Anti-drying wide temperature range liquid aluminum electrolytic capacitor and preparation method thereof

Abstract

The application discloses a dry-out prevention wide-temperature-range liquid aluminum electrolytic capacitor and a preparation method thereof, and relates to the technical field of capacitors. The application comprises the following steps: firstly, cutting pretreated anode foils, cathode foils and electrolytic paper into predetermined sizes; then, riveting anode lead pins with the pretreated anode foils, riveting cathode lead pins with the cathode foils, and winding the pretreated anode foils, the cathode foils and the electrolytic paper into a core package after the riveting treatment; then, loading modified electrolyte into an aluminum shell, immersing the core package in the modified electrolyte, and then performing sealing, assembling, casing, aging treatment to obtain the dry-out prevention wide-temperature-range liquid aluminum electrolytic capacitor. The pretreatment of the anode foils effectively improves the dry-out prevention performance and stability of the capacitor; the components such as the synergist introduced in the modified electrolyte further improve the cycle life, the stability at low temperature and high temperature. Therefore, the capacitor has a more extensive application prospect.

Description

Technical Field

[0001] This invention relates to the field of capacitor technology, specifically to a wide-temperature-range liquid aluminum electrolytic capacitor with anti-drying properties and its preparation method. Background Technology

[0002] Liquid capacitors typically consist of electrodes, an electrolyte, and an insulating medium. Their working principle is based on the fundamental characteristics of capacitance. When a voltage is applied to the two electrodes, positive and negative charges accumulate on the electrodes respectively. Ions in the electrolyte can then move under the influence of the electric field, assisting in the storage and release of charge, thereby achieving the function of storing electrical energy. Common liquid capacitors are aluminum electrolytic capacitors and tantalum electrolytic capacitors. Aluminum electrolytic capacitors use aluminum foil as electrodes and paper or other porous materials impregnated with electrolyte as the insulating medium. Due to their lower cost, higher rated voltage, wider capacitance range, mature manufacturing process, and widely available materials compared to tantalum electrolytic capacitors, aluminum electrolytic capacitors have a wider range of applications in audio circuits, communication equipment, industrial control, automotive electronics, and consumer electronics.

[0003] The electrolyte in aluminum electrolytic capacitors is formulated with various chemical reagents according to the required conductivity and flash voltage. It is the true negative electrode of the capacitor, and the main solvents are generally ethylene glycol and deionized water. Its conductivity directly affects the capacitor's losses and equivalent series resistance; the flash voltage determines the highest voltage the electrolyte can withstand; and the pH value affects the corrosiveness to the leads. Therefore, the electrolyte has a crucial impact on the electrochemical performance of aluminum electrolytic capacitors. However, existing electrolytes still suffer from a significant decrease in electrochemical performance at high and low temperatures.

[0004] To address this technical problem, patent document CN104217860B proposes an ultra-high temperature, long-life, low-voltage liquid aluminum electrolytic capacitor. This invention includes an aluminum shell containing electrolytic paper. The electrolytic paper wraps around an anode foil and a cathode foil, both connected to leads. The electrolytic paper is rolled into a core package using adhesive tape, and a rubber stopper is inserted at the top. The aluminum shell contains electrolyte, and a sleeve covers the outside of the shell. The electrolyte consists of γ-butyrolactone, ethylene glycol silica, and o-nitroanisole. The preparation method involves adding γ-butyrolactone, ethylene glycol silica, and o-nitroanisole together to a reaction vessel, heating to 140°C and maintaining the temperature for 24 hours to allow for complete reaction. After preparation, the mixture is cooled to 30°C. This invention can operate for 8000 hours at an ultra-high temperature of 135°C. However, these existing optimization methods mostly focus on improving the high-temperature resistance of capacitors, without considering the impact of low temperatures on capacitor performance. Therefore, the expansion of the operating temperature range of capacitors is limited. Summary of the Invention

[0005] The purpose of this invention is to provide a wide-temperature-range liquid aluminum electrolytic capacitor that prevents drying and its preparation method, thereby solving the following technical problems:

[0006] Existing liquid aluminum electrolytic capacitors still suffer from problems such as the need to broaden their operating temperature range and the short lifespan caused by the drying out of the electrolyte.

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

[0008] A method for preparing a wide-temperature-range liquid aluminum electrolytic capacitor that prevents drying out includes the following steps:

[0009] Step S1: Cut the pretreated anode foil, cathode foil, and electrolytic paper into predetermined sizes;

[0010] Step S2: Rivet the anode guide pin to the pretreated anode foil, rivet the cathode guide pin to the cathode foil, and wind the riveted pretreated anode foil, cathode foil, and electrolytic paper into a core package;

[0011] Step S3: Fill the aluminum shell with modified electrolyte, then immerse the core in the modified electrolyte, and then seal, assemble, sleeve, and age to obtain a wide-temperature-range liquid aluminum electrolytic capacitor that is resistant to drying.

