High-stability aluminum electrolytic capacitor and preparation method thereof

Abstract

The invention discloses a high-stability aluminum electrolytic capacitor and a preparation method thereof. The method comprises the following steps: riveting; winding the element; performing drying treatment; carrying out electrolyte impregnation treatment; packaging and aging; wherein the electrolyte is composed of the following components in percentage by mass: 45-65% of a solvent, 25-45% of a solute and 5-10% of an additive; the solvent contains ethylene glycol monomethyl ether and 1, 10-dodecanedioic acid. According to the high-stability aluminum electrolytic capacitor provided by the invention, through the synergistic cooperation of the solvent, the solute and the additive in the electrolyte, the capacitor can still keep stable electrochemical performance under an extreme temperature condition, the working temperature range can reach-40 DEG C to 105 DEG C, and the high-stability aluminum electrolytic capacitor is particularly suitable for application requirements in extreme temperature environments such as new energy storage.

Description

Technical Field

[0001] This invention relates to the field of aluminum electrolytic capacitor technology, and more specifically, to a highly stable aluminum electrolytic capacitor and its preparation method. Background Technology

[0002] Driven by the rapid development of the new energy industry, aluminum electrolytic capacitors, as key components of energy storage systems, face significant technical challenges. With the widespread adoption of renewable energy sources such as photovoltaics and wind power, as well as electric vehicles and smart grids, energy storage systems place higher demands on capacitor performance. They must not only withstand operating voltages above 500V and extreme temperatures ranging from -40℃ to +105℃, but also possess excellent stability and reliability. However, traditional aluminum electrolytic capacitors suffer from problems such as electrolyte drying at high temperatures, capacity decay, decreased ion conductivity at low temperatures, and increased ESR. When dealing with complex operating conditions such as grid fluctuations and instantaneous overvoltage, they are prone to increased dielectric losses, increased leakage current, and even breakdown failure, severely restricting their application in high-end energy storage fields.

[0003] While existing technologies, such as the ultra-wide temperature and low-pressure electrolyte disclosed in Chinese invention patent CN107103998B, have expanded the operating temperature range to some extent, they still have significant shortcomings in dealing with harsh conditions such as extreme temperature fluctuations and short-term overvoltage. Particularly at high temperatures, electrolyte evaporation and chemical decomposition accelerate capacitor aging, leading to capacity decay and increased ESR; conversely, at low temperatures, the sharp increase in electrolyte viscosity significantly reduces capacitor charging and discharging efficiency. These issues directly affect the long-term operational stability of energy storage systems in extremely cold and high-temperature environments, increasing system maintenance costs and failure risks.

[0004] Therefore, there is an urgent need to provide a new type of aluminum electrolytic capacitor with wide temperature range stability, high voltage resistance, and long lifespan, suitable for new energy storage. Summary of the Invention

[0005] Therefore, in order to address the above-mentioned technical problems, this invention provides a highly stable aluminum electrolytic capacitor and its preparation method.

[0006] To address the aforementioned technical problems, this invention proposes a method for preparing a highly stable aluminum electrolytic capacitor, comprising the following steps: riveting; element winding; drying treatment; electrolyte impregnation treatment; and encapsulation aging; wherein the electrolyte is composed of the following components by mass percentage: solvent 45-65%, solute 25-45%, and additives 5-10%; the solvent contains ethylene glycol methyl ether and 1,10-dodecanoic acid.

[0007] Furthermore, the electrolytic paper adopts a double-layer structure, with the inner layer having a thickness of 25–35 μm and the outer layer having a thickness of 35–45 μm.

[0008] Furthermore, the solvent is composed of the following components in mass percentage: 42-60% ethylene glycol methyl ether, 25-35% 1,10-dodecanoic acid, 10-15% diethylene glycol monobutyl ether, and 2-8% dimethyl carbonate.

[0009] Furthermore, the solute is composed of the following components in mass percentage: ammonium acetate 35-55%, ammonium benzoate 25-40%, triethylamine 10-18%, ammonium metasilicate 5-10%, and diethylene glycol dibutyl ether 2-6%.

