A corrosion-resistant stainless steel positive electrode current collector and its preparation method

Abstract

This invention relates to the field of stainless steel current collector technology, specifically disclosing a corrosion-resistant stainless steel positive electrode current collector and its preparation method. First, 316L stainless steel foil is subjected to plasma cleaning and passivation. Then, a chromium / molybdenum co-deposition layer, a chromium nitride@amorphous carbon layer, and a molybdenum carbide / titanium carbide layer are sequentially deposited on its surface by magnetron sputtering. Finally, a conductive paste containing fillers such as polyvinylidene fluoride-hexafluoropropylene copolymer and Li6PS5Cl@UIO-66 is coated and cured to form a corrosion-resistant stainless steel positive electrode current collector with good corrosion resistance, good conductivity, and good mechanical properties under high voltage conditions.

Description

Technical Field

[0001] This invention relates to the field of stainless steel current collector technology, specifically to a corrosion-resistant stainless steel positive electrode current collector and its preparation method. Background Technology

[0002] Solid-state batteries are a type of battery that uses a solid electrolyte instead of a liquid electrolyte. They conduct lithium ions through solid electrodes and a solid electrolyte. Compared to current lithium-ion batteries, they have advantages such as high energy density, low energy density, and good safety, and are considered to be the new mainstream battery that will replace lithium-ion batteries in the future.

[0003] Currently, among various solid-state electrolytes, sulfide solid-state electrolytes are the closest to industrialization due to their near-liquid electrolyte ionic conductivity and excellent mechanical ductility. However, the selection of solid electrode materials remains a challenge. Widely used copper foil experiences pitting corrosion when in contact with tungsten sulfide solid-state electrolytes, severely impacting battery cycle life and safety. Since iron-based materials such as stainless steel form an oxide passivation film upon contact with sulfides, inhibiting pitting corrosion, battery researchers and manufacturers have attempted to use stainless steel current collectors instead of copper current collectors in solid-state batteries. However, stainless steel has a much lower conductivity than copper and aluminum, stainless steel current collectors still corrode under high voltage conditions, and their poor mechanical ductility leads to high processing costs—all problems that need to be addressed. Therefore, enhancing the corrosion resistance, conductivity, and mechanical ductility of stainless steel current collectors is crucial for the development of solid-state batteries. Summary of the Invention

[0004] The purpose of this invention is to provide a corrosion-resistant stainless steel positive electrode current collector and its preparation method, thereby solving the problems of poor conductivity, insufficient corrosion resistance under high voltage conditions, and poor mechanical properties of stainless steel current collectors.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0006] A method for preparing a corrosion-resistant stainless steel positive electrode current collector, specifically comprising:

[0007] Step 1: Grind and polish the surface of 316L stainless steel foil, then perform plasma cleaning and passivation to obtain surface-pretreated stainless steel foil.

[0008] Step 2: Sequentially deposit a chromium / molybdenum co-deposition layer, a chromium nitride@amorphous carbon layer, and a molybdenum carbide / titanium carbide layer on the surface-pretreated stainless steel foil to obtain a surface transition layer of 316L stainless steel foil;

[0009] Step 3: Prepare conductive paste using polyvinylidene fluoride-hexafluoropropylene copolymer and Li6PS5Cl@UIO-66 as raw materials;

[0010] Step 4: Apply conductive paste to the 316L stainless steel foil surface transition layer, heat to cure, and hot press to bond, thus obtaining a corrosion-resistant stainless steel positive current collector.

[0011] The thickness of the chromium / molybdenum co-deposited layer is 40-50 nm; the thickness of the chromium carbide@amorphous carbon layer is 60-70 nm; the thickness of the molybdenum carbide / titanium carbide layer is 50-60 nm; and the thickness of the dry film formed after the conductive paste in step 4 is 1.3-1.5 μm.

[0012] As a limitation of the present invention, step 1 specifically includes:

[0013] After grinding and polishing, the 316L stainless steel foil is placed in a PECVD machine and vacuumed to 5×10⁻⁶. -4 -7×10 -4 Pa, the stainless steel foil is preheated to 280-300℃, then oxygen is introduced, the plasma power supply is started, and impurities on the surface are cleaned. Then the replacement gas is a mixture of argon and hydrogen. The stainless steel foil is activated by plasma treatment. After the treatment is completed, it is rapidly cooled to 50-60℃. Then the replacement gas is nitrogen and ammonia to generate a chromium nitride passivation film, and the pretreated 316L stainless steel foil is obtained.

[0014] After plasma cleaning of stainless steel foil, it is treated with argon and hydrogen to reconstruct grain boundaries and activate the surface. Argon plasma physical sputtering removes residual organic impurities from the surface, while hydrogen plasma penetrates the stainless steel grain boundaries to form Fe-H solid solution, which lowers the grain boundary energy, promotes dislocation slip, reduces grain size, and promotes nanocrystal formation. At the same time, hydrogen plasma reduces surface chromium oxide, exposing active chromium sites and promoting the formation of chromium nitride passivation film. Nitrogen provides a stable nitrogen source for the formation of chromium nitride passivation film, and ammonia plasma dissociates into NH2· / H· free radicals, reducing surface chromium oxide and improving the adhesion between the passivation film and the stainless steel foil.

[0015] A chromium nitride passivation film is formed on the surface of stainless steel foil. The chromium-rich region in the passivation film forms an electrostatic potential trap. Combined with the chemical adsorption of nitrogen vacancies, the leaching rate of iron, nickel, and chromium in the stainless steel foil is reduced. The wide bandgap semiconductor properties of chromium nitride increase the breakdown potential and dynamically seal defects through a self-healing reaction (CrN+O2→Cr2O3+N2), reducing the corrosion current density and thus improving the high-voltage corrosion resistance of the current collector. Chromium nitride nanocrystals are embedded in the stainless steel grain boundaries to form a mechanically interlocked structure, which, together with the Fe-O-Cr covalent bonds on the surface, improves the adhesion of the coating. The nanocrystal structure absorbs rolling stress and improves the rolling resistance of the current collector.

