Current collector and preparation method thereof

Abstract

The invention provides a current collector and a preparation method thereof. The current collector comprises a conductive base material and a conductive layer which are compounded with each other, and the material of the conductive base material is different from that of the conductive layer; a strip-shaped groove is formed in the surface, close to the conducting layer, of the conducting base material, and the roughness A of the surface, close to the conducting layer, of the conducting base material and the roughness B of the surface, away from the conducting layer, of the conducting base material meet the requirement of 0.2 micrometer lt; a < = 2.0 [mu] m and A > B. According to the current collector provided by the invention, the grooves are formed in the surfaces of the conductive base material, the roughness of the two surfaces of the conductive base material is controlled within the range, and the surface which is provided with the grooves and has higher roughness is compounded with the conductive layer, so that the bonding force between the conductive base material and the conductive layer can be improved; and the roughness of one surface, far away from the conductive layer, of the conductive substrate is smaller than that of the other surface, so that the risk of depositing a negative electrode metal material on the surface, far away from the conductive layer, of the conductive substrate during preparation of the conductive layer can be reduced, and the current collector with a purer positive electrode surface is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of current collectors, and particularly to a current collector and a preparation method thereof. Background Art

[0002] The problems of energy crisis and environmental hazards seriously hinder the development of traditional automobiles, while electric vehicles solve the problems of energy crisis and environmental hazards brought by traditional automobiles to a certain extent. At present, the power batteries used in electric vehicles usually achieve high voltage by connecting individual battery cells in series through tabs. However, this method often weakens the power output due to too high resistance at the wire contact, increases the technical cost, and reduces the space utilization rate.

[0003] A bipolar battery is a battery that obtains high voltage by coating active materials with different polarities on both sides of a current collector and realizing internal structure series connection through superposition. It has the advantages of high energy density and simple structure, and reduces the technical cost and improves the space utilization rate. Among them, the current collector includes a negative electrode metal layer and a positive electrode metal layer at the same time. The negative electrode metal layer is used to combine with the negative electrode active material layer, and the positive electrode metal layer is used to combine with the positive electrode active material layer.

[0004] However, the existing current collector has the problem of poor bonding force between the positive and negative electrode metal layers. Summary of the Invention

[0005] In order to solve the problem of poor bonding force between the positive and negative electrode metal layers of the existing current collector, the present invention provides a current collector and a preparation method thereof.

[0006] According to the first aspect of the present invention, there is provided a current collector, which includes a conductive substrate and a conductive layer that are mutually compounded, and the materials of the conductive substrate and the conductive layer are different; strip-shaped grooves are provided on the surface of the conductive substrate close to the conductive layer. Taking the surface roughness Ra of the conductive substrate close to the conductive layer as A, and the surface roughness Ra of the conductive substrate far from the conductive layer as B, A and B satisfy 0.2 μm < A ≤ 2.0 μm and A > B.

[0007] The current collector provided by the present invention comprises a conductive substrate and a conductive layer which are compounded with each other. By providing strip-shaped grooves on one surface of the conductive substrate and regulating the roughness of both surfaces of the conductive substrate to meet the above range, first, compounding the surface of the conductive substrate with grooves and higher roughness with the conductive layer can improve the adhesion between the conductive substrate (positive electrode metal surface / positive electrode metal layer) and the conductive layer (negative electrode metal surface / negative electrode metal layer), reduce the risk of peeling off during subsequent rolling or actual use of the current collector, and improve the mechanical strength of the current collector. Second, controlling the surface roughness Ra of the surface of the conductive substrate with strip-shaped grooves to be greater than 0.2 and less than or equal to 2.0 μm helps to improve the uniformity and durability of the adhesion between the conductive substrate and the conductive layer. The lower surface roughness can also reduce the friction and wear during over-rolling in the production process, extend the service life of the roller, and at the same time make the roughness of the surface of the conductive substrate far from the conductive layer less than that of the side close to the conductive layer, which can reduce the risk of depositing negative electrode metal materials on the surface of the conductive substrate far from the conductive layer during the preparation of the conductive layer, thereby obtaining a current collector with a purer positive electrode surface. Moreover, during the preparation process of the electrode sheet using this current collector, the bonding force between the conductive substrate and the subsequent carbon coating or active material can be ensured, thereby improving the electrolyte corrosion resistance of the electrode sheet using this current collector as a whole, reducing the corrosion of the electrolyte at the interface junction in the current collector, and finally enhancing the cycle stability and durability of the battery using it.

[0008] During the charge and discharge process of the battery, the electrode material will undergo volume changes due to the insertion and extraction of lithium ions. If the metal layer materials in the metal layers (conductive substrate and conductive layer) located on both sides of the current collector are different, the volume changes of the conductive substrate and the conductive layer during the charge and discharge process may lead to an asymmetric stress state on both sides. Specifically, one metal layer may be subjected to greater stress due to volume expansion, while the stress on the other metal layer may be relatively smaller. This asymmetric stress state may cause the accumulation of plastic deformation in the metal layer during the cyclic charge and discharge process. Over time, this accumulated deformation may lead to local stress concentration in the metal layer, thereby affecting the overall performance of the current collector, especially when the thickness of one of the metal layers is relatively thin, this adverse effect is more serious.

[0009] The current collector provided by the present invention controls the roughness of two surfaces of the conductive substrate by providing strip-shaped grooves on the surface of the conductive substrate close to the conductive layer. First, it can increase the contact area and complexity of the interface between the conductive substrate and the conductive layer, making the stress distribution more uniform at the interface. This structure can disperse local stress concentration and avoid crack initiation and propagation caused by stress concentration. Second, it can promote the redistribution of stress changes between different regions and avoid excessive concentration of stress changes in a specific region. Third, the strip-shaped grooves are used to increase the difficulty of crack or deformation expansion, which can effectively inhibit the expansion of cracks or deformations. Through the above three aspects, the bending resistance of the current collector can be improved.

[0010] Preferably, the depth of the strip-shaped grooves on the surface of the conductive substrate is 0.1-1 μm.

[0011] By controlling the depth of the strip-shaped grooves on the surface of the conductive substrate within the above range, the bending resistance of the current collector can be further improved.

