Degradable ultrafine fibers, methods of making the same, nanobased energy storage separators, and ultrathin high-strength supercapacitor separator materials

Abstract

The application discloses a preparation method of degradable superfine fibers, and belongs to the technical field of capacitor diaphragm materials.The preparation method comprises the following steps: (1) liquid nitrogen quenching and freeze-drying of Tencel fibers, then soaking in a polar small molecule solution, and stretching at-50 DEG C to-30 DEG C; (2) using a pulper to prepare a raw slurry with a mass concentration of 5% to 20% from the pretreated Tencel fibers; (3) fibrillation treatment of the raw slurry, and then obtaining superfine fibers through defibration.The application further discloses a nanometer-based energy storage diaphragm and an ultrathin high-strength supercapacitor diaphragm material prepared from the superfine fibers.The preparation method of the application can form microcracks in Tencel fibers while ensuring the mechanical properties of the fibers through liquid nitrogen quenching, freeze-drying, polar small molecule soaking and low-temperature stretching, and then the superfine fibers with uniform diameters and good mechanical properties can be obtained through mechanical treatment, which is suitable for the technical field of capacitor diaphragm materials.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of capacitor separator materials, and particularly relates to a degradable ultrafine fiber, a preparation method thereof, a nano-based energy storage separator and an ultra-thin high-strength super capacitor separator material. BACKGROUND

[0002] In modern battery technology, the separator, as a key component, plays a decisive role in the performance and safety of the battery. The rapid development of energy storage devices such as lithium ion batteries and super capacitors puts extremely strict requirements on the performance of the separator. Not only does it need to have the function of isolating the positive and negative electrodes and preventing internal short circuit, but it also needs to provide an efficient channel for ion transmission, while taking into account the thermal stability, electrolyte wettability and other performances.

[0003] At present, the most widely used lithium battery separator in commercial applications is mainly PE film and PP film. With its cost advantage and certain mechanical properties, it dominates the market. However, with the increasing demand for the improvement of battery energy density, the inherent defects of polyolefin separators gradually become prominent. For example, the poor electrolyte wettability leads to low ion conductivity, which limits the performance of the battery in high-power output scenarios, and the poor wettability also affects the electrochemical stability of the battery.

[0004] In view of the many shortcomings of PE film and PP film, researchers have turned their attention to biomass cellulose materials, hoping to develop a separator with better performance. As a solvent-type regenerated cellulose fiber, Tencel fiber has a unique core-sheath structure, high crystallinity, good orientation, and molecular chains tend to align along the fiber axis. The transverse bonding force between the fibrils is relatively weak. This structural feature makes it easy for the bonding force between the fibrils to be weakened when subjected to external factors such as shear force, friction force, mechanical force, etc., and then peeled off to form fibrillated fibers. At the same time, the molecular chains of Tencel fiber are short and the crystal lattice voids are large, so solvent molecules can easily penetrate into the interior of the fiber. When applied to the preparation of a separator, the fibrillated Tencel fiber can form a unique microstructure, making the prepared separator have the advantages of small pore size and high porosity, and perform well in isolation performance, effectively preventing the short circuit of the positive and negative electrodes of the battery, while providing a fast channel for ion transmission, meeting the key performance requirements of the battery for the separator.

[0005] Despite the significant potential of Tencel fiber in membrane fabrication, current methods for fibrillating Tencel fibers still require improvement. Traditional fibrillation methods, such as mechanical beating, are not only energy-intensive and inefficient but also struggle to precisely control the degree of fibrillation, resulting in inconsistent quality of the produced fibrillated Tencel fibers. During beating, fibers are easily over-cut, significantly reducing the final fiber length and impacting membrane strength. Using chemical reagents like acids and alkalis to assist fibrillation disrupts glycosidic bonds in the cellulose molecular chain, leading to chemical degradation, reduced polymerization, and a tendency for "over-fragmentation" rather than "orderly exfoliation" during fibrillation, ultimately affecting the membrane's mechanical properties.

