Multilayer composite structure for packaging lithium ion batteries and method for manufacturing the same, and lithium ion batteries

Abstract

A multilayer composite structure for packaging lithium ion batteries, a method for manufacturing the same, and lithium ion batteries are provided. [Solution] This product comprises an inner connecting layer film and an outer skeletal structure layer film laminated together, with both the inner connecting layer film and the outer skeletal structure layer film containing a moisture barrier additive. Conventional exterior laminate structures generally have a three-layer or more composite structure, including an outer layer with high mechanical strength, an intermediate layer that prevents water vapor penetration, an inner layer with good thermal adhesion, and a transition layer between them. The present invention simplifies this structure by using a moisture barrier additive instead of metal aluminum foil to achieve the purpose of preventing water vapor penetration, and by utilizing the good compatibility between the outer and inner surfaces, it reduces processing steps, reduces costs, and improves safety performance.

Description

[Technical Field]

[0001] The present invention relates to the technical field of new energy, and in particular to a multi-layer composite structure for packaging lithium ion batteries and a manufacturing method thereof, and a lithium ion battery. [Background technology]

[0002] Lithium batteries (lithium secondary batteries) use electrolytes composed of polymer solids, polymer gels, or liquids, and charge transfer occurs through the movement of lithium ions. The positive and negative electrode active materials are composed of polymers. A lithium secondary battery consists of a positive current collector (aluminum or nickel), a positive active material layer (polymer positive electrode materials such as metal oxides, carbon black, metal sulfides, electrolytes, and polyacrylonitrile), an electrolyte layer (carbonate-based electrolytes such as polypropylene carbonate, ethylene carbonate, dimethyl carbonate, and ethylene methyl carbonate, or inorganic solid or gel electrolytes composed of lithium salts), a negative active material layer (negative electrode materials such as lithium metal, alloys, carbon, electrolytes, and polymers), and a negative current collector (copper, nickel, or stainless steel), and an outer packaging that packages these components. Lithium secondary batteries, with their high volumetric and weight efficiency, are widely used in electronic devices, automobiles, and small aircraft. Especially in the field of drones, capacity and weight efficiency are very important considerations, and current lithium-ion batteries cannot guarantee the long-term operating requirements of aircraft.

[0003] The properties required for lithium batteries, namely, steam resistance, sealing properties, puncture resistance, insulating properties, heat resistance, cold resistance, electrolyte resistance (resistance to electrolyte solution), and corrosion resistance (resistance to hydrofluoric acid generated by deterioration of the electrolyte and hydrolysis), must be comprehensively considered when designing a lithium battery packaging laminate.

[0004] Currently, there are three types of packaging methods for lithium-ion batteries: 1) flexible packaging using aluminum laminate film. Aluminum laminate film structures can be molded into an appropriate shape to fit the space of electronic devices or electronic components, allowing for a certain degree of freedom in designing the shape of the electronic devices or electronic components, thereby achieving miniaturization and weight reduction. Patent Document 1 relates to an exterior packaging material for secondary batteries with an aluminum laminate film structure. The packaging material described in Patent Document 1 has three main functional layers. The outer layer uses a polymer film to improve mechanical strength, and is made of PET, PEN, or nylon. The intermediate layer is primarily intended to prevent the penetration of water vapor and is typically made of aluminum foil, while the inner layer exhibits good heat-sealing performance.

[0005] Conventional laminates have a laminate structure consisting of an outer base layer, an aluminum foil intermediate layer, and an inner layer. Using aluminum foil as an intermediate moisture barrier layer improves the moisture barrier effect, but it also introduces new problems. To improve bonding strength after adding the aluminum foil, the bonding problem between the outer and inner layers and the metal moisture barrier layer must be resolved. Currently, a thermal adhesive resin with excellent adhesion to metals is added between the outer layer and the metal moisture barrier layer in the inner layer of a laminate. For example, an acid-modified olefin resin grafted with an unsaturated hydroxy acid is used in the inner layer of the laminate. Patent Document 1, for example, proposes a method for optimizing the adhesive strength between aluminum foil and an olefin resin layer with excellent adhesion to metals by forming a chemical conversion coating using a chemical conversion coating solution containing an aminated phenolic polymer, a trivalent chromium compound, and a phosphorus compound.

