Aluminum electrolytic capacitor electrode material formation solution, its preparation method and application

Abstract

This invention belongs to the field of electrode material technology and relates to a forming solution for aluminum electrolytic capacitor electrode materials, comprising a main solute, additives, and water. The additives include inorganic acids and / or inorganic acid salts, organic acids, and oleic acid amide-based surfactants. A method for preparing the forming solution involves adding the oleic acid amide-based surfactant to water and mixing thoroughly. During stirring, the main solute and other additives are added to prepare a forming solution with a conductivity of 1–10 mS / cm and a pH of 4.0–7.0. An application of the forming solution in the anodizing of aluminum foil is also discussed. This invention enables the deposition of a uniform and dense nano-oxide film layer on the surface of aluminum foil, resulting in fewer defects, significantly reduced voltage rise time, improved hydration resistance and leakage current performance, and extended capacitor lifespan.

Description

Technical Field

[0001] This invention belongs to the field of electrode material technology, and relates to an electrode material forming solution, particularly to an aluminum electrolytic capacitor electrode material forming solution, its preparation method, and its application. Background Technology

[0002] Electrochemically formed foil is a product made by electrochemically or chemically etching specially made high-purity aluminum foil to expand its surface area, and then electrochemically forming an oxide film on the surface.

[0003] Aluminum electrolytic capacitors experience high ripple current and rapid charging / discharging during operation, which generates significant heat internally, shortening their lifespan. Improving the quality of the anode foil, specifically reducing its voltage rise time, is crucial for minimizing heat generation. The quality of the oxide film dielectric layer directly impacts the capacitor's performance. Furthermore, during anodizing, water ionizes into hydrogen and hydroxide ions. Under the influence of an electric field, aluminum ions may penetrate the existing oxide film and migrate towards the electrolyte side. Besides combining with oxygen ions to form amorphous alumina, they also combine with hydroxide ions to form hydrated aluminum oxides. Simultaneously, hydroxide ions, under the influence of the electric field, enter the oxide film layer and combine with aluminum ions to form hydrated oxides. Therefore, the oxide film formed in existing technologies has poor hydration resistance during use, easily reacting with water to form hydrated oxides, thus degrading the dielectric properties of the aluminum oxide film and reducing the capacitor's lifespan. Summary of the Invention

[0004] The purpose of this invention is to address the above-mentioned problems by providing a solution for the formation of aluminum electrolytic capacitor electrode materials;

[0005] Another objective of this invention is to address the aforementioned problems by providing a method for preparing an aluminum electrolytic capacitor electrode material solution.

[0006] Another object of the present invention is to provide an application of aluminum electrolytic capacitor electrode material in solution to address the above-mentioned problems.

[0007] This invention creatively proposes a solution for the formation of electrode materials for aluminum electrolytic capacitors, comprising a main solute, additives, and water, wherein the additives include inorganic acids and / or inorganic acid salts, organic acids, and oleic acid amide surfactants.

[0008] This invention uses a combination of mixed acid and oleic amide-based surfactant as an additive. The oleic amide-based surfactant is an oleic amide-based nonionic surfactant. The oleic amide group reduces the friction between the aluminum foil and the main solute and provides a certain passivation effect, resulting in the deposition of a uniform and dense nano-oxide film layer on the aluminum foil surface. This results in fewer defects and a significantly reduced voltage rise time, making it suitable for medium- and ultra-high voltage formation processes in the etching and sintering of aluminum foil. The oleic amide-based surfactant increases the resistance to water molecule diffusion to the oxide film surface, thereby improving hydration resistance and leakage current performance, and extending the lifespan of the capacitor.

[0009] In the above-mentioned aluminum electrolytic capacitor electrode material forming solution, the additives contain, by mass percentage, inorganic acid and / or inorganic acid salts at a content of 0.01 to 0.1 wt% of the total forming solution, organic acid at a content of 0.01 to 0.1 wt% of the total forming solution, and glycerol at a content of 0.05 to 0.2 wt% of the total forming solution.

