Low esr wide temperature range aluminum electrolytic capacitor and method of manufacturing the same

Abstract

The application discloses a kind of low ESR wide temperature range aluminum electrolytic capacitor and preparation method thereof, first to anode foil multistage corrosion treatment, then preparation electrolyte, then the positive pole foil strip and negative pole foil strip are riveted on anode foil and cathode foil respectively, then electrolytic paper is intervened between anode foil and cathode foil and is wound into element, then the element obtained by winding is dried, then the element after drying is immersed in electrolyte and is immersed, then the element after immersion is loaded into aluminum shell and is sealed, finally the capacitor after packaging is aged treatment;The electrolyte is composed of the following mass percentage components: solvent 40-60%, solute 30-50%, additive 3-10%;The additive is composed of the following mass percentage components: alkyl phosphate 30-55%, mannitol 20-40%, monobutyl phosphate 15-25%, aminoacetic acid 1-5%.The aluminum electrolytic capacitor provided by the application has low ESR, high flashover voltage and good low-temperature performance, and is suitable for high-end data center power supply and AI server power supply.

Description

Technical Field

[0001] This invention relates to the field of aluminum electrolytic capacitor technology, and more specifically, to a low ESR wide-temperature-range aluminum electrolytic capacitor and its preparation method. Background Technology

[0002] As a key energy storage and filtering component, aluminum electrolytic capacitors are rapidly transforming from general-purpose to high-performance and high-reliability types. With AI server power systems trending towards higher voltage and higher power density, the market urgently demands capacitors with higher voltage withstand, smaller size, lower ESR, and better high-temperature stability. This means providing faster, more stable, and more efficient instantaneous energy supply in confined spaces and under more demanding operating conditions to ensure a stable and reliable power supply for computing systems.

[0003] However, traditional aluminum electrolytic capacitors, due to their slow response speed and high high-frequency impedance, are unable to effectively suppress power supply ripple and transient load fluctuations, becoming a key bottleneck restricting chip performance release and system stability. Especially under high-current conditions (AI accelerator cards can consume kilowatts instantaneously), the relatively high ESR of liquid aluminum electrolytic capacitors leads to significant IR. 2 R heat loss leads to severe self-heating and accelerated internal aging, creating a vicious cycle.

[0004] To address the aforementioned issues, some related technologies have attempted to improve the electrolyte. For example, Chinese patent application CN202010350214.7 discloses an electrolyte for high-temperature resistant aluminum electrolytic capacitors, which exhibits good service life at 135℃. However, this technical solution still has the following shortcomings: its solvent system is mainly ethylene glycol, resulting in poor low-temperature performance and making it difficult to meet the requirements of low-temperature applications below -40℃; its solute voltage resistance is insufficient, making it difficult to meet the needs of high-voltage (above 450V) applications.

[0005] Therefore, there is an urgent need to develop an aluminum electrolytic capacitor that combines low ESR, high flash voltage, wide temperature range adaptability, and long lifespan to meet the demanding requirements of high-end data center power supplies and AI server power supplies. Summary of the Invention

[0006] Therefore, it is necessary to address the above-mentioned technical problems by providing a low ESR wide-temperature-range aluminum electrolytic capacitor and its preparation method.

[0007] To address the aforementioned technical problems, this invention provides a method for preparing a low-ESR, wide-temperature-range aluminum electrolytic capacitor, comprising the following steps: first, subjecting the anode foil to multi-stage etching treatment; then, preparing the electrolyte; then, riveting the positive and negative conductive foil strips onto the anode and cathode foils respectively; next, inserting electrolytic paper between the anode and cathode foils and winding it into a core; then, drying the wound core; then, immersing the dried core in the electrolyte for impregnation treatment; then, packing the impregnated core into an aluminum shell and sealing it; and finally, aging the encapsulated capacitor.

[0008] The electrolyte is composed of the following components by mass percentage: solvent 40%~60%, solute 30%~50%, and additives 3%~10%.

[0009] The additive is composed of the following components by mass percentage: 30%~55% alkyl phosphate, 20%~40% mannitol, 15%~25% monobutyl phosphate, and 1%~5% glycine.

