A copper ion concentration stable copper dissolving method, electrolytic copper foil and preparation method thereof

Abstract

This invention relates to the field of electrolytic copper foil technology, and more particularly to a method for dissolving copper with stable copper ion concentration, electrolytic copper foil, and a method for preparing the same. This copper dissolving method includes the following steps: adding copper material and sulfuric acid solution into a first reaction vessel; introducing compressed air into the first reaction vessel to carry out the main dissolution reaction, obtaining a reaction solution; the aeration intensity of the compressed air introduced into the first reaction vessel is 0.8–1.0 m³ / s. 3 / (m 2 •h); The reaction solution in the first reaction vessel overflows into the second stabilizing vessel; Compressed air is introduced into the second stabilizing vessel for homogenization and oxidation to obtain an electrolyte for copper foil production; The aeration intensity of the compressed air introduced into the second stabilizing vessel is 0.2–0.3 m. 3 / (m 2 (h). This invention reduces the fluctuation range of copper ion concentration in the final electrolyte to ≤1.5 g / L through two-stage gradient dissolution and micro-aeration stabilization; and the copper foil thickness uniformity deviation based on this electrolyte is within ±0.1 μm, meeting the requirements for ultra-thin lithium battery copper foil.

Description

Technical Field

[0001] This invention relates to the field of electrolytic copper foil technology, and in particular to a method for dissolving copper with stable copper ion concentration, electrolytic copper foil, and a method for preparing the same. Background Technology

[0002] In the production of electrolytic copper foil, electrolyte preparation is a crucial preliminary step that determines the quality of the final product. Existing technologies, such as traditional copper dissolution methods, suffer from problems such as uneven air distribution, low dissolution efficiency, excessive acid mist, unstable copper solution concentration, and high energy consumption.

[0003] To efficiently convert metallic copper into high-concentration copper sulfate electrolyte, some copper foil manufacturers are proposing a process combining a copper dissolving tank with compressed air aeration. By introducing compressed air into the tank, the oxygen in the air oxidizes the copper into copper ions. Simultaneously, the rising bubbles create turbulence in the solution, enhancing mass transfer and thus improving dissolution efficiency. While aeration significantly accelerates copper dissolution, it has significant drawbacks in practical applications: First, fluctuations in compressed air flow and pressure directly lead to drastic changes in the oxidation reaction rate, making it difficult to stabilize the copper ion concentration. These fluctuations often exceed the ±2.5 g / L threshold required for high-end copper foil processes. Second, uneven aeration creates localized "dead zones" and "over-dissolved zones" within the tank, resulting in uneven electrolyte distribution. This rapid concentration fluctuation is directly transmitted to the foil-forming process, causing abnormal current density distribution during electrolytic deposition, ultimately resulting in poor copper foil thickness uniformity (deviations exceeding ±0.3 μm), severely impacting the mechanical properties of the copper foil and the safety of lithium batteries.

[0004] A patent document with publication number CN113019277A discloses a method for dissolving copper in electrolytic copper foil, including the following steps: copper material and sulfuric acid solution are put into a first copper dissolving tank; an air compressor is started to inject compressed air into the first copper dissolving tank, and the copper material gradually dissolves to form a copper sulfate solution; a heat exchanger is used to heat the solution in the first copper dissolving tank; sulfuric acid solution is continuously added to the first copper dissolving tank, and the overflow port is opened to allow the copper sulfate solution to enter a second copper dissolving tank from the overflow port of the first copper dissolving tank; the air compressor is started to introduce compressed air into the second copper dissolving tank, and the oxygen in the air reacts with the monovalent copper ions in the solution to generate divalent copper ions, which are then filtered by a filter device and overflow through the overflow structure into a waste liquid tank through the outlet, thus completing the copper dissolving operation.

