Lithium-sulfur battery separator with ball-chain metal oxide structure and preparation method thereof

Abstract

The present application discloses a lithium-sulfur battery separator with a spherical chain metal oxide structure and a preparation method thereof, belonging to the technical field of membrane preparation. The metal oxide is obtained by a hydrothermal method; a conductive polymer is wrapped around the chain-shaped metal oxide to obtain a metal oxide chain-shaped ternary composite material; the metal oxide chain-shaped ternary composite material is mixed with a PVDF adhesive in a certain mass ratio, coated on a polypropylene film, and dried; and the metal oxide nanoparticles are dispersed in an ethanol solution and filtered onto the back of the separator, thereby preparing a lithium-sulfur battery separator with a spherical chain metal oxide structure. The separator can slow down the shuttle effect of polysulfides and inhibit the growth of lithium dendrites, and can be used to improve the stability and capacity of lithium-sulfur batteries.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-sulfur battery separator preparation, and in particular relates to a lithium-sulfur battery separator with a spherical chain metal oxide structure and a preparation method thereof. Background Art

[0002] Lithium-sulfur batteries are a potential choice for next-generation energy storage due to their high theoretical specific capacity (1675 mAh g -1 ), high energy density (2600Wh kg -1 ) and lower cost. However, the widespread application of lithium-sulfur batteries faces various challenges. The dissolution of lithium polysulfides (LiPSs) in organic electrolytes is a key issue, which can lead to severe capacity degradation, low Coulombic efficiency and poor rate performance. During the charge and discharge process of the battery, LiPSs will shuttle back and forth between the positive and negative electrodes, forming the so-called "shuttle effect", which will not only cause the loss of active materials, but also increase the internal resistance of the battery, thereby affecting the performance and life of the battery. The formation of lithium dendrites is another major challenge. During the charge and discharge process of the battery, lithium ions are unevenly deposited on the negative electrode, which easily forms lithium dendrites. These lithium dendrites will continue to grow and pierce the battery separator, resulting in direct contact between the positive and negative electrodes, causing a short circuit, and may even cause the battery to overheat, catch fire or explode. These problems have seriously hindered the commercial development of lithium-sulfur batteries. Summary of the Invention

[0003] Technical issues solved:

[0004] The present application addresses the deficiencies in the prior art and solves the technical problems that lithium polysulfides can cause serious capacity degradation, low Coulombic efficiency and poor rate performance, the shuttle effect causes an increase in battery internal resistance, thereby affecting battery performance and life, and lithium dendrites can cause battery overheating, fire or explosion. The application provides a lithium-sulfur battery separator with a spherical chain metal oxide structure and a preparation method thereof. The separator can inhibit the shuttle effect and lithium dendrite growth, and improve the ionic conductivity, enhance the diffusion efficiency of lithium ions, improve the cycle stability and rate performance of the lithium-sulfur battery, and improve the electrochemical performance of the lithium-sulfur battery.

[0005] Technical solution:

[0006] To achieve the above objectives, this application is implemented through the following technical solutions:

[0007] A method for preparing a lithium-sulfur battery separator having a spherical chain metal oxide structure comprises the following steps:

[0008] The first step is to dissolve 2-4 g of metal salt in 80-100 mL of deionized water according to the mass-to-volume ratio, add acid to adjust the pH value to 0.68 to obtain a metal salt solution, and then immerse 40-60 mg of chain-shaped conductive material in the metal salt solution. After stirring for 1 hour, centrifuge, wash and disperse in 50 mL of deionized water to obtain a dispersion. The dispersion is transferred to an RC-HP-CV high-pressure volume variable reactor for hydrothermal treatment. When the reactor temperature drops to room temperature, the black product after hydrothermal treatment is collected, washed three times with deionized water and anhydrous ethanol, transferred to a vacuum drying oven, and dried to obtain a precursor of a chain-shaped metal oxide.

[0009] Step 2: Grind the precursor of the chain-shaped metal oxide and place it on a quartz boat, which is then placed in a tube furnace. Then, calcinate it in air for 2 hours, and after cooling, obtain a chain-shaped metal oxide powder.

