Composite solid-state electrolyte based on porous interstitial aramid nanofiber membrane and fluorinated metal-organic framework

Abstract

The application provides a composite solid-state electrolyte based on a porous meta-aramid nanofiber membrane and a fluorinated metal organic framework, a preparation method thereof comprises the following steps: preparing a porous meta-aramid nanofiber membrane; synthesizing and fluorinated modifying a fluorinated metal organic framework through two-step heat treatment; finally, coating a polymer electrolyte matrix comprising the fluorinated metal organic framework, polyethylene oxide and a lithium salt on the nanofiber membrane to obtain the composite solid-state electrolyte. Through the synergistic effect of the porous meta-aramid nanofiber membrane and the fluorinated metal organic framework, the mechanical strength of the composite solid-state electrolyte is significantly improved, the dendrite inhibition ability is inhibited, the lithium ion transmission is effectively promoted, and the interface impedance is reduced, and the prepared composite solid-state electrolyte is suitable for preparing a high-safety and high-performance solid-state lithium metal battery.

Description

Technical Field

[0001] This application relates to the field of battery technology, specifically to a composite solid electrolyte based on a porous meta-aramid nanofiber membrane and a fluorinated metal-organic framework. Background Technology

[0002] Solid-state lithium batteries use solid electrolytes instead of traditional liquid electrolytes, which is expected to fundamentally solve the safety hazards such as combustion and explosion caused by flammable organic solvents. They also allow for better matching with high-capacity lithium metal anodes and high-voltage cathodes, thus significantly improving battery energy density and representing an important development direction for next-generation energy storage devices. Solid-state electrolytes are mainly divided into solid-state inorganic electrolytes (SIEs), solid-state polymer electrolytes (SPEs), and composite solid-state electrolytes (CSEs). Composite solid-state electrolytes have become a current research hotspot because they can overcome the inherent defects of single-component systems such as solid-state inorganic electrolytes and solid-state polymer electrolytes.

[0003] Polyethylene oxide (PEO) solid polymer electrolytes have been extensively studied due to their excellent film-forming properties, interfacial wettability with electrodes, and chemical stability. However, PEO electrolytes exhibit high crystallinity at room temperature, resulting in low ionic conductivity; their mechanical strength is also poor, making it difficult to effectively suppress the growth and penetration of lithium dendrites. To address these issues, researchers typically employ modification methods such as blending, copolymerization, crosslinking, or the addition of inorganic fillers.

[0004] Metal-organic frameworks (MOFs), with their regular and ordered pore structure, functionalizable organic ligands, and unsaturated metal sites, can be introduced into polymer electrolytes as fillers to reduce polymer crystallinity, promote lithium salt dissociation, provide additional lithium-ion transport channels, and improve interfacial stability. On the other hand, introducing high-strength nanofiber networks can significantly improve the mechanical properties of the electrolyte and enhance its ability to suppress dendrite penetration.

[0005] However, single-modification methods often fail to simultaneously meet multiple performance requirements, such as ionic conductivity, mechanical strength, and interfacial stability. For example, ordinary metal-organic framework fillers have limited ability to promote lithium salt dissociation; while the interfacial compatibility between inorganic nanofiber frameworks and polymer matrices, as well as their ion transport performance, need improvement. Therefore, achieving synergistic enhancement effects among different components through material design and structural control is key to developing high-performance composite solid electrolytes. Summary of the Invention

[0006] To address the aforementioned technical problems, this application provides a composite solid electrolyte based on a porous meta-aramid nanofiber membrane and a fluorinated metal-organic framework.

[0007] In a first aspect, this application provides a method for preparing a composite solid electrolyte based on a porous meta-aramid nanofiber membrane and a fluorinated metal-organic framework, comprising the following steps:

[0008] S1: Dissolve the poly(m-phenylene isophthalamide) stock solution in a mixed solvent composed of N,N-dimethylacetamide (DMAc) and glycerol to prepare a spinning solution; perform electrospinning on the spinning solution to obtain a nanofiber membrane; immerse the obtained nanofiber membrane in a hot water bath and sonicate it, and then dry it to obtain a porous poly(m-phenylene isophthalamide) nanofiber membrane;

[0009] S2: Zirconium chloride, benzoic acid, and 5,10,15,20-tetra(4-carboxyphenyl)porphyrin (TCPP) were dissolved in a solvent and subjected to heat treatment. The heat-treated solution was filtered and dried to obtain the metal-organic framework PCN-222. The metal-organic framework was dispersed in a solvent, trifluoroacetic acid was added, and heat treatment was performed. After centrifugation and drying, the fluorinated metal-organic framework PCN-222-CF3 was obtained.

