A method for preparing a high ionic conductivity polymer electrolyte based on a beaded fiber structure

Abstract

This invention discloses a method for preparing a high-ionic-conductivity polymer electrolyte based on a beaded fiber structure. By employing reverse thinking, the common "beading" defect in electrospinning is transformed into a functional advantage. The method involves electrospinning by adding a beading structure inducer and precisely controlling parameters such as ambient humidity, spinning voltage, and receiving distance to actively induce and form a fiber membrane with a periodic "fiber-bead" necklace-like structure. A phase inversion treatment is then used to create hollow primordia within the beads. The resulting gel polymer electrolyte is obtained by immersing the beads in a liquid electrolyte under an inert atmosphere. This electrolyte utilizes the beads as "ion reservoirs" and rapid transport nodes, constructing a low-torsion ion channel and increasing the contact area with the electrode. This simultaneously achieves high ionic conductivity, excellent mechanical strength, and a stable electrode / electrolyte interface, significantly improving the rate performance, cycle life, and safety of lithium batteries.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery polymer electrolyte technology, and relates to a method for preparing a polymer electrolyte with high ionic conductivity, specifically a method for preparing a polymer electrolyte with high ionic conductivity based on a beaded fiber structure for lithium batteries. Background Technology

[0002] With the increasing urgency of high-safety lithium batteries for electric vehicles and large-scale energy storage, solid-state or quasi-solid-state polymer electrolytes have become a research hotspot due to their ability to avoid safety hazards such as leakage and combustion associated with liquid electrolytes. Among them, porous fiber membranes prepared by electrospinning technology, with their high porosity, large specific surface area, and continuous three-dimensional network structure, are easily wetted by liquid electrolytes to form gel electrolytes, combining the safety of solid electrolytes with the high ionic conductivity of liquid electrolytes, showing promising application prospects. However, traditional electrospinning processes aim to prepare continuous nanofibers with uniform diameters, and ion transport heavily relies on the liquid electrolyte filling the fiber pores. The long migration path and high transport resistance of ions in the tortuous pore channels limit further improvement in overall ionic conductivity. In addition, the contact between the electrolyte membrane and the electrode (especially the lithium metal anode) is mostly planar, with a limited actual contact area, which can easily lead to uneven current distribution at the interface, excessively high local lithium ion flux, and thus induce lithium dendrite growth, accompanied by large interfacial impedance.

[0003] In electrospinning, improper control of process parameters often results in a "beaded" structure, considered a "defect," consisting of periodically or randomly distributed spherical or spindle-shaped protrusions on the fiber. Traditional research has focused on eliminating these beads to achieve perfect fiber morphology. Due to their large volume, beads can serve as "enrichment zones" or "ion reservoirs" for loading lithium salts and electrolytes, while the fine fibers connecting the beads form the mechanical framework. However, conventional beaded fibers are mostly solid structures, and their ability to store electrolyte as an "ion reservoir" is limited by the swelling degree of the polymer matrix itself, leaving limited room for improvement. If hollow beads can be periodically and controllably introduced onto the fiber to form a necklace-like structure of "fiber-bead-fiber," it is hoped that a high-speed ion transport network can be constructed, with beads as nodes and fibers as connecting lines. Ions can then undergo low-barrier "jumping" transport between the highly swollen beads, significantly shortening the effective migration path and potentially breaking through the ceiling of ionic conductivity in traditional uniform fiber gel electrolytes. Therefore, developing a high-performance polymer electrolyte preparation method that can actively and controllably construct beaded fiber structures and fully utilize their "ion warehouse" and "fast channel" functions is of great significance for promoting the development of high-safety, high-energy-density lithium batteries. Summary of the Invention