[0012] Preferably, strip-shaped grooves are provided on the surface of the conductive layer away from the conductive substrate. Taking the surface roughness Ra of the conductive layer away from the conductive substrate as C, C satisfies 0.2 μm < C ≤ 2.0 μm.

[0013] By providing strip-shaped grooves on the surface of the conductive layer away from the conductive substrate and regulating the roughness of this surface to satisfy the above range, stress can be further dispersed, the bending resistance of the current collector can be improved, and finally, a significant improvement in the performance of the battery using this current collector can be achieved.

[0014] It should be noted that the strip-shaped grooves on the surface of the conductive substrate or the conductive layer of the current collector can be arranged irregularly or regularly.

[0015] Irregularly arranged strip-shaped grooves are provided on the surface of the conductive layer away from the conductive substrate. First, it can significantly increase the surface area of the conductive layer, thereby enhancing the contact area between the negative electrode active material and the conductive layer of the current collector, which helps improve the efficiency of the electrochemical reaction, and further increases the capacity and power density of the battery. Second, the irregular surface can provide more anchor points, enabling the negative electrode active material to adhere more firmly to the conductive layer of the current collector, thus reducing the risk of shedding of the negative electrode active material and extending the service life of the battery. Third, the increased surface area and better material adhesion contribute to reducing the interfacial impedance between the current collector and the negative electrode active material, improving the overall electrochemical performance of the battery. Fourth, the irregularly shaped strip-shaped grooves can, to a certain extent, alleviate the volume change of the negative electrode active material during charge and discharge, reducing the impact of the expansion and contraction of the negative electrode active material on the current collector and enhancing the mechanical stability of the structure. Fifth, the irregular surface helps form more channels or paths within the negative electrode material, thereby promoting the transport of ions in the electrolyte and increasing the charge and discharge speed of the battery. Regularly arranged strip-shaped grooves are provided on the surface of the conductive layer away from the conductive substrate, which can make the grooves more evenly distributed on the surface of the conductive layer, make the performance of the current collector more uniform, and thus endow the current collector with better consistency.

[0016] Preferably, the material of the conductive substrate includes at least one of aluminum, aluminum alloy, silver, silver alloy, copper, copper alloy, gold, gold alloy, nickel, nickel alloy, iron, iron alloy, titanium, titanium alloy, manganese, and manganese alloy.

[0017] Preferably, the material of the conductive layer includes at least one of copper, copper alloy, silver, silver alloy, gold, gold alloy, nickel, nickel alloy, iron, iron alloy, titanium, titanium alloy, manganese, and manganese alloy.

[0018] Preferably, the D50 particle size of the material of the conductive layer is 300 - 600 nm.

[0019] Large-sized metal particles may not form a uniform and dense coating during electroplating and may form "protrusions". These protrusions will generate additional resistance when current passes through, resulting in a reduction in circuit efficiency. When the particle size is too small, a coating with sufficient thickness may not be formed, leading to a decline in the coating quality. Such a weak coating may be more susceptible to corrosion and wear. By controlling the D50 particle size of the material in the conductive layer of the current collector within the above range, the quality of the conductive layer and its bonding force with other layers can be ensured to a certain extent, and the resistance of the current collector can be maintained at a relatively low level.

[0020] Preferably, the conductive substrate is aluminum foil.

[0021] Preferably, the conductive layer is a copper layer.

[0022] Preferably, the current collector further includes a primer layer, and the conductive substrate, the primer layer, and the conductive layer are sequentially laminated; the material of the primer layer includes at least one of nickel-chromium alloy, alumina, silica, titanium nitride, silicon nitride, and polyurethane.

[0023] By providing a primer layer containing the above materials between the conductive substrate and the conductive layer, the adhesion between the conductive substrate and the conductive layer can be further improved, and the mechanical strength of the current collector can be further enhanced.

[0024] Preferably, the thickness of the conductive substrate is 10 to 50 μm.

[0025] Controlling the thickness of the conductive substrate within the above range can not only ensure that the conductive substrate provides sufficient support for the conductive layer and / or the primer layer, but also does not affect the adhesion between the conductive substrate and the conductive layer or the primer layer.

[0026] If the thickness of the conductive substrate is too thick, firstly, it will increase the material cost, and secondly, it will cause stress concentration, resulting in a decrease in the adhesion between the conductive substrate and the conductive layer or the primer layer; if the thickness of the conductive substrate is too thin, it will be difficult to obtain sufficient support during the preparation of the conductive layer and / or the primer layer, thus affecting the quality and uniformity of the conductive layer and / or the primer layer, and further causing defects such as cracks and holes in the conductive layer and / or the primer layer, deteriorating the performance of the current collector.

[0027] Preferably, the thickness of the primer layer is 30 to 50 nm.

[0028] Controlling the thickness of the primer layer within the above range can not only ensure the adhesion between the primer layer and the conductive layer, but also provide sufficient support for the plating of the conductive layer.

[0029] If the thickness of the primer layer is too thick, it is easy to cause a decrease in the adhesion between the conductive layer and the primer layer, and the too thick primer layer will introduce too much interfacial stress, increasing the overall internal stress, and further resulting in peeling or cracking of the conductive layer and / or the primer layer; if the thickness of the primer layer is too thin, it is difficult for the primer layer to provide sufficient adhesion, resulting in a decrease in the adhesion between the conductive substrate and the conductive layer.

[0030] Preferably, the thickness of the conductive layer is 800 to 2000 nm.

[0031] Controlling the thickness of the conductive layer within the above range, first, it will increase the cost, and second, it can ensure the adhesion between the conductive layer and the primer layer and the mechanical strength of the current collector.

[0032] If the thickness of the conductive layer is too thick, it will increase the production cost, and the too thick conductive layer is likely to cause uneven, rough or protruding phenomena on the surface of the current collector, thereby affecting the mechanical properties such as the strength, hardness and toughness of the current collector; if the thickness of the conductive layer is too thin, it is likely to cause insufficient adhesion between the conductive layer and the underlayer, resulting in the shedding or delamination of the conductive layer, and also reducing the mechanical properties, wear resistance and corrosion resistance of the current collector, making it more vulnerable to wear and corrosion during use.

