Preparation method of composite current collector, lithium ion battery and electric device

Abstract

The invention relates to the technical field of lithium battery composite current collectors, in particular to a preparation method of a composite current collector, a lithium ion battery and an electric device. Forming a first current collecting layer on the upper surface of the polymer base film, and preparing a first middleware; performing pore forming on the polymer base membrane in the first middleware to form a through hole only penetrating through the polymer base membrane, and preparing a second middleware; and forming a second current collecting layer on the lower surface of the polymer base film, the inner wall of the through hole and the first current collecting layer exposed in the through hole. By adopting the preparation method provided by the invention, on one hand, the through holes do not penetrate through the whole composite current collector, so that the problem of material leakage during later electrode material coating is avoided; meanwhile, in the process of preparing the second current collecting layer, the second current collecting layer is deposited on the hole wall of the through hole and also deposited on the first current collecting layer exposed in the through hole, so that the combination area of the current collecting layers on the surfaces of the two sides of the polymer base film is increased, and the mechanical property of the composite current collector is improved.

Description

Technical Field

[0001] This application relates to the field of lithium battery composite current collector technology, and in particular to a method for preparing a composite current collector, a lithium-ion battery, and an electrical device. Background Technology

[0002] Composite current collectors consist of an insulating support layer and current collector layers disposed on both sides of the support layer. Since the current collector layers on both sides are not conductive, the conductivity of composite current collectors is significantly degraded compared to traditional pure metal current collectors. In order to improve the conductivity of composite current collectors, porous composite current collectors have emerged.

[0003] The traditional preparation process of porous composite current collectors is as follows: current collector layers are formed on both sides of the support layer with through-hole structure and on the pore walls of the through-holes. The through-holes penetrate the entire composite current collector, and the current collector layers on both sides are connected through the current collector layers on the pore walls, thereby improving the conductivity of the composite current collector.

[0004] However, since the current collectors on both sides are only connected through the current collectors on the pore walls, the mechanical properties of the composite current collector are poor. Simultaneously, because the support layer contains through-hole structures with pore sizes typically ranging from 20μm to 200μm, while the fineness of the conductive pastes for the positive and negative electrode active materials is generally between 5μm and 30μm, there is a risk of material leakage during the coating process. That is, when the positive / negative electrode active conductive paste is coated on one side of the support layer, the paste may flow through the through-holes to the other surface, resulting in the inability to coat the active material in the pore area and around the pores. Summary of the Invention

[0005] Based on this, this application provides a method for preparing a composite current collector, a lithium-ion battery, and an electrical device to solve the problem of material leakage when coating electrode active materials on a porous composite current collector.

[0006] The first aspect of this application provides a method for preparing a composite current collector, comprising the following steps: providing a polymer base film; forming a first current collector layer on the upper surface of the polymer base film to prepare a first intermediate component; creating pores in the polymer base film in the first intermediate component to form through holes that only penetrate the polymer base film to prepare a second intermediate component; and forming a second current collector layer on the lower surface of the polymer base film, the inner wall of the through hole, and the first current collector layer exposed in the through hole.

[0007] In some embodiments, the step of forming a second current collector layer on the lower surface of the polymer base film, the inner wall of the through hole, and the first current collector layer exposed in the through hole includes: placing a second intermediate in a vapor deposition apparatus; wherein the first current collector layer faces the cooling device in the vapor deposition apparatus, and the lower surface of the polymer base film faces the evaporation boat in the vapor deposition apparatus.

[0008] The film-forming material is deposited on the lower surface of the polymer base film, the inner wall of the through hole, and the first current collector layer exposed in the through hole, forming a second current collector layer.

[0009] In some embodiments, the cooling device is provided with staggered baffles; the center of the through hole is placed in correspondence with the staggered baffle in the cooling device, and the distance between any two adjacent center holes is equal to the distance between any two adjacent staggered baffles.

[0010] In some embodiments, the cooling device satisfies at least one of the following characteristics: (1) the temperature of the coolant in the cooling device is 5℃±2℃; (2) the flow rate of the coolant in the cooling device is 5m³ / h. 3 / min~15m 3 / min.

[0011] In some embodiments, after the step of forming the second current collector layer, the following steps are also included: placing the through hole corresponding to the microhole on the micro-groove roller in the dotting roller device; rotating the micro-groove roller to coat the conductive paste in the microhole into the through hole; and after baking, forming a conductive layer on the second current collector layer in the through hole.

[0012] In some embodiments, at least one of the following technical features is satisfied: (1) the pore size of the micropore is 1.2 to 1.5 times that of the through hole; (2) the conductive paste includes conductive material, binder and additives in a mass ratio of (93 to 97): (2 to 5): (1 to 2); (3) the viscosity of the conductive paste is 1000 Pa·s to 2000 mPa·s; (4) the solid content of the conductive paste is 20% to 35%; (5) the surface energy of the conductive paste is 30 mN / m to 35 mN / m.