[0006] This leads to the following problems: Problem 1: Safety Issues. The laminate structure is composed of a substrate layer, a barrier layer made of metal foil such as aluminum, and an inner layer. The lithium battery uses a lithium hexafluorophosphate solution as its electrolyte. When the lithium hexafluorophosphate solution reacts with moisture, it produces hydrofluoric acid. This hydrofluoric acid easily reacts with the aluminum foil and spreads along the interface between the aluminum foil and the inner and outer layers, reducing the adhesive strength between the metal foil and the inner and outer structures, causing peeling and decomposition, and shortening the battery's lifespan.

[0007] Problem 2: Risk of short circuit. Conventional products typically use a heat-sealing method to seal metal connection terminals, sandwiching them between laminates. Under high heat, the metal terminals can come into contact with the intermediate barrier layer of the laminate, which is made of aluminum foil, potentially resulting in short circuit problems. Furthermore, when abnormal external stress damages the inner layer structure, microcracks form on the inner layer surface, allowing the electrolyte to penetrate through the cracks into the aluminum foil barrier layer. The high chemical activity of aluminum metal can damage battery function. Aluminum foil has excellent ductility and processability, making it highly effective at blocking moisture intrusion from the outside. However, it also has disadvantages, such as complex processing techniques, the risk of battery short circuit and failure, and high costs. Furthermore, moisture penetration from the edges of the inner layer adhesive is significant. As a result, moisture penetrates the inner layer and reacts with the electrolyte to produce hydrofluoric acid, separating the inner layer from the barrier layer made of metal foil, such as aluminum.

[0008] Problem 3: High processing costs. In conventional laminated structures, the bond between the middle layer and the inner and outer layers is poor. To improve the bond between them, other treatment processes and methods, such as chrome treatment, must be introduced to improve the surface activity of the barrier layer, which inevitably increases the processing steps and costs. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Chinese Patent No. CN101087687A Summary of the Invention [Problem to be solved by the invention]

[0010] To solve the problems of the prior art, the present invention provides a multilayer composite structure for packaging lithium-ion batteries, a manufacturing method thereof, and a lithium-ion battery. A lithium-ion battery typically includes an electrolyte, positive and negative electrode leads, and an exterior. Conventional exterior laminate structures typically have a three- or more-layer composite structure, including an outer layer with high mechanical strength, an intermediate layer that prevents water vapor penetration, an inner layer with good thermal adhesion, and a transition layer between the two. The present invention aims to simplify this structure by using a moisture barrier additive instead of metallic aluminum foil to prevent water vapor penetration, while providing a multilayer composite structure that utilizes good compatibility between the outer and inner surfaces to reduce processing steps, reduce costs, and improve safety performance.

[0011] The first object of the present invention is to provide a multilayer composite structure for packaging lithium ion batteries, comprising an inner connection layer film and an outer skeletal structure layer film laminated together, wherein both the inner connection layer film and the outer skeletal structure layer film contain moisture barrier additives. [Means for solving the problem]

[0012] In a preferred embodiment of the present invention, The moisture barrier additives in the inner connecting layer film and the outer skeletal structure layer film may be the same or different, and each independently may be at least one of an inorganic moisture barrier agent and an organic moisture barrier agent; The inorganic moisture barrier agent is preferably at least one of titanium nitride, aluminum nitride, titanium aluminum nitride compound (TiAlN), and / or The organic moisture barrier agent is preferably at least one of perfluorocompounds (PFCs), more preferably at least one of perfluorooctane sulfonic acid, perfluorooctanoic acid, and Teflon®.

