Corrosion resistant slot die

Abstract

This utility model relates to the field of coating die manufacturing technology, and in particular to a corrosion-resistant slot coating die, comprising a substrate layer, a transition layer, a discharge slot, a rounded chamfer, and a functional layer; the rounded chamfer is provided at the discharge end of the discharge slot, and the chamfer radius is 0.1-0.5mm; the functional layer covers both sides of the discharge slot; one side of the transition layer is metallurgically bonded to the functional layer, and the other side of the transition layer is tightly connected to the substrate layer; the substrate layer of this utility model is a rigid support structure, and the interface structure of the transition layer buffers thermal stress; the functional layer is a dense surface layer covering the inner wall of the slot, and its surface forms a continuous passivation film structure. Through the multi-layer structure, the penetration of corrosive media is blocked, and the rounded chamfer design effectively eliminates the dead zone of slurry flow, which can ensure mechanical strength while significantly improving corrosion resistance, and has the advantages of long service life, high precision, and reduced use of precious metals.

Description

Technical Field

[0001] This utility model relates to the field of coating dies, and in particular to a corrosion-resistant slit coating die. Background Technology

[0002] In lithium-ion battery electrode manufacturing, the coating process is a crucial step that determines the uniformity of electrode thickness, the consistency of areal density, and battery performance. The slit extrusion coating die, through its precise flow channel design, controls the slurry flow rate and distribution, directly impacting the coating quality.

[0003] In terms of corrosion resistance, existing die head materials mainly employ stainless steel or cemented carbide. Stainless steel dies are low in cost and easy to process, but their chemical corrosion resistance is insufficient, especially in NMP (N-methylpyrrolidone)-based slurries, high pH values, or fluorine-containing binder systems, where pitting and uniform corrosion are prone to occur. Cemented carbide dies exhibit excellent wear resistance, but their resistance to chemical corrosion in strong acid / alkali slurries is limited, and their processing costs are high.

[0004] Surface coating technologies often employ ceramic coatings or DLC (diamond-like carbon) coatings. While ceramic coatings improve wear resistance, they are brittle and prone to cracking, and peeling off the coating accelerates substrate corrosion. Although DLC coatings have good chemical inertness, their adhesion decreases at high temperatures, and they are also very expensive.

[0005] Material alternatives often include Hastelloy / titanium alloys and engineering plastics. Hastelloy / titanium alloys have excellent corrosion resistance, but they are difficult to process and cost 5-10 times more than stainless steel, making them difficult to use on a large scale. Engineering plastics have strong chemical corrosion resistance, but their rigidity is insufficient and cannot meet the requirements of high-precision coating.

[0006] Among refractory metals, tantalum (Ta) possesses a high melting point, an extremely low ductile-brittle transition temperature, good plasticity and formability, excellent corrosion resistance, wear resistance, creep resistance, and high-temperature mechanical properties. It is widely used in many high-tech fields such as aerospace, nuclear industry, metallurgy, chemical industry, and national defense. Niobium (Nb) has a melting point of 2467℃ and a density of 8.6 g / cm³. 2 It has excellent plasticity and good high-temperature performance. It maintains high plasticity, strength and thermal conductivity at 1000℃ and has good corrosion resistance at room temperature. Utility Model Content

[0007] This invention aims to provide a corrosion-resistant slot coating die head that achieves strong bonding between the substrate layer and the functional layer through a transition layer, effectively eliminates dead zones in slurry flow by utilizing a rounded chamfer design, ensures mechanical strength while significantly improving corrosion resistance, and combines long life, high precision, and reduced use of precious metals.

[0008] To achieve the above objectives, this utility model provides a corrosion-resistant slot coating die, comprising a substrate layer, a transition layer, a discharge slot, a rounded chamfer, and a functional layer;

[0009] The rounded chamfer is provided at the discharge end of the discharge slit, and the chamfer radius of the rounded chamfer is 0.1 to 0.5 mm;

[0010] The discharge slit is covered with functional layers on both sides;

[0011] One side of the transition layer is metallurgically bonded to the functional layer, and the other side of the transition layer is tightly connected to the substrate layer;

[0012] In the aforementioned corrosion-resistant slot coating die, the width of the discharge slot is 50–500 μm; and the thickness of the substrate layer is 5–15 mm.

