Electrolyte for repairing anode oxide film of high-voltage solid-state capacitor and film coating process thereof

Abstract

The invention discloses a high-voltage solid capacitor positive electrode oxide film repairing electrolyte and a film coating process thereof, and belongs to the technical field of solid capacitors. The electrolyte comprises ammonium azelate, azelaic acid, ammonium dihydrogen phosphate, phosphoric acid, a reducing agent, a functional additive, ethylene glycol, deionized water and other components; the electrolyte can effectively repair the positive electrode foil oxidation film when the positive electrode foil oxidation film has defects, and the film coating process comprises the steps of acid pickling pretreatment, electrolyte repair, silane coupling agent treatment, film forming liquid impregnation and curing and the like, according to the invention, the oxidation film on the surface of the positive electrode foil is repaired through the electrolyte, and the uniform and compact protection film is formed through a film coating process, so that the mechanical strength and corrosion resistance of the oxidation film are enhanced, the leakage current value of the capacitor is effectively reduced, and the service life of the capacitor is prolonged. The performance of the capacitor is improved, and the corrosion of the external environment to the oxidation film is isolated.

Description

Technical Field

[0001] The present invention relates to the technical field of solid-state capacitor technology, and particularly relates to a high-voltage solid-state capacitor positive electrode oxide film repair electrolyte and its film covering process. Background Art

[0002] The positive electrode foil of a high-voltage solid-state capacitor is a key component of the high-voltage solid-state capacitor. The oxide film formed on its surface not only serves as the dielectric layer of the capacitor but also undertakes important functions such as withstanding high voltages and preventing electrolyte leakage. However, in the actual production process, due to various factors such as material quality and processing conditions, various defects will inevitably appear on the oxide film of the positive electrode foil, such as pinholes, cracks, etc. These defects will cause an increase in the leakage current of the capacitor, not only reducing the energy storage efficiency of the capacitor but also possibly accelerating the aging process of the capacitor, seriously affecting the service life of the product.

[0003] In the manufacturing process of traditional liquid electrolyte capacitors, if there are defects in the oxide film of the positive electrode foil, a certain degree of repair can be carried out through subsequent electrolyte treatment processes, thereby improving the quality of the oxide film, reducing the leakage current value, and enhancing the overall performance of the capacitor. However, in the production of solid polymer capacitors, since the negative electrode material is a conductive polymer rather than a liquid electrolyte, once the production process enters the stage of adding the negative electrode material, the oxide film of the positive electrode foil can no longer be repaired.

[0004] If there are many defects in the oxide film of the positive electrode foil at the initial stage of production, then these defects will be retained in the subsequent manufacturing process, resulting in an increase in the leakage current value of the capacitor, seriously affecting the electrical properties and service life of the product. In addition, due to the closer contact between the negative electrode material and the positive electrode foil of the solid polymer capacitor, any minor defect in the oxide film may become a potential risk point for the performance degradation of the capacitor.

[0005] Therefore, in the production process of solid polymer capacitors, how to effectively repair the defects of the oxide film of the positive electrode foil has become an urgent technical problem to be solved. The existing technical means lack an effective repair method for the oxide film of the positive electrode foil in the production process of solid-state capacitors, which has limited the improvement and wide application of the performance of solid-state capacitors to a certain extent. Summary of the Invention

[0006] In view of the technical defects existing in the background art, the present invention proposes a high-voltage solid-state capacitor positive electrode oxide film repair electrolyte and its film covering process, which solves the above technical problems and meets the actual needs. The specific technical solutions are as follows:

[0007] A repair electrolyte for the positive electrode oxide film of a high-voltage solid capacitor, comprising raw materials in the following mass percentages: ammonium azelate 7-9%, azelaic acid 4-4.5%, ammonium dihydrogen phosphate 1-1.5%, phosphoric acid 0.5-1%, reducing agent 0.4-0.5%, functional additive 0.11-0.52%, deionized water 10-15%, and the balance being ethylene glycol.

[0008] As a further technical solution of the present invention, the reducing agent is any one of phosphorous acid or hypophosphorous acid.

[0009] As a further technical solution of the present invention, the functional additives are respectively: 2-mercaptobenzimidazole 0.01-0.02%, 1-butyl-3-methylimidazolium tetrafluoroborate 0.1-0.5%.

