Intrinsic conductive solid-state capacitor diaphragm and preparation method thereof

Abstract

The invention relates to an intrinsic conductive solid aluminum electrolytic capacitor diaphragm and a preparation method thereof, and belongs to the technical field of aluminum electrolytic capacitors. The diaphragm is prepared from 50-80wt% of high-temperature-resistant fibrillated fibers, 10-30wt% of conductive fibers and 10-20wt% of adhesive fibers through a wet papermaking process. The high-temperature-resistant fibrillated fibers are selected from aramid fibers, polyacrylonitrile fibers or poly-p-phenylene benzobisoxazole (PBO) fibers, and are subjected to pulping treatment to form a micro-nano three-dimensional network skeleton, so that the diaphragm is endowed with excellent heat resistance and structural stability; the conductive fibers are selected from aluminum fibers, copper fibers, stainless steel fibers, carbon fibers, graphene modified fibers, polyacetylene fibers, polyaniline fibers, polypyrrole fibers and polythiophene fibers, a continuous conductive path is constructed, and the resistance of the diaphragm body is remarkably reduced; the bonding fibers are low-melting-point hot melting fibers, bonding nodes are formed through hot pressing, and the interlayer bonding force is enhanced. The diaphragm is suitable for solid-state capacitors in high-frequency and high-temperature scenes.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of aluminum electrolytic capacitor separators, and particularly relates to an intrinsically conductive solid-state capacitor separator and a preparation method thereof. BACKGROUND

[0002] Solid-state aluminum electrolytic capacitors are widely used in power filtering, signal coupling and other fields of high-density electronic devices due to their low equivalent series resistance (ESR), high ripple current resistance and wide working temperature range. However, with the increasing demand for miniaturization and high frequency of electronic devices, solid-state capacitors face severe challenges in high-temperature processes such as reflow soldering (temperature up to 260-280℃). As the core component of solid-state capacitors, the separator needs to have the functions of adsorbing conductive polymers and isolating the electrode plates, and its heat resistance, conductivity and structural stability directly affect the performance and reliability of the capacitor.

[0003] Traditional separators are mostly made by mixing plant fibers and ordinary chemical fibers (such as PET, nylon), but plant fibers are easily carbonized and decomposed at high temperatures, and chemical fibers are easily melted and shrunk, leading to the destruction of the structure of the separator (CN109024084A). Although existing technologies try to improve heat resistance by multi-layer composite (CN113106786A) or the introduction of high-melting-point fibers (such as aramid fibers), there are still the following problems:

[0004] Insufficient conductivity: The separator relies on the adsorbed conductive polymer to transfer charge, and lacks its own conductive path, which limits the further reduction of ESR;

[0005] Weak interlayer bonding: Multi-layer separators use physical stacking or ordinary bonding processes, which are easily delaminated at high temperatures, affecting the structural stability;

[0006] Poor material compatibility: The mixed system of plant fibers and chemical fibers easily produces interface defects due to the difference in thermal expansion coefficient at high temperatures.

[0007] To solve the above problems, existing improvement schemes focus on single performance optimization, such as adjusting the pore size by using ultra-fine fibers (CN108074744A) or avoiding carbonization by using fully synthetic fibers (CN117831956A), but they cannot comprehensively solve the simultaneous improvement of conductivity, heat resistance and structural stability. In addition, the conductive polymer impregnation process can reduce ESR, but due to the insulating properties of the separator itself, it cannot build an efficient conductive network.

[0008] Therefore, it is urgent to develop a new type of separator material that can improve heat resistance while enhancing intrinsic conductivity, optimize pore size distribution and strengthen interlayer bonding through innovative fiber combination and structure design, to meet the high performance requirements of solid-state capacitors in high-frequency and high-temperature scenarios. SUMMARY

[0009] To address the problems of insufficient heat resistance, reliance on external conductive polymers for conductivity, weak interlayer bonding, and mismatched thermal expansion coefficients in existing solid aluminum electrolytic capacitor separators, this invention proposes an intrinsically conductive solid capacitor separator and its preparation method. Through innovative fiber combination and structural design, it exhibits no shrinkage at high temperatures and combines high permeability, uniform pore structure, high tensile strength, and low equivalent series resistance, achieving a synergistic improvement in high-temperature resistance, intrinsic conductivity, and structural stability, thus meeting the high-performance requirements of capacitors in high-frequency and high-temperature applications.

