A solid-state electrolyte based on a viscoelastic MOF material, and a method of making the same and a metal battery

Abstract

The present application relates to the field of electrochemistry and secondary battery technology, and particularly relates to a solid-state electrolyte based on a viscoelastic MOF material and a preparation method thereof and a metal battery. The present application obtains MOF powder based on a hydrothermal / solvothermal synthesis method, and realizes controllable reduction of the melting point of the MOF material by regulating and controlling the grafting of flexible side chain functional groups of the MOF material, and synthesizes a room-temperature flowable viscoelastic MOF system. In the absence of any additional organic solvent, the viscoelastic MOF material is used to dissolve lithium salt, and a solid-state electrolyte based on a viscoelastic glassy metal organic framework material is prepared. The secondary battery prepared based on the above electrolyte has excellent ion conductivity, thermal stability, chemical stability, an electrochemical window of the electrolyte, and interface compatibility with battery materials, battery safety and other advantages.

Description

Technical Field

[0001] This invention relates to the fields of electrochemistry and secondary battery technology, and particularly to a solid electrolyte based on viscoelastic MOF materials, its preparation method, and a metal battery. Background Technology

[0002] With the development of electric vehicles, wearable devices, and large-scale energy storage systems, the demand for batteries with high energy density, high safety, and long lifespan is increasing. Solid-state electrolytes, as one of the core components of batteries, can significantly improve battery safety and energy density. However, currently commonly used solid-state electrolytes include sulfides, halides, and oxides. Solid-state electrolytes still have many shortcomings in terms of lithium-ion conductivity, mechanical strength, structural stability, and interface compatibility. For example, traditional solid-state electrolytes are usually crystalline structures. The presence of grain boundaries in solid-state electrolyte particles greatly restricts lithium-ion migration, increases electrolyte resistance, and results in poor ionic conductivity (especially at low temperatures). Secondly, traditional solid-state electrolyte materials are unstable in air and are prone to hydrolysis or oxidation, making the preparation process relatively complex. Furthermore, conventional solid-state electrolytes are often brittle and prone to cracking or mechanical damage, further affecting the ionic conductivity and their application in practical batteries. These shortcomings of conventional solid-state electrolytes greatly limit the development of all-solid-state batteries.

[0003] Metal-organic frameworks (MOFs), as porous materials, possess tunable nano / sub-nano pore structures, high specific surface area, flexible structural design, easy processing, excellent ion conductivity, electrochemical stability, and interfacial compatibility. In recent years, they have been increasingly used by researchers as metal salt and electrolyte solvent carriers to develop novel quasi-solid-state electrolytes, exhibiting remarkable physicochemical properties.

[0004] However, due to inherent defects in the material and the film-forming process, this system exhibits numerous grain boundaries and poor solid-solid contact, resulting in low conductivity and poor interfacial compatibility. Specifically, powdered crystalline MOF particles prepared using conventional methods are prone to collapse or loss of their ordered structure under high-temperature treatment or other conditions, easily leading to pore blockage or discontinuous ion transport pathways, thus affecting ion transport within the pores. Secondly, powdered MOF particles prepared using conventional methods contain inherent defects, and the interfacial discontinuities in the MOF structure may result in high interfacial impedance. Furthermore, polymer binders are used in the preparation of novel solid-state electrolytes based on powdered crystalline MOF materials, inevitably creating gaps / pores between particles, further reducing the electrolyte's ionic conductivity. Finally, powdered crystalline MOF materials are highly rigid and prone to cracking or failure under mechanical stress. This brittleness limits their application in practical batteries, especially in applications requiring high mechanical strength and flexibility. More importantly, the liquid electrolyte filling the pores of powdered MOF materials poses potential safety hazards such as leakage, combustion, and volatilization.

[0005] Therefore, there is a need to develop a high-performance MOF-based solid electrolyte that is free of cracks / pores / defects, free of organic solvents, has high interfacial continuity, high ionic conductivity, excellent mechanical strength, and interfacial compatibility. Summary of the Invention

[0006] This invention provides a solid electrolyte based on viscoelastic MOF materials, its preparation method, and a metal battery, aiming to solve the problems of existing MOF materials such as high rigidity, easy collapse and pore blockage, and high interfacial impedance.

[0007] To achieve the above objectives, this invention provides a method for preparing a solid electrolyte based on a viscoelastic MOF material, comprising the following steps: S1. Grafting oligoethylene oxide chains onto MOF powder containing hydroxyl-modified groups in a solution, followed by magnetic stirring to obtain viscoelastic MOF material; the degree of polymerization of the oligoethylene oxide chains is 100,000-600,000, and the mass ratio of the oligoethylene oxide chains to the MOFs material is 1:25 to 1:1000. More preferably, the mass ratio of the oligoethylene oxide chain to the MOF material is 1:200; S2. The viscoelastic MOF material is vacuum dried in an inert atmosphere and then cooled to obtain the dried viscoelastic MOF material. S3. Mix the metal salt directly with the dried viscoelastic MOF material described in S2, and heat and stir at 30~80 ℃ for 2~24 h, then let it stand for 10~48 h to obtain a solid electrolyte based on the viscoelastic MOF material.

