Microwave-assisted electrolytic method for improving the etching capacity of electrode foil for aluminum electrolytic capacitor

Abstract

The application discloses a microwave-assisted electrolysis method for improving the corrosion capacity of an electrode foil for an aluminum electrolytic capacitor, relates to the field of aluminum electrolytic capacitors, and opens a double-frequency microwave radiation source to alternately radiate the electrode foil in electrolyte in an electrolytic tank with double-frequency microwaves, simultaneously starts a direct-current power supply to apply a direct-current electric field to the aluminum foil, and forms an alternating microwave-assisted electrolysis environment; the microwave power and the electrolysis current are controlled, so that the aluminum foil is subjected to a high-efficiency corrosion reaction under the joint action of alternating microwaves and direct current until the required corrosion degree is reached. When the double-frequency microwaves are alternately radiated, the low-frequency microwaves have strong penetrability, can uniformly heat the whole electrolyte, make the temperature distribution of the electrolyte more uniform, avoid local overheating, and simultaneously promote the migration rate of ions in the electrolyte; the high-frequency microwaves have strong focusing property, and energy is more easily gathered on the surface of the aluminum foil, so that the surface atoms of the aluminum foil are activated through non-thermal effects, the activation energy of the corrosion reaction is reduced, and the kinetic process of the oxidation of the surface of the aluminum foil is accelerated.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of aluminum electrolytic capacitors, and particularly to a microwave-assisted electrolysis method for improving the corrosion capacity of electrode foils for aluminum electrolytic capacitors. BACKGROUND

[0002] Currently, aluminum electrolytic capacitors are widely used in electronic devices, and the performance of one of their core components, electrode foils, directly affects the capacity, operating voltage, and stability of the capacitors. Traditional electrode foils are usually prepared using chemical etching and direct current electrolysis processes, which can achieve a certain etching effect, but have obvious shortcomings in terms of etching efficiency, energy consumption, and environmental protection.

[0003] The main problems faced by existing technologies are low etching efficiency, high energy consumption, and high wastewater treatment costs, which have a certain impact on the environment.

[0004] Existing solutions and their limitations: Existing research attempts to improve etching efficiency by optimizing electrolyte formulations or adjusting electrolysis parameters, but these methods often result in decreased etching uniformity and increased energy consumption while improving etching speed, making it difficult to achieve both efficiency and environmental protection.

[0005] Challenges and opportunities: As electronic products become smaller and more energy-efficient, the market demand for high-capacity, low-loss aluminum electrolytic capacitors is increasing. At the same time, energy-saving and emission-reduction policies provide opportunities for green manufacturing technologies. Microwave-assisted technology is considered a key technology to solve the above problems due to its high efficiency and cleanliness. SUMMARY

[0006] To solve the technical problem of improving the etching efficiency of aluminum electrolytic capacitor electrode foils, the present application provides a microwave-assisted electrolysis method for improving the corrosion capacity of electrode foils for aluminum electrolytic capacitors. The technical solution is as follows:

[0007] The microwave-assisted electrolysis method for improving the corrosion capacity of electrode foils for aluminum electrolytic capacitors includes the following steps:

[0008] Step 1: Place the aluminum foil in the electrolyte in the electrolysis tank;

[0009] Step 2: Turn on the dual-frequency microwave radiation source to alternately irradiate the electrode foil in the electrolyte in the electrolysis tank with dual-frequency microwaves, and simultaneously start the direct current power supply to apply a direct current electric field to the aluminum foil, forming an alternating microwave-assisted electrolysis environment;

[0010] Step 3: Control the microwave power and electrolysis current to cause the aluminum foil to undergo a high-efficiency etching reaction under the combined action of alternating microwaves and direct current, until the desired etching degree is reached;

[0011] Step 4, stop microwave irradiation and direct current supply, take out the aluminum foil, clean and dry to obtain an electrode foil with high corrosion capacity.

[0012] By adopting the technical scheme, when the double-frequency microwave is alternately radiated, the low-frequency microwave has strong penetration and can uniformly heat the whole electrolyte, so that the temperature distribution of the electrolyte is more uniform, local overheating is avoided, and the migration rate of ions in the electrolyte is promoted; the high-frequency microwave has strong focusing, and energy is more easily gathered on the surface of the aluminum foil, so that the surface atoms of the aluminum foil are activated through non-thermal effect, the activation energy of the corrosion reaction is reduced, and the kinetics of the surface oxidation of the aluminum foil is accelerated.

[0013] The alternate radiation mode can avoid the problem of uneven distribution of single-frequency microwave energy (for example, single-frequency high-frequency is easy to cause local excess of surface energy, and single-frequency low-frequency is easy to cause insufficient reaction rate), realize the synergy of overall uniform heating-surface efficient activation, and improve the energy utilization efficiency.