[0013] In the aforementioned corrosion-resistant slot coating die, the thickness of the transition layer is 5–10 μm; the thickness of the functional layer is 5–20 μm; and the surface roughness is Ra≤0.1 μm.

[0014] The aforementioned corrosion-resistant slit coating die head has a functional layer surface coated with a Ta2O5 passivation film, the thickness of which is 3-10 nm.

[0015] In the aforementioned corrosion-resistant slot coating die, the chamfer is a continuous ring structure surrounding the edge of the discharge slot port, and the chamfer consistency error along the length of the discharge slot is ≤0.05mm.

[0016] In the aforementioned corrosion-resistant slit coating die, the functional layer completely covers the inner walls on both sides of the discharge slit and the edge of the port.

[0017] The aforementioned corrosion-resistant slot coating die head has a textured structure formed by sandblasting pretreatment on the interface between the substrate layer and the transition layer.

[0018] Compared with the prior art, the technical solution provided by this utility model has at least the following beneficial effects or advantages:

[0019] 1. This utility model improves corrosion resistance through a three-layer composite structure design: it adopts a layered structure in which "substrate layer - transition layer - functional layer" are connected in sequence. The substrate layer is a rigid support structure. The interface structure of the transition layer buffers thermal stress. The functional layer is a dense surface layer covering the inner wall of the slit. A continuous passivation film structure is formed on its surface. The multi-layer structure works together to block the penetration of corrosive media.

[0020] 2. This utility model achieves a balance between performance and economy through structural optimization: the functional layer adopts a design with the same thickness as the transition layer, and together with the dense oxide film structure of the transition layer, a gradient protection system is formed; the surface of the substrate layer is provided with a textured structure with sandblasting pretreatment to enhance the bonding strength of the transition layer, thereby reducing the amount of precious metals used and achieving long-term corrosion resistance. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 A schematic diagram of the cross-sectional structure of a corrosion-resistant slit coating die.

[0023] Figure 2 This is a magnified view of the rounded chamfer at the end of the discharge slit.

[0024] Explanation of reference numerals in the attached figures:

[0025] 1. Substrate layer; 2. Transition layer; 3. Discharge slit;

[0026] 4. Rounded corners; 5. Functional layers. Detailed Implementation

[0027] The technical solution of this utility model will be described below with reference to embodiments. However, this utility model is not limited to the following embodiments. Unless otherwise specified, the experimental and detection methods described in each embodiment are conventional methods; the reagents and materials described are commercially available unless otherwise specified. Unless otherwise specified, all percentages in the following embodiments refer to mass percentages. Unless otherwise specified, all proportions in the following embodiments refer to mass ratios.

[0028] Example 1: This example provides a corrosion-resistant slot coating die, comprising a substrate layer 1, a transition layer 2, a discharge slot 3, a rounded chamfer 4, and a functional layer 5;

[0029] The rounded chamfer 4 is set at the discharge end of the discharge slit 3, and the chamfer radius of the rounded chamfer 4 is 0.3mm; to avoid the dead zone and stress concentration of slurry flow caused by the traditional right angle port, and to reduce the risk of slurry residue and blockage.

[0030] Functional layers 5 are covered on both sides of the discharge slit 3. The functional layers 5 are directly placed in the key areas that come into contact with the slurry, which prioritizes the corrosion resistance of the inner wall of the discharge slit 3 and extends the service life of the core working surface of the die head.

