Lithium-sulfur battery composite positive electrode material based on 1T-phase molybdenum disulfide composite graphene material and preparation method of lithium-sulfur battery composite positive electrode material
By using 1T-phase molybdenum disulfide composite graphene-based materials in lithium sulfur batteries and composited with sulfur element, the problems of sulfur element insulation and lithium polysulfide dissolution in lithium sulfur batteries are solved, and higher circulation performance and active substance utilization are achieved.
Patent Information
- Application Number
- CN202510380459.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-28
- Publication Date
- 2025-06-24
AI Technical Summary
Because the sulfur element of lithium-sulfur batteries is an electron and ionic insulator, the electrochemical reaction is unfavorable, and lithium polysulfide is easily soluble in the electrolyte, resulting in loss of active substances and attenuation of battery capacity.
The composite positive electrode material of 1T phase molybdenum disulfide is used as a support and is combined with sulfur element. The composite positive electrode material is prepared by multi-step heat treatment technology. The catalytic conversion and adsorption of 1T phase molybdenum disulfide is used to slow down the dissolution and shuttle of lithium polysulfide.
It improves the circulation performance and utilization rate of active substances of lithium-sulfur batteries, reduces the loss of active sulfur, enhances the kinetics of electrochemical reactions, and extends the service life of the battery.
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Figure CN120199804A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of electrode materials for new energy, and specifically relates to a lithium-sulfur battery composite positive electrode material based on 1T phase molybdenum disulfide composite graphene material and a preparation method thereof. Background Art
[0002] In the current era of rapid technological development, with the continuous development of new energy vehicles and mobile electronic devices, higher requirements are placed on battery energy density. However, the existing lithium-ion batteries have approached their theoretical energy density upper limit, which is about 250 Wh / kg in terms of technological development. The development of high-energy-density power batteries has become a key issue that needs to be solved urgently. Lithium-sulfur batteries have become one of the most promising next-generation high-energy-density secondary batteries due to their high theoretical specific energy, which is about 2600 Wh / kg, far higher than the energy density of commercial lithium-ion batteries. In addition, sulfur has the advantages of abundant resources, low price, and environmental friendliness. This makes sulfur, as a positive electrode material, widely concerned by scholars. However, the shortcomings of lithium-sulfur batteries are also very fatal. Sulfur is an electronic and ionic insulator at room temperature, which is not conducive to electrochemical reactions. The lithium polysulfide produced during charging and discharging is easily soluble in the electrolyte and shuttles between the positive and negative electrodes, resulting in loss of active materials and battery capacity decay. The lithium sulfide product of lithium sulfide is also an electronic and ionic insulator. The density difference between it and sulfur will cause the volume expansion of the electrode and affect the mechanical stability of the electrode. These problems seriously lead to low utilization rate of active materials in lithium-sulfur batteries, poor cycle performance and rate performance. Therefore, the key to the research of sulfur cathode in lithium-sulfur batteries is how to effectively improve the conductivity of sulfur cathode and inhibit the shuttle of lithium polysulfide.
[0003] In order to solve the above problems, carbon-based materials with excellent conductive properties are used as the main materials of sulfur cathodes. However, due to the non-polar characteristics of carbon materials, people realize that it is difficult to effectively inhibit the shuttling of polysulfides by the physical confinement of carbon-based materials alone. Therefore, heteroatom doping and single atom modification are added on the basis of carbon nanoframes to improve the solid loading capacity of lithium polysulfides. With the in-depth study of sulfur positive electrode carrier materials by scholars, high-polarity materials including metal compounds such as metal oxides, sulfides, and nitrides have gradually become the research hotspots of positive electrode carrier materials for lithium-sulfur batteries. These materials not only adsorb polysulfides but also have a certain catalytic effect on polysulfides, which can effectively promote the electrochemical reaction process of lithium-sulfur batteries and improve the utilization rate of active substances. This makes the commercialization of lithium-sulfur batteries possible, but with the increase of sulfur positive electrode active substances, the disadvantage of low conductivity of metal compounds begins to appear. Therefore, the combination of highly conductive carbon-based materials and metal compounds with excellent catalytic properties may achieve a comprehensive improvement in the electrochemical performance of lithium-sulfur batteries. Summary of the invention
[0004] To solve the above problems, the present invention provides a composite cathode material for lithium-sulfur batteries based on 1T-phase molybdenum disulfide composite graphene-like materials and a preparation method thereof. By utilizing the efficient catalytic conversion and strong adsorption of metal-containing 1T-phase molybdenum disulfide on polysulfide lithium, the dissolution and shuttle of polysulfide lithium in ether-based electrolytes are slowed down, thereby improving the cycling performance of lithium-sulfur batteries.