[0014] The aluminum foil acts as an anode and undergoes an oxidation reaction under the action of a direct current field, forming corrosion pits on the surface; the electrolyte The oxidizing agent migrates to the anode under the action of the electric field, accelerates the dissolution of aluminum ions and the expansion of the corrosion pits, and the sulfate ions participate in the regulation of the pore size and distribution of the corrosion pits, inhibit excessive dissolution, and promote the formation of a porous structure.

[0015] Microwave radiation reduces the energy barrier of the aluminum foil corrosion reaction through thermal and non-thermal effects; a direct current field provides directional electrochemical driving force to ensure that the corrosion reaction proceeds in an orderly manner along the direction of the electric field. The synergy of the two significantly improves the rate and controllability of the corrosion reaction.

[0016] The synergy of double-frequency microwave alternate radiation and a direct current field can promote the formation of more intensive, deeper, and uniformly distributed corrosion pits on the surface of the aluminum foil, significantly increasing the specific surface area of the electrode foil, and thus greatly improving the corrosion capacity compared to traditional methods.

[0017] Through the synergy of double-frequency microwave and a direct current field, multiple optimizations are achieved in terms of improving corrosion capacity, reducing energy consumption, improving uniformity, and increasing efficiency, providing an efficient path for the green preparation of high-performance electrode foils.

[0018] Optionally, in step 1, the pretreated aluminum foil is immersed in a mixed electrolyte containing sulfuric acid and nitric acid.

[0019] Optionally, the mixed electrolyte is prepared by mixing sulfuric acid and nitric acid in a volume ratio of 1.5:1 to 3:1, and the pH value of the mixed electrolyte is adjusted to 2.5-3.0.

[0020] Optionally, 0.1wt%-0.3wt% of two-dimensional boron nitride nanosheets are added to the mixed electrolyte.

[0021] By adopting the technical scheme, the pretreated aluminum foil (after the steps of degreasing and pickling, etc. to remove the surface oil stains and the oxide layer) ensures that the aluminum foil substrate is directly in contact with the electrolyte, avoiding the obstruction of impurities to the corrosion reaction:

[0022] After the oxide layer is removed, the fresh metal substrate on the surface of the aluminum foil is exposed, and the redox reaction rate of the fresh metal substrate with sulfuric acid and nitric acid in the electrolyte is increased, thereby shortening the corrosion start-up time.

[0023] The mixed electrolyte (sulfuric acid-nitric acid volume ratio 1.5:1 to 3:1, pH 2.5-3.0) precisely regulates the corrosion environment to achieve a balance between efficient corrosion and structure protection.

[0024] Sulfuric acid provides a stable acidic environment for the corrosion reaction, and nitric acid accelerates the dissolution of the aluminum foil surface as a strong oxidizing agent. The ratio of the two can be flexibly adapted to different corrosion needs (such as high nitric acid ratio to increase the initial corrosion rate, high sulfuric acid ratio to inhibit excessive dissolution and promote the formation of deep hole structures), thereby significantly increasing the specific surface area.

[0025] Stabilizing the pH value at 2.5-3.0 can avoid excessive or insufficient acidity, reduce side reactions such as hydrolysis, and reduce production costs. 3+

[0026] Adding 0.1wt%-0.3wt% of two-dimensional boron nitride nanosheets (BNNS) to the electrolyte, the lateral size of BNNS is 50-200nm, and the thickness is ≤5nm. BNNS is directionally arranged to form an ion transmission channel in the electrolyte. BNNS has a high specific surface area and surface hydroxyl active sites, can adsorb Al 3+ and guide the corrosion pits to grow along the edges, so that the corrosion pit density is higher than that without addition, and the aperture deviation is controlled within 10%;

[0027] The insulation of BNNS can inhibit local electron transfer and avoid local over-corrosion (such as cracks and perforations) caused by the needle tip effect.

[0028] The dispersion of BNNS can reduce the surface tension of the electrolyte and reduce the adsorption of bubbles on the surface of the aluminum foil (bubbles are easy to cause local reaction interruption), so that the corrosion process is continuous and stable, thereby indirectly improving the capacity consistency of the electrode foil.

[0029] In step 2, the microwave power of the dual-frequency microwave radiation source is 300w-500w.

[0030] Optionally, the radiation frequency of the dual-frequency microwave radiation source is low frequency 2.0GHz-2.45GHz and high frequency 4.5GHz-5.8GHz, and the power ratio of low frequency and high frequency radiation is 1:2 to 2:1.

[0031] ​Optionally, in step 2, the dual-frequency microwave radiation source adopts a pulse microwave mode, and a phase synchronization controller is used to match the microwave pulse with the direct current pulse in reverse, so that the microwave pulse opening period accounts for 30%-70% of the direct current pulse period, and the microwave peak power appears at the zero phase of the direct current electric field.

