阅读说明：本技术 一种锂电池用耐腐蚀软包装膜制备方法 (Preparation method of corrosion-resistant flexible packaging film for lithium battery ) 是由 胡伟 李汪洋 吴磊 周正发 任凤梅 张伟 孙晓华 徐凤锦 刘志强 王若愚 张德顺 于 2019-10-15 设计创作，主要内容包括：本发明公开了一种锂电池用耐腐蚀软包装膜的制备方法,该锂电池用耐腐蚀软包装膜包括耐腐蚀内层、耐腐蚀中间层和耐腐蚀外层；采用多层聚丙烯共挤微交联形成内层基膜,内层基膜与聚对苯二甲酸乙二醇酯薄膜等复合形成内层膜；用高延展性的铝箔表面涂覆纳米级二氧化钛制成中间层；双向拉伸尼龙与改性聚对苯二甲酸乙二醇酯薄膜复合并在薄膜上涂覆二氧化硅涂层制成外层；外层、中间层、内层采用干式复合工艺有效复合,使其整体形成高耐腐蚀的多层膜结构；此方法在达到膜层耐腐蚀效果的同时,避免了一般复合中交联剂不耐电解液溶剂的缺点,多层结构也实现了膜层的耐穿刺、高阻隔、高绝缘、高热封强度的特点。(The invention discloses a preparation method of a corrosion-resistant flexible packaging film for a lithium battery, wherein the corrosion-resistant flexible packaging film for the lithium battery comprises a corrosion-resistant inner layer, a corrosion-resistant intermediate layer and a corrosion-resistant outer layer; adopting multi-layer polypropylene co-extrusion micro-crosslinking to form an inner-layer base film, and compounding the inner-layer base film with a polyethylene glycol terephthalate film and the like to form an inner-layer film; coating nano-scale titanium dioxide on the surface of the high-ductility aluminum foil to form a middle layer; the biaxially oriented nylon and the modified polyethylene glycol terephthalate film are compounded and coated with a silicon dioxide coating to prepare an outer layer; the outer layer, the middle layer and the inner layer are effectively compounded by adopting a dry compounding process, so that a high-corrosion-resistance multilayer film structure is integrally formed; the method has the advantages that the corrosion resistance effect of the film is achieved, the defect that a cross-linking agent in common composite is not resistant to an electrolyte solvent is overcome, and the characteristics of puncture resistance, high barrier, high insulation and high heat seal strength of the film are realized through a multi-layer structure.)

1. A preparation method of a corrosion-resistant flexible packaging film for a lithium battery is characterized in that the corrosion-resistant flexible packaging film for the lithium battery is prepared from a corrosion-resistant inner layer, a corrosion-resistant intermediate layer and a corrosion-resistant outer layer by a dry compounding method;

the corrosion-resistant inner layer comprises a layer A, a layer B, a layer C and a layer D from bottom to top in sequence, and the preparation steps are as follows:

s1: uniformly mixing 5-15 parts of ternary copolymer polypropylene, 0.1-3 parts of crosslinking monomer, 0.1-3 parts of initiator, 0.1-1 part of N- (3-fluoro-5-carboxyphenyl) maleimide and 1-5 parts of graphene to obtain a layer A raw material;

uniformly mixing 15-20 parts of homo-polypropylene, 0.1-3 parts of a crosslinking monomer, 0.1-3 parts of an initiator, 0.1-1 part of N- (3-fluoro-5-carboxyphenyl) maleimide and 1-5 parts of graphene to obtain a layer B raw material;

uniformly mixing 5-15 parts of mixed polypropylene, 0.1-3 parts of crosslinking monomer, 0.1-3 parts of initiator and 1-5 parts of graphene to obtain a C-layer raw material;

s2: respectively adding A, B, C mixed raw materials and 5-25 parts of nylon into A, B, C, D four double-screw extruders, and extruding and plasticizing;

s3: feeding the plasticized material in a molten state into a distributor, and then carrying out T-shaped die head and tape casting cooling forming to obtain an inner base film with a four-layer structure;

