A high-voltage stable solid electrolytic capacitor and its preparation method

Abstract

The present invention discloses a high-voltage stable solid electrolytic capacitor and a preparation method thereof. The preparation method of the high-voltage stable solid electrolytic capacitor comprises the following steps: Step (1): Dissolve sodium silicate and acetic acid in water, then add grafted NH2-POSS, and after stirring treatment, obtain a mixed solution. Finally, immerse the anodized aluminum foil after secondary anodization treatment in the mixed solution for surface modification to obtain a modified anodized aluminum foil; Step (2): Add the composite PEDOT:PSS material and polyvinylidene fluoride into N-methyl-2-pyrrolidone, and after stirring treatment, obtain a slurry. Then, drop-cast the slurry on one side surface of the modified anodized aluminum foil. After vacuum drying, sequentially coat a graphite layer and a conductive silver paste layer on the same side of the drop-cast aluminum foil, and lead out the positive and negative electrodes with wires respectively to prepare a high-voltage stable solid electrolytic capacitor. The high-voltage stable solid electrolytic capacitor prepared by the present invention has characteristics such as low high-frequency impedance, wide working temperature range, long service life, high stability, good temperature characteristics, and strong pressure tolerance.

Description

Technical Field

[0001] The present invention belongs to the technical field of electronic chemicals, and particularly relates to a high-voltage stable solid electrolytic capacitor and a preparation method thereof. Background Art

[0002] Aluminum electrolytic capacitors are widely used in many electronic fields due to their excellent dielectric properties such as high capacitance, high withstand voltage, high energy density, and low cost. However, due to electrolyte evaporation and high equivalent series resistance (ESR), overheating and reduced ripple current occur, resulting in higher voltage fluctuations, so their lifespan is limited. In recent years, solid electrolytes have been considered one of the most promising technologies for significantly improving the performance of aluminum electrolytic capacitors due to their low high-frequency impedance, wide operating temperature range, long lifespan, high stability, and good temperature characteristics.

[0003] However, although solid electrolytes have high conductivity, their withstand voltage performance still needs to be improved. Therefore, it is urgent to improve the withstand voltage ability and service life of solid aluminum electrolytic capacitors. Summary of the Invention

[0004] The purpose of the present invention is to provide a high-voltage stable solid electrolytic capacitor and a preparation method thereof to solve the technical problems of the prior art.

[0005] The technical solution for the present invention to solve the above technical problems is as follows: A preparation method of a high-voltage stable solid electrolytic capacitor includes the following steps:

[0006] Step (1): Dissolve sodium silicate and acetic acid in water, then add grafted NH2-POSS, stir to obtain a mixed solution, and finally immerse the anodized aluminum foil after secondary anodization treatment in the mixed solution for surface modification to obtain a modified anodized aluminum foil;

[0007] In the above process, the active silicon solution formed by the reaction of sodium silicate and acetic acid contains silicate ions and acetate ions; the imino group in grafted NH2-POSS reacts with silicate ions to form amino silicate, and at the same time, the silane oxy group reacts with acetate ions to form acetic acid silicon ester. The amino silicate and acetic acid silicon ester are adsorbed or bonded to the surface of the anodized aluminum foil after secondary anodization treatment to form a modified anodized aluminum foil.

[0008] Step (2): Add the composite PEDOT:PSS material and polyvinylidene fluoride to N-methyl-2-pyrrolidone, stir to obtain a slurry, then drop-cast the slurry on one side surface of the modified anodized aluminum foil, after vacuum drying, sequentially coat a graphite layer and a conductive silver paste layer on the same side of the cast aluminum foil, and lead out the positive and negative electrodes with wires respectively to obtain a high-voltage stable solid electrolytic capacitor.

[0009] In the above process, the film prepared with the composite PEDOT:PSS material replaces the electrolytic paper in the traditional capacitor.