[0005] However, in this existing technology, the purpose of introducing compressed air into the second copper melting tank is to complete the chemical oxidation of monovalent copper ions, addressing the chemical purity of the electrolyte rather than the physical concentration uniformity. It still fails to recognize and resolve the concentration gradient problem existing at the physical level in the electrolyte: as mentioned above, due to fluctuations in the flow rate and pressure of compressed air, the solution overflowing into the second copper melting tank itself carries significant concentration fluctuations. Furthermore, no specific homogenization measures are taken in the second copper melting tank, resulting in significant non-uniform turbulence and local concentration gradients within it. This leads to the electrolyte concentration entering the foil-making process remaining in a state of drastic macroscopic fluctuation. Summary of the Invention

[0006] The present invention aims to solve the above-mentioned problems by providing a copper dissolution method that can fundamentally eliminate concentration fluctuations in the prepared electrolyte and achieve long-term high stability control of copper ion concentration, as well as an electrolytic copper foil based on this copper dissolution method and its preparation method.

[0007] The technical solution to the problem solved by this invention is:

[0008] Firstly, a method for dissolving copper with a stable copper ion concentration is provided, comprising the following steps:

[0009] S1. Copper material and sulfuric acid solution are added to the first reaction vessel, and compressed air is introduced into the first reaction vessel to carry out the main dissolution reaction, obtaining a reaction solution; the aeration intensity of the compressed air introduced into the first reaction vessel is 0.8–1.0 m. 3 / (m 2 ·h);

[0010] S2. Allow the reaction solution in the first reaction vessel to overflow into the second stabilizing vessel;

[0011] S3. Compressed air is introduced into the second stabilizing tank for homogenization and oxidation to obtain an electrolyte for copper foil production; the aeration intensity of the compressed air introduced into the second stabilizing tank is 0.2–0.3 m. 3 / (m 2 ·h).

[0012] In this invention, the two seemingly contradictory functions of "efficient dissolution" and "concentration stability" are achieved independently in two separate tanks: the first reaction tank is dedicated to maximizing the dissolution rate, and the concentration gradient within it is allowed to exist as a process product and is accepted by the system; the second stabilizing tank is dedicated to concentration homogenization, creating a homogeneous environment with low turbulent kinetic energy and orderly flow by precisely limiting the aeration intensity, thus physically suppressing concentration fluctuations from upstream inputs; thereby reducing the copper ion concentration fluctuation range in the final electrolyte from >2.5 g / L in the prior art to ≤1.5 g / L.

[0013] It is worth noting that although existing technologies control the pressure and flow rate of compressed air entering the first copper melting tank, these indicators only reflect the total amount of gas input into the tank and cannot characterize the aeration intensity per unit area or the local mass transfer efficiency between the gas and liquid phases. Under this control method, the actual gas volume per unit area varies greatly in different regions of the tank, which is the physical root cause of the "over-dissolving zone" and "dead zone". In the field of copper melting technology, existing technologies, driven by the single control objective of "achieving the concentration target", have long been satisfied with using pressure and macroscopic volumetric flow rate as process control indicators, lacking an understanding of the root cause of the aforementioned non-uniformity problem.

[0014] This invention is the first to recognize that when the process objective is upgraded to "concentration meeting standards and achieving high stability," the macroscopic total quantity parameter system cannot meet the requirements for precise control. Therefore, it creatively introduces aeration intensity into the control parameter system of the copper melting process. Aeration intensity is an area-normalized unit, representing the volume of gas passing through a unit aeration disc area per unit time. It controls local bubble density and fluid turbulence intensity, rather than the macroscopic total quantity. By introducing aeration intensity as a control parameter, the control objective is directly shifted from macroscopic total quantity to microscopic mass transfer flux, enabling precise differential gradient settings for the aeration conditions of the two-stage tanks, thereby achieving a stable output effect with concentration fluctuations ≤1.5 g / L.

[0015] In step S1 An aeration intensity of 0.8–1.0 m³ is introduced into the first reaction tank. 3 / (m 2 Compressed air (·h); for example, the aeration intensity can be 0.8 m 3 / (m 2 ·h), 0.82 m 3 / (m 2 ·h), 0.85 m 3 / (m 2 ·h), 0.87 m 3 / (m 2 ·h), 0.9 m 3 / (m 2 ·h), 0.92 m 3 / (m 2 ·h), 0.95 m 3 / (m 2 ·h), 0.97 m 3 / (m 2 ·h), 1 m 3 / (m 2 ·h).

