Composite aluminum foil

Abstract

The composite aluminum foil comprises a supporting layer, a non-metal layer is arranged on the surface of the supporting layer, a metal aluminum layer is arranged on the surface of the non-metal layer, the surface density of the metal aluminum layer is 2.0 g / m < 2 >-3 g / m < 2 >, the average particle size of particles of the metal aluminum layer is D, the thickness of the non-metal layer is H, wherein the average particle size D of the metal aluminum layer and the thickness H of the non-metal layer meet the following relation: 2lt; d / Hlt; 4. Through multiple experiments, the inventor finds that when the surface density of the metal aluminum layer ranges from 2.0 g / m < 2 > to 3g / m < 2 >, the particle size D of the metal aluminum layer and the thickness H of the aluminum oxide layer meet 2lt; d / Hlt; and 4, the composite aluminum foil can have relatively high overcurrent capability.

Description

Technical Field

[0001] The invention relates to the field of batteries, and in particular to a composite aluminum foil. Background Art

[0002] At present, the composite aluminum foil has a non-conductive material in the middle and an aluminum material on the surface. It is widely used in packaging, batteries and other fields. Compared with traditional foils, composite aluminum foil can pass the needle puncture test 100%, and the battery energy density can be increased by 5%-10%, and the life can be increased by about 5%, thereby improving the battery performance; as a kind of composite current collector, composite aluminum foil can provide a large resistance through fusing and insulating materials when there is a short circuit in the battery, and cut off or reduce the short-circuit current in a short time, which greatly avoids the fire hazard and enhances the safety of the battery; the cost of composite aluminum foil after large-scale mass production is expected to be lower than that of traditional foil, which can effectively cope with the rise in metal prices and is more suitable for iron-lithium batteries that are more sensitive to prices, reducing costs. When composite aluminum foil is used in batteries, since the composite aluminum foil is mainly responsible for converging current, heat will be generated on the surface of the composite aluminum foil, which will increase the battery temperature. The increase in battery temperature will promote the decomposition of electrolyte and active materials, etc., causing thermal runaway of the battery. However, the current method of solving the overcurrent capacity of composite aluminum foil is costly, inconvenient to operate, and greatly increases the weight of the composite aluminum foil. Therefore, the existing technology needs to be improved and improved. Summary of the invention

[0003] In view of the above-mentioned deficiencies in the prior art, an object of the present invention is to provide a composite aluminum foil.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0005] The present invention provides a composite aluminum foil, comprising a support layer, a non-metal layer is arranged on the surface of the support layer, a metal aluminum layer is arranged on the surface of the non-metal layer, and the surface density of the metal aluminum layer is 2.0 g / m 2 -3g / m 2 , the average particle size of the metal aluminum layer is D, the thickness of the non-metal layer is H, wherein the average particle size D of the metal aluminum layer and the thickness H of the non-metal layer satisfy the following relationship: <D / H<4。

[0006] Furthermore, in the composite aluminum foil, the non-metallic layer is an aluminum oxide layer.

[0007] Furthermore, in the composite aluminum foil, the thickness of the metal aluminum layer is greater than the thickness of the non-metal layer.

[0008] Further, for the composite aluminum foil, the thickness of the metallic aluminum layer is 800 nm - 1.5 μm, the average particle size of the particles in the metallic aluminum layer is larger than the average particle size of the particles in the non-metallic layer, the areal density of the aluminum oxide layer is larger than the areal density of the metallic aluminum layer, and the areal density of the aluminum oxide layer is 1.5 - 2 times that of the metallic aluminum layer.

[0009] Further, for the composite aluminum foil, the mass of the metallic aluminum layer is less than the mass of the support layer.

[0010] Further, for the composite aluminum foil, the mass of the non-metallic layer is less than the mass of the support layer.

[0011] Further, for the composite aluminum foil, the support layer is a plastic layer with a straight-chain crystal or a sheaf crystal.

[0012] Further, for the composite aluminum foil, the crystallinity of the support layer is 50% - 70%.

[0013] Further, for the composite aluminum foil, the crystal size of the microscopic crystal form of the support layer is less than the average particle size of the particles in the metallic aluminum layer.

[0014] Further, for the composite aluminum foil, the support layer is a film formed by one or more of polyamide, polyimide, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyethylene, polypropylene, polypropylene styrene, acrylonitrile-butadiene-styrene copolymer, polyvinyl alcohol, polystyrene, polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, sodium polystyrene sulfonate, polyacetylene, silicone rubber, polyoxymethylene, polyphenylene ether, polyphenylene sulfide, polyethylene glycol, sulfur nitride polymer materials, polyphenylene, polypyrrole, polyaniline, polythiophene, polypyridine, cellulose, starch, protein, epoxy resin, phenolic resin.