[0010] Step 3: Prepare a mixed solution of concentrated hydrochloric acid and deionized water at a volume ratio of 1:38-40, take 39-41 mL of the mixed solution and divide it into two equal parts, respectively, and place them in two beakers, respectively, record them as A and B, add 200-300 μL of conductive polymer monomer dropwise into beaker A and ultrasonically treat it, and disperse the chain-shaped metal oxide powder into the ultrasonically treated solution; add 0.5-0.7 g of ammonium persulfate to beaker B and stir to dissolve it, then add the solution dropwise into beaker A, finally stir for 4 hours, and then obtain the metal oxide chain-shaped ternary composite material after centrifugation, washing and drying;

[0011] Step 4: Dissolve 2-4 g of the metal salt in 80-100 mL of deionized water according to a mass-to-volume ratio, add acid to adjust the pH to 0.68 to obtain a metal salt solution, stir for 1 hour, centrifuge, wash, and disperse in 50 mL of deionized water to obtain a dispersion, transfer the dispersion to an RC-HP-CV high-pressure variable-volume reactor, and perform hydrothermal treatment. When the reactor temperature drops to room temperature, collect the hydrothermally treated product, wash it three times with deionized water and anhydrous ethanol, transfer it to a vacuum drying oven, and dry it to obtain a precursor of metal oxide nanoparticles;

[0012] Step 5: Grind the precursor of the metal oxide nanoparticles and place it on a quartz boat, which is then placed in a tube furnace. Then, calcine it in air for 2 hours, and after cooling, obtain the metal oxide nanoparticles.

[0013] Step 6: Preparation of slurry: magnetically stirring the metal oxide chain ball ternary composite material and polyvinylidene fluoride (PVDF) binder to form a slurry after mixing evenly;

[0014] Step 7: Use a mold to evenly apply the slurry on the commercial PP separator Celgard 2500, and then transfer the Celgard 2500 separator to a drying oven for drying to obtain a metal oxide chain ball ternary composite separator;

[0015] Step 8: Disperse 0.5 g of metal oxide nanoparticles in 50 mL of anhydrous ethanol solution according to the mass-to-volume ratio to form a uniform suspension. The suspension is then filtered using a suction flask onto the back of the metal oxide chain ball-shaped ternary composite membrane. The membrane is then transferred to a vacuum drying oven and dried at 40°C for 4 hours.

[0016] Step 9, preparation of the diaphragm: Cut the diaphragm dried in step 8 into small discs with a diameter of 19 mm to obtain a lithium-sulfur battery diaphragm with a ball-chain metal oxide structure.

[0017] Furthermore, the metal oxide is one or more of tin oxide, iron oxide, aluminum oxide, vanadium pentoxide, niobium pentoxide, and titanium dioxide; the chain-like conductive material is one or more of carbon nanotubes, carbon fibers, silver nanowires, silicon carbide nanowires, and titanium nanowires; the conductive polymer is one or more of polyaniline, polypyrrole, and polyacetylene; the metal salt is one or more of stannous chloride dihydrate, ferric chloride, aluminum chloride hexahydrate, and niobium pentachloride; the acid is concentrated hydrochloric acid, and the concentrated hydrochloric acid is 37% concentrated hydrochloric acid.

[0018] Furthermore, the hydrothermal process is specifically as follows:

[0019] Stage 1: The temperature was raised from room temperature to 120°C at a rate of 5°C / min, with the reactor volume maintained at 65 mL, for 20 minutes.

[0020] Stage 2: The temperature was raised from 120°C to 190°C at a rate of 2°C / min, and the reactor volume was increased from 65 mL to 85 mL over a period of 70 minutes.

[0021] Stage 3: The temperature was maintained at 190°C, the reactor volume was maintained at 85 mL, and the duration was 110 minutes;

[0022] The fourth stage: the temperature is naturally cooled from 190 ° C to 90-100 ° C, and the volume of the reactor is increased from 85 mL to 100 mL. The time is 75-125 minutes;

[0023] Stage 5: The temperature was lowered from 90°C to room temperature by natural cooling, and the volume of the reactor was maintained at 100 mL.

[0024] Furthermore, the centrifugation and washing process in the first, third and fourth steps is to centrifuge the solution at 6600 rpm for 15 minutes, pour off the supernatant to obtain a precipitate, add deionized water and centrifuge again, repeat twice to obtain the final precipitate product; the drying temperature in the first, third and fourth steps is 60°C and the time is 8-12 hours; the calcination temperature in the second and fifth steps is 360°C.

