A method for producing an electrode foil for a capacitor and an electrode foil for a capacitor

Abstract

The application discloses a preparation method of an electrode foil for a capacitor, and aims at solving the problem that a conductive polymer cannot be filled densely in a micro-hole of an aluminum foil. The method comprises the following steps: coating an insulating shielding glue on a non-effective reaction area of the aluminum foil; generating a conductive polymer network in micro-holes of an effective reaction area by alternately immersing a monomer solution and an oxidant solution for multiple times; infiltrating a solidifiable gel electrolyte precursor into the network and solidifying in situ to form a solid gel electrolyte filled in the network; and finally forming a composite conductive layer on the effective reaction area. By constructing a double transmission channel with electronic and ionic conduction functions and optimizing a charge extraction interface, the application significantly improves the capacity extraction rate, high-temperature stability and reliability of the capacitor, and reduces an equivalent series resistance.

Description

Technical Field

[0002] This invention relates to the field of capacitor manufacturing technology, and in particular to a method for preparing electrode foil for capacitors. Background Technology

[0003] Multilayer polymer aluminum electrolytic capacitors are widely used in automotive electronics, communication power supplies, and other fields due to their low equivalent series resistance and excellent high-frequency characteristics. Their performance hinges on the use of aluminum foil, which has a large specific surface area after etching treatment, as the electrode. Current technology typically involves in-situ polymerization within the microporous structure of the aluminum foil to form a conductive polymer layer to construct the electrode.

[0004] However, with the increasing demand for higher capacitance and smaller size in capacitors, the micropores formed by aluminum foil etching have increasingly higher aspect ratios. Existing in-situ polymerization methods struggle to achieve complete and dense filling of the micropores in this deep-pore structure. This results in numerous discontinuous and incompletely covered defects in the formed conductive polymer network, preventing the full utilization of the aluminum foil's large internal surface area and leading to a lower actual capacitance extraction rate for the capacitor. Furthermore, the incomplete conductive network increases the path resistance for charge to be conducted from the depths of the micropores to the external circuit. Simultaneously, traditional electrolytes are prone to performance degradation under high-temperature conditions. These defects collectively limit the improvement of the capacitor's overall performance, making it difficult to meet the stringent requirements of high-power, high-reliability applications. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing electrode foil for capacitors and an electrode foil for capacitors prepared by the method, which aims to solve the charge transport bottleneck problem caused by the non-dense and discontinuous filling of conductive polymer deep in the micropores of aluminum foil electrodes in the prior art. This problem is specifically manifested as low capacitance extraction rate, high equivalent series resistance, and unstable high-temperature performance.

[0006] To achieve the above objectives, the present invention provides a method for preparing electrode foil for capacitors, comprising the following steps: dividing an effective reaction region and an ineffective reaction region on an aluminum foil having a microporous structure and an alumina dielectric layer, and coating the ineffective reaction region with an insulating shielding adhesive that does not wet the monomer solution and the oxidant solution; generating a conductive polymer network in situ within the micropores of the effective reaction region by repeatedly and alternately impregnating the monomer solution and the oxidant solution; coating a curable gel electrolyte precursor onto the effective reaction region and allowing it to penetrate into the conductive polymer network, then heating to cure the curable gel electrolyte precursor in situ, forming a solid gel electrolyte filled in the conductive polymer network; and coating the effective reaction region to form a composite conductive layer.

[0007] Optionally, the monomer solution contains 3,4-ethylenedioxythiophene, and the oxidant solution contains persulfate.

[0008] Optionally, the number of alternating impregnation cycles is 15-20 times.

[0009] Optionally, the curable gel electrolyte precursor comprises polyethylene glycol diacrylate.

[0010] Optionally, the heating temperature is 90-110°C.

[0011] Optionally, the step of forming the composite conductive layer includes: sequentially forming a conductive carbon layer and a conductive silver layer.

[0012] Optionally, the conductive carbon layer comprises at least one selected from graphene and carbon nanotubes.