[0033] Preferably, the current collector further includes a first antioxidant layer and a second antioxidant layer. The first antioxidant layer is disposed on the surface of the conductive substrate away from the underlayer, and the second antioxidant layer is disposed on the surface of the conductive layer away from the underlayer.

[0034] Preferably, the first antioxidant layer and the second antioxidant layer independently contain at least one of azole compounds and azole compound derivatives.

[0035] Preferably, the first antioxidant layer includes at least one of 2-mercaptobenzimidazole, 2,5-dimercapto-1,3,4-thiadiazole, benzotriazole, and 4-methylimidazole.

[0036] Preferably, the second antioxidant layer includes at least one of 2-mercaptobenzimidazole, 2,5-dimercapto-1,3,4-thiadiazole, benzotriazole, and 4-methylimidazole.

[0037] Using azole compounds and their derivatives to prepare the antioxidant layer, on the one hand, it does not contain chromium and phosphorus, is environmentally friendly, has little environmental pollution, is easy to clean and has no residue. On the other hand, it enables the current collector to effectively delay the corrosion of the PCB copper surface in high-humidity and high-acid-base environments, has a long antioxidant time, and is beneficial to improving the performance of the current collector in subsequent manufacturing processes.

[0038] Preferably, the thickness of the first antioxidant layer is 5 - 200 nm

[0039] Preferably, the thickness of the second antioxidant layer is 5 - 200 nm.

[0040] According to the second aspect of the present invention, there is provided a method for preparing the above-mentioned current collector, including the following steps:

[0041] S1. Melting, casting, rolling and winding the materials for preparing the conductive substrate to obtain a semi-finished product;

[0042] S2. Cold rolling the semi-finished product to obtain the conductive substrate;

[0043] S3. Depositing a first conductive layer on the surface of the conductive substrate by means of a magnetron sputtering process;

[0044] In S3, control the power density of the magnetron sputtering process to be 7.0 - 15 W / cm 2, the argon flow rate is 50-120 mL / min, and the vacuum degree is 0.08-0.1 Pa;

[0045] S4. Prepare a second conductive layer on the surface of the first conductive layer by using the hydroelectroplating process to obtain a current collector;

[0046] In S4, control the current density of the hydroelectroplating process to be 0.5-2 A / dm 2 , and the electroplating solution used in the hydroelectroplating process includes the following components: 100-130 g / L of copper sulfate, 100-130 g / L of sulfuric acid, and 40-60 mg / L of chloride ions.

[0047] In the method for preparing the current collector provided in this solution, after melting, casting and rolling the raw materials for preparing the conductive substrate and cold rolling the semi-finished product after winding, and cold rolling to form strip-shaped grooves on one surface of the prepared conductive substrate and the surface roughness Ra of this surface is higher than 0.2 μm and less than or equal to 2.0 μm. At the same time, the surface roughness of the conductive substrate near the conductive layer is greater than the surface roughness of the conductive substrate far from the conductive layer. First, it can improve the adhesion between the conductive substrate and the conductive layer, reduce the risk of peeling off during subsequent roll pressing or actual use of the current collector, and improve the mechanical strength of the current collector. Second, it helps to improve the uniformity and durability of the adhesion between the conductive substrate and the conductive layer. The lower surface roughness can also reduce the friction and wear of the roll during the production process, extend the service life of the roll, and reduce the risk of depositing metal materials on the surface of the conductive substrate far from the conductive layer during the preparation of the conductive layer, so as to obtain a current collector with a more pure surface. Moreover, when applying the prepared current collector to the preparation of the electrode sheet, it can ensure the bonding force between the conductive substrate and the subsequent carbon coating or active material, thereby improving the electrolyte corrosion resistance of the electrode sheet using this current collector as a whole, reducing the corrosion of the electrolyte to the interface junction in the current collector, and finally improving the cycle stability and durability of the battery using it.

[0048] It should be noted that in the current collector and its preparation process, the formation and regulation methods of the strip-shaped grooves and roughness on the surfaces of the conductive substrate and the conductive layer include: First, during cold rolling, there are protrusions on the surface of the rolling roll, and the protrusion structure is used to make the surface of the conductive substrate have grooves. In addition, by controlling the size of the convex points, the height of the protrusions, and the distribution density on the surface of the rolling roll; Second, adding a shielding object during the electroplating process; and so on. The above-mentioned methods can be combined in one or more of them, and the corresponding conditions in each method can be regulated to achieve the purpose of forming strip-shaped grooves on the surfaces of the conductive substrate and the conductive layer and regulating the roughness of the two surfaces of the conductive substrate and the conductive layer.

[0049] Preferably, in S3, before preparing the first conductive layer on the surface of the conductive substrate by using a magnetron sputtering process, the following operations of treating the conductive substrate with a mixed solution are further included: preparing a mixed solution by using sodium hydroxide and sodium carbonate, soaking the conductive substrate in the mixed solution, and then performing a drying treatment at 60-80°C, wherein the concentration of sodium hydroxide in the mixed solution is 10-30 g / L and the concentration of sodium carbonate is 10-30 g / L.

[0050] Preferably, in S3, after the operation of treating the conductive substrate with the mixed solution, the following operation of treating the conductive substrate with plasma is further included: placing the conductive substrate under the conditions of an argon atmosphere, a vacuum degree of 0.03-0.05 Pa, and a discharge power of 80-120 W for microwave discharge treatment for 30-60 s.

[0051] Performing plasma treatment on the conductive substrate can, on the one hand, remove the oxide layer on the surface of the conductive substrate, and on the other hand, increase the surface roughness of the substrate, which is beneficial to improving the bonding force between the conductive substrate and the underlayer or the conductive layer.

[0052] Preferably, in S3, the thickness of the first conductive layer is 50-100 nm.

[0053] Preferably, in S3, the power density of the magnetron sputtering process is controlled to be 7.0-15 W / cm 2 , the argon flow rate is 50-120 mL / min, and the vacuum degree is 0.08-0.1 Pa.

