Electrolyte for electrolytic capacitor with long service life and preparation method

Abstract

The invention discloses a long-life electrolyte for an electrolytic capacitor and a preparation method. The electrolyte comprises the following components in percentage by mass: 35-45% of a first solvent, 15-25% of a second solvent, 5-10% of a third solvent, 5-15% of a solute and 3-8% of an additive, the first solvent is ethylene glycol; the second solvent is diethylene glycol; the third solvent is one or more of 1, 2-pentanediol, N, N-dimethylformamide, glycerol, isopropanol, benzyl alcohol, ethylene glycol monobutyl ether, y-butyrolactone and polyethylene glycol; according to the invention, the electrolytic paper and the electrolyte form the cathode of the electrolytic capacitor together, and the porosity of the electrolytic paper is utilized to adsorb and store enough working electrolyte so as to play a role of a cathode (electrolyte) carrier. Therefore, the electrolyte can fully cover the surface of the aluminum foil, the purpose of maximizing the capacity of a capacitor product is achieved, the voltage resistance of the capacitor can be ensured, and the absorptivity of the electrolyte can also be ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of electrolytes, in particular to an electrolyte for long-life electrolytic capacitors and a preparation method thereof. Background Art

[0002] In recent years, with the improvement of the quality of life, people have higher and higher requirements for the quality and life of electrical appliances and equipment, which is closely related to the performance stability of each accessory, so the requirements for the safety, stability and long-term stable operation of capacitors are also indispensable. Some performance decay will occur in the process of use of capacitors, and for users, working conditions are the main factors affecting the life of aluminum electrolytic capacitors, such as temperature rise (welding temperature, ambient temperature, AC ripple), overvoltage, transient voltage, very high frequency or reverse bias, etc. Among them, the biggest factor affecting the life of electrolytic capacitors is temperature rise. The temperature rise causes the negative electrode liquid to gradually disappear. When it decreases to a certain extent, the capacitance falls below the threshold and the life ends.

[0003] High temperature and high pressure are the biggest factors that lead to reduced lifespan. High ambient temperature, self-heating, and body heating caused by ripple current will cause the loss of electrolyte, which will directly lead to capacitor failure. The direct reason for the decrease in capacitor capacitance is that the actual area of ​​the aluminum electrolytic capacitor electrode has decreased, while the anode basically does not change during use, and it is the cathode that has decreased. The actual area of ​​the cathode is guaranteed by the electrolyte. If the electrolyte decreases due to volatilization, the actual area of ​​the cathode will decrease, and the capacitor life will also be reduced. Summary of the invention

[0004] In order to overcome the above-mentioned shortcomings of the prior art, the object of the present invention is to provide an electrolyte for long-life electrolytic capacitors and a preparation method thereof.

[0005] The technical solution adopted by the present invention to solve its technical problem is: an electrolyte for a long-life electrolytic capacitor, wherein the mass percentage of the electrolyte is: 35%-45% of a first solvent, 15%-25% of a second solvent, 5%-10% of a third solvent, 5%-15% of a solute and 3%-8% of an additive; the first solvent is ethylene glycol; the second solvent is diethylene glycol; the third solvent is one or more of 1,2-pentanediol, N,N-dimethylformamide, glycerol, isopropyl alcohol, benzyl alcohol, ethylene glycol monobutyl ether, y-butyrolactone and polyethylene glycol.

[0006] As a further improvement of the present invention: the percentage of gamma-butyrolactone is 10%-15%.

[0007] As a further improvement of the present invention: the solute package is one or more of boric acid, phthalic acid, ammonium sebacate, ammonium adipate, and ammonium dodecanedioate.

[0008] As a further improvement of the present invention: the percentage of the boric acid is 1%-3%, and the percentage of the phthalic acid is 1%-6%.

[0009] As a further improvement of the present invention: the percentage of the ammonium sebacate or ammonium dodecanedioate is 1%-6%, and the percentage of the ammonium adipate is 1%-15%.

[0010] As a further improvement of the present invention: the additive is one or more raw materials of p-nitrophenol, p-nitrobenzyl alcohol, 3,5-dinitrobenzoic acid, silver citrate, silver benzoate, EDTA, nitrilotriacetic acid, mannitol, ammonium hypophosphite, PVA, 3,4-dihydroxybenzoic acid, strontium nitrate, Dynol 104E, Tuyile FS-204, EFKA-3580, OP-30, hydrogen removers with different functions, low leakage agents, flash fire removers, stabilizers, waterproof mixtures, and corrosion inhibitors.

[0011] As a further improvement of the present invention: the percentage of the PVA is 0.5%-10%.

[0012] As a further improvement of the present invention: the percentage of p-nitrobenzyl alcohol is 1%-10%.

[0013] As a further improvement of the present invention: Step 1: uniformly mix the ethylene glycol of the first solvent and the diethylene glycol of the second solvent, heat to 40° C. and keep the temperature constant for 10 minutes;

[0014] Step 2: Add one or more of the third solvents 1,2-pentanediol, N,N-dimethylformamide (DMF), glycerol, isopropanol, benzyl alcohol, ethylene glycol monobutyl ether, γ-butyrolactone (GBL), polyethylene glycol, stir, and heat to 60°C for 30 minutes;

[0015] Step 3: Raise the temperature to 80°C, add some solutes from boric acid, phthalic acid, ammonium sebacate, ammonium adipate, and ammonium dodecanedioate, and keep the temperature constant for 30 minutes after dissolving;

[0016] Step 4: Raise the temperature to 130°C, and add one or more additives such as high temperature stabilizer, flash retardant, surfactant, etc. in sequence;

[0017] Step 5: Cool down to 80-90°C, add the remaining solutes in boric acid, phthalic acid, ammonium sebacate, ammonium adipate, and ammonium dodecanedioate, and keep the temperature constant for 30 minutes after dissolution.

