Preparation method of sintered anode foil, sintered anode foil and aluminum electrolytic capacitor

Abstract

The invention provides a preparation method of a sintered anode foil, the sintered anode foil and an aluminum electrolytic capacitor, and the preparation method comprises the following steps: (1) mixing a dispersant and a binder, fully dissolving, adding aluminum powder, and uniformly dispersing to obtain slurry; the binder comprises at least one of aliphatic polycarbonates shown in the following general formula I: # imgabs0 #, m is an integer from 1 to 10, and n is an integer from 100 to 2000; (2) respectively coating two sides of a base material foil with the slurry, and drying to obtain a coated foil; (3) sintering the coated foil to obtain a sintered foil; and (4) forming the sintered foil to obtain the sintered anode foil. According to the preparation method disclosed by the invention, the aliphatic polycarbonate as shown in the general formula I is used as a binder, has a relatively good dispersion effect on micron-sized aluminum powder, and is easier to remove in a sintering stage, so that the sintered anode foil with low carbon residue and leakage current is prepared, and the preparation energy consumption is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrolytic capacitors, and particularly relates to a preparation method of a sintered anode foil, a sintered anode foil and an aluminum electrolytic capacitor. Background Art

[0002] With the rapid development of the information industry, electronic products are developing rapidly towards being thinner, lighter, smaller. As an aluminum electrolytic capacitor that still plays an irreplaceable role in the circuit, its relatively large volume has become a limiting factor. In this context, it is urgent to develop new technologies to greatly improve the capacitance of aluminum electrolytic capacitors to meet the increasingly urgent miniaturization requirements. Since the capacitance of a capacitor mainly depends on the capacitance of the anode foil, increasing the specific capacitance of the anode foil is an effective way to increase the capacitance of the capacitor. At present, the main method to improve the specific capacitance of the anode foil is the corrosion and surface area expansion technology. With the development of the corrosion process, the surface area expansion ratio of the aluminum foil has gradually approached the theoretical limit value, and it is very difficult to further improve the specific capacitance of the anode foil by corrosion with the existing industrial level. At the same time, during the process of corrosion and surface area expansion, a large amount of raw materials will be wasted, and acidic waste liquid containing aluminum ions will be formed, bringing serious environmental problems.

[0003] In recent years, the gradually developed sintered anode foil technology is a technology that generates a porous structure with a high specific surface area by sintering aluminum powder on an aluminum foil substrate. Compared with the traditional corrosion and surface area expansion technology, it not only greatly reduces the manufacturing cost, but also saves energy, reduces emissions and is environmentally friendly. In the process of preparing the sintered anode foil, adding a cellulose-based or resin-based polymer material as a binder can make the aluminum powder adhere tightly to the aluminum foil substrate, and at the same time decompose and volatilize during the sintering process to increase the porosity. However, as a binder, traditional polymer materials have two problems. One is that the dispersion performance for aluminum powder with a micron-sized particle diameter is not good, and additional additives such as surfactants need to be added to the slurry. The other is that there are defects such as incomplete decomposition or the need to use a higher sintering temperature during the sintering process, resulting in a relatively high carbon residue content in the sintered anode foil, and further leading to too large leakage current of the anode foil. Summary of the Invention

[0004] Based on this, the purpose of the present invention is to provide a preparation method of a sintered anode foil, which can effectively reduce the carbon residue content of the sintered anode foil and prepare an anode foil with low leakage current.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions.

[0006] A preparation method of a sintered anode foil includes the following steps: (1) Mix a dispersant and a binder and dissolve them fully, then add aluminum powder and disperse evenly to obtain a slurry; the binder includes at least one of aliphatic polycarbonates shown in the following general formula Ⅰ: Wherein, m is an integer from 1 to 10, and n is an integer from 100 to 2000;

[0007] (2) coating the slurry on both sides of the substrate foil respectively and drying to obtain a coated foil;

[0008] (3) sintering the coated foil to obtain a sintered foil;

[0009] (4) Forming the sintered foil to obtain the sintered anode foil.

[0010] In some embodiments, the aliphatic polycarbonate is selected from at least one of polyethylene carbonate, polypropylene carbonate, and polybutylene carbonate.

[0011] In some embodiments, the sintering in step (3) includes: desolventizing treatment, debonding treatment and sintering treatment; the sintering treatment temperature is 600° C. to 650° C., and the time is 1 hour to 20 hours.

