WO2023216410A1

WO2023216410A1 - Outer packing material for lithium-ion battery device

Info

Publication number: WO2023216410A1
Application number: PCT/CN2022/104944
Authority: WO
Inventors: 庄志; 张茜; 黎秋生; 程跃
Original assignee: 江苏睿捷新材料科技有限公司
Priority date: 2022-05-13
Filing date: 2022-07-11
Publication date: 2023-11-16
Also published as: CN114919257A

Abstract

The present invention provides a metal composite film, which comprises a metal layer, an inner bonding layer, a hot-melting resin layer, an outer bonding layer and an outer layer, wherein the outer layer is arranged on one side of the metal layer, and the hot-melting resin layer is arranged on the other side of the metal layer; the inner bonding layer is arranged between the metal layer and the first hot-melting resin layer; the outer bonding layer is arranged between the outer layer and the metal layer; two sides of the metal layer can be respectively provided with an anti-corrosion layer; and the hot-melting resin layer is of a layer structure formed by block or random copolymerization of a fluorine-containing resin and other polar groups. The metal composite film has a high heat-sealing strength, and has good tolerance when used in the formation of a soft pack battery.

Description

An outer packaging material for lithium-ion battery devices

Technical field

The present invention relates to the technical field related to battery packaging materials, and particularly relates to an outer packaging material for lithium-ion battery devices.

Background technique

At present, lithium-ion batteries are mainly divided into three categories: square, cylindrical and soft-packed. Among them, square and cylindrical casings are mainly made of aluminum alloy, stainless steel and other hard shells. The aluminum alloy casing can be aluminum, while the soft casing is made of metal and resin. The outer shell of the battery pack is made of metal composite film, which greatly improves the problem of inflexible shape design of hard-mounted batteries.

There are two main product types of metal composite films. One is the dry-process product, which consists of the outer base material resin layer, outer adhesive layer, middle metal layer, inner adhesive layer and thermal welding resin from outside to inside. layer. The other type is the thermal method, that is, the outer base material resin layer, the outer adhesive layer, the middle metal layer and the inner thermal welding resin layer are composed from the outside to the inside as the battery outer packaging material.

Currently, higher requirements are put forward for the high temperature resistance, corrosion resistance, durability and safety of battery packaging materials. On the one hand, 3C products will generate a certain amount of heat during the charging and discharging process, and power lithium-ion batteries will generate more heat. Heat, the durability of 3C equipment is 2-5 years, which is relatively short. In contrast, EV power supplies require more than 10 years of life performance, and there are still some shortcomings in long-term life; on the other hand, the ignition of lithium-ion batteries Accidents often occur, and safety issues still exist. All-solid-state batteries have been proposed and developed, which are inherently safe, thin, lightweight, flexible, and long-life. All-solid-state batteries have higher requirements for high-temperature resistance of outer packaging materials than lithium-ion batteries. At present, the market mainly uses modified polypropylene as the inner adhesive layer, with a melting point between 70°C and 80°C; polypropylene as the inner thermal welding resin layer, with a melting point between 140°C and 160°C. Polypropylene materials are resistant to Stress whitening, puncture resistance, and excellent bending resistance. The current use of its product characteristics makes the metal composite film have certain deficiencies in terms of heat resistance, corrosion resistance, durability and safety. Swelling of the electrolyte and penetration of the electrolyte will occur, which will reduce the stable operation of the chemical system inside the battery. In severe cases, it will bulge and crack, and poor insulation will occur, seriously affecting the safety of use. It also cannot meet the needs of next-generation all-solid-state batteries, which need to be used at high temperatures. Consider using fluororesins with higher melting points. The H atoms on the main chain or side chains of the fluoropolymer molecules are partially or entirely replaced by F. This special structure allows the fluoropolymer to have special properties that other polymers do not have. , the bond energy of the C-F bond is as high as 485kJ/mol, which is much higher than the bond energy of the C-H bond. It is the chemical bond with the largest energy among all covalent single bonds. In addition, the electron cloud of F atoms has a stronger shielding effect on C-C bonds than H atoms, which can well protect the C-C bonds on the main chain from external influences. The existence of large C-F bond groups makes fluorine-containing polymers possess Excellent oxidation resistance, corrosion resistance, weather resistance, low friction, low refraction, low capacitance, low surface energy, low moisture absorption and other properties. Its heat resistance, corrosion resistance and durability are even better. However, it cannot be used as a heat sealing layer alone, mainly because it is difficult to heat seal and has poor fluidity. During heat sealing, the two films in contact with each other cannot be well fused, which will lead to low heat sealing strength. On the other hand, because the melting point is too high, the heat sealing High temperature is required. Since the melting point of NY in the outer layer is 220°C, NY melts and destroys, and the existing heat sealing process cannot dissolve the heat seal. Therefore, the outer layer material is made of more high-temperature resistant materials, such as fluorine-based resin, polyimide resin, etc.

