A method for manufacturing a lithium-sulfur battery

Abstract

The application relates to a preparation method of a lithium-sulfur battery, and relates to a preparation method of a lithium-sulfur battery with a double-conduction high charge transfer rate as a positive electrode material. The application aims to solve the problems of poor sulfur conductivity in the positive electrode of the lithium-sulfur battery prepared by the existing method and the shuttle effect caused by polysulfide dissolution. The method is as follows: 1. preparation of nanometer spherical lithium lanthanum titanium oxide; 2. preparation of porous carbon coated nanometer spherical lithium lanthanum titanium oxide; 3. preparation of a lithium-sulfur battery positive electrode material of porous carbon coated nanometer spherical lithium lanthanum titanium oxide loaded with sulfur; and 4. assembly of the lithium-sulfur battery. The porous carbon coated nanometer spherical lithium lanthanum titanium oxide prepared by the method is used as the positive electrode of the lithium-sulfur battery, a positive electrode carrier with a mixed ion / electron double-conduction type is adopted to construct a double-phase interface, the rate of charge transfer on the surface of the positive electrode material is enhanced, the utilization rate of sulfur is improved, the preparation process is simple, the cost is low, the operation is safe, and the application is suitable for commercial application. The application is applied to the field of lithium-sulfur batteries.

Description

Technical Field

[0001] This invention relates to a method for preparing a lithium-sulfur battery. Background Technology

[0002] Lithium-sulfur batteries have a high theoretical energy density (2600 Wh / kg). -1 Lithium-sulfur batteries, with their inherent advantages of low cost and environmental friendliness, are considered one of the best alternatives to lithium-ion batteries (LIBs). However, current lithium-sulfur batteries are still hampered by a series of problems, such as the poor conductivity of elemental sulfur and the discharge product lithium sulfide, as well as the "shuttle effect" caused by soluble lithium polysulfides (LiPS), which lead to slow redox kinetics and rapid capacity decay, hindering their commercialization. Therefore, addressing the problems of poor conductivity of cathode materials, the inability to simultaneously conduct ions and electrons, low utilization of active materials, slow efficiency of charge transfer on electrode material surfaces, and the shuttle effect caused by polysulfide dissolution in lithium-sulfur batteries is currently a research hotspot. Summary of the Invention

[0003] The purpose of this invention is to address the problems of poor insulation of sulfur, low charge transfer efficiency of electrode materials, and shuttle effect in lithium-sulfur batteries, and to provide a method for preparing lithium-sulfur batteries using porous carbon-coated nanospheres of lithium lanthanum titanium oxide as the lithium-sulfur cathode material, characterized by dual ion / electron conductivity. The method for preparing a lithium-sulfur battery according to this invention is carried out according to the following steps:

[0004] I. Preparation of Nanospheres of Lithium Lanthanum Titanium Oxide

[0005] Dissolve 3–8 mmol of La(NO3)3·6H2O, 3–8 mmol of LiNO3, and citric acid in 20–40 ml of ethanol. Stir at room temperature for 1–3 h, then add 8–10 mmol of tetrabutyl titanate and 0.1 mol of ethylene glycol sequentially. Continue stirring, transfer to a high-pressure reactor, and perform hydrothermal synthesis at 120–160 °C. After cooling, open the reactor, wash the suspension in the reactor with deionized water by centrifugation, and dry in an oven at 40–60 °C for 10–12 h. Anneal the obtained powder in a tube furnace at 500–700 °C for 2–4 h to obtain Li. 0.5 La 0.5 TiO3 nanospheres, namely nano-spherical lithium lanthanum titanium oxide;

[0006] II. Preparation of porous carbon-coated spherical lithium lanthanum titanium oxide nanospheres

[0007] 1–3 g of nano-spherical lithium lanthanum titanium oxide was ultrasonically dispersed in 20–40 ml of deionized water to obtain a lithium lanthanum titanium oxide suspension. 2–4 g of hexadecyltrimethylammonium bromide, 1–3 g of resorcinol, 20–40 ml of ethanol, and 0.5–0.8 ml of ammonia were added sequentially to the lithium lanthanum titanium oxide suspension and stirred until homogeneous. Then, 2–4 ml of formaldehyde was added, and the mixture was stirred at 30–35 °C for 30–60 min. The mixture was washed 6–8 times by centrifugation with deionized water and dried in an oven at 40–60 °C for 10–12 h. The resulting powder was annealed in a tube furnace under N2 protection at 500–700 °C to obtain porous carbon-coated Li. 0.5 La 0.5 TiO3 nanospheres are porous carbon-coated nanospheres of lithium lanthanum titanium oxide as positive electrode carrier material for lithium-sulfur batteries.