[0010] S3: Disperse the fluorinated metal-organic framework PCN-222-CF3 in a solvent, add polyethylene oxide and lithium salt, stir to dissolve, and obtain a polymer electrolyte matrix; coat the polymer electrolyte matrix onto the porous poly(m-phenylene isophthalamide) nanofiber membrane prepared in step S1, and dry to obtain a composite solid electrolyte.

[0011] Poly(m-phenylene isophthalamide) (PMIA) is also known as meta-aramid.

[0012] Nanofiber membranes are self-supporting, porous aggregates formed by the random deposition and physical entanglement of continuous nanofibers. They can be peeled off from the receiving substrate as a whole without disintegrating. The receiving substrate can be one of aluminum foil, stainless steel mesh, or copper foil.

[0013] Furthermore, in step S1, the poly(m-phenylene isophthalamide) stock solution is a solution formed by dissolving poly(m-phenylene isophthalamide) in N,N-dimethylacetamide, and the mass fraction of poly(m-phenylene isophthalamide) in the poly(m-phenylene isophthalamide) stock solution is 25-35%; preferably, the mass fraction of poly(m-phenylene isophthalamide) is 30%.

[0014] Furthermore, in step S1, the mass ratio of N,N-dimethylacetamide to glycerol in the spinning solution is (2-4):1; preferably, the mass ratio of N,N-dimethylacetamide to glycerol is 3:1.

[0015] Furthermore, in step S1, the electrospinning conditions are as follows: electrospinning of the spinning solution is performed under the following conditions: voltage of 15-25 kV, injection speed of 0.8-1.2 mL / h, and receiving distance of 15-20 cm.

[0016] Furthermore, in step S1, the temperature of the hot water bath is 90-100℃; the duration of the hot water bath is 6-8 hours.

[0017] Further, in step S2, the molar ratio of zirconium chloride to 5,10,15,20-tetra(4-carboxyphenyl)porphyrin is (9-11):1; preferably, the molar ratio of zirconium chloride to 5,10,15,20-tetra(4-carboxyphenyl)porphyrin is 10:1.

[0018] Furthermore, in step S2, the molar ratio of zirconium chloride to benzoic acid is 1:(44-46); preferably, the molar ratio of zirconium chloride to benzoic acid is 1:45.

[0019] Furthermore, in step S2, the volume-to-mass ratio of trifluoroacetic acid to the metal-organic framework PCN-222 is 250-350 μL / g; preferably, the volume-to-mass ratio of trifluoroacetic acid to the metal-organic framework PCN-222 is 300 μL / g.

[0020] Furthermore, in step S2, zirconium chloride, benzoic acid, and 5,10,15,20-tetra(4-carboxyphenyl)porphyrin (TCPP) are dissolved in a solvent and subjected to heat treatment at a temperature of 110-130°C for 10-14 hours.

[0021] Furthermore, in step S2, the metal-organic framework PCN-222 is dispersed in a solvent, trifluoroacetic acid is added, and heat treatment is performed at a temperature of 55-65°C for 10-14 hours.

[0022] Furthermore, the solvent in step S2 is N,N-dimethylformamide.

[0023] Furthermore, based on the total mass of the polymer and lithium salt, the mass fraction of the fluorinated metal-organic framework PCN-222-CF3 in step S3 is 4%-6%; preferably, the mass fraction of the fluorinated metal-organic framework PCN-222-CF3 is 5%.

[0024] The polymer used in step S3 of this application is not limited to polyethylene oxide, but also includes polymers such as polypropylene carbonate, polyacrylonitrile, or polyvinylidene fluoride-hexafluoropropylene copolymer that can dissolve lithium salts and form an ion-conducting phase.

[0025] Furthermore, in step S3, the lithium salt is at least one of lithium bis(trifluoromethanesulfonylimide), lithium hexafluorophosphate, and lithium perchlorate.

[0026] Furthermore, in step S3, the molar ratio of ether oxygen atoms in polyethylene oxide to lithium ions is (10-14):1; preferably, the molar ratio of ether oxygen atoms in polyethylene oxide to lithium ions is 12:1.

[0027] Furthermore, the solvent in step S3 is anhydrous acetonitrile.

[0028] Furthermore, the drying temperature in step S3 is 45-55℃.

[0029] Furthermore, in step S3, the polymer electrolyte matrix is ​​coated onto the porous poly(m-phenylene isophthalamide) nanofiber membrane prepared in step S1 by means of scraping or casting.

[0030] Secondly, this application provides a composite solid electrolyte based on a porous meta-aramid nanofiber membrane and a fluorinated metal-organic framework, which is prepared by the method of the first aspect.