Contents of the invention

The object of the present invention is to provide a metal composite film, which includes: a metal layer, an inner adhesive layer, a hot-melt grease layer, an outer adhesive layer and an outer layer. The outer layer is arranged on the metal On one side of the layer, the heat-fusion resin layer is provided on the other side of the metal layer, the inner adhesive layer is provided between the metal layer and the first heat-fusion resin layer, and the outer adhesive layer Disposed between the outer layer and the metal layer, two anti-corrosion layers may be provided on both sides of the metal layer. The thermally welded resin layer is a layer structure formed by fluorine-containing resin inlay or random copolymerization of polar groups.

Optionally, the fluorine-containing resin is any one or more of tetrafluoroethylene resin, vinylidene fluoride resin, copolymers of tetrafluoroethylene and ethylene, or tetrafluoroethylene and perfluoroalkyl ether.

Optionally, the polar group is any one or more of an acidic group, halogen, epoxy, and ether group; preferably, the acidic group can be maleic anhydride, fumaric acid, Any one or more of itaconic acid, and the ether group can be any one or more of polyvinyl methyl ether and polyvinyl ethyl ether.

Optionally, the outer layer is made of fluorine resin, polyethylene terephthalate resin, polybutylene terephthalate resin, urea resin, epoxy resin, acrylic resin, polyamide resin, poly Any one or more of imide resin, polyamide-imide resin, polyurethane resin, and phenolic resin.

Optionally, the outer adhesive layer is a two-component polyurethane adhesive formed by using polyester polyol and polyurethane-modified polyol as the main glycol agent, and aromatic or aliphatic isocyanate as the curing agent. The curing agent can be selected according to the functional group of the adhesive component, such as a polyfunctional epoxy resin, a polymer containing methylsulfonic acid, a polyamine resin, an inorganic acid, etc., and can be appropriately selected. A more preferred combination of the outer adhesive layer in the present invention is one or two types of binary or polyester polyester, polyurethane modified polyester, and isocyanate. Isocyanates are not specifically defined as compounds having two or more isocyanate groups in the molecule. For example, isophorone diisocyanate (IPDI), toluene diisocyanate (TDI), diphenylmethane-4,4'-diisocyanate (MDI), 1,6-hexamethylene diisocyanate (HDI) and other polymers or a mixture of two or more.

Optionally, the inner adhesive layer is any one or more of the fluororesin, propylene resin, and propylene and ethylene copolymer resin, and the propylene and ethylene copolymer is composed of the anticorrosive resin and the The layer is composed of a copolymer of polypropylene resin and vinyl resin with thermally reactive functional groups. Preferably, the inner adhesive layer resin is modified with a modifying group, and the modified group is a carboxyl group, an acid anhydride group, an acid halide group, an epoxy group, a hydroxyl group, an amino group, a sulfhydryl group, a carbonate bond, an amide group. Any one or more of bond, urethane bond, and urea bond.

Optionally, the metal layer may undergo anti-corrosion treatment to form an anti-corrosion layer on both sides of the metal layer.

According to the present invention, a small amount of polar molecules are introduced into the linear fluororesin chain, and block copolymerization or random copolymerization is performed to destroy its symmetry, thereby increasing the MFR to more than 20g/10 minutes, making it easier to heat seal the material. The better the flow performance, the better the heat sealing effect.