[0010] A film coating process for the repair electrolyte of the positive electrode oxide film of a high-voltage solid capacitor, comprising the following steps:

[0011] S1, pickling: putting the positive electrode foil into an acid solution for pickling, and then washing with deionized water to obtain the first positive electrode foil.

[0012] S2, oxide film repair: immersing the first positive electrode foil in the repair electrolyte for the positive electrode oxide film and applying a voltage, the applied voltage value being 1-1.5 times the forming voltage value of the formed aluminum foil, and then separating the first positive electrode foil from the repair electrolyte for the positive electrode oxide film and drying to obtain the second positive electrode foil.

[0013] S3, pretreatment: immersing the second positive electrode foil in a 0.01-0.05% ethanol pure solution of silane coupling agent, and then separating the second positive electrode foil from the ethanol pure solution of silane coupling agent and drying to obtain the third positive electrode foil.

[0014] S4, immersing the third positive electrode foil in a film-forming solution, and then drying and curing to complete the film coating process of the positive electrode of the solid capacitor.

[0015] As a further technical solution of the present invention, in step S1, the acid solution is any one of sulfuric acid solution, nitric acid solution, and perchloric acid solution, the concentration of the acid solution is 50-60 g / L, the pickling temperature is 40-50 °C, and the pickling time is 1-5 min.

[0016] As a further technical solution of the present invention, in step S2, the preparation method of the repair electrolyte for the positive electrode oxide film is: adding ammonium azelate, ammonium dihydrogen phosphate, and deionized water into ethylene glycol, mixing evenly, and heating to 60 °C, adding azelaic acid and phosphoric acid into the above mixed solution, stirring evenly, heating to 75 °C after fully dissolving, stopping heating, adding phosphorous acid, 2-mercaptobenzimidazole, and 1-butyl-3-methylimidazolium tetrafluoroborate after the solution temperature drops to 50 °C, mixing evenly, and naturally cooling to room temperature to obtain the repair electrolyte for the positive electrode oxide film.

[0017] As a further technical solution of the present invention, in step S3, the positive electrode foil two is impregnated in an ethanol solution of a silane coupling agent for 5 minutes, taken out, and then placed in an oven at 105 °C for 30 minutes of curing. The silane coupling agent is γ-methacryloxypropyltrimethoxysilane.

[0018] As a further technical solution of the present invention, in step S4, the positive electrode foil three is put into a film-forming solution and impregnated for 10 - 30 minutes, the impregnation temperature is 20 - 30 °C, the impregnation pressure is 0.3 - 0.7 MPa, then taken out and heated and cured for 30 - 70 minutes under the condition of 80 - 90 °C; the film-forming solution includes the following raw materials in parts by mass: 15 - 21 parts of a film-forming agent, 279 - 285 parts of ethanol, and 0.015 - 0.03 parts of ammonium persulfate.

[0019] As a further technical solution of the present invention, the relative molecular mass of the film-forming agent is 3500 - 4600, and the intrinsic viscosity of the film-forming agent at 30 °C with water as the solvent is 3.2 - 3.7.

[0020] As a further technical solution of the present invention, the preparation method of the film-forming agent is as follows: Under nitrogen protection, 0.10 mol of maleic anhydride is added to a four-necked flask equipped with a stirrer and a drying tube. Pyridine and a chloroform solution containing 0.10 mol of diethanolamine are added under an ice-water bath and reacted for 6 hours in the ice-water bath. The solvent is distilled off under reduced pressure to obtain the N,N-di(hydroxyethyl)maleic monoamide monomer. Then, p-toluenesulfonic acid with a mass fraction of 0.20% is added and melt-polymerized at 160 °C to obtain the film-forming agent.