[0025] Furthermore, in the third step, the mass volume ratio of the chain spherical metal oxide powder, aniline and ammonium persulfate is 0.4g:200μL:0.5g; the amount of concentrated hydrochloric acid and deionized water used in the third step is 1ml and 40ml respectively; the stirring speed in the third step is 155 rpm; and the drying condition is 60°C for 12 hours.

[0026] Furthermore, in the fourth step, the mass volume ratio of stannous chloride dihydrate, hydrochloric acid and deionized water is 2g:1.4ml:80ml, and the hydrochloric acid is 37% concentrated hydrochloric acid.

[0027] Furthermore, in the sixth step, the mass ratio of the metal oxide chain ball-shaped ternary composite material to polyvinylidene fluoride (PVDF) is 8:2, and the mixture is magnetically stirred at a speed of 75 rpm for 8 hours, and the mixture is evenly mixed to form a slurry.

[0028] Furthermore, in the seventh step, the mold is a scraper, the slurry coating thickness is 60-90 microns, and it is dried in a drying oven at 40° C. for 10 hours to obtain a metal oxide chain ball-shaped ternary composite material diaphragm.

[0029] Furthermore, in the eighth step, the mass volume ratio of SnO2 nanoparticles to anhydrous ethanol solution is 0.5g:50mL; 1.5mL of the suspension is used for each filtration, and the diameter of the filtration flask is 4cm.

[0030] The present application also discloses a lithium-sulfur battery separator having a spherical chain metal oxide structure obtained by any of the above-mentioned preparation methods, wherein the separator on the sulfur cathode side is coated with a metal oxide chain spherical ternary composite material; the metal oxide chain spherical ternary composite material can catalyze the conversion of polysulfides, inhibit the shuttle effect, and improve the diffusion and migration of lithium ions; the lithium anode side of the separator is metal oxide nanoparticles, which can make the lithium anode electric field uniformly distributed and inhibit the irregular growth of lithium dendrites.

[0031] Beneficial effects:

[0032] The present application provides a lithium-sulfur battery separator having a spherical chain metal oxide structure and a preparation method thereof, which has the following advantages compared with the prior art:

[0033] 1. The lithium-sulfur battery separator having a spherical chain metal oxide structure prepared in the present application, wherein the chain conductive material on the sulfur cathode side serves as a conductive framework providing a fast electron / ion transmission channel. The spherical metal oxide is a polar material with a small particle size and good dispersibility. The modified chain conductive material can provide more active sites, can effectively chemically adsorb polysulfides, and can significantly inhibit the shuttling effect of polysulfides between the positive and negative electrodes;

[0034] 2. The lithium-sulfur battery separator with a spherical chain metal oxide structure prepared in this application has a better hydrophilicity for the electrolyte on the sulfur cathode side, which enables the electrolyte to diffuse and migrate more quickly, enhances the compatibility with the electrolyte, ensures more efficient migration of lithium ions, accelerates the kinetics of the electrochemical reaction, reduces polarization, and improves the lithium ion conductivity of the battery;

[0035] 3. The lithium-sulfur battery separator with a spherical chain metal oxide structure prepared in this application has metal oxide nanoparticles uniformly deposited on the anode side, which ensures a more uniform distribution of the interfacial electric field, uniformly distributes the lithium ion concentration, promotes uniform lithium deposition, and reduces dendrite growth;

[0036] 4. The fast ion transport channels on the cathode side and the uniform electric field distribution on the anode side jointly optimize the transport and distribution of lithium ions within the battery. At the same time, the entire structure catalyzes the conversion of polysulfides and accelerates the electrochemical reaction kinetics, enabling more efficient energy conversion during the battery's charge and discharge processes, further improving battery performance.

[0037] 5. Dynamic filling degree regulation of dispersibility Hydrothermal technology effectively improves the dispersibility of materials. By rationally regulating the pressure, volume and other parameters of the reaction system, metal oxide nanoparticles can be more evenly distributed on carbon nanotubes. For example, during the hydrothermal process, the precise control of temperature and volume at different stages avoids particle agglomeration caused by excessive local concentration, thereby making the material present a better dispersed state. The dynamic hydrothermal method provides a high degree of process controllability and can flexibly adjust parameters such as filling degree according to the characteristics of the material, thereby achieving precise control of the final material properties. For example, by adjusting the pressure and volume changes during the hydrothermal process, the nucleation and growth process of quantum dots can be controlled, making their size distribution more uniform and the dispersion higher, thereby improving the adsorption and catalytic properties of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 is a scanning electron microscope (SEM) image of the metal oxide chain ball-shaped ternary composite material obtained in Example 1 of the present application;

[0039] Figure 2This is a scanning electron microscope (SEM) image of the metal oxide nanoparticles obtained in Example 1 of the present application. DETAILED DESCRIPTION

[0040] To facilitate understanding of the present invention, the principles and features of the present invention are fully and carefully described below in conjunction with the accompanying drawings and preferred embodiments. The embodiments are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0041] All raw materials of the present invention are not particularly limited in their sources and can be purchased from the market or prepared according to conventional methods well known to those skilled in the art.

