Preparation method of anode foil of aluminum electrolytic capacitor

Abstract

The invention belongs to the technical field of aluminum electrolytic capacitors, and particularly relates to a preparation method of an anode foil of an aluminum electrolytic capacitor. The invention provides a method for preparing an anode foil of an aluminum electrolytic capacitor, which comprises the following steps of: providing aluminum paste which comprises aluminum powder, a binder, a pore-forming agent and an organic solvent; and coating two sides of an aluminum foil with the aluminum paste, and sequentially drying and sintering to obtain the aluminum electrolytic capacitor anode foil. According to the method, the pore-forming agent is added into the aluminum paste, after sintering is completed, due to the fact that the pore-forming agent is added, more large holes are formed in the obtained anode foil, stress is reduced when the anode foil is bent or stressed, and therefore the anti-bending performance of the anode foil is greatly improved. And the larger the diameter of the hole is, the better the anti-bending effect is. The preparation method provided by the invention is simple and suitable for industrial production.

Description

Technical Field

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

[0002] At present, most domestic aluminum electrolytic capacitors use etched foils. However, in the application of medium and high-voltage aluminum electrolytic capacitors, it is difficult to further increase the surface specific capacitance by means of acid and alkali etching. With the development of the industry, medium and high-voltage foils have emerged, which are prepared by first making spherical aluminum powder into aluminum paste, double-sidedly coating it on an anode substrate, and then high-temperature sintering it on an anode foil substrate. This medium and high-voltage foil has a higher surface area, further improving the electrostatic capacitance of the anode foil. Moreover, the preparation process is simple and no waste acid or waste liquid is generated.

[0003] However, the medium and high-voltage foil prepared by the above method has very poor bending resistance. It is easy to break the foil during subsequent processes such as cutting and curling. Summary of the Invention

[0004] The purpose of the present invention is to provide a preparation method of an anode foil for an aluminum electrolytic capacitor. The anode foil prepared by the method provided by the present invention has excellent bending resistance.

[0005] In order to achieve the above purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a preparation method of an anode foil for an aluminum electrolytic capacitor, comprising the following steps:

[0007] Providing aluminum paste, wherein the aluminum paste comprises aluminum powder, binder, pore-forming agent and organic solvent;

[0008] Coating the aluminum paste on both sides of the aluminum foil, and sequentially drying and sintering to obtain the anode foil of the aluminum electrolytic capacitor.

[0009] Preferably, by mass percentage, the aluminum paste comprises: 50-70% of aluminum powder, 3-10% of binder, 0.5-40% of pore-forming agent and 25-40% of organic solvent.

[0010] Preferably, the pore-forming agent comprises one or more of starch, paraffin, polyethylene wax, polypropylene wax and polymer;

[0011] The polymer comprises one or more of polypropylene, polyethylene, polyethylene terephthalate, polystyrene, phenolic resin and polyacrylic resin.

[0012] Preferably, the particle size of the pore-forming agent is 3-50 μm.

[0013] Preferably, the particle size of the aluminum powder is 3-6 μm.

[0014] Preferably, the binder includes at least one of ethyl cellulose and polyvinyl alcohol.

[0015] Preferably, the organic solvent includes at least one of terpineol, tributyl citrate, ethylene glycol monomethyl ether, diethylene glycol dimethyl ether, diethylene glycol monobutyl ether, ethylene glycol dibutyl ether, butyl carbitol, ethylene glycol, and polyethylene glycol.

[0016] Preferably, the method for preparing the aluminum paste includes the following steps:

[0017] Dissolve the binder in the organic solvent to obtain a mixed solution;

[0018] Mix the mixed solution, aluminum powder, and pore-forming agent to obtain the aluminum paste.

[0019] Preferably, the thickness of the slurry layer formed on each side of the dried aluminum foil is 30 - 50 μm.

[0020] Preferably, the sintering includes first sintering and second sintering carried out in sequence;

[0021] The temperature of the first sintering is 250 - 500 °C, and the heat preservation time is 3 - 20 h;

[0022] The temperature of the second sintering is 550 - 650 °C, and the heat preservation time is 2 - 10 h.

[0023] The present invention provides a method for preparing an anode foil of an aluminum electrolytic capacitor, including the following steps: providing an aluminum paste, the aluminum paste including aluminum powder, a binder, a pore-forming agent, and an organic solvent; coating the aluminum paste on both sides of an aluminum foil, and sequentially drying and sintering to obtain the anode foil of the aluminum electrolytic capacitor. By adding a pore-forming agent to the aluminum paste in the present invention, after sintering is completed, due to the addition of the pore-forming agent, more large pores are formed in the obtained anode foil, reducing stress when the anode foil is bent or stressed, thereby greatly improving the anti-bending performance of the anode foil. And the larger the pore diameter, the better the anti-bending effect. The preparation method provided by the present invention is simple and suitable for industrial production. Description of the Drawings

[0024] Figure 1 It is a schematic diagram of the bending test of the present invention. Detailed Embodiments

[0025] The present invention provides a method for preparing an anode foil of an aluminum electrolytic capacitor, including the following steps:

[0026] Provide an aluminum paste, the aluminum paste including aluminum powder, a binder, a pore-forming agent, and an organic solvent;

[0027] Coat the aluminum paste on both sides of the aluminum foil, and sequentially dry and sinter to obtain the anode foil of the aluminum electrolytic capacitor.