[0016] The technical objective of step S1 is to establish a reaction environment dominated by dissolution kinetics to maximize the dissolution rate of copper. It should be noted that the high-intensity aeration conditions described above in the first reaction tank, while achieving efficient dissolution, inevitably lead to significant spatial differences in the concentration distribution of copper ions in localized areas within the tank (i.e., concentration gradients). This invention does not attempt to eliminate this concentration gradient within the first reaction tank, but rather treats it as the object of treatment in the following second stabilization tank process.

[0017] As a preferred embodiment of the present invention, pulse aeration is employed in the first reaction vessel. Pulse aeration refers to aeration performed in a regular "on-off" alternating cycle, which can improve the uniformity of mass transfer at the solid-liquid interface and provide a buffer period for local heat dissipation.

[0018] Preferably, in each cycle of the pulse aeration, the ratio of aeration time to stop time is (2-3):1; for example, it can be 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, or 3:1. If the aeration time is too short, the effective reaction time in each cycle is insufficient, and the overall dissolution rate decreases significantly; if the stop time is too short, it is insufficient to completely smooth the flow field, and the pulse mode degenerates into a quasi-continuous mode, losing its homogenization and heat dissipation functions.

[0019] More preferably, in each cycle of the pulse aeration, the aeration duration is 4 to 6 minutes and the stop duration is 1.5 to 2.5 minutes.

[0020] As a preferred embodiment of the present invention, the temperature of the main dissolution reaction in the first reaction vessel is 50–55°C; for example, the temperature can be 51°C, 52°C, 53°C, 54°C, or 55°C; preferably 52±1°C. Temperature is a key thermodynamic parameter affecting the copper dissolution reaction rate. If the reaction temperature is too low, the reaction rate constant and diffusion coefficient will both be at a low level, and the copper dissolution rate will decrease significantly. If the reaction temperature is too high, the solution evaporation rate will increase significantly, the amount of acid mist generated will increase, and the effect of improving the dissolution rate will enter a decreasing region, and the increased energy consumption will no longer be proportional to the rate improvement obtained.

[0021] As a preferred embodiment of the present invention, the main dissolution reaction time in the first reaction vessel is 25–35 min; for example, the time can be 25 min, 26 min, 27 min, 28 min, 29 min, 30 min, 31 min, 32 min, 33 min, 34 min, or 35 min. This ensures that the copper material dissolution reaction reaches the preset conversion level, while avoiding negative effects caused by excessive residence time.

[0022] As a preferred embodiment of the present invention, the first reaction tank is aerated by an aeration device installed at the bottom of the tank.

[0023] Preferably, the aeration pore size in the first reaction tank is 1.0–1.5 mm; for example, it can be 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, or 1.5 mm. Fine bubbles generated by 1.0–1.5 mm pores follow a nearly straight trajectory during their ascent, with weak interaction between bubbles, which is conducive to forming an orderly and uniform bubble cluster throughout the aeration area, rather than chaotic bubble-like turbulence. When the pore size is too large, the gas exit velocity at the pore is high, easily forming local jets and causing sudden changes in local turbulence. When the pore size is too small, the generated bubble diameter is too small. Although the mass transfer interface area increases, the small bubble size also leads to a significant surface tension effect, increasing the tendency for bubble aggregation. In actual operation, it is difficult to maintain a stable bubble size distribution, and the filter element is prone to clogging.

[0024] Preferably, the aeration device in the first reaction tank uses a titanium alloy microporous sintered filter element. This filter element is a porous material formed by solid-phase diffusion bonding of titanium alloy powder at high temperature, exhibiting a three-dimensional interconnected pore network with uniform pore size distribution and high porosity, capable of generating microbubbles of uniform diameter.

[0025] Preferably, computational fluid dynamics (CFD) simulation is used to optimize the pore size and distribution of the aeration device. This ensures the uniformity of bubble distribution and reduces abrupt changes in local turbulence.