[0031] One side of the transition layer 2 is metallurgically bonded to the functional layer 5, and the other side of the transition layer 2 is tightly connected to the substrate layer 1; the slit width of the discharge slit 3 is 280μm; the thickness of the substrate layer 1 is 10mm, and the width range of the discharge slit 3 covers the coating requirements of mainstream lithium battery electrode sheets; the thickness of the substrate layer 1 ensures that the die head does not deform under conventional coating pressure, thus ensuring the coating dimensional accuracy.

[0032] Furthermore, the transition layer 2 has a thickness of 8 μm; the functional layer 5 has a thickness of 12 μm and a surface roughness of Ra≤0.1 μm, ensuring sufficient stress buffering capacity while avoiding interface defects caused by excessive thickness.

[0033] In this embodiment, the surface of the functional layer 5 is coated with a Ta2O5 passivation film with a thickness of 7nm. The chemical inertness of the nanoscale Ta2O5 passivation film enhances the acid corrosion resistance of the functional layer 5, making it particularly suitable for fluoride-containing or strongly acidic slurry systems.

[0034] In this embodiment, the rounded chamfer 4 is a continuous ring structure surrounding the edge of the outlet slit 3 port, and the chamfer consistency error along the length of the outlet slit 3 is ≤0.05mm, ensuring the uniformity of flow along the entire length of the outlet slit 3.

[0035] In this embodiment, the functional layer 5 completely covers the inner walls on both sides of the discharge slit 3 and the edge of the port, avoiding localized corrosion caused by incomplete coverage of the functional layer 5.

[0036] In this embodiment, the bonding surface between the substrate layer 1 and the transition layer 2 is provided with a textured structure formed by sandblasting pretreatment, thereby improving the interfacial bonding strength between the transition layer 2 and the substrate layer 1 and avoiding the peeling problem of traditional planar bonding.

[0037] Example 2: This example provides a corrosion-resistant slot coating die, comprising a substrate layer 1, a transition layer 2, a discharge slot 3, a rounded chamfer 4, and a functional layer 5;

[0038] The rounded chamfer 4 is set at the discharge end of the discharge slit 3, and the chamfer radius of the rounded chamfer 4 is 0.1mm; to avoid the dead zone and stress concentration of slurry flow caused by the traditional right-angle port, and to reduce the risk of slurry residue and blockage.

[0039] Functional layers 5 are covered on both sides of the discharge slit 3. The functional layers 5 are directly placed in the key areas that come into contact with the slurry, which prioritizes the corrosion resistance of the inner wall of the discharge slit 3 and extends the service life of the core working surface of the die head.

[0040] One side of the transition layer 2 is metallurgically bonded to the functional layer 5, and the other side of the transition layer 2 is tightly connected to the substrate layer 1; the slit width of the discharge slit 3 is 50μm; the thickness of the substrate layer 1 is 5mm, and the width range of the discharge slit 3 covers the coating requirements of mainstream lithium battery electrode sheets; the thickness of the substrate layer 1 ensures that the die head does not deform under conventional coating pressure, thus ensuring the coating dimensional accuracy.

[0041] Furthermore, the transition layer 2 has a thickness of 5 μm; the functional layer 5 has a thickness of 5 μm and a surface roughness of Ra ≤ 0.1 μm, ensuring sufficient stress buffering capacity while avoiding interface defects caused by excessive thickness.

[0042] In this embodiment, the surface of the functional layer 5 is coated with a Ta2O5 passivation film with a thickness of 3nm. The chemical inertness of the nano-scale Ta2O5 passivation film enhances the acid corrosion resistance of the functional layer 5, making it particularly suitable for fluoride-containing or strongly acidic slurry systems.

[0043] In this embodiment, the rounded chamfer 4 is a continuous ring structure surrounding the edge of the outlet slit 3 port, and the chamfer consistency error along the length of the outlet slit 3 is ≤0.05mm, ensuring the uniformity of flow along the entire length of the outlet slit 3.

[0044] In this embodiment, the functional layer 5 completely covers the inner walls on both sides of the discharge slit 3 and the edge of the port, avoiding localized corrosion caused by incomplete coverage of the functional layer 5.