[0031] Furthermore, the solid electrolyte based on the porous aramid nanofiber membrane and fluorinated metal-organic framework composite includes a porous poly(m-phenylene isophthalamide) nanofiber membrane and a polymer electrolyte matrix coated on the porous poly(m-phenylene isophthalamide) nanofiber membrane.

[0032] The polymer electrolyte matrix comprises a polymer, a lithium salt, and a fluorinated metal-organic framework PCN-222-CF3; the fluorinated metal-organic framework PCN-222-CF3 is a trifluoroacetic acid-modified metal-organic framework PCN-222, and electronegative CF3 functional groups are grafted onto the metal-organic framework PCN-222.

[0033] Thirdly, this application provides a porous poly(m-phenylene isophthalamide) nanofiber membrane, which is prepared according to step S1 of the first aspect.

[0034] Furthermore, the porous poly(m-phenylene isophthalamide) nanofiber membrane has a through-pore structure on the fiber surface and inside.

[0035] Fourthly, this application provides a fluorinated metal-organic framework PCN-222-CF3, which is prepared according to step S2 of the first aspect.

[0036] Furthermore, the fluorinated metal-organic framework PCN-222-CF3 is a trifluoroacetic acid-modified metal-organic framework PCN-222, on which electronegative CF3 functional groups are grafted.

[0037] Fifthly, this application provides a solid-state battery, comprising a composite solid electrolyte based on a porous meta-aramid nanofiber membrane and a fluorinated metal-organic framework prepared by the method of the first aspect, or a composite solid electrolyte based on a porous meta-aramid nanofiber membrane and a fluorinated metal-organic framework provided by the second aspect, or a porous poly(m-phenylene isophthalamide) nanofiber membrane provided by the third aspect, or a fluorinated metal-organic framework PCN-222-CF3 provided by the fourth aspect.

[0038] In the preparation method of the first aspect of this application, the mass fraction of poly(m-phenylene isophthalamide) in the poly(m-phenylene isophthalamide) stock solution is 25-35%. Within this range, the polymer chains have a moderate degree of entanglement, which can provide sufficient viscoelasticity to resist the rupture caused by electric field stretching and surface tension during electrospinning, thereby forming a continuous, uniform, and diameter-controllable nanofiber jet. This is a prerequisite for obtaining a high-quality fiber membrane, and it can maintain the high mechanical strength of the fiber itself while forming a porous structure.

[0039] In step S1, the hot water bath temperature is 90-100℃. This temperature provides sufficient heat energy to intensify the movement of glycerol molecules and fully utilizes the infinite miscibility of glycerol with hot water, allowing for thorough extraction from the nanoscale pores of the fiber, ensuring complete removal of the non-solvent glycerol. During electrospinning, the nanofiber surface rapidly solidifies, but the internal phase separation process may not have fully reached thermodynamic equilibrium. The hot water bath treatment provides a mild annealing environment. In the hot water bath, the nanofibers are fully swollen, and the polymer chains gain some mobility. This allows the incomplete phase separation structure during spinning to continue evolving and reach a more stable state, resulting in a more complete and uniform porous structure, which is then fixed, improving the uniformity and batch stability of the fiber membrane structure. Long-term treatment at 90-100℃ is beneficial for relaxing the polymer molecular chains inside the nanofibers and perfecting some crystalline regions. Without damaging the porous morphology, it moderately improves the bulk modulus and mechanical stability of the nanofibers, making the three-dimensional skeleton more robust. In addition, trace amounts of N,N-dimethylacetamide remain during the rapid electrospinning process. Hot water bath treatment helps to further volatilize and diffuse the residual N,N-dimethylacetamide, ensuring that the nanofiber membrane does not contain volatile solvents in subsequent use.

[0040] In step S2, the molar ratio of zirconium chloride to 5,10,15,20-tetra(4-carboxyphenyl)porphyrin is (9-11):1. The metal-organic framework PCN-222 is a crystal composed of a [Zr6O4(OH)4] metal cluster linked to 5,10,15,20-tetra(4-carboxyphenyl)porphyrin. If the molar ratio of zirconium chloride to 5,10,15,20-tetra(4-carboxyphenyl)porphyrin is too low (e.g., below 9:1), the metal source is relatively insufficient, leading to incomplete reaction of the 5,10,15,20-tetra(4-carboxyphenyl)porphyrin ligands. This results in unreacted ligands or the formation of other metal-deficient impurities in the product. More seriously, it fails to provide enough metal clusters to construct a complete and extended three-dimensional framework, resulting in numerous structural defects, poor crystallinity, and decreased stability within the metal-organic framework. If the ratio is too high (e.g., above 11:1), there will be a large excess of metal source. However, the excess zirconium ions may form amorphous zirconium oxide or other zirconium-based impurities, which may encapsulate or mix in the PCN-222 crystal, block the metal-organic framework channels, reduce its specific surface area and porosity, and introduce inactive impurities.

