A copper current collector and a method for manufacturing the same

Abstract

This invention discloses a copper current collector and its preparation method, belonging to the field of current collector preparation technology. The preparation method provided by this invention includes: providing a cathode and an anode, the anode being pure copper; placing the cathode and anode in an acidic sulfate electrodeposition solution, applying a pulsed current for electrodeposition, and applying ultrasound during the electrodeposition process; wherein, the parameters of the pulsed current exhibit a dynamic gradient change during the deposition process, the dynamic gradient change including: a first stage, where the peak current density continuously changes from high to low, while the on-time continuously changes from short to long, and the off-time continuously changes from long to short; a second stage, where the peak current density continuously changes from low to high, while the on-time continuously changes from long to short, and the off-time continuously changes from short to long. This invention effectively solves the problem of simultaneously achieving high plasticity, interface stability, and conductivity in copper current collectors in existing technologies through dynamic pulsed electrodeposition combined with ultrasonic treatment.

Description

Technical Field

[0001] This invention relates to the field of current collector preparation technology, and in particular to a copper current collector and its preparation method. Background Technology

[0002] Copper foil, as the negative electrode current collector in lithium-ion batteries, is crucial for improving the volumetric energy density of the battery. Using thinner current collectors is an effective way to increase the proportion of active material, but this requires the copper foil to have both higher strength and ductility to withstand the risks of wrinkles and breakage during processing. In existing technologies, alloying or mechanical post-processing can improve strength, but this often leads to a significant decrease in conductivity or makes it unsuitable for ultra-thin specifications. Optimizations to the electrodeposition process, such as introducing nanotwins or constructing multilayer structures, while improving mechanical properties to some extent, suffer from defects such as high internal stress, poor interlayer bonding, and insufficient precision in grain size and distribution control. This results in unsatisfactory material strength, plasticity, and interfacial stability, making it difficult to meet the comprehensive performance requirements of high-energy-density batteries for current collectors. Summary of the Invention

[0003] In view of this, the present invention provides a copper current collector and its preparation method. The present invention successfully prepares a gradient nanostructured copper foil with ultra-high strength, excellent ductility, and high conductivity through dynamic pulse electrodeposition combined with ultrasonic treatment, effectively solving the problem of simultaneously achieving high ductility, interfacial stability, and conductivity in existing copper current collectors.

[0004] In a first aspect, the present invention provides a method for preparing a copper current collector, comprising the following steps: A cathode and an anode are provided, wherein the anode is pure copper; The cathode and anode are placed in an acidic sulfate electrodeposition solution, and a pulsed current is applied for electrodeposition, while ultrasound is applied during the electrodeposition process. The parameters of the pulse current exhibit dynamic gradient changes during the deposition process. These dynamic gradient changes include: a first stage in which the peak current density continuously changes from high to low, while the on-time continuously changes from short to long and the off-time continuously changes from long to short; and a second stage in which the peak current density continuously changes from low to high, while the on-time continuously changes from long to short and the off-time continuously changes from short to long.

[0005] Preferably, in the first stage, the peak current density is from 5 to 15 A / dm². 2 Gradually reduce to 0.5~3A / dm 2 The turn-on time gradually increases from 10-30ms to 40-80ms, while the turn-off time gradually decreases from 40-80ms to 10-30ms; in the second stage, the peak current density ranges from 0.5-3A / dm². 2 Gradually increase to 5~15A / dm2 The turn-on time gradually decreased from 40~80ms to 10~30ms, and the turn-off time gradually increased from 10~30ms to 40~80ms.

[0006] Preferably, the duty cycle changes continuously from low to high in the first stage, and the duty cycle changes continuously from high to low in the second stage.

[0007] Furthermore, in the first stage, the duty cycle gradually increases from 20-30% to 65-85%, and in the second stage, the duty cycle gradually decreases from 65-85% to 20-30%.

[0008] Preferably, the electrodeposition time in the first stage is 20-40 min, and the electrodeposition time in the second stage is 20-40 min.

[0009] Preferably, the frequency of the ultrasonic wave is 15~25WHz.

[0010] Preferably, the acidic sulfate electrodeposition solution comprises: CuSO4·5H2O 300~400g / L, H2SO4 30~35g / L, NaCl 5~10g / L, polyethylene glycol (PEG) 0.1~1g / L, sodium polydisulfide dipropane sulfonate (SPS) 0.01~1.0g / L, sodium dodecyl sulfate (SDS) 0.01~2.0g / L, and a pH value of 1~3.

[0011] Preferably, the cathode is a titanium sheet or a stainless steel sheet; the purity of the pure copper is ≥99.9%.

[0012] Preferably, the method further includes an annealing step for the copper foil obtained by electrodeposition, wherein the annealing temperature is 150~250℃ and the annealing time is 0.3~2h.

[0013] Secondly, the present invention provides a copper current collector, which is prepared by the above-described preparation method.

[0014] Compared with the prior art, the present invention has achieved the following beneficial effects: (1) This invention utilizes the synergistic effect of dynamic gradient pulse electrodeposition and ultrasound to construct a gradient nanostructure with a continuous transition in grain size from the surface to the interior in the copper deposition layer. This avoids the interfacial stress concentration caused by abrupt changes in grain size in traditional multilayer structures, significantly improving the structural integrity and interlayer bonding of the copper current collector. Simultaneously, the dynamically changing pulse parameters effectively suppress abnormal grain growth, promoting the formation of a dense and uniform equiaxed grain structure. This optimizes the stress distribution state while imparting high strength to the material, resulting in excellent strength-plasticity combination. Introducing ultrasound into the dynamic pulse electrodeposition process utilizes its micromechanical impact and cavitation effect to promptly release the internal stress accumulated within the deposition layer, reduce microscopic defects, and promote grain refinement and dislocation migration, thereby further improving the material's deformation limit and mechanical stability. The combined effect of ultrasound and dynamic pulse provides a process guarantee for obtaining a uniformly structured and stable gradient nanostructured copper foil.