[0013] The present invention also provides an electrode foil for a capacitor, comprising an aluminum foil having a microporous structure and an alumina dielectric layer, wherein the aluminum foil is divided into an effective reaction region and an ineffective reaction region, wherein a composite electrolyte system consisting of a conductive polymer network and a solid gel electrolyte filled therebetween is formed in the micropores within the effective reaction region; a composite conductive layer is disposed on the surface of the effective reaction region; and an insulating shielding layer is disposed on the surface of the ineffective reaction region.

[0014] Optionally, the conductive polymer network is a poly(3,4-ethylenedioxythiophene) network.

[0015] Optionally, the composite conductive layer includes a conductive carbon layer and a conductive silver layer, and the conductive carbon layer contains at least one selected from graphene and carbon nanotubes.

[0016] The beneficial effects of this invention are as follows: 1. Significantly improved capacity extraction rate: Through multiple cycles of alternating impregnation polymerization, a dense and continuous conductive polymer network can be formed within the micropores of the aluminum foil, greatly improving the utilization rate of the effective surface area of ​​the aluminum foil micropores. Compared with existing processes with incomplete filling, the capacity extraction rate is significantly improved. 2. Improved charge extraction efficiency and high-temperature stability: By forming a solid gel electrolyte through in-situ curing, a dual transport channel with both electronic and ion conduction functions is constructed together with the conductive polymer network, solving the bottleneck of charge conduction deep within the micropores and improving charge extraction efficiency. At the same time, the structurally stable solid gel electrolyte fundamentally improves the high-temperature operating performance and long-term reliability of the capacitor. 3. Effectively reduced equivalent series resistance: By coating the surface to form a composite conductive layer, a gradient-buffered low-resistance extraction interface is constructed, effectively reducing the equivalent series resistance of the capacitor and improving its high-frequency response characteristics. 4. Improved product consistency and reliability: By coating the reaction zone with an insulating shielding adhesive that does not wet the monomer solution and the oxidant solution before polymerization, ineffective polymerization at the electrode edges and potential leakage paths are avoided, thereby improving product consistency and reliability. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a flowchart of a method for preparing electrode foil for a capacitor according to an embodiment of the present invention.

[0019] Figure 2 This is a comparative schematic diagram of the formation process of the conductive polymer network in the micropores in an embodiment of the present invention.

[0020] Figure 3 This is a schematic diagram of the microstructure and principle of the "dual transmission channel" inside the micropore in an embodiment of the present invention.

[0021] Figure 4 This is a schematic cross-sectional view of the electrode foil for a capacitor prepared according to an embodiment of the present invention.

[0022] In the figure: 10, aluminum foil; 20, alumina dielectric layer; 31, loose PEDOT layer; 32, dense PEDOT network; 40, solid gel electrolyte; 50, electron conduction path; 60, ion conduction path; 200, alumina dielectric layer containing microporous structure; 300, PEDOT / gel composite electrolyte layer; 400, conductive carbon layer; 500, conductive silver layer. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings. The described embodiments should not be considered as limitations on this application. All other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application. Unless otherwise defined, all technical and scientific terms used in the embodiments of this application have the same meaning as commonly understood by those skilled in the art. The terminology used in the embodiments of this application is for the purpose of describing the embodiments of this application only and is not intended to limit this application.

[0024] Before providing a further detailed description of the embodiments of this application, some of the nouns and terms involved in the embodiments of this application will be explained. The nouns and terms involved in the embodiments of this application are subject to the following interpretations.

[0025] (1) Effective reaction area / ineffective reaction area: refers to the areas on the aluminum foil that serve as the substrate, which are artificially divided according to the needs of capacitor design. The effective reaction area is the core working area where conductive polymers are expected to polymerize, form electrode active materials, and ultimately contribute to capacitance; the ineffective reaction area is the area where no reaction is expected to occur, such as the edge of the electrode foil or near the lead end. It is protected by coating with insulating shielding adhesive to prevent ineffective polymerization, avoid leakage, and ensure the consistency of product performance.

