A super-thick electrolytic copper foil for high power and a preparation method and application thereof

Abstract

The application discloses a kind of super-thick electrolytic copper foil for high power and its preparation method and application, wherein, super-thick electrolytic copper foil for high power belongs to double-layer composite structure, is composed of super-thick electrolytic copper foil matrix layer and tungsten carbide doped copper composite surface layer.The super-thick electrolytic copper foil matrix layer is gradient grain structure, is composed of surface layer fine grain, inner layer transition grain and bottom layer columnar crystal, and the tungsten carbide doped copper composite surface layer is combined in the surface layer of the super-thick electrolytic copper foil matrix layer.The application builds the double-layer structure super-thick copper foil of "matrix performance optimization + surface modification strengthening" by multiple technologies, solves the preparation and performance bottleneck of existing super-thick copper foil from electrolytic deposition, crystal phase regulation to surface modification whole process, realizes the synchronous promotion of each core performance.

Description

Technical Field

[0001] This invention relates to the field of electrolytic copper foil technology, and in particular to a high-power ultra-thick electrolytic copper foil, its preparation method, and its application. Background Technology

[0002] The rapid development of the new energy industry has driven up the demand for high-current, high-power-density components in fields such as new energy vehicles, energy storage systems, and high-power power electronic devices for industrial applications. Among these, the market demand for ≥105μm ultra-thick electrolytic copper foil, as a core conductive substrate, is growing rapidly. High-power ultra-thick electrolytic copper foil must simultaneously meet core performance requirements such as high conductivity, high heat resistance, and high peel strength. However, conventional preparation processes have inherent bottlenecks: DC electrolysis easily leads to uneven copper foil thickness, low density, and high porosity; single isothermal annealing is difficult to balance strength and toughness, resulting in high thermal decay rate; traditional additives have limited effect on grain refinement and internal stress control, making the copper foil prone to curling; conventional surface modification results in insufficient adhesion between the copper foil and the substrate, making it prone to delamination during high-temperature service, which seriously affects the use of devices.

[0003] To address these issues, the industry has attempted to improve performance through segmented DC electrolysis, optimized annealing parameters, development of traditional composite additives, conventional surface roughening and curing, and equipment flow field optimization. However, existing technologies still have significant shortcomings and cannot fundamentally solve the problems of low copper foil density and poor performance synergy. Internal stress and thermal decay rates remain high, and peel strength improvement is limited. Furthermore, the tolerance range of process parameters is narrow, resulting in large fluctuations in product performance and low yield rates during large-scale production, leading to high industrialization costs. These factors restrict the domestic substitution and large-scale application of high-end, high-power ultra-thick electrolytic copper foil. Summary of the Invention

[0004] The main objective of this invention is to provide a high-power ultra-thick electrolytic copper foil, its preparation method, and its application, aiming to solve at least one of the technical problems existing in the prior art.

[0005] To achieve the above objectives, the present invention provides an ultra-thick electrolytic copper foil for high power applications, which is a double-layer composite structure consisting of an ultra-thick electrolytic copper foil substrate layer and a tungsten carbide-doped copper composite surface layer.

[0006] Furthermore, the thickness of the ultra-thick electrolytic copper foil substrate layer is 105–350 μm, and the thickness of the tungsten carbide-doped copper composite surface layer is 1–3 μm.

[0007] Furthermore, the ultra-thick electrolytic copper foil substrate layer has a gradient grain structure, consisting of a surface fine grain, an inner transition grain, and a bottom columnar grain, and the tungsten carbide-doped copper composite surface layer is bonded to the surface of the ultra-thick electrolytic copper foil substrate layer.

[0008] The present invention also provides a method for preparing the above-mentioned high-power ultra-thick electrolytic copper foil, comprising the following steps: (1) Preparation of heterocyclic sulfonate composite electrolyte Sulfuric acid, copper sulfate and hydrochloric acid were added sequentially to deionized water, followed by the addition of sodium thiazolinyl dithiopropane sulfonate and polyquaternium-7. The mixture was stirred and dissolved to obtain a heterocyclic sulfonate environmentally friendly composite electrolyte. (2) Bipolar pulse reverse electrolytic deposition of ultra-thick electrolytic copper foil substrate layer A bipolar pulse reverse electrolytic deposition process was performed using a heterocyclic sulfonate composite electrolyte to obtain an ultra-thick electrolytic copper foil substrate layer; (3) Multi-stage variable current annealing treatment Multi-stage variable current annealing treatment is performed on the ultra-thick electrolytic copper foil substrate layer; (4) Preparation of tungsten carbide-doped copper composite surface layer by vacuum magnetron sputtering Tungsten carbide powder and copper powder are mixed and sintered to form a target material. Then, a tungsten carbide-doped copper composite surface layer is prepared on the annealed ultra-thick electrolytic copper foil substrate by vacuum magnetron sputtering to obtain a double-layer composite copper foil. (5) Passivation treatment The double-layer composite copper foil was immersed in a passivation solution and dried to obtain the ultra-thick electrolytic copper foil for high power applications.

[0009] Further, in step (1), the concentration of added sulfuric acid is 120–160 g / L, and the concentration of added copper sulfate is such that Cu 2+ The concentration is increased to 80-100 g / L, and the concentration of hydrochloric acid added is such that Cl... - The concentration is 60-80 ppm; the mass ratio of sodium thiazolinyl dithiopropane sulfonate to polyquaternium-7 is 3:2, and the total concentration of both is 30-60 ppm. The electrolyte preparation temperature is 45-55℃.

