Composite electrolytic paper and method for producing the same

Abstract

The present application relates to the technical field of aluminum electrolytic capacitor, and relates to a composite electrolytic paper and a preparation method. The composite electrolytic paper comprises nanofibers forming a network and microparticles distributed in the network formed by the nanofibers. The present application also provides a method for preparing the composite electrolytic paper by combining electrospinning and electrostatic spraying. In the composite electrolytic paper provided by the present application, the surfaces of the microparticles are tightly combined with the plurality of nanofibers by a large number of hydrogen bond actions and van der Waals forces. Due to the constraint force of the microparticles, the nanofibers are bound in a certain space and are difficult to separate from the nanofiber network, effectively solving the problems of poor combination between fibers, loose electrolytic paper and easy fiber falling of the traditional artificial fiber electrolytic paper.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aluminum electrolytic capacitor, in particular to a composite electrolytic paper and a preparation method thereof, more particularly to a nanofiber composite electrolytic paper and a preparation method thereof. BACKGROUND

[0002] As one of the three main components of capacitors, electrolytic paper is used to prevent short circuit between cathode foil and anode foil, and also can absorb a large amount of electrolyte as a cathode carrier. In recent years, the anti-dumping policy of electrolytic paper has caused a sharp reduction in the import of electrolytic paper, and the domestic electrolytic paper supply chain mainly relies on domestic electrolytic paper production leading enterprises such as Kane, Minfeng and Xianhu. With the rapid expansion of the capacitor market and the increasing demand for high-end products, the demand for high-quality electrolytic paper in the capacitor market is increasing. The quality of domestic electrolytic paper is still some distance from imported electrolytic paper such as NKK from Japan, and there is still a gap in the supply of domestic electrolytic paper. Domestic capacitor factories still need to spend a lot of capital and high anti-dumping tax to buy imported electrolytic paper.

[0003] Therefore, developing high-performance electrolytic paper and seeking an efficient preparation process for electrolytic paper are of great significance to solve the domestic demand problem of electrolytic paper and promote the industrial upgrading of China's component industry.

[0004] At present, traditional electrospinning method can directly and efficiently prepare artificial fiber electrolytic paper, but there are the following problems: the solvent electrospun artificial fiber is randomly stacked between fibers, the bonding force is poor, the prepared electrolytic paper is fluffy and the artificial fiber is easy to fall off, which reduces the pressure resistance; the fallen fibers are easy to block the pores of the formed foil, which reduces the electrical performance; the too fluffy artificial fiber electrolytic paper leads to large volume of core package, and the winding adhesive tape has no anchoring point. On the other hand, the bonding force between fibers is poor, and the artificial fiber electrolytic paper has a certain plasticity. During the assembly of the capacitor, due to the tension effect, the electrolytic paper is stretched and deformed, and the length, thickness and shape are changed, which makes the performance of the capacitor unstable and the consistency poor.

[0005] Therefore, it is necessary to develop an electrolytic paper capable of improving the above technical problems. SUMMARY

[0006] The present application aims to solve one of the above technical problems to some extent, and therefore provides a nanofiber composite electrolytic paper and a preparation method thereof.

[0007] Specifically, the present application provides the following technical solutions.

[0008] In a first aspect, the present application provides a composite electrolytic paper, comprising:

[0009] nanofibers, the nanofibers forming a network; and

[0010] microparticles, the microparticles being distributed in the network formed by the nanofibers.

[0011] According to the composite electrolytic paper provided by the present application, the microparticles are uniformly distributed in the network formed by the nanofibers, and the surfaces of the microparticles are tightly combined with the plurality of nanofibers by a large number of hydrogen bonds and van der Waals forces. Due to the constraint force of the microparticles, the nanofibers are bound in a certain space and are difficult to separate from the nanofiber network, effectively solving the problems of poor combination between fibers, loose electrolytic paper and easy fiber shedding of the traditional artificial fiber electrolytic paper. In addition, the composite electrolytic paper has the advantages of high pressure resistance, high tensile strength, low loss and the like.

[0012] According to the embodiments provided by the present application, the composite electrolytic paper can further include the following additional technical features.

[0013] According to the embodiments provided by the present application, the diameter of the nanofiber is 50-1000 nm, preferably 50-600 nm, and more preferably 50-400 nm.

[0014] Specifically, the diameter of the nanofiber can be listed as: 50 nm, 80 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, 750 nm, 800 nm, 850 nm, 900 nm, 950 nm, 1000 nm, and the like.

[0015] According to the embodiments provided by the present application, the particle size of the microparticle is 0.1-10 μm, preferably 0.5-5 μm.

[0016] Specifically, the particle size of the microparticle can be listed as: 0.1 μm, 0.3 μm, 0.5 μm, 0.8 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, and the like.

[0017] According to the embodiments provided by the present application, the pore size of the network formed by the nanofiber is 0.1-20 μm, preferably 0.1-10 μm, and more preferably 0.1-5 μm.

[0018] The pore size of the network formed by the nanofiber is 0.1-20 μm, which means that the average pore size of the network formed by the nanofiber is 0.1-20 μm.