[0013] In some embodiments, laser drilling is used to create pores in the polymer base film. The laser drilling method satisfies at least one of the following characteristics: (1) the light source is an ultraviolet laser; (2) the spot diameter is 10μm~20μm; (3) the power is 3W~15W.

[0014] In some embodiments, the polymer base film satisfies at least one of the following characteristics: (1) the thickness is 2 μm to 10 μm; (2) the polymer base film includes one or more of polyethylene terephthalate film, polyethylene film, polystyrene film, polyvinyl chloride film, polycarbonate film, polyoxymethylene film and polypropylene film.

[0015] In some embodiments, the method further includes the step of forming a third current collector layer on the surface of the first current collector layer, wherein the third current collector layer is a copper layer or an aluminum layer.

[0016] In some implementations, the laser resistance of the first current collector layer is higher than that of the third current collector layer.

[0017] The second aspect of this application provides a lithium-ion battery, including a composite current collector prepared according to the method for preparing the composite current collector provided in the first aspect of this application.

[0018] A third aspect of this application provides an electrical device including a lithium-ion battery as provided in the second aspect of this application, the lithium-ion battery being used to provide electrical energy to the electrical device.

[0019] Compared with the prior art, this application has the following beneficial effects:

[0020] This application first forms a first current collector layer on one side of a polymer base film, then forms a through-hole in the polymer base film that penetrates only the polymer base film, and finally forms a second current collector layer on the other side of the polymer base film and within the through-hole. On one hand, the through-hole does not penetrate the entire composite current collector, avoiding leakage problems during subsequent electrode material coating. On the other hand, during the preparation of the second current collector layer, it is deposited not only on the wall of the through-hole but also on the first current collector layer exposed within the through-hole, increasing the bonding area between the current collector layers on both sides of the polymer base film, improving the mechanical properties (tensile strength, elongation at break) of the composite current collector, and further reducing its sheet resistance. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments or related technologies of this application, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of a method for preparing a composite current collector according to an embodiment of this application.

[0023] Figure 2 This is a schematic diagram of the composite current collector in one embodiment of this application.

[0024] Figure 3 This is a schematic diagram of the composite current collector in another embodiment of this application.

[0025] Figure 4 This is a diagram showing the distribution of vias on the polymer base film in some embodiments of this application.

[0026] Figure 5 This is a partial structural diagram of the cooling device in the vapor deposition equipment of this application.

[0027] Figure 6 This is a schematic diagram of the composite current collector in another embodiment of this application.

[0028] Explanation of reference numerals in the attached figures

[0029] 1. Composite current collector; 11. Polymer base film; 12. First current collector layer; 13. Through hole; 14. Second current collector layer; 15. Third current collector layer; 16. Conductive layer; 2. Serpentine tube; 21. Staggered baffle. Detailed Implementation

[0030] A detailed reference is now provided to embodiments of this application, one or more of which are described below. Each embodiment is provided for explanation and not for limitation. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made to this application without departing from its scope or spirit. For example, features described or illustrated as part of one embodiment may be used in another embodiment to produce further embodiments.

[0031] Therefore, this application is intended to cover such modifications and variations falling within the scope of the appended claims and their equivalents. Other objects, features, and aspects of this application are disclosed in or will be apparent from the following detailed description. It will be understood by those skilled in the art that this discussion is merely a description of exemplary embodiments and is not intended to limit the broader aspects of this application.

[0032] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0033] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0034] In this article, when referring to units of data ranges, if a unit is only followed by the right endpoint, it means that the units of the left and right endpoints are the same.

[0035] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0036] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0037] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0038] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0039] like Figure 1 As shown, the first aspect of this application provides a method for preparing a composite current collector 1, comprising the following steps:

[0040] S1, Provide a polymer base film 11.

[0041] S2. A first current collection layer 12 is formed on the upper surface of the polymer base film 11 to prepare the first intermediate component.

[0042] S3. Create pores in the polymer base film 11 in the first intermediate to form through holes 13 that only penetrate the polymer base film 11, and prepare the second intermediate.

[0043] S4. A second current collector 14 is formed on the lower surface of the polymer base film 11 of the second intermediate, the inner wall of the through hole 13, and the first current collector 12 exposed in the through hole 13.

