Composite current collector preparation method and preparation device

Abstract

The present application relates to a kind of composite current collector preparation method and preparation device, by selective pre-treatment in the middle of the surface of base material strip Forming active area, pre-treatment in the process will not be processed to blank area, so the edge of the two sides of base material strip will not be damaged.And, in the process of forming metal layer, only the operation for active area is carried out, and the blank area does not form a metal layer.During the formation of the metal layer, the damage to the base material strip, such as perforation, often occurs at the edge of the metal layer. It can be seen that the damage to the edge of the base material strip during the preparation process can be minimized to maintain the high mechanical strength of the base material strip. Moreover, the damage at the edge of the metal layer can be subsequently removed. Therefore, the above-mentioned composite current collector preparation method can significantly improve the yield.

Description

Technical Field

[0001] This invention relates to the field of lithium battery equipment technology, and in particular to a method and apparatus for preparing a composite current collector. Background Technology

[0002] Considering factors such as reducing the weight of lithium batteries and increasing their energy density, composite current collectors using polymer materials as substrates are receiving increasing attention. A composite current collector consists of a substrate and metal layers formed on the upper and lower surfaces of the substrate, forming a "sandwich structure." The substrate provides support, while the metal layers on both sides provide conductivity.

[0003] Currently, the common preparation method is to first deposit a metal film of a certain thickness on both sides of the substrate using physical vapor deposition, and then electroplate or chemically plate the substrate with metal films on both sides to thicken the metal films on both sides until the conductivity and physical properties of the composite current collector meet the requirements of lithium batteries.

[0004] Vacuum physical vapor deposition (VPV) involves high temperatures, which can easily lead to problems such as deformation, wrinkling, blistering, perforation, and brittleness in the substrate. Furthermore, the substrate is very thin, making it susceptible to perforation and damage from high-energy particle impacts during vacuum sputtering, corrosion during electroless plating, and edge current effects during electroplating. Particularly during roll-to-roll fabrication, the substrate must withstand the tension of the conveyor belt, making edge damage highly prone to strip breakage. Therefore, existing methods result in low yield rates when fabricating composite current collectors. Summary of the Invention

[0005] Therefore, it is necessary to provide a method and apparatus for preparing composite current collectors that can improve the yield rate in order to address the above problems.

[0006] A method for preparing a composite current collector includes the following steps:

[0007] Provide base material strip;

[0008] An active region is formed in the middle of the surface of the base material strip, and blank regions are formed on both sides of the base material strip along the width direction. Both the active region and the blank regions are strip-shaped and extend along the length direction of the base material strip.

[0009] A metal layer is formed in the active region;

[0010] The metal layer is removed from both sides of the width direction, or from the blank area, to obtain a composite current collector.

[0011] In one embodiment, the steps of forming an active region in the middle of the surface of the base material strip and forming blank regions on both sides of the base material strip along the width direction include:

[0012] The middle part of the surface of the base material strip is roughened;

[0013] The roughened area is coated with a sensitizing and activating solution to form the active region;

[0014] The blank areas are formed by the areas on both sides of the base material strip along the width direction that are not roughened and are not coated with sensitizing activating liquid.

[0015] In one embodiment, the step of roughening the middle part of the surface of the base material strip includes: roughening a plurality of strip regions on the surface of the base material strip, the strip regions being located in the middle part of the surface of the base material strip and being spaced apart along the width direction of the base material strip;

[0016] Specifically, the strip-shaped regions after roughening are coated with a sensitizing and activating solution to form the active regions, while the areas between adjacent strip-shaped regions that have not undergone roughening and have not been coated with the sensitizing and activating solution form the blank areas.

[0017] In one embodiment, the composite current collector includes a negative electrode composite current collector, and the step of forming a metal layer in the active region includes:

[0018] The base material strip is chemically plated to form a metal film attached to the active region;

[0019] Electroplating is performed on the base material strip that has undergone chemical plating to form a metal layer of a predetermined thickness on the surface of the metal film.

[0020] In one embodiment, the base material strip is electroplated using a brush plating method.

[0021] In one embodiment, the composite current collector includes a positive electrode composite current collector, and the step of forming a metal layer in the active region includes: chemically plating the base material strip to form a metal layer of a predetermined thickness in the active region.

[0022] In one embodiment, after the step of forming a metal layer in the active region, the step further includes: forming an antioxidant layer on the surface of the metal layer opposite to the base material strip.

[0023] In one embodiment, the base material strip is unwound in a continuous conveyor belt manner; the resulting composite current collector is wound in a continuous conveyor belt manner.

[0024] A composite current collector preparation device, comprising:

[0025] An unwinding mechanism is used to provide the base material strip;

[0026] A pretreatment mechanism is used to form an active region in the middle of the surface of the base material strip and to form blank regions on both sides of the base material strip along the width direction. Both the active region and the blank regions are strip-shaped and extend along the length direction of the base material strip.

[0027] A coating mechanism for forming a metal layer in the active region;

[0028] The edge-cutting mechanism is used to cut off the edge portions of the metal layer on both sides along the width direction or the blank area to obtain a composite current collector.

[0029] In one embodiment, the unwinding mechanism is capable of continuously unwinding the base material strip, and the composite current collector preparation device further includes a winding mechanism capable of continuously winding the composite current collector.

[0030] The aforementioned composite current collector preparation method and apparatus selectively pre-treat to form an active region in the center of the base material strip surface, while creating untreated regions along the width of both sides of the base material strip. These untreated regions prevent damage to the edges of the base material strip. Furthermore, during the metal layer formation process, only the active region is treated; the untreated regions do not form a metal layer. Damage such as perforation caused to the base material strip during metal layer formation typically occurs at the edges of the metal layer. Therefore, the preparation process minimizes damage to the edges of the base material strip, maintaining its high mechanical strength. Moreover, damage at the metal layer edges can be subsequently removed. Thus, the aforementioned composite current collector preparation method significantly improves the yield rate. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the 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.

