A high-reliability aluminum electrolytic capacitor for industrial power supplies and its preparation method

Abstract

This invention discloses a high-reliability aluminum electrolytic capacitor for industrial power supplies and its preparation method. The preparation method includes riveting, core winding, drying, electrolyte impregnation, encapsulation, and aging. The electrolyte contains 40%–60% solvent, 30%–50% solute, and 3%–10% additives, including monobutyl phosphate, borate, diethyl carbonate, and benzotriazole. The impregnation employs a stepped pressure impregnation method. The aluminum electrolytic capacitor is applied to industrial power supplies. This invention effectively suppresses high-temperature evaporation and gas generation of the electrolyte through the synergistic effect of the electrolyte components; achieves uniform wetting of the core by the electrolyte through stepped pressure impregnation; and significantly improves the breakdown voltage through a composite electrolytic paper system. These three factors work together to achieve long life and high reliability of the capacitor under harsh high-temperature and high-ripple conditions.

Description

Technical Field

[0001] This invention relates to the field of aluminum electrolytic capacitor technology, and more specifically, to a high-reliability aluminum electrolytic capacitor for industrial power supplies and its preparation method. Background Technology

[0002] With the continuous increase in industrial power supply switching frequencies, traditional aluminum electrolytic capacitors exhibit poor high-frequency performance, and their lifespan is limited by electrolyte evaporation and decomposition. Under long-term full-load conditions, their service life cannot meet the requirements of industrial equipment. Under high-frequency operating conditions, the ion mobility inside the electrolyte cannot keep up with the changes in current, causing the equivalent series resistance to spike nonlinearly, and making them prone to drying out and leakage at high temperatures. When industrial power supplies operate under overload in a closed, high-temperature environment, the electrolyte evaporation rate accelerates exponentially, severely affecting the reliability and lifespan of the capacitors.

[0003] Chinese patent CN107256799B discloses an electrolyte for aluminum electrolytic capacitors, which uses diethylamine salt as shown in formula (I) as the main solute, combined with ammonium sebacate, ammonium dodecanoate, and other secondary solutes, as well as additives such as ammonium hypophosphite and p-nitrobenzoic acid, aiming to improve the high-temperature performance of the working electrolyte and extend the high-temperature life of the capacitor. The electrolyte described in this patent showed minimal changes in parameters such as moisture content and conductivity during a high-temperature storage test at 115°C. Capacitors made from this electrolyte, after a life test at 105°C, exhibited a capacity decay rate of approximately 44% to 47% after about 5000 hours. However, this patent primarily addresses the issue of high-temperature storage stability of the electrolyte. The evaporation suppression effect of the electrolyte under harsh conditions such as high temperature and high ripple current still has room for improvement, and it does not involve optimization of the impregnation process or electrolytic paper materials.

[0004] Therefore, there is an urgent need to develop a high-temperature resistant, long-life, and highly reliable aluminum electrolytic capacitor suitable for industrial power supplies, as well as its preparation method. Summary of the Invention

[0005] Therefore, it is necessary to address the above-mentioned technical problems by providing a high-reliability aluminum electrolytic capacitor for industrial power supplies and its preparation method.

[0006] To address the aforementioned technical problems, this invention provides a method for preparing a high-reliability aluminum electrolytic capacitor for industrial power supplies, comprising the following steps: S1 riveting: Rivet the positive electrode conductive foil strip and the negative electrode conductive foil strip to the anode foil and the cathode foil respectively; S2 core package winding: Electrolytic paper is inserted between the anode foil and the cathode foil and wound into a core package; S3 Drying process: The wound core package is baked and dried; S4 Electrolyte Impregnation: The core package from step S3 is immersed in an electrolyte for a stepped pressure impregnation treatment; the electrolyte includes a solvent, a solute, and additives, wherein the solvent accounts for 40% to 60% of the total mass of the electrolyte, the solute accounts for 30% to 50% of the total mass of the electrolyte, and the additives account for 3% to 10% of the total mass of the electrolyte; the additives include monobutyl phosphate, borate, diethyl carbonate, and benzotriazole; S5 Packaging: The core from step S4 is encapsulated in the shell and sealed with a rubber stopper; S6 aging; The aluminum electrolytic capacitor is used in industrial power supplies.

