Preparation method and production system of copper foil for semi-solid battery

Abstract

A method for preparing copper foil for semi-solid batteries includes the following steps: preparing a copper sulfate solution. Taking copper wire and sulfuric acid, placing them in a copper dissolving tank, dissolving to obtain a mixed copper sulfate solution, wherein: the concentration of sulfuric acid is 340-360g / L, and the ambient temperature in the copper dissolving tower is 65-85°C; copper sulfate enters a clean liquid tank after multi-stage filtration; the copper acid concentration of the clean liquid is between 60-75ppm; adding additives to the clean liquid tank to form an electrolyte, that is, adding collagen to the clean liquid tank, adding sodium polydisulfide dipropane sulfonate to the clean liquid tank; adding hydroxyethyl cellulose to the clean liquid tank; electrolyzing the foil. In the electrolytic tank, 50m 3 A predetermined amount of electrolyte is added at a rate of 1000 psi / h. After power is applied to the electrolytic cell, copper foil is produced using a cathode roller with a surface roughness of less than 0.3 μm. The copper foil is then peeled off. The copper foil formed on the cathode roller surface is peeled off using a stripping roller, and then acid is sprayed on the cathode roller surface. The cathode roller surface is then treated with acid spraying. The copper foil is then treated to prevent oxidation.

Description

Technical Field

[0001] The present invention belongs to the technical field of semi-solid batteries, and in particular relates to a method for preparing a copper foil specially used for semi-solid batteries. Background Art

[0002] With the development and progress of society, environmental pollution and energy scarcity are becoming increasingly serious, and clean energy is becoming more prevalent. With the rise of new energy sources, electric vehicle range is a major concern, and the development of lithium-ion batteries with higher energy density is urgent. Solid-state batteries have been brought to the forefront as the next generation of batteries. However, solid-state batteries are difficult to develop and require high process requirements, making mass production impossible. Therefore, semi-solid-state batteries have emerged as a transitional product.

[0003] In semi-solid-state batteries, lithium ions are conducted through a semi-solid gel electrolyte filled between the positive and negative electrodes. However, compared to liquid electrolytes, semi-solid electrolytes are restricted by the solid-solid interface, resulting in poor lithium ion conduction. Semi-solid-state batteries typically use silicon as the negative electrode material due to its high theoretical specific capacity. However, during the battery's charge and discharge process, there is a serious volume expansion problem, which can easily cause the negative electrode current collector to break during expansion and contraction, and the negative electrode slurry to fall off, affecting the battery's internal resistance and cycle life. Therefore, the tensile strength, elongation, and roughness of the negative electrode current collector are particularly important.

[0004] Copper foil is a key material for the negative electrode of lithium-ion batteries. According to its thickness, it can be divided into thick copper foil (greater than 70μm), regular thickness copper foil (greater than 18μm and less than 70μm), thin copper foil (greater than 12μm and less than 18μm), and ultra-thin copper foil (less than 12μm); according to its surface condition, it can be divided into single-sided treated copper foil (single-sided rough), double-sided treated copper foil (double-sided rough), smooth treated copper foil (double-sided rough), double-sided smooth copper foil (double smooth) and very low profile copper foil (VLP copper foil).

[0005] Currently, the semi-solid lithium battery copper foil on the market is essentially single-sided rough copper foil. The production process for single-sided rough copper foil is as follows: copper dissolution → filtration → electrolytic foil production → copper foil post-processing → winding. Additives are added before electrolytic foil production to improve the physical properties of the copper foil. The purpose of copper foil post-processing is primarily to improve the flatness and roughness of the foil surface and prevent oxidation. The post-processing process generally involves pickling → roughening → curing → roughening → curing → nickel plating → zinc plating → chromium plating → chlorosilane spraying → drying. Pickling involves cleaning oxides from the copper foil surface with acid; roughening involves polishing the copper foil with sandpaper or a grinding wheel to increase the surface roughness; curing smoothes the copper foil and reduces the roughness of the roughened layer. Nickel, zinc, chromium, and other plating processes are used to prevent oxidation.