[0016] As a limitation of the present invention, the process parameters for cleaning impurities are: oxygen flow rate 150-170 sccm, plasma power supply power 200-220W, and sputtering time 12-15s.

[0017] During activation, the process parameters are: plasma power supply 400-500W, argon flow rate 195-198sccm, hydrogen flow rate 2-5sccm, and processing time 1.5-3s.

[0018] The process parameters for generating the chromium nitride passivation film are as follows: plasma power 350-380W, nitrogen flow rate 90-95sccm, ammonia flow rate 5-10sccm, and processing time 4-6s.

[0019] As a limitation of the present invention, in step 2, before deposition, the 316L stainless steel foil is preheated to 480-500℃; when depositing the chromium / molybdenum co-deposited layer, the process parameters are: argon flow rate 150-160sccm, chromium target power supply 4-5KW, molybdenum target power supply 4-5KW, and deposition time 3-4min.

[0020] When depositing chromium nitride@amorphous carbon layer, the process parameters are: argon flow rate 120-130 sccm, nitrogen flow rate 40-50 sccm, methane flow rate 5-15 sccm, DC power supply power for chromium target 5-6KW, RF power supply power 200-300W, and deposition time 3-5 min.

[0021] When depositing molybdenum carbide / titanium carbide layers, the process parameters are: argon flow rate 100-110 sccm, methane flow rate 15-25 sccm, DC power supply for molybdenum target 5-6 kW, DC power supply for titanium target 5-6 kW, and deposition time 4-6 min. After deposition, carbonization is performed, and the process parameters are: argon flow rate 120-130 sccm, propane flow rate 40-50 sccm, and carbonization time 10-12 min.

[0022] A chromium / molybdenum co-deposited layer is deposited on the surface of pretreated stainless steel foil. Chromium target sputtering forms nanocrystal nuclei, and molybdenum atoms enter the chromium lattice through substitutional solid solution to form a single-phase body-centered cubic (BCC) solid solution, which improves the matching degree of thermal expansion coefficient with the substrate. It forms a coherent lattice interface with chromium nitride, which improves the coating adhesion performance. The solid solution reduces the resistance of the coating and improves the conductivity of the coating.

[0023] Deposited chromium nitride@amorphous carbon layer, chromium nitride nanocrystals embedded in sp 3 In the hybrid amorphous carbon matrix, the carbon layer forms a molecular sieve structure to improve ion barrier performance; the amorphous carbon blocks electrolyte penetration and reduces corrosion current density; the amorphous carbon layer provides buffering and improves the current collector's resistance to rolling pressure.

[0024] The deposition and carbonization of molybdenum carbide / titanium carbide layers form a metastable (Ti,Mo)C solid solution. The delocalization of electrons in the metal-carbon covalent bonds enhances electrical conductivity. Molybdenum improves the matching degree of thermal expansion coefficients. The solid solution strengthens the coating hardness, thereby improving the coating wear resistance. The metastable phase inhibits the formation of the brittle TiC phase, thereby improving the fracture toughness of the coating.

[0025] As a limitation of the present invention, step 3 specifically includes:

[0026] Polyvinylidene fluoride-hexafluoropropylene copolymer was added to N-methylpyrrolidone and stirred evenly at 60-70℃. Then, Li6PS5Cl@UIO-66, titanium nitride nanowires, boron nitride nanosheets, graphene, and DVB crosslinking agent were added sequentially. The mixture was dispersed by ball milling at 300-500 rpm for 1-2 h, and then degassed under vacuum at (-0.08)-(-0.1) MPa for 30-40 min. After filtration, a conductive slurry was obtained.

[0027] As a limitation of the present invention, the conductive paste contains, by mass fraction: 8-12 wt% polyvinylidene fluoride-hexafluoropropylene copolymer, 15-20 wt% Li6PS5Cl@UIO-66, 4-7 wt% titanium nitride nanowires, 3-6 wt% boron nitride nanosheets, 2-5 wt% graphene, and 0.8-1.2 wt% DVB crosslinking agent.

[0028] The UIO-66 metal-organic framework adsorbs and encapsulates lithium-phosphorus-sulfur-chlorine solid electrolytes, forming directional ion channels, reducing interfacial impedance, and improving the ionic conductivity of the coating. Simultaneously, the metal-organic framework enhances the coating's temperature resistance. Titanium nitride nanowires (axial) and graphene (facing) construct a three-dimensional electronic network, reducing the coating's surface resistance through percolation. Polyvinylidene fluoride-hexafluoropropylene copolymer serves as the binder matrix; its HFP flexible chains synergistically facilitate interlayer slippage with graphene, improving the current collector's toughness and resistance to rolling. DVB crosslinking agent forms a three-dimensional crosslinking network, inhibiting coating swelling and improving peel strength. Boron nitride nanosheets, through horizontally oriented stacking, block the penetration of electrolytes and hydrogen sulfide, improving the current collector's voltage stability and corrosion resistance, while also dispersing stress and enhancing the coating's impact resistance.

[0029] As a limitation of this invention, the preparation method of Li6PS5Cl@UIO-66 is as follows:

[0030] Lithium-phosphorus-sulfur-chlorine solid electrolyte was added to acetonitrile and stirred evenly. Then, UIO-66 powder that had been dehydrated under vacuum at 130-150℃ for 8-12 hours was added. The mixture was then impregnated at 60-70℃ and (-0.08)-(-0.1) MPa for 12-16 hours. After impregnation, the mixture was centrifuged, washed with acetonitrile, and dried under vacuum at 70-80℃ to obtain Li6PS5Cl@UIO-66.

