Solid-state electrolyte membrane, preparation method thereof and solid-state battery

Abstract

The invention provides a solid-state electrolyte membrane, a preparation method thereof and a solid-state battery, and relates to the technical field of solid-state electrolyte. The preparation method of the solid electrolyte membrane provided by the invention comprises the following steps: mixing Fe-based MOFs particles with a fiber-forming polymer, and carrying out electrostatic spinning to obtain a rigid skeleton; an ionic liquid electrolyte is permeated into the rigid framework to prepare a basement membrane; and mixing the polyether polymer and the cyanogen-containing plasticizer, and permeating the mixture into the basement membrane to prepare the solid electrolyte membrane. By utilizing the coordination effect of iron ions and cyano groups, the stability of the cyano group plasticizer is effectively improved, and competitive coordination of lithium ions, the cyano group-containing plasticizer, the polyether polymer and anions is cooperatively regulated and controlled, so that a stable lithium ion transmission path is constructed, and the structural stability and the electrochemical performance of the solid electrolyte membrane are effectively improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solid-state electrolyte, and particularly relates to a solid-state electrolyte film, a preparation method thereof and a solid-state battery. BACKGROUND

[0002] As a cutting-edge direction of energy storage technology, solid-state batteries have attracted much attention due to their intrinsic safety and high energy density. Solid-state polymer electrolytes (SPEs) have become the core material system due to their high safety, good mechanical flexibility, electrochemical stability and scalable processing characteristics. However, SPEs are always bound by a fundamental contradiction: the ion conductivity and the interface stability are inversely proportional. When introducing high dielectric constant plasticizers such as succinonitrile (SN), the contradiction tends to be more acute. Although the free cyan group (-CN) can promote lithium ion transmission and improve ion conductivity, it can also cause catastrophic interface failure through side reactions and lithium dendrite proliferation.

[0003] Currently, the prior art mainly tries to alleviate the negative effects of SN by the following three strategies: (1) using inorganic oxides such as garnet-type Li7La3Zr2O 12 (LLZO) or polar polymers such as polyacrylonitrile (PAN) for physical / chemical confinement to inhibit the side reactions of SN, but this traditional physical / chemical confinement cannot precisely control the molecular behavior of SN, and can only partially limit the migration and side reactions of SN, resulting in continuous degradation of the interface in long-term cycling; (2) using hydroxyl-rich frameworks such as cellulose composites for hydrogen bond capture to physically anchor SN and enhance the stability of the solid electrolyte interface phase (SEI), but hydrogen bonds are weak interactions and are easily broken in electrochemical cycling (especially at high temperature or high pressure), which may still allow SN to be free and participate in side reactions; (3) using lithium ion-conducting ceramics to enhance conductivity, promote salt dissociation and stabilize SN dynamics, but the compatibility of ceramic particles with the polymer matrix is poor, which easily forms a high impedance interface to hinder lithium ion transmission, and in addition, although ceramic materials can optimize the local lithium ion solvation environment, they cannot completely inhibit the redox side reactions of SN at the electrode interface. These methods only alleviate the symptoms but not the root cause, and still cannot solve the problem. Therefore, there is an urgent need to provide a solution to improve the above problems. SUMMARY

[0004] The present application aims to provide a solid-state electrolyte film, a preparation method thereof and a solid-state battery, which effectively improve the stability of the cyan plasticizer by utilizing the coordination of iron ions and cyan groups, and synergistically regulate the competitive coordination of lithium ions, cyan-containing plasticizers, polyether polymers and anions, thereby constructing a stable lithium ion transmission path and effectively improving the structural stability and electrochemical performance of the solid-state electrolyte film.

[0005] In a first aspect, the present application provides a method for preparing a solid-state electrolyte membrane, comprising: mixing Fe-based MOFs particles with fiber-forming polymers to electrospun a rigid framework; infiltrating an ionic liquid electrolyte into the rigid framework to obtain a base membrane; infiltrating a polyether polymer mixed with a cyan-containing plasticizer into the base membrane to obtain the solid-state electrolyte membrane.

[0006] Optionally, the Fe-based MOFs particles are formed by coordination of iron ions and aromatic dicarboxylic acid; the source of the iron ions includes one of ferric chloride, ferric nitrate, and iron triflate, and the aromatic dicarboxylic acid includes one of terephthalic acid, 2,6-naphthalene dicarboxylic acid, and 4,4'-biphenyl dicarboxylic acid.

[0007] Optionally, the cyan-containing plasticizer includes one of succinonitrile, glutaronitrile, and adiponitrile; and / or, the polyether polymer includes one of polyethylene oxide and polypropylene oxide; and / or, the fiber-forming polymer includes one of polyacrylonitrile, polyvinylidene fluoride, and polyimide.

[0008] Optionally, the ionic liquid electrolyte includes an ionic liquid and a first lithium salt dissolved in the ionic liquid; the ionic liquid includes one of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, and N-methyl-N-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide; and the first lithium salt includes one of lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, and lithium hexafluorophosphate.

[0009] Optionally, the Fe-based MOFs particles are mixed with the fiber-forming polymers at a mass ratio of 1:(0.5-2); and / or, the Fe-based MOFs particles are mixed with the fiber-forming polymers to obtain a mixed suspension; and / or, the rigid framework is obtained by drying after electrospinning; and / or, the electrospinning is performed at a voltage of 8kV-12kV.