[0010] Preferably, in the step (1), the dosage ratio of sodium silicate, acetic acid, water, and grafted NH2-POSS is (80 - 120) g : (80 - 120) g : (180 - 220) mL : (20 - 25) g; the stirring treatment time is 10 - 20 min.

[0011] Preferably, in the step (2), the dosage ratio of the composite PEDOT:PSS material, polyvinylidene fluoride, and N-methyl-2-pyrrolidone is (16 - 32) g : (4 - 8) g : (120 - 160) mL; the stirring treatment time is 10 - 20 min; the vacuum drying conditions are: the vacuum drying temperature is 75 - 85 °C and the vacuum drying time is 12 - 24 h.

[0012] Preferably, in the step (1), the preparation method of the anodic aluminum foil by secondary anodic oxidation treatment includes the following steps:

[0013] S1: Under the conditions of a temperature of 5 - 10 °C and a voltage of 10 - 20 V, electrochemically polish the aluminum foil with a 60 wt% HCLO4 / ethanol solution for 4 - 6 min to obtain electrochemically polished aluminum foil.

[0014] S2: Immerse the electrochemically polished aluminum foil in hot MiLLi-Q water at 92 - 98 °C for 8 - 12 min to obtain hydrated aluminum foil.

[0015] S3: Under the conditions of a voltage of 700 V, an initial current density of 10 mA / cm², and a temperature of 80 - 90 °C, treat the hydrated aluminum foil in a 0.5 moL / L boric acid solution for 8 - 12 min, then wash it with MiLLi-Q water 3 - 5 times, and then dry it with cold air at 0 - 10 °C to obtain anodized aluminum foil.

[0016] In the above process, the electrochemically polished aluminum foil is immersed in hot MiLLi-Q water to obtain aluminum foil with a hydrated oxide layer.

[0017] S4: Immerse the anodized aluminum foil in hot MiLLi-Q water at 92 - 98 °C for 8 - 12 min to obtain secondary hydrated aluminum foil.

[0018] In the above process, through secondary hydration treatment, a uniformly distributed nano-hole layer is formed on the alumina film, and at the same time, the surface area of the alumina film is increased to promote the secondary anodic oxidation reaction.

[0019] S5: Under the conditions of a voltage of 200 - 630 V, an initial current density of 10 mA / cm², and a temperature of 80 - 90 °C, the hydrated and post-treated aluminum foil is treated in a 0.5 moL / L boric acid solution for 8 - 12 min, then washed 3 - 5 times with MiLLi-Q water, and then dried with cold air at 0 - 10 °C for 20 - 30 min to obtain the second anodized aluminum foil.

[0020] Preferably, in the step (1), the preparation method of the grafted NH2-POSS includes the following steps:

[0021] In a nitrogen atmosphere, 20 - 40 g of 4,4'-diaminodiphenyl ether is added to 200 - 400 mL of dimethylacetamide, stirred until completely dissolved, then 52 - 104 g of 4,4'-(4,4'-isopropyl diphenoxy) bis(phthalic anhydride) is added, stirred at room temperature for 5 - 7 h, then 2 - 4 g of NH2-POSS is added, and stirring is continued for 36 - 54 h. Then, it is kept warm at 30 - 50 °C for 5 - 7 h, and then the solvent is evaporated at 170 - 180 °C to obtain the grafted NH2-POSS.

[0022] The structural formula of the grafted NH2-POSS is as follows:

[0023] In the above process, 4,4'-diaminodiphenyl ether and 4,4'-(4,4'-isopropyl diphenoxy) bis(phthalic anhydride) react to form polyimide, and then polycondense with the amino group of NH2-POSS to form the grafted NH2-POSS.