[0041] In step S2, the molar ratio of zirconium chloride to benzoic acid is 1:(44-46). Under heat treatment conditions, zirconium chloride rapidly forms [Zr6O4(OH)4] metal clusters. This process is very fast and easily leads to a large number of disordered nuclei, resulting in agglomeration or amorphous products. The carboxyl group of benzoic acid has a strong coordination ability with zirconium ions and can compete with 5,10,15,20-tetra(4-carboxyphenyl)porphyrin ligands for metal sites. Excess benzoic acid will temporarily cap some surface sites of the metal clusters, slowing down the binding rate of 5,10,15,20-tetra(4-carboxyphenyl)porphyrin ligands to the clusters, and controlling the number of crystal nuclei and the morphology and size of the crystals.

[0042] In step S2, the volume-to-mass ratio of trifluoroacetic acid to the metal-organic framework (MOF) is 250-350 μL / g. This aims to graft as many strongly electronegative CF3 functional groups as possible onto the PCN-222 MOF while maximizing the integrity and porous structure of the PCN-222 framework. Insufficient trifluoroacetic acid (e.g., below 250 μL / g) will not fully penetrate and modify the porous system of the MOF, resulting in incomplete reaction, low grafting rate of CF3 groups, and uneven distribution. This significantly reduces the function of the fluorinated MOF filler in promoting lithium salt dissociation and optimizing the interface, limiting performance improvement. Excessive trifluoroacetic acid (e.g., above 350 μL / g) will result in excessive acidity and concentration, causing acidolysis of the MOF framework.

[0043] In step S2, the metal-organic framework is prepared at a temperature of 110-130℃ to ensure sufficient formation of the metal cluster and strong coordination with the ligands, thereby obtaining the highly crystalline metal-organic framework PCN-222. Fluorination modification is carried out at a relatively low temperature of 55-65℃ because trifluoroacetic acid has a certain acidity; excessively high temperatures would disrupt the zirconium-oxygen bonds of the PCN-222 metal-organic framework, leading to framework collapse.

[0044] In step S3, the mass fraction of the fluorinated metal-organic framework is 4%-6%, which ensures that the CF3 groups promote lithium salt dissociation and provide transport pathways, while maintaining excellent film-forming properties and interfacial characteristics. Insufficient fluorinated metal-organic framework filler cannot form a continuous permeation network in the polyoxyethylene ether, resulting in limited improvement in ionic conductivity and mechanical strength; excessive fluorinated metal-organic framework filler is prone to aggregation, increasing interfacial defects, which in turn blocks ion channels and reduces the flexibility of the electrolyte and the interfacial contact with the electrode.

[0045] In step S3, the molar ratio of ether oxygen atoms to lithium ions in polyethylene oxide is (10⁻¹⁴):1, which provides sufficient lithium ions as charge carriers and maintains the mobility of polymer chain segments. If the lithium ion concentration is too low, the ionic conductivity decreases; if the lithium ion concentration is too high, the lithium ions will coordinate with the ether oxygen bonds, resulting in impeded movement of polyethylene oxide chain segments, increased crystallinity, and decreased ionic conductivity.

[0046] In step S3, the polymer electrolyte matrix is ​​coated onto the porous poly(m-phenylene isophthalamide) nanofiber membrane prepared in step S1, using either a blade coating or a casting method. This method ensures that the polymer electrolyte matrix fully wets and fills the pores of the porous poly(m-phenylene isophthalamide) nanofiber membrane framework, forming a three-dimensional composite structure where the polymer electrolyte matrix is ​​completely filled within the porous poly(m-phenylene isophthalamide) nanofiber membrane framework, and fluorinated metal-organic framework fillers are dispersed within the polymer electrolyte matrix, resulting in a strong interfacial bond.

[0047] Compared with the prior art, this application includes the following beneficial technical effects:

[0048] The first aspect of this application provides a method for preparing a composite solid electrolyte based on a porous meta-aramid nanofiber membrane and a fluorinated metal-organic framework. The method utilizes porous poly(m-phenylene isophthalamide) (PMIA, meta-aramid) material. PMIA possesses excellent high-temperature resistance and flame retardancy, which can improve the thermal safety of the composite solid electrolyte. The spinning solution is used to form a nanofiber membrane, such as through electrospinning, allowing the PMIA to form continuous, uniform fibers with diameters at the nanoscale. This provides the composite electrolyte with an extremely high specific surface area and a flexible three-dimensional network framework. The spinning solution includes a solvent-nonsolvent system of N,N-dimethylacetamide (DMAc) and glycerol in a specific ratio. This utilizes the solvent-nonsolvent-induced phase separation principle, which is key to controlling the porous morphology inside and on the surface of the nanofibers. During electrospinning, because N,N-dimethylacetamide has a lower boiling point than glycerol, it is more efficient during jet propagation. During the process, N,N-dimethylacetamide initially evaporates rapidly. As the amount of N,N-dimethylacetamide decreases, the concentration of glycerol in the spinning jet increases. When the glycerol concentration further increases, the originally homogeneous ternary system of poly(m-phenylene isophthalamide), N,N-dimethylacetamide, and glycerol becomes thermodynamically unstable. The poly(m-phenylene isophthalamide) polymer and the solvent-non-solvent system separate. The solvent-non-solvent system is subsequently removed in a hot water bath treatment. Glycerol dissolves in hot water, and N,N-dimethylacetamide has largely evaporated, leaving pores in situ. Meanwhile, the poly(m-phenylene isophthalamide) solidifies to form the fiber skeleton. Therefore, the porous poly(m-phenylene isophthalamide) nanofiber membrane prepared based on electrospinning technology, as a supporting substrate for composite solid electrolytes, not only enhances the mechanical strength of poly(m-phenylene isophthalamide) and inhibits lithium dendrite puncture, but also improves the safety of electrolyte use due to the flame retardancy of poly(m-phenylene isophthalamide).

[0049] The first aspect of this application provides a method for preparing a composite solid electrolyte based on a porous meta-aramid nanofiber membrane and a fluorinated metal-organic framework (MOF). The prepared MOF serves as the filler for the composite solid electrolyte. The MOF, PCN-222, originates from Zr-O bonds and possesses excellent thermal and chemical stability and one-dimensional large-pore channels. These regular channels provide an additional, rapid transport path for lithium ions. The introduced -CF3 modifying group exhibits strong electronegativity, strongly attracting bis(trifluoromethanesulfonyl)imide, hexafluorophosphate, or perchloric acid groups, thereby weakening the Coulomb force between lithium ions and lithium salt anions. This significantly promotes lithium salt dissociation, increases the concentration of free lithium ions, induces uniform lithium ion deposition, stabilizes the lithium metal interface, suppresses dendrite formation, and improves the safety and overall performance of the composite solid electrolyte or solid-state battery. Furthermore, fluorine possesses low electronic conductivity and a wide electrochemical stability window, which can improve the high-voltage withstand capability of the prepared solid-state battery, matching the high-voltage cathode.

[0050] In summary, this application utilizes the synergistic effect of porous poly(m-phenylene isophthalamide) nanofiber membranes and fluorinated metal-organic frameworks to significantly enhance the mechanical strength and dendrite suppression ability of the composite solid electrolyte, while effectively promoting lithium-ion transport and reducing interfacial impedance. The prepared composite solid electrolyte is suitable for preparing high-safety, high-performance solid lithium metal batteries. Attached Figure Description

[0051] The present application will be described in further detail below with reference to the accompanying drawings and preferred embodiments. However, those skilled in the art will understand that these drawings are drawn only for the purpose of explaining the preferred embodiments and therefore should not be construed as limiting the scope of this disclosure. Furthermore, unless specifically indicated, the drawings are only schematic representations of the composition or structure of the described objects and may contain exaggerated depictions, and the drawings are not necessarily drawn to scale.

[0052] Figure 1 This is a schematic diagram of the preparation process of composite solid electrolytes.

[0053] Figure 2 The images shown are SEM images of the porous poly(m-phenylene isophthalamide) nanofibers prepared in Example 1, wherein (a) is a surface SEM image of the porous poly(m-phenylene isophthalamide) nanofibers; and (b) is a cross-sectional SEM image of the porous poly(m-phenylene isophthalamide) nanofibers.

[0054] Figure 3 SEM image of porous poly(m-phenylene isophthalamide) nanofibers prepared in Example 2.

[0055] Figure 4 SEM image of porous poly(m-phenylene isophthalamide) nanofibers prepared in Example 3.

[0056] Figure 5 The image shows a comparison of the XRD patterns of the fluorinated metal-organic framework PCN-222-CF3 prepared in Example 1 and the unfluorinated metal-organic framework PCN-222.

[0057] Figure 6 The FTIR spectra of the fluorinated metal-organic framework PCN-222-CF3 and the unfluorinated metal-organic framework PCN-222 prepared in Example 1 are shown.

[0058] Figure 7 SEM image of the fluorinated metal-organic framework PCN-222-CF3 prepared in Example 1.

[0059] Figure 8 The surface elemental distribution analysis diagram of the fluorinated metal-organic framework PCN-222-CF3 prepared in Example 1 is shown.

