High-voltage aluminum capacitor dehydrogenation agent and application in aluminum electrolytic capacitor electrolyte

Abstract

The invention discloses a hydrogen elimination agent for a high-voltage aluminum capacitor and application of the hydrogen elimination agent in an aluminum electrolytic capacitor electrolyte, and the hydrogen elimination agent has an excellent hydrogen elimination effect in the aluminum electrolytic capacitor electrolyte and is very excellent in dissolving property. And even if the hydrogen eliminating agent is in a low-temperature ethylene glycol and low-temperature gamma-butyrolactone system, the hydrogen eliminating agent is not separated out and does not generate negative effects on electrolyte performance (such as sparking voltage and conductivity). The hydrogen eliminating agent provided by the invention has the characteristics of high solubility, long service life, good stability, obvious hydrogen eliminating effect and high pressure resistance.

Description

Technical Field

[0001] This invention relates to the field of electrochemical technology, specifically to a hydrogen scavenger for high-voltage aluminum capacitors and its application in the electrolyte of aluminum electrolytic capacitors. Background Technology

[0002] Aluminum electrolytic capacitors are mainly composed of aluminum foil, alumina dielectric film, electrolyte, and aluminum shell. The electrolyte is a key basic material in the production of aluminum electrolytic capacitors, accounting for 30%-70% of the production cost along with the electrode foil.

[0003] Hydrogen scavenger is an indispensable functional additive in the preparation of electrolyte for aluminum electrolytic capacitors. It can remove hydrogen gas generated during the repair of the dielectric oxide film through chemical reaction, thereby avoiding the bulging and deformation of the capacitor caused by hydrogen accumulation and extending the service life of aluminum electrolytic capacitors.

[0004] For example, patent document CN1744247A discloses a working electrolyte for an aluminum electrolytic capacitor, which uses one or more of p-nitrophenol, p-nitrobenzoic acid and p-nitrobenzyl alcohol as hydrogen scavengers added to the electrolyte.

[0005] Patent document US6562255A1 discloses the use of 3-nitroacetophenone or 2-nitroanisole as hydrogen scavenging agents.

[0006] Patent document CN109390156A discloses the use of 2-butyl-2-(3-nitrobenzyl)-5-hydroxy-1,3-dioxane and 2-methyl-2-(3-nitrophenyl)-5-hydroxymethyl-1,3-dioxane as hydrogen scavengers.

[0007] Currently, hydrogen scavenging agents suitable for the production of electrolytes for high-end aluminum electrolytic capacitors mainly include p-nitrobenzoic acid, p-nitrobenzyl alcohol, m-nitroacetophenone, and o-nitroanisole. In these hydrogen scavenging agents, the nitro group on the benzene ring is the key functional group that plays a role in hydrogen scavenging. Therefore, hydrogen scavenging agents with a high nitro mass ratio can achieve hydrogen scavenging effect with a smaller amount of addition.

[0008] In the application of aluminum capacitors, p-nitrobenzoic acid has the problem of high chloride content, which reduces the flashover voltage of the electrolyte. p-Nitrobenzyl alcohol is very expensive, and its low withstand voltage and flashover characteristics limit its use in high-voltage aluminum capacitors.

[0009] m-Nitroacetophenone has poor solubility in ethylene glycol and tends to crystallize at low temperatures (-40°C). As an electrolyte for high-voltage aluminum capacitors, it has drawbacks such as low solubility, irritation, and reduced flashover properties.

[0010] o-Nitroanisole contains many impurities, which can cause blackening of lead wire riveting points and reduced flashover in actual use. Due to its high toxicity, it is banned by the EU environmental protection authorities and is no longer used in the industry.

[0011] 2-Butyl-2-(3-nitrobenzyl)-5-hydroxy-1,3-dioxane has the disadvantages of high viscosity and reduced conductivity, and the low mass percentage of nitro groups means that a larger amount needs to be used to achieve the same effect.

[0012] Furthermore, the hydrogen scavenging agents currently used in high-voltage aluminum electrolytic capacitors often cause the explosion-proof valve to fail to open under excessively high voltage, resulting in explosions or breakdowns. This leads to the aluminum capacitor failing to open its valve properly, affecting its safety and service life, and seriously restricting the high-quality development of high-end aluminum electrolytic capacitors.