s4: extruding and compounding the inner base film with 5-10 parts of polyethylene glycol terephthalate to form a layer of polyethylene glycol terephthalate film on the inner base film, coating a layer of polyvinyl alcohol or polyvinylidene chloride with the thickness of 1-5 mu m on the surface of the polyethylene glycol terephthalate film to obtain a semi-finished inner film, and extruding and compounding the semi-finished inner film with 1-10 parts of ethylene-vinyl alcohol copolymer and 1-10 parts of polyvinyl butyral to obtain a corrosion-resistant inner layer;

the corrosion-resistant flexible packaging film for the lithium battery is prepared by a dry compounding method,

the method comprises the following steps: uniformly coating a layer of adhesive on the upper surface of the corrosion-resistant middle layer, drying by an oven, and then hot-pressing and attaching the corrosion-resistant outer layer on a composite roller;

step two: and uniformly coating a layer of adhesive on the lower surface of the corrosion-resistant middle layer, drying by an oven, and then hot-pressing and attaching the corrosion-resistant middle layer and the corrosion-resistant inner layer on a composite roller to obtain the corrosion-resistant flexible packaging film.

2. The method for preparing a corrosion-resistant flexible packaging film for a lithium battery as claimed in claim 1, wherein the crosslinking monomer is one or more of pentaerythritol tetraacrylate, glycerol triacrylate, divinylbenzene, and triacrylate isocyanurate.

3. The method of claim 1, wherein the initiator is one or more selected from the group consisting of dicumyl peroxide, 2, 5-dimethyl-2, 5-di (t-butylperoxy) hexane, diisopropyl peroxydicarbonate, dicyclohexyl peroxydicarbonate, and bis (o-methylbenzoyl) peroxide.

4. The method of claim 1, wherein the method for preparing the N- (3-fluoro-5-carboxyphenyl) maleimide comprises the following steps:

(1) dissolving 2 parts by mass of maleic anhydride in a solvent of N, N-dimethylformamide and toluene at a volume ratio of 1: 3-1: 4 to prepare a maleic anhydride solution with the concentration of 5-7 mol/L;

(2) adding 1 part by mass of 3-fluoro-5-carboxyl phenyl into a maleic anhydride solution and stirring for 1-3 hours;

(3) adding 0.01 part by mass of p-toluenesulfonic acid and 0.01 part by mass of hydroquinone into the solution (2), heating to 110-;

(4) and washing, drying and recrystallizing the crude product of the N- (3-fluoro-5-carboxyphenyl) maleimide to obtain the N- (3-fluoro-5-carboxyphenyl) maleimide.

5. The method for preparing the corrosion-resistant flexible packaging film for the lithium battery as claimed in claim 1, wherein the mixed polypropylene is prepared by mixing 0-20% by mass, 10-20% by mass and 60-90% by mass of binary polypropylene, ternary polypropylene and homo-polypropylene.

6. The method as claimed in claim 1, wherein the head temperature of the twin-screw extruder is 150-220 ℃, and the rotation speed is 170-210 r/min.

7. The method for preparing a corrosion-resistant flexible packaging film for a lithium battery as claimed in claim 1, wherein the corrosion-resistant intermediate layer is an aluminum foil, and a titanium dioxide or silicon dioxide coating layer with a thickness of 10-200nm is coated on the surface of the aluminum foil.

8. The method for preparing the corrosion-resistant flexible packaging film for the lithium battery as claimed in claim 1, wherein the corrosion-resistant outer layer is prepared by selecting 10-25 parts of nylon as a main material, extruding and compounding the nylon and 1-10 parts of modified polyethylene terephthalate, coating silica with the thickness of 10-200nm on the modified polyethylene terephthalate layer, and performing cold stamping molding.

9. The method as claimed in claim 7, wherein the modified polyethylene terephthalate film used in the corrosion-resistant outer layer is one of polyethylene terephthalate modified with adipic acid, polyethylene glycol, polyethylene adipate and epoxy resin.