[0026] (2) Insulating shielding adhesive: refers to a material that does not wet the monomer solution and oxidant solution used in the embodiments of the present invention. After being coated on the non-effective reaction area, it can form a physical barrier, effectively preventing the subsequent chemical solution from contacting and penetrating to the aluminum foil surface in that area, thereby achieving precise physical isolation and regional selective reaction.

[0027] (3) Conductive polymer network: refers to a three-dimensional, continuous conductive polymer framework formed in the microporous structure and pores of an aluminum foil substrate through in-situ chemical polymerization. This network serves as the main pathway for electron conduction within the micropores, and its density and continuity directly affect the charge collection efficiency and capacity extraction rate. In the preferred embodiment of this application, this network is specifically a poly(3,4-ethylenedioxythiophene) (PEDOT) network.

[0028] (4) Solid gel electrolyte: refers to a solid ionic conductor formed by in-situ solidification of a liquid curable gel electrolyte precursor through heating or other means, filling the gaps in a conductive polymer network. As the main pathway for ion migration and conduction within the micropores, the solid-state properties of this electrolyte endow the capacitor with excellent high-temperature stability and long-term reliability.

[0029] (5) Composite electrolyte system: refers to a composite structure formed by the above-mentioned conductive polymer network and the solid gel electrolyte filled therein, which are interpenetrated and tightly combined. This system has both electronic and ion conduction functions at the microscopic level, and is the core structure for achieving efficient charge transport in this application.

[0030] (6) Dual transport channels: This refers to the coexistence of electron transport channels composed of conductive polymer networks and ion transport channels composed of solid gel electrolytes in the above-mentioned composite electrolyte system. These two channels work together at the microscale to solve the problem of efficient and rapid charge transport deep within microporous structures with large depth-to-width ratios.

[0031] Please see Figure 1 This application aims to provide a method for preparing electrode foil for capacitors, thereby solving the technical problems in the prior art, such as low capacitance extraction rate, high equivalent series resistance, and unstable high-temperature performance, caused by the non-dense and discontinuous filling of conductive polymer deep within the micropores of aluminum foil electrodes. The core of this method lies in constructing a highly efficient charge transport system within the microporous structure through a series of synergistic process steps.

[0032] The method first includes a region definition step (S102). Specifically, on an aluminum foil 10 that has been pre-etched and formed, with a microporous structure and an alumina dielectric layer 20 already formed on its surface, effective reaction areas and ineffective reaction areas are artificially divided. Subsequently, an insulating shielding adhesive is coated on the surface of the ineffective reaction areas (such as the edges of the electrode foil). The purpose of this step is to precisely define the area where subsequent chemical reactions will occur through physical isolation. In the prior art, due to inadequate control of the reaction area, ineffective conductive polymer deposition often occurs in non-working areas such as electrode edges. This not only wastes expensive chemical raw materials, but more seriously, it may form potential leakage paths, affecting the reliability and consistency of the final product. By coating with an insulating shielding adhesive that does not wet the subsequent reaction solution, this step solves this problem at its source, ensuring that all subsequent high-value process steps act precisely on the pre-defined effective reaction area, thereby improving the product yield and the uniformity of electrical performance.

[0033] Next, an in-situ polymerization step (S103) of the conductive polymer network is performed. This step generates a conductive polymer network 32 within the micropores of a region-defined effective reaction area by repeatedly cyclically impregnating the monomer solution and oxidant solution. The principle is that in each cycle, monomer molecules first adsorb onto the inner wall of the micropores, and then polymerization is initiated by the introduced oxidant, forming a thin polymer layer. By repeating this process multiple times, the polymer layer grows layer by layer, ultimately forming a dense and continuous three-dimensional network structure. (See also...) Figure 2 In existing technologies, the few polymerization processes often only form a loose PEDOT layer 31 at the micropore opening or in a shallow layer, failing to effectively penetrate and fill the micropores with large aspect ratios, resulting in a significant waste of internal surface area. This application achieves effective filling of the deep micropores through a "multiple cyclic alternating impregnation" method, forming a layer such as... Figure 2 The dense PEDOT network 32 shown solves the fundamental problem of non-dense and discontinuous filling of conductive polymers, and builds a solid framework for efficient electron conduction.

