Method for preparing lithium-sulfur battery based on cubic alkane tetranuclear copper iodine cluster metal organic framework modified diaphragm coating

Abstract

The invention belongs to the technical field of lithium-sulfur battery materials, and particularly relates to a method for preparing a lithium-sulfur battery based on a cubic alkane tetranuclear copper iodine cluster metal organic framework modified diaphragm coating, and the method comprises the following steps: weighing isonicotinic acid powder, dissolving the isonicotinic acid powder in N, N-dimethylformamide, and after the isonicotinic acid powder is fully dissolved, dropwise adding a proper amount of triethylamine into a solution to obtain a solution A; dissolving cuprous iodide and zinc salt powder in an ethanol solution to obtain a solution B; slowly dropwise adding the solution A into the heated and stirred solution B; putting the solution into a drying oven to react, cooling, washing and drying to obtain a cubic alkane tetranuclear copper iodine cluster metal organic framework crystal material; the prepared crystalline material is ground into slurry, and the slurry is coated on a PP diaphragm for assembling a lithium-sulfur battery. The cubic alkane tetranuclear copper iodine cluster metal organic framework synthesized by solvothermal self-assembly of CuI, Zn < 2 + > and INA ligands is applied to the diaphragm material of the lithium-sulfur battery; the lithium-sulfur battery prepared by the method can efficiently adsorb lithium ions, is beneficial to rapid transmission of the lithium ions, improves the cycle performance of the lithium-sulfur battery, and has the initial capacity of 710.6 mAh.g <-1 > under the current density of 0.1 C.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-sulfur battery materials, and in particular relates to a method for preparing a lithium-sulfur battery by modifying a diaphragm coating based on a cubane tetranuclear copper-iodine cluster metal-organic framework. Background Art

[0002] As a new generation of high energy chemical power system, lithium sulfur battery has a high capacity of 1675 mAh g -1 Theoretical specific capacity and 2600 Wh kg -1 Due to its energy density advantage, it is regarded as one of the most promising candidate systems to break through the bottleneck of existing energy storage technology. However, the soluble lithium polysulfide (LiPSs) intermediates generated during the operation of this system will irreversibly migrate to the lithium negative electrode to trigger a shuttle effect, resulting in problems such as loss of active materials, negative electrode passivation and rapid capacity decay, which has become a key bottleneck restricting its industrial application. In response to the above challenges, the research community has mainly carried out research in the following directions: by constructing a new sulfur host structure to achieve confined transformation of active materials, developing a highly stable electrolyte system to inhibit the dissolution of LiPSs, designing a functional diaphragm modification layer to construct an ion screening barrier, and constructing a lithium negative electrode interface protection system to reduce the activity of side reactions, and promoting the transformation of lithium-sulfur batteries from laboratory to commercial application through multi-dimensional collaborative innovation.

[0003] As a key component, the separator plays a dual role in maintaining the physical isolation of the electrodes and promoting the transfer of lithium ions. The polyethylene (PE) and polypropylene (PP) based separators currently used have significant limitations: first, the difference in material polarity leads to poor electrolyte wettability; second, insufficient thermal stability easily causes structural shrinkage; third, the inherent pore structure (usually 30-40%) is difficult to effectively block the migration of polysulfides. This characteristic defect triggers a chain reaction: soluble polysulfides (Li2S x , 4≤x≤8) causes irreversible loss of positive electrode active materials, and at the same time forms a Li2S / Li2S2 passivation layer at the negative electrode interface, further exacerbating capacity decay. In recent years, researchers have modified the diaphragm by coating it with carbon materials, polymer materials, inorganic compound materials, metal organic frameworks, covalent organic framework materials and other metal compounds to increase its conductivity and lithium ion transmission capacity. However, commercial diaphragms cannot effectively resist the shuttling of polysulfides generated by the positive electrode during the electrochemical reaction, and are extremely easily penetrated by the dendrites of the negative electrode, causing battery short circuits and low battery life. Therefore, further research is needed on the modification of diaphragms.

[0004] Patent publication number "CN 117986604 A" discloses a copper-based metal-organic framework (MOF) with a tetracoordinate structure comprising pyridinic nitrogen atoms on two different ligands and carboxylic acid oxygen atoms on two different ligands. The problems are: 1. The tetracoordinate structure of pyridine and carboxylic acid ligands forms a localized electron distribution, resulting in poor conductivity and high impedance, requiring reliance on external conductive agents to improve electron transfer efficiency and unsatisfactory cycle performance; 2. It is susceptible to oxidation or protonation in high potential or strong acid / base environments, causing framework collapse and poor stability. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for preparing a lithium-sulfur battery by modifying a diaphragm coating based on a cubane tetranuclear copper iodine cluster metal-organic framework, so as to solve the problems of poor conductivity and easy oxidation or protonation that lead to framework collapse in the prior art.

