MOF-based single ion conductor solid electrolyte and preparation method and application thereof

Abstract

The invention provides an MOF-based single ion conductor solid electrolyte as well as a preparation method and application thereof, and belongs to the technical field of solid electrolytes. The preparation method provided by the invention comprises the following steps: 1) carrying out heating reaction on ZrCl4 or ZrOCl2 and pyromellitic acid in a weakly acidic aqueous solution, and collecting a precipitation product after the reaction is completed; (2) soaking the precipitation product with a first organic solvent, washing, and drying, so as to obtain Zr-UiO-66-2COOH powder; and (3) carrying out oil bath heating reaction on the Zr-UiO-66-2COOH powder, LiOH and a second organic solvent in protective gas, and filtering after the reaction is completed, so as to obtain the Zr-UiO-66-2COOLi powder. Compared with other solid-state electrolytes, the single-ion conductor solid-state electrolyte provided by the invention has the core advantages that no lithium salt is added, only migration of working ions (Li) is allowed, and the concentration polarization phenomenon can be effectively inhibited, so that the cycling stability of the battery is improved. In addition, the dendritic crystal growth problem can be relieved through uniform ion flow distribution, and the safety is further improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid electrolytes, and in particular relates to a MOF-based single-ion conductor solid electrolyte and a preparation method and application thereof. Background Art

[0002] Solid-state lithium metal batteries are considered to be one of the most promising energy storage devices of the next generation due to their high energy density and safety. Solid-state electrolytes, as the core components of solid-state lithium metal batteries, mainly play the role of ion transport and physical isolation of positive and negative electrodes. They have attracted much attention due to their many advantages such as non-flammability, high mechanical properties and good compatibility with lithium metal.

[0003] To date, mainstream solid electrolyte materials include inorganic solid electrolytes, polymer solid electrolytes, and organic-inorganic composite solid electrolytes. Among inorganic solid electrolytes, sulfides primarily suffer from electrochemical instability and susceptibility to moisture decomposition, while oxides suffer from poor electrode interface compatibility and high high-temperature sintering costs. Polymer solid electrolytes also suffer from low ionic conductivity and insufficient thermal stability. In contrast, composite electrolytes combine the advantages of both inorganic and organic materials, offering both high structural stability and better interfacial contact.

[0004] Metal-organic frameworks (MOFs), as porous materials, have attracted attention in the battery field in recent years due to their potential ionic conductivity, designable pores, ultra-high specific surface area, and abundant surface functional groups (such as carboxylic acid and amino groups). MOFs are composed of metal ions (or clusters) and organic bridging ligands, which form a multidimensional porous network through coordination, providing channels for lithium ion transport.

[0005] At present, MOF-based solid electrolytes generally need to rely on the addition of lithium salts to maintain ion transport. For example, patent document CN120165057A discloses a preparation method for a solid electrolyte obtained by mixing lithium salts, organic polymers, ceramic fillers and organic solvents. This method mixes multiple materials. Although it has advantages over general solid electrolytes in terms of electrolyte structural strength and interface contact, due to the addition of lithium salts, its hygroscopicity still leads to poor electrolyte air stability and low lithium ion migration number. The addition of lithium salts in the prior art still leads to the following problems that are difficult to solve: 1. Lithium salts are very easy to absorb moisture, which leads to electrolyte structural failure; 2. The free anions generated by the dissociation of lithium salts are enriched at the electrode interface, which easily causes concentration polarization, thereby exacerbating the problem of non-uniform deposition and dendrite growth of lithium ions. Therefore, the design and development of a new single-ion conductor MOF solid electrolyte with no lithium salt addition, high ion conductivity and good air stability is of great significance to the development of solid-state batteries. Summary of the Invention

[0006] Therefore, the present application aims to provide a MOF-based single-ion conductor solid-state electrolyte, a preparation method and application thereof.

[0007] In order to achieve the above-mentioned application purposes, the present application provides the following technical solutions.