[0013] Therefore, there are very few hydrogen scavenging agents suitable for high-end aluminum electrolytic capacitors, and those that exist have some shortcomings. There is an urgent need to develop a new type of highly efficient hydrogen scavenging agent to meet the requirements of high-end aluminum capacitors that are small in size, large in capacitance, withstand high voltage, and have a long lifespan. This hydrogen scavenging agent should possess the following four characteristics: First, it has excellent solubility and does not precipitate at low temperatures; Second, the nitro group has a high mass percentage; Third, it is economically inexpensive and environmentally friendly; Fourth, it does not affect the flashover voltage and is resistant to high voltage. Summary of the Invention

[0014] This invention provides a hydrogen removal agent for high-voltage aluminum capacitors, which solves one of the many problems in the prior art.

[0015] In view of this, the solution of the present invention is as follows: The first aspect of the present invention is to provide a high-voltage aluminum capacitor hydrogen scavenger having a structural formula as shown in Formula I: ; In Formula I, a = 1 or 2; R1 is a nitro group, R2 represents an organic group containing 1 to 5 carbon atoms, and R3 is hydrogen or an organic group containing 1 to 5 carbon atoms.

[0016] Furthermore, in Formula I, R2 and R3 are each independently selected from hydrogen, hydrocarbon groups having 1 to 5 carbon atoms, or hydrocarbon groups having 1 to 5 carbon atoms containing substituents; the substituents are selected from one or more of hydroxyl, alcohol hydroxyl, and aryl.

[0017] Preferably, the hydrogen scavenger is 2-[(2-nitrophenyl)oxy]eth-1-ol, 2-[(3-nitrophenyl)oxy]eth-1-ol, 2-[(4-nitrophenyl)oxy]eth-1-ol, 3-[(2-nitrophenyl)oxy]prop-1-ol, or 1-[(2-nitrophenyl)oxy]eth-1,2-diol.

[0018] A second aspect of the present invention is to provide a method for preparing a high-voltage capacitor hydrogen scavenger, wherein, under the action of a catalyst, a compound of formula II and a carbonate are added to a solvent and reacted at 70°C to 180°C, the solvent is then removed, and the high-voltage capacitor hydrogen scavenger is obtained by cooling, separation and purification; the carbonate has the structure shown in formula III. , ; In Formula II, R1 is a nitro group, and b = 1 or 2; In Formula III, R4 represents hydrogen or an organic group containing 1 to 2 carbon atoms, specifically one of hydrogen, methyl, ethyl, or hydroxymethyl.

[0019] Furthermore, the compound represented by Formula II is selected from 2-nitrophenol, 3-nitrophenol, or 4-nitrophenol.

[0020] Furthermore, the carbonate is selected from ethylene carbonate, propylene carbonate, or glycerol carbonate.

[0021] Furthermore, the molar ratio of the compound shown in Formula II to the carbonate is 1:(0.8 to 4).

[0022] Furthermore, the reaction time is 3–40 hours. Preferably, the reaction temperature is 80°C–130°C, and the reaction time is 4–20 hours. At this temperature, the reactivity of each raw material is higher than at other temperatures, and the reaction time can be relatively shorter.

[0023] Furthermore, the solvent is selected from at least one of ethers, alcohol ethers, amides, toluene, xylene, ethylbenzene, sulfones, sulfoxides, acetonitrile, and 1,2-dichloroethane.

[0024] Furthermore, the catalyst is selected from at least one of potassium carbonate, sodium carbonate, sodium bicarbonate, sodium hydroxide, potassium fluoride, imidazole, N-methylimidazolium, 4-dimethylaminopyridine, 1,3-dimethylimidazolium iodide, lithium carbonate, cesium carbonate, potassium phosphate, sodium phosphate, disodium hydrogen phosphate, potassium hydroxide, DBU, and tetramethylguanidine.

[0025] Furthermore, the purification process can be any one of distillation, extraction, or crystallization. The reaction product obtained by distillation, extraction, or crystallization has a purity of up to 99.8%, preferably vacuum distillation.

[0026] A third aspect of the present invention is to provide the application of the high-voltage capacitor hydrogen scavenger described in the first aspect, or the high-voltage capacitor hydrogen scavenger prepared by the preparation method described in the second aspect, in the electrolyte of an aluminum electrolytic capacitor, wherein the solvent in the aluminum electrolytic capacitor electrolyte is ethylene glycol or γ-butyrolactone.

[0027] A fourth aspect of the present invention is to provide an electrolyte for an aluminum electrolytic capacitor, comprising, by mass percentage: 2-15% hydrogen scavenger, 62.5-75.5% ethylene glycol, 1-5% ammonium pentaborate, 1-4% ammonium sebacic acid, 1-5% 10,11-dioctyleicosanoic acid, 1-5% 10-(6-(7-carboxyheptyl)-2,3-dihexylcyclohexyl)decanoic acid, 1-5% 8-[7,8-bis(7-carboxyheptyl)-4,5-dihexyl-6-octyl-decanonaphth-1-yl]octanoic acid, 1-5% polyvinyl alcohol, 1-4% mannitol, 0.1-0.5% ammonium hypophosphite, 0.1-0.5% diethylene glycol butyl ether, 1-3% ammonium potassium methylbenzeneate, and the balance being water; The hydrogen scavenging agent is the high-voltage capacitor hydrogen scavenging agent described in the first aspect, or the high-voltage capacitor hydrogen scavenging agent prepared by the preparation method described in the second aspect.

