High temperature resistant solid state capacitor and method of making same

Abstract

The application discloses a high-temperature-resistant solid capacitor and a preparation method thereof, and relates to the technical field of capacitors.The high-temperature-resistant solid capacitor provided by the application comprises at least an anode foil, a cathode foil and a solid electrolyte filled between the anode foil and the cathode foil; the anode foil and the cathode foil are subjected to surface modification treatment by using an amino silane coupling agent; and the solid electrolyte is composed of the following raw materials in parts by mass: a conductive polymer matrix 50-80 parts, sulfonated hollow mesoporous carbon spheres 10-30 parts, a diphenylmethane type bismaleimide 5-15 parts and an interface coupling agent 2-8 parts.The solid capacitor provided by the application has the advantages of greater capacity, smaller loss, smaller leakage current and lower equivalent series resistance, and the high-temperature-resistant performance of the capacitor is improved, and the service life of the product is prolonged.

Description

Technical Field

[0001] This invention relates to the field of capacitor technology, specifically to high-temperature resistant solid capacitors and their preparation methods. Background Technology

[0002] Due to rapid development in various fields, electrolytic capacitors are being used more and more widely. An electrolytic capacitor mainly consists of an anode, a dielectric layer, and a cathode. The anode is a metal, and its surface is corroded to form an electrolyte oxide film. The other material in contact with the dielectric is called the cathode, and its properties affect the overall performance of the capacitor.

[0003] Liquid electrolytic capacitors use an ion-conducting electrolyte as the actual cathode, resulting in low conductivity and a high risk of explosion during use, posing a safety hazard. Gradually, solid-state electrolytic capacitors have replaced liquid electrolytic capacitors, gaining a dominant market share. The latest solid-state electrolytic capacitors use PEDOT or PEDOT:PSS films as the solid electrolyte, achieving conductivity close to that of a conductor while maintaining high stability.

[0004] However, current solid-state aluminum electrolytic capacitors still have significant shortcomings in high-temperature resistance. At high temperatures, the molecular structure of the cathode material (such as commonly used conductive polymers) changes, leading to a decrease in conductivity and a sharp increase in equivalent series resistance. Furthermore, the thermal expansion coefficients of the metal oxide dielectric layer of the electrode and the solid electrolyte are mismatched, easily causing microcracks and interface delamination under high-temperature thermal stress, forming a high-impedance interface layer, increasing losses and accelerating performance degradation. These problems become even more pronounced when the operating temperature exceeds 125°C, severely impacting the reliability and lifespan of capacitors in high-temperature industrial applications (such as oil extraction and metallurgy) and new energy vehicle applications (such as battery management systems and motor drive systems). Therefore, existing high-temperature resistant solid-state capacitors suffer from short high-temperature lifespan, poor high-temperature interface stability, and high failure rates, severely limiting the application of this technology. Summary of the Invention

[0005] The purpose of this invention is to provide a high-temperature resistant solid capacitor and its preparation method, thereby solving the following technical problems:

[0006] Existing high-temperature solid capacitors suffer from problems such as short service life at high temperatures, poor interface stability at high temperatures, and high failure rate.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] High-temperature resistant solid capacitors, including at least:

[0009] An anode foil, a cathode foil, and a solid electrolyte filling the space between the anode foil and the cathode foil;

[0010] The anode foil and the cathode foil are surface modified with an aminosilane coupling agent;

[0011] The solid electrolyte is composed of the following raw materials in parts by weight: 50-80 parts of conductive polymer matrix, 10-30 parts of sulfonated hollow mesoporous carbon spheres, 5-15 parts of diphenylmethane-type bismaleimide, and 2-8 parts of interfacial coupling agent.

[0012] As a further aspect of the present invention, the surface modification treatment of the anode foil includes at least the following steps:

[0013] After forming a metal oxide layer on the metal foil, immerse it in anhydrous ethanol for 10-20 minutes and air dry it. Then immerse it in an ethanol solution of 1-3 wt% aminosilane coupling agent for 5-15 minutes and dry it at 140-150℃ for 20-30 minutes.

[0014] As a further aspect of the present invention: the surface modification treatment methods for the anode foil and the cathode foil are the same, and the metal foil is one of aluminum, tantalum, niobium or titanium.

[0015] As a further aspect of the present invention: the aminosilane coupling agent is at least one of 3-aminopropyltrimethoxysilane and N-2-aminoethyl-3-aminopropyltrimethoxysilane.