[0006] To achieve the above-mentioned object, the technical solution adopted by the present invention is: a method for preparing a lithium-sulfur battery based on a modified diaphragm coating of a cubane tetranuclear copper iodine cluster metal-organic framework, the specific steps of which are as follows: Step 1: Weigh isonicotinic acid powder and dissolve it in N,N-dimethylformamide. Heat and stir to fully dissolve it. Add an appropriate amount of triethylamine dropwise until the solution becomes transparent and clear in a glass bottle to obtain solution A. Step 2: Dissolve cuprous iodide and zinc salt powder in ethanol solution, heat and stir until the solution becomes turbid in a glass bottle to obtain solution B; Step 3: Slowly add solution A dropwise to the heated and stirred solution B, and the solution turns light green; Step 4: Place the light green solution in an oven for reaction, take it out and cool it to room temperature, wash it three times with N,N-dimethylformamide, and dry it to obtain a cubane tetranuclear copper iodine cluster metal organic framework crystal material; Step 5: After the crystal material is made into a modified diaphragm, it is assembled into a lithium-sulfur battery.

[0007] Furthermore, in the above step 1, the amount of isonicotinic acid powder and N,N-dimethylformamide added is 0.5 mmol: 3-4.5 ml.

[0008] Furthermore, in the above step 1, the triethylamine can be replaced by triethanolamine.

[0009] Furthermore, in the above step 1, the amount of isonicotinic acid powder and N,N-dimethylformamide added is 0.5 mmol:4 ml.

[0010] Furthermore, in the above step 2, the molar ratio of zinc salt powder, isonicotinic acid powder and cuprous iodide is 3:1:1, and the volume ratio of N,N-dimethylformamide and ethanol solution is 2:1.

[0011] Furthermore, in the above step 3, the zinc salt is zinc nitrate or zinc acetate.

[0012] Furthermore, in the above step 4, the temperature of the oven is set to 100~120 o C, the reaction time is 48~72 hours.

[0013] Furthermore, in the above step 4, the temperature of the oven is set to 100 o C, the reaction time is 72 hours.

[0014] Compared with the prior art, the advantages of the present invention are: 1. The present invention proposes for the first time that CuI and Zn 2+ The cubane tetranuclear copper iodine cluster metal organic framework synthesized by solvothermal self-assembly with INA ligands is applied to the separator material of lithium-sulfur batteries, where the INA ligands have soft and hard coordination modes to create a 3d system about Cu and Zn, which can inhibit the shuttling of polysulfides. 2+ The Zn clusters formed with INA ligands synergize with the open framework of the Cu4I4 cluster to form a stable structural framework, shortening the ion diffusion path. The cubane tetranuclear copper iodine cluster metal-organic framework material provided by the present invention has a tetrahedral crystal structure similar to that of cubane. Its crystal framework has large molecular pores and porosity, resulting in more efficient lithium ion solvation, effectively inducing lithium ion transport, and providing a path for lithium ion transfer.

[0015] 2. This invention utilizes heterometallic clusters (Zn and copper-iodine clusters) as nodes to form a unique heterometallic framework. Copper-iodine clusters possess intrinsically high catalytic activity, promoting the efficient conversion of polysulfides during lithium-sulfur battery transport. The introduction of Zn may enhance the chemical adsorption of polysulfides by regulating the coordination environment. In contrast, traditional copper-based MOFs primarily rely on the physicochemical synergy of a single metal or a homogeneous bimetallic structure and require exogenous materials for conductivity. These differences give cubane tetranuclear copper-iodine clusters potential advantages in suppressing the shuttle effect and improving reaction kinetics.

[0016] 3. In the synthesis of cubane tetranuclear copper iodine cluster metal organic framework materials, [Cu4I4(INA)4] 4− The geometric shape of the metal ligand is similar to that of a tetrahedral metal-organic framework material in the shape of cubane. The N atom of HINA contained in the structure A of the material is combined with the tetrahedral Cu center, and the O atom in its carboxylate group is coordinated with the two Zn centers. The separator layer can efficiently adsorb lithium ions and promote the transmission of lithium ions.