10. The method for preparing the corrosion-resistant flexible packaging film for the lithium battery as claimed in claim 1, wherein the adhesive is one or more of polyurethane adhesive, epoxy resin adhesive, acrylic resin adhesive, polyester adhesive and acid-modified resin adhesive, and the thickness of the coating is 1-10 μm; the drying temperature of the oven is 60-100 ℃.

Technical Field

The invention relates to the field of polymers, in particular to a preparation method of a corrosion-resistant flexible packaging film for a lithium battery.

Background

With the development of microelectronic technology, the demand of lithium batteries is increasing day by day, and particularly in new energy vehicles, the flexible package of lithium ion batteries has the advantages of good safety performance, light weight, large capacity, small internal resistance, flexible design and the like compared with the traditional steel shell and aluminum shell packages, so that the flexible package research of the lithium ion batteries becomes popular. The flexible packaging material of the flexible packaging lithium ion battery is made of a multilayer film (substrate layer/aluminum foil layer/heat sealing layer). In the use process of the battery, electrochemical reaction is continuously carried out in the battery core, electrolyte in the battery core contains various organic solvents, the organic solvents can swell, dissolve and absorb flexible packaging materials in the use process of the battery, the bonding effect between composite layers is damaged, the concentration of each component in the electrolyte is changed, the electrical property of the battery is further influenced, and even expansion leakage of a lithium battery can be caused.

Chinese patent publication No. CN 108408245 a discloses a method for coating a corrosion-resistant organic coating and an inorganic oxide coating on the surface of an intermediate layer aluminum foil to improve the corrosion resistance of the film layer. However, the problem that the cross-linking agent in each layer of the composite in the method is not resistant to the corrosion of the electrolyte solvent is not solved.

Disclosure of Invention

The invention aims to provide a preparation method of a corrosion-resistant flexible packaging film for a lithium battery, wherein a crosslinking monomer containing a plurality of functional groups is added into a prepared corrosion-resistant inner layer, and the crosslinking monomer can perform free radical substitution crosslinking reaction with polypropylene under the action of an initiator, so that the functional groups of the crosslinking monomer are uniformly distributed in the polypropylene, the corrosion resistance of a polymer is improved through the synergistic effect of the functional groups, and the problem of insufficient corrosion resistance of the flexible packaging film for the lithium battery in the prior art is solved.

In order to achieve the purpose, the invention provides the following technical scheme:

a preparation method of a corrosion-resistant flexible packaging film for a lithium battery is characterized in that the corrosion-resistant flexible packaging film for the lithium battery is prepared from a corrosion-resistant inner layer, a corrosion-resistant intermediate layer and a corrosion-resistant outer layer by a dry compounding method;

the corrosion-resistant inner layer comprises a layer A, a layer B, a layer C and a layer D from bottom to top in sequence, and the preparation steps are as follows:

s1: uniformly mixing 5-15 parts of ternary copolymer polypropylene, 0.1-3 parts of crosslinking monomer, 0.1-3 parts of initiator, 0.1-1 part of N- (3-fluoro-5-carboxyphenyl) maleimide and 1-5 parts of graphene to obtain a layer A raw material, wherein the layer A is a heat sealing layer, the ternary copolymer polypropylene has a lower melting point, good hot melt property and a wider heat sealing temperature, so that the heat sealing strength of the material can be improved by selecting the ternary copolymer polypropylene as a layer A base material;

uniformly mixing 10-20 parts of homopolymerized polypropylene, 0.1-3 parts of crosslinking monomer, 0.1-3 parts of initiator, 0.1-1 part of N- (3-fluoro-5-carboxyl phenyl) maleimide and 1-5 parts of graphene to obtain a layer B raw material, wherein the layer B is a supporting layer and plays a role in supporting a film, and the homopolymerized polypropylene is selected as a layer B substrate so that the toughness and the stiffness of the film can be improved;