[0008] III. Preparation of Porous Carbon-Coated Spherical Lithium Lanthanum Titanium Oxide Sulfur-Loaded Lithium-Sulfur Battery Cathode Material: Elemental sulfur and the porous carbon-coated spherical lithium lanthanum titanium oxide lithium-sulfur battery cathode carrier material obtained in step II were ground in a mortar for 1–2 hours at a mass ratio of 1:7 to 3:7. The mixture was then melt-diffused at 150–160°C for 10–12 hours under nitrogen protection. After cooling to room temperature, the porous carbon-coated spherical lithium lanthanum titanium oxide sulfur-loaded lithium-sulfur battery cathode material was obtained. The lithium-sulfur battery cathode material with nano-spherical lithium lanthanum titanium oxide loaded with sulfur was dispersed with acetylene black and polyvinylidene fluoride in 1-4 ml of N-methylpyrrolidone solvent at a mass ratio of 8:1:1. The mixture was stirred to obtain a uniform slurry, which was then coated onto an aluminum foil current collector using a doctor blade and dried in a drying oven at 20-60℃ to obtain an ion / electron dual-conductivity lithium-sulfur battery cathode. The obtained lithium-sulfur battery cathode was then cut into circular slices with a diameter of 14 mm using a coin cell slicing machine for later use.

[0009] IV. Assembly of Lithium-Sulfur Batteries

[0010] The lithium-sulfur battery cathode material obtained in step three was dried in an oven. The battery was then assembled under a helium atmosphere in a vacuum glove box. The coin cell was assembled in the following order: 2025 coin cell cathode shell, 14 mm diameter lithium-sulfur battery cathode, 16 mm diameter Celgard 2500 separator, 20–50 μl organic electrolyte, 15.6 mm diameter lithium sheet, and 2025 coin cell anode shell. The coin cell was then sealed with a sealing machine to complete the battery assembly, which was then used for electrochemical performance testing.

[0011] Furthermore, the concentration of citric acid in step one is 10-30 mmol to obtain nano-spherical lithium lanthanum titanium oxide. Citric acid is a strong complexing agent, and the citric acid-ethylene glycol system forms stable chelates with lithium, lanthanum and titanium ions. In the subsequent solvothermal process, this is beneficial for the precipitates to have a spherical morphology with low surface energy.

[0012] Furthermore, the continued stirring time mentioned in step one is 20 to 40 minutes, which is conducive to the thorough stirring to form a citric acid-ethylene glycol system, so that La(NO3)3, LiNO3 and tetrabutyl titanate are uniformly dissolved in the citric acid-ethylene glycol system and form complexes with it.

[0013] Furthermore, the hydrothermal synthesis in step one takes 6 hours. The hydrothermal synthesis reaction is completed within a fixed time of 6 hours, forming a fixed phase composition.

[0014] Furthermore, the suspension in the washing vessel is centrifuged with deionized water 6 to 10 times as described in step one to thoroughly wash away impurities such as nitrate ions.

[0015] Furthermore, the annealing time mentioned in step two is 2-4 hours, and a fixed annealing time will form a fixed Li 0.5 La 0.5 TiO3 pure phase.

[0016] Furthermore, the stirring time mentioned in step three is 10 to 12 hours. Thorough stirring is a homogenization process, which determines the uniform distribution of the positive electrode material to avoid the formation of lithium dendrites in the negative electrode.

[0017] Furthermore, the drying time mentioned in step three is 10 to 12 hours to ensure thorough drying, remove moisture, prevent lithium from reacting with water, improve battery performance, and avoid safety hazards.

[0018] Furthermore, the thickness of the coating applied to the aluminum foil current collector by the scraper in step three is 80–200 μm to ensure a suitable surface current density.

[0019] Furthermore, in step four, the lithium-sulfur battery cathode material obtained in step three is placed in an oven at 50–70°C and dried for 20–40 minutes to prevent moisture from damaging the battery performance.