[0005] The present invention is achieved through the following technical solutions: The present invention discloses a preparation method of a composite cathode material for lithium-sulfur batteries based on 1T-phase molybdenum disulfide composite graphene-like materials. Using the 1T-phase molybdenum disulfide composite graphene-like materials as a carrier, it is compounded with sulfur to prepare a composite cathode material for lithium-sulfur batteries.
[0006] Furthermore, it specifically includes the following steps: Step 1: Prepare 1T-phase molybdenum disulfide composite graphene-like materials by combining hydrothermal and annealing processes using a molybdenum source, a sulfur source compound, and graphene-like materials. Step 2: Mix and grind the 1T-phase molybdenum disulfide composite graphene-like materials obtained in Step 1 with sulfur to obtain a mixture of the target carrier material and sulfur. Place it in a reaction kettle and perform heat treatment under a specific atmosphere to obtain a composite cathode material for lithium-sulfur batteries.
[0007] Furthermore, the preparation method of the 1T-phase molybdenum disulfide composite graphene-like materials is as follows: Dissolve the molybdenum source and the sulfur source compound in an aqueous solution of a polymer, add graphene-like materials after stirring, transfer the obtained mixture to an autoclave for hydrothermal reaction after ultrasonic treatment. After cooling to room temperature, wash with deionized water and absolute ethanol and then dry, and calcine in a tubular furnace under an argon atmosphere to obtain 1T-phase molybdenum disulfide composite graphene-like materials.
[0008] Furthermore, the molybdenum source is ammonium molybdate dihydrate, and the sulfur source compound is one of thioacetamide and L-cysteine.
[0009] Furthermore, the polymer is polyethylene glycol with a molecular weight of ~20000.
[0010] Furthermore, the graphene-like materials are one of nitrogen-doped graphene and graphene.
[0011] Furthermore, the temperature during the hydrothermal reaction is 200 - 220 °C, and it is kept at a constant temperature in an oven for 24 h; the annealing temperature of the tubular furnace is 300 - 400 °C.
[0012] Furthermore, the mass ratio of 1T-phase molybdenum disulfide composite graphene and sulfur in Step 2 is 28:72.
[0013] Furthermore, the specific conditions for heat treatment in Step 2 are to keep the temperature at 155 °C for 12 h under an argon atmosphere.
[0014] The present invention also discloses a composite cathode material for lithium-sulfur batteries based on 1T-phase molybdenum disulfide composite graphene-like materials prepared by the above preparation method.
[0015] The beneficial effects of the present invention are as follows: (1) The present invention uses a multi-step heat treatment technique. First, 1T-phase molybdenum disulfide composite graphene-like materials are prepared by combining solvothermal and annealing processes; then, the composite cathode material is obtained by further heat treatment and compounding with sulfur. The process is mature and the method is simple, and the sulfur content of the obtained composite cathode material is controllable; (2) As a polar carrier of the sulfur cathode, the 1T-phase molybdenum disulfide composite graphene-like material can effectively improve the catalytic activity of polysulfide conversion by regulating the carrier-catalyst heterojunction interface, prompting the target carrier material to have a strong chemical adsorption effect and excellent catalytic conversion effect on polar lithium polysulfide, reducing the loss of active sulfur, thereby improving the reaction kinetics, slowing down the shuttle effect, and then obtaining a composite cathode material for lithium-sulfur batteries with excellent performance. Description of the Drawings
[0016] Figure 1 XRD patterns of the 1T-phase molybdenum disulfide composite graphene-like carriers prepared in Examples 1 to 4; Figure 2 Initial charge-discharge curves of the composite cathode materials for lithium-sulfur batteries prepared in Examples 1 to 4 at a rate of 0.1 C at room temperature. Detailed Embodiments
[0017] The present invention provides a composite cathode carrier material for lithium-sulfur batteries based on 1T-phase molybdenum disulfide composite graphene-like materials and a preparation method thereof. Unless otherwise specified, the materials and reagents used in the present invention can be obtained from commercial products in the art.