[0012] In some preferred embodiments, the temperature of the desolventizing treatment is 150°C to 200°C, and the time is 5 min to 60 min; and / or the temperature of the degumming treatment is 250°C to 350°C, and the time is 0.5 h to 4 h.

[0013] In some embodiments, the single-side coating thickness of the coated foil in step (2) is 30 μm to 60 μm.

[0014] In some embodiments, the drying method in step (2) is drying at 70°C to 120°C for 5 minutes to 60 minutes.

[0015] In some embodiments, the thickness of the substrate foil in step (2) is 10 μm to 50 μm.

[0016] In some embodiments, the dispersant is selected from at least one of ethyl lactate, ethyl acetate, butyl acetate, and N-methylpyrrolidone.

[0017] In some embodiments, the aluminum powder has an average particle size D50 of 1 μm to 4 μm and a purity of 99.99%.

[0018] In some embodiments, the mass ratio of the binder to the dispersant is 1:5-10; and / or the mass ratio of the binder to the aluminum powder is 1:6-12.

[0019] The present invention also provides a sintered anode foil prepared by the preparation method as described above, which has lower carbon residue and low leakage current.

[0020] The present invention also provides an aluminum electrolytic capacitor, which comprises a sintered anode foil prepared by the preparation method described above.

[0021] The present invention provides a method for preparing a sintered anode foil. The method uses an aliphatic polycarbonate represented by the general formula I as a binder, which has a good dispersing effect on micron-sized aluminum powder and is more easily decomposed and removed during the sintering stage, thereby effectively reducing the carbon residue of the obtained sintered anode foil and obtaining an anode foil with low leakage current. At the same time, the aliphatic polycarbonate material represented by the general formula I can use a lower temperature during the sintering and degumming stage, reducing the energy consumption during the preparation process while improving the electrical properties of the anode foil. Detailed Embodiments

[0022] In the experimental methods of the following embodiments of the present invention that do not specify specific conditions, they are generally carried out according to conventional conditions or according to the conditions recommended by the manufacturer. All common chemical reagents used in the embodiments are commercially available products.

[0023] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the description of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0024] The terms "comprising" and "having" and any variations thereof in the present invention are intended to cover non-exclusive inclusion. For example, a process, method, device, product, or equipment that includes a series of steps is not limited to the listed steps or modules, but optionally further includes steps not listed, or optionally further includes other steps inherent to these processes, methods, products, or equipment.

[0025] "At least one" mentioned in the present invention refers to one or more than one. "And / or" describes the relationship between related objects and indicates that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone.

[0026] The following describes the sintered anode foil and its preparation method of the present invention with reference to specific embodiments.

[0027] Example 1

[0028] This example provides a method for preparing a sintered anode foil, including the following steps:

[0029] Step 1: Mix polyvinyl carbonate and N-methylpyrrolidone in a ratio of 1:6 and stir to dissolve, and then add spherical aluminum powder with an average particle size of 4 μm in a ratio of polyvinyl carbonate to aluminum powder of 1:8, and disperse at a rotational speed of 2000 r / min for 2 h by means of high-speed dispersion.

[0030] Step 2: Coat both sides of the aluminum foil substrate with the slurry prepared in Step 1 by doctor blade coating. The coating thickness on one side is controlled to be 50 μm. The substrate is an aluminum foil with a purity of 99.99% and a thickness of 20 μm. Then, dry the coated sample at 90 °C for 30 min.

[0031] Step 3: Place the coated foil obtained in Step 2 in a tube furnace and heat it at a rate of 3 °C / min under an argon atmosphere. First, raise the temperature from room temperature to 150 °C and hold for 30 min to remove the solvent. Then, raise the temperature to 350 °C and hold for 60 min to remove the binder. Continue to raise the temperature to 620 °C and hold for 120 min to sinter the aluminum powder.

[0032] Step 4: Anodize the sintered foil in a 10% boric acid solution (90 °C) to 560 V. The anodizing current density is 10 mA·cm -2 , constant voltage for 20 min, anneal in air at 500 °C for 2 min, and perform post-formation for 5 min to obtain a sintered anode foil for aluminum electrolytic capacitors.

