Electrolyte for aluminum electrolytic capacitor, aluminum electrolytic capacitor and preparation method thereof

Abstract

The present invention relates to the technical field of capacitors, and in particular to an electrolyte for aluminum electrolytic capacitors, an aluminum electrolytic capacitor and a preparation method thereof. The aluminum electrolytic capacitor is composed of an anode aluminum foil, an electrolytic paper, a cathode aluminum foil and an electrolyte; wherein the electrolyte comprises the following raw materials in parts by weight: 60 to 90 parts of a solvent, 1 to 5 parts of a modified polycarboxylic acid, 5 to 20 parts of an organic carboxylic acid ammonium salt, 1 to 4 parts of an inhibitor, 2 to 15 parts of a flash voltage enhancer and 1 to 3 parts of a hydrogen absorber. The present invention also provides a preparation method thereof. Compared with the prior art, the aluminum electrolytic capacitor prepared by the present invention has a higher electrostatic capacitance and good corrosion resistance, and also exhibits excellent low temperature performance.

Description

Technical Field

[0001] The present invention relates to the technical field of capacitors, and in particular to an electrolyte for an aluminum electrolytic capacitor, an aluminum electrolytic capacitor and a preparation method thereof. Background Art

[0002] Aluminum electrolytic capacitors are capacitors whose anodes consist of aluminum foil and cathodes consist of paper and aluminum foil soaked in electrolyte. The main features of aluminum electrolytic capacitors include: Large capacity: Aluminum electrolytic capacitors have large capacitance values ​​due to their special structural design and process manufacturing technology. This is mainly because the oxide film (Al2O3) formed on the surface of the anode aluminum foil is very thin and dense. This oxide film, as a dielectric, has a high dielectric constant and can effectively store charge. In addition, the electrochemical etching process of the aluminum foil increases the surface area, thereby increasing the capacitance value. Aluminum electrolytic capacitors usually adopt a structural design that winds up a flat capacitor. This design allows the surface area of ​​the electrode to be increased in a relatively small space, thereby increasing the capacity of the capacitor. There are positive and negative polarities: Aluminum electrolytic capacitors have clear positive and negative polarities, and attention must be paid to the correct connection of the positive and negative electrodes when using them. If connected in reverse, the capacitor will not only fail to work properly, but may also heat up due to excessive leakage current, damage the oxide film, and even explode. This phenomenon is called the "valve effect" and is the reason why aluminum electrolytic capacitors have polarity. Withstand voltage limit: The withstand voltage of aluminum electrolytic capacitors is mainly limited by the thickness of the aluminum oxide film and the unevenness of the aluminum foil surface. The thickness of the aluminum oxide film is proportional to the withstand voltage, but an overly thick oxide film is prone to become brittle and crack on the rough and porous surface of the aluminum foil, resulting in cracks and leakage. The unevenness of the aluminum foil surface will also affect the withstand voltage of the capacitor, because the unevenness may cause local voltage concentration, which may lead to breakdown. Self-healing function of the oxide film: During the operation of the aluminum electrolytic capacitor, the aluminum oxide film will gradually thicken to form a protective layer to prevent aluminum from being dissolved in the electrolyte. When a fault occurs inside the capacitor, the capacitor will automatically start the self-healing function, and through the thermal effect and ion diffusion effect, the aluminum oxide film will be re-formed and thickened, and finally restore its normal working state.

[0003] CN112927938A discloses an electrolyte for an aluminum electrolytic capacitor, an aluminum electrolytic capacitor and an electronic device, and relates to the field of electrochemical technology. The electrolyte for the aluminum electrolytic capacitor includes the following components: an alcohol solvent, an auxiliary solvent, a solute, a flash voltage enhancer, a corrosion inhibitor and a new type of dehydrogenating agent. The electrolyte for the aluminum electrolytic capacitor proposed in the invention, firstly, introduces a solute with a long carbon chain and a branched chain to inhibit the esterification reaction of the electrolyte at high temperature, reduce the generation of water, and improve the high temperature stability of the product; secondly, through the synergistic effect of the auxiliary solvent and the new type of dehydrogenating agent, the internal air pressure of the aluminum electrolytic capacitor is maintained within a stable range, which is safe and stable, prevents the aluminum electrolytic capacitor from bulging, and improves the life of the aluminum electrolytic capacitor.