[0034] After forming a dense conductive polymer network 32, a solid gel electrolyte filling step (S104) is performed. An aluminum foil with the conductive polymer network 32 is coated with a curable gel electrolyte precursor, which is then fully incorporated into the gaps between the conductive polymer network 32. The foil is then cured in situ by heating to form a solid gel electrolyte 40. (See also...) Figure 3 The design goal of this step is to construct an efficient ion conduction pathway that coexists with the electronic conduction pathway. The conductive polymer network 32 itself is an excellent electronic conductor but lacks ion conduction capability. By generating a solid gel electrolyte 40 in situ within its gaps, an ion conduction path 60 is formed. In this way, electrons can be transported through the electronic conduction path 50 (i.e., the conductive polymer network 32), while ions required for capacitor operation can migrate through the ion conduction path 60 (i.e., the solid gel electrolyte 40). This interwoven and complementary "dual transport channel" structure completely overcomes the "last mile" of charge transport deep within the micropores, solving the bottleneck of only having an electronic pathway while ion transport is blocked. Simultaneously, the use of a solid electrolyte fundamentally improves the high-temperature stability and safety of the capacitor.

[0035] Finally, a composite conductive layer is coated onto the surface of the effective reaction region (S105). The purpose of this step is to provide a low-resistance collection and extraction channel for the charge conducted from the micropores. While the conductive polymer network 32 inside the micropores solves the internal conduction problem, the charge still needs to be efficiently discharged to the external circuit. By constructing one or more specialized conductive layers on the electrode foil surface, the overall equivalent series resistance (ESR) of the electrode can be effectively reduced, improving its high-frequency response characteristics. Through the synergistic effect of the above four steps, the electrode foil prepared by this method achieves significant improvements in capacity, internal resistance, and stability.

[0036] Furthermore, in a preferred embodiment, to generate a conductive polymer network 32 with higher conductivity and better stability, the monomer solution may contain 3,4-ethylenedioxythiophene (EDOT), while the oxidant solution may contain persulfate, such as sodium persulfate or ammonium persulfate. EDOT is a precursor for generating the conductive polymer poly(3,4-ethylenedioxythiophene) (PEDOT), which is currently recognized as one of the conductive polymers with the best overall performance, exhibiting extremely high conductivity and excellent chemical and thermal stability. Using persulfate as an oxidant results in mild reaction conditions that are easy to control and are relatively inexpensive. This material system ensures that the conductive polymer network 32 generated on the inner wall of the micropores has excellent electronic conductivity, laying a solid material foundation for constructing an efficient electronic conduction path 50.

[0037] In another preferred embodiment, the number of alternating impregnation cycles is limited to 15-20 times. This is an optimized process window determined after extensive experimental verification. The principle is that if the number of cycles is too low (e.g., less than 15 times), the polymer deposition will be insufficient, making it impossible to form a polymer layer as described above. Figure 2 The dense PEDOT network 32 shown has discontinuous conductive pathways, still exhibiting a low capacity extraction rate. While excessive cycling (e.g., exceeding 20 cycles) slightly improves network density, it can lead to overfilling or even clogging of micropores, hindering ion migration. Furthermore, it significantly increases production time and cost, reducing economic efficiency. Therefore, by controlling the number of cycles to 15-20, an optimal balance can be achieved between ensuring the formation of a high-quality conductive network and controlling production costs, thus unifying technical effectiveness and economic efficiency.

[0038] Furthermore, in an optional embodiment, the curable gel electrolyte precursor may comprise polyethylene glycol diacrylate (PEGDA). PEGDA is a common photocurable or thermocurable monomer, and the polymer network formed after curing exhibits good flexibility and solvation ability for electrolyte ions. The principle is that the ether oxygen bonds in the PEGDA molecular chain can coordinate with the cations of the electrolyte salt, facilitating ion dissociation and migration, thereby ensuring that the formed solid gel electrolyte 40 has high ionic conductivity. Simultaneously, the flexible network structure formed after cross-linking and curing can well adapt to the volume changes of the electrode during charging and discharging, buffering stress and improving the structural stability of the composite electrolyte system 300. By using PEGDA, a solid gel electrolyte 40 with both high ionic conductivity and excellent mechanical properties can be prepared.

