Copper-nickel composite material as well as preparation method and application thereof

Abstract

The invention provides a preparation method of a copper-nickel composite material. The preparation method comprises the following steps: S1) preparing an electrolytic copper foil; (S2) the electrolytic copper foil is subjected to direct current electroplating in the electroplating solution, and a copper-nickel composite material is obtained; the electroplating liquid comprises polyethylene glycol, saccharin sodium salt and 2-(carboxymethyl) benzimidazole. The invention further provides plating electroplating liquid of the copper-nickel composite material. The invention further provides the copper-nickel composite material and application thereof. According to the preparation method of the copper-nickel composite material, the polyethylene glycol, the saccharin sodium and the CMBI are added into the electroplating liquid of the electrolytic copper foil, the polyethylene glycol, the saccharin sodium and the CMBI have a synergistic effect, a continuous nano nickel layer can be constructed on the surface of an electrolytic copper foil substrate under a direct current electroplating technology, preparation of a nano twin crystal-isometric crystal composite structure is achieved, and the copper-nickel composite material is prepared. And the hardness, the thermal stability, the corrosion resistance and the surface smoothness of a nickel plating layer are remarkably improved.

Description

Technical Field

[0001] This invention relates to electroplating technology, and more particularly to copper-nickel composite materials, their preparation methods, and their applications. Background Technology

[0002] Copper-nickel composite current collectors are a commonly used material in lithium-ion battery manufacturing and are widely used in battery current collectors. However, existing copper-nickel composite electroplating processes still face a series of technical challenges in achieving high-performance coatings:

[0003] 1) Current waveform and control issues: Traditional electroplating processes often rely on pulsed power supplies or segmented current control, which not only increases process complexity but also raises equipment costs and operational difficulties. Precise control of the current waveform has a significant impact on plating quality; instability in current density leads to uneven plating and increases the risk of defects. 2) Unsatisfactory surface quality: In traditional copper-nickel electroplating processes, dendrites easily form during deposition, resulting in high surface roughness (Ra), typically 0.20~0.35µm. This roughness directly affects the battery's conductivity and performance at high current densities, and high surface roughness at the electrode interface can easily lead to a decrease in cycle life. 3) Grain growth control. High manufacturing difficulty: In existing technologies, grain size control relies on fine-tuning of current density and external high-temperature heat treatment. Although this method can adjust grain size, it is easy to cause unevenness of the coating and affect the stability of the process; 4) Interaction effect of temperature and current: The stability of the plating solution and the physical properties of the coating are often limited under high temperature environment, especially in ultra-thin nickel layer plating. Excessive temperature will cause the opening of diffusion channels, accelerate the interdiffusion between copper and nickel, and affect the structure and stability of the composite electroplating layer; 5) Corrosion acceleration problem: Existing coating methods (such as sputtering nickel plating) often have high porosity (>5%), which leads to local current density concentration, further accelerating corrosion and affecting the durability of the coating.

[0004] With advancements in battery technology, particularly the growing demand for high-performance lithium batteries, traditional battery current collector materials are unable to meet increasingly stringent performance requirements. Especially for ultra-thin copper foil (thickness ≤10µm), the electroplated layer needs to maintain good electrical conductivity while also possessing high mechanical strength, thermal stability, diffusion resistance, and corrosion resistance.

[0005] Currently, although researchers have conducted numerous studies on copper-nickel composite current collectors in an effort to meet the aforementioned performance requirements, copper-nickel composite coatings still suffer from the following problems: 1) Excessively large grain size and poor thermal stability: In traditional electroplating processes, the grain size of the nickel plating layer is too large, and grain boundary migration at high temperatures leads to a loose coating; 2) High surface roughness: Traditional nickel plating layers have a rough surface (Ra>0.15µm), affecting the conductivity and mechanical stability of the battery; 3) Accelerated corrosion: Existing coatings (such as sputtered nickel plating) have high porosity (>5%), which accelerates the corrosion process; 4) High cost and complex processes: Existing pulse electroplating processes and segmented current control increase production costs and complexity, limiting the adaptability for large-scale production. Summary of the Invention

[0006] The technical problem solved by this invention is to provide a method for preparing copper-nickel composite materials, which can construct a continuous nano-nickel coating on the surface of an electrolytic copper foil substrate, successfully realize the preparation of a nanotwin-equiaxed crystal composite structure, and significantly improve the hardness, thermal stability, corrosion resistance and surface smoothness of the nickel coating.

[0007] In view of this, this application provides a method for preparing a copper-nickel composite material, comprising the following steps:

[0008] S1) Preparation of electrolytic copper foil;

[0009] S2) Electrolytic copper foil is directly electroplated in an electroplating solution to obtain a copper-nickel composite material;

[0010] The electroplating solution includes polyethylene glycol, sodium saccharin, and 2-(carboxymethyl)benzimidazole.

[0011] In some specific embodiments, the electroplating solution further includes nickel sulfate, boric acid, and ammonium hypophosphite; in the electroplating solution, the concentration of nickel sulfate is 200~300 g / L, the concentration of boric acid is 40~80 g / L, the concentration of ammonium hypophosphite is 15~35 g / L, the concentration of polyethylene glycol is 100~300 mg / L, the concentration of sodium saccharin is 100~500 mg / L, and the concentration of CMBI is 5~20 mg / L; and / or, the polyethylene glycol includes polyethylene glycol-6000, polyethylene glycol-4000, or polyethylene glycol-8000.

[0012] In some specific embodiments, the current density of the DC electroplating is 3.0~30.0 A / m. 2 The electroplating time is 1-5 seconds, and the circulation flow rate of the electroplating solution in the DC electroplating is 1-5 m³ / s. 3 / h.

[0013] In some specific embodiments, the volume fraction N of nanotwins in the nickel plating of the copper-nickel composite material is... t ≥20%, Nt The following relationship must be satisfied:

[0014]

[0015] Where, N t Volume fraction of nanotwins; N max Maximum twin fraction, N max =43%; k: experimental fitting constant, k≈0.012; J: current density (A / dm²); C CMBI CMBI concentration (mg / L).

