Composite current collector and its manufacturing method, electrode piece and secondary battery

Abstract

The present invention relates to a composite current collector, a method for producing the same, an electrode piece, and a secondary battery. [Solution] The composite current collector includes a polymer-based film and an aluminum plating layer provided on both surfaces of the polymer-based film. The aluminum plating layer includes a first sublayer and a second sublayer, the first sublayer is closer to the polymer-based film than the second sublayer, the aluminum particles in the first sublayer have a particle size of 10 nm to 30 nm, and the aluminum particles in the second sublayer have a particle size of 80 nm to 100 nm. The composite current collector not only has high electrical conductivity, but also has high surface energy, which can obviously improve the interfacial internal resistance between the battery pole piece and the current collector during the coating process of the active material, and improve the capacity and cycle performance of the lithium battery.

Description

[Technical Field]

[0001] This invention relates to the field of batteries, and more particularly to composite current collectors and methods for manufacturing the same, electrode pieces, and secondary batteries. [Background technology]

[0002] The positive electrode current collector of a typical non-aqueous secondary battery is manufactured using high-purity aluminum foil through a rolling process. To ensure the flatness of the aluminum foil, the surface of the press rolls used in the rolling process is very smooth. As a result, the surface energy of the current collector is low, which prevents the active material of the positive electrode from adhering effectively to the current collector when it is applied. Furthermore, the interfacial resistance between the active material and the current collector becomes too high, affecting the performance of the battery. [Overview of the Initiative] [Problems that the invention aims to solve]

[0003] Therefore, there is a need to provide a composite current collector that can increase the surface energy of the current collector and reduce the interfacial resistance between it and the active material.

[0004] Furthermore, it is also necessary to provide a method for manufacturing a composite current collector, an electrode piece including the composite current collector, and a secondary battery. [Means for solving the problem]

[0005] A composite current collector comprising a polymer base film and aluminum plating layers provided on both surfaces of the polymer base film, wherein the aluminum plating layers comprise a first sub-layer and a second sub-layer, the first sub-layer being closer to the polymer base film than the second sub-layer, the aluminum particle size in the first sub-layer being 10 nm to 30 nm, and the aluminum particle size in the second sub-layer being 80 nm to 100 nm.

[0006] In one embodiment, the thickness of each aluminum plating layer is independently 0.3 μm to 3 μm.

[0007] In one embodiment, the first sublayer is comprised of multiple layers, and these multiple first sublayers are sequentially stacked and arranged between the polymer base film and the second sublayer.

[0008] In one embodiment, the number of the first sublayers is 19 or less.

[0009] In one embodiment, the thickness of the polymer-based film is 1 μm to 25 μm.

[0010] In one embodiment, the polymer-based film is at least one selected from polyethylene, polypropylene, polymethylpentene, and polyethylene terephthalate.

[0011] A method for manufacturing a composite current collector, comprising the step of manufacturing a composite current collector by forming aluminum plating layers on both surfaces of a polymer base film, wherein the aluminum plating layers include a first sub-layer and a second sub-layer, the first sub-layer being closer to the polymer base film than the second sub-layer, the particle size of the aluminum particles in the first sub-layer being 10 nm to 30 nm, and the particle size of the aluminum particles in the second sub-layer being 80 nm to 100 nm.

[0012] In one embodiment, the aluminum plating layer is formed by vacuum deposition or magnetron sputtering.

[0013] In one embodiment, during the process of forming the aluminum plating layer, the process parameters are such that the evaporation temperature is 600°C or higher, the vacuum level is less than 0.01 Pa, the plating rate is greater than 10 m / min, and the evaporation temperature for forming the first sublayer is greater than the evaporation temperature for forming the second sublayer.

[0014] The evaporation temperature for forming the first sublayer is 700°C to 750°C, and the evaporation temperature for forming the second sublayer is 600°C to 700°C.

[0015] The electrode piece comprises a current collector which is a composite current collector or a composite current collector manufactured by the method for manufacturing a composite current collector described above, and an active material coated on both sides of the current collector.

[0016] A secondary battery, comprising the electrode pieces described above. [Effects of the Invention]

[0017] The above-described composite current collector comprises a polymer base film and an aluminum plating layer. The polymer base film is used to support the aluminum plating layer. The aluminum plating layer has a structure consisting of two layers with different particle sizes. The first sublayer has small particle sizes and high density, ensuring that the aluminum plating layer has high conductivity. The second sublayer has large particle sizes and low density, resulting in high surface energy of the aluminum plating layer, effectively solving the problem of high interfacial resistance of conventional aluminum foil. Therefore, by controlling the particle sizes in the different sublayers of the aluminum plating layer, the composite current collector can have high surface energy and high conductivity, significantly improving the internal interfacial resistance between the battery electrode and the current collector during the application process of the active substance, thereby improving the capacity and cycle performance of the lithium battery. [Brief explanation of the drawing]

[0018] [Figure 1] This is a schematic diagram of the structure of a composite current collector in one embodiment. [Figure 2] This is a comparison diagram of the internal resistance of lithium batteries manufactured using the composite current collectors in Example 1 and Comparative Example 1. [Modes for carrying out the invention]

[0019] Hereinafter, for facilitating understanding of the present invention, the present invention will be described more comprehensively in connection with specific embodiments. Preferred examples of the present invention are provided in the specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the examples described in the present specification. On the contrary, the purpose of providing these examples is to make the understanding of the disclosure of the present invention more complete and comprehensive.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention pertains. The terms used in the specification of the present invention are merely for describing specific examples and are not intended to limit the present invention.