[0008] The preparation and application mechanism of the solid electrolyte based on viscoelastic MOF materials of the present invention is as follows: This invention obtains MOF powder based on hydrothermal / solvothermal / sol-gel synthesis method, and achieves controllable reduction of the melting point of MOF material by regulating the flexible side chain functional groups of organic ligands of MOF material (containing hydroxyl-modified groups) (grafted oligoethylene oxide chains), thus synthesizing a viscoelastic MOF system that can flow at room temperature.

[0009] This application describes a method for preparing a solid electrolyte based on viscoelastic MOFs by directly dissolving lithium salts using viscoelastic MOFs materials without adding any additional liquid electrolyte or organic solvents. The viscoelastic MOFs, which are flowable at room temperature and intrinsically non-flammable, serve as a confined matrix, retaining the ordered pore structure of MOFs while also possessing the flexibility of polymers and the flow and wettability of liquids, thus opening up a completely new material form for solid electrolytes.

[0010] Preferably, the MOF powder in step S1 includes any one of zinc-based MOFs, copper-based MOFs, iron-based MOFs, or aluminum-based MOFs.

[0011] Preferably, the method for preparing the MOF powder includes the following steps: A metal salt is dissolved in solvent A to form solution A; an organic ligand is dissolved in solvent B to form solution B; the organic ligand contains at least one of a hydroxyl group, a carboxyl group, or an ester group; solutions A and B are mixed, washed, and dried to obtain MOF powder.

[0012] Preferably, solvent A comprises at least one selected from methanol, ethanol, acetone, water, phosphoric acid, dimethylformamide, or N-methylpyrrolidone, and the concentration of solvent A is 0.01~5 mol / L; solvent B comprises at least one selected from methanol, ethanol, acetone, water, phosphoric acid, dimethylformamide, or N-methylpyrrolidone, and the concentration of solvent B is 0.01~5 mol / L; the organic ligand comprises benzene-1,3,5-tricarboxylic acid (BTC), benzene-1,4-dicarboxylic acid (BDC), 2,3-pyrazine dicarboxylate (PZDC), pyrazine (PYZ), 1,4-naphthalene dicarboxylate (NDC), D-camphoric acid (D-CAM), 4,4′-(hexafluoroisopropylidene)bis(benzoic acid), 9,10-anthracite dicarboxylate, 5-tert-butylisophthalic acid (TBIP), tetracarboxylic acid (BPTC), 4-carbohydrate, etc. One or more of the following: xycinnamicacid (CNC), 1,12-dihydroxydicarbonyl-1,12-dicarbazo-closed-dodecorane ligand (p-cdc), 1,3,5-benzenetribenzoate (btb), naphthalene dicarboxylate (ndc), ZIF-7, ZIF-8, ZIF-22, 2,4-pyridinedicarboxylic acid (2,4-pdc), or 1,4,5,8-naphthalenetetracarboxylic acid (ntc) with cobalt as the metal central ion, at a concentration of 0.01 M to 10 M; and at a mass ratio to the metal salt of 0.01:1 to 50:1.

[0013] Preferably, step S1, grafting oligoethylene oxide chains onto MOF powder containing hydroxyl-modified groups in solution, specifically includes: dissolving hydroxyl-modified MOF powder in solution and heating and stirring at 30~120°C, wherein the grafting occurs between the hydroxyl-modified groups and the oligoethylene oxide chains.

[0014] Preferably, the vacuum drying temperature in step S2 is 80~200 ℃, the vacuum degree is 0.2~600 MPa, the drying time is 20-90 min, and the cooling rate is 10-50 ℃ / min.

[0015] Preferably, the metal salt in step S3 is at least one of LiPF6, LiTFSI, LiFSI, LiDFOB, LiBOB, LiBF4, LiNO3, LiAsF6, LiClO4, KFSI, KTFSI, KClO4, NaTFSI, NaFSI, and NaClO4, and the heating and stirring takes place in a glove box with a vacuum degree of 10 Pa.

[0016] Under the same technical concept, the present invention also provides a solid electrolyte based on viscoelastic MOF material prepared by the preparation method described above, wherein the pore size of the solid electrolyte is 0.1~6 nm.

[0017] The viscoelastic MOFs of this application, which are flowable at room temperature and intrinsically non-flammable, serve as a confined matrix (for dissolving metal salts). They retain the ordered pore structure of MOFs while also possessing the flexibility of polymers and the flow and wettability of liquids, thus opening up a completely new material form for solid electrolytes.