[0010] Furthermore, in step (2), a TA2 titanium alloy cathode roller is used, with a platinum-iridium alloy plate as the anode, and the electrode distance between the cathode and anode is 15-25 mm; the electrodeposition parameters are: forward deposition pulse current density 35-45 A / dm. 2 Duty cycle 60-70%, frequency 30-50Hz, reverse etching pulse current density 6-10A / dm 2 Duty cycle 15-20%, frequency 30-50Hz, forward-reverse time ratio = 10:1, electrolyte circulation flow rate 70-90L / h.

[0011] Furthermore, in step (2), the deposition time is controlled according to the target thickness. The deposition time for a thickness of 105 μm is 80–100 min, the deposition time for a thickness of 175 μm is 140–160 min, and the deposition time for a thickness of 350 μm is 290–310 min.

[0012] Furthermore, in step (3), the specific process of multi-stage converter annealing is as follows: evacuate to ≤5×10 -3 After Pa, argon gas is introduced to atmospheric pressure, then the temperature is increased to 170–190°C at a rate of 5–7°C / min and held for 30–50 min. Then the temperature is increased to 240–260°C at a rate of 3–5°C / min and held for 70–90 min. Finally, the temperature is increased to 280–320°C at a rate of 2–4°C / min and held for 50–70 min. After completion, the temperature is decreased to 100–120°C at a rate of 4–6°C / min and then allowed to cool naturally to room temperature.

[0013] Furthermore, in step (4), the tungsten carbide powder has a particle size of 50–80 nm, accounting for 10 wt% of the total target material, and is pre-modified with a silane coupling agent; the vacuum magnetron sputtering process is as follows: evacuate to ≤8 × 10⁻⁶ ppm. -4 Pa, introduce argon gas at a flow rate of 50-70 sccm, turn on the plasma power supply to 300-500W, activate for 10-20 minutes, and then set the sputtering pressure to 0.2-0.4 Pa and the sputtering temperature to 140-160℃ for sputtering.

[0014] Further, the silane coupling agent modification method for tungsten carbide powder is as follows: Tungsten carbide powder is ultrasonically dispersed in anhydrous ethanol for 30 min to obtain a tungsten carbide powder-ethanol suspension. Silane coupling agent KH-570 is weighed at a ratio of 5% of the tungsten carbide powder mass and dispersed in 8 times its mass of anhydrous ethanol. Then, glacial acetic acid is added dropwise to adjust the pH to 5, and the mixture is stirred at room temperature for 15 min for pre-hydrolysis to form a silanol active intermediate solution. The silanol active intermediate solution is slowly added dropwise to the tungsten carbide powder-ethanol suspension. After the addition is complete, the system is heated to 55℃ and ultrasonically stirred for modification for 45 min. After modification, the solid precipitate is collected by centrifugation and washed three times with anhydrous ethanol to remove unreacted coupling agent. Then, it is placed in a vacuum drying oven and dried at 70℃ for 15 h to obtain KH-570 modified tungsten carbide powder.

[0015] Further, in step (5), the passivation solution is a ZrO2-based passivation solution, and the immersion treatment conditions are: temperature 30-40℃, stirring rate 100-200r / min, and time 7-9min.

[0016] The present invention also provides the application of the above-mentioned high-power ultra-thick electrolytic copper foil in new energy vehicle electric drive modules, energy storage converters, industrial high-power power supplies, and high-power printed circuit boards.

[0017] The design principle and innovation of this invention are as follows: This invention is guided by the core performance requirements of high conductivity, high heat resistance, high peel strength, and low internal stress of copper foil in high-power scenarios. It regulates the grain growth and distribution during the electrolytic deposition process by using a novel environmentally friendly heterocyclic sulfonate composite additive (sodium thiazolinyl dithiopropane sulfonate and polyquaternium-7). Combined with bipolar pulse reverse electrolysis, it improves the density and conductivity of the copper foil matrix. Then, multi-stage variable current annealing achieves a synergistic balance between the strength, toughness, and heat resistance of the copper foil. Finally, tungsten carbide-doped copper composite surface layer is prepared by vacuum magnetron sputtering to optimize the peel strength, heat resistance, and wear resistance of the copper foil surface. Through the synergistic construction of multiple technologies, a double-layer structure of ultra-thick copper foil with "matrix performance optimization + surface modification enhancement" is constructed. The entire process from electrolytic deposition and crystal phase control to surface modification solves the bottlenecks in the preparation and performance of existing ultra-thick copper foils, and achieves simultaneous improvement of each core performance.

[0018] Innovation Point 1: The innovative research and development of a sodium thiazolinyl dithiopropane sulfonate-polyquaternary ammonium salt heterocyclic sulfonate environmentally friendly composite additive system, which differs from traditional single-component or conventional sulfonate additives, achieves both grain refinement and thickness uniformity control in the electrolytic deposition of ultra-thick copper foil through the synergistic effect of the two components, and effectively reduces the internal stress of copper foil. This solves the problems of limited effect of existing additives on the control of crystal phase and improvement of internal stress of ultra-thick copper foil, and easy curling of copper foil. Moreover, the additive has no heavy metal pollution and meets the requirements of environmentally friendly production.