[0007] Furthermore, the solvent is composed of the following components in weight percentage: 40%~60% propylene carbonate, 25%~37% ethylene glycol monobutyl ether, 10%~18% diethylene glycol monomethyl ether, and 1%~5% dimethyl adipate.

[0008] Furthermore, the solute is composed of the following components in mass percentage: ammonium dodecanoate 35%~55%, ammonium isoserbate 25%~42%, ammonium 2-butyloctanoate 8%~15%, and diethylene glycol dibutyl ether 2%~8%.

[0009] Furthermore, the additive is composed of the following components in weight percentage: 38%~58% monobutyl phosphate, 20%~41% borate, 12%~18% diethyl carbonate, and 1%~3% benzotriazole.

[0010] Furthermore, the stepped pressurized impregnation described in step S4 includes the following steps in sequence: P1 stage: pressure is 0.5MPa; P2 stage: pressure is 0.8MPa; P3 stage: pressure is 1.0MPa; P4 stage: pressure is 1.2MPa; P5 stage: pressure is released to 0.1MPa.

[0011] Furthermore, the holding time for stage P1 is 10-15 minutes, the holding time for stage P2 is 15-20 minutes, the holding time for stage P3 is 20-25 minutes, the holding time for stage P4 is 25-30 minutes, and the holding time for stage P5 is 10-15 minutes.

[0012] Furthermore, the electrolytic paper mentioned in step S2 is a composite system electrolytic paper of natural fibers and synthetic fibers, wherein the natural fibers are wood pulp fibers and the synthetic fibers are polyolefin fibers.

[0013] Furthermore, the drying temperature in step S3 is 95~105℃, and the drying time is 1~2 hours.

[0014] Furthermore, the aging process described in step S6 specifically involves: maintaining at room temperature for 2 hours, then hot charging at 95°C for 4 hours, followed by cold charging at room temperature for 1 hour; the initial aging voltage is applied in a stepwise manner from low to high, namely 140~160V, 240~260V, 340~360V, 440~460V, 490~510V, and 520~540V, with each voltage stage lasting 25~60 minutes, the hot charging voltage being 510~530V, and the subsequent cold charging voltage being 510~530V.

[0015] The present invention also provides a high-reliability aluminum electrolytic capacitor for industrial power supplies, which is prepared by the above-described preparation method.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention discloses a high-reliability aluminum electrolytic capacitor for industrial power supplies and its preparation method. By adding monobutyl phosphate, borate, diethyl carbonate, and benzotriazole to the electrolyte, and combining this with a stepped pressurized impregnation process, the technical problems of traditional electrolytes being prone to volatilization and gas generation at high temperatures, leading to capacitor failure, are solved. Monobutyl phosphate and borate synergistically form a composite dielectric layer with a gradient refractive index on the oxide film surface, effectively improving the flashover voltage; benzotriazole and diethyl carbonate synergistically block the vicious cycle of gas generation and corrosion; the stepped pressurized impregnation process, through a step-by-step pressurization, allows the electrolyte to gradually penetrate from the surface to the micropores of the core package, achieving gas venting without dead zones and uniform distribution, significantly reducing ESR batch dispersion. This invention also comprehensively improves the reliability of the capacitor through the synergistic optimization of the solvent and solute systems, the composite electrolytic paper system, and the mutual coordination of the above-mentioned technical elements. The solvent employs a multi-component synergistic approach to reduce viscosity and improve the high-frequency ion mobility; the solute achieves high flash voltage and low evaporation rate through the synergistic effect of the main solute and auxiliary solute; the electrolytic paper uses a composite system with natural fibers as the matrix and synthetic fibers as the reinforcing skeleton, which significantly improves the breakdown voltage.