[0018] The solid electrolyte based on viscoelastic MOFs in this application directly uses viscoelastic MOFs as the substrate material to dissolve metal salts without adding any liquid electrolyte or organic solvent, thus completely replacing organic solvents and constructing a novel all-solid electrolyte.

[0019] The solid electrolyte based on viscoelastic MOFs material in this application eliminates grain boundaries at the source, reconstructs the discontinuous solid-solid interface into a highly wettable solid-liquid interface, builds a smooth ion network, reduces interfacial impedance, improves the ionic conductivity of the solid electrolyte, and enhances battery safety.

[0020] The solid electrolyte based on viscoelastic MOFs material proposed in this application completely eliminates the safety hazards such as leakage, combustion, and volatilization caused by liquid components, greatly improving the safety of the battery, while avoiding side reactions between the solvent and electrode materials.

[0021] The solid electrolyte based on viscoelastic MOF materials in this application has high ionic conductivity (1.22 x 10⁻⁶). -4 With a high efficiency (S / cm) and a wide electrochemical stability window (above 5.2 V), excellent thermal and chemical stability, good interfacial compatibility with battery materials, and battery safety (non-flammable electrolyte), the novel all-solid-state battery is conducive to achieving high-performance metal batteries. The assembled battery exhibits excellent electrochemical performance.

[0022] Under the same technical concept, the present invention also provides a metal battery, the metal battery comprising a solid electrolyte based on viscoelastic MOF material prepared by the preparation method described above or the solid electrolyte based on viscoelastic MOF material described above; the metal battery comprises metal positive and negative electrodes or graphite electrodes and a metal negative electrode.

[0023] Preferably, the metal battery is a potassium metal battery; the positive electrode material of the potassium metal battery includes at least one of the following: alkali metal, carbon material, LNMO, nickel-cobalt-manganese ternary materials NCM811, NCM622, NCM532, NCM333, nickel-cobalt-aluminum ternary materials NCA, Li2MnO4, LiCoMnO4, lithium-rich manganese-based crystalline oxide, LiCoO2, LiNiO2, LiFePO4, S, or Li2O2 / LiO2; the alkali metal is at least one of lithium metal, sodium metal, potassium metal, magnesium metal, or zinc metal; the carbon material is at least one of graphite, soft carbon, hard carbon, or silicon carbide.

[0024] The above-described solution of the present invention has the following beneficial effects: (1) This invention pioneers a new viscoelastic MOF material morphology that is flowable at room temperature. By controlling the flexible side chains (oligoethylene oxide chains) of the organic ligands, the melting point of MOFs can be controlled to reduce, thus obtaining a viscoelastic MOF system that is flowable at room temperature for the first time. This material retains the ordered pore structure of MOFs while possessing both the flexibility of polymers and the flow and wettability of liquids, opening up a completely new material morphology for solid electrolytes. When the degree of polymerization of the oligoethylene oxide chains is between 100,000 and 600,000, and the mass ratio of oligoethylene oxide chains to MOF materials is 1:25 to 1:1000, the viscoelastic MOF materials maintain the integrity of the framework structure with their rigid core, while the flexible side chains exhibit significant conformational dynamic behavior (such as oscillation). This dynamic characteristic makes the material liquid at room temperature and promotes lithium-ion transport through the oscillation mechanism of the side chains, thus eliminating the need to introduce additional liquid solvents.

[0025] (2) Achieving an all-solid-state electrolyte without liquid components significantly improves safety. Without adding any liquid electrolyte or organic solvent, metal salts are directly dissolved using viscoelastic MOFs to construct a true all-solid-state electrolyte, completely eliminating safety hazards such as leakage, combustion, and volatilization. At the same time, the electrolyte is intrinsically non-flammable and has excellent thermal and chemical stability, avoiding side reactions between solvents and electrode materials.

[0026] (3) Reconstruct the interface contact to eliminate grain boundaries and reduce interface impedance from the source. By utilizing the high wettability of viscoelastic MOFs, the discontinuous solid-solid interface in the traditional solid electrolyte is reconstructed into a highly wettable solid-liquid interface, eliminating grain boundaries from the source, constructing a smooth ion transport network, and effectively reducing the electrode / electrolyte interface impedance.

[0027] (4) Excellent electrochemical performance and wide applicability to battery systems. This solid electrolyte has high ionic conductivity (1.22 × 10⁻⁶). -4 With a high S / cm ratio and a wide electrochemical stability window (above 5.2 V), it can meet the requirements of high-voltage batteries and is suitable for various metal secondary battery systems such as lithium-ion and potassium-ion batteries, which is conducive to realizing high-performance and high-safety metal batteries.

