A high ripple current aluminum electrolytic capacitor and a method of manufacturing the same

Abstract

The application discloses a high-ripple-current aluminum electrolytic capacitor and a preparation method thereof. The capacitor comprises a core package and a shell, the core package is adsorbed with electrolyte, the electrolyte comprises a solvent, a solute and an additive, the solvent accounts for 40-60% of the total mass of the electrolyte, the solute accounts for 30-50%, and the additive accounts for 3-10%; the additive is composed of ammonium adipate, ammonium pentaborate, tetraethylphosphonium tetrafluoroborate, nano silicon dioxide, p-nitrophenyl ether and tetraethylammonium; the solvent comprises gamma-butyrolactone, sulfolane, ethylene carbonate, diethylene glycol methyl ether and 3-methoxypropionitrile; and the solute comprises ammonium sebacate, dodecyl diacid, tetramethylammonium and multi-branched ammonium salt of dicarboxylic acid. The aluminum electrolytic capacitor prepared by the application is suitable for high-frequency switching scenarios of silicon carbide and gallium nitride server power supplies, and has high-ripple-current bearing capacity and long high-temperature life.

Description

Technical Field

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

[0002] Aluminum electrolytic capacitors are key passive components in switching power supplies, widely used for energy storage and filtering in PFC and DC-Link stages. With the rapid adoption of new power devices such as silicon carbide (SiC) and gallium nitride (GaN) in server power supplies, power switching frequencies are constantly increasing, placing higher demands on the ESR and ripple current capabilities of capacitors. High-voltage, high-capacity liquid aluminum electrolytic capacitors remain the mainstream choice for these applications due to their high cost-effectiveness, high capacity, and mature supply chain.

[0003] Currently, there are technical solutions for improving the ripple current withstand capability of aluminum electrolytic capacitors by optimizing the electrolyte formulation. For example, Chinese patent CN110648848A discloses an aluminum electrolytic capacitor that can withstand large ripple currents at 115℃. Its electrolyte uses a mixed solvent of γ-butyrolactone, ethylene glycol, and polyols, with long-chain ammonium carboxylate as the first solute and fatty alcohol sulfate as the second solute, and additives such as 8-carboxyquinoline are added. By reducing the saturated vapor pressure and the complexation effect of aluminum ions, the temperature resistance is increased from 105℃ to 115℃, which improves the capacitor's ripple current withstand capability to a certain extent.

[0004] However, the aforementioned existing technologies are mainly designed for low-frequency or power-frequency ripple conditions in conventional switching power supplies, and are difficult to adapt to high-frequency switching applications. First, under high-frequency conditions, the ESR of capacitors has a more significant impact on ripple current withstand capability, and the ion mobility and high-frequency response capability of existing electrolyte systems are insufficient. Second, the internal hot spot temperature of server power supplies continues to rise, and the traditional lifespan index of 105℃ / 2000h is difficult to meet the actual usage requirements in high-power scenarios. Third, aluminum electrolytic capacitors have limited tolerance to instantaneous overvoltage and reverse voltage, and are prone to oxide film breakdown. The temperature rise of capacitors caused by high-frequency switching will accelerate electrolyte evaporation and drying, leading to capacitance decay, increased ESR, and ultimately failure.

[0005] Therefore, there is an urgent need to develop an aluminum electrolytic capacitor that can adapt to high-frequency switching characteristics, has high ripple current withstand capability, and long high-temperature life. Summary of the Invention

[0006] Therefore, it is necessary to address the above-mentioned technical problems by providing a high ripple current aluminum electrolytic capacitor and its preparation method.

[0007] This invention provides a high ripple current aluminum electrolytic capacitor, comprising a core and a casing. The core is coated with an electrolyte, which contains a solvent, a solute, and an additive. The solvent accounts for 40-60% of the total mass of the electrolyte, the solute accounts for 30-50% of the total mass of the electrolyte, and the additive accounts for 3-10% of the total mass of the electrolyte. The additive is composed of ammonium adipate, ammonium pentaborate, tetraethylphosphonium tetrafluoroborate, nano-silica, p-nitroanisole, and tetraethylammonium.

[0008] Furthermore, the mass percentage of each component in the additive is as follows: ammonium adipate 30-55%, ammonium pentaborate 20-32%, tetraethylphosphonium tetrafluoroborate 8-15%, nano silica 5-10%, p-nitroanisole 3-8%, and tetraethylammonium 1-5%.