[0026] Preferably, the aeration device in the first reaction tank is acid-washed regularly to prevent blockage. Preferably, the aeration device is acid-washed every 80 to 100 days.

[0027] In step S2 This allows the reaction solution in the first reaction vessel to overflow into the second stabilizing vessel. The overflow is driven by gravity, and the solution flows without the pulsation effect and shear interference of a mechanical pump, maintaining its original concentration information when entering the overflow port. At the same time, the overflow ensures independent hydraulic and gas pressure isolation between the first reaction vessel and the second stabilizing vessel, avoiding mutual interference between the two vessels.

[0028] In step S3 Compressed air with an aeration rate of 0.2–0.3 m³ / (m²·h) is introduced into the second stabilizing tank; for example, the aeration rate can be 0.2 m³ / (m²·h). 3 / (m 2 ·h), 0.21 m 3 / (m 2 ·h), 0.22 m 3 / (m 2 ·h), 0.23 m 3 / (m 2 ·h), 0.24 m 3 / (m 2 ·h), 0.25 m 3 / (m 2 ·h), 0.26 m 3 / (m 2 ·h), 0.27 m 3 / (m 2 ·h), 0.28 m 3 / (m 2 ·h), 0.29 m 3 / (m 2 ·h), 0.3 m 3 / (m 2 ·h).

[0029] The technical objective of step S3 is to establish a reaction environment with concentration homogenization as the primary goal, to smooth out concentration fluctuations in the reaction solution from the first reaction vessel, and at the same time, to oxidize residual cuprous ions.

[0030] As a preferred embodiment of the present invention, the volume ratio of the first reaction vessel and the second stabilizing vessel is (40-60):1; for example, it can be 40:1, 45:1, 50:1, 55:1, or 60:1. The reaction solution output from the first reaction vessel carries significant concentration fluctuations. If the volume of the second stabilizing vessel is too large relative to the first reaction vessel, concentration fluctuation clumps entering the second stabilizing vessel at different times will coexist in the vessel for a long time, forming a complex concentration field with superimposed old and new fluctuations, which increases the difficulty of homogenization. If the volume of the second stabilizing vessel is too small relative to the first reaction vessel, the solution will not stay in the vessel for long enough, resulting in insufficient homogenization. An appropriate volume ratio range can provide sufficient physical space for homogenization while avoiding the superposition of concentration fluctuations and sluggish response of the control system caused by excessively large vessel volumes.

[0031] As a preferred embodiment of the present invention, constant flow aeration is employed in the second stabilizing tank. Unlike the pulse aeration mode of the first reaction tank, constant flow aeration maintains a constant aeration intensity over time, working in synergy with low aeration intensity to ensure that no new sources of fluctuation are introduced into the second stabilizing tank in either time or space, thus providing a physically homogeneous and chemically stable environment.

[0032] As a preferred embodiment of the present invention, the second stabilizing tank is aerated via an aeration device installed at its inner bottom. The design requirements and function of the aeration device in the second stabilizing tank are the same as those in the first reaction tank.

[0033] Preferably, the aeration orifice diameter in the second stabilizing tank is 1.0 to 1.5 mm; for example, it can be 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, or 1.5 mm.

[0034] Preferably, the aeration device in the second stabilizing tank uses a titanium alloy microporous sintered filter element.

[0035] Preferably, computational fluid dynamics (CFD) simulation is used to optimize the pore size and distribution of the aeration disc. More preferably, the lower support feet of the aeration device near the corner of the tank wall are removed, allowing the gas and fluid at the bottom to diffuse evenly in a radial pattern without dead angles.

[0036] Preferably, the aeration device in the second stabilizing tank is acid-washed regularly to prevent blockage. More preferably, the aeration device is acid-washed every 80 to 100 days.

[0037] As a preferred embodiment of the present invention, the copper dissolution method of the present invention further includes the following steps:

[0038] Step S4 The concentration of copper ions in the electrolyte is monitored in real time through the outlet pipeline of the second stabilizing tank, and the copper dissolution parameters are adjusted according to the deviation between the monitoring results and the set target concentration. The copper dissolution parameters include at least one of the following: the flow rate of sulfuric acid solution, the copper material feeding rate, the aeration intensity of the first reaction tank, and the main dissolution reaction temperature.