[0060] Figure 9 XRD comparison diagrams of three solid electrolytes: polyethylene oxide solid electrolyte, polyethylene oxide solid electrolyte based on fluorinated metal-organic framework, and composite solid electrolyte based on porous meta-aramid nanofiber membrane and fluorinated metal-organic framework.

[0061] Figure 10 A comparison of the interfacial impedance of a full cell assembled with a composite solid electrolyte and a full cell assembled with polyethylene oxide as the electrolyte. Detailed Implementation

[0062] The following is in conjunction with the appendix Figures 1 to 10 This application will be described in detail.

[0063] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0064] Chemicals and reagents:

[0065] Poly(m-phenylene isophthalamide): Yantai Taihe New Materials Sales Co., Ltd.

[0066] Polyethylene oxide: Shanghai Aladdin Biochemical Technology Co., Ltd.; Average Mv ~600,000.

[0067] Unless otherwise specified, all other reagents used in the embodiments of this application are from conventional commercially available products.

[0068] The specific implementation method of this application is as follows.

[0069] Example 1

[0070] This embodiment provides a method for preparing a composite solid electrolyte based on a porous meta-aramid nanofiber membrane and a fluorinated metal-organic framework, such as... Figure 1 As shown, Figure 1 In the middle HV, high voltage is represented. PCN-222-CF3 / PEO / LiTFSI represents a polymer electrolyte matrix containing a fluorinated metal-organic framework PCN-222-CF3. PCN-222-CF3 represents the fluorinated metal-organic framework PCN-222-CF3.

[0071] A method for preparing a composite solid electrolyte based on a porous meta-aramid nanofiber membrane and a fluorinated metal-organic framework includes the following steps:

[0072] 3g of poly(m-phenylene isophthalamide) stock solution (meta-aramid stock solution, composed of 0.9g poly(m-phenylene isophthalamide) and 2.1g N,N-dimethylacetamide) was dissolved in a mixed solvent of 2.1g N,N-dimethylacetamide (DMAc) and 1.4g glycerol. The solution was stirred for 2 hours until completely dissolved, and then transferred to a pipette for electrospinning. The parameters were set as follows: receiving distance 13cm, spinning solution extrusion speed 1mL / h, spinning needle inner diameter 0.8mm, and spinning voltage 25kV. Aluminum foil was used to receive the nanofibers to form a nanofiber membrane. The nanofiber membrane obtained by spinning was immersed in a 95℃ hot water bath for 8 hours and ultrasonicated, and then dried to obtain a porous poly(m-phenylene isophthalamide) nanofiber membrane.

[0073] 0.25 g of zirconium chloride (ZrCl4), 5.5 g of benzoic acid, and 0.1 g of 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin (TCPP) were weighed and dissolved in 30 mL of N,N-dimethylformamide (DMF). The mixture was thoroughly stirred and then transferred to an oven for heat treatment at 120 °C for 12 h. The heat-treated solution was filtered and dried under vacuum at 110 °C for 12 h to obtain the metal-organic framework PCN-222. 0.3 g of PCN-222 particles were dispersed in 12 mL of N,N-dimethylformamide, and 90 μl of trifluoroacetic acid was added. After thorough stirring, the mixture was transferred to an oven for heat treatment at 60 °C for 12 h. The product was centrifuged and dried under vacuum at 100 °C for 12 h to obtain the fluorinated metal-organic framework PCN-222-CF3.

[0074] Preparation of composite solid electrolyte: 0.15 g of fluorinated metal-organic framework PCN-222-CF3 was dispersed in 17 g of anhydrous acetonitrile, and then 1.84 g of polyethylene oxide (PEO) and 1 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) were dissolved in it to prepare a polymer electrolyte matrix containing fluorinated metal-organic framework PCN-222-CF3. The polymer electrolyte matrix was coated onto a porous poly(m-phenylene isophthalamide) nanofiber membrane. The resulting sample was dried at 50 °C for 24 h, and then transferred to an argon glove box to ensure complete solvent removal, thus obtaining the composite solid electrolyte.

[0075] Based on Example 1, this application investigated the mass ratio of N,N-dimethylacetamide to glycerol. The remaining steps and parameters were exactly the same as in Example 1, and the specific parameters are shown in Table 1.