[0010] Furthermore, the additive is composed of the following components in mass percentage: 35-50% boron nitrate, 30-42% 3,5-dihydroxybenzoic acid, 12-18% tributyl phosphate, 5-12% tripropylamine, and 1-5% tetramethylammonium hydroxide.

[0011] Furthermore, the impregnation treatment involves completely immersing the dried seed in an electrolyte solution and impregnating it at 60–70°C for 4–6 hours.

[0012] Furthermore, the electrolyte is prepared at 95–100°C and with a pH value maintained at 5.5–6.8.

[0013] Furthermore, the riveting pressure is controlled at 125~175N±5%, the rivet thickness is 6.0~6.8mm, the contact resistance is ≤1.0mΩ and the contact area is ≥90%.

[0014] Furthermore, the inner layer structure of the electrolytic paper is insulating wood pulp fiber, with a porosity of 42-48%, and the outer layer structure of the electrolytic paper is Tencel fiber, with a porosity of 32-38%.

[0015] The second aspect of this invention provides a highly stable aluminum electrolytic capacitor with a capacitance retention rate of ≥85% in a temperature range of -40℃ to 105℃.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] This invention provides a highly stable aluminum electrolytic capacitor that achieves excellent performance through a specific electrolyte formulation and synergistic structural design. The synergistic effect of 1,10-dodecanoic acid and ethylene glycol methyl ether in the electrolyte significantly improves the stability and ion conductivity of the electrolyte over a wide temperature range (-40℃ to 105℃). Simultaneously, the synergistic film-forming effect of ammonium metasilicate hydrolysis products and the electrode surface effectively enhances the capacitor's high-temperature tolerance and long-term reliability. Furthermore, the BO bond complex structure formed by boron nitronitride and 3,5-dihydroxybenzoic acid synergistically suppresses side reactions in the electrolyte system, while the gradient pore structure design of the bilayer composite electrolytic paper synergistically optimizes electrolyte wettability and ion migration channels. Through the synergistic effect of the solvent, solute, and additives in the electrolyte, the capacitor maintains stable electrochemical performance over a wide temperature range of -40℃ to +105℃, making it particularly suitable for applications in extreme temperature environments such as new energy storage. 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] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below.

[0020] Example 1

[0021] This embodiment provides a method for preparing a highly stable aluminum electrolytic capacitor, which includes the following steps:

[0022] S1. Riveting: Rivet the positive electrode conductive foil strip and the negative electrode conductive foil strip to the anode foil and cathode foil respectively; adopt a double conductive foil strip structure, and pad the negative electrode foil rivet with electrolytic paper;

[0023] S2. Element winding: Electrolytic paper is inserted between the anode foil and the cathode foil and wound into an element; the electrolytic paper adopts a double-layer structure, the inner layer has a thickness of 30μm and a porosity of 45%, and the outer layer has a thickness of 40μm and a porosity of 35%; further, the inner layer is insulating wood pulp fiber, and the outer layer is Tencel fiber.

[0024] S3. Drying treatment: The rolled rice grains are baked and dried.

[0025] S4. Electrolyte impregnation: The dried seeds are completely immersed in the electrolyte and impregnated at 65°C for 5 hours.

[0026] S5. Packaging step: Insert the element from step S4 into the shell and seal it with a rubber stopper;

[0027] The riveting process employs an automatic riveting machine with precise pressure control within the range of 150N±5%, and a laser thickness gauge monitors the rivet thickness in real time (6.4±0.1mm). The punch is equipped with a ±0.5mm self-alignment mechanism. After riveting, the contact resistance is tested to be ≤1.0mΩ and the contact area is ≥90%.

[0028] S6, Aging;

[0029] The electrolyte is composed of the following components by mass percentage: solvent 55%, solute 38%, and additives 7%;

[0030] The solvent is composed of the following components in mass percentage: 50% ethylene glycol methyl ether, 30% 1,10-dodecanoic acid, 12% diethylene glycol monobutyl ether, and 8% dimethyl carbonate;

[0031] The solute is composed of the following components by mass percentage: ammonium acetate 40%, ammonium benzoate 32%, triethylamine 15%, ammonium metasilicate 8%, and diethylene glycol dibutyl ether 5%.

[0032] The additive is composed of the following components by weight percentage: 40% boron nitrate, 35% 3,5-dihydroxybenzoic acid, 15% tributyl phosphate, 7% tripropylamine, and 3% tetramethylammonium hydroxide.