[0015] Compared with the prior art, the present invention provides a composite aluminum foil, including a support layer, on the surface of which a non-metallic layer is provided, and on the surface of the non-metallic layer, a metallic aluminum layer is provided. The areal density of the metallic aluminum layer is 2.0 g / m 2 - 3 g / m 2 , the average particle size of the particles in the metallic aluminum layer is D, and the thickness of the non-metallic layer is H. Wherein, the average particle size D of the particles in the metallic aluminum layer and the thickness H of the non-metallic layer satisfy the following relationship: 2 < D / H < 4. The inventor has found through multiple experiments that when the areal density of the metallic aluminum layer is between 2.0 g / m 2 - 3 g / m 2 , and the particle size D of the metallic aluminum layer and the thickness H of the aluminum oxide layer satisfy 2 < D / H < 4, the composite aluminum foil can have a relatively large over-current capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0017] Figure 1 This is a schematic structural diagram of the composite aluminum foil provided by the present invention.

[0018] Description of Figure Numbers:

[0019] Support layer 100

[0020] Non-metallic layer 200

[0021] Metal aluminum layer 300 DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0024] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or suggesting their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0025] like Figure 1As shown, the present invention provides a composite aluminum foil, including a support layer 100, on the surface of which a non-metal layer 200 is provided, and on the surface of the non-metal layer 200 a metallic aluminum layer 300 is provided. The areal density of the metallic aluminum layer 300 is 2.0 g / m 2 -3 g / m 2 , the average particle size of the particles of the metallic aluminum layer 300 is D, and the thickness of the non-metal layer 200 is H. Wherein, the average particle size D of the particles of the metallic aluminum layer 300 and the thickness H of the non-metal layer 200 satisfy the following relationship: 2 < D / H < 4. Further, for the composite aluminum foil provided by the present invention, the non-metal layer 200 is preferably an alumina layer. The inventors have found through multiple experiments that when the areal density of the metallic aluminum layer 300 is between 2.0 g / m 2 -3 g / m 2 , and the particle size D of the metallic aluminum layer 300 and the thickness H of the alumina layer satisfy 2 < D / H < 4, the composite aluminum foil can have a relatively large over-current capacity. The average particle size is a scale for describing the geometric size of a particle group. For non-spherical particles, their particle size is usually represented by an average value. Common methods for representing the average particle size include the arithmetic mean method, the geometric mean method, the area average diameter, the volume average diameter, and the weight average diameter, etc. These methods calculate the average particle size based on different physical quantities (such as length, surface area, volume, or weight) to reflect the overall size characteristics of the particle group. As a kind of current collector for lithium batteries, the composite aluminum foil shows significant advantages in terms of safety through its unique design. Specifically, the composite aluminum foil is not easily pierced through the separator: compared with traditional aluminum foil, due to the presence of the middle polymer material layer, the composite aluminum foil is less likely to pierce through the battery separator, thus reducing the risk of internal short circuit. The melting point of the middle polymer material layer in the composite aluminum foil is much lower than that of aluminum metal. Once a fault such as a short circuit occurs, this layer can quickly fuse or melt to cut off the short-circuit current. The polymer material layer is easily fusible, effectively preventing battery thermal runaway and fire accidents. The areal density of the composite aluminum foil, as part of its physical properties, although directly affects the energy density and performance of the battery, through optimized design and manufacturing processes, while ensuring the energy density of the battery, the safety of the battery can be significantly improved.

[0026] Furthermore, in the composite aluminum foil provided by the present invention, the thickness of the metal aluminum layer 300 is greater than the thickness of the non-metallic layer 200. This is beneficial to improving the current convergence capacity of the metal aluminum layer 300. Furthermore, in the composite aluminum foil provided by the present invention, the thickness of the metal aluminum layer 300 is 800nm-1.5um, and the average particle size of the metal aluminum layer 300 is greater than the average particle size of the non-metallic layer 200. The thickness of the metal aluminum layer 300 is 800nm-1.5um. Within this range, on the one hand, the conductive properties of aluminum can be guaranteed, and on the other hand, the support layer 100 can be prevented from becoming brittle. In the present invention, the particle size of the metal aluminum layer 300 is preferably greater than the average particle size of the aluminum oxide layer, and the average particle size of the aluminum oxide layer is greater than the average particle size of the support layer 100. This has the advantage that when the composite aluminum film is punctured by the outside, it is more resistant to puncture. In the present invention, the surface density of the aluminum oxide layer is greater than the surface density of the metal aluminum layer 300, which can prevent the composite aluminum foil from curling due to heat, and can also prevent the support layer 100 of the present invention from becoming brittle, and can also reduce the mass of the composite aluminum foil of the present invention. Because the surface density of the aluminum oxide layer is greater than that of the metal aluminum layer 300, the support layer 100 has strong high temperature resistance when forming the metal aluminum layer 300, and will not be affected by the heat of evaporation. At the same time, when the composite aluminum foil works in the battery, it will not be affected by the heat generated by current convergence.

