Current collector and preparation method thereof, pole piece, and secondary battery

Abstract

A current collector, a preparation method thereof, a pole piece, and a secondary battery, belonging to the field of battery technology. The current collector comprises a base film and a metal layer attached to at least one side of the base film. The current collector has a surface contact angle of 60° to 80° and a sheet resistance of 2 to 200 mΩ / □. The current collector has a low surface contact angle, enabling strong adhesion to the active material layer when used as a pole piece. Furthermore, the low sheet resistance of the current collector provides good electrical conductivity and adaptability to high-current operating conditions.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a current collector and a preparation method thereof, a pole piece, and a secondary battery. Background Art

[0002] Lithium batteries are used as power batteries for new energy vehicles and batteries for 3C digital products due to their high energy density, high output power and long cycle life.

[0003] In recent years, with the popularity of new energy vehicles, lithium batteries have garnered widespread attention. However, a growing number of safety incidents involving lithium battery combustion and explosions have necessitated increased attention to their safety performance. Most combustion and explosion incidents are caused by a short circuit within the battery. High current discharge in the battery cell generates significant heat, burning the diaphragm and causing a further short circuit. This heat builds up in the cell, causing the electrolyte to decompose into gas, resulting in excessive internal pressure. When the cell's outer casing can no longer withstand this pressure, the cell explodes.

[0004] Someone has proposed a new composite current collector with a structure of conductor layer-polymer layer-conductor layer. The metal layer is used to carry the electrode active material layer. This structure has the following characteristics: 1. During the temperature rise stage caused by overshoot and short circuit, the plastic insulating layer melts or swells, and the metal layer (copper) becomes discontinuous, so the resistance increases rapidly and the current decreases rapidly, which suppresses the generation of Joule heat. 2. The thickness of the metal layer is reduced (from 6 to 2 microns), which reduces the probability of burrs on the metal layer and reduces the risk of short circuit. Therefore, the new current collector with this structure can effectively reduce the local temperature surge caused by short circuit in the battery, and reduce the risk of fire and explosion of lithium-ion batteries.

[0005] Currently, composite current collectors are typically made by depositing a metal layer on a polymer layer via sputtering to metallize the polymer surface, followed by a single electroplating and anti-oxidation process to thicken the metal layer. However, the conductor layer of the composite current collector has a large contact angle (80° to 110°), resulting in hydrophobic regions during the negative electrode slurry coating process. After coating, the electrode sheet exhibits insufficient peel strength, resulting in poor battery cycling performance. Summary of the Invention

[0006] The present application provides a current collector and a preparation method thereof, a pole piece, and a secondary battery, so that the current collector surface has a lower contact angle, thereby increasing its adhesion to the active material layer when used as a pole piece.

[0007] In a first aspect, an embodiment of the present application provides a current collector, which includes a base film and a metal layer attached to the surface of the base film, the surface contact angle of the current collector is 60° to 80°, and the square resistance of the current collector is 2 to 200 mΩ / □.

[0008] In the above implementation process, the current collector has a low surface contact angle, which enables strong adhesion to the active material layer when used as a pole piece. At the same time, the current collector has a low square resistance, which makes it have good conductivity and can adapt to high current conditions.

[0009] As an optional embodiment, the base film material of the current collector includes at least one of polyethylene, biaxially oriented polypropylene, polystyrene, polyethylene terephthalate, polybutylene terephthalate and polypropylene; and / or

[0010] The thickness of the base film of the current collector is 2 μm to 20 μm; and / or

[0011] The thickness of the metal layer of the current collector is 0.1 μm to 10 μm.

[0012] In the above implementation process, by using a suitable material as the base film and / or selecting a suitable base film thickness and / or selecting a suitable metal layer thickness, the current collector has better comprehensive performance.

[0013] In a second aspect, an embodiment of the present application provides a method for preparing a current collector, the method comprising:

[0014] Obtaining a surface metallized base film;

[0015] performing electroplating on the surface metallized base film to thicken the metal layer of the surface metallized base film to obtain a primary current collector;

[0016] performing an anti-oxidation treatment on the primary current collector to form an anti-oxidation layer to obtain a current collector;

[0017] The electroplating process includes at least two stages of electroplating, and the last stage of electroplating is a grain refinement strengthening stage of electroplating.

[0018] In the above implementation process, by adopting an electroplating treatment process with at least two stages of electroplating, and controlling the last stage of electroplating to be a fine-grained strengthening stage of electroplating, and combining it with anti-oxidation treatment, the contact angle of the collector surface is reduced, its hydrophilicity is improved, and thereby its adhesion to the active material layer is increased when used as a pole piece.

[0019] As an optional implementation, the electroplating process in the grain refinement strengthening stage meets the following requirements: electroplating time is 5s to 30s, electroplating current density is 0.2ASD to 1ASD, and electroplating temperature is 20°C to 30°C.

[0020] In the above implementation process, by selecting appropriate electroplating process parameters in the grain refinement stage, it is more conducive to reducing the contact angle of the current collector surface, thereby increasing its adhesion to the active material layer when used as a pole piece.

[0021] As an optional embodiment, the electroplating process includes four stages of electroplating.

[0022] As an optional embodiment, the first stage of the four-stage electroplating is current ramp stage electroplating, and the process of the current ramp stage electroplating meets the following requirements: electroplating time is 0.5min~1min, electroplating current density is 0.2ASD~1ASD, and electroplating temperature is 30℃~50℃.

[0023] In the above implementation process, by controlling the process parameters of electroplating in the current ramping stage, the current density of electroplating in the current ramping stage is made smaller, thereby preventing the base metal from falling off due to excessive current.

[0024] As an optional embodiment, the second stage of the four-stage electroplating is a stable continuous stage electroplating, and the process of the stable continuous stage electroplating meets the following requirements: the electroplating time is 1min to 3min, the electroplating current density is 1ASD to 3ASD, and the electroplating temperature is 20℃ to 50℃.

[0025] In the above implementation process, by controlling the process parameters of the electroplating in the stable continuous stage, the metal layer generated by the electroplating in the stable continuous stage has low sheet resistance and good conductivity, and can adapt to high current conditions.