[0008] The present application provides a preparation method of a MOF-based single-ion conductor solid-state electrolyte, comprising the following steps:

[0009] 1) ZrCl4 or ZrOCl2 and pyromellitic acid are subjected to a heating reaction in a weak acid aqueous solution, and after the reaction is completed, the precipitate product is collected;

[0010] 2) The precipitate product collected in step 1) is subjected to soaking and washing with a first organic solvent, and after drying, Zr-UiO-66-2COOH powder is obtained;

[0011] 3) The Zr-UiO-66-2COOH powder obtained in step 2), LiOH and a second organic solvent are subjected to an oil bath heating reaction in a protective gas, and after the reaction is completed, filtration is performed, and Zr-UiO-66-2COOLi powder is obtained.

[0012] Preferably, the molar ratio of ZrCl4 or ZrOCl2 to pyromellitic acid is 1-4:1-5 mmol.

[0013] Preferably, the weak acid aqueous solution comprises at least one of dilute hydrochloric acid, formic acid and glacial acetic acid.

[0014] Preferably, the heating temperature in step 1) is 70-150 DEG C, and the heating time is 2-12 h.

[0015] Preferably, the first organic solvent in step 2) comprises at least one of methanol, ethanol, propanol and acetone.

[0016] Preferably, the second organic solvent in step 3) comprises at least one of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide and ethanol.

[0017] The present application also provides a MOF-based single-ion conductor solid-state electrolyte prepared by the above preparation method.

[0018] The application further provides a preparation method of the MOF-based single-ion conductor solid-state electrolyte film, which comprises the following steps: mixing the Zr-UiO-66-2COOLi powder, a dispersing agent, a PTFE water emulsion and Nafion-Li, and then performing roll forming to obtain the MOF-based single-ion conductor solid-state electrolyte film.

[0019] Preferably, the preparation method of the Nafion-Li comprises the following steps: drying a Nafion solution to obtain solid Nafion; dispersing the solid Nafion in a LiOH aqueous solution, stirring at 40-100 DEG C for 2-5 hours, and then performing suction filtration to obtain a solid product, i.e., the Nafion-Li.

[0020] The application further provides an application of the MOF-based single-ion conductor solid-state electrolyte in the preparation of a lithium battery.

[0021] In the application, UiO-66 is a framework structure with three-dimensional channels formed by connecting zirconium-oxygen clusters or cerium-oxygen clusters (Zr6O4(OH)4 / Ce6O4(OH)4) as metal nodes and terephthalic acid as an organic ligand through strong coordination bonds. The structure has the advantages of good structural rigidity, high stability and modifiability. Based on the above characteristics, the application prepares a Zr-UiO-66-2COOH MOF material with two free carboxyl groups, and the two free carboxyl groups are exchanged into Li + by a lithiation process. + , thereby obtaining a single-ion conductor electrolyte (Zr-UiO-66-2COOLi).

[0022] The core advantage of the single-ion conductor solid-state electrolyte provided by the application compared with other solid-state electrolytes is that the single-ion conductor solid-state electrolyte truly realizes no lithium salt addition and only allows the migration of working ions (Li + ), and can effectively inhibit the concentration polarization phenomenon, thereby improving the cycle stability of the battery. In addition, the uniform ion flow distribution can relieve the dendrite growth problem, and further strengthen the safety. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 It is a preparation flowchart of the single-ion conductor solid-state electrolyte in Example 1.

[0024] Figure 2 It is an XRD graph of the Zr-UiO-66-2COOLi powder in Example 1.

[0025] Figure 3 It is a solid-state electrolyte film real object graph of the Zr-UiO-66-2COOLi in Example 1.