[0004] To address the problems of traditional electrospun gel electrolytes, such as tortuous ion transport paths, low conductivity, and poor interfacial contact, this invention provides a method for preparing a high-ionic-conductivity polymer electrolyte based on a beaded fiber structure. The beaded fiber membrane prepared by this method possesses a unique and controllable "fiber-bead" morphology, where the beaded structure serves as ion enrichment and transport nodes, while the fibers act as a mechanical support framework and connecting channels. On the electrode surface, the spherical structure of the beads generates more point contacts. Under pressure, these contact points allow the beads to adhere more tightly to the electrode, and the electrolyte to better fill the microscopic voids. This not only reduces interfacial impedance but also significantly improves ion transport efficiency. This electrolyte can significantly improve ionic conductivity and lithium-ion transference number, reduce interfacial impedance between the electrolyte and the electrode, promote uniform lithium-ion deposition, and thus improve the rate performance, cycle stability, and safety of the battery.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A method for preparing a polymer electrolyte with high ionic conductivity based on a beaded fiber structure includes the following steps:

[0007] Step 1: Dissolve the polymer matrix and bead structure inducer in an organic solvent and stir to obtain a homogeneous and stable spinning solution. The amount of bead structure inducer added is 2-45% of the polymer matrix mass, and the mass concentration of the polymer matrix and bead structure inducer in the spinning solution is 0.05-0.9 g / mL.

[0008] Step 2: Inject the spinning solution obtained in Step 1 into a precision injection pump for electrospinning. By precisely controlling the ambient humidity, propulsion rate, applied voltage, and receiving distance of the spinning solution, the jet undergoes periodic or unstable disturbances during the stretching process, thereby depositing a beaded fiber membrane on the receiving device. The ambient humidity is 45-80%, the receiving distance is 10-25 cm, the applied voltage is 8-16 kV, the propulsion rate is 0.02-0.15 mm / min, and the beads are quasi-periodicly distributed along the fiber axis.

[0009] Step 3: Quickly immerse the beaded fiber membrane in a water bath for phase inversion treatment, allowing solvent exchange inside the beads to initially form a hollow structure, which serves as an "ion transfer station".

[0010] Step 4: Dry the collected spun membrane to completely remove residual solvent, so as to obtain a hollow beaded fiber membrane.

[0011] Step 5: In an inert atmosphere glove box, add the in-situ cured electrolyte precursor solution to the hollow beaded fiber membrane. After it swells, add an initiator to carry out the in-situ curing reaction, thus obtaining a gel polymer electrolyte with high ionic conductivity. The in-situ cured electrolyte precursor solution is composed of lithium salt, polymer monomer, ionic liquid, diluent and film-forming additive. The concentration of lithium salt is 1 M, the mass concentration of film-forming additive is 0.5~10%, and the volume ratio of polymer monomer, ionic liquid and diluent is 1~4:2~5:1~3.

[0012] Compared with the prior art, the present invention has the following advantages:

[0013] (1) This invention transforms a “defect” into an “advantage” by actively constructing a hollow beaded structure through a phase transformation method. The hollow beads, acting as an “ion warehouse,” can accumulate a large amount of lithium salt and electrolyte, providing a rich source of mobile lithium ions. The necklace-like structure of “fiber-bead-fiber” essentially constructs a low-torsion ion transport channel network with beads as nodes. Ions tend to migrate rapidly between beads with high swelling degree. Compared with migration in the tortuous pores of traditional uniform fibers, the path is more direct and the resistance is lower, thereby achieving an order-of-magnitude increase in ion conductivity.

[0014] (2) Precise control of the morphology and internal structure of the beaded structure has been achieved. This invention achieves effective control of the morphology and density of the beads by introducing a structure inducing agent and synergistically controlling parameters such as environmental humidity and spinning voltage.

[0015] (3) The beaded structure enhances the toughness of the membrane, and the continuous fiber skeleton ensures the integrity and mechanical strength of the polymer membrane, which can withstand the stress during battery assembly and cycling, and suppress the physical puncture of lithium dendrites.

[0016] (4) The beaded structure increases the contact area between the electrolyte membrane and the electrode surface at the microscopic level, forming more "point contacts," which is beneficial for the uniform flow distribution of lithium ions at the interface. This not only reduces the interfacial impedance but also effectively guides the uniform deposition of lithium ions, alleviates interfacial polarization, and inhibits the formation of lithium dendrites, thereby improving the cycle life and safety of the battery.

[0017] (5) This invention achieves controllable preparation of beaded structures by adjusting conventional electrospinning parameters (such as humidity, voltage, and solution properties), without the need for complex templates or post-processing steps. The raw materials used are all common materials, and the preparation process is highly compatible with existing battery production lines, possessing the potential for large-scale industrial application.