[0026] As an optional embodiment, the third stage of the four-stage electroplating is the grain coarsening stage electroplating, and the process of the grain coarsening stage electroplating meets the following requirements: the electroplating time is 10s to 20s, the electroplating current density is 2.5ASD to 3ASD, and the electroplating temperature is 50°C to 60°C.

[0027] In the above implementation process, by controlling the process parameters of electroplating in the grain coarsening stage, the metal particles of the metal layer electroplated in the grain coarsening stage are larger, which is more conducive to the conductivity and mechanical properties of the current collector.

[0028] As an optional embodiment, the electroplating process includes: electroplating in a current ramping stage, electroplating in a stable continuous stage, electroplating in a grain coarsening stage, and electroplating in a grain refinement and strengthening stage;

[0029] The components of the electroplating solution for the electroplating in the current ramping stage, the electroplating in the stable continuous stage, and the electroplating in the grain refinement and strengthening stage satisfy any one of the following (A) to (F):

[0030] (A) The mass concentration of CuSO4·5H2O is 100g / L to 300g / L;

[0031] (B) The mass concentration of H2SO4 is 20g / L to 90g / L;

[0032] (C)Cl - The mass concentration is 10mg / L~100mg / L;

[0033] (D) the mass concentration of tetrahydrothiazolidinethione is 0.0005 g / L to 0.001 g / L;

[0034] (E) the mass concentration of poly(2,6-bis(2,6-propanesulfonate)) sodium is 0.01 g / L to 0.02 g / L;

[0035] (F) The mass concentration of polyethylene glycol is 0.03 g / L to 0.05 g / L;

[0036] The components of the electroplating solution in the grain coarsening stage satisfy any one of the following (G) to (J):

[0037] (G) The mass concentration of CuSO4·5H2O is 30g / L to 100g / L;

[0038] (H) The mass concentration of H2SO4 is 20g / L to 90g / L;

[0039] (I) The mass concentration of glucose is 15 g / L to 25 g / L;

[0040] (J) The mass concentration of ammonium molybdate is 10 g / L to 20 g / L.

[0041] In the above implementation process, by controlling the composition of the plating solution at each stage, the metal layer can be better deposited, so that the current collector has better performance. For example, in the plating solution of the grain coarsening stage, the use of low metal ion concentration combined with high current density is more conducive to the formation of large particles of metal.

[0042] As an optional embodiment, the anti-oxidation treatment includes immersing the primary current collector in an anti-oxidation liquid, wherein the anti-oxidation liquid includes a BTA corrosion inhibitor and ammonium molybdate.

[0043] In the above implementation process, the anti-oxidation liquid is formed by combining BTA corrosion inhibitor and ammonium molybdate, which can further reduce the contact angle of the current collector surface, thereby increasing the adhesion of the current collector to the active material layer when used as a pole piece.

[0044] As an optional embodiment, the mass concentration of the BTA corrosion inhibitor in the anti-oxidation solution is 5 mg / L to 60 mg / L; and / or

[0045] The mass concentration of ammonium molybdate in the anti-oxidation solution is 5 mg / L to 80 mg / L; and / or

[0046] The soaking time is 2 min to 5 min; and / or

[0047] The soaking temperature is 30°C to 70°C.

[0048] In the above implementation process, by controlling the process parameters during the immersion process, the anti-oxidation treatment can be better achieved, which is beneficial to the anti-oxidation performance of the current collector.

[0049] In a third aspect, an embodiment of the present application provides a pole piece, which includes the current collector provided in the first aspect or the current collector produced by the method provided in the second aspect.

[0050] In a fourth aspect, an embodiment of the present application provides a secondary battery, comprising the electrode provided in the third aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0052] Figure 1 A schematic diagram of the structure of the current collector provided in an embodiment of the present application;

[0053] Figure 2 A flowchart of the method provided in an embodiment of the present application;

[0054] Figure 3 A schematic diagram of the structure of the electrode provided in an embodiment of the present application.

[0055] Reference numerals: 1 - current collector; 11 - base film; 12 - metal layer; 2 - active material layer. DETAILED DESCRIPTION

[0056] The embodiments of the present application will be described in detail below with reference to the examples, but it will be understood by those skilled in the art that the following examples are merely illustrative of the present application and should not be considered as limiting the scope of the present application. In the examples, if specific conditions are not specified, the conditions are carried out according to conventional conditions or manufacturer recommendations. The reagents or instruments used are not specified by the manufacturer and are conventional products that can be purchased commercially.

[0057] Currently, composite current collectors are typically made by depositing a metal layer on a polymer layer via sputtering to metallize the polymer surface, followed by a single electroplating and anti-oxidation process to thicken the metal layer. However, the conductor layer of the composite current collector has a large contact angle (80° to 110°), resulting in hydrophobic regions during the negative electrode slurry coating process. After coating, the electrode sheet exhibits insufficient peel strength, resulting in poor battery cycling performance.

[0058] The present application intends to provide a current collector having a lower contact angle on its surface, thereby increasing its adhesion to the active material layer when used as a pole piece.

[0059] Figure 1 The schematic diagram of the structure of the current collector provided in the embodiment of the present application is as follows: Figure 1 As shown, an embodiment of the present application provides a current collector, the current collector 1 includes a base film 11 and a metal layer 12 , and in the thickness direction of the base film 11 , both sides of the base film 11 are directly connected to the metal layer 12 .

[0060] It should be noted that the thickness of the base film is not limited and can be adjusted according to actual needs.

[0061] As an example, the thickness of the base film is 2 μm to 20 μm, for example but not limited to any one of 2 μm, 5 μm, 10 μm, 15 μm and 20 μm, or a range between any two of the thicknesses.

[0062] In this embodiment, limiting the thickness of the base film to a specific range can ensure that the base film has an appropriate thickness, thereby enabling the base film to have suitable mechanical and electrochemical properties.

[0063] It should be noted that the thickness of a single metal layer is not limited and can be adjusted according to actual needs.

[0064] As an example, the thickness of a single metal layer is 0.1 μm to 10 μm, for example but not limited to any one of 0.1 μm, 2 μm, 4 μm, 6 μm, 8 μm and 10 μm, or a range between any two of the thicknesses.

