阅读说明：本技术 一种二氧化硅内酯溶胶、制备方法以及铝电解电容器用电解液 (Silica lactone sol, preparation method and electrolyte for aluminum electrolytic capacitor ) 是由 王文功 赵大成 黄丽青 王明杰 于 2020-04-15 设计创作，主要内容包括：为克服现有技术中添加了乙二醇硅溶胶的内酯类电解液在高温储存下,电导率大幅衰减的问题,本发明提供了一种二氧化硅内酯溶胶,以内酯类化合物为溶剂,分散表面改性二氧化硅胶粒,控制表面改性二氧化硅的每平方纳米表面上羟基数量小于3,表面改性二氧化硅的粒径大小为5～200nm。本发明还提供一种二氧化硅内酯溶胶的制备方法。本发明还提供一种铝电解电容器用电解液,包括主溶剂、主溶质和使用二氧化硅内酯溶胶。本发明提供的二氧化硅内酯溶胶,明显提高内酯类电解液的闪火电压,使内酯类电解液在耐高温储存中电导率保持稳定,而且能稳定存在于内酯类电解液中。(In order to solve the problem that the conductivity of a lactone electrolyte added with glycol silica sol is greatly attenuated under high-temperature storage in the prior art, the invention provides the silica lactone sol, which takes a lactone compound as a solvent, disperses surface modified silica colloidal particles, controls the number of hydroxyl groups on each square nanometer surface of the surface modified silica to be less than 3, and controls the particle size of the surface modified silica to be 5-200 nm. The invention also provides a preparation method of the silica lactone sol. The invention also provides an electrolyte for the aluminum electrolytic capacitor, which comprises a main solvent, a main solute and the silica lactone sol. The silicon dioxide lactone sol provided by the invention obviously improves the sparking voltage of the lactone electrolyte, so that the conductivity of the lactone electrolyte is kept stable in high-temperature-resistant storage, and the lactone electrolyte can stably exist in the lactone electrolyte.)

1. A silica lactone sol characterized by comprising the following components:

a solvent and surface modified silica;

the solvent comprises a lactone compound, the number of hydroxyl groups on the surface of each square nanometer of the surface modified silicon dioxide is less than 3, and the particle size of the surface modified silicon dioxide is 5-200 nm.

2. The silica lactone sol of claim 1, wherein the solvent is present in an amount of 30% to 99% and the surface-modified silica is present in an amount of 1% to 40%, based on 100% by weight of the silica lactone sol.

3. The silica lactone sol of claim 1, wherein the lactone-based compound comprises gamma-butyrolactone and/or gamma-valerolactone.

4. The silica lactone sol of claim 2, wherein the surface-modified silica is present in an amount of 5% to 20%.

5. The silica lactone sol of claim 2, wherein the surface-modified silica is prepared by reacting silica powder, a basic catalyst, an alkyl reagent, and water;

the alkaline catalyst comprises one or more of ammonia water, ethylenediamine, sodium hydroxide, sodium bicarbonate, sodium carbonate and silicate.

6. The silica lactone sol of claim 5, wherein the alkyl reagent comprises a silane coupling agent comprising gamma-aminopropyltriethoxysilane, gamma- (2, 3-epoxypropoxy) propyltrimethoxysilane, gamma- (methacryloyloxy) propyltrimethoxysilane, gamma-mercaptopropyltriethoxysilane, gamma-mercaptopropyltrimethoxysilane, N- (beta-aminoethyl) -gamma-aminopropylmethyldimethoxysilane, gamma-aminoethylaminopropyltrimethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, vinyltris (beta-methoxyethoxy) silane, phenyltrimethoxysilane, phenyltriethoxysilane, gamma-glycidyloxy-propyltrimethoxysilane, gamma-glycidyloxy-propyltriethoxysilane, gamma-glycidyloxy-propyltrimethoxysilane, gamma-glycidyloxy-propyltriethoxysilane, vinyltrimethoxysilane, vinyltris (beta-methoxyethoxy) silane, phenyltrimethoxysilane, phenyltriethoxysilane, gamma-glycidyloxy-propyltriethoxysilane, gamma-butyltrimethoxysilane, vinyltriethoxysilane, vinyltris (beta-methoxyethoxy-butyltrimethoxysilane, vinyltriethoxysilane, vinyltris (beta-methoxysilane, gamma-butyltrimethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, or a-vinyltriethoxysilane, or a mixture of a compound, or a compound having a structure and a structure having a structure and a structure, One or more of diphenyldimethoxysilane and diphenyldiethoxysilane.