[0027] Furthermore, in the composite aluminum foil provided by the present invention, the mass of the metal aluminum layer 300 is less than the mass of the support layer 100. In this way, the total mass of the composite aluminum foil of the present invention is small, so that the electrical device using the product of the present invention, such as a lithium battery, can be lighter and have a higher energy density. Further, in the composite aluminum foil provided by the present invention, the mass of the non-metal layer 200 is less than the mass of the support layer 100, which is conducive to reducing the total mass of the composite aluminum foil of the present invention. The lower-quality aluminum oxide layer can also reduce the formation of holes in the support layer 100 by the aluminum oxide layer, and can also reduce the cost of the composite aluminum foil of the present invention, because the non-metal layer 200 of the present invention requires less amount and the energy consumption of the production process is also low. In this embodiment, the thickness of the support layer 100 can be 3um-8um, which can reduce the mass of the composite aluminum foil. The use of the support layer 100 as a non-conductive material is greatly improved in terms of safety performance compared to pure metal aluminum foil. In the present invention, the surface density of the aluminum oxide layer is 1.5-2 times the surface density of the metal aluminum layer 300, so that while reducing the mass, the heat resistance of its support layer can be greatly improved.

[0028] Furthermore, in the composite aluminum foil provided by the present invention, the support layer 100 is a plastic layer of linear crystals or crystal strings. The use of plastics of linear crystals or crystal strings can greatly improve the tensile strength of the composite aluminum foil of the present invention. Furthermore, in the composite aluminum foil provided by the present invention, the support layer 100 has a crystallinity of 50%-70%. Such a support layer 100 can achieve a balance in flexibility, hardness and transparency. The appropriate flexibility allows the support layer 100 of the composite aluminum foil to be well coated in the vacuum coating equipment. The good hardness performance can prevent the film of the present application from being easily scratched, and the high transparency can make the composite aluminum foil of the present invention convenient for the CCD visual inspection system to detect holes. Further, in the composite aluminum foil provided by the present invention, the crystal size of the microscopic crystal of the support layer 100 is smaller than the average particle size of the particles of the metal aluminum layer 300, which is conducive to preventing the support layer 100 from being scalded during the aluminum oxide coating process. Because of the small size, the microscopic grains of the support layer 100 have a large contact area with the aluminum oxide particles, which can better buffer the impact of the aluminum oxide particles. The microscopic grain size of the support layer 100 of the composite aluminum foil of the present invention can be achieved by adding a nucleating agent during the formation of the support layer 100. Further, specifically, in the composite aluminum foil provided by the present invention, the support layer 100 is a film formed by one or more of polyamide, polyimide, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyethylene, polypropylene, polypropylene, acrylonitrile-butadiene-styrene copolymer, polyvinyl alcohol, polystyrene, polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, sodium polystyrene sulfonate, polyacetylene, silicone rubber, polyoxymethylene, polyphenylene oxide, polyphenylene sulfide, polyethylene glycol, polysulfur nitride polymer materials, polyphenylene, polypyrrole, polyaniline, polythiophene, polypyridine, cellulose, starch, protein, epoxy resin, and phenolic resin. The support layer 100 can be a film made of any non-conductive material.