[0028] In summary, to overcome the shortcomings of existing solid-state electrolyte preparation technologies based on powdered crystalline MOF materials, this invention provides a method for preparing a solid-state electrolyte based on viscoelastic MOF materials. By controlling the flexible side-chain functional groups of the organic ligands in the MOF materials (containing hydroxyl-modified groups) (grafted oligoethylene oxide chains), the melting point of the MOF materials can be controlled to decrease, synthesizing a room-temperature flowable viscoelastic MOF system. Without adding any additional liquid electrolyte or organic solvent, lithium salts are directly dissolved using viscoelastic MOF materials to obtain a solid-state electrolyte based on viscoelastic MOF materials with high ionic conductivity, a wide electrochemical stability window, excellent thermal stability, chemical stability, interfacial compatibility, and high safety, ultimately significantly improving the electrochemical performance of all-solid-state metal batteries. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 These are digital photographs of three viscoelastic MOFs materials prepared in Example 1 of this invention; wherein, a is a digital photograph (25) of viscoelastic MOF material-1 (the degree of polymerization of the oligoethylene oxide chain is 100,000, and the mass ratio of the oligoethylene oxide chain to the MOFs material is 1:200). o C represents a flowable viscoelastic material; b represents a digital photograph (65) of viscoelastic MOF material-2 (the degree of polymerization of the oligoethylene oxide chain is 300,000, and the mass ratio of the oligoethylene oxide chain to the MOF material is 1:200). o Below C is a flowable viscoelastic material; c is a digital photograph (120) of viscoelastic MOF material-3 (the degree of polymerization of the oligoethylene oxide chain is 600,000, and the mass ratio of the oligoethylene oxide chain to the MOF material is 1:200). o (C represents a flowable viscoelastic material). Figure 2 These are digital photographs of three viscoelastic MOFs-based solid electrolytes prepared by mixing the three viscoelastic MOFs materials prepared in Example 1 of this invention with potassium salt; wherein, a is a digital photograph of viscoelastic MOF-based solid electrolyte-1; b is a digital photograph of viscoelastic MOF-based solid electrolyte-2; and c is a digital photograph of viscoelastic MOF-based solid electrolyte-3. Figure 3Impedance spectroscopy and linear voltammetry (LSV) of the viscoelastic MOF-based solid electrolyte-1 prepared in Example 1 of this invention are shown; where a is the impedance spectrum at room temperature; and b is the linear voltammetry test result. Figure 4 Impedance spectroscopy and linear voltammetry (LSV) of the viscoelastic MOF-based solid electrolyte-2 prepared in Example 1 of this invention are shown; where a is the impedance spectrum at room temperature; and b is the linear voltammetry test result. Figure 5 Impedance spectroscopy and linear voltammetry (LSV) of the viscoelastic MOF-based solid electrolyte-3 prepared in Example 1 of this invention are shown; where a is the impedance spectrum at room temperature; and b is the linear voltammetry test result. Figure 6 The impedance spectrum and linear voltammetry (LSV) of the MOFs-based solid electrolyte prepared in Comparative Example 1 of this invention are shown; where a is the impedance spectrum at room temperature; and b is the linear voltammetry test result. Figure 7 Ignition experiments were conducted on the three viscoelastic MOF-based solid electrolytes prepared in Example 1 of this invention. Figure 8 The electrochemical performance of an all-solid-state potassium symmetric battery prepared using three viscoelastic MOF-based solid electrolytes obtained in Example 1 of this invention is shown in the figure; the test conditions are 0.2 mA / cm². 2 0.2 mAh / cm 2 b is 0.4 mA / cm 2 0.4mAh / cm 2 Under the test conditions; the comparative data is the electrochemical cycle diagram of a potassium symmetric battery based on liquid electrolyte.

[0031] Figure 9 The image shows the electrochemical performance of an all-solid-state potassium symmetric battery prepared with the MOF-based solid electrolyte obtained in Comparative Example 1 of this invention; the test conditions are 0.2 mA / cm². 2 0.2 mAh / cm 2 .

[0032] Figure 10 The diagram shows the electrochemical cycling of the potassium / / copper half-cell and potassium / / graphite battery assembled based on viscoelastic MOFs-based solid electrolytes prepared in Example 1 of this invention; where a represents the potassium / / copper half-cell at 0.2 mA / cm². 2 -0.5 mAh / cm 2 b is the coulombic efficiency under the test conditions; b is the cycle life diagram of the potassium / / graphite half-cell at a current of 200 mA / g; the comparative data are the corresponding electrochemical cycle diagrams of the two batteries based on liquid electrolyte. Detailed Implementation

[0033] To make the technical problems, solutions, and advantages of this invention clearer, a detailed description will be provided below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0034] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0035] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a locking connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0036] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0037] Example 1 (1) Preparation of MOF powder containing modified groups: 560 mg ZrCl4, 300 mg phenyl-1,4-dicarboxylic acid, and 100 mg acetic acid were dissolved in DMF under ultrasonic conditions. The solution was then added to a 100 mL polytetrafluoroethylene-lined reactor and reacted at 120 °C for 24 h. The reactants were then centrifuged (8000 rpm, 15 min) to obtain a solid product. The product was then washed three times with DMF and acetone, respectively. Finally, the solid product was dried in a vacuum oven (60 °C, 12 h) to obtain a UiO-66-OH powder sample (hydroxyl-modified group). The preliminarily dried UiO-66-OH MOF powder was then placed in a vacuum drying oven at 80 °C (vacuum degree 120 Pa) for 12 h for the first activation to remove solvent and moisture introduced during the synthesis process.