[0010] Furthermore, the solvent is composed of the following components in mass percentage: γ-butyrolactone 40%~60%, N,N-dimethylformamide 20%~37%, propylene glycol 10%~15%, and diethylene glycol monobutyl ether 1%~8%.

[0011] Furthermore, the solute is composed of the following components in mass percentage: 30%~50% ammonium decanedicarboxylate, 25%~40% triammonium hydrogen citrate, 10%~20% mixture of branched polycarboxylic acids and ammonium diammonium, and 2%~10% adipic acid diamide.

[0012] Furthermore, the branched polycarboxylic acid ammonium mixture is selected from one or more of the following: a mixture of branched dicarboxylic acids with a carbon chain length ≥9 and branched tetracarboxylic acids with alkyl branches.

[0013] Furthermore, the multi-stage corrosion treatment includes the following steps: (1) Pretreatment: Immerse the anode aluminum foil in an alkaline or acidic solution to remove surface oil and natural oxide film; (2) DC primary pit formation: The pretreated aluminum foil is immersed in a mixed etching solution containing sodium perchlorate and sodium chloride, and a DC current is applied to form initial pits on the surface of the aluminum foil; (3) Secondary porosimetry: Keep the corrosion solution system unchanged, gradually reduce the DC current density, and guide the porosity to grow in the depth direction; (4) Chemical pore enlargement: The aluminum foil after secondary pore enlargement is transferred to a chemical etching solution containing diethylenetriamine pentacarboxylic acid or its salts for immersion, and the pores are enlarged into the aluminum foil by chemical energy. (5) Post-treatment: The aluminum foil after chemical pore expansion is immersed in nitric acid solution to wash away residual ions, form a passivation film, and then dried.

[0014] Furthermore, during the winding process, the tension of the foil and electrolytic paper is detected in real time by tension sensors installed on the guide rollers, and the sensor signals are fed back to the controller.

[0015] Furthermore, the drying temperature is 100~120℃, and the drying time is 1~2 hours, so that the internal moisture content of the seed is less than 0.5%; the impregnation treatment includes two stages: vacuum impregnation and pressure permeation. The vacuum impregnation conditions are vacuum degree -0.08~-0.095MPa, temperature 60~70℃, vacuum impregnation for 40~60 minutes, and then release the vacuum and soak at normal pressure for 15~25 minutes; the pressure permeation conditions are pressure 0.8~1.2MPa and time 120~150 minutes.

[0016] Furthermore, the aging treatment conditions are as follows: apply a DC voltage of 1.15 to 1.25 times the rated voltage and age at 95 to 105°C until the leakage current stabilizes.

[0017] The present invention also provides a low ESR wide-temperature-range aluminum electrolytic capacitor, which is prepared by any of the above-described preparation methods.

[0018] This invention also provides an application of a low ESR wide-temperature-range aluminum electrolytic capacitor, wherein the aluminum electrolytic capacitor prepared by the preparation method described in any of the above technical solutions is applied to a high-end data center power supply or an AI server power supply.

[0019] Compared with the prior art, the present invention has the following beneficial effects: This invention discloses a low-ESR, wide-temperature-range aluminum electrolytic capacitor and its preparation method. Regarding the electrolyte, a high-performance and stable electrolyte is obtained through the synergistic effect of the solvent system, solute system, and additives. Specifically, the solvent system, composed of γ-butyrolactone, N,N-dimethylformamide, propylene glycol, and diethylene glycol monobutyl ether in a specific ratio, achieves optimal flash voltage and low-temperature conductivity simultaneously. The solute system, composed of decanedicarboxylic acid ammonium, triammonium citrate, a mixture of branched polycarboxylic acids and adipic acid diamide, balances the relationship between high dissociation and high withstand voltage. The additives, including alkyl phosphates, mannitol, monobutyl phosphate, and glycine, simultaneously achieve oxide film repair, hydrogen removal, and pH stabilization. In particular, the amphoteric buffering effect of glycine stabilizes the electrolyte pH and inhibits oxide film corrosion. The synergistic hydrogen removal effect of mannitol and monobutyl phosphate effectively reduces the internal pressure of the capacitor, preventing bulging and bursting.