[0029] The composite aluminum foil of the present invention can be prepared by a variety of methods. The preparation method of the composite aluminum foil of the present invention can be, first take the support layer 100, and then use a variety of methods to form the desired thickness of the aluminum oxide layer and the thickness of the metal aluminum layer 300 on the support layer 100. The method of forming aluminum oxide on the support layer 100 of the present invention can be, forming an aluminum oxide layer on the support layer 100 by vacuum evaporation. Vacuum evaporation, referred to as evaporation, refers to a process method in which a coating material (or film material) is evaporated and gasified by a certain heating evaporation method under vacuum conditions, and the particles fly to the surface of the substrate to condense into a film. Evaporation is an earlier and more widely used vapor deposition technology, which has the advantages of simple film forming method, high film purity and density, unique film structure and performance. The physical process of evaporation includes: the deposition material evaporates or sublimates into gaseous particles → the gaseous particles are quickly transported from the evaporation source to the substrate surface → the gaseous particles are attached to the substrate surface to nucleate and grow into a solid film → the film atoms are reconstructed or chemically bonded. The substrate is placed in a vacuum chamber, and the film material is heated by resistance, electron beam, laser, etc., so that the film material evaporates or sublimates, and gasifies into particles (atoms, molecules or atomic groups) with a certain energy (0.1-0.3eV). The gaseous particles are rapidly transmitted to the substrate in a linear motion without collision. Part of the particles reaching the surface of the substrate are reflected, and the other part is adsorbed on the substrate and diffuses on the surface. Two-dimensional collisions occur between the deposited atoms to form clusters, and some may evaporate after staying on the surface for a short time. The particle clusters constantly collide with the diffused particles, or adsorb single particles, or release single particles. This process is repeated. When the number of aggregated particles exceeds a certain critical value, it becomes a stable nucleus, and then continues to adsorb diffused particles and gradually grows. Finally, a continuous film is formed through the contact and merging of adjacent stable nuclei. Evaporation is a physical phase deposition (PVD) method that melts the metal into a liquid state, forms metal vapor and begins to volatilize, and then condenses the copper atoms in the vapor and deposits and grows on the surface of the polymer material. The present invention can form aluminum oxide on the support layer 100 by using an evaporation boat. The main method is to put aluminum wire in the evaporation boat, melt the aluminum wire at high temperature and then evaporate it onto the support layer 100. In the process of aluminum metal rising to the support layer 100, oxygen is introduced to oxidize it into aluminum oxide and form it on the support layer 100. The metal aluminum layer 300 of the present invention is formed on aluminum oxide by the following method. In the vacuum chamber, aluminum metal can be placed in a crucible, and the crucible is heated to melt it and finally evaporate it onto the aluminum oxide.

[0030] The following will illustrate the effects of the composite aluminum foil claimed in this application in combination with experimental data. The inventor produced a comparative example and an example in the same production manner. Both the comparative example and the example used a PET film with the same thickness as the support layer, with a thickness of 8 μm. Then, alumina layers were formed on both the upper and lower surfaces of the support layer, and then a metallic aluminum layer was formed on the alumina layer (non-metallic layer). The differences between the comparative example and the example are as follows: In Example 1, the areal density of the metallic aluminum layer is 2.5 g / m 2 , the thickness of the non-metallic layer is 30 nm, and the average particle size of the metallic aluminum layer is 63 nm. In Example 2, the areal density of the metallic aluminum layer is 2.7 g / m 2 , the thickness of the non-metallic layer is 40 nm, and the average particle size of the metallic aluminum layer is 120 nm. In Comparative Example 1, the areal density is 2.5 g / m 2 , the thickness of the non-metallic layer is 30 nm, and the average particle size of the metallic aluminum layer is 60 nm. In Comparative Example 2, the areal density of the metallic aluminum layer is 2.7 g / m 2 , the thickness of the non-metallic layer is 40 nm, and the average particle size of the metallic aluminum layer is 120 nm.

[0031] Then, the overcurrent capabilities of the above comparative examples and examples were tested in a battery. The overcurrent capability was measured according to the charging temperature rise. The lower the charging temperature rise, the stronger the overcurrent capability of the composite current collector.

[0032] Comparative Example Overcurrent capability (charging temperature rise) Comparative Example 1 4.4℃ Comparative Example 2 4.8℃ Example 1 3.0℃ Example 2 3.4℃

[0033] As can be seen from the above, Example 1 and Example 2 are obviously superior to Comparative Example 1 and Comparative Example 2, and the composite aluminum foil of the present invention has a stronger overcurrent capability.

[0034] In summary, the present invention provides a composite aluminum foil, including a support layer, on the surface of which a non-metallic layer is provided, on the surface of which a metallic aluminum layer is provided. The areal density of the metallic aluminum layer is 2.0 g / m 2 -3 g / m 2 , the average particle size of the metallic aluminum layer is D, and the thickness of the non-metallic layer is H, where the average particle size D of the metallic aluminum layer and the thickness H of the non-metallic layer satisfy the following relationship: 2 < D / H < 4. Further, for the composite aluminum foil provided by the present invention, the non-metallic layer is preferably an alumina layer. The inventor found through multiple experiments that when the areal density of the metallic aluminum layer is between 2.0 g / m 2 -3 g / m 2 , and the particle size D of the metallic aluminum layer and the thickness H of the alumina layer satisfy 2 < D / H < 4, the composite aluminum foil can have a relatively large overcurrent capability.