[0033] The electrolyte is prepared at 98°C and pH 6 to ensure that the solute is fully dissolved and reacted completely, so that ammonium metasilicate forms a dense protective film layer, while maintaining the stability of the electrolyte and preventing silica gelation and corrosion of the aluminum foil.

[0034] Ten aluminum electrolytic capacitors prepared in Example 1 were subjected to performance tests, including: high-temperature load test (105°C, 5000 hours), thermal shock cycle test (-40°C for 30 minutes / 105°C for 30 minutes, 5 cycles), temperature characteristic test (-40°C for 2 hours), and stepped short-time overvoltage test (initial voltage 1.2 times the rated voltage, increasing by 10V in each stage after 1 minute of charging until the capacitor opens). These tests comprehensively evaluated the high-temperature stability, temperature adaptability, and withstand voltage reliability of the capacitors. The test results of Example 1 are shown in Table 1 below. In this embodiment, all examples and comparative examples used the same test methods for performance evaluation.

[0035] Table 1. Performance test results of the sample in Example 1

[0036]

[0037] Example 2

[0038] This embodiment provides a method for preparing a highly stable aluminum electrolytic capacitor, which differs from Embodiment 1 in that:

[0039] The electrolytic paper described in step S2 has a double-layer structure, with the inner layer having a thickness of 35 μm and a porosity of 42%, and the outer layer having a thickness of 45 μm and a porosity of 32%.

[0040] Step S4 Electrolyte impregnation: The dried seed is completely immersed in the electrolyte and impregnated at 60°C for 6 hours;

[0041] The riveting process employs an automatic riveting machine with precise pressure control within the range of 175N±5%, and a laser thickness gauge monitors the rivet thickness in real time (6.8±0.1mm). After riveting, the contact resistance is measured to be ≤1.0mΩ and the contact area is ≥90%.

[0042] The electrolyte is composed of the following components by mass percentage: solvent 45%, solute 45%, and additives 10%.

[0043] The solvent is composed of the following components in mass percentage: 42% ethylene glycol methyl ether, 35% 1,10-dodecanoic acid, 15% diethylene glycol monobutyl ether, and 8% dimethyl carbonate;

[0044] The solute is composed of the following components by mass percentage: ammonium acetate 35%, ammonium benzoate 40%, triethylamine 18%, ammonium metasilicate 5%, and diethylene glycol dibutyl ether 2%.

[0045] The additive is composed of the following components by mass percentage: 35% boron nitrate, 42% 3,5-dihydroxybenzoic acid, 12% tributyl phosphate, 8% tripropylamine, and 3% tetramethylammonium hydroxide.

[0046] The electrolyte was prepared at 95°C and with the pH maintained at 5.5.

[0047] The aluminum electrolytic capacitor prepared in Example 2 was subjected to performance testing, and the test results are shown in Table 2 below.

[0048] Table 2. Performance test results of the sample in Example 2

[0049]

[0050] Example 3

[0051] This embodiment provides a method for preparing a highly stable aluminum electrolytic capacitor, which differs from Embodiment 1 in that: the electrolytic paper in step S2 adopts a double-layer structure, with the inner layer having a thickness of 25 μm and a porosity of 48%, and the outer layer having a thickness of 35 μm and a porosity of 38%.

[0052] Step S4 Electrolyte impregnation: The dried seed is completely immersed in the electrolyte and impregnated at 70°C for 4 hours.

[0053] The riveting process employs an automatic riveting machine with precise pressure control within the range of 125N±5%, and a laser thickness gauge monitors the rivet thickness in real time (6.0±0.1mm). After riveting, the contact resistance is measured to be ≤1.0mΩ and the contact area is ≥90%.

[0054] The electrolyte is composed of the following components by mass percentage: solvent 65%, solute 25%, and additives 10%.

[0055] The solvent is composed of the following components by mass percentage: 60% ethylene glycol methyl ether, 25% 1,10-dodecanoic acid, 10% diethylene glycol monobutyl ether, and 5% dimethyl carbonate.

[0056] The solute is composed of the following components by mass percentage: ammonium acetate 55%, ammonium benzoate 25%, triethylamine 10%, ammonium metasilicate 8%, and diethylene glycol dibutyl ether 2%.

