Low-leakage solid aluminum electrolytic capacitor and preparation method thereof

Abstract

The invention discloses a low-leakage solid aluminum electrolytic capacitor, which comprises an anode foil, a cathode foil and electrolytic paper arranged between the anode foil and the cathode foil, and the electrolytic paper is coating electrolyte electrolytic paper and comprises a composite fiber precursor paper base and a conductive polymer electrolyte coating compounded on the surface of the paper base. By adopting the novel coating electrolyte electrolytic paper, the electrolyte distribution continuity and the interface bonding state are fundamentally improved, and the leakage current is remarkably reduced. The invention further discloses a preparation method of the low-electric-leakage solid-state aluminum electrolytic capacitor, and the method ensures that a continuous, compact and stable ion transmission network is formed in the capacitor through the synergistic effect of the optimized process and the novel electrolytic paper.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aluminum electrolytic capacitor manufacturing, in particular to a low-leakage solid-state aluminum electrolytic capacitor and a preparation method thereof. BACKGROUND

[0002] The solid-state aluminum electrolytic capacitor has become an indispensable key element in high-end electronic devices such as new energy vehicles, 5G communication base stations, and server power supplies, due to its high capacity, low equivalent series resistance, high ripple current resistance, and excellent frequency characteristics. However, the relatively large leakage current is a common technical problem that has long plagued the further improvement of the performance of solid-state aluminum electrolytic capacitors. The large leakage current not only increases the power consumption and heat generation of the capacitor itself, affecting the efficiency and reliability of the entire machine, but also shortens the service life of the capacitor, becoming a bottleneck restricting its application in higher reliability scenarios.

[0003] Technical analysis shows that one of the core causes of the leakage current problem lies in the performance shortcomings of the ordinary electrolytic paper used inside the capacitor. Traditional solid-state aluminum electrolytic capacitors usually use electrolytic paper made from single plant fibers. This ordinary electrolytic paper has the following inherent defects: first, its fiber structure is single, and the uniformity of thickness and density is poor, which is prone to produce physical defects such as wrinkles, slag, micron-sized holes, and even holes during the papermaking process. These defects directly constitute potential charge leakage channels. Second, the mechanical strength of the single plant fiber paper base is limited, and under the action of mechanical stress or thermal stress during the high-speed winding process of the capacitor core and subsequent use, fiber breakage or structural deformation easily occurs, further expanding the leakage path. Third, the surface properties of ordinary electrolytic paper are not compatible with the aluminum oxide dielectric layer formed on the surface of the anode foil (anode foil medium oxide film), and the adsorption capacity of the conductive polymer electrolyte is limited, which makes it difficult for the electrolyte to uniformly and fully fill the paper base pores, and easily forms micro voids or "dead corners" at the interface between the paper base and the anode foil. These discontinuous electrolyte distribution and poor interface contact make the ion transport channel have breakpoints, and provide a shortcut for charge to leak along the interface or directly through the defects, which seriously deteriorates the leakage performance of the capacitor.

[0004] Therefore, how to start from the key internal component of electrolytic paper, through the fundamental innovation of material and structure, to improve its mechanical strength and uniformity, while significantly improving its adsorption capacity for electrolyte and interface compatibility with the anode foil, thereby systematically suppressing the generation of leakage current, has become a technical problem that needs to be solved in the field. SUMMARY

[0005] The primary objective of this invention is to overcome the shortcomings of the prior art and provide a low-leakage solid aluminum electrolytic capacitor, which fundamentally improves the continuity of electrolyte distribution and the interface bonding state by adopting a novel coated electrolyte electrolytic paper, thereby significantly reducing leakage current.

[0006] Another objective of this invention is to provide a method for preparing the aforementioned low-leakage solid aluminum electrolytic capacitor, which, through the synergistic effect of optimized processes and novel electrolytic paper, ensures the formation of a continuous, dense, and stable ion transport network inside the capacitor.

[0007] To achieve the above objectives, the present invention provides the following technical solution: On one hand, the present invention provides a low-leakage solid aluminum electrolytic capacitor, including an anode foil, a cathode foil, and an electrolytic paper disposed between the anode foil and the cathode foil. The electrolytic paper is a coated electrolyte electrolytic paper, which includes a composite fiber precursor paper base and a conductive polymer electrolyte coating coated on the surface of the paper base.