[0010] Optionally, the ratio of the ionic liquid electrolyte to the rigid framework in the base membrane is 0.5mL / g-2mL / g; and / or, the ionic liquid electrolyte is infiltrated by being coated on the surface of the rigid framework; and / or, the method for preparing the ionic liquid electrolyte includes: dissolving and stirring the first lithium salt in the ionic liquid and then drying, and the molar ratio of lithium in the first lithium salt to the ionic liquid is 1:(3-8).

[0011] Optionally, a second lithium salt, a polyether polymer, and a cyan-containing plasticizer are dissolved to obtain a composite solution, and the composite solution is infiltrated into the base membrane to obtain the solid-state electrolyte membrane; wherein the mass content of the cyan-containing plasticizer in the composite solution is 20%-40%; and / or, the molar ratio of the polyether polymer to the second lithium salt is (15-20):1; and / or, the second lithium salt includes one of lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, and lithium hexafluorophosphate.

[0012] In a second aspect, the present application provides a solid-state electrolyte membrane prepared by any of the optional preparation methods described above, comprising a rigid framework embedded with Fe-based MOFs particles and an ionic liquid electrolyte permeating the rigid framework, further comprising a polyether polymer filling the rigid framework, and a cyano-containing plasticizer, wherein the cyano group in the cyano-containing plasticizer is bonded to the iron ion in the Fe-based MOFs particles through coordination bonding.

[0013] In a third aspect, the present application provides a solid-state battery comprising the solid-state electrolyte membrane prepared by any of the optional preparation methods described above.

[0014] The solid-state electrolyte membrane provided by the present application has at least one of the following beneficial technical effects compared with the prior art: 1. By utilizing the coordination action between iron ions and cyano groups, the stability of the cyano-containing plasticizer is effectively improved, and the competitive coordination among lithium ions, the cyano-containing plasticizer, the polyether polymer, and anions is synergistically controlled, thereby constructing a stable lithium ion transmission path, and effectively improving the structural stability and electrochemical performance of the solid-state electrolyte membrane; 2. The three-dimensional network formed by the electrospinning of the fiber-forming polymer and the Fe-based MOFs particles can effectively support the MOFs particles to prevent their agglomeration, not only can the ordered framework be constructed, but also the Fe-based MOFs particles can be arranged along the fiber direction, thereby providing a stable three-dimensional ion transmission channel. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 The infrared spectrum and X-ray photoelectron spectroscopy characterization graphs of the solid-state electrolyte membranes prepared in Example 1 and Comparative Examples 1 to 2 of the present application are shown in the following figures: Figure 2 The scanning electron microscope characterization graphs of the Fe-BDC MOFs particles, the PAN / Fe-BDC rigid framework, and the solid-state electrolyte membrane prepared in Example 1 of the present application are shown in the following figures: Figure 3 The energy spectrum analysis characterization graphs of the solid-state electrolyte membrane prepared in Example 1 of the present application are shown in the following figures: Figure 4 The X-ray diffraction characterization graphs of the Fe-BDC MOFs particles, the PAN / Fe-BDC rigid framework, and pure PAN and SN prepared in Example 1 of the present application are shown in the following figures: Figure 5 The scanning electron microscope and energy spectrum analysis characterization graphs of the interface and surface of the solid-state electrolyte membranes prepared in Example 1 and Comparative Examples 1 to 2 of the present application are shown in the following figures: Figure 6 The ion conductivity comparison graphs of the solid-state electrolyte membranes prepared in Example 1 and Comparative Examples 1 to 2 of the present application are shown in the following figures: Figure 7A comparison chart of crystallinity of solid-state electrolyte membranes prepared for the present embodiment 1, comparative example 1 to comparative example 2 under differential scanning calorimetry evaluation; Figure 8 A comparison chart of electronic conductivity of solid-state electrolyte membranes prepared for the present embodiment 1, comparative example 1 to comparative example 2; Figure 9 A comparison chart of lithium ion transport capacity of solid-state electrolyte membranes prepared for the present embodiment 1, comparative example 1 to comparative example 2; Figure 10 A comparison chart of tensile stress-strain of solid-state electrolyte membranes prepared for the present embodiment 1, comparative example 1 to comparative example 2; Figure 11 A comparison chart of discharge specific capacity of solid-state batteries (LFP / FAEIS / Li, LFP / FAES / Li, LFP / AES / Li) at 0.2C, 0.5C, 1C, 2C discharge rate; Figure 12 A comparison chart of charge-discharge cycle test of solid-state batteries (LFP / FAEIS / Li, LFP / FAES / Li) at 2C discharge rate at 25℃, 60℃, and a comparison chart of charge-discharge cycle test of solid-state batteries at 10C discharge rate at 60℃; Figure 13 A comparison chart of charge-discharge cycle test of solid-state batteries (NCM811 / FAEIS / Li, NCM811 / FAES / Li) at 4.4V, 1C for 100 cycles. DETAILED DESCRIPTION

[0016] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of the present application. Unless otherwise defined, the technical terms or scientific terms used herein should have the usual meanings understood by those of ordinary skill in the art.

