Electrolyte for solid-liquid mixed type electrolytic capacitor and electrolytic capacitor

Abstract

The application discloses a solid-liquid mixed electrolyte for electrolytic capacitors and an electrolytic capacitor, and relates to the technical field of capacitors.The solid-liquid mixed electrolyte for electrolytic capacitors provided by the application comprises at least the following components: a liquid component: gamma-butyrolactone 40-50%, N-methylpyrrolidone 8-12%, straight-chain carboxylic acid ammonium salt 2-5%, long-chain dicarboxylic acid ammonium salt containing a branched chain 5-15%, silane coupling agent 1-2%, and additive 0.5-5%; and a solid component: surface-modified carboxylated PEDOT nanofiber 10-20% and nanoparticle 1-4%. The solid-liquid mixed electrolyte for electrolytic capacitors provided by the application has high conductivity, high flashover voltage and good high-temperature and low-temperature stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of capacitors, in particular to an electrolyte for solid-liquid mixed electrolytic capacitors and an electrolytic capacitor. BACKGROUND

[0002] The strong applicability of aluminum electrolytic capacitors makes them widely used in many industries and fields, such as electrical equipment, communication equipment, medical equipment, electronic instruments, automotive equipment, entertainment equipment, aerospace, etc. With the development of national infrastructure construction and networking, aluminum electrolytic capacitors have also begun to expand into various new industries, providing more space for the development of aluminum electrolytic capacitors; the working electrolyte of aluminum electrolytic capacitors, as the actual negative electrode of aluminum electrolytic capacitors, plays an extremely important role in aluminum electrolytic capacitor products, as it affects the long-term normal working life of the product and has the function of optimizing the electrical performance of the capacitor. With the increasing demand for high-power, small-size electrical products (including power supplies) on the market, this has also led electrical manufacturers (including power supply manufacturers) to demand smaller aluminum electrolytic capacitor manufacturers with larger ripple current. Under this call, only solid-liquid mixed capacitors can meet the requirements of large ripple, long life and small size. Solid-liquid mixed capacitors, also known as solid-liquid mixed electrolytic capacitors, combine the advantages of both conventional liquid and solid electrolytic capacitors, and are more flexible than liquid capacitors in use. Although mixed capacitors cannot provide the same voltage and capacity as traditional electrolytic capacitors, they do have the ability to generate and repair the oxide film dielectric layer on the surface of the anode aluminum foil, and greatly reduce the equivalent series resistance of the capacitor.

[0003] The existing solid-liquid mixed electrolytic capacitor usually adopts a combination of liquid electrolyte and solid-state conductive polymer, but still has problems such as traditional solvent evaporation at high temperature, leading to a decrease in capacitor life, insufficient solute conductivity, insufficient interface contact between solid-state conductive polymer and liquid electrolyte, leading to an increase in equivalent series resistance (ESR), and insufficient compatibility between liquid and solid electrolytes, which can easily separate at high temperatures. Therefore, the existing solid-liquid mixed electrolytic capacitor has the defects of low solid-liquid mixed electrolyte conductivity, poor temperature performance, and short high-temperature life, which limits the use of this technology. SUMMARY

[0004] The purpose of the present application is to provide an electrolyte for solid-liquid mixed electrolytic capacitors and an electrolytic capacitor, which solves the following technical problems:

[0005] The existing solid-liquid mixed electrolytic capacitor has the problems of low electrolyte conductivity, poor temperature performance, and short high-temperature life.

[0006] The purpose of the present application can be achieved by the following technical solutions:

[0007] The electrolyte for solid-liquid mixed electrolytic capacitor comprises at least the following components:

[0008] Liquid component: gamma-butyrolactone 40-50%, N-methyl pyrrolidone 8-12%, straight-chain carboxylic acid ammonium salt 2-5%, branched-chain long-chain dicarboxylic acid ammonium salt 5-15%, silane coupling agent 1-2%, and additive 0.5-5%;

[0009] Solid component: surface-modified carboxylated PEDOT nanofiber 10-20% and nanoparticle 1-4%.

[0010] As a further scheme of the present application, the branched-chain long-chain dicarboxylic acid ammonium salt has 8-12 carbon atoms in the main chain.

[0011] As a further scheme of the present application, the preparation method of the branched-chain long-chain dicarboxylic acid ammonium salt comprises at least the following steps:

[0012] Cyclohexanone and hydrogen peroxide are added to methanol, and reacted under the catalysis of FeSO4 to obtain a straight-chain carboxylic acid;

[0013] Methyl methacrylate is added to the straight-chain carboxylic acid, and the first fractionated product is collected after reaction;

[0014] Ammonium hydroxide is added to the first fractionated product, and the pH value is adjusted to be acidic after reaction, and the second fractionated product is collected;

[0015] The second fractionated product is added to an ethylene glycol solution, and the pH value is adjusted to be 6-7 by introducing ammonia to obtain an ethylene glycol solution of the branched-chain long-chain dicarboxylic acid ammonium salt.

[0016] As a further scheme of the present application, the molar ratio of the cyclohexanone, the methyl methacrylate and the methanol is 1-2:1-2:10.

[0017] As a further scheme of the present application, the content of the branched-chain long-chain dicarboxylic acid ammonium salt in the ethylene glycol solution of the branched-chain long-chain dicarboxylic acid ammonium salt is 15-20%.

[0018] As a further scheme of the present application, the preparation method of the surface-modified carboxylated PEDOT nanofiber comprises at least the following steps:

[0019] PEDOT / PSS nanofiber is dispersed in deionized water, and acrylic acid is added, and the mixture is reacted under ultraviolet light irradiation, and then washed and dried to obtain carboxylated PEDOT nanofiber;

[0020] The carboxylated PEDOT nanofiber is dispersed in a buffer solution, and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and N-hydroxysuccinimide are added and stirred to obtain activated nanofiber.

[0021] The polyethylene glycol is added into the activated nanofiber, and then the reaction, centrifugation, washing and drying are carried out to obtain the surface-modified carboxylated PEDOT nanofiber.

[0022] As a further scheme of the present application, the mass ratio of the PEDOT / PSS nanofiber and the polyethylene glycol is 3-4:1.

[0023] As a further scheme of the present application, the linear carboxylic acid ammonium salt at least includes one of ammonium tetrafluoroborate, ammonium pentaborate, ammonium benzoate, linear polybasic carboxylic acid ammonium salt with carbon atom number of 5-20, branched polybasic carboxylic acid ammonium salt with carbon atom number of 5-20, and the addition at least includes one of phosphoric acid, citric acid, ammonium phosphite, ammonium hypophosphite, p-nitrobenzyl alcohol, p-nitrobenzoic acid, nitrophenol, p-nitrophenyl ether, mannitol, sorbitol, xylitol or alkyl phosphate.

[0024] As a further scheme of the present application, the silane coupling agent at least includes one of gamma-(methacryloyloxy)propyltrimethoxysilane, gamma-glycidoxypropyltrimethoxysilane, N-(beta-aminoethyl)-gamma-aminopropyltrimethoxysilane and gamma-aminopropyltriethoxysilane, and the nanoparticles at least include one of nano-silicon dioxide particles or nano-titanium dioxide particles.

[0025] An electrolytic capacitor, wherein the electrolyte of the electrolytic capacitor at least includes the electrolyte for the solid-liquid mixed type electrolytic capacitor according to any one of the above.

[0026] The present application has the following beneficial effects:

[0027] The electrolyte for the solid-liquid mixed type electrolytic capacitor prepared by using the branched linear long-chain dicarboxylic acid ammonium salt as the main electrolyte, gamma-butyrolactone as the main solvent, and the carboxylation and surface modification of the conductive polymer has high conductivity, high flashover voltage and good high-temperature and low-temperature stability. The liquid component and the solid component obtained in the present application synergistically act, so that the high-voltage aluminum electrolytic capacitor prepared by using the working electrolyte has the advantages of low leakage current, large ripple resistance, high-frequency resistance and long service life at high temperature.

[0028] The liquid component of the electrolyte for the solid-liquid mixed electrolytic capacitor provided in the present application contains branched long-chain dicarboxylic acid ammonium salt as the main solute and straight-chain carboxylic acid ammonium salt as the auxiliary solute, and the chain length is controlled to balance the solubility and viscosity. The higher content of branched long-chain dicarboxylic acid ammonium salt can significantly increase the conductivity of the electrolyte, and the use of straight-chain carboxylic acid ammonium salt is reduced, so that the electrolyte has a wider temperature range and high and low temperature stability. In the present application, γ-butyrolactone is used as the main solvent and N-methyl pyrrolidone is used as the cosolvent to reduce the volatility at high temperature and reduce the polarity difference with the solid component, thereby significantly improving the flashover voltage of the electrolyte and enhancing the wettability of the solid-state conductive polymer. The present application further adds preservatives, flashover enhancers, hydrogen scavengers and the like as additives, which can improve the comprehensive performance of the aluminum electrolytic capacitor electrolyte such as corrosion resistance and flashover voltage, and the hydrogen scavenger can eliminate the gas released in the working electrolyte to reduce the internal pressure of the capacitor.

[0029] The solid component of the electrolyte for the solid-liquid mixed electrolytic capacitor provided in the present application is modified by carboxylation of the conductive polymer and surface coating of polyethylene glycol. The carboxylation increases the surface polarity, improves the liquid affinity and interface compatibility of the material, and the polyethylene glycol modification enables the liquid component to be adsorbed on the surface of the solid conductive polymer, thereby avoiding the increase of interface impedance. Nanoparticles are further added to stabilize the two-phase interface through physical adsorption, solve the high-temperature delamination problem, and improve the comprehensive performance of the capacitor. At the same time, a silane coupling agent is added to the liquid component of the electrolyte to form a chemical bond at the interface between the liquid and the solid, thereby enhancing the bonding force and significantly improving the compatibility of the solid-liquid mixed electrolyte. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be described below in a clear and complete manner. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0031] The preparation method of the ethylene glycol solution of branched long-chain dicarboxylic acid ammonium salt in Example 1 includes the following steps:

[0032] 20 mL of cyclohexanone and 27.5% concentration of hydrogen peroxide are added to 60 mL of methanol, and the reaction is carried out under the catalysis of FeSO4 to obtain a straight-chain carboxylic acid;

[0033] 20 mL of methyl methacrylate is added to the straight-chain carboxylic acid prepared above, and the reaction is carried out at 50-60°C for 60-120 minutes. After the reaction, the fraction with a boiling point of 125-135°C is collected to obtain a first fraction;

[0034] Add 10 mL of 10% ammonium hydroxide to the first fraction product obtained above, and heat to about 98°C, reflux for 4 h. After the reaction, add sulfuric acid to adjust the pH to 2, and collect the second fraction product;

[0035] Add the second fraction product prepared above to an ethylene glycol solution, and adjust the pH to 7 by passing in ammonia gas, to obtain an ethylene glycol solution of branched long-chain dicarboxylic acid ammonium salt with a content of 20%.

[0036] The preparation method of the ethylene glycol solution of branched long-chain dicarboxylic acid ammonium salt of Example 2 comprises the following steps:

[0037] Add 20 mL of cyclohexanone and 27.5% hydrogen peroxide to 90 mL of methanol, and react under the catalysis of FeSO4, to obtain a linear carboxylic acid;

[0038] Add 25 mL of methyl methacrylate to the linear carboxylic acid prepared above, and react at 50-60°C for 60-120 min. After the reaction, collect the fraction at 125-135°C, to obtain a first fraction product;

[0039] Add 10 mL of 10% ammonium hydroxide to the first fraction product obtained above, and heat to about 98°C, reflux for 4 h. After the reaction, add sulfuric acid to adjust the pH to 2, and collect the second fraction product;

[0040] Add the second fraction product prepared above to an ethylene glycol solution, and adjust the pH to 7 by passing in ammonia gas, to obtain an ethylene glycol solution of branched long-chain dicarboxylic acid ammonium salt with a content of 20%.

[0041] The preparation method of the surface-modified carboxylated PEDOT nanofiber of Example 3 comprises the following steps:

[0042] Disperse 10 g of PEDOT / PSS nanofiber in 100 mL of deionized water, add 4 g of acrylic acid, and ultrasonically disperse. React under ultraviolet light for 2 h, wash and dry, to obtain carboxylated PEDOT nanofiber;

[0043] Disperse the carboxylated PEDOT nanofiber obtained above in 100 mL of MES buffer with a pH of 5.5, and add 0.8 g of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and 0.3 g of N-hydroxysuccinimide, and stir, to obtain activated nanofiber;

[0044] Add 3 g of polyethylene glycol to the activated nanofiber above, adjust the pH to 7.4, and react at 40°C for 12 h. After centrifugation, washing and freeze-drying, surface-modified carboxylated PEDOT nanofiber is obtained.

[0045] Example 4 The preparation method of the electrolyte for solid-liquid mixed electrolytic capacitor includes the following steps:

[0046] Liquid component: 45% γ-butyrolactone and 10% N-methyl pyrrolidone are heated to 120°C, 5% ammonium adipate and 10% branched long-chain dicarboxylic acid ammonium salt ethylene glycol solution prepared in Example 1 (effective substance) are added, after complete dissolution, the temperature is lowered to 50°C, deionized water, 1% γ-aminopropyl triethoxysilane, 0.5% ammonium hypophosphite, 0.5% citric acid, 0.5% p-nitrobenzoic acid and 0.5% ammonium benzoate are added, after complete dissolution, the liquid component of the electrolyte for solid-liquid mixed electrolytic capacitor is obtained.

[0047] Solid component: 18% surface-modified carboxylated PEDOT nanofiber prepared in Example 3 and 2% nanosilica are dispersed in deionized water to obtain the solid component of the electrolyte for solid-liquid mixed electrolytic capacitor.

[0048] Example 5 The preparation method of the electrolyte for solid-liquid mixed electrolytic capacitor includes the following steps:

[0049] Liquid component: 45% γ-butyrolactone and 10% N-methyl pyrrolidone are heated to 120°C, 3% ammonium adipate and 12% branched long-chain dicarboxylic acid ammonium salt ethylene glycol solution prepared in Example 1 (effective substance) are added, after complete dissolution, the temperature is lowered to 50°C, deionized water, 1% γ-aminopropyl triethoxysilane, 0.5% ammonium hypophosphite, 0.5% citric acid, 0.5% p-nitrobenzoic acid and 0.5% ammonium benzoate are added, after complete dissolution, the liquid component of the electrolyte for solid-liquid mixed electrolytic capacitor is obtained.

[0050] Solid component: 18% surface-modified carboxylated PEDOT nanofiber prepared in Example 3 and 2% nanosilica are dispersed in deionized water to obtain the solid component of the electrolyte for solid-liquid mixed electrolytic capacitor.

[0051] Comparative Example 1 In the preparation steps of the electrolyte for solid-liquid mixed electrolytic capacitor, compared with Example 4, the branched long-chain dicarboxylic acid ammonium salt prepared in Example 1 added in the preparation process of the liquid component is replaced by an equal amount of ammonium adipate, and the remaining components and preparation method are completely consistent with Example 4.

[0052] Comparative Example 2 In the preparation steps of the electrolyte for solid-liquid mixed electrolytic capacitor, compared with Example 4, the surface-modified carboxylated PEDOT nanofiber prepared in Example 3 added in the preparation process of the solid component is replaced by an equal amount of PEDOT nanofiber without surface modification and carboxylation, and the remaining components and preparation method are completely consistent with Example 4.

[0053] Preparation of solid-liquid mixed electrolytic capacitor:

[0054] The positive aluminum foil, negative titanium foil, chemical fiber electrolytic paper, and guide needle are wound to form a core package;

[0055] The positive aluminum foil and the guide needle are subjected to electric current repair, and the formation liquid used for formation can be composed of one or more of ammonium adipate, ammonium dihydrogen phosphate, phosphoric acid, and ammonium bicarbonate. After the electric current repair, the core package should be dried to remove the moisture in the core package, so as to obtain the core package after formation.

[0056] The core after the above formation is immersed in the solid components of the electrolyte obtained in Examples 4-5 and Comparative Examples 1-2 to form a solid electrolyte in the core package. The immersion is carried out in an alternating environment of vacuum and air pressure, wherein the vacuum is 95 Kpa, and the pressure can be 0.3 Mpa. After the immersion is completed, heating and drying are carried out, wherein the drying temperature can be selected to be 115°C.

[0057] The core after the above formation is immersed in the solid components of the electrolyte obtained in Examples 4-5 and Comparative Examples 1-2 to form a solid electrolyte in the core package. The immersion is carried out in an alternating environment of vacuum and air pressure, wherein the vacuum is 95 Kpa, and the pressure can be 0.3 Mpa. After the immersion is completed, heating and drying are carried out, wherein the drying temperature can be selected to be 115°C.

[0058] The core package after the above immersion of the electrolyte liquid components is assembled and sealed with an aluminum shell and a glue cover. In a heated environment, the capacitor is subjected to aging by direct current, and the aging temperature is 105-125°C, so as to obtain a solid-liquid mixed electrolytic capacitor.

[0059] Performance detection

[0060] The solid-liquid mixed electrolytic capacitor obtained in Examples 4-5 and Comparative Examples 1-2 is tested for conductivity and flashover voltage performance at -40°C, 30°C, and 120°C. The test results are shown in Tables 1 and 2.

[0061] The solid-liquid mixed electrolytic capacitor obtained in Examples 4-5 and Comparative Examples 1-2 is subjected to a life determination experiment, and a 1.8A / only ripple current experiment is carried out. The test time is 2000 hours, wherein Tanδ is the loss angle, LC is the leakage current, and ΔC is the change in capacitor capacity, all of which are better the smaller. The test results are shown in Table 2.

[0062] Table 1 Performance test results of products in Examples 4-5 and Comparative Examples 1-2 after reflow soldering

[0063]

[0064] Table 2 Performance test results of products in Examples 4-5 and Comparative Examples 1-2 after reflow soldering

[0065]

[0066] As can be seen from Table 1 and Table 2, the electrolyte for solid-liquid mixed electrolytic capacitor prepared by the method of the present application has high conductivity, high flashover voltage and good high and low temperature stability, and the capacitor using the electrolyte prepared by the present application has low leakage current, high ripple resistance and high temperature long life performance. The electrolyte prepared in Comparative Example 1 does not contain branched long-chain dicarboxylic acid ammonium salt, and the PEDOT nanofiber in the solid component prepared in Comparative Example 2 is not surface modified and carboxylated, and the obtained electrolyte has poor temperature stability, and the obtained solid-liquid mixed electrolytic capacitor has short high temperature life.

[0067] The above has described one embodiment of the present application in detail, but the content described is only a preferred embodiment of the present application, and cannot be considered as limiting the scope of the present application. Any equivalent changes and improvements made within the scope of the present application should still belong to the patent scope of the present application.

Claims

1. An electrolytic solution for a solid-liquid mixed electrolytic capacitor, characterized by comprising: At least comprising the following components: Liquid component: gamma-butyrolactone 40-50%, N-methyl pyrrolidone 8-12%, straight-chain carboxylic acid ammonium salt 2-5%, branched-chain long-chain dicarboxylic acid ammonium salt 5-15%, silane coupling agent 1-2%, additive 0.5-5%; The branched-chain long-chain dicarboxylic acid ammonium salt has 8-12 carbon atoms in the main chain; Solid component: surface-modified carboxylated PEDOT nanofiber 10-20%, nanoparticle 1-4%.

2. The solid-liquid mixed type electrolytic capacitor electrolyte according to claim 1, wherein The preparation method of the branched-chain long-chain dicarboxylic acid ammonium salt at least comprises the following steps: Cyclohexanone and hydrogen peroxide are added to methanol, and reacted under the catalysis of FeSO4 to obtain a straight-chain carboxylic acid; Methyl methacrylate is added to the straight-chain carboxylic acid, and after reaction, a first fraction product is collected; Ammonium hydroxide is added to the first fraction product, and after reaction, the pH value is adjusted to be acidic, and a second fraction product is collected; The second fraction product is added to an ethylene glycol solution, ammonia gas is introduced to adjust the pH value to 6-7, and a branched-chain long-chain dicarboxylic acid ammonium salt ethylene glycol solution is obtained.

3. The solid-liquid mixed type electrolytic capacitor electrolyte according to claim 2, wherein The molar ratio of the cyclohexanone, the methyl methacrylate and the methanol is 1-2:1-2:

10.

4. The solid-liquid mixed type electrolytic solution for an electrolytic capacitor according to claim 2, wherein The content of the branched-chain long-chain dicarboxylic acid ammonium salt in the branched-chain long-chain dicarboxylic acid ammonium salt ethylene glycol solution is 15-20%.

5. The solid-liquid mixed electrolytic capacitor electrolyte according to claim 1, wherein The preparation method of the surface-modified carboxylated PEDOT nanofiber at least comprises the following steps: PEDOT / PSS nanofiber is dispersed in deionized water, acrylic acid is added, and reacted under ultraviolet light irradiation, washed and dried to obtain carboxylated PEDOT nanofiber; The carboxylated PEDOT nanofiber is dispersed in a buffer solution, and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and N-hydroxysuccinimide are added and stirred to obtain activated nanofiber; Polyethylene glycol is added to the activated nanofiber, and after reaction, centrifugation, washing and drying, surface-modified carboxylated PEDOT nanofiber is obtained.

6. The solid-liquid mixed electrolytic solution for an electrolytic capacitor according to claim 5, wherein The mass ratio of the PEDOT / PSS nanofiber and the polyethylene glycol is 3-4:

1.

7. The solid-liquid mixed electrolytic solution for an electrolytic capacitor according to claim 1, wherein The straight-chain carboxylic acid ammonium salt at least comprises one of ammonium benzoate and straight-chain polycarboxylic acid ammonium salt with 5-20 carbon atoms, and the additive at least comprises one of phosphoric acid, citric acid, ammonium phosphite, ammonium hypophosphite, p-nitrobenzyl alcohol, p-nitrobenzoic acid, nitrophenol, p-nitrophenyl ether, mannitol, sorbitol, xylitol or alkyl phosphate ester.

8. The solid-liquid mixed electrolytic solution for an electrolytic capacitor according to claim 1, wherein The silane coupling agent at least comprises one of gamma-(methacryloyloxy) propyl trimethoxysilane, gamma-glycidyl ether propyl trimethoxysilane, N-(beta-aminoethyl)-gamma-aminopropyl trimethoxysilane and gamma-aminopropyl triethoxysilane, and the nanoparticle at least comprises one of nano-silicon dioxide particles or nano-titanium dioxide particles.

9. An electrolytic capacitor characterized by The electrolyte of the electrolytic capacitor at least comprises the electrolyte for solid-liquid mixed electrolytic capacitor according to any one of claims 1-8.

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