CN111508711A - Aluminum foil pretreatment method, preparation method of medium-high voltage anode foil and electrolytic capacitor - Google Patents

Abstract

The present invention provides a pretreatment method for aluminum foil before pore corrosion, a method for preparing high-voltage anode foil using the method, and an electrolytic capacitor. The preparation method of the medium- and high-voltage anode foil includes electrostatic spinning pre-pore arrangement, pre-treatment, dissolution treatment, primary pore arrangement, secondary pore expansion, and post-treatment, wherein the electrostatic spinning pre-pore arrangement includes: electrostatic spinning a polymer slurry on the surface of the aluminum foil to obtain an aluminum foil with a polymer fiber layer; the dissolution treatment includes: soaking the aluminum foil after the pre-treatment in an organic solution to remove the polymer fiber layer on the surface of the aluminum foil. The electrostatic spinning pre-pore arrangement can improve the uniformity of pores, reduce pores, and increase the capacity of the medium- and high-voltage anode foil.

Description

Aluminum foil pretreatment method, preparation method of medium and high voltage anode foil, electrolytic capacitor

technical field

The invention relates to the technical field of supercapacitors, in particular to a pretreatment method before porosity corrosion of aluminum foil, a method for preparing high-voltage anode foil by using the method, and an electrolytic capacitor.

Background technique

Aluminum electrolytic capacitors are gradually developing towards miniaturization, which puts forward higher performance requirements for medium and high voltage anode foils. The medium and high voltage anode foil is obtained from the light foil through the steps of pretreatment, primary hole formation, secondary hole expansion, post-treatment and drying. Among them, the uniformity of surface porosity distribution and the consistency of tunnel pore length are the keys to obtain high-performance medium and high voltage anode foils.

In order to improve the uniformity of etching holes on the surface of medium and high voltage anode foils and the uniformity of the length of tunnel holes, Japanese application JP2018006617A discloses a preparation method of electrode foil. First, a UV-sensitive compound layer is coated on the surface of the light foil; Then, a polymer thermoplastic layer is covered on the surface, and the thermal nano-printing technology is used to make pits on the thermoplastic polymer layer, and UV irradiation is used to oxidize the pits. Thermoplastic plastic layer, polymer layer and UV-sensitive compound layer; then electro-etch the recessed position, and finally remove the UV-sensitive compound layer, polymer layer and thermoplastic polymer layer on the medium and high voltage anode foil. The above method can be used to obtain a corrosion foil with a uniform distribution of pores on the surface. However, this method is cumbersome, and requires multiple layers of materials to be coated on the surface of the aluminum foil, and a variety of equipment is used, which increases the production cost. At the same time, the coated multilayer materials are difficult to remove. It will adversely affect the performance of the electrode foil.

Therefore, developing a simple method for pre-distributing holes to obtain medium and high voltage anode foils with uniform distribution of surface corrosion holes and uniform length of tunnel holes plays an important role in reducing production costs and improving product performance.

SUMMARY OF THE INVENTION

The present invention aims to solve at least one of the following technical problems:

(1) After using the conventional pretreatment process, electrochemical porosity is performed, and the porosity distribution is uneven, resulting in a large number of clusters and pores, resulting in low specific volume of the medium and high voltage anode foil;

(2) After using the conventional pretreatment process, the surface state of the light foil varies greatly, the distribution of the hole current is uneven, the uniformity of the length of the tunnel hole is poor, and the sandwich layer is not obvious, resulting in low bending performance of the medium and high voltage anode foil;

(3) In the prior art, after the surface of the aluminum foil is coated, thermal nano-imprinting and ultraviolet irradiation techniques can be used to improve the uniformity of the distribution of the pores on the surface of the medium and high voltage anode foil. However, the method is cumbersome, needs to coat the surface of the aluminum foil with multiple layers of materials, uses a variety of equipment, increases the production cost, and at the same time, the coated material is difficult to remove, which adversely affects the performance of the electrode foil.

For this reason, the present invention provides the following technical solutions:

In one aspect, the present invention provides a pretreatment method for aluminum foil porosity corrosion, including pre-distribution of electrospinning holes, pretreatment, and dissolution treatment, wherein the pre-distribution of electrospinning holes includes: disposing polymer slurry in Electrospinning is performed on the surface of the aluminum foil to obtain an aluminum foil with a polymer fiber layer; the dissolving treatment includes: soaking the pretreated aluminum foil in an organic solution to remove the polymer fiber layer on the surface of the aluminum foil.