[0018] A preparation method of a composite cathode material for lithium-sulfur batteries based on 1T-phase molybdenum disulfide composite graphene-like materials specifically includes the following steps: Step 1. Preparation of 1T-phase molybdenum disulfide composite graphene-like materials: Dissolve 10 mmol of molybdenum source and 20 mmol of sulfur source in 30 mL of 0.25 mmol aqueous polymer solution, where the molybdenum source is ammonium molybdate dihydrate, the sulfur source compound is one of thioacetamide and L-cysteine, and the polymer is polyethylene glycol with a molecular weight of ~20000. Stir vigorously for 0.5 h, then add 10 mmol of commercial graphene-like material, which is one of nitrogen-doped graphene and graphene. And perform strong ultrasonic treatment. Transfer the obtained mixture to a 60 mL autoclave and keep it in a forced-air oven for 24 h, and the specific temperature of the forced-air oven is 200~220 °C. After cooling to room temperature, wash it three times with deionized water and anhydrous ethanol respectively, and then dry it in an oven at 60 °C. Finally, calcine it in a tubular furnace under an argon atmosphere for 2 h, and the annealing temperature of the tubular furnace is 300~400 °C to obtain a 1T-phase molybdenum disulfide composite graphene-like material.
[0019] Step 2: Compound the 1T-phase molybdenum disulfide composite graphene-like material obtained in Step 1 with sulfur: Mix the 1T-phase molybdenum disulfide composite graphene-like material and sulfur in a mass ratio of 28:72, and grind to obtain a mixture of the target carrier material and sulfur; put the mixture of the target carrier material and sulfur into a reaction kettle, and then keep it at 155 °C for 12 h under an argon atmosphere to obtain a composite cathode material for lithium-sulfur batteries.
[0020] The present invention will be further described below in conjunction with the accompanying drawings and specific preferred embodiments, but the protection scope of the present invention is not limited thereby.
[0021] Example 1 A composite cathode material for lithium-sulfur batteries based on a 1T-phase molybdenum disulfide composite nitrogen-doped graphene carrier is specifically prepared according to the following steps: Step 1: Preparation of 1T-phase molybdenum disulfide composite nitrogen-doped graphene: Dissolve 10 mmol of ammonium molybdate dihydrate and 20 mmol of thioacetamide in 30 mL of an aqueous solution of 0.25 mmol polyethylene glycol, stir vigorously for 0.5 h, then add 10 mmol of commercial nitrogen-doped graphene, and perform strong ultrasonic treatment. Transfer the obtained mixture to a 60 mL autoclave and keep it at 200 °C for 24 h. After cooling to room temperature, wash it three times with deionized water and anhydrous ethanol respectively, and then dry it in an oven at 60 °C. Finally, calcine it in an argon atmosphere at 300 °C for 2 hours to obtain 1T-phase molybdenum disulfide composite nitrogen-doped graphene (1T-MoS2 / N-G-1).
[0022] Step 2: Compound the 1T-phase molybdenum disulfide composite nitrogen-doped graphene obtained in Step 1 with sulfur: Mix 1T-phase molybdenum disulfide composite nitrogen-doped graphene and sulfur in a mass ratio of 28:72, and grind to obtain a mixture of the target carrier material and sulfur; place the crucible containing the mixture of the target carrier material and sulfur in a reaction kettle under an argon atmosphere, and then heat it at 155 °C for 12 h in an autoclave encapsulated with argon to obtain a composite cathode material for lithium-sulfur batteries (S / 1T-MoS2 / N-G-1).
[0023] Example 2 A composite cathode material for lithium-sulfur batteries based on a 1T-phase molybdenum disulfide composite nitrogen-doped graphene carrier is prepared specifically according to the following steps: Step 1, Preparation of 1T-phase molybdenum disulfide composite nitrogen-doped graphene: Dissolve 10 mmol of ammonium molybdate dihydrate and 20 mmol of L-cysteine in 30 mL of an aqueous solution of 0.25 mmol of polyethylene glycol, stir vigorously for 0.5 h, then add 10 mmol of commercial nitrogen-doped graphene, and perform sonication. Transfer the resulting mixture to a 60 mL autoclave and hold at 220 °C for 24 h. After cooling to room temperature, wash three times with deionized water and anhydrous ethanol respectively, and then dry in an oven at 60 °C. Finally, calcine in an argon atmosphere at 400 °C for 2 hours to obtain 1T-phase molybdenum disulfide composite nitrogen-doped graphene (1T-MoS2 / N-G-2).
[0024] Step 2, Composite of the 1T-phase molybdenum disulfide composite nitrogen-doped graphene obtained in Step 1 and sulfur: Mix 1T-phase molybdenum disulfide composite nitrogen-doped graphene and sulfur in a mass ratio of 28:72, and grind to obtain a mixture of the target carrier material and sulfur; place the crucible containing the mixture of the target carrier material and sulfur in a reaction kettle under an argon atmosphere, and then heat it at 155 °C for 12 h in an autoclave encapsulated with argon to obtain a composite cathode material for lithium-sulfur batteries (S / 1T-MoS2 / N-G-2).