[0057] The additive is composed of the following components by mass percentage: 50% boron nitrate, 30% 3,5-dihydroxybenzoic acid, 14% tributyl phosphate, 5% tripropylamine, and 1% tetramethylammonium hydroxide.

[0058] The electrolyte was prepared at 100°C and with the pH maintained at 6.8.

[0059] The aluminum electrolytic capacitor prepared in Example 3 was subjected to performance testing, and the test results are shown in Table 3 below.

[0060] Table 3. Performance test results of the sample in Example 3

[0061]

[0062] Example 4

[0063] This embodiment provides a method for preparing a highly stable aluminum electrolytic capacitor, which differs from Embodiment 1 in that:

[0064] The electrolyte is composed of the following components by mass percentage: solvent 60%, solute 35%, and additives 5%;

[0065] The solvent is composed of the following components by mass percentage: 55% ethylene glycol methyl ether, 30% 1,10-dodecanoic acid, 13% diethylene glycol monobutyl ether, and 2% dimethyl carbonate;

[0066] The solute is composed of the following components by mass percentage: ammonium acetate 42%, ammonium benzoate 30%, triethylamine 13%, ammonium metasilicate 10%, and diethylene glycol dibutyl ether 6%.

[0067] The additive is composed of the following components by weight percentage: 35% boron nitronitrazine, 30% 3,5-dihydroxybenzoic acid, 18% tributyl phosphate, 12% tripropylamine, and 5% tetramethylammonium hydroxide.

[0068] The aluminum electrolytic capacitor prepared in Example 4 was subjected to performance testing, and the test results are shown in Table 4 below.

[0069] Table 4. Performance test results of the sample in Example 4

[0070]

[0071] Test data from Examples 1-4 show that the aluminum electrolytic capacitor proposed in this invention exhibits excellent stability over a wide temperature range of -40℃ to 105℃. Under high-temperature loads, the average capacitance retention rate reaches 88.8%, and at low temperatures of -40℃, it still retains more than 86.3% of its capacitance. After thermal shock cycling, the capacitance change rate is less than 0.5%. All samples maintained normal appearance after rigorous testing, fully verifying the reliability and durability of the product in extreme environments.

[0072] Comparative Example 1

[0073] This comparative example provides a method for preparing a highly stable aluminum electrolytic capacitor. The difference between this method and Example 1 is that the electrolyte solvent does not contain 1,10-dodecanoic acid, and the mass of this component is redistributed to the remaining solvent components in the original proportion, with the total mass of the solvent still accounting for 55%.

[0074] The aluminum electrolytic capacitor prepared in Comparative Example 1 was subjected to performance testing, and the test results are shown in Table 5 below.

[0075] Table 5. Performance test results of Comparative Example 1

[0076]

[0077] Compared to Example 1, the electrolyte performance of this comparative example showed significant deterioration after the removal of 1,10-dodecanoic acid. Table 5 shows the experimental results. Comparative Example 1 exhibited a capacitance decrease of -21.78% under high-temperature load conditions (Example 1: -11.78%), a DF increase of 414.62% (Example 1: 173.33%), and all samples showed aluminum shell bulging, indicating that this component effectively suppresses high-temperature side reactions and gas generation; the LC increase after thermal shock was 753.46% (Example 1: 131.39%). The molecular structure of 1,10-dodecanoic acid effectively maintains electrolyte stability at high temperatures while maintaining excellent ion conductivity at low temperatures. When used in combination with ethylene glycol methyl ether, the resulting composite system allows the electrolyte to maintain suitable viscosity and stable ion conductivity over a wide temperature range from -40°C to 105°C, thus meeting the requirements for use under various extreme environments.

[0078] Comparative Example 2

[0079] This comparative example provides a method for preparing a highly stable aluminum electrolytic capacitor. The difference between this method and Example 1 is that the electrolyte solute does not contain ammonium metasilicate, and the mass of this component is redistributed to the remaining solute components in the original proportion, with the total mass of the solute still accounting for 38%.

[0080] The aluminum electrolytic capacitor prepared in Comparative Example 2 was subjected to performance testing, and the test results are shown in Table 6 below.