[0038] (2) Three oligoethylene oxide chains with different degrees of polymerization (degrees of polymerization of 100,000, 300,000, and 600,000 respectively, with a mass ratio of each oligoethylene oxide chain to MOF material of 1:200; the oligoethylene oxide chains were purchased from Sigma-Aldrich, trade name: polyethylene oxide) were grafted onto the obtained dehydrated sample. Specifically, 100 mg of oligoethylene oxide chain was mixed with 20 g of UiO-66-OH MOF powder and heated (60 °C) and stirred for 12 h using a magnetic stirrer to obtain a viscoelastic MOF material that is flowable at room temperature. The viscoelastic MOF material was then vacuum dried in an inert atmosphere and cooled to obtain solvent-free viscoelastic MOF materials (labeled as viscoelastic MOF-1, viscoelastic MOF-2, and viscoelastic MOF-3, respectively); wherein the vacuum drying temperature was 80 °C and the time was 60 min.

[0039] (3) Potassium salt KFSI was directly mixed with the three viscoelastic MOF materials and placed in a glove box. It was heated and stirred at 60 °C for 6 h and then allowed to stand for 12 h to obtain a new solid electrolyte based on viscoelastic MOF materials (labeled as viscoelastic MOF-based solid electrolyte-1, viscoelastic MOF-based solid electrolyte-2, and viscoelastic MOF-based solid electrolyte-3, respectively).

[0040] Comparative Example 1 (1) 560 mg ZrCl4, 300 mg phenyl-1,4-dicarboxylic acid, and 100 mg acetic acid were dissolved in DMF under ultrasonic conditions. The solution was then added to a 100 mL polytetrafluoroethylene-lined reactor and reacted at 120 °C for 24 hours. The reactants were then centrifuged (8000 rpm, 15 min) to obtain a solid product. The product was then washed three times with DMF and acetone. Finally, the solid product was dried in a vacuum oven (60 °C, 12 h) to obtain a UiO-66-OH powder sample (hydroxyl-modified group). The preliminarily dried UiO-66-OH MOF powder was then placed in a vacuum drying oven (120 Pa) at 80 °C for 12 hours for the first activation to remove the solvent and moisture introduced during the synthesis process.

[0041] (2) Mix 90 wt.% dehydrated UiO-66-OH MOF powder with an aqueous solution containing 10 wt% polytetrafluoroethylene (PTFE) until homogeneous. During the mixing process, add a small amount of ethanol to the mixed solution and stir at room temperature to obtain a gel-like substance. Spread the gel-like substance on a glass plate and roll it out multiple times with a glass rod to obtain a flexible and bendable self-supporting film. Dry the obtained flexible and bendable MOF self-supporting film at room temperature, then remove it from the glass plate and dry it in a forced-air drying oven at a drying temperature of 40-80℃ for 4-24 hours. Activate the dried flexible and bendable self-supporting film under vacuum at 60-180℃ for 8-72 hours. Then cut the obtained MOF film into small pieces (16 mm in diameter) and vacuum at 180℃ for 72 hours, and then transfer it to a glove box for further use.

[0042] (4) Immerse the obtained MOF self-supporting membrane in KFSI-DME electrolyte and heat it in a glove box at 30-120℃ for 1-24 hours, then let it stand in the glove box for 10-48 hours; take out the self-supporting membrane, absorb the surface liquid, physically press and squeeze out the liquid electrolyte in the self-supporting membrane, and reduce the gaps between particles; then vacuum dry at 30-120℃ for 12-48 hours to obtain MOF-based solid electrolyte.

[0043] Performance testing and results analysis: The three viscoelastic MOF materials (viscoelastic MOF-1, viscoelastic MOF-2, and viscoelastic MOF-3) prepared in Example 1 were photographed electronically, and the results are as follows: Figure 1 As shown. By Figure 1 As can be seen from this, the viscoelastic MOF-1 prepared in Example 1 of this application is at 25 o At room temperature, MOF-2 is in a flowable state and exhibits some viscoelasticity; the viscoelastic MOF-2 is at 65°C. oAt room temperature, MOF-3 is in a flowable state and exhibits some viscoelasticity; the viscoelastic MOF-3 is at 120°C. o At room temperature, it is in a flowable dynamic state and has a certain degree of viscoelasticity.