[0010] The intrinsically conductive solid capacitor diaphragm provided by this invention is composed of three types of fibers with different functions. The high-temperature resistant fibers are fully pulped and fibrillated to form micro- and nano-fibers, which serve as the main component and act as the skeleton of the diaphragm. Due to the excellent heat resistance of the fibers, the diaphragm can be kept from shrinking at high temperatures, thus improving the thermal stability of the diaphragm. The conductive fibers, as the main carriers for improving the conductivity of the diaphragm, are uniformly distributed in the diaphragm and together with the high-temperature resistant fibrillated fibers, they form a three-dimensional network structure to build an efficient electronic pathway. The bonding fibers are distributed in the three-dimensional network structure. When the diaphragm is hot-pressed, the skin first melts and then solidifies, acting as bonding nodes to tightly bind the different fibers together, thereby improving the structural stability of the diaphragm.

[0011] This invention provides an intrinsically conductive solid capacitor separator, which is made from the following mass percentages of high-temperature resistant fibrillated fibers, conductive fibers, and bonding fibers via a wet papermaking process, as detailed below:

[0012] High-temperature resistant fibrillated fiber: 50-80wt%;

[0013] Conductive fiber: 10-30 wt%;

[0014] Bonding fiber: 10-20 wt%.

[0015] Preferably, the high-temperature resistant fibrillated fiber is selected from one or more of aramid fiber, polyacrylonitrile fiber, and poly(p-phenylenebenzodioxazole) (PBO) fiber.

[0016] Preferably, the high-temperature resistant fibrillated fiber is pulped to a pulping degree of 20-80°SR, forming a hierarchical microfiber structure with a fiber length of 2-8mm, thus optimizing the electrolyte wetting and conductive polymer distribution.

[0017] Preferably, the conductive fiber is selected from one or more of metal fibers, carbon-based fibers, and intrinsically conductive polymer fibers. The metal fibers include one or more of aluminum fibers, copper fibers, and stainless steel fibers, with a diameter of 1-20 μm and an aspect ratio ≥100. The carbon-based fibers include one or more of carbon fibers and graphene-modified fibers, with a surface resistivity ≤10⁻⁶. 2Ω·cm; intrinsically conductive polymer fibers include one or more of polyacetylene fibers, polyaniline fibers, polypyrrole fibers, and polythiophene fibers, with a conductivity ≥10-2S / cm.

[0018] Preferably, the surface of the metal fiber is coated with an antioxidant layer, which is a polydopamine or silane coupling agent film (10-50 nm thick) to enhance antioxidant properties.

[0019] Preferably, the bonding fiber is a low-melting-point hot-melt fiber, including one or more of polyethylene / polyethylene terephthalate (PE / PET) core-sheath fiber and polyethylene / polypropylene (PE / PP) core-sheath fiber-based hot-melt fiber.

[0020] This invention also provides a method for preparing an intrinsically conductive solid capacitor separator, the specific steps of which include:

[0021] (1) Mix the high-temperature resistant fibrillated fibers that have undergone pulping treatment with water to prepare fiber suspension A;

[0022] (2) The conductive fiber is mixed with water to prepare a conductive fiber suspension, and the conductive fiber suspension is pulped to obtain fiber suspension B; the bonding fiber is mixed with water to prepare a bonding fiber suspension, and the bonding fiber suspension is pulped and then an antifoaming agent is added to obtain fiber suspension C.

[0023] (3) After mixing fiber suspension A, fiber suspension B and fiber suspension C according to the mass percentage of fiber raw materials, the fiber suspension D is obtained by disintegrating it for 5-100 minutes in a disintegrating machine. The fiber suspension D is then fed into the paper machine flow system and prepared by wet papermaking process to obtain the base paper.

