WO2021081882A1

WO2021081882A1 - Reaming etching solution, etching process and electrode foil

Info

Publication number: WO2021081882A1
Application number: PCT/CN2019/114664
Authority: WO
Inventors: 余英凤; 何凤荣; 邓利松; 朱荣贵; 向云刚; 温益凡
Original assignee: 东莞东阳光科研发有限公司; 乳源瑶族自治县东阳光化成箔有限公司
Priority date: 2019-10-31
Filing date: 2019-10-31
Publication date: 2021-05-06
Also published as: CN114600210A; CN114600210B

Abstract

Disclosed are a reaming etching solution, an etching process and an electrode foil prepared by the etching process in the technical field of electrode materials for capacitors. The reaming etching solution contains a gallium-based liquid metal nanoparticle dispersion, which is obtained by dispersing a gallium-based liquid metal in a polymer solution of a polystyrene sulfonic acid and sodium polystyrenesulfonate, wherein the mass fraction of the gallium-based liquid metal is 0.3%-1.5%. The electrode foil prepared by the etching process for reaming a hole with a reaming etching solution has an increased hole depth, reduced branch holes or small holes, a good hole consistency, and higher electrostatic capacitance and anti-bending strength.

Description

Reaming corrosive liquid, corrosion process and electrode foil

Technical field

The invention belongs to the technical field of electrode materials for capacitors, and specifically relates to a hole-expanding corrosion solution, a corrosion process and an electrode foil prepared by the corrosion process.

Background technique

With the development of miniaturization of electronic equipment, there is an urgent need for aluminum electrolytic capacitors to reduce their volume and increase their specific capacitance. As the core material of aluminum electrolytic capacitors, electrode foil plays a decisive role in the various characteristics of the capacitor. The anode foil for aluminum electrolytic capacitors generally generates a large number of vertical tunnel holes on its surface through electrochemical corrosion to increase its effective surface area, thereby increasing the capacity of the electrode foil; then a dense aluminum oxide film is formed on the surface of the corrosion hole through chemical conversion. The voltage resistance of aluminum electrolytic capacitors is determined by the thickness of the oxide film, but its capacity, tensile strength and bending performance depend on the corrosion technology.

The conventional corrosion foil manufacturing process mainly includes pre-treatment, primary pore corrosion, secondary pore expansion corrosion, post-treatment and other processes. The primary pores are carried out in the sulfuric acid-hydrochloric acid mixture to form high-density, uniform and small tunnel holes. The secondary hole expansion is generally carried out in nitric acid solution. The diameter of the small tunnel hole is enlarged to a degree larger than the thickness of the high-pressure oxide film to obtain a high specific volume. Corrosion determines the density of the tunnel hole, the uniformity of the hole distribution and The depth of the hole, etc. A large number of studies have found that the tunnel hole in the aluminum foil is tapered after the hole is formed. When the hole is expanded, the tunnel hole will continue to be tapered. As a result, the diameter of a part of the tunnel hole is always smaller than the thickness of the high-pressure oxide film. Blocking causes an increase in useless holes and limits the increase in capacity. In addition, as the reaming depth increases, the hydrogen ions in the pores interact with aluminum metal to continue to consume, and a large amount of aluminum ions are enriched inside the pores, making the external hydrogen ion solution unable to enter quickly, resulting in insufficient reaming depth or horizontal branch holes. The capacity and bending performance of the corroded foil are reduced.

Summary of the invention

The present invention addresses the problems of insufficient reaming depth, too many branch holes or small holes in the reaming stage of the existing corrosion process, which leads to the reduction of the capacity of the corroded foil and the deterioration of the bending performance, and provides a reaming etching solution and Corrosion process.

The first object of the present invention is to provide a hole-reaming etching solution, the etching solution comprising a gallium-based liquid metal nanoparticle dispersion liquid, the gallium-based liquid metal nanoparticle dispersion liquid is composed of gallium-based liquid metal in polystyrene sulfonate Dispersed in a polymer solution of acid and sodium polystyrene sulfonate, wherein the mass fraction of the gallium-based liquid metal in the gallium-based liquid metal nanoparticle dispersion is 0.3-1.5%.

Preferably, the mass ratio of the polystyrene sulfonic acid and sodium polystyrene sulfonate is 20:80-50:50.

Preferably, the etching solution further includes a nitric acid solution with a concentration of 5-20 wt%, and the mass of the gallium-based liquid metal nanoparticle dispersion is 0.1-5% of the mass of the nitric acid solution.

Preferably, the gallium-based liquid metal includes gallium and indium, and the mass ratio of gallium to indium is 60-75:40-25.

The second object of the present invention is to provide a method for preparing the above-mentioned hole expanding etching solution, which includes:

Mixing polystyrene sulfonic acid and sodium polystyrene sulfonate according to a certain mass ratio to obtain a polymer solution;

The gallium-based liquid metal is added dropwise to the above-mentioned polymer solution, mixed and processed to obtain a liquid metal nanoparticle dispersion, wherein the mass fraction of the gallium-based liquid metal in the gallium-based liquid metal nanoparticle dispersion is 0.3 -1.5%;

The above-mentioned gallium-based liquid metal nanoparticle dispersion is added dropwise to a nitric acid solution with a concentration of 5-20wt%, and mixed treatment to obtain a hole-expanding etching solution, wherein the mass of the gallium-based liquid metal nanoparticle dispersion is equal to that of the nitric acid solution. 0.1%-5%.