[0033] Example 2

[0034] This example provides a method for preparing a sintered anode foil, including the following steps:

[0035] Step 1: Mix polycarbonate propylene carbonate and N-methylpyrrolidone in a ratio of 1:6 and stir to dissolve. Then, add spherical aluminum powder with an average particle size of 4 μm in a ratio of polycarbonate propylene carbonate to aluminum powder of 1:8, and disperse it at a rotation speed of 2000 r / min for 2 h by high-speed dispersion.

[0036] Step 2: Coat both sides of the aluminum foil substrate with the slurry prepared in Step 1 by doctor blade coating. The coating thickness on one side is controlled to be 50 μm. The substrate is an aluminum foil with a purity of 99.99% and a thickness of 20 μm. Then, dry the coated sample at 90 °C for 30 min.

[0037] Step 3: Place the coated foil obtained in Step 2 in a tube furnace and heat it at a rate of 3 °C / min under an argon atmosphere. First, raise the temperature from room temperature to 150 °C and hold for 30 min to remove the solvent. Then, raise the temperature to 350 °C and hold for 60 min to remove the binder. Continue to raise the temperature to 620 °C and hold for 120 min to sinter the aluminum powder.

[0038] Step 4: Anodize the sintered foil in a 10% boric acid solution (90 °C) to 560 V. The anodizing current density is 10 mA·cm -2 , constant voltage for 20 min, anneal in air at 500 °C for 2 min, and perform post-formation for 5 min to obtain a sintered anode foil for aluminum electrolytic capacitors.

[0039] Example 3

[0040] This example provides a preparation method for a sintered anode foil, including the following steps:

[0041] Step 1: Mix poly(butylene carbonate) and N-methylpyrrolidone in a ratio of 1:8 and stir to dissolve. Then, add spherical aluminum powder with an average particle size of 4 μm in a ratio of poly(butylene carbonate) to aluminum powder of 1:10, and disperse it at a speed of 2000 r / min for 2 h by high-speed dispersion.

[0042] Step 2: Coat the slurry prepared in Step 1 on both sides of the aluminum foil substrate by the doctor blade method, with the unilateral coating thickness controlled at 50 μm. The substrate is an aluminum foil with a purity of 99.99% and a thickness of 20 μm. Then, dry the coated sample at 90 °C for 30 min.

[0043] Step 3: Place the coated foil prepared in Step 2 in a tubular furnace, heat it at a rate of 3 °C / min in an argon atmosphere. First, raise the temperature from room temperature to 150 °C and hold for 30 min to remove the solvent. Then, raise the temperature to 350 °C and hold for 60 min to remove the binder. Continue to raise the temperature to 620 °C and hold for 120 min to sinter the aluminum powder.

[0044] Step 4: Anodize the sintered foil in a 10% boric acid solution (90 °C) to 560 V. The anodizing current density is 10 mA·cm -2 , keep the voltage constant for 20 min, anneal in air at 500 °C for 2 min, and perform supplementary formation for 5 min to obtain a sintered anode foil for aluminum electrolytic capacitors.

[0045] Example 4

[0046] This example provides a preparation method for a sintered anode foil, including the following steps:

[0047] Step 1: Mix poly(ethylene carbonate), poly(propylene carbonate) and N-methylpyrrolidone in a ratio of 1:1:20 and stir to dissolve. Then, add spherical aluminum powder with an average particle size of 4 μm in a ratio of poly(ethylene carbonate) to aluminum powder of 1:20, and disperse it at a speed of 2000 r / min for 2 h by high-speed dispersion.

[0048] Step 2: Coat the slurry prepared in Step 1 on both sides of the aluminum foil substrate by the doctor blade method, with the unilateral coating thickness controlled at 50 μm. The substrate is an aluminum foil with a purity of 99.99% and a thickness of 20 μm. Then, dry the coated sample at 90 °C for 30 min.

[0049] Step 3: Place the coated foil prepared in Step 2 in a tube furnace, heat it at a rate of 3 °C / min under an argon atmosphere. First, raise the temperature from room temperature to 150 °C and hold for 30 min to remove the solvent. Then, raise the temperature to 350 °C and hold for 60 min to remove the binder. Continue to raise the temperature to 620 °C and hold for 120 min to sinter the aluminum powder.

[0050] Step 4: Anodize the sintered foil in a 10% boric acid solution (90 °C) to 560 V. The current density of anodization is 10 mA·cm -2 , keep the voltage constant for 20 min, anneal in air at 500 °C for 2 min, and perform supplementary formation for 5 min to obtain a sintered anode foil for aluminum electrolytic capacitors.