[0017] The present application provides a preparation method of a solid-state electrolyte membrane, comprising the following steps: electrospinning a rigid framework by mixing Fe-based MOFs particles with fiber-forming polymers; permeating an ionic liquid electrolyte into the rigid framework to prepare a base membrane; permeating a polyether polymer mixed with a cyano-containing plasticizer into the base membrane to prepare a solid-state electrolyte membrane.

[0018] In fact, the preparation method provided by the application can fix the cyano-containing plasticizer in the nanopores of the MOFs particles by using the coordination bond between iron ions and cyano groups as a molecular anchor, and can synergistically regulate the competitive coordination of lithium ions in the MOFs particles with the cyano-containing plasticizer, the polyether polymer and the anion, thereby establishing a three-dimensional and continuous lithium ion transmission path by using a double regulation strategy, and effectively inhibiting the side reactions caused by the cyano-containing plasticizer, so as to improve the room temperature conductivity, lithium ion transference number and electrochemical window stability of the solid electrolyte membrane.

[0019] In some embodiments, the Fe-based MOFs particles used are formed by coordination of iron ions and aromatic dicarboxylic acid, and specifically, the iron ions are trivalent iron ions. Further, the source of the iron ions includes one of ferric chloride, ferric nitrate and iron triflate, and the aromatic dicarboxylic acid includes one of terephthalic acid, 2,6-naphthalene dicarboxylic acid and 4,4'-biphenyldicarboxylic acid.

[0020] In some embodiments, when synthesizing the Fe-based MOFs particles by coordination of iron ions and aromatic dicarboxylic acid, the molar ratio of iron ions to carboxylic acid can be controlled to be (0.5-2.0):1, thereby regulating the structure changes such as the pore size and specific surface area of the MOFs particles, helping the MOFs particles to form a stable porous framework, and effectively balancing the density of the anchoring sites of iron ions and cyano groups and the lithium ion transmission channels in the pores of the MOFs particles, while also avoiding the defects of residual uncoordinated metal sites or excessive ligands leading to reduced skeleton integrity.

[0021] In some embodiments, when synthesizing the Fe-based MOFs particles by coordination of iron ions and aromatic dicarboxylic acid, the iron source and the aromatic dicarboxylic acid can be reacted at 80-120°C for 8-16h. In fact, reacting at high temperature helps to promote the coordination reaction of iron ions and aromatic dicarboxylic acid, thereby forming long-range ordered and highly crystalline crystal MOFs particles. Specifically, the iron source and the aromatic dicarboxylic acid can be dissolved in a first solvent to ensure sufficient contact between the iron ions and the aromatic dicarboxylic acid, thereby improving the uniformity and efficiency of the coordination reaction.

[0022] Preferably, when synthesizing the Fe-based MOFs particles, ferric chloride can be dissolved in N,N-dimethylformamide (DMF) to obtain a ferric chloride solution, and then terephthalic acid (H2BDC) is stirred and dissolved in the ferric chloride solution to perform a coordination reaction, thereby obtaining the Fe-based MOFs particles. In fact, the anions produced by the ionization of ferric chloride can avoid interfering with the crystallization process of the MOFs, and the iron ions and the terephthalic acid have matching ionic radii, thereby being able to coordinate to build a rigid and stable MOF porous framework, providing a basic mechanical support and ion transmission channel. In addition, the Fe 3+Fe-based MOFs can form strong coordination bonds with -CN (cyano), which can anchor the cyano-containing plasticizer.

[0023] In some embodiments, the nanopores in the Fe-based MOFs particles used have a pore size of 1-2 nm. In fact, by precisely regulating the pore size of the MOFs, effective confinement of the cyano-containing plasticizer can be achieved, avoiding leakage of the cyano-containing plasticizer and allowing free transmission of lithium ions, while a pore size larger than the diameter of the solvation sheath of lithium ions can reduce the resistance of lithium ion transmission, thereby helping to optimize the ion transmission channel.

[0024] In some embodiments, the Fe-based MOFs particles can be mixed with the fiber-forming polymer at a mass ratio of 1:(0.5-2) to prepare a mixed suspension. In fact, by adjusting the mass content of MOFs particles in the mixed suspension, the loading of MOFs particles in the prepared rigid skeleton can be adjusted, promoting uniform attachment of MOFs particles along the fiber direction and ensuring the continuity of the pores, while the fiber structure formed by the fiber-forming polymer helps to form the basic skeleton.

[0025] In some embodiments, the fiber-forming polymer and the Fe-based MOFs particles can be added to a second organic solvent and stirred to prepare a mixed suspension. Specifically, the second organic solvent used can be one of N,N-dimethylformamide, N,N-dimethylacetamide or dimethyl sulfoxide. In fact, the Fe-based MOFs particles, the fiber-forming polymer and the second organic solvent can be mixed at a mass ratio of (0.5-2):(0.5-2):(5-10), and by optimizing the amount of the second solvent, uniform dispersion of the MOFs particles can be ensured, while facilitating the gradient volatilization of the second solvent during electrospinning, thereby forming through channels in the rigid skeleton.

[0026] In some embodiments, the mixed suspension can be electrospun in an electrospinning device at a voltage of 8-12 kV and then dried to prepare a rigid skeleton. Specifically, the receiver of the electrospinning device can be controlled to rotate at a speed of 500-800 rpm, thereby effectively improving the uniformity of the rigid skeleton, and the flow rate of the mixed suspension can be controlled at 0.3-0.8 mL / h. In fact, by adjusting the electrospinning voltage, the fibers in the rigid skeleton can form homogeneous fibers, and by adjusting the flow rate, the gradient volatilization of the second solvent during spinning can be promoted, avoiding adhesion of the fibers in the rigid skeleton.