[0019] Specifically, the pore size of the network formed by the nanofibers can be listed as follows: 0.1 μm, 0.3 μm, 0.5 μm, 0.8 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, and the like.

[0020] According to the embodiments provided by the present application, the mass ratio of the microparticles in the composite electrolytic paper is 2-50%, preferably 3-20%.

[0021] Specifically, the mass ratio of the microparticles can be listed as follows: 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, and the like.

[0022] According to the embodiments provided by the present application, the thickness of the composite electrolytic paper is 10-100 μm.

[0023] According to the embodiments provided by the present application, the surface roughness of the composite electrolytic paper is 0.5-10 μm, which is much lower than that of the plant fiber electrolytic paper (20-200 μm). The lower roughness makes the product have a more flat micro-surface, which provides guarantee for the consistency of the product in terms of thickness uniformity, burr resistance and pressure resistance.

[0024] According to the embodiments provided by the present application, the specific surface area of the composite electrolytic paper is 1-1000 m 2 / g. Compared with the conventional electrolytic paper of the same volume, the electrolyte adsorption capacity of the composite electrolytic paper is 2.7 times that of the ordinary electrolytic paper, which is conducive to the transmission of ions and charges in the capacitor product.

[0025] According to the embodiments provided by the present application, the tensile strength of the composite electrolytic paper is 0.1-1.0 MPa, which is comparable to that of the conventional electrolytic paper, and meets the performance requirements of the electrolytic paper for capacitors. Compared with the artificial fiber electrolytic paper, the composite electrolytic paper has a compact structure, and has no tensile deformation, no fracture phenomenon and no peeling of the core adhesive tape during the winding process.

[0026] According to the embodiments provided by the present application, the material forming the nanofiber is selected from at least one of polyacrylonitrile, ethylene-vinyl acetate copolymer, acrylonitrile-butadiene-styrene copolymer, polyimide, parylene and polybenzimidazole.

[0027] According to the embodiments provided by the present application, the material forming the microparticle is selected from at least one of polyvinylpyrrolidone, polyethylene glycol, polyvinyl alcohol, polyvinylidene fluoride, polyacrylonitrile, polyimide and polyvinyl butyral.

[0028] In a second aspect, the present application provides a device for preparing the composite electrolytic paper, comprising a positive high-voltage electrode plate, a liquid supply device, a spinneret, a track and a hot-pressing roller pair.

[0029] The positive high-voltage electrode plate and the track form a high-voltage electrostatic field therebetween.

[0030] The liquid supply device is located below the positive high-voltage electrode plate and is used to supply electrospinning liquid and electrostatic spraying liquid.

[0031] The spinneret is connected with the liquid supply device and is used to electrospun and spray the electrospinning liquid and the electrostatic spraying liquid to form a composite nanofiber membrane.

[0032] The track is placed on the ground and forms a high-voltage electrostatic field with the positive high-voltage electrode plate, and is used to collect the composite nanofiber membrane and continuously transfer the composite nanofiber membrane to the hot-pressing roller pair.

[0033] The hot-pressing roller pair is used to roll and shape the composite nanofiber membrane to obtain the composite electrolytic paper. On one hand, the composite nanofiber membrane is compressed to a certain thickness by roll shaping, and on the other hand, the composite electrolytic paper blank is obtained by rapid heat treatment of the composite nanofiber membrane, which plays a role in accelerating solvent evaporation and removing polymer macromolecular side chain groups, and can make the obtained composite electrolytic paper more stably exist under electrolyte or high temperature conditions.

[0034] According to the embodiments provided by the present application, the liquid supply device comprises a syringe pump and a liquid supply pipe, the spinneret is slidingly connected with the liquid supply pipe, and the spinneret can slide horizontally along the liquid supply pipe to ensure that the nanofiber and the microparticle are uniformly deposited on the surface of the track.

[0035] According to the embodiments provided by the present application, the device can further comprise a winding roller for collecting the obtained composite electrolytic paper.

[0036] According to other embodiments provided by the present application, the device can further comprise a cutting roller for cutting the composite electrolytic paper blank to a specific width before winding.

[0037] In a third aspect, the present application also provides a method for preparing the composite electrolytic paper by using the device, comprising the following steps:

[0038] S1, preparing electrospinning solution: dissolving the first polymer in the first solvent to obtain the electrospinning solution;

[0039] S2, preparing electro-spraying solution: dissolving the second polymer in the second solvent to obtain the electro-spraying solution;

[0040] S3, electrospinning and spraying: transferring the electrospinning solution and the electro-spraying solution to the spinneret through the liquid supply device, setting the spinning and spraying parameters, performing electrospinning and spraying, transferring the composite nanofiber membrane obtained by electrospinning and spraying to the hot pressing counter roller through the track, and performing hot pressing to obtain the composite electrolytic paper.

[0041] According to the embodiments provided by the present application, the first polymer is selected from at least one of polyacrylonitrile, ethylene-vinyl acetate copolymer, acrylonitrile-butadiene-styrene copolymer, polyimide, parylene and polybenzimidazole; and the first solvent is selected from at least one of N,N dimethylformamide, ethyl acetate, toluene, xylene, tetrahydrofuran and n-hexane.