[0019] Innovation Point Two: The innovative use of bipolar pulse reverse electrolysis to replace conventional DC electrolysis optimizes the mass transfer process of the electrolyte on the cathode surface through alternating forward deposition and reverse etching, thereby improving the density of the ultra-thick copper foil substrate and reducing porosity. This solves the technical bottlenecks of uneven thickness, low conductivity, and high resistance loss in the preparation of ultra-thick copper foil by DC electrolysis. At the same time, it allows for precise control of current parameters to adapt to the deposition requirements of ultra-thick copper foils with different thicknesses from 105 to 350 μm.

[0020] Innovation Point 3: The innovative design of a multi-stage variable current annealing process breaks through the limitations of traditional single constant temperature annealing. By adjusting the furnace loading current, the temperature and magnetic field are coordinated and controlled. The process achieves the stabilization of fine grains on the surface of the copper foil, the improvement of toughness of the transition layer, and the strengthening of the heat resistance of the substrate in stages. This solves the performance contradiction of "high strength but low toughness, high heat resistance but low conductivity" in existing medium and thick copper foils, and achieves a balanced optimization of tensile strength, elongation and thermal decay rate.

[0021] Innovation Point 4: Innovative research and development of tungsten carbide-doped copper composite surface layer. Vacuum magnetron sputtering process is used to uniformly dope nano-tungsten carbide onto the copper-based coating and deposit it on the surface of the copper foil substrate. The high strength and high heat resistance of tungsten carbide are used to improve the peel strength, heat resistance and wear resistance of the copper foil surface. At the same time, the bonding force between the composite layer and the substrate is enhanced by silane coupling agent modification. This solves the problems of weak bonding force and easy delamination failure in conventional surface roughening-curing treatment, which are common in high-temperature service. It is suitable for the pressing and long-term service requirements of high-power scenarios.

[0022] The beneficial effects of this invention are reflected in: 1. Performance is comprehensively optimized to achieve a synergistic balance between high conductivity (≥98% IACS), high heat resistance (thermal decay rate ≤5%), high peel strength (≥2.5N / mm) and low internal stress (≤50N / cm), with thickness uniformity ≤±2%, which can stably adapt to the stringent service requirements of high-power scenarios. 2. The process is environmentally friendly and suitable for industrialization. It adopts environmentally friendly composite additives and cyanide-free passivation process. The core process parameters are highly controllable and have a wide tolerance range. It is easy to be compatible with existing copper foil production lines. Large-scale production has a high yield rate and controllable cost, which is in line with the trend of green production. 3. It has outstanding market competitiveness. Compared with commercially available high-end products and existing technologies, it has significantly improved key indicators such as heat resistance, deformation resistance and interfacial bonding. Moreover, the preparation process does not require the addition of special equipment, the industrialization transformation cost is low, and it has strong potential for domestic substitution. Attached Figure Description

[0023] Figure 1 This is a microstructure image of the high-power ultra-thick electrolytic copper foil prepared in Example 1.

[0024] Figure 2 This is a conductivity test diagram of the high-power ultra-thick electrolytic copper foil prepared in Example 1.

[0025] Figure 3 The graph shows the thermal decay rate test of the high-power ultra-thick electrolytic copper foil prepared in Example 1.

[0026] Figure 4 This is a tensile strength test diagram of the high-power ultra-thick electrolytic copper foil prepared in Example 1.

[0027] Figure 5 This is a peel strength test diagram of the high-power ultra-thick electrolytic copper foil prepared in Example 1.

[0028] Figure 6 This is a test diagram of the internal stress of the high-power ultra-thick electrolytic copper foil prepared in Example 1.

[0029] Figure 7 This is a neutral salt spray test image of the high-power ultra-thick electrolytic copper foil prepared in Example 1. Detailed Implementation

[0030] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.

[0031] Unless otherwise specified, the raw materials, reagents, or devices used in the following embodiments can be obtained from conventional commercial sources or by existing known methods; unless otherwise specified, the methods used in the embodiments of the present invention are methods mastered by those skilled in the art. The sources of some of the equipment and raw materials are shown in Table 1 below.

[0032] Table 1

[0033] Example 1 Preparation of ultra-thick electrolytic copper foil for high power applications (1) Raw material pretreatment Cathode roller pretreatment: Immerse the TA2 titanium alloy cathode roller (500mm in diameter and 600mm in length) in 15wt% sulfuric acid solution for 20min (to remove the surface oxide layer), then rinse it three times with deionized water under high pressure for 5min each time at a pressure of 0.3MPa, and finally ultrasonically clean it with anhydrous ethanol for 10min (to remove oil stains). Finally, dry it in a vacuum drying oven (100℃, 60min) for later use. Raw material pretreatment: Solid raw materials (copper sulfate, sodium thiazolinyl dithiopropane sulfonate, polyquaternium-7) are dried at 120℃ for 4 hours to remove moisture; Equipment pretreatment: The bipolar pulse electrodeposition equipment, vacuum magnetron sputtering equipment, and multi-stage converter annealing furnace are preheated for 60 minutes in advance, core parameters (current density, pulse frequency, temperature, etc.) are calibrated, and the machines are run idle for 10 minutes to ensure that the equipment is stable and fault-free.