[0012] Preferably, the method for preparing the pretreated anode foil is as follows:

[0013] Step A1: Immerse the aluminum foil in a sodium hydroxide solution at 50-60℃ for 2-5 minutes, rinse it with deionized water 3-5 times, then immerse it in a nitric acid solution for 1-2 minutes. After rinsing and drying, use it as the anode and a lead plate as the cathode. Place it in a sulfuric acid electrolyte for anodic oxidation. After rinsing and drying, you will obtain aluminum oxide foil.

[0014] Step A2: Under a nitrogen atmosphere, polytetrahydrofuran diol, isophorone diisocyanate and hydroxyethyl methacrylate are mixed and heated to 60-80℃, then dibutyltin dilaurate is added and reacted for 3-5 hours to obtain a polyurethane acrylate composite.

[0015] Step A3: Add tetrabutyl titanate and tetraethyl orthosilicate to anhydrous ethanol, stir evenly, then add hydrochloric acid solution, stir for 2-5 hours, then add polyurethane acrylate composite and dimethyl benzoate, stir evenly, then immerse alumina foil, and then cure under ultraviolet light to obtain pretreated anode foil.

[0016] Preferably, the sodium hydroxide solution in step A1 has a mass fraction of 5%-10%;

[0017] The mass fraction of the nitric acid solution mentioned in step A1 is 15%-20%.

[0018] Preferably, the mass ratio of polytetrahydrofuran diol, isophorone diisocyanate, hydroxyethyl methacrylate, and dibutyltin dilaurate in step A2 is 30-60:44-66:13-26:0.1-0.45.

[0019] Preferably, the concentration of the hydrochloric acid solution in step A3 is 0.5 mol / L;

[0020] The ratio of tetrabutyl titanate, tetraethyl orthosilicate, anhydrous ethanol, hydrochloric acid solution, polyurethane acrylate complex, and dimethyl benzoate used in step A3 is 3.4-10.2g: 2-6g: 10mL: 2mL: 70-90g: 0.05-0.15g.

[0021] Preferably, the outer layer of the core package is wrapped with 1-2 layers of electrolytic paper and fixed with tape.

[0022] Preferably, the modified electrolyte is prepared by the following method:

[0023] Step B1: Add 50-60 mL of propylene carbonate to 120-150 mL of ethylene glycol, stir for 3-5 h, then add 20-30 g of ammonium adipate, heat to 50-55 °C and continue stirring until completely dissolved to obtain a composite solvent;

[0024] Step B2: While stirring, add 4.5-5g of synergist, 0.6-1g of 2,6-di-tert-butyl-p-cresol, 1.2-1.5g of benzotriazole, 0.2-0.5g of nitrobenzene, and 2-5g of 2,2,2-trifluoroethyl acrylate sequentially to 150-200mL of composite solvent. Then continue stirring at 60-65℃ for 1-2.5h, and filter to obtain the modified electrolyte.

[0025] Preferably, the pore size of the filter membrane used in step B2 is 0.22-0.25 μm.

[0026] Preferably, the synergist is prepared by the following method:

[0027] Step C1: Add 10-15g of nano-silica to 100-150mL of anhydrous ethanol, ultrasonically disperse for 20-30min, then add 0.1-1g of silane coupling agent-KH550 and stir at 60-80℃ for 3-4h. After centrifugation, washing and drying, pretreated silica is obtained.

[0028] Step C2: At 0-5℃, dissolve 9.3-11.2g of aniline in 100-150mL of 1mol / L hydrochloric acid solution, then slowly add 100mL of ammonium persulfate solution, and continue stirring the reaction for 6-8h to obtain polyaniline composite solution;

[0029] Step C3: Add pretreated silica to 100-150 mL of polyaniline composite solution, ultrasonically disperse for 30-45 min, then stir and react at 60-70℃ for 2-3 h, then centrifuge, wash, dopant with ammonia, and finally vacuum dry at 55-60℃ to obtain the synergist.

[0030] Preferably, the concentration of the ammonium persulfate solution is 1 mol / L;

[0031] The ultrasonic power during ultrasonic dispersion is 80-90W; the ultrasonic frequency during ultrasonic dispersion is 30-45kHz.

[0032] As a further aspect of the present invention.

[0033] The beneficial effects of this invention are:

[0034] This invention provides a dry-proof, wide-temperature-range liquid aluminum electrolytic capacitor and its preparation method. The invention effectively improves the capacitor's service life and expands its operating temperature range through the following methods.

