CN103325574A - Method for manufacturing cathode of total-tantalum electrolytic capacitor - Google Patents

Abstract

The embodiment of the present invention discloses a method for manufacturing the cathode of an all-tantalum electrolytic capacitor, comprising: sandblasting and polishing the inner surface of the tantalum shell of the all-tantalum electrolytic capacitor; adding graphene oxide into a dispersion solvent to disperse to obtain a graphene oxide dispersion; The graphene oxide dispersion liquid is added into the tantalum shell, so that the graphene oxide is dispersed on the inner surface; the graphene oxide dispersed on the inner surface is reduced; and an electrochemical method is used to form a ruthenium oxide layer on the inner surface. In the method in the embodiment of the present invention, through the composite of graphene and ruthenium oxide, not only can greatly increase the cathode area of the all-tantalum capacitor, increase the effective area of the tantalum capacitor, but also introduce a pseudocapacitance on the tantalum shell, Can increase the capacity of the capacitor.

Description

A method of manufacturing all-tantalum electrolytic capacitor cathode

technical field

The invention relates to the technical field of electronic materials, in particular to a method for manufacturing a cathode of an all-tantalum electrolytic capacitor.

Background technique

Liquid tantalum electrolytic capacitors have the advantages of large capacity, medium and high voltage resistance, and low leakage current, and are especially suitable for use in large-capacity circuits under medium and high voltage conditions. However, liquid tantalum electrolytic capacitors use an acidic liquid electrolyte, and if the liquid leaks, it may short the circuit board and cause serious failure of the device.

All tantalum fully sealed liquid tantalum electrolytic capacitors came into being. It has excellent sealing performance and no liquid leakage, and because of the tantalum shell, it has high environmental stability and can withstand large ripple currents. , suitable for equipment requiring high reliability. The structure of the all-tantalum liquid tantalum electrolytic capacitor is basically the same as that of the ordinary silver shell liquid tantalum electrolytic capacitor. The high-temperature sintered tantalum core is used as the anode, and the amorphous Ta ₂ O ₅ dielectric film is oxidized on the surface of the anode as the dielectric layer. The metal shell and The acid electrolyte is used as the cathode. The difference is that the common liquid tantalum electrolytic capacitor uses a silver casing as the cathode, and the all-tantalum liquid tantalum electrolytic capacitor uses a tantalum casing as the cathode. As the cathode, the tantalum casing faces a problem that it is not easy to plate platinum black, which makes the cathode area smaller and it is not easy to increase the capacity of the capacitor.

Contents of the invention

One of the objectives of the present invention is to provide a method for manufacturing an all-tantalum electrolytic capacitor cathode with stable performance, large specific surface area, high specific capacity, and suitable for assembly of high-reliability all-tantalum electrolytic capacitors.

The technical solutions disclosed in the present invention include:

Provided is a method for manufacturing the cathode of an all-tantalum electrolytic capacitor, which is characterized in that it comprises: step A: sandblasting the inner surface of the tantalum shell of the all-tantalum electrolytic capacitor to make the inner surface rough; step B: adding graphene oxide adding a dispersion solvent to disperse to obtain a graphene oxide dispersion; step C: adding the graphene oxide dispersion to the tantalum shell, and rotating the tantalum shell at a predetermined speed to make the graphene oxide dispersion The graphene oxide dispersed on the inner surface; step D: reducing the graphene oxide dispersed on the inner surface; step F: forming a ruthenium oxide layer on the inner surface by an electrochemical method.

Further, in the sandblasting and polishing, the sandblasting abrasive is 400 mesh steel grit, the sandblasting pressure is 0.6 to 0.8 MPa, and the sandblasting time is 0.5 to 3 minutes.

Further, after sandblasting the inner surface of the tantalum shell of the all-tantalum electrolytic capacitor, it also includes: ultrasonically cleaning the tantalum shell with acetone for 0.5 to 1 hour; cleaning the tantalum shell with deionized water for 0.5 to 1 hour; drying the tantalum shell tantalum case.