[0021] In the present specification, the particle size of aluminum particles refers to the median diameter.

[0022] Referring to Figure 1, in one embodiment, a composite current collector 100 includes a polymer-based film 110 and aluminum-plated layers 120 provided on both surfaces of the polymer-based film 110. The aluminum-plated layer 120 includes a first sub-layer 122 and a second sub-layer 124, the first sub-layer 122 is closer to the polymer-based film 110 than the second sub-layer 124 is, the particle size of aluminum particles in the first sub-layer 122 is 10 nm to 30 nm, and the particle size of aluminum particles in the second sub-layer 124 is 80 nm to 100 nm.

[0023] Specifically, the particle size of aluminum particles in the first sub-layer 122 is 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 10 nm to 15 nm, 15 nm to 20 nm, 10 nm to 20 nm, 15 nm to 25 nm, 20 nm to 25 nm, or 25 nm to 30 nm, for example. The particle size of aluminum particles in the second sub-layer 124 is 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, 80 nm to 85 nm, 85 nm to 90 nm, 90 nm to 95 nm, 95 nm to 100 nm, 80 nm to 90 nm, or 85 nm to 95 nm.

[0024] Furthermore, there are multiple first sublayers 122, and these multiple first sublayers 122 are sequentially stacked and arranged between the polymer base film 110 and the second sublayer 124. Moreover, the number of first sublayers 122 is 19 or less. For example, the number of first sublayers 122 is 2, 5, 8, 10, 12, 15, 17, or 19. Preferably, the number of first sublayers 122 is 8 to 12.

[0025] Among these, the thickness of each aluminum plating layer 120 is 5 μm or less. Furthermore, the thickness of each aluminum plating layer 120 is independently between 0.3 μm and 3 μm. For example, the thickness of each aluminum plating layer 120 is independently 0.3 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 0.3 μm to 0.5 μm, 0.5 μm to 1 μm, 1 μm to 1.5 μm, 1.5 μm to 2 μm, 2 μm to 2.5 μm, 2.5 μm to 3 μm, 0.3 μm to 1 μm, 0.5 μm to 1.5 μm, 1 μm to 2 μm, 1.5 μm to 2.5 μm, 2 μm to 3 μm, etc. Furthermore, the aluminum plating layer 120 is provided symmetrically on both surfaces of the polymer base film 110.

[0026] Because the aluminum particles in the first sublayer 122 have a small particle size and high density, it is possible to ensure that the aluminum plating layer 120 has high conductivity. Furthermore, because the aluminum particles in the second sublayer 124 have a large particle size and low density, the surface energy of the outermost layer of the aluminum plating layer 120 is high, which effectively solves the problem of high interfacial resistance of conventional aluminum foils.

[0027] Furthermore, the purity of the aluminum plating layer 120 is 99.8% or higher.

[0028] Specifically, the thickness of the polymer-based film 110 is between 1 μm and 25 μm. For example, the thickness of the polymer-based film 110 can be 1 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 1 μm to 10 μm, 5 μm to 15 μm, 10 μm to 20 μm, 1 μm to 5 μm, 5 μm to 10 μm, 10 μm to 15 μm, 15 μm to 20 μm, 20 μm to 25 μm, etc.

[0029] Specifically, the polymer-based film 110 is at least one selected from polyethylene, polypropylene, polymethylpentene, and polyethylene terephthalate. Because the density of the polymer-based film 110 is low, the density of the composite current collector 100 can be further reduced, thereby improving the energy density of the lithium-ion battery.

[0030] In one embodiment, the peeling force between the aluminum plating layer 120 and the polymer base film 110 is 2 N / m or more.

[0031] Specifically, the thickness of the composite current collector 100 is 3 μm to 30 μm. For example, the thickness of the composite current collector 100 is 3 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 3 μm to 5 μm, 5 μm to 10 μm, 10 μm to 15 μm, 15 μm to 20 μm, 25 μm to 30 μm, 3 μm to 10 μm, 5 μm to 15 μm, 10 μm to 20 μm, 15 μm to 25 μm, or 20 μm to 30 μm. Preferably, the thickness of the composite current collector 100 is 3 μm to 16 μm.

[0032] Furthermore, in this embodiment, the composite current collector 100 is a positive electrode current collector.