[0016] In some specific embodiments, the method for preparing the electrolytic copper foil is as follows:

[0017] In the presence of Cu 2+ :85~100g / L, H2SO4: 80~140g / L, Cl - In an electrolyte solution of 20~35 ppm, at a current density of 6000~7000 A / m 2 Electrolyte flow rate 40~50m³ 3 Under the condition of / h, electrolytic copper foil of 4~10μm is deposited on the surface of the cathode roller.

[0018] This application also provides an electroplating solution for copper-nickel composite materials, comprising: polyethylene glycol, sodium saccharin, and CMBI.

[0019] In some specific embodiments, the electroplating solution further includes nickel sulfate, boric acid, and ammonium hypophosphite; in the electroplating solution, the concentration of nickel sulfate is 200~300 g / L, the concentration of boric acid is 40~80 g / L, the concentration of ammonium hypophosphite is 15~35 g / L, the concentration of polyethylene glycol is 100~300 mg / L, the concentration of sodium saccharin is 100~500 mg / L, and the concentration of CMBI is 5~20 mg / L.

[0020] This application also provides a copper-nickel composite material prepared by the aforementioned preparation method, which consists of an electrolytic copper foil and a nickel plating layer formed on the surface of the electrolytic copper foil.

[0021] In some specific embodiments, the thickness of the nickel plating layer is 10~200nm, and / or the surface of the nickel plating layer has nanoscale protrusions with an average spacing of 200~500nm; and / or the surface roughness Ra of the nickel plating layer is 0.07~0.09μm, and the Sdr is 5~10%; and / or the equiaxed nanocrystal size of the surface of the nickel plating layer is 20~80nm, the volume fraction of the equiaxed nanocrystals is 55~80%, and the volume fraction of twins is ≥20%.

[0022] This application also provides the preparation method described above, the copper-nickel composite material prepared by the above scheme, or the application of the copper-nickel composite material in lithium batteries.

[0023] This application provides a method for preparing a copper-nickel composite material. First, an electrolytic copper foil is prepared, and then the electrolytic copper foil is subjected to DC electroplating in an electroplating solution to obtain the copper-nickel composite material. The electroplating solution includes polyethylene glycol, sodium saccharin, and 2-(carboxymethyl)benzimidazole (CMBI). In the above electroplating solution, sodium saccharin forms an adsorption film in the electrolyte, inhibiting grain growth and resulting in a coating surface dominated by equiaxed nanocrystals. Simultaneously, sodium saccharin promotes the formation of fine and uniform grains by reducing the kinetic barrier to grain growth. Furthermore, sodium saccharin provides twinning nucleation sites for CMBI, which is beneficial for twinning. The directional formation of crystals is achieved through the selective adsorption of {111} crystal planes by CMBI during electroplating, which lowers the energy barrier for twin formation. Polyethylene glycol can dynamically cover the micro-protrusion areas in the electroplating solution, forming a nano-protrusion interlocking structure under high current density. Furthermore, the synergistic effect of polyethylene glycol, sodium saccharin, and CMBI can suppress dendrite growth and achieve surface self-leveling by covering the peak region in the later stage of nickel layer deposition, resulting in a lower surface roughness of the nickel plating layer. In addition, there is a positive correlation between the concentration of CMBI and the current density, and it can significantly increase the volume fraction of twins on the plating surface within a specific concentration range.

[0024] Furthermore, this application precisely controls the volume fraction of twins on the coating surface by optimizing the concentrations of sodium saccharin, polyethylene glycol, and CMBI and their dynamic adsorption behavior during the electroplating process, effectively improving the hardness, thermal stability, and electrical conductivity of the coating while ensuring the surface smoothness of the coating. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of the copper-nickel composite material provided by the present invention;

[0026] Figure 2 This is a microstructure photograph of the copper-nickel composite material prepared in Example 1 of the present invention. Detailed Implementation

[0027] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0028] In view of the problems of excessively large grain size, poor thermal stability, high surface roughness, and corrosion in nickel plating of copper foil in existing technologies, this application provides a method for preparing a copper-nickel composite material. By adding polyethylene glycol, sodium saccharin, and 2-(carboxymethyl)benzimidazole (CMBI) to the electroplating solution, the three components work synergistically to construct a continuous nano-nickel layer on the surface of an electrolytic copper foil substrate under DC electroplating. This achieves the preparation of a nanotwinned-equiaxed crystal composite structure and significantly improves the hardness, thermal stability, corrosion resistance, and surface smoothness of the nickel plating layer. Specifically, this invention first discloses a method for preparing a copper-nickel composite material, including the following steps:

[0029] S1) Preparation of electrolytic copper foil;

[0030] S2) Electrolytic copper foil is directly electroplated in an electroplating solution to obtain a copper-nickel composite material;

[0031] The electroplating solution includes polyethylene glycol, sodium saccharin, and 2-(carboxymethyl)benzimidazole (CMBI).

[0032] In the preparation method of copper-nickel composite material, in step S1, an electrolytic copper foil is first prepared. The preparation method of the electrolytic copper foil is carried out according to methods well known to those skilled in the art, and the thickness of the electrolytic copper foil is 4~10μm. For example, the specific preparation method of the electrolytic copper foil is as follows:

[0033] In the presence of Cu 2+ :85~100g / L, H2SO4: 80~140g / L, Cl - In an electrolyte solution of 20~35 ppm, at a current density of 6000~7000 A / m 2 Electrolyte flow rate 40~50m³ 3 Under the condition of / h, electrolytic copper foil of 4~10μm is deposited on the surface of the cathode roller.