[0028] The present invention provides an aluminum paste.

[0029] In the present invention, the aluminum paste comprises aluminum powder, binder, pore former and organic solvent. In the present invention, by mass percentage, the aluminum paste preferably comprises: 50-70% of aluminum powder, 3-10% of binder, 0.5-40% of pore former and 25-40% of organic solvent.

[0030] By mass percentage, the aluminum paste provided by the present invention preferably comprises 50-70% of aluminum powder, specifically it can be 50%, 55%, 60%, 65%, 70%. In the present invention, the aluminum powder is preferably spherical aluminum powder, and the particle size of the aluminum powder is preferably 3-6 μm.

[0031] By mass percentage, the aluminum paste provided by the present invention preferably comprises 3-10% of binder, specifically it can be 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%. In the present invention, the binder preferably comprises at least one of ethyl cellulose and polyvinyl alcohol.

[0032] By mass percentage, the aluminum paste provided by the present invention preferably comprises 0.5-40% of pore former, specifically it can be 0.5%, 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%. In the present invention, the pore former preferably comprises one or several of starch, paraffin, polyethylene wax, polypropylene wax and polymer; the polymer preferably comprises one or several of polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), polystyrene (PS), phenolic resin and polyacrylic resin. In the present invention, the particle size of the pore former is preferably 3-50 μm, specifically it can be 3 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm.

[0033] By mass percentage, the aluminum paste provided by the present invention preferably comprises 25-40% of organic solvent, specifically it can be 25%, 30%, 35%, 40%. In the present invention, the organic solvent preferably comprises at least one of terpineol, tributyl citrate, ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, ethylene glycol dibutyl ether, butyl carbitol, ethylene glycol and polyethylene glycol.

[0034] In the present invention, the preparation method of the aluminum paste preferably comprises the following steps:

[0035] Dissolve the binder in the organic solvent to obtain a mixed solution;

[0036] Mix the mixed solution, aluminum powder and pore former to obtain the aluminum paste.

[0037] In the present invention, the temperature of dissolution is preferably 100 °C. In the present invention, after dissolution, it is further preferred to cool the obtained system to room temperature. In the present invention, the mixing is preferably carried out under stirring conditions.

[0038] After obtaining the aluminum paste, in the present invention, the aluminum paste is coated on both sides of the aluminum foil, and the aluminum electrolytic capacitor anode foil is obtained by drying and sintering in sequence.

[0039] In the present invention, the thickness of the aluminum foil is preferably 30 μm. The present invention has no special limitation on the drying process, and those well-known to those skilled in the art can be adopted. In the present invention, the thickness of the slurry layer formed on each side of the aluminum foil after drying is preferably 30 - 50 μm.

[0040] In the present invention, the sintering preferably includes first sintering and second sintering in sequence; the temperature of the first sintering is preferably 250 - 500 °C, specifically it can be 250 °C, 300 °C, 350 °C, 400 °C, 450 °C, 500 °C; the heat preservation time is preferably 3 - 20 h, specifically it can be 3 h, 6 h, 12 h, 15 h, 18 h, 20 h; the temperature of the second sintering is preferably 550 - 650 °C, specifically it can be 550 °C, 600 °C, 650 °C; the heat preservation time is preferably 2 - 10 h, specifically it can be 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h. After the sintering, in the present invention, it is further preferred to naturally cool the obtained material to room temperature.

[0041] Unless otherwise specified, the materials and equipment used in the present invention are all commercially available products in the art.

[0042] Next, the technical solutions in the present invention will be clearly and completely described in conjunction with the embodiments in the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0043] Example 1

[0044] In terms of mass percentage, the aluminum paste in this example includes 5% ethyl cellulose, 25% terpineol, 60% spherical aluminum powder and 10% polystyrene, wherein the particle size of the spherical aluminum powder is 3 μm and the particle size of the polystyrene is 5 μm;

[0045] Add ethyl cellulose to terpineol, heat to 100 °C for dissolution, and after cooling to room temperature, obtain a mixed solution; then add spherical aluminum powder and polystyrene and stir evenly to obtain the aluminum paste;

[0046] The aluminum paste is coated on both sides of the base material aluminum foil (foil thickness: 30 μm) and dried. After drying, the thickness of the paste layer formed on each side is 50 μm;

[0047] The coated aluminum foil is placed in a sintering furnace for sintering. It is heated from room temperature to 450 °C and held for 3 h, then heated to 650 °C and held for 2 h, and then cooled naturally to obtain the anode foil of the aluminum electrolytic capacitor.

