Universal low-impedance electrolyte for high-voltage aluminum electrolytic capacitor and high-voltage aluminum electrolytic capacitor

Abstract

The invention discloses a universal low-impedance electrolyte for a high-voltage aluminum electrolytic capacitor and the high-voltage aluminum electrolytic capacitor in the technical field of electrolytes for capacitors, the universal low-impedance electrolyte is suitable for high-voltage lead type, ox horn type and bolt type aluminum electrolytic capacitors, and the universal low-impedance electrolyte comprises the following components in percentage by mass: 60-80% of a solvent, 10-18% of a main solute, 2-6% of a solute improver and 0.5-4% of a special solute, 5-15 wt% of a PVA and SiO2 aerosol compound, and 2-7 wt% of other functional additives; according to the universal low-impedance electrolyte for the high-voltage aluminum electrolytic capacitor and the high-voltage aluminum electrolytic capacitor, the conductivity and the sparking voltage of the electrolyte are properly improved, so that the internal resistance and the breakdown risk of the capacitor are reduced, various electrolytes are replaced, the production efficiency is greatly improved, and the production cost is reduced; the method can be applied to manufacturing of 450V and below lead, ox horn and bolt aluminum electrolytic capacitors, the production line impregnation efficiency is greatly improved, and the production cost is saved.

Description

Technical Field

[0001] The present invention relates to the technical field of electrolyte for capacitors, and in particular to a general-purpose low-impedance electrolyte for high-voltage aluminum electrolytic capacitors and a high-voltage aluminum electrolytic capacitor. Background Art

[0002] The selection of electrolyte for high-voltage aluminum electrolytic capacitors has a significant impact on the performance indicators of the capacitors. Suitable working electrolytes can improve the working temperature range, rated voltage, loss factor, impedance, rated ripple current and other performance parameters of aluminum electrolytic capacitors, which is more beneficial to extending the working life of capacitors. For electrolytes used in medium and high voltage aluminum electrolytic capacitors, the main consideration is whether they have good solubility and excellent thermal stability. At present, the working electrolytes of capacitors on the market generally use linear carboxylic acid ammonium salts (such as ammonium sebacate, ammonium hydrogen azelaic acid, etc.) as the main electrolyte dissolved in ethylene glycol solvent. Due to its solubility and thermal stability defects, and the voltage resistance is not ideal, the rate of repairing damaged aluminum oxide film is low, which reduces the safety and reliability of aluminum electrolytic capacitors.

[0003] At the same time, the flash voltage and conductivity of the finished electrolyte are two main parameters that have an important impact on the performance of aluminum electrolytic capacitors. The flash voltage of the electrolyte determines the working stability of the aluminum electrolytic capacitor under specific conditions. The smaller the conductivity, the slower the ion migration in the electrolyte, the larger the internal resistance of the capacitor, and the more serious the heating of the electrolytic capacitor, which will affect the working stability and life of the capacitor. But the biggest challenge is that within a certain range, the flash voltage is a technical feature that is inversely proportional to the conductivity. The technical indicators of mature commercial electrolytes at present: when the flash voltage is ≥500V, the conductivity is generally ≤1.7ms / cm. In addition, for production lines, too many types of electrolytes significantly increase the frequency of cleaning and replacement of impregnation equipment, reduce the utilization rate of impregnation equipment, and greatly affect production efficiency. For this reason, we propose a universal low-impedance electrolyte for high-voltage aluminum electrolytic capacitors and high-voltage aluminum electrolytic capacitors. Summary of the invention