[0017] This invention, through the synergistic combination of electrolyte formulation, composite electrolytic paper, and stepped impregnation process, can effectively reduce internal heat generation and delay electrolyte drying, enabling capacitors to have long life and high reliability under harsh conditions of high temperature and high ripple, thus meeting the requirements of industrial power supplies for higher efficiency, higher power density, and more stringent environments. Detailed Implementation

[0018] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0019] Example 1

[0020] This embodiment provides a method for preparing a high-reliability aluminum electrolytic capacitor for industrial power supplies, specifically including the following steps: S1 Riveting: The positive electrode conductive foil strip and the negative electrode conductive foil strip are riveted to the anode foil and the cathode foil respectively; the number of riveting welds is 14, the weld size is 3.0mm long × 0.8mm wide, and the spacing is 2mm.

[0021] S2 Core Packaging Winding: Electrolytic paper is inserted between the anode foil and the cathode foil and wound into a core pack; the electrolytic paper is a composite system of natural fiber and synthetic fiber, wherein the natural fiber is wood pulp fiber and the synthetic fiber is polyolefin fiber.

[0022] S3 Drying process: The wound core package is baked and dried; the drying temperature is 95°C and the drying time is 2 hours.

[0023] S4 Electrolyte Impregnation: The core package from step S3 is immersed in the electrolyte for impregnation treatment; the impregnation adopts a stepped pressurization impregnation method, with the target pressure set at 1.2 MPa. The specific stepped pressurization method is as follows: Phase P1: Pressure 0.5 MPa, holding time 10 minutes; Phase P2: Pressure 0.8 MPa, held for 15 minutes; Phase P3: Pressure 1.0 MPa, holding time 20 minutes; Phase P4: Pressure 1.2 MPa, holding time 25 minutes; P5 stage: Depressurize to 0.1 MPa, then maintain for 10 minutes; The electrolyte is composed of the following components by mass percentage: The solvent accounts for 50% of the total mass of the electrolyte and is composed of 50% propylene carbonate, 30% ethylene glycol monobutyl ether, 15% diethylene glycol monomethyl ether, and 5% dimethyl adipate. The solute accounts for 42% of the total mass of the electrolyte and is composed of 50% ammonium dodecanoate, 32% ammonium isoserbate, 12% ammonium 2-butyloctanoate, and 6% diethylene glycol dibutyl ether. The additive accounts for 8% of the total mass of the electrolyte and is composed of 55% monobutyl phosphate, 28% borate, 15% diethyl carbonate, and 2% benzotriazole. The borate is selected from at least one of ammonium borate and ammonium pentaborate. In this embodiment, the borate is ammonium borate.

[0024] S5 Packaging: The core from step S4 is encapsulated in a shell and sealed with a rubber stopper; the cover plate of the package has a thickness of 3.0 mm.

[0025] S6 Aging: The aging process is as follows: 2 hours at room temperature, followed by hot charging at 95℃ for 4 hours, and then cold charging at room temperature for 1 hour. The initial aging voltage is applied in a stepwise manner from low to high, namely 150V, 250V, 350V, 450V, 500V, and 530V. Each voltage stage is maintained for 30 minutes. The hot charging voltage is 520V, and the subsequent cold charging voltage is 520V.

[0026] Example 2

[0027] This embodiment provides a method for preparing a high-reliability aluminum electrolytic capacitor for industrial power supplies, which differs from Embodiment 1 in that: S3 drying treatment: drying temperature is 105℃, drying time is 1 hour.