[0032] Figure 1 This is a schematic diagram of the structure of the composite current collector prepared in one embodiment of the present invention;

[0033] Figure 2 This is a schematic flowchart of a composite current collector preparation method in one embodiment of the present invention;

[0034] Figure 3 for Figure 2 A schematic diagram of the processing scenario corresponding to the composite current collector preparation method shown;

[0035] Figure 4 for Figure 3 Detailed schematic diagrams of scenes (d) to (e) are shown;

[0036] Figure 5 This is a schematic diagram of the composite current collector preparation device in one embodiment of the present invention;

[0037] Figure 6 for Figure 5 A schematic diagram of the unwinding mechanism in the composite current collector preparation device shown;

[0038] Figure 7 for Figure 5 A schematic diagram of the roughening treatment mechanism in the composite current collector preparation device shown.

[0039] Figure 8 This is a schematic diagram of the roughening mechanism in another embodiment;

[0040] Figure 9 for Figure 5 A schematic diagram of the activation treatment mechanism in the composite current collector preparation device shown;

[0041] Figure 10 for Figure 5 A schematic diagram of the electroless plating mechanism in the composite current collector preparation device shown.

[0042] Figure 11 for Figure 5 A schematic diagram of the electroplating mechanism in the composite current collector preparation device shown.

[0043] Figure 12 This is a schematic diagram of the composite current collector preparation device in another embodiment;

[0044] Figure 13 A top view of the composite current collector prepared in another embodiment;

[0045] Figure 14 for Figure 13 A schematic diagram of the cross-section of the composite current collector is shown. Detailed Implementation

[0046] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0047] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention 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 invention.

[0048] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0049] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0050] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0051] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0052] This invention provides a method for preparing composite current collectors, which is used to prepare such as Figure 1 The composite current collector 200 shown is described. The composite current collector 200 includes a base material strip 210 and metal layers 220 located on two opposite surfaces of the base material strip 210.

[0053] The base material strip 210 is an insulating material, which can be any of the polymer materials selected from polyethylene terephthalate, polypropylene, polyamide, polyimide, polyvinyl chloride, and polystyrene. The base material strip 210 is in the form of a thin film, providing support, and its thickness is generally between 2 μm and 12 μm. The metal layer 220 serves a conductive function, and its thickness is generally between 700 nm and 2000 nm. The composite current collector 200 can be used as either the positive or negative electrode of a lithium battery, the difference being the material of the metal layer 220.

[0054] When the composite current collector 200 is used as the negative electrode current collector, the metal layer 220 is generally made of copper or a copper alloy. Alternatively, the metal layer 220 can also be a multilayer composite structure with copper comprising at least 80% of its mass. When the composite current collector 200 is used as the positive electrode current collector, the metal layer 220 is generally made of aluminum or an aluminum alloy. Similarly, the metal layer 220 can also be a multilayer composite structure with aluminum comprising at least 80% of its mass.

[0055] Please see Figure 2 and Figure 3 The composite current collector preparation method in one embodiment of the present invention includes steps S110 to S140.

[0056] Step S110: Provide base material strip 210.

[0057] Specifically, the base material strip 210 is generally unwound in the form of a strip, which can be pre-prepared and stored on the unwinding shaft. The provided base material strip 210 travels along a preset direction, which is the length direction of the base material strip 210, and the direction perpendicular to the length direction is the width direction of the base material strip 210. This step corresponds to... Figure 3 The scene shown is (a).

[0058] In step S120, an active region 201 is formed in the middle of the surface of the base material strip 210, and blank regions 202 are formed on both sides of the width direction of the surface of the base material strip 210. The active region 201 and the blank regions 202 are strip-shaped and extend along the length direction of the base material strip 210.

[0059] Because the material properties of the base material strip 210 differ significantly from those of metals, its surface has poor adhesion to metal materials. Directly performing coating operations on the surface of the base material strip 210 will make it difficult to form a satisfactory metal layer 220. Therefore, pretreatment of the surface of the base material strip 210 is necessary before coating to obtain the active region 201. The purpose of pretreatment is to enhance the adhesion of the base material strip 210 surface to metal materials. This step corresponds to... Figure 3 The scene shown is (b).

[0060] It should be noted that the pretreatment does not treat the entire surface of the base material strip 210. Specifically, the pretreatment only targets the central region of the base material strip 210 surface; this treated area is the active region 201, which enhances the adhesion of the metal material. The two edges along the width of the base material strip 210 surface are not pretreated, thus creating blank regions 202. This ensures that the edges of the base material strip 210 are generally not damaged during pretreatment, thereby avoiding or reducing defects such as perforations at the edges. The central region refers to the area between the blank regions 202 on both sides of the base material strip 210.

[0061] Both the active region 201 and the blank region 202 extend along the length of the base material strip 210. Typically, the active region 201 is a single unit located in the middle of the base material strip 210, while the blank regions 202 are distributed only on both sides of the base material strip 210, resulting in a composite current collector 200 as shown below. Figure 3 The single structure shown in (e) is shown in the middle.

[0062] In other embodiments, multiple active regions 201 spaced apart along the width direction of the base material strip 210 may be formed on the surface of the base material strip 210. Besides the blank regions 202 distributed on both sides of the width direction of the base material strip 210, blank regions 202 are also formed between adjacent active regions 201. Therefore, the resulting composite current collector 200 is as follows: Figure 13 and Figure 14 The diagram shows a multi-stripe structure resembling zebra stripes.

[0063] In this embodiment, step 120 includes: roughening the middle part of the surface of the base material strip 210; coating the roughened area of ​​the base material strip 210 surface with a sensitizing and activating liquid to form an active region 201.