[0033] Conventional positive electrode current collectors are made of aluminum foil, which is manufactured by a rolling process. The specific steps are as follows:

[0034] a. The electrolytic aluminum molten material is fed into the smelting furnace, and aluminum ingots equivalent to 20% to 40% of the total weight of the electrolytic aluminum molten material are added. The temperature of the molten material is controlled to 750°C to 780°C, and the mass percentages of each element in the molten material are adjusted to be Si: 0.1% to 0.15%, Fe: 0.45% to 0.5%, Cu: 0.1% to 0.15%, Mn: 1.1% to 1.2%, Ti: 0.02% to 0.04%, with the remainder being Al. The molten material is smelted by blowing a scouring agent onto it with pure nitrogen gas or pure argon gas, and is stirred thoroughly and uniformly for 8 to 10 minutes. After that, it is left to stand for 15 to 25 minutes to remove the dross from the surface of the aluminum molten material, and then placed in a standing furnace, where the temperature inside the standing furnace is controlled to 750°C to 760°C. In a static furnace, aluminum molten material is fed into a trough, and aluminum-titanium-boron filaments are added in the opposite direction to refine the crystal grain. Subsequently, the aluminum molten material is degassed in a degassing box with pure nitrogen gas or pure argon gas. After degassing, the aluminum molten material is filtered and purified using a ceramic foam filter sheet. The purified aluminum molten material is fed into a rolling mill and rolled to produce billets with a thickness of 5.0 mm to 10.0 mm.

[0035] b. The billet obtained in step a is cold-rolled to a thickness of 3.0 mm to 5.0 mm, and then subjected to homogenization annealing. The homogenization annealing temperature is 440°C to 490°C, and the annealing time is 20 to 30 hours.

[0036] c. The homogenized annealed billet is cold-rolled to a thickness of 0.2 mm to 0.6 mm, and then recrystallized annealing is performed. The recrystallized annealing temperature is 270°C to 330°C, and the annealing time is 12 to 19 hours.

[0037] d. The recrystallized annealed billet can be rolled to the required thickness for the anodized aluminum foil.

[0038] The surface energy of the current collector manufactured by the conventional method described above is low, which prevents the active material of the positive electrode from effectively adhering to the current collector when it is applied. Furthermore, the interfacial resistance between the active material and the current collector becomes excessively high, affecting the performance of the battery.

[0039] The composite current collector in this embodiment includes a polymer base film and an aluminum plating layer. The polymer base film is used to support the aluminum plating layer. The aluminum plating layer has a structure consisting of two layers with different particle sizes. The aluminum particles in the first sublayer have a small particle size and high density, ensuring that the aluminum plating layer has high conductivity. The aluminum particles in the second sublayer have a large particle size and low density, resulting in a high surface energy in the outermost layer of the aluminum plating layer, effectively solving the problem of high interfacial resistance of conventional aluminum foils. Therefore, the composite current collector not only has high conductivity but also high surface energy, significantly improving the internal interfacial resistance between the battery electrode and the current collector during the application process of the active substance, thereby improving the capacity and cycle performance of the lithium battery.

[0040] Furthermore, since the aluminum foil produced by conventional rolling processes is limited by the process, it is difficult to manufacture thin aluminum foil. However, in this embodiment, by combining a polymer-based film with an aluminum plating layer, the thickness of the composite current collector can be reduced.

[0041] Specifically, in this embodiment, the surface energy of the surface layer of the composite current collector is greater than 65 dynes / cm, and the conductivity of the aluminum plating layer on one side is 3.7 × 10⁻⁶. 6 The ratio is S / M or higher. The composite current collector has a puncture strength of 50gf or more, a tensile strength MD of 150MPa or more, a tensile strength TD of 150MPa or more, an elongation MD of 10% or more, and an elongation TD of 10% or more. Therefore, the above composite current collector ensures conductivity, improves surface energy, and has good strength and elongation, making it applicable to batteries as a replacement for conventional aluminum foil.

[0042] A method for manufacturing a composite current collector in one embodiment includes the following steps.

[0043] A composite current collector is manufactured by forming aluminum plating layers on both sides of a polymer-based film.

[0044] In this structure, the aluminum plating layer includes a first sublayer and a second sublayer, with the first sublayer being closer to the polymer base film than the second sublayer. The aluminum particle size in the first sublayer is 10 nm to 30 nm, while the aluminum particle size in the second sublayer is 80 nm to 100 nm.

[0045] Specifically, the aluminum plating layer is formed by vacuum deposition or magnetron sputtering. Furthermore, the aluminum plating layer is formed using high-purity aluminum ingots (purity of 99.8% or higher) as the raw material.

[0046] In one embodiment, during the process of forming the aluminum plating layer, the process parameters were: evaporation temperature of 600°C or higher, vacuum level of less than 0.01 Pa, and deposition temperature exceeding 10 m / min. Furthermore, the vacuum level was 0.002 Pa to 0.005 Pa, and the deposition rate was 80 m / min to 120 m / min.