[0004] CN107910183A discloses a high-voltage aluminum electrolytic capacitor resistant to low temperatures of -40°C, including a shell and a cover, a core package is arranged in the shell, the core package is soaked in an electrolyte, the conductivity of the electrolyte at -40°C is above 1.4ms / cm, the core package is formed by overlapping and winding an anode foil, a cathode foil and an electrolytic paper, wherein the same side of the cathode foil and the anode foil is respectively provided with electrolytic paper as a substrate, the electrolytic paper includes an inner layer of electrolytic paper and an outer layer of electrolytic paper, the inner layer of electrolytic paper is made of Manila hemp and kraft paper. The outer layer of electrolytic paper is made of plant fiber that has not been coated and bleached. The invention improves the process steps and conditions, and the overall coordination increases the electrostatic capacity of the high-voltage aluminum electrolytic capacitor under low temperature conditions of -40°C to 65%~80% under 20°C conditions, effectively improves the low temperature resistance of the high-voltage aluminum electrolytic capacitor, can reduce costs, reduce the size of the capacitor, and better meet the current stringent electronic design technology requirements.

[0005] Aluminum electrolytic capacitors are widely used in power filtering, decoupling, signal coupling and time constant setting. Their advantages include large capacitance per unit volume and low price, but their disadvantages are large dielectric loss and capacitance error, poor low temperature resistance and corrosion resistance. Usually, electrolyte precipitation or electrolyte freezing is prone to occur below -25°C, resulting in a sharp decrease in capacitor capacity. When the low-temperature capacity decrease exceeds a certain value, the whole machine may not start. As well as the anode corrosion phenomenon of electrolytic capacitors, the service life of electrolytic capacitors will be greatly reduced. Summary of the invention

[0006] In view of the above-mentioned defects in the prior art, the technical problem to be solved by the present invention is to provide an electrolyte for aluminum electrolytic capacitors, an aluminum electrolytic capacitor and a preparation method thereof.

[0007] The electrolyte is a key component in aluminum electrolytic capacitors. This is because the electrolyte is closely related to the performance of aluminum electrolytic capacitors. As the actual cathode of aluminum electrolytic capacitors, the electrolyte plays an important role in providing oxygen ions and repairing the aluminum anodized film. The electrolytes in the working electrolytes of the common liquid aluminum electrolytic capacitors on the market are mostly linear polycarboxylic acids, which leads to problems such as low flash voltage, poor low-temperature performance, and poor thermal stability of the electrolyte, which greatly limits the performance of aluminum electrolytic capacitors. The electrolyte significantly affects the electrostatic capacity, charge and discharge rate, long-term reliability, and temperature characteristics of the capacitor through its conductivity, dielectric constant, chemical stability, amount, additives, and solvent chemical properties. Therefore, choosing a suitable electrolyte is crucial to optimizing the overall performance of the capacitor. The present invention provides a modified polycarboxylic acid and an organic carboxylic acid ammonium salt as electrolytes in an electrolyte. The modified polycarboxylic acid has a ring structure and non-polar groups and sulfonic acid groups, so it has more stable low-temperature electrical properties and higher electrostatic capacity. The sulfonic acid group has higher chemical stability and acidity and can form a stable adsorption layer with the metal surface, thereby inhibiting the corrosion of the metal. Therefore, in the electrolyte of an aluminum electrolytic capacitor, the sulfonic acid group can be used as a part of a corrosion inhibitor, and through acting on the surface of an aluminum foil, the pitting and surface corrosion peeling of the aluminum foil during the corrosion process are reduced, the distribution of surface tunnel holes is improved, and the performance and life of the capacitor are improved.

[0008] To achieve the above object, the present invention provides an aluminum electrolytic capacitor, which is composed of an anode aluminum foil, an electrolytic paper, a cathode aluminum foil and an electrolyte; wherein the electrolyte comprises the following raw materials in parts by weight: 60 to 90 parts of a solvent, 1 to 5 parts of a modified polycarboxylic acid, 5 to 20 parts of an organic carboxylic acid ammonium salt, 1 to 4 parts of an inhibitor, 2 to 15 parts of a flash voltage enhancer and 1 to 3 parts of a hydrogen absorber.