[0032] By adopting the above technical solution, the frequency band (2.0-2.45 GHz) has stronger penetration and can uniformly act on the whole electrolyte, ensuring uniform temperature distribution of the electrolytic system and avoiding damage to the aluminum foil substrate caused by local overheating; the high-frequency band (4.5-5.8 GHz) energy is easier to focus on the surface of the aluminum foil, activates the surface atoms through molecular high-frequency vibration, reduces the corrosion reaction activation energy, and accelerates the surface oxidation and dissolution process. The two work together to achieve energy distribution of overall environment stability and local reaction intensification, which greatly improves the energy utilization rate compared with single-frequency microwave energy.

[0033] The overall heating effect of low-frequency microwave suppresses the edge effect, and the surface focusing effect of high-frequency microwave avoids the center under-corrosion, so that the size deviation of the aluminum foil surface corrosion pit is smaller.

[0034] The phase synchronization controller is used to make the microwave pulse reach the peak power at the zero phase of the direct current electric field, avoiding the energy redundancy caused by the superposition of microwave and direct current electric field energy. In the traditional synchronization mode, the superposition of energy easily causes local temperature to rise sharply, causing energy waste. The reverse matching mode can reduce the energy consumption per corrosion capacity.

[0035] The microwave pulse opening period accounts for 30%-70% of the direct current period, which can be dynamically adjusted according to the corrosion stage: 70% in the initial stage to improve the reaction rate, and 30% in the later stage to reduce energy input and further optimize energy consumption distribution.

[0036] At the zero phase of the direct current electric field, there is no directional electrochemical dissolution on the surface of the aluminum foil, and at this time the microwave peak power mainly acts on the diffusion of the corrosion products (such as Al 3+ ), avoiding the accumulation of the corrosion products in the corrosion pit to hinder the reaction, while reducing the excessive etching of the aluminum foil substrate. Compared with the traditional continuous microwave mode, the crack rate of the aluminum foil surface is reduced, and the integrity of the substrate structure is significantly improved.

[0037] The intermittent period of the pulse mode provides a buffer time for ion replenishment in the electrolyte, avoiding the sharp drop in local ion concentration caused by continuous reaction, making the corrosion rate more stable, and greatly improving the corrosion efficiency compared with the continuous radiation mode.

[0038] Optionally, in step 3, it further includes a step of dynamically optimizing the corrosion parameters based on in-situ optical monitoring data.

[0039] Optionally, the dynamic optimization of the corrosion parameters includes the following steps:

[0040] Step 31, collecting the aluminum foil surface reflection spectrum by the corrosion-resistant optical fiber sensor;

[0041] Step 32, analyzing the uniformity of the corrosion pit distribution based on the convolutional neural network;

[0042] Step 33, dynamically adjusting the microwave power ratio based on the analysis result.

[0043] By adopting the above technical solution, the corrosion-resistant optical fiber sensor can collect the aluminum foil surface reflection spectrum in real time (once every set time), and the spectral characteristics directly correspond to the density, size and distribution of the corrosion pits (for example, the reflectivity of the corrosion pit dense area will decrease due to scattering enhancement), which can reflect the local corrosion difference in real time compared with the traditional offline monitoring.

[0044] The convolutional neural network (CNN) can quickly identify the abnormal area of the corrosion pit distribution (such as local over-dense or over-sparse) by training a large number of corrosion samples containing different uniformity of corrosion pit images and spectral data, and the analysis accuracy is more than 95%, which is far superior to the subjective error of artificial judgment.

[0045] Based on the analysis result of CNN, the power ratio of the dual-frequency microwave is adjusted in real time, such as increasing the high-frequency microwave power to enhance the local activity in the under-corrosion area, and increasing the low-frequency microwave power to balance the overall reaction in the over-corrosion area, so that the size deviation of the aluminum foil surface corrosion pit is controlled within 5%, thereby ensuring the stability of the corrosion capacity.

[0046] By dynamically adjusting the microwave power ratio, the one-size-fits-all power setting can be avoided, and the energy can be more concentrated in the area that needs to be strengthened corrosion, and the energy consumption per unit corrosion capacity is reduced compared with the fixed parameter method.

[0047] Optionally, in step 4, the aluminum foil surface image and spectral data are collected every set time, the corrosion pit density, average size, uniformity index are calculated, and the CNN-LSTM model is used to analyze the corrosion degree index, and the microwave radiation and direct current supply are stopped when the set target corrosion degree index is reached.

[0048] By adopting the above technical solution, the aluminum foil surface image and spectral data are collected every 5 seconds, which can track the subtle changes of the corrosion reaction in real time, such as the dynamic evolution of the corrosion pit from sparse shallow hole to dense deep hole, and avoid the over-corrosion or under-corrosion caused by raw material difference (such as aluminum foil purity fluctuation) or environmental interference in the traditional timing control.

