High-voltage-resistant aluminum electrolytic capacitor and preparation method thereof

Abstract

The invention relates to a high-voltage-resistant aluminum electrolytic capacitor, which comprises a core bag, a shell and a sealing element, the core bag is arranged in the shell through a sealing piece; the core cladding is formed by winding an anode foil, electrolytic paper and a cathode foil, and the core cladding is impregnated with an electrolyte; and a PVA film is coated on the electrolytic paper. According to the method, the surface of the conventional electrolytic paper is coated with a layer of PVA, in the impregnation process of capacitor manufacturing, the electrolytic paper adsorbs a low-viscosity electrolyte, the electrolyte can effectively permeate into aluminum foil holes, and in the electrolyte permeation process and the aging process, the PVA is dissolved in the electrolyte under the effect of self heating of the capacitor, so that the capacitor is prevented from being damaged, and the service life of the capacitor is prolonged. And the high-voltage resistance of the capacitor can be effectively improved.

Description

Technical Field

[0001] The present invention relates to an aluminum electrolytic capacitor, and in particular to a high-voltage-resistant aluminum electrolytic capacitor and a preparation method thereof. Background Art

[0002] As one of the three major passive components in circuit design, aluminum electrolytic capacitors play an irreplaceable role in circuits. Aluminum electrolytic capacitors are important components of filter capacitors used at the input end of circuit design. With the replacement and upgrading of various electronic products and the application requirements of new energy / vehicle 800V ultra-high voltage charging piles, the rated working voltage of aluminum electrolytic capacitors has been increased from the traditional 400V / 450V rated working voltage requirements to 750V / 800V rated working voltage. The development and design of aluminum electrolytic capacitors with such a high rated working voltage faces many difficulties; one of the difficulties is the bottleneck problem of electrolyte and electrolytic paper. In order to increase the rated voltage of aluminum electrolytic capacitors, from the perspective of electrolytic paper and electrolyte; generally, the thickness of the electrolytic paper is increased, or the viscosity of the electrolyte is increased to achieve; however, increasing the thickness of the electrolytic paper will increase the volume of the core package or reduce the capacitor capacity, and increasing the viscosity of the electrolyte will make it more difficult to immerse the core package in the electrolyte, the electrolyte impregnation is less, and the ESR value is large. Summary of the invention

[0003] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a high-voltage resistant aluminum electrolytic capacitor and a preparation method thereof.

[0004] In order to solve the above technical problems, the technical solution proposed in the present invention is: a high-voltage resistant aluminum electrolytic capacitor, comprising a core package, a shell and a seal; the core package is arranged in the shell through the seal; the core package is wound by an anode foil, an electrolytic paper and a cathode foil, and the core package is impregnated with an electrolyte; the electrolytic paper is coated with a PVA film.

[0005] In the above-mentioned high-voltage aluminum electrolytic capacitor, preferably, the PVA film on the electrolytic paper is in contact with the anode foil.

[0006] In the above-mentioned high-voltage aluminum electrolytic capacitor, preferably, two or three layers of electrolytic paper are arranged between the anode foil and the cathode foil; a layer of PVA film is coated on the electrolytic paper on the side of the anode foil, and the PVA film on the electrolytic paper is in contact with the anode foil.

[0007] In the above-mentioned high-voltage aluminum electrolytic capacitor, preferably, the viscosity of the electrolyte is less than or equal to 100 mPa·s.

[0008] A method for preparing a high-voltage aluminum electrolytic capacitor comprises the following steps: 1) Coating PVA aqueous solution on electrolytic paper; 2) drying the electrolytic paper coated with the PVA aqueous solution in step 1) to form a PVA film on the electrolytic paper; 3) Winding the anode foil, cathode foil and electrolytic paper from step 2) together into a core package; 4) The core contains an electrolyte; 5) Assembly; 6) Aging test.

[0009] In the above-mentioned method for preparing a high-voltage aluminum electrolytic capacitor, preferably, the molecular weight of PVA in the PVA aqueous solution is between 5000 and 200000, and the weight concentration of PVA in the PVA aqueous solution is between 2% and 8%.