[0006] As can be seen, the preparation process for single-sided rough copper foil requires multiple post-processing steps, which can easily introduce impurities such as Fe, Ni, and Zn, resulting in color differences. Furthermore, because the copper foil is very thin, post-processing can easily lead to wrinkling and a decrease in tensile strength. Summary of the Invention

[0007] In view of the problems in the existing process of ultra-thin single-sided rough copper foil such as the introduction of more impurities, easy wrinkling and reduced tensile strength, the present invention provides a method for preparing copper foil specifically for semi-solid state batteries.

[0008] At the same time, the present invention also provides a production system for copper foil specially used for semi-solid batteries.

[0009] A method for preparing copper foil for semi-solid-state batteries comprises the following steps:

[0010] Step S1: Prepare a copper sulfate solution. Copper wire and sulfuric acid are placed in a copper dissolving tank and dissolved to obtain a mixed copper sulfate solution. The concentration of the sulfuric acid is 340-360 g / L, and the ambient temperature in the copper dissolving tank is 65-85°C. The copper sulfate passes through multiple filtration stages and enters a clean liquid tank. The copper acid concentration of the clean liquid is between 60-75 ppm.

[0011] Step S2: Add additives to the clean liquid tank to form an electrolyte, namely:

[0012] Add collagen to the clean liquid tank at a rate of 5 g / L and 10 L / h;

[0013] Add sodium polydisulfide dipropane sulfonate to the clean liquid tank at a rate of 8 g / L and 10 L / h;

[0014] Add hydroxyethyl cellulose to the clean liquid tank at a rate of 1 g / L and 10 L / h;

[0015] Step S3, electrolysis of foil. 3 A predetermined amount of electrolyte is added at a rate of / h, and then power is applied in the electrolytic cell. Copper foil is produced using a cathode roller with a surface roughness of less than 0.3μm.

[0016] Step S4: peeling the copper foil. The copper foil formed on the surface of the cathode roller is peeled off by a peeling roller, and then acid is sprayed on the surface of the cathode roller to remove the oxide layer on the surface of the cathode roller.

[0017] Step S5: spraying acid on the surface of the cathode roller.

[0018] Step S6: Anti-oxidation treatment of the copper foil: The peeled copper foil is subjected to chromate anti-oxidation electroplating treatment.

[0019] A system production system for copper foil for semi-solid batteries includes a copper dissolving tank, a multi-stage filter, a liquid purification tank, an electrolytic device, a chromate electroplating device, and a winding roller. The liquid outlet of the copper dissolving tank is connected to the liquid inlet of the multi-stage filter through a pipeline, the liquid outlet of the multi-stage filter is connected to the liquid inlet of the liquid purification tank through a pipeline, the liquid outlet of the liquid purification tank is connected to the upper end of the electrolytic device, and the winding roller is located at the rear end of the chromate electroplating device. The electrolytic device includes an electrolytic cell, a cathode roller, a stripping roller, a polishing brush, and a spray pipe. The cathode roller is located directly above the electrolytic cell. The stripping roller, polishing brush, and spray pipe are successively arranged around the upper end of the cathode roller. The nozzle of the spray pipe is at an angle of 35 to 40 degrees to the horizontal direction.

[0020] Beneficial effects: Compared with the prior art, the method for preparing copper foil for semi-solid batteries of the present invention first optimizes the formulation of additives, so that the surface roughness of the electrolyzed copper foil is within the range of 0.2 to 0.3 μm and the tensile strength is greater than or equal to 320 MPa, which can effectively reduce the occurrence of copper foil wrinkling. After the copper foil is peeled off, the surface of the cathode roller is immediately sprayed with acid to promptly remove the oxide layer on the surface of the cathode roller. In this way, the roughness of the surface of the cathode roller can be maintained, and the cathode roller is prevented from becoming smooth due to surface oxidation, and the copper foil does not need to be roughened. At the same time, the oxide on the surface of the cathode roller is promptly removed to prevent iron oxide from adhering to the copper foil during the production process. Chromate anti-oxidation electroplating treatment is then directly performed. In this way, the introduction of impurities such as Fe, Ni, and Zn can be effectively avoided, while significantly shortening the post-processing process of the copper foil. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The present invention is a flow chart of a method for preparing a copper foil specifically for semi-solid batteries.