[0024] Preferably, in the step (2), the preparation method of the composite PEDOT:PSS material includes the following steps:

[0025] P1: 80 - 100 g of reduced graphene oxide powder is dispersed in 80 - 100 L of deionized water, ultrasonically treated at a frequency of 20 - 100 KHz for 5 - 10 min to obtain a dispersion, then 240 - 300 g of thiourea is added, stirred until the thiourea is completely dissolved, transferred to a Teflon-lined autoclave, heated at 130 - 150 °C for 6 - 10 h, then naturally cooled, centrifuged, washed 3 - 5 times with ethanol and deionized water, and finally vacuum dried at 55 - 65 °C for 12 - 36 h to obtain sulfur and nitrogen co-doped reduced graphene oxide;

[0026] In the above process, sulfur and nitrogen co-doped reduced graphene oxide is prepared by a hydrothermal method.

[0027] P2: Dissolve 30 - 60 g of sulfur and nitrogen - doped reduced graphene oxide in 100 - 200 L of 30 wt% ethanol aqueous solution, ultrasonically treat it for 0.5 - 1.5 h at a frequency of 20 - 100 KHz, then add 5.4 - 10.8 L of 1.3 wt% PEDOT:PSS aqueous solution, and continue to ultrasonically treat it for 1.5 - 2.5 h at a frequency of 20 - 100 KHz to obtain a mixture;

[0028] P3: Keep the mixture at 2 - 5 °C by the ice - bath method, slowly add 1.5 - 3 L of H2SO4, then slowly add 5 - 10 L of 0.1 g / mL ammonium persulfate solution, and continue to stir at 2 - 5 °C for 20 - 28 h. Then transfer it to a Teflon - lined autoclave, heat it at 154 - 155 °C for 14 - 22 h, centrifuge it, and after natural cooling, rinse it 3 - 5 times with ethanol and deionized water, and finally dry it at 95 - 105 °C for 12 - 24 h to obtain the composite PEDOT:PSS material.

[0029] In the above process, under the action of the oxidant ammonium persulfate, PEDOT:PSS polymerizes on the sulfur and nitrogen - doped reduced graphene oxide and is uniformly coated on the sulfur and nitrogen - doped reduced graphene oxide.

[0030] A high - voltage stable solid - state electrolytic capacitor prepared by using the preparation method of the high - voltage stable solid - state electrolytic capacitor.

[0031] In summary, due to the adoption of the above - mentioned technical solutions, the beneficial effects of the present invention are as follows:

[0032] 1. The high - voltage stable electrolytic capacitor prepared by the present invention through secondary hydration treatment and secondary anodic oxidation treatment of the anodic aluminum foil, and simultaneously grafting NH2 - POSS and coating the composite PEDOT:PSS material has characteristics such as low high - frequency impedance, wide operating temperature range, long service life, high stability, good temperature characteristics, and strong pressure tolerance.

[0033] 2. In the present invention, PEDOT:PSS is polymerized on sulfur and nitrogen-doped reduced graphene oxide to prepare a composite PEDOT:PSS material with high conductivity, high surface area, good mechanical strength and cost-effectiveness. The S and N atoms in the sulfur and nitrogen-doped reduced graphene oxide framework enhance the conductivity of reduced graphene oxide, and the S and N atoms act as spacers between different layers, improving the dispersibility of sulfur and nitrogen-doped reduced graphene oxide. Therefore, sulfur and nitrogen-doped reduced graphene oxide has excellent conductivity and electrochemical properties, and can cooperate with PEDOT:PSS to improve the electrochemical properties, mechanical stability and cycling stability of the composite PEDOT:PSS material; at the same time, the interaction between sulfur and nitrogen-doped reduced graphene oxide and PEDOT:PSS hinders the chain mobility in the polymer material, improving the thermal stability of the composite PEDOT:PSS material; the PEDOT:PSS layer formed on or inside the sulfur and nitrogen-doped reduced graphene oxide layer makes the surface more fluffy, obtaining more redox reaction sites and a larger active area, improving the capacitance.