[0010] In the above-mentioned aluminum electrolytic capacitor electrode material forming solution, the inorganic acid includes hypophosphite, and the inorganic acid salt includes at least one of sodium hypophosphite, potassium hypophosphite, and ammonium hypophosphite.

[0011] The additive of the present invention contains hypophosphite, which can inhibit the reaction between alumina surface and water, and further inhibit the hydration of oxide film surface.

[0012] In the above-mentioned aluminum electrolytic capacitor electrode material forming solution, the organic acid includes maleic acid and fumaric acid.

[0013] Maleic acid and fumaric acid are both succinic acids. Under the action of an external electric field, they can react with the hydroxyl groups on the surface of the oxide film, thereby improving the hydration resistance.

[0014] In the above-mentioned aluminum electrolytic capacitor electrode material forming solution, the main solute includes at least one of boric acid, ammonium pentaborate, borax, citric acid, ammonium adipate, and adipic acid;

[0015] The additive of this invention can be used to prepare solutions with different main solutes, and has a wide range of applications.

[0016] The content of the main solute is 1 to 10 wt% of the total amount of the chemically formed solution.

[0017] In the above-mentioned aluminum electrolytic capacitor electrode material forming solution, the water is pure water with a resistivity of not less than 2 MΩ·cm.

[0018] In the above-mentioned aluminum electrolytic capacitor electrode material forming solution, the conductivity of the forming solution is 1-10 ms / cm and the pH value is 4.0-7.0.

[0019] This invention creatively proposes a method for preparing a chemical solution, in which an oleic acid amide-based surfactant is added to water and mixed evenly, and a main solute and other additives are added during stirring to prepare a chemical solution with a conductivity of 1-10 mS / cm and a pH of 4.0-7.0.

[0020] This invention creatively proposes the application of a chemical conversion solution in the anodizing of aluminum foil.

[0021] In the application of the above-mentioned forming solution in the anodizing of aluminum foil, the forming solution is placed in a forming tank to form the aluminum foil, and the liquid temperature of the forming solution is controlled at 80-95℃.

[0022] Compared with the prior art, the advantages of the present invention are as follows:

[0023] 1) This invention uses a combination of mixed acid and oleic acid amide-based surfactant as an additive. The oleic acid amide-based surfactant, also known as oleic acid amide-based nonionic surfactant (OMA), is synthesized from oleic acid, maleic anhydride, and diethanolamine through a two-step reaction involving addition and amidation. The oleic acid amide group reduces the friction between the aluminum foil and the main solute and provides a certain passivation effect, resulting in the deposition of a uniform and dense nano-oxide film layer on the aluminum foil surface with fewer defects and a significantly reduced voltage rise time. The oleic acid amide-based surfactant increases the resistance to water molecule diffusion to the oxide film surface, thereby improving hydration resistance and leakage current performance, and extending the capacitor's lifespan.

[0024] 2) In this invention, the organic acid in the additive can react with the hydroxyl groups on the surface of the oxide film under the action of an external electric field, and the additive contains hypophosphite, which can inhibit the reaction between the alumina surface and water, and further inhibit the hydration of the oxide film surface.

[0025] 3) In this invention, the additive can be used to prepare formation solutions with different main solutes, and has a wide range of applications. It is suitable for medium- and ultra-high pressure formation production of etched and sintered aluminum foil. Detailed Implementation

[0026] The following specific examples further illustrate this point;

[0027] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the invention is not limited to the specific embodiments disclosed below.

[0028] Example 1

[0029] A forming solution for an aluminum electrolytic capacitor electrode material comprises a main solute consisting of a mixture of boric acid, ammonium pentaborate, and borax in a mass ratio of 18:1:1, with a total content of 2 wt% of the main solute. The additives are a mixture of hypophosphite and sodium hypophosphite in a mass ratio of 1:1 (0.02 wt%), maleic acid, and oleic acid amide-based surfactant. The remainder is pure water with a resistivity of not less than 2 MΩ·cm, forming a solution with a conductivity of 1.3 mS / cm and a pH of 7.0.

