A method for preparing a negative electrode current collector

Abstract

The present invention discloses a method for preparing a negative electrode current collector, comprising the following steps: a) coating an organic base layer containing palladium nano-catalytic particles on the upper and lower surfaces of a flexible substrate; b) curing the organic base layer; c) roughening the surface of the organic base layer; d) electroplating copper. The present invention reduces the process steps, improves the production efficiency, reduces the production cost, and improves the production yield. The nano-palladium catalyst is blended with the organic solid component, and the catalyst uniformly dispersed in the organic solid component is evenly dispersed, and the system is stable. The palladium nano-particles are more dense and uniform in the organic base layer, and further, based on the uniform catalyst nucleation points, the electrolessly deposited copper film is also more uniform and dense. It is suitable for a wide range of flexible substrates, the copper layer in the organic adhesive layer is more uniform, and the adhesion of the copper film is also better.

Description

Technical Field

[0001] The present invention belongs to the field of chemical technology, and particularly relates to a method for preparing a negative electrode current collector. Background Art

[0002] In recent years, with the rapid development of new energy vehicles, the industry's demand for secondary batteries with high energy density and low cost has been continuously increasing. Among them, the negative electrode current collector based on a flexible substrate is beneficial to the preparation of high-energy-density batteries due to its thinner structure and higher mechanical strength. At the same time, the preparation of the negative electrode current collector by chemical deposition method has attracted attention due to its lower production cost.

[0003] In the invention previously disclosed by the applicant, the negative electrode current collector was prepared by chemically plating copper after coating a catalyst on the organic adhesive layer on the surface of the substrate. The difficulty in the process of preparing a copper layer of higher quality lies in maintaining the stability of the palladium nano-catalyst system, reducing the agglomeration of the catalyst during the coating process, and improving its uniform dispersion, which poses relatively high requirements for the catalyst formulation. The inventor has also conducted extensive research on this problem in the disclosed invention.

[0004] The present invention provides another solution to this problem, which can not only eliminate the decline in copper plating quality caused by the aging instability or increased dosage of the colloidal palladium nano-catalyst resulting in agglomeration, but also reduce the process flow, lower the production cost, and improve the process yield. The copper film prepared by this solution also has better adhesion and density. Summary of the Invention

[0005] To solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A method for preparing a negative electrode current collector, comprising the following steps:

[0007] a) Coating an organic base layer slurry containing palladium nano-colloidal particles on the upper and lower surfaces of a flexible substrate;

[0008] b) Curing or drying the organic base layer slurry to form an organic base layer;

[0009] c) Roughening the surface of the organic base layer;

[0010] d) Plating copper on the surface of the roughened organic base layer;

[0011] The flexible substrate selected in the present invention is the substrate selected for conventional flexible current collectors, with a thickness of 1-15 μm, and includes one of polycarbonate, polyethylene naphthalate, polyethylene terephthalate, polymethyl methacrylate, polyvinyl chloride, polypropylene, polystyrene, polydimethylsiloxane, and polyimide

[0012] In the present invention, the substrate with the surface of the organic base layer roughened can be placed in an electroless copper plating solution for copper plating, and the copper plating thickness is 500 nm - 1000 nm, or first perform electroless copper plating of 100 - 200 nm, and then complete the remaining required copper layer thickness via electroplating.

[0013] In step a), the organic base layer paste is a curing system paste or a thermoplastic system paste; the curing system paste is composed of 100 parts by weight of a photoresist or a thermoresist and 5 - 15 parts by weight of a palladium-based high-efficiency catalyst; the thermoplastic system paste is composed of 100 parts by weight of a thermoplastic resin solution and 5 - 18 parts by weight of a palladium-based high-efficiency catalyst;

[0014] The palladium-based high-efficiency catalyst adopted in the present invention has palladium nanoparticles with a small average particle size and uniform distribution, and a large specific surface area. It can prepare a negative electrode current collector with good copper plating quality with a small addition amount. Among them, the palladium nanoparticles of the palladium-based high-efficiency catalyst are dispersed in the organic base layer, which is a hybrid system of organic solids and inorganic palladium nanocolloid catalytic particles; the mass ratio of the palladium nanoparticles of the palladium-based high-efficiency catalyst in the system to the organic solid components in the system plays an important role in preparing a negative electrode current collector with good copper plating quality. The inventor has found through a large number of experiments that the curing system paste is composed of 100 parts by weight of a photoresist or a thermoresist and 5 - 15 parts by weight of a palladium-based high-efficiency catalyst; the thermoplastic system paste is composed of 100 parts by weight of a thermoplastic resin solution and 5 - 18 parts by weight of a palladium-based high-efficiency catalyst. In the scheme for preparing the negative electrode current collector in the present invention, it is the best range that can initiate copper plating and can obtain a negative electrode current collector with good copper plating quality).

[0015] In step c), the roughening treatment is to adopt a wet method to treat the surface of the cured organic base layer; the surface roughness Sa of the organic base layer after the wet treatment of the surface is > 60 nm.

[0016] In the preparation scheme adopted in the present invention, the catalyst and the organic paste are applied to the surface of the flexible substrate as a mixed system, and the catalyst is uniformly dispersed in the organic paste. The surface of the organic base layer formed by curing the organic paste is flat. After experimental verification, when the surface roughness after roughening reaches more than 60 nm, it can expose the catalytic core sites in the system, thereby obtaining better catalytic efficiency and better copper plating quality.

[0017] As a preferred scheme, in step c), the roughening treatment of adopting a wet method to treat the surface of the cured organic base layer is as follows:

[0018] When the organic base layer slurry is a curing system slurry, the organic base layer is developed with a developer, and the developer is any one of a 0.5-1 wt% potassium hydroxide aqueous solution, a 0.5-1 wt% sodium hydroxide aqueous solution, and a 0.3-1 wt% tetramethylammonium hydroxide aqueous solution, and any selected developer further includes 0.2-0.6 wt% sodium lauryl sulfate;

[0019] When the organic base layer slurry is a thermoplastic system slurry, the surface of the organic base layer is etched successively with a 60-75 wt% aqueous solution of carbinol and an aqueous solution containing 0.2-0.6 wt% diethanolamine and 0.4-0.8 wt% sodium lauryl sulfate.

[0020] As a preferred solution, when the organic base layer slurry is a curing system slurry, that is, a curing system, in step b), the curing rate of the organic base layer is controlled between 75% and 85%.

[0021] The inventors found that by regulating the curing rate of the organic base layer of the curing system to control the curing rate between 75% and 85%, and at the same time selecting corresponding wet treatment liquids for roughening treatment for organic base layers of different systems, a better roughening effect can be obtained, thereby obtaining sufficient effective palladium catalytic centers.

[0022] As a preferred solution, the photoresist and the thermoresist are made from the following raw materials: resin: 10-25 wt%, polyfunctional acrylic monomer: 5-15 wt%, initiator: 0.5-1 wt%, leveling agent: 0.1-0.5 wt%, inhibitor: 0.01-0.2 wt%, and the rest is solvent; the initiator is a photoinitiator or a thermal initiator.