[0035] (1) This invention forms an alumina layer with suitable pore size and porosity on the surface of a substrate aluminum foil through anodizing. Its function is to enhance the bonding force between the substrate aluminum foil and the subsequent surface functional layer, and at the same time play a certain role in regulating ion transport in the electrolyte. Then, a sol-gel method is used to combine a mixed sol of nano-titanium dioxide and nano-silica with polyurethane acrylate containing fluorocarbon segments, and a thin film layer with good flexibility, corrosion resistance and thermal stability is formed on the alumina foil. Among them, the introduction of fluorocarbon segments improves the hydrophobicity of the coating and reduces the adhesion and drying risk of electrolyte on the electrode foil surface; nano-titanium dioxide and nano-silica enhance the mechanical strength and chemical stability of the coating, and at the same time have a certain shielding effect against ultraviolet rays, preventing the electrode foil from aging faster due to ultraviolet radiation at high temperature, and also promotes the migration of ions in the electrolyte to a certain extent, improving the performance of the capacitor at low temperature.

[0036] (2) Ethylene glycol has limited low-temperature performance. At low temperatures, its viscosity increases significantly, and its fluidity deteriorates, affecting the performance of electrolytic capacitors. Propylene carbonate, on the other hand, possesses good chemical stability, thermal stability, a relatively low freezing point, and good low-temperature fluidity. When added to ethylene glycol in a specific ratio, it can reduce the evaporation and decomposition of the electrolyte at high temperatures, lower the overall freezing point of the mixed solvent, and improve the fluidity of the electrolyte at low temperatures. This allows the electrolytic capacitor to maintain good performance over a wide temperature range, especially at low temperatures, reducing problems such as capacitance decrease and increased equivalent series resistance caused by low temperatures. Furthermore, propylene carbonate has good solubility for some electrolyte salts. When mixed with ethylene glycol, it can expand the solubility range and concentration of electrolytes in the electrolyte, allowing for better dissolution and dispersion of the electrolyte, forming a uniform and stable solution system. This improves the ion transport efficiency in the electrolyte, ensuring the performance stability and consistency of the electrolytic capacitor.

[0037] (3) The addition of a specific ratio of 2,2,2-trifluoroethyl acrylate can introduce a strong electron-withdrawing trifluoromethyl group, thereby reducing the viscosity of the electrolyte and increasing the ion mobility; at the same time, the polymer network formed after polymerization can stabilize the electrolyte structure and inhibit the decomposition of the electrolyte at low temperature.

[0038] (4) Nano-silica-polyaniline composite particles possess excellent conductivity and adsorption properties. In the electrolyte, nano-silica can serve as a supporting framework, improving the stability of the electrolyte and preventing its delamination and drying. Polyaniline can enhance the conductivity of the electrolyte, especially under high-temperature conditions, effectively maintaining the electrical performance of the capacitor. Simultaneously, the presence of the composite particles can improve the interfacial contact between the electrolyte and the electrode, reduce the equivalent series resistance, and improve the charging and discharging efficiency of the capacitor. Therefore, the addition of synergists can effectively improve the stability of the electrolyte and the stability and electrochemical performance of the capacitor.

[0039] Therefore, the anti-drying wide-temperature-range liquid aluminum electrolytic capacitor prepared by this invention has superior anti-drying ability, low-temperature stability, high-temperature stability, and storage life. Detailed Implementation

[0040] 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.

[0041] Example 1: The preparation method of a wide-temperature-range liquid aluminum electrolytic capacitor with anti-drying properties is as follows:

[0042] S1: Aluminum foil with a thickness of 10 μm and a purity of 99.99% is immersed in a 5% sodium hydroxide solution at 50°C for 2 minutes, rinsed three times with deionized water, and then immersed in a 15% nitric acid solution for 1 minute. After rinsing and drying, it is used as the anode, and a lead plate is used as the cathode. The foil is placed in a sulfuric acid electrolyte and anodized at 20°C with an oxidation voltage of 10V and an oxidation time of 10 minutes. After rinsing three times with deionized water and drying at 80°C, aluminum oxide foil is obtained. The sulfuric acid electrolyte is a 15% sulfuric acid solution.

[0043] S2: Under a nitrogen atmosphere, 30g of polytetrahydrofurandiol, 44g of isophorone diisocyanate and 13g of hydroxyethyl methacrylate were mixed and heated to 60°C. Then, 0.1g of dibutyltin dilaurate was added and reacted for 3h to obtain a polyurethane acrylate composite.