In the preparation method, the gallium-based liquid metal is coated with a polymer solution first, and then mixed with a nitric acid solution. By coating the gallium-based liquid metal, a polymer protective layer is formed on the surface, and then prepared into nano particles, which can stably exist in the aqueous solution, so that it can be used in an aqueous environment, and the pore expansion corrosion is more uniform.

Preferably, the gallium-based liquid metal is added dropwise to the above-mentioned polymer solution and mixed by stirring and ultrasonic vibration, the stirring speed is 800-2000 rpm, and the ultrasonic vibration frequency is 20-40 KHz.

Preferably, the gallium-based liquid metal nanoparticle dispersion is added dropwise to a nitric acid solution with a concentration of 5-20 wt%, and mixed by stirring and ultrasonic vibration, the stirring speed is 2000-4000 rpm, and the ultrasonic vibration frequency is 20 -40KHz.

The third object of the present invention is to provide an electrode foil etching process that uses the above-mentioned hole-expanding etching solution to perform hole-expanding etching.

In the process of corrosive hole expansion, gallium-based liquid metal nanoparticles enter the corroded hole to efficiently corrode the hole wall and the aluminum matrix at the bottom of the hole. Because of its phagocytosis of aluminum, it reduces the expansion of the tapered hole and the enrichment of aluminum ions. And the consumption of hydrogen ions accelerate the rapid entry of hydrogen ions into the holes, increase the depth of the hole expansion, reduce the generation of branch holes or small holes, improve the corrosion efficiency and capacity, and improve the consistency of the corrosion foil.

Further preferably, the etching process of the electrode foil includes:

1) Pre-treatment: Wash the aluminum foil in 1-5g/L sodium hydroxide solution, and then clean it in pure water;

2) Pore: place the pre-treated aluminum foil in a mixed solution of 20-60wt% sulfuric acid and 1-10wt% hydrochloric acid to make holes;

3) Wash once with water; wash the aluminum foil with pores in pure water;

4) Hole reaming: the aluminum foil washed once with water is placed in a hole-reaming etching solution containing a gallium-based liquid metal nanoparticle dispersion liquid for reaming;

5) Secondary water washing: Wash the aluminum foil after the hole expansion treatment in pure water;

6) Drying: drying the aluminum foil after the second water washing to obtain an electrode foil.

Preferably, in the pretreatment, the temperature of washing the aluminum foil in the sodium hydroxide solution is 30-60° C., and the washing time is 15-30s; the temperature of washing in pure water is room temperature, and the time is 15-30s.

Preferably, in the pores, the conditions for the pores are: the temperature is 40-80° C., the current density is 0.5-3.0 A/cm ² , and the time for pores is 5-20s.

Preferably, the temperature of the one-time washing is room temperature, and the time is 15-30s.

The specific composition of the hole expanding etching solution is as described above.

Preferably, the conditions for the hole expansion are: the temperature is 20-50° C., the current density is 0.1-1 A/cm ² , and the hole expansion time is 20-50 s.

Preferably, the temperature of the second water washing is room temperature, and the time is 15-30s.

Optionally, the drying temperature is 100-300°C, and the time is 2-10 min.

In another aspect, the present invention provides electrode foils prepared by the etching process described in the present invention.

On the other hand, the present invention also provides an aluminum electrolytic capacitor including the above-mentioned electrode foil.

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

(1) In the present invention, gallium-based liquid metal is introduced in the process of hole expansion and corrosion. The gallium-based liquid metal is highly corrosive to aluminum and has high corrosion efficiency.

(2) In the present invention, gallium-based liquid metal is coated to form a polymer protective layer on its surface, and then prepared into nano-particles, which stably exist in an aqueous solution, so that they can be used in an aqueous environment and expand the hole. Corrosion is more uniform.

(3) During the corrosive hole expansion process of the present invention, the gallium-based liquid metal nanoparticles enter the corroded hole to efficiently corrode the hole wall and the aluminum matrix at the bottom of the hole. Because of its corrosive effect on aluminum, it reduces the expansion and expansion of the tapered hole. The enrichment of aluminum ions and the consumption of hydrogen ions accelerate the rapid entry of hydrogen ions into the holes, increase the depth of hole expansion, reduce the generation of branch holes or small holes, improve the corrosion efficiency and capacity, and improve the consistency of the corroded foil.

(4) Compared with the etched foil obtained by the traditional etching process, the electrode foil (etched foil) prepared by the etching process of the present invention has an electrostatic capacity increased by at least about 7%, bending at least increased by about 35%, and a reduction in corrosion thinning 2μm, which improves the utilization rate of aluminum foil.

Description of the drawings

Figure 1: Scanning electron microscope (SEM) morphology of the cross-section of the corroded foil prepared in Example 1 of the present invention;

Figure 2: Scanning electron microscope (SEM) morphology of the cross-section of the corroded foil prepared in Comparative Example 1 of the present invention.

Detailed ways

The preparation and etching process of the hole expanding etching solution provided by the present invention will now be described in detail.