[0047] Furthermore, the evaporation temperature during the formation of the first sublayer is higher than the evaporation temperature during the formation of the second sublayer. By controlling the temperature during the formation of the first and second sublayers, the particle size of the aluminum particles in the first and second sublayers is controlled. Moreover, the evaporation temperature during the formation of the first sublayer is 700°C to 750°C, and the evaporation temperature during the formation of the second sublayer is 600°C to 700°C.

[0048] In some embodiments, there are multiple first sublayers, which are sequentially laminated and arranged between the polymer base film and the second sublayer. Furthermore, the number of first sublayers is 19 or less. For example, the number of first sublayers is 2, 5, 8, 10, 12, 15, 17, or 19. Preferably, the number of first sublayers is 8 to 12.

[0049] Specifically, the thickness of each aluminum plating layer is 5 μm or less. Furthermore, the thickness of each aluminum plating layer is independently between 0.3 μm and 3 μm. For example, the thicknesses of each aluminum plating layer are independently 0.3 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 0.3 μm to 0.5 μm, 0.5 μm to 1 μm, 1 μm to 1.5 μm, 1.5 μm to 2 μm, 2 μm to 2.5 μm, 2.5 μm to 3 μm, 0.3 μm to 1 μm, 0.5 μm to 1.5 μm, 1 μm to 2 μm, 1.5 μm to 2.5 μm, 2 μm to 3 μm, etc. Moreover, the aluminum plating layers are provided symmetrically on both surfaces of the polymer base film 110.

[0050] Specifically, the thickness of the polymer-based film ranges from 1 μm to 25 μm. For example, the thicknesses of the polymer-based film include 1 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 1 μm to 10 μm, 5 μm to 15 μm, 10 μm to 20 μm, 1 μm to 5 μm, 5 μm to 10 μm, 10 μm to 15 μm, 15 μm to 20 μm, and 20 μm to 25 μm.

[0051] Specifically, the polymer-based film is at least one selected from polyethylene, polypropylene, polymethylpentene, and polyethylene terephthalate. Because the density of the polymer-based film is low, the density of the composite current collector 100 can be further reduced, thereby improving the energy density of the lithium-ion battery.

[0052] In one embodiment, the peeling force between the aluminum plating layer and the polymer base film is 2 N / m or more.

[0053] Specifically, the thickness of the composite current collector is 3 μm to 30 μm. For example, the thickness of the composite current collector can be 3 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 3 μm to 5 μm, 5 μm to 10 μm, 10 μm to 15 μm, 15 μm to 20 μm, 25 μm to 30 μm, 3 μm to 10 μm, 5 μm to 15 μm, 10 μm to 20 μm, 15 μm to 25 μm, or 20 μm to 30 μm. Preferably, the thickness of the composite current collector is 3 μm to 16 μm.

[0054] Furthermore, in this embodiment, the composite current collector is a positive electrode current collector.

[0055] Furthermore, the polymer-based film is unwound under an unwinding tension of 5N to 30N. The process further includes a winding step after forming an aluminum plating layer. The winding tension is 5N to 25N.

[0056] The above-described method for manufacturing the composite current collector is simple in process and involves multiple depositions to create a bilayer structure with aluminum plating layers of different particle sizes. The small particle size and high density of the aluminum particles in the first sublayer ensure high conductivity of the aluminum plating layer. The larger particle size and low density of the aluminum particles in the second sublayer result in high surface energy of the aluminum plating layer, effectively solving the problem of high interfacial resistance associated with conventional aluminum foils. Therefore, the composite current collector prepared by this method not only possesses high conductivity but also high surface energy, significantly improving the internal interfacial resistance between the battery electrode and the current collector during the active substance coating process, thereby enhancing the capacity and cycle performance of the lithium battery.

[0057] An electrode piece according to one embodiment includes a current collector which is a composite current collector in the above embodiment, and an active substance coated on both sides of the current collector. Furthermore, the electrode piece is a positive electrode piece. The active substance may be a positive electrode active substance commonly used in this field, and will not be described repeatedly here.

[0058] A secondary battery according to one embodiment includes the electrode piece described above. Specifically, the electrode piece is a positive electrode piece. The secondary battery further includes a negative electrode piece, a separator, and an electrolyte. The specific negative electrode piece, separator, and electrolyte may be those commonly used in the art and will not be described repeatedly here.

[0059] In one embodiment, the secondary battery is a non-aqueous secondary battery, such as a lithium battery. The secondary battery of this embodiment has low interfacial resistance, high capacity, and excellent cycle performance.

[0060] The following is a section detailing a specific example.

[0061] Example 1 This embodiment provides a composite current collector with a thickness of 8 micrometers, comprising a polymer-based PET film with a thickness of 6 micrometers and aluminum plating layers symmetrically provided on both sides of the polymer-based film, with one aluminum plating layer having a thickness of 1 micrometer. The manufacturing process is specifically as follows.

[0062] (1) A polymer-based PET film with a thickness of 6 micrometers and a high-purity aluminum ingot with a purity of 99.9% were selected.