[0009] Obviously, the present invention also simultaneously provides an electrolyte for aluminum electrolytic capacitors, comprising the following raw materials in parts by weight: 60-90 parts of solvent, 1-5 parts of modified polycarboxylic acid, 5-20 parts of organic carboxylic acid ammonium salt, 1-4 parts of inhibitor, 2-15 parts of flash voltage enhancer and 1-3 parts of hydrogen absorber.

[0010] The preparation method of the modified polycarboxylic acid comprises the following steps:

[0011] X1. Mix 4-hydroxycyclohexane-1-sulfonic acid, sodium and anhydrous tetrahydrofuran under an inert atmosphere, wherein the molar ratio of 4-hydroxycyclohexane-1-sulfonic acid to sodium is 1:1-1.5, heat to 40-50° C. and stir for 6-10 hours, filter and concentrate to obtain a residue for the next step;

[0012] X2. Add the product of the previous step to ethylene glycol, then add 2-bromotetradecanoic acid ethyl ester, heat to 70-80°C, stir for 4-8h, then add aqueous sodium hydroxide solution, the molar ratio of the product of the previous step to 2-bromotetradecanoic acid ethyl ester and sodium hydroxide is 1:1-2:1-2. After stirring for hydrolysis, add phosphoric acid to adjust the pH to acidic.

[0013] Furthermore, the solvent is one of ethylene glycol and γ-butyrolactone or a mixture of both.

[0014] Furthermore, the organic carboxylic acid ammonium salt includes one or a mixture of diethylamine sebacate, ammonium sebacate, and ammonium azelate.

[0015] Furthermore, the inhibitor is one of phosphoric acid, phosphorous acid or hypophosphorous acid.

[0016] Furthermore, the flash voltage enhancer is one of mannitol, polyvinyl alcohol borate or polymerized fatty acid and ammonium salt.

[0017] Furthermore, the hydrogen absorber is one of p-nitrobenzoic acid, p-nitrobenzyl alcohol or p-nitrophenol.

[0018] The method for preparing the electrolyte for aluminum electrolytic capacitor comprises the following steps:

[0019] Heat the solvent to 100-120°C and add the modified polycarboxylic acid, heat to 130-150°C and keep warm for 1-2h, cool to 100-120°C and add the organic carboxylic acid ammonium salt, continue to cool to 80-90°C and add the inhibitor, flash voltage enhancer and hydrogen absorber, mix well and cool to room temperature to obtain the electrolyte for aluminum electrolytic capacitors.

[0020] The present invention also provides a method for preparing an aluminum electrolytic capacitor, comprising the following steps:

[0021] The anode aluminum foil, electrolytic paper and cathode aluminum foil are wound into a core package, and the core package is immersed in an electrolyte, pressurized and impregnated, and charged and aged to obtain the result.

[0022] Furthermore, the pressurization is 3 to 5 atmospheres.

[0023] Beneficial effects of the present invention:

[0024] The present invention provides a modified polycarboxylic acid and an organic carboxylic acid ammonium salt as electrolytes in an electrolyte. The modified polycarboxylic acid has a ring structure and non-polar groups and sulfonic acid groups, so it has more stable low-temperature electrical properties and higher electrostatic capacity. The sulfonic acid group has higher chemical stability and acidity and can form a stable adsorption layer with the metal surface, thereby inhibiting the corrosion of the metal. Therefore, in the electrolyte of an aluminum electrolytic capacitor, the sulfonic acid group can be used as a part of a corrosion inhibitor, and through acting on the surface of an aluminum foil, the pitting and surface corrosion peeling of the aluminum foil during the corrosion process are reduced, the distribution of surface tunnel holes is improved, and the performance and life of the capacitor are improved. DETAILED DESCRIPTION

[0025] 4-Hydroxycyclohexane-1-sulfonic acid, CAS No.: 58730-94-2.