[0044] This application first forms a first current collector layer 12 on one side of the polymer base film 11, then forms a through-hole 13 that penetrates only the polymer base film 11, and finally forms a second current collector layer 14 on the other side of the polymer base film 11 and within the through-hole 13. On one hand, the through-hole 13 does not penetrate the entire composite current collector 1, avoiding leakage problems during subsequent electrode material coating. On the other hand, during the preparation of the second current collector layer 14, it is deposited not only on the pore wall of the through-hole 13 but also on the first current collector layer 12 exposed within the through-hole 13, increasing the bonding area of ​​the current collector layers on both sides of the polymer base film 11, improving the mechanical properties of the composite current collector 1, and further reducing the sheet resistance of the composite current collector.

[0045] In some embodiments, a second current collector layer 14 is formed on the lower surface of the polymer base film 11 and inside the through hole 13 in the second intermediate by chemical plating or by first magnetron sputtering and then electroplating.

[0046] However, during the preparation of the second current collector layer 14 using chemical plating and magnetron sputtering followed by electroplating, researchers found that due to the presence of the first current collector layer 12, the through holes 13 of the polymer base film 11 are actually blind holes in the first intermediate part, and the plating solution may not be able to completely enter the holes, resulting in incomplete plating.

[0047] Furthermore, during the subsequent coating of electrode active material, there is a risk that the blind holes may not be completely filled by the electrode active material because the gas in the blind holes cannot be expelled in time. If the blind holes are not filled, after the subsequent baking process, there will be no direct contact between some of the dried electrode active material and the composite current collector 1, making it easy to fall off. In addition, the composite current collector 1 in the area corresponding to the blind hole cannot transfer electrons to the electrode active material, which increases the internal resistance of the battery.

[0048] Based on this, this application provides a method for preparing the second current collector layer 14 by vapor deposition, the method comprising the following steps:

[0049] The second intermediate component is placed in the vapor deposition apparatus; wherein the first current collector 12 faces the cooling device in the vapor deposition apparatus, and the lower surface of the polymer base film 11 faces the evaporation boat in the vapor deposition apparatus.

[0050] A film-forming material is vapor-deposited onto the lower surface of the polymer base film 11, the inner wall of the through hole 13, and the first current collector layer 12 exposed within the through hole 13, forming a second current collector layer 14.

[0051] In some implementations, the cooling device is equipped with staggered baffles.

[0052] The preparation of the second current collector layer 14 by vapor deposition includes the following steps:

[0053] S10. Place the second intermediate component in the vapor deposition apparatus. The first current collector 12 faces the cooling device in the vapor deposition apparatus, and the lower surface of the polymer base film 11 faces the evaporation boat in the vapor deposition apparatus.

[0054] S20. Place the center of the through hole 13 in correspondence with the staggered baffle 21 in the cooling device, such that the distance between any two adjacent center holes is equal to the distance between any two adjacent staggered baffles 21.

[0055] S30. Evaporation of film-forming material, which is deposited on the lower surface of polymer base film 11, the inner wall of through hole 13, and the first current collector layer 12 exposed in through hole 13, to form second current collector layer 14.

[0056] It is understood that the term "film-forming material" in this application refers to metallic copper and / or metallic aluminum.

[0057] Because the cooling device is equipped with staggered baffles 21, the staggered baffles 21 force the fluid to continuously change its flow direction during the flow of the coolant, forming turbulence before and after the staggered baffles 21. Since the location of the staggered baffles 21 is the area with the most intense turbulence, the heat exchange efficiency is the highest at this location. In this application, by placing the center of the through hole 13 corresponding to the staggered baffles 21, the temperature at the bottom of the hole is lower than the temperature of the hole wall and the lower surface of the polymer base film 11. Therefore, during vapor deposition, the metal vapor preferentially condenses and nucleates at the bottom of the hole, making the thickness of the current collection layer deposited at the bottom of the hole greater than the thickness of the current collection layer formed on the hole wall, and also greater than the thickness of the current collection layer deposited on the lower surface of the polymer base film 11. This effectively fills the holes, reduces the volume of the blind holes, and increases the ratio of the blind hole diameter to the blind hole depth, which is beneficial for the subsequent entry of the electrode active material into the blind holes and reduces the risk that the blind holes will not be filled when the electrode active material is coated later. At the same time, the second current collection layer 14 with the T-shaped structure significantly enhances the mechanical properties (tensile strength, elongation at break) of the composite current collector 1.

[0058] In some embodiments, the vapor deposition apparatus includes a winding and unwinding mechanism, an evaporation boat, and a cooling device located above the evaporation boat. The cooling device contains a serpentine tube 2, and the inner wall of the serpentine tube 2 is provided with staggered baffles 21 (e.g., Figure 5 (as shown), and the cooling device can rotate axially.

[0059] During the vapor deposition process, the second intermediate component is moved by the unwinding and rewinding mechanism. During the movement, the first current collection layer 12 in the second intermediate component is in contact with the cooling device, and the center of the through hole 13 is placed in correspondence with the staggered baffle 21. The lower surface of the polymer base film 11 in the second intermediate component faces the evaporation boat.