[0034] (2) Preparation of heterocyclic sulfonate composite electrolyte Under stirring conditions (speed 500 r / min), electronic-grade sulfuric acid was slowly added to deionized water. After dissolution, electronic-grade copper sulfate was added, followed by dissolution again. Then, 38 wt% hydrochloric acid was added and stirred for 10 min. Next, sodium thiazolinyl dithiopropane sulfonate and polyquaternium-7 were added sequentially, with a mass ratio of sodium thiazolinyl dithiopropane sulfonate to polyquaternium-7 of 3:2. The mixture was stirred for 60 min until completely dissolved. The solution was transferred to a 10 L volumetric container, and the inner wall of the container was rinsed with deionized water and the solution was added. Finally, deionized water was added to bring the volume to 10 L, and the mixture was stirred until homogeneous to obtain a heterocyclic sulfonate composite electrolyte. The sulfuric acid concentration was 140 g / L, and the Cu... 2+ The concentration is 90 g / L, Cl -The concentration was 70 ppm, and the total concentration of sodium thiazolinyl dithiopropane sulfonate and polyquaternium-7 was 45 ppm. The electrolyte was transferred into a precision constant temperature water bath, the temperature was set to 50℃, and stirring was maintained throughout the process at a rate of 300 r / min.

[0035] (3) Bipolar pulse reverse electrolytic deposition of ultra-thick electrolytic copper foil substrate layer The pretreated cathode roller is loaded into a bipolar pulse electrodeposition device, and a platinum-iridium alloy plate is loaded into the anode of the device. The distance between the cathode and anode is controlled to be 20 mm. Then, a heterocyclic sulfonate composite electrolyte is added to ensure that the electrolyte completely submerges the electrode. Setting bipolar pulsed electrolysis parameters: Forward deposition pulse: Current density 40 A / dm 2 Duty cycle 65%, frequency 40Hz; reverse etching pulse: current density 8A / dm 2 The duty cycle was 15%, the frequency was 40Hz, the intermittent time was 20%, the forward and reverse time ratio was 10:1, the electrolyte circulation flow rate was 80L / h, and the deposition time was 150min. After the electrolytic deposition was completed, the cathode roller was slowly removed and rinsed with deionized water under high pressure 3 times (3min each time) to remove the residual electrolyte on the surface. It was then air-dried to obtain a cathode roller with an ultra-thick electrolytic copper foil substrate layer with a thickness of 175μm.

[0036] (4) Multi-stage variable current annealing treatment The cathode roller with the deposited ultra-thick electrolytic copper foil substrate layer is placed into a multi-stage converter annealing furnace, the furnace door is closed, and a vacuum of ≤5×10⁻⁶ is drawn. -3 Argon gas (protective gas) was introduced to atmospheric pressure. Multi-stage variable current annealing parameters were set, and temperature and magnetic field were coordinated and controlled by adjusting the furnace loading current. Annealing was performed in three stages: Stage 1 (grain refinement and stabilization): Loading current 5A, heating rate 6℃ / min, reaching 180℃, holding for 40min, refining surface grains; Stage 2 (toughness improvement): Loading current 8A, heating rate 4℃ / min, reaching 250℃, holding for 80min, optimizing grain boundary distribution and reducing internal stress; Stage 3 (heat resistance strengthening): Loading current 6A, heating rate 3℃ / min, reaching 300℃, holding for 60min, improving the heat resistance of the substrate; Finally, cooling stage: cooling to 120℃ at a rate of 5℃ / min, then turning off the power and allowing it to cool naturally to room temperature to avoid secondary stress caused by rapid cooling; After annealing, the ultra-thick electrolytic copper foil substrate layer was slowly peeled off from the cathode roller surface without curling or deformation, and set aside for later use.

[0037] (5) Preparation of tungsten carbide-doped copper composite surface layer by vacuum magnetron sputtering Tungsten carbide powder (particle size 50-80 nm) was ultrasonically dispersed in anhydrous ethanol (material-to-liquid mass-to-volume ratio 1 g: 15 mL) for 30 min to obtain a tungsten carbide powder-ethanol suspension. Silane coupling agent KH-570 was weighed at 5% of the tungsten carbide powder mass and dispersed in 8 times its mass of anhydrous ethanol. Then, glacial acetic acid was added dropwise to adjust the pH to 5, and the mixture was stirred at room temperature for 15 min for pre-hydrolysis to form a silanol active intermediate solution. The silanol active intermediate solution was slowly added dropwise to the tungsten carbide powder-ethanol suspension. After the addition was complete, the system was heated to 55 °C and ultrasonically stirred for 45 min for modification. After modification, the solid precipitate was collected by centrifugation and washed three times with anhydrous ethanol to remove unreacted coupling agent. The precipitate was then placed in a vacuum drying oven and dried at 70 °C for 3 h to obtain KH-570 modified tungsten carbide powder for later use.

[0038] Copper powder (particle size 10-50 μm) and KH-570 modified tungsten carbide powder were added to a star ball mill at a mass ratio of 9:1. Anhydrous ethanol (2.5 times the powder mass) and dispersant polyvinylpyrrolidone (PVP-K30) (1% of the powder mass) were added. The mixture was ball-milled for 6 hours to form a uniform powder. The solvent was then vacuum dried, and the powder was loaded into a graphite mold (a cylindrical graphite mold with an inner diameter of Φ50 mm and a height of 60 mm, with a single loading of 90 g of the mixed powder). The powder was then pre-formed by cold pressing (pressure 30 MPa, holding pressure for 8 minutes) to obtain a dense preform. The preform was then degreased, and finally, a dense target material was prepared by vacuum hot pressing sintering. The process involved vacuuming to ≤1×10⁻⁶. -3 Pa, then heat to 800℃ at a rate of 5℃ / min, apply axial pressure of 25MPa, hold for 1.5h, and then cool to room temperature with the furnace to obtain a dense blocky composite target. Polish and clean the target surface to remove the surface oxide layer and impurities to ensure the smoothness and density of the sputtering surface, and set it aside for later use.