[0031] As a limitation of this invention, the mass ratio of lithium phosphorus sulfur chlorine solid electrolyte and UIO-66 powder is 1:(3-5).

[0032] As a limitation of the present invention, during the heating and curing process in step 4, the heating and curing are carried out in stages under nitrogen protection. First, the temperature is raised to 70-80℃ and cured for 90-100 seconds. Then, the temperature is raised to 100-110℃ and cured for 3-4 minutes. Finally, the temperature is raised to 130-135℃ and cured for 50-60 seconds. After the heating and curing are completed, hot pressing is performed. The hot pressing temperature is 110-120℃, the hot pressing pressure is 6-7 MPa, and the hot pressing time is 3-5 minutes.

[0033] A corrosion-resistant stainless steel positive current collector is prepared by any of the above-mentioned preparation methods.

[0034] Compared with the prior art, the beneficial effects of the present invention are:

[0035] This invention sequentially deposits a chromium / molybdenum co-deposition layer, a chromium nitride@amorphous carbon layer, and a molybdenum carbide / titanium carbide layer on a stainless steel foil. Through the synergistic effect of solid solution, amorphous carbon, and carbon-metal covalent bonds, the conductivity of the coating is improved, the penetration of electrolyte and hydrogen sulfide and the leaching of metal ions from the stainless steel foil are blocked, and the mechanical properties of the coating are improved at the same time.

[0036] This invention utilizes a conductive paste to solidify and form a conductive layer. The directional ion channels and three-dimensional conductive network within this layer synergistically enhance the conductivity of the stainless steel current collector. The flexible HFP segments and three-dimensional cross-linked network within the layer improve the mechanical properties of the coating. The metal-organic framework within the layer enhances temperature resistance. Boron nitride nanosheets within the layer improve corrosion resistance through barrier properties. The synergistic effect of these multiple materials improves the high-voltage corrosion resistance, conductivity, and mechanical properties of the stainless steel current collector. Detailed Implementation

[0037] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. The terminology used in the embodiments is for describing specific implementation schemes, not for limiting the scope of protection of the present invention. The dosages in the embodiments are laboratory-scale tests and can be scaled up proportionally. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] 316L stainless steel foil (thickness: 10μm), chromium target (purity: 99.9%), molybdenum target (purity: 99.9%), titanium target (purity: 99.9%), lithium-phosphorus-sulfur-chlorine solid electrolyte (Li6PS5Cl, particle size D50: 5μm), UIO-66 powder (specific surface area: 1200m²). 2 / g, Zr content: 20.5wt%), polyvinylidene fluoride-hexafluoropropylene copolymer (Mw: 43W-47W, HFP content: 12wt%, crystallinity: ≤35%), titanium nitride nanowires (diameter: 20nm, length: 1μm), boron nitride nanosheets (lateral dimension: 500nm, thickness: 2-5nm), graphene (sheet diameter: 5μm, specific surface area: 500m²). 2 / g).

[0039] Example 1: A method for preparing a corrosion-resistant stainless steel positive electrode current collector, specifically as follows:

[0040] Step 1: Grind and polish the 316L stainless steel foil, then place it in a PECVD machine and evacuate it to a vacuum of 5×10. -4 Pa, stainless steel foil is preheated to 280℃, then oxygen is introduced at a flow rate of 150 sccm, plasma power is set to 200W, sputtering for 15s to clean surface impurities, then the replacement gas is a mixture of argon and hydrogen, plasma power is set to 400W, argon flow rate is 198 sccm, hydrogen flow rate is 2 sccm, and processing time is 1.5s, after which it is rapidly cooled to 50℃, then the replacement gas is nitrogen and ammonia, plasma power is set to 350W, nitrogen flow rate is 95 sccm, ammonia flow rate is 5 sccm, and processing time is 4s, generating a chromium nitride passivation film, thus obtaining pretreated 316L stainless steel foil;

[0041] Step 2: Transfer the pretreated 316L stainless steel foil to a magnetron sputtering deposition apparatus, preheat to 500°C, and simultaneously evacuate to 5×10⁻⁶ ℃. -4At 10:00 AM, argon gas was introduced, and the DC power supplies for the chromium and molybdenum targets were started. The argon flow rate was set to 150 sccm, the power supply power for the chromium target to 4 kW, and the power supply power for the molybdenum target to 4 kW. The deposition time was 4 min, and a 40 nm chromium / molybdenum co-deposited layer was deposited on the pretreated 316L stainless steel foil surface. Subsequently, the replacement gases were argon, nitrogen, and methane. The RF auxiliary power supply for the chromium target was started, and the argon flow rate was set to 120 sccm, the nitrogen flow rate to 40 sccm, the methane flow rate to 5 sccm, the DC power supply power for the chromium target to 5 kW, and the RF power supply power to 200 W. The deposition time was 5 min, and a 60 nm chromium nitride@non-chromium co-deposited layer was deposited on the chromium / molybdenum co-deposited layer. A crystalline carbon layer was deposited using argon and methane as the replacement gases. The DC power supplies for the molybdenum target and titanium target were started, with the argon flow rate set to 100 sccm, the methane flow rate to 15 sccm, the power of the molybdenum target DC power supply to 5 kW, and the deposition time to 6 min. A 50 nm molybdenum carbide / titanium carbide layer was deposited on the chromium nitride@amorphous carbon layer. After deposition, the temperature was increased to 580 °C at a rate of 5 °C / min. The replacement gases were argon and propane, with the argon flow rate set to 120 sccm and the propane flow rate to 40 sccm. Carbonization was carried out for 10 min, and after carbonization, the temperature was rapidly cooled to 100 °C to obtain a 316L stainless steel foil surface transition layer.

