Battery soft package composite film and preparation method thereof

Abstract

The invention belongs to the technical field of battery packaging, and particularly relates to a battery soft package composite film and a preparation method thereof. The battery soft package composite film comprises an organic silicon polyurethane coating, a first aluminum foil anti-corrosion treatment layer, an aluminum foil layer, a second aluminum foil anti-corrosion treatment layer, an easy-to-adhere resin layer and a polypropylene heat sealing layer which are sequentially arranged from outside to inside. According to the battery soft package composite film, the organic silicon polyurethane coating is adopted to replace an outer layer material in a conventional aluminum plastic film structure, and by means of the weather resistance, temperature resistance and chemical stability of the organic silicon polyurethane coating, the overall forming performance of the aluminum plastic film can be improved; the organosilicon polyurethane coating has a certain smooth effect, so that the surface friction coefficient is reduced to a certain extent; in addition, due to the hydrophobic performance of the organic silicon structure, the long-term high-temperature and high-humidity performance is also improved to a certain extent.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of battery packaging, and particularly relates to a battery soft package composite film and a preparation method thereof. BACKGROUND

[0002] In the lithium battery industry, solid-state battery technology, which is a future development direction, has achieved certain large-scale production. The solid-state battery has a significantly improved energy density, and has high energy density and high safety, and thus puts forward higher requirements on packaging materials. The main requirements include the following aspects: 1. High flexibility and ductility: the solid-state electrolyte (such as sulfide and oxide) has high hardness but poor flexibility, and the packaging material needs to have high ductility to buffer the volume expansion in the charging and discharging process (such as the expansion rate of silicon-based negative electrode can reach 300%), so as to avoid mechanical stress and cause the battery to crack. The aluminum plastic film is the preferred solution for soft package solid-state batteries due to its flexibility and lightweight advantage (30% weight reduction compared with metal shell).

[0003] 2. High barrier performance: the solid-state battery is extremely sensitive to water and oxygen penetration (water and oxygen content needs to be less than 1 ppm), and the packaging material needs to have extremely low water vapor transmission rate (<0.1 g / m 2 ·day) and oxygen transmission rate (<0.1 cm 3 / m 2 ·day). The aluminum plastic film can meet the strict environmental isolation requirements of the solid-state battery through the aluminum foil barrier layer (thickness of 6-20 μm) and the modified polypropylene inner layer.

[0004] 3. Thermal stability and safety: although the thermal runaway temperature of the solid-state battery is higher than that of the liquid battery (such as the thermal decomposition temperature of sulfide electrolyte > 300℃), the packaging material still needs to withstand high temperature above 200℃ and not release toxic gas. When the aluminum plastic film is in thermal runaway, it only bulges and releases pressure, and there is no risk of fire, while the metal hard shell may burst due to the accumulation of internal pressure.

[0005] The common aluminum plastic film mainly includes a nylon layer, an aluminum layer, a PP (inner heat sealing layer) and an adhesive layer. With the rise of power storage batteries, the aluminum plastic film will also have a PET layer due to higher requirements on the process. The polyester film layer of the outer layer is mainly made of polyethylene terephthalate (PET), polyamide 6 (PA6), polyamide 6,6 (PA6,6) and the like. The service life of these materials is usually only 3-4 years, especially when the battery works at a high temperature for a long time, which further aggravates the aging of the material. Therefore, higher requirements are put forward for the punching performance, high temperature resistance and aging resistance of the aluminum plastic film. SUMMARY

[0006] The application aims to provide a battery soft package composite film and a preparation method thereof to solve the problems of insufficient forming, insufficient temperature resistance and aging resistance, and insufficient electrical insulation of the existing aluminum plastic film.