7. The method for producing the silica lactone sol of any one of claims 1 to 6, comprising the steps of:

dissolving silicon powder in water, adding an alkaline catalyst, and filtering and concentrating to obtain silicon dioxide hydrosol;

adding a silane reagent into the silicon dioxide hydrosol to obtain surface modified silicon dioxide;

uniformly mixing the surface modified silicon dioxide and a solvent lactone compound, and distilling to remove water to obtain the silicon dioxide lactone sol;

the number of hydroxyl groups on the surface of each square nanometer of the surface modified silicon dioxide is less than 3, and the particle size of the surface modified silicon dioxide is 5-200 nm.

8. The method for producing a silica lactone sol of claim 7, comprising the steps of:

dissolving the required silicon powder in water accounting for 300-2000% of the mass of the silicon powder, adding an alkaline catalyst, keeping the pH value at 9-10.5, the reaction temperature at 30-90 ℃ and the reaction time at 2-24 h, and filtering and concentrating to obtain silicon dioxide hydrosol with the mass fraction of 5-35% of silicon dioxide;

heating the silica hydrosol to 30-90 ℃, and adding an alkyl reagent with the silica content of 1-30% to obtain surface modified silica;

uniformly mixing the surface modified silicon dioxide and a solvent lactone compound, wherein the adding amount of the solvent is 50-900% of the mass of the silicon dioxide hydrosol, and distilling to remove water to obtain a silicon dioxide lactone sol;

the number of hydroxyl groups on the surface of each square nanometer of the surface modified silicon dioxide is less than 3, and the particle size of the surface modified silicon dioxide is 5-200 nm.

9. An electrolyte for an aluminum electrolytic capacitor, comprising a main solvent, a main solute and the silica lactone sol according to any one of claims 1 to 6.

10. The electrolyte of claim 9, wherein the primary solvent is a lactone-type compound.

Technical Field

The invention belongs to the field of electrolyte for aluminum electrolytic capacitors, and particularly relates to a silica lactone sol, a preparation method and electrolyte for an aluminum electrolytic capacitor.

Background

The sparking voltage is one of the important parameters of the working electrolyte of the aluminum electrolytic capacitor and directly determines the rated working voltage of the capacitor. The additives for increasing the sparking voltage are generally the following: (1) the macromolecular carboxylic acid is easily adsorbed by an alumina film, and the macromolecular carboxylic acid ionizes to form anions in a solvent and is directionally adsorbed to the surface of the anode under the action of an electric field to form an adsorption layer. The adsorption layer has the function of shielding an electric field, and the electric field applied to the electrode is uniform, so that the edge effect is eliminated. Meanwhile, the adsorption layer has strong oxidation capacity and can also improve the sparking voltage; (2) some electrolytes (such as adipic acid and the like) with good formation performance and some substances with strong oxidizability (such as ammonium dichromate, maleic acid and the like) are easy to release oxygen, can quickly repair the damage of a dielectric film, improve the formation performance and are more beneficial to improving the sparking voltage; (3) phosphoric acid and its salts, such as phosphoric acid, hypophosphorous acid and ammonium dihydrogen phosphate, can repair dielectric film, prevent hydration, and ensure sparking voltage.