[0018] (6) The beaded fiber structure of the present invention can serve as an excellent substrate material. By adjusting the polymer matrix, lithium salt, and inducing agent, it can be compatible with different battery systems (such as lithium metal batteries and sodium metal batteries). At the same time, this structure can also be easily combined with other functional strategies, such as introducing inorganic fillers into the fiber or beads, or combining it with other functional layers to further optimize the overall performance. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the beaded fiber prepared in Example 1;

[0020] Figure 2 SEM image of the beaded fiber membrane prepared in Example 1;

[0021] Figure 3 SEM image of the beaded fiber membrane prepared in Example 2;

[0022] Figure 4 SEM image of the beaded fiber membrane prepared in Example 3;

[0023] Figure 5 SEM image of the beaded fiber membrane prepared in Example 4;

[0024] Figure 6 SEM image of the beaded fiber membrane prepared in Example 5;

[0025] Figure 7 SEM image of the beaded fiber membrane prepared in Example 6. Detailed Implementation

[0026] The technical solution of the present invention will be further described below with reference to the accompanying drawings, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention that do not depart from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.

[0027] This invention provides a method for preparing a high-ionic-conductivity polymer electrolyte based on a beaded fiber structure. By employing reverse thinking, the common "beading" defect in electrospinning is transformed into a functional advantage. The method involves electrospinning by adding a beading structure inducer and precisely controlling parameters such as environmental humidity, spinning voltage, and receiving distance to actively induce and form a fiber membrane with a periodic "fiber-bead" necklace-like structure. A phase inversion treatment is then used to create hollow primordia within the beads. The resulting gel polymer electrolyte is obtained by immersing the beads in a liquid electrolyte under an inert atmosphere. This electrolyte utilizes the beads as "ion reservoirs" and rapid transport nodes, constructing a low-torsion ion channel and increasing the contact area with the electrode. This simultaneously achieves high ionic conductivity, excellent mechanical strength, and a stable electrode / electrolyte interface, significantly improving the rate performance, cycle life, and safety of lithium batteries. The specific steps are as follows:

[0028] Step 1: Dissolve a certain amount of polymer matrix with high mechanical strength and ion conduction ability, and bead structure inducer that can change the homogeneity of the solution in an organic solvent, and stir at a certain temperature to obtain a homogeneous and stable spinning solution.

[0029] In this step, the polymer matrix is ​​selected from one or more of polypropylene carbonate (PPC), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyimide (PI), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), polyethylene oxide (PEO), polyvinyl carbonate (PVC), polychlorotrifluoroethylene (PCTFE), and polytrimethylene carbonate (PTMC).

[0030] In this step, the bead structure inducer is one or more of polyethylene glycol (PEG), polyvinylpyrrolidone (PVP), ammonium citrate, dichloromethane, and diethyl ether.

[0031] In this step, the amount of the bead structure inducer added is 2 to 65% of the polymer matrix mass, preferably 5 to 45%.

[0032] In this step, the organic solvent is selected from one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide (DMSO), acetone, and ethyl acetate.

[0033] In this step, the mass concentration of the polymer matrix and the bead structure inducer is 0.02~0.9 g / mL, preferably 0.05~0.6 g / mL.

[0034] In this step, the temperature is 20~100℃, preferably 25~60℃, and the stirring time is 10~15h.

[0035] Step 2: The spinning solution obtained in Step 1 is injected into a precision injection pump, and electrospinning is performed in a high-humidity environment chamber. By precisely controlling the ambient humidity, propulsion rate, applied voltage, and receiving distance of the spinning solution, the jet undergoes periodic or unstable disturbances during the stretching process, thereby depositing a fiber membrane with a certain ordered beaded structure on the receiving device. The beads are quasi-periodicly distributed along the fiber axis.

[0036] In this step, the ambient humidity is 45-80%, preferably 50-70%.

[0037] In this step, the receiving distance is 10~25cm, preferably 15~20cm.

[0038] In this step, the applied voltage is 8~16kV, preferably 10~12kV.