[0063] (2) The polymer-based film and the high-purity aluminum ingot were placed in a vacuum deposition apparatus.

[0064] (3) A high-purity aluminum ingot was plated with aluminum onto two surfaces, the upper and lower, of a polymer base film using a vacuum deposition apparatus to obtain an aluminum plating layer. The unwinding tension of the polymer base film was 8N. The aluminum plating layer on one side required 16 depositions. First, 15 depositions were made to obtain 15 first sublayers, each with an aluminum particle size of 20nm. Then, the 16th deposition was made to obtain a second sublayer, with an aluminum particle size of 85nm. The process parameters during the deposition process were a vacuum of 5 × 10⁻⁶. -2The pressure was Pa and the evaporation rate was 50 m / min. The evaporation temperature for the first 15 cycles was 700°C, and the evaporation temperature for the 16th cycle was 620°C.

[0065] (4) After the vapor deposition was completed, a winding operation was performed, and the winding tension was 6N, thus obtaining the composite current collector of this embodiment.

[0066] Example 2 This embodiment provides a composite current collector with a thickness of 8 micrometers, comprising a polymer-based PET film with a thickness of 6 micrometers and aluminum plating layers symmetrically provided on both sides of the polymer-based film, with one aluminum plating layer having a thickness of 1 micrometer. The manufacturing process is specifically as follows.

[0067] (1) A polymer-based PET film with a thickness of 6 micrometers and a high-purity aluminum ingot with a purity of 99.9% were selected.

[0068] (2) The polymer-based film and the high-purity aluminum ingot were placed in a vacuum deposition apparatus.

[0069] (3) A high-purity aluminum ingot was plated with aluminum onto two surfaces, the upper and lower, of a polymer base film using a vacuum deposition apparatus to obtain an aluminum plating layer. The unwinding tension of the polymer base film was 8N. The aluminum plating layer on one side required two depositions. The first deposition yielded the first sublayer, with an aluminum particle size of 20nm, and the second deposition yielded the second sublayer, with an aluminum particle size of 85nm. The process parameters during the deposition process were a vacuum of 5 × 10⁻⁶. -2 The pressure is Pa and the evaporation rate is 50 m / min. The first evaporation temperature is 700°C, and the second evaporation temperature is 620°C.

[0070] (4) After the vapor deposition was completed, a winding operation was performed, and the winding tension was 6N, thus obtaining the composite current collector of this embodiment.

[0071] Example 3 This embodiment provides a composite current collector with a thickness of 8 micrometers, comprising a polymer-based PET film with a thickness of 6 micrometers and aluminum plating layers symmetrically provided on both sides of the polymer-based film, with one aluminum plating layer having a thickness of 1 micrometer. The manufacturing process is specifically as follows.

[0072] (1) A polymer-based PET film with a thickness of 6 micrometers and a high-purity aluminum ingot with a purity of 99.9% were selected.

[0073] (2) The polymer-based film and the high-purity aluminum ingot were placed in a vacuum deposition apparatus.

[0074] (3) A high-purity aluminum ingot was plated with aluminum onto two surfaces, the upper and lower, of a polymer base film using a vacuum deposition apparatus to obtain an aluminum plating layer. The unwinding tension of the polymer base film was 8N. The aluminum plating layer on one side required 16 depositions. First, 15 depositions were performed to obtain 15 first sublayers, each with an aluminum particle size of 10nm. Then, the 16th deposition was performed to obtain a second sublayer, each with an aluminum particle size of 100nm. The process parameters during the deposition process were a vacuum of 5 × 10⁻⁶. -2 The pressure was Pa and the evaporation rate was 50 m / min. The evaporation temperature for the first 15 cycles was 740°C, and the evaporation temperature for the 16th cycle was 650°C.

[0075] (4) After the vapor deposition was completed, a winding operation was performed, and the winding tension was 6N, thus obtaining the composite current collector of this embodiment.

[0076] Comparative Example 1 Comparative Example 1 provides a conventional aluminum foil positive electrode current collector with a manufacturing thickness of 8 micrometers. The manufacturing process is specifically as follows.

[0077] (1) The electrolytic aluminum molten material was fed into a smelting furnace, and aluminum ingots equivalent to 30% of the total weight of the electrolytic aluminum molten material were added, controlling the molten material temperature to 770°C. The mass percentages of each element in the molten material were adjusted to be Si: 0.15%, Fe: 0.48%, Cu: 0.13%, Mn: 1.3%, Ti: 0.03%, with the remainder being Al. The molten material was refined by blowing a scouring agent onto it with pure nitrogen gas or pure argon gas, stirring thoroughly and uniformly for 9 minutes. After that, it was left to stand for 20 minutes to remove the dross from the surface of the aluminum molten material, and then placed in a standing furnace, where the temperature was controlled to 755°C. The aluminum molten material in the standing furnace was fed into a trough, and aluminum titanium boron filaments were added in the opposite direction to refine the crystal grain. After that, the aluminum molten material was degassed in a degassing box with pure nitrogen gas or pure argon gas. After degassing, the aluminum liquid was filtered and purified using a ceramic foam filter sheet. The purified aluminum liquid was then fed into a rolling mill and rolled to produce billets with a thickness of 4.0 mm.