The present invention is made by the inventor based on the following knowledge:

Usually, the function of pretreatment is to remove the oil film and oxide film on the surface of the aluminum foil, activate the aluminum foil, provide conditions for the subsequent pore corrosion, and promote the development of the pore. However, due to the uneven thickness of oxide film, oil film and other pollution layers formed on the surface of aluminum foil during rolling and high-temperature annealing, the surface structure of aluminum foil is uneven, and the existing aluminum foil pretreatment process cannot fundamentally solve the surface structure. The problem of uneven structure is that in the corrosion stage, the porosity is mostly concentrated in the area with high potential energy, causing a large number of parallel pores in the above area, while other areas have fewer or no pores, resulting in poor pore uniformity. For this reason, the inventor first pre-arranged holes on the surface of the aluminum foil by electrospinning to form a network-like polymer fiber layer on the surface of the aluminum foil, and then pretreated the aluminum foil. After the treatment, the pores can be formed normally, and the place covered by the polymer fibers retains the oxide film, which is not easy to pore, so as to achieve the purpose of uniform pore formation and reduction of undesired phenomena such as parallel pores. After the pretreatment, the polymer fiber layer is soaked and dissolved in an organic solution to prevent it from reducing the conductivity of the aluminum foil, thus completing the invention. In addition, the polymer fiber layer can also be removed after pore etching. However, considering that the existence of the polymer fiber layer will affect the contact time between the pore etching solution and the aluminum foil substrate, on the other hand, The pore etching solution is generally a strong acid solution, which may cause part of the polymer fiber layer to fall off, thereby affecting the corrosion effect. Therefore, in the present invention, the polymer fiber layer is preferably removed uniformly before pore etching.

According to some embodiments provided by the present invention, the polymer is polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polycaprolactone (PCL), polylactic-co-glycolic acid (PLGA), polylactic acid (PLLA), at least one of polyamides.

According to some embodiments provided by the present invention, the thickness of the electrospun polymer fiber layer is 2-15 μm.

According to some embodiments provided by the present invention, the organic solution includes water and an organic solvent, and the mass ratio of the organic solvent and water is 5-25:95-75.

According to some embodiments provided by the present invention, the organic solvent is at least one of ethanol, acetic acid, ethylene glycol, n-butanol, N,N-dimethylformamide, chloroform, and diethyl ether.

According to some embodiments provided by the present invention, the soaking temperature is 25-50° C., and the soaking time is 1-3 min.

According to some embodiments provided by the present invention, the pretreatment includes: immersing the aluminum foil after the electrospinning pre-holes is immersed in an aqueous solution containing 0.1-1.0wt.% aluminum ions and 0.5-5wt.% phosphoric acid at 45-75°C, Process 2-6min.

On the other hand, the present invention provides a method for preparing a medium and high voltage anode foil, which uses the above-mentioned pretreatment method to pretreat the aluminum foil.

According to some embodiments provided by the present invention, the preparation method of the medium and high voltage anode foil includes electrospinning pre-distribution, pre-treatment, dissolution treatment, first-stage hole formation, second-stage hole expansion and post-treatment, wherein the electrostatic The spinning pre-distribution holes include: electrospinning the polymer slurry on the surface of the aluminum foil to obtain an aluminum foil with a polymer fiber layer; the dissolving treatment includes: soaking the pre-treated aluminum foil in an organic solution to remove the aluminum foil Polymer fiber layer on the surface.

The method for preparing a medium and high voltage anode foil provided according to an embodiment of the present invention may further include the following additional technical features.

The pre-treatment, primary hole opening, secondary hole expansion and post-treatment can be performed according to methods known in the art. Preferably, it is carried out according to an embodiment of the present invention.

The conditions for the electrospinning pre-holes, pretreatment, and dissolution treatment are as described in the pretreatment method before the aluminum foil porosity corrosion, which will not be repeated here.

According to some embodiments provided by the present invention, the primary pore formation comprises: placing the aluminum foil after dissolution treatment at 65-85° C. containing 1.0-5.0 wt.% hydrochloric acid, 30-40 wt.% sulfuric acid and 0.5 wt. Electrochemical corrosion was carried out in an aqueous solution of -1.5wt.% aluminum ions, a decaying current waveform was used, the effective charging time of each section was 18-35s, the initial current density was 1.0-1.8A/cm ² , and the terminal current density was 0.1-0.2 A/cm ² .