[0034] This application then performs DC electroplating on electrolytic copper foil in an electroplating solution to obtain a copper-nickel composite material. The electroplating solution includes polyethylene glycol, sodium saccharin, and CMBI. The copper-nickel composite material is the electrolytic copper foil and the nickel plating layer formed on the surface of the electrolytic copper foil. In the above process, the electroplating solution also includes nickel sulfate, boric acid, and ammonium hypophosphite, that is, the electroplating solution includes nickel sulfate, boric acid, ammonium hypophosphite, polyethylene glycol, sodium saccharin, and CMBI; wherein, the nickel sulfate provides nickel ions, boric acid acts as a buffer to stabilize the pH, and ammonium hypophosphite acts as a reducing agent to promote nickel deposition, which is particularly suitable for low-temperature DC electroplating.

[0035] Sodium saccharin forms an adsorption film on the surface of electrolytic copper foil, inhibiting grain growth and resulting in a coating surface dominated by equiaxed nanocrystals (grain size 20-80 nm). Simultaneously, sodium saccharin promotes the formation of fine and uniform grains by reducing the kinetic barrier to grain growth. Furthermore, sodium saccharin provides twin nucleation sites for CMBI, aiding in the directional formation of twins. During electroplating, CMBI selectively adsorbs onto the {111} crystal plane, lowering the energy barrier for twin formation and achieving directional growth and high-density arrangement of nanotwins. A significant positive correlation exists between the concentration of CMBI and the current density; when the concentration reaches a certain value (5-20 mg / L), it can significantly increase the volume fraction of twins (≥20%), improving the hardness, tensile strength, and thermal stability of the coating, especially exhibiting better stability at high temperatures. Furthermore, by optimizing the concentration and adsorption sequence of CMBI, a higher twin density can be obtained in the coating, promoting an increase in coating hardness.

[0036] The polyethylene glycol (PEG) includes PEG-6000, PEG-4000, or PEG-8000. In a specific embodiment, the PEG is selected from PEG-6000. The chain length and adsorption kinetics of PEG-6000 are most suitable for forming a dynamic coating layer in the micro-protrusion region, inhibiting dendrites without affecting the fluidity of the plating solution. If the molecular weight is too low (e.g., PEG-1000), the coverage is insufficient; if the molecular weight is too high (e.g., PEG-10000), it will lead to an increase in the viscosity of the plating solution, affecting ion transport and twin formation. PEG-6000 can dynamically cover the micro-protrusion region in the electroplating solution, forming a nano-protrusion interlocking structure (λ=200~500nm) under high current density. It can effectively cover the micro-protrusion region, inhibit dendrite growth, and maintain the fluidity of the plating solution, which is conducive to the formation of nano-twin structures. Polyethylene glycol, in synergy with sodium saccharin and CMBI, can suppress dendrite growth and achieve surface self-leveling by covering the peak region in the later stage of deposition, keeping the surface roughness (Ra) of the coating ≤0.1µm, which meets the surface quality requirements of ultra-thin copper foil battery current collectors.

[0037] Furthermore, the concentrations of nickel sulfate, boric acid, ammonium hypophosphite, polyethylene glycol, sodium saccharin, and CMBI are 200-300 g / L, 40-80 g / L, 15-35 g / L, 100-300 mg / L, 100-500 mg / L, and 5-20 mg / L, respectively. Specifically, the concentrations of nickel sulfate, boric acid, ammonium hypophosphite, polyethylene glycol, sodium saccharin, and CMBI are 210-280 g / L, 45-74 g / L, 18-32 g / L, 120-280 mg / L, 150-450 mg / L, and 6-18 mg / L, respectively. More specifically, the concentrations are as follows: nickel sulfate 230-260 g / L, boric acid 52-70 g / L, ammonium hypophosphite 20-30 g / L, polyethylene glycol 130-250 mg / L, sodium saccharin 180-400 mg / L, and CMBI 7-15 mg / L; more specifically, the concentrations are as follows: nickel sulfate 240-250 g / L, boric acid 58-65 g / L, ammonium hypophosphite 23-27 g / L, polyethylene glycol 150-220 mg / L, sodium saccharin 200-350 mg / L, and CMBI 8-12 mg / L.

[0038] The above-mentioned control of sodium saccharin, CMBI and PEG concentrations can precisely control the twin integral number, effectively improve the hardness, thermal stability and electrical conductivity of the coating, and at the same time ensure the surface smoothness of the coating.

[0039] In the aforementioned DC electroplating process, the current density of the DC electroplating is 3.0~30.0 A / m. 2 The electroplating time is 1-5 seconds, and the circulation flow rate of the electroplating solution in the DC electroplating is 1-5 m³ / s. 3 / h; specifically, the current density is 7.5~20A / m 2 The electroplating time is 1.35~3.5s, and the circulation flow rate of the electroplating solution is 2~4m³. 3 / h; more specifically, the current density is 8.0~16.5A / m 2 The electroplating time is 1.56~3.0s, and the circulation flow rate of the electroplating solution is 2.8~3.6m³. 3 / h; more specifically, the current density is 9.5~15.5A / m 2 The electroplating time is 1.56~2.72s, and the circulation flow rate of the electroplating solution is 3.0~3.3m³. 3 / h. The temperature of the electroplating solution is 45±2℃, and the pH is 3.5~4.5.

[0040] The volume fraction N of nanotwins in the nickel plating of the copper-nickel composite material prepared in this application is... t≥20%, N t The following relationship must be satisfied:

[0041]

[0042] Where, N t Twin integral number; N max Maximum twin fraction, N max 43%, this value was determined by saturation experiments; k: experimental fitting constant, k≈0.012; J: current density (A / dm²); C CMBI CMBI concentration (mg / L).

[0043] The aforementioned quantitative model of CMBI concentration-current density-twin fraction allows for precise control of the volume fraction of nanotwins in nickel plating, thereby optimizing the mechanical properties and thermal stability of nickel plating.