[0034] 3. In the present invention, through secondary hydration treatment, a uniformly distributed nano-void layer is formed on the alumina film, improving the breakdown voltage of the anodic aluminum foil and avoiding capacitance reduction. At the same time, the surface area of the alumina film is increased, promoting the progress of the secondary anodization reaction. However, this will lead to an increase in leakage current. Therefore, through secondary anodization treatment, the voids in the dielectric layer are repaired, reducing the leakage current of the anodic aluminum foil and improving the high-voltage resistance and service life of the solid electrolytic capacitor; a small amount of composite PEDOT:PSS material is incorporated into the nano-voids, increasing the capacitance, and the highly dispersed nano-voids formed by the combination of the modified anodic aluminum foil and the composite PEDOT:PSS material avoid current concentration in local areas, effectively improving the dielectric breakdown voltage.

[0035] 4. The wide bandgap of NH2-POSS, about 6.6 eV, increases the energy band level of the polyimide and induces the formation of local deep traps in the hybrid film, thus significantly inhibiting carrier transport and improving the dielectric properties; NH2-POSS has excellent dielectric properties and high-temperature stability, and successfully improves the dielectric breakdown strength of the polymer when doped into the polymer. The NH2-POSS-capped polyimide avoids filler agglomeration and interfacial defects caused by the polycondensation reaction. By introducing NH2-POSS into the polyimide molecular chain, the conduction loss is reduced, suppressing energy loss and heat generation, and avoiding thermal breakdown of the capacitor film at high temperatures; the surface of the anodic aluminum foil treated by secondary anodization is grafted with NH2-POSS for surface modification, which can not only inhibit the breakdown of aluminum electrolytic capacitor products through the densely dispersed organosilane on the surface of the aluminum oxide film, but also make the combination of the composite PEDOT:PSS film and the anodic aluminum foil treated by secondary anodization more firm through the hydrogen bond interaction between the silane oxy group and the alkoxy group in the composite PEDOT:PSS material, and the capacitor performance is more stable. Brief Description of the Drawings

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0037] Figure 1 is the process flow chart for preparing a high-voltage stable solid electrolytic capacitor of the present invention;

[0038] Figure 2 is the line graph of the withstand voltage and leakage current of the solid electrolytic capacitor of the present invention;

[0039] Figure 3 is the bar graph of the initial capacitance and capacitance retention rate of the solid electrolytic capacitor of the present invention. Detailed Embodiments

[0040] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0041] The substances and sources involved in the following examples and comparative examples are shown in Table 1:

[0042] Table 1

[0043] Example 1

[0044] This example discloses a preparation method for anodic aluminum foil by secondary anodization treatment, including the following steps:

[0045] S1: Under the conditions of a temperature of 7.5 °C and a voltage of 15 V, electrochemically polish the aluminum foil with a 60 wt% HCLO4 / ethanol solution for 5 min to obtain electrochemically polished aluminum foil;

[0046] S2: Immerse the electrochemically polished aluminum foil in hot MiLLi-Q water at 95 °C for 10 min to obtain hydrated aluminum foil;

[0047] S3: Under the conditions of a voltage of 700 V, an initial current density of 10 mA / cm², and a temperature of 85 °C, the hydrated aluminum foil is treated in a 0.5 moL / L boric acid solution for 10 min, then washed 4 times with MiLLi-Q water, and then dried with cold air at 5 °C for 25 min to obtain an anodized aluminum foil;

[0048] S4: Immerse the anodized aluminum foil in hot MiLLi-Q water at 95 °C for 10 min to obtain a secondary hydrated aluminum foil;

[0049] S5: Under the conditions of a voltage of 400 V, an initial current density of 10 mA / cm², and a temperature of 85 °C, the secondary hydrated aluminum foil is treated in a 0.5 moL / L boric acid solution for 10 min, then washed 4 times with MiLLi-Q water, and then dried with cold air at 6 °C for 25 min to obtain a secondary anodized aluminum foil. Example 2

[0050] This example discloses a preparation method of grafted NH2-POSS, including the following steps:

[0051] In a nitrogen atmosphere, 30 g of 4,4'-diaminodiphenyl ether is added to 300 mL of the solvent dimethylacetamide. After stirring until completely dissolved, 77 g of 4,4'-(4,4'-isopropyl diphenoxy) bis(phthalic anhydride) is added. After stirring at room temperature for 6 h, 3 g of NH2-POSS is added, and stirring is continued for 48 h. Then, it is kept warm at 40 °C for 6 h, and then the solvent is evaporated at 175 °C to obtain grafted NH2-POSS. Example 3

[0052] This example discloses a preparation method of a composite PEDOT:PSS material, including the following steps:

[0053] P1: Disperse 90 g of reduced graphene oxide powder in 90 L of deionized water. After ultrasonic treatment at a frequency of 60 KHz for 7 min, 240 - 300 g of thiourea is added. After stirring until the thiourea is completely dissolved, it is transferred to a Teflon-lined autoclave and heated at 140 °C for 8 h. Then, it is naturally cooled, centrifuged, washed 4 times with ethanol and deionized water, and finally vacuum dried at 60 °C for 24 h to obtain sulfur and nitrogen co-doped reduced graphene oxide;

[0054] P2: Dissolve 45 g of sulfur and nitrogen co-doped reduced graphene oxide in 150 L of a 30 wt% ethanol aqueous solution. Ultrasonic treatment is carried out at a frequency of 60 KHz for 1 h, and then 7.9 L of a 1.3 wt% PEDOT:PSS aqueous solution is added, and ultrasonic treatment is continued at a frequency of 60 KHz for 2 h to obtain a mixture;

[0055] P3: Keep the mixture at 4 °C by the ice bath method, slowly add 2.2 L of H2SO4, then slowly add 7.5 L of ammonium persulfate solution at 0.1 g / mL, and continue stirring at 4 °C for 24 h. Then transfer it to a Teflon-lined autoclave, heat it at 155 °C for 18 h, centrifuge it, and after natural cooling, rinse it 4 times with ethanol and deionized water. Finally, dry it at 100 °C for 18 h to obtain the composite PEDOT:PSS material. Example 4

[0056] Refer to Figure 1 As shown, this example discloses a preparation method of a high-voltage stable solid electrolytic capacitor, including the following steps:

[0057] Step (1): Dissolve 100 g of sodium silicate and 100 g of acetic acid in 200 mL of water, then add 22 g of the grafted NH2-POSS prepared in Example 2, stir for 15 min to obtain a mixed solution, and finally immerse the anodized aluminum foil prepared in Example 1 in the mixed solution for surface modification to obtain a modified anodized aluminum foil;

[0058] Step (2): Add 24 g of the composite PEDOT:PSS material prepared in Example 3 and 6 g of polyvinylidene fluoride to 140 mL of N-methyl-2-pyrrolidone, stir for 15 min to obtain a slurry, then cast the slurry on one side surface of the modified anodized aluminum foil, vacuum dry it at 80 °C for 18 h, and then sequentially coat a graphite layer and a conductive silver paste layer on the same side of the cast aluminum foil, and lead out the positive and negative electrodes with wires respectively to obtain a high-voltage stable solid electrolytic capacitor. Example 5

[0059] Refer to Figure 1 As shown, this example discloses a preparation method of a high-voltage stable solid electrolytic capacitor, including the following steps:

[0060] Step (1): Dissolve 80 g of sodium silicate and 120 g of acetic acid in 180 mL of water, then add 25 g of the grafted NH2-POSS prepared in Example 2, stir for 10 min to obtain a mixed solution, and finally immerse the anodized aluminum foil prepared in Example 1 in the mixed solution for surface modification to obtain a modified anodized aluminum foil;

[0061] Step (2): Add 32 g of the composite PEDOT:PSS material prepared in Example 3 and 4 g of polyvinylidene fluoride to 160 mL of N-methyl-2-pyrrolidone, stir for 10 min to obtain a slurry, then cast the slurry on one side surface of the modified anodized aluminum foil, vacuum dry it at 85 °C for 12 h, and then sequentially coat a graphite layer and a conductive silver paste layer on the same side of the cast aluminum foil, and lead out the positive and negative electrodes with wires respectively to obtain a high-voltage stable solid electrolytic capacitor. Example 6