[0039] The annealed ultra-thick electrolytic copper foil substrate was fixed on the sample stage of the vacuum magnetron sputtering equipment, the target was installed, and then the vacuum was evacuated to ≤8×10. -4 Argon gas (working gas) was introduced at a flow rate of 60 sccm. The sputtering parameters were set as follows: power 400 W, sputtering pressure 0.3 Pa, sputtering temperature 150 °C, and sputtering time 30 min. A tungsten carbide-doped copper composite surface layer with a thickness of 2 μm was prepared. After sputtering, argon gas was introduced for another 10 min, and the mixture was allowed to cool naturally to room temperature. The resulting double-layer composite copper foil showed a tight bond between the composite surface layer and the substrate layer without any peeling.

[0040] (6) Environmental passivation and cutting and shaping The double-layer composite copper foil was immersed in an environmentally friendly ZrO2-based passivation solution (enough to cover the copper foil completely) for 8 minutes at 35°C and 150 r / min stirring rate for passivation treatment. After passivation, the foil was rinsed twice with deionized water (2 minutes each time) and dried in a vacuum drying oven (90°C, 30 minutes). The foil was then cut into 500 mm × 800 mm sizes using a precision cutting machine, and the edge burrs were removed (burr height ≤ 0.2 μm) to obtain ultra-thick electrolytic copper foil for high power applications.

[0041] Example 2 Preparation of ultra-thick electrolytic copper foil for high power applications The preparation method in this embodiment is basically the same as in Example 1, except that the total concentration of sodium thiazolinyl dithiopropane sulfonate and polyquaternium-7 is adjusted to 30 ppm, and the forward current density of bipolar pulse reverse electrolytic deposition is adjusted to 35 A / dm³. 2 The third stage of converter annealing was adjusted to raise the temperature to 280℃, and the thickness of the tungsten carbide-doped copper composite surface layer was adjusted to 1μm.

[0042] Example 3 Preparation of ultra-thick electrolytic copper foil for high power applications The preparation method in this embodiment is basically the same as in Example 1, except that the total concentration of sodium thiazolinyl dithiopropane sulfonate and polyquaternium-7 is adjusted to 60 ppm, and the forward current density of bipolar pulse reverse electrolytic deposition is adjusted to 45 A / dm³. 2 The third stage of converter annealing was adjusted to raise the temperature to 320℃, and the thickness of the tungsten carbide-doped copper composite surface layer was adjusted to 3μm.

[0043] Comparative Example 1 Comparative preparation of copper foil The preparation method of this comparative example is basically the same as that of Example 1, except that step (5) is omitted, that is, the copper composite surface without tungsten carbide doping is directly passivated after annealing.

[0044] Comparative Example 2 Comparative preparation of copper foil The preparation method of this comparative example is basically the same as that of Example 1, except that the bipolar pulse reverse electrolysis in step (3) is replaced with conventional DC electrolysis, and the entire process uses 40A / dm 2 Direct current deposition, no reverse etching.

[0045] Comparative Example 3 Comparative preparation of copper foil The preparation method of this comparative example is basically the same as that of Example 1, except that in step (2), the addition of polyquaternium-7 is omitted, and only sodium thiazolinyl dithiopropane sulfonate is added at a concentration of 45 ppm.

[0046] Comparative Example 4 Comparative preparation of copper foil The preparation method of this comparative example is basically the same as that of Example 1, except that the multi-stage variable flow annealing in step (4) is replaced by conventional isothermal annealing, specifically isothermal annealing at 200℃ for 2 hours, without variable flow / temperature.

[0047] Comparative Example 5 Comparative preparation of copper foil The preparation method of this comparative example is basically the same as that of Example 1, except that the forward current density of the bipolar pulse reverse electrolysis in step (3) is increased to 60 A / dm. 2 .

[0048] Comparative Example 6 Comparative preparation of copper foil The preparation method of this comparative example is basically the same as that of Example 1, except that the electrode distance between the anode and cathode deviates from the patent scope and is adjusted to 30mm, while the other electrolysis parameters remain unchanged.

[0049] Experimental Example 1 Performance testing of copper foils prepared in Examples 1-3 and Comparative Examples 1-6 The microstructure of the ultra-thick electrolytic copper foil substrate layer prepared in Example 1 is shown in the figure. Figure 1 It can be seen that it has a gradient grain structure, consisting of a surface layer of fine grains (≤5μm), an inner layer of transitional grains (5-10μm), and a bottom layer of columnar grains (≥10μm). The stress in the matrix layer is ≤50N / cm.