[0065] In this embodiment, the thickness of the single metal layer is limited to a specific range, so that the single metal layer can have an appropriate thickness, thereby ensuring the conductivity while taking into account the low preparation cost.

[0066] It should be noted that the sheet resistance of a single metal layer is not limited and can be adjusted according to actual needs.

[0067] Sheet resistance (also known as sheet resistance) refers to the edge-to-edge resistance of a square thin film conductive material. Sheet resistance is defined as: Sheet resistance R = ρ / d, where ρ is the resistivity of the material and d is the thickness of the material.

[0068] As an example, the square resistance of a single metal layer is 2 to 200 mΩ / □, for example, but not limited to, the square resistance is any one of 2 mΩ / □, 50 mΩ / □, 100 mΩ / □, 150 mΩ / □ and 200 mΩ / □, or a range between any two of them.

[0069] In this embodiment, limiting the thickness of a single metal layer to a specific range enables the single metal layer to have an appropriate sheet resistance, thereby achieving an appropriate conductivity. For example, a current collector metal layer thickness of 0.1 μm to 10 μm corresponds to a sheet resistance of 2 to 200 mΩ.

[0070] It should be noted that the surface contact angle of the current collector is not limited and can be adjusted according to actual needs.

[0071] As an example, the surface contact angle of the current collector is 60° to 80°, for example but not limited to any point value among 60°, 65°, 70°, 75° and 80°, or a range of values ​​between any two of them.

[0072] In this embodiment, limiting the surface contact angle of the current collector to a specific range can ensure that the surface of the current collector has a suitable contact angle, thereby ensuring that the current collector has a suitable bonding force with the active material layer.

[0073] It is understandable that the relative positions of the two metal layers can be adjusted taking into account the regularity of the current collector and the ease of preparation.

[0074] As an example, in the thickness direction of the base film, the orthographic projections of the two metal layers completely overlap.

[0075] In this embodiment, the orthographic projections of the two metal layers in the thickness direction of the base film completely overlap, that is, the two metal layers are distributed along the thickness direction of the base film and are symmetrical about the base film, so that the overall structure of the current collector is relatively regular and it is also convenient for process preparation.

[0076] In other possible implementations, in the thickness direction of the base film, the orthographic projections of the two metal layers may also partially overlap, that is, one metal layer is longer and the other metal layer is shorter.

[0077] Figure 2 For a flowchart of the method provided in the embodiment of this application, please refer to Figure 2 Based on a general inventive concept, an embodiment of the present application also provides a method for preparing the current collector provided above.

[0078] This method is used to prepare the above-mentioned current collector. The specific content of the current collector can be referred to the above-mentioned embodiment. Since this method adopts part or all of the technical solutions of the above-mentioned embodiment, it at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiment, which will not be repeated here.

[0079] In some embodiments, the method comprises:

[0080] S1. Obtaining a surface metallized base film;

[0081] It should be noted that, the “base film with metallized surface” herein means that it can be obtained by direct purchase or prepared according to conventional processes in the art.

[0082] For example, a specific process for obtaining a surface-metallized base film may be to deposit metal on both sides of the base film to obtain the surface-metallized base film.

[0083] It should be noted that the specific method of metal deposition is not limited and can be performed according to conventional methods in the art.

[0084] As an example, in the step of depositing metal, at least one of physical vapor deposition and chemical plating is adopted; wherein physical vapor deposition includes at least one of vacuum evaporation, magnetron sputtering and ion beam evaporation coating.

[0085] It should be noted that the specific process of the chemical plating treatment and the components and ratios of the corresponding reagents used are not limited and can be set according to conventional selections in the art.

[0086] As an example, in the process of chemical plating, the plating solution includes CuSO4, complexing agent - triethanolamine, Na2CO3, potassium sodium tartrate, thiourea, NaOH and formaldehyde; wherein, the concentration of CuSO4 is 5-7 g / L, the concentration of complexing agent - triethanolamine is 8-10 mg / L, the concentration of Na2CO3 is 8-10 mg / L, the concentration of potassium sodium tartrate is 70-75 g / L, the concentration of thiourea is 0.005-0.01 g / L, the concentration of formaldehyde is 8-10 mg / L, NaOH is used as a pH regulator until the pH of the solution is 12, the treatment temperature is 40-50°C, and the treatment time is 10-30 min.

[0087] It should be noted that based on different metal deposition processes, the preparation process can be adjusted accordingly taking into account the effect of metal deposition.

[0088] As an example, before the step of depositing the metal by chemical plating, the base film is subjected to roughening, sensitization and activation treatments in sequence.

[0089] It should be noted that the specific processes of roughening, sensitization and activation treatments, as well as the components and ratios of the corresponding reagents used are not limited and can be set according to conventional selections in the art.

[0090] As an example, during the roughening treatment process, the roughening liquid includes sulfuric acid, water and chromic acid; wherein, the volume ratio of sulfuric acid to water in the roughening liquid is 4:6, chromic acid is added as a component until the mixed solution is saturated, the treatment temperature is 60-70°C, and the treatment time is 20-30 minutes.

[0091] As an example, during the sensitization process, the sensitizing solution includes SnCl and HCl; wherein the concentration of SnCl is 0.05-0.1 g / L, the concentration of HCl is 0.2-0.4 g / L, and the treatment time is 2-4 min.

[0092] As an example, during the activation treatment, the activation solution includes AgNO3 and ammonia water; wherein the concentration of AgNO3 is 3 to 5 g / L, ammonia water is added as a component until the solution becomes transparent, and the treatment time is 5 to 10 minutes.

[0093] It is understandable that, since different types of metals have different physical and chemical properties, the optimal deposition process can be selected or adjusted according to actual needs in consideration of the effect of metal deposition.

[0094] As an example, the metal is Al. In the metal deposition step, a vacuum evaporation method in a physical vapor deposition method is used to deposit metal Al on the surface of the base film to form a metal layer. The vacuum degree is 1.3×10 -4 ~1.3×10 -2 Within the Pa range, the processing temperature is 500~2500℃.

[0095] It is understandable that since the evaporation temperature affects the density of the metal layer, the better the density, the stronger its bonding with the base film. Considering the bonding strength between the formed metal layer and the base film, the evaporation temperature can be further limited.