[0021] The beneficial effects of the present invention are as follows:

[0022] The high-voltage solid-state capacitor positive electrode oxide film repair electrolyte and its film coating process of the present invention can effectively repair the positive electrode foil oxide film in the case of defects through the cooperation of multiple components of the electrolyte, reduce the leakage current value of the capacitor, and improve the capacitor performance. In addition, the electrolyte of the present invention has characteristics such as high conductivity, high oxidation efficiency, and low saturated vapor pressure. In the film coating process, through pickling pretreatment and electrolyte repair, the carbon-carbon double bond introduced by the silane coupling agent on the positive electrode surface and the conjugated double bond in the film-forming agent undergo cross-linking polymerization under the initiation of ammonium persulfate to form a three-dimensional network protective film, forming a uniform and dense protective film on the surface of the positive electrode foil, which not only enhances the mechanical strength and corrosion resistance of the oxide film but also effectively isolates the erosion of the external environment on the oxide film. Specific embodiments

[0023] The embodiments of the present invention will be described below in conjunction with relevant embodiments. The embodiments of the present invention are not limited to the following embodiments, and the present invention relates to relevant necessary components in the technical field, which should be regarded as well-known technologies in the technical field and can be known and mastered by those skilled in the technical field.

[0024] A high-voltage solid-state capacitor positive electrode oxide film repair electrolyte solution, comprising raw materials in the following mass percentages: ammonium azelate 7-9%, azelaic acid 4-4.5%, ammonium dihydrogen phosphate 1-1.5%, phosphoric acid 0.5-1%, reducing agent 0.4-0.5%, functional additive 0.11-0.52%, deionized water 10-15%, and the balance being ethylene glycol.

[0025] The electrolyte solution of the present invention has characteristics such as high conductivity, high oxidation efficiency, and low saturated vapor pressure. Specifically, ammonium azelate ((NH 4 ) 2 C 9 H 12 O 4 ) and ammonium dihydrogen phosphate (NH 4 H 2 PO 4 ) in the ethylene glycol solvent dissociate to generate migratable ions such as NH 4 ⁺, PO 3 ³⁻, H 2 PO 4 ⁻, etc., forming an ion conduction network to achieve high conductivity and being suitable for high-voltage repair scenarios. Azelaic acid acts as a pH buffer to ensure rapid cycling between local dissolution and recrystallization of aluminum oxide, accelerating defect repair. When applying the forming voltage, electrochemical migration (such as NH 4 ⁺, PO 3 ³⁻) can directionally fill the micropores of the oxide film, improving the repair rate. The reducing agent inhibits side reactions, thus rapidly repairing the oxide film at the defects of the positive electrode foil to achieve high-efficiency oxide film repair. The saturated vapor pressure of ethylene glycol (≈0.06 mmHg at 20°C) is much lower than that of water, which can reduce the volatilization of the electrolyte solution and ensure long-term stability. The vapor pressure of 1-butyl-3-methylimidazolium tetrafluoroborate (ionic liquid) is extremely low, further inhibiting volatilization, thereby reducing the saturated vapor pressure of the electrolyte solution.

[0026] In the above electrolyte solution, ammonium azelate and ammonium dihydrogen phosphate form a coordination network in the ethylene glycol solvent system. When applying 1-1.5 times the forming voltage, the ammonium salt decomposes to generate ions such as NH 4 ⁺ and PO 3 ³⁻, which penetrate to the lattice defects of aluminum oxide through electrochemical migration and form stable [Al(NH 3 ) 2 (H 2 O)4 ³⁺ coordination complex to fill pinholes and cracks. Azelaic acid acts as a pH buffer to maintain the pH value of the system within the range of 3.5 - 4.2, ensuring the local dissolution-recrystallization dynamic equilibrium of alumina, promoting the reconstruction of the oxide film at the defect sites. The introduction of phosphoric acid can regulate the dielectric constant of the oxide film and improve the uniformity of the dielectric layer.

[0027] Specifically, ammonium azelate and azelaic acid form a stable buffer system in ethylene glycol solution. Under the action of an electric field, carboxylate ions (RCOO⁻) are preferentially adsorbed at the defect sites of the oxide film and fill the Al 2 O 3 lattice vacancies through electrochemical migration. When heated, the treatment promotes the decomposition of ammonium carboxylate, releasing NH 3 to form a local alkaline microenvironment, inducing the hydrolysis of Al³⁺ to generate Al(OH) 3 , which is further transformed into dense Al 2 O 3 . Phosphate ions (PO 4 ³⁻) have strong coordination ability and form AlPO 4 complexes to block the micropores of the oxide film. The reducing agent can inhibit the oxygen evolution side reaction in the anodic process and reduce the damage to the oxide film structure.

[0028] As a further technical solution of the present invention, the reducing agent is any one of phosphorous acid or hypophosphorous acid.

[0029] Furthermore, the reducing agent is preferably phosphorous acid.