[0009] Furthermore, the solvent comprises γ-butyrolactone, sulfolane, ethylene carbonate, diethylene glycol methyl ether, and 3-methoxypropionitrile; the solute comprises ammonium sebacate, dodecyl diacid, tetramethylammonium, and ammonium salts of multi-branched dicarboxylic acids.

[0010] Furthermore, the mass percentage of each component in the solvent is as follows: γ-butyrolactone 35~55%, sulfolane 20~39%, ethylene carbonate 10~15%, diethylene glycol methyl ether 2~8%, and 3-methoxypropionitrile 1~3%.

[0011] Furthermore, the mass percentage of each component in the solute is as follows: ammonium sebacate 35-55%, dodecyl diacid 25-45%, tetramethylammonium 10-20%, and ammonium salt of multi-branched dicarboxylic acids 2-8%.

[0012] Furthermore, the multi-branched dicarboxylic acid ammonium salt is 2-ethyl-2-methylsuccinate ammonium.

[0013] Furthermore, the particle size of the nano-silica is 20~50nm.

[0014] Furthermore, the core package is formed by winding an anode foil, a cathode foil, and electrolytic paper between the two. The anode foil is formed using a three-dimensional etching technique with a voltage of 1.3 to 1.5 times the rated withstand voltage. The winding and starting stage is controlled as follows: the empty roll length of the electrolytic paper is 80 to 95 mm, the number of paper layers between the positive and negative foils is pulled apart to 2 to 4 layers, the pre-wound length of the anode foil is 2.0 to 3.0 mm, and the delay length of the cathode foil is: the anode foil leads the cathode foil by 5 to 7 mm.

[0015] This invention also provides a method for preparing a high ripple current aluminum electrolytic capacitor, comprising the following steps: S1: The positive electrode conductive foil and the negative electrode conductive foil are riveted to the anode foil and the cathode foil respectively. The anode foil is formed by three-dimensional etching technology to form a voltage of 1.3 to 1.5 times the rated withstand voltage. S2: Electrolytic paper is inserted between the anode foil and the cathode foil and wound into a core package. The winding and starting stage is controlled as follows: the empty roll length of the electrolytic paper is 80~95mm, the number of paper layers between the positive and negative foils is pulled apart to 2~4 layers, the pre-wound length of the anode foil is 2.0~3.0mm, and the delay length of the cathode foil is: the anode foil leads the cathode foil by 5~7mm. S3: Bake and dry the wound core package for 1-2 hours; S4: Prepare the electrolyte as described in any of the above technical solutions; S5: Immerse the dried core package from S3 into the electrolyte prepared in S4 for impregnation treatment, and then remove the liquid after impregnation; S6: After the S5 impregnation and dehydration, the core is packed into the shell and sealed with a rubber stopper. The thickness of the encapsulated waist wheel is 1.0~2.0mm. S7: Perform aging treatment on the packaged capacitor.

[0016] Furthermore, the electrolyte is prepared as follows: (1) Mix γ-butyrolactone, sulfolane, ethylene carbonate, diethylene glycol methyl ether, and 3-methoxypropionitrile in the specified proportions and heat to 110~120℃; (2) Add ammonium sebacate, dodecyl diacid, and ammonium salt of multi-branched dicarboxylic acid, and stir until completely dissolved; (3) Cool down to 110~120℃, add ammonium adipate and ammonium pentaborate, and stir to dissolve; (4) Cool down to 90~100℃, add tetramethylammonium, tetraethylphosphonium tetrafluoroborate and tetraethylammonium, and stir until completely dissolved; (5) Cool down to 80~90℃, add nano-silica, and disperse until a uniform and stable suspension system is formed; (6) Cool down to ≤80℃, add p-nitroanisole, stir until completely dissolved, and let stand to remove bubbles to obtain the finished electrolyte.