[0096] As an example, the metal is Cu, and after the step of depositing the metal is completed and before the step of removing the portion of the base film corresponding to the edge area of ​​the metal layer, the metal layer is further thickened.

[0097] S2. Electroplating the surface metallized base film to thicken the metal layer of the surface metallized base film to obtain a primary current collector;

[0098] In some embodiments, the electroplating process includes at least two stages of electroplating. Further, the electroplating process includes four stages of electroplating.

[0099] The first stage of the four-stage electroplating is the current ramp stage electroplating, wherein the mass concentration of CuSO4·5H2O in the electroplating solution of the current ramp stage electroplating is 100g / L~300g / L, the mass concentration of H2SO4 is 20g / L~90g / L, and the mass concentration of Cl is 100g / L~300g / L. - The mass concentration of 10mg / L to 100mg / L, the mass concentration of tetrahydrothiazolidinethione is 0.0005g / L to 0.001g / L, the mass concentration of sodium polydimethylsilanesulfonate is 0.01g / L to 0.02g / L, and the mass concentration of polyethylene glycol (e.g., PEG-6000) is 0.03g / L to 0.05g / L. The electroplating process in the current ramping stage meets the following requirements: an electroplating time of 0.5min to 1min, an electroplating current density of 0.2ASD to 1ASD, and an electroplating temperature of 30°C to 50°C. The current density in this stage is relatively low, which can prevent the base metal from falling off due to excessive current.

[0100] As an example, the mass concentration of CuSO4·5H2O is any one of 100 g / L, 150 g / L, 200 g / L, 250 g / L and 300 g / L, or a range between any two of them. The mass concentration of H2SO4 is any one of 20 g / L, 30 g / L, 40 g / L, 50 g / L, 60 g / L, 70 g / L, 80 g / L and 90 g / L, or a range between any two of them. - The mass concentration of is 10 g / L, 20 g / L, 30 g / L, 40 g / L, 50 g / L, 60 g / L, 70 g / L, 80 g / L, 90 g / L and 100 g / L, or a range between any two thereof. The mass concentration of tetrahydrothiazolidinethione is 0.0005 g / L, 0.0006 g / L, 0.0007 g / L, 0.0008 g / L, 0.0009 g / L and 0.001 g / L, or a range between any two thereof. The mass concentration of sodium poly(2,6-bis(dimethylamino)propane sulfonate) is 0.01 g / L, 0.015 g / L and 0.02 g / L, or a range between any two thereof. The mass concentration of polyethylene glycol (e.g., PEG-6000) is any one of 0.03 g / L, 0.04 g / L, and 0.05 g / L, or a range thereof. The electroplating time is any one of 0.5 min, 0.6 min, 0.7 min, 0.8 min, 0.9 min, and 1 min, or a range thereof. The electroplating current density is any one of 0.2 ASD, 0.4 ASD, 0.6 ASD, 0.8 ASD, and 1 ASD, or a range thereof. The electroplating temperature is any one of 30° C., 40° C., and 50° C., or a range thereof.

[0101] The second electroplating stage of the four-stage electroplating is a stable continuous stage electroplating, wherein the mass concentration of CuSO4·5H2O in the electroplating solution of the stable continuous stage electroplating is 100g / L to 300g / L, the mass concentration of H2SO4 is 20g / L to 90g / L, and the mass concentration of Cl is 100g / L to 300g / L. - The mass concentration of 10mg / L to 100mg / L of thiazolidinethione is 0.0005g / L to 0.001g / L, the mass concentration of poly(2,6-bis(propanesulfonate)) is 0.01g / L to 0.02g / L, and the mass concentration of polyethylene glycol (e.g., PEG-6000) is 0.03g / L to 0.05g / L. The stable continuous electroplating process meets the following requirements: an electroplating time of 1 to 3 minutes, an electroplating current density of 1ASD to 3ASD, and an electroplating temperature of 20°C to 50°C. The metal layer formed in this stage has low sheet resistance and good conductivity, making it suitable for high current operating conditions.

[0102] As an example, the mass concentration of CuSO4·5H2O is any one of 100 g / L, 150 g / L, 200 g / L, 250 g / L and 300 g / L, or a range between any two of them. The mass concentration of H2SO4 is any one of 20 g / L, 30 g / L, 40 g / L, 50 g / L, 60 g / L, 70 g / L, 80 g / L and 90 g / L, or a range between any two of them. - The mass concentration of is 10 g / L, 20 g / L, 30 g / L, 40 g / L, 50 g / L, 60 g / L, 70 g / L, 80 g / L, 90 g / L and 100 g / L, or a range between any two thereof. The mass concentration of tetrahydrothiazolidinethione is 0.0005 g / L, 0.0006 g / L, 0.0007 g / L, 0.0008 g / L, 0.0009 g / L and 0.001 g / L, or a range between any two thereof. The mass concentration of sodium poly(2,6-bis(dimethylamino)propane sulfonate) is 0.01 g / L, 0.015 g / L and 0.02 g / L, or a range between any two thereof. The mass concentration of polyethylene glycol (eg, PEG-6000) is any one of 0.03 g / L, 0.04 g / L, and 0.05 g / L, or a range between any two of them.

[0103] The third stage of the four-stage electroplating is the grain coarsening stage electroplating. The mass concentration of CuSO4·5H2O in the electroplating solution of the grain coarsening stage is 30g / L to 100g / L, the mass concentration of H2SO4 is 20g / L to 90g / L, the mass concentration of glucose is 15g / L to 25g / L, and the mass concentration of ammonium molybdate is 10g / L to 20g / L. The electroplating process of the grain coarsening stage meets the following requirements: electroplating time is 10s to 20s, electroplating current density is 2.5ASD to 3ASD, and electroplating temperature is 50℃ to 60℃. Low Cu is used in this stage. 2+ concentration, high current density, thereby reducing a large Cu particle layer at the cathode.