[0028] S4 electrolyte impregnation: In the stepped pressurization scheme, P1 is held for 15 minutes, P2 for 20 minutes, P3 for 25 minutes, P4 for 30 minutes, and P5 for 15 minutes. The electrolyte is composed of the following components by mass percentage: The solvent accounts for 40% of the total mass of the electrolyte and is composed of 40% propylene carbonate, 37% ethylene glycol monobutyl ether, 18% diethylene glycol monomethyl ether, and 5% dimethyl adipate. The solute accounts for 50% of the total mass of the electrolyte and is composed of 35% ammonium dodecanoate, 42% ammonium isoserbate, 15% ammonium 2-butyloctanoate, and 8% diethylene glycol dibutyl ether. The additive accounts for 10% of the total mass of the electrolyte and consists of 38% monobutyl phosphate, 41% borate, 18% diethyl carbonate, and 3% benzotriazole.

[0029] S6 Aging: The aging process is as follows: 2 hours at room temperature, followed by hot charging at 95℃ for 4 hours, and then cold charging at room temperature for 1 hour. The initial aging voltage is applied in a stepwise manner from low to high, namely 160V, 260V, 360V, 460V, 510V, and 540V. Each voltage stage is maintained for 25 minutes. The hot charging voltage is 530V, and the subsequent cold charging voltage is 530V.

[0030] Example 3

[0031] This embodiment provides a method for preparing a high-reliability aluminum electrolytic capacitor for industrial power supplies, which differs from Embodiment 1 in that: S3 drying treatment: drying temperature is 100℃, drying time is 1.5 hours.

[0032] S4 Electrolyte Impregnation: In the stepped pressurization scheme, P1 is held for 12 minutes, P2 for 18 minutes, P3 for 22 minutes, P4 for 28 minutes, and P5 for 12 minutes; the electrolyte is composed of the following components by mass percentage: The solvent accounts for 60% of the total mass of the electrolyte and is composed of 60% propylene carbonate, 25% ethylene glycol monobutyl ether, 10% diethylene glycol monomethyl ether, and 5% dimethyl adipate. The solute accounts for 30% of the total mass of the electrolyte and is composed of 55% ammonium dodecanoate, 25% ammonium isoserbate, 12% ammonium 2-butyloctanoate, and 8% diethylene glycol dibutyl ether. The additive accounts for 10% of the total mass of the electrolyte and consists of 58% monobutyl phosphate, 21% borate, 18% diethyl carbonate, and 3% benzotriazole.

[0033] S6 Aging: The aging process is as follows: 2 hours at room temperature, followed by hot charging at 95°C for 4 hours, and then cold charging at room temperature for 1 hour. The initial aging voltage is applied in a stepwise manner from low to high, namely 140V, 240V, 340V, 440V, 490V, and 520V. Each voltage stage is maintained for 50 minutes. The hot charging voltage is 510V, and the subsequent cold charging voltage is 510V.

[0034] Example 4

[0035] This embodiment provides a method for preparing a high-reliability aluminum electrolytic capacitor for industrial power supplies, which differs from Embodiment 1 in that: S4 Electrolyte Impregnation: The electrolyte consists of the following components by mass percentage: The solvent accounts for 52% of the total mass of the electrolyte and is composed of 49% propylene carbonate, 35% ethylene glycol monobutyl ether, 15% diethylene glycol monomethyl ether, and 1% dimethyl adipate. The solute accounts for 45% of the total mass of the electrolyte and is composed of 50% ammonium dodecanoate, 33% ammonium isoserbate, 15% ammonium 2-butyloctanoate, and 2% diethylene glycol dibutyl ether. The additive accounts for 3% of the total mass of the electrolyte and consists of 58% monobutyl phosphate, 29% borate, 12% diethyl carbonate, and 1% benzotriazole.

[0036] Comparative Example 1 This comparative example provides a method for preparing an aluminum electrolytic capacitor, which differs from Example 1 only in that: in the electrolyte of step S4, ammonium isodecanate is not added as a solute component, and the mass fraction of ammonium isodecanate is distributed according to the original proportions of the remaining solute components ammonium dodecanoate, ammonium 2-butyloctanoate, and diethylene glycol dibutyl ether; the remaining steps and parameters are the same as in Example 1.