[0042] Step 3: Add 2g of lithium phosphorus sulfur chlorine solid electrolyte to 100g of acetonitrile, stir evenly, then add 6g of UIO-66 powder that has been dehydrated under vacuum at 150℃ for 12h, and impregnate at 60℃ and -0.1MPa for 12h. After impregnation, centrifuge, wash with acetonitrile, and dry under vacuum at 80℃ to obtain Li6PS5Cl@UIO-66.

[0043] Step 4: Add 8g of polyvinylidene fluoride-hexafluoropropylene copolymer to 67g of N-methylpyrrolidone, stir evenly at 60℃, then add 15g of Li6PS5Cl@UIO-66, 4g of titanium nitride nanowires, 3g of boron nitride nanosheets, 2g of graphene and 0.8g of DVB crosslinking agent in sequence, disperse by ball milling at 300rpm for 2h with zirconia balls, degas under vacuum at -0.1MPa for 30min, filter through a 200-mesh sieve to obtain conductive slurry;

[0044] Step 5: The conductive paste is coated onto the 316L stainless steel foil of the surface transition layer. Under nitrogen protection, it is pre-cured at 70℃ for 90s, cured at 110℃ for 3min, and cured at 130℃ for 60s to form a 1.3μm dry film. Then, it is hot-pressed at 120℃ and 6MPa for 3min to obtain the corrosion-resistant stainless steel positive current collector.

[0045] Example 2: A method for preparing a corrosion-resistant stainless steel positive electrode current collector, specifically as follows:

[0046] Step 1: Grind and polish the 316L stainless steel foil, then place it in a PECVD machine and evacuate it to a vacuum of 5×10. -4 Pa, stainless steel foil is preheated to 290℃, then oxygen is introduced at a flow rate of 160 sccm, plasma power is set to 200W, sputtering for 14s to clean surface impurities. Then the replacement gas is a mixture of argon and hydrogen, plasma power is set to 450W, argon flow rate is 196 sccm, hydrogen flow rate is 4 sccm, and processing time is 1.5s. After processing, it is rapidly cooled to 50℃, then the replacement gas is nitrogen and ammonia, plasma power is set to 350W, nitrogen flow rate is 95 sccm, ammonia flow rate is 5 sccm, and processing time is 6s to generate a chromium nitride passivation film, thus obtaining pretreated 316L stainless steel foil;

[0047] Step 2: Transfer the pretreated 316L stainless steel foil to a magnetron sputtering deposition apparatus, preheat to 500°C, and simultaneously evacuate to 5×10⁻⁶ ℃. -4 Argon gas was introduced, and the DC power supplies for the chromium and molybdenum targets were started. The argon flow rate was set to 155 sccm, the power supply power for the chromium target to 4 kW, and the power supply power for the molybdenum target to 4 kW. The deposition time was 4 min, and a 42 nm chromium / molybdenum co-deposited layer was deposited on the pretreated 316L stainless steel foil surface. Subsequently, the replacement gases were argon, nitrogen, and methane. The RF auxiliary power supply for the chromium target was started, and the argon flow rate was set to 125 sccm, the nitrogen flow rate to 45 sccm, the methane flow rate to 5 sccm, the DC power supply power for the chromium target to 5 kW, and the RF power supply power to 200 W. The deposition time was 5 min, and a 63 nm chromium nitride@amorphous carbon was deposited on the chromium / molybdenum co-deposited layer. The replacement gases were argon and methane. The DC power supplies for the molybdenum target and titanium target were started, with the argon flow rate set to 110 sccm, the methane flow rate to 20 sccm, the power of the molybdenum target DC power supply to 5.5 kW, and the deposition time to 6 min. A 55 nm molybdenum carbide / titanium carbide layer was deposited on the chromium nitride@amorphous carbon layer. After deposition, the temperature was increased to 580 °C at 5 °C / min. The replacement gases were argon and propane, with the argon flow rate set to 120 sccm and the propane flow rate to 40 sccm. The carbonization time was 11 min. After carbonization, the temperature was rapidly cooled to 100 °C to obtain a surface transition layer of 316L stainless steel foil.

[0048] Step 3: Add 2g of lithium phosphorus sulfur chlorine solid electrolyte to 100g of acetonitrile, stir evenly, then add 8g of UIO-66 powder that has been dehydrated under vacuum at 150℃ for 12h, and impregnate at 60℃ and -0.1MPa for 12h. After impregnation, centrifuge, wash with acetonitrile, and dry under vacuum at 80℃ to obtain Li6PS5Cl@UIO-66.

[0049] Step 4: Add 9g of polyvinylidene fluoride-hexafluoropropylene copolymer to 62g of N-methylpyrrolidone, stir evenly at 60℃, then add 16g of Li6PS5Cl@UIO-66, 5g of titanium nitride nanowires, 4g of boron nitride nanosheets, 3g of graphene and 1g of DVB crosslinking agent in sequence, disperse by ball milling at 300rpm for 2h with zirconia balls, degas under vacuum at -0.1MPa for 30min, filter through a 200-mesh sieve to obtain conductive slurry;

[0050] Step 5: The conductive paste is coated onto the 316L stainless steel foil of the surface transition layer. Under nitrogen protection, it is pre-cured at 80℃ for 90s, cured at 100℃ for 4min, and cured at 135℃ for 50s to form a 1.4μm dry film. Then, it is hot-pressed at 120℃ and 6MPa for 4min to obtain the corrosion-resistant stainless steel positive current collector.

