Carbon quantum dots modified electronic aluminum foil electrode sheet and preparation method and application thereof
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HENAN CONRON ELECTRONICS ALUMINUM FOIL
- Filing Date
- 2026-02-11
- Publication Date
- 2026-06-09
AI Technical Summary
Traditional porous electronic aluminum foil has many defects and low dielectric constant in the inner wall of the micropores, which makes it difficult to improve the specific capacitance of aluminum electrolytic capacitors.
A method for preparing carbon quantum dot modified electronic aluminum foil electrode sheets is adopted. Carbon quantum dots are embedded into the micropores of porous electronic aluminum foil by immersion and then form a composite dielectric film with an alumina dielectric film during the anodizing process, thereby improving the dielectric constant of the dielectric film.
It significantly enhances the charge storage and transmission capabilities of aluminum electrolytic capacitors, increases specific capacitance by 15%~17.5%, and extends cycle life to over 10,000 hours, combining high capacity with high reliability.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of aluminum electrolytic capacitor technology, and relates to a carbon quantum dot modified electronic aluminum foil electrode sheet, its preparation method and application. Background Technology
[0002] Aluminum electrolytic capacitors are widely used in power circuits, energy storage systems, and other fields due to their large capacity, low cost, and high reliability. Their performance depends on the specific surface area of the porous electronic aluminum foil in the anode and the properties of the dielectric film. Traditional porous electronic aluminum foil forms a microporous structure through etching or sintering processes, but the dielectric film on the inner wall of the micropores has many defects and a low dielectric constant, making it difficult to further improve the specific capacitance of the capacitor.
[0003] Carbon quantum dots, as a novel zero-dimensional carbon nanomaterial, possess excellent conductivity, high dielectric constant, and good dispersibility, making them promising for applications in biosensing, drug delivery, luminescent materials, and energy storage. Furthermore, carbon-based quantum dots contain abundant edge defects and oxygen-containing functional groups, and their small size effect results in very high chemical reactivity. However, due to their low yield and tendency to aggregate, carbon quantum dots are rarely used alone. Currently, no publicly available methods have been developed for modifying aluminum electrolytic capacitor electrodes with carbon quantum dots. Summary of the Invention
[0004] This invention addresses the technical problem of low specific capacitance in aluminum electrolytic capacitors by providing a carbon quantum dot-modified electronic aluminum foil electrode sheet. The immersion method ensures that the carbon quantum dots adhere only to the inner walls of the micropores, without blocking the micropore channels, thus preserving the high specific surface area advantage of the porous electronic aluminum foil. During the anodizing process, the carbon quantum dots effectively fill the defects in the alumina dielectric film, forming a composite dielectric film with the alumina dielectric film, thereby increasing the dielectric constant of the dielectric film. This achieves dual optimization of specific surface area and dielectric properties, improving the capacitance and cycle stability of the aluminum electrolytic capacitor.
[0005] To achieve the above objectives, the present invention adopts the following technical solution:
[0006] In a first aspect, the present invention provides a carbon quantum dot modified electronic aluminum foil electrode sheet, the electrode sheet comprising a porous electronic aluminum foil, carbon quantum dots embedded in the micropores of the porous electronic aluminum foil, and an alumina dielectric film formed on the surface of the porous electronic aluminum foil and the inner wall of the micropores by anodizing.
[0007] In the above technical solution, the porous electronic aluminum foil is prepared by etching or sintering, with a pore size of 0.1~1.5 μm and a porosity of 30~50%; the carbon quantum dots have a particle size of 5~20 nm.
[0008] Secondly, the present invention provides a method for preparing the above-mentioned carbon quantum dot modified electronic aluminum foil electrode sheet, comprising the following steps:
[0009] 1) Preparation of carbon quantum dots: Select carbon source and modifier, prepare carbon quantum dots by hydrothermal reaction, and obtain carbon quantum dot powder after purification and drying;
[0010] 2) Preparation of carbon quantum dot solution: Disperse the carbon quantum dot powder obtained in step 1) in deionized water, add a dispersant and sonicate to obtain a carbon quantum dot dispersion solution with a mass fraction of 0.5~2%;
[0011] 3) Modified porous electronic aluminum foil: Immerse the porous electronic aluminum foil in the carbon quantum dot dispersion solution obtained in step 1) to allow the carbon quantum dots to embed into the micropores of the porous electronic aluminum foil, remove the modified porous electronic aluminum foil, and dry it;
[0012] 4) Energizing treatment: The modified porous electronic aluminum foil obtained in step 3) is placed in a forming solution for anodic oxidation to form an aluminum oxide dielectric film on the surface of the modified porous electronic aluminum foil and the inner wall of the micropores.