[0039] In a preferred embodiment, when using a PEGDA system containing a thermal initiator, the curing temperature can be controlled between 90-110°C. This is also an optimized process temperature range. The principle is that below 90°C, the decomposition rate of the thermal initiator is too slow, leading to incomplete gel curing or excessively long curing time, affecting production efficiency and product performance. Above 110°C, on the one hand, the solvent inside the gel may evaporate too quickly, causing bubble defects; on the other hand, it may trigger unnecessary side reactions, or even cause thermal damage to the formed conductive polymer network 32. Therefore, controlling the curing temperature between 90-110°C ensures that the gel cures completely and uniformly within a reasonable time, forming a dense and stable solid gel electrolyte 40.

[0040] Furthermore, to maximize the reduction of charge extraction resistance, the step of forming the composite conductive layer (S105) can specifically include: sequentially forming a conductive carbon layer 400 and a conductive silver layer 500. The design principle of this dual-layer structure lies in constructing a functionally graded interface. The conductive carbon layer 400, which is in direct contact with the composite electrolyte system 300, has a material (such as graphite or carbon paste) that closely matches the work function of the conductive polymer, resulting in low contact resistance and the ability to gently collect the charge conducted from numerous micropores. On top of the conductive carbon layer 400, a conductive silver layer 500 with extremely low resistivity is coated as the primary current collection and extraction layer. This gradient structure of "carbon layer collection, silver layer extraction" effectively avoids problems such as the Schottky barrier that may arise from direct contact between highly conductive materials (such as silver) and semiconducting conductive polymers, thereby achieving a lower equivalent series resistance than a single conductive layer.

[0041] In another preferred embodiment, to further enhance the conductivity of the conductive carbon layer 400, it may include at least one selected from graphene and carbon nanotubes. The principle is that both graphene (a two-dimensional sheet structure) and carbon nanotubes (a one-dimensional tubular structure) possess extremely high aspect ratios and excellent intrinsic conductivity. Incorporating them into the conductive carbon paste allows for the construction of a long-range, highly efficient conductive network within the carbon layer, much like building a "highway" on top of existing conductive pathways, significantly improving the collection and transport efficiency of charge in the planar direction of the carbon layer. In this way, the equivalent series resistance of the electrode can be significantly reduced, improving its response characteristics at high frequencies.

[0042] Please see Figure 4 This application also provides an electrode foil for a capacitor prepared using any of the methods described above. This electrode foil has a novel multilayer composite structure. Its main body is an aluminum foil 10, on which an alumina dielectric layer 200, formed by etching and formation processes and containing a microporous structure, is disposed. Effective reaction regions and ineffective reaction regions are divided on the aluminum foil. An insulating shielding layer is disposed on the surface of the ineffective reaction regions. This insulating shielding layer is the structure formed after the insulating shielding adhesive applied in the method steps has cured, and its function is electrical isolation and physical protection.

[0043] Within the effective reaction region, its microstructure is the core of this invention. Inside the micropores of the alumina dielectric layer 200, a composite electrolyte system 300 is formed, consisting of a dense conductive polymer network 32 and a solid gel electrolyte 40 filled therebetween. This system possesses both electronic and ionic conduction capabilities, thus constituting the aforementioned "dual transport channel." Furthermore, a composite conductive layer is disposed on the surface of the effective reaction region, i.e., on top of the composite electrolyte system 300. This composite conductive layer collects and extracts the charges conducted from deep within the micropores. This complete and optimized structure, from the substrate to the surface, from the microscopic to the macroscopic, gives this electrode foil a fundamental performance advantage over existing products.