[0022] Figure 2 This is a schematic structural diagram of the system production system of the semi-solid-state battery-specific copper foil of the present invention.

[0023] Among them: copper dissolving tank 10, multi-stage filter 20, clean liquid tank 30, electrolysis device 40, electrolytic cell 401, cathode roller 402, stripping roller 403, polishing brush 404, spray pipe 405, chromate electroplating device 50, squeezing roller 501, winding roller 60, knife groove roller 70, air knife 80. DETAILED DESCRIPTION

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following is a brief introduction to the drawings required for use in the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Please see Figure 1 A method for preparing a copper foil for a semi-solid battery comprises the following steps:

[0026] Step S1: Prepare a copper sulfate solution. Copper wire and sulfuric acid are placed in a copper dissolving tank 10 to dissolve the copper wire and obtain a mixed copper sulfate solution. The concentration of the sulfuric acid is 340-360 g / L, and the ambient temperature in the copper dissolving tank is 65-85°C. The copper sulfate passes through multiple filtration stages and enters a clean solution tank 30. The clean solution has a copper acid concentration between 60-75 ppm.

[0027] In a preferred embodiment, copper sulfate enters the clean liquid tank 30 after undergoing four-stage filtration.

[0028] Step S2: Add additives to the clean liquid tank 30 to form an electrolyte, namely:

[0029] Add collagen to the clean liquid tank 30 at a flow rate of 5 g / L and 10 L / h;

[0030] Sodium polydisulfide dipropane sulfonate was added to the clean liquid tank 30 at a flow rate of 8 g / L and 10 L / h.

[0031] Add hydroxyethyl cellulose to the clean liquid tank 30 at a rate of 1 g / L and 10 L / h;

[0032] Adding collagen can change the roughness of the copper foil. If the collagen content is too low, the roughness of the copper foil will be too large, and it will be easily wrinkled and scrapped. On the contrary, the roughness of the copper foil is too small and it cannot be tightly bonded with the electroplating material. At the same time, downstream clients also have requirements for the surface roughness of the copper foil. Within a reasonable range, the greater the roughness, the stronger the adhesion between the copper foil and the slurry, which can effectively reduce the risk of breakage and shedding of the negative electrode slurry during the expansion and contraction process of the semi-solid battery cycle. After a large number of experiments by technicians, collagen was added to the clean liquid tank 30 at a flow rate of 5g / L and 10L / h, and then combined with an appropriate amount of sodium polydisulfide dipropylene sulfonate and subsequent processes. The ultra-thin single-sided rough copper foil produced is not easy to wrinkle, can be tightly bonded with the electroplating material, and can also meet the production requirements of downstream clients.

[0033] With the addition of collagen and sodium polydisulfide dipropane sulfonate, although the copper foil can be controlled within a suitable range, the tensile strength of the copper foil will also decrease. Therefore, the present invention also adds an appropriate amount of hydroxyethyl cellulose.

[0034] Adding hydroxyethyl cellulose can change the tensile strength of copper foil. Since the tensile strength and elongation of copper foil are inversely related, after a large number of experiments by technicians, when hydroxyethyl cellulose is added to the clean liquid tank 30 at a flow rate of 1g / L and 10L / h, the produced ultra-thin single-sided rough copper foil can meet both the tensile strength requirements and the elongation requirements.

[0035] Step S3, electrolysis of foil. 3 A predetermined amount of electrolyte is added at a rate of / h, and then power is applied in the electrolytic cell 401, and copper foil is produced using a cathode roller 402 with a surface roughness of less than 0.3 μm.

[0036] Step S4 , stripping the copper foil: The copper foil formed on the surface of the cathode roller 402 is stripped off by the stripping roller 403 , and then acid is sprayed on the surface of the cathode roller 402 to remove the oxide layer on the surface of the cathode roller 402 .

[0037] Step S5: spraying acid on the surface of the cathode roller 402.