[0013] In a preferred embodiment of the present invention, The inner connection layer film is manufactured by mixing components including a thermal adhesive polymer and the moisture barrier additive, and the thermal adhesive polymer is preferably at least one of polypropylene and modified polypropylene, and the modified polypropylene is preferably at least one of ET20, ET70, and ET80 manufactured by Okamoto Corporation of Japan; and / or The outer skeletal structure layer film is produced by mixing components including a high-melting point polymer and the moisture barrier additive, and the high-melting point polymer is a polymer having a melting point in the range of 200 to 350°C, and is preferably at least one of polyethylene terephthalate (PET) and nylon, and the nylon is preferably at least one of nylon 6 and nylon 66.

[0014] In a preferred embodiment of the present invention, The blending amount of each component in the inner connection layer film is based on 100 parts by weight of the thermal adhesive polymer, The moisture barrier additive is present in an amount of 0.01 to 1 part by weight, preferably 0.06 to 0.8 parts by weight, and / or When the moisture barrier additive is an inorganic moisture barrier agent, the blending amount is preferably 0.01 to 0.3 parts by weight, more preferably 0.06 to 0.08 parts by weight, and / or When the moisture barrier additive is an organic moisture barrier agent, the blending amount is preferably 0.1 to 1 part by weight, more preferably 0.2 to 0.8 parts by weight, The blending amount of each component in the outer skeleton structure layer film is based on 100 parts by weight of the high-melting point polymer, The moisture barrier additive is present in an amount of 0.01 to 1 part by weight, preferably 0.06 to 0.8 parts by weight, and / or When the moisture barrier additive is an inorganic moisture barrier agent, the blending amount is preferably 0.01 to 0.3 parts by weight, more preferably 0.06 to 0.08 parts by weight, and / or When the moisture barrier additive is an organic moisture barrier agent, the blending amount is preferably 0.1 to 1 part by weight, more preferably 0.2 to 0.8 parts by weight.

[0015] In a preferred embodiment of the present invention, The inner connecting layer film and the outer skeletal structure layer film also contain conventional toughening additives, nucleating agents, antioxidants, silicone oils and modifying aids in the art, and the amounts of these are also conventional amounts, which can be added by those skilled in the art according to the actual situation.

[0016] The toughening additives in the inner tie layer film and the outer skeletal structure layer film may be the same or different and are each independently at least one of maleic anhydride, polyolefin elastomer (POE), preferably Dow 7457; and / or The nucleating agent in the inner tie layer film and the outer skeletal structure layer film may be the same or different, and is preferably Milliken Milliken 3988i; and / or The antioxidants in the inner tie layer film and the outer skeletal structure layer film may be the same or different and are preferably BASF Irgafos 168; and / or The silicone oil in the inner tie layer film and the outer skeletal structure layer film may be the same or different, and is preferably Dow Corning PMX-200; and / or The modifying aids in the inner tie layer film and the outer skeletal structure layer film may be the same or different and are preferably Lanxess Mesamoll.

[0017] In the present invention, preferably, the blending amount of each component in the inner connection layer film is based on 100 parts by weight of the thermal adhesive polymer, Thermal adhesive polymer 100 parts by weight Toughness additive: 2 to 10 parts by weight, preferably 2 to 7 parts by weight Nucleating agent: 1 to 3 parts by weight, preferably 1.2 to 2 parts by weight Antioxidant: 1 to 2 parts by weight, preferably 1.2 to 1.5 parts by weight Silicone oil: 0.2 to 0.5 parts by weight, preferably 0.3 to 0.4 parts by weight Modification aid: 2 to 8 parts by weight, preferably 3 to 5 parts by weight.

[0018] In the present invention, preferably, the blending amount of each component in the outer skeleton structure layer film is based on 100 parts by weight of the high-melting point polymer, High melting point polymer 100 parts by weight Toughness additive: 2 to 10 parts by weight, preferably 2 to 7 parts by weight Nucleating agent: 1 to 3 parts by weight, preferably 1.2 to 2 parts by weight Antioxidant: 1 to 2 parts by weight, preferably 1.2 to 1.5 parts by weight Silicone oil: 0.2 to 0.5 parts by weight, preferably 0.3 to 0.4 parts by weight Modification aid: 2 to 8 parts by weight, preferably 3 to 5 parts by weight.