[0027] In some embodiments, the used fiber-forming polymer includes one of polyacrylonitrile, polyvinylidene fluoride, and polyimide. In fact, the three-dimensional network formed by electrospinning the fiber-forming polymer and the Fe-based MOF particles can effectively support the MOF particles to prevent their agglomeration, not only can complete the construction of the ordered skeleton, but also can arrange the Fe-based MOF particles along the fiber direction, thereby providing a stable three-dimensional ion transport channel. In addition, the interaction between the polymer chains in the fiber-forming polymer and the polar groups on the surface of the Fe-based MOF particles can effectively enhance the interface compatibility and interface stability, and at the same time improve the tensile strength of the solid electrolyte membrane.

[0028] In some embodiments, the ionic liquid electrolyte includes an ionic liquid and a first lithium salt dissolved in the ionic liquid, and the preparation method of the ionic liquid electrolyte includes: stirring and dissolving the first lithium salt in the ionic liquid and then drying. In fact, the used first lithium salt includes one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, and lithium hexafluorophosphate. Preferably, the first lithium salt can be lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), which has strong ion delocalization and helps to promote the dissociation of lithium ions, and LiTFSI has strong thermal stability and can well compatible with the high-voltage positive electrode environment. -

[0029] In some embodiments, the used ionic liquid includes one of 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, and N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide salt. Preferably, the ionic liquid can be 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt (BMIM-TFSI), which can effectively lubricate the interface of the rigid skeleton, thereby improving the interface compatibility, and TFSI + - can homogenize the lithium ion flux, which helps to maintain the interface stability, so as to synergistically improve the conductivity.

[0030] In some embodiments, the ionic liquid electrolyte can be coated on the surface of the rigid skeleton and gradually penetrate into the interior of the rigid skeleton. Specifically, the ratio of the ionic liquid electrolyte to the rigid skeleton in the base film is 0.5 mL / g-2 mL / g. Further, the molar ratio of lithium element in the first lithium salt to the ionic liquid in the ionic liquid electrolyte is 1:(3-8).

[0031] ​​In some embodiments, the second lithium salt, the polyether polymer and the cyano-containing plasticizer are dissolved to form a composite solution, and the composite solution is infiltrated into the substrate film to form the solid-state electrolyte film. In practice, the mass content of the cyano-containing plasticizer in the composite solution is 20%-40%, and the molar ratio of the polyether polymer to the second lithium salt is (15-20):1. Specifically, the second lithium salt used includes one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, and lithium hexafluorophosphate.

[0032] In some embodiments, the cyano-containing plasticizer used includes one of succinonitrile, glutaronitrile, and adiponitrile. Preferably, the cyano-containing plasticizer can be selected from succinonitrile (SN) with good dielectric properties. The cyano group in succinonitrile has strong polarity, which can promote the dissociation of lithium salt and effectively improve the ionic conductivity of the solid-state electrolyte film. At the same time, after the cyano group forms coordination with the iron ions in the MOFs particles, it can also inhibit the leakage of the cyano-containing plasticizer and the interface side reactions caused by the leakage of the cyano-containing plasticizer.

[0033] In practice, the binding energy of the coordination bond formed by the cyano group in the cyano-containing plasticizer and the iron ions in the Fe-based MOFs particles in the solid-state electrolyte film is-0.8eV to-1.2eV. In addition, through the strong coordination bond between the cyano group and the iron ions, not only can the cyano-containing plasticizer be anchored inside the nanopores of the MOFs particles, but also the strength of the MOF framework can be improved by using the cyano-containing plasticizer and the coordination bond, which can avoid the collapse of the MOF framework during battery cycling, and help to improve the cycle stability and mechanical strength of the solid-state electrolyte film.

[0034] In some embodiments, the polyether polymer used includes one of polyethylene oxide and polypropylene oxide. Preferably, the polyether polymer can use polyethylene oxide (PEO) with high ether oxygen bond density and strong coordination ability with lithium ions. By coordinating the ether oxygen bond in polyethylene oxide with lithium ions to form a dynamic solvation sheath, it helps to build a continuous lithium ion transmission channel, and can promote the dissociation of lithium ions and increase the number of lithium ion migration.

[0035] The application also provides a solid-state electrolyte film prepared by the preparation method of any one of the above embodiments, which includes a rigid framework embedded with Fe-based MOFs particles and an ionic liquid electrolyte infiltrated into the rigid framework, and further includes a polyether polymer and a cyano-containing plasticizer filled in the rigid framework, wherein the cyano group in the cyano-containing plasticizer is bonded to the iron ions in the Fe-based MOFs particles through a coordination bond.

