Multilayer current collector and method for producing same

Abstract

The present invention relates to a multi-layered current collector and a manufacturing method thereof. The multi-layered current collector includes a thin polymer layer, and a laminate is provided on each of two opposite surfaces of the thin polymer layer, and the laminate includes a carbon coating layer and a metal plating layer that are alternately provided on each other.

Description

[Technical field]

[0001] The present invention relates to the technical field of secondary batteries, and in particular to a multi-layered current collector and a method for manufacturing the same. [Background technology]

[0002] Current collectors are mainly of two types: copper collectors and aluminum collectors. Both the copper collectors and aluminum collectors are composed of two parts, including a polymer thin film layer in the middle and a metal plating layer on the two surfaces opposite the polymer thin film layer. The current collector is manufactured by a vacuum deposition process, and the thickness of the first deposition plating layer in the current deposition process is between 32nm and 500nm. However, as the number of metal plating layers increases, the increase in thickness of the metal plating layer in each subsequent layer becomes smaller and smaller. To achieve a certain number of layers, the required thickness can be achieved by continuously depositing the polymer thin film layer 15 to 20 times, but after the metal plating layer is repeatedly deposited, many voids exist inside, so the porosity of the metal plating layer is as high as 30%. The existence of these voids reduces the current passing area of ​​the metal plating layer, affecting the transport of electrons, and increases the sheet resistance inside the metal plating layer, increasing the polarization of the battery and seriously affecting the battery performance. At the same time, after multiple depositions, the intermediate polymer thin film layer undergoes tens of rounds of quenching and heating, which causes the mechanical properties of the polymer thin film layer to decay quickly, resulting in a relatively large decay in both the tensile strength and elongation of the multi-layered current collector. Summary of the Invention [Problem to be solved by the invention]

[0003] As a result, the number of times of deposition of the metal plating layer and the polymer thin film layer can be reduced, the attenuation of the mechanical performance of the polymer thin film layer can be reduced, and the battery performance can be effectively ensured, thereby providing a multilayer structure current collector and a manufacturing method thereof that can effectively improve the mechanical performance and electrical conductivity of the product. [Means for solving the problem]

[0004] A multilayer current collector comprising a polymer thin film layer having a laminate provided on each of two opposite surfaces of the polymer thin film layer, the laminate including a carbon coating layer and a metal plating layer that are alternately laminated, wherein an outermost layer and an innermost layer of the laminate are both the carbon coating layer, and a thickness ratio of any one of the carbon coating layers to an adjacent metal plating layer is 3:1 to 2:1.

[0005] In some embodiments, the stack includes two or more carbon coating layers, wherein any two carbon coating layers may have similar or different thicknesses.

[0006] In some embodiments, the laminate comprises one or more metal plating layers, hi some embodiments, the laminate comprises two or more metal plating layers, wherein any two metal plating layers may have similar or different thicknesses.

[0007] In some embodiments, the carbon coating layer comprises at least one of carbon black, carbon nanotubes, graphite, acetylene black, and graphene.

[0008] In some embodiments, the metal plating layer is an aluminum metal layer or a copper metal layer.

[0009] In some embodiments, the purity of both the metal plating layer and the carbon coating layer is 99.8% or higher.

[0010] In some embodiments, the polymeric thin film layer comprises at least one of an insulating polymeric material, an insulating polymeric composite material, a conductive polymeric material, or a conductive polymeric composite material.

[0011] In some embodiments, the polymer thin film layer has a thickness ranging from 1 μm to 25 μm, any one of the metal plating layers has a thickness ranging from 50 nm to 130 nm, and any one of the carbon coating layers has a thickness ranging from 150 nm to 260 nm.

[0012] The present application provides a method for producing the above-mentioned multilayer current collector, comprising the steps of: forming the laminate by alternately providing the carbon coating layer and the metal plating layer on two opposite surfaces of the polymer thin film layer, The present invention further provides a method for producing a multi-layer current collector, wherein both the outermost layer and the innermost layer of the laminate are the carbon coating layer.

[0013] In some embodiments, the innermost carbon coating layer directly contacts the surface of the polymeric thin film layer.

[0014] In some embodiments, the method for providing the carbon coating layer on the two opposing surfaces of the polymer thin film layer and the surface of the metal plating layer employs sputtering.