[0037] Comparative Example 2 This comparative example provides a method for preparing an aluminum electrolytic capacitor, which differs from Example 1 only in that: in the electrolyte of step S4, 2-butyloctanoic acid ammonium is not added as a solute component, and the mass fraction of 2-butyloctanoic acid ammonium is distributed according to the original proportion of the remaining solute components ammonium dodecanoate, ammonium isoserbate and diethylene glycol dibutyl ether; the remaining steps and parameters are the same as in Example 1.

[0038] Comparative Example 3 This comparative example provides a method for preparing an aluminum electrolytic capacitor, which differs from Example 1 only in that: in the electrolyte of step S4, monobutyl phosphate is not added as an additive component, and the mass fraction of monobutyl phosphate is allocated according to the original proportions of the remaining additive components borate, diethyl carbonate, and benzotriazole; the remaining steps and parameters are the same as in Example 1.

[0039] Comparative Example 4 This comparative example provides a method for preparing an aluminum electrolytic capacitor, which differs from Example 1 only in that: in the electrolyte of step S4, benzotriazole is not added as an additive component, and the mass fraction of benzotriazole is allocated according to the original proportions of the remaining additive components monobutyl phosphate, borate, and diethyl carbonate; the remaining steps and parameters are the same as in Example 1.

[0040] Comparative Example 5 This comparative example provides a method for preparing an aluminum electrolytic capacitor, which differs from Example 1 only in that: the impregnation in step S4 adopts the traditional single-pressure impregnation process, that is, maintaining a pressure of 1.2 MPa for 90 minutes and then depressurizing to atmospheric pressure, instead of adopting the stepped pressurization scheme of Example 1; the remaining steps and parameters are the same as those in Example 1.

[0041] Comparative Example 6 This comparative example provides a method for preparing an aluminum electrolytic capacitor, which differs from Example 1 only in that: in the impregnation process of step S4, the pressure of stage P4 is changed to 0.9 MPa, and the holding time is the same as in Example 1; the remaining steps and parameters are the same as in Example 1.

[0042] Comparative Example 7 This comparative example provides a method for preparing an aluminum electrolytic capacitor, which differs from Example 1 only in that: in the impregnation process of step S4, the pressure of stage P4 is changed to 1.5 MPa, and the holding time is the same as in Example 1; the remaining steps and parameters are the same as in Example 1.

[0043] Comparative Example 8 This comparative example provides a method for preparing an aluminum electrolytic capacitor, which differs from Example 1 only in that: the electrolytic paper in step S2 uses conventional pure wood pulp fiber electrolytic paper instead of the composite system electrolytic paper in Example 1 with natural fiber as the matrix and synthetic fiber as the reinforcing skeleton; the remaining steps and parameters are the same as in Example 1.

[0044] Verification Example The aluminum electrolytic capacitor samples prepared in Examples 1-4 and Comparative Examples 1-8 were subjected to the following performance tests, with 50 samples in each group.

[0045] (1) High temperature load life test: The capacitor was placed in a constant temperature chamber at 105℃, the rated voltage was applied, and it was taken out after 5000 hours. The capacitance decay rate, DF growth rate, ESR growth rate, leakage current change rate were tested, and the air expansion rate and appearance were recorded. The average value was taken after testing 50 samples in each group. The air expansion rate was calculated as the percentage of samples that showed air expansion. The results are shown in Table 1.

[0046] (2) Electrolytic paper breakdown voltage test: Under the environment of temperature 23±2℃ and relative humidity 50±5%RH, the electrolytic paper was placed between spherical copper electrodes using a withstand voltage tester, and the voltage was increased at a rate of 100V / s until breakdown. The breakdown voltage value was recorded, and the results are shown in Table 2.

[0047] (3) ESR consistency test: Under the condition of temperature 20±2℃, the ESR values ​​of 50 capacitors in each group were tested at a frequency of 100kHz using an LCR bridge. The dispersion rate ((maximum value - minimum value) / average value × 100%) and CPK value of the 50 samples were calculated. The average ESR value is the arithmetic mean. The results are shown in Table 3.