[0062] Refer to Figure 1 As shown, this embodiment discloses a preparation method of a high-voltage stable solid electrolytic capacitor, including the following steps:

[0063] Step (1): Dissolve 120 g of sodium silicate and 80 g of acetic acid in 220 mL of water, then add 20 g of the grafted NH2-POSS prepared in Example 2, stir for 20 min to obtain a mixed solution, and finally immerse the anodic aluminum foil subjected to secondary anodic oxidation prepared in Example 1 into the mixed solution for surface modification to obtain a modified anodic aluminum foil;

[0064] Step (2): Add 16 g of the composite PEDOT:PSS material prepared in Example 3 and 8 g of polyvinylidene fluoride to 120 mL of N-methyl-2-pyrrolidone, stir for 20 min to obtain a slurry, then drop-cast the slurry on one side surface of the modified anodic aluminum foil, vacuum dry at 75 °C for 24 h, and then sequentially coat a graphite layer and a conductive silver paste layer on the same side of the drop-cast aluminum foil, and lead out the positive and negative electrodes with wires respectively to obtain a high-voltage stable solid electrolytic capacitor. Example 7

[0065] Refer to Figure 1 As shown, this embodiment discloses a preparation method of a high-voltage stable solid electrolytic capacitor, including the following steps:

[0066] Step (1): Dissolve 90 g of sodium silicate and 110 g of acetic acid in 210 mL of water, then add 21 g of the grafted NH2-POSS prepared in Example 2, stir for 12 min to obtain a mixed solution, and finally immerse the anodic aluminum foil subjected to secondary anodic oxidation prepared in Example 1 into the mixed solution for surface modification to obtain a modified anodic aluminum foil;

[0067] Step (2): Add 28 g of the composite PEDOT:PSS material prepared in Example 3 and 5 g of polyvinylidene fluoride to 150 mL of N-methyl-2-pyrrolidone, stir for 17 min to obtain a slurry, then drop-cast the slurry on one side surface of the modified anodic aluminum foil, vacuum dry at 77 °C for 16 h, and then sequentially coat a graphite layer and a conductive silver paste layer on the same side of the drop-cast aluminum foil, and lead out the positive and negative electrodes with wires respectively to obtain a high-voltage stable solid electrolytic capacitor. Example 8

[0068] Refer to Figure 1 As shown, this embodiment discloses a preparation method of a high-voltage stable solid electrolytic capacitor, including the following steps:

[0069] Step (1): Dissolve 110 g of sodium silicate and 90 g of acetic acid in 190 mL of water, then add 24 g of the grafted NH2-POSS prepared in Example 2, stir for 18 min to obtain a mixed solution, and finally immerse the anodized aluminum foil prepared in Example 1 in the mixed solution for surface modification to obtain a modified anodized aluminum foil;

[0070] Step (2): Add 18 g of the composite PEDOT:PSS material prepared in Example 3 and 7 g of polyvinylidene fluoride to 130 mL of N-methyl-2-pyrrolidone, stir for 12 min to obtain a slurry, then drop-cast the slurry on one side surface of the modified anodized aluminum foil, vacuum dry at 82 °C for 22 h, and then sequentially coat a graphite layer and a conductive silver paste layer on the same side of the cast aluminum foil, and lead out the positive and negative electrodes with wires respectively to prepare a high-voltage stable solid electrolytic capacitor.

[0071] Comparative Example 1

[0072] Compared with Example 4, in Comparative Example 1, step (1) is not carried out, that is, the anodized aluminum foil treated by secondary anodization is used instead of the modified anodized aluminum foil, and other conditions remain unchanged.

[0073] Comparative Example 2

[0074] Compared with Example 4, in step (1) of Comparative Example 2, commercially available anodized aluminum foil is used instead of the anodized aluminum foil treated by secondary anodization, and other conditions remain unchanged.