[0024] (4) The original paper is fed into a hot press to obtain an intrinsically conductive solid capacitor diaphragm.

[0025] Preferably, the amount of defoamer used is 0.01wt%-2.00wt% of the total weight of the high-temperature resistant fibrillated fibers, conductive fibers and bonding fibers.

[0026] Preferably, the paper machine is one of the following: a slanted wire paper machine, a rotary wire paper machine, or a super rotary wire paper machine.

[0027] Preferably, the hot pressing pressure of the hot press is 1.5-3.0 MPa, the hot pressing time is 30-120 s, and the hot pressing temperature is 140℃-200℃.

[0028] The beneficial effects of this invention are:

[0029] (1) High-temperature resistant fibrillated fibers serve as the skeleton of the diaphragm. Their excellent thermal stability prevents the diaphragm from shrinking at high temperatures, giving the diaphragm excellent high-temperature resistance.

[0030] (2) The continuous pathways constructed by conductive fibers reduce the bulk resistance of the diaphragm to ≤10 Ω. 3 Ω·cm can effectively improve the intrinsic conductivity of the diaphragm and reduce the equivalent series resistance (ESR) of solid capacitors.

[0031] (3) The bonding fibers are uniformly distributed in the three-dimensional network structure. When the diaphragm is hot-pressed, the skin first melts and then solidifies, acting as bonding nodes to tightly bind different fibers together, effectively improving the structural stability of the diaphragm.

[0032] (4) The wet papermaking process is compatible with existing production lines, and the hot pressing parameters are matched with the reflow soldering process to avoid secondary heat damage. Detailed Implementation

[0033] The present invention will be described below with reference to specific embodiments. Those skilled in the art will understand that these embodiments are for illustrative purposes only and do not limit the scope of the invention in any way.

[0034] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, all reagents and materials used in the following examples are commercially available products.

[0035] Example 1

[0036] The raw materials used are fiber materials in the following weight percentages:

[0037] High-temperature resistant fibrillated fiber: 50wt% (aramid fiber, beating degree 40°SR), conductive fiber: 30wt% (stainless steel fiber, surface coated with polydopamine film, thickness 50nm), bonding fiber: 20wt% (PE / PET core-sheath fiber);

[0038] Aramid fibers that have undergone pulping are mixed with water to prepare fiber suspension A; stainless steel fibers are mixed with water to prepare conductive fiber suspension, and the conductive fiber suspension is pulped to obtain fiber suspension B; PE / PET core-sheath fibers are mixed with water to prepare bonding fiber suspension, and the bonding fiber suspension is pulped and then 0.10 wt% of defoamer (total weight of high-temperature fibrillated fibers, conductive fibers, and bonding fibers) is added to obtain fiber suspension C; fiber suspension A, fiber suspension B, and fiber suspension C are mixed according to the mass percentage of fiber raw materials and then dispersed for 5 minutes to obtain fiber suspension D with a concentration of 0.01 wt%; fiber suspension D is fed into a wire paper machine and prepared by wet papermaking process to obtain base paper; the base paper is fed into a hot press for hot pressing at a pressure of 1.5 MPa, a temperature of 160°C, and a time of 30 seconds to obtain an intrinsically conductive solid capacitor separator.

[0039] Example 2

[0040] The raw materials used are fiber materials in the following weight percentages:

[0041] High-temperature resistant fibrillated fiber: 80wt% (aramid fiber, beating degree 80°SR), conductive fiber: 10wt% (carbon fiber), bonding fiber: 10wt% (PE / PP core-sheath fiber);

[0042] Aramid fibers that have undergone pulping are mixed with water to prepare fiber suspension A; carbon fibers are mixed with water to prepare conductive fiber suspension, and the conductive fiber suspension is pulped to obtain fiber suspension B; PE / PP core-sheath fibers are mixed with water to prepare bonding fiber suspension, and the bonding fiber suspension is pulped and then 0.05 wt% of defoamer (total weight of high-temperature fibrillated fibers, conductive fibers, and bonding fibers) is added to obtain fiber suspension C; fiber suspension A, fiber suspension B, and fiber suspension C are mixed according to the mass percentage of fiber raw materials and then dissolved for 100 min to obtain fiber suspension D with a concentration of 0.05 wt%; fiber suspension D is fed into a wire paper machine and prepared by wet papermaking process to obtain base paper; the base paper is fed into a hot press for hot pressing at a pressure of 1.5 MPa, a temperature of 160°C, and a time of 120 s to obtain an intrinsically conductive solid capacitor diaphragm.