[0042] To further illustrate the present invention, the lithium-sulfur battery separator having a spherical chain metal oxide structure and the preparation method thereof provided by the present invention are described in detail below with reference to the examples.

[0043] Example 1

[0044] A method for preparing a lithium-sulfur battery separator having a spherical chain metal oxide structure, comprising the following steps:

[0045] The first step: dissolving 2 g of stannous chloride dihydrate in 80 mL of deionized water, adding 1.4 mL of 37% concentrated hydrochloric acid, adjusting the pH value to 0.68 to obtain a stannous chloride dihydrate solution, and then immersing 40 mg of carbon nanotubes in the stannous chloride dihydrate solution. After stirring for 1 hour, centrifugation, washing and dispersion in 50 mL of deionized water to obtain a dispersion. The dispersion is transferred to a RC-HP-CV high-pressure volume variable reactor and hydrothermally treated according to the method in Table 1. When the reactor temperature drops to room temperature, the black product after hydrothermal treatment is collected, washed three times with deionized water and anhydrous ethanol, transferred to a vacuum drying oven, and dried at 60°C for 12 hours to obtain a SnO2 precursor; the centrifugation and washing process is to centrifuge the solution at 6600 rpm for 15 minutes, pour off the supernatant to obtain a precipitate, add deionized water and centrifuge, repeat twice to obtain the final precipitate product;

[0046] Step 2: The SnO2 precursor is then ground and placed on a quartz boat, which is then placed in a tube furnace. The mixture is then calcined at 360°C for 2 hours in an air environment, and then cooled to obtain a chain-shaped metal oxide powder.

[0047] Step 3: Prepare a mixed solution of concentrated hydrochloric acid and deionized water by adding 1 mL of concentrated hydrochloric acid and 38 mL of deionized water. Take the mixed solution and place it in two beakers, respectively designated A and B. Add 200 μL of polyaniline dropwise into beaker A and ultrasonically treat it. Disperse the chain-shaped metal oxide powder into the ultrasonically treated solution. Add 0.5 g of ammonium persulfate to beaker B and stir to dissolve it. Then add the solution dropwise to beaker A and stir it at a speed of 155 rpm for 4 hours. Centrifuge the solution at 6600 rpm for 15 minutes, discard the supernatant, and obtain a precipitate. Add deionized water and centrifuge again. Repeat twice to obtain the final precipitated product, a metal oxide chain-shaped ternary composite material.

[0048] Figure 1 This is a scanning electron microscope (SEM) image of the metal oxide chain ball ternary composite material obtained in Example 1 of the present invention. PANI wraps the surface of SnO2-CNT, thereby increasing the diameter of the metal oxide chain ball ternary composite material to 25-60nm. The resulting rough surface with many small protruding particles leads to a larger specific surface area and increased catalytic sites.

[0049] Step 4: Dissolve 2 g of stannous chloride dihydrate in 80 mL of deionized water, add 1.4 mL of 37% concentrated hydrochloric acid, adjust the pH to 0.68, stir for 1 hour, centrifuge the solution at 6600 rpm for 15 minutes, pour off the supernatant to obtain a precipitate, add deionized water and centrifuge, repeat twice to obtain the final precipitate product, and disperse it in 50 mL of deionized water, then transfer it to a RC-HP-CV high-pressure volume variable reactor and perform hydrothermal treatment according to Table 1; when the reactor temperature drops to room temperature, collect the white product after hydrothermal treatment, wash it three times with deionized water and anhydrous ethanol, transfer it to a vacuum drying oven, and dry it at 60 ° C for 12 hours to obtain a SnO2 precursor;

[0050] Step 5: Grind the SnO2 precursor and place it on a quartz boat, then place the quartz boat in a tube furnace. Then, calcine it at 360°C for 2 hours in an air environment. After cooling, SnO2 nanoparticles can be obtained.