In the traditional electrolyte preparation materials, the most effective method for improving the sparking voltage of the electrolyte is to add macromolecular carboxylic acid to form an adsorption layer on the surface of an anode, but the macromolecular carboxylic acid inevitably increases the viscosity and the resistivity of the electrolyte, which is unfavorable for the service performance of a capacitor. The silica sol is applied to the working electrolyte of the aluminum capacitor due to the characteristics of small particle size, charged charge, uniform dispersion, high purity, high temperature resistance, strong adsorbability and the like. The high-purity silica sol can effectively improve the breakdown resistance of the aluminum foil, thereby improving the sparking voltage of the aluminum electrolytic capacitor. Compared with macromolecular carboxylic acid, the viscosity of the silica sol is low, so that the viscosity and the resistivity of the electrolyte cannot be influenced when the silica sol is added into the electrolyte. Compared with the flash-fire voltage promoting agent of adipic acid, partial substances with strong oxidizing property, phosphoric acid and salts thereof and the like, the flash-fire voltage promoting effect is better than that of the materials.

Because the nano material has small particle size, high specific surface area and large surface energy and is in an energy unstable state, the nano powder is easy to agglomerate to cause sedimentation and delamination, so that the good characteristics of the nano powder can not be well exerted. The nano powder can be uniformly and stably dispersed in the solution only after special treatment, and can be added into the working electrolyte. At present, the silica sol applied to the field of the electrolyte of the aluminum electrolytic capacitor is generally nano silica glycol sol, and the effect of improving flash fire is generally between 20 and 40V due to the difference of the electrolyte. The most widely applied liquid aluminum electrolytic capacitor working electrolyte in the market is mainly two solvent systems of ethylene glycol and gamma-butyrolactone, and the two solvent systems account for more than 95% of the liquid aluminum electrolytic capacitor working electrolyte market. The nano-silica glycol sol is widely used in working electrolyte using glycol solvent as a system. The nano-silica glycol sol has good effect of improving the sparking voltage, and can not influence other parameters of the capacitor. For the working electrolyte using a gamma-butyrolactone system, the existing method for increasing the voltage is basically to add nano-silica glycol sol. The flash fire voltage of the electrolyte can be improved by adding the nano-silica glycol sol, but the glycol is introduced into the gamma-butyrolactone solution. The introduction of ethylene glycol can cause a large reduction in conductivity of the electrolyte during high-temperature storage, affecting the electrical performance of the capacitor.

Disclosure of Invention

The invention aims to solve the technical problem that the conductivity of a lactone electrolyte added with silica glycol sol in the prior art is greatly attenuated under high-temperature storage, and provides a silica lactone sol, a preparation method and an electrolyte for an aluminum electrolytic capacitor.

The technical scheme adopted by the invention for solving the problems is as follows:

in one aspect, the invention provides a silica lactone sol comprising the following components:

a solvent and surface modified silica;

the solvent comprises a lactone compound, the number of hydroxyl groups on the surface of each square nanometer of the surface modified silicon dioxide is less than 3, and the particle size of the surface modified silicon dioxide is 5-200 nm.

Optionally, the content of the solvent is 30% to 99% and the content of the surface-modified silica is 1% to 40% based on 100% of the total weight of the silica lactone sol.

Optionally, the lactone-type compound comprises gamma-butyrolactone and/or gamma-valerolactone.

Optionally, the content of the surface-modified silica is 5% to 20%.

Optionally, the surface modified silicon dioxide is prepared by reacting silicon powder, an alkaline catalyst, an alkyl reagent and water;

the alkaline catalyst comprises one or more of ammonia water, ethylenediamine, sodium hydroxide, sodium bicarbonate, sodium carbonate and silicate.

Optionally, the silane agent includes a silane coupling agent, the silane coupling agent comprises one or more of gamma-aminopropyltriethoxysilane, gamma- (2, 3-epoxypropoxy) propyltrimethoxysilane, gamma- (methacryloyloxy) propyltrimethoxysilane, gamma-mercaptopropyltriethoxysilane, gamma-mercaptopropyltrimethoxysilane, N- (beta-aminoethyl) -gamma-aminopropylmethyldimethoxysilane, gamma-aminoethylaminopropyltrimethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, vinyltris (beta-methoxyethoxy) silane, phenyltrimethoxysilane, phenyltriethoxysilane, diphenyldimethoxysilane and diphenyldiethoxysilane.