Description of the drawings

Figure 1 is a schematic cross-sectional structural diagram of the metal composite film in Embodiment 1 to present the metal composite film according to the specific embodiment of the present invention; wherein,

1. Outer layer;

2. Outer adhesive layer;

3. Anti-corrosion layer;

4. Metal layer;

5. Anti-corrosion layer;

6. Inner adhesive layer;

7. Heat weld the resin layer.

Detailed ways

Specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described here are only used to illustrate and explain the present invention, and are not intended to limit the present invention.

The specific embodiment of the present invention provides an outer packaging material for a battery device, including an outer layer 1, an outer adhesive layer 2, an anti-corrosion layer 3, a metal layer 4, an anti-corrosion layer 5, an inner adhesive layer 6, a thermal The resin layer 7 is welded, and the metal layer 4 is subjected to anti-corrosion treatment on both sides to form an anti-corrosion layer 3 and an anti-corrosion layer 5. The outer adhesive layer 2 is provided between the outer layer 1 and the anti-corrosion layer 3, and the inner adhesive layer 6 is provided Between the anti-corrosion layer 5 and the thermally welded resin layer 7 .

Outer layer 1:

The outer layer 1 needs to be able to withstand higher heat sealing temperatures. In the present invention, the outer layer is a single-layer or multi-layer structure of any resin with a softening temperature above 180°C or a melting point above 230°C.

Outer bonding layer 2:

The outer adhesive layer is a two-component polyurethane adhesive formed by using polyester polyol and polyurethane-modified polyol as the main glycol agent, and aromatic or aliphatic isocyanate as the curing agent. The curing agent can be selected according to the functional group of the adhesive component, such as a polyfunctional epoxy resin, a polymer containing methylsulfonic acid, a polyamide resin, an inorganic acid, and the like. A more preferred combination of the outer adhesive layer in the present invention is one or two types of binary or polyester polyester, polyurethane modified polyester, and isocyanate. Isocyanates are not specifically defined as compounds having two or more isocyanate groups in the molecule. For example, isophorone diisocyanate (IPDI), toluene diisocyanate (TDI), diphenylmethane-4,4'-diisocyanate (MDI), 1,6-hexamethylene diisocyanate (HDI) and other polymers or a mixture of two or more.

Metal layer 4:

The metal material used in the intermediate metal layer can be, specifically, aluminum alloy, stainless steel, titanium steel, nickel-plated iron plate, etc. When used as a metal foil, it can be one or more layers. It is preferable to contain at least one of aluminum alloy foil, nickel-plated iron plate and stainless steel foil.

Inner adhesive layer 6:

The inner adhesive layer is any one or more of the fluororesin, propylene resin, and propylene and ethylene copolymer resin. The copolymer of propylene and ethylene is made of a resin that thermally reacts with the anti-corrosion layer. It is composed of a copolymer of polypropylene resin and vinyl resin with functional groups. Preferably, the inner adhesive layer resin is modified with a modifying group, and the modified group is a carboxyl group, an acid anhydride group, an acid halide group, an epoxy group, a hydroxyl group, an amino group, a sulfhydryl group, a carbonate bond, an amide group. Any one or more of bond, urethane bond, and urea bond.

Anti-corrosion layer 3, anti-corrosion layer 5:

The metal layer 4 undergoes anti-corrosion treatment on both sides to form an anti-corrosion layer 3 and an anti-corrosion layer 5. There are now known a variety of anti-corrosion fluids, which mainly contain phosphates, nitric acid, chromates, fluorides and rare earth oxides. Chemical conversion treatments using phosphates and chromates mainly include, for example, chromate treatment, chromium phosphate treatment, phosphoric acid-chromate treatment, chromate treatment, etc. Examples of chromium compounds used in these treatments include Chromium nitrate, chromium fluoride, chromium sulfate, chromium acetate, chromium oxalate, chromium diphosphate, chromium acetate, chromium chloride, chromium sulfate. The main chromate treatment methods include etching chromate treatment, electrolytic chromate treatment, coating chromate treatment, etc., but coating chromate treatment is preferred. In this coating type chromate treatment, phosphates such as Cr (chromium) phosphate, Ti (titanium) phosphate, Zr (zirconium) phosphate, and Zn (metallic lead) phosphate are used on the degreasing surface. A treatment liquid in which a metal salt or a mixture of these metal salts is the main component, or a treatment liquid in which a non-metallic phosphate and a mixture of these non-metal salts is the main component, is mixed with a synthetic resin and used as a treatment liquid through roller coating or gravure printing Coating and drying are performed using known coating methods such as method and dipping method. Various solvents such as water, alcohol-based solvents, hydrocarbon-based solvents, ketone-based solvents, ester compound-based solvents, and ether-based solvents can be used as the treatment liquid, but water is preferred. In addition, as the resin component used therein, water-soluble polymers such as aminated phenol and polyacrylic resin can be selected.