[0018] As a further improvement of the present invention, one of p-nitrophenol and p-nitrobenzyl alcohol is added as a dehydrogenating agent and the temperature is kept constant for 20 minutes; finally, the temperature is lowered to room temperature to obtain an electrolyte with good moisture retention performance, a wide operating temperature range and stability.

[0019] As a further improvement of the present invention: ethylene glycol has a higher boiling point and good solubility, so that it can effectively improve the conductivity and reduce the resistance in the electrolyte. Ethylene glycol also has strong antioxidant and thermal decomposition resistance, which helps to extend the service life of the capacitor. Ethylene glycol becomes the core component of the electrolyte of a long-life electrolytic capacitor.

[0020] As a further improvement of the present invention: diethylene glycol, as an important solvent and additive, has multiple functions such as adjusting dielectric constant, reducing impedance, and improving antioxidant capacity.

[0021] As a further improvement of the present invention: N,N-dimethylformamide as an electrolyte component can significantly improve the performance of the capacitor. DMF has good solubility and high dielectric strength, which can not only improve the conductivity of the electrolyte, but also enhance its chemical stability and temperature adaptability. This allows the electrolyte containing DMF to still maintain stable electrochemical properties in a high temperature environment, greatly extending the service life of the capacitor.

[0022] As a further improvement of the present invention: Solubility of N,N-dimethylformamide: DMF has good solubility and can dissolve a variety of organic and inorganic compounds, especially for some substances that are difficult to dissolve in other solvents; Stability: It is stable at room temperature and pressure, but may undergo decomposition reactions at high temperatures or in the presence of specific catalysts. It is usually more stable when isolated from moisture; Reducibility: Under laboratory conditions, DMF exhibits certain reducibility and can be used as a reducing agent to participate in organic synthesis reactions; Weak alkalinity: DMF shows weak alkalinity, and its pK_b value is 33.1. This means that it can accept protons to generate corresponding acyl ammonium ions; Hydrolysis reaction: DMF undergoes a slow hydrolysis reaction in water to generate dimethylamine and formic acid. This reaction is accelerated under acidic or alkaline conditions; Thermal stability: Although DMF is relatively stable at high temperatures, it may still decompose when exposed to high temperature environments for a long time, producing by-products such as dimethylamine, carbon monoxide and carbon dioxide; Acid-base reaction: DMF can react with strong acids and strong bases to generate corresponding salts.

[0023] As a further improvement of the present invention: glycerol, as a polyol, has strong hydrogen bonding ability and good thermal stability. Glycerol has lower volatility and higher boiling point, and can remain stable in a wider temperature range. Its physical properties make it possible to effectively reduce the evaporation and leakage of electrolyte when glycerol is used as an electrolyte solvent, thereby improving the life and reliability of the capacitor. In addition, glycerol has good affinity and stability for oxide film, which helps to form a more uniform and dense oxide film on the electrode surface, further improving the performance of the capacitor.

[0024] As a further improvement of the present invention: propylene glycol has a high boiling point: about 290°C, which is significantly higher than ethylene glycol (about 197°C), indicating that it is more stable in high temperature environments; low volatility: compared with ethylene glycol, it has a lower vapor pressure, is suitable for high temperature environment applications, and reduces volatility losses; hygroscopicity: can adsorb moisture, maintain the equilibrium state of the electrolyte, and reduce the fluctuation of electrolyte performance caused by moisture; good solubility: can dissolve a variety of electrolyte components well and promote the movement of conductive ions; moderate viscosity: provides a good ion conduction path and wettability, which is beneficial to the electrochemical reaction inside the capacitor; hydrogen bonding: the molecule contains multiple hydroxyl groups, which are easy to form hydrogen bonds, enhance the degree of dissociation and stabilize the properties of the electrolyte.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The invention ensures that the long working life of the electrolytic capacitor is inseparable from the electrolyte. The working electrolyte can repair the capacitor's anodic oxide film at any time and is the real cathode of the capacitor. It is very important for the performance of the electrolytic capacitor. It not only determines the capacitor's leakage current, rated voltage, loss factor, impedance, rated ripple current, loss and operating temperature range, but also directly affects the use of the aluminum electrolytic capacitor.

[0027] By adding one or more surfactants such as Dynol 104E, Tuyile FS-204, EFKA-3580, and OP-30, the surface tension of the electrolyte is reduced, the permeability of the electrolyte in the electrolytic paper is enhanced, and an electrolyte with good moisturizing properties is prepared, the chemical stability of the electrolyte is improved, and the service life of the electrolyte is extended. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of experimental data of the present invention;

[0029] Figure 2 It is a schematic diagram of experimental data of conventional electrolyte;

[0030] Figure 3 It is a schematic diagram of the electrolyte experimental data of the present invention; DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the specific embodiments of the present invention and the corresponding drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0032] It should be noted that the terms "including" and "having" and any variations thereof in the specification and claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or apparatus.

[0033] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0034] The present invention is further described with reference to the accompanying drawings and embodiments: Figure 1-3 An electrolyte for a long-life electrolytic capacitor is shown, wherein the mass percentages of the electrolyte are: 35%-45% of a first solvent, 15%-25% of a second solvent, 5%-10% of a third solvent, 5%-15% of a solute and 3%-8% of an additive; the first solvent is ethylene glycol; the second solvent is diethylene glycol; the third solvent is one or more of 1,2-pentanediol, N,N-dimethylformamide, glycerol, isopropanol, benzyl alcohol, ethylene glycol monobutyl ether, y-butyrolactone, and polyethylene glycol.

[0035] As a preferred embodiment, the percentage of γ-butyrolactone is 10%-15%.

[0036] As a preferred embodiment, the solute package is one or more of boric acid, phthalic acid, ammonium sebacate, ammonium adipate, and ammonium dodecanedioate.

[0037] As a preferred embodiment, the percentage of the boric acid is 1%-3%, and the percentage of the phthalic acid is 1%-6%.

[0038] As a preferred embodiment, the percentage of the ammonium sebacate or ammonium dodecanedioate is 1%-6%, and the percentage of the ammonium adipate is 1%-15%.