[0017] Beneficial effects of the invention This invention discloses a high ripple current aluminum electrolytic capacitor and its preparation method, achieving performance improvement through the synergistic effect of multiple components in the electrolyte. The electrolyte adopts a multi-component mixed solvent system composed of γ-butyrolactone, sulfolane, ethylene carbonate, diethylene glycol methyl ether, and 3-methoxypropionitrile. Combined with the viscosity-reducing effect of diethylene glycol methyl ether and the high dielectric strengthening effect of 3-methoxypropionitrile, it possesses both high thermal stability and high ionic conductivity. The solute uses a combination of ammonium sebacate, dodecyl diacid, tetramethylammonium, and multi-branched dicarboxylic acid ammonium salts to improve flashover voltage and high-temperature stability. Among the additives, tetraethylphosphonium tetrafluoroborate synergistically achieves dynamic repair of the oxide film with nano-silica. Ammonium adipate and ammonium pentaborate are used together; ammonium adipate provides basic conductivity, while ammonium pentaborate provides film formation and voltage withstand capability. Their synergy gives the electrolyte both high conductivity and strong film-forming and repair capabilities. p-Nitroanisole and tetraethylammonium synergistically eliminate hydrogen, effectively suppressing side reactions.

[0018] Furthermore, the coordinated control of three parameters during the winding and unwinding stage can prevent short circuits in the first roll, and the three-dimensional etching of the anode foil can improve capacitance retention. Testing showed that the capacitor provided by this invention, after being loaded at 105°C and rated ripple current for 2000 hours, exhibited capacitance decay and ESR growth rates that met the relevant standard's acceptable limits. It is suitable for high-frequency switching applications such as silicon carbide and gallium nitride server power supplies, possessing both high ripple current withstand capability and long high-temperature lifespan. Detailed Implementation

[0019] 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.

[0020] Example 1

[0021] This embodiment provides a method for preparing a high ripple current aluminum electrolytic capacitor, the specific steps of which include: S1: Riveting The positive electrode conductive foil and the negative electrode conductive foil are riveted to the anode foil and the cathode foil, respectively.

[0022] The anode foil is treated using a three-dimensional etching technique. High-purity aluminum foil is placed in a mixed electrolyte containing hydrochloric acid and sulfuric acid for electrochemical etching. By controlling process parameters such as electrolyte composition, temperature, and current density, the etching is guided to propagate longitudinally along specific crystal orientations of the aluminum foil, forming a tunnel-type microporous array structure. After etching, the anode foil undergoes a formation treatment to achieve a voltage 1.4 times its rated withstand voltage.

[0023] S2: Core wrapping winding Electrolytic paper is inserted between the anode foil and the cathode foil, and then wound into a core package. The parameters for the winding and starting stage are controlled as follows: (1) The length of the empty roll of electrolytic paper is 90mm (4.5 turns), and the number of paper layers between the positive and negative foils is pulled apart to 3 layers; (2) The anode foil is pre-wound to a length of 2.5 mm, so that the cut edge of the anode foil is rolled inward to avoid burrs sticking outward; (3) Cathode foil delay length: The anode foil leads the cathode foil by 6mm, that is, the anode and cathode are misaligned by 6mm when they start to roll, further widening the slit spacing.

[0024] S3: Drying treatment The wound core package is baked and dried for 1-2 hours.

[0025] S4: Electrolyte preparation The electrolyte in this embodiment is composed of the following components by mass percentage: solvent 45%, solute 45%, and additives 10%; The mass percentages of each component in the solvent are as follows: γ-butyrolactone 47%, sulfolane 30%, ethylene carbonate 15%, diethylene glycol methyl ether 6%, and 3-methoxypropionitrile 2%. The mass percentages of each component in the solute are: ammonium sebacate 45%, dodecyl diacid 40%, tetramethylammonium 10%, and ammonium salt of multi-branched dicarboxylic acids 5%. The mass percentages of each component in the additive are as follows: ammonium adipate 48%, ammonium pentaborate 25%, tetraethyl tetrafluoroborate phosphonium 10%, nano silica 8%, p-nitroanisole 6%, and tetraethyl ammonium 3%.

[0026] Among them, the multi-branched dicarboxylic acid ammonium salt is selected from 2-ethyl-2-methylsuccinate ammonium salt; the particle size of nano-silica is 30nm.