[0030] The reducing agent can contribute to stabilizing the structure of the oxide film, improving its corrosion resistance and durability through reduction. Specifically, the reducing agent can inhibit the oxygen evolution side reaction in the anodic process (4OH⁻ → O 2 ↑ + 2H 2 O + 4e⁻), reduce the damage to the oxide film structure. At the same time, by its own oxidation (H 3 PO 3 → H 3 PO 4 + 2H⁺ + 2e⁻), it consumes the locally excessive OH⁻ to maintain the stability of the electrolyte.

[0031] As a further technical solution of the present invention, the functional additives are respectively: 0.01 - 0.02% of 2-mercaptobenzimidazole and 0.1 - 0.5% of 1-butyl-3-methylimidazolium tetrafluoroborate.

[0032] The S, N heterocyclic structure in 2-mercaptobenzimidazole forms a monolayer on the surface of the oxide film through chemisorption. The sulfur atom forms a coordination bond with Al³⁺, which can block the penetration of corrosive media. At the same time, 2-mercaptobenzimidazole forms a C-S-Al bridge bond through the condensation reaction between the mercapto group (-SH) and the hydroxyl group (-OH) on the surface of the oxide film, enhancing the interfacial binding energy. 1-butyl-3-methylimidazolium tetrafluoroborate can reduce the viscosity of the electrolyte and improve the ion mobility. At the same time, the cation [BMIM]⁺ of 1-butyl-3-methylimidazolium tetrafluoroborate is electrostatically adsorbed on the surface of the oxide film to form a double-layer structure, making the distribution of the repair electric field uniform.

[0033] A film coating process for the positive electrode oxide film of a high-voltage solid capacitor repair electrolyte includes the following steps:

[0034] S1, pickling: Put the positive electrode foil into the acid solution for pickling, and then wash it with deionized water to obtain the first positive electrode foil.

[0035] S2, oxide film repair: Immerse the first positive electrode foil in the positive electrode oxide film repair electrolyte and apply a voltage. The applied voltage value is 1 - 1.5 times the forming voltage value of the formed aluminum foil. Then separate the first positive electrode foil from the positive electrode oxide film repair electrolyte and dry it to obtain the second positive electrode foil.

[0036] S3, pretreatment: Immerse the second positive electrode foil in a 0.01 - 0.05% ethanol pure solution of silane coupling agent, and then separate the second positive electrode foil from the ethanol pure solution of silane coupling agent and dry it to obtain the third positive electrode foil.

[0037] S4, Immerse the third positive electrode foil in the film-forming solution, and then dry and cure it to complete the film coating process of the positive electrode of the solid capacitor.

[0038] In the above film coating process, putting the positive electrode foil into the acid solution for cleaning aims to remove the impurities and pollutants on the surface of the positive electrode foil and create a clean and uniform basis for the subsequent oxide film repair. After pickling, wash the positive electrode foil with deionized water to obtain the treated first positive electrode foil.

[0039] Next, enter the oxide film repair stage. Immerse the first positive electrode foil in the positive electrode oxide film repair electrolyte and apply a certain voltage to promote the chemical reaction between the active components in the electrolyte and the oxide film on the surface of the positive electrode foil to repair the defects in the oxide film. After immersion, separate the positive electrode foil from the electrolyte and perform a drying treatment to obtain the repaired second positive electrode foil.

[0040] Then, pre-treatment is carried out. The positive electrode foil two is immersed in an ethanol pure solution containing a silane coupling agent. The silane coupling agent introduces carbon-carbon double bonds on the surface of the positive electrode. These double bonds will serve as the active sites for cross-linking and polymerization of the subsequent film-forming agent. After impregnation, the positive electrode foil is separated from the solution and cured in an oven to obtain the treated positive electrode foil three.

[0041] Finally, film-forming treatment is carried out. The positive electrode foil three is immersed in a film-forming solution. The film-forming solution contains components such as a film-forming agent, ethanol, and ammonium persulfate. During the impregnation process, the conjugated double bonds in the film-forming agent and the carbon-carbon double bonds introduced by the silane coupling agent undergo cross-linking and polymerization under the initiation of ammonium persulfate to form a network protective film. After impregnation, the positive electrode foil is taken out and heated and cured, thus completing the film coating process of the solid-state capacitor positive electrode.