[0019] In a preferred embodiment of the present invention, The total thickness of the multilayer composite structure is 50 to 200 μm, preferably 80 to 150 μm, and / or the thickness of the inner layer polymer film is 20 to 100 μm, preferably 40 to 80 μm, and / or the thickness of the outer skeletal structure layer film is 20 to 100 μm, preferably 40 to 80 μm.

[0020] The total thickness of the multilayer composite structure of the present invention is reduced compared to conventional processes, allowing for an increase in the volume density of the battery under the same volume space conditions.

[0021] In a preferred embodiment of the present invention, The multilayer composite structure further comprises an intermediate barrier film, the material of which is preferably at least one of titanium nitride, copper, and polytetrafluoroethylene, and the intermediate barrier film can further block the ingress of water vapor; and / or The thickness of the intermediate barrier film is in the range of 3 to 20 μm, preferably in the range of 3 to 10 μm.

[0022] When the material of the intermediate barrier film is polytetrafluoroethylene, the intermediate barrier film is obtained by extruding polytetrafluoroethylene. The extrusion can be performed by a conventional extrusion method in the prior art, as long as the thickness of the intermediate barrier film obtained by extrusion is in the range of 3 to 20 μm.

[0023] When the intermediate barrier film is made of at least one of titanium nitride and copper, the intermediate barrier film is obtained by chemical plating or electroplating at least one of titanium nitride and copper on the bonding side between the inner connection layer film and the outer skeletal structure layer film or on the bonding side of the outer skeletal structure layer film to the inner connection layer film. The chemical plating or electroplating can be a conventional chemical plating or electroplating method in the prior art, as long as the thickness of the obtained intermediate barrier film is within the range of 3 to 20 μm.

[0024] A second object of the present invention is to provide a method for manufacturing a multilayer composite structure for packaging lithium ion batteries according to the first object of the present invention, which includes a step of laminating film layers including an inner connection layer film and an outer skeletal structure layer film, and then obtaining the multilayer composite structure by double-roll heat pressing.

[0025] In a preferred embodiment of the present invention, The method comprises: melt-mixing ingredients including a thermal adhesive polymer and a moisture barrier additive, followed by extrusion to obtain the inner tie layer film; and / or The method includes the step of melt-mixing ingredients including a high melting point polymer and a moisture barrier additive, followed by extrusion molding to obtain the outer skeletal structure layer film.

[0026] The inner connecting layer film and the outer skeletal structure layer film can both be extruded using conventional extrusion methods in the prior art, as long as the thickness of the film layer obtained by extrusion meets the required thickness.

[0027] In a preferred embodiment of the present invention, The temperature of the double roll heat press is in the range of 140 to 200° C., preferably in the range of 160 to 180° C., and the pressure is in the range of 1 to 3 MPa.

[0028] The present invention can preferably adopt the following specific technical means: First, the thermoadhesive polymer is mixed with a moisture barrier additive, a toughening additive, and silicone oil in a high-speed homogenizer. Then, a nucleating agent, antioxidant, and modifying aid are added, and the mixture is melt-mixed uniformly. The mixture is then extruded through a twin-screw extruder and wound onto a metal drum. The inner adhesive layer film is then rapidly cooled, shaped, trimmed, and wound up. The extrusion process involves a drying temperature of 120-140°C, a drying time of 0.1-5 hours, and a nozzle temperature of 240-280°C (stage control): stage 1 240-280°C, stage 2 240-270°C, and stage 3 250-280°C, with a pressure of 5-10 MPa. First, a high-melting-point polymer is mixed with a moisture barrier additive, a toughening additive, and silicone oil in a high-speed homogenizer. Then, a nucleating agent, an antioxidant, and a modifying aid are added, and the mixture is melted and mixed uniformly. The mixture is then extruded through a twin-screw extruder and wound onto a metal drum. It is rapidly cooled, shaped, trimmed, and wound up to obtain an outer skeletal structure layer film. The extrusion process involves a drying temperature of 120-140°C, a drying time of 0.1-5 hours, and a nozzle temperature of 240-280°C (stage control): stage 1 240-280°C, stage 2 240-270°C, and stage 3 250-280°C, with a pressure of 5-10 MPa. After laminating the film layers including the outer skeletal structure layer film and the inner connecting layer film, as shown in Figure 3, the outer skeletal structure layer film containing the moisture barrier additive and the inner connecting layer film are continuously passed through a hot rolling roll to complete the molding process and obtain a two-layer composite structure.