[0027] Specifically, the electrolyte preparation method is as follows: (1) Add γ-butyrolactone, sulfolane, ethylene carbonate, diethylene glycol methyl ether, and 3-methoxypropionitrile to the reaction vessel according to the ratio, stir and mix evenly, and heat to 110~120℃; (2) Add ammonium sebacate, dodecyl diacid, and ammonium salt of multi-branched dicarboxylic acid, and stir until completely dissolved; (3) Cool down to 110~120℃, add ammonium adipate and ammonium pentaborate, and stir to dissolve; (4) Cool to 90~100℃, add tetramethylammonium, tetraethylphosphonium tetrafluoroborate, and tetraethylammonium, and stir until completely dissolved (avoid temperatures above 105℃ to inhibit BF4). - hydrolysis); (5) Cool down to 80~90℃, slowly add nano-silica to the above solution, and continue to disperse at high speed until a uniform and stable suspension system without visible particles is formed; (6) Cool down to ≤80℃, add p-nitroanisole, stir for 30 minutes until completely dissolved, and let stand to remove bubbles to obtain the finished electrolyte.

[0028] S5: Electrolyte impregnation The dried core package of S3 is immersed in the electrolyte prepared by S4 for impregnation treatment; after impregnation, it is dehydrated by centrifugal dehydrator for 60 seconds at a frequency of 30Hz.

[0029] S6: Package After the S5 impregnation and dehydration process, the core is packaged into a shell and sealed with a rubber stopper; the thickness of the encapsulated waist wheel is 1.5±0.5mm.

[0030] S7: Aging The encapsulated capacitors undergo an aging process.

[0031] Example 2

[0032] This embodiment provides a method for preparing a high ripple current aluminum electrolytic capacitor, which differs from Embodiment 1 in that: S1: Riveting The anode foil is treated with three-dimensional etching technology to form a voltage 1.3 times the rated withstand voltage.

[0033] S2: Core wrapping winding The empty roll length of the electrolytic paper is 80mm (4 turns), and the number of paper layers between the positive and negative foils is pulled apart to 2; the pre-wound length of the anode foil is 2.0mm; the delayed length of the cathode foil is 5mm (the anode foil leads the cathode foil by 5mm).

[0034] S4: Electrolyte preparation The electrolyte in this embodiment is composed of the following components by mass percentage: 60% solvent, 30% solute, and 10% additives; The mass percentages of each component in the solvent are as follows: γ-butyrolactone 35%, sulfolane 39%, ethylene carbonate 15%, diethylene glycol methyl ether 8%, and 3-methoxypropionitrile 3%. The mass percentages of each component in the solute are: ammonium sebacate 35%, dodecyl diacid 45%, tetramethylammonium 18%, and ammonium salt of multi-branched dicarboxylic acids 2%; The mass percentages of each component in the additive are as follows: ammonium adipate 30%, ammonium pentaborate 32%, tetraethyltetrafluoroborate phosphonium 15%, nano silica 10%, p-nitroanisole 8%, and tetraethylammonium 5%.

[0035] The particle size of the nano-silica is 20 nm.

[0036] The preparation method is the same as S4 in Example 1.

[0037] The remaining steps are the same as in Example 1.

[0038] Example 3

[0039] This embodiment provides a method for preparing a high ripple current aluminum electrolytic capacitor, which differs from Embodiment 1 in that: S1: Riveting The anode foil is treated with three-dimensional etching technology to form a voltage 1.5 times the rated withstand voltage.

[0040] S2: Core wrapping winding The empty roll length of the electrolytic paper is 95mm (5 turns), and the number of paper layers between the positive and negative foils is pulled apart to 4; the pre-wound length of the anode foil is 3.0mm; the delayed length of the cathode foil is 7mm (the anode foil leads the cathode foil by 7mm).

[0041] S4: Electrolyte preparation The electrolyte in this embodiment is composed of the following components by mass percentage: solvent 40%, solute 50%, and additives 10%. The mass percentages of each component in the solvent are as follows: γ-butyrolactone 55%, sulfolane 20%, ethylene carbonate 14%, diethylene glycol methyl ether 8%, and 3-methoxypropionitrile 3%; The mass percentages of each component in the solute are: ammonium sebacate 55%, dodecyl diacid 25%, tetramethylammonium 18%, and ammonium salt of multi-branched dicarboxylic acids 2%; The mass percentages of each component in the additive are as follows: ammonium adipate 55%, ammonium pentaborate 20%, tetraethyl tetrafluoroborate 8%, nano silica 9%, p-nitroanisole 3%, and tetraethyl ammonium 5%.

[0042] The particle size of the nano-silica is 50 nm.

[0043] The preparation method is the same as S4 in Example 1.

[0044] The remaining steps are the same as in Example 1.