[0026] Example 1

[0027] A method for preparing an aluminum electrolytic capacitor comprises the following steps:

[0028] The anode aluminum foil, electrolytic paper and cathode aluminum foil are wound into a core package, the core package is immersed in the electrolyte, and the pressure is increased to 5 atmospheres for impregnation. The specifications and dimensions of the capacitor core package are selected as follows: 400V, 500μF, Ф35×50mm, and the product is obtained after charging and aging.

[0029] The method for preparing the electrolyte for aluminum electrolytic capacitors comprises the following steps, measured in parts by weight:

[0030] Heat 60 parts of ethylene glycol and 15 parts of γ-butyrolactone to 120°C, add 4 parts of modified polycarboxylic acid, heat to 140°C and keep warm for 1h, cool to 120°C, add 8 parts of ammonium sebacate and 8 parts of ammonium azelaic acid, continue to cool to 85°C, add 2 parts of phosphorous acid, 9 parts of mannitol and 1 part of p-nitrobenzoic acid, mix well, and cool to room temperature to obtain an electrolyte for aluminum electrolytic capacitors;

[0031] The preparation method of the modified polycarboxylic acid comprises the following steps:

[0032] X1. Mix 4-hydroxycyclohexane-1-sulfonic acid, sodium and anhydrous tetrahydrofuran under an inert atmosphere, wherein the molar ratio of 4-hydroxycyclohexane-1-sulfonic acid to sodium is 1:1, heat to 45° C. and stir for 8 h. Filter and concentrate to obtain a residue for the next step;

[0033] X2. Add the product of the previous step to ethylene glycol, then add 2-bromotetradecanoic acid ethyl ester, heat to 80°C and stir for 6 hours, then add 1 mol / L sodium hydroxide aqueous solution, the molar ratio of the product of the previous step to 2-bromotetradecanoic acid ethyl ester and sodium hydroxide is 1:1:1.5, stir and hydrolyze, then add phosphoric acid to adjust to pH=6.

[0034] Example 2

[0035] It is basically the same as Example 1, the only difference being that the amount of the modified polycarboxylic acid is 2 parts.

[0036] Example 3

[0037] It is basically the same as Example 1, the only difference being that the amount of the modified polycarboxylic acid is 3 parts.

[0038] Example 4

[0039] It is basically the same as Example 1, the only difference being that the amount of the modified polycarboxylic acid is 5 parts.

[0040] Comparative Example 1

[0041] A method for preparing an aluminum electrolytic capacitor comprises the following steps:

[0042] The anode aluminum foil, electrolytic paper and cathode aluminum foil are wound into a core package, the core package is immersed in the electrolyte, and the pressure is increased to 5 atmospheres for impregnation. The specifications and dimensions of the capacitor core package are selected as follows: 400V, 500μF, Ф35×50mm, and the product is obtained after charging and aging.

[0043] The method for preparing the electrolyte for aluminum electrolytic capacitors comprises the following steps, measured in parts by weight:

[0044] Heat 60 parts of ethylene glycol and 15 parts of γ-butyrolactone to 120°C, add 10 parts of ammonium sebacate and 10 parts of ammonium azelaic acid, continue to cool to 85°C, add 2 parts of phosphorous acid, 9 parts of mannitol and 1 part of p-nitrobenzoic acid, mix well, and cool to room temperature to obtain the electrolyte for aluminum electrolytic capacitors.

[0045] Comparative Example 2

[0046] A method for preparing an aluminum electrolytic capacitor comprises the following steps:

[0047] The anode aluminum foil, electrolytic paper and cathode aluminum foil are wound into a core package, the core package is immersed in the electrolyte, and the pressure is increased to 5 atmospheres for impregnation. The specifications and dimensions of the capacitor core package are selected as follows: 400V, 500μF, Ф35×50mm, and the product is obtained after charging and aging.

