4,4 '-diaminodiphenyl disulfide, 3' -dithiodipropylamine and hexamethylene diamine.

3. The preparation method of the self-repairing polyamide packaging material for the soft package of the lithium battery, according to claim 1, is characterized in that: the molar ratio of diamine to diacid chloride is controlled to be 1.05:1, taking into account the side reactions of acid chloride groups with the solvent.

4. The preparation method of the self-repairing polyamide packaging material for the soft package of the lithium battery, according to claim 1, is characterized in that: the diacid chloride is at least one of 2,2 '-dithiodibenzoyl chloride, 3' -dithiodipropionyl chloride, adipic acid and terephthaloyl chloride.