[0049] The comprehensive judgment ability of the CNN-LSTM model: the CNN (Convolutional Neural Network) extracts the spatial distribution characteristics (such as the uniformity index) of the corrosion pits in the image, the LSTM (Long Short-Term Memory Network) combines the historical spectral data to predict the corrosion trend, and the corrosion degree index (0-1, 1 for the target state) output by the fusion of the two can quantize the corrosion progress, which is significantly reduced in error compared with single image or spectral analysis. When the index reaches the set value, the machine is automatically stopped, so that the corrosion capacity deviation is controlled within 3%.

[0050] In summary, the present application includes at least one of the following beneficial technical effects:

[0051] The present application can provide a microwave-assisted electrolysis method for improving the corrosion capacity of electrode foil for aluminum electrolytic capacitors. When double-frequency microwaves are alternately radiated, low-frequency microwaves have strong penetration and can uniformly heat the entire electrolyte, making the temperature distribution of the electrolyte more uniform and avoiding local overheating, while promoting the migration rate of ions in the electrolyte. High-frequency microwaves have strong focusing and energy is more easily concentrated on the surface of the aluminum foil, activating the surface atoms of the aluminum foil through non-thermal effects, reducing the activation energy of the corrosion reaction, and accelerating the kinetics of the oxidation process on the surface of the aluminum foil.

[0052] The alternating radiation mode can avoid the problem of uneven distribution of single-frequency microwave energy, achieving a synergy of overall uniform heating and surface efficient activation, and improving energy utilization efficiency.

[0053] Microwave radiation reduces the energy barrier of the aluminum foil corrosion reaction through thermal and non-thermal effects; a direct current electric field provides directional electrochemical driving force to ensure that the corrosion reaction proceeds in an orderly manner along the direction of the electric field. The synergy of the two makes the surface of the aluminum foil simultaneously subjected to energy activation and electrochemical driving, significantly improving the rate and controllability of the corrosion reaction.

[0054] Through the synergy of double-frequency microwaves and a direct current electric field, multiple optimizations are achieved in terms of improving corrosion capacity, reducing energy consumption, improving uniformity, and improving efficiency, providing an efficient path for the green preparation of high-performance electrode foil. BRIEF DESCRIPTION OF DRAWINGS

[0055] Figure 1 is a flowchart of the microwave-assisted electrolysis method for improving the corrosion capacity of electrode foil for aluminum electrolytic capacitors according to the present application; DETAILED DESCRIPTION

[0056] The present application will be further described in detail below with reference to the accompanying drawings.

[0057] The present application discloses a microwave-assisted electrolysis method for improving the corrosion capacity of electrode foil for aluminum electrolytic capacitors.

[0058] Reference Figure 1 , Example 1, a microwave-assisted electrolysis method for improving the corrosion capacity of electrode foil for aluminum electrolytic capacitors, comprising the following steps:

[0059] Step 1, place the aluminum foil in the electrolyte in the electrolytic cell;

[0060] Step 2, turn on the dual-frequency microwave radiation source to alternately irradiate the electrode foil in the electrolyte in the electrolytic cell with dual-frequency microwaves, and at the same time start the direct current power supply to apply a direct current electric field to the aluminum foil, forming an alternating microwave-assisted electrolysis environment;

[0061] Step 3, control the microwave power and electrolysis current to make the aluminum foil undergo high-efficiency corrosion reaction under the combined action of alternating microwaves and direct current, until the desired corrosion degree is reached;

[0062] Step 4, stop the microwave radiation and direct current supply, take out the aluminum foil, and clean and dry it to obtain an electrode foil with high corrosion capacity.

[0063] When alternately irradiated with dual-frequency microwaves, low-frequency microwaves have strong penetration and can uniformly heat the entire electrolyte, making the temperature distribution of the electrolyte more uniform and avoiding local overheating, while promoting the migration rate of ions in the electrolyte; high-frequency microwaves have strong focusing ability and their energy is more easily concentrated on the surface of the aluminum foil, activating the surface atoms of the aluminum foil through non-thermal effects, reducing the activation energy of the corrosion reaction, and accelerating the kinetics of the oxidation process on the surface of the aluminum foil.

[0064] The alternating radiation mode can avoid the problem of uneven distribution of microwave energy at a single frequency (such as excessive local energy at a single high frequency, and insufficient reaction rate at a single low frequency), achieving a synergy of overall uniform heating and efficient surface activation, and improving energy utilization efficiency.