[0045] In this embodiment, the bonding surface between the substrate layer 1 and the transition layer 2 is provided with a textured structure formed by sandblasting pretreatment, thereby improving the interfacial bonding strength between the transition layer 2 and the substrate layer 1 and avoiding the peeling problem of traditional planar bonding.

[0046] Example 3: This example provides a corrosion-resistant slot coating die, comprising a substrate layer 1, a transition layer 2, a discharge slot 3, a rounded chamfer 4, and a functional layer 5;

[0047] The rounded chamfer 4 is set at the discharge end of the discharge slit 3, and the chamfer radius of the rounded chamfer 4 is 0.5mm; to avoid the dead zone and stress concentration of slurry flow caused by the traditional right angle port, and to reduce the risk of slurry residue and blockage.

[0048] Functional layers 5 are covered on both sides of the discharge slit 3. The functional layers 5 are directly placed in the key areas that come into contact with the slurry, which prioritizes the corrosion resistance of the inner wall of the discharge slit 3 and extends the service life of the core working surface of the die head.

[0049] One side of the transition layer 2 is metallurgically bonded to the functional layer 5, and the other side of the transition layer 2 is tightly connected to the substrate layer 1; the slit width of the discharge slit 3 is 500μm; the thickness of the substrate layer 1 is 15mm, and the width range of the discharge slit 3 covers the coating requirements of mainstream lithium battery electrode sheets; the thickness of the substrate layer 1 ensures that the die head does not deform under conventional coating pressure, thus ensuring the coating dimensional accuracy.

[0050] Furthermore, the transition layer 2 has a thickness of 10 μm; the functional layer 5 has a thickness of 20 μm, and the surface roughness is Ra≤0.1 μm, ensuring sufficient stress buffering capacity while avoiding interface defects caused by excessive thickness.

[0051] In this embodiment, the surface of the functional layer 5 is coated with a Ta2O5 passivation film with a thickness of 10 nm. The chemical inertness of the nanoscale Ta2O5 passivation film enhances the acid corrosion resistance of the functional layer 5, making it particularly suitable for fluoride-containing or strongly acidic slurry systems.

[0052] In this embodiment, the rounded chamfer 4 is a continuous ring structure surrounding the edge of the outlet slit 3 port, and the chamfer consistency error along the length of the outlet slit 3 is ≤0.05mm, ensuring the uniformity of flow along the entire length of the outlet slit 3.

[0053] In this embodiment, the functional layer 5 completely covers the inner walls on both sides of the discharge slit 3 and the edge of the port, avoiding localized corrosion caused by incomplete coverage of the functional layer 5.

[0054] In this embodiment, the bonding surface between the substrate layer 1 and the transition layer 2 is provided with a textured structure formed by sandblasting pretreatment, thereby improving the interfacial bonding strength between the transition layer 2 and the substrate layer 1 and avoiding the peeling problem of traditional planar bonding.

[0055] Example 4: This example verifies the difference in corrosion resistance between the corrosion-resistant slot coating die (Group 1) in Example 1 and the traditional 316L stainless steel electroplating hard chrome die (Group 2). The specific experimental steps are as follows:

[0056] Step 1: Immerse the two sets of mold heads in acetone and ultrasonically clean for 10 minutes. After drying, weigh them and use a micrometer to measure the initial thickness of the functional layer.

[0057] Step 2: Immerse both sets of mold heads completely in a 10% H2SO4 solution at 60℃, seal and store in the dark for 20 days; replace the H2SO4 solution every 2 days to avoid changes in solution composition affecting the results.

[0058] Step 3: Take out the two sets of mold heads, rinse the surface with deionized water to remove residual acid, dry and weigh.

[0059] Calculate the corrosion rate: Weight corrosion rate = weight loss / surface area × time (mg / cm²)2 ·h)

[0060] The results are shown in Table 1:

[0061] Table 1: Data on Weight Loss and Weight Corrosion Rate

[0062]

[0063] As shown in Table 1, the corrosion rate of Group 1 is only 5.2% of that of Group 2. The corrosion resistance of the corrosion-resistant slot coating die of this invention is about 19 times higher than that of the traditional die.