According to some embodiments provided by the present invention, the secondary hole reaming comprises: placing the aluminum foil after primary hole formation at 70-75° C. containing 1.5-6.5 wt.% nitric acid, 0.01-0.1 wt.% DC electrochemical corrosion is performed in an aqueous solution of phosphoric acid and 0.2-1.0 wt. % aluminum ions, the current density is 0.1-0.2 A/cm ² , and the corrosion time is 6-10 min.

According to some embodiments provided by the present invention, the post-treatment includes: treating the aluminum foil after secondary hole expansion in an aqueous solution of nitric acid containing 3-10 wt % for 2-5 min at a temperature of 60-80°C.

On the other hand, the present invention provides the medium and high voltage anode foil obtained by the above preparation method.

In another aspect, the present invention provides an aluminum electrolytic capacitor, comprising an anode foil obtained by subjecting the above-mentioned medium and high voltage anode foil to chemical conversion treatment.

Compared with the prior art, the present invention has the following beneficial effects:

(1) The present invention adopts electrospinning technology to pre-distribute holes, obtains medium and high voltage anode foil with uniform distribution of porosity on the surface, reduces parallel holes, and can improve its capacity;

(2) The present invention pre-arranges holes by electrospinning, reduces the surface state difference of the aluminum foil, distributes the hole current evenly, improves the length consistency of the tunnel hole, and improves the bending performance of the medium and high voltage anode foil;

(3) In the present invention, the polymer fiber layer is removed by a simple organic solvent soaking treatment, thereby reducing equipment investment and production cost.

Description of drawings

Fig. 1 shows the production process flow chart of the medium and high voltage anode foil provided by the embodiment of the present invention:

FIG. 2 shows a schematic view of the structure of the aluminum foil provided by the embodiment of the present invention after the electrospinning pre-holes are arranged;

In Figure 2: 1 is an aluminum foil, and 2 is a polymer fiber layer;

Fig. 3 shows the SEM image of the corrosion foil surface provided in Example 1 of the present invention;

Fig. 4 shows the SEM image of the corrosion foil cross-section provided in Example 1 of the present invention;

Figure 5 shows the SEM image of the surface of the etched foil provided in Example 2 of the present invention;

Fig. 6 shows the SEM image of the corrosion foil cross-section provided in Example 2 of the present invention;

Figure 7 shows a SEM image of the surface of the corroded foil provided by Comparative Example 1 of the present invention; and

FIG. 8 shows a cross-sectional SEM image of the corroded foil provided by Comparative Example 1 of the present invention.

Detailed ways

The following describes in detail the embodiments of the present invention, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary, and are intended to explain the present invention and should not be construed as limiting the present invention. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. All patents and publications referred to herein are incorporated by reference in their entirety. The term "comprising" or "including" is an open-ended expression, ie, it includes what is specified in the present invention, but does not exclude other aspects.

The preparation method of the medium and high voltage anode foil provided by the present invention is shown in FIG. 1 , including pre-distribution of electrospinning holes, pre-treatment, dissolution treatment, first-stage hole formation, second-stage hole expansion and post-treatment.

Specifically, according to an embodiment of the present invention, the preparation method of the medium and high voltage anode foil includes:

1) Electrospinning prefabricated holes

Electrospinning the polymer slurry on the surface of the aluminum foil to obtain an aluminum foil with a polymer fiber layer;

2) Pretreatment

The pretreatment includes: immersing the aluminum foil after electrospinning pre-holes into an aqueous solution containing 0.1-1.0wt.% aluminum ion and 0.5-5wt.% phosphoric acid at 45-75°C for 2-6min;

3) Dissolution treatment

Soak the pretreated aluminum foil in an organic solution to remove the polymer fiber layer on the surface of the aluminum foil.

4) Primary hair hole

The aluminum foil after dissolution treatment is placed in an aqueous solution containing 1.0-5.0 wt.% hydrochloric acid, 30-40 wt.% sulfuric acid and 0.5-1.5 wt.% aluminum ions at 65-85 ° C for electrochemical corrosion, using decay current waveform, the effective power-on time of each segment is 18-35s, the initial current density is 1.0-1.8A/cm ² , and the terminal current density is 0.1-0.2A/cm ² .