[0054] Preferably, in S3, before plating the first conductive layer on the surface of the conductive substrate provided with a strip-shaped groove, the operation of plating an underlayer on the surface of the conductive substrate provided with a strip-shaped groove by using a magnetron sputtering process is further included, wherein the power density of the magnetron sputtering process is controlled to be 2-15 W / cm 2 , the argon flow rate is 80-120 mL / min, and the vacuum degree is 0.08-0.1 Pa.

[0055] Preferably, in S4, the current density of the electroplating process is controlled to be 0.5-2 A / dm 2 .

[0056] During the process of preparing the second conductive layer on the surface of the first conductive layer by using the electroplating process, controlling the current density within the above range can not only make the deposition rate of the conductive metal moderate, reduce the risk of dissolution of the first conductive layer during electroplating, but also ensure that the metal is deposited on the other side of the conductive substrate, thereby obtaining a more pure current collector on the surface, and at the same time, it can also ensure that the current collector has excellent adhesion performance and mechanical properties.

[0057] If the current density used in the process of preparing the second conductive layer on the surface of the first conductive layer by the hydroelectroplating process is too low, it will lead to too long deposition of conductive metal, and during this process, the first conductive layer is likely to dissolve in the acidic electroplating solution; if the current density used in the process of preparing the second conductive layer on the surface of the first conductive layer by the hydroelectroplating process is too high, on the one hand, it is easy to deposit metal materials on the other surface of the conductive substrate, and on the other hand, the second conductive layer obtained by the hydroelectroplating process is prone to "burning". This is mainly because the thickness of the first conductive layer obtained by magnetron sputtering is relatively thin, and heat generation will occur due to too high current density during the process of electroplating the second conductive layer on the surface of the first conductive layer, which will affect the conductive layer and change its shape.

[0058] Preferably, in S4, the current density of the hydroelectroplating process is controlled to be 0.5 - 1.5 A / dm 2 .

[0059] Preferably, in S4, the electroplating solution used in the hydroelectroplating process comprises the following components: 100 - 130 g / L copper sulfate, 100 - 130 g / L sulfuric acid, 40 - 70 mg / L chloride ions.

[0060] Preferably, in S4, the electroplating solution used in the hydroelectroplating process comprises the following components: 100 - 120 g / L copper sulfate, 100 - 120 g / L sulfuric acid, 40 - 60 mg / L chloride ions.

[0061] Preferably, in S4, the electroplating solution further comprises brighteners, inhibitors and leveling agents.

[0062] Preferably, the brightener is selected from at least one of sodium ethanethiolate propane sulfonate (HP), sodium dimethylformamide sulfonate (TPS), sodium polydithiodipropane sulfonate, and thiamidazole dithiopropane sulfonic acid.

[0063] Preferably, the inhibitor is selected from at least one of gelatin, polyethylene glycol, organic sulfides, and fatty alcohol polyoxyethylene ether.

[0064] Preferably, the leveling agent is selected from at least one of Janus green B (JGB), diazine black (DB), alcian blue (ABPV), and ethylene thiourea.

[0065] Preferably, in S4, after preparing the second conductive layer on the surface of the first conductive layer by the hydroelectroplating process, it further includes the operation of soaking it in an antioxidant solution containing 0.5 - 3 g / L 2-mercaptobenzimidazole and 0.5 - 3 g / L 2,5-dimercapto-1,3,4-thiadiazole for 10 - 30 s Description of the Drawings

[0066] Figure 1Metallographic microscope morphology diagram (×100) of the conductive substrate (pure aluminum foil) prepared in Example 1.

[0067] Figure 2 Metallographic microscope morphology diagram (×100) of one side (copper side) of the first conductive layer after magnetron sputtering the first conductive layer on the surface of the conductive substrate in Example 1.

[0068] Figure 3 Metallographic microscope morphology diagram (×100) of one side (aluminum side) of the conductive substrate after magnetron sputtering the first conductive layer on the surface of the conductive substrate in Example 1.

[0069] Figure 4 Metallographic microscope morphology diagram (×100) of one side (copper side) of the second conductive layer after electroplating the second conductive layer on the surface of the first conductive layer using the electroplating process in Example 1.

[0070] Figure 5 Metallographic microscope morphology diagram (×100) of one side (aluminum side) of the conductive substrate after electroplating the second conductive layer on the surface of the first conductive layer using the electroplating process in Example 1.

[0071] Figure 6 SEM diagram (×30K) of one side (aluminum side) of the conductive substrate after electroplating the second conductive layer on the surface of the first conductive layer using the electroplating process in Comparative Example 4. Detailed implementation manners

[0072] The technical features in the technical solutions provided by the present invention will be further clearly and completely described below in conjunction with the detailed implementation manners. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts fall within the protection scope of the present invention.

[0073] Example 1

[0074] A current collector, which includes a conductive substrate, a first conductive layer, and a second conductive layer that are sequentially compounded;

[0075] The current collector provided in this embodiment is prepared through the following steps:

[0076] S1. Melting, casting, and winding the material (aluminum ingot) used to prepare the conductive substrate to obtain a semi-finished product;

[0077] S2. Cold roll the semi-finished product to obtain a conductive substrate with a thickness of 30 μm. During the cold rolling process, by setting a convex structure on the surface of the rolling roll and regulating its size, height, distribution density, etc., a number of strip-shaped grooves with a depth of 1 μm are formed on one surface of the conductive substrate, and the surface roughness Ra = 2.0 μm. The surface roughness Ra of the other surface is 1.0 μm. The metallographic microscope morphology diagram (×100) of the conductive substrate (pure aluminum foil) is as shown in Figure 1 shown;

[0078] S3. Place the conductive substrate in a magnetron sputtering machine. Using metallic copper (purity of 99.99%) as the target, deposit a first conductive layer with a thickness of 75 nm on the surface of the conductive substrate with strip-shaped grooves under the conditions of a power density of 11 W / cm 2 , an argon flow rate of 80 mL / min, and a vacuum degree of 0.09 Pa. After magnetron sputtering the first conductive layer on the surface of the conductive substrate, the metallographic microscope morphology diagram (×100) of one side (copper side) of the first conductive layer is as shown in Figure 2 shown, and the metallographic microscope morphology diagram (×100) of one side (aluminum side) of the conductive substrate after magnetron sputtering the first conductive layer on the surface of the conductive substrate is as shown in Figure 3 shown;