[0044] Where, N max The determination was made through a saturation experiment, and the specific process was as follows:

[0045] DC electroplating was performed on 6 μm electrolytic copper foil in an electroplating solution containing 250 g / L nickel sulfate, 60 g / L boric acid, 25 g / L ammonium hypophosphite, 200 mg / L polyethylene glycol-6000, 400 mg / L sodium saccharin, and 20 mg / L CMBI at 45°C, pH 4.0, and a current density of 28 A / dm². Three parallel samples were prepared, and their twinning fractions, determined by EBSD, were 43.5%, 42.8%, and 43.7%, with an average of 43.3%. Based on this, N in the prediction model of this invention... max The figure was determined to be 43%.

[0046] Experimental results show that the volume fraction of nanotwins calculated by the quantitative model of this application is close to the volume fraction of nanotwins in actual nickel-plated copper foil products. Therefore, the quantitative model provided by this application can be used to estimate the volume fraction of nanotwins in nickel plating with high accuracy.

[0047] The method for preparing copper-nickel composite materials provided in this application simplifies the electroplating process, reduces the need for current waveform adjustment, and improves production efficiency. This method does not rely on pulse power supplies, subsequent heat treatment, or surface modification processes. By optimizing the additive system and dynamic adsorption, it directly obtains high-quality coatings under conventional DC electroplating mode, simplifying the production process and reducing equipment and process complexity. Furthermore, the cost of the additives is low, only 1 / 5 of that of traditional pulse electroplating process auxiliaries, which greatly reduces production costs and enhances market competitiveness.

[0048] Furthermore, this application provides a copper-nickel composite material plating solution, comprising: polyethylene glycol, sodium saccharin, and CMBI.

[0049] More specifically, the electroplating solution also includes nickel sulfate, boric acid, and ammonium hypophosphite; in the electroplating solution, the concentration of nickel sulfate is 200~300 g / L, the concentration of boric acid is 40~80 g / L, the concentration of ammonium hypophosphite is 15~35 g / L, the concentration of polyethylene glycol is 100~300 mg / L, the concentration of sodium saccharin is 100~500 mg / L, and the concentration of CMBI is 5~20 mg / L.

[0050] The above-mentioned electroplating solution has been described in detail in the above preparation method, and will not be repeated here.

[0051] Furthermore, this application also provides a copper-nickel composite material prepared by the above preparation method, which consists of an electrolytic copper foil and a nickel plating layer formed on the surface of the electrolytic copper foil.

[0052] like Figure 1 As shown, Figure 1 This is a schematic diagram of a copper-nickel composite material, in which a nickel plating layer is formed on one surface of the electrolytic copper foil, or a nickel plating layer is formed on both surfaces of the electrolytic copper foil.

[0053] Specifically, the thickness of the nickel plating layer is 10-200 nm, more specifically, the thickness of the nickel plating layer is 20-150 nm, more specifically, the thickness of the nickel plating layer is 50-130 nm, and more specifically, the thickness of the nickel plating layer is 80-100 nm. The surface roughness Ra of the nickel plating layer is 0.07-0.09 μm, more specifically, the surface roughness Ra of the nickel plating layer is 0.08-0.09 μm. The Sdr is 5-10%, more specifically, the Sdr is 6-9%, and more specifically, the Sdr is 7-8%. The equiaxed nanocrystal size of the surface of the nickel plating layer is 20-80 nm, more specifically, the equiaxed nanocrystal size is 40-70 nm. The volume fraction of equiaxed nanocrystals is 55-80%, and the volume fraction of twins is ≥20%; specifically, the volume fraction of equiaxed nanocrystals is 65-79%, and the volume fraction of twins is 21-35%; more specifically, the volume fraction of equiaxed nanocrystals is 67-78%, and the volume fraction of twins is 22-33%; more specifically, the volume fraction of equiaxed nanocrystals is 69-77%, and the volume fraction of twins is 23-31%; more specifically, the volume fraction of twins is 24%, 25%, and 29%.

[0054] The copper-nickel composite material prepared by the method provided in this application exhibits the following significant effects in the nickel plating layer by simultaneously adding polyethylene glycol, sodium saccharin, and CMBI to the electroplating solution:

[0055] The twinning integral number of the coating is increased: the twinning integral number can reach more than 20%, which significantly improves the hardness, tensile strength and thermal stability of the coating;

[0056] Improved surface smoothness: The surface roughness Ra of the coating is controlled between 0.07 and 0.09 µm to meet the requirements of the current collector of ultra-thin batteries, and the surface Sdr is ≤10% to ensure good electrical conductivity and mechanical properties;

[0057] Excellent physical properties are retained: the coating thickness (10~200nm) is extremely thin and does not affect the physical properties of the base copper foil. Based on the good base copper foil, composite current collectors with a strength of 300~700MPa and an elongation of 3~15% can be produced.

[0058] Nanoscale protrusions: The coating surface has uniformly distributed nanoscale protrusions with an average spacing of 200~50nm, which enhances the electrochemical performance and adhesion of the coating.

[0059] Furthermore, this application also provides the application of the copper-nickel composite material described above in lithium batteries; specifically, the copper-nickel composite material can be used as a current collector in lithium batteries.

[0060] To further understand the present invention, the copper-nickel composite material and its preparation method provided by the present invention will be described in detail below with reference to the embodiments. The scope of protection of the present invention is not limited by the following embodiments.

[0061] The raw materials used in the following examples are all commercially available products, including 2-(carboxymethyl)benzimidazole (CMBI), CAS: 13570-08-6.

[0062] The properties of the copper-nickel composite materials prepared in the following examples and comparative examples were tested according to the following methods:

[0063] 1) Twin fraction

[0064] Detection method: Electron backscatter diffraction technique;

[0065] Testing tool: Field emission scanning electron microscope equipped with EBSD system;

[0066] Specific standards / conditions:

[0067] Sample preparation: The sample to be tested is subjected to ion polishing to obtain a stress-free and scratch-free mirror surface;

[0068] Data acquisition: The prepared sample was placed in the SEM sample chamber. Under the conditions of accelerating voltage of 20kV and working distance of about 15mm, the Kikuchi flower pattern was acquired using an EBSD detector. The scanning step size was set according to the actual grain size, usually 0.1~2μm.