[0016] As a further aspect of the present invention, the method for preparing the sulfonated hollow mesoporous carbon spheres includes the following steps:

[0017] Tetrapropoxysilane, ethanol and ammonia were added to deionized water and mixed. Then resorcinol and formaldehyde were added and stirred to react. After centrifugation, washing, drying and carbonization, the silica was removed by adding sodium hydroxide solution to obtain hollow mesoporous carbon spheres.

[0018] Sodium nitrite was added to a hydrochloric acid solution of p-aminobenzenesulfonate, and after the reaction, the mixture was filtered and washed to obtain 4-benzenediazosulfonate.

[0019] The 4-benzenediazosulfonate, ethanol, and deionized water were mixed, and then the hollow mesoporous carbon spheres and hypophosphite aqueous solution were added. The mixture was centrifuged, washed, and dried to obtain sulfonated hollow mesoporous carbon spheres.

[0020] As a further aspect of the present invention: the pore size of the hollow mesoporous carbon sphere is 5-19 nm, the diameter of the sulfonated hollow mesoporous carbon sphere is 50-200 nm, and the content of sulfonic acid groups on the surface of the sulfonated hollow mesoporous carbon sphere is 0.5-2.0 mmol / g.

[0021] As a further aspect of the present invention: the conductive polymer matrix is ​​a copolymer of polythiophene and poly(3,4-ethylenedioxythiophene), and the mass ratio of the polythiophene to the poly(3,4-ethylenedioxythiophene) is 2-5:8-5.

[0022] As a further aspect of the present invention: the interface coupling agent is at least one of silane coupling agents.

[0023] A method for preparing a high-temperature resistant solid capacitor as described in any one of the above claims includes at least the following preparation steps:

[0024] The anode lead and cathode lead are connected to the surface-modified anode foil and cathode foil respectively by riveting, and then wound to obtain a core package;

[0025] An electrolyte slurry is prepared by mixing a conductive polymer matrix, sulfonated hollow mesoporous carbon spheres, diphenylmethane-type bismaleimide, and an interfacial coupling agent. The electrolyte slurry is then filled into the core package by vacuum impregnation and cured at 150-180°C for 2-4 hours to obtain a solid electrolyte.

[0026] The core-packaged solid electrolyte is then aged to obtain a high-temperature resistant solid capacitor.

[0027] The beneficial effects of this invention are:

[0028] In this invention, by performing surface treatment of the anode and cathode foils with aminosilane and modifying the solid electrolyte material, the solid capacitor obtained by the method for preparing high-temperature resistant solid capacitors provided by this invention has the advantages of larger capacity, lower loss, lower leakage current, and lower equivalent series resistance, thereby improving the high-temperature resistance of the capacitor and the product yield. Specifically, an aminosilane coupling agent is used to modify the surface of the metal foil. The metal foil with a metal oxide dielectric on its surface is immersed in an aminosilane coupling agent solution for surface modification. The amino functional groups of the aminosilane coupling agent can bridge the metal oxide dielectric and the conductive polymer. In this invention, the aminosilane coupling agent can form strong chemical bonds with the conductive polymer, diphenylmethane-type bismaleimide, and sulfonic acid groups of sulfonated hollow mesoporous carbon spheres in the solid electrolyte, which greatly improves the adhesion strength and thermal stability of the electrode-electrolyte interface, effectively suppresses interfacial delamination and side reactions during high-temperature cycling, improves interfacial thermal stability, and greatly extends the service life of the product at high temperatures.

[0029] The solid electrolyte prepared in this invention comprises a conductive polymer matrix, sulfonated hollow mesoporous carbon spheres, diphenylmethane-type bismaleimide, and an interfacial coupling agent. The conductive copolymer matrix formed by polythiophene / poly(3,4-ethylidene dioxythiophene) provides good processability and initial conductivity. The diphenylmethane-type bismaleimide, acting as a crosslinking agent, synergistically enhances the high-temperature resistant conductive network formed by the composite of the nanofiller sulfonated hollow mesoporous carbon spheres, improving the high-temperature resistance and conductivity of the solid capacitor. The sulfonated hollow mesoporous carbon spheres prepared in this invention possess both a hollow structure and surface sulfonic acid groups. The hollow structure can accommodate conductive polymer molecules, while the mesoporous channels provide ordered ion transport pathways, buffering them at high temperatures and reducing cracking caused by thermal shrinkage. The surface sulfonic acid groups interact with the polar segments of the conductive polymer, promoting the ordered arrangement of polymer molecular chains and improving conductivity. Meanwhile, diphenylmethane-type bismaleimide acts as a crosslinking agent, forming a high-temperature resistant crosslinking network with the polymer matrix and sulfonated hollow mesoporous carbon spheres. This constructs a stable ion-electron hybrid conductive framework within the electrolyte, enabling the capacitor to maintain high capacitance and low equivalent series resistance growth rate at high temperatures of 150-200℃. Furthermore, the rigid mesoporous carbon shell of the sulfonated hollow mesoporous carbon spheres, combined with the three-dimensional crosslinking network formed by the diphenylmethane-type bismaleimide, provides excellent mechanical support for the electrolyte, suppressing high-temperature creep and further improving the high-temperature resistance of the prepared solid capacitor. Detailed Implementation