[0023] When the organic base layer slurry is a curing system slurry, the thermoresist uses a thermal initiator, and the organic base layer is cured by heating; the photoresist uses a photoinitiator and is cured by UV light irradiation;

[0024] As a preferred solution, the resin is one or a mixture of any of the following resins: aromatic acid acrylic polymer, polyester acrylate polymer, epoxy acrylate polymer, organosilicon-modified acrylate polymer, and polyurethane acrylate polymer, acrylic-epoxy resin copolymer, and acrylic-styrene resin copolymer.

[0025] The resin selected in the present invention plays a role in adjusting the adhesion in the whole structure. For different flexible base layers, by adjusting the type of resin, better adhesion of the organic bonding layer can be obtained. And the selected resin has good chemical resistance after curing, and can have good stability and corrosion resistance in subsequent chemical processes.

[0026] As a preferred embodiment, the multi-functional acrylic monomer is any one or more of alkoxylated bisphenol A di(methacrylate), trimethylolpropane triacrylate (TMPTA), pentaerythritol triacrylate (PETA), tris(2-hydroxyethyl) isocyanurate triacrylate, pentaerythritol tetraacrylate (PETTA), dipentaerythritol pentaacrylate (DPPA), and dipentaerythritol hexaacrylate (DPHA).

[0027] The polymerization monomers selected in the present invention are acrylic acids. After curing and polymerization, the organic adhesive layer system has good plasticity and will not completely prevent the copper plating solution from penetrating into the palladium nanoparticle catalytic core points in the organic adhesive layer during the copper plating process. Therefore, a metal phase can penetrate through the organic base layer and be connected to the metal layer to achieve good adhesion.

[0028] As a preferred embodiment, the photoinitiator is a cleavage-type free radical photoinitiator, preferably any one or more of acetophenone compounds (DEAP), acylphosphine oxides (BAP0), and α-aminoketone derivatives (907);

[0029] As a preferred embodiment, the thermal initiator is an organic or inorganic peroxide, azo, or redox thermal initiator, preferably any one or more of azobisisobutyronitrile (AIBN), azobisisovaleronitrile (AMBN), and azobisisoheptonitrile (ABVN).

[0030] The photoinitiator selected in the present invention has a fast photo-curing speed. After the light irradiation stops, the curing reaction stops and will not further cure. Therefore, a controllable curing rate can be ensured, and the organic adhesive layer will not be over-cured due to continuous curing, resulting in a reduction in the catalytic activity of the palladium nanoparticle catalytic core points due to encapsulation. Furthermore, a dense and good metal coating can be formed during the electroless copper plating process.

[0031] As a preferred embodiment, the leveling agent is a polyether-modified silicone surfactant, an acrylic leveling agent, or a fluorocarbon leveling agent.

[0032] As a preferred embodiment, the inhibitor is any one or more of phenols, quinones, aromatic amines, aromatic nitro compounds, and aluminum tris(N-nitroso-N-phenylhydroxylamine).

[0033] It can prevent the curing of the organic layer caused by free radicals generated by thermal initiation to a small extent, further prevent the further curing of the organic adhesive layer after the curing rate reaches the target value, and increase the threshold of the curing reaction.

[0034] As a preferred solution, the solvent is any one or a mixture of ethyl lactate, acetone, propylene glycol methyl ether acetate, propylene glycol methyl ether acetate, butyl acetate, and acetylacetone.

[0035] As a preferred solution, the thermoplastic resin solution is made from the following raw materials: 20-30 wt% thermoplastic resin, 0.1-2 wt% leveling agent, 5-10 wt% organic acid, and the balance is organic solvent.

[0036] As a preferred solution, the thermoplastic resin is a thermoplastic acrylic resin, preferably a hydroxy acrylic resin, any one or more of polyester-modified polypropylene resin and methyl methacrylate / butyl acrylate copolymer; more preferably BR-85 and 90 series resins of Mitsubishi.

[0037] As a preferred solution, the organic acid is any one or more of acetylacetone, 2-ketobutyric acid, and pyruvic acid.

[0038] As a preferred solution, the thickness of the organic base layer is 100-950 nm.

[0039] As a preferred solution, the preparation method of the palladium-based high-efficiency catalyst includes the following steps:

[0040] 1) Preparation of palladium nanoparticles: Weigh 100 parts by weight of a reducing solvent, 3-10 parts by weight of a palladium salt, and 5-32 parts by weight of a dispersant. Add all the reducing solvent, palladium salt, and half of the dispersant to the reaction vessel in sequence. After stirring evenly, heat to the reaction temperature for reaction. After reacting for 30 min, add the remaining half of the dispersant dropwise and finish dropping within 1 h, and control the mass ratio of the dispersant to the palladium salt in the reaction system to be maintained at 1.5-6:1. After the reaction ends, continue to stir and naturally cool to room temperature to obtain a mother liquor containing palladium nanoparticles;

[0041] The inventor found through a large number of creative experiments that when the mass ratio of the dispersant to the (composite) palladium salt is less than 1.5:1, the synthesized palladium nanoparticles have large particle sizes, uneven distribution, and poor stability; when the mass ratio of the dispersant to the palladium salt is greater than 6:1, the particle size and stability of the synthesized palladium nanoparticles do not change significantly, but the catalytic activity will decrease significantly due to excessive dispersant, resulting in rough copper plating and difficulty in plating.

[0042] In addition, as the reaction progresses, the content of palladium nanoparticles obtained by the reaction will be higher and higher. By adding a dispersant to coat and disperse the palladium nanoparticles, the dispersion stability of the palladium nanoparticles in the mother liquor of the present invention can be effectively provided.

[0043] 2) Filter the mother liquor containing palladium nanoparticles, then add deionized water and a fluorosurfactant, and stir and mix evenly to obtain the high-efficiency palladium-based catalyst.

[0044] In step 2), the weight percentage content of pure water in the high-efficiency palladium-based catalyst is 80% - 98%, and the weight percentage content of the fluorosurfactant is 0.1% - 2%.

[0045] The preparation method of the high-efficiency palladium-based catalyst of the present invention can generate palladium nanoparticles with a target particle size through the selection of raw materials and proportion configuration, as well as the control of the reaction process. The content of palladium nanoparticles in the mother liquor of the high-efficiency palladium-based catalyst within the target particle size range is high, the reduction degree of preparation is high, and the yield is relatively high.

[0046] Through the selection of raw materials and proportion configuration, as well as the control of the reaction process, palladium nanoparticles with a target particle size can be generated. The average particle size of palladium nanoparticles in the high-efficiency palladium-based catalyst within the target particle size range is small and evenly distributed, all within the range of 2 - 8 nm.

[0047] Through the selection of raw materials and proportion configuration, as well as the control of the reaction process, palladium nanoparticles with a target particle size can be generated. The high-efficiency palladium-based catalyst within the target particle size range has good stability at room temperature; and the larger the particle size, the earlier precipitation appears.

[0048] Through the selection of raw materials and proportion configuration, as well as the control of the reaction process, palladium nanoparticles with a target particle size can be generated. The high-efficiency palladium-based catalyst within the target particle size range has a large specific surface area of palladium nanoparticles, high efficiency in catalytic preparation of current collectors, and good effects (the performance of the prepared current collectors is excellent).