[0015] (2) The copper current collector prepared by this invention exhibits excellent comprehensive performance. Its tensile strength can reach more than 800 MPa, its elongation can reach more than 8%, and its conductivity can reach more than 95% IACS. It achieves a synergistic improvement in high strength, high ductility and high conductivity, which can effectively resist the risk of wrinkles and breakage during the electrode processing, and can better meet the stringent requirements of high energy density secondary batteries for the comprehensive performance of current collectors. Attached Figure Description

[0016] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation thereof. Obviously, those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0017] Figure 1 This is a schematic diagram of the cross-sectional copper grain size structure of the copper current collector in a specific embodiment of the present invention; Figure 2 This is the hardness distribution curve of the copper current collector cross section in Embodiment 2 of the present invention; Figure 3 These are X-ray diffraction (XRD) patterns of the copper current collectors in Examples 1-2, Comparative Example 1, and Comparative Example 6 of the present invention. Detailed Implementation

[0018] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0019] This invention reveals that traditional electrodeposition methods, whether constant current deposition or simple alternating pulse deposition, struggle to achieve precise control over a continuous gradient of grain size from the surface inwards. For example, constant current deposition tends to result in uniform grain size, failing to create a gradient; while simple alternating high and low current deposition easily produces abrupt grain size interfaces, leading to decreased interlayer bonding and stress concentration. Furthermore, if the internal stress generated during conventional electrodeposition is not released in a timely manner, it accumulates, forming microscopic defects and ultimately affecting the overall performance of the material. Therefore, this invention, through in-depth research, proposes a synergistic process combining dynamic pulse electrodeposition with ultrasonic treatment to address the aforementioned problems.

[0020] This invention provides a method for preparing a copper current collector, comprising the following steps: A cathode and an anode are provided, wherein the anode is pure copper; The cathode and anode are placed in an acidic sulfate electrodeposition solution, and a pulsed current is applied for electrodeposition, while ultrasound is applied during the electrodeposition process. The parameters of the pulse current exhibit dynamic gradient changes during the deposition process. These dynamic gradient changes include: a first stage in which the peak current density continuously changes from high to low, while the on-time continuously changes from short to long and the off-time continuously changes from long to short; and a second stage in which the peak current density continuously changes from low to high, while the on-time continuously changes from long to short and the off-time continuously changes from short to long.

[0021] In this invention, the cathode serves as the electrodeposition substrate, and its surface condition directly affects the quality of the deposited layer. The anode is made of pure copper, which can continuously provide copper ions during the electrodeposition process, maintaining the stability of the electrolyte composition. The anode purity is preferably ≥99.9%, and more preferably 99.99%, to avoid contamination of the deposited layer by impurity elements.

[0022] This invention achieves a high current density to promote the formation of numerous crystal nuclei in the early stages of deposition by continuously varying the peak current density, conduction time, and turn-off time in the first stage. Subsequently, the current density gradually decreases and the conduction time increases, allowing for continuous but controlled grain growth, thus forming a structure transitioning from fine to coarse grains on one side of the deposition layer. In the second stage, the above parameters are continuously varied in the opposite direction, with the current density gradually increasing again and the conduction time shortening near the middle of the deposition layer, promoting the formation of new crystal nuclei. Ultimately, a fine-grained layer is formed again on the other side of the deposition layer, resulting in a bidirectional symmetrical gradient structure from fine surface grains to coarse core grains and back to fine surface grains. Compared to unidirectional or alternating gradients, this bidirectional dynamic gradient adjustment can better balance surface strength and core toughness, and avoids interfacial stress concentration caused by abrupt changes in grain size. The coordinated variation of on-time and off-time ensures effective deposition during the energized period in each pulse cycle, while the de-energized period fully replenishes the copper ions consumed near the cathode, temporarily halting grain growth and promoting renucleation. This "deposition-replenishment-renucleation" cycle, combined with the dynamic variation of current density, enables continuous and precise control of grain size from nanometer to micrometer scale.

[0023] In this invention, the specific ranges of peak current density, on-time, and off-time can be adjusted according to the target thickness and performance requirements. Preferably, in the first stage, the peak current density is from 5 to 15 A / dm. 2 Gradually reduce to 0.5~3A / dm 2 The turn-on time gradually increases from 10-30ms to 40-80ms, while the turn-off time gradually decreases from 40-80ms to 10-30ms; in the second stage, the peak current density ranges from 0.5-3A / dm². 2 Gradually increase to 5~15A / dm 2 The on-time is gradually reduced from 40-80ms to 10-30ms, while the off-time is gradually increased from 10-30ms to 40-80ms. More preferably, the peak current density in the first stage is 8-12A / dm². 2 Gradually reduce to 0.8~1.2 A / dm 2 The on-time gradually increases from 18-22ms to 50-70ms, while the off-time gradually decreases from 50-70ms to 18-22ms; the peak current density in the second stage increases from 0.8-1.2A / dm². 2 Gradually increase to 8~12A / dm 2 The turn-on time gradually decreases from 50-70ms to 18-22ms, while the turn-off time gradually increases from 18-22ms to 50-70ms. For example, in one specific embodiment, the peak current density in the first stage is 10A / dm². 2Gradually reduce to 1A / dm 2 The turn-on time gradually increased from 20ms to 60ms, while the turn-off time gradually decreased from 60ms to 20ms; the peak current density in the second stage increased from 1A / dm². 2 Gradually increase to 10A / dm 2 The turn-on time was gradually reduced from 60ms to 20ms, and the turn-off time was gradually increased from 20ms to 60ms.

[0024] In this invention, the change in duty cycle (i.e., the ratio of conduction time to pulse period) directly reflects the ratio of effective deposition time to ion replenishment time per unit time, and has a significant impact on grain morphology and gradient structure. Preferably, the duty cycle changes continuously from low to high in the first stage, and from high to low in the second stage. This change pattern is coordinated with the change in peak current density: in the early stage of the first stage, a low duty cycle combined with a high current density can form a large number of crystal nuclei in a very short time; as the duty cycle gradually increases, the deposition time of each pulse is prolonged, which is conducive to the continuous growth of the formed crystal nuclei. In the second stage, the duty cycle decreases from high, which, combined with the increase in current density, further promotes nucleation. This synergistic change in duty cycle and current density is the key to achieving a continuous transition in grain size from fine to coarse and then back to fine. Furthermore, the duty cycle gradually increases from 20-30% to 65-85% in the first stage, and gradually decreases from 65-85% to 20-30% in the second stage. For example, the duty cycle in the first phase can be gradually increased from 25% to 75%, and in the second phase it can be gradually decreased from 75% to 25%.