[0065] The aluminum foil, as the anode, undergoes oxidation reaction under the action of the direct current electric field, forming corrosion pits on the surface; the Oxidizing agents in the electrolyte migrate to the anode under the action of the electric field, accelerating the dissolution of aluminum ions and the expansion of corrosion pits, while sulfate ions participate in the regulation of the pore size and distribution of the corrosion pits, inhibiting excessive dissolution and promoting the formation of a porous structure.

[0066] Microwave radiation reduces the energy barrier of the aluminum foil corrosion reaction through thermal and non-thermal effects; the direct current electric field provides directional electrochemical driving force to ensure that the corrosion reaction proceeds in an orderly manner along the direction of the electric field. The synergy of the two significantly improves the rate and controllability of the corrosion reaction.

[0067] The synergy of dual-frequency microwave alternating radiation and direct current electric field can promote the formation of more intensive, deeper, and uniformly distributed corrosion pits on the surface of the aluminum foil, significantly increasing the specific surface area of the electrode foil, and thus greatly improving the corrosion capacity compared to traditional methods.

[0068] Through the synergistic innovation of dual-frequency microwave and direct current electric field, multiple optimizations are achieved in terms of improving corrosion capacity, reducing energy consumption, improving uniformity and efficiency, providing an efficient path for green preparation of high-performance electrode foil.

[0069] In step 1 of Example 2, the pretreated aluminum foil is immersed in a mixed electrolyte containing sulfuric acid and nitric acid.

[0070] In Example 3, the mixed electrolyte is prepared by mixing sulfuric acid and nitric acid in a volume ratio of 1.5:1 to 3:1, and the pH value of the mixed electrolyte is adjusted to 2.5-3.0.

[0071] In Example 4, 0.1wt%-0.3wt% of two-dimensional boron nitride nanosheets are added to the mixed electrolyte.

[0072] The pretreated aluminum foil (after degreasing, pickling and other steps to remove surface dirt and oxide layer) ensures that the aluminum foil substrate is directly in contact with the electrolyte, avoiding the interference of impurities on the corrosion reaction:

[0073] After removing the oxide layer, the fresh metal substrate on the surface of the aluminum foil is exposed, which increases the redox reaction rate with sulfuric acid and nitric acid in the electrolyte, shortening the corrosion start-up time;

[0074] The mixed electrolyte (sulfuric acid-nitric acid volume ratio 1.5:1 to 3:1, pH 2.5-3.0) precisely controls the corrosion environment to achieve a balance between efficient corrosion and structure protection;

[0075] Sulfuric acid provides a stable acidic environment for the corrosion reaction, and nitric acid acts as a strong oxidizing agent to accelerate the dissolution of the aluminum foil surface. The ratio of the two can be flexibly adapted to different corrosion needs (such as high nitric acid ratio to increase the initial corrosion rate, high sulfuric acid ratio to inhibit excessive dissolution and promote deep hole structure formation), significantly increasing the specific surface area;

[0076] Stabilizing the pH value at 2.5-3.0 can avoid excessive or insufficient acidity, reduce Al 3+ hydrolysis and other side reactions, and reduce production costs;

[0077] Adding 0.1wt%-0.3wt% of two-dimensional boron nitride nanosheets (BNNS) to the electrolyte, the lateral size of BNNS is 50-200nm, and the thickness is ≤5nm. BNNS forms ion transport channels by directional arrangement in the electrolyte, has high specific surface area and surface hydroxyl active sites, can adsorb Al 3+ and guide the corrosion pits to grow along its edge, making the corrosion pit density higher than without adding BNNS, and the aperture deviation controlled within 10%;

[0078] The insulating property of BNNS can inhibit local electron transfer and avoid local over-corrosion (such as cracks and perforations) caused by the needle tip effect;

[0079] The dispersion of BNNS can reduce the surface tension of electrolyte, reduce the adsorption of bubbles on the surface of aluminum foil (bubbles can easily cause local reaction interruption), improve the continuity and stability of the corrosion process, and indirectly improve the capacity consistency of the electrode foil.

[0080] In step 2 of Example 5, the microwave power of the dual-frequency microwave radiation source is 300-500 W.

[0081] In Example 6, the radiation frequency of the dual-frequency microwave radiation source is low frequency 2.0-2.45 GHz and high frequency 4.5-5.8 GHz, and the power ratio of low frequency to high frequency radiation is 1:2 to 2:1.

[0082] In step 2 of Example 7, the dual-frequency microwave radiation source uses pulse microwave mode, and a phase synchronization controller is used to match the microwave pulse and the direct current pulse in reverse, so that the microwave pulse opening period accounts for 30%-70% of the direct current pulse period, and the microwave peak power appears at the zero phase of the direct current electric field.