[0008] Preferably, the composite fiber precursor paper base comprises plant fibers and chemical fibers. More preferably, the plant fibers are softwood pulp fibers, and the chemical fibers are polyester fibers and / or glass fibers; the mass ratio of the plant fibers to the chemical fibers is (1:0.1) to (1:0.5).

[0009] More preferably, the porosity of the composite fiber precursor paper base is 60% to 75%.

[0010] Preferably, the conductive polymer electrolyte coating comprises PEDOT / PSS (poly(3,4-ethylenedioxythiophene) / polystyrene sulfonic acid); the PEDOT / PSS penetrates into the interfiber gaps of the composite fiber precursor paper base to form a fiber-electrolyte interlocking structure.

[0011] More preferably, the conductive polymer electrolyte coating is laminated onto both sides of the composite fiber precursor paper substrate using a gravure coating process.

[0012] On the other hand, the present invention provides a method for preparing the low-leakage solid aluminum electrolytic capacitor as described above, comprising the following steps: S1: Provides an anode foil, a cathode foil, and a coated electrolyte electrolytic paper, wherein the coated electrolyte electrolytic paper comprises a composite fiber precursor paper base and a conductive polymer electrolyte coating laminated on its surface; S2: The anode foil, cathode foil, and coated electrolyte electrolytic paper are wound or stacked to form a capacitor element; S3: Perform formation repair treatment on the capacitor elements; S4: The capacitor elements after chemical formation repair are subjected to vacuum curing to obtain a low-leakage solid aluminum electrolytic capacitor.

[0013] Preferably, in step S1, the composite fiber precursor paper base is prepared by a papermaking process using a mixed pulp containing plant fibers and chemical fibers.

[0014] Preferably, in step S3, the conditions for the formation repair treatment include: being carried out in an aqueous solution containing a weak organic acid and / or its salt, applying a voltage of 1.05 to 1.3 times the rated voltage of the capacitor, and a temperature of 80°C to 110°C.

[0015] Preferably, in step S4, the conditions for the vacuum curing process include: a vacuum degree of less than 10 Pa, a temperature of 120°C to 160°C, and a time of 1 to 4 hours.

[0016] This invention systematically solves the leakage problem of solid aluminum electrolytic capacitors through a synergistic innovation integrating materials, structure, and process. Its beneficial effects are mainly reflected in: 1. The composite fiber precursor paper base provides an ideal substrate with high strength, high uniformity and suitable porosity, eliminating direct leakage paths caused by defects (pores, wrinkles) and mechanical damage of the paper base itself.

[0017] 2. The PEDOT / PSS electrolyte coating and paper-based fibers form an "interlocking structure", realizing the integration of electrolyte and carrier, greatly enhancing the interfacial bonding force and eliminating micro gaps.

[0018] 3. The optimized formation repair process "reinforces" the anodic oxide film, while the vacuum curing process ensures the full penetration and filling of the electrolyte in the three-dimensional space of the capacitor core. Together with the new electrolytic paper, it constructs a complete, low-resistance, and defect-free charge storage and transport system from the anode dielectric layer, through the electrolyte / paper-based composite, to the cathode.

[0019] 4. While maintaining the advantages of high capacitance and low equivalent series resistance of solid capacitors, the final product significantly reduces leakage current, and effectively improves reliability, ripple current withstand capability and service life. It is particularly suitable for high-end applications with extremely high power consumption and reliability requirements. Attached Figure Description

[0020] Fig. 1 This is a schematic cross-sectional view of the core structure of the low-leakage solid aluminum electrolytic capacitor of the present invention. Fig. 2 This is a physical image of the coated electrolyte electrolytic paper used in the low-leakage solid aluminum electrolytic capacitor of this invention.

[0021] In the figure: 1. Anode foil; 2. Electrolytic paper; 21. Composite fiber precursor paper base; 22. Conductive polymer electrolyte coating; 3. Cathode foil. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] like Figs. 1-2 As shown, this invention provides a low-leakage solid-state aluminum electrolytic capacitor, comprising an anode foil 1, a cathode foil 3, and an electrolytic paper 2 disposed between the anode foil and the cathode foil. The electrolytic paper 2 is a coated electrolyte electrolytic paper, comprising a composite fiber precursor paper base 21 and a conductive polymer electrolyte coating 22 laminated on the surface of the paper base. By replacing the conventional single-material ordinary electrolytic paper with a coated electrolyte electrolytic paper containing a composite fiber precursor paper base and a conductive polymer electrolyte coating, the problems of limited electrolyte adsorption capacity and poor interfacial compatibility of traditional electrolytic paper are fundamentally solved. This integrated structure not only provides a stable electrolyte storage carrier, but its surface conductive coating also directly serves as an ion transport medium, ensuring the continuity and uniformity of the ion channel between the anode foil and the cathode foil, thereby reducing charge leakage channels caused by uneven electrolyte distribution or interface defects from the source.