[0078] (2) The billet obtained in step (1) is cold-rolled to a thickness of 4.0 mm, and then homogenized annealing is performed at a temperature of 470°C for a duration of 25 hours.

[0079] (3) The homogenized annealed billet is cold-rolled to a thickness of 0.5 mm, and then recrystallized annealing is performed at a temperature of 300°C for a duration of 15 hours.

[0080] (4) The recrystallized annealed billet was rolled into an 8-micrometer aluminum foil to obtain the current collector of Comparative Example 1.

[0081] Comparative Example 2 Comparative Example 2 provides a composite current collector with a thickness of 8 micrometers, comprising a polymer-based PET film with a thickness of 6 micrometers and aluminum plating layers symmetrically provided on both sides of the polymer-based film, with one aluminum plating layer having a thickness of 1 micrometer. The manufacturing process is specifically as follows.

[0082] (1) A polymer-based PET film with a thickness of 6 micrometers and a high-purity aluminum ingot with a purity of 99.9% were selected.

[0083] (2) The polymer-based film and the high-purity aluminum ingot were placed in a vacuum deposition apparatus.

[0084] (3) A high-purity aluminum ingot was plated with aluminum onto two surfaces, the top and bottom, of a polymer base film using a vacuum deposition apparatus to obtain an aluminum plating layer. The unwinding tension of the polymer base film was 8N. The aluminum plating layer on one side required 16 depositions. The particle size of the aluminum particles in each layer obtained was 20nm. The process parameters during the deposition process were an evaporation temperature of 700°C and a vacuum of 5 × 10⁻⁶. -2 The pressure is Pa, and the deposition rate is 50 m / min.

[0085] (4) After the vapor deposition was completed, a winding operation was performed, and the winding tension was 6N, obtaining the composite current collector of Comparative Example 2.

[0086] Comparative Example 3 Comparative Example 3 provides a composite current collector with a thickness of 8 micrometers, comprising a polymer-based film PP with a thickness of 6 micrometers and aluminum plating layers symmetrically provided on both sides of the polymer-based film, with one aluminum plating layer having a thickness of 1 micrometer. The manufacturing process is specifically as follows.

[0087] (1) A polymer-based PET film with a thickness of 6 micrometers and a high-purity aluminum ingot with a purity of 99.9% were selected.

[0088] (2) The polymer-based film and the high-purity aluminum ingot were placed in a vacuum deposition apparatus.

[0089] (3) A high-purity aluminum ingot was plated with aluminum onto two surfaces, the top and bottom, of a polymer base film using a vacuum deposition apparatus to obtain an aluminum plating layer. The unwinding tension of the polymer base film was 8N. One side of the aluminum plating layer required 16 depositions. The particle size of the aluminum particles in each layer obtained was 85nm. The process parameters during the deposition process were an evaporation temperature of 620°C and a vacuum of 5 × 10⁻⁶. -2 The pressure is Pa, and the deposition rate is 50 m / min.

[0090] (4) After the vapor deposition was completed, a winding operation was performed, and the winding tension was 6N, obtaining the composite current collector of Comparative Example 3.

[0091] Comparative Example 4 Comparative Example 4 provides a composite current collector with a thickness of 8 micrometers, comprising a polymer-based PET film with a thickness of 6 micrometers and aluminum plating layers symmetrically provided on both sides of the polymer-based film, with one aluminum plating layer having a thickness of 1 micrometer. The manufacturing process is specifically as follows.

[0092] (1) A polymer-based PET film with a thickness of 6 micrometers and a high-purity aluminum ingot with a purity of 99.9% were selected.

[0093] (2) The polymer-based film and the high-purity aluminum ingot were placed in a vacuum deposition apparatus.

[0094] (3) A high-purity aluminum ingot was plated with aluminum onto two surfaces, the upper and lower, of a polymer base film using a vacuum deposition apparatus to obtain an aluminum plating layer. The unwinding tension of the polymer base film was 8N. The aluminum plating layer on one side required 16 depositions. First, 15 depositions were made to obtain 15 first sublayers, each with an aluminum particle size of 85nm. Then, the 16th deposition was made to obtain a second sublayer, each with an aluminum particle size of 20nm. The process parameters during the deposition process were a vacuum of 5 × 10⁻⁶. -2The pressure was Pa and the evaporation rate was 50 m / min. The evaporation temperature for the first 15 cycles was 620°C, and the evaporation temperature for the 16th cycle was 700°C.

[0095] (4) After the vapor deposition was completed, the winding operation was performed, and the winding tension was 6N, obtaining the composite current collector of Comparative Example 4.

