Method for continuously preparing gradient porous electrolytic copper foil

Abstract

The invention discloses a method for continuously preparing gradient porous electrolytic copper foil, and particularly relates to the technical field of electrolytic copper foil. The method comprises the following steps: firstly, preparing a nonporous electrolytic copper foil base layer by utilizing a base layer electrolyte through pulse current; then, the porous electrolyte is continuously used for further electrolytic deposition of the porous copper foil on the non-porous copper foil base layer by using gradient current; finally, the obtained porous copper foil is subjected to a chromium-free passivation technology and a gradient drying technology, and the gradient porous electrolytic copper foil suitable for the solid-state battery is obtained. The forward pulse and the reverse pulse are adopted, the density can be improved, the internal stress and the warping risk are reduced, and a stable substrate is provided for the porous layer; a porous layer is constructed through gradient current, gradient distribution of pores is achieved, interlayer binding force is enhanced, and interface stripping is avoided; and gradient drying is adopted, oxidation is prevented, and the micro-crack risk is eliminated.

Description

Technical Field

[0001] The invention relates to the technical field of electrolytic copper foil, and in particular to a method for continuously preparing gradient porous electrolytic copper foil. Background Art

[0002] In the fields of electronic devices, electric vehicles, and energy storage, driven by global energy shortages, technological advancements, policy support, and expanding market demand, lithium batteries, characterized by safety, no memory effect, excellent cycle performance, and long life, will continue to experience rapid growth in the future. Electrolytic copper foil, a key core material in lithium batteries, serves as both a carrier for the negative electrode active material and a collector and conductor for negative electrode electrons. As lithium batteries develop, it will also generate significant market demand.

[0003] Lithium metal, with its high theoretical specific capacity of 3860 mAh / g, minimum density of 0.59 g / cm3, and the most negative electrochemical potential compared to the standard hydrogen electrode (-3.04 V), is an ideal anode material for the next generation of high-energy-density batteries. However, lithium metal batteries face more severe challenges than lithium-ion batteries, such as lithium dendrite growth and solid-solid interface issues. Compared to flat copper foil, porous copper foil, due to its unique three-dimensional structure, can significantly increase the contact area between the current collector and the active material, inhibit dendrite formation, and alleviate volume expansion stress, making it a key material for the next generation of solid-state batteries.

[0004] Chinese invention CN116288543A discloses a method for producing porous copper foil through electrolysis. The method involves spraying a dotted insulating, acid-resistant coating on the surface of a cathode roller, followed by continuous electroplating to produce the porous electrolytic copper foil. Chinese patent CN109440108A discloses a copper foil punching machine and production process based on chemical etching. Using a 20wt% ferric chloride solution as the etching solution improves the quality of the finished product, while continuous production increases production efficiency and makes the production process more environmentally friendly. However, porous copper foil produced through chemical etching is susceptible to oxidation, resulting in high resistivity. Mechanical punching can easily leave copper shavings, while laser cutting requires significant equipment investment. While these patents allow for continuous production to a certain extent, the irregular through-holes in the porous copper foil can easily cause the foil to tear when peeled from the cathode roller, leading to breakage and production stagnation. Furthermore, insulating material can easily fall off during the peeling process and remain in the pores, requiring subsequent impurity removal.

[0005] Chinese patent CN110016697A discloses a method for preparing electrolytic copper foil for high-temperature and high-elongation power batteries and its additives. The additive mainly uses a grain refiner, and the grain refiner is a substance such as a polyethyleneimine derivative, sodium thiopropane sulfonate, polyethylene glycol and an aqueous solution of ethylenethiourea. Although this patent increases the elongation to a certain extent, the tensile strength is relatively low; Chinese patent CN113481550A discloses a method for preparing low-warpage ultra-thin electrolytic copper foil by a subtractive process. By using subtractive processing, the curling rate is reduced to a certain extent, but the process is complicated. Summary of the Invention

[0006] To this end, the present invention provides a method for continuously preparing gradient porous electrolytic copper foil to solve the problems in the prior art.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] According to the present invention, a method for continuously preparing a gradient porous electrolytic copper foil is provided, the method comprising:

[0009] Step 1: Base Deposition

[0010] A non-porous electrolytic copper foil base layer is prepared using a base electrolyte by using a pulse current;

[0011] Step 2: Porous layer deposition

[0012] Using a gradient current, the porous electrolyte is further electrolytically deposited on the non-porous copper foil base layer to form a porous copper foil;

[0013] Step 3: Post-processing

[0014] The porous copper foil obtained in step 2 is subjected to a chromium-free passivation process and a gradient drying technology to obtain a gradient porous electrolytic copper foil suitable for solid-state batteries;

[0015] Among them, the base electrolyte contains 90-110 g / L of Cu 2+ , 100-120 g / L H2SO4, 5-15 mg / L Cl - and 40-70 mg / L of a base layer additive comprising sodium poly(dipropylene glycol disulfide), a sulfur-based compound, enzymatically hydrolyzed collagen peptides, hydroxyethyl cellulose, and polyethylene glycol. The enzymatically hydrolyzed collagen peptides (molecular weight 1500-3000 Da) exhibit enhanced thermal stability (no degradation at ≤55°C), reducing brittleness caused by gelatin decomposition and improving base layer elongation. The sulfur-based compound is preferably sodium 2-mercaptoethanol sulfonate, which synergizes with the sodium poly(dipropylene glycol disulfide) to refine grain size and increase tensile strength.