Further, the concentration of the graphene oxide dispersion is 1 to 5 mg/ml, and the rotating the tantalum shell at a predetermined speed includes: rotating the tantalum shell at a speed of 50 to 100 rpm for 20 to 60 Second.

Further, the reduction treatment of the graphene oxide dispersed on the inner surface includes: reducing and dispersing the graphene oxide on the inner surface in an environment with a vacuum degree higher than 5×10-4 Pa and a temperature of 200 to 220 degrees Celsius on graphene oxide for 0.5 to 1 hr.

Further, before the step F, it also includes: repeating the step C and the step D 3 to 5 times.

Further, the electrochemical method of forming a ruthenium oxide layer on the inner surface includes: preparing an electrolyte; adding the electrolyte into the tantalum shell; using the tantalum shell as a working electrode and a platinum wire as a counter The electrode, silver/silver chloride, was used as a reference electrode, and a ruthenium oxide layer was formed on the inner surface of the tantalum shell by cyclic voltammetry.

Further, the electrolyte includes: ruthenium trichloride with a concentration of 0.01-0.02 moles/liter, potassium chloride with a concentration of 0.1-0.2 moles/liter and hydrogen chloride with a concentration of 0.01-0.03 moles/liter. The temperature of the liquid is 40°C~60°C.

Further, in the cyclic voltammetry, the cycle voltage is -0.2-1 volt, the scan speed is 100-800 mV/s, and the number of cycles is 100-500 times.

Further, after forming the ruthenium oxide layer on the inner surface of the tantalum casing, the method further includes: annealing at a temperature of 180-250°C for 2-3 hours at a vacuum degree higher than 5×10-4 Pa.

In the method in the embodiment of the present invention, through the composite of graphene and ruthenium oxide, not only can greatly increase the cathode area of the all-tantalum capacitor, increase the effective area of the tantalum capacitor, but also introduce a pseudocapacitance on the tantalum shell, Can increase the capacity of the capacitor. the

Description of drawings

FIG. 1 is a schematic flowchart of a method for manufacturing an all-tantalum electrolytic capacitor cathode according to an embodiment of the present invention.

2 is a graph showing parameters of a sample of an all-tantalum electrolytic capacitor cathode fabricated according to the method of an embodiment of the present invention.

Detailed ways

The specific steps of the method for manufacturing the cathode of an all-tantalum electrolytic capacitor according to the embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

As shown in FIG. 1 , in an embodiment of the present invention, a method for manufacturing an all-tantalum electrolytic capacitor cathode includes step 10 , step 12 , step 16 , step 18 and step 20 . Each step is described in detail below.

Step 10: Sand blast the inner surface of the tantalum case.

As mentioned above, the structure of all-tantalum fully-sealed liquid tantalum electrolytic capacitors is basically the same as that of ordinary silver-shell liquid tantalum electrolytic capacitors. The high-temperature sintered tantalum core is used as the anode, and the amorphous Ta ₂ O ₅ dielectric film is oxidized on the surface of the anode as the anode. The dielectric layer, the metal case and the acid electrolyte are used as the cathode. The difference is that the common liquid tantalum electrolytic capacitor uses the silver case as the cathode, and the all-tantalum liquid tantalum electrolytic capacitor uses the tantalum case as the cathode.

The method of the invention relates to a method for manufacturing a tantalum shell of an all-tantalum electrolytic capacitor.

In the method of the embodiment of the present invention, in step 10, the tantalum casing of the all-tantalum electrolytic capacitor can be obtained, and then the inner surface of the tantalum casing is roughened, that is, the inner surface of the tantalum casing becomes rough.

In the embodiment of the present invention, the roughening treatment may be performed by sandblasting, that is, the inner surface of the tantalum casing of the all-tantalum electrolytic capacitor is sandblasted to make the inner surface rough. For example, in one embodiment, 400-mesh steel grit can be used as the blasting abrasive, and the inner surface of the tantalum shell can be sandblasted and polished at a blasting pressure of 0.6 to 0.8 MPa, and the blasting time can be 0.5 to 3 minutes .