[0024] The composite fiber precursor paper base 21 comprises both plant fibers and chemical fibers. By limiting the composite fiber precursor paper base to include both plant fibers and chemical fibers, the problems of low mechanical strength, poor heat resistance, and easy breakage or deformation during winding and use of single plant fiber paper bases are solved. Plant fibers contribute flexibility and liquid absorption, while chemical fibers provide a reinforcing skeleton. The synergy between the two gives the paper base good processing adaptability, structural stability, and load-bearing capacity for subsequent electrolyte coatings, reducing the risk of leakage caused by physical damage to the paper base.

[0025] The plant fiber is softwood pulp fiber, and the chemical fiber is polyester fiber and / or glass fiber; the mass ratio of plant fiber to chemical fiber is (1:0.1) to (1:0.5). This specific combination and ratio optimizes the balance between the pore structure, mechanical strength and thermal stability of the paper base, ensuring that the paper base can best realize its dual function as an electrolyte carrier and structural support, and laying a uniform and robust foundation for low leakage performance.

[0026] The porosity of the composite fiber precursor paper base 21 is 60% to 75%. The optimized pore structure provides ample storage space for the conductive polymer electrolyte while ensuring sufficient strength and regularity of the fiber network, enabling the electrolyte to permeate uniformly and remain stable, thus avoiding discontinuous ion transport caused by local electrolyte depletion or accumulation.

[0027] The conductive polymer electrolyte coating 22 comprises PEDOT / PSS (poly-3,4-ethylenedioxythiophene / polystyrene sulfonic acid). PEDOT / PSS penetrates into the interfiber gaps of the composite fiber precursor paper substrate, forming a fiber-electrolyte interlocking structure. While acting as a conductive medium, the penetration and interlocking effect of PEDOT / PSS significantly enhances the integration of the coating and the paper substrate, greatly improves interfacial compatibility, eliminates microscopic voids between the paper substrate and the electrolyte, thereby effectively blocking charge leakage paths along the interface and enhancing the overall mechanical strength of the electrolytic paper.

[0028] The conductive polymer electrolyte coating 22 is laminated onto both sides of the composite fiber precursor paper substrate 21 using a gravure coating process. The gravure coating process enables high-precision and highly uniform coating, ensuring a continuous, dense, and controllable thickness electrolyte layer on both sides of the paper substrate. This uniform coating structure guarantees uniform and efficient ion transport throughout the entire electrolytic paper plane, avoiding current concentration and leakage points caused by localized thinning or absence of the coating.

[0029] This invention provides a method for preparing the above-described low-leakage solid aluminum electrolytic capacitor, comprising the following steps: S1: Provides an anode foil 1, a cathode foil 3, and a coated electrolyte electrolytic paper 2, wherein the coated electrolyte electrolytic paper includes a composite fiber precursor paper base 21 and a conductive polymer electrolyte coating 22 coated on its surface; In step S1, the composite fiber precursor paper base 21 is prepared by a papermaking process using a mixed pulp containing plant fibers and chemical fibers. The standardized papermaking process can uniformly interweave the mixed fibers to form a high-quality precursor paper base with uniform thickness and density, free from defects such as wrinkles and holes, providing a reliable base material for subsequent uniform coating and stable performance. S2: The anode foil, cathode foil, and coated electrolyte electrolytic paper are wound or stacked to form a capacitor element; S3: Perform formation repair treatment on the capacitor element; in step S3, the formation repair treatment conditions include: carrying out the treatment in an aqueous solution containing a weak organic acid and / or its salt, applying a voltage of 1.05 to 1.3 times the rated voltage of the capacitor, and a temperature of 80°C to 110°C. These optimized formation repair conditions enable a gentle yet effective secondary repair of the anode foil dielectric layer after capacitor element assembly, healing minor imperfections and forming a more complete and robust dielectric barrier, thereby reducing leakage current caused by imperfections in the dielectric layer itself from another perspective. S4: The capacitor elements after formation repair are subjected to vacuum curing to obtain a low-leakage solid aluminum electrolytic capacitor. In step S4, the vacuum curing conditions include: a vacuum level below 10 Pa, a temperature of 120°C to 160°C, and a time of 1 to 4 hours. By limiting the vacuum curing process to low vacuum, specific temperature, and time, the problems of insufficient penetration of the solid electrolyte into the elements, and the potential presence of air bubbles or unfilled gaps, are solved. The vacuum environment facilitates the removal of gas from the gaps, while the high temperature promotes the flow and further penetration of the PEDOT / PSS electrolyte. This process ensures that the electrolyte can fully fill the pores of the electrolytic paper and the microscopic gaps inside the elements, forming a continuous, dense, and defect-free solid electrolyte bulk phase, achieving omnidirectional connectivity of ion transport channels and minimizing bulk phase leakage points.