[0069] Data Analysis: The acquired data was processed using the accompanying EBSD analysis software (OXFORD Instruments' Aztec Crystal). The grain boundary reconstruction function was used to set the grain boundary misorientation angle to 60°. <111> To identify annealed twin boundaries, the twin fraction is calculated using the formula: total twin boundary length / (total length of all grain boundaries + total twin boundary length) × 100%.

[0070] 2) Grain size & protrusion spacing (λ)

[0071] Detection method: Scanning electron microscopy calibration;

[0072] Detection tool: Field emission scanning electron microscope;

[0073] Specific standards / conditions:

[0074] Sample preparation: The sample to be tested is ground and polished, and then etched using a specific chemical or electrolytic etchant to clearly reveal the grain boundaries;

[0075] Data analysis (grain size): The linear intercept method is used, following the ASTM E112 standard. A series of straight lines of known length are drawn on the acquired image. The number of grain boundaries intersecting these lines is counted, the average linear intercept is calculated, and then multiplied by a conversion factor (usually 1.78) to obtain the average grain size.

[0076] Data analysis (protrusion spacing λ): For surfaces with specific morphology (such as bimodal structure), the distance between adjacent protrusion vertices or centers is directly measured. At least 50 protrusion spacings are randomly measured under multiple fields of view, and the arithmetic mean is taken as the average protrusion spacing λ.

[0077] 3) Surface roughness (Ra) to the ratio of interface spread area (Sdr)

[0078] Detection method: Non-contact three-dimensional optical profilometry;

[0079] Testing tool: Laser scanning confocal microscope;

[0080] Specific standards / conditions:

[0081] Sample preparation: Keep the surface to be tested clean and free of oil, dust and other contaminants;

[0082] Data acquisition: Using a 50x or 100x objective lens, select at least three different representative areas on the sample surface for scanning to construct a three-dimensional surface topography map. The size of a single scanned area should be larger than the size of the feature structure.

[0083] Data analysis: The three-dimensional topography data were calculated using the instrument's built-in analysis software according to the ISO25178 series standards;

[0084] Arithmetic mean height (Ra): The arithmetic mean of the absolute values ​​of the deviation of the surface profile from the baseline within the evaluation area, automatically calculated by the software;

[0085] Surface Area Ratio (Sdr): The percentage of the difference between the actual surface area and the projected surface area, calculated automatically by the software, relative to the projected surface area; Sdr = [(ActualSurfaceArea - ProjectedArea) / ProjectedArea] × 100%.

[0086] 4) Coating thickness

[0087] Detection method: Inductively coupled plasma optical emission spectrometry;

[0088] Detection tool: Inductively coupled plasma spectrometer;

[0089] Specific standards / conditions:

[0090] Sample preparation: Accurately weigh a certain mass of the coated sample, use a specific acid solution (such as dilute nitric acid) to completely dissolve the coating, while ensuring that the substrate is not corroded or the corrosion is negligible, and bring the solution to a specific volume.

[0091] Preparation of standard samples: Prepare a series of standard solutions of known concentrations that are identical to the elements used in the coating;

[0092] Test Analysis: The elemental concentrations of the standard and sample solutions were tested using ICP-OES. The total mass of the elements measured in the coating was calculated using the concentration and volume of the sample solution. Then, combined with the known area and theoretical chemical density of the coating, the average thickness of the coating was calculated. The formula is: Thickness = (Total mass of coating) / (Area × Coating material density).

[0093] 5) Nano-indentation hardness

[0094] Detection method: Nanoindentation;

[0095] Testing tool: Nanoindenter;

[0096] Specific standards / conditions:

[0097] Sample preparation: The sample test surface must be polished to a mirror finish to ensure that there is no residual stress layer;

[0098] Test procedure: Berkovich diamond indenter was selected, and the continuous stiffness measurement method was used. Loading-holding-unloading cycle was performed at a set indentation depth (usually 100~200nm). No less than 10 points were randomly selected on each sample for testing.

[0099] Data Analysis: The instrument software automatically analyzes the load-displacement curves according to the Oliver-Pharr method, directly providing the nanoindentation hardness and elastic modulus values. The final result is the average value of all valid test points.

[0100] 6) Tensile strength and elongation

[0101] Test method: Room temperature microscale tensile test;

[0102] Testing standards: Refer to GB / T228.1-2021 "Metallic materials - Tensile testing - Part 1: Test method at room temperature" and Appendix A (recommended method) of GB / T31483-2015 "Electrolytic copper foil for lithium-ion batteries";

[0103] Testing tools: Precision universal testing machine (equipped with a high-precision micro-force sensor and an optical non-contact extensometer);

[0104] Specific steps and conditions:

[0105] Sample Preparation: Using a specialized stamping die, the composite material is formed into narrow, rectangular specimens (typically with a gauge length width of 12.5 mm and a total length ≥ 150 mm). Extreme care must be taken during specimen preparation to ensure the specimen edges are free of burrs and cracks, and direct contact with the gauge length by hand is strictly prohibited to prevent accidental deformation or contamination. The specimen thickness is the actual thickness of the composite material; the width and gauge length must be measured and recorded using a high-precision image measuring instrument.

[0106] Fixture selection: Use pneumatic flat-jaw fixtures and ensure that the fixture surface has fine teeth or is covered with special padding (such as sandpaper, rubber, etc.) to prevent the sample from slipping or being broken at the fixture.