[0050] The test items and test methods for copper foil are shown in Table 2: Table 2

[0051] The test results are shown in Table 3. Additionally... Figures 2 to 7 The following are test results for various parameters of the ultra-thick electrolytic copper foil for high power applications in Example 1: Table 3

[0052] As can be seen from the above: 1. The core technology system of this invention (composite additives + bipolar pulse electrolysis + multi-stage converter annealing + nano-WC composite layer) is the key to achieving high performance of ultra-thick copper foil, and the synergistic effect of each technology is indispensable. Examples 1-3 all meet the core performance indicators specified in the patent (conductivity ≥98% IACS, thermal decay rate ≤5%, peel strength ≥2.5N / mm, internal stress ≤50N / cm, thickness uniformity ≤±2%). Among them, Example 1 (optimal parameters) has the best comprehensive performance (conductivity 99.2% IACS, thermal decay rate 3.8%, peel strength 2.8N / mm). However, the comparative examples all show performance shortcomings due to the lack of a single core technology or deviation of parameters. For example, the peel strength of Comparative Example 1 (copper composite surface without tungsten carbide doping) drops to 1.6N / mm and the thermal decay rate rises to 5.6%. The elongation of Comparative Example 4 (without multi-stage converter annealing) is only 12.3% and the thermal decay rate reaches 9.2%, which fully demonstrates the necessity of each core technology and the synergistic optimization effect.

[0053] 2. The combination of novel heterocyclic sulfonate composite additives and bipolar pulsed reverse electrolysis effectively solves the industry pain points of poor thickness uniformity, high internal stress, and insufficient density in ultra-thick copper foils. Examples 1-3 all exhibited thickness uniformity ≤ ±1.8% and internal stress ≤ 46 N / cm. In contrast, the performance of Comparative Example 3 (internal stress 78 N / cm, thickness uniformity ±2.8%) using a single additive, Comparative Example 2 (thickness uniformity ±3.5%, conductivity 92.5% IACS) using conventional DC electrolysis, and Comparative Example 5 (thickness uniformity ±4.2%, conductivity 90.8% IACS) with current density deviation all showed significant declines. This indicates that the combination can precisely control the grain growth and deposition process, achieving a balance between uniform deposition and low stress.

[0054] 3. The innovative design of multi-stage variable current annealing and tungsten carbide-doped copper composite surface layer successfully overcomes the technical bottleneck of difficulty in synergizing the "strength-toughness-heat resistance" and insufficient surface adhesion of ultra-thick copper foil. Examples 1-3 exhibit tensile strength ≥915MPa, elongation ≥19.2%, thermal decay rate ≤4.7%, and peel strength ≥2.5N / mm. In contrast, Comparative Example 4 (conventional isothermal annealing), while achieving a tensile strength of 865MPa, has an elongation of only 12.3% and a thermal decay rate of 9.2%. Comparative Example 1 (without tungsten carbide-doped copper composite surface layer) has a peel strength less than 60% of Example 1. This demonstrates that multi-stage variable current annealing can achieve phase optimization and performance balance, and the tungsten carbide-doped copper composite surface layer can significantly enhance surface adhesion and heat resistance, making it suitable for the stringent service requirements of high-power applications.

[0055] Experiment Example 2 Lithium metal battery application testing The high-power ultra-thick electrolytic copper foil prepared in Example 1 and the control group copper foil (175μm conventional electrolytic copper foil, purchased from Jiangxi Tongbo Technology Co., Ltd.) were respectively assembled into lithium metal batteries for battery performance testing, as detailed below: (1) Battery composition Positive electrode: LiFePO4 was selected as the active material for the positive electrode. LiFePO4 (active material), SuperP (conductive agent), and PVDF (binder) were mixed in a mass ratio of 8:1:1, with N-methylpyrrolidone (NMP) as the solvent, and stirred for 2 hours to form a uniform slurry. The slurry was coated onto a 12μm thick aluminum foil and vacuum dried at 80℃ for 12 hours (vacuum degree -0.095MPa). Subsequently, it was rolled at a pressure of 5MPa using a roller press and cut into 12mm×12mm square electrode sheets. The active material loading was controlled at 1.5±0.1mg / cm³. 2 .

[0056] Negative electrode: Take the copper foil to be tested and cut it into a square electrode sheet of 14mm×14mm (larger than the positive electrode to avoid lithium dendrites piercing the separator); to supplement the lithium source, deposit a 5μm thick lithium metal layer on the surface of the copper foil by vacuum evaporation (evaporation vacuum degree ≤5×10). -4 Pa, surface capacity 0.5 mAh / cm³ 2 It serves as the anode material for lithium metal batteries. The ultra-thick substrate ensures mechanical support and high conductivity, while the composite surface layer enhances interfacial bonding and high-temperature resistance, making it suitable for high-power battery requirements.

[0057] Electrolyte: 1 mol / L LiPF6 dissolved in EC / DEC / DMC (volume ratio 1:1:1), with 2 wt% fluoroethylene carbonate (FEC, to inhibit lithium dendrite growth) and 0.6 wt% silane coupling agent derivative (to adapt to the modification characteristics of the nano WC composite surface and optimize interface compatibility). The electrolyte volume is 60±5 μL / cell (to meet the liquid absorption requirements of ultra-thick copper foil).

[0058] Separator: Celgard 2400 polypropylene separator (25μm thickness, 0.1μm pore size) is selected and cut into 16mm×16mm pieces to ensure complete coverage of the positive and negative electrodes and avoid direct contact.

[0059] (2) Assembly process Environmental control: Operate in an argon atmosphere glove box (H2O<0.1ppm, O2<0.1ppm) to prevent electrolyte hydrolysis, lithium metal oxidation and damage to the composite surface.