[0016] The porous electrolyte contains 80-90 g / L of Cu 2+, 90-100 g / L H2SO4, 5-15 mg / L Cl - The invention also comprises a porous layer additive at 60-100 mg / L and a pore-forming agent at 100-200 mg / L. The porous layer additive comprises sodium polydisulfide dipropylene glycol sulfonate, carboxymethylated collagen, hydroxyethyl cellulose, and polyethylene glycol. The pore-forming agent comprises EDTA-2Na, potassium tartrate, and a polyethylene oxide-polypropylene oxide block copolymer. The polyethylene oxide-polypropylene oxide block copolymer is preferably Pluronic F127, which forms dynamic micelles, producing more uniform nanoscale pores (porosity controllable between 15-35%).

[0017] Generally, they are brighteners, leveling agents, and dispersants: sodium polydisulfide dipropylene sulfonate and sulfur-based compounds are brighteners to refine grains and increase tensile strength; enzymatic collagen peptides are leveling agents to obtain a smooth surface; hydroxyethyl cellulose and polyethylene glycol are dispersants to promote the movement of protons such as copper to obtain a dense layer.

[0018] Furthermore, the base additive comprises 10-15 mg / L of sodium polydisulfide dipropane sulfonate, 0.5-1 mg / L of sulfide compound, 10-15 mg / L of enzymatically hydrolyzed collagen peptide, 5-10 mg / L of hydroxyethyl cellulose and 15-30 mg / L of polyethylene glycol.

[0019] Furthermore, the porous layer additives include 10-15 mg / L sodium polydisulfide dipropane sulfonate, 30-45 mg / L carboxymethylated collagen, 5-10 mg / L hydroxyethyl cellulose, and 15-30 mg / L polyethylene glycol. The carboxymethylated collagen (molecular weight 3000-5000 Da) can further improve the heat resistance and prevent uneven porosity caused by failure at high temperatures.

[0020] Furthermore, the pore-forming agent includes 50-100 mg / L of EDTA-2Na, 50-100 mg / L of potassium tartrate, and 15-30 mg / L of polyethylene oxide-polypropylene oxide block copolymer.

[0021] Furthermore, the porous layer additives also include a dispersant, with the dispersant added in an amount of 1-2 mg / L. For example, a preferred dispersant is sodium dodecyl sulfate, which reduces the surface tension to ≤40 dyn / cm, improves the dispersibility of the pore-forming agent in the electrolyte, increases pore uniformity, and reduces pore collapse.

[0022] Furthermore, the porous layer additives also include carboxymethylated collagen and an antioxidant, with the antioxidant being 3-8 mg / L. As an example, the antioxidant is preferably 5 mg / L of hydroquinone, which inhibits the oxidative degradation of polyethylene glycol and prolongs the life of the electrolyte.

[0023] Furthermore, in step 1, the pulse current is a forward pulse of 70 to 90 A / dm 2 ,8-12ms; reverse pulse: -3 to -8A / dm 2 ,0.5-1.5ms. Improve density, reduce internal stress and reduce warping.

[0024] Furthermore, in step 2, the starting current of the gradient current is 65-75A / dm 2 , 45-55A / dm at the end 2 . Make the pores gradually change from the surface to the inside, and improve the bonding strength between layers.

[0025] Furthermore, in step three, the surface treatment process employs passivation treatment, and the passivation solution comprises 0.5-2 g / L sodium molybdate, 1-3 g / L nickel sulfate, and 1-3 g / L ascorbic acid; preferably, 0.5 g / L sodium molybdate, 1 g / L nickel sulfate, and 1 g / L ascorbic acid. Passivation improves the copper foil's oxidation resistance.

[0026] Furthermore, in step 3, the gradient drying is divided into a pre-drying zone at 75-80°C, a main drying zone at 100-110°C, and a slow cooling zone at 65-75°C. As an example, low dew point nitrogen (dew point ≤ -40°C) can be introduced to prevent oxidation of the porous layer and avoid microcracks caused by rapid dehydration.

[0027] The gradient porous electrolytic copper foil obtained by the invention has a thickness of 6-12 μm, a tensile strength of ≥300 MPa, an elongation of ≥3%, and a warpage of ≤10 mm, wherein the base layer has a thickness of 3-9 μm, the porous layer has a thickness of 1-6 μm, and the porous layer has a porosity of 10%-30%.