[0048] The method for preparing the electrolyte for aluminum electrolytic capacitors comprises the following steps, measured in parts by weight:

[0049] Heat 60 parts of ethylene glycol and 15 parts of γ-butyrolactone to 120°C, add 4 parts of modified polycarboxylic acid, heat to 140°C and keep warm for 1h, cool to 120°C, add 8 parts of ammonium sebacate and 8 parts of ammonium azelaic acid, continue to cool to 85°C, add 2 parts of phosphorous acid, 9 parts of mannitol and 1 part of p-nitrobenzoic acid, mix well, and cool to room temperature to obtain an electrolyte for aluminum electrolytic capacitors;

[0050] The preparation method of the modified polycarboxylic acid comprises the following steps:

[0051] X1. Mix cyclohexanol, sodium and anhydrous tetrahydrofuran under an inert atmosphere, wherein the molar ratio of cyclohexanol to sodium is 1:1, heat to 45°C and stir for 8 hours, filter and concentrate to obtain a residue for the next step;

[0052] X2. Add the product of the previous step to ethylene glycol, then add 2-bromotetradecanoic acid ethyl ester, heat to 80°C and stir for 6 hours, then add 1 mol / L sodium hydroxide aqueous solution, the molar ratio of the product of the previous step to 2-bromotetradecanoic acid ethyl ester and sodium hydroxide is 1:1:1.5, stir and hydrolyze, then add phosphoric acid to adjust to pH=6.

[0053] Comparative Example 3

[0054] A method for preparing an aluminum electrolytic capacitor comprises the following steps:

[0055] The anode aluminum foil, electrolytic paper and cathode aluminum foil are wound into a core package, the core package is immersed in the electrolyte, and the pressure is increased to 5 atmospheres for impregnation. The specifications and dimensions of the capacitor core package are selected as follows: 400V, 500μF, Ф35×50mm, and the product is obtained after charging and aging.

[0056] The method for preparing the electrolyte for aluminum electrolytic capacitors comprises the following steps, measured in parts by weight:

[0057] Heat 60 parts of ethylene glycol and 15 parts of γ-butyrolactone to 120°C, add 4 parts of modified polycarboxylic acid, heat to 140°C and keep warm for 1h, cool to 120°C, add 8 parts of ammonium sebacate and 8 parts of ammonium azelaic acid, continue to cool to 85°C, add 2 parts of phosphorous acid, 9 parts of mannitol and 1 part of p-nitrobenzoic acid, mix well, and cool to room temperature to obtain an electrolyte for aluminum electrolytic capacitors;

[0058] The preparation method of the modified polycarboxylic acid comprises the following steps:

[0059] X1. Mix cyclohexylmethanol, sodium and anhydrous tetrahydrofuran under an inert atmosphere, wherein the molar ratio of cyclohexylmethanol to sodium is 1:1, heat to 45°C and stir for 8 hours, filter and concentrate to obtain a residue for the next step;

[0060] X2. Add the product of the previous step to ethylene glycol, then add 2-bromotetradecanoic acid ethyl ester, heat to 80°C and stir for 6 hours, then add 1 mol / L sodium hydroxide aqueous solution, the molar ratio of the product of the previous step to 2-bromotetradecanoic acid ethyl ester and sodium hydroxide is 1:1:1.5, stir and hydrolyze, then add phosphoric acid to adjust to pH=6.

[0061] Test Example 1

[0062] The aluminum electrolytic capacitors prepared in the examples and control examples were tested for electrostatic capacitance, equivalent series resistance (ESR), conductivity, and flash voltage at room temperature. Specific data are shown in Table 1.