In another aspect, the present invention also provides a method for preparing the silica lactone sol described in any one of the above, comprising the steps of:

dissolving silicon powder in water, adding an alkaline catalyst, and filtering and concentrating to obtain silicon dioxide hydrosol;

adding a silane reagent into the silicon dioxide hydrosol to obtain surface modified silicon dioxide;

uniformly mixing the surface modified silicon dioxide and a solvent lactone compound, and distilling to remove water to obtain the silicon dioxide lactone sol;

the number of hydroxyl groups on the surface of each square nanometer of the surface modified silicon dioxide is less than 3, and the particle size of the surface modified silicon dioxide is 5-200 nm.

Optionally, the preparation method of the silica lactone sol comprises the following steps:

dissolving the required silicon powder in water accounting for 300-2000% of the mass of the silicon powder, adding an alkaline catalyst, keeping the pH value at 9-10.5, the reaction temperature at 30-90 ℃ and the reaction time at 2-24 h, and filtering and concentrating to obtain silicon dioxide hydrosol with the mass fraction of 5-35% of silicon dioxide;

heating the silica hydrosol to 30-90 ℃, and adding an alkyl reagent with the silica content of 1-30% to obtain surface modified silica;

uniformly mixing the surface modified silicon dioxide and a solvent lactone compound, wherein the adding amount of the solvent is 50-900% of the mass of the silicon dioxide hydrosol, and distilling to remove water to obtain silicon dioxide lactone sol;

the number of hydroxyl groups on the surface of each square nanometer of the surface modified silicon dioxide is less than 3, and the particle size of the surface modified silicon dioxide is 5-200 nm.

In another aspect, the present invention also provides an electrolyte for an aluminum electrolytic capacitor, comprising a main solvent, and the silica lactone sol described in any one of the above.

Optionally, the main solvent is a lactone compound.

The silicon dioxide lactone sol provided by the invention takes the lactone compound as a solvent, the surface modified silicon dioxide is added, the number of hydroxyl groups on each square nanometer surface of the surface modified silicon dioxide is controlled to be less than 3, the particle size of the surface modified silicon dioxide is 5-200 nm, the uniformity and stability of the surface modified silicon dioxide dispersed in the lactone solvent are ensured, the conductivity of the lactone electrolyte added with the nano silicon dioxide glycol sol is greatly attenuated under high-temperature storage due to the fact that the nano silicon dioxide glycol sol contains glycol, the flashover voltage of the lactone electrolyte is improved by preparing the silicon dioxide lactone sol, the conductivity of the lactone electrolyte can be kept stable in high-temperature storage, and the silicon dioxide lactone sol can stably exist in the lactone electrolyte.

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects solved by the present invention more apparent, the present invention is further described in detail below with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The invention provides an electrolyte for an aluminum electrolytic capacitor, which comprises the following components:

in one aspect, the invention provides a silica lactone sol additive comprising the following components:

a solvent and surface modified silica;

the solvent comprises a lactone compound, the number of hydroxyl groups on the surface of each square nanometer of the surface modified silicon dioxide is less than 3, and the particle size of the surface modified silicon dioxide is 5-200 nm.

The silicon dioxide lactone sol provided by the invention takes an lactone compound as a solvent, surface modified silicon dioxide is added, the number of hydroxyl groups on the surface of each square nanometer of the surface modified silicon dioxide is controlled to be less than 3, the particle size of the surface modified silicon dioxide is 5-200 nm, and the uniformity and the stability of the surface modified silicon dioxide dispersed in the lactone solvent are ensured. The nano-silica glycol sol contains glycol, so that the conductivity of the lactone electrolyte added with the nano-silica glycol sol is greatly reduced under high-temperature storage, the flashover voltage of the lactone electrolyte is improved by preparing the silica lactone sol, the conductivity of the lactone electrolyte can be kept stable under high-temperature storage, and the silica lactone sol can stably exist in the lactone electrolyte.

In some embodiments of the present invention, the solvent is present in an amount of 30% to 99% and the surface-modified silica is present in an amount of 1% to 40%, based on 100% by weight of the total silica lactone sol.