[0028] The present invention has the following advantages:

[0029] The addition of enzymatically hydrolyzed collagen peptides to the base additives of the present invention can improve thermal stability, significantly reduce brittleness, and increase the elongation of copper foil; the addition of sulfur-based compounds synergistically acts with sodium polydisulfide dipropylene sulfonate to refine grains and increase tensile strength. The use of carboxymethylated collagen as a porous layer additive can achieve better high-temperature resistance and avoid uneven pores caused by failure during high-temperature electrolysis. Dispersants can reduce the surface tension of the electrolyte, enhance wettability to the base layer, and reduce pore collapse. Antioxidants can inhibit the oxidative degradation of polyethylene glycol and extend the service life of the electrolyte. The pore-forming agent uses a mixture of EDTA-2Na, potassium tartrate, and polyethylene oxide-polypropylene oxide block copolymers to form dynamic micelles, generate uniform and controllable nanoscale pores, and synergistically regulate the stability of the pore structure.

[0030] In the preparation method of the present invention, forward pulses and reverse pulses are used to improve density, reduce internal stress and warping risks, and provide a stable substrate for the porous layer; gradient current is used to construct the porous layer, achieve pore gradient distribution, enhance interlayer bonding, and avoid interface peeling; gradient drying is used to prevent oxidation and eliminate the risk of microcracks.

[0031] The gradient pore structure of the present invention, with fine surface pores that enhance electrode interface contact and large internal pores that provide lithium ion transmission channels, is adapted to the special current collector requirements of solid-state batteries. The present invention also optimizes mechanical properties. The refined grain size of the sulfur-based compound provides high tensile strength in the base layer, while the collagen peptides resist brittle fracture and provide good ductility in the porous layer, resolving the strength-flexibility trade-off in porous materials.

[0032] The present invention is provided with a gradient structure (dense base layer + gradually changing porous layer) to fundamentally solve the peeling and tearing problem. The peeling stress is evenly dispersed by the base layer, and the warping is reduced.

[0033] The method of the present invention achieves the controllable preparation of high-performance gradient porous copper foil through material formulation innovation (composite additives / pore-forming agents), precise process control (pulse / gradient current / gradient drying) and environmentally friendly design (chromium-free passivation), solving the pain points of traditional porous copper foil such as uneven porosity, poor mechanical properties, and unstable process, and especially meeting the strict requirements of solid-state batteries for current collectors. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the embodiments or the description of the prior art. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other implementation drawings based on the provided drawings without inventive effort.

[0035] The structures, proportions, sizes, etc. illustrated in this specification are intended only to complement the contents disclosed herein and to facilitate understanding and reading by persons familiar with the art. They are not intended to limit the conditions under which the present invention may be implemented and therefore have no substantive technical significance. Any structural modifications, changes in proportions, or adjustments in sizes, without affecting the efficacy and objectives of the present invention, shall still fall within the scope of the technical contents disclosed herein.

[0036] Figure 1 A device for preparing a porous electrolytic copper foil provided in Example 1 of the present invention;

[0037] Figure 2 A schematic cross-sectional view of a gradient porous copper foil provided in Example 1 of the present invention;

[0038] Figure 3A device for preparing a porous electrolytic copper foil provided in Example 2 of the present invention;

[0039] Figure 4 A schematic cross-sectional view of a gradient porous copper foil provided in Example 2 of the present invention;

[0040] Figure 5 A device for preparing a porous electrolytic copper foil provided in Example 3 of the present invention;

[0041] Figure 6 A schematic cross-sectional view of a gradient porous copper foil provided in Example 3 of the present invention;

[0042] In the figure: 1-winding roller; 2-electrolytic gradient copper foil; 3-drying box; 4-surface treatment; 5-peeling roller; 6-base electrolyte inlet pipe; 7-cathode roller; 8-anode tank; 9-liquid outlet; 10-liquid outlet pipe; 11-porous electrolyte inlet pipe; 12-first porous electrolyte inlet pipe; 13-second porous electrolyte inlet pipe. DETAILED DESCRIPTION

[0043] The following describes the implementation of the present invention using specific embodiments. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. Obviously, the embodiments described are only a portion of the present invention, not all of it. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are intended to fall within the scope of protection of the present invention.

[0044] A device for continuously preparing gradient porous electrolytic copper foil:

[0045] The cathode roller 7 rotates in the anode tank 8 containing the electrolyte in the direction of the arrow shown on the cathode roller 7. When the cathode roller 7 rotates and immerses in the electrolyte in the anode tank 8, the base layer electrolyte is first electrolyzed using the base layer electrolyte inlet pipe 6 to quickly obtain a thinner base layer, and the remaining base layer electrolyte is discharged through the outlet hole 9 and the outlet pipe 10; then, the cathode roller 7 continues to rotate, and the porous electrolyte inlet pipe 11 is used to continue electrolytically depositing the porous copper foil on the base layer; finally, the base layer and the porous layer copper foil are peeled off by the peeling roller 5, and then conventional surface treatment 4, drying in the drying box 3, and the electrolytic gradient copper foil 2 is wound by the winding roller 1 to obtain a gradient porous electrolytic copper foil suitable for solid-state batteries.

[0046] Preferably, the anode tank 8 has a base electrolyte inlet tank hole axially opened at one end where the cathode roller 7 is rotated and immersed, and the base electrolyte tank hole is the same as the axial length of the surface of the cathode roller 7. The base electrolyte tank hole is connected to the base electrolyte inlet pipe 6, and the inner cavity diameters of the base electrolyte tank hole and the base electrolyte inlet pipe 6 are equal; the base electrolyte is transported through the base electrolyte inlet pipe 6, flows into the anode tank 8 through the base electrolyte tank hole, and then flows out through the outlet pipe 9 below the anode tank 8.