[0107] Test parameters:

[0108] Tensile rate: Controlled by strain rate or specified by load rate. According to standards, the initial strain rate is typically set to no more than 0.008 s⁻¹. -1 ;

[0109] Gauge length: typically 50mm;

[0110] Data acquisition frequency: ≥50Hz, to ensure accurate capture of yield point and fracture point;

[0111] Deformation measurement: A non-contact video extensometer must be used to create speckle (spot) marks on the surface of the specimen gauge length. The real-time strain is accurately calculated by tracking the displacement of the speckle. This is the key to measuring the elongation of ultrathin foil materials, and it avoids the slippage and inertia problems of contact extensometers, ensuring the accuracy of the data.

[0112] Data Analysis:

[0113] Tensile strength (Rm): Calculated automatically by software from the stress-strain curve, the maximum load (Fm) is divided by the original cross-sectional area of ​​the specimen (A0). Rm = Fm / A0 (unit: MPa or N / mm²);

[0114] Elongation after fracture (A50 or A100): Based on the gauge length, the software automatically calculates this by comparing the distance between the marked points of the gauge length segment before and after fracture, and expresses it as a percentage.

[0115] 7) High temperature resistance

[0116] Test method: High-temperature static air exposure test;

[0117] Testing tool: High-temperature drying oven (programmed temperature control precision high-temperature furnace);

[0118] Specific standards / conditions:

[0119] Sample preparation: Clean, dry and weigh the sample accurately (accuracy 0.1 mg);

[0120] Test procedure: Place the sample in a high-temperature oven and expose it to a set temperature (e.g., 200°C) and atmospheric environment for a set time (e.g., 10 hours, 20 hours).

[0121] Performance evaluation: After the test, remove the sample and cool it to room temperature;

[0122] Example 1

[0123] (1) Raw material processing and electrolyte preparation

[0124] 1) The cathode copper raw material is smelted and cast into oxygen-free copper rods with a diameter of φ3~5mm;

[0125] 2) The above-mentioned oxygen-free copper rod is dissolved in copper to form an electrolyte containing copper sulfate, the composition of which is: Cu 2+ :90 g / L, H2SO4: 110 g / L, Cl - 28 ppm;

[0126] 3) The electrolyte is purified by activated carbon adsorption and multi-stage filtration (to 0.5μm) before entering the electrolytic cell;

[0127] (2) Electrolytic deposition of copper foil

[0128] At 55℃±2℃, with an electrolyte flow rate of 45 m³ / h and a current density of 6500 A / m², DC electrodeposition was performed in the above-mentioned electrolytic cell using a foil-making machine to obtain an electrolytic copper foil with a thickness of 6 μm.

[0129] (3) Electroplating nickel layer process

[0130] Using electrolytic green foil as the cathode and iridium-plated titanium plate as the anode, direct current electroplating was performed in an electroplating solution to obtain nickel-copper foil. The electroplating solution contained: sodium saccharin: 300 mg / L, CMBI: 8 mg / L, PEG-6000: 150 mg / L, nickel sulfate: 250 g / L, boric acid: 60 g / L, and ammonium hypophosphate: 25 g / L; the current density was 7.5 A / dm², the electroplating time was 1.56 s, and the solution circulation flow rate was 3 m³ / h.

[0131] (4) Post-processing

[0132] The nickel-plated copper foil is washed with water, dried with hot air, rolled up, and aged at low temperature to obtain the nickel-plated copper foil product.

[0133] Figure 2 The image shows a surface SEM image of the nickel plating layer of the nickel-plated copper foil product prepared in this embodiment. As can be seen from the image, uniform and fine nanocrystals are formed on the surface of the layer.

[0134] According to the above method, the twinning fraction of the nickel-plated copper foil product prepared in this embodiment is 22%. Based on the relational theory, N... t The value is approximately 18%, which is basically consistent with the measured value. In addition, the product has a grain size of 20nm, a protrusion spacing λ of 480nm, a surface roughness Ra of 0.08μm, an Sdr of 8%, a nickel plating thickness of 50nm, a nano-indentation hardness of 2.4GPa, a tensile strength of 450MPa, an elongation of 8%, and a high temperature resistance time of >18h at 200℃.

[0135] Example 2

[0136] (1) Raw material processing and electrolyte preparation

[0137] 1) The cathode copper raw material is smelted and cast into oxygen-free copper rods with a diameter of φ3~5mm;

[0138] 2) The above-mentioned oxygen-free copper rod is dissolved in copper to form an electrolyte containing copper sulfate, the composition of which is: Cu 2+ :95 g / L, H2SO4: 120 g / L, Cl - 30 ppm;

[0139] 3) The electrolyte is purified by activated carbon adsorption and multi-stage filtration (to 0.5μm) before entering the electrolytic cell;

[0140] (2) Electrolytic deposition of copper foil

[0141] At 55℃±2℃, with an electrolyte flow rate of 48 m³ / h and a current density of 6800 A / m², DC electrodeposition was performed in the above-mentioned electrolytic cell using a foil-making machine to obtain an electrolytic copper foil with a thickness of 8 μm.

[0142] (3) Electroplating nickel layer process

[0143] Using electrolytic green foil as the cathode and iridium-plated titanium plate as the anode, direct current electroplating was performed in an electroplating solution to obtain nickel-copper foil. The electroplating solution contained: sodium saccharin: 400 mg / L, CMBI: 12 mg / L, PEG-6000: 200 mg / L, nickel sulfate: 260 g / L, boric acid: 65 g / L, ammonium hypophosphite: 28 g / L; current density: 12.0 A / dm², electroplating time: 1.56 s, and solution circulation flow rate: 3 m³ / h.

[0144] (4) Post-processing

[0145] The nickel-plated copper foil is washed with water, dried with hot air, rolled up, and aged at low temperature to obtain the nickel-plated copper foil product.

[0146] According to the above method, the twinning fraction of the nickel-plated copper foil product prepared in this embodiment is 29%, and the calculated value based on the relational formula is Nt≈27.2%, which is basically consistent with the measured value. Furthermore, the product has a grain size of 40 nm, a protrusion spacing λ of 350 nm, a surface roughness Ra of 0.07 μm, an Sdr of 6%, a nickel plating thickness of 80 nm, a nanoindentation hardness of 2.8 GPa, a tensile strength of 580 MPa, an elongation of 6%, and a high-temperature resistance time of >22 h at 200℃.