[0039] In this step, the propulsion speed is 0.02~0.15 mm / min, preferably 0.05~0.1 mm / min.

[0040] Step 3: Quickly immerse the beaded fiber membrane in a water bath for phase inversion treatment, allowing solvent exchange inside the beads to initially form a hollow structure, which serves as an "ion transfer station".

[0041] In this step, the water bath treatment time for the beaded fiber membrane is 0.5~5 min, preferably 1~3 min.

[0042] Step 4: Dry the collected spun membrane to completely remove residual solvent, so as to obtain a hollow beaded fiber membrane.

[0043] In this step, the drying temperature is 45~120℃, preferably 55~80℃, and the time is 2~12h, preferably 4~8h.

[0044] Step 5: In an inert atmosphere glove box, add a certain amount of in-situ cured electrolyte precursor solution, which consists of lithium salt, polymer monomer, ionic liquid, diluent and film-forming additive, to the hollow beaded fiber membrane. After it swells, use 0.5 wt% azobisisobutyronitrile (AIBN) as an initiator to carry out an in-situ curing reaction to obtain a gel polymer electrolyte with high ionic conductivity.

[0045] In this step, the lithium salt comprises one of LiPF6, LiTFSI, and LiODFB.

[0046] In this step, the polymer monomer comprises one or more of polyethylene glycol diacrylate (PEGDA), ethoxylated trimethylolpropane triacrylate (ETPTA), and pentaerythritol tetraacrylate (PETEA).

[0047] In this step, the ionic liquid comprises one of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMIM-TFSI), ionic liquid comprising 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (BMIM-TFSI), and N-butyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imide salt (PYR14TFSI).

[0048] In this step, the diluent contains one of ethoxy(pentafluoro)cyclotriphosphatazole and 2,2,2-trifluoroethyltrifluoromethanesulfonate.

[0049] In this step, the film-forming additive comprises one of fluoroethylene carbonate (FEC), vinylene carbonate (VC), and lithium nitrate (LiNO3).

[0050] In this step, the in-situ solidified electrolyte precursor solution is prepared with the following ratio: 1 M lithium salt added to polymer monomer: ionic liquid: diluent = 1~4: 2~5: 1~3 + 0.5~10% film-forming additive, where the ratio is a volume ratio and the percentage is a mass fraction.

[0051] In this step, the in-situ curing temperature is 60~80℃ and the time is 2~24h, preferably 4~12h.

[0052] Example 1

[0053] 1.5 g of polyacrylonitrile (PAN) and 0.3 g of bead structure inducer polyethylene glycol (PEG) were dissolved in 16 mL of N,N-dimethylformamide at room temperature. The solution was magnetically stirred at 60 °C for 12 h, and then allowed to stand for 1 h to completely remove the air bubbles generated during the stirring process, resulting in a uniform, stable spinning solution with a certain viscosity.

[0054] The obtained spinning solution was electrospun in a spinning chamber at an ambient temperature of 25℃ and a relative humidity precisely controlled at 60%. Specific process parameters were as follows: an applied DC voltage of 11kV, a spinning solution feed rate of 0.08mm / min, and a fixed distance of 18cm between the needle tip and the high-speed rotating roller receiver. Under these parameters, the jet generated controllable unstable disturbances, ultimately depositing a fiber membrane with an ordered beaded structure onto the aluminum foil-covered receiving roller.

[0055] After spinning, the aluminum foil attached to the fiber membrane was quickly peeled off and immersed in a glass dish containing deionized water for phase inversion treatment for 2 minutes. The membrane was then removed, its surface moisture was gently wiped with filter paper, and it was placed in a 60°C vacuum drying oven for 6 hours to completely remove residual solvent and moisture, resulting in a structurally stable beaded fiber membrane. (See [link to relevant documentation]). Figure 1 .Depend on Figure 2As shown in the SEM images, the beaded fiber membrane prepared in this embodiment has a regular morphology, with a large number of axially distributed spherical beads attached to the fiber surface, and the fiber network pores are evenly distributed.