[0030] The core of this preparation method lies in replacing ordinary electrolytic paper with coated electrolyte electrolytic paper, and combining formation repair and vacuum curing processes. This solves the problem of simply changing the material without matching the processes, which fails to fully utilize the advantages of the new material. Through systematic process integration, this method ensures that the new electrolytic paper works synergistically with the dielectric layer of the anode foil inside the capacitor. It not only utilizes the excellent properties of the electrolytic paper itself, but also further optimizes the overall interface and bulk structure through subsequent processes, which is a key process guarantee for achieving low leakage current performance in capacitors.

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, specific embodiments will be listed below to further describe the invention in detail. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention.

[0032] Example 1: Preparation of a low-leakage solid aluminum electrolytic capacitor.

[0033] (1) Preparation of coated electrolyte electrolytic paper: (1.1) Preparation of precursor paper base: Softwood pulp fiber (plant fiber) and polyester fiber (chemical fiber) are mixed at a mass ratio of 1:0.2, and then prepared into pulp after hydraulic pulping and refining. The pulp is then formed using a wire paper machine, with the basis weight controlled at 40 g / m². After drying and calendering, a composite fiber precursor paper base with uniform thickness and no visible defects is obtained. Its porosity is measured to be approximately 68%.

[0034] (1.2) Electrolyte Coating: A PEDOT / PSS aqueous dispersion with a solid content of 3.0 wt% was prepared as the coating liquid. A gravure coating machine was used to uniformly coat both sides of the paper substrate obtained in step (1.1), with the coating amount controlled to 5 g / m² of dry film weight on one side. After coating, the substrate was dried and cured with hot air at 110℃ to form a conductive polymer electrolyte coating. PEDOT / PSS penetrates into the gaps between the paper substrate fibers, forming an interlocking structure, resulting in coated electrolyte electrolytic paper.

[0035] (2) Capacitor fabrication: (2.1) Provides an anode foil formed by anodizing, an etched aluminum foil for cathode as cathode foil, and a coated electrolyte electrolytic paper obtained in step (1).

[0036] (2.2) The anode foil, cathode foil and coated electrolyte electrolytic paper are stacked in sequence and wound into a cylindrical core (core) by an automatic winding machine.

[0037] (2.3) Chemical repair: Immerse the core in an aqueous solution containing ammonium adipate and apply a DC voltage of 30V (1.2 times the rated voltage of 25V) at 90°C for 60 minutes.

[0038] (2.4) Vacuum curing: After chemical transformation repair, the core is taken out, cleaned and dried, and then placed in a vacuum oven. It is treated for 2 hours under a vacuum of 5 Pa and a temperature of 140 °C.

[0039] (2.5) Subsequent processes: The vacuum-cured core is installed into the aluminum shell, sealed with adhesive, and after standard processes such as aging and testing, the finished capacitor is obtained.

[0040] Example 2: Preparation of a low-leakage solid aluminum electrolytic capacitor.

[0041] (1) Preparation of coated electrolyte electrolytic paper: The precursor paper base is made by mixing softwood pulp fiber and glass fiber at a mass ratio of 1:0.3 and controlling the porosity to 72%. The coating liquid is a PEDOT / PSS dispersion with a solid content of 2.5wt%, and the single-sided dry film weight is controlled to be 4g / m². The rest is the same as step 1 in Example 1.