[0048] (4) High ripple temperature rise test: 10 samples were tested in each group. A small hole (Φ≈1mm) was drilled in the center of the capacitor explosion-proof valve. A K-type miniature thermocouple was inserted into the capacitor body along the axis to the depth of the core package geometric center (about 40% to 50% of the capacitor length). The opening was sealed with high-temperature resistant sealant (such as epoxy resin / silicone rubber) to ensure airtightness. The thermocouple lead was led out from the terminal side and connected to the data acquisition instrument to record the core package temperature rise. The results are shown in Table 4.

[0049] Table 1. High-temperature load life test results (105℃, 5000h)

[0050] Table 1 shows that after 5000 hours of high-temperature load testing, the capacity decay rate, DF growth rate, ESR growth rate, and leakage current change rate of Examples 1-4 were significantly lower than those of the respective comparative examples, the gas expansion rate was 0%, and there were no visible abnormalities. The leakage current change rate of Examples 1-4 was negative, indicating that the oxide film was effectively repaired and maintained during the high-temperature aging process.

[0051] Comparative Example 1, lacking ammonium isoserbate, exhibited a significantly higher capacity decay rate than the Example. The high concentration of ammonium isoserbate alters the solvation structure of the electrolyte system through a high-concentration co-solute effect. The interaction between its molecules and solvent molecules preferentially occupies the solvation layer, thereby inhibiting the association and aggregation between ammonium dodecanoate molecules and delaying its saturation precipitation point. The absence of this component significantly reduces solute solubility, accelerating solute precipitation and failure at high temperatures.

[0052] Comparative Example 2, lacking ammonium 2-butyloctanoate, exhibited significantly higher capacity decay and ESR growth rates compared to the Example, along with a markedly increased gas expansion rate. This is because the branched structure of ammonium 2-butyloctanoate can fill the gaps between solute molecules, forming a volatile shielding network at the gas-liquid interface together with diethylene glycol dibutyl ether. The absence of this component significantly accelerates electrolyte evaporation, leading to rapid capacity decay and gas expansion.

[0053] Comparative Example 3, lacking monobutyl phosphate, also exhibited a higher capacity decay rate than the Example. This is because monobutyl phosphate and borate synergistically form a composite dielectric layer with a gradient refractive index on the oxide film surface. The absence of this component significantly reduces the flashover voltage, making the oxide film more susceptible to breakdown.

[0054] Comparative Example 4 showed a significantly increased gas expansion rate due to the absence of benzotriazole. This is because benzotriazole, as a metal ion chelating agent, can adsorb onto the surface of the cathode aluminum foil to form a dense protective film, synergistically blocking the vicious cycle of gas production and corrosion with diethyl carbonate. Without this component, the hydrogen evolution reaction at the cathode is difficult to inhibit.

[0055] The capacity decay rates of Comparative Examples 5-8 were all higher than those of the Example, indicating that the stepped impregnation process, optimized pressure parameters, and composite electrolytic paper all have a positive effect on improving the service life at high temperatures.

[0056] Table 2. Electrolytic paper breakdown voltage test results

[0057] As shown in Table 2, the breakdown voltages of the composite electrolytic paper used in Examples 1-4 and Comparative Examples 1-7 were significantly higher than those in Comparative Example 8, with significantly smaller standard deviations. Comparative Example 8, using conventional pure wood pulp fiber electrolytic paper, had a significantly lower breakdown voltage. The composite electrolytic paper of this invention significantly improved the breakdown voltage and uniformity.

[0058] Table 3 ESR conformance test results (100kHz, n=50)

[0059] As shown in Table 3, Examples 1-4 and Comparative Examples 1-4 and 6-8, employing a stepped pressure impregnation process, exhibited significantly lower ESR dispersion and significantly higher CPK values. Comparative Example 5, using a traditional single-pressure impregnation process, showed a significantly higher ESR dispersion and significantly lower CPK values. Comparative Example 6 adjusted the pressure in stage P4 to 0.9 MPa (below 1.2 MPa), and Comparative Example 7 adjusted the pressure in stage P4 to 1.5 MPa (above 1.2 MPa); both showed lower CPK values ​​than Examples 1-4.