Thermal welding resin layer 7:

The thermally welded resin layer is a layer structure formed by inlay forging of fluorine-containing resin or random copolymerization of other polar groups.

The fluorine-containing resin is any one or more of tetrafluoroethylene resin, vinylidene fluoride resin, copolymers of tetrafluoroethylene and ethylene, or tetrafluoroethylene and perfluoroalkyl ether.

The fluorine-containing resin is a copolymer of tetrafluoroethylene, ethylene and polar groups, in which the tetrafluoroethylene content rate can be more than 50%, and the material ratio of tetrafluoroethylene and ethylene is between 60:40. Preferably between 55:45.

Thermal welding resin layer 7 can be a copolymer of tetrafluoroethylene, ethylene and perfluoro (alkyl vinyl ether) with polar groups. The perfluoroalkyl ether has an Rf side group, and a small amount of comonomer enters the polymerization After the structure of the polymer is changed, the crystallinity of the polymer will decrease significantly, mainly because the introduced side groups destroy the regularity of the main chain. As the content of perfluoroalkyl ether increases, the thickness of the crystal-forming wafer will be greatly reduced. When a larger amount of comonomer enters the polymer structure, the crystallinity of the polymer will significantly decrease or even become an amorphous structure, and the internal heat In order to achieve barrier properties, the welded resin layer requires a certain degree of crystallinity. The dense structure improves electrolyte resistance. The perfluoroalkyl ether is controlled below 4%. The content of polar groups is 0.1%-10% (based on tetrafluoroethylene). , based on the total number of moles of ethylene and perfluoroalkyl ether), the mass ratio of tetrafluoroethylene and ethylene is between 40:55 and 55:40.

The thermal fusion resin layer 7 may be a block copolymer of tetrafluoroethylene, perfluoroalkyl ether and alkylene ether. Among them, the material ratio of tetrafluoroethylene and perfluoro(alkyl vinyl ether) is between 60:40, and the vinyl ether content rate is 1%-10% (based on the total mole of tetrafluoroethylene and perfluoroalkyl ether). number as the basis).

The vinyl ether can be polyvinyl methyl ether, polyvinyl ethyl ether, etc. 1% vinyl ether is enough to significantly reduce the crystallinity of the tetrafluoroethylene and perfluoroalkyl ether copolymer segments and make its melt viscosity low. This facilitates melt processing; this is related to the change in chain conformation. The polytetrafluoroethylene chain still adopts an extended conformation even in the melt. The introduction of non-fluorine groups increases the mobility of the chain segments. Therefore, When it is well below the decomposition temperature, that is, slightly above its melting temperature Tm, a transition equivalent to the transition from an extended conformation to a curled conformation occurs.

The above-mentioned polar groups can be acidic groups, or they can be halogen, epoxy, ether groups, etc. Preferably, the acidic groups can be: maleic anhydride, fumaric acid, itaconic acid, etc.

Example 1:

A metal composite film is provided, including:

Outer layer 1: biaxially stretched polyimide film, thickness 25um;

Outer adhesive layer 2: The outer adhesive layer is a two-component polyurethane adhesive formed by using polyester polyol and polyurethane-modified polyol as the main glycol agent and aliphatic isocyanate as the curing agent.

Anti-corrosion layer 3, anti-corrosion layer 5: perform anti-corrosion treatment with anti-corrosion liquid. The anti-corrosion liquid contains trivalent chromium compound, inorganic acid, and organic resin. The content ratio is 2:2:1. The trivalent chromium compound is phosphoric acid. Chromium, the inorganic acid is nitric acid, the organic resin is polyacrylic acid resin, and a cross-linking agent that reacts thermally with the inner layer adhesive resin is added to the anti-corrosion layer. The cross-linking agent is amino resin.