[0039] As a preferred embodiment, the additive is one or more raw materials selected from p-nitrophenol, p-nitrobenzyl alcohol, 3,5-dinitrobenzoic acid, silver citrate, silver benzoate, EDTA, nitrilotriacetic acid, mannitol, ammonium hypophosphite, PVA, 3,4-dihydroxybenzoic acid, strontium nitrate, Dynol 104E, Tuyile FS-204, EFKA-3580, OP-30, dehydrogenation agents with different functions, low leakage agents, flash fire retardants, stabilizers, waterproof mixtures, and corrosion inhibitors.

[0040] As a preferred embodiment, the percentage of PVA is 0.5%-10%.

[0041] As a preferred embodiment, the percentage of p-nitrobenzyl alcohol is 1%-10%.

[0042] As a preferred embodiment, the first step is to evenly mix the ethylene glycol of the first solvent and the diethylene glycol of the second solvent, heat to 40° C. and keep the temperature constant for 10 minutes;

[0043] Step 2: Add one or more of the third solvents 1,2-pentanediol, N,N-dimethylformamide (DMF), glycerol, isopropanol, benzyl alcohol, ethylene glycol monobutyl ether, γ-butyrolactone (GBL), polyethylene glycol, stir, and heat to 60°C for 30 minutes;

[0044] Step 3: Raise the temperature to 80°C, add some solutes from boric acid, phthalic acid, ammonium sebacate, ammonium adipate, and ammonium dodecanedioate, and keep the temperature constant for 30 minutes after dissolving;

[0045] Step 4: Raise the temperature to 130°C, and add one or more additives such as high temperature stabilizer, flash retardant, surfactant, etc. in sequence;

[0046] Step 5: Cool down to 80-90°C, add the remaining solutes in boric acid, phthalic acid, ammonium sebacate, ammonium adipate, and ammonium dodecanedioate, and keep the temperature constant for 30 minutes after dissolution.

[0047] As a preferred embodiment, one of p-nitrophenol and p-nitrobenzyl alcohol is added as a dehydrogenating agent and the temperature is kept constant for 20 minutes; finally, the temperature is lowered to room temperature to obtain an electrolyte with good moisture retention performance, a wide operating temperature range and stability.

[0048] As a preferred embodiment, 1,2-pentanediol, as a diol, has excellent chemical stability and high dielectric constant, and its application in electrolytic capacitors has gradually attracted attention. Unlike traditional ethylene glycol and other solvents, 1,2-pentanediol not only exhibits good solubility and low volatility at room temperature, but also maintains high electrochemical stability under high temperature conditions, which gives it a significant advantage in improving the long life and reliability of capacitors.

[0049] As a preferred embodiment, the physical properties of 1,2-pentanediol are:

[0050] Appearance: colorless transparent liquid; Odor: slightly sweet and bitter; Boiling point: 188.2℃; Melting point: -27℃; Density: 1.036g / cm 3 ; Refractive index: 1.4325 (20℃); Flash point: 99℃ (closed cup); Solubility: easily soluble in water, ethanol and ether, miscible in esters, ketones and hydrocarbons; Viscosity: highly temperature-dependent, and decreases significantly with increasing temperature.

[0051] Chemical properties of 1,2-pentanediol:

[0052] Reactivity: Due to the presence of two free hydroxyl groups, 1,2-pentanediol has strong chemical reactivity and is prone to esterification, etherification, condensation and other reactions. For example, 1,2-pentanediol can react with carboxylic acids to form esters and with aldehydes to form acetals. In addition, it can also participate in polymerization reactions to form polyesters or polyethers.

[0053] Hydrogen bonding: The hydrogen atoms on the hydroxyl group easily form hydrogen bonds with other hydroxyl groups or carbonyl groups, which enhances the interaction between 1,2-pentanediol and other substances. This property makes it have good solubility and high stability at low temperatures.

[0054] Thermal stability: 1,2-Pentanediol is relatively stable at high temperatures, but it can undergo dehydration reaction in the presence of an acidic catalyst to form corresponding olefins or ether compounds.

[0055] High dielectric constant: 1,2-Pentanediol has a higher dielectric constant than general solvents, which can improve the conductivity and capacitance performance of the electrolyte.

[0056] Low volatility: Compared with other low molecular weight alcohols, 1,2-pentanediol has lower volatility, which reduces the evaporation loss of the electrolyte during use and improves the stability and life of the capacitor.

[0057] Good solubility: It can effectively dissolve a variety of electrolytes, especially used to support the working medium in aluminum electrolytic capacitors, ensure that the electrolyte is evenly distributed in the solution, and improve the overall performance of the capacitor.

[0058] Thermal stability: Its stable properties at high temperatures make 1,2-pentanediol suitable for electrolytic capacitors working in high temperature environments, reducing performance degradation caused by temperature changes.

[0059] Strong hydrogen bonding: It can form hydrogen bonds with other components in the electrolyte, thereby increasing the viscosity and wettability of the electrolyte, which is beneficial to the full contact between the electrolyte and the electrode.

[0060] As a preferred embodiment, the mechanism of action of isopropanol in the electrolyte is: Improve salt solubility: Isopropanol can stabilize the solubility of lithium salts and prevent the deposition of lithium salts on the negative electrode of the battery, thereby extending the life of the battery. This feature is particularly critical for improving the cycle performance of the battery; Improve battery cycle performance and capacity retention: By introducing isopropanol, the cycle performance and capacity retention of the battery can be significantly improved. Studies have shown that the cycle life of the battery is extended after the addition of isopropanol; Reduce side reactions: The addition of isopropanol can reduce side reactions in the electrolyte, such as electrolyte decomposition and dissolution of metal ions, thereby improving the safety and stability of the battery; Enhance conductivity: Since isopropanol helps to increase the solubility of lithium salts, it can also enhance the conductivity of the electrolyte, which is crucial to improving the energy conversion efficiency of the battery.