[0030] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Example 1: The preparation method of sulfonated hollow mesoporous carbon spheres includes the following steps:

[0032] Under stirring conditions in a 30°C water bath, 6.92 mL of tetrapropoxysilane was added to a mixed solution containing 40 mL of deionized water, 120 mL of ethanol, and 6 mL of 25 wt% ammonia. After 15 min, 0.8 g of resorcinol and 1.12 mL of 37 wt% formaldehyde were added and the mixture was stirred continuously for 24 h. After the reaction, the precipitate was separated by centrifugation, washed three times with deionized water / ethanol, dried overnight at 60°C, and then carbonized at 700°C for 5 h under nitrogen atmosphere at a heating rate of 2°C / min. Finally, the silica was removed with 24 mL of 4 mol / L sodium hydroxide solution to obtain hollow mesoporous carbon spheres.

[0033] 20 mL of 1 mol / L sodium nitrite was added dropwise to a solution containing 2 g of p-aminobenzenesulfonic acid and 40 mL of 1 mol / L hydrochloric acid. The mixture was stirred in an ice-water bath for 1 h. The resulting white precipitate was filtered and washed with water to obtain 4-benzenediazosulfonate.

[0034] The above-mentioned 4-benzenediazosulfonate was transferred to a solution containing 27 mL of deionized water and 8 mL of ethanol. Then, 0.2 g of the above-mentioned hollow mesoporous carbon spheres and 13 mL of 32 wt% hypophosphite aqueous solution were added sequentially and stirred for 30 min. Then, 7 mL of 32 wt% hypophosphite aqueous solution was added again and stirred until no nitrogen gas was generated. The mixture was centrifuged, washed thoroughly with acetone and distilled water, and then dried overnight at 50 °C in a vacuum drying oven to obtain sulfonated hollow mesoporous carbon spheres.

[0035] Example 2: The preparation method of a high-temperature resistant solid capacitor includes the following steps:

[0036] Cut aluminum foil was treated with 2% NaOH solution at room temperature for 10 minutes to remove the oxide film and oil on the surface. After oxidation, an aluminum oxide dielectric layer was formed on the surface of the aluminum foil. The foil was then immersed in anhydrous ethanol for 15 minutes and air-dried at room temperature for 30 minutes. It was then immersed in 1 wt% 3-aminopropyltrimethoxysilane ethanol solution for 10 minutes and finally dried at 150°C for 20 minutes to obtain the surface-modified anode foil and cathode foil.

[0037] The anode lead and cathode lead are connected to the surface-modified anode foil and cathode foil respectively by riveting, and then wound to obtain a core package;

[0038] An electrolyte slurry was prepared by mixing 20 parts by mass of polythiophene, 45 parts by mass of poly(3,4-ethylenedioxythiophene), 20 parts by mass of sulfonated hollow mesoporous carbon spheres prepared in Example 1, 10 parts by mass of diphenylmethane-type bismaleimide, and 5 parts by mass of the interfacial coupling agent vinyltriethoxysilane. The electrolyte slurry was then filled into the core package by vacuum impregnation and cured at 160°C for 3 hours to obtain a solid electrolyte.

[0039] The core package forming the solid electrolyte is assembled with an aluminum shell and a stopper to obtain a semi-finished capacitor. The semi-finished capacitor is then charged and aged by applying voltages of 0.5 times, 1 times, and 1.2 times the rated voltage to perform segmented aging treatment, thereby obtaining a high-temperature resistant solid capacitor.

[0040] Example 3: The preparation method of a high-temperature resistant solid capacitor includes the following steps:

[0041] Cut aluminum foil was treated with 2% NaOH solution at room temperature for 10 minutes to remove the oxide film and oil on the surface. After oxidation, an aluminum oxide dielectric layer was formed on the surface of the aluminum foil. The foil was then immersed in anhydrous ethanol for 15 minutes and air-dried at room temperature for 30 minutes. It was then immersed in 1 wt% 3-aminopropyltrimethoxysilane ethanol solution for 10 minutes and finally dried at 150°C for 20 minutes to obtain the surface-modified anode foil and cathode foil.