[0004] The object of the present invention is to provide a general-purpose low-impedance electrolyte for high-voltage aluminum electrolytic capacitors and a high-voltage aluminum electrolytic capacitor to solve the problems raised in the above-mentioned background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions: a universal low-impedance electrolyte for high-voltage aluminum electrolytic capacitors and a high-voltage aluminum electrolytic capacitor, which are suitable for high-voltage lead-type, horn-type and bolt-type aluminum electrolytic capacitors, comprising the following components: by mass ratio Wt%: solvent 60~80Wt%, main solute 10~18Wt%, solute enhancer 2~6Wt%, special solute 0.5~4Wt%, PVA and SiO2 aerosol compound 5~15wt%, and other functional additives 2~7Wt%; primary solutes, solute enhancers, and special solutes; The R of the main solute comprises a main chain and a branch chain, and does not contain an oxygen-containing group, wherein the number of carbon atoms in the straight chain is 8 to 11, the number of branches is 1 to 3, and the number of carbon atoms in each branch is 3 to 5. The total number of carbon atoms in R of the solute enhancer is 12 to 15, the number of branches is 1 to 2, the branch chain or main chain of R also contains a hydroxyl group, the number of hydroxyl groups is 1 to 4, and the remaining carbon atoms are all alkyl or hydrogen atoms. The total number of carbon atoms in R of the special solute is 20 to 28, the number of branches is 2 to 4, and at least one branch contains 7 to 10 carbon atoms. R also contains an oxygen-containing group of a carbonyl or ester group, and the number of oxygen atoms is 3 to 6.

[0006] Preferably, the solvent of the electrolyte contains two substances, one is ethylene glycol, and the other is one of GBL, DMF, NMP, and glycerol, wherein the content of ethylene glycol is not less than 70wt%; Ethylene glycol is a commonly used solvent for electrolyte. It has good solubility and excellent basic flash voltage. However, if the viscosity of the electrolyte is too high, it will not only reduce the impregnation of the capacitor core package, but also affect the migration of ions and thus reduce the conductivity. Therefore, the purpose of another solvent is to act as a viscosity regulator to maintain a reasonable viscosity of the electrolyte. At the same time, it can also improve the capacitance decay and impedance characteristics at low temperatures. However, if the content of this solvent exceeds 30wt%, it will greatly change the basic characteristics of the combined solvent such as solubility and flash voltage, so its content should be controlled below 30wt%.

[0007] Preferably, the PVA and SiO2 aerosol composite solution, wherein the PVA is one of the ones with a degree of polymerization between 500 and 2400, and the PVA content is not less than 80wt%; The preparation method comprises: mixing ethylene glycol and PVA, heating to 110-140°C, maintaining a constant temperature and stirring to completely melt the PVA, then cooling to 70-90°C, subsequently adding SiO2 aerosol, maintaining the temperature and stirring for 10-30 minutes, and obtaining a composite solution of PVA and SiO2 aerosol; SiO2 aerosol has a large specific surface area, can improve the dispersibility of each component in the electrolyte, and has a strong adsorption capacity, reduces the activity of ions, and partially changes the dielectric constant of the aluminum foil surface. After being compounded with PVA, the aerosol can better adhere to the electrode foil, which can not only reduce the corrosion of salts and moisture in the electrolyte, but also enable the electrolyte to ensure the flash voltage while improving the conductivity of the electrolyte.

[0008] Preferably, the functional additives include conventional dehydrogenating agents and hydration-resistant agents. The dehydrogenating agent is one of p-nitrophenol, p-nitrobenzyl alcohol, ammonium p-nitrobenzoate, p-benzoquinone, and m-nitroacetophenone. These substances can react with hydrogen ions generated by the electrolysis reaction, thereby reducing the generation of hydrogen, reducing the internal pressure of the capacitor, and improving the durability of the capacitor. The hydration-resistant agent is one or more of ammonium hypophosphite, phosphorous acid, and dibutyl phosphate. The phosphates in these substances react with aluminum ions to form an aluminum phosphate passivation layer, thereby inhibiting the hydration reaction and reducing the leakage current.

[0009] Preferably, the method comprises the following steps: S1, stirring and mixing the solvent, heating to 90-100°C, stirring and maintaining for 10-15 minutes, and then heating to 125-145°C; S2, adding the main solute, solute enhancer and special solute, stirring at a constant temperature for 30-45 minutes, and then cooling the mixed solution to 115-125°C; S3, adding PVA and SiO2 aerosol composite solution thereto, stirring at a constant temperature for 30-45 minutes, and then cooling the mixed solution to 90-100°C; S4, adding a dehydrogenating agent and a water-resistant agent, stirring at a constant temperature for 45 to 60 minutes, and then naturally cooling to room temperature to obtain an aluminum electrolytic capacitor electrolyte.