[0061] As a preferred embodiment, benzyl alcohol, as an aromatic compound containing hydroxyl groups, has a high boiling point and excellent solubility, and its application in electrolytes has gradually attracted the attention of researchers. Studies have shown that benzyl alcohol can be used as a co-solvent in electrolytes to increase the flash voltage and reduce the equivalent series resistance (ESR). In addition, benzyl alcohol can also form a stable solution with other organic solvents and electrolytes, further improving the electrochemical stability of the electrolyte.

[0062] As a preferred embodiment, benzyl alcohol improves the flash voltage: benzyl alcohol has a high dielectric strength, which can significantly improve the flash voltage of the electrolyte, thereby increasing the safety and working stability of the capacitor; reducing ESR: the addition of benzyl alcohol can reduce the ionic impedance in the electrolyte, thereby reducing the equivalent series resistance of the capacitor and improving its electrochemical performance; antioxidant performance: benzyl alcohol has a certain antioxidant ability, which can delay the oxidation and deterioration of the electrolyte during use, thereby increasing the life of the capacitor; solubility and compatibility: benzyl alcohol has good miscibility with a variety of organic solvents and electrolytes, and can form a uniform and stable solution system, which helps to improve the overall performance of the electrolyte.

[0063] As a preferred embodiment, ethylene glycol monobutyl ether improves the stability of the electrolyte: ethylene glycol monobutyl ether has a low saturated vapor pressure and good chemical stability, which helps to reduce the volatilization and decomposition of the electrolyte at high temperature, thereby improving the stability of the electrolyte. This is particularly important for long-life electrolytic capacitors, because the stability of the electrolyte directly affects the service life and reliability of the capacitor; improve the conductivity of the electrolyte: ethylene glycol monobutyl ether, as one of the solvents, helps to improve the conductivity of the electrolyte, thereby reducing the internal resistance and energy consumption of the capacitor. This is of great significance for improving the efficiency and performance of the capacitor; promote the stabilization of the cathode interface: ethylene glycol monobutyl ether reduces the solubility of lithium ions through the steric hindrance effect in its molecular structure, and helps to form a solid electrolyte interface (SEI) derived from anions and having layered characteristics. This stable cathode interface is crucial to improving the cycle performance of the mSi negative electrode, which in turn helps to extend the service life of the electrolytic capacitor; enhance the wettability of the electrolyte: ethylene glycol monobutyl ether has good wettability, which helps the uniform distribution and penetration of the electrolyte on the electrode surface, thereby improving the capacity and efficiency of the capacitor.

[0064] Working principle of the present invention:

[0065] The present invention allows the electrolyte to have a wider working range by combining low-melting-point alcohol and high-boiling-point alcohol. The addition of surfactant can not only reduce the surface tension of the electrolyte and enhance the permeability of the electrolyte in the electrolytic paper, but also wet the solid-liquid interface of the substrate and emulsify the electrolyte, so that the solute and solvent are mixed more evenly and fully, and the performance of the electrolyte is more stable.

[0066] Electrolytic paper and electrolyte together form the cathode of the electrolytic capacitor. The porosity of the electrolytic paper is used to absorb and store enough working electrolyte, acting as a cathode (electrolyte) carrier. The electrolyte is more fully covered on the surface of the aluminum foil to maximize the capacity of the capacitor product. Therefore, the electrolytic paper is made of double-layer paper made of composite pulp and long round net composite paper. The density of the electrolytic paper is 70g / cm 3 , with a thickness of 40μm, which can not only ensure the voltage resistance of the capacitor but also ensure the absorption of the electrolyte.

[0067] Implementation case 1:

[0068] like Figure 1-3An electrolyte for a long-life electrolytic capacitor is shown, wherein the mass percentages of the electrolyte are: 35%-45% of a first solvent, 15%-25% of a second solvent, 5%-10% of a third solvent, 5%-15% of a solute and 3%-8% of an additive; the first solvent is ethylene glycol; the second solvent is diethylene glycol; the third solvent is one or more of 1,2-pentanediol, N,N-dimethylformamide, glycerol, isopropanol, benzyl alcohol, ethylene glycol monobutyl ether, y-butyrolactone, and polyethylene glycol.

[0069] The percentage of γ-butyrolactone is 10%-15%, the solute package is one or more of boric acid, phthalic acid, ammonium sebacate, ammonium adipate, and ammonium dodecanedioate, the percentage of boric acid is 1%-3%, the percentage of phthalic acid is 1%-6%, the percentage of ammonium sebacate or ammonium dodecanedioate is 1%-6%, the percentage of ammonium adipate is 1%-15%, the additives are p-nitrophenol, p-nitrobenzyl alcohol, 3,5-dinitrobenzoic acid, One or more raw materials selected from the group consisting of silver citrate, silver benzoate, EDTA, nitrilotriacetic acid, mannitol, ammonium hypophosphite, PVA, 3,4-dihydroxybenzoic acid, strontium nitrate, Dynol104E, Tuyile FS-204, EFKA-3580, OP-30 and dehydrogenation agents, low leakage agents, flash fire inhibitors, stabilizers, waterproofing agents and corrosion inhibitors with different functions, wherein the percentage of PVA is 0.5%-10%, and the percentage of p-nitrobenzyl alcohol is 1%-10%.

[0070] Step 1: Mix the ethylene glycol of the first solvent and the diethylene glycol of the second solvent evenly, heat to 40°C and keep the temperature constant for 10 minutes;

[0071] Step 2: Add one or more of the third solvents 1,2-pentanediol, N,N-dimethylformamide (DMF), glycerol, isopropanol, benzyl alcohol, ethylene glycol monobutyl ether, γ-butyrolactone (GBL), polyethylene glycol, stir, and heat to 60°C for 30 minutes;

[0072] Step 3: Raise the temperature to 80°C, add some solutes from boric acid, phthalic acid, ammonium sebacate, ammonium adipate, and ammonium dodecanedioate, and keep the temperature constant for 30 minutes after dissolving;

[0073] Step 4: Raise the temperature to 130°C, and add one or more additives such as high temperature stabilizer, flash retardant, surfactant, etc. in sequence;

[0074] Step 5: Cool down to 80-90°C, add the remaining solutes in boric acid, phthalic acid, ammonium sebacate, ammonium adipate, and ammonium dodecanedioate, keep the temperature constant for 30 minutes after dissolution, add one of the hydrogen scavengers, p-nitrophenol and p-nitrobenzyl alcohol, and keep the temperature constant for 20 minutes; finally, cool down to room temperature to obtain a stable electrolyte with good moisturizing properties and a wide operating temperature range.