[0045] Example 4

[0046] This embodiment provides a method for preparing a high ripple current aluminum electrolytic capacitor, which differs from Embodiment 1 in that: S4: Electrolyte preparation The electrolyte in this embodiment is composed of the following components by mass percentage: solvent 50%, solute 47%, and additives 3%; The mass percentages of each component in the solvent are as follows: γ-butyrolactone 52%, sulfolane 35%, ethylene carbonate 10%, diethylene glycol methyl ether 2%, and 3-methoxypropionitrile 1%. The mass percentages of each component in the solute are: ammonium sebacate 42%, dodecyl diacid 30%, tetramethylammonium 20%, and ammonium salt of multi-branched dicarboxylic acids 8%. The mass percentages of each component in the additive are as follows: ammonium adipate 45%, ammonium pentaborate 30%, tetraethyltetrafluoroborate phosphonium 12%, nano silica 5%, p-nitroanisole 7%, and tetraethylammonium 1%.

[0047] The particle size of the nano-silica is 30nm.

[0048] The preparation method is the same as S4 in Example 1.

[0049] The remaining steps are the same as in Example 1.

[0050] Comparative Example 1 This comparative example provides a method for preparing an aluminum electrolytic capacitor. The difference between this method and Example 1 is that 3-methoxypropionitrile is not added to the solvent of the electrolyte. The original proportion of 3-methoxypropionitrile is allocated according to the proportion of other components in the solvent, that is, the solvent is 48.0% γ-butyrolactone, 30.6% sulfolane, 15.3% ethylene carbonate, and 6.1% diethylene glycol methyl ether. The components and proportions of solute and additives are the same as in Example 1.

[0051] The remaining preparation steps are the same as in Example 1.

[0052] Comparative Example 2 This comparative example provides a method for preparing an aluminum electrolytic capacitor. The difference between this method and Example 1 is that no multi-branched dicarboxylic acid ammonium salt is added to the solute of the electrolyte. The original proportion of the multi-branched dicarboxylic acid ammonium salt is allocated according to the proportion of other components in the solute, that is, the solute is ammonium sebacate 47.4%, dodecyl diacid 42.1%, and tetramethylammonium 10.5% (total 100%). The solvent and additive components and their proportions are the same as in Example 1.

[0053] The remaining preparation steps are the same as in Example 1.

[0054] Comparative Example 3 This comparative example provides a method for preparing an aluminum electrolytic capacitor. The difference between this method and Example 1 is that nano-silica is not added to the electrolyte additives. The original proportion of nano-silica is allocated according to the proportions of other components in the additives, namely, the additives are ammonium adipate 52.2%, ammonium pentaborate 27.2%, tetraethylphosphonium tetrafluoroborate 10.9%, p-nitroanisole 6.5%, and tetraethylammonium 3.2% (total 100%). The solvent and solute components and ratios are the same as in Example 1. The remaining preparation steps are the same as in Example 1.

[0055] Comparative Example 4 This comparative example provides a method for preparing an aluminum electrolytic capacitor. The difference between this method and Example 1 is that tetraethylphosphonium tetrafluoroborate is not added to the electrolyte additives. The original proportion of tetraethylphosphonium tetrafluoroborate is allocated according to the proportions of other components in the additives, i.e., the additives are ammonium adipate 53.3%, ammonium pentaborate 27.8%, nano-silica 8.9%, p-nitroanisole 6.7%, and tetraethylammonium 3.3% (total 100%). The solvent and solute components and ratios are the same as in Example 1. The remaining preparation steps are the same as in Example 1.

[0056] Comparative Example 5 This comparative example provides a method for preparing an aluminum electrolytic capacitor. The difference between this method and Example 1 is that no linkage control is used in the winding stage: the length of the empty roll of electrolytic paper is 50 mm (about 2.5 turns), and the number of paper layers between the positive and negative foils is pulled apart to 1 layer; there is no pre-winding of the anode foil, no delay of the cathode foil, and the anode foil and cathode foil are rolled up flush with each other without misalignment.

[0057] The remaining preparation steps are the same as in Example 1.

[0058] Comparative Example 6 This comparative example provides a method for preparing an aluminum electrolytic capacitor. The difference between this method and Example 1 is that the anode foil is prepared using a conventional DC etching process instead of a stereolithography process, resulting in a voltage 1.3 times the rated withstand voltage.