After sandblasting, the inner surface of the tantalum shell was roughened, facilitating the dispersion of graphene oxide on the inner surface in a subsequent step (details below).

After sandblasting and grinding the inner surface of the tantalum casing, in the embodiment of the present invention, a cleaning step may also be included, that is, cleaning the sandblasting and grinding tantalum casing.

For example, in one embodiment, the cleaning step may include: ultrasonically cleaning the tantalum case with acetone for 0.5 to 1 hour; cleaning the tantalum case with deionized water for 0.5 to 1 hour; and then drying the tantalum case.

Here, "ultrasonic cleaning" refers to placing the tantalum shell to be cleaned in a cleaning solution (such as the aforementioned acetone and deionized water), and then irradiating it with ultrasonic waves, so that the tantalum shell is cleaned.

Step 12: preparing a graphene oxide dispersion.

In the embodiment of the present invention, in step 12, graphene oxide may be added into the dispersion solvent, and the graphene oxide may be fully dispersed in the dispersion solvent to obtain a graphene oxide dispersion.

In the embodiment of the present invention, the concentration of the graphene oxide dispersion liquid may be 1-5 mg/mL (mg/mL).

In the embodiment of the present invention, the sequence of step 10 and step 12 is not limited.

Step 16: Dispersing graphene oxide on the inner surface of the tantalum shell.

In the embodiment of the present invention, after obtaining the tantalum shell whose inner surface is roughened and the graphene oxide dispersion, the graphene oxide dispersion is added to the tantalum shell, and the tantalum shell is rotated at a predetermined speed to make the graphite oxide Graphene oxide in the olefin dispersion is dispersed on the inner surface of the tantalum shell. Here, since the inner surface of the tantalum shell has been roughened, the graphene oxide in the graphene oxide dispersion can be dispersed on the inner surface of the tantalum shell during the treatment in step 16 .

In an embodiment of the present invention, the aforementioned process of rotating the tantalum shell added with the graphene oxide dispersion at a predetermined rotational speed may include: rotating the tantalum shell at a rotational speed of 50 to 100 rpm for 20 to 60 seconds.

After the treatment in step 16, the graphene oxide in the graphene oxide dispersion liquid is dispersed on the inner surface of the tantalum shell.

Step 18: Restore processing.

After the graphene oxide is dispersed on the inner surface of the tantalum shell in step 16, in step 18, the graphene oxide dispersed on the inner surface is reduced, so that the graphene oxide dispersed on the inner surface of the tantalum shell is reduced become graphene.

For example, in one embodiment, the graphene oxide dispersed on the inner surface of the tantalum shell can be reduced to graphene using a high temperature vacuum reduction process. For example, in one embodiment, the reduction treatment may include: reducing graphene oxide dispersed on the inner surface of the tantalum shell by ^0.5 to 1 Hour.

Through the reduction treatment in step 18, the graphene oxide dispersed on the inner surface of the tantalum shell in step 16 is reduced to graphene.

In an embodiment of the present invention, before step 20, step 16 and step 18 may be repeated 3 to 5 times, so that the graphene can be well dispersed on the entire inner surface of the tantalum shell.

Step 20: Forming a ruthenium oxide layer on the inner surface.

After the graphene oxide dispersed on the inner surface of the tantalum shell is reduced to graphene in step 18, in step 20 a layer of ruthenium oxide may be formed on the inner surface. For example, a ruthenium oxide layer is electrochemically formed on the inner surface.

In one embodiment of the present invention, the specific steps of forming a ruthenium oxide layer on the inner surface of the tantalum shell by electrochemical methods may include:

Prepare electrolyte;

Add the electrolyte to the tantalum case;

Taking the tantalum shell as the working electrode, the platinum wire as the counter electrode, and the silver/silver chloride as the reference electrode, a ruthenium oxide layer is formed on the inner surface of the tantalum shell by cyclic voltammetry.