[0042] (2) Capacitor preparation: Anode foil with a formation voltage of 20V was used. Formation repair conditions: In a solution containing ammonium sebate, the capacitor was treated at 85°C with an applied DC voltage of 18V (1.125 times the rated voltage of 16V) for 70 minutes. Vacuum curing conditions: Vacuum degree 3Pa, temperature 150°C, time 1.5 hours. The remaining steps were the same as step 2 in Example 1.

[0043] Comparative Example: Anode and cathode foils of the same specifications as in Example 1 were used, but the electrolytic paper was replaced with ordinary electrolytic paper (porosity approximately 65%) made from traditional single-fiber softwood pulp. After the core was wound, no special chemical formation repair or vacuum curing was performed; instead, a conventional process of impregnating conductive polymer monomers and chemically polymerizing the solid electrolyte was used. The remaining encapsulation and aging steps were the same.

[0044] Performance testing: Key electrical performance tests were conducted on the capacitor samples prepared in Examples 1 and 2 and the comparative examples. The results are shown in Table 1: Table 1 Comparison of capacitor performance.

[0045] Test results show that the capacitors using the technical solution of the present invention (Examples 1 and 2) maintain excellent levels of capacitance and low equivalent series resistance, while the leakage current is reduced by more than an order of magnitude compared with products using traditional processes (comparative examples), and they also exhibit better high-temperature life stability.

[0046] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A low-leakage solid aluminum electrolytic capacitor, comprising an anode foil (1), a cathode foil (3), and electrolytic paper (2) disposed between the anode foil (1) and the cathode foil (3), characterized in that, The electrolytic paper (2) is a coated electrolyte electrolytic paper, which includes a composite fiber precursor paper base (21) and a conductive polymer electrolyte coating (22) coated on the surface of the paper base.

2. The low-leakage solid aluminum electrolytic capacitor according to claim 1, characterized in that, The composite fiber precursor paper base (21) comprises plant fibers and chemical fibers.

3. The low-leakage solid aluminum electrolytic capacitor according to claim 2, characterized in that, The plant fiber is softwood pulp fiber, and the chemical fiber is polyester fiber and / or glass fiber; the mass ratio of the plant fiber to the chemical fiber is (1:0.1) to (1:0.5).

4. The low-leakage solid aluminum electrolytic capacitor according to any one of claims 1 to 3, characterized in that, The porosity of the composite fiber precursor paper base (21) is 60% to 75%.

5. The low-leakage solid aluminum electrolytic capacitor according to claim 1, characterized in that, The conductive polymer electrolyte coating (22) contains PEDOT / PSS; the PEDOT / PSS penetrates into the fiber gaps of the composite fiber precursor paper base (21) to form a fiber-electrolyte interlocking structure.

6. The low-leakage solid aluminum electrolytic capacitor according to claim 5, characterized in that, The conductive polymer electrolyte coating (22) is applied to both sides of the composite fiber precursor paper base (21) by a gravure coating process.

7. A method for preparing a low-leakage solid aluminum electrolytic capacitor as described in any one of claims 1 to 6, characterized in that, Includes the following steps: S1: Provide an anode foil (1), a cathode foil (3), and a coated electrolyte electrolytic paper (2), wherein the coated electrolyte electrolytic paper (2) comprises a composite fiber precursor paper base (21) and a conductive polymer electrolyte coating (22) composited on its surface. S2: The anode foil (1), cathode foil (3) and coated electrolyte electrolytic paper (2) are wound or stacked to form a capacitor element; S3: Perform formation repair treatment on the capacitor elements; S4: The capacitor elements after chemical formation repair are subjected to vacuum curing to obtain a low-leakage solid aluminum electrolytic capacitor.

8. The preparation method according to claim 7, characterized in that, In step S1, the composite fiber precursor paper base (21) is prepared by papermaking process using a mixed pulp containing plant fibers and chemical fibers.

9. The preparation method according to claim 7, characterized in that, In step S3, the conditions for the formation repair treatment include: being carried out in an aqueous solution containing a weak organic acid and / or its salt, applying a voltage of 1.05 to 1.3 times the rated voltage of the capacitor, and a temperature of 80°C to 110°C.

10. The preparation method according to claim 7, characterized in that, In step S4, the conditions for the vacuum curing process include: a vacuum degree of less than 10 Pa, a temperature of 120°C to 160°C, and a time of 1 to 4 hours.

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