[0015] In some embodiments, the method for applying the carbon coating layer to the two opposing surfaces of the polymeric thin film layer and the surface of the metal plating layer employs evaporation.

[0016] In some embodiments, the evaporation temperature is 500 to 900°C when the metal plating layer is deposited, and the evaporation temperature is 900 to 1200°C when the carbon coating layer is deposited. Effect of the Invention

[0017] In the above-mentioned embodiment, the laminate is provided on each of the two opposite surfaces of the polymer thin film layer, and the thickness ratio of any one of the carbon coating layers to the adjacent metal plating layer is 3:1 to 2:1, so that the number of depositions of the metal plating layer and the polymer thin film layer can be effectively reduced, the porosity and sheet resistance of the product can be effectively reduced, and the battery performance can be effectively ensured, and the attenuation of the mechanical performance of the polymer thin film layer can be reduced, so that the attenuation of the mechanical performance of the product can be reduced. At the same time, the carbon coating layer has good electrical conductivity and high mechanical performance and chemical stability, so that the mechanical performance, electrical conductivity and corrosion resistance of the product can be effectively improved. By providing the carbon coating layer on each of the two opposite surfaces of the polymer thin film layer, it can play a protective role for the polymer thin film layer. By making the outermost layer of the laminate a carbon coating layer, it is possible to effectively reduce the interface resistance between the multi-layered current collector and the active material and effectively improve the adhesion. [Brief description of the drawings]

[0018] The drawings constituting a part of this application are used to provide a further understanding of the present invention, and the illustrative embodiments of the present invention and the description thereof are intended to interpret the present invention and are not intended to unduly limit the present application.

[0019] In order to more clearly describe the technical solutions in the embodiments of the present invention, the drawings that need to be used in the description of the embodiments are briefly described below. The drawings in the following description are some embodiments of the present invention, and it is obvious to those skilled in the art that they can obtain other drawings according to these drawings without paying creative labor.

[0020] [Figure 1] FIG. 2 is a structural schematic diagram of a multi-layer current collector according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] In order to more clearly explain the above objects, features and advantages of the present invention, the following detailed description of the specific embodiment of the present invention will be given with reference to the drawings. In order to fully understand the present invention, many specific details are described in the following description. However, the present invention is not limited by the specific examples disclosed below, since the present invention can be implemented in other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the spirit of the present invention.

[0022] In the description of the present invention, the orientations and positional relationships indicated by terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like are based on the orientations and positional relationships shown in the drawings, and are merely intended to facilitate and simplify the description of the present application, and are not intended to indicate or suggest that the devices or elements mentioned have a specific orientation and must be configured and operated in a specific orientation. Therefore, they should not be understood to limit the present invention.

[0023] Additionally, the terms "first" and "second" are merely descriptive and should not be understood as implicitly indicating the number of the designated technical features, indicating or suggesting their relative importance. Thus, a feature qualified as "first" or "second" may explicitly or implicitly include at least one of the feature. In the description of the present invention, "plurality" means at least two, e.g., two, three, etc., unless otherwise limited.

[0024] In the description of the present invention, the terms "attached", "connected", "connected" and "fixed" should be understood in a broad sense unless otherwise clearly specified or limited. For example, they may be fixedly connected, detachably connected or integral, mechanically connected, electrically connected, directly connected, indirectly connected via an intermediate medium, or communicated inside two parts or interacting with each other. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific situation.

[0025] In the present invention, unless otherwise clearly specified or limited, a first feature being "above" or "below" a second feature may mean that the first feature and the second feature are in direct contact with each other, or that the first feature and the second feature are in indirect contact with each other via an intermediate medium. Furthermore, a first feature being "above," "above," and "on the upper surface" of a second feature means that the first feature may be directly above and diagonally above the second feature, or simply that the first feature is higher in horizontal height than the second feature. A first feature being "below," "below," and "on the lower surface" of a second feature means that the first feature may be directly below and diagonally below the second feature, or simply that the first feature is lower in horizontal height than the second feature.

[0026] It should be noted that when an element is referred to as being "fixed" or "mounted" on another element, the element may be directly on the other element, or there may be intervening elements present. When an element is referred to as being "connected" to another element, it may be directly connected to the other element, or there may be intervening elements present at the same time. As used herein, the terms "vertical," "horizontal," "top," "bottom," "left," "right," and similar terms are merely for descriptive purposes and do not represent the only embodiments.