[0043] Example 3

[0044] The raw materials used are fiber materials in the following weight percentages:

[0045] High-temperature resistant fibrillated fiber: 65wt% (polyacrylonitrile fiber, beating degree 50°SR), conductive fiber: 20wt% (polyaniline fiber), bonding fiber: 15wt% (PE / PET core-sheath fiber);

[0046] Polyacrylonitrile fibers that have undergone pulping are mixed with water to prepare fiber suspension A; polyaniline fibers are mixed with water to prepare conductive fiber suspension, and the conductive fiber suspension is pulped to obtain fiber suspension B; PE / PET core-sheath fibers are mixed with water to prepare bonding fiber suspension, and the bonding fiber suspension is pulped and then 1.00 wt% of defoamer (total weight of high-temperature fibrillated fibers, conductive fibers, and bonding fibers) is added to obtain fiber suspension C; fiber suspension A, fiber suspension B, and fiber suspension C are mixed according to the mass percentage of fiber raw materials and then dissolved for 100 min to obtain fiber suspension D with a concentration of 3.00 wt%; fiber suspension D is fed into a wire paper machine and prepared by wet papermaking process to obtain base paper; the base paper is fed into a hot press for hot pressing at a pressure of 1.5 MPa, a temperature of 150°C, and a time of 75 s to obtain an intrinsically conductive solid capacitor separator.

[0047] Example 4

[0048] The raw materials used are fiber materials in the following weight percentages:

[0049] High-temperature resistant fibrillated fiber: 70wt% (poly(p-phenylenebenzodioxazole) (PBO) fiber, freeness 30°SR), conductive fiber: 15wt% (aluminum fiber, surface coated with silane coupling agent, thickness 10nm), bonding fiber: 15wt% (PE / PET core-sheath fiber).

[0050] PBO fibers that have undergone pulping are mixed with water to prepare fiber suspension A; aluminum fibers are mixed with water to prepare conductive fiber suspension, and the conductive fiber suspension is pulped to obtain fiber suspension B; PE / PET core-sheath fibers are mixed with water to prepare bonding fiber suspension, and the bonding fiber suspension is pulped and then 0.01 wt% of defoamer (total weight of high-temperature fibrillated fibers, conductive fibers, and bonding fibers) is added to obtain fiber suspension C; fiber suspensions A, B, and C are mixed according to the mass percentage of fiber raw materials and then dissolved for 100 min to obtain fiber suspension D with a concentration of 0.05 wt%; fiber suspension D is fed into a wire paper machine and prepared by wet papermaking process to obtain base paper; the base paper is fed into a hot press for hot pressing at a pressure of 2.5 MPa, a temperature of 140°C, and a time of 60 s to obtain an intrinsically conductive solid capacitor separator.

[0051] Example 5

[0052] The raw materials used are fiber materials in the following weight percentages:

[0053] High-temperature resistant fibrillated fiber: 60wt% (aramid fiber + polyacrylonitrile fiber mixed at a mass ratio of 1:1, both with a freeness of 40°SR), conductive fiber: 20wt% (graphene modified fiber), bonding fiber: 20wt% (PE / PET core-sheath fiber).

