Branched chain polycarboxylic acid mixture as well as preparation method and application thereof

Abstract

The invention provides a branched chain polycarboxylic acid mixture and a preparation method and application thereof, and belongs to the field of electrolyte for aluminum electrolytic capacitors. The electrolyte consisting of the ammonium salt of the branched chain polycarboxylic acid mixture has the characteristics of excellent low-temperature conductivity and high sparking voltage, and has a relatively good application prospect in the field of aluminum electrolytic capacitors.

Description

Technical Field

[0001] This application relates to the field of electrolytes for aluminum electrolytic capacitors, specifically to a branched polycarboxylic acid mixture, its preparation method, and its application. Background Technology

[0002] Aluminum electrolytic capacitors are widely used in filtering, bypassing, coupling, resonance, phase shifting, and energy storage due to their large capacitance per unit volume, small size, light weight, and low price.

[0003] Electrolyte is the main component of capacitor. The working electrolyte of aluminum electrolytic capacitor consists of solvent, solute and appropriate additives. For high voltage aluminum electrolytic capacitor, the solute in the working electrolyte is crucial to the performance of aluminum electrolytic capacitor, such as withstand voltage and conductivity.

[0004] However, existing aluminum electrolytic capacitors with electrolyte solutes still have technical problems such as unsatisfactory conductivity and withstand voltage. Summary of the Invention

[0005] The purpose of this application is to provide a branched polycarboxylic acid mixture, its preparation method and application. The ammonium salt of the branched polycarboxylic acid mixture is used as the main solute in the electrolyte for aluminum electrolytic capacitors, which enables the aluminum electrolytic capacitors to have better conductivity and voltage withstand capability compared with the prior art.

[0006] The first aspect of this application is to provide a branched polycarboxylic acid mixture, which, based on the total mass of the mixture, comprises the following components in mass percentage:

[0007]

[0008] A second aspect of this application is to provide an electrolyte comprising a main solute, wherein the main solute is an ammonium salt of each component in the branched polycarboxylic acid mixture described in the first aspect;

[0009] Based on the total mass of the electrolyte, the mass percentage content of the main solute is 2% to 10%;

[0010] Preferably, the mass percentage content of the main solute is 4% to 10% based on the total mass of the electrolyte.

[0011] In some embodiments, the electrolyte includes a cosolvent;

[0012] The cosolvent includes one or more of ammonium dodecanoate and ammonium azelate.

[0013] In some embodiments, the mass percentage content of the cosolvent is 0% to 6% based on the total mass of the electrolyte.

[0014] In some embodiments, the electrolyte includes a main solvent and a secondary solvent;

[0015] Preferably, the main solvent comprises ethylene glycol;

[0016] Preferably, based on the total mass of the electrolyte, the mass percentage content of the main solvent is 40% to 70%;

[0017] Preferably, the co-solvent comprises any one or more of diethylene glycol, propylene glycol, glycerol, n-butanol, n-octanol, diethylene glycol monobutyl ether, diethylene glycol dibutyl ether, diethylene glycol monomethyl ether, diethylene glycol methyl ether, diethylene glycol diethyl ether, γ-butyrolactone, polyethylene glycol, or butyl acetate.

[0018] Preferably, the mass percentage content of the co-solvent is 5% to 20% based on the total mass of the electrolyte.

[0019] In some embodiments, the electrolyte includes additives;

[0020] Preferably, the additive content is 0% to 24% by mass, based on the total mass of the electrolyte;

[0021] Preferably, the additive includes one or more of the following: a flash fire enhancer, a hydrogen scavenger, and a waterproofing agent.

[0022] A third aspect of this application is to provide a method for preparing the branched polycarboxylic acid mixture described in the first aspect, comprising the following preparation process:

[0023] 1,4-Cyclohexanedione is given by ring-opening reaction to a straight-chain hexadecyl carboxylic acid ester with a free radical;

[0024] The linear hexadecanoic acid ester with free radicals is contacted with (Z)-9-octadecenoic acid to obtain a mixture of branched polycarboxylic acid esters;

[0025] The branched polycarboxylic acid ester mixture is obtained by hydrolysis and acidification.

[0026] In some embodiments, the ring-opening reaction is carried out at a temperature of 5°C to 1°C and for a reaction time of 10 min to 80 min.

[0027] The fourth aspect of this application is to provide a method for preparing the electrolyte described in the second aspect, the method comprising dispersing the branched polycarboxylic acid mixture described in the first aspect or the branched polycarboxylic acid mixture prepared by the method described in the third aspect into a main solvent to form a premix of the branched polycarboxylic acid mixture; and ammonifying the premix of the branched polycarboxylic acid mixture until the final pH value is ≥7.0 to obtain a premix of ammonium salt of branched polycarboxylic acid.