[0029] If the multilayer composite structure also includes an intermediate barrier film, the intermediate barrier film is placed between the outer skeletal structure layer film and the inner connecting layer film, and then the films are laminated together, and then the films are passed through a hot rolling mill continuously to complete the forming process and obtain a multilayer composite structure with an intermediate barrier film.

[0030] A third object of the present invention is to provide a lithium-ion battery packaged using the multilayer composite structure of the first object of the present invention or the multilayer composite structure produced by the method of the second object of the present invention.

[0031] The method for packaging using the multi-layer composite structure of the present invention can adopt conventional packaging methods in the prior art. In the present invention, it is preferable to first manufacture the multi-layer composite structure as a rectangular groove structure with one open end (the open end of the rectangular groove structure has an outer annular flange) and a groove cover structure that fits the open end of the rectangular groove structure, and then package the multi-layer composite structure. [Effects of the Invention]

[0032] The advantageous effects of the present invention are as follows:

[0033] The present invention improves and designs the stacking structure of conventional aluminum laminate films, ensuring sufficient barrier properties while improving product reliability and reducing costs. Based on the existing structure of conventional aluminum laminate films, the intermediate aluminum foil barrier layer is eliminated, and the associated transition layer processing (processing measures to improve the bonding strength between the aluminum laminate film and the inner or outer layer) is eliminated. At the same time, to improve the water vapor barrier effect, the present invention employs a method of adding moisture barrier additives to the inner and outer layers, thereby improving the effectiveness of preventing water vapor penetration into the internal electrolyte. Because the intermediate metal aluminum foil layer is eliminated, the multilayer composite film can be produced in one go using a double-roll heat press method.

[0034] The multilayer composite structure of the present invention replaces the metal foil moisture barrier structure used in conventional aluminum laminate films by adding a moisture barrier component (moisture barrier additive). While ensuring mechanical strength and electrolyte resistance, the processing method for conventional laminate structures is modified to achieve rapid formation of multilayer film structures. Compared to conventional methods, this method, combined with the lattice-shaped automobile chassis design, reduces the processing and manufacturing difficulties while also increasing the thickness of the unit cell, exceeding the limit of 10 mm for unit cells packaged with aluminum laminate films. The thickness of a unit cell using the multilayer composite structure of the present invention can reach 14 mm or more.

[0035] The multilayer composite structure of the present invention has good support strength, does not soften even when made into a bag shape, is easy to inject electrolyte into, and has extremely strong moisture barrier properties, reducing exposure to the external environment (air moisture) during secondary packaging. The multilayer composite structure of the present invention has high mechanical strength, electrolyte resistance, and thermal processability.

[0036] The multilayer composite structure of the present invention is suitable for packaging automobile batteries, energy storage batteries and motorcycle batteries (all of which are lithium ion batteries), but is not suitable for packaging small digital cells. [Brief explanation of the drawings]