[0036] Embodiment 1:

[0037] The embodiment 1 provides a preparation method of a solid-state electrolyte film, which includes the following steps: S1, 0.500 g of terephthalic acid (H2BDC) was stirred and dissolved in 200 mL of N, N-dimethylformamide (DMF), and then 0.553 g of FeCl3·6H2O was stirred and dissolved to prepare a mixed solution, the mixed solution was transferred into a high-pressure reaction kettle, reacted at 100°C for 12 h, cooled to room temperature, and the precipitate was separated, then washed with DMF and anhydrous ethanol for three cycles, and dried to constant weight to obtain Fe-BDC MOFs particles; S2, Fe-BDC MOFs particles, polyacrylonitrile (PAN, Mw=15000), and DMF were stirred and mixed at a mass ratio of 1:1:7.5 to prepare a mixed suspension, and the mixed suspension was electrospun using an electrospinning device at a spinning voltage of 10 kV, a flow rate of 0.5 mL / h, a receiver rotation speed of 600 rpm, and a nozzle-receiver distance of 15 cm, and then vacuum dried at 80°C for 12 h to obtain a PAN / Fe-BDC rigid skeleton; S3, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (BMIM-TFSI) were mixed at a molar ratio of 1:4 and stirred at room temperature for 12 h, then dried in a vacuum drying oven at 150°C for 12 h to obtain a lithium ionic liquid, and the lithium ionic liquid was coated in the PAN / Fe-BDC rigid skeleton at a ratio of 1 mL:1 g to allow it to penetrate fully, and then a PAN / Fe-BDC / IL base film was obtained; S4, polyethylene oxide (PEO, Mw=600000), LiTFSI, and succinonitrile (SN) were stirred and dissolved in 22 mL of acetonitrile to prepare a composite solution, and the molar ratio of EO to Li + in the composite solution was adjusted to 18:1, and the SN content was 30%, and the composite solution was added dropwise to the PAN / Fe-BDC / IL base film to allow the composite solution to penetrate fully, then naturally volatilized for 12 h, transferred to a vacuum drying oven and dried at 50°C for 12 h to obtain a solid-state electrolyte film (FAEIS).

[0038] Comparative Example 1: This comparative example 1 provides a method for preparing a solid-state electrolyte film, which is different from example 1 in that step S3 is not performed, and the composite solution is added dropwise to the PAN / Fe-BDC rigid skeleton in step S4, and finally a solid-state electrolyte film (FAES) is obtained.

[0039] Comparative Example 2: The comparative example 2 provides a preparation method of a solid-state electrolyte film, which is different from the example 1 in that the steps S1 and S3 are not performed, the PAN and DMF are directly stirred and mixed to prepare a mixed suspension in a mass ratio of 1:7.5 in the step S2, and the electrospinning is performed to prepare a PAN skeleton, the composite solution is added drop by drop to the rigid skeleton in the step S4, and finally the solid-state electrolyte film (AES) is prepared.

[0040] Structural characterization: The solid-state electrolyte films (FAEIS, FAES and AES) prepared in the example 1 and the comparative examples 1 to 2 are characterized by infrared spectroscopy and X-ray photoelectron spectroscopy (XPS) as shown in A and B of Figure 1 respectively. It can be seen from Figure 1 that the -CN peak at 2250 cm -1 in the infrared spectrum is shifted to a higher wave number direction after the addition of MOFs, and in addition, the Fe 3+ 2p and -CN characteristic peaks are all shifted, which can confirm that the MOFs-SN interacts, and this interaction can effectively inhibit the reaction of SN with lithium metal, thereby being beneficial to reducing the side reaction in the battery and improving the utilization efficiency of lithium metal.

[0041] The Fe-BDC MOFs particles, the PAN / Fe-BDC rigid skeleton and the solid-state electrolyte film (FAEIS) prepared in the example 1 are characterized by a scanning electron microscope (SEM) as shown in A, B and C of Figure 2 respectively. It can be seen from A of Figure 2 that the Fe-BDC MOFs particles have a dodecahedron structure and good size uniformity, it can be seen from B of Figure 2 that the Fe-BDC MOFs particles can be uniformly dispersed along the PAN fiber tube in the support skeleton, and the electrospinning does not change the crystal structure of the MOFs particles, and it can be seen from C of Figure 2 that the surface of the solid-state electrolyte film is uniform and wrinkle-free.

[0042] The solid-state electrolyte film (FAEIS) prepared in the example 1 is characterized by an energy dispersive spectrometer (EDS) as shown in Figure 3 . It can be seen from Figure 3 that the carbon, oxygen and iron elements can be uniformly dispersed in the solid-state electrolyte film.

[0043] The Fe-BDC MOFs particles, the PAN / Fe-BDC rigid skeleton, and the pure PAN and SN are characterized by an X-ray diffractometer (XDR) as shown in Figure 4 . It can be seen from Figure 4As can be seen, the MOF particles exhibit strong diffraction peaks at 2θ values ​​of 9.5°, 12.7°, 19.0°, and 22.1°, indicating the successful synthesis of Fe-BDC MOF particles. Furthermore, these characteristic peaks are preserved within the rigid PAN / Fe-BDC framework, demonstrating that the MOF particles can be retained and provide support within the rigid framework. Additionally, SN shows two strong diffraction peaks at 2θ values ​​of 19.6° and 23.8°.