[0006] Therefore, developing an efficient, precise, green and environmentally friendly method for the fibrillation of Tencel fibers is of urgent practical significance for improving the performance of Tencel fiber-based separators and promoting their widespread application in the battery field. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing biodegradable microfibers. This method involves pretreatment of Tencel fibers using liquid nitrogen rapid cooling, freeze-drying, immersion in polar small molecules, and low-temperature stretching. This process creates microcracks in the Tencel fibers while maintaining their mechanical properties. Then, mechanical treatment is used to form microfibers, improving the diameter uniformity and mechanical properties of the microfibers and solving the problem of poor quality in existing microfiber preparation techniques.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is: a method for preparing biodegradable microfibers, characterized in that the preparation method includes the following steps:

[0009] Step 1: Pre-treat the Tencel fiber. The pre-treatment method is as follows: rapid cooling with liquid nitrogen followed by freeze drying, then immersion in a polar small molecule solution, and stretching at -50℃ to -30℃.

[0010] Step 2: The pretreated Tencel fibers from Step 1 are processed into a pulp with a mass concentration of 5% to 20% using a pulping machine;

[0011] Step 3: The raw pulp obtained in Step 2 is subjected to fibrillation treatment, and then ultrafine fibers are obtained through decomposition.

[0012] The application realizes rapid freezing of the whole fiber by rapidly cooling the Tencel fiber under the ultra-low temperature environment through liquid nitrogen quenching, because the heat transfer path of the Tencel fiber with a diameter of 10-30 μm is short; during the freezing process, the thermal motion of the cellulose molecular chain is sharply limited, and the hydrogen bond in the amorphous region is instantaneously contracted, thereby forming uniform micro stress cracks on the surface and inside of the Tencel fiber, especially at the interface between the skin layer and the core layer of the skin-core structure, and weakening the dense layer structure on the surface of the Tencel fiber, thereby providing a "breakthrough" for subsequent fibrillation treatment, and avoiding disorderly breaking of the Tencel fiber caused by mechanical treatment at normal temperature; then, ice crystals are sublimated through freeze-drying, thereby avoiding surface tension caused by water evaporation during conventional drying, and causing fiber structure collapse or fibril adhesion, and further preserving the loose structure induced by liquid nitrogen quenching;

[0013] By the soaking treatment in the polar small molecule solution, the polar small molecules penetrate into the amorphous region and micro cracks of the cellulose, form hydrogen bonds with the hydroxyl groups on the cellulose molecular chain, partially replace the original hydrogen bonds between the cellulose molecules, weaken the binding force between the molecular chains, play a lubricating role, maintain a certain flexibility while preserving the dispersion state of the crystalline region, avoid fiber breakage caused by excessive brittleness during subsequent low-temperature stretching, and provide protection for ordered deformation; in addition, the polar small molecules can repair defects and strengthen the crystal boundary through hydrogen bonds, thereby long-term maintaining the strengthening effect on the crystalline region;

[0014] By performing low-temperature stretching, the cellulose molecular chain has weak thermal motion under the low-temperature environment, and is more prone to "forced orientation" rather than disorderly sliding during stretching, thereby improving the crystallinity and mechanical strength of the Tencel fiber, and meeting the requirement of the battery separator on mechanical stability; when the stretching stress is transmitted along the fiber axis, it will act on the micro cracks and the weak structure weakened by the polar small molecules, and promote the ordered peeling of the fibrils on the surface and inside of the Tencel fiber along the axial direction; at the same time, the stretching can make the peeled fibrils directionally arrange along the stress direction, and improve the mechanical anisotropy; then, the fibrillation treatment is performed through the high-concentration mill or the disc mill, so that the Tencel fiber forms superfine fibers under the friction and shearing action, and because the Tencel fiber is pretreated before fibrillation, the subsequent mechanical processing time can be effectively shortened, and the production cost can be reduced.

[0015] The preparation method of the degradable superfine fiber has the characteristics that the polar small molecule in the step one is one or two or more than two of a polyol, an amine and a urea, the mass concentration of the polar small molecule solution is 3%-15%, and the soaking treatment time is not less than 60 min.

[0016] The application can quickly enter the micro-cracks or the edge of the crystalline region of the Tencel fiber by selecting a small polar molecule with a polar group, a small size and easy penetration, and the small polar molecule can form a hydrogen bond or a polar interaction with the molecules of the material, can strengthen the intermolecular force, adjust the flexibility, help the Tencel fiber to be more easily oriented and arranged during stretching, and improve the crystallinity; the quality concentration and soaking time are controlled to avoid the strong plasticizing effect caused by the excessive concentration, the hydroxyl group of glycerol forms a competitive hydrogen bond with the cellulose molecules, the interaction between the molecular chains in the amorphous region is further reduced, and the fibrils are more easily separated from the main body.