[0025] The allocation of deposition time in the first and second stages affects the overall thickness of the final copper foil and the symmetry of the gradient structure. Preferably, the electrodeposition time in the first stage is 20-40 min, and the electrodeposition time in the second stage is 20-40 min. A total deposition time of 40-80 min can produce a copper foil with a thickness of approximately 10-20 μm. More preferably, the electrodeposition time in the first stage is 25-35 min, the electrodeposition time in the second stage is 25-35 min, and the total deposition time is approximately 50-70 min. More preferably, the electrodeposition time in the first and second stages is the same to ensure the formation of a gradient symmetrical structure. For example, in one specific embodiment, both the first and second stages are 30 min, the total deposition time is 60 min, and the prepared copper foil has a thickness of approximately 12 μm.

[0026] In this invention, the introduction of ultrasound into the electrodeposition process has multiple effects. The mechanical effect of ultrasound can generate strong microjets and shock waves, which can promptly break up excessively grown grains and promote grain refinement; its cavitation effect can generate local high temperature and high pressure, accelerating ion mass transfer and reducing concentration polarization; at the same time, ultrasound can effectively release the internal stress accumulated inside the deposited layer and reduce the formation of micro-defects (such as pores and microcracks). The synergistic effect of ultrasound and dynamic pulses makes the deposited layer structure more dense and uniform, and the grain size gradient transition more gradual and continuous, laying the foundation for obtaining excellent comprehensive performance. The frequency of ultrasound has a significant impact on the above effects. Preferably, the frequency of the ultrasound is 15~25WHz. Within this frequency range, the mechanical effect and cavitation effect of ultrasound are well balanced, which can effectively refine grains and release stress, without causing excessive energy decay or excessive impact on the deposited layer due to excessive frequency. More preferably, it is 18~22WHz, for example, 20WHz.

[0027] In this invention, the composition of the electrodeposition solution plays a decisive role in the quality and microstructure of the deposited layer. Preferably, the acidic sulfate electrodeposition solution comprises: CuSO4·5H2O 300~400 g / L, H2SO4 30~35 g / L, NaCl 5~10 g / L, polyethylene glycol (PEG) 0.1~1 g / L, sodium polydisulfide dipropane sulfonate (SPS) 0.01~1.0 g / L, sodium dodecyl sulfate (SDS) 0.01~2.0 g / L, with a pH value of 1~3. CuSO4·5H2O serves as the main salt, providing copper ions, and its concentration directly affects the deposition rate and grain size. Too low a concentration results in a slow deposition rate and low production efficiency; too high a concentration easily leads to coarse grains and a rough coating. The concentration of CuSO4·5H2O is more preferably 320~380 g / L, and even more preferably 350 g / L. H₂SO₄ is used to improve the conductivity of the solution, reduce the tank voltage, and inhibit the hydrolysis of copper ions; if the concentration is too low, the conductivity will be insufficient; if the concentration is too high, the risk of hydrogen evolution may increase; its concentration is more preferably 31~34 g / L, and even more preferably 32~33 g / L. NaCl provides chloride ions, which work synergistically with additives during electrodeposition to promote grain refinement and improve coating smoothness; its concentration is more preferably 6~9 g / L, and even more preferably 8 g / L.

[0028] Polyethylene glycol (PEG) is a nonionic surfactant that can form an adsorption film on the cathode surface, inhibiting the abnormal reduction of copper ions and playing a role in leveling and refining grains. If its concentration is too low, the leveling effect will be insufficient; if the concentration is too high, the adsorption film may become too thick, hindering normal deposition. The preferred concentration of PEG is 0.2~0.8 g / L, more preferably 0.3~0.6 g / L, for example, 0.5 g / L. The preferred molecular weight of PEG is 2000~10000, more preferably 4000~8000. Sodium polydisulfide dipropane sulfonate (SPS) is a sulfur-containing organic additive with a strong grain-refining effect, which can significantly improve the brightness and density of the coating; its preferred concentration is 0.05~0.8 g / L, more preferably 0.1~0.6 g / L, for example, 0.5 g / L. Sodium dodecyl sulfate (SDS) is an anionic surfactant that can reduce the interfacial tension between the electrode and solution, promote the desorption of hydrogen bubbles, and reduce pinhole defects. It also forms a composite additive system with PEG and SPS, producing a synergistic effect that jointly promotes grain refinement and the formation of gradient structures. The SDS concentration is preferably 0.05~1.5 g / L, more preferably 0.1~1.0 g / L, for example, 0.5 g / L. Maintaining a pH value within the strongly acidic range of 1~3 effectively inhibits the hydrolysis of copper ions, maintains solution stability, and promotes the adsorption and function of the additives. The preferred pH value is 1.5~2.5, more preferably 2.0.

[0029] The material and condition of the cathode have a significant impact on the adhesion and ease of peeling of the deposited layer. Preferably, the cathode is a titanium or stainless steel sheet with a thickness of 0.15~0.3mm. Titanium and stainless steel have good corrosion resistance in acidic electrolytes and moderate adhesion to copper, facilitating the subsequent peeling of the deposited copper foil from the cathode without damaging the foil. The cathode requires pretreatment before use, including polishing, cleaning, and acid pickling, to remove the surface oxide layer and oil stains, ensuring uniform deposition. Polishing can be done using sandpaper, progressing from coarse to fine, for example, using 200#, 400#, 800#, 1200#, 2000#, and 3000# sandpaper sequentially until a mirror-like finish is achieved. Acid pickling can be performed by soaking in dilute hydrochloric acid (e.g., 5ml / L) for 2~10 minutes to activate the surface.

[0030] In this invention, temperature control during the electrodeposition process affects the ion diffusion rate, additive adsorption behavior, and internal stress of the deposited layer. Preferably, electrodeposition is performed under a water bath at 20–30°C to maintain a uniform and stable temperature. Too low a temperature results in slow ion diffusion and a low deposition rate; too high a temperature weakens additive adsorption and leads to coarser grains. More preferably, the temperature is 22–28°C, for example, 25°C. The average current density (i.e., the average current over the total deposition time) is preferably 1–4 A / dm³. 2This ensures that the overall deposition rate is moderate and the structure is controllable during dynamic changes.