[0007] The first aspect of the application provides a battery soft package composite film, comprising: The organic silicon polyurethane coating layer, the first aluminum foil corrosion-resistant treatment layer, the aluminum foil layer, the second aluminum foil corrosion-resistant treatment layer, the easy-to-adhere resin layer, and the polypropylene heat-sealing layer are sequentially arranged from the outside to the inside; wherein The composition of the organic silicon polyurethane coating layer comprises component A, component B, and component C. The component A is a polyurethane prepolymer. The component B is a hydroxyl-terminated organic silicon modified polyether or polyester polyol. The component C contains at least one of a chain extender, a catalyst, a diluent, or a filler.

[0008] In an embodiment of the application, the diluent can be one of ethyl acetate, toluene, and butanone; and the catalyst can be an ammonium salt, such as benzyl triethyl ammonium chloride, tetrabutyl ammonium bromide, octyl trimethyl ammonium salt, etc.

[0009] In an embodiment of the application, the molecular chain end of the polyurethane prepolymer is an isocyanate group.

[0010] In an embodiment of the application, the polyurethane prepolymer contains an organosiloxane in the molecular chain segment.

[0011] In an embodiment of the application, the composition of the organic silicon polyurethane coating layer comprises, by weight fraction, 100 parts of component B, 10-40 parts of component A, and 3-30 parts of component C.

[0012] In an embodiment of the application, a nylon layer and an adhesive layer are further arranged between the organic silicon polyurethane coating layer and the first aluminum foil corrosion-resistant treatment layer.

[0013] In an embodiment of the application, the nylon layer can be polyamide 6 (PA6) or polyamide 6,6 (PA6,6), and the thickness can be 5-50 um; and the adhesive layer can be a two-component polyurethane glue, and the thickness can be 2-5 um.

[0014] In an embodiment of the application, the coating thickness of the organic silicon polyurethane coating layer is 5-60 um; and / or The thickness of the aluminum foil is 10-100 um; and / or The easy-to-adhere resin layer is a modified polyolefin, and the thickness is 10-60 um; and / or The thickness of the polyolefin heat-sealing layer is 20-120 um.

[0015] In one embodiment of this application, the silicone polyurethane coating and / or nylon layer are coated using one of the following methods: gravure roller coating, anilox roller coating, and spray coating.

[0016] In one embodiment of this application, the first aluminum foil anti-corrosion treatment layer and the second aluminum foil anti-corrosion treatment layer are coated on the surface of the aluminum foil layer using trivalent chromium solvent or rare earth element oxides.

[0017] The first aspect of this application provides a method for preparing a battery soft-pack composite film, comprising: Anti-corrosion treatment of aluminum foil surface; A silicone polyurethane coating is applied to one side of the aluminum foil; or, a nylon adhesive is applied to the surface of the aluminum foil, and a silicone polyurethane coating is applied to the nylon. High-temperature baking; The resin layer and the polyolefin heat-sealing layer are bonded together using a hot-method double-layer co-extrusion composite technology. After forming a film in the molten state, they are directly thermally bonded to the other side of the aluminum foil.

[0018] In one embodiment of this application, the easy-bonding resin layer is an acid-modified polypropylene layer; this can enhance the adhesion between the easy-bonding resin layer and the aluminum foil, giving the aluminum-plastic film better electrolyte resistance and stronger inner layer peel strength. The polyolefin heat-sealing layer is copolymerized from two or more monomers of propylene, ethylene, and butene; it can provide sufficient heat-sealing strength for aluminum-plastic film.

[0019] The beneficial effects of this invention are: Unlike existing technologies, this application provides a battery soft-pack composite film, comprising: an organosilicon polyurethane coating, a first aluminum foil anti-corrosion treatment layer, an aluminum foil layer, a second aluminum foil anti-corrosion treatment layer, an easy-bonding resin layer, and a polypropylene heat-sealing layer, arranged sequentially from the outside to the inside. The battery soft-pack composite film of this invention replaces the outer layer material in conventional aluminum-plastic film structures with an organosilicon polyurethane coating. The organosilicon polyurethane coating, with its weather resistance, temperature resistance, and chemical stability, is beneficial for improving the overall molding performance of the aluminum-plastic film. Furthermore, the organosilicon polyurethane coating has a certain slip-reducing effect, which lowers the surface friction coefficient. Additionally, the hydrophobic properties of the organosilicon structure also improve long-term high-temperature and high-humidity performance.