[0020] In terms of manufacturing process, this invention uses a multi-stage etching process to treat the anode foil. Compared with conventional single-stage etching, it can form a deeper and more uniform tunnel hole structure, significantly improving specific capacitance and electrolyte wettability. The multi-stage etched anode foil, combined with the above-mentioned electrolyte formulation, further reduces ESR, increases flash voltage, improves low-temperature performance, and suppresses high-temperature gas generation and leakage current growth, thereby obtaining a low-ESR wide-temperature-range aluminum electrolytic capacitor suitable for high-end data center power supplies and AI server power supplies. Detailed Implementation

[0021] 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.

[0022] Example 1

[0023] This embodiment provides a method for preparing a low ESR wide-temperature-range aluminum electrolytic capacitor, which includes the following steps: S1, Multi-stage corrosion treatment of anolyte foil (1) Pretreatment: Immerse the 110μm thick anode aluminum foil in a sodium hydroxide aqueous solution with a temperature of 38℃ and a mass concentration of 4% for 75 seconds to remove surface oil and natural oxide film, and then rinse and dry with deionized water.

[0024] (2) DC primary etching: Immerse the aluminum foil treated in step (1) into a mixed etching solution containing 0.8 mol / L sodium perchlorate and 1.2 mol / L sodium chloride. The solution temperature is controlled at 38°C, and a current density of 0.5 A / cm is applied. 2 A direct current was applied for 4 minutes, which formed a high density of initial pits on the surface of the aluminum foil.

[0025] (3) Secondary porosity formation: Keeping the etching solution system of step (2) unchanged, reduce the DC current density to 0.2 A / cm 2 Continue to apply power for 6 minutes to guide the hole to grow deeper.

[0026] (4) Chemical pore enlargement: Take out the aluminum foil after step (3) and transfer it to a 3% diethylenetriamine pentacarboxylic acid aqueous solution at a temperature of 75°C and a mass concentration of 3% for 12 minutes. Use chemical energy to widen the pores into the aluminum foil.

[0027] (5) Post-treatment: Immerse the aluminum foil treated in step (4) in a 2% nitric acid aqueous solution at room temperature for 6 minutes to wash away residual ions and form a dense passivation film on the surface. Then rinse with deionized water and dry.

[0028] S2, Preparation of electrolyte In this embodiment, the total mass of the solvent accounts for 50% of the electrolyte, the total mass of the solute accounts for 45% of the electrolyte, and the total mass of the additives accounts for 5% of the electrolyte.

[0029] The solvent is composed of the following components by mass percentage: 50% γ-butyrolactone, 30% N,N-dimethylformamide, 15% propylene glycol, and 5% diethylene glycol monobutyl ether.

[0030] The solute is composed of the following components by mass percentage: 42% ammonium decanedicarboxylate, 30% triammonium hydrogen citrate, 20% a mixture of branched polycarboxylic acids and ammonium dicarboxylate, and 8% adipic acid diamide. The branched polycarboxylic acid mixture is selected from one or more of branched dicarboxylic acids and branched tetracarboxylic acids with a carbon chain length ≥9 and alkyl branches. In this embodiment, it is specifically a mixture of 2-methylammonium azelaate and 7,8-dimethyl-1,7,8,14-tetradecanetetracarboxylate, with a mass ratio of 1:1.

[0031] The additive consists of the following components by weight percentage: 50% alkyl phosphate, 28% mannitol, 18% monobutyl phosphate, and 4% glycine.

[0032] Mix all solvent components thoroughly, heat to 70°C, add solute components sequentially, stir until completely dissolved, add additive components last, continue stirring for 30 minutes, cool to room temperature, and obtain electrolyte.

[0033] S3, riveting The positive electrode conductive foil and the negative electrode conductive foil are riveted to the anode foil and cathode foil prepared by S1 by a riveting machine.

[0034] S4, element winding (1) Insert two layers of electrolytic paper (one inner layer of electrolytic paper and one outer layer of electrolytic paper) between the anode foil and cathode foil after S3 riveting, and put them into an automatic winding machine for winding to obtain a cylindrical element, wherein the cathode foil is 2mm longer than the anode foil, so that the bottom of the core is exposed to the cathode.