[0035] Moreover, the thickness of the metal aluminum layer is 800nm-1.5um. Within this range, on the one hand, the electrical conductivity of aluminum can be guaranteed, and on the other hand, the supporting layer can be prevented from becoming brittle. In the present invention, the particle size of the metal aluminum layer is preferably larger than the average particle size of the aluminum oxide layer, and the average particle size of the aluminum oxide layer is larger than the average particle size of the supporting layer. The advantage of this is that when the composite aluminum film is punctured by the outside, it is more resistant to puncture. In the present invention, the surface density of the aluminum oxide layer is greater than the surface density of the metal aluminum layer, which can prevent the composite aluminum foil from curling due to heat, and also prevent the supporting layer of the present invention from becoming brittle, and can also reduce the mass of the composite aluminum foil of the present invention. Because the surface density of the aluminum oxide layer is greater than that of the metal aluminum layer, the supporting layer has strong high temperature resistance when forming the metal aluminum layer, and will not be affected by the heat of evaporation. At the same time, when the composite aluminum foil works in the battery, it will not be affected by the heat generated by current convergence.

[0036] In addition, the support layer is a plastic layer of linear crystals or crystal strings. The use of plastics of linear crystals or crystal strings can greatly improve the tensile strength of the composite aluminum foil of the present invention. Furthermore, in the composite aluminum foil provided by the present invention, the crystallinity of the support layer is 50%-70%. Such a support layer can achieve a balance in flexibility, hardness and transparency. The appropriate flexibility allows the support layer of the composite aluminum foil to be well coated in the vacuum coating equipment. The good hardness performance prevents the film of the present application from being easily scratched. The high transparency allows the composite aluminum foil of the present invention to facilitate the CCD visual inspection system to detect holes. Furthermore, in the composite aluminum foil provided by the present invention, the crystal size of the microscopic crystals of the support layer is smaller than the average particle size of the particles of the metal aluminum layer, which is conducive to preventing the support layer from being burned during the aluminum oxide plating process. Because of the smaller size, the microscopic grains of the support layer have a larger contact area with the aluminum oxide particles, which can better buffer the impact of the aluminum oxide particles.

[0037] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A composite aluminum foil, characterized in that: The invention comprises a supporting layer, a non-metallic layer is arranged on the surface of the supporting layer, a metal aluminum layer is arranged on the surface of the non-metallic layer, and the surface density of the metal aluminum layer is 2.0 g / m 2 -3g / m 2 , the average particle size of the metal aluminum layer is D, the thickness of the non-metal layer is H, wherein the average particle size D of the metal aluminum layer and the thickness H of the non-metal layer satisfy the following relationship: <D / H<4。 2. The composite aluminum foil according to claim 1, characterized in that: The non-metal layer is an aluminum oxide layer.

3. The composite aluminum foil according to claim 2, characterized in that: The thickness of the metal aluminum layer is greater than the thickness of the non-metal layer.

4. The composite aluminum foil according to claim 3, characterized in that: The thickness of the metal aluminum layer is 800nm-1.5um, the average particle size of the metal aluminum layer is greater than the average particle size of the non-metallic layer, the surface density of the aluminum oxide layer is greater than the surface density of the metal aluminum layer, and the surface density of the aluminum oxide layer is 1.5-2 times the surface density of the metal aluminum layer.

5. The composite aluminum foil according to claim 2, characterized in that: The mass of the metal aluminum layer is smaller than the mass of the support layer.

6. The composite aluminum foil according to claim 5, characterized in that: The mass of the non-metallic layer is less than the mass of the supporting layer.

7. The composite aluminum foil according to claim 1, characterized in that: The support layer is a plastic layer of linear crystals or skewers.

8. The composite aluminum foil according to claim 7, characterized in that: The support layer has a crystallinity of 50%-70%.

9. The composite aluminum foil according to claim 8, characterized in that: The crystal size of the microscopic crystals of the support layer is smaller than the average particle size of the particles of the metal aluminum layer.

10. The composite aluminum foil according to any one of claims 1 to 9, characterized in that: The support layer is a film formed by one or more of polyamide, polyimide, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyethylene, polypropylene, polypropylene, acrylonitrile-butadiene-styrene copolymer, polyvinyl alcohol, polystyrene, polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, sodium polystyrene sulfonate, polyacetylene, silicone rubber, polyformaldehyde, polyphenylene ether, polyphenylene sulfide, polyethylene glycol, polysulfur nitride polymer materials, polyphenylene, polypyrrole, polyaniline, polythiophene, polypyridine, cellulose, starch, protein, epoxy resin, and phenolic resin.

Images