[0042] According to the embodiments provided by the present application, in the electrospinning solution, the mass percentage of the first polymer is 10%-40%, and the mass percentage of the first solvent is 60%-90%.

[0043] According to the embodiments provided by the present application, the second polymer is selected from at least one of polyvinylpyrrolidone, polyethylene glycol, polyvinyl alcohol, polyvinylidene fluoride, polyacrylonitrile, polyimide and polyvinyl butyral; and the second solvent is selected from at least one of ethanol, N,N dimethylformamide, ethyl acetate, toluene, tetrahydrofuran, deionized water and ethylene glycol.

[0044] According to the embodiments provided by the present application, in the electro-spraying solution, the mass percentage of the second polymer is 0.1%-5%, and the mass percentage of the second solvent is 95%-99.9%.

[0045] In the preparation method, the concentration of the electrostatic spinning liquid and the electrostatic spraying liquid has important influence on the microstructure and performance of the composite electrolytic paper. Within a certain concentration range, the higher the concentration of the electrostatic spinning liquid is, the thicker the diameter of the spun nanofiber is, and the higher the tensile strength and the anti-spur breakdown capacity of the final composite electrolytic paper are. The solute polymer in the electrostatic spraying liquid contains a large number of side chain groups, and the spraying particles are quickly combined with the spun nanofiber through hydrogen bonds and van der Waals forces before the solvent volatilizes, so as to constrain the nanofiber in a certain space, improve the compactness and tensile strength of the nanofiber membrane. When the concentration of the electrostatic spraying liquid is too low, the mist drop mainly contains a large amount of solvent, so that the nanofiber membrane with high specific surface area is partially dissolved and the structure is collapsed; when the concentration of the electrostatic spraying liquid is too high, the spraying state is broken, and the electrostatic spinning is changed into, so that only the nanofiber membrane with loose structure and low tensile strength can be obtained.

[0046] According to the embodiment provided by the application, the setting of the spinning and spraying parameters comprises:

[0047] The humidity is 10%-40%, and the temperature is 20-50℃;

[0048] The positive high-voltage electrode plate voltage is 20-100kV;

[0049] The spinning or spraying distance is 15-40cm;

[0050] The spinning or spraying liquid supply rate is 0.1-5L / h, and preferably, the ratio of the spinning liquid supply rate to the spraying liquid supply rate is (0.2-7):1

[0051] The sliding speed of the spinneret is 0-50cm / s;

[0052] The hot-pressing roller distance is 10-100μm, and the temperature of the hot-pressing roller is 100-300℃;

[0053] The winding speed is 0.1-10m / min.

[0054] Compared with the prior art, the application has the following beneficial effects:

[0055] (1) The application adopts the electrostatic spinning combined with the electrostatic spraying one-step method to prepare the electrolytic paper, and compared with the artificial fiber electrolytic paper in the prior art, since the rinsing and impurity removal process in the traditional process is omitted, the whole process has no sewage discharge, the whole device can work in a closed space, the volatilized solvent is recycled and reused through the condensation tank, the cost is low, the method is high in efficiency, energy saving and pollution-free.

[0056] (2) The fibers in the electrolytic paper prepared by using the traditional papermaking process are randomly interlaced, and various auxiliary materials such as fillers, sizing materials and sizing agents need to be used to improve the mechanical properties of the paper; in the present application, the electrospinning and electrostatic spraying processes are carried out simultaneously, the nanofibers and the sprayed microparticles are interwoven together, the hydrogen bonds and the van der Waals force bonding between the nanofibers and the large number of sprayed microparticles are ingeniously utilized, the sprayed microparticles constrain the nanofibers in a certain space, the porous structure of the electrospun fibers can be retained, and the problems of poor bulkiness, poor tensile property and easy fiber falling of the electrolytic paper can be solved.

[0057] (3) The surface roughness of the composite electrolytic paper provided by the present application is 0.5-10 mu m, which is much lower than that of the plant fiber electrolytic paper (20-200 mu m), and the lower roughness makes the product have a more flat micro-surface, which provides guarantee for the consistency of the product from the aspects of thickness uniformity, burr resistance and pressure resistance.

[0058] (4) The cross section of the nanofiber prepared by using electrospinning in the present application is cylindrical, which shortens the current path and is beneficial to the transmission of ions, and the loss is reduced. The ESR of the electrolytic capacitor product assembled by using the composite electrolytic paper is reduced by about 50% compared with that of the product assembled by using the traditional electrolytic paper.

[0059] (5) The high-voltage breakdown performance of the composite electrolytic paper provided by the present application is all above 1000V, which is much higher than that of the ordinary electrolytic paper. After the electrolytic capacitor product is assembled, the product failure rate is greatly reduced compared with the ordinary electrolytic paper.

[0060] (6) The specific surface area of the composite electrolytic paper provided by the present application is 1-1000 m 2 / g. Compared with the traditional electrolytic paper with the same volume, the electrolyte adsorption capacity of the composite electrolytic paper is 2.7 times that of the ordinary electrolytic paper, which is beneficial to the transmission of ions and charges in the capacitor product.