[0104] As an example, the mass concentration of CuSO4·5H2O is any one of 30 g / L, 50 g / L, 70 g / L, 90 g / L, and 100 g / L, or a range between any two thereof. The mass concentration of H2SO4 is any one of 20 g / L, 30 g / L, 40 g / L, 50 g / L, 60 g / L, 70 g / L, 80 g / L, and 90 g / L, or a range between any two thereof. The mass concentration of glucose is any one of 15 g / L, 16 g / L, 17 g / L, 18 g / L, 19 g / L, 20 g / L, 21 g / L, 22 g / L, 23 g / L, 24 g / L, and 25 g / L, or a range between any two thereof. The mass concentration of ammonium molybdate is any one of 10 g / L, 15 g / L, and 20 g / L, or a range between any two thereof. The electroplating time is any one of 10 s, 15 s, and 20 s, or a range between any two of them. The electroplating current density is any one of 2.5 ASD, 2.6 ASD, 2.7 ASD, 2.8 ASD, 2.9 ASD, and 3 ASD, or a range between any two of them. The electroplating temperature is any one of 50° C., 55° C., and 60° C., or a range between any two of them.

[0105] The fourth electroplating stage in the four-stage electroplating is a fine grain strengthening stage electroplating. The mass concentration of CuSO4·5H2O in the electroplating solution of the fine grain strengthening stage electroplating is 100g / L to 300g / L, the mass concentration of H2SO4 is 20g / L to 90g / L, and the mass concentration of Cl is 100g / L to 300g / L. -The mass concentration of 10mg / L to 100mg / L of thiazolidinethione is 0.0005g / L to 0.001g / L, the mass concentration of sodium polydimethylsilanesulfonate is 0.01g / L to 0.02g / L, and the mass concentration of polyethylene glycol (e.g., PEG-6000) is 0.03g / L to 0.05g / L. The electroplating process in the grain refinement stage meets the following requirements: an electroplating time of 5s to 30s, an electroplating current density of 0.2ASD to 1ASD, and an electroplating temperature of 20°C to 30°C. This stage uses a low current to continue depositing a finer copper layer on the large copper layer to prevent the large copper particles from falling off.

[0106] As an example, the mass concentration of CuSO4·5H2O is any one of 100 g / L, 150 g / L, 200 g / L, 250 g / L and 300 g / L, or a range between any two of them. The mass concentration of H2SO4 is any one of 20 g / L, 30 g / L, 40 g / L, 50 g / L, 60 g / L, 70 g / L, 80 g / L and 90 g / L, or a range between any two of them. - The mass concentration of is 10 g / L, 20 g / L, 30 g / L, 40 g / L, 50 g / L, 60 g / L, 70 g / L, 80 g / L, 90 g / L and 100 g / L, or a range between any two thereof. The mass concentration of tetrahydrothiazolidinethione is 0.0005 g / L, 0.0006 g / L, 0.0007 g / L, 0.0008 g / L, 0.0009 g / L and 0.001 g / L, or a range between any two thereof. The mass concentration of sodium poly(2,6-bis(dimethylamino)propane sulfonate) is 0.01 g / L, 0.015 g / L and 0.02 g / L, or a range between any two thereof. The mass concentration of polyethylene glycol (e.g., PEG-6000) is any one of 0.03 g / L, 0.04 g / L, and 0.05 g / L, or a range thereof. The electroplating time is any one of 5 s, 10 s, 15 s, 20 s, 25 s, and 30 s, or a range thereof. The electroplating current density is any one of 0.2 ASD, 0.4 ASD, 0.6 ASD, 0.8 ASD, and 1 ASD, or a range thereof. The electroplating temperature is any one of 20° C., 25° C., and 30° C., or a range thereof.

[0107] S3. Performing an anti-oxidation treatment on the primary current collector to form an anti-oxidation layer to obtain a current collector.

[0108] In some embodiments, the anti-oxidation treatment includes immersing the primary current collector in an anti-oxidation solution comprising a BTA corrosion inhibitor and ammonium molybdate. The combination of BTA corrosion inhibitor and ammonium molybdate to form the anti-oxidation solution can further reduce the contact angle of the current collector surface, thereby increasing the adhesion between the current collector and the active material layer when used as a pole piece.

[0109] Furthermore, the mass concentration of the BTA corrosion inhibitor in the anti-oxidation solution is 5 mg / L to 60 mg / L, and the mass concentration of ammonium molybdate is 5 mg / L to 80 mg / L; the immersion time is 2 to 5 minutes; and the immersion temperature is 30° C. to 70° C. By controlling the process parameters during the immersion process, the anti-oxidation treatment can be better achieved, which is beneficial to the anti-oxidation performance of the current collector.

[0110] As an example, the mass concentration of the BTA corrosion inhibitor is any one of 5 mg / L, 10 mg / L, 20 mg / L, 30 mg / L, 40 mg / L, 50 mg / L, and 60 mg / L, or a range between any two thereof. The mass concentration of ammonium molybdate is any one of 5 mg / L, 10 mg / L, 20 mg / L, 30 mg / L, 40 mg / L, 50 mg / L, 60 mg / L, 70 mg / L, and 80 mg / L, or a range between any two thereof. The immersion time is any one of 2 min, 3 min, 4 min, and 5 min, or a range between any two thereof; and the immersion temperature is any one of 30°C, 40°C, 50°C, 60°C, and 70°C, or a range between any two thereof.

[0111] Figure 3 The schematic diagram of the structure of the electrode provided in the embodiment of the present application is as follows: Figure 3 As shown, based on a general inventive concept, an embodiment of the present application further provides a pole piece, which includes the current collector provided above.

[0112] The pole piece is realized based on the above-mentioned current collector. The specific content of the current collector can be referred to the above-mentioned embodiment. Since the pole piece adopts part or all of the technical solutions of the above-mentioned embodiment, it has at least all the beneficial effects brought by the technical solutions of the above-mentioned embodiment, which will not be repeated here.

[0113] It should be noted that the specific type of the electrode is not limited and can be adjusted according to the type of the current collector.

[0114] Illustratively, the current collector is a positive electrode current collector, and the pole piece is a positive electrode pole piece; the current collector is a negative electrode current collector, and the pole piece is a negative electrode pole piece.