[0031] In this invention, after electrodeposition, the obtained copper foil still needs to undergo post-processing. Specifically, this includes: removing the cathode with the copper foil attached, washing it sequentially with deionized water and anhydrous ethanol to remove residual electrolyte and additives from the surface; then placing it in a vacuum drying oven and drying it at 40~60℃ for 0.5~1h; finally, gently peeling the copper foil from the edge of the cathode with tweezers or other tools to obtain a self-supporting copper foil.

[0032] To further optimize the microstructure and overall properties, the preparation method further includes an annealing step for the electrodeposited copper foil. Annealing can eliminate internal stress generated during deposition, promote atomic diffusion, make the grain size gradient more gradual and continuous, and introduce an appropriate amount of annealing twins, further improving the material's strength, plasticity, and conductivity. Preferably, the annealing temperature is 150~250℃, and the annealing time is 0.3~2h. If the annealing temperature is too low, stress release will be insufficient, and the microstructure optimization effect will be limited; if the annealing temperature is too high, it may lead to excessive grain growth, destroying the original gradient structure. More preferably, the annealing temperature is 180~220℃, and the annealing time is 0.4~1h. For example, in one specific embodiment, the annealing temperature is 200℃, and the annealing time is 0.5h. The annealing treatment can be carried out under vacuum or inert gas protection to prevent high-temperature oxidation.

[0033] The present invention also provides a copper current collector, which is prepared by the above preparation method.

[0034] This copper current collector possesses unique microstructural features. Due to the synergistic effect of dynamic pulsed gradient electrodeposition and ultrasound during its fabrication, a gradient nanostructure with continuously transitioning grain sizes from the surface to the interior is formed within the copper current collector. The cross-sectional hardness exhibits a continuous gradient distribution without abrupt changes at interlayer interfaces. A schematic diagram of its cross-sectional copper grain size structure is shown below. Figure 1 As shown, it exhibits a gradient distribution structure of "nanocrystalline-ultrafine-microcrystalline-ultrafine-nanocrystalline". This structure ensures that the surface layer has the high strength provided by nano-scale fine grains, while the core has the good toughness provided by micro-scale coarse grains. At the same time, because there are no obvious physical interfaces, it avoids the stress concentration and interlayer delamination risks caused by the presence of interfaces in traditional multilayer structures.

[0035] Thanks to the aforementioned structural features, this copper current collector exhibits excellent overall performance. Preferably, the copper current collector has a tensile strength ≥800MPa, an elongation ≥8%, and a conductivity ≥95% IACS. In one specific embodiment, the copper current collector achieves a tensile strength of 848MPa, an elongation of 9.2%, and a conductivity of 98.2% IACS, achieving an excellent balance between high strength, good ductility, and high conductivity.

[0036] The thickness of the copper current collector can be adjusted according to application requirements. Preferably, the thickness of the copper current collector is 3-50 μm. For high-energy-density lithium-ion battery applications, a thickness of 5-30 μm is further preferred, and more preferably 6-15 μm, to minimize the proportion of inactive materials and improve the volumetric energy density of the battery while ensuring mechanical strength.

[0037] The copper current collector provided by this invention can be used as a negative electrode current collector in secondary batteries such as lithium-ion batteries, sodium-ion batteries, and potassium-ion batteries. During the battery electrode preparation process, the surface of this copper current collector is coated with a negative electrode active material slurry, and then dried, rolled, and slit to form a negative electrode sheet. This negative electrode sheet is then assembled with a positive electrode sheet, a separator, and an electrolyte to form a battery. Because this copper current collector possesses high strength, high ductility, and high conductivity, it is less prone to wrinkling and breakage during electrode coating and rolling, significantly improving production yield. During battery charging and discharging, it can effectively withstand the volume expansion stress of the active material, maintaining electrode structural stability. Its high conductivity helps reduce battery internal resistance, decrease polarization, and improve rate performance and cycle stability.

[0038] The technical solution of the present invention will be further described below with reference to specific embodiments. The present invention does not impose any special restrictions on the source of reagents used in the following embodiments; commercially available products well known to those skilled in the art can be used.

[0039] Example 1 This embodiment provides a method for preparing a copper current collector, including the following steps: (1) Cathode pretreatment: Polish the 0.25mm thick stainless steel sheet with sandpaper until it is bright. The sandpaper grades used for polishing are 200#, 400#, 800#, 1200#, 2000#, and 3000# in sequence. After polishing, rinse it with clean water, then place it in deionized water for ultrasonic cleaning for 15 minutes, and then pickle it with hydrochloric acid with a concentration of 5ml / L for 5 minutes to remove the surface oxide layer and oil stains. Connect the treated stainless steel sheet to the negative terminal of the power supply.

[0040] (2) Anode preparation: A pure copper plate with a purity of 99.9wt% is used as the anode. After grinding and cleaning, it is wrapped in a filter bag and connected to the positive terminal of the power supply.

[0041] (3) Preparation of electrodeposition solution: Prepare an acidic sulfate electrodeposition solution with the following composition: CuSO4·5H2O 350g / L, H2SO4 30g / L, NaCl 10g / L, polyethylene glycol (PEG) 0.2g / L, sodium polydisulfide dipropane sulfonate (SPS) 0.5g / L, sodium dodecyl sulfate (SDS) 0.02g / L, and pH value of 1~3.

[0042] (4) Electrodeposition: Place the container containing the above electrodeposition solution in a water bath at 25°C to maintain a uniform temperature. Insert the pretreated cathode and anode into the electrodeposition solution, turn on the ultrasonic generator at a frequency of 20 WHz, and simultaneously connect the pulse power supply for electrodeposition. The pulse current parameters change dynamically during the deposition process, specifically including: Phase 1: Peak current density from 10A / dm 2 Gradually reduce to 1A / dm 2 The on-time was gradually increased from 20ms to 60ms, the off-time was gradually decreased from 60ms to 20ms, the duty cycle was gradually increased from 25% to 75%, and the electrodeposition time was 30min. Phase 2: Peak current density from 1A / dm 2 Gradually increase to 10A / dm 2 The on-time was gradually reduced from 60ms to 20ms, the off-time was gradually increased from 20ms to 60ms, the duty cycle was gradually reduced from 75% to 25%, and the electrodeposition time was 30min.