[0010] Preferably, the method comprises the following steps: Winding: Winding the anode foil, electrolytic paper, cathode foil and lead wire together to obtain a core package; Impregnation: immersing the core package in the electrolyte for the high-voltage aluminum electrolytic capacitor; Assembly: The impregnated core is packed into the shell, and the positive and negative electrodes are led out, and the damaged oxide film is repaired after aging to form an aluminum electrolytic capacitor.

[0011] Compared with the prior art, the beneficial effects of the present invention are: the universal low-impedance electrolyte for high-voltage aluminum electrolytic capacitors and the high-voltage aluminum electrolytic capacitors, the electrolyte flash voltage can reach 530V, the conductivity can reach 1.95ms / cm, have good electrochemical properties, improve the solubility and thermal stability of the electrolyte solute, and appropriately increase the conductivity and flash voltage of the electrolyte to help reduce the internal resistance and breakdown risk of the capacitor, replace a variety of electrolytes to greatly improve production efficiency and reduce production costs, can be used in the manufacture of 450V and below lead, horn and bolt aluminum electrolytic capacitors, greatly improve the impregnation efficiency of the production line, and save production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a schematic diagram of the temperature characteristics of the lead capacitor 450V158.2*16 according to Example 1 of the present invention; Figure 2 This is a schematic diagram of the temperature characteristics of the horn capacitor 450V120035*80 according to Example 2 of the present invention; Figure 3 This is a schematic diagram of the temperature characteristics of the bolt capacitor 450V560076*130 according to Example 3 of the present invention. DETAILED DESCRIPTION

[0013] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0014] Embodiment 1: The present invention provides a technical solution: a general-purpose low-impedance electrolyte for high-voltage aluminum electrolytic capacitors and a high-voltage aluminum electrolytic capacitor. The lead capacitor is made by using the electrolyte of the present invention and compared with the capacitor of the same specification made by the electrolyte of comparative example 1, and the test specification is 450V158.2*16.

[0015] Embodiment 2: The present invention provides a technical solution: a universal low-impedance electrolyte for high-voltage aluminum electrolytic capacitors and a high-voltage aluminum electrolytic capacitor. The electrolyte of the present invention is used to make horn capacitors, which are compared with capacitors of the same specifications made by the electrolytes of comparative examples 3 and 4. The test specifications are 450V120035*80.

[0016] Embodiment three: The present invention provides a technical solution: a general-purpose low-impedance electrolyte for high-voltage aluminum electrolytic capacitors and a high-voltage aluminum electrolytic capacitor. Bolt capacitors are made by using the electrolyte of the present invention and compared with capacitors of the same specification made by the electrolyte of comparative example 2. The test specification is 450V560076*130; The high voltage aluminum electrolytic capacitors of the above three embodiments were manufactured according to the preparation method and the same test conditions were adopted; 1) Test its basic parameters Cap, DF, ESR, and LC; 2) Test the low temperature characteristics of the manufactured capacitor at -40~55℃, that is, test its capacity attenuation and impedance ratio at different temperatures, where C0 and Z0 are the capacity and impedance at 20℃; 3) Carry out 105℃ high temperature storage and 105℃ high temperature load tests, and compare the parameter changes △Cap, △DF, and △LC before and after the reliability test; As shown in Table 4, from the analysis of the initial parameters of the electrolyte: the conductivity of the electrolyte of the present invention is similar to that of Comparative Example 1, higher than that of Comparative Examples 2-4, and can effectively reduce the DF / ESR and ripple temperature rise of the product; the flash voltage is similar to that of Comparative Examples 3-4, higher than that of Comparative Examples 1-2; the water content of the HW2612 electrolyte is the lowest, which can effectively reduce the reaction activity of the product and thus prolong the life. The electrolyte of the present invention combines the flash voltage, conductivity and water content, and realizes low ESR and high reliability of the capacitor from the perspective of electrolyte materials; According to the analysis of the basic parameters of capacitors in Examples 1-3 in Tables 1-3: the electrolyte of the present invention achieves low ESR characteristics in lead, horn and bolt capacitors compared with the mainstream electrolyte in use. For example, the ESR of the lead capacitor in Table 1 is reduced from 3.93 to 3.49Ω / 120Hz; as shown in Table 2, the ESR of the horn capacitor is reduced from 0.14 in Comparative Example 3 and 0.107 in Comparative Example 4 to 0.061Ω / 120Hz; as shown in Table 3, the ESR of the bolt capacitor is reduced from 0.021 to 0.016Ω / 120Hz; at the same time, the performance of other parameters is similar. These data clearly show that the electrolyte of the present invention has excellent low ESR characteristics in lead, horn and bolt capacitors, and can be compatible with mainstream electrolytes on the market at the same time, greatly improving the impregnation efficiency of the production line; According to the parameter change analysis of Examples 1-3 before and after the reliability test in Tables 1-3: as shown in Table 1, for the lead capacitor, the present invention passed the reliability tests of 105°C high-temperature storage and high-temperature load, and the characteristic change rates before and after the test were basically close, meeting the capacitor performance requirements; as shown in Table 2, the present invention is still compatible with the horn capacitor, the parameter change rates of the high-temperature load are basically close, and the △DF and △LC of the high-temperature load are advantageous; as shown in Table 3, the high-temperature storage characteristics of the present invention are close to those of the bolt capacitor, and the △DF change rate of the high-temperature load is small; comprehensively speaking, the electrolyte of the present invention has advantages in capacitor reliability testing, the parameter change rates are relatively small, and it has higher reliability.