[0049] During the preparation process of the palladium nanoparticles, the uniform stirring means that the stirring temperature is 40 - 50 °C, the stirring speed is 400 - 800 rpm, and the stirring time is 30 - 60 min (so as to ensure that the palladium salt is fully dissolved and reduce problems such as the reduction of conversion rate caused by incomplete dissolution of the palladium salt); the reaction temperature during the reaction process is 95 - 125 °C, the stirring speed is 400 - 800 rpm, and the reaction time is 1.5 - 2.5 h.

[0050] In the preparation method of the high-efficiency palladium-based catalyst of the present invention, the reducing solvent is a mixed composite solvent of ethyl lactate and triethylene glycol, and the palladium salt is a mixed composite palladium salt of palladium acetate and tetraammine palladium nitrate. Among them, the reducing solvent simultaneously acts as a solvent and a reducing agent, and no additional reducing agent needs to be added, which reduces the reduction reaction rate, makes the synthesized nanoparticles (particles) smaller and more uniform.

[0051] However, when the existing reaction temperature is 50 - 80°C, the reaction system of the present invention will not react, that is, the highly efficient palladium-based catalyst of the present invention cannot be prepared. Through a large number of creative experiments, the inventors found that the reaction process control is "during the preparation process of the palladium nanoparticles, the uniform stirring is carried out at a stirring temperature of 40 - 50°C, a stirring speed of 400 - 800 rpm, and a stirring time of 30 - 60 min; the reaction temperature during the reaction process is 95 - 125°C, the stirring speed is 400 - 800 rpm, and the reaction time is 1.5 - 2.5 h". That is, a reasonable reaction temperature range and an appropriate stirring rate enable the reaction system of the present invention to react relatively slowly and at a more uniform rate to produce smaller and more uniform nanoparticles (particles) with a larger specific surface area.

[0052] In practical applications, the reducing solvent can be any one or more of ethyl lactate, tetraethylene glycol, and triethylene glycol.

[0053] As a preferred embodiment, in step 1), the reducing solvent is a mixed composite solvent of ethyl lactate and triethylene glycol.

[0054] As a more preferred embodiment, in the mixed composite solvent of ethyl lactate and triethylene glycol, the mass ratio of ethyl lactate to triethylene glycol is 100:25 - 35.

[0055] In the preparation method of the highly efficient palladium-based catalyst of the present invention, the inventors found through a large number of creative experiments that: the reducing solvent is a mixed composite solvent of ethyl lactate and triethylene glycol in a certain proportion. The reducibility of ethyl lactate is stronger than that of triethylene glycol. When they are used in a mass ratio of 100:25 - 35, they play a good synergistic role and cooperate with other components (the mixed composite palladium salt of palladium acetate and palladium tetraammine nitrate). Combined with the reaction process control, it can make the reaction system of the present invention maintain a slow and uniform reaction rate to produce smaller and more uniform nanoparticles (particles) with a larger specific surface area; it can effectively avoid too fast reaction rate locally and improve the continuous stability of the reduction reaction; it can also increase the boiling point of the mixed solvent and further ensure the continuous stability of the reaction system.

[0056] In practical applications, the palladium salt can be at least one of ammonium chloropalladate, palladium tetraammine nitrate, palladium nitrate, palladium acetate, and palladium chloride.

[0057] As a preferred embodiment, in step 1), the palladium salt is a mixed composite palladium salt of palladium acetate and palladium tetraammine nitrate.

[0058] As a more preferred embodiment, in the mixed composite palladium salt of palladium acetate and palladium tetraammine nitrate, the mass ratio of palladium acetate to palladium tetraammine nitrate is 1:0.1 - 0.15.

[0059] In the preparation method of the palladium-based high-efficiency catalyst of the present invention, the inventors found through a large number of creative experiments that after palladium acetate (which dissolves slowly when used alone) and palladium diammine nitrate are dissolved in the reducing solvent, palladium diammine nitrate can generate amino groups, consume hydrogen ions in the reaction system, enhance the reaction activity of the reducing solvent, increase the content of palladium ions liberated by palladium acetate in the reaction system of the present invention, and increase the concentration of free palladium ions in the reaction system. When the two are used in a mass ratio of 1:0.1 - 0.15, they play a good synergistic effect, can keep the palladium ion concentration in the reaction system constant within a certain range, thereby ensuring and cooperating with other components (the reducing solvent). By controlling the reaction process, the reaction system of the present invention can be maintained to slowly and uniformly react to produce smaller and more uniform nanoparticles (particles) with a larger specific surface area.

[0060] As a preferred solution, the dispersant is any one or more of Solsperse-3000, Solsperse-9000, Solsperse-24000, Solsperse-46000, and Solsperse-20000 of Lubrizol in the United States.

[0061] As a more preferred solution, the dispersant is Solsperse-46000.

[0062] Compared with other dispersants, when the dispersant is Solsperse-46000, its molecular weight is relatively large, and the wrapping and protection effect on the synthesized nanoparticles is better, making the synthesized particles smaller, more stable, and less likely to agglomerate. However, an overly large molecular weight will result in overly strong wrapping on the outer surface of the synthesized particles, reducing the catalytic effect to a certain extent.

[0063] As a preferred solution, the fluorocarbon surfactant is any one or more of perfluorinated end-carboxylate, perfluoroalkyl ethyl sulfonate, perfluorooctyl methyl sulfate, perfluoroalkyl ether phosphate, perfluoropolyether carboxylic acid, fluoroalkylamine quaternary ammonium salt, fluoroalkyl acylamino quaternary ammonium salt, fluoroalkyl ammonium salt, carboxybetaine, sulfobetaine, sulfate betaine, fluoroalkyl polyoxyethylene ether alcohol, fluoroalkyl sulfonamido alcohol, fluoroalkyl benzene, and fluoroalkane.

[0064] The beneficial effects of the present invention are:

[0065] (1) In the preparation solution of the negative electrode current collector of the present invention, the preparation of the organic binder layer and the catalytic system can be completed only by one-step coating method, which reduces the process steps, improves the production efficiency, reduces the production cost, and improves the production yield.

[0066] (2) The highly efficient nano-palladium catalyst provided in the present invention is blended with the organic solid component, and the catalyst dispersed in the organic solid component is evenly dispersed, the system is stable, and there will be no precipitation of the catalyst in the aqueous dispersion and agglomeration during coating. The organic solid component and the nano-palladium catalyst are premixed, so that the palladium nanoparticles are more densely and uniformly distributed in the organic base layer, and then, based on the uniform catalyst nucleation points, the electrolessly deposited copper film is also more uniform and dense.

[0067] (3) The preparation scheme provided by the present invention is suitable for a wide range of flexible substrates. Through the formulation control of the organic adhesive layer, strong chemical bonds can be formed with the surface of the flexible substrate, and it has good adhesion.

[0068] (4) In the preparation scheme provided by the present invention, the curing rate of the adhesive layer is controlled by the exposure energy and the baking temperature. Through surface chemical surface treatment, the surface roughness of the organic adhesive layer is controlled. The electroless copper plating solution can penetrate into the organic adhesive layer system, and copper plating occurs simultaneously at the palladium nano-catalytic nucleation points inside and on the surface of the organic adhesive layer, forming a copper layer that penetrates the organic phase. Moreover, the concentration gradient of the palladium nanoparticles in the organic coating in the direction perpendicular to the substrate is consistent, so the copper layer formed in the organic adhesive layer is more uniform, and the adhesion of the copper film is also better.