[0060] In some embodiments, the temperature of the coolant in the cooling device is 5℃±2℃, including but not limited to 3℃, 4℃, 5℃, 6℃, and 7℃.

[0061] In some embodiments, the flow rate of the coolant in the cooling device is 5m³ / h. 3 / min~15m 3 / min, including but not limited to 5m 3 / min, 8m 3 / min, 10m 3 / min, 12m 3 / min, 15m 3 / min.

[0062] In one specific embodiment, a second current collector layer 14 is formed on the lower surface of the polymer base film 11 and inside the through hole 13 in the second intermediate by resistive evaporation.

[0063] In some embodiments, the feeding speed of the film-forming material is 3m / min to 10m / min, the belt speed of the take-up and unwinding mechanism is 10m / min to 30m / min, and the evaporation power of the evaporation boat is 5KW to 10KW.

[0064] In some embodiments, the thickness of the current collection layer deposited at the bottom of the through-hole 13 is 1.1 to 1.3 times the thickness of the current collection layer formed on the hole wall, including but not limited to 1.1, 1.2, and 1.3 times. The thickness of the current collection layer deposited at the bottom of the through-hole 13 is 1.2 to 1.5 times the thickness of the current collection layer deposited on the lower surface of the polymer base film 11, including but not limited to 1.2, 1.3, 1.4, and 1.5 times.

[0065] See Figure 2 , Figure 2 The diagram below shows the structure of the composite current collector 1 in some embodiments of this application. It includes a polymer base film 11, a first current collector layer 12, and a second current collector layer 14. The polymer base film 11 is provided with a through hole 13. The first current collector layer 12 is disposed on the upper surface of the polymer base film 11. The second current collector layer 14 is disposed on the lower surface of the polymer base film 11, the inner wall of the through hole 13, and the first current collector layer 12 exposed in the through hole 13.

[0066] It is understood that "upper surface" and "lower surface" refer to the two opposite sides of the polymer base film 11 and do not limit the structure. They are merely for the purpose of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0067] In some implementations, after the step of forming the second current collector 14, the following steps are also included:

[0068] S40. Align the through hole 13 with the microhole on the micro-concave roller in the dotting roller equipment.

[0069] S50. Rotate the micro-concave roller to coat the conductive paste inside the micro-hole into the through hole 13.

[0070] S60. After baking, a conductive layer 16 is formed on the second current collector layer 14 inside the through hole 13.

[0071] It is understandable that the process of S40~S60 described above is as follows: the lower half of the micro-grooved roller is immersed in the conductive paste, and the upper half is in contact with the lower surface of the composite current collector 1. The rotating micro-grooved roller carries the conductive paste out, and the conductive paste on the surface of the micro-grooved roller is scraped off by a scraper. The rotating micro-grooved roller coats the conductive paste in the micropores into the through hole 13. Then, it is baked in an oven to evaporate the solvent in the conductive paste, thereby forming a conductive layer 16 on the second current collector layer 14 in the through hole 13, so as to further fill the through hole 13.

[0072] In some embodiments, the conductive paste comprises a conductive material, a binder, and additives in a mass ratio of (93~97):(2~5):(1~2).

[0073] It is understood that no particular limitation is made to the conductive materials, binders, and additives in this application. Any known conductive materials, binders, and additives can be used in this application without departing from the overall inventive concept. As an example only, the conductive material can be, for example, conductive carbon black; the binder can be, for example, styrene-butadiene rubber (SBR); and the additive can be, for example, sodium carboxymethyl cellulose (CMC).

[0074] In some embodiments, the viscosity of the conductive paste is 1000 Pa·s to 2000 mPa·s, including but not limited to 1000 Pa·s, 1500 Pa·s, and 2000 Pa·s.

[0075] In some embodiments, the solvent is deionized water, and the solid content of the conductive paste is 20% to 35%, including but not limited to 20%, 25%, 30%, and 35%.

[0076] In some embodiments, the surface energy of the conductive paste is 30mN / m to 35mN / m, including but not limited to 30mN / m, 31mN / m, 32mN / m, 33mN / m, 34mN / m, and 35mN / m.

[0077] In some embodiments, the pore size of the micropores is 1.2 to 1.5 times the pore size of the through-hole 13, including but not limited to 1.2, 1.3, 1.4, and 1.5 times. The larger pore size ensures that the coated conductive paste can cover the through-hole 13, while avoiding excessive conductive paste residue on the second current collector layer 14, which would result in an uneven surface of the second current collector layer 14.