[0035] (2) During the winding process, the tension of the anode foil, cathode foil, and electrolytic paper is detected in real time by a tension sensor installed on the guide roller. The sensor signal is fed back to the PLC controller, which can effectively avoid problems such as foil breakage due to excessive tension or loose winding and poor heat dissipation due to insufficient tension. The sensor is installed at the feed end before the material enters the winding roller, 150~200mm away from the winding roller. In this embodiment, the distance from the winding roller is 180mm. The tension settings are: anode foil 2.5~3.5N, cathode foil 2.0~3.0N, electrolytic paper 1.5~2.5N. In this embodiment, they are set to 3.0N, 2.5N, and 2.0N respectively, and the tension fluctuation is controlled within ±0.2N. The edge alignment error is controlled within 0.1~0.2mm by the photoelectric correction system. In this embodiment, it is 0.15mm. After winding, the ends of the element are fixed with high-temperature tape.

[0036] S5. Drying treatment The seed obtained by winding S4 is placed in an oven and dried at 100~120℃ for 1~2 hours. In this embodiment, it is dried at 110℃ for 1.5 hours to make the internal moisture content of the seed less than 0.5%.

[0037] S6, Electrolyte impregnation After drying the raw material in S5, transfer it to an impregnation tank. Inject the electrolyte prepared in S2 into the impregnation tank and perform vacuum impregnation first: under the conditions of vacuum degree of -0.08~-0.095MPa and temperature of 60~70℃, vacuum impregnate for 40~60 minutes. In this embodiment, the vacuum degree is -0.09MPa, the temperature is 65℃, and the vacuum impregnation is 50 minutes. Then release the vacuum and soak under normal pressure for 15~25 minutes. In this embodiment, the normal pressure soaking is 20 minutes. Finally, perform pressure permeation: maintain a pressure of 0.8~1.2MPa for 120~150 minutes. In this embodiment, the pressure is 1.0MPa and the time is 135 minutes to allow the electrolyte to fully penetrate into the raw material.

[0038] S7, Package After the S6 impregnation, the element is placed into an aluminum shell. A layer of fixing glue is poured into the bottom of the aluminum shell to assist in heat dissipation and prevent displacement due to vibration or external force. Then, the glue plug is pressed into the open end of the aluminum shell to seal it.

[0039] S8, Aging Treatment The encapsulated capacitor is subjected to a DC voltage of 1.15 to 1.25 times the rated voltage and aged at 95 to 105°C. In this embodiment, 1.2 times the rated voltage is applied and aged at 100°C. After the leakage current stabilizes, the capacitor is cooled down to obtain the finished aluminum electrolytic capacitor.

[0040] Example 2

[0041] This embodiment provides a method for preparing a low ESR wide-temperature-range aluminum electrolytic capacitor. The difference between this method and Example 1 is that the process parameters in S1 and the electrolyte formulation in S2 are different, while the remaining steps are the same as in Example 1.

[0042] S1, Multi-stage corrosion treatment of anolyte foil (1) Pretreatment: Immerse the 105μm thick anode aluminum foil in a sodium hydroxide aqueous solution with a temperature of 35℃ and a mass concentration of 3.5% for 90 seconds to remove surface oil and natural oxide film, then rinse with deionized water and dry.

[0043] (2) DC primary etching: Immerse the aluminum foil treated in step (1) into a mixed etching solution containing 0.6 mol / L sodium perchlorate and 1.0 mol / L sodium chloride. The solution temperature is controlled at 35°C, and a current density of 0.3 A / cm is applied. 2 A direct current was applied for 5 minutes, which formed a high density of initial pits on the surface of the aluminum foil.

[0044] (3) Secondary porosity formation: Keeping the etching solution system of step (2) unchanged, reduce the DC current density to 0.1 A / cm 2 Continue to apply power for 8 minutes to guide the hole to grow deeper.

[0045] (4) Chemical pore enlargement: Take out the aluminum foil after step (3) and transfer it to a 2.5% aqueous solution of diethylenetriaminepentacarboxylic acid at a temperature of 65°C and a mass concentration of 2.5%. Soak it for 15 minutes and use chemical energy to widen the pores into the aluminum foil.

[0046] (5) Post-treatment: Immerse the aluminum foil treated in step (4) in a nitric acid aqueous solution with a mass concentration of 1.5% at room temperature for 8 minutes to wash away residual ions and form a dense passivation film on the surface. Then rinse with deionized water and dry.