[0079] S4. Place the conductive substrate with the first conductive layer deposited on its surface in a hydroplating equipment containing electroplating solution. Using the conductive substrate with the first conductive layer deposited on its surface as the cathode and a phosphor copper electrode as the anode, under the condition of a current density of 1.5 A / dm 2 , carry out hydroplating on the first conductive layer to prepare a second conductive layer with a material particle size D50 of 400 nm and a thickness of 1 μm, thus obtaining a current collector. During the hydroplating process, by adding a shielding object and regulating its size, distance, etc., a number of strip-shaped grooves are formed on the surface of the second conductive layer far from the conductive substrate, and the surface roughness Ra = 2.0 μm. After plating the second conductive layer on the surface of the first conductive layer using the hydroplating process, the metallographic microscope morphology diagram (×100) of one side (copper side) of the second conductive layer is as shown in Figure 4 shown, and the metallographic microscope morphology diagram (×100) of one side (aluminum side) of the conductive substrate after plating the second conductive layer on the surface of the first conductive layer using the hydroplating process is as shown in Figure 5 shown.

[0080] Example 2

[0081] This embodiment provides a current collector. Compared with Embodiment 1, the difference in composition is as follows: In the preparation step S2 of the current collector, during the cold rolling process, by setting a convex structure on the surface of the rolling mill and regulating its size, height, distribution density, etc., a plurality of strip-shaped grooves with a depth of 0.1 μm are formed on one surface of the conductive substrate, and the surface roughness Ra = 0.5 μm, while the surface roughness Ra of the other surface is 0.3 μm.

[0082] Except for the above differences, the materials, formulation ratios, and preparation operations used in this embodiment are strictly the same as those in Embodiment 1.

[0083] Embodiment 3

[0084] This embodiment provides a current collector. Compared with Embodiment 1, the difference in composition is as follows: In the preparation step S2 of the current collector, during the cold rolling process, by setting a convex structure on the surface of the rolling mill and regulating its size, height, distribution density, etc., a plurality of strip-shaped grooves with a depth of 0.5 μm are formed on one surface of the conductive substrate, and the surface roughness Ra = 1.0 μm, while the surface roughness Ra of the other surface is 0.5 μm.

[0085] Except for the above differences, the materials, formulation ratios, and preparation operations used in this embodiment are strictly the same as those in Embodiment 1.

[0086] Embodiment 4

[0087] This embodiment provides a current collector. Compared with Embodiment 1, the difference in composition is as follows: In the preparation step S4 of the current collector, during the electroplating process with water, by increasing the shielding objects and regulating their size, distance, etc., a plurality of strip-shaped grooves are formed on the surface of the second conductive layer away from the conductive substrate, and the surface roughness Ra = 0.2 μm.

[0088] Except for the above differences, the materials, formulation ratios, and preparation operations used in this embodiment are strictly the same as those in Embodiment 1.

[0089] Embodiment 5

[0090] This embodiment provides a current collector. Compared with Embodiment 1, the difference in composition is as follows: In the preparation step S4 of the current collector, during the electroplating process with water, by increasing the shielding objects and regulating their size, distance, etc., a plurality of strip-shaped grooves are formed on the surface of the second conductive layer away from the conductive substrate, and the surface roughness Ra = 1.0 μm.

[0091] Except for the above differences, the materials, formulation ratios, and preparation operations used in this embodiment are strictly the same as those in Embodiment 1.

[0092] Embodiment 6

[0093] This embodiment provides a current collector. Compared with Embodiment 1, the difference in composition is as follows: In the preparation step S4 of the current collector, during the electroplating process in water, by adding a shielding object and adjusting its size, distance, etc., several strip-shaped grooves are formed on the surface of the second conductive layer away from the conductive substrate, and the surface roughness Ra = 2.5 μm.

[0094] Except for the above differences, the materials, formula ratios, and preparation operations used in this embodiment are strictly the same as those in Embodiment 1.

[0095] Embodiment 7

[0096] This embodiment provides a current collector. Compared with Embodiment 1, the difference in composition is as follows: (1) A primer layer is further provided between the conductive substrate of the current collector and the first conductive layer; (2) In the preparation step S3 of the current collector, before plating the first conductive layer on the surface of the conductive substrate with strip-shaped grooves, the conductive substrate is placed in a magnetron sputtering machine. Using nickel-chromium alloy (purity 99.99%) as the target, under the conditions of a power density of 8 W / cm 2 , an argon flow rate of 100 mL / min, and a vacuum degree of 0.09 Pa, a primer layer with a thickness of 40 nm is plated on the surface of the conductive substrate with strip-shaped grooves.

[0097] Except for the above differences, the materials, formula ratios, and preparation operations used in this embodiment are strictly the same as those in Embodiment 1.

[0098] Embodiment 8

[0099] This embodiment provides a current collector. Compared with Embodiment 1, the difference in composition is as follows: (1) A first antioxidant layer is further provided on the surface of the conductive substrate of the current collector, and a second antioxidant layer is further provided on the surface of the second conductive layer; (2) In the preparation step S4 of the current collector, after preparing the second conductive layer on the surface of the first conductive layer using the electroplating process in water, it further includes the operation of soaking it in an antioxidant solution containing 2 g / L 2-mercaptobenzimidazole and 2 g / L 2,5-dimercapto-1,3,4-thiadiazole for 20 s and drying at 60 °C.

[0100] Except for the above differences, the materials, formula ratios, and preparation operations used in this embodiment are strictly the same as those in Embodiment 1.

[0101] Embodiment 9

[0102] This embodiment provides a current collector. Compared with Embodiment 1, the differences in composition are as follows: (1) In step S3 of preparing the current collector, before preparing the first conductive layer on the surface of the conductive substrate by using the magnetron sputtering process, the following operations of treating the conductive substrate with a mixed solution are further included: A mixed solution is prepared by using sodium hydroxide and sodium carbonate. After the conductive substrate is soaked in the mixed solution, it is dried at 70 °C. Among them, the concentration of sodium hydroxide in the mixed solution is 20 g / L, and the concentration of sodium carbonate is 20 g / L; (2) In step S3 of preparing the current collector, after the operation of treating the conductive substrate with the mixed solution, the following operations of treating the conductive substrate with plasma are further included: The conductive substrate is placed under the conditions of an argon atmosphere, a vacuum degree of 0.04 Pa, and a discharge power of 100 W for microwave discharge treatment for 45 s.