[0075] The electrolyte is mainly composed of solutes, solvents and additives. The solute is the main component of the positive and negative ions or ion groups that repair the oxide film and maintain the normal operation of the capacitor. Auxiliary solutes can also be added appropriately. The solute generally determines the conductivity, maximum flash voltage and stability of the electrolyte. For the selection of solutes, materials such as ammonium sebacate with longer carbon chains, more branches, polymers and small molecules are selected, because the flash voltage of the electrolyte generally increases with the increase of the number of carbon atoms in the solute. Branched carboxylates are preferred because branched carboxylates have higher solubility and stronger oxidation ability than straight-chain carboxylates. The solvent is the basis of the working electrolyte and mainly determines the operating temperature range of the capacitor. In order to make the operating temperature range of the electrolyte reach a wide temperature range of -25℃-135℃, the low-boiling point ethylene glycol is selected and combined with the high-boiling point 1,2-pentanediol, which can effectively expand the operating temperature range of the electrolyte. Additives are added to improve certain characteristics of the electrolyte or to compensate for the deficiencies of certain characteristics of the electrolyte, usually including adjusting electrolyte viscosity, conductivity, increasing flash voltage, improving electrolyte stability, passivating oxide film, inhibiting hydrogen, etc. Compared with other electrolyte formulas, this electrolyte formula only considers p-nitrobenzoic acid dehydrogenation agent, mannitol flash agent, nano-SiO2 high temperature resistant auxiliary agent, and specially adds one or more surfactants such as Dynol 104E, Tuyile FS-204, EFKA-3580, and OP-30. It focuses on the surface tension of the electrolyte, enhances the permeability of the electrolyte in the electrolytic paper, and the absorption and moisture retention of the electrolytic paper. It can also wet the solid-liquid interface of the substrate, emulsify the electrolyte, make the solute and solvent mix more evenly and fully, and make the electrolyte performance more stable. This ensures that the electrolyte is no longer easily affected by the high temperature and high pressure environment and easily evaporates and dries up, causing the capacitor to fail directly.

[0076] Implementation case 2:

[0077] In this embodiment, Figure 1-3 The electrolyte and preparation method for a long-life electrolytic capacitor shown are consistent with the electrolyte and preparation method of implementation case 1 in terms of technical means.

[0078] Using different chemical reagent ratios, we trial-produced aluminum electrolytic capacitors 450V820UF / 35*60. For specific test verification data, see Figure 1As shown; the optimal electrolyte formula of the above-mentioned preparation is compared with the commonly used electrolyte formula for verification, and the aluminum electrolytic capacitor 450V470UF / 35*40 product is trial-produced. The anode foil withstand voltage is selected as 620VF foil. The conventional design life is about 2000H. By using the electrolyte prepared by the present invention, the life of the aluminum electrolytic capacitor is increased to more than 4000H. The specific test verification data is shown in Figure 2-3 As shown;

[0079] γ-Butyrolactone improves the operating temperature range: GBL-based electrolytes show excellent stability and reliability in high temperature environments. Its high boiling point (204°C) and low melting point (-43°C) enable capacitors to operate normally in a wider temperature range, solving the problem of traditional ethylene glycol-based electrolytes being easily volatile and decomposed at high temperatures. Experimental results show that GBL-based electrolytes can still maintain good capacitance characteristics and low leakage current at a high temperature of 150°C.

[0080] Extending capacitor life: High temperature accelerated life tests show that the aging rate of GBL-based electrolytes is significantly lower than that of ethylene glycol-based electrolytes. After 500 hours of high temperature stress testing, the capacitance loss of capacitors using GBL-based electrolytes was only 5%, while the loss of capacitors using ethylene glycol-based electrolytes was as high as 15%. GBL's high oxidation resistance and chemical inertness effectively slow down the deterioration process of the electrolyte and significantly extend the service life of the capacitor.

[0081] Improved electrical performance: The results of electrochemical impedance spectroscopy (EIS) show that the impedance of GBL-based electrolytes is lower than that of ethylene glycol-based electrolytes at both room temperature and high temperature, especially in high-frequency applications. Cyclic voltammetry (CV) shows that GBL-based electrolytes have high electrochemical activity at various temperatures and no obvious side reaction peaks, indicating that they have more stable electrochemical behavior in the actual operating voltage window. These characteristics give GBL-based electrolytes a clear advantage in high-reliability and high-performance applications.

[0082] Polyethylene glycol increases the flash voltage: Polyethylene glycol, as a flash voltage enhancer, can significantly increase the flash voltage of the electrolyte. This means that during the operation of the electrolytic capacitor, it can withstand higher voltages without breakdown, thereby improving the safety and reliability of the capacitor.

[0083] Inhibit the decrease of conductivity: Under high temperature environment, the electrolyte in the electrolyte is prone to esterification reaction, resulting in a decrease in conductivity. Polyethylene glycol can effectively inhibit the occurrence of this reaction through its specific chemical structure and maintain the stability of the conductivity of the electrolyte.

[0084] Enhance electrolyte stability: Polyethylene glycol has good solubility and stability, and can form a stable solution system in the electrolyte. This helps to reduce stratification and precipitation of the electrolyte during storage and use, thereby extending the service life of the electrolyte.

[0085] Improve capacitor performance: By adding polyethylene glycol, the electrolyte formula can be optimized and the overall performance of the capacitor can be improved. For example, it can reduce the ESR (equivalent series resistance) of the capacitor, reduce the loss of the capacitor at high frequencies, and improve the working efficiency of the capacitor.