[0064] Before roughening, degreasing may be necessary. Roughening can be physical, chemical, or a combination of both. Physical roughening methods include laser etching, ultraviolet irradiation, plasma irradiation, and corona treatment of the target area. Chemical roughening methods include immersing the target area in an aqueous solution containing one or more of hydrogen peroxide, sulfuric acid, chromic acid, and potassium permanganate. Furthermore, cleaning and drying may be performed after chemical roughening, depending on the specific circumstances.

[0065] After roughening treatment, a microstructure forms in the corresponding area. This microstructure increases the surface roughness of the base material strip 210, thereby improving its adhesion to the metal material. After roughening treatment, a sensitizing and activating solution can be applied to the roughened area using a precision coating method. Specifically, the sensitizing and activating solution can be an aqueous solution containing one or more ions or colloids selected from copper, tin, silver, platinum, palladium, and manganese. After sensitization treatment, the adhesion between the central area of ​​the base material strip 210 surface and the metal material is further increased, thus obtaining the desired active area 201.

[0066] After activating the middle part of the surface of the base material strip 210, the base material strip 210 can also be cleaned and dried as needed.

[0067] In another embodiment, step 120 includes: roughening a plurality of strip-shaped regions on the surface of the base material strip 210, the strip-shaped regions being located in the middle of the surface of the base material strip 210 and spaced apart along the width direction of the base material strip 210. A sensitizing activation liquid is coated onto the roughened strip-shaped regions to form active regions 201, and blank regions 202 are formed between adjacent strip-shaped regions where the base material strip 210 has not been roughened and has not been coated with the sensitizing activation liquid.

[0068] Thus, the active regions 201 on the surface of the base material strip 210 are multiple and spaced apart along the width direction of the base material strip 210. In addition to being distributed on both sides of the width direction of the base material strip 210, blank regions 202 are also formed between two adjacent active regions 201.

[0069] Step S130: A metal layer 220 is formed in the active region 201.

[0070] Specifically, a metal layer 220 can be formed on the active region 201 of the base material strip 210 surface through various coating methods such as physical vapor deposition, chemical vapor deposition, electroless plating, and electroplating.

[0071] In this embodiment, step S130 includes: chemically plating the base material strip 210 to form a metal film 221 attached to the active region 201. This step corresponds to... Figure 3 The scenario shown (c) involves electroplating the chemically plated base material strip 210 to form a metal layer 220 of a predetermined thickness on the surface of the metal film 221. This step corresponds to... Figure 3 The scene shown is (d).

[0072] It should be noted that, due to the relatively reactive chemical properties of aluminum, it is prone to rapid oxidation by combining with oxygen during the electroplating process. Therefore, the above-mentioned method of forming the metal layer 220 is generally only applicable to the preparation of negative electrode current collectors, and the resulting metal layer 220 is a copper layer, a copper alloy layer, or a copper-containing multilayer composite structure.

[0073] During electroless plating, the base material strip 210 can be immersed in a metal electroless plating solution, such as a copper plating solution, a nickel plating solution, or a copper-nickel alloy plating solution. The resulting metal film 221 can be a nickel plating layer, a copper plating layer, a copper-nickel alloy layer, or a combination thereof. The thickness of the metal film 221 is much smaller than that of the metal layer 220, typically between 20 nm and 400 nm, and the sheet resistance of the metal film 221 can range from 200 mΩ / square to 1000 mΩ / square. After electroless plating and before electroplating, the metal film 221 generally needs to be cleaned and dried. Furthermore, acidification treatment can be performed on the metal film 221 if necessary.

[0074] Electroplating is used to deposit more metal material on the surface of the metal film 221, gradually thickening it until a metal layer 220 of the desired thickness is obtained. For example, the thickness of the metal layer 200 can be 700 nm to 2000 nm. In this case, the sheet resistance of the metal layer 200 is 1 mΩ / square to 180 mΩ / square, exhibiting good conductivity. When the materials of the metal film 221 and the metal layer 220 are the same, the final metal layer 220 will be integrated with the metal film 221.

[0075] Chemical plating can successfully form a thin metal film 221 on the surface of a non-metallic base material strip 210, thus providing a foundation for the subsequent formation of the metal layer 220. Moreover, compared to physical vapor deposition, chemical plating offers a milder environment and causes less impact on the surface of the base material strip 210. Conversely, electroplating is more efficient in forming the metal layer 220 than chemical plating, resulting in a denser metal layer with better conductivity. Therefore, this method combines the advantages of both chemical plating and electroplating.

[0076] Furthermore, specifically in this embodiment, the base material strip 210 is electroplated using a brush plating method. Since brush plating does not require a plating tank, the equipment is simple, occupies a small area, and has a low cost. Moreover, when using brush plating, the non-plated areas, i.e., the blank areas 202, do not need to be covered with protective material, thus simplifying the operation process and improving the preparation efficiency.

[0077] It should be noted that, in other embodiments, an adhesive layer may be formed in the activation region 201 before electroless plating. This adhesive layer acts as a transition layer and can form a strong bond with both the polymer and the metal material. For example, the adhesive layer may include a polyurethane-based adhesive.

[0078] like Figure 4 As shown, since the metal layer 220 is formed only in the active region 201, i.e., the middle of the base material strip 210, and the blank region 202 does not form a metal layer 220, the perforation or damage caused by the edge current effect during electroplating will mainly be concentrated in the middle of the base material strip 210 and the position corresponding to the edge of the metal layer 220, while the edge of the base material strip 210 will maintain good integrity. Defects in the middle of the base material strip 210 have a smaller impact on the mechanical strength of the base material strip 210 than defects at the edge, so the base material strip 210 is not easily damaged or broken during the tape running process. In addition, since the base material strip 210 with undamaged edges can withstand greater tension, the tape running speed of the base material strip 210 can be increased without breaking the tape, thereby further improving the preparation efficiency of the composite current collector 200.