[0028] A fifth aspect of the present invention is to provide the application of the aluminum electrolytic capacitor electrolyte described in the fourth aspect in an aluminum electrolytic capacitor.

[0029] Compared with the prior art, the present invention has the following beneficial effects: The hydrogen scavenger provided by this invention exhibits excellent hydrogen scavenging effect in the electrolyte of aluminum electrolytic capacitors, and its solubility is also excellent. Furthermore, even in low-temperature ethylene glycol and low-temperature γ-butyrolactone systems, this hydrogen scavenger does not precipitate and does not negatively affect electrolyte performance (e.g., flashover voltage and conductivity). The hydrogen scavenger provided by this invention features high solubility, long lifespan, good stability, significant hydrogen scavenging effect, and high voltage resistance.

[0030] The method for preparing hydrogen scavenger provided by this invention has simple process conditions, is safe and environmentally friendly in production, does not introduce impurity ions in the process, and has a product yield of over 85%, making it suitable for large-scale industrial production.

[0031] The hydrogen scavenger provided by this invention can be added to the electrolyte in a higher proportion without causing solute precipitation or reducing the flashover voltage. It can pass capacitor load tests at 105°C for more than 2000 hours. In multiple sets of tests at 600V for 30 seconds and 620V for 50 seconds, it can stabilize the opening of the capacitor under overvoltage, greatly reducing the risk of explosion-proof valve failure. Attached Figure Description

[0032] Figure 1 The hydrogen scavenger prepared in Example 1 of this invention 1 H-NMR results.

[0033] Figure 2 The hydrogen scavenger prepared in Example 1 of this invention 13 C-NMR results.

[0034] Figure 3 The GC-MS results are for the hydrogen scavenger prepared in Example 1 of this invention.

[0035] Figure 4 The HPLC results are for the hydrogen scavenger prepared in Example 1 of this invention. Detailed Implementation

[0036] The technical solution of the present invention will now be clearly and completely described in conjunction with preferred embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. 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.

[0037] This invention provides a hydrogen scavenging agent for use in the electrolyte of aluminum electrolytic capacitors, the structural formula of which is shown in Formula I: ; In Formula I, a = 1 or 2; R1 is a nitro group, R2 represents an organic group containing 1 to 5 carbon atoms; R3 represents hydrogen or an organic group containing 1 to 5 carbon atoms. In a preferred embodiment, in Formula I, R2 and R3 are each independently selected from hydrogen, a hydrocarbon group having 1 to 5 carbon atoms, or a hydrocarbon group having 1 to 5 carbon atoms containing a substituted group; the substituted group is selected from one or more of hydroxyl, alcohol hydroxyl, and aryl.

[0038] In a preferred embodiment, the hydrogen scavenger shown in Formula I is 2-[(2-nitrophenyl)oxy] ethylene-1-ol, 2-[(3-nitrophenyl)oxy] ethylene-1-ol, 2-[(4-nitrophenyl)oxy] ethylene-1-ol, 3-[(2-nitrophenyl)oxy] prop-1-ol, or 1-[(2-nitrophenyl)oxy] ethylene-1,2-diol.

[0039] In the above embodiments, the hydrogen scavenger exhibits excellent hydrogen scavenging effect in the electrolyte of aluminum electrolytic capacitors, and its solubility is also excellent. Furthermore, even in low-temperature (below 25°C) ethylene glycol and low-temperature γ-butyrolactone systems, the hydrogen scavenger shows no precipitation and does not negatively affect electrolyte performance (e.g., flashover voltage and conductivity). The hydrogen scavenger provided by this invention features high solubility, long lifespan, good stability, significant hydrogen scavenging effect, and high voltage resistance.

[0040] The embodiments of the present invention also provide a method for preparing the hydrogen scavenger, comprising the following steps: In the presence of a catalyst, the first and second reactants are added to a solvent and transesterification is carried out at 70℃~160℃. The solvent was then removed, and the product was obtained by cooling and separation, containing the hydrogen scavenger. Wherein, the first reactant has the structural formula shown in Formula II, and the second reactant has the structural formula shown in Formula III; ; In Formula II, R1 is a nitro group, and b = 1 or 2; ; In Formula III, R4 represents hydrogen or an organic group containing 1 to 2 carbon atoms, specifically one of hydrogen, methyl, ethyl, or hydroxymethyl. Specifically, the preparation route of the hydrogen scavenger of the present invention is as follows:

[0041] In a preferred embodiment, the first reactant is selected from 2-nitrophenol, 3-nitrophenol, or 4-nitrophenol; the second reactant is selected from ethylene carbonate, propylene carbonate, or glycerol carbonate.