[0044] S3: Add 3.4g tetrabutyl titanate and 2g tetraethyl orthosilicate to 10mL anhydrous ethanol, stir well, then add 2mL of 0.5mol / L hydrochloric acid solution, stir for 2h, then add 70g polyurethane acrylate composite and 0.05g benzoin dimethyl ether, stir well, then immerse alumina foil in it, and then cure it under ultraviolet irradiation to obtain pretreated anode foil;

[0045] S4: Add 10g of nano silica to 100mL of anhydrous ethanol and ultrasonically disperse it for 20min at an ultrasonic power of 80W and ultrasonic frequency. Then add 0.1g of silane coupling agent-KH550 and stir at 60℃ for 3h. After centrifugation, washing and drying, pretreated silica is obtained.

[0046] S5: At 0℃, 9.3g of aniline was dissolved in 100mL of 1mol / L hydrochloric acid solution, and then 100mL of 1mol / L ammonium persulfate solution was slowly added dropwise. After stirring and reacting for 6h, a polyaniline composite solution was obtained.

[0047] S6: Add pretreated silica to 100 mL of polyaniline composite solution, and ultrasonically disperse it for 30 min at an ultrasonic power of 80 W and an ultrasonic frequency. Then stir and react at 60 °C for 2 h, then centrifuge, wash, dopant with ammonia, and finally vacuum dry at 55 °C to obtain the synergist.

[0048] S7: Add 50 mL of propylene carbonate to 120 mL of ethylene glycol, stir for 3 h, then add 20 g of ammonium adipate, heat to 50 °C and continue stirring until completely dissolved to obtain a composite solvent;

[0049] S8: While stirring, add 4.5g of synergist, 0.6g of 2,6-di-tert-butyl-p-cresol, 1.2g of benzotriazole, 0.2g of nitrobenzene, and 2g of 2,2,2-trifluoroethyl acrylate to 150mL of composite solvent in sequence. Then continue stirring at 60℃ for 1h. After filtering with a filter membrane with a pore size of 0.22μm, the modified electrolyte is obtained.

[0050] S9: Cut the pretreated anode foil, cathode foil and electrolytic paper into predetermined sizes;

[0051] S10: Rivet the anode guide pin to the pretreated anode foil, rivet the cathode guide pin to the cathode foil, and wind the riveted pretreated anode foil, cathode foil, and electrolytic paper into a core package; wherein, the core package is wrapped with one layer of electrolytic paper and fixed with tape;

[0052] S11: A modified electrolyte is filled into an aluminum shell, and then the core is immersed in the modified electrolyte. After sealing, assembly, sheathing, and aging treatment, a wide-temperature-range liquid aluminum electrolytic capacitor with anti-drying properties is obtained.

[0053] Example 2: The preparation method of a wide-temperature-range liquid aluminum electrolytic capacitor with anti-drying properties is as follows:

[0054] S1: Aluminum foil with a thickness of 20 μm and a purity of 99.99% is immersed in an 8% sodium hydroxide solution at 55°C for 4 min, rinsed 4 times with deionized water, and then immersed in an 18% nitric acid solution for 1.5 min. After rinsing and drying, it is used as the anode, and a lead plate is used as the cathode. The foil is placed in a sulfuric acid electrolyte and anodized at 25°C with an oxidation voltage of 20V and an oxidation time of 20 min. After rinsing 3 times with deionized water and drying at 80°C, aluminum oxide foil is obtained. The sulfuric acid electrolyte is a 20% sulfuric acid solution.

[0055] S2: Under a nitrogen atmosphere, 45g of polytetrahydrofuran diol, 55g of isophorone diisocyanate and 20g of hydroxyethyl methacrylate were mixed and heated to 70°C. Then, 0.3g of dibutyltin dilaurate was added and reacted for 4h to obtain a polyurethane acrylate composite.

[0056] S3: Add 7g tetrabutyl titanate and 4g tetraethyl orthosilicate to 10mL anhydrous ethanol, stir well, then add 2mL of 0.5mol / L hydrochloric acid solution, stir for 3h, then add 80g polyurethane acrylate composite and 0.1g benzoin dimethyl ether, stir well, then immerse alumina foil in it, and then cure it under ultraviolet light to obtain pretreated anode foil;

[0057] S4: Add 13g of nano-silica to 130mL of anhydrous ethanol and ultrasonically disperse it for 25min at an ultrasonic power of 85W and ultrasonic frequency. Then add 0.5g of silane coupling agent-KH550 and stir at 70℃ for 3.5h. After centrifugation, washing and drying, pretreated silica is obtained.

[0058] S5: At 3℃, 10.3g of aniline was dissolved in 120mL of 1mol / L hydrochloric acid solution, and then 100mL of 1mol / L ammonium persulfate solution was slowly added dropwise. After stirring and reacting for 7h, a polyaniline composite solution was obtained.

[0059] S6: Add pretreated silica to 130 mL of polyaniline composite solution, and ultrasonically disperse it for 40 min at an ultrasonic power of 85 W and an ultrasonic frequency. Then stir and react at 65 °C for 2.5 h. After centrifugation, washing, doping with ammonia, and finally vacuum drying at 58 °C, the synergist is obtained.