[0037] [Figure 1] 1 is a schematic diagram of the multilayer composite structure of the present invention excluding the intermediate barrier film (in the figure, 1 is the inner connecting layer film, and 2 is the outer skeletal structure layer film). [Figure 2] 1 is a schematic diagram of a multilayer composite structure of the present invention including an intermediate barrier film (in the figure, 1 is an inner connecting layer film, 2 is an outer skeletal structure layer film, and 3 is an intermediate barrier film). [Figure 3] 1 is a schematic diagram of a double roll heat press forming method for the multi-layer composite structure of the present invention. [Figure 4] FIG. 1 is a schematic diagram of a lithium-ion battery using a multilayer film structure. [Figure 5] FIG. 1 is a schematic diagram of a method for extracting an electrode from a lithium ion battery using a multilayer film structure. [Figure 6] FIG. 1 is a schematic diagram of a battery compression molding method using a multilayer film structure. [Figure 7] This is a schematic diagram of the heat-pressing and sealing method for compression molding a battery using a multilayer film structure. DETAILED DESCRIPTION OF THE INVENTION

[0038] The present invention will be described in detail below with reference to specific examples and drawings, but it should be noted here that the following examples are only used to further explain the present invention and should not be understood as limiting the protection scope of the present invention. Those skilled in the art will recognize that some non-essential improvements and adjustments made to the present invention based on the summary of the present invention will also fall within the protection scope of the present invention.

[0039] The raw materials used in the examples and comparative examples are all conventional, commercially available raw materials.

[0040] The reference standard for thickness measurement of multilayer composite structures in the examples and comparative examples is GB / T6672-2001; Electrolyte resistance test process: Multilayer composite structure specimens are immersed in an electrolyte containing 200 ppm of water (electrolyte composition EMC:DMC:LIF6P=1:1:1) for 24 hours (temperature 60°C), then cut into 15 mm width specimens and test whether they can be peeled off with a tensile force of 10 N using a CTM8000 tensile tester. The reference standard for whether the specimen can be peeled off with a tensile tester is GB / T 8808-1988. Break resistance test process: After the multi-layer composite structure is heat-sealed, it is placed in a DZF6120 type vacuum box and observed whether the product breaks within 30 minutes under a pressure of 0.9Mpa.

[0041] Test process for short circuit withstand capability: Using a BT5300 type internal resistance tester, connect the positive electrode to the inner layer of the multi-layer composite structure, connect the negative electrode to the outer layer of the multi-layer composite structure, apply a voltage of 500V, and evaluate the conduction time.

[0042] Water vapor transmission rate measurement process: A water vapor transmission rate tester is used to measure the water vapor transmission rate of the multi-layer composite structure.

[0043] Formability testing process: The cut multi-layer composite structure is placed between the male and female molds of an MSK-120 flexible battery packaging molding machine (casing length x width 100mm x 80mm), the male mold is heated to 100°C, and the female mold is heated to 110°C, and the multi-layer composite structure is extruded. The extrusion time is about 3 seconds and the holding time is about 6 seconds. After extrusion, a fracture test is conducted under a pressure of 30MPa in a DZF6120 vacuum box to test the limit forming depth of the multi-layer composite structure (i.e., the maximum thickness that can be formed by extrusion of the multi-layer composite structure; at this thickness it will not fracture, but above this thickness it will fracture). [Example]