[0078] Understandably, during the micro-grooving process, when the conductive paste remaining in the micropores is transferred to the second current collector layer 14 located on the lower surface of the polymer base film 11, due to the high viscosity of the conductive paste, it is not easy for the conductive paste to spread and level, and it is not easy for it to level on the surface of the second current collector layer in a direction away from the through-holes 14. Since the surface energy of the conductive paste is lower than that of the second current collector layer 14, the conductive paste easily wets the second current collector layer 14. Moreover, the structure of the through-holes 13 can expand the wetting effect. Therefore, during the coating process, the conductive paste tends to fill the pores. Furthermore, during the subsequent baking process, the evaporation of the solvent in the conductive paste causes the surface tension between the conductive paste and the second current collector layer 14 to weaken, resulting in shrinkage. Therefore, this application controls the shrinkage rate of the conductive slurry during solvent evaporation within a suitable range by adjusting the ratio of the pore size of the micropores to the pore size of the through holes 13, the solid content of the conductive slurry, and the surface energy of the conductive slurry. This ensures that the conductive layer 16 formed after shrinkage can cover the through holes 13. At the same time, the height of the conductive layer 16 protruding from the second current collector layer 14 located on the lower surface of the polymer base film 11 is controlled within a reasonable range to prevent the electrode active material layer in the subsequent conductive layer 16 region from being too thin, which would have an adverse effect on battery performance.

[0079] See Figure 3 , Figure 3 The diagram below illustrates the structure of the composite current collector 1 in some embodiments of this application. The composite current collector 1 includes a polymer base film 11, a first current collector layer 12, a second current collector layer 14, and a conductive layer 16. The polymer base film 11 has through holes 13. The first current collector layer 12 is disposed on the upper surface of the polymer base film 11. The second current collector layer 14 is disposed on the lower surface of the polymer base film 11 and within the through holes 13. The conductive layer 16 is disposed on the second current collector layer 14 within the through holes 13.

[0080] In some embodiments, the thickness of the polymer base film 11 is 2μm to 10μm, including but not limited to 2μm, 4μm, 6μm, 8μm, and 10μm.

[0081] In some embodiments, the polymer base film 11 includes one or more of polyethylene terephthalate film, polyethylene film, polystyrene film, polyvinyl chloride film, polycarbonate film, polyoxymethylene film, and polypropylene film.

[0082] In some embodiments, the first current collector layer 12 is formed on the upper surface of the polymer base film 11 by means of one or more of evaporation, chemical plating, and magnetron sputtering followed by electroplating.

[0083] In some embodiments, laser drilling is used to create holes in the polymer base film 11, and the light source for laser drilling is an ultraviolet laser.

[0084] In some embodiments, the spot diameter of the ultraviolet laser is 10μm to 20μm, including but not limited to 10μm, 14μm, 16μm, 18μm, and 20μm.

[0085] In some embodiments, the power of the ultraviolet laser is 3W to 15W. This application controls the power within this range so that the laser only damages the polymer base film 11 and cannot damage the first current collector layer 12, thereby forming a through hole 13 that only penetrates the polymer base film 11.

[0086] In some implementations, the feed rate is 2 m / min to 5 m / min, including but not limited to 2 m / min, 3 m / min, 4 m / min, and 5 m / min.

[0087] Understandably, nitrogen gas at 0.1MPa~0.2MPa is used as an auxiliary gas during laser drilling. High-pressure nitrogen gas is used to purge residual laser material from the hole and control the heat-affected zone, reducing thermal damage to the polymer base film 11 outside the laser-heated area.

[0088] In some implementations, see Figure 4 , Figure 4 This is a diagram showing the distribution of vias 13 on the polymer base film 11. The polymer base film 11 includes a plurality of arrayed vias 13. The pore size of the vias 13 is 20 μm to 60 μm. In the first direction X, the spacing between the centers of two adjacent vias 13 is 0.5 mm to 2 mm, and in the second direction Y, the spacing between the centers of two adjacent vias 13 is 1 mm to 3 mm.

[0089] In some embodiments, the first current collector 12 and the second current collector 14 are independently selected from copper and / or aluminum layers, respectively, with the thickness of the first current collector 12 being 0.8 μm to 1.5 μm and the thickness of the second current collector 14 being 0.8 μm to 1.5 μm.

[0090] In some embodiments, the method for preparing the composite current collector 1 further includes the following step: forming a third current collector layer 15 on the surface of the first current collector layer 12, wherein the third current collector layer 15 is a copper layer or an aluminum layer.