[0060] S7: Add 55 mL of propylene carbonate to 135 mL of ethylene glycol, stir for 4 h, then add 25 g of ammonium adipate, heat to 53 °C and continue stirring until completely dissolved to obtain a composite solvent;

[0061] S8: While stirring, add 4.8g of synergist, 0.8g of 2,6-di-tert-butyl-p-cresol, 1.4g of benzotriazole, 0.4g of nitrobenzene, and 4g of 2,2,2-trifluoroethyl acrylate to 180mL of composite solvent in sequence. Then continue stirring at 63℃ for 1.5h. After filtering with a filter membrane with a pore size of 0.24μm, the modified electrolyte is obtained.

[0062] S9: Cut the pretreated anode foil, cathode foil and electrolytic paper into predetermined sizes;

[0063] S10: Rivet the anode guide pin to the pretreated anode foil, rivet the cathode guide pin to the cathode foil, and wind the riveted pretreated anode foil, cathode foil, and electrolytic paper into a core package; wherein, the core package is wrapped with two layers of electrolytic paper and fixed with tape;

[0064] S11: A modified electrolyte is filled into an aluminum shell, and then the core is immersed in the modified electrolyte. After sealing, assembly, sheathing, and aging treatment, a wide-temperature-range liquid aluminum electrolytic capacitor with anti-drying properties is obtained.

[0065] Example 3: The preparation method of a wide-temperature-range liquid aluminum electrolytic capacitor with anti-drying properties is as follows:

[0066] S1: Aluminum foil with a thickness of 20 μm and a purity of 99.99% is immersed in a 10% sodium hydroxide solution at 60°C for 5 minutes, rinsed 5 times with deionized water, and then immersed in a 20% nitric acid solution for 2 minutes. After rinsing and drying, it is used as the anode, and a lead plate is used as the cathode. The foil is placed in a sulfuric acid electrolyte and anodized at 30°C for 30 minutes with an oxidation voltage of 30V. After rinsing 3 times with deionized water and drying at 80°C, aluminum oxide foil is obtained. The sulfuric acid electrolyte is a 25% sulfuric acid solution.

[0067] S2: Under a nitrogen atmosphere, 60g of polytetrahydrofurandiol, 66g of isophorone diisocyanate and 26g of hydroxyethyl methacrylate were mixed and heated to 80°C. Then, 0.45g of dibutyltin dilaurate was added and the mixture was reacted for 5h to obtain a polyurethane acrylate composite.

[0068] S3: Add 10.2g tetrabutyl titanate and 6g tetraethyl orthosilicate to 10mL anhydrous ethanol, stir well, then add 2mL of 0.5mol / L hydrochloric acid solution, stir for 5h, then add 90g polyurethane acrylate composite and 0.15g benzoin dimethyl ether, stir well, then immerse alumina foil in it, and then cure it under ultraviolet irradiation to obtain pretreated anode foil;

[0069] S4: Add 15g of nano silica to 150mL of anhydrous ethanol and ultrasonically disperse it for 30min at an ultrasonic power of 90W and ultrasonic frequency. Then add 1g of silane coupling agent-KH550 and stir at 80℃ for 4h. After centrifugation, washing and drying, pretreated silica is obtained.

[0070] S5: At 5℃, 11.2g of aniline was dissolved in 150mL of 1mol / L hydrochloric acid solution, and then 100mL of 1mol / L ammonium persulfate solution was slowly added dropwise. After stirring and reacting for 8h, a polyaniline composite solution was obtained.

[0071] S6: Add pretreated silica to 150 mL of polyaniline composite solution, and ultrasonically disperse it for 45 min at an ultrasonic power of 90 W and an ultrasonic frequency. Then stir and react at 70 °C for 3 h, then centrifuge, wash, dopant with ammonia, and finally vacuum dry at 60 °C to obtain the synergist.

[0072] S7: Add 60 mL of propylene carbonate to 150 mL of ethylene glycol, stir for 5 h, then add 30 g of ammonium adipate, heat to 55 °C and continue stirring until completely dissolved to obtain a composite solvent;

[0073] S8: While stirring, add 5g of synergist, 1g of 2,6-di-tert-butyl-p-cresol, 1.5g of benzotriazole, 0.5g of nitrobenzene, and 5g of 2,2,2-trifluoroethyl acrylate to 200mL of composite solvent in sequence. Then continue stirring at 65℃ for 2.5h. After filtering with a filter membrane with a pore size of 0.25μm, the modified electrolyte is obtained.