[0027] Referring to FIG. 1, one embodiment of the present invention provides a multi-layered current collector 10 including a polymer thin film layer 100 having a laminate on each of two opposite surfaces of the polymer thin film layer 100, and the laminate includes a carbon coating layer 200 and a metal plating layer 300 that are alternately laminated. Specifically, the outermost layer and the innermost layer of the laminate are both carbon coating layers 200. By providing the carbon coating layer 200 on the two opposite surfaces of the polymer thin film layer 100, the polymer thin film layer 100 can be protected. By using the carbon coating layer 200 as the outermost layer of the laminate, the interfacial resistance between the multi-layered current collector 10 and the active material can be effectively reduced and the adhesive strength can be effectively improved.

[0028] Specifically, the thickness ratio between any one of the carbon coating layers 200 and the adjacent metal plating layer 300 is 3:1 to 2:1.

[0029] The carbon coating layer 200 and the metal plating layer 300 are alternately provided on two opposite surfaces of the polymer thin film layer 100, and the thickness ratio between any one of the carbon coating layers 200 and the adjacent metal plating layer 300 is 3:1 to 2:1, thereby effectively reducing the number of depositions of the metal plating layer 300, reducing the voids inside the metal plating layer 300, effectively reducing the porosity of the metal plating layer 300 and the sheet resistance inside the metal plating layer 300, effectively reducing the porosity and sheet resistance of the product, and effectively ensuring the battery performance. At the same time, the number of depositions of the polymer thin film layer 100 is effectively reduced, reducing the attenuation of the mechanical performance of the polymer thin film layer 100, thereby reducing the attenuation of the mechanical performance of the product. In addition, the carbon coating layer 200 has good electrical conductivity and high mechanical performance and chemical stability, so that the mechanical performance, electrical conductivity and corrosion resistance of the product can be effectively improved.

[0030] The multilayered current collector 10 has a puncture strength of 50 gf or more, an MD stretch strength of 150 MPa or more, a TD stretch strength of 150 MPa or more, an MD elongation rate of 10% or more, and a TD elongation rate of 10% or more. Exemplarily, the multilayered current collector 10 has a puncture strength of 80 gf, an MD elongation strength of 280 MPa, and a TD elongation strength of 280 MPa. The MD elongation rate is 60% and the TD elongation rate is 60%. Note that MD (Machine Direction) refers to the vertical direction, and TD (Transverse Direction, perpendicular to the mechanical direction) refers to the horizontal direction.

[0031] Referring to FIG. 1, according to some embodiments of the present application, the carbon coating layer 200 preferably includes at least one of carbon black, carbon nanotubes, graphite, acetylene black, and graphene. Specifically, carbon black has good electrical conductivity, mechanical performance, and thermal conductivity. Carbon nanotubes have good mechanical performance, high electrical conductivity, and high thermal conductivity. Graphite has good mechanical performance, high temperature resistance, high electrical conductivity, good thermal conductivity, high chemical stability, thermal shock resistance, plasticity, and other performances. Acetylene black has good mechanical performance, extremely low resistivity, and excellent electrical conductivity, thermal conductivity, and antistatic effect. Graphene has good electrical conductivity, extremely good thermal conductivity, and other performances.

[0032] Referring to FIG. 1, according to some embodiments of the present application, the metal plating layer 300 is preferably an aluminum metal layer or a copper metal layer. Specifically, the purity of the metal layer 300 is 99.8% or more. That is, the metal layer 300 in the present application adopts a high-purity metal. In one embodiment, the metal layer adopts an aluminum metal layer, and the purity of the aluminum metal layer is 99.8% or more. High-purity aluminum metal has properties such as low deformation resistance, high electrical conductivity, and good plasticity. In another embodiment, the metal layer adopts a copper metal layer, and the purity of the copper metal layer is 99.8% or more. High-purity copper metal has properties such as good ductility, thermal conductivity, and electrical conductivity.

[0033] 1, according to some embodiments of the present application, the purity of the carbon coating layer 200 is preferably 99.8% or more. The high purity carbon coating layer 200 has high mechanical properties, high chemical stability, high electrical conductivity, a dense and uniform structure, good wear resistance, low resistivity, etc.