[0103] Except for the above differences, the materials, formula ratios, and preparation operations used in this embodiment are strictly the same as those in Embodiment 1.

[0104] Embodiment 10

[0105] This embodiment provides a current collector. Compared with Embodiment 7, the difference in composition is that in step S3 of preparing the current collector, the power density used when preparing the underlayer by using the magnetron sputtering process is 4 W / cm 2 . Except for the above differences, the materials, formula ratios, and preparation operations used in this embodiment are strictly the same as those in Embodiment 1.

[0106] Embodiment 11

[0107] This embodiment provides a current collector. Compared with Embodiment 7, the difference in composition is that: in step S3 of preparing the current collector, the power density used when preparing the underlayer by using the magnetron sputtering process is 6 W / cm 2 . Except for the above differences, the materials, formula ratios, and preparation operations used in this embodiment are strictly the same as those in Embodiment 1.

[0108] Embodiment 12

[0109] This embodiment provides a current collector. Compared with Embodiment 7, the difference in composition is that: in step S3 of preparing the current collector, the power density used when preparing the underlayer by using the magnetron sputtering process is 10 W / cm 2 . Except for the above differences, the materials, formula ratios, and preparation operations used in this embodiment are strictly the same as those in Embodiment 1.

[0110] Embodiment 13

[0111] This embodiment provides a current collector. Compared with Embodiment 7, the difference in composition is that in the preparation step S4 of the current collector, when preparing the second conductive layer by hydroelectroplating process, the current density used is 2.4 A / dm 2 , and the particle size D50 of the material in the obtained second conductive layer is 200 nm. Except for the above differences, the materials, formula ratios, and preparation operations used in this embodiment are strictly the same as those in Embodiment 1.

[0112] Embodiment 14

[0113] This embodiment provides a current collector. Compared with Embodiment 7, the difference in composition is that in the preparation step S4 of the current collector, when preparing the second conductive layer by hydroelectroplating process, the current density used is 2.0 A / dm 2 , and the particle size D50 of the material in the obtained second conductive layer is 300 nm. Except for the above differences, the materials, formula ratios, and preparation operations used in this embodiment are strictly the same as those in Embodiment 1.

[0114] Embodiment 15

[0115] This embodiment provides a current collector. Compared with Embodiment 7, the difference in composition is that in the preparation step S4 of the current collector, when preparing the second conductive layer by hydroelectroplating process, the current density used is 0.5 A / dm 2 , and the particle size D50 of the material in the obtained second conductive layer is 600 nm. Except for the above differences, the materials, formula ratios, and preparation operations used in this embodiment are strictly the same as those in Embodiment 1.

[0116] Embodiment 16

[0117] This embodiment provides a current collector. Compared with Embodiment 7, the difference in composition is that in the preparation step S4 of the current collector, when preparing the second conductive layer by hydroelectroplating process, the current density used is 0.4 A / dm 2 , and the particle size D50 of the material in the obtained second conductive layer is 700 nm. Except for the above differences, the materials, formula ratios, and preparation operations used in this embodiment are strictly the same as those in Embodiment 1.

[0118] Embodiment 17

[0119] This embodiment provides a current collector. Compared with Embodiment 1, the difference in composition is that in the preparation step S2 of the current collector, during the cold rolling process, by setting a convex structure on the surface of the rolling mill and regulating its size, height, and distribution density, etc., a number of strip-shaped grooves with a depth of 1.5 μm are formed on one surface of the conductive substrate. Except for the above differences, the materials, formula ratios, and preparation operations used in this embodiment are strictly the same as those in Embodiment 1.

[0120] Comparative Example 1

[0121] This comparative example provides a current collector. Compared with Example 1, the difference in composition is that in the preparation step S2 of the current collector, the surface of the rolling mill used in the cold rolling process does not contain protrusions, and strip-shaped grooves are not formed on the surface of the obtained conductive substrate.

[0122] Except for the above differences, the materials, formulation ratios, and preparation operations used in this comparative example are strictly the same as those in Example 1.

[0123] Comparative Example 2

[0124] This comparative example provides a current collector. Compared with Example 1, the difference in composition is that in the preparation step S2 of the current collector, during the cold rolling process, by setting a protrusion structure on the surface of the rolling mill and regulating its size, height, distribution density, etc., a plurality of strip-shaped grooves with a depth of 2 μm are formed on one surface of the conductive substrate, and the surface roughness Ra of this surface is 2.5 μm, and the surface roughness Ra of the other surface is 1.5 μm.

[0125] Except for the above differences, the materials, formulation ratios, and preparation operations used in this comparative example are strictly the same as those in Example 1.

[0126] Comparative Example 3

[0127] This comparative example provides a current collector. Compared with Example 1, the difference in composition is that in the preparation step S2 of the current collector, during the cold rolling process, by setting a protrusion structure on the surface of the rolling mill and regulating its size, height, distribution density, etc., a plurality of strip-shaped grooves with a depth of 3 μm are formed on one surface of the conductive substrate, and the surface roughness Ra of this surface is 3.3 μm, and the surface roughness Ra of the other surface is 2.0 μm.

[0128] Except for the above differences, the materials, formulation ratios, and preparation operations used in this comparative example are strictly the same as those in Example 1.