[0044] Electron imaging was performed on the three viscoelastic MOF-based solid electrolytes prepared in Example 1, and the results are as follows: Figure 2 As shown. By Figure 2 It can be seen that the viscoelastic MOF material prepared in Example 1 of this application still maintains its room temperature fluidity and viscoelasticity even after being heated and mixed with potassium salt to form a viscoelastic MOF-based solid electrolyte, and there is no obvious undissolved potassium salt present, indicating that the viscoelastic MOF material can completely dissolve potassium salt.

[0045] The viscoelastic MOF-based solid electrolyte prepared in Example 1 was combined with potassium metal / / potassium metal, potassium metal, and stainless steel sheets to assemble batteries. The potassium-ion conductivity and electrochemical stability window of the solid-state electrolysis based on viscoelastic MOF materials were tested. Specifically, R2032 button cells were used, and the batteries were packaged in the following order: negative electrode shell, spring sheet, gasket, potassium metal, solid electrolyte, stainless steel / potassium metal sheet, and positive electrode shell. After the packaged batteries were left to stand for 16 hours, impedance spectroscopy and linear voltammetry (LSV) tests were performed on the solid electrolyte using an electrochemical workstation, and the potassium-ion conductivity and electrochemical stability window of the solid electrolyte were calculated. The results are as follows: Figures 3-5 As shown. By Figure 3 As can be seen from the impedance spectrum of the viscoelastic MOF-1-based solid electrolyte prepared in Example 1 of this application at room temperature, the calculated potassium ion conductivity of the viscoelastic MOF-1-based solid electrolyte is 1.22 × 10⁻⁶. -4 S / cm; by Figure 3 As can be seen from b, the electrochemical stability window of the viscoelastic MOF-1-based solid electrolyte prepared in Example 1 of this application exceeds 5.2 V. From Figure 4 As can be seen from the impedance spectrum of the viscoelastic MOF-2-based solid electrolyte prepared in Example 1 of this application at room temperature, the calculated potassium ion conductivity of the viscoelastic MOF-2-based solid electrolyte is 1.04 × 10⁻⁶. -4 S / cm; by Figure 4 As can be seen from b, the viscoelastic MOF-2-based solid electrolyte prepared in Example 1 of this application has an electrochemical stability window exceeding 5.0 V. From Figure 5 As can be seen from the impedance spectrum of the viscoelastic MOF-3-based solid electrolyte prepared in Example 1 of this application at room temperature, the calculated potassium ion conductivity of the viscoelastic MOF-3-based solid electrolyte is 0.98 × 10⁻⁶. -4 S / cm; by Figure 5As can be seen from b, the electrochemical stability window of the viscoelastic MOF-1-based solid electrolyte prepared in Example 1 of this application exceeds 4.6 V.

[0046] In summary, this demonstrates that the solid electrolyte based on viscoelastic MOF material prepared in Example 1 of this application has an electrochemical stability window exceeding 5.5 V, verifying the high ionic conductivity and wide electrochemical stability window of the solid electrolyte based on viscoelastic MOF material obtained in this application, laying the foundation for subsequent assembly of high-performance potassium metal batteries.

[0047] Comparative Example 1 uses conventional MOF powder, which is uniformly mixed with PVDF binder to prepare MOF membrane; an appropriate amount of liquid electrolyte is filled into the obtained MOF membrane to obtain MOF-based solid electrolyte (quasi-solid).

[0048] The MOF-based solid electrolyte prepared in Comparative Example 1 was combined with potassium metal / / potassium metal, potassium metal, and stainless steel sheets to assemble batteries. The potassium-ion conductivity and electrochemical stability window of the MOF-based solid-state electrolysis were then tested. Specifically, R2032 coin cells were used, and the batteries were packaged in the following order: negative electrode shell, spring sheet, gasket, potassium metal, solid electrolyte, stainless steel / potassium metal sheet, and positive electrode shell. After the packaged batteries were left to stand for 16 hours, impedance spectroscopy and linear voltammetry (LSV) tests were performed on the solid electrolyte using an electrochemical workstation, and the potassium-ion conductivity and electrochemical stability window of the solid electrolyte were calculated. The results are shown below. Figure 6 As shown. By Figure 6 As can be seen from the impedance spectrum of the MOF-based solid electrolyte prepared in Comparative Example 1 of this application at room temperature, the calculated potassium ion conductivity of the MOF-based solid electrolyte is 0.89 × 10⁻⁶. -4 S / cm; by Figure 6 As can be seen from b, the electrochemical stability window of the viscoelastic MOF-1-based solid electrolyte prepared in Example 1 of this application exceeds 4.5 V.

[0049] The three viscoelastic MOF-based solid electrolytes prepared in Example 1 were loaded onto a membrane and ignition experiments were conducted. The results are as follows: Figure 7 As shown. By Figure 7 It can be seen that the membrane adsorbed with liquid electrolyte (1M KFSI-DME) burns rapidly under open flame, while the membrane loaded with solid electrolyte based on three viscoelastic MOFs is non-flammable under open flame, demonstrating excellent safety.