[0091] See Figure 6 , Figure 6The diagram below illustrates the structure of the composite current collector 1 in some embodiments of this application. The composite current collector 1 includes a polymer base film 11, a first current collector layer 12, a second current collector layer 14, a third current collector layer 15, and a conductive layer 16. The polymer base film 11 has a through-hole 13. The first current collector layer 12 is disposed on the upper surface of the polymer base film 11. The third current collector layer 15 is disposed on the side of the first current collector layer 12 away from the polymer base film 11. The second current collector layer 14 is disposed on the lower surface of the polymer base film 11 and within the through-hole 13. The conductive layer 16 is disposed on the second current collector layer 14 within the through-hole 13. In some embodiments, the material of the first current collector layer 12 is selected to be more laser-resistant than copper or aluminum, i.e., the material of the first current collector layer 12 has better laser resistance than copper or aluminum, to prevent laser penetration of the first current collector layer 12 during the hole-forming process.

[0092] Specifically, the material of the first current collector layer 12 can be a metal or metal oxide material with a melting point higher than that of copper or aluminum, such as nickel, chromium, aluminum oxide, nickel oxide, and chromium oxide.

[0093] The material of the first current collector layer 12 can be a metal or metal oxide material with a reflectivity higher than that of copper or aluminum, such as gold or silver.

[0094] The material of the first current collector layer 12 can also be a metal material or metal oxide material with a thermal conductivity higher than that of copper or aluminum, such as silver.

[0095] In some embodiments, the third current collector 15 is a copper and / or aluminum layer, serving as the conductive substrate. The first current collector 12 acts as a laser blocker, preventing the third current collector 15, which forms the conductive substrate, from being penetrated by the laser.

[0096] In some embodiments, the combined thickness of the first current collector layer 12 and the third current collector layer 15 is 0.8 μm to 1.5 μm.

[0097] In some embodiments, the method of forming the third current collector layer 15 on the first current collector layer 12 includes, but is not limited to, one or more of vapor deposition, electroless plating, and magnetron sputtering followed by electroplating.

[0098] In one embodiment of this application, the third current collector layer 15 is prepared after the first current collector layer 12 is prepared and before laser drilling. During the laser drilling process, the third current collector layer 15 can act as a heat conduction path, increasing heat dissipation and reducing the risk of the first current collector layer 12 and the third current collector layer 15 being penetrated by the laser.

[0099] Furthermore, the first current collector layer 12 is prepared by magnetron sputtering followed by electroplating. Compared with other coating methods, the film obtained by magnetron sputtering followed by electroplating has higher density, is more resistant to laser processing, and is less likely to be penetrated by laser.

[0100] In some embodiments, the magnetron sputtering equipment has a chamber pressure of 0.001 Pa to 0.005 Pa, an argon flow rate of 100 sccm to 200 sccm, a target power of 1 kW to 10 kW, and a conveyor speed of 2 m / min to 15 m / min. The third current collector 15 prepared by this process has a high density, with a density-to-intrinsic-density ratio of 0.97 to 0.99.

[0101] The second aspect of this application provides a lithium-ion battery, including a composite current collector prepared according to the method for preparing the composite current collector provided in the first aspect of this application.

[0102] A third aspect of this application provides an electrical device including a lithium-ion battery as provided in the second aspect of this application, the lithium-ion battery being used to provide electrical energy to the electrical device.

[0103] Furthermore, this application provides the following specific embodiments and comparative examples to further illustrate the specific implementation of this application and its advantages.

[0104] Example 1

[0105] A polypropylene membrane with a thickness of 6 μm is provided. A first current collector layer 12, which is a copper layer with a thickness of 1 μm, is formed on the upper surface of the polypropylene membrane.

[0106] With the assistance of nitrogen at 0.2 MPa, an ultraviolet laser with a power of 8 W was used to create pores in the polypropylene film, forming multiple through holes 13 arranged in an array that penetrate only the polyethylene film. The pore diameter of the through holes 13 is 30 μm.

[0107] A polypropylene film with through-holes 13 is placed in a resistive evaporation apparatus. The first current collector 12 faces the cooling device in the resistive evaporation apparatus, and the lower surface of the polymer base film 11 (the surface of the polymer base film 11 away from the first current collector 12) faces the evaporation boat in the resistive evaporation apparatus. The centers of the through-holes 13 are correspondingly placed with the staggered baffles 21 in the cooling device, and the distance between any two adjacent centers is equal to the distance between any two adjacent staggered baffles 21. The temperature of the coolant in the cooling device is 5°C, and the flow rate of the coolant is 10 m³ / s. 3 / min.

[0108] Copper material is vapor-deposited onto the lower surface of the polymer base film 11, the inner wall of the through-hole 13, and the first current collector layer 12 exposed within the through-hole 13, forming a second current collector layer 14. The thickness of the second current collector layer 14 on the lower surface of the polymer base film 11 is 1 μm, the thickness of the second current collector layer 14 on the inner wall of the through-hole 13 is 1.1 μm, and the thickness of the second current collector layer 14 exposed within the through-hole 13 is 1.3 μm.