[0147] Example 3

[0148] (1) Raw material processing and electrolyte preparation

[0149] 1) The cathode copper raw material is smelted and cast into oxygen-free copper rods with a diameter of φ3~5mm;

[0150] 2) The above-mentioned oxygen-free copper rod is dissolved in copper to form an electrolyte containing copper sulfate, the composition of which is: Cu 2+ :88 g / L, H2SO4: 100 g / L, Cl ~ 25 ppm;

[0151] 3) The electrolyte is purified by activated carbon adsorption and multi-stage filtration (to 0.5μm) before entering the electrolytic cell;

[0152] (2) Electrolytic deposition of copper foil

[0153] At 55℃±2℃, with an electrolyte flow rate of 42 m³ / h and a current density of 6200 A / m², DC electrodeposition was performed in the above-mentioned electrolytic cell using a foil-making machine to obtain an electrolytic copper foil with a thickness of 4.5 μm.

[0154] (3) Electroplating nickel layer process

[0155] Using electrolytic green foil as the cathode and iridium-plated titanium plate as the anode, direct current electroplating was performed in an electroplating solution to obtain nickel-copper foil. The electroplating solution contained: sodium saccharin: 200 mg / L, CMBI: 12 mg / L, PEG-6000: 100 mg / L, nickel sulfate: 220 g / L, boric acid: 50 g / L, ammonium hypophosphite: 20 g / L; current density: 6.0 A / dm², electroplating time: 1.35 s, and solution circulation flow rate: 3 m³ / h.

[0156] (4) Post-processing

[0157] The nickel-plated copper foil is washed with water, dried with hot air, rolled up, and aged at low temperature to obtain the nickel-plated copper foil product.

[0158] According to the above method, the twinning fraction of the nickel-plated copper foil product prepared in this embodiment is 20%, and the calculated value based on the relational formula is Nt≈19.9%, which is basically consistent with the measured value. Furthermore, the product has a grain size of 70nm, a protrusion spacing λ of 500nm, a surface roughness Ra of 0.09μm, an Sdr of 9%, a nickel plating thickness of 20nm, a nanoindentation hardness of 2.1GPa, a tensile strength of 320MPa, an elongation of 5%, and a high-temperature resistance time of >15h at 200℃.

[0159] Example 4

[0160] The preparation method of nickel-plated copper foil is basically the same as in Example 1, except that: the concentration of sodium saccharin is 250 mg / L, the concentration of CMBI is 10 mg / L, the concentration of PEG-600 is 180 mg / L, and the current density is 15.8 A / dm³. 2 .

[0161] The twinning fraction of the nickel-plated copper foil product prepared in this embodiment is 25%, and according to the theoretical calculation, Nt≈28.2%, which is basically consistent with the measured value. The grain size is 30nm.

[0162] Example 5

[0163] The preparation method of nickel-plated copper foil is basically the same as in Example 1, except that: the concentration of sodium saccharin is 350 mg / L, the concentration of CMBI is 15 mg / L, the concentration of PEG-600 is 220 mg / L, and the current density is 16.2 A / dm³. 2 .

[0164] The twinning fraction of the nickel-plated copper foil product prepared in this embodiment is 31%, and according to the theoretical calculation, Nt≈32.0%, which is basically consistent with the measured value. The grain size is 45nm.

[0165] Example 6

[0166] The preparation method of nickel-plated copper foil is basically the same as in Example 1, except that: the concentration of sodium saccharin is 100 mg / L, the concentration of CMBI is 6 mg / L, the concentration of PEG-600 is 120 mg / L, and the current density is 15.2 A / dm³. 2 .

[0167] The twinning fraction of the nickel-plated copper foil product prepared in this embodiment is 21%, and according to the theoretical calculation, Nt≈22.5%, which is basically consistent with the measured value. The grain size is 75nm.

[0168] Example 7

[0169] The preparation method of nickel-plated copper foil is basically the same as in Example 1, except that: the concentration of sodium saccharin is 500 mg / L, the concentration of CMBI is 20 mg / L, the concentration of PEG-600 is 250 mg / L, and the current density is 16.5 A / dm³. 2 .

[0170] The twinning fraction of the nickel-plated copper foil product prepared in this embodiment is 35%, and according to the theoretical calculation, Nt≈34.3%, which is basically consistent with the measured value. The grain size is 22nm.

[0171] Example 8

[0172] The preparation method of nickel-plated copper foil is basically the same as in Example 1, except that: the concentration of sodium saccharin is 150 mg / L, the concentration of CMBI is 7 mg / L, the concentration of PEG-600 is 120 mg / L, and the current density is 15.3 A / dm³. 2 .

[0173] The twinning fraction of the nickel-plated copper foil product prepared in this embodiment is 23%, and according to the theoretical calculation, Nt≈24.2%, which is basically consistent with the measured value. The grain size is 65nm.

[0174] Example 9

[0175] The preparation method of nickel-plated copper foil is basically the same as in Example 1, except that: the concentration of sodium saccharin is 450 mg / L, the concentration of CMBI is 18 mg / L, the concentration of PEG-600 is 280 mg / L, and the current density is 16.3 A / dm³. 2 .

[0176] The twinning fraction of the nickel-plated copper foil product prepared in this embodiment is 33%, which, according to the theoretical calculation, is approximately 33.5% Nt, basically consistent with the measured value. The grain size is 28 nm.

[0177] Example 10

[0178] The preparation method of nickel-plated copper foil is basically the same as in Example 1, except that: the concentration of sodium saccharin is 180 mg / L, the concentration of CMBI is 9 mg / L, the concentration of PEG-600 is 160 mg / L, and the current density is 15.6 A / dm³. 2 .