[0013] In the above technical solution, the carbon source in step 1) is selected from one or more of citric acid, glucose, urea, and polyvinyl alcohol; the modifier is selected from one of ethylenediamine, ammonia, and thioglycolic acid.
[0014] In the above technical solution, the mass ratio of carbon source to modifier in step 1) is (5~10):1; the temperature of the hydrothermal reaction is 160~220℃, and the reaction time is 4~8 h.
[0015] In the above technical solution, the purification in step 1) involves dialysis with a dialysis bag containing a molecular weight cutoff of 3000~5000 D for 12~24 h; the drying is freeze drying at a temperature of -40~-60℃, a vacuum of 10~20 Pa, and a drying time of 24~36 h.
[0016] In the above technical solution, the dispersant in step 2) is sodium dodecyl sulfate or Tween-80, and the amount of dispersant added is 1~3% of the mass of carbon quantum dots; the ultrasonic treatment power is 300~500 W, and the ultrasonic time is 30~60 min.
[0017] In the above technical solution, the soaking temperature in step 3) is 25~40℃, the soaking time is 2~6 h, and 50~100 W ultrasonic oscillation is used during the soaking process to promote the embedding of carbon quantum dots into the micropores.
[0018] In the above technical solution, the formation solution in step 4) is a boric acid solution with a pH value of 6.0~7.0; the anodizing process parameters are: voltage 100~700 V, temperature 70~100℃, and oxidation time 1~3 h. Under the action of an electric field, a dense alumina dielectric film is formed on the surface of the electronic aluminum foil and the inner wall of the micropores, and carbon quantum dots fill the defects in the dielectric film, thereby improving the dielectric properties.
[0019] Thirdly, the present invention provides the application of the above-mentioned carbon quantum dot modified electronic aluminum foil electrode sheet in aluminum electrolytic capacitors. The carbon quantum dot modified electronic aluminum foil electrode sheet is used as the anode sheet of the aluminum electrolytic capacitor. It is wound together with the cathode sheet and electrolytic paper to form a core package, and then impregnated with electrolyte, encapsulated and aged to obtain the aluminum electrolytic capacitor.
[0020] The core mechanism by which this invention improves the performance of aluminum electrolytic capacitors through carbon quantum dot modification of porous electronic aluminum foil is mainly reflected in three aspects:
[0021] 1. Synergistic enhancement of dielectric properties: Carbon quantum dots themselves have high dielectric constants. After being embedded in the micropores of porous aluminum foil, they form a composite dielectric film with the subsequent alumina dielectric film, which increases the overall dielectric constant of the dielectric film from the traditional 9~10 to 15~18. According to the specific capacitance calculation formula C=ε·S / (4πkd), the increase in dielectric constant ε directly increases the specific capacitance.
[0022] 2. Dielectric film defect filling: Carbon quantum dots are nano-sized particles that can precisely fill the lattice defects and microcracks on the inner walls of micropores in the alumina dielectric film, reduce leakage current channels in the dielectric film, lower leakage current density, improve the insulation and withstand voltage of the dielectric film, and ensure the stable operation of aluminum electrolytic capacitors under high voltage.
[0023] 3. Charge Storage Optimization: Carbon quantum dots act as electron acceptors and donors, and can form an interfacial dipole layer with the alumina dielectric film, capturing more free charges and contributing additional capacitance. Simultaneously, the immersion method ensures that carbon quantum dots adhere only to the inner walls of the micropores, without clogging the micropore channels. This preserves the high specific surface area advantage of porous electronic aluminum foil and avoids the micropore clogging and specific surface area reduction problems caused by excessively thick coatings in traditional coating methods, achieving dual optimization of specific surface area and dielectric properties.
[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0025] 1. This invention uses a hydrothermal method to prepare carbon quantum dots, which is simple and low in cost. The carbon quantum dots prepared have good dispersibility, uniform particle size (5~20 nm), excellent dielectric properties, and good matching with the micropores of porous electronic aluminum foil.
[0026] 2. The immersion method is used to achieve uniform embedding of carbon quantum dots in the micropores of porous aluminum foil. The modification process is mild and easy to industrialize. Compared with the traditional coating method, it avoids the problem of micropore blockage and fully preserves the high specific surface area advantage of porous electronic aluminum foil.