[0054] Aramid fibers and polyacrylonitrile fibers that have undergone pulping are mixed with water to prepare fiber suspension A; graphene-modified fibers are mixed with water to prepare conductive fiber suspension, and the conductive fiber suspension is pulped to obtain fiber suspension B; PE / PET core-sheath fibers are mixed with water to prepare bonding fiber suspension, and the bonding fiber suspension is pulped and then 1.00 wt% of defoamer (total weight of high-temperature resistant fibrillated fibers, conductive fibers, and bonding fibers) is added to obtain fiber suspension C; fiber suspension A, fiber suspension B, and fiber suspension C are mixed according to the mass percentage of fiber raw materials and then dissolved for 100 min to obtain fiber suspension D with a concentration of 0.05 wt%; fiber suspension D is fed into a wire paper machine and prepared by wet papermaking process to obtain base paper; the base paper is fed into a hot press and hot-pressed at a pressure of 2.8 MPa, a temperature of 160℃, and a time of 50 s to obtain an intrinsically conductive solid capacitor separator.

[0055] Example 6

[0056] The raw materials used are fiber materials in the following weight percentages:

[0057] High-temperature resistant fibrillated fiber: 75wt% (poly(p-phenylenebenzodioxazole) fiber, freeness 50°SR), conductive fiber: 15wt% (copper fiber, polydopamine coated, thickness 30nm), bonding fiber: 10wt% (PE / PP core-sheath fiber).

[0058] PBO fibers that have undergone pulping are mixed with water to prepare fiber suspension A; copper fibers are mixed with water to prepare conductive fiber suspension, and the conductive fiber suspension is pulped to obtain fiber suspension B; PE / PP core-sheath fibers are mixed with water to prepare bonding fiber suspension, and the bonding fiber suspension is pulped and then 1.00 wt% of defoamer (total weight of high-temperature fibrillated fibers, conductive fibers, and bonding fibers) is added to obtain fiber suspension C; fiber suspension A, fiber suspension B, and fiber suspension C are mixed according to the mass percentage of fiber raw materials and then dissolved for 90 min to obtain fiber suspension D with a concentration of 0.05 wt%; fiber suspension D is fed into a wire paper machine and prepared by wet papermaking process to obtain base paper; the base paper is fed into a hot press for hot pressing at a pressure of 2.0 MPa, a temperature of 130°C, and a time of 100 s to obtain an intrinsically conductive solid capacitor separator.

[0059] Example 7

[0060] The raw materials used are fiber materials in the following weight percentages:

[0061] High-temperature resistant fibrillated fiber: 60wt% aramid fiber (beating degree 20°SR), conductive fiber: 20wt% (polyaniline fiber), bonding fiber: 20wt% (PE / PET core-sheath fiber);

[0062] Aramid fibers that have undergone pulping are mixed with water to prepare fiber suspension A; polyaniline fibers are mixed with water to prepare conductive fiber suspension, and the conductive fiber suspension is pulped to obtain fiber suspension B; PE / PET core-sheath fibers are mixed with water to prepare bonding fiber suspension, and the bonding fiber suspension is pulped and then 1.00 wt% of defoamer (total weight of high-temperature fibrillated fibers, conductive fibers, and bonding fibers) is added to obtain fiber suspension C; fiber suspension A, fiber suspension B, and fiber suspension C are mixed according to the mass percentage of fiber raw materials and then dissolved for 20 min to obtain fiber suspension D with a concentration of 0.05 wt%; fiber suspension D is fed into a wire paper machine and prepared by wet papermaking process to obtain base paper; the base paper is fed into a hot press and hot-pressed at a pressure of 3.0 MPa, a temperature of 200℃, and a time of 100 s to obtain an intrinsically conductive solid capacitor separator.

[0063] Comparative Example 1

[0064] The raw materials used are fiber materials in the following weight percentages:

[0065] High-temperature resistant fibrillated fiber: 40wt% (aramid fiber, beating degree 40°SR), conductive fiber: 30wt% (stainless steel fiber, surface coated with polydopamine film, thickness 50nm), bonding fiber: 30wt% (PE / PET core-sheath fiber); the preparation process is the same as in Example 1, the difference being the different components and the proportion of bonding fiber used exceeds the scope of the claims.