[0020] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention are realized and obtained through the structures particularly pointed out in the description and the drawings.

[0021] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0022] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of a battery soft-pack composite film according to a preferred embodiment of the present invention; Figure 2 This is a process diagram of the preparation of a battery soft-pack composite film according to a preferred embodiment of the present invention; Figure 3 This is a battery soft-pack composite film according to another preferred embodiment of the present invention; Figure 4 This is a process diagram for preparing the battery soft-pack composite film according to another preferred embodiment of the present invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] The first aspect of the embodiment is prepared as follows: Figure 1 The process route for the battery pouch composite film shown is described in [reference needed]. Figure 2 .

[0026] In embodiments of this aspect: (1) Organosilicon polyurethane component A accounts for 30% of the formulation; the isocyanate group (-NCO) content is 12%, which can be an adduct of HDI (hexamethylene diisocyanate) or IPDI (isophorone diisocyanate) and TMP (trimethylolpropane), and is grafted with an aminosilane structure.

[0027] (2) Organosilicon polyurethane component B accounts for 40% of the formulation; its polyester polyol structure has an OH value (hydroxyl value) of 72 and a molecular weight of 2000.

[0028] (3) Component C of the silicone polyurethane coating formulation is ethyl acetate, accounting for 30% of the formulation; (4) The silicone polyurethane coating is cured by thermosetting. (5) The thickness of the silicone polyurethane coating is 10-40 μm; (6) The coating is applied using an anilox roller. (7) The aluminum layer thickness is 40 μm; (8) The aluminum foil anti-corrosion coating uses trivalent chromium passivation solution; (9) The easy-to-adhere resin layer (maleic anhydride modified polypropylene) and the polyolefin heat-sealing layer adopt a hot double-layer co-extrusion composite technology. After forming a film in the molten state, it is directly thermally composited with the aluminum foil layer with a thickness of 80um.

[0029] The thickness and performance tests of each layer in the embodiments and comparative examples in this regard are shown in the table below: The performance testing methods are as follows: ① Molding test: Molding mold: film size 200mm×200mm, 69mm×50mm, corner radius: 0.6mm, vertical radius: 1.0mm. After molding, visually inspect for small holes and cracks. ② Surface dynamic friction coefficient: friction coefficient meter; ③ Long-term reliability: After the aluminum-plastic film is formed, it is stored in a constant temperature and humidity chamber at 85℃ and 85%RH for 4 weeks to observe whether there is any delamination between the outer material and the aluminum foil.

[0030] Compared with the comparative examples, the increased thickness of the silicone polyurethane coating is beneficial to improving the overall molding performance of the aluminum-plastic film; since the silicone polyurethane coating has a certain slippery effect, it reduces the surface friction coefficient to a certain extent; in addition, due to the hydrophobic properties of the silicone structure, it also has a certain effect on improving long-term high temperature and high humidity performance.

[0031] The second aspect of the embodiment is prepared as follows: Figure 3 The process route for the battery pouch composite film shown is described in [reference needed]. Figure 4 .

[0032] In embodiments of this aspect: (1) Organosilicon polyurethane component A accounts for 35% of the formulation; the isocyanate group (-NCO) content is 16%, which can be an adduct of HDI (hexamethylene diisocyanate) or IPDI (isophorone diisocyanate) and TMP (trimethylolpropane), and is grafted with an aminosilane structure.