[0039] As a preferred embodiment of the present invention, the electrolyte concentration is monitored in real time using an online copper ion concentration meter with X-ray fluorescence (XRF).

[0040] As a preferred embodiment of the present invention, when the deviation between the detection result and the set target concentration exceeds 1.5%, adjustment is performed.

[0041] Preferably, when the detected concentration is higher than the set target concentration range, the flow rate of the sulfuric acid solution is increased and / or the copper material feeding rate is decreased. When the detected concentration is lower than the set target concentration range, the aeration intensity of the first reaction tank is fine-tuned and / or the main dissolution reaction temperature is increased. Fine-tuning means that a single adjustment does not exceed 10% of the aeration intensity. For example, the set target concentration is 92±1.5 g / L; the PLC system collects concentration data every 5 seconds. If three consecutive detection values ​​are >93.5 g / L, the replenishment valve is opened; if <90.5 g / L, the aeration intensity of the first reaction tank is increased by 10%.

[0042] It is worth noting that the feedback control system in step S4 of this invention is a fine-tuning method acting on the output solution that has been physically stabilized and is in a relatively stable state, rather than a forced correction method acting directly on a solution with violent fluctuations. The effectiveness of the feedback control system is highly dependent on the stability of the controlled object itself. When the output fluctuation of the controlled object is too large or too frequent, the feedback control system will face fundamental engineering limitations. For example, there is a non-negligible time delay in the entire process from detecting an abnormal concentration, to the PLC calculating the adjustment amount and outputting the command, to the actuator taking effect, and finally to the adjusted solution reaching the concentration detection point. When the controlled object itself fluctuates violently, this delay will cause the concentration to have changed again by the time the adjustment action takes effect. The adjustment will not only fail to correct the deviation but may even amplify the fluctuation.

[0043] Secondly, another objective of this invention is to provide a method for preparing electrolytic copper foil, including a copper dissolving process and a foil forming process, wherein the copper dissolving process includes the copper dissolving method described above.

[0044] As a preferred embodiment of the present invention, the electrolyte obtained by the copper dissolution method is filtered through multiple stages before entering the foil production process; the filtration precision of the multiple stages decreases.

[0045] Preferably, the multi-stage filtration is a three-stage filtration with filtration accuracies of 4–6 μm, 0.5–1.5 μm, and 0.1–0.3 μm, respectively.

[0046] The foil-making process is unrestricted and can employ any commonly used foil-making process in existing technologies. For example, a multi-stage filtered electrolyte is fed into an electrolytic cell at a current density of 13000–18000 A / m. 2 Electrolytic deposition is carried out under conditions of electrolyte temperature of 50–60℃ and electrode spacing of 6–12 mm to obtain electrolytic copper foil. The obtained copper foil can be subjected to anti-oxidation treatment or surface passivation treatment as needed.

[0047] Thirdly, another object of the present invention is to provide an electrolytic copper foil prepared as described in the method.

[0048] As a preferred embodiment of the present invention, the thickness uniformity deviation of the electrolytic copper foil is within ±0.1 μm, the tensile strength is not less than 350 MPa, and its surface roughness Rz value is reduced by at least 20% compared with that of copper foil made from single-stage copper dissolving electrolyte.

[0049] The thickness uniformity deviation is defined as the absolute value of the maximum deviation between the thickness values ​​at at least 10 equally spaced measurement points along the width of the copper foil and the nominal thickness. The tensile strength is determined according to GB / T 5230-2020 Electrolytic Copper Foil for Printed Circuit Boards. The surface roughness Rz is determined according to ISO 4287 standard.

[0050] The beneficial effects of this invention are:

[0051] 1. This invention provides a copper dissolution method with stable copper ion concentration. Through two-stage gradient dissolution and micro-aeration stabilization, the fluctuation range of copper ion concentration is reduced from >2.5 g / L in the prior art to ≤1.5 g / L.