[0043] The total electrodeposition time was 60 min.

[0044] (5) Post-treatment: After electrodeposition, the cathode was removed and the sample was washed with deionized water and anhydrous ethanol in sequence to remove residual electrolyte and additives on the surface. Then it was placed in a vacuum drying oven at 60℃ and dried for 1 hour. After drying, the copper foil was gently peeled off from the cathode to obtain a copper current collector with a thickness of about 12 μm.

[0045] Example 2 This embodiment provides a method for preparing a copper current collector, including the following steps: (1) Cathode pretreatment: Polish the 0.25mm thick stainless steel sheet with sandpaper until it is bright. The sandpaper grades used for polishing are 200#, 400#, 800#, 1200#, 2000#, and 3000# in sequence. After polishing, rinse it with clean water, then place it in deionized water for ultrasonic cleaning for 15 minutes, and then pickle it with hydrochloric acid with a concentration of 5ml / L for 5 minutes to remove the surface oxide layer and oil stains. Connect the treated stainless steel sheet to the negative terminal of the power supply.

[0046] (2) Anode preparation: A pure copper plate with a purity of 99.9wt% is used as the anode. After grinding and cleaning, it is wrapped in a filter bag and connected to the positive terminal of the power supply.

[0047] (3) Preparation of electrodeposition solution: Prepare an acidic sulfate electrodeposition solution with the following composition: CuSO4·5H2O 350g / L, H2SO4 30g / L, NaCl 10g / L, polyethylene glycol (PEG) 0.2g / L, sodium polydisulfide dipropane sulfonate (SPS) 0.5g / L, sodium dodecyl sulfate (SDS) 0.02g / L, and pH value of 1~3.

[0048] (4) Electrodeposition: Place the container containing the above electrodeposition solution in a water bath at 25°C to maintain a uniform temperature. Insert the pretreated cathode and anode into the electrodeposition solution, turn on the ultrasonic generator at a frequency of 20 WHz, and simultaneously connect the pulse power supply for electrodeposition. The pulse current parameters change dynamically during the deposition process, specifically including: Phase 1: Peak current density from 10A / dm 2 Gradually reduce to 1A / dm 2 The on-time was gradually increased from 20ms to 60ms, the off-time was gradually decreased from 60ms to 20ms, the duty cycle was gradually increased from 25% to 75%, and the electrodeposition time was 30min. Phase 2: Peak current density from 1A / dm 2 Gradually increase to 10A / dm 2 The on-time was gradually reduced from 60ms to 20ms, the off-time was gradually increased from 20ms to 60ms, the duty cycle was gradually reduced from 75% to 25%, and the electrodeposition time was 30min.

[0049] The total electrodeposition time was 60 min.

[0050] (5) Post-treatment: After electrodeposition, the cathode was removed and the sample was washed with deionized water and anhydrous ethanol in sequence to remove residual electrolyte and additives on the surface. Then, it was placed in a vacuum drying oven at 60°C for 1 hour. After drying, the copper foil was gently peeled off from the cathode to obtain a copper foil with a thickness of about 12 μm.

[0051] (6) Annealing treatment: The copper foil after electrodeposition and stripping in step (5) is placed in a vacuum annealing furnace and annealed at 200°C for 0.5h to obtain a copper current collector with a thickness of about 12μm.

[0052] Comparative Example 1 This comparative example provides a method for preparing a copper current collector using direct current electrodeposition, comprising the following steps: (1) Cathode pretreatment: Polish the 0.25mm thick stainless steel sheet with sandpaper until it is bright. The sandpaper grades used for polishing are 200#, 400#, 800#, 1200#, 2000#, and 3000# in sequence. After polishing, rinse it with clean water, then place it in deionized water for ultrasonic cleaning for 15 minutes, and then pickle it with hydrochloric acid with a concentration of 5ml / L for 5 minutes to remove the surface oxide layer and oil stains. Connect the treated stainless steel sheet to the negative terminal of the power supply.

[0053] (2) Anode preparation: A pure copper plate with a purity of 99.9wt% is used as the anode. After grinding and cleaning, it is wrapped in a filter bag and connected to the positive terminal of the power supply.

[0054] (3) Preparation of electrodeposition solution: Prepare an acidic sulfate electrodeposition solution with the following composition: CuSO4·5H2O 350g / L, H2SO4 30g / L, NaCl 10g / L, polyethylene glycol (PEG) 0.2g / L, sodium polydisulfide dipropane sulfonate (SPS) 0.5g / L, sodium dodecyl sulfate (SDS) 0.02g / L, and pH value of 1~3.

[0055] (4) Electrodeposition: Place the container containing the electrodeposition solution in a 25°C water bath for heat preservation, insert the cathode and anode into the electrodeposition solution, and connect the DC power supply to perform electrodeposition. The DC current density is 0.5 A / dm³. 2 Electrodeposition time: 60 min.

[0056] (5) Post-treatment: After electrodeposition, the cathode was removed and the sample was washed with deionized water and anhydrous ethanol in sequence to remove residual electrolyte and additives on the surface. Then it was placed in a vacuum drying oven at 60℃ and dried for 1 hour. After drying, the copper foil was gently peeled off from the cathode to obtain a copper current collector with a thickness of about 12 μm.

[0057] Comparative Example 2 This comparative example provides a method for preparing a copper current collector, which employs multilayer direct current electrodeposition and includes the following steps: (1) Cathode pretreatment: Polish the 0.25mm thick stainless steel sheet with sandpaper until it is bright. The sandpaper grades used for polishing are 200#, 400#, 800#, 1200#, 2000#, and 3000# in sequence. After polishing, rinse it with clean water, then place it in deionized water for ultrasonic cleaning for 15 minutes, and then pickle it with hydrochloric acid with a concentration of 5ml / L for 5 minutes to remove the surface oxide layer and oil stains. Connect the treated stainless steel sheet to the negative terminal of the power supply.

[0058] (2) Anode preparation: A pure copper plate with a purity of 99.9wt% is used as the anode. After grinding and cleaning, it is wrapped in a filter bag and connected to the positive terminal of the power supply.