Metal layer 4: 35um thick 8021 series aluminum material with a surface wettability of 68dyn/cm;

Inner adhesive layer 6: The inner adhesive layer is a copolymer of propylene and ethylene. It is composed of a copolymer of polypropylene resin and ethylene resin containing functional groups that react thermally with the anti-corrosion layer. The modifying group of the modified resin forming the inner adhesive layer resin layer is maleic anhydride, and the curing agent is a multifunctional isocyanate curing agent.

And heat-fusion resin layer 7: The heat-fusion resin layer is a block copolymer of tetrafluoroethylene and ethylene and maleic anhydride. The above-mentioned three macromolecules are connected head-to-tail to form a copolymer. The thickness of the inner heat-fusion resin layer is 80um. .

The thermally welded resin layer is tetrafluoroethylene and a block copolymer of ethylene and maleic anhydride. The copolymer formed by the head-to-tail connection of the three macromolecules has a tetrafluoroethylene content rate of 60%, and the mass ratio of tetrafluoroethylene and ethylene is 55:45. The content of maleic anhydride is 6% (based on the total number of moles of tetrachlorethylene and ethylene). The melting point of tetrafluoroethylene and the block copolymer resin of ethylene and maleic anhydride is 240°C. When the melt viscosity (MFR) is measured at a temperature of 50°C relative to the melting point, it is 20 g/10 minutes. The heat sealing strength at 120℃ is 110N.

Example 2:

A metal composite film is provided, including:

Outer layer 1: biaxially stretched polyimide film, thickness 25um;

And, heat-fusion resin layer 7: heat-fusion resin layer 7 is an inner heat-fusion resin layer made of tetrafluoroethylene, a block copolymer of ethylene, perfluoroalkyl ether and maleic anhydride. A copolymer formed by connecting the four macromolecules head to tail

Perfluoroalkyl ether is controlled below 3%, the content of maleic anhydride is 6% (based on the total number of moles of tetrafluoroethylene, ethylene and perfluoroalkyl ether), and the material ratio of tetrafluoroethylene and ethylene is It is 55:40. The melting point of the block copolymer of tetrafluoroethylene, ethylene and perfluoroalkyl ether and maleic anhydride is 230°C. When the melt viscosity (MFR) is measured at a temperature of 50°C relative to the melting point, it is 30g/ 10 minutes. The thickness of the internal thermal welding resin layer is 80um.

The heat sealing strength at 120℃ is 110N.

Example 3:

A metal composite film is provided, including:

Outer layer 1: biaxially stretched polyimide film, thickness 25um;

Inner adhesive layer 6: The inner adhesive layer is a copolymer of propylene and ethylene. It is composed of a copolymer of polypropylene resin and ethylene resin containing functional groups that react thermally with the anti-corrosion layer. The modifying group of the modified resin forming the inner adhesive layer resin layer is maleic anhydride, and the curing agent is a multifunctional isocyanate-based curing agent.

And, heat-fusion resin layer 7: heat-fusion resin layer 7 is a block copolymer of tetrafluoroethylene, perfluoroalkyl ether and alkylene ether. A copolymer formed by connecting the three macromolecules head-to-tail. Among them, the material ratio of tetrafluoroethylene and perfluoro(alkyl vinyl ether) is 60:40, and the vinyl ether content is 6% (based on the total number of moles of tetrachloroethylene and perfluoroalkyl ether). The melting point of the resin is 240°C, and when the melt viscosity (MFR) was measured at a temperature of 50°C relative to the melting point, it was 23 g/10 minutes. The thickness of the internal thermal welding resin layer is 80um. The heat sealing strength at 120℃ is 100N.

Example 4:

A metal composite film is provided, including:

Outer layer 1: biaxially stretched polyimide film, thickness 25um;

And, heat-fusion resin layer 7: heat-fusion resin layer 7 is tetrafluoroethylene, a random copolymer of ethylene and acrylic resin. The three macromolecules undergo random copolymerization through free radical addition. The molecular chain is tetrafluoroethylene, and ethylene and acrylic acid are randomly arranged and connected to form a non-uniform copolymer. The material ratio of tetrafluoroethylene and ethylene is 55:45. The content of acrylic acid is 5% (based on the total number of moles of tetrachlorethylene and ethylene). The melting point of tetrafluoroethylene, a random copolymer of ethylene and acrylic resin, is 220°C. When the melt viscosity (MFR) is measured at a temperature of 50°C relative to the melting point, it is 26 g/10 minutes. The thickness of the internal thermal welding resin layer is 80um, and the heat sealing strength at 120°C is 90N.