[0051] Example 5

[0052] This example provides a method for preparing a sintered anode foil, including the following steps:

[0053] Step 1: Mix polycarbonate, polypropylene carbonate, and N-methylpyrrolidone in a ratio of 1:1:20 and stir to dissolve. Then, add spherical aluminum powder with an average particle size of 4 μm in a ratio of polycarbonate to aluminum powder of 1:24, and disperse it at a rotational speed of 2000 r / min for 2 h by means of high-speed dispersion.

[0054] Step 2: Coat both sides of the aluminum foil substrate with the slurry prepared in Step 1 by means of knife coating. The unilateral coating thickness is controlled to be 50 μm. The substrate is an aluminum foil with a purity of 99.99% and a thickness of 20 μm. Then, dry the coated sample at 90 °C for 30 min.

[0055] Step 3: Place the coated foil prepared in Step 2 in a tube furnace, heat it at a rate of 3 °C / min under an argon atmosphere. First, raise the temperature from room temperature to 150 °C and hold for 30 min to remove the solvent. Then, raise the temperature to 350 °C and hold for 60 min to remove the binder. Continue to raise the temperature to 600 °C and hold for 120 min to sinter the aluminum powder.

[0056] Step 4: Anodize the sintered foil in a 10% boric acid solution (90 °C) to 560 V. The current density of anodization is 10 mA·cm -2 , keep the voltage constant for 20 min, anneal in air at 500 °C for 2 min, and perform supplementary formation for 5 min to obtain a sintered anode foil for aluminum electrolytic capacitors.

[0057] Comparative Example 1

[0058] This comparative example provides a method for preparing a sintered anode foil, including the following steps:

[0059] Step 1: Mix polyvinyl butyral and N-methylpyrrolidone in a ratio of 1:6 and stir to dissolve. Then, add spherical aluminum powder with an average particle size of 4 μm in a ratio of polyvinyl butyral to aluminum powder of 1:8. Disperse it at a rotational speed of 2000 r / min for 2 h by means of high-speed dispersion.

[0060] Step 2: Coat both sides of the aluminum foil substrate with the slurry prepared in Step 1 by means of scraping. Control the unilateral coating thickness to be 50 μm. Select an aluminum foil with a purity of 99.99% and a thickness of 20 μm as the substrate. Then, dry the coated sample at 90 °C for 30 min.

[0061] Step 3: Place the coated foil prepared in Step 2 in a tube furnace. Heat it at a rate of 3 °C / min under an argon atmosphere. First, raise the temperature from room temperature to 150 °C and hold for 30 min to remove the solvent. Then, raise the temperature to 350 °C and hold for 60 min to remove the binder. Continue to raise the temperature to 620 °C and hold for 120 min to sinter the aluminum powder.

[0062] Step 4: Anodize the sintered foil in a 10% boric acid solution (90 °C) to 560 V. The anodizing current density is 10 mA·cm -2 , keep the voltage constant for 20 min, anneal in air at 500 °C for 2 min, and perform supplementary formation for 5 min to obtain a sintered anode foil for aluminum electrolytic capacitors.

[0063] Comparative Example 2

[0064] This comparative example provides a method for preparing a sintered anode foil, including the following steps:

[0065] Step 1: Mix ethyl cellulose and N-methylpyrrolidone in a ratio of 1:6 and stir to dissolve. Then, add spherical aluminum powder with an average particle size of 4 μm in a ratio of polycarbonate to aluminum powder of 1:8. Disperse it at a rotational speed of 2000 r / min for 2 h by means of high-speed dispersion.

[0066] Step 2: Coat both sides of the aluminum foil substrate with the slurry prepared in Step 1 by means of scraping. Control the unilateral coating thickness to be 50 μm. Select an aluminum foil with a purity of 99.99% and a thickness of 20 μm as the substrate. Then, dry the coated sample at 90 °C for 30 min.

[0067] Step 3: Place the coated foil prepared in Step 2 in a tube furnace. Heat it at a rate of 3 °C / min under an argon atmosphere. First, raise the temperature from room temperature to 150 °C and hold for 30 min to remove the solvent. Then, raise the temperature to 350 °C and hold for 60 min to remove the binder. Continue to raise the temperature to 620 °C and hold for 120 min to sinter the aluminum powder.