[0017] The preparation method of the degradable ultrafine fiber has the characteristics that the stretching ratio of the stretching in step one is 1.1-1.3 times, and the stretching speed of the stretching is not greater than 10 mm / min.

[0018] The application can make the molecular chains orderly orient under low-temperature constraint by controlling the stretching ratio and speed, and the stability of the original crystalline region is not damaged, the stress concentration caused by excessive stretching in the local part is avoided, the crystalline region structure is damaged, the molecular chains cannot stably keep the orientation structure in the stretching process due to the low-temperature slow relaxation effect, the orientation degree is insufficient, and the strength improvement is difficult to realize.

[0019] The application further discloses the degradable ultrafine fiber obtained by the preparation method.

[0020] The application further discloses a nanometer-based energy storage diaphragm material, and has the characteristics that the raw materials of the nanometer-based energy storage diaphragm material include ultrafine fibers, nanometer fibers and modified ceramic fibers, the mass ratio of the ultrafine fibers, the nanometer fibers and the modified ceramic fibers is 70-95:1-20:1-15, and the nanometer fibers are one or two or more than two of cellulose nanocrystals, cellulose nanofibers and bacterial cellulose.

[0021] The application forms a macroscopic skeleton of the nanometer-based energy storage diaphragm material by using the ultrafine fibers, provides the basic mechanical strength, the macroscopic skeleton, the pore channel and the stable overall structure of the nanometer-based energy storage diaphragm material, adds the micron-level modified ceramic fibers and the nanometer-level nanometer fibers, the modified ceramic fibers can be used as a dispersant, hydrogen bonds are formed between the amino groups on the surface of the modified ceramic fibers and the hydroxyl groups of the nanometer fibers, the uniform distribution of the nanometer fibers is promoted, and the modified ceramic fibers and the nanometer fibers are dispersed in the macroscopic skeleton.

[0022] The micro network is formed by the entanglement and lap joint between the fibers, the part of the pores of the macro skeleton is filled, the interface performance is optimized, the super fine fibers are combined with the micro base material through the hydrogen bond, the specific surface area of the micro base material is increased, the pore size of the micro base material is reduced, the contact area between the micro base material and the electrolyte is significantly increased, and the liquid retention capacity is improved; meanwhile, more nano channels are provided for ion transmission, and the ion migration rate is accelerated.

[0023] The nano-based energy storage diaphragm material has the following characteristics: the modification step of the modified ceramic fiber is as follows:

[0024] In step one, the modification component is dissolved in a diluent, and then a Lewis acid is added to obtain a modifier; the mass ratio of the modification component to the diluent is 1:15-30, the modification component is one or more than two of 2-[2-(2,6-dichlorophenyl)ethyl]hydrazine carboxamide, N-amidyl-2-(2,6-dichlorophenyl)acetamide, and N,N-di(4-chlorophenyl)ethyl amid, and the diluent is one or more than two of tetrahydrofuran, dichloromethane, dichloroethane, and trichloromethane;

[0025] In step two, the ceramic fiber is soaked in the modifier obtained in step one at 60-75 DEG C for 6-8 hours, and then washed with the diluent in step one and dried.

[0026] The present application modifies the ceramic fiber by using the amidine-containing modification component to introduce the amino group, optimizes the ion transmission path through the lyophilicity of the amino group to the electrolyte and the weak interaction with lithium ions, and makes up for the high-temperature resistance defect of the tencel fiber.

[0027] The nano-based energy storage diaphragm material has the following characteristics: the modification step of the modified ceramic fiber is as follows:

[0028] The nanometer-based energy storage diaphragm material has the following preparation method: super fine fibers, nanofibers and modified ceramic fibers are respectively added with water to prepare super fine fiber slurry, nanofiber slurry and modified ceramic fiber slurry, then the super fine fiber slurry, the nanofiber slurry and the modified ceramic fiber slurry are respectively mixed into slurry A and slurry B, the slurry A and the slurry B are respectively placed on two wire meshes of a double-cylinder paper machine to form, then pressing, drying, gluing, coating, drying, polishing, scanning detection, curling and slitting are performed to obtain the nanometer-based energy storage diaphragm material, and the mass ratio of the modified ceramic fibers in the slurry A and the slurry B is 0.5-1:2.