[0051] Example 3: A method for preparing a corrosion-resistant stainless steel positive electrode current collector, specifically as follows:

[0052] Step 1: Grind and polish the 316L stainless steel foil, then place it in a PECVD machine and evacuate it to a vacuum of 5×10. -4 Pa, stainless steel foil is preheated to 280℃, then oxygen is introduced at a flow rate of 150 sccm, plasma power is set to 200W, sputtering for 15s to clean surface impurities, then the replacement gas is a mixture of argon and hydrogen, plasma power is set to 400W, argon flow rate is 198 sccm, hydrogen flow rate is 2 sccm, and processing time is 1.5s, after which it is rapidly cooled to 50℃, then the replacement gas is nitrogen and ammonia, plasma power is set to 350W, nitrogen flow rate is 95 sccm, ammonia flow rate is 5 sccm, and processing time is 4s, generating a chromium nitride passivation film, thus obtaining pretreated 316L stainless steel foil;

[0053] Step 2: Transfer the pretreated 316L stainless steel foil to a magnetron sputtering deposition apparatus, preheat to 500°C, and simultaneously evacuate to 5×10⁻⁶ ℃. -4Argon gas was introduced, and the DC power supplies for the chromium and molybdenum targets were started. The argon flow rate was set to 150 sccm, the power supply power for the chromium target to 5 kW, and the power supply power for the molybdenum target to 5 kW. The deposition time was 4 min, and a 45 nm chromium / molybdenum co-deposited layer was deposited on the pretreated 316L stainless steel foil surface. Subsequently, the replacement gases were argon, nitrogen, and methane. The RF auxiliary power supply for the chromium target was started, and the argon flow rate was set to 130 sccm, the nitrogen flow rate to 50 sccm, the methane flow rate to 10 sccm, the DC power supply power for the chromium target to 5 kW, and the RF power supply power to 200 W. The deposition time was 5 min, and a 65 nm chromium nitride@amorphous carbon was deposited on the chromium / molybdenum co-deposited layer. The replacement gases were argon and methane. The DC power supplies for the molybdenum target and titanium target were started, with the argon flow rate set to 110 sccm, the methane flow rate to 20 sccm, the power of the molybdenum target DC power supply to 5.5 kW, and the deposition time to 6 min. A 55 nm molybdenum carbide / titanium carbide layer was deposited on the chromium nitride@amorphous carbon layer. After deposition, the temperature was increased to 580 °C at 5 °C / min. The replacement gases were argon and propane, with the argon flow rate set to 120 sccm and the propane flow rate to 40 sccm. The carbonization time was 11 min. After carbonization, the temperature was rapidly cooled to 100 °C to obtain a surface transition layer of 316L stainless steel foil.

[0054] Step 3: Add 2g of lithium phosphorus sulfur chlorine solid electrolyte to 100g of acetonitrile, stir evenly, then add 10g of UIO-66 powder that has been dehydrated under vacuum at 150℃ for 12h, and impregnate at 60℃ and -0.1MPa for 12h. After impregnation, centrifuge, wash with acetonitrile, and dry under vacuum at 80℃ to obtain Li6PS5Cl@UIO-66;

[0055] Step 4: Add 10g of polyvinylidene fluoride-hexafluoropropylene copolymer to 57g of N-methylpyrrolidone, stir evenly at 60℃, then add 17g of Li6PS5Cl@UIO-66, 6g of titanium nitride nanowires, 5g of boron nitride nanosheets, 4g of graphene and 1g of DVB crosslinking agent in sequence, disperse by ball milling at 300rpm for 2h with zirconia balls, degas under vacuum at -0.1MPa for 30min, filter through a 200-mesh sieve to obtain conductive slurry;

[0056] Step 5: The conductive paste is coated onto the 316L stainless steel foil of the surface transition layer. Under nitrogen protection, it is pre-cured at 80℃ for 100s, cured at 110℃ for 4min, and cured at 135℃ for 60s to form a 1.5μm dry film. Then, it is hot-pressed at 120℃ and 6MPa for 5min to obtain the corrosion-resistant stainless steel positive current collector.

[0057] Based on Example 1, the following comparative experiments were conducted, specifically Comparative Example 1, Comparative Example 2, and Comparative Example 3, as described below:

[0058] Comparative Example 1: This comparative example relates to a method for preparing a corrosion-resistant stainless steel positive electrode current collector. The difference from Example 1 is that a chromium nitride passivation film is not formed in step 1. Specifically:

[0059] Step 1: Grind and polish the 316L stainless steel foil, then place it in a magnetron sputtering deposition apparatus, preheat to 500℃, and simultaneously evacuate to 5×10⁻⁶. -4 At 10 min, argon and nitrogen gases were introduced, and the DC power supply to the chromium target was started. The argon flow rate was set to 180 sccm, the nitrogen flow rate to 50 sccm, the power supply power to 7 kW, and the deposition time to 10 min. A 120 nm chromium nitride transition layer was deposited on the pretreated 316L stainless steel foil surface. Subsequently, the replacement gases were argon and acetylene. The RF auxiliary power supply to the chromium target was started, and the argon flow rate was set to 150 sccm, the acetylene flow rate to 10 sccm, the DC power supply power to 5 kW, and the RF power supply power to 200 W. The deposition time was 6 min. An 80 nm chromium carbide / amorphous carbon layer was deposited on the chromium nitride transition layer. The replacement gases were argon and methane. The DC power supply for the molybdenum target was started, with the argon flow rate set to 120 sccm, the methane flow rate to 15 sccm, the DC power supply power for the molybdenum target to 8 kW, and the DC power supply power for the chromium target to 1 kW. The deposition time was 4 min. A 50 nm molybdenum carbide@chromium transition layer was deposited on the chromium carbide / amorphous carbon layer. After deposition, the temperature was increased to 600 °C at 5 °C / min. The replacement gases were argon and acetylene, with the argon flow rate set to 150 sccm and the acetylene flow rate to 30 sccm. Carbonization was carried out for 10 min. After carbonization, the temperature was rapidly cooled to 100 °C to obtain a 316L stainless steel foil surface transition layer.