[0017] 4. In the preparation of the cubane tetranuclear copper iodine cluster metal organic framework modified diaphragm, PP diaphragm is selected as the substrate of the lithium-sulfur battery diaphragm. The metal organic framework A synthesized from zinc acetate, isonicotinic acid and cuprous iodide has good thermal stability, a large number of mesopores and micropores, and a high specific surface area. It is mixed with conductive carbon black and a binder to form a uniform slurry, which is then scraped on the surface of the PP diaphragm. This modified diaphragm has higher ionic conductivity and excellent thermal stability, which is conducive to the rapid transmission of lithium ions and improves the cycle performance of the lithium-sulfur battery. The present invention is based on the method of preparing a lithium-sulfur battery by using a cubane tetranuclear copper iodine cluster metal organic framework modified diaphragm coating. The metal organic framework diaphragm coating is applied to the PP diaphragm by scraping. At a current density of 0.1C, it has a capacity of 710.6mAh·g -1 First capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a flow chart of the method for preparing a lithium-sulfur battery based on a cubane tetranuclear copper iodine cluster metal organic framework modified diaphragm coating; Figure 2 is the X-ray diffraction pattern of Example 1; Figure 3 is a crystal structure diagram of Example 1; Figure 4 is a graph showing the relationship between current density and potential (CV) of the lithium-sulfur battery assembled in Example 1; Figure 5 1 is an electrochemical impedance spectroscopy diagram of a lithium-sulfur battery assembled in Example 1 and a lithium-sulfur battery assembled with a PP separator; Figure 6 1 is a graph showing the relationship between efficiency and specific capacity of the lithium-sulfur battery of Example 1 after 100 cycles at a rated capacitance of 0.1C. DETAILED DESCRIPTION

[0019] The present invention will be further described below with reference to specific embodiments.

[0020] The present invention provides a method for preparing a lithium-sulfur battery using a cubane tetranuclear copper iodine cluster metal-organic framework-based modified diaphragm coating, which comprises synthesizing a cubane tetranuclear copper iodine cluster metal-organic framework material, blending the cubane tetranuclear copper iodine cluster metal-organic framework material with conductive carbon black (SuperP) and a binder PVDF to prepare a slurry, which is then coated on a PP diaphragm to obtain a modified diaphragm, and assembling the modified diaphragm with a sulfur positive electrode and a lithium negative electrode to form a lithium-sulfur battery.

[0021] Example 1: See Figure 1 A method for preparing a lithium-sulfur battery based on a cubane tetranuclear copper iodine cluster metal organic framework modified diaphragm coating comprises the following steps: Step 1: Weigh isonicotinic acid (0.062 g, 0.5 mmol) and dissolve it in N,N-dimethylformamide (4 mL). Stir at 60°C to dissolve it. Add 2 drops of triethylamine until the solution becomes transparent and clear in a glass bottle to obtain Solution A. Step 2: Dissolve cuprous iodide (0.095 g, 0.5 mmol) and zinc acetate (0.06 g, 1.5 mmol) powder in ethanol (2 ml) and heat with stirring until the solution becomes turbid in a glass bottle to obtain solution B. Step 3: Slowly add solution A dropwise into the heated and stirred solution B. The solution turns light green.

[0022] Step 4: The light green solution was placed in a 100°C oven for reaction for 3 days, then cooled to room temperature, washed three times with N,N-dimethylformamide, and dried to obtain a cubic tetranuclear copper iodine cluster metal organic framework crystal material A; Step 5: Assemble the lithium-sulfur battery. The specific steps are: Crystal material A, conductive carbon black and binder were mixed in an agate mortar at a mass ratio of 7:2:1 and ground thoroughly. After grinding evenly, an appropriate amount of N-methylpyrrolidone solution was added dropwise to the mortar to form a uniform and viscous slurry B. The cut PP diaphragm was cleaned with anhydrous ethanol, and the slurry B obtained in step 2 was evenly coated on the surface of the diaphragm by a doctor blade method to a thickness of 75 nm. The coated diaphragm was naturally dried at room temperature to obtain a uniform modified diaphragm C; The modified separator C was taken out and cut into 19 mm discs to obtain a modified battery separator D. The modified battery separator D was transferred to a vacuum drying oven at 60°C and dried for 12 h to obtain the battery separator E. The battery separator E, sublimated sulfur-loaded carbon nanotube composite positive electrode material and negative electrode material lithium sheet were assembled into a lithium-sulfur battery with shrapnel and gasket in an argon-filled glove box, and the impedance, cycle and CV were tested at different currents.

[0023] Example 2: The difference from Example 1 is that the amount of N,N-dimethylformamide is 3 mL and the thickness of the coating film is 50 mm.

[0024] Example 3: The difference from Example 1 is that the mass ratio of crystal material A, conductive carbon black and binder is 6:2:1.

[0025] The above embodiment 1 is the best embodiment. The lithium-sulfur battery assembled in embodiment 1 was tested for impedance, cycle, and CV at different currents. The results showed that: like Figure 2As shown, it can be clearly seen from the XRD pattern that the crystal peaks of the crystalline material are basically consistent with the standard curve, indicating that the cubane tetranuclear copper iodine cluster metal organic framework material has been successfully synthesized.

[0026] like Figure 3 As shown, it can be seen that the synthesized [Cu4I4(INA)4] 4− The geometric shape of the metal ligand is exactly a tetrahedral metal organic framework material. The N atom of INA contained in the material A is combined with the tetrahedral Cu center, and the O atom in its carboxylate is coordinated with two Zn centers. There are a large number of mesopores and micropores, and it has a high specific surface area, indicating that the material has excellent channels and can promote Li + transfer.