[0069] (5) The preparation method of the palladium-based highly efficient catalyst of the present invention can generate palladium nanoparticles with a target particle size through the selection and proportioning of raw materials and the control of the reaction process. Moreover, the preparation has a high reduction degree and a high yield (the reaction is complete, close to 100%). The content of palladium nanoparticles in the mother liquor of the palladium-based highly efficient catalyst with palladium nanoparticles within the target particle size range is high;

[0070] Through the selection and proportioning of raw materials and the control of the reaction process, palladium nanoparticles with a target particle size can be generated. The average particle size of the palladium nanoparticles in the palladium-based highly efficient catalyst with palladium nanoparticles within the target particle size range is small and evenly distributed, all within the range of 2 - 8 nm;

[0071] Through the selection and proportioning of raw materials and the control of the reaction process, palladium nanoparticles with a target particle size can be generated. The palladium-based highly efficient catalyst with palladium nanoparticles within the target particle size range has good stability when placed at room temperature;

[0072] Through the selection and proportioning of raw materials and the control of the reaction process, palladium nanoparticles with a target particle size can be generated, and the average particle size of the palladium nanoparticles is small and evenly distributed. Through calculation, the specific surface area of the palladium nanoparticles of the present invention is 180 m 2 / g - 450 m 2 / g, that is, the specific surface area of the palladium nanoparticles in the palladium-based highly efficient catalyst with palladium nanoparticles within the target particle size range is large, the efficiency of catalytically preparing the current collector is high, and the effect is good (the performance of the prepared current collector is excellent). Description of the Drawings

[0073] Figure 1 It is a comparative diagram of the adhesion test of the samples of Example 7 and Comparative Examples 10 and 11 of the present invention;

[0074] Figure 2 It is a comparative SEM diagram of the cross-section of the copper film of the samples of Example 7 and Comparative Example 10 of the present invention;

[0075] Figure 3 It is a comparative roughness test diagram of the film surface before copper plating after roughening of Example 7 and Comparative Example 12 of the present invention. Detailed Embodiments

[0076] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0077] Example 1:

[0078] A preparation method of a palladium-based high-efficiency catalyst includes the following steps:

[0079] 1) Preparation of palladium nanoparticles: Weigh 100 parts by weight of a reducing solvent, 5 parts by weight of a palladium salt, and 25 parts by weight of a dispersant. Add all the reducing solvent, palladium salt, and half of the dispersant to the reaction vessel in sequence. After stirring evenly, heat to the reaction temperature for reaction. After reacting for 30 minutes, add the remaining half of the dispersant dropwise, and finish dropping within 1 hour, and control the mass ratio of the dispersant to the palladium salt in the reaction system to be maintained at 5:1. After the reaction ends, continue to stir and naturally cool to room temperature to obtain a mother liquor containing palladium nanoparticles;

[0080] 2) Filter the mother liquor containing palladium nanoparticles, and then add deionized water and a fluorosurfactant, and stir and mix evenly to obtain the palladium-based high-efficiency catalyst;

[0081] In step 2), the weight percentage content of pure water in the palladium-based high-efficiency catalyst is 85%, and the weight percentage content of the fluorosurfactant is 0.8%.

[0082] In this embodiment, during the preparation process of the palladium nanoparticles, the uniform stirring means that the stirring temperature is 42°C, the stirring speed is 500 rpm, and the stirring time is 50 minutes; the reaction temperature during the reaction process is 105°C, the stirring speed is 500 rpm, and the reaction time is 2 hours.

[0083] In this embodiment, in step 1), the reducing solvent is a mixed composite solvent of ethyl lactate and triethylene glycol.

[0084] In this embodiment, in the mixed composite solvent of ethyl lactate and triethylene glycol, the mass ratio of ethyl lactate to triethylene glycol is 100:28.

[0085] In this embodiment, in step 1), the palladium salt is a mixed composite palladium salt of palladium acetate and tetraamminepalladium nitrate.

[0086] In this embodiment, in the mixed composite palladium salt of palladium acetate and tetraamminepalladium nitrate, the mass ratio of palladium acetate to tetraamminepalladium nitrate is 1:0.12.

[0087] In this embodiment, the dispersant is Solsperse-46000 from Lubrizol.

[0088] The fluorocarbon surfactant is a perfluorinated end-group carboxylate and a fluoroalkyl polyoxyethylene ether alcohol with a mass ratio of 1:1.

[0089] A highly efficient palladium-based catalyst is prepared by using the preparation method of the highly efficient palladium-based catalyst described above.

[0090] Example 2:

[0091] A preparation method of a highly efficient palladium-based catalyst includes the following steps:

[0092] 1) Preparation of palladium nanoparticles: Weigh 100 parts by weight of a reducing solvent, 8 parts by weight of a palladium salt, and 24 parts by weight of a dispersant. Add all the reducing solvent, palladium salt, and half of the dispersant to a reaction vessel in sequence. After stirring evenly, heat to the reaction temperature for reaction. After reacting for 30 min, add the remaining half of the dispersant dropwise, and finish dropping within 1 h. Control the mass ratio of the dispersant to the palladium salt in the reaction system to be maintained at 3:1. After the reaction ends, continue stirring and naturally cool to room temperature to obtain a mother liquor containing palladium nanoparticles.

[0093] 2) Filter the mother liquor containing palladium nanoparticles, then add deionized water and a fluorine-containing surfactant, and stir and mix evenly to obtain the highly efficient palladium-based catalyst.

[0094] In step 2), the weight percentage content of pure water in the highly efficient palladium-based catalyst is 94%, and the weight percentage content of the fluorine-containing surfactant is 1.6%.

[0095] In this embodiment, during the preparation of the palladium nanoparticles, the uniform stirring is carried out at a stirring temperature of 47 °C, a stirring speed of 700 rpm, and a stirring time of 40 min; during the reaction process, the reaction temperature is 115 °C, the stirring speed is 700 rpm, and the reaction time is 2 h.

[0096] In this embodiment, in step 1), the reducing solvent is a mixed composite solvent of ethyl lactate and triethylene glycol.

[0097] In this embodiment, in the mixed composite solvent of ethyl lactate and triethylene glycol, the mass ratio of ethyl lactate to triethylene glycol is 100:32.

[0098] In this embodiment, in step 1), the palladium salt is a mixed composite palladium salt of palladium acetate and tetraamminepalladium nitrate.

[0099] In this embodiment, in the mixed composite palladium salt of palladium acetate and tetraamminepalladium nitrate, the mass ratio of palladium acetate to tetraamminepalladium nitrate is 1:0.14.

[0100] In this embodiment, the dispersant is Solsperse-46000 from Lubrizol, USA.

[0101] The fluorocarbon surfactant is fluoroalkyl polyoxyethylene ether alcohol.

[0102] A highly efficient palladium-based catalyst is prepared by using the preparation method of the highly efficient palladium-based catalyst described above.