At this time, the electrolyte is placed in the tantalum shell, and the platinum wire and the silver/silver chloride electrode are inserted into the tantalum shell without contacting the shell, that is, the entire tantalum shell is an electrochemical reaction cell, and the electrolyte can be added to a height of It is 80%~90% of the height of the tantalum case.

In an embodiment of the present invention, the electrolyte here may include: ruthenium trichloride with a concentration of 0.01 to 0.02 moles/liter, potassium chloride with a concentration of 0.1 to 0.2 moles/liter, and potassium chloride with a concentration of 0.01 to 0.03 moles/liter. Hydrogen chloride, the temperature of the electrolyte is 40°C to 60°C. Among them, hydrogen chloride is used to adjust the pH value of the electrolyte. In the embodiment of the present invention, the pH value of the electrolyte may be between 2.2 and 2.5.

In an embodiment of the present invention, in the cyclic voltammetry, the cycle voltage may be -0.2-1 volt, the scan speed may be 100-800 mV/s, and the number of cycles may be 100-500 times.

After the aforementioned electrochemical treatment, a ruthenium oxide layer can be formed on the inner surface of the tantalum shell.

In the embodiment of the present invention, the thickness of the ruthenium oxide layer can be determined according to actual conditions.

In the embodiment of the present invention, by forming a ruthenium oxide layer on the inner surface of the tantalum shell, the cathode area of the all-tantalum electrolytic capacitor can be greatly increased, thereby increasing the capacity of the capacitor.

In an embodiment of the present invention, after the ruthenium oxide layer is formed on the inner surface of the tantalum shell, an annealing step is also included. For example, in one embodiment, the annealing step includes: the vacuum degree is higher than 5×10-4 Pa, the temperature Anneal at 180~250°C for 2~3 hours.

In the method in the embodiment of the present invention, the electrochemically synthesized ruthenium oxide is used as the continuous phase, and the graphene dispersed on the tantalum shell is used as the dispersed phase, and the specific capacity can be increased through the synergistic effect of the two. At the same time, porous ruthenium oxide is formed on the rough surface of graphene to increase the specific surface area. In this way, the combination of graphene and ruthenium oxide can not only greatly increase the cathode area of the all-tantalum capacitor, increase the effective area of the tantalum capacitor, but also introduce a pseudocapacitance on the tantalum shell, thereby increasing the capacity of the capacitor.

The detailed steps of the method of the present invention will be described below based on several specific examples.

Example 1:

(1) Use 400-mesh steel grit to blast the inner surface of the tantalum shell of Φ10×100mm under the pressure of 0.6Mpa for 1min;

(2) The tantalum case after sandblasting was ultrasonically cleaned with acetone and deionized water for 1 hour, and dried at 100°C for later use;

(3) Add 2 ml of graphene oxide dispersion at a concentration of 2 mg/ml to the cleaned tantalum shell;

(4) Rotate the tantalum shell containing the graphene oxide dispersion for 30s at a rate of 50 rpm;

(5) Keep the tantalum shell at a vacuum of 1.1×10 ^-4 pa and a temperature of 200°C for 1 hour, at which time graphene oxide is reduced to graphene;

(6) Repeat (4)~(5) process 3 times;

(7) Use the entire tantalum shell as the electrochemical reaction tank and working electrode, add 7ml of electrolyte, insert platinum wire and silver/silver chloride electrode respectively, and the cycle voltage is -0.2~1V, and the scanning speed is 200mV/s. The number of cycles was 100 times to prepare a ruthenium oxide electrode;

(8) After the preparation is completed, rinse the inner surface of the tantalum shell with deionized water for 3 to 5 times;

(9) Anneal the tantalum case at a vacuum degree of 3.2×10 ^-4 pa at a temperature of 200°C for 2 hours.

In this way, an all-tantalum electrolytic capacitor cathode sample 1 was obtained.