5) Secondary reaming

The aluminum foil after primary pore formation is placed in an aqueous solution containing 1.5-6.5 wt.% nitric acid, 0.01-0.1 wt.% phosphoric acid and 0.2-1.0 wt.% aluminum ions at 70-75 ° C for DC electrochemical corrosion. , the current density is 0.1-0.2A/cm ² , and the corrosion time is 6-10min.

6) Post-processing

The aluminum foil after the secondary hole expansion is treated in an aqueous solution of nitric acid containing 3 to 10 wt % for 2 to 5 minutes, and the temperature is 60 to 80°C.

The processing conditions of each step in the preparation method of the medium and high voltage anode foil will be described in detail below.

1) Electrospinning prefabricated holes

According to some embodiments provided by the present invention, the composition of the polymer slurry includes: based on the total weight of the slurry as 100 parts, 50-60 parts of polymer, 10-15 parts of binder, and the balance is organic solvent .

In some embodiments, the composition of the polymer slurry is: 60 parts by weight of a polymer, 10 parts by weight of a binder, and 30 parts by weight of an organic solvent.

The preparation of the cellulose pulp can be carried out according to methods known in the art. The preparation method of the polymer slurry used in the embodiment of the present invention includes: stirring and mixing 60 parts by weight of a polymer, 10 parts by weight of a binder, and 30 parts by weight of an organic solvent at 25-50° C. for 0.5-24 hours to obtain the polymer slurry.

According to some embodiments provided by the present invention, the polymer is at least one of PVDF, PAN, PCL, PLGA, PLLA, and polyamide.

In some embodiments, the polymer is any one of PVDF, PAN, PCL, PLGA, PLLA, polyamide.

According to some embodiments provided by the present invention, the organic solvent is at least one of ethanol, acetic acid, ethylene glycol, n-butanol, N,N-dimethylformamide, chloroform, and ether, preferably ethanol.

According to some embodiments provided by the present invention, the binder is polyethylene glycol (PEG), polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), polypyrrole (PPy) or vinyl acetate resin (EVA). One or a combination of , preferably polyvinyl alcohol.

The electrospinning pre-distribution holes are carried out with E05 multifunctional intelligent integrated electrospinning equipment.

The thickness of the electrospun pre-porous polymer fiber layer is 2-15 μm, for example: 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, etc. Wait.

According to some embodiments provided by the present invention, the thickness of the electrospun pre-porous polymer fiber layer is 3-10 μm.

Figure 2 shows a schematic diagram of the structure of the aluminum foil obtained after electrospinning pre-holes.

2) Pretreatment

According to some embodiments provided by the present invention, the temperature of the pretreatment is 45-75°C, for example: 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, and the like.

According to some embodiments provided by the present invention, the time of the pretreatment is 2-6min, for example: 2min, 3min, 4min, 5min, 6min, and the like.

According to some embodiments provided by the present invention, in the aqueous solution for pretreatment, the concentration of phosphoric acid is 0.5-5wt.%, for example: 0.5wt.%, 0.8wt.%, 1.0wt.%, 1.2wt.%, 1.5 wt.%, 1.8wt.%, 2.0wt.%, 2.3wt.%, 2.5wt.%, 2.8wt.%, 3.0wt.%, 3.2wt.%, 3.5wt.%, 3.8wt.%, 4.0 %, 4.2 wt. %, 4.5 wt. %, 4.8 wt. %, 5.0 wt. %, etc.

In some embodiments, in the aqueous solution for pretreatment, the concentration of phosphoric acid is 2-5 wt.%.

According to some embodiments provided by the present invention, in the aqueous solution for pretreatment, the concentration of aluminum ions is 0.1-1.0wt.%, for example: 0.1wt.%, 0.2wt.%, 0.3wt.%, 0.4wt.% , 0.5 wt. %, 0.6 wt. %, 0.7 wt. %, 0.8 wt. %, 0.9 wt. %, 1 wt. %, etc.

3) Dissolution treatment

According to some embodiments provided by the present invention, the organic solution includes water and an organic solvent.

According to some embodiments provided by the present invention, the mass ratio of the organic solvent and water is 5-25:95-75, preferably 10-25:90-75, for example: 10:90, 15:85, 20: 80, 25:75, etc.

According to some embodiments provided by the present invention, the organic solvent is at least one of ethanol, acetic acid, ethylene glycol, n-butanol, N,N-dimethylformamide, chloroform, and diethyl ether.