[0027] 3. During the anodizing process, carbon quantum dots effectively fill the defects in the alumina dielectric film, forming a composite dielectric film with the alumina dielectric film, which improves the dielectric constant of the dielectric film and significantly enhances the charge storage and transmission capabilities of aluminum electrolytic capacitors. The specific capacitance of 130 μm thick aluminum foil increases by 15% at a formation voltage of 520 V and by 17.5% at a formation voltage of 640 V, which is far higher than the improvement effect of traditional modification processes. Moreover, the filling effect of carbon quantum dots greatly reduces the loss angle of the dielectric film, improves cycle stability, and extends the cycle life to more than 10,000 h, combining high capacity and high reliability.
[0028] 4. The manufacturing process is compatible with existing aluminum electrolytic capacitor production lines, requiring no large-scale equipment modifications, and has good prospects for industrial production. Detailed Implementation
[0029] The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of protection of the present invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the test methods in the following embodiments are conventional methods.
[0030] This invention discloses a method for preparing carbon quantum dot modified electronic aluminum foil electrode sheets, specifically comprising the following steps:
[0031] (1) Preparation of carbon quantum dots
[0032] Weigh carbon source (e.g., citric acid) and modifier (e.g., ethylenediamine) at a mass ratio of 5-10:1, dissolve them in deionized water to prepare a mixed solution with a concentration of 0.2-0.5 g / mL, stir until completely dissolved, and then transfer to a hydrothermal reactor. Place the reactor in an oven and heat to 160-220℃, maintaining the temperature for 4-8 h. After the reaction, allow it to cool naturally to room temperature, pour the product into a dialysis bag (molecular weight cutoff 3000-5000 D), and dialyze with deionized water for 12-24 h to remove impurities. Place the dialyzed dispersion in a freeze dryer and dry it at -40 to -60℃ and a vacuum of 10-20 Pa for 24-36 h to obtain carbon quantum dot powder with a particle size of 5-20 nm.
[0033] (2) Preparation of carbon quantum dot solution
[0034] Weigh out carbon quantum dot powder and disperse it in deionized water, while adding a dispersant (such as sodium dodecyl sulfate) at 1-3% of the mass of the carbon quantum dots. Place the mixed solution in an ultrasonic cleaner and ultrasonically treat it at 300-500 W for 30-60 minutes to obtain a uniform and stable carbon quantum dot dispersion solution with a mass fraction of 0.5-2%.
[0035] (3) Modified porous electronic aluminum foil
[0036] Porous electronic aluminum foil (prepared by etching or sintering) with a porosity of 30-50% and a pore size of 0.1-1.5 μm was selected, cut to the specified size, cleaned, and dried for later use. The porous electronic aluminum foil was completely immersed in a carbon quantum dot dispersion solution, with the immersion temperature controlled at 25-40 °C and the immersion time at 2-6 h. During the immersion process, ultrasonic vibration at 50-100 W was used to promote the embedding of carbon quantum dots into the micropores. After immersion, the aluminum foil was removed and dried in an oven at 60-80 °C for 1-2 h to obtain carbon quantum dot-modified porous electronic aluminum foil.
[0037] (4) Empowerment processing
[0038] The modified porous electronic aluminum foil was used as the anode and placed in a boric acid solution (pH 6.0–7.0). A constant-voltage anodizing process was employed, applying a voltage of 100–700 V, controlling the solution temperature at 70–100 °C, and an oxidation time of 1–3 h. Under the influence of the electric field, a dense alumina dielectric film formed on the surface of the aluminum foil and the inner walls of the micropores. Carbon quantum dots filled the defects in the dielectric film, improving the dielectric properties. After oxidation, the aluminum foil was removed, cleaned with deionized water, and dried.
[0039] Example 1
[0040] (1) Preparation of carbon quantum dots: Citric acid and ethylenediamine were weighed at a mass ratio of 8:1, dissolved in deionized water to prepare a 0.3 g / mL solution, transferred to a hydrothermal reactor, and reacted at 200 °C for 6 h. The product was dialyzed (molecular weight cutoff 5000 D) for 20 h, and then freeze-dried at -50 °C and 15 Pa for 30 h to obtain carbon quantum dot powder with a particle size of about 10 nm.