Example 2:

(1) Use 400 mesh steel grit on the inner surface of the tantalum shell of Φ20×120mm, and blast it for 2 minutes under the pressure of 0.6Mpa;

(2) The tantalum case after sandblasting was ultrasonically cleaned with acetone and deionized water for 1 hour, and dried at 100°C for later use;

(3) Add 9 ml of graphene oxide dispersion at a concentration of 2 mg/ml to the cleaned tantalum shell;

(4) Rotate the tantalum shell containing the graphene oxide dispersion for 30s at a rate of 50 rpm;

(5) Keep the tantalum shell at a vacuum of 9.7×10 ^-5 pa and a temperature of 200°C for 1 hour, at which time graphene oxide is reduced to graphene;

(6) Repeat (4)~(5) process 3 times;

(7) Use the entire tantalum shell as the electrochemical reaction tank and working electrode, add 32ml of electrolyte, insert platinum wire and silver/silver chloride electrode respectively, and the cycle voltage is -0.2~1V, and the scanning speed is 250mV/s. The number of cycles was 100 times to prepare a ruthenium oxide electrode;

(8) After the preparation is completed, rinse the inner surface of the tantalum shell with deionized water for 3 to 5 times;

(9) Anneal the tantalum case at a vacuum of 3.5×10 ^-4 Pa at a temperature of 200°C for 2 hours.

In this way, an all-tantalum electrolytic capacitor cathode sample 2 was obtained.

Example 3:

(1) Use 400-mesh steel grit to blast the inner surface of the tantalum shell of Φ10×100mm under the pressure of 0.6Mpa for 1min;

(2) The tantalum case after sandblasting was ultrasonically cleaned with acetone and deionized water for 1 hour, and dried at 100°C for later use;

(3) Add 2 ml of graphene oxide dispersion at a concentration of 5 mg/ml to the cleaned tantalum shell;

(4) Rotate the tantalum shell containing the graphene oxide dispersion for 30s at a rate of 50 rpm;

(5) Keep the tantalum shell at a vacuum of 8.7×10 ^-5 pa and a temperature of 200°C for 1.5 hours, at which time graphene oxide is reduced to graphene;

(6) Repeat (4)~(5) process 3 times;

(7) Use the entire tantalum shell as the electrochemical reaction tank and working electrode, add 7ml of electrolyte, insert platinum wire and silver/silver chloride electrode respectively, and the cycle voltage is -0.2~1V, and the scanning speed is 200mV/s. The number of cycles was 100 times to prepare a ruthenium oxide electrode;

(8) After the preparation is completed, rinse the inner surface of the tantalum shell with deionized water for 3 to 5 times;

(9) Anneal the tantalum case at a vacuum degree of 1.2×10 ^-4 pa at a temperature of 200°C for 2 hours.

In this way, an all-tantalum electrolytic capacitor cathode sample 3 was obtained.

Example 4:

(1) Use 400 mesh steel grit on the inner surface of the tantalum shell of Φ20×120mm, and blast it for 2 minutes under the pressure of 0.6Mpa;

(2) The tantalum case after sandblasting was ultrasonically cleaned with acetone and deionized water for 1 hour, and dried at 100°C for later use;

(3) Add 9 ml of graphene oxide dispersion at a concentration of 5 mg/ml to the cleaned tantalum shell;

(4) Rotate the tantalum shell containing the graphene oxide dispersion for 30s at a rate of 50 rpm;

(5) Keep the tantalum shell at a vacuum of 9.4×10 ^-5 pa and a temperature of 200°C for 1.5 hours, at which time graphene oxide is reduced to graphene;

(6) Repeat (4)~(5) process 3 times;

(7) Use the entire tantalum shell as the electrochemical reaction tank and working electrode, add 32ml of electrolyte, insert platinum wire and silver/silver chloride electrode respectively, and the cycle voltage is -0.2~1V, and the scanning speed is 250mV/s. The number of cycles was 100 times to prepare a ruthenium oxide electrode;

(8) After the preparation is completed, rinse the inner surface of the tantalum shell with deionized water for 3 to 5 times;

(9) Anneal the tantalum shell for 2 hours at a vacuum of 4.1×10 ^-4 Pa at a temperature of 200°C.

In this way, an all-tantalum electrolytic capacitor cathode sample 4 was obtained.