[0048] The obtained anode foil of the aluminum electrolytic capacitor is sampled according to the industry standard for the bending performance test. The specific test method is as follows: Use a foil bending performance tester to conduct anti-bending detection on the anode foil, shake the bending machine to count, take a 90-degree bend as one time, and stop counting until the electrode foil breaks. The number of times measured is the number of times of resistance to bending. Figure 1 Figure 1 is a schematic diagram of the bending test. After testing, the anode foil obtained in this example can be bent 100 times.

[0049] Example 2

[0050] The anode foil of the aluminum electrolytic capacitor is prepared in the same way as in Example 1, except that the aluminum paste includes 5% ethyl cellulose, 25% terpineol, 55% spherical aluminum powder, and 15% polystyrene.

[0051] Sampling is carried out for the bending performance test in the same way as in Example 1, and the number of bends reaches 120 times.

[0052] Example 3

[0053] The anode foil of the aluminum electrolytic capacitor is prepared in the same way as in Example 1, except that the particle size of the polystyrene is 25 μm.

[0054] Sampling is carried out for the bending performance test in the same way as in Example 1, and the number of bends reaches 110 times.

[0055] Example 4

[0056] The anode foil of the aluminum electrolytic capacitor is prepared in the same way as in Example 3, except that the aluminum paste includes 5% ethyl cellulose, 25% terpineol, 55% spherical aluminum powder, and 15% polystyrene, and the particle size of the polystyrene is 30 μm.

[0057] Sampling is carried out for the bending performance test in the same way as in Example 1, and the number of bends reaches 140 times.

[0058] Comparative Example 1

[0059] The anode foil of the aluminum electrolytic capacitor is prepared in the same way as in Example 1, except that the aluminum paste includes 5% ethyl cellulose, 25% terpineol, and 70% spherical aluminum powder (i.e., no pore-forming agent is added).

[0060] Sampling is carried out for the bending performance test in the same way as in Example 1, and the number of bends reaches 20 times.

[0061] Although the above embodiments have described the present invention in detail, they are only a part of the embodiments of the present invention, rather than all embodiments. Other embodiments can also be obtained based on these embodiments without creative efforts, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing an anode foil for an aluminum electrolytic capacitor, characterized in that: The following steps are involved: Providing aluminum paste, wherein the aluminum paste comprises aluminum powder, a binder, a pore former and an organic solvent; The aluminum paste is coated on both sides of the aluminum foil, and then dried and sintered in sequence to obtain the aluminum electrolytic capacitor anode foil.

2. The preparation method according to claim 1, characterized in that: Calculated by mass percentage, the aluminum paste comprises: 50-70% aluminum powder, 3-10% binder, 0.5-40% pore former and 25-40% organic solvent.

3. The preparation method according to claim 1 or 2, characterized in that: The pore-forming agent includes one or more of starch, paraffin wax, polyethylene wax, polypropylene wax and high molecular polymer; The high molecular polymer includes one or more of polypropylene, polyethylene, polyethylene terephthalate, polystyrene, phenolic resin and polyacrylic resin.

4. The preparation method according to claim 3, characterized in that: The particle size of the pore-forming agent is 3 to 50 μm.

5. The preparation method according to claim 1 or 2, characterized in that: The particle size of the aluminum powder is 3 to 6 μm.

6. The preparation method according to claim 1 or 2, characterized in that: The binder includes at least one of ethyl cellulose and polyvinyl alcohol.

7. The preparation method according to claim 1 or 2, characterized in that: The organic solvent includes at least one of terpineol, tributyl citrate, ethylene glycol methyl ether, diethylene glycol methyl ether, diethylene glycol butyl ether, ethylene glycol dibutyl ether, butyl carbitol, ethylene glycol and polyethylene glycol.

8. The preparation method according to claim 1 or 2, characterized in that: The preparation method of the aluminum paste comprises the following steps: dissolving a binder in an organic solvent to obtain a mixed solution; The mixed solution, aluminum powder and a pore-forming agent are mixed to obtain the aluminum paste.

9. The preparation method according to claim 1 or 2, characterized in that: The thickness of the slurry layer formed on each side of the aluminum foil after drying is 30-50 μm.

10. The preparation method according to claim 1 or 2, characterized in that: The sintering includes sequentially performing a first sintering and a second sintering; The first sintering temperature is 250-500°C and the holding time is 3-20h; The second sintering temperature is 550-650° C., and the heat preservation time is 2-10 hours.

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