[0044] Furthermore, in a preferred product form, the conductive polymer network is a poly(3,4-ethylenedioxythiophene) (PEDOT) network. This means that the product is prepared using 3,4-ethylenedioxythiophene as a monomer, and therefore its internal electronic conduction path 50 has extremely high conductivity and stability, ensuring that the electrode foil has an excellent electrochemical performance basis.

[0045] In another preferred embodiment, the composite conductive layer comprises a conductive carbon layer 400 and a conductive silver layer 500, wherein the conductive carbon layer 400 contains at least one selected from graphene and carbon nanotubes. This corresponds to a product prepared using an optimized charge extraction scheme. Its structure is as follows. Figure 4 As shown, from bottom to top, the structure consists of an aluminum foil 10, an alumina dielectric layer 200 containing a microporous structure, a PEDOT / gel composite electrolyte layer 300 filled within the micropores, a conductive carbon layer 400 containing nanomaterials, and an outermost conductive silver layer 500. This structure fully embodies the end-to-end optimization concept of this invention, from charge generation inside the micropores to the output from the external circuit, representing the optimal performance form of this invention.

[0046] The technical solution of this application will be described in more detail below through more specific embodiments. It should be understood that these embodiments are merely examples used to more clearly illustrate the core technology of the present invention, and do not constitute any limitation on the scope of protection of the present invention.

[0047] In a basic implementation, a method for preparing electrode foil for a capacitor can be referred to... Figure 1 As shown. First, an aluminum foil 10, having undergone conventional etching and formation treatment, with an alumina dielectric layer 20 having a nanoscale microporous structure formed on its surface, is taken. Using precision coating techniques such as screen printing, a layer of insulating shielding adhesive that does not wet subsequent reaction solutions is uniformly coated on the edges and other predetermined non-effective reaction areas of the aluminum foil. This adhesive is then cured by heating or ultraviolet light to form a strong physical isolation layer. This step (S102) ensures that all subsequent chemical processes occur precisely in the central effective reaction area.

[0048] Subsequently, the aluminum foil undergoes multiple cycles of alternating impregnation to generate a conductive polymer network 32 (S103). Specifically, the aluminum foil is first impregnated in a monomer solution, and vacuuming or other methods are used to ensure that the solution penetrates deep into the micropores and adsorbs onto the inner wall of the alumina dielectric layer 20. After removal, it is impregnated again in an oxidant solution, initiating in-situ polymerization of the adsorbed monomers. This completes one cycle. This cycle is repeated multiple times, allowing the conductive polymer to grow layer by layer on the inner wall of the micropores. Figure 2 As shown, this method overcomes the problem of uneven filling caused by traditional one-time polymerization. It can gradually build a dense PEDOT network 32 from a loose PEDOT layer 31 state, thereby making the maximum use of the huge specific surface area of ​​the aluminum foil obtained by corrosion and building a continuous pathway (electron conduction path 50) for efficient electron conduction.

[0049] After the network is constructed, the dual transmission channels are constructed (S104). An aluminum foil with a dense conductive polymer network 32 is impregnated or coated with a liquid, curable gel electrolyte precursor, which can be achieved using vacuum-assisted methods to ensure that the precursor liquid completely fills all the voids in the conductive polymer network 32. Then, the impregnated aluminum foil is heated to cause the precursor to undergo an in-situ cross-linking and curing reaction, transforming it into a solid gel electrolyte 40. Figure 3 As shown, the final structure is a composite electrolyte system 300 in which the conductive polymer network 32 and the solid gel electrolyte 40 are interwoven and tightly bonded. The solid gel electrolyte 40 forms a continuous ion conduction path 60, coexisting with the electron conduction path 50, constituting a highly efficient "dual transport channel." This structure not only solves the ion transport bottleneck deep within the micropores, but the introduction of the solid electrolyte also fundamentally improves the working stability and service life of the electrode foil under high-temperature environments.