[0060] Traditional single-pressure impregnation can only extract large air bubbles. The gas inside the micropores is compressed under high pressure instead of being expelled. After the pressure is released, the gas re-expands to form cavitation, resulting in insufficient electrolyte wetting in some areas and the appearance of local dry areas, which manifests as a large ESR dispersion rate and a low CPK value.

[0061] This invention employs a step-by-step approach, applying different pressures from the surface inwards: At 0.5 MPa, the electrolyte gently enters the large pores through capillary action and expels air, preventing excessive pressure from causing gas blockage and forming gas embolisms; at 0.8 MPa, the electrolyte is driven into the medium-sized secondary pores, further expelling gas from the branch pores; at 1.0 MPa, the more viscous electrolyte is forced into the smallest micropores and cracks, ensuring close contact between the electrolyte and the alumina dielectric layer; at 1.2 MPa, the most difficult-to-wet nanoscale pores and dead zones are saturated, promoting the full adsorption and pre-reaction of additives on the oxide film surface, forming a stable interface layer; finally, the pressure is released to 0.1 MPa to prevent a sudden drop in pressure from drawing out the already penetrated electrolyte or generating microbubbles. In the stepped pressurization scheme proposed in this invention, the pressure parameter of 1.2 MPa in the P4 stage is particularly critical: when the pressure is below 1.2 MPa, the nanoscale pores are difficult to completely fill, resulting in incomplete wetting; when the pressure is above 1.2 MPa, the oxide film and electrode structure may be damaged. Therefore, by adopting a stepped pressurization impregnation process with a P4 stage pressure of 1.2 MPa, the electrolyte can be physically forced to efficiently and thoroughly penetrate into every micropore of the core package, achieving venting without dead zones and making the electrolyte distribution extremely uniform, thereby obtaining extremely low ESR batch dispersion.

[0062] Table 4 High ripple temperature rise test (center temperature rise △T≦5℃ is the standard)

[0063] As shown in Table 4, the allowable ripple current for Examples 1-4 was higher than that for the comparative examples, while the center temperature rise was significantly lower. Comparative Example 2, lacking ammonium 2-butyloctanoate, exhibited a significantly lower allowable ripple current and a significantly higher center temperature rise, indicating that the volatile shielding network formed by ammonium 2-butyloctanoate and diethylene glycol dibutyl ether at the gas-liquid interface plays a crucial role in suppressing high-temperature evaporation of the electrolyte. Comparative Examples 1, 3, and 4 all had lower allowable ripple currents than the examples, but higher center temperature rises, demonstrating that the composite solute system and the synergistic additive system composed of monobutyl phosphate, borate, diethyl carbonate, and benzotriazole are indispensable. Comparative Examples 5 to 8 all had lower allowable ripple currents than the examples, but higher center temperature rises, indicating that the stepped impregnation process, optimized pressure parameters, and composite electrolytic paper all play important roles in improving the high-temperature, high-ripple resistance of the capacitors. Meanwhile, the center temperature rise of the embodiment was significantly lower than that of the comparative examples, indicating that the present invention can effectively reduce internal heat generation and improve capacitor reliability under dynamic operating conditions through the synergistic effect of electrolyte formulation, composite electrolytic paper and stepped impregnation process.

[0064] The above results show that the present invention significantly extends the service life of the capacitor at 105°C through the synergistic effect of the key components in the electrolyte system, greatly improves the breakdown voltage and uniformity through the composite system electrolytic paper, and achieves the technical effect of extremely low ESR batch dispersion through the stepped pressure impregnation process and optimized pressure parameters. The three work together to achieve long service life and high reliability of the capacitor under harsh conditions of high temperature and high ripple.