[0038] During the copper foil production process, cathode roller 402 is oxidized, reducing its roughness and resulting in a thinner copper foil produced by electrolysis. Spraying acid on the surface of cathode roller 402 can reduce the copper foil's brightness and increase its surface roughness. When the spray angle is relatively small relative to the horizontal, the acid remains on cathode roller 402 for a relatively short time due to gravity, affecting the effectiveness of removing the oxide layer. However, when the spray angle is increased, the acid remains on the surface of cathode roller 402 for an extended period of time, corroding cathode roller 402 and forming black spots on its surface, which shortens its service life.

[0039] After comprehensively considering factors such as acid utilization rate, oxide layer removal effect, and copper foil roughness, and after a large number of experiments by technicians, the angle between the acid spray direction and the horizontal direction is 35-40 degrees. Accordingly, the rotation speed of the cathode roller 402 is 7.6 meters / minute, and the acid spray flow rate is 1-1.5 cubic meters / hour.

[0040] Despite this, the cathode roller 402 may still oxidize after prolonged use, affecting the roughness of the copper foil. Therefore, the surface of the cathode roller 402 needs to be regularly or irregularly treated by polishing and grinding. Polishing uses a polishing brush 404, and grinding uses a 320-grit grinding wheel to slow the formation of an oxide layer on the surface of the cathode roller 402 and maintain the copper foil surface roughness below 0.3 μm.

[0041] Step S6, anti-oxidation treatment: The peeled copper foil is subjected to chromate anti-oxidation electroplating treatment.

[0042] The preparation process of chromate solution is as follows: chromic anhydride, phosphoric acid and water are prepared in a certain proportion to prepare chromate passivation solution. After the solution is prepared, the concentration of chromium ion is 1g / L and the concentration of phosphate ion is 1500mg / L.

[0043] The anti-oxidation electroplating process involves applying an anode plate to each of the matte and polished sides of the copper foil. When the anode plate is energized, the copper foil acts as a cathode, and chromium ions slowly migrate to the copper foil through the electric field, forming a thin layer of chromium-copper alloy on the surface of the copper foil. The deposited amount on the copper foil is 4.96 mg / m². 2 The electroplating amount of the smooth surface is 2.66mg / m 2 The electrostatic amount of the rough surface is 2.30mg / m 2 .

[0044] After the chrome plating anti-oxidation treatment, the copper foil can be wound up, omitting the post-processing steps in the prior art (rough curing, galvanizing, nickel plating, and silane spraying). In order to minimize the oxidation problem of the copper foil during the process from peeling to winding, the distance from the peeling roller 403 to the winding roller 60 does not exceed 5 meters. At the same time, it was found in the test that when the copper foil is wound up, if the winding tension is too high, it is easy to cause problems such as edge tearing and water ripples. If the winding tension is too low, the copper foil is easy to deviate during winding, and air is easy to enter the copper foil winding area, causing wrinkles. After a large number of tests by the test personnel, the copper foil is wound best when the winding tension is 120N.

[0045] Parameters such as copper ion concentration, sulfuric acid concentration, electrolyte temperature, electrolyte flow rate, flow rate, and additive selection, combination, and addition method all interact and function independently. The method for preparing copper foil for semi-solid-state batteries of the present invention first optimizes the additive formulation to ensure that the surface roughness of the electrolytic copper foil is within the range of 0.2-0.3 μm and the tensile strength is greater than or equal to 320 MPa, effectively reducing the occurrence of copper foil wrinkling. After stripping the copper foil, the surface of the cathode roller 402 is immediately sprayed with acid to promptly remove the oxide layer on the surface of the cathode roller 402. This ensures the surface roughness of the cathode roller 402 and prevents it from becoming smooth due to surface oxidation, eliminating the need for roughening treatment of the copper foil. Furthermore, the oxide layer on the cathode roller 402 is promptly removed to prevent iron oxide from adhering to the copper foil during the production process. Chromium anti-oxidation plating is then performed directly. This effectively prevents the introduction of impurities such as Fe, Ni, and Zn, while significantly shortening the copper foil post-processing process.