[0020] The gain effect of the present invention:

[0021] First, this invention uses lanthanum nitrate, lithium nitrate, citric acid, tetrabutyl titanate, and ethylene glycol as raw materials. Through hydrothermal annealing, spherical lithium lanthanum titanium oxide nanomaterials are obtained. Citric acid acts as a complexing agent with multidentate ligands. The citric acid-ethylene glycol system forms stable chelates with lithium, lanthanum, and titanium ions. The citric acid-ethylene glycol system, in conjunction with lanthanum, titanium, and lithium ions, undergoes a hydrothermal reaction to form spherical nanomaterials. During the subsequent hydrothermal synthesis, due to solvothermal activity, to minimize system energy, the precipitated phase tends to have a spherical morphology with low surface energy. During calcination, the citric acid-ethylene glycol system thermally decomposes, leaving pores. Thus, spherical lithium lanthanum titanium oxide nanomaterials are formed. Simultaneously, the significant volume shrinkage during the calcination and crystallization of lithium lanthanum titanium oxide also promotes pore formation. The porous structure can confine and adsorb sulfur and polysulfides, better restricting polysulfide shuttle movement, which is beneficial for sulfur encapsulation, thereby improving the cycle performance of lithium-sulfur batteries.

[0022] Secondly, a porous carbon-coated spherical lithium lanthanum titanium oxide nanomaterial with ion / electron dual-conductivity was employed. The combined use of lithium lanthanum titanium oxide and porous carbon as a lithium-sulfur battery carrier demonstrated enhanced charge transfer behavior at the interface between sulfur and the porous carbon-coated spherical lithium lanthanum titanium oxide nanomaterial compared to traditional three-phase interfaces. The spherical coating expands the active surface area, thereby accelerating the electrochemical reaction process of sulfur. This process exhibits high sulfur utilization and excellent yield. In practical applications, it promotes charge transfer and suppresses the shuttle effect of polysulfides, thus improving the sulfur loading capacity of the carrier.

[0023] Finally, the positive electrode of the lithium-sulfur battery is cut into 14mm diameter discs using a coin cell slicing machine. These discs are then combined with a 15.6mm diameter negative electrode and a 16mm diameter separator to prevent open circuits and ensure battery safety. The manufacturing process of this invention is simple, low-cost, and produces batteries with excellent performance, making it suitable for large-scale production and commercialization. Attached Figure Description

[0024] To more clearly illustrate the modified results of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0025] Figure 1 A flowchart illustrating the preparation process of porous carbon-coated spherical lithium lanthanum titanium oxide nanoparticles for a lithium-sulfur battery.

[0026] Figure 2 SEM image of nanosphere lithium lanthanum titanium oxide for a method of preparing lithium-sulfur batteries;

[0027] Figure 3 XRD pattern of nanosphere lithium lanthanum titanium oxide for a method of preparing lithium-sulfur batteries;

[0028] Figure 4SEM image of porous carbon-coated nanosphere lithium lanthanum titanium oxide carrier material in a 15 mmol citric acid system for the preparation of a lithium-sulfur battery;

[0029] Figure 5 SEM image of carbon-coated lanthanum titanium oxide nanospheres in a 5 mmol citric acid system for the preparation of a lithium-sulfur battery;

[0030] Figure 6 Charge-discharge curves of carbon-coated spherical lithium lanthanum titanium oxide cathode material in a 5 mmol citric acid system for the preparation of a lithium-sulfur battery.

[0031] Figure 7 The charge-discharge curves of a lithium-sulfur battery with porous carbon-coated nanospheres of lithium lanthanum titanium oxide as the positive electrode in a 15 mmol citric acid system as a preparation method for a lithium-sulfur battery.

[0032] Figure 8 This is a diagram illustrating the practical application of a lithium-sulfur battery, which is a method for preparing lithium-sulfur batteries. Detailed Implementation

[0033] The following embodiments further illustrate the above-mentioned content of the present invention in detail. However, the subject matter of the present invention is not limited to the following embodiments, and all technologies implemented based on the above-mentioned content of the present invention fall within the scope of the present invention.

[0034] Experimental drugs

[0035]

[0036]

[0037] Specific Implementation Method 1: The preparation method of a lithium-sulfur battery in this embodiment is carried out according to the following steps:

[0038] I. Preparation of Nanospheres of Lithium Lanthanum Titanium Oxide

[0039] Dissolve 3–8 mmol of La(NO3)3·6H2O, 3–8 mmol of LiNO3, and citric acid in 20–40 ml of ethanol. Stir at room temperature for 1–3 h, then add 8–10 mmol of tetrabutyl titanate and 0.1 mol of ethylene glycol sequentially. Continue stirring, transfer to a high-pressure reactor, and perform hydrothermal synthesis at 120–160 °C. After cooling, open the reactor, wash the suspension in the reactor with deionized water by centrifugation, and dry in an oven at 40–60 °C for 10–12 h. Anneal the obtained powder in a tube furnace at 500–700 °C for 2–4 h to obtain Li. 0.5 La 0.5 TiO3 nanospheres, namely nano-spherical lithium lanthanum titanium oxide;