1. Preparation of corrosive solution for reaming

According to the embodiment provided by the present invention, the preparation of the hole reaming etching solution includes:

1) Mixing polystyrene sulfonic acid and sodium polystyrene sulfonate according to a certain mass ratio to obtain a polymer solution;

2) Adding the gallium-based liquid metal dropwise to the above-mentioned polymer solution and mixing processing to obtain a gallium-based liquid metal nanoparticle dispersion, wherein the mass fraction of the gallium-based liquid metal is 0.3-1.5%;

3) The above-mentioned gallium-based liquid metal nanoparticle dispersion is added dropwise to a nitric acid solution with a concentration of 5-20wt%, and mixed treatment to obtain a pore-reaming etching solution, wherein the quality of the gallium-based liquid metal nanoparticle dispersion is a nitric acid solution 0.1-5% of the quality.

Examples of the mass ratio of gallium and indium include but are not limited to: 60:40, 61:39, 62:38, 63:37, 64:36, 65:35, 66:34, 67:33, 68:32 , 69:31, 70:30, 71:39, 72:28, 73:27, 74:26, 75:25.

In the present invention, a polymer solution of polystyrene sulfonic acid and sodium polystyrene sulfonate is used to coat the gallium-based liquid metal to prepare a gallium-based liquid metal nanoparticle dispersion, and the polystyrene sulfonic acid and polystyrene are limited. The mass ratio of sodium ethylene sulfonate is 20:80-50:50. The reason is: polystyrene sulfonic acid is easy to form a film on the surface of gallium-based liquid metal and has a slow dissolution rate in aqueous solution, while polystyrene sulfonate has a slower film-forming ability on the surface of gallium-based liquid metal, but it is in an aqueous solution. The dissolution rate is relatively fast. The speed of polymer film formation on the surface of gallium-based liquid metal can be controlled by the mixing and compounding of polystyrene sulfonic acid and sodium polystyrene sulfonate, thereby regulating the size of gallium-based liquid metal nanoparticles; while ensuring gallium The surface polymer film will not dissolve quickly after the liquid metal nanoparticles are added to the pore expansion corrosion. After they enter the corrosion holes, the surface polymer film can dissolve as soon as possible to release the gallium-based liquid metal nanoparticles.

Examples of the mass ratio of polystyrene sulfonic acid and sodium polystyrene sulfonate include, but are not limited to: 20:80, 25:75, 30:70, 35:65, 40:60, 45:55, 50: 50.

In the coating treatment of step 2), the specific conditions are as follows:

The dropping acceleration of the gallium-based liquid metal is 1-20 mL/min.

In some embodiments, the dropping rate of the gallium-based liquid metal is 1-10mL/min, for example: 1mL/min, 2mL/min, 3mL/min, 4mL/min, 5mL/min, 6mL/min, 7mL/min min, 8mL/min, 9mL/min, 10mL/min.

In some embodiments, the dropping rate of the gallium-based liquid metal is 10-20mL/min, for example: 10mL/min, 11mL/min, 12mL/min, 13mL/min, 14mL/min, 15mL/min, 16mL/min min, 17mL/min, 18mL/min, 19mL/min, 20mL/min.

Preferably, the gallium-based liquid metal is added dropwise to the above-mentioned polymer solution, and mixed by stirring and ultrasonic vibration, and the stirring speed is 800-2000rpm (800rpm, 900rpm, 1000rpm, 2100rpm, 1200rpm, 1300rpm, 1400rpm, 1500rpm, 1600rpm, 1700rpm, 1800rpm, 1900rpm, 2000rpm), the frequency of the ultrasonic oscillation is 20-40KHz (20KHz, 25KHz, 30KHz, 35KHz, 40KHz).

In some embodiments, in the gallium-based liquid metal nanoparticle dispersion, the mass fraction of the gallium-based liquid metal is 0.5-1.5%, for example: 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0% , 1.1%, 1.2%, 1.3%, 1.4%, 1.5%.

In step 3), the specific processing conditions are as follows:

The dropping rate is 0.1-5 mL/min.

In some embodiments, the dropping rate is 0.1-0.5 mL/min, for example: 0.1 mL/min, 0.2 mL/min, 0.3 mL/min, 0.4 mL/min, 0.5 mL/min.

In some embodiments, other preferred ranges of the dropping rate may include: 0.5-1.0 mL/min, 1.0-2.0 mL/min, 2.0-3.0 mL/min, 3.0-4.0 mL/min, 4.0-5.0 mL/min min.

Preferably, the gallium-based liquid metal nanoparticle dispersion is added dropwise to a nitric acid solution with a concentration of 5-20wt%, and mixed by stirring and ultrasonic vibration, and the stirring speed is 2000-4000rpm (2000rpm, 2300rpm, 2500rpm, 2800rpm, 3000rpm, 3300rpm, 3500rpm, 3800rpm, 4000rpm), the frequency of ultrasonic vibration is 20-40KHz (20KHz, 25KHz, 30KHz, 35KHz, 40KHz).

Preferably, the added amount of the gallium-based liquid metal nanoparticle dispersion is 0.1% to 5%, that is, preferably, in the pore expanding etching solution, the mass of the gallium-based liquid metal nanoparticle dispersion is nitric acid. 0.3%-5% of the mass of the solution.

In some embodiments, the mass of the gallium-based liquid metal nanoparticle dispersion is 0.3%-1% of the mass of the nitric acid solution, for example: 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9% %,1%.

In some embodiments, the mass of the gallium-based liquid metal nanoparticle dispersion is 1% to 5% of the mass of the nitric acid solution, for example: 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4 %, 4.5%, 5%.