[0103] Example 3:

[0104] A preparation method of a highly efficient palladium-based catalyst includes the following steps:

[0105] 1) Preparation of palladium nanoparticles: Weigh 100 parts by weight of the reducing solvent, 6.5 parts by weight of the palladium salt, and 26 parts by weight of the dispersant. Add all the reducing solvent, palladium salt, and half of the dispersant to the reaction vessel in sequence. After stirring evenly, heat to the reaction temperature for reaction. After reacting for 30 min, add the remaining half of the dispersant dropwise, and finish adding it within 1 h, and control the mass ratio of the dispersant to the palladium salt in the reaction system to be maintained at 4:1. After the reaction ends, continue to stir and naturally cool to room temperature to obtain a mother liquor containing palladium nanoparticles;

[0106] 2) Filter the mother liquor containing palladium nanoparticles, then add deionized water and a fluorine-containing surfactant, and stir and mix evenly to obtain the highly efficient palladium-based catalyst;

[0107] In step 2), the weight percentage content of pure water in the highly efficient palladium-based catalyst is 90%, and the weight percentage content of the fluorine-containing surfactant is 0.12%.

[0108] In this embodiment, during the preparation of the palladium nanoparticles, the uniform stirring is carried out at a stirring temperature of 45°C, a stirring speed of 600 rpm, and a stirring time of 40 min; during the reaction process, the reaction temperature is 110°C, the stirring speed is 600 rpm, and the reaction time is 2 h.

[0109] In this embodiment, in step 1), the reducing solvent is a mixed composite solvent of ethyl lactate and triethylene glycol.

[0110] In this embodiment, in the mixed composite solvent of ethyl lactate and triethylene glycol, the mass ratio of ethyl lactate to triethylene glycol is 100:30.

[0111] In this embodiment, in step 1), the palladium salt is a mixed composite palladium salt of palladium acetate and tetraamminepalladium nitrate.

[0112] In this embodiment, in the mixed composite palladium salt of palladium acetate and tetraamminepalladium nitrate, the mass ratio of palladium acetate to tetraamminepalladium nitrate is 1:0.13.

[0113] In this embodiment, the dispersant is Solsperse-46000 from Lubrizol Corporation, USA.

[0114] The fluorocarbon surfactant is a perfluorinated end-group carboxylate.

[0115] A highly efficient palladium-based catalyst is prepared by using the preparation method of the highly efficient palladium-based catalyst described above.

[0116] Comparative Example 0:

[0117] The difference from Example 3 is that in step 1), the mass ratio of the dispersant to the palladium salt in the reaction system is maintained at 1:1, and the others are the same as in Example 3.

[0118] Comparative Example 1:

[0119] The difference from Example 3 is that in step 1), the mass ratio of the dispersant to the palladium salt in the reaction system is maintained at 7:1, and the others are the same as in Example 3.

[0120] Comparative Example 2:

[0121] The difference from Example 3 is that during the preparation of the palladium nanoparticles, the reaction temperature is 80°C, and the others are the same as in Example 3.

[0122] Comparative Example 3:

[0123] The difference from Example 3 is that the reducing solvent is replaced with butyl acetate, and the others are the same as in Example 3.

[0124] Comparative Example 4:

[0125] The difference from Example 3 is that the reducing solvent only uses ethyl lactate and does not use triethylene glycol, and the others are the same as in Example 3.

[0126] Comparative Example 5:

[0127] The difference from Example 3 is that the palladium salt is palladium nitrate, and the others are the same as in Example 3.

[0128] Comparative Example 6:

[0129] The difference from Example 3 is that the palladium salt is palladium acetate and does not contain tetraammine palladium nitrate, and the others are the same as in Example 3.

[0130] Comparative Example 7:

[0131] The difference from Example 3 is that the dispersant is Solsperse-24000 of Lubrizol, USA, and the others are the same as in Example 3.

[0132] Next, performance tests were carried out on the preparation methods of the palladium-based highly efficient catalysts obtained in Examples 1 to 3 and Comparative Examples 0 to 7 of the present invention and the ordinary palladium-based catalysts (obtained by reduction with a reducing agent), and the test results are shown in Table 1:

[0133] Among them, the test method for the reaction degree of the mother liquor: Take 1 mL of the mother liquor in a test tube, add 5 mL of saturated NaCl solution, shake evenly, and filter with a 1 μm glass fiber filter membrane to obtain the supernatant. Observe the color of the supernatant. If the reaction is complete, it is colorless and transparent. If it is yellow to orange-yellow, it means that there is unreacted palladium salt.

[0134] Among them, the test method for the average particle size and particle size distribution of palladium nanoparticles is as follows: Dilute the catalyst 8-10 times with electronic grade ethyl lactate, prepare a sample by the TEM sample preparation method for transmission electron microscopy, take a photo with a transmission electron microscope TEM, and count the particle size of palladium nanoparticles to calculate the average particle size of palladium nanoparticles.

[0135] The method for evaluating the stability over time: For the prepared palladium-based highly efficient catalyst, take 30 mL of the sample in a transparent glass sample bottle, place it for one week, observe whether there is precipitation at the bottom of the bottle, and filter with a 1 μm glass fiber filter membrane to observe whether there are particles precipitated.

[0136] Table 1

[0137]

[0138]

[0139] Note: In the above table, "-" indicates that since no reaction product was obtained, this test item has no statistical significance.

[0140] As can be seen from the above table, the preparation method of the palladium-based high-efficiency catalyst of the present invention has the following advantages: By selecting raw materials and configuring their proportions, and controlling the reaction process, palladium nanoparticles with a target particle size can be generated, and the preparation has a high reduction degree and a high yield (the reaction is complete, close to 100%). The content of palladium nanoparticles in the mother liquor of the palladium-based high-efficiency catalyst with the palladium nanoparticle size within the target range is high.

[0141] By selecting raw materials and configuring their proportions, and controlling the reaction process, palladium nanoparticles with a target particle size can be generated. The average particle size of the palladium nanoparticles in the palladium-based high-efficiency catalyst with the palladium nanoparticle size within the target range is small and evenly distributed, all within the range of 2 - 8 nm.

[0142] By selecting raw materials and configuring their proportions, and controlling the reaction process, palladium nanoparticles with a target particle size can be generated. The palladium-based high-efficiency catalyst with the palladium nanoparticle size within the target range has good stability when placed at room temperature.

[0143] By selecting raw materials and configuring their proportions, and controlling the reaction process, palladium nanoparticles with a target particle size can be generated, and the average particle size of the palladium nanoparticles is small and evenly distributed. Through calculation, the specific surface area of the palladium nanoparticles of the present invention is 180 m 2 / g - 450 m 2 / g, that is, the specific surface area of the palladium nanoparticles in the palladium-based high-efficiency catalyst with the palladium nanoparticle size within the target range is large, the efficiency of catalytically preparing the current collector is high, and the effect is good (the performance of the prepared current collector is excellent).