[0060] Step 2: Add 2g of lithium phosphorus sulfur chlorine solid electrolyte to 100g of acetonitrile, stir evenly, then add UIO-66 powder that has been dehydrated under vacuum at 150℃ for 12h, and impregnate at 60℃ and -0.1MPa for 12h. After impregnation, centrifuge, wash with acetonitrile, and dry under vacuum at 80℃ to obtain Li6PS5Cl@UIO-66.

[0061] Step 3: Add 8g of polyvinylidene fluoride-hexafluoropropylene copolymer to 67g of N-methylpyrrolidone, stir evenly at 60℃, then add 15g of Li6PS5Cl@UIO-66, 4g of titanium nitride nanowires, 3g of boron nitride nanosheets, 2g of graphene and 0.8g of DVB crosslinking agent in sequence, disperse by ball milling at 300rpm for 2h, degas under vacuum at -0.1MPa for 30min, filter through a 200-mesh sieve to obtain conductive slurry;

[0062] Step 4: The conductive paste is coated onto the 316L stainless steel foil of the surface transition layer. Under nitrogen protection, it is pre-cured at 70℃ for 90s, cured at 110℃ for 3min, and cured at 130℃ for 60s to form a 1.3μm dry film. Then, it is hot-pressed at 120℃ and 6MPa for 3min to obtain the corrosion-resistant stainless steel positive current collector.

[0063] Comparative Example 2: This comparative example relates to a method for preparing a corrosion-resistant stainless steel positive current collector. The difference from Example 1 is that magnetron sputtering deposition was not performed. Specifically:

[0064] Step 1: Grind and polish the 316L stainless steel foil, then place it in a PECVD machine and evacuate it to a vacuum of 5×10. -4 Pa, stainless steel foil is preheated to 280℃, then oxygen is introduced at a flow rate of 150 sccm, plasma power is set to 200W, sputtering for 15s to clean surface impurities, then the replacement gas is a mixture of argon and hydrogen, plasma power is set to 400W, argon flow rate is 198 sccm, hydrogen flow rate is 2 sccm, and processing time is 1.5s, after which it is rapidly cooled to 50℃, then the replacement gas is nitrogen and ammonia, plasma power is set to 350W, nitrogen flow rate is 95 sccm, ammonia flow rate is 5 sccm, and processing time is 4s, generating a chromium nitride passivation film, thus obtaining pretreated 316L stainless steel foil;

[0065] Step 2: Add 2g of lithium phosphorus sulfur chlorine solid electrolyte to 100g of acetonitrile, stir evenly, then add UIO-66 powder that has been dehydrated under vacuum at 150℃ for 12h, and impregnate at 60℃ and -0.1MPa for 12h. After impregnation, centrifuge, wash with acetonitrile, and dry under vacuum at 80℃ to obtain Li6PS5Cl@UIO-66.

[0066] Step 3: Add 8g of polyvinylidene fluoride-hexafluoropropylene copolymer to 67g of N-methylpyrrolidone, stir evenly at 60℃, then add 15g of Li6PS5Cl@UIO-66, 4g of titanium nitride nanowires, 3g of boron nitride nanosheets, 2g of graphene and 0.8g of DVB crosslinking agent in sequence, disperse by ball milling at 300rpm for 2h, degas under vacuum at -0.1MPa for 30min, filter through a 200-mesh sieve to obtain conductive slurry;

[0067] Step 4: Coat the conductive paste onto the pretreated 316L stainless steel foil, pre-cur it at 70℃ for 90s under nitrogen protection, cure it at 110℃ for 3min, and cure it at 130℃ for 60s to form a 1.3μm dry film. Then, hot press it at 120℃ and 6MPa for 3min to obtain a corrosion-resistant stainless steel positive current collector.

[0068] Comparative Example 3: This comparative example relates to a method for preparing a corrosion-resistant stainless steel positive electrode current collector. The difference from Example 1 is that Li6PS5Cl@UIO-66 was not added to the conductive paste. Specifically:

[0069] Step 1: Grind and polish the 316L stainless steel foil, then place it in a PECVD machine and evacuate it to a vacuum of 5×10. -4 Pa, stainless steel foil is preheated to 280℃, then oxygen is introduced at a flow rate of 150 sccm, plasma power is set to 200W, sputtering for 15s to clean surface impurities, then the replacement gas is a mixture of argon and hydrogen, plasma power is set to 400W, argon flow rate is 198 sccm, hydrogen flow rate is 2 sccm, and processing time is 1.5s, after which it is rapidly cooled to 50℃, then the replacement gas is nitrogen and ammonia, plasma power is set to 350W, nitrogen flow rate is 95 sccm, ammonia flow rate is 5 sccm, and processing time is 4s, generating a chromium nitride passivation film, thus obtaining pretreated 316L stainless steel foil;