In some embodiments, the organic solvent is one or both of ethanol, acetic acid, ethylene glycol, n-butanol, N,N-dimethylformamide, chloroform, and diethyl ether.

According to some embodiments provided by the present invention, the soaking temperature in the organic solution is 25-50°C, for example: 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, and the like.

According to some embodiments provided by the present invention, the soaking time in the organic solution is 1-3min, for example: 1min, 1.5min, 2min, 2.5min, 3min, and the like.

4) Primary hair hole

According to some embodiments provided by the present invention, the temperature of the primary pores is 65-85°C, for example: 65°C, 70°C, 71°C, 75°C, 80°C, 85°C, and the like.

According to some embodiments provided by the present invention, in the aqueous solution for primary pores, the concentration of hydrochloric acid is 1.0-5.0wt.%, for example: 1.0wt.%, 1.2wt.%, 1.5wt.%, 1.8wt.% %, 2.0wt.%, 2.3wt.%, 2.5wt.%, 2.6wt.%, 3.0wt.%, 3.2wt.%, 3.5wt.%, 3.8wt.%, 4.0wt.%, 4.2wt.% %, 4.5 wt. %, 4.8 wt. %, 5.0 wt. %, etc.

In some embodiments, the concentration of hydrochloric acid in the aqueous solution for primary pores is 2-5 wt.%.

According to some embodiments provided by the present invention, in the aqueous solution for primary pores, the concentration of sulfuric acid is 30-40wt.%, for example: 30wt.%, 31wt.%, 32wt.%, 33wt.%, 34wt.% , 35 wt. %, 36 wt. %, 37 wt. %, 38 wt. %, 39 wt. %, 40 wt. %, etc.

According to some embodiments provided by the present invention, in the aqueous solution for primary pore formation, the concentration of aluminum ions is 0.5-1.5wt.%, for example: 0.5wt.%, 0.6wt.%, 0.7wt.%, 0.8 %, 0.9 wt. %, 1 wt. %, 1.2 wt. %, 1.3 wt. %, 1.4 wt. %, 1.5 wt. %, etc.

In some embodiments, in the aqueous solution for primary pore formation, the concentration of hydrochloric acid is 2.6 wt.%, the concentration of sulfuric acid is 35 wt.%, and the concentration of aluminum ions is 1.2 wt.%.

According to some embodiments provided by the present invention, the first-stage pore current adopts a decaying current waveform, and the effective power-on time of each segment is 18-35s (for example: 18s, 20s, 22s, 24s, 26s, 28s, 30s, 32s, 34s, 35s, etc.) with an initial current density of 1.0-1.8A/ ^cm2 (eg: 1.0A/ ^cm2 , 1.2A/ ^cm2 , 1.6A/ ^cm2 , 1.8A/ ^cm2 , etc.), The terminal current density is 0.1-0.2 A/cm ² (eg: 0.12 A/cm ² , 0.14 A/cm ² , 0.16 A/cm ² , 0.18 A/cm ² , 0.2 A/cm ² , etc.).

In some embodiments, the primary pore current is a decaying current waveform with an initial current density of 1.6 A/cm ² and a terminal current density of 0.16 A/cm ² .

In some embodiments, each effective power-up period is 20-33s.

In some embodiments, the effective power-on time of each stage of the primary hole is 22s.

5) Secondary reaming

According to some embodiments provided by the present invention, the temperature of the secondary hole expansion is 70-75°C, for example: 70°C, 71°C, 72°C, 73°C, 74°C, 75°C, and the like.

According to some embodiments provided by the present invention, in the aqueous solution for secondary hole expansion, the concentration of nitric acid is 1.5-6.0wt.%, for example: 1.5wt.%, 1.8wt.%, 2.0wt.%, 2.3wt.% %, 2.5wt.%, 2.8wt.%, 3.0wt.%, 3.2wt.%, 3.5wt.%, 3.8wt.%, 4.0wt.%, 4.2wt.%, 4.5wt.%, 4.8wt.% %, 5.0 wt.%, 5.2 wt.%, 5.5 wt.%, 5.8 wt.%, 6.0 wt.%, etc.