[0050] The three viscoelastic MOF-based solid electrolytes prepared in Example 1 were assembled with potassium metal to form an all-solid-state potassium||potassium symmetric battery, and the cycle life of the battery was tested. Specifically, using R2032 button cells, the battery was packaged in the following order: negative electrode shell, spring sheet, gasket, potassium metal, the three viscoelastic MOF-based solid electrolytes, potassium metal, and positive electrode shell. The packaged batteries were left to stand for 16 hours, and electrochemical tests were performed on the assembled batteries using the Blue Battery Testing System. A potassium||potassium symmetric battery based on a liquid electrolyte (1M KFSI-DME) was also assembled and tested as a comparison. The results are as follows: Figure 8 As shown. By Figure 8 It is known that potassium-potassium symmetric batteries based on conventional liquid electrolytes can only achieve stable cycling for about 780 hours under the same test conditions, and the battery voltage polarization changes significantly. In contrast, all-solid-state potassium-potassium symmetric batteries can achieve stable cycling at 0.2 mA / cm². 2 -0.2 mAh / cm 2 All tested cells showed significantly improved cycle life. The symmetric cell based on viscoelastic MOF-based solid electrolyte-1 could cycle stably for 3000 hours with voltage polarization stable at about 30 mV; the symmetric cell based on viscoelastic MOF-based solid electrolyte-2 had slightly lower cycle life, but could cycle stably for more than 2200 hours with overpotential stable at about 40 mV; the symmetric cell based on viscoelastic MOF-based solid electrolyte-3 could cycle stably for more than 1800 hours with the largest overpotential, about 50 mV.

[0051] The MOF-based solid electrolyte prepared in Comparative Example 1 was assembled with potassium metal to form an all-solid-state potassium||potassium symmetric battery, and the cycle life of the battery was tested. Specifically, using an R2032 coin cell, the battery was packaged in the following order: negative electrode shell, spring plate, gasket, potassium metal, MOF-based solid electrolyte, potassium metal, and positive electrode shell. After the packaged battery was left to stand for 16 hours, electrochemical tests were performed on the assembled battery using a Blue Battery Testing System under the test conditions of 0.2 mA / cm². 2 0.2 mAh / cm 2 The result is as follows Figure 9 As shown. By Figure 9 It is known that the potassium||potassium symmetric battery based on MOF-based solid electrolyte can only cycle stably for about 1500 hours under the same test conditions, and the battery voltage polarization change is relatively large, about 90 mV. The above results further verify the excellent interfacial compatibility between the viscoelastic MOF-based solid electrolyte and potassium metal in this application.

[0052] The viscoelastic MOF-based solid electrolyte-1 prepared in Example 1 was combined with potassium metal||copper to assemble an all-solid-state potassium||copper asymmetric battery, and the cycle life and coulombic efficiency of the battery were tested. Specifically, using R2032 button cells, the battery was packaged in the following order: negative electrode shell, spring sheet, gasket, potassium metal, copper foil, and positive electrode shell. After the packaged battery was left to stand for 16 hours, electrochemical tests were performed on the assembled battery using a Blue Battery Testing System. The results are as follows: Figure 10 As shown in a, by Figure 10 From a, we can know that at 0.2 mA / cm 2 -0.5 mAh / cm 2 Under the test conditions described in this application, the all-solid-state potassium||copper asymmetric battery prepared based on viscoelastic MOF-based solid electrolyte-1 can cycle stably for over 1000 hours, with an average coulombic efficiency higher than 99%. In contrast, the potassium||copper asymmetric battery based on a conventional liquid electrolyte can only cycle stably for about 300 hours under the same test conditions, and its coulombic efficiency varies significantly, with an average coulombic efficiency less than 99%. The viscoelastic MOF-based solid electrolyte-1 prepared in Example 1 and potassium metal||graphite were combined to assemble an all-solid-state potassium||graphite battery, and the cycle life of the battery was tested. Specifically, using R2032 button cells, the battery was packaged in the following order: negative electrode shell, spring sheet, gasket, potassium metal, graphite, and positive electrode shell. After the packaged battery was left to stand for 16 hours, electrochemical tests were performed on the assembled battery using a Blue Battery Testing System. The results are as follows: Figure 10 As shown in b, by Figure 10 As shown in b, under the test condition of 200 mA / g, the all-solid-state potassium||graphite battery prepared based on viscoelastic MOF-based solid electrolyte-1 in this application can stably cycle for more than 1600 cycles while maintaining a capacity retention of more than 72%. In contrast, potassium||graphite batteries based on conventional liquid electrolytes can only cycle for about 300 cycles under the same test conditions and have a capacity retention of less than 40%. The above results further verify the excellent ionic conductivity and interfacial compatibility of viscoelastic MOF-based solid electrolyte-1.