[0081] Table 6. Performance test results of Comparative Example 2

[0082]

[0083] In this comparative example, the high-temperature performance of the capacitor significantly decreased after ammonium metasilicate was removed. Test results showed that under high-temperature load conditions, the capacitance decayed by -25.28% (compared to -11.78% in Example 1), and the leakage current (DF) increased by a staggering 706.67% (compared to 173.33% in Example 1). Furthermore, some samples exhibited aluminum shell valve failure. This result verifies the crucial role of ammonium metasilicate in the electrolyte. The SiO2 protective film generated by the hydrolysis of ammonium metasilicate effectively inhibits anodic corrosion, reduces leakage current, and improves flashover voltage, thereby significantly enhancing device reliability. In addition, the thermal shock test in this comparative example showed an ESR increase of 16.49% (compared to 10.26% in Example 1), and the DF increase after temperature characteristic testing reached 12487.34% (compared to 4087.90% in Example 1), further confirming that ammonium metasilicate, through its interfacial film-forming mechanism, can maintain system stability even at extreme temperatures.

[0084] Comparative Example 3

[0085] This comparative example provides a method for preparing a highly stable aluminum electrolytic capacitor. The difference between this method and Example 1 is that the additive does not contain 3,5-dihydroxybenzoic acid, and the mass of this component is redistributed to the remaining additive components in the original proportion, with the total mass of the additive still accounting for 7%.

[0086] The performance of the aluminum electrolytic capacitor prepared in Comparative Example 3 was tested, and the test results are shown in Table 7 below.

[0087] Table 7. Performance test results of Comparative Example 3

[0088]

[0089] Comparative Example 4

[0090] This comparative example provides a method for preparing a highly stable aluminum electrolytic capacitor. The difference between this method and Example 1 is that the additive does not contain nitrotriborium, and the mass of this component is redistributed to the remaining additive components in the original proportion, with the total mass of the additive still accounting for 7%.

[0091] The performance of the aluminum electrolytic capacitor prepared in Comparative Example 4 was tested, and the test results are shown in Table 8 below.

[0092] Table 8. Performance test results of Comparative Example 4

[0093]

[0094] Experimental data from Comparative Examples 3 and 4 show that the synergistic effect of boron nitronitride and 3,5-dihydroxybenzoic acid has a significant impact on electrolyte stability. Both Comparative Example 3 (removal of 3,5-dihydroxybenzoic acid) and Comparative Example 4 (removal of boron nitronitride) exhibited significant performance degradation: ESR increases of 304.57% and 305.39% under high-temperature loads (compared to 150.78% in Example 1), and DF increases of 9056.35% and 9487.13% after temperature characteristic testing (compared to 4087.90% in Example 1). In Comparative Example 4, some samples short-circuited after a short-term overvoltage test. This performance degradation stems from the disruption of the stable coordination structure formed by the two additives through BO bonds. This coordination structure effectively suppresses side reactions, increases flash voltage, and maintains ion conduction stability over a wide temperature range of -40 to 105 °C, thereby ensuring reliable capacitor performance under extreme conditions. Experiments have shown that the synergistic effect of nitrotriborone and 3,5-dihydroxybenzoic acid plays an important role in regulating the overall performance of the electrolyte system.

[0095] Comparative Example 5

[0096] This comparative example provides a method for preparing a highly stable aluminum electrolytic capacitor, which differs from Example 1 in that the amount of tetramethylammonium hydroxide added is increased to 8%, and the additive is composed of the following components by mass percentage: 38% boron nitronitrazine, 35% 3,5-dihydroxybenzoic acid, 14% tributyl phosphate, 5% tripropylamine, and 8% tetramethylammonium hydroxide.

[0097] The performance of the aluminum electrolytic capacitor prepared in Comparative Example 5 was tested, and the test results are shown in Table 9 below.