[0026] Figure 4A scanning electron microscope (SEM) characterization graph of the Zr-UiO-66-2COOLi powder in Example 1;

[0027] Figure 5 A lithium metal full battery cycle graph assembled for the Zr-UiO-66-2COOLi solid electrolyte in Example 2. DETAILED DESCRIPTION

[0028] The application provides a preparation method of a MOF-based single-ion conductor solid electrolyte, comprising the following steps:

[0029] 1) ZrCl4 or ZrOCl2 is subjected to a heating reaction with pyromellitic acid in a weak acid aqueous solution, and after the reaction is completed, a precipitate product is collected;

[0030] 2) The precipitate product collected in step 1) is subjected to soaking and washing with a first organic solvent, and after drying, Zr-UiO-66-2COOH powder is obtained;

[0031] 3) The Zr-UiO-66-2COOH powder obtained in step 2), LiOH and a second organic solvent are subjected to an oil bath heating reaction in a protective gas, and after the reaction is completed, filtration is performed, and Zr-UiO-66-2COOLi powder is obtained.

[0032] The application does not have special limitations on the sources of the ZrCl4, ZrOCl2 and pyromellitic acid, and conventional commercially available products in the field can be used.

[0033] In the application, the water is preferably distilled water, deionized water or ultrapure water.

[0034] In the application, the container for the reaction is preferably a shouxin bottle or a high-pressure reaction kettle.

[0035] In the application, the protective gas is preferably argon.

[0036] The application further provides a preparation method of a MOF-based single-ion conductor solid electrolyte film, comprising: mixing the Zr-UiO-66-2COOLi powder, a dispersing agent, a PTFE water emulsion and Nafion-Li, and then performing roll forming, to obtain a MOF-based single-ion conductor solid electrolyte film.

[0037] In the application, the preparation method of the Nafion-Li preferably comprises: drying a Nafion solution to obtain solid Nafion; dispersing the solid Nafion in a LiOH aqueous solution, stirring at 40-100 DEG C for 2-5 hours, and then performing suction filtration to obtain a solid product, which is the Nafion-Li.

[0038] In the present invention, the dispersant is preferably methanol, ethanol or isopropanol.

[0039] The present invention has no special limitation on the sources of the dispersant, PTFE aqueous emulsion, and Nafion solution, and conventional commercial products in the art may be used.

[0040] In the present invention, the Nafion solution is preferably dried in a 40-120° C. forced air oven to dry the solvent.

[0041] In the present invention, the mass ratio of the Zr-UiO-66-2COOLi powder, the PTFE aqueous emulsion and the Nafion-Li is preferably 6 to 7:2 to 3:1.

[0042] The present invention also provides the use of the MOF-based single-ion conductor solid electrolyte in the preparation of lithium batteries.

[0043] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0044] Example 1

[0045] 1. Synthesis of Zr-UiO-66-2COOH Powder: 1 mmol of ZrCl₄ was dissolved in 20 mL of dilute hydrochloric acid, followed by the addition of 10 mL of deionized water. After stirring for 3 minutes, 1 mmol of pyromellitic acid was added, ultrasonically dissolved, and stirred for another 3 minutes. The mixture was then transferred to an autoclave. The precursor solution was placed in a forced-air oven at 70°C for 2 hours. After the reaction, the autoclave was allowed to cool naturally to room temperature. The white precipitate was collected, dispersed in methanol, and soaked for 5 hours before being washed several times with methanol. The white powder was then dried at high temperature and ground thoroughly for subsequent experiments.

[0046] 2. Synthesis of Zr-UiO-66-2COOLi powder: 1 mmol LiOH was placed in a 250 mL two-necked flask and 40 mL of dimethyl sulfoxide (DMSO) was added, followed by the Zr-UiO-66-2COOH powder obtained in the above step. Under argon atmosphere, the oil bath was heated to 40 ° C and stirred for 5 h. After cooling to room temperature, the precipitate was collected by filtration.

[0047] Preparation of Nafion-Li: Pipette 5 mL of Nafion solution into a small beaker and then place the solution in a 40°C forced air oven to dry the solvent to obtain solid Nafion. Disperse the solid Nafion in a LiOH aqueous solution and stir at 60°C for 2 hours. Filter and collect the solid product for later use.