[0109] Example 2

[0110] A polypropylene membrane with a thickness of 6 μm is provided. A first current collector layer 12, which is a copper layer with a thickness of 1 μm, is formed on the upper surface of the polypropylene membrane.

[0111] With the assistance of nitrogen at 0.2 MPa, an ultraviolet laser with a power of 8 W was used to create pores in the polypropylene membrane, forming multiple through holes 13 arranged in an array that penetrate only the polypropylene membrane. The pore diameter of the through holes 13 is 30 μm.

[0112] A polypropylene film with through-holes 13 is placed in a resistive evaporation apparatus, with the first current collector 12 facing the cooling device (which does not have staggered baffles 21) in the resistive evaporation apparatus, and the lower surface of the polymer base film 11 (the surface of the polymer base film 11 away from the first current collector 12) facing the evaporation boat in the resistive evaporation apparatus. The temperature of the coolant in the cooling device is 5°C, and the flow rate of the coolant is 10 m³ / s. 3 / min.

[0113] Copper material is vapor-deposited onto the lower surface of the polymer base film 11, the inner wall of the through-hole 13, and the first current collector layer 12 exposed within the through-hole 13, forming a second current collector layer 14. The thickness of the second current collector layer 14 on the lower surface of the polymer base film 11 is 1 μm, the thickness of the second current collector layer 14 on the inner wall of the through-hole 13 is 1 μm, and the thickness of the second current collector layer 14 exposed within the through-hole 13 is 1 μm.

[0114] The through-hole 13 is aligned with the micro-hole on the micro-grooved roller in the dotting roller device. The micro-grooved roller is rotated to coat the conductive paste inside the micro-hole into the through-hole 13. After baking, a conductive layer 16 is formed on the second current collector layer 14 inside the through-hole 13. The end of the conductive layer 16 away from the first current collector layer 12 is flush with the outer surface of the second current collector layer 14 on the lower surface of the polymer base film 11. The conductive paste is composed of conductive carbon black, styrene-butadiene rubber, and sodium carboxymethyl cellulose in a mass ratio of 93:5:2.

[0115] Example 3

[0116] The preparation process of this embodiment is basically the same as that of Embodiment 2. The main difference is that the conductive paste is composed of conductive carbon black, styrene-butadiene rubber and sodium carboxymethyl cellulose in a mass ratio of 97:2:1.

[0117] Comparative Example 1

[0118] Polyethylene film is provided, and polypropylene film has a thickness of 6μm.

[0119] With the assistance of nitrogen at 0.2 MPa, an ultraviolet laser with a power of 8 W was used to create pores in the polyethylene film, forming multiple through holes 13 arranged in an array that penetrate only the polyethylene film. The pore diameter of the through holes 13 is 30 μm.

[0120] A polyethylene film with through holes 13 is placed in a vapor deposition apparatus. A first current collector layer 12 is formed on the upper surface of the polyethylene film, and a second current collector layer 14 is formed on the lower surface of the polyethylene film and on the inner wall of the through holes 13. Both the first current collector layer 12 and the second current collector layer 14 are copper layers with a thickness of 1 μm.

[0121] Test case

[0122] The composite current collector 1 prepared in the examples and comparative examples was subjected to leakage detection, tensile strength and sheet resistance measurement. The results are shown in Table 1 below.

[0123] Leakage detection method: Apply slurry to one side of the composite current collector and bake for 3 minutes. Visually observe whether there is any slurry residue on the other side of the composite current collector. The slurry consists of 40% graphite, 3% sodium carboxymethyl cellulose, and 57% water by mass ratio.

[0124] Tensile strength testing method: A universal tensile testing machine was used. The current collector sample width was 15 mm, the clamp distance was 50 mm, and the testing speed was 200 m / min. The tensile strength is the strength at which the metal layer of the current collector breaks.

[0125] Sheet resistance testing method: The sheet resistance of the composite current collector is measured by contacting one side of the composite current collector with a four-probe sheet resistance tester.

[0126] Table 1

[0127] Is there any leakage? tensile strength Fang Zu Example 1 no 172MPa 13mΩ / □ Example 2 no 175MPa 11mΩ / □ Example 3 no 174MPa 10.8mΩ / □ Comparative Example 1 yes 160MPa 16mΩ / □

[0128] As shown in Table 1, compared with Comparative Example 1, the composite current collector 1 prepared by the preparation method provided in this application did not exhibit material leakage, had higher tensile strength, and lower sheet resistance.