[0017] In addition, an important indicator for evaluating electrolyte is the temperature characteristics of capacitance, which is a key factor in evaluating whether capacitors can be used normally in cold plateau conditions. Capacitance attenuation and impedance at low temperatures are the most critical indicators, especially at -40°C. Figure 1-3 , clearly showing that the capacitance decay and impedance of various capacitors of Examples 1-3 at -40°C have obvious advantages, especially in Comparative Example 3, which is reduced from -30.21% to -15.86%. Therefore, based on the basic parameters, reliability test and temperature characteristic test, the electrolyte of the present invention achieves versatility, low ESR and high reliability under the premise of ensuring quality; Table 1, basic parameters and reliability test parameters of lead capacitor 450V158.2*16 in Example 1 Table 2, basic parameters and reliability test parameters of horn capacitor 450V120035*80 in Example 2 Table 3, basic parameters and reliability test parameters of bolt capacitor 450V560076*130 in Example 3 Table 4. Basic parameters and applicable ranges of the electrolyte of the present invention and the electrolytes of Comparative Examples 1-4

[0018] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0019] Although the present invention has been described above with reference to the embodiments, various modifications may be made thereto and parts thereof may be replaced with equivalents without departing from the scope of the present invention. In particular, as long as there is no structural conflict, the various features in the embodiments disclosed by the present invention may be used in combination with each other in any manner, and the fact that these combinations are not exhaustively described in this specification is only for the sake of omitting space and saving resources. Therefore, the present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A general-purpose low-impedance high-voltage aluminum electrolytic capacitor electrolyte, characterized in that: It includes the following components: by weight ratio Wt%: solvent 60~80Wt%, main solute 10~18Wt%, solute enhancer 2~6Wt%, special solute 0.5~4Wt%, PVA and SiO2 aerosol compound 5~15wt%, and other functional additives 2~7Wt%; primary solutes, solute enhancers, and special solutes; The R of the main solute comprises a main chain and a branch chain, and does not contain an oxygen-containing group, wherein the number of carbon atoms in the straight chain is 8 to 11, the number of branches is 1 to 3, and the number of carbon atoms in each branch is 3 to 5. The total number of carbon atoms in R of the solute enhancer is 12 to 15, the number of branches is 1 to 2, the branch chain or main chain of R also contains a hydroxyl group, the number of hydroxyl groups is 1 to 4, and the remaining carbon atoms are all alkyl or hydrogen atoms. The total number of carbon atoms in R of the special solute is 20 to 28, the number of branches is 2 to 4, and at least one branch contains 7 to 10 carbon atoms. R also contains an oxygen-containing group of a carbonyl or ester group, and the number of oxygen atoms is 3 to 6.