[0061] (7) The tensile strength of the composite electrolytic paper provided by the present application is 0.1-1.0 MPa, which can be comparable to that of the traditional electrolytic paper, and meets the performance requirements of the electrolytic paper for capacitors; compared with the artificial fiber electrolytic paper, the composite electrolytic paper has a compact structure, and has no tensile deformation, no fracture phenomenon and no peeling of the core adhesive tape during the winding process. BRIEF DESCRIPTION OF DRAWINGS

[0062] Figure 1 The figure shows a preparation device schematic diagram of the composite electrolytic paper provided by the present application;

[0063] Among them: 1-positive high-voltage plate; 2-liquid supply device, 21-injection pump, 22-liquid supply pipe; 3-nozzle; 4-track; 5-hot pressing roller; 6-cutting roller; 7-rolling roller;

[0064] Figure 2A SEM image of the composite electrolytic paper obtained in Example 1 of the present application is shown;

[0065] Figure 3 A photo of the composite electrolytic paper obtained in Example 1 of the present application is shown;

[0066] Figure 4 A SEM image of the electrolytic paper obtained in Comparative Example 1 is shown; and

[0067] Figure 5 A SEM image of the electrolytic paper obtained in Comparative Example 2 is shown. DETAILED DESCRIPTION

[0068] Embodiments of the present application are described in detail below, examples of which are shown in the accompanying drawings. The embodiments described below by reference to the drawings are exemplary and are intended to explain the present application, and should not be understood as limiting the present application. Unless otherwise specified, all technical terms used in the present application have the same meaning as commonly understood by those skilled in the art to which the present application pertains. All patents and publications related to the present application are incorporated herein by reference in their entirety. The term "comprising" or "including" is an open-ended expression, i.e., includes the indicated content, but does not exclude other aspects.

[0069] The preparation device and method of the composite electrolytic paper described in the present application are described in detail below.

[0070] 1. Preparation device of composite electrolytic paper

[0071] As shown in Figure 1 , the preparation device of the composite electrolytic paper provided by the present application comprises a positive high-voltage electrode plate 1, a liquid supply device 2, a spinneret 3, a track 4, a hot-pressing pair of rollers 5, a cutting roller 6, and a winding roller 7.

[0072] Among them:

[0073] The positive high-voltage electrode plate 1 and the track 4 form a high-voltage electrostatic field, ensuring that the electrospinning and electrostatic spraying processes continue to proceed.

[0074] In some embodiments, the liquid supply device 2 is located below the positive high-voltage electrode plate, and the liquid supply device 2 comprises a syringe pump 21 and a liquid supply pipe 22, one liquid supply pipe for supplying electrospinning liquid and the other liquid supply pipe for supplying electrostatic spraying liquid.

[0075] The spinneret 3 is slidably connected with the liquid supply pipe 22, and the spinneret 3 can slide horizontally along the liquid supply pipe 22 to ensure that the nanofibers formed by electrospinning and the microparticles formed by electrostatic spraying are uniformly deposited on the surface of the track, obtaining a composite nanofiber membrane.

[0076] The caterpillar 4 is placed on the ground to collect the composite nanofiber film and continuously transfer the composite nanofiber film to the hot pressing roller 5.

[0077] The hot pressing roller 5 is used to roll the composite nanofiber film into shape. On the one hand, the composite nanofiber film is compressed to a certain thickness by roll forming, and on the other hand, the composite electrolytic paper blank is obtained by rapid heat treatment of the composite nanofiber film, which plays a role in accelerating solvent evaporation and removing polymer macromolecular side chain groups, and can make the obtained composite electrolytic paper more stable in electrolyte or high temperature conditions.

[0078] After the composite nanofiber film is hot pressed by the hot pressing roller 5, it is cut to a certain width by the cutting roller 6, and finally wound by the winding roller 7 to obtain the finished composite electrolytic paper product.

[0079] 2. Preparation of composite electrolytic paper

[0080] S1. Preparation of electrospinning solution

[0081] The first high molecular polymer is stirred and dissolved in the first solvent to obtain an electrospinning solution.

[0082] The first high molecular polymer is a high temperature resistant high molecular polymer, and preferably, the first high molecular polymer is selected from at least one of polyacrylonitrile, ethylene-vinyl acetate copolymer, acrylonitrile-butadiene-styrene copolymer, polyimide, parylene and polybenzimidazole.

[0083] The first solvent is selected from at least one of N,N-dimethylformamide, ethyl acetate, toluene, xylene, tetrahydrofuran and n-hexane. The first solvent matches the first high molecular polymer to ensure that the first high molecular polymer is fully dissolved.

[0084] The concentration of the electrospinning solution has an important influence on the microstructure and performance of the composite electrolytic paper. Within a certain concentration range, the higher the concentration of the electrospinning solution, the thicker the diameter of the spinning nanofiber, and the higher the tensile strength and the stronger the resistance to burr breakdown of the final composite electrolytic paper. According to the embodiments provided by the present application, the mass fraction of the first high molecular polymer in the electrospinning solution is 10%-40%, and the mass fraction of the first solvent is 60%-90%. The electrospinning solution in this concentration range has better tensile strength and burr breakdown resistance of the obtained composite electrolytic paper.