[0063] Table 1 Electrical properties of aluminum electrolytic capacitors

[0064] Electrostatic capacitance and equivalent series resistance are two important parameters of capacitors, which describe the behavior characteristics of capacitors in circuits. Electrostatic capacitance is the ability of a capacitor to store charge. The size of a capacitor determines how much charge it can store and how much charge it can store at a given voltage. Equivalent series resistance refers to the equivalent resistance of a capacitor in an AC circuit due to factors such as leakage, dielectric loss, and conductor resistance. ESR describes the effect of these non-ideal factors on the performance of a capacitor. ESR has an important influence on the charge and discharge speed, ripple current tolerance, and heat loss of a capacitor. The lower the ESR, the higher the charge and discharge efficiency of the capacitor, the stronger the ripple current tolerance, and the smaller the heat loss. From the test data in Table 1, it can be seen that the aluminum electrolytic capacitors prepared by the present invention have a higher electrostatic capacitance and a lower equivalent series resistance. Conductivity refers to an indicator of the conductive performance of a capacitor, which indicates the ability of a current per unit length or unit area to pass through a capacitor. The higher the conductivity, the stronger the conductive capacity of the capacitor. The flashover voltage refers to the voltage at which a flashover (i.e., electrical breakdown) occurs in the working electrolyte of a capacitor. The flash voltage is an important parameter to measure the insulation performance of capacitors, which is related to the conductivity and water content of the electrolyte. From the data in Table 1, it can be seen that compared with the control example 1, the aluminum electrolytic capacitors in the embodiment and control examples 2-3 have higher conductivity and flash voltage. This may be because compared with the branched carboxylic acid ammonium in the control example 1, the modified polycarboxylic acid in the embodiment and control examples 2-3 not only has an alkane branch, but also has a ring structure and a non-polar group. The ring tension of the ring structure leads to a more stable ion movement rate in the solution, thereby having better electrical properties. Compared with other embodiments, embodiment 1 has the best conductivity and flash voltage. This may be because the electrolyte is a key repair factor for repairing the anode foil oxide film in the electrolyte. When the content of these repair factors is low, the repair ability in the electrolyte is insufficient and cannot compete with the discharge ability of oxygen anions, resulting in poor electrical performance. On the contrary, if the content of the electrolyte is too high, the acidity of the electrolyte is enhanced, and the concentration of oxygen-containing acid ions increases accordingly, which will increase the possibility of oxygen anion discharge, thereby causing the flash voltage to drop. Therefore, the aluminum electrolytic capacitor in Example 1 exhibits the best electrical performance.

[0065] Test Example 2

[0066] The aluminum electrolytic capacitors prepared in the embodiment and the control example were subjected to a durability test at low temperature, with a voltage of 450 V and a ripple current of 1.33 A applied. After a 2000 h durability test (120 Hz) at -50°C, -25°C, and 20°C, the capacity loss and leakage current were tested, as shown in Table 2.

[0067] Table 2 Low temperature electrical durability of aluminum electrolytic capacitors

[0068]

[0069] From the data in Table 2, it can be seen that compared with Control Example 1, the aluminum electrolytic capacitors prepared in other examples of the present invention have good low-temperature performance. This may be because the electrolytes used in other examples not only have branched carboxylic acid ammonium salts but also modified polycarboxylic acids, which contain non-polar groups such as ether bonds. The alkyl groups have a higher potential and will also hinder the generation of oxygen anions. The ring tension of the ring structure also ensures that the ion movement rate in the solution is relatively stable, so that good electrical properties can be maintained even at low temperatures.

[0070] Test Example 3

[0071] Twenty samples of the aluminum electrolytic capacitors of each embodiment and the control example were taken and life tests were carried out in a 105° C. constant temperature convection oven to observe the corrosion conditions and record the shortest life time and the amount of corrosion, as shown in Table 3.

[0072] Table 3 Corrosion resistance of aluminum electrolytic capacitors

[0073] Experimental protocol Life span / h Corrosion quantity / piece Example 1 6000 0 Example 2 6000 0 Example 3 6000 0 Example 4 5500 0 Comparative Example 1 2500 16 Comparative Example 2 3500 14 Comparative Example 3 3500 15

[0074] From the corrosion resistance test, it can be seen that the aluminum electrolytic capacitor prepared in the embodiment has better corrosion resistance than the control example. This may be because the modified polycarboxylic acid prepared in the embodiment has an additional sulfonic acid group, and the sulfonic acid group has high chemical stability and acidity, and can form a stable adsorption layer with the metal surface, thereby inhibiting the corrosion of the metal. In the electrolyte of the aluminum electrolytic capacitor, the sulfonic acid group can be used as a part of the corrosion inhibitor. By interacting with the surface of the aluminum foil, it can reduce the pitting and surface corrosion peeling of the aluminum foil during the corrosion process, improve the distribution of the surface tunnel holes, and improve the performance and life of the capacitor. In contrast, there is only a branched carboxylic acid ammonium salt in Control Example 1, and the modified polycarboxylic acids in Control Examples 2 to 3 do not have a sulfonic acid group, so the corrosion resistance is poor.