[0029] The nanometer-based energy storage diaphragm material is prepared by controlling the mass ratio of the modified ceramic fibers in the slurry A and the slurry B and using the double-cylinder paper machine, and an amino gradient is formed; the high-amino side contacts the positive electrode, forms a coordination complex through a coordination bond to efficiently capture metal ions dissolved from the positive electrode, reduces migration of the metal ions to the negative electrode, and avoids capacity attenuation or short circuit risk caused by deposition of the metal ions on the negative electrode; the low-amino side contacts the negative electrode, promotes ion transmission through weak interaction with lithium ions, and avoids increase of ion conduction resistance caused by excessive amino groups.

[0030] The application further discloses a super-thin high-strength supercapacitor diaphragm material, and the raw materials of the super-thin high-strength supercapacitor diaphragm material include super fine fibers, flax fibers, acrylonitrile super fine fibers and aramid fibers, and the mass ratio of the super fine fibers, the flax fibers, the acrylonitrile super fine fibers and the aramid fibers is 70-90:8-15:2-10:2-5.

[0031] The super-thin high-strength supercapacitor diaphragm material has the following preparation method: super fine fibers, flax fibers, acrylonitrile super fine fibers and aramid fibers are respectively added with water to prepare super fine fiber slurry, flax fiber slurry, acrylonitrile super fine fiber slurry and aramid fiber slurry, then the super fine fiber slurry, the flax fiber slurry, the acrylonitrile super fine fiber slurry and the aramid fiber slurry are mixed and formed by using a long net or a cylinder paper machine, then pressing, drying, curling and slitting are performed to obtain the super-thin high-strength supercapacitor diaphragm material.

[0032] Compared with the prior art, the application has the following advantages:

[0033] 1. The application realizes the ordered fibrillation of Tencel fibers by pretreating the Tencel fibers, under the synergistic effect of rapid cooling induced pre-fibrillation, structure shape retention, force weakening and directional stretching, combined with mechanical fibrillation treatment, and taking into account the mechanical properties of strength and flexibility; compared with traditional fibrillation methods, the preparation method of the application can greatly reduce the damage of Tencel fibers and improve the mechanical properties of superfine fibers after fibrillation, and is more suitable for preparing battery separators with strict requirements on strength, structure uniformity and electrochemical stability.

[0034] 2. The application forms a macroscopic morphology of nanometer-based energy storage separator material by superfine fibers, adds micron-sized modified ceramic fibers and nanometer-sized nanofibers, and forms an integrated separator structure of macroscopic support + microscopic regulation under the interaction of hydrogen bonds, amino groups and hydroxyl groups, achieving synergistic enhancement in mechanical strength, thermal stability, ion conductivity and the like.

[0035] 3. The application adds flax fibers with hollow structure and natural gully in the skeleton composed of superfine fibers, which can reduce the fiber accumulation amount in unit volume, improve the overall porosity and reduce the thickness of the separator; by adding aramid fibers with ultra-high strength, high modulus and high temperature resistance, the tensile strength and puncture resistance of the separator are improved, which can inhibit the dimensional deformation under high temperature environment while ensuring the small thickness of the separator material, avoiding the short circuit risk caused by structure collapse; by adding small-diameter acrylonitrile superfine fibers to fill the gaps between other fibers, a finer three-dimensional network is formed, which indirectly improves the tensile strength by increasing the contact between points and surfaces without increasing the overall density; then the uniform distribution of flax fibers, acrylonitrile superfine fibers and aramid fibers is ensured by water dispersion, reducing the local high-density area caused by fiber agglomeration, and finally obtaining an ultra-thin high-strength supercapacitor separator material.

[0036] 4. The superfine fibers prepared by the application have small and uniform diameter, greatly improved specific surface area and strong hydrophilicity, which can significantly improve the wettability of the separator and reduce the interface resistance; when the separator is prepared by papermaking method, the pore size between fibers will be finer, and the pore distribution will be very narrow, avoiding the problem of large pore inclusion caused by mixing of coarse and fine fibers, which can accurately control the size of the permeated material, while allowing fast migration of lithium ions, and the transmission path is more uniform, reducing the risk of local short circuit.