[0052] 2. This invention provides an electrolytic copper foil and its preparation method. The copper foil is prepared using an electrolyte with a copper ion concentration fluctuation range of ≤1.5 g / L obtained by the above-mentioned copper dissolution method. The thickness uniformity deviation of the copper foil is within ±0.1 μm, which meets the stringent tolerance requirements of 4.5 μm ultra-thin lithium battery copper foil. Furthermore, the tensile strength is increased to ≥350 MPa, and the surface roughness (Rz) is reduced by 20%.

[0053] Under this process, the yield of copper foil is increased by 12% to 15%, and the overall production cost is reduced by 8% to 10%. At the same time, the stable electrolyte concentration reduces safety hazards during battery cycling. Attached Figure Description

[0054] Figure 1 This is a process flow diagram of a copper dissolution method with stable copper ion concentration;

[0055] Figure 2 This is a comparison of the copper ion concentration fluctuation trends of the two-stage copper dissolution method of this invention and the traditional single-stage copper dissolution method during continuous operation for 72 hours. Detailed Implementation

[0056] The following are specific embodiments of the present invention, and the technical solution of the present invention will be further described in conjunction with the accompanying drawings. However, the present invention is not limited to these embodiments.

[0057] Example 1

[0058] A copper dissolution method with stable copper ion concentration, such as Figure 1 As shown, it includes the following steps:

[0059] Prepare a volume of 52 m³ 3 The first reaction vessel has a volume of 1 m³ 3The first reaction tank has a copper feed port and a sulfuric acid solution inlet at the top, and an overflow port on the upper side wall. The inlet of the second stabilizer is connected to the overflow port of the first reaction tank via an overflow pipe, which is inclined downwards to ensure gravity flow. At the bottom of both the first and second stabilizers are titanium alloy microporous sintered filter cartridges with pore size distribution and gas distribution point positions optimized by computational fluid dynamics (CFD) simulation. The filter cartridge pore size ranges from 1.0 to 1.5 mm. Each aeration cartridge is connected to an air compressor via an independent air supply line, which is equipped with a gas flow meter, an electric regulating valve, and a check valve. An online X-ray fluorescence (XRF) copper ion concentration meter is installed on the outlet pipe of the second stabilizer, and its signal output is electrically connected to a PLC controller. The PLC controller is electrically connected to the electric regulating valve on the air supply line of the first reaction tank and the electric replenishment valve on the sulfuric acid solution replenishment line, forming a closed-loop feedback control system.

[0060] S1. The cleaned copper plates or blocks are fed into the first reaction tank through the feed inlet, while simultaneously pumping dilute sulfuric acid solution into the tank. The air compressor is started, and compressed air is introduced into the aeration disc at the bottom of the first reaction tank via an electric regulating valve, setting the aeration intensity to 0.9 m. 3 / (m 2 •h). The aeration mode in the first reaction tank adopts a pulse mode: that is, it alternates between 5 minutes on and 2 minutes off as one cycle. At the same time, the temperature of the solution in the tank is maintained at 52±1℃ using an external heat exchanger. Under aeration and heating conditions, the copper material undergoes the main dissolution reaction in the first reaction tank, with a total reaction time of 30 minutes. The acid mist generated during the reaction is sent to the acid mist treatment system through the exhaust pipe.

[0061] S2. The reaction solution in the first reaction vessel flows automatically into the second stabilizing vessel through the overflow pipe.

[0062] S3. Compressed air is introduced into the aeration disc at the bottom of the second stabilizing tank via another set of electric regulating valves, and the aeration intensity is set to 0.25 m. 3 / (m 2 •h), and a constant flow continuous aeration mode is adopted. Under this low-intensity micro-aeration condition, an orderly macroscopic circulation is formed in the tank, which physically homogenizes the solution from the first reaction tank and eliminates the concentration gradient; at the same time, the trace residual monovalent copper ions in the solution are uniformly and slowly oxidized to divalent copper ions.