Comparative example 1

Using the aforementioned method, the outer base material resin layer/outer layer adhesive layer (3 μm)/aluminum alloy foil layer is made as a composite outer base material resin composite film, which is combined with the inner adhesive layer and the inner thermal welding layer to form an aluminum-plastic composite film.

The thickness of the inner thermal welding resin layer is 80 μm, the inner layer welding resin is random polypropylene (r-pp) with a melting point of 142°C, 18 parts by weight of acid-modified polypropylene modified with maleic anhydride and homopolymer with a melting point of 162°C. The melting point of propylene (h-pp), a resin modified with maleic anhydride, is 155°C. The melting point of the inner layer welding resin is 135°C. MFR is 7.0g/10 minutes (230℃).

Comparative example 2

The aforementioned method is used to prepare the outer base material resin layer/outer layer adhesive layer (3um)/aluminum alloy foil layer as the composite outer base material resin composite film, which is combined with the inner adhesive layer and the inner thermal welding resin layer to form an aluminum-plastic composite film. .

The inner thermal welding resin layer is a copolymer of tetrafluoroethylene and ethylene, which is generated by the copolymerization reaction of tetrafluoroethylene and ethylene free radicals. The polymer has a high degree of alternation, with a tetrafluoroethylene content of 60% and an alternating sequence content of 88%, giving it a high melting point and crystallinity, with a melting point close to 270°C. The thickness of the internal thermal welding resin layer is 80um.

Comparative example 3

The inner thermal welding resin layer is polyvinylidene fluoride resin. The fluorine content is 59%, the crystallinity is about 60%, and the melting point is 170°C. When the melt viscosity (MFR) is measured at a temperature of 50°C relative to the melting point, it is 10g/10 minutes. The thickness of the internal thermal welding resin layer is 80um.

Comparative example 4

Using the aforementioned method, the outer base material resin layer/outer layer adhesive layer (3um)/aluminum alloy foil layer is made as a composite outer base material resin composite film, which is combined with the inner adhesive layer and the inner thermal welding layer to form an aluminum-plastic composite film.

The internal thermal welding resin layer is polypropylene, and the polypropylene resin is random polypropylene (r-pp). The melting point of the resin is 135℃, MFR: 7.0g/10min (230℃) and the melting point is 160℃, MFR2.0g/10min ( 30 parts by weight of block polypropylene (b-pp) resin at 230°C), melting point 124°C, MFR: 10g/10 minutes (230°C) 30 parts by weight of random polypropylene (r-pp) resin with a melting point of 124 It is composed of 40 parts by weight of mixed resin of ethylene-polypropylene elastomer at 130°C. The melting point of the resin is 130°C, and MFR: 12.0g/10 minutes (230°C). The thickness of the internal thermal welding resin layer is 80um.

The composite membranes in the examples and comparative examples were tested according to the following methods.

Test Methods:

Heat sealing strength (80/120℃) test method:

Heat sealing machine: Fuqiang customized equipment

Heating seat: (pressure 10KN) The compressive pressure is: 0.84MPa, the melting point of aluminum bronze is 1035℃, the mechanical properties are stable at 500℃, the tensile strength is 600MPa, and the Rockwell hardness is 200-250;

Sealing knife: pressure 10KN, width 7mm), the compressive pressure is: 4.76MPa, the melting point of nickel-chromium alloy is 1350℃, the maximum operating temperature is 1150℃, the tensile strength is 650MPa, the pressure the sealing knife withstands is much less than the tensile strength of nickel-chromium alloy

Rallying machine: Shimadzu, AGS-X-10KN.