[0079] Step S140: Remove the edge portions or blank areas 202 on both sides of the metal layer 220 along the width direction to obtain the composite current collector 200.

[0080] Since the blank area 202 does not have conductive properties, it cannot be used as an electrode and needs to be removed before electrode fabrication. During the removal operation, only the portion of the base material strip 210 corresponding to the blank area 202 can be removed, or a portion of the metal layer 220 can be removed at the same time as the blank area 202 is removed.

[0081] like Figure 4 and Figure 13 As shown, specifically in this embodiment, when cutting off the blank area 202, the cutting component 341 cuts along the dotted line shown in the figure. Therefore, the width of the cut is greater than the width of the blank area 202, thereby removing the edge portions of the metal layer 220 along both sides of the width direction. In this way, during the process of cutting off the blank area 202, damage at the edge position of the metal layer 220 can be removed accordingly, thereby obtaining a composite current collector 200 with better quality and significantly improving the yield of the composite current collector 200.

[0082] In this embodiment, after step S130, the method further includes forming an antioxidant layer on the surface of the metal layer 220. The antioxidant layer can be a passivation layer formed on the metal layer 220 after passivation treatment, thereby giving the metal layer 220 better antioxidant properties. Specifically, the composite current collector 200 can be introduced into a passivation bath, and the surface of the metal layer 220 can be passivated using a solution containing chromium or nickel.

[0083] In this embodiment, the base material strip 210 is unwound using a continuous conveyor belt method, and the resulting composite current collector 200 is wound up using the same method. Thus, the above method enables continuous roll-to-roll preparation of the composite current collector 200, which helps improve efficiency.

[0084] The wound composite current collector 200 can be stored in roll form and unwound directly when needed. Obviously, in other embodiments, the winding step can be omitted, and the resulting composite current collector 200 can directly proceed to the next process such as coating or slicing for the preparation of lithium battery electrodes.

[0085] The preparation methods of the above-mentioned composite current collectors will be explained below with reference to several specific preparation processes of negative electrode current collectors:

[0086] 1. A negative electrode current collector for Cu / PET / Cu with a width of 1200mm.

[0087] We provide polyethylene terephthalate (PET) tape with a thickness of 6μm and a width of 1750mm. The tape speed of the PET tape is approximately 40m / min.

[0088] First, a corona treatment is used to roughen the 1300mm wide area in the middle of the PET strip, with a corona power of approximately 360W to 1200W. Then, a sensitizing and activating solution, an aqueous solution containing 1g / L to 2g / L AgNO3, is coated onto the roughened area in the middle 1300mm wide area of ​​the PET strip using inkjet printing. After the sensitizing and activating solution is coated, the surface is activated by double-sided ultraviolet irradiation, thus making the 1300mm wide area in the middle of the PET strip the active area 201.

[0089] The surface-activated PET strip is immersed in a metal electroless plating solution for electroless plating. The electroless plating temperature is generally controlled between 35℃ and 53℃. The metal electroless plating solution is an aqueous solution containing 10g / L to 15g / L copper sulfate, 18g / L to 24g / L sodium potassium tartrate, 8g / L to 12g / L EDTA (ethylenediaminetetraacetic acid), 0.02g / L to 0.03g / L potassium ferrocyanide, 2.5g / L to 3.5g / L formaldehyde, 6g / L to 7g / L sodium hydroxide, and 3g / L to 6g / L sodium carbonate, as well as a small amount of other additives. After a certain period of time, a copper-containing metal film 221 is obtained in the active area 201 of the PET strip.

[0090] The chemically plated PET strip is then subjected to electrobrush copper plating to thicken the metal film 221 until it reaches a thickness of 700nm to 2000nm. The copper plating solution is an aqueous solution containing 150g / L to 250g / L copper sulfate, 50g / L to 70g / L sulfuric acid, and small amounts of other additives. During electrobrush copper plating, the PET strip feed speed is 30m / min to 50m / min; therefore, a tension control mechanism is required for buffering and releasing to ensure that the feed speeds of each process are matched.

[0091] After the electroplating is completed, the resulting metal layer 220 is first cleaned with deionized water, then immersed in an aqueous solution containing chromate or dichromate for passivation, and finally cleaned again with deionized water and dried. Next, 275mm wide material is cut off from both sides of the PET strip in the width direction to obtain a 1200mm wide negative electrode current collector.

[0092] 2. 700mm wide Cu / PET / Cu negative electrode current collector

[0093] We provide PET tapes with a thickness of 4.5μm and a width of 1200mm;

[0094] First, the PET strip is degreased and dried in an ethanol degreasing and cleaning tank. Then, a roughening solution containing 80g / L to 120g / L sulfuric acid and 100g / L to 250g / L chromic anhydride at a temperature of 40℃ to 50℃ is applied to an 800mm wide area in the middle of the PET strip for chemical roughening. After roughening, it is washed with deionized water at 40℃ to 50℃ and dried with hot air. Next, a sensitizing and activating solution is applied to the roughened area using gravure coating. The sensitizing and activating solution is a palladium colloidal solution containing 0.5g / L to 1.5g / L palladium chloride, 30g / L to 40g / L stannous chloride, and 260g / L to 320ml / L concentrated hydrochloric acid. After activation, it is washed with an aqueous solution containing 35g / L to 55g / L sulfuric acid, thus making the 800mm wide area in the middle of the PET strip the active area 201.