[0053] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a solid electrolyte based on viscoelastic MOF materials, characterized in that, Includes the following steps: S1. Grafting oligoethylene oxide chains onto MOF powder containing hydroxyl-modified groups in a solution, followed by magnetic stirring to obtain viscoelastic MOF material; the degree of polymerization of the oligoethylene oxide chains is 100,000-600,000, and the mass ratio of the oligoethylene oxide chains to the MOFs material is 1:25 to 1:1000. S2. The viscoelastic MOF material is vacuum dried in an inert atmosphere and then cooled to obtain the dried viscoelastic MOF material. S3. Mix the metal salt directly with the dried viscoelastic MOF material described in S2, and heat and stir at 30~80 ℃ for 2~24 h, then let it stand for 10~48 h to obtain a solid electrolyte based on the viscoelastic MOF material.

2. The preparation method according to claim 1, characterized in that, The MOF powder mentioned in step S1 includes any one of zinc-based MOFs, copper-based MOFs, iron-based MOFs, or aluminum-based MOFs.

3. The preparation method according to claim 2, characterized in that, The method for preparing the MOF powder includes the following steps: A metal salt is dissolved in solvent A to form solution A; an organic ligand is dissolved in solvent B to form solution B; the organic ligand contains at least one of a hydroxyl group, a carboxyl group, or an ester group; solutions A and B are mixed, washed, and dried to obtain MOF powder.

4. The preparation method according to claim 3, characterized in that, Solvent A comprises at least one of methanol, ethanol, acetone, water, phosphoric acid, dimethylformamide, or N-methylpyrrolidone, and the concentration of solvent A is 0.01~5 mol / L; solvent B comprises at least one of methanol, ethanol, acetone, water, phosphoric acid, dimethylformamide, or N-methylpyrrolidone, and the concentration of solvent B is 0.01~5 mol / L; the organic ligand comprises phenyl-1,3,5-tricarboxylic acid, phenyl-1,4-dicarboxylic acid, 2,3-pyrazine dicarboxylate, pyrazine, 1,4-naphthalene dicarboxylate, D-camphoric acid, 4,4′-(hexafluoroisopropylidene)bis(benzoic acid), 9,10-anthracite dicarboxylate, 5-tert-butylisophthalic acid, tetracarboxylic acid, 4-carboxycinnamic acid, etc. One or more of the following: acid, 1,12-dihydroxydicarbonyl-1,12-dicarbazo-closed-dodecorane ligand, 1,3,5-benzenetribenzoate, naphthalene dicarboxylate, ZIF-7, ZIF-8, ZIF-22 with cobalt as the metal central ion, 2,4-pyridinedicarboxylic acid or 1,4,5,8-naphthalenetetracarboxylic acid, at a concentration of 0.01 M to 10 M; with a mass ratio to the metal salt of 0.01:1 to 50:

1.

5. The preparation method according to claim 1, characterized in that, The step S1 of grafting oligoethylene oxide chains onto MOF powder containing hydroxyl-modified groups in solution specifically includes: dissolving hydroxyl-modified MOF powder in solution and heating and stirring at 30~120°C, wherein the grafting occurs between the hydroxyl-modified groups and the oligoethylene oxide chains.

6. The preparation method according to claim 1, characterized in that, The vacuum drying temperature in step S2 is 80~200℃, the vacuum degree is 0.2~600 MPa, the drying time is 20-90 min, and the cooling rate is 10-50 ℃ / min.

7. The preparation method according to claim 1, characterized in that, The metal salt mentioned in step S3 is at least one of LiPF6, LiTFSI, LiFSI, LiDFOB, LiBOB, LiBF4, LiNO3, LiAsF6, LiClO4, KFSI, KTFSI, KClO4, NaTFSI, NaFSI, and NaClO4. The heating and stirring take place inside a glove box with a vacuum degree of 10 Pa.

8. A solid electrolyte based on a viscoelastic MOF material prepared by the preparation method according to any one of claims 1 to 7, characterized in that, The solid electrolyte has a pore size of 0.1~6 nm.

9. A metal battery, characterized in that, The metal battery includes a solid electrolyte based on viscoelastic MOF material prepared by the preparation method according to any one of claims 1 to 7 or a solid electrolyte based on viscoelastic MOF material according to claim 8; the metal battery includes metal positive and negative electrodes or graphite electrodes and a metal negative electrode.

10. The metal battery as described in claim 9, characterized in that, The metal battery is a potassium metal battery; the positive electrode material of the potassium metal battery includes at least one of the following: alkali metal, carbon material, LNMO, nickel-cobalt-manganese ternary materials NCM811, NCM622, NCM532, NCM333, nickel-cobalt-aluminum ternary materials NCA, Li2MnO4, LiCoMnO4, lithium-rich manganese base oxide, LiCoO2, LiNiO2, LiFePO4, S, or Li2O2 / LiO2; the alkali metal is at least one of lithium metal, sodium metal, potassium metal, magnesium metal, or zinc metal; the carbon material is at least one of graphite, soft carbon, hard carbon, or silicon carbon.

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