[0042] The anode lead and cathode lead are connected to the surface-modified anode foil and cathode foil respectively by riveting, and then wound to obtain a core package;

[0043] An electrolyte slurry was prepared by mixing 22 parts by mass of polythiophene, 33 parts by mass of poly(3,4-ethylenedioxythiophene), 30 parts by mass of sulfonated hollow mesoporous carbon spheres prepared in Example 1, 12 parts by mass of diphenylmethane-type bismaleimide, and 3 parts by mass of interfacial coupling agent γ-(2,3-epoxypropoxy)propyltrimethoxysilane. The electrolyte slurry was then filled into the core package by vacuum impregnation and cured at 160°C for 3 hours to obtain a solid electrolyte.

[0044] The core package forming the solid electrolyte is assembled with an aluminum shell and a stopper to obtain a semi-finished capacitor. The semi-finished capacitor is then charged and aged by applying voltages of 0.5 times, 1 times, and 1.2 times the rated voltage to perform segmented aging treatment, thereby obtaining a high-temperature resistant solid capacitor.

[0045] Example 4: The preparation method of a high-temperature resistant solid capacitor includes the following steps:

[0046] Cut aluminum foil was treated with 2% NaOH solution at room temperature for 10 minutes to remove the oxide film and oil on the surface. After oxidation, an aluminum oxide dielectric layer was formed on the surface of the aluminum foil. The foil was then immersed in anhydrous ethanol for 15 minutes and air-dried at room temperature for 30 minutes. It was then immersed in 1 wt% 3-aminopropyltrimethoxysilane ethanol solution for 10 minutes and finally dried at 150°C for 20 minutes to obtain the surface-modified anode foil and cathode foil.

[0047] The anode lead and cathode lead are connected to the surface-modified anode foil and cathode foil respectively by riveting, and then wound to obtain a core package;

[0048] An electrolyte slurry was prepared by mixing 15 parts by mass of polythiophene, 60 parts by mass of poly(3,4-ethylenedioxythiophene), 12 parts by mass of sulfonated hollow mesoporous carbon spheres prepared in Example 1, 8 parts by mass of diphenylmethane-type bismaleimide, and 5 parts by mass of the interfacial coupling agent vinyltriethoxysilane. The electrolyte slurry was then filled into the core package by vacuum impregnation and cured at 160°C for 3 hours to obtain a solid electrolyte.

[0049] The core package forming the solid electrolyte is assembled with an aluminum shell and a stopper to obtain a semi-finished capacitor. The semi-finished capacitor is then charged and aged by applying voltages of 0.5 times, 1 times, and 1.2 times the rated voltage to perform segmented aging treatment, thereby obtaining a high-temperature resistant solid capacitor.

[0050] Compared with Example 2, Comparative Example 1 only replaced the sulfonated hollow mesoporous carbon spheres prepared in Example 1 with hollow mesoporous carbon spheres prepared in Example 1 by the same mass. The remaining components and preparation methods were completely the same as those in Example 2.

[0051] Compared with Example 2, Comparative Example 2 only did not add the sulfonated hollow mesoporous carbon spheres prepared in Example 1, while the other components and preparation methods were completely the same as in Example 2.

[0052] Compared with Example 2, Comparative Example 3 does not perform surface modification treatment on the metal foil used to produce metal oxides. After forming an aluminum oxide dielectric layer on the surface of the aluminum foil, it is directly wound to form a core package. The remaining components and preparation methods are completely consistent with Example 2.

[0053] Compared with Example 2, Comparative Example 4 only did not add diphenylmethane-type bismaleimide in the preparation of the electrolyte slurry; the other components and preparation methods were completely the same as those in Example 2.

[0054] Performance testing

[0055] Ten high-temperature resistant solid capacitors were fabricated for Examples 1-4 and Comparative Examples 1-3, with a capacitor specification of 68μF / 35V and a size of Φ6.3*7mm. The capacitance (CAP), dissipation factor (DF), and equivalent series resistance (ESR) of these seven products were tested at a frequency of 120Hz, and the leakage current (LC) was tested at 35V. The test results are shown in Table 1. The capacitance, dissipation factor, ESR, leakage current, and capacitance decay were measured after 4000 hours of loading at 200℃. The test results are shown in Table 2.