[0075] Comparative Example 3

[0076] Compared with Example 4, in step (2) of Comparative Example 3, PEDOT:PSS is used instead of the composite PEDOT:PSS material, and other conditions remain unchanged.

[0077] Experimental Example

[0078] Test the high-voltage stable solid electrolytic capacitors prepared in Examples 4-8 and Comparative Examples 1-3:

[0079] Test the capacitance, leakage current, withstand voltage, and ripple current withstand of the capacitor according to the national standards GB / T6346.25-2018 and GB / T 6346.2501-2018. Test the capacitance with a digital bridge LCR at a frequency of 120 Hz; test the leakage current and withstand voltage with a leakage current tester; the ripple current withstand is tested by applying a ripple current to measure the temperature rise of the capacitor.

[0080] The performance of the high-voltage stable solid electrolytic capacitors prepared in Examples 4-8 and Comparative Examples 1-3 is shown in Table 2:

[0081] Table 2

[0082]

[0083] The initial capacity and cyclic capacity retention rate with high-voltage stability are shown in Table 3 as follows:

[0084] Table 3

[0085]

[0086] From the test results in Table 2 and Table 3, it can be seen that the solid electrolytic capacitors with high-voltage stability prepared in Examples 4-8 of the present invention have the characteristics of withstand voltage, reducing the leakage current of the product, increasing the initial capacity of the product, increasing the cyclic capacity retention rate, and ripple current resistance. From the comparison between Comparative Example 1 and Example 4, it can be seen that the modified anodic aluminum foil in the present invention can improve the performance of the solid electrolytic capacitor with high-voltage stability; from the comparison between Comparative Example 2 and Example 4, it can be seen that using the secondary anodization treatment for the anodic aluminum foil in the present invention can improve the performance of the solid electrolytic capacitor with high-voltage stability; from the comparison between Comparative Example 3 and Example 4, it can be seen that using the composite PEDOT:PSS material in the present invention can improve the performance of the solid electrolytic capacitor with high-voltage stability.

[0087] The above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, making equivalent substitutions or changes, shall be covered by the protection scope of the present invention.