[0076] Table 1. Mass ratio parameters of N,N-dimethylacetamide to glycerol in Examples 1-3

[0077]

[0078] This application performed scanning electron microscopy (SEM) analysis on the surface or cross-section of the porous poly(m-phenylene isophthalamide) nanofibers prepared in Examples 1-3, and the results are as follows: Figures 2-4 As shown. Figures 2-4 SEM images of the surface or cross-section of porous poly(m-phenylene isophthalamide) nanofibers under different mass ratios of N,N-dimethylacetamide and glycerol. Figures 2-4 It is known that the weight ratio of N,N-dimethylacetamide and glycerol in the spinning solution has a significant impact on the porous morphology of nanofibers. Because the electrospinning solution uses a solvent-non-solvent system, the low-boiling-point solvent N,N-dimethylacetamide evaporates first during spinning, and the system spontaneously enriches the non-solvent glycerol, resulting in phase separation. When the content of non-solvent glycerol is low (N,N-dimethylacetamide to glycerol mass ratio 4:1), it is difficult to form a significant porous structure on the surface and inside of the nanofibers. Figure 3 As shown; when the glycerol content is high (N,N-dimethylacetamide to glycerol mass ratio 2:1), the nanofiber pore structure breaks down, as... Figure 4 As shown. When the mass ratio of the mixed solvent N,N-dimethylacetamide to glycerol in the spinning solution is 3:1, nanofibers with better internal and external pore structures are obtained, such as... Figure 2 As shown, when the polymer electrolyte matrix is ​​fully filled, the contact area between the nanofiber membrane and the polymer electrolyte matrix can be increased, thereby increasing the ion transport path.

[0079] This application compares the XRD and FTIR analyses of the fluorinated metal-organic framework PCN-222-CF3 prepared in Example 1 with the unfluorinated metal-organic framework PCN-222. The results are as follows: Figures 5-6 As shown. By Figure 5 and Figure 6 It can be seen that Example 1 successfully fluorinated the metal-organic framework PCN-222, and the fluorinated metal-organic framework material has good crystallinity.

[0080] This application performed scanning electron microscopy (SEM) analysis and surface elemental distribution analysis on the fluorinated metal-organic framework PCN-222-CF3 prepared in Example 1. The results are as follows: Figures 7-8 As shown. By Figure 7 and Figure 8 It is known that the fluorinated metal-organic framework PCN-222-CF3 exhibits the shape of an integral one-dimensional nanorod with uniform fluorine distribution, which can provide a one-dimensional transport channel for lithium ions. Its relatively high aspect ratio can significantly increase the interfacial contact area with the polymer matrix, promote interfacial ion transport, and induce uniform lithium ion deposition.

[0081] Figure 9The image shows a comparison of XRD patterns for three solid-state electrolytes: a polyethylene oxide (PEO / LiTFSI) solid-state electrolyte, a fluorinated metal-organic framework-based PEO solid-state electrolyte (5PCN-222-CF3 / PEO / LiTFSI), and a composite solid-state electrolyte based on a porous meta-aramid nanofiber membrane and a fluorinated metal-organic framework (5PCN-222-CF3 / PMIA / PEO / LiTFSI). Figure 9 It is evident that the introduction of fluorinated metal-organic framework PCN-222-CF3 into polyoxyethylene electrolytes can significantly reduce the crystallinity of polyoxyethylene. The introduction of porous poly(m-phenylene isophthalamide) nanofibers can further significantly reduce the crystallinity of polyoxyethylene. The synergistic effect of fluorinated metal-organic framework PCN-222-CF3 and porous poly(m-phenylene isophthalamide) nanofibers can jointly reduce the crystallinity of polyoxyethylene and promote the rapid transport of lithium ions in the electrolyte.

[0082] This application uses the composite solid electrolyte prepared in Example 1 to assemble a battery with a lithium sheet / composite solid electrolyte / lithium iron phosphate (LiFePO4) cathode structure. A comparative study of the full-cell interfacial impedance was conducted with a battery assembled using polyethylene oxide as the electrolyte with a lithium sheet / polyethylene oxide electrolyte / lithium iron phosphate (LiFePO4) cathode structure. The study used a CHI660D electrochemical workstation and combined it with electrochemical impedance spectroscopy (EIS) to test the ionic conductivity of the cathode structure battery. The test temperature was 50°C, and the test frequency was 10. 6 Hz to 10 -1 Hz. Test results are as follows Figure 10 As shown, Figure 10 In the middle, the horizontal axis (Z) ’ The vertical axis (Z) represents the real part of the impedance (resistive component), and the vertical axis (Z) represents the imaginary part of the impedance (capacitive component). Li||PEO||LiFePO4 represents a lithium-ion battery / polyethylene oxide electrolyte / lithium iron phosphate cathode assembly, while Li||CSE||LiFePO4 represents a lithium-ion battery / composite solid-state electrolyte / lithium iron phosphate cathode assembly. Figure 10 It can be seen that, compared with the full cell assembled using the composite solid electrolyte prepared in Example 1, the full cell exhibits a smaller semi-circular diameter in the high-frequency region and a lower interface impedance.

