Long-carbon-chain hydroxyl-containing branched-chain dicarboxylic acid as well as preparation method and application thereof

Abstract

The invention relates to the technical field of an electrolyte of an aluminum electrolytic capacitor, and discloses a long-carbon-chain hydroxyl-containing branched-chain dicarboxylic acid and a preparation method and application thereof. The preparation method of the long-carbon-chain hydroxyl-containing branched-chain dicarboxylic acid comprises the following steps: under the action of an oxidizing agent and acid, sequentially carrying out an olefinic bond epoxidation reaction and a ring-opening hydrolysis reaction on dimer acid as shown in a formula (II), wherein n is an integer from 1 to 10, and m is an integer from 5 to 15. The synthesized long-carbon-chain hydroxyl-containing branched-chain dicarboxylic acid contains a plurality of hydroxyl groups, has a long carbon chain, and shows comprehensive properties such as good solubility, high sparking voltage, good heat resistance and the like. # imgabs0 #

Description

Technical Field

[0001] The invention relates to the technical field of electrolytes for aluminum electrolytic capacitors, and in particular to a long carbon chain hydroxyl-containing branched dicarboxylic acid and a preparation method and application thereof. Background Art

[0002] Aluminum electrolytic capacitors are mainly composed of aluminum oxide electrode foil, electrolyte and diaphragm. The electrolyte plays a key role in the performance of the capacitor, determining the operating temperature range, rated voltage, loss, impedance, ripple current, service life, etc. of the capacitor. The electrolyte of aluminum electrolytic capacitors mainly includes three parts: solvent, solute and additive. The solvent is a carrier for dissolving solutes and additives. In the composition of the electrolyte, the solvent accounts for 70-90wt%, mainly composed of ethylene glycol, propylene glycol, γ-butyrolactone and other systems. The solute is the core component of the electrolyte, playing a key role in repairing the defects of the anode foil oxide film and improving the conductivity of the electrolyte. It is mainly a linear or branched carboxylic acid ammonium salt. Additives are characteristic modifiers of the electrolyte, mainly including flash voltage enhancers, preservatives, dehydrogenation agents, stabilizers, etc.

[0003] At present, the electrolyte solutes of aluminum electrolytic capacitors are mainly linear or branched carboxylic acid ammonium salts, including ammonium succinate, 2-ethyl-ammonium adipate, 2-butyl ammonium suberate, ammonium azelaic acid, 2-methyl ammonium azelaic acid borate, etc. The solubility, stability, flash voltage, working life and other characteristics of branched carboxylic acid ammonium salts are significantly better than those of linear carboxylic acids. They belong to the third generation of organic aluminum capacitor working electrolyte solutes, are the current mainstream development direction of aluminum capacitor electrolytes, and are also a research hotspot. For example, patent application CN1602532A discloses a method for preparing α-branched dicarboxylic acids using malonic acid esters as starting materials, and reacting with monohaloalkane and dihaloalkane in sequence through substitution, saponification, high-temperature decarboxylation, etc., and preparing them into electrolytes with conductivity of about 2mS / cm and flash voltage between 450 and 540V. Patent application CN115116751A discloses a method of using dibenzhydrylcyclohexanone and hydroxyketoglutarate as raw materials, and obtaining a dibasic hydroxycarboxylic acid through addition reaction under the action of methylthiazole bromide and phase transfer catalyst, converting it into ammonium salt and preparing electrolyte, and its flash voltage is between 480 and 495V, and its conductivity is about 2.2mS / cm. Patent application CN114380684A discloses using cyclohexanedione and methanol as raw materials, and preparing branched carboxylic acid through ring-opening reaction, esterification of straight-chain carboxylic acid, saponification of branched carboxylic acid, acidification of branched carboxylic acid salt, etc., to obtain branched carboxylic acid containing carbonyl group, and preparing it into ethylene glycol electrolyte, and its conductivity is 1.24mS / cm, and its impedance is 857.4Ω·cm, but its flash voltage value has not been measured. Patent application JP2007126611A discloses that ricinoleate is used as raw material, PCC is added to selectively oxidize the hydroxyl groups therein to obtain ricinoleate, and then the ricinoleate is converted into ricinoleate by HWE (Horner-Wadsworth-Emmons) reaction, and then further saponified and acid treated to obtain branched long-chain dicarboxylic acids, the conductivity of which is between 1.3 and 1.6 mS / cm in the working electrolyte, the flash voltage is above 550 V, and it exhibits good heat resistance. However, these methods for preparing branched dicarboxylic acids have problems such as multi-step reactions, high-temperature decarboxylation leading to more side reactions, low overall synthesis yield, poor solubility of some compounds, low flash voltage of the electrolyte after compounding, and poor heat resistance, which are difficult to meet the needs of the modern high-end capacitor industry. Summary of the invention

[0004] The purpose of the present invention is to overcome the problems of low flash voltage and poor heat resistance of branched carboxylic acid ammonium salts in the prior art, and to provide a long carbon chain hydroxyl-containing branched dicarboxylic acid and a preparation method and application thereof. The long carbon chain hydroxyl-containing branched dicarboxylic acid of the present invention contains multiple hydroxyl groups, exhibits good solubility, high flash voltage and good heat resistance, and meets the application requirements of high-end aluminum capacitors.

[0005] In order to achieve the above object, the present invention provides a long carbon chain hydroxyl-containing branched dicarboxylic acid, the structural formula of the long carbon chain hydroxyl-containing branched dicarboxylic acid is shown in formula (I),

[0006]

[0007] Wherein, n is an integer of 1-10, and m is an integer of 5-15.

[0008] The second aspect of the present invention provides a method for preparing the above-mentioned long carbon chain hydroxyl-containing branched dicarboxylic acid, the method comprising: subjecting the dimer acid represented by formula (II) to olefin epoxidation reaction and ring-opening hydrolysis reaction in sequence under the action of an oxidant and an acid;

[0009]

[0010] Wherein, n is an integer of 1-10, and m is an integer of 5-15.

[0011] Preferably, the molar ratio of the dimer acid to the oxidant is 1:2-10.

[0012] Preferably, the oxidant is at least one of m-chloroperbenzoic acid, tert-butyl hydroperoxide, peracetic acid, hydrogen peroxide, acetic acid / hydrogen peroxide and sodium hypochlorite.

[0013] Preferably, the solvent for the olefinic epoxidation reaction is at least one of dichloromethane, dichloroethane, chloroform, chlorobenzene and water.

[0014] Preferably, the temperature of the olefin bond epoxidation reaction is -10°C to 60°C.

[0015] Preferably, the molar ratio of the acid to the dimer acid is 0.5 to 5:1.

[0016] Preferably, the acid is an organic acid or an inorganic acid.

[0017] Preferably, the organic acid is at least one of acetic acid, propionic acid and trifluoroacetic acid.

[0018] Preferably, the inorganic acid is at least one of sulfuric acid, phosphoric acid and hydrochloric acid.

[0019] Preferably, the solvent for the ring-opening hydrolysis reaction is at least one of methanol, ethanol, methyl tert-butyl ether and N,N-dimethylformamide.

[0020] Preferably, the temperature of the ring-opening hydrolysis reaction is room temperature to 100°C.

[0021] The third aspect of the present invention provides an electrolyte, which contains the ammonium salt of the long carbon chain hydroxyl-containing branched dicarboxylic acid described in the present invention and a solvent.

[0022] Preferably, in the electrolyte, the concentration of the ammonium salt of the long carbon chain hydroxyl-containing branched dicarboxylic acid is 10-30 wt %.

[0023] Preferably, the pH value of the electrolyte is 7-8.

[0024] Preferably, the solvent is at least one of ethylene glycol, glycerol and γ-butyrolactone.

[0025] A fourth aspect of the present invention provides a method for preparing the electrolyte described above, the method comprising: dissolving the long carbon chain hydroxyl-containing branched dicarboxylic acid in the solvent, and then introducing ammonia gas.

[0026] A fifth aspect of the present invention provides use of the above-mentioned electrolyte in an aluminum electrolytic capacitor.

[0027] Through the above technical scheme, the present invention uses bio-based dimer acid as a raw material, and synthesizes the target product long carbon chain hydroxyl-containing branched dicarboxylic acid through two-step reaction, the reaction is simple, the yield is high; the raw material source is wide, cheap and easy to obtain, the equipment requirements are simple, and it is easy to expand the synthesis. The synthesized long carbon chain hydroxyl-containing branched dicarboxylic acid contains multiple hydroxyl groups, a long carbon chain, and exhibits comprehensive properties such as good solubility, high flash voltage, and good heat resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is the nuclear magnetic hydrogen spectrum of the dicarboxylic acid C32-HDA prepared in Example 1 ( 1 H-NMR);

[0029] Figure 2 is the NMR carbon spectrum of the dicarboxylic acid C32-HDA prepared in Example 1 ( 13 C-NMR);

[0030] Figure 3 is the infrared spectrum (FT-IR) of the dicarboxylic acid C32-HDA prepared in Example 1;

[0031] Figure 4 is the infrared spectrum (FT-IR) of the dicarboxylic acid C36-HDA prepared in Example 2;

[0032] Figure 5 is the mass spectrum (ESI-MS) of the dicarboxylic acid C32-HDA prepared in Example 1;

[0033] Figure 6 This is the mass spectrum (ESI-MS) of the dicarboxylic acid C36-HDA prepared in Example 2. DETAILED DESCRIPTION

[0034] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0035] The structural formula of the long carbon chain hydroxyl-containing branched dicarboxylic acid of the present invention is shown in formula (I),

[0036]

[0037] In formula (I), n is an integer of 1-10, specifically, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10, preferably 2-5.

[0038] In formula (I), m is an integer of 5-15, specifically, for example, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15, preferably 6-10.

[0039] In a more preferred embodiment, the long carbon chain hydroxyl-containing branched dicarboxylic acid is 11-[2-(8-carboxyoctyl)-3,4-dihydroxy-5,6-dipropylcyclohexyl]-9,10-dihydroxyundecanoic acid and / or 11-[2-(8-carboxyoctyl)-3,4-dihydroxy-5,6-dipentylcyclohexyl]-9,10-dihydroxyundecanoic acid.

[0040] The present invention also provides a method for preparing the above-mentioned long carbon chain hydroxyl-containing branched dicarboxylic acid, which comprises: subjecting the dimer acid represented by formula (II) to olefinic epoxidation reaction and ring-opening hydrolysis reaction in sequence under the action of an oxidant and an acid;

[0041]

[0042] The definitions of n and m are the same as described above.

[0043] According to the method of the present invention, the dimer acid is used as a raw material, and olefin epoxidation reaction and ring-opening hydrolysis reaction are carried out in sequence to obtain the long carbon chain hydroxyl-containing branched dicarboxylic acid of the present invention. The specific reaction process is shown in the following formula.

[0044]

[0045] In the method of the present invention, the molar ratio of the dimer acid to the oxidant may be 1:2-10, preferably 1:2-5, and most preferably 1:3.

[0046] In the method described in the present invention, the dimer acid can be derived from vegetable oleic acid, or obtained by addition of vegetable oleic acid and other long-chain unsaturated carboxylic acids. As specific examples, the dimer acid includes dimer octadecenoic acid (i.e., 11-(2-(8-carboxyoctyl)-5,6-dipentylcyclohex-3-ene-1-yl)undecenoic acid, in formula (II), m=7, n=4), dimer hexadecenoic acid (i.e., 11-(2-(8-carboxyoctyl)-5,6-dipropylcyclohex-3-ene-1-yl)undecenoic acid, in formula (II), m=7, n=2), etc.

[0047] In the method of the present invention, the oxidant can be at least one of m-chloroperbenzoic acid, tert-butyl hydroperoxide, peracetic acid, hydrogen peroxide, acetic acid / hydrogen peroxide and sodium hypochlorite. In a more preferred embodiment, the oxidant is acetic acid / hydrogen peroxide.

[0048] In the method of the present invention, the reaction system of the olefinic epoxidation reaction may contain a solvent or may not contain a solvent. The solvent used in the olefinic epoxidation reaction may be at least one of dichloromethane, dichloroethylene, chloroform, chlorobenzene and water, preferably dichloromethane and / or water.

[0049] In the method of the present invention, the temperature of the olefin epoxidation reaction can be -10°C to 60°C, preferably -5°C to room temperature.

[0050] In the method of the present invention, the molar ratio of the acid to the dimer acid may be 0.5 to 5:1, preferably 0.8 to 2:1, and most preferably 1:1.

[0051] In the method of the present invention, the acid may be an organic acid or an inorganic acid. As an example, the organic acid may be at least one of acetic acid, propionic acid and trifluoroacetic acid; the inorganic acid may be at least one of sulfuric acid, phosphoric acid and hydrochloric acid.

[0052] In the method of the present invention, the reaction system of the ring-opening hydrolysis reaction may contain a solvent or may not contain a solvent. The solvent used in the ring-opening hydrolysis reaction may be at least one of methanol, ethanol, methyl tert-butyl ether and N,N-dimethylformamide, preferably ethanol.

[0053] In the method of the present invention, the temperature of the ring-opening hydrolysis reaction can be room temperature to 100°C, most preferably 60°C.

[0054] The method described in the present invention also includes a separation and purification step. Specifically, after the reaction is completed, an appropriate amount of water and ethyl acetate are added to the reaction system, the liquids are separated, washed, and the organic phase is retained; the organic phase is dried, filtered, and the solvent is distilled off to obtain the target product.

[0055] The present invention also provides an electrolyte, which contains the ammonium salt of the long carbon chain hydroxyl-containing branched dicarboxylic acid described in the present invention and a solvent.

[0056] In the electrolyte, the concentration of the ammonium salt of the long carbon chain hydroxyl-containing branched dicarboxylic acid may be 10-30wt%, preferably 10wt%. The pH value of the electrolyte may be 7-8, most preferably 7.5.

[0057] In the electrolyte, the solvent may be an electrolyte solvent commonly used in the art. As an example, the solvent may be at least one of ethylene glycol, glycerol and γ-butyrolactone.

[0058] The present invention also provides a method for preparing the electrolyte described above, which comprises: dissolving the long carbon chain hydroxyl-containing branched dicarboxylic acid in the solvent, and then introducing ammonia gas.

[0059] In some embodiments, the preparation method of the electrolyte includes: dissolving the long carbon chain hydroxyl-containing branched dicarboxylic acid in ethylene glycol, then introducing ammonia into the prepared ethylene glycol solution, and adjusting the pH value of the ethylene glycol solution to about 7.5 to obtain the electrolyte.

[0060] The present invention also provides the application of the above-mentioned electrolyte in aluminum electrolytic capacitors. In actual application, the electrolyte exhibits good solubility, high flash voltage, good heat resistance, etc. without adding any additives, and can meet the application requirements of high-end aluminum capacitors.

[0061] The following examples further illustrate the long carbon chain hydroxyl-containing branched dicarboxylic acid and its preparation method and application of the present invention. The examples are implemented based on the technical solution of the present invention, and detailed implementation methods and specific operation processes are given, but the protection scope of the present invention is not limited to the following examples.

[0062] The experimental methods in the following examples, unless otherwise specified, are all conventional methods in the art. The experimental materials used in the following examples, unless otherwise specified, are all commercially available.

[0063] In the following examples, 11-(2-(8-carboxyoctyl)-5,6-dipropylcyclohex-3-en-1-yl)undecenoic acid (C 32 H 56 O4) and 11-(2-(8-carboxyoctyl)-5,6-dipentylcyclohex-3-en-1-yl)undecenoic acid (C 36 H 64 O4) were purchased from Shanghai Titan Technology Co., Ltd.

[0064] Example 1

[0065] Synthesis of 11-[2-(8-carboxyoctyl)-3,4-dihydroxy-5,6-dipropylcyclohexyl]-9,10-dihydroxyundecanoic acid (C32-HDA)

[0066] 11-(2-(8-carboxyoctyl)-5,6-dipropylcyclohex-3-ene-1-yl)undecenoic acid (50.5 g, 100.0 mmol), acetic acid (6.0 g, 100.0 mmol) and 0.5 mL of concentrated sulfuric acid were added to a 250 mL round-bottom flask, stirred and heated to 40°C, and hydrogen peroxide (34.0 g, 300.0 mmol) was slowly added dropwise. After the addition was completed, the temperature was slowly raised to 60°C and the reaction was continued for 6 hours. The reaction end point was monitored by TLC. Then, an appropriate amount of ethyl acetate was added to dissolve the reaction mixture, washed with secondary water 3 times, the organic phase was retained and dried over anhydrous Na2SO4, filtered and dried to obtain the target product 11-[2-(8-carboxyoctyl)-3,4-dihydroxy-5,6-dipropylcyclohexyl]-9,10-dihydroxyundecanoic acid (C32-HDA).

[0067] C32-HDA: 3.33 g orange-yellow transparent viscous liquid, yield 97%. 1 H NMR (400MHz, CDCl3) 5.30 (s, 4H), δ2.35 (p, J = 7.4Hz, 6H), 2.10 (t, 4H)), 1.62 (d, J = 7.2Hz, 4H), 1.40–1.21 (m, 36H), 0.88 (t, J = 5.9Hz, 6H). 13 C NMR(101MHz, CDCl3)δ176.92(s),81.15(s),53.44(s),,33.99(s),31.86(s),29.70(s) ),29.02(s),26.73(s),25.05(s),24.60(s),22.67(s),20.77(s),14.11(s).ESI-MS(M + )cal.for[C 32 H 58 O8 2+ ]285.21, found 258.22.

[0068] The H NMR spectrum of dicarboxylic acid C32-HDA ( 1 H-NMR), nuclear magnetic carbon spectrum ( 13 C-NMR), infrared spectrum (FT-IR) and mass spectrum (ESI-MS) are shown as Figure 1 , 2 , 3 and 5 as shown.

[0069] Example 2

[0070] Synthesis of 11-[2-(8-carboxyoctyl)-3,4-dihydroxy-5,6-dipentylcyclohexyl]-9,10-dihydroxyundecanoic acid (C36-HDA)

[0071] 11-(2-(8-carboxyoctyl)-5,6-dipentylcyclohex-3-ene-1-yl)undecenoic acid (56.1 g, 100.0 mmol), acetic acid (6.0 g, 100.0 mmol) and 0.5 mL of concentrated sulfuric acid were added to a 250 mL round-bottom flask, stirred and heated to 40°C, hydrogen peroxide (34.0 g, 300.0 mmol) was slowly added dropwise, and after the addition was completed, the temperature was slowly raised to 60°C and the reaction was continued for 6 hours. An appropriate amount of ethyl acetate was added to dissolve the reaction mixture, and the mixture was washed with secondary water 3 times. The organic phase was retained and dried over anhydrous Na2SO4, filtered and then spin-dried to obtain the target product 11-(2-(8-carboxyoctyl)-3,4-dihydroxy-5,6-dipentylcyclohexyl)-9,10-dihydroxyundecanoic acid (C36-HDA).

[0072] C36-HDA: 5.13 g yellow transparent viscous liquid, yield 91%. 1 H NMR (400MHz, CDCl3) δ5.30 (s, 4H), 2.63–2.43 (m, 4H), 2.35 (p, J = 7.5Hz, 6H), 1.63 (t, J = 7.2Hz, 4H), 1.46–1.08 (m, 44H), 0.96–0.79 (t, 6H). 13 C NMR(101MHz, CDCl3)δ179.84(s),69.62(s),53.43(s),34.01(s),31.94(s),29. 34(s),28.95(s),25.01(s),24.67(s),23.57(s),22.70(s),14.13(s).ESI-MS(M + )cal.for[C 36 H 66 O8 2+ ]313.24, found 313.24.

[0073] The infrared spectrum (FT-IR) and mass spectrum (ESI-MS) of dicarboxylic acid C36-HDA are shown as follows: Figure 4 and 6 shown.

[0074] Example 3

[0075] Preparation of electrolyte

[0076] The dicarboxylic acid C32-HDA was further purified, ions were removed, ethylene glycol was added, and a 10 wt% ethylene glycol solution was prepared. Ammonia gas was introduced for ammoniation, and the end point was monitored until the solution pH value was about 7.5, and the carboxylic acid ammonium salt electrolyte C32-HDA-NH4 was obtained. + .

[0077] Example 4

[0078] Preparation of electrolyte

[0079] The dicarboxylic acid C36-HDA was further purified, ions were removed, ethylene glycol was added, and a 10 wt% ethylene glycol solution was prepared. Ammonia gas was introduced for ammoniation, and the end point was monitored until the solution pH value was about 7.5, and the carboxylic acid ammonium salt electrolyte C36-HDA-NH4 was obtained. + .

[0080] Test Case

[0081] (1) Flash voltage of electrolyte

[0082] Without adding other additive components, the carboxylate ammonium salt electrolytes prepared in the above Examples 3 and 4 were used as working electrolytes for aluminum electrolytic capacitors, and the relevant properties of each working electrolyte were tested and compared with the electrolyte prepared with the existing dibasic ammonium salt. The results are shown in Table 1.

[0083] Table 1: Properties of synthetic carboxylic acid working electrolytes

[0084] Electrolyte pH Moisture content (wt%) Flash voltage(V) <![CDATA[Example 3: C32-HDA-NH4 + > 7.47 0.18 532 <![CDATA[Example 4: C36-HDA-NH4 + > 7.51 0.16 526 Ammonium Sebacate 7.42 0.12 427 2-Ethylammonium adipate 7.39 0.17 442

[0085] It can be seen from the data in Table 1 that when the solute prepared from the long carbon chain hydroxyl-containing branched dicarboxylic acid of the present invention is used as the electrolyte, its flash voltage is significantly improved compared with the existing representative straight-chain carboxylic acid ammonium salts and branched carboxylic acid ammonium salts, and the improvement value is about 70 to 90V.

[0086] (2) Temperature resistance of electrolyte

[0087] The prepared ammonium carboxylate electrolyte was kept at a constant temperature of 105°C, and the conductivity changes thereof were measured for different time periods. The results are shown in Table 2.

[0088] Table 2: Changes in conductivity of electrolyte at 105℃ for different time periods

[0089]

[0090] It can be seen from the data in Table 2 that when the solute prepared from the long carbon chain hydroxyl-containing branched dicarboxylic acid of the present invention is used as the electrolyte, its temperature resistance is significantly improved compared with the existing representative straight-chain carboxylic acid ammonium salts and branched carboxylic acid ammonium salts, with an improvement of about 50%.

[0091] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A long carbon chain hydroxyl-containing branched dicarboxylic acid, characterized in that: The structural formula of the long carbon chain hydroxyl-containing branched dicarboxylic acid is shown in formula (I), Wherein, n is an integer of 1-10, and m is an integer of 5-15.

2. A method for preparing the long carbon chain hydroxyl-containing branched dicarboxylic acid according to claim 1, characterized in that: The method comprises: under the action of an oxidant and an acid, subjecting the dimer acid represented by formula (II) to sequential olefin epoxidation reaction and ring-opening hydrolysis reaction; Wherein, n is an integer of 1-10, and m is an integer of 5-15.

3. The method according to claim 2, characterized in that The molar ratio of the dimer acid to the oxidant is 1:2-10; Preferably, the oxidant is at least one of m-chloroperbenzoic acid, tert-butyl hydroperoxide, peracetic acid, hydrogen peroxide, acetic acid / hydrogen peroxide and sodium hypochlorite.

4. The method according to claim 2 or 3, characterized in that: The solvent for the olefinic bond epoxidation reaction is at least one of dichloromethane, dichloroethylene, chloroform, chlorobenzene and water; and / or The temperature of the olefin bond epoxidation reaction is -10°C to 60°C.

5. The method according to claim 2, characterized in that: The molar ratio of the acid to the dimer acid is 0.5 to 5:

1.

6. The method according to claim 2 or 5, characterized in that: The acid is an organic acid or an inorganic acid, Preferably, the organic acid is at least one of acetic acid, propionic acid and trifluoroacetic acid; Preferably, the inorganic acid is at least one of sulfuric acid, phosphoric acid and hydrochloric acid.

7. The method according to claim 2, 5 or 6, characterized in that: The solvent of the ring-opening hydrolysis reaction is at least one of methanol, ethanol, methyl tert-butyl ether and N,N-dimethylformamide; and / or The temperature of the ring-opening hydrolysis reaction is room temperature to 100°C.

8. An electrolyte, characterized in that: The electrolyte contains the ammonium salt of the long carbon chain hydroxyl-containing branched dicarboxylic acid according to claim 1 and a solvent; Preferably, in the electrolyte, the concentration of the ammonium salt of the long carbon chain hydroxyl-containing branched dicarboxylic acid is 10-30wt%; Preferably, the pH value of the electrolyte is 7-8; Preferably, the solvent is at least one of ethylene glycol, glycerol and γ-butyrolactone.

9. A method for preparing the electrolyte according to claim 8, characterized in that: The method comprises: dissolving the long carbon chain hydroxyl-containing branched dicarboxylic acid in the solvent, and then introducing ammonia gas.

10. Use of the electrolyte according to claim 8 in aluminum electrolytic capacitors.

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