[0095] The surface-activated PET strip is immersed in a metal electroless plating solution for electroless nickel plating. The temperature of the electroless nickel plating is generally controlled between 75℃ and 90℃. The metal plating solution is an aqueous solution with a pH of 4.8 to 5.6 containing 23g / L to 30g / L nickel sulfate, 25g / L to 35g / L sodium hypophosphite, 15g / L to 23g / L malic acid, 12g / L to 24g / L sodium acetate, and a small amount of other additives. During electroless nickel plating, the conveyor belt speed of the PET strip is approximately 35m / min. After electroless nickel plating, a nickel-containing metal film 221 is obtained in the activated area 201.

[0096] After being cleaned with an aqueous solution containing 35 g / L to 55 g / L sulfuric acid, the PET strip is immersed again in a chemical copper plating solution for electroless copper plating. The temperature for electroless copper plating is generally controlled between 65℃ and 73℃. The metal plating solution is an aqueous solution with a pH of 11.5 to 12.5 containing 10 g / L to 15 g / L copper sulfate, 38 g / L to 47 g / L disodium EDTA, 3.5 g / L to 4.5 ml / L formaldehyde, and 2.6 g / L to 3.7 g / L sodium hydroxide. During electroless copper plating, the conveyor belt speed of the PET strip is between 30 m / min and 50 m / min. After electroless copper plating, a copper-containing metal film will be formed on the surface of the original nickel-containing metal film.

[0097] After cleaning the PET strip with an aqueous solution containing 35g / L to 55g / L sulfuric acid, electroplating and passivation are performed in the same manner as described above, forming a metal layer 220 of a predetermined thickness in the active region 201. Next, 250mm wide material is removed from both sides of the PET strip in the width direction to obtain a 700mm wide negative electrode current collector.

[0098] 3. 1100mm wide Cu / PP / Cu negative electrode current collector

[0099] We provide polypropylene (PP) strips with a thickness of 8μm and a width of 1600mm. The conveyor belt speed of the PP strips is approximately 43m / min.

[0100] The surface of a 1200mm wide area in the middle of the PP strip is roughened using femtosecond laser etching. Then, a sensitizing and activating solution is applied to this roughened area using inkjet printing. The sensitizing and activating solution is a copper colloidal solution containing 20g / L–30g / L copper sulfate, 8g / L–12g / L gelatin, 6g / L–9g / L sodium borohydride, and 15g / L–25ml / L n-butanol. After activation, the area is cleaned with an aqueous solution containing 35g / L–55g / L concentrated sulfuric acid, thus making the 1200mm wide area in the middle of the PP strip the active region 201.

[0101] By performing chemical plating, brush plating, and passivation in the same manner as in the preparation of the first type of negative electrode current collector described above, a metal layer 220 of a predetermined thickness can be formed in the active region 201. Next, by removing 250mm wide material from both sides of the PP strip in the width direction, a negative electrode current collector with a width of 1100mm can be obtained.

[0102] Based on actual testing, the product and processing parameters of the above three types of negative electrode current collectors are as follows:

[0103]

[0104] As shown in the table above, the sheet resistivity of the three negative electrode current collectors prepared using the aforementioned composite current collector preparation method meets the requirements of lithium batteries, with a pass rate of 95%–98%, a yield rate of over 97%, and a preparation speed of 30 m / min–50 m / min. Therefore, the aforementioned composite current collector preparation method has the advantages of high yield and high efficiency.

[0105] As mentioned earlier, due to the special chemical properties of aluminum, the coating method combining chemical plating and electroplating is not suitable for forming an aluminum-containing metal layer 220, that is, it is not suitable for the preparation of positive electrode current collectors.

[0106] To address this issue, in another embodiment, step S130 includes: performing chemical plating on the base material strip 210 to form a metal layer 220 of a predetermined thickness in the active region 201. Compared to the previous embodiment, the electroplating process is omitted, thus requiring a longer chemical plating time. Furthermore, the type of metal chemical plating solution used also differs.

[0107] Specifically, the metal electroless plating solution can be a molten salt aluminum plating solution, etc. After a relatively long electroless plating period, an aluminum layer, aluminum alloy layer, or aluminum-containing multilayer composite structure of a predetermined thickness can be directly formed in the active region 201. The preparation method of the above-mentioned composite current collector will be explained below with reference to a specific positive electrode current collector preparation process:

[0108] We provide PET strips with a thickness of 6μm and a width of 1750mm, with a conveyor speed of approximately 40m / min.

[0109] First, a corona treatment method is used to roughen the area within a 1300mm width range in the middle of the PET strip, with a corona power of 360W to 1200W. Then, a sensitizing and activating solution, an aqueous solution containing 1g / L to 2g / L AgNO3, is coated onto the roughened area within the 1300mm width range using inkjet printing. After the sensitizing and activating solution is coated, the surface is activated by double-sided ultraviolet irradiation, thus making the area within the 1300mm width range in the middle of the PET strip the active area 201.

[0110] The surface-activated PET strip is immersed in a metal electroless plating solution for electroless aluminum plating. The electroless plating temperature is generally controlled between 15℃ and 45℃, and the metal electroless plating solution is AlCl3-EMIC. The conveyor speed of the PET strip during electroless plating is also approximately 40m / min. After a certain period of time, an aluminum-containing metal layer 220 of a predetermined thickness can be obtained in the active region 201 of the PET strip.

[0111] By cutting off 275mm wide material from both sides of the PET strip in the width direction, a 1200mm wide Al / PET / Al positive current collector can be obtained.

[0112] The aforementioned composite current collector preparation method selectively pre-treats to form an active region 201 in the center of the surface of the base material strip 210, and creates untreated regions 202 along the width of both sides of the base material strip 210. These untreated regions 202 prevent damage to the edges of the base material strip 210. Furthermore, during the formation of the metal layer 220, only the active region 201 is processed; the untreated regions 202 do not form the metal layer 220. Damage such as perforation caused to the base material strip 210 during metal layer 220 formation typically occurs at the edges of the metal layer 220. Therefore, the preparation process minimizes damage to the edges of the base material strip 210, maintaining its high mechanical strength. Moreover, damage at the edges of the metal layer 220 can be subsequently removed. Thus, the aforementioned composite current collector preparation method significantly improves the yield rate.