[0046] Table 1 shows the copper foil properties of a single additive and the additive of the present invention, wherein:

[0047] Comparative Example 1: Add the additive hydroxyethyl cellulose to the clean liquid tank 30 at a concentration of 1 g / L and a flow rate of 10 L / h;

[0048] Comparative Example 2: Collagen was added as an additive at a rate of 5 g / L and 10 L / h into the clean liquid tank 30;

[0049] Comparative Example 3: The additive sodium polydisulfide dipropane sulfonate was prepared and added to the clean liquid tank 30 at a flow rate of 8 g / L and 10 L / h;

[0050] Table 1: Copper foil performance parameters

[0051] Tensile strength (Mpa) MRz(um) Comparative Example 1 307 3.35 Comparative Example 2 284 3.95 Comparative Example 3 183 4.1 The present invention 320 2.67

[0052] It can be seen from Table 1 that compared with a single additive, the additive prepared in the present invention has better tensile properties and smaller surface roughness, and the copper foil is less likely to wrinkle.

[0053] At the same time, in order to match the preparation method of copper foil specifically for semi-solid batteries and to reduce the occurrence of wrinkling of copper foil, the present invention carries out synchronous transformation on the equipment to provide a production system for copper foil specifically for semi-solid batteries.

[0054] For details, please see Figure 2 The production system of copper foil for semi-solid batteries includes a copper dissolving tank 10, a multi-stage filter 20, a clean liquid tank 30, an electrolysis device 40, a chromate electroplating device 50, and a winding roller 60. The liquid outlet of the copper dissolving tank 10 is connected to the liquid inlet of the multi-stage filter 20 through a pipeline, the liquid outlet of the multi-stage filter 20 is connected to the liquid inlet of the clean liquid tank 30 through a pipeline, the liquid outlet of the clean liquid tank 30 is connected to the upper end of the electrolysis device 40, and the winding roller 60 is located at the rear end of the chromate electroplating device 50. The electrolysis device 40 includes an electrolytic cell 401, a cathode roller 402, a stripping roller 403, a polishing brush 404, and a spray pipe 405. The cathode roller 402 is located directly above the electrolytic cell 401. The stripping roller 403, the polishing brush 404, and the spray pipe 405 are successively arranged around the upper end of the cathode roller 402. The nozzle of the spray pipe 405 is at an angle of 35 to 40 degrees to the horizontal direction.

[0055] The copper dissolving tank 10 is used to mix copper and sulfuric acid to completely dissolve the copper in the sulfuric acid to generate a copper sulfate solution.

[0056] The multi-stage filter 20 is used to remove insoluble impurities in the copper sulfate solution, thereby obtaining a pure copper sulfate solution. The multi-stage filter 20 is preferably a four-stage filter.

[0057] The clean liquid tank 30 is used to mix the copper sulfate solution and additives to form an electrolyte to be used;

[0058] The electrolysis device 40 is used to generate copper foil by energizing the copper ions in the electrolyte. The sulfuric acid generated after electrolysis can be reused to dissolve the copper wire.

[0059] The chromate electroplating device 50 is used to electroplate an anti-oxidation layer on the surface of the copper foil;

[0060] The winding roller 60 is used to wind up the copper foil.

[0061] To extend the service life of cathode roller 402 and increase the roughness of the copper foil, the electrolysis device 40 of the present invention utilizes a post-acid spraying process. After the copper foil is stripped by stripping roller 403, a spray pipe 405 is positioned on one side of cathode roller 402 to spray acid onto cathode roller 402. A polishing brush 404 is positioned between stripping roller 403 and spray pipe 405.

[0062] At the same time, since it is not desirable for the copper foil tension to be too large or too small, and the distance between the chromate electroplating device 50 and the winding roller 60 to be too large will cause the tension of the copper foil to be uncontrollable under the influence of gravity, in order to make the tension of the copper foil controllable, a knife groove roller 70 is set between the chromate electroplating device 50 and the winding roller 60. The knife groove roller 70 can not only support the copper foil, but also rely on the knife groove structure to form a stable friction force between the copper foil and the knife groove roller 70, so that the tension of the copper foil is more controllable.

[0063] In order to remove the surface liquid of the copper foil after electroplating, an extrusion roller 501 and two air knives 80 are also arranged between the electroplating device and the knife groove roller 70. The extrusion roller 501 is located in front of the air knife 80, first squeezing the surface of the copper foil, and then blowing the surface of the copper foil dry through the air knife 80.