[0047] Preferably, the anode tank 8 has at least one porous electrolyte inlet hole axially opened at the end of the cathode roller 7 where the cathode roller 7 rotates for leaching, and the same length as the axial length of the cathode roller 7. The porous electrolyte hole is connected to a porous electrolyte inlet pipe 11, and the inner diameters of the porous electrolyte hole and the porous electrolyte inlet pipe 11 are equal. The porous electrolyte is transported through the porous electrolyte inlet pipe 11, flows through the porous electrolyte hole into the anode tank 8, and then flows out through the outlet pipe 10 below the anode tank 8.

[0048] Preferably, the bottom of the anode tank 8 has an axially defined liquid outlet hole 9 extending the same axial length as the surface of the cathode roller 7. A liquid outlet pipe 10 is connected to the liquid outlet hole 9. The bottom of the anode tank 8 extends from the immersion end of the cathode roller 7 to the leaching end of the anode tank 8, extending from 1 / 2 to 3 / 4 of the circumference. The inner diameters of the liquid outlet hole 9 and the liquid outlet pipe 10 of the anode tank 8 are equal. The porous electrolyte is transported through the liquid outlet pipe 10, flows through the liquid outlet hole 9 into the anode tank 8, and then returns through the overflow pipes at both ends of the anode tank 8.

[0049] Preferably, in order to better control the flow balance of the base electrolyte and the porous electrolyte in the anode tank 8, the cross-sectional area of ​​the base electrolyte inlet pipe 6 is equal to the cross-sectional area of ​​the porous electrolyte inlet pipe 11, the flow rates of the base electrolyte and the porous electrolyte are equal, and the sum of the cross-sectional area of ​​the base electrolyte inlet pipe 6 and the cross-sectional area of ​​the porous electrolyte inlet pipe 11 is ≤ the cross-sectional area of ​​the outlet pipe.

[0050] Example 1

[0051] This embodiment provides an apparatus and process for producing 6μm gradient porous electrolytic copper foil:

[0052] The device is as Figure 1 As shown, it includes a winding roller 1; an electrolytic gradient copper foil 2; a drying box 3; a surface treatment 4; a stripping roller 5; a base electrolyte inlet pipe 6; a cathode roller 7; an anode tank 8; a liquid outlet 9; a liquid outlet pipe 10; and a porous electrolyte inlet pipe 11.

[0053] The liquid outlet pipe 10 is located at the bottom of the anode tank 8 near the outlet, that is, at 1 / 2 of the direction from the immersion end to the leaching end of the cathode roller 7 along the circumferential direction of the anode tank 8.

[0054] The cathode roller 7 rotates in the anode tank 8 containing the electrolyte along the direction of the arrow shown on the cathode roller 7. When the cathode roller 7 rotates and immerses into the electrolyte in the anode tank 8, the base electrolyte is first electrolyzed by the base electrolyte inlet pipe 6, and then quickly (flow rate 40-60m 3 / h) to obtain a thinner base layer, and the remaining base electrolyte is discharged through the outlet hole 9 and the outlet pipe 10; then, the cathode roller 7 continues to rotate, and the porous electrolyte inlet pipe 11 is used to feed the porous electrolyte (the flow rate is the same as the base electrolyte flow rate, 40-60m 3 / h) continuing to electrolytically deposit a porous copper foil on the base layer; finally, the base layer and the porous layer copper foil are peeled off by a peeling roller 5, and then subjected to a conventional surface treatment 4, dried in a drying oven 3, and the electrolytic gradient copper foil 2 is wound up by a winding roller 1 to obtain a gradient porous electrolytic copper foil suitable for solid-state batteries.

[0055] Specific preparation process:

[0056] Step 1: Base Deposition

[0057] By pulse current (forward pulse 70A / dm 2 ,12ms; reverse pulse: -3A / dm 2 ,1.5ms, base electrolyte temperature 50℃, flow rate 48m 3 / h), using the base electrolyte to prepare a non-porous electrolytic copper foil base;

[0058] Step 2: Porous layer deposition

[0059] Using gradient current (initial current is 65A / dm 2 , 55A / dm at the end 2 , temperature 50℃, flow rate 48m 3 / h), further electrolytically depositing porous copper foil on the non-porous copper foil base layer with the porous electrolyte;

[0060] Step 3: Post-processing

[0061] The porous copper foil obtained in step 2 is subjected to a chromium-free passivation process and a gradient drying technology to obtain a gradient porous electrolytic copper foil suitable for solid-state batteries; the cross-sectional diagram of the gradient porous copper foil is shown in FIG. Figure 2 shown.