[0113] Compared with traditional metal foil current collectors, the composite current collector 200 prepared by the above method has the following advantages: Using a polymer base material strip 210 as a support reduces the use of metal, resulting in a weight reduction of 40%–70%, and increases battery energy density, offering potential for cost reduction in the face of high metal prices; furthermore, it improves the flexibility and processing performance of the composite current collector 200. Finally, under abnormal operating conditions, such as internal short circuits or physical punctures, the composite current collector 200 can break the circuit, thereby improving battery safety performance.

[0114] The present invention also provides a composite current collector preparation apparatus, which is capable of performing the above-described composite current collector preparation method to obtain, as described above, a composite current collector. Figure 1 The composite current collector 200 is shown.

[0115] Please refer to the following: Figure 5 In one embodiment of the present invention, the composite current collector preparation device 300 includes an unwinding mechanism 310, a pretreatment mechanism 320, a coating mechanism 330, and a trimming mechanism 340.

[0116] The unwinding mechanism 310 is used to provide the base material strip 210; the pretreatment mechanism 320 is used to form an active region 201 in the middle of the surface of the base material strip 210 and to form blank regions 202 on both sides of the width direction of the surface of the base material strip 210. The active region 201 and the blank regions 202 are strip-shaped and extend along the length direction of the base material strip 210; the coating mechanism 330 is used to form a metal layer 220 in the active region 201; the edge trimming mechanism 340 is used to cut off the edge portions or blank regions 202 on both sides of the width direction of the metal layer 220 to obtain the composite current collector 200.

[0117] It should be noted that the functions of the unwinding mechanism 310, the pretreatment mechanism 320, the coating mechanism 330 and the trimming mechanism 340 correspond to the specific processes of steps S110 to S140 of the above-mentioned composite current collector preparation method, and therefore will not be described again here.

[0118] In this embodiment, the composite current collector preparation apparatus 300 further includes a winding mechanism 350. The unwinding mechanism 310 continuously unwinds the base material strip 210, while the winding mechanism 350 continuously winds the composite current collector 200. A pretreatment mechanism 320 and a coating mechanism 330 are disposed between the unwinding mechanism 310 and the winding mechanism 350. Therefore, the composite current collector preparation apparatus 300 can achieve continuous roll-to-roll production of the composite current collector 200, thereby helping to improve efficiency.

[0119] Moreover, since the pretreatment mechanism 320 and the coating mechanism 330 only process the middle part of the base material strip 210, while leaving blank areas 202 at the edges on both sides of the base material strip 210, the base material strip 210 can maintain high mechanical strength, thereby enabling the base material strip 210 to withstand greater tension during winding, making it less prone to breakage and significantly improving the yield.

[0120] Please refer to the following: Figure 6 Specifically, in this embodiment, the unwinding mechanism 310 includes an unwinding roller 311, a first tape receiving device 312, a first correction device 313, and a first tension adjusting device 314.

[0121] The base material strip 210 can be stored in the unwinding roller 311 in the form of a roll and unwound by the unwinding shaft 311. The first tape-connecting device 312 can ensure the continuity of the unwinding of the base material strip 210. The first tension adjusting device 314 is generally composed of multiple guide rollers, and the relative distance between the multiple guide rollers is adjustable. When the tape speed fluctuates in each process, the multiple guide rollers can buffer or release the base material strip 210 by moving closer or further apart from each other, thereby maintaining the stability of the tension of the base material strip 210. In addition, in order to change the tape direction of the base material strip 210, the unwinding mechanism 310 generally also includes multiple guide rollers (not shown in the figure).

[0122] The structure of the winding mechanism 350 is largely the same as that of the unwinding mechanism 310, differing only in the belt travel direction, and therefore will not be described further here. In addition, the winding mechanism 350 may also include an edge trimming assembly 341 and an edge material collection assembly 342 (see...). Figure 4 The edge-cutting assembly 314 can cut off the blank area 202 in the base material strip 210 from the composite current collector 200, and the edge material collection assembly 342 collects the waste material obtained from the cutting. When cutting off the blank area 202, the width of the cut is greater than the width of the blank area 202, so that the defective part of the metal layer 220 can be cut off together, thereby obtaining a composite current collector 200 with better quality.

[0123] In this embodiment, the pretreatment mechanism 320 includes a roughening mechanism 321 and an activation mechanism 322. The roughening mechanism 321 is used to roughen the middle part of the surface of the base material strip 210 to form a microstructure; the activation mechanism 322 is used to coat the roughened area of ​​the surface of the base material strip 210 with a sensitizing activation liquid to form an active region 201.

[0124] The roughening treatment mechanism 321 can roughen the surface of the base material strip 210 using physical or chemical methods. For example, please refer to... Figure 7 In one embodiment, the roughening treatment mechanism 321 includes a physical roughening component 3211 and guide rollers 3212 located upstream and downstream of the material roughening component 3211.

[0125] The physical roughening assembly 3211 typically comprises two components arranged opposite each other, used to simultaneously roughen both sides of the base material strip 210. The physical roughening assembly 3211 can be a laser emitter, ultraviolet emitter, plasma emitter, or corona discharge assembly, etc. The base material strip 210 unwound by the unwinding mechanism 310 enters the working range of the physical roughening assembly 3211 after being guided by the upstream guide roller 3212, to roughen the middle portion of the surface of the base material strip 210. After roughening is completed, the base material strip 210 is discharged by the downstream guide roller 3212.