In some embodiments of the invention, the lactone-based compound comprises gamma-butyrolactone and/or gamma-valerolactone.

Preferably, the purity of the gamma butyrolactone is of electronic grade.

In some embodiments of the invention, the surface modified silica is present in an amount of 5% to 20%.

In some embodiments of the invention, the surface modified silica is prepared by reacting silica powder, a basic catalyst, an alkyl reagent and water;

the alkaline catalyst comprises one or more of ammonia water, ethylenediamine, sodium hydroxide, sodium bicarbonate, sodium carbonate and silicate.

Wherein the purity of the silicon powder is more than or equal to 99 percent, the granularity is 200-500 meshes, the water is deionized water, and pure water with the ion content of 3ppb is preferred.

In some embodiments of the invention, the alkyl reagent comprises a silane coupling agent, preferably an aromatic group or aromatic alkyl group containing silane coupling agent.

The silane coupling agent comprises one or more of gamma-aminopropyltriethoxysilane, gamma- (2, 3-epoxypropoxy) propyltrimethoxysilane, gamma- (methacryloyloxy) propyltrimethoxysilane, gamma-mercaptopropyltriethoxysilane, gamma-mercaptopropyltrimethoxysilane, N- (beta-aminoethyl) -gamma-aminopropylmethyldimethoxysilane, gamma-aminoethylaminopropyltrimethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, vinyltris (beta-methoxyethoxy) silane, phenyltrimethoxysilane, phenyltriethoxysilane, diphenyldimethoxysilane and diphenyldiethoxysilane.

In some embodiments of the present invention, the surface-modified silica is present in the silica lactone sol in an amount of 20%.

The invention also provides a preparation method of the silica lactone sol, which comprises the following steps:

dissolving silicon powder in water, adding an alkaline catalyst, and filtering and concentrating to obtain silicon dioxide hydrosol;

adding a silane reagent into the silicon dioxide hydrosol to obtain surface modified silicon dioxide;

uniformly mixing the surface modified silicon dioxide and a solvent lactone compound, and distilling to remove water to obtain the silicon dioxide lactone sol;

the number of hydroxyl groups on the surface of each square nanometer of the surface modified silicon dioxide is less than 3, and the particle size of the surface modified silicon dioxide is 5-200 nm.

In some embodiments of the present invention, the method for preparing the silica lactone sol comprises the following steps:

dissolving the required silicon powder in water accounting for 300-2000% of the mass of the silicon powder, adding an alkaline catalyst, keeping the pH value at 9-10.5, the reaction temperature at 30-90 ℃ and the reaction time at 2-24 h, and filtering and concentrating to obtain silicon dioxide hydrosol with the mass fraction of 5-35% of silicon dioxide;

heating the silica hydrosol to 30-90 ℃, and adding an alkyl reagent with the silica content of 1-30% to obtain surface modified silica;

uniformly mixing the surface modified silicon dioxide and a solvent lactone compound, wherein the adding amount of the solvent is 50-900% of the mass of the silicon dioxide hydrosol, and distilling to remove water to obtain silicon dioxide lactone sol;

the number of hydroxyl groups on the surface of each square nanometer of the surface modified silicon dioxide is less than 3, and the particle size of the surface modified silicon dioxide is 5-200 nm.

The solution after the silicon powder reaction can be filtered by a PE filter membrane of 10um, and then the filtrate passes through a resin column of anion and cation resin to remove ions, so as to obtain the silica hydrosol.

The invention also provides an electrolyte for an aluminum electrolytic capacitor, which comprises a main solvent, a main solute and the silica lactone sol.

In some embodiments of the invention, the primary solvent is a lactone-type compound.

The present invention will be further illustrated by the following examples. It is to be understood that the present invention is not limited to the following embodiments, and methods are regarded as conventional methods unless otherwise specified. Materials are commercially available from the open literature unless otherwise specified.

Example 1

This example illustrates the silica lactone sol and the method of making the same disclosed herein.