[0044] 100 parts by weight of polypropylene (Yanshan Petrochemical K8303) was mixed with 0.08 parts by weight of titanium nitride, 5 parts by weight of toughening additive (Dow 7457), and 0.3 parts by weight of silicone oil in a high-speed homogenizer. Then, 1.5 parts by weight of nucleating agent (Milliken Miliken 3988i), 1.3 parts by weight of antioxidant (BASF Irgafos 168), and 4 parts by weight of modifier (Lanxess Mesamoll) were added. The mixture was melt-mixed and extruded through a twin-screw extruder. The film was then wrapped around a metal drum, rapidly cooled, shaped, trimmed, and wound up to obtain the inner connecting layer film. The extrusion process was as follows: drying temperature 130°C, drying time 0.7 hours, nozzle temperature (stage control): 270°C in the first stage, 250°C in the second stage, and 270°C in the third stage, pressure 8.5 MPa. 100 parts by weight of PET (Shanghai Yuanbo CB-602) was mixed in a high-speed homogenizer with 0.07 parts by weight of titanium nitride, 5 parts by weight of a toughening additive (Dow 7457), and 0.3 parts by weight of silicone oil. Then, 1.5 parts by weight of a nucleating agent (Milliken Miliken 3988i), 1.3 parts by weight of an antioxidant (BASF Irgafos 168), and 4 parts by weight of a modifier (Lanxess Mesamoll) were added. The mixture was melted and mixed uniformly. The mixture was then extruded through a twin-screw extruder, wrapped around a metal drum, rapidly cooled, shaped, trimmed, and wound up to obtain an inner connecting layer film. The extrusion process was as follows: drying temperature 130°C, drying time 0.7 hours, nozzle temperature (stage control): 270°C in the first stage, 250°C in the second stage, and 270°C in the third stage, pressure 8.5 MPa. The outer skeletal structure layer film and the inner connecting layer film obtained above were laminated together and then passed continuously through a hot rolling mill (temperature 170°C, pressure 2 MPa) to obtain a multilayer composite structure. The thickness of the inner connecting layer film in the multilayer composite structure was 60 microns, and the thickness of the outer skeletal structure layer film was 80 microns. The properties of the multilayer composite structure are shown in Table 1. [Example]

[0045] The manufacturing process for Example 2 was the same as that for Example 1, except that the inner tie layer film contained 0.16 parts by weight of titanium nitride and the outer skeletal structure layer contained 0.14 parts by weight of titanium nitride. The resulting multilayer composite structure had an inner tie layer film thickness of 60 microns and an outer skeletal structure layer film thickness of 80 microns. The properties of the multilayer composite structure are shown in Table 1. [Example]

[0046] The manufacturing process for Example 3 was the same as that for Example 2, except for the addition of an intermediate barrier film. The intermediate barrier film manufacturing process involved melting polytetrafluoroethylene (Zhejiang Juhua JTF-305) and extruding it through a twin-screw extruder. The extrusion process involved rapid cooling, shaping, trimming, and winding to obtain the intermediate barrier film. The extrusion temperature was 130°C, the drying time was 0.7 hours, and the nozzle temperature (step-controlled) was 270°C in the first stage, 250°C in the second stage, and 270°C in the third stage. The pressure was 9 MPa.

[0047] The resulting multilayer composite structure had an inner connecting layer film thickness of 60 microns, an outer skeletal structure layer film thickness of 80 microns, and an intermediate barrier film thickness of 4 microns. The properties of the multilayer composite structure are shown in Table 1. [Example]

[0048] The manufacturing process of Example 4 was the same as that of Example 1, except that the thickness of the inner connecting layer film in the resulting multilayer composite structure was 40 microns and the thickness of the outer skeletal structure layer film was 60 microns. The properties of the multilayer composite structure are shown in Table 1. [Example]

[0049] The manufacturing process of Example 5 was the same as that of Example 1, except that the thickness of the inner connecting layer film in the resulting multilayer composite structure was 40 microns and the thickness of the outer skeletal structure layer film was 80 microns. The properties of the multilayer composite structure are shown in Table 1. (Comparative Example 1)

[0050] The manufacturing process for Comparative Example 1 was the same as that for Example 3, except that neither the outer skeletal structure layer film nor the inner tie layer film contained a moisture barrier additive. The resulting multilayer composite structure had an inner tie layer film thickness of 60 microns, an outer skeletal structure layer film thickness of 80 microns, and an intermediate barrier film thickness of 4 microns. The properties of the multilayer composite structure are shown in Table 1.

[0051] [Table 1]

[0052] As can be seen from Examples 1 to 5, Comparative Example, and Table 1, compared to conventional aluminum laminate films, the multilayer composite structure of the present invention has superior electrolyte resistance. Because double-roll hot press molding is used, the molding depth can reach 20 mm, which is significantly greater than the 8 mm achievable with aluminum laminate films. The multilayer composite structure of the present invention also has excellent fracture resistance, short-circuit resistance, and water vapor resistance, meeting application requirements. Compared to Comparative Example 1, the outer skeletal structure layer film and inner connecting layer film of Comparative Example 1 do not contain a moisture barrier additive, so both the electrolyte resistance and water vapor permeability are inferior to those of the multilayer composite structures of Examples 1 to 5 of the present invention.