[0030] The above-mentioned formation solution is prepared by adding oleic acid amide surfactant to water according to the set mass and mixing it evenly. During the stirring process, the main solute and other additives are added to prepare a formation solution with a conductivity of 1.3 ms / cm and a pH of 7.0.

[0031] The forming solution is placed in a forming tank to form aluminum foil, and the temperature of the forming solution is controlled at 80-95℃.

[0032] Example 2

[0033] A forming solution for an aluminum electrolytic capacitor electrode material comprises a main solute consisting of a mixture of boric acid, ammonium pentaborate, and borax in a mass ratio of 40:1:1, with a total content of 8 wt%. Additives include a mixture of hypophosphite and potassium hypophosphite in a mass ratio of 1:2 (0.05 wt%), fumaric acid, and oleic acid amide-based surfactant. The remainder is pure water with a resistivity of not less than 2 MΩ·cm, forming a solution with a conductivity of 6.8 mS / cm and a pH of 3.5.

[0034] The above-mentioned formation solution is prepared by adding oleic acid amide surfactant to water according to the set mass and mixing it evenly. During the stirring process, the main solute and other additives are added to prepare a formation solution with a conductivity of 6.8 ms / cm and a pH of 3.5.

[0035] The forming solution is placed in a forming tank to form aluminum foil, and the temperature of the forming solution is controlled at 80-95℃.

[0036] Example 3

[0037] A forming solution for an aluminum electrolytic capacitor electrode material comprises a main solute of 1 wt% boric acid and citric acid in a mass ratio of 10:1, an additive of 0.1 wt% hypophosphite and potassium hypophosphite in a mass ratio of 1:3, 0.1 wt% fumaric acid and 0.01 wt% oleic acid amide surfactant, and the remainder being pure water with a resistivity of not less than 2 MΩ·cm, to form a forming solution with a conductivity of 1 mS / cm and a pH of 6.5.

[0038] The above-mentioned formation solution is prepared by adding oleic acid amide surfactant to water according to the set mass and mixing evenly. During the stirring process, the main solute and other additives are added to prepare a formation solution with a conductivity of 1 mS / cm and a pH of 6.5.

[0039] The forming solution is placed in a forming tank to form aluminum foil, and the temperature of the forming solution is controlled at 80-95℃.

[0040] Example 4

[0041] A forming solution for an aluminum electrolytic capacitor electrode material comprises a main solute of 5 wt% ammonium adipate and adipic acid in a mass ratio of 1:4, additives of 0.03 wt% hypophosphite and ammonium hypophosphite in a mass ratio of 1:1, 0.04 wt% maleic acid and 0.01 wt% oleic acid amide-based surfactant, and the remainder being pure water with a resistivity of not less than 2 MΩ·cm, to form a forming solution with a conductivity of 7.3 mS / cm and a pH of 4.0.

[0042] The above-mentioned formation solution is prepared by adding oleic acid amide surfactant to water according to the set mass and mixing it evenly. During the stirring process, the main solute and other additives are added to prepare a formation solution with a conductivity of 7.3 mS / cm and a pH of 4.0.

[0043] The forming solution is placed in a forming tank to form aluminum foil, and the temperature of the forming solution is controlled at 80-95℃.

[0044] Comparative Example 1

[0045] This comparative example is basically the same as Example 1, except that it does not contain oleic acid amide surfactant.

[0046] Comparative Example 2

[0047] This comparative example is basically the same as Example 1, except that maleic acid is replaced by an equal amount of hypophosphite.