[0040] II. Preparation of porous carbon-coated spherical lithium lanthanum titanium oxide nanospheres

[0041] 1–3 g of nano-spherical lithium lanthanum titanium oxide was ultrasonically dispersed in 20–40 ml of deionized water to obtain a lithium lanthanum titanium oxide suspension. 2–4 g of hexadecyltrimethylammonium bromide, 1–3 g of resorcinol, 20–40 ml of ethanol, and 0.5–0.8 ml of ammonia were added sequentially to the lithium lanthanum titanium oxide suspension and stirred until homogeneous. Then, 2–4 ml of formaldehyde was added, and the mixture was stirred at 30–35 °C for 30–60 min. The mixture was washed 6–8 times by centrifugation with deionized water and dried in an oven at 40–60 °C for 10–12 h. The resulting powder was annealed in a tube furnace under N2 protection at 500–700 °C to obtain porous carbon-coated Li. 0.5 La 0.5 TiO3 nanospheres are porous carbon-coated nanospheres of lithium lanthanum titanium oxide as positive electrode carrier material for lithium-sulfur batteries.

[0042] III. Preparation of Porous Carbon-Coated Spherical Lithium Lanthanum Titanium Oxide Sulfur-Loaded Lithium-Sulfur Battery Cathode Material: Elemental sulfur and the porous carbon-coated spherical lithium lanthanum titanium oxide lithium-sulfur battery cathode carrier material obtained in step II were ground in a mortar for 1–2 hours at a mass ratio of 1:7 to 3:7. The mixture was then melt-diffused at 150–160°C for 10–12 hours under nitrogen protection. After cooling to room temperature, the porous carbon-coated spherical lithium lanthanum titanium oxide sulfur-loaded lithium-sulfur battery cathode material was obtained. The lithium-sulfur battery cathode material with nano-spherical lithium lanthanum titanium oxide loaded with sulfur was dispersed with acetylene black and polyvinylidene fluoride in 1-4 ml of N-methylpyrrolidone solvent at a mass ratio of 8:1:1. The mixture was stirred to obtain a uniform slurry, which was then coated onto an aluminum foil current collector using a doctor blade and dried in a drying oven at 20-60℃ to obtain an ion / electron dual-conductivity lithium-sulfur battery cathode. The obtained lithium-sulfur battery cathode was then cut into circular slices with a diameter of 14 mm using a coin cell slicing machine for later use.

[0043] IV. Assembly of Lithium-Sulfur Batteries

[0044] The lithium-sulfur battery cathode material obtained in step three was dried in an oven. The battery was then assembled under a helium atmosphere in a vacuum glove box. The coin cell was assembled in the following order: 2025 coin cell cathode shell, 14 mm diameter lithium-sulfur battery cathode, 16 mm diameter Celgard 2500 separator, 20–50 μl organic electrolyte, 15.6 mm diameter lithium sheet, and 2025 coin cell anode shell. The coin cell was then sealed with a sealing machine to complete the battery assembly, which was then used for electrochemical performance testing.

[0045] This embodiment uses lanthanum nitrate, lithium nitrate, citric acid, tetrabutyl titanate, and ethylene glycol as raw materials. Spherical lithium lanthanum titanium oxide nanomaterials are obtained through hydrothermal annealing. Citric acid acts as a complexing agent with multidentate ligands. The citric acid-ethylene glycol system forms stable chelates with lithium, lanthanum, and titanium ions. The citric acid-ethylene glycol system, in conjunction with lanthanum, titanium, and lithium ions, undergoes a hydrothermal reaction to form spherical nanomaterials. During the subsequent hydrothermal synthesis, due to solvothermal activity, to minimize system energy, the precipitated phase tends to have a spherical morphology with low surface energy. During calcination, the citric acid-ethylene glycol system thermally decomposes, leaving pores. This results in the formation of spherical lithium lanthanum titanium oxide nanomaterials. Simultaneously, significant volume shrinkage occurs during the calcination and crystallization of lithium lanthanum titanium oxide, further promoting pore formation. The porous structure can confine and adsorb sulfur and polysulfides, better restricting polysulfide shuttle movement, which is beneficial for sulfur encapsulation and thus improves the cycle performance of lithium-sulfur batteries.