[0144] Example 4

[0145] A method for preparing a negative current collector includes the following steps:

[0146] a) Coat an organic base layer slurry containing palladium nanocolloid particles on both the upper and lower surfaces of a 5-um flexible substrate polyethylene terephthalate;

[0147] b) Dry the organic base layer slurry until the solid content is 85% to form an organic base layer;

[0148] c) Roughen the surface of the organic base layer;

[0149] d) Deposit copper on the surface of the roughened organic base layer;

[0150] In step a), the organic base layer slurry is a thermoplastic system slurry; it consists of 100 parts by weight of a thermoplastic resin solution and 15 parts by weight of a palladium-based high-efficiency catalyst;

[0151] In step c), the roughening treatment is to wet-treat the surface of the cured organic base layer; after the wet treatment of the surface of the organic base layer, the surface roughness Sa of the organic base layer is > 60 nm.

[0152] In this embodiment, in step c), the roughening treatment of wet-treating the surface of the cured organic base layer is as follows:

[0153] Soak and erode the surface of the organic base layer with an aqueous solution of 70 wt% carbinol and an aqueous solution containing 0.4 wt% diethanolamine and 0.5 wt% sodium lauryl sulfate for 30 s in sequence;

[0154] In this embodiment, the thermoplastic resin solution is made from the following raw materials: 25 wt% thermoplastic resin (BR-85 of Mitsubishi), 0.1 wt% leveling agent (BYK-33), 5 wt% organic acid (acetylacetone), 69.9 wt% ethyl lactate.

[0155] In this embodiment, the thickness of the organic base layer is 500 nm.

[0156] In this embodiment, for the preparation method of the negative electrode current collector, the preparation method of the palladium-based highly efficient catalyst is the preparation method of the palladium-based highly efficient catalyst in Example 1, and the palladium-based highly efficient catalyst is obtained.

[0157] In this embodiment, the copper plating on the surface of the roughened organic base layer in step d) is as follows:

[0158] The product after roughening treatment is subjected to electroless plating of a double-sided metallic copper layer in an electroless copper plating solution at 38 °C for 296 s;

[0159] The initial components of the electroless copper plating solution include: copper sulfate 5 g / L, potassium sodium tartrate 25 g / L, disodium EDTA 5 g / L, sodium hydroxide 7 g / L, formaldehyde 7 g / L, methanol 2.5 g / L, potassium ferrocyanide 20 mg / L, 2,2'-bipyridine 15 mg / L.

[0160] Example 5

[0161] A preparation method of a negative electrode current collector includes the following steps:

[0162] a) Coat a layer of organic base layer slurry containing palladium nanocolloid particles on each of the upper and lower surfaces of a 5-μm flexible substrate polyethylene terephthalate;

[0163] b) Cure the organic base layer slurry to form an organic base layer;

[0164] c) Roughen the surface of the organic base layer;

[0165] d) Copper plating is carried out on the surface of the roughened organic base layer;

[0166] In step a), the organic base layer slurry is a curing system slurry; the curing system slurry is composed of 100 parts by weight of a thermally induced resist and 5 parts by weight of a palladium-based high-efficiency catalyst;

[0167] In step c), the roughening treatment is to wet-treat the surface of the cured organic base layer; after the wet treatment of the surface of the organic base layer, the surface roughness Sa of the organic base layer is > 60 nm.

[0168] In this embodiment, in step c), the roughening treatment of wet-treating the surface of the cured organic base layer is as follows:

[0169] The cured sample is immersed and rinsed in an aqueous solution of 1 wt% potassium hydroxide and 0.4 wt% sodium lauryl sulfate for 90 s;

[0170] In this embodiment, in step b), the curing rate of the organic base layer is controlled at 75%.

[0171] In this embodiment, the thermally induced resist is made from the following raw materials: 15 wt% resin (Changxing Chemical 6072), 10 wt% dipentaerythritol hexaacrylate (DPHA), 1 wt% thermal initiator (azodiisovaleronitrile), 0.4 wt% leveling agent (BYK-33), 0.2 wt% phenolic inhibitor (2,5-di-tert-butylhydroquinone), and the rest is propylene glycol methyl ether solvent;

[0172] In this embodiment, the thickness of the organic base layer is 300 nm.

[0173] In this embodiment, for the preparation method of the negative electrode current collector, the preparation method of the palladium-based high-efficiency catalyst is the preparation method of the palladium-based high-efficiency catalyst in Example 2 to obtain a palladium-based high-efficiency catalyst.

[0174] In this embodiment, in step d), copper plating on the surface of the roughened organic base layer is as follows:

[0175] The roughened product is subjected to electroless plating of a double-sided metal copper layer in an electroless copper plating solution at 38 °C for 296 seconds;

[0176] The initial components of the electroless copper plating solution include: copper sulfate 5 g / L, potassium sodium tartrate 25 g / L, disodium EDTA 5 g / L, sodium hydroxide 7 g / L, formaldehyde 7 g / L, methanol 2.5 g / L, potassium ferrocyanide 20 mg / L, 2,2′-bipyridine 15 mg / L.

[0177] Example 6

[0178] A preparation method of a negative electrode current collector, comprising the following steps:

[0179] a) Coating an organic base layer slurry containing palladium nanocolloid particles on both the upper and lower surfaces of a 5-μm flexible substrate polyethylene terephthalate;

[0180] b) Curing the organic base layer slurry to form an organic base layer;

[0181] c) Roughening the surface of the organic base layer;

[0182] d) Electroplating copper on the surface of the roughened organic base layer;

[0183] In step a), the organic base layer slurry is a curing system slurry; the organic base layer slurry is composed of 100 parts by weight of a photoresist and 10 parts by weight of a palladium-based high-efficiency catalyst;

[0184] In step c), the roughening treatment is to wet-treat the surface of the cured organic base layer; the surface roughness Sa of the organic base layer after wet treatment is > 60 nm.

[0185] In this embodiment, in step c), the roughening treatment of wet-treating the surface of the cured organic base layer is as follows:

[0186] When the organic base layer slurry is a curing system slurry, the organic base layer is developed with a developer, and the developer is:

[0187] Immersing and rinsing the cured sample in an aqueous solution of 0.8 wt% sodium hydroxide and 0.45 wt% sodium lauryl sulfate for 84 s;

[0188] In this embodiment, in step b), the curing rate of the organic base layer is controlled at 85%.

[0189] In this embodiment, the photoresist is made from the following raw materials: aromatic acid acrylic oligomer (Sartomer Sarbox SB-400): 13 wt%, dipentaerythritol hexaacrylate (DPHA): 12 wt%, acylphosphine oxide photoinitiator (BAP0): 1 wt%, leveling agent (BYK-33): 0.5 wt%, inhibitor p-methoxyphenol (MEHQ): 0.01 - 0.2 wt%, and the balance is propylene glycol methyl ether solvent;

[0190] In this embodiment, the thickness of the organic base layer is 300 nm.

[0191] In this embodiment, for the preparation method of the negative electrode current collector, the preparation method of the palladium-based high-efficiency catalyst is the preparation method of the palladium-based high-efficiency catalyst in Example 3 to obtain the palladium-based high-efficiency catalyst.