[0065] Obviously, the embodiments described above are merely some embodiments of this application, not all embodiments, and do not limit the patent scope of this application. This application can be implemented in many different forms; on the contrary, the purpose of providing these embodiments is to make the disclosure of this application more thorough and comprehensive. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing specific embodiments, or make equivalent substitutions for some of the technical features. Any equivalent structures made using the content of this application's specification, directly or indirectly applied to other related technical fields, are similarly within the patent protection scope of this application.

Claims

1. A method for preparing a high-reliability aluminum electrolytic capacitor for industrial power supplies, characterized in that, Includes the following steps: S1 riveting: Rivet the positive electrode conductive foil strip and the negative electrode conductive foil strip to the anode foil and the cathode foil respectively; S2 core package winding: Electrolytic paper is inserted between the anode foil and the cathode foil and wound into a core package; S3 Drying process: The wound core package is baked and dried; S4 Electrolyte Impregnation: The core package from step S3 is immersed in an electrolyte for a stepped pressure impregnation treatment; the electrolyte includes a solvent, a solute, and additives, wherein the solvent accounts for 40% to 60% of the total mass of the electrolyte, the solute accounts for 30% to 50% of the total mass of the electrolyte, and the additives account for 3% to 10% of the total mass of the electrolyte; the additives include monobutyl phosphate, borate, diethyl carbonate, and benzotriazole; S5 Packaging: The core from step S4 is encapsulated in the shell and sealed with a rubber stopper; S6 aging; The aluminum electrolytic capacitor is used in industrial power supplies.

2. The preparation method according to claim 1, characterized in that, The solvent is composed of the following components by mass percentage: 40%~60% propylene carbonate, 25%~37% ethylene glycol monobutyl ether, 10%~18% diethylene glycol monomethyl ether, and 1%~5% dimethyl adipate.

3. The preparation method according to claim 1, characterized in that, The solute is composed of the following components by mass percentage: ammonium dodecanoate 35%~55%, ammonium isoserbate 25%~42%, ammonium 2-butyloctanoate 8%~15%, and diethylene glycol dibutyl ether 2%~8%.

4. The preparation method according to claim 1, characterized in that, The additive is composed of the following components by mass percentage: 38%~58% monobutyl phosphate, 20%~41% borate, 12%~18% diethyl carbonate, and 1%~3% benzotriazole.

5. The preparation method according to claim 1, characterized in that, The stepped pressurized impregnation process in step S4 includes the following steps in sequence: P1 stage: pressure is 0.5MPa; P2 stage: pressure is 0.8MPa; P3 stage: pressure is 1.0MPa; P4 stage: pressure is 1.2MPa; P5 stage: pressure is released to 0.1MPa.

6. The preparation method according to claim 5, characterized in that, The holding time for stage P1 is 10-15 minutes, the holding time for stage P2 is 15-20 minutes, the holding time for stage P3 is 20-25 minutes, the holding time for stage P4 is 25-30 minutes, and the holding time for stage P5 is 10-15 minutes.

7. The preparation method according to claim 1, characterized in that, The electrolytic paper mentioned in step S2 is a composite system electrolytic paper of natural fiber and synthetic fiber, wherein the natural fiber is wood pulp fiber and the synthetic fiber is polyolefin fiber.

8. The preparation method according to claim 1, characterized in that, The drying temperature in step S3 is 95~105℃, and the drying time is 1~2 hours.

9. The preparation method according to claim 1, characterized in that, The aging process described in step S6 is as follows: maintaining at room temperature for 2 hours, then hot-charging at 95°C for 4 hours, followed by cold-charging at room temperature for 1 hour; the initial aging voltage is applied in a stepwise manner from low to high, namely 140~160V, 240~260V, 340~360V, 440~460V, 490~510V, and 520~540V, with each voltage stage lasting 25~60 minutes, the hot-charging voltage being 510~530V, and the subsequent cold-charging voltage being 510~530V.

10. A high-reliability aluminum electrolytic capacitor for industrial power supplies, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 9.

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