[0115] The secondary battery formed by the electrode can be applied to various electrical devices, such as mobile phones, portable devices, laptops, battery vehicles, electric vehicles, ships, spacecraft, electric toys, energy storage devices and power tools.

[0116] The present application will be further described below in conjunction with specific examples. It should be understood that these examples are intended to illustrate the present application only and are not intended to limit the scope of the present application. The experimental methods in the following examples where specific conditions are not specified are usually measured in accordance with national standards. If there are no corresponding national standards, then the methods are carried out in accordance with general international standards, conventional conditions, or according to the conditions recommended by the manufacturer.

[0117] Example 1

[0118] A composite current collector, the preparation process of which is as follows:

[0119] S1. Obtaining a surface metallized base film;

[0120] S2. Electroplating the surface metallized base film to thicken the metal layer of the surface metallized base film to obtain a primary current collector;

[0121] S3. Performing an anti-oxidation treatment on the primary current collector to form an anti-oxidation layer to obtain a current collector.

[0122] The process of electroplating is:

[0123] ① In the first stage, a small current is used to cover the metallized base film with a dense and fine copper layer, which is appropriately thickened to reduce its square resistance. The current density is 0.5ASD and the electroplating time is 1 minute. The plating solution formula is: CuSO4·5H2O concentration is 200g / L, H2SO4 concentration is 50g / L, and the inorganic additive is Cl - The concentration of the organic additives is 20 mg / L, including thiazolidinethione at a concentration of 0.001 g / L, poly(2,6-bis(propane sulfonate) sodium at a concentration of 0.015 g / L, and PEG-6000 at a concentration of 0.04 g. The electroplating temperature is room temperature (25°C), and the plating solution is stirred continuously during the electroplating process to reduce concentration polarization.

[0124] ② The second stage uses high current to further thicken the coating, further improving copper plating efficiency. After the first stage of thickening, the metallization layer's sheet resistance has been reduced, making it suitable for high-current operation. The plating solution formula for this stage is the same as the first stage, but the current density is increased to 2ASD.

[0125] ③ In the third stage, a large-grain copper layer is grown on the plated copper layer by manipulating the electroplating solution formula and current density. The formula for this stage is: 60g / L CuSO4·5H2O, 80g / L H2SO4, 18g / L glucose, and 16g / L ammonium molybdate. The electroplating time is 15s, the current density is increased to 3ASD, and the temperature is heated to 45°C using a heating rod. Constant stirring is maintained during the electroplating process.

[0126] ④ The fourth stage uses a low current to deposit a thin copper layer, which is used to fix the large copper particles in the third step to prevent them from falling off. The formula for this stage is the same as the electroplating formula in the first stage. The thinning process is: electroplating time 30 seconds, current density 0.2ASD, temperature 25℃.

[0127] The process of anti-oxidation treatment is:

[0128] Immerse the metal film after continuous electroplating in the prepared corrosion inhibitor for 2 minutes at a temperature of 45°C. The formula of this slow-release solution is: BTA concentration is 12 mg / L, and ammonium molybdate concentration is 15 mg / L.

[0129] Example 2

[0130] A composite current collector, the preparation process of which is as follows:

[0131] S1. Obtaining a surface metallized base film;

[0132] S2. Electroplating the surface metallized base film to thicken the metal layer of the surface metallized base film to obtain a primary current collector;

[0133] S3. Performing an anti-oxidation treatment on the primary current collector to form an anti-oxidation layer to obtain a current collector.

[0134] The process of electroplating is:

[0135] ① In the first stage, a small current is used to cover the metallized base film with a dense and fine copper layer, which is appropriately thickened to reduce its square resistance. The current density is 0.5ASD and the electroplating time is 1 minute. The plating solution formula is: CuSO4·5H2O concentration is 200g / L, H2SO4 concentration is 50g / L, and the inorganic additive is Cl - The concentration of the organic additives is 20 mg / L, including thiazolidinethione at a concentration of 0.001 g / L, poly(2,6-bis(propane sulfonate) sodium at a concentration of 0.015 g / L, and PEG-6000 at a concentration of 0.04 g. The electroplating temperature is room temperature (25°C), and the plating solution is stirred continuously during the electroplating process to reduce concentration polarization.

[0136] ② The second stage uses high current to further thicken the coating, further improving copper plating efficiency. After the first stage of thickening, the metallization layer's sheet resistance has been reduced, making it suitable for high-current operation. The plating solution formula for this stage is the same as the first stage, but the current density is increased to 2ASD.

[0137] ③ In the third stage, a large-grain copper layer is grown on the plated copper layer by manipulating the electroplating solution formula and current density. The formula for this stage is: 60g / L CuSO4·5H2O, 80g / L H2SO4, 18g / L glucose, and 16g / L ammonium molybdate. The electroplating time is 15s, the current density is increased to 3ASD, and the temperature is heated to 45°C using a heating rod. Constant stirring is maintained during the electroplating process.

[0138] ④ The fourth stage uses a low current to deposit a thin copper layer, which is used to fix the large copper particles in the third step to prevent them from falling off. The formula for this stage is the same as the electroplating formula in the first stage. The thinning process is: electroplating time 30 seconds, current density 0.2ASD, temperature 25℃.

[0139] The process of anti-oxidation treatment is:

[0140] Immerse the metal film after continuous electroplating in the prepared corrosion inhibitor for 2 minutes at a temperature of 45°C. The formula of this slow-release solution is: BTA concentration is 15 mg / L.

[0141] Example 3

[0142] A composite current collector, the preparation process of which is as follows:

[0143] S1. Obtaining a surface metallized base film;

[0144] S2. Electroplating the surface metallized base film to thicken the metal layer of the surface metallized base film to obtain a primary current collector;

[0145] S3. The primary current collector is subjected to a roughening treatment, and then subjected to an anti-oxidation treatment to form an anti-oxidation layer to obtain a current collector.

[0146] The process of electroplating is:

[0147] ① In the first stage, a small current is used to cover the metallized base film with a dense and fine copper layer, which is appropriately thickened to reduce its square resistance. The current density is 0.5ASD and the electroplating time is 1 minute. The plating solution formula is: CuSO4·5H2O concentration is 200g / L, H2SO4 concentration is 50g / L, and the inorganic additive is Cl -The concentration of the organic additives is 20 mg / L, including thiazolidinethione at a concentration of 0.001 g / L, poly(2,6-bis(propane sulfonate) sodium at a concentration of 0.015 g / L, and PEG-6000 at a concentration of 0.04 g. The electroplating temperature is room temperature (25°C), and the plating solution is stirred continuously during the electroplating process to reduce concentration polarization.