[0028] The premixed solution of the branched polycarboxylic acid ammonium salt is further dispersed into the main solvent to form an electrolyte with a main solute mass ratio of 2% to 10%.

[0029] The fifth aspect of this application is to provide an aluminum electrolytic capacitor comprising the electrolyte described in the second aspect or the electrolyte prepared in the fourth aspect.

[0030] The beneficial technical effects of this application are as follows:

[0031] The ammonium salt of the branched polycarboxylic acid mixture in this application forms the main solute of the electrolyte. The ammonium salt introduces an oxygen-containing group into the carbon chain. This group can form hydrogen bonds with the solvent, which improves the solubility of the large long carbon chain polycarboxylic acid ammonium in the solvent. This makes the working electrolyte prepared with this main solute have the advantages of higher pressure resistance and thermal stability. In addition, the conductivity, flash voltage and high and low temperature resistance of the electrolyte can be effectively improved.

[0032] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Detailed Implementation

[0033] The following detailed description discloses embodiments of the branched polycarboxylic acid mixtures, their preparation methods, and applications. However, unnecessary details may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of essentially the same structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the following description is provided to enable those skilled in the art to fully understand this application and is not intended to limit the subject matter of the claims.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification and claims of this application are intended to cover non-exclusive inclusion.

[0035] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0036] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60–120 and 80–110 are listed for a specific parameter, it is also expected that ranges of 60–110 and 80–120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "2-10" indicates that all real numbers between "2-10" have been listed in this article; "2-10" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0037] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A exists, A and B exist simultaneously, and B exists. In addition, the character " / " in this document generally indicates that the related objects before and after it have an "or" relationship.

[0038] Aluminum electrolytic capacitors are widely used in filtering, bypassing, coupling, resonance, phase shifting, and energy storage due to their large capacitance per unit volume, small size, light weight, and low price.

[0039] With the rapid development of new technologies (such as high-voltage frequency converters, electric vehicles, wind power and photovoltaic power generation, implantable medical devices, etc.), higher requirements are placed on aluminum electrolytic capacitors: (1) They must have high withstand voltage (working voltage > 600V, i.e., ultra-high voltage aluminum electrolytic capacitors), be able to withstand high surge voltages, and must operate with very small voltage drops; (2) They must have the ability to withstand higher ripple currents. High-frequency ripple currents will cause the internal temperature of the capacitor to rise. If the core heats up severely, the electrolyte will dry up quickly, leading to capacitor failure; (3) They must be able to work normally at the highest required temperature and have high thermal stability.

[0040] Electrolyte is the main component of capacitor. The working electrolyte of aluminum electrolytic capacitor consists of solvent, solute and appropriate additives. For high voltage aluminum electrolytic capacitor, the solute in the working electrolyte is crucial to the performance of aluminum electrolytic capacitor, such as withstand voltage and conductivity.

[0041] Existing technologies, such as CN119480467A, disclose the preparation of electrolytes using branched-chain carboxylic acids and their ammonium salts as the main solute. Compared with straight-chain carboxylic acids or their ammonium salts, the solubility, thermal stability, conductivity, and flash voltage of this electrolyte are significantly improved. However, with the increasing demands on aluminum electrolytic capacitors, how to obtain an electrolyte with better conductivity and higher flash voltage while using less main solute is the actual technical problem that this application aims to solve.

[0042] To address the aforementioned technical problems, in a first aspect, this application provides a branched polycarboxylic acid mixture, which comprises the components with the mass contents shown in Table 1 below:

[0043] Table 1. List of components and contents of the branched polycarboxylic acid mixture.

[0044]

[0045] The structural formulas and contents of each component in Table 1 were determined by gas chromatography-mass spectrometry.

[0046] In some embodiments of this application, the ammonium salts of each component in the above-mentioned branched polycarboxylic acid mixture are disclosed as forming the main solute of the electrolyte. The ammonium salts of each component are illustrated in Table 2.

[0047] Table 2. Component list of the branched polycarboxylic acid ammonium salt mixture

[0048]

[0049]

[0050] In these embodiments, this application discloses that, based on the total mass of the branched polycarboxylic acid mixture, the mass percentage content of 7,7'-(octadecane-9,10-diethyl)bis(4-oxopentadecanoic acid) is any one of 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, or any one of the ranges of both above.