[0037] The technical solutions of the application will be further described in detail below with reference to the drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 The micrograph of the superfine fiber prepared in Example 1.

[0039] Figure 2A micrograph of the superfine fiber prepared in Comparative Example 1. DETAILED DESCRIPTION

[0040] Example 1

[0041] The method for preparing the superfine fiber in this example includes the following steps:

[0042] Step 1, the Tencel fiber with fineness of 1.4DTEX-2.0DTEX is quenched by liquid nitrogen and freeze-dried, then soaked in a glycerol solution with mass concentration of 15% for 60 min, and stretched at -30°C; the stretching ratio of the stretching is 1.2 times, and the stretching rate of the stretching is not more than 10 mm / min;

[0043] Step 2, the pretreated Tencel fiber in Step 1 is made into stock pulp with mass concentration of 10%-20% by a pulper;

[0044] Step 3, the stock pulp obtained in Step 2 is fibrillated by a high-concentration refiner for 1.5h-2h, and then defiberized by a refiner to obtain the superfine fiber.

[0045] The glycerol in this example can also be replaced by one or more than two of the following: polyols, amines, and ureas.

[0046] The superfine fiber prepared in this example has a diameter of not more than 0.2μm and uniform diameter, as shown in Figure 1

[0047] Example 2

[0048] The method for preparing the superfine fiber in this example includes the following steps:

[0049] Step 1, the Tencel fiber with fineness of 1.4DTEX-2.0DTEX is quenched by liquid nitrogen and freeze-dried, then soaked in a polar small molecule solution for 100 min, and stretched at -40°C; the stretching ratio of the stretching is 1.3 times, and the stretching rate of the stretching is not more than 10 mm / min; the polar small molecule solution contains glycerol with mass concentration of 5% and urea with mass concentration of 5%;

[0050] Step 2, the pretreated Tencel fiber in Step 1 is made into stock pulp with mass concentration of 5%-10% by a pulper;

[0051] Step 3, the stock pulp obtained in Step 2 is fibrillated by a single-disc refiner for 2.5h-3.5h, and then defiberized by a refiner to obtain the superfine fiber.

[0052] It is found by inspection that the superfine fiber prepared in this example has a diameter of not more than 0.2μm and uniform diameter.​

[0053] Comparative Example 1

[0054] The preparation method of the superfine fiber of the present comparative example comprises the following steps:

[0055] Step one, the Tencel fiber with fineness of 1.4DTEX-2.0DTEX is added water to pass through a pulper to form a stock with mass concentration of 5%-10%;

[0056] Step two, the stock obtained in step one is fibrillated by a single disc refiner for 6h, and then is defibered by a refiner to obtain the superfine fiber.

[0057] The superfine fiber prepared in the present comparative example has a large difference in diameter between the superfine fibers as shown in Figure 2

[0058] Example 3

[0059] The preparation method of the superfine fiber of the present example comprises the following steps:

[0060] Step one, the Tencel fiber with fineness of 1.4DTEX-2.0DTEX is quenched by liquid nitrogen, then is freeze-dried, and then is immersed in an ethylenediamine solution with mass concentration of 3% for 80min, and is stretched at-50℃; the stretching ratio of the stretching is 1.1 times, and the stretching rate of the stretching is not more than 10mm / min;

[0061] Step two, the pretreated Tencel fiber in step one is passed through a pulper to form a stock with mass concentration of 5%-10%;

[0062] Step three, the stock obtained in step two is fibrillated by a single disc refiner for 1h-1.5h, and then is fibrillated by a double disc refiner for 1h-1.5h, and then is defibered by a refiner to obtain the superfine fiber.

[0063] After inspection, the diameter of the superfine fiber prepared in the present example is not more than 0.15μm, and the diameter is uniform.