[0062] Passivation process: The passivation solution includes sodium molybdate, nickel sulfate and ascorbic acid (sodium molybdate 0.5g / L, nickel sulfate 1g / L, ascorbic acid 1g / L, the same below); the pH of the passivation solution is 3.4, the passivation treatment temperature is 30-35°C, and the passivation treatment current is 2A / dm 2 ;

[0063] Gradient drying: 75℃, 10s pre-drying zone, 100℃, 15s main drying zone and 65℃, 5s slow cooling zone.

[0064] Low dew point nitrogen (dew point ≤ -40°C) is introduced to prevent oxidation of the porous layer and avoid micro cracks caused by rapid dehydration.

[0065] Among them, the base electrolyte contains 90g / L Cu 2+ , 100g / L H2SO4, 5mg / L Cl - and 70 mg / L of base additives; base additives 10 mg / L of sodium polydisulfide propane sulfonate, 1 mg / L of sulfur-based compounds, 15 mg / L of enzymatic collagen peptides, 5 mg / L of hydroxyethyl cellulose and 15 mg / L of polyethylene glycol.

[0066] Porous electrolyte: including 90g / L Cu 2+ , 90g / L H2SO4, 5mg / L Cl - , 100 mg / L of porous layer additives, 1 mg / L of sodium dodecyl sulfate, and 100 mg / L of pore-forming agent; the porous layer additives contain 10 mg / L of sodium polydisulfide dipropylene sulfonate, 45 mg / L of carboxymethylated collagen, 5 mg / L of hydroxyethyl cellulose, 5 mg / L of hydroquinone and 15 mg / L of polyethylene glycol; the pore-forming agents include 100 mg / L of EDTA-2Na, 50 mg / L of potassium tartrate and 15 mg / L of polyethylene oxide-polypropylene oxide block copolymer.

[0067] Testing revealed that the electrolytic copper foil had a thickness of 6.5 μm, a tensile strength of 311 MPa, an elongation of 3.1%, and a warpage of 8.3 mm. The base layer had a thickness of 3.6 μm, the porous layer had a thickness of 2.9 μm, and the porosity of the porous layer was 12%.

[0068] Example 2

[0069] This embodiment provides an apparatus and process for producing 6μm gradient porous electrolytic copper foil:

[0070] The device is as Figure 3 As shown, except for the liquid outlet pipe 10 and the liquid outlet hole 9, which are different from those in Example 1, the other devices are exactly the same as those in Example 1. The liquid outlet pipe 10 is located at the bottom of the anode tank 8 near the outlet, that is, at 3 / 4 of the distance from the cathode roller immersion end to the leaching end along the circumference of the anode tank 8.

[0071] Specific preparation process:

[0072] Step 1: Base Deposition

[0073] By pulse current (forward pulse 80A / dm 2 ,10ms; reverse pulse: -5A / dm2 ,1.0ms, base electrolyte temperature 50℃, flow rate 48m 3 / h), using the base electrolyte to prepare a non-porous electrolytic copper foil base;

[0074] Step 2: Porous layer deposition

[0075] Using gradient current (70A / dm 2 , 50A / dm at the end 2 , temperature 50℃, flow rate 48m 3 / h), further electrolytically depositing porous copper foil on the non-porous copper foil base layer with the porous electrolyte;

[0076] Step 3: Post-processing

[0077] The porous copper foil obtained in step 2 is subjected to a chromium-free passivation process and a gradient drying technology to obtain a gradient porous electrolytic copper foil suitable for solid-state batteries; the cross-sectional diagram of the gradient porous copper foil is shown in FIG. Figure 4 shown.

[0078] Passivation process: The passivation solution includes sodium molybdate, nickel sulfate and ascorbic acid; the pH of the passivation solution is 3.4, the passivation treatment temperature is 30-35°C, and the passivation treatment current is 2A / dm 2 ;

[0079] Gradient drying: 80℃, 10s pre-drying zone, 110℃, 15s main drying zone and 75℃, 5s slow cooling zone.

[0080] Low dew point nitrogen (dew point ≤ -40°C) is introduced to prevent oxidation of the porous layer and avoid micro cracks caused by rapid dehydration.

[0081] Among them, the base electrolyte contains 110g / L Cu 2+ , 120g / L H2SO4, 10mg / L Cl - and 70 mg / L of base additives; base additives 10 mg / L of sodium polydisulfide propane sulfonate, 0.5 mg / L of sulfur-based compounds, 10 mg / L of enzymatic collagen peptides, 10 mg / L of hydroxyethyl cellulose and 30 mg / L of polyethylene glycol.

[0082] Porous electrolyte: including 80g / L Cu 2+ , 100g / L H2SO4, 15mg / L Cl -, 100 mg / L of porous layer additives and 100 mg / L of pore-forming agent; the porous layer additives contain 15 mg / L of sodium polydisulfide dipropylene sulfonate, 30 mg / L of carboxymethylated collagen, 5 mg / L of hydroxyethyl cellulose and 30 mg / L of polyethylene glycol; the pore-forming agents include 50 mg / L of EDTA-2Na, 100 mg / L of potassium tartrate and 15 mg / L of polyethylene oxide-polypropylene oxide block copolymer.