[0098] Table 9. Performance test results of Comparative Example 5

[0099]

[0100] In this comparative example, increasing the tetramethylammonium hydroxide content to 8% resulted in a significant deterioration in capacitor performance. Specifically, during high-temperature load testing, the capacitance decreased by -32.97% (compared to -11.78% in Example 1), the aluminum shell bulging rate reached 90%, and 10% of the samples experienced short-circuit failure. After temperature characteristic testing, the ESR increased by 1130.39% (compared to 568.72% in Example 1), and the impedance increased by 1252.64% (compared to 431.52% in Example 1). In Comparative Example 5, some samples experienced short circuits after a short-term overvoltage test. These results indicate that excessive tetramethylammonium hydroxide causes multiple problems: firstly, it leads to excessively alkaline electrolyte, accelerating aluminum foil corrosion; secondly, it promotes the generation of large amounts of hydrogen at high temperatures; and finally, it disrupts the ion balance of the electrolyte system. Therefore, the tetramethylammonium hydroxide content must be strictly controlled below 5% to ensure the reliability and lifespan of the capacitor.

[0101] Comparative Example 6

[0102] This comparative example provides a method for preparing a highly stable aluminum electrolytic capacitor. The difference between this method and Example 1 is that a single-layer insulating wood pulp electrolytic paper is used instead of the original double-layer composite structure. The paper has a thickness of 70 μm and a porosity of 40%.

[0103] The performance of the aluminum electrolytic capacitor prepared in Comparative Example 6 was tested, and the test results are shown in Table 10 below.

[0104] Table 10. Performance test results of Comparative Example 6

[0105]

[0106] Comparative Example 6, employing a single-layer electrolytic paper structure, exhibited significant performance disadvantages in temperature characteristic tests: the DF (dielectric flux density) increased by a staggering 6101.94%, and the impedance increased by 1263.85%, nearly three times that of Example 1 (431.52%). This is primarily due to the performance defects of the single-layer structure at low temperatures. Its uniform pore size distribution exacerbates the tendency for electrolyte crystallization, significantly increasing ion migration resistance. Furthermore, its poor mechanical strength makes it more prone to microcracks during rapid temperature changes, further deteriorating electrical performance. The results demonstrate that the gradient pore design of the proposed double-layer electrolytic paper structure effectively alleviates these low-temperature problems, enabling the capacitor to maintain good electrical performance stability even at -40℃.

[0107] Verification Example 1

[0108] For the low-temperature verification of the electrolytes in Examples 1-4 and Comparative Examples 1-4, 5 ml of electrolyte samples from each example and comparative example were placed in sealed glass tubes. After equilibration at 25°C, a stepwise cooling process was performed: first, the temperature was lowered to 0°C and maintained for 2 hours, then further lowered to -25°C and maintained for 2 hours, and finally lowered to -40°C and held for 2 hours. After completing the low-temperature test, the samples at -40°C were restored to 25°C, and the state changes were recorded after 4 hours and 72 hours of restoration. The evaluation results are shown in Table 11 below.

[0109] Table 11. Results of Low-Temperature Stability Test of Electrolyte

[0110]

[0111] The electrolytes in Examples 1-4 all exhibited appropriate viscosity at -25°C, completely solidified at -40°C, and were completely resoluble after returning to room temperature, demonstrating excellent low-temperature reversibility. In contrast, Comparative Example 1, lacking 1,10-dodecanoic acid, showed irreversible crystallization and irreversible stratification after being left at room temperature. Comparative Example 3, due to the removal of 3,5-dihydroxybenzoic acid, showed wall adhesion after being left at room temperature for 4 hours. This indicates the important role of 1,10-dodecanoic acid and 3,5-dihydroxybenzoic acid in maintaining electrolyte homogeneity and inhibiting crystallization; their absence led to local component separation.

[0112] Verification Example 2

[0113] To clarify the effect of ammonium metasilicate content on the protective film thickness, samples with ammonium metasilicate additions of 3%, 5%, 8%, 10%, and 12% were prepared under fixed process conditions and subjected to film formation according to the impregnation and heat treatment process described in Example 1. The film thickness was precisely measured using transmission electron microscopy (TEM), and the results are shown in Table 12 below.