[0059] (3) Preparation of electrodeposition solution: Prepare an acidic sulfate electrodeposition solution with the following composition: CuSO4·5H2O 350g / L, H2SO4 30g / L, NaCl 10g / L, polyethylene glycol (PEG) 0.2g / L, sodium polydisulfide dipropane sulfonate (SPS) 0.5g / L, sodium dodecyl sulfate (SDS) 0.02g / L, and pH value of 1~3.

[0060] (4) Electrodeposition: Multilayer deposition was performed using direct current, with the current density and deposition time being 4 A / dm. 2 Deposition for 5 min, 2 A / dm 2 Deposition for 10 min, 0.5 A / dm 2 Deposition for 40 min, 2 A / dm 2 Deposition for 10 min, 4 A / dm 2 Deposition time was 5 minutes, with a total electrodeposition time of 60 minutes.

[0061] (5) Post-treatment: After electrodeposition, the cathode was removed and the sample was washed with deionized water and anhydrous ethanol in sequence to remove residual electrolyte and additives on the surface. Then it was placed in a vacuum drying oven at 60℃ and dried for 1 hour. After drying, the copper foil was gently peeled off from the cathode to obtain a copper current collector with a thickness of about 12 μm.

[0062] Comparative Example 3 This comparative example provides a method for preparing a copper current collector, which uses direct current electrodeposition combined with ultrasound, and includes the following steps: (1) Cathode pretreatment: Polish the 0.25mm thick stainless steel sheet with sandpaper until it is bright. The sandpaper grades used for polishing are 200#, 400#, 800#, 1200#, 2000#, and 3000# in sequence. After polishing, rinse it with clean water, then place it in deionized water for ultrasonic cleaning for 15 minutes, and then pickle it with hydrochloric acid with a concentration of 5ml / L for 5 minutes to remove the surface oxide layer and oil stains. Connect the treated stainless steel sheet to the negative terminal of the power supply.

[0063] (2) Anode preparation: A pure copper plate with a purity of 99.9wt% is used as the anode. After grinding and cleaning, it is wrapped in a filter bag and connected to the positive terminal of the power supply.

[0064] (3) Preparation of electrodeposition solution: Prepare an acidic sulfate electrodeposition solution with the following composition: CuSO4·5H2O 350g / L, H2SO4 30g / L, NaCl 10g / L, polyethylene glycol (PEG) 0.2g / L, sodium polydisulfide dipropane sulfonate (SPS) 0.5g / L, sodium dodecyl sulfate (SDS) 0.02g / L, and pH value of 1~3.

[0065] (4) Electrodeposition: Place the container containing the electrodeposition solution in a 25°C water bath for heat preservation, turn on the ultrasonic generator with an ultrasonic frequency of 20WHz, and connect the DC power supply for electrodeposition with a DC current density of 0.5A / dm³. 2 Electrodeposition time: 60 min.

[0066] (5) Post-treatment: After electrodeposition, the cathode was removed and the sample was washed with deionized water and anhydrous ethanol in sequence to remove residual electrolyte and additives on the surface. Then it was placed in a vacuum drying oven at 60℃ and dried for 1 hour. After drying, the copper foil was gently peeled off from the cathode to obtain a copper current collector with a thickness of about 12 μm.

[0067] Comparative Example 4 This comparative example provides a method for preparing a copper current collector, which employs multilayer DC electrodeposition combined with ultrasound, and includes the following steps: (1) Cathode pretreatment: Polish the 0.25mm thick stainless steel sheet with sandpaper until it is bright. The sandpaper grades used for polishing are 200#, 400#, 800#, 1200#, 2000#, and 3000# in sequence. After polishing, rinse it with clean water, then place it in deionized water for ultrasonic cleaning for 15 minutes, and then pickle it with hydrochloric acid with a concentration of 5ml / L for 5 minutes to remove the surface oxide layer and oil stains. Connect the treated stainless steel sheet to the negative terminal of the power supply.

[0068] (2) Anode preparation: A pure copper plate with a purity of 99.9wt% is used as the anode. After grinding and cleaning, it is wrapped in a filter bag and connected to the positive terminal of the power supply.

[0069] (3) Preparation of electrodeposition solution: Prepare an acidic sulfate electrodeposition solution with the following composition: CuSO4·5H2O 350g / L, H2SO4 30g / L, NaCl 10g / L, polyethylene glycol (PEG) 0.2g / L, sodium polydisulfide dipropane sulfonate (SPS) 0.5g / L, sodium dodecyl sulfate (SDS) 0.02g / L, and pH value of 1~3.

[0070] (4) Electrodeposition: The container containing the electrodeposition solution was placed in a 25°C water bath for heat preservation. The ultrasonic generator was turned on, and the ultrasonic frequency was 20WHz. A direct current was used for multilayer deposition, and the current density and deposition time were 4A / dm. 2 Deposition for 5 min, 2 A / dm 2 Deposition for 10 min, 0.5 A / dm 2 Deposition for 40 min, 2 A / dm 2 Deposition for 10 min, 4 A / dm 2 Deposition time was 5 minutes, with a total electrodeposition time of 60 minutes.

[0071] (5) Post-treatment: After electrodeposition, the cathode was removed and the sample was washed with deionized water and anhydrous ethanol in sequence to remove residual electrolyte and additives on the surface. Then it was placed in a vacuum drying oven at 60℃ and dried for 1 hour. After drying, the copper foil was gently peeled off from the cathode to obtain a copper current collector with a thickness of about 12 μm.

[0072] Comparative Example 5 This comparative example provides a method for preparing a copper current collector, which uses fixed-parameter pulse electrodeposition and includes the following steps: (1) Cathode pretreatment: Polish the 0.25mm thick stainless steel sheet with sandpaper until it is bright. The sandpaper grades used for polishing are 200#, 400#, 800#, 1200#, 2000#, and 3000# in sequence. After polishing, rinse it with clean water, then place it in deionized water for ultrasonic cleaning for 15 minutes, and then pickle it with hydrochloric acid with a concentration of 5ml / L for 5 minutes to remove the surface oxide layer and oil stains. Connect the treated stainless steel sheet to the negative terminal of the power supply.

[0073] (2) Anode preparation: A pure copper plate with a purity of 99.9wt% is used as the anode. After grinding and cleaning, it is wrapped in a filter bag and connected to the positive terminal of the power supply.