[0126] Please refer to the following: Figure 8In another embodiment, the roughening treatment mechanism 321 includes an oil removal tank 3213, at least two chemical roughening coating devices 3214, a first drying and heating device 3215, a second tension adjusting device 3216, and a first cleaning tank 3217.

[0127] The chemical roughening coating apparatus 3214 can apply the chemical roughening solution using methods such as gravure coating, inkjet printing, extrusion coating, or spraying. The chemical roughening solution can be an aqueous solution containing one or more of hydrogen peroxide, sulfuric acid, chromic acid, and potassium permanganate. The first drying and heating apparatus 3215 can use hot air heating, infrared heating, laser heating, or a combination thereof for heating.

[0128] In addition, to ensure smooth belt feeding, the roughening treatment mechanism 321 is generally equipped with multiple guide rollers (not shown in the figure) to change the feeding direction of the base material belt 210. Moreover, to prevent the base material belt 210 from carrying away the cleaning agent, each degreasing tank 3213 and the output end of the first cleaning tank 3217 are also equipped with a liquid intercepting roller (not shown in the figure). The cleaning agent in the first cleaning tank 3217 can be deionized water.

[0129] Please refer to the following: Figure 9 Specifically, in this embodiment, the activation treatment mechanism 322 includes at least two activation liquid coating devices 3221, an activation and drying heating device 3222, a third tension adjustment device 3223, and a second cleaning tank 3224.

[0130] The activation solution coating device 3221 can coat the activation sensitizing solution using methods such as gravure coating, inkjet printing, extrusion coating, or spraying. The sensitizing activation solution can be an aqueous solution containing one or more ions or colloids selected from copper, tin, silver, platinum, palladium, and manganese. The activation and drying heating device 3222 can perform activation by heating or ultraviolet irradiation, and the heating method can be hot air heating, infrared heating, laser heating, or a combination thereof. In addition, the activation treatment mechanism 322 is generally equipped with multiple guide rollers (not shown in the figure) to change the belt direction of the base material belt 210. Moreover, each second cleaning tank 3224 is also equipped with a liquid intercepting roller (not shown in the figure) at its output end, and the cleaning agent in the second cleaning tank 3224 can be deionized water.

[0131] Please refer to it again. Figure 5 In this embodiment, the coating mechanism 330 includes a chemical plating mechanism 331 and an electroplating mechanism 332. The chemical plating mechanism 331 is used to chemically platrude the base material strip 210 to form a metal film 221 with the active region 201 attached. The electroplating mechanism 332 is used to electroplat the chemically plated base material strip 210 to form a metal layer 220 of a predetermined thickness on the surface of the metal film 221.

[0132] It should be noted that, due to the relatively reactive chemical properties of aluminum, it is prone to rapid oxidation by combining with oxygen during the electroplating process. Therefore, the aforementioned coating mechanism 330 is generally only suitable for the preparation of negative electrode current collectors, and the resulting metal layer 220 is a copper layer, a copper alloy layer, or a copper-containing multilayer composite structure.

[0133] Please refer to the following: Figure 10 Specifically, in this embodiment, the electroless plating mechanism 331 includes an electroless plating bath 3311, a stirring device 3312 and a temperature control device 3313 disposed in the electroless plating bath 3311, a fourth tension adjustment device 3314, a third cleaning bath 3315, a drying device 3316 and an online thickness measuring device 3317.

[0134] The stirring device 3312 can be a paddle stirrer, ultrasonic stirrer, or airflow stirrer. The online thickness measuring device 3317 adopts a non-contact thickness measuring method, which can be laser thickness measuring, X-ray thickness measuring, β-ray thickness measuring, eddy current thickness measuring, or resistance value thickness measuring. In addition, in order to achieve smooth belt feeding, the electroless plating mechanism 331 is generally equipped with multiple guide rollers (not shown in the figure) to change the feeding direction of the base material belt 210. Moreover, in order to prevent the base material belt 210 from carrying away liquid, each electroless plating bath 3311 and the output end of the third cleaning bath 3315 are also equipped with a liquid intercepting roller (not shown in the figure). The cleaning agent in the third cleaning bath 3315 can be deionized water.

[0135] The electroplating mechanism 332 in this embodiment uses an electroplating device. Please refer to the following: Figure 11 Specifically, in this embodiment, the electroplating mechanism 332 includes a cathode roller device 3321, an anode brush device 3322, a power control device 3323, a plating solution supply and recovery device 3324, a fourth cleaning tank 3325, a second drying device 3326, and a second online thickness measuring device 3327.

[0136] There are two cathode roller devices 3321 and two anode brush devices 3322, used to coat the front and back sides of the base material strip 210 respectively. The cathode roller devices 3321, anode brush devices 3322, and power control device 3323 are connected and controlled by a circuit. The cathode roller device 3321 includes a non-conductive cathode back roller and a conductive cathode roller; the anode brush device 3322 has a shape matching that of the cathode roller device 3321, including an anode back roller and an anode sheath. The anode sheath can be made of porous fabric. The plating solution supply and recovery device 3324 includes a plating solution storage tank, a stirring assembly, a temperature control assembly, a plating solution recovery tank, a filter device, a supply pump, and nozzles. The second drying device 3326 and the second online thickness measuring device 3327 have the same structure and function as the aforementioned drying device 3316 and online thickness measuring device 3317.

[0137] In addition, to ensure smooth conveyor belt transport, the electroplating mechanism 332 is generally equipped with multiple guide rollers (not shown in the figure) to change the conveyor direction of the base material belt 210. Moreover, to prevent the base material belt 210 from carrying out liquid, each fourth cleaning tank 3325 is equipped with a liquid intercepting roller (not shown in the figure) at its output end. The cleaning agent in the fourth cleaning tank 3325 can be deionized water.