[0051] In these embodiments, this application discloses that, based on the total mass of the branched polycarboxylic acid mixture, the mass percentage content of 8-(5-carboxy-3-oxopentyl)-7-octyl-4-oxohexadecanedioic acid is any one of 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, or any one of the ranges of both above.

[0052] In these embodiments, this application discloses that, based on the total mass of the branched polycarboxylic acid mixture, the mass percentage content of 9-(5-carboxy-3-oxopentyl)-10,11-di-n-eicosanoic acid is any one of 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, or any one of the ranges of both above.

[0053] In these embodiments, this application discloses that, based on the total mass of the branched polycarboxylic acid mixture, the mass percentage content of 8-hydroxy-7-octyl-4-oxohexadecanedioic acid is any one of 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any one of the ranges of both above.

[0054] In these embodiments, this application discloses that, based on the total mass of the branched polycarboxylic acid mixture, the mass percentage content of (E)-7-octyl-4-oxohexadecano-8-enediaic acid is any one of 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, or any one of the ranges of both above.

[0055] In these embodiments, this application discloses that, based on the total mass of the branched polycarboxylic acid mixture, the mass percentage content of dodecanoic acid is any one of 0.5%, 1%, 1.5%, 2%, 2.5%, or any one of the ranges of both above.

[0056] The ammonium salt of the branched polycarboxylic acid mixture in this application forms the main solute of the electrolyte. The ammonium salt introduces an oxygen-containing group into the carbon chain. This group can form hydrogen bonds with the solvent, which improves the solubility of the large long carbon chain polycarboxylic acid ammonium in the solvent. This makes the working electrolyte prepared with this main solute have the advantages of higher pressure resistance and thermal stability. In addition, the conductivity, flash voltage and high and low temperature resistance of the electrolyte can be effectively improved.

[0057] A second aspect of this application is to provide an electrolyte comprising a main solute, wherein the main solute is an ammonium salt of each component in the branched polycarboxylic acid mixture described in the first aspect;

[0058] Based on the total mass of the electrolyte, the mass percentage content of this main solute is 2% to 10%.

[0059] In these embodiments, this application discloses that the total mass of the electrolyte contains the main solute at a mass percentage of 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, and 10%.

[0060] In these embodiments, this application discloses that, based on the total mass of the electrolyte, the main solute has a mass percentage content of 2% to 10%, and each component of the main solute has good solubility in the electrolyte solvent. The synergistic effect between the branched polycarboxylic acid ammonium salts can significantly improve the conductivity and flash voltage of the electrolyte, as well as the high and low temperature resistance, voltage withstand performance, and safety and stability performance of the capacitor.

[0061] In some embodiments, the mass percentage content of the main solute is 4% to 10% based on the total mass of the electrolyte.

[0062] In some embodiments, the electrolyte includes a cosolvent.

[0063] In some embodiments, the cosolvent includes one or more of ammonium dodecanoate and ammonium azelate.

[0064] In some embodiments, the mass percentage content of the cosolvent is 0% to 6% based on the total mass of the electrolyte.

[0065] In these embodiments, this application discloses that, based on the total mass of the electrolyte, the mass percentage content of the cosolvent is any one of 0%, 1%, 2%, 3%, 4%, 5%, 6%, or any one of the ranges of both of the above.

[0066] In some embodiments, the electrolyte comprises a primary solvent and a secondary solvent.

[0067] In some embodiments, the mass percentage content of the main solvent is 40% to 70% based on the total mass of the electrolyte; in these embodiments, this application discloses that the mass percentage content of the main solvent is any one of 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70% based on the total mass of the electrolyte, or any one of the ranges of both above.

[0068] In some embodiments, the mass percentage content of the co-solvent is 5% to 20% based on the total mass of the electrolyte. In these embodiments, this application discloses that the mass percentage content of the co-solvent is any one of 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20% based on the total mass of the electrolyte, or any one of the ranges of both of the above.

[0069] In some embodiments, the primary solvent includes ethylene glycol.

[0070] In some embodiments, the co-solvents include any one or more of diethylene glycol, propylene glycol, glycerol, n-butanol, n-octanol, diethylene glycol monobutyl ether, diethylene glycol dibutyl ether, diethylene glycol monomethyl ether, diethylene glycol methyl ether, diethylene glycol diethyl ether, γ-butyrolactone, polyethylene glycol, or butyl acetate.

[0071] In some embodiments, the electrolyte includes additives.

[0072] In some embodiments, the mass percentage content of the additive is 0% to 24% based on the total mass of the electrolyte.

[0073] In some embodiments, based on the total mass of the electrolyte, the mass percentage content of the above-mentioned additive is any one of 0, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, or any one of the ranges of both of the above.