[0064] Example 4

[0065] The superfine fiber prepared in Example 1 is used to prepare a nanometer-based energy storage diaphragm material, and the preparation method comprises the following steps:

[0066] Step one, a modifying component is dissolved in a diluent, and then a Lewis acid is added to obtain a modifier with pH of 6; the mass ratio of the modifying component to the diluent is 1:20, the modifying component is 2-[2-(2,6-dichlorophenyl)ethyl]hydrazine carboxamide and N-amido-2-(2,6-dichlorophenyl)acetamide, and the diluent is tetrahydrofuran;

[0067] ​Step two, soaking the ceramic fiber with a diameter of 1-4 μm in the modifier obtained in step one at 60℃ for 7.5 h, then cleaning with tetrahydrofuran and drying to obtain modified ceramic fiber;

[0068] Step three, dispersing the ultra-fine fiber, nanofiber with a diameter of 20-30 nm and modified ceramic fiber obtained in step two in water respectively to prepare ultra-fine fiber slurry, nanofiber slurry and modified ceramic fiber slurry, then mixing the three slurries under ultrasonic assistance to form a mixed slurry, forming by long net or circular net paper machine, then performing pressing, drying, sizing, coating, drying, calendering, scanning detection, curling and slitting to obtain nanometer-based energy storage separator material; the nanofiber is cellulose nanocrystal and cellulose nanofiber, and the mass ratio of ultra-fine fiber, nanofiber and modified ceramic fiber in the mixed slurry is 75:10:15.

[0069] Comparative example 2

[0070] The difference between this comparative example and example 4 is that the ultra-fine fiber prepared in comparative example 1 is used to prepare the separator material.

[0071] Example 5

[0072] The difference between this example and example 4 is that in step three, the ultra-fine fiber, nanofiber and modified ceramic fiber are dispersed in water respectively to prepare ultra-fine fiber slurry, nanofiber slurry and modified ceramic fiber slurry, then the ultra-fine fiber slurry, nanofiber slurry and modified ceramic fiber slurry are mixed under ultrasonic assistance to form slurry A and slurry B, and slurry A and slurry B are respectively placed on two circular nets of a double circular net paper machine to form, then performing pressing, drying, sizing, coating, drying, calendering, scanning detection, curling and slitting to obtain nanometer-based energy storage separator material; the nanofiber is bacterial cellulose and cellulose nanofiber; the mass ratio of ultra-fine fiber, nanofiber and modified ceramic fiber in slurry A is 80:5:7, and the mass ratio of ultra-fine fiber, nanofiber and modified ceramic fiber in slurry B is 80:5:14.

[0073] Example 6

[0074] The difference between this example and example 5 is that in step three, the mass ratio of ultra-fine fiber, nanofiber and modified ceramic fiber in slurry A is 90:3:2, and the mass ratio of ultra-fine fiber, nanofiber and modified ceramic fiber in slurry B is 90:3:8.

[0075] Example 7

[0076] The nanometer-based energy storage separator material is prepared by using the ultra-fine fiber prepared in example 2, and the preparation method comprises the following steps:

[0077] Step one, dissolving the modified component in diluent, then adding Lewis acid, obtaining the modifier with pH 5; the mass ratio of the modified component to diluent is 1:30, the modified component is 2-[2-(2,6-dichlorophenyl)ethyl]hydrazine carboxamide and N,N-di(4-chlorophenyl)acetamide, and the diluent is tetrahydrofuran;

[0078] Step two, soaking the ceramic fiber with a diameter of 1-4 μm in the modifier obtained in step one at 75℃ for 8 hours, then cleaning with dichloromethane and drying to obtain modified ceramic fiber;

[0079] Step three, dispersing the superfine fiber, nanofiber with a diameter of 30-50 nm, and the modified ceramic fiber obtained in step two in water respectively to prepare superfine fiber slurry, nanofiber slurry, and modified ceramic fiber slurry, then mixing them under ultrasonic assistance to form mixed slurry, using long net or round net paper machine to form, then carrying out pressing, drying, sizing, coating, drying, calendering, scanning detection, curling and slitting to obtain nanobased energy storage separator material; the nanofiber is cellulose nanocrystal, and the mass ratio of superfine fiber, nanofiber, and modified ceramic fiber in the mixed slurry is 95:1:4.