[0034] The peel strength between the carbon coating layer 200 and the polymer thin film layer 100 is 3 N / m or more. Exemplarily, the peel strength between the carbon coating layer 200 and the polymer thin film layer 100 is 5 N / m. Since the peel strength between the carbon coating layer 200 and the polymer thin film layer 100 is high, the peel strength between the carbon coating layer 200 and the polymer thin film layer 100 can be reinforced, and the falling off phenomenon between the carbon coating layer 200 and the polymer thin film layer 100 is unlikely to occur, thereby ensuring the electrical performance and safety of the battery.

[0035] Referring to FIG. 1, according to some embodiments of the present application, the polymer thin film layer 100 preferably includes at least one of an insulating polymer material, an insulating polymer composite material, a conductive polymer material, and a conductive polymer composite material. The polymer thin film layer 100 has a pin puncture strength of 100 gf or more, an MD elongation strength of 200 MPa or more, and a TD elongation strength of 200 MPa or more. The MD elongation is 30% or more, and the TD elongation is 30% or more. Exemplarily, the polymer thin film layer 100 has a pin puncture strength of 180 gf, an MD elongation strength of 500 MPa, and a TD elongation strength of 500 MPa. The MD elongation is 130% and the TD elongation is 130%.

[0036] Specifically, the insulating polymer material includes at least one of polyamide (PA), polyterephthalate, polyimide (PI), polyethylene (PE), polypropylene (PP), polystyrene (PPE), polyvinyl chloride (PVC), aramid, acrylonitrile-butadiene-styrene copolymer (ABS), polybutylene terephthalate (PET), polyparaphenylene terephthalamide (PPTA), polypropylene (PPE), polyoxymethylene (POM), epoxy resin, phenolic resin, polytetrafluoroethylene (PTEE), polyvinylidene fluoride (PVDF), silicone rubber, polycarbonate (PC), polyvinyl alcohol (PVA), polyethylene glycol (PEG), cellulose, starch, protein, derivatives thereof, crosslinked bodies thereof, and copolymers thereof.

[0037] The insulating polymer composite material may be a composite material made of an insulating polymer material and an inorganic material, in which the inorganic material may be at least one of a ceramic material, a glass material, and a ceramic composite material.

[0038] The conductive polymer material may be at least one of doped polythiazyl and doped polyacetylene.

[0039] The conductive polymer composite material may be a composite material made of an insulating polymer material and a conductive material. Specifically, the conductive material may be at least one of a conductive carbon material, a metal material, and a composite conductive material. More specifically, the conductive carbon material is at least one selected from carbon black, carbon nanotubes, graphite, acetylene black, and graphene. The metal material is at least one selected from metallic nickel, metallic iron, metallic copper, metallic aluminum, or an alloy of the above metals. The composite conductive material is at least one selected from graphite powder coated with metallic nickel and carbon fiber coated with metallic nickel.

[0040] Referring to FIG. 1, according to some embodiments of the present application, the thickness range of the polymer thin film layer 100 is preferably 1 μm to 25 μm, the thickness range of the metal plating layer 300 is preferably 32 nm to 500 nm, and the thickness range of the carbon coating layer 200 is preferably 140 nm to 1000 nm. Preferably, the thickness range of the metal plating layer 300 is 50 nm to 130 nm, and the thickness range of the carbon coating layer 200 is preferably 150 nm to 260 nm. The thickness range of the multilayered current collector 10 of the present application is preferably 3 μm to 30 μm. Exemplarily, the thickness of the polymer thin film layer 100 is 20 μm, and the thickness of any one of the metal plating layers 300 is 60 nm. The thickness of any one of the carbon coating layers 200 is 160 nm.

[0041] Working Example: The following examples are provided to more specifically describe the contents disclosed in the present invention, and these examples are provided for descriptive purposes only, and it is obvious to those skilled in the art that various modifications and changes may be made within the scope of the contents disclosed in the present invention. Unless otherwise specified, the parts, percentages and ratios described in the following examples are all based on weight, and all reagents used in the examples are all commercially available or can be synthesized by conventional methods, and can be used as is without the need for further treatment. In addition, all equipment used in the examples are commercially available.