[0085] Specifically, the mass fraction of the first high molecular polymer can be listed as: 10%, 15%, 20%, 25%, 30%, 35%, 40%, and the like.

[0086] The mass percentage of the first solvent can be 60%, 65%, 70%, 75%, 80%, 85%, 90%, etc.

[0087] In some embodiments, the mass percentage of the first high-molecular polymer in the electrostatic spinning solution is 10%-30%, and the mass percentage of the first solvent is 70%-90%.

[0088] The temperature for stirring and dissolving can be selected according to the type of the first high-molecular polymer, and the stirring time is not particularly limited, as long as the first high-molecular polymer is dissolved. According to the embodiments provided in the present application, the temperature for stirring and dissolving is 25-100°C.

[0089] S2, preparing an electrostatic spraying solution

[0090] The second high-molecular polymer is stirred and dissolved in a second solvent to obtain an electrostatic spraying solution.

[0091] The second high-molecular polymer is selected from at least one of polyvinylpyrrolidone, polyethylene glycol, polyvinyl alcohol, polyvinylidene fluoride, polyacrylonitrile, polyimide and polyvinyl butyral.

[0092] The second solvent is selected from at least one of ethanol, N,N-dimethylformamide, ethyl acetate, toluene, tetrahydrofuran, deionized water and ethylene glycol. The second solvent is matched with the first high-molecular polymer to ensure that the second high-molecular polymer is fully dissolved.

[0093] Preferably, the mass percentage of the second high-molecular polymer in the electrostatic spraying solution is 0.1%-5%, and the mass percentage of the second solvent is 95%-99.9%.

[0094] The concentration of the electrostatic spraying solution has a decisive influence on the microstructure and performance of the composite electrolytic paper. The electrostatic spraying solution needs to be kept at a low concentration, and the low-concentration solution is sprayed into droplets in a high-voltage electrostatic field, and the solvent volatilizes rapidly to form microparticles. Within a certain concentration range, the electrostatic spraying solution will quickly form a large number of droplets in a high-voltage electrostatic field, and the spraying particles will quickly combine with the spinning nanofibers through hydrogen bonds and van der Waals forces before the solvent volatilizes, thereby restraining the nanofibers in a certain space and improving the compactness and tensile strength of the nanofiber membrane. When the concentration of the electrostatic spraying solution is lower than 0.1%, the droplets mainly contain a large amount of solvent, which causes the partial dissolution of the nanofiber membrane with high specific surface area and the collapse of the structure; when the concentration of the electrostatic spraying solution is higher than 5%, the spraying state is broken, and becomes electrospinning, and only a loose nanofiber membrane with low tensile strength can be obtained.

[0095] Specifically, the mass percentage of the second high molecular polymer can be 0.1%, 0.3%, 0.5%, 0.8%, 1%, 1.3%, 1.5%, 1.8%, 2%, 2.3%, 2.5%, 2.8%, 3%, 3.3%, 3.5%, 3.8%, 4%, 4.3%, 4.5%, 4.8%, 5%, and the like.

[0096] The mass percentage of the second solvent can be 95%, 95.2%, 95.5%, 95.7%, 96%, 96.2%, 96.5%, 96.7%, 97%, 97.2%, 97.5%, 957.7%, 98%, 98.2%, 98.5%, 98.7%, 99%, 99.2%, 99.5%, 99.7%, 99.9%, and the like.

[0097] In some embodiments, the mass percentage of the second high molecular polymer in the electrostatic spraying liquid is 1%-3%, and the mass percentage of the second solvent is 97%-99%.

[0098] S3, electrospinning and spraying

[0099] Utilizing Figure 1 The electrospinning liquid and the electrostatic spraying liquid are respectively introduced into the liquid supply pipe 22 through the injection pump 21 by using the preparation device shown in the figure, the spinning and spraying parameters are set, the electrostatic spinning and spraying are performed through the spinning head 3, the composite nanofiber membrane obtained by the electrostatic spinning and spraying is transferred to the hot pressing counter roller 5 through the caterpillar 4, after hot pressing, it is cut through the cutting roller 6, and then it is wound through the winding roller 7 to obtain the composite electrolytic paper.

[0100] According to the embodiments provided by the application, the setting of the spinning and spraying parameters comprises:

[0101] The environmental conditions are preferably: humidity of 10%-40% and temperature of 20-50℃;

[0102] The positive high-voltage electrode plate voltage is 20-100kV, for example: 20kV, 25kV, 30kV, 35kV, 40kV, 45kV, 50kV, 55kV, 60kV, 65kV, 70kV, 75kV, 80kV, 85kV, 90kV, 95kV, 100kV, and the like.

[0103] The spinning distance is 15-40cm, that is, the vertical distance between the spinning head and the caterpillar is 15-40cm, for example: 15cm, 20cm, 25cm, 30cm, 35cm, 40cm, and the like.

[0104] The spraying distance is 15-40 cm, i.e. the vertical distance between the spinneret and the belt is 15-40 cm, for example: 15 cm, 20 cm, 25 cm, 30 cm, 35 cm, 40 cm, etc.