[0080] Example 8

[0081] Using the superfine fiber prepared in Example 3 to prepare nanobased energy storage separator material, the preparation method comprising the following steps:

[0082] Step one, dissolving the modified component in diluent, then adding Lewis acid, obtaining the modifier with pH 5; the mass ratio of the modified component to diluent is 1:15, the modified component is 2-[2-(2,6-dichlorophenyl)ethyl]hydrazine carboxamide, N-amidino-2-(2,6-dichlorophenyl)acetamide and N,N-di(4-chlorophenyl)acetamide, and the diluent is dichloromethane;

[0083] Step two, soaking the ceramic fiber with a diameter of 1-4 μm in the modifier obtained in step one at 70℃ for 6 hours, then cleaning with dichloromethane and drying to obtain modified ceramic fiber;

[0084] Step three, dispersing the superfine fiber, nanofiber with a diameter of 15-25 nm, and the modified ceramic fiber obtained in step two in water respectively to prepare superfine fiber slurry, nanofiber slurry, and modified ceramic fiber slurry, then mixing them under ultrasonic assistance to form mixed slurry, using long net or round net paper machine to form, then carrying out pressing, drying, sizing, coating, drying, calendering, scanning detection, curling and slitting to obtain nanobased energy storage separator material; the nanofiber is cellulose nanocrystal, and the mass ratio of superfine fiber, nanofiber, and modified ceramic fiber in the mixed slurry is 70:20:15.

[0085] Example 9

[0086] The preparation method of the ultra-thin high-strength supercapacitor separator material prepared by using the superfine fibers prepared in Example 1 is as follows: superfine fibers are dispersed by using a combing machine to prepare superfine fiber slurry, flax fibers are dispersed by using a beater to prepare flax fiber slurry, acrylonitrile superfine fibers are soaked in water at 40-50°C for 3h to prepare acrylonitrile superfine fiber slurry, aramid fibers are dispersed by using a combing machine to prepare aramid fiber slurry, and then the superfine fiber slurry, the flax fiber slurry, the acrylonitrile superfine fiber slurry and the aramid fiber slurry are ultrasonically assisted to mix to form a mixed slurry, which is formed by using a long net or a round net paper machine, followed by pressing, drying, curling and cutting to obtain the ultra-thin high-strength supercapacitor separator material; the mass ratio of the superfine fibers, the flax fibers, the acrylonitrile superfine fibers and the aramid fibers in the mixed slurry is 70:8:10:5.

[0087] Example 10

[0088] The preparation method of the ultra-thin high-strength supercapacitor separator material prepared by using the superfine fibers prepared in Example 2 is as follows: superfine fibers are dispersed by using a combing machine to prepare superfine fiber slurry, flax fibers are dispersed by using a beater to prepare flax fiber slurry, acrylonitrile superfine fibers are soaked in water at 40-50°C for 3h to prepare acrylonitrile superfine fiber slurry, aramid fibers are dispersed by using a combing machine to prepare aramid fiber slurry, and then the superfine fiber slurry, the flax fiber slurry, the acrylonitrile superfine fiber slurry and the aramid fiber slurry are ultrasonically assisted to mix to form a mixed slurry, which is formed by using a long net or a round net paper machine, followed by pressing, drying, curling and cutting to obtain the ultra-thin high-strength supercapacitor separator material; the mass ratio of the superfine fibers, the flax fibers, the acrylonitrile superfine fibers and the aramid fibers in the mixed slurry is 80:15:2:4.

[0089] Example 11

[0090] The difference between this example and Example 10 is that the mass ratio of the superfine fibers, the flax fibers, the acrylonitrile superfine fibers and the aramid fibers in the mixed slurry is 90:10:3:2.

[0091] The separator materials prepared in Comparative Example 2 and Examples 4-11 are heated at 150°C for 1h, and the separator materials all show smooth surface, no holes or molten dripping; the separator materials prepared in Comparative Example 2 and Examples 4-11 are detected for various performances, and the results are shown in Table 1.

[0092] Table 1 Performance of the separator materials prepared in Examples 4-11

[0093]

[0094] The above merely describes preferred embodiments of the present application, and is not intended to limit the present application. Any simple modification, change, and equivalent structural transformation of the above embodiments according to the technical essence of the present application are still within the protection scope of the technical solution of the present application.

Claims

1. A process for the production of degradable ultrafine fibers, characterized in that, The preparation method includes the following steps: Step 1: Pre-treat the Tencel fiber; the pre-treatment method is as follows: rapid cooling with liquid nitrogen followed by freeze drying, then immersion in a polar small molecule solution, and stretching at -50℃ to -30℃. Step 2: The pretreated Tencel fibers from Step 1 are processed into a pulp with a mass concentration of 5% to 20% using a pulping machine; Step 3: The raw pulp obtained in Step 2 is subjected to fibrillation treatment, and then ultrafine fibers are obtained through decomposition.