According to some embodiments provided by the present invention, the concentration of phosphoric acid in the aqueous solution for secondary hole expansion is 0.01-1.0wt.%, for example: 0.01wt.%, 0.02wt.%, 0.03wt.%, 0.04wt.% %, 0.05 wt. %, 0.06 wt. %, 0.07 wt. %, 0.08 wt. %, 0.09 wt. %, 0.1 wt. %, and the like.

According to some embodiments provided by the present invention, in the aqueous solution for secondary hole expansion, the concentration of aluminum ions is 0.2-1.0wt.%, for example: 0.2wt.%, 0.3wt.%, 0.4wt.%, 0.5 %, 0.6 wt. %, 0.7 wt. %, 0.8 wt. %, 0.9 wt. %, 1 wt. %, etc.

In some embodiments, in the aqueous solution for secondary hole expansion, the concentration of nitric acid is 2.0-5.0 wt.%, the concentration of phosphoric acid is 0.05-1.0 wt.%, and the concentration of aluminum ions is 0.5-1.0 wt.%.

According to some embodiments provided by the present invention, the current density of the secondary hole expansion DC corrosion is 0.1-0.2A/cm ² , for example: 0.13A/cm ² , 0.15A/cm ² , 0.17A/cm ² , 0.19 A/cm ² , preferably 0.14 A/cm ² .

According to some embodiments provided by the present invention, the power-on time of the secondary hole reaming DC corrosion is 6-10min, for example: 6min, 7min, 8min, 9min, 10min, etc.; preferably 8min.

6) Post-processing

According to some embodiments provided by the present invention, the temperature of the post-treatment is 60-80°C, for example: 60°C, 65°C, 70°C, 75°C, 80°C, and the like.

According to some embodiments provided by the present invention, the post-processing time is 2-5 min, for example: 2 min, 3 min, 4 min, 5 min, and the like.

According to some embodiments provided by the present invention, in the post-treatment aqueous solution, the concentration of nitric acid is 3-10wt.%, for example: 3.0wt.%, 3.5wt.%, 4.0wt.%, 4.5wt.%, 5.0 wt.%, 5.5wt.%, 6.0wt.%, 6.5wt.%, 7.0wt.%, 7.5wt.%, 8.0wt.%, 8.5wt.%, 9.0wt.%, 9.5wt.%, 10wt .%,and many more.

In some embodiments, the concentration of nitric acid in the post-treatment aqueous solution is 5 wt.%.

The embodiments of the present invention will be described in detail below with reference to the examples, but those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. If the specific conditions are not indicated in the examples, it is carried out according to the conventional conditions or the conditions suggested by the manufacturer. The reagents or instruments used without the manufacturer's indication are conventional products that can be purchased from the market.

Example 1

1) Electrospinning pre-distribution holes: PAN polymer is used, and the thickness of the electrospinning polymer fiber layer is 3 μm;

2) Pretreatment

Immerse the aluminum foil after electrospinning pre-holes in an aqueous solution containing 0.3wt.% aluminum ions and 5.0wt.% phosphoric acid at 65°C for 4 minutes;

3) Dissolution treatment

Soak the pre-treated aluminum foil in an organic solution at 35°C for 1 min to remove the polymer fiber layer on the surface of the aluminum foil. The organic solution is composed of ethylene glycol, n-butanol, and water in a mass ratio of 10:5:85;

4) Primary hair hole

The dissolved aluminum foil was placed in an aqueous solution containing 2.6 wt.% hydrochloric acid, 35 wt.% sulfuric acid and 1.2 wt.% aluminum ions at 71 °C for electrochemical corrosion. The decaying current waveform was used, and each effective power-on time was used. is 22s, the initial current density is 1.6A/cm ² , and the terminal current density is 0.16A/cm ² ;

5) Secondary reaming

The aluminum foil after primary pore formation was placed in an aqueous solution containing 2.0 wt.% nitric acid, 0.05 wt.% phosphoric acid and 0.5 wt.% aluminum ions at 71 °C for DC electrochemical corrosion, and the current density was 0.14 A/cm ² , the corrosion time is 8min.

6) Post-processing

The aluminum foil after the secondary hole expansion was treated in an aqueous solution containing 5.0 wt % of nitric acid for 2 min at a temperature of 65°C.

Fig. 3 shows the surface topography of the corroded foil obtained in this example. After pre-holes are distributed by electrospinning, the surface corroded holes are evenly distributed, and the hole area is greatly reduced, and the capacity of the corroded foil is improved; Fig. 4 is obtained in this example. The cross-sectional topography of the corroded foil shows that the length of the tunnel holes is basically the same, and there is an obvious sandwich layer, which ensures that the corroded foil has strong bending performance.