[0042] In a preferred embodiment, the molar ratio of the first reactant to the second reactant is 1:0.8 to 4. Preferably, the molar ratio of the first reactant to the second reactant is 1:1.05 to 2.0, ensuring a slight excess of the second reactant, which is beneficial for the forward reaction.

[0043] In a preferred embodiment, the solvent is selected from ethers, alcohol ethers, amides, toluene, xylene, ethylbenzene, sulfone, sulfoxide, acetonitrile, and 1,2-dichloroethane; the catalyst is selected from at least one of potassium carbonate, sodium carbonate, sodium bicarbonate, sodium hydroxide, potassium fluoride, imidazole, N-methylimidazolium, 4-dimethylaminopyridine, 1,3-dimethylimidazolium iodide, lithium carbonate, cesium carbonate, potassium phosphate, sodium phosphate, disodium hydrogen phosphate, potassium hydroxide, DBU, and tetramethylguanidine.

[0044] The preparation of the aforementioned hydrogen scavenger requires heating, with a reaction temperature of 70-180℃ and a reaction time of 3-40 hours. The preferred reaction temperature is 80℃-130℃, and the reaction time is 4-20 hours. At this temperature, the reactivity of each raw material is higher compared to other temperatures, and the reaction time can be relatively shorter.

[0045] In the preparation process of the above-mentioned hydrogen scavenger, after the reaction is completed, the solvent is removed, and the product containing the hydrogen scavenger is obtained by cooling and separation. No impurity ions are introduced in the above reaction process, and the product yield is as high as 85% or more.

[0046] The preparation process of the aforementioned hydrogen scavenger also includes purifying the reaction product. Purification increases the purity of the reaction product, reducing the negative impact of impurities on the capacitor. Preferably, the purification process is any one of distillation, extraction, or crystallization. The reaction product obtained through distillation, extraction, or crystallization has a purity of up to 99.8%.

[0047] In another embodiment, an electrolyte for aluminum electrolytic capacitors is provided, comprising an electrolyte in which a hydrogen scavenger is added at a concentration of 2% to 15%; the electrolyte comprises, by mass percentage:

[0048] The above electrolyte meets the following performance requirements: Electrical conductivity (30℃) is 1700~1900 uS / cm: Flashover voltage ≥ 480V.

[0049] In this context, higher dosage is more beneficial for hydrogen removal without affecting product performance parameters. This hydrogen removal agent is miscible with the electrolyte, allowing for higher addition ratios without the precipitation of other solutes or reduction of flashover voltage. Its electrolyte exhibits high voltage resistance, long service life, good stability, and excellent electrochemical properties, meeting the performance requirements of high-voltage and ultra-high-voltage capacitors. It effectively prevents capacitor capacity decay and reduces the risk of explosion-proof valve failure. Specifically, in some embodiments, capacitors made with this electrolyte can pass capacitor load tests at 105°C for over 2000 hours. In multiple tests at 600V 30S and 620V 50S, the capacitor can stably open under overvoltage, significantly reducing the risk of explosion-proof valve failure.

[0050] Example 1

[0051] A method for preparing a hydrogen scavenging agent for aluminum electrolytic capacitors includes the following steps: 1) Weigh 69.56 g (0.50 mol) of o-nitrophenol, 70.45 g (0.80 mol) of ethylene carbonate, and 74.12 g (1.00 mol) of n-butanol and add them to a 500 ml three-necked flask. After stirring evenly, add 6.90 g (0.05 mol) of potassium carbonate and heat to 120 °C and reflux for 18 h. 2) After completion, distill to remove the solvent; 3) The reaction product was subjected to vacuum distillation, and 78.86 g of the product was obtained. After sampling and testing, the product was mainly 2-[(2-nitrophenyl)oxy]ethane-1-ol, denoted as S1, with an overall yield of approximately 86%.

[0052] The prepared hydrogen scavenging agent was analyzed and tested. 1 H-NMR results are as follows Figure 1 As shown, 13 C-NMR results are as follows Figure 2 As shown, the GC-MS results are as follows: Figure 3 As shown, the HPLC results are as follows: Figure 4 As shown.