[0048] Following the method described in T / CECA22-2017 "Electrode Foil for Aluminum Electrolytic Capacitors", the electrolytic foil test pieces prepared in Examples 1-4, Comparative Example 1, and Comparative Example 2 were subjected to medium- and high-voltage anodic electrolytic foil withstand voltage tests. 90% of the rated withstand voltage value was recorded as the voltage rise time Tr, and the capacitance C0 was recorded. The results are as follows:

[0049]

[0050] The results show that the pressure rise time Tr of the formed foil test piece prepared using the forming solution of the present invention is significantly shorter than that of Comparative Example 1, indicating that the forming solution of the present invention can reduce the pressure rise time of the formed foil. The use of oleic acid amide-based surfactants can reduce the friction between the aluminum foil and the main solute and provide a certain passivation effect, resulting in the deposition of a uniform and dense nano-oxide film layer on the aluminum foil surface with fewer defects and a significantly reduced pressure rise time.

[0051] After hydration treatment, the electrolytic capacitor foil test piece was subjected to a withstand voltage test. The time taken for the voltage to rise to 90% of Vfe from the start of energization was recorded as the voltage rise time Tr60 after hydration treatment, and the capacitance C was also recorded. The results are as follows:

[0052]

[0053] The results show that the aluminum foil treated with the formation solution of the present invention exhibits a significantly increased voltage rise rate and virtually no decrease in capacitance, indicating that the present invention can improve the hydration resistance of aluminum foil. The oleic acid amide-based surfactant increases the resistance to water molecule diffusion to the oxide film surface, thereby improving hydration resistance, and consequently enhancing electrical performance and extending the capacitor's lifespan.

[0054] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

[0055] Although this document frequently uses terms such as main solute, additive, inorganic acid, inorganic acid salt, organic acid, oleic amide surfactant, sodium phosphite, potassium hypophosphite, and ammonium hypophosphite, these terms are used merely for the convenience of describing and explaining the essence of this invention. Interpreting them as any additional limitation would contradict the spirit of this invention.

Claims

1. A solution for forming electrode materials for aluminum electrolytic capacitors, comprising a main solute, additives, and water, characterized in that: The additives include inorganic acids and / or inorganic acid salts, organic acids, and oleic acid amide-based surfactants; the inorganic acids include hypophosphite; the organic acids include maleic acid and fumaric acid; the main solutes include at least one of boric acid, ammonium pentaborate, borax, citric acid, ammonium adipate, and adipic acid; the oleic acid amide-based surfactant is an oleic acid amide-based nonionic surfactant, which is synthesized from oleic acid, maleic anhydride, and diethanolamine through a two-step reaction of addition and amidation.

2. The aluminum electrolytic capacitor electrode material forming solution as described in claim 1, characterized in that: The additive contains, by mass percentage, 0.02-0.1 wt% inorganic acid and / or inorganic acid salt, 0.02-0.1 wt% organic acid, and 0.01-0.03 wt% oleic acid amide surfactant.

3. The aluminum electrolytic capacitor electrode material forming solution as described in claim 1, characterized in that: The inorganic acid salt includes at least one of sodium hypophosphite, potassium hypophosphite, and ammonium hypophosphite.

4. The aluminum electrolytic capacitor electrode material forming solution as described in claim 1, characterized in that: The content of the main solute is 1 to 10 wt% of the total amount of the chemically formed solution.

5. The aluminum electrolytic capacitor electrode material forming solution as described in claim 1, characterized in that: The water in question is pure water with a resistivity of not less than 2 MΩ·cm.

6. The aluminum electrolytic capacitor electrode material forming solution as described in claim 1, characterized in that: The conductivity of the formation solution is 1~10 ms / cm, and the pH value is 4.0~7.

0.

7. The method for preparing the formation solution according to any one of claims 1-6, characterized in that: Oleic amide surfactants are added to water and mixed evenly. During stirring, the main solute and other additives are added to prepare a chemical solution with a conductivity of 1~10 ms / cm and a pH of 4.0~7.

0.

8. The application of any one of the formation solutions as described in claims 1-6 in the anodizing of aluminum foil.

9. The application of the formation solution as described in claim 8 in the anodizing of aluminum foil, characterized in that: The forming solution is placed in a forming tank to form aluminum foil, and the temperature of the forming solution is controlled at 80-95℃.

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