[0105] The sliding speed of the spinneret is 0-50 cm / s, for example: 0 cm / s, 5 cm / s, 10 cm / s, 15 cm / s, 20 cm / s, 25 cm / s, 30 cm / s, 35 cm / s, 40 cm / s, 45 cm / s, 50 cm / s, etc.

[0106] The spinning liquid supply rate is 0.1-5 L / h, for example: 0.1 L / h, 0.5 L / h, 1 L / h, 1.5 L / h, 2 L / h, 2.5 L / h, 3 L / h, 3.5 L / h, 4 L / h, 4.5 L / h, 5 L / h, etc.

[0107] The spraying liquid supply rate is 0.1-5 L / h, for example: 0.1 L / h, 0.5 L / h, 1 L / h, 1.5 L / h, 2 L / h, 2.5 L / h, 3 L / h, 3.5 L / h, 4 L / h, 4.5 L / h, 5 L / h, etc.

[0108] The winding speed is 0.1-10 m / min, for example: 0.1 m / min, 0.5 m / min, 1 m / min, 1.5 m / min, 2 m / min, 2.5 m / min, 3 m / min, 3.5 m / min, 4 m / min, 4.5 m / min, 5 m / min, 5.5 m / min, 6 m / min, 6.5 m / min, 7 m / min, 7.5 m / min, 8 m / min, 8.5 m / min, 9 m / min, 9.5 m / min, 10 m / min, etc.

[0109] The hot-pressing roller distance is 10-100 μm, for example: 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, 100 μm, etc.

[0110] The temperature of the hot-pressing roller is controlled at 100-300 °C, for example: 100 °C, 150 °C, 200 °C, 250 °C, 300 °C, etc.

[0111] On the one hand, the composite nanofiber membrane is compressed to a certain thickness by roller molding, and on the other hand, the composite electrolytic paper blank is obtained by rapid heat treatment of the composite nanofiber membrane, which plays a role in accelerating solvent volatilization and removing polymer macromolecular side chain groups, so that it is more stable in electrolyte or high temperature conditions.

[0112] The supply ratio of the electrospinning liquid and the electro-spraying liquid affects the comprehensive performance of the composite electrolytic paper. When the supply rate of the electrospinning liquid is controlled, if the supply rate of the electro-spraying liquid is too fast, the content of the microparticles in the composite electrolytic paper is too high, the density is too high, the adsorption electrolyte capacity is small, and the ion transmission channel is easily blocked, high ESR and high loss are caused. If the supply rate of the electro-spraying liquid is too slow, the binding force between the nanofiber and the spraying particles is weakened, the composite electrolytic paper is easy to form a fluffy structure, and the tensile strength and the burr resistance are decreased.

[0113] Preferably, the ratio of the spinning liquid supply rate to the spraying liquid supply rate is (0.2-7):1, for example: 0.2:1, 0.5:1, 0.8:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 6.5:1, 7:1, and the like.

[0114] In some embodiments, the ratio of the spinning liquid supply rate to the spraying liquid supply rate is (1-4):1.

[0115] The embodiments of the present application will be described in detail below with reference to the examples, but those skilled in the art will understand that the following examples are only for illustration of the present application and should not be regarded as limiting the scope of the present application. If the specific conditions are not specified in the examples, the conventional conditions or the conditions recommended by the manufacturer are used. If the reagents or instruments used are not specified by the manufacturer, they are all conventional products that can be purchased on the market.

[0116] Example 1

[0117] Taking the preparation process of the polyimide nanofiber / polyvinylidene fluoride particle composite electrolytic paper as an example, the following steps are mainly included:

[0118] First step, preparation of electrospinning liquid: dissolve 4,4'-oxydianiline and pyromellitic dianhydride with a molar ratio of 1:1 in a certain amount of N,N-dimethylformamide, wherein the mass fraction of the solute is 15%, and fully stir at 25°C to obtain a clear electrospinning liquid;

[0119] Second step, preparation of electro-spraying liquid: add a certain amount of polyvinylidene fluoride powder to a certain amount of N,N-dimethylformamide, wherein the mass fraction of the solute is 3%, and fully stir at 60°C to obtain a clear electro-spraying liquid;

[0120] Third step, use Figure 1The preparation device shown, the electrospinning liquid and the electrostatic spraying liquid are introduced into the double-row liquid supply pipe 22 through the injection pump 21 respectively. The parameters are set as follows: the electrospinning liquid supply rate is 1 L / h, the electrostatic spraying liquid supply rate is 0.25 L / h, the positive high-voltage plate voltage is 50 kV, the moving rate and the travel range of the spinneret are 5 cm / s and 60 cm respectively, the rates of the track, the hot-pressing roller, the cutting roller and the winding roller are 3 m / min respectively, the temperature of the hot-pressing roller is 280℃, the roller spacing is 30 μm, and the cutting width of the cutting roller is 50 cm;

[0121] Finally, the voltage is turned on, the composite nanofiber membrane is pulled to the hot-pressing roller through the paper guide, passes through the cutting roller to the winding roller, and the high-strength nanofiber composite electrolytic paper can be continuously collected in a roll.