[0053] Example 2

[0054] A method for preparing a hydrogen scavenging agent for aluminum electrolytic capacitors includes the following steps: 1) Weigh 69.56 g (0.50 mol) of o-nitrophenol, 87.08 g (0.75 mol) of propylene carbonate, and 76.09 g (1.00 mol) of ethylene glycol monomethyl ether and add them to a 500 ml three-necked flask. After stirring evenly, add 6.11 g (0.05 mol) of 4-dimethylaminopyridine and heat to 125 °C under reflux for 15 h. 2) After completion, distill to remove the solvent; 3) The reaction product was subjected to vacuum distillation, and 87.74 g of the product was obtained. After sampling and analysis, the product was mainly 3-[(2-nitrophenyl)oxy]prop-1-ol, denoted as S2, with an overall yield of approximately 89%.

[0055] Example 3

[0056] A method for preparing a hydrogen scavenging agent for aluminum electrolytic capacitors includes the following steps: 1) Weigh 69.56 g (0.50 mol) of p-nitrophenol, 70.45 g (0.80 mol) of ethylene carbonate, and 73.09 g (1.00 mol) of N,N-dimethylformamide and add them to a 500 ml three-necked flask. After stirring evenly, add 6.90 g (0.05 mol) of potassium carbonate and heat to 110 °C and reflux for 15 h. 2) After completion, distill to remove the solvent; 3) The reaction product was subjected to vacuum distillation, and 77.85 g of the product was obtained. After sampling and testing, the product was mainly 2-[(4-nitrophenyl)oxy]ethanol-1-ol, denoted as S3, with an overall yield of about 85%.

[0057] Example 4

[0058] A method for preparing a hydrogen scavenging agent for aluminum electrolytic capacitors includes the following steps: 1) Weigh 69.56 g (0.50 mol) of o-nitrophenol, 52.84 g (0.60 mol) of glyceryl carbonate, and 73.09 g (1.00 mol) of N,N-dimethylformamide and add them to a 500 ml three-necked flask. After stirring evenly, add 3.26 g (0.01 mol) of cesium carbonate and heat to 110 °C and reflux for 16 h. 2) After completion, distill to remove the solvent; 3) The reaction product was subjected to vacuum distillation, and 90.61 g of the product was obtained. After sampling and testing, the product was mainly 3-(2-nitrophenoxy)propane-1,2-diol, denoted as S4, with an overall yield of about 85%.

[0059] Example 5

[0060] A method for preparing a hydrogen scavenging agent for aluminum electrolytic capacitors includes the following steps: 1) Weigh 69.56 g (0.50 mol) of m-nitrophenol, 52.84 g (0.60 mol) of ethylene carbonate, and 106.17 g (1.00 mol) of o-xylene and add them to a 500 ml three-necked flask. After stirring evenly, add 5.68 g (0.04 mol) of disodium hydrogen phosphate and heat to 145 °C and reflux for 12 h. 2) After completion, distill to remove the solvent; 3) The reaction product was subjected to vacuum distillation, and 73.36 g of the product was obtained. After sampling and testing, the product was mainly 2-[(3-nitrophenyl)oxy]ethanol-1-ol, denoted as S5, with an overall yield of about 80%.

[0061] Example 6

[0062] A method for preparing a hydrogen scavenging agent for aluminum electrolytic capacitors includes the following steps: 1) Weigh 69.56 g (0.50 mol) of o-nitrophenol, 80.48 g (0.60 mol) of ethyl-2-hydroxyethyl carbonate, and 106.17 g (1.00 mol) of ethylbenzene and add them to a 500 ml three-necked flask. After stirring evenly, add 0.68 g (0.01 mol) of imidazole and heat to 136 °C and reflux for 16 h. 2) After completion, distill to remove the solvent; 3) The reaction product was subjected to vacuum distillation, and 82.42 g of product was obtained. After sampling and testing, the product was mainly 2-[(2-nitrophenyl)oxy]ethane-1-ol, and the total yield was about 90%.

[0063] Comparative Example 1

[0064] Using o-nitroanisole as a comparison, its solubility in ethylene glycol and electrolyte A were compared. The formulation of electrolyte A is shown in Table 1, and the amounts of o-nitroanisole added in ethylene glycol and electrolyte A are shown in Table 2. During the solubility test, the amount of ethylene glycol solvent in the electrolyte was adjusted according to the amount of o-nitroanisole added to ensure that the total electrolyte volume was 100%.

[0065] Comparative Example 2

[0066] Using p-nitrobenzyl alcohol as a comparison, its solubility in ethylene glycol and electrolyte A were compared. The formulation of electrolyte A is shown in Table 1, and the amounts of p-nitrobenzyl alcohol added in ethylene glycol and electrolyte A are shown in Table 2. During the solubility test, the amount of ethylene glycol solvent in the electrolyte was adjusted according to the amount of p-nitrobenzyl alcohol added to ensure that the total electrolyte volume was 100%.