[0041] (2) Preparation of carbon quantum dot solution: Weigh carbon quantum dot powder, disperse it in deionized water, add sodium dodecyl sulfate accounting for 2% of the mass of carbon quantum dots, and sonicate at 400 W for 45 min to obtain a carbon quantum dot dispersion solution with a mass fraction of 1%.
[0042] (3) Modified porous electronic aluminum foil: Select porous electronic aluminum foil with a porosity of 40%, a pore size of 0.8 μm and a thickness of 0.130 mm, immerse it in carbon quantum dot solution at 30℃, and soak it with 80 W ultrasonic oscillation for 4 h. After taking it out, dry it at 70℃ for 1.5 h.
[0043] (4) Energizing treatment: The modified porous electronic aluminum foil was placed in boric acid solution (pH=6.5) and anodized at 520 V and 85℃ for 1 h, then cleaned and dried.
[0044] (5) Capacitor assembly: The modified porous electronic aluminum foil after transformation and energy conversion is used as the anode sheet, and is rolled together with the cathode aluminum foil and electrolytic paper to form a core package. Ethylene glycol-based electrolyte is injected, and after encapsulation, it is aged at 95°C for 18 h to obtain an aluminum electrolytic capacitor.
[0045] Example 2
[0046] (1) Preparation of carbon quantum dots: Glucose and ammonia were weighed at a mass ratio of 5:1, dissolved in deionized water to prepare a 0.2 g / mL solution, transferred to a hydrothermal reactor, and reacted at 180℃ for 8 h. The product was dialyzed (molecular weight cutoff 3000 D) for 12 h, and then freeze-dried at -40℃ and 10 Pa for 24 h to obtain carbon quantum dot powder with a particle size of about 10 nm.
[0047] (2) Preparation of carbon quantum dot solution: Weigh carbon quantum dot powder, disperse it in deionized water, add Tween-80 accounting for 1% of the mass of carbon quantum dots, and sonicate at 300 W for 60 min to obtain a carbon quantum dot dispersion solution with a mass fraction of 0.5%.
[0048] (3) Modified porous electronic aluminum foil: Select porous electronic aluminum foil with a porosity of 35%, a pore size of 1.2 μm and a thickness of 0.130 mm, immerse it in carbon quantum dot solution at 25℃, and soak it with 50 W ultrasonic oscillation for 6 h. After taking it out, dry it at 60℃ for 2 h.
[0049] (4) Energizing treatment: The modified porous electronic aluminum foil was placed in boric acid solution (pH=6.5) and anodized at 640V and 85℃ for 1.5 h, then cleaned and dried.
[0050] (5) Capacitor assembly: The modified porous electronic aluminum foil after transformation and energy conversion is used as the anode sheet, and is rolled together with the cathode aluminum foil and electrolytic paper to form a core package. Ethylene glycol-based electrolyte is injected, and after encapsulation, it is aged at 85°C for 24 h to obtain an aluminum electrolytic capacitor.
[0051] Comparative Example 1
[0052] A porous electronic aluminum foil with a porosity of 40%, a pore size of 0.8 μm, and a thickness of 0.130 mm was selected and etched. It was then placed in a boric acid solution (pH=6.5) and anodized at 520 V and 85℃ for 30 min, followed by cleaning and drying. The modified porous electronic aluminum foil, after formation enhancement, was used as the anode sheet, stacked with a cathode aluminum foil and electrolytic paper, and wound into a core package. Ethylene glycol-based electrolyte was injected, and after encapsulation, the package was aged at 95℃ for 18 h to obtain an aluminum electrolytic capacitor.
[0053] Comparative Example 2
[0054] A porous electronic aluminum foil with a porosity of 35%, a pore size of 1.2 μm, and a thickness of 0.130 mm was selected and etched. It was then placed in a boric acid solution (pH=6.5) and anodized at 640 V and 85℃ for 30 min, followed by cleaning and drying. The modified porous electronic aluminum foil, after formation enhancement, was used as the anode sheet and stacked with a cathode aluminum foil and electrolytic paper to form a core package. Ethylene glycol-based electrolyte was injected, and after encapsulation, the package was aged at 85℃ for 24 h to obtain an aluminum electrolytic capacitor.
[0055] The samples from Examples 1-2 and Comparative Examples 1-2 were cut into 10 mm × 50 mm standard samples. The specific capacitance was tested on a digital bridge tester according to the national standard SJ / T 11140-2012. The specific capacitance test solution was an 8% (NH4)B5O8 solution with a mass fraction of (30±2)℃. The results are shown in Table 1.