[0047] S2, Preparation of electrolyte In this embodiment, the total mass of the solvent accounts for 40% of the electrolyte, the total mass of the solute accounts for 50% of the electrolyte, and the total mass of the additives accounts for 10% of the electrolyte.

[0048] The solvent is composed of the following components by mass percentage: γ-butyrolactone 40%, N,N-dimethylformamide 37%, propylene glycol 15%, and diethylene glycol monobutyl ether 8%.

[0049] The solute is composed of the following components by mass percentage: 30% ammonium decanedicarboxylate, 40% triammonium hydrogen citrate, 20% a mixture of branched polycarboxylic acids and ammonium dicarboxylate, and 10% adipic acid diamide. The branched polycarboxylic acid mixture is the same as in Example 1.

[0050] The additive consists of the following components by weight percentage: 30% alkyl phosphate, 40% mannitol, 25% monobutyl phosphate, and 5% glycine.

[0051] Mix all solvent components thoroughly, heat to 70°C, add solute components sequentially, stir until completely dissolved, add additive components last, continue stirring for 30 minutes, cool to room temperature, and obtain electrolyte.

[0052] Example 3

[0053] This embodiment provides a method for preparing a low ESR wide-temperature-range aluminum electrolytic capacitor. The difference between this method and Example 1 is that the process parameters in S1 and the electrolyte formulation in S2 are different, while the remaining steps are the same as in Example 1.

[0054] S1, Multi-stage corrosion treatment of anolyte foil (1) Pretreatment: Immerse the 120μm thick anode aluminum foil in a 5% sodium hydroxide aqueous solution at 45℃ for 60 seconds to remove surface oil and natural oxide film, then rinse with deionized water and dry.

[0055] (2) DC primary etching: Immerse the aluminum foil treated in step (1) into a mixed etching solution containing 1.0 mol / L sodium perchlorate and 1.5 mol / L sodium chloride. The solution temperature is controlled at 42℃, and a current density of 0.8 A / cm is applied. 2 A direct current was applied for 3 minutes, which formed a high density of initial pits on the surface of the aluminum foil.

[0056] (3) Secondary porosity formation: Keeping the etching solution system of step (2) unchanged, reduce the DC current density to 0.3 A / cm 2 Continue to apply power for 5 minutes to guide the hole to grow deeper.

[0057] (4) Chemical pore enlargement: Take out the aluminum foil after step (3) and transfer it to a 4% diethylenetriamine pentacarboxylic acid aqueous solution at a temperature of 90°C. Soak it for 10 minutes and use chemical energy to widen the pores into the aluminum foil.

[0058] (5) Post-treatment: Immerse the aluminum foil treated in step (4) in a 3% nitric acid aqueous solution at room temperature for 5 minutes to wash away residual ions and form a dense passivation film on the surface. Then rinse with deionized water and dry.

[0059] S2, Preparation of electrolyte In this embodiment, the total mass of the solvent accounts for 60% of the electrolyte, the total mass of the solute accounts for 30% of the electrolyte, and the total mass of the additives accounts for 10% of the electrolyte.

[0060] The solvent is composed of the following components by mass percentage: 60% γ-butyrolactone, 20% N,N-dimethylformamide, 12% propylene glycol, and 8% diethylene glycol monobutyl ether.

[0061] The solute is composed of the following components by mass percentage: 50% ammonium decanedicarboxylate, 25% triammonium hydrogen citrate, 17% a mixture of branched polycarboxylic acids and ammonium dicarboxylate, and 8% adipic acid diamide. The branched polycarboxylic acid mixture is the same as in Example 1.

[0062] The additive consists of the following components by weight percentage: 55% alkyl phosphate, 20% mannitol, 20% monobutyl phosphate, and 5% glycine.

[0063] Mix all solvent components thoroughly, heat to 70°C, add solute components sequentially, stir until completely dissolved, add additive components last, continue stirring for 30 minutes, cool to room temperature, and obtain electrolyte.

[0064] Example 4

[0065] This embodiment provides a method for preparing a low ESR wide-temperature-range aluminum electrolytic capacitor. The difference between this method and that of Embodiment 1 is that the electrolyte formulation in S2 is different, while the remaining steps are the same as those in Embodiment 1.