[0042] Example 1 An embodiment of the present application further provides a method for manufacturing the above-mentioned multi-layered current collector 10, which includes the following steps.

[0043] Step 1: Select a 6 μm polymer thin film layer 100, a 99.9% pure aluminum metal layer, and a 99.9% pure graphite layer, in which the polymer thin film layer 100 is made of polybutylene terephthalate (PET).

[0044] Step 2: Alternating layers of 99.9% pure graphite and 99.9% pure metallic aluminum were deposited on two opposing surfaces of the polymer thin film layer 100 until a set thickness was reached, forming a laminate.

[0045] The outermost layer and the innermost layer of the laminate are both carbon coating layers 200. That is, graphite is deposited on two opposite surfaces of the polymer thin film layer 100, and the outermost layer of the laminate is graphite. The set thickness is 8 μm. The metallic aluminum layer is two layers, and the graphite is three layers. That is, in this embodiment, the thickness of each metal plating layer 300 is 125 nm. The thickness of each carbon coating layer 200 is 250 nm. Since the metallic aluminum layer is two layers and the graphite is three layers, in order to manufacture a multi-layered current collector 10 of 8 μm, a total of 10 layers of structures need to be deposited on the polymer thin film layer 100, that is, the polymer thin film layer 100 undergoes 10 deposition processes. After the innermost carbon coating layer 200 is deposited on the two opposite surfaces of the polymer thin film layer, a complete multi-layered current collector 10 can be manufactured by depositing an additional 8-layer structure. That is, after the manufacture of the innermost carbon coating layer 200 in contact with the polymer thin film layer 100 is completed, eight more depositions are performed. After the manufacture of the metal plating layer 300 close to the polymer thin film layer 100 is completed, a further six layers are deposited to form a complete multi-layered current collector 10. That is, after the manufacture of the metal plating layer 300 close to the polymer thin film layer 100 is completed, six more depositions are performed. The deposition of the metal plating layer 300 and the carbon coating layer 200 is repeated in sequence, and after two depositions of the outermost carbon coating layer 200 are completed, a complete multi-layered current collector 10 is formed.

[0046] After the manufacturing of the multilayered current collector 10 was completed, the multilayered current collector 10 was divided, wound, and vacuum packaged. Specifically, in this embodiment, the unwinding tension was 10 N, and the unwinding tension was 8 N.

[0047] Referring to FIG. 1, according to some embodiments of the present application, preferably, when depositing the metal plating layer 300, the evaporation temperature is 500 to 900° C. When depositing the carbon coating layer 200, the evaporation temperature is 900 to 1200° C. When depositing the carbon coating layer 200, the evaporation temperature is 850° C. Exemplarily, when depositing the metal plating layer 300, the evaporation temperature is 1000° C. When depositing the carbon coating layer 200, the evaporation temperature is 1000° C. When alternately depositing the graphite with a purity of 99.9% and the metallic aluminum layer with a purity of 99.9% on two opposite surfaces of the polymer thin film layer 100, the vacuum degree is 0.05 Pa. When alternately depositing the graphite with a purity of 99.9% and the metallic aluminum layer with a purity of 99.9% on two opposite surfaces of the polymer thin film layer 100, the deposition speed is 100 m / min.

[0048] Referring to FIG. 1, according to some embodiments of the present application, the method for providing the carbon coating layer 200 on the two opposing surfaces of the polymer thin film layer 100 and the surface of the metal plating layer 300 is preferably sputtering.

[0049] Example 2 The differences between this embodiment and embodiment 1 are as follows: the polymer thin film layer 100 has a thickness of 25 μm; there is one metal aluminum layer and two graphite layers; that is, in this embodiment, the thickness of each metal plating layer 300 is 500 nm; and the thickness of each carbon coating layer 200 is 1000 nm. Finally, a 30 μm multilayered current collector 10 was manufactured.

[0050] Example 3 The differences between this embodiment and embodiment 1 are as follows: the thickness of each metal plating layer 300 is 125 nm, and the thickness of each carbon coating layer 200 is 375 nm. Therefore, the thickness of the multilayered current collector 10 is 8.75 μm.

[0051] Comparative Example 1 The method for producing the multilayer current collector 10 according to the first comparative example includes the following steps.