[0129] Comparative Example 4

[0130] This comparative example provides a current collector. Compared with Example 1, the differences in composition are as follows: (1) In the preparation step S2 of the current collector, during the cold rolling process, by setting a convex structure on the surface of the rolling mill and regulating its size, height, distribution density, etc., a plurality of strip-shaped grooves with a depth of 1 μm are formed on one surface of the conductive substrate, and the surface roughness Ra = 1.0 μm, while the surface roughness Ra of the other surface = 2.0 μm; (2) In the preparation step S3 of the current collector, a first conductive layer with a thickness of 75 nm is plated on the surface of the conductive substrate provided with strip-shaped grooves; (3) In the preparation step S4 of the current collector, after plating the second conductive layer on the surface of the first conductive layer by the electroplating process, the scanning electron microscope (SEM) image (×30K) of one side (aluminum side) of the conductive substrate is as shown in Figure 6 shown. Except for the above differences, the materials, formula ratios, and preparation operations used in this comparative example are strictly the same as those in Example 1.

[0131] Test Example

[0132] 1. Test Subjects

[0133] In this test example, the current collectors prepared in Examples 1 to 17 and Comparative Examples 1 to 4 were used as test subjects for relevant performance tests.

[0134] 2. Test Contents

[0135] (1) Roughness and Groove Depth

[0136] a. The detection method of roughness refers to GB / T 3505 - 2000. The surface roughness was tested using a stylus roughness meter, and the steps are as follows:

[0137] Clean the surface of the sample to be tested, remove impurities such as oil stains and dust, and ensure that the measurement area is flat and free of burrs; calibrate the instrument using a standard sample block, check the wear condition of the stylus (to avoid measurement errors caused by stylus wear), and confirm that the stylus is in vertical contact with the surface after calibration; manually or automatically adjust the stylus to the surface of the sample to be tested, start the measurement program, and the stylus slides along the direction perpendicular to the rolling direction at a constant speed (usually 0.5 - 2 mm / s) to obtain the roughness value.

[0138] b. The depth of the groove was tested using a profiler, and the test steps are as follows:

[0139] Paste the sample to be tested on the sample stage, ensure that the surface is flat and free of wrinkles, calibrate the instrument using a standard step sample block, and after starting the program, the stylus slides along the surface, and the height change is recorded by a capacitance sensor or a laser interferometer to obtain the measured value, which is the depth of the groove.

[0140] (2) Tensile Strength, Elongation at Break

[0141] The test was carried out with reference to GB / T 1040.3-2006. In this test example, the results are all the test data in the MD direction.

[0142] (3) Adhesive force

[0143] A layer of 3M double-sided tape was adhered to the smooth stainless-steel surface with a thickness of 3 mm. After rolling, a current collector was adhered above the double-sided tape. Then, a layer of 3M double-sided tape was adhered above the copper surface (i.e., the conductive layer) of the current collector. After rolling again, a small strip (150 mm × 15 mm) of ethylene acrylic copolymer film was covered above the current collector to obtain a sample strip. Finally, the ethylene acrylic copolymer film of the sample strip was fixed to the upper fixture of the tensile machine, and the rest was fixed to the lower fixture. After fixing, the two were peeled at an angle of 90° and a speed of 100 mm / min to test the peel force, that is, the adhesive force between copper (conductive layer) and aluminum (conductive substrate).

[0144] (4) Flexural resistance

[0145] The YT-6003 microcomputer-controlled electronic universal testing machine was used to test the flexural resistance of the current collector. The method is as follows:

[0146] The test piece (with a size of 10 mm × 100 mm) was placed on the fixture of the testing machine. The test piece size was 10 mm × 100 mm. The set test bending radius R was 0.5 ± 0.05 mm, the load was 2.5 ± 0.05 N, the bending angle was 180 ± 2°, and the bending back-and-forth speed was 6 times / s (each 90-degree bend is one time). The bending test experiment was started and counted until the specimen broke, and the number of bends at this time was recorded.

[0147] (5) Appearance evaluation

[0148] The metallographic microscope was used to detect the appearance of the current collector to characterize the surface purity of the current collector. Among them, the grading reference standard of the metallographic microscope evaluation method is as follows:

[0149] A. Grade 1: The copper-plated surface (i.e., the conductive layer) and the aluminum foil surface (i.e., the conductive substrate) are bright, without oil stains, whitening, burning, etc., with excellent compactness, and there should be no copper particle deposition on the non-magnetron surface of the aluminum foil;

[0150] B. Grade 2: The brightness of the copper-plated surface and the aluminum foil surface is slightly poor. Slight whitening, burning and other defects on the surface can be basically ignored. The compactness is good, and the amount of copper particle deposition on the non-magnetron surface of the aluminum foil is small;

[0151] C. Grade 3: The brightness of the copper-plated surface is poor, with serious burning, whitening, etc., the compactness is poor, and the amount of copper particle deposition on the non-magnetron surface of the aluminum foil is large.

[0152] 3. Experimental results

[0153] Table 1 Roughness and material particle size involved in the conductive substrate, primer layer, and conductive layer in the current collector

[0154]

[0155]

[0156] Table 2 Test results of relevant properties of the current collector

[0157]

[0158] For the current collectors prepared in Examples 1 to 17 and Comparative Examples 1 to 4, the roughness and material particle size parameters involved in the conductive substrate, primer layer, and conductive layer are shown in Table 1, and the test results of the relevant properties of the current collectors prepared in Examples 1 to 17 and Comparative Examples 1 to 4 are shown in Table 2.

[0159] Compared with Comparative Examples 1 to 4, in the current collectors provided by Examples 1 to 17, the surface of the conductive substrate close to the conductive layer is provided with strip-shaped grooves, the roughness Ra of the surface of the conductive substrate close to the conductive layer is greater than 0.2 μm and less than or equal to 2.0 μm, and the roughness of the surface of the conductive substrate on the side close to the conductive layer is greater than that on the side far from the conductive substrate. The test results show that the adhesion between the conductive substrate and the conductive layer and the bending resistance performance of the current collectors provided by Examples 1 to 17 are both better than those of Comparative Examples 1 to 4, and they have good tensile strength and elongation at break. This is mainly because the current collectors provided by Examples 1 to 17 can improve the adhesion between the conductive substrate and the conductive layer by setting strip-shaped grooves on one surface of the conductive substrate and regulating the roughness of the two surfaces of the conductive substrate to meet the above range, reduce the risk of peeling off during subsequent rolling or actual use of the current collector, and improve the mechanical strength of the current collector.