[0074] S9: Cut the pretreated anode foil, cathode foil and electrolytic paper into predetermined sizes;

[0075] S10: Rivet the anode guide pin to the pretreated anode foil, rivet the cathode guide pin to the cathode foil, and wind the riveted pretreated anode foil, cathode foil, and electrolytic paper into a core package; wherein, the core package is wrapped with two layers of electrolytic paper and fixed with tape;

[0076] S11: A modified electrolyte is filled into an aluminum shell, and then the core is immersed in the modified electrolyte. After sealing, assembly, sheathing, and aging treatment, a wide-temperature-range liquid aluminum electrolytic capacitor with anti-drying properties is obtained.

[0077] Comparative Example 1:

[0078] Compared with Example 1, this comparative example only replaces the "pretreated manganese dioxide" added during the core pack preparation process with the "alumina foil" prepared in S1. All other steps and parameters are the same, and will not be repeated in this comparative example. Finally, a wide-temperature-range liquid aluminum electrolytic capacitor with anti-drying properties is obtained.

[0079] Comparative Example 2:

[0080] Compared with Example 1, this comparative example only replaces the "pretreated manganese dioxide" added during the core pack preparation process with the "aluminum foil with a thickness of 20 μm and a purity of 99.99%" used in S1. All other steps and parameters are the same, and will not be repeated in this comparative example. Finally, a wide-temperature-range liquid aluminum electrolytic capacitor with anti-drying properties is obtained.

[0081] Comparative Example 3:

[0082] Compared with Example 1, this comparative example only replaces "50 mL propylene carbonate" added during the preparation of the composite solvent with "50 mL ethylene glycol". All other steps and parameters are the same, and will not be repeated here. The final result is a wide-temperature-range liquid aluminum electrolytic capacitor that is resistant to drying.

[0083] Comparative Example 4:

[0084] Compared with Example 1, this comparative example only replaces the "4.5g synergist, 0.6g 2,6-di-tert-butyl-p-cresol, 1.2g benzotriazole, 0.2g nitrobenzene, 2g 2,2,2-trifluoroethyl acrylate" added during the preparation of the modified electrolyte with "4.5g synergist, 0.6g 2,6-di-tert-butyl-p-cresol, 1.2g benzotriazole, 2g nitrobenzene, 0.2g 2,2,2-trifluoroethyl acrylate". All other steps and parameters are the same, and will not be repeated in this comparative example. Finally, a wide-temperature-range liquid aluminum electrolytic capacitor with anti-drying properties is obtained.

[0085] Comparative Example 5:

[0086] This comparative example differs from Example 1 only in that no synergist was added during the preparation of the modified electrolyte; all other steps and parameters are the same. This comparative example will not be repeated here. The final product is a wide-temperature-range liquid aluminum electrolytic capacitor that is resistant to drying out.

[0087] Performance testing:

[0088] Tests on resistance to drying out:

[0089] The rate of change in electrolyte content in each capacitor was measured after storage at 125℃ for 1000 hours. The anti-drying capability (%) of the anti-drying wide-temperature-range liquid aluminum electrolytic capacitors prepared in Examples 1-3 and Comparative Examples 1-5 was measured according to this method, and the results are shown in Table 1.

[0090] Measurement of capacitance loss:

[0091] The capacitance values ​​of the capacitors were measured and recorded using the same method at 20°C, -60°C (group a), 125°C for 1000 hours of storage (group b), and 105°C for 1000 hours of high-temperature load life test with rated voltage applied (group c). The capacitance loss (relative to 20°C) after 1000 hours of storage at -60°C and 105°C, and after 1000 hours of high-temperature load life test with rated voltage applied at 105°C, was then calculated. The capacitance loss (%) of the anti-drying wide-temperature-range liquid aluminum electrolytic capacitors prepared in Examples 1-3 and Comparative Examples 1-5 was measured using this method, and the results are shown in Table 1.

[0092] Determination of the rate of change of equivalent series resistance (ESR):

[0093] The equivalent series resistance of the capacitors was measured and recorded using the same method after storage at 20°C, -60°C (group a), 125°C for 1000 hours (group b), and 105°C for 1000 hours of high-temperature load life test with rated voltage applied (group c). The change rate of equivalent series resistance (relative to 20°C) after storage at -60°C and 105°C for 1000 hours, and after the 1000 hours of high-temperature load life test with rated voltage applied at 105°C, was then calculated. The change rate (%) of equivalent series resistance of the anti-drying wide-temperature-range liquid aluminum electrolytic capacitors prepared in Examples 1-3 and Comparative Examples 1-5 was measured using this method, and the results are shown in Table 1.