[0050] Finally, to efficiently extract charge from the electrode foil, a composite conductive layer (S105) is coated onto the surface of the effective reaction area. A layer of conductive carbon paste can be coated, followed by a layer of conductive silver paste, and then subjected to appropriate curing to form a low-resistance charge collection layer. During charging and discharging, the prepared electrode foil allows for rapid and efficient charge (electrons and ions) transport within the "dual transport channels" inside the micropores, ultimately exchanging charge with the external circuit through the surface composite conductive layer. Compared to existing technologies, the electrode foil prepared using this method significantly improves capacitor capacity, reduces internal resistance, and enhances operational stability and lifespan under high-temperature conditions.

[0051] In a preferred embodiment, specific material systems and process parameters are employed to obtain superior electrochemical performance. In the polymerization step (S103), an aqueous solution of 3,4-ethylenedioxythiophene (EDOT) is used as the monomer solution, and an aqueous solution of sodium persulfate is used as the oxidant solution. The aluminum foil is subjected to 18 alternating impregnation cycles. In each cycle, to ensure sufficient penetration and reaction, the aluminum foil is first vacuum impregnated in the EDOT solution for 60 seconds at a constant temperature of 70°C, then vacuum impregnated in the sodium persulfate solution for 70 seconds, followed by a constant temperature reaction for 10 minutes. Through 18 cycles, a highly dense poly(3,4-ethylenedioxythiophene) (PEDOT) network 32 is formed within the micropores.

[0052] In the subsequent gel curing step (S104), a curable gel electrolyte precursor is prepared, the components of which, by mass percentage, are: 3.5% polyethylene glycol diacrylate (PEGDA), 1.4% organic carboxylic acid ion source, 0.25% thermal free radical initiator, and the balance being deionized water. An aluminum foil with a PEDOT network 32 is immersed in this precursor and then cured at 100°C for 60 minutes. At 100°C, the thermal initiator decomposes to generate free radicals, initiating cross-linking polymerization of PEGDA, while simultaneously locking the ion source and water molecules within the three-dimensional network, forming a stable solid gel electrolyte 40 that is tightly interwoven with the PEDOT network 32. Through this preferred method, the prepared electrode foil exhibits a capacity extraction rate that is more than 30% higher than that of conventional processes, an equivalent series resistance that is more than 40% lower, and a capacity decay rate of less than 10% after 1000 hours of operation at 105°C, demonstrating excellent overall performance.

[0053] Furthermore, to minimize charge extraction resistance and improve the high-frequency performance of the capacitor, the preparation of the composite conductive layer (S105) can be optimized based on the above preferred embodiment. After completing the polymerization and gel curing steps, firstly, a layer of composite conductive carbon paste containing graphene and carbon nanotubes is uniformly coated on the surface of the PEDOT / gel composite electrolyte layer 300 by screen printing or scraping, and then dried at 60°C to form a conductive carbon layer 400. Graphene and carbon nanotubes construct a long-range conductive network within the carbon layer, significantly improving the lateral charge collection efficiency. Then, a layer of conductive silver paste is uniformly coated on the surface of the conductive carbon layer 400 and cured by heating at 80°C to form a conductive silver layer 500. The final cross-sectional structure of the finished electrode foil is as follows. Figure 4 As shown, after the charge is conducted from the PEDOT network 32 to the surface, it is first collected through the conductive carbon layer 400, which has good compatibility with PEDOT and enhanced conductivity, and then rapidly discharged through the conductive silver layer 500 with extremely low resistivity. The electrode foil prepared in this embodiment has a further reduced equivalent series resistance compared to electrode foils using only ordinary carbon paste, and its high-frequency response characteristics are superior, making it particularly suitable for applications with extremely high requirements for efficiency and power density.