[0051] Figure 2 This is a scanning electron microscope (SEM) image of SnO2 obtained in Example 1 of the present invention. The prepared SnO2 nanoparticles show a spherical morphology with a diameter of about 5-10 nm.

[0052] Step 6: Preparation of slurry: 0.8 g of the metal oxide chain ball ternary composite material and 0.2 g of PVDF binder were magnetically stirred at a speed of 75 rpm for 8 hours to form a slurry after mixing;

[0053] Step 7: Use a scraper to evenly apply the slurry on the commercial PP separator Celgard 2500. The slurry coating thickness is 60-90 microns. Then transfer Celgard 2500 to a vacuum drying oven and dry it at 40°C for 10 hours to obtain a metal oxide chain ball ternary composite separator.

[0054] Step 8: 0.5 g of SnO2 nanoparticles were evenly dispersed in 50 mL of anhydrous ethanol solution to form a uniform suspension. The suspension was then filtered using a suction flask onto the back of the metal oxide chain ball-shaped ternary composite membrane. The membrane was then transferred to a vacuum drying oven and dried at 40 ° C for 4 hours.

[0055] Step 9: Preparation of the diaphragm: Cut the dried diaphragm into small discs with a diameter of 19 mm to obtain a lithium-sulfur battery diaphragm with a ball-chain metal oxide structure.

[0056] Preparation of the positive electrode: Sublimed sulfur, conductive carbon black, and binder polyvinylidene fluoride (PVDF) were ground and stirred at 75 rpm for 6 hours to form a slurry. The slurry was evenly coated onto aluminum foil using a mold. The foil was then dried in a vacuum drying oven at 50°C for 10 hours. The dried foil was cut into small discs with a diameter of 16 mm. These discs became the positive electrode.

[0057] Preparation of lithium-sulfur batteries: The prepared positive electrode sheet and circular Celgard 2500 were used as the separator, and the commercial metal lithium sheet was used as the negative electrode. A DOL / DME (volume ratio of 1:1) electrolyte of 0.1M LiNO3+1M LiTFSI was added and the 2032 button cell was assembled in an argon-filled glove box with a water and oxygen content of less than 0.1ppm. After standing for 12 hours, the assembled battery was tested for long-cycle electrochemical performance on a battery test cabinet (Neware BTS 7.6.0).

[0058] The present invention discloses a lithium-sulfur battery separator having a spherical chain metal oxide structure and a preparation method thereof. The hydrothermal process comprises placing a chain conductive material and a metal salt in a reaction device with a controllable volume for hydrothermal treatment. The hydrothermal process is divided into five stages, as shown in Table 1.

[0059] Metal oxide nanoparticles need to be distributed as evenly as possible on the chain-like conductive material. In lithium-sulfur battery applications, evenly distributed metal oxide nanoparticles can provide adsorption sites on a larger surface area. Metal oxides can make full use of the larger surface area of ​​the chain-like conductive material, thereby more effectively adsorbing LiPSs. Evenly distributed metal oxide nanoparticles can form a relatively stable and uniform catalytic environment on the chain-like conductive material. For the catalytic conversion process of polysulfides, a uniform catalytic environment helps to improve the catalytic efficiency. If the metal oxide nanoparticles are unevenly distributed, it may cause the local catalytic activity to be too high or too low, affecting the overall catalytic conversion effect of polysulfides.

[0060] When metal oxide nanoparticles are evenly distributed on the chain-like conductive material, a more stable interaction between the particles and the chain-like conductive material is achieved. This uniform distribution results in a more uniform binding force between the particles and the chain-like conductive material, enabling better resistance to external stress and strain, and improving the structural stability of the material. This prevents agglomeration of metal oxide nanoparticles due to localized high concentrations. Particle agglomeration can reduce the material's specific surface area, affecting its adsorption and catalytic properties, and potentially damaging its structural stability.

[0061] Generally speaking, when the pressure is low, the molecular distances in the reaction system are relatively large, and the intermolecular interactions are weak. This may lead to a slower diffusion rate of the reactants and a relatively slow nucleation and growth process of the quantum dots. The number of gas molecules in the reaction system is small, and the gas phase space is relatively large. This may accelerate the volatilization rate of the solute in the liquid phase, resulting in unstable solute concentration in the quantum dot growth environment, affecting the nucleation and growth process of the quantum dots, making their size distribution uneven and their dispersion decreased. Low pressure may result in fewer nucleation sites for quantum dots and a relatively insufficient nucleation process. This will result in a relatively small number of quantum dots and an uneven distribution. During the growth process, due to the slow diffusion rate of the reactants and the weak interaction between quantum dots, the growth of quantum dots may be incomplete or uneven, thereby affecting their dispersion.