[0074] In some embodiments, the additives include one or more of the following: flash fire enhancers, hydrogen scavengers, and waterproofing agents.

[0075] In some embodiments, the flashover enhancer comprises conventional types in the art, such as polyethylene glycol (PEG), polypropylene glycol, polyacrylamide, polymeric fatty acids, polymeric fatty acid amines, nano-inorganic oxide particles, etc.

[0076] In some embodiments, the above-mentioned flashover enhancer is preferably polyethylene glycol 1000 (PEG1000).

[0077] In some embodiments, the hydrogen scavenger comprises conventional types in the art, such as resorcinol, p-nitrophenol, p-nitrobenzyl alcohol, o-nitroanisole, p-benzoquinone, o-nitroanisole, etc.

[0078] In some embodiments, the waterproofing agent comprises conventional types in the art, such as mannitol, phosphoric acid and its ammonium salts, hypophosphite and its ammonium salts, silica compounds, aluminum salts, etc.

[0079] A third aspect of this application is to provide a method for preparing the branched polycarboxylic acid mixture described in the first aspect, comprising the following preparation process:

[0080] 1,4-Cyclohexanedione is given by ring-opening reaction to a straight-chain hexadecyl carboxylic acid ester with a free radical;

[0081] The above-mentioned straight-chain hexadecyl carboxylic acid ester with free radicals is contacted with (Z)-9-octadecenoic acid to obtain a mixture of branched polycarboxylic acid esters;

[0082] The above-mentioned branched polycarboxylic acid ester mixture was subjected to hydrolysis and acidification to obtain a branched polycarboxylic acid mixture.

[0083] In some embodiments, the temperature of the ring-opening reaction is 5°C to 1°C, and the reaction time is 10 min to 80 min.

[0084] This application discloses in these embodiments that the temperature of the ring-opening reaction is any one of 5°C, 4°C, 3°C, 2°C, 1°C, 0°C, and 1°C, or any one of the ranges of both of the above. The ring-opening reaction time is any one of 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, 70 min, and 80 min, or any one of the ranges of both of the above.

[0085] This application discloses a detailed method for preparing a mixture of branched polycarboxylic acids in some embodiments, which specifically includes the following steps:

[0086] S100 and 1,4-cyclohexanedione undergo a ring-opening reaction in the presence of an alcohol solvent, an acid catalyst, and a strong oxidant to yield a linear hexadecane carboxylic acid ester with a free radical. The ring-opening reaction is carried out at a temperature of 5°C to 1°C and for a reaction time of 10 min to 80 min. The alcohol solvent used in this step includes any one or more of anhydrous methanol, methanol, ethanol, n-butanol, isopropanol, and tert-butanol. The acid catalyst includes any one or more of concentrated nitric acid, concentrated sulfuric acid, and concentrated hydrochloric acid. The strong oxidant is at least one of sodium persulfate, hydrogen peroxide, potassium peroxide, and sodium peroxide.

[0087] S200: The reaction solution of a straight-chain hexadecanoic acid ester with free radicals is contacted with (Z)-9-octadecenoic acid, and a reducing agent is added to continue the reaction to obtain a branched polycarboxylic acid ester mixture. The reducing agent is removed by water extraction, and the solvent is removed by distillation to obtain a branched polycarboxylic acid ester mixture with improved purity. The reaction temperature of this step is 5℃~1℃, and the reducing agent includes any one or more of cuprous chloride, cuprous sulfate, ferrous chloride, ferrous sulfate, ferrous sulfate heptahydrate, sodium sulfite, and potassium sulfite.

[0088] S300: The branched polycarboxylic acid ester mixture with improved purity obtained in step S200 is added to an alkaline solution to undergo a saponification reaction, thereby obtaining an aqueous solution of sodium branched polycarboxylic acid; wherein, the alkaline solution in this step includes an aqueous solution of any one or more of sodium carbonate, sodium hydroxide, potassium carbonate, and potassium hydroxide; in these embodiments, this application also discloses that the mass percentage concentration of the alkaline solution is 8% to 15%.

[0089] S400: The aqueous solution of branched polycarboxylic acid sodium from step S300 is acidified and then extracted and purified to obtain a branched polycarboxylic acid mixture with improved purity. In these embodiments, this application discloses that the acidification treatment is carried out in an acidic solution, which includes an aqueous solution of sulfuric acid. In these embodiments, this application also discloses that the mass percentage concentration of the acidic solution is 45% to 55%.