[0067] Comparative Example 3

[0068] Using m-nitroacetophenone as a comparison, its solubility in ethylene glycol and electrolyte A were compared. The formulation of electrolyte A is shown in Table 1, and the amounts of p-nitrobenzyl alcohol added to ethylene glycol and electrolyte A are shown in Table 2. During the solubility test, the amount of ethylene glycol solvent in the electrolyte was adjusted according to the amount of p-nitrobenzyl alcohol added to ensure that the total electrolyte volume was 100%.

[0069] Comparative Example 4

[0070] Using 2-butyl-2-(3-nitrobenzyl)-5-hydroxy-1,3-dioxane as a comparison, its solubility in ethylene glycol and electrolyte A were compared. The formulation of electrolyte A is shown in Table 1, and the amounts of p-nitrobenzyl alcohol added to ethylene glycol and electrolyte A are shown in Table 2. During the solubility test, the amount of ethylene glycol solvent in the electrolyte was adjusted according to the amount of p-nitrobenzyl alcohol added to ensure that the total electrolyte volume was 100%.

[0071] Comparative Example 5

[0072] Using 2-methyl-2-(3-nitrophenyl)-5-hydroxymethyl-1,3-dioxane as a comparison, its solubility in ethylene glycol and electrolyte A were compared. The formulation of electrolyte A is shown in Table 1, and the amounts of p-nitrobenzyl alcohol added to ethylene glycol and electrolyte A are shown in Table 2. During the solubility test, the amount of ethylene glycol solvent in the electrolyte was adjusted according to the amount of p-nitrobenzyl alcohol added to ensure that the total electrolyte volume was 100%.

[0073] Table 1: Electrolyte A formulation is as follows

[0074] The products S1 to S5 prepared in Examples 1 to 5 of the present invention and the substances of Comparative Examples 1 to 5 were dissolved in ethylene glycol solution and electrolyte A respectively for dissolution comparison. The specific results are shown in Table 2.

[0075] Table 2: Comparison of the solubility and nitro content of products S1-S5 prepared in Examples 1-5 and substances in Comparative Examples 1-5 in ethylene glycol solution and electrolyte A at 25°C.

[0076] As shown in Table 2, the products prepared in Examples 1 to 5 have excellent solubility in ethylene glycol and electrolyte A. Examples 1, 2 and 4 are miscible with ethylene glycol at 25°C in any ratio and will not precipitate or cause other solutes to precipitate in the electrolyte. Their solubility is far superior to other types of hydrogen scavengers.

[0077] Example 7

[0078] The hydrogen scavenger S1 prepared in Example 1 was added to the electrolyte A formulation according to the dosage shown in the table to prepare the electrolyte. When preparing the electrolyte, the amount of ethylene glycol solvent was adjusted according to the amount of hydrogen scavenger added to ensure that the total electrolyte volume was 100%. Conductivity, pH value, moisture content, viscosity, flashover voltage performance, and solubility were tested, and the specific test results are shown in Table 3.

[0079] Table 3: Electrolyte Performance Tests for Different Amounts of Hydrogen Eliminator Added in Example 1

[0080] As shown in Table 3, the hydrogen scavenger added in Example 1 at a concentration of 2% to 15% has good performance on the electrolyte. After being applied to the capacitor, it can operate at 85°C for 5000 hours without any bottoming phenomenon. In contrast, the hydrogen scavengers in other comparative examples have already reached their solubility limit and are no longer soluble in the electrolyte.

[0081] Examples 8-10, Comparative Examples 6-10

[0082] The hydrogen scavengers S1, S2, and S3 prepared in Examples 1, 2, and 3, along with o-nitrobenzyl ether, p-nitrobenzyl alcohol, m-nitrobenzyl ketone, 2-butyl-2-(3-nitrobenzyl)-5-hydroxy-1,3-dioxane, and 2-methyl-2-(3-nitrophenyl)-5-hydroxymethyl-1,3-dioxane, were added to the electrolyte A formulation according to the amounts shown in the table to prepare the electrolyte. When preparing the electrolyte, the amount of ethylene glycol solvent was adjusted according to the amount of hydrogen scavenger added to ensure that the total electrolyte volume was 100%. Conductivity, pH value, moisture content, viscosity, flashover voltage performance, and solubility were tested, and the specific test results are shown in Table 4.