[0059] The remaining preparation steps are the same as in Example 1.

[0060] Performance testing To verify the technical effect of the present invention, the capacitors prepared in Examples 1-4 and Comparative Examples 1-6 were subjected to performance comparison tests.

[0061] A capacitor with a specification of 450V 820μF and a size of Φ30×60mm was fabricated according to the methods of the embodiments and comparative examples. The testing equipment included an LCR digital bridge, a leakage current tester, and a flashover voltage tester.

[0062] Initial performance testing (take a set of 10 samples): Measure the initial capacity at 20℃ and 120Hz; measure the initial ESR at 20℃ and 100kHz; test the leakage current for 300s at 20℃ and rated voltage of 450V.

[0063] High-temperature ripple loading test for 2000 hours (using the same group of samples after the initial performance test): The above 10 samples were placed in a constant temperature environment of 105℃, and a rated voltage of 450Vdc and a rated ripple current of 2.40A / 120Hz were applied (the peak voltage after superimposed ripple does not exceed 450V) for 2000 hours. After the loading was completed, the samples were cooled to 20℃ and allowed to recover for 16 hours. The capacitance, ESR, and leakage current were then remeasured. The capacitance decay rate was calculated as ΔC / C0=(C-C0) / C0×100%, and the ESR growth rate was calculated as ΔESR / ESR0=(ESR-ESR0) / ESR0×100%.

[0064] Flash voltage test (using a separate core impregnated with the electrolyte to be tested): at 10mA / cm 2 The current density is constant current boosted, with a boost rate of 0.5~1V / s. The voltage-time curve is monitored in real time, and the voltage value corresponding to the first voltage drop is recorded, which is the flashover voltage of the sample. The average value of 10 samples is taken.

[0065] High-temperature load life test (10 additional new samples): A rated voltage of 450V and a rated ripple current of 2.40A / 120Hz were continuously applied at a constant temperature of 105℃ (Note: Ensure the peak voltage does not exceed 450V). The load was interrupted every 500 hours, cooled to 20℃, and then allowed to recover for 16 hours before retesting the capacity, ESR, and leakage current. Failure criteria were based on IEC 60384-4: a capacity change rate exceeding ±20% of the initial value, an ESR change rate exceeding twice the initial value, or a leakage current exceeding the specification limit. Failure was deemed complete upon meeting any of these conditions, and the cumulative load time was recorded.

[0066] The test results are shown in Tables 1-4.

[0067] Table 1. Initial performance parameters (mean) of each embodiment and comparative example

[0068] Table 2. Performance parameters (mean values) of each embodiment and comparative example after 2000 hours of high-temperature ripple loading.

[0069] Table 3. Flashover voltage (mean) of each embodiment and comparative example

[0070] Table 4. High-Temperature Load Life Test Results of Each Example and Comparative Example

[0071] Note: Lifetime testing is performed every 500 hours. Comparative data indicates that all samples failed at this testing point; example data indicates that all samples were still valid at the 3000-hour testing point, and the test was terminated.

[0072] As shown in Tables 1-4, the embodiments of the present invention all exhibit excellent high-temperature and high-ripple durability. After being subjected to 105°C, rated voltage, and rated ripple current for 2000 hours, Examples 1-4 showed significantly better capacity decay rate, ESR growth rate, and leakage current than the comparative examples. No samples failed within 2000 hours, and all samples appeared normal. In contrast, the comparative examples all showed varying degrees of failure, with some samples exhibiting aluminum shell bulging and explosion-proof valve opening.

[0073] The flash voltage of the embodiments of the present invention is significantly better than that of Comparative Examples 1-4. The flash voltages of Examples 1-4 are all at a high level, while the flash voltage of Comparative Example 1 is at a low level. The electrolytes of Comparative Examples 1-4 lack key components, and their flash voltages are significantly lower than those of Example 1. The flash voltage tests were not repeated for Comparative Examples 5 and 6 because their electrolyte formulations were the same as those of Example 1.