Remove the beginning of the sample (roll) and ensure that the sampling location is flat and wrinkle-free. Take one sample each from M, MC, C, GC, and G (N=1). The sampling positions are evenly distributed in the TD direction of the sample. Wear gloves during operation when the sample size is TD76mm*MD200mm or more. Pay attention to different models. Samples and batches must be labeled. Turn on the heat sealing machine and set the temperature, time and surface pressure of the upper and lower sealing knives. Fold the heat-welded surface of the sample in half along the MD direction. After folding, the two heat-welded surfaces face each other, with dimensions of TD76mm*MD100mm. Wrap the sample with a thin release film, and heat-seal in parallel at a position 10mm away from the folding line. In the middle of the heat-sealed sample , cut 3 samples (n=3) with a width of 15mm. The cutting line is perpendicular to the heat sealing line. Open the stretching machine, set the chuck distance to 50mm, the stretching speed to 300mm/min, the measuring stroke to 30mm, and open the air valve. Adjust the air pressure to 0.6Mpa-0.8Mpa, and set the temperature as needed. After the temperature is stable, put the spline in. Put the spline vertically into the chuck, clamp both ends of the spline (single layer), and the heat-sealed part in the middle faces inward. After the temperature reaches the set value and stabilizes for 2 minutes, start testing and record the data. At the end of the test, the heat sealing part should be fully opened and the maximum value of the whole process should be recorded. Pay attention to distinguish M, MC, C, GC, G (M is the personnel side, G is the driving side, select five points of equal width in sequence). Close the stretching machine and air valve, and clean the equipment.

MFR test method equipment: Ray-Ran MFR300

Place the polymer (plastic) raw material to be measured into a small tank. A thin tube is connected to the end of the tank. The diameter of the thin tube is 2.095mm and the length of the tube is 8mm. After heating to a certain temperature (fluororesin is set to 350°C), the upper end of the raw material is pressed downward by a piston applying a certain weight. The weight of the raw material extruded within 10 minutes is measured, which is the flow of the plastic. index. Under specified conditions, the amount of thermoplastic material extruded within a certain period of time, that is, the mass of the melt passing through the capillary of the standard die every 10 minutes, is expressed in MFR, and the unit is g/10min.

Determination method of insulation: after heat sealing

Equipment: Kikusui TOS9200

Cut the sample to 200mm in the MD direction and 76mm in the TD direction. Fold the sample in half along the MD direction. Add the tab in the middle. The tab is made of Ni and heat seal the tab. Heat sealing in MD direction, heat sealing conditions are: heat sealing temperature 190℃ (certain), heat sealing pressure 1.0MPa, heat sealing time 3 seconds. Use sandpaper to polish the area near the heat sealing part of the tab to expose the AL. Place the negative electrode in contact with the tab and the positive electrode in contact with the exposed AL. Measure the resistance value under 250V voltage conditions. (In order to make the positive electrode better contact with the AL of the polished part, drop a drop of pure water from the dropper). The test data are shown in Table 1.

Table 1.

test data analysis,

A small amount of polar molecules are introduced into the linear fluororesin chain, and block copolymerization or random copolymerization is performed to destroy its symmetry, thereby increasing the MFR from 10 to more than 20, making it easier to heat seal and achieve better flow properties of the material. , the heat sealing and dissolving effect is good.