[0053] As can be seen from this, the multilayer composite structure of the present invention replaces the metal foil moisture barrier structure used in conventional aluminum laminate films by adding a moisture barrier component (moisture barrier additive). While ensuring mechanical strength and electrolyte resistance, the processing method for conventional laminate structures is changed, and rapid formation of multilayer film structures is achieved.

Claims

1. The film comprises an inner connection layer film and an outer skeleton structure layer film bonded together, and the inner connection layer film and the outer skeleton structure layer film each contain a moisture barrier additive. A multilayer composite structure for packaging lithium-ion batteries, comprising:

2. the moisture barrier additives in the inner connection layer film and the outer skeletal structure layer film may be the same or different, and each independently may be at least one of an inorganic moisture barrier agent and an organic moisture barrier agent; The inorganic moisture barrier agent is preferably at least one of titanium nitride, aluminum nitride, and titanium aluminum nitride compounds; and / or The organic moisture barrier agent is preferably at least one of perfluoro compounds, and more preferably at least one of perfluorooctanesulfonic acid, perfluorooctanoic acid, and Teflon (registered trademark). The multi-layer composite structure for packaging lithium ion batteries according to claim 1.

3. The inner connection layer film is produced after mixing components including a thermal adhesive polymer and the moisture barrier additive, and the thermal adhesive polymer is preferably at least one of polypropylene and modified polypropylene; and / or The outer skeleton structure film is produced by mixing components including a high-melting point polymer and the moisture barrier additive, and the high-melting point polymer is a polymer having a melting point in the range of 200 to 350°C, and is preferably at least one of polyethylene terephthalate and nylon. The multi-layer composite structure for packaging lithium ion batteries according to claim 1.

4. The blending amount of each component in the inner connection layer film is based on 100 parts by weight of the thermal adhesive polymer, and the blending amount of the moisture barrier additive is 0.01 to 1 part by weight, preferably 0.06 to 0.8 parts by weight, The blending amount of each component in the outer skeleton structure layer film is based on 100 parts by weight of the high melting point polymer, and the moisture barrier additive is 0.01 to 1 part by weight, preferably 0.06 to 0.8 parts by weight. The multi-layer composite structure for packaging lithium ion batteries according to claim 3.

5. The total thickness of the multilayer composite structure is 50-200 μm, preferably 80-150 μm, and / or the thickness of the inner layer polymer film is 20-100 μm, preferably 40-80 μm. The multi-layer composite structure for packaging lithium ion batteries according to claim 1.

6. The multilayer composite structure further includes an intermediate barrier film, the material of which is preferably at least one of titanium nitride, copper, and polytetrafluoroethylene, and the thickness of the intermediate barrier film is in the range of 3 to 20 μm. The multi-layer composite structure for packaging lithium ion batteries according to claim 1.

7. 7. A method for manufacturing a multi-layer composite structure for packaging lithium ion batteries according to any one of claims 1 to 6, comprising the steps of: The method includes laminating the film layers including the inner connecting layer film and the outer skeletal structure layer film, and then performing double-roll heat pressing to obtain the multilayer composite structure. A manufacturing method characterized by:

8. melt-mixing ingredients including a thermal adhesive polymer and a moisture barrier additive, followed by extrusion to obtain the inner tie layer film; and / or and a step of melt-mixing components including a high-melting point polymer and a moisture barrier additive, followed by extrusion molding to obtain the outer skeleton structure layer film. The method of claim 7.

9. The temperature of the double roll heat press is in the range of 140 to 200°C, and the pressure is in the range of 1 to 3 MPa. The method of claim 7.

10. A lithium ion battery packaged with a multilayer composite structure according to any one of claims 1 to 6 or a multilayer composite structure produced by the method according to any one of claims 7 to 9. A lithium-ion battery characterized by:

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