[0066] Comparative Example 2

[0067] The raw materials used are fiber materials in the following weight percentages:

[0068] High-temperature resistant fibrillated fiber: 50wt% (aramid fiber, beating degree 60°SR), conductive fiber: 5wt% (carbon fiber), bonding fiber: 45wt% (PE / PP core-sheath fiber); the preparation process is the same as in Example 2, except that the composition is different, the proportion of conductive fiber is insufficient and the proportion of bonding fiber is excessive.

[0069] Comparative Example 3

[0070] The raw materials used are fiber materials in the following weight percentages:

[0071] High-temperature resistant fibrillated fiber: 50wt% (aramid fiber, beating degree 40°SR), conductive fiber: 30wt% (uncoated stainless steel fiber, no anti-oxidation layer), bonding fiber: 20wt% (PE / PET core-sheath fiber); the preparation process is the same as in Example 1, except that the raw material processing method is different and the surface of the conductive fiber is not treated.

[0072] Comparative Example 4

[0073] The raw materials used are fiber materials in the following weight percentages:

[0074] High-temperature resistant fiber: 50wt% (non-fibrillated aramid fiber, beating degree 0°SR), conductive fiber: 30wt% (stainless steel fiber, surface coated with polydopamine film, thickness 50nm), bonding fiber: 20wt% (PE / PET core-sheath fiber); the preparation process is the same as in Example 1, the difference being the raw material processing method, the aramid fiber is not subjected to beating and fibrillation treatment.

[0075] Comparative Example 5

[0076] The raw materials used are fiber materials in the following weight percentages:

[0077] High-temperature resistant fibrillated fiber: 80wt% (aramid fiber, beating degree 60°SR), conductive fiber: 0wt% (no conductive fiber added), bonding fiber: 20wt% (PE / PP core-sheath fiber); the preparation process is the same as in Example 2, but no conductive fiber is added.

[0078] Comparative Example 6

[0079] The raw materials used are fiber materials in the following weight percentages:

[0080] High-temperature resistant fibrillated fiber: 60 wt% (aramid fiber, beating degree 60°SR), conductive fiber: 40 wt% (carbon fiber), bonding fiber: 0 wt% (no bonding fiber added); the preparation process is the same as in Example 2, but no bonding fiber is added.

[0081] Comparative Example 7

[0082] The raw materials used are fiber materials in the following weight percentages:

[0083] High-temperature resistant fibrillated fiber: 50wt% (aramid fiber, beating degree 40°SR), conductive fiber: 30wt% (stainless steel fiber, surface coated with polydopamine film, thickness 50nm), bonding fiber: 20wt% (PE / PET core-sheath fiber); hot pressing temperature is 130℃, and the rest of the preparation process is the same as in Example 1, except that the hot pressing temperature is different.

[0084] Table 1. Components and process parameters in each embodiment and comparative example.

[0085]

[0086]

[0087]

[0088] Performance testing

[0089] 1. Testing method:

[0090] (1) Thickness μm

[0091] The thickness of the diaphragm paper was measured using an L&W No. 251 thickness gauge, with a sample area of ​​200 mm². 2 .

[0092] (2) Air permeability (mm / s)

[0093] Breathability was tested using FX3 300LabAirIV at a pressure of 200Pa and a test area of ​​20cm². 2 .

[0094] (3) Average pore size μm

[0095] The pore size was measured using a Capillary Flow Porometer-1100A manufactured by PMI Corporation, USA, with Galwick wetting solution and a surface tension of 20.1 Dynes / cm.

[0096] (4) 10-minute aspiration height (longitudinal) mm and 10-minute aspiration height (lateral) mm

[0097] Cut the diaphragm paper into strips 15mm wide. Draw a straight line with a pencil at one end of each strip, 5mm away. Hang the strips vertically on an iron stand, immersing the end with the line in pure water, keeping the liquid level with the line. Soak for 10 minutes and measure the liquid rise height (mm). The higher the liquid rise height, the better the liquid absorption.

[0098] (5) Tensile strength (15mm longitudinal) N / m and tensile strength (15mm transverse) N / m

[0099] Tensile strength was determined using a universal testing machine, in accordance with standard B453-89.