[0062] Under high pressure, the molecular distances in the reaction system decrease, and the intermolecular interactions strengthen. This may accelerate the diffusion of reactants and, accordingly, the nucleation and growth of quantum dots. High pressure compresses the gas phase, increasing the number of molecules in the gas phase and slowing the volatilization of solutes in the liquid phase, resulting in a relatively stable solute concentration in the quantum dot growth environment. This promotes uniform nucleation and growth of quantum dots and improves their dispersion. High pressure may increase the number of quantum dot nucleation sites, promoting the large-scale nucleation of quantum dots. However, if the nucleation rate is too rapid, it may lead to collisions and aggregation between quantum dots, reducing dispersion.

[0063] Table 1 Temperature and time conditions of each stage of hydrothermal

[0064]

[0065]

[0066] Example 2

[0067] The method is the same as Example 1, except that the metal oxide is iron oxide, iron oxide quantum dots are hydrothermally generated, and the chain-like conductive material is silver nanowires.

[0068] Example 3

[0069] The method is the same as Example 1, except that the metal oxide is aluminum oxide, aluminum oxide quantum dots are hydrothermally generated, and the chain-like conductive material is carbon fiber.

[0070] Example 4

[0071] The same as Example 1, except that the conductive polymer is polypyrrole, the polypyrrole conductive material is used for coating, and the chain-shaped conductive material is carbon nanotubes.

[0072] Example 5

[0073] The same as Example 1, except that the metal oxide is niobium pentoxide, the conductive polymer is polyacetylene, and the chain-like conductive material is carbon fiber.

[0074] Comparative Examples 1-4

[0075] The same as Example 1-4, except that the dynamic gas phase atmosphere method was not used for control during the hydrothermal treatment. The hydrothermal temperature was 190° C. and the heating rate was 5° C. / min.

[0076] The final prepared metal oxide chain ball-shaped ternary composite material was characterized, and the life and performance of the lithium-sulfur battery assembled with it were tested.

[0077] Table 2 Evaluation of the starting and ending capacity and cycle life of the ternary composite lithium-sulfur battery at 1C for the solutions used in the examples of the present invention and the prepared metal oxide chain balls

[0078]

[0079] Table 3 Evaluation of the start-stop capacity and cycle life of the ternary composite lithium-sulfur battery at 1C for the solution used in the examples of the present invention and the prepared metal oxide chain ball-shaped battery.

[0080]

[0081] Analysis of the Examples and Comparative Examples: By comparing Table 2 and Table 3, it can be found that the materials in the Examples using the dynamic filling degree control dispersibility hydrothermal technology generally outperformed the control group in terms of dispersibility. Specifically, the materials in Table 2 exhibited a better dispersion state, while the materials in the control group in Table 3 had poor dispersibility. This shows that the dynamic filling degree control dispersibility hydrothermal technology effectively improved the dispersibility of the materials, thereby significantly improving the performance of the materials. At the same time, the dynamic filling degree control dispersibility hydrothermal technology helps to better control the performance of the materials. The regulated materials in Table 2 showed significant improvements in dispersibility and performance compared to the unregulated materials in Table 3, indicating that this technology can achieve a better balance between high performance and good dispersibility while improving dispersibility. This means that the dynamic filling degree control dispersibility hydrothermal technology does not sacrifice other material properties, but instead better maintains the stability and performance of the material through reasonable filling degree control. The dynamic filling degree control dispersibility hydrothermal technology provides a high degree of process controllability, and can flexibly adjust parameters such as filling degree according to the characteristics of the material, thereby achieving precise control of the final material properties. This makes this process have broad application potential and can adapt to complex and changing material preparation needs.

[0082] Test method description:

[0083] (1) The constant current charge and discharge performance of the lithium-sulfur battery was tested using a charge and discharge instrument from Shenzhen Xinwei Co., Ltd. The test temperature in this article was the ambient temperature of 25°C, the charge and discharge voltage cutoff range was 1.7-2.8V, and the charge and discharge current was set to 1C. The starting capacity is the discharge capacity at the initial discharge of the battery, and the end capacity is the previous discharge capacity when the battery cannot be charged or discharged normally.