The concentration of the nitric acid solution may include: 5wt%, 6wt%, 8wt%, 10wt%, 12wt%, 15wt%, 18wt%, 20wt%.

In some embodiments, the method for preparing the hole-reaming etching solution includes:

1) Mixing polystyrene sulfonic acid and sodium polystyrene sulfonate in a mass ratio of 20:80-50:50 to obtain a polymer solution;

2) Add the gallium-based liquid metal dropwise to the above polymer solution at a speed of 1-20mL/min, and apply stirring and ultrasonic vibration. The stirring speed is 800-2000rpm, the ultrasonic vibration frequency is 20-40KHz, and the flow rate is 1- 20 mL/min to obtain a gallium-based liquid metal nanoparticle dispersion, wherein the mass fraction of the gallium-based liquid metal is 0.3-1.5%;

3) The above-mentioned gallium-based liquid metal nanoparticle dispersion is added dropwise to a nitric acid solution with a concentration of 5-20wt% at a rate of 0.1-5mL/min, and stirring and ultrasonic vibration are applied at a flow rate of 0.1-5mL/min, stirring The speed is 2000-4000rpm, the ultrasonic oscillation frequency is 20-40KHz, and the pore expansion etching solution is obtained, wherein the mass of the gallium-based liquid metal nanoparticle dispersion liquid is 0.1-5% of the mass of the nitric acid solution.

2. Corrosion process of electrode foil

According to the embodiment provided by the present invention, the etching process of the electrode foil includes:

3) Wash once with water; wash the aluminum foil with pores in pure water;

Specifically, the process conditions of each step are as follows:

1), pre-treatment

Before pore corrosion, the aluminum foil generally needs to be cleaned and pre-treated, the purpose is to remove the oil stain and oxide layer on the surface of the aluminum foil. The pretreatment can be carried out in an alkaline solution or/and an acid solution.

In the embodiment of the present invention, the pre-processing includes:

Put the aluminum foil in 1-5g/L (for example: 1g/L, 2g/L, 3g/L, 4g/L, 5g/L) sodium hydroxide solution at 30-60℃ (for example: 30℃, 35 ℃, 40℃, 45℃, 50℃, 55℃, 60℃) washing for 15-30s, and then placed in pure water at room temperature for 15-30s.

In some embodiments, the pre-treatment is: washing the aluminum foil in a 3 g/L sodium hydroxide solution at 50° C. for 15 seconds, and then washing it in pure water at room temperature for 15 seconds.

2) Hair holes

The pore etching solution is a mixed solution of sulfuric acid with a concentration of 20-60 wt% and hydrochloric acid with a concentration of 1-10 wt%.

In some embodiments, the concentration of sulfuric acid in the mixed solution is 20-40wt%, for example: 20wt%, 23wt%, 25wt%, 28wt%, 30wt%, 33wt%, 35wt%, 38wt%, 40wt%.

In some embodiments, the concentration of sulfuric acid in the mixed solution is 40-60wt%, for example: 40wt%, 43wt%, 45wt%, 48wt%, 50wt%, 53wt%, 55wt%, 58wt%, 60wt%.

In some embodiments, the concentration of hydrochloric acid in the mixed solution is 1-5 wt%, for example: 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%.

In some embodiments, the concentration of hydrochloric acid in the mixed solution is 5-10wt%, for example: 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%.

In some embodiments, the pore etching solution is a mixed solution of sulfuric acid with a concentration of 40 wt% and hydrochloric acid with a concentration of 5 wt%.

In some embodiments, the hole temperature is 40-60°C, for example: 40°C, 45°C, 50°C, 55°C, 60°C.

In some embodiments, the pore temperature is 60-80°C, for example: 60°C, 65°C, 70°C, 75°C, 80°C.

In some embodiments, the current density of the holes is 1-3A/cm ² , for example: 1A/cm ² , 1.5A/cm ² , 1.8A/cm ² , 2A/cm ² , 2.5A/cm ² , 2.8 A/cm ² , 3A/cm ² .

In some embodiments, the time for making holes is 5-10s, for example: 5s, 6s, 7s, 8s, 9s, 10s.

In some embodiments, the time for making holes is 10-20s, for example: 10s, 11s, 12s, 13s, 14s, 15s, 16s, 17s, 18s, 19s, 20s.

3) One wash

Place the aluminum foil after the hole treatment in pure water for 15-30s at room temperature: for example: 15s, 16s, 17s, 18s, 19s, 20s, 21s, 22s, 23s, 24s, 25s, 26s, 27s, 28s, 29s , 30s.

In some embodiments, the aluminum foil after the pore treatment is placed in pure water and washed for 30 seconds at room temperature.

4) Reaming

In the present invention, gallium-based liquid metal is used to replace part of the acid solution for corrosion to achieve the purpose of hole expansion. However, due to the poor dispersibility of gallium-based liquid metal in water, the gallium-based liquid metal is coated, and the gallium-based liquid metal is coated with a polymer solution to obtain a gallium-based liquid metal nanoparticle dispersion. Then mix it with an acid solution to obtain a hole-expanding etching solution.