Example 2

1) Electrospinning pre-distribution holes: PAN polymer is used, and the thickness of the electrospinning polymer fiber layer is 9 μm;

2) Pretreatment

Immerse the aluminum foil after electrospinning pre-holes in an aqueous solution containing 0.3wt.% aluminum ions and 5.0wt.% phosphoric acid at 65°C for 4 minutes;

3) Dissolution treatment

Soak the pre-treated aluminum foil in an organic solution at 35°C for 1 min to remove the polymer fiber layer on the surface of the aluminum foil. The organic solution is composed of ethylene glycol, n-butanol, and water in a mass ratio of 10:5:85;

4) Primary hair hole

The dissolved aluminum foil was placed in an aqueous solution containing 2.6 wt.% hydrochloric acid, 35 wt.% sulfuric acid and 1.2 wt.% aluminum ions at 71 °C for electrochemical corrosion. The decaying current waveform was used, and each effective power-on time was used. is 22s, the initial current density is 1.6A/cm ² , and the terminal current density is 0.16A/cm ² ;

5) Secondary reaming

The aluminum foil after primary pore formation was placed in an aqueous solution containing 2.0 wt.% nitric acid, 0.05 wt.% phosphoric acid and 0.5 wt.% aluminum ions at 71 °C for DC electrochemical corrosion, and the current density was 0.14 A/cm ² , the corrosion time is 8min.

6) Post-processing

The aluminum foil after the secondary hole expansion was treated in an aqueous solution containing 5.0 wt % of nitric acid for 2 min at a temperature of 65°C.

Fig. 5 shows the surface topography of the etched foil obtained in this example. After pre-distributing holes by electrospinning, the uniformity of the surface etched hole distribution is further improved, and the hole area basically disappears, and the capacity of the corroded foil is further improved; Fig. 6 is this embodiment. The cross-sectional topography of the corroded foil obtained by the example shows that the length consistency of the tunnel hole is further improved, the sandwich layer is obvious, and the bending performance of the corroded foil is higher.

Comparative Example 1

preprocessing

Immerse the aluminum foil in an aqueous solution containing 0.3wt.% aluminum ions and 5.0wt.% phosphoric acid at 65°C for 4min;

first class pores

The pre-treated aluminum foil was placed in an aqueous solution containing 2.6wt.% hydrochloric acid, 35wt.% sulfuric acid and 1.2wt.% aluminum ions at 71°C for electrochemical corrosion. The decay current waveform was used, and each section of pores was effective. The power-on time was 22s, the initial current density was 1.6A/cm ² , and the terminal current density was 0.16A/cm ² ;

Secondary reaming

The aluminum foil after primary pore formation was placed in an aqueous solution containing 2.0 wt.% nitric acid, 0.05 wt.% phosphoric acid and 0.5 wt.% aluminum ions at 71 °C for DC electrochemical corrosion, and the current density was 0.14 A/cm ² , the corrosion time is 8min.

post-processing

The aluminum foil after the secondary hole expansion was treated in an aqueous solution containing 5.0 wt % of nitric acid for 2 min at a temperature of 65°C.

Figure 7 is the surface topography of the corroded foil obtained in Comparative Example 1, with many parallel holes and low specific volume of the corroded foil; Figure 8 is the cross-sectional topography of the corroded foil obtained in Comparative Example 1, the tunnel hole length is poor in consistency, and there is no obvious The core layer of the corroded foil has a cross-penetration phenomenon in some areas, which greatly reduces the bending performance of the corroded foil.

Performance Testing

1. Bending performance: The size of the test sample is 10mm×150mm (the punching burr should be less than 0.1mm), and the MIT-DA model bending tester of YAFENG company is used. Test conditions: the curvature radius R at the bend is 1.0±0.1mm, The load is 2.5±0.5N, the bending angle is 90±2°, the bending speed is 6 times/s, and the distance between the upper and lower chucks is 70

±2mm.

2. Surface map: After polishing the surface of the etched foil to 10μm, it was taken with a scanning electron microscope magnified by 1000 times.