[0074] (3) Preparation of electrodeposition solution: Prepare an acidic sulfate electrodeposition solution with the following composition: CuSO4·5H2O 350g / L, H2SO4 30g / L, NaCl 10g / L, polyethylene glycol (PEG) 0.2g / L, sodium polydisulfide dipropane sulfonate (SPS) 0.5g / L, sodium dodecyl sulfate (SDS) 0.02g / L, and pH value of 1~3.

[0075] (4) Electrodeposition: Place the container containing the electrodeposition solution in a 25°C water bath and keep it warm. Turn on the pulse power supply to perform electrodeposition. The pulse parameters are fixed: peak current density 1A / dm³. 2 The on-time is 20ms, the off-time is 20ms, and the electrodeposition time is 60min.

[0076] (5) Post-treatment: After electrodeposition, the cathode was removed and the sample was washed with deionized water and anhydrous ethanol in sequence to remove residual electrolyte and additives on the surface. Then it was placed in a vacuum drying oven at 60℃ and dried for 1 hour. After drying, the copper foil was gently peeled off from the cathode to obtain a copper current collector with a thickness of about 12 μm.

[0077] Comparative Example 6 This comparative example provides a method for preparing a copper current collector using dynamic gradient pulse electrodeposition, comprising the following steps: (1) Cathode pretreatment: Polish the 0.25mm thick stainless steel sheet with sandpaper until it is bright. The sandpaper grades used for polishing are 200#, 400#, 800#, 1200#, 2000#, and 3000# in sequence. After polishing, rinse it with clean water, then place it in deionized water for ultrasonic cleaning for 15 minutes, and then pickle it with hydrochloric acid with a concentration of 5ml / L for 5 minutes to remove the surface oxide layer and oil stains. Connect the treated stainless steel sheet to the negative terminal of the power supply.

[0078] (2) Anode preparation: A pure copper plate with a purity of 99.9wt% is used as the anode. After grinding and cleaning, it is wrapped in a filter bag and connected to the positive terminal of the power supply.

[0079] (3) Preparation of electrodeposition solution: Prepare an acidic sulfate electrodeposition solution with the following composition: CuSO4·5H2O 350g / L, H2SO4 30g / L, NaCl 10g / L, polyethylene glycol (PEG) 0.2g / L, sodium polydisulfide dipropane sulfonate (SPS) 0.5g / L, sodium dodecyl sulfate (SDS) 0.02g / L, and pH value of 1~3.

[0080] (4) Electrodeposition: The container containing the electrodeposition solution is placed in a 25°C water bath for heat preservation, and a pulse power supply is turned on to perform electrodeposition. The pulse current parameters change dynamically, specifically including: Phase 1: Peak current density from 10A / dm 2 Gradually reduce to 1A / dm 2 The on-time was gradually increased from 20ms to 60ms, the off-time was gradually decreased from 60ms to 20ms, the duty cycle was gradually increased from 25% to 75%, and the electrodeposition time was 30min. Phase 2: Peak current density from 1A / dm 2 Gradually increase to 10A / dm 2 The on-time was gradually reduced from 60ms to 20ms, the off-time was gradually increased from 20ms to 60ms, the duty cycle was gradually reduced from 75% to 25%, and the electrodeposition time was 30min.

[0081] The total electrodeposition time was 60 minutes, without the application of ultrasound.

[0082] (5) Post-treatment: After electrodeposition, the cathode was removed and the sample was washed with deionized water and anhydrous ethanol in sequence to remove residual electrolyte and additives on the surface. Then it was placed in a vacuum drying oven at 60℃ and dried for 1 hour. After drying, the copper foil was gently peeled off from the cathode to obtain a copper current collector with a thickness of about 12 μm.

[0083] Test case 1. Copper current collector performance test: (1) Mechanical property testing: The copper current collectors prepared in the examples and comparative examples were made into dumbbell-shaped tensile specimens. The gauge length of the specimen was 25 mm long and 12.5 mm wide, the clamping section was 15 mm wide, and the total length of the specimen was 200 mm. Tensile properties were tested using a Shimadzu AG-IS / 1KN universal testing machine. The tensile rate was controlled within an appropriate range, and the tensile strength, yield strength, and elongation of the specimens were recorded. Each group of samples was tested 3 times, and the average value was taken as the final result.

[0084] (2) Conductivity test: The resistivity of the copper foil was tested using a four-probe resistance meter, and the test temperature was controlled at room temperature. Based on the measured resistivity, it was converted to the International Standard for Annealed Copper (%IACS) conductivity. The calculation formula is: Conductivity (%IACS) = 0.017241 / ρ × 100%, where ρ is the measured resistivity (μΩ·cm). Each group of samples was tested 3 times, and the average value was taken.

[0085] (3) Microstructure and performance characterization: The hardness distribution of the copper foil cross-section was tested using a microhardness tester (model MC010). The test load was 4.9 N, and the holding time was 15 s. Multiple test points were selected at equal intervals along the thickness direction of the cross-section. Each test point was measured 3 times, and the average value was taken as the hardness value of that point. The hardness distribution curve was plotted. The crystal orientation of the copper foil was analyzed using an X-ray diffractometer (Rigaku SmartLab SE, CuKα target, working voltage 40 kV, working current 40 mA). The scanning speed was 1° / min, and the scanning range was 20-80°.

[0086] The performance test results of the copper current collectors prepared in the examples and comparative examples are shown in Table 1.

[0087] Table 1. Performance comparison of copper current collectors in Examples 1-2 and Comparative Examples 1-6 serial number Tensile strength (MPa) Yield strength (MPa) The ratio of yield strength Elongation (%) Conductivity (% IACS) Comparative Example 1 294 152.9 0.52 10.1 90.3 Comparative Example 2 624 393.0 0.75 8.2 87.6 Comparative Example 3 428 273.9 0.64 9.3 93.5 Comparative Example 4 670 433.2 0.76 8.1 89.3 Comparative Example 5 484 211.2 0.55 9.5 88.3 Comparative Example 6 707 388.5 0.64 8.7 91.3 Example 1 834 667.2 0.80 8.4 96.2 Example 2 848 686.9 0.81 9.2 98.2 As shown in Table 1, the copper foil prepared by multilayer DC electrodeposition (variable current) (Comparative Example 2) exhibits a significantly increased tensile strength (from 294 MPa to 624 MPa) compared to single-layer DC electrodeposition (Comparative Example 1), but its elongation decreases from 10.1% to 8.2%, and its conductivity also declines. This indicates that while multilayer structures can improve strength, they sacrifice ductility and conductivity, and stress concentration and bonding issues may exist at the interfaces of multilayer structures.