[0046] Secondly, a porous carbon-coated spherical lithium lanthanum titanium oxide nanomaterial with ion / electron dual-conductivity was employed. The combined use of lithium lanthanum titanium oxide and porous carbon as a lithium-sulfur battery carrier demonstrated enhanced charge transfer behavior at the interface between sulfur and the porous carbon-coated spherical lithium lanthanum titanium oxide nanomaterial compared to traditional three-phase interfaces. The spherical coating expands the active surface area, thereby accelerating the electrochemical reaction process of sulfur. This process exhibits high sulfur utilization and excellent yield. In practical applications, it promotes charge transfer and suppresses the shuttle effect of polysulfides, thus improving the sulfur loading capacity of the carrier.

[0047] Finally, the preparation process of this embodiment is simple, low-cost, and produces excellent battery performance, making it suitable for large-scale production and commercialization.

[0048] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the concentration of citric acid in step one is 10–30 mmol to obtain nano-spherical lithium lanthanum titanium oxide. Citric acid is a strong complexing agent, and the citric acid-ethylene glycol system forms stable chelates with lithium, lanthanum, and titanium ions. In the subsequent solvothermal process, this is beneficial for the precipitates to have a low surface energy spherical morphology. Everything else is the same as in Specific Implementation Method One.

[0049] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that the continued stirring time in step one is 20-40 minutes. Everything else is the same as in Specific Implementation Method One or Two.

[0050] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the hydrothermal synthesis time in step one is 6 hours. Everything else is the same as in Specific Implementation Methods One to Three.

[0051] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that the suspension in the reactor is washed 6 to 10 times with deionized water in step one. Everything else is the same as in Specific Implementation Methods One to Four.

[0052] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that the annealing time in step two is 2 to 4 hours. Everything else is the same as in Specific Implementation Methods One to Five.

[0053] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that the stirring time in step three is 10-12 hours. It is the same as Specific Implementation Methods One to Six.

[0054] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that the drying time in step three is 10-12 hours. Everything else is the same as in Specific Implementation Methods One to Seven.

[0055] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that the thickness of the coating applied to the aluminum foil current collector using a scraper in step three is 80–200 μm. Everything else is the same as in Specific Implementation Methods One to Eight.

[0056] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods One to Nine in that: in step four, the lithium-sulfur battery cathode material obtained in step three is placed in an oven at 50–70°C and dried for 20–40 minutes to prevent moisture from damaging battery performance. Everything else is the same as in Specific Implementation Methods One to Nine.

[0057] Example 1

[0058] The beneficial effects of the present invention were verified through the following experiments:

[0059] The preparation method of a lithium-sulfur battery in this experiment is carried out according to the following steps:

[0060] 5 mmol of La(NO3)3·6H2O, 6 mmol of LiNO3, and 15 mmol of citric acid were dissolved in 20 ml of ethanol. After stirring at room temperature for 1–3 h, 8 mmol of tetrabutyl titanate and 0.1 mol of ethylene glycol were added sequentially, and stirring was continued for 35 min. The mixture was then transferred to a high-pressure reactor and hydrothermally heated at 120 °C for 6 h. After cooling, the reactor was opened, and the suspension was washed with deionized water by centrifugation. The mixture was then dried in an oven at 60 °C for 12 h. The resulting powder was annealed in a tube furnace at 700 °C for 2 h to obtain Li. 0.5 La 0.5 TiO3 nanospheres, namely nano-spherical lithium lanthanum titanium oxide;

[0061] II. Preparation of porous carbon-coated spherical lithium lanthanum titanium oxide nanospheres

[0062] 1 g of nano-spherical lithium lanthanum titanium oxide was ultrasonically dispersed in 30 ml of deionized water to obtain a lithium lanthanum titanium oxide suspension. 2 g of hexadecyltrimethylammonium bromide, 2 g of resorcinol, 25 ml of ethanol, and 0.8 ml of ammonia were added sequentially to the lithium lanthanum titanium oxide suspension and stirred until homogeneous. Then, 3 ml of formaldehyde was added, and the mixture was stirred at 35°C for 60 min. The mixture was washed 7 times by centrifugation with deionized water and dried in an oven at 60°C for 12 h. The resulting powder was annealed in a tube furnace under N2 protection at 700°C for 2 h to obtain porous carbon-coated Li. 0.5 La 0.5 TiO3 nanospheres are porous carbon-coated nanospheres of lithium lanthanum titanium oxide as positive electrode carrier material for lithium-sulfur batteries.