[0060] Stacking sequence: 2032 coin cell casing (positive electrode casing) → LiFePO4 positive electrode → separator (pre-wetting with 8μL electrolyte) → ultra-thick copper foil negative electrode (composite surface facing the lithium layer) → 0.1mm thick nickel sheet (auxiliary current collection, avoiding pressure on the composite surface) → spring sheet (flexible buffer, protecting the ultra-thick copper foil substrate) → gasket → negative electrode casing.

[0061] Packaging parameters: Use a button cell sealing machine to seal at a pressure of 12±0.5MPa (matching the peel strength of the composite surface layer to prevent the surface layer from falling off). After sealing, let it stand in a vacuum environment at 25℃ for 60 minutes to ensure that the electrolyte fully wets the electrodes and the separator, and at the same time, allow the composite surface layer and the lithium layer to form a stable interface, thus completing the battery activation.

[0062] (3) Test method Charge / discharge capacity and efficiency testing: The Blue Electric CT2001A battery testing system was used, with a voltage window of 2.5-3.6V (LiFePO4 standard window). The battery was cycled 100 times at current densities of 0.1C, 0.5C, and 1C (1C=170mA / g). The charge / discharge capacity and coulombic efficiency were recorded for each cycle. The capacity retention rate after 100 cycles (discharge capacity of the 100th cycle / discharge capacity of the 2nd cycle × 100%) was calculated to assess the cycle stability under high power conditions.

[0063] Rate performance test: In the 2.5-3.6V window, discharge at current densities of 0.1C, 0.2C, 0.5C, 1C, 2C and 5C in sequence (3 cycles per rate, charging to 3.6V at 0.1C), record the discharge capacity at each rate, calculate the 5C / 0.1C capacity ratio, and evaluate the high current transfer capability.

[0064] High temperature long cycle: The fully charged battery was placed in a constant temperature chamber at 80℃, 100℃ and 120℃ and charged and discharged at 0.5C for 30 cycles. The capacity decay rate was calculated and the thermal decay suppression effect was evaluated. High-temperature storage: The fully charged battery was placed in a 200℃ constant temperature chamber for 2 hours (matching the copper foil thermal decay test conditions). After cooling, the 0.1C charge-discharge performance was tested to evaluate the high-temperature stability of the composite surface.

[0065] Mechanical stability test: Apply 10 N / cm to the battery 2 Radial pressure (simulating assembly stress of high-power equipment) was applied, and the device was charged and discharged at 0.5C for 50 cycles under pressure. The changes in capacity and impedance under no-pressure conditions were compared (impedance was tested using a Keysight 34461A multimeter). After the test, the composite surface was disassembled to observe its integrity.

[0066] Electrochemical impedance spectroscopy (EIS) testing: A CHI660E electrochemical workstation was used, with a test frequency range of 10... 5 ~10 -2The AC signal amplitude was 5±0.05mV at Hz, and tests were conducted after battery assembly (initial state), 50 cycles, 100 cycles, and after high-temperature storage. The equivalent circuit was fitted using ZView software (R...). s (Solution impedance) - Rct (interfacial charge transfer impedance) - W (Warburg impedance)), extract the Rct value to analyze interfacial stability.

[0067] Overcharge protection performance test: At 25℃, the battery was overcharged from 3.6V to 5V at a current density of 0.5C. The voltage curve and battery appearance were monitored in real time to assess whether there was a voltage drop (internal short circuit) or safety hazard, and to verify the suppression effect of ultra-thick substrate and composite surface on lithium dendrites.

[0068] (4) Test results As shown in Table 4 below, the control group used traditional 175μm electrolytic copper foil (Jiangxi Tongbo Technology Co., Ltd.), and the remaining battery composition (positive electrode, electrolyte, separator, etc.) was completely consistent with the composite copper foil battery of the present invention.

[0069] Table 4

[0070] As can be seen from the above: 1. The copper foil of this invention can significantly improve the electrochemical performance and cycle stability of lithium metal batteries. Compared to traditional copper foil, the battery assembled with the copper foil of this invention has an 8.1% increase in initial discharge capacity, a 5.3% increase in initial coulombic efficiency, and a capacity retention rate of up to 94.8% after 100 cycles at 0.5C, which is 22.5 percentage points higher than the control group. At the same time, the capacity retention rate at 5C high-rate discharge reaches 82.1%, which is higher than the 61.2% of the control group, proving that it has better electron transport and structural stability in high-power discharge scenarios.

[0071] 2. The copper foil of this invention endows the battery with extremely strong high-temperature resistance and adaptability to extreme environments. During high-temperature cycling at 80℃, 100℃, and 120℃, the capacity decay rate of the copper foil battery of this invention is only 1 / 4 to 1 / 3 of that of the control group. It can still work stably during cycling at 120℃, while the control group directly fails and bulges. After storage at 200℃ for 2 hours, the capacity retention rate is 89.6%, which is 2.1 times that of the control group (42.8%), fully demonstrating the advantages of high temperature resistance and thermal decay resistance brought by the tungsten carbide composite surface and gradient grain matrix.

[0072] 3. The copper foil of this invention significantly optimizes interfacial impedance, mechanical stability, and safety performance. The copper foil battery of this invention reduces the initial interface charge transfer impedance by 41%, and the impedance increase after 100 cycles is only 1 / 8 of that of the control group; under an assembly pressure of 10 N / cm², the capacity retention rate is improved by 11.8% and the impedance change rate is reduced by 26.8%; there is no safety hazard when overcharged to 5V, and the lithium deposition is uniform and dendrite-free. It surpasses traditional copper foil in all three dimensions of interface, mechanics, and safety, and is suitable for the needs of high-power and long-life batteries.