[0096] Comparative Example 5 Comparative Example 5 provides a composite current collector with a thickness of 8 micrometers, comprising a polymer-based PET film with a thickness of 6 micrometers and aluminum plating layers symmetrically provided on both sides of the polymer-based film, with one aluminum plating layer having a thickness of 1 micrometer. The manufacturing process is specifically as follows.

[0097] (1) A polymer-based PET film with a thickness of 6 micrometers and a high-purity aluminum ingot with a purity of 99.9% were selected.

[0098] (2) The polymer-based film and the high-purity aluminum ingot were placed in a vacuum deposition apparatus.

[0099] (3) A high-purity aluminum ingot was plated with aluminum onto two surfaces, the upper and lower, of a polymer base film using a vacuum deposition apparatus to obtain an aluminum plating layer. The unwinding tension of the polymer base film was 8N. The aluminum plating layer on one side required 16 depositions. First, 15 depositions were performed to obtain 15 first sublayers, each with an aluminum particle size of 50nm. Then, the 16th deposition was performed to obtain a second sublayer, with an aluminum particle size of 85nm. The process parameters during the deposition process were a vacuum of 5 × 10⁻⁶. -2 The pressure was Pa and the evaporation rate was 50 m / min. The evaporation temperature for the first 15 cycles was 720°C, and the evaporation temperature for the 16th cycle was 620°C.

[0100] (4) After the vapor deposition was completed, a winding operation was performed, and the winding tension was 6N, obtaining the composite current collector of Comparative Example 5.

[0101] Comparative Example 6 Comparative Example 6 provides a composite current collector with a thickness of 8 micrometers, comprising a polymer-based PET film with a thickness of 6 micrometers, and aluminum plating layers symmetrically disposed on both sides of the polymer-based film, wherein the thickness of the aluminum plating layer on one side is 1 micrometer. The manufacturing process is specifically as follows.

[0102] (1) A polymer-based PET film with a thickness of 6 micrometers and a high-purity aluminum ingot with a purity of 99.9% were selected.

[0103] (2) The polymer-based film and the high-purity aluminum ingot were respectively charged into a vacuum vapor deposition apparatus.

[0104] (3) Aluminum from the high-purity aluminum ingot was plated on the upper and lower two surfaces of the polymer-based film by the vacuum vapor deposition apparatus to obtain aluminum plating layers. Wherein, the unwinding tension of the polymer-based film is 8 N. The aluminum plating layer on one side requires 16 times of vapor deposition. Wherein, 15 times of vapor deposition are performed first to obtain 15 first sub-layers, the particle size of aluminum particles in each first sub-layer is 20 nm; the 16th time of vapor deposition is performed to obtain a second sub-layer, and the particle size of aluminum particles in the second sub-layer is 120 nm. The process parameters in the vapor deposition process are a vacuum degree of 5×10 -2 Pa, and a vapor deposition rate of 50 m / min. The evaporation temperature for the first 15 times is 700°C, and the evaporation temperature for the 16th time is 600°C.

[0105] (4) After the vapor deposition is completed, a winding operation is performed with a winding tension of 6 N, and the composite current collector of Comparative Example 6 is obtained.

[0106] The performance of the composite current collectors obtained in the above examples and comparative examples was tested, and the test results shown in Table 1 below were obtained. Among these, the conductivity of one side of the aluminum plating layer was tested using a 4-probe measuring instrument, and the surface energy of the aluminum plating layer was tested using a Dyne Pen. A positive electrode piece was obtained by combining the composite current collector with a positive electrode active material, and assembled as a lithium battery together with a negative electrode piece, electrolyte, and separator, and the internal resistance and capacity retention rate after 1000 cycles of the lithium battery (capacity 50Ah) were measured. The results of the internal resistance of lithium batteries manufactured using the current collectors of Example 1 and Comparative Example 1 are shown in Figure 2.

[0107] [Table 1]

[0108] As can be seen from the experimental data above, by using the composite current collector in the example, it is possible to improve surface energy while maintaining conductivity, further improve the battery's capacity retention rate, and reduce internal resistance.

[0109] The technical features of the embodiments described above can be combined in any way. For the sake of simplicity, not all possible combinations of the technical features in each embodiment described above are described, but as long as the combination of these technical features is inconsistent, they should all be considered to be within the scope described herein.

[0110] The above embodiments are merely illustrative of some embodiments of the present invention and are intended to provide a concrete and detailed understanding of the technical proposal of the present invention, but should be understood not to limit the scope of the present invention. Those skilled in the art should point out that several modifications and improvements can be made without departing from the concept of the present invention, and all of these fall within the scope of protection of the present invention. Those skilled in the art should understand that any technical proposal obtained by logical analysis, estimation, or finite testing based on the technical proposal according to the present invention falls within the scope of the claims of the present invention. Therefore, the scope of protection of the present invention is in accordance with the claims, and the specification and drawings are used to interpret the contents described in the claims.