[0083] Testing revealed that the electrolytic copper foil had a thickness of 6.2 μm, a tensile strength of 331 MPa, an elongation of 3.3%, and a warpage of 5.2 mm. The base layer had a thickness of 4.2 μm, the porous layer had a thickness of 2.0 μm, and the porosity of the porous layer was 14%.

[0084] Example 3

[0085] This embodiment provides an apparatus and process for producing 6μm gradient porous electrolytic copper foil:

[0086] The device of this embodiment is as follows Figure 5 As shown, the device differs from the device of Example 1 in that the porous electrolyte inlet pipe is divided into a first porous electrolyte inlet pipe 12 and a second porous electrolyte inlet pipe 13; they are respectively arranged at the end of the cathode roller 7 rotating and leaching and at a position 3 / 4 of the way from the immersion end of the cathode roller 7 to the leaching end along the circumference of the anode tank 8. The outlet pipe 10 is located at the bottom of the anode tank 8 near the outlet, that is, at a position 1 / 2 of the way from the immersion end of the cathode roller 7 to the leaching end along the circumference of the anode tank 8.

[0087] Specific preparation process:

[0088] Step 1: Base Deposition

[0089] By pulse current (forward pulse 90A / dm 2 ,8ms; reverse pulse: -8A / dm 2 ,0.5ms, base electrolyte temperature 50℃, flow rate 48m 3 / h), using the base electrolyte to prepare a non-porous electrolytic copper foil base;

[0090] Step 2: Double porous layer deposition

[0091] Using gradient current (75A / dm 2 , 45A / dm at the end 2 , temperature 50℃, flow rate 48m 3 / h), further electrolytically depositing porous copper foil on the non-porous copper foil base layer using porous electrolyte 1 and porous electrolyte 2 respectively;

[0092] Step 3: Post-processing

[0093] The porous copper foil obtained in step 2 is subjected to a chromium-free passivation process and a gradient drying technology to obtain a gradient porous electrolytic copper foil suitable for solid-state batteries; the cross-sectional diagram of the gradient porous copper foil is shown in FIG. Figure 6 shown.

[0094] Passivation process: The passivation solution includes sodium molybdate, nickel sulfate and ascorbic acid; the pH of the passivation solution is 3.4, the passivation treatment temperature is 30-35°C, and the passivation treatment current is 2A / dm 2 ;

[0095] Gradient drying: 80℃, 10s pre-drying zone, 110℃, 15s main drying zone and 65℃, 5s slow cooling zone.

[0096] Low dew point nitrogen (dew point ≤ -40°C) is introduced to prevent oxidation of the porous layer and avoid micro cracks caused by rapid dehydration.

[0097] Among them, the base electrolyte: contains 100g / L Cu 2+ , 110g / L H2SO4, 10mg / L Cl - and 50 mg / L of base additives; base additives 12 mg / L of sodium polydisulfide propane sulfonate, 0.8 mg / L of sulfur-based compounds, 12 mg / L of enzymatic collagen peptides, 8 mg / L of hydroxyethyl cellulose and 20 mg / L of polyethylene glycol.

[0098] Porous electrolyte 1: including 85g / L Cu 2+ , 95g / L H2SO4, 10mg / L Cl - , 80 mg / L of porous layer additives and 150 mg / L of pore-forming agent; the porous layer additives contain 12 mg / L of sodium polydisulfide dipropylene sulfonate, 35 mg / L of carboxymethylated collagen, 8 mg / L of hydroxyethyl cellulose and 20 mg / L of polyethylene glycol; the pore-forming agents include 80 mg / L of EDTA-2Na, 80 mg / L of potassium tartrate and 20 mg / L of polyethylene oxide-polypropylene oxide block copolymer.

[0099] Porous electrolyte 2: including 80g / L Cu 2+ , 100g / L H2SO4, 15mg / L Cl - , 100 mg / L of porous layer additives and 100 mg / L of pore-forming agent; the porous layer additives contain 15 mg / L of sodium polydisulfide dipropylene sulfonate, 30 mg / L of carboxymethylated collagen, 5 mg / L of hydroxyethyl cellulose and 30 mg / L of polyethylene glycol; the pore-forming agents include 50 mg / L of EDTA-2Na, 100 mg / L of potassium tartrate and 15 mg / L of polyethylene oxide-polypropylene oxide block copolymer.

[0100] Testing revealed that the electrolytic copper foil had a thickness of 6.1 μm, a tensile strength of 316 MPa, an elongation of 3.0%, and a warpage of 4.2 mm. The base layer had a thickness of 3.3 μm, the porous layer had a thickness of 2.8 μm, the porous layer had a porosity of 14%, and the porous layer 1 had a porosity of 30%.

[0101] Comparative Example 1

[0102] This comparative example provides an apparatus and process for producing 6μm gradient porous electrolytic copper foil:

[0103] The base electrolyte of this comparative example does not contain collagen peptides and sulfur-based compounds, and is otherwise identical to that of Example 1.

[0104] Testing revealed that the electrolytic copper foil had a thickness of 6.2 μm, a tensile strength of 278 MPa, an elongation of 1.8%, and a warpage of 12.1 mm. The base layer had a thickness of 4.1 μm, the porous layer had a thickness of 2.1 μm, and the porosity of the porous layer was 9%.