[0086] Boric acid improves conductivity: Boric acid derivatives such as boric acid glycerol polyester can increase the conductivity of the electrolyte, thereby improving the performance of the capacitor.

[0087] Reduce moisture content: Boric acid can react with solvents such as ethylene glycol in the electrolyte to produce condensation water. Although this will increase the moisture content inside the electrolyte system, the effect of moisture on capacitor performance can be balanced through reasonable formulation and process control.

[0088] Improve the flash voltage: Boric acid and its derivatives, as part of the electrolyte, help to increase the flash voltage of the electrolyte, thereby improving the safety and stability of the capacitor.

[0089] Enhanced high temperature resistance: The application of boric acid and its derivatives in the electrolyte makes the electrolyte have better high temperature resistance, which is crucial for long-life capacitors.

[0090] Phthalic acid improves high temperature stability: Phthalic acid and its derivatives, such as phthalic anhydride compounds, are used as electrolyte additives to improve the performance of capacitors in high temperature environments. They can form a stable protective film on the electrode surface, reduce the adverse reaction between the electrolyte and the electrode, and thus improve the high temperature storage performance and cycle stability of the capacitor.

[0091] Enhanced conductivity: As one of the solutes in the electrolyte, phthalic acid helps maintain the conductivity of the electrolyte, which is essential for the normal operation of the capacitor. Electrolytes with high conductivity can conduct current more effectively and improve the charging and discharging efficiency of the capacitor.

[0092] Repairing oxide film: During the operation of the capacitor, the solute in the electrolyte needs to continuously repair the oxide film damaged by the operation. Phthalic acid and its salts have good formation ability and conductivity, which can effectively repair the oxide film and extend the service life of the capacitor.

[0093] Ammonium sebacate improves the high temperature resistance of capacitors: through reasonable proportions, ammonium sebacate works synergistically with other ingredients, allowing electrolytic capacitors to work stably in high temperature environments, meeting the requirements for high-power energy-saving lamps in green lighting, engine control circuits in automotive electronics, etc. for high temperature stability.

[0094] Prolong the service life of capacitors: The addition of ammonium sebacate helps reduce the performance degradation of capacitors during long-term use, such as increased leakage current and increased equivalent series resistance, thereby effectively extending the service life of capacitors.

[0095] Improve the electrochemical properties of capacitors: As a part of the electrolyte, ammonium sebacate can optimize the ion conduction path of the electrolyte, reduce the viscosity and freezing point of the electrolyte, and improve the wettability and stability of the electrolyte, thereby improving the overall electrochemical properties of the capacitor.

[0096] Improved safety and reliability of capacitors: Because ammonium sebacate helps increase the flash voltage of the electrolyte, capacitors are better able to prevent breakdown under overvoltage conditions, thereby improving the safety and reliability of capacitors.

[0097] Ammonium adipate improves capacitor performance: Using ammonium adipate as the main solute in the electrolyte can significantly improve the electrochemical properties of the capacitor, such as conductivity and flash voltage. This improvement not only enhances the performance of the capacitor, but also keeps it stable under high-load working conditions and reduces the failure rate.

[0098] Enhanced thermal stability: The branched structure of ammonium adipate helps improve the thermal stability of the electrolyte, allowing it to maintain good performance in high temperature environments. This thermal stability is particularly important for capacitors used in high temperature working environments, such as automotive electronics and green lighting.

[0099] Improve safety: The use of ammonium adipate can also improve the flame retardant properties of the electrolyte, which is of great significance for reducing the safety risks of capacitors during use.

[0100] By introducing non-polar groups and highly electronegative elements, such as ether groups and fluorine, the generation of oxygen anions can be effectively inhibited, thereby maintaining the stability and safety of the electrolyte.

[0101] Ammonium dodecanedioate improves the flash voltage: Ammonium dodecanedioate, as an auxiliary solute, can significantly increase the flash voltage of the working electrolyte of aluminum electrolytic capacitors. When 1.2% of ammonium dodecanedioate is added, the conductivity reaches 1.262mS / cm, the water content is 3.92%, and the flash voltage can reach or exceed 500V. This high flash voltage is essential for the stable operation of electrolytic capacitors under high temperature and high pressure environments.

[0102] Enhanced high temperature resistance: The use of ammonium dodecanedioate helps improve the high temperature resistance of electrolytic capacitors. For example, the electrolyte of medium and high voltage aluminum electrolytic capacitors using ammonium dodecanedioate as the main electrolyte can work stably under the conditions of 105°C and 500-800V, and no leakage current occurs after 1000 hours of testing, showing good high temperature resistance.

[0103] Extended service life: Since ammonium dodecanedioate can improve the flash voltage and high temperature resistance of the electrolyte, it helps to extend the service life of electrolytic capacitors. Especially in high temperature environments, the performance of electrolytic capacitors tends to decay faster, and the application of ammonium dodecanedioate can slow down this process, allowing the capacitor to maintain stable performance for a longer period of time.

[0104] Improve electrochemical properties: ammonium dodecanedioate and other raw materials (such as ammonium sebacate, ammonium pentaborate, sorbitol, etc.) can be used together to produce an electrolyte with good electrochemical properties. This electrolyte not only has a high flash voltage, but also has moderate conductivity and low water content, which is conducive to the long-term stable operation of electrolytic capacitors.

[0105] Implementation case three:

[0106] In this embodiment, Figure 1-3 The electrolyte and preparation method for a long-life electrolytic capacitor shown are consistent with the electrolyte and preparation method of implementation case 1 in terms of technical means.

[0107] To prepare and test the capacitor samples, the following experimental equipment was used:

[0108] Constant temperature oven: used for high temperature durability test of capacitors.

[0109] Electrochemical workstation: used to measure the electrochemical impedance and ripple current performance of capacitors.

[0110] Precision electronic balance: used to accurately weigh various materials and reagents.

[0111] Scanning electron microscope (SEM): used to observe changes in the internal structure of the capacitor.