[0088] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the present invention to only the specific embodiments. Obviously, many modifications and variations can be made according to the content of this specification. This specification selects and specifically describes these embodiments to better explain the principle and practical application of the present invention, so that those skilled in the art in the relevant technical field can well understand and utilize the present invention. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. A method for preparing a high-voltage stable solid electrolytic capacitor, characterized in that: The following steps are involved: Step (1) dissolving sodium silicate and acetic acid in water, adding grafted NH2-POSS, stirring to obtain a mixed solution, and finally immersing the secondary anodized anode aluminum foil in the mixed solution for surface modification to obtain a modified anode aluminum foil; Step (2) adding the composite PEDOT:PSS material and polyvinylidene fluoride into N-methyl-2-pyrrolidone, stirring to obtain a slurry, then drop-casting the slurry on one side of the modified anode aluminum foil, vacuum drying, coating a graphite layer and a conductive silver paste layer on the same side of the drop-cast aluminum foil in sequence, and respectively leading out the positive and negative electrodes with wires to obtain a high-voltage stable solid electrolytic capacitor; The method for preparing the secondary anodized anode aluminum foil comprises the following steps: S1: electrochemically polishing the aluminum foil with 60wt% HCLO4 / ethanol solution for 4-6min at a temperature of 5-10°C and a voltage of 10-20V to obtain an electrochemically polished aluminum foil; S2: immersing the electrochemically polished aluminum foil in hot MiLLi-Q water at 92-98° C. for 8-12 min to obtain a hydrated aluminum foil; S3: Under the conditions of voltage of 700V, initial current density of 10mA / cm² and temperature of 80-90°C, the hydrated aluminum foil is treated in 0.5moL / L boric acid solution for 8-12min, then washed with MilLi-Q water for 3-5 times, and then dried with cold air at 0-10°C to obtain anodized aluminum foil; S4: immersing the anodized aluminum foil in hot MilLi-Q water at 92-98° C. for 8-12 minutes to obtain a secondary hydration treated aluminum foil; S5: Under the conditions of voltage of 200-630V, initial current density of 10mA / cm² and temperature of 80-90°C, the hydrated treated aluminum foil is treated in 0.5moL / L boric acid solution for 8-12min, then washed with MilLi-Q water for 3-5 times, and then dried with cold air at 0-10°C for 20-30min to obtain a secondary anodized aluminum foil; The preparation method of the grafted NH2-POSS comprises the following steps: In a nitrogen atmosphere, 20-40 g of 4,4'-diaminodiphenyl ether is added to 200-400 mL of dimethylacetamide, and stirred until completely dissolved, and then 52-104 g of 4,4'-(4,4'-isopropyldiphenyloxy)bis(phthalic anhydride) is added, and stirred at room temperature for 5-7 hours, and then 2-4 g of [3-(2-aminoethyl)amino]propyl-heptylisobutyl-polysiloxane (NH2-POSS) is added, and the stirring treatment is continued for 36-54 hours, and then the mixture is kept at 30-50° C. for 5-7 hours, and then the solvent is evaporated and removed at 170-180° C. to obtain grafted NH2-POSS; The preparation method of the composite PEDOT:PSS material comprises the following steps: P1: 80-100 g of reduced graphene oxide powder is dispersed in 80-100 L of deionized water, and after ultrasonic treatment at a frequency of 20-100 KHz for 5-10 min, 240-300 g of thiourea is added, and the mixture is stirred until the thiourea is completely dissolved, and then transferred to a Teflon-lined autoclave, and heated at 130-150 ° C for 6-10 h, and then naturally cooled, centrifuged, washed with ethanol and deionized water for 3-5 times, and finally vacuum dried at 55-65 ° C for 12-36 h to obtain sulfur-nitrogen doped reduced graphene oxide; P2: 30-60 g of sulfur-nitrogen-doped reduced graphene oxide was dissolved in 100-200 L of 30 wt% ethanol aqueous solution, and ultrasonically treated at a frequency of 20-100 KHz for 0.5-1.5 h, and then 5.4-10.8 L of 1.3 wt% PEDOT:PSS aqueous solution was added, and ultrasonically treated at a frequency of 20-100 KHz for 1.5-2.5 h to obtain a mixture; P3: The mixture was kept at 2-5°C with an ice bath, 1.5-3L H2SO4 was slowly added, and then 5-10L 0.1g / mL ammonium persulfate solution was slowly added, and stirring was continued at 2-5°C for 20-28h, then transferred to a Teflon-lined autoclave, heated at 154-155°C for 14-22h, centrifuged, and rinsed with ethanol and deionized water 3-5 times after natural cooling, and finally dried at 95-105°C for 12-24h to obtain a composite PEDOT:PSS material.

2. The method for preparing a high-voltage stable solid electrolytic capacitor according to claim 1, characterized in that: In the step (1), the usage ratio of sodium silicate, acetic acid, water, and grafted NH2-POSS is (80-120) g: (80-120) g: (180-220) mL: (20-25) g; and the stirring treatment time is 10-20 min.

3. The method for preparing a high-voltage stable solid electrolytic capacitor according to claim 1, characterized in that: In the step (2), the usage ratio of the composite PEDOT:PSS material, polyvinylidene fluoride, and N-methyl-2-pyrrolidone is (16-32) g:(4-8) g:(120-160) mL.

4. The method for preparing a high-voltage stable solid electrolytic capacitor according to claim 1, characterized in that: In the step (2), the stirring treatment time is 10-20 minutes; the vacuum drying conditions are: the vacuum drying temperature is 75-85°C, and the vacuum drying time is 12-24 hours.

5. A high-voltage stable solid electrolytic capacitor prepared by the method according to any one of claims 1 to 4.

Images