[0070] Step 2: Transfer the pretreated 316L stainless steel foil to a magnetron sputtering deposition apparatus, preheat to 500°C, and simultaneously evacuate to 5×10⁻⁶ ℃. -4 At 10 min, argon and nitrogen gases were introduced, and the DC power supply to the chromium target was started. The argon flow rate was set to 180 sccm, the nitrogen flow rate to 50 sccm, the power supply power to 7 kW, and the deposition time to 10 min. A 120 nm chromium nitride transition layer was deposited on the pretreated 316L stainless steel foil surface. Subsequently, the replacement gases were argon and acetylene. The RF auxiliary power supply to the chromium target was started, and the argon flow rate was set to 150 sccm, the acetylene flow rate to 10 sccm, the DC power supply power to 5 kW, and the RF power supply power to 200 W. The deposition time was 6 min. An 80 nm chromium carbide / amorphous carbon layer was deposited on the chromium nitride transition layer. The replacement gases were argon and methane. The DC power supply for the molybdenum target was started, with the argon flow rate set to 120 sccm, the methane flow rate to 15 sccm, the DC power supply power for the molybdenum target to 8 kW, and the DC power supply power for the chromium target to 1 kW. The deposition time was 4 min. A 50 nm molybdenum carbide@chromium transition layer was deposited on the chromium carbide / amorphous carbon layer. After deposition, the temperature was increased to 600 °C at 5 °C / min. The replacement gases were argon and acetylene, with the argon flow rate set to 150 sccm and the acetylene flow rate to 30 sccm. Carbonization was carried out for 10 min. After carbonization, the temperature was rapidly cooled to 100 °C to obtain a 316L stainless steel foil surface transition layer.

[0071] Step 3: Add 8g of polyvinylidene fluoride-hexafluoropropylene copolymer to 67g of N-methylpyrrolidone, stir evenly at 60℃, then add 4g of titanium nitride nanowires, 3g of boron nitride nanosheets, 2g of graphene and 0.8g of DVB crosslinking agent in sequence, disperse by ball milling at 300rpm for 2h, degas under vacuum at -0.1MPa for 30min, filter through a 200-mesh sieve to obtain conductive slurry;

[0072] Step 4: The conductive paste is coated onto the 316L stainless steel foil of the surface transition layer. Under nitrogen protection, it is pre-cured at 70℃ for 90s, cured at 110℃ for 3min, and cured at 130℃ for 60s to form a 1.3μm dry film. Then, it is hot-pressed at 120℃ and 6MPa for 3min to obtain the corrosion-resistant stainless steel positive current collector.

[0073] Testing experiment:

[0074] High-voltage corrosion resistance test: A corrosion-resistant stainless steel positive current collector was cut into 10mm × 10mm pieces. A 200μm thick Li6PS5Cl solid sheet was attached to one side of the surface and hot-pressed at 5MPa and 150℃ for 10min. A copper wire was soldered to the other side, and the sample was encapsulated with E-51 epoxy resin to prepare the test sample. The test sample was placed in a Garmy Interface 5000P electrochemical workstation (supporting 0-6V). The workstation's electrolytic cell contained a three-electrode system (working electrode: test sample; reference electrode: Li / Li). + Lithium metal electrode; counter electrode: platinum sheet), temperature 60℃, power on electrochemical workstation, stabilize at open circuit potential (OCP) for 30 min, set potentiodynamic scanning, range from OCP-0.3V→OCP+1.0V, scan rate 0.1mV / s, record Tafel curve (current density versus overpotential curve), output corrosion current density and pitting potential of current collector.

[0075] Conductivity test: A corrosion-resistant stainless steel current collector was cut into 20mm×50mm pieces. The four probes of an MCP-T370 four-probe surface resistance meter were pressed equidistantly (10mm spacing, 1MPa pressure) onto the corrosion-resistant stainless steel current collector. The surface resistance meter was started, the current source output was 10mA, the voltage was read, and the surface resistance of the corrosion-resistant stainless steel current collector was calculated. Five different locations were selected for testing, and the average value of the results was taken. Another corrosion-resistant stainless steel current collector of the same size (20mm×50mm) was cut. A Li6PS5Cl solid sheet (200μm thick) was fixed between it and the lithium metal sheet, and a pressure of 5MPa was applied to make it fit tightly. The Solartron 1260A impedance analyzer was connected, the frequency was set to 1MHz-10MHz, the amplitude was 10mV, and the ionic conductivity of the corrosion-resistant stainless steel current collector was calculated.

[0076] Mechanical performance testing: The corrosion-resistant stainless steel current collector was cut into φ30mm circular samples. A φ20mm aluminum ingot was bonded to the center of the corrosion-resistant stainless steel current collector surface with epoxy adhesive. After curing at 25℃ for 24 hours, it was cured at 80℃ for 2 hours. The aluminum ingot and the current collector were clamped separately with fixtures. An Instorn 5943 tensile testing machine was started, and the coating was stretched vertically at a rate of 1mm / min until it peeled off. The peel force was recorded, and the bonding strength of the coating was calculated. In addition, referring to the cupping test method, a 100mm×100mm corrosion-resistant stainless steel current collector was cut. A 20mm diameter stainless steel punch provided with the ERICHSEN cupping test machine was used to press into the corrosion-resistant stainless steel current collector. The punching rate was set to 5mm / min. The state of the coating was observed in real time with a 100x high-definition microscope, and the indentation depth when the coating cracked was recorded.

[0077]

[0078] Conclusion: The test data shows that the bonding strength and penetration depth of the corrosion-resistant stainless steel positive electrode current collector in the embodiment are superior to those in the comparative example, indicating that the mechanical properties of the stainless steel positive electrode current collector in the embodiment are better than those in the comparative example. In addition, the corrosion current density, pitting potential, surface resistivity, and conductivity of the stainless steel positive electrode current collector in the embodiment are all superior to those in the comparative example. In summary, the stainless steel positive electrode current collector provided by this invention has good conductivity, good high-voltage corrosion resistance, and good mechanical properties.