[0094] Determination of the rate of change of the loss tangent (D):

[0095] The loss tangent of the capacitors was measured and recorded using the same method after 1000 hours of storage at 20°C, -60°C (Group a), 125°C (Group b), and 1000 hours of high-temperature load life test with rated voltage applied at 105°C (Group c). The rate of change of the loss tangent (relative to 20°C) after 1000 hours of storage at -60°C and 105°C, and then after 1000 hours of high-temperature load life test with rated voltage applied at 105°C, was then calculated. The rate of change (%) of the loss tangent of the anti-drying wide-temperature-range liquid aluminum electrolytic capacitors prepared in Examples 1-3 and Comparative Examples 1-5 was also measured using this method, and the results are shown in Table 1.

[0096] Table 1: Performance test results of Examples 1-3 and Comparative Examples 1-5

[0097]

[0098] Data Analysis:

[0099] As can be seen from Table 1, the anti-drying wide-temperature-range liquid aluminum electrolytic capacitor prepared by the present invention has superior anti-drying ability, low-temperature stability, high-temperature stability, and storage life.

[0100] This may be due to:

[0101] (1) The high-purity aluminum foil selected in this invention has good conductivity and mechanical properties, providing basic conductive support for the electrode foil. Then, an alumina layer with suitable pore size and porosity is formed on the surface of the substrate aluminum foil through anodizing process. Its function is to enhance the bonding force between the substrate aluminum foil and the subsequent surface functional layer, and at the same time play a certain role in regulating ion transport in the electrolyte. Then, the nano-titanium dioxide and nano-silica mixed sol is compounded with polyurethane acrylate containing fluorocarbon segments by sol-gel method, and a thin film layer with good flexibility, corrosion resistance and thermal stability is formed on the alumina foil. Among them, the introduction of fluorocarbon segments improves the hydrophobicity of the coating and reduces the adhesion and drying risk of electrolyte on the surface of the electrode foil; nano-titanium dioxide and nano-silica enhance the mechanical strength and chemical stability of the coating, and at the same time have a certain shielding effect against ultraviolet rays, preventing the electrode foil from aging faster due to ultraviolet radiation in high temperature environment, and also promotes the migration of ions in the electrolyte to a certain extent, improving the performance of the capacitor in low temperature environment.

[0102] (2) Ethylene glycol has limited low-temperature performance. At low temperatures, its viscosity increases significantly, and its fluidity deteriorates, affecting the performance of electrolytic capacitors. Propylene carbonate, on the other hand, possesses good chemical stability, thermal stability, a relatively low freezing point, and good low-temperature fluidity. When added to ethylene glycol in a specific ratio, it can reduce the evaporation and decomposition of the electrolyte at high temperatures, lower the overall freezing point of the mixed solvent, and improve the fluidity of the electrolyte at low temperatures. This allows the electrolytic capacitor to maintain good performance over a wide temperature range, especially at low temperatures, reducing problems such as capacitance decrease and increased equivalent series resistance caused by low temperatures. Furthermore, propylene carbonate has good solubility for some electrolyte salts. When mixed with ethylene glycol, it can expand the solubility range and concentration of electrolytes in the electrolyte, allowing for better dissolution and dispersion of the electrolyte, forming a uniform and stable solution system. This improves the ion transport efficiency in the electrolyte, ensuring the performance stability and consistency of the electrolytic capacitor.

[0103] (3) The addition of a specific ratio of 2,2,2-trifluoroethyl acrylate can introduce a strong electron-withdrawing trifluoromethyl group, thereby reducing the viscosity of the electrolyte and increasing the ion mobility; at the same time, the polymer network formed after polymerization can stabilize the electrolyte structure and inhibit the decomposition of the electrolyte at low temperature.

[0104] (4) Nano-silica-polyaniline composite particles possess excellent conductivity and adsorption properties. In the electrolyte, nano-silica can serve as a supporting framework, improving the stability of the electrolyte and preventing its delamination and drying. Polyaniline can enhance the conductivity of the electrolyte, especially under high-temperature conditions, effectively maintaining the electrical performance of the capacitor. Simultaneously, the presence of the composite particles can improve the interfacial contact between the electrolyte and the electrode, reduce the equivalent series resistance, and improve the charging and discharging efficiency of the capacitor. Therefore, the addition of synergists can effectively improve the stability of the electrolyte and the stability and electrochemical performance of the capacitor.