[0160] Compared with Example 1, on the surface of the second conductive layer of the current collectors provided by Examples 4 and 6 far from the conductive substrate, several strip-shaped grooves are formed, and the roughness Ra of this surface is 0.2 μm and 2.5 μm respectively. Their mechanical strengths (such as tensile strength, elongation at break, and bending resistance performance) are all lower than those of Example 1, and the adhesion between the conductive substrate and the conductive layer is also lower than that of Example 1.

[0161] The depth of the strip-shaped grooves formed on one surface of the conductive substrate of the current collector provided by Example 1 is 1 μm. Compared with Example 1, the depth of the strip-shaped grooves formed on one surface of the conductive substrate of the current collector provided by Example 17 is 1.5 μm. Although the adhesion between the conductive substrate and the conductive layer provided by Example 17 is slightly higher than that of Example 1, its mechanical properties are worse than those of Example 1, specifically reflected in that the tensile strength, elongation at break, and bending resistance performance are all worse than those of Example 1.

[0162] The current densities adopted by the current collectors provided in Examples 7, 14, and 15 during the preparation of the second conductive layer using the hydroelectroplating process are 1.5 A / dm 2 , 2.0 A / dm 2 , 0.5 A / dm 2 , and the particle sizes D50 of the materials in the prepared second conductive layers are 400 nm, 300 nm, and 600 nm respectively. Compared with Examples 7, 14, and 15, the current densities adopted by the current collectors provided in Examples 13 and 16 during the preparation of the second conductive layer using the hydroelectroplating process are 2.4 A / dm 2 , 0.4 A / dm 2 , neither of which meets the range of 0.5 - 2 A / dm 2 . The particle sizes D50 of the materials in the prepared second conductive layers are 200 nm and 700 nm respectively. The test results show that the tensile strength, elongation at break, and bending resistance of the current collectors prepared in Examples 13 and 16 are all worse than those in Examples 7, 14, and 15. In addition, although the adhesion between the conductive substrate and the conductive layer of the current collector prepared in Example 16 is higher than that in Example 7, its tensile strength, elongation at break, and bending resistance are all worse than those in Example 7. This is mainly because although using a smaller current density during the preparation of the second conductive layer using the hydroelectroplating process in Example 16 can improve the adhesion between the conductive substrate and the conductive layer to a certain extent, it will deteriorate the mechanical strength of the current collector, making it difficult for the prepared current collector to have both excellent adhesion performance and mechanical performance.

[0163] The above examples are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the above examples, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced, but such modifications or replacements are all within the protection scope of the present invention.

Claims

1. A current collector, characterized in that: The current collector includes a conductive substrate and a conductive layer that are composited with each other, and the materials of the conductive substrate and the conductive layer are different; The surface of the conductive substrate close to the conductive layer is provided with strip-shaped grooves. Taking the roughness Ra of the surface of the conductive substrate close to the conductive layer as A and the roughness Ra of the surface of the conductive substrate far from the conductive layer as B, A and B satisfy 0.2μm < A ≤ 2.0μm and A > B.

2. The current collector according to claim 1, wherein: The depth of the strip-shaped grooves on the surface of the conductive substrate is 0.1 - 1μm.

3. The current collector according to claim 1, characterized in that: The surface of the conductive layer far from the conductive substrate is provided with strip-shaped grooves. Taking the roughness Ra of the surface of the conductive layer far from the conductive substrate as C, C satisfies 0.2μm < C ≤ 2.0μm.

4. The current collector according to claim 1, wherein: The material of the conductive substrate includes at least one of aluminum, aluminum alloy, silver, silver alloy, copper, copper alloy, gold, gold alloy, nickel, nickel alloy, iron, iron alloy, titanium, titanium alloy, manganese, manganese alloy, and / or the material of the conductive layer includes at least one of copper, copper alloy, silver, silver alloy, gold, gold alloy, nickel, nickel alloy, iron, iron alloy, titanium, titanium alloy, manganese, manganese alloy.

5. The current collector according to claim 4, wherein: The conductive substrate is an aluminum foil, and / or the conductive layer is a copper layer.

6. The current collector according to claim 1, characterized in that: The current collector further includes an underlayer, and the conductive substrate, the underlayer, and the conductive layer are composited in sequence; The material of the underlayer includes at least one of nickel-chromium alloy, aluminum oxide, silicon oxide, titanium nitride, silicon nitride, polyurethane.

7. The current collector according to claim 1, wherein: The particle size D50 of the material of the conductive layer is 300 - 600nm.

8. The current collector according to claim 6, wherein: The thickness of the conductive substrate is 10 - 50μm, and / or the thickness of the underlayer is 30 - 50nm, and / or the thickness of the conductive layer is 800 - 2000nm.

9. The current collector according to claim 6, wherein: The current collector further includes a first antioxidant layer and a second antioxidant layer. The first antioxidant layer is disposed on the surface of the conductive substrate far from the underlayer, and the second antioxidant layer is disposed on the surface of the conductive layer far from the underlayer; The first antioxidant layer and the second antioxidant layer independently contain at least one of azole compounds and azole compound derivatives, and / or the thickness of the first antioxidant layer is 5 - 200nm, and / or the thickness of the second antioxidant layer is 5 - 200nm.

10. The preparation method of the current collector according to any one of claims 1 to 9, characterized in that, Including the following steps: S1. Melting, casting and rolling, and winding the material for preparing the conductive substrate to obtain a semi-finished product; S2. Cold-rolling the semi-finished product to obtain a conductive substrate; S3. Depositing a first conductive layer on the surface of the conductive substrate by a magnetron sputtering process; In the step S3, the power density of the magnetron sputtering process is controlled to be 7.0 - 15 W / cm 2 , the argon gas flow rate is 50 - 120 mL / min, and the vacuum degree is 0.08 - 0.1 Pa; S4. Depositing a second conductive layer on the surface of the first conductive layer by a hydro-electroplating process to obtain the current collector; In S4, the current density of the hydroelectroplating process is controlled to be 0.5 - 2 A / dm 2 , and the electroplating solution used in the hydroelectroplating process comprises the following components: 100 - 130 g / L of copper sulfate, 100 - 130 g / L of sulfuric acid, and 40 - 60 mg / L of chloride ions.

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