The preparation of the silica lactone sol comprises the following components:

(1) silicon powder 5g

(2) 15g of pure water

(3) Sodium hydroxide

(4) Gamma- (2, 3-epoxypropoxy) propyltrimethoxysilane 1.26g

(5) 25g of gamma-butyrolactone

The preparation method comprises the following steps:

(1) adding 5g of silicon powder into an aqueous solution at 55 ℃, stirring for 1h, pouring out an upper-layer aqueous solution after precipitation, washing twice to remove impurities attached to the surface of the silicon powder;

(2) adding 15g of pure water into the silicon powder, adding sodium hydroxide, and adjusting the pH value of the solution to 9, wherein the reaction temperature is kept at 30 ℃ for 24 hours;

(3) filtering the reacted solution by using a 10-micrometer PE filter membrane to obtain 21.4g of milky white filtrate, and collecting unreacted silicon powder for the next experiment;

(4) slowly passing the filtrate through a resin column filled with anion and cation resin to obtain 93g of silica hydrosol;

(5) heating the silica hydrosol to 50 ℃, slowly adding 1.26g of gamma- (2, 3-epoxypropoxy) propyl trimethoxy silane with the silica content of 5%, and reacting for 5 hours at 50 ℃ to obtain surface modified silica;

(6) adding 25g of gamma-butyrolactone into the surface modified silicon dioxide, and removing water by reduced pressure distillation to obtain the nano silicon dioxide gamma-butyrolactone sol marked as S1.

Example 2

This example illustrates the silica lactone sol and the method of making the same disclosed herein.

The preparation of the silica lactone sol comprises the following components:

(1) silicon powder 5g

(2) 50g of pure water

(3) Sodium hydroxide

(4) 2.52g of gamma-aminopropyltriethoxysilane

(5) 25g of gamma-butyrolactone

The preparation method comprises the following steps:

(1) adding 5g of silicon powder into an aqueous solution at 70 ℃, stirring for 1h, pouring out an upper-layer aqueous solution after precipitation, washing twice to remove impurities attached to the surface of the silicon powder;

(2) adding 50g of pure water into the silicon powder, adding sodium hydroxide, and adjusting the pH value of the solution to 9, wherein the reaction temperature is kept at 60 ℃ for 6 hours;

(3) filtering the reacted solution by using a 10-micrometer PE filter membrane to obtain 56.1g of milky white filtrate, and collecting unreacted silicon powder for the next experiment;

(4) slowly passing the filtrate through a resin column filled with anion and cation resin to obtain 72.3g of silica hydrosol;

(5) heating the hydrosol to 65 ℃, slowly adding 2.52g of gamma-aminopropyl triethoxysilane with 10 percent of silicon dioxide content, and reacting for 8 hours at 65 ℃ to obtain surface modified silicon dioxide;

(6) adding 25g of gamma-butyrolactone into the surface modified silicon dioxide, and removing water by reduced pressure distillation to obtain the nano silicon dioxide gamma-butyrolactone sol marked as S2.

Example 3

This example illustrates the silica lactone sol and the method of making the same disclosed herein.

The preparation of the silica lactone sol comprises the following components:

(1) silicon powder 5g

(2) 90g of pure water

(3) Sodium hydroxide

(4) Phenyltrimethoxysilane 3.78g

(5) 25g of gamma-butyrolactone

The preparation method comprises the following steps:

(1) adding 5g of silicon powder into an aqueous solution at 90 ℃, stirring for 1h, pouring out an upper-layer aqueous solution after precipitation, washing twice to remove impurities attached to the surface of the silicon powder;

(2) adding 90g of pure water into the silicon powder, adding sodium hydroxide, and adjusting the pH value of the solution to 9, wherein the reaction temperature is kept at 60 ℃ for 10 hours;

(3) filtering the reacted solution by using a 10-micrometer PE filter membrane to obtain 96.4g of milky white filtrate, and collecting unreacted silicon powder for the next experiment;

(4) slowly passing the filtrate through a resin column filled with anion and cation resin to obtain 105g of silica hydrosol;

(5) heating the silica hydrosol to 90 ℃, slowly adding 3.78g of phenyltrimethoxysilane with the silica content of 15%, and reacting at 90 ℃ for 12h to obtain surface modified silica;

(6) adding 25g of gamma-butyrolactone into the surface modified silicon dioxide, and removing water by reduced pressure distillation to obtain the nano silicon dioxide gamma-butyrolactone sol marked as S3.