[0105] 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 method for preparing a wide-temperature-range liquid aluminum electrolytic capacitor with anti-drying properties, characterized in that, Includes the following steps: Step S1: Cut the pretreated anode foil, cathode foil, and electrolytic paper into predetermined sizes; Step S2: Rivet the anode guide pin to the pretreated anode foil, rivet the cathode guide pin to the cathode foil, and wind the riveted pretreated anode foil, cathode foil, and electrolytic paper into a core package; Step S3: Fill the aluminum shell with modified electrolyte, then immerse the core in the modified electrolyte, and then seal, assemble, sleeve, and age to obtain a dry-proof wide-temperature-range liquid aluminum electrolytic capacitor. The method for preparing the pretreated anode foil is as follows: Step A1: Immerse the aluminum foil in a sodium hydroxide solution at 50-60℃ for 2-5 minutes, rinse it with deionized water 3-5 times, then immerse it in a nitric acid solution for 1-2 minutes. After rinsing and drying, use it as the anode and a lead plate as the cathode. Place it in a sulfuric acid electrolyte for anodic oxidation. After rinsing and drying, you will obtain aluminum oxide foil. Step A2: Under a nitrogen atmosphere, polytetrahydrofuran diol, isophorone diisocyanate and hydroxyethyl methacrylate are mixed and heated to 60-80℃, then dibutyltin dilaurate is added and reacted for 3-5 hours to obtain a polyurethane acrylate composite. Step A3: Add tetrabutyl titanate and tetraethyl orthosilicate to anhydrous ethanol, stir evenly, then add hydrochloric acid solution, stir for 2-5 hours, then add polyurethane acrylate composite and dimethyl benzoate, stir evenly, then immerse alumina foil, and then cure under ultraviolet light to obtain pretreated anode foil. The modified electrolyte is prepared as follows: Step B1: Add 50-60 mL of propylene carbonate to 120-150 mL of ethylene glycol, stir for 3-5 h, then add 20-30 g of ammonium adipate, heat to 50-55 °C and continue stirring until completely dissolved to obtain a composite solvent; Step B2: While stirring, add 4.5-5g of synergist, 0.6-1g of 2,6-di-tert-butyl-p-cresol, 1.2-1.5g of benzotriazole, 0.2-0.5g of nitrobenzene, and 2-5g of 2,2,2-trifluoroethyl acrylate sequentially to 150-200mL of composite solvent. Then continue stirring at 60-65℃ for 1-2.5h. After filtration, the modified electrolyte is obtained. The preparation method of the synergist is as follows: Step C1: Add 10-15g of nano-silica to 100-150mL of anhydrous ethanol, ultrasonically disperse for 20-30min, then add 0.1-1g of silane coupling agent-KH550 and stir at 60-80℃ for 3-4h. After centrifugation, washing and drying, pretreated silica is obtained. Step C2: At 0-5℃, dissolve 9.3-11.2g of aniline in 100-150mL of 1mol / L hydrochloric acid solution, then slowly add 100mL of ammonium persulfate solution, and continue stirring the reaction for 6-8h to obtain polyaniline composite solution; Step C3: Add pretreated silica to 100-150 mL of polyaniline composite solution, ultrasonically disperse for 30-45 min, then stir and react at 60-70℃ for 2-3 h, then centrifuge, wash, dopant with ammonia, and finally vacuum dry at 55-60℃ to obtain the synergist.

2. The method for preparing a wide-temperature-range liquid aluminum electrolytic capacitor with anti-drying properties according to claim 1, characterized in that, The sodium hydroxide solution mentioned in step A1 has a mass fraction of 5%-10%; The nitric acid solution mentioned in step A1 has a mass fraction of 15%-20%.

3. The method for preparing a wide-temperature-range liquid aluminum electrolytic capacitor with anti-drying properties according to claim 1, characterized in that, The mass ratio of polytetrahydrofuran diol, isophorone diisocyanate, hydroxyethyl methacrylate, and dibutyltin dilaurate in step A2 is 30-60:44-66:13-26:0.1-0.

45.

4. The method for preparing a wide-temperature-range liquid aluminum electrolytic capacitor with anti-drying properties according to claim 1, characterized in that, The concentration of the hydrochloric acid solution mentioned in step A3 is 0.5 mol / L; The ratio of tetrabutyl titanate, tetraethyl orthosilicate, anhydrous ethanol, hydrochloric acid solution, polyurethane acrylate complex, and dimethyl benzoate used in step A3 is 3.4-10.2g: 2-6g: 10mL: 2mL: 70-90g: 0.05-0.15g.

5. The method for preparing a wide-temperature-range liquid aluminum electrolytic capacitor with anti-drying properties according to claim 1, characterized in that, The outer layer of the core package is wrapped with 1-2 layers of electrolytic paper and fixed with tape.

6. The method for preparing a wide-temperature-range liquid aluminum electrolytic capacitor with anti-drying properties according to claim 1, characterized in that, The filter membrane used in step B2 has a pore size of 0.22-0.25 μm.

7. The method for preparing a wide-temperature-range liquid aluminum electrolytic capacitor with anti-drying properties according to claim 1, characterized in that, The concentration of the ammonium persulfate solution is 1 mol / L; The ultrasonic power during ultrasonic dispersion is 80-90W; the ultrasonic frequency during ultrasonic dispersion is 30-45kHz.

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