[0056] Table 1. Performance test results of the products in Examples 2-4 and Comparative Examples 1-4.

[0057]

[0058] Table 2. Performance test results of products subjected to high-temperature load in Examples 2-4 and Comparative Examples 1-4.

[0059]

[0060] As shown in Table 1, the capacitors prepared using the method of this invention have large capacitance, low loss, low leakage current, and low equivalent series resistance. As shown in Table 2, the high-temperature resistant solid capacitors obtained using the preparation method of this invention still exhibit larger capacitance, lower loss, lower leakage current, and lower equivalent series resistance after being subjected to a load of 4000 hours at 200°C. Furthermore, compared to comparative examples 1-4, the ΔC / C (capacitance decay) is significantly reduced. This demonstrates that the process of this invention improves the high-temperature resistance of the product, enabling it to achieve a longer service life.

[0061] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0062] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should still fall within the patent coverage of this invention.

Claims

1. A high temperature resistant solid state capacitor characterized in that, At least comprising: an anode foil, a cathode foil and a solid-state electrolyte filled between the anode foil and the cathode foil; the anode foil and the cathode foil are subjected to surface modification treatment of amino silane coupling agent; the solid-state electrolyte is composed of the following raw materials in parts by mass: conductive polymer matrix 50-80 parts, sulfonated hollow mesoporous carbon spheres 10-30 parts, diphenylmethane type bismaleimide 5-15 parts, and interface coupling agent 2-8 parts; wherein the surface modification treatment of the anode foil at least includes the following steps: after forming a metal oxide layer on the metal foil, immerse in anhydrous ethanol for 10-20 min and dry, then immerse in 1-3 wt% amino silane coupling agent ethanol solution for 5-15 min, and dry at 140-150℃ for 20-30 min; the preparation method of the sulfonated hollow mesoporous carbon spheres includes the following steps: add tetrapropyl silane, ethanol and ammonia water into deionized water and mix, then add resorcinol and formaldehyde and stir to react, centrifuge, wash, dry and carbonize, then add sodium hydroxide solution to remove silicon dioxide, and obtain hollow mesoporous carbon spheres; add sodium nitrite into hydrochloric acid solution of p-aminobenzenesulfonothiole, after reaction, filter and wash to obtain 4-benzene diazonium sulfonate; mix the 4-benzene diazonium sulfonate, ethanol and deionized water, then add the hollow mesoporous carbon spheres and aqueous hypophosphorous acid solution, centrifuge, wash and dry to obtain sulfonated hollow mesoporous carbon spheres.

2. The high-temperature-resistant solid-state capacitor of claim 1, wherein, The surface modification treatment methods of the anode foil and the cathode foil are the same, and the metal foil is one of aluminum, tantalum, niobium or titanium.

3. The high-temperature-resistant solid-state capacitor of claim 1, wherein, The amino silane coupling agent is at least one of 3-aminopropyltrimethoxysilane and N-2-aminoethyl-3-aminopropyltrimethoxysilane.

4. The high-temperature solid state capacitor of claim 1, wherein, The pore size of the hollow mesoporous carbon spheres is 5-19 nm, the diameter of the sulfonated hollow mesoporous carbon spheres is 50-200 nm, and the content of sulfonic acid groups on the surface of the sulfonated hollow mesoporous carbon spheres is 0.5-2.0 mmol / g.

5. The high-temperature-resistant solid-state capacitor of claim 1, wherein, The conductive polymer matrix is a copolymer of polythiophene and poly(3,4-ethylenedioxythiophene), and the mass ratio of the polythiophene to the poly(3,4-ethylenedioxythiophene) is 2-5:8-5.

6. The high-temperature-resistant solid-state capacitor of claim 1, wherein, The interface coupling agent is at least one of silane coupling agents.

7. A method of making a high-temperature-resistant solid-state capacitor as claimed in any one of claims 1-6, characterized in that, At least comprising the following preparation steps: connect the anode lead and the cathode lead to the surface-modified anode foil and cathode foil respectively by riveting to obtain a core package; mix the conductive polymer matrix, sulfonated hollow mesoporous carbon spheres, diphenylmethane type bismaleimide and interface coupling agent to prepare electrolyte slurry, fill the electrolyte slurry into the core package by vacuum impregnation method, and solidify at 150-180℃ for 2-4 h to obtain a solid-state electrolyte; encapsulate and age the core package forming the solid-state electrolyte to obtain a high-temperature-resistant solid-state capacitor.

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