3. Specific volume: Use Agilent 4263B meter to test the sample capacity.

Table 1

Example 1 Example 2 Comparative Example 1 Specific volume/(μF/cm²) 0.828 0.858 0.796 Bend (R1.0)/back 82 88 68

From the test data in Table 1, it can be seen that the specific volume and bending strength of the anode foil obtained by the embodiment of the present invention are obviously better than those of Comparative Example 1, indicating that the aluminum foil pretreatment method of the present invention has a significant effect on improving the specific volume and bending effect of the anode foil. .

In the description of this specification, description with reference to the terms "some embodiments," "examples," "examples," etc. means that a particular feature, structure, material, or characteristic described in connection with the example or example is included in at least one aspect of the present invention. in one embodiment or example. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, those skilled in the art may combine and combine the different embodiments or examples described in this specification, as well as the features of the different embodiments or examples, without conflicting each other.

Although the embodiments and examples of the present invention have been shown and described above, it should be understood that the above-mentioned embodiments and examples are exemplary and should not be construed as limiting the present invention. Variations, modifications, substitutions and alterations may be made to the above-described embodiments and examples within the scope of .

Claims (12)

1. A pretreatment method before corrosion of aluminum foil pores is characterized by comprising electrostatic spinning hole pre-distribution, pretreatment and dissolution treatment; wherein the electrospinning pre-distribution holes comprise: performing electrostatic spinning on the polymer slurry on the surface of the aluminum foil to obtain the aluminum foil with a polymer fiber layer; the dissolution treatment comprises: and soaking the pretreated aluminum foil in an organic solution to remove the polymer fiber layer on the surface of the aluminum foil.

2. The pretreatment method before the corrosion of the aluminum foil pores, according to claim 1, wherein the polymer is at least one of PVDF, PAN, PC L, P L GA, P LL A and polyamide.

3. The pretreatment method before the corrosion of the aluminum foil open pores, according to claim 1, characterized in that the organic solution comprises water and an organic solvent, the mass ratio of the organic solvent to the water is 5-25:95-75, and the organic solvent is at least one of ethanol, acetic acid, ethylene glycol, N-butanol, N-dimethylformamide, chloroform and diethyl ether.

4. The pretreatment method before the corrosion of the aluminum foil open pores, according to claim 1, characterized in that the soaking temperature is 25-50 ℃ and the soaking time is 1-3 min.

5. The method for pretreating aluminum foil before pitting corrosion according to claim 1, wherein the pretreatment comprises: immersing the aluminum foil subjected to electrostatic spinning and pre-hole distribution in an aqueous solution containing 0.1-1.0 wt.% of aluminum ions and 0.5-5 wt.% of phosphoric acid at 45-75 ℃ for 2-6 min.

6. A method for preparing a medium-high voltage anode foil, characterized in that an aluminum foil is pretreated using the pretreatment method of any one of claims 1 to 5.

7. The method for preparing a high-voltage anode foil according to claim 6, comprising the steps of electrostatic spinning pre-hole distribution, pretreatment, dissolution treatment, primary hole formation, secondary hole expansion and post-treatment.

8. The method for preparing a medium-high voltage anode foil according to claim 7, wherein the primary perforation comprises: placing the aluminum foil after dissolution treatment in 65-85 deg.C aqueous solution containing 1.0-5.0 wt.% hydrochloric acid, 30-40 wt.% sulfuric acid and 0.5-1.5 wt.% aluminum ions for electrochemical corrosion, and adopting decay current waveform with initial current density of 1.0-1.8A/cm²The current density at the end is 0.1-0.2A/cm²。

9. The method for preparing a medium-high voltage anode foil according to claim 7, wherein the secondary hole reaming comprises: placing the aluminum foil after primary pore forming in an aqueous solution containing 1.5-6.5 wt.% of nitric acid, 0.01-0.1 wt.% of phosphoric acid and 0.2-1.0 wt.% of aluminum ions at 70-75 ℃ for direct electrochemical corrosion, wherein the current density is 0.1-0.2A/cm²The etching time is 6-10 min.

10. The method for producing a medium-high voltage anode foil according to claim 7, wherein the post-treatment comprises: and (3) treating the aluminum foil subjected to secondary hole expanding in a nitric acid water solution containing 3-10 wt% for 2-5min at the temperature of 60-80 ℃.

11. The medium-high voltage anode foil obtained by the production method according to any one of claims 6 to 10.

12. An aluminum electrolytic capacitor comprising the anode foil obtained by subjecting the medium-high voltage anode foil according to claim 11 to a chemical conversion treatment.

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