[0025] Example 3 A composite cathode material for lithium-sulfur batteries based on a 1T-phase molybdenum disulfide composite graphene carrier is prepared specifically according to the following steps: Step 1, Preparation of 1T-phase molybdenum disulfide composite graphene: Dissolve 10 mmol of ammonium molybdate dihydrate and 20 mmol of thioacetamide in 30 mL of an aqueous solution of 0.25 mmol of polyethylene glycol, stir vigorously for 0.5 h, then add 10 mmol of commercial graphene, and ultrasonically treat strongly. Transfer the resulting mixture to a 60 mL autoclave and maintain at 200 °C for 24 h. After cooling to room temperature, wash three times with deionized water and anhydrous ethanol each, and then dry in an oven at 60 °C. Finally, calcine in an argon atmosphere at 300 °C for 2 h to obtain 1T-phase molybdenum disulfide composite graphene (1T-MoS2 / G-3).
[0026] Step 2, compound the 1T-phase molybdenum disulfide composite graphene obtained in Step 1 with sulfur: Mix the 1T-phase molybdenum disulfide composite graphene and sulfur in a mass ratio of 28:72, grind to obtain a mixture of the target carrier material and sulfur; place the crucible of the mixture of the target carrier material and sulfur in a reaction kettle under an argon atmosphere, and then heat at 155 °C for 12 h in an autoclave encapsulated with argon to obtain a composite cathode material for lithium-sulfur batteries (S / 1T-MoS2 / G-3).
[0027] Example 4 A composite cathode material for lithium-sulfur batteries based on a 1T-phase molybdenum disulfide composite graphene carrier is prepared specifically according to the following steps: Step 1, Preparation of 1T-phase molybdenum disulfide composite graphene: Dissolve 10 mmol of ammonium molybdate dihydrate and 20 mmol of L-cysteine in 30 mL of an aqueous solution of 0.25 mmol of polyethylene glycol, stir vigorously for 0.5 h, then add 10 mmol of commercial graphene, and ultrasonically treat strongly. Transfer the resulting mixture to a 60 mL autoclave and maintain at 220 °C for 24 h. After cooling to room temperature, wash three times with deionized water and anhydrous ethanol each, and then dry in an oven at 60 °C. Finally, calcine in an argon atmosphere at 400 °C for 2 h to obtain 1T-phase molybdenum disulfide composite graphene (1T-MoS2 / G-4).
[0028] Step 2, compound the 1T-phase molybdenum disulfide composite graphene obtained in Step 1 with sulfur: Mix the 1T-phase molybdenum disulfide composite graphene and sulfur in a mass ratio of 28:72, grind to obtain a mixture of the target carrier material and sulfur; place the crucible of the mixture of the target carrier material and sulfur in a reaction kettle under an argon atmosphere, and then heat at 155 °C for 12 h in an autoclave encapsulated with argon to obtain a composite cathode material for lithium-sulfur batteries (S / 1T-MoS2 / G-4).
[0029] The composite cathode materials prepared in Examples 1 to 4 were made into electrode sheets according to the following process, and batteries were assembled for testing: (1) Electrode sheet preparation Select the prepared composite cathode material, Super-P conductive agent, and polyvinylidene fluoride (PVDF), and grind them evenly for 0.5 h according to a mass ratio of 8:1:1. Dissolve them in N-methylpyrrolidone (NMP), and stir until a uniform slurry is obtained. Then coat it on an aluminum foil with a carbon coating and dry it at 60 °C for 12 h to make an electrode sheet with a diameter of 10 mm.
[0030] (2) Battery assembly Use a lithium sheet as the negative electrode and Celgard 2325 as the separator. Assemble a 2032-type coin cell in a glove box filled with argon. The assembly sequence is negative electrode case – spring piece – gasket – lithium sheet – electrolyte – separator – electrolyte – positive electrode sheet – positive electrode case. The electrolyte is composed of 1.0 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and 0.2 M lithium nitrate (LiNO3) additive dissolved in 1,2-dimethoxyethane (1,2-Dimethoxyethane, DME) and 1,3-dioxolane (1,3-dioxolane, DOL) (v / v, 1:1). The ratio of electrolyte to sulfur (E / S) is 20 μL mg -1 . Place the obtained 2032 coin cell on a battery test system. After standing for 6 h, perform charge-discharge tests at a rate of 0.1 C. Set the voltage cut-off range to 1.7~2.8 V, and use the composite cathode material as the active material to calculate the discharge specific capacity of the battery. By comparison, it is obtained that the composite cathode material prepared in Example 1 has the highest specific capacity and the best cycle performance. Specifically, the first-cycle discharge specific capacity of the composite cathode material obtained in Example 1 is 903.7 mAh / g, and the discharge specific capacity remains 736.7 mAh / g after 50 cycles, and the capacity retention rate is 81.5%. The data of other examples are listed in Table 1.