[0066] S2, Preparation of electrolyte In this embodiment, the total mass of solvent accounts for 47% of the electrolyte, the total mass of solute accounts for 50% of the electrolyte, and the total mass of additives accounts for 3% of the electrolyte.

[0067] The solvent is composed of the following components by mass percentage: γ-butyrolactone 56%, N,N-dimethylformamide 33%, propylene glycol 10%, and diethylene glycol monobutyl ether 1%.

[0068] The solute is composed of the following components by mass percentage: 50% ammonium decanedicarboxylate, 38% triammonium hydrogen citrate, 10% a mixture of branched polycarboxylic acids and ammonium diammonium, and 2% adipic acid diamide. The branched polycarboxylic acid mixture is the same as in Example 1.

[0069] The additive consists of the following components by weight percentage: 49% alkyl phosphate, 35% mannitol, 15% monobutyl phosphate, and 1% glycine.

[0070] Mix all solvent components thoroughly, heat to 70°C, add solute components sequentially, stir until completely dissolved, add additive components last, continue stirring for 30 minutes, cool to room temperature, and obtain electrolyte.

[0071] Comparative Example 1 This embodiment provides a method for preparing a low ESR wide-temperature-range aluminum electrolytic capacitor. The only difference between this method and Example 1 is that glycine is not added in step S2; the remaining steps S1, S3 to S8 are the same as in Example 1. Any missing additive components are made up by the remaining components in the additive in their original relative proportions.

[0072] Comparative Example 2 This embodiment provides a method for preparing a low ESR wide-temperature-range aluminum electrolytic capacitor. The only difference between this method and Example 1 is that the amount of glycine added in S2 is increased from 4% to 10%. The remaining steps S1, S3 to S8 are the same as in Example 1.

[0073] Preparation of S2 electrolyte: The amount of glycine in the additive is increased to 10%, while the amounts of alkyl phosphate, mannitol, and monobutyl phosphate are reduced proportionally according to their original relative proportions to maintain the total mass of the additive. The adjusted mass percentages of each component in the additive are: alkyl phosphate 46.88%, mannitol 26.25%, monobutyl phosphate 16.87%, and glycine 10%. The components and proportions of the solvent and solute remain unchanged.

[0074] Comparative Example 3 This embodiment provides a method for preparing a low-ESR, wide-temperature-range aluminum electrolytic capacitor. The only difference between this method and Example 1 is that monobutyl phosphate is not added in step S2; the remaining steps S1, S3 to S8 are the same as in Example 1. Any missing additive components are made up by the remaining components in the additive in their original relative proportions.

[0075] Comparative Example 4 This embodiment provides a method for preparing a low-ESR, wide-temperature-range aluminum electrolytic capacitor. The only difference between this method and Example 1 is that adipamide is not added in step S2; the remaining steps S1, S3 to S8 are the same as in Example 1. Any missing solute components are made up by the remaining components in the solute in their original relative proportions.

[0076] Comparative Example 5 This embodiment provides a method for preparing a low-ESR, wide-temperature-range aluminum electrolytic capacitor. The only difference between this method and Example 1 is that N,N-dimethylformamide is not added in step S2; the remaining steps S1, S3 to S8 are the same as in Example 1. The missing solvent components are supplemented by the remaining components in the solvent in their original relative proportions.

[0077] Comparative Example 6 This embodiment provides a method for preparing a low-ESR, wide-temperature-range aluminum electrolytic capacitor. The only difference between this method and Example 1 is that diethylene glycol monobutyl ether is not added in step S2; the remaining steps S1, S3 to S8 are the same as in Example 1. The missing solvent components are supplemented by the remaining components in the solvent in their original relative proportions.

[0078] Comparative Example 7 This embodiment provides a method for preparing a low ESR wide-temperature-range aluminum electrolytic capacitor. The only difference between this method and Example 1 is that the anode foil uses conventional single-stage etched aluminum foil, and the secondary pore formation and chemical pore expansion steps in Example 1 are not performed.

[0079] Step S1 only involves pretreatment, single-stage DC etching, and post-treatment, omitting secondary etching and chemical reaming. The remaining steps S2 to S8 are the same as in Example 1.

[0080] Verification Example The aluminum electrolytic capacitors (all with specifications of 450V / 1300μF, cylindrical with solder pins) prepared in Examples 1-4 and Comparative Examples 1-7 were subjected to the following performance tests.