[0090] In some embodiments, the molar ratio of 1,4-cyclohexanedione to oleic acid is 1:(0.5 to 1.5).

[0091] In these embodiments, this application discloses that the molar ratio of 1,4-cyclohexanedione to oleic acid is any one of 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5 or any one of the above ranges.

[0092] A fourth aspect of this application is to provide a method for preparing the electrolyte described in the second aspect, the method comprising:

[0093] S500: Disperse the branched polycarboxylic acid mixture described in the first aspect or the branched polycarboxylic acid mixture prepared by the method described in the third aspect into a main solvent to form a premix of the branched polycarboxylic acid mixture, and ammonify the premix of the branched polycarboxylic acid mixture until the final pH value is ≥7.0 to obtain a premix of ammonium salt of branched polycarboxylic acid.

[0094] S600, the premixed solution of the branched polycarboxylic acid ammonium salt is further dispersed into the main solvent to form an electrolyte with a main solute mass ratio of 2% to 10%.

[0095] The fifth aspect of this application is to provide an aluminum electrolytic capacitor comprising the electrolyte described in the second aspect or the electrolyte prepared in the fourth aspect.

[0096] The following examples further illustrate this application, but are not intended to limit the scope of this application.

[0097] Example 1

[0098] A method for preparing the main solute of an electrolyte is provided, comprising the following preparation steps:

[0099] S100. Add anhydrous methanol (8 mol) and 1,4-cyclohexanedione (1 mol) to a 1000 mL three-necked flask and place the flask in a -5 °C cooling bath. While stirring, slowly add 0.05 mol of concentrated sulfuric acid (concentration: 98%) dropwise to the flask through a dropping funnel, keeping the temperature between -5 °C and 0 °C. After the addition is complete, react for 15 min. Then, slowly add 111 g of 27.5% hydrogen peroxide dropwise to the flask through a dropping funnel, keeping the temperature between 5 °C and 0 °C. After the addition is complete, react for another 15 min.

[0100] S200. Add 0.65 mol of oleic acid ((Z)-9-octadecenoic acid) to the flask (in the reaction system obtained in step S100), maintain the temperature at 5-0℃, and react for 15 min. Slowly add 1.39 g of ferrous sulfate heptahydrate to the flask, maintain the temperature at -5-0℃, and react for 20 min. Transfer the material to a separatory funnel and allow it to stand and separate into layers. The upper layer is the product, and the lower layer waste liquid is discharged. Wash the upper layer product with pure water to remove impurity ions from the product, and discharge the washing wastewater. Distill the washed upper layer product to remove the solvent, and a relatively pure branched polycarboxylic acid ester mixture is obtained.

[0101] S300. The branched polycarboxylic acid ester mixture obtained in step S200 is added to 380g of sodium hydroxide solution with a mass concentration of 10%. The temperature is raised to about 98°C, and the mixture is refluxed for 4 hours. The temperature is then lowered and the reaction solution is filtered to obtain a clear sodium salt solution of branched polycarboxylic acid.

[0102] S400. Add 180g of 50% dilute sulfuric acid to the clear branched polycarboxylic acid sodium salt solution obtained in step S300 for acidification. After stirring for 30 minutes, allow it to stand and separate into layers. The lower aqueous phase has a pH value <2 and is considered waste liquid. The upper layer is the desired product, thus obtaining a mixture of branched polycarboxylic acids.

[0103] The above-mentioned branched polycarboxylic acid mixture was purified to remove ions, yielding a branched polycarboxylic acid mixture. LC-MS spectral characterization in negative ion mode yielded the following results: m / z = 793.67 (approximately 71%), m / z = 511.42 (approximately 12%), m / z = 693.57 (approximately 7%), m / z = 413.92 (approximately 6%), m / z = 395.33 (approximately 3%), and m / z = 229.13 (approximately 1%).

[0104] The components and contents of this branched polycarboxylic acid mixture are shown in Table 3-1.

[0105] Table 3-1 List of components and contents of branched polycarboxylic acid mixtures

[0106]

[0107] S500: Prepare a 20% ethylene glycol solution from the branched polycarboxylic acid mixture obtained in step S400, and pass ammonia gas through it for ammoniation. The endpoint is a pH of about 7.0, which yields an ethylene glycol solution of branched polycarboxylic acid ammonium salt (premixed solution of branched polycarboxylic acid ammonium salt).

[0108] Example 2

[0109] A method for preparing the main solute of an electrolyte is provided. The method differs from that in Example 1 in that: S200, oleic acid (1.0 mol) is added to the flask and the temperature is maintained at -5 to 0°C for 15 min; 1.39 g of ferrous sulfate heptahydrate is slowly added to the flask and the temperature is maintained at -5 to 0°C for 15 min.

[0110] Everything else remains the same as in Example 1.

[0111] The components and contents of the branched polycarboxylic acid mixture in step S400 are shown in Table 3-2.

[0112] Table 3-2 List of components and contents of branched polycarboxylic acid mixtures

[0113]

[0114] Example 3

[0115] A method for preparing the main solute of an electrolyte is provided. The method differs from that in Example 1 in that: S200, oleic acid (0.5 mol) is added to a flask, the temperature is maintained at -3 to 0°C, and the mixture is stirred for 20 min; 1.39 g of ferrous sulfate heptahydrate is slowly added to the flask, the temperature is maintained at -3 to 0°C, and the mixture is stirred for 20 min.

[0116] Everything else remains the same as in Example 1.

[0117] The components and contents of the branched polycarboxylic acid mixture in step S400 are shown in Table 3-3.

[0118] Table 3-3 List of components and contents in the branched polycarboxylic acid mixture

[0119]

[0120]

[0121] Example 4

[0122] A method for preparing the main solute of an electrolyte is provided. The method differs from that in Example 1 in that: S200, oleic acid (1.5 mol) is added to a flask, the temperature is maintained at -3 to 0°C, and the mixture is stirred for 20 min; 1.39 g of ferrous sulfate heptahydrate is slowly added to the flask, the temperature is maintained at -3 to 0°C, and the mixture is stirred for 15 min.

[0123] Everything else remains the same as in Example 1.

[0124] The components and contents of the branched polycarboxylic acid mixture in step S400 are shown in Table 3-4.

[0125] Table 3-4 List of components and contents in the branched polycarboxylic acid mixture

[0126]

[0127] Comparative Example 1

[0128] A commercially available electrolyte with a main solute of tricresane branched dicarboxylic acid ammonium salt is provided, manufactured by Okamura Oil.

[0129] Comparative Example 2

[0130] A commercially available electrolyte with a main solute of polycarboxylate ammonium salt, manufactured by Okamura Oil, is provided.

[0131] Comparative Example 3

[0132] A method for preparing the main solute of an electrolyte is provided, and the specific preparation method is as follows:

[0133] Preparation of a mixture of branched polycarboxylic acids and ammonium compounds:

[0134] S100. Add anhydrous methanol (8 mol) and cyclohexanone (1 mol) to a 1000 mL three-necked flask; place the flask in a 5 °C cooling bath; while stirring, slowly add 0.05 mol of concentrated sulfuric acid (concentration: 98%) dropwise to the flask through a dropping funnel, keeping the temperature between 5 and 0 °C. After the addition is complete, stir for 15 min; then slowly add 111 g of 27.5% hydrogen peroxide dropwise to the flask through a dropping funnel, keeping the temperature between 5 and 0 °C. After the addition is complete, stir for another 15 min.

[0135] S200, add (Z)-9-octadecenoic acid (0.65 mol) to the flask, keep the temperature at 5-0℃, and stir for 15 min; slowly add 1.39 g of ferrous sulfate heptahydrate to the flask, keep the temperature at 5-0℃, and stir for 20 min;

[0136] The material is transferred to a separatory funnel and allowed to stand and separate into layers. The upper layer is the product, and the lower layer of waste liquid is discharged. The upper product is washed with pure water to remove impurity ions, and the washing wastewater is discharged. The washed upper product is distilled to remove the solvent, thus obtaining a relatively pure mixture of branched polycarboxylic acid esters.

[0137] S300. The above-mentioned branched polycarboxylic acid ester mixture is added to 380g of sodium hydroxide solution with a mass concentration of 10%, heated to about 98°C, refluxed for 4 hours, cooled and filtered to obtain a clear branched polycarboxylic acid sodium salt solution.

[0138] S400. Add 180g of 50% dilute sulfuric acid to a clear solution of branched polycarboxylic acid sodium salt for acidification. Stir for 30 minutes, allow to stand and separate into layers until the pH of the lower aqueous phase is <2. The lower layer is waste liquid; the upper layer is the desired product, which is the branched polycarboxylic acid.

[0139] S500. The above branched polycarboxylic acid is purified to remove ions and prepared into a 20% ethylene glycol solution. Ammonia gas is then introduced to ammonify the solution until the pH value reaches approximately 7.0, thus obtaining an ethylene glycol solution containing a mixture of branched polycarboxylic acids and ammonium.

[0140] Experimental Example 1-1

[0141] S600. The ethylene glycol solution of the branched polycarboxylic acid ammonium salt provided in Example 1 above is dispersed in the main solvent to form the electrolyte shown in Table 4-1.

[0142] Table 4-1 List of components in the electrolyte

[0143]

[0144]

[0145] Experimental Examples 1-2

[0146] The ethylene glycol solution of the branched polycarboxylic acid ammonium salt provided in Example 1 above was dispersed in the main solvent to form the electrolyte shown in Table 4-2.

[0147] Table 4-2 List of components in the electrolyte

[0148]

[0149]

[0150] Experimental Examples 1-3

[0151] The ethylene glycol solution of the branched polycarboxylic acid ammonium salt provided in Example 1 above was dispersed in the main solvent to form the electrolyte shown in Table 4-3.

[0152] Table 4-3 List of components in the electrolyte

[0153]

[0154] Experimental Examples 1-4

[0155] The ethylene glycol solution of the branched polycarboxylic acid ammonium salt provided in Example 1 above was dispersed in the main solvent to form the electrolyte shown in Table 4-4.

[0156] Table 4-4 List of components in the electrolyte

[0157]

[0158]

[0159] Experimental Example 2

[0160] The branched polycarboxylic acid ammonium salt solution provided in Example 2 above was dispersed in the main solvent, and other aspects were kept the same as in Experimental Example 1-1.

[0161] Experimental Example 3

[0162] The branched polycarboxylic acid ammonium salt solution provided in Example 3 above was dispersed in ethylene glycol into the main solvent, and all other aspects remained the same as in Experimental Example 1-1.

[0163] Test Example 4

[0164] The branched polycarboxylic acid ammonium salt solution provided in Example 4 was dispersed in ethylene glycol into the main solvent, and all other aspects remained the same as in Experimental Example 1-1.

[0165] Comparative Test Example 1

[0166] The ethylene glycol solution of the tridecane branched dicarboxylic acid ammonium salt provided in Comparative Example 1 was dispersed in the main solvent, and all other aspects remained the same as in Experimental Example 1-1.

[0167] Comparative Test Example 2

[0168] The ethylene glycol solution of the polycarboxylic acid ammonium salt provided in Comparative Example 2 was dispersed in the main solvent, and all other aspects remained the same as in Experimental Example 1-1.

[0169] Comparative Test Example 3

[0170] The branched polycarboxylic acid ammonium salt solution provided in Comparative Example 3 was dispersed in ethylene glycol into the main solvent, and all other aspects remained the same as in Experimental Example 1-1.

[0171] Characterization and testing of electrolyte:

[0172] (1) Test the water content (wt%) in the electrolyte: Add about 0.25g of the electrolyte to be tested to the balanced Swiss Metrohm 915-TI-Touch moisture tester, record the test results, perform three parallel tests, and take the average value of the three parallel results;

[0173] (2) Test the pH value of the electrolyte: Immerse the test electrode of the Mettler S470-B-KU-pH tester fully in the electrolyte to be tested. After the instrument stabilizes, record the results.

[0174] (3) Test the conductivity of the electrolyte at 30℃ and -40℃: After the electrolyte to be tested is kept at 30℃ and -40℃ for 1 hour, the electrodes of the Mettler S470-B-KU conductivity meter are fully immersed in the electrolyte to be tested and the results are recorded.

[0175] (4) Test the flash voltage of the electrolyte: Immerse an aluminum foil with a conversion voltage of 1000V in a beaker containing a certain amount of electrolyte to be tested, and test it at 30±1℃ using a TV characteristic / leakage current / electrolyte intelligent tester, and record the results;

[0176] (5) Test the stability of the electrolyte at -40℃: Store the electrolyte under test at -40℃ for 96 hours and observe the phenomenon.

[0177] Table 5 lists the performance of each electrolyte in the test cases.

[0178]

[0179]

[0180] As can be seen from the data in Table 5, the electrolytes prepared by the mixture of branched polycarboxylic acids provided in this application as the main solute, compared with the main solutes of tridecane branched dicarboxylic acid ammonium salt (Comparative Example 1) or polycarboxylic acid ammonium salt (Comparative Example 2), showed significantly improved conductivity, flashover voltage and high and low temperature resistance of the electrolytes prepared in Examples 1-1, 2, 3 and 4.

[0181] Compared with Comparative Example 3, Test Example 1-1 of this application differs only in the specific structure of the main solute. However, the electrolyte prepared by Test Example 1-1 of this application has better conductivity, flash voltage, and high and low temperature resistance than the electrolyte prepared by Comparative Example 3. This is because the mixture of branched polycarboxylic acid ammonium salts provided in this application introduces oxygen-containing groups into the carbon chain. These groups can form hydrogen bonds with the solvent, which improves the solubility of the large long carbon chain polycarboxylic acid ammonium salt in the solvent. This results in the electrolyte prepared with this main solute having higher pressure resistance and thermal stability.

[0182] Compared with comparative test example 3, the conductivity of test examples 1-2 in this application did not show a better advantage, which may be due to excessive solvent content. However, the flash voltage of test examples 1-2 was significantly higher than that of comparative test example 3.

[0183] In Examples 1-2 of this application, the amount of solvent (especially the main solvent) was excessive. Therefore, the conductivity of the electrolyte prepared in Examples 1-2 at 30°C and -40°C was lower than that of the electrolytes prepared in Examples 1-1, 2, 3 and 4.

[0184] In Examples 1-4 of this application, the amount of solute (especially the main solute) was excessive. The flash voltage of the electrolyte prepared in Examples 1-4 was lower than that of the electrolyte prepared in Examples 1-1, 2, 3 and 4, but all were better than the comparative examples.

[0185] In summary, the main solute provided in this application, when applied to the electrolyte of aluminum electrolytic capacitors, effectively improves the electrolyte's conductivity, flashover voltage, and high and low temperature resistance.

[0186] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A mixture of branched polycarboxylic acids, characterized in that: The mixture comprises the following components in the following mass percentage:

2. An electrolyte, characterized by: The main solute is an ammonium salt of each component in the branched polycarboxylic acid mixture of claim 1; The mass percentage of the main solute is 2% to 10% based on the total mass of the electrolyte; Preferably, the mass percentage of the main solute is 4% to 10% based on the total mass of the electrolyte.

3. The electrolyte of claim 2, wherein: The auxiliary solute comprises any one or more of ammonium dodecanedioate and ammonium azelate. The mass percentage of the auxiliary solute is 0% to 6% based on the total mass of the electrolyte.

4. The electrolyte of claim 3, wherein: The main solvent and the auxiliary solvent are included; 5. The electrolyte according to any one of claims 2 to 4, characterized in that: Preferably, the main solvent comprises ethylene glycol; Preferably, the mass percentage of the main solvent is 40% to 70% based on the total mass of the electrolyte; Preferably, the auxiliary solvent comprises any one or more of diethylene glycol, propylene glycol, glycerol, n-butanol, n-octanol, diethylene glycol monobutyl ether, diethylene glycol dibutyl ether, diethylene glycol monomethyl ether, diethylene glycol methyl ether, diethylene glycol diethyl ether, gamma-butyrolactone, polyethylene glycol, and butyl acetate; Preferably, the mass percentage of the auxiliary solvent is 5% to 20% based on the total mass of the electrolyte. The additive is included; 6. The electrolyte according to any one of claims 2 to 4, characterized in that: Preferably, the mass percentage of the additive is 0% to 24% based on the total mass of the electrolyte; Preferably, the additive comprises any one or more of flash boosters, hydrogen scavengers, and hydration inhibitors. The preparation process comprises the following steps:

7. A process for the preparation of the branched polycarboxylic acid mixture of claim 1, characterized by: 1,4-cyclohexanone is subjected to a ring-opening reaction to obtain a linear hexanecarboxylic acid ester with free radicals; The linear hexanecarboxylic acid ester with free radicals is contacted with (Z)-9-octadecenoic acid to obtain a branched polycarboxylic acid ester mixture; The branched polycarboxylic acid ester mixture is subjected to a hydrolysis reaction and acidification treatment to obtain a branched polycarboxylic acid mixture. The ring-opening reaction is performed at a temperature of 5°C to 1°C for 10 minutes to 80 minutes.

8. The method of claim 7, wherein: The branched polycarboxylic acid mixture of claim 1 or the branched polycarboxylic acid mixture prepared by the method of any one of claims 7 to 8 is dispersed in a main solvent to form a premix of the branched polycarboxylic acid mixture, and the premix of the branched polycarboxylic acid mixture is subjected to an ammoniation treatment until the end point pH value is greater than or equal to 7.0 to obtain a premix of branched polycarboxylic acid ammonium salt; 9. A method for the preparation of an electrolyte according to any one of claims 2 to 6, characterized in that: The premix of branched polycarboxylic acid ammonium salt is further dispersed in a main solvent to form an electrolyte in which the mass percentage of the main solute is 2% to 10%. The electrolyte of any one of claims 2 to 6 or the electrolyte prepared by the preparation method of claim 9 is included.

10. An aluminum electrolytic capacitor characterized by: ​

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