[0056] In an argon-filled glove box, an in-situ curing precursor solution of 1 M LiPF6-PEGDA:EMIM-TFSI:ethoxy(pentafluoro)cyclotriphosphatazole = 1:1:1 + 5wt%FEC + 0.5wt%AIBN was dropped onto a beaded fiber membrane. After standing at 60°C for 12 h to swell, a gel polymer electrolyte with high ionic conductivity was obtained.

[0057] Example 2

[0058] 1.0 g of polyacrylonitrile (PAN), 0.5 g of polyethylene oxide (PEO) and 0.6 g of bead-forming inducing agent polyvinylpyrrolidone (PVP) were dissolved in 16 mL of N,N-dimethylformamide at room temperature. The solution was magnetically stirred at 60 °C for 12 h, and then allowed to stand for 1 h to completely remove the air bubbles generated during stirring, resulting in a homogeneous, stable spinning solution with a certain viscosity.

[0059] The obtained spinning solution was electrospun in a spinning chamber at an ambient temperature of 25℃ and a relative humidity precisely controlled at 60%. Specific process parameters were as follows: an applied DC voltage of 11kV, a spinning solution feed rate of 0.08 mm / min, and a fixed distance of 18cm between the needle tip and the high-speed rotating roller receiver. Under these parameters, the jet generated controllable unstable disturbances, ultimately depositing a fiber membrane with an ordered beaded structure onto the aluminum foil-covered receiving roller.

[0060] After spinning, the aluminum foil attached to the fiber membrane was quickly peeled off and immersed in a glass dish containing deionized water for phase inversion treatment for 2 minutes. The membrane was then removed, its surface moisture was gently wiped with filter paper, and it was placed in a 60℃ vacuum drying oven for 6 hours to completely remove residual solvent and moisture, resulting in a structurally stable beaded fiber membrane. Figure 3 As shown in the SEM images, the beaded fiber membrane prepared in this embodiment has a regular morphology, with a large number of axially distributed spherical beads attached to the fiber surface, and the fiber network pores are evenly distributed.

[0061] In an argon-filled glove box, an in-situ curing precursor solution of 1 M LiPF6-PEGDA: EMIM-TFSI: ethoxy(pentafluoro)cyclotriphosphatazole = 1:1:1 + 5% FEC + 0.5% AIBN was dropped onto a beaded fiber membrane. After standing at 60°C for 12 h to swell, a gel polymer electrolyte with high ionic conductivity was obtained.

[0062] Example 3

[0063] 1.0 g of polyacrylonitrile (PAN), 0.5 g of polyethylene oxide (PEO) and 0.3 g of bead-forming inducing agent polyethylene glycol (PEG) were dissolved in 16 mL of N-methylpyrrolidone at room temperature. The solution was magnetically stirred at 60 °C for 12 h, and then allowed to stand for 1 h to completely remove the air bubbles generated during stirring, resulting in a homogeneous, stable spinning solution with a certain viscosity.

[0064] The obtained spinning solution was electrospun in a spinning chamber at an ambient temperature of 25℃ and a relative humidity precisely controlled at 60%. Specific process parameters were as follows: an applied DC voltage of 11kV, a spinning solution feed rate of 0.08 mm / min, and a fixed distance of 18cm between the needle tip and the high-speed rotating roller receiver. Under these parameters, the jet generated controllable unstable disturbances, ultimately depositing a fiber membrane with an ordered beaded structure onto the aluminum foil-covered receiving roller.

[0065] After spinning, the aluminum foil attached to the fiber membrane is quickly peeled off and immersed in a glass dish containing deionized water for phase inversion treatment for 2 minutes. The membrane is then removed, its surface moisture is gently wiped with filter paper, and it is placed in a 60℃ vacuum drying oven for 6 hours to completely remove residual solvent and moisture, resulting in a structurally stable beaded fiber membrane. Figure 4 As shown in the SEM images, the beaded fiber membrane prepared in this embodiment has a regular morphology, with a large number of axially distributed spherical beads attached to the fiber surface, and the fiber network pores are evenly distributed.

[0066] In an argon-filled glove box, an in-situ curing precursor solution of 1 M LiPF6-PEGDA: EMIM-TFSI: ethoxy(pentafluoro)cyclotriphosphatazole = 1:1:1 + 2% VC + 0.5% AIBN was dropped onto a beaded fiber membrane. After standing at 60°C for 12 hours to allow swelling, a gel polymer electrolyte with high ionic conductivity was obtained.