[0063] III. Preparation of Porous Carbon-Coated Spherical Lithium Lanthanum Titanium Oxide Battery Cathode Material with Sulfur Loading: Elemental sulfur and the porous carbon-coated spherical lithium lanthanum titanium oxide lithium-sulfur battery cathode support material obtained in step II were ground in a mortar for 1.5 h at a mass ratio of 7:3. The mixture was then melt-diffused at 155 °C for 12 h under nitrogen protection. After cooling to room temperature, the porous carbon-coated spherical lithium lanthanum titanium oxide lithium-sulfur battery cathode material with sulfur loading was obtained. Sulfur-loaded lithium-sulfur battery cathode material, acetylene black, and polyvinylidene fluoride were dispersed in 2 ml of N-methylpyrrolidone solvent at a mass ratio of 8:1:1 and stirred for 12 h to obtain a uniform slurry. The slurry was then coated onto an aluminum foil current collector with a thickness of 120 μm using a doctor blade and dried in a drying oven at 60 °C for 12 h to obtain an ion / electron dual-conductivity lithium-sulfur battery cathode. The lithium-sulfur battery cathode was then cut into 14 mm diameter discs using a coin cell slicing machine for later use.

[0064] IV. Assembly of Lithium-Sulfur Batteries

[0065] The lithium-sulfur battery cathode material obtained in step three was dried in an oven. Battery assembly was then completed under a helium atmosphere in a vacuum glove box. The coin cell was assembled in the following order: 2025 coin cell cathode shell, 14mm diameter lithium-sulfur battery cathode, 16mm diameter Celgard 2500 separator, 40μl organic electrolyte, 15.6mm diameter lithium sheet, and 2025 coin cell anode shell. The coin cell was then sealed with a sealing machine to complete the battery assembly. Electrochemical performance testing revealed a discharge specific capacity of 1230 mAh g at 0.5C. -1 .

[0066] Comparative Example 1

[0067] The difference between this comparative example and the previous example is that the amount of citric acid added in step one is 5 mmol; the other steps are the same as in Example 1. Figure 5As shown, the obtained carbon-coated lithium lanthanum titanium oxide material consists of amorphous particles that cannot form a complete Earth-shaped structure and are uneven. Figure 6 It can be seen that the lithium-sulfur battery prepared with this material has a discharge specific capacity of 670.6 mAh g at 0.5C. -1 .

[0068] Performance characterization was performed on the above comparative examples and embodiments.

[0069] 1) Scanning Electron Microscopy (SEM) Testing. The surface morphology and elemental distribution of the cathode material were tested using SEM, with accelerating voltages ranging from 0.2 to 30 kV. The instrument used was a FEI Sirion 200 with a resolution of 20 kV and accelerating voltages of 0.2-30 kV. Sample Preparation: The test sample was adhered to conductive adhesive, the surrounding sample was dispersed, and after a 20-second gold sputtering process, it was placed on the sample stage for testing.

[0070] 2) Charge and discharge test. The LAND battery testing system is used for charge and discharge testing, with a voltage range of 1.5V-3.0V, to analyze electrochemical performance parameters such as battery discharge specific capacity, charge and discharge efficiency, and voltage plateau.

[0071] 3) X-ray diffraction (XRD) analysis. X-ray diffraction (XRD) was used to analyze the structure, interlayer spacing, and crystallinity of the material. In this paper, XRD was used to analyze the interlayer spacing of the material. The instrument model was X'Pert PRO, and the parameters were voltage 45kV and current 40mA. The X-ray source was Cu target Kα rays (wavelength 0.154nm), and the scanning range was from 0° to 90°.

[0072] Figure 1 This diagram illustrates a process for preparing porous carbon-coated spherical lithium lanthanum titanium oxide nanoparticles for lithium-sulfur batteries. Using citric acid as a complexing agent, and lithium nitrate, lanthanum nitrate, tetrabutyl titanate, and ethylene glycol as raw materials, porous carbon-coated spherical lithium lanthanum titanium oxide nanoparticles are obtained through hydrothermal treatment followed by annealing in a tube furnace. Hollow carbon spheres are then obtained by carbonization in a tube furnace using phenolic resin as the carbon source. This method yields a core-shell structured hybrid ionic conductor material with advantages such as simple synthesis process and readily available raw materials.

[0073] Figure 2 SEM images of nanospheres of lithium lanthanum titanium oxide for a method of preparing lithium-sulfur batteries, by [source missing]. Figure 2 It can be seen that porous carbon-coated nanosphere lithium lanthanum titanium oxide material was successfully prepared with uniform size. The uniform size is conducive to uniform charge deposition.