[0192] In this embodiment, step d) of copper plating on the surface of the roughened organic base layer is as follows:

[0193] The product after roughening treatment is subjected to electroless plating of a double-sided metal copper layer in an electroless copper plating solution at 38°C for 296 seconds;

[0194] The initial components of the electroless copper plating solution include: 5 g / L of copper sulfate, 25 g / L of sodium potassium tartrate, 5 g / L of disodium EDTA, 7 g / L of sodium hydroxide, 7 g / L of formaldehyde, 2.5 g / L of methanol, 20 mg / L of potassium ferrocyanide, and 15 mg / L of 2,2'-bipyridine.

[0195] Example 7

[0196] A method for preparing a negative electrode current collector includes the following steps:

[0197] a) Coating a layer of organic base layer slurry containing palladium nanocolloid particles on each of the upper and lower surfaces of a 5-μm flexible substrate polyethylene terephthalate;

[0198] b) Curing the organic base layer slurry to form an organic base layer;

[0199] c) Roughening the surface of the organic base layer;

[0200] d) Copper plating on the surface of the roughened organic base layer;

[0201] In step a), the organic base layer slurry is a curing system slurry; the organic base layer slurry is composed of 100 parts by weight of a photoresist and 13 parts by weight of a palladium-based high-efficiency catalyst;

[0202] In step c), the roughening treatment is to wet-treat the surface of the cured organic base layer; the surface roughness Sa of the organic base layer after wet treatment of the surface is > 60 nm.

[0203] In this embodiment, in step c), the roughening treatment of wet-treating the surface of the cured organic base layer is as follows:

[0204] Immerse and rinse the cured sample in an aqueous solution of 1 wt% sodium hydroxide and 0.5 wt% sodium lauryl sulfate for 84 s;

[0205] In this embodiment, in step b), the curing rate of the organic base layer is controlled at 80%.

[0206] In this embodiment, the photoresist is made from the following raw materials: aromatic acid acrylic oligomer (Sartomer Sarbox SB-400): 13 wt%, dipentaerythritol hexaacrylate (DPHA): 12 wt%, acylphosphine oxide photoinitiator (BAP0): 1 wt%, leveling agent (BYK-33): 0.5 wt%, inhibitor p-methoxyphenol (MEHQ): 0.01 - 0.2 wt%, and the balance is propylene glycol methyl ether solvent;

[0207] In this embodiment, the thickness of the organic base layer is 300 nm.

[0208] In this embodiment, in the preparation method of the negative current collector, the preparation method of the palladium-based high-efficiency catalyst is the preparation method of the palladium-based high-efficiency catalyst in Example 3, and the palladium-based high-efficiency catalyst is obtained.

[0209] In this embodiment, step d) of copper plating on the surface of the roughened organic base layer is as follows:

[0210] The roughened product is subjected to electroless plating of a double-sided metal copper layer in an electroless copper plating solution at 38 °C for 296 seconds;

[0211] The initial components of the electroless copper plating solution include: copper sulfate 5 g / L, potassium sodium tartrate 25 g / L, disodium EDTA 5 g / L, sodium hydroxide 7 g / L, formaldehyde 7 g / L, methanol 2.5 g / L, potassium ferrocyanide 20 mg / L, 2,2'-bipyridine 15 mg / L.

[0212] Comparative Example 8:

[0213] The difference from Example 7 is that in the preparation method of the negative current collector, the preparation method of the palladium-based high-efficiency catalyst is the preparation method of the palladium-based high-efficiency catalyst in Comparative Example 0 (after filtration), and the palladium-based high-efficiency catalyst is obtained, and the others are the same as in Example 7.

[0214] Comparative Examples 9 - 10:

[0215] The difference from Example 7 is that the organic base layer slurry is composed of 100 parts by weight of photoresist and 3 and 18 parts by weight of palladium-based high-efficiency catalyst respectively, and the others are the same as in Example 7.

[0216] Comparative Examples 11 - 12:

[0217] The difference from Example 7 is that in step b), the curing rate of the organic base layer is controlled to be 70% and 90% respectively, and the others are the same as in Example 7.

[0218] Comparative Example 13:

[0219] The difference from Example 7 is that "step c) roughening the surface of the organic base layer;" is missing, and the rest is the same as Example 7.

[0220] Copper plating film quality evaluation method: Conductivity test ---- Take the prepared sample with a size larger than 10x10 cm, and use a 4-probe square resistance meter to test the surface resistance of 9 points on the surface of the sample, and calculate its average value.

[0221] Adhesion test ---- On the surface of the prepared sample, use a cross-cut knife to cut horizontally and vertically in the specified area, stick with 3M 610 type tape, drive away the air bubbles, and then tear it off within 1-2 s. Observe the peeling situation in the cross-cut area. If there is no peeling, it passes the 5B level; if there is peeling, determine the grade according to the peeling ratio, and use a confocal microscope to observe the height of the sample residue to confirm the peeling failure layer.

[0222] Copper film density test ---- Take the sample after copper plating is completed, and use a SEM scanning electron microscope (FEI helios660) to test the cross-section of the copper film to observe the copper film density.

[0223] According to the above-mentioned evaluation method of the conductivity of the copper plating film, test the surface average resistance of the above-mentioned comparative examples and examples.

[0224] According to the above-mentioned copper plating film adhesion test method, evaluate the adhesion of the above-mentioned comparative examples and examples.

[0225] According to the above-mentioned copper film density test, test the cross-sectional morphology of the copper layer of Comparative Example 10 and Example 7

[0226] The surface average resistance of the negative electrode current collector films of different examples and comparative examples is shown in the following table:

[0227]

[0228]

[0229] The adhesion of Comparative Example 10 and 11 is 4B, and the rest is 5B.

[0230] As can be seen from the above table, the negative current collectors obtained according to the preparation method provided by the present invention all have good conductivity and copper film adhesion, and with the increase of the palladium catalytic core sites, the copper plating effect is good. Under the same copper plating conditions, the copper plating speed increases in turn, manifested as the surface resistance decreases in turn.

[0231] From the comparison between Example 7 and Comparative Example 9, it can be seen that under the same coating thickness and exposure energy, when the catalyst content is too small, the catalytic sites are not enough to initiate the copper plating reaction, the copper plating quality is poor, and the surface resistance is large.

[0232] From Example 7 and Comparative Example 8, it can be seen that under the condition that other conditions are the same, using the preferred catalyst of the present invention is beneficial to obtaining better copper plating quality. The catalyst selected in the comparative example has poor dispersibility, the obtained copper film has poor compactness, and the surface resistance is also large.

[0233] From the resistance test and adhesion test data of Example 7, Comparative Example 9 and 10, it can be seen that as the amount of the catalyst increases, the copper plating speed further increases, and a smaller surface resistance can also be obtained. However, an excessive amount of the catalyst causes the surface copper layer to grow faster. Figure 2 It can be seen that the growth of the metal layer infiltrated inside the sample of Comparative Example 10 is poor, resulting in a decrease in the anchoring ability and a decrease in the adhesion of the copper film.

[0234] From the comparison between Example 7 and Comparative Examples 11 and 12, it can be seen that under the condition that the coating amount and the catalyst content are the same, the surface copper plating speed decreases with the increase of the curing rate. As the curing rate increases, the organic bonding layer becomes difficult to be swollen by the copper plating solution. Figure 3 It can be seen that the roughening effect of Comparative Example 12 also becomes poor, resulting in a relatively reduced number of catalyst nuclei in contact with the copper plating solution, causing the copper plating speed to decrease, which is manifested as an increasing trend of the resistance with the increase of the curing rate. Figure 1 It can be seen that when the curing rate is reduced, there is a risk of peeling off of the organic bonding layer.