[0048] 4. Preparation of Zr-UiO-66-2COOLi into a film (N-UIO-66-SSE): A certain amount of Zr-UiO-66-2COOLi was weighed into a clean mortar, then a proper amount of dispersant methanol was added to make the MOF s evenly dispersed; then PTFE water emulsion and Nafion-Li (the mass ratio of MOF s, PTFE and Nafion-Li is 7:2:1) were added and ground thoroughly until a dough-like block was formed, which was then transferred to a pear-shaped paper and rolled into a uniform solid electrolyte film by using an electric roller machine for multiple times.

[0049] Example 2

[0050] 1. Synthesis of Zr-UiO-66-2COOH powder: 4 mmol of ZrOCl2 was dissolved in 50 mL of formic acid, then 30 mL of deionized water was added; after stirring for 15 min, 5 mmol of pyromellitic acid was added, ultrasonic dissolution was performed and stirring was continued for 15 min; then it was transferred to a high-pressure reaction kettle; the above precursor solution was placed in a temperature of 150°C air oven for reaction for 12 h; after the reaction was completed, the reaction kettle was naturally cooled to room temperature; then the white precipitate product was collected, the precipitate was dispersed in methanol and soaked for 20 h, then washed several times with methanol; finally, the white powder was dried at high temperature and ground thoroughly for subsequent experimental use.

[0051] 2. Synthesis of Zr-UiO-66-2COOLi powder: 5 mmol of LiOH was placed in a 250 mL two-necked flask and 170 mL of dimethyl sulfoxide (DMSO) was added, then the Zr-UiO-66-2COOH powder obtained in the above step was added, under the condition of argon atmosphere, oil bath heating to 100°C and stirring for 12 h, after cooling to room temperature, the precipitate was collected by filtration.

[0052] 3. Preparation of Nafion-Li: 5 mL of Nafion solution was dropped into a small beaker, then it was placed in a 120°C air oven to dry the solvent, and solid Nafion was obtained; the solid Nafion was dispersed in LiOH aqueous solution, then stirred at 60°C for 5 hours, the solid product was collected by suction filtration and reserved for use.

[0053] 4. Preparation of Zr-UiO-66-2COOLi into a membrane (N-UIO-66-SSE): A certain mass of Zr-UiO-66-2COOLi was weighed and placed in a clean mortar. An appropriate amount of dispersant ethanol was then added to evenly disperse the MOFs. PTFE aqueous emulsion and Nafion-Li (the mass ratio of MOFs to PTFE to Nafion-Li was 6:3:1) were then added and thoroughly ground until a dough-like mass was formed. The mixture was then transferred to pear-shaped paper and rolled multiple times using an electric roller mill to form a uniform solid electrolyte membrane.

[0054] Example 3

[0055] Lithium metal full battery assembly process of solid electrolyte of the present invention

[0056] 1. Preparation of lithium iron phosphate (LFP) positive electrode sheet

[0057] 0.08g of polyvinylidene fluoride (PVDF) binder was fully dissolved in an appropriate amount (2.3mL) of N-methylpyrrolidone (NMP), and then a mixture containing 0.8g of lithium iron phosphate (LiFeO4, LFP) and 0.12g of acetylene black conductive agent (Li-400) was added (the two were mixed and fully ground in advance); the slurry was homogenized using a high-speed homogenizer for 10 minutes and then stirred for 12 hours; finally, a black slurry with a certain fluidity was formed. The above slurry was evenly coated on aluminum foil using a scraper and placed in a 60°C oven to dry for 6 hours to remove most of the solvent; then transferred to a vacuum drying oven and vacuum dried at 120°C for 24 hours, and finally cut into 12mm diameter discs using a cutting machine and placed in an ultra-clean glove box for use; by weighing and calculating, the active material loading of each electrode was 1.0-1.2mg·cm -2 .

[0058] 2. Anode preparation

[0059] The negative electrode material of the present invention adopts a metal lithium sheet (diameter 8-10mm).