[0074] Figure 3 XRD pattern of nanospheres of lithium lanthanum titanium oxide for a method of preparing lithium-sulfur batteries. Figure 3It can be seen that there are obvious peaks near 26°, 33°, 40°, 46° and 58°. The structure of the nano-spherical lithium lanthanum titanium oxide (LLTO) obtained by comparison with standard card 01-089-0125 is consistent with the cubic structure of LLTO.

[0075] Figure 4 This is a SEM image of a porous carbon-coated spherical lithium lanthanum titanium oxide carrier material in a 15 mmol citric acid system for the preparation of a lithium-sulfur battery. Some broken spheres were observed in the SEM image, indicating that the hollow carbon spheres successfully coated the lithium lanthanum titanium oxide. The image shows that the porous carbon-coated spherical lithium lanthanum titanium oxide carrier material has a uniform structure and a smooth surface. Hexadecyltrimethylammonium bromide, as a surfactant, can make the phenolic resin carbon spheres uniformly cover the surface of the lithium lanthanum titanium oxide spheres.

[0076] Figure 5 This is a SEM image of carbon-coated lithium lanthanum titanium oxide in a 5 mmol citric acid system for the preparation of a lithium-sulfur battery. The carbon-coated lithium lanthanum titanium oxide material in the 5 mmol citric acid system is an amorphous particle that cannot form a complete earth-shaped structure and is not uniform.

[0077] Figure 6 The charge-discharge curves of carbon-coated spherical lithium lanthanum titanium oxide cathode material in a 5 mmol citric acid system are shown in the figure for a method of preparing a lithium-sulfur battery. The results show that the lithium-sulfur battery prepared with this material has a discharge specific capacity of 670.6 mAh g at 0.5C. -1 Furthermore, the Coulomb efficiency is unstable.

[0078] Figure 7 The charge-discharge curves of a lithium-sulfur battery prepared using a 15 mmol citric acid system with porous carbon-coated spherical lithium lanthanum titanium oxide as the positive electrode are shown. The initial discharge specific capacity at 0.5C is 1230.5 mAh g. -1 It maintains a high capacity of 701mAh g after 180 cycles. -1 The coulombic efficiency is >90%, indicating that the hybrid bidirectional interface structure improves the charge transfer efficiency, realizes the preparation of ion / electron dual-carrier materials, and the porous carbon-coated nanosphere lithium lanthanum titanium oxygen-loaded sulfur lithium battery cathode material effectively alleviates problems such as volume expansion.

[0079] Figure 8 A method for preparing a lithium-sulfur battery and a practical application diagram of the lithium-sulfur battery. The lithium-sulfur battery can light up 12 light-emitting diodes in a series-parallel combined circuit, and has excellent practical value.

[0080] The porous carbon-coated spherical lithium lanthanum titanium oxide nanoparticles obtained in this invention realize the preparation of a lithium-sulfur battery cathode with dual ion / electron conduction. This cathode exhibits excellent confined sulfur and adsorption of lithium polysulfides, fundamentally solving the shuttle effect. This results in a lithium-sulfur battery with excellent charge-discharge performance, achieving an initial discharge specific capacity of 1230.5 mAh g at 0.5C. -1 It maintains a high capacity of 701mAh g after 180 cycles. -1 Coulomb efficiency > 90%.