[0122] The microstructure of the composite electrolytic paper prepared in this example is shown in Figure 2 The composite electrolytic paper is mainly composed of polyimide nanofibers and polyvinylidene fluoride particles. The diameter of the nanofibers is 50-200 nm, the particle size is 1-10 μm, and the nanofiber network pore size is about 0.1-20 μm; the particles are uniformly distributed in the nanofiber network, and the particle surface is tightly combined with multiple nanofibers through a large number of hydrogen bonding and van der Waals force, and the nanofiber bundles are bound in a certain space, making it difficult to separate from the nanofiber network.

[0123] Figure 3 The photo of the composite electrolytic paper prepared in this example shows that the surface is very smooth, and the fiber membrane structure remains intact under the action of external force friction due to its relatively stable structure.

[0124] Example 2

[0125] In this example, the difference from Example 1 is that the mass fraction of solute in the electrospinning liquid is adjusted to 20%, and other parameters remain unchanged.

[0126] Example 3

[0127] In this example, the difference from Example 1 is that the mass fraction of solute in the electrospinning liquid is adjusted to 10%, and other parameters remain unchanged.

[0128] Example 4

[0129] In this example, the difference from Example 1 is that the supply rate of the electrostatic spraying liquid is adjusted to 1 L / h, and other parameters remain unchanged.

[0130] Example 5

[0131] In this example, the difference from Example 1 is that the supply rate of the electrostatic spraying liquid is adjusted to 0.5 L / h, and other parameters remain unchanged.

[0132] Comparative Example 1

[0133] On the basis of Example 1, the electrospinning solution supply valve was closed, the electrostatic spraying solution supply rate was set to 1 L / h, and other parameters were unchanged. The microstructure of the deposited layer on the conveyor belt is shown in FIG. 2B. Only a deposited particle layer could be collected on the conveyor belt, the particle diameter was 0.5-5 μm, and there was a small amount of nanofiber between the particles. Due to the loss of the series connection of the nanofiber, the binding force between the particles was poor. Macrostructure observation found that the mechanical properties of the film layer structure were extremely poor, the film layer was tightly combined with the conveyor belt, and the flexibility was poor. Once the film layer was separated from the conveyor belt, it quickly broke and collapsed, and could not form a continuous film structure. Figure 4

[0134] Comparative Example 2

[0135] On the basis of Example 1, the electrostatic spraying solution supply valve was closed, the electrospinning solution supply rate was set to 1 L / h, and other parameters were unchanged. The microstructure of the electrolytic paper obtained is shown in FIG. 3B. The electrolytic paper was mainly composed of continuous nanofibers, the fiber aspect ratio was extremely high, the diameter was distributed in the range of 0.1-0.8 μm, and the fibers were in a disordered lap joint state. Macrostructure found that the electrolytic paper structure was fluffy, and a certain degree of tensile deformation occurred during the traction process. Under the action of external force friction, the nanofibers on the surface of the electrolytic paper were easily detached. Figure 5

[0136] Comparative Example 3

[0137] The conventional N-30 electrolytic paper with a thickness of 30 μm was cut according to the required specifications for testing and product testing to prepare a comparative test standby.

[0138] Performance Test

[0139] The composite electrolytic paper prepared in Examples 1-5 and the electrolytic paper in Comparative Examples 1-3 were tested for roughness, density, tensile strength, breakdown voltage, and specific surface area.

[0140] Among them, the roughness of the electrolytic paper was tested by atomic force microscopy;

[0141] Density test: the thickness of ten layers of superimposed electrolytic paper was tested by a thickness tester, the average value of five test points was taken and divided by 10 as the thickness of the sample, the electrolytic paper with a length and width of 10 cm was cut, its weight was measured, and the density was calculated according to the following formula: density (g / cm 3 ) = weight (g) / (length (cm) * width (cm) * thickness (cm));

[0142] Tensile strength was tested by a tensile testing machine;

[0143] ​​The breakdown voltage test was performed at a rate of 30V per step, starting from 350V, until the electrolytic paper was broken down, and the breakdown voltage value was recorded. Each sample was tested twice in parallel.

[0144] The specific surface area was measured by a specific surface analyzer.

[0145] The test results are shown in Table 1.

[0146] The composite electrolytic paper prepared in Examples 1-5 and the electrolytic paper in Comparative Examples 1-3 were each assembled into 1000 aluminum electrolytic capacitor products. The product specification was 500V 100μF, and the product size was 18*45mm. The preparation process was as follows: first, the two kinds of electrolytic paper, aluminum foil and lead strip were cut into rolls; then the rolls were riveted with the two kinds of electrolytic paper respectively to form the cores, the cores were soaked with the prepared electrolyte, and the aluminum shell and sleeve were printed and assembled, and finally the composite electrolytic paper capacitor and the traditional electrolytic paper capacitor were obtained after aging, and the equivalent series resistance and product failure rate of the electrolytic capacitor were tested and calculated. The results are shown in Table 1.