[0112] Infrared spectrometer (FTIR): used to analyze electrolyte composition and chemical reaction process.

[0113] Initial performance test: The electrochemical impedance and ripple current performance tests of the newly prepared capacitors were carried out using an electrochemical workstation.

[0114] High temperature durability test: The capacitors were placed in a 125°C constant temperature oven for accelerated aging test, and samples were taken out regularly for performance testing.

[0115] Microstructure observation: SEM was used to observe the internal structure of the capacitor at different stages and to check the changes in the electrode surface morphology.

[0116] Component analysis: FTIR is used to analyze the changes in electrolyte composition and determine the reaction mechanism of diethylene glycol in the electrolyte.

[0117] After 5,000 hours of high-temperature durability testing at 125°C, the capacitors with diethylene glycol added still maintained 90% of their original capacity, while the capacity of the capacitors without diethylene glycol added decreased by 15%. This verifies the positive role of diethylene glycol in extending the life of capacitors.

[0118] Through the analysis of experimental data, the following conclusions can be drawn:

[0119] Diethylene glycol in the electrolyte not only improves the conductivity of the electrolyte, but also enhances the oxidation resistance and thermal stability of the entire system.

[0120] The results of high-temperature aging tests show that diethylene glycol can significantly extend the service life of capacitors, which may be related to the hydroxyl groups in its molecular structure, which can react with free radicals in the electrolyte and reduce the occurrence of oxidation reactions.

[0121] SEM and FTIR analyses further confirmed the protective effect of diethylene glycol on the electrode surface and its advantages in chemical stability.

[0122] Nitrophenol improves flash voltage: By adding ingredients such as nitrophenol, the flash voltage of the electrolyte can be significantly improved, which is crucial to ensure the safe operation of capacitors in high voltage environments.

[0123] Extending service life: The application of nitrophenol helps to reduce gas accumulation inside the capacitor, thereby reducing the risk of failure due to excessive internal pressure. At the same time, it can also improve the electrochemical characteristics of the electrolyte, improve the overall performance of the capacitor, and thus extend its service life.

[0124] Optimizing the preparation process: During the preparation of the electrolyte, the interaction between nitrophenol and other components may help to form a more stable electrolyte system, making the electrolyte preparation process more controllable and efficient.

[0125] 4-Nitrobenzyl alcohol prolongs service life: 4-Nitrobenzyl alcohol helps prolong the service life of electrolytic capacitors because it can increase the flash voltage and improve electrical performance. This effect is particularly evident in harsh environments such as high temperature and high voltage.

[0126] Improve reliability: Electrolytic capacitors will produce gases such as hydrogen when working, which will increase the pressure inside the capacitor and even cause the explosion-proof valve to open. As a hydrogen absorber, p-nitrobenzyl alcohol can absorb these gases, reduce the pressure inside the capacitor, and thus improve the reliability of the capacitor.

[0127] Optimize electrolyte formula: p-nitrobenzyl alcohol works synergistically with other electrolyte components (such as ethylene glycol, glycerol, dimethylformamide, etc.) to further optimize the performance of the electrolyte. For example, ethylene glycol and glycerol as the main solvents can better dissolve other raw materials; dimethylformamide can reduce the viscosity of the electrolyte and enhance the working performance of the capacitor at high temperatures.

[0128] 3,5-Dinitrobenzoic acid improves the formation ability of the electrolyte: 3,5-Dinitrobenzoic acid, as a dehydrogenation agent, can effectively reduce the hydrogen in the electrolyte, thereby improving the formation ability of the electrolyte. This has a significant effect on improving the electrical properties of the capacitor, such as reducing loss and leakage current.

[0129] Improve the electrical performance of capacitors: By adding 3,5-dinitrobenzoic acid, the composition of the electrolyte can be optimized, thereby improving the electrical performance of the capacitor, which can be manifested in reducing losses and leakage current, thereby extending the service life of the capacitor.

[0130] Improve the flash voltage: In some electrolyte formulations, 3,5-dinitrobenzoic acid is also used as part of the flash voltage enhancer. The flash voltage is one of the important indicators to measure the performance of electrolytic capacitors. Improving the flash voltage helps to improve the high voltage resistance and high temperature resistance of capacitors.

[0131] Enhance the stability of the electrolyte: 3,5-Dinitrobenzoic acid, as an additive in the electrolyte, can also enhance the stability of the electrolyte. This helps to reduce the performance fluctuations of the capacitor during use, thereby extending its service life.

[0132] Silver citrate increases the flash voltage: As an additive, silver citrate can ionize anions in the solvent and adsorb on the anode surface under the action of the electric field to form an adsorption layer. This adsorption layer has the function of shielding the electric field and makes the electric field acting on the electrode uniform, eliminating the edge effect. This feature helps to increase the flash voltage (Us) of the electrolytic capacitor, thereby improving the working stability and safety of the capacitor.

[0133] Enhanced oxidation efficiency: The addition of silver citrate may help improve the oxidation efficiency of the electrolyte, restore the damaged dielectric oxide film as soon as possible, and extend the high temperature life of the product. This is especially important for long-life electrolytic capacitors, because the integrity of the oxide film is directly related to the performance and life of the capacitor.

[0134] Improve electrolyte performance: As one of the additives, silver citrate works together with other functional protective agents on the electrolyte to improve the performance of the electrolyte, making it more stable and reliable. Although these additives are used in small amounts, they play a very important role in improving the performance of the electrolyte.

[0135] Environmental protection and safety: As a chemical substance, the use of silver citrate needs to consider environmental protection and safety factors. However, in the application of electrolytic capacitors, it is usually present in lower concentrations and is subject to strict process control and testing verification to ensure that it does not cause harm to the environment and human body.

[0136] Silver benzoate improves flash voltage: As an additive in the electrolyte, silver benzoate can significantly increase the flash voltage of the capacitor. This is very important for high voltage applications, because high flash voltage means that the capacitor can work stably at higher voltages without breakdown. By adding silver benzoate, the conductivity and stability of the electrolyte are improved, thereby improving the overall performance.