[0100] (6) Equivalent series resistance μΩ

[0101] Using an LCR meter, the ESR (Equivalent Series Resistance) of a solid electrolytic capacitor, which is composed of an intrinsically conductive solid capacitor diaphragm manufactured by the above method, was measured at a temperature of 25°C and a frequency of 100 kHz.

[0102] (7) Thermal shrinkage rate %

[0103] Cut the diaphragm into 100mm×100mm paper pieces, place them in a 250℃ oven for 10 minutes, and measure the deformation of the diaphragm before and after treatment.

[0104] 2. Test Results

[0105] Table 2 Performance test results of each embodiment and comparative example

[0106]

[0107]

[0108]

[0109] Observing Table 2, the membrane thicknesses obtained in Examples 1-7 are 35-50 μm. A thinner membrane reduces the thickness of the conductive polymer film to some extent, thus lowering the ESR value of the solid-state electrolytic capacitor. Furthermore, the membrane thickness is not so thin that aluminum foil burrs could puncture the membrane, leading to failure. The average pore size is less than 1.6 μm, and the air permeability is greater than 12 mm / s, which macroscopically characterizes the membrane's porosity. More uniform membrane pores result in more uniform conductive polymer loading, further reducing the ESR value of the solid-state electrolytic capacitor. The longitudinal tensile strength is consistently higher than 240 N / m, indicating that the bonding fibers and fibrillated fibers synergistically enhance structural stability. The longitudinal liquid absorption height is consistently greater than 28 mm, suggesting that the micro / nano structure of the fibrillated fibers optimizes electrolyte wettability. All ESR values ​​are below 5 μΩ, with Example 5 exhibiting the lowest ESR value, demonstrating a significant optimization effect after adding conductive fibers to the membrane. The thermal shrinkage rate of the diaphragm after heat treatment in a 250℃ oven for 10 minutes was less than 1.2%, indicating that the fibrillated heat-resistant fiber provided good thermal stability.

[0110] Comparing Example 1 and Comparative Example 1, Comparative Example 1 showed a significant decrease in liquid absorption and an increase in ESR value, indicating that excessive bonding fibers would affect the uniform distribution of conductive fibers and reduce the wettability and uniformity of the diaphragm. Comparing Example 2 and Comparative Example 2, the solid-state electrolytic capacitor using the diaphragm prepared in Comparative Example 2 as a component had a higher ESR value and poorer wettability, indicating that insufficient conductive fibers and excessive bonding fibers led to an imbalance in diaphragm performance. Comparing Example 1 and Comparative Example 3, the solid-state electrolytic capacitor using the diaphragm prepared in Comparative Example 3 as a component had a significantly higher ESR than that of Example 1, indicating that conductive fibers are necessary for capacitor compatibility. The working environment of the device requires certain surface treatment. Comparing Example 1 and Comparative Example 4, Comparative Example 4 has a large pore structure and poor wetting properties and tensile strength, indicating that fibrillated fibers have many advantages in forming the diaphragm skeleton. Comparing Example 2 and Comparative Example 5, the solid electrolytic capacitor using the diaphragm prepared in Comparative Example 5 as a component has a higher ESR value, indicating that conductive fibers have a significant effect on reducing the ESR value of solid electrolytic capacitors. Comparing Example 2 and Comparative Example 6, Comparative Example 6 has low tensile strength and poor diaphragm paper-forming properties, indicating that the addition of bonding fibers is an effective method to improve diaphragm strength. Comparing Example 1 and Comparative Example 7, it is shown that insufficient hot-pressing temperature makes it difficult for the bonding fibers to fully melt, resulting in limited reinforcing effect on the diaphragm, and the strength of Comparative Example 7 decreases significantly.

[0111] In summary, the beneficial effects of the present invention are as follows:

[0112] (1) High-temperature resistant fibrillated fibers serve as the skeleton of the diaphragm. Their excellent thermal stability prevents the diaphragm from shrinking at high temperatures, giving the diaphragm excellent high-temperature resistance.