[0044] The cross-sections and surfaces of the solid electrolyte membranes (FAEIS, FAES, AES) prepared in Example 1 and Comparative Examples 1 to 2 were characterized using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Figure 5 As shown. From Figure 2 As can be seen from C, the solid electrolyte membrane prepared in Example 1 has a smooth, non-porous, and wrinkle-free surface morphology. Figure 5 The cross-sectional SEM image of the FAEIS membrane shows an average film thickness of 45.7 μm, and the EDS characterization image confirms that the elements are uniformly distributed across the cross-section. In contrast, the solid electrolyte membranes (FAES and AES) in Comparative Examples 1 and 2 exhibit wrinkled surfaces and visible pores, with thicknesses of approximately 41.3 μm and 65.5 μm, respectively. The EDS characterization images show that various elements are uniformly distributed on the surface and in the cross-sectional region. This indicates that the presence of the PAN / Fe-BDC rigid framework promotes the volatilization of acetonitrile in step S4, which is beneficial for forming a smooth and uniform morphology on the surface of the solid electrolyte membrane. Furthermore, the addition of lithium-ion liquid helps improve the interfacial compatibility of the solid electrolyte membrane.

[0045] The ionic conductivity of the solid electrolyte membranes in Example 1, Comparative Examples 1 to 2 was measured as follows: Figure 6 As shown. From Figure 6 As can be seen from the data, the solid electrolyte membrane prepared in Example 1 exhibits the highest ionic conductivity at room temperature, reaching 1.16 × 10⁻⁶. -3 The S / cm value was 6.58 × 10⁻⁶, while the solid electrolyte membranes in Comparative Examples 1 and 2 had values ​​of 6.58 × 10⁻⁶. -4 S / cm, 3.94×10 -4 S / cm, and the ion migration activation energies of the solid electrolyte membranes in Example 1, Comparative Examples 1 to 2 were found to be 0.32 eV, 0.34 eV, and 0.38 eV, respectively, by fitting the Arrhenius equation. This indicates that the increased ionic conductivity of the solid electrolyte membrane in Example 1 is mainly attributed to the addition of succinate and Fe-BDC MOF particles, which synergistically enhance the Li-ion conductivity through a dual regulatory mechanism. +The coordination environment reduces the internal order of the polymer matrix, thereby reducing crystallinity. Overall, the solid electrolyte membranes in Example 1 and Comparative Examples 1 to 2 all meet the ion conduction criteria.

[0046] The crystallinity of the solid electrolyte membranes in Example 1, Comparative Examples 1 to 2 was evaluated using differential scanning calorimetry. Figure 7 As shown. From Figure 7 As can be seen from the data, the glass transition temperatures (Tg) of the solid electrolyte membranes in Example 1, Comparative Examples 1 to 2 are -55.1℃, -50.9℃, and -50.5℃, respectively, and the melting temperatures (Tm) are 24.5℃, 25.6℃, and 28.5℃, respectively. Furthermore, the solid electrolyte membranes in Example 1 and Comparative Example 1 are both in an amorphous state at 30℃, with the solid electrolyte membrane in Example 1 exhibiting the lowest crystallinity. Figure 4 As can be seen, although PEO shows two distinct characteristic peaks at 2θ values ​​of 19.2° and 23.3°, the absence of these peaks in Example 1 and Comparative Examples 1 to 2 indicates a transition to a more amorphous state, which further illustrates the decrease in crystallinity of the solid electrolyte membrane.

[0047] The electronic conductivity of the solid electrolyte membranes in Example 1, Comparative Examples 1 to 2 was measured as follows: Figure 8 As shown. From Figure 8 As can be seen from the data, the electronic conductivity of the solid electrolyte membranes in Example 1, Comparative Examples 1 to 2 are 2.01 × 10⁻⁶, respectively. - 9 S / cm, 1.82×10 -10 S / cm, 1.90×10 -9 The S / cm indicates that the addition of Fe-BDC MOF particles can reduce the electronic conductivity of the solid electrolyte membrane, while the addition of lithium-ion liquid will slightly increase the electronic conductivity. However, in general, the solid electrolyte membranes in Example 1, Comparative Examples 1 to 2 all meet the electronic insulation standard.

[0048] The lithium-ion transport capacity of the solid electrolyte membranes in Example 1, Comparative Examples 1 to 2 was measured as follows: Figure 9 As shown. From Figure 9 As can be seen from the above, the tLi of the solid electrolyte membrane in Example 1, Comparative Examples 1 to 2 is... + The lithium-ion transference numbers were 0.8, 0.72, and 0.41, respectively. It can also be seen that, due to the dual coordination-driven mechanism, the solid electrolyte membrane in Example 1 can release more beneficial lithium ions, while the rigid PAN / Fe-BDC framework can provide lithium... + The transport provides more channel frameworks, and the addition of lithium-ion liquid helps to further improve interfacial wettability, thereby forming a continuous Li...+ Conductive network, in addition, the SN as plasticizer can produce a large number of amorphous region to promote Li + Migration, and the electronegative nitrogen atom of SN can inhibit the aggregation of anions at the cross section, thereby leading to lower polarization and higher tLi + , thereby making the solid electrolyte film in Example 1 a super-high lithium flux conductor.

[0049] The solid electrolyte films in Example 1, Comparative Example 1 to Comparative Example 2 were subjected to tensile stress-strain tests as shown in Figure 10 It can be seen from Figure 10 that the mechanical strength of the three solid electrolyte films did not show significant difference, all between 23 MPa-25 MPa, from Comparative Example 1 and Comparative Example 2, it can be seen that the addition of Fe-BDC MOF particles can enhance the interaction between PAN and Fe-BDC, thereby moderately enhancing the tensile strength of the solid electrolyte film, this increase in mechanical strength is conducive to inhibiting the growth of lithium dendrites in the solid electrolyte film, thereby improving the use safety of lithium ion batteries.