[0083] The frequency band (2.0-2.45 GHz) has stronger penetration and can uniformly act on the whole electrolyte, ensuring uniform temperature distribution of the electrolytic system and avoiding damage to the aluminum foil substrate caused by local overheating; the high frequency band (4.5-5.8 GHz) can easily focus energy on the surface of the aluminum foil, activate surface atoms through high-frequency molecular vibration, reduce the activation energy of the corrosion reaction, and accelerate the surface oxidation and dissolution process. The two work together to achieve energy distribution that stabilizes the overall environment and strengthens the local reaction, greatly improving the energy utilization rate compared to single-frequency microwave energy.

[0084] The overall heating effect of low-frequency microwave suppresses the edge effect, and the surface focusing effect of high-frequency microwave avoids central under-corrosion, so that the size deviation of the aluminum foil surface corrosion pits is smaller.

[0085] The microwave pulse reaches the peak power at the zero phase of the direct current electric field through the phase synchronization controller, avoiding the energy redundancy caused by the superposition of microwave and direct current electric field energy. In the traditional synchronization mode, the superposition of energy can easily cause a sudden rise in local temperature, resulting in energy waste. This reverse matching mode can reduce the energy consumption per unit corrosion capacity.

[0086] The microwave pulse opening period accounts for 30%-70% of the direct current period, which can be dynamically adjusted according to the corrosion stage: 70% in the early stage to improve the reaction rate, and 30% in the later stage to reduce energy input and further optimize energy consumption distribution.

[0087] During the zero phase of the direct current electric field, there is no directional electrochemical dissolution on the surface of the aluminum foil, and at this time the microwave peak power mainly acts on the corrosion products (such as Al 3+) diffusion, avoid its accumulation in the corrosion pits hinder the reaction, while reducing the excessive etching of aluminum foil substrate. Compared with the traditional continuous microwave mode, the aluminum foil surface crack rate is reduced, and the substrate structure integrity is significantly improved.

[0088] The pause period of the pulse mode provides buffer time for ion replenishment in the electrolyte, avoiding the sudden drop in local ion concentration caused by continuous reaction, making the corrosion rate more stable, and the corrosion efficiency is greatly improved compared with the continuous radiation mode.

[0089] In step 3 of example 8, it also includes a dynamic optimization step of corrosion parameters based on in-situ optical monitoring data.

[0090] In example 9, the dynamic optimization of corrosion parameters includes the following steps:

[0091] Step 31, collecting aluminum foil surface reflection spectrum by corrosion-resistant optical fiber sensor;

[0092] Step 32, analyzing the uniformity of corrosion pit distribution based on convolutional neural network;

[0093] Step 33, dynamically adjusting the microwave power ratio based on the analysis results.

[0094] Corrosion-resistant optical fiber sensor can collect aluminum foil surface reflection spectrum in real time (once every set time), and the spectral features directly correspond to the density, size and distribution of corrosion pits (for example, the reflectivity of the corrosion pit dense area will decrease due to scattering enhancement), which can reflect the local corrosion difference in real time compared with traditional offline monitoring.

[0095] Convolutional neural network (CNN) can quickly identify abnormal areas of corrosion pit distribution (such as local over-dense or over-sparse) by training a large number of corrosion samples containing corrosion pit images and spectral data with different uniformity, and the analysis accuracy is more than 95%, which is far superior to the subjective error of artificial judgment.

[0096] Based on the analysis results of CNN, the power ratio of double-frequency microwave is adjusted in real time, such as increasing the high-frequency microwave power to enhance the local activity in the under-corrosion area, and increasing the low-frequency microwave power to balance the overall reaction in the over-corrosion area, so that the size deviation of aluminum foil surface corrosion pit is controlled within 5%, thereby ensuring the stability of corrosion capacity.

[0097] By dynamically adjusting the microwave power ratio, it can avoid the one-size-fits-all power setting, so that the energy can be more concentrated in the area that needs to be strengthened corrosion, and the energy consumption per unit corrosion capacity is reduced compared with the fixed parameter method.

[0098] In Example 10, Step 4, surface images and spectral data of the aluminum foil are collected at regular intervals, the corrosion pit density, average size, uniformity index are calculated, and the CNN-LSTM model is used to analyze the corrosion degree index. When the set target corrosion degree index is reached, the microwave radiation and direct current supply are stopped.

[0099] Surface images and spectral data of the aluminum foil are collected every 5 seconds, allowing real-time tracking of subtle changes in the corrosion reaction, such as the dynamic evolution of corrosion pits from sparse shallow holes to dense deep holes, avoiding over-corrosion or under-corrosion caused by raw material differences (such as fluctuations in aluminum foil purity) or environmental interference.