[0113] (2) The continuous pathways constructed by conductive fibers reduce the bulk resistance of the diaphragm to ≤10 Ω. 3 Ω·cm can effectively improve the intrinsic conductivity of the diaphragm and reduce the equivalent series resistance (ESR) of solid capacitors.

[0114] (3) The bonding fibers are uniformly distributed in the three-dimensional network structure. When the diaphragm is hot-pressed, the skin first melts and then solidifies, acting as bonding nodes to tightly bind different fibers together, effectively improving the structural stability of the diaphragm.

[0115] (4) The wet papermaking process is compatible with existing production lines, and the hot pressing parameters are matched with the reflow soldering process to avoid secondary heat damage.

[0116] The above description of specific embodiments of the present invention does not limit the present invention. Those skilled in the art can make various changes or modifications based on the present invention, and as long as they do not depart from the spirit of the present invention, they should all fall within the scope of the appended claims.

Claims

1. A solid capacitor separator with intrinsic conductivity, characterized in that, Made from the following percentages of fiber raw materials using a wet papermaking process: High-temperature resistant fibrillated fibers: 50-80%; Conductive fibers 10-30%; Bonding fiber 10-20%.

2. The intrinsically conductive solid capacitor separator according to claim 1, characterized in that, The high-temperature resistant fibrillated fiber is selected from one or more of the following: aramid fiber, polyacrylonitrile fiber, and poly(p-phenylenebenzodioxazole) (PBO) fiber.

3. The intrinsically conductive solid capacitor separator according to claim 1, characterized in that, The high-temperature resistant fibrillated fiber is pulped to a freeness of 20-80°SR.

4. The intrinsically conductive solid capacitor separator according to claim 1, characterized in that, The conductive fiber is selected from one or more of the following: aluminum fiber, copper fiber, stainless steel fiber, carbon fiber, graphene modified fiber, polyacetylene fiber, polyaniline fiber, polypyrrole fiber, and polythiophene fiber.

5. The intrinsically conductive solid capacitor separator according to claim 4, characterized in that, The aluminum fiber, copper fiber, and stainless steel fiber are coated with an antioxidant layer, which is a polydopamine or silane coupling agent film with a thickness of 10-50 nm.

6. The intrinsically conductive solid capacitor separator according to claim 1, characterized in that, The bonding fiber is a low-melting-point hot-melt fiber, including one or more of polyethylene / polyethylene terephthalate (PE / PET) core-sheath fiber and polyethylene / polypropylene (PE / PP) core-sheath fiber-based hot-melt fiber.

7. The method for preparing an intrinsically conductive solid capacitor separator according to claim 1, characterized in that, Includes the following steps: (1) Mix the high-temperature resistant fibrillated fibers that have undergone pulping treatment with water to prepare fiber suspension A; (2) The conductive fiber is mixed with water to prepare a conductive fiber suspension, and the conductive fiber suspension is pulped to obtain fiber suspension B; the bonding fiber is mixed with water to prepare a bonding fiber suspension, and the bonding fiber suspension is pulped and then an antifoaming agent is added to obtain fiber suspension C. (3) After mixing fiber suspension A, fiber suspension B and fiber suspension C according to the mass percentage of fiber raw materials, the fiber suspension D is obtained by disintegrating it for 5-100 minutes in a disintegrating machine. The fiber suspension D is then fed into the paper machine flow system and prepared by wet papermaking process to obtain the base paper. (4) The original paper is fed into a hot press to obtain an intrinsically conductive solid capacitor diaphragm.

8. The preparation method according to claim 7, characterized in that, In step (2), the amount of defoamer used is 0.01wt%-2.00wt% of the total weight of the high-temperature resistant fibrillated fiber, conductive fiber and bonding fiber.

9. The preparation method according to claim 7, characterized in that, In step (3), the paper machine used is one of the following: a slanted wire paper machine, a rotary wire paper machine, or a super rotary wire paper machine.

10. The preparation method according to claim 7, characterized in that, In step (4), the hot pressing pressure of the hot press is 1.5-3.0 MPa, the hot pressing time is 30-120 s, and the hot pressing temperature is 140℃-200℃.

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