2. The method for preparing biodegradable microfiber according to claim 1, characterized in that, The polar small molecules mentioned in step one are one or more of polyols, amines, and ureas, the mass concentration of the polar small molecule solution is 3% to 15%, and the soaking treatment time is not less than 60 minutes.

3. The method for preparing biodegradable microfiber according to claim 1, characterized in that, The stretching ratio in step one is 1.1 to 1.3 times, and the stretching rate is no more than 10 mm / min.

4. Biodegradable microfiber, characterized in that, It is obtained by the preparation method described in any one of claims 1 to 3.

5. The nano-based energy storage membrane material prepared using the biodegradable ultrafine fibers according to claim 4, characterized in that, The raw materials of the nano-based energy storage membrane material include ultrafine fibers, nanofibers, and modified ceramic fibers, and the mass ratio of ultrafine fibers, nanofibers, and modified ceramic fibers is 70-95:1-20:1-15; the nanofibers are one or more of cellulose nanocrystals, cellulose nanofibers, and bacterial cellulose.

6. The nano-based energy storage membrane material according to claim 5, characterized in that, The modification steps for the modified ceramic fiber are as follows: Step 1: Dissolve the modified component in a diluent, then add Lewis acid to obtain the modifier; the mass ratio of the modified component to the diluent is 1:15-30, the modified component is one or more of 2-[2-(2,6-dichlorophenyl)ethyl]hydrazine, N-amidinyl-2-(2,6-dichlorophenyl)acetamide, and N,N-bis(4-chlorophenyl)acetamide, and the diluent is one or more of tetrahydrofuran, dichloromethane, dichloroethane, chloroform, and chloroethane; Step 2: Soak the ceramic fiber in the modifier obtained in Step 1 at 60℃~75℃ for 6h~8h, then clean it with the diluent described in Step 1 and dry it.

7. The nano-based energy storage membrane material according to claim 5, characterized in that, The preparation method of the nano-based energy storage membrane material is as follows: ultrafine fibers, nanofibers, and modified ceramic fibers are respectively added to water to make ultrafine fiber slurry, nanofiber slurry, and modified ceramic fiber slurry. After mixing, they are formed by a long wire or cylinder paper machine, and then pressed, dried, sizing, coated, dried, calendered, scanned and detected, rolled and slit to obtain the nano-based energy storage membrane material.

8. The nano-based energy storage membrane material according to claim 7, characterized in that, The preparation method of the nano-based energy storage membrane material is as follows: ultrafine fibers, nanofibers, and modified ceramic fibers are respectively mixed with water to prepare ultrafine fiber slurry, nanofiber slurry, and modified ceramic fiber slurry. Then, the ultrafine fiber slurry, nanofiber slurry, and modified ceramic fiber slurry are respectively mixed to form slurry A and slurry B. Slurry A and slurry B are respectively placed on two cylindrical wires of a double-cylinder paper machine for forming. Subsequently, they are pressed, dried, sized, coated, dried, calendered, scanned and detected, rolled and slit to obtain the nano-based energy storage membrane material. The mass ratio of modified ceramic fibers in slurry A and slurry B is 0.5 to 1:

2.

9. The ultrathin, high-strength supercapacitor membrane material prepared using the biodegradable ultrafine fibers described in claim 4, characterized in that, The raw materials of the ultra-thin high-strength supercapacitor separator material include microfiber, flax fiber, acrylonitrile microfiber, and aramid fiber, and the mass ratio of microfiber, flax fiber, acrylonitrile microfiber, and aramid fiber is 70-90:8-15:2-10:2-5.

10. The ultra-thin high-strength supercapacitor separator material according to claim 9, characterized in that, The preparation method of the ultra-thin high-strength supercapacitor separator material is as follows: ultra-fine fiber, flax fiber, acrylonitrile ultra-fine fiber and aramid fiber are respectively added with water to make ultra-fine fiber slurry, flax fiber slurry, acrylonitrile ultra-fine fiber slurry and aramid fiber slurry, respectively. After mixing, they are formed by long wire or cylinder paper machine, and then pressed, dried, rolled and slit to obtain ultra-thin high-strength supercapacitor separator material.

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