[0063] S4. Set the target copper ion concentration to 92 g / L, with an allowable fluctuation range of ±1.5 g / L (i.e., 90.5~93.5 g / L). The XRF online concentration meter collects solution concentration data at the outlet of the second stabilizing tank every 5 seconds and transmits it to the PLC controller. The PLC controller judges and adjusts according to the following logic: if three consecutive detection values ​​are higher than 93.5 g / L, the PLC issues a command to open the replenishment valve of the first reaction tank, increasing the flow rate of dilute sulfuric acid to dilute the copper ion concentration in the system; if three consecutive detection values ​​are lower than 90.5 g / L, the PLC issues a command to increase the opening of the electric regulating valve on the air supply pipeline of the first reaction tank by 10%, reducing the aeration intensity from 0.9 m 3 / (m 2 •h) increased to approximately 0.99 m 3 / (m 2 (h). After each adjustment, the PLC continues to monitor the concentration change until the concentration stabilizes within the target range.

[0064] like Figure 2 As shown, the method of this embodiment was used to run continuously for 72 hours. The online monitoring data showed that the concentration of copper ions in the electrolyte at the outlet of the second stabilizer was always controlled within a range of 92.5 g / L, with a maximum deviation of no more than ±1.5 g / L.

[0065] An electrolytic copper foil is prepared by the following steps:

[0066] (1) The copper sulfate electrolyte at the outlet of the second stabilizer is filtered in three stages (5 μm, 1 μm and 0.2 μm precision filters in sequence) and then enters the electrolytic cell of the foil production process.

[0067] (2) The electrolyte temperature in the tank is maintained at 52±1℃, and the current density is set to 15000 A / m 2 The electrode spacing is 8 mm. Under the action of direct current, copper ions are continuously deposited on the cathode surface to form electrolytic copper foil. After peeling, washing, passivation treatment and drying, the copper foil is wound up.

[0068] The obtained copper foil was tested at multiple points using an online thickness gauge, and its thickness uniformity deviation was within ±0.1 μm, meeting the tolerance requirements for ultra-thin lithium battery copper foil; the tensile strength of the copper foil reached 375 MPa, and the surface roughness Rz value was 2.5 μm.

[0069] Comparative Example 1

[0070] Comparative Example 1 is a traditional single-stage copper melting process, which includes the following steps:

[0071] Prepare a volume of 53 m³ 3A single-stage copper melting tank (total volume equivalent to the sum of the first reaction tank and the second stabilizing tank in Example 1). The top of the copper melting tank has a copper feed inlet and a sulfuric acid solution inlet, while the lower part of the tank side wall has an outlet. A conventional aeration disc is installed at the bottom of the tank, with multiple mechanically drilled holes of 1–3 mm evenly distributed on the disc. The aeration disc is connected to an air compressor via an air supply pipeline, which is equipped with an electric regulating valve and a gas flow meter.

[0072] The cleaned copper plates or blocks are fed into the copper melting tank through the inlet, while a dilute sulfuric acid solution is pumped into the tank simultaneously. The air compressor is started, and compressed air is introduced into the aeration disc at the bottom of the copper melting tank via an electric regulating valve. The compressed air pressure is set to 0.5 MPa and the volumetric flow rate to 280 m³ / s using the regulating valve and gas flow meter. 3 / h. Simultaneously, an external heat exchanger maintains the solution temperature inside the tank at 75℃. Under aeration and heating conditions, continuous operation is performed (or: total reaction time is 90 min). Acid fumes generated during the reaction are sent to the acid fumes treatment system via exhaust pipes. For example... Figure 2 As shown, the method of this comparative example was used to run continuously for 72 hours. The online monitoring data showed that the copper ion concentration of the electrolyte at the outlet fluctuated between 88 and 97 g / L, with a maximum deviation of more than ±2.5 g / L.

[0073] The copper sulfate solution in the copper melting tank is discharged directly from the outlet and enters the electrolytic cell of the foil production process after being filtered through three stages (5 μm, 1 μm and 0.2 μm in sequence).