[0105] Without the addition of collagen peptides and sulfur-based compounds, the elongation and tensile strength will be reduced, indicating that collagen peptides play a key role in improving toughness and sulfur-based compounds have a strengthening effect in refining grains; the increase in warpage also shows that without the addition of collagen peptides and sulfur-based compounds, stress will be out of control. It can be seen that enzymatic hydrolysis of collagen peptides improves ductility and sulfur-based compounds strengthen tensile strength.

[0106] Comparative Example 2

[0107] This comparative example provides an apparatus and process for producing 6μm gradient porous electrolytic copper foil:

[0108] In this comparative example, the collagen peptide in the base electrolyte was replaced with gelatin, and the rest was exactly the same as in Example 1.

[0109] Testing revealed that the electrolytic copper foil had a thickness of 6.4 μm, a tensile strength of 292 MPa, an elongation of 2.5%, and a warpage of 10.8 mm. The base layer had a thickness of 3.8 μm, the porous layer had a thickness of 2.6 μm, and a porosity of 10%.

[0110] Gelatin has a large molecular weight and poor dispersibility, and cannot be effectively embedded in the copper lattice like enzymatic collagen peptides, resulting in weakened inter-granular bonding and reduced toughness. Gelatin has weak adsorption and insufficient control over the electrolyte flow field, hindering the uniform distribution of pore-forming agents. Gelatin's stress buffering effect is weaker than collagen peptides, and the internal stress of the deposit increases.

[0111] Comparative Example 3

[0112] This comparative example provides an apparatus and process for producing 6μm gradient porous electrolytic copper foil:

[0113] The base electrolyte of this comparative example does not contain sulfur-based compounds, and the rest is completely consistent with Example 1.

[0114] Testing revealed that the electrolytic copper foil had a thickness of 6.2 μm, a tensile strength of 288 MPa, an elongation of 2.8%, and a warpage of 9.5 mm. The base layer had a thickness of 4.2 μm, the porous layer had a thickness of 2.0 μm, and the porosity of the porous layer was 11%.

[0115] Sulfur-based compounds are strong grain refiners. Their absence increases grain size and reduces strength. Collagen peptides still provide some toughness support. Sulfur-based compounds promote the adsorption of pore-forming agents, but their absence reduces pore uniformity.

[0116] Comparative Example 4

[0117] This comparative example provides an apparatus and process for producing 6μm gradient porous electrolytic copper foil:

[0118] In this comparative example, the carboxymethylated collagen in the porous layer additive was replaced with hydrolyzed collagen (CAS), and the rest was the same as in Example 1.

[0119] Testing revealed that the electrolytic copper foil had a thickness of 6.3 μm, a tensile strength of 301 MPa, an elongation of 3.2%, and a warpage of 9.1 mm. The base layer had a thickness of 3.6 μm, the porous layer had a thickness of 2.7 μm, and the porosity of the porous layer was 10%.

[0120] Carboxymethylated collagen contains hydrophilic groups (-CH2COOH), which can guide the self-assembly of pore-forming agents at the electrode interface. Hydrolyzed collagen lacks this function, resulting in a disordered pore structure. Hydrolyzed collagen also has a weak ability to complex copper ions, reducing the deposition rate.

[0121] Comparative Example 5

[0122] This comparative example provides an apparatus and process for producing 6μm gradient porous electrolytic copper foil:

[0123] The pore-forming agents in this comparative example are EDTA-2Na and potassium tartrate, and the rest are completely consistent with those in Example 1.

[0124] Testing revealed that the electrolytic copper foil had a thickness of 6.4 μm, a tensile strength of 352 MPa, an elongation of 2.2%, and a warpage of 5.3 mm. The base layer had a thickness of 4.2 μm, the porous layer had a thickness of 2.2 μm, and the porosity of the porous layer was 8%.

[0125] The polyethylene oxide-polypropylene oxide block copolymer serves as the core of the pore-forming template, its micellar structure promoting the formation of through-pores. Using EDTA / potassium tartrate alone only produces micropores (<100 nm) with insufficient macroporosity. This reduction in porosity leads to increased density but decreased elongation.

[0126] Comparative Example 6

[0127] This comparative example provides an apparatus and process for producing 6μm gradient porous electrolytic copper foil:

[0128] This comparative example does not use forward pulse and reverse pulse, and directly uses the current density of 80A / dm 2 , and the rest are completely consistent with Example 1.

[0129] Testing revealed that the electrolytic copper foil had a thickness of 6.6 μm, a tensile strength of 265 MPa, an elongation of 1.6%, and a warpage of 15.3 mm. The base layer had a thickness of 2.4 μm, the porous layer had a thickness of 4.2 μm, and a porosity of 1.6%.

[0130] Pulse current (forward deposition + reverse dissolution) can inhibit the formation of copper foil columnar crystals and obtain equiaxed fine grains; constant current (80A / dm 2 ) leads to the coarsening of columnar grains and a surge in brittleness. High-speed deposition causes residual stress accumulation, and the stress release is uneven after the copper foil is peeled off from the cathode roller surface.