[0074] The increased flash voltage in this invention stems from the synergistic effect of multiple components in the electrolyte. Ammonium 2-ethyl-2-methylsuccinate has a methyl group and an ethyl group simultaneously attached to the α-carbon. This branched structure forms a stereoadsorption configuration on the electrode surface, and its steric hindrance effect inhibits the diffusion and adsorption of solvent molecules to the electrode surface, and reduces the catalytic decomposition reaction rate of solvent molecules at the electrode interface; the phosphonium cation (P...) of tetraethylphosphonium tetrafluoroborate... + The center possesses strong polarization adsorption capabilities, enabling it to form an adsorption layer at the anode interface to reduce the surface concentration of negative ions and enhance the flashover voltage. The three-dimensional network structure of nano-silica fixes phosphonium cations near the anode interface, allowing them to function more concentratedly. The synergistic effect of the electrolyte components comprehensively improves the flashover voltage, making the capacitor less prone to oxide film breakdown under transient overvoltage and reverse voltage conditions.

[0075] In terms of high-temperature, high-ripple durability and lifespan, the components of the electrolyte of this invention also exhibit synergistic effects. The capacity decay rate and ESR growth rate of Comparative Examples 2-5 after 2000 hours were higher than those of Example 1, with Comparative Example 3 (without nano-SiO2) and Comparative Example 4 (without tetraethylphosphonium tetrafluoroborate) showing the most significant performance degradation. The mechanism of action is as follows: the nano-SiO2 particles form a three-dimensional network structure through hydrogen bonding, and the network pore size matches the size of the phosphonium cations, which can delay the diffusion of phosphonium cations into the bulk electrolyte, maintaining a high local concentration near the anode interface; the phosphonium cations (P... + Compared to conventional quaternary ammonium cations (N... +Phosphorus cations possess higher polarizability and stronger coordination ability, enabling them to undergo directional chemical interactions with silanol groups (Si-OH) on the surface of the SiO2 network and embed themselves into the network framework. Under an electric field, the fixed phosphonium cations can be released at microscopic defects in the oxide film and participate in the electrochemical repair reaction. When either nano-SiO2 or tetraethyltetrafluoroborate phosphonium is lacking, the above-mentioned synergistic mechanism is disrupted, accelerating oxide film degradation and electrolyte drying. Furthermore, the P of tetraethyltetrafluoroborate phosphonium... + Center is more than N + The center has higher thermal stability, higher ion pair dissociation and stronger hydrophobicity, which correspond to the performance requirements of the electrolyte in terms of high temperature and long life, low ESR and inhibition of hydration failure.

[0076] Regarding process control, Comparative Example 5, which lacks linkage control during the winding process, exhibits significantly higher 2000-hour capacity decay rate and ESR growth rate compared to Example 1. When the electrolytic paper is not sufficiently wrapped during the winding stage, a micro-short circuit risk exists between the anode and cathode foils. Outward-curling burrs cause localized current density concentration and increased temperature rise, accelerating electrolyte consumption and capacity decay. This demonstrates that the coordinated control of the three parameters in S2—the empty roll length of the electrolytic paper, the pre-wound length of the anode foil, and the delayed length of the cathode foil—plays a crucial role in improving the long-term reliability of the product. Comparative Example 6, with its anode foil subjected to ordinary DC corrosion, shows inferior 2000-hour capacity decay rate and ESR growth rate compared to Example 1. This is because the anode foil in Example 1 utilizes a three-dimensional corrosion technique to form an ordered tunnel-type microporous array structure, resulting in a uniform electric field distribution and good mechanical strength. Combined with the repair capabilities of the electrolyte in this invention, this leads to a slower capacity decay of the capacitor throughout its entire lifespan.

[0077] In summary, the high ripple current aluminum electrolytic capacitor provided by this invention has excellent high temperature and high ripple durability and long life characteristics, and is suitable for high-frequency switching scenarios such as silicon carbide and gallium nitride server power supplies.

[0078] 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 high ripple current aluminum electrolytic capacitor, comprising a core and a housing, wherein the core is coated with an electrolyte, characterized in that, The electrolyte comprises a solvent, a solute, and an additive. The solvent accounts for 40-60% of the total mass of the electrolyte, the solute accounts for 30-50% of the total mass of the electrolyte, and the additive accounts for 3-10% of the total mass of the electrolyte. The additive is composed of ammonium adipate, ammonium pentaborate, tetraethylphosphonium tetrafluoroborate, nano-silica, p-nitroanisole, and tetraethylammonium.

2. The high ripple current aluminum electrolytic capacitor according to claim 1, characterized in that, The mass percentages of each component in the additive are as follows: ammonium adipate 30-55%, ammonium pentaborate 20-32%, tetraethyltetrafluoroborate phosphonium 8-15%, nano silica 5-10%, p-nitroanisole 3-8%, and tetraethylammonium 1-5%.