[0137] Extended service life: Silver benzoate helps reduce the moisture content inside the capacitor, which is one of the key factors in extending the life of the capacitor. In high temperature environments, silver benzoate can inhibit the generation and accumulation of moisture, preventing capacitor failure caused by excessive moisture.

[0138] Improved thermal stability: Silver benzoate has good thermal stability and can maintain its chemical properties unchanged under high temperature conditions. This allows electrolytic capacitors to work stably in high temperature environments and is not prone to thermal decomposition or performance degradation.

[0139] Reduced internal resistance: After adding silver benzoate, the ion mobility of the electrolyte is improved, resulting in a lower internal resistance of the capacitor. Low internal resistance means less energy loss during charging and discharging, and higher efficiency.

[0140] The main functions of the present invention are:

[0141] The invention ensures that the long working life of the electrolytic capacitor is inseparable from the electrolyte. The working electrolyte can repair the capacitor's anodic oxide film at any time and is the real cathode of the capacitor. It is very important for the performance of the electrolytic capacitor. It not only determines the capacitor's leakage current, rated voltage, loss factor, impedance, rated ripple current, loss and operating temperature range, but also directly affects the use of the aluminum electrolytic capacitor.

[0142] By adding one or more surfactants such as Dynol 104E, Tuyile FS-204, EFKA-3580, and OP-30, the surface tension of the electrolyte is reduced, the permeability of the electrolyte in the electrolytic paper is enhanced, and an electrolyte with good moisturizing properties is prepared, the chemical stability of the electrolyte is improved, and the service life of the electrolyte is extended.

[0143] In summary, after reading the present invention document, ordinary technicians in this field can make various other corresponding transformation schemes based on the technical scheme and technical concept of the present invention without creative mental work, which all fall within the scope of protection of the present invention.

[0144] In the description of the present invention, it needs to be understood that the orientations or positional relationships indicated by terms such as "upper end face", "lower end face", "top", "bottom", "left" and "right" are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of the description of the present invention. Therefore, they cannot be understood as limiting the actual use direction of the present invention.

[0145] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some or all of the technical features thereof may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention, and should all be included in the scope of the claims and specification of the present invention.

Claims

1. An electrolyte for a long-life electrolytic capacitor, characterized in that: The electrolyte comprises by weight: 35%-45% of a first solvent, 15%-25% of a second solvent, 5%-10% of a third solvent, 5%-15% of a solute and 3%-8% of an additive; The first solvent is ethylene glycol; The second solvent is diethylene glycol; The third solvent is one or more of 1,2-pentanediol, N,N-dimethylformamide, glycerol, isopropanol, benzyl alcohol, ethylene glycol monobutyl ether, y-butyrolactone, and polyethylene glycol.

2. The electrolyte for a long-life electrolytic capacitor according to claim 1, characterized in that: The percentage of gamma-butyrolactone is 10%-15%.

3. The electrolyte for a long-life electrolytic capacitor according to claim 1, characterized in that: The solute package is one or more of boric acid, phthalic acid, ammonium sebacate, ammonium adipate, and ammonium dodecanedioate.

4. The electrolyte for a long-life electrolytic capacitor according to claim 3, characterized in that: The percentage of the boric acid is 1%-3%, and the percentage of the phthalic acid is 1%-6%.

5. The electrolyte for a long-life electrolytic capacitor according to claim 3, characterized in that: The percentage of the ammonium sebacate or ammonium dodecanedioate is 1%-6%, and the percentage of the ammonium adipate is 1%-15%.

6. The electrolyte for a long-life electrolytic capacitor according to claim 1, characterized in that: The additive is one or more raw materials selected from p-nitrophenol, p-nitrobenzyl alcohol, 3,5-dinitrobenzoic acid, silver citrate, silver benzoate, EDTA, nitrilotriacetic acid, mannitol, ammonium hypophosphite, PVA, 3,4-dihydroxybenzoic acid, strontium nitrate, Dynol 104E, Tuyile FS-204, EFKA-3580, OP-30, dehydrogenation agents with different functions, low leakage agents, flash fire retardants, stabilizers, waterproof mixtures, and anticorrosive agents.

7. The electrolyte for a long-life electrolytic capacitor according to claim 6, characterized in that: The percentage of PVA is 0.5%-10%.

8. The electrolyte for a long-life electrolytic capacitor according to claim 6, characterized in that: The percentage of p-nitrobenzyl alcohol is 1%-10%.

9. The method for preparing an electrolyte for a long-life electrolytic capacitor according to claim 1, comprising the following steps: Step 1: Mix the ethylene glycol of the first solvent and the diethylene glycol of the second solvent evenly, heat to 40°C and keep the temperature constant for 10 minutes; Step 2: Add one or more of the third solvents 1,2-pentanediol, N,N-dimethylformamide (DMF), glycerol, isopropanol, benzyl alcohol, ethylene glycol monobutyl ether, γ-butyrolactone (GBL), polyethylene glycol, stir, and heat to 60°C for 30 minutes; Step 3: Raise the temperature to 80°C, add some solutes from boric acid, phthalic acid, ammonium sebacate, ammonium adipate, and ammonium dodecanedioate, and keep the temperature constant for 30 minutes after dissolving; Step 4: Raise the temperature to 130°C, and add one or more additives such as high temperature stabilizer, flash retardant, surfactant, etc. in sequence; Step 5: Cool down to 80-90°C, add the remaining solutes in boric acid, phthalic acid, ammonium sebacate, ammonium adipate, and ammonium dodecanedioate, and keep the temperature constant for 30 minutes after dissolution.

10. The method for preparing an electrolyte for a long-life electrolytic capacitor according to claim 9, characterized in that: Add one of the dehydrogenating agents, p-nitrophenol and p-nitrobenzyl alcohol, and keep the temperature constant for 20 minutes; finally, cool the temperature to room temperature to obtain a stable electrolyte with good moisturizing properties and a wide operating temperature range.

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