[0079] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A method for preparing a corrosion-resistant stainless steel positive electrode current collector, characterized in that: Specifically: Step 1: Grind and polish the surface of 316L stainless steel foil, then perform plasma cleaning and passivation to obtain surface-pretreated stainless steel foil. Step 2: Sequentially deposit a chromium / molybdenum co-deposition layer, a chromium nitride@amorphous carbon layer, and a molybdenum carbide / titanium carbide layer on the surface-pretreated stainless steel foil to obtain a surface transition layer of 316L stainless steel foil; Step 3: Prepare conductive paste using polyvinylidene fluoride-hexafluoropropylene copolymer and Li6PS5Cl@UIO-66 as raw materials; Step 4: Apply conductive paste to the 316L stainless steel foil surface transition layer, heat to cure, and hot press to bond, thus obtaining a corrosion-resistant stainless steel positive current collector.

2. The method for preparing a corrosion-resistant stainless steel positive electrode current collector according to claim 1, characterized in that: Step 1 is as follows: After grinding and polishing, the 316L stainless steel foil is placed in a PECVD machine and vacuumed to 5×10⁻⁶. -4 -7×10 -4 Pa, the stainless steel foil is preheated to 280-300℃, then oxygen is introduced, the plasma power supply is started, and impurities on the surface are cleaned. Then the replacement gas is a mixture of argon and hydrogen. The stainless steel foil is activated by plasma treatment. After the treatment is completed, it is rapidly cooled to 50-60℃. Then the replacement gas is nitrogen and ammonia to generate a chromium nitride passivation film, and the pretreated 316L stainless steel foil is obtained.

3. The method for preparing a corrosion-resistant stainless steel positive electrode current collector according to claim 2, characterized in that: When cleaning impurities, the process parameters are: oxygen flow rate 150-170 sccm, plasma power 200-220W, sputtering time 12-15s; when activating, the process parameters are: plasma power 400-500W, argon flow rate 195-198 sccm, hydrogen flow rate 2-5 sccm, processing time 1.5-3s; when generating a chromium nitride passivation film, the process parameters are: plasma power 350-380W, nitrogen flow rate 90-95 sccm, ammonia flow rate 5-10 sccm, processing time 4-6s.

4. The method for preparing a corrosion-resistant stainless steel positive electrode current collector according to claim 1, characterized in that: In step 2, before deposition, the 316L stainless steel foil is preheated to 480-500℃. When depositing the chromium / molybdenum co-deposited layer, the process parameters are: argon flow rate 150-160 sccm, chromium target power supply 4-5 KW, molybdenum target power supply 4-5 KW, deposition time 3-4 min. When depositing the chromium nitride@amorphous carbon layer, the process parameters are: argon flow rate 120-130 sccm, nitrogen flow rate 40-50 sccm, methane flow rate 5-15 sccm, chromium target DC power supply 5-6... For deposition of molybdenum carbide / titanium carbide layers, the process parameters are: argon flow rate 100-110 sccm, methane flow rate 15-25 sccm, DC power supply for molybdenum target 5-6 KW, DC power supply for titanium target 5-6 KW, deposition time 4-6 min. After deposition, the carbonization process parameters are: argon flow rate 120-130 sccm, propane flow rate 40-50 sccm, carbonization time 10-12 min.

5. The method for preparing a corrosion-resistant stainless steel positive electrode current collector according to claim 1, characterized in that: Step 3 specifically involves: Polyvinylidene fluoride-hexafluoropropylene copolymer was added to N-methylpyrrolidone and stirred evenly at 60-70℃. Then, Li6PS5Cl@UIO-66, titanium nitride nanowires, boron nitride nanosheets, graphene, and DVB crosslinking agent were added sequentially. The mixture was dispersed by ball milling at 300-500 rpm for 1-2 h, and then degassed under vacuum at (-0.08)-(-0.1) MPa for 30-40 min. After filtration, a conductive slurry was obtained.

6. The method for preparing a corrosion-resistant stainless steel positive electrode current collector according to claim 5, characterized in that: By mass fraction, the conductive paste contains: 8-12 wt% polyvinylidene fluoride-hexafluoropropylene copolymer, 15-20 wt% Li6PS5Cl@UIO-66, 4-7 wt% titanium nitride nanowires, 3-6 wt% boron nitride nanosheets, 2-5 wt% graphene, and 0.8-1.2 wt% DVB crosslinking agent.

7. The method for preparing a corrosion-resistant stainless steel positive electrode current collector according to claim 5, characterized in that: The preparation method of Li6PS5Cl@UIO-66 is as follows: Lithium-phosphorus-sulfur-chlorine solid electrolyte was added to acetonitrile and stirred evenly. Then, UIO-66 powder that had been dehydrated under vacuum at 130-150℃ for 8-12 hours was added. The mixture was then impregnated at 60-70℃ and (-0.08)-(-0.1) MPa for 12-16 hours. After impregnation, the mixture was centrifuged, washed with acetonitrile, and dried under vacuum at 70-80℃ to obtain Li6PS5Cl@UIO-66.

8. The method for preparing a corrosion-resistant stainless steel positive electrode current collector according to claim 7, characterized in that: The mass ratio of lithium phosphorus sulfur chlorine solid electrolyte to UIO-66 powder is 1:(3-5).

9. The method for preparing a corrosion-resistant stainless steel positive electrode current collector according to claim 1, characterized in that: In step 4, during the curing process, the temperature is raised in stages under nitrogen protection. First, the temperature is raised to 70-80℃ and cured for 90-100 seconds. Then, the temperature is raised to 100-110℃ and cured for 3-4 minutes. Finally, the temperature is raised to 130-135℃ and cured for 50-60 seconds. After the curing process is completed, hot pressing is performed at a temperature of 110-120℃, a pressure of 6-7 MPa, and a time of 3-5 minutes.

10. A corrosion-resistant stainless steel positive electrode current collector, characterized in that: It is prepared by any one of the preparation methods according to claims 1-9.

Images