In the process of hole expansion and corrosion, gallium-based liquid metal nanoparticles quickly enter the corrosion hole under the action of electric power, and efficiently corrode the hole wall and the aluminum matrix at the bottom of the hole. On the one hand, it reduces the expansion of the tapered hole and the consumption of hydrogen ions; On the one hand, unlike conventional acid corrosion, the corrosion effect of gallium-based liquid metal on aluminum is phagocytosis, which does not produce aluminum ions, reduces the concentration of aluminum ions in the solution, accelerates the rapid entry of hydrogen ions into the pores, and increases the depth of hole expansion. , Reduce the generation of branch holes or small holes, improve the corrosion efficiency and capacity, and improve the consistency of the corroded foil.

Specifically, the pore reaming etching solution includes a gallium-based liquid metal nanoparticle dispersion, and the gallium-based liquid metal nanoparticle dispersion is composed of a polymer of gallium-based liquid metal in polystyrene sulfonic acid and sodium polystyrene sulfonate. Dispersed in the solution, wherein the mass fraction of the gallium-based liquid metal is 0.3-1.5%.

With this composition, the gallium-based liquid metal has a low melting point, has good fluidity after being in a liquid state, and has a low surface tension. It is easy to disperse in a polymer solution and facilitates the preparation of gallium-based liquid metal nanoparticles.

According to an embodiment of the present invention, examples of the mass ratio of polystyrene sulfonic acid and sodium polystyrene sulfonate include, but are not limited to: 20:80, 25:75, 30:70, 35:65, 40:60 , 45:55, 50:50.

When the content of gallium-based liquid metal is too low, the effect is not obvious in the subsequent hole expansion; if the added amount is too high, it will not be easy to disperse in the polymer solution, and the particle size will be large, and it will not be easy to enter later. Corrosion in the hole.

Further, the acid solution may include: hydrochloric acid solution, nitric acid solution, etc., preferably nitric acid solution.

According to an embodiment of the present invention, the concentration of the nitric acid solution is 5-20wt%, for example: 5wt%, 6wt%, 8wt%, 10wt%, 12wt%, 15wt%, 18wt%, 20wt%.

Preferably, the mass of the gallium-based liquid metal nanoparticle dispersion is 0.1-5% of the mass of the nitric acid solution, that is, preferably, the mass of the gallium-based liquid metal nanoparticle dispersion is It is 0.3%-5% of the mass of the nitric acid solution.

When the gallium-based liquid metal nanoparticle dispersion is added in a small amount, only part of the holes can be corroded, and the effect is not obvious. When the addition amount is too high, in addition to part of the gallium-based liquid metal nanoparticles entering the hole to corrode, some remain in the solution, corroding the hole of the hole, causing the expansion of the tapered hole and the phenomenon of merging, which will corrode the foil. The capacity is reduced.

Preferably, the conditions for the hole expansion are: the temperature is 20-50° C., the current density is 0.1-1 A/cm2, and the hole expansion time is 20-50s.

The expansion temperature may include: 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, and 50°C.

The current density of the reaming is 0.1-1A/cm ² , for example: 0.1A/cm ² , 0.2A/cm ² , 0.3A/cm ² , 0.4A/cm ² , 0.5A/cm ² , 0.6A/cm 2 cm ² , 0.7A/cm ² , 0.8A/cm ² , 0.9A/cm ² , 1A/cm ² .

The time for the holes can be listed as: 20s, 23s, 25s, 28s, 30s, 33s, 35s, 38s, 40s, 43s, 45s, 48s, 50s.

In some embodiments, the conditions for forming the holes are: a temperature of 50° C., a current density of 0.5 A/cm ² , and a hole forming time of 30 seconds.

5) Secondary washing

Place the expanded aluminum foil in pure water for 15-30s at room temperature: for example: 15s, 16s, 17s, 18s, 19s, 20s, 21s, 22s, 23s, 24s, 25s, 26s, 27s, 28s, 29s , 30s.

In some embodiments, the aluminum foil after the hole expansion treatment is placed in pure water and washed for 20 seconds at room temperature.

6) Dry

The aluminum foil after the second water washing is dried at 100-300° C. for 2-10 minutes to obtain electrode foil.

The drying temperature may include: 100°C, 120°C, 150°C, 180°C, 200°C, 220°C, 250°C, 280°C, and 300°C.

The drying time may include: 2min, 3min, 4min, 5min, 6min, 7min, 8min, 9min, 10min.

According to an embodiment of the present invention, the etching process of the electrode foil includes:

2) Pore: place the pre-treated aluminum foil in a mixed solution of 20-60wt% sulfuric acid and 1-10wt% hydrochloric acid to make holes at a temperature of 40-80°C and a current density of 0.5-3.0A /cm ² , the time for making holes is 5-20s;

3) Wash once with water; wash the aluminum foil with pores in pure water;

4) Hole expansion: Place the aluminum foil washed once in a hole expansion corrosion solution containing a gallium-based liquid metal nanoparticle dispersion liquid for hole expansion, the temperature is 20-50℃, the current density is 0.1-1A/cm ² , and the hole is expanded. The time is 20-50s;

The "room temperature" in the present invention refers to a temperature of 20-30°C.

The following are the preferred embodiments of the present invention, and the protection of the present invention is not limited to the following preferred embodiments. It should be pointed out that for those skilled in the art, a number of modifications and improvements made on the basis of the inventive concept of this invention belong to the protection scope of the present invention.

Example 1

1) Mixing polystyrene sulfonic acid and sodium polystyrene sulfonate in a mass ratio of 30:70 to obtain a polymer solution.