[0081] (1) High temperature load life test: Each capacitor was placed in a constant temperature chamber at 105℃ and the rated voltage of 450V was applied for continuous power supply for 2000 hours. After the test, the ESR was measured and the ESR growth rate was calculated: ESR growth rate = (ESR after test - initial ESR) / initial ESR × 100%, and the appearance of the capacitor was observed. The test results are shown in Table 1.

[0082] (2) Flash voltage test: The DC boost method is used to boost the voltage at a rate of 0.5V / s and record the voltage value when the capacitor flashes.

[0083] (3) Low temperature conductivity test: Cool each electrolyte sample to -40℃ and measure its conductivity using a conductivity meter.

[0084] (4) Leakage current test: Under the condition of 20℃, the rated voltage of 450V is applied to test the initial leakage current and the leakage current value after 2000h high temperature load, and calculate the leakage current growth rate: leakage current growth rate = (leakage current after 2000h - initial leakage current) / initial leakage current × 100%. The test results are shown in Table 2.

[0085] Table 1. Results of High Temperature Load Life Test Table 2. Test results of flashover voltage, low-temperature conductivity and leakage current. As shown in Tables 1 and 2, the leakage current growth rate of the electrolyte in Comparative Example 1 (without glycine) was significantly higher than that of the examples containing glycine after high-temperature load testing, and the capacitor casing exhibited varying degrees of bulging. This is because glycine, as an amphoteric compound, can effectively adsorb onto the surface of anodic aluminum oxide, blocking micropores or weak points in the oxide film, altering the double-layer structure at the oxide film-electrolyte interface, increasing the overpotential of the hydrogen evolution reaction, thereby suppressing gas generation, stabilizing the electrolyte pH, and extending the high-temperature lifespan of the capacitor. In Comparative Example 2, when the glycine content was too high, the conductivity of the electrolyte at -40°C decreased, and its overall performance was inferior to Examples 1-4, indicating that there is an optimal range for glycine content, and excessive addition has an adverse effect on performance.

[0086] Comparative Example 3, lacking monobutyl phosphate in its electrolyte, showed significantly worse ESR growth rate, flashover voltage, and appearance after high temperature. Furthermore, the bulging height and leakage current growth rate increased significantly, confirming the hydrogen elimination effect of using monobutyl phosphate in combination with mannitol: monobutyl phosphate can assist in repairing the oxide film and inhibit hydrogen production, while mannitol reacts with the generated hydrogen to consume it; both work together to reduce the internal pressure of the capacitor. Comparative Example 4, lacking adipamide in its electrolyte, exhibited a significantly lower flashover voltage, a significantly higher ESR growth rate, and noticeable bulging after high temperature. This is because adipamide can physically lock the entire system through a strong hydrogen bond network, resisting physical processes such as volatilization, flow, and interfacial erosion that lead to failure.

[0087] The electrolyte in Comparative Example 5 did not contain N,N-dimethylformamide, and the electrolyte in Comparative Example 6 did not contain diethylene glycol monobutyl ether. The low-temperature conductivity and flash voltage of both electrolytes decreased significantly, indicating that N,N-dimethylformamide can reduce viscosity and prevent low-temperature crystallization, while diethylene glycol monobutyl ether can improve dielectric strength and solute solubility. The specific ratio of these two electrolytes with γ-butyrolactone and propylene glycol plays a key role in balancing low-temperature performance and pressure resistance.

[0088] Comparative Example 7 used conventional single-stage etched aluminum foil, and the initial ESR was significantly increased. After high temperature, obvious bulging appeared and the leakage current growth rate was significantly increased. This shows that the tunnel hole structure formed by the multi-stage etched process of the present invention can form better wetting and cooperation with the electrolyte, further reducing ESR, suppressing high-temperature gas generation and leakage current growth.

[0089] In summary, the aluminum electrolytic capacitors prepared according to Examples 1-4 of this invention achieve excellent results in reducing ESR, increasing flashover voltage, improving low-temperature performance, and suppressing high-temperature gas generation and leakage current growth. The leakage current in Examples 1-4 showed a decreasing trend after high-temperature load testing, indicating that the additives such as glycine and alkyl phosphates in the electrolyte of this invention have a continuous repair effect on the anodic oxide film under high-temperature and voltage conditions, effectively suppressing the leakage current growth caused by oxide film defects, further demonstrating the capacitor's excellent long-life self-healing characteristics.