[0129] Possible reasons are speculated as follows: In Example 1, the second current collector layer 14 exposed on the first current collector layer 12 inside the through hole 13, and the second current collector layer 14 on the inner wall of the through hole 13 connect the current collector layers on the upper and lower surfaces of the polymer base film 11 into one; in Examples 2 and 3, the second current collector layer 14 exposed on the first current collector layer 12 inside the through hole 13, the second current collector layer 14 on the inner wall of the through hole 13, and the conductive layer 16 connect the current collector layers on the upper and lower surfaces of the polymer base film 11 into one. On the one hand, this expands the lateral electron transport path of the composite current collector 1 in Examples 1 and 3 compared to the composite current collector 1 in Comparative Example 1; on the other hand, it achieves a larger portion or even complete filling of the through hole 13. Therefore, compared to the comparative example, the composite current collector 1 prepared in Examples 1 and 3 does not leak material, has higher tensile strength, and lower sheet resistance.

[0130] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0131] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for preparing a composite current collector, characterized in that, Includes the following steps: Provide polymer-based films; A first current collection layer is formed on the upper surface of the polymer-based film to prepare a first intermediate component; A second intermediate is prepared by creating pores in the polymer base film of the first intermediate to form through-holes that penetrate only the polymer base film. A second current collection layer is formed on the lower surface of the polymer base film, the inner wall of the through hole, and the first current collection layer exposed in the through hole.

2. The method for preparing the composite current collector according to claim 1, characterized in that, The step of forming a second current collector layer on the inner wall of the through-hole on the lower surface of the polymer base film and on the first current collector layer exposed within the through-hole includes: The second intermediate component is placed in a vapor deposition apparatus; wherein the first current collector faces the cooling device in the vapor deposition apparatus, and the lower surface of the polymer base film faces the evaporation boat in the vapor deposition apparatus; A film-forming material is vapor-deposited onto the lower surface of the polymer base film, the inner wall of the through-hole, and the first current-collecting layer exposed within the through-hole, thereby forming the second current-collecting layer.

3. The method for preparing the composite current collector according to claim 2, characterized in that, The cooling device is equipped with staggered baffles inside; The center of the through hole is placed corresponding to the staggered baffle in the cooling device, and the distance between any two adjacent center holes is equal to the distance between any two adjacent staggered baffles.

4. The method for preparing the composite current collector according to claim 3, characterized in that, The cooling device satisfies at least one of the following characteristics: (1) The temperature of the coolant in the cooling device is 5℃±2℃; (2) The flow rate of the coolant in the cooling device is 5m³ / h. 3 / min~15m 3 / min.

5. The method for preparing the composite current collector according to claim 2, characterized in that, After the step of forming the second current collector layer, the following steps are also included: The through holes are aligned with the microholes on the micro-concave roller in the dot-coating roller device; Rotate the micro-concave roller to coat the conductive paste inside the micropores into the through holes; After baking, a conductive layer is formed on the second current collector layer inside the through hole.

6. The method for preparing the composite current collector according to claim 5, characterized in that, It meets at least one of the following technical features: (1) The diameter of the micropore is 1.2 to 1.5 times the diameter of the through hole; (2) The conductive paste comprises conductive materials, binders and additives in a mass ratio of (93~97):(2~5):(1~2); (3) The viscosity of the conductive paste is 1000 Pa·s to 2000 mPa·s; (4) The solid content of the conductive paste is 20%~35%; (5) The surface energy of the conductive paste is 30mN / m~35mN / m.

7. The method for preparing the composite current collector according to any one of claims 1 to 6, characterized in that, The polymer-based film is perforated using laser drilling, and the laser drilling method satisfies at least one of the following characteristics: (1) The light source is an ultraviolet laser; (2) The spot diameter is 10μm~20μm; (3) Power is 3W~15W.

8. The method for preparing the composite current collector according to any one of claims 1 to 6, characterized in that, The polymer-based film satisfies at least one of the following characteristics: (1) Thickness is 2μm~10μm; (2) The polymer base film includes one or more of polyethylene terephthalate film, polyethylene film, polystyrene film, polyvinyl chloride film, polycarbonate film, polyoxymethylene film and polypropylene film.

9. The method for preparing the composite current collector according to any one of claims 1 to 6, characterized in that, It also includes the following steps: A third current collector layer is formed on the surface of the first current collector layer, and the third current collector layer is a copper layer or an aluminum layer.

10. The method for preparing the composite current collector according to claim 9, characterized in that, The laser resistance of the first current collector layer is higher than that of the third current collector layer.

11. A lithium-ion battery, characterized in that, The composite current collector includes the composite current collector prepared by the method according to any one of claims 1 to 10.

12. An electrical appliance, characterized in that, Includes the lithium-ion battery of claim 11, wherein the lithium-ion battery is used to provide electrical energy to the electrical device.

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