[0064] The above disclosure is only a preferred embodiment of the present invention, and it is certainly not intended to limit the scope of the present invention. A person skilled in the art can understand that all or part of the processes of the above embodiment and equivalent changes made in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. A method for preparing copper foil for semi-solid batteries, characterized by: The following steps are involved: Step S1, preparing a copper sulfate solution, taking copper wire and sulfuric acid, placing them in a copper dissolving tank, and dissolving them to obtain a mixed copper sulfate solution, wherein: the concentration of sulfuric acid is 340-360g / L, and the ambient temperature in the copper dissolving tank is 65-85°C; the copper sulfate enters a clean liquid tank after multi-stage filtration; the clean liquid copper acid concentration is between 60-75ppm; Step S2: Add additives to the clean liquid tank to form an electrolyte, namely: Add collagen to the clean liquid tank at a rate of 5 g / L and 10 L / h; Add sodium polydisulfide dipropane sulfonate to the clean liquid tank at a rate of 8 g / L and 10 L / h; Add hydroxyethyl cellulose to the clean liquid tank at a rate of 1 g / L and 10 L / h; Step S3, electrolytically producing foil, in an electrolytic cell at 50m 3 A predetermined amount of electrolyte is added at a rate of / h, and then power is applied in the electrolytic cell, and copper foil is produced using a cathode roller with a surface roughness of less than 0.3μm; Step S4: stripping the copper foil. The copper foil formed on the surface of the cathode roller is stripped off by a stripping roller. Then, acid is sprayed on the surface of the cathode roller. The angle between the spray direction of the acid and the horizontal direction is 35-40 degrees. The rotation speed of the cathode roller is 7.6 m / min. The acid spray flow rate is 1-1.5 cubic meters per hour. This removes the oxide layer on the surface of the cathode roller. No roughening treatment of the copper foil is required. Step S5, anti-oxidation treatment of the copper foil, performing chromate anti-oxidation electroplating treatment on the peeled copper foil, wherein the chromate solution has a chromium ion concentration of 1 g / L and a phosphate ion concentration of 1500 mg / L.

2. The method for preparing a copper foil for a semi-solid battery according to claim 1, wherein: The following steps are also included: Step S6: regularly polishing and grinding the surface of the cathode roller to make the surface roughness of the copper foil less than 0.3 μm.

3. The method for preparing a copper foil for a semi-solid battery according to claim 1, wherein: A 320-grit grinding wheel is used for grinding.

4. The method for preparing a copper foil for a semi-solid battery according to claim 1, wherein: The following steps are also included: Step S7, winding the copper foil, the distance between the stripping roller and the winding roller is no more than 5 meters, and the winding tension is 120N.

5. The method for preparing a copper foil for a semi-solid battery according to claim 1, wherein: It is achieved through a production system for copper foil specifically for semi-solid batteries, wherein the production system for copper foil specifically for semi-solid batteries includes a copper dissolving tank, a multi-stage filter, a liquid purification tank, an electrolysis device, a chromate electroplating device, and a winding roller. The liquid outlet of the copper dissolving tank is connected to the liquid inlet of the multi-stage filter through a pipeline, the liquid outlet of the multi-stage filter is connected to the liquid inlet of the liquid purification tank through a pipeline, the liquid outlet of the liquid purification tank is connected to the upper end of the electrolysis device, and the winding roller is located at the rear end of the chromate electroplating device. The electrolysis device includes an electrolytic cell, a cathode roller, a stripping roller, a polishing brush, and a spray pipe. The cathode roller is located directly above the electrolytic cell, and the stripping roller, polishing brush, and spray pipe are successively arranged around the upper end of the cathode roller. The nozzle of the spray pipe is at an angle of 35 to 40 degrees to the horizontal direction.

6. The method for preparing a copper foil for a semi-solid battery according to claim 5, wherein: A knife groove roller is arranged between the chromate electroplating device and the winding roller.

7. The method for preparing a copper foil for semi-solid-state batteries according to claim 5, wherein: An extrusion roller and two air knives are also provided between the electroplating device and the knife groove roller, and the extrusion roller is located before the air knife.

8. The method for preparing a copper foil for semi-solid-state batteries according to claim 5, wherein: The multi-stage filter uses a four-stage filter.

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