2) Add the gallium-based liquid metal (gallium: indium=65:35) dropwise to the above polymer solution at a speed of 3mL/min, and apply stirring and ultrasonic vibration, the stirring speed is 1500rpm, and the ultrasonic vibration frequency is 35KHz, to obtain The gallium-based liquid metal nanoparticle dispersion liquid, wherein the mass fraction of the gallium-based liquid metal is 0.8%.

3) The above-mentioned gallium-based liquid metal nanoparticle dispersion was added dropwise to a 6 wt% nitric acid solution at a speed of 0.5 mL/min, and stirring and ultrasonic vibration were applied, the stirring speed was 3500 rpm, and the ultrasonic vibration frequency was 40 KHz to obtain A hole-expanding etching solution, wherein the mass of the gallium-based liquid metal nanoparticle dispersion liquid is 1.5% of the mass of the nitric acid solution.

4) Pre-treatment: Use 3g/L sodium hydroxide solution to treat the aluminum foil to remove the oil and oxide layer on the surface. The temperature is 50℃, and the treatment time is 15s. Then the aluminum foil is cleaned in pure water at room temperature 15s.

5) Pore formation: the pre-treated aluminum foil is energized in an etching bath solution, which is a mixed solution of sulfuric acid with a concentration of 40 wt% and hydrochloric acid with a concentration of 5 wt%, at a temperature of 40°C, and a current The density is 1.8A/cm ² , and the hole making time is 20s.

6) One-time washing: Wash the aluminum foil with pores in pure water for 30s at room temperature.

7) Reaming: The aluminum foil washed with water is placed in the reaming etching solution prepared in step 3) and then electrified for reaming treatment. The temperature is 50° C., the current density is 0.5 A/cm ² , and the reaming time is 30 seconds.

8) Secondary water washing: Wash the expanded aluminum foil in pure water at room temperature for 20 seconds.

9) Drying: The aluminum foil after the second water washing is dried at 220°C, and the drying time is 3 minutes.

The cross-sectional scanning electron microscope (SEM) morphology of the electrode foil (etched foil) obtained in this embodiment is shown in FIG. 1. It can be seen from the figure that the hole diameter and length of the corroded foil are relatively uniform, the thickness of the middle sandwich layer is uniform, and the hole reaming depth is consistent.

Example 2

1) Mixing polystyrene sulfonic acid and sodium polystyrene sulfonate in a mass ratio of 20:80 to obtain a polymer solution.

2) Add the gallium-based liquid metal (gallium: indium=60:40) dropwise to the above polymer solution at a rate of 15mL/min, and apply stirring and ultrasonic vibration, the stirring speed is 1000rpm, the ultrasonic vibration frequency is 20KHz, and the result is The gallium-based liquid metal nanoparticle dispersion liquid, wherein the mass fraction of the gallium-based liquid metal is 0.5%.

3) The above-mentioned gallium-based liquid metal nanoparticle dispersion was added dropwise to a nitric acid solution with a concentration of 15 wt% at a speed of 0.1 mL/min, and stirring and ultrasonic vibration were applied, the stirring speed was 4000 rpm, and the ultrasonic vibration frequency was 40 KHz to obtain A hole-expanding etching solution, wherein the mass of the gallium-based liquid metal nanoparticle dispersion liquid is 0.3% of the mass of the nitric acid solution.

Example 3

1) Mixing polystyrene sulfonic acid and sodium polystyrene sulfonate in a mass ratio of 50:50 to obtain a polymer solution.

2) Add the gallium-based liquid metal (gallium: indium=75:25) dropwise to the above polymer solution at a speed of 5mL/min, and apply stirring and ultrasonic vibration, the stirring speed is 800rpm, and the ultrasonic vibration frequency is 40KHz to obtain The gallium-based liquid metal nanoparticle dispersion liquid, wherein the mass fraction of the gallium-based liquid metal is 1.5%.

3) The above-mentioned gallium-based liquid metal nanoparticle dispersion was added dropwise to a nitric acid solution with a concentration of 20 wt% at a rate of 0.1 mL/min, and stirring and ultrasonic vibration were applied, the stirring speed was 2000 rpm, and the ultrasonic vibration frequency was 40 KHz to obtain A hole expanding etching solution, wherein the mass of the gallium-based liquid metal nanoparticle dispersion liquid is 5% of the mass of the nitric acid solution.

Example 4

1) Mixing polystyrene sulfonic acid and sodium polystyrene sulfonate in a mass ratio of 40:60 to obtain a polymer solution.

2) Add gallium-based liquid metal (gallium: indium=70:30) dropwise to the above polymer solution at a speed of 20 mL/min, and apply stirring and ultrasonic vibration, the stirring speed is 2000 rpm, and the ultrasonic vibration frequency is 40 KHz, to obtain The gallium-based liquid metal nanoparticle dispersion liquid, wherein the mass fraction of the gallium-based liquid metal is 0.8%.

3) The above-mentioned gallium-based liquid metal nanoparticle dispersion was added dropwise to a nitric acid solution with a concentration of 8 wt% at a rate of 0.1 mL/min, and stirring and ultrasonic vibration were applied, the stirring speed was 2000 rpm, and the ultrasonic vibration frequency was 40 KHz to obtain A hole-expanding etching solution, wherein the mass of the gallium-based liquid metal nanoparticle dispersion is 5% of the mass of the nitric acid solution.