[0042] In summary, the principle of the film coating process is to form a uniform and dense protective film on the surface of the positive electrode foil through a series of steps such as pickling pre-treatment, electrolyte repair, silane coupling agent treatment, and film-forming solution impregnation and curing. This protective film not only enhances the mechanical strength and corrosion resistance of the oxide film but also effectively isolates the erosion of the external environment on the oxide film, thereby improving the performance and stability of the capacitor.

[0043] As one of the preferred embodiments of the present invention, in step S1, the acid solution is any one of a sulfuric acid solution, a nitric acid solution, and a perchloric acid solution. The concentration of the acid solution is 50 - 60 g / L, the pickling temperature is 40 - 50 °C, and the pickling time is 1 - 5 min.

[0044] Furthermore, the acid solution is a sulfuric acid solution with a concentration of 50 g / L, the pickling temperature is 40 °C, and the pickling time is 5 min.

[0045] The sulfuric acid solution has strong oxidizing and corrosive properties and can effectively remove impurities, contaminants, and oxide layers on the surface of the positive electrode foil. The concentration of the acid solution is 50 g / L, which can not only ensure the pickling effect but also avoid excessive corrosion of the foil or other adverse reactions caused by too high a concentration. By setting the pickling temperature at 40 °C and the pickling time at 5 min, the reaction rate between the acid solution and the foil surface can be accelerated, and the pickling efficiency can be improved. At the same time, the appropriate temperature can also prevent the foil from deforming or being damaged due to too high a temperature.

[0046] As one of the preferred embodiments of the present invention, in step S2, the preparation method of the positive electrode oxide film repair electrolyte is as follows: Add ammonium azelate, ammonium dihydrogen phosphate, and deionized water to ethylene glycol, mix evenly, and heat to 60 °C. Add azelaic acid and phosphoric acid to the above mixed solution, stir evenly, and heat to 75 °C after full dissolution. Stop heating, and after the solution temperature drops to 50 °C, add phosphorous acid, 2-mercaptobenzimidazole, and 1-butyl-3-methylimidazolium tetrafluoroborate, mix evenly, and naturally cool to room temperature to obtain the positive electrode oxide film repair electrolyte.

[0047] Specifically, for the above-mentioned positive electrode oxide film repair electrolyte, the mass percentages of each component raw material are specifically as follows: ammonium azelate 9%, azelaic acid 4.5%, ammonium dihydrogen phosphate 1.5%, phosphoric acid 0.5%, reducing agent 0.5%, functional additive 0.52%, deionized water 10%, and ethylene glycol 73.48%.

[0048] As one of the preferred embodiments of the present invention, in step S3, the positive electrode foil two is immersed in an ethanol solution of a silane coupling agent for 5 minutes, taken out, and then placed in an oven at 105 °C for 30 minutes of curing. The silane coupling agent is γ-methacryloxypropyltrimethoxysilane.

[0049] In step S3 of the present invention, a silane coupling agent (γ-methacryloxypropyltrimethoxysilane) is used to treat the surface of the positive electrode foil. Functional groups such as methoxy groups in the silane coupling agent can undergo chemical reactions with hydroxyl groups or metal ions on the surface of the positive electrode foil to form strong chemical bonds. At the same time, functional groups such as carbon-carbon double bonds in the silane coupling agent molecule provide active sites for cross-linking polymerization of the conjugated double bonds in the subsequent film-forming agent.

[0050] The positive electrode foil is immersed in a pure ethanol solution of 0.05% silane coupling agent for 5 minutes, and the silane coupling agent molecules are fully adsorbed and penetrate into the surface of the positive electrode foil. Subsequently, the positive electrode foil is separated from the silane coupling agent solution and placed in an oven for curing treatment (cured in an oven at 105 °C for 30 minutes). During the curing process, the silane coupling agent molecules form stable chemical bonds with the surface of the positive electrode foil and introduce active sites such as carbon-carbon double bonds on the surface.

[0051] As one of the preferred embodiments of the present invention, in step S4, the positive electrode foil three is put into the film-forming solution and immersed for 10 - 30 minutes, the immersion temperature is 20 - 30 °C, the immersion pressure is 0.3 - 0.7 MPa, and then taken out and heated and cured for 30 - 70 minutes under the condition of 80 - 90 °C; the film-forming solution includes the following raw materials in parts by mass: 15 - 21 parts of film-forming agent, 279 - 285 parts of ethanol, and 0.015 - 0.03 parts of ammonium persulfate.