[0083] The present application has been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present application. The descriptions of the embodiments above are only for the purpose of helping to understand the present disclosure and its core ideas. It should be noted that those skilled in the art can make several improvements and modifications to the present application without departing from the principles of the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application.

Claims

1. A method for preparing a composite solid electrolyte based on a porous meta-aramid nanofiber membrane and a fluorinated metal-organic framework, characterized in that, Includes the following steps: S1: Dissolve the poly(m-phenylene isophthalamide) stock solution in a mixed solvent composed of N,N-dimethylacetamide and glycerol to prepare a spinning solution; perform electrospinning on the spinning solution to obtain a nanofiber membrane; immerse the obtained nanofiber membrane in a hot water bath and sonicate it, and then dry it to obtain a porous poly(m-phenylene isophthalamide) nanofiber membrane. S2: Zirconium chloride, benzoic acid, and 5,10,15,20-tetra(4-carboxyphenyl)porphyrin were dissolved in a solvent and subjected to heat treatment. The heat-treated solution was filtered and dried to obtain the metal-organic framework PCN-222. The metal-organic framework PCN-222 was dispersed in a solvent, trifluoroacetic acid was added, and the solution was subjected to heat treatment. After centrifugation and drying, the fluorinated metal-organic framework PCN-222-CF3 was obtained. S3: Disperse the fluorinated metal-organic framework PCN-222-CF3 in a solvent, add polyethylene oxide and lithium salt, stir to dissolve, and obtain a polymer electrolyte matrix; coat the polymer electrolyte matrix onto the porous poly(m-phenylene isophthalamide) nanofiber membrane prepared in step S1, and dry to obtain a composite solid electrolyte.

2. The preparation method of the composite solid electrolyte based on porous meta-aramid nanofiber membrane and fluorinated metal-organic framework as described in claim 1, characterized in that, In step S1, the poly(m-phenylene isophthalamide) stock solution is a solution formed by dissolving poly(m-phenylene isophthalamide) in N,N-dimethylacetamide, and the mass fraction of poly(m-phenylene isophthalamide) in the poly(m-phenylene isophthalamide) stock solution is 25-35%.

3. The method for preparing the composite solid electrolyte based on porous meta-aramid nanofiber membrane and fluorinated metal-organic framework as described in claim 2, characterized in that, In step S1, the mass ratio of N,N-dimethylacetamide to glycerol in the spinning solution is (2-4):

1.

4. The method for preparing the composite solid electrolyte based on porous meta-aramid nanofiber membrane and fluorinated metal-organic framework as described in claim 1, characterized in that, In step S2, the molar ratio of zirconium chloride to 5,10,15,20-tetra(4-carboxyphenyl)porphyrin is (9-11):

1.

5. The method for preparing the composite solid electrolyte based on porous meta-aramid nanofiber membrane and fluorinated metal-organic framework as described in claim 1, characterized in that, In step S2, the volume-to-mass ratio of trifluoroacetic acid to the metal-organic framework PCN-222 is 250-350 μL / g; the solvent in step S2 is N,N-dimethylformamide.

6. The method for preparing the composite solid electrolyte based on porous meta-aramid nanofiber membrane and fluorinated metal-organic framework as described in claim 1, characterized in that, Based on the total mass of the polymer and lithium salt, the mass fraction of the fluorinated metal-organic framework PCN-222-CF3 in step S3 is 4%-6%; the solvent in step S3 is anhydrous acetonitrile.

7. The method for preparing the composite solid electrolyte based on porous meta-aramid nanofiber membrane and fluorinated metal-organic framework as described in claim 1, characterized in that, In step S3, the lithium salt is at least one of lithium bis(trifluoromethanesulfonylimide), lithium hexafluorophosphate, and lithium perchlorate. The molar ratio of ether oxygen atoms to lithium ions in polyethylene oxide is (10-14):

1.

8. The method for preparing the composite solid electrolyte based on porous meta-aramid nanofiber membrane and fluorinated metal-organic framework as described in claim 1, characterized in that, In step S2, zirconium chloride, benzoic acid, and 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin are dissolved in a solvent and subjected to heat treatment at a temperature of 110-130℃. In step S2, the metal-organic framework PCN-222 is dispersed in a solvent, trifluoroacetic acid is added, and heat treatment is performed at a temperature of 55-65℃.

9. A composite solid electrolyte based on a porous meta-aramid nanofiber membrane and a fluorinated metal-organic framework, prepared by any one of the preparation methods of claims 1-8.

10. A solid-state battery, comprising a composite solid electrolyte based on a porous meta-aramid nanofiber membrane and a fluorinated metal-organic framework, prepared by any one of the preparation methods of claims 1-8.

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