[0010] In the above-mentioned method for preparing a high-voltage-resistant aluminum electrolytic capacitor, preferably, the PVA film on the electrolytic paper is in contact with the anode foil.

[0011] In the above-mentioned method for preparing a high-voltage aluminum electrolytic capacitor, preferably, two or three layers of electrolytic paper are arranged between the anode foil and the cathode foil; a layer of PVA film is coated on the electrolytic paper on the side of the anode foil, and the PVA film on the electrolytic paper is in contact with the anode foil.

[0012] In the above method for preparing a high-voltage aluminum electrolytic capacitor, preferably, the viscosity of the electrolyte is less than or equal to 100 mPa·s.

[0013] Compared with the prior art, the advantages of the present invention are as follows: in the present invention, a layer of PVA is coated on the surface of conventional electrolytic paper. During the impregnation process of capacitor manufacturing, the electrolytic paper absorbs low-viscosity electrolyte, and the electrolyte can effectively penetrate into the holes of the aluminum foil. During the electrolyte penetration process and the aging process, under the action of the capacitor's own heat, the PVA dissolves in the electrolyte, which can effectively improve the high-voltage resistance characteristics of the capacitor. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 Graph showing the withstand voltage test results of the aluminum electrolytic capacitors of Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0015] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and carefully in combination with preferred embodiments below, but the protection scope of the present invention is not limited to the following specific embodiments.

[0016] It should be noted that when an element is described as being "fixed, fixed, connected or connected to" another element, it can be directly fixed, fixed, connected or connected to the other element, or it can be indirectly fixed, fixed, connected or connected to the other element through other intermediate connectors.

[0017] Unless otherwise defined, all the professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention. Example 1

[0018] A high-voltage resistant aluminum electrolytic capacitor comprises a core package, a shell and a seal, wherein the seal may be a rubber plug or a cover plate; the core package is arranged in the shell through the seal; the core package is wound by an anode foil, an electrolytic paper and a cathode foil, and the core package is impregnated with an electrolyte; and the electrolytic paper is coated with a PVA film.

[0019] In this embodiment, two or three layers of electrolytic paper are arranged between the anode foil and the cathode foil; a layer of PVA film is coated on the electrolytic paper on the side of the anode foil, and the PVA film on the electrolytic paper is in contact with the anode foil. In other embodiments, the electrolytic paper may also be a single layer; when the electrolytic paper is a single layer, the PVA film on the electrolytic paper is in contact with the anode foil.

[0020] In this embodiment, the viscosity of the electrolyte is less than or equal to 100mPa·s. The electrolyte cannot guarantee high withstand voltage at this viscosity; the withstand voltage value of the electrolyte with a viscosity of 100mPa·s is generally 650V; the viscosity of the electrolyte is less than or equal to 100mPa·s, which is conducive to the impregnation of the electrolyte into the core package; the electrolyte can effectively penetrate into the holes on the surface of the anode foil, thereby facilitating the extraction of the capacity on the anode foil.

[0021] In this embodiment, although the viscosity of the electrolyte itself cannot guarantee high withstand voltage, during the impregnation process of capacitor production, after the electrolytic paper absorbs the low-viscosity electrolyte, the electrolyte can effectively penetrate into the pores of the aluminum foil. During the aging process of production, under the combined effects of the capacitor's own heat and external high-temperature aging conditions, the PVA coated on the surface of the electrolytic paper dissolves in the electrolyte, and the large amount of OH- in the PVA molecules is used to improve the polymerization ability of the electrolyte, thereby changing the viscosity of the original electrolyte and improving the stability of the electrolyte structure. The flash voltage of the electrolyte is effectively improved by the dissolution of PVA, which can effectively improve the high-voltage withstand characteristics of the capacitor.

[0022] In this embodiment, the main solvent of the electrolyte is generally ethylene glycol, water, propylene glycol, etc., and the main solvent forms hydrogen bonds with the hydroxyl groups in the PVA molecules, thereby dissolving the PVA in the electrolyte; taking ethylene glycol as an example, the hydroxyl groups in the ethylene glycol molecules form hydrogen bonds with the hydroxyl groups in the PVA molecules, thereby dissolving the PVA in the electrolyte.