[0083] Table 4: Electrolyte performance test parameters for Examples 8-10 and Comparative Examples 6-10

[0084] As shown in Table 4, in Examples 8-10, adding more hydrogen scavengers to the electrolyte does not affect the electrochemical performance of the electrolyte. In application, a higher proportion of hydrogen scavengers can be added to achieve better hydrogen scavenging performance and extend the life of the capacitor. However, other hydrogen scavengers have reached their maximum addable amount, and adding more will cause solute precipitation and reduce the flashover problem.

[0085] The electrolytes of Examples 8-10 and Comparative Examples 6-10 of this invention were added to a 450V 120μF capacitor and subjected to a 2000h load test at 105℃ (Vp=450Vdc, l=2.25A@120Hz, temperature 105℃). The initial capacitor capacity, loss tangent angle Tanδ, and leakage current were measured, and the capacitor capacity, loss tangent angle Tanδ, leakage current, and capacitor height Lc were measured after 2000h of operation. The specific measurement results are shown in Tables 5-7.

[0086] Table 5: Initial test parameters for capacitors under 105℃ load test

[0087] Table 6: Test results of capacitors under load tests at 105℃ for 500h and 1000h

[0088] Table 7: Test results of capacitors under load tests at 105℃ for 1500h and 2000h

[0089] As shown in Tables 5-7, in Examples 8-10, after a 2000-hour capacitor load test, the capacitors exhibited smaller capacitance changes and greater stability, with significantly smaller Lc changes and better bulging of the capacitor appearance. This indicates that the examples were more effective in suppressing gas generation, reducing capacitor volume expansion, and demonstrating superior hydrogen elimination performance compared to Comparative Examples 6-10, thus resulting in a longer capacitor lifespan.

[0090] The electrolytes from Examples 8-10 and Comparative Examples 6-10 of this invention were added to 450V 120μF capacitors (anode foil 625VF, 0.62, 120-125μm, 31mm) and subjected to 8 sets of voltage boost explosion-proof tests at 1A / 10V for 1 min. "KF" indicates that the capacitor opens normally under overvoltage, and "ZK" indicates that the capacitor explodes under overvoltage and fails to open normally. The specific measurement results are shown in Tables 8-9.

[0091] Table 8: Test parameters for capacitors undergoing a 600V 30S boost explosion-proof test

[0092] Table 9: Test parameters for capacitors undergoing a 620V 50S boost explosion-proof test

[0093] As shown in Tables 8 and 9, in multiple experiments conducted under 600V for 30 seconds and 620V for 50 seconds, Examples 8 and 10 consistently enabled the capacitor to open its valve stably under overvoltage, allowing for normal aging without explosion or fire. In contrast, Comparative Examples 6 and 10 showed multiple instances of explosion under overvoltage without proper valve opening. This indicates that the hydrogen scavenging agent in these examples exhibits better stability under high pressure, effectively suppressing hydrogen evolution in the electrolyte, reducing internal pressure in the capacitor, and thus minimizing the risk of explosion due to excessive pressure. This significantly reduces the risk of the explosion-proof valve failing to open.

[0094] From Tables 2-9, we can see that: (1) Solubility: The hydrogen scavengers in Examples 1-5 have excellent solubility in ethylene glycol and electrolyte, and can even be miscible in any ratio, avoiding the risk of capacitor failure due to precipitation in electrolyte or at low temperature; (2) Regarding the performance of the electrolyte: In Example 1, the amount of hydrogen scavenger added was 2% to 15%, which had good electrolyte performance, while the hydrogen scavengers in other comparative examples had already reached their solubility limit and were no longer soluble in the electrolyte; The nitro content of the hydrogen scavengers in Examples 1 to 5 was much higher than that in Comparative Examples 3 to 4, and adding the same proportion of hydrogen scavenger could achieve a better hydrogen scavenging effect; After adding a larger amount of the hydrogen scavenger of the present invention in Examples 8 to 10, there was still no effect on the conductivity, viscosity and flash voltage, which shows that the hydrogen scavenger of the present invention can be added to the electrolyte in a larger dose to extend the life of the capacitor; (3) In terms of hydrogen elimination performance and practical application: In Examples 8-10, the Lc change was significantly smaller after 2000h capacitor load test, and the appearance of the capacitor was better, indicating that the effect of suppressing gas generation was better, reducing the expansion of capacitor volume, and showing better hydrogen elimination performance than Comparative Examples 6-10. (4) In terms of high pressure performance: Examples 8 to 10 passed the 600V 30S and 620V 50S boost explosion-proof test, which has excellent high pressure stability, reduces the risk of valve opening failure, and enables the capacitor to open the valve stably under overvoltage. Compared with other hydrogen scavenging agents, it exhibits high pressure resistance, high stability and reliability.