[0100] The comprehensive judgment ability of the CNN-LSTM model: CNN (Convolutional Neural Network) extracts the spatial distribution features of corrosion pits in the image (such as uniformity index), LSTM (Long Short-Term Memory Network) combines historical spectral data to predict corrosion trends, and the corrosion degree index (0-1, 1 for the target state) output by the fusion of the two can quantify the corrosion progress, significantly reducing the error of single image or spectral analysis. When the index reaches the set value, the machine is automatically stopped, allowing the corrosion capacity deviation to be controlled within 3%.

[0101] The following specific examples illustrate the implementation principles of the microwave-assisted electrolysis method for improving the corrosion capacity of electrode foil for aluminum electrolytic capacitors:

[0102] I. Experimental materials and equipment:

[0103] Aluminum foil: purity 99.9%, thickness 100 μm, size after pretreatment 200 mm x 100 mm (pretreatment steps: 5% NaOH solution 50°C degreasing 5 min, 10% nitric acid room temperature pickling 3 min, deionized water washing to neutral, drying);

[0104] Electrolyte: sulfuric acid and nitric acid mixed at a volume ratio of 2:1, pH adjusted to 2.8, and 0.2wt% two-dimensional boron nitride nanosheet (BNNS, lateral size 50-200 nm, thickness ≤5 nm, ultrasonic dispersion 300W for 30 min) added;

[0105] Equipment: dual-frequency microwave electrolytic cell (with corrosion-resistant optical window), phase-synchronous controller, direct current source (0-5A / dm 2 Adjustable), corrosion-resistant optical fiber sensor (wavelength 400-800 nm), high-definition camera (20 million pixels), CNN-LSTM control system.

[0106] II. Preparation steps:

[0107] Step 1: Place the electrolyte and aluminum foil:

[0108] The prepared electrolyte is injected into the electrolytic cell, and the pretreated aluminum foil is completely immersed in the electrolyte to ensure that the surface is free of bubbles. The aluminum foil is connected to the anode of a direct current power supply, and the stainless steel plate is the cathode.

[0109] Step 2: Dual-frequency pulse microwave and direct current field start:

[0110] Turn on the dual-frequency microwave radiation source: low frequency 2.45 GHz, high frequency 5.8 GHz, power ratio 1:1. Total power 400 W, i.e. low frequency 200 W + high frequency 200 W;

[0111] Start pulse mode: microwave pulse frequency 2 Hz, duty cycle 50%, through phase synchronization controller to make microwave pulse and direct current pulse reverse matching (microwave peak power appears in direct current field zero phase, microwave on period accounts for 50% of direct current period);

[0112] Apply direct current field: current density 1.5 A / dm 2 , direct current pulse period 1 s (0.5 s power on, 0.5 s zero).

[0113] Step 3: In-situ monitoring and dynamic parameter optimization:

[0114] Corrosion-resistant optical fiber sensor collects aluminum foil surface reflectance spectrum every 0.5 seconds, and high-definition camera synchronously collects surface image;

[0115] Convolutional neural network (CNN) analyzes the uniformity of corrosion pit distribution in real time (input image and spectrum data, output uniformity index);

[0116] When local under-corrosion is detected (uniformity index <0.8), automatically increase the high-frequency microwave power of the area to 220 W (low frequency remains 200 W); when local over-corrosion (uniformity index >0.95), reduce the high-frequency power of the area to 180 W, dynamically maintain the uniformity of corrosion.

[0117] Step 4: End point control and post-processing:

[0118] CNN-LSTM model calculates corrosion pit density (number / μm 2 ), average size (nm), and uniformity index every 0.5 seconds, and outputs corrosion degree index;

[0119] When the corrosion degree index reaches 0.95 (preset target), automatically stop microwave radiation and direct current supply (total electrolysis time 45 min);

[0120] Take out the aluminum foil, rinse with deionized water 3 times (1 min each time), vacuum dry at 60°C for 2 h, and obtain the target electrode foil.

[0121] High corrosion capacity electrode foil detection report:

[0122] Test object: electrode foil prepared in the above example (No. S1), electrode foil prepared by conventional direct current electrolysis method (control group, No. CK);

[0123] The test results are shown in Table 1:

[0124] Table 1

[0125]

[0126] The corrosion capacity of example S1 reaches 128 μF / cm 2 , which is increased by 34.7% compared with the control group, mainly due to the synergistic effect of double-frequency microwave and direct current field, the double-frequency alternating radiation promotes the intensive growth of corrosion pits (density 85 / μm 2 ), the BNNS guides the directional deepening of the corrosion pits (depth 800 nm), and significantly increases the specific surface area (0.85 m 2 / g).

[0127] The surface roughness Ra of example S1 is 0.32 μm, which is only 55.2% of the control group, which benefits from the dynamic parameter optimization (CNN analysis + power ratio adjustment) of in-situ optical monitoring, the size deviation of the corrosion pits is controlled within 5%, and the edge over-corrosion problem of the control group is avoided.