[0023] This embodiment also provides a method for preparing a high-voltage resistant aluminum electrolytic capacitor, which is characterized by comprising the following steps: 1) Coating a PVA aqueous solution on the electrolytic paper; the molecular weight of PVA in the PVA aqueous solution is between 5000 and 200000, and the weight concentration of PVA in the PVA aqueous solution is between 2% and 8%.

[0024] 2) Drying the electrolytic paper coated with the PVA aqueous solution in step 1) to form a PVA film on the electrolytic paper.

[0025] 3) The anode foil, cathode foil and the electrolytic paper of step 2) are rolled together into a core package; two or three layers of electrolytic paper are arranged between the anode foil and the cathode foil; a layer of PVA film is coated on the electrolytic paper on the side of the anode foil, and the PVA film on the electrolytic paper is in contact with the anode foil.

[0026] 4) The core contains an electrolyte; 5) Assembly; 6) Aging test: During aging, the temperature of the capacitor is generally heated to about 85°C. At this temperature, the PVA on the electrolytic paper can quickly dissolve in the electrolyte, thereby increasing the viscosity of the electrolyte.

[0027] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that no PVA film is provided on the electrolytic paper in Comparative Example 1; the rest is the same as Example 1.

[0028] The aluminum electrolytic capacitors of Example 1 and Comparative Example 1 with a voltage of 700V and 90μF were respectively selected for withstand voltage test. The results are as follows: Figure 1 As shown, the aluminum electrolytic capacitor of comparative example 1 is broken down at about 680V, ​​while the withstand voltage of embodiment 1 can reach the withstand voltage of the anode foil of 800V. The withstand voltage of the oxide film on the surface of the formed foil used in embodiment 1 and comparative example 1 is 1100Vf; the electrolyte used is a boric acid electrolyte with a moisture content of 5%; the formation is carried out at 85°C and the current is 10mA / Pc.

Claims

1. A high voltage resistant aluminum electrolytic capacitor, characterized in that: It comprises a core package, an outer shell and a seal; the core package is arranged in the outer shell through the seal; the core package is wound by an anode foil, an electrolytic paper and a cathode foil, and the core package is impregnated with electrolyte; the electrolytic paper is coated with a PVA film.

2. The high voltage aluminum electrolytic capacitor according to claim 1, characterized in that: The PVA film on the electrolytic paper is in contact with the anode foil.

3. The high voltage aluminum electrolytic capacitor according to claim 1, characterized in that: Two or three layers of electrolytic paper are arranged between the anode foil and the cathode foil; a layer of PVA film is coated on the electrolytic paper on the side of the anode foil, and the PVA film on the electrolytic paper is in contact with the anode foil.

4. The high voltage aluminum electrolytic capacitor according to claim 1, characterized in that: The viscosity of the electrolyte is less than or equal to 100 mPa·s.

5. A method for preparing a high-voltage aluminum electrolytic capacitor, characterized in that: The following steps are involved: 1) Coating PVA aqueous solution on electrolytic paper; 2) drying the electrolytic paper coated with the PVA aqueous solution in step 1) to form a PVA film on the electrolytic paper; 3) Winding the anode foil, cathode foil and electrolytic paper from step 2) together into a core package; 4) The core contains electrolyte; 5) Assembly; 6) Aging test.

6. The method for preparing a high voltage resistant aluminum electrolytic capacitor according to claim 5, characterized in that: The molecular weight of PVA in the PVA aqueous solution is between 5000 and 200000, and the weight concentration of PVA in the PVA aqueous solution is between 2% and 8%.

7. The method for preparing a high voltage resistant aluminum electrolytic capacitor according to claim 5, characterized in that: The PVA film on the electrolytic paper is in contact with the anode foil.

8. The method for preparing a high voltage resistant aluminum electrolytic capacitor according to claim 5, characterized in that: Two or three layers of electrolytic paper are arranged between the anode foil and the cathode foil; a layer of PVA film is coated on the electrolytic paper on the side of the anode foil, and the PVA film on the electrolytic paper is in contact with the anode foil.

9. The method for preparing a high voltage resistant aluminum electrolytic capacitor according to claim 5, characterized in that: The viscosity of the electrolyte is less than or equal to 100 mPa·s.

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