Claims

1. A method for preparing a lithium-sulfur battery, characterized in that, A method for preparing a lithium-sulfur battery is carried out according to the following steps: I. Preparation of Nanospheres of Lithium Lanthanum Titanium Oxide Dissolve 3–8 mmol of La(NO3)3∙6H2O, 3–8 mmol of LiNO3, and citric acid in 20–40 ml of ethanol. Stir at room temperature for 1–3 h, then add 8–10 mmol of tetrabutyl titanate and 0.1 mol of ethylene glycol sequentially. Continue stirring, transfer to a high-pressure reactor, and perform hydrothermal synthesis at 120–160 °C. After cooling, open the reactor, wash the suspension with deionized water by centrifugation, and dry in an oven at 40–60 °C for 10–12 h. Anneal the obtained powder in a tube furnace at 500–700 °C for 2–4 h to obtain Li. 0.5 La 0.5 TiO3 nanospheres, namely nano-spherical lithium lanthanum titanium oxide; II. Preparation of porous carbon-coated spherical lithium lanthanum titanium oxide nanospheres 1–3 g of nano-spherical lithium lanthanum titanium oxide was ultrasonically dispersed in 20–40 ml of deionized water to obtain a lithium lanthanum titanium oxide suspension. 2–4 g of hexadecyltrimethylammonium bromide, 1–3 g of resorcinol, 20–40 ml of ethanol, and 0.5–0.8 ml of ammonia were added sequentially to the lithium lanthanum titanium oxide suspension and stirred until homogeneous. Then, 2–4 ml of formaldehyde was added, and the mixture was stirred at 30–35 °C for 30–60 min. The mixture was washed 6–8 times by centrifugation with deionized water and dried in an oven at 40–60 °C for 10–12 h. The resulting powder was annealed at 500–700 °C in a tube furnace under N2 protection to obtain porous carbon-coated Li. 0.5 La 0.5 TiO3 nanospheres are porous carbon-coated nanospheres of lithium lanthanum titanium oxide as positive electrode carrier material for lithium-sulfur batteries. III. Preparation of Porous Carbon-Coated Nanospherical Lithium Lanthanum Titanium Oxide-Supported Sulfur-Ion Battery Cathode Material Elemental sulfur and the porous carbon-coated spherical lithium lanthanum titanium oxide lithium battery cathode carrier material obtained in step two were ground in a mortar at a mass ratio of 1:7 to 3:7 for 1 to 2 hours. The mixture was then melt-diffused at 150 to 160 °C for 10 to 12 hours under nitrogen protection. After cooling to room temperature, a porous carbon-coated spherical lithium lanthanum titanium oxide lithium battery cathode material with sulfur load was obtained. This material was then dispersed with acetylene black and polyvinylidene fluoride at a mass ratio of 8:1:1 in 1 to 4 ml of N-methylpyrrolidone solvent. The mixture was stirred to obtain a uniform slurry, which was then coated onto an aluminum foil current collector using a scraper and dried in a drying oven at 20 to 60 °C to obtain an ion / electron dual-conductivity lithium-sulfur battery cathode. The obtained lithium-sulfur battery cathode was then cut into 14 mm diameter discs using a coin cell slicing machine for later use. IV. Assembly of Lithium-Sulfur Batteries The lithium-sulfur battery cathode material obtained in step three was dried in an oven. The battery was then assembled under a helium atmosphere in a vacuum glove box. The coin cell was assembled in the following order: 2025 coin cell cathode shell, 14 mm diameter lithium-sulfur battery cathode, 16 mm diameter Celgard 2500 separator, 20-50 μl organic electrolyte, 15.6 mm diameter lithium sheet, and 2025 coin cell anode shell. The coin cell was then sealed with a sealing machine to complete the battery assembly, which was then used for electrochemical performance testing.

2. The method for preparing a lithium-sulfur battery according to claim 1, characterized in that... The amount of citric acid used in step one is 10~30 mmol to obtain nano-spherical lithium lanthanum titanium oxide. Citric acid is a strong complexing agent. The citric acid-ethylene glycol system forms stable chelates with lithium, lanthanum and titanium ions, which is beneficial for the precipitates to have a spherical morphology with low surface energy in the subsequent solvothermal process.

3. A method for preparing a lithium-sulfur battery according to claim 1, characterized in that, The stirring time mentioned in step one is 20-40 minutes.

4. A method for preparing a lithium-sulfur battery according to claim 1, characterized in that, The hydrothermal synthesis time described in step one is 6 hours.

5. The method for preparing a lithium-sulfur battery according to claim 1, characterized in that... The suspension in the vessel is washed 6-10 times with deionized water by centrifugation as described in step one.

6. A method for preparing a lithium-sulfur battery according to claim 1, characterized in that, The annealing time mentioned in step two is 2 to 4 hours.

7. The method for preparing a lithium-sulfur battery according to claim 1, characterized in that, The stirring time mentioned in step three is 10-12 hours.

8. A method for preparing a lithium-sulfur battery according to claim 1, characterized in that, The drying time mentioned in step three is 10-12 hours.

9. A method for preparing a lithium-sulfur battery according to claim 1, characterized in that, The thickness of the coating applied to the aluminum foil current collector using a scraper in step three is 80~200 μm.

10. A method for preparing a lithium-sulfur battery according to claim 1, characterized in that, In step four, the lithium-sulfur battery cathode material obtained in step three is placed in an oven at 50-70°C for 20-40 minutes to dry, in order to prevent moisture from damaging the battery performance.

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