[0056] Table 1 Performance Test Results
[0057]
[0058] It can be seen that, compared with the unmodified corroded porous electronic aluminum foil, the carbon quantum dot modified electronic aluminum foil (130 μm thickness) of the present invention has a 15% increase in specific capacitance at a formation voltage of 520 V and a 17.5% increase in specific capacitance at a formation voltage of 640 V.
[0059] The embodiments described above are merely preferred embodiments of the present invention and are only used to explain the present invention. They are not intended to limit the scope of the present invention. For those skilled in the art, other implementation methods can be easily made by substitution or modification based on the technical content disclosed in this specification. Therefore, all changes and improvements made on the principle of the present invention should be included within the scope of the patent application of the present invention.
Claims
1. A carbon quantum dot modified electronic aluminum foil electrode sheet, characterized in that, The electrode sheet includes a porous electronic aluminum foil, carbon quantum dots embedded in the micropores of the porous electronic aluminum foil, and an aluminum oxide dielectric film formed on the surface of the porous electronic aluminum foil and the inner wall of the micropores by anodizing.
2. The carbon quantum dot modified electronic aluminum foil electrode sheet according to claim 1, characterized in that, The porous electronic aluminum foil is prepared by etching or sintering, with a pore size of 0.1~1.5 μm and a porosity of 30~50%; the carbon quantum dots have a particle size of 5~20 nm.
3. The method for preparing the carbon quantum dot modified electronic aluminum foil electrode sheet according to claim 1 or 2, characterized in that, Includes the following steps: 1) Preparation of carbon quantum dots: Select carbon source and modifier, prepare carbon quantum dots by hydrothermal reaction, and obtain carbon quantum dot powder after purification and drying; 2) Preparation of carbon quantum dot solution: Disperse the carbon quantum dot powder obtained in step 1) in deionized water, add a dispersant and sonicate to obtain a carbon quantum dot dispersion solution with a mass fraction of 0.5~2%; 3) Modified porous electronic aluminum foil: Immerse the porous electronic aluminum foil in the carbon quantum dot dispersion solution obtained in step 1) to allow the carbon quantum dots to embed into the micropores of the porous electronic aluminum foil, remove the modified porous electronic aluminum foil, and dry it; 4) Energizing treatment: The modified porous electronic aluminum foil obtained in step 3) is placed in a forming solution for anodic oxidation to form an aluminum oxide dielectric film on the surface of the modified porous electronic aluminum foil and the inner wall of the micropores.
4. The preparation method according to claim 3, characterized in that, The carbon source mentioned in step 1) is selected from one or more of citric acid, glucose, urea, and polyvinyl alcohol; the modifier is selected from one of ethylenediamine, ammonia, and thioglycolic acid.
5. The preparation method according to claim 3, characterized in that, The mass ratio of carbon source to modifier in step 1) is (5~10):1; the temperature of the hydrothermal reaction is 160~220℃, and the reaction time is 4~8 h.
6. The preparation method according to claim 3, characterized in that, The purification described in step 1) involves dialysis with a dialysis bag containing a molecular weight cutoff of 3000~5000 D for 12~24 h; the drying is freeze drying at a temperature of -40~-60 ℃, a vacuum degree of 10~20 Pa, and a drying time of 24~36 h.
7. The preparation method according to claim 3, characterized in that, The dispersant in step 2) is sodium dodecyl sulfate or Tween-80, and the amount of dispersant added is 1-3% of the mass of carbon quantum dots; the ultrasonic treatment power is 300-500 W, and the ultrasonic time is 30-60 min.
8. The preparation method according to claim 3, characterized in that, The soaking temperature in step 3) is 25~40 ℃, the soaking time is 2~6 h, and ultrasonic oscillation of 50~100 W is used during the soaking process.
9. The preparation method according to claim 3, characterized in that, The formation solution mentioned in step 4) is a boric acid solution with a pH value of 6.0~7.0; the anodizing process parameters are: voltage 100~700 V, temperature 70~100℃, and oxidation time 1~3 h.
10. The application of the carbon quantum dot modified electronic aluminum foil electrode sheet according to claim 1 or 2 in aluminum electrolytic capacitors, characterized in that, The carbon quantum dot modified electronic aluminum foil electrode sheet is used as the anode sheet of the aluminum electrolytic capacitor. It is rolled together with the cathode sheet and electrolytic paper to form a core package, and then impregnated with electrolyte, encapsulated and aged to obtain the aluminum electrolytic capacitor.