[0052] Furthermore, the relative molecular mass of the film-forming agent is 3500 - 4600, and the intrinsic viscosity of the film-forming agent at 30 °C with water as the solvent is 3.2 - 3.7.

[0053] Specifically, the preferred conditions for each item in step S4 are: the positive electrode foil three is immersed in the film-forming solution for 30 minutes, the immersion temperature is 30 °C, the immersion pressure is 0.7 MPa, and it is heated and cured for 70 minutes under the condition of 90 °C.

[0054] The weight percentages of the raw materials of the film-forming solution are specifically: 15 parts of film-forming agent, 279 parts of ethanol, and 0.015 parts of ammonium persulfate.

[0055] Raw materials such as the film-forming agent, ethanol, and ammonium persulfate in the film-forming solution undergo chemical reactions with the three surfaces of the positive electrode foil during the impregnation process. Under the initiation of ammonium persulfate, the conjugated double bonds in the film-forming agent crosslink and polymerize with the carbon-carbon double bonds introduced by the silane coupling agent in step S3, forming a protective film with a network structure. The protective film uniformly and densely covers the surface of the positive electrode foil, enhancing the mechanical strength and corrosion resistance of the oxide film.

[0056] Under preferred conditions, the positive electrode foil three is impregnated in the film-forming solution for 30 minutes, the impregnation temperature is 30 °C, and the impregnation pressure is 0.7 MPa. These conditions help the film-forming agent to fully penetrate to the surface of the positive electrode foil and undergo an effective crosslinking polymerization reaction with the active sites on the surface. The impregnated positive electrode foil needs to be heated and cured at 90 °C for 70 minutes to ensure that the protective film is completely cured and a stable network structure is formed.

[0057] As one of the preferred embodiments of the present invention, the preparation method of the film-forming agent is as follows: Under nitrogen protection, 0.10 mol of maleic anhydride is added to a four-necked flask equipped with a stirrer and a drying tube. Pyridine and a chloroform solution containing 0.10 mol of diethanolamine are added under an ice-water bath, and the reaction is carried out for 6 hours in the ice-water bath. The solvent is distilled off under reduced pressure to obtain the N,N-dihydroxyethyl maleic acid monoamide monomer. Then, p-toluenesulfonic acid with a mass fraction of 0.20% is added, and melt polymerization is carried out at 160 °C to obtain the film-forming agent.

[0058] In the above preparation method of the film-forming agent, the maleic anhydride molecule contains double bonds and carboxylic anhydride groups, providing active sites for subsequent polymerization reactions. Diethanolamine reacts with maleic anhydride to form an amide monomer containing hydroxyl groups, providing hydrophilicity and crosslinkability for the film-forming agent. Pyridine acts as a solvent and catalyst to promote the reaction between maleic anhydride and diethanolamine. p-toluenesulfonic acid acts as a catalyst for the polymerization reaction to promote the melt polymerization of the monomers. During the polymerization process, p-toluenesulfonic acid added to the monomers acts as a catalyst for the polymerization reaction, and melt polymerization reaction is carried out at 160 °C. The active sites between the monomer molecules crosslink and polymerize to form a high-molecular compound with a network structure. After the polymerization reaction is completed, the film-forming agent is obtained.

[0059] Example 1

[0060] A film coating process for repairing the oxide film of the positive electrode of a high-voltage solid capacitor electrolyte, comprising the following steps:

[0061] S1, Pickling: Immerse the positive electrode foil in a sulfuric acid, nitric acid or perchloric acid solution with a concentration of 50 - 60 g / L, and pickle it at 40 - 50 °C for 1 - 5 min. Preferably, pickle it in a 50 g / L sulfuric acid solution at 40 °C for 5 min. Then, wash it 3 times with deionized water to remove surface impurities and residual acid solution, and obtain a clean positive electrode foil one.