[0054] To verify the effectiveness and universality of the process parameter range described in this invention, studies on variations in process parameters can also be conducted. Based on the above-mentioned preferred material system, two sets of comparative schemes can be designed. Scheme A (Economic): The number of cycles in the polymerization step (S103) is set to 15, and the heating temperature in the gel curing step (S104) is set to 90°C. Under this scheme, 15 cycles are sufficient to form a basically continuous conductive network, and curing at 90°C ensures complete cross-linking of the gel. Although the network density and curing rate are relatively low, the process time is short and energy consumption is low, achieving a good balance between cost and performance. Scheme B (Performance): The number of cycles in the polymerization step is set to 20, and the heating temperature in the gel curing step is set to 110°C. This scheme aims to achieve the ultimate filling density and curing stability. 20 cycles can form a denser network, and the curing rate at 110°C is faster, resulting in the best electrochemical performance. However, care must be taken to prevent side reactions that may be caused by excessively high temperatures. Experimental results show that the electrode foils prepared using schemes A and B have significantly improved performance compared to existing technologies. This fully demonstrates that the present invention is effective and feasible within the range of 15-20 polymerization cycles and curing temperature of 90-110℃, providing strong support for the scope of the claims.

[0055] This invention has a wide range of applications, especially in high-end fields with stringent performance requirements. For example, in the automotive electronics field, with the development of intelligent and electric vehicles, onboard ECUs, ADAS systems, and BMS battery management systems place extremely high demands on the stability and reliability of power supplies. The capacitors manufactured using the electrode foil prepared by this invention, due to their low ESR, high capacitance, and excellent high-temperature stability, can provide high-quality filtering and energy storage support for these critical electronic modules, ensuring their reliable operation in a wide temperature range and complex vibration environments. In the field of communication power supplies such as 5G communication base stations and data center servers, high-frequency, high-efficiency DC-DC converters are core components. The electrode foil prepared by this invention, with its excellent high-frequency response characteristics, can significantly improve the conversion efficiency and power density of power modules, meeting the urgent needs of next-generation information infrastructure for miniaturization and high efficiency. Furthermore, this invention also has application value in fields such as industrial automation, aerospace, and high-end consumer electronics.

Claims

1. A method for preparing electrode foil for capacitors, characterized in that, Includes the following steps: An effective reaction region and an ineffective reaction region are divided on an aluminum foil with a microporous structure and an alumina dielectric layer, and an insulating shielding adhesive that does not wet the monomer solution and the oxidant solution is coated on the ineffective reaction region. A conductive polymer network is generated in situ within the micropores of the effective reaction region by repeatedly and alternately impregnating monomer solution and oxidant solution; A curable gel electrolyte precursor is coated onto the effective reaction area and allowed to penetrate into the conductive polymer network. Then, heating is applied to solidify the curable gel electrolyte precursor in situ, forming a solid gel electrolyte filled within the conductive polymer network. A composite conductive layer is formed by coating the effective reaction area.

2. The method according to claim 1, characterized in that, The monomer solution contains 3,4-ethylenedioxythiophene, and the oxidant solution contains persulfate.

3. The method according to claim 1 or 2, characterized in that, The number of times the immersion is repeated is 15-20 times.

4. The method according to claim 1, characterized in that, The curable gel electrolyte precursor contains polyethylene glycol diacrylate.

5. The method according to claim 4, characterized in that, The heating temperature is 90-110℃.

6. The method according to claim 1, characterized in that, The step of forming the composite conductive layer includes: sequentially forming a conductive carbon layer and a conductive silver layer.

7. The method according to claim 6, characterized in that, The conductive carbon layer contains at least one selected from graphene and carbon nanotubes.

8. An electrode foil for a capacitor, comprising an aluminum foil having a microporous structure and an alumina dielectric layer, wherein the aluminum foil is divided into effective reaction regions and ineffective reaction regions, characterized in that, Within the effective reaction region, a composite electrolyte system consisting of a conductive polymer network and a solid gel electrolyte filled therebetween is formed in the micropores. A composite conductive layer is disposed on the surface of the effective reaction region; and An insulating shielding layer is provided on the surface of the non-effective reaction area.

9. The electrode foil for a capacitor according to claim 8, characterized in that, The conductive polymer network is a poly(3,4-ethylenedioxythiophene) network.

10. The electrode foil for a capacitor according to claim 8 or 9, characterized in that, The composite conductive layer includes a conductive carbon layer and a conductive silver layer, and the conductive carbon layer contains at least one selected from graphene and carbon nanotubes.

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