[0095] In summary, the hydrogen scavenger provided by this invention exhibits excellent solubility, electrochemical properties, economy, hydrogen scavenging performance, and high-pressure resistance.

[0096] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A hydrogen scavenging agent for high-voltage aluminum capacitors, characterized in that, It has the structural formula shown in Equation I: ； In Formula I, a = 1 or 2; R1 is a nitro group, R2 represents an organic group containing 1 to 5 carbon atoms, and R3 is hydrogen or an organic group containing 1 to 5 carbon atoms.

2. The high-voltage capacitor hydrogen scavenger according to claim 1, characterized in that, R2 and R3 are each independently selected from hydrogen, hydrocarbon groups having 1 to 5 carbon atoms, or hydrocarbon groups having 1 to 5 carbon atoms containing substituents; the substituents are selected from one or more of hydroxyl, alcohol hydroxyl, and aryl.

3. The high-voltage capacitor hydrogen scavenger according to claim 1, characterized in that, The hydrogen scavenger is 2-[(2-nitrophenyl)oxy] ethylene-1-ol, 2-[(3-nitrophenyl)oxy] ethylene-1-ol, 2-[(4-nitrophenyl)oxy] ethylene-1-ol, 3-[(2-nitrophenyl)oxy] prop-1-ol, or 1-[(2-nitrophenyl)oxy] ethylene-1,2-diol.

4. A method for preparing a high-voltage capacitor hydrogen scavenger, characterized in that, Under the action of a catalyst, the compound shown in Formula II and the carbonate are added to a solvent and reacted at 70°C to 180°C. The solvent is then removed, and the mixture is obtained by cooling, separation and purification. The carbonate has the structure shown in Formula III. 、 ； In Formula II, R1 is a nitro group, and b = 1 or 2; In Formula III, R4 represents hydrogen or an organic group containing 1 to 2 carbon atoms, specifically one of hydrogen, methyl, ethyl, or hydroxymethyl.

5. The preparation method according to claim 4, characterized in that, The compound represented by Formula II is selected from 2-nitrophenol, 3-nitrophenol, or 4-nitrophenol; And / or, the carbonate is selected from ethylene carbonate, propylene carbonate or glycerol carbonate.

6. The preparation method according to claim 4, characterized in that, The molar ratio of the compound shown in Formula II to the carbonate is 1:(0.8-4). And / or, the reaction time is 3 to 40 hours.

7. The preparation method according to claim 4, characterized in that, The solvent is selected from at least one of ethers, alcohol ethers, amides, toluene, xylene, ethylbenzene, sulfones, sulfoxides, acetonitrile, and 1,2-dichloroethane; And / or, the catalyst is selected from at least one of potassium carbonate, sodium carbonate, sodium bicarbonate, sodium hydroxide, potassium fluoride, imidazole, N-methylimidazolium, 4-dimethylaminopyridine, 1,3-dimethylimidazolium iodide, lithium carbonate, cesium carbonate, potassium phosphate, sodium phosphate, disodium hydrogen phosphate, potassium hydroxide, DBU, and tetramethylguanidine.

8. The application of the high-voltage capacitor hydrogen scavenger according to any one of claims 1 to 3, or the high-voltage capacitor hydrogen scavenger prepared by the preparation method according to any one of claims 4 to 7, in the electrolyte of an aluminum electrolytic capacitor, wherein the solvent in the electrolyte of the aluminum electrolytic capacitor is ethylene glycol or γ-butyrolactone.

9. An electrolyte for an aluminum electrolytic capacitor, characterized in that, The components, by mass percentage, are: 2-15% hydrogen scavenger, 62.5-75.5% ethylene glycol, 1-5% ammonium pentaborate, 1-4% ammonium sebacic acid, 1-5% 10,11-dioctyleicosanoic acid, 1-5% 10-(6-(7-carboxyheptyl)-2,3-dihexylcyclohexyl)decanoic acid, 1-5% 8-[7,8-bis(7-carboxyheptyl)-4,5-dihexyl-6-octyl-decanonaphth-1-yl]octanoic acid, 1-5% polyvinyl alcohol, 1-4% mannitol, 0.1-0.5% ammonium hypophosphite, 0.1-0.5% diethylene glycol butyl ether, 1-3% ammonium potassium methylbenzeneate, and the balance being water; The hydrogen scavenger is the high-voltage capacitor hydrogen scavenger according to any one of claims 1 to 3, or the high-voltage capacitor hydrogen scavenger prepared by the preparation method according to any one of claims 4 to 7.

10. The application of the aluminum electrolytic capacitor electrolyte of claim 9 in aluminum electrolytic capacitors.

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