uniformly mixing 5-15 parts of mixed polypropylene, 0.1-3 parts of crosslinking monomer, 0.1-3 parts of initiator and 1-5 parts of graphene to obtain a C-layer raw material, wherein the C-layer is a corona outer layer, and the surface tension of the film layer can be improved by selecting the mixed polypropylene;

s2: respectively adding A, B, C mixed raw materials and 5-25 parts of nylon into A, B, C, D four double-screw extruders, and extruding and plasticizing;

s3: feeding the plasticized material in a molten state into a distributor, and then carrying out T-shaped die head and tape casting cooling forming to obtain an inner base film with a four-layer structure;

s4: extruding and compounding the inner layer with 5-10 parts of polyethylene glycol terephthalate, coating a layer of polyvinyl alcohol or polyvinylidene chloride with the thickness of 1-5 mu m on the surface of the polyethylene glycol terephthalate to obtain a semi-finished inner layer film, and extruding and compounding 1-10 parts of ethylene-vinyl alcohol copolymer and 1-10 parts of polyvinyl butyral on the semi-finished inner layer film to obtain a corrosion-resistant inner layer; the polyethylene terephthalate has excellent physical and mechanical properties, can be used for a long time at the temperature of 100 ℃, and has excellent electrical insulation performance; the polyvinyl alcohol and the polyvinylidene chloride are easy to form a film, the mechanical property is excellent after the film is formed, and the film has good barrier effect on aprotic polar solvent, non-polar solvent and the like; the ethylene-vinyl alcohol copolymer and the polyvinyl butyral have good thermal stability, permeability resistance, water resistance and corrosion resistance, and also have good machining performance; the corrosion-resistant inner layer compounded by the materials can meet the performance required by the lithium battery;

the corrosion-resistant flexible packaging film for the lithium battery is prepared by a dry compounding method,

the method comprises the following steps: uniformly coating a layer of adhesive on the upper surface of the corrosion-resistant middle layer, drying by an oven, and then hot-pressing and attaching the corrosion-resistant outer layer on a composite roller to obtain a semi-finished film;

step two: and uniformly coating a layer of adhesive on the lower surface of the semi-finished film, drying by an oven, and then hot-pressing and attaching the adhesive to the corrosion-resistant inner layer on a composite roller to obtain the corrosion-resistant flexible packaging film.

As a further scheme of the invention, the crosslinking monomer is one or more of pentaerythritol tetraacrylate, glycerol triacrylate, divinylbenzene and triacrylate isocyanurate.

As a further scheme of the invention, the initiator is one or more of dicumyl peroxide, 2, 5-dimethyl-2, 5-di (tert-butylperoxy) hexane, dicumyl peroxydicarbonate, dicyclohexyl peroxydicarbonate and di-o-methylbenzoyl peroxide.

As a further embodiment of the present invention, the N- (3-fluoro-5-carboxyphenyl) maleimide is prepared as follows:

(1) dissolving 2 parts by mass of maleic anhydride in a solvent of N, N-dimethylformamide and toluene at a volume ratio of 1: 3-1: 4 to prepare a maleic anhydride solution with the concentration of 5-7 mol/L;

(2) adding 1 part by mass of 3-fluoro-5-carboxyphenyl into the maleic anhydride solution in batches, and stirring for 1-3 hours;

(3) adding 0.01 part by mass of p-toluenesulfonic acid and 0.01 part by mass of hydroquinone into the solution (2), heating to 110-;

(4) and washing, drying and recrystallizing the crude product of the N- (3-fluoro-5-carboxyphenyl) maleimide to obtain the N- (3-fluoro-5-carboxyphenyl) maleimide.

As a further scheme of the invention, the mixed polypropylene is formed by mixing 0-20% by mass, 10-20% by mass and 60-90% by mass of binary polypropylene, ternary polypropylene and homo-polypropylene.

As a further scheme of the invention, the head temperature of the double-screw extruder is 150-220 ℃, and the rotating speed is 170-210 r/min.

As a further scheme of the invention, the corrosion-resistant intermediate layer is made of aluminum foil, and a titanium dioxide or silicon dioxide coating with the thickness of 10-200nm is coated on the surface of the aluminum foil.