[0088] Comparing Comparative Examples 1 and 3, and Comparative Examples 2 and 4, it is evident that introducing ultrasound during the DC electrodeposition process (Comparative Examples 3 and 4) can refine the grains and improve tensile strength and conductivity to a certain extent. For example, the tensile strength (428 MPa) and conductivity (93.5% IACS) of Comparative Example 3 are both superior to those of Comparative Example 1 (294 MPa, 90.3% IACS), indicating that ultrasound-assisted deposition has a positive effect.

[0089] Comparative Example 5, employing fixed-parameter pulsed electrodeposition, exhibited superior tensile strength (484 MPa) and conductivity (88.3% IACS) compared to Comparative Example 1, but lower than other comparative examples and embodiments. This demonstrates that while fixed pulsed electrodeposition is superior to DC, its effect is limited. Comparative Example 6, using dynamic gradient pulsed electrodeposition, achieved a tensile strength of 707 MPa and a conductivity of 91.3% IACS, significantly outperforming all comparative examples (Comparative Examples 1-4) using DC electrodeposition and Comparative Example 5 with fixed pulsed electrodeposition. This indicates that dynamic gradient pulsed electrodeposition itself possesses significant advantages, enabling the construction of gradient structures through continuous parameter variations, thereby enhancing overall performance.

[0090] Example 1, based on the dynamic gradient pulse of Comparative Example 6, introduced the synergistic effect of ultrasound, further increasing its tensile strength to 834 MPa and conductivity to 96.2% IACS. Compared to Comparative Example 6, it achieved a simultaneous leap in strength and conductivity, fully demonstrating the significant synergistic effect of ultrasound and dynamic gradient pulse. Example 2, based on Example 1, further underwent annealing treatment (200℃, 0.5h), achieving a tensile strength of 848 MPa, an elongation increase to 9.2%, and a conductivity as high as 98.2% IACS. Compared to Comparative Example 6, Example 2 showed an increase in tensile strength of approximately 20% and an increase in conductivity of approximately 7.6%. This indicates that annealing treatment can effectively eliminate internal stress, optimize the gradient structure, and introduce an appropriate amount of annealing twins, achieving an optimal balance in the overall performance of the material.

[0091] The hardness distribution curve of the copper current collector cross section in Example 2 is shown below. Figure 2 As shown, the hardness decreases gradually from the surface to the inner layer, and the overall cross-section shows a gradient symmetrical distribution of hardness, indicating that the copper current collector in Example 2 has smaller surface grains and larger internal grains.

[0092] The X-ray diffraction (XRD) patterns of the copper current collectors in Examples 1-2, Comparative Examples 1 and 6 are shown below. Figure 3 As shown, it can be seen that <111> The comparison of crystal phase ratios is as follows: Example 2 > Example 1 > Comparative Example 6 > Comparative Example 1, which is consistent with the conductivity test results.

[0093] In summary, this invention successfully prepared a copper current collector with ultra-high strength (≥830 MPa), good ductility (≥8%), and high conductivity (≥96% IACS) through the synergistic effect of dynamic gradient pulse electrodeposition and ultrasound, combined with annealing. Example 2 exhibits the best overall performance, with a tensile strength of 848 MPa, an elongation of 9.2%, and a conductivity of 98.2% IACS, achieving an excellent balance of strength, ductility, and conductivity, thus better meeting the stringent requirements of high-energy-density secondary batteries for current collectors.

[0094] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a copper current collector, characterized in that, Includes the following steps: A cathode and an anode are provided, wherein the anode is pure copper; The cathode and anode are placed in an acidic sulfate electrodeposition solution, and a pulsed current is applied for electrodeposition, while ultrasound is applied during the electrodeposition process. The parameters of the pulse current exhibit dynamic gradient changes during the deposition process. These dynamic gradient changes include: a first stage in which the peak current density continuously changes from high to low, while the on-time continuously changes from short to long and the off-time continuously changes from long to short; and a second stage in which the peak current density continuously changes from low to high, while the on-time continuously changes from long to short and the off-time continuously changes from short to long.

2. The preparation method according to claim 1, characterized in that, In the first stage, the peak current density ranges from 5 to 15 A / dm. 2 Gradually reduce to 0.5~3A / dm 2 The turn-on time gradually increases from 10-30ms to 40-80ms, while the turn-off time gradually decreases from 40-80ms to 10-30ms; in the second stage, the peak current density ranges from 0.5-3A / dm². 2 Gradually increase to 5~15A / dm 2 The turn-on time gradually decreased from 40~80ms to 10~30ms, and the turn-off time gradually increased from 10~30ms to 40~80ms.

3. The preparation method according to claim 1, characterized in that, In the first stage, the duty cycle changes continuously from low to high, and in the second stage, the duty cycle changes continuously from high to low.

4. The preparation method according to claim 3, characterized in that, In the first stage, the duty cycle gradually increases from 20-30% to 65-85%, and in the second stage, the duty cycle gradually decreases from 65-85% to 20-30%.

5. The preparation method according to claim 1, characterized in that, The electrodeposition time for the first stage is 20-40 min, and the electrodeposition time for the second stage is 20-40 min.

6. The preparation method according to claim 1, characterized in that, The frequency of the ultrasound is 15~25WHz.

7. The preparation method according to claim 1, characterized in that, The acidic sulfate electrodeposition solution comprises: CuSO4·5H2O 300~400g / L, H2SO4 30~35g / L, NaCl 5~10g / L, polyethylene glycol 0.1~1g / L, sodium polydisulfide dipropane sulfonate 0.01~1.0g / L, sodium dodecyl sulfate 0.01~2.0g / L, and a pH value of 1~3.

8. The preparation method according to claim 1, characterized in that, The cathode is a titanium sheet or a stainless steel sheet; the purity of the pure copper is ≥99.9%.

9. The preparation method according to claim 1, characterized in that, It also includes a step of annealing the copper foil obtained by electrodeposition, with an annealing temperature of 150~250℃ and an annealing time of 0.3~2h.

10. A copper current collector, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 9.

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