[0084] (2) Life cycle: Each charge and discharge cycle is a cycle. When the lithium-sulfur battery cannot complete a charge and discharge process normally, or when the capacity drops rapidly by more than 50% within 5 cycles, the life of the lithium-sulfur battery can be determined to have ended. This rapid capacity drop usually means that a serious side reaction has occurred inside the battery or the structure has rapidly deteriorated, resulting in a sharp decline in battery performance and no longer being able to meet the needs of practical applications. Through such strict judgment criteria, the service life of the lithium-sulfur battery can be accurately determined.

Claims

1. A method for preparing a lithium-sulfur battery separator having a chain-shaped metal oxide structure, characterized in that: Here are the steps: Step 1: Dissolve 2-4 g of metal salt in 80-100 mL of deionized water according to a mass-to-volume ratio, add acid to adjust the pH to 0.68 to obtain a metal salt solution, then immerse 40-60 mg of chain-shaped conductive material in the metal salt solution, stir for 1 hour, centrifuge, wash, and disperse in 50 mL of deionized water to obtain a dispersion, transfer the dispersion to a high-pressure variable-volume reactor, and perform hydrothermal treatment. When the reactor temperature drops to room temperature, collect the black product after hydrothermal treatment, wash it three times with deionized water and anhydrous ethanol, transfer it to a vacuum drying oven, and dry it to obtain a precursor of a chain-shaped metal oxide; Step 2: Grind the precursor of the chain-shaped metal oxide and place it on a quartz boat, which is then placed in a tube furnace. Then, calcinate it in air for 2 hours, and after cooling, obtain a chain-shaped metal oxide powder. Step 3: Prepare a mixed solution of concentrated hydrochloric acid and deionized water at a volume ratio of 1:38-40, take 39-41 mL of the mixed solution and divide it into two equal parts, respectively, and place them in two beakers, respectively, record them as A and B, add 200-300 μL of conductive polymer monomer dropwise into beaker A and ultrasonically treat it, and disperse the chain-shaped metal oxide powder into the ultrasonically treated solution; add 0.5-0.7 g of ammonium persulfate to beaker B and stir to dissolve it, then add the solution dropwise into beaker A, finally stir for 4 hours, and then obtain the metal oxide chain-shaped ternary composite material after centrifugation, washing and drying; Step 4: Dissolve 2-4 g of the metal salt in 80-100 mL of deionized water according to a mass-to-volume ratio, add acid to adjust the pH to 0.68 to obtain a metal salt solution, stir for 1 hour, centrifuge, wash, and disperse in 50 mL of deionized water to obtain a dispersion. The dispersion is transferred to a high-pressure variable-volume reactor for hydrothermal treatment. When the reactor temperature drops to room temperature, the hydrothermally treated product is collected, washed three times with deionized water and anhydrous ethanol, and transferred to a vacuum drying oven for drying to obtain a metal oxide quantum dot precursor. Step 5: Grind the precursor of the metal oxide quantum dots and place it on a quartz boat, which is then placed in a tube furnace. Then, calcine it in air for 2 hours, and after cooling, the metal oxide quantum dots are obtained. Step 6: Preparation of slurry: magnetically stirring the metal oxide chain ball ternary composite material and polyvinylidene fluoride (PVDF) binder to form a slurry after mixing evenly; Step 7: Use a mold to evenly apply the slurry on the commercial PP separator Celgard 2500, and then transfer the Celgard 2500 separator to a drying oven for drying to obtain a metal oxide chain ball ternary composite separator; Step 8: Disperse 0.5 g of metal oxide quantum dots uniformly in 50 mL of anhydrous ethanol solution according to the mass-to-volume ratio to form a uniform suspension. Filter the suspension onto the back of the metal oxide chain ball-shaped ternary composite membrane using a suction flask. Then transfer the membrane to a vacuum drying oven and dry it at 40°C for 4 hours. Step 9: Making a diaphragm: Cut the diaphragm dried in step 8 into small discs with a diameter of 19 mm to obtain a lithium-sulfur battery diaphragm with a chain-shaped metal oxide structure; The hydrothermal process is specifically as follows: Stage 1: The temperature was raised from room temperature to 120°C at a rate of 5°C / min, with the reactor volume maintained at 65 mL, for 20 minutes. Stage 2: The temperature was raised from 120°C to 190°C at a rate of 2°C / min, and the reactor volume was increased from 65 mL to 85 mL over a period of 70 minutes. Stage 3: The temperature was maintained at 190°C, the reactor volume was maintained at 85 mL, and the duration was 110 minutes; The fourth stage: the temperature is naturally cooled from 190 ° C to 90-100 ° C, and the volume of the reactor is increased from 85 mL to 100 mL. The time is 75-125 minutes; Stage 5: The temperature was lowered from 90°C to room temperature by natural cooling, and the volume of the reactor was maintained at 100 mL.