[0067] Example 4

[0068] 1.0 g of polyacrylonitrile (PAN), 0.5 g of polyethylene oxide (PEO) and 0.3 g of bead-forming inducing agent polyethylene glycol (PEG) were dissolved in 16 mL of dimethyl sulfoxide (DMSO) at room temperature. The solution was magnetically stirred at 60 °C for 12 h, and then allowed to stand for 1 h to completely remove the air bubbles generated during the stirring process, resulting in a homogeneous, stable spinning solution with a certain viscosity.

[0069] The obtained spinning solution was electrospun in a spinning chamber at an ambient temperature of 25℃ and a relative humidity precisely controlled at 60%. Specific process parameters were as follows: a DC voltage of 10kV was applied, the spinning solution feed rate was set to 0.08mm / min, and the distance from the needle tip to the high-speed rotating roller receiver was fixed at 18cm. Under these parameters, the jet generated controllable unstable disturbances, ultimately depositing a fiber membrane with an ordered beaded structure on the aluminum foil-covered receiving roller.

[0070] After spinning, the aluminum foil attached to the fiber membrane is quickly peeled off and immersed in a glass dish containing deionized water for phase inversion treatment for 2 minutes. The membrane is then removed, its surface moisture is gently wiped with filter paper, and it is placed in a 60℃ vacuum drying oven for 6 hours to completely remove residual solvent and moisture, resulting in a structurally stable beaded fiber membrane. Figure 5 As shown in the SEM images, the beaded fiber membrane prepared in this embodiment has a regular morphology, with a large number of axially distributed spherical beads attached to the fiber surface, and the fiber network pores are evenly distributed.

[0071] In an argon-filled glove box, an in-situ curing precursor solution of 1 M LiTFSI-PEGDA: EMIM-TFSI: ethoxy(pentafluoro)cyclotriphosphatazole = 1:1:1 + 2% VC + 0.5% AIBN was dropped onto a beaded fiber membrane. After standing at 60°C for 12 hours to swell, a gel polymer electrolyte with high ionic conductivity was obtained.

[0072] Example 5

[0073] 1.0 g of polyacrylonitrile (PAN), 0.5 g of polyethylene oxide (PEO) and 0.3 g of bead-forming inducing agent polyethylene glycol (PEG) were dissolved in 16 mL of N,N-dimethylformamide at room temperature. The solution was magnetically stirred at 60 °C for 12 h, and then allowed to stand for 1 h to completely remove the air bubbles generated during the stirring process, resulting in a homogeneous, stable spinning solution with a certain viscosity.

[0074] The obtained spinning solution was electrospun in a spinning chamber at an ambient temperature of 25℃ and a relative humidity precisely controlled at 70%. Specific process parameters were as follows: an applied DC voltage of 8kV, a spinning solution feed rate of 0.08mm / min, and a fixed distance of 18cm between the needle tip and the high-speed rotating roller receiver. Under these parameters, the jet generated controllable unstable disturbances, ultimately depositing a fiber membrane with an ordered beaded structure on the aluminum foil-covered receiving roller.

[0075] After spinning, the aluminum foil attached to the fiber membrane is quickly peeled off and immersed in a glass dish containing deionized water for phase inversion treatment for 2 minutes. The membrane is then removed, its surface moisture is gently wiped with filter paper, and it is placed in a 60℃ vacuum drying oven for 6 hours to completely remove residual solvent and moisture, resulting in a structurally stable beaded fiber membrane. Figure 6 As shown in the SEM images, the beaded fiber membrane prepared in this embodiment has a regular morphology, with a large number of axially distributed spherical beads attached to the fiber surface, and the fiber network pores are evenly distributed.

[0076] In an argon-filled glove box, an in-situ curing precursor solution of 1 M LiTFSI-PEGDA: EMIM-TFSI: ethoxy(pentafluoro)cyclotriphosphatazole = 1:1:1 + 2% VC + 0.5% AIBN was dropped onto a beaded fiber membrane. After standing at 60°C for 12 hours to swell, a gel polymer electrolyte with high ionic conductivity was obtained.