[0147] Table 1

[0148]

[0149] It can be found from Comparative Examples 1, 4 and 5 that under the condition of keeping the total supply amount of the electrospinning liquid and the electrostatic spraying liquid constant, adjusting the supply rate ratio of the electrospinning liquid and the electrostatic spraying liquid can obtain composite electrolytic paper with different densities. The higher the electrostatic spraying rate, the greater the density of the composite electrolytic paper, and the tensile strength also increases to a certain extent. This is because the more the microparticles, the stronger the constraint of the electrospinning fibers, and the better the compactness of the fiber membrane. At the same time, the more the microparticles, the more the combination sites of the electrospinning fibers and the microparticles, and the tighter the overall combination, so the tensile strength of the composite electrolytic paper also increases to a certain extent.

[0150] It can be found from the performance of the electrolytic capacitors assembled by the products of Comparative Examples 1-5 and Comparative Examples 1-3 that the breakdown voltage resistance of the composite electrolytic paper in Examples 1-5 is significantly higher than that of the traditional electrolytic paper. The equivalent series resistance (ESR) of the capacitor products assembled by Examples 1-5 is about 50% lower than that of the electrolytic capacitor products assembled by N-30 electrolytic paper. When assembling electrolytic capacitors with electrolytic paper of the same thickness, the product failure rate of the electrolytic capacitors assembled by the composite electrolytic paper is less than 3%, which is much lower than the product failure rate of the electrolytic capacitors assembled by N-30 electrolytic paper.

[0151] In the description of the specification, the description using the terms "one embodiment", "another embodiment", "an embodiment", "example", etc. means that the specific feature, structure, material or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present application. Descriptive expressions of the above terms in the specification do not necessarily refer to the same embodiment or example. Also, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. Furthermore, the person skilled in the art can combine and combine the different embodiments or examples described in the specification and the features of the different embodiments or examples, without contradiction.

[0152] Although the embodiments and examples of the present application have been shown and described above, it is understood that the above-described embodiments and examples are exemplary and are not to be construed as limiting the present application, and the person skilled in the art can make changes, modifications, replacements and variations to the above-described embodiments and examples within the scope of the present application.

Claims

1. A method for preparing composite electrolytic paper using a composite electrolytic paper apparatus, characterized in that, Includes the following steps: S1. Preparation of electrospinning solution: Dissolve the first polymer in the first solvent to obtain the electrospinning solution; S2. Preparation of electrostatic spray solution: Dissolve the second polymer in the second solvent to obtain the electrostatic spray solution; S3. Electrospinning and spraying: The electrospinning solution and electrospinning spray solution are transferred to the spinneret through the liquid supply device. The spinning and spraying parameters are set, and electrospinning and spraying are carried out. The composite nanofiber membrane obtained by electrospinning and spraying is transferred to the hot press rollers through the conveyor belt. After hot pressing, the composite electrolytic paper is obtained. The composite electrolytic paper device includes a positive high voltage electrode plate, a liquid supply device, a spinneret, a conveyor belt, and hot-pressing rollers; Wherein: a high-voltage electrostatic field is formed between the positive high-voltage electrode plate and the track; The liquid supply device is located below the positive high voltage electrode plate and is used to provide electrospinning solution and electrostatic spray solution; The spinneret is connected to the liquid supply device and is used to electrospin and spray the electrospinning solution and electrospinning spray solution to form a composite nanofiber membrane. The track is grounded and used to collect the composite nanofiber membrane and continuously transfer the composite nanofiber membrane to the hot-pressing rollers; The hot-pressing rollers are used to roll-press the composite nanofiber membrane into shape to obtain composite electrolytic paper; The liquid supply device includes an injection pump and a liquid supply tube, and the spinneret is slidably connected to the liquid supply tube; The composite electrolytic paper apparatus also includes a take-up roller for collecting the obtained composite electrolytic paper; The first polymer is selected from polyimide; the first solvent is selected from N,N-dimethylformamide; In the electrospinning solution, the mass percentage of the first polymer is 10%-40%, and the mass percentage of the first solvent is 60%-90%. The second polymer is selected from polyvinylidene fluoride; the second solvent is selected from N,N-dimethylformamide; In the electrostatic spray liquid, the second polymer accounts for 0.1%-5% by mass, and the second solvent accounts for 95%-99.9% by mass. The spinning or spray liquid supply rate is 0.1-5 L / h, and the ratio of the spinning liquid supply rate to the spray liquid supply rate is (0.2-7):

1.

2. The method for preparing composite electrolytic paper according to claim 1, characterized in that, The spinning and spraying parameters are set as follows: humidity 10%-40% and temperature 20℃-50℃.

3. The method for preparing composite electrolytic paper according to claim 1, characterized in that, The voltage of the positive high voltage electrode plate is 20-100kV.

4. The method for preparing composite electrolytic paper according to claim 1, characterized in that, The spinning or spraying distance is 15-40cm.

5. The method for preparing composite electrolytic paper according to claim 1, characterized in that, The sliding speed of the spinneret is 0-50 cm / s.

6. The method for preparing composite electrolytic paper according to claim 1, characterized in that, The gap between the hot pressing rollers is 10-100μm, and the temperature of the hot pressing rollers is 100-300℃.

7. The method for preparing composite electrolytic paper according to claim 1, characterized in that, The winding speed is 0.1-10 m / min.

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