[0114] Table 12. Effect of Ammonium Metasilicate Addition on Anodized Film Thickness

[0115] ammonium metasilicate wt% 3％ 5％ 8％ 10％ 12％ Film thickness(nm) 30 50 80 100 120

[0116] The amount of ammonium metasilicate added showed a significant positive correlation with the film thickness. Experimental data indicated that when the amount of ammonium metasilicate added was in the range of 3%–12%, the film thickness increased linearly from 30 nm to 120 nm. The mechanism of action is as follows: ammonium metasilicate undergoes a hydrolysis reaction in the electrolyte to generate silicon dioxide, and these products form a dense protective film layer on the electrode surface. This protective film effectively blocks side reactions between the electrode and the electrolyte, significantly reducing leakage current and increasing flashover voltage.

[0117] When the protective film thickness is less than 30 nm, its physical barrier properties and chemical stability are significantly reduced, failing to effectively inhibit electrolyte corrosion of the electrode; exceeding 80 nm affects electrode reaction kinetics. Simultaneously, when the ammonium metasilicate addition exceeds 8%, the film uniformity decreases significantly; at 10%–12% addition, localized porous structures appear in the sample, leading to a significant increase in interfacial impedance. Therefore, this invention controls the ammonium metasilicate addition within the range of 5%–8%, keeping the protective film thickness within the optimal performance range (30–80 nm). This optimized range, in conjunction with 1,10-dodecanoic acid and nitrotriborone in the electrolyte, enables the aluminum electrolytic capacitor to maintain good electrochemical stability even under extreme temperature conditions ranging from -40°C to 105°C.

[0118] Obviously, the embodiments described above are merely some embodiments of this application, not all embodiments. This application can be implemented in many different forms. Rather, 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 scope of patent protection of this application.

Claims

1. A method for preparing a high-stability aluminum electrolytic capacitor, characterized in that, Includes the following steps: Riveting; Elements wind and roll; Drying process; Electrolyte impregnation treatment; Encapsulation aging; wherein the electrolyte is composed of the following components by mass percentage: solvent 45-65%, solute 25-45%, additives 5-10%; the solvent contains ethylene glycol methyl ether and 1,10-dodecanoic acid.

2. The method for preparing a high-stability aluminum electrolytic capacitor according to claim 1, characterized in that, The electrolytic paper has a double-layer structure, with the inner layer having a thickness of 25–35 μm and the outer layer having a thickness of 35–45 μm.

3. The method for preparing a high-stability aluminum electrolytic capacitor according to claim 1, characterized in that, The solvent is composed of the following components in mass percentage: 42-60% ethylene glycol methyl ether, 25-35% 1,10-dodecanoic acid, 10-15% diethylene glycol monobutyl ether, and 2-8% dimethyl carbonate.

4. The method for preparing a high-stability aluminum electrolytic capacitor according to claim 1, characterized in that, The solute is composed of the following components in mass percentage: ammonium acetate 35-55%, ammonium benzoate 25-40%, triethylamine 10-18%, ammonium metasilicate 5-10%, and diethylene glycol dibutyl ether 2-6%.

5. The method for preparing a high-stability aluminum electrolytic capacitor according to claim 1, characterized in that, The additive is composed of the following components in mass percentage: 35-50% boron nitrate, 30-42% 3,5-dihydroxybenzoic acid, 12-18% tributyl phosphate, 5-12% tripropylamine, and 1-5% tetramethylammonium hydroxide.

6. The method for preparing a high-stability aluminum electrolytic capacitor according to claim 1, characterized in that, The impregnation treatment involves completely immersing the dried seeds in an electrolyte solution and impregnating them at 60–70°C for 4–6 hours.

7. The method for preparing a high-stability aluminum electrolytic capacitor according to claim 6, characterized in that, The electrolyte is prepared at 95–100°C and with a pH value maintained at 5.5–6.

8.

8. The method for preparing a high-stability aluminum electrolytic capacitor according to claim 1, characterized in that, The riveting pressure is controlled at 125-175N, the rivet thickness is 6.0-6.8mm, the contact resistance is ≤1.0mΩ and the contact area is ≥90%.

9. The method for preparing a high-stability aluminum electrolytic capacitor according to claim 2, characterized in that, The inner layer structure of the electrolytic paper is insulating wood pulp fiber, with a porosity of 42-48%, and the outer layer structure is Tencel fiber, with a porosity of 32-38%.

10. A highly stable aluminum electrolytic capacitor prepared by any one of claims 1 to 9, characterized in that, Capacity retention is ≥85% within a temperature range of -40℃ to 105℃.

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