[0062] S2, Oxide film repair: Immerse the positive electrode foil one in the positive electrode oxide film repair electrolyte (containing 9% ammonium azelate, 4.5% azelaic acid, 1.5% ammonium dihydrogen phosphate, 0.5% phosphoric acid, 0.5% phosphorous acid, 0.02% 2 - mercaptobenzimidazole, 0.5% 1 - butyl - 3 - methylimidazolium tetrafluoroborate, 10% deionized water, 73.48% ethylene glycol), apply a voltage 1.5 times the formation voltage, keep the impregnation temperature at 60 °C, take it out after 30 min of treatment, and dry it in a vacuum drying oven at 80 °C for 2 h to obtain a positive electrode foil two with the oxide film density increased to 98.5%.

[0063] S3, Pretreatment: Immerse the positive electrode foil two in a 0.05% γ - methacryloxypropyltrimethoxysilane ethanol solution, impregnate it at 25 °C for 5 min, take it out and cure it in an oven at 105 °C for 30 min to form a chemical bonding layer containing C = C double bonds on the surface of the oxide film with the silane coupling agent.

[0064] S4, Film formation and curing: Immerse the positive electrode foil three in the film - forming solution (15 parts of film - forming agent, 279 parts of ethanol, 0.015 parts of ammonium persulfate), impregnate it at 30 °C and 0.7 MPa for 30 min, and then cure it in a hot air circulation oven at 90 °C for 70 min to cause the maleic anhydride derivative (intrinsic viscosity 3.7) in the film - forming agent to undergo free - radical cross - linking polymerization with the double bonds in the silane layer to form a network protective film.

[0065] Comparative Example 1

[0066] The difference between Comparative Example 1 and Example 1 is that in the original electrolyte formula of Comparative Example 1, ammonium azelate is not added, and other components remain unchanged.

[0067] Comparative Example 2

[0068] The difference between Comparative Example 2 and Example 1 is that in the original electrolyte formula of Comparative Example 2, phosphorous acid is not added, and other components remain unchanged.

[0069] Comparative Example 3

[0070] The difference between Comparative Example 3 and Example 1 is that in the original electrolyte formula of Comparative Example 3, 2 - mercaptobenzimidazole and 1 - butyl - 3 - methylimidazolium tetrafluoroborate are not added, and other components remain unchanged.

[0071] Comparative Example 4

[0072] The difference between Comparative Example 4 and Example 1 is that in the original process of Comparative Example 4, the S3 step is skipped, the silane coupling agent treatment is not carried out, and film formation and curing are directly carried out. The components of the electrolyte and the film-forming solution are the same as those in the original solution.

[0073] The positive electrode foils prepared in the above Example 1 and Comparative Examples 1-4 were made into capacitors with a specification of 25V470μF and a size of 10×12.5. The leakage current (LC) was measured using a leakage current tester (the test voltage was the rated working voltage of the capacitor). The test results are shown in the following table:

[0074]

[0075] By analyzing the above test results, it can be seen that the absence of ammonium azelate (Comparative Example 1) leads to a significant increase in the leakage current, indicating that its role as the core repair agent of the electrolyte in filling the defects of the oxide film through the coordination network is irreplaceable. The skipping of the silane coupling agent treatment (Comparative Example 4) causes the leakage current to rise, proving that the formation of the subsequent protective film is important for long-term stability and corrosion resistance. The absence of phosphorous acid (Comparative Example 2) increases the leakage current, indicating that the reducing agent maintains the integrity of the oxide film by inhibiting side reactions (such as oxygen evolution) and plays an auxiliary role in the repair process. The absence of the functional additive (Comparative Example 3) only slightly increases the leakage current, indicating that its role is more to optimize the performance of the surface protective layer (such as anti-permeation and electric field uniformity), rather than being the core of the repair process.

[0076] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can still be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A high-voltage solid-state capacitor positive electrode oxide film repair electrolyte, characterized in that: The invention comprises the following raw materials in percentage by weight: 7-9% ammonium azelaate, 4-4.5% azelaic acid, 1-1.5% diammonium phosphate, 0.5-1% phosphoric acid, 0.4-0.5% reducing agent, 0.11-0.52% functional additive, 10-15% deionized water, and the balance is ethylene glycol.

2. The high-voltage solid-state capacitor positive electrode oxide film repair electrolyte according to claim 1, characterized in that: The reducing agent is any one of phosphorous acid or hypophosphorous acid.