[0235] From the comparison between Comparative Example 13 and Example 7, it can be seen that under the same preparation conditions, if the organic bonding layer of the curing system is not roughened, it will also cause a reduction in the catalytic core sites in contact with the surface and the copper plating solution, and a decrease in the catalytic activity. Under the same copper plating conditions, the copper plating quality deteriorates.

[0236] It is worth mentioning that the specific components and other technical features of the copper plating solution involved in this invention patent application should be regarded as the prior art. For the specific structures, working principles, and possible control methods and spatial arrangement methods of these technical features, conventional selections in the art can be adopted, and they should not be regarded as the invention points of this invention patent. This invention patent will not be further specifically elaborated.

[0237] The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and variations based on the concept of the present invention without creative work. Therefore, all technical solutions that can be obtained by those skilled in the art in the technical field based on the concept of the present invention through logical analysis, reasoning, or limited experiments on the basis of the prior art should be within the protection scope determined by the claims.

Claims

1. A method for preparing a negative electrode current collector, characterized in that, It includes the following steps: a) Coating an organic base layer slurry containing palladium nanocolloid particles on both the upper and lower surfaces of a flexible substrate; b) Curing the organic base layer slurry to form an organic base layer; c) Roughening the surface of the organic base layer; d) Copper plating on the surface of the roughened organic base layer; In step a), the organic base layer slurry is a curing system slurry or a thermoplastic system slurry; the curing system slurry consists of 100 parts by weight of a photoresist or a thermoresist and 5 - 15 parts by weight of a highly efficient palladium-based catalyst; the thermoplastic system slurry consists of 100 parts by weight of a thermoplastic resin solution and 5 - 18 parts by weight of a highly efficient palladium-based catalyst; In step c), the roughening treatment is to wet-treat the surface of the cured organic base layer; after the wet treatment of the surface of the organic base layer, the surface roughness Sa of the organic base layer is > 60 nm, so that the catalytic core sites in the system are exposed; The curing of the organic base layer slurry is drying curing or UV curing after drying. In step b), the curing rate of the organic base layer is controlled between 75% - 85%; In step c), the roughening treatment of wet-treating the surface of the cured organic base layer is as follows: When the organic base layer slurry is a curing system slurry, the organic base layer is developed with a developer, and the developer is any one of a 0.5 - 1 wt% potassium hydroxide aqueous solution, a 0.5 - 1 wt% sodium hydroxide aqueous solution, and a 0.3 - 1 wt% tetramethylammonium hydroxide aqueous solution, and any one of the selected developers also includes 0.2 - 0.6 wt% of sodium lauryl sulfate; When the organic base layer slurry is a thermoplastic system slurry, the surface of the organic base layer is eroded in sequence with a 60 - 75 wt% aqueous solution of carbinol and an aqueous solution containing 0.2 - 0.6 wt% of diethanolamine and 0.4 - 0.8 wt% of sodium lauryl sulfate.

2. The preparation method of the negative electrode current collector according to claim 1, characterized in that, The photoresist and the thermoresist are made from the following raw materials: resin: 10 - 25 wt%, polyfunctional acrylic monomer: 5 - 15 wt%, initiator: 0.5 - 1 wt%, leveling agent: 0.1 - 0.5 wt%, inhibitor: 0.01 - 0.2 wt%, and the rest is solvent; the initiator is a photoinitiator or a thermoinitiator.

3. The method for preparing the negative electrode current collector according to claim 2, characterized in that, The resin is one or any mixture of more than one resin selected from aromatic acid acrylate polymers, polyester acrylate polymers, epoxy acrylate polymers, organosilicon-modified acrylate polymers, polyurethane acrylate polymers, acrylic-epoxy resin copolymers, and acrylic-styrene resin copolymers; The polyfunctional acrylic monomer is any one or more of alkoxylated bisphenol A di(methacrylate), trimethylolpropane triacrylate (TMPTA), pentaerythritol triacrylate (PETA), tris(2-hydroxyethyl) isocyanurate triacrylate, pentaerythritol tetraacrylate (PETTA), and dipentaerythritol hexaacrylate (DPHA).

4. The method for preparing a negative electrode current collector according to claim 2, characterized in that, The photoinitiator is a cleavage-type free radical photoinitiator; the thermal initiator is an organic or inorganic peroxide, azo, or redox thermal initiator.

5. The preparation method of the negative electrode current collector according to claim 2, characterized in that, The leveling agent is a polyether-modified silicone surfactant, an acrylic leveling agent, or a fluorocarbon leveling agent; The inhibitor is any one or more of phenols, quinones, aromatic amines, aromatic nitro compounds, and aluminum tris(N-nitroso-N-phenylhydroxylamine); The solvent is any one or a mixture of any of ethyl lactate, acetone, propylene glycol methyl ether acetate, propylene glycol methyl ether acetate, butyl acetate, and acetylacetone.

6. The preparation method of the negative electrode current collector according to claim 1, wherein, The thermoplastic resin solution is made from the following raw materials: 20-30 wt% thermoplastic resin, 0.1-2 wt% leveling agent, 5-10 wt% organic acid, and the balance being an organic solvent.

7. The method for preparing the negative electrode current collector according to claim 6, characterized in that, The thermoplastic resin is a thermoplastic acrylic resin; The organic acid is any one or more of acetylacetone, 2-ketobutyric acid, and pyruvic acid.

8. The preparation method of the negative electrode current collector according to claim 1, characterized in that, The preparation method of the palladium-based high-efficiency catalyst comprises the following steps: 1) Preparation of palladium nanoparticles: Weigh 100 parts by weight of a reducing solvent, 3-10 parts by weight of a palladium salt, and 5-32 parts by weight of a dispersant. Add all of the reducing solvent, palladium salt, and half of the dispersant to a reaction vessel in sequence. After stirring evenly, heat to the reaction temperature for reaction. After reacting for 30 min, add the remaining half of the dispersant dropwise, and finish dropping within 1 h. Control the mass ratio of the dispersant to the palladium salt in the reaction system to be maintained at 1.5-6:

1. After the reaction ends, continue stirring and naturally cool to room temperature to obtain a mother liquor containing palladium nanoparticles; 2) Filter the mother liquor containing palladium nanoparticles, and then add deionized water and a fluorosurfactant, and stir and mix evenly to obtain the palladium-based high-efficiency catalyst; In step 2), the weight percentage content of deionized water in the palladium-based high-efficiency catalyst is 80%-98%, and the weight percentage content of the fluorosurfactant is 0.1%-2%.

9. The preparation method of the negative electrode current collector according to claim 4, wherein, The cleavage-type free radical photoinitiator is any one or more of acetophenone compounds, acylphosphine oxides, and a-amino ketone derivatives.

10. The method for preparing the negative electrode current collector according to claim 7, wherein The thermoplastic acrylic resin is any one or more of hydroxyl acrylic resins, polyester-modified polypropylene resins, and methyl methacrylate / butyl acrylate copolymers.

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