[0074] The electrolyte temperature in the tank was maintained at 52±1℃, and the current density was set to 15000 A / m. 2 The electrode spacing is 8 mm. Under the action of direct current, copper ions are continuously deposited on the cathode surface to form electrolytic copper foil. After peeling, washing, passivation treatment and drying, the copper foil is wound up.

[0075] The obtained copper foil was tested at multiple points using an online thickness gauge. The thickness uniformity deviation exceeded ±0.3 μm, and the thickness deviation in some areas reached ±0.4 μm, which could not meet the thickness tolerance requirements of ultra-thin lithium battery copper foil. The average tensile strength of the copper foil was 335 MPa, and the surface roughness Rz value was 3.2 μm.

[0076] Comparing Example 1 and Comparative Example 1, it is evident that, under the premise that the copper material type, sulfuric acid concentration, target concentration, total tank volume, filtration accuracy, and foil production conditions remain consistent, whether or not the two-stage gradient copper dissolution structure, aeration intensity control parameter system, and closed-loop feedback control strategy of this invention are adopted has a significant impact on the concentration stability of the final electrolyte and the quality of the copper foil product. The embodiments of this invention improve concentration fluctuation control by approximately 40% compared to the traditional single-stage process (from >±2.5 g / L to ≤±1.5 g / L), improve copper foil thickness uniformity deviation from more than ±0.3 μm to within ±0.1 μm, increase tensile strength from 335 MPa to 375 MPa, and reduce surface roughness by approximately 22%.

[0077] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A method for dissolving copper with stable copper ion concentration, characterized in that: Includes the following steps: S1. Copper material and sulfuric acid solution are added to the first reaction vessel, and compressed air is introduced into the first reaction vessel to carry out the main dissolution reaction, obtaining a reaction solution; the aeration intensity of the compressed air introduced into the first reaction vessel is 0.8–1.0 m. 3 / (m 2 ·h); S2. Allow the reaction solution in the first reaction vessel to overflow into the second stabilizing vessel; S3. Compressed air is introduced into the second stabilizing tank for homogenization and oxidation to obtain an electrolyte for copper foil production; the aeration intensity of the compressed air introduced into the second stabilizing tank is 0.2–0.3 m. 3 / (m 2 ·h).

2. The copper dissolution method with stable copper ion concentration according to claim 1, characterized in that: Pulse aeration is used in the first reaction tank, and constant flow aeration is used in the second stabilization tank.

3. The copper dissolution method with stable copper ion concentration according to claim 2, characterized in that: In each cycle of the pulse aeration, the ratio of aeration duration to stop duration is (2-3):

1.

4. A method for dissolving copper with stable copper ion concentration according to claim 1 or 2, characterized in that: The main dissolution reaction temperature in the first reaction vessel is 50-55℃, and the time is 25-35 min.

5. The copper dissolution method with stable copper ion concentration according to claim 1, characterized in that: The aeration orifice diameters in the first reaction tank and the second stabilizing tank are independently 1.0 to 1.5 mm.

6. The copper dissolution method with stable copper ion concentration according to claim 1, characterized in that: The volume ratio of the first reaction vessel to the second stabilizer is (40-60):

1.

7. The copper dissolution method with stable copper ion concentration according to claim 1, characterized in that: It also includes the following steps: S4. The concentration of copper ions in the electrolyte is monitored in real time on the outlet pipeline of the second stabilizer, and the copper dissolution parameters are adjusted according to the deviation between the monitoring results and the set target concentration. The copper dissolution parameters include at least one of the following: the flow rate of sulfuric acid solution, the copper material feeding rate, the aeration intensity of the first reaction tank, and the main dissolution reaction temperature.

8. A method for preparing electrolytic copper foil, comprising a copper dissolving step and a foil forming step, characterized in that: The copper dissolving process includes the copper dissolving method as described in any one of claims 1 to 7.

9. The method for preparing electrolytic copper foil according to claim 8, characterized in that: The electrolyte obtained by the copper dissolution method is filtered through multiple stages before entering the foil production process; the filtration precision decreases with each stage of filtration.

10. An electrolytic copper foil prepared by the method according to any one of claims 8 to 9.

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