[0111] (Note) (Note 1) The material comprises a polymer-based film and aluminum plating layers provided on both surfaces of the polymer-based film. The aluminum plating layer comprises a first sublayer and a second sublayer, wherein the first sublayer is closer to the polymer base film than the second sublayer, the particle size of the aluminum particles in the first sublayer is 10 nm to 30 nm, and the particle size of the aluminum particles in the second sublayer is 80 nm to 100 nm. A composite current collector characterized by the following features.

[0112] (Note 2) The thickness of each aluminum plating layer is independently 0.3 μm to 3 μm. A composite current collector as described in Appendix 1, characterized by the features described herein.

[0113] (Note 3) The first sublayer consists of multiple layers, which are sequentially stacked and arranged between the polymer base film and the second sublayer. A composite current collector as described in Appendix 1, characterized by the features described herein.

[0114] (Note 4) The number of the first sublayers is 19 or less. A composite current collector as described in Appendix 3, characterized by the features described herein.

[0115] (Note 5) The thickness of the polymer-based film is 1 μm to 25 μm. A composite current collector as described in any one of the appendices 1 to 4, characterized by the features described herein.

[0116] (Note 6) The polymer-based film is at least one selected from polyethylene, polypropylene, polymethylpentene, and polyethylene terephthalate. A composite current collector as described in any one of the appendices 1 to 4, characterized by the features described herein.

[0117] (Note 7) A method for manufacturing a composite current collector, comprising the step of forming an aluminum plating layer on both surfaces of a polymer base film to manufacture a composite current collector, The aluminum plating layer comprises a first sublayer and a second sublayer, wherein the first sublayer is closer to the polymer base film than the second sublayer, the particle size of the aluminum particles in the first sublayer is 10 nm to 30 nm, and the particle size of the aluminum particles in the second sublayer is 80 nm to 100 nm. A method for manufacturing a composite current collector, characterized by the above.

[0118] (Note 8) The aluminum plating layer is formed by vacuum deposition or magnetron sputtering. A method for manufacturing a composite current collector as described in Appendix 7, characterized by the features described herein.

[0119] (Note 9) In the process of forming the aluminum plating layer, the process parameters are such that the evaporation temperature is 600°C or higher, the vacuum level is less than 0.01 Pa, the plating rate is greater than 10 m / min, and the evaporation temperature for forming the first sublayer is greater than the evaporation temperature for forming the second sublayer. A method for manufacturing a composite current collector as described in Appendix 8, characterized by the features described above.

[0120] (Note 10) The evaporation temperature for forming the first sublayer is 700°C to 750°C, and the evaporation temperature for forming the second sublayer is 600°C to 700°C. A method for manufacturing a composite current collector as described in Appendix 9, characterized by the features described therein.

[0121] (Note 11) A current collector comprising a composite current collector manufactured by any one of the composite current collectors described in Appendix 1 to 6 or by any one of the composite current collector manufacturing methods described in Appendix 7 to 10, and an active material coated on both sides of the current collector, An electrode piece characterized by the following features.

[0122] (Note 12) Including the electrode piece described in Appendix 11, A secondary battery characterized by the following features.

Claims

1. The material comprises a polymer-based film and aluminum plating layers provided on both surfaces of the polymer-based film. The aluminum plating layer comprises a first sublayer and a second sublayer, wherein the first sublayer is closer to the polymer base film than the second sublayer, the particle size of the aluminum particles in the first sublayer is 10 nm to 30 nm, and the particle size of the aluminum particles in the second sublayer is 80 nm to 100 nm. A composite current collector characterized by the following features.

2. The thickness of each aluminum plating layer is independently 0.3 μm to 3 μm. The composite current collector according to feature 1.

3. The first sublayer is comprised of multiple layers, and these multiple first sublayers are sequentially stacked and arranged between the polymer base film and the second sublayer. The composite current collector according to feature 1.

4. The number of the first sublayers is 19 or less. The composite current collector according to feature 3.

5. The thickness of the polymer-based film is 1 μm to 25 μm. A composite current collector according to any one of claims 1 to 4.

6. The polymer-based film is at least one selected from polyethylene, polypropylene, polymethylpentene, and polyethylene terephthalate. A composite current collector according to any one of claims 1 to 4.

7. A method for manufacturing a composite current collector, comprising the step of forming an aluminum plating layer on both surfaces of a polymer base film to manufacture a composite current collector, The aluminum plating layer comprises a first sublayer and a second sublayer, wherein the first sublayer is closer to the polymer base film than the second sublayer, the particle size of the aluminum particles in the first sublayer is 10 nm to 30 nm, and the particle size of the aluminum particles in the second sublayer is 80 nm to 100 nm. A method for manufacturing a composite current collector, characterized by the above.

8. The aluminum plating layer is formed by vacuum deposition or magnetron sputtering. A method for manufacturing a composite current collector according to feature 7.

9. A current collector which is a composite current collector as described in claim 1, and an active material coated on both sides of the current collector, An electrode piece characterized by the following features.

10. Including the electrode piece described in claim 9, A secondary battery characterized by the following features.

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