[0033] (2) Organosilicon polyurethane component B accounts for 35% of the formulation; its polyester polyol structure has an OH value (hydroxyl value) of 51 and a molecular weight of 1800. (3) Component C of the silicone polyurethane coating formulation is ethyl acetate, accounting for 30% of the formulation; (4) The silicone polyurethane coating is cured by thermosetting. (5) The thickness of the silicone polyurethane coating is 5-20 μm; (6) The coating is applied using an anilox roller. (7) The nylon layer is nylon 6, and the adhesive layer uses two-component polyurethane adhesive; (8) The aluminum layer has a thickness of 40 μm; (9) The anti-corrosion coating of aluminum foil uses trivalent chromium passivation solution; (10) The easy-to-adhere resin layer (maleic anhydride modified polypropylene) and the polyolefin heat-sealing layer adopt the hot double-layer co-extrusion composite technology. After the resin layer particles are extruded into a film in the molten state, they are directly thermally composited with the aluminum foil layer with a thickness of 80um.

[0034] The thickness and performance tests of each layer in the embodiments and comparative examples in this regard are shown in the table below: Compared with the various embodiments and comparative examples, the increased thickness of the silicone polyurethane coating is beneficial to improving the overall molding performance of the aluminum-plastic film; since the silicone polyurethane coating has a certain slippery effect, it reduces the surface friction coefficient to a certain extent; in addition, due to the hydrophobic properties of the silicone structure, it also has a certain effect on improving the long-term high temperature and high humidity performance.

[0035] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification.

Claims

1. A battery soft-pack composite film, characterized in that, include: The layers are arranged sequentially from the outside to the inside: an organosilicon polyurethane coating, a first aluminum foil anti-corrosion treatment layer, an aluminum foil layer, a second aluminum foil anti-corrosion treatment layer, an easy-bonding resin layer, and a polypropylene heat-sealing layer. in The components of the organosilicon polyurethane coating include component A, component B and component C; Component A is a polyurethane prepolymer; Component B is an organosilicon-modified polyether or polyester polyol containing terminal hydroxyl groups. The component C contains at least one of the following: a chain extender, a catalyst, a diluent, or a filler.

2. The battery soft-pack composite film according to claim 1, characterized in that, The molecular chain ends of the polyurethane prepolymer are isocyanate groups.

3. The battery soft-pack composite film according to claim 1, characterized in that, The molecular chain segments of the polyurethane prepolymer contain organosiloxanes.

4. The battery soft-pack composite film according to claim 1, characterized in that, The components of the organosilicon polyurethane coating, by weight, include component B: 100 parts, component A: 10-40 parts, and component C: 3-30 parts.

5. The battery soft-pack composite film according to claim 1, characterized in that, A nylon layer and an adhesive layer are also provided between the silicone polyurethane coating and the first aluminum foil anti-corrosion treatment layer.

6. The battery soft-pack composite film according to claim 1, characterized in that, The thickness of the silicone polyurethane coating is 5-60 μm; and / or The aluminum foil has a thickness of 10-100 μm; and / or The easily bonded resin layer is a modified polyolefin with a thickness of 10-60 μm; and / or The thickness of the polyolefin heat-sealing layer is 20-120 μm.

7. The battery soft-pack composite film according to claim 6, characterized in that, The silicone polyurethane coating and / or nylon layer are applied using one of the following methods: gravure roller coating, anilox roller coating, or spray coating.

8. The battery soft-pack composite film according to claim 1, characterized in that, The first and second aluminum foil anti-corrosion treatment layers are coated on the surface of the aluminum foil using trivalent chromium solvent or rare earth element oxides.

9. A method for preparing a battery soft-pack composite film as described in any one of claims 1-8, characterized in that, include: Anti-corrosion treatment of aluminum foil surface; An organosilicon polyurethane coating is applied to one side of the aluminum foil. Alternatively, nylon adhesive can be applied to the surface of aluminum foil, and silicone polyurethane coating can be applied to nylon. High-temperature baking; The resin layer and the polyolefin heat-sealing layer are bonded together using a hot-method double-layer co-extrusion composite technology. After forming a film in the molten state, they are directly thermally bonded to the other side of the aluminum foil.

10. The method for preparing the battery soft-pack composite film according to claim 9, characterized in that, The easily bondable resin layer is an acid-modified polypropylene layer; The polyolefin heat-sealing layer is a copolymer of two or more monomers selected from propylene, ethylene, and butene.

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