[0031] From the above test results, it can be seen that the lithium-sulfur battery composite cathode materials provided by the present invention, which are regulated by different sulfur source initiators and graphene-based materials with the same molar amount, all exhibit excellent electrochemical performance. Among them, the composite cathode material obtained in Example 1 has the highest initial discharge specific capacity and capacity retention rate. This shows that the sulfur supported on the 1T-phase molybdenum disulfide composite nitrogen-doped graphene carrier has excellent catalytic conversion and strong chemical adsorption of polysulfide, and a lithium-sulfur battery composite cathode material with both high capacity and high cycle stability can be obtained.
[0032] It should be noted that although the present invention has been described through the above embodiments, the present invention can also have many other embodiments. Without departing from the spirit and scope of the present invention, those skilled in the art can obviously make various corresponding changes and modifications to the present invention, but these changes and modifications should all fall within the scope protected by the appended claims of the present invention and their equivalents.
Claims
1. A method for preparing a lithium-sulfur battery composite positive electrode material based on 1T phase molybdenum disulfide composite graphene material, characterized in that: 1T phase molybdenum disulfide composite graphene material is used as a carrier and combined with sulfur to prepare a lithium-sulfur battery composite positive electrode material.
2. The method for preparing a lithium-sulfur battery composite positive electrode material based on 1T phase molybdenum disulfide composite graphene material according to claim 1, characterized in that: The specific steps include: Step 1: Prepare 1T phase molybdenum disulfide composite graphene material by combining a molybdenum source, a sulfur source compound and a graphene material through a hydrothermal and annealing process: Step 2: Mix and grind the 1T phase molybdenum disulfide composite graphene material obtained in step 1 with sulfur to obtain a mixture of the target carrier material and sulfur, put it into a reactor, and perform heat treatment under a specific atmosphere to obtain a lithium-sulfur battery composite positive electrode material.
3. The method for preparing a lithium-sulfur battery composite positive electrode material based on 1T phase molybdenum disulfide composite graphene material according to claim 1 or 2, characterized in that: The preparation method of 1T phase molybdenum disulfide composite graphene material is as follows: dissolving a molybdenum source and a sulfur source compound in an aqueous solution of a polymer, adding a graphene material after stirring, transferring the obtained mixture to an autoclave for hydrothermal reaction after ultrasonic treatment, cooling to room temperature, washing with deionized water and anhydrous ethanol and then drying, and calcining in an argon atmosphere tubular furnace to obtain a 1T phase molybdenum disulfide composite graphene material.
4. The method for preparing a lithium-sulfur battery composite positive electrode material based on 1T phase molybdenum disulfide composite graphene material according to claim 3, characterized in that: The molybdenum source is ammonium molybdate dihydrate, and the sulfur source compound is one of thioacetamide and L-cysteine.
5. The method for preparing a lithium-sulfur battery composite positive electrode material based on 1T phase molybdenum disulfide composite graphene material according to claim 3, characterized in that: The polymer is polyethylene glycol with a molecular weight of ~20,000.
6. The method for preparing a lithium-sulfur battery composite positive electrode material based on 1T phase molybdenum disulfide composite graphene material according to claim 3, characterized in that: The graphene-based material is one of nitrogen-doped graphene and graphene.
7. The method for preparing a lithium-sulfur battery composite positive electrode material based on 1T phase molybdenum disulfide composite graphene material according to claim 3, characterized in that: The temperature during the hydrothermal reaction is 200-220°C, and the constant temperature is maintained in the oven for 24 hours; the tubular furnace annealing temperature is 300-400°C.
8. The method for preparing a lithium-sulfur battery composite positive electrode material based on 1T phase molybdenum disulfide composite graphene material according to claim 2, characterized in that: In step 2, the mass ratio of 1T phase molybdenum disulfide composite graphene and sulfur element is 28:
72.
9. The method for preparing a lithium-sulfur battery composite positive electrode material based on 1T phase molybdenum disulfide composite graphene material according to claim 2, characterized in that: The specific conditions of the heat treatment in step 2 are to keep the temperature at 155 °C for 12 h in an argon atmosphere.
10. A lithium-sulfur battery composite positive electrode material based on 1T phase molybdenum disulfide composite graphene material prepared according to the preparation method according to any one of claims 1 to 9.