2. The method for preparing a lithium-sulfur battery separator having a chain-shaped metal oxide structure according to claim 1, characterized in that: The metal oxide is one or more of tin oxide, iron oxide, aluminum oxide, vanadium pentoxide, niobium pentoxide, and titanium dioxide; the chain-shaped conductive material is one or more of carbon nanotubes, carbon fibers, silver nanowires, silicon carbide nanowires, and titanium nanowires; the conductive polymer is one or more of polyaniline, polypyrrole, and polyacetylene; the metal salt is one or more of stannous chloride dihydrate, ferric chloride, aluminum chloride hexahydrate, and niobium pentachloride; the acid is concentrated hydrochloric acid, and the concentrated hydrochloric acid is 37% concentrated hydrochloric acid by mass.

3. The method for preparing a lithium-sulfur battery separator having a chain-shaped metal oxide structure according to claim 1, characterized in that: The centrifugation and washing process in the first, third and fourth steps is to centrifuge the solution at 6600 rpm for 15 minutes, discard the supernatant to obtain a precipitate, add deionized water and centrifuge again, repeat twice to obtain the final precipitate product; The drying temperature in the first, third and fourth steps is 60° C. and the drying time is 8-12 h; the calcination temperature in the second and fifth steps is 360° C.

4. The method for preparing a lithium-sulfur battery separator having a chain-shaped metal oxide structure according to claim 1, wherein: In the third step, the mass volume ratio of the chain spherical metal oxide powder, aniline and ammonium persulfate is 0.4g:200μL:0.5g; the amounts of concentrated hydrochloric acid and deionized water used in the third step are 1ml and 40ml respectively; the stirring speed in the third step is 155 rpm; and the drying condition is 60°C for 12 hours.

5. The method for preparing a lithium-sulfur battery separator having a chain-shaped metal oxide structure according to claim 1, wherein: In the fourth step, the mass volume ratio of the metal salt, the acid and the deionized water is 2g:1.4ml:80ml, and the hydrochloric acid is concentrated hydrochloric acid with a mass concentration of 37%.

6. The method for preparing a lithium-sulfur battery separator having a chain-shaped metal oxide structure according to claim 1, wherein: In the sixth step, the mass ratio of the metal oxide chain ball ternary composite material to polyvinylidene fluoride (PVDF) is 8:2, and magnetic stirring is performed at a speed of 75 rpm for 8 hours to prepare a slurry after uniform mixing.

7. The method for preparing a lithium-sulfur battery separator having a chain-shaped metal oxide structure according to claim 1, characterized in that: In the seventh step, the mold is a scraper, the slurry coating thickness is 60-90 μm, and the slurry is dried in a drying oven at 40° C. for 10 hours to obtain a metal oxide chain ball-shaped ternary composite material diaphragm.

8. The method for preparing a lithium-sulfur battery separator having a chain-shaped metal oxide structure according to claim 1, characterized in that: In the eighth step, the mass volume ratio of the metal oxide quantum dots to the anhydrous ethanol solution is 0.5 g:50 mL; 1.5 mL of the suspension is used for each filtration, and the diameter of the filtration flask is 4 cm.

9. A lithium-sulfur battery separator having a chain-shaped metal oxide structure obtained by the preparation method according to any one of claims 1 to 8, characterized in that: The sulfur cathode-side separator is coated with a metal oxide chain ball ternary composite material; the metal oxide chain ball ternary composite material can catalyze the conversion of polysulfides, inhibit the shuttle effect, and improve the diffusion and migration of lithium ions; The lithium anode side of the diaphragm is made of metal oxide quantum dots, which can make the lithium anode electric field uniformly distributed and inhibit the irregular growth of lithium dendrites.

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