[0050] Application Example 1: The application example 1 provides a preparation method of a group of solid-state batteries, comprising the following steps: Y1, lithium iron phosphate active material, conductive carbon black (Super P), polyvinylidene fluoride (PVDF) are added to N-methyl pyrrolidone (NMP) in a mass ratio of 8:1:1 to stir and mix to prepare an active slurry, the active slurry is coated on the surface of an aluminum-plated carbon foil, then dried at 60°C, and then cut into positive electrode sheets with a diameter of 12 mm; Y2, using metal lithium as the negative electrode sheet, the positive electrode sheet in step Y1, and the solid electrolyte films prepared in Example 1, Comparative Example 1 to Comparative Example 2, are assembled into 2032 type button solid-state batteries (LFP / FAEIS / Li, LFP / FAES / Li, LFP / AES / Li) in a glove box.

[0051] The three solid-state batteries prepared in Application Example 1 were subjected to electrochemical tests in the voltage range of 2.5V-4.0V using a new Wei electrochemical test system, and the discharge specific capacity of the solid-state batteries at 0.2C, 0.5C, 1C, 2C charge-discharge rate was measured as shown in Figure 11 From Figure 11As can be seen, the discharge specific capacity of the LFP / FAEIS / Li solid-state battery corresponding to Example 1 at various rates is 170.6 mAh / g, 155.4 mAh / g, 135.9 mAh / g, and 113.7 mAh / g, respectively. When the cycle is completed and returned to 0.2C, it recovers to 167.9 mAh / g. This indicates that the solid-state battery corresponding to Example 1 has excellent capacity retention and cycle reversibility. In contrast, the discharge specific capacity of the LFP / FAEIS / Li solid-state battery corresponding to Comparative Example 1 at various rates is 170.3 mAh / g, 145.9 mAh / g, and 126.9 mAh / g, respectively. The discharge specific capacity of Comparative Example 1 was 99.3 mAh / g, but recovered to 167.9 mAh / g when the cycle was completed and returned to 0.2C. This indicates that the solid-state battery corresponding to Comparative Example 1 exhibits comparable performance to Example 1 at low rates, but poorer performance at high rates. The discharge specific capacity of the LFP / AES / Li solid-state battery corresponding to Comparative Example 2 was 155.7 mAh / g, 139.7 mAh / g, 121.5 mAh / g, and 95.6 mAh / g at various rates, and recovered to 167.9 mAh / g when returning to 0.2C. Although it maintained cycle reversibility, its capacity was significantly inferior to that of Example 1 and Comparative Example 1. This shows that the LFP / FAEIS / Li solid-state battery corresponding to Example 1 has the lowest polarization at all rates, indicating that the FAEIS solid electrolyte membrane has the least hindrance to lithium-ion migration.

[0052] The two solid-state batteries (LFP / FAEIS / Li and LFP / FAES / Li) prepared in Example 1 were subjected to charge-discharge cycle tests at a 2C charge-discharge rate, at room temperature of 25°C and at high temperature of 60°C, respectively, as shown below. Figure 12 As shown in A and B in the diagram. From... Figure 12 As can be seen from A in Example 1, the LFP / FAEIS / Li solid-state battery maintained stable cycling for more than 1200 cycles at room temperature, with an initial discharge capacity of 111.7 mAh / g and a final capacity of 94.5 mAh / g, and a capacity retention rate of 85.6%. In contrast, the LFP / FAEIS / Li solid-state battery in Comparative Example 1 exhibited rapid capacity decay and significant polarization during cycling, maintaining capacity for only 400 cycles before its discharge capacity decreased from the initial 110.0 mAh / g to 61.9 mAh / g, with a capacity retention rate of only 56.2%.

[0053] from Figure 12As can be seen from C in the table, the initial discharge capacity of the LFP / FAEIS / Li solid-state battery corresponding to Example 1 is 120.8 mAh / g, and the discharge capacity attenuates to 98.6 mAh / g after 800 cycles, with a capacity retention rate of 81.6%. The initial discharge capacity of the LFP / FAES / Li battery corresponding to Comparative Example 1 is 107.9 mAh / g, and the discharge capacity attenuates to 62.5 mAh / g after 800 cycles, with a capacity retention rate of only 57.9%.

[0054] The two solid-state batteries (LFP / FAEIS / Li, LFP / FAES / Li) prepared in Example 1 were subjected to charge-discharge cycle tests at a high temperature of 60°C and a 10C charge-discharge rate, as shown in C in the table. Figure 12 Figure 12 As can be seen from C in the table, the initial discharge capacity of the LFP / FAEIS / Li battery corresponding to Example 1 is 120.8 mAh / g, and the discharge capacity attenuates to 98.6 mAh / g after 800 cycles, with a capacity retention rate of 81.6%. The initial discharge capacity of the LFP / FAES / Li battery corresponding to Comparative Example 1 is 107.9 mAh / g, and the discharge capacity attenuates to 62.5 mAh / g after 800 cycles, with a capacity retention rate of only 57.9%. Figure 12 As can be seen from C in the table, the initial discharge capacity of the LFP / FAEIS / Li battery corresponding to Example 1 is 120.8 mAh / g, and the discharge capacity attenuates to 98.6 mAh / g after 800 cycles, with a capacity retention rate of 81.6%. The initial discharge capacity of the LFP / FAES / Li battery corresponding to Comparative Example 1 is 107.9 mAh / g, and the discharge capacity attenuates to 62.5 mAh / g after 800 cycles, with a capacity retention rate of only 57.9%.