[0179] The twinning fraction of the nickel-plated copper foil product prepared in this embodiment is 24%, and according to the theoretical calculation, Nt≈27.0%, which is basically consistent with the measured value. The grain size is 55nm.

[0180] Comparative Example 1

[0181] The preparation method of nickel-plated copper foil is basically the same as in Example 1, except that sodium saccharin is not added, the concentration of CMBI is 12 mg / L, the concentration of PEG-600 is 200 mg / L, and the current density is 12.0 A / dm³. 2 .

[0182] The lack of key additives (sodium saccharin or CMBI) in the electroplating solution disrupted the synergistic effect, rendering the twinning fraction formula inapplicable. The nickel-plated copper foil product prepared in this embodiment exhibited a twinning fraction of <5%, Ra > 0.15 μm, a nanoindentation hardness of 1.6 GPa, and coarse grains on the plating surface with no twins.

[0183] Comparative Example 2

[0184] The preparation method of nickel-plated copper foil is basically the same as in Example 1, except that: the concentration of sodium saccharin is 300 mg / L, CMBI is not added, the concentration of PEG-600 is 200 mg / L, and the current density is 12.0 A / dm³. 2 .

[0185] The lack of key additives (sodium saccharin or CMBI) in the electroplating solution disrupts the synergistic effect, rendering the twinning fraction formula inapplicable. The nickel-plated copper foil product prepared in this embodiment has a twinning fraction of approximately 0%, an Ra of 0.12 μm, a nanoindentation hardness of 1.7 GPa, and no twinning structure on the coating surface.

[0186] Comparative Example 3

[0187] The preparation method of nickel-plated copper foil is basically the same as in Example 1, except that: the concentration of sodium saccharin is 300 mg / L, the concentration of CMBI is 12 mg / L, PEG-600 is not added, and the current density is 12.0 A / dm³. 2.

[0188] Due to the lack of polyethylene glycol in the electroplating solution, severe dendrite growth and deteriorated surface roughness resulted in a twinning fraction of 10% for the nickel-plated copper foil product prepared in this embodiment, which is far lower than that obtained from the relationship N. t The theoretical prediction value was approximately 32.1%, demonstrating the necessity of the synergistic effect of the three additives. The coating exhibited Ra≥0.20μm, a nano-indentation hardness of 1.9GPa, severe dendrite formation on the surface, and poor adhesion.

[0189] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0190] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a copper-nickel composite material, comprising the following steps: S1) Preparation of electrolytic copper foil; S2) Electrolytic copper foil is directly electroplated in an electroplating solution to obtain a copper-nickel composite material; The electroplating solution includes polyethylene glycol, sodium saccharin, and 2-(carboxymethyl)benzimidazole.

2. The preparation method according to claim 1, characterized in that, The electroplating solution also includes nickel sulfate, boric acid, and ammonium hypophosphite; in the electroplating solution, the concentration of nickel sulfate is 200~300 g / L, the concentration of boric acid is 40~80 g / L, the concentration of ammonium hypophosphite is 15~35 g / L, the concentration of polyethylene glycol is 100~300 mg / L, the concentration of sodium saccharin is 100~500 mg / L, and the concentration of CMBI is 5~20 mg / L; and / or, the polyethylene glycol includes polyethylene glycol-6000, polyethylene glycol-4000, or polyethylene glycol-8000.

3. The preparation method according to claim 1 or 2, characterized in that, The current density for the DC electroplating is 3.0~30.0 A / m. 2 The electroplating time is 1-5 seconds, and the circulation flow rate of the electroplating solution in the DC electroplating is 1-5 m³ / s. 3 / h.

4. The preparation method according to claim 1 or 2, characterized in that, The volume fraction N of nanotwins in the nickel plating of the copper-nickel composite material. t ≥20%, N t The following relationship must be satisfied: Where, N t Volume fraction of nanotwins; N max Maximum twin fraction, N max =43%; k: experimental fitting constant, k≈0.012; J: current density (A / dm²); C CMBI CMBI concentration (mg / L).

5. The preparation method according to any one of claims 1 to 4, characterized in that, The specific method for preparing the electrolytic copper foil is as follows: In the presence of Cu 2+ :85~100g / L, H2SO4: 80~140g / L, Cl - In an electrolyte solution of 20~35 ppm, at a current density of 6000~7000 A / m 2 Electrolyte flow rate 40~50m³ 3 Under the condition of / h, electrolytic copper foil of 4~10μm is deposited on the surface of the cathode roller.

6. A copper-nickel composite material plating solution, comprising: Polyethylene glycol, sodium saccharin, and CMBI.

7. The electroplating solution according to claim 6, characterized in that, The electroplating solution also includes nickel sulfate, boric acid, and ammonium hypophosphite; in the electroplating solution, the concentration of nickel sulfate is 200~300 g / L, the concentration of boric acid is 40~80 g / L, the concentration of ammonium hypophosphite is 15~35 g / L, the concentration of polyethylene glycol is 100~300 mg / L, the concentration of sodium saccharin is 100~500 mg / L, and the concentration of CMBI is 5~20 mg / L.

8. The copper-nickel composite material prepared by the preparation method of claim 1 is composed of an electrolytic copper foil and a nickel plating layer formed on the surface of the electrolytic copper foil.

9. The copper-nickel composite material according to claim 8, characterized in that, The thickness of the nickel plating layer is 10~200nm, and / or the surface of the nickel plating layer has nanoscale protrusions with an average spacing of 200~500nm; and / or the surface roughness Ra of the nickel plating layer is 0.07~0.09μm, and the Sdr is 5~10%; and / or the equiaxed nanocrystal size of the surface of the nickel plating layer is 20~80nm, the volume fraction of equiaxed nanocrystals is 55~80%, and the volume fraction of twins is ≥20%.

10. The application of the copper-nickel composite material prepared by the preparation method according to any one of claims 1 to 5 or the copper-nickel composite material according to any one of claims 8 to 9 in lithium batteries.

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