3. The high-voltage solid-state capacitor positive electrode oxide film repair electrolyte according to claim 1, characterized in that: The functional additives are: 0.01-0.02% of 2-mercaptobenzimidazole and 0.1-0.5% of 1-butyl-3-methylimidazole tetrafluoroborate.

4. The coating process of the electrolyte for repairing the positive oxide film of the high-voltage solid capacitor according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1, pickling, placing the positive electrode foil in an acid solution for pickling, and then washing with deionized water to obtain a positive electrode foil 1; S2, oxide film repair, immersing the positive electrode foil 1 in the positive electrode oxide film repair electrolyte as described in any one of claims 1 to 3 and applying a voltage, the applied voltage value is 1 to 1.5 times the formation voltage value of the aluminum foil, and then separating the positive electrode foil 1 from the positive electrode oxide film repair electrolyte and drying to obtain the positive electrode foil 2; S3, pretreatment, immersing the positive electrode foil 2 in a 0.01-0.05% silane coupling agent ethanol pure solution, and then separating the positive electrode foil 2 from the silane coupling agent ethanol pure solution, and drying to obtain a positive electrode foil 3; S4, immersing the positive electrode foil into the film-forming liquid, and then drying and curing it, thereby completing the coating process of the positive electrode of the solid-state capacitor.

5. The coating process of the electrolyte for repairing the positive oxide film of the high-voltage solid capacitor according to claim 4 is characterized in that: In step S1, the acid solution is any one of a sulfuric acid solution, a nitric acid solution, and a perchloric acid solution, the concentration of the acid solution is 50-60 g / L, the pickling temperature is 40-50° C., and the pickling time is 1-5 min.

6. The coating process of the electrolyte for repairing the positive oxide film of the high-voltage solid capacitor according to claim 4 is characterized in that: In step S2, the preparation method of the positive electrode oxide film repair electrolyte is as follows: add ammonium azelaic acid, diammonium phosphate, and deionized water to ethylene glycol, mix evenly, and heat to 60°C, add azelaic acid and phosphoric acid to the above mixed solution, stir evenly, and heat to 75°C after fully dissolved, stop heating, and after the solution temperature drops to 50°C, add phosphorous acid, 2-mercaptobenzimidazole, and 1-butyl-3-methylimidazole tetrafluoroborate, mix evenly, and naturally cool to room temperature to obtain a positive electrode oxide film repair electrolyte.

7. The coating process of the electrolyte for repairing the positive oxide film of the high-voltage solid capacitor according to claim 4 is characterized in that: In step S3, the second positive electrode foil is immersed in an ethanol solution of a silane coupling agent for 5 minutes, taken out, and then placed in an oven at 105° C. for curing for 30 minutes. The silane coupling agent is γ-methacryloxypropyltrimethoxysilane.

8. The coating process of the electrolyte for repairing the positive oxide film of the high-voltage solid capacitor according to claim 4 is characterized in that: In step S4, the positive electrode foil is immersed in the film-forming liquid for 10-30 minutes, the immersion temperature is 20-30°C, the immersion pressure is 0.3-0.7MPa, and then taken out and heated and cured at 80-90°C for 30-70 minutes; the film-forming liquid includes the following raw materials in parts by weight: 15-21 parts of film-forming agent, 279-285 parts of ethanol, and 0.015-0.03 parts of ammonium persulfate.

9. The coating process of the electrolyte for repairing the positive oxide film of the high-voltage solid capacitor according to claim 8 is characterized in that: The relative molecular weight of the film-forming agent is 3500-4600, and the intrinsic viscosity of the film-forming agent is 3.2-3.7 at 30° C. and with water as the solvent.

10. The coating process of the electrolyte for repairing the positive oxide film of the high-voltage solid capacitor according to claim 8 is characterized in that: The preparation method of the film-forming agent is as follows: under nitrogen protection, 0.10 mol of maleic anhydride is added into a four-necked bottle equipped with a stirrer and a drying tube, pyridine and a chloroform solution containing 0.10 mol of diethanolamine are added in an ice-water bath, and the mixture is reacted in the ice-water bath for 6 hours, and the solvent is evaporated under reduced pressure to obtain N,N-dihydroxyethyl maleic acid monoamide monomer, and then p-toluenesulfonic acid with a mass fraction of 0.20% is added, and melt polymerization is carried out at 160° C. to obtain the film-forming agent.

Images