[0055] Application Example 2: The application example 2 provides a preparation method of a group of solid-state batteries, which comprises the following steps: Y1, NCM811, conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) are added to N-methyl pyrrolidone (NMP) in a mass ratio of 8:1:1 to prepare an active slurry, and the active slurry is coated on the surface of an aluminum-plated carbon foil, dried at 60°C, and then cut into an anode sheet with a diameter of 12 mm; Y2, using metal lithium as a negative electrode sheet, the anode sheet in step Y1, and the solid-state electrolyte films prepared in Example 1 and Comparative Examples 1 to 1, respectively, are assembled into 2032 type button solid-state batteries (NCM811 / FAEIS / Li, NCM811 / FAES / Li) in a glove box.

[0056] The two solid-state batteries (LFP / FAEIS / Li, LFP / FAES / Li) prepared in Example 1 were subjected to high-voltage electrochemical cycle tests at 1C rate for 100 cycles at 4.4V, and the test results are shown in A and B in the table, respectively. Figure 13 Figure 13 ​​As can be seen, both solid electrolyte membranes can meet the high-voltage electrochemical cycling standard, and the solid-state battery corresponding to the FAEIS prepared in Example 1 exhibits more superior charge-discharge performance, is more stable in cycling, has better capacity, and has lower polarization.

[0057] While the embodiments of the application have been illustrated and described in detail, it will be apparent to those skilled in the art that various modifications and changes can be made therein without departing from the scope and spirit of the application as defined in the claims. Moreover, the application described herein can have other embodiments and be practiced or carried out in various ways.

Claims

1. A method for preparing a solid electrolyte membrane, characterized in that, include: Fe-based MOF particles were mixed with fiber-forming polymers and electrospun to obtain a rigid skeleton; an ionic liquid electrolyte was permeated into the rigid skeleton to obtain a base membrane; a polyether polymer was mixed with a cyanide-containing plasticizer and permeated into the base membrane to obtain a solid electrolyte membrane.

2. The preparation method according to claim 1, characterized in that, The Fe-based MOF particles are formed by coordination of iron ions with aromatic dicarboxylic acids; the sources of the iron ions include one of ferric chloride, ferric nitrate, and ferric trifluoromethanesulfonate, and the aromatic dicarboxylic acids include one of terephthalic acid, 2,6-naphthalenedicarboxylic acid, and 4,4'-biphenyl dicarboxylic acid.

3. The preparation method according to claim 1, characterized in that, The cyanide-containing plasticizer includes one of succinic anhydride, glutaronitrile, and adiponitrile; and / or, the polyether polymer includes one of polyethylene oxide and polypropylene oxide; and / or, the fiber-forming polymer includes one of polyacrylonitrile, polyvinylidene fluoride, and polyimide.

4. The preparation method according to claim 1, characterized in that, The ionic liquid electrolyte comprises an ionic liquid and a first lithium salt dissolved in the ionic liquid; the ionic liquid comprises one of 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, and N-methyl-N-propylpyrrolidine bis(trifluoromethanesulfonyl)imide salt, and the first lithium salt comprises one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, and lithium hexafluorophosphate.

5. The preparation method according to claim 1, characterized in that, Fe-based MOF particles are mixed with fiber-forming polymers at a mass ratio of 1:(0.5-2); and / or, Fe-based MOF particles are mixed and dissolved with fiber-forming polymers to obtain a mixed suspension; and / or, after electrospinning, the suspension is dried to obtain a rigid skeleton; and / or, electrospinning is performed at 8kV-12kV.

6. The preparation method according to claim 1, characterized in that, The ratio of ionic liquid electrolyte to rigid framework in the basement membrane is 0.5 mL / g to 2 mL / g; And / or, the ionic liquid electrolyte is coated onto the surface of a rigid framework for permeation; and / or, the method for preparing the ionic liquid electrolyte includes: stirring and dissolving a first lithium salt in an ionic liquid and then drying it, wherein the molar ratio of lithium element in the first lithium salt to the ionic liquid is 1:(3-8).

7. The preparation method according to claim 1, characterized in that, A composite solution is prepared by dissolving a second lithium salt, a polyether polymer, and a cyanide-containing plasticizer. The composite solution is then permeated into a base membrane to obtain a solid electrolyte membrane. The mass content of the cyanide-containing plasticizer in the composite solution is 20%-40%. The molar ratio of the polyether polymer to the second lithium salt is (15-20):

1. The second lithium salt includes one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, and lithium hexafluorophosphate.

8. A solid electrolyte membrane prepared by the preparation method according to any one of claims 1 to 7, characterized in that, It includes a rigid framework embedded with Fe-based MOF particles and an ionic liquid electrolyte permeated with the rigid framework, as well as a polyether polymer filling the rigid framework and a cyanide-containing plasticizer, wherein the cyanide groups in the cyanide-containing plasticizer are bonded to the iron ions in the Fe-based MOF particles through coordination bonds.

9. A solid-state battery, characterized in that, Includes solid electrolyte membranes prepared by the preparation method according to any one of claims 1 to 7.

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