Comparative example 1

1) Pre-treatment: Use 3g/L sodium hydroxide solution to treat the aluminum foil to remove the oil and oxide layer on the surface. The temperature is 50℃, and the treatment time is 15s. Then the aluminum foil is cleaned in pure water at room temperature 15s.

2) Pore formation: the pre-treated aluminum foil is energized in an etching bath solution, which is a mixed solution of sulfuric acid with a concentration of 40wt% and hydrochloric acid at a concentration of 5wt%, at a temperature of 40°C, and a current The density is 1.8A/cm ² , and the hole making time is 20s.

3) One-time washing: Wash the aluminum foil with pores in pure water for 30s at room temperature.

4) Reaming: The aluminum foil washed with water is placed in a 6% nitric acid reaming solution and electrified for reaming treatment, the temperature is 50°C, the current density is 0.5A/cm ² , and the reaming time is 30s.

5) Secondary water washing: Wash the expanded aluminum foil in pure water at room temperature for 20 seconds.

6) Drying: The aluminum foil after the second water washing is dried at 220°C, and the drying time is 3 minutes.

The cross-sectional scanning electron microscope (SEM) morphology of the electrode foil (etched foil) obtained in this embodiment is shown in FIG. 2. It can be seen from the figure that the pore size and length of the corroded foil are uneven, the thickness uniformity of the middle sandwich layer is very poor, even perforation occurs, and the consistency of the reaming depth is not good.

Comparative example 2

1) Add gallium-based liquid metal (gallium: indium=65:35) dropwise to a 6wt% nitric acid solution at a speed of 0.5mL/min, and apply stirring and ultrasonic vibration. The stirring speed is 3500rpm and the ultrasonic vibration frequency It is 40KHz to obtain a hole-expanding etching solution, wherein the mass of the gallium-based liquid metal nanoparticle dispersion liquid is 1.5% of the mass of the nitric acid solution.

2) Pre-treatment: Use 3g/L sodium hydroxide solution to process the aluminum foil to remove the oil stains and oxide layers on the surface. The temperature is 50℃, the treatment time is 15s, and then the aluminum foil is cleaned in pure water at room temperature. 15s.

3) Pore formation: the pre-treated aluminum foil is energized in an etching bath solution, which is a mixed solution of 40wt% sulfuric acid and 5wt% hydrochloric acid, at a temperature of 40°C, and a current The density is 1.8A/cm ² , and the hole making time is 20s.

4) One-time washing: Wash the aluminum foil after pore treatment in pure water for 30s at room temperature.

5) Reaming: The aluminum foil washed with water is placed in the reaming etching solution prepared in step 3) and then electrified for reaming treatment. The temperature is 50° C., the current density is 0.5 A/cm ² , and the reaming time is 30 seconds.

6) Secondary water washing: Wash the expanded aluminum foil in pure water at room temperature for 20 seconds.

7) Drying: The aluminum foil after the second water washing is dried at 220°C, and the drying time is 3 minutes.

Comparative example 3

1) Mixing polystyrene sulfonic acid and sodium polystyrene sulfonate in a mass ratio of 10:90 to obtain a polymer solution.

Comparative example 4

2) Add the gallium-based liquid metal (gallium: indium=50:50) dropwise to the above polymer solution at a speed of 3mL/min, and apply stirring and ultrasonic vibration, the stirring speed is 1500rpm, and the ultrasonic vibration frequency is 35KHz, to obtain The gallium-based liquid metal nanoparticle dispersion liquid, wherein the mass fraction of the gallium-based liquid metal is 0.8%.

Comparative example 5

3) The above-mentioned gallium-based liquid metal nanoparticle dispersion was added dropwise to a 6 wt% nitric acid solution at a speed of 0.5 mL/min, and stirring and ultrasonic vibration were applied, the stirring speed was 3500 rpm, and the ultrasonic vibration frequency was 40 KHz to obtain A hole-expanding etching solution, wherein the mass of the gallium-based liquid metal nanoparticle dispersion is 8% of the mass of the nitric acid solution.

Performance Testing

According to the standard detection method described in the national standard "SJ/T 11140-2012 Electrode Foil for Aluminum Electrolytic Capacitors", the performance test of the electrode foils for aluminum electrolytic capacitors prepared in the above examples and comparative examples was performed. The test results are shown in Table 1.

Table 1

It can be seen from the data in the above table that the corrosion foil prepared by the corrosion process of the present invention has a reduction of 2μm in corrosion thinning compared with the existing corrosion process (Comparative Example 1), a capacity increase of at least about 7%, and a bending increase of at least about 35%, effectively reducing the generation of branch holes or small holes, improving corrosion efficiency and capacity.

It can be seen from Comparative Example 2 that the gallium-based liquid metal is directly added to the reaming solution without coating treatment, and the amount of corrosion and thinning is the largest. Because the gallium-based liquid metal has poor dispersibility in the aqueous solution, its large amount of aggregation acts on On the surface of the aluminum foil, the aluminum foil is swallowed, which increases the amount of surface corrosion, resulting in a decrease in capacity and poor bending performance.

It can be seen from Comparative Example 3 that the mass ratio of polystyrene sulfonic acid and sodium polystyrene sulfonate is 10:90. The polymer film formed on the surface of the liquid metal is mainly sodium polystyrene sulfonate. After being added to the reaming solution, the polymer film on the surface of the gallium-based liquid metal nanoparticles quickly dissolves, and the gallium-based liquid metal is released. Part of the aluminum foil is corroded on the surface of the aluminum foil and the openings of the holes, resulting in an increase in the thinning of the aluminum foil, an enlarged tapered hole, and a decrease in capacity.