[0060] 3. Battery assembly method

[0061] The obtained solid electrolyte membrane was sandwiched between the positive electrode sheet and the negative electrode lithium sheet, encapsulated in a button battery in an argon-filled glove box, and then the battery was left to stand at room temperature for 24 hours to ensure the stability of the electrolyte / electrode interface.

[0062] 4. Battery testing method

[0063] The assembled batteries were tested on a LAND battery test system. Constant current charge-discharge cycling was performed to evaluate long-term cycling and rate capability performance. The charge / discharge protocol used the "C-rate" notation, where 1 C corresponds to the current required to fully discharge the nominal capacity (170 mAh g -1 LiFePO4) in 1 hour. The voltage window was limited between 2.8 V and 3.9 V to ensure operation within the thermodynamic stability range of the electrode materials. The test results Figure 5 ) show that the battery can be stably cycled for 250 cycles with a capacity retention of 95.35% and coulombic efficiency of 99.95% at a rate of 0.1 C at 55°C, which is superior to the battery assembled with the electrolyte film without ligand modification (only 80 cycles and rapid capacity decay).

[0064] The above description is only preferred embodiments of the present application, and it should be pointed out that for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, which should be considered as the protection scope of the present application.

Claims

1. A method for preparing a MOF-based single-ion conductor solid electrolyte, characterized in that: The following steps are involved: 1) heating ZrCl4 or ZrOCl2 with pyromellitic acid in a weakly acidic aqueous solution to react, and collecting the precipitated product after the reaction is complete; 2) soaking and washing the precipitated product collected in step 1) with a first organic solvent, and drying the precipitated product to obtain Zr-UiO-66-2COOH powder; 3) The Zr-UiO-66-2COOH powder obtained in step 2), LiOH and a second organic solvent are subjected to an oil bath heating reaction under protective gas. After the reaction is complete, the Zr-UiO-66-2COOLi powder is obtained by filtering.

2. The method for preparing a MOF-based single-ion conductor solid electrolyte according to claim 1, characterized in that: The molar ratio of ZrCl4 or ZrOCl2 to pyromellitic acid is 1-4:1-5 mmol.

3. The method for preparing a MOF-based single-ion conductor solid electrolyte according to claim 1, characterized in that: The weakly acidic aqueous solution includes at least one of dilute hydrochloric acid, formic acid and glacial acetic acid.

4. The method for preparing a MOF-based single-ion conductor solid electrolyte according to claim 1, wherein: The heating temperature in step 1) is 70-150° C., and the heating time is 2-12 hours.

5. The method for preparing a MOF-based single-ion conductor solid electrolyte according to claim 1, characterized in that: In the step 2), the first organic solvent comprises at least one of methanol, ethanol, propanol and acetone.

6. The method for preparing a MOF-based single-ion conductor solid electrolyte according to claim 1, characterized in that: The second organic solvent in step 3) includes at least one of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide and ethanol.

7. A MOF-based single-ion conductor solid electrolyte prepared by the method for preparing a MOF-based single-ion conductor solid electrolyte according to any one of claims 1 to 6.

8. A method for preparing a MOF-based single-ion conductor solid electrolyte membrane, characterized in that: include: The Zr-UiO-66-2COOLi powder, dispersant, PTFE aqueous emulsion and Nafion-Li according to claim 1 are mixed and then roll-formed to obtain a MOF-based single-ion conductor solid electrolyte membrane.

9. The method for preparing a MOF-based single-ion conductor solid electrolyte membrane according to claim 8, characterized in that: The preparation method of Nafion-Li comprises: drying the solvent of Nafion solution to obtain solid Nafion; dispersing the solid Nafion in a LiOH aqueous solution, stirring at 40-100° C. for 2-5 hours, and filtering to obtain a solid product, namely Nafion-Li.

10. Use of the MOF-based single-ion conductor solid electrolyte according to claim 7 in the preparation of lithium batteries.

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