[0027] like Figure 4 As shown, the reversible redox peak pairs exhibited in the cyclic voltammetry curves confirm that the material of Example 1 undergoes significant sulfur species redox reactions during the charge and discharge processes. This typical electrochemical response reflects the material system's high redox activity and excellent kinetics, demonstrating that the sulfur active material can achieve rapid and efficient electrochemical reactions during the electrode process.

[0028] like Figure 5 As shown in the figure, it can be seen that the radius of the mid-frequency region of the impedance curve of the battery assembled with the modified diaphragm is smaller, indicating that the charge transfer resistance is small and the interfacial reaction kinetics of the battery is faster.

[0029] like Figure 6 As shown in the figure, the coulombic efficiency of the lithium-sulfur battery prepared in Example 1 is still close to 100% after 100 cycles at a rated capacitance of 0.1C. This is because the cubane tetranuclear copper iodine cluster metal organic framework modified diaphragm material has high conductivity and thermal stability, which can promote the transfer of lithium ions, thereby improving the cycle stability of the lithium-sulfur battery.

[0030] From the above analysis, it can be seen that the crystal peak of the cubane tetranuclear copper iodine cluster crystal material synthesized in Example 1 is basically consistent with the standard curve, indicating that it has been successfully synthesized, and the impedance radius of the assembled lithium-sulfur battery is smaller than the impedance radius of the lithium-sulfur battery assembled by PP.

[0031] The above description is an explanation of the specific implementation of the present invention, rather than a limitation of the present invention. Those skilled in the relevant technical field can also make various equivalent technical solutions without departing from the scope of the present invention, so all equivalent technical solutions should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a lithium-sulfur battery based on a modified diaphragm coating of a cubane tetranuclear copper iodine cluster metal-organic framework, characterized in that: The specific steps are as follows: Step 1: Weigh isonicotinic acid powder and dissolve it in N,N-dimethylformamide. Heat and stir to fully dissolve it. Add an appropriate amount of triethylamine dropwise until the solution becomes transparent and clear in a glass bottle to obtain solution A. Step 2: Dissolve cuprous iodide and zinc salt powder in ethanol solution, heat and stir until the solution becomes turbid in a glass bottle to obtain solution B; Step 3: Slowly add solution A dropwise to the heated and stirred solution B, and the solution turns light green; Step 4: Place the light green solution in an oven for reaction, take it out and cool it to room temperature, wash it three times with N,N-dimethylformamide, and dry it to obtain a cubane tetranuclear copper iodine cluster metal organic framework crystal material; Step 5: After the crystal material is made into a modified diaphragm, it is assembled into a lithium-sulfur battery.

2. The method for preparing a lithium-sulfur battery based on a cubane tetranuclear copper iodine cluster metal organic framework modified diaphragm coating according to claim 1, characterized in that: In the step 1, the amount of isonicotinic acid powder and N,N-dimethylformamide added is 0.5 mmol: 3-4.5 ml.

3. The method for preparing a lithium-sulfur battery based on a cubane tetranuclear copper iodine cluster metal organic framework modified diaphragm coating according to claim 1, characterized in that: In the step 1, the amount of isonicotinic acid powder and N,N-dimethylformamide added is 0.5 mmol: 3-4.5 ml.

4. The method for preparing a lithium-sulfur battery based on a cubane tetranuclear copper iodine cluster metal organic framework modified diaphragm coating according to claim 1, characterized in that: In the step 1, the amount of isonicotinic acid powder and N,N-dimethylformamide added is 0.5 mmol:4 ml.

5. The method for preparing a lithium-sulfur battery based on a cubane tetranuclear copper iodine cluster metal organic framework modified diaphragm coating according to claim 2 or 3, characterized in that: In the step 2, the molar ratio of zinc salt powder, isonicotinic acid powder and cuprous iodide is 3:1:1, and the volume ratio of N,N-dimethylformamide and ethanol solution is 2:

1.

6. The method for preparing a lithium-sulfur battery based on a cubane tetranuclear copper iodine cluster metal organic framework modified diaphragm coating according to claim 4, characterized in that: In the step 3, the zinc salt is zinc nitrate or zinc acetate.

7. The method for preparing a lithium-sulfur battery based on a cubane tetranuclear copper iodine cluster metal organic framework modified diaphragm coating according to claim 4, characterized in that: In step 4, the temperature of the oven is set to 100-120 o C, the reaction time is 48~72 hours.

8. The method for preparing a lithium-sulfur battery based on a cubane tetranuclear copper iodine cluster metal organic framework modified diaphragm coating according to claim 6, characterized in that: In step 4, the temperature of the oven is set to 100 o C, the reaction time is 72 hours.

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