[0128] The unit energy consumption of example S1 is 0.85 kWh / m 2 , which is reduced by 19.8% compared with the control group, which is due to the reverse matching of pulsed microwave and direct current pulse (reducing energy redundancy) and electrolyte recycling; the leakage current is reduced by 46.7%, which is due to the synergistic effect of BNNS inhibiting local over-corrosion and phosphoric acid passivation film, which improves the insulation stability of the electrode foil.

[0129] In this embodiment, through the synergistic effect of double-frequency microwave alternating radiation, pulse phase matching, in-situ intelligent control and other technologies, the corrosion capacity of the prepared electrode foil reaches 128 μF / cm 2 , which is increased by 34.7% compared with the conventional method, and the energy consumption is reduced by 19.8%, the uniformity is significantly improved, which fully meets the demand of high-end aluminum electrolytic capacitor (such as automobile electronics, aerospace field) for high-capacity, low-loss electrode foil.

[0130] The above are preferred embodiments of the present application, but do not limit the protection scope of the present application, therefore: any equivalent changes made according to the structure, shape, principle of the present application should be covered within the protection scope of the present application.

Claims

1. A microwave-assisted electrolysis method for improving the corrosion capacity of electrode foil in aluminum electrolytic capacitors, characterized in that, Includes the following steps: Step 1: Place the aluminum foil in the electrolyte in the electrolytic cell; Step 2: Turn on the dual-frequency microwave radiation source to irradiate the electrode foil in the electrolyte in the electrolytic cell with alternating dual-frequency microwaves. At the same time, turn on the DC power supply to apply a DC electric field to the aluminum foil to form an alternating microwave-assisted electrolysis environment. Step 3: Control the microwave power and electrolysis current to make the aluminum foil undergo a highly efficient corrosion reaction under the combined action of alternating microwaves and direct current until the desired degree of corrosion is achieved; Step 4: Stop microwave radiation and DC power supply, remove aluminum foil, clean and dry it to obtain electrode foil with high corrosion capacity; The radiation frequencies of the dual-frequency microwave radiation source are low frequency 2.0GHz-2.45GHz and high frequency 4.5GHz-5.8GHz, and the power ratio of low frequency to high frequency radiation is 1:2 to 2:

1. In step 2, the dual-frequency microwave radiation source adopts pulsed microwave mode, and the microwave pulse is matched with the DC pulse in reverse through the phase synchronization controller, so that the microwave pulse on period accounts for 30%-70% of the DC pulse period, and the microwave peak power appears at the DC electric field zero phase.

2. The microwave-assisted electrolysis method for improving the corrosion capacity of electrode foil in aluminum electrolytic capacitors according to claim 1, characterized in that, In step 1, the pretreated aluminum foil is immersed in a mixed electrolyte containing sulfuric acid and nitric acid.

3. The microwave-assisted electrolysis method for improving the corrosion capacity of electrode foil in aluminum electrolytic capacitors according to claim 2, characterized in that, The mixed electrolyte is composed of sulfuric acid and nitric acid in a volume ratio of 1.5:1 to 3:1, and the pH value of the mixed electrolyte is adjusted to 2.5-3.

0.

4. The microwave-assisted electrolysis method for improving the corrosion capacity of electrode foil in aluminum electrolytic capacitors according to claim 3, characterized in that, Add 0.1wt%-0.3wt% of two-dimensional boron nitride nanosheets to the mixed electrolyte.

5. The microwave-assisted electrolysis method for improving the corrosion capacity of electrode foil in aluminum electrolytic capacitors according to claim 1, characterized in that, In step 2, the microwave power of the dual-frequency microwave radiation source is 300W-500W.

6. The microwave-assisted electrolysis method for improving the corrosion capacity of electrode foil in aluminum electrolytic capacitors according to claim 5, characterized in that, Step 3 also includes a dynamic optimization step for corrosion parameters based on in-situ optical monitoring data.

7. The microwave-assisted electrolysis method for improving the corrosion capacity of electrode foil in aluminum electrolytic capacitors according to claim 6, characterized in that, Dynamic optimization of corrosion parameters includes the following steps: Step 31: Collect the surface reflectance spectrum of the aluminum foil using a corrosion-resistant fiber optic sensor; Step 32: Analyze the uniformity of corrosion pit distribution based on convolutional neural networks; Step 33: Dynamically adjust the microwave power ratio based on the analysis results.

8. The microwave-assisted electrolysis method for improving the corrosion capacity of electrode foil in aluminum electrolytic capacitors according to claim 7, characterized in that, In step 4, images and spectral data of the aluminum foil surface are collected at set intervals to calculate the corrosion pit density, average size, and uniformity index. The corrosion degree index is analyzed using a CNN-LSTM model. When the set target corrosion degree index is reached, microwave radiation and DC power supply are stopped.

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