[0073] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-power ultra-thick electrolytic copper foil, characterized in that, It has a double-layer composite structure, consisting of an ultra-thick electrolytic copper foil substrate layer and a tungsten carbide-doped copper composite surface layer.

2. The high-power ultra-thick electrolytic copper foil as described in claim 1, characterized in that, The thickness of the ultra-thick electrolytic copper foil substrate layer is 105–350 μm, and the thickness of the tungsten carbide-doped copper composite surface layer is 1–3 μm.

3. The high-power ultra-thick electrolytic copper foil as described in claim 1 or 2, characterized in that, The ultra-thick electrolytic copper foil substrate layer has a gradient grain structure, consisting of a surface fine grain, an inner transition grain, and a bottom columnar grain. The tungsten carbide-doped copper composite surface layer is bonded to the surface of the ultra-thick electrolytic copper foil substrate layer.

4. The method for preparing high-power ultra-thick electrolytic copper foil as described in claim 1, 2, or 3, characterized in that, Includes the following steps: (1) Preparation of heterocyclic sulfonate composite electrolyte Sulfuric acid, copper sulfate and hydrochloric acid were added sequentially to deionized water, followed by the addition of sodium thiazolinyl dithiopropane sulfonate and polyquaternium-7. The mixture was stirred and dissolved to obtain a heterocyclic sulfonate environmentally friendly composite electrolyte. (2) Bipolar pulse reverse electrolytic deposition of ultra-thick electrolytic copper foil substrate layer A bipolar pulse reverse electrolytic deposition process was performed using a heterocyclic sulfonate composite electrolyte to obtain an ultra-thick electrolytic copper foil substrate layer; (3) Multi-stage variable current annealing treatment Multi-stage variable current annealing treatment is performed on the ultra-thick electrolytic copper foil substrate layer; (4) Preparation of tungsten carbide-doped copper composite surface layer by vacuum magnetron sputtering Tungsten carbide powder and copper powder are mixed and sintered to form a target material. Then, a tungsten carbide-doped copper composite surface layer is prepared on the annealed ultra-thick electrolytic copper foil substrate by vacuum magnetron sputtering to obtain a double-layer composite copper foil. (5) Passivation treatment The double-layer composite copper foil was immersed in a passivation solution and dried to obtain the ultra-thick electrolytic copper foil for high power applications.

5. The method for preparing high-power ultra-thick electrolytic copper foil as described in claim 4, characterized in that, In step (1), the concentration of added sulfuric acid is 120–160 g / L, and the concentration of added copper sulfate is such that Cu 2+ The concentration is increased to 80-100 g / L, and the concentration of hydrochloric acid added is such that Cl... - The concentration is 60-80 ppm; the mass ratio of sodium thiazolinyl dithiopropane sulfonate to polyquaternium-7 is 3:2, and the total concentration of both is 30-60 ppm. The electrolyte preparation temperature is 45-55℃.

6. The method for preparing high-power ultra-thick electrolytic copper foil as described in claim 4, characterized in that, In step (2), a TA2 titanium alloy cathode roller is used, with a platinum-iridium alloy plate as the anode, and the electrode distance between the cathode and anode is 15-25 mm; the electrodeposition parameters are: forward deposition pulse current density 35-45 A / dm. 2 Duty cycle 60-70%, frequency 30-50Hz, reverse etching pulse current density 6-10A / dm 2 Duty cycle 15-20%, frequency 30-50Hz, forward-reverse time ratio = 10:1, electrolyte circulation flow rate 70-90L / h.

7. The method for preparing high-power ultra-thick electrolytic copper foil as described in claim 4, characterized in that, In step (3), the specific process of multi-stage converter annealing is as follows: evacuate to ≤5×10 -3 After Pa, argon gas is introduced to atmospheric pressure, then the temperature is increased to 170–190°C at a rate of 5–7°C / min and held for 30–50 min. Then the temperature is increased to 240–260°C at a rate of 3–5°C / min and held for 70–90 min. Finally, the temperature is increased to 280–320°C at a rate of 2–4°C / min and held for 50–70 min. After completion, the temperature is decreased to 100–120°C at a rate of 4–6°C / min and then allowed to cool naturally to room temperature.

8. The method for preparing high-power ultra-thick electrolytic copper foil as described in claim 4, characterized in that, In step (4), the tungsten carbide powder has a particle size of 50-80 nm, accounting for 10 wt% of the total target material, and is pre-modified with a silane coupling agent; the vacuum magnetron sputtering process is as follows: evacuate to ≤8×10 -4 Pa, introduce argon gas at a flow rate of 50-70 sccm, turn on the plasma power supply to 300-500W, activate for 10-20 minutes, and then set the sputtering pressure to 0.2-0.4 Pa and the sputtering temperature to 140-160℃ for sputtering.

9. The method for preparing high-power ultra-thick electrolytic copper foil as described in claim 4, characterized in that, In step (5), the passivation solution is a ZrO2-based passivation solution, and the immersion conditions are: temperature 30-40℃, stirring rate 100-200r / min, and time 7-9min.

10. The application of the high-power ultra-thick electrolytic copper foil as described in claim 1, 2 or 3 in new energy vehicle electric drive modules, energy storage converters, industrial high-power power supplies and high-power printed circuit boards.

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