It can be seen from Comparative Example 4 that when the composition ratio of gallium-based liquid metal is gallium:indium=50:50, the fluidity of gallium-based liquid metal is poor, and the prepared gallium-based liquid metal nanoparticles are large in size and cannot enter the corrosion hole. , Staying on the surface of the aluminum foil or the opening of the hole, resulting in an increase in the thinning of the aluminum foil, the expansion of the tapered hole, and the reduction of the capacity.

It can be seen from Comparative Example 5 that when the mass fraction of the gallium-based liquid metal nanoparticle dispersion in the reaming solution is increased to 8%, the concentration of the gallium-based liquid metal nanoparticle is higher and the migration rate is slower, which makes part of the In the hole, some will stay on the surface of the aluminum foil or the hole at the same time, which causes the thinning of the aluminum foil to increase, the tapered hole to expand, and the capacity to decrease.

Although the present invention has been described in detail, and some specific examples have been listed, for those skilled in the art, as long as they do not depart from the spirit of the present invention, various adjustments made to the method are deemed to be included in the present invention. Within the scope of the invention.

Claims

A hole expanding etching solution, characterized in that the etching solution comprises a gallium-based liquid metal nanoparticle dispersion liquid, and the gallium-based liquid metal nanoparticle dispersion liquid is composed of gallium-based liquid metal in polystyrene sulfonic acid and polystyrene It is obtained by dispersing in a polymer solution of sodium sulfonate, wherein the mass fraction of the gallium-based liquid metal in the liquid metal nanoparticle dispersion is 0.3-1.5%.
The pore expanding etching solution according to claim 1, wherein the mass ratio of the polystyrene sulfonic acid and sodium polystyrene sulfonate is 20:80-50:50.
The reaming etching solution according to claim 1, wherein the etching solution further comprises a nitric acid solution with a concentration of 5-20 wt%, and the mass of the gallium-based liquid metal nanoparticle dispersion is 0.1 of the mass of the nitric acid solution. -5%.
The hole expanding etching solution according to claim 1, wherein the gallium-based liquid metal comprises gallium and indium, and the mass ratio of gallium to indium is 60-75:40-25.
A method for preparing a hole-expanding etching solution, characterized in that, the preparation method includes:

Mixing polystyrene sulfonic acid and sodium polystyrene sulfonate according to a certain mass ratio to obtain a polymer solution;

The gallium-based liquid metal is added dropwise to the above-mentioned polymer solution, mixed and processed to obtain a liquid metal nanoparticle dispersion, wherein the mass fraction of the gallium-based liquid metal in the gallium-based liquid metal nanoparticle dispersion is 0.3 -1.5%;

The above-mentioned gallium-based liquid metal nanoparticle dispersion is added dropwise to a nitric acid solution with a concentration of 5-20% by weight, and mixed processing is performed to obtain a pore expansion etching solution, wherein the mass of the liquid metal nanoparticle dispersion is equal to that of the nitric acid solution 0.1-5%.
The method for preparing a hole expanding etching solution according to claim 5, wherein the mass ratio of the polystyrene sulfonic acid and sodium polystyrene sulfonate is 20:80-50:50.
The method for preparing a hole expanding etching solution according to claim 5, wherein the gallium-based liquid metal comprises gallium and indium, and the mass ratio of gallium to indium is 60-75:40-25.
An etching process for electrode foil, which is characterized in that the hole expansion etching solution according to any one of claims 1 to 4 is used for hole expansion.
8. The etching process of electrode foil according to claim 8, wherein the etching process comprises:

1) Pre-treatment: Wash the aluminum foil in 1-5g/L sodium hydroxide solution, and then clean it in pure water;

2) Pore: place the pre-treated aluminum foil in a mixed solution of 20-60wt% sulfuric acid and 1-10wt% hydrochloric acid to make holes;

3) Wash once with water; wash the aluminum foil with pores in pure water;

4) Reaming: Place the aluminum foil washed with water once in the reaming etching solution according to any one of claims 1 to 4 for reaming;

5) Secondary water washing: Wash the aluminum foil after the hole expansion treatment in pure water;

6) Drying: drying the aluminum foil after the second water washing to obtain an electrode foil.
The electrode foil corrosion process according to claim 9, characterized in that, in the pretreatment, the temperature of washing the aluminum foil in the sodium hydroxide solution is 30-60°C, and the washing time is 15-30s; the pure water The cleaning temperature is room temperature and the time is 15-30s.
The corrosion process of electrode foil according to claim 9, wherein the conditions for the hole formation are: temperature is 40-80°C, current density is 0.5-3.0 A/cm 2 , and the hole formation time is 5- 20s;

Optionally, the conditions for the hole expansion are: the temperature is 20-50° C., the current density is 0.1-1 A/cm 2 , and the hole expansion time is 20-50 s.
The electrode foil corrosion process according to claim 9, wherein the temperature of the first water washing and the second water washing is room temperature, and the time is 15-30s;

Optionally, the drying temperature is 100-300°C, and the time is 2-10 min.
An electrode foil, characterized in that it is prepared according to the etching process of any one of claims 8-12.
An aluminum electrolytic capacitor is characterized by comprising the electrode foil according to claim 13.