[0148] ② The second stage uses high current to further thicken the coating, further improving copper plating efficiency. After the first stage of thickening, the metallization layer's sheet resistance has been reduced, making it suitable for high-current operation. The plating solution formula for this stage is the same as the first stage, but the current density is increased to 2ASD.

[0149] ③ In the third stage, a large-grain copper layer is grown on the plated copper layer by manipulating the electroplating solution formula and current density. The formula for this stage is: 60g / L CuSO4·5H2O, 80g / L H2SO4, 18g / L glucose, and 16g / L ammonium molybdate. The electroplating time is 15s, the current density is increased to 3ASD, and the temperature is heated to 45°C using a heating rod. Constant stirring is maintained during the electroplating process.

[0150] ④ The fourth stage uses a low current to deposit a thin copper layer, which is used to fix the large copper particles in the third step to prevent them from falling off. The formula for this stage is the same as the electroplating formula in the first stage. The thinning process is: electroplating time 30 seconds, current density 0.2ASD, temperature 25℃.

[0151] The process of roughening is:

[0152] The surface copper layer is etched and roughened using the principle of chemical corrosion. The composite copper foil prepared in the first step is immersed in a roughening solution for 0.5 minutes. The roughening solution temperature is 40°C and the roughening solution formula is: hydrogen peroxide concentration of 130ml / L; sulfuric acid solution concentration of 50ml / L; chloride ion concentration of 10ppm; copper ion concentration of 25g / L.

[0153] The process of anti-oxidation treatment is:

[0154] Immerse the metal film after continuous electroplating in the prepared corrosion inhibitor for 2 minutes at a temperature of 45°C. The formula of this slow-release solution is: BTA concentration is 12 mg / L, and ammonium molybdate concentration is 15 mg / L.

[0155] Comparative Example 1

[0156] A composite current collector, the preparation process of which is as follows:

[0157] S1. Obtaining a surface metallized base film;

[0158] S2. Electroplating the surface metallized base film to thicken the metal layer of the surface metallized base film to obtain a primary current collector;

[0159] S3. The primary current collector is subjected to a roughening treatment, and then subjected to an anti-oxidation treatment to form an anti-oxidation layer to obtain a current collector.

[0160] The process of electroplating is:

[0161] The surface metallized film was thickened using a conventional one-step electroplating process. The current density was 0.6 ASD and the electroplating time was 7 min. The plating solution formula was: CuSO4·5H2O concentration was 220 g / L, H2SO4 concentration was 60 g / L, and the inorganic additive was Cl - The concentration was 18 mg / L. Organic additives included thiazolidinethione at 0.0015 g / L, poly(2,6-bis(propanesulfonate) sodium at 0.02 g / L, and PEG-6000 at 0.05 g. The plating temperature was room temperature (25°C), and the bath was continuously stirred during the plating process to reduce concentration polarization.

[0162] The process of roughening is:

[0163] The surface copper layer is etched and roughened using the principle of chemical corrosion. The composite copper foil prepared in the first step is immersed in a roughening solution for 0.5 minutes. The roughening solution temperature is 40°C and the roughening solution formula is: hydrogen peroxide concentration of 130ml / L; sulfuric acid solution concentration of 50ml / L; chloride ion concentration of 10ppm; copper ion concentration of 25g / L.

[0164] The process of anti-oxidation treatment is:

[0165] Immerse the metal film after continuous electroplating in the prepared corrosion inhibitor for 2 minutes at a temperature of 45°C. The formula of this slow-release solution is: BTA concentration is 12 mg / L, and ammonium molybdate concentration is 15 mg / L.

[0166] Comparative Example 2

[0167] A composite current collector, the preparation process of which is as follows:

[0168] S1. Obtaining a surface metallized base film;

[0169] S2. Electroplating the surface metallized base film to thicken the metal layer of the surface metallized base film to obtain a primary current collector;

[0170] S3. Performing an anti-oxidation treatment on the primary current collector to form an anti-oxidation layer to obtain a current collector.

[0171] The process of electroplating is:

[0172] The surface metallized film was thickened by conventional one-step electroplating process. The current density was 0.6ASD and the electroplating time was 5min. The plating solution formula was: CuSO4·5H2O concentration was 220g / L, H2SO4 concentration was 60g / L, and the inorganic additive was Cl - The concentration was 18 mg / L. Organic additives included thiazolidinethione at 0.0015 g / L, poly(2,6-bis(propanesulfonate) sodium at 0.02 g / L, and PEG-6000 at 0.05 g. The plating temperature was room temperature (25°C), and the bath was continuously stirred during the plating process to reduce concentration polarization.

[0173] The process of anti-oxidation treatment is:

[0174] Immerse the metal film after continuous electroplating in the prepared corrosion inhibitor for 2 minutes at a temperature of 45°C. The formula of this slow-release solution is: BTA concentration is 12 mg / L, and ammonium molybdate concentration is 15 mg / L.

[0175] The contact angle test was performed on the composite current collector provided in each embodiment and comparative example, and the prepared negative electrode slurry (mainly graphite) was coated on the composite current collector, dried, and rolled to obtain a lithium battery negative electrode sheet. The peel strength of the negative electrode slurry from the current collector surface was tested using a standard peel test method; the prepared negative electrode sheet was then installed in a battery according to the lithium battery soft pack battery preparation process, and the battery cycle performance was measured using the national standard cycle test method;

[0176] The test method for peel strength is as follows:

[0177] Pole strips: size 30mm×70mm,

[0178] Fixing method: The pressure-sensitive 3M-VHB double-sided tape is attached to the electrode surface, and the other side is attached to the stainless steel plate.

[0179] Test process: The stainless steel plate and current collector are fixed on the two fixtures of the equipment, and then a 180-degree peel test is performed at a speed of 100 mm / min and a load of 10 N.