2. The electrolyte for a universal low-impedance high-voltage aluminum electrolytic capacitor according to claim 1, characterized in that: The electrolyte solvent comprises two substances, one is ethylene glycol, and the other is one of GBL, DMF, NMP, and glycerol, wherein the content of ethylene glycol is not less than 70wt%; Ethylene glycol is a commonly used solvent for electrolyte. It has good solubility and excellent basic flash voltage. However, if the viscosity of the electrolyte is too high, it will not only reduce the impregnation of the capacitor core package, but also affect the migration of ions and thus reduce the conductivity. Therefore, the purpose of another solvent is to act as a viscosity regulator to maintain a reasonable viscosity of the electrolyte. At the same time, it can also improve the capacitance decay and impedance characteristics at low temperatures. However, if the content of this solvent exceeds 30wt%, it will greatly change the basic characteristics of the combined solvent such as solubility and flash voltage, so its content should be controlled below 30wt%.

3. The electrolyte for a universal low-impedance high-voltage aluminum electrolytic capacitor according to claim 1, characterized in that: The PVA and SiO2 aerosol composite solution, wherein the PVA is one of the ones with a degree of polymerization between 500 and 2400, and the PVA content is not less than 80wt%; The preparation method comprises: mixing ethylene glycol and PVA, heating to 110-140°C, maintaining a constant temperature and stirring to completely melt the PVA, then cooling to 70-90°C, subsequently adding SiO2 aerosol, maintaining the temperature and stirring for 10-30 minutes to obtain a composite solution of PVA and SiO2 aerosol. The SiO2 aerosol has a large specific surface area, can improve the dispersibility of each component in the electrolyte, and has a strong adsorption capacity, reduces the activity of ions, and locally changes the dielectric constant of the aluminum foil surface. After being compounded with PVA, the aerosol can better adhere to the electrode foil, which can not only reduce the corrosion of salts and moisture in the electrolyte, but also enable the electrolyte to ensure the flash voltage while improving the conductivity of the electrolyte.

4. The electrolyte for a universal low-impedance high-voltage aluminum electrolytic capacitor according to claim 1, characterized in that: The functional additives include conventional dehydrogenating agents and hydration-resistant agents. The dehydrogenating agent is one of p-nitrophenol, p-nitrobenzyl alcohol, ammonium p-nitrobenzoate, p-benzoquinone, and m-nitroacetophenone. These substances can react with hydrogen ions generated by the electrolysis reaction, thereby reducing the generation of hydrogen, reducing the internal pressure of the capacitor, and improving the durability of the capacitor. The hydration-resistant agent is one or more of ammonium hypophosphite, phosphorous acid, and dibutyl phosphate. The phosphate radicals in these substances react with aluminum ions to form an aluminum phosphate passivation layer, thereby inhibiting the hydration reaction and reducing the leakage current.

5. A method for preparing an electrolyte for a high-voltage aluminum electrolytic capacitor, characterized in that: The method for preparing the electrolyte for the high-voltage aluminum electrolytic capacitor comprises the following steps: S1, stirring and mixing the solvent, heating to 90-100°C, stirring and maintaining for 10-15 minutes, and then heating to 125-145°C; S2, adding the main solute, solute enhancer and special solute, stirring at a constant temperature for 30-45 minutes, and then cooling the mixed solution to 115-125°C; S3, adding PVA and SiO2 aerosol composite solution thereto, stirring at a constant temperature for 30-45 minutes, and then cooling the mixed solution to 90-100°C; S4, adding a dehydrogenating agent and a water-resistant agent, stirring at a constant temperature for 45 to 60 minutes, and then naturally cooling to room temperature to obtain an aluminum electrolytic capacitor electrolyte.

6. A method for preparing a high voltage aluminum electrolytic capacitor, characterized in that: The following steps are involved: Winding: Winding the anode foil, electrolytic paper, cathode foil and lead wire together to obtain a core package; Impregnation: immersing the core package in the electrolyte for the high-voltage aluminum electrolytic capacitor; Assembly: The impregnated core is packed into the shell, and the positive and negative electrodes are led out, and the damaged oxide film is repaired after aging to form an aluminum electrolytic capacitor.

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