As a further scheme of the invention, the corrosion-resistant outer layer is made of 10-25 parts of nylon as a main material, the nylon and 1-10 parts of modified polyethylene terephthalate are extruded and compounded, silica with the thickness of 10-200nm is coated on the modified polyethylene terephthalate layer, and the corrosion-resistant outer layer is obtained through cold stamping and forming.

In a further embodiment of the present invention, the modified polyethylene terephthalate film used in the corrosion-resistant outer layer is one of polyethylene terephthalate modified with adipic acid, polyethylene glycol, polyethylene adipate and epoxy resin.

As a further scheme of the invention, the adhesive uses one or more of polyurethane adhesive, epoxy resin adhesive, acrylic resin adhesive, polyester adhesive and acid modified resin adhesive, and the thickness of the coating is 1-10 μm; the drying temperature of the oven is 60-100 ℃.

Compared with the prior art, the invention has the beneficial effects that:

in the preparation of the corrosion-resistant inner layer: the ternary copolymer polypropylene is used as the innermost layer of the four-layer inner-layer base film, and the lower melting point of the ternary copolymer polypropylene is utilized, so that the heat sealing temperature can be properly reduced, and the heat sealing strength is improved; by adding graphene into the raw materials of each layer, the barrier property of the film layer can be effectively improved, and the copper wire or the aluminum wire in the battery can be prevented from puncturing the film layer; adding a crosslinking monomer, an initiator and N- (3-fluoro-5-carboxyphenyl) maleimide into a double-screw extruder together for extrusion compounding, so that micro-crosslinking reaction can be generated among polypropylene layers, the compounding of each layer is firmer, the crosslinking degree of the crosslinking monomer can be effectively controlled by adding the N- (3-fluoro-5-carboxyphenyl) maleimide, and an acid group is introduced into a crosslinking product, so that the corrosion resistance is improved to a certain extent, and the N- (3-fluoro-5-carboxyphenyl) maleimide is not added into the corona outer layer so as to ensure that the surface tension of the outer layer is not influenced; the inner base film is compounded with the polyethylene glycol terephthalate film, the ethylene-vinyl alcohol copolymer and the polyvinyl butyral, so that the defect that a cross-linking product in general compounding is not resistant to an electrolyte solvent can be avoided, and the corrosion resistance effect is effectively improved.

In the preparation of the corrosion-resistant intermediate layer, the surface of the aluminum foil is coated with a nano-scale titanium dioxide or silicon dioxide coating, and the reactive activity of the film layer to corrosive substances is greatly reduced by utilizing the passivation effect of the titanium dioxide and the silicon dioxide.

In the preparation of the corrosion-resistant outer layer, the biaxially oriented nylon and the modified polyethylene terephthalate film are compounded, so that the overall corrosion resistance of the flexible packaging film is further improved, and the silicon dioxide coating is coated on the film, so that the stronger pressure of a cold stamping forming process can be met.

The outer layer, the middle layer and the inner layer are effectively compounded by adopting a dry compounding process, so that a high-corrosion-resistance multilayer film structure is integrally formed.

Drawings

FIG. 1 is a cross-sectional view of a dispenser;

FIG. 2 is an enlarged view of area A of FIG. 1;

FIG. 3 is a schematic view of a feed hopper in the distributor;

FIG. 4 is a schematic view of a speed limiting plate in the dispenser;

FIG. 5 is a schematic view of the rear of the dispenser;

in the figure: 1. a housing; 2. a material channel; 3. a feed inlet; 4. an annular cover; 5. a feed hopper; 6. bolt holes; 7. a through hole; 8. an end cap; 9. a speed limiting plate; 10. rotating the block; 11. a threaded rod; 12. a chute; 13. a restrictor plate; 14. a fixing plate; 15. an annular plate; 16. a bolt; 17. a groove; 18. a seal ring; 19. a bump; 20. a threaded bore.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

With reference to FIGS. 1-5