[0131] Comparative Example 7

[0132] This comparative example provides an apparatus and process for producing 6μm gradient porous electrolytic copper foil:

[0133] This comparative example does not use a gradient current, but directly uses a current density of 60A / dm 2 , and the rest are completely consistent with Example 1.

[0134] Testing revealed that the electrolytic copper foil had a thickness of 6.1 μm, a tensile strength of 321 MPa, an elongation of 2.6%, and a warpage of 11.7 mm. The base layer had a thickness of 3.8 μm, the porous layer had a thickness of 2.3 μm, and the porosity of the porous layer was 9%.

[0135] Gradient current (65→55A / dm 2 ) makes the pores increase from the base layer to the surface layer; constant current (60A / dm 2 ) leads to uneven pore distribution (dense near the base layer and sparse on the surface), which induces interfacial stress.

[0136] Although the present invention has been described in detail above using general descriptions and specific embodiments, it will be apparent to those skilled in the art that modifications and improvements may be made thereto. Therefore, such modifications and improvements, without departing from the spirit of the present invention, are intended to be within the scope of protection claimed herein.

Claims

1. A method for continuously preparing gradient porous electrolytic copper foil, characterized in that: The method comprises: Step 1: Base Deposition A non-porous electrolytic copper foil base layer is prepared using a base electrolyte by using a pulse current; Step 2: Porous layer deposition Using a gradient current, the porous electrolyte is further electrolytically deposited on the non-porous copper foil base layer to form a porous copper foil; Step 3: Post-processing The porous copper foil obtained in step 2 is subjected to a chromium-free passivation process and a gradient drying technology to obtain a gradient porous electrolytic copper foil suitable for solid-state batteries; Among them, the base electrolyte contains 90-110 g / L of Cu 2+ , 100-120 g / L H2SO4, 5-15 mg / L Cl - and 40 to 70 mg / L of a base additive, wherein the base additive comprises sodium polydisulfide dipropane sulfonate, a sulfur-based compound, enzymatically hydrolyzed collagen peptide, hydroxyethyl cellulose, and polyethylene glycol; The porous electrolyte contains 80-90 g / L of Cu 2+ , 90-100 g / L H2SO4, 5-15 mg / L Cl - , 60-100 mg / L of a porous layer additive and 100-200 mg / L of a pore-forming agent, wherein the porous layer additive comprises sodium polydisulfide dipropylene sulfonate, carboxymethylated collagen, hydroxyethyl cellulose and polyethylene glycol, and the pore-forming agent comprises EDTA-2Na, potassium tartrate and polyethylene oxide-polypropylene oxide block copolymer.

2. The method for continuously preparing a gradient porous electrolytic copper foil according to claim 1, characterized in that: The base additive comprises 10-15 mg / L of sodium polydisulfide dipropane sulfonate, 0.5-1 mg / L of sulfide-based compounds, 10-15 mg / L of enzymatically hydrolyzed collagen peptides, 5-10 mg / L of hydroxyethyl cellulose, and 15-30 mg / L of polyethylene glycol.

3. The method for continuously preparing a gradient porous electrolytic copper foil according to claim 1, characterized in that: The porous layer additive contains 10-15 mg / L of sodium polydisulfide dipropane sulfonate, 30-45 mg / L of carboxymethylated collagen, 5-10 mg / L of hydroxyethyl cellulose and 15-30 mg / L of polyethylene glycol.

4. The method for continuously preparing a gradient porous electrolytic copper foil according to claim 1, characterized in that: The pore-forming agent comprises 50-100 mg / L of EDTA-2Na, 50-100 mg / L of potassium tartrate and 15-30 mg / L of polyethylene oxide-polypropylene oxide block copolymer.

5. The method for continuously preparing a gradient porous electrolytic copper foil according to claim 3, characterized in that: The porous layer additive also includes a dispersant, and the amount of the dispersant added is 1-2 mg / L.

6. The method for continuously preparing gradient porous electrolytic copper foil according to claim 3, characterized in that: The porous layer additive also includes an antioxidant, and the added amount of the antioxidant is 3-8 mg / L.

7. The method for continuously preparing a gradient porous electrolytic copper foil according to claim 1, characterized in that: In step 1, the pulse current is a positive pulse of 70 to 90A / dm 2 ,8-12ms; reverse pulse: -3 to -8A / dm 2 ,0.5-1.5ms.

8. The method for continuously preparing a gradient porous electrolytic copper foil according to claim 1, characterized in that: In step 2, the starting current of the gradient current is 65-75A / dm 2 , 45-55A / dm at the end 2 .

9. The method for continuously preparing gradient porous electrolytic copper foil according to claim 1, characterized in that: In the step 3, the surface treatment process adopts passivation treatment, and the passivation solution includes sodium molybdate, nickel sulfate and ascorbic acid.

10. The method for continuously preparing gradient porous electrolytic copper foil according to claim 1, characterized in that: In the step 3, the gradient drying is divided into a pre-drying zone at 75-80°C, a main drying zone at 100-110°C and a slow cooling zone at 65-75°C.

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