Comparative Examples 1, 2, 3, and 4. The melting point of maleic anhydride-modified polypropylene resin in Comparative Example 1 is 135°C, and the heat resistance is low. The battery will generate heat during use and charging and discharging. If the heat resistance is If it is low, the middle metal layer and the inner thermally welded resin layer will peel off at high temperatures. The heat sealing strength at 120°C is 30N. On the one hand, in the presence of electrolyte, the force of the heat sealing electrolyte vaporizing at high temperature is It will easily cause defects and cracks in the heat-sealed part. The electrolyte will have a higher probability of coming into contact with the metal foil, and the insulation performance will decrease. In addition, pressurization causes the resin in the squeezed part inside the battery to flow to the unsqueezed edge part. The expansion and contraction of the battery and the external force of bending processing cause cracks. The electrolyte will penetrate into the middle metal layer through the cracks, causing internal heat welding. The insulation resistance of the resin layer decreases, leakage occurs, and the battery life will be shortened. Comparing Examples 1, 2, 3, and 4, and Comparative Examples 2 and 3, the copolymers of tetrafluoroethylene and ethylene and polyvinylidene fluoride resin have low MFR values. , poor thermoplasticity. When used as the heat sealing layer of aluminum plastic film, the resin has low fluidity and poor heat sealing effect, which is manifested as low heat sealing strength. In the embodiment, after the fluorine-containing resin is modified with polar groups, the polymer The crystallinity of the polymer will decrease significantly, mainly because the introduced polar groups destroy the regularity of the main chain. The crystallinity of the polymer will decrease significantly, the MFR will increase, the fluidity will increase, the heat sealing effect will be excellent, and the heat sealing strength will increase. high. Comparative Examples 1, 2, 3, 4, Comparative Example 4. Polypropylene has not been modified in any other way. Its melting point is 130°C and its heat resistance is low. The battery will generate heat during use and charging and discharging. If the heat resistance is low, the middle metal layer and the internal thermal welding resin layer will break down at high temperatures. In the case of peeling, the heat sealing strength at 120°C is 30N, which is low heat sealing strength. When the battery is powered on during use, the insulation performance is low. Once the electrolyte contacts the aluminum foil to form a short circuit, it will cause serious and unsafe consequences.

The endpoints of ranges and any values disclosed herein are not limited to the precise range or value, but these ranges or values are to be understood to include values approaching such ranges or values. For numerical ranges, the endpoint values of each range, the endpoint values of each range and individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges. These values The scope shall be deemed to be specifically disclosed herein.

The above content related to common knowledge will not be described in detail, and those skilled in the art can understand it.

The above are only some specific embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the present invention. within the scope of protection. The technical scope of the present invention is not limited to the content in the description, and must be determined based on the scope of the claims.

Claims

A metal composite film, which includes: a metal layer, an inner adhesive layer, a hot-melt grease layer, an outer adhesive layer and an outer layer, characterized in that the outer layer is provided on the metal layer side, the heat-fusion resin layer is provided on the other side of the metal layer, the inner adhesive layer is provided between the metal layer and the first heat-fusion resin layer, and the outer adhesive layer is provided on Between the outer layer and the metal layer, the thermally welded resin layer is a layer structure formed of fluorine-containing resin inlay or random copolymerization of polar groups.
The metal composite film according to claim 1, wherein the fluorine-containing resin is a copolymer of tetrafluoroethylene resin, vinylidene fluoride resin, tetrafluoroethylene and ethylene, or tetrafluoroethylene and perfluoroalkyl ether. any one or more.
The metal composite film according to claim 1, wherein the polar group is any one or more of an acidic group, a halogen, an epoxy, and an ether group.
The metal composite film according to claim 3, wherein the acidic group is any one or more of maleic anhydride, fumaric acid, and itaconic acid.
The metal composite film according to claim 3, wherein the ether group is any one or more of polyvinyl methyl ether and polyvinyl ethyl ether.
The metal composite film according to claim 1, wherein the MFR value of the fluorine-containing resin is 20-30g/10 minutes.
The metal composite film according to claim 1, wherein anti-corrosion layers are provided on both sides of the metal layer.
The metal composite film according to claim 1, wherein the outer layer is made of fluorine resin, polyethylene terephthalate resin, polybutylene terephthalate resin, urea resin, or epoxy resin. , any one or more of acrylic resin, polyamide resin, polyimide resin, polyamide-imide resin, polyurethane resin, and phenolic resin.
The metal composite film according to claim 1, characterized in that the outer adhesive layer is formed of polyester polyol and polyurethane-modified polyol as the main glycol agent, and aromatic or aliphatic isocyanate as the curing agent. Two-component polyurethane adhesive.
The metal composite film according to claim 1, wherein the inner adhesive layer is any one or more of the fluororesin, acrylic resin, and propylene-ethylene copolymer resin.
The metal composite film according to claim 10, wherein the inner adhesive layer has a layer structure modified with a modifying group.
The metal composite film according to claim 11, wherein the modified group is a carboxyl group, an acid anhydride group, an acid halide group, an epoxy group, a hydroxyl group, an amino group, a mercapto group, a carbonate bond, an amide bond, an aminomethyl group, or a carboxyl group. Any one or more of acid ester bond and urea bond.