[0077] Example 6

[0078] 1.0 g of polyacrylonitrile (PAN), 0.5 g of polyethylene oxide (PEO) and 0.3 g of bead-forming inducing agent polyethylene glycol (PEG) were dissolved in 16 mL of N,N-dimethylformamide at room temperature. The solution was magnetically stirred at 60 °C for 12 h, and then allowed to stand for 1 h to completely remove the air bubbles generated during the stirring process, resulting in a homogeneous, stable spinning solution with a certain viscosity.

[0079] The obtained spinning solution was electrospun in a spinning chamber at an ambient temperature of 25℃ and a relative humidity precisely controlled at 70%. Specific process parameters were as follows: an applied DC voltage of 8kV, a spinning solution feed rate of 0.06 mm / min, and a fixed distance of 14cm between the needle tip and the high-speed rotating roller receiver. Under these parameters, the jet generated controllable unstable disturbances, ultimately depositing a fiber membrane with an ordered beaded structure on the aluminum foil-covered receiving roller.

[0080] After spinning, the aluminum foil attached to the fiber membrane was quickly peeled off and immersed in a glass dish containing deionized water for phase inversion treatment for 2 minutes. The membrane was then removed, its surface moisture was gently wiped with filter paper, and it was placed in a 60℃ vacuum drying oven for 6 hours to completely remove residual solvent and moisture, resulting in a structurally stable beaded fiber membrane. Figure 7 As shown in the SEM images, the beaded fiber membrane prepared in this embodiment has a regular morphology, with a large number of axially distributed spherical beads attached to the fiber surface, and the fiber network pores are evenly distributed.

[0081] In an argon-filled glove box, an in-situ curing precursor solution of 1 M LiTFSI-PEGDA: EMIM-TFSI: ethoxy(pentafluoro)cyclotriphosphatazole = 1:1:1 + 2% VC + 0.5% AIBN was dropped onto a beaded fiber membrane. After standing at 60°C for 12 hours to swell, a gel polymer electrolyte with high ionic conductivity was obtained.

[0082] The CR2032 coin cells assembled in the above embodiments were tested in an argon glove box. Lithium || LiNi 0.8 Co 0.1 Mn 0.1 Battery: LiNi 0.8 Co 0.1 Mn 0.1 Positive electrode active material, Super P conductive carbon black, and PVDF binder were mixed in N-methylpyrrolidone at a mass ratio of 8:1:1 and thoroughly ground and stirred to prepare a uniform positive electrode slurry. This slurry was uniformly coated onto the surface of an aluminum foil current collector, vacuum dried, and then die-cut into 14 mm diameter discs as the positive electrode. A lithium metal sheet was used as the negative electrode, and the gel polymer electrolyte prepared in the above examples served as both the separator and electrolyte, assembling a full cell. All cells were activated by three charge-discharge cycles at a current density of 40 mA / g (0.2C) within the voltage range of 3.0–4.3 V, followed by long-cycle performance testing at a 1C rate within the same voltage window. All experiments were conducted at room temperature.

[0083] Ionic conductivity determination: A blocked electrode method was used, with two stainless steel sheets as the working and counter electrodes, and a steel sheet || steel sheet symmetrical battery assembled using the gel electrolyte membrane from the above embodiment. The conductivity value was obtained by dividing the thickness of the beaded fiber membrane by (cross-sectional area of ​​the stainless steel sheet × battery internal resistance), where the battery internal resistance was obtained by EIS testing. Tensile strength tests were performed on 5cm × 1cm strips of the beaded fiber membrane using stress experiments. Thermogravimetric analysis was used to test the thermal stability of the prepared gel electrolyte.