[0064] Example 5: This example aims to illustrate the difference in corrosion resistance between the corrosion-resistant slot coating dies prepared in Examples 1 to 3 and the traditional 316L electroplated hard chrome dies under typical corrosive environments, and to quantify the corrosion rate.

[0065] The design scheme is detailed in Table 2:

[0066] Table 2: Experimental Design Table

[0067] Group mold type Test Scenario feature Experimental group 1 Example 1 80℃ lithium battery paste Ta-10%Nb functional layer, R0.3mm chamfer. Experimental group 2 Example 2 <![CDATA[60℃10%H2SO4]]> Pure Ta functional layer, R0.1mm chamfer. Experimental group 3 Example 3 Acetone circulation flushing Ta-5%Nb functional layer, R0.5mm chamfer. control group Traditional chrome plating die head All scenes 20μm electroplated chromium layer, right-angle slit

[0068] Set the corrosive environment in Table 3:

[0069] Table 3: Corrosive Environmental Conditions

[0070]

[0071]

[0072] The corrosion depth rate was calculated using the experimental methods and steps described in Example 4, and the results are shown in Table 4.

[0073] Corrosion depth rate = weight loss / functional layer density × exposed surface area of ​​functional layer × corrosion time (μm / h).

[0074] Table 4: Comparison of corrosion depth rates between the experimental group and the control group

[0075] Group Corrosive media Corrosion rate (μm / h) Corrosion rate of control group (μm / h) Experimental group 1 <![CDATA[NMP+LiPF6]]> 0.0032 0.128 Experimental group 2 <![CDATA[10%H2SO4]]> 0.0025 0.210 Experimental group 3 acetone 0 0.015

[0076] As shown in Table 4, the corrosion depth rate of the coating die prepared in Example 1 in LiPF6 is only 2.5% of that of the conventional die, and the passivation film significantly blocks electrolyte erosion.

[0077] The coating die prepared in Example 2 showed almost no corrosion in H2SO4, while the traditional electroplated chromium layer failed rapidly due to microcracks.

[0078] The coating die prepared in Example 3 has zero acetone penetration, while the traditional die is corroded due to the increased surface roughness caused by the oxidation of the chromium layer.

[0079] Example 6: This example is intended to illustrate the effect of the rounded chamfer in Example 1 on the coating performance of the coating die.

[0080] Experimental group: The corrosion-resistant slit coating die prepared in Example 1 has a chamfer radius of 0.3 mm.

[0081] Control group: Except for the discharge slit 3 being designed at a right angle, all other parameters are exactly the same as the experimental group.

[0082] The slurry used in this embodiment is a lithium battery cathode slurry with a solid content of 70% and a viscosity of 5000 cP.

[0083] In this embodiment, the coating speed was 20 m / min, the substrate was copper foil, and the experiment was conducted continuously for 7 days at room temperature and 30% humidity.

[0084] During the 7-day operation, every 12 hours, a 10cm×10cm coating area was sampled, and 100 points were measured using a laser thickness gauge. The standard deviation of the thickness (%) was calculated, and the time of the first blockage and the number of blockages within 7 days were recorded. After the machine was stopped, the die head was disassembled, and the weight (mg) of the residual slurry in the slit was weighed.