[0138] Both the chemical plating mechanism 331 and the electroplating mechanism 332 can be chemical plating equipment and electroplating equipment commonly used in the prior art. Therefore, the specific structure and working process of the chemical plating mechanism 331 and the electroplating mechanism 332 will not be described in detail here.

[0139] Chemical plating can successfully form a thin metal film 221 on the surface of the non-metallic base material strip 210, thus providing a foundation for the subsequent formation of the metal layer 220. Moreover, compared with physical vapor deposition, chemical plating has a milder environment and less impact on the surface of the base material strip 210. Compared with chemical plating, electroplating is more efficient in forming the metal layer 220, and the formed metal layer 220 is denser and has better conductivity. Therefore, the coating mechanism 330 can combine the advantages of both chemical plating and electroplating processes.

[0140] Furthermore, compared to vacuum physical vapor deposition equipment, the film formation conditions of the electroless plating unit 331 and the electroplating unit 332 are less different, thus facilitating their connection into a complete roll-to-roll production line. The substrate strip 210 can directly enter the electroplating unit 332 from the output end of the electroless plating unit 331, avoiding excessively long buffering times. This effectively prevents water and oxygen in the air from forming an oxide film on the surface of the substrate strip 210, ensuring the quality of the final product.

[0141] As mentioned earlier, due to the special chemical properties of aluminum, the coating mechanism 330 that combines chemical plating and electroplating is not suitable for forming an aluminum-containing metal layer 220, that is, it is not suitable for the preparation of positive electrode current collectors.

[0142] To resolve this issue, please refer to Figure 12 In another embodiment of the present invention, the coating mechanism 330 is capable of chemically plating the base material strip 210 to form a metal layer 220 of a predetermined thickness in the active region 201.

[0143] Compared to the previous embodiment, the coating mechanism 330 omits the electroplating process, thus making it suitable for the preparation of positive electrode current collectors. The coating mechanism 330 can directly employ commonly used electroless plating equipment, and the type of metal electroless plating solution used in the electroless plating process differs from the previous embodiment. Specifically, the metal electroless plating solution can be a molten salt aluminum plating solution, etc. After a relatively long electroless plating process, the coating mechanism 330 can directly form an aluminum layer, aluminum alloy layer, or aluminum-containing multilayer composite structure of a predetermined thickness in the active region 201.

[0144] 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.

[0145] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing a composite current collector, characterized in that, Including the following steps: Provide base material strip; An active region is formed in the middle of the surface of the base material strip, and blank regions are formed on both sides of the base material strip along the width direction. Both the active region and the blank regions are strip-shaped and extend along the length direction of the base material strip. A metal layer is formed in the active region; when the composite current collector is a negative electrode composite current collector, the step of forming a metal layer in the active region includes: chemically plating the base material strip to form a metal film attached to the active region; electroplating the chemically plated base material strip to form a metal layer of a predetermined thickness on the surface of the metal film; when the composite current collector is a positive electrode composite current collector, the step of forming a metal layer in the active region includes: chemically plating the base material strip to form a metal layer of a predetermined thickness in the active region; The metal layer is removed from both sides of the width direction, or from the blank area, to obtain a composite current collector.

2. The method for preparing a composite current collector according to claim 1, characterized in that, The steps of forming an active region in the middle of the surface of the base material strip and forming blank regions on both sides of the base material strip along the width direction include: The middle part of the surface of the base material strip is roughened; The roughened area is coated with a sensitizing and activating solution to form the active region; The blank areas are formed by the areas on both sides of the base material strip along the width direction that are not roughened and are not coated with sensitizing activating liquid.

3. The method for preparing a composite current collector according to claim 2, characterized in that, The step of roughening the middle part of the surface of the base material strip includes: roughening multiple strip-shaped regions on the surface of the base material strip, wherein the strip-shaped regions are located in the middle part of the surface of the base material strip and are spaced apart along the width direction of the base material strip; Specifically, the strip-shaped regions after roughening are coated with a sensitizing and activating solution to form the active regions, while the areas between adjacent strip-shaped regions that have not undergone roughening and have not been coated with the sensitizing and activating solution form the blank areas.

4. The method for preparing a composite current collector according to claim 1, characterized in that, The base material strip is electroplated using an electroplating method.

5. The method for preparing a composite current collector according to claim 1, characterized in that, After the step of forming a metal layer in the active region, the method further includes the step of forming an antioxidant layer on the surface of the metal layer opposite to the base material strip.

6. The method for preparing a composite current collector according to claim 1, characterized in that, The base material strip is unwound in a continuous conveyor belt manner; the composite current collector is wound up in a continuous conveyor belt manner.

7. A composite current collector preparation device, characterized in that, include: An unwinding mechanism is used to provide the base material strip; A pretreatment mechanism is used to form an active region in the middle of the surface of the base material strip and to form blank regions on both sides of the base material strip along the width direction. Both the active region and the blank regions are strip-shaped and extend along the length direction of the base material strip. A coating mechanism is used to form a metal layer in the active region. When the composite current collector is a negative electrode composite current collector, the coating mechanism can perform chemical plating on the base material strip to form a metal film attached to the active region; and electroplating is performed on the chemically plated base material strip to form a metal layer of a predetermined thickness on the surface of the metal film. When the composite current collector is a positive electrode composite current collector, the coating mechanism can perform chemical plating on the base material strip to form a metal layer of a predetermined thickness in the active region. The edge-cutting mechanism is used to cut off the edge portions of the metal layer on both sides along the width direction or the blank area to obtain a composite current collector.

8. The composite current collector preparation apparatus according to claim 7, characterized in that, The unwinding mechanism is capable of continuously unwinding the base material strip, and the composite current collector preparation device also includes a winding mechanism, which is capable of continuously winding the composite current collector.

Images