[0068] Step 4: Anodize the sintered foil in a 10% boric acid solution (90 °C) up to 560 V. The anodizing current density is 10 mA·cm -2 , constant voltage for 20 min, anneal at 500 °C in air for 2 min, and perform supplementary formation for 5 min to obtain a sintered anode foil for aluminum electrolytic capacitors.

[0069] Test the carbon residue and leakage current of the sintered anode foils prepared in Test Examples 1-4 and Comparative Examples 1-2. The test method is as follows:

[0070] 1. Test method for carbon residue: Refer to GB / T 20975.26-2013 Chemical analysis methods for aluminium and aluminium alloys.

[0071] 2. Test method for leakage current: Refer to SJ / T 11140-2022 Electrode foils for aluminium electrolytic capacitors.

[0072] Fill the results in Table 1.

[0073] Table 1

[0074] Group Carbon residue content (wt%) <![CDATA[Leakage current (μA / cm 2 )]]> Example 1 0.053 51 Example 2 0.057 56 Example 3 0.054 58 Example 4 0.052 52 Example 5 0.054 57 Comparative Example 1 0.113 89 Comparative Example 2 0.102 93

[0075] The above results show that the sintered anode foil prepared by the preparation method of the present invention has a lower carbon residue and leakage current. In the preparation method of the present invention, an aliphatic polycarbonate is used as the binder, and the aliphatic polycarbonate material can be effectively decomposed and removed at a lower temperature, thereby obtaining a sintered anode foil with a low carbon residue and leakage current.

[0076] Compared with Example 1, Comparative Example 1 uses polyvinyl butyral as the binder, and Comparative Example 2 uses ethyl cellulose as the binder, both of which significantly increase the carbon residue of the prepared sintered anode foil, resulting in a significant increase in leakage current.

[0077] In summary, the preparation method of the present invention uses an aliphatic polycarbonate as the binder, which can effectively reduce the carbon residue and leakage current of the prepared sintered anode foil, and has lower energy consumption.

[0078] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0079] The above-described embodiments merely represent several implementation manners of the present invention. The description thereof is relatively specific and detailed, but it should not be construed as a limitation to the scope of the patent for the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all fall within the protection scope of the present invention. Therefore, the protection scope of the patent for the present invention shall be subject to the appended claims.

Claims

1. A preparation method of a sintered anode foil, characterized in that, The method comprises the following steps: (1) dispersant and binder are mixed and fully dissolved, and then aluminum powder is added and dispersed evenly to obtain a slurry; the binder comprises at least one aliphatic polycarbonate represented by the following general formula I: wherein m is an integer from 1 to 10, and n is an integer from 100 to 2000; (2) Coating the slurry on both sides of the substrate foil respectively and drying to obtain a coated foil; (3) Sintering the coated foil to obtain a sintered foil; (4) Forming the sintered foil to obtain the sintered anode foil.

2. The preparation method according to claim 1, characterized in that, The aliphatic polycarbonate is selected from at least one of poly(ethylene carbonate), poly(propylene carbonate), and poly(butylene carbonate).

3. The preparation method according to claim 1, characterized in that, The sintering in step (3) includes: solvent removal treatment, degumming treatment, and sintering treatment; the temperature of the sintering treatment is 600°C to 650°C, and the time is 1h to 20h.

4. The preparation method according to claim 3, characterized in that, The temperature of the solvent removal treatment is 150°C to 200°C, and the time is 5min to 60min; and / or, the temperature of the degumming treatment is 250°C to 350°C, and the time is 0.5h to 4h.

5. The preparation method according to claim 1, characterized in that, The single-sided coating thickness of the coated foil in step (2) is 30μm to 60μm.

6. The preparation method according to claim 1, characterized in that, The dispersant is selected from at least one of ethyl lactate, ethyl acetate, butyl acetate, and N-methylpyrrolidone.

7. The preparation method according to claim 1, characterized in that, The average particle size D50 of the aluminum powder is 1μm to 4μm.

8. The preparation method according to claim 1, characterized in that, The mass ratio of the binder to the dispersant is 1:5 to 10; and / or, the mass ratio of the binder to the aluminum powder is 1:6 to 12.

9. A sintered anode foil prepared by the preparation method according to any one of claims 1 to 8.

10. An aluminum electrolytic capacitor, characterized in that, The aluminum electrolytic capacitor includes a sintered anode foil prepared by the preparation method according to any one of claims 1 to 8.

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