[0180] The specific cycle performance test method is as follows:

[0181] At room temperature (25°C), the battery was charged at a constant current and constant voltage (CCCV) of 1C for 150 minutes and discharged at a constant current of 1C to 2.75V for one cycle. The number of cycles was 500.

[0182] The results are shown in the following table:

[0183]

[0184] As can be seen from Example 1 and Comparative Example 2, compared to single electroplating, the contact angle of the coating surface after multiple continuous electroplating decreased significantly, from 97.6° to 70.6°, and the hydrophobic surface was modified into a hydrophilic surface. The smaller the contact angle, the smaller the surface tension during negative electrode slurry coating, the greater the bonding force, and the greater the peel strength. The greater the peel strength, the better the cycle performance of the final battery end. Although the single electroplating + chemical roughening process used in Comparative Example 1 can also reduce the surface contact angle to a certain extent, its preparation process will be more complicated.

[0185] As can be seen from Example 1 and Example 2, after the same roughening treatment, different passivation solution formulas also have a very significant impact on the contact angle. The interface after the BTA+ammonium molybdate composite passivation solution formula is treated has a smaller contact angle than the interface after the BTA passivation solution is treated alone. The applicant believes that the reason may be that the passivation film formed by the reaction of pure BTA with the copper surface has a large amount of hydrophobic groups (phenyl rings), resulting in a larger interface contact angle, while in the BTA+ammonium molybdate composite passivation solution, a large amount of hydrophobic groups (phenyl rings) are replaced by hydrophilic groups (ammonium radicals), showing better wetting properties.

[0186] It can be seen from Examples 1 and 3 that the contact angle can be further reduced by combining a chemical roughening process with a continuous multi-stage electroplating process.

[0187] The foregoing description is merely a specific embodiment of the present application and is not intended to limit the present application. Persons skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A method for preparing a current collector, characterized in that: The method comprises: Obtaining a surface metallized base film; Electroplating the surface metallized base film to obtain a primary current collector; performing an anti-oxidation treatment on the primary current collector to obtain a current collector; Among them, the electroplating treatment includes four stages of electroplating, the third stage of the four stages of electroplating is the electroplating in the grain coarsening stage, and the process of the electroplating in the grain coarsening stage meets the following requirements: the electroplating time is 10s~20s, the electroplating current density is 2.5ASD~3ASD, and the electroplating temperature is 50℃~60℃; the last stage of the electroplating treatment is the electroplating in the fine grain strengthening stage; the process of the electroplating in the fine grain strengthening stage meets the following requirements: the electroplating time is 5s~30s, the electroplating current density is 0.2ASD~1ASD, and the electroplating temperature is 20℃~30℃.

2. The method for preparing a current collector according to claim 1, wherein: The first electroplating stage of the four electroplating stages is electroplating in the current ramping stage, and the electroplating process in the current ramping stage meets the following requirements: electroplating time is 0.5 min to 1 min, electroplating current density is 0.2 ASD to 1 ASD, and electroplating temperature is 30° C. to 50° C.

3. The method for preparing a current collector according to claim 1, wherein: The second stage of the four-stage electroplating is a stable continuous stage electroplating, and the process of the stable continuous stage electroplating meets the following requirements: electroplating time is 1 min to 3 min, electroplating current density is 1 ASD to 3 ASD, and electroplating temperature is 20° C. to 50° C.

4. The method for preparing a current collector according to claim 1, wherein: The electroplating process includes: electroplating in the current ramping stage, electroplating in the stable continuous stage, electroplating in the grain coarsening stage and electroplating in the grain refinement and strengthening stage; The components of the plating solutions for the electroplating in the current ramping stage, the electroplating in the stable continuous stage, and the electroplating in the grain refinement and strengthening stage satisfy any one of the following (A) to (F): (A) The mass concentration of CuSO4·5H2O is 100g / L~300g / L; (B) The mass concentration of H2SO4 is 20g / L~90g / L; (C)Cl - The mass concentration is 10mg / L~100mg / L; (D) The mass concentration of tetrahydrothiazolidinethione is 0.0005g / L~0.001g / L; (E) The mass concentration of sodium poly(2,6-bis(2,6-propane sulfonate)) is 0.01 g / L to 0.02 g / L; (F) The mass concentration of polyethylene glycol is 0.03g / L~0.05g / L; The components of the electroplating solution in the grain coarsening stage satisfy any one of the following (G) to (J): (G) The mass concentration of CuSO4·5H2O is 30g / L~100g / L; (H) The mass concentration of H2SO4 is 20g / L~90g / L; (I) The mass concentration of glucose is 15g / L~25g / L; (J) The mass concentration of ammonium molybdate is 10g / L~20g / L.

5. The method for preparing a current collector according to claim 1, wherein: The anti-oxidation treatment comprises immersing the primary current collector in an anti-oxidation solution, wherein the anti-oxidation solution comprises a BTA corrosion inhibitor and ammonium molybdate.

6. The method for preparing a current collector according to claim 5, wherein: The mass concentration of the BTA corrosion inhibitor in the anti-oxidation solution is 5 mg / L to 60 mg / L; and / or The mass concentration of ammonium molybdate in the anti-oxidation solution is 5 mg / L to 80 mg / L; and / or The soaking time is 2 min to 5 min; and / or The soaking temperature is 30°C to 70°C.

7. A current collector, characterized in that: The current collector is prepared by the preparation method according to any one of claims 1 to 6.

8. The current collector according to claim 7, wherein The base film material of the current collector includes at least one of polyethylene, biaxially oriented polypropylene, polystyrene, polyethylene terephthalate, polybutylene terephthalate and polypropylene; and / or The base film thickness of the current collector is 2 μm to 20 μm; and / or The thickness of the metal layer of the current collector is 0.1 μm to 10 μm; and / or The square resistance of the current collector is 0.5~500mΩ / □; The surface contact angle of the current collector is 60° to 80°.

9. A pole piece, characterized in that: The pole piece includes the current collector according to any one of claims 7 to 8 or the current collector prepared by the method according to any one of claims 1 to 6.

10. A secondary battery, characterized in that: The secondary battery comprises the electrode piece according to claim 9.

Images