3. The high ripple current aluminum electrolytic capacitor according to claim 1, characterized in that, The solvent comprises γ-butyrolactone, sulfolane, ethylene carbonate, diethylene glycol methyl ether, and 3-methoxypropionitrile; the solute comprises ammonium sebacate, dodecyl diacid, tetramethylammonium, and ammonium salts of multi-branched dicarboxylic acids.

4. The high ripple current aluminum electrolytic capacitor according to claim 3, characterized in that, The mass percentages of each component in the solvent are as follows: γ-butyrolactone 35-55%, sulfolane 20-39%, ethylene carbonate 10-15%, diethylene glycol methyl ether 2-8%, and 3-methoxypropionitrile 1-3%.

5. The high ripple current aluminum electrolytic capacitor according to claim 3, characterized in that, The mass percentages of each component in the solute are: ammonium sebacate 35-55%, dodecyl diacid 25-45%, tetramethylammonium 10-20%, and multi-branched dicarboxylic acid ammonium salt 2-8%.

6. The high ripple current aluminum electrolytic capacitor according to claim 3, characterized in that, The multi-branched dicarboxylic acid ammonium salt is 2-ethyl-2-methylsuccinate ammonium.

7. The high ripple current aluminum electrolytic capacitor according to claim 1, characterized in that, The particle size of the nano-silica is 20~50nm.

8. The high ripple current aluminum electrolytic capacitor according to claim 1, characterized in that, The core package is formed by winding an anode foil, a cathode foil, and electrolytic paper between the two. The anode foil is formed by three-dimensional etching technology with a voltage of 1.3 to 1.5 times the rated withstand voltage. The winding and starting stage is controlled as follows: the empty roll length of the electrolytic paper is 80 to 95 mm, the number of paper layers between the positive and negative foils is pulled apart to 2 to 4 layers, the pre-wound length of the anode foil is 2.0 to 3.0 mm, and the delay length of the cathode foil is: the anode foil leads the cathode foil by 5 to 7 mm.

9. A method for preparing a high ripple current aluminum electrolytic capacitor, characterized in that, Includes the following steps: S1: The positive electrode conductive foil and the negative electrode conductive foil are riveted to the anode foil and the cathode foil respectively. The anode foil is formed by three-dimensional etching technology to form a voltage of 1.3 to 1.5 times the rated withstand voltage. S2: Electrolytic paper is inserted between the anode foil and the cathode foil and wound into a core package. The winding and starting stage is controlled as follows: the empty roll length of the electrolytic paper is 80~95mm, the number of paper layers between the positive and negative foils is pulled apart to 2~4 layers, the pre-wound length of the anode foil is 2.0~3.0mm, and the delay length of the cathode foil is: the anode foil leads the cathode foil by 5~7mm. S3: Bake and dry the wound core package for 1-2 hours; S4: Prepare the electrolyte according to any one of claims 1 to 7; S5: Immerse the dried core package from S3 into the electrolyte prepared in S4 for impregnation treatment, and then remove the liquid after impregnation; S6: After the S5 impregnation and dehydration, the core is packed into the shell and sealed with a rubber stopper. The thickness of the encapsulated waist wheel is 1.0~2.0mm. S7: Perform aging treatment on the packaged capacitor.

10. The preparation method according to claim 9, characterized in that, The electrolyte is prepared as follows: (1) Mix γ-butyrolactone, sulfolane, ethylene carbonate, diethylene glycol methyl ether, and 3-methoxypropionitrile in the specified proportions and heat to 110~120℃; (2) Add ammonium sebacate, dodecyl diacid, and ammonium salt of multi-branched dicarboxylic acid, and stir until completely dissolved; (3) Cool down to 110~120℃, add ammonium adipate and ammonium pentaborate, and stir to dissolve; (4) Cool down to 90~100℃, add tetramethylammonium, tetraethylphosphonium tetrafluoroborate and tetraethylammonium, and stir until completely dissolved; (5) Cool down to 80~90℃, add nano-silica, and disperse until a uniform and stable suspension system is formed; (6) Cool down to ≤80℃, add p-nitroanisole, stir until completely dissolved, and let stand to remove bubbles to obtain the finished electrolyte.

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