[0090] 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 low ESR wide-temperature-range aluminum electrolytic capacitor, characterized in that, First, the anode foil undergoes multi-stage corrosion treatment, then the electrolyte is prepared. Next, the positive and negative electrode conductive foil strips are riveted to the anode and cathode foils respectively. Then, electrolytic paper is inserted between the anode and cathode foils and wound into a core. The core is then dried, and the dried core is immersed in the electrolyte for impregnation treatment. The impregnated core is then packed into an aluminum shell and sealed. Finally, the encapsulated capacitor undergoes aging treatment. The electrolyte is composed of the following components by mass percentage: solvent 40%~60%, solute 30%~50%, and additives 3%~10%; The additive is composed of the following components by mass percentage: 30%~55% alkyl phosphate, 20%~40% mannitol, 15%~25% monobutyl phosphate, and 1%~5% glycine.

2. The preparation method according to claim 1, characterized in that, The solvent is composed of the following components by mass percentage: γ-butyrolactone 40%~60%, N,N-dimethylformamide 20%~37%, propylene glycol 10%~15%, and diethylene glycol monobutyl ether 1%~8%.

3. The preparation method according to claim 1, characterized in that, The solute is composed of the following components by mass percentage: 30%~50% ammonium decanedicarboxylate, 25%~40% triammonium hydrogen citrate, 10%~20% a mixture of branched polycarboxylic acids and ammonium diammonium, and 2%~10% adipic acid diamide.

4. The preparation method according to claim 1, characterized in that, The multi-stage corrosion treatment includes the following steps: (1) Pretreatment: Immerse the anode aluminum foil in an alkaline or acidic solution to remove surface oil and natural oxide film; (2) DC primary pit formation: The pretreated aluminum foil is immersed in a mixed etching solution containing sodium perchlorate and sodium chloride, and a DC current is applied to form initial pits on the surface of the aluminum foil; (3) Secondary porosimetry: Keep the corrosion solution system unchanged, gradually reduce the DC current density, and guide the porosity to grow in the depth direction; (4) Chemical pore enlargement: The aluminum foil after secondary pore enlargement is transferred to a chemical etching solution containing diethylenetriamine pentacarboxylic acid or its salts for immersion, and the pores are enlarged into the aluminum foil by chemical energy. (5) Post-treatment: The aluminum foil after chemical pore expansion is immersed in nitric acid solution to wash away residual ions, form a passivation film, and then dried.

5. The preparation method according to claim 1, characterized in that, The branched polycarboxylic acid ammonium mixture is selected from one or more of the following: a carbon chain length ≥ 9, a branched dicarboxylic acid ammonium mixture with alkyl branches, and a branched tetracarboxylic acid ammonium mixture.

6. The preparation method according to claim 1, characterized in that, During the winding process, the tension of the foil and electrolytic paper is detected in real time by a tension sensor installed on the guide roller, and the sensor signal is fed back to the controller.

7. The preparation method according to claim 1, characterized in that, The drying temperature is 100~120℃, and the drying time is 1~2 hours, so that the internal moisture content of the seed is less than 0.5%. The impregnation treatment includes two stages: vacuum impregnation and pressure permeation. The vacuum impregnation conditions are -0.08~-0.095MPa, temperature 60~70℃, vacuum impregnation for 40~60 minutes, followed by immersion in normal pressure for 15~25 minutes. The pressure permeation conditions are 0.8~1.2MPa and time 120~150 minutes.

8. The preparation method according to claim 1, characterized in that, The aging treatment conditions are as follows: apply a DC voltage of 1.15 to 1.25 times the rated voltage and age at 95 to 105°C until the leakage current stabilizes.

9. A low ESR wide-temperature-range aluminum electrolytic capacitor, characterized in that, It is prepared by any one of claims 1 to 8.

10. An application of a low ESR wide-temperature-range aluminum electrolytic capacitor, characterized in that, The aluminum electrolytic capacitor prepared by any one of claims 1 to 8 is applied to high-end data center power supplies or AI server power supplies.

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