After testing, the specific parameters of the four samples obtained above are shown in Figure 2.

It can be seen from FIG. 2 that the cathode of the all-tantalum electrolytic capacitor manufactured according to the method of the present invention has stable performance, large specific surface area and high specific capacity, and is suitable for assembly of high-reliability all-tantalum electrolytic capacitors.

The present invention has been described above through specific examples, but the present invention is not limited to these specific examples. Those skilled in the art should understand that various modifications, equivalent replacements, changes, etc. can also be made to the present invention. As long as these changes do not deviate from the spirit of the present invention, they should all be within the protection scope of the present invention. In addition, "one embodiment" described in many places above represents different embodiments, and of course all or part of them may be combined in one embodiment.

Claims (10)

1. A method for manufacturing an all-tantalum electrolytic capacitor cathode, is characterized in that, comprising: Step A: Sandblasting and grinding the inner surface of the tantalum shell of the all-tantalum electrolytic capacitor to make the inner surface rough; Step B: adding graphene oxide into ultrapure water to disperse to obtain a graphene oxide dispersion; Step C: adding the graphene oxide dispersion liquid into the tantalum shell, and rotating the tantalum shell at a predetermined speed, so that the graphene oxide in the graphene oxide dispersion liquid is dispersed on the inner surface, and drying; Step D: reducing the graphene oxide dispersed on the inner surface; Step F: forming a ruthenium oxide layer on the inner surface electrochemically. 2. The method according to claim 1, characterized in that: in the sandblasting process, the sandblasting abrasive is 400 mesh steel grit, the sandblasting pressure is 0.6 to 0.8 MPa, and the sandblasting time is 0.5 to 3 minutes . 3. The method according to claim 1, characterized in that: after sandblasting the inner surface of the tantalum shell of the all-tantalum electrolytic capacitor, it also includes: Ultrasonic cleaning of the tantalum housing with acetone for 0.5 to 1 hour; Cleaning the tantalum case with deionized water for 0.5 to 1 hour; Dry the tantalum case. 4. The method according to claim 1, characterized in that: the concentration of the graphene oxide dispersion is 1 to 5 mg/ml, and the rotating the tantalum shell at a predetermined speed comprises: rotating at 50 to 100 Rotate the tantalum housing at a rpm of 20 to 60 seconds. 5. The method according to claim 1, characterized in that: said reducing the graphene oxide dispersed on said inner surface comprises: at a vacuum degree higher than 5×10 ^-4 Pa, at a temperature of 200 to The graphene oxide dispersed on the inner surface is reduced for 0.5 to 1 hour in an environment of 220 degrees Celsius. 6. The method according to claim 1, further comprising: repeating said step C and said step D 3 to 5 times before said step F. 7. The method according to claim 1, characterized in that: forming a ruthenium oxide layer on the inner surface by an electrochemical method comprises: Prepare electrolyte; adding the electrolyte solution into the tantalum case; Using the tantalum shell as a working electrode, platinum wire as a counter electrode, and silver/silver chloride as a reference electrode, a ruthenium oxide layer is formed on the inner surface of the tantalum shell by cyclic voltammetry. 8. method as claimed in claim 7, is characterized in that, described electrolytic solution comprises: concentration is the ruthenium trichloride of 0.01～0.02 mol/liter, concentration is the potassium chloride of 0.1～0.2 mol/liter and concentration is 0.01-0.03 mol/liter of hydrogen chloride, the temperature of the electrolyte is 40°C-60°C. 9. The method according to claim 7, characterized in that: in the cyclic voltammetry, the cycle voltage is -0.2 ~ 1 volt, the scan rate is 100 ~ 800 mV/s, and the number of cycles is 100 ~ 500 Second-rate. 10. The method according to claim 7, characterized in that: after forming the ruthenium oxide layer on the inner surface of the tantalum shell, further comprising: when the vacuum degree is higher than 5×10 ^-4 Pa and the temperature is 180~ Anneal at 250°C for 2~3 hours.

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