[0084]

Claims

1. A method for preparing a polymer electrolyte with high ionic conductivity based on a beaded fiber structure, characterized in that... The method includes the following steps: Step 1: Dissolve the polymer matrix and bead structure inducer in an organic solvent and stir to obtain a homogeneous and stable spinning solution. The amount of bead structure inducer added is 2-45% of the polymer matrix mass, and the mass concentration of the polymer matrix and bead structure inducer in the spinning solution is 0.05-0.9 g / mL. Step 2: Inject the spinning solution obtained in Step 1 into a precision injection pump for electrospinning. By precisely controlling the ambient humidity, propulsion rate, applied voltage and receiving distance of the spinning solution, the jet undergoes periodic or unstable disturbances during the stretching process, thereby depositing a sequenced beaded fiber membrane on the receiving device. Step 3: Quickly immerse the beaded fiber membrane in a water bath for phase transformation treatment, allowing solvent exchange inside the beads to initially form a hollow structure, which serves as an "ion transfer station". Step 4: Dry the collected spun membrane to completely remove residual solvent, so as to obtain a hollow beaded fiber membrane. Step 5: In an inert atmosphere glove box, add the in-situ curing electrolyte precursor solution to the hollow beaded fiber membrane. After it swells, add an initiator to carry out the in-situ curing reaction, and a gel polymer electrolyte with high ionic conductivity is obtained.

2. The method for preparing a high ionic conductivity polymer electrolyte based on a beaded fiber structure according to claim 1, characterized in that... In step one, the polymer matrix is ​​selected from one or more of polypropylene carbonate, polyvinylidene fluoride-hexafluoropropylene, polyimide, polyacrylonitrile, polymethyl methacrylate, polyoxyethylene, polyvinyl carbonate, polychlorotrifluoroethylene, and polytrimethylene carbonate; the bead structure inducer is one or more of polyethylene glycol, polyvinylpyrrolidone, ammonium citrate, dichloromethane, and diethyl ether; and the organic solvent is selected from one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, acetone, and ethyl acetate.

3. The method for preparing a high ionic conductivity polymer electrolyte based on a beaded fiber structure according to claim 1, characterized in that... In step one, the temperature is 20~100℃ and the stirring time is 10~15h.

4. The method for preparing a high ionic conductivity polymer electrolyte based on a beaded fiber structure according to claim 1, characterized in that... In step two, the ambient humidity is 45-80%, the receiving distance is 10-25cm, the applied voltage is 8-16kV, the advancing speed is 0.02-0.15mm / min, and the beads are distributed quasi-periodically along the fiber axis.

5. The method for preparing a high ionic conductivity polymer electrolyte based on a beaded fiber structure according to claim 4, characterized in that... The ambient humidity is 50-70%, the receiving distance is 15-20cm, the applied voltage is 10-12kV, and the propulsion speed is 0.05-0.1mm / min.

6. The method for preparing a high ionic conductivity polymer electrolyte based on a beaded fiber structure according to claim 1, characterized in that... In step three, the water bath treatment time for the beaded fiber membrane is 0.5~5 minutes.

7. The method for preparing a high ionic conductivity polymer electrolyte based on a beaded fiber structure according to claim 1, characterized in that... In step four, the drying temperature is 45~120℃ and the time is 2~12h.

8. The method for preparing a high ionic conductivity polymer electrolyte based on a beaded fiber structure according to claim 1, characterized in that... In step four, the in-situ solidified electrolyte precursor solution is composed of lithium salt, polymer monomer, ionic liquid, diluent and film-forming additive. The concentration of lithium salt is 1 M, the mass concentration of film-forming additive is 0.5~10%, and the volume ratio of polymer monomer, ionic liquid and diluent is 1~4:2~5:1~3.

9. The method for preparing a high ionic conductivity polymer electrolyte based on a beaded fiber structure according to claim 8, characterized in that... The lithium salt comprises one of LiPF6, LiTFSI, and LiODFB; the polymer monomer comprises one or more of polyethylene glycol diacrylate, ethoxylated trimethylolpropane triacrylate, and pentaerythritol tetraacrylate; the ionic liquid comprises one of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, the ionic liquid comprises one of 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, and N-butyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imide; the diluent comprises one of ethoxy(pentafluoro)cyclotriphosphatazole and 2,2,2-trifluoroethyltrifluoromethanesulfonate; and the film-forming additive comprises one of fluoroethylene carbonate, vinylene carbonate, and lithium nitrate.

10. The method for preparing a high ionic conductivity polymer electrolyte based on a beaded fiber structure according to claim 1, characterized in that... In step four, the in-situ curing temperature is 60~80℃ and the time is 2~24h.

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