[0085] The experimental results are shown in Table 5:

[0086] Table 5: Data on the Influence of Rounded Chamfers on Coating Performance

[0087] Test metrics Experimental group (chamfer R0.3mm) Control group (right angle) Performance improvement Thickness standard deviation (%) ±1.1 ±3.5 Reduced by 68.6% First congestion time (h) Not blocked 112 Extended congestion time Slurry residue (mg) 12±3 85±10 Reduced by 85.9% Slit morphology after operation No slurry buildup, smooth surface Hard lumps of slurry accumulated at right angles Elimination of dead zones

[0088] As shown in Table 5, the rounded chamfer design in Example 1 makes the slurry flow more smoothly at the outlet of the discharge slit 3, reducing thickness fluctuations caused by turbulence. The standard deviation of the experimental group decreased from ±3.5% to ±1.1%, meeting the stringent industry standard of ±1.5% for high-nickel ternary electrodes. Furthermore, the experimental group operated without clogging for 7 days, while the control group required shutdown and cleaning after only 112 hours due to slurry accumulation at the right angle. Therefore, the chamfer design of this invention reduces the flow dead zone, significantly extending continuous operation time. Finally, the residual slurry in the slit of the experimental group was only 12mg, reducing cleaning difficulty and material waste, and greatly improving the working efficiency of the coating die.

[0089] In summary, the corrosion-resistant slot coating die provided by this invention uses conventional stainless steel or low-alloy steel for the substrate layer 1 to ensure mechanical strength. Combined with the transition layer 2, this effectively mitigates thermal expansion differences and ensures high bonding strength between the functional layer 5 and the substrate layer 1. The functional layer 5 is made of tantalum-based alloy and forms a dense passivation film, exhibiting both excellent corrosion resistance and wear resistance. Furthermore, niobium solid solution treatment reduces material costs. The unique rounded chamfer 4 design eliminates stress concentration at the slot endpoints, significantly reducing slurry retention and flow dead zones, thus improving coating uniformity. The innovative manufacturing process integrates precision wire cutting, vacuum thermal diffusion, and low-temperature magnetron sputtering technologies to achieve ultra-low surface roughness processing and reduce slurry adhesion. Through material synergistic optimization and structural innovation, the overall solution ensures long lifespan and high-precision coating requirements while also considering economic efficiency and scalable production feasibility, making it suitable for highly corrosive applications such as lithium batteries and PCB inks.

[0090] As described above, the basic principles, main features, and advantages of this utility model have been well described. The above embodiments and specifications are merely preferred embodiments of this utility model, and this utility model is not limited to the above embodiments. Various changes and improvements made to the technical solutions of this utility model by those skilled in the art without departing from the spirit and scope of this utility model should fall within the protection scope defined by this utility model.

Claims

1. A corrosion-resistant slot coating die, characterized in that, It includes a base layer (1), a transition layer (2), a discharge slit (3), a rounded chamfer (4), and a functional layer (5); The circular chamfer (4) is provided at the discharge end of the discharge slit (3), and the chamfer radius of the circular chamfer (4) is 0.1 to 0.5 mm; The discharge slit (3) is covered with functional layers (5) on both sides; One side of the transition layer (2) is metallurgically bonded to the functional layer (5), and the other side of the transition layer (2) is tightly connected to the substrate layer (1).

2. The corrosion-resistant slot coating die according to claim 1, characterized in that, The width of the discharge slit (3) is 50-500 μm; the thickness of the substrate layer (1) is 5-15 mm.

3. The corrosion-resistant slot coating die according to claim 1, characterized in that, The thickness of the transition layer (2) is 5-10 μm; the thickness of the functional layer (5) is 5-20 μm, and the surface roughness is Ra≤0.1 μm.

4. The corrosion-resistant slot coating die according to claim 1, characterized in that, The surface of the functional layer (5) is coated with a Ta2O5 passivation film, the thickness of which is 3-10 nm.

5. The corrosion-resistant slot coating die according to claim 1, characterized in that, The circular chamfer (4) is a continuous ring structure around the edge of the discharge slit (3) port, and the chamfer consistency error along the length of the discharge slit (3) is ≤0.05mm.

6. The corrosion-resistant slot coating die according to claim 1, characterized in that, The functional layer (5) completely covers the inner walls on both sides and the edge of the port of the discharge slit (3).

7. The corrosion-resistant slot coating die according to claim 1, characterized in that, The interface between the substrate layer (1) and the transition layer (2) is provided with a textured structure formed by sandblasting pretreatment.

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