[0075] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. An aluminum electrolytic capacitor, characterized in that: It is composed of anode aluminum foil, electrolytic paper, cathode aluminum foil and electrolyte; The electrolyte comprises the following raw materials in parts by weight: 60-90 parts of solvent, 1-5 parts of modified polycarboxylic acid, 5-20 parts of organic carboxylic acid ammonium salt, 1-4 parts of inhibitor, 2-15 parts of flash voltage enhancer and 1-3 parts of hydrogen absorber; the preparation method of the modified polycarboxylic acid comprises the following steps: X1. Mix 4-hydroxycyclohexane-1-sulfonic acid, sodium and anhydrous tetrahydrofuran under an inert atmosphere, wherein the molar ratio of 4-hydroxycyclohexane-1-sulfonic acid to sodium is 1:1-1.5, heat to 40-50° C. and stir for 6-10 hours, filter and concentrate to obtain a residue for the next step; X2. Add the product of the previous step to ethylene glycol, then add 2-bromotetradecanoic acid ethyl ester, heat to 70-80°C, stir for 4-8h, then add aqueous sodium hydroxide solution, the molar ratio of the product of the previous step to 2-bromotetradecanoic acid ethyl ester and sodium hydroxide is 1:1-2:1-2. After stirring for hydrolysis, add phosphoric acid to adjust the pH to acidic.

2. The aluminum electrolytic capacitor according to claim 1, wherein: The solvent is one of ethylene glycol and gamma-butyrolactone or a mixture of the two.

3. The aluminum electrolytic capacitor according to claim 1, wherein: The organic carboxylic acid ammonium salt includes one or a mixture of diethylamine sebacate, ammonium sebacate and ammonium azelate.

4. The aluminum electrolytic capacitor according to claim 1, wherein: The inhibitor is one of phosphoric acid, phosphorous acid or hypophosphorous acid.

5. The aluminum electrolytic capacitor according to claim 1, wherein: The flash voltage enhancer is one of mannitol, polyvinyl alcohol borate or polymerized fatty acid and ammonium salt.

6. The aluminum electrolytic capacitor according to claim 1, wherein: The hydrogen absorbent is one of p-nitrobenzoic acid, p-nitrobenzyl alcohol or p-nitrophenol.

7. The aluminum electrolytic capacitor according to claim 1, wherein: The preparation method of the electrolyte comprises the following steps: Heat the solvent to 100-120°C and add the modified polycarboxylic acid, heat to 130-150°C and keep warm for 1-2 hours, cool to 100-120°C and add the organic carboxylic acid ammonium salt, continue to cool to 80-90°C and add the inhibitor, flash voltage enhancer and hydrogen absorber, mix well and cool to room temperature to obtain the electrolyte.

8. A method for preparing an aluminum electrolytic capacitor according to any one of claims 1 to 7, characterized in that: The steps include: The anode aluminum foil, electrolytic paper and cathode aluminum foil are wound into a core package, and the core package is immersed in an electrolyte, pressurized and impregnated, and charged and aged to obtain the result.

9. An electrolyte for an aluminum electrolytic capacitor, characterized in that: The method comprises the following raw materials in parts by weight: 60-90 parts of solvent, 1-5 parts of modified polycarboxylic acid, 5-20 parts of organic carboxylic acid ammonium salt, 1-4 parts of inhibitor, 2-15 parts of flash voltage enhancer and 1-3 parts of hydrogen absorber; The preparation method of the modified polycarboxylic acid comprises the following steps: X1. Mix 4-hydroxycyclohexane-1-sulfonic acid, sodium and anhydrous tetrahydrofuran under an inert atmosphere, wherein the molar ratio of 4-hydroxycyclohexane-1-sulfonic acid to sodium is 1:1-1.5, heat to 40-50° C. and stir for 6-10 hours, filter and concentrate to obtain a residue for the next step; X2. Add the product of the previous step to ethylene glycol, then add 2-bromotetradecanoic acid ethyl ester, heat to 70-80°C, stir for 4-8h, then add aqueous sodium hydroxide solution, the molar ratio of the product of the previous step to 2-bromotetradecanoic acid ethyl ester and sodium hydroxide is 1:1-2:1-2. After stirring for hydrolysis, add phosphoric acid to adjust the pH to acidic.

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