[0052] Step 1: A 6 μm polymer thin film layer 100 and a 99.9% pure metal aluminum layer are selected, where the polymer thin film layer 100 is made of polybutylene terephthalate (PET).

[0053] Step 2: A metallic aluminum layer with a purity of 99.9% was deposited on two opposing surfaces of the polymer thin film layer 100. A multiple-suspension vacuum deposition process was used for the process of depositing the metallic aluminum layer on the two opposing surfaces of the polymer thin film layer 100. In this embodiment, the metallic aluminum layer has a thickness of 125 nm. The metallic aluminum layer has eight layers. Since the thickness of a single metallic aluminum layer is 125 nm, in order to manufacture an 8 μm multi-layered current collector 10, the polymer thin film layer 100 needs to be deposited successively 16 times.

[0054] After the production of the multilayered current collector 10 was completed, the multilayered current collector 10 was subjected to the processes of dividing, winding and vacuum packaging.

[0055] Comparative Example 2 The differences between this embodiment and embodiment 1 are as follows: The polymer thin film layer 100 has a thickness of 25 μm. The metal aluminum layer has five layers. In this embodiment, the metal plating layer 300 has a thickness of 500 nm. Finally, a multi-layered current collector 10 having a thickness of 30 μm is manufactured. In this embodiment, the polymer thin film layer 100 needs to be vapor-deposited ten times in succession.

[0056] Comparative Example 3 The differences between this comparative example and Example 1 are as follows: the innermost layer of the laminate is a metal plating layer 300, the outermost layer is a carbon coating layer 200, the number of carbon coating layers 200 in each of the metal plating layers 300 is two, each metal plating layer 300 is 125 nm thick, and each carbon coating layer 200 is 250 nm thick, so that the thickness of the current collector is 7.5 μm.

[0057] Comparative Example 4 The differences between this comparative example and Example 1 are as follows: the outermost layer of the laminate is a metal plating layer 300, the innermost layer is a carbon coating layer 200, the number of carbon coating layers 200 in each of the metal plating layers 300 is two, the thickness of each metal plating layer 300 is 125 nm, and the thickness of each carbon coating layer 200 is 250 nm, so that the thickness of the current collector is 7.5 μm.

[0058] Comparative Example 5 The differences between this comparative example and Example 1 are as follows: The thickness of each carbon coating layer is 200 μm, and therefore the thickness of the current collector is 7.7 μm.

[0059] Comparative Example 6 The differences between this comparative example and Example 1 are as follows: The thickness of each carbon coating layer is 400 μm, and therefore the thickness of the current collector is 8.9 μm.

[0060] The porosity of the multilayer current collector 10 of Examples 1 to 3 and Comparative Examples 1 and 2 was measured, and the effect data shown in Table 1 was obtained. The porosity was measured as follows. The multilayer current collector sample was washed, and the pretreated thin film sample was placed in a pore adsorption device to balance the adsorption of gas in the pores of the film. The specific surface area of ​​the film and the distribution of the pore size were calculated from the isotherm of the adsorbent, and the porosity of the thin film was analyzed from the data from the device. Table 1 shows the measurement data of the porosity of the multilayer current collector 10.

[0061] [Table 1]

[0062] As can be seen from the above table, the porosity of the multilayer current collector 10 of the present application was lower than that of the comparative example. As can be seen from Table 1, the fewer the number of times the metal plating layer 300 was vapor-deposited, the lower the porosity of the multilayer current collector 10. Furthermore, the multilayer current collector 10 of the present application was able to improve the current passing area of ​​the metal plating layer 300 without affecting the transport of electrons.

[0063] The sheet resistance of the multilayer current collector 10 of Examples 1 to 3 and Comparative Examples 1 and 2 was measured, and the effect data shown in Table 2 was obtained. The sheet resistance of the multilayer current collector 10 was measured as follows. The current collector was cut into a sample with a length and width of about 200 mm, and the sheet resistance of the sample was measured using a sheet resistance device.

[0064] Table 2 shows the measurement data of the sheet resistance of the multilayer current collector 10.

[0065] [Table 2]

[0066] As can be seen from the above table, the sheet resistance of the multilayer current collector 10 of the present application was lower than that of the comparative example. As can be seen from Table 2, the fewer the number of depositions of the metal plating layer 300, the lower the sheet resistance of the multilayer current collector 10. The multilayer current collector 10 of the present application has a small sheet resistance, which can reduce polarization of the battery and effectively ensure battery performance.

[0067] The stretch strength, elongation percentage, and puncture strength of the multilayered current collectors 10 of Examples 1 to 3 and Comparative Examples 1 and 2 were measured, and the effect data shown in Table 3 was obtained.

[0068] The method for measuring the stretch strength and elongation rate of the multi-layered current collector 10 is as follows. One end of the multi-layered current collector was clamped by the upper clamping head of the tensile tester, and the other end was clamped by the lower clamping head of the tensile tester, and held on the same axis. Parameters such as the specifications, speed, and unit of the test device were set. During the measurement process, the stretch length and load value of the sample were measured and recorded. The stretch strength and elongation rate of the multi-layered current collector were calculated according to the measurement results.

[0069] The puncture strength of the multilayer current collector 10 was measured as follows. A rectangular sample of uniform size was cut from the multilayer current collector. The sample was clamped and fixed to a puncture table so as to ensure the flatness of the sample surface. A circular probe (round tip diameter 3.0 mm) was used to apply pressure to the sample at a speed of 1 mm / s until a predetermined peak was reached or the sample burst. Typically, the peak pressure was 50 N and the puncture depth was 25 mm. The maximum force applied by the probe at each puncture point was recorded. The puncture strength of the sample was calculated by analyzing the measurement data.

[0070] Table 3 shows the measurement data of the stretch strength, elongation percentage and puncture strength of the multi-layered current collector 10.

[0071] [Table 3]

[0072] As can be seen from the above table, the stretching strength, elongation rate and puncture strength of the multilayer current collector 10 of the present invention were all higher than those of the comparative example. As can be seen from Table 2, the fewer the number of depositions of the polymer thin film layer 100, the higher the stretching strength, elongation rate and puncture strength of the multilayer current collector 10. The mechanical performance and conductivity of the multilayer current collector 10 of the present invention were significantly improved compared to the comparative example.

[0073] The sheet resistance change rate, peel force, peel force after corrosion by an electrolyte, peel force change rate, and elastic modulus of the multilayered current collectors 10 of Example 1 and Comparative Examples 3 to 6 were measured, and the effect data shown in Table 4 was obtained.

[0074] The method for measuring the rate of change in sheet resistance after stretching is as follows: The sheet resistance a of the current collector before stretching was measured with a sheet resistance meter, and after the current collector was stretched by 2%, the sheet resistance b was measured with the sheet resistance meter. [Formula 1] Sheet resistance change rate after stretching = (ba) / a

[0075] The corrosion-free peel force was measured as follows. An 11 cm long tape was attached to a steel plate, and then a 10 cm long current collector was attached to the tape. A 22 cm long tape was attached to the current collector, and the steel plate was fixed to a peel force measuring device. The 22 cm long tape was bent into a U-shape, and the free end of the 22 cm long tape was clamped by the collet of the peel force measuring device. The peel force measuring device was then started, and the tape was pulled to separate the plating layer and the polymer thin film layer, and the peel force c was measured.

[0076] The peel force after corrosion by the electrolyte was measured as follows. An 11 cm long tape was attached to a steel plate, and then a 10 cm long current collector that had been immersed in the electrolyte for 24 hours was attached to the tape. A 22 cm long tape was attached to the current collector, and the steel plate was fixed to a peel force measuring device. The 22 cm long tape was bent into a U-shape, and the free end of the 22 cm long tape was clamped by the collet of the peel force measuring device. The peel force measuring device was then started and the tape was pulled to separate the plating layer and the polymer thin film layer, and the peel force d was measured. [Formula 2] Peel force change rate after corrosion = (cd) / c

[0077] Table 4 shows the rate of change in sheet resistance after stretching of the multilayer current collector 10, the peel force before corrosion, the peel force after corrosion, the rate of change in peel force after corrosion, and the elastic modulus.

[0078] [Table 4]

[0079] As can be seen from the above table, by comparing Example 1 with Comparative Example 3, the current collector having both the innermost and outermost carbon coating layers exhibits a smaller change in peel strength after corrosion by an electrolyte compared to the current collector having only the outermost carbon coating layer, and is therefore more resistant to corrosion by an electrolyte when applied to a battery.

[0080] Comparing Example 1 with Comparative Example 4, the sheet resistance change rate after stretching was smaller when both the innermost layer and the outermost layer were carbon coating layers than when only the innermost layer was a carbon coating layer. During the manufacturing process of a battery, the current collector may be pulled, and during the pulling process, small cracks are likely to occur in the metal plating layer, which affects the sheet resistance, and the carbon coating layer located in the outermost layer is not likely to burst during the pulling process, and can still ensure that the current flows between the current collector and the active material applied to the current collector. The carbon coating layer, which is not likely to deform, reduces the size of the cracks in the metal plating layer and further avoids the increase in sheet resistance, so that the current collector of the present application has a smaller impact on the electrical performance of the battery due to pulling after being applied to the battery.

[0081] Comparing Example 1 with Comparative Examples 5 and 6, the peel strength between the carbon coating layer and the polymer thin film layer was low when the thickness ratio between the carbon coating layer and the metal plating layer was greater than 3. When the thickness ratio between the carbon coating layer and the metal plating layer was less than 2, the elastic modulus of the current collector increased, making it difficult for the current collector to deform, and increasing the difficulty of the next winding.

[0082] The technical features of the above embodiments can be arbitrarily combined. For the sake of simplicity, all possible combinations of the technical features in the above embodiments are not described, but as long as there is no contradiction in the combination of these technical features, they should all be considered within the scope of the present specification.

[0083] It should be understood that the above examples are merely illustrative of some embodiments of the present invention, and the description is specific and detailed, but does not limit the scope of the present invention. It should be noted that a person skilled in the art can make some modifications and improvements without departing from the concept of the present invention, and all of these are within the scope of protection of the present invention. Therefore, the scope of protection of the present invention is based on the scope of the attached claims. [Explanation of symbols]

[0084] 10: multi-layered current collector; 100: polymer thin film layer; 200: carbon coating layer; 300: metal plating layer.

Claims

1. A polymer thin film layer having a laminate on each of two opposite surfaces of the polymer thin film layer, the laminate includes carbon coating layers and metal plating layers that are alternately laminated, wherein the outermost layer and the innermost layer of the laminate are both the carbon coating layers, and the thickness ratio of any one of the carbon coating layers to the adjacent metal plating layer is 3:1 to 2:1; A multilayer current collector comprising:

2. The carbon coating layer contains at least one of carbon black, carbon nanotubes, graphite, acetylene black, and graphene.

2. The multilayer current collector according to claim 1 .

3. The metal plating layer is a metal aluminum layer or a metal copper layer.

2. The multilayer current collector according to claim 1 .

4. The purity of the metal plating layer and the carbon coating layer is 99.8% or more.

2. The multilayer current collector according to claim 1 .

5. The polymer thin film layer includes at least one of an insulating polymer material, an insulating polymer composite material, a conductive polymer material, and a conductive polymer composite material.

2. The multilayer current collector according to claim 1 .

6. The polymer thin film layer has a thickness ranging from 1 μm to 25 μm, the metal plating layer has a thickness ranging from 50 nm to 130 nm, and the carbon coating layer has a thickness ranging from 150 nm to 260 nm.

2. The multilayer current collector according to claim 1 .

7. A method for producing the multilayer current collector according to any one of claims 1 to 6, comprising the steps of: forming the laminate by alternately providing the carbon coating layer and the metal plating layer on two opposite surfaces of the polymer thin film layer, wherein the outermost layer and the innermost layer of the laminate are both the carbon coating layer; A method for producing a multilayer current collector comprising the steps of:

8. The carbon coating layer is formed on the two opposite surfaces of the polymer thin film layer and on the surface of the metal plating layer by sputtering. The method for producing a multi-layered current collector according to claim 7 .

9. The carbon coating layer is formed on the two opposite surfaces of the polymer thin film layer and on the surface of the metal plating layer by evaporation. The method for producing a multi-layered current collector according to claim 7 .

10. When depositing the metal plating layer, the evaporation temperature is 500 to 900° C.; When depositing the carbon coating layer, the evaporation temperature is 900 to 1200°C. The method for producing a multi-layered current collector according to claim 9 .

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