Comparative example 1

This comparative example is intended to illustrate the silica lactone sols disclosed herein.

A silica glycol sol of model CS2 manufactured by Fushan drugs Ltd is denoted by D1.

Comparative example 2

This comparative example is intended to illustrate the silica lactone sols disclosed herein.

The comparative silica lactone sols were prepared comprising the following components:

(1) silicon powder 5g

(2) 15g of pure water

(3) Sodium hydroxide

(4) 25g of gamma-butyrolactone

The preparation method comprises the following steps:

(1) adding 5g of silicon powder into an aqueous solution at 55 ℃, stirring for 1h, pouring out an upper-layer aqueous solution after precipitation, washing twice to remove impurities attached to the surface of the silicon powder;

(2) adding 15g of pure water into the silicon powder, adding sodium hydroxide, and adjusting the pH value of the solution to 9, wherein the reaction temperature is kept at 30 ℃ for 24 hours;

(3) filtering the reacted solution by using a 10-micrometer PE filter membrane to obtain 21.4g of milky white filtrate, and collecting unreacted silicon powder for the next experiment;

(4) slowly passing the filtrate through a resin column filled with anion and cation resin to obtain 93g of silica hydrosol;

(5) 25g of gamma-butyrolactone was added to the silica hydrosol, and the system was gelled, labeled D2, during the removal of water by distillation under reduced pressure.

Comparative example 3

This comparative example is used to illustrate the silica lactone sol and the method of making the same disclosed herein.

The preparation of the silica lactone sol comprises the following components:

(1) silicon powder 5g

(2) 50g of pure water

(3) Sodium hydroxide

(4) 1.92g of gamma-aminopropyltriethoxysilane

(5) 25g of gamma-butyrolactone

The preparation method comprises the following steps:

(1) adding 5g of silicon powder into an aqueous solution at 70 ℃, stirring for 1h, pouring out an upper-layer aqueous solution after precipitation, washing twice to remove impurities attached to the surface of the silicon powder;

(2) adding 50g of pure water into the silicon powder, adding sodium hydroxide, and adjusting the pH value of the solution to 8, wherein the reaction temperature is kept at 60 ℃ for 1 hour;

(3) filtering the reacted solution by using a 10-micrometer PE filter membrane to obtain 46.1g of milky filtrate, and collecting unreacted silicon powder for the next experiment;

(4) slowly passing the filtrate through a resin column filled with anion and cation resin to obtain 52.3g of silica hydrosol;

(5) heating the hydrosol to 65 ℃, slowly adding 1.92g of gamma-aminopropyl triethoxysilane with the silicon dioxide content of 12%, and reacting for 8h at 65 ℃ to obtain surface modified silicon dioxide;

(6) adding 25g of gamma-butyrolactone into the surface modified silicon dioxide, and removing water by reduced pressure distillation to obtain the nano silicon dioxide gamma-butyrolactone sol, which is marked as D3.

Performance testing

Testing parameters of surface-modified silica

1. Determination of the number of surface hydroxyl groups:

10.0g of nano SiO with a solid content of 20% are weighed₂The hydrosol was placed in a 200mL beaker, and 25mL of absolute ethanol and 75mL of 20% NaCl solution were added. After stirring, the pH was adjusted to 4.0 with 0.1mol/L HCl solution or 0.1mol/L NaOH. Then, 0.1mol/L NaOH solution was slowly added to raise the pH to 9.0, and the pH was maintained for 20 seconds. Calculating according to formula (1) per (nm)²The number (N) of hydroxyl groups on the surface area of the nano SiO 2:

in the formula (1), C is the concentration of NaOH (0.1mol/L), V is the volume of NaOH (mL) of 0.1mol/L consumed when the pH value rises from 4.0 to 9.0, NA is the Avogarduo constant, and S is nano SiO₂Specific surface area (nm)²In g), m is nano SiO₂Mass (g) of (c).

2. The particle size distribution of the modified silicon dioxide is tested by a dynamic light flash nanometer particle size analyzer, and the average particle size is calculated.

The test results obtained are shown in table 1.

TABLE 1

Numbering	Number of hydroxyl groups on square nanometer surface	Average particle size/nm
			S1	1.2	26
S2	2.3	65
			S3	1.5	34
D1	1.4	28
			D2	/	/
D3	3.6	219

The γ -butyrolactone solution was heated, and the imidazolium phthalate was added thereto and dissolved with stirring. The prepared additives S1-S3 and comparative samples D1-D3 are added into gamma-butyrolactone and main solute phthalic acid imidazole salt to prepare working electrolyte of the aluminum electrolytic capacitor, and the working electrolyte is marked as SS1, SS2, SS3, DD1, DD2 and DD3 respectively. The amounts added are shown in Table 2. The capacitor used to verify additive performance was 47f/100V, 10 x 13mm in size and 143Vf in capacity.

TABLE 2

1. And respectively taking the electrolytes SS 1-SS 3 to be tested and the electrolytes DD 1-DD 3 to test the conductivity and the sparking voltage at the temperature of 30 ℃.

(1) Electrical conductivity of

And (3) carrying out conductivity test on the electrolytes SS 1-SS 3 and the electrolytes DD 1-DD 3 by using a conductivity detector.

(2) Sparking voltage

And respectively putting electrolytes SS 1-SS 3 to be detected and electrolytes DD 1-DD 3 into a clean and dry beaker, and respectively connecting the positive electrode and the negative electrode with the optical foil by using an alligator clip, wherein the liquid level of the optical foil is about 1 cm. And the part of the foil immersed in the liquid surface can not be attached to the cup wall, and the distance between the two electrode plates is more than 2 cm.

Turning on a power switch of a spark voltmeter, setting the gear of a voltage stepping switch to be 800V, simultaneously turning on computer test software, entering a test system, inputting a test project name and a batch number, setting the current required by constant current boosting to be 20mA, starting the test system to test, and starting the test.

When the voltage rises to the point that the spark occurs on the optical foil or the voltage drops (more than or equal to 2V), reading the first peak voltage of the test curve, namely the sparking voltage of the electrolyte; and when the voltage rises to the point that the spark occurs on the optical foil or the voltage drops (more than or equal to 2V), reading the time under the first peak voltage of the test curve, namely the flash time of the electrolyte.

The test results obtained are shown in table 3.

TABLE 3

2. Respectively taking electrolytes SS 1-SS 3 to be tested and electrolytes DD 1-DD 3 to test the conductivity, the conductivity change rate, the sparking voltage and the moisture under the condition of high-temperature storage at 125 ℃, wherein the test process of the high-temperature storage is as follows: and placing the electrolyte to be tested into a steel cylinder, sealing the bottle opening, baking in an oven, and taking out the electrolyte for a fixed time to test electrical performance parameters.

The obtained test results are shown in table 4 and table 5.

TABLE 4

TABLE 5

From tables 4 and 5, it can be seen that the conductivities, the conductivity change rates and the flash voltages of the electrolytes SS1 to SS3 are relatively stable even when the electrolytes are stored at 125 ℃ for 1500 hours, and the conductivities of the electrolytes DD1 to DD2 are obviously reduced when the electrolytes are stored at 125 ℃ for 250 hours, which shows that the added silica lactone sol of the present invention has excellent high temperature storage resistance and the conductivities and the flash voltages are relatively stable under long-term high temperature storage; the water content can influence the conductivity, and the conductivity is relatively stable under the condition that the water content of the electrolytes SS 1-SS 3 is equivalent to that of the electrolyte DD1 and the high-temperature storage for a long time; when the number of hydroxyl groups on the surface of each square nanometer of the electrolyte DD3 surface modified